JPH0635720B2 - Release paper - Google Patents

Description

TECHNICAL FIELD The present invention relates to a release paper, and more particularly to a release paper that does not cause curling and can form an adhesive paper that is excellent in paper-passability and copyability. Is.

"Prior Art" Adhesive paper is used as a label, a sticker, a sticker, a patch, etc. in a very wide range of applications such as commercial, office and household. The general constitution of this adhesive paper is a state in which an adhesive material is sandwiched between a surface base material and a release paper, and paper, film, metal foil, etc. are used for the surface base material, Is a high-density base paper such as glassine paper, clay-coated paper, or polylaminate base paper coated with a release agent such as a silicon compound or a fluorine compound. As the pressure-sensitive adhesive, a solvent-type pressure-sensitive adhesive, an emulsion-type pressure-sensitive adhesive, a hot melt-type pressure-sensitive adhesive or the like is used.

"Problems to be Solved by the Invention" In such an adhesive paper, curling is likely to occur due to the release paper. That is, in a general manufacturing process of pressure-sensitive adhesive paper, a release agent is applied to a release base paper and dried, and then an adhesive is applied to the release agent-coated surface and dried, and then the release base paper is adhered to the release agent. In the agent applying step, the agent is dried twice and contracted, and the reactivity to water is extremely high.
Therefore, when uneven moisture absorption or water absorption occurs due to changes in the external environment, curling occurs immediately. In particular, when high-beating, high-density paper such as glassine paper is used as the base paper, it shrinks more than ordinary paper when dried,
There are very few voids to absorb the swelling of fibers caused by moisture absorption and water absorption, and as a result, curling is particularly remarkable.

In this way, the curl of adhesive paper caused by release paper is
For example, when printing, die cutting (punching), sheet cutting, etc. on adhesive paper to process labels and stickers etc., problems such as paper feeding failure, paper misalignment, printing misalignment occur, and when copying with a copier In this case, a paper passing failure or a transfer failure occurs, which is a very serious obstacle in terms of workability and quality.

In order to correct the curl of the adhesive paper, the use of a curl breaker that bends the adhesive paper in a direction opposite to the curl direction at an acute angle, a method of attaching an air conditioner and performing steam damping, etc. are proposed. In addition to the complexity, the effect is insufficient, and the satisfactory results are not always obtained.

In view of the current situation, the present inventors have earnestly studied the method for preventing the curl of the adhesive paper due to the release paper, the base paper for the release paper has a specific monomer composition and a glass transition temperature, And, by forming an undercoat layer containing a water-soluble copolymer containing a specific amount of an emulsifier as a main component, and then providing a release agent layer, it has been found that the above-mentioned difficulties can be solved very efficiently, and further earnest efforts have been made. As a result of repeated studies, the present invention has been completed.

"Means for Solving the Problem" The present invention relates to a release paper having a release agent layer provided on at least one surface of a base paper via an undercoat layer, and the main component of the undercoat layer is composed of the following monomer composition. A copolymer containing 2 to 10% by weight of an emulsifier and having an average particle size of 0.3 by neutralizing a carboxyl group with an alkaline substance.
Glass transition temperature of 60 μm or less water-soluble copolymer-60
It is a release paper characterized by being a copolymer of -20 ° C.

(a) Ethylenically unsaturated carboxylic acid-containing monomer: 2 to 40
Wt% (b) (meth) alkyl ester monomer of C _{4 ~ 10} acrylic acid: 50 to 90 wt% (c) these monomers and other copolymerizable monomers: 0-4
0% by weight “action” Examples of the ethylenically unsaturated carboxylic acid-containing monomer that constitutes the above specific water-soluble copolymer used in the present invention include acrylic acid, methacrylic acid, crotonic acid, maleic acid and itaconic acid. , Fumaric acid, monoalkyl maleic acid, monoalkyl itaconic acid, monoalkyl fumaric acid and the like.

