NL7907493A - PAPER AND PAPER WITH A COATING. - Google Patents

Description

"I β -1-20975 / Vk / iv t

Applicant: Hercules Incorporated, Wilmington, Delaware, United States of America.

Short designation: Paper and paper coated.

The invention relates to paper provided with a coating consisting of a paper substrate with a coating composition applied on at least one surface thereof, composed of a bonding material and an organic pigment. The invention further relates to paper made from cellulose fibers and an organic pigment, wherein the organic pigment is dispersed substantially evenly throughout the paper by adding an aqueous dispersion of the cellulosic fibers before the paper product is formed.

The invention particularly relates to new paper products with coatings or fillers based on organic substances.

Paper and other cellulosic substrates are often coated to improve appearance and printability. These coatings usually consist of an inorganic pigment such as clay, calcium carbonate or titanium dioxide and a binder that binds the pigment particles to the substrate. The applied coating provides a soft, ink-absorbing surface suitable for printing. Furthermore, the inorganic pigraent particles reflect light, and make the coated substrate layer opaque and clear. Such particles are also used as a filler to improve the opaque and strength of the paper.

Recently, polymer particles such as finely divided polystyrene particles have been used as a substitute or partial substitute for the inorganic pigments in paper coatings or fillers. These polymer particles are referred to as organic pigments. It is desirable to obtain better compatibility between the organic pigments and the cellulose of the paper and the binders commonly used in the paper coatings.

According to the invention, improved paper products are obtained with organic particles in the form of coatings or fillers, and the paper is then characterized in that the organic pigment is a substantially insoluble particulate graft copolymer consisting mainly of the free radical-catalyzed grafts. copolymerization product of ♦ 7907493,% I * -2 «20975 / Vk / iv 1) at least one ethylene-like unsaturated monomer and 2) a water-soluble prepolymer with an RSV value of about 0.1 to 2.5 (1 M NaCl , 1%, - 25 ° C), wherein the prepolymer parts of the graft copolymer particles are present on the surface of the particles and the monomer is selected, from 1) a group consisting of methyl α-chloroacrylate, ethyl-od- chloroacrylate, methyl methacrylate, isopropyl methacrylate, phenyl methacrylate, vinyl chloride, acrylonitrile, methacrylonitrile, and monomers of formula 1 as listed below. ^ 10 carbon (Y) '' n where R is hydrogen or methyl, Y is methyl or chlorine and n is 0, 1, 2 or 3 and 2) the prepolymer is selected from a group consisting of anionic prepolymers and not ionic prepolymers prepared by an addition polymerization of a vinyl monomer or mixtures of vinyl monomers and the amount of prepolymer 2) used in preparing the graft copolymer particles is comprised between 1 and 25 wt. parts on every 100 wt. parts of monomer used 1) and the graft copolymer has a glass transition temperature Tg equal to or higher than 75 ° C.

Paper products according to the invention in which the particles are present in a coating will usually contain a binding material such as the substances used with inorganic pigments. The organic particles in the products of the invention are suitably compatible with such binders as well as more compatible with cellulose than the known polystyrene-based organic pigments.

In carrying out the process of the invention, an aqueous solution of the water-soluble prepolymer which may be an anionic prepolymer or a non-ionic prepolymer is first prepared. The prepolymers can be homopolymers or copolymers of two or more monomers. These polymers will be described in more detail below. To the aqueous solution of the prepolymer are added a free radical polymerization initiator and the desired monoethylene-like unsaturated monomer and 7907493-32075 / Vk / iv * * t the free radical graft copolymerization is carried out at a temperature from about 40 ° C to about 90 ° C. The exact temperature used in the graft copolymerization is known to a person skilled in the art and will depend on the initiator and the monomer used. A very stable latex is obtained. In some instances, the water may be removed if desired by drying to obtain a free-flowing particulate graft copolymer.

The primary function of the water-soluble anionic or non-ionic prepolymer is to stabilize the suspension and to prevent coagulation of the individual particles. After the first graft copolymerization is accomplished, some homopolymerization of the monomer can take place within the particles. A significant portion of the anionic or nonionic prepolymer will be grafted onto the surface of the graft copolymer particles. Substantially stable latex of the graft copolymer particles is prepared according to the invention without the need for additional stabilizer to be present.

The water-soluble anionic and non-ionic prepolymers used in the invention can be prepared by addition polymerizing vinyl monomers and mixtures thereof and are known as water-soluble addition type polymers. Examples of nonionic monomers are,, 3-ethylenically unsaturated amides such as acrylamide, methacryl amide, Ν, Ν-dimethylacrylamide, N-methyl acrylamide, N-methylol acrylamide and diacetone acrylamide. Other suitable non-ionic monomers are hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and N-vinyl pyrrolidone. Monomers that can be used to prepare anionic prepolymers are oc, p-ethylenically unsaturated mono- and polycarboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid. Other suitable monomers that can be used to prepare the anionic prepolymers are vinyl sulfonic acid, allylsulfonic acid, styrene sulfonic acid and 2-sulfoethyl methacrylate.

Non-ionic prepolymers include homopolymers and copolymers of the above-mentioned non-ionic monomers such as, for example, polyacrylamide, the homopolymer of acrylamide, polymethacrylamide, the homopolymer of methacrylamide, a polymer of acrylamide and hydroxyethyl acrylate, a co-55 polymer of methacrylamide and hydroxypropyl copolylamide 790 74 93 V i -4- 20975 / Vk / iv acrylamide and hydroxyethyl methacrylate.

Other suitable water-soluble nonionic polymers that can be used according to the invention are polyvinyl alcohol and polyethylene oxide.

Examples of anionic prepolymers are copolymers of acrylic amide and acrylic acid, copolymers of methacrylamide and acrylic acid, copolymers of acrylamide and methacrylic acid and copolymers of methacrylamide and methacrylic acid. As will be known to a person skilled in the art, these prepolymers are only anionic in the neutralized form. Therefore, to take advantage of the anionic properties, it is necessary to use these prepolymers in the neutralized form. This poses no problem when the organic pigments are prepared from these anionic prepolymers to prepare the coating for the paper because coating on paper is usually carried out at an alkaline pH value.

Other suitable water-soluble polymers are the naturally occurring polymers such as starch, non-ionic, the non-ionic and anionic derivatives of starch, and the naturally occurring polymers that have been water-solubilized by a derivative treatment such as hydroxyethyl cellulose (non-ionic) and the sodium salt of carboxymethyl cellulose (anionic). The water-soluble anionic and non-ionic prepolymers are easily and quickly prepared by simultaneously adding the desired monomers in the desired amounts and a water-soluble free radical polymerization initiator each in an aqueous solution to a reaction vessel with water held at a temperature from about 80 ° C to about 90 ° C. Suitable free-radical polymerization initiators are those used for the preparation of the graft copolymerization particles of the invention and are further explained below. The amount of initiator used will be such that it is a sufficient amount to obtain water-soluble prepolymers having an RSV (Reduced Specific Viscosity) y of from about 0.1 to about 2.5, preferably from about 0, 1 to about 1, measured as a 1% solution in 1 m NaCl at 25 ° C, (1M NaCl, 1%, 25 ° C) or an RSV value from about 0.1 to about 2.5, at preferably about 0.15 to about 1, measured as a 1% solution in 0.1 M NaCl at 25 ° C (0.1 M NaCl, 1%, 25 ° C).

