JPH0826272B2 - Coating composition and cast-coated paper obtained by applying the composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating composition for cast-coated paper which can be produced at high speed, and a cast-coated paper obtained by applying the composition.

<< Conventional Technology >> Cast-coated paper is produced by a direct method, a coagulation method, a rewetting method, or the like. The direct method is a method in which a water-based paint containing a pigment and an adhesive is applied to a base paper, and then adhered to a high-temperature mirror drum (hereinafter referred to as a cast drum) in a wet state and dried. The coagulation method adds a coagulant to the water-based paint. This method is a method in which a coagulant is applied to a base paper after applying a water-based paint to a base paper and then a coagulant is applied and dried in a wet state on a cast drum. The rewetting method is a method in which a water-based paint is applied to a base paper, dried once, re-wet, and then adhered and dried on a cast drum. Therefore, while high-gloss art paper is supercalendered in a dry state, cast-coated paper is smoothed by any method in a wet state, that is, in a state in which the coating layer has high plasticity. A higher and higher gloss coated surface is obtained.

However, after the coated surface containing a large amount of water is brought into close contact with the cast drum surface and dried, it is possible to release the coated surface from the cast drum surface without resistance to obtain a coated surface with high gloss and no defect. This is an important requirement. Conventionally, the good adhesion to the cast drum for imparting high gloss causes a problem that the releasability is greatly reduced, so it has high gloss and few coating surface defects such as pinholes. Advanced technology was required to obtain cast coated paper. In particular, if the release speed of the coated surface from the cast drum is increased for high-speed production, the release resistance also increases, and sometimes the coating film adheres to the drum and is partially picked up. A coating surface having no defect and uniform gloss was not obtained. Another problem during high-speed production is that it is necessary to quickly evaporate the water on the cast drum, but the higher the speed of operation, the shorter the time the coated paper stays on the drum. Is a new problem that arises due to the requirement for high water vapor movement speed. That is, particularly in the rewet method, the surface is formed under high pressure on the cast drum, but during high-speed operation, water often forms a pool between the drum surface and the coating film. It was difficult to sufficiently remove this water through the pores of the coating film. As a result, pits of a different type from the pits formed by the pickup were formed in the coating film, and defects were remarkably generated on the surface of the cast coated paper.

{Problems to be solved by the invention} Therefore, a latex containing a pigment and an unsaturated carboxylic acid as a monomer component in order to solve the above-mentioned problems of cast-coated paper even a little and enable high-speed production while maintaining the coating surface quality. A method has been proposed in which a sulfate, nitrate, formate, acetate, etc., such as zinc, aluminum, magnesium, etc., is added as a coagulant to a paint containing an adhesive such as casein as a main component (JP-B-60-146097). However, even with this method, the production rate was still low and insufficient.

Therefore, an object of the present invention is to produce a cast coated paper, particularly in a rewet method which has a relatively high production rate, and has excellent releasability, high shine and good surface strength with no pits even at high speed production which has not been hitherto known. It is intended to provide a coating composition capable of obtaining the cast coated paper having the above and a cast coated paper obtained by applying the composition.

{Means for Solving the Problems} As means for solving the above problems, in a paint for cast coated paper containing a pigment and an adhesive as main components, an average of 100 parts by weight of the pigment is used as the adhesive. 6-18 parts by weight of a rubber-based latex (A) having a particle size of 0.1-0.3 μm in solid content and 3-12 parts by weight of an acrylic emulsion (B) having an average particle size of 0.5-1.5 μm in solid content, and a rubber-based latex Provided are a coating composition for cast coated paper containing 9-30 parts by weight of (A) and an acrylic emulsion (B) as a solid content, and a cast coated paper obtained by coating the composition.

In the present invention, two kinds of synthetic binders (A) and (B) are added in a total solid content of 9- to 100 parts by weight of the pigment.
The reason why it is specified to use 30 parts by weight is that the surface strength of the cast-coated paper of the paint obtained by using the total amount of the synthetic binder is less than 9 parts by weight and the practical printing cannot be endured. When the total amount exceeds 30 parts by weight, the resulting coating has a poor releasability from the drum surface of the cast-coated paper, which makes high-speed production, which is the object of the present invention, difficult. The preferred total amount of synthetic binder used is 10-25 parts by weight.

