NO802401L - DIFFERENT DISPATCHES FOR PREPARATION OF COATING MASSES - Google Patents

Abstract

1. Claims for the Contracting States : BE, CH, DE, FR, GB, IT, LI, NL, SE Aqueous pigment-containing dispersions having a solids content of 35 - 65% by weight of a) polymers A, used as a binder, and optionally containing hydrophilic groups, which contain incorporated therein 70 - 100% by weight of polymerised units of styrene/butadiene, butadiene/acrylonitrile, ethylene/vinyl chloride, styrene/(meth)-acrylic acid ester, vinyl acetate/ethylene or vinyl acetate/vinyl chloride, 0 - 15% by weight of other monomers and 0 - 15% by weight of unsaturated carboxylic acids, the amides thereof and/or other hydrophilic monomers containing sulphonic acid, amino or hydroxyl groups, and b) water-soluble polymers B, used as co-binder, characterised in that the water-soluble polymers B 1) consist of poly(meth)acrylamide, polyvinyl pyrrolidone, and/or copolymers of vinyl alcohol/vinyl acetate, vinyl pyrrolidone/vinyl acetate, (meth)acrylamide/styrene or ethylene oxide/propylene oxide having molecular weights of 1,000 to 1,000,000, 2) polymer B is mixed in a quantity of 0.5 - 50% by weight, based on polymer A, with the latter, 3) polymer B being partially or completely bonded to polymer A and the quantity of bonded polymer B amounting to at least 0.5% by weight of polymer A, 4) the non-bonded polymer B not exceeding 2% by weight of the pigment composition and 5) polymer B being added to the latex of polymer A before the binder and the pigment are mixed. 1. Claims for the Contracting State : AT Process for the production of aqueous pigment-containing dispersions having a solids content of 35 - 65% by weight of a) polymers A, used as a binder, and optionally containing hydrophilic groups, which contain incorporated therein 70 - 100% by weight of polymerised units of styrene/butadiene, butadiene/acrylonitrile, ethylene/vinyl chloride, styrene/(meth)acrylic acid ester, vinyl acetate/ethylene or vinyl acetate/vinyl chloride, 0 - 15% by weigh of other monomers and 0 - 15% by weight of unsaturated carboxylic acids, the amides thereof and/or other hydrophilic monomers containing sulphonic acid, amino or hydroxyl groups, and b) water-soluble polymers B, used as co-binder, characterised in that the water-soluble polymers B 1) consist of poly(meth)acrylamide, polyvinyl pyrrolidone, and/or copolymers of vinyl alcohol/vinyl acetate, vinyl pyrrolidone/vinyl acetate, (meth)acrylamide/styrene or ethylene oxide/propylene oxide having molecular weights of 1,000 to 1,000,000, 2) polymer B is mixed in a quantity of 0.5 - 50% by weight, based on polymer A, with the latter, 3) polymer B being partially or completely bonded to polymer A and the quantity of bonded polymer B amounting to at least 0.5% by weight of polymer A, 4) the non-bonded polymer B not exceeding 2% by weight of the pigment composition and 5) polymer B being added to the latex of polymer A before the binder and the pigment are mixed.

Description

The invention relates to aqueous dispersions

which contain a) polymers in dispersed form (polymerisate A) and b) water-soluble polymers (polymerisate B) in such amounts that at least 0.5% by weight of its specific weight of polymer B is bound to the polymer A. These aqueous dispersions are suitable for the production of improved coating compositions for flat substrates, especially for coated print carriers.

For the production of coated printing media, especially coated paper, which is suitable for printing, the natural binders, such as e.g. casein and/or starch in whole or in part of synthetic binders based on copolymers of acrylic acid esters, styrene, butadiene and unsaturated carboxylic acids, which are available in the form of aqueous dispersions. The binder based on natural products has the disadvantage that they do not always appear in the same quality,

often have a disturbing colouration, are sensitive to attack by micro-organisms, and are dissolved by a cumbersome process, and give a highly viscous solution. ■with a low solids content. Binders based on synthetic high polymers do not have these shortcomings, and in addition have advantages.

