JP2000273387A - Paper surface improver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface coating agent comprising an aqueous solution of a high-molecular but lowly viscous acrylamide polymer. SOLUTION: This improver comprises an aqueous solution of an acrylamide polymer obtained by subjecting an aqueous solution of a mixture comprising at least 40 mol% acrylamide, 0.1-30 mol% anionic monomer, and 0.05-10 mol% methacrylonitrile to a polymerization reaction. It is desirable that the aqueous solution of the mixture further contains at least one member selected from among a vinyl cyanide compound, a crosslinking agent, and a chain transfer agent in an amount of 0.1-45 mol% based on the entire weight of the monomers constituting the acrylamide polymer when the mixture contains the vinyl cyanide compound, 0.005-3 mol% based on the entire weight of the monomers when it contains the crosslinking agent, or 0.01-8 mol% based on the entire weight of the monomers when it contains the chain transfer agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface coating agent capable of exerting excellent effects such as improvement of surface strength, internal strength and water resistance by coating on paper surface.

[0002]

2. Description of the Related Art In recent years, in the papermaking industry, the use of waste paper and hardwood has been increasing, and the content of fine fibers has also tended to increase in printing paper, so that the bonding between fibers has weakened, making it difficult to obtain the strength of paper. . On the other hand, in the printing process, higher speed and higher quality have been advanced, and higher levels of characteristics such as surface strength, internal strength, and water resistance have been required for printing paper. In order to respond to these demands, medicines are often added internally and externally (coated). In particular, in the case of internal additives, the higher the amount used, the lower the yield of the drug,
Operational troubles such as machine contamination are liable to occur. However, in the case of an external additive, the operation is advantageous because the yield is almost 100%.

Conventionally, surface coating agents applied for the purpose of improving the surface strength and printability of paper include starches such as oxidized starch, celluloses such as carboxymethyl cellulose, and polyvinyl alcohol (hereinafter abbreviated as PVA). And acrylamide polymers. Most of the most frequently used starch-based or PVA-based chemicals require a cooking step when used, have poor workability, and have various problems such as foaming during application and machine staining. Further, in the case of starch-based drugs, there are also problems such as spoilage and aging.

On the other hand, as acrylamide-based polymers, acrylamide-based polymers having an anionic group introduced have been proposed for the purpose of improving the surface strength (Japanese Patent Publication No. 43-43).
-27529), but the effect of improving the surface strength was not sufficient.

In order to improve these problems, use of an acrylamide polymer containing a specific vinyl compound, a crosslinkable monomer and an unsaturated dicarboxylic acid has been proposed (JP-A-9-169946). If so, the product tends to be low-viscosity or high-viscosity and gel, and it is difficult to control the viscosity. Further, it has been proposed to obtain a surface paper quality improver by polymerizing an acrylamide polymer in the presence of ureas (JP-A-5-3022).
98, 8-260384), urea is decomposed due to a rise in pH during polymerization or during hydrolysis, and a foaming phenomenon of the viscous polymer occurs, which is a problem in production.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for obtaining a branched acrylamide polymer having the same high molecular weight and low viscosity as in the prior art. An object of the present invention is to provide a surface coating agent which is uniformly introduced, uses the polymer thus obtained as an active ingredient, and exhibits an excellent effect of improving surface strength.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to develop a surface coating agent having even higher performance, and as a result, methacrylonitrile exhibiting a chain transfer effect and a crosslinking effect is essential. The inventors have found that the object is achieved by using an acrylamide-based copolymer obtained by copolymerizing a monomer mixture containing a component, and have completed the present invention. That is, the present invention provides an acrylamide-based polymer obtained by subjecting a mixed aqueous solution containing 40 mol% or more of acrylamides, 0.1 to 30 mol% of anionic monomer and 0.05 to 10 mol% of methacrylonitrile to a polymerization reaction. A surface coating agent composed of an aqueous solution.

In the present invention, acrylamides include acrylamide and / or methacrylamide, which may be used alone or in combination.

Examples of anionic monomers include monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid and citraconic acid, vinylsulfonic acid and styrenesulfonic acid. And sulfonic acid-based organic acids having a vinyl group such as 2,2-acrylamido-2-methylpropanesulfonic acid. These organic acids may be salts such as sodium salts and potassium salts. Further, these anionic monomers may be used alone or in combination of two or more.

Acrylamide and / or methacrylamide are 40 mol% or more, preferably 60 mol% or more, anionic monomer is 0.1 to 30 mol%, preferably 0.5 to 20 mol%, and methacrylonitrile is ,
The content is 0.05 to 10 mol%, preferably 0.1 to 5 mol%.