There are two main conditions for the graft copolymer particles 7907493-5-209T5 / Vk / iv which have been prepared according to the method of the invention and these are the following. They must be 1) water insoluble and 2) have a sufficiently high melting or softening point so that they are not deformed to a significant degree under the conditions of heat or pressure or both, which are subject to use. Preferably, the graft copolymer will have a second order transition temperature (glass transition temperature Tg) equal to or greater than 75 ° C.

Any monomer that undergoes graft copolymerization with the water-soluble prepolymers to be described below to obtain graft copolymer particles meeting the above requirements can be used in accordance with the invention. Suitable monomers are the monoethylene-like unsaturated monomers such as acrylic acid esters, in particular methyl-chloro-acrylate and ethyl-chloroacrylate, methacrylic acid esters such as methyl methacrylate, isopropyl methacrylate and phenyl methacrylate and monomers of the formula II as mentioned above, wherein R is hydrogen or a methyl group, Y is a methyl group or chlorine and n has the value 0, 1, 2 or 3. Examples of such monomers are styrene, o'-methylstyrene, monochlorostyrene, dichloro-styrene. trichlorstyrene, monomethylstyrene, dimethylstyrene and trimethylstyrene. Other suitable monomers are vinyl chloride, acrylonitrile, and methacrylonitrile.

Mixtures of two or more monoethylenically unsaturated monomers can be used in the practice of the process of the invention, provided that the graft copolymer obtained is water insoluble in particulate form and has a Tg value equal to or greater than 75 ° C. Also polyethylene-like unsaturated monomers such as divinylbenzene, trivinylbenzene, divenylnaphthalene, diallylphthalate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethyl acrylate, dimethyl acrylate, dimethyl acrylate, polypropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polypropylene glycol dimethyl acrylate More of these compounds can be used as a mixture with monoethylenically unsaturated monomers to obtain the cross-linked graft copolymer particles.

Of the above monoethylene-like unsaturated monomers, styrene, vinyl chloride, acrylonitrile and methyl methacrylate are preferred.

Of the above-mentioned polyethylene-like unsaturated monomers, divinylbenzene, diallylphthalate, ethylene glycol dimethacrylate and 1,3-butyl-glycol dimethacrylate are preferred.

In some instances, it is desirable that the prepolymer moiety of the graft copolymer particles contain a group that is reactive. Such reactivity will usually increase the bonding properties of the particles together and to the surface to which they are applied. Reactive groups can be fed to some monomers for the preparation of a prepolymer, they can be fed to a prepolymer after its preparation or they can be fed to the graft copolymer particles after their preparation.

Reactive groups can be fed in the form of an aldehyde such as with formaldehyde, glyoxal and glutaraldehyde with the monomers having an amide function such as acrylamide and monomers having hydroxyl groups such as hydroxyethyl acrylate and with prepolymers having amide functions such as poly (acrylamide) or hydroxyl groups such as poly (vinyl alcohol). Using dialdehydes such as glyoxal, the reactive group will be an aldehyde. Using formaldehyde, the reactive group will be N-methylol.

The amount of aldehyde used to obtain the graft copolymer particles having sufficient reactive groups will be about 0.25 mole to about 3 mole, preferably about 1 mole to about 2 mole for each mole of amide or hydroxyl function. The reaction will be carried out at a temperature from about 20 ° C to about 60 ° C at a pH of about 8-10, except when formaldehyde is used as aldehyde because the reaction is then carried out at a pH of about 2-3.

The presence of reactive groups on the surface of the particles of the invention improves adhesion by the reactions between the particles or between the particle and the substrate.

The amount of water-soluble prepolymer used in the preparation of the graft copolymers according to the method of the invention can range from about 1 part to about 25 parts, based on 100 parts of monomer or ronomer mixture. The preferred amounts are from about 2 to 10 parts per 100 parts of monomer or monomer mixture.

As indicated above, the graft copolymerization is performed by adding the graft copolymerisable monomer to a solution of a water-soluble prepolymer in the presence of a polymerization initiator.

790 74 93 • «i -7- 20975 / Vk / iv t

The prepolymer can be present in the reaction vessel from the beginning or it can be added together with the monomers. The polymerization initiator is usually added continuously along with the monomer.

A wide variety of chemical polymerization initiators can be used to prepare the latex of the invention, with peroxy compounds being most suitable. The initial step of the polymerization involves the formation of a graft copolymer between the monomer and the water-soluble prepolymer. The initiator probably first introduces free radical sites on the prepolymer. The addition of monomer to these sites then gives the desired graft copolymer particles.

The water-soluble suitable initiators include those which are activated by heat, such as sodium persulfate and ammonium persulfate. The polymerizations are carried out with these initiators at a temperature usually located at 70-95 ° C. Other water-soluble initiators that can be suitably used are the so-called redox initiator systems such as ammonium persulfate sodium bisulfite iron (II) ion and t-butyl hydroperoxide sodium formaldehyde sulfoxylate. Redox initiators are activated at relatively low temperatures and the polymerizations using these systems can be carried out at temperatures between 20 and 80 ° C.

The amount of initiator used will be known to a person skilled in the art. Usually, the amount is from 0.1 part to about 5 parts initiator for 100 parts of monomer.

The invention will be further elucidated by means of the following examples, wherein the parts are parts by weight unless stated otherwise.

Example Ia

The prepolymer used in this example was 92% acrylamide-8% acrylic acid copolymer. The Brookfield viscosity of a 12.5% aqueous solution of the prepolymer was 1286 centipoise measured at 26 ° C.

A 12-liter reactor was equipped with a stirrer, thermometer, cooler and three dropping funnels. The reaction vessel was charged with 2250 g of distilled water. A dropping funnel was charged with 3500 g of styrene, a second funnel with 80 g of ammonium persulfate dissolved in 400 g of distilled water and the third funnel with 2200 g of an 8% aqueous solution of the above mentioned 790 74 93 -8- 20975 / Vk / iv prepolymer. The water in the reaction vessel was heated to 78 ° C. The contents of the three dropping funnels are added dropwise to the reaction vessel over a period of about 3 hours. During this time, the contents of the reaction vessel were kept at a temperature of 80-595 ° C. The resulting latex with a solid content of 46.8% was cooled to room temperature (about 25 ° C).

