JPH10259597A - Substrate for release paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a substrate for a sheet of release paper, capable of carrying out the direct coating with a solution of a silicone, etc., in an organic solvent without requiring a polyethylene laminate, having excellent releasability and further capable of recovering the used substrate and reutilizing the recovered substrate for a papermaking process. SOLUTION: This substrate for a sheet of release paper comprises an undercoating layer consisting essentially of a pigment (kaolin, etc.) and a binder resin, which contains at least polyvinyl alcohol and an aqueous emulsifiable copolymer, containing 0.5-10wt.% nonionic emulsifying agent and prepared by carrying out the emulsion copolymerization of (a) 5-90wt.% of a 4-18C alkyl ester monomer of (meth)acrylic acid, (b) 1-20wt.% of an ethylenically unsaturated carboxylic acid-containing monomer and (c) 0-90wt.% of other monomers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a base material for release paper. More specifically, the present invention relates to a base material of a release paper of an adhesive tape mainly used for packing an adhesive label, an adhesive seal, a packaging container, and the like to be attached to the surface of a product or a product container. More specifically, the present invention relates to a reusable release paper base material which has an excellent solvent barrier property, does not require lamination of polyethylene on base paper, and can be produced by directly applying an organic solvent solution containing a release agent such as silicone. Things.

[0002]

2. Description of the Related Art Conventionally, a base material of a release paper has been used as a release agent or a release agent in order to improve the releasability of a label or a seal upper paper or the releasability of a tape wound in a cylindrical shape. For example, a release layer is formed by applying a solution in which a silicone resin is dissolved in an organic solvent such as toluene. As a base material of the release paper, papers such as a polyethylene laminate type, a glassine type, a super calendered type, and a clay coated type are known.

[0003] Among these base materials, the penetration of the above-mentioned silicone coating solution onto the surface of high quality paper, matte paper, kraft paper or the like made mainly of wood pulp is suppressed as much as possible, and the releasability is maximized. Extrusion method, thickness of 10
It is common to form a polyethylene film layer of about 25 microns. However, the release paper substrate manufactured by the above-described method of laminating polyethylene has a strong continuous film made of polyethylene and is insoluble in water. Recycling is not possible and is a major problem in industrial waste disposal today.

On the other hand, there has been attempted a method in which glassine paper or the like made of extremely beaten pulp is used as a base paper, and an organic solvent solution of silicone is directly coated on the base paper without laminating polyethylene. However, such base paper has a drawback that it is not easily dispersed in water because pulp as a raw material is extremely beaten and used, and furthermore, the bonding between fibers is strengthened by calendering or the like. Furthermore, even if it can be dispersed in water by strengthening the mechanical force and introducing chemical treatment, it is difficult to reuse it as a raw material for general paper because the fibers are significantly damaged by the strengthening of the beating treatment. is there.

[0005] Further, even in a super calendered craft type substrate which has been densified by mechanical pressure, it is still impossible to completely close the minute voids, and furthermore, when the organic solvent solution in which silicone is dissolved comes into contact, At the same time, swelling of the base material occurs, and it is impossible to completely block the penetration of the excellent silicone organic solvent solution comparable to the case of laminating polyethylene (hereinafter referred to as solvent barrier property).

On the other hand, JP-B-1-35959 and JP-A-4-23876 disclose base paper for a release paper obtained by directly applying a silicone solution without laminating polyethylene. There is disclosed a clay coat type substrate in which a coating mainly composed of an inorganic pigment and an organic adhesive is applied to the surface to form an undercoat layer. In such a base material, the effect of covering the minute voids (hereinafter referred to as pinholes) in the base paper with the undercoat layer is observed. However, there are countless minute voids between the pigments of the undercoat layer, and the organic solvent solution of silicone permeates into the base paper through fine continuous holes. For this reason, a large amount of expensive silicone must be applied as compared with the method of laminating with polyethylene.

For the above reasons, there is a strong demand for a base material for release paper which has an excellent solvent barrier property comparable to that of polyethylene laminated paper and which can be directly coated with an organic solvent solution of a silicone resin. A substrate which can sufficiently satisfy these requirements has not been provided yet.

