U.S. patent application number 10/787567 was filed with the patent office on 2004-08-26 for barium sulfate, process for its preparation, and its use.
Invention is credited to Amirzadeh-Asl, Djamschid, Schwarz, Karl-Heinz.
Application Number | 20040167251 10/787567 |
Document ID | / |
Family ID | 7630323 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040167251 |
Kind Code |
A1 |
Amirzadeh-Asl, Djamschid ;
et al. |
August 26, 2004 |
Barium sulfate, process for its preparation, and its use
Abstract
Barium sulfate particles having an average particle diameter
d.sub.50 of from 0.1 to 10 .mu.m which are produced by
precipitation can be dispersed better if they are covered with at
least one organic additive.
Inventors: |
Amirzadeh-Asl, Djamschid;
(Moers, DE) ; Schwarz, Karl-Heinz; (Rheinberg,
DE) |
Correspondence
Address: |
FULBRIGHT & JAWORSKI, LLP
666 FIFTH AVE
NEW YORK
NY
10103-3198
US
|
Family ID: |
7630323 |
Appl. No.: |
10/787567 |
Filed: |
February 26, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10787567 |
Feb 26, 2004 |
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10182592 |
Mar 12, 2003 |
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10182592 |
Mar 12, 2003 |
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PCT/EP01/00453 |
Jan 17, 2001 |
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Current U.S.
Class: |
523/200 ;
106/471 |
Current CPC
Class: |
C01P 2004/84 20130101;
Y10T 428/2991 20150115; C01P 2004/62 20130101; C09C 1/027 20130101;
C01F 11/462 20130101; C01P 2004/61 20130101; Y10T 428/2998
20150115 |
Class at
Publication: |
523/200 ;
106/471 |
International
Class: |
C09C 001/02; C08K
009/00; G03C 008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2000 |
DE |
100 05 685.7 |
Claims
1. Barium sulfate having an average particle diameter d.sub.50 of
from 0.1 to 10 .mu.m, precipitated by mixing of barium- and of
sulfate-containing solution, characterised in that the barium
sulfate particles are covered with at least one organic additive,
the organic additive being selected from one or more of the
substances or groups of substances: carboxylic acids, soaps,
metallic soaps, alcohols; polyhydric alcohols, such as
pentaerythritol, neopentyl glycol and trimethylolpropane;
polyalcohols, such as polypropylene glycol and polyethylene glycol;
organic esters, such as neopentyl glycol dibenzoate; silanes,
siloxanes, silicone oils, organic sulfones corresponding to the
formula RSO.sub.2R, organic ketones (R--(C.dbd.O)--R), organic
nitrites (RCN), organic sulfoxides (R.sub.2--SO.sub.2), organic
amides (R--(C.dbd.O)--NR'R or R--(S.dbd.O)--ONR'R).
2. Barium sulfate according to claim 1, characterised in that the
content of organic additive, based on the content of barium
sulfate, is 0.1 to 30 wt. %.
3. Barium sulfate according to claim 2, characterised in that the
content of organic additive, based on the content of barium
sulfate, is 0.1 to 10 wt. %.
4. Process for the preparation of barium sulfate having an average
particle diameter d.sub.50 of from 0.1 to 10 .mu.m and precipitated
by mixing of barium- and of sulfate-containing solution,
characterised in that the separated filter cake is processed to
form a paste, the paste is homogeneously mixed with organic
additive and then dried, the organic additive being selected from
one or more of the substances or groups of substances: carboxylic
acids, soaps, metallic soaps, alcohols; polyhydric alcohols, such
as pentaerythritol, neopentyl glycol and trimethylolpropane;
polyalcohols, such as polypropylene glycol and polyethylene glycol;
organic esters, such as neopentyl glycol dibenzoate; silanes,
siloxanes, silicone oils, organic sulfones corresponding to the
formula RSO.sub.2R, organic ketones (R--(C.dbd.O)--R), organic
nitriles (RCN), organic sulfoxides (R.sub.2--SO.sub.2), organic
amides (R--(C.dbd.O)--NR'R or R--(S.dbd.O)--ONR'R).
