Paper coating slips based on low-crosslink binders

Details Paper coating slips based on low-crosslink binders Paper coating slips based on low-crosslink binders

2001-02-01

2002-09-10

Nakarani, D. S. (Department: 1773)

Stock material or miscellaneous articles

Composite

Of addition polymer from unsaturated monomers

C428S511000, C428S522000, C526S318000, C526S318430, C526S325000, C526S329200, C526S329700, C526S341000

Reexamination Certificate

active

06447926

ABSTRACT:

DESCRIPTION
The present invention relates to paper coating slips comprising as their binder a copolymer built up from
from 45 to 74.8% by weight of at least one monomer whose homopolymer has a glass transition temperature <20° C. (monomers A),
from 25 to 54.8% by weight of at least one monomer whose homopolymer has a glass transition temperature >50° C. (monomers B),
from 0.001 to 1.0% by weight of at least one crosslinking monomer having at least two nonconjugated vinyl groups (monomers C), and optionally
from 0 to 10% by weight of at least one monomer containing acid groups (monomers D), and
from 0 to 10% by weight of at least one further monomer (monomers E).
The invention relates additionally to papers coated with said paper coating slips and to a process for printing these papers.
Paper coating slips consist essentially of a polymeric binder and a white pigment. Coating with paper slips gives untreated papers a smooth white surface. Paper coating slips are intended in particular to bring about an improvement in printability.
The binders used in paper coating slips are, conventionally, acrylate or styrene/butadiene copolymers. Paper coating slips of this kind are described, for example, in WO 97/00776.
It is an object of the present invention to provide paper coating slips having improved properties or alternative paper coating slips having a novel raw-material base.
We have found that this object is achieved by paper coating slips comprising as their binder a copolymer built up from
from 45 to 74.8% by weight of at least one monomer whose homopolymer has a glass transition temperature <20° C. (monomers A),
from 25 to 54.8% by weight of at least one monomer whose homopolymer has a glass transition temperature >50° C. (monomers B),
from 0.001 to 1.0% by weight of at least one crosslinking monomer having at least two nonconjugated vinyl groups (monomers C), and optionally
from 0 to 10% by weight of at least one monomer containing acid groups (monomers D), and
from 0 to 10% by weight of at least one further monomer (monomers E).
By the glass transition temperature (T
g
) is meant the limiting value approached by the glass transition temperature with increasing molecular weight in accordance with G. Kanig (Kolloid-Zeitschrift & Zeitschrift für Polymere, Vol. 190, page 1, equation 1). The glass transition temperature is determined by the technique of DSC (Differential Scanning Calorimetry, 20 K/min, midpoint measurement, DIN 53765). The T
g
values for the homopolymers of the majority of monomers are known and are listed, for example, in Ullmann's Encyclopedia of Industrial Chemistry, VCH Weinheim, 1992, 5th Edition, Vol. A21, p. 169; further sources of glass transition temperatures of homopolymers are, for example, J. Brandrup, E. H. Immergut, Polymer Handbook, 1st Ed., J. Wiley, New York, 1966, 2nd Ed. J.Wiley, New York, 1975, and 3rd Ed. J. Wiley, New York, 1989.
C
1
to C
10
alkyl groups hereinbelow are linear or branched alkyl radicals having 1 to 10 carbon atoms, for example, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, tert-pentyl, n-hexyl, 2-ethylhexyl, n-nonyl and n-decyl. C
5
to C
10
cycloalkyl groups are preferably cyclopentyl or cyclohexyl groups, unsubstituted or substituted by 1, 2 or 3 C
1
to C
4
alkyl groups.
In accordance with the invention, the binder used comprises a copolymer containing in copolymerized form from 45 to 74.8% by weight, preferably from 50 to 65% by weight, based in each case on the copolymer, of at least one monomer A. Accordingly, the copolymer is obtained by polymerizing a monomer mixture comprising said at least one monomer A in an amount of from 45 to 74.8% by weight, preferably from 50 to 65% by weight, based in each case on the overall amount of the monomer mixture. It is noted at this point that the percentage amounts specified in the description for the monomers A to E copolymerized in the copolymer are intended generally to correspond to the amounts of these monomers in the monomer mixture to be polymerized, and vice versa.