[0008]

DISCLOSURE OF THE INVENTION The present invention does not require a polyethylene laminate, can directly apply an organic solvent solution such as silicone, has excellent releasability, and recovers a used substrate. The present invention also provides a release paper substrate that can be reused in the papermaking process.

[0009]

Means for Solving the Problems We have excellent solvent barrier properties comparable to this without laminating polyethylene on base paper, and can be easily disaggregated and reused in water. As a result of intensive studies on the material and coating method of the barrier layer formed on the base paper substrate in order to obtain a base material for a release paper, a release paper base material that can satisfy these requirements has been finally obtained.

That is, the present invention relates to a release paper in which an undercoat layer and a release agent layer are sequentially provided on at least one surface of a base paper,
The undercoat layer contains a pigment and a binder resin as main components, the binder resin contains at least polyvinyl alcohol and an aqueous emulsion copolymer, and the aqueous emulsion copolymer contains a nonionic (nonionic) emulsifier in an amount of 0.5%. containing 10 wt%, monomer a) (meth) C ₄ ~ ₁₈ alkyl ester monomers of acrylic acid having the following composition: 5 to 90% by weight, b) an ethylenically unsaturated carboxylic acid-containing monomers: 1-20
% By weight, c) Other monomers copolymerizable with these monomers: 0-9
0% by weight in emulsion copolymerization.

In the present invention, the undercoat layer may contain polyvinyl alcohol in an amount of 30 to 100 parts by weight of the solid content of the pigment.
It is a base material for release paper containing 500 parts by weight and 10 to 100 parts by weight of an aqueous emulsion copolymer. Furthermore, the present invention provides
The base material for a release paper, wherein the pigment constituting the undercoat layer is kaolin.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result of detailed analysis of the function of polyethylene on a conventional substrate laminated with polyethylene, the present inventors found that wood pulp was produced as a main raw material and that the pore diameter was 0.1%. (1) To base paper which has fine voids of ~ 1.0 micron and is porous and rich in liquid absorption
A barrier layer is formed that can simultaneously suppress permeation of the organic solvent solution of silicone and (2) pinholes having a pore diameter of 1 to 200 microns scattered in the base paper. Has been found to be an effective means of obtaining a substrate having a solvent barrier property comparable to a polyethylene laminate substrate.

The present inventors have conducted intensive studies to establish the above means, and as a result, pigments and binder resins are mainly used as materials capable of simultaneously achieving the function of preventing the penetration of the silicone organic solvent solution and the function of blocking the pinholes. As a component, and the binder resin contains at least polyvinyl alcohol and an aqueous emulsion copolymer, and the aqueous emulsion copolymer contains 0.5 to 10% by weight of a nonionic emulsifier, and a monomer having the following composition a) (meth) C ₄ ~ ₁₈ alkyl ester monomers of acrylic acid: 5 to 90 wt%, b) an ethylenically unsaturated carboxylic acid-containing monomers: 1-20
% By weight, c) Other monomers copolymerizable with these monomers: 0-9
0% by weight, emulsion-copolymerized, and the content of polyvinyl alcohol and aqueous emulsion copolymer is maintained at a specific ratio with respect to the pigment, whereby the effect can be further enhanced. It has been found that is a kaolin that satisfies the above requirements and exhibits an excellent effect, and has completed the present invention.

In the present invention, the ionicity of the aqueous emulsion copolymer constituting the undercoat layer is very important in terms of the function of preventing the penetration of the silicone organic solvent solution and the function of blocking the pinhole. Furthermore, it is necessary to include a pigment and polyvinyl alcohol as essential components. The amount of the aqueous emulsion copolymer to be used is 5 to 150 parts by weight, particularly preferably 10 to 100 parts by weight, per 100 parts by weight of the pigment. If the amount is less than 5 parts by weight, the effect of the combined use with polyvinyl alcohol is poor, and if it exceeds 150 parts by weight, the film does not become hard and the pinhole sealing effect is excellent, but the penetration preventing effect is inferior.