If the proportion of these ethylenically unsaturated carboxylic acid-containing monomers in the copolymer is less than 2% by weight of the total amount, the water solubility of the resulting copolymer will be insufficient, and conversely 4
If it exceeds 0% by weight, the drying property becomes insufficient, the film becomes hard, and the curl improving effect is deteriorated. Therefore, these ethylenically unsaturated carboxylic acid-containing monomers have 2 to 4% by weight.
It is necessary to copolymerize in the range of 0% by weight.

On the other hand, examples of the alkyl ester monomer of (meth) acrylic acid constituting the water-soluble copolymer used in the present invention include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate. , (Eth) butyl acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, (meth)
Stearyl acrylate and the like can be mentioned.

The proportion of these alkyl ester monomers of (meth) acrylic acid in the copolymer is adjusted in the range of 50 to 90% by weight of all the monomers.

In the present invention, among these alkyl ester monomers of (meth) acrylic acid, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, and (meth) acrylic acid-2 are particularly preferable. - having an alkyl group of C _{4 ~ 10} as ethylhexyl (meth) acrylate monomer is preferably used.

Further, other monomers copolymerizable with the above-mentioned monomers constituting the water-soluble copolymer used in the present invention include, for example, vinyl acetate, vinyl chloride, vinylidene chloride, (meth) acrylonitrile, styrene. , Ethylene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, 1,3 -Butylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, divinylbenzene, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di ( Meta) Relate, glycidyl (meth) acrylate, methylglycidyl (meth) acrylate, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N'-methylenebis (meth) Examples include acrylamide.

The proportion of these other copolymerizable monomers in the copolymer is adjusted in the range of 0 to 40% by weight based on the total monomers.

The water-soluble copolymer of the present invention is produced by a method of emulsion-copolymerizing or graft-copolymerizing each monomer as described above in the presence of an emulsifier (protective colloid), chain transfer agent, polymerization initiator, etc. in an aqueous system. However, the amount of the emulsifier used is particularly important, and the emulsifier is contained in the range of 2 to 10% by weight based on the total amount of the monomers constituting the copolymer. If the amount used is less than 2% by weight, the stability of the obtained emulsion will be insufficient and the particle size of the polymer will be large. Further, if it is used in a large amount such as more than 10% by weight, the adhesion between the undercoat layer and the release agent layer deteriorates.

Examples of the emulsifier include anionic emulsifiers such as sodium dodecylbenzene sulfonate and sulfates of alkaryl polyethers: nonionic emulsifiers such as polyoxyethylene nonylphenol ether and polyoxyethylene / polyoxypropylene block copolymers. A cationic emulsifier such as laurylpyridinium chloride or cetyltrimethylammonium bromide; a polyvinyl having at least one functional group selected from polyvinyl alcohol, a (meth) acryloyl group, a haloalkyl (meth) acryloyl group and an N-methylolacrylamide group. Examples thereof include protective colloids such as alcohol, polyacrylamide, polyethylene glycol derivatives, casein and the like.

Further, as the chain transfer agent, for example, thioglycerol,
Ethylene thioglycol, thioglycolic acid, n-dodecyl mercaptan and the like are exemplified, and as the polymerization initiator,
For example, hydrogen peroxide, potassium persulfate, ammonium persulfate or a so-called redox type polymerization initiator composed of a combination thereof with a reducing agent such as sodium sulfite and acidic sodium sulfite can be used.

In the present invention, the glass transition temperature of the water-soluble copolymer thus obtained is also important, and a water-soluble copolymer having a glass transition temperature of −60 to 20 ° C., more preferably −40 to 0 ° C. is selectively selected. used. By the way, the glass transition temperature is −
If the temperature is lower than 60 ° C, the adhesion of the film becomes too strong,
On the other hand, when the temperature is higher than 20 ° C, the obtained film becomes too hard and is not practical.