Example Ib

Example Ia was repeated using the following conditions: The prepolymer was used in an amount of 2400 g as a 7.3% aqueous solution. The ammonium persulfate in the solution consisted of 60 g of ammonium persulfate dissolved in 250 g of distilled water and the resulting latex was diluted with 1100 g of distilled water to obtain a latex with a solids content of 39.5%.

Example 1c Example 1b was repeated except that initially distilled water was added to the reaction vessel in an amount of 3150g instead of 2250g and the ammonium persulfate solution consisting of 48g ammonium persulfate dissolved in 200g distilled water. In this example, no additional water was added to the prepared latex as indicated in Example Ib. The latex prepared had a solids content of 39.6%.

Example Id

Example Ic was repeated except that the ammonium persulfate solution consisted of 46.4 g ammonium persulfate and 210 g distilled water. The latex prepared had a solids content of 41%.

Example Ie

Example Ic was repeated except that the ammonium persulfate solution consisted of 38.4 g ammonium persulfate in 160 g distilled water. The latex prepared had a solids content of 41%.

Example Ha 30 The latex mentioned in Examples Ia, Ib, Ic, 1d and Ie was combined and a coating color was prepared from a portion of this latex. To a vessel equipped with a stirrer operating under high shear stress, 26.5 kg of 70% aqueous clay pigment suspension added under constant stirring was marketed under the designation "Ultra-white 90", 6, 8 kg of a 2% aqueous solution of a 7907493 -9- 20975 / Vk / iv water-soluble medium viscosity sodium carboxymethyl cellulose (degree of substitution about 0.9) and 15.5 kg of 47.7% polyvinyl acetate-latex binder The pH of the resulting mixture was adjusted to 8.8 with concentrated NH 2 OH 11.1 Kg of the combined latex from Examples 5 Ia-Ie was added under high shear effect by stirring. adjusted to 8.5 with concentrated NH4 OH.

The total solids content of the resulting coating colorant was 56.4%. This is shown as coating color 3.

Example 11b Example 11a was repeated except that 11.6 kg of polyvinyl acetate latex binder was used instead of 15.5 kg and 0.8 kg of water was added to obtain a coating dye having a solid content of 55> 7% · This is shown as coating color 4.

Example IIc Example 11a was repeated except that 7> 7 kg of polyvinyl acetate latex was used as the binder instead of 15.5 kg and 1.5 kg of additional water was added to obtain a coating dye with a solid content of 56.9%. This material is indicated as coating color 5.

20 Sample member

64.8 kg of an aqueous clay suspension as used in Example 11a, 4.6 kg of water, 6.8 kg of a 2% aqueous, were added to a reactor provided with a stirrer with which a high shear can be effected. sodium carboxymethyl cellulose solution used in Example 11a and 15.5 kg of 47% polyvinyl acetate latex as a binder as used in Example 11a. The pH of the resulting mixture was adjusted to 8.5 with concentrated NH 2 OH. This coating dye, designated as coating color 1, had a solids content of 55.8%.

Example 50 Example paragraph was repeated except that the amount of added aqueous clay suspension was 58.3 kg. The amount of water added was 1.6 kg, the amount of polyvinyl acetate latex as the binder was 15.5 kg, and * 9.4 kg of a 48% aqueous dispersion of polystyrene-containing organic pigment was also added to the mixture. This coating 55 dye, designated as coating color 2, had a solids content of 55.9% 790 7493 -10-20975 / Vk / iv

Table A lists the amounts of sodium carboxymethyl cellulose and binder composition of the above coating colors.

Table A

pigments polyvinyl-5 _ (parts by weight) _ acetate coating clay poly * - binder CMC color styrene image (parts by weight) (parts by weight) _ _ _ Ia-Ie _ _ 1 100 - - 16 0.3 10 2 90 '10 - 16 0.3 3 90 - 10 16' 0.3 4 90 - 10 12 0.3 5 90 - 10 8 0.3 15 * sodium carboxymethyl cellulose used as a viscosity enhancing additive.

Each coating dye was applied to commercially available 50-lb. paper using a scraper blade from a pilot coating machine. Several tests were conducted with respect to the coated paper. For example, uniformity, opaqueness and clarity were determined on uncalend coated paper. Other tests were performed with the coated paper layers that had been calendered by passing the coated paper through a hot calendar (71 ° C) which was done four times at 1500 µl. These tests and the results obtained are shown in Table B.

25 Table B

coating weight Sheffield opaque clarity color coating similarity original K & N

(lb / moderation _ 3000 ft ^ _ _ _.__ 30 1 5.0 23 88.1 85.7 55.8 2 4.8 21 88.5 86.0 54.9 3 4.0 26 87.3 85.8 55.7 4 4.6 29 86.9 86.2 53.1 5 4.5 31 87.7 86.2 51.6 35 790 7 4 93 t -11- 20975 / Vk / iv fcabel B (continued) coating 75 ° mirror gloss calendared ink set-off ** water IGT color 4 slits at 71 ° C ** _ (density) dispersion Pick 500 1000 1500 '2000 30 60 90 thing (feet / 5 _ pli pli pli pli sec »sec» sec, (density) minute) 1 49.5 58.8 63.7 69.0 0.88 0.73 0.63 1.58 '197 2 61.8 73.7 78.8 79.7 0.78 0.63 0.54 1.61 236 3 48.3 62.2 69.2 71.5 0.82 0.66 0.58 1.44 276 4 52.5 63.0 68 .5 71.3 0.66 0.54 0.47 0.61 236 10 5 56.2 65.8 71.2 73.5 0.56 0.39 0.34 1.69 177 TAPPI Standard UM-518 (average of 5 tests) TAPPI Standard T-425, Hunter Opaque Meter (average of 5 tests) ** TAPPI Standard T-452 (average of 6 tests) 15 TAPPI Standard UM-553 (average of 2 tests) __ ** TAPPI Standard T-480 (average of 12 tests) pli =. Pounds per linear inch (1 pound is 0.45 kg and 1 in. ch is 2.54 cm) ** Jansen, F.B., "Application of the IGT-Paintability Tester", third updated edition, IGT Monograph 12, Amsterdam, Stichting Instituut voor.

20 Graphic technology TNO, 1972, p. 14, IPI No. 3 degree of tackiness of the ink used (average of 3 tests) ** Parsons, CL, TAPPI, 58 (5), 123 (1975), equipment operating at a constant speed of 2 m / second and at a split pressure of 40 kgf.