If the aqueous emulsion copolymer is nonionic,
There is no mutual bonding with the pigment and polyvinyl alcohol, and the viscosity of the paint and the generation of aggregates are suppressed. In addition, the nonionic aqueous emulsion copolymer has excellent compatibility with the pigment and excellent film-forming properties at low temperatures, and polyvinyl alcohol forms a strong film. In other words, the nonionic aqueous emulsion copolymer and pigment instantaneously form a film, pinholes on the substrate are caught, and then polyvinyl alcohol has excellent coverage and a strong film to penetrate the substrate. Suppresses and exhibits solvent barrier properties comparable to polyethylene laminated substrates. However, if the aqueous emulsion copolymer is ionic, it is mutually bonded to pigments and the like, forming aggregates, becoming a cage or high viscosity, and has fluidity, coating properties, and film forming properties on a substrate. Become scarce.

Therefore, it is necessary to adjust the ionicity of the aqueous emulsion copolymer to a nonionic property so that the desired effects of the present invention are exhibited.

The ethylenically unsaturated carboxylic acid-containing monomer constituting the specific aqueous emulsion copolymer used in the present invention includes, for example, acrylic acid, methacrylic acid,
Crotonic acid, maleic acid, itaconic acid, fumaric acid, monoalkyl fumaric acid and the like.

The proportion of these ethylenically unsaturated carboxylic acid-containing monomers in the copolymer is 1% by weight of all monomers.
When the content is less than 10, the dispersion stability of the obtained copolymer becomes insufficient, and when it exceeds 20% by weight, the drying property becomes insufficient. It is necessary to copolymerize in the range of 1 to 20% by weight.

Meanwhile, as the C ₄ ~ ₁₈ alkyl ester monomers of the present invention constituting the aqueous copolymer used in the (meth) acrylic acid, for example, (meth) acrylate, butyl (meth) hexyl acrylate Octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Lauryl (meth) acrylate, stearyl (meth) acrylate and the like can be mentioned. Occupying in the copolymer the proportion of C ₄ ~ ₁₈ alkyl ester monomers of these (meth) acrylic acid is adjusted in the range of 5 to 90 wt%.

In the present invention, among the C ₄ ~ ₁₈ alkyl ester monomers of these (meth) acrylic acid are preferably used, especially butyl acrylate, from the viewpoint of such copolymerizable acrylic acid 2-ethylhexyl .

Other monomers copolymerizable with the above-mentioned monomers constituting the aqueous copolymer used in the present invention include, for example, methyl (meth) acrylate, (meth)
Ethyl acrylate, propyl (meth) acrylate, vinyl acetate, vinyl chloride, vinylidene chloride, (meth) acrylonitrile, styrene, ethylene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, di (meth) acrylate Triethylene glycol acrylate, (poly) ethylene glycol (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, di (meth) acrylate
Acrylic acid (poly) propylene glycol, di (meth)
1,3-butylene glycol acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, divinylbenzene, 1,4-butanediol di (meth) acrylate, (meth) Glycidyl acrylate, methyl glycidyl (meth) acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth)
Acrylamide, N, N'-methylenebis (meth) acrylamide and the like can be mentioned.

The proportion of these other copolymerizable monomers in the copolymer is adjusted in the range of 0 to 90% by weight.

In the present invention, among these other monomers capable of copolymerization, in particular, methyl (meth) acrylate, (meth) acrylonitrile, (meth) acrylamide, etc., have a glass transition temperature, solvent resistance, It is also preferably used in terms of heat resistance and the like.

The aqueous emulsion copolymer of the present invention is produced by a method of emulsion-copolymerizing the above monomers in an aqueous system in the presence of an emulsifier, a chain transfer agent, a polymerization initiator and the like. The type is important. That is, in the present invention, a nonionic emulsifier is selectively used. Specific examples thereof include polyoxyethylene derivatives such as polyoxyethylene alkylphenyl ether and polyoxyethylene sorbitan fatty acid ester, oxyethylene / oxypropylene / block polymer, sorbitan fatty acid ester, and fatty acid monoglyceride.

