JPH0411679B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a paper processing agent that has excellent coating properties and can significantly improve surface gloss after processing. Vinyl ester resins, particularly polyvinyl alcohol (hereinafter abbreviated as PVA) resins, have been widely used as coating agents for improving the surface properties of paper, such as surface strength, smoothness, and gloss. Paper coated with such a coating agent is passed through a calendar roll in order to improve its gloss and smoothness, but conventionally, in order to further exhibit this effect, the water content in the paper must be considerably increased. . As a result, the coating agent tends to adhere to the calender roll, and strict control is essential to keep the moisture content in the paper within a certain range.
Alternatively, there is a desire to develop a processing agent that can provide a sufficient calendering effect even in the absence of any moisture. However, the present inventors have developed a coating agent, namely
With the aim of improving the calendering effect by improving PVA-based resin and further improving the surface gloss of paper than before, we have conducted extensive research and found that unsaturated monomers with oxyalkylene groups and vinyl acetate A processing agent whose main ingredient is a vinyl ester resin (hereinafter referred to as a vinyl ester resin having an oxyalkylene group) consisting of a copolymer of The present invention was completed based on the discovery that the process does not require a large amount of water content during the process, so there is no need to worry about the roll becoming dirty. The oxyalkylene group referred to in the present invention has the general formula [However, R ¹ and R ² are hydrogen or an alkyl group, X is hydrogen,
Organic residues such as alkyl groups, alkyl ester groups, alkylamido groups, sulfonic acid groups, n is 1 to
Indicates an integer of 300. ] It has a structure represented by the following. X is usually hydrogen. Oxyalkylene groups in which the number n is preferably 2 to 300, particularly preferably 5 to 300, are practical, and polyoxyethylene groups, polyoxypropylene groups, polyoxybutylene groups, etc. are effective. Examples of the unsaturated monomer having an oxyalkylene group include the following. However, the present invention is not limited to these. (Meth)acrylic acid ester type General formula (where R is hydrogen or a methyl group, A is an alkylene group, substituted alkylene group, phenylene group,
Substituted phenylene group, m is an integer of 0 or 1 or more, n
is 1 to 300, preferably 2 to 300, particularly preferably 5
~300 integer), such as polyoxyethylene (meth)acrylate and polyoxypropylene (meth)acrylate. (Meth)acrylic acid amide type General formula (However, R ³ is hydrogen or an alkyl group or

[Formula] A, R, R ¹ , R ² , m, n are the same as above), polyoxyethylene (meth)acrylic acid amide, polyoxypropylene (meth)acrylic acid amide, polyoxyethylene (1- (meth)acrylamide-1,1-dimethylpropyl) ester and the like. (Meth)allyl alcohol type General formula (R, R ¹ , R ² , n are the same as above) and examples thereof include polyoxyethylene (meth)allyl ether, polyoxypropylene (meth)allyl ether, and the like. Vinyl ether type General formula (A, R ¹ , R ² , m, n are the same as above)
Examples include polyoxyethylene vinyl ether and polyoxypropylene vinyl ether. Among such monomers, (meth)allyl alcohol type monomers are preferably used. As the vinyl ester, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, vinyl stearate, etc. are used alone or in combination. Vinyl acetate is particularly practical. In the present invention, during such polymerization, an unsaturated monomer having an oxyalkylene group as described above,
Polymerization may be carried out in the presence of 50 mol% or less of a general monomer other than vinyl ester. Examples of these monomers are shown below. Ethylenically unsaturated carboxylic acids and their alkyl esters, etc. (meth)acrylic acid, crotonic acid, (anhydrous) maleic acid, fumaric acid, itaconic acid, and their alkali metal salts, ammonium salts, etc. (meta)
Methyl acrylate, ethyl (meth)acrylate,
(meth)propyl acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate,
Decyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, etc.