With the ever-increasing demands on the quality of

printed paper, better properties of the binder are always required. Improvements in this respect are achieved by adding so-called c-binders, e.g. of mixed polymers of vinyl acetate and acrylamide (DOS 2 4.50 039, G. Hirsch, Das Papier 32 (10 A), 1978, 66-72). However, one thereby achieves . an improvement of some properties, however not a simultaneous quality improvement, for the majority of the required properties.

From DOS 27 03-418 it is known pigment-containing paper srykema.sse 'for which, without an optional binder, synthetic latex is used on the basis of polyacrylates, polymethacrylates, styrene-butadiene polymers or polymers of vinyl acetate in the form of aqueous dispersions contains as a co-binder a high molecular weight water-soluble polymer. Essential for these paper ironing masses is the production of the water-soluble polymer by polymerisation in a water-in-oil emulsion. This improves the viscosity ratio, the water retention capacity and the wear resistance.

However, as before, a problem remains,

to obtain high film hardnesses at the same time with good binding ability, small tendencies towards migration in the pigment matrix, particularly good fiber coverage, good opacity and, especially with LWC paper (low basis weight), a small rejection of printing inks in the paper. Just in recent times, the demand for paper with a low basis weight is clearly increasing (lowering of raw material and shipping costs) so that for this area of LWC and gravure paper, the smoothness of the coat, fiber coverage, opacity and the knock-off ratio of drawing colors are of greatest technical and economic importance.

The. it has now been found that improved pigment-containing paper ironing compounds that satisfactorily meet the above-mentioned requirements,

can be produced with dispersions that, next to a sé.m binder, suitable synthetic polymer as co-binder, content

is a relatively low molar water-soluble polymer,

which is wholly or partly bound to the synthetic polymer chemically and/or physically. Thereby, particles of the synthetic polymer present in the dispersion are completely or partially surrounded by a casing of water-soluble polymer.

The object of the invention is aqueous dispersions with a solids content between 35 and 65% by weight.

a) Polymers A serving as binders, optionally containing hydrophilic groups, which are made up of a or

several of the minomeric styrene, butadiene, isoprene, acrylonitrile, C|-Cj ^-alkyl esters of acrylic and methacrylic acid, ethylene, vinyl acetate and vinyl chloride and

b) Water-soluble polymers B serving as co-binder, the dispersion being characterized by

that the water-soluble polymers B

1. Contains at least 4-0 mol% of unpolymerized units of amides and unsaturated carboxylic acids, vinyl pyrrolidone, ethylene oxides, vinyl alcohols and allyl alcohols, 2. Is present in an amount of 0.5-50% by weight, referred to polymer A, and 3. The mixture is wholly or partially polymerized A, as the amount of bound polymerized B is at least 0.5% by weight of polymerized A.

By polymers A, which form the disperse phase of the aqueous dispersion, within the scope of the invention are understood all synthetic polymers suitable as binders. They consist of homopolymers and butadiene, styrene, C^-^^-alkyl esters of (meth)acrylic acid, vinyl acetate, ethylene<p>g vinyl chloride and/or mixed polymers, which to 70 - 100% by weight are made up of polymerized units of s^ urene/butadiene, acrylonitrile/butadiene, methyl methacrylate/butadiene, styrene/isoprene, styrene/C^^2-alkyl ester of acrylic acid, vinyl acetate/ethylene, ethylene/vinyl chloride or vinyl acetate/vinyl chloride, to 0-15% by weight of a hydrophilic monomer which unsaturated carboxylic acids and their amides, e.g. fumaric, itaconic, maleic and (meth)acrylic acid and (meth)acrylamide and/or monomers with sulphonic acid, amino and hydroxyl groups and to 0-15 wt% of one or more further monomers.

Preferably, the polymers A consist of styrene/butadiene mixture polymers with 30-75% by weight of styrene, 17-69% by weight of butadiene and 1-8% by weight of one or more; unsaturated carboxylic acids.