Inmont jet halftone black ink was applied (average of 3 25 tests)

* 9 TAPPI Standard T-499 (No. 24 Sticky Polybutene Oil was used instead of Sticky Ink, test temperature is 22 ° C (average of 3 tests) Example III

A one liter polymerization vessel, equipped with a jacket that can be cooled with water, provided with a stirrer. a thermometer, a cooler and three dropping funnels were used to carry out the next polymerization. To this end, a dropping funnel was filled with a solution of 97.5 g of acrylamide dissolved in 390 g of distilled water, the second dropping funnel was filled with a solution of 2.5 g of acrylic acid dissolved in 10 g of distilled water and the third dropping funnel was filled dissolved in 2.5 g of distilled water with 2.5 g of ammonium per 790 74 93 t -12- 20975 / Uk / iv sulfate. The polymerization vessel was charged with 117 g of distilled water and heated to 85 ° C-87 ° C while passing nitrogen. The contents of the three dropping funnels were added dropwise to the polymerization vessel over a period of 2 3/4 hours 5 to obtain a prepolymer solution. The prepolymer was a 97.5% acrylamide-2.5% acrylic acid copolymer. The RSV value of the prepolymer was 0.34 (0.1 M NaCl, 1%, 25 ° C). Measured as a 1% solution in 1M NaCl at 25 ° C, (1M NaCl, 1%, 25 ° C), the prepolymer had an RSV value of 0> 29 · The prepolymer solution had a solid content of 15.8 wt .%. This prepolymer 10 was diluted with distilled water to obtain a solids content of 10%.

Then, a reaction was effected in a one liter polymerization vessel equipped with a water jacket, the polymerization vessel being provided with a stirrer, a thermomether, a cooler and two dropping funnels. The polymerization vessel was charged with 163 g of the above 10% prepolymer solution and 326 g of distilled water. One dropping funnel was charged with 327 g styrene and the other dropping funnel with 8.6 g ammonium persulfate dissolved in 34.5 g distilled water. The contents of the vessel were heated to 85 ° C by circulating hot water in the jacket. The contents of the two dropping funnels were added dropwise to the polymerization vessel over a period of 2 hours. After the addition was complete, the contents of the polymerization vessel were stirred at a temperature of 89-91 ° C for 15 minutes, after which the contents were cooled to room temperature. The latex obtained was filtered through a 100 mesh filter (150 µm). The latex obtained contained a small amount of agglomerated material and to crush it, the latex was passed through a homogenizer. The latex had a solids content of 41% and the particles had a particle size of 0.6 µm. The particle size was determined by performing a turbidity measurement according to a method indicated by A.B. Loebel (Official Digest, 200, February 1959). The latex was mixed with an amount of glyoxal which was molar equivalent to the amount of acrylamide used in the preparation of the prepolymer.

Example IV

Three coating dyes were prepared. These coating dyes are designated as coating colors 6, 7 and 8. These dyes were prepared by carefully mixing, under high shear stress, the compounds listed in Table 7907493 -13-20975 / Vk / iv τ. C. The adjustment of the pH value was done as stated in table C. In the table the amount is indicated in grams (g).

5 Table C

* coating color £ J_ 8_ latex composition (example III) - - 61 g polystyrene pigment 10 (48% aqueous dispersion) - 52 g CMC * (3% aqueous solution) 13.3 g 13.3 g 13.3 g polyvinyl acetate- latex (binder (47.7% solids) 51.9g 51.9g 51.9g distilled water 25.3g 9g 15 clay pigment _ (70% aqueous dispersion) 178.6g 142.8g 142.8 g pH adjusted with concentrated ΝΗή0Η to 999% solid 55.4 55.7 55.2 20 * CMC sodium carboxymethyl cellulose soluble in medium viscosity water, a substitution degree of about 0.9, used as a viscosity enhancing additive .

Table D shows the composition for the pigment, sodium carboxymethyl cellulose and binder for the above-mentioned coating dyes.

Table D

pigments (parts by weight) polyvinyl coating clay poly particles CMC * acetate 30 color styrene pre. (parts by weight) binder _ _ ______ image UI _ (parts by weight) 6 100 - - 0.3 20 7 80 20 - 0.3 20 8 80 - 20 0.3 20 35 * sodium carboxymethyl cellulose, used as a viscosity enhancing additive.

790 7493 -14- 20975 / Uk / iv

Each coating dye was applied to the felt side of paper (55-lb) using a Meyer rod. The coated paper layers were dried in an oven through which air was passed at a temperature of 100 ° C for 45 seconds. When the paper was coated 5, with coating color 6, all tests except the gloss test (which was performed as stated) were performed on coated paper sheets which had been calendared by passing the coated sheets through a heated calender at a temperature of 71 ° C, which was accomplished four times (four slits) at 250 µl. When paper 10 was coated with coating colors 7 and 8, all tests except the gloss test (which was performed as mentioned) were performed on coated paper sheets which had been calendared by passing the coated sheets through a heated calender at a temperature of 71 ° C, which was accomplished four times (four slits) at 250 µl.

Table E

coating weight opaque brightness_

coating color originally K & N

(lb / * '** 4 (1 _ 3000 ft2) _ _ _ 20 6 7.1 88.4 74.4 49.7 7 6.5 88.3 76.1 49.3 8 7.2 88, 2 75.3 48.4

Table JS (continued)

25 coating 75 ° mirror gloss caked set-off IGT

color loin, 250 pli, 71 ° C ** (density) * 5 Peak after 2 after 3 after 4 30 60 90 (feet /

-%YOU

slits slits slits sec, sec, sec. minute) 6 57 60 63 0.9 0.8 0.6 561 30 7 68 71 74 0.8 0.6 0.5 525 8 70 71 73 0.6 0.4 0.4 570 TAPPI Standard T-425 , Hunter Opaque meter (average of 5 tests) TAPPI Standard T-452 (average of 6 tests) 35 * i TAPPI Standard UM-553 (average of 2 tests) vt) TAPPI Standard T-480 (average of 12 tests) * 9 see from table B (average of 3 tests) * ksee * j from table B (average of 3 tests) 7907493 ψ * -15- 20975 / Vk / iv

Example V

A 10% solution of a water-soluble prepolymer was prepared by dissolving 43.7 g of poly (acrylamide) in 393.1 g of distilled water. The poly (acrylamide) had an RSV value of 0.45 (1M NaCl, 1%, 25 ° C).

A one liter jacketed polymerization vessel through which water can be fed was equipped with a stirrer, a thermometer, a cooler and three dropping funnels. The vessel was filled with 108.8 g of prepolymer solution and 986 g of distilled water. A dropping funnel was filled with 436 g of styrene, the second dropping funnel with 328 g of prepolymer solution and the third drop funnel was filled with a solution of 12 g (NH 2 SgOg dissolved in 48.4 g of distilled water. The contents of the polymerization vessel were heated to 85-86 ° C while passing nitrogen, by recirculating hot water in the jacket The contents of the dropping funnels were added dropwise to the vessel over a period of two hours. Furthermore, as catalyst 1 g (NH4) ^ 8202, dissolved in 4 g of distilled water, added to the reaction vessel to complete polymerization The resulting latex, after filtering through a 100 mesh (150 µm) filter, had a solids content of 25.6% and the particles in the latex had a particle size of 0.5 to 0.8 µm. The particle size was measured according to Transmission Electron Microscopy.