Methyl crotonate, ethyl crotonate, methyl itaconate, ethyl itaconate, methyl sorbate, ethyl sorbate, monoalkyl maleate, dialkyl maleate, alkyl oleate, etc. Allyl esters of saturated carboxylic acids: allyl stearate, allyl laurate, allyl coconut oil fatty acid, allyl octylate, allyl butyrate, etc. α-Olefin Ethylene, propylene, α-hexene, α-octene, α-decene, α-dodecene, α-hexadecene, α-octadecene, etc. Alkyl vinyl ether propyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether, dodecyl vinyl ether, tetradecyl vinyl ether, hexadecyl vinyl ether, octadecyl vinyl ether, etc. Alkyl allyl ether Propyl allyl ether, butyl allyl ether, hexyl allyl ether, octyl allyl ether, decyl allyl ether, dodecyl allyl ether, tetradecyl allyl ether, hexadecyl allyl ether, octadecyl allyl ether, etc. In addition, (meth)acrylamide, (meth)acrylonitrile, (meth)allylsulfonate, ethylenically unsaturated sulfonate, styrene, vinyl chloride, etc. can also be used. Copolymerization is not particularly limited and any known polymerization method may be used, but solution polymerization using an alcohol such as methanol or ethanol as a solvent is usually carried out. In this method, the monomers are charged by first adding the entire amount of vinyl ester and a portion of the oxyalkylene group-containing unsaturated monomer to start polymerization, and then continuously adding the remaining unsaturated monomers during the polymerization period. Any method may be used, such as a method of adding the former to or in parts, or a method of adding the former at once. The copolymerization reaction is carried out using a known radical polymerization catalyst such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, and lauroyl peroxide. Further, the reaction temperature is selected from a range of about 50°C to the boiling point. Such resins can be further saponified to convert them into vinyl alcohol components. Saponification is carried out by dissolving the copolymer in alcohol and in the presence of an alkali catalyst. Examples of the alcohol include methanol, ethanol, butanol, and the like. The concentration of copolymer in alcohol is 20-50% by weight
selected from the range. As the saponification catalyst, it is necessary to use an alkali catalyst such as an alkali metal hydroxide or alcoholate such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate, etc. The amount of such catalyst used is 1 to
It is necessary to make 100 mmol equivalents. In such cases, there is no particular restriction on the saponification temperature, but
The temperature is usually selected from the range of 10 to 70°C, preferably 30 to 40°C. The reaction is usually carried out over a period of 2 to 3 hours. The preferred degree of saponification is 10 to 100 mol%,
It is particularly preferably selected from the range of 50 to 100 mol%. However, in the vinyl ester resin having an oxyalkylene group of the present invention, the content of the group is not particularly limited, but is usually 1 to 80% by weight, more preferably 5 to 60% by weight based on the entire resin. be. The paper processing agent thus obtained is generally used after being dissolved in water, but it can also be used in a solvent system. The type of solvent may be appropriately selected depending on the content of oxyalkylene groups and the composition of the resin. For example, vinyl acetate resin or a material with a relatively low degree of saponification is obtained in the form of a paste, so the solvent used for polymerization or saponification may be used as is, or solvent replacement may be performed if necessary. In particular, when it is necessary to impart water solubility to the vinyl acetate resin when producing polyvinyl alcohol containing a low oxyalkylene group content or a low degree of saponification,
Unsaturated monomers having hydrophilic groups such as carboxylates and ammonium salts, such as (meth)acrylic acid,
Copolymerization of an alkali metal salt such as maleic acid or ammonium salt, or a copolymer of a carbosyl group-containing unsaturated monomer and vinyl acetate, is further dissolved in an aqueous alkali solution or an aqueous ammonia solution to form an aqueous system, as appropriate. be done. There are no particular restrictions on the preparation of the coating solution, and in short, water and a vinyl ester resin having an oxyalkylene group may be mixed. The concentration may be adjusted as appropriate depending on the purpose, but a particularly preferable concentration of the resin is usually 1 to 20% by weight considering workability etc.
Selected from a range of degrees. The processing agent of the present invention may further include known water-resistant agents such as glyoxal and urea resin, antifoaming agents, mold release agents, surfactants, preservatives, insect repellents, rust preventives, thickeners, etc. It is also possible to add other paper processing agents, such as conventionally known PVA, starch, carboxymethyl cellulose, acrylic latex, as long as the characteristics of the present invention are not impaired.
