U.S. patent application number 10/653288 was filed with the patent office on 2004-03-04 for paper and paperboard production process and corresponding novel retention and drainage aids, and papers and paperboards thus obtained.
This patent application is currently assigned to SNF SA. Invention is credited to Hund, Rene, Jehn-Rendu, Christian.
Application Number | 20040040683 10/653288 |
Document ID | / |
Family ID | 27665302 |
Filed Date | 2004-03-04 |
United States Patent
Application |
20040040683 |
Kind Code |
A1 |
Hund, Rene ; et al. |
March 4, 2004 |
Paper and paperboard production process and corresponding novel
retention and drainage aids, and papers and paperboards thus
obtained
Abstract
The invention relates to an improved paper production process,
according to which a branched polymer prepared in reverse phase
emulsion is used as the main retention aid, and then bentonite is
used as the secondary retention aid (a dual type system). The two
additions are separated by a stage for shearing the fibrous
suspension (or mass). A distinctly improved retention of the fines
is obtained, and also a distinct improvement in drainage. Moreover,
the bentonite content in the white water is reduced.
Inventors: |
Hund, Rene; (Villars,
FR) ; Jehn-Rendu, Christian; (Saint Etienne Cedex,
FR) |
Correspondence
Address: |
ARENT FOX KINTNER PLOTKIN & KAHN
1050 CONNECTICUT AVENUE, N.W.
SUITE 400
WASHINGTON
DC
20036
US
|
Assignee: |
SNF SA
|
Family ID: |
27665302 |
Appl. No.: |
10/653288 |
Filed: |
September 3, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10653288 |
Sep 3, 2003 |
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10228093 |
Aug 27, 2002 |
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10228093 |
Aug 27, 2002 |
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09701556 |
Mar 16, 2001 |
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Current U.S.
Class: |
162/164.1 ;
162/158; 162/168.3; 162/179; 162/181.6; 162/183; 524/801 |
Current CPC
Class: |
D21H 23/14 20130101;
D21H 17/37 20130101; C08F 220/56 20130101; D21H 23/765 20130101;
C08F 222/385 20130101; D21H 17/375 20130101; D21H 17/455 20130101;
D21H 21/10 20130101; D21H 23/16 20130101; C08F 220/34 20130101;
D21H 17/68 20130101 |
Class at
Publication: |
162/164.1 ;
162/158; 162/179; 162/183; 162/181.6; 524/801; 162/168.3 |
International
Class: |
D21H 017/55; D21H
017/68 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 1998 |
FR |
98/07144 |
Claims
1. Process for producing a sheet of paper, paperboard or the like
having improved retention and drainage properties, of the type
which uses a dual system of an acrylic polymer and bentonite or a
possibly treated kaolin as the primary and secondary retention
aids, respectively, the introductions of which are separated by a
stage for shearing the suspension or fibrous mass or paper pulp,
characterized in that said polymer is a branched acrylic
(co)polymer prepared in the form of a reverse phase water-in-oil
emulsion, used either in emulsion inverted in water, or in a
solution of the powder obtained by drying the emulsion.
2. Process according to claim 1, characterized in that the branched
acrylic (co)polymer prepared in reverse phase emulsion is
introduced into the paper pulp at a concentration of 0.03 to one
per mill (0.03 to 1% o) by weight, or 30 to 1,000 g/t, of the dry
weight of the fibrous suspension of paper pulp, preferably 0.15 to
0.5 per mill (0.15 to 0.5% o), or 150 to 500 g/t.
3. Process according to claim 1 or 2, characterized in that the
branched acrylic (co)polymer prepared in reverse phase emulsion is
a cationic copolymer of acrylamide and of an unsaturated cationic
ethylenic monomer chosen from the group comprising
dimethylaminoethyl acrylate (ADAME), dimethylaminoethyl
methacrylate (MADAME), quaternized or salified by different acids
and quaternizing agents, benzyl chloride, methyl chloride, alkyl or
aryl chlorides, dimethyl sulfate, diallyldimethylammonium chloride
(DADMAC), acrylamidopropyltrimethylammon- ium chloride (APTAC), and
methacrylamidopropyltrimethylammonium chloride (MAPTAC).
4. Process according to any of claims 1 through 3, characterized in
that the branched acrylic (co)polymer in reverse phase emulsion is
branched by means of a branching agent constituted by a
polyfunctional compound having at least two reagent groups chosen
from the group comprising the double bonds, the aldehyde bonds or
the epoxy bonds.
