U.S. patent application number 10/574344 was filed with the patent office on 2007-05-31 for method for producing paper, paperboard and cardboard.
This patent application is currently assigned to BASF Aktiengesellschaft. Invention is credited to Oliver Birkert, Rainer Blum, Volker Braig, Simon Champ, Dieter Distler, Oliver Koch, Reinhold J. Leyrer, Volker Schadler.
Application Number | 20070119560 10/574344 |
Document ID | / |
Family ID | 34353346 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070119560 |
Kind Code |
A1 |
Birkert; Oliver ; et
al. |
May 31, 2007 |
Method for producing paper, paperboard and cardboard
Abstract
Paper, board and cardboard are produced by adding (i) at least
one retention aid and (ii) ionic, water-insoluble, uncrosslinked,
organic microparticles which have an average particle size of less
than 500 nm and a content of polymerized ionic monomers of less
than 1% by weight or water-insoluble, uncrosslinked, organic
microparticles having an average particle size of less than 500 nm
and a content of polymerized ionic monomers of not more than 10% by
weight, which are obtainable by polymerizing the monomers in the
presence of silica, waterglass, bentonite and/or mixtures thereof,
to a paper stock and draining the paper stock over a wire.
Inventors: |
Birkert; Oliver; (Mannheim,
DE) ; Blum; Rainer; (Mannheim, DE) ; Braig;
Volker; (Weinheim-Lutzelsachsen, DE) ; Champ;
Simon; (Ludwigshafen, GB) ; Distler; Dieter;
(Bietigheim-Bissingen, DE) ; Leyrer; Reinhold J.;
(Dannstadt, DE) ; Schadler; Volker; (Strasbourg,
DE) ; Koch; Oliver; (Eppelheim, DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
BASF Aktiengesellschaft
Ludwigshafen
DE
67056
|
Family ID: |
34353346 |
Appl. No.: |
10/574344 |
Filed: |
October 2, 2004 |
PCT Filed: |
October 2, 2004 |
PCT NO: |
PCT/EP04/11023 |
371 Date: |
April 3, 2006 |
Current U.S.
Class: |
162/158 ;
162/168.1; 162/175; 162/183 |
Current CPC
Class: |
D21H 21/52 20130101;
D21H 17/29 20130101; D21H 17/375 20130101; D21H 21/18 20130101;
D21H 21/16 20130101; D21H 11/08 20130101; D21H 17/67 20130101; D21H
17/71 20130101; D21H 17/33 20130101; D21H 21/10 20130101; D21H
23/04 20130101 |
Class at
Publication: |
162/158 ;
162/168.1; 162/175; 162/183 |
International
Class: |
D21H 21/10 20060101
D21H021/10 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2003 |
DE |
103 46 750.5 |
Claims
1. A process for the production of paper, board and cardboard
comprising: adding ionic, water-insoluble, uncrosslinked, organic
microparticles and at least one retention aid to a paper stock; and
draining the paper stock over a wire, wherein the organic
microparticles used are water-insoluble, uncrosslinked, organic
polymers having an average particle size of less than 500 nm and a
content of polymerized ionic monomers of less than 1% by weight of
water-insoluble, uncrosslinked, organic polymers having an average
particle size of less than 500 nm and a content of polymerized
ionic monomers of not more than 10% by weight, which are obtainable
by polymerizing the monomers in the presence of silica, waterglass,
bentonite and/or mixtures thereof.
2. The process according to claim 1, wherein the average particle
size of the water-insoluble, uncrosslinked, organic polymers is
from 10 to 100 nm; and the content of polymerized ionic monomers is
from 0.1 to 0.95% by weight.
3. The process according to claim 1, wherein the average particle
size of the water-insoluble, uncrosslinked, organic polymers is
from 10 to 80 nm; and the content of polymerized ionic monomers is
from 0.2 to 0.7% by weight.
4. The process according to claim 1, wherein the average particle
size of the water-insoluble, uncrosslinked, organic polymers is
from 15 to 50 nm.
5. The process according to claim 1, wherein the water-insoluble,
uncrosslinked, organic polymers comprise at least one anionic
monomer incorporated in the form of polymerized units.
6. The process according to claim 1, wherein the water-insoluble,
uncrosslinked, organic polymers comprise at least one cationic
monomer incorporated in the form of polymerized units.
7. The process according to claim 1, wherein water-insoluble,
uncrosslinked, organic polymers which are obtainable by free
radical aqueous emulsion polymerization of a monomer mixture
comprising: (a) from 30 to 55 parts by weight of at least one
monomer whose homopolymer has a glass transition temperature
T.sub.g of <20.degree. C.; (b) from 45 to 70 parts by weight of
at least one monomer whose homopolymer has a glass transition
temperature T.sub.g of >50.degree. C.; and (c) from 0.01 to less
than 1 part by weight of a monomer having ionic groups, the sum of
the parts by weight of (a) and (b) always being 100, are used.
8. The process according to claim 7, wherein the monomer (a) is
selected from at least one C.sub.1- to C.sub.10-alkyl acrylate,
C.sub.5- to C.sub.10-alkyl methacrylate, C.sub.5- to
C.sub.10-cycloalkyl(meth)acrylate, C.sub.1- to C.sub.10-dialkyl
maleate and/or C.sub.1- to C.sub.10-dialkyl fumarate; and the
monomer (b) is selected from at least one vinylaromatic monomer
and/or one .alpha.,.beta.-unsaturated carbonitrile or
carbodinitrile.
9. The process according to claim 7, wherein the monomer (c) is
selected from .alpha.,.beta.-unsaturated C.sub.3- to
C.sub.6-carboxylic acids, .alpha.,.beta.-unsaturated C.sub.4- to
C.sub.8-dicarboxylic acids, anhydrides thereof, monoethylenically
unsaturated alkanesulfonic acids, monoethylenically unsaturated
phosphonic acids and/or monoethylenically unsaturated arylsulfonic
acids.
