JPS61225394A - Paper coating composition for gravure printing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a gravure printing paper coating composition. More specifically, the present invention provides a paper coating composition that produces fewer misdots during gravure printing on coated paper, has excellent halftone dot reproducibility, and has high surface strength.

[Conventional technology]

Gravure printing has become increasingly widely used in recent years because it provides images with vivid tones and depth. Furthermore, as a result of the widespread use of rotogravure printing methods and faster printing speeds, the demand for coated paper for gravure printing has increased rapidly recently.

Incidentally, since gravure printing is a method in which ink is transferred from the recesses of the printing plate to the printing paper, transfer defects unique to gravure printing, such as so-called misdots and poor halftone dot reproducibility, are likely to occur.

These transfer defects significantly impair the aesthetic appearance of printed matter and, in turn, significantly reduce the commercial value of the coated paper for gravure printing itself. Therefore, efforts have been made to improve the suitability for gravure printing (misdot resistance and halftone dot reproducibility) of coated papers by improving coating compositions. One such consideration is the consideration of binders, including natural binders such as starch, casein, soy protein, and cellulose, styrene-butiene copolymers, ester copolymers of acrylic acid or methacrylic acid, vinyl acetate copolymers, and polyvinyl. The use of synthetic binders such as alcohols alone and in combination has been investigated, and some findings have been disclosed.

For example, reducing the amount of binder in the coating liquid improves the suitability of coated paper for gravure printing, but reduces its surface strength, and using latex, which has strong interaction with pigments, reduces the suitability of coated paper for gravure printing. However, this also means that the surface strength becomes insufficient (Paper Bag Technical Association Journal, Vol. 38, 12).
Issue, pp. 18-23, 1984), although the use of vinyl acetate/acrylic acid ester synthetic emulsions is suitable for gravure printing on coated paper, its surface strength is weak. This shows that it is difficult to improve suitability and surface strength at the same time.

Insufficient surface strength of the coated paper is a serious problem because it leads to the occurrence of calender roll stains during supercalendering, and the productivity of the coated paper is significantly degraded due to the removal of the stains.

It has been proposed that a formulation using only a synthetic emulsion without using a natural binder (sole binder formulation) is effective for solving the above-mentioned defective back pressure (D, 1.L
ae, Tappi Coating Conference
ce Preprint, P 25 A+41.1
975), and even more specific knowledge (Unexamined Japanese Patent Publication No. 1983-14)
5746, 56-70071, 57-77374)
However, according to the studies conducted by the present inventors, all of the findings were unsatisfactory for simultaneously improving the suitability for gravure printing and the surface strength of coated paper.

[Problem that the invention seeks to solve]

The present inventors have taken into account the shortcomings of the prior art.

We conducted extensive research in order to obtain a synthetic latex that has excellent surface strength and suitability for gravure printing on coated paper.

[Means to solve the problem]

As a result, we discovered a fact beyond our expectations that the above objective can be achieved by using a copolymer latex with a specific composition as shown below and a gel content within a specific range as a binder, and based on this knowledge, The present invention has now been completed.

That is, the present invention comprises 35 to 80% by weight of aliphatic conjugated diene, 0.2 to 15% by weight of ethylenically unsaturated carboxylic acid monomer, and 0.2 to 15% by weight of ethylenically unsaturated linear amine monomer. or/and its quaternary salt, and the remaining monoolefin monomer, and has a gel content of 40 to 95
A coating composition for gravure printing paper, characterized in that it contains a copolymer latex and a pigment in the following proportions by weight.

The copolymer latex used in the present invention is (1
) aliphatic conjugated diene 35-80% by weight, preferably 55% by weight
~75% by weight, (2) ethylenically unsaturated carboxylic acid monomer 0.2-15% by weight, preferably 0.5-10% by weight
, particularly preferably 0.5 to 6% by weight, (3) ethylenically unsaturated linear amine monomer or/and quaternary salt thereof 0.
5-15% by weight, preferably 0.5-10% by weight, particularly preferably 0.5-6% by weight.

