JPS5991178A - Foamed self-adhesive tape or sheet - Google Patents

Abstract

PURPOSE:To provide the titled tape or sheet having high mechanical strength and flexibility and exhibiting strong adhesion of base material to adhesive layer, prepared by forming an adhesive layer on one or both sides of a specified crosslinked plastic foam with closed cells. CONSTITUTION:A foaming agent is added to a 1:9-9:1 mixture of (A) linear low-density polyethylene obtained by copolymerizing 1-10mol% alpha-olefin with ethylene and having a density of 0.915-0.940g/cm<3> and a melt index of 0.5-50g/ 10min and (B) ethylene/vinyl acetate copolymer with a vinyl acetate content of 5-30wt% or ethylene/ethyl acrylate copolymer with an ethyl acrylate content of 7-25wt%. The mixture is formed into a sheet at a temperature and under a pressure which does not cause decomposition of the foaming agent. The sheet is irradiated with an ionizing radiation for crosslinking and is foamed under heating into a crosslinked plastic foam 1 with closed cells. An adhesive layer is then formed on one or both sides of the foam 1 and release paper 3 is attached.

Description

[Detailed description of the invention] The present invention relates to foam adhesive tapes or sheets.

Conventionally, foam adhesive tapes have mainly used neoprene rubber or EPT rubber sponge as the foam base material. When manufacturing these foams, it is not possible to make them thin, so thick foam is sliced and used, and because the cells of the air bubbles on the surface are cut, the adhesive penetrates into the air bubbles, resulting in a large amount of foam. There were drawbacks that made it necessary. Further, there were disadvantages such as the strength of the base material was low, the layers were likely to crack, the expansion ratio was low, and the base material was heavy and expensive.

In order to improve these drawbacks, it has been proposed to use cross-linked foam of low density polyethylene as a base material, but this foam also lacks sufficient mechanical strength such as tensile strength and elongation, and The problem was that the adhesive layer peeled off from the material.

An object of the present invention is to eliminate the drawbacks of the conventional foam adhesive tapes mentioned above, and to provide a foam adhesive tape or sheet that has high strength and does not cause peeling of the adhesive layer.

The gist of the present invention is to provide an adhesive layer on one or both sides of a closed-cell synthetic resin crosslinked foam containing linear low-density polyethylene and an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer. A foam adhesive tape or sheet is provided with a foam adhesive tape or sheet.

The linear low-density polyethylene used in the present invention refers to ethylene, propylene, butene-1, pentene-1, hexene-1
By copolymerizing a small amount (approximately 1 to 10 mol%) of an α-olefin such as octene-1,4-methylpentene-1, an appropriate number of short chain branches are introduced into the linear backbone polymer. It is a polymer whose density has been lowered to the range of ordinary high-pressure low-density polyethylene, with a density of 0.915 to
0.940g/cJ, melt index 0.5-50
g/10 min is preferable, more preferably 1.0~
10.0g710 minutes, for example Ultzex
-202OL, 3021F (Mitsui Petrochemical ■), D
Examples include NGA7342 and GR3N7345 (manufactured by Union Carbide).

The ethylene-vinyl acetate copolymer used in the present invention is a copolymer of ethylene and vinyl acetate,
It is preferable that the vinyl acetate content is 5 to 3θ% from the viewpoint of moldability, flexibility of the foam, adhesiveness, etc. If the vinyl acetate content is too low, the adhesiveness and flexibility of the foam will be poor, and if it is too high, the moldability of the foam will be poor.

The ethylene-ethyl acrylate copolymer used in the present invention is a copolymer of ethylene and ethyl acrylate, and those with an ethyl acrylate content of 7 to 25% have good moldability and flexibility of the foam. , is preferable from the viewpoint of adhesiveness and the like. If the content of ethyl acrylate is too small, the adhesiveness and flexibility of the foam will be poor, and if it is too large, the moldability of the foam will be poor.

In the present invention, a mixture of the above-mentioned linear low-density polyethylene and an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer, or a mixture in which the above-mentioned mixture is further mixed with ordinary low-density polyethylene, etc. It is a cross-linked foam made of cells.

As a method for manufacturing a closed-cell crosslinked foam, a method similar to that used for manufacturing a conventional crosslinked foam of low density polyethylene can be used. For example, a blowing agent is added to the above resin mixture, kneaded and melted using an extruder or the like at a temperature and pressure that does not substantially decompose the blowing agent, and formed into a sheet, and the sheet-like molded product is irradiated with ionizing radiation. A method for obtaining a closed-cell crosslinked foam by crosslinking the foam by heating the foam to a temperature higher than the decomposition temperature of the foaming agent, or adding a foaming agent and a crosslinking agent to the above resin mixture and adding the foaming agent to the foaming agent using an extruder or the like. and crosslinking by cross-melting at a temperature and pressure at which the crosslinking agent does not substantially decompose, forming it into a sheet, heating it to a temperature at which the crosslinking agent decomposes, and then crosslinking, and further heating above the decomposition temperature of the blowing agent. Examples include a method of obtaining a closed-cell crosslinked foam. According to these methods, it is possible to obtain a thin foam.

The mixing ratio of linear low density polyethylene and ethylene-vinyl acetate copolymer or ethylene-ac, ethyl lylate copolymer is in the range of 1:9 to 9:1, particularly preferably 1:4 to 4. :1 is preferable from the viewpoint of mechanical strength, flexibility, adhesiveness, moldability, etc. of the foam. If the amount of linear low density polyethylene is too small, mechanical strength such as tensile strength will be insufficient, and if it is too large, flexibility and adhesiveness will be insufficient. Of course, in the above mixing, the ethylene-vinyl acetate copolymer and the ethylene-ethyl acrylate copolymer may be used together.

