JPH02480B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the improvement of coating compositions used in the production of coated processed paper, in which specified kaolin and heavy calcium carbonate are used in combination as pigments (coatings), and vinyl cyanide-based The present invention relates to a coating composition with a high solid content concentration that uses a copolymer emulsion, which is an emulsion polymer of a monomer and another monomer, as an adhesive. In the production of coated processed paper, which involves applying a coating composition containing pigments and adhesives to base paper and drying it, a coating composition with a high solid content concentration of 65 to 82% is used. With the blade coating method, the drying speed of the coated layer is fast, so the equipment required for drying,
This method not only saves energy and costs, but also has the advantage of imparting excellent gloss and smoothness to coated paper because the coating layer hardens before moving along the uneven surface of the base paper. However, various technical problems associated with coating and defects in the quality of the resulting coated paper have not yet been solved, and coating compositions with such high solids concentrations cannot be applied on an industrial scale. The reality is that it is almost never implemented. For example, in a coating composition with a high solid content concentration, when the pigment component is composed only of kaolin, the viscosity of the composition under high shear stress (hereinafter referred to as high shear viscosity)
Because it has a high water retention capacity and poor water retention, problems with streaks and scratches occur during coating. For this reason, in Japanese Patent Publication No. 46-43244, the high shear viscosity of the composition was improved by using together as a pigment heavy calcium carbonate with a relatively large average particle size in which the content of particles of 2 microns or less was 40% or less. Proposals have been made to reduce the However, in this method, although the high shear fluidity of the coated composition is improved by increasing the blending ratio of ground calcium carbonate, the gloss and smoothness of the coated paper obtained are reduced accordingly. A problem arises. Furthermore, as seen in JP-A-55-62296, coating compositions with high solid content concentrations that use fine grained heavy calcium carbonate with a controlled particle size distribution as the sole pigment component are also known. Although the workability has been improved, coated paper coated with this material has a particle shape of heavy calcium carbonate that is cubic or substantially spherical, even though it is atomized. The gloss and smoothness obtained using kaolin having a plate-like and flat shape cannot be obtained. In other words, if conventionally known coating compositions with high solid content concentration have relatively good coating suitability, they tend to cause defects in the quality of coated paper, and high quality coated paper can be obtained. The coating compositions that were likely to be coated lacked coating suitability. Furthermore, coated paper obtained by coating with these conventional high solids concentration coating compositions has serious defects in printability. That is, due to the high solid content concentration, the migration of the adhesive in the coating composition to the surface of the coating layer during the drying process after coating is significantly reduced, so that when printing the resulting coated processed paper, The problem is that the ink holdout properties of the ink are deteriorated. In other words, as the solid content concentration increases, the ink absorption becomes faster and the coating layer becomes inferior in ink hold-out properties. This is accompanied by a serious defect in that the gloss and printing smoothness are significantly deteriorated compared to coated paper obtained by coating with a coating composition having a normal solid content concentration. In order to solve the above-mentioned drawbacks of coating compositions with high solid content concentrations, the present invention uses kaolin having a specified particle size and heavy calcium carbonate together as pigments, and also uses vinyl cyanide monomers. By using a copolymer emulsion, which is an emulsion polymer of and other monomers, as an adhesive, coated paper with a high solid content concentration that has excellent coatability and can provide high quality coated paper can be produced. This is what we provide. That is, in the coating composition according to the present invention, in a coating composition containing a pigment and an adhesive and having a high solid content concentration, (a) the content of particles of 1 micron or less as pigment is
80wt% or more with particle content of 0.5 micron or less
Kaolin with a viscosity of 50 wt% or more and a viscosity of 4.0 × 10 ⁵ dyne centimeter or less at a shear rate of 5000 sec ^-1 in an aqueous slurry with a solid content concentration of 71 wt% is 10 to 80 wt% of the total pigment, and is 2 microns or less. Contains 20 to 90 wt% of the total pigment, and (b) vinyl cyanide adhesive as an adhesive. A copolymer emulsion obtained by emulsion polymerization of 3 to 40 parts by weight of monomer and 97 to 60 parts by weight of other monomers is 3 to 20 wt% of the total pigment.