5. Process according to any of claims 1 through 4, characterized in
that the branched acrylic (co)polymer in reverse phase emulsion is
branched by means of a branching agent constituted by
methylenebisacrylamide (MBA).
6. Process according to claim 5, characterized in that the MBA is
introduced at a concentration of 5 to 200 moles per million moles
of monomers.
7. Process according to claim 5 or 6, characterized in that the
bentonite is a semisodic bentonite, used at a rate of 0.1 to 0.5
percent (0.1 to 0.5%) of the dry weight of the fibrous
suspension.
8. Process according to claim 5, 6 or 7, characterized in that the
pulp used, which contains the filler, is diluted, after which the
polymer is added as the main retention aid a shearing stage is
carried out, for example in the mixing pump or "fan pump," then the
bentonite is added as the secondary retention aid.
9. Process according to claim 8, characterized in that the quantity
of branched polyacrylamide (or more generally of branched acrylic
(co)polymer), introduced either in reverse phase water-in-oil
emulsion inverted in water, or in a solution of the powder obtained
by drying the emulsion, is between 0.03 and 1% o, or between thirty
and one thousand grams per ton (30 and 1,000 g/t) of dry pulp.
10. Process according to claim 8 or 9, characterized in that the
quantity of branched polyacrylamide (or more generally of branched
acrylic (co)polymer), introduced either in reverse phase
water-in-oil emulsion inverted in water, or in a solution of the
powder obtained by drying the emulsion, is between 0.15 and 0.5% o
(or between 150 and 500 g/t).
11. Process according to claim 8, 9 of 10, characterized in that
the bentonite is replaced by kaolin, possibly pretreated with an
electrolyte, as the secondary retention aid.
12. Process according to any of claims 1 through 11, characterized
in that the branched polymer prepared in reverse phase emulsion is
injected or introduced (either in emulsion inverted in water, or in
a solution of the powder obtained by drying the emulsion), before a
shearing stage, into the paper pulp (or fibrous mass to be
flocculated), which is more or less diluted according to the
experience of one skilled in the art, and generally into the
diluted paper pulp or "thin stock," i.e. a pulp diluted to about
0.7-1.5% solid matter such as cellulose fibers, possible fillers,
and the various additives common in papermaking.
13. Process according to any of claims 1 through 12, characterized
in that some of the branched polymer in emulsion is introduced at
the level of the stage for preparing the "thick stock" with about
5% or more solid matter, or even at the level of the preparation of
the thick stock before a shearing stage.
14. Novel retention aid for the production of a sheet of paper,
paperboard or the like, characterized in that it comprises a
branched polyacrylamide (or more generally a branched acrylic
(co)polymer) in reverse phase (or oil-in-water) emulsion (either in
reverse phase emulsion dissolved or "inverted" in water, or in a
solution of the powder obtained by drying the reverse phase
emulsion, especially by means of spray-drying).
15. Novel retention aid for the productions of a sheet of paper,
paperboard or the like according to claim 14, characterized in that
the branching agent is a branching agent constituted by a
polyfunctional compound having at least two reagent groups chosen
from the group comprising the double bonds, the aldehyde bonds or
the epoxy bonds, particularly methylenebisacrylamide (MBA).
16. Novel retention aid for the production of a sheet of paper,
paperboard or the like according to claim 15, characterized in that
the branching agent is introduced at a rate of five to two hundred
(5 to 200) moles per million moles of monomers, preferably 5 to
50.
17. Novel retention aid for the production of a sheet of paper,
paperboard or the like according to claim 14, 15 or 16,
characterized in that the branched polyacrylamide is a cationic
copolymer of acrylamide and of an unsaturated cationic ethylenic
monomer, chosen from the group comprising dimethylaminoethyl
acrylate (ADAME), dimethylaminoethyl methacrylate (MADAME),
quaternized or salified by different acids and quaternizing agents,
benzyl chloride, methyl chloride, alkyl or aryl chlorides, dimethyl
sulfate, diallyldimethylammonium chloride (DADMAC),
acrylamidopropyltrimethylammonium chloride (APTAC), and
methacrylamidopropyltrimethylammonium chloride (MAPTAC).
18. Novel retention aid for the production-of a sheet of paper,
paperboard or the like according to any of claims 14 through 17,
characterized in that its UL viscosity is >3.
19. Novel retention aid for the production of a sheet of paper,
paperboard or the like according to any of claims 14 through 18,
characterized in that its UL viscosity is >3.5.
20. Novel retention aid for the production of a sheet of paper,
paperboard or the like according to any of claims 14 through 19,
characterized in that its UL viscosity is >4.
