JPH07179714A - Undercoating agent for release paper - Google Patents

Abstract

PURPOSE:To obtain an undercoating agent which contains, as a main component, a water-soluble resin prepared by emulsion polymerization of a monofunctional and a polyfunctional vinyl monomers in the presence of PVA and water, thus shows excellent coatability, adhesion to silicon resins and gives readily recoverable release paper. CONSTITUTION:In the presence of polyvinyl alcohol and water, a radically polymerizable monofunctional vinyl monomer such as methyl methacrylate and a polyfunctional vinyl monomer such as methylene bis(methacrylate) are emulsified at a certain speed agitation and heated under a nitrogen flow up to 70 deg.C. Then, a redox initiator comprising equimolar amounts of potassium persulfate to sodium thiosulfate is added to effect emulsion polymerization to give a water-soluble resin. The product resin is used as a principal component and a completely saponified polyvinyl alcohol is added to adjust the concentration whereby the undercoating with easily recoverable release paper is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an undercoat agent for release paper.

[0002]

2. Description of the Related Art Release paper is widely used in the field of adhesives for labels and seals, and the production amount thereof is increasing year by year. Such release papers were mainly manufactured by a method of directly applying a release agent liquid such as a solvent-type or emulsion-type silicone resin to the backing paper, but since the coating liquid penetrates into the backing paper, release papers have been manufactured in recent years. In doing so, a method of first laminating polyethylene on a mount and applying a solvent-type silicone resin on it is becoming mainstream.

However, due to resource and environmental problems, it has become necessary to recycle paper into recycled paper, so that the polyethylene-based release paper, which has poor recoverability, should be replaced with easily recoverable release paper. The Ministry of International Trade and Industry has issued notification instructions. As a method of making the release paper easily collectable, instead of laminating polyethylene on the backing paper, latexes such as SBR and acrylic emulsion as undercoat agents, and various water-soluble polymers such as polyvinyl alcohol and polyacrylamide are used. A method of applying it on a mount is being studied.

Of these methods, latexes such as SBR and acrylic emulsion have excellent coatability, but have poor solvent resistance, so that the toluene solution penetrates into the mount when the toluene solution of the silicone resin is coated. There's a problem. On the other hand, a water-soluble polymer typified by polyvinyl alcohol needs to use a high-molecular weight water-soluble polymer (that is, a highly viscous water-soluble polymer) in order to improve solvent resistance, and thus the stability of the aqueous solution over time. , There is a problem of poor workability. Further, when the coating is carried out at a low concentration for improving the workability, the drying time becomes long and the solution permeates into the backing paper, so that sufficient gloss cannot be obtained. Further, the adhesion between the undercoating agent and the silicone resin is also an important factor, but some water-soluble polymers have inferior adhesion. Therefore, a water-soluble polymer having a good balance of coatability and adhesion is Not yet obtained.

[0005]

DISCLOSURE OF THE INVENTION The present invention is suitable for easily recoverable release paper, and even when a solvent type silicone resin is coated on a backing paper, the silicone resin does not penetrate into the paper layer. It is an object of the present invention to provide an undercoat agent for release paper, which has good adhesion to a silicone resin, can impart excellent gloss, and has excellent coatability.

[0006]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, according to the water-based resin shown below, an undercoating agent for release paper which can solve the above-mentioned problems We have found that we can provide. The present invention has been completed based on this new finding.

That is, the present invention comprises (1) as a main component, an aqueous resin obtained by emulsion-polymerizing a radical-polymerizable monofunctional vinyl monomer and a polyfunctional vinyl monomer in the presence of polyvinyl alcohol and water. An undercoat agent for release paper, characterized by comprising: (2) Obtained by emulsion-polymerizing a radically polymerizable monofunctional vinyl monomer and a polyfunctional vinyl monomer in the presence of polyvinyl alcohol, an emulsifier and water. The present invention relates to an undercoat agent for release paper, which contains an aqueous resin as a main component.

First, the constituent components of the aqueous resin which is the main component of the undercoat agent (1) for release paper will be described.