5. Process for the preparation of barium sulfate having an average
particle diameter d.sub.50 of from 0.1 to 10 .mu.m and precipitated
by mixing of barium- and of sulfate-containing solution,
characterised in that the separated filter cake is suspended in
water, the suspension is mixed with organic additive and then
dried, the organic additive being selected from one or more of the
substances or groups of substances: carboxylic acids, soaps,
metallic soaps, alcohols; polyhydric alcohols, such as
pentaerythritol, neopentyl glycol and trimethylolpropane;
polyalcohols, such as polypropylene glycol and polyethylene glycol;
organic esters, such as neopentyl glycol dibenzoate; silanes,
siloxanes, silicone oils, organic sulfones corresponding to the
formula RSO.sub.2R, organic ketones (R--(C.dbd.O)--R), organic
nitriles (RCN), organic sulfoxides (R.sub.2--SO.sub.2), organic
amides (R--(C.dbd.O)--NR'R or R--(S.dbd.O)--ONR'R).
6. Process for the preparation of barium sulfate having an average
particle diameter d.sub.50 of from 0.1 to 10 .mu.m and precipitated
by mixing of barium- and of sulfate-containing solution,
characterised in that the separated filter cake is dried and then
homogeneously mixed with organic additive, the organic additive
being selected from one or more of the substances or groups of
substances: carboxylic acids, soaps, metallic soaps, alcohols;
polyhydric alcohols, such as pentaerythritol, neopentyl glycol and
trimethylolpropane; polyalcohols, such as polypropylene glycol and
polyethylene glycol; organic esters, such as neopentyl glycol
dibenzoate; silanes, siloxanes, silicone oils, organic sulfones
corresponding to the formula RSO.sub.2R, organic ketones
(R--(C.dbd.O)--R), organic nitrites (RCN), organic sulfoxides
(R.sub.2--SO.sub.2), organic amides (R--(C.dbd.O)--NR'R or
R--(S.dbd.O)--ONR'R).
7. Process according to one of claims 4 to 6, characterised in that
the dry barium sulfate covered with organic additive is subjected
to a pulverisation, preferably by means of an impact mill or jet
mill.
8. Process according to one of claims 4 to 7, characterised in that
the drying is carried out in a spray dryer or mill dryer.
9. Process according to one of claims 4 to 8, characterised in that
the barium sulfate is precipitated by mixing of BaCl.sub.2 solution
or Ba(OH).sub.2 solution with Na.sub.2SO.sub.4 solution or
H.sub.2SO.sub.4.
10. Use of the barium sulfate according to one of claims 1 to 3 in
the production of thermoplastics, thermosetting plastics and
elastomers, in which the barium sulfate particles are
dispersed.
11. Use of the barium sulfate according to one of claims 1 to 3 for
dispersion in plastics compositions for the production of fibres,
coating materials, adhesives, films, film supports and the like.
Description
[0001] This invention relates to barium sulfate having an average
particle diameter d.sub.50 of from 0.1 to 10 .mu.m and precipitated
by mixing of barium- or of sulfate-containing solution, a process
for its preparation and its use.
[0002] Such barium sulfate is used in particular in the production
of photographic paper, paints and plastics as well as in medical
diagnosis and in medical plastics. For use in the medical field, in
addition to the high standards as regards purity, there are also
legal requirements for pharmaceutical products which have to be
complied with. Barium sulfate is a high-quality, pure white, inert,
acid- and alkali-resistant filler which is completely
weather-resistant.
[0003] Very finely-divided barium sulfate imparts colour stability
and gloss to photographic paper. When used in paints, the very
finely-divided barium sulfate produces resistance to flocculation
in organic and inorganic pigments, so that segregation phenomena
are largely prevented, depth of colour and purity of colour are
increased and brightness and fogging are improved. Moreover, the
mechanical properties of the plastics are improved as a result of
the nucleating action of the barium sulfate powder.
[0004] In stretched films made from thermoplastics, in particular
polymers containing incorporated very finely-divided barium
sulfate, the latter acts as a white pigment, scattering light at
the boundaries of the barium sulfate particles to the air, so that
the films have an opaque colouring and a high gloss. A suitable
thermoplastic is, in particular polyester, in which glycol
suspension containing barium-sulfate has been incorporated,
generally during the polycondensation. Here an adequate dispersion
of the barium sulfate particles in the polyester is an essential
precondition for opacity and high gloss in the stretched films. In
the event of inadequate dispersion of the barium sulfate particles
in the polymer, specks--these are agglomerates of barium sulfate
particles--are formed after the stretching process and these can
considerably impair the quality of the film surface.
[0005] DE-A 26 47 713 describes an opaque, simple thermoplastic
film support made of a molecularly oriented film of a synthetic,
linear polyester, in which 5 to 50 wt. %, based on the weight of
the polyester, of barium sulfate particles having an average
particle size of from 0.5 to 10 .mu.m is dispersed, with the
proviso that the actual particle size of 99.9% of the particles
does not exceed 50 .mu.m and that at least one light-sensitive
image layer is disposed on at least one surface of the film
support.