The amount of the emulsifier used is in the range of 0.5 to 10% by weight based on the monomers constituting the copolymer. If the amount is less than 0.5% by weight, the particle size of the polymer becomes large, and the stability of the obtained emulsion becomes insufficient. When used in a large amount as the amount exceeds 10% by weight, the adhesion between the undercoat layer and the release agent layer decreases.

Examples of the chain transfer agent include thioglycerol, ethylene thioglycol, thioglycolic acid, n-dodecyl mercaptan and the like. Examples of the polymerization initiator include hydrogen peroxide, potassium persulfate, ammonium persulfate and the like. A so-called redox polymerization initiator comprising a combination of these with a reducing agent such as sodium zincate or sodium acid sulfite is exemplified.

The specific aqueous copolymers as described above are capable of converting a carboxyl group in the copolymer to a suitable one such as sodium hydroxide, potassium hydroxide, ammonia, various primary, secondary and tertiary amines. It is stabilized by neutralization with an alkaline substance, and has a concentration of 20 to 60% by weight, preferably 30 to 60% by weight.
It is used after being adjusted to about 50% by weight.

The pigment used in the barrier layer in the present invention is not particularly limited.
It can be appropriately selected from inorganic pigments such as kaolin, talc, titanium dioxide, and aluminum hydroxide, but from the viewpoint of the solvent barrier property, kaolin, a plate-like pigment capable of forming a dense barrier layer, is preferred.

As for the polyvinyl alcohol, the degree of saponification and the degree of polymerization are appropriately selected and used. For example, various modified polyvinyl alcohols such as carboxyl group-modified and acetoacetyl group-modified can also be used effectively. The number of parts to be used is 30 to 50 parts by weight per 100 parts by weight of the pigment.
When the amount is less than 30 parts by weight, the effect of preventing pinholes with respect to the solvent is high, but the effect of preventing penetration is poor. If it exceeds 500 parts by weight, the effect of preventing penetration is exhibited, but the effect of preventing pinholes is low. Furthermore, the adhesiveness of the film becomes too strong, and blocking and the like become a problem, which is not preferable.

The base paper used in the present invention is a hardwood bleached clad.
Chemical pulp such as soft pulp, softwood bleached kraft pulp, etc.
Use mechanical pulp such as GP, RGP, TMP as raw material
Fourdrinier multi-cylinder paper machine, Fourdrinier Yankee type paper machine or
High quality paper, medium quality paper, single gloss paper and black paper
It includes acid paper such as raft paper and neutral paper.
Paper strength enhancer, sizing agent, filler, yield improver, etc. in base paper
May be included. Especially limited
The base paper is 50-150g / m ^Twodegree
Is adopted.

The equipment for applying the undercoat layer to the base paper includes a size press, a gate roll coater, a bar coater,
It can be arbitrarily selected from a roll coater, an air knife coater, a blade coater and the like. Further, in consideration of the filling effect and the price of the coating material, it is desirable that the barrier layer formed on the base paper is prepared so as to be coated at an absolute dry weight of ² to ²⁰ g / m ² .

The undercoat layer coating liquid of the present invention is an aqueous coating liquid containing an aqueous adhesive as a main component. If necessary, a dispersing agent, a coloring agent, a waterproofing agent, a lubricant, a preservative, and the like can be used. May be blended.

The coating liquid for forming the barrier layer may be applied to the base paper by two or more coating operations. As described above, the silicone is usually dissolved in an organic solvent such as toluene or hexane and applied. However, as described above, the undercoat layer of the present invention can exhibit excellent barrier properties to the monomer even in a solventless system in which the silicone and the monomer are mixed and cured with ultraviolet rays or electron beams as described above. it can.

Since the release paper using the base material of the present invention does not have a laminate layer of polyethylene release paper and does not have a silicone release agent penetrating therein, it can be easily subjected to a papermaking material recycling step after recovery. . That is, when put into water in the regeneration step, the undercoat layer separates from the base paper, so that only the pulp can be easily collected and reused. In addition, since the recycled pulp does not contain water-repellent silicone, the silicone does not enter the papermaking process of printing paper and the like, and does not cause trouble such as repelling.

[0035]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited by these examples. In addition, the coating amount, the number of copies, the mixing ratio, and the like in the examples are all represented by solid contents. Further, “parts” indicates “parts by weight” unless otherwise specified.