In the present invention, the glass transition temperature [Tg] of the copolymer is estimated based on the following general formula (1).

Tg: glass transition temperature of the copolymer Tg _i : glass transition temperature of the i-th monomer homopolymer W _i : weight fraction of the i-th monomer The specific water-soluble copolymer as described above is a copolymer. The carboxyl group in the solution is neutralized with an appropriate alkaline substance such as sodium hydroxide, potassium hydroxide, ammonia, and various primary, secondary, and tertiary amines to prepare an aqueous solution, which is a base paper for release paper. Is coated or impregnated to form an undercoat layer on at least one surface of the polymer, but the greater the penetration into the base paper, the better the curl prevention effect. Therefore, the particle size of the polymer should be adjusted to 0.3 μm or less. Is desirable. The concentration of the aqueous solution is adjusted to 5 to 60% by weight, preferably 10 to 45% by weight before use.

In such an undercoat aqueous solution, for example, a cellulose derivative such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, dextrin, acid-treated starch, oxidized starch, cross-linked starch, starch ester, and graft within a range that does not impair the desired effects of the present invention. Various water-soluble natural polymers such as starch derivatives such as copolymer starch; polyhydric alcohols such as ethylene glycol, glycerin, trimethylolpropane and diethylene glycol, water-soluble polyalkylene glycols such as polyethylene glycol and polypropylene glycol Plasticizer;
Crosslinking agents such as urea / formaldehyde resins, melamine / formaldehyde resins, polyamide / polyamine / epichlorohydrin resins, polyacrylamide resins, epoxy resins; further inorganic salts; fillers; defoamers; wetting agents; leveling agents; curing agents; A viscous agent; a film-forming aid and the like can be added as appropriate.

The method for applying or impregnating the undercoat aqueous solution to the release paper base paper is not particularly limited, and for example, an air knife coater,
Various devices such as a roll coater, a gravure coater, a bar coater, a blade coater, and a size press coater are appropriately used. The amount of coating or impregnation is 0.
It is preferably adjusted with from 1 to 20 g / m ² approximately, especially in the range of about 1 to 10 g / m ² is desirable.

By subjecting the undercoat layer surface thus formed to corona discharge treatment, the adhesion between the undercoat layer and the release agent layer is improved,
Such treatment is one of the preferred embodiments of the present invention.
Further, the specific electric resistance value of the surface of the undercoat layer is 1.0 × 10 ¹⁰
When it is larger than Ω, for example, when it is formed on an adhesive paper and recorded by an electrostatic recording device or the like, there is a possibility that a paper passing defect or a transfer defect may occur due to the influence of static electricity. Therefore, the specific electric resistance value of the undercoat layer surface is 1 It is desirable to adjust to less than 0.0 × 10 ¹⁰ Ω.

In the release paper of the present invention, the base paper has a normal basis weight of 30.
Various fiber sheets having a thickness of about 300 to 300 g / m ² and a thickness of about 30 to 300 μm are used.

The release agent applied on the undercoat layer is not particularly limited, and various silicone compounds, fluorine compounds and the like are applied according to a conventional method.

The release paper of the present invention thus obtained is obtained by copolymerizing a base paper with an acrylic resin having a specific monomer composition and a glass transition temperature using a specific amount of an emulsifier, and neutralizing with an alkaline substance. Since an undercoat layer containing a water-soluble copolymer as the main component having an average particle size is formed, curling is particularly effectively prevented, and a pressure-sensitive adhesive paper excellent in paper-passability and copyability is constructed. Is something that can be done.

The method for forming an adhesive paper using the release paper of the present invention is not particularly limited, and for example, a solvent-based adhesive, an emulsion-based adhesive, a hot-melt adhesive, etc. may be used according to a conventional method. Adhesive paper is appropriately finished by applying, drying, and controlling the humidity.

[Examples] The present invention will be described in more detail with reference to examples below, but is not of course limited thereto, and the coating amount, the number of parts, the mixing ratio, and the like in the examples are all solids. Indicated.

