JP2640379B2 - Matte coated paper coating composition for web offset printing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a paper coating composition used for producing a matte coated paper for web offset printing. More specifically, it has improved printing smoothness, low gloss on white paper, high ink gloss after printing, and improved matte coated paper for offset rotary printing with good blister resistance. Paper coating composition.

(Problems to be solved by the prior art and the present invention) In recent years, coated paper has been
It is used for various types of printed materials, and in particular, among periodicals such as Lee and monthly newspapers, the number of cases where coated paper is used for all pages is increasing. In the production of coated paper, technical efforts are often made to increase white paper gloss (gloss before printing) and ink gloss (gloss after printing) in order to obtain a high printing effect.

On the other hand, matte coated paper is characterized by low blank gloss, contrary to many common coated papers. Generally, JI
The gloss of the matte coated paper measured according to S P8142 is 5 to 40%. Compared to general coated paper with high blank gloss, the practical features of glazed coated paper are as follows: (1) Since the printed pattern looks sharp and elegant, it can be used for commercials such as advertising and posters. Gives high quality to printed matter, photo book, picture book, etc. (2) The printed characters are clear, so that the reader's eyes are not tired.

As a method for producing such matte coated paper, a method of applying a coating composition containing a large amount of a relatively coarse pigment to paper, or a method of suppressing the glossiness of white paper by a light calendering process, and the like are known. I have. For this reason, there has been a problem that the coated paper has a low ink gloss after printing, which is necessary for obtaining print smoothness at the time of printing and sharpness of patterns, characters, and the like.

A method for producing a matte coated paper having improved ink gloss is also a method using a synthetic polymer latex which expands in the coating composition and shrinks after coating and drying (Japanese Patent Laid-Open No. 62-299597). A method of blending calcium carbonate and talc having a specific average particle diameter in a coating composition in a specific ratio (Japanese Patent Application Laid-Open No. 62-149995), and a method of forming a specific layered copolymer latex in a coating composition And a method of blending calcium carbonate and calcium carbonate in a specific ratio (Japanese Patent Publication No. 231-2112) have been proposed, but the ink gloss is lower and the print smoothness is lower than that of coated paper that still has high white gloss. Therefore, this improvement has been strongly desired.

Also, with the recent increase in printing speed, offset printing (hereinafter referred to as "off-wheel printing") has been adopted, and its spread has been remarkable. Blister resistance is one of the most important performances of this off-wheel printing aptitude, but matte coated paper produced by the conventional manufacturing method is also inferior in blister resistance. Was rare.

The present inventors have conducted intensive studies to solve such problems, and as a result, completed the present invention.

(Means for Solving the Problems) That is, the present invention provides: (A) 50 to 10 calcium carbonate and / or talc;
(B) 20 to 50% by weight of an aliphatic conjugated diene monomer, 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, and An average particle size of less than 100 nm obtained by emulsion-copolymerizing 2 to 50% by weight of an acid ester monomer and / or vinyl cyanide monomer and 0 to 77.5% by weight of another polymerizable monomer; 5 to 25 parts by weight of a copolymer latex having a gel content of 60% by weight or less and a matte coating for off-press printing that provides high ink gloss, high print smoothness and good blister resistance. An object of the present invention is to provide an excellent paper coating composition used for paper.

 Hereinafter, the present invention will be described in more detail.

Conventionally known calcium carbonate and talc can be used for the present invention. Calcium carbonate and / or talc are used at 50-100% by weight of the total pigment used. If the content of calcium carbonate and / or talc is less than 50% by weight, the glossiness of white paper becomes too high even in a light calender, so that it is not suitable for matte coated paper.

Further, in the present invention, pigments such as carion, aluminum hydroxide, titanium dioxide, and satin white can also be used, and these can be used alone or in combination of two or more. 50% by weight or less. Particularly, the use of Karion is preferred.

Examples of the aliphatic conjugated diene-based monomer constituting the copolymer latex of the present invention include 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-methylbutadiene and the like. Can be used alone or in combination of two or more. Particularly, 1,3-butadiene is preferred. The aliphatic conjugated diene-based monomer is used in an amount of 20 to 50% by weight. If the amount is less than 20% by weight, the dry pick strength decreases, and if it exceeds 50% by weight, the wet pick strength decreases, which is not preferable.

Examples of the ethylenically unsaturated carboxylic acid monomer constituting the copolymer latex of the present invention include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and itaconic acid, and may be used alone or in combination of two or more. it can. The ethylenically unsaturated carboxylic acid monomer is used in an amount of 0.5 to 10% by weight. If the amount is less than 0.5% by weight, the stability of the copolymer latex polymerization decreases, and if the amount exceeds 10% by weight, the viscosity of the latex increases. It is not preferable because it becomes too much.