Further, in the present invention, a rubber-based latex used for 100 parts by weight of the pigment (hereinafter, simply referred to as latex)
The reason why the amount of (A) is limited to 6-18 parts by weight in terms of solid content is as follows.
When the latex (A) is less than 6 parts by weight, the surface strength of the cast coated paper obtained thereby is low, and when the latex (A) exceeds 18 parts by weight, the cast drum surface of the coated paper. This is due to the fact that there are many pits on the coated surface, which has poor releasability from and has low air permeability. The preferred amount of the latex (A) is 7-16 parts by weight.

Furthermore, in the present invention, the reason why the amount of acrylic emulsion (B) used is limited to 3 to 12 parts by weight based on 100 parts by weight of the pigment is that the amount of acrylic emulsion (B) used is less than 3 parts by weight. Has poor adhesion to the surface of the cast drum, resulting in a decrease in gloss and more pits. If the amount of acrylic emulsion (B) used exceeds 12 parts by weight, the releasability from the cast drum becomes poor, and it is also obtained. A pit occurs on the coated surface of the cast-coated paper. The preferred amount of acrylic emulsion (B) used is 4-10 parts by weight.

In the present invention, the average particle size of the latex (A) is 0.
The reason for limiting the particle size to 1-0.3 μm is that when the average particle size is less than 0.1 μm, the average particle size of the acrylic emulsion (B) is
Even if it is 0.5-1.5 μm, the viscosity of the obtained coating is high, the releasability of the coated paper from the cast drum surface becomes poor, and it is difficult to obtain a smooth coated surface without pits. On the other hand, when the average particle diameter of the latex (A) exceeds 0.3 μm, the cast coated paper of the latex (A) has low surface strength and generates many pits, so that high-speed production which is the object of the present invention is difficult. Becomes In the present invention, the reason why the average particle size of the acrylic emulsion (B) is limited to 0.5-1.5 μm is that the average particle size of the acrylic emulsion (B) is 0.5 μm.
If it is less than m, the air permeability of the cast coated paper of the paint using this is low, many pits are generated and high-speed production is difficult, and the average particle size of the acrylic emulsion (B) is
When it exceeds 1.5 μm, the surface strength of the cast coated paper of the paint using this is extremely low, and printing cannot be practically performed. Here, it is important that the average particle size of the latex (A) and the acrylic emulsion (B) is the particle size described above in the step after the preparation of the coating composition. It need not have a particle size. For example, latex (A) is synthesized to have a particle size of 0.1-0.3 μm, which is excellent in chemical stability, and an acrylic emulsion having a particle size of 0.1-0.3 μm is separately synthesized, and then polyvalent metal cations such as calcium ion and aluminum ion are added. An acrylic emulsion is prepared by adding a small amount to perform an aggregation operation to adjust the average particle size to 0.5 to 1.5 μm, and thereafter stabilizing treatment by adding a surfactant or a protective colloid agent to obtain (B). The state of the coating material using the thus prepared synthetic binder at each adjustment stage was observed by a transmission electron microscope. As a result, the synthetic binders (A) and (B) each independently had a particle size at the time of adjustment. It was confirmed by holding the difference in the density of the particles. That is, the latex (A) was a dark image and was present in a single state, and the acrylic emulsion (B) was a pale image and was present in the state of being aggregated into several pieces. This adjusting method is an example, and it is also possible to control the particle size in the mixing process of the paint (hereinafter, a small amount of a polyvalent metal cation such as the above acrylic emulsion is added or an aggregation operation in the adjusting process of the paint. The acrylic emulsion which is converted to the acrylic emulsion (B) of the present invention by the method is referred to as an acrylic emulsion (B) precursor}.
Further, as the acrylic emulsion (B), those produced so that the particle diameter falls within the range claimed in the present invention at the time of synthesis can be used, but it is not economical.