10. The process according to claim 9, wherein the monomer (c) is
used in the polymerization in the form partly or completely
neutralized with alkali metal, alkaline earth metal and/or ammonium
bases.
11. The process according to claim 7, wherein the water-insoluble,
uncrosslinked, organic polymers are composed of: from 35 to 50
parts by weight of monomer units (a); from 50 to 65 parts by weight
of monomer units (b); and from 0.01 to 0.95 part by weight of
monomer units (c), the sum of the monomer units (a) and (b) always
being 100.
12. The process according to claim 7, wherein the water-insoluble,
uncrosslinked, organic polymers are obtainable by polymerizing the
monomers in the presence of silica, waterglass, bentonite and/or
mixtures thereof.
13. The process according to claim 1, wherein at least one fixing
agent, strength agent for paper and/or an engine size are also
added to the paper stock.
14. The process according to claim 13, wherein the fixing agent
used is a polymer comprising vinylamine units,
polydiallyldimethylammonium chloride, polyethylenimine,
polyalkylenepolyamine and/or dicyandiamide polymer.
15. The process according to claim 1, wherein water-insoluble,
uncrosslinked, organic polymers having an average particle size of
less than 500 nm and a content of polymerized ionic monomers of
less than 1% by weight are metered together with at least one
cationic, anionic, amphoteric or neutral synthetic organic polymer
and/or cationic starch as a retention aid to the paper stock before
the final shear stage upstream of the headbox.
16. The process according to claim 1, wherein water-insoluble,
uncrosslinked, organic polymers having an average particle size of
less than 500 nm and a content of polymerized ionic monomers of
less than 1% by weight are metered together with at least one
retention aid and one finely divided inorganic component to the
paper stock after the final shear stage upstream of the headbox; or
wherein the retention aid is metered before the final shear stage
upstream of the headbox and water-insoluble, uncrosslinked, organic
polymers having an average particle size of less than 500 nm and a
content of polymerized ionic monomers of less than 1% by weight are
metered alone or together with the finely divided inorganic
component after the final shear stage upstream of the headbox.
Description
[0001] The present invention relates to a process for the
production of paper, board and cardboard by adding uncrosslinked
organic microparticles and at least one retention aid to the paper
stock and draining the paper stock over a wire.
[0002] Inorganic microparticles, such as bentonite or colloidal
silica sols, are used in the production of paper together with
cationic polymers for improving the retention and the drainage of
the paper stock, cf. EP-A-0 235 893, EP-A-0 335 575, EP-A-0 310
959, U.S. Pat. No. 4,388,150 and WO-A-94/05595. In this process, a
cationic polymer is metered in an amount of more than 0.03% by
weight, based on dry paper stock, the mixture is then subjected to
the action of a shear field, the initially formed flocks being
broken up into microflocks, bentonite or silica is then added and
the pulp thus obtained is drained without further action of shear
forces. According to the process of DE-A-102 36 252, a
microparticle system comprising a cationic polymer and a finely
divided inorganic component is metered to the paper stock after the
final shear stage upstream of the headbox and the paper stock is
then drained. Compared with the use of cationic polymers alone as
retention aids, papers having an improved formation are obtained
using the multicomponent systems comprising cationic polymers and
inorganic microparticles.
[0003] EP-A-0 462 365 discloses organic microparticles which may be
uncrosslinked or crosslinked and which in each case comprise at
least 1, but generally at least 5, % by weight of an ionic
comonomer incorporated in the form of polymerized units. The
particle size of the uncrosslinked, water-insoluble microparticles
is below 60 nm, while that for the crosslinked microparticles is
less than 750 nm. The organic microparticles are used in
papermaking together with a high molecular weight ionic polymer as
a retention aid. In addition to the organic microparticles,
bentonite or finely divided silica may also be used in papermaking.
Suitable high molecular weight polymers are both synthetic organic
polymers and polysaccharides.
[0004] EP-A-0 810 274 discloses binders based on aqueous
styrene/acrylate polymer dispersions having a mean film formation
temperature of less than 10.degree. C. The polymers can, if
appropriate, comprise up to 1% by weight of a monomer comprising
acid groups. The particle size of the disperse polymer particles is
preferably in the range from 100 to 300 nm. The binders are used,
for example, for the preparation of coating materials, such as
plastics dispersion renders, tile adhesives, coating materials and
in particular low-emission emulsion paints.
[0005] WO-A-02/101145 discloses aqueous mixtures which comprise
anionic, crosslinked, polymeric particles having a particle size in
the unswollen state of less than 750 nm, in particular from 25 to
300 nm, and colloidal anionic silica particles. The mixtures are
used in papermaking together with a cationic polymer as drainage
and retention aids.
[0006] However, they can also be used as flocculants and for
treating wastewater and sludges.
[0007] Further microparticle systems which are used as an additive
to the paper stock in papermaking are disclosed in EP-A-0 497 030
and EP-A-0 0635 602. U.S. Pat. No. 6,083,997 discloses the
preparation of an anionic nanocomposite which is used as a
retention aid and drainage aid in papermaking. As is evident
therefrom, waterglass is mixed with an anionic polyelectrolyte
based on polysulfonates, polyacrylates or polyphosphates and either
silica is added or the silica is produced in situ.
[0008] It is an object of the present invention to provide a
further process for the production of paper, board and cardboard
using a microparticle system.
[0009] We have found that this object is achieved, according to the
invention, by a process for the production of paper, board and
cardboard by adding ionic, water-insoluble, uncrosslinked, organic
microparticles and at least one retention aid to a paper stock and
draining the paper stock over a wire, if the organic microparticles
used are water-insoluble, uncrosslinked, organic polymers having an
average particle size of less than 500 nm and a content of
polymerized ionic monomers of less than 1% by weight or
water-insoluble, uncrosslinked, organic microparticles having an
average particle size of less than 500 nm and a content of
polymerized ionic monomers of not more than 10% by weight, which
are obtainable by polymerizing the monomers in the presence of
silica, waterglass, bentonite and/or mixtures thereof.
