JPH06200499A - Coating composition for paper coating and paper for web offset printing - Google Patents

Abstract

PURPOSE:To obtain the subject composition consisting essentially of a pigment and an adhesive containing a latex obtained by subjecting an olefin to emulsion polymerization with a conjugated diene and methacrylic amides and capable of providing paper for web offset printing having high strength and blister resistance. CONSTITUTION:A dispersing agent and sodium hydroxide are added to a pigment such as kaolin or calcium carbonate and water is dispersed thereto using Caurres dispersing equipment, etc., to prepare pigment slurry having 70% concentration, and then, a composition obtained by mixing a latex obtained by subjecting (A) 55-74 pts.wt. olefin-based monomer (e.g. styrene) to emulsion polymerization with (B) 25-40 pts.wt. aliphatic conjugated diolefin-based monomer (e.g. butadiene) and (C) 1-5 pts.wt. methacrylic amide and its N-substitution product (e.g. N-methoxymethyl methacrylic amide) with modified starch, a water-resisting agent and a lubricant, etc., is added to the pigment slurry and finally, water is added thereto so as to adjust solid content to 60% to provide the objective coating composition for web offset printing excellent in high strength and having blister resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for paper coating and offset rotary printing paper, which has a particularly excellent surface strength and blister resistance, and has a printing process of the offset rotary type, which is unprecedented. The present invention relates to a coating composition capable of obtaining a suitable coated paper, and an offset rotary paper obtained by coating the same.

[0002]

2. Description of the Related Art In recent years, due to the visualization and high quality of printed matter, the growth of offset printing has been remarkable. Above all, compared with the offset sheet-fed method which has been the mainstream in the past,
The number of offset rotary printing methods with good printing efficiency is increasing.
Due to the characteristics of the printing method, the offset rotary method usually uses heat-set type ink, and because the ink is set by heating and drying, the coated paper used will not blister, so-called blisters, Sex is an important item. Conventionally, as a method of imparting blister resistance to coated paper, the content weight ratio of the latex insoluble in the solvent (hereinafter referred to as gel content ratio) to be used as an adhesive in the coating composition is set to a specific ratio. A method (Japanese Patent Publication No. 54-6575) is known. However, since blister resistance and adhesive strength are contradictory physical properties, this method improves blister resistance, but the adhesive strength was not sufficient.

[0003]

DISCLOSURE OF THE INVENTION In producing a coated paper to be subjected to offset rotary printing, the present inventors have described the above-mentioned contradictory physical properties, that is, the adhesive strength and the blister resistance.
As a result of earnest studies, they have found that particularly excellent adhesive strength can be obtained by using methacrylamide and a latex using an N-substituted product thereof as an adhesive, and arrived at the present invention. According to the present invention, it is possible to reduce the amount of adhesive used as compared with the conventional one, and to provide a coating composition for paper coating that enables the production of offset rotary paper that has extremely good physical properties contradictory to blister resistance. To do.

[0004]

That is, according to the present invention, in a coating composition containing a pigment and an adhesive as main components, the adhesive contains a latex obtained by emulsion polymerization of the following monomers. The present invention provides a coating composition for paper coating characterized by the above, and an offset rotary paper obtained by coating the same. (1) Olefin-based monomer 55-74 parts by weight (2) Aliphatic conjugated diolefin-based monomer 25-40 parts by weight (3) Methacrylamide and its N-substituted product 1-5 parts by weight It enables the production of offset rotary coated paper having high strength and excellent blister resistance.

The present invention will be described in more detail below. In the latex used as the adhesive of the present invention, the amount of the olefinic monomer is appropriately in the range of 55 to 74% by weight, preferably 60 to 69% by weight, based on all the constituent polymer components. Examples of the olefinic monomer used in the present invention include styrene, α-methylstyrene, olefinic aromatic monomers such as chlorostyrene and dimethylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, (meth ) Butyl acrylate, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylonitrile, and olefinic aliphatic monomers such as vinyl acetate. If necessary, for example, acrylic acid, crotonic acid, isocrotonic acid, vinyl acetic acid, methacrylic acid, tiglic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, maleic acid, maleic anhydride, alkyl maleic acid monoester, Fumaric acid, alkyl fumaric acid monoester, citraconic acid, tetraconic acid, itaconic acid, itaconic acid alkyl monoester, etc., aliphatic unsaturated carboxylic acids, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, meta One or a mixture of two or more selected from the group of aliphatic unsaturated carboxylic acid esters containing a hydroxy group such as hydroxypropyl acrylate can be used. These monomers are examples, and other copolymerizable monomers can be used.