Example 1 270 g of butyl acrylate, 16 g of acrylic acid, 114 g of acrylonitrile, 10 g of a polyoxyethylene octylphenyl ether emulsifier (trade name "Emulgen 810" manufactured by Kao Corporation) (ionic: nonionic), ion An emulsion monomer mixture {A} consisting of 170 g of exchanged water was prepared.

Next, 240 g of ion-exchanged water, 2 g of the above-mentioned emulsifier, and 0.8 g of potassium persulfate were charged into a 2 L four-necked flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction tube, and a thermometer, followed by purging with nitrogen. After the temperature was raised to 70 ° C., 1/6 of the above-mentioned emulsified monomer mixture {A} was added dropwise. When the reaction rate reached 90%, the remaining emulsified monomer mixture {A} was dropped over 2 hours to polymerize. After completion of the dropwise addition, the mixture was aged at 70 ° C. for 2 hours to complete the reaction.

After the completion of aging, the contents of the flask were cooled to 40 ° C., a neutralization reaction was carried out by adding an aqueous solution of sodium hydroxide, and after completion of the reaction, the mixture was vigorously stirred to obtain the aqueous emulsion copolymer (1) used in the present invention. ) Got. (Emulsifier amount: 3.0% by weight)

As a coating liquid, a coating liquid prepared as an undercoat layer having the following composition was used, and was coated on a high quality base paper of 80 g / m ^{2 by} a bar coater to a dry weight of 5 g / m ² and dried. A coated paper having a later moisture content of 5% was obtained. Component Weight Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts Aqueous emulsion copolymer (1) 25 parts Polyvinyl alcohol (trademark: PVA203, manufactured by Kuraray) 125 parts Oxidized modified starch (trademark: Oji Ace A, Oji) Constarch) 25 parts

Example 2 190 g of 2-ethylhexyl butyl acrylate, 60 g of methyl methacrylate, 120 g of acrylonitrile, 30 g of acrylic acid, polyoxyethylene derivative emulsifier 1
0g (trade name "Emulgen A-6" manufactured by Kao Corporation)
0 ") (ionic: non-ionic), ion-exchanged water 170
g of an emulsion monomer mixture {B} was prepared.

Next, 240 g of ion-exchanged water, 2 g of the above-mentioned emulsifier, and 0.8 g of potassium persulfate were charged into a 2 L four-necked flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction tube, and a thermometer, followed by purging with nitrogen. After the temperature was raised to 70 ° C., 1/6 of the above-mentioned emulsified monomer mixture {B} was added dropwise. When the reaction rate reached 90%, the remaining emulsion monomer mixture {B} was dropped over 2 hours to polymerize. After completion of the dropwise addition, the mixture was aged at 70 ° C. for 2 hours to complete the reaction.

After completion of the aging, the contents of the flask were cooled to 40 ° C., a neutralization reaction was carried out by adding an aqueous sodium hydroxide solution, and after completion of the reaction, the mixture was vigorously stirred to obtain the aqueous emulsion copolymer (2) used in the present invention. ) Got. (Emulsifier amount: 3.0% by weight)

As a coating solution, a coating solution prepared as an undercoat layer having the following composition was used, and was coated on a high-quality base paper of 80 g / m ^{2 by} a bar coater to a dry weight of 5 g / m ² and dried. A coated paper having a later moisture content of 5% was obtained. Component weight Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts Aqueous emulsion copolymer (2) 10 parts Polyvinyl alcohol (trademark: PVA203, manufactured by Kuraray) 80 parts

Example 3 In Example 1, polyvinyl alcohol (trademark: PVA) was used.
203, manufactured by Kuraray Co., Ltd.), and a coated paper was obtained in the same manner as in Example 1 except that the amount was changed to 480 parts.

Example 4 In Example 1, polyvinyl alcohol (trade name: PVA) was used.
203, manufactured by Kuraray Co., Ltd.), and a coated paper was obtained in the same manner as in Example 1 except that the composition was changed to 40 parts.