21. Novel retention aid for the production of a sheet of paper,
paperboard or the like according to any of claims 14 through 20,
characterized in that it is "moderately branched," for example with
10 ppm of branching agent relative to the active material.
22. Sheet of paper, paperboard or the like, characterized in that
it is obtained with the use of a retention aid according to any of
claims 14 through 21.
23. Sheet of paper, paperboard or the like, characterized in that
it is obtained with the use of a process according to any of claims
1 through 13.
Description
[0001] The present invention relates to the technical field of
paper production and the polymers used in this field.
[0002] The invention relates to a process for producing a paper or
paperboard with improved retention and other properties.
[0003] During the production of paper, paperboard, or the like, it
is well known to introduce into the pulp retention aids whose
function is to retain a maximum of fines and fillers in the sheet.
The beneficial effects that result from the utilization of a
retention aid are essentially:
[0004] increased production and reduction of production costs:
energy savings, more reliable operation of the machine, higher
yield in terms of fibers, fines, fillers and anionic finishing
products, lower acidity in the circuit linked to a decrease in the
use of aluminum sulfate, and hence a reduction in corrosion
problems;
[0005] an improvement in quality: better formation and better
look-through, an improvement in the moisture content, the opacity,
the gloss, and the absorptive capacity of the sheet, and a
reduction in the porosity of the paper.
[0006] Long ago, it was proposed that bentonite be added to the
pulp, possibly together with other mineral products such as
aluminum sulfates or even synthetic polymers, notably polyethylene
imine (see for example the documents DE-A-2 262 906 and U.S. Pat.
No. 2,368,635).
[0007] In the document U.S. Pat. No. 3,052,595, it was proposed to
associate the bentonite with a polyacrylamide of an essentially
linear nature. This process met with competition from systems that
were easier to use yet performed just as well. Moreover, even with
the current linear polyacrylamides, the retention capacity is still
insufficient.
[0008] In the document EP-A-0 017 353, it was proposed, for the
retention of low-filler pulps (less than 5% fillers), to associate
the bentonite with a nonionic to slightly anionic linear
copolyacrylamide. This process has not been very widely used, since
these polymers perform relatively poorly in terms of retention,
especially that of pulps containing fillers, no doubt as a result
of insufficient synergy between these copolymers and bentonite,
which does not have much of a tendency to recoagulate.
[0009] In the document EP-A-0-235 893, it was proposed to use
essentially linear cationic polyacrylamides having molecular
weights of greater than one million, of thirty million and higher.
This results in the obtainment of a retention effect that is
satisfactory, but is still deemed inadequate in the papermaking
application; since the use of bentonite causes problems during the
subsequent treatment of the effluents issuing from the machine,
users select this system only if there are significant
advantages.
[0010] In the notes presented at the lecture given in Seattle on
Oct. 11-13, 1989, published under the title "Supercoagulation in
the control of wet end chemistry by synthetic polymer and activated
bentonite," R. Kajasvirta described the mechanism of
supercoagulation of activated bentonite in the presence of a
cationic polyacrylamide, without specifying its exact nature. This
process has the same drawbacks as above.
[0011] Lastly, European Patent 0 574 335 produced an important
improvement by proposing the use branched polymers (particularly
polyacrylamides) in powder form.
[0012] The invention eliminates the drawbacks mentioned above.
[0013] Its object is to obtain an improved process of the type in
question, which is comprised of adding to the suspension or fibrous
mass or paper pulp to be flocculated, as the main retention aid, an
agent consisting of or comprising a branched polyacrylamide which
is characterized in that it has been prepared in reverse phase or
water-in-oil emulsion, and bentonite as the second retention aid (a
so-called "dual" system of the type also known as
"microparticulate").
[0014] The phrase "exists in reverse phase emulsion" or similar
expressions related to the polymer used (i.e., injected or
introduced into the pulp to be flocculated) according to the
invention, will be understood by one skilled in the art to
designate the reverse phase water-in-oil emulsion that is dissolved
in water before its injection or its introduction into the mass or
pulp to be flocculated (this dissolution in water results in what
is known as the "reversal" of the initial reverse phase
water-in-oil emulsion; these processes are well known to one
skilled in the art).