[0010] Said particle sizes are always the weight average particle
sizes d50. Said particle size was determined by dynamic light
scattering on a 0.01% strength by weight dispersion at 23.degree.
C. by means of an lic autosizer from Malvern Instruments, UK. The
average particle size of the water-insoluble, uncrosslinked,
organic polymers is preferably from 10 to 100 nm and the content of
polymerized ionic monomers is from 0.1 to 0.95% by weight.
Microparticles having average particle sizes of the
water-insoluble, uncrosslinked, organic polymers of from 10 to 80
nm and a content of polymerized ionic monomers of from 0.2 to 0.7%
by weight are particularly preferred. In general, the average
particle size of the microparticles is in the range from 15 to 50
nm.
[0011] The microparticles comprising water-insoluble,
uncrosslinked, organic polymers comprise either at least one
anionic monomer or one cationic monomer incorporated in the form of
polymerized units. Aqueous dispersions which comprise anionic
microparticles are disclosed in EP-A-0 810 274, page 3, line 3 to
page 15, line 59, disclosed in connection with the prior art.
Suitable water-insoluble, uncrosslinked, organic polymers which
carry an ionic charge are obtainable, for example, by free radical
aqueous emulsion polymerization of a monomer mixture comprising
[0012] (a) from 30 to 55 parts by weight of at least one monomer
whose homopolymer has a glass transition temperature T.sub.g of
<20.degree. C., [0013] (b) from 45 to 70 parts by weight of at
least one monomer whose homopolymer has a glass transition
temperature T.sub.g of >50.degree. C. and [0014] (c) from 0.01
to less than 1 part by weight of a monomer having ionic groups, the
sum of the parts by weight of (a) and (b) always being 100. The
monomers having ionic groups can impart to the polymer either an
anionic charge, if, for example, monoethylenically unsaturated
monomers having acidic groups are used in the polymerization, or a
cationic charge, if the polymerization is carried out in the
presence of monoethylenically unsaturated, basic monomers. The
glass transition temperature T.sub.g is understood as meaning the
limit of the glass transition temperature to which said glass
transition temperature tends with increasing molecular weight,
according to G. Kanig (cf. Kolloid-Zeitschrift & Zeitschrift
fur Polymere, Volume 190, page 1, equation 1). It is determined by
the DSC method (differential scanning calorimetry, 20 K/min,
midpoint). The T.sub.g values for the homopolymers of most monomers
are known, cf. for example Ullmann's Encyclopedia of Industrial
Chemistry, Verlag Chemie Weinheim, 1992, Part 5, Vol. A21, page
169.
[0015] The monomer (a) is, for example, selected from at least one
C.sub.1- to C.sub.10-alkyl acrylate, C.sub.5- to C.sub.10-alkyl
methacrylate, C.sub.5- to C.sub.10-cycloalkyl (meth)acrylate,
C.sub.1- to C.sub.10-dialkyl maleate and/or C.sub.1- to
C.sub.10-dialkyl fumarate. Typical monomers (b) are, for example,
selected from at least one vinylaromatic monomer and/or one
.alpha.,.beta.-unsaturated carbonitrile or carbodinitrile.
[0016] C.sub.1- to C.sub.n-alkyl groups are to be understood as
meaning linear or branched alkyl radicals of 1 to n carbon atoms,
e.g. methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl,
tert-butyl, pentyl, n-hexyl, 2-ethylhexyl, n-octyl, isooctyl and
n-decyl. C.sub.5- to C.sub.10-Cycloalkyl groups are, for example,
cyclopentyl, cyclohexyl or cyclooctyl, which may optionally be
substituted in each case by 1, 2 or 3 alkyl groups of 1 to 4 carbon
atoms.
[0017] The water-insoluble, uncrosslinked, organic polymer is
preferably composed of
from 35 to 50 parts by weight of monomer units (a),
from 50 to 65 parts by weight of monomer units (b) and
from 0.01 to 0.95 part by weight of monomer units (c),
the sum of the monomer units (a) and (b) always being 100.
[0018] Where it is an anionic monomer, the monomer (c) is, for
example, selected from .alpha.,.beta.-unsaturated C.sub.3- to
C.sub.6-carboxylic acids, .alpha.,.beta.-unsaturated C.sub.4- to
C.sub.8-dicarboxylic acids, anhydrides thereof, monoethylenically
unsaturated alkanesulfonic acids, monoethylenically unsaturated
phosphonic acids and/or monoethylenically unsaturated arylsulfonic
acids. The monomer (c) may be used in the polymerization if
appropriate in a form partly or completely neutralized with alkali
metal, alkaline earth metal and/or ammonium bases. Moreover, it is
possible for polymers which comprise the monomers (c) incorporated
by polymerization in the form of the free acid groups to be
neutralized during or after the end of the polymerization. Suitable
bases are, for example, sodium hydroxide solution, potassium
hydroxide solution, sodium carbonate, potassium carbonate, sodium
bicarbonate, ammonia, amines, such as trimethylamine, propylamine
or butylamine, pyridine, piperidine, morpholine and alkanolamines,
such as monoethanolamine, diethanolamine and triethanolamine,
calcium oxide, calcium hydroxide, magnesium oxide and magnesium
hydroxide. Preferred monomers of group (c) are acrylic acid,
methacrylic acid, crotonic acid, maleic acid, fumaric acid, maleic
anhydride, itaconic acid, itaconic anhydride, vinylsulfonic acid,
methallylsulfonic acid, vinylbenzenesulfonic acid,
acrylamidoethanesulfonic acid, acrylamido-2-methylpropanesulfonic
acid, 2-sulfoethyl(meth)acrylate and sulfopropyl(meth)acrylate.