Example 5 The aqueous emulsion copolymer (1) prepared in Example 1 was mixed with 9
A coated paper was obtained in the same manner as in Example 1 except that the amount was changed to 0 parts.

COMPARATIVE EXAMPLE 1 The coating liquid used was an undercoat layer having the following composition.
The coated paper was coated on a high quality base paper of 80 g / m ^{2 by} a gate roll coater so that the dry weight was 5 g / m ^2, and the coated paper having a moisture content of 5% after drying was obtained. Component weight Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts Aqueous emulsion copolymer (1) 75 parts

Comparative Example 2 As a coating liquid, an undercoat layer having the following composition was prepared.
The coated paper was coated on a high quality base paper of 80 g / m ^{2 by} a gate roll coater so that the dry weight was 5 g / m ^2, and the coated paper having a moisture content of 5% after drying was obtained. Component weight Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts Polyvinyl alcohol (trademark: PVA203, manufactured by Kuraray) 75 parts

Comparative Example 3 270 g of butyl acrylate, 16 g of acrylic acid, 114 g of acrylonitrile, 10 g of polyoxyethylene nonyl phenyl ether sodium ethyl emulsifier (Kao Corporation)
An emulsion monomer mixture {C} composed of 170 g of ion-exchanged water was prepared (trade name: Ramtell E-975) (ionic: anionic).

Next, 240 g of ion-exchanged water, 2 g of the above-mentioned emulsifier, and 0.8 g of potassium persulfate were charged into a 2 L four-necked flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction tube, and a thermometer. After the temperature was raised to 70 ° C., 1/6 of the emulsified monomer mixture {C} was dropped. When the reaction rate reached 90%, the remaining emulsified monomer mixture {C} was dropped over 2 hours to polymerize. After completion of the dropwise addition, the mixture was aged at 70 ° C. for 2 hours to complete the reaction.

After completion of the aging, the contents of the flask were cooled to 40 ° C., and a neutralization reaction was performed by adding an aqueous sodium hydroxide solution. After the completion of the reaction, the mixture was vigorously stirred to obtain an aqueous emulsion copolymer (3). (Emulsifier amount: 3.0% by weight)

The coating liquid was prepared by preparing an undercoat layer having the following composition, and was coated on a high quality base paper of 80 g / m ^{2 by} a bar coater at a dry weight of 5 g / m ² and dried. A coated paper having a later moisture content of 5% was obtained. Component Weight Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts Aqueous emulsified copolymer (3) 25 parts Polyvinyl alcohol (trademark: PVA203, manufactured by Kuraray) 125 parts Oxidized modified starch (trademark: Oji Ace A, Oji) Constarch) 25 parts

Comparative Example 4 270 g of butyl acrylate, 16 g of acrylic acid, 114 g of acrylonitrile, 1 g of a polyoxyethylene octylphenyl ether emulsifier (trade name "Emulgen 810" manufactured by Kao Corporation) (ionic: nonionic), ion An emulsion monomer mixture {D} consisting of 170 g of exchanged water was prepared.

Next, 240 g of ion-exchanged water, 0.2 g of the above emulsifier, and 0.8 g of potassium persulfate were charged into a 2 L four-necked flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction tube, and a thermometer. After the temperature was raised to 70 ° C. while replacing, 1/6 of the above-mentioned emulsified monomer mixture {D} was dropped. When the reaction rate reached 90%, the remaining emulsified monomer mixture {D} was dropped over 2 hours to polymerize. After completion of the dropwise addition, the mixture was aged at 70 ° C. for 2 hours to complete the reaction.

After completion of the aging, the contents of the flask were cooled to 40 ° C., and a neutralization reaction was performed by adding an aqueous sodium hydroxide solution. After the completion of the reaction, the mixture was vigorously stirred to obtain an aqueous emulsion copolymer (4). (Emulsifier amount: 0.30% by weight)

The coating solution was prepared by preparing an undercoat layer having the following composition, and was coated on a high quality base paper of 80 g / m ^{2 by} a bar coater at a dry weight of 5 g / m ² and dried. A coated paper having a later moisture content of 5% was obtained. Component Weight Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts Aqueous emulsion copolymer (4) 25 parts Polyvinyl alcohol (trademark: PVA203, manufactured by Kuraray) 125 parts Oxidized modified starch (trademark: Oji Ace A, Oji) Constarch) 25 parts

Comparative Example 5 270 g of butyl acrylate, 16 g of acrylic acid, 114 g of acrylonitrile, 60 g of a polyoxyethylene octylphenyl ether emulsifier (trade name "Emulgen 810" manufactured by Kao Corporation) (ionic: nonionic), ion An emulsified monomer mixture {E} composed of 170 g of exchanged water was prepared.