Example 1 Emulsifying monomer consisting of 270 g of butyl acrylate, 15 g of acrylic acid, 113 g of acrylonitrile, 2 g of N-methylolacrylamide, 5 g of polyoxyethylene nonylphenol ether emulsifier, 5 g of oxyethylene / oxypropylene block polymer emulsifier, and 170 g of ion-exchanged water. A mixed solution [I] was prepared.

Next, stirrer, cooler, dropping funnel, nitrogen suction pipe,
To a two-necked flask equipped with a thermometer, 240 g of ion-exchanged water, 2 g of a 1: 1 mixture of the emulsifier and 0.8 g of potassium persulfate were charged, and the temperature was raised to 70 ° C. while substituting with nitrogen. 1/6 of the emulsion monomer mixture liquid [I] was added dropwise. When the reaction rate reached 90%, the remaining emulsified monomer mixture liquid [I] was added dropwise over 2 hours for polymerization.
After completion of dropping, the reaction was completed by aging at 70 ° C. for 2 hours.

After completion of the aging, the contents of the flask were cooled to 60 ° C., an aqueous solution of sodium hydroxide was added to carry out a neutralization reaction, and after completion of the reaction, strong stirring was carried out to obtain a water-soluble copolymer used in the present invention.

The glass transition temperature of the obtained water-soluble copolymer was −29 ° C., and the average particle size was 0.3 μm.

To 75 parts by weight of this water-soluble copolymer, 24 parts by weight of an aqueous solution of oxidized starch (trade name: Ace C, manufactured by Oji Corn Starch Co., Ltd.) was added, and further colloidal silica (trade name: Snowtex 30, manufactured by Nissan Chemical Industries, Ltd.). ) Was added to prepare an undercoat aqueous solution having a concentration of 30% by weight.

The above undercoating aqueous solution was applied to a woodfree paper having a basis weight of 40 g / m ² and a thickness of 55 μm by a bar coater so that the dry weight was 5 g / m ^2, and dried at 120 ° C. for 1 minute to obtain a release base paper. The specific electric resistance of the surface of the release base paper was 2 × 10 ⁸ Ω.

The surface of the release base paper is oscillated at a frequency of 30 kHz and an output voltage of 3
Corona discharge treatment at 4 KV, output 0.7 KW, treatment speed 4 m / min, and coating of commercially available silicone release agent on the treated surface,
The release paper of the present invention was obtained by drying.

The release base paper had a very good barrier property against the release agent coating liquid, and a uniform light release release paper was obtained. Further, when a pressure-sensitive adhesive paper was produced using this release paper, curling did not occur, and a pressure-sensitive adhesive paper having extremely good paper-passability and copyability in a copying machine was obtained.

Example 2 Emulsion monomer mixture consisting of 190 g of 2-ethylhexyl acrylate, 60 g of methyl methacrylate, 120 g of acrylonitrile, 30 g of acrylic acid, 8 g of polyoxyethylene alkylphenyl sulfate emulsifier, 8 g of sodium dioctyl sulfosuccinate emulsifier, 170 g of ion-exchanged water. Liquid [I] was prepared.

Polymerization was carried out in the same manner as in Example 1 except that the obtained emulsion monomer mixture [I] was used, and the reaction was completed by aging at 70 ° C. for 2 hours.

After completion of aging, the contents of the flask were cooled to 50 ° C., an aqueous solution of potassium hydroxide was added to carry out a neutralization reaction, and after completion of the reaction, strong stirring was carried out to obtain a water-soluble copolymer [A] used in the present invention. It was The water-soluble copolymer [A] thus obtained had a glass transition temperature of -6 ° C and an average particle size of 0.2 µm.

