U.S. patent application number 09/778920 was filed with the patent office on 2001-10-25 for precipitated aragonite and a process for producing it.
Invention is credited to Yaniv, Isaac.
Application Number | 20010033820 09/778920 |
Document ID | / |
Family ID | 24069619 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010033820 |
Kind Code |
A1 |
Yaniv, Isaac |
October 25, 2001 |
Precipitated aragonite and a process for producing it
Abstract
Disclosed is a novel form of particulate precipitated aragonite,
a novel process for producing it and compositions containing
it.
Inventors: |
Yaniv, Isaac; (Halfa,
IL) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
8th Floor
1100 North Glebe Road
Arlington
VA
22201-4714
US
|
Family ID: |
24069619 |
Appl. No.: |
09/778920 |
Filed: |
February 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09778920 |
Feb 8, 2001 |
|
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09519749 |
Mar 6, 2000 |
|
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Current U.S.
Class: |
423/432 ;
423/265 |
Current CPC
Class: |
C01F 11/182 20130101;
C01F 11/183 20130101; B01J 20/043 20130101; C05D 3/02 20130101;
A23P 10/43 20160801; C11D 3/1233 20130101; C01P 2006/10 20130101;
C01P 2004/10 20130101; C01B 32/60 20170801; A61Q 17/04 20130101;
B01J 20/28011 20130101; C08K 2003/265 20130101; A23L 27/77
20160801; C05D 3/00 20130101; A61Q 13/00 20130101; C08K 3/26
20130101; B01J 20/30 20130101; A61K 33/10 20130101; A61K 8/19
20130101; D21H 17/675 20130101; H01B 1/08 20130101; A23K 20/24
20160501; C01P 2002/72 20130101; A23L 29/294 20160801 |
Class at
Publication: |
423/432 ;
423/265 |
International
Class: |
C01F 011/18 |
Claims
1. A process for producing a particulate precipitated aragonite
calcium carbonate, which comprises reacting an aqueous calcium
hydroxide slurry with a gas selected from the group consisting of
carbon dioxide and a gas containing it, wherein the parameters of
said process, including at least one preselected active agent, mode
of operation, operating concentrations of raw materials, operating
temperature, operating mixer speed and operating pH, are such that
(A) the specific gravity of the product after drying for 12 hours
at 120.degree. C. is <2.5 g/cm.sup.3; and (B) the specific
gravity of this dry product after ignition for eight hours at
500.degree. C. is <2.5 g/cm.sup.3.
2. A process according to claim 1, in which said at least one
active agent is selected from the group consisting of carboxylic
acids of formula RCOOH, where R is an organic group containing 7-20
carbon atoms, their carboxylate salts, their acid anhydrides, their
esters, their acyl halides and their ketenes.
3. A process according to claim 2, in which said at least one
active agent is selected from the group consisting of carboxylic
acids of formula C.sub.nH.sub.2n+1COOH, where n is 8-17, their
carboxylate salts, their acid anhydrides, their esters, their acyl
halides and their ketenes of the formula
C.sub.nH.sub.2n+1C.dbd.C.dbd.O, where n is 7-16.
4. A process according to claim 2, which is further characterized
by the following features: (a) said at least one active agent is
selected from the group consisting of carboxylic acids of formula
CH.sub.3(CH.sub.2).sub.nCOOH, where n is 7-16, their carboxylate
salts, their acid anhydrides, their esters, their acyl halides and
their ketenes of the formula CH.sub.3(CH.sub.2).sub.nC.dbd.C.dbd.O,
where n is 6-15; (b) said concentration of the at least one active
agent is within the range between 0.2 wt. % and 10 wt. %,
calculated as carboxylic acid(s) and based on the weight of calcium
carbonate; (c) said slurry contains calcium hydroxide in a
concentration within the range of from 3 to 30 wt. %; (d) said pH
is within the range of from 8 to 11; (e) said temperature is in the
range between 60.degree. C. and the boiling temperature of the
reaction mixture; (f) said mode of operation is selected from a
continuous and a semi-continuous (intermittent) mode of operation;
(g) said mixer peripheral speed (tip-speed) is above 5 m/sec.; (h)
said at least one active agent is added in a manner selected from
introduction into the carbonation reactor and premixing with said
calcium hydroxide slurry prior to reaction with said gas.
5. A process according to claim 4, which is further characterized
by at least one of the following features: (a) said at least one
active agent is selected from the group consisting of carboxylic
acids of formula CH.sub.3(CH.sub.2).sub.nCOOH, where n is 7-16, and
the calcium salts thereof; (b) said concentration of the at least
one active agent is within the range between 0.3 wt. % and 5 wt. %,
calculated as carboxylic acid(s) and based on the weight of calcium
carbonate; (c) said slurry contains calcium hydroxide in a
concentration within the range of from 4 to 20 wt. %; (d) said pH
is within the range of from 9 to 10; (e) said temperature is in the
range between 80.degree. C. and the boiling temperature of the
reaction mixture; (f) said mode of operation is a continuous mode
of operation.
6. A process according to claim 5, which is further characterized
by at least one of the following features, namely: (a) said active
agent is selected from the group consisting of decanoic acid and
the calcium salts thereof, (b) said concentration of said at least
one active agent is within the range between 0.4 wt. % and 3 wt. %,
calculated as carboxylic acid and based on the weight of calcium
carbonate, (c) said temperature is in the range between 90.degree.
C. and the boiling temperature of the reaction mixture, and (d)
said slurry contains calcium hydroxide in a concentration within
the range of from 5 to 15 wt. %.
7. A process according to claim 2, which is further characterized
by at least feature (a) of the following features: (a) said at
least one active agent is selected from the group consisting of
carboxylic acids of formula C.sub.nH.sub.2n-1COOH, where n is 8-17,
their carboxylate salts, their acid anhydrides, their esters, their
acyl halides and their ketenes of the formula
C.sub.nH.sub.2n-1C.dbd.C.dbd.O, where n is 7-16; (b) said
concentration of the at least one active agent is within the range
between 0.2 wt. % and 10 wt. %, calculated as carboxylic acid(s)
and based on the weight of calcium carbonate; (c) said slurry
contains calcium hydroxide in a concentration within the range of
from 3 to 30 wt. %; (d) said pH is within the range of from 8 to
11; (e) said temperature is in the range between 60.degree. C. and
the boiling temperature of the reaction mixture; (f) said mode of
operation is selected from a continuous and a semi-continuous
(intermittent) mode of operation; (g) said mixer peripheral speed
(tip-speed) is above 5 m/sec.; (h) said at least one active agent
is added in a manner selected from introduction into the
carbonation reactor and premixing with said calcium hydroxide
slurry prior to reaction with said gas.
8. A process according to claim 7, which is further characterized
by at least one of the following features, namely: (a) said active
agent is selected from the group consisting of undecylenic acid and
the calcium salts thereof, (b) said concentration of said at least
one active agent is within the range between 0.4 wt. % and 3 wt. %,
calculated as carboxylic acid and based on the weight of calcium
carbonate, (c) said temperature is in the range between 90.degree.
C. and the boiling temperature of the reaction mixture, and (d)
said slurry contains calcium hydroxide in a concentration within
the range of from 5 to 15 wt. %.
9. A process according to claim 1, which is conducted as a
flotation process in a flotation cell.
10. A process according to claim 9, and substantially as
hereinbefore described with reference to FIG. 3 of the attached
drawings.
11. A particulate precipitated aragonite produced by the process of
claim 1.
12. A particulate precipitated aragonite according to claim 11,
which is characterized by at least one of the following features:
(i) it contains at least one calcium salt of carboxylic acids
selected from those of the general formulae C.sub.nH.sub.2n+1COOH
and C.sub.nH.sub.2n-1COOH, where n is 8-17, in an amount between
0.2 and 10 wt. %, calculated as carboxylic acid(s) and based on the
weight of calcium carbonate; (ii) it has an XRD spectrum
substantially in accordance with FIG. 5 of the attached
drawings.
13. A particulate precipitated aragonite according to claim 12,
which contains at least one calcium salt of carboxylic acids
selected from those of the general formula:
CH.sub.3(CH.sub.2).sub.nCOOH, where n=7-16, in an amount between
0.2 and 10 wt. %, calculated as carboxylic acid(s) and based on the
weight of calcium carbonate.
14. A particulate precipitated aragonite according to claim 11,
having a specific gravity <2.3 g/cm.sup.3 after drying at
120.degree. C. for twelve hours, and a specific gravity <2.3
g/cm.sup.3 after ignition for eight hours at 500.degree. C.
15. A particulate precipitated aragonite according to claim 14,
having a specific gravity <2.0 g/cm.sup.3 after drying at
120.degree. C. for twelve hours.
16. A particulate precipitated aragonite according to claim 15,
having a specific gravity <1.8 g/cm.sup.3 after drying at
120.degree. C. for twelve hours.
17. A particulate precipitated aragonite according to claim 16,
having a specific gravity <1.5 g/cm.sup.3 after drying at
120.degree. C. for twelve hours.
18. A particulate precipitated aragonite according to claim 11,
having a specific gravity <2.1 g/cm.sup.3 after drying at
120.degree. C. for twelve hours, and a specific gravity <2.1
g/cm.sup.3 after ignition for eight hours at 500.degree. C.
19. A particulate precipitated aragonite which has (A) a specific
gravity <2.5 g/cm.sup.3 after drying for 12 hours at 120.degree.
C., and (B) a specific gravity <2.5 g/cm.sup.3 after ignition
for eight hours at 500.degree. C. of the product dried in (A).
20. A particulate precipitated aragonite which has (A) a specific
gravity <2.3 g/cm.sup.3 after drying at 120.degree. C., and (B)
a specific gravity <2.3 g/cm.sup.3 after ignition for eight
hours at 500.degree. C. of the product dried in (A).
21. A particulate precipitated aragonite which has a specific
gravity <2.1 g/cm.sup.3 after drying at 120.degree. C. for
twelve hours, and a specific gravity <2.1 g/cm.sup.3 after
ignition for eight hours at 500.degree. C.
22. A particulate precipitated aragonite which has (A) a specific
gravity <1.8 g/cm.sup.3 after drying at 120.degree. C., and (B)
a specific gravity <2.3 g/cm.sup.3 after ignition for eight
hours at 500.degree. C. of the product dried in (A).
23. A particulate precipitated aragonite which has (A) a specific
gravity <1.5 g/cm.sup.3 after drying at 120.degree. C., and (B)
a specific gravity <2.3 g/cm.sup.3 after ignition for eight
hours at 500.degree. C. of the product dried in (A).
24. A particulate precipitated aragonite which has (A) a specific
gravity <1.5 g/cm.sup.3 after drying at 120.degree. C., and (B)
a specific gravity <2.1 g/cm.sup.3 after ignition for eight
hours at 500.degree. C. of the product dried in (A).
25. A particulate precipitated aragonite which has a specific
gravity <2.5 g/cm.sup.3 after ignition for eight hours at
500.degree. C.
26. A particulate precipitated aragonite which has a specific
gravity <2.3 g/cm.sup.3 after ignition for eight hours at
500.degree. C.
27. A particulate precipitated aragonite which has a specific
gravity <2.1 g/cm.sup.3 after ignition for eight hours at
500.degree. C.
28. A particulate precipitated aragonite according to any one of
claims 19 to 27, which is characterized by at least one of the
following features: (i) it contains at least one calcium salt of
carboxylic acids selected from those of the general formulae
C.sub.nH.sub.2n+1COOH and C.sub.nH.sub.2n-1COOH, where n is 8-17,
in an amount between 0.2 and 10 wt. %, calculated as carboxylic
acid(s) and based on the weight of calcium carbonate; (ii) it has
an XRD spectrum substantially in accordance with FIG. 5 of the
attached drawings.
29. A particulate precipitated aragonite according to claim 28,
which contains at least one calcium salt of carboxylic acids
selected from those of the general formula:
CH.sub.3(CH.sub.2).sub.nCOOH, where n=7-16, in an amount between
0.2 and 10 wt. %, calculated as carboxylic acid(s) and based on the
weight of calcium carbonate.
30. A particulate precipitated aragonite according claim 28, which
contains at least one calcium salt of carboxylic acids selected
from those of the general formula: C.sub.nH.sub.2n-1COOH, where n
is 8-17, in an amount between 0.2 and 10 wt. %, calculated as
C.sub.nH.sub.2n-1COOH and based on the weight of calcium
carbonate.
31. A particulate precipitated aragonite according to any one of
claims 11 to 27, of crystallographic purity
(aragonite/(aragonite+calcite)) at least 90%.
32. A particulate precipitated aragonite according to any one of
claims 11 to 27, of crystallographic purity
(aragonite/(aragonite+calcite))<90%.
33. A process according to any one of claims 1 to 10, wherein said
specific gravity is determined substantially as described in
Example 14(F).
34. A particulate precipitated aragonite according to any one of
claims 11 to 27, wherein said specific gravity is determined
substantially as described in Example 14(F).
35. A coating composition which comprises a particulate
precipitated aragonite as defined in any one of claims 11 to
27.
36. A coating composition according to claim 35, which comprises
substantially dry particulate precipitated aragonite.
37. A coating composition according to claim 35, which comprises
particulate precipitated aragonite in aqueous dispersion.
38. A paper composition which comprises a particulate precipitated
aragonite as defined in any one of claims 11 to 27.
39. A paper composition according to claim 38, which comprises
substantially dry particulate precipitated aragonite.
40. A paper composition according to claim 38, which comprises
particulate precipitated aragonite in aqueous dispersion.
41. A plastics composition which comprises a particulate
precipitated aragonite as defined in any one of claims 11 to
27.
42. A plastics composition according to claim 41, which comprises
substantially dry particulate precipitated aragonite.
43. A rubber composition which comprises a particulate precipitated
aragonite as defined in any one of claims 11 to 27.
44. A rubber composition according to claim 43, which comprises
substantially dry particulate precipitated aragonite.
45. An adsorbent composition which comprises a particulate
precipitated aragonite as defined in any one of claims 11 to
27.
46. An adsorbent composition according to claim 45, which comprises
substantially dry particulate precipitated aragonite.
47. A powder detergent composition which comprises a particulate
precipitated aragonite as defined in any one of claims 11 to
27.
48. A powder detergent composition according to claim 47, which
comprises substantially dry particulate precipitated aragonite.
49. A pharmaceutical composition which comprises a particulate
precipitated aragonite as defined in any one of claims 11 to
27.
50. A pharmaceutical composition according to claim 49, which
comprises substantially dry particulate precipitated aragonite.
51. A pharmaceutical composition according to claim 49, which
comprises particulate precipitated aragonite in aqueous
dispersion.
52. An agrochemical composition which comprises a particulate
precipitated aragonite as defined in any one of claims 11 to
27.
53. An agrochemical composition according to claim 52, which
comprises substantially dry particulate precipitated aragonite.
54. An agrochemical composition according to claim 52, which
comprises particulate precipitated aragonite in aqueous
dispersion.
55. A flavor composition which comprises a particulate precipitated
aragonite as defined in any one of claims 11 to 27.
56. A flavor composition according to claim 55, which comprises
substantially dry particulate precipitated aragonite.
57. A flavor composition according to claim 55, which comprises
particulate precipitated aragonite in aqueous dispersion.
58. A fragrance composition which comprises a particulate
precipitated aragonite as defined in any one of claims 11 to
27.
59. A fragrance composition according to claim 58, which comprises
substantially dry particulate precipitated aragonite.
60. A fragrance composition according to claim 58, which comprises
particulate precipitated aragonite in aqueous dispersion.
61. A food composition which comprises a particulate precipitated
aragonite as defined in any one of claims 11 to 27.
62. A food composition according to claim 61, which comprises
substantially dry particulate precipitated aragonite.
63. A food composition according to claim 61, which comprises
particulate precipitated aragonite in aqueous dispersion.
64. A feed composition which comprises a particulate precipitated
aragonite as defined in any one of claims 11 to 27.
65. A feed composition according to claim 64, which comprises
substantially dry particulate precipitated aragonite.
66. A feed composition according to claim 64, which comprises
particulate precipitated aragonite in aqueous dispersion.
67. A sunscreen composition which comprises a particulate
precipitated aragonite as defined in any one of claims 11 to
27.
68. A sunscreen composition according to claim 67, which comprises
substantially dry particulate precipitated aragonite.
69. A sunscreen composition according to claim 67, which comprises
particulate precipitated aragonite in aqueous dispersion.
70. A conductive powder composition which comprises a particulate
precipitated aragonite as defined in any one of claims 11 to
27.
71. A conductive powder composition according to claim 70, which
comprises substantially dry particulate precipitated aragonite.
72. A particulate precipitated aragonite, which after drying it for
12 hours at 120.degree. C., has a Loose Bulk Density
(L.B.D.)<0.4 g/cm.sup.3.
73. A particulate precipitated aragonite according to claim 72,
wherein said L.B.D. is determined substantially as described in
Example 14(G).
Description
FIELD AND BACKGROUND OF THE INVENTION
[0001] The present invention relates to a novel form of particulate
precipitated calcium carbonate, and particularly to a novel form of
particulate precipitated aragonite, and to a novel process for
producing it.
[0002] Various routes are known for the production of calcium
carbonate, which finds use as a thickening material, as a filler,
as an extender, and most of all as a pigment, in a variety of
industries such as pharmaceuticals, agrochemicals, plastics,
adhesives, printing, coating (paint), paper, rubber and in
filtration. For such purposes, there may be used ground calcium
carbonate (GCC) or precipitated calcium carbonate (PCC). PCC in
general possesses advantages over GCC, in that it is economical to
produce and its precise composition, or purity, can be more
strictly controlled.
[0003] The most frequently used chemical process for producing PCC
is based on the carbonation of aqueous suspensions of calcium
hydroxide (also known as "milk of lime" or "slaked lime") with
carbon dioxide gas, or with a carbon dioxide containing gas. This
process gives rise to relatively pure precipitated calcium
carbonate and is a preferred process, because there are no serious
problems of contamination of the product with undesired salts, and
moreover it can be controlled in order to adjust the properties of
the final product. Thus, the process is based essentially on four
stages: firstly, calcination of raw limestone to produce calcium
oxide or "quicklime" and carbon dioxide gas or a carbon dioxide
containing gas; secondly, "slaking" of the quicklime with water to
produce an aqueous suspension of calcium hydroxide; thirdly,
carbonation of the calcium hydroxide with carbon dioxide gas or a
carbon dioxide containing gas; and finally, downstream operations
such as dewatering, drying, deagglomeration, grinding, surface
treatment, surface coating, mixing with other minerals (e.g.
titanium dioxide, talc, kaolin, GCC, PCC--including aragonite PCC)
and dyeing, which allow optimization of the properties of the
precipitated calcium carbonate particles in order to be adapted to
their intended uses.
[0004] Calcium carbonate can be precipitated from aqueous calcium
hydroxide slurries or solutions in three different crystallographic
forms (polymorphs): the vaterite form which is thermodynamically
unstable, the aragonite form which is metastable under normal
ambient conditions of temperature and pressure, and the calcite
form which is the most stable and the most abundant in nature.
These forms of calcium carbonate can be prepared by carbonation of
slaked lime by suitable variations of the process conditions.
[0005] The calcite form is easy to produce on industrial scales, as
precipitated calcium carbonate particles. It exists in several
different shapes, of which the most common are the rhombohedral
shape and the scalenohedral shape.
[0006] Aragonite forms crystals having a length/width ratio
(hereinafter--"aspect ratio") in the range between>1:1 and 100:1
of which a typical aspect ratio is 10, in which case the aragonite
forms long, thin needles. Therefore, aragonite having a high aspect
ratio may be denoted hereinafter--"acicular aragonite" or
"needle-shaped aragonite". The production of aragonite is a slow
process and is very difficult to control on an industrial
scale.
[0007] PCC particles are used as thickening materials, fillers,
extenders and, most of all, as inexpensive pigments. The latter use
implies that a particularly desirable property of this material is
its light scattering characteristics, in order to be able to impart
opacity and brightness to the products containing it. Such
characteristics are optimized, when the pigment particles are very
effectively dispersed and are apart by an average distance in the
range between 0.2 .mu.m and 0.4 .mu.m in their final products, and
their size distribution is in the range between 0.2 .mu.m and 0.41
.mu.m, namely, in the range of half a wavelength of the visible
light. That means that either the production of the PCC should be
adjusted to produce small particles in order to avoid expensive
downstream particle size reduction operations and to cope with the
expensive problems of dewatering and drying the product, or,
alternatively, the process should be adjusted to produce large
particles, and subsequently effect the downstream dewatering and
grinding operations. In both cases, the production costs of
precipitated calcium carbonate of pigment grades may be doubled or
tripled just because of these unavoidable downstream steps.
[0008] High light scattering pigments currently available to the
above-mentioned industries include titanium dioxide particles,
which are very effective to scatter the light due to their
relatively high refractive index (2.76; for the rutile form) and
their meticulously controlled particle size distribution of which
median is in the range between 0.2 .mu.m and 0.4 .mu.m. However,
this product is of a high specific gravity (.about.4.0 g/cm.sup.3),
of a high surface area due to its small particles, and most of all,
is quite expensive. Fine kaolin particles are also being used as
pigments, but this product, which has a much lower refractive index
(1.56), is of limited whiteness and is still relatively expensive.
Particulate calcium carbonate is the ideal least expensive pigment
and could replace much more of the titanium dioxide and kaolin
pigments in their respective present applications, if it could be
prepared in a form having improved light scattering properties.
[0009] Calcium carbonate pigments are produced in part by grinding
coarse natural rocks and in part by precipitation processes. Of the
precipitated calcium carbonate particles, a particulate
precipitated aragonite is considered to be the most effective light
scattering calcium carbonate pigment, of which refractive indices
are 1.530, 1.681 and 1.685, depending on its crystallographic
surfaces, its specific gravity is above 2.5 g/cm.sup.3, and is the
most suitable for same applications. However, its production rate
is characteristically very slow and its production conditions are
very difficult to control, industrially.
[0010] While the majority of references, cited hereinafter, relate
to the technology for producing a particulate precipitated
aragonite, some of the references are included in order to better
present the state of the art for the production of PCC more
generally, including the downstream operations, which may be common
to all these processes and also to the present invention.
[0011] 1. U.S. Pat. No. 2,081,112 (N. Statham et al.) describes a
process for producing precipitated calcium carbonate by carbonating
milk of lime with carbon dioxide containing gas, where the
temperature in the gas absorber is maintained at 50-60.degree. C.,
preferably around 55.degree. C. It is recognized that the more
violent the agitation in the gas absorber, the finer will be the
product; the aim being to create a fine mist of calcium hydroxide
slurry.
[0012] 2. U.S. Pat. No. 2,964,382 (G. E. Hall, Jr.) describes
production of precipitated calcium carbonate by various chemical
routes, in which calcium ions are contacted with carbonate ions in
a precipitation zone, the process including also carbonation of
milk of lime with carbon dioxide gas. A high shear stator/rotor
agitator is used to provide turbulence by rotating at a peripheral
speed of at least 1160 feet per minute (589 cm per second) in the
precipitation zone. Also, this patent teaches that it is desirable
to operate the process at pH values of at least 8.5 and that at
temperatures above 60.degree. C., needle-shaped precipitated
aragonite particles are formed, which however produce an adverse
flow property effect.