[0015] The additions of the polymer and the bentonite are separated
by a shearing stage, for example at the level of the mixing pump
known as a "fan pump." In this field, the reader is referred to the
specification of U.S. Pat. No. 4,753,710, as well as to a vast body
of prior art related to the addition point of the retention aid
relative to the shearing stages existing in the machine, including
U.S. Pat. No. 3,052,595; Unbehend, TAPPI Vol. 59, No. 10, October,
1976; Luner, 1984 Papermakers Conference or TAPPI, April, 1984, pp.
95-99; Sharpe, Merck and Co., Inc., Rahway, N.J., USA, around 1980,
Chapter 5, "Polyelectrolyte Retention Aids"; Britt, TAPPI Vol. 56,
October 1973, p. 46 ff.; and Waech, TAPPI, March, 1983, p. 137; or
even U.S. Pat. No. 4,388,150 (Eka Nobel).
[0016] The reader is also referred to U.S. Pat. No. 4,753,710 for
all of the generalities related to paper production, the usual
additives used, and similar details.
[0017] It is possible to replace the bentonite, as the secondary
retention aid, with a kaolin, as described in the Applicant's
French patent application 95 13051, this kaolin preferably being
pretreated with a polyelectrolyte. One skilled in the art can refer
to this French patent application 95 13051.
[0018] This process makes it possible to obtain a distinctly
improved retention of fines and fillers without a reverse effect.
An additional characteristic of this improvement is that the
drainage properties are improved.
[0019] The branched polyacrylamide (or more generally the branched
(co)polymer) is introduced into the suspension, in a distinctly
preferred way, in the form of a reverse phase water-in-oil emulsion
at a rate of 0.03 to one per mill (0.03 to 1% o, or 30 to 1,000
g/t) by weight of active material (polymer) relative to the dry
weight of the fibrous suspension, preferably 0.15 to 0.5 per mill,
or 150 to 500 g/t.
[0020] In a way that is known to one skilled in the art, the
reverse phase emulsion polymer is diluted in water and inverted
(solubized) by this dilution before its introduction, as described
above.
[0021] This selection of the reverse phase emulsion form makes it
possible, in the papermaking application for the retention of
fillers and fines, to reach a level of performance unequalled up to
now. Moreover, the utilization of branched polymers makes it
possible to obtain a better retention of the bentonite in the
sheet, as described in the above-mentioned European patent 0 574
335, and thus to limit its negative effects on the subsequent
treatment of the effluents issuing from the machine. Furthermore,
the choice of this branched polyacrylamide increases the fixation
capacity of the bentonite in the sheet, consequently resulting in a
synergy, and hence a recoagulation, which reduces the bentonite
content in the white water.
[0022] It is understood that it is essential according to the
invention that the polymer be prepared by means of a reverse phase
oil-in-water emulsion polymerization. However, this polymer can
then be used (i.e., injected or introduced into the mass or pulp to
be flocculated) either in the form--preferably--of this reverse
phase emulsion after its dissolution in water, or in the form of a
powder obtained by drying (especially drying by means of "spray
drying") the reverse phase emulsion from the polymerization, and
then redissolving this powder in water, for example at a
concentration on the order of 5 g of active polymer/liter, the
solution thus obtained then being injected into the pulp at
substantially the same polymer dosages.
[0023] Advantageously, in practice, the branched (co)polyacrylamide
is a cationic copolymer of acrylamide and of an unsaturated
cationic ethylenic monomer, chosen from the group comprising
dimethylaminoethyl acrylate (ADAME), dimethylaminoethyl
methacrylate (MADAME), quaternized or salified by different acids
and quaterinizing agents, benzyl chloride, methyl chloride, alkyl
or aryl chloride, dimethyl sulfate, diallyldimethylammonium
chloride (DADMAC), acrylamidopropyltrimethylammon- ium chloride
(APTAC), and methacrylamidopropyltrimethylammonium chloride
(MAPTAC).
[0024] In a known way, this copolymer is branched by a branching
agent constituted by a compound having at least two reagent groups
chosen from the group comprising the double bonds, aldehyde bonds,
or epoxy bonds. These compounds are well known and are described,
for example, in the document EP-A-0 374 458 (see also the
Applicant's document FR-A-2 589 145).
[0025] As is known, a "branched" polymer is a polymer that has in
the chain branches, groups or branchings globally disposed in one
plane and not in the three directions, unlike a "cross-linked"
polymer; branched polymers of this type, of high molecular weight,
are well known as flocculating agents. These branched
polyacrylamides are distinguished from the cross-linked
polyacrylamides by the fact that in the latter, the groups are
disposed three dimensionally so as to lead to practically insoluble
products of infinite molecular weight.