In the present invention, the mixed aqueous solution may further contain at least one of a vinyl cyanide compound, a crosslinking agent and a chain transfer agent. Examples of the vinyl cyanide compound include ethylene-based nitrile compounds such as acrylonitrile having a structure similar to methacrylonitrile. The amount of these vinyl cyanide compounds is 0.1 to 0.1 with respect to all monomers constituting the acrylamide polymer.
It is 45 mol%, preferably 0.1 to 35 mol%.

Examples of the crosslinking agent include methylene bis (meth) acrylamide, ethylene bis (meth) acrylamide, ethylene glycol di (meth) acrylamide, diethylene glycol di (meth) acrylamide,
Bifunctional crosslinking agents such as triethylene glycol di (meth) acrylamide, divinylbenzene, diallyl acrylamide, or 1,3,5-triacryloylhexahydro-S-triazine, triallyl isocyanurate, pentaerythritol triacrylate, triacrylate Multifunctional crosslinking agents such as methylolpropane acrylate and diacryloyl imide; N-type such as dimethyl acrylamide, diacetone acrylamide, isopropyl acrylamide
-Substituted acrylamide monomers. The cross-linking agent can be used in combination, if necessary, as long as the object of stabilizing the polymerization control of the present invention is not impaired.

As described above, these crosslinking agents can be used alone or in combination of two or more. However, since the crosslinking effect by methacrylonitrile itself also works, the amount of the crosslinking agent may be smaller than usual crosslinking conditions. 0.005 to 3 mol%, preferably 0.01 to 1 mol%, based on the total amount of all monomers.

The chain transfer agent can be used within a range that does not impair the purpose of stabilizing the polymerization control of the present invention. Examples of chain transfer agents include, in addition to isopropyl alcohol, mercapto-based compounds such as mercaptoethanol, thiourea, thioglycolic acid, mercaptopropionic acid, thiosalicylic acid, thiolactic acid, aminoethanethiol, thioglycerol, thiomalic acid, allyl alcohol, Allyl-based compounds such as sodium allylsulfonate and sodium methallylsulfonate are exemplified.

One or more of these chain transfer agents can be used. However, since methacrylonitrile itself, which is an essential component, exhibits a chain transfer effect, the amount of the chain transfer agent used may be smaller than usual. And 0.01 to 8 mol%, preferably 0.03 to 4 mol%, based on the total amount of all monomers.

In the present invention, in addition to the above-mentioned components as monomers, other monomer components may be contained as long as the object of improving the surface strength of the present invention is not impaired. Such monomer components include cationic monomers and nonionic monomers.

Examples of the cationic monomer include (meth) acrylate derivatives such as dialkylaminoethyl (meth) acrylate and dialkylaminopropyl (meth) acrylate, which are monomers having a tertiary amino group, and dialkylaminoethyl (meth). Acrylamide,
Dialkylaminopropyl (meth) acrylamide,
(Meth) acrylamide derivatives such as (meth) acrylamide-3-methylbutyldimethylamine. In addition, as the cationic monomer, a salt of the above monomer having a tertiary amino group can be used. The salt may be a salt with an inorganic acid such as hydrochloric acid or sulfuric acid, or a salt with an organic acid such as formic acid or acetic acid. Further, a quaternary salt obtained by quaternizing a tertiary amino group with methyl chloride, methyl bromide, benzyl chloride, benzyl bromide, dimethyl sulfate, epichlorohydrin or the like may be used. The cationic monomer may be used alone or two or more kinds may be used.

Further, examples of the nonionic monomer include diacetone acrylamide, alkyl acrylate, hydroxy acrylate, vinyl acetate, styrene, α-methylstyrene and the like.

In the present invention, urea may be added after the polymerization reaction. Examples of such urea include urea, thiourea and ethylene urea, and urea is preferred. The weight ratio of urea / monomer is 2-50% / 9
8 to 50%, preferably 10 to 40% / 90 to 60%. The urea can be added if the polymerization is completed and the temperature of the reaction system is lowered to at least 90 ° C. or less by cooling, and preferably 85 to 60 ° C. Note that Japanese Patent Application Laid-Open
No. 302298 indicates that the polymerization reaction is carried out in the presence of urea. However, in this method, urea is decomposed by heat or a change in pH, foaming is poor, and the workability is poor. There is a problem that the entire amount of urea charged cannot be present in the product. In the present invention, by adding urea after polymerization, the operation becomes easy without loss or foaming due to decomposition of urea during polymerization.

In the present invention, when the mixed aqueous solution is subjected to a polymerization reaction, conventionally known various polymerization methods can be applied. For example, the essential monomer and water, if necessary, other monomers, a cross-linking agent, and a chain transfer agent are charged into a predetermined reaction vessel, a catalyst is added, and the mixture is heated under stirring to obtain a target acrylamide-based polymer aqueous solution (hereinafter referred to as a co-polymer). (Sometimes referred to as a polymer aqueous solution). Also,
The reaction may be performed while dropping part or all of the monomer into the reaction vessel. The catalyst can be charged even once, but after the prepolymer is formed by the first-stage reaction,
By adding a catalyst and further completing the polymerization, a copolymer aqueous solution containing a high-molecular weight polymer having a high degree of branching may be obtained. The reaction temperature is usually about 40 to 100 ° C, and the reaction time is about 0.5 to 8 hours.