Particularly preferred monomers of this group are acrylic acid,
methacrylic acid and acrylamido-2-methylpropanesulfonic acid,
mixtures of these monomers and alkali metal and ammonium salts
thereof, in particular sodium salts thereof.
[0019] If the monomer (c) is a cationic monomer, this is to be
understood as meaning, for example, the following monomers:
diallyldimethylammonium chloride, di-C.sub.1- to
C.sub.2-alkylamino-C.sub.2- to C.sub.4-alkyl(meth)acrylates and
di-C.sub.1- to C.sub.2-alkylamino-C.sub.2- to
C.sub.4-alkyl(meth)acrylamides. Said
dialkylaminoalkyl(meth)acrylates and
dialkylaminoalkyl(meth)acrylamides are preferably used in the form
of salts with mineral acids or organic acids or in quaternized
form. The quaternizing agent used is, for example, methyl chloride,
ethyl chloride or dimethyl sulfate. Examples of preferably used
cationic monomers are diallyldimethylammonium chloride and the
following salts of sulfuric acid or hydrochloric acid or compounds
quaternized with methyl chloride: dimethylaminoethyl methacrylate,
dimethylaminoethyl acrylate, dimethylaminopropyl methacrylate,
dimethylaminoethylmethacrylamide and
dimethylaminopropyl(meth)acrylamide. The polymers may also
comprise, as cationic groups, vinylamine units in the form of salts
with mineral acids or in quaternized form. Polymers having such
groups are obtained, for example, if the polymerization is carried
out in the presence of vinylformamide as a comonomer, and the
vinylformamide units present in the copolymer are then hydrolyzed
with sulfuric acid to give vinylamine units.
[0020] Monomers of group (c) are present in an amount of less than
1 part by weight, based on 100 parts by weight of the sum of the
monomers (a) and (b), in the monomer mixture which is subjected to
the polymerization. Preferably, the monomer mixture comprises from
0.01 to 0.95, in particular from 0.2 to 0.7, part by weight, based
on 100 parts by weight of the monomer (a) and (b), of at least one
monomer (c).
[0021] In addition to said polymers of the components (a), (b) and
(c), those microparticles of water-insoluble, uncrosslinked,
organic polymers having an average particle size of less than 500
nm and a content of polymerized ionic monomers of up to 10% by
weight which are obtainable by polymerizing the monomers on which
these polymers are based in the presence of silica, waterglass,
bentonite and/or mixtures thereof are also suitable for
papermaking. In the case of this type of microparticles, the
content of monomers of group (c) is, for example, from 0.1 to 10,
preferably from 1.5 to 7, in particular from 2 to 5, % by
weight.
[0022] Examples of monomers (a) are vinyl ethers of C.sub.3- to
C.sub.10-alkanols, branched and straight-chain C.sub.3- to
C.sub.10-olefins, C.sub.1- to C.sub.10-alkyl acrylates, C.sub.5- to
C.sub.10-alkyl methacrylates, C.sub.5- to
C.sub.10-cycloalkyl(meth)acrylates, C.sub.1- to C.sub.10-dialkyl
maleates and/or C.sub.1- to C.sub.10-dialikyl fumarates.
Particularly preferred monomers of this group are, for example,
ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl
acrylate, isobutyl acrylate, n-hexyl acrylate, 2-ethylhexyl
acrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate,
di-n-butyl maleate and/or di-n-butyl fumarate.
[0023] Examples of suitable monomers (b) are vinylaromatic
monomers, such as styrene or .alpha.-methylstyrene, and styrene or
.alpha.-methylstyrene substituted by 1, 2 or 3 C.sub.1- to
C.sub.4-alkyl groups, chlorine and/or methoxy groups. Preferred
monomers of group (b) have a glass transition temperature above
80.degree. C. Examples of these are styrene, .alpha.-methylstyrene,
o- or p-vinyltoluene, acrylonitrile, methacrylonitrile,
maleodinitrile, fumarodinitrile or mixtures thereof.
[0024] The copolymers may if appropriate comprise further
monoethylenically unsaturated monomers, such as acrylamide,
methacrylamide, N-vinylpyrrolidone and N-vinylcaprolactam,
incorporated in the form of polymerized units. The amounts are, for
example, from 0 to 10 parts by weight, based on 100 parts by weight
of the monomers (a) and (b).
[0025] The polymerization of the monomers is effected by the known
methods of emulsion polymerization in the presence of initiators
which form free radicals under the polymerization conditions, such
as peroxides, hydroperoxides, azo compounds or redox initiators,
and in the presence of emulsifiers. Further information in this
context can be obtained from the abovementioned EP-A-0 810 274,
pages 4 and 5. The polymerization of the suitable monomers can,
however, also be carried out in the presence of silica, waterglass,
bentonite and/or mixtures thereof. Aqueous dispersions of ionic,
water-insoluble, uncrosslinked, organic polymers having an average
particle size below 500 nm are obtained. The polymerization can,
however, also be effected by preparing an emulsion from water, the
monomers, a hydrocarbon which is liquid at room temperature, such
as hexane, pentane, isooctane, toluene and/or xylene, and at least
one surfactant and polymerizing the monomers in the presence of
free radical initiators.
[0026] Preferred polymers are those which comprise [0027] (a) at
least one monomer from the group consisting of n-butylacrylate,
isobutyl acrylate, n-propyl acrylate, isopropyl acrylate, ethyl
acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate and
methyl acrylate, [0028] (b) at least one monomer from the group
consisting of styrene, .alpha.-methylstyrene, acrylonitrile and
methacrylonitrile and [0029] (c) at least one monomer from the
group consisting of acrylic acid, methacrylic acid, maleic acid and
acrylamido-2-methylpropanesulfonic acid in the abovementioned
amounts, incorporated in the form of polymerized units. Copolymers
which comprise, incorporated in the form of polymerized units
n-butyl acrylate and styrene in the weight ratio of 1:1 and from
0.2 to 0.7% by weight of methacrylic acid or acrylic acid are
particularly preferred.