[0026] The branching can be carried out preferably during (or
possibly after) the polymerization, for example by reaction of two
soluble polymers having counter-ions, or by reaction on
formaldehyde or a polyvalent metal compound. Often, the branching
is carried out during the polymerization by the addition of a
branching agent, and this method is clearly preferred according to
the invention. These processes for polymerization with branching
are well known.
[0027] The branching agents that can be incorporated comprise ionic
branching agents such as polyvalent metal salts, formaldehyde,
glyoxal, or even, preferably, covalent cross linkers that will
copolymerize with the monomers, preferably monomers with
diethylenic unsaturation (like the family of diacrylate esters such
as the diacrylates of polyethylene glycol PEG) or polyethylenic
unsaturation, of the type classically used for the cross-linking of
water-soluble polymers, and particularly methylenebisacrylamide
(MBA), or any of the other known acrylic branching agents.
[0028] These agents are often identical to the cross linkers, but
cross-linking can be avoided when desiring to obtain a polymer that
is branched but not cross-linked, by optimizing polymerization
conditions such as the concentration of the polymerization, type
and quantity of transfer agent, temperature, type and quality of
initiators, and the like.
[0029] In practice, the branching agent is methylenebisacrylamide
(MBA), introduced at a rate of five to two hundred (5 to 200) moles
per million moles of monomers, preferably 5 to 50.
[0030] Advantageously, the quantity of branched polyacrylamide
introduced into the suspension to be flocculated is between thirty
and one thousand grams of active polymer/ton of dry pulp (30 and
1,000 g/t), or between 0.03 per mill and one per mill, preferably
150 to 500 g/t; it was observed that if the quantity is lower than
0.03% o (0.03 per mill), no significant retention is obtained;
likewise, if this quantity exceeds 1% o (1 per mill), no
proportional improvement is observed; however, unlike the linear
cationic polyacrylamides, as described in the documents EP-A-0 017
353 and EP 0 235 893 mentioned in the preamble, there is no
observed reverse dispersion effect by recirculation in the closed
circuits of the excess polymer not retained in the sheet.
Preferably, the quantity of branched polyacrylamide introduced is
between 0.15 and 0.5 per mill (0.15 and 0.5% o) of the quantity of
dry pulp, or between 150 g/t and 500 g/t.
[0031] As stated above, it is important that the branched polymer
be prepared in reverse phase (water-in-oil) emulsion form in order
to achieve the improvement of the invention. Emulsions of this type
and the process for preparing them are well known to one skilled in
the art.
[0032] This approach was condemned in the above-mentioned European
patent 0 574 335, in which it was indicated that if a branched
polymer is used in emulsion, the indispensable presence of
surfactants in these emulsions promotes the formation of foams
during the production of the paper and the appearance of
disparities in the physical properties of the finished paper
(modification of the absorbency in the places where part of the oil
phase of the emulsion is retained in the sheet).
[0033] Therefore, it was not obvious to consider a fortiori the
reverse phase water-in-oil emulsions whose oil content is clearly
high.
[0034] The invention was even more difficult to achieve in that it
was important to stay within the field of branched polymers and not
to cross over to the field of cross-linked polymers. It is known
that technically, especially on an industrial production scale, the
borderline between the two areas is very easily crossed, in a way
that is, moreover, irreversible. Since the branched area is very
limited, the difficulty of developing the invention is
considerable, and the Applicant deserves credit for undertaking to
use of this technology in the field of paper production, which
poses particular problems and has strict quality requirements.
[0035] The risk of failure, which may explain the fact that this
technology had not been used, was even greater in that crosslinked
emulsions are not known to provide any particular advantage in
paper.
[0036] In comparison with the linear polymers, the branched
polymers in powder form of the above-mentioned European patent 0
574 335 had already made substantial progress relative to the
properties and the paper production process. The improvement was on
the order of 20 to 40% depending on the properties.
[0037] With the present branched emulsions, an improvement on the
order of 50 to 60% is obtained, which would not have been
foreseeable since, on the contrary, it was known that the
crosslinked products did not work.
[0038] According to the invention, in a preferred but non-limiting
way, a "moderately branched" polymer is used, for example with 10
ppm of branching agent relative to the active material.
[0039] As already indicated above, the polymer can be used either
in the form of its synthetic reverse-phase emulsion, dissolved or
"inverted" in water, or in the form of the solution in water of the
powder obtained by drying said synthetic emulsion, particularly by
means of spray-drying. Spray-drying is a process that is also known
to one skilled in the art. The reader is referred to the tests
below in order to verify that the results are comparable.