Next, 100 g of butyl acrylate, 250 g of methyl methacrylate, 50 g of acrylic acid, 5 g of polyoxyethylene nonylphenol ether emulsifier, 5 g of oxyethylene, oxypropylene block polymer emulsifier,
Emulsified monomer mixture liquid consisting of 170 g of ion-exchanged water [II]
Was prepared and polymerized and aged in the same manner as in Example 1.

After completion of the aging, the contents of the flask were cooled to 50 ° C., a potassium hydroxide aqueous solution was added to carry out a neutralization reaction, and after completion of the reaction, co-stirring to obtain a water-soluble copolymer [B] used in the present invention. It was The water-soluble copolymer [B] obtained had a glass transition temperature of 42 ° C. and an average particle diameter of 0.3 μm.

30 parts by weight of the water-soluble copolymer [B] was added to 70 parts by weight of the water-soluble copolymer [A] to prepare an undercoat aqueous solution having a concentration of 35% by weight.

The above undercoating aqueous solution was applied to a wood free paper having a basis weight of 50 g / m ² and a thickness of 65 μm by a blade coater so that the dry weight was 4 g / m ^2, and dried at 150 ° C. for 30 seconds to obtain a release base paper. The specific electric resistance of the surface of the release base paper was 8 × 10 ⁷ Ω.

A commercially available silicone release agent was applied to this release base paper and dried to obtain the release paper of the present invention. The release base paper had a very good barrier property against the release agent coating liquid, and a uniform light release release paper was obtained. Further, when a pressure-sensitive adhesive paper was produced using this release paper, curling did not occur, and a pressure-sensitive adhesive paper having extremely good paper-passability and copyability in a copying machine was obtained.

Example 3 Emulsion copolymerization was carried out in the same manner as in Example 2 except that a monomer mixture of 300 g of butyl acrylate, 80 g of acrylic acid and 8 g of acrylamide was used, a neutralization reaction with sodium hydroxide and the like were carried out, and the concentration was 30% by weight. A water-soluble copolymer was obtained. The glass transition temperature of this water-soluble copolymer was −36 ° C., and the average particle size was 0.2 μm.

To 60 parts by weight of this water-soluble copolymer, 30 parts by weight of the water-soluble copolymer [B] of Example 2, 5 parts by weight of polyethylene glycol and an epoxy compound (trade name: Denacol EX-85
1, Nagase Chemical Industry Co., Ltd.) 5 parts by weight to add a concentration of 25
A wt% undercoat aqueous solution was prepared.

The above undercoating aqueous solution was applied to a wood free paper having a basis weight of 64 g / m ² and a thickness of 70 μm by a bar coater so that the dry weight was 7 g / m ^2, and dried at 130 ° C. for 1 minute to obtain a release base paper. The specific electric resistance of the surface of the release base paper was 9 × 10 ⁷ Ω.

The surface of this release base paper was subjected to corona discharge treatment in the same manner as in Example 1, and a commercially available silicone release agent was applied to the treated surface and dried to obtain a release paper of the present invention. In addition, the barrier property against the release agent coating liquid of this release base paper was also very good, and a uniform light release release paper was obtained. Further, when a pressure-sensitive adhesive paper was produced using this release paper, curling did not occur, and a pressure-sensitive adhesive paper having extremely good paper-passability and copyability in a copying machine was obtained.

Example 4 300 g of 2-ethylhexyl acrylate, 20 g of acrylic acid, 78 g of methyl methacrylate, 2 g of polyethylene glycol dimethacrylate, 10 g of polyoxyethylene alkylphenyl sulfate emulsifier, 10 g of dioctyl sodium sulfosuccinate emulsifier, 1 ion-exchanged water 1
An emulsified monomer mixture liquid [I] consisting of 70 g was prepared.

Polymerization was carried out in the same manner as in Example 1 except that the obtained emulsion monomer mixture [I] was used, and the reaction was completed by aging at 70 ° C. for 2 hours. The glass transition temperature of this copolymer is -28.
It was ℃.

