JPS5998186A - Release sheet - Google Patents

Abstract

PURPOSE:To manufacture a release sheet having excellent barrier property to the releasing agent solution, adhesivity to the releasing agent, heat resistance, and heat-shrinkage resistance, by coating at least a surface of a substrate sheet with a releasing layer interposing a prime-coating layer therebetween. CONSTITUTION:The objective release sheet can be manufactured by coating at least a surface of (A) a sheet substrate consisting of a paper substrate, a polymer sheet, a metallic foil, etc. with (B) a primer layer composed of a soap- free acrylic resin emulsion (preferably the monomer is composed mainly of an acrylic acid ester, and added with a small amount of unsaturated carboxylic acid and acrylonitrile), and after drying, coating the coated substrate with (C) a releasing agent. A preferable example of the component (B) is an emulsion containing <=2pts.wt. of a nonionic or anionic surface active agent per 100pts.wt. of the acrylic resin by solid basis.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a release sheet comprising a release agent layer provided on at least one side of a sheet-like support via an undercoat layer.

Currently, a wide variety of release sheets are used for adhesive products such as adhesive tapes and labels, as well as for manufacturing processes of synthetic leather, molded products, and the like. The main role and required performance of the release sheet is that in the case of adhesive products, it must protect the adhesive surface of the adhesive sheet and have good releasability during use; Workability: It has good peelability and the strength of the sheet is suitable for various processes. ・Such a release sheet has a release agent layer provided on at least one side of a sheet-like support via multiple layers of undercoat. be.

As the sheet-like support, an inert polymer film, metal foil, paper base material, etc. are used. Among these sheet-like supports, it is difficult to obtain arbitrary peelability with a polymer film having an inactive surface, and its use when used alone is limited. Moreover, for polymer films and metal foils, there is no primer coating agent that has good adhesion with the release agent. Therefore, corona discharge treatment is mainly performed to improve adhesion, but the adhesion is not fully satisfactory. Not obtained.

On the other hand, for paper base materials among sheet-like supports, arbitrary release properties can be obtained by appropriately selecting the type of release agent, and stable film can be obtained by forming a uniform multi-layered undercoat film on the surface of the paper base material. It is used in many fields because it provides a release sheet with releasability. Currently, the following are widely used as undercoat layers: (2) coated with a water-soluble polymer such as polyvinyl alcohol, and (3) extrusion coated with polyethylene. however,
(1) has poor adhesion with the release agent, (2) has poor heat shrinkage resistance, and (3) has poor heat resistance. As mentioned above, conventional release sheets have various drawbacks. There is no release sheet with nine layers of undercoat that satisfies all the performances required of a wide variety of adhesive products and the performance required of release sheets through advanced processing in the manufacturing process. is strongly desired.

An object of the present invention is to improve the above-mentioned drawbacks and to provide a base material for a release sheet that has excellent release agent coating liquid barrier properties, release agent adhesion, heat resistance, and heat shrinkage resistance.

The release sheet according to the present invention is characterized in that the undercoat layer formed on at least one side of the sheet-like support is formed from a soap-free type acrylic resin emulsion.

In other words, by coating a soap-free type acrylic resin emulsion on one or both sides of a sheet-like support, drying it, and then providing a release agent layer, it is possible to improve the properties of release agent coating solution, clear properties, release agent adhesion, and heat resistance. and a release sheet with excellent shrinkability.

Examples of the sheet-like support constituting the release sheet of the present invention include paper base materials, polymer films, and metal foils. These may be used alone or in the form of a stack of these.

The paper base material usually has a basis weight of 30 to 300 &/m 1
Kraft paper, high quality paper, white paperboard, etc. with a thickness of 30 to 350 μm are used.

Examples of polymer films include polyolefin films such as polyethylene, polypropylene, polybutene, polymethylpentene, and methylpentene copolymers with a thickness of 3 to 150 μm, polyethylene terephthalate films, polyvinyl chloride films, polyvinylidene chloride films, and fluororesin films.・Polyhexamethylene adipamide film, etc. may be mentioned.

As the metal foil, copper foil, aluminum foil, tin foil, etc. with a thickness of 3 to 100 μm are used.

The soap-free type acrylic resin emulsion used in the present invention refers to one that does not contain a surfactant that acts as an emulsifier, or a soap-free type acrylic resin emulsion that does not contain a surfactant that acts as an emulsifier.
Refers to an acrylic resin emulsion containing 1 part by weight or less.

Acrylic resin emulsions that do not contain surfactants generally include (1) emulsified with protective film colloid, (2)
There are those emulsified with a crosslinking emulsifier and (3) an aqueous dispersion of an acrylic resin copolymerized with a water-soluble polymer-forming monomer, but according to the study of the present inventors, (1) is a release agent. Poor adhesion and water resistance IC1(2) is not suitable for use in the present invention because it has poor solvent resistance. (3) is
There are no problems like (1) and (2), and it can be used. However, the soap-free type acrylic resin emulsion preferably used in the present invention contains at most 2 parts by weight, more preferably at most 1 part by weight, of a nonionic or anionic surfactant based on 100 parts by weight of the solid content of the acrylic resin. This is an acrylic resin emulsion containing low surfactant.