[0013] 3. U.S. Pat. No. 3,320,026 (W. F. Waldeck) describes the
production of various forms of precipitated calcium carbonate.
[0014] 4. GB Patent No. 941,900 (assigned to Kaiser Aluminium &
Chemical corporation) describes the production of precipitated
aragonite particles, for use as a filter aid, by reacting
continuously sodium carbonate solution and aqueous calcium
hydroxide slurry at temperatures higher than 60.degree. C. in a
multistage system. The product and the solution are withdrawn at
the third stage from the bottom of the reactor, the product is then
separated from the solution and part of the crystals are recycled
to the various stages of the process as seeds for further
precipitation of the precipitated aragonite particles.
[0015] 5. U.S. Pat. No. 3,669,620 (M. C. Bennett et al.) describes
a continuous process for the production of a particulate
precipitated aragonite by carbonating aqueous calcium hydroxide
slurry in sucrose solutions. However, due to the cost of the
sucrose, the solution had to be recycled and detrimental materials
had to be removed by anion exchange resin. The preferred
temperature range was between 60.degree. C. and 90.degree. C.; the
pH values were in the range between 7 and 9; and the concentration
of the calcium hydroxide was quite low--in the range between
one-half and one-twentieth molar.
[0016] 6. U.S. Pat. No. 4,018,877 (R. D. A. Woode) describes
carbonation of calcium hydroxide slurry, wherein a complexing agent
for Ca.sup.++ is added to the suspension in the gas absorber, after
the calcium carbonate primary nucleation stage and before
completion of the carbonation step, the complexing agent being e.g.
citric acid, ethylenediamine tetraacetic acid (EDTA),
aminotriacetic acid, aminodiacetic acid or a hydroxy polycarboxylic
acid. Optionally, long-chain fatty acids or their salts can be
added, preferably, after the final carbonation stage.
[0017] 7. U.S. Pat. No. 4,157,379 (J. Arika et al.) describes the
production of a chain-structured precipitated calcium carbonate by
the carbonation of calcium hydroxide suspended in water in the
presence of chelating agents, such as aliphatic carboxylic acids,
and water-soluble metal salts.
[0018] 8. U.S. Pat. No. 4,244,933 (H. Shibazaki et al.) describes a
multi-stage production process for producing a particulate
precipitated aragonite, using aqueous calcium hydroxide slurry and
carbon dioxide gas or a carbon dioxide containing gas, in the
presence of phosphoric acids and water-soluble salts thereof.
[0019] 9. U.S. Pat. No. 4,420,341(T. H. Ferrigno) describes
inorganic fillers (including calcium carbonate) surface modified
with carboxylic acids, antioxidants and high-boiling non-reactive
liquid agents.
[0020] 10. JP Patent Publication No. 63260815 (H. Shibata et al.)
describes the production of a particulate precipitated aragonite,
by reacting carbon dioxide gas with an aqueous calcium hydroxide
slurry in presence of phosphoric acid, a phosphoric acid compound,
a barium compound and a strontium compound.
[0021] 11. JP Patent No. 1261225 (H. Shibata et al.) describes
reacting carbon dioxide gas with an aqueous calcium hydroxide
slurry, in order to produce a particulate precipitated aragonite,
which is stated to have improved properties compared with
particulate precipitated calcite.
[0022] 12. U.S. Pat. No. 4,824,654 (Y. Ota et al.) describes a
process for producing precipitated needle-shaped (5-100 .mu.m)
particulate precipitated aragonite, in which a relatively dilute
aqueous calcium hydroxide solution (0.04-0.17 wt. %) and carbon
dioxide gas or a carbon dioxide-containing gas are reacted together
at a temperature of not less than 60.degree. C., in a continuous or
semi-continuous (intermittent) manner.
[0023] 13. U.S. Pat. No. 5,043,017 (J. D. Passaratti) describes a
process for producing acid-stabilized precipitated calcium
carbonate particles.
[0024] 14. U.S. Pat. No. 5,164,172 (H. Katayama et al.) describes a
process for producing a particulate precipitated aragonite, in
which a mixture of aqueous calcium hydroxide slurry, aragonite
calcium carbonate particles and a water-soluble phosphoric acid
compound are premixed prior to the addition of carbon dioxide
gas.
[0025] 15. U.S. Pat. No. 5,342,600 (I. S. Bleakley et al.) describe
a process of producing particulate precipitated calcium carbonate,
in which aqueous calcium hydroxide slurries of varying
concentrations are reacted with carbon dioxide-containing gas under
a controlled mixing speed. It is recommended therein to prepare the
aqueous calcium hydroxide suspension under high shear mixing and
subsequently to lower the energy and shear agitation in the
reaction mixture in which the precipitated calcium carbonate
particles are formed.
[0026] 16. U.S. Pat. No. 5,376,343 (P. M. Fouche) describes a
process for producing various forms of particulate PCC. In the case
of aragonite, a mixture of quite dilute aqueous calcium hydroxide
solution and a water-soluble source of specific anions (e.g.
ammonium nitrate) are premixed prior to addition of CO.sub.2
gas.
[0027] 17. U.S. Pat. No. 5,380,361 (R. A. Gill) describes inter
alia calcium carbonate particles coated with C12-C22 fatty acids
salts.
[0028] 18. U.S. Pat. No. 5,593,489 (K -T. Wu) describes a process
for producing acid-resistant calcium carbonate particles for making
neutral to weakly acid paper.
[0029] 19. U.S. Pat. No. 5,833,747 (I. S. Bleakley et al.)
describes a process for producing a particulate precipitated
aragonite, in which an aqueous calcium hydroxide slurry (148 g
Ca(OH).sub.2 per liter of suspension) is reacted with carbon
dioxide gas at an exceptionally slow rate of 0.0026 moles per
minute per mole of Ca(OH).sub.2 in a batch operation.
[0030] 20. WO 9852870 (B. Jackson et al.) describes a multi-stage
commercial process for producing a particulate precipitated
aragonite, using coarse-grained precipitated aragonite particles as
a seeding material. Though the process is claimed to be
industrially applicable, it is quite slow and thus of very limited
economical value.
[0031] 21. U.S. Pat. No. 5,846,500 (J. W. Bunger et al.) describes
a process for producing a particulate precipitated aragonite, in
which an aqueous calcium hydroxide solution is reacted with
CO.sub.2 gas in a plug-flow reaction system.
[0032] 22. U.S. Pat. No. 5,846,382 (A. von Raven) describes a
process for producing inorganic fillers and pigments, including
particulate calcium carbonate, of improved whiteness, brightness
and chromaticity.
[0033] 23. U.S. Pat. No. 5,861,209 (W. J. Haskins et al.) describes
a process for producing a particulate precipitated aragonite, for
printing, in which an aqueous calcium hydroxide slurry is first
mixed with precipitated aragonite particles for seeding and then it
is reacted quite slowly with carbon dioxide gas in a batch
operation. After dewatering the product to a cake containing about
70% solids, it is mixed with a typical dispersant, e.g. sodium
polyacrylate, and it is further dispersed. This patent discloses
the use of mixtures of a particulate precipitated aragonite, with
TiO.sub.2 and other inorganic fillers, pigments and flame
retardants.
[0034] 24. U.S. Pat. No. 5,939,036 (A. L. Porter et al.) describes
a process for producing a particulate precipitated aragonite, in
which aqueous mixtures of organic compounds and acids (e.g.
ethanolamine and HCl) are used to dissolve impure CaO and to form a
calcium hydroxide mixture, which is then reacted with carbon
dioxide gas to yield various forms of PCC, depending on the
temperature. Controlling the temperature of the carbonation at
about 95.degree. C. leads to aragonite.
[0035] 25. U.S. Pat. No. 6,022,517 and U.S. Pat. No. 6,071,336 (G.
H. Fairchild et al.) describe a process for producing mixtures of
precipitated acicular calcite and acicular aragonite particles in
the ratio of 75:25 to 25:75, by reacting carbon dioxide gas or a
carbon dioxide containing gas and aqueous calcium hydroxide in the
presence of a water soluble aluminum compound, by controlling the
specific conductivity in a range >4.0 and up to about 7.0,
milliSiemens/cm, at a reaction temperature of from 25-60.degree.
C.
[0036] 26. Pigment Handbook (Vol. I-III; Edited by T. C. Patton;
John Wiley & Sons, New York (1973)) describes the properties,
the production processes and various uses of aragonite calcium
carbonate pigment (c.f. Vol. 1; Pages 119-128), as well as those of
other pigments that compete in the same market like titanium
dioxide, kaolin, GCC, etc. The discussion concerning the influence
of the film porosity on the hiding power or opacity of a coating
film (c.f. Vol. III; Pages 203-217 and especially on Page 212) may
help in understanding some aspects of the present invention.
[0037] The entire contents of the above-cited literature, including
patents and publications, are incorporated herein by reference. It
is apparent from the state of the art that known processes for the
industrial production of substantially pure particulate
precipitated aragonite (>90 parts aragonite: <10 parts
calcite), by reacting aqueous calcium hydroxide slurries with
carbon dioxide gas or a carbon dioxide containing gas, exhibit
serious drawbacks that affect the quality and cost of the final
product, as follows:
[0038] A. Some of the processes for producing particulate
precipitated aragonite are conducted in aqueous solutions of
extremely low concentrations of calcium hydroxide. In some cases it
is specified that clear solutions, which contain less than 1 wt. %
calcium hydroxide, should be used.
[0039] B. In those processes for producing particulate precipitated
aragonite, which allow use of aqueous calcium hydroxide slurries,
the production rates are very slow and difficult to control.
[0040] C. To increase somewhat the rates of production in processes
of A and B, the prior art recommends seeding with previously
produced aragonite particles. However, this complicates the
production processes, especially those operated continuously, and
which are otherwise of great commercial potential.
[0041] D. Dewatering of particulate precipitated calcium carbonate,
and particularly particulate precipitated aragonite, obtained
according to the known art gives rise to relatively wet filter
cakes of which the water content is not below 30% and which may
thus require a very expensive subsequent drying step.
[0042] E. Particulate precipitated calcium carbonate, and
particularly particulate precipitated aragonite, of the prior art
requires extensive grinding operations to optimize its particle
size distribution (PSD) in order to meet the effective PSD in the
range between 0.21 .mu.m and 0.4 .mu.m, mentioned above. Moreover,
the grinding operation tends to contaminate the product, due to
attrition of the grinding media, unless very expensive materials of
construction are used for this purpose.
[0043] F. The known particulate precipitated calcium carbonate, and
particularly particulate precipitated aragonite, is of limited
whiteness, mainly due to the high residual impurities in the
CaCO.sub.3/CaO feedstock, which it is quite difficult to remove
thoroughly, on the industrial scale. Also, the low whiteness of the
product is a limiting factor in choosing the suitable sources of
its raw materials (CaCO.sub.3/CaO).
[0044] G. Particulate precipitated calcium carbonate, and
particularly particulate precipitated aragonite, frequently
requires one or more post-manufacturing treatment step(s), in order
to ensure that the particle surface is hydrophobic, by coating with
suitable long-chain carboxylic acids and esters and/or other
materials such as silicon greases, e.g. for efficient dispersal in
hydrophobic media such as rubber or plastics, and/or to ensure
resistance to acidic environments for use e.g. in the paper
industry and in the coating industry.
[0045] H. Efforts in the prior art to increase the effective
refractive index of particulate precipitated calcium carbonate, and
particularly of particulate precipitated aragonite, has not so far
succeeded in making this material a serious competitor to titanium
dioxide.
[0046] Accordingly, it is an object of the present invention to
overcome all or most of the problems encountered in the prior art,
as mentioned in paragraphs A-H, above.
[0047] It is an object of the present invention to provide
particulate precipitated calcium carbonate, and particularly
particulate precipitated aragonite, as stated in the preceding
paragraphs, by a process which is more efficient and less
expensive, than those available in the prior art.
[0048] It is yet a further object of the present invention to
effect such a more efficient and less expensive process as stated
in the preceding paragraph, using sources of CaCO.sub.3/CaO, which
are presently not suitable raw materials for use as e.g. fillers,
extenders and pigments, and for other applications, in all of which
uses require pigments of high optical properties and high
performance, whereby production costs are lowered.
[0049] Still another object of the present invention is to provide
a particulate precipitated calcium carbonate, and particularly
particulate precipitated aragonite, of a superior quality as stated
above, in which the produced particles are treated in situ with a
hydrophobic agent in order to avoid an extra downstream step and to
fine-tune their properties to meet the requirements of consumer
products like detergents and cleaning products, especially in the
powder forms, toothpastes, sunscreen lotions, pharmaceuticals,
agrochemicals, rubber, plastics, coatings (especially durable
paints in acidic environments), inks and paper industries
(especially paper production in weakly acidic media), an effect of
said in situ treatment being lowering of production costs.
[0050] Still another object of the present invention is to carry
out the above-stated more efficient and less expensive process, in
a manner which gives rise to filter cakes which are relatively dry,
e.g. with no more than about 20 wt. % water, right after the
dewatering stage, and thus additionally lowering production
costs.
[0051] Another object of the invention is to effect the
above-stated more efficient and less expensive process, in such a
manner that the particulate precipitated calcium carbonate, and
particularly particulate precipitated aragonite, does not require,
for most applications, any downstream grinding operations, except
for the regular mixing systems which are in any event usually
installed in the industries mentioned above, and thus additionally
lowering production costs.
[0052] Most of all, it is a particular object of the present
invention to provide a particulate precipitated calcium carbonate,
and particularly a particulate precipitated aragonite, of a better
quality than that obtained in the prior art, and especially having
a higher whiteness, a lower specific gravity and a higher effective
refractive index.
[0053] Other objects of the invention will appear from the
description, which follows.
SUMMARY OF THE INVENTION
[0054] It has been surprisingly found in accordance with the
present invention particulate precipitated calcium carbonate, and
particularly particulate precipitated aragonite calcium carbonate,
which is characterized by its high whiteness, high effective
refractive index, and especially by its low specific gravity (below
2.5 g/cm.sup.3), can be produced, and that the above-mentioned
objects of the present invention can be achieved, by a process
which comprises reacting an aqueous calcium hydroxide slurry with a
gas selected from carbon dioxide and a gas containing it, wherein
the parameters of the process, including e.g. at least one
preselected active agent, modes of operation, operating
concentrations of raw materials, operating temperatures, operating
pH range and high shear mixing speeds, are strictly controlled such
that the desired product is obtained. In a particular embodiment,
flotation of the product occurs during such process.
[0055] The process of the invention for producing a particulate
precipitated aragonite in accordance with the invention, is
preferably further characterized by at least one, and preferably
all, of the following features: (a) the active agent comprises at
least one member selected from the group consisting of carboxylic
acids of formula RCOOH, where the organic group R (which may be
e.g. a saturated or unsaturated aliphatic group, such as a
hydrocarbon group which may be substituted or unsubstituted)
contains 8-20 carbon atoms, and their carboxylate salts, esters,
anhydrides, acyl halides, and their ketenes (b) more specifically,
the active agent comprises at least one member selected from the
group consisting of carboxylic acids of formula
C.sub.nH.sub.2n+1COOH, where n is 8-16, and their carboxylate
salts, esters, anhydrides, acyl halides, and their ketenes; (c)
also, the active agent comprises at least one member selected from
the group consisting of carboxylic acids of formula
C.sub.nH.sub.2n-1COOH, where n is 8-16, and their carboxylate
salts, esters, anhydrides, acyl halides, and their ketenes; (d)
more specifically, the active agent comprises at least one member
selected from the group consisting of carboxylic acids of formula
CH.sub.3(CH.sub.2).sub.nCOOH, where n is 7-16, and their
carboxylate salts, esters, anhydrides, acyl halides, and their
ketenes of formula CH.sub.3(CH.sub.2).sub.n-1C.dbd.C.dbd.O; (e) the
concentration of the active agent is within the range of between
0.2 wt. % and 10 wt. %, calculated as RCOOH and based on the weight
of calcium carbonate; (f) the slurry contains calcium hydroxide in
a concentration within the range of from 3 to 30 wt. %, more
preferably 4 to 20 wt. %; (g) the product is produced at a pH
between 8 and 11, preferably between 9 and 10; (h) the process is
effected at a temperature in the range between 60.degree. C.,
desirably between 80.degree. C., and the boiling temperature of the
reaction mixture; (i) the process is effected either in a
semi-continuous (intermittent) mode of operation, or more
preferably in a continuous manner; (j) the process is effected
under high shear mixing e.g. with a mixer comprising a rotor/stator
or a rotor only, the mixer peripheral (tip) speed being preferably
at least 5 m/sec. In a particular embodiment, this process is
effected in a continuous mode of operation under high shear mixing
with a mixer comprising a rotor/stator or a rotor only, at a
temperature in the range between 90.degree. C. and the boiling
temperature of the reaction mixture, the active agent--preferably
present in an amount in the range between 0.2% and 10 wt. %,
calculated on the weight of calcium carbonate--being selected from
the carboxylic acids and their calcium salts, and the slurry
contains calcium hydroxide in a concentration within the range of
from 5 to 15 wt. %, the active agent being desirably premixed with
the calcium hydroxide slurry prior to reaction with carbon
dioxide.
[0056] The present invention also provides as a novel chemical
substance--which is of course obtainable in accordance with the
present process, a particulate precipitated aragonite, which has a
specific gravity of <2.5 g/cm.sup.3 (preferably <2.3
g/cm.sup.3, more preferably <2.0 g/cm.sup.3, even more
preferably <1.5 g/cm.sup.3) after drying at 120.degree. C., and
a specific gravity <2.5 g/cm.sup.3 (preferably <2.3
g/cm.sup.3, even more preferably <2.1 g/cm.sup.3) after ignition
for eight hours at 500.degree. C. In a particular embodiment, the
product has a specific gravity of <2.3 g/cm.sup.3 after drying
at 120.degree. C., and a specific gravity <2.3 g/cm.sup.3 after
ignition for eight hours at 500.degree. C. and in another
particular embodiment, the product has a specific gravity of
<2.1 g/cm.sup.3 after drying at 120.degree. C., and a specific
gravity <2.1 g/cm.sup.3 after ignition for eight hours at
500.degree. C.
[0057] A typical such product may be further characterized by at
least one of the following features: it contains said carboxylic
acid calcium salt(s) in an amount between 0.2 and 10 wt. %,
calculated as CH.sub.3(CH.sub.2).sub.nCOOH and based on the weight
of calcium carbonate; it has a specific gravity <2.2 g/cm.sup.3,
preferably <2.0 g/cm.sup.3, more preferably <1.8 g/cm.sup.3,
and even more preferably <1.5 g/cm.sup.3; a product previously
dried at 120.degree. C. for 12 hours has a loss on drying at
300.degree. C. for 8 hours of about <10% wt. %, based on the
weight of calcium carbonate; a product previously dried at
120.degree. C. for 12 hours has a loss on ignition at 500.degree.
C. for 8 hours of about <10% wt. %, based on the weight of
calcium carbonate; after drying at 120.degree. C. for 12 hours,
and/or drying for 8 hours at 300.degree. C., and/or firing for 8
hours at 500.degree. C., it still has a specific gravity <2.5
g/cm.sup.3; after drying at 120.degree. C. for 12 hours, and/or
drying for 8 hours at 300.degree. C., and/or firing for 8 hours at
500.degree. C., it has also a preferable typical loose bulk density
well below 0.5 g/cm.sup.3.
[0058] In another aspect, the present invention provides a
particulate precipitated aragonite which contains at least one
calcium salt of carboxylic acids selected from those of the general
formula: C.sub.nH.sub.2n+1COOH, where n=8-17, in an amount between
0.2 and 10 wt. %, calculated as C.sub.nH.sub.2n+1COOH and based on
the weight of calcium carbonate, and which has (A) a specific
gravity <2.5 g/cm.sup.3 after drying for 12 hours at 120.degree.
C., and/or (B) a specific gravity <2.5 g/cm.sup.3 after ignition
for eight hours at 500.degree. C. of the product dried, preferably,
in (A).
[0059] In still another aspect, the present invention provides a
particulate precipitated aragonite which contains at least one
calcium salt of carboxylic acids selected from those of the general
formula: CH.sub.3(CH.sub.2).sub.nCOOH, where n=7-16, in an amount
between 0.2 and 10 wt. %, calculated as
CH.sub.3(CH.sub.2).sub.nCOOH and based on the weight of calcium
carbonate, and which has (A) a specific gravity <2.5 g/cm.sup.3
after drying for 12 hours at 120.degree. C., and/or (B) a specific
gravity <2.5 g/cm.sup.3 after ignition for eight hours at
500.degree. C. of the product dried, preferably, in (A).
[0060] In still another aspect, the present invention provides a
particulate precipitated aragonite which contains at least one
calcium salt of carboxylic acids selected from nonanoic acid,
decanoic acid, undecanoic acid and undecylenic acid in an amount
between 0.2 and 10 wt. %, calculated as
CH.sub.3(CH.sub.2).sub.nCOOH and based on the weight of calcium
carbonate, and which has (A) a specific gravity <2.5 g/cm.sup.3
after drying for 12 hours at 120.degree. C., and/or (B) a specific
gravity <2.5 g/cm.sup.3 after ignition for eight hours at
500.degree. C. of the product dried, preferably, in (A).
[0061] The product of the present invention can be used as a
builder, an anticaking material, an encapsulant, an adsorbent, a
thickening material, a sunscreen, a filler, an extender and
particularly as a pigment for the detergent, pharmaceuticals,
agrochemicals, plastics, adhesives, printing, coating (paint),
paper, rubber, filtration, toiletries and many other industries.
Thus, in accordance with further aspects of the present invention,
there are provided a coating composition, a paper composition, a
plastics composition, a rubber composition, an adsorbent
composition, a powder detergent composition, a pharmaceutical
composition, an agrochemical composition, a flavor composition, a
fragrance composition, a food composition, a feed composition, and
a sunscreen composition, each of which comprises a particulate
precipitated aragonite in accordance with the invention. For this
purpose, such compositions may comprise, for example, substantially
dry particulate precipitated aragonite, or particulate precipitated
aragonite in aqueous dispersion.
[0062] The PCC of the present invention can be used in most of the
(consumer) products that the prior art particulate calcium
carbonate is being used (and quite probably in all of them).
However, the PCC of the present invention will manifest its
advantages and unique properties when these (consumer) products are
to be produced and/or be used under conditions that exploit its
porous nature as an adsorbent for liquids (e.g. in powders or
detergent powders, in pharmaceuticals, in agrochemicals and in
various household products like food and feed formulations. Also,
as an encapsulating agent for flavors and fragrances,
pharmaceuticals and agrochemicals), and/or an anticaking agent
(e.g. in powders or detergent powders, in pharmaceuticals,
agrochemicals, food, and feed formulations), as a "light" component
to reduce the bulk density of products (e.g. when it is used as a
filler and/or a builder in powders or detergent powders), as a
thickening material (e.g. in glues, sealants, adhesives, coatings
(paints), and in paper), as filler, as an extender and,
particularly, as a pigment (e.g. in sunscreen formulations,
plastics, adhesives, printing (inks), coatings (paints), paper
(especially formulations for coating paper, and particularly for
high gloss paper products), rubber, filtration, and many
others).
