JP2009068130A - Highly calcium carbonate-containing composition for coating paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly calcium carbonate-containing composition for coating paper, which is excellent in dry pick strength, also excellent in wet pick strength, ink set, and print glossiness despite that it is a high calcium carbonate formulation. <P>SOLUTION: The highly calcium carbonate-containing composition for coating the paper consists of a pigment (I) containing 90 wt.% or more of calcium carbonate and copolymer latex (II) obtained by performing emulsion polymerization of 30-70 wt.% (A) aliphatic conjugated diene-based monomer, 1-15 wt.% (B) an ethylenic unsaturated carboxylic acid monomer and/or (C) ethylenic unsaturated monomer containing a functional group other than the component(B), and 15-69 wt.% (D) another monomer copolymerizable with the monomers (total of the monomers is 100 wt.%), and having an acid density of 1.0×10<SP>-3</SP>to 1.0×10<SP>-2</SP>meq/m<SP>2</SP>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a high calcium carbonate-containing paper coating composition. More specifically, the present invention relates to a high calcium carbonate-containing paper coating composition that is excellent in dry pick strength, wet pick strength, ink set, and printing gloss despite being a high calcium carbonate formulation.

In recent years, coated paper has been used in a large number of printed materials because of its high printing effect. Even in periodicals such as quarterly and monthly papers, the use of coated paper on all pages has increased considerably. In particular, most direct mails and product catalogs in the mail order business use coated paper for all pages.
In general, a paper coating composition is a water dispersion composed of a pigment dispersion in which a white pigment such as clay or calcium carbonate is dispersed in water, a binder for adhering and fixing the pigments to each other and a base paper, and other additives. It is a paint. As the binder, a synthetic emulsion binder represented by styrene-butadiene copolymer latex and a natural binder represented by starch and casein are used. Among them, styrene-butadiene copolymer latex has a large degree of freedom in quality design and is widely used as the most suitable binder for paper coating compositions today. Is known to affect the performance of the paper coating composition or the quality of the final coated paper product, such as surface strength and printing gloss.
On the other hand, in recent years, the cost of pigments has been reduced due to soaring pigment costs, and the blending ratio of expensive kaolin to inexpensive calcium carbonate has increased. Paper coating suitable for such high calcium carbonate formulations The effect of coating compositions, especially latex, on coated paper is becoming increasingly important.
In JP-A-2006-152484 (Patent Document 1), 60% or more of heavy calcium carbonate is contained in 100% by mass of the total pigment, and the binder is a core part of 70 to 95 parts by mass composed of a copolymer, A composition for matte coated paper, comprising a copolymer latex containing 30-5 parts by mass of a copolymer shell part and containing a core-shell type copolymer having an average particle diameter of 150 nm or less by a light scattering method In addition, Japanese Patent Application Laid-Open No. 11-50390 (Patent Document 2) coats with a blade coater, and 30 heavy calcium carbonate having an average particle size of 0.1 to 0.4 μm is used as the pigment. -100% by mass and a copolymer latex having an average particle size of 0.15 to 0.30 μm as the adhesive is used for printing based on 5% to 20% by mass relative to the total pigment. Light on coated paper Technology that unevenness is finished in almost no high-quality have been introduced.

However, these various improvement techniques have not yet reached a level that sufficiently satisfies the performance required for a paper coating composition containing high calcium carbonate, and further improvements have been strongly demanded particularly for latex. .
JP 2006-152484 A Japanese Patent Laid-Open No. 11-50390

  An object of the present invention is to provide a high calcium carbonate-containing paper coating composition that is excellent in dry pick strength, wet pick strength, ink set, and printing gloss.

That is, the present invention relates to pigment (I) containing 90% by weight or more of calcium carbonate, aliphatic conjugated diene monomer (A) 30 to 70% by weight, ethylenically unsaturated carboxylic acid monomer (B) and 1/15% by weight of functional group-containing ethylenically unsaturated monomer (C) other than component (B) and 15-69% by weight of other monomer copolymerizable with these (D) High calcium carbonate-containing paper comprising copolymer latex (II) having an acid density of 1.0 × 10 ^{−3 to} 1.0 × 10 ⁻² meq / m ² obtained by emulsion polymerization of a total of 100% by weight) A composition for coating is provided.