Suitable monomers A are preferably vinyl ethers of C
3
to C
10
alkanols, branched and unbranched C
3
to C
10
olefins, C
1
to C
10
alkyl acrylates, C
5
to C
10
alkyl methacrylates, C
5
to C
10
cycloalkyl acrylates and methacrylates, C
1
to C
10
dialkyl maleates and/or C
1
to C
10
dialkyl fumarates. Particular preference is given to those monomers A whose homopolymers have T
g
values <0° C. Particularly preferred monomers A are ethyl acrylate, n-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, sec-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, di-n-butyl maleate and/or di-n-butyl fumarate or mixtures thereof.
Suitable monomers B are vinylaromatic monomers, C
1
to C
4
alkyl methacrylates and/or &agr;,&bgr;-unsaturated carbonitriles or dicarbonitriles. They are used in amounts of from 25 to 54.8% by weight and preferably from 35 to 50% by weight, based in each case on the overall amount of the monomer mixture, for the polymerization. Accordingly, the copolymer used in accordance with the invention is built up to the extent of from 25 to 54.8% by weight, and preferably 35 to 50% by weight, of at least one monomer B in copolymerized form. By vinylaromatic monomers are meant in particular derivatives of styrene or of &agr;-methylstyrene in which the phenyl rings are unsubstituted or substituted by 1, 2 or 3 C
1
to C
4
alkyl groups, chloro and/or methoxy groups. Preference is given to those monomers B whose homopolymers have a glass transition temperature of >80° C. Particularly preferred monomers B are styrene, &agr;-methylstyrene, o- or p-vinyltoluene, methyl methacrylate, acrylonitrile, methacrylonitrile, maleonitrile, fumaronitrile or mixtures thereof.
Said at least one monomer C is used in an amount of from 0.001 to 1% by weight in the monomer mixture, based on its overall amount. Accordingly, the copolymer is built up from 0.001 to 1% by weight of at least one monomer C in copolymerized form. Preferably, the copolymer contains from 0.001 to 0.5% by weight or from 0.001 to 0.1% by weight of copolymerized monomer C. The copolymer frequently contains ≧0.001% by weight, ≧0.002% by weight, ≧0.003% by weight, ≧0.004% by weight, ≧0.005% by weight, ≧0.006% by weight, ≧0.007% by weight, ≧0.008% by weight, ≧0.009% by weight, ≧0.01% by weight, ≧0.02% by weight, ≧0.03% by weight, ≧0.04% by weight, ≧0.05% by weight, ≧0.06% by weight, ≧0.07% by weight, ≧0.08% by weight, ≧0.09% by weight, ≧0.1% by weight, ≧0.2% by weight, ≧0.3% by weight, ≧0.4% by weight, ≧0.5% by weight, ≧0.6% by weight, ≧0.7% by weight, ≧0.8% by weight, ≧0.9% by weight and 1% by weight or <1% by weight, ≦0.9% by weight, ≦0.8% by weight, ≦0.7% by weight, ≦0.6% by weight, ≦0.5% by weight, ≦0.4% by weight, ≦0.3% by weight, ≦0.2% by weight, ≦0.1% by weight, ≦0.09% by weight, ≦0.08% by weight, ≦0.07% by weight, ≦0.06% by weight, ≦0.05% by weight, and all values in between, of at least one monomer C in copolymerized form. Monomers suitable as said at least one monomer C are those having at least two nonconjugated ethylenically unsaturated double bonds. Examples thereof are monomers having two vinyl radicals, monomers having two vinylidene radicals, and monomers having two alkenyl radicals. Particularly advantageous in this context are the diesters of dihydric alcohols with &agr;,&bgr;-monoethylenically unsaturated monocarboxylic acids, among which acrylic acid and methacrylic acid are preferred. Examples of such monomers having two nonconjugated ethylenically unsaturated double bonds are alkylene glycol diacrylates and dimethacrylates, such as ethylene glycol diacrylate, 1,2-propylene glycol diacrylate, 1,3-propylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylates and ethylene glycol dimethacrylate, 1,2-propylene glycol dimethacrylate, 1,3-pro

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