[0006] These film supports are highly impermeable to moisture and
are therefore suitable for use as supports for photographic prints
and copies for which it is possible to avoid a considerable part of
the washing process which normally has to be carried out in the
treatment of prints and copies on supports made of paper.
[0007] DE-C 44 31 735 discloses the coating of barium sulfate
particles with phosphorus pentoxide, aluminium oxide and silicon
dioxide in order to achieve an excellent adhesion between the
barium sulfate particles serving as filler and the polymer, so that
the light scattering does not occur.
[0008] DE-A 22 46 818 provides a continuous process for the
preparation of crystalline barium sulfate powder having an average
particle size d.sub.50>2 .mu.m to 20 .mu.m by precipitating
barium sulfate from barium chloride solution using sulfuric acid,
wherein the barium sulfate particles having the intended particle
size are deposited in the outlet of the precipitation vessel and
the smaller barium sulfate particles remain in the upper region of
the precipitation vessel.
[0009] DE-A 36 35 050 provides a process for the continuous
preparation of barium sulfate having a defined particle-size range,
wherein barium sulfate is precipitated in a first step by the
reaction of barium ions with sulfate ions. The suspension
containing barium sulfate is withdrawn and transferred to a
single-stage or multistage wet-grinding step, in which the grinding
to the required particle-size range is carried out. The barium
sulfate and mother liquor are subsequently separated.
[0010] The barium sulfate powder chemically precipitated by the
known methods has an undesirable tendency to form agglomerates
which prevent a homogeneous dispersion of the barium sulfate
particles as white pigment and/or filler in the thermoplastics.
[0011] The object of the present invention is to provide barium
sulfate precipitated by mixing of barium- and of sulfate-containing
solution and, having an average particle diameter d.sub.50 of from
0.1 to 10 .mu.m; this barium sulphate is to show no tendency to
form agglomerates and consequently is to have excellent properties
as regards dispersibility and freedom from specks and is to produce
an optimal film surface.
[0012] This object is achieved by covering the barium sulfate with
at least one organic additive, the organic additive being selected
from one or more of the substances or groups of substances:
carboxylic acids, soaps, metallic soaps, alcohols; polyhydric
alcohols, such as pentaerythritol, neopentyl glycol and
trimethylolpropane; polyalcohols, such as polypropylene glycol and
polyethylene glycol; organic esters, such as neopentyl glycol
dibenzoate; silanes, siloxanes, silicone oils, organic sulfones
corresponding to the formula RSO.sub.2R, organic ketones
(R--(C.dbd.O)--R), organic nitriles (RCN), organic sulfoxides
(R.sub.2--SO.sub.2), organic amides (R--(C.dbd.O)--NR'R or
R--(S.dbd.O)--ONR'R).
[0013] The organic additive content is given in claims 2 and 3.
[0014] The organic additives can be used in liquid or in solid
form.
[0015] The barium sulfate particles can be covered with organic
additive by a process described in claims 4 to 6. Further
developments of this process are given in claims 7 to 9.
[0016] To achieve an optimal distribution of liquid organic
additives on the surface of the barium sulfate particles, the
solution containing organic additive is sprayed onto the barium
sulfate particles with an even-speed mixer, or the solution is
added to a suspension of BaSO.sub.4 and the mixture is homogenised
by means of a dispersing apparatus.
[0017] When solid organic additives are used, first of all an
aqueous or organic solution or suspension is prepared and is then
sprayed onto the barium sulfate particles. In this way a very
homogeneous distribution of the organic substances on the surfaces
of the barium sulfate particles is achieved.
[0018] A particular advantage is that the barium sulfate particles
aftertreated according to the invention render possible the
preparation of masterbatches (pigment and filler concentrates) and
compounds (mixtures) of thermoplastics in which the barium sulfate
particles are so excellently dispersed that high-quality products
can be made from them without special additional expense. The
superior dispersibility in plastics of the barium sulfate particles
aftertreated according to the invention is clearly shown by the
fact that no specks arise in these plastics containing barium
sulfate and the filter does not clog during a pressure filter
test.
[0019] The barium sulfate particles according to the invention are
suitable in particular for dispersion in plastics compositions,
such as thermoplastics, thermosetting plastics and elastomers. The
plastics thus treated are used in the production of fibres, coating
materials, adhesives, films, film supports and the like.