The polyvinyl alcohol used in the present invention is not particularly limited as long as it is water-soluble, but usually has a polymerization degree of about 200 to 2500 and a saponification degree of 75% to.
100% partially saponified or fully saponified is preferred. In addition, silicon-containing polyvinyl alcohol, modified polyvinyl alcohol having a functional group such as a carboxyl group, an acetoacetyl group, and an acetal group can be similarly used.
Further, since polyvinyl alcohol affects the solvent resistance of the obtained undercoat agent, the amount used is appropriately determined in consideration of these properties. That is, the amount of polyvinyl alcohol used is 1% of the total amount of monofunctional vinyl monomer.
The amount is usually 5 to 900 parts by weight, preferably 40 to 250 parts by weight, based on 00 parts by weight. If it is less than 5 parts by weight, the solvent resistance of the obtained undercoating agent becomes poor, and if it exceeds 900 parts by weight, the viscosity of the aqueous resin solution as the undercoating agent for release paper obtained becomes high, which is not preferable in terms of workability. .

In the present invention, it is preferable to use a (meth) acrylic acid alkyl ester and / or a styrene compound as the radically polymerizable monofunctional vinyl monomer. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and (meth).
Iso-propyl acrylate, n- (meth) acrylate
Butyl, iso-butyl (meth) acrylate, (meth)
Examples thereof include 2-ethylhexyl acrylate and stearyl (meth) acrylate. Examples of styrene compounds include styrene, α-methylstyrene, vinyltoluene and the like.

As the radical-polymerizable monofunctional vinyl monomer, in addition to the (meth) acrylic acid alkyl ester and the styrene compound, various anionic monofunctional vinyl monomers and cationic monofunctional vinyl monomers are used. Vinyl monomers and nonionic monofunctional vinyl monomers other than the above can be used.

Examples of the anionic monofunctional vinyl monomer include monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid and muconic acid, and vinyl sulfone. Acid, styrene sulfonic acid, 2-acrylamide-
Organic sulfonic acids such as 2-methylpropanesulfonic acid, 2
Examples thereof include phosphoric acid vinyl monomers such as-(meth) acryloyloxyethyl acid phosphate, and sodium salts and potassium salts of these various organic acids.

As the cationic monofunctional vinyl monomer, a tertiary amino group such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide and the like can be used. A vinyl monomer having or a salt of an inorganic acid or an organic acid thereof such as hydrochloric acid, sulfuric acid or acetic acid, or a tertiary amino group-containing vinyl monomer and a quaternizing agent such as methyl chloride, benzyl chloride, dimethylsulfate or epichlorohydrin Examples thereof include vinyl monomers containing a quaternary ammonium salt obtained by the reaction.

Examples of the nonionic monofunctional vinyl monomer include (meth) acrylamide, (meth) acrylonitrile, vinyl acetate, methyl vinyl ether, 2-hydroxyethyl (meth) acrylate, and (meth) acrylic acid 2
-Hydroxypropyl, hydroxy group-containing (meth) acrylates such as 2-hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate, N-methylol (meth) acrylamide, urethane acrylates, diphenyl-2 (meth) Examples thereof include phosphoric acid ester vinyl monomers such as acryloyloxyphosphate.

The amount of the anionic monofunctional vinyl monomer exemplified here, the cationic monofunctional vinyl monomer and the nonionic monofunctional vinyl monomer is usually about 40% by weight or less of the monofunctional vinyl monomer. , Preferably 30% by weight or less.

In the present invention, it is essential to use a polyfunctional vinyl monomer in addition to the monofunctional vinyl monomer exemplified above. For example, as the bifunctional vinyl monomer, di (meth) acrylates such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene glycol di (meth) acrylate, methylenebis (meth) acrylate, methylenebis ( Bis (meth) acrylamides such as (meth) acrylamide, ethylenebis (meth) acrylamide, hexamethylenebis (meth) acrylamide, divinyl adipate, divinyl sebacate and the like, allyl methacrylate, diallylamine, diallyldimethylammonium, diallyl Examples thereof include phthalate, diallyl chlorendate and divinylbenzene. Further, as the trifunctional monomer, 1,
3,5-triacryloylhexahydro-S-triazine, triallyl isocyanurate, triallyl amine,
Examples thereof include triallyl trimellitate and N, N-diallyl acrylamide. As the tetrafunctional vinyl monomer, tetramethylolmethane tetraacrylate, tetraallyl pyromellitate, N, N, N ′, N′-tetraallyl-1 , 4-diaminobutane, tetraallylamine salt, tetraallyloxyethane and the like.

