JP2844031B2 - Gravure printing paper coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gravure printing paper coating composition which is excellent in operation stability during high-speed coating and in which the obtained coated paper shows excellent suitability for gravure printing.

[0002]

2. Description of the Related Art Gravure printing is so-called intaglio printing, in which ink filled in the concave portions of a plate is printed on paper. It is excellent in reproducibility, and it is possible to obtain a printed matter with a rich and rich expression. For this reason, it has spread rapidly in recent years, combined with the colorization and visualization of magazines.

In order to sufficiently exhibit such features of gravure printing, coated paper for gravure printing which is excellent in gravure printing suitability is generally used. Coated paper for gravure printing is improved in smoothness, cushioning properties, oil absorbency, etc., and during printing, ink transfer leaks from individual cells of the gravure plate,
It is designed to minimize so-called misdots as much as possible, and has much better gravure printing suitability than ordinary coated paper.However, higher printing speeds in recent years have required even better gravure printing suitability. It has become.

On the other hand, in the production process of coated paper for gravure printing, attempts have been made to apply the coating at a higher speed than before in order to improve productivity. However, as the coating speed increases, operational problems such as streaks and bleeding due to the fluidity and water retention of the paint tend to occur, and the suitability of the final product coated paper for gravure printing also decreases. It is strongly desired to solve these problems.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on the above problems and found that a gravure obtained by using a copolymer latex obtained by emulsion polymerization in the presence of a specific compound as a binder. It has been found that the printing paper coating composition has excellent performance, and the present invention has been completed.

That is, the present invention relates to a gravure printing paper coating composition containing a copolymer latex as a pigment and a binder, wherein the copolymer latex contains 30 to 80% by weight of an aliphatic conjugated diene monomer and an ethylene 0.5 to 10% by weight of an unsaturated carboxylic acid monomer and 10 to 69.5% by weight of another monomer copolymerizable therewith are combined with a cyclic unsaturated carbon having one unsaturated bond in the ring. A gravure printing paper coating composition characterized by being a copolymer latex obtained by emulsion polymerization in the presence of hydrogen.

Hereinafter, the present invention will be described in detail.

The aliphatic conjugated diene monomer in the present invention includes 1,3-butadiene and 2-methyl-1,3-
Butadiene, 2,3-dimethyl-1,3 butadiene, 2
-Chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and the like, and one or more kinds can be used. In particular, 1,3-butadiene is preferred.

Examples of the ethylenically unsaturated carboxylic acid monomer include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid.

Other monomers copolymerizable with the aliphatic conjugated diene monomer and the ethylenically unsaturated carboxylic acid monomer include alkenyl aromatic monomers and unsaturated carboxylic acid alkyl ester monomers. And unsaturated monomers containing a hydroxyalkyl group, vinyl cyanide monomers, unsaturated carboxylic acid amide monomers and the like.

The alkenyl aromatic monomers include styrene, α-methylstyrene, methyl α-methylstyrene,
Vinyl toluene and divinyl benzene, and the like,
One or more kinds can be used. Particularly, styrene is preferred.

Examples of the unsaturated carboxylic acid alkyl ester monomer include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl malate, dimethyl dimethyl Examples include itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate, and the like, and one or more kinds can be used. Particularly, methyl methacrylate is preferred.

Examples of the unsaturated monomer containing a hydroxyalkyl group include β-hydroxyethyl acrylate and β-hydroxyethyl acrylate.
-Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,
Hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di- (ethylene glycol) maleate,
Di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl)
Maleate, 2-hydroxyethyl methyl fumarate and the like can be mentioned, and one kind or two or more kinds can be used. Particularly, β-hydroxyethyl acrylate is preferable.

Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like.
One or more kinds can be used. Acrylonitrile is particularly preferred.

The unsaturated carboxylic acid amide monomers include:
Acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N,
N-dimethylacrylamide and the like can be mentioned, and one kind or two or more kinds can be used. Acrylamide is particularly preferred.

The above monomer composition is composed of 30 to 80% by weight of an aliphatic conjugated diene monomer, 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer and other copolymerizable with them. The amount of the monomer is 10 to 69.5% by weight.

When the amount of the aliphatic conjugated diene monomer is less than 30% by weight, the gravure printing suitability of the coated paper obtained is poor, and when it exceeds 80% by weight, roll stains occur during supercalendering of the coated paper. Not preferred. When the amount of the ethylenically unsaturated carboxylic acid monomer is less than 0.5% by weight, the mechanical stability of the copolymer latex is inferior. When the amount exceeds 10% by weight, the viscosity of the copolymer latex is undesirably high. If the other copolymerizable monomer is less than 10% by weight,
Roll stains occur during the supercalender treatment of the coated paper obtained, and if it exceeds 69.5% by weight, the gravure printing suitability of the coated paper is poor, which is not preferable.

