JPH0321687A - Mold release sheet - Google Patents

Abstract

PURPOSE:To obtain a mold release sheet, stable for a long period and capable of exhibiting excellent releasability without containing a silicon-based compound in a mold release agent layer by forming a resin composition layer consisting essentially of specific ethylene/vinyl acetate copolymer as the mold release agent layer. CONSTITUTION:The objective sheet obtained by forming a resin composition layer consisting essentially of ethylene/vinyl acetate copolymer (preferably <=50wt.% vinyl acetate content) having <=20 melt index through or without an undercoating layer on a sheetlike support, such as paper, nonwoven fabric, plastic film or metal foil, as a mold release agent layer according to an extrusion laminating method, etc.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a release sheet for adhesive-treated tapes, labels, sheets, etc. More specifically, the present invention relates to release sheets such as adhesive-treated tapes, labels, sheets, etc. The present invention relates to a release sheet that does not contain any compound and exhibits stable and good releasability over a long period of time.

(Prior Art) A wide variety of release sheets are used to protect the adhesive surface of adhesive processed products such as adhesive tapes, labels, and sheets. These release sheets usually have a release agent layer on the surface of which an undercoat layer is provided when the sheet support is an absorbent material such as porous paper, and a filler layer is formed. In the case of a non-absorbent base material such as a plastic film or aluminum foil, a release agent layer is provided directly on the surface of the base material. As the mold release agent, in most cases a silicone resin or a composition containing a silicone resin as a main component is used.

(Problems to be Solved by the Invention) However, when a silicone resin or a composition mainly composed of a silicone resin is used as the mold release agent layer as described above, a trace amount of unreacted water present in the resin If silicone or silicone-based substances such as low-molecular-weight materials migrate to the adhesive layer of adhesive tapes, labels, sheets, etc., there is a risk that the adhesive performance will deteriorate, especially when printing or painting processes are included in subsequent processes. In some cases, transferred silicon-based substances may be brought into the painting workshop via peripheral equipment, auxiliary tools, workers, etc., causing painting defects and causing major damage.

Therefore, in the above-mentioned applications, there is a strong demand for a mold release sheet that is coated with a mold release agent layer that does not contain silicone materials, and shellac, polyethylene, polyvinyl alcohol, Various resins or resin composite materials such as fluorine-based materials or resins have been proposed so far. However, the adhesive layer of adhesive tapes, labels, sheets, etc. uses either rubber-based or acrylic resin-based adhesives, except for special cases where silicone-based adhesives are used, so they are relatively long-lasting. When stored or used over a period of time, the peeling resistance gradually increases and eventually peeling becomes impossible, and fluorine-based substances and resins have good properties as mold release agents. However, it is very expensive and has poor workability. Therefore, at present, a non-silicon-based mold release agent that is inexpensive, versatile, and stably usable has not been developed.

<Means for Solving the Problems> The present inventors have previously filed an application in Japanese Patent Publication No. 57-2 No. 1404, in which an ethylene/vinyl acetate copolymer was used as a release agent layer for a release sheet of a silicone adhesive. However, as a result of considering the use of a release agent layer for adhesive tapes, labels, or sheets coated with rubber-based or acrylic adhesives, we found that silicone Sheets with a surface layer made of a resin or a resin composition based on a resin other than those based on resins have a high affinity for adhesive tapes, labels, or sheets based on rubber-based or acrylic-based adhesives. Although it is said that it is not effective as a release sheet, the MI value (AS
(Based on TM D1238) A resin composition layer containing 20 or less ethylene/vinyl acetate copolymer as a main component is provided as a release agent layer on a sheet-like support with or without an undercoat layer. The release sheet constructed by the above exhibits excellent release properties for adhesive tapes, labels, and sheets coated with silicone-based adhesives, as well as rubber-based or acrylic adhesives, and has a long-term lifespan. The present invention was completed by discovering that there was almost no change in peel resistance even after storage.