[0030] The average molar mass M.sub.w of the polymers is, for
example, from 500 000 to 5 million, preferably from 1 to 3
million.
[0031] The ionic, water-insoluble, uncrosslinked, organic
microparticles described above are added together with at least one
retention aid to the paper stock in papermaking. The organic
microparticles promote the action of the retention aid. The organic
microparticles are used, for example, in amounts of from 0.1 to 1,
preferably in amounts of from 0.2 to 0.6, % by weight, based on dry
paper stock. The amounts of retention aid are, for example, from
0.01 to 0.09, preferably from 0.02 to 0.04, % by weight, based on
dry paper stock. Retention aids which may be used are all
conventional polymers which are known for this purpose, for example
polyacrylamides, cationic polyacrylamides, such as copolymers of
acrylamide and dimethylaminoethyl acrylate which is quaternized
with methyl chloride, polyvinylamines, polydiallyldimethylammonium
chlorides, anionic polyacrylamides, such as copolymers of
acrylamide and acrylic acid or copolymers of acrylamide and
methacrylic acid, and also polydialkylaminoalkyl(meth)acrylamides,
such as polydimethylaminoethyl-acrylamide and
polydimethylaminoethylmethacrylamide, which in each case are used
in protonated or in quaternized form, and polyethylene oxides,
which if appropriate may be cationically and/or anionically
modified. Furthermore, polyamidoamines which are grafted with
ethylenimine and crosslinked with dichlorohydrin ethers of
polyethylene glycols are suitable as retention aids. Further
conventional retention aids are cationic starches. Such starches
are prepared, for example, by reacting starch with cationizing
agents, such as 3-chloro-2-hydroxypropyltrimethylammonium chloride.
The degree of substitution of the cationic starch is, for example
from 0.01 to 1, preferably from 0.02 to 0.5. Amphoteric starches
may also be used as retention aids provided that they have an
excess cationic charge. The retention aids are known to have a high
molecular weight and thus differ substantially from fixing agents
which are based on the same monomers. The molecular weight M.sub.w
of the retention aids is, for example, at least 500 000, preferably
>1 million, generally >2 million, in particular >5
million.
[0032] According to the novel process, all paper qualities can be
produced, for example cardboard, single-ply/multiply cardboard for
folding cartons, single-ply/multiply liners, corrugated material,
newsprint, so-called medium-ply writing and printing papers,
natural gravure printing paper and light-weight coating papers. In
order to produce these papers, it is possible to start, for
example, from groundwood, thermomechanical pulp (TMP),
chemothermomechanical pulp (CTMP), pressure groundwood (PGW), wood
pulp and sulfite and sulfate pulp. The chemical pulps may be either
short-fiber or long-fiber. According to the novel process,
wood-free qualities, which give highly white paper products, are
preferably produced.
[0033] The papers can if appropriate comprise up to 40, in general
from 5 to 35, % by weight of fillers. Suitable fillers are, for
example, titanium dioxide, natural and precipitated chalk, talc,
kaolin, satin white, calcium sulfate, barium sulfate, clay and/or
alumina.
[0034] Paper can also be produced in the presence of conventional
process chemicals. For example, at least one fixing agent, strength
agent for paper and/or an engine size can also be added to the
paper stock. Suitable fixing agents are, for example, polymers
comprising vinylamine units, polydiallyldimethylammonium chloride,
polyethylenimines, polyalkylenepolyamines and/or dicyandiamide
polymers. The molecular weight M.sub.w of the fixing agent is, for
example, up to 300 000, in general in the range from 50 000 to 1
million.
[0035] According to the invention, water-insoluble, uncrosslinked,
organic polymers having an average particle size of less than 500
nm and a content of polymerized ionic monomers of less than 1% by
weight are metered together with at least one cationic, anionic,
amphoteric or neutral synthetic organic polymer and/or cationic
starch as a retention aid to the paper stock before the final shear
stage upstream of the headbox. In an embodiment of the novel
process, water-insoluble, uncrosslinked, organic polymers having an
average particle size of less than 500 nm and a content of
polymerized ionic monomers of less than 1% by weight are metered
together with at least one retention aid and a finely divided
inorganic component to the paper stock after the final shear stage
upstream of the headbox. However, it is also possible to use a
procedure in which the retention aid is metered before the final
shear stage upstream of the headbox and water-insoluble,
uncrosslinked, organic polymers having an average particle size of
less than 500 nm and a content of polymerized ionic monomers of
less than 1% by weight, alone or together with the finely divided
inorganic component, are metered after the final shear stage
upstream of the headbox.
[0036] In addition, combinations of a polymeric organic retention
aid and those water-insoluble, uncrosslinked, organic
microparticles having an average particle size of less than 500 nm
and a content of polymerized ionic monomers of not more than 10% by
weight which are obtainable by polymerizing the monomers in the
presence of silica, waterglass, bentonite and/or mixtures thereof
can be used in papermaking.
[0037] In a further embodiment of the novel process,
water-insoluble, uncrosslinked, organic polymers having an average
particle size of less than 500 nm and a content of polymerized
ionic monomers of less than 1% by weight are used together with
polymers of monoethylenically unsaturated carboxylic acids, for
example homopolymers of acrylic acid or methacrylic acid,
copolymers of acrylic acid and methacrylic acid, copolymers of
acrylic acid and maleic acid and/or copolymers of methacrylic acid
and maleic acid. These polymers may if appropriate comprise further
monomers, such as acrylamide and/or methacrylamide, incorporated in
the form of polymerized units. The molecular weight M.sub.w of this
group of polymers is, for example, from 2 000 to 200 000,
preferably in the range from 5 000 to 110 000. These polymers
result in an increase in the charge of the microparticles or
preaggregation of the microparticles and hence improved retention
in papermaking.
