ES2660743T3 - Composition for paper coating - Google Patents

Abstract

Paper coating compositions comprising a) from 30 to 80% by weight of inorganic pigment; b) from 0.05 to 3.0 parts by weight of every 100 parts by weight of pigment of at least one polyurethane in water-soluble non-ionic comb containing polyoxyethylene side chains each having a molecular weight greater than 500 and an ethylene oxide content of 80 to 99.9% by weight; c) at least 15% by weight of water; d) from 0.01 to 3% by weight of a dispersing agent; e) from 1 to 15% by weight of a binder, the paper coating compositions have a Brookfield® viscosity at 25 ° C and 100 rpm of less than 3,000 mPa * s.

Description

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DESCRIPTION

Composition for paper coating

FIELD OF THE INVENTION

The present invention relates to paper coating compositions containing water soluble hydroscopic comb polyurethanes containing polyoxyethylene side chains as deflocculants and water retention agents.

TECHNICAL BACKGROUND

It is well known that the printing surface of the paper sheets is commonly coated with a paper coating formulation that improves the printing capacity and so that it is smooth and shiny.

Paper coating compositions generally comprise filler materials or water dispersed pigments, polymeric binders, rheology modifiers, water retention agents and dispersing agents.

Dispersing agents are indispensable for reducing viscosity in the presence of the high solids contents that are common in paper coating compositions and for maintaining a desired processing viscosity constant; Examples of conventional dispersing agents are complex phosphates, salts of polyphosphoric acid and salts of polycarboxylic acids.

Water retention agents prevent dehydration of the coating composition upon contact with the surface of the paper sheet; A usual water retention agent for the paper coating composition is carboxymethyl cellulose.

Rheology modifiers are added to modulate the viscosity of the paper coating.

The binders are responsible for the final cohesion of the coating and its attachment to the paper sheet.

It is known that some conventional paper coating additives perform more than one function; by way of example, carboxymethyl cellulose acts both as a rheology modifier as well as a water retention agent, while polyvinyl alcohol acts as a water retention agent and as an optical brightness enhancer.

WO 01/96007, WO 2004/044022, WO 2004/041883 and WO 2007/069037 describe the use of polyacrylic anionic copolymers in the paper industry, for the manufacture or coating of paper; polyacrylic anionic copolymers contain at least one ethylenically unsaturated anionic monomer having monocarboxylic functionality and at least one ethylenically unsaturated nonionic monomer having poly (C2-4-alkylene oxide) functionalities. These are said to be useful as dispersing and / or polishing agents, as agents for improving the activation of optical brightness, as water retention agents, as viscosity and gloss enhancers.

Unfortunately, when known ionic substances are used in aqueous dispersions according to the prior art, their effectiveness depends on the pH value of the dispersion.

It has now been discovered that specific hydrophilic comb polyurethanes are suitable as water retention agents and as gloss enhancers for paper coating compositions; The paper coating compositions of the invention are stable over a wide viscosity range, regardless of their pH value, and give a good printing and gloss ability to the coated paper.

Hydrophilic comb polyurethanes containing polyoxyethylene side chains are known and have been described in the patent literature.

EP 60,430 describes a process for manufacturing a polyurethane having polyalkylene oxide side chains, but does not mention the use of polyurethane in paper coating compositions.

WO 03/046038 describes a wide family of polyurethane dispersants comprising from 35 to 90% by weight of poly (C2-4-alkylene oxide) based on the total weight of the polyurethane polymer, but

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He mentions nothing about the possibility of using polyurethanes in paper coating compositions.

SUMMARY OF THE INVENTION The object of the invention is a paper coating composition according to claim 1.

DETAILED DESCRIPTION

The paper coating compositions of the invention comprise: a) from 30 to 80% by weight of inorganic pigment; b) from 0.05 to 3.0 parts by weight per 100 parts by weight of the comb polyurethane pigment described above; c) at least 15% by weight of water, d) from 0.01 to 3% by weight of a dispersing agent; e) from 1 to 15% by weight of a binder, and have a Brookfield® viscosity at 25 ° C and 100 rpm of less than 3,000 mPa * s, preferably 500 to 2,000 mPa * s.

The paper coating compositions according to the present invention also comprise from 0.01 to 3% by weight of a dispersing agent, because the comb polyurethane does not per se act as a pigment dispersant; The compositions may also contain a specific rheological modifier.