and (c) a solid content concentration of 65 to 80 wt%. Kaolin, which is used as a pigment component in the coating composition of the present invention, is a component that mainly contributes to the gloss and smoothness of coated paper, and this includes a particle content of 1 micron or less. is 80 wt% or more, the particle content of 0.5 microns or less is 50 wt% or more, and the high shear viscosity at a shear rate of 5000 sec ^-1 of a slurry with a solid content concentration of 71 wt% is 4.0 × 10 ⁵ dyne-cm or less. Some kaolin is used. The amount of kaolin used is 10 to 80wt of the total pigment.
If it is less than 10 wt%, sufficient gloss and smoothness cannot be imparted to the coated paper, and if it exceeds 80 wt%, the coating suitability of the composition deteriorates. Heavy calcium carbonate, which is used as a pigment component together with the above-mentioned kaolin, is a component that mainly contributes to the coatability of coated paper. However, if too rough heavy calcium carbonate is used, as in the above-mentioned Special Publication No. 46-43244, not only will streak problems such as streaks and scratches occur during coating, but also the glossiness and smoothness of the white paper will deteriorate. Furthermore, since the ink gloss after printing is also reduced, in the present invention, the content of particles of 2 microns or less is 70 to 100 wt%, preferably 80 to 100 wt%, and the content of particles of 1 micron or less is 55 to 95 wt%. , preferably 60-95wt
% fine ground calcium carbonate is used.
The amount of heavy calcium carbonate used is 20~ of the total weight.
If it is less than 20wt%, the high shear viscosity of the composition will increase and trouble will occur during coating, and if it exceeds 90wt%, the gloss and smoothness of the coated paper will deteriorate and it will become difficult after printing. The gloss of the ink also decreases. In the coating composition of the present invention, the pigment component is most commonly composed of the above-mentioned kaolin and heavy calcium carbonate, but if necessary, other pigment components may be added, such as light calcium carbonate, satin, etc. White, titanium dioxide, calcium sulfite, aluminum hydroxide, talc, barium sulfate, zinc oxide, calcium sulfate, plastic pigments, etc. can be blended. However, their blending amount should be limited to 50 wt% or less of the total pigment, and is generally preferably 20 wt% or less. Note that ordinary kaolin other than kaolin having the above-mentioned specific particle content and high shear viscosity can also be blended. For example, if the kaolin has a particle content of 1 micron or less and 50 wt% or more, the total pigment content is 50 wt% or more.
It can be blended up to about 60wt%. In the coating composition of the present invention, a copolymer emulsion, which is an emulsion polymer of a vinyl cyanide monomer and another monomer, is used as the adhesive component. This copolymer emulsion is a component that mainly contributes to the printability of coated paper, but
3 to 40 parts by weight of vinyl cyanide monomer, and 0
~45 parts by weight of an aliphatic conjugated diolefin monomer, 0 to 15 parts by weight of an ethylenically unsaturated carboxylic acid monomer, and 0 to 97 parts by weight of a copolymerizable monoolefin monomer are emulsion polymerized in a conventional manner. However, during emulsion polymerization, each monomer may be added to the reaction system all at once, or each monomer may be added sequentially. Furthermore, it is also possible to carry out emulsion copolymerization in multiple stages to obtain, for example, a copolymer having a heterogeneous double structure. Among the above-mentioned monomers, the vinyl cyanide monomers include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-chloroacrylonitrile, and α-chloroacrylonitrile.