Example VI

A one liter polymerization vessel with an Aquarius count was equipped with a stirrer, a thermometer, a cooler and two dropping funnels. The vessel was filled with 1854 g of prepolymer solution and 3685 g of distilled water.

The prepolymer solution was an aqueous solution of 97.5% acrylamide-2.5% acrylic acid copolymer. The solution contained 10% by weight of the prepolymer and the prepolymer had an RSV value of 0.39 (1M NaCl, 1%, 25 ° C). A dropping funnel was charged with 3532 g of styrene and 176.6 g of divinyl benzene. The second dropping funnel was filled with a solution of 97.4 g of ammonium persulfate dissolved in 390 g of distilled water. The contents of the polymerization vessel were heated to about 92-94 ° C under nitrogen. The contents of the two dropping funnels were added dropwise to the polymerization vessel over a period of about 4 hours. The latex was stirred for 15 minutes after the addition was finished and then filtered through a 100 mesh (150 µm) sieve 790 7 4 93 -16- 20975 / Vk / iv. The latex had a solids content of 40%. The particle size was about 0.7yftm. The particle size was determined by a turbidity measurement according to the method of A.B. Loebel (Official Digest, 200, February 1959).

Example VII

A 2 liter polymerization vessel with a water jacket was equipped with a cooler, two thermometers, two dropping funnels, a burette, nitrogen supply tube and a mechanical stirrer. The polymerization vessel was charged with 986 g of distilled water, 108.8 g of a 10% aqueous solution of 10 polyacrylamide with an RSV value of 0.45 (1M NaCl, 1%, 25 ° C). A dropping funnel was charged with 328 g of a 10% aqueous solution of. polyacrylamide with the same RSV value as mentioned above. The second dropping funnel was filled with 436 g of styrene and the burette was filled with a solution of 12 g of ammonium persulfate dissolved in 48.4 g of distilled water.

The contents of the polymerization vessel were heated to 85 ° C by circulating hot water through the jacket. The contents of the two dropping funnels and the burette were added dropwise to the polymerization vessel over a period of two hours. An exothermic reaction was observed after about 90 minutes and was easily controlled by cooling the polymerization vessel. After the addition was. the resulting latex was stirred for 15 minutes. A slight styrene odor was observed and 1 g of ammonium persulfate dissolved in 4 g of distilled water was added to complete the polymerization.

The latex was filtered through a 100 raesh (150 µm) sieve. The latex obtained had a solids content of 25.6%. The latex was evaporated to a solids content of 38.4%. The particles in the latex had a particle size of 0.5-0.8 fkm measured with a Coulter Counter.

The above latex was reacted with glyoxal as follows. To this end, 599 g of the latex with a solids content of 38.4% was placed in a reaction flask and the pH was adjusted to a value of 1.6-9.0 with 50 cc of 1M NaOH. 85.5 g of a 40% solution of glyoxal was added to obtain a pH of 5.7. The pH was reset with 1M NaOH to a value of 8.8. Sufficient water was added to the reaction mass to obtain a solids content of 29.7%. The latex was stirred for 55 minutes, during which time a significant increase in viscosity 790 7 493-17 20975 / Vk / iv cosity was observed. The pH was changed from 7.9 to 3.0 with 2 ral concentrated hydrochloric acid.

s

Example VIII

A copolymer was prepared of 97.5% acrylamide-2.5% acrylic acid.

Hefc copolymer had an RSV value of 0.34 (0.1M NaCl, 1%, 25 ° C). A 2 liter polymerization vessel with a water jacket was equipped in the manner as in Example VII and charged with 217 g of distilled water and 108.8 g of a 10% aqueous solution of the above copolymer. One dropping funnel was charged with 218 g of styrene and the other dropping funnel with 5.7 g of aramonium persulfate dissolved in 23 g of distilled water. The contents of the polymerization vessel were heated to 86 ° C by circulating hot water through the jacket. The contents of the two dropping funnels were added dropwise over a period of 2.5 hours. An exothermic reaction was observed after about 1.75 hours, which was easily controllable by cooling the polymerization vessel. The prepared latex was filtered through a 100 mesh (150 µm) sieve. The latex had a solids content of 41.1%. The particles had a particle size of 0.64 µm.

The particle size was determined by a turbidity measurement performed according to the method of A.B. Loebel (Official Digest, 200, February 1959)

Example IX

A latex was prepared according to the procedure described in Example VIII, except that the copolymer was used as a 90% acrylamide -10% acrylic acid copolymer with an RSV value of 0.44 (0.1 M NaCl, 1%, 25 ° C). The latex had a solids content of 41.1%. The particles had a particle size of 1.62 determined in the same manner as in Example VIII.

Example X.

264.1 g of the latex referred to in Example VIII was mixed with 49.2 g of a 40% aqueous solution of glyoxal (19.7 g of glyoxal). The aqueous solution obtained had a solids content of 41%.

Example XI

249 g of the latex indicated in Example IX was mixed with 42.5 g of a 40% aqueous solution of glyoxal (17.1 g of glyoxal). The resulting aqueous solution had a solids content of 41%.

35 79074 93 -18-. 20975 / Uk / iv

Example XII

Four coating dyes were prepared. These coating dyes are indicated as coating colors 9, 10, 11 and 12. These coating dyes were prepared by mixing well the compounds listed 5 in Table F. The pH value was adjusted as stated in Table F. Each coating dye was applied to the felt side of 55 lb paper using a Meyer rod. The coated sheets were dried in an oven through which air was passed at a temperature of 100 ° C for 45 seconds. The coated sheets were calendared by passing them through a heated calendar at a temperature of 71 ° C at 750 pounds per linear inch (pli, 1 pound is 0.45 kg and 1 inch is 2.54 cm).

The gloss measurements reported in Table G were made with sheets passed through the calender (two slits), three times (three slits) and four times (four slits) twice. With the color coated paper 10, all other tests were performed after the coated sheets were passed through the calender (four slits) four times. With paper coated with the coating dye 9 and 12, all other tests were performed after the coated sheets were passed through the calender (three slits) 20 three times. With paper coated with a color 11 coating, all other tests were performed after the coated sheets had been passed through the calender twice. The test results are shown in Table G.

Table F

25 coating color 9 10 11 12 latex composition according to example X 61 g latex composition according to example XI - 61 g 30 polystyrene pigment (48% aqueous dispersion) - - - 52 g CMC "* (3% aqueous solution) 13.3 g 13.3 g 13.3 g 13.3 g polyvinyl acetate latex binder (47.7% solids) 52.4 g 52.4 g 52.4 g 52.4 g 35 distilled water 2.1 g 2.1 g 27.3 g 11.1 g 790 7493 r -19- 20975 / Vk / iv table F (continued) coating color 9 10 11 12 clay pigment (70% aqueous dispersion) 142.8 g 142.8 g 178.6 g 142.8 g 5 initial pH 3.6 3.7 4.8 5.0 pH adjusted with concentrated NH4 OH to 9.0 9.0 9.0 9.0 CMC is sodium carboxymethyl cellulose soluble in water with a medium-viscosity, a degree of substitution of about 0.9, used as a viscosity enhancing additive.