Such an acrylic resin emulsion can be prepared, for example, by polymerizing in a system containing 2 parts by weight or less of a surfactant per 100 parts by weight of the solid content of the acrylic resin.

Conventional so-called soap-in-place acrylic resin emulsions prepared using a relatively large amount of emulsifier (i.e., about 3 parts by weight or more per 100 parts by weight of resin solids) have poor adhesion to the release agent and poor coating film quality due to the influence of the emulsifier. Poor material adhesion. The above-mentioned low surfactant-containing acrylic resin emulsion preferably used in the present invention is disclosed in Japanese Patent Application Laid-Open No. 54-8
No. 8392.

The acrylic resin emulsion used in the present invention is prepared by known emulsion polymerization methods, such as those described in the above-mentioned patent applications. The monomers constituting the acrylic resin include a combination of acrylic esters, methacrylic esters, and vinyl monomers copolymerizable with these esters. Acrylic acid esters include methyl acrylate,
Examples of methacrylic acid ester include ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, etc. Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, glycidyl methacrylate, etc. Examples of the polymer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, acrylamide, methacrylamide, acrylonitrile, and styrene. One preferred monomer combination is one containing an acrylic acid ester as a main component, combined with a small amount of an unsaturated carboxylic acid and acrylonitrile. The acrylic acid ester provides the ability to form an undercoat layer on the sheet-like support, and the unsaturated carboxylic acid provides a stable emulsion, and also improves the adhesion between the undercoat layer and the sheet-like support and the release agent. Acrylonitrile contributes to adhesion, and also imparts toughness, solvent resistance, heat resistance, and heat absorption properties to the undercoat film.

In addition, viscosity modifiers, wetting agents, film-forming aids, etc. may be added for the purpose of improving the suitability for processing the acrylic resin emulsion into a sheet-like support and other properties, as long as the purpose of the present invention is not impaired. That is optional.

To form an undercoat layer of acrylic resin emulsion on a sheet-like support, the acrylic resin emulsion is coated with a roll coater, etc. according to a conventional method. Just wipe it with a cloth and dry it. The release agent to be used is not particularly limited, and any commonly used release agent can be used, and the release agent layer may be formed according to a conventional method.

The release sheet according to the present invention has excellent release agent coating liquid barrier properties, release agent adhesion, heat resistance, and heat shrinkage resistance. This will be explained with reference to the following examples, but the present invention is not limited thereto.

Example Sheet-like support: (1) High-quality paper (basis weight 64 Vm
, thickness 80 μ), (2) polypropylene film (thickness 50 μ), (3) At foil (thickness 30 μ),
A soap-free type acrylic emulsion (trade name "Bonron 5X-123J and [S-482
J: All coated with Mitsui Toatsu Kagaku M) using a roll coater.
El/m2 (solid content) was applied and dried (sample 1~
6). In addition, as a comparative sample, (1) was placed on the above support.
Acrylic emulsion with cross-linking emulsifier (product name: "Girimar 5EK101" manufactured by Nippon Tsumugi Co., Ltd.), (2) Soap-in-tive acrylic emulsion (product name: [0X-1]
007J: Zeon Corporation'JA)
Q coating liquid (clay/SBR latex weight ratio = 10
0720, concentration 48% by weight), (4) polyvinyl alcohol (PVA), (5) n]? Liethylene (PK)
were created by masonry (comparative samples 1 to 15).
).

For each sample, the release agent coating liquid barrier property, release agent adhesion, heat resistance, and heat shrinkage resistance were measured.61 (Measurement method) (1) Release agent coating liquid barrier property Silicone release agent diluted with toluene. Coating liquid (concentration: 5
(weight) and visually observe the state of penetration of the coating liquid.

○: No penetration ○ (Good)〉△〉X cups possible〕△: Slight penetration with a lot of scratches (2) Release agent adhesion The sample coated in the previous section (1) was dried and cured.

Next, toluene was applied to this coated surface and visually observed to see if the silicone release agent had fallen off.

O (Good)〉△〉×(Unknown ○: No falling off △: Slight falling off ×: A lot of falling off Measure the temperature at which discoloration or deterioration occurs.

(4) Side heat shrinkability (heat shrinkability) After heating the sample to 150°C, measure the shrinkage rate that occurs when cooling to 20°C.

patent applicant Oji Paper Co., Ltd. patent application agent Patent attorney Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney 1) Yukio Patent attorney Akira Yamaguchi

Claims (1)

[Claims] 1. A release sheet comprising a release agent layer provided on at least one side of a sheet-like support via a multilayer undercoat, wherein the multilayer undercoat is formed from a soap-free type acrylic resin emulsion.