Resins such as SBR latex can also be mixed. The paper to be coated with the processing agent of the present invention is not particularly limited, but for example, paperboard such as manila ball, white ball, and liner, printing paper such as general high-quality paper, and gravure paper are suitably used. In coating such paper with the processing agent, any known method such as size press coating, roll coater method, air doctor method, blade coater method, etc. can be employed. Therefore, it is appropriate that the coating amount of the finishing agent be such that the oxyalkylene group-containing vinyl ester resin is 0.1 to 5 g/m ² (solid content equivalent), particularly preferably about 0.5 to 3 g/m ² . . Of course, the method is not limited to the above-mentioned method, and any other method may be used, such as the so-called internal size method in which paper is made by dissolving the processing agent of the present invention in a pulp dispersion, or further mixing the processing agent of the present application in the form of powder or fibers into paper. A processing agent can then be applied to the paper. The processing agent of the present invention is mainly used as a clear coating agent as described above, but it can also be suitably used as a binder for pigment coating. As the pigment, known pigments such as clay, calcium carbonate, kaolin, diatomaceous earth, titanium oxide, iron oxide, and satin white are used. With such a binder, there is no concern about clayey shock (a phenomenon in which the pigment aggregates when a binder is added to a dispersed state of the pigment), which has been a problem in conventional pigment coatings, and the dispersibility of the pigment is also very good. Demonstrates excellent effectiveness. The present invention will be explained in more detail below with reference to Examples. In the examples, "parts" or "%" are based on weight unless otherwise specified. ●Resin description Resin-1: Copolymer of vinyl acetate and polyoxyethylene monoallyl ether (n=100) (oxyalkylene group content in resin: 50%) Resin-2: 40 mol% of resin-1 Saponified resin-3: 88 mol% of resin-1 Saponified resin-4: Completely saponified product of resin-1 Comparison resin 2: Polyvinyl alcohol (saponification degree
99.0 mol%, degree of polymerization 1500) was post-reacted with ethylene oxide (oxyalkylene group content 50
% graft copolymer) Resin-5: Terpolymer of vinyl acetate, polyoxyethylene monoallyl ether (n=100), and monomethyl maleate (oxyalkylene group content 50%, monomethyl maleate content 4) %) Comparative resin-1: Polyvinyl alcohol (completely saponified product, degree of polymerization 1800) Example 1 4 parts of vinyl ester resins of Resins 1 to 5 were each dissolved in 96 parts of water. This processing agent was size press coated (90 m/min, 11 Kg/cm, 6% aqueous solution) onto high-quality paper having a basis weight of 65 g/m ² so that the resin solid content was 1.2 g/m ² . 110 in a cylindrical rotary dryer
After drying at ℃ for 3 minutes, finishing was performed using a super calendar. The workability in this case (passability through a calendar roll) and the surface characteristics of the obtained paper (white paper gloss, smoothness) were evaluated. The results are shown in Table 1. Comparative Example 1 Comparative Resin 1 and Comparative Resin 2 were used in place of the vinyl ester resin used in Example 1, and the same treatment as in Example 1 was carried out and the results were evaluated. The results are also shown in Table 1. Example 2 20 parts of the vinyl ester resins of Resins 1 to 5 were dissolved in 80 parts of water to obtain an aqueous solution with a concentration of 20%. Meanwhile, 100 parts of kaolin, 0.4 parts of sodium pyrophosphate
25 parts of the above vinyl ester resin aqueous solution was mixed into this dispersion, and then 24 parts of SBR latex (manufactured by Asahi Dow Chemical, trade name Dow-636) was mixed. After that, a clay coating liquid with a solid content of 56% was obtained. The liquid had excellent stability of valenic acid, and no cracking was observed. This liquid was coated at 65g/m ² using a Dickson coater.
A coated paperboard with a dry solid content of 18 g was obtained by coating on high quality paper. The paper thus obtained was evaluated in the same manner as in Example 1. The results are shown in Table 2. Comparative Example 2 Comparative Resin 1 and Comparative Resin 2 were used instead of the vinyl ester resin used in Example 2 to obtain an aqueous solution with a concentration of 20%, and 25 parts of the aqueous solution had the same composition as that used in Example 2. was mixed with a dispersion of
At this time, cracking was observed, but by continuing strong stirring for 0.5 hours, a clear coating solution that was uniform on the surface was obtained. This liquid was applied to high-quality paper using a Dickson coater in the same manner as in Example 2 to obtain a coated paperboard. The thus obtained paper was evaluated. The results are also shown in Table 2.

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Claims (1)

[Claims] 1. A paper processing agent whose main ingredient is a vinyl ester resin made of a copolymer of an unsaturated monomer having an oxyalkylene group and vinyl acetate.