The ethylene/vinyl acetate copolymer which is the main component of the resin composition forming the release agent layer of the release sheet of the present invention is one containing a tertiary component such as vinyl chloride, or one containing a carboxyl group or a hydroxyl group. Those modified with groups are also effectively used, and those with a vinyl acetate content of 50% or less (by weight, the same applies hereinafter) are preferred, but they are all limited to those with an MI value of 20 or less.

Examples of the sheet-like support for forming the release sheet of the present invention include paper base materials, nonwoven fabrics, plastic films, metal foils, etc., and these can be used alone or in a laminate in combination of two or more types. I can do it.

Paper base materials include kraft paper, high-quality paper, white paperboard, glassine paper, etc., and usually have a basis weight of 20 to 300
g/ra' and a thickness of 20 to 350 μm are used.

Non-woven fabrics can be manufactured using synthetic fibers, wet methods, dry methods, or direct methods such as spunbond methods, and have a basis weight of 10 to 200.
g/rrf, thickness 20 to 500 μm (co)polymers of olefins represented by birene, butene, methylpentene, etc.; (co)polymers of vinyl halides such as vinyl chloride, vinylidene chloride, vinyl buttide, etc. , various types of nylon, polyamide, polyester, etc. films, and those having a thickness of 5 to 150 μm are usually used.

Metal foils include copper, aluminum, and aluminum with a thickness of 3 to 100μ.
Foils such as pots and stainless steel are used.

In the release sheet of the present invention, the undercoat layer provided between the sheet support and the release agent layer, if necessary, may be formed by coating a clay coating agent or a water-soluble resin such as polyvinyl alcohol. , those made by extrusion coating of polyethylene, etc. In the case of non-absorbent plastic films and metal foils, depending on the nature of their surfaces, they can be used as is, or treated with corona discharge treatment, or treated with various resins such as vinyl, acrylic, urethane, and epoxy. The system is primed.

The release agent layer of the release sheet of the present invention may be formed of an ethylene/vinyl acetate copolymer having an MI value of 20 or less, or may be formed of a resin composition. Suitable additives to be used include tackifiers, waxes, and other materials that contribute to mold release properties, can adjust hardness and plasticity, and also facilitate the formation of a mold release agent layer. Additives normally used in resin compositions, such as inorganic fillers, pigments, and lubricants, can be optionally added as necessary.

For example, a basic example of a preferred resin composition for coating with molten R is (a) ethylene/vinyl acetate copolymer (MI
Value 20 or less>25-60%, (b) Tackifiers O-60% and <C> Waxes O-60% (However,
(a) + (b) + (c) = 100%).

The method for producing the release sheet of the present invention may be carried out by appropriately utilizing known methods.
A resin composition containing an ethylene/vinyl acetate copolymer with a value of 20 or less as a main component is applied as a solution in an appropriate solvent, or the resin composition is applied in a molten state using a roll or gravure plate. Extrusion lamination may be used, or alternatively, the resin composition may be made into a film by extrusion molding or the like and then laminated directly or with a suitable adhesive. (Functions and Effects) The present invention is a release sheet used for adhesive-treated tapes, labels, sheets, etc., which does not use a silicone compound in the release agent layer and has an MI value of 20 or less. The release agent layer is a resin composite layer containing ethylene/vinyl acetate copolymer as the main component.

The ethylene-vinyl acetate copolymer or its derivative, which is the main component of the release agent layer of the release sheet of the present invention, must have an MI value of less than 20. In the case of a release sheet using an ethylene/vinyl acetate copolymer with an MI value of 20 or more, it is presumed that the intermolecular cohesive force of the ethylene/vinyl acetate copolymer becomes smaller.
When manufacturing a release sheet, the workability of compounding and coating a release agent becomes easier, but the affinity with rubber-based or acrylic adhesives increases, reducing the release effect and causing problems in the initial stage of adhesion. Although it may exhibit releasability, over time the peeling resistance increases and eventually peeling becomes impossible.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example I Ethylene-vinyl acetate copolymer with an MI value of 6, manufactured by DuPont Mitsui Polychemicals, trade name: Evaflex #260
, vinyl acetate content 28%>40%, tackifier (
Manufactured by Yasuyu Kogyo ■, product name: YS Resin #1150. Softening point: 115°C > 30% and polyethylene wax (manufactured by Mitsui Petrochemical Industries, product name: Hiwax IOOP)
A resin composition for a mold release agent layer was manufactured by uniformly melting and mixing 30% of the mixture.