  The high calcium carbonate-containing composition for paper coating of the present invention is excellent in dry pick strength and has an effect that a coated paper excellent in wet pick strength, ink set, and printing gloss can be obtained.

The present invention is described in detail below.
Examples of the aliphatic conjugated diene monomer (A) in the present invention include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-chloro-1. , 3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and the like, and one or more of them can be used. In particular, the use of 1,3-butadiene is preferred.

  Examples of the ethylenically unsaturated carboxylic acid monomer (B) include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Or 2 or more types can be used.

Examples of the functional group-containing ethylenically unsaturated monomer (C) other than the ethylenically unsaturated carboxylic acid monomer include the following monomers.
Unsaturated carboxylic acid amide monomers such as acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N, N-dimethylacrylamide, or β-hydroxyethyl acrylate, β-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-hydroxy Ethyl) maleate, 2-hydroxyethylmethyl fumarate, and the like, and other unsaturated monomers containing a hydroxyalkyl group. Species or two or more can be used. In particular, use of acrylamide, methacrylamide, or β-hydroxyethyl acrylate is preferable.

  Functional group-containing ethylenically unsaturated monomer (C) other than the above aliphatic conjugated diene monomer (A), ethylenically unsaturated carboxylic acid monomer (B), and ethylenically unsaturated carboxylic acid monomer Examples of the other monomer (D) that can be copolymerized with a vinyl cyanide monomer, an alkenyl aromatic monomer, and an unsaturated carboxylic acid alkyl ester monomer.

  Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, and the like, and one or more of these can be used. In particular, the use of acrylonitrile or methacrylonitrile is preferred.

  Examples of the alkenyl aromatic monomer include styrene, α-methylstyrene, methyl α-methylstyrene, vinyltoluene and divinylbenzene, and these can be used alone or in combination. In particular, use of styrene is preferable.

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

  The monomer composition is composed of an aliphatic conjugated diene monomer (A) 30 to 70% by weight, an ethylene-based unsaturated carboxylic acid monomer (B) and / or a functional group-containing ethylene other than the component (B). It is 1 to 15% by weight of the system unsaturated monomer (C) and 15 to 69% by weight of other monomer (D) copolymerizable therewith (total monomer of 100% by weight).

  If the aliphatic conjugated diene monomer is less than 30% by weight, the adhesiveness such as dry pick strength required at the time of printing, and if it exceeds 70% by weight, the wet adhesiveness such as the wet pick strength required at the time of printing. Is inferior and is not preferred. More preferably, it is 40 to 60% by weight.

  When the content of the ethylenically unsaturated carboxylic acid monomer (B) and / or the functional group-containing ethylenically unsaturated monomer (C) other than the component (B) is less than 1% by weight, the copolymer latex itself and paper coating are used. The mechanical stability of the composition is inferior, and if it exceeds 15% by weight, the viscosity of the latex is increased, which may cause problems in handling the copolymer latex itself, which is not preferable. More preferably, it is 2 to 15% by weight.

  If the other copolymerizable monomer exceeds 69% by weight, the adhesiveness such as dry pick strength is inferior, which is not preferable.

  In the present invention, when the above-mentioned monomer is emulsion-polymerized, any one of single-stage polymerization, two-stage polymerization, multi-stage polymerization, seed polymerization, power feed polymerization method and the like may be employed.

  In the emulsion polymerization, conventional emulsifiers, chain transfer agents, polymerization initiators, hydrocarbon solvents, electrolytes, polymerization accelerators, chelating agents and the like can be used.

  As an emulsifier, anionic surfactants such as sulfate esters of higher alcohols, alkylbenzene sulfonates, alkyl diphenyl ether sulfonates, aliphatic sulfonates, aliphatic carboxylates, sulfate salts of nonionic surfactants, etc. One or two or more nonionic surfactants such as an alkyl ester type, an alkyl phenyl ether type, and an alkyl ether type of polyethylene glycol can be used in combination.

  Examples of chain transfer agents include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan, dimethylxanthogen disulfide, diisopropylxanthogen disulfide, etc. Xanthogen compounds, terpinolene, thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide, α-methylstyrene dimer, 2,6-di-t-butyl-4-methylphenol, styrenation Phenolic compounds such as phenol, allyl compounds such as allyl alcohol, halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, carbon tetrabromide, α -Vinyl ethers such as benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglycolate, etc. These can be used alone or in combination of two or more.