The aliphatic conjugated diolefin-based monomer used in the present invention is contained in an amount of 25 to 40% by weight based on all constituent polymer components.
A range of 28 to 37% by weight is preferable. As the aliphatic conjugated diolefin-based monomer, for example, one kind or a mixture of two or more kinds selected from the group of butadiene, isoprene and 2-chlorobutadiene can be used. The methacrylamide and its N-substituted product used in the present invention are 1 to 5% by weight, preferably 2 to 4% by weight based on all the constituent polymer components.
A range of weight percent is suitable. The methacrylamide and N-substituted methacrylamide include one or a mixture of two or more selected from the group of methacrylamide and N-substituted methacrylamides such as methacrylamide, N-methylolmethacrylamide, N-methoxymethylmethacrylamide and the like. Can be used. By applying a coating composition using a latex using these methacrylamide and its N-substituted product, amide, N-methylolacrylamide, and N-methoxymethyl, which are conventionally used amide monomers, are used. Particularly excellent adhesive strength is obtained as compared with the group of acrylamide and the like.

The olefinic monomer of the latex used as the adhesive of the present invention is contained in 55% of all the constituent polymer components.
The reason for limiting the content of the aliphatic conjugated diolefin-based monomer to the range of 25 to 40% by weight based on all the constituent polymer components is as follows. That is, if the olefinic monomer is less than 55% by weight, the aliphatic conjugated diolefinic monomer is required to be 40% by weight or more.
Even if used in parts by weight, the wet strength of the coated paper using the latex thus obtained becomes insufficient. Further, when the olefinic monomer is 74% by weight or more, the amount of the aliphatic conjugated diolefinic monomer is less than 25% by weight, and methacrylamide and its N-substituted compound are used in an amount of 1 to 5% by weight in all the constituent polymer components. However, the coated paper using the latex thus obtained has insufficient dry strength. The reason why the methacrylamide and the N-substituted methacrylamide of the latex used as the adhesive of the present invention are limited to the range of 1 to 5 parts by weight in all the constituent polymer components is as follows. That is, if the amount of methacrylamide and its N-substituted product is less than 1% by weight, the adhesive strength of the coated paper using the latex thus obtained will be insufficient, and if the amount of methacrylamide and its N-substituted product is 5% by weight or more. However, the viscosity of the obtained latex is significantly increased, which makes practical use difficult.

Examples of the emulsifier used in the emulsion polymerization of the present invention include anionic activators such as alkyl sulfonate, alkyl allyl sulfonate, alkyl sulfate, alkyl naphthalene sulfonate and alkyl succinate sulfonate, and polyoxyethylene alkyl ether. Nonionic activators such as polyoxyethylene alkyl allyl ether and polyoxyethylene aliphatic ester may be used alone or in combination.
The amount of these emulsifiers to be used is usually 5% by weight or less with respect to the total latex polymer component, and the average particle size can be arbitrarily adjusted. The particle size of latex is
Particle size analyzer [manufactured by Nikkaki Co., Ltd .; COULTERmo
del N4SD SUB-MICRON PARTI
CLE ANALYZER], and the average particle size of the latex (hereinafter abbreviated as particle size)
Is usually preferably in the range of 100 to 250 nm. As the polymerization initiator, an oxidizing agent such as potassium, sodium or ammonium salt of persulfate, hydrogen peroxide, diisobutylbenzoyl peroxide, cumene hydroperoxide or lauryl peroxide may be used alone or may be oxidized. The agent can be used in combination with a reducing agent such as sodium sulfite, sodium bisulfite and sodium thiosulfate, that is, a redox system. In the latex, the content ratio by weight of the toluene insoluble content (hereinafter referred to as the gel content) is adjusted by alkylmercaptans such as butyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan and carbon tetrabromide during emulsion polymerization. It can be carried out by using one kind or two or more kinds of chain transfer agents such as alcohols. Usually, the gel content of a latex used as an adhesive in a coating composition for offset rotary coated paper is 20 to 70.
A weight% range is preferred.