- Aliphatic unsaturated nitriles such as ethyl acrylonitrile can be used. Examples of aliphatic conjugated diolefin monomers include 1,3-butadiene, isoprene, 2-methyl-1,3-butadiene,
Examples include 2,3-dimethyl-1,3-butadiene and 2-chloro-1,3-butadiene. Examples of ethylenically unsaturated carboxylic acid monomers include monocarboxylic acids such as acrylic acid and methacrylic acid, and dicarboxylic acids such as fumaric acid, itaconic acid and maleic acid. Monoolefin monomers copolymerizable with these monomers include aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and divinylbenzene, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, Unsaturated carboxylic acid alkyl esters such as butyl methacrylate, 2-ethylhexyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, diethyl maleate, dimethyl maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, β- Hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate,
3-chloro-2-hydroxybutyl methacrylate, di-(ethylene glycol) malate, di-
(ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis(hydroxyethyl) maleate, 2-hydroxyethyl methyl fumarate and other hydroxyalkyl group-containing monomers,
Further examples include inertial monomers such as vinyl acetate, vinyl chloride, acrylamide, and ethylene. In obtaining the copolymer emulsion of the present invention,
Vinyl cyanide monomers account for 3 to 3 of all monomers.
It is possible to use 40wt%, preferably 5 to 30wt%. This is because if it is less than 3 wt%, sufficient printability cannot be imparted to the coated processed paper, whereas if it exceeds 40 wt%, the stability decreases and the coating suitability of the coating composition is impaired. Although aliphatic conjugated diolefin monomers are not essential monomer components, they account for 10% of the total monomers.
It is preferable to use it in the range of ~40wt%. However, if the amount exceeds 45 wt%, there is a risk of deteriorating the water resistance of the coated paper, so the amount of this monomer component used should be 45 wt% or less of the total monomers. The ethylenically unsaturated carboxylic acid monomer is also not an essential monomer component, but since the stability of the copolymer emulsion is improved when this component is used, it is preferably used in the range of 0.2 to 10 wt% of the total monomers. However, if this monomer component exceeds 15wt% of the total monomers, the viscosity of the resulting copolymer emulsion will increase, so the amount used should be adjusted accordingly.
It is allowed to be less than 15wt%. Although copolymerizable monoolefin monomers are not necessarily essential components for the present invention, 97wt of all monomers
% or less, preferably in the range of 20 to 84.4 wt%. Use of this monoolefin monomer in an amount exceeding 97 wt% should be avoided as it will deteriorate the printability of the coated paper. As described above, the copolymer emulsion of the present invention can be prepared by a conventional emulsion polymerization method, and conventional emulsifiers can be used. However, the amount of emulsifier used is preferably 2 wt% or less of the total monomers so as not to adversely affect the water resistance of the coated paper. In carrying out the emulsion polymerization, it is of course possible to use commonly used polymerization initiators, electrolytes, polymerization promoters, chain transfer agents, chelating agents, and the like. Regardless of the monomers used and the emulsion polymerization method used, the average particle size of the copolymer emulsion of the present invention is preferably in the range of 0.08 to 0.5 microns, preferably 0.1 to 0.3 microns. The copolymer emulsion described above is used as an adhesive in the coating composition of the present invention, and the amount used is 3 to 30% of the total pigment in the coating composition in terms of solid content.