The catalyst is not particularly limited as long as it is a radical polymerization initiator usually used for a polymerization reaction in an aqueous solution as a polymerization initiator. Examples thereof include hydrogen peroxide, benzoyl peroxide, and t-butyl peroxide. Such as peroxide catalysts, persulfate catalysts such as ammonium persulfate, sodium persulfate and potassium persulfate, bromate catalysts such as sodium bromate and potassium bromate, and perborates such as sodium perborate Acid salt catalysts. Also, a redox catalyst or an azo catalyst in which these are combined with a reducing agent such as a sulfite, a hydrogen sulfite, a transition metal salt, or an organic amine can be used. These may be used alone or in combination of two or more. These catalysts are used in an amount of 0.01 to 10% by weight, preferably 0.05 to 10% by weight, based on the total weight of the monomers.
4 wt%.

As the additional catalyst, the above-mentioned catalysts can be used, but persulfates are most suitable in terms of catalyst efficiency and cost. Of course, if a large amount of catalyst remains after the prepolymer is formed, it is not necessary to add a catalyst. The temperature of the additional polymerization reaction is 40 ° C. or higher, preferably 70 to
It is preferably 95 ° C. and higher than the reaction temperature of the first stage. The amount used is 0.01 to 10 wt%, preferably 0.1 to 10 wt%.
It is 0.5-4 wt%. When adding the catalyst, a monomer can be added as needed. In this case, the monomer composition may be the same as or different from the initially charged monomer composition in the first-stage reaction.

In the present invention, by using methacrylonitrile as an essential component, the radical generated by the radical catalyst is resonance-stabilized by the nitrile group of methacrylonitrile, and acts as a chain transfer agent, while acting as a methyl group. To form a cross-linking point by a pull-out reaction. As described above, methacrylonitrile alone functions as a crosslinking agent / chain transfer agent, which facilitates control of the polymerization reaction without a sharp increase in viscosity.

According to the method of the present invention, it is possible to easily obtain an aqueous solution of a copolymer having a low viscosity while having a high molecular weight. A high improvement effect is obtained not only in strength but also in internal strength. The surface coating agent of the present invention includes surface coating agents such as starch-based, PVA-based, cellulose-based, and polyacrylamide-based, surface sizing agents, water-proofing agents, anti-slip agents, preservatives, defoamers, and mold release agents. It can be used in combination with various agents such as agents and dyes.

In using the surface coating agent of the present invention, the coating solution concentration is 0.1 to 10% and the viscosity is 3 to 350 cps.
It is preferable to perform coating. As a coating method,
Examples of the method include a commonly used method, a size press, a gate roll coater, a calender, a blade coater, and a spray. Further, the coating agent of the present invention is used for paperboard such as liners and coated balls, coated base paper (acidic and neutral), PP
It can be applied to various base papers such as C paper, foam paper, printing paper, newsprint paper, inkjet paper, etc. It not only improves the fluffiness, vessel pick, paper dust, surface abrasion and other paper surface strength, but also paper It is extremely effective in improving the internal strength.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically below with reference to examples and comparative examples. All parts and percentages are by weight unless otherwise specified.

Example 1 A 50% acrylamide aqueous solution 33 was placed in a four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet.
8 parts, 20 parts of acrylic acid, 9.4 parts of methacrylonitrile and 500 parts of water were charged, and the pH was adjusted with an alkali to pH.
It was adjusted to 3.5, and oxygen in the reaction system was removed through nitrogen gas. The system was heated to 40 ° C., and 40 parts of a 10% aqueous ammonium persulfate solution and 24 parts of a 10% aqueous sodium bisulfite solution were added as a polymerization initiator with stirring. After the temperature of the reaction system was raised to 90 ° C., 20 parts of a 10% ammonium persulfate aqueous solution was further added, and the temperature was maintained for 2 hours. After the completion of the polymerization, 50 parts of water was charged, and the pH was 4.7 and the solid content was 2
A 0.4% aqueous solution of a copolymer having a viscosity (25 ° C.) of 8,400 cps and a weight average molecular weight of 1,650,000 was obtained.