(4) The remaining copolymerizable monoolefin monomers are copolymerized with the remainder, preferably 10 to 44% by weight, in the presence of a chain transfer agent to reduce the gel content to 40 to 95% by weight.
, preferably 60 to 90% by weight, and a known emulsion polymerization method can be used for this purpose.

In order to maintain high polymerization stability and fully exhibit the effects of the present invention, the monomers (1), (2), and (4) above are first emulsion polymerized, and the ethylene-based monomers (2) are p of the yarn after 90% or more of the saturated carboxylic acid monomers have completed polymerization.
H is set to 4 or more, and then the ethylenically unsaturated linear amine or/and quaternary salt of (3) above is added, or this is added together with the monomers of (1) or/and (4) above to carry out polymerization. Preferably completed.

In the composition of the copolymer latex, if the aliphatic conjugated diene content is less than 35% by weight, the copolymer will lack flexibility and adhesion, resulting in insufficient gravure printability and surface strength of the coated paper. If the amount exceeds 80% by weight, the adhesiveness of the copolymer will be insufficient and the surface strength of the coated paper will be insufficient.

In particular, in the range of 55 to 75% by weight, the suitability for gravure printing of coated paper and the adhesive strength of copolymer latex are generally inversely correlated, but both of these properties may exhibit excellent effects. can.

If the content of the ethylenically unsaturated carboxylic acid monomer is less than 0.2% by weight, the mechanical stability and adhesive strength of the latex will be insufficient, and if it exceeds 15% by weight, the amount of aggregates during polymerization will increase, making it difficult to coat. This is not preferable because it causes insufficient water resistance of the paper.

If the amount of the ethylenically unsaturated linear amine monomer is less than 0.2% by weight, the gravure printability of the coated paper will not be sufficient, and if it exceeds 15% by weight, the amount of aggregates during polymerization will increase, which is not good. .

Furthermore, by adjusting the gel content of the copolymer latex to 40 to 95% by weight, the present invention provides a paper coating composition that is excellent in both gravure printability and surface strength of coated paper. becomes possible.

In addition, in the paper coating composition of the present invention, 0.5 to 12 parts by weight of the copolymer latex is usually added to 100 parts by weight of the pigment.
It is preferably used in a proportion of 4 to 10 parts by weight.

The aliphatic conjugated dienes used in the production of the copolymer latex of the present invention include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, Butadiene and other hydrocarbon analogs of 1,3-butadiene, as well as 2-chloro-1,3
-butadiene, substituted 1,3-butadiene such as 2-cyano-1,3-butadiene, and the like. Among these, 1,3-butadiene is preferred from the viewpoint of price, ease of availability, and excellent properties of the resulting copolymer.

Ethylenically unsaturated carboxylic acid monomers include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, dicarboxylic acids such as itaconic acid, maleic acid, and fumaric acid, and acid anhydrides and monoalkyl esters of these dicarboxylic acids. Monoamides can also be used.

As the ethylenically unsaturated linear amine monomer or/and quaternary salt, compounds represented by the following general formula (1) and those reacted with sulfuric esters such as dimethyl sulfate, alkyl halides such as methyl chloride, etc. These include quaternary ammonium salts obtained by the above methods, and betaine-type upper salts obtained by reacting them with monochloroacetic acid, β-propiolactone, and the like.

For example, amylethyl (meth)acrylate, methylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)
Aminoalkyl esters of ethylenically unsaturated carboxylic acids such as acrylate, dibutylaminoethyl (meth)acrylate, aminopropyl (meth)acrylate, methylaminopropyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, aminoethyl (meth)acrylate, etc. ) Acrylamide.

Methylaminoethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, diethylaminoethyl (meth)acrylamide.

Dibutylaminoethyl (meth)acrylamide.