[0038] According to a further process variant, the water-insoluble,
uncrosslinked, organic polymers having a content of polymerized
ionic monomers of less than 1% by weight are used together with
inorganic microparticles from the group consisting of bentonite,
colloidal silica, sheet silicates and/or finely divided calcium
carbonate. The particle size of said inorganic substances is, for
example, from 1 to 100 000 nm, preferably from 5 to 500 nm. These
particle size data are based in each case on the inorganic
substances dispersed in water. For example, from 0.01 to 10,
preferably from 0.05 to 2, in particular from 0.1 to 1.2, parts by
weight of at least one type of inorganic microparticles are used
per part by weight of the organic microparticles. If organic
microparticles containing up to not more than 10% by weight of
monomers of group (c) are prepared by polymerizing the monomers in
the presence of silica, waterglass and/or bentonite, corresponding
amounts, based on the weight of the microparticles formed, of
inorganic microparticles are used in the polymerization.
[0039] For example, bentonite, colloidal silica, silicates and/or
calcium carbonate are suitable as the inorganic component of the
microparticle system. Colloidal silica is to be understood as
meaning those products which are based on silicates, e.g. silica
microgel, silica sol, polysilicates, aluminum silicates,
borosilicates, polyborosilicates, clay or zeolites. Calcium
carbonate may be used, for example, in the form of chalk, ground
calcium carbonate or precipitated calcium carbonate as the
inorganic component of the microparticle system. Bentonite is
understood generally as meaning sheet silicates which are swellable
in water. These are in particular the clay mineral montmorillonite
and similar clay minerals, such as nontronite, hectorite, saponite,
sauconite, beidellite, allevardite, illite, halloysite, attapulgite
and sepiolite. These sheet silicates are preferably activated
before they are used, i.e. converted into a form better swellable
in water by treating the sheet silicates with an aqueous base, such
as aqueous solutions of sodium hydroxide, potassium hydroxide,
sodium carbonate or potassium carbonate. Bentonite in the form
treated with sodium hydroxide solution is preferably used as the
inorganic component of the microparticle system. The platelet
diameter of the bentonite dispersed in water, in the form treated
with sodium hydroxide solution, is, for example, from 1 to 2 .mu.m,
and the thickness of the platelets is about 1 nm. Depending on the
type and activation, the bentonite has a specific surface area of
from 60 to 800 m.sup.2/g. Typical bentonites are described, for
example, in EP-B-0235893. In the papermaking process, bentonite is
added to the cellulose suspension typically in the form of an
aqueous bentonite slurry. This bentonite slurry may comprise up to
10% by weight of bentonite. Usually, the slurries comprise about
3-5% by weight of bentonite.
[0040] Products from the group consisting of silicon-based
particles, silica microgels, silica sols, aluminum silicates,
borosilicates, polyborosilicates or zeolites may be used as
colloidal silica. These have a specific surface area of 50-1 000
m.sup.2/g and an average particle size distribution of 1-250 nm,
usually in the range 40-100 nm. The preparation of such components
is described, for example, in EP-A-0041056, EP-A-0185068 and U.S.
Pat. No. 5,176,891.
[0041] Clay or kaolin is a water-containing aluminum silicate
having a lamellar structure. The crystals have a layer structure
and an aspect ratio (ratio of diameter to thickness) of up to 30:1.
The particle size is such that at least 50% of the particles are
smaller than 2 mm.
[0042] Carbonates, preferably calcium carbonate, used may be
natural calcium carbonate (ground calcium carbonate, GCC) or
precipitated calcium carbonate (PCC). GCC is prepared by milling
and classification processes using milling assistants. It has a
particle size such that 40-95% of the particles are smaller than 2
mm, and the specific surface area is in the range of 6-13
m.sup.2/g. PCC is prepared by passing carbon dioxide into calcium
hydroxide solution. The average particle size is in the range of
0.03-0.6 mm, and the specific surface area can be greatly
influenced by the choice of the precipitation conditions. It is in
the range from 6-13 m.sup.2/g.
[0043] Papers having a particularly good strength are obtained by
the novel process. The retention of fillers is improved compared
with known processes.
[0044] Unless evident otherwise from the context, the stated
percentages in the examples are always by weight. The molar masses
of the polymers were determined by light scattering.
EXAMPLES
Test Methods:
[0045] Sheet Formation [0046] Apparatus: Rapid-Kothen laboratory
sheet former with accessories; testing according to DIN 54 358 Part
1 Production of laboratory sheets for physical tests=Rapid-Kothen
method ISO 5269/2
[0047] Ash Retention: First Pass Ash Retention (FPAR) [0048] A
dynamic drainage jar was brought to 900 rpm and then filled with
500 ml of stock suspension (8 g/l). After stirring for 10 seconds,
x % of a polyacrylamide solution were added and stirring was
effected for 20 seconds at 900 rpm and then reduced to 400 rpm.
Thereafter, x %, based on stock, of the anionic flocculent
component were added as dilute dispersion and stirring was effected
for a further 15 seconds at 400 rpm. The dead volume of 25 ml was
removed and discarded. 100 ml were collected in a volumetric flask
and filtered with suction over a weighed Weissband filter. The
filters were dried in a drying oven at 120.degree. C., weighed, and
ashed at 550.degree. C. Depending on the filler composition, the
filler content was calculated from the residue according to the
following relationship (1-(filler in the filtrate/filler in the
sample)).times.100
[0049] Dry Breaking Length, Wet Breaking Length: [0050] Apparatus:
BXC-FR2.5TN.D09-002 from Zwick/Roell
[0051] Structural Strength [0052] Apparatus: BXZ2.5TS1S-006 from
Zwick-Roell [0053] Tests according to DIN ISO 3 781 Starting
Materials Cationic Polymer A
[0054] Commercial cationic polyacrylamide having a molar mass of
from 4 to 6 million and a solids content of 45% (Polymin.RTM. KE
2020 from BASF Aktiengesellschaft)
Silica
[0055] Commercial colloidal silica having an average particle size
of from 5 to 10 nm and a solids content of 10% by weight.