  As the polymerization initiator, water-soluble polymerization initiators such as potassium persulfate, sodium persulfate, and ammonium persulfate, redox polymerization initiators, and oil-soluble polymerization initiators such as benzoyl peroxide can be appropriately used. In particular, the use of a water-soluble polymerization initiator is preferred.

  In the polymerization, saturated hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane and cycloheptane, and unsaturated hydrocarbons such as pentene, hexene, heptene, cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene and 1-methylcyclohexene. Hydrocarbon compounds such as aromatic hydrocarbons such as benzene, toluene and xylene may be used.

In the present invention, the acid density of the copolymer latex is important, and the range is required to be 1.0 × 10 ^{−3 to} 1.0 × 10 ⁻² meq / m ² . When the acid density of the copolymer latex is less than 1.0 × 10 ⁻³ meq / m ² , the dry pick strength is inferior, and when it exceeds 1.0 × 10 ⁻² meq / m ² , the wet topic is inferior. Absent. In addition, as a method of adjusting the acid density, for example, the amount of the functional group-containing ethylenically unsaturated monomer (C) other than the ethylenically unsaturated carboxylic acid monomer (B) and / or the component (B) is used. It can be adjusted by the addition method, the amount of polymerization water, the polymerization temperature and the like.

  The number average particle diameter of the copolymer latex used in the present invention is preferably 50 to 150 nm. When the number average particle diameter is less than 50 nm, the latex viscosity is high, and when it exceeds 150 nm, the wet pick strength tends to be inferior.

  Further, the gel content of the copolymer latex used in the present invention is not particularly limited, but is 50 to 100% by weight. If it is less than 50%, the dry strength is inferior.

  In the composition for paper coating in the present invention, a pigment containing 90% by weight or more of calcium carbonate is used. Examples of other pigments include kaolin clay, talc, barium sulfate, titanium oxide, and water. Inorganic pigments such as aluminum oxide, zinc oxide, and satin white, or organic pigments such as polystyrene latex can be used alone or in combination.

  If necessary, modified starch such as starch, oxidized starch and esterified starch, natural binder such as soybean protein and casein, or water-soluble synthetic binder such as polyvinyl alcohol may be used. In addition, synthetic latex such as polyvinyl acetate latex and acrylic latex may be used in combination with the copolymer latex of the present invention. However, starch and carboxymethyl cellulose are preferably used. In particular, in the present invention, use of carboxymethyl cellulose is preferable. Most preferably.

  When preparing a paper coating composition using the copolymer latex of the present invention, other auxiliary agents such as a dispersant (sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate, etc.), antifoaming Agent (polyglycol, fatty acid ester, phosphate ester, silicone oil, etc.), leveling agent (funnel oil, dicyandiamide, urea, etc.), preservative, mold release agent (calcium stearate, paraffin emulsion, etc.), fluorescent dye, color water retention An improver (such as sodium alginate) may be added as necessary.

  Further, any known technique such as an air knife coater, blade coater, roll coater or bar coater may be used as a method for applying the paper coating composition to the coated paper. Also, after coating, the surface is dried and finished by calendaring or the like.

[Example]
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded. In the examples, parts and percentages indicating percentages are based on weight unless otherwise specified. In addition, various physical properties in the examples were evaluated by the following methods.

Evaluation of dry pick strength of coated paper Judge the degree of picking when each coated paper sample is printed at the same time with an RI printer, and (excellent) ◎>○>△> × (poor) relatively evaluated.
Evaluation of wet pick strength of coated paper Immediately after applying a dampening solution to each coated paper sample with a Molton roll using an RI printer, and immediately after printing each coated paper sample with an ink roll The degree of picking was determined with the naked eye, and was evaluated relatively to (excellent) ◎>○>Δ> × (poor).

Evaluation of ink set on coated paper When a sample is printed with an RI printer, and then the white paper is superimposed and pressure-bonded with a roll, the accumulated time is sequentially 20 seconds, 60 seconds, 90 seconds, and 120 seconds respectively from the end of the sample. The image was transferred to this white paper with an interval of ≧, and the density was visually evaluated relatively (transfer density is low) ◎>○>Δ> × (transfer density is high).

Evaluation of Print Gloss of Coated Paper Each coated paper sample was printed with a process ink (0.5 g) using an RI printer, and was then allowed to stand overnight, and the glossiness of the printed surface was measured according to JIS P-8142. The larger the value, the better the print gloss.