In another preferred form, the polymers A according to the invention consist of the mixed polymer with 30-75% by weight of styrene, 17-69% by weight of a C 1-2 alkyl ester of acrylic acid and 1-8% by weight of unsaturated carboxylic acids.

In a particularly preferred form, the polymerizate A according to the invention consists of the mixed polymerizate with 30-75% by weight of styrene, 17-69% by weight of butyl acrylate and 1-8% by weight of unsaturated carboxylic acids.

In a further preferred form, polymerizate A according to the invention consists of 30-75% by weight of styrene, 17-69% by weight of butadiene and 1-8% by weight of unsaturated acid amides.

The water-soluble polymers B according to the invention consist of homopolymers of unsaturated acid amides, vinyl pyrrolidone, ethylene oxide, vinyl alcohol, allyl alcohol and/or mixed polymers, in which at least 4-0 mol% of polymerized units have the above-mentioned monomer content, the molecular weight of the water-soluble polymer being between 1000 and 1,000,000.

Unsaturated acid amides mean amides and unsaturated monocarboxylic acids, e.g. (meth)acrylic acid and crotonic acid, N-substituted amides, such as e.g. N-methylol-(meth)acrylamide and/or mono- or diamides of dicarboxylic acids, e.g. of itaconic, fumaric and maleic acids. Preferably, the water-soluble polymers B according to the invention contain at least 70 mol-% of unpolymerized units of vinyl alcohol, ethylene oxide, unsaturated acid amides, vinyl pyrrolidone and/or allyl alcohol, the molecular weight of the water-soluble polymers being between 5,000 and 200,000.

As comonomers for the water-soluble polymers B according to the invention, the mentioned water-soluble monomers include vinyl alcohol, (with Acrylamide, vinylpyrrolidone and allyl alcohol, all known monomers copolymerizable with these monomers. The example must be mentioned. "Monoolefinically unsaturated aliphatic monomers, monoolefinically unsaturated aromatic monomers, conjugated diene monomers, esters and/or half-esters of alcohols, including amino alcohols with unsaturated mono- and dicarboxylic acids, half-esters of dialcohols with unsaturated mono- and/or dicarboxylic acids, esters or half-esters of unsaturated mono- and dialcohols with saturated mono- and dicarboxylic acids, ni

unsaturated alcohols, unsaturated mono- and dicarboxylic acids,

as well as unsaturated aldehydes and ketones.

The listed monomers can also be used alone

which are also combined with each other as comonomers in the water-soluble polymer B.

Suitable monoolefinically unsaturated aliphatic monomers are fj. e.g. ethylene, propylene, butylene, and iso-butylene, as well as such monomers where hydrogen is replaced by halogen and cyano groups, as is the case with acrylonitrile, methacrylonitrile, vinyl chloride and vinylidene chloride.

As monoolefinic unsaturated aromatic monomers, styrene, substituted styrenes (e.g. styrene with halogen, alkoxy, cyano or alkyl substituents) and vinyl naphthalene are suitable.

Some special examples are substituted styrenes are α-methylstyrene, Ar-methylstyrene, Ar-ethylstyrene, α-Ar-dimethylstyrene, Ar-α-dimethylstyrene, Ar-tert.-butylstyrene, methoxystyrene, cyanostyrene, monochlorostyrene, dichlorostyrene.

Acyclic conjugated dienes are e.g. butadiene, substituted butadienes and other acyclic compounds having at least two C-C double bonds in conjugation. Special examples of such monomers are isoprene, chloroprene, 2,3-dichlorobutadiene, 2,3-dimethylbutadiene and pentadiene-1,3.

Esters of unsaturated carboxylic acids with saturated alcohols are e.g. esters of methyl, ethyl, butyl and higher alcohols with (meth)acrylic acid, crotonic and vinylacetic acid. The mentioned alcohols can also be esterified as half-esters or diesters with unsaturated dicarboxylic acids such as e.g. with fumaric, maleic and itaconic acid.

As examples of half-esters of dialcohols and unsaturated acids, mention should be made of 3-hydroxyethyl acrylate and 8-hydroxyethyl methacrylate.