Bentonite
[0056] Commercial swellable clay of the montmorillonite type having
a solids content of 90% and 10% of water (cf. U.S. Pat. No.
4,306,781), obtainable under the trademark Mikrofloc.RTM. XFB from
BASF Aktiengesellschaft
Fixing Agent A
[0057] Commercial polyvinylamine having a molecular weight M.sub.w
of 250 000 and a solids content of 21%, obtainable under the name
Catiofast.RTM. VFH from BASF Aktiengesellschaft
Anionic Polymer A
[0058] Copolymer of acrylic acid and maleic acid having a molecular
weight M.sub.w of 70 000 and a solids content of 45%, obtainable
under the name Sokalan.RTM. CP45 from BASF Aktiengesellschaft
Nanohybrids A
[0059] Mixture of polymer 1 and silica in the weight ratio 1:1
Solvitose.RTM. BPN
[0060] Cold-soluble starch having a solids content of 95%,
obtainable from Avebe.
Preparation of Polymers 1 to 4
Polymer 1
[0061] 560 g of water and 633 g of a 15 percent strength by weight
aqueous solution of aryl sulfonate were initially taken in a
polymerization vessel, the solution was heated to 85.degree. C. and
50 g of a 7% strength aqueous sodium persulfate solution were then
added.
[0062] The monomer mixture (feed 1) and the amount of initiator
(feed 2) were then metered into the polymerization vessel via two
separate feeds, beginning at the same time, in the course of 180
minutes, while maintaining the temperature.
[0063] After the end of the feeds, the 85.degree. C. were
maintained for a further 30 minutes, and the reaction mixture was
then cooled to room temperature. A pH of 4 was established with 3%
strength aqueous sodium hydroxide solution. TABLE-US-00001 Feed 1:
245 g Styrene 250 g n-Butyl acrylate 3 g Methacrylic acid
[0064] TABLE-US-00002 Feed 2: 1.5 g Sodium persulfate 20 g
Demineralized water
[0065] The solids content of the dispersion was about 33%. The
copolymer comprised 0.6% of methacrylic acid incorporated in the
form of polymerized units. The light transmittance of a 0.01%
strength solution was 99%. The weight average particle size d50 was
61 nm. The pH of the dispersoin was 4.0 and the glass transition
temperature T.sub.g of the polymer was 23.degree. C.
Polymer 2
[0066] 800 g of a 2.5% strength Zeofloc.RTM. solution (J.M. Huber
Corporation) and 253 g of a 15% strength aqueous solution of aryl
sulfonate were initially taken in a polymerization vessel, the
solution was heated to 85.degree. C. and 20 g of a 7% strength
aqueous sodium persulfate solution were then added.
[0067] Thereafter, the monomer emulsion (feed 1) was added to the
polymerization vessel in the course of 180 minutes and the
initiator solution (feed 2) in the course of 195 minutes, via two
separate feeds, beginning at the same time, while maintaining the
temperature.
[0068] After the end of the feed, the 85.degree. C. were maintained
for a further 30 minutes, and the reaction mixture was then cooled
to room temperature and filtered over a filter having a mesh size
of 45 .mu.m. The pH was then brought to 4.0 by adding 3% strength
aqueous sodium hydroxide. TABLE-US-00003 Feed 1: 100 g n-Butyl
acrylate 98 g Styrene 1.9 g Methacrylic acid
[0069] TABLE-US-00004 Feed 2: 1.0 g Sodium persulfate 26 g
Demineralized water
[0070] The solids content of the dispersion was about 16%. The
copolymer comprised 0.95% of methacrylic acid incorporated in the
form of polymerized units. The weight average particle size d50 was
76 nm. The pH of the dispersion was 4.0 and the glass transition
temperature T.sub.g of the polymer was 31.degree. C.
Polymer 3
[0071] 300 g of water, 507 g of a 15% strength aqueous solution of
aryl sulfonate, 12 g of methacrylic acid and 800 g of a 5% strength
aqueous soda waterglass solution having a pH of 11.2 were initially
taken in a polymerization vessel, the solution was heated to
85.degree. C. and 40 g of a 7% strength aqueous sodium persulfate
solution were added.
[0072] Thereafter, the monomer mixture (feed 1) was added to the
polymerization vessel in the course of 180 minutes and the
initiator solution (feed 2) in the course of 210 minutes, via two
separate feeds, beginning at the same time, while maintaining the
temperature.
[0073] After the end of the feeds, the 85.degree. C. was maintained
for a further 30 minutes and the dispersion formed was then cooled
to room temperature and filtered over a filter having a mesh size
of 400 .mu.m. The pH was then brought to 6.7 by adding 3% strength
aqueous sodium hydroxide. TABLE-US-00005 Feed 1: 176 g Styrene 200
g n-Butyl acrylate 12 g Methacrylic acid
[0074] TABLE-US-00006 Feed 2: 40 g Sodium persulfate solution (7%
strength, aqueous)
[0075] The solids content of the dispersion was about 25%. The
copolymer comprised 3% of methacrylic acid incorporated in the form
of polymerized units. The weight average particle size d50 was 68
nm. The pH of the dispersion was 6.7. The glass transition
temperature T.sub.g of the polymer was 21.degree. C. The dispersion
was divided. A 3% strength aqueous sodium hydroxide was then added
to one part of the dispersion in an amount sufficient to bring the
pH to 10.5. An aqueous dispersion having a solids content of about
23.5% was obtained.