Examples of useful dispersing agents are non-crosslinked anionic polyacrylate derivatives, such as sodium polyacrylate, having a molecular weight of 5,000 to 40,000.

Typically useful rheology modifiers are carboxymethyl cellulose, hydroxypropyl guar, hydroxypropylmethyl cellulose, xanthan, ASA polymers (Alkali Swellable Acrylic polymers), or alkali swellable acrylic polymers.

Dispersing agents, which are common ingredients of paper coating compositions, generally cannot prevent flocculation of the finest particles, especially when the paper coating composition is applied on the paper sheet, that is, under conditions of High stress and particle flocculation is detrimental to the smoothness and brightness of the resulting coated paper.

Comb-shaped polyurethanes containing polyoxyethylene side chains having each molecular weight greater than 500, preferably 2,000 to 20,000, and ethylene oxide content of 80 to 99.9% by weight are particularly effective as deflocculants, avoiding deflocculation. formation of groups of fine particles, which may tend to settle, and characterize the paper coating compositions of the present invention.

The inorganic pigments of the paper coating compositions, which preferably have 40 to 90% finer particles than 2 micrometers, are normally used in the paper coating, and are particularly kaolin, calcium carbonate, talc, dioxide of titanium, barium sulfate, plaster and mixtures thereof. The paper coating compositions of the invention usually also comprise 1 to 15% by weight of a binder, preferably a polymeric acrylic binder.

Among the preferred polymeric acrylic binder for the realization of the invention, we cite the polymers of acrylic or methacrylic acid esters, copolymers of acrylic ester monomers and vinyl acetate, styrene, butadiene or mixtures thereof.

Other conventional additives, such as antifoaming agents, biocides, optical brighteners, may be present in paper coating compositions.

The water soluble comb polyurethane useful for carrying out the invention comprises a main chain (main chain) containing urethane and urea bonds with multiple trifunctional branching points (branching points) of each of which emanate side chains of polyoxyethylene

In the present text, with the expression "polyoxyethylene side chains" we refer to side chains containing - (CH2CH2OV units with n> 9.

The main chain containing urethane and urea bonds has uniformly spaced branching points, the distribution of which can be predicted from the molar ratios and the chemical nature of the reagents and does not depend on the reaction conditions or catalysts used. Therefore, the fine comb polyurethane structure can be advantageously reproduced and possibly modulated as desired.

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The polyurethane column should be per se insoluble in water and, preferably, not containing any internal or terminal polyoxyethylene chain.

In comb polyurethane, the total content of ethylene oxide, that is, the sum of - (CH2CH2O) - units, is preferably greater than 50% by weight, more preferably greater than 70% by weight.

Preferred comb polyurethanes have a molecular weight greater than 100,000, more preferably 300,000 to 3,000,000, and polyoxyethylene side chains having a molecular weight of 2,000 to 20,000 and ethylene oxide content of 90 to 99.9% by weight.

The polyoxyethylene side chains of the comb-shaped polyurethane are distributed along the main chain at intervals of less than 100, preferably less than 50, covalent bonds.

High molecular weight hydrophilic comb polyurethanes can be prepared by any method known in the art.

The polyoxyethylene side chains of the comb polyurethane are introduced by reacting in one of the preparation steps an organic isocyanate group with at least one compound having a molecular weight greater than 500, preferably 2,000 to 20,000, more preferably 4000 to 6000 , ethylene oxide content of 80 to 99.9% by weight, preferably 90 to 99.9% by weight, and having a group that reacts with isocyanates.

Combined comb polyurethanes having polyoxyethylene side chains with a molecular weight of 2,000 to 20,000 and ethylene oxide content of 90 to 99.9% by weight are preferred for use in paper coating compositions, because they impart better water retention. , with only a slight loss in brightness values.

Any compound having a molecular weight greater than 500, ethylene oxide content of 80 to 99.9% by weight and having a group reacting with isocyanates can be used to introduce the polyoxyethylene side chains into the comb polyurethane.

Suitable examples of such compounds are C1-C4 poly (oxyethylene) monoalkyl ether, such as poly (oxyethylene) monomethyl ether and poly (oxyethylene) monobutyl ether, poly (oxyethylene) monomethyl ether being those having a molecular weight of 4,000 to 6,000 the most preferred compound.