Next, 25 g of butyl acrylate and 6 of acrylonitrile
0 g, acrylic acid 15 g, polyoxyethylene alkylphenyl sulfate emulsifier 3 g, sodium dioctyl sulfosuccinate emulsifier 3 g, ammonium persulfate 0.2
g. An emulsion monomer mixed liquid [II] consisting of 100 g of ion-exchanged water was prepared.

In the previously polymerized copolymer, the temperature in the flask was adjusted to 70 ° C.
While maintaining the above, the emulsion monomer mixture liquid [II] was appropriately placed for 1 hour, reacted for 3 hours, and then cooled to obtain a graft copolymer. An aqueous solution of potassium hydroxide was added to this to carry out a neutralization reaction, followed by vigorous stirring to obtain a water-soluble graft copolymer. The average particle size of the obtained water-soluble graft copolymer was 0.1 μm.

To 90 parts by weight of this water-soluble copolymer, 8 parts by weight of polyethylene glycol and 2 parts by weight of colloidal silica (trade name: Snowtex 30, manufactured by Nissan Chemical Industries, Ltd.) were added to give a concentration of 3
A 3 wt% undercoat aqueous solution was prepared.

This undercoating aqueous solution was applied to a high-quality paper having a basis weight of 40 g / m ² and a thickness of 55 μm by a blade coater so that the dry weight was 5 g / m ^2, and dried at 120 ° C. for 1 minute to obtain a release base paper. The specific electric resistance of the surface of the release base paper was 5 × 10 ⁸ Ω.

The surface of this release base paper was subjected to corona discharge treatment in the same manner as in Example 1, and a commercially available silicone release agent was applied to the treated surface and dried to obtain a release paper of the present invention. In addition, the barrier property against the release agent coating liquid of this release base paper was also very good, and a uniform light release release paper was obtained. Further, when a pressure-sensitive adhesive paper was produced using this release paper, curling did not occur, and a pressure-sensitive adhesive paper having extremely good paper-passability and copyability in a copying machine was obtained.

Comparative Example 1 Styrene-maleic acid copolymer (trade name: Script Set 520, manufactured by Monsanto Co., Ltd.) as an undercoating aqueous solution was applied to a woodfree paper having a basis weight of 50 g / m ² and a thickness of 65 μm with a bar coater to give a dry weight of 5 g / m 2. ^It was applied so that it would be ^2, and dried at 150 ° C. for 1 minute to obtain a release base paper.

The aqueous undercoating solution had a concentration of 12% by weight and a glass transition temperature of 156 ° C. The specific electric resistance of the surface of the obtained release base paper was 8 × 10 ⁸ Ω.

A commercially available silicone release agent was applied to this release base paper and dried to obtain a release paper. The release base paper had a good barrier property against the release agent coating liquid, but when an adhesive paper was produced using the release paper obtained, curling occurred remarkably, and it was suitable for paper-passing and copying in a copying machine. Only the extremely bad adhesive paper of No. 1 was obtained.

Comparative Example 2 120 g of isopropyl alcohol and 56 g of water were charged into a four-necked flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction tube, and a thermometer, and heated to a reflux temperature under nitrogen stream with stirring. . Butyl acrylate 60g, acrylic acid 30g, acrylonitrile 1 in the dropping funnel
0 g, 2,2'-azobisisobutyronitrile 0.5 g
Was charged, and this homogeneous solution was added dropwise over 2 hours, followed by aging for 2 hours. The polymerization and aging were carried out at a reflux temperature, and after the aging, the contents of the flask were cooled to 50 ° C. and an aqueous sodium hydroxide solution was added to carry out a neutralization reaction. After completion of the neutralization reaction, the temperature was raised to remove isopropyl alcohol from the system by azeotropic distillation with water, and after cooling, the concentration was adjusted to 3
It was diluted to 0% by weight to obtain a water-soluble copolymer. The glass transition temperature of the obtained water-soluble copolymer was -11 ° C.