Polymer 4
[0076] The other part of the aqueous dispersion of polymer 3,
having a pH of 6.7, was brought to a pH of 10.5 by adding 5%
strength aqueous soda waterglass solution. The solids content of
the dispersion thus obtainable was 19.7%.
Examples 1 to 6, Comparative Examples 1 to 4
[0077] The efficiency of the polymers described above as retention
aids was first tested on a stock model comprising a 70/30 pine
sulfate/birch sulfate mixture with 70% Schopper Riegler 33 and 30%
Schopper Riegler 70, 30% of Hydrocarb OG (based on pulp) and 0.6%
of Solvitose.RTM. BPN (based on pulp) by the abovementioned test
method. The pulp had in each case a consistency of 8 g/l and the pH
of the pulp was 6.7. The type and amount of the starting material
and the results are stated in tables 1 to 4. TABLE-US-00007 TABLE 1
Micro- FPAR Examples Amount* Polymer Amount* particles [%]
Comparison 0.4 Cationic 1 Silica 68 1 polymer A Example 1 0.4
Cationic 1 Polymer 1 73 polymer A *Amount added, kg of commercial
product/t of paper
[0078] TABLE-US-00008 TABLE 2 Micro- FPAR Examples Amount* Polymer
Amount* particles [%] Comparison 0.4 Cationic 4 Bentonite 87 2
polymer A Example 2 0.4 Cationic 4 Polymer 1 89 polymer A Example 3
0.4 Cationic 4 Nanohybrid 90 polymer A A *Amount added, kg of
commercial product/t of paper
[0079] TABLE-US-00009 TABLE 3 Micro- FPAR Examples Amount* Polymer
Amount* particles [%] Comparison 0.4 Cationic 4 Bentonite 88 3
polymer A Example 4 0.4 Cationic 2 Polymer 2 91 polymer A *Amount
added, kg of commercial product/t of paper
[0080] TABLE-US-00010 TABLE 4 Micro- FPAR Examples Amount* Polymer
Amount* particles [%] Comparison 0.4 Cationic 3 Bentonite 90 4
polymer A Example 5 0.4 Cationic 3 Polymer 3 94 polymer A Example 6
0.4 Cationic 3 Polymer 4 96 polymer A *Amount added, kg of
commercial product/t of paper
Example 7 and Comparative Example 5
[0081] The stock model used was a wood-free paper stock having a
consistency of 8 .mu.l and a pH of 6.7. 0.1%, based on dry paper
stock, of fixing agent A (commercial product) was metered, the pulp
was thoroughly mixed, the amounts of cationic polymer A and
microparticles stated in table 5 were then added, thorough mixing
of the components was ensured and the pulp was drained as described
above. The results are shown in table 5.
Example 8
[0082] Example 7 was repeated, except that the use of fixing agent
A was dispensed with. The results are shown in table 5.
TABLE-US-00011 TABLE 5 Micro- FPAR Examples Amount* Polymer Amount*
particles [%] Comparison 0.4 Cationic 3 Bentonite 88 5 polymer A
Example 7 0.4 Cationic 3 Polymer 1 100 polymer A Example 8 0.4
Cationic 3 Polymer 1** 77 polymer A *Amount added, kg of commercial
product/t of paper **Without addition of fixing agent
Example 9 and Comparative Example 6
[0083] The stock model used was a wood-free paper stock having a
consistency of 8 .mu.l and a pH of 6.7.1%, based on the amount of
microparticles used, of anionic polymer A was added, the pulp was
thoroughly mixed, the amounts of cationic polymer A and
microparticles stated in table 6 were then added, thorough mixing
of the components was ensured and the pulp was drained as described
above. The results are shown in table 6.
Example 10 and Comparative Example 7
[0084] Example 9 was repeated, except that the use of anionic
polymer A was dispensed with. The results are shown in table 6.
TABLE-US-00012 TABLE 6 Micro- FPAR Examples Amount* Polymer Amount*
particles [%] Comparison 0.4 Cationic 4 Bentonite 79 6 polymer A
Comparison 0.4 Cationic 4 Bentonite** 83 7 polymer A Example 9 0.4
Cationic 4 Polymer 1 89 polymer A Example 10 0.4 Cationic 4 Polymer
1** 83 polymer A *Amount added, kg of commercial product/t of paper
**Without addition of Sokalan CP 45
Testing of the Performance Characteristics
[0085] 500 ml of the stock suspension described above (consistency
8 g/l) were initially taken in a stirred vessel equipped with a
propeller stirrer and was stirred at a speed of 900 revolutions per
minute (rpm). After 10 seconds, a polyacrylamide solution
(retention agent) was added, as in the testing of the ash
retention, and stirring was effected for 20 seconds at 900 rpm and
then at 400 rpm. Thereafter, the products stated in table 7
(bentonite and polymer 1) were metered in an amount of in each case
2 kg of commercial product per t of paper. Thereafter, the mixture
was introduced into a Rapid-Kothen sheet former, and sheets having
a basis weight of 80 g/m.sup.2 were produced. Dry and wet breaking
length and the structural strength of the sheets were then
determined by the methods described above. The results are shown in
table 7. TABLE-US-00013 TABLE 7 Paper test Bentonite Polymer 1 Dry
breaking length [m] 3 442 4 298 Wet breaking length [m] 205 299
Structural strength 366 430 [F max in N, z direction]
Example 11
[0086] Example 1 was repeated, except that 0.4 kg of commercial
product of cationic polymer A per t of paper and 2 kg of polymer 1
per t of paper were used. The ash retention (FPAR) was 89%.
Comparative Example 8
[0087] Example 1 was repeated, except that 0.4 kg of commercial
product of cationic polymer A per t of paper and 2 kg of an
anionically emulsified styrene latex having a particle size of 30
nm and a solids content of 33% were used. The ash retention (FPAR)
was 81%.
* * * * *