The term molecular weight used in this text means the average molecular weight in number when it comes to polymers.

The processes for preparing the comb polyurethanes of the invention comprise, as a key intermediate, a bifunctional isocyanate containing polyoxyethylene side chains having each molecular weight greater than 500, preferably 2,000 to 20,000, and ethylene oxide content of 80 to 99.9% by weight which is reacted with one or more compounds having a molecular weight of 34 to 300 and two groups that react with isocyanates, to extend the main chain, increase the molecular weight of the bifunctional isocyanate and obtain a polyurethane in high molecular weight comb.

According to a preferred method of preparation (Procedure A), the comb polyurethane is obtained by reacting in a first stage approximately one mole of a compound having a molecular weight of 92 to 1,200 and having three groups that react with isocyanates with approximately 3 moles of a diisocyanate (step a1); in a second stage, the trifunctional isocyanate thus obtained is reacted with equimolar amounts of one or more compounds having a molecular weight greater than 500, preferably 2,000 to 20,000, with ethylene oxide content of 80 to 99.9% in weight and having a group that reacts with isocyanates (step a2); In a third stage, the bifunctional isocyanate thus obtained is reacted with one or more compounds having a molecular weight of 34 to 300 and having two groups that react with isocyanates (step a3).

According to another preferred method of preparation (method B), the comb polyurethane is obtained by reacting in a first stage a polyisocyanate with one or more compounds having a molecular weight greater than 500, preferably 2,000 to 20,000, with oxide content of ethylene of 80 to 99.9% by weight and having a group that reacts with isocyanates (step b1) to obtain, on average, a bifunctional isocyanate; In a second stage, the isocyanate thus obtained is reacted with one or more compounds having a molecular weight of 34 to 300 and having two groups that react with isocyanates (step b2).

According to another preferred method of preparation (Procedure C), the comb polyurethane is obtained by reacting in a first stage a diisocyanate with equimolar amounts of one or more compounds having a molecular weight greater than 500, preferably 2,000 to 20,000, with

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ethylene oxide content of 80 to 99.9% by weight and having a group that reacts with isocyanates (step c1); In a second stage, the monofunctional isocyanate thus obtained is reacted with equimolar amounts of one or more compounds having a molecular weight of 34 to 300 and having at least one group -NH- that reacts with isocyanates and at least two hydroxyl groups which react with isocyanates (step c2); in a third stage, the compound thus obtained having two groups that react with isocyanates is reacted with diisocyanates in order to obtain an intermediate compound covered by two side groups of isocyanate (step c3); In a fourth stage, the bifunctional isocyanate thus obtained is reacted with one or more compounds having a molecular weight of 34 to 300 and having two groups that react with isocyanates (step c4).

The compound of step a1 that has a molecular weight of 92 to 1,200 and that has three groups that react with isocyanates is preferably a trifunctional alcohol. Examples of useful trifunctional alcohols are glycerin, polypropylene glycol triol, trimethylolpropane, trimethylolethane,

Any organic diisocyanate having a molecular weight below 500 and an average functionality of -NCO of 2.0 to 2.1 in step a1 and c1 can be used as the diisocyanate.

Examples of useful diisocyanates are 1,6-hexamethylene diisocyanate (HDI); tetramethylene diisocyanate; 1-Isocyanate-3-isocyanate-methyl-3,5,5-trimethyl-cyclohexane (or isophorone diisocyanate) (IPDI); 4,4'-dicyclohexyl methanediisocyanate; 2,4-toluenediisocyanate, alone or mixed with 2,6-toluene diisocyanate (TDI); 4,4-diphenylmethane diisocyanate (MDI); methetramethylxylthylenedium diisocyanate (TMXDI); 1,5-naphthalene diisocyanate, and mixtures thereof; Cycloaliphatic and aliphatic diisocyanate are preferred, with IPDI being most preferred.

Compounds having a molecular weight of 34 to 300 and two groups that react with isocyanates used in steps a3, b2 and c4 are preferably diamines. Examples of usable diamines are hydrazine, ethylenediamine, piperazine, 1,5-pentanediamine, 1,6-dihexanediamine, isophoronadiamine, diethylenetriamine.