Measurement of number average particle size of copolymer latex The number average particle size of the copolymer latex was measured by a dynamic light scattering method. In the measurement, LPA-3000 / 3100 (manufactured by Otsuka Electronics) was used.

Measurement of gel content of copolymer latex A latex film is prepared at room temperature. Thereafter, about 1 g of the latex film is weighed and placed in 400 cc of toluene to be dissolved for 48 hours. Thereafter, this was filtered through a 300-mesh wire mesh, and the toluene insoluble portion captured by the wire mesh was dried and weighed, and the ratio of the weight to the weight of the first latex film was calculated as a gel content in wt%.

Measurement of acid density of copolymer latex 50 g of 0.1N sodium hydroxide aqueous solution and 3 g of carbon tetrachloride were added to copolymer latex diluted to 5% by weight and stirred for 1 hour. Thereafter, the latex particles were centrifugally settled by a centrifugal separator to separate the supernatant layer and the latex particle layer. The obtained latex particle layer was diluted with pure water, and after adding an excessive amount of 0.1N hydrochloric acid, it was bound to the latex particles from the electric conductivity curve obtained by back titration with a 0.1N aqueous sodium hydroxide solution. The amount of carboxyl groups was determined. The acid density (meq / m ² ) on the surface of the latex particles was calculated from the amount of carboxyl groups and the particle size of the latex.

Preparation of copolymer latex In a pressure resistant polymerization reactor, 150 parts of polymerization water and 1 part of potassium persulfate were charged and stirred sufficiently, and then each monomer and other compounds shown in Table 1 were added to 70 ° C. In the second-stage polymerization, when the polymerization conversion rate of the first-stage monomer reaches 90% or more, the second-stage monomers are added and polymerized to obtain the final polymerization conversion. The polymerization was terminated when the rate exceeded 95% (in the first stage polymerization, the polymerization was terminated when the final polymerization addition rate exceeded 95%).
Next, the pH of the latex of these copolymer latexes is adjusted to 7.5 using sodium hydroxide, unreacted monomers and other low-boiling compounds are removed by steam distillation, and copolymer latexes AD , And EJ were obtained.

Preparation and Evaluation of Composition for Paper Coating Using copolymer latexes A to D and E to J according to the formulation formulas 1 and 2 shown below, the pH is adjusted to 9.5 with NaOH, and the paper coating shown in Table 2 A working composition was prepared.
(Formulation formulation of paper coating composition)
Formulation 1
Heavy calcium carbonate 100 parts Modified starch 3 parts Copolymer latex 9 parts ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・
Solid content 65%

Formulation 2
Heavy calcium carbonate 100 parts Carboxymethyl cellulose 0.3 parts Copolymer latex 9 parts ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・
Solid content 65%

Preparation and Evaluation of Coated Paper Coated paper (basis weight 55 g / m ² ) is coated with the above-mentioned composition for paper coating using a wire bar so that the coating amount per side is 10 g / m ^2. After being worked and dried, a super calender treatment was performed under the conditions of a linear pressure of 60 kg / cm and a temperature of 50 ° C. to obtain a coated paper. The obtained coated paper was subjected to each test and evaluated. The results are shown in Table 2.

  As described above, by using the high calcium carbonate-containing paper coating composition obtained in the present invention, a coated paper excellent in dry pick strength, wet pick strength, ink set, and printing gloss is obtained. It is what

Claims (3)

Pigment (I) containing 90% by weight or more of calcium carbonate and aliphatic conjugated diene monomer (A) 30 to 70% by weight, ethylenically unsaturated carboxylic acid monomer (B) and / or (B) component Other than the functional group-containing ethylenically unsaturated monomer (C) 1 to 15% by weight and other monomers (D) 15 to 69% by weight copolymerizable therewith (total monomer 100% by weight) A high calcium carbonate-containing paper coating composition comprising a copolymer latex (II) having an acid density of 1.0 × 10 ^{−3 to} 1.0 × 10 ⁻² meq / m ² obtained by emulsion polymerization.   The high-calcium carbonate-containing paper coating composition according to claim 1, wherein the number average particle diameter of the copolymer latex (II) is 50 to 150 nm. The high calcium carbonate-containing paper coating composition according to claim 1 or 2, which contains carboxymethylcellulose (III).