An ester of amino alcohols and unsaturated acids with a cationic character is, e.g. N,N-dimethylaminoethyl (meth)-acrylate.

Of the series of esters and half-esters and unsaturated alcohols with saturated mono- and dicarboxylic acids, e.g. mention is made of allyl acetate, vinyl acetate, vinyl laurate vinyl benzoate, vinyl palmitate and diallyl phthalate.

Of the series of unsaturated alcohols, it must

mention is made of allyl alcohol from the series of unsaturated aldehydes and ketones, methyl vinyl ketone and acrolein must be mentioned. Finally, unsaturated acids and their salts are suitable, e.g. (meth)acrylic acid, crotonic and vinylacetic acid, as well as dicarboxylic acids,

like for example. fumaric, maleic and itaconic acids, as comonomers.

As comonomers for ethylene oxide in the water-soluble polymers B according to the invention, epoxides such as e.g. propylene oxide and such compounds which can be linked over an OH group with (poly)-ethylene oxide, such as e.g. saturated and unsaturated alcohol. In the case of the unsaturated alcohols, there is still the possibility of carrying out a radical polymerization by the vinylic double bond with suitable monomers. This principle can also be used when an OH-group-containing polyethylene oxide is reacted with unsaturated carboxylic acids, and then a radical polymerization ay, the vinyl double bond, is carried out with suitable comonomers.

Finally, copolymers with built-in units of ethylene oxide for water-soluble polymers B according to the invention can also be obtained by reacting OH group-containing polyethylene oxides with isocyanates or polymers in so cyanates.

Particularly preferably, the water-soluble polymers B according to the invention consist of homopolymers of (meth)acrylamide, vinylpyrrolidone, vinylalcohol whose OH groups can meanwhile be acetalized and ethylene oxide and/or mixed polymers of (meth)acrylamide-styrene, vinylpyrrolidone-vinylacetate, vinylalcohol -vinyl acetate, (meth)acrylamide/vinyl acetate and ethylene oxide-propylene oxide, the molecular weight being between 5,000 and 500,000. Preferably, aqueous dispersions according to the invention contain water-soluble polymers B in an amount of 0.5-30% by weight, referred to polymer A, as to polymerisate A at least 0.5% by weight of its specific weight of polymerisate B is bound.

Particularly preferably, aqueous dispersions according to the invention contain water-soluble polymers B in an amount of 0.5-15 wt.$, referred to polymerizate A, the polymerizate A being bound at least 0.5 wt$ of its specific weight of polymerizate B.

The production of the aqueous dispersion according to the invention takes place simply by reconstituting the aqueous solution of the water-soluble polymer B, and mixing to form a polymer dispersion containing polymer A as dispersed phase. The quantities are thereby sized so that referred to polymer A, 0.5-50% by weight of polymer B is present in the aqueous dispersion.

Such a mixture is particularly suitable as a binder for the production of coating materials on pressure carriers. In addition to the binder, these coating compounds contain pigments of possibly common thickeners (such as polyacrylate). Mineral products are mainly taken into account as pigments, however, organic pigments can be partially or completely used. Common pigments are e.g. clay types, titanium dioxide, calcium carbonate, calcium sulphate, barium sulphate, blank-fix, satin white, aluminum hydroxide and zinc pigments such as zinc oxide and zinc sulphide.

The amount of water-soluble polymer B depends on the affinity between water-soluble polymer B and polymer A, and the particle size of the latex particles made up of polymer A, and must be sized so that the unbound water-soluble polymer B does not exceed 2% by weight of the pigment mass. Preferably, the quantity of water-soluble polymer B must be dimensioned so that the unbound polymer B does not exceed 1 by weight of the pigment mass.

In relation to hitherto known systems, where a cp binder is added to a latex, it is essential for the improvement of the properties of the coating compounds for pressure carriers by the aqueous dispersion according to the invention that before mixing the binder and pigment, the water-soluble polymer B is added to the latex with the disperse phase of the polymerizate A, and the water-soluble polymerizate B, is partially or completely bound to the polymerizate A, technically or physically. Surprisingly, the improvement does not occur when the water-soluble polymer B is bound to polymer A, or is first added to the mixture of the binding agent of pigment or, however, first to the pigment slurry.