A range of 20wt% is appropriate. If it is less than 3 wt%, it will not be possible to give the coated paper the desired gloss and smoothness, and if it exceeds 20 wt%, the smoothness will have to be reduced in the finishing process of the coated paper. In the coating composition of the present invention, the above-mentioned copolymer emulsion and general adhesives and thickeners for coating compositions,
Can be used in combination with water retention agents and flow modifiers. Examples of things that can be used in combination include casein, soybean protein,
Protein-based adhesives such as petroleum protein, oxidized starch, etherified starch, esterified starch, starch-based adhesives such as reaction products of styrene-maleic anhydride copolymer and starch, styrene-butadiene-based, styrene-acrylic-based , alkali-sensitive or alkali-insensitive adhesives such as acetic acid-vinyl acrylic, ethylene-vinyl acetate, butadiene-methyl methacrylic, acetic acid-butyl acrylate, and polyvinyl acetate, as well as polyvinyl So-called water-soluble adhesives such as alcohol, maleic anhydride-styrene copolymer, isobutene-maleic anhydride copolymer, acrylic acid-methyl methacrylate copolymer, sodium alginate, guar gum, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose Examples include cellulose derivatives such as methylcellulose, thickeners such as kaolinated adhesives, water retention agents, and flow modifiers. However, when using these adhesives, it is preferable that the amount used be equal to or less than the amount of the copolymer emulsion of the present invention. The coating composition of the present invention contains the aforementioned kaolin and heavy calcium carbonate as pigments, the aforementioned copolymer emulsion as an adhesive, and has a solid content concentration of 65 to 80 wt%. As required, various auxiliary agents such as a dispersant, an antifoaming agent, a dye, a lubricant, and a waterproofing agent can be appropriately blended into this coating composition. The above-mentioned copolymer emulsion containing 3 to 40 parts by weight of vinyl cyanide monomer used in the present invention is as described in JP-A-50-94034,
It tends to improve the ink gloss after printing of coated paper obtained even when used in a conventional coating composition having a solid content concentration of around 50 wt%. However, as in the present invention, it is only when used in a coating composition with a high solid content concentration of 65 wt% or more and in combination with a specific pigment that a significant improvement in printability is exhibited. Note that even if the copolymer emulsion of the present invention is used in a coating composition that does not contain a specific pigment and has only a high solid content concentration, the improvement effect as achieved in the present invention cannot be obtained; The poor ink gloss of the resulting coated paper after printing, which is one of the serious defects when coating the composition, cannot be improved at all. The base paper to which the coating composition of the present invention is coated is medium-quality base paper for coating made using acidic or neutral paper using high-yield pulp or mechanical pulp, and high-quality base paper for coating using bleached pulp. Then, one or both sides of these base papers are blade coated on or off-machine so that the coated amount on one side is an appropriate amount of 4 to 30 g/m ² . Blade coaters include coaters with bevel or bent blades, bill blades,
Various blade coaters such as twin blade, rod blade, short dwell, and triplex are preferably used. The coated paper obtained by coating the coating composition of the present invention exhibits the excellent properties of the coating composition of the present invention when it is manufactured into a product through finishing equipment such as a super calender or a gloss calender. However, it can also be used as coated matte paper with light finishing treatment or without finishing treatment. The printing method for coated paper is offset printing,
Any of gravure printing, letterpress printing, and flexo printing can be used, and either sheet or roll printing can be used. The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples. Note that parts and percentages shown in the examples mean parts by weight and percentages by weight unless otherwise specified. Preparation of copolymer emulsion In a pressure-resistant reaction vessel, add 95 parts of water, 1.5 parts of sodium dodecylbenzenesulfonate, and dodecyl mercaptan.
0.2 parts, sodium carbonate 0.4 parts, potassium persulfate 0.8 parts
After that, as the first stage of emulsion copolymerization, the monomers shown in Table 1 were added in the proportions shown in Table 1, and the polymerization was carried out by heating to 60°C, until the polymerization conversion rate was 85. %, in the second step, the monomers shown in Table 1 are added in the proportions shown in Table 1 to complete the polymerization, resulting in copolymer emulsions A, E, and F and I were prepared. Note that emulsions B, C, G, and H were prepared by charging and polymerizing all monomers in the first step. In addition, the alkali-sensitive emulsion D was placed in a pressure-resistant polymerization container equipped with a dropping funnel and a stirrer.
70 parts seed latex (styrene) with an average particle size of 250 Å
0.8 part of styrene-acrylic acid copolymer emulsion consisting of 96% acrylic acid and 4% acrylic acid, 0.1 part of sodium dodecylbenzenesulfonate, and 0.05 part of sodium ethylenediaminetetraacetate were charged and heated to 90°C. Next, after purging the inside of the container with nitrogen, the pressure was reduced and the monomer mixture as shown in the upper row of Table 1 was mixed.