As the ethylenically unsaturated carboxylic acid ester monomer constituting the copolymer latex of the present invention, methyl acrylate, methyl methacrylate, ethyl acrylate,
Ethyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, glycidyl methacrylate,
Dimethyl fumarate, dimethyl fumarate, diethyl fumarate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate and the like can be mentioned, and one kind or two or more kinds can be used. Particularly, methyl methacrylate is preferred.

Examples of the vinyl cyanide monomer constituting the copolymer latex of the present invention include acrylonitrile, α-chloroacrylonitrile, methacrylonitrile, α-ethylacrylonitrile, and the like, and one or more kinds thereof can be used. Acrylonitrile is particularly preferred.

These ethylenically unsaturated carboxylic acid ester monomers and / or vinyl cyanide monomers are used in an amount of 2 to 50% by weight.
If it exceeds 50% by weight, the dry pick strength or wet topic strength is reduced.

Other copolymerizable monomers that can constitute the copolymer latex of the present invention include alkenyl aromatic monomers, unsaturated monomers containing a hydroxyalkyl group,
Examples include ethylenically unsaturated carboxylic acid amide monomers and the like, and one or more kinds can be used.

Examples of the alkenyl aromatic monomer include styrene, α-methylstyrene, methyl-α-methylstyrene, and vinyltoluene, with styrene being particularly preferred.

Examples of unsaturated monomers containing a hydroxyalkyl group include β-hydroxyethylene acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxybutyl methacrylate, and di- (ethylene glycol) Maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate,
Bis- (2-hydroxyethyl) maleate, 2-hydroxyethyl fumarate and the like can be mentioned.

As the ethylenically unsaturated carboxylic acid amide monomer,
Acrylamide, methacrylamide, N-methylolacrylamide, diacetone acrylamide and the like can be mentioned. Acrylamide is particularly preferred.

These other copolymerizable monomers are used in an amount of 0 to 77.5% by weight, but when the amount exceeds 77.5% by weight, the dry pick strength decreases. Desirably, it is 0 to 50% by weight.

The average particle size of the latex such as a copolymer used in the present invention is less than 100 nm. If it is 100 nm or more, the gloss of the ink decreases, which is not preferable. Also, if the average particle size is too low, the viscosity of the copolymer latex will increase and a problem will arise in handling it, so that it is preferably at least 40 nm or more.

The gel content of the copolymer latex used in the present invention is 60% by weight or less. If it exceeds 60% by weight, the blister resistance will be reduced. It is desirably 50% by weight or less.

In producing the copolymer latex of the present invention, a known emulsion polymerization method, for example, a batch polymerization method, a two-stage polymerization method, or a power feed polymerization method can be employed. The method for adding the various components 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, conventional polymerization initiators, electrolytes, polymerization accelerators, chain transfer agents, chelating agents and the like may be used.

The copolymer latex used in the present invention is a pigment 100
When used in an amount of 5 to 25 parts by weight, the dry pick strength is reduced when the amount is less than 5 parts by weight, and the blister resistance is reduced when the amount exceeds 25 parts by weight. Preferably, it is 8 to 20 parts by weight.

Further, the paper coating composition of the present invention includes generally used binders such as starch, casein, and polyvinyl alcohol, as well as a thickener, a crosslinking agent, a water retention agent, an alkali stabilizer, an antifoaming agent, and a surfactant. Various additives such as agents may be used as needed.

(Examples) Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the examples. The percentages and parts used in the examples all mean% by weight and parts by weight unless otherwise specified.

Example-1 <Production of Copolymer Latex A> A monomer other than the ethylenically unsaturated carboxylic acid monomer in the number shown in Table 1 was charged into a monomer mixing vessel, and the mixture was thoroughly stirred. A mixture was obtained.

In a pressure vessel of 10 parts, 15 parts of the above monomer mixture, the ethylenically unsaturated carboxylic acid monomer having the number of parts shown in Table 1, 3 parts of sodium dodecylbenzenesulfonate, and potassium acid downstream
Emulsion polymerization was started at 65 ° C. while 0.8 part of sodium hydrogencarbonate 0.15 part and pure water 150 parts were charged and stirred. The remaining monomer mixture and tert-dodecyl mercaptan shown in Table 1 as a chain transfer agent were continuously added to the pressure-resistant vessel over 6 hours.

The polymerization conversion of the obtained copolymer latex was 97%. Next, after adjusting the pH of the copolymer latex to 7 with an aqueous sodium hydroxide solution, unreacted monomers were removed by steam distillation to obtain a copolymer latex A.

The average particle size of the copolymer latex A measured by an electron micrograph was 72 nm.

The gel content of the copolymer latex A measured according to the following measurement method was 38% by weight.