Aminoalkylamides of ethylenically unsaturated carboxylic acids such as aminopropyl 5(meth)acrylamide, methylaminopropyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, aminoethyl vinyl ether, methylaminoethyl vinyl ether, dimethylaminoethyl vinyl ether, Aminoalkyl vinyl ethers such as aminopropyl vinyl ether, methylaminopropyl vinyl ether, and dimethylaminopropyl vinyl ether; quaternary ammonium salts obtained by reacting them with sulfuric esters such as dimethyl sulfate; alkyl halides such as methyl chloride; Examples include betaine type monomers obtained by reacting monochloroacetic acid, β-propiolactone, and the like.

In particular, dimethylaminopropyl (meth)acrylamide, 3-(meth)acrylamidopropyltrimethylammonium chloride, and 3-( Preference is given to meth)acrylamidopropyldimethylammonioacetate.

As monoolefin monomers, aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyltoluene;
Alkyl esters of ethylenically unsaturated carboxylic acids such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; acrylamide, methacrylamide, N-methylolacrylamide, etc. Examples include alkylamides of ethylenically unsaturated carboxylic acids; carboxylic acid vinyl esters such as vinyl acetate, and acrylonitrile.

The gel content of the copolymer latex can be controlled by the use of chain transfer agents used in conventional emulsion polymerizations, such as halogenated hydrocarbons, such as chloroform, bromoform, carbon tetrachloride, carbon tetrabromide, etc. -Mercaptans such as hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, xanthogens such as dithyl xanthogen disulfide, diisopropyl xanthogen disulfide, etc. Can be used in normal emulsion polymerization. Everything can be used. These can be used alone or in combination of two or more. The addition method may be one-time addition, multi-part addition, or continuous addition.

The paper coating composition of the present invention comprises mineral pigments commonly used for paper coating, such as clay, barium sulfate, titanium oxide, calcium carbonate, satin white, and the like, and a copolymer of the present invention as a pigment binder. Latex, as well as casei, starch, cellulose, and polyvinyl alcohol if necessary.

It can be obtained by blending natural or synthetic binders and thickeners such as alkaline thickening emulsions.

Furthermore, various commonly used compounding agents 1 such as water resistance improvers, water resistance reaction accelerators, pigment dispersants, viscosity modifiers,
Coloring pigments, fluorescent dyes, and pH regulators can also be optionally added.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

In the examples, parts and % indicating percentages mean parts by weight and % by weight, respectively.

Example 1 A compound of the following formulation 1 was placed in an autoclave equipped with a stirrer and heated to 60°C to initiate a reaction.

Formula 1 Water 400.0 parts Butadiene 60.0 parts Styrene
20.0 parts Methyl methacrylate 15.0 parts Acrylic acid 2.0 parts Carbon tetrachloride
4.0 parts (A) Potassium persulfate
0.1 part When the polymerization conversion rate of the above monomer reaches 92%, an aqueous sodium hydroxide solution is added to reduce the p of the latex.
H was adjusted to 7.0. Next, a mixture of 7.0 parts of water and 3.0 parts of dimethylaminopropylacrylamide was added to continue the reaction, and after 4 hours, a copolymer latex (A) was obtained with a polymerization conversion rate of 99%.

Furthermore, in the above formulation 1, (A) 4.0 parts of carbon tetrachloride, (B) 6.0 parts of carbon tetrachloride, (C) 6.0 parts of carbon tetrachloride
part and 0.5 part of t-dodecyl mercaptan, (D) 6.0 parts of carbon tetrachloride and 1.0 part of t-dodecyl mercaptan, (
E) Copolymer latexes (B), (C), (D) and (E) were obtained in the same manner as in the production of copolymer latex (A) except that carbon tetrachloride was changed to 0.2 part. Ta.

In addition, the above copolymer latex (A), (B), (C)
The copolymer latexes obtained by using methyl methacrylate in place of dimethylaminopropylacrylamide in the production of are referred to as (a), (b), and (e), respectively.

A paper coating composition was prepared using the latexes (A) to (E) and (a) to (c) according to the following formulation 2.