To 80 parts by weight of this water-soluble copolymer, 18 parts by weight of an aqueous solution of oxidized starch (trade name: Ace C, manufactured by Oji Corn Starch) was added, and further colloidal silica (trade name: Snowtex 30, manufactured by Nissan Chemical Industries, Ltd.). 2 parts by weight was added to prepare an undercoat aqueous solution having a concentration of 24% by weight.

The above undercoating aqueous solution was applied to a high quality paper having a basis weight of 50 g / m ² and a thickness of 65 μm with a bar coater at a line speed of 40 m / min, an oven length of 20 m, a drying temperature of 150 ° C. and a dry weight of 7 g / m ² to form a release machine paper. Obtained. The specific electric resistance of the surface of the release base paper was 6 × 10 ⁸ Ω. In addition, the dryness of the undercoat aqueous solution was poor, the paper was frequently cut, and the productivity was extremely poor.

A commercially available silicone release agent was applied to this release base paper and dried to obtain a release paper. The release base paper had good barrier properties against the release agent coating liquid, but the adhesive paper produced using the obtained release paper had extremely poor suitability for paper passing in a copying machine.

Comparative Example 3 Anionic emulsifier (sodium lauryl sulfate) 0.2
g, ammonium persulfate 0.5 g, and water 125 g are put in a reactor, heated with stirring and kept at 75 ° C., and a mixture consisting of butyl acrylate 85 g, methyl methacrylate 7 g, acrylic acid 5 g, and β-hydroxyethyl methacrylate 3 g is continuously added. Over 3 hours. 7 after addition
The reaction was completed by holding at 5 ° C for 3 hours. The glass transition temperature of the obtained emulsion was −45 ° C., and the average particle size was 0.6 μm.

To 75 parts by weight of this emulsion, 25 parts by weight of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Corn Starch Co., Ltd.) was added to prepare an undercoating aqueous solution having a concentration of 25% by weight. The stability of this aqueous solution was poor, and the tendency for starch to settle was observed.

The above base coat aqueous solution was applied to a wood free paper having a basis weight of 50 g / m ² and a thickness of 65 μm by a bar coater so that the dry weight was 5 g / m ^2, and dried at 120 ° C. for 1 minute to obtain a release base paper. ,
Aggregates were observed on the surface of the release base paper. The specific electric resistance of the surface of the release base paper was 4 × 10 ⁸ Ω.

A commercially available silicone release agent was applied to this release base paper and dried to obtain a release paper. However, the release base paper has insufficient barrier agent coating liquid barrier properties, and an adhesive paper produced using this release paper. Caused peeling failure.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-98186 (JP, A) JP-B 57-54598 (JP, B2) Emulsion / Latex Handbook Editing Committee, “Emulsion Latex Handbook” SAK 57 -2-5 Taiseisha Co., Ltd. P. 241-246 "Resin Processing Separate Volume Recent Emulsion Latex Industry" Sho 37-10-10 P. 48-49

Claims (3)

[Claims] 1. A release paper comprising a base paper and a release agent layer provided on at least one surface of the base paper with an undercoat layer interposed therebetween.
Copolymer having a glass transition temperature of −60 to 20 ° C., which is a water-soluble copolymer having a weight average content of 0.3 μm or less by neutralizing a carboxyl group with an alkaline substance. Release paper characterized by being. (a) Ethylenically unsaturated carboxylic acid-containing monomer: 2 to 40
Wt% (b) (meth) C _{4 ~ 10} alkyl ester monomers of acrylic acid: 50 to 90 wt% (c) these monomers and other copolymerizable monomers: 0-4
0% by weight " 2. The release paper according to claim 1, wherein the surface of the undercoat layer is subjected to corona discharge treatment. 3. The specific electric resistance of the surface of the undercoat layer is 1.0 × 1.
The release paper according to claim (2), which has a resistance of 0 ¹⁰ Ω or less.