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] FIG. 1 shows a schematic flow sheet for production of
particulate precipitated calcium carbonate according to the prior
art.
[0064] FIG. 2 shows a schematic flow sheet for production of a
particulate precipitated aragonite, in accordance with an
embodiment of the present invention.
[0065] FIG. 3 shows in schematic vertical section, a
reactor/flotation cell for producing a particulate precipitated
aragonite, in accordance with an embodiment of the present
invention.
[0066] FIG. 4 shows a SEM picture of a substantially pure
particulate precipitated aragonite, in accordance with an
embodiment of the present invention.
[0067] FIG. 5 shows an XRD spectrum of a substantially pure
particulate precipitated aragonite, in accordance with an
embodiment of the present invention.
[0068] FIG. 6 shows a SEM picture of, ARP-76, a substantially pure
particulate precipitated aragonite, in accordance with an
embodiment of the present invention.
[0069] FIG. 7 shows an XRD spectrum of, ARP-76, a substantially
pure particulate precipitated aragonite, in accordance with an
embodiment of the present invention.
[0070] FIG. 8 shows a SEM picture of, ARP-70, a mixture of
.about.50% particulate precipitated aragonite and .about.50%
particulate precipitated calcite, in accordance with an embodiment
of the present invention.
[0071] FIG. 9 shows an XRD spectrum of, ARP-70, a mixture of
.about.50% particulate precipitated aragonite and .about.50%
particulate precipitated calcite, in accordance with an embodiment
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0072] In the process of the present invention, a slurry of calcium
hydroxide in water and carbon dioxide gas or a carbon dioxide
containing gas is reacted together in the presence of the active
agent under stringent process conditions, to generate a particulate
precipitated aragonite having unique properties.
[0073] The product of the present invention is characterized by its
low production cost and by its unique physical properties (high
whiteness, high effective refractive index and low specific gravity
(<2.5 g/cm3)) and by its excellent chemical properties
(hydrophobicity and resistance to weak acids), which make it
particularly suitable as an adsorbent for liquids, an anticaking
material, a thickening material, a builder, a filler, an extender
and most of all as a pigment for the printing, coating (paint),
paper, rubber, plastics, filtration, adhesives, sealants,
pharmaceuticals, agrochemicals, food, feed, detergents and many
other industries.
[0074] As stated above, FIG. 1 shows a flow sheet for production of
particulate precipitated calcium carbonate according to the prior
art. By contrast, in order to define the most suitable conditions
to operate the carbonation stage of the present invention, a
detailed description of parameters for the present process is given
below. These also include some details of how to operate the
upstream and downstream stages of the carbonation stage, as these
may affect the final outcome (c.f. FIGS. 2 and 3).
[0075] In FIG. 1, which is a schematic representation of a prior
art procedure for making a precipitated calcium carbonate,
quicklime (CaO) and water, which react together giving slaked lime,
are fed to reactor 20 via respective conduits 1 and 2, and optional
additives such as aragonite calcium carbonate particles for
seeding, phosphoric acids and salts, aluminum salts, oxides and
hydroxide (other than CaO/Ca(OH).sub.2), chelating agents,
dispersants, and surface active agents, may also be added at this
stage via conduit 3. The initial product "milk of lime" (calcium
hydroxide) is fed via filter or hydrocyclone 4 (large solid
particles being removed at 12) into carbonator 22, to which there
is also fed gaseous carbon dioxide (or a gas containing it) via
conduit 5 and the aforementioned optional additives via conduit 6.
The reaction product including any contaminants exits carbonator 22
as an underflow via conduit 7 and/or an overflow via conduit 8, to
further operations (at site 24) such as dewatering, grinding and
coating; for such further operations there may be added optionally
via conduit 9, e.g. dispersants, surface active agents, greases,
silicon greases, long-chain carboxylic acids and their salts and
esters, organic and inorganic pigments, powder metals, coal, carbon
black or activated carbon, and/or dyeing agents. The filtrate and
water vapors exit the system via conduit(s) 10, while the final
product (which may be wet or dry and optionally post-treated) exits
via conduit 11.
[0076] In FIG. 2, which is a schematic representation of a
procedure for making a particulate precipitated aragonite in
accordance with the present invention, quicklime (CaO) and water
which react together giving slaked lime are fed to reactor 30 via
respective conduits 1 and 2, and the present active agent (and
optionally also additives such as phosphoric acids and salts,
chelating agents, dispersants, and surface active agents) may be
added at this stage via conduit 13. The initial product "milk of
lime" (calcium hydroxide) together with active agent if added to 30
(and optional additives) is fed via filter or hydrocyclone 14
(large solid particles being removed at 12) into carbonator 32, to
which there is also fed gaseous carbon dioxide (or a gas containing
it) via conduit 5 and the active agent (and possibly the
aforementioned optional additives) via conduit 16. It will be
appreciated that the active agent may be added either to reactor 30
or to carbonator 32, or to both. Contaminants and liquid exit
carbonator 32 as an underflow via conduit 7, whereas--owing to the
fact that an embodiment of the present process includes
simultaneous flotation--the desired product exits as an overflow
via conduit 18, to further operations (at site 34) such as
dewatering, grinding and coating; for such further operations there
may be added optionally via conduit 19, e.g. dispersants, surface
active agents, greases, silicon greases, long-chain carboxylic
acids and their salts (including if desired those within the
definition of the present active agents) and esters, organic and
inorganic pigments, powder metals, coal, carbon black or activated
carbon, and/or dyeing agents. The filtrate and water vapors exit
the system via conduit(s) 10, while the final product (which may be
wet or dry and optionally post-treated) exits via conduit 11.
[0077] Slaking of Quicklime
[0078] Though this operation is well known in the prior art, it is
worthwhile to choose a preferred mode of operation, which is best,
adapted to the process of the present invention. Thus, fresh slaked
lime is preferably prepared in a continuous mode of operation,
which enables operation of the downstream carbonation stage using
low inventories and exploiting to its maximum the energy that is
liberated in the reaction between the water and the CaO, before
this precious energy is lost to the surroundings. The present
invention desirably makes use of this energy to effect the step of
carbonation of the aqueous calcium hydroxide slurry at relatively
high temperatures, more preferably without cooling or heating, or
in other words, without adding or subtracting energy, and thus
utilizing only the energy liberated by the carbonation reaction
together with the energy produced by a powerful mixing system. Once
again, use of fresh and still warm milk of lime is preferably an
important factor in the success of the carbonation stage and this
is more preferably effected, as mentioned above, in a continuous
mode of operation, the temperature of the slaked lime being
preferably maintained at about the temperature of the carbonation
stage. However, in the alternative, a batch mode of operation may
also be used for process of the present invention or the CaO can be
introduced directly into the carbonator, as is demonstrated in the
prior art.
[0079] Mixing of Quicklime
[0080] In some prior art patents it is recommended to use high
shear mixers to slake the CaO with water. The process the present
invention is quite tolerant to the kind of mixing, as long as the
slaking reaction is complete and the maximum energy is liberated.
Mixers that comprise rotor/stator mixing systems and mixers that
comprise rotors only are suitable.
[0081] Purification of Slaked Lime Prior to Carbonation
[0082] There are numerous methods of purifying slaked lime before
its utilization in the carbonation stage. Filtration by filters to
remove large insoluble particles and/or separation of these
particles by hydrocyclones are two efficient methods for this
purpose. Usually, particles of greater diameter than 40 .mu.m (up
to 70 .mu.m) are removed prior to the carbonation stage and the
coarse particles can then be discarded or used in the construction
industry, for example. The fine slurry is then ready for
carbonation in the subsequent downstream stage. Naturally, feeding
CaO directly into the carbonator, as mentioned above, does not
allow to make use of such purification methods.
[0083] Sources of CaCO.sub.3/CaO:
[0084] Many sources of CaCO.sub.3/CaO are too contaminated to be
used to produce, by known methods, a particulate precipitated
aragonite for the printing, (inks), coating (paint), paper, rubber,
plastics, filtration, adhesives and sealants, pharmaceuticals,
household and personal care and other industries, and their main
use is, as very inexpensive materials, in the construction
industry. On the other hand, the present invention may allow
utilizing many of these "impure" CaCO.sub.3/CaO sources and turning
them into a particulate precipitated aragonite, of filler, extender
and pigment grades. The present invention, as is manifested in the
carbonation stage, is superior over any state of the art technology
in salvaging CaCO.sub.3 mines and turning them to profitable use,
without changing greatly the state of the art methods for preparing
the slaked lime.
[0085] Use of Additives
[0086] The state of the art technology for slaking quicklime
includes adding a variety of additives into the milk of lime prior
to the carbonation stage. According to the present invention, one
of the preferred modes of operation is to add the active agent into
the milk of lime prior to the carbonation reaction. Those skilled
in the art of producing precipitated calcium carbonate must
carefully check that the other additives, if any are present in the
milk of lime, do not interfere with the ability of the active agent
to enhance formation of the particulate precipitated aragonite and
to cause its flotation in the carbonation reactor. For instance,
the use of 1 wt. % (based on the calcium carbonate) of phthalic
acid or trimelitic acid with about 1 wt. % (based on the calcium
carbonate) one of the most potent active agents of the present
invention, n-decanoic acid, cause the formation of mostly the
particulate calcite polymorph in the carbonation stage, under the
specific conditions that are described in the experimental section,
instead of obtaining mostly the aragonite polymorph. In other
cases, the additives may cause the formation of mixtures of various
concentrations of particulate precipitated calcite and aragonite,
instead of quite pure particulate precipitated aragonite calcium
carbonate.
[0087] The Reaction/Carbonation Stage
[0088] This operation is well known in the prior art. However, as
this stage is the essence of the present invention, it is
worthwhile to choose the mode of operation that suits it best. For
example, although the use of aragonite particles for seeding is a
recommended procedure in the prior art, it seems at the present
time that this practice is unlikely to have any particular utility
in the process of the present invention, since use of the active
agent enables all desired objectives to be achieved.
[0089] As the most important functions of the active agent in the
present invention are to catalyze the production of particulate
precipitated aragonite, of improved physical and chemical
properties and to cause its flotation in the carbonation reactor,
all necessary measures should be taken in order to maximize these
functions.
[0090] The Nature of the Active Agent and Its Origin
[0091] While the scope of the present invention is not to be
regarded as limited by any theory, nevertheless, it may be likely
that the calcium salts of the carboxylic acids of the general
formula RCOOH (of which more specific chemical structures have been
mentioned already in greater details hereinbefore) operate in
practice as the functioning active agent in the present process. It
should not be ruled out, however, that for example, other
derivatives of such acids within the scope of the invention may
participate in similar activity.
[0092] The above-mentioned calcium salts of the relevant acids may
be used as raw materials in the present invention. However, other
compounds, which undergo chemical transformations to form the
active agent under the process conditions, also serve this purpose
as raw materials in the production of the desired particulate
precipitated aragonite.
[0093] In a particular embodiment of the invention, which will
serve here as an example, the active agent is selected from
carboxylic acids of the general formula:
CH.sub.3(CH.sub.2).sub.nCOOH, where n=7-16, and including mixtures
thereof. All these acids can be quite easily introduced into any of
the production facilities. Pumping of these acids when their
temperature is held above their melting points (e.g. >60.degree.
C.) seems to be a very useful method to deliver the acids into the
suitable production units. Under such conditions, these thermally
stable acids are immediately converted into their respective
calcium salts when they are mixed with the hot aqueous calcium
hydroxide slurry or with the hot carbonation mixture at pH>7. As
water is the only by-product of the reaction between the calcium
hydroxide and the respective carboxylic acids, the use of these
acids, as raw materials in the process of the present invention,
seems to have no harmful side effect.
[0094] The respective acid anhydrides of the general formula:
(CH.sub.3(CH.sub.2).sub.nCO).sub.2O, including mixtures thereof,
where n=7-16, are as good a source for the active agent, as the
corresponding acids. However, the anhydrides are much less safe to
handle and they are much more expensive than the respective
acids.
[0095] The carboxylate salts of the acids of the general formula:
CH.sub.3(CH.sub.2).sub.nCOOH, including mixtures thereof, where
n=7-16, can serve as raw materials in the process of the present
invention, e.g. where the cations are selected from Na.sup.+,
K.sup.+, NH.sub.4.sup.+, Li.sup.+, Mg.sup.++ and especially
Ca.sup.++, but, generally, the use of these salts does not appear
to have any advantage over the free acids. On the contrary, the
salts are usually more expensive, they are not as easy to handle on
an industrial scale as the respective acids and, except the
Ca.sup.++ salts, all the other salts add cations that, so far as is
presently known, are not required in the present process. The
Mg.sup.++ salts present a special case, as they leads to the
formation of hydromagnesite and thereby to a dramatic rise of the
surface area of the product, to its contamination and to a large
increase in the water content in the wet filter cake. Therefore, in
the process of the present invention only limited concentrations of
this cation are allowed, i.e. <1 wt. %, based on the calcium
hydroxide (this limitation is removed if it is desired to exploit
the process of the present invention to produce hydromagnesite or
mixtures of hydromagnesite and PCC of the present invention. On the
contrary, then Mg.sup.++ can also be introduced as other Mg salts
or, preferably, as MgO/Mg(OH).sub.2).
[0096] Esters of the following general formula:
CH.sub.3(CH.sub.2).sub.nCO- OR', where n=7-16 and R is an
esterification radical such as alkyl, e.g. CH.sub.3,
C.sub.2H.sub.5, C.sub.3H.sub.7, etc., are also suitable candidates
for the active agent in the present invention. However, in order
for these compounds to generate e.g. the corresponding calcium
salts, they have to undergo a basic hydrolysis, which may
preferably be done by premixing them in the hot and basic aqueous
calcium hydroxide slurry, in which they are hydrolyzed and thus
converted to the respective Ca.sup.++ salts. However, the use of
these esters in the process of the present invention appears to be
inferior to the use of the respective acids, for reasons, which
will be self-evident to the skilled person.
[0097] Chemically equivalent to the other preferred active agents
specifically mentioned above, are ketenes of the general formula:
CH.sub.3(CH.sub.2).sub.n-1C.dbd.C.dbd.O, wherein n=7-16, and
including mixtures thereof, behave in a similar manner and entail
similar drawbacks, as for the acid anhydrides, as mentioned
above.
[0098] Therefore, the acids of the general formula:
CH.sub.3(CH.sub.2).sub.nCOOH, wherein n=7-16, including mixtures
thereof, are the presently preferred source for the active agent to
be used in the process of the present invention. More specifically,
decanoic acid (wherein n=8) is presently one of the most potent and
preferred acids, as it leads to products of the present invention
of which the content of the aragonite isomorph is the highest,
under comparable conditions. Lauric acid (wherein n=10), myristic
acid ((wherein n=12) or even stearic acid (wherein n=16),
relatively abundant and less expensive raw materials, may be
preferred in some other cases, in which the maximum content of the
aragonite ismorph in the product is not critical or in cases in
which controlled concentrations of the calcite isomorph in the
product of the present invention may even be desirable.
[0099] It seems that the process of the present invention is quite
more general than it was thought originally. It was also found out
that undecylenic (or 10-undecenoic) acid
(CH.sub.2.dbd.CH(CH.sub.2).sub.8COOH) is also a very potent active
agent in the process of the present invention and others will,
probably, be sorted out in the future, using the conditions of the
novel process of the present invention and the simple and
straight-forward methodology of how to determine which compound
(carboxylic acid) is an active agent.
[0100] The Reactor/Carbonator/Flotation Cell
[0101] As already mentioned above, the carbonation stage can be
conducted in any well-stirred reactor according to the prior art.
However, due to the fact that the active agent is a unique material
that can enhance the formation of the particulate precipitated
aragonite of the present invention, in the reaction between aqueous
calcium hydroxide slurries and carbon dioxide gas or a carbon
dioxide containing gas, and also due to the fact that the active
agent can cause this product to float, the presently preferred
carbonators to be used in the process of the present invention are
flotation cells.
[0102] These cells may be operated somewhat differently from the
regular carbonators and the regular flotation cells, as both
functions (carbonation and flotation) take place in the same
production unit of the particulate precipitated aragonite, of the
present invention. The exact set-up of these flotation cells can
vary, as this will depend on, for example, the preferences of the
skilled designer, the precise nature of the desired product, the
quality of the aqueous calcium hydroxide slurries, etc. For
example, a flotation cell like that depicted in FIG. 3, containing
stator/rotor or rotor only S, is suitable for carrying out the
inventive process, and of which the main features are as
follows:
[0103] A. The stream of slaked lime (14) is preferably introduced
near the inner circumference of the reactor and above the stirring
blades.
[0104] B. The stream (5) of carbon dioxide gas or carbon dioxide
containing gas is preferably introduced through suitable spargers
at a point below the stirring blades, but still not too close to
the bottom of the cell, to avoid excessive mixing near the outlet
stream (7) of the contaminants and liquid.
[0105] C. The wet product and the gas are preferably discharged
from the top (18) of the cell. The customary skimmer for skimming
the product out of the flotation cell, and hydrocyclones for
efficient product/gas separation, are not shown in FIG. 3.
[0106] Mode of Operation in the Carbonation Step
[0107] Continuous reaction/carbonation of the aqueous calcium
hydroxide slurry with carbon dioxide gas or a carbon dioxide
containing gas is the most suitable mode of operation for the
present invention, especially because of the huge potential market
for the produced particulate precipitated calcium carbonate, and
particularly particulate precipitated aragonite.
[0108] Semi-continuous (intermittent) operations may also be used.
However, as may be understood from the desirability of operating
the process at its utmost efficiency, e.g. as a flotation
operation, it is unlikely that an intermittent mode of operation
can compete economically with the continuous mode of operation.
[0109] A "real" batch mode of operation, in which the milk of lime
and the active agent are mixed together and carbon dioxide gas or a
carbon dioxide containing gas is introduced to precipitate the
desired product until the reaction mixture turns neutral (at about
pH.about.7), appears not to be viable, probably because the active
agent is not efficient in catalyzing the formation of desired
product, at the high initial pH characteristic of the batch mode of
operation in this case, and/or because the active agent is adsorbed
onto the surface of the first formed crystals of particulate
precipitated calcium carbonate, where it is then "buried" under the
subsequent PCC. In such circumstances, the active agent is very
quickly depleted from the reaction zone, and the process of the
invention, as such, is likely to become inoperable.
[0110] Temperature of the Carbonation Step
[0111] The prior art teaches producing a particulate precipitated
aragonite, at a temperature range between 60.degree. C. and the
boiling temperature of the reaction mixture, at ambient pressure,
and the present process is preferably conducted similarly, because
lower temperatures favor the formation of calcite.
[0112] On the other hand, operating the process at a temperature as
close as possible to the boiling point of the reaction mixture is
presently particularly preferred, since these conditions give a
product of relatively lower water content in the wet filter cake,
which is a great advantage in many applications of the product.
[0113] While the present process may be operated at higher
temperatures and pressures (since the active agent is stable under
such conditions), this kind of operation is associated with serious
technological problems that may adversely affect the whole
economics of the process.
[0114] Concentration of Ca(OH).sub.2 slurry in the Carbonation
Step
[0115] The prior art method for producing a particulate
precipitated aragonite, may be classified into three principle
modes of operation. The first mode is operated at very low
concentrations of the calcium hydroxide in water, and in some cases
a clear solution of <1 wt. % calcium hydroxide is used. In the
second mode, there are used aqueous calcium hydroxide slurries and
active agents to induce the formation of the desired particulate
precipitated aragonite, albeit, at very low production rates. In
the third mode, particulate precipitated aragonite is used for
seeding, in order to improve production rates.
[0116] The present invention requires relatively high
concentrations in the aqueous calcium hydroxide slurries and the
production rates are very fast. Actually, at the range of very low
concentrations of <2 wt. % (based on the calcium hydroxide) the
present process may not "ignite" right away and under these
circumstances no desirable "porous" product of the present
invention is obtained, but rather, only precipitated calcite
calcium carbonate particles, or mixtures of mainly such
particles.
[0117] The present invention can use quite dense aqueous calcium
hydroxide slurries of up to about 30 wt. % calcium hydroxide, but
such dense slurries are very viscous and are very difficult to
handle. Therefore, the preferred range of concentrations of the
aqueous calcium hydroxide slurries, according to the present
invention, are in the range between 4% and 20 wt. %, and more
preferably between 5% and 15 wt. % calcium hydroxide. In these
ranges, the viscosity of the reaction mixture permits smooth
operation, while the energy maintained already in the feed of
aqueous calcium hydroxide slurry (as discussed above), plus the
energy liberated by the carbonation reaction, as well as the energy
liberated by the mixing system, are sufficient to maintain the
desired reaction temperature without any external heating or
cooling.
[0118] Concentration of Active Agent in the Carbonation Step
[0119] To simplify the calculations of how much active agent is
needed in the process and how much of it may be included in the
product of the present invention, we prefer to use the weights of
the respective acids, since the carboxylate moieties differ from
their respective acids by less than 1%. Therefore, in cases that
suitable ketenes, esters, carboxylate salts, acid anhydrides and/or
acyl halides are being used, the equivalent weight of the
respective acid should be calculated, unless otherwise indicated.
Moreover, as we are presently aware of differences among the
activities of the acids of the general formula e.g.
CH.sub.3(CH.sub.2).sub.nCOOH, wherein n=7-16, including mixtures
thereof, their individual contribution to the total weight of the
active agent should be calculated arithmetically, namely by adding
the weight of each individual acid, as if these are of the same
chemical entity. This concept is important for understanding this
invention and particularly the claims, unambiguously. The
difference between the molecular weights of the respective acids
(.about..+-.30%) is not a great problem, because a person skilled
in the art will in any event check carefully what is the exact
amount of the relevant carboxylic acids that is necessary to
operate the process in a manner, which is not sensitive to even
larger variations of the concentrations of the active agent,
namely, of >.+-.30 wt. %, based on CaCO.sub.3. Moreover, when
using decanoic acid as the presently preferred active agent, the
present invention will not even be subject to the above-mentioned
inaccuracy.
[0120] To determine the concentration range of the active agent in
the present invention, it is important to be aware of the various
functions of this agent in the production process and the effects
that it produces in the final product.
[0121] The prior art describes many additives that assist in
producing particulate precipitated aragonite, but none of these
additives is comparable to the present active agent, under the
selected process parameters, for the following two major
reasons:
[0122] 1. The active agent leads to a dramatic reduction of the
specific gravity of the particulate product and allows use of the
flotation method to separate the "light" particulate precipitated
aragonite, from the "heavy" contaminants (containing
aluminosilicates and heavy metal salts, carbonates and oxides).
These "heavy" particles sink down to the bottom of the
carbonator/flotation cell and are discharged from the production
unit without reaching the downstream filter, and
[0123] 2. The optical properties of the particulate precipitated
product are altered and its effective refractive index is increased
dramatically.