In the present invention, latex is a general term for rubber emulsions, and from that meaning, the components contained in the latex include butadiene, isoprene, and diene monomers such as 2-chlorobutadiene as an essential component. Is a general term for a polymer emulsion which does not contain these diene-based monomers and has a monomer as described below as a main component. Aromatic alkenyl compounds such as styrene, α-methylstyrene, chlorostyrene and dimethylstyrene as the main monomer component in the acrylic emulsion as a copolymerization monomer component other than the diene monomer in the latex. And methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate , Glycidyl methacrylate, acrylamide, N-methylrollacrylamide, N-methoxymethylacrylamide, methacrylamide, N-methylolmethacrylamide, N-methoxymethylmethacrylamide, acrylic acid, meta Mono-olefinic unsaturated compounds such as phosphoric acid, crotonic acid, fumaric acid alkyl ester, itaconic acid alkyl ester, acrylonitrile, methacrylonitrile, and vinyl acetate are used as the monomer, and these monomer components are a combination of two or more kinds. Can also be used in.

In the production of the synthetic binder of the present invention, the above-mentioned monomer is used, and a conventional initiator such as potassium persulfate, sodium persulfate, ammonium persulfate, or a water-soluble peroxide or a bisulfite thereof is used as a polymerization initiation catalyst. It is also possible to use in combination with a water-soluble reducing agent such as soda, sodium sulfite, and sodium thiosulfate. The polymerization temperature of the monomers is usually 50 to 100 ° C., and the pressure is 0 to 10 kg / cm ^{2 as} a gauge pressure. The addition of all the monomers used can be carried out by any of batch addition, divisional addition and continuous addition. For the stabilization of particles during polymerization, for example, sodium alkylbenzene sulfonate,
It is also possible to add emulsifiers such as sodium alkyl sulfate and sodium alkyl alcohol sulfate, and protective colloid agents such as hydroxyethyl cellulose, carboxymethyl cellulose and polyvinyl alcohol. At this time, if the addition amount of the emulsifier to all the monomers is increased, the particle diameter becomes smaller,
The smaller the number, the larger the particle size. Further, as a molecular weight regulator, mercaptans such as alkyl mercaptan and tertiary mercaptan, carbon tetrachloride, higher alcohols and the like can be used. Accordingly, the particle diameters of the present invention of 0.1-0.3 μm and 0.5-1.5 μ
The synthetic binder composition of m can be freely prepared.

The latex and acrylic emulsion used in the present invention preferably contain a certain amount or more of the toluene insoluble matter (usually referred to as gel content) of the dry film, which is related to the molecular weight and the degree of crosslinking of the polymer, and is an object of the present invention. In order to ensure high-speed productivity, 15% by weight or more is preferable. The pigments used in the paint are clay, calcium carbonate, titanium white, satin white, aluminum hydroxide, barium sulfate, zinc oxide, magnesium oxide, and other inorganic pigments commonly used in coated paper, and plastic pigments, white urea. All organic pigments such as resin pigments can be used, and there is no particular limitation on the selection of pigments for the purpose of the present invention.

In addition to the synthetic binders (A) and (B) described above, water-soluble polymers such as casein and modified starch can be used in an amount of 2-15 parts by weight with respect to 100 parts by weight of the pigment in the paint.

In the coating composition of the present invention, a known coagulant such as calcium formate, magnesium formate, zinc formate, calcium acetate, magnesium acetate, and zinc acetate or a known release agent such as magnesium stearate and zinc stearate is appropriately used. You can do it. Addition of anionic surfactant, nonionic surfactant, etc. to the coating composition in addition to the stabilizer contained in advance in order to stably maintain the aggregated state of the particles of the acrylic emulsion (B) in the coating composition. You can also

The cast coated paper of the present invention is a known coating device generally used for producing pigment coated paper such as an air knife coater, a roll coater, and a blade coater using the coating composition of the present invention thus obtained as a base paper. It can be obtained by applying it once, drying it once, rewetting it with wet water, and press-bonding it to a cast drum heated to 60 ° C. or higher at a linear pressure of 10 kg / cm or more. The base paper used is not particularly limited, and any of those usually used for pigment-coated paper may be used.