Steps a3, b2 and c4 are preferably performed by dispersing the bifunctional isocyanate in water and adding to the dispersion the diamine, possibly dissolved in water.

The compound having a molecular weight of 34 to 300 of step c2 is preferably diethanolamine.

Any organic polyisocyanate with an average functionality of -NCO of 2.4 to 3.8 (trifunctional isocyanate) and having a molecular weight below 800 can be used in step b1.

Examples of trifunctional isocyanates are the compounds obtained from trimerization, biuretization, urethaneization or allophanage of difunctional isocyanates, such as those mentioned above, and mixtures thereof.

Useful trifunctional isocyanates are HDI biuret, HDI isocyanurate, IPDI trimers and the combination of the above trifunctional isocyanates with diisocyanates.

Preferred trifunctional isocyanates are isocyanurate and biuret obtained from hexamethylene diisocyanate, for example, asymmetric HDI isocyanurate, low viscosity HDI biuret and those obtained by combinations of IPDI trimmers and HDI trimers .

For the purpose of the present invention, in order to obtain the desired high molecular weight comb polyurethane, it is preferred to minimize the amount of diisocyanate that may be present together with the trifunctional isocyanates during step b1, which is well known by A person skilled in the field.

For the purpose of the present invention, the ratio between the equivalents of isocyanate groups and the equivalent of groups that react with isocyanate during step c3 is between 1.1 and 2.3.

Water-soluble comb polyurethanes are preferably non-ionic compounds, devoid of acidic groups, such as carboxylic and sulfonic acid groups.

Suitable solvents can be used in the preparation steps, but it is also possible to carry out all the preparation steps with the pure reagents, without the use of water or organic solvents.

The water soluble comb polyurethanes according to the invention are useful as water retention agents, deflocculants and viscosity stabilizers for paper coating compositions and provide a paper with a coating that has excellent printability, gloss and gloss.

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Another advantageous feature of the polyurethanes of the invention is the fact that they act as rheology and water retention buffers on different batches of industrial paper coating compositions having the same recipe; This means that, in the industrial coating process, the usual deviations of the theoretical amounts of the ingredients from the paper coating do not affect the rheology and water retention characteristics.

EXAMPLES

In the examples, the following materials were used:

TRIOL1: polypropylene glycol triol, molecular weight 1000 g / mol, Voranol CP 1055, from Dow Chemical Company.

ETHOXY1: polyethoxylated butanol, molecular weight 3000 g / mol.

ETHOXY2: polyethoxylated methanol, molecular weight 5000 g / mol.

ETHOXY3: polyethoxylated butanol, molecular weight 5000 g / mol.

ETHOXY4: polyethoxylated methanol, molecular weight 750 g / mol.

DIISOCIANATE 1: isophorone diisocyanate, molecular weight 222.3 g / mol, Desmodur I from Bayer Material Science.

TRIISOCYANATE1: hexamethylene diisocyanate trimer, NCO content 24.0%, NCO 3.1 functionality, Desmodur XP2410 from Bayer Material Science.

AMINE1: isophorone diamine, molecular weight 170.3 g / mol, from Sigma Aldrich.

AMINE2: diethanolamine, molecular weight 105.14 g / mol, from Sigma Aldrich

AMINE3: ethylenediamine, molecular weight 60.10 g / mol, from Sigma Aldrich.

AMINE4: 24% hydrazine hydrate solution, molecular weight 32.3 g / mol, from Sigma Aldrich. EXAMPLE I

Preparation of a comb polyurethane with procedure A

A reaction vessel, equipped with an internal thermometer, stirrer and cooler, was filled in a nitrogen atmosphere and at room temperature, with 100.0 g of TRIOL1 and 300.0 g of ETHOXY1. The mixture was heated under stirring conditions at 85 ° C and 0.15 g of 85% phosphoric acid was added. At 85 ° C, 69.0 g of DIISOCYANATE 1 were loaded into the homogeneous mixture, with stirring; after 20 minutes, 0.3 g of dibutyltindilaurate (DBTL) was added. The reaction temperature was maintained at 85 ° C until the titrimetric determination of the free groups of

-NCO still present gave a calculated value of 1.7% (value determined in this example and in the other examples according to the standard procedure ASTM D2572).