The binding of water-soluble polymer B to polymer A of a latex can be investigated by filling a sample of the latex by centrifugation in a first phase which mainly consists of polymer (A+B) and-a 2...

phase of the serum, and detects any remaining part of the water-soluble polymer B in the serum. Detection of water-soluble polymer B can be done by chemical or spectroscopic methods. These methods are e.g. described for polyvinyl alcohols and copolymers of vinyl alcohol and vinyl acetate in J. appl. Polym. Pollock. (1965) 2393 and for polyethylene oxide and polyacrylamide in ■Br. Polym.

J. 7 (1975) 135.

With the help of the aqueous dispersions according to the invention, the most important and most of the required paper stretching properties can be simultaneously optimized in a way that leads to better results than with previous co-binding methods. Aqueous dispersions according to the invention are preferably used for the production of paper-stretching compounds, however, other areas of application are also conceivable and possible, such as e.g. production of coating compounds for other substrates, such as cardboard, cardboard, textiles and leather.

The method according to the invention enables the simultaneous optimization of many properties as well as the targeted excellent optimization of special ironing properties, such as compressibility, microporosity, color absorption, smoothness and binding ability.

When using aqueous dispersions, i.e. with modified latex according to the present invention, there is the surprising production of drawing paper with a low basis weight, as the latex does not penetrate the paper,

that fiber coverage is improved and a homogeneous, even ironing matrix is formed. Thereby, opacity, degree of whiteness and smoothness are improved, and an even and fast draft color absorption is achieved by consistent, resp. improved bonding ability. The further advantage of the binder according to the invention is that it avoids irreversible thickening, which can occur with the previously common use of e.g. polyvinyl alcohol in ironing colours.

Compared to the state of the art, the latexes modified according to the invention produce more voluminous and uniformly microporous layers. In the case of offset printing, this requires a fast, even color uptake, which offers special advantages in multi-colour printing, wet on wet.

For intaglio printing, the latexes modified according to the invention cause a high compressibility and smoothness of the coat by reducing the calendering work. With the aforementioned strength structures, a high, fast color absorption and a high print gloss are achieved.

As with offset paper, there is also a desire for a stiffer paper with gravure printing. The manufacture of stiffer paper was not possible until now, because when using latexes with hard films, a clear progression in the printing defects occurred: Uneven porosity, reduced compressibility, poor expression (missing dots). According to the invention, modified lathxV with hard film enables a green surface of the special smooth structure while maintaining the properties required for intaglio printing to first print stiff paper in the intaglio printing process.

By simultaneously embedding the modified binder in an ironing matrix, due to its high binding capacity, the binder content in the ironing mass can be reduced, which ultimately leads to a further improvement of the printability properties.

The invention shall be explained in more detail by means of some examples where the percentages and parts refer to weight, if nothing else is stated.

Example 1

Addition of partially saponified polyvinyl acetate to various paper stry chelate.e.x. -

a) Modification of latex.

The latices discussed further below are different

polymer composition for the production of paper ironing compounds is adjusted with water to a solids content of 4-5% which is the same for all. For modification, a 10% aqueous solution of a partially saponified polyvinyl acetate is slowly added to these latices while stirring. Tl the set quantity amounts to 5% (referred to fixed to fixed). The partially saponified polyvinyl acetate has a degree of hydrolysis of 88 mol% and a molecular weight of 25,000.

The following latex types are modified according to the invention as discussed above:

SBR latex, type 1

Carbdxylated styrene-butadiene latex with normal film hardness and high pigment binding capacity (commercial paper-ironing latex (60% styrene, 36% butadiene and 1% (meth)acrylic acid).

In modified form = latex A

SBR latex, type 2

Carboxylated styrene-butadiene latex with high film hardness with reduced pigment binding capacity.

In modified form = latex B

Acrylate latex

Styrene-acrylic acid butyl ester latex with a slightly higher film hardness but less pigment binding capacity than SBR latex type 1 (commercial paper ironing latex)

In modified form = latex C

For the formation of a clay equilibrium, the modified latex was stored before further processing for 24 hours.