A solution consisting of 0.3 parts of tert-dodecyl mercaptan, 50 parts of water, 0.1 part of sodium dodecylbenzenesulfonate, 0.15 parts of sodium hydroxide, and 0.5 parts of potassium persulfate was added dropwise at the same time, and the temperature was maintained at 90°C for 6 hours. Dripping completed. In this way, average particle size 0.17 microns, PH4.0, conversion rate 99.0%
An aqueous dispersion of was obtained. Next, a solution consisting of the monomer mixture shown in the lower row of Table 1, 24 parts of water, 0.017 part of sodium dodecylbenzenesulfonate, and 0.07 part of potassium persulfate was simultaneously added dropwise into this aqueous dispersion, and the temperature was raised to 85°C. The dropwise addition was completed in 3 hours. In this way,
An alkali-sensitive emulsion D having an average particle size of 0.2 microns, a pH of 3.2, and a conversion rate of 99.5% was obtained.

[Table] Examples 1 to 3 and Comparative Examples 1 to 10 A pulp composition consisting of 35 parts of stone ground pulp, 40 parts of softwood bleached kraft pulp, and 25 parts of hardwood bleached kraft pulp (all parts by weight of bone dry pulp), and a sizing agent 0.1 part of alkyl ketene dimer (manufactured by Deitzk Hercules, Haakon),
0.05 part of polyamide epichlorohydrin (manufactured by Deitsku Hercules Co., Ltd., Kaimen) as a fixing agent, 1.0 part of cationic starch (manufactured by Oji Nacional Co., Ltd.) as a paper strength enhancer, and heavy calcium carbonate 10 with a specific surface area of 0.8 m ² /g as a filler. Neutral paper is made from paper stock with 50 parts added.
A base paper for coated paper of g/m ² was obtained. In a Coles disperser, the pigment shown in Table 2, the copolymer emulsion obtained from the monomer composition shown in Table 1, and the auxiliary agent shown in Table 2 are mixed in the proportions shown in Table 2,
A coating composition was obtained. Next, the coating composition obtained above was coated on the base paper with a pilot blade coater at a speed of 800 m/min so that the dry coating amount was 36 g/m ² on both sides, and after drying, it was rolled up and further coated with a super coat. A double-sided coated paper was produced by rendering. viscosity of the coating composition,
Operability during coating (the degree of occurrence of structite, scratches, and streaks on the blade edge is visually evaluated, and the criteria are ◎: Very good 〇: Slight occurrence, but continuous operation is possible ×: Product yield decreases. Table 2 lists the quality evaluations of the coated processed paper, the blank paper, and the quality after printing. Example 4 and Comparative Example 11 0.3 parts of rosin size, 3 parts of aluminum sulfate, and 10 parts of talc as a filler were added to a pulp composition consisting of 40 parts of softwood kraft pulp and 60 parts of hardwood kraft pulp (all parts by weight of bone-dry pulp). The resulting paper stock was made into paper and subjected to size press treatment with a size press solution consisting of 2 parts of oxidized starch and 1 part of carboxyl group-modified polyvinyl alcohol to obtain a base paper for coated paper weighing 45 g/m ² . A coating composition was obtained using a Coles disperser in the same manner as in the previous Examples and Comparative Examples. This composition was coated on the base paper with a pilot blade coater for 1000 m/m2 so that the dry coating amount was 18 g/ ^m2 on both sides.
The paper was coated at a speed of 1 minute, dried, rolled up, and subjected to super calendering to produce double-sided coated paper. The viscosity of the coating composition, the operability during coating, and the quality evaluation of the coated processed paper as a blank paper and after printing are listed in Table 2, respectively. In Table 2, Examples 1, 2, 4, Comparative Examples 3, 5, 6, 7,
The kaolin used for 8, 9, 10, and 11 is Amazon 88.
(manufactured by The Caulim da Amasonia Ltda.) and added 0.35% of sodium pyrophosphate (TSPP) as a dispersant.