[0124] Thus, according to one of the preferred modes of operation,
the pure product of the present invention, on the flotation
embodiment, is being carried to the top of the
reactor/carbonator/flotation cell, by the small bubbles that adhere
to the tiny precipitated particles, and this relatively pure
product is discharged from the top of the carbonator/flotation cell
prior to any downstream operation. Thus, in this embodiment, the
present process entails an intrinsic, built-in, extra purification
operation, prior to the downstream dewatering operation, which is
not so common in the prior art.
[0125] This unique property of the active agent to cause the
flotation of the "light" particulate precipitated calcium
carbonate, is also a reason why this embodiment of the present
invention is superior over any of the prior art production
technologies in exploiting highly contaminated sources of
CaCO.sub.3/CaO, which have hitherto been unsuitable as raw
materials for production of a particulate precipitated calcium
carbonate, and particularly particulate precipitated aragonite, of
filler, extender and pigment quality grades. Such sources can now
be utilized successfully, using this novel technology of the
present invention.
[0126] Since the aqueous calcium hydroxide slurry is usually quite
contaminated and the impurities are liable to affect performance of
the active agent, the threshold (minimum) concentration of the
active agent will vary, but is within the competence of a skilled
person to determine, under any particular set of circumstances.
Moreover, the threshold concentration will also vary with the kind
of active carboxylic acids that will be used. In any case, it is
desirable to avoid this threshold concentration at the carbonation
stage, as this is a point of instability and would involve
unnecessary risk to the desired objective. When considering use of
a new feedstock of CaCO.sub.3/CaO, laboratory experiments will
reveal the minimum concentration of the active agent, which is
necessary to start the production of the desirable particulate
precipitated calcium carbonate, and particularly particulate
precipitated aragonite, without any faults (vis-a-vis the pertinent
CaCO.sub.3/CaO feedstock). This value is expected to be in most
cases above 0.2 wt. %, preferably within the range 0.4% to 3 wt. %,
based on the calcium carbonate.
[0127] It is very important to note that this threshold
concentration, discussed above, for catalyzing the production of
particulate precipitated aragonite, of the present invention
(.about.0.2% wt. %, based on CaCO.sub.3) is substantially above the
threshold concentration that is required to cause the flotation of
this product in aqueous solutions (.about.0.02% wt. %, based on
CaCO.sub.3) and that by operating in the concentration range merely
for a "proper" flotation process, nothing that is disclosed in the
present invention really happens. Actually, the optimal physical
and chemical properties of the particulate precipitated aragonite
calcium carbonate, of the present invention are attained at above
100 fold of this concentration (.about.2-3 wt. %, based on
CaCO.sub.3).
[0128] Other factors may indicate use of even higher concentrations
of the active agent in the production process of the present
invention. For instance, coating the surface of the particulate
precipitated aragonite, with a predetermined rather thick layer of
the active agent, in situ, in a carbonator/flotation cell, may
require quite high concentrations of this material, which may
exceed 5%, 10% and even 15 wt. %, based on CaCO.sub.3, in order to
produce good surface coated hydrophobic and acid resistant
particulate precipitated aragonite (e.g. for master batches).
Naturally, at such high active agent concentrations, the cost
component of the coating should then be compared to the alternative
possibilities of downstream coating, which are also available in
the prior art, as well as in the present invention (c.f. FIGS. 1
and 2, respectively). Another serious reason to avoid operating the
process at too low concentrations, is the fact that the chemical
and physical properties of the product, and especially its optical
properties and specific gravity, which are quite interdependent,
are dramatically affected by the concentration of the active
agent.
[0129] In between the upper limit and the threshold limit of the
concentration of the active agent in the process of the present
invention, the optimum concentration should also be determined by
one skilled in this art, either vis-a-vis the quality of the
CaCO.sub.3/CaO, or whenever the properties of the product are to be
changed. The active agent is not an expensive material, but still
it may throw an economical burden on the total cost of the final
product due to the fact that even quite pure particulate
precipitated aragonite is a relatively inexpensive material.
[0130] Intuitively, the concentration of 10 wt. %, based on the
calcium carbonate, seems to be an economical upper limit of the
active agent, while 0.2 wt. %, wt; based on the CaCO.sub.3, seems
to be its threshold (minimum) concentration.
[0131] Carbon Dioxide in the Carbonation Step
[0132] Use of carbon dioxide gas or a carbon dioxide containing gas
is well known in the prior art methods for producing precipitated
calcium carbonate particles. The process of the present invention
is similar in this respect to the prior art processes that operate
with substantially pure carbon dioxide gas as well as with mixtures
of carbon dioxide with up to about 92 v% inert gases (e.g. air). At
lower concentrations of the carbon dioxide in the feed gas (<8
wt. %), however, the efficiency of the process may be too low,
mainly, due to the cooling effect of the excessive gas.
[0133] In order to understand how to control the process of the
present invention, It is worthwhile to describe the major effects
that are observed at the two limits, namely, when using "rich" feed
gas of about 100% carbon dioxide on the one hand and using "lean"
feed gas of about 8 v % carbon dioxide on the other hand. It was
found that "rich" carbon dioxide gas feed leads to a PCC, of the
present invention, that gives rise to products of much higher gloss
than those that are produced from the PCC, of the present
invention, that are produced with a "lean" carbon dioxde feed under
similar production conditions. Namely, the gloss of the final
(consumer) products can easily be fine-tuned by just choosing the
right CO.sub.2/inert gas (air) ratio. This fact may be exploited,
especially, in using the product of the present invention in
formulations that are intended to be used e.g. in the coating
industry, which requires quite often low gloss products and in the
paper industry for coating paper and obtaining a desirable product
of high gloss.
[0134] Another phenomenon that is observed when using "lean" feed
gas is that it leads to a PCC, of the present invention, of lower
specific gravity and of higher hiding power, compared to a PCC, of
the present invention, that is produced with "rich" feed gas under
similar conditions. That, in turn, allows to include carboxylic
acids within the patent range, which otherwise could not meet the
constrains that were set up to determine which carboxylic acid is
within the borders of this invention and can be used as an active
agent to produce the product of the present invention. For
instance, under the conditions of the screening test (Example 1;
that is described hereinafter), Lauric acid could not be considered
active agents (its product was considered "Calcite" as its
crystallographic purity (aragonite/(aragonite+calcite)) was only
20%-25% and its specific gravity (in tall oil; after drying it at
120.degree. C. for twelve hours) was only 2.54 g/cm.sup.3. When
using a "lean" feed gas of 26% CO.sub.2 (by volume) the specific
gravity of the product decrease dramatically to 1.78 g/cm.sup.3.
Therefore, based on the too high specific gravity values that were
obtained for lauric acid, for palmitic acid and for stearic acid,
the myristic acid was not considered, at that time, to be a viable
candidate to catalyze the process of the present invention and,
thus, due to the time constrains, it was not tested and not
included in Table 1. The use of very "lean" gas feed allows to sort
out and use much more carboxylic acids (lauric acid, myristic acid
and even stearic acid) to serve as the active agents of the process
of the present invention, using the simple and straight forward
methods that were developed herein.
[0135] Additives in the Process:
[0136] The process of the present invention is quite
self-sufficient and requires only the active agent in suitable
quantities, as discussed above. The active agent can be introduced
preferably already premixed with the aqueous calcium hydroxide
slurry, or alternatively (or additionally) it can be introduced
directly into the carbonator. The active agent can also be used
downstream the carbonation stage, but that, naturally, has no
effect on the production of the particulate precipitated calcium
carbonate, and particularly the particulate precipitated aragonite,
in the carbonator.
[0137] It appears that the active agent has a surprising affinity
to the aragonite, which is unlikely to be adversely affected by the
presence of other additives. Consequently, additives like
phosphoric acids and water soluble salts thereof, can be used in
the present invention to modify the product properties by
increasing the aspect ratio of the thus formed acicular crystals;
polyacrylates, polyacrylamides and some short-chain carboxylic
acids can be used to modify the rheology of the product mixtures
and allow operation at higher calcium hydroxide concentrations and,
consequently, at higher throughputs; chelating agents can be used
to convert heavy metals into water-soluble species and once again
lead to super-pure products; metal powders and carbon black may be
introduced to obtain electrically conductive powders; soluble
aluminum salts may affect the shape of the calcite particles; and
magnesium salts or preferably MgO/Mg(OH).sub.2 may lead to
hydromagnesite. The prior art is infested with examples of
additives that are used to achieve improved particulate calcium
carbonate products. These additives and many others may,
potentially, be used in the product (process) of the present
invention.
[0138] It is nevertheless prudent to check carefully the effect
that well known additives of the prior art may have on the action
of the active agent, but in most cases the active agent will be the
dominant catalyst for the purpose of the present invention and,
therefore, such additives can usually be introduced at various
stages of the process, as is customary in the prior art (c.f. FIGS.
1 and 2).
[0139] The Mixing System
[0140] The need for high shear mixing in this process is well known
in the relevant art. The mixers may be a rotor/stator type or a
rotor only type. Usually, the latter one is used to produce
relatively larger product particles, while the rotor/stator type
leads to much higher attrition of the acicular crystals. On the
other hand, the rotor/stator type may allow a more efficient
dispersion of the gas bubbles, thereby improving the quality of the
product. The skilled operator will utilize the preferred mixing
system for working or enhancing the present process. The type of
mixers and the rotor speed should be optimized according to the
desired carbonation performance and the desired product
characteristics.
[0141] The lower limit of the rotor speed (hereinafter--"Tip Speed"
or "Peripheral Speed") is known in the prior art. A requirement of
a minimum tip speed of about 5 m/sec., to effect the formation of
desired product is not unusual in this art.
[0142] The upper limit of the rotor speed is determined by mixer
technology, cost of the specific mixer, the nature of the desired
product and the energy that is to be used. For instance, the higher
the rotor speed, the lower may be the reaction time (in a
continuous process, the reaction time is termed HUT (Hold Up Time)
and it is calculated as follows: HUT=V (the carbonator volume)/F
(the discharge rate of the product mixture out of the carbonator)).
This in turn may lead to small particles. A skilled person in this
art will know how to optimize the kind of mixers and rotor speeds
above the minimal peripheral speed, which is preferably 5
m/sec.
[0143] The Reaction Duration in the Reactor/Carbonator/Flotation
Cell
[0144] As already mentioned above, the carbonation step is
preferably conducted in a continuous mode of operation. In such a
case, "reaction duration" is hardly relevant, but we can calculate
the HUT (Hold Up Time), which lies essentially within the range
between 5 minutes and 180 minutes. At below the lower limit of the
HUT the yields may be too low and the PSD (Particle Size
Distribution) of the product may be too small, while at the upper
limit of the HUT the process throughput may be too low, the yields
may be excellent and the PSD may be too small, because of excessive
attrition of the product in the flotation cell. Once again, the
skilled person will be able to determine by experiment, suitable
working parameters vis-a-vis the desired product properties and to
optimize its quality and cost.
[0145] The Specific Gravity and the Loose Bulk Density (L.B.D.) of
the Particulate Precipitated Calcium Carbonate of the Present
Invention
[0146] The specific gravity of the PCC of the present invention is
measured for the following three major reasons: (a) to distinguish
the product of the present invention from the products of the prior
art; (b) to distinguish the process of the present invention from
the processes of the prior art; and (c) to control and optimize the
process and the product of the present invention. More
specifically, the specific gravity of the product of the present
invention, after igniting it at 500.degree. C. for eight hours, as
is described in Example 14 hereinafter, is the most decisive and
accurate criterion to determine that the relevant product has a
specific gravity of <2.5 g/cm.sup.3 (preferably <2.3
g/cm.sup.3 and more preferably <2.1 g/cm.sup.3) and, therefore,
it is indeed the product of the present invention. Therefore, also
the process that produced such a product is the process of the
present invention. The total elimination of the carboxylates from
the PCC particles after such a thermal treatment (N.D. i.e. <1
ppm; as measured by GC-MS analyses), circumvents the problem of
adhering gas bubbles onto the surface of the measured PCC samples,
and thus the specific gravity values for products of the prior art
(calcite, as well as, aragonite) are always >2.5 g/cm.sup.3
(even >2.65 g/cm.sup.3), while the products of the present
invention are characterized, by definition as such, by their
specific gravity values <2.5 g/cm.sup.3 (preferably <2.3
g/cm.sup.3 and even more preferably <2.1 g/cm.sup.3).
[0147] However, the PCC particles are usually being used in
practice without any such a drastic ignition treatment (at
500.degree. C. for 8 hours) and in most cases the PCC particles are
even not being dried, but rather dispersed in water, after the
dewatering step, using known dispersants to obtain stable
dispersions (slurries of >50 wt %). Therefore, the PCC particles
of the prior art may be coated with carboxylates, and therefore,
they may be surrounded by gas (usually air) bubbles that lead to a
seemingly "reduced" specific gravity, of which value is
substantially below 2.5 g/cm.sup.3. However, this erroneous
situation last only until these PCC particles are subjected to high
shear forces (e.g. in the processes of making coatings, inks and
paper) that causes the separation of these gas bubbles, unless they
are "hidden" deep below the surface of the PCC particles, and that
is the basis of the present invention. Therefore, any suggestion
that is made herein to measure the specific gravity of the PCC
particles, after drying them at 120.degree. C. for 12 hours only,
is just to get the notion that indeed the respective product may be
of suitable properties and be further ignited at about 500.degree.
C. for the time that is necessary to remove all the organic
moieties, before further specific gravity tests are conducted. A
person skilled in the art may choose other conditions to perform
this task, but then he should make sure that the organic compounds
are no longer in/onto the tested PCC particles.
[0148] Contrary to what was thought before, that the "pores" in the
PCC particles of the present invention are closed, we know now that
these "pores" are semipermeable (or selectively permeable) to
liquids and gases. Any attempt to use the regular gas phase
pycnometer measurements to determine the specific gravity of
commercial PCC particles, as well as the PCC of the present
invention, will lead to values above 2.5 g/cm.sup.3, irrespective
of the kind and source of these calcium carbonate products or the
kind of treatment that these samples received prior to the specific
gravity analyses (c.f. Example 14(D)). Namely, using such a
practice would have resulted in totally overlooking the present
invention. However, conducting specific gravity analyses of the PCC
particles of the present invention (after treatment at 500.degree.
C. for eight hours) in liquids like water, oleic acid (>97%),
cold pressed edible olive oil, refined edible sunflower oil,
refined edible corn oil, refined edible soybeans oil, refined
canola oil, and tall oil, leads to values <2.5 g/cm.sup.3
(preferably <2.3 g/cm.sup.3 and more preferably <2.1
g/cm.sup.3). Similar measurements of the specific gravity of
commercially available GCC (calcite) and PCC (calcite and
aragonite) gave always rise to values that were >2.5 g/cm.sup.3
(even >2.6 g/cm.sup.3 and even >2.7 g/cm.sup.3). When the
measurements of the specific gravity were conducted in water, the
specific gravity of the products of the present invention were
<2.5 g/cm.sup.3, but however, when a small amount of sodium
dioctylsulfosuccinate (2%) was added to the slurry, the specific
gravity of the PCC particles increased quite fast and ended up at
values >2.7 g/cm.sup.3 (such a phenomenon could not be observed
in the case of the prior art GCC or PCC products). This phenomenon
of penetration of liquids into the "pores" of the product of the
present invention has a lot of benefits, but when this happens on
preparing the usual stable slurries of PCC (of >50 wt %) by
mixing the PCC, water and a suitable dispersants, it results in a
very thick, high viscose mass. At the preparation stage, PCC
slurries made of a product of the prior art look, superficially,
quite similar to those that are made of the product of the present
invention, but this superficial appearance may mislead. For
instance, measuring the specific gravity (S.G.) of the PCC
particles of the prior art will result in values that are >2.5
g/cm.sup.3, while the S.G. of the PCC particles of the present
invention will be considerably lower values. Moreover, the addition
of a wetting agent, like the sodium dioctylsulfosuccinate, to these
slurries will reveal a much more dramatic behavior. Namely, such
slurries of the PCC particles of the prior art may not be affected
much, but the slurries made of the PCC particles of the present
invention will turn into a dense and thick high-viscose mass and
the S.G. values of the particles therein will increase to >2.7
g/cm.sup.3, due to the penetration of the aqueous phase into the
PCC particles.
[0149] Due to the fact that the "pores" in the products of the
present invention are not closed to gases and to some liquids, it
is important to avoid the customary gas pycnometer specific gravity
(S.G.) measurements when analyzing the product of the present
invention, and rather follow the exact instructions of how to do it
(c.f. in Example 14 and especially in Example 14(F)). These
measurements reveal best the desired properties of the novel
products of the present invention and of the process of the present
invention and give a close picture of how these PCC particles are
going to improve the final (consumer) products, due to their unique
property--"porosity".
[0150] Another observation can be made, based on the experimental
data that was collected thus far, that the loose bulk density
(L.B.D.) of the products of the present invention have remarkably
lower values (<0.5 g/cm.sup.3 and even <0.4 g/cm.sup.3), than
those of similar products of the prior art (usually >0.5
g/cm.sup.3). Therefore, we may also use this phenomenon to serve as
an additional criterion to indicate whether a product of such low
L.B.D. is in the domain of the present invention. The exact
procedure of how to perform this test will be detailed in Example
14(G). Generally, particulate PCC products, previously dried at
120.degree. C. for twelve hours, that are of SSA (Specific Surface
Area) (BET) .ltoreq.13 m.sup.2/g will belong to the domain of the
present invention if they have a L.B.D. of less than 0.4
g/cm.sup.3, provided that they are coated by e.g. decanoic acid,
dodecanoic acid, myristic acid, undecylenic acid, stearic acid and
alike carboxylic acids that are used as the active agent in the
particular case, as instructed in Example 14(G). Products of higher
SSA will not be tested according to this L.B.D. test, but rather by
only the S.G. test, as instructed in Example 14(F).
[0151] The present invention will now be described in more detail
by way of Examples, which are presented for illustration purposes
only and are not be construed restrictively.
[0152] Experimental:
[0153] Raw Materials:
[0154] A. All raw materials were purchased from Aldrich, unless
otherwise specified.
[0155] B. Ethyl decanoate was prepared by reacting decanoyl
chloride with ethanol in the presence of triethylamine at about
50.degree. C. After about 3 hours the product was washed with water
to remove water-soluble residues and it was then dried at about
50.degree. C. under a vacuum of about 30 mm/Hg.
[0156] C. Sodium decanoate was prepared by thoroughly mixing
decanoic acid with 2% aqueous NaOH at about 70.degree. C. until the
pH passed 10.
[0157] D. Potassium decanoate was prepared by thoroughly mixing
decanoic acid with 2% aqueous KOH at about 70.degree. C. until the
pH passed 10.
[0158] 5th. CaO(1)--of Arad, Israel.
[0159] 6th. CaO(2)--of Shfeya, Israel.
[0160] G. Commercial PCC--Aragonite; of Specialty Minerals Inc.
(SMI); Opacarb.RTM. A40.
[0161] H. CO.sub.2--Cylinders of 100% pure compressed gas of
Mifalay Hamzan Ltd., Haifa.
[0162] I. Tall Oil (Sylvatal 20S) of Arizona Chemical, USA.
[0163] J. Ultrafine stearic acid coated GCC--Omya UFT 95 ex
Omya-Pluess-Staufer--Switzerland.
[0164] K. A commercial ultrafine stearic acid coated--Ultraflex PCC
ex SMI--USA.
[0165] L. A commercial ultrafine talc--Ultratalc 609 ex
SMI--USA.
[0166] M. Isostearic Acid--Emersol 875 ex Henkel--Germany.
[0167] N. The Paint Constituents:
[0168] Nopco NDW of Henkel
[0169] Cellosize QP 15000 (hydroxy ethyl cellulose) of Union
Carbide
[0170] Disperse One (45% N.V.) of Tambour, Israel
[0171] Synperonic NP10 of ICI
[0172] TiO.sub.2 (Kronos 2160) of Kronos (However, similar
TiO.sub.2 pigments, like Tioxide R-TC90 and Tioxide TR92, of which
their D.sub.50=220 nm.+-.20 nm may serve equally well)
[0173] Synthetic sodium aluminum silicate (p820) of Degussa
[0174] Kaolin clay (D.sub.50=3.1 micron) of Engelhard
[0175] CaCO.sub.3 powder (d.sub.50=3.5 microns) of Polychrom,
Israel--"Girulite-8"
[0176] Talc (D.sub.50=12.3 micron) of Lusenac Val Chisone
[0177] Copolymer vinyl acetate acrylate emulsion (55% N.V.) of
Cerafon, Israel
[0178] Butyl diglycol acetate of Union Carbide
[0179] Kathon LXE of Rohm & Haas
[0180] Ammonia (25%) of Frutarom, Israel
[0181] Antioxidant (irganox B225 ex Ciba Specialty
Chemicals--Switzerland)
[0182] Lubricant (Wax PE 520 ex Hoechst-Celanese--USA)
[0183] Polypropylene copolymer (Capilene-TR50 ex Carmel
Olefins--Israel).
[0184] Instruments and Accessories:
[0185] 1. pH meter/controller; Jenco; Model 3671; Made in
China.
[0186] 2. pH electrode; Hanna Industries; type HI 1131 B (Glass
Probe).
[0187] 3. Thermometer; Jenco Model 3671; Made in China.
[0188] 4. Peristaltic pump; Watson-Marlow; Model 505u (variable
speed).
[0189] 5. Agitator; Ika; Model RW-20 (variable speed).
[0190] 6. Dissolver; Hsiangtal; Model HD-550; Made in Taiwan
[0191] 7. Ultra-turrax.RTM. T50; Ika; rotor d=3.8 cm; stator d=4
cm.
[0192] 8. Disk type rotor of d=12 cm.
[0193] 9. Disk type rotor of d=8 cm.
[0194] 10. Saw-blade type rotor of d=9 cm.
[0195] 11. Saw-blade type rotor of d=4.8 cm.
[0196] 12. Hydrocyclone 2"; Mozely; P=50 psi; vortex finder=11 mm;
spigot=6.4 mm.
[0197] 13. Vacuum pump; Vacuumbrand GmbH; Model MD 4C.
[0198] 14. Buchner+filter cloth with 8-10 .mu.m pores.
[0199] 15. XRD (X-Rays Diffractometer); Siemens D-500 for the
crystallographic phases.
[0200] 16. SEM (Scanning Electron Microscope); Jeol 5400 for the
shapes of the particles.
[0201] 17. Colorimeter; Hunterlab D25-PC2 for whiteness
measurements.
[0202] 18. Colorimeter; ACS instrument (Applied Color Systems).
[0203] 19. Ultrasonic bath (10 l); Selecta, Spain--"ULTRASONS".
[0204] 20. Ultrasonic cleaners (baths) of limited power (<100
Amp.Volt.) e.g. P-08890-01/06 ex Cole Parmer--USA.
[0205] 21. Analytical Balance; Shekel Ltd., Israel.
[0206] 22. HPLC Analyzer; Waters HPLC Analyzer (Detector
486+Autosampler 717+Pump 510+millenium Software).