The chain transfer agent used in the present invention includes:
n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan and other alkyl mercaptans, xanthogen compounds such as dimethyl xanthogen disulfide, diisopropyl xanthogen disulfide, and α- Methylstyrene dimer, terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide,
Thiuram compounds such as tetramethylthiuram monosulfide, phenol compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, dichloromethane, dibromomethane, carbon tetrachloride , Halogenated hydrocarbon compounds such as carbon tetrabromide, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide , triphenylethane, pentaphenylethane, acrolein, methacrolein, and thioglycolic acid Thiomalic acid, 2-ethylhexyl thioglycolate, and the like, and one or more kinds can be used.

The use amount of these chain transfer agents is not limited at all, and can be appropriately adjusted according to the performance required for the copolymer latex, but is preferably 0.1 to 100 parts by weight of the monomer mixture. 05 to 10 parts by weight.

Most of the cyclic unsaturated hydrocarbon having one unsaturated bond in the ring used in the present invention remains unreacted after the polymerization, and it is necessary to recover the unreacted product. Therefore, those having a boiling point of 140 ° C. or less are preferable.
Specific examples include cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and the like.

The amount of the compound used in the present invention is 0.1 to 30 parts by weight based on 100 parts by weight of the monomer mixture. If the amount is less than 0.1 part by weight, the effect of the present invention is insufficient, and if it exceeds 30 parts by weight, the amount of the compound remaining as an unreacted substance relatively increases, and the energy required for the recovery is reduced. It is not preferable because it becomes enormous. Preferably it is 0.5 to 15 parts by weight.

The method of adding the various components in the present invention is not particularly limited, and any of a batch addition method, a division addition method, and a continuous addition method can be employed. Further, in the emulsion polymerization, a commonly used emulsifier, polymerization initiator, electrolyte, polymerization accelerator, chelating agent and the like can be used.

In the present invention, any one of single-stage polymerization, two-stage polymerization and multi-stage polymerization can be employed, but it is particularly preferable to carry out emulsion polymerization by the following method.

That is, as the first stage, 3 to 40% by weight, preferably 5 to 30% by weight of the monomers are polymerized with respect to all the monomers, and the polymerization conversion of the first stage is 50% or more. Preferably, the remaining monomer is polymerized when it becomes 70% or more, and the polymerization is substantially completed. In the above-mentioned production method, it is particularly preferable to use the ethylenically unsaturated carboxylic acid monomer in the first stage in total amount.

Examples of the emulsifier include anionic salts such as sulfates of higher alcohols, alkyl benzene sulfonates, alkyl diphenyl ether sulfonates, aliphatic sulfonates, aliphatic carboxylates, and sulfate esters of nonionic surfactants. A surfactant or a nonionic surfactant such as an alkyl ester type, an alkyl phenyl ether type or an alkyl ether type of polyethylene glycol is used alone or in combination of two or more.

As the initiator, a water-soluble initiator such as potassium persulfate, ammonium persulfate and sodium persulfate, a redox initiator, or an oil-soluble initiator such as benzoyl peroxide can be used.

By adopting the above production method, the copolymer latex used in the present invention can be obtained with good polymerization stability, but one unsaturated bond is present in the ring used in the production step. Cyclic unsaturated hydrocarbon having
In the end use, it is not preferable from the viewpoint of working environment hygiene. In the present invention, after the copolymer latex is polymerized by the production method, the compound remaining as an unreacted substance is substantially (copolymer latex ( 0.5 parts by weight or less, more preferably 0.1 parts by weight or less based on 100 parts by weight of solids).

Known methods for removing the compound include:
For example, it can be removed by steam distillation, vacuum distillation, or blowing of an inert gas.

The gravure printing paper coated paper composition of the present invention is prepared as an aqueous dispersion together with the above-mentioned copolymer latex together with a pigment and, if necessary, other binders, thickeners and auxiliaries.

At this time, the copolymer latex of the present invention is used in an amount of 3 to 20 parts by weight, based on 100 parts by weight of the pigment in terms of solid content.
Preferably, 4 to 10 parts by weight are blended.

Here, as the pigment, kaolin clay,
Talc, barium sulfate, titanium oxide, calcium carbonate,
Examples thereof include inorganic pigments such as aluminum hydroxide, zinc oxide and satin white, and organic pigments such as polystyrene latex, and these are used alone or in combination.

Further, as other binders and thickeners,
Modified starches such as starch, oxidized starch and esterified starch, natural binders such as soy protein and casein, or synthetic latexes such as polyvinyl alcohol, polyvinyl acetate latex, acrylic latex, and alkali -soluble copolymer latex are used. You.

To prepare the paper coating composition of the present invention,
Furthermore, other auxiliaries, such as dispersants (sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate, etc.), defoamers (polyglycols, fatty acid esters, phosphate esters, silicone oils, etc.), leveling agents (funnel oil, Dicyandiamide, urea, etc.),
Preservatives, water resistant agents (formalin, hexamine, melamine resin, urea resin, glyoxal, etc.), release agents (calcium stearate, paraffin emulsion, etc.), fluorescent dyes, color water retention improvers (carboxymethyl cellulose, sodium alginate, etc.) It is added as needed.