{Action} As described in detail above, in the coating composition obtained by the present invention, that is, the coating material for cast coated paper containing a pigment and an adhesive as main components, two kinds of latex (A) and acrylic emulsion (B) are used. The total amount is 100 pigments in the paint.
9-30 parts by weight is used with respect to parts by weight, and the particle size of each synthetic binder is 0.1-0.3 μm for (A) and 0.1 for (B).
A coating composition adjusted to have a latex (A) of 6-18 parts by weight and an acrylic emulsion (B) of 3-12 parts by weight in a range of 5-1.5 μm was applied by a known method, and then cast drum. The cast-coated paper obtained by contact-drying with 1. has excellent surface gloss, has a uniform surface quality without pits, and has excellent air permeability and releasability, so that high-speed production is possible. The coating composition of the present invention is also useful as a coating material for cast coated paper by a direct method other than the rewet method, a coagulation method or the like as in the rewet method.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited by these Examples. Parts and% in these are based on weight unless otherwise specified.

Example 1 First, production examples of the latex (A) and the acrylic emulsion (B) used in this example are shown, and then a preparation example of the coating material is shown.

<Production Example of Latex (A-1)> 120 parts of deionized water in an autoclave purged with nitrogen,
0.2 parts of sodium dodecylbenzenesulfonate, 0.8 part of potassium persulfate, 0.6 part of tertiary decyl mercaptan, 40 parts of butadiene as a monomer composition, 45 parts of styrene, 8 parts of methyl methacrylate, 2 parts of acrylic acid and 2 parts of acrylamide as a functional group monomer Parts and a total of 100 parts of hydroxyethyl methacrylate were charged and polymerized at 70 ° C., and the polymerization rate exceeded 98% in 15 hours after the start of the polymerization. To obtain a latex (A-1). The particle size was 0.15 μm.

<Production Example of Acrylic Emulsion (B) Precursor> Deionized water was placed in a nitrogen-replaced three-necked glass reactor.
0 part, 0.1 part of sodium dodecylbenzene sulfonate, 0.8 part of ammonium persulfate and 40 parts of butyl acrylate as a monomer composition, 50 parts of styrene, 7 parts of methyl methacrylate,
A total of 100 parts of 3 parts of methacrylic acid was charged, and the polymerization was carried out at 70 ° C. The polymerization rate exceeded 97% in 8 hours after the start of the polymerization, so the reaction was stopped and after cooling, the pH was adjusted to 7 with an aqueous ammonia solution and the acrylic emulsion was obtained. A precursor of (B) was obtained. The particle size is
It was 0.18 μm.

<Preparation of paint> A casein aqueous solution obtained by heating and dissolving using 0.8 parts of 28% ammonia water, 8 parts of Michle casein and 44.5 parts of water 5
3.3 parts (equivalent to 8 parts in terms of solid content) and 100 parts of water are put into a cowless mixer, and 40 parts of calcium carbonate (TP-222HS made by Okutama Kogyo) and kaolin (UW-90 made by EMC) while stirring.
After adding 60 parts and mixing and dispersing, 20% calcium acetate aqueous solution 3.
After adding 5 parts (corresponding to 0.7 part in terms of solid content), 12 parts of latex (A-1) in solid content and 7 parts of precursor of acrylic emulsion (B) in solid content were added. Finally, the coating solid content was adjusted to 40% to obtain a coating composition-1 for cast coated paper of the present invention. The paint viscosity was 30 cps when measured with a Brookfield viscometer at 25 ° C. and 60 rpm. The particle size of the synthetic binder in the paint was confirmed by a transmission electron microscope. As a result, the particle size of the latex (A-1) was 0.15 μm, whereas the particle size of the acrylic emulsion (B) was 0.85-1.0. It was μm. The raw material blending ratios and physical properties of these coating compositions-1 are shown in Table-1.

Example 2-7 Amount of casein used in Example-1, latex (A
-1) and the total amount of the precursor of the acrylic emulsion (B) and the total amount thereof, and the addition amount of calcium acetate was changed as shown in Table-1. Each coating composition from composition-2 to coating composition-7 was obtained. Solids concentration of these compositions, Brookfield viscosity, latex in paint (A
-1) and the particle size of the acrylic emulsion (B) were measured and observed by the same method as in Example-1, and the results are shown in Table-1.

Example 8 An example of producing the latex (A-2) used in this example is shown, and then an example of adjusting the coating is shown.