In the present invention, it is also possible to add ordinary resins such as low density polyethylene, high density polyethylene, ethylene-propylene copolymer, polypropylene, etc. to the mixture.

In the present invention, an adhesive layer is provided on one or both sides of the closed-cell crosslinked foam.

As the adhesive layer, an adhesive such as an acrylic adhesive, a rubber adhesive, a urethane adhesive, or a silicone adhesive is used. To provide the adhesive layer, the adhesive may be applied to the surface of the foam. When providing this adhesive layer, it is preferable to use a primer or to subject the surface of the foam to a corona discharge treatment, etc., so that the foam of the base material and the adhesive layer can be bonded more firmly.

The foam adhesive tape or sheet of the present invention is based on a closed-cell synthetic resin crosslinked foam containing linear low-density polyethylene and an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer. Because it is used as a material, it has excellent mechanical strength such as tensile strength and elongation, flexibility, and excellent adhesion between the base material and the adhesive layer.

Therefore, the foam adhesive tape or sheet of the present invention can be suitably used in a wide variety of applications, such as adhesive tapes for adhering moldings such as automobile window frames, and dew-proof tapes for light electrical appliances.

The present invention will be explained below using examples.

Example 1 Density 0.918 g/cd, melt index 2°0
g/10 min linear low density polyethylene 30 weight liter, vinyl acetate content 19%, metomatoindesox 2.4 g/10 min ethylene-vinyl acetate copolymer 70
parts by weight, 5 parts by weight of a blowing agent (azodicarbonamide), and 5.5 parts by weight of an auxiliary agent, and formed into a sheet using an extruder, and then exposed to 2.5 Mrad electrons using an electron beam irradiation machine. The material was crosslinked by irradiation with a wire, and then heated and foamed by continuously passing through a hot air oven at 250° C. to obtain a foamed sheet with a thickness of about 1 fi. The obtained foam sheet has a smooth surface, uniformly dispersed closed cells, flexibility, and a density of 0.14.
It was 4g/cJ.

As shown in Figure 1, this foamed sheet is used as a base material 1, both surfaces of which are subjected to corona discharge treatment, an acrylic adhesive is applied thereon to form an adhesive layer 2, and a release paper is applied on top of the foamed sheet. 3 were pasted together to create a foam adhesive tape having adhesive layers 2 on both sides.

Example 2 The same procedure was carried out except that in place of the ethylene-vinyl acetate copolymer in Example 1, 70 parts by weight of an ethylene-ethyl acrylate copolymer with an ethyl acrylate content of 18% and a melt index of 6 g/10 minutes was used. A foamed sheet was produced in the same manner as in Example 1. The obtained foam sheet had a smooth surface, uniformly dispersed closed cells, flexibility, and a density of 0.158 g/cl. A foam adhesive tape similar to that in Example 1 was prepared using this foam sheet.

Example 3 30 parts by weight of the same linear low density polyethylene as Example 1,
50 parts by weight of the same ethylene-vinyl acetate copolymer as in Example 1 and a density of 0.923 g/cJ.

20 parts by weight of low-density polyethylene with a melt index of 4.0 g/10 minutes, 5 parts by weight of a blowing agent, and 5.5 parts by weight of an auxiliary agent were mixed, extruded into a sheet, and then
Crosslinking is carried out by irradiation with an electron beam of M r a d, and then 25
The mixture was heated and foamed at 0° C. to obtain a foam sheet with a thickness of about 1 tuna. The obtained foam sheet has a smooth surface, uniformly dispersed closed cells, flexibility, and a density of 0.128.
g/d. A foam adhesive tape similar to that in Example 1 was prepared using this foam sheet.

Comparative Example 9 - The same method as in Example 3 except that the resin was changed to only 100 parts by weight of low density polyethylene, which was the same as in Example 3, to a thickness of approximately IKm.
A foamed sheet was obtained. The resulting foamed sheet had a smooth surface, uniformly dispersed closed cells, flexibility, and a density of 0.133 g/cJ. A foam adhesive tape similar to that in Example 1 was prepared using this foam sheet.

Table 1 shows the results of comparing the mechanical properties of the foam sheets serving as the base materials of the above examples and comparative examples.

As is clear from Table 1, linear low density polyethylene,
The foamed sheet of the present invention containing an ethylene-vinyl acetate copolymer or a 10-ethylene-ethyl acrylate copolymer has significantly better mechanical properties such as tensile strength, directionality, and elongation than those of comparative examples. It has become an excellent product.

Next, when the release papers of the foam adhesive tapes of Examples 1 to 3 and Comparative Examples were subjected to a high-speed peel test, the adhesive of the Comparative Examples was transferred to the release paper surface, but the adhesive of the Examples was not transferred. It didn't happen at all.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Base material, 2... Adhesive layer, 3... Release paper. patent applicant Sekisui Chemical Co., Ltd. Representative Fujinuma profiteering 11- 1st mouth

Claims (1)

[Claims] 1. On one or both sides of a closed-cell synthetic resin crosslinked foam containing linear low-density polyethylene and an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer. A foam adhesive tape or sheet provided with an adhesive layer. 2. Claim 1, wherein the mixing ratio of linear low density polyethylene and ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer is in the range of 1:9 to 9:1. foam adhesive tape or sheet.