The amount of the polyfunctional vinyl monomer used is 1 based on 100 parts by weight of the total of the monofunctional vinyl monomers.
The amount is about 0 parts by weight or less, preferably 0.1 to 5 parts by weight. When the amount of the polyfunctional vinyl monomer exceeds 10 parts by weight, aggregation occurs and it becomes difficult to obtain a high-concentration aqueous resin solution, which is not preferable.

Next, the constituent components of the aqueous resin which is the main component of the undercoat agent (2) for release paper will be described.

The composition of the water-based resin of the release paper undercoat agent (2) is different from the composition of the water-based resin of the release paper undercoat agent (1) only in that an emulsifier is used.
Therefore, the same polyvinyl alcohol, radical-polymerizable monofunctional vinyl monomer, and polyfunctional vinyl monomer described in the undercoat agent (1) for release paper can be used in the undercoat agent (2) for release paper. .

The emulsifier is not particularly limited, and various known anionic emulsifiers, nonionic emulsifiers and the like can be used. Examples of the anionic emulsifier include long-chain sodium α-olefin sulfonate, alkyldiphenyloxyethylene alkylaryl ether sulfate ester salt and the like, and examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene block polymer, Examples thereof include polyoxyethylene alkyl phenyl ether. These anionic emulsifiers and nonionic emulsifiers may be used alone or in combination of two or more.

When such an emulsifier is used, generation of agglomerates can be suppressed in the production process of the water-based resin, but it adversely affects the solvent resistance of the undercoat agent for release paper and the adhesion with the silicone resin. The amount used should be kept to the minimum required. Usually, it is about 15 parts by weight or less, preferably 5 parts by weight or less, based on 100 parts by weight of the monofunctional vinyl monomer.

Next, the method for producing the aqueous resin of the present invention will be described. The method for producing the aqueous resin of the present invention may be carried out by a known emulsion polymerization method. For example, in the case of (1), polyvinyl alcohol and water are charged into a predetermined reaction vessel and dissolved while heating, then a monofunctional vinyl monomer and a polyfunctional vinyl monomer are charged, and after emulsification, a radical polymerization initiator is added. A method of heating with stirring may be used. Further, in the case of (2), polyvinyl alcohol and water are charged into a predetermined reaction vessel and dissolved while heating, then a monofunctional vinyl monomer, an emulsifier and a polyfunctional vinyl monomer are charged and emulsified, and then a radical polymerization initiator. Is added and the mixture is heated with stirring. The monofunctional vinyl monomer, the polyfunctional vinyl monomer and the radical initiator may be added by a dropping method, and the dropping method may be a batch dropping method or a divided dropping method.

The solid content of the reaction system is usually 10 to 5
It is about 0% by weight, preferably 15 to 30% by weight. In addition, the pH during polymerization is usually preferably in the range of about 3-9. The reaction temperature may be in the temperature range for activating the polymerization catalyst, and is usually about 40 to 90 ° C, preferably 50 to 80 ° C, and the reaction time is usually about 30 minutes to 2 hours.

Examples of the radical polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide, water-soluble radical polymerization initiators such as aqueous azo initiators, and the above persulfates. Examples thereof include redox-based polymerization initiators in the form of a combination with a reducing agent such as sodium hydrogen sulfite and sodium thiosulfate. Usually, the amount of the initiator used is about 0.05 to 5% by weight, preferably 0.1 to 3% by weight, based on the total amount of the vinyl monomers (monofunctional vinyl monomer and polyfunctional vinyl monomer).
It is good to say

Thus, the average particle size is usually 10 to 10.
An aqueous resin solution containing fine particles of about 300 nm is obtained. When the aqueous resin solution is used as an undercoat agent for release paper, the nonvolatile content is usually 10 to 30.
The viscosity is about 100 cps or less at 25% by weight (25 ° C)
It is better to adjust to.