The kaolin used in Comparative Example 1 was S-23 (manufactured by EMC) with the addition of 0.05 part of TSPP.The kaolin used in Comparative Example 2 was Klondyke (manufactured by EMC), The kaolin used in Example 3 was prepared by adding 0.05 part of TSPP to Amazon 88 kaolin, Ultra White 90 and
Examples 1, 4, Comparative Examples 1, 2, 3, 5, 6,
The heavy calcium carbonate used in 7. is Carbital-90 (manufactured by Fuji Kaolin Co., Ltd.) The heavy calcium carbonate used in Examples 2 and 3 and Comparative Examples 4 and 10 is a micron mill with a content of 2 microns or less at 3%. A slurry of heavy carbonaceous powder ground in 2008 was made into a slurry using 0.9 parts of sodium polyacrylate and pigment as a dispersant, and the slurry was pulverized using a sand mill (Pearl Mill) manufactured by Dreiswerke, West Germany. The heavy carbonate used in Comparative Example 9 was Escalon.
1500 (manufactured by Sankyo Seifun Co., Ltd.) The calcium carbonate used in Example 2 was Escalon.
1500 (manufactured by Sankyo Seifun Co., Ltd.) The light calcium carbonate used in Comparative Example 8 was Brilliant (manufactured by Shiraishi Kogyo Co., Ltd.), abbreviated as light coal. The calcium carbonate used in Comparative Example 10 was Softon.
2200 (manufactured by Bihoku Funka Co., Ltd.) Carboxymethyl cellulose used as an auxiliary agent is abbreviated as CMC, and hydroxyethyl cellulose is abbreviated as HEC.

【table】

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[Table] As is clear from the results in Table 2, in each of the examples of the present invention, the coating operability was good, and the quality of the coated paper obtained was high in white paper gloss. The paper had good smoothness, and especially excellent printing gloss and smoothness after printing, and it was an excellent coated paper for printing without defects such as roughening or blistering even as an off-wheel printing paper.

Claims (1)

[Scope of Claims] 1. A coating composition for coated processed paper with a high solids concentration containing a pigment and an adhesive, wherein (a) the content of particles of 1 micron or less as pigment is 80 wt% or more; Kaolin with a particle content of 0.5 microns or less of 50 wt% or more and a viscosity of 4.0 x 10 ⁵ dyne centimeter or less at a shear rate of 5000 sec ^-1 in an aqueous slurry with a solid content concentration of 71 wt% is used as the total pigment. Ten~
80wt%, particle content of 2 microns or less is 70~
At 100wt%, the particle content of 1 micron or less is 55~
95wt% of heavy calcium carbonate is 20% of the total pigment.
Contains ~90 wt%, (b) 3 to 40 parts by weight of vinyl cyanide monomer and 97 to 60 parts by weight of other monomers as an adhesive.
A coated processed paper characterized in that a copolymer emulsion obtained by emulsion polymerization with parts by weight contains 3 to 20 wt% of the total pigment in terms of solid content, and (c) the solid content concentration is 65 to 80 wt%. Coating composition for use. 2 Particle content of 2 microns or less is 80-100wt%
The particle content of 1 micron or less is 60 to 95 wt%.
The coating composition according to claim 1, which uses heavy calcium carbonate. 3 3 to 40 parts by weight of vinyl cyanide monomer, 0 to 45 parts by weight of aliphatic conjugated diolefin monomer,
A copolymer emulsion obtained by emulsion polymerization of 0 to 15 parts by weight of an ethylenically unsaturated carboxylic acid monomer and 0 to 97 parts by weight of a monoolefin monomer copolymerizable with these, the average particle size of which is
2. The coating composition according to claim 1, wherein a copolymer emulsion having a diameter of 0.1 to 0.3 microns is used as an adhesive. 4 The adhesive contains 5 to 30 parts by weight of vinyl cyanide monomer and 10 to 40 parts by weight of aliphatic conjugated diolefin monomer.
Part by weight, ethylenically unsaturated carboxylic acid monomer
The coating composition according to claim 3, which is a copolymer emulsion obtained by emulsion polymerization of 0.2 to 10 parts by weight and 20 to 84.4 parts by weight of a monoolefin monomer copolymerizable with these.