The above resin composition for a mold release agent layer was laminated with a polyethylene film having a thickness of 15 μm using an extrusion film forming machine to a thickness of 80 μm.
Using μ kraft paper as a sheet-like support, 80 g. A release sheet was manufactured by coating at a ratio of 1/1.

Rubber-based craft adhesive tape (NQ7 1 2 manufactured by Nitto Electric Industries Ltd.) and acrylic double-sided adhesive tape (NQ501 manufactured by Nitto Electric Industries Ltd.) were applied to the obtained release sheet, respectively.
A sample for peel resistance measurement was prepared by gluing F) together.

The sample was stored in a constant temperature bath at 40°C, and the peel resistance values at the initial stage, after 1 month, and after 3 months were measured using an autograph (manufactured by Shimadzu Corporation) at a peel rate of Jt 300 m+/min. 1 1 3 g. for adhesive tape and acrylic double-sided adhesive tape, respectively. /25
m+a, 1 2 0 g. /25mm, 1 1 7g.
/25m and 78 g- /25mm, 76
g. /25nv, 8 1 g. /25 mm, and exhibited good properties as a release sheet with no increase in peel resistance over time.

Example 2 Ethylene-vinyl acetate copolymer with an Ml value of 2 (manufactured by DuPont Mitsui Polychemicals, trade name: Evaflex #360)
, vinyl acetate content 25%) 27%, tackifier (
A resin for the mold release agent layer is prepared by uniformly melting and mixing 30% of YS resin #1150 (softening point: 115°C) manufactured by Yasuyu Kogyo Co., Ltd. and 43% of paraffin wax (manufactured by Nippon Seiso Co., Ltd., 130). A composition was manufactured, a release sheet was manufactured in the same manner as in Example 1, and a sample for peel resistance measurement was prepared, and the change in peel resistance value over time was investigated. system double-sided adhesive tape, 8 5 g. each. /25++lIm, 91g. /25 hours,
94 g-/25mm and 57 g. /25va
, 60 g. /25+am, 56 g. /25m
It was a+.

Comparative Example 1 In Example 1, the ethylene-vinyl acetate copolymer was
I value product (Mitsui DuPont Polychemical ■, product name: Evaflex #150, MI value 30, vinyl acetate content 33
%> except that a release sheet was manufactured in the same manner, a sample for peel resistance measurement was prepared, and the change in peel resistance value over time was investigated. 1 1 2 g each for adhesive tape
．． /25mm, 207 g. /25mn+, 4 4
5 g. /25n+m and 1 1 0g. /25m
m, 1 5 4 g. /25mm. 1 9 1 g. /
25+am, the peeling resistance value increased in all cases, and peeling became heavier and more difficult over time.

Example 3 In Example 1, a polyethylene terephthalate film whose surface to be coated was subjected to corona discharge treatment was used as the sheet-like support, and other operations were performed in the same manner as in Example 1 to produce a release sheet and to measure peel resistance. The samples were treated and the changes in peel resistance values over time were investigated. 10 each for rubber-based kraft adhesive tape and acrylic-based double-sided adhesive tape
1 g. /25++v, 9 7 g. /25mm, 99
g. /25 questions and 7 2 g. /25n+m, 7
0 g-/25+u+, 7 5 g. /25+sm
'c, and no increase in peel resistance over time was observed.

Claims (1)

[Claims] A resin composition layer mainly composed of an ethylene/vinyl acetate copolymer having a melt index (hereinafter referred to as MI) of 20 or less is applied onto a sheet-like support with or without an undercoat layer as a mold release agent. A release sheet characterized by being provided as a layer.