As a comparison, two SBR latexes (type 1 and type 2) and the acrylate latex in unmodified form were also examined.

The binding properties are listed in Table 1.

Note:

Viscosity: Brookfield LVT. Spindle 3" or 4-» 60 RPM 20°C. b) Production of paper ironing materials and implementation of the ironing search.

In an aqueous solution of 0.2 parts of sodium polyacrylate, 0.2 parts of sodium polyphosphate and 1 part of ammonium hydroxide, 100 parts of kaolin are stirred using a high-speed stirrer, and it is dispersed into a homogeneous suspension.

As a binder, 10% (solid on solid, ref. to clay) of the latex mentioned under a) is added each time. Adjust the pH to 8.5 with ammonia-water. The possible composition is shown in table 2.

The properties of the ironing compound are listed in table 3.

After calming and dehumidification, the thus produced ironing masses are ironed using a Schaber experimental ironing machine, with a firmness of 200 m/min., onto a wood-containing bleached raw paper of 55% wood pulp, and 5% bleached sulphite cellulose (coniferous wood), a ash content of 9" 9%, and a surface weight of 50 g/m 2 on o both sides, with an application weight of o 8 10 g/m 2pr. side (dry).

Even after a longer operating time, no coagulate or coating forms with the ironing compounds with modified latex, neither on the scraper nor on the counter roller. Likewise, penetration of the ironing mass on the counter roller cannot be determined. The coated paper is then satinized over a super calender (2 passes) and after conditioning at 20°C and 65% relative humidity is examined.

The test results are listed in table i.

Note:

Mention of the test procedure, see example 1, part d.

Note:

For a discussion of the test procedure, see example 1, part D.

c) Assessment

The ironed paper from experiments 1-3»if

ironing compound containing the inventively modified 1 atex,_, shows clearly improved printability properties, ironing flatness, opacity and, above all, high fiber coverage compared to paper coated with ordinary latex (experiments 4-6). Likewise, the gloss was increased. The sticking point of these ironing compounds was reduced so that an early immobilization of the coating before the actual drying is possible,

and the binder migration can be suppressed.

It is surprising that even one coat containing a relatively hard binder (test 2) has very good printability for intaglio printing. In this way, you get a paper with a low basis weight, with high bending stiffness, which is suitable for gravure printing.

d) Test methods

The following test methods were used':

(Test climate, unless otherwise stated: 20°C; 65% relative humidity)'

pH value: electrometric"' if 01 See Din 53 785.

Solid -

content: a) for latex according to Din 53 1 89.

b) for ironing compound: Differential weighing after drying at 110°C.

Viscosity: to Din 53 788

a) measuring device: Brookfield viscometer LVT, Spindle 3" resp. in 60 Opm.

Test temperature: 20°C

b) measuring device for recording rheograms: Rheomat 15" measuring system A-C, sample temperature

20°C.

Ironing mass

stick point: 100 g of the ironing mass is poured onto an unglazed clay plate dried under constant conditions. As soon as the moisture level from the surface of the ironing compound has disappeared, a sample is taken to determine the solids content.

The solids content in % determined in this way denotes the stick point.

water back-

holding- ~

ability: 10 cm of the ironing mass is ironed with a small squeegee, slit height 0.2 mm, within a few tenths of a second. - constant ironing speed - over a test surface of the paper to be ironed. As water from the ironing compound penetrates the paper, the relative humidity on the underside of the paper increases. This humidity search as a function of time is continuously recorded with a hygroscopic humidity sensor. The stronger the humidity search is per time, the worse the water retention ability of the ironing compound.

Humidity sensor: VAISALA (Equipment HM 11)

Measurement in climate room (65% relative humidity).

application

weight: Area weight difference between conditioned^.samples

of coated and uncoated paper (according to DIN 53 111).

Thickness: Determination according to DIN 53 105-

water up-

please according

Cobb: Determination according to DIN 53 132, 60 sec.