Next, 240 g of ion-exchanged water, 12 g of the above emulsifier, and 0.8 g of potassium persulfate were charged into a 2 L four-necked flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction tube, and a thermometer. After the temperature was raised to 70 ° C., 1/6 of the emulsified monomer mixture {E} was added dropwise. When the reaction rate reached 90%, the remaining emulsion monomer mixture {E} was dropped over 2 hours to polymerize. After completion of the dropwise addition, the mixture was aged at 70 ° C. for 2 hours to complete the reaction.

After completion of the aging, the contents of the flask were cooled to 40 ° C., and a neutralization reaction was performed by adding an aqueous sodium hydroxide solution. After the completion of the reaction, the mixture was vigorously stirred to obtain an aqueous emulsion copolymer (5). (Emulsifier amount: 18.0% by weight)

As the coating liquid, a coating liquid prepared as an undercoat layer having the following composition was used, and was coated on a high quality base paper of 80 g / m ^{2 by} a bar coater to a dry weight of 5 g / m ² and dried. A coated paper having a later moisture content of 5% was obtained. Component Weight Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts Aqueous emulsion copolymer (5) 25 parts Polyvinyl alcohol (trademark: PVA203, manufactured by Kuraray) 125 parts Oxidized modified starch (trademark: Oji Ace A, Oji) Constarch) 25 parts

Comparative Example 6 270 g of butyl acrylate, 3 g of acrylic acid, 114 g of acrylonitrile, 10 g of a polyoxyethylene octylphenyl ether emulsifier (trade name "Emulgen 810" manufactured by Kao Corporation) (ionic: nonionic), ion An emulsion monomer mixture {F} consisting of 170 g of exchanged water was prepared.

Next, 240 g of ion-exchanged water, 2 g of the above-mentioned emulsifier, and 0.8 g of potassium persulfate were charged into a 2 L four-necked flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction tube, and a thermometer, followed by purging with nitrogen. After the temperature was raised to 70 ° C., 1/6 of the emulsified monomer mixture {F} was added dropwise. When the reaction rate reached 90%, the remaining emulsified monomer mixture {F} was dropped over 2 hours to polymerize. After completion of the dropwise addition, the mixture was aged at 70 ° C. for 2 hours to complete the reaction.

After completion of the aging, the contents of the flask were cooled to 40 ° C., and a neutralization reaction was performed by adding an aqueous sodium hydroxide solution. After the completion of the reaction, the mixture was vigorously stirred to obtain an aqueous emulsion copolymer (6). (Amount of emulsifier: 3.1% by weight)

A coating solution prepared by preparing an undercoat layer having the following composition was coated on a high quality base paper of 80 g / m ^{2 by} a bar coater to a dry weight of 5 g / m ² and dried. A coated paper having a later moisture content of 5% was obtained. Component Weight Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts Aqueous emulsion copolymer (6) 25 parts Polyvinyl alcohol (trademark: PVA20, manufactured by Kuraray) 125 parts Oxidized modified starch (trademark: Oji Ace A, Oji) Constarch) 25 parts

Comparative Example 7 270 g of butyl acrylate, 120 g of acrylic acid, 114 g of acrylonitrile, 10 g of a polyoxyethylene octylphenyl ether emulsifier (trade name “Emulgen 810” manufactured by Kao Corporation) (ionic: nonionic),
Emulsion monomer mixture liquid {G} consisting of 170 g of ion-exchanged water
Was prepared.