<Production Example of Latex (A-2)> 120 parts of deionized water in an autoclave purged with nitrogen,
Sodium dodecylbenzene sulfonate 0.3 parts, potassium persulfate 0.8 parts, tertiary dodecyl mercaptan 0.6 parts and butadiene 40 parts as monomer composition, styrene 45 parts, methyl methacrylate 8 parts and acrylic acid 2 parts as functional group monomer, acrylamide 2 And a total of 100 parts of hydroxyethyl methacrylate 3 parts were charged and polymerization was carried out at 70 ° C. The polymerization rate exceeded 98% in 14 hours after the initiation of the polymerization, so the reaction was stopped and cooled, and the pH was adjusted to 7 with sodium hydroxide. To obtain a latex (A-2). The particle size was 0.1 μm.

<Preparation of paint> Aqueous solution of casein 5 obtained by heating and dissolving 28% ammonia water 0.8 parts, milk casein 8 parts and water 44.5 parts.
3.3 parts (equivalent to 8 parts in terms of solid content) and 100 parts of water are put into a cowless mixer and 40 parts of calcium carbonate (TP-222HS made by Okutama Kogyo) and kaolin (UW-90 made by EMC) while stirring.
After adding 60 parts and mixing and dispersing, a 20% calcium acetate aqueous solution 1.
After adding 5 parts (equivalent to 0.3 part in terms of solid content), 12 parts of latex (A-2) in solid content and 7 parts of precursor of acrylic emulsion (B) in solid content were added. Finally, the coating solid content was adjusted to 40% to obtain a coating composition-8 for cast coated paper of the present invention. The paint viscosity was 115 cps when measured with a Brookfield viscometer at 25 ° C. and 60 rpm. The particle size of the latex in the paint was confirmed by a transmission electron microscope. As a result, the particle size of the latex (A-2) was 0.1 μm, whereas the particle size of the acrylic emulsion (B) was 0.1-0.7. It was μm. Table 1 shows the raw material mixing ratio, physical properties, and the like of these coating composition-8.

Example 9 A coating composition-9 was obtained according to the same procedure and conditions as in Example-8, except that the amount of calcium acetate added was changed as shown in Table-1. The solid content concentration, Brookfield viscosity, particle size of the latex (A-2) and acrylic emulsion (B) in the coating composition, etc. of these compositions were measured and observed by the same method as in Example-8. The results are also shown in Table-1.

Example 10 An example of producing the latex (A-3) used in this example is shown, and then an example of preparing a coating is shown.

<Production Example of Latex (A-3)> 120 parts of deionized water in an autoclave purged with nitrogen,
0.15 part of sodium dodecylbenzenesulfonate, 0.8 part of potassium persulfate, 0.6 part of tertiary decyl mercaptan, 40 parts of butadiene as a monomer composition, 45 parts of styrene, 8 parts of methyl methacrylate, 2 parts of acrylic acid and 2 parts of acrylamide as a functional group monomer Parts and 3 parts of hydroxyethyl methacrylate were charged and polymerized at 70 ° C., and the polymerization rate exceeded 98% 16 hours after the polymerization was started. The reaction was stopped, and after cooling, the pH was adjusted to 7 with sodium hydroxide. To obtain a latex (A-3). The particle size was 0.3 μm.

<Preparation of paint> A casein aqueous solution obtained by heating and dissolving using 0.8 parts of 28% ammonia water, 8 parts of Michle casein and 44.5 parts of water 5
3.3 parts (equivalent to 8 parts in terms of solid content) and 100 parts of water are put into a cowless mixer, and 40 parts of calcium carbonate (TP-222HS made by Okutama Kogyo) and kaolin (UW-90 made by EMC) while stirring.
After adding 60 parts and mixing and dispersing, a 20% calcium acetate aqueous solution 1.
After adding 5 parts (corresponding to 0.3 part in terms of solid content), 12 parts of latex (A-3) in solid content and 7 parts of precursor of acrylic emulsion (B) in solid content were added. Finally, the coating solids content was adjusted to 40% to obtain a coating composition for cast-coated paper-10 of the present invention. The paint viscosity was 35 cps when measured with a Brookfield viscometer at 25 ° C. and 60 rpm. Moreover, as a result of confirming the particle size of the latex in the coating material with a transmission electron microscope, the particle size of the latex (A-3) is
While the particle size of the acrylic emulsion (B) was 0.3 μm, the particle size was 0.5 to 0.7 μm. Table 1 shows the raw material mixing ratio and physical properties of these coating compositions-10.