<Method for Measuring Gel Content in Copolymer Latex> a) A film of the copolymer latex was prepared by drying at room temperature, and the film was poured into toluene about 200 to 800 times and left for 48 hours. Use No.2 paper.

b) The solution is dried under reduced pressure at 70 ° C., weighed, and the toluene soluble component (%) of the copolymer latex film is determined.

c) The value obtained by subtracting the above-mentioned toluene-soluble component (%) from 100%, that is, the toluene-soluble component (%) is calculated as the gel content.

<Preparation of coated paper and evaluation of printability> Using copolymer latex A, blending was performed based on the formulation shown in Table 2, and prepared with pure water to a solid content shown in Table 2 to obtain paper. A coating composition was prepared. Each composition was coated on the same coating base paper so that the coating amount would be the same, and dried under the same conditions. Thereafter, calendering was performed so that the white paper gloss (JIS P8142) of each coated paper became 30 to 40%, and coated papers 1 to 6 were obtained.

For the obtained coated papers 1 to 6 and commercially available coated paper for web offset printing having high blank gloss, RI wet pick strength, RI
Dry pick strength, print smoothness, white paper gloss, ink gloss and blister resistance were tested. Table 3 shows the results.
Shown in

(Measurement method) ・ RI wet pick strength The degree of picking when printing using dampening water with an RI printing machine is judged with the naked eye, and grades 1 (best) to 5 (worst) The evaluation was made according to a five-step method. The average value of 6 times is shown.

-RI dry pick strength Except not using fountain solution, it evaluated by the same method as the above-mentioned RI wet pick strength measuring method.

・ Print smoothness Using an RI printing machine, the degree of white spots (parts not printed) when printing with a 0.15 cc offset rotary printing black ink is visually judged, and the level is evaluated from the first class (the best one) to 5 The evaluation was made according to a five-grade scale (the worst). The average value of 6 times is shown.

-Blank glossiness Measured at an angle of 75 ° based on JIS P8142.

・ Ink gloss Using an RI printing machine, 0.25cc of cyan ink for rotary printing and 0.35cc of the same magenta ink are overprinted and dried in a heat oven at 120 ° C for 20 seconds.
The gloss of the overprinted portion was measured at 0 °.

-Blister resistance After the double-sided printing coated paper was conditioned to about 6%, it was put into a heated oil bath, and the lowest temperature at which blisters were generated was shown.

Example-2 <Copolymer latex B, C, D, E, F, G, I, J
Production> Polymerization was carried out in the same manner as for copolymer latex A, except that the monomers shown in Table 1 were used. The polymerization conversion rates of the obtained copolymer latexes were all 97% or more.

Next, after adjusting the pH of the copolymer latex to 7 with an aqueous sodium hydroxide solution, unreacted monomers were removed by steam distillation, and the copolymer latexes B, C, D, E, F,
G, I and J were obtained.

The average particle size and gel content are shown in Table 1.

<Production of copolymer latexes H and K> A method similar to that for copolymer latex A, except that the monomers shown in Table 1 were used, 100 parts of pure water and 2 parts of sodium dodecylbenzenesulfonate were used. , Copolymer latexes H and K were obtained. Table 1 shows the average particle size and gel content.
1 is shown.

<Production of coated paper and evaluation of printability> Using the copolymer latexes A to K shown in Table 1,
Each was blended based on the following formula, and adjusted to a solid content of 60% with pure water to prepare a paper coating composition,
Coated papers 7 to 17 were obtained in the same manner as in Example-1.

With respect to the obtained coated papers 7 to 17, a printability test was performed in the same manner as in Example-1. The results are shown in Table-4.

(Preparation) Drying part Primary Karion 20 Secondary Karion 20 Light calcium carbonate 10 Heavy calcium carbonate 40 Talc 10 Modified starch 5 Copolymer latex 13 Solid (%) 60 (%) (Effect of the Invention) As described above, by using the paper coating composition of the present invention, a matte coated paper for offset rotary printing paper having excellent print smoothness, ink gloss and blister resistance can be obtained. Things.

Claims (1)

(57) [Claims] (A) 20 to 50% by weight of an aliphatic conjugated diene monomer, 100% by weight of a pigment in which calcium carbonate and / or talc occupies 50 to 100% by weight, ethylenically unsaturated 0.5 to 10% by weight of carboxylic acid monomer, 2 to 50% by weight of ethylenically unsaturated carboxylic acid ester monomer and / or vinyl cyanide monomer and 0 to 77.5% by weight of other copolymerizable monomer The average particle size obtained by emulsion copolymerization is less than 100 nm, and the gel content is 5 to 25 parts by weight of a copolymer latex having a gel content of 60% by weight or less. Composition for coating paper.