Next, 240 g of ion-exchanged water, 2 g of the above emulsifier, and 0.8 g of potassium persulfate were charged into a 2 L four-necked flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction tube, and a thermometer. After the temperature was raised to 70 ° C., 1/6 of the above-mentioned emulsified monomer mixture {G} was dropped. When the reaction rate reached 90%, the remaining emulsified monomer mixture {G} was dropped over 2 hours to polymerize. After completion of the dropwise addition, the mixture was aged at 70 ° C. for 2 hours to complete the reaction.

After completion of the aging, the contents of the flask were cooled to 40 ° C., a neutralization reaction was carried out by adding an aqueous solution of sodium hydroxide, and after completion of the reaction, the mixture was vigorously stirred to obtain the aqueous emulsion copolymer (7) used in the present invention. ) Got. (Emulsifier amount: 2.4% by weight)

The coating liquid was prepared by preparing an undercoat layer of the following composition, and was coated on a high quality base paper of 80 g / m ^{2 by} a bar coater so that the dry weight was 5 g / m ² and dried. A coated paper having a later moisture content of 5% was obtained. Component Weight Kaolin (trade name: HT clay, manufactured by Engelhard) 100 parts Aqueous emulsion copolymer (7) 25 parts Polyvinyl alcohol (trade name: PVA203, manufactured by Kuraray) 125 parts Oxidized modified starch (trade names: Oji Ace A, Oji) Constarch) 25 parts

The toluene permeation prevention effect, pinhole prevention effect, and silicone permeation prevention effect of the release paper substrates obtained in the above Examples and Comparative Examples were evaluated according to the following methods. Table 1 shows the test results.

(1) Toluene-preventing effect and pinhole-preventing effect: Oil-soluble dye "Oleosol Re"
Toluene colored with "DB" (manufactured by Sumitomo Chemical Co., Ltd.) was applied, and after 2 seconds, it was wiped off with a gauze.

(2) Silicon Permeation Prevention Effect A silicone solution having the following composition was prepared. Component Weight Addition reaction type silicone (trademark: KS3752, manufactured by Shin-Etsu Chemical) 5.8 parts Platinum catalyst (trademark: CAT-PL-8, manufactured by Shin-Etsu Chemical) 0.2 parts Toluene 94 parts The above solution is placed on a paper piece. 1.0% dry by Meyer bar
g / m ^2, and the obtained surface was observed to evaluate the penetration of silicone.

[0072]

[Table 1] Note] * 1 ◎: Very good ○: Good △: Somewhat bad ×: Very bad

As is clear from Table 1, the release paper substrates of Examples 1 to 5 according to the present invention each obtained satisfactory results, but the release paper substrates of Comparative Examples 1 to 7 each showed satisfactory results. The material was unsatisfactory in any of the properties.

[0074]

The release paper substrate of the present invention has excellent solvent barrier properties comparable to a polyethylene-laminated release substrate, and is easy to use with existing paper machines and coating machines. It can be manufactured and has excellent releasability, and the used substrate can be collected and reused in the papermaking process.
It is extremely excellent in practicality.

Claims (3)

[Claims] 1. A release paper comprising a base paper and an undercoat layer and a release agent layer sequentially provided on at least one side of the base paper, wherein the undercoat layer comprises a pigment and a binder resin as main components, and the binder resin comprises at least polyvinyl alcohol and an aqueous emulsion. includes a polymer and the aqueous emulsion copolymer is a nonionic emulsifier containing 0.5-10 wt%, monomer a having the following composition) (meth) C ₄ ~ ₁₈ alkyl ester monomer of acrylic acid Body: 5 to 90% by weight, b) ethylenically unsaturated carboxylic acid-containing monomer: 1 to 20
% By weight, c) Other monomers copolymerizable with these monomers: 0-9
A base material for release paper, wherein 0% by weight of the base material is emulsion-copolymerized. 2. The release paper substrate according to claim 1, wherein the undercoat layer contains 30 to 500 parts by weight of polyvinyl alcohol and 10 to 100 parts by weight of an aqueous emulsion copolymer based on 100 parts by weight of the solid content of the pigment. . 3. The release paper substrate according to claim 1, wherein the pigment constituting the undercoat layer is kaolin.