[0040] Bentonite, also known as "smectic swelling clay," from the
montmorillonite family, is well known and there is no need to
describe it in detail here; these compounds, formed of
microcrystallites, comprise surface sites having a high cation
exchange capacity capable of retaining water (see for example the
document U.S. Pat. No. 4,305,781, which corresponds to the document
EP-A-0 017 353 mentioned above, and FR-A-2 283 102).
[0041] Preferably, a semisodic bentonite is used, which is
introduced just upstream from the headbox, at a rate of 0.1 to 0.5
percent (0.1 to 0.5%) of the dry weight of the fibrous
suspension.
[0042] As a filler, it is possible to use kaolins, GCC or ground
CaCO.sub.3, precipitated CaCO.sub.3 or PCC, and the like.
[0043] The branched polymer in reverse phase emulsion according to
the invention is injected or introduced prior to a shearing stage
into the paper pulp (or fibrous mass to be flocculated), which is
more or less diluted according to the experience of one skilled in
the art, and generally into the diluted paper pulp or "thin stock,"
i.e. a pulp diluted to about 0.7 to 1.5% solid matter such as
cellulose fibers, possible fillers, and the various additives
commonly used in papermaking.
[0044] According to a variant of the invention with fractionated
introduction, some of the branched polymer in emulsion according to
the invention is introduced at the level of the stage for preparing
the "thick stock" with about 5% or more solid matter, or even at
the level of the preparation of the thick stock before a shearing
stage.
[0045] The following examples illustrate the invention without
limiting its scope.
EXAMPLE 1
[0046] Production of a Branched Polymer in the Form of a Reverse
Phase Water-in-Oil Emulsion
[0047] In a reactor A, the constituents of the organic phase of the
emulsion to be synthesized are mixed at the ambient
temperature.
[0048] a) Organic Phase
[0049] 252 g of Exxsol D100
[0050] 18 g of Span 80
[0051] 4 g of Hypermer 2296
[0052] b) In a Beaker B, the Aqueous Phase of the Emulsion to be
Produced is Prepared by Mixing:
[0053] 385 g of acrylamide at 50%
[0054] 73 g of ethyl acrylate trimethyl ammonium chloride 80%
[0055] 268 g of water
[0056] 0.5 g of methylenebisacrylamide at 0.25%
[0057] 0.75 ml of sodium bromate at 50 g l.sup.-1
[0058] 20 ppm of sodium hypophosphite relative to the active
material
[0059] 0.29 ml of Versenex at 200 g l.sup.-1
[0060] The contents of B are mixed into A under agitation. After
the mixing of the phases, the emulsion is sheared in the mixer for
1 minute in order to create the reverse phase emulsion. The
emulsion is then degassed by means of a nitrogen bubbling; then
after 20 minutes the gradual addition of the metabisulfite causes
the initiation followed by the polymerization.
[0061] Once the reaction is finished, a "burn out" (treatment with
the metabisulfite) is carried out in order to reduce the free
monomer content.
[0062] The emulsion is then incorporated with its inverting
surfactant in order to subsequently release the polymer in the
aqueous phase. It is necessary to introduce 2 to 2.4% ethoxylated
alcohol. The standard Brookfield viscosity of said polymer is 4.36
cps (viscosity measured at 0.1% in a 1 M NaCl solution at
25.degree. C. at sixty rpm).
[0063] In accordance with a variation of the MBA content from 5 to
20 ppm, the results in terms of UL viscosity are the following:
1TABLE of Example 1: UL MBA NaH.sub.2PO.sub.2 Vis- IR (1) IVR (2)
Test ppm ppm (*) cosity (%) (%) State R 52 5 20 4.56 12.8 0
Branched R 102 10 20 3.74 28.9 0 Branched SD 102 10 20 3.70 26 0
Branched X 104 10 40 2.31 45 50 Cross- linked X 204 20 40 2.61 54.8
50 Cross- linked EM 140CT 0 15 4.5 0 <0 Linear EM 140L 0 30 3.82
0 0 Linear EM 140LH 0 40 3.16 0 <0 Linear EM 140BD 5 0 1.85 80
100 Cross- linked FO 4198 5 20 3.2 5 <0 Branched FO 4198: a
branched powder containing 20 ppm transfer agent and 5 ppm
branching agent. (*): sodium hypophosphite, transfer agent (1)
ionic regain in % (2) intrinsic viscosity regain in % EM 140CT: a
standard emulsion of very high molecular weight containing no
branching agent EM 140L: a standard emulsion of high molecular
weight containing no branching agent EM 140LH: an emulsion of
average molecular weight containing no branching agent EM 140BD: a
cross-linked emulsion containing no transfer agent and 5 ppm cross
linker SD 102: the emulsion R 102 dried by spray-drying, and the
powder obtained dissolved in water to 5 g of active
polymer/liter
[0064] It is noted that the linear products do not develop any
ionic regain IR, and their intrinsic viscosity IV decreases under
the effect of an intense shearing (two of the IV values are
negative); the branched products in emulsion develop an ionic
regain IR, but no IV (values <=0); the cross-linked products
develop a high ionic regain and a very high IV regain.