Table G

coating weight 75 ° mirror gloss * l IGT * 2 color coating at 71 ° C, 750 pli Peak 15 (lb / 234 (feet / 2 _ 3000 ft) slits slits slits minute) 9 7.4 70 71 73 482 10 7.5 63 66 69 299 11 6.7 60 61 61 299 20 12 7.1 71 71 75 323

coating ink set-off * 3 clear-opaque-K&N

color (density) _ nity * h nity ink * ^ 30 60 90 15 _____ sec, sec, sec. _____ _ _ 9 0.55 0.45 0.39 74.6 89.8 48.6 10 0.71 0.60 0.47 73.7 89.3 47.8 11 0.82 0.72 0, 67 75.8 90.4 49.8 12 0.78 0.58 0.50 76.5 91.1 49.1 I0 * 1 TAPPI Standard T-480 (average of 12 tests) * 2 See * 3 from table B (average of 3 tests) * 5 See *} of Table B (average of 3 tests) * ij TAPPI Standard T-452 (average of 6 tests) 5 * 5 TAPPI Standard T-425, Hunter Opaque Meter (average of 5 tests) TAPPI Standard UM-553 (average of 2 tests) 790 74 93 -20- 20975 / Vk / iv t

Example XIII

A one-liter polymerization vessel with a water jacket was equipped with a stirrer, a thermometer, a cooler and three dropping funnels.

The polymerization vessel was charged with 2.5 g of water-soluble sodium carboxymethyl cellulose of low viscosity and a degree of substitution of 0.7 * and 300 g of distilled water. The dropping funnels were filled with 250 g of styrene, 2.4 g of sodium formaldehyde sulfoxylate in 50 g of distilled water and 3.4 g of 70% tertiary butyl hydroperoxide in 50 g of distilled water. The contents of the polymerization vessel were heated to 73 ° C by circulating hot water in the jacket 10. 10% of the styrene and 20% of the catalyst solution were added to the reaction vessel. After ensuring that latex was formed after about 10 minutes, the rest of the contents of the dropping funnel were added dropwise over a period of 3 hours. The yield was 566.7 g of white latex with 38.5% solids. The product had a Brook-15 field viscosity of 370 cps (60 rpm) and an average particle size (by the method of Loebel, Official Digest, 200, Feb. 1959) of 0.35.

Example XIV

A one liter polymerization vessel with a water jacket, was equipped with a stirrer, thermometer, cooler and three dropping funnels. A dropping funnel was filled with a solution of 90 g of acrylamide dissolved in 360 g of distilled water, the second dropping funnel was filled with a solution of 10 g of acrylic acid in 40 g of distilled water and the third dropping funnel was filled with 3.75 g of ammonium persulfate dissolved in 71 g of distilled water. The polymerization vessel was charged with 195 g of distilled water and heated to 86-89 ° C while passing nitrogen. The contents of the three dropping funnels were added dropwise to the polymerization vessel over a period of 2 hours, after which the reaction mass was heated to -88.5 -90 ° C for 15 minutes. The copolymer solution was cooled to room temperature. The RSV value of the copolymer was 0.38 (1M NaCl, 1%, 25 ° C). The total solid was 14.2%. The prepolymer was diluted with distilled water to a solids content of 10%.

A 2 liter polymerization vessel, with a water jacket, was equipped with a stirrer, a thermometer, a cooler and two dropping funnels. The polymerization vessel was charged with 108.8 g of the above-mentioned prepolymer 790 7 493 S- * -21-20975 / Vk / iv as 10% solution and to this was added 217 g of distilled water.

One dropping funnel was charged with 218 g of styrene and the other with 5.7 g of ammonium persulfate dissolved in 23 g of distilled water. The polymerization vessel contents were heated to 86.5 ° C by circulating hot water through the jacket. The contents of the two dropping funnels were added dropwise to the polymerization vessel over 2 hours. After the addition was complete, the contents of the polymerization vessel were stirred at a temperature of 88-90 ° C for 15 minutes, followed by cooling to room temperature. The resulting latex was filtered through a 100 mesh screen (150 µm). No grit was separated. The latex obtained had a solids content of 41.5% and a particle size of 0.7 / ua (Loebel method, Official Digest, 200, February 1959)

Example XV

A portion of the latex prepared according to Example XIV was treated with glyoxal as follows. 180.8 g of the latex was placed in a beaker. To this was added 12.6 g of a 40% aqueous solution of glyoxal (5.02 g of glyoxal). The pH achieved was 1.8 and the solid content was 41.4%. The reaction with glyoxal was carried out by taking 100 g of the above-mentioned latex-glyoxal mixture, raising its pH from 1.8 to 8-8.5 with 5M 20 NaOH with stirring for 15 minutes, diluting to 10% solid substance and adjust the pH to about 2 with concentrated sulfuric acid.

Example XVI

The compositions of Examples XIV and XV were tested as a filler for paper. Sheets were manufactured using a Noble & 25 Wood "handsheet" device. The pulp consisted of a 50:50 blend of bleached hard wood: bleached soft wood pulp processed into a 500 cc "Canadian Standard Freeness". The paper was adjusted to a pH value of 4.5 (1% alum).

The latex was tested for addition levels of 4% and 8% (dry basis) using 0.05% high molecular weight cationic acrylamide as a retention aid. The results of the examination of the paper are shown in Table H. The test results are the average of the test results obtained with four sheets of paper.

790 74 93 V - -22- 20975 / Vk / iv l

Table Η Example filler base dry "Mules Opaque * Tensile Burst Weight" (lb / strength (psi) 5 _ _ 3000 ft2) (lb / in) _ _ XIV 4% 41.5 19.2 31.8 86, 3 '8% 42.1 18.1 26.8 88.2 XV 4% 41.8 18.3 32.5 86.4 8% 42.6 18.2 29.0 88.4 10 * TAPPI Standard T -425 (Hunter Opacity Meter).

Example XVII

The equipment used in these examples consisted of a two liter jacketed vessel equipped with a five neck top 15 piece, a cooler, two thermometers, a mechanical stirrer, a dropping funnel in which an adjustable pressure could be set and a burette for feeding the catalyst.