Smoothness

according to Bekk: Provision according to DIN 53 107.

The tranquility

according to

Bendtsen: Determination according to DIN 53 108.

bend stiff-

hot according to Schlenker: Determination according to DIN 53 121, Bending angle 4-0 o.

Wear and tear-

firmness: Determination according to Tappi-Standard T 499 Su

64- with IGT apparatus, type AC2, and a compressive stress of o 35 kg/cm 2. IGT abrasion test paints of low viscosity served as wear colors.

K+N test

(Print ink -

absorption) Determination of color absorption of coated paper usually according to Tappi routine control methods RC 19» exposure time: 3 min. The K+N value

is the difference in the degree of whiteness between untreated paper and paper treated with a test colour.

Measuring device: Elrefo, filter R 457

Sample colour: K+N sample ink, from K+N laboratory

in .jtories Inc, Melrose Park.

Microcontour p

test: The test procedure for assessing ironing evenness, execution equivalent to the K + N erasure test, exposure time however only 2 minutes, test colour: blue test color 3811 from the company Lorilleux Druckfarben GmbH, Ratingen. The assessment takes place visually using a five-step assessment scale from the number 1 for an absolutely homogeneous, rib-, hole- and blur-free test surface to the number 5

for a highly disturbed, uneven test surface with many fault locations.

Print test: Intaglio test print on proof printing machine system Dr. Dtlrner. The print result was examined visually, and assessed according to the sharpness of the raster reproduction in evenness and color absorption, closedness of expression, translucence and the like. Thereby, three classes have been determined:

1= very good,

2= good

3= bad.

Gloss: Determination of gloss according to Din 67 530 against a comparison standard at a measuring angle of 60°, measuring device: Lange reflectometer.

Opacity: Determination according to Din 53 14-6.

Whiteness s -

degree: Measurement with remittance photometer Elrefo, filter

R 457.

Fiber-

coverage: The iron-on color is applied to a black cardboard (Påo guide weight: 8-10 g/m 2 dry) and dried carefully. The degree of whiteness is then measured

(Elrefo, filter R 4-57) of the ironed cardboard side. Is the higher the stronger the coat covers the black underground.

A further assessment of fiber coverage remains

1 following method:

The coated cardboard surface is treated with a very narrowly focused beam from a spectral photometer, and the emission is recorded continuously over a width of the cardboard of approx. 10 cm. The resulting remission fluctuations provide a stochastic assessment, a measure of the evenness of the fiber coverage. Illumination beam cross-section 0.3 x

2

2 mm, straight edge bezel.

Example 2

Addition of different co-binders to a paper-iron latex.

a) Modification of the latex.

As discussed in example 1 under a) is added to

SBR latex, type 1, each time 5% (referenced from solid to solid) of the following co-binders in the form of 10 µg aqueous solutions: Block blend polymer of hydrophilic polyoxy-ethylene groups (amount approx. 80 mol%) and hydrophobic polyoxy-propylene groups, total molecular weight approx. 16,000.

Characterization: PEO-PPO, in latex D,

Polyvinylpyrrolidone with a molecular weight of approx.

40,000.

Characterization: PVP, gives latex E.

Polyacrylamide, with a molecular weight of 30,000-40,000. Characterization: PAA, gives latex F.

Acetalized polyvinyl alcohol (saponification number

"20) lnol weight_approx. 70,000.

Characterization: PVA acetalized gives latex G.

In comparison

Partially saponified polyvinyl acetate as discussed in example 1

Characterization: PVAC ti. saponified, gives latex A.

pH values and viscosity of the modified latexes are listed in Table 5-

Solids content: 38.6%

Note: Viscosity: Brookfield LVT, Spindle 3" or in,

60 RPM 20°C.

b) Production of paper ironing paste and carrying out ironing research.

Takes place under the same conditions as ex-

example 1, under b). The compositions are discussed in table 6, the properties of the ironing compound in table 7.

Also in these tests, no coagulate or coating appeared on the scraper after a longer period of operation.