300 g of the product obtained were dispersed by vigorous stirring in 890 g of water cooled to 18 ° C. After 20 minutes, 9.7 g of AMINE1 dissolved in 39.3 g of water were added.

[0060] The product obtained had a solid content of 25.55%, a viscosity of 48 mPa * s (measured with a Brookfield® viscometer at 20 rpm) and a pH of 6.5.

EXAMPLE II

Preparation of a comb polyurethane with procedure A

A reaction vessel, equipped with an internal thermometer, stirrer and cooler, was filled in an atmosphere

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of nitrogen and at room temperature, with 50.0 g of TRIOL1 and 250.0 g of ETHOXY2. The mixture was heated under stirring at 85 ° C and 0.11 g of 85% phosphoric acid was added. At 85 ° C, 34.5 g of DIISOCYANATE 1 were loaded into the homogeneous mixture under stirring conditions; after 20 minutes, 0.3 g of dibutyltindilaurate (DBTL) was added. The reaction temperature was maintained at 85 ° C until the titrimetric determination of the free -NCO groups still present gave a calculated value of 1.26%.

300 g of the product obtained was dispersed by vigorous stirring in 893.1 g of water cooled to 18 ° C. After 20 minutes, 6.9 g of AMINE1 dissolved in 27.4 g of water was added.

The product obtained had a solid content of 26.15%, a viscosity of 62 mPa * s (measured with a Brookfield® viscometer at 20 rpm) and a pH of 6.4.

EXAMPLE III

Preparation of a comb polyurethane with procedure B

A reaction vessel, equipped with an internal thermometer, stirrer and cooler, was filled in a nitrogen atmosphere and at room temperature, with 300.0 g of ETHOXY1 and 0.11 g of 85% phosphoric acid. The mixture was heated under stirring conditions at 85 ° C and 56.6 g of TRIISOCYANATE1 were charged; after 20 minutes, 0.3 g of dibutyltindilaurate (DBTL) was added. The reaction temperature was maintained at 85 ° C until the titrimetric determination of the free -NCO groups still present gave a calculated value of 2.5%.

300 g of the product obtained by vigorous stirring were dispersed in 862.6 g of water cooled to 18 ° C. After 20 minutes, 12.8 g of AMINE1 dissolved in 51.5 g of water was added.

The product obtained had a solids content of 25.98%, a viscosity of 196 mPa * s (measured with a Brookfield® viscometer at 20 rpm) and a pH of 6.6.

EXAMPLE IV

Preparation of a comb polyurethane with procedure B

A reaction vessel, equipped with an internal thermometer, stirrer and refrigerator, was filled in a nitrogen atmosphere and at room temperature, with 274.5 g of ETHOXY 2 and 0.11 g of 85% phosphoric acid. The mixture was heated under stirring at 85 ° C and 31.1 g of TRIISOCYANATE1 were charged; after 20 minutes, 0.3 g of dibutyltindilaurate (DBTL) was added. The reaction temperature was maintained at 85 ° C until the titrimetric determination of the free -NCO groups still present gave a calculated value of 1.6%.

275 g of the product obtained by vigorous stirring were dispersed in 795.3 g of water cooled to 18 ° C. After 20 minutes, 7.6 g of AMINE1 dissolved in 30.2 g of water were added.

The product obtained had a solid content of 25.51%, a viscosity of 246 mPa * s (measured with a Brookfield® viscometer at 20 rpm) and a pH of 5.5.

EXAMPLE V

Preparation of a comb polyurethane with procedure B

A reaction vessel, equipped with an internal thermometer, stirrer and cooler, was filled in a nitrogen atmosphere and at room temperature, with 300.0 g of ETHOXY3 and 0.11 g of 85% phosphoric acid. The mixture was heated under stirring at 85 ° C and 22.0 g of TRISCOIANATE 1 and 10.1 g of DIISOCIANATE 1 were charged; after 20 minutes, 0.3 g of dibutyltindilaurate (DBTL) was added. The reaction temperature was maintained at 85 ° C until the titrimetric determination of the free -NCO groups still present gave a calculated value of 1.8%.

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280 g of the product obtained by vigorous stirring were dispersed in 826.4 g of water cooled to 18 ° C. After 20 minutes, 9.4 g of AMINE4 dissolved in 9.8 g of water was added.