When the undercoating agent for release paper of the present invention is applied to a backing paper, a crosslinking agent such as glyoxal or a water-soluble zirconium compound is used in combination to improve the adhesiveness to the silicone resin at high temperature and high humidity. It can be further improved. As a coating method of the undercoat agent for release paper, a wire bar, a blade coater,
An air knife coater, a roll coater, or the like can be used, and a known drying device such as an oven or a drum dryer can be used for drying. Further, a calendar process may be performed to adjust the smoothness to a desired level.

[0027]

EFFECTS OF THE INVENTION According to the present invention, even when a release agent (for example, a toluene solution of a silicone resin) is applied to a backing paper, the release agent is not absorbed in the paper layer and the coating property is excellent. Moreover, it is possible to provide an undercoat agent for release paper, which has good adhesion to a silicone resin and has excellent gloss. Furthermore, the release paper obtained by using the undercoating agent for release paper is easy to collect and can contribute to resource saving and environmental problems.

[0028]

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition,% in each example is based on weight unless otherwise specified.

Example 1 A reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen gas introduction tube, a monomer dropping funnel and a thermometer was charged with acetoacetylated polyvinyl alcohol (trade name: Gohseheimer Z10).
0, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., and 40 g of water and 420 g of water were charged and dissolved by stirring while heating to obtain an aqueous solution.
The aqueous solution was cooled to 40 ° C. Next, 60 g of a mixed monomer consisting of butyl methacrylate and methyl methacrylate (weight mixing ratio is 40:60 in sequence) and 3 g of methylene bismethacrylate were added to the mixture at a constant speed (250 ± 10).
emulsified at (rpm). The temperature is raised under a nitrogen stream, and a redox type initiator (concentration in the system: 6.0 × 10 ⁻³ mol / liter) consisting of equimolar amounts of potassium persulfate and sodium thiosulfate is added at 70 ° C. to start polymerization. It was The reaction was carried out for 60 minutes so that the polymerization temperature did not exceed 80 ° C to obtain an aqueous resin solution. The non-volatile content of the obtained aqueous resin solution is 20%, pH
The viscosity at 4.9 and 25 ° C. was 85 cps.

Example 2 A completely saponified polyvinyl alcohol (trade name: PVA105, manufactured by PVA 105) having a degree of polymerization of 500 was placed in the same reaction vessel as in Example 1.
40 g of Kuraray Co., Ltd.) and 420 g of water were charged and stirred with heating to dissolve the mixture into an aqueous solution. 40 parts of this aqueous solution
After cooling to 0 ° C, 60 g of a mixed monomer consisting of ethyl methacrylate, styrene and 2-hydroxyethyl methacrylate (weight mixing ratio is 57: 37: 6 in order) and 3 g of ethylene glycol diacrylate were added to the mixture at a constant speed (250 ± 10 rpm). ) Emulsified with. The temperature was raised under a nitrogen stream, and potassium persulfate and sodium thiosulfate were added at 60 ° C. so that the concentration in the system was 6.0 × 10 ⁻³ mol / liter to initiate polymerization. The reaction was carried out for 60 minutes so that the polymerization temperature did not exceed 80 ° C to obtain an aqueous resin solution. The resulting aqueous resin solution has a nonvolatile content of 20%, pH 4.0, and 25 ° C.
The viscosity at was 90 cps.

Example 3 In the same manner as in Example 1, except that 0.6 g of polyoxyethylene alkylphenyl ether (trade name: Emulgit, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was charged as an emulsifier together with water. An aqueous resin solution was obtained. The nonvolatile content of the obtained aqueous resin solution is 20%, pH 4.8, 25 ° C.
The viscosity at was 95 cps.

Example 4 In the same manner as in Example 2 except that 0.6 g of polyoxyethylene alkyl ether (trade name: Neugen ET165, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was charged as an emulsifier together with water. An aqueous resin solution was obtained. The resulting aqueous resin solution had a nonvolatile content of 20%, a pH of 3.8, and a viscosity at 25 ° C. of 95 cps.