For comparison, in "additional trial 12, a similar trial 4-t example 1 was carried out, with the corresponding part of the section for the soaped polyvinyl acetate afterwards being added to the finished iron color.

The two coated papers were then satined over a super calender and examined for conditioning. The ironing properties are listed in table 8.

Note:

For a discussion of the test procedures see example 1, part d).

c) Assessment

As additions 7-11 show, the modification of

the latex with co-binder according to the present invention to improve the ironing properties and thus to very good printing technical properties above all in gravure printing.

Experiment 12, on the other hand, shows that a later addition of co-binder to ironing colors does not bring about the desired improvement.

Claims (1)

1. Aqueous dispersions with a solids content of 35-65 wtf, of a) serving as binder, possibly hydrophilic-group-containing polymers A, which are made up of one or more of the monomers styrene, butadiene, isoprene, acrylonitrile, C| ^2-alkyl esters, acrylic and methacrylic acid, ethylene, vinyl acetate and vinyl chloride and b) water-soluble polymers B serving as co-binders characterized in that the water-soluble polymers B 1 ) contains at least 4-0 mol% of unpolymerized units of amides of unsaturated carboxylic acids vinylpyrrolidone, ethylene ethylene oxide, vinyl alcohol and allyl alcohol, 2) is present in an amount of 0.5-50% by weight, referred to polymer A, and 3) is partially or completely bound to polymerisate A, the amount of bound polymerisate B being at least 0.5% by weight of polymerisate A. 2. Aqueous dispersions according to claim 1, characterized in that polymer A contains 70-100 by weight of polymerized units of styrene/butadiene, butadiene/acrylonitrile, ethylene/vinyl chloride, styrene (meth)acrylic acid ester, vinyl acetate/ethylene or vinyl acetate/vinyl chloride, 0 -15% by weight of additional monomers and 0-15% by weight of unsaturated carboxylic acid, their amides and/or other hydrophilic monomers with sulphonic acid, amino or hydroxyl groups. 3. Aqueous dispersions according to claim 1, characterized in that the water-soluble polymer B consists of polyvinyl alcohol, poly(meth)acrylamide, polyethylene oxide, polyvinylpyrrolidene, polyallyl alcohol and/or copolymers such as vinyl alcohol/vinyl acetate, (meth)acrylamide/vinyl acetate, vinylpyrrolidone/vinyl acetate, vinyl alcohol/ (meth)acrylamide, (meth)acrylamide/styrene or ethylene oxide/propylene oxide with molecular weights from 1,000 to 1,000,000. 4-. Aqueous dispersions according to claim 3> characterized in that the water-soluble polymer B has a molecular weight of from 5,000 to 200,000. 5" Aqueous dispersions according to claim 2, characterized in that polymerizate A is a mixed polymerizate of 30-75% by weight styrene, 17-69% by weight butadiene and 1-8% by weight of one or more unsaturated carboxylic acids. 6. Aqueous dispersions according to claim 2, characterized in that polymerizate A is a mixed polymerizate of 30-75% by weight styrene, 17-69% by weight of a C12~ alkyl ester of (meth)-acrylic acid and 1-8% by weight of one or several unsaturated carboxylic acids. 7. Aqueous dispersions according to claim 2, characterized in that polymerizate A is a mixed polymerizate of 30-75% by weight styrene, 17-69% by weight butadiene and 1-8% by weight of unsaturated acid amides. 8. Aqueous dispersions according to claim 3" characterized in that the water-soluble polymers B are homopolymers of (meth)acrylamide, vinyl pyrrolidone, vinyl alcohol, ethylene oxide and/or mixed polymers of (meth)acrylamide/styrene, vinyl pyrrolidone/vinyl acetate, vinyl alcohol/vinyl acetate, in (imét )acrylamide/vinyl acetate or propylene oxide/ethylene oxide. 9. Use of the aqueous dispersions according to claims 1-8 as a binder for the production of coating compounds for pressure carriers. 10. Use of aqueous dispersions according to claim 9, characterized in that an aqueous dispersion added to the pigment mass contains less than 2% by weight, referred to the pigment of non-bonded polymer B.