The reaction vessel was charged with 218 ml of distilled water and 114.5 g of prepolymer solution. The prepolymer solution was an aqueous solution of 97.5% acrylamide and 2.5% acrylic acid copolymer. The solution contained 10 wt% prepolymer and the prepolymer had an RSV value of 0.40 (1M NaCl, 1%, 25 ° C). The resulting solution was stirred under heat to 85-87 ° C. 218 g of Styrene and 10.9 g of diallylphthalate were mixed and added to the dropping funnel. The contents of this dropping funnel and a solution of ammonium persulfate (6 g of 25 dissolved in 24 cc of distilled water) were added dropwise to the contents of the reaction vessel over a period of 2.5 hours. An exothermic reaction was observed for about 1.75 hours and this reaction was controlled by passing cooling water through the jacket. After the addition was complete, the resulting latex was stirred for 15 minutes and cooled to room temperature. After filtering through a 100 mesh (ΙδΟ ^ πι) screen, the latex showed a slight agglomeration, which was easily overcome with a Cowles dissolver. The pH of the latex was adjusted to a value of 5.2 with 5M NaOH. The latex had a solids content of 41.6% and the particles in the latex had a particle size of about 0.8 µm. The particle size was determined by a turbidity measurement according to the method of 790 7 4 93 5 * -23- 20975 / Vk / iv

T

Α.Β. Loebel (Official Digest, 200, February 1959).

Examples XVIII-XXVII

Example XVII was repeated using the same prepolymer as indicated in Example XVII with different polyethylene-like unsaturated monomers as cross-linking agents as indicated in Table J.

The amounts of the additives to be added and the condition loss are also listed in Table J.

Table J

example water prepolystyrene cross-linking agent 10 '(ml) more (g) (g) compound amount (g) XVIII 227 11.3 218 ethylene glycol-8.7 dimethacrylate XIX 226 11.2 218 1,3-butylene glycol-6, 54 dimethacrylate 15 XX 226 11.2 218 diallyl phthalate 6.54 XXI 226 11.2 218 1,6-hexanediol 6,54 dimethacrylate XXII 226 11,2 218 polyethylene glycol 6,54 dimethacrylate 20 XXIII 226 11,2 218 polypropylene gly- 6.54 cold dimethacrylate XXIV 227 11.45 218 trimethyl propane 10.9 trirethacrylate XXV 227 11.45 218 pentaerythritol- 10.9 25 tetracrylate XXVI 227 11.45 218 diallyl fumarate 10.9 XXVII 227 11.45 218 diallyl maleate 10.9 * Ό added as 10% solution 30 7907493. .f · ϊ * -24- 20975 / Vk / iv

Table J (continued) example ammonium temperature pH of the total particle pressure (hours) latex solid size 11 ^ phate2 ^ (° C). 13 (^ ym) 5 (g) by content _ ___ _ _ _____ ill_ 1_ XVIII 5.95 87-91 2.9 5.2 39.0 0.83 XIX 5.9 86.5-95 2 .5 5.5 40.3 0.77 XX 5.9 86-94 2.4 5.7 41.3 0.7 10 XXI 5.9 86-95 2.5 5.4 40.3 0.72 XXII 5.9 87-95 2.5 5.2 40.2 0.68 XXIII 5.9 87-95 2.5 5.6 '40.0 0.73 XXIV 6 87-94.5 2.5 6 , 9 39.9 0.76 XXV 6. 87-90.5 2.5 6.9 38.1 1.0 15 XXVI 6 87-95 2.5 7.1 40.8 0.72 XXVII 6 87-94 2.5 7.0 40.8 0 , 73 790 74 93

2) added as 20% solution # 3) adjusted with 5M NaOH

20 determined according to a turbidity reading (see Example III).

Example XXVIII

A. reaction vessel was charged with 506.2 kg of demineralized water and 175.2 kg of prepolymer solution. The prepolymer solution was an aqueous solution of 97.5% acrylamide-2.5% acrylic acid copolymer. The solution contained 13% by weight of the prepolymer and the prepolymer had an RSV value of 0.44 (1M NaCl, 1%, 25 ° C). The contents of the reaction vessel were heated to about 89 ° C and slowly added simultaneously over a period of four hours 1) a mixture of 431.3 kg of styrene and 22.7 kg of divinylbenzene and 2) a solution of 12 kg ammonium persulfate dissolved in 48.1 kg of demineralized water.

The resulting latex was stirred and filtered to remove the agglomerated particles. The latex had a solids content of 39.3%.

The particle size was about 0.52 / tm determined by a turbidity measurement according to the method of A.B. Loebel (Official Digest, 200, February 1959).

-25- 20975 / Vk / iv <

Example XXIX

Two coating dyes were prepared. The coating dyes are indicated as coating colors 13 and 14. The coating dyes were prepared by mixing well the components listed in Table K.

The pH was adjusted as indicated in Table K. Each coating dye was applied to the felt side of 55 lb paper using a Meyer rod. The coated sheets were dried in an oven through which air was fed at a temperature of 100 ° C for 45 seconds. The coated sheets were calendered by passing through a heated calender at a temperature of 71 ° C at 750 lb per linear inch (pli, 1 lb is 0.45 kg, 1 inch is 2.54 cm ). The gloss measurements, the results of which are reported in Table M, were performed on the sheets passed through the calender twice (two slits), three times (3 slits) and four times (4 slits), respectively. With paper coated with color 13 coating, all tests were performed after the coated sheets were passed through a calender (2 slits) twice. All papers were coated with paper coated with coating dyes 14 after these sheets had been passed through a calender 20 times (4 slits). The results thus obtained are shown in Table M.

Table K.

coating color 13 14 latex composition of example mill (g) 63.6 25 CMC * '^ (3% aqueous solution) (g) 13.3 13.3 styrene butadiene latex as binder (50% solid JL (g) 50 .0 52.3 distilled water (g) 19 »5 45 clay pigment (70% aqueous dispersion) (g) 142.8 178.6 30 initial pH 5» 85 6.0 pH after adjustment with concentrated NH 4 OH 8 8.6 * ') CIC - sodium carboxymethyl cellulose water soluble, medium viscosity, degree of substitution about 0.9, used as a viscosity enhancing additive.

790 7 493 «r v -26- 20975 / Vk / iv«

Table M

O 3M

coating weighted 75 mirror gloss color 'coating at 71 ° C, 750 pli_ (lb / (lb / 2 slits 3 slits 4 slits 5 __ 3000 ft2) "13 7.0 71 74 76 14 7.2 66 69 72

Table M (continued)

10 coating 'IGT clear-opaque- K & N

color Peak * 1ness * * ink * s (feet / _ minute) _ _ __ 13 170 80 89 64; 15 14 174 78 88 71 * 1 TAPPI Standard T-480 (average of 12 tests)

See * 3 of Table B (average of 3 tests) ^ 3 TAPPI Standard T-452 (average of 4 tests) 20 TAPPI Standard T-425, Diano Instrument ... (average of 4 tests) ^ ς TAPPI Standard UM-553 (average of 2 tests)

Although the organic pigments of the invention are particularly well suited for paper coatings, they can also be used as a filler for paper. When used as pigments in paper coatings, they can only be used in combination with other organic pigments or in combination with inorganic pigments or in combination with inorganic pigments and other organic pigments.

When used in paper coatings in combination with inorganic pigments such as clay, the amount used will range from 5 to 100% by weight based on the inorganic pigment.