The pigment that can be used in the coating composition for offset rotary printing paper of the present invention includes kaolin clay, light calcium carbonate, heavy calcium carbonate, titanium oxide and aluminum hydroxide, which are commonly used in coated paper. , Satin white, barium sulfate, magnesium oxide, inorganic pigments such as talc and colloidal silica, and organic pigments such as plastic pigments and white urea resin pigments can all be used, and usually two or more kinds are used in combination. Although the present invention uses latex as a main component as an adhesive, it further uses general water-soluble polymers such as casein, oxidized starch, phosphate esterified starch, soybean protein, carboxymethyl cellulose, and hydroxyethyl cellulose. It is also effective, and preferably 3 to 8 parts by weight is used with respect to 100 parts by weight of the pigment. Incidentally, it is also effective to add an auxiliary agent such as a defoaming agent, a dispersant, a water-proofing agent, a preservative, a coloring agent, and a release agent, if necessary. The coating composition thus obtained is coated by a coating device such as an air knife coater, a blade coater, a roll coater or a bar coater in the same manner as in general coated paper production. The solid content of the coating composition for coated paper is usually 5
5 to 67% by weight.

As the base paper for offset rotary printing paper of the present invention, the basis weight of general printing coated paper is 52.3 to 157.
A high-quality paper, a medium-quality paper, etc. having a coating composition of g / m ² and a coated paper obtained by previously coating and drying the coating composition on these are used as the base paper. The coating amount of the coating composition for coated paper on these base papers is usually 10 to 25 g / m < ² > on one side in dry weight. After being coated in this manner, a calender finish or the like is used. As the calender, a super calender, a mat calender, or the like is used. The coating composition for paper coating of the present invention is a coating composition containing a pigment and an adhesive as main components, and by using a latex obtained by emulsion-polymerizing the specific monomer as the adhesive, The present invention provides a coating composition for an offset rotary coated paper, which makes it possible to manufacture an offset rotary coated paper having high strength and excellent blister resistance, which has never been achieved. .

[0011]

The present invention will be described in more detail below with reference to examples and comparative examples of the present invention, but the present invention is not limited thereto. In addition, the parts and% used in the following examples
Indicates weight basis unless otherwise specified. First, a production example of a latex used in this example is shown, and then a formulation example of a coating composition and an application example to offset rotary coated paper are shown. (Production Example of Latex) Production Example 1 (Production of Latex A-1) 151 parts of deionized water, 0.15 part of sodium lauryl sulfate, 0.8 part of potassium persulfate, and normal dodecyl were placed in a nitrogen-substituted autoclave with a stirrer. 0.9 parts of mercaptan and 33 parts of butadiene as a polymer monomer, 39 parts of styrene, 15 parts of methyl methacrylate, 8 parts of acrylonitrile, 1 part of maleic acid,
Total 10 parts of itaconic acid 1 part and methacrylamide 3 parts
0 part was charged and the polymerization was carried out at 70 ° C. and 10
A latex having a polymerization rate of 98% was obtained over time. Then 25%
After adjusting the pH to 8 with a caustic soda aqueous solution and performing steam stripping, deionized water was added to adjust the solid content concentration to 50% to obtain latex A-1. The types and amounts of the polymer monomers used in the production are shown in Table-1, and the solid content and viscosity of the obtained latex are shown in Table-1.

Production Examples 2 and 3 (Production of Latex A-2 to A-5) The Latex A
-1 in the same manner as in Production Example 1, except that the amounts of butadiene, styrene, methyl methacrylate, etc. used were changed as shown in Table 1.
A-5 was obtained. The solid content and viscosity of the obtained latex are shown in Table 1.

Comparative Production Examples 1 to 7 (Production of Latex A-6 to A-12) This Comparative Production Example is for comparison with the coating composition for offset rotary printing paper of the present invention and is outside the scope of the present invention. Is latex. That is, in Production Example 1, latex A-6 to Latex A-6 were prepared in the same manner as in Production Example 1 except that the polymerization was performed using the types and amounts of the polymer monomers shown in Table 1.
A-12 was obtained. The solid content and viscosity of the obtained latex are shown in Table-1.