Example 11 A coating composition-11 was prepared in exactly the same manner and conditions as in Example-10, except that the amount of calcium acetate added was changed as shown in Table-1. The solid content concentration, Brookfield viscosity, particle size of the latex (A-3) and acrylic emulsion (B) in the coating composition of these compositions were also measured and observed by the same method as in Example-10. The results are also shown in Table-1.

Comparative Example 1-6 In Example-1, the amount of casein used and the amount of calcium acetate used were changed, and the amounts of the precursors of the latex (A-1) and the acrylic emulsion (B) used or the total amount thereof were shown in Table 1. 1
As shown in FIG. 5, each of the comparative coating compositions from Comparative coating composition-1 to Comparative coating composition-6 obtained under the same conditions and conditions as in Example 1 except that the coating composition is outside the scope of the present invention. The solid content concentration, the Brookfield viscosity, and the particle diameters of the latex (A-1) and acrylic emulsion (B) in the paint are also shown in Table 1.

Comparative Examples 7 and 8 In this comparative example, in order to further clarify the usefulness of the combined use of the latex (A-1) and the acrylic emulsion (B),
The case where the latex (A-1) and the acrylic emulsion (B) are used alone will be exemplified. That is, as shown in Table-1, the same procedure and conditions as in Example-1 were used except that the amount of calcium acetate used in Example-1 was changed and the latex and the acrylic emulsion used were used alone and in the same amount as the total amount. Comparative Paint Composition-7 and Comparative Paint Composition-8 were obtained. Table 1 also shows the solid content concentration of these paints, Brookfield viscosity, and particle size of latex and acrylic emulsion in the paint.

Comparative Example 9 A production example of the latex (A-4) used in this comparative example is shown, and then a preparation example of the coating material is shown.

<Production Example of Latex (A-4)> 120 parts of deionized water in an autoclave purged with nitrogen,
0.4 parts of sodium dodecylbenzenesulfonate, 0.8 part of potassium persulfate, 0.6 part of tertiary decyl mercaptan, 40 parts of butadiene as a monomer composition, 45 parts of styrene, 8 parts of methyl methacrylate, 2 parts of acrylic acid and 2 parts of acrylamide as a functional group monomer Parts and a total of 100 parts of hydroxyethyl methacrylate were charged and polymerized at 70 ° C. The polymerization rate exceeded 99% 13 hours after the start of the polymerization. The reaction was stopped, and after cooling, the pH was adjusted to 7 with sodium hydroxide. To obtain a latex (A-4). The particle size was 0.08 μm.

<Preparation of paint> A casein solution obtained by heating and dissolving 5 parts of 0.8% 28% ammonia water, 8 parts of Michle casein and 44.5 parts of water 5
3.3 parts (equivalent to 8 parts in terms of solid content) and 100 parts of water were put into a cowless mixer and 40 parts of calcium carbonate (TP-222HS manufactured by Okutama) and kaolin (UW-90 manufactured by EMC) under stirring. 60
Then, 12 parts of the latex (A-4) as a solid content and 7 parts of a precursor of the acrylic emulsion (B) as a solid content were added. Finally, the coating solid content was adjusted to 40% to obtain Comparative coating composition-9. The paint viscosity was measured with a Brookfield viscometer at 25 ° C and 60 rpm. The result was 460 cp.
It was s. As a result of confirming the particle size of the latex in the paint with a transmission electron microscope, the particle size of the latex (A-4) was 0.08 μm and the particle size of the acrylic emulsion (B) was 0.18 μm. The raw material compounding ratios and physical properties of these comparative coating compositions-9 are shown in Table-1.

Comparative Example 10 A production example of the latex (A-5) used in this Comparative Example is shown, and then a preparation example of the coating material is shown.