The product obtained had a solid content of 26.07%, a viscosity of 412 mPa * s (measured with a Brookfield® viscometer at 20 rpm) and a pH of 6.8.

EXAMPLE VI

Preparation of a comb polyurethane with procedure B

A reaction vessel, equipped with an internal thermometer, stirrer and cooler, was filled in a nitrogen atmosphere and at room temperature, with 300.0 g of ETHOXY3 and 0.11 g of 85% phosphoric acid. The mixture was heated under stirring at 85 ° C and 22.0 g of TRISCOIANATE 1 and 10.1 g of DIISOCIANATE 1 were charged; after 20 minutes, 0.3 g of dibutyltindilaurate (DBTL) was added. The reaction temperature was maintained at 85 ° C until the titrimetric determination of the free -NCO groups still present gave a calculated value of 1.8%.

280 g of the product obtained by vigorous stirring were dispersed in 838.1 g of water cooled to 18 ° C. After 20 minutes, 2.7 g of AMINE3 dissolved in 10.0 g of water were added.

The product obtained had a solids content of 25.84%, a viscosity of 256 mPa * s (measured with a Brookfield® viscometer at 20 rpm) and a pH of 6.8.

EXAMPLE VII

Preparation of a comb polyurethane with procedure C

A reaction vessel, equipped with an internal thermometer, stirrer and cooler, was filled in a nitrogen atmosphere and at room temperature, with 300.0 g of ETHOXY2 and 0.11 g of 85% phosphoric acid. The mixture was heated under stirring at 85 ° C and 15.3 g of DIISOCYANATE 1 were charged; after 10 minutes, 0.3 g of dibutyltindilaurate (DBTL) was added. The reaction temperature was brought to 85 ° C until the titrimetric determination of the free -NCO groups still present gave a calculated value of 0.9%. The mixture was then cooled to 55 ° C and 6.6 of AMINE2 dissolved in 6.6 g of N-methylpyrrolidone were charged dropwise. After 20 minutes, the titrimetric determination of the free -NCO groups gave a calculated value of 0.0%. The reaction temperature was then brought to 85 ° C and 28.5 g of DIISOCYANATE1 were charged and reacted until the titrimetric determination of the free -NCO groups gave a calculated value of 1.5%.

300 g of the product obtained was dispersed by vigorous stirring in 898.0 g of water cooled to 18 ° C. After 20 minutes, 2.9 g of AMINE3 dissolved in 10.7 g of water were dropped.

The product obtained had a solid content of 24.99%, a viscosity of 194 mPa * s (measured with a Brookfield® viscometer at 20 rpm) and a pH of 6.3.

EXAMPLE VIII

Preparation of a comb polyurethane with procedure B

A reaction vessel, equipped with an internal thermometer, stirrer and cooler, was filled in a nitrogen atmosphere and at room temperature, with 300.0 g of ETHOXY4 and 0.11 g of 85% phosphoric acid. The mixture was heated under stirring at 85 ° C and 226.2 g of TRIISOCYANATE1 were charged; after 10 minutes, 0.3 g of dibutyltindilaurate (DBTL) was added. The reaction temperature was maintained at 85 ° C until the titrimetric determination of the free -NCO groups still present gave a calculated value of 5.9%. 470 g of the product obtained by vigorous stirring was dispersed in 1360 g of water cooled to 18 ° C. After 20 minutes, 16.7 g of AMINE3 dissolved in 62.1 g of water were placed.

The product obtained had a solid content of 25.1%.

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Application Examples

Compositions for coating the paper based on 100% carbonate (Hydrocarb 90, from Omya, Switzerland) were prepared using the comb polyurethanes of Examples I-VIII and with a prior art water retention agent.

The constitution of the compositions for coating the paper are shown in Table 1; The amounts of the ingredients are parts by weight.

Compositions for paper coating were defined by performing the following measurements:

• pH

• Brookfield @ viscosity, 100 rpm

• Dry material

• Water retention - Tappi T710 procedure

The data obtained are also shown in table 1.

The paper coating compositions were applied (13 g / m2) on offset sheets (80 g / m2); the sheets were conditioned for 24 hours at 21 ° C and 50% relative humidity and calendering (cylinder temperature 55 ° C, pressure 67.5 kg / cm, 4 contact points). The brightness and luster were measured and are shown in table 2.