The organic pigments according to the invention can be used in paint, ink and the like. They can also be used as a coating, together with a suitable binder for processing a glass surface, metal surface, wood surface, plaster, plastic surface and the like.

The organic pigments prepared according to the process of the invention are essentially spherical graft copolymer particles. Graft copolymer particles are prepared according to the method of the invention and have a particle size ranging from about 0.1 to about 2 µm.

The particularly suitable water-soluble prepolymers to be used for preparing graft copolymer particles according to the invention are 1) the homopolymers of cc, β-ethylene-like unsaturated amides, especially poly {acrylamide) and poly (methacrylamide) and 2) copolymers such as a) 98 to about 50% (wt%) οί, ρ-ethylene-unsaturated amide, especially acrylamide and methacrylamide, and b) about 2 to about 50% of an,, β-ethylene-like unsaturated acid especially acrylic acid and methacrylic acid.

Graft copolymer particles which are particularly suitable as organic pigments or as filler for paper or as a component for a paper coating composition have been obtained by the graft copolymerization of styrene or a mixture of styrene and divinylbenzene and a homopolymer or copolymer (1) or (2) as described above. Graft copolymer particles with reactive groups as described above on the surface thereof are also particularly suitable for use as organic pigments.

The binders used to prepare the coating compositions of the invention are not solvents for the organic pigments and are suitable for use in coating preparation processes to obtain an adhesive, uniform glossy layer. Suitable binders are known and include the natural binders and synthetic binders. Suitable natural binders include starch, soybean protein and casein. Modified starch binders such as oxidized, enzyme-converted and hydroxyethylated starch can be used. Suitable synthetic binders are styrene-butadiene copolymer latex and latex of polymers of alkyl esters of ol, β-ethylenically unsaturated carboxylic acids such as the alkyl acrylates and methacrylates and copolymers thereof with a small amount of ethylene-unsaturated carboxylic acid copolymer. Other suitable binders include latexes of copolymers of butadiene and acrylonitrile, latexes of copolymers of vinyl- 79074 93 'V' - -28- 20975 / Vk / iv acetate and alkyl acrylates, latex of copolymers of butadiene and methyl methacrylate, latex of copolymers of vinyl chloride and vinylidene chloride, latex of vinyl chloride copolymers, latex of vinylidene chloride copolymers,. aqueous dispersions of polybutadiene, polyvinyl acetate and polyvinyl alcohol.

The amount of binder used in preparing the coating composition to carry out the process of the invention is the amount that binds the pigment component thereof to the coated paper substrate so that the pigment is not removed from the coated paper during normal treatment or during further processing such as printing. The amount of binder used is known to a person skilled in the art. Usually, the amount of binder will range from about 2 parts to about 30 parts per 100 parts of pigment used.

It will be understood that within the above examples and descriptions, a number of variations may be made which are to be considered to be within the scope of the invention.

- CONCLUSIONS - 20 79074 93

Claims (10)

1. Paper provided with a coating consisting of a paper substrate with a coating composition applied at least on a surface thereof, composed of a binding material and an organic pigment, characterized in that the organic pigment grafts a substantially insoluble particulate in water copolymer consisting essentially of the free radical-catalyzed graft copolymerization product of 1. at least one ethylene-like unsaturated monomer and 10 2) a water-soluble prepolymer having an RSV value of about 0.1 to 2.5 (1M NaCl, 1%, 25 ° C), wherein the prepolymer parts of the graft copolymer particles are present on the surface of the particles and the monomer is selected from 1} a group consisting of methyl-o-chloroacrylate, ethyl-o6-chloroacrylate , methyl methacrylate, isopropyl methacrylate, phenyl methacrylate, vinyl chloride, acrylonitrile, methacrylonitrile and monomers of formula R r ^ ^ YC == CH- · on 20 · where R is hydrogen or a methyl group, Y is methyl or chlorine and n is 0, 1, 2 or 3 and 2. The prepolymer is selected from a group consisting of anionic prepolymers and non-ionic prepolymers prepared by an addition polymerization of a vinyl monomer or mixtures vinyl monomers and the amount of prepolymer 2) used in preparing the graft copolymer particles is between 1 and 25 wt. parts to 100 parts by weight of monomer 1) and the graft copolymer has a glass transition temperature Tg equal to or higher than 75 ° C. 2. Paper consisting of cellulose fibers and an organic pigment, the organic pigment being dispersed almost uniformly through the paper substrate by adding an aqueous dispersion to the cellulose fibers before the paper product is formed, characterized in that the organic pigment particles are water substantially insoluble graft copolymer particles consisting essentially of graft copolymerization product catalyzed with free radicals of 1. at least one ethylene-like unsaturated monomer and 2. a water-soluble prepolymer with an RSV value of from about 0.1 to about 2.5 (1M NaCl, 1%, 25 ° C), wherein the prepolymer unit of the graft copolymer is in particulate form on the surface of the particles, and the monomer 1) selected from the group consisting of methyl-cc-chloroacrylate, ethyl-chloroacrylate, methyl methacrylate, isopropyl methacrylate, phenyl methacrylate, vinyl chloride, acr ylonitrile, methacrylonitrile and monomers of formula 10 Ft C = CH »-mJ n where R is hydrogen or a methyl group, Y is a methyl group or 15 chlorine and n is 0, 1, 2 or 3 and the prepolymers 2) are selected from a group consisting of anionic prepolymers and non-ionic prepolymers prepared by the addition polymerization of vinyl monomers or mixtures of vinyl monomers, the amount of prepolymer 2) used in preparing the graft copolymer particles being between 1 part to 25 wt. parts for every 20 100 wt. parts of monomer 1) wherein the graft copolymer has a glass transition temperature Tg equal to or higher than 75 ° C. Paper according to claims 1-2, characterized in that the prepolymer 2) has an RSV value of 0.1 to 1 (1M NaCl, 1%, 25 ° C) and is selected from a group consisting of polyacrylamide, polymethacrylamide, copolymers of a) 98 wt% to 50 wt% of an amide selected from the group consisting of acrylamide and methacrylamide and b) 2 wt% to 50 wt% of an acid selected from acrylic acid and methacrylic acid . Paper according to claims 1-3, characterized in that styrene is used as monomer 1). Paper according to claims 1-4, characterized in that in combination with styrene a polyethylene-like unsaturated monomer is used in an amount at least such that cross-linked graft copolymer particles are obtained. Paper according to claims 1 to 5, characterized in that the polyethylene-35-like unsaturated monomer is divinylbenzene. 790 7493 -31- 20975 / Uk / iv Paper according to claims 1-6, characterized in that the prepolymer is 2} poly (acrylamide). 8. Paper according to claims 1-6, characterized in that the prepolymer 2) is a copolymer with 98% to 50% acrylamide and 2-50% by weight acrylic acid. Paper according to claims 1 to 7, characterized in that the prepolymer unit of the particles chemically bound thereto has an aldehyde. 10 790 7493