[0207] 23. HPLC Column; Phenomenex C18(250 mm.times.4.3 mm; 5 .mu.m
Particle size).
[0208] 24. AccPyc 1330 ex Micromeritics--USA.
[0209] 25. Glossmeter (Minigloss 101N ex Sheen
Instruments--England).
[0210] 26. Reflectometer (Ref. 310 Sheen-Opac ex Sheen
Instruments--England).
[0211] 27. Twin-screw compounder (UD=24 ex Dr.
Collin--Germany).
[0212] 28. Injection machine (25 t ex Dr. Boy--Germany).
[0213] 29. Screen-shaker (Rotap Model RX-29-10 ex W.S. Tyler
Inc.--USA).
[0214] 30. GC-MS for trace analysis--of HP Model 5890/5971
[0215] Preparation I--Preparation of Aqueous Calcium Hydroxide
Slurries:
[0216] The aqueous calcium hydroxide slurry was prepared in the
laboratory in a batch mode of operation as follows: 40 kg of tap
water were introduced into a 50 l. stainless steel 316 reactor that
was equipped with a steam heated jacket, a thermometer and with the
Hsiangtal Dissolver with a rotor of d=12 cm. The Dissolver was
operated at 200 rpm, 4 kg of CaO (Shfeya) were added to the reactor
during less than 10 minutes and the slurry was allowed to stir for
10-80 minutes. At that time the temperature rose to above
60.degree. C. and when it reached its maximal temperature at
80-90.degree. C., the mixture was ready for its purification prior
to the carbonation stage, as follows:
[0217] a. The slurry passed a stainless steel 316 screen to remove
particles of d>2 mm, and
[0218] b. The filtered slurry passed a hydrocyclone to remove
particles of d>50 .mu.m.
[0219] Notes:
[0220] At this point the warm aqueous calcium hydroxide slurry was
ready for its use in the carbonation stage and its temperature was
maintained at a preset value by heating the slurry in the above
reactor in order to control the temperature in the carbonator.
[0221] The potential active agent(s) and any optional additives
could be blended into the warm slurry at a preset concentration
before the purification steps a. and b. or thereafter.
[0222] This batch mode of operation is used only in the laboratory
tests. The production plant is intended to be operated under a
continuous mode of operation, as is discussed herein.
[0223] Preparation II--Preparation of Aqueous Calcium Hydroxide
Slurries:
[0224] PREPARATION I was repeated using CaO of Arad, a
substantially purer raw material than that of Shfeya (the
respective whitenesses are >95% and 88%).
EXAMPLE 1
[0225] Screening Test for the Potential Active Agents:
[0226] Possible active agents were investigated by producing
particulate precipitated calcium carbonate according to the
following procedure:
[0227] 2 kg tap water were added to a 3.2 l. stainless steel 316
reactor (of inner diameter d=15 cm and length .about.18 cm),
equipped with a steam heated jacket, a pH electrode, a thermometer
and the Hsiangtal Dissolver with a saw-blade rotor of d=4.8 cm
(c.f. FIG. 3). The Dissolver was operated at a preset speed and
carbon dioxide gas or a carbon dioxide containing gas and the
aqueous calcium hydroxide slurry of PREPARATION I, containing
already the active agent, were fed simultaneously into the reactor,
while maintaining the pH, the temperature and the production rate
at preset values. The product was collected at the top of the
reactor, and the impurities were discharged from the bottom of the
reactor (naturally, the product exited from the bottom of the
reactor when the experimental active agent did not lead to a
particulate precipitated aragonite and to its flotation).
[0228] The first 10 l. of resulting slurry were discarded. The
residual slurry was collected and it was filtered through a
filter-cloth on the Buchner using a vacuum pump to dewater the
product. The filter cake was dried for 12 hours at 120.degree. C.
and the crystallographic morphologies and the shapes of the
crystals of the precipitated calcite and/or aragonite calcium
carbonate particles were determined using XRD and SEM analyses,
respectively. The results are shown in the Table 1, below.
[0229] The Process Set Points--Continuous Mode of Operation:
[0230] 1. Rotor Speed=4000 rpm (Tip Speed .about.10 m/sec.).
[0231] 2. pH=9.5.
[0232] 3. Temperature=85.degree. C.
[0233] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0234] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10%
(wt)=.about.6 L.P.H. (to maintain the preset pH value).
[0235] 6. Potential active agent concentration=1 wt. %, based on
CaCO.sub.3.
1TABLE 1 the results of EXAMPLE 1 Test Number of Product # Active
Agent Carbons (Isomorph) 1 Propionic acid 3 Calcite 2 Lactic acid 3
Calcite 3 Pyruvic acid 3 Calcite 4 Acrylic acid 3 Calcite 5
Methoxyacetic acid. 3 Calcite 6 Methacrylic acid. 4 Calcite 7
Butanoic acid 4 Calcite 8 Pentanoic acid 5 Calcite 9 Hexanoic acid
6 Calcite 10 Heptanoic acid 7 Calcite 11 Octanoic acid 8 Calcite 12
Phthalic acid 8 Calcite 13 Terephthalic acid 8 Calcite 14
2-Ethylhexanoic acid 8 Calcite 15 Nonanoic acid 9 Aragonite 16
Nonanoic acid* 9 Aragonite 17 Azelaic acid 9 Calcite 18 Trimelitic
acid 9 Calcite 19 Decanoic acid 10 Aragonite 20 Decanoic acid* 10
Aragonite 21 Sodium decanoate 10 Aragonite 22 Potassium decanoate
10 Aragonite 23 Ethyl decanoate 12 Aragonite 24 Decanoyl chloride
10 Aragonite 25 Decanoic acid anhydride 20 Aragonite 26 Undecanoic
acid 11 Aragonite 27 Undecanoic acid* 11 Aragonite 28
4-Butylbenzoic acid 11 Calcite 29 Dodecanoic acid** 12 Calcite 30
Palmitic acid 16 Calcite 31 Stearic acid 18 Calcite 32 Oleic acid
18 Calcite 33 MgCl.sub.2 -- Calcite 34 AlCl.sub.3 -- Calcite 35
C.sub.12H.sub.25C.sub.6H.sub.4SO.- sub.3H (LABSA) 18 Calcite *- Was
pumped continuously and directly into the carbonator. **- This
experiment led to mostly calcite (of a crystallographic purity
(aragonite/(aragonite + calcite)) .about.20%-25%) and to a specific
gravity (S. G.) = 2.54 g/cm.sup.3 (measured according to Example
14A), which is outside the limits of the present invention (S. G.
< 2.5 g/cm3). However, the use of CO2 containing gas (26% by
volume CO2 and 74% by volume Air) and 1.5% dodecanoic acid in an
experiment similar to that described in Example 10, led to a
product of mostly #aragonite (of a crystallographic purity
(aragonite: (aragonite + calcite)) >50%) and to a specific
gravity (S. G.) = 1.78 g/cm3 (measured according to Example
14A).
EXAMPLE 2
[0236] A Screening Test for Interfering Compounds:
[0237] EXAMPLE 1 was repeated, except that in all the experiments
1% (wt; based on the calcium carbonate) decanoic acid was premixed
in the aqueous calcium hydroxide slurry feed and in each experiment
an additional experimental active agent was added to study its
effect on the activity of the decanoic acid. The results are shown
in Table 2, below.
[0238] The Process Set Points--Continuous Mode of Operation:
[0239] 1. Rotor Speed=4000 rpm (Tip Speed .about.10 m/sec.)
[0240] 2. pH=9.5.
[0241] 3. Temperature=85.degree. C.
[0242] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0243] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10%
(wt)=.about.6 L.P.H. (to maintain the preset pH value).
[0244] 6. Active agents concentrations=1 wt. % decanoic acid+1 wt.
% potential active agent based on CaCO.sub.3.
2TABLE 2 the results of EXAMPLE 2 Test Number of Product # Active
Agent Carbons (Isomorph) 1 Propionic acid 3 Aragonite 2 Lactic acid
3 Aragonite 3 Pyruvic acid 3 Aragonite 4 Acrylic acid 3 Aragonite 5
Methoxyacetic acid 3 Aragonite 6 Methacrylic acid 4 Aragonite 7
Butanoic acid 4 Aragonite 8 Pentanoic acid 5 Aragonite 9 Hexanoic
acid 6 Aragonite 10 Heptanoic acid 7 Aragonite 11 Octanoic acid 8
Aragonite 12 Phthalic acid 8 Calcite 13 2-Ethylhexanoic acid 8
Aragonite 14 Nonanoic acid 9 Aragonite 15 Azelaic acid 9 Aragonite
16 Trimelitic acid 9 Calcite 17 Decanoic acid 10 Aragonite 18
Undecanoic acid 11 Aragonite 19 4-ButylBenzoic acid 11 Aragonite 20
Dodecanoic acid 12 Aragonite 21 Palmitic acid 16 Aragonite 22
Stearic acid 18 Aragonite 23 Oleic acid 18 Aragonite 24 MgCl.sub.2
-- Aragonite 25 AlCl.sub.3 -- Aragonite 26
C.sub.12H.sub.25C.sub.6H.sub.4SO.sub.3H (LABSA) 18 Aragonite
EXAMPLE 3
[0245] A Batch Mode of Operation:
[0246] A batch mode of operation, of which parameters were as close
as possible to those of EXAMPLE 1, was attempted. Only particulate
precipitated calcite of rhombohedral shape was obtained. No
particulate precipitated aragonite could be obtained when using
decanoic acid or any other active agent that was mentioned as being
effective in EXAMPLE 1. The experiment was conducted as
follows:
[0247] The active agents were investigated by producing
precipitated calcium carbonate particles according to the following
procedure:
[0248] 2 kg aqueous calcium hydroxide slurry, containing already
the respective active agent (c.f. EXAMPLE 1) were added to the 3.2
l. stainless steel 316 reactor of EXAMPLE 1. The Dissolver was
operated at 4000 rpm, the temperature was maintained at 85.degree.
C. and the production rate was determined by controlling the feed
rate of the carbon dioxide gas. The carbonation was stopped after
about 20-30 minutes, when the pH reached 7. The product mixture was
then removed from the reactor through its bottom outlet.
[0249] The resulting slurry was filtered through a filter cloth on
the Buchner using a vacuum pump to dewater the product. The filter
cake was dried for 12 hours at 120.degree. C. and the
crystallographic morphologies and the shapes of the crystals of the
precipitated calcite particles were determined using XRD and SEM
analyses, respectively. As mentioned above, no precipitated
aragonite particles were obtained.
[0250] The Process Set Points--Batch Mode of Operation:
[0251] 1. Rotor Speed=4000 rpm (Tip Speed .about.10 m/sec.).
[0252] 2. pH=14.fwdarw.7.
[0253] 3. Temperature=85.degree. C.
[0254] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0255] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10% (wt)=2
kg.
[0256] 6. Potential active agent concentration=1 wt. %, based on
CaCO.sub.3.
EXAMPLE 4
[0257] Parametric Studies--the Effect of the Temperature:
[0258] Similar experiments to EXAMPLE 1 were conducted using
decanoic acid only. The results are as follows:
[0259] The Process Set Points--Continuous Mode of Operation:
[0260] 1. Rotor Speed=4800 rpm (Tip Speed .about.12 m/sec.).
[0261] 2. pH=9.5.
[0262] 3. Temperature=variable.
[0263] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0264] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10 wt.
%=.about.6 L.P.H. (to maintain the p
[0265] 6. Active agent concentration=decanoic acid; 0.5 wt. %,
based on CaCO.sub.3.
3TABLE 3 the results of EXAMPLE 4 Test Temperature Mineralogical
Phase # .degree. C. XRD 1 87 Aragonite 2 80 Aragonite 3 70
Aragonite 4 60 Aragonite 5 50 Calcite
EXAMPLE 5
[0266] Parametric Studies--Effect of the pH:
[0267] Similar experiments to EXAMPLE 1 were conducted using
decanoic acid only. The results are as follows:
[0268] The Process Set Points--Continuous Mode of Operation:
[0269] 1. Rotor Speed=4800 rpm (Tip Speed .about.12 m/sec.).
[0270] 2. pH=variable.
[0271] 3. Temperature=87.degree. C.
[0272] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour)
[0273] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10 wt.
%=.about.6 L.P.H. (to maintain the present pH value).
[0274] 5. Active agent concentration=decanoic acid; 0.5 wt. % based
on CaCO.sub.3.
4TABLE 4 the results of EXAMPLE 5 Test Mineralogical Phase # pH XRD
1 10 Aragonite 2 9.5 Aragonite 3 9 Aragonite 4 8.5 Aragonite 5 8.0
Calcite 6 7.0 Calcite
EXAMPLE 6
[0275] Parametric Studies--Concentration Effect of the Active
Agent
[0276] Similar experiments to EXAMPLE 1 were conducted using
decanoic acid only. The results are as follows:
[0277] The Process Set Points--Continuous Mode of Operation:
[0278] 1. Rotor Speed=4800 rpm (Tip Speed .about.12 m/sec.).
[0279] 2. pH=9.5.
[0280] 3. Temperature=87.degree. C.
[0281] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0282] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10%
(wt)=.about.6 L.P.H. (to maintain the preset pH value).
[0283] 6. Active agent concentration=decanoic acid; variable wt. %;
based on CaCO.sub.3.
5TABLE 5 the results of EXAMPLE 6 Test Decanoic acid Mineralogical
Phase # % (wt) XRD 1 1.0 Aragonite 2 0.5 Aragonite 3 0.3 Aragonite
+ Calcite* 4 0.2 Aragonite + Calcite* 5 0.1 Calcite *- A
crystallographic purity (aragonite/(aragonite + calcite))
<90%.
[0284] Note: Though the present invention is especially aimed at
obtaining substantially pure particulate precipitated aragonite
calcium carbonate of crystallographic purity (aragonite
phase/(aragonite phase+calcite phase)) .gtoreq.90% and even
>95%, there are still applications that can utilize mixtures of
these isomorphs where such crystallographic purity is <90%, and
such mixtures are within the scope of the present invention. In
such cases the boundary conditions of the present invention (c.f.
Tests #3 and #4, above) may still be used.
EXAMPLE 7
[0285] Parametric Studies--Concentration Effect of the
Ca(OH).sub.2
[0286] Similar experiments to EXAMPLE 1 were conducted using
decanoic acid only. The results are as follows:
[0287] The Process Set Points--Continuous Mode of Operation:
[0288] 1. Rotor Speed=4800 rpm (Tip Speed .about.12 m/sec.).
[0289] 2. pH=9.5.
[0290] 3. Temperature=87.degree. C.
[0291] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour)
[0292] 5. Aqueous calcium hydroxide slurry (of Shfeya) -variable
wt. %=variable L.P.H. (to maintain the preset pH value).
[0293] 6. Active agent concentration=decanoic acid; 0.5 wt. % based
on CaCO.sub.3.
6TABLE 6 the results of EXAMPLE 7 Solids in Test Slaked Lime
Mineralogical Phase # % (wt) XRD 1 8 Aragonite 2 4 Aragonite 3 3
Aragonite + Calcite* 4 2 Aragonite + Calcite* 5 1 Calcite *- A
crystallographic purity (aragonite: (aragonite + calcite)) <90%
and c.f. the above note at the end of Example 6.
EXAMPLE 8
[0294] Parametric Studies--Rotor Speed Effect:
[0295] Similar experiments to EXAMPLE 1 were conducted using
decanoic acid only. The results are as follows:
[0296] The Process Set Points--Continuous Mode of Operation:
[0297] 1. Rotor Speed=variable rpm (Tip Speed .about.variable).
[0298] 2. pH=9.5.
[0299] 3.Temperature=87.degree. C.
[0300] 4. Carbon dioxide flow rate=180 L.P.H (liters/hour).
[0301] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10 wt.
%=.about.6 L.P.H. (to maintain the preset pH value).
[0302] 6. Active agent concentration=decanoic acid; 0.5 wt. % based
on CaCO.sub.3.
7TABLE 7 the results of EXAMPLE 8 Test Rotor Speed Tip Speed
Mineralogical Phase # rpm m/sec. XRD 1 10000 25 Aragonite 2 4800 12
Aragonite 3 2000 5 Aragonite + Calcite* 4 1000 2.5 Calcite *- A
crystallographic purity (aragonite: (aragonite + calcite)) <90%
and c.f. the above note at the end of Example 6.
EXAMPLE 9
[0303] Parametric Studies--Effect of the CO.sub.2 Flow Rate
(F.R.)
[0304] Similar experiments to EXAMPLE 1 were conducted using
decanoic acid only. The results are as follows:
[0305] The Process Set Points--Continuous Mode of Operation:
[0306] 1. Rotor Speed=4800 rpm (Tip Speed .about.12 m/sec.).
[0307] 2. pH=9.5.
[0308] 3. Temperature=87.degree. C.
[0309] 4. Carbon dioxide flow rate=variable L.P.H.
(liters/hour)
[0310] 5. Aqueous calcium hydroxide slurry (of Shfeya) -variable
wt. %=variable L.P.H. (to maintain the preset pH value).
[0311] 6. Active agent concentration=decanoic acid; 0.5 wt. % based
on CaCO.sub.3.
8TABLE 8 the results of EXAMPLE 9 Test CO.sub.2 Flow Rate
Mineralogical Phase # L.P.H. XRD 1 240 Aragonite 2 180 Aragonite 3
120 Aragonite
EXAMPLE 10
[0312] Parametric Studies--Effect of the CO.sub.2/Air Ratio:
[0313] Similar experiments to EXAMPLE 1 were conducted using
decanoic acid only. The results are as follows:
[0314] The Process Set Points--Continuous Mode of Operation:
[0315] 1. Rotor Speed=4800 rpm (Tip Speed .about.12 m/sec.).
[0316] 2. pH=9.5.
[0317] 3. Temperature=87.degree. C.
[0318] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0319] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10%
(wt)=.about.6 L.P.H. (to maintain the preset pH value).
[0320] 6. Active agent concentration=decanoic acid; 0.5 wt. %;
based on CaCO.sub.3.
[0321] 7. Air=variable.
9TABLE 9 the results of EXAMPLE 10 Test Mineralogical Phase #
Air/CO.sub.2 XRD 1 0 Aragonite 2 0.33 Aragonite 3 0.66
Aragonite
EXAMPLE 11
[0322] The Effect of Active Agent on Content of the Wet Filter
Cake:
[0323] Similar experiments to EXAMPLE 1 were conducted using
decanoic acid only. The content of CaCO.sub.3 in the wet filter
cake was determined after drying 12 hours at 120.degree. C.
Relatively pure (aragonite phase/(aragonite phase+calcite
phase)).gtoreq.95% and dry precipitated acicular aragonite calcium
carbonate particles were obtained. The results are as follows:
[0324] The Process Set Points--Continuous Mode of Operation:
[0325] 1. Rotor Speed=4800 rpm (Tip Speed .about.12 m/sec.).
[0326] 2. pH=9.5.
[0327] 3. Temperature=90.degree. C.
[0328] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0329] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10 wt.
%=.about.6 L.P.H. (to maintain the preset pH value).
[0330] 6. Active agent concentration=decanoic acid; 0.7; 1.0; 2.0
wt. %; based on CaCO.sub.3.
10TABLE 10 the results of EXAMPLE 11 Test Dosage Product CaCO.sub.3
Crystallographic # % (wt) (Isomorph) % (wt)* Purity** 1 0.7
Aragonite >80 .gtoreq.95% 2 1.0 Aragonite >80 .gtoreq.95% 3
2.0 Aragonite >80 .gtoreq.95% *- % (wt) CaCO.sub.3 = 100 .times.
wt. of dry filter cake / wt. of wet filter cake **- As determined
by the XRD analyses (for Test #2 - c.f. FIGS. 4 and 5)
[0331] Note:
[0332] By choosing relatively standard conditions for the present
process, it is possible to reduce the water content in the wet
filter cake below 20 wt. %.
EXAMPLE 12
[0333] The Effect of the Active Agent on the Resistivity to
Acids:
[0334] Similar experiments to EXAMPLE 1 were conducted using
decanoic acid only, the resistivity of the dry samples to acidic
aqueous solutions being determined as follows. A 5 l. solution of
HCl in water at pH=3.5 was prepared for all the following
experiments, so as to assure equal starting experimental
conditions. 100 ml of this HCl solution were poured into a 100 ml
graduated cylinder, 5 g of precipitated CaCO.sub.3 particles were
added and the pH was measured after 20 minutes. Evolution of
CO.sub.2 was observed visually, as was the behavior of the
commercial sample #C, the calcite #BM-37, and it was found that the
aragonite samples of the present invention (#12-3, #12-4, #12-5)
were markedly different. It is worthwhile to note that sample #12-5
produced few bubbles that did not detach from the surface of the
precipitated aragonite particles. The results are as follows:
[0335] The Process Set Points--Continuous Mode of Operation:
[0336] 1. Rotor Speed=5200 rpm (Tip Speed .about.13 m/sec.).
[0337] 2. pH=9.5.
[0338] 3. Temperature=90.degree. C.
[0339] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0340] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10 wt.
%=.about.6 L.P.H. (to maintain the preset pH value).
[0341] 6. Active agent concentration=decanoic acid; 0.7%; 1.0%; 2%
wt. % based on CaCO.sub.3.
11TABLE 11 the results of EXAMPLE 12 Test Sample Active agent
Product pH after 20 # # (wt. %) (Isomorph) mins. Note 1 C* Unknown
Aragonite >6 Violent Evolution of CO.sub.2 2 BM-37** 1.0 Calcite
>5 Evolution of CO.sub.2 3 12-3 0.7 Aragonite <4 Slight
Evolution of CO.sub.2 4 12-4 1.0 Aragonite <4 Slight Evolution
of CO.sub.2 5 12-5 2.0 Aragonite <4 No Evolution of CO.sub.2 * -
Commercial PCC - Aragonite; of Specialty Minerals Inc. (SMI);
Opacarb .RTM. A40 ** - This sample was taken from the batch mode of
operation in EXAMPLE 3
[0342] Note:
[0343] By choosing relatively standard conditions for the present
process, it is possible to increase the resistance of the product
towards acids by using quite low concentrations of the active agent
and obtain excellent product for the paper industry of which
processes are acidic and for the coating industry for durable
paints for acidic environments.
EXAMPLE 13
[0344] Effect of Raw Material/Process on Whiteness of the
Product:
[0345] EXAMPLE 1 and EXAMPLE 3 were conducted using the aqueous
calcium hydroxide slurries of PREPARATION I and of PREPARATION II
for comparison. The whitenesses of the products are compared.
[0346] The results are as follows:
[0347] The Process Set Points--Continuous Mode of Operation:
[0348] 1. Rotor Speed=4000 rpm (Tip Speed .about.10 m/sec.).
[0349] 2. pH=9.5.
[0350] 3. Temperature=85.degree. C.
[0351] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour)
[0352] 5. Aqueous calcium hydroxide slurry (of Arad/Shfeya) -10 wt.
% =.about.6 L.P.H. (to maintain the preset pH value).
[0353] 6. Active agent concentration=decanoic acid; 1 wt. % based
on CaCO.sub.3.