Examples 2 to 10 In Example 1, the types of the copolymerization components or the proportions used were changed as shown in Tables 1 and 2, and the amount of the catalyst was adjusted so as to obtain an appropriate viscosity. The same operation as in Example 1 was performed to obtain various copolymer aqueous solutions. The urea-added products of Example 6 and after were cooled to about 85 ° C. to 80 ° C. after completion of the polymerization, and urea was added so that the urea content became a predetermined amount shown in Table 2 with respect to the total monomer weight. Obtained. Examples 7 and 8
Is carried out by separately dropping a monomer / crosslinking agent mixed solution and a catalyst / chain transfer agent mixed aqueous solution into 80 ° C. hot water over 120 minutes, and then adding a catalyst in the same manner as in Example 1 to carry out a reaction. Was done. Table 3 shows the property values of the obtained aqueous copolymer solutions.

[0029]

[Table 1]

[0030]

[Table 2]

In Tables 1 and 2, AM: acrylamide,
MAN: methacrylonitrile anionic monomer,
AA: acrylic acid, IA: itaconic acid, FA: fumaric acid, NSS: sodium styrenesulfonate, MBAM: methylenebisacrylamide, DMA as a crosslinking agent
M: dimethylacrylamide, IP as a chain transfer agent
A: Isopropyl alcohol, MAS: Sodium methallyl sulfonate, AS: Sodium allyl sulfonate, and DM: dimethylaminoethyl methacrylate and St: styrene as other monomers, respectively.

Comparative Examples 1 to 5 The same procedures as in Example 1 were carried out except that the types of the copolymer components or the proportions used were changed as shown in Tables 1 and 2, and various copolymer aqueous solutions were used. I got Comparative Example 3
In Nos. 5 to 5, products with a viscosity of 5000 cps or more were obtained. However, the viscosity tends to increase rapidly in the latter half of the polymerization reaction. A product of viscosity was obtained. Table 3 shows the property values of the obtained aqueous copolymer solutions.

[0033]

[Table 3]

[0034]

[Coating method] Newspaper base paper with a basis weight of 43 g / m ² is 12 c long
m, cut to 24 cm in width, and the top of the paper was fixed on a flat glass plate with cellophane tape. 3% of synthesized polymer
And 2% with water. The coating was performed on one side using a coating roll bar of No. 3. The absorption amount of the coating solution was measured to be 8.2 g / m ² , and 0.3% for the 3% dilution.
25 g / m ^2, at 2% dilution had a coating weight of 0.16 g / m ^2. Immediately after the coating, drying was performed for 90 seconds with a drum dryer adjusted to 105 ° C. to obtain a sample paper. The obtained sample paper is placed in a constant temperature and humidity chamber (temperature 20 ° C, humidity 65%)
The evaluation was carried out after humidity control for one day.

[0035]

[Evaluation method] The measurement was performed according to the following method.・ RI pick: RI-II type printing tester (Meiji Seisakusho),
Toyo Ink, ink tack 15, ink amount 2 ml, rotation speed 60 rpm, paper peeling state after printing was observed with the naked eye,
Was evaluated as good and 1 was evaluated as poor. The numerical values are represented by the average value of the print evaluations of five sheets. -Internal strength: Internal bond tester (manufactured by Kumagai Riki Kogyo Co., Ltd.)-Breaking length: JIS P 8113

[0036]

[Table 4]

[0037]

As shown in Table 3, according to the present invention, the viscosity of the aqueous copolymer solution can be controlled in a wide range, and problems such as gelation are less likely to occur. As described above, it has an excellent effect of improving the surface strength as a surface paper quality improver.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J038 CG161 CG171 FA102 JB18 JB24 KA03 KA04 MA08 MA09 NA04 NA11 PC10 4L055 AG34 AG35 AG36 AG63 AG70 AG71 AG72 AG74 AG93 AH13 AH16 AH50 BE08 EA32 FA13 FA19 GA06 GA08 GA19 GA11 GA16

Claims (5)

[Claims] 1. An aqueous acrylamide polymer solution obtained by subjecting a mixed aqueous solution containing at least 40 mol% of acrylamides, 0.1 to 30 mol% of an anionic monomer and 0.05 to 10 mol% of methacrylonitrile to a polymerization reaction. Surface coating agent consisting of 2. A mixed aqueous solution comprising a vinyl cyanide compound,
In the case of a vinyl cyanide compound, at least one of a cross-linking agent and a chain transfer agent is used in an amount of 0.1 to 45 mol% based on the total amount of all monomers constituting the acrylamide polymer, and in the case of a cross-linking agent, based on the total amount of all monomers. 0.005 to 3 mol%, and in the case of a chain transfer agent, 0.0 to 3 mol% based on the total amount of all monomers.
The surface coating agent according to claim 1, further comprising 1 to 8 mol%. 3. The polymerization reaction according to claim 1, wherein the polymerization is completed after forming a prepolymer in the first stage.
Or the surface coating agent according to 2. 4. The surface coating agent according to claim 1, wherein a urea is added to the product after the polymerization reaction. 5. The surface coating agent according to claim 1, wherein a persulfate is used as a polymerization catalyst.