[0014]

[Table 1]

(Preparation of coating composition) Example 1 Kaolin (manufactured by Engelhardt, USA: trade name UW90)
50 parts, kaolin (manufactured by Engelhardt, USA: trade name H
T) 30 parts, calcium carbonate (manufactured by Fuji Kaolin: trade name Carbital 90) 20 parts, Aron T-40 as a dispersant
0.3 part (manufactured by Toagosei) was added, 0.1 part caustic soda was added thereto, and dispersed in water using a Cowles disperser to prepare a pigment slurry having a concentration of 70%. Next, modified starch as an adhesive (MS-4600 manufactured by Nippon Food Processing Co., Ltd.) 3.
5 parts, Sumirez 636 (made by Sumitomo Chemical) as a waterproofing agent
0.35 parts, 1.0 part of calcium stearate (Nopcoat C-104 manufactured by San Nopco) as a lubricant, and 12 parts of the latex A-1 of the present invention were added, and finally water was added to adjust the solid content concentration of the paint. It was adjusted to 60% to obtain a coating composition for offset rotary printing paper of the present invention. (Production Example of Offset Rotary Printing Paper) The coating composition for offset rotary printing paper obtained in the above Example 1 was used in a basis weight of 6
The coating amount of the coating composition on the base paper of 4 g / m ² by an applicator bar coater is 15 g / m ^{2 on} one side in dry weight.
After coating and drying so as to obtain, the mixture was passed through a super calendar. The calender linear pressure was 150 kg / cm, and the temperature was 60 ° C. Moreover, the coated paper properties of the obtained offset rotary printing paper were measured, and the results are shown in Table 2. The glossiness was measured according to JIS P-8142. The gloss after printing was measured using an RI printing machine with 0.4 cc of commercially available rotary offset printing ink, and immediately after drying at 150 ° C for 15 seconds, JIS
It measured according to P-8142. The surface strength was printed by an RI printing tester (manufactured by Akira Seisakusho Co., Ltd.), and 10-level evaluation was performed by observing the picking of the surface. The blister resistance was measured by applying the above-described offset rotary printing paper coating composition to the back surface of a commercial art paper having a basis weight of 84.9 g / m ² according to the offset rotary printing paper production example of the present invention. After making printing paper, humidity 80
The blister test was carried out by immersing the product in an oil bath (manufactured by Sanyo Rikagaku Kikai Seisakusho) with a precision temperature control device for 5 seconds at a temperature of 170% for 5 seconds. Determined by observing the surface after the test.
Blister occurred on the whole and was bad).

Examples 2 to 5 In place of A-1 used in Example 1, latexes A-2 to A-5 were used, and the same operation as in Example 1 was carried out. Four coating compositions were obtained.
Further, an offset rotary printing paper was made as a trial by the same operation as in Example 1, and the physical properties of the coated paper were measured.

Comparative Example 1 In this comparative example, first, an example of a coating composition for offset rotary printing paper using an amount of methacrylamide and its N-substituted product, which is outside the range of the present invention, is shown. A coating composition for offset rotary printing paper was obtained in the same manner as in Example 1, except that 12 parts of A-6 was used as the adhesive instead of the latex A-1 used in Example 1. It was
Further, an offset rotary printing paper was prepared by the same operation as in Example 1, and the physical properties of the coated paper were measured. The results are shown in Table-2. Comparative Example 2 A coating composition for offset rotary printing paper was obtained in the same manner as in Example 1, except that 12 parts of latex A-7 was used in place of the latex A-1 used in Example 1. It was Further, an offset rotary printing paper was prototyped by the same operation as in Example 1, the physical properties of the coated paper were measured, and the results are shown in Table 1.
Shown in 2. Comparative Examples 3 to 7 The latex used in Examples 1 to 5 and Comparative Production Examples outside the limited range of the present invention, Latex A-3 to 7 were added, and the same operation as in Example 1 was performed to Comparative Examples 3 to 7. A coating composition for offset rotary printing paper of No. 7 was obtained. Further, an offset rotary printing paper was trial-produced by the same operation as in Example 1, physical properties of the coated paper were measured, and the results are shown in Table 2.

[0018]

[Table 2]

[0019]

The offset rotary printing paper obtained by the coating composition for offset rotary printing paper according to the examples of the present invention shows that a coated paper excellent in surface strength and blister resistance can be produced. It is clear from Table 2 that it is a very useful coating composition that has never been used as a coating composition for coated paper to be subjected to offset rotary printing.

Claims (2)

[Claims] 1. A paper coating composition comprising a pigment and an adhesive as main components, wherein the adhesive contains a latex obtained by emulsion polymerization of the following monomers. Coating composition. (1) 55-74 parts by weight of olefin-based monomer (2) 25-40 parts by weight of aliphatic conjugated diolefin-based monomer (3) 1-5 parts by weight of methacrylamide and its N-substituted compound 2. An offset rotary paper coated with the coating composition for paper coating according to claim 1.