[0354] The Process Set Points--Batch Mode of Operation:
[0355] 1. Rotor Speed=4000 rpm (Tip Speed .about.10 m/sec.).
[0356] 2. pH=.about.14.fwdarw.7.
[0357] 3. Temperature=85.degree. C.
[0358] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0359] 5. Aqueous calcium hydroxide slurry (of Arad/Shfeya) -10 wt.
%=2 kg.
[0360] 6. Active agent concentration=decanoic acid 1 wt. % based on
CaCO.sub.3.
12TABLE 12 the results of EXAMPLE 13 CaO of Arad whiteness =
>95% CaO of Shfeya (whiteness = .about.88%) Continuous Batch
Continuous Batch AR-83A BM37A AR-83 BM37 Aragonite CaCO.sub.3
Calcite CaCO.sub.3 Aragonite CaCO.sub.3 Calcite CaCO.sub.3
Whiteness = Whiteness = Whiteness = Whiteness = 98-9% 97-8% 97-9%
92-5%
[0361] Notes:
[0362] 1. When the raw material (CaO) is relatively pure, the
whiteness of the products (AR-83A and BM37A) is not (and should not
be) much different. However, when the CaO is relatively impure, the
whiteness of the precipitated aragonite particles (AR-83) is
dramatically higher than the corresponding calcite (BM37), due to
the unique effect of the process of the present invention.
[0363] 2. The whiteness of the precipitated particulate aragonite
obtained according to the present process attains top quality,
independently of the calcium hydroxide source.
EXAMPLE 14
[0364] Effect of the Active Agent/Process on the Specific Gravity
(S.G.) of Precipitated Particulate Calcium Carbonate:
[0365] EXAMPLE 1 was repeated using the aqueous calcium hydroxide
slurry of PREPARATION I, except that the concentration of decanoic
acid was gradually increased.
[0366] (A) Determination of the Specific Gravity (S.G.) in Tall Oil
of a Product Dried at 120.degree. C.
[0367] 1. The wet filter cake of the CaCO.sub.3 sample was dried
for 12 hours at 120.degree. C. to remove all free water.
[0368] 2. A weighed quantity of the dry CaCO.sub.3 sample (Wc)+a
weighed quantity of tall oil (Wo) (Density of 0.93 g/cm.sup.3) were
introduced into a 1 l. glass beaker.
[0369] 3. The mixture was stirred with the Hasiangtal HD-550
Dissolver for 10 minutes, at 4000 rpm (using a saw-blade rotor of
d=4.8 cm).
[0370] 4. The slurry was poured into a 250 ml graduated glass
settling column and was sonicated gently in an ultrasound bath for
20 minutes, until all the visible trapped bubbles were released
from the surface of the PCC particles. In order not to destroy the
structure of the "porous" product of the present invention while
sonicating it, thereby leading to higher S.G. values, the use of
ultrasonic cleaners (baths) of limited power (<100 Amp.Volt.)
e.g. P-08890-01/06 ex Cole Parmer--USA, is recommended.
[0371] 5. The settling column was then evaluated at 20-22.degree.
C. for:
[0372] (a) the volume of the slurry--V
[0373] (b) the total net weight of the slurry--W
[0374] Based on the above measurements, the following was
calculated:
[0375] (1) from the equation: D=W/V g/cm.sup.3, the density of the
slurry;
[0376] (2) from the equation
1/D=[Wc(Wo+Wc)]/S.G.+[Wo(Wo+Wc)]/0.93,
[0377] the S.G. of the CaCO.sub.3 sample was calculated.
[0378] 6. The loose bulk density (B.D.) of the dry powder was
measured using a balance and a graduated cylinder.
[0379] The Process Set Points--Continuous Mode of Operation:
[0380] 1. Rotor Speed=4000 rpm (Tip Speed .about.10 m/sec.)
[0381] 2. pH=9.5.
[0382] 3. Temperature=85.degree. C.
[0383] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0384] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10 wt.
%=.about.6 L.P.H. (to maintain the preset pH value).
[0385] 6. Active agent concentration=decanoic acid; 0.5; 1; 2; 5;
2; 1 wt. % based on CaCO.sub.3.
[0386] The results are as follows:
13TABLE 13 the results of EXAMPLE 14 (A) Mineralogical Loose Test
Sample Active Dosage Phase S.G..dagger. B.D..dagger. # Code agent
(wt. %) XRD g/cm.sup.3 g/cm.sup.3 1 Natural -- -- Calcite 2.63 0.65
CaCO.sub.3 2 BM-37* decanoic 1 Calcite 2.54 0.37.sup.BM acid 3 C**
N.A. N.A. Aragonite 2.56 0.54 4 AR-81 decanoic 0.5 Aragonite 2.02
0.31 acid 5 AR-83 decanoic 1 Aragonite 1.90 0.30 acid 6 AR-118
decanoic 2 Aragonite 1.75 0.25 acid 7 AR-119 decanoic 5***
Aragonite 1.67 0.29 acid 8 AR-135 nonanoic 1 Aragonite 1.88 0.31
acid 9 AR-120 decanoic 2 Aragonite 1.72 0.23 acid * - The sample
was taken from the batch mode of operation in - EXAMPLE 3. ** -
Commercial PCC - Aragonite; of Specialty Minerals Inc. (SMI);
Opacarb .RTM. A40. *** - 5g of AR-119 were dissolved in a 10% HCl
solution. The decanoic acid was extracted with 1 ,2-dichloroethane.
HPLC analysis using a C18 column revealed 4.93% (wt; based on the
calcium carbonate) of this acid in the sample. - 50 ppm of
phosphoric acid were used in addition to the decanoic acid to
increase the aspect ratio of the acicular aragonite. .dagger. - A
dry powder after drying for 12 hours at 120.degree. C. BM - The
relatively low L.B.D. of this product should not be compared to the
other L.B.D. of Tests = 3-9, as BM-37 is a calcite form, while the
others are acicular aragonite form. N.A. - Not available.
[0387] Notes:
[0388] 1. The determination of a specific gravity (S.G.) of
particulate precipitated aragonite calcium carbonate of the present
invention, in a range below 2.5 g/cm.sup.3 (after drying at
120.degree. C. for twelve hours as described above, as well as
after ignition of the dried material at 500.degree. C. for eight
hours) is actually an important and decisive test to consider if
the technology that was used is under the domain of the present
invention.
[0389] 2. Only the inclusion of gas (probably, as tiny bubbles or
"blisters") in closed pores can account for the dramatic reduction
of the S.G. of particulate precipitated aragonite calcium carbonate
of the present invention. The L.O.D. and the L.O.I. in the latter
tests (c.f. (B) and (C), respectively) do not leave many logical
choices to account for this phenomenon. Also, this is in accordance
with the facts i. that the product of the present invention is
obtained under flotation conditions, and ii. that the high hiding
power of the paints, in which the particulate precipitated
aragonite calcium carbonate of the present invention was used, are
probably due to the high effective refractive index of this product
of the present invention, which is much higher than that expected
of similar products that are produced according to the prior art
(c.f. data collected in EXAMPLE 15 and the comparison made to paint
formulations that were based on raw materials of the prior
art).
[0390] 3. The idea of using porous particles, to increase their
effective refractive index in coatings, is not new. For instance,
Rohm & Haas produces a series of such products, e.g.
Ropaque.RTM. OP96 and Ropaque.RTM. OP3000. However, these particles
are of an organic polymeric nature of which cost and adaptation to
the environment is not to be compared with precipitated calcium
carbonate particles.
[0391] (B) Determination of the Specific Gravity (S.G.) in Tall Oil
of a Product Calcined at 300.degree. C.
[0392] 1. The wet filter cake of the CaCO.sub.3 sample was dried
for 12 hours at 120.degree. C. to remove all the free water.
[0393] 2. The weighed dry sample was heated for 8 hours at
300.degree. C. The loss on drying (L.O.D.) was then determined.
[0394] 3. The S.G. of the heated powder was measured as above (c.f.
(A)).
[0395] 4. The loose bulk density (B.D.) of the dry powder was
measured using a balance and a graduated cylinder.
[0396] The results are as follows:
14TABLE 14 the results of EXAMPLE 14 (B) L.O.D. Loose Test Sample
Active Dosage wt. % S.G..dagger. B.D..dagger. # Code agent (wt. %)
300.degree. C. g/cm.sup.3 g/cm.sup.3 10 Natural -- -- 0.10 2.63
0.651 CaCO.sub.3 11 BM-37* decanoic 1 2.21 2.64 0.372 acid 12 C**
N.A. N.A. 1.3 2.63 0.54 13 AR-81 decanoic 0.5 0.83 2.19 0.255 acid
14 AR-83 decanoic 1 0.89 2.11 0.265 acid 15 AR-118 decanoic 2 2.32
2.03 0.200 acid 16 AR-119 decanoic 5 5.73 2.01 0.200 acid 17 AR-135
nonanoic 1 0.95 2.12 0.238 acid 18 AR-120 decanoic 2 2.27 2.02
0.235 acid * - The sample was taken from the batch mode of
operation in-EXAMPLE 3. ** - Commercial PCC - Aragonite; of
Specialty Minerals Inc. (SMI); Opacarb .RTM. A40. - 50 ppm of
phosphoric acid were used in addition to the decanoic acid.
.dagger. - A dry powder after heating for 8 hours at 300.degree. C.
N.A. - Not available.
[0397] (C) Determination of the Specific Gravity (S.G.) in Tall Oil
of a Product Calcined 500.degree. C.
[0398] 1. The wet filter cake of the CaCO.sub.3 sample was dried
for 12 hours at 120.degree. C. to remove all the free water.
[0399] 2. The dry sample was calcined for 8 hours at 500.degree. C.
The loss on ignition (L.O.I.) was then determined.
[0400] 3. The S.G. of the calcined powder was measured as
above.
[0401] 4. The loose bulk density (B.D.) of the dry powder was
measured using a balance and a graduated cylinder.
[0402] The results are as follows:
15TABLE 15 the results of EXAMPLE 14 (C) L.O.I. Loose Test Sample
Dosage % (wt) S.G..dagger. B.D..dagger. # Code % (wt) 500.degree.
C. g/cm.sup.3 g/cm.sup.3 19 Natural -- 0.18 2.70 0.75 CaCO.sub.3 20
BM-37 1* 2.58 2.60 0.38 21 C** N.A. 2.02 2.71 0.55 22 AR-81 0.5
1.32 2.13 0.23 23 AR-83 1 1.44 2.03 0.22 24 AR-118 2 2.07 2.01 0.18
25 AR-119 5*** 5.25 1.93 0.19 26 AR-135 1 1.44 2.01 0.24 27 AR-120
2 2.37 1.91 0.18 * - The sample was taken from the batch mode of
operation in -EXAMPLE 3. ** - Commercial PCC - Aragonite; of
Specialty Minerals Inc. (SMI); Opacarb .RTM. A40. *** - 5 g of
AR-hg were dissolved in a 10% HCl solution. No decanoic acid could
be extracted or detected, as is expected of such molecules when
they are subjected to heating for 8 hours at 500.degree. C. - 50
ppm of phosphoric acid were used in addition to the decanoic acid.
- Aragonite is converted into calcite at T >400.degree. C.
.dagger. - Table 13 - the results of EXAMPLE 14 (A)hours at
500.degree. C. N.A. - Not available.
[0403] (D) Determination of the Gravity (S.G.)--by a Gas
Pycnometer
[0404] CaCO.sub.3 powder (d.sub.50=3.5 Polychrom,
Israel--"Girulite-8" and AR-118, a product of the present
invention, were tested in a AccPyc 1330 ex Micromeritics--USA. The
results are given in Table 15a, as follows:
16TABLE 15a the results of EXAMPLE 14 (D): Sample S.G. Average S.G.
Code Test # (g/cm.sup.3) (g/cm.sup.3) G-8 1 2.7544 2.7538 2 2.7549
3 2.7547 4 2.7529 5 2.7523 AR-118 1 2.9070 2.8903* 2 2.8918 3
2.8932 4 2.8846 5 2.8750 * - This experiment demonstrates that: (i)
the product of the present invention is permeable to air
(especially under vacuum and pressure) and (ii) the product of the
present invention would not have been discovered had this routine
technique used to determine the S.G. of the products of the present
invention and even those skilled in the art could overlook the
whole phenomenon of "porous" PCC, which is the basis of this
invention.
[0405] (E) Determination of the Specific Gravity (S.G.) of a
Product Calcined at 500.degree. C.--in a Water Pycnometer
[0406] It seems that the practice described in EXAMPLE 14(A) and
14(C) of determining the specific gravity (S.G.) of the PCC of the
present invention in tall oil, is quite tedious and it may lead to
mistakes, especially due to the adhering bubbles to hydrophobic
surface of the PCC particles, and also as a result of using
excessive sonication energies, which may cause the penetration of
the tall oil into the "pores" in the product of the present
invention. Therefore, it is recommended to use a simple and more
accurate test to distinguish between a product (process) of the
present invention and a product (process) of the prior art. The
test is based on the fact that the product of the present art,
after calcining it at 500.degree. C. for eight hours, looses the
hydrophobic compounds, but the "pores" that have been created in
the PCC particles during the process of the present invention, do
(can) not disappear. Once the hydrophobic nature of the particles
have been "eliminated", pure water can easily wet the surface of
these particles, and even to penetrate somewhat into "pores" that
are close to the surface. For this test, a skilled person in the
art does not need any sonication, but rather a gentle mixing for 5
mins. of the slurry of pure water (e.g. HPLC grade) and the
calcined PCC at 500.degree. C. for eight hours, using a laboratory
magnetic stirrer. Beyond that the steps of such an analysis are
very similar to those described in EXAMPLE 14(A)--steps 1-5, as
follows:
[0407] 1. The wet filter cake of the CaCO.sub.3 sample should be
calcined for eight hours at 500.degree. C. to remove all water and
organic molecules (the sample can be dried first at 120.degree. C.
for twelve hours. However, this option may be considered a G.M.P.,
but it is not all mandatory).
[0408] 2. A weighed quantity of the calcined CaCO.sub.3 sample (Wc)
(at about ambient temperature)+a weighed quantity of pure water
(Ww) (of a density that is practically 1.0 g/cm.sup.3) are
introduced into a 1 l. glass pycnometer (a 100 ml, 250 ml or 500 ml
pycnometers can also be used, depending on the accuracy of the lab.
balance).
[0409] 3. The mixture is stirred with a laboratory magnetic stirrer
for exactly 5 minutes.
[0410] 4. The magnet is "fished-out"; and more pure water is added
to fill the pycnometer to the desire volume.
[0411] 5. The pycnometer bottle is then evaluated at 21.degree.
C..+-.1.degree. C. for:
[0412] (a) the volume of the slurry--V
[0413] (b) the total net weight of the slurry--W
[0414] Based on the above measurements, the following was
calculated:
[0415] (1) from the equation: D=W/V g/cm.sup.3, the density of the
slurry;
[0416] (2) from the equation
1/D=[Wc(Ww+Wc)]/S.G. +[Ww(Ww+Wc)]/1.0,
[0417] the S.G. of the CaCO.sub.3 sample was calculated.
[0418] The results are as follows:
17TABLE 15b the results of EXAMPLE 14 (E) S.G. 500.degree. C. Test
Sample CO.sub.2 Dosage in Water # Code Active agent (%) (wt %)
(g/cm.sup.3) 28 Natural -- -- -- 2.71 CaCO.sub.3 29 GCC-8.sup.1 --
-- -- 2.73 30 GCC-8.sup.2 Decanoic A. N.A. 2.0 2.63 31 PCC.sup.3
N.A. N.A. N.A. 2.75 32 PCC.sup.4 Decanoic A. N.A. 2.0 2.69 33
OM-95.sup.A -- -- -- 2.63 34 UPCC.sup.B N.A. N.A. N.A. 2.63 35
BM-37 Decanoic A. 100.0 1* 2.67 36 AR-81 Decanoic A. 100.0 0.5 2.41
37 AR-83 Decanoic A. 100.0 1 2.33 38 AR-118 Decanoic A. 100.0 2
2.21 39 AR-119 Decanoic A. 100.0 5** 2.16 40 AR-135 Decanoic A.
100.0 1 2.35 41 AR-120 Decanoic A. 100.0 2*** 2.19 42 ARP-35
Decanoic A. 26.0 1.5 2.26 43 ARP-36 Decanoic A. 26.0 2.0 2.02 44
ARP-61 Decanoic A. 100.0 2.0 1.98 45 ARP-62-1 Decanoic A. 100.0 3.0
2.01 46 ARP-51 Lauric A. 26.0 1.5 2.15 47 ARP-65 Lauric A. 50.0 1.5
2.30 48 ARP-76 Undecylenic A. 50.0 1.5 2.24 49 ARP-77 Myristic A.
50.0 1.5 2.36 50 ARP-70 Stearic A. 50.0 1.5 2.18 51 ARP-71
Isostearic A. 50.0 1.5 2.63 52 ARP-72 Oleic A. 50.0 1.5 2.70 53
ARP-83 Palmitic A. 50.0 1.5 2.61 * - The sample was taken from the
batch mode of operation in -EXAMPLE 3 is quite pure calcite) ** - 5
g of AR-119 were dissolved in a 10% HCl solution. No decanoic acid
could be extracted or detected, as is expected of such molecules
when they are subjected to heating for 8 hours at 500.degree. C.
*** - 50 ppm of phosphoric acid were used in addition to the
decanoic acid. .sup.1 -"Girulite-8" CaCO3 powder (d50 = 3.5
microns) ex Polychrom - Israel. .sup.2 -"Girulite-8" CaCO3 powder
(d50 = 3.5 microns) ex Polychrom - Israel, which was coated using 2
wt % n-decanoic acid. .sup.3 - Commercial PCC - Aragonite; of
Specialty Minerals Inc. (SMI); Opacarb .RTM. A40. .sup.4 -
Commercial PCC - Aragonite; of Specialty Minerals Inc. (SMI);
Opacarb .RTM. A40, which was coated using 2 wt % n-decanoic acid.
.sup.5 - 50 ppm of phosphoric acid were used in addition to the
decanoic acid. .sup.A -Commercial ultrafine stearic acid coated -
UFT 95 GCC natural calcite (95 wt % pass 2.mu. size) ex
Omya-Pluess-Staufer - Switzerland. .sup.B - Commercial ultrafine
stearic acid coated - Ultraflex PCC calcite ex SMI - USA. N.A. -
Not Available.
[0419] (F) The Final Determination of the Specific Gravity (S.G.)
of a Product Calcined at 500.degree. C.
[0420] In most practical instances the use of EXAMPLE 14(A) and
EXAMPLE 14(C) or the use of only EXAMPLE 14(E) to determine the
specific gravity of the PCC products, may not cause any dispute and
a person skilled in the art can observe quite easily that the
product of the present invention is quite different from the
product of the prior art, by just observing the considerable
differences between the loose bulk density (L.B.D.) of the
aragonite particles of the present invention compared to those of
the aragonite particles of the prior art. (Table 13, 14, and 15).
However, when the specific gravity (S. G.) of the PCC particles, in
question, is quite close to 2.5 g/cm.sup.3, the accuracy of the
analytical method may be of prime importance. As it seems now, the
determination of the specific gravity of the PCC particles that
were calcined first is quite accurate, and that this procedure
according EXAMPLE 14(E) is also quite simpler and faster.
Therefore, the determination of the S.G. values should be conducted
as follows:
[0421] (a) The specific gravity (S.G.) determination should be
conducted according to. EXAMPLE 14(A) and EXAMPLE 14(C), and
separately, according to ii. EXAMPLE 14(E), (independently of the
results in i.).
[0422] (b) The lowest of the S.G. results obtained for a certain
product in (a), according to EXAMPLE 14(C) and according to EXAMPLE
14(E), independently, will determine whether the product (and the
process) is in the domain of the present invention (namely,
S.G.<2.5 g/cm.sup.3).
[0423] (G) Determination of the Loose Bulk Density (L.B.D.) of a
Product Dried at 120.degree. C.
[0424] The L.B.D. of a dry sample (at 120.degree. C. for twelve
hours) was determined, separately and independently of the S.G.
analyses, according to the ASTM D1895, as follows. A sample is
de-agglomerated gently in a mortar/pestle and sieved through a 0.6
mm screen. The fine powder that passes the screen is introduced
into a 250 ml plastic graduate cylinder, which is then mounted on a
screen-shaker (Rotap Model RX-29-10 ex W.S. Tyler Inc.--USA), the
apparatus being then operated for exactly 5 minutes. This test is
repeated three times for each sample, the reported L.B.D. being the
average of these tests. The results are reported already in Table
13 (above) and in Table 15c as follows:
18TABLE 15c the results of EXAMPLE 14 (G) L.B.D. L.B.D. Test Sample
CO.sub.2 Dosage 120.degree. C. 500.degree. C. # Code Active agent
(%) (wt %) (g/cm.sup.3) (g/cm.sup.3) 54 Natural -- -- -- 0.65 0.75
55 GCC-8.sup.1 -- -- -- 0.65 0.56 56 GCC-8.sup.2 Decanoic A. N.A.
2.0 0.64 0.56 57 PCC.sup.3 N.A. N.A. N.A. 0.71 0.55 58 PCC.sup.4
Decanoic A. N.A. 2.0 0.70 0.53 59 OM-95.sup.A -- -- -- 0.66 0.49 60
UPCC.sup.B N.A. N.A. N.A. 0.50 0.37 61 BM-37 Decanoic A. 100.0 1*
0.37.sup.BM 0.38 62 AR-81 Decanoic A. 100.0 0.5 0.31 0.23 63 AR-83
Decanoic A. 100.0 1 0.30 0.22 64 AR-118 Decanoic A. 100.0 2 0.25
0.18 65 AR-119 Decanoic A. 100.0 5** 0.29 0.19 66 AR-135 Decanoic
A. 100.0 1 0.31 0.24 67 AR-120 Decanoic A. 100.0 2*** 0.23 0.18 68
ARP-35 Decanoic A. 26.0 1.5 0.33 0.18 69 ARP-36 Decanoic A. 26.0
2.0 0.33 0.20 70 ARP-61 Decanoic A. 100.0 2.0 0.38 0.25 71 ARP-62-1
Decanoic A. 100.0 3.0 0.31 0.28 72 ARP-51 Lauric A. 26.0 1.5 0.31
0.17 73 ARP-65 Lauric A. 50.0 1.5 0.38 0.21 74 ARP-76.sup.6
Undecylenic 50.0 1.5 0.38 0.18 A. 75 ARP-77 Myristic A. 50.0 1.5
0.37 0.18 76 ARP-70.sup.7 Stearic A. 50.0 1.5 0.37 0.19 77 ARP-71
Isostearic A. 50.0 1.5 0.69 0.53 78 ARP-72 Oleic A. 50.0 1.5 0.70
0.53 79 ARP-83 Palmitic A. 50.0 1.5 0.86 0.54 * - The sample was
taken from the batch mode of operation in - EXAMPLE 3 is quite pure
calcite) ** - 5 g of AR-119 were dissolved in a 10% HCl solution.