The method for applying the paper coating composition of the present invention to coated paper can be performed by a known technique such as an air knife coater.
It is performed by a coating machine such as a blade coater, a roll coater, and a bar coater. After the application, the surface is dried and finished with a calender ring or the like.

[Examples] The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist thereof. In the examples, parts and percentages indicating percentages are based on weight. The measurement of various physical properties in the examples was based on the following methods.

The amount of fine coagulated material of several μm to 50 μm is observed with a microcoagulated product microscope. ○: very small △: small ×: large Evaluation is made in these three stages.

Gel content A latex film is prepared by drying at room temperature. Thereafter, about 1.0 g of the latex film was accurately weighed, put in 400 cc toluene, left to dissolve for 48 hours, filtered through a 300-mesh wire gauze, dried, and the toluene-insoluble matter (gel) on the wire gauze was weighed to calculate the gel content. I do.

The viscosity of the paper coating composition is measured at a rotational speed of 4000 rpm using Bob F with a fluid Hercules high-shear viscometer. The lower the viscosity, the better the fluidity.

The composition for coating the water-retaining paper is coated on commercially available high-quality paper using a wire rod bar. The time immediately after the coating is set to 0 second, the time until the moisture disappears from the surface of the coating layer and the gloss disappears is measured, and the value is regarded as the water retention. The higher the value, the better the water retention.

Gravure printing suitability Using a gravure printing machine of the Ministry of Finance of Japan, printing was performed using a halftone gravure plate, and the halftone misdots were counted and classified into ◎ (excellent) to × (poor). .

Preparation of Copolymer Latex In a 20 liter autoclave, 100 parts by weight of water, 0.4 part of sodium dodecylbenzenesulfonate, 0.3 part of sodium hydrogen carbonate, 1.0 part of potassium persulfate, and Tables 1 and 2 The first-stage polymerization was carried out at 70 ° C. by charging the first-stage monomer mixture, the chain transfer agent, and the cyclic unsaturated hydrocarbon having one unsaturated bond in the ring shown in FIG. When the conversion of the first-stage emulsion polymerization reached 70%, the second-stage polymerization was performed by continuously adding the monomer mixture, the chain transfer agent, and the unsaturated hydrocarbon in the second-stage for 6 hours. . Thereafter, in order to complete the polymerization, the polymerization was further continued and terminated at a polymerization conversion of 97%. After adjusting the pH of the obtained copolymer latex to 8 using sodium hydroxide, unreacted monomers and unsaturated hydrocarbons remaining as unreacted substances are removed by steam distillation, and copolymer latex a to k was obtained.

In the table, the left side indicates the amount of the first stage and the right side indicates the amount of the second stage, with "/" therebetween.

Preparation Example of Paper Coating Composition-1 Copolymer latexes a to c and h and i were each adjusted with pure water so as to have a solid concentration of 60% based on the following formulation. Coating compositions 1 to 5 were prepared. Table 3 shows the fluidity and water retention of the obtained paper coating composition.

(Formulation) Dry parts by weight 1 kaolin 80 parts Heavy calcium carbonate 20 parts Dispersant 0.5 parts Sodium hydroxide 0.2 parts Copolymer latex 8 parts Thickener 0.5 parts ─────────── 60% solids

Preparation Example of Paper Coating Composition-1 Each of the copolymer latexes d to g and j was adjusted with pure water so as to have a solid content of 63% based on the following formulation. Compositions 6 to 10 were prepared. Table 4 shows the fluidity and water retention of the obtained paper coating composition.

(Formulation) Dry parts by weight 1 kaolin 80 parts heavy calcium carbonate 20 parts dispersant 0.5 part sodium hydroxide 0.2 parts copolymer latex 6.5 parts starch oxide 2 parts ─────────────── ６３ 63% solids

Preparation of Coated Paper for Gravure Printing A commercially available high-quality paper (64 g / m ² ) was coated using a wire rod bar so that the coating amount of the paper coating composition was 13 g / m ^{2 on} one side. Then, it was immediately dried with a hot air dryer at 140 ° C. After humidity control, a super calender treatment was performed to obtain a coated paper. Tables 3 and 4 show the gravure printability of the obtained coated paper.

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[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

[0051]

[Table 4]

Claims (1)

(57) [Claims] In a gravure printing paper coating composition containing a pigment and a copolymer latex as a binder, the copolymer latex contains 30 to 80% by weight of an aliphatic conjugated diene-based monomer, 0.5 to 10% by weight of a saturated carboxylic acid monomer and 10 to 69.5% by weight of another monomer copolymerizable therewith are combined with a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring. A gravure printing paper coating composition, which is a copolymer latex obtained by emulsion polymerization in the presence of a.