Formulation 2 Kaolinite clay (1) 100.0 part powder
(2) 0.2 part sodium hydroxide 0.1 part starch (3)
2.0 parts latex (as solid content)
6.0 parts water Add appropriate amount so that the total solid content is 60% (1) Hydrosperse manufactured by J, M, Huber (2) Aron T-40 manufactured by Toagosei Co., Ltd. (3)
Tamago Ace C manufactured by Tamago Cornstarch Co., Ltd. Furthermore, an appropriate amount of sodium hydroxide aqueous solution was added to adjust the pH of each composition to 9.
．． Adjusted to 0.

Each composition was coated on the base paper at a coating amount of 13°0±0.5 on one side.
The coating was applied using an electric blade coater (manufactured by Kumagai Riki Co., Ltd.) so as to give a coating film of g/rrr, and dried for 15 seconds in a gear oven at 120°C. The obtained coated paper was heated at 20°C and 65% R.
, H, for one day and night under indoor conditions, and then the linear pressure was set to 250.
kg/am and a roll temperature of 50° C., supercalender treatment was performed four times, and the following tests were conducted. At the same time, the gel content of the copolymer latex was measured.

The results are shown in Table 1.

Table 1 Test method Note 1) The resulting copolymer latex was adjusted to pH 8.5, coagulated with methanol, washed and dried, and then mixed with a predetermined amount (approx.
．． 3g) of the sample in a predetermined amount (100mm) of benzene.
Soak for 0 hours. The benzene insoluble content is measured and expressed in weight percent relative to the sample.

Note 2) Based on RI printing tester (manufactured by Akashi Seisakusho).

The test piece is fixed on a drum and printed one time, and then the paper is turned to make a judgment. Those with less paper peeling have excellent surface strength. Evaluation on a 5-point scale; 5 (excellent) to 1 (poor) Note 3) Print a test piece using a Ministry of Finance Printing Bureau type gravure printing tester (manufactured by Kumagai Riki Co., Ltd.).

Use halftone gravure as an illustration.

It is defined as the ratio of the number of misdots that occur to the total number of halftone dots. Percentage display.

Note 4) Indicates the compatibility between the printed halftone dot shape and the illustration halftone dot shape. Observe each halftone dot shape under magnification.

judge.

4-step process of O, O1Δ, and X; ◎ (excellent) to A polymer latex was produced. However, since latex (d) did not use an amine monomer, the polymerization was completed in one step.

Table 2 Using the copolymer latex shown in Table 2, gel content measurements and coated paper tests were carried out in accordance with Example 1. The results are shown in Table 3.

Table 3 [Effects of the Invention] - As is clear from the results in Tables 1 and 3, the coated paper using the paper coating composition of the present invention has fewer misdots during gravure printing and reproduces halftone dots. The present invention provides an extremely excellent coating composition for gravure printing paper, which has excellent properties and high surface strength.

Claims (3)

[Claims] (1) 35-80% by weight aliphatic conjugated diene, 0.2-80% by weight
15% by weight of ethyleyically unsaturated carboxylic acid monomer, 0.
A copolymer consisting of 2 to 15% by weight of an ethylenically unsaturated linear amine monomer or/and its quaternary salt, the remainder being a monoolefin monomer, and having a gel content of 40 to 95% by weight. A gravure printing paper coating composition containing latex and a pigment. (2) The copolymer latex emulsion polymerizes an aliphatic conjugated diene, an ethylenically unsaturated carboxylic acid monomer, and a monoolefin monomer, and 90% or more of the ethylenically unsaturated carboxylic monomer is polymerized. After completing the process, the pH of the system is set to 4 or more, and then an ethylenically unsaturated linear amine or/and a quaternary salt, or this is added together with an aliphatic conjugated diene and/or a monoolefin monomer to initiate polymerization. Claim No. 1, which is a completed copolymer latex (
The composition described in item 1). (3) The composition according to claim (1) or (2), wherein the copolymer latex is contained in an amount of 0.5 to 12 parts by weight based on 100 parts by weight of the pigment.