[0020] The subject matter of the invention is explained in more
detail by the following Examples.
[0021] First of all, a BaSO.sub.4 suspension was prepared. For this
purpose, an aqueous solution of Na.sub.2SO.sub.4 and an aqueous
solution of BaCl.sub.2 in a molar ratio of 1:0.98 were
simultaneously introduced into a precipitation apparatus. The
precipitation conditions were established as in the prior art, in
such a way that the precipitated BaSO.sub.4 in the aqueous solution
had an average particle size d.sub.50=0.52 .mu.m. The precipitated
BaSO.sub.4 was then filtered and washed several times with
deionised water. The filter cake obtained was dispersed in water.
The suspension of barium sulfate had a solids content of
approximately 250 g/l and was further processed in the following
manner.
COMPARATIVE EXAMPLE A
[0022] A portion of the suspension was dried in a spray dryer. The
BaSO.sub.4 powder obtained had a d.sub.50 of 0.52 .mu.m and was
used as a control (sample A).
EXAMPLE 1
[0023] 1 wt. % (based on BaSO.sub.4) of neopentyl glycol was added
to a portion of the suspension, which was then dried as described
in Comparison Example A. The white BaSO.sub.4 powder obtained had a
d.sub.50 of 0.51 .mu.m (sample 1) and a carbon content of 0.1 wt.
%.
EXAMPLE 2
[0024] 1 wt. % (based on BaSO.sub.4) of
2,2-dihydroxymethyl-1-butanol was added to a portion of the
suspension, which was then dried as described in Comparative
Example A. The barium sulfate powder had a d.sub.50 of 0.51 .mu.m
(sample 2) and a carbon content of 0.17 wt. %.
EXAMPLE 3
[0025] 1 wt. % (based on BaSO.sub.4) of polyethylene glycol 2000
was added to a portion of the suspension, which was then dried as
described in Comparison Example A. The barium sulfate powder had a
d.sub.50 of 0.50 .mu.m (sample 3) and a carbon content of 0.48 wt.
%.
EXAMPLE 4
[0026] 5 wt. % (based on BaSO.sub.4) of polyethylene glycol 2000
was added to a portion of the suspension, which was then dried as
described in Comparative Example A. The barium sulfate powder had a
d.sub.50 of 4.9 .mu.m (sample 4) and a carbon content of 2.5 wt.
%.
EXAMPLE 5
Preparation of Polyester Masterbatches, and Their Properties
[0027] Samples A and 1 to 4 were extruded in a twin-screw extruder,
with PETP (polyethylene terephthalate) in a mass ratio of 30:70
(BaSO.sub.4:PETP) at a temperature of approximately 270.degree. C.
A 30% masterbatch was prepared in each case.
[0028] These masterbatches were subjected to a pressure filter
test. During the filtration of the polymer melts through a screen
pack (consisting of nozzle, seal, perforated plate, 14 .mu.m screen
with support screen), any pigment agglomerates and/or impurities
which may be present bring about a build-up of pressure in front of
the filter. This increase in pressure is a measure of the quality
of the polymer melt. The lower the increase in pressure, the better
is the pigment dispersed in the polymer.
[0029] The results of the pressure filter test are shown in Table
1.
1 TABLE 1 Sample A 1 2 3 4 Pressure filter value 15.47 1.74 2.53
5.89 0.27 (bar .times. cm.sup.3/g), on a 14 .mu.m screen after 60
min
[0030] It can be seen from the Table that a BaSO.sub.4 untreated
with an organic substance (Comparison Example A) exhibits a very
high pressure filter value. A comparison of untreated BaSO.sub.4
with BaSO.sub.4 treated according to the invention (samples 1 to 4)
shows that the treated BaSO.sub.4 can be dispersed significantly
better and consequently contains little material (agglomerates)
which adheres to filters and would result in a blockage of the
filter.
EXAMPLE 6
Production of 18% Polyethylene Terephthalate Films (PETP Films)
[0031] The 30% masterbatch control A and the 30% masterbatch sample
1 (containing neopentyl glycol) according to the invention were
diluted to a solids content of 18% and directly extruded to form
films.
[0032] The PETP film produced using untreated BaSO.sub.4 (sample A)
contained clearly visible non-dispersible particles, which were
present as agglomerates (so-called specks). In contrast, the PETP
film produced using treated BaSO.sub.4 (sample 1) contained
scarcely any such specks, which is to be attributed to the
considerably better dispersibility of the BaSO.sub.4 treated
according to the invention.
* * * * *