Example 5 Same as Example 1 except that 3.0 g of polyoxyethylene alkylphenyl ether (trade name: Emulgit 49, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was charged as an emulsifier together with water. To obtain an aqueous resin solution. The resulting aqueous resin solution has a nonvolatile content of 21%, pH 4.8, 2
The viscosity at 5 ° C. was 90 cps.

Comparative Example 1 An aqueous resin solution was obtained in the same manner as in Example 1, except that the acetoacetylated polyvinyl alcohol was not used and the amount of water used was 250 g. The resulting aqueous resin solution had a nonvolatile content of 20%, a pH of 4.0, and a viscosity of 15 cps at 25 ° C.

Comparative Example 2 250 g of ion-exchanged water and a dialkyl sulfosuccinic acid ester soda salt (trade name Neocor P, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., nonvolatile content 75) were placed in the same reaction vessel as in Example 1.
%) 6.5 g was charged and dissolved. 80 ° C under nitrogen stream
100 g of a mixed monomer composed of butyl methacrylate, cyclohexyl methacrylate and glycidyl methacrylate (weight mixing ratio is 59: 39: 2 in order).
Then, an aqueous potassium persulfate solution was continuously added dropwise to carry out polymerization. A water-soluble resin solution was obtained by reacting for 90 minutes so that the polymerization temperature did not exceed 80 ° C. The resulting aqueous resin solution had a nonvolatile content of 25.5%, a pH of 5.2, and a viscosity at 25 ° C. of 50 cps.

(Performance Evaluation) Examples 1 to 5 and Comparative Examples 1 to 1
After adjusting the aqueous resin solution obtained in 2 and a completely saponified polyvinyl alcohol having a degree of polymerization of 500 (trade name PVA105, manufactured by Kuraray Co., Ltd.) (Comparative Example 3) to a coating concentration shown in Table 1, solid content is attached. PPC paper is coated and dried so that the amount becomes 5 g / m ^2, and further calendered (5
0 Kg / cm). Using this as a sample, a performance test was conducted according to the following method. The results are shown in Table 1.

(Smoothness) The smoothness was measured by an Oken type air permeability smoothness tester.

(Solvent resistance) Toluene in which a dye was dissolved was applied to the coated surface with a paintbrush and the presence or absence of strikethrough was observed. ◯: No strikethrough. △: There are strikethroughs in places. X: Many strikethroughs.

(Silicone Adhesion) 1% of a curing catalyst (CAT-PL-8 manufactured by Shin-Etsu Chemical Co., Ltd.) was added to a silicone resin (KS776A manufactured by Shin-Etsu Chemical Co., Ltd.) diluted with toluene to a concentration of 5% (KS766A). (Based on the solid content) and coated so that the solid content is 1 g / m ² , then first dried at 70 ° C. for 30 seconds, then 14
It was dried and cured at 0 ° C. for 1 minute. After that, 20 ℃, humidity 6
After leaving it under 5% condition for 1 day (condition 1),
After leaving for 1 week under each condition of humidity 90% (condition 2),
The coated surface was rubbed with a finger and the peeled state of the silicone was observed. ◯: Does not peel. Δ: A little peeled off. X: Completely peeled.

[0040]

[Table 1]

Although the coating concentration of the polyvinyl alcohol of Comparative Example 3 was 10% which is half that of the Example, unevenness occurred during coating.

Claims (3)

[Claims] 1. An exfoliation characterized by containing an aqueous resin obtained as a main component by emulsion polymerization of a radically polymerizable monofunctional vinyl monomer and a polyfunctional vinyl monomer in the presence of polyvinyl alcohol and water. Undercoat agent for paper. 2. A water-based resin obtained by emulsion-polymerizing a radically polymerizable monofunctional vinyl monomer and a polyfunctional vinyl monomer in the presence of polyvinyl alcohol, an emulsifier and water as a main component. Undercoat agent for release paper. 3. The undercoat agent for release paper according to claim 1, wherein the monofunctional vinyl monomer is a (meth) acrylic acid alkyl ester and / or a styrene compound.