[0065] Definitions of the Ionic Regains and Intrinsic Viscosity
Regains:
2 Ionic regain IR = (X-Y)/Y .times. 100 with X ionicity after
shearing in meq/g. Y ionicity before shearing in meq/g. Intrinsic
viscosity regain IVR = (V1-V2)/V2 .times. 100 with V1 intrinsic
viscosity after shearing in dl/g V2 intrinsic viscosity before
shearing in dl/g
[0066] Some of the emulsions cited above will be the subjects of a
study of effectiveness in retention and drainage in an automated
sheet former at the Center for Paper Technology.
3 Pulp used: mixture of 70% bleached hardwood kraft KF 10% bleached
softwood kraft KR 20% mechanical pulp PM 20% natural calcium
carbonate.
[0067] Sizing in a neutral medium with 2% of an alkyl ketene dimer
emulsion.
[0068] The pulp used is diluted to a consistency of 1.5%. A sample
of 2.24 dry g of pulp, or 149 g of pulp at 150%, is taken, then
diluted to 0.4% with clear water.
[0069] The 560 ml volume is introduced into the plexiglass cylinder
of the automated sheet former, and the sequence is begun.
4 t = 0 s, start of agitation at 1500 rpm. t = 10 s, addition of
the polymer. t = 60 s, automatic reduction to 1000 rpm and, if
necessary, addition of the bentonite. t = 75 s, stopping of the
agitation, formation of the sheet with vacuum under the wire,
followed by reclamation of the white water.
[0070] The following operations are then carried out:
[0071] measurement of the turbidity of the water under the
wire.
[0072] dilution of a beaker of thick stock for a new sheet with the
reclaimed water under the wire.
[0073] drying of the so-called 1st pass sheet.
[0074] start of a new sequence for producing the so-called 2nd pass
sheet.
[0075] After 3 passes, the products to be tested are changed.
[0076] The following analyses are then performed:
[0077] measurement of the matter in suspension in the water under
the wire (TAPPI standard: T 656 cm/83)
[0078] measurement of the ash in the sheets (TAPPI standard: T 211
om-93)
[0079] measurement of turbidity 30' after the fibers are deposited
in order to learn the state of the ionic medium.
[0080] measurement of the degree of drainability of the pulp with a
Canadian Standard Freeness (CSF; TAPPI standard T 227 om-94).
5 Notes for Tables (I) and (II) below: X so-called first-pass
measurement R1 so-called second pass-measurement (1st recycling) R2
so-called third pass measurement (2nd recycling)
[0081] Ash %=% by weight of ash retained (=filler retention) in the
sheet/weight of the sheet.
[0082] Comments on the Results: See Tables (I) and (II) Below
Relative to Example 1, and FIGS. 1 Through 10, Which Represent the
Corresponding Histograms
[0083] The cross-linked polymers have no advantage as to the
flocculation and the retention of fines and fillers in spite of the
high rate of shear applied during the process to the fibrous mass
(and not applied to the polymer itself), in this case 1,500 rpm,
which is characteristic of this type of microparticulate retention
system. They show a poor capture of fillers and colloidal matter,
since no reduction in turbidity is observed.
[0084] The combination with bentonite does not significantly
improve the effectiveness in terms of retention and only slightly
improves the effectiveness in terms of drainage.
[0085] As for the linear polymer, its behavior follows the tendency
to improve the retention of fillers and fines.
[0086] The combination according to the invention of a branched
polymer in reverse phase emulsion and bentonite provides a net gain
in filler retention and in total retention, and is revealed to be
superior to the known linear polymer/bentonite system.
[0087] The coagulation capacity is better for a branched polymer in
emulsion, which translates into an excellent reduction in the
turbidity at 30' (30 min.).