No decanoic acid could be extracted or detected, as is expected of
such molecules when they are subjected to heating for 8 hours at
500.degree. C. *** - 50 ppm of phosphoric acid were used in
addition to the decanoic acid. .sup.1 -"Girulite-8 CaCO3 powder
(d50 = 3.5 microns) ex Polychrom - Israel. .sup.2 -"Girulite-8"
CaCO3 powder (d50 = 3.5 microns) ex Polychrom - Israel, which was
coated using 2 wt % n-decanoic acid. .sup.3 - Commercial PCC -
Aragonite; of Specialty Minerals Inc. (SMI); Opacarb .RTM. A40.
.sup.4 - Commercial FCC - Aragonite; of Specialty Minerals Inc.
(SMI); Opacarb .RTM. A40, which was coated using 2 wt % n-decanoic
acid. .sup.5 - 50 ppm of phosphoric acid were used in addition to
the decanoic acid. .sup.6 -The XRD spectrum and SEM of ARP-76 are
presented in FIG. 6 and FIG. 7, respectively. .sup.7 -The XRD
spectrum and SEM of ARP-70 are presented in FIG.8 and FIG. 9,
respectively. .sup.A -Commercial ultrafine stearic acid coated -
UFT 95 GCC natural calcite (95 wt % pass 2.mu. size) ex
Omya-Pluess-Staufer - Switzerland. .sup.B - Commercial ultrafine
stearic acid coated - Ultraflex FCC calcite ex SMI - USA. .sup.BM -
The product of the batch mode operation is a calcite FCC. N.A. -
Not Available.
[0425] The results in Tables 13 and in Table 15c represent the
products of the present invention if they have a L.B.D.<0.4
g/cm.sup.3. However, those results count, if the SSA (BET) of the
specific samples in test are <13 m.sup.2/g. Those samples that
do not meet this requirement, can only be tested according to
EXAMPLE 14(F).
[0426] Note:
[0427] It is worthwhile to observe the dramatic L.B.D. changes that
occur when the products of the present invention are subjected to
high temperature treatment (at 300.degree. C. and especially at
500.degree. C.), which is probably due to the thermal collapse of
the "porous" structure of these particles.
[0428] (H) Determination of the Specific Gravity (S.G.) in Oils of
Products Dried at 120.degree. C.
[0429] The specific gravity of various calcium carbonate particles
was measured in various oils, as described in Example 14(A). The
results indicate that the low S.G. values is not due to the tall
oil that we used, but it is rather common to many similar liquids.
In cases at which the S.G. values are close to 2.5 g/cm.sup.3, the
well-defined oleic acid (of purity >97%) can be used to resolve
any dispute, and in any case, the instructions in EXAMPLE 14(F) and
EXAMPLE 14(G), still prevail.
[0430] The Process Set Points--Continuous Mode of Operation:
[0431] 1. Rotor Speed=2500 rpm (Rotor Diameter=8.5 cm)
[0432] 2. pH=9.5.+-.0.2
[0433] 3. Temperature=85.degree. C..+-.3
[0434] 4. Carbon dioxide flow rate=2 m.sup.3/hr.
[0435] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10 wt.
%=.about.50-70 L.P.H. (to maintain the preset pH value).
[0436] 6. Active agent concentration=decanoic acid; 0-2 wt. % based
on CaCO.sub.3.
[0437] 7. Reactor Volume=30 l. (Diameter=8.7 cm).
[0438] The results are:
19TABLE 15d the results of EXAMPLE 14 (H): Liquid.sup.6,7 in
S.G..sup.7 Test Sample Dosage CO.sub.2 Pycno-- g/cm.sup.3 # Code
Active agent (wt %) (%) meter 120.degree. C. 80 GCC--8.sup.1 -- --
-- Sylvatal 2.63 20S 81 PCC.sup.3 -- -- N.A. Sylvatal 2.56 20S 82
GCC--8.sup.2 Decanoic A. 2.0 -- Sylvatal 2.23 20S 83 PCC.sup.4
Decanoic A. 2.0 N.A. Sylvatal 2.31 20S 84 AR--118.sup.5 Decanoic A.
2.0 100.0 Sylvatal 1.77 20S 85 AR--118.sup.5 Decanoic A. 2.0 100.0
Sylvatal-- 1.75 20S 86 AR--118.sup.5 Decanoic A. 2.0 100.0 Oleic
1.79 (>97%) 87 ARP--29 Decanoic A. 0.7 26.0 Sylvatal 1.98 20S 88
ARP--31 Decanoic A. 1.0 26.0 Sylvatal 1.65 20S 89 ARP--35 Decanoic
A. 1.5 26.0 Sylvatal 1.57 20S 90 ARP--35 Decanoic A. 1.5 26.0 Oleic
1.64 (>97%) 91 ARP--35 Decanoic A. 1.5 26.0 Oleic 1.62 (>97%)
92 ARP--35 Decanoic A. 1.5 26.0 Canola Oil 1.66 93 ARP--35 Decanoic
A. 1.5 26.0 Soybean 1.60 Oil 94 ARP--35 Decanoic A. 1.5 26.0
Sunflower 1.58 Oil 95 ARP--35 Decanoic A. 1.5 26.0 Corn Oil 1.61 96
ARP--35 Decanoic A. 1.5 26.0 Mazola 1.59 Oil 97 ARP--35 Decanoic A.
1.5 26.0 Olive Oil 1.63 98 ARP--36 Decanoic A. 2.0 26.0 Sylvatal
1.34 20S 99 ARP--36 Decanoic A. 2.0 26.0 Sylvatal-- 1.35 20S 100
ARP--36 Decanoic A. 2.0 26.0 Oleic 1.36 (>97%) 101 ARP--37
Decanoic A. 2.0 15.0 Sylvatal 1.28 20S 102 ARP--51 Lauric A. 1.5
26.0 Sylvatal 1.78 20S 103 ARP--61 Decanoic A. 2.0 100.0 -- -- 104
ARP--62--1 Decanoic A. 3.0 100.0 -- -- 105 ARP--65 Lauric A. 1.5
50. Sylvatal 2.04 20S 106 ARP--70 Stearic A. 1.5 50 Sylvatal 2.36
20S 108 ARP--71 Isostearic A. 1.5 50 Sylvatal 2.71 20S 109 ARP--72
Oleic A. 1.5 50 Sylvatal 2.58 20S 110 ARP--76 Undecylenic 1.5 50
Sylvatal 2.02 20S A. 111 ARP--77 Myristic A. 1.5 50 Sylvatal 2.15
20S 112 ARP--77/1 Palmitic A. 1.5 50 Sylvatal 2.61 20S 113 ARP--78
Linoleic A. 1.5 50 Sylvatal 2.59 20S .sup.1 --"Girulite--8" CaCO3
powder (d50 = 3.5 microns) ex Polychrom--Israel. .sup.2
--"Girulite--8" CaCO3 powder (d50 = 3.5 microns) ex
Polychrom--Israel, which was coated using 2 wt % n--decanoic acid.
.sup.3 --Commercial PCC--Aragonite; of Specialty Minerals Inc.
(SMI); Opacarb .RTM. A40. .sup.4 --Commercial PCC--Aragonite; of
Specialty Minerals Inc. (SMI); Opacarb .RTM. A40, which was coated
using 2 wt % n--decanoic acid. .sup.5 --AR--118, a product of the
present invention, mentioned already in EXAMPLE 14 (A), above.
.sup.6 --The specific gravity of the liquids were as follows: Oleic
A. = 0.887 g/cm.sup.3; Tall Oil (Sylvatal 20S ex Arizona
Chemical--USA) = 0.930 g/cm.sup.3; Refined Canola Oil (ex
Milumor--Israel) = 0.910 g/cm.sup.3; Refined Corn Oil (ex Milumor
--Israel) = 0.910 g/cm.sup.3; Refined Corn Oil (Mazola ex
Bestfoods--USA) = 0.91 5 g/cm.sup.3; Refined Soybean Oil (ex
Milumor --Israel) = 0.920 g/cm.sup.3; Refined Sunflower Oil (ex
Milumor--#Israel) = 0.918 g/cm.sup.3; Cold Pressed olive Oil (ex
Shemen Industries--Israel) = 0.893 g/cm.sup.3 .sup.7 --The S.G.
analyses were conducted at 21.degree. C. .+-. 1.degree. C.
N.A.--Not available
EXAMPLE 15
[0439] Preparation of Exterior White Paint--Hercules Inc.
[0440] The procedure for the preparation of this paint was obtained
from Hercules Inc.; Cellulose & Protein Products D.;
Wilmington, Del. 19899 (USA). The procedure followed quite closely
the Celanese Resins Formulation No. EP-48-222 for the production of
this Exterior White Paint (Vinyl Acetate & Acrylate).
[0441] (A) The ingredients Used for the 52% PVC Paint and Their
Function are as Follows:
[0442] 1. Tap water.
[0443] 2. Nopco NDW defoamer.
[0444] 3. Cellosize QP 15000 thickener (hydroxy ethyl
cellulose).
[0445] 4. Disperse One (45% N.V.) (dispersant).
[0446] 5. Synperonic NP10 surfact; wetting agent.
[0447] 6. Kronos 2160 TiO.sub.2 pigment.
[0448] 7. Synthetic sodium aluminum silicate (p820) (spacer).
[0449] 8. Kaolin clay (D.sub.50=3.1 micron)(spacer).
[0450] 9. CaCO.sub.3 (spacer)--A GCC product of Polichrom Ltd.,
Israel.
[0451] 10. Talc (D.sub.50=12.3 micron)(spacer).
[0452] 11. PCC--Aragonite of the present invention (samples used
contained >80% CaCO.sub.3 in the wet cake products before their
drying; no diminution operation took place prior to this use.
Namely, the PCC--Aragonite used is not necessarily yet optimized
for its purpose).
[0453] 12. Copolymer vinyl acetate acrylate (55% N.V.)
(emulsion).
[0454] 13. Butyl diglycol acetate solvent (coalescent agent).
[0455] 14. Kathon LXE preservative.
[0456] 15. 25% Ammonia (base).
[0457] 16. Tap water.
[0458] Tap water (1), defoamer (2) and thickener (3) were added to
a plastic container (d=20 cm; h=30 cm) equipped with a disk (d=8
cm) attached to a Dissolver (Homo Dispers Model HD-550 (0.75 HP) of
Hsiangtai Machinery Industry Co. Ltd.; Taiwan). The mixture was
stirred at 500 rpm for 5 minutes, after which the dispersant (4)
and the wetting agent (5) were added, and stirring was continued at
500 rpm for additional 5 minutes. At this point the stirring speed
was increased to 1500 rpm and the respective ingredients for the
respective formulations 1-10 were added consecutively, each
ingredient over a 5 minute period, according to the order in the
above list of reagents (6-16).
[0459] The physical properties of the above paints were measured,
including the most important property--the hiding power (%) of 90
.mu.m layers of paint were determined with an ACS instrument
(Applied Color Systems) and the results are given in the following
Tables 19 and 20:
20TABLE 19 the results of EXAMPLE 15 Exterior White Paint -
Hercules Inc. Evaluation of the 52% PVC Paints Based on the
Precipitated Aragonite Calcium Carbonate Particles of the Present
Invention (PCC - Aragonite) 1 2 3 4 5 6 Raw Material % (wt) Tap
Water 25.0 25.0 25.0 25.0 25.0 25.0 Defoamer 0.1 0.1 0.1 0.1 0.1
0.1 Thickener 0.3 0.3 0.3 0.3 0.3 0.3 (15K) Dispersant 0.9 0.9 0.9
0.9 0.9 0.9 (45%) Wetting Agent 0.35 0.35 0.35 0.35 0.35 0.35
TiO.sub.2; Kronos 14.0 9.0 9.0 9.0 9.0 8.4 Silicate 3.7 3.7 3.7 3.7
4.0 3.9 CaCO.sub.3 - GCC 7.0 -- -- -- -- -- Kaolin Clay 6.5 6.5 6.5
6.5 10.7 6.8 Talc 6.3 -- -- -- -- -- PCC- -- 17.75 17.75 17.75
13.00 17.75 Aragonite* Copolymer 24.5 25.5 25.5 25.5 25.4 25.4
(55%) Coalescent 0.1 0.1 0.1 0.1 0.1 0.1 Agent Preservative 0.5 0.5
0.5 0.5 0.5 0.5 Ammonia 0.3 0.3 0.3 0.3 0.3 0.3 Tap Water 10.45
10.0 10.0 10.0 10.35 10.2 Total 100. 100. 100. 100. 100. 100. The
Characteristics of the Paint Solids (%) 50.98 50.98 50.98 50.98
50.67 50.82 P.V.C. (%) 51.77 51.32 51.32 51.32 51.51 51.55 Hiding
Power 94.0 94.4 94.9 95.5 95.1 94.9 (%) Viscosity 92.0 92.0 93.2
98.0 100.0 98.0 (K.U.) Hegman 4.5 5.5 5.5 5.0 4.0 4.5 Bulk Density
1.317 1.259 1.257 1.248 1.226 1.221 Saving of -- 35.7 35.7 35.7
35.7 40.0 TiO.sub.2 (%) Weight -- 4.4 4.6 5.2 6.9 7.3 Saving (%)
Formulation Sample Active Active Agent No. Pigment* Code Agent %
(wt) 1 Reference Paint -- -- -- 2 PCC - Aragonite AR-81 Decanoic
0.5 3 PCC - Aragonite AR-83 Decanoic 1.0 4 PCC - Aragonite AR-118
Decanoic 2.0 5 PCC - Aragonite AR-119 Decanoic 5.0 6 PCC -
Aragonite AR-118 Decanoic 2.0
[0460]
21TABLE 20 the results of EXAMPLE 15 Exterior White Paint -
Hercules Inc. Evaluation of the 52% Pvc Paints Based on the
Precipitated Aragonite Calcium Carbonate Particles of the Present
Invention (PCC - Aragonite) 1 7 8 9 10 Raw Material % (wt) Tap
Water 25.0 25.0 25.0 25.0 25.0 Defoamer 0.1 0.1 0.1 0.1 0.1
Thickener (15K) 0.3 0.3 0.3 0.3 0.3 Dispersant (45%) 0.9 0.9 0.9
0.9 0.9 Welling Agent 0.35 0.35 0.35 0.35 0.35 TiO.sub.2; Kronos
14.0 7.0 7.0 6.3 12.0 Silicate 3.7 4.8 4.2 4.2 3.7 CaCO.sub.3-GCC
7.0 -- -- -- -- Kaolin Clay 6.5 7.1 12.5 13.1 6.5 Talc 6.3 -- -- --
-- PCC-Aragonite* -- 17.75 13.0 13.0 15.3* Copolymer (55%) 24.5
25.5 26.0 26.0 24.5 Coalescent Agent 0.1 0.1 0.1 0.1 0.1
Preservative 0.5 0.5 0.5 0.5 0.5 Ammonia 0.3 0.3 0.3 0.3 0.3 Tap
Water 10.45 10.3 9.75 9.85 10.45 Total 100. 100. 100. 100. 100. The
Characteristics of the Paint Solids (%) 50.98 50.98 50.98 50.98
50.98 P.V.C. (%) 51.77 51.32 51.32 51.32 51.91 Hiding Power (%)
94.0 94.2 94.3 94.0 92.7 Viscosity (K.U.) 92.0 96.8 98.8 98.0 90.2
Hegman 4.5 4.5 4.5 4.5 4.5 BulkDensity 1.317 1.179 1.159 1.224
1.300 Saving of TiO.sub.2 (%) -- 50.0 50.0 55.0 14.3 Weight Saving
(%) -- 10.5 12.0 7.0 1.3 Formulation Sample Active Active Agent No.
Pigment* Code Agent % (wt) 1 Reference Paint -- -- -- 7 PCC -
Aragonite AR-118 Decanoic 2.0 8 PCC - Aragonite AR-119 Decanoic 5.0
9 PCC - Aragonite AR-119 Decanoic 5.0 10 PCC - Aragonite C** N.A.
N.A. **Commercial PCC - Aragonite; of Specialty Minerals Inc.
(SMI); Opacarb .RTM. A40.
[0461] (B) The Ingredients of the 32% PVC Paint and Their Function
are as Follows:
[0462] 1. Tap water.
[0463] 2. Nopco NDW defoamer.
[0464] 3. Cellosize QP 15000 thickener (hydroxy ethyl
cellulose).
[0465] 4. Disperse One (45% N.V.) (dispersant).
[0466] 5. Synperonic NP10 surfactant; wetting agent.
[0467] 6. Kronos 2160 TiO.sub.2 pigment. 7.
[0468] 7. Synthetic Na--Al silicate (p820) (spacer).
[0469] 8. Kaolin clay (D.sub.50=3.1 micron)(spacer)
[0470] 9. CaCO.sub.3 (spacer)--a GCC product of Polichrom Ltd.,
Israel
[0471] 10. Talc (D.sub.50=12.3 micron)(spacer)
[0472] 11. PCC--aragonite of the present invention (samples used
contained >80% CaCO.sub.3 in the wet cake products before their
drying; no diminution operation took place prior to this use.
However, the PCC--aragonite used is not necessarily yet optimized
for its purpose).
[0473] 12. Propylene glycol (solvent).
[0474] 13. Copolymer vinyl acetate acrylate (55% N.V.)
(emulsion).
[0475] 14. Butyl diglycol acetate solvent (coalescent agent).
[0476] 15. Kathon LXE preservative.
[0477] 16. 25% Ammonia (base).
[0478] 17. Tap water.
[0479] Tap water (1), defoamer (2) and thickener (3) were added to
a plastic container (d=20 cm; h=30 cm) equipped with a disk (d=8
cm) attached to a Dissolver (Homo Dispers Model HD-550 (0.75 HP) of
Hsiangtai Machinery Industry Co. Ltd.; Taiwan). The mixture was
stirred at 500 rpm for 5 minutes, after which the dispersant (4)
and the wetting agent (5) were added, and stirring was continued at
500 rpm for additional 5 minutes. At this point the stirring speed
was increased to 1500 rpm and the respective ingredients for the
respective formulations 1-10 were added consecutively, each
ingredient over a 5 minute period, according to the order in the
above list of reagents (6-15).
[0480] The physical properties of the above paints were measured,
including the most important property--the hiding power (%) of 90
.mu.m layers of paint were determined with an ACS instrument
(Applied Color Systems) and the results are given in the following
Table 21:
22TABLE 21 the results of EXAMPLE 15 Exterior White Paint -
Hercules Inc. Evaluation of the 32% Pvc Paints Based on the
Precipitated Aragonite Calcium Carbonate Particles of the Present
Invention (PCC - Aragonite) 11 12 13 14 15 16 Raw Material % (wt)
Tap Water 17.8 17.8 17.8 17.8 17.8 17.8 Defoamer 0.15 0.15 0.15
0.15 0.15 0.15 Thickener 0.22 0.22 0.22 0.22 0.22 0.22 (15K)
Dispersant 0.60 0.60 0.60 0.60 0.60 0.60 (45%) Welling Agent 0.34
0.34 0.34 0.34 0.34 0.34 TiO.sub.2; Kronos 22.5 20.0 20.0 19.0 18.0
19.0 Silicate 2.25 2.25 2.25 2.25 2.25 -- CaCO3-GCC 5.0 -- -- -- --
-- PCC- -- 7.5 7.5 8.5 9.25 13.0 Aragonite* Propylene 2.70 2.70
2.70 2.70 2.70 2.70 Glycol Copolymer 37.45 37.45 37.45 37.45 38.0
33.4 (55%) Coalescent 0.18 0.18 0.18 0.18 0.18 0.18 Agent
Preservative 0.45 0.45 0.45 0.45 0.45 0.45 Ammonia 0.30 0.30 0.30
0.30 0.30 0.30 Tap Water 10.06 10.06 10.06 10.06 9.76 11.86 Total
100. 100. 100. 100. 100. 100. The Characteristics of the Paint
Solids (%) 50.35 50.35 50.35 50.35 50.35 50.37 P.V.C. (%) 32.59
32.64 32.64 32.93 32.64 36.73 Hiding Power 91.0 91.4 91.4 91.0 90.8
91.0 (%) Viscosity 87.2 98.0 97.4 96.2 87.8 90.2 (K.U.) Hegman 5.5
5.5 5.5 5.5 5.0 5.5 Bulk Density 1.18 1.128 1.127 1.109 1.005 1.073
Saving of -- 11.1 11.1 15.5 20.0 15.5 TiO.sub.2 (%) Weight Saving
-- 4.4 4.5 6.0 14.8 6.8 (%) Formulation Sample Active Active Agent
No. Pigment* Code Agent % (wt) 11 Reference Paint -- -- -- 12 PCC -
Aragonite AR-118 Decanoic 2.0 13 PCC - Aragonite AR-119 Decanoic
5.0 14 PCC - Aragonite AR-119 Decanoic 5.0 15 PCC - Aragonite
AR-119 Decanoic 5.0 16 PCC - Aragonite AR-118 Decanoic 2.0
[0481] Notes:
[0482] 1. The particulate precipitated aragonite calcium carbonate
of the present invention (PCC-Aragonite) can be used to produce
paints without a substantial prior size reduction, except that
effected by the mixing system of the production of the paint, which
is anyway being used in this art to thoroughly disperse the
pigments in the various formulations.
[0483] 2. Though the particulate precipitated aragonite calcium
carbonate of the present invention (PCC-Aragonite) is not yet
optimized for its use in the production of paints and though the
formulations used are by no means optimized, still this product is
able to substitute over 50% of the expensive titanium oxide pigment
without any deterioration of the resulting paint, as it manifested
by the hiding power measured.
[0484] 3. As the coatings (paints) are being sold and used by
volume, and not by weight, the additional saving resulting from
using the particulate precipitated aragonite calcium carbonate of
the present invention (PCC-Aragonite) can surpass 10% on all the
constituents of the coating, including the titanium oxide.
[0485] 4. For simplicity in formulating the above mentioned paints,
dry samples of The particulate precipitated aragonite calcium
carbonate of the present invention (PCC-Aragonite), were used.
However, wet filter cakes that contain even more water than 20% wt.
%, based on wet CaCO.sub.3 cake, can be used, provided that this
water is being taken in account. However, on an industrial scale,
dry PCC-Aragonite will be rarely used, due to the economy of using
the wet product.
[0486] (C) A Comparison of Modified Paint Formulations Containing
Various GCC/PCC
[0487] The experimental of EXAMPLE 15(A) was repeated, except that
the paint compositions contained only one selected PCC/GCC pigment
(>50 wt %) at a time and the minimum required ingredients that
were necessary to prepare these basic modified paint formulations.
A standard (STD) interior paint formulation was used as a general
reference.
[0488] The paint compositions are as follows:
23TABLE 22 STD vs. Modified paint formulation of EXAMPLE 15 (C) Raw
Material STD Modified Water 28.25 28.87 Defoamer 0.30 0.38
Thickener 0.20 0.09 Dispersant 0.40 0.00 Wetting Agent 0.30 0.00
TiO.sub.2 7.5 0.00 Silicate 3.5 0.00 Talc 13.0 0.00 G.C.C. 34.0
0.00 AR-pigment 0.00 57.28 Propylene glycol 1.00 0.56 Copolymer -
50% solids 11.40 12.72 Biocide 0.15 0.10 Total 100.0 100.0 % Solids
in paint 63.7 64.3
[0489] The physical and optical properties of the pigments used and
the paint obtained are reported as follows:
24TABLE 23 the pigments properties in EXAMPLE 15 (C) S.S.A.