<Production Example of Latex (A-5)> 120 parts of deionized water in an autoclave purged with nitrogen,
0.1 part of sodium dodecylbenzenesulfonate, 0.8 part of potassium persulfate, 0.6 part of tertiary decyl mercaptan, 40 parts of butadiene as a monomer composition, 45 parts of styrene, 8 parts of methyl methacrylate, 2 parts of acrylic acid and 2 parts of acrylamide as a functional group monomer And a total of 100 parts of 3 parts of hydroxyethyl methacrylate were charged and polymerized at 70 ° C. The polymerization rate exceeded 97% 18 hours after the start of the polymerization, and the reaction was stopped. To obtain a latex (A-5). The particle size was 0.35 μm.

<Preparation of paint> Aqueous solution of casein 5 obtained by heating and dissolving 28% ammonia water 0.8 parts, milk casein 8 parts and water 44.5 parts.
3.3 parts (equivalent to 8 parts in terms of solid content) and 100 parts of water are put into a cowless mixer, and 40 parts of calcium carbonate (TP-222HS made by Okutama Kogyo) and kaolin (UW-90 made by EMC) while stirring.
After adding 60 parts and mixing and dispersing, 20% calcium acetate aqueous solution 7
Parts (corresponding to 1.4 parts in terms of solid content) were added, and then 12 parts of latex (A-5) in solid content and 7 parts of precursor of acrylic emulsion (B) in solid content were added. Finally, the paint solid content was adjusted to 40% to obtain Comparative Paint Composition-10. The paint viscosity was 25 cps when measured with a Brookfield viscometer at 25 ° C. and 60 rpm. The particle size of the latex in the paint was confirmed by a transmission electron microscope. As a result, the particle size of the latex (A-5) was 0.35 μm, whereas the particle size of the acrylic emulsion (B) was 1.08-2.16.
μm. The raw material blending ratios and physical properties of these comparative coating compositions-10 are shown in Table-1.

Application Examples The coating compositions obtained in the above-mentioned Examples and Comparative Examples were prepared using a basis weight of 6
Using an atom of 4.0 g / m ² , each coating composition was coated with an air knife coater so that the dry weight was 25 g / m ^2, and after drying, a rewetting liquid was applied and passed through a cast drum. Casting diameter is 1200mm, pressing pressure is 50Kg / cm, surface temperature is 95-100.
Using a drum at ℃, the maximum casting speed at which good releasability and good pits were not found on the coated paper surface was determined. The air permeability of the coated paper before casting was measured, and the resulting cast coated paper was evaluated for glossiness and surface strength. The results are shown in Table 2. The air permeability was measured by an Oken type air permeability tester, and the glossiness was measured according to JIS P-8142. Surface strength is RI printing tester (Myo Seisakusho)
Printing was carried out and the picking state of the surface was visually observed and evaluated on a scale of 10 (10 is the best without picking on the surface, 1 is the poorest because picking occurs on the entire surface, and this is divided into 10 levels for evaluation. did).

<< Effects of the Invention >> As shown by the numerical values in Table 2, the coating compositions of Examples in the limited range of the present invention were produced in spite of high-speed production. It has excellent quality balanced in temper. From this, it is clear that the present invention is a very useful coating composition which has never been used as a coating composition for cast-coated paper.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location D21H 19/36 25/00 (72) Inventor Akio Hyugaji 3-14 Shodo, Sakae-ku, Yokohama-shi, Kanagawa 14 (72) Inventor Akio Tanaka 21-12 Kaminocho, Sakae-ku, Yokohama-shi, Kanagawa (56) Reference JP-A-60-139762 (JP, A) JP-A-62-215092 (JP, A) JP-A-57 -117694 (JP, A) JP-A-62-85094 (JP, A)

Claims (2)

[Claims] 1. A paint for cast coated paper, which comprises a pigment and an adhesive as main components, and a rubber latex (A) having an average particle diameter of 0.1 to 0.3 .mu.m as the adhesive with respect to 100 parts by weight of the pigment. ) Is an acrylic emulsion (B) having a solid content of 6-18 parts by weight and an average particle size of 0.5 to 1.5 μm.
3-12 parts by weight of solid content, and rubber latex (A)
And 9-30 parts by weight of acrylic emulsion (B) as a solid content, cast coating paper coating composition. 2. A cast-coated paper coated with the composition according to claim 1.