[0088] The R 52 test and the R 102 test show that the invention
makes it possible to obtain branched products having UL viscosities
higher than those accessible through gel polymerization as
described in European patent 0 574 335. Any attempt to reach such
highly advantageous UL viscosity values using a gel polymerization
process with drying into a powder would result in a product that
was totally insoluble and therefore totally unusable in the
industry.
[0089] The SD 102 test shows that the polymer used in the form of a
solution in water of the powder obtained by drying the reverse
phase emulsion from the synthesis of the polymer behaves like the
polymer used in the form of the solution in water of said synthetic
reverse phase emulsion. In particular, no degradation of the
polymer is observed during the stage for drying by means of
spray-drying.
[0090] It is useful to compare the R 52 test to the FO 4198 test
(powder), since the polymers have the same chemistry, hence the
same cationicity, and the same % of MBA, while the R52 of the
invention is far superior to the powder in terms of drainage and
retention (96.3 as compared to 87.6); compare also the turbidity in
NTU after 30 minutes, 32 as compared to 75 NTU units.
[0091] Such UL viscosity values specifically result in
substantially improved drainage.
[0092] The invention also relates to a novel retention aid for the
production of a sheet of paper, paperboard or the like, which is
comprised of a branched acrylic (co)polymer as described above, in
reverse phase emulsion, which is characterized in that its UL
viscosity is >3, or >3.5 or >4. Said agent can be used
either in emulsion, inverted in water, or in a solution of the
powder obtained by drying the emulsion, as described above.
EXAMPLE 2
[0093] Production of a Branched Acrylamidopropyltrimethylammonium
Chloride (APTAC) Based Polymer in the Form of a Reverse Phase
Oil-in-Water Emulsion:
[0094] In a reactor A, the constituents of the organic phase of the
emulsion to be synthesized are mixed at the ambient
temperature.
[0095] a) Organic Phase
[0096] 252 g of Exxsol D100
[0097] 18 g of Span 80
[0098] 4 g of Hypermer 2296
[0099] b) In a Beaker B, the Phase of the Emulsion to be Produced
is Prepared by Mixing:
[0100] 378 g of acrylamide at 50%
[0101] 102.2 g of acrylamidopropyltrimethylamonium chloride
(60%)
[0102] 245.7 g of water
[0103] 0.5 g of methylenebisacrylamide at 0.25%
[0104] 0.75 ml of sodium bromate at 50 g/l
[0105] 20 ppm of sodium hypophosphite relative to the active
material
[0106] 0.29 ml of Versenex at 200 g/l
[0107] The contents of B are mixed into A under agitation. After
the mixing of the phases, the emulsion is sheared in the mixer for
1 minute in order to create the reverse-phase emulsion. The
emulsion is then degassed by means of a nitrogen bubbling; then
after 20 minutes, the gradual addition of the metabisulfite causes
the initiation followed by the polymerization.
[0108] Once the reaction is finished, a "burn out" is carried out
in order to reduce the free monomer content.
[0109] The emulsion is then incorporated with its inverting
surfactant in order to subsequently free the polymer in the aqueous
phase.
6TABLE of Example 2: UL MBA NaH.sub.2PO.sub.2 Vis- IR (1) IVR (2)
Test ppm ppm (*) cosity (%) (%) State M 52 5 20 4.20 14.2 0
Branched M 102 10 20 3.34 21.3 0 Branched XM 104 10 40 2.11 37 50
Cross- linked XM 204 20 40 1.94 58 55 Cross- linked EK 190 0 15
4.35 0 0 Linear EK 190BD 5 0 1.85 78 60 Cross- linked
[0110] EK 190: a standard emulsion of a copolymer of acrylamide and
acrylamidopropyltrimethylammonium chloride, linear.
[0111] Procedure for Testing the Emulsions
[0112] (Identical to that of Example 1)
[0113] Comments on the Results: see Table (III) Below Relative to
Example 2, and FIGS. 11 Through 20, which Represent the
Corresponding Histograms
[0114] The results invite the same comments as those of Example 1
and confirm the great advantage of the present invention.
[0115] The invention also relates to the novel retention aids
described above, characterized in that they consist of, or
comprise, at least one branched (co)polymer of the type described,
prepared in reverse phase emulsion, intended to cooperate with a
secondary retention aid after an intermediate stage for shearing
the paper pulp, as well as to the processes for producing sheets of
paper, paperboard or the like using the agents according to the
invention or the process according to the invention, and the sheets
of paper, paperboard and the like thus obtained.
[0116] Said agent can be used either in emulsion inverted in water,
or in a solution of the powder obtained by drying the emulsion, as
described above.
* * * * *