Table 1

 COMPOSITIONS FOR PAPER COATING:

 1 2 3 4 5 6 7 8 96)

 HYDROCARB 90

 100 100 100 100 100 100 100 100 100

 Dow LATEX 9351)

 10 10 10 10 10 10 10 10 10

 REOTAN A2)

 0.045 0.045 0.045 0.045 0.045 0.045 0.045 0.045 0.045

 DEFOMEX 1083)

 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

 TINOPAL ABP-Z4)

 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8

 Example 1

 0.45 / / / / / / / / /

 Example 2

 / 0.45 / / / / / / /

 Example 3

 / / 0.45 / / / / / /

 Example 4

 / / / 0.45 / / / / /

 Example 5

 / / / / 0.45 / / / /

 Example 6

 / / / / / 0.45 / / /

 Example 7

 / / / / / / 0.45 / /

 Example 8

 / / / / / / / 0.45 /

 Viscolam GP375)

 / / / / / / / / 0.15

 CHARACTERISTICS OF THE COMPOSITIONS FOR PAPER COATING

 Dry material (%)

 70.32 70.40 70.18 70.16 69.95 69.95 69.97 70.21 70.18

 PH

 8.85 9.02 8.85 8.91 8.97 9.08 9.06 8.87 8.95

 Viscosity (mPa * s)

 550 655 570 650 600 770 650 450 960

 Water retention (g / m2)

 150 140 155 145 130 145 140 165 112

 1) Binder, styrene butadiene latex (Dow Chemical Co., USA) 2) Dispersant, sodium polyacrylate (Lamberti SpA., IT) 3) Antifoam agent, (Lamberti SpA., IT) 4) Optical brightener ( CIBA., CH) 5) ASE Thickener de Lamberti SpA. 6) Comparative.

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Table 2

 COMPOSITIONS FOR PAPER COATING:

 ° Brightness1) Gloss @ 75 ° 2)

 one

 100.8 72.5

 2

 100.6 72.1

 3

 101.1 72.8

 4

 100.5 72.0

 5

 100.3 72.4

 6

 100.4 72.7

 7

 100.9 72.6

 8

 100.6 75.2

 93)

 99.2 65.8

 1) Brightness, Tappi T452 procedure 2) Specular luster at 75 °, Tappi T480 procedure 3) comparative

Claims (7)

5 10 fifteen twenty 25 30 1. Paper coating compositions comprising a) from 30 to 80% by weight of inorganic pigment; b) from 0.05 to 3.0 parts by weight of every 100 parts by weight of pigment of at least one polyurethane in water-soluble non-ionic comb containing polyoxyethylene side chains each having a molecular weight greater than 500 and an ethylene oxide content of 80 to 99.9% by weight; c) at least 15% by weight of water; d) from 0.01 to 3% by weight of a dispersing agent; e) from 1 to 15% by weight of a binder, the paper coating compositions have a Brookfield® viscosity at 25 ° C and 100 rpm of less than 3,000 mPa * s. 2. Compositions for the paper coating according to claim 1, wherein the comb polyurethane has a total ethylene oxide content exceeding 50% by weight. 3. Compositions for coating paper according to claim 2, wherein the comb polyurethane has a total ethylene oxide content exceeding 70% by weight. 4. Compositions for paper coating according to claim 2 or 3, wherein the comb polyurethane has a molecular weight greater than 100,000 and polyoxyethylene side chains having a molecular weight of 2,000 to 20,000 and ethylene oxide content of the 90 to 99.9% by weight. 5. Compositions for the paper coating according to claim 1 wherein the comb polyurethane is obtained by reacting a bifunctional isocyanate containing polyoxyethylene side chains each having a molecular weight greater than 500 and an ethylene oxide content of 80 to 99.9% by weight with one or more compounds having a molecular weight of 34 to 300 and two groups that react with isocyanates. 6. Paper coating compositions according to claim 1, wherein the dispersing agent is derived from uncrosslinked anionic polyacrylate having a molecular weight of 5,000 to 40,000. 7. Compositions for the paper coating according to claim 1 wherein the inorganic pigment has 40 to 90% by weight of particles that are thinner than 2 microns and which are chosen from kaolins, calcium carbonate, talc, titanium dioxide, barium sulfate, gypsum and mixtures thereof.