PSD.sup.4 Pigment Active Dosage CO.sub.2 (BET) .mu. Paint Code
Agent (wt %).sup.3 (v %( (m.sup.2/g) D.sub.90 D.sub.50 STD -- -- --
-- -- -- -- 1 PCC.sup.1 -- -- -- 12.0 2.0 0.8 2 GCC.sup.2 -- -- --
4.0 5.0 2.1 3 ARP-29 Decanoic A. 0.7 26.0 5.7 4.49 1.98 4 ARP-31
Decanoic A. 1.0 26.0 6.2 3.54 1.68 5 ARP-34 Decanoic A. 1.5 100
11.1 2.68 1.27 6 ARP-35 Decanoic A. 1.5 26.0 11.5 3.0 1.65 7 ARP-36
Decanoic A. 2.0 26.0 15.4 2.51 0.73 8 ARP-37 Decanoic A. 2.0 15.0
10.9 2.20 0.93 9 ARP-51 Lauric A. 1.5 26.0 4.14 2.39 10 ARP-61
Decanoic A. 2.0 100 15.5 1.8 0.68 11 APR-65 Lauric A. 1.5 50.0 8.2
5.4 3.1 12 ARP-70 Stearic A. 1.5 50.0 4.3 5.3 1.6 13 ARP-71
Isostearic 1.5 50.0 1.9 9.3 5.9 14 ARP-72 Oleic A. 1.5 50.0 3.7
10.9 6.5 15 ARP-76 Undecylenic 1.5 50.0 13.1 2.7 1.5 A. 16 ARP-77
Myristic A. 1.5 50.0 5.2 3.8 2.3 17 ARP-83 Palmitic A. 1.5 50.0
.sup.1- Commercial stable PCC Slurry of Aragonite (Opacarb .RTM.
A40 ex SMI - USA). Calculation of the S.G. of the aragonite
particles in a 69.6% commercial slurry resulted in 2.83 g/cm.sup.3.
Naturally, this slurry was used to produce the paint above. .sup.2-
CaCO3 (spacer) - a GCC (Calcite ex Polichrom Ltd. - Israel).
.sup.3- Calculated as the acid form, based on the CaCO3. .sup.4-
The PCC of the present invention has not undergone any size
reduction prior to its use, except the size reduction that may
happen during regular operations.
[0490]
25TABLE 24 the paint properties in EXAMPLE 15 (C) S.G..sup.4
500.degree. C. Paint Paint Pigment Active Dosage CO.sub.2 Water
Hiding.sup.6 Code Code Agent (wt %).sup.3 (v %( (g/m.sup.3)
Gloss.sup.5 Power STD -- -- -- -- -- 2.1 83.7 1 PCC -- -- --
2.69.sup.1 31.9 88.0 2 GCC.sup.2 -- -- -- 2.62 2.2 80.9 3 ARP-29
Decanoic A. 0.7 26.0 2.32 3.0 92.6 4 ARP-31 Decanoic A. 1.0 26.0
2.29 3.6 96.5 5 ARP-34 Decanoic A. 1.5 100 2.38 7.5 96.3 6 ARP-35
Decanoic A. 1.5 26.0 2.26 4.0 99.6 7 ARP-36 Decanoic A. 2.0 26.0
2.02 5.5 98.1 8 ARP-37 Decanoic A. 2.0 15.0 1.90 5.2 99.5 9 ARP-51
Lauric A. 1.5 26.0 2.15 4.3 94.8 10 ARP-61 Decanoic A. 2.0 100 1.98
11.5 98.3 11 APR-65 Lauric A. 1.5 50.0 2.25 4.0 93.7 12 ARP-70
Stearic A. 1.5 50.0 2.18 2.6 94.1 13 ARP-71 Isostearic 1.5 50.0
2.63 1.8 70.0 14 ARP-72 Oleic A. 1.5 50.0 2.70 1.9 74.9 15 ARP-76
Undecylenic 1.5 50.0 2.38 4.7 96.8 A..sup.7 16 ARP-77 Myristic A.
1.5 50.0 2.36 3.5 95.1 17 ARP-83 Palmitic A. 1.5 50.0 2.0 79.3
.sup.1- Commercial PCC a stable slurry of Aragonite (Opacarb .RTM.
A40 ex SMI - USA). .sup.2- CaCO3 (spacer) - a GCC (Calcite ex
Polichrom Ltd. - Israel). .sup.3- Calculated as the acid form,
based on the CaCO3. .sup.4- Measured according to Example 14 (E) in
pure water, after calcining at 500.degree. C. for eight hours.
.sup.5- Measured at 60.degree. with a Glossmeter (Minigloss 101N ex
Sheen Instruments - England). .sup.6- The hiding power of a 90.mu.
layer was measured with a reflectometer (Ref. 310 Sheen-Opac ex
Sheen Instruments - England). .sup.7- This compound, for example,
can be brominated and thus serves also as a flame retardant.
[0491] Notes:
[0492] 1. The gloss increases as the v % of the CO.sub.2 in the
feed gas increases. The gloss increases as the wt % of the active
agent increases. The gloss increases as the specific gravity (S.G.)
of the PCC decreases.
[0493] These facts are particularly important in controlling the
PCC of the present invention, and more specifically, in formulating
high-gloss paper coatings on the one hand and it is particularly
important in formulating low-gloss paints on the other hand.
[0494] 2. The opacity increases as the wt % of the active agent
increases. The opacity increases as the V % of the air in the feed
gas increases. The opacity increases as the specific gravity (S.G.)
of the PCC decreases.
[0495] n-Decanoic acid seems to exhibit, thus far, the best
performance, however, the optimal w % seems to be in the range
between 1.5 wt % to 3 wt % for this purpose of forming products of
high hiding power.
EXAMPLE 16
[0496] The preparation of the Plastic (Polypropylene Copolymer--PP)
Formulations
[0497] The composition of the various formulations was as follows:
40% Filler, 0.3% antioxidant (irganox B225 ex Ciba Specialty
Chemicals--Switzerland), 0.5% lubricant (Wax PE 520 ex
Hoechst-Celanese--USA) and 59.2% polypropylene copolymer
(Capilene-TR50 ex Carmel Olefins--Israel).
[0498] (A) Preparation of the Particulate Precipitated
Aragonite
[0499] Three samples of particulate precipitated aragonite of the
present invention were used and three of the top quality commercial
samples were used for comparison. The preparation parameters of the
aragonite samples and their properties are given in Table 25, as
follows:
[0500] The Process Set Points--Continuous Mode of Operation:
[0501] 1. Rotor Speed=4000 rpm (Tip Speed .about.10 m/sec.)
[0502] 2. pH=9.5.
[0503] 3. Temperature=90.degree. C.
[0504] 4. Carbon dioxide flow rate=180 L.P.H. (liters/hour).
[0505] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10 wt.
%=.about.6 L.P.H. (to maintain the preset pH value).
[0506] 6. Active agent concentration=decanoic acid; 0.5; 1; 2 wt. %
based on CaCO.sub.3.
26TABLE 25 the results of EXAMPLE 16(A) Aragonite SSA Sample
Aragonite + Calcite D.sub.90.sup.1 B** (BET) # Code Active agent
(wt. %) XRD .mu. (%) m.sup.2/g 1 AR-213 Decanoic Acid 0.5* 93-96%
5.92 95.8 3.6 2 AR-214 Decanoic Acid 1.0* 93-96% 4.38 98.3 6.4 3
AR-215 Decanoic Acid 2.0* 96-98% 1.56 98.2 12.8 *- 50 ppm of
phosphoric acid were used in addition to the decanoic acid to
increase the aspect ratio of the acicular aragonite. **-
Brightness. .sup.1- The PCC of the present invention has not
undergone any size reduction prior to its use, except the size
reduction that may happen during regular operations.
[0507] (B) Compounding of the Plastic (Polypropylene Copolymer)
Formulations
[0508] The formulations were processed in a co-rotating twin-screw
compounder (L/D=24 ex Dr. Collin--Germany). The compounding
conditions are given in Table 26, as follows:
27TABLE 26 the compounding conditions of EXAMPLE 16(B) Melt Screws
Temp. Speed Pressure Torque # Filler (.degree. C.) (rpm) (bar)
(N.m) 1 AR-215 203 200 16 .+-. 5 42 .+-. 5 2 AR-214 203 200 15 .+-.
5 40 .+-. 2 3 AR-213 202 200 18 .+-. 5 43 .+-. 2 4 OM-95.sup.A 201
175 30 .+-. 5 63 .+-. 2 5 UPCC.sup.B 203 174 30 .+-. 5 60 .+-. 3 6
UTALC.sup.C 202 195 17 .+-. 2 49 .+-. 2 .sup.ACommercial ultrafine
stearic acid coated - UFT 95 GCC natural calcite (95 wt % pass
2.mu. size) ex Omya-Pluess-Staufer - Switzerland. .sup.BCommercial
ultrafine stearic acid coated - Ultraflex PCC calcite ex SMI - USA.
.sup.CCommercial ultrafine talc - Ultratalc 609 ex SMI - USA.
[0509] Note:
[0510] The results of the compounding step, in Table 16b, indicate
that the PCC of the present invention is superior over the
commercial products of the top qualities and top prices in the
market.
[0511] (C) Injection of the Plastic (Polypropylene Copolymer)
Formulations
[0512] The resulting granules were fed to an injection machine (25
t ex Dr. Boy--Germany). Specimens of 127.times.12.7.times.3.2 mm we
produced. The injection conditions are given in Table 27 as
follows:
28TABLE 27 the compounding conditions of EXAMPLE 16c Injection
Injection Injection Temp. Speed Pressure Pressure # Filler
(.degree. C.) (cm.sup.3/sec.) (bar) (bar) 1 AR-215 170-180 66 250
250 2 AR-214 170-180 66 250 250 3 AR-213 170-180 66 250 300 4
OM-95.sup.A 170-180 66 250 300 5 UPCC.sup.B 170-180 66 400 400 6
UTALC.sup.C 170-180 66 400 400 .sup.Aa commercial ultrafine stearic
acid coated GOC ex Omya-Pluess-Staufer - Switzerland. .sup.Ba
commercial ultrafine stearic acid coated - Ultraflex PCC ex SMI -
USA. .sup.Ca commercial ultrafine talc - Ultratalc 609 ex SMI -
USA.
[0513] Note:
[0514] Only OM-95 behaves quite close to the PCC of the present
invention (AR-213, Ar-214 and AR-215) in the injection compartment.
The relatively (very) expensive talc is unable to compete with
AR-213, Ar-214 and AR-215.
[0515] (D) The Mechanical Tests
[0516] The resulting specimens were conditioned at 25.degree. C.
under 50% RH for at least 72 hrs. before testing them.
[0517] Two test were performed as follows:
[0518] Flexure testing (3 point) was conducted according to ASTM
D-790.
[0519] Impact testing--Izod notched was conducted according to ASTM
D-256.
[0520] The results are given in table 28, as follows:
29TABLE 28 the results of the mechanical tests of EXAMPLE 16d Flex.
Modulus Impact # Filler (Mpa) J/m 0 --* 793 538 1 AR-215 1603 .+-.
60 225 .+-. 21.7 2 AR-214 1872 .+-. 90 281 .+-. 18.7 3 AR-213 1735
.+-. 31 397 .+-. 14.5 4 OM-95.sup.A 1107 .+-. 20 192 .+-. 20.4 5
UPCC.sup.B 1006 .+-. 13 51 .+-. 6.4 6 UTALC.sup.C 1749 .+-. 54 151
.+-. 5.3 *Capilene - TR50 as reported by its producer. .sup.Aa
commercial ultrafine stearic acid coated GOC ex Omya-Pluess-Staufer
- Switzerland. .sup.Ba commercial ultrafine stearic acid coated -
Ultraflex FCC ex SMI - USA. .sup.Ca commercial ultrafine talc -
Ultratalc 609 ex SMI - USA.
[0521] Notes:
[0522] 1. Fillers are usually added to the polypropylene (PP)
formulations to increase their flexural modulus. In the proper
loading range, the higher the concentration of the filler, the
higher is the flexural modulus. However, as the concentration of
the filler increases, the Izod impact characteristics are decreased
dramatically. Namely, the final loading of the filler in the
polymer is the result of optimizing both characteristics of the
final (consumer) products. Under the same experimental conditions,
the particulate precipitated calcium carbonate of the present
invention (AR-213, Ar-214 and AR-215) are by far superior over
commercial products of the highest quality in the market.
[0523] 2. The overall properties of the PCC of the present
invention are superior over the commercial products of top
qualities in the market, as it may leads to faster operations and
to better (consumer) products.
EXAMPLE 17
[0524] Adsorption Experiments Using the PCC of the Present
Invention
[0525] The PCC/GCC particles of the prior art can adsorb limited
quantities of liquids and in all cases that will take place quite
fast onto their surface.
[0526] The PCC of the present invention exhibits a varied behavior,
depending on the environment at which these particles are
located.
[0527] (A) The PCC Particles of the Present Invention in the Gas
Phase
[0528] The results that were obtained by using the gas pycnometer
to determine the specific gravity (S.G.) of the product of the
present invention (c.f. EXAMPLE 14(D)) do not indicate at all that
these particles contain some kind of "pores" or "bubbles" or
"blisters" to any extend. However, the following results will
demonstrate that this view is entirely wrong.
[0529] (B) The PCC Particles of the Present Invention in Stable
Aqueous Dispersions
[0530] The Process Set Points--Continuous Mode of Operation:
[0531] 1. Rotor Speed=1200 rpm (Rotor Diameter=10 cm)
[0532] 2. pH=9.5.+-.0.2
[0533] 3. Temperature=85.degree. C..+-.2
[0534] 4. Carbon dioxide flow rate=2.5 m.sup.3/hr.
[0535] 5. Aqueous calcium hydroxide slurry (of Shfeya) -10 wt.
%=.about.80-100 L.P.H. (to maintain the preset pH value).
[0536] 6. CO.sub.2 (v %) in the feed gas=30%
[0537] 7. Active agent concentration=decanoic acid; 1.5 wt. % based
on CaCO.sub.3.
[0538] 8. Reactor Volume=50 l. (Diameter=30 cm).
[0539] 9. The product (of the present invention)--ARP-73
[0540] Preparation of Stable Slurries (60-70 wt %) in Water:
[0541] The wet cake of ARP-73, which was obtained after dewatering
of the product, was mixed with about 2 wt % dispersant (resulting
in calculated .about.1:1 dry weight ratio; Dispex N-40 (.about.45
wt % solids) ex Allied Colloids--GB) and water in a 10 l. (d=30 cm)
tank that was equipped with laboratory dissolver (DVH-020-18/6; 2.5
HP ex a Dantco Inc.--USA; rotor diameter=10 cm) for 60 mins. At
1200 rpm. The resulting slurries exhibit the following
characteristics:
30TABLE 29 the results of EXAMPLE 17 (B) S.G. of Slurry Solids
(g/cm.sup.3).sup.4 S.G. of Solids Sample In Slurry After After
ARP-73 Code (wt %).sup.1 Preparation.sup.1 7 Days.sup.2
(g/cm.sup.3).sup.1 ARP-73-1 60.2 1.47 1.47 2.13 ARP-73-2 69.3 1.61
1.61 2.20 ARP-73-3 63.0 1.55 .sup. 1.68.sup.3 2.30 .sup.1Was
measured and/or calculated immediately after the preparation of the
slurry. .sup.2Was measured and calculated. .sup.3The addition of 2
wt % sodium dioctylsulfosuccinate (75% in ethanol; ex Cytec USA) -
a potent wetting agent - to the water at the end of the preparation
stage (+ a short stirring thereafter), led to the formation of a
very dense and viscose mass after 7 days (most of the water have
been absorbed by the PCC of the present invention!), which could
not be stirred. This mass was disintegrated by adding more of the
wetting agent and stirring the mass. The S.G. was then measured and
calculated to be >2.79 g/cm.sup.3. Such behavior is
unprecedented in the prior art of PCC/GCC products. .sup.4The low
S.G. values are also observed in the paint compositions containing
the products of the present invention, which gives rise to an
additional advantage, as was explained already in EXAMPLE 15.
[0542] (C) Dispersions of the PCC Particles of the Present
Invention in Organic Solvents
[0543] Attempts to obtain stable slurries of the PCC of the present
invention in organic solvents such as alcohols (e.g. ethanol,
isopropanol), ketones (e.g. acetone, methyl ethyl ketone), esters
(e.g. methyl acetate, ethyl acetate), aromatic solvents (e.g.
toluene, xylene, chlorobenzene, o-dichlorobenzene), and many
others, result in the formation of mixtures in which the specific
gravity (S.G.) of the PCC particles is >2.5 g/cm.sup.3 (usually,
water and oils (e.g. those that are mentioned as liquids in Example
14), permeate very slowly during very long periods and in some
cases it is impractical to measure their permeation rates). More
polar solvents such as ethylene glycol penetrate more slowly into
the PCC of the present invention, and eventually the S.G. values
reach the ultimate value that characterizes calcite, and especially
aragonite, calcium carbonate (namely, .about.2.7-2.9 g/cm.sup.3,
depending on the specific crystallographic purity of the tested
products). Naturally, the increase of the S.G. is dependent on many
factors such as pressure, temperature, viscosity, surface tension,
purity, and naturally the quality of the PCC product of the present
invention.
[0544] It is worthwhile noting that the unique properties of the
original PCC particles of the present invention are fully restored
once the organic solvent is evaporated to dryness, and this product
can be used in the same application or another one as the original
sample. More specifically, after the removal of e.g. acetone,
toluene, or ethyl acetate, all the properties of a used sample e.g.
of AR-120, matched the original sample.
[0545] The phenomenon described in this EXAMPLE 17 leads to the
conclusion that the PCC of the present invention can readily be
used as an adsorbent for liquids (solvent), as a carrier
(encapsulant) for liquids and solids (by dissolving them in a
suitable solvent; allowing the solution to penetrate into the
"pores" of the PCC; and removing the solvent by e.g. evaporation or
dissolution of the solvent in another solvent that reduces the
solubility of the substrate. The PCC of the present invention can
encapsulate many compounds, including e.g. pharmaceuticals
(medicines), agrochemicals, flavors, fragrances and sunscreen
agents (this PCC itself is particularly suitable for protecting the
human skin, once its particles are fine-tuned for that purpose. Due
to the embedded "pores" in the PCC of the present invention, this
task of fine-tuning the PSD to meet the requirements to protect
from incoming light at 300-400 m.mu., is expected to be much less
expensive than of e.g. the TiO.sub.2, which is used for this
purpose quite often). Therefore, the PCC of the present invention
offers two functions in one material, namely, encapsulation and
efficient light dispersion). Moreover, the "porous" nature of this
PCC makes it a preferable candidate to serve as a filler, a builder
and/or an anticaking agent in e.g. powder detergents, etc.
[0546] To summarize, the PCC of the present invention can serve in
any capacity that calcium carbonate particles of the prior art
serve, and additionally it possesses many advantages due to its
"porous" nature.
[0547] (C) The "porous" Nature of Calcined PCC Particles of the
Present Invention--at 500.degree. C. for Eight Hours.
[0548] By merely coating the surfaces of GCC/PCC particles of the
prior art with e.g. n-decanoic acid, their S.G. is reduced due to
adhering bubbles (c.f. EXAMPLE 14(H), Tests #82 and #83). However,
the performance such prior art products iss inferior to the
products of the present invention. In particular, their fundamental
characteristics are revealed once they are calcined at 500.degree.
C. for eight hours to remove all organic compounds, when the
calcinations product has an S.G.>2.5 g/cm.sup.3,(c.f. EXAMPLE
14(E), Tests #30 and #32), whereas the products of the present
invention always remain "light" and "porous" (S.G.<2.5
g/cm.sup.3). To further demonstrate this, we compared various
calcined prior art products with products of the present invention.
The kinetics of increasing the specific gravity of the calcined
samples in ethylene glycol and in water were conducted as follows:
the selected samples were calcined at 500.degree. C. for eight
hours and were introduced into excess of liquid (c.f. EXAMPLE
14(E)). The S.G. results were recorded at 5 mins, 24 hrs. and 48
hrs, after mixing with the respective liquids. The results are
given in Table 30, as follows:
31TABLE 30 the results of EXAMPLE 17 (C) Sample Code 5 mins. 24
hrs. 48 hrs S.G. in Ethylene glycol g/cm.sup.3 GCC-8.sup.1 >2.7
>2.7 >2.7 GCC-8.sup.2 >2.7 >2.7 >2.7 PCC.sup.3
>2.7 >2.7 >2.7 PCC.sup.4 >2.7 >2.7 >2.7
ARP-35.sup.5 2.25 2.35 2.38 ARP-36.sup.5 2.13 2.22 2.27
ARP-62-1.sup.5 2.17 2.24 2.30 S.G. in Water g/cm.sup.3 GCC-8.sup.1
>2.7 >2.7 >2.7 GCC-8.sup.2 >2.7 >2.7 >2.7
PCC.sup.3 >2.7 >2.7 >2.7 PCC.sup.4 >2.7 >2.7 >2.7
ARP-35.sup.5,6 2.25 2.49 2.54 ARP-36.sup.5,6 2.36 2.40 2.46
ARP-62-1.sup.5 2.01 2.29 2.31 .sup.1"Girulite-8" CaCO3 powder (d50
= 3.5 microns) ex Polychrom - Israel. .sup.2"Girulite-8" CaCO3
powder (d50 = 3.5 microns) ex Polychrom - Israel, which was coated
using 2 wt % n-decanoic acid. .sup.3Commercial PCC - Aragonite; of
Specialty Minerals Inc. (SMI); Opacarb .RTM. A40. .sup.4Commercial
PCC - Aragonite; of Specialty Minerals Inc. (SMI); Opacarb .RTM.
A40, which was coated using 2 wt % n-decanoic acid. .sup.5Their
production is described already (c. f. EXAMPLE 14 (E)). .sup.62 wt
% sodium dioctylsulfosuccinate were added to the water.
[0549] Notes:
[0550] 1. Determination of the S.G. of the calcined PCC of the
present invention in water seems to be a simple, fast, and quite
accurate method to distinguish between the products of the of the
present invention, and therefore, the process of the present
invention, and the product of the prior art, and therefore, the
process of the prior art (also, c.f. EXAMPLE 14(F)).
[0551] 2. The "porous" product of the present invention may absorb
considerable quantities of solvents (>50% of its weight).
[0552] 3. The existence of "pores" in the PCC of the present
invention has been established by direct and indirect evidence.
However, it is not of much consequence if we are still not too
accurate in depicting the exact properties that are responsible for
the effects that were encountered.
[0553] While the invention has been described with respect to a
limited number of embodiments, it will be appreciated that many
variations, modifications and other applications of the invention
may be made.
* * * * *