JPS61136568A - Surface protective film - Google Patents

Abstract

PURPOSE:To provide a surface protective film which has an adhesive layer with high initial bond strength and prevents contamination of adherends, prepared by forming a foamed pressure-sensitive adhesive layer on a thin base sheet. CONSTITUTION:A foamed pressure-sensitive adhesive is prepared by adding 10pts.wt. or lower, pref. 0.01-5pts.wt. foaming agent (e.g. toluenesulfonylhydrazide) to 100pts.wt. pressure-sensitive adhesive material obtained by adding tackifier resin, softener, filler, age resistor, etc., to a base material such as acrylic rubber, natural rubber, polyisobutylene rubber or acrylic copolymer. The surface protective film covered with a foamed pressure sensitive adhesive layer having a fine cellular structure in the size of 0.1-30mum at an expansion ratio of less than 2.7, pref. 1.05-2, is obtained by applying the above adhesive in the thickness of 5-50mum to the surface of a thin plastic film (e.g. polyethylene film) of 3-150mum thickness so that it may have a contact area of 50% or higher.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a temporary method for protecting the surface of adherends such as stainless steel plates, metal plates such as zinc plates, other decorative plates, glass plates, and aluminum sashes. This relates to surface protection films (or sheets and tapes) that are attached to surfaces.

<Prior Art> A large number of adhesive type surface protection films for the purpose of protecting the surface of adherends such as metal plates and decorative boards have been proposed and implemented.

Such surface protection films are particularly required to have the ability to be peeled off without deforming the adherend or leaving any residue on the adherend surface after being pasted on the adherend surface. Many efforts have been made to suppress the increase in adhesive strength.

For example, one proposed technique is to incorporate a specific surfactant into the pressure-sensitive adhesive layer that constitutes the surface protection film.

Other ideas are related to the pressure-sensitive adhesive material constituting the pressure-sensitive adhesive layer, such as increasing the average molecular weight of the base polymer of the material, raising the glass transition temperature, or increasing the acrylic adhesive material. In pressure-sensitive adhesive materials, attempts are being made to solve the problem by modifying the physical properties of pressure-sensitive adhesive materials, such as by reducing the amount of polar monomers used.

<Problems to be Solved by the Invention> However, although the use of the surfactant can be suppressed within the desired range to increase the adhesive strength over time, it may contaminate the surface of the adherend. However, there is the problem that cleaning is required as a post-process, and the modification of the physical properties of the pressure-sensitive adhesive material has the problem that the initial adhesive strength of the pressure-sensitive adhesive layer is low, resulting in peeling of the ends.

<Means for Solving the Problems> In view of the state of the prior art, the present inventors have proposed a surface protection film having a pressure-sensitive adhesive layer that does not contaminate the adherend and has a predetermined initial adhesive strength. As a result of intensive research, we have arrived at the present invention.

That is, the present invention provides a surface protection film characterized in that the surface K of a thin sheet material is provided with a foamed pressure-sensitive adhesive layer.

According to the present invention, by microfoaming the pressure-sensitive adhesive layer, it is possible to significantly reduce the flow rate of the adhesive layer, which is a factor in increasing adhesive strength, and to prevent a decrease in initial adhesive strength. have

The foamed pressure-sensitive adhesive used in the practice of the present invention is formed by foaming a pressure-sensitive adhesive material by adding a predetermined amount of a foaming agent, and the material includes acrylic rubber, The paste base is made of natural rubber, polyisobutylene rubber, acrylic copolymer, etc., and if necessary, adhesion-imparting resins, softeners, fillers, anti-aging agents, etc. are blended into this paste, resulting in pressure-sensitive adhesive properties at room temperature. Foaming agents include azodicarbonamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine,
．． 4'-oxidibisbenzenesulfonyl hydrazide, para-toluenesulfonyl hydrazide, toluenesulfonyl hydrazide, or (c) water can be used.

It is desirable that the amount of the blowing agent for the substance that has pressure-sensitive adhesive properties at room temperature does not exceed at most 10 parts by weight per 100 parts by weight of the substance, and practically 0.
．． The range is 0.01 to 5 parts by weight.

A foamed pressure-sensitive adhesive layer obtained by adding a foaming agent to a material that has pressure-sensitive adhesive properties at room temperature and foaming it has a foamed pressure-sensitive adhesive layer of approximately 0.1
~30) It has a fine cell structure of tm, and its foaming ratio is desirably not exceeding 2.7 times at most, and is practically in the range of 1.05 to 2 times. This is what is said to be. If the foaming ratio exceeds this range, it is not preferable because the adhesive force to a smooth surface such as a stainless steel plate may decrease.

In addition, the surface of the foamed pressure-sensitive adhesive layer must be operated so that it is essentially smooth, at least 50%, preferably 55% or more, of a smooth surface such as a stainless steel plate. be.

Such a foamed pressure-sensitive adhesive layer is formed to a thickness of about 5 to 50 pm on the surface of a thin material made of a plastic film such as polyethylene, polypropylene, polyvinyl chloride, polyester, etc., and has a thickness of about 3 to 150 μm. It is considered to be a protective film.

<Effects of the Invention> Since the surface protection film of the present invention is constructed as described above, it has a characteristic that the adhesive force over time due to the fluidity of the adhesive layer is small and has sufficient initial adhesive force. It has the following.

<Examples> Examples of the present invention will be shown below. The text middle part means the weight part.

Example 1 20% by weight of a surface protection composition consisting of 100 parts of acrylic rubber (acrylic acid ester-acrylonitrile copolymer), 5 parts of a polyisocyanate compound, and a blowing agent (toluenesulfonyl hydrazide) in the amount shown in Table 1. A toluene solution is applied to a flexible polyvinyl chloride film with a thickness of 70/1 m so that the thickness after drying is 1 (ltffZ), dried at 140 ° C, and has fine cells of 0.1 to 15 gm. A surface protection film having a foamed pressure-sensitive adhesive layer was obtained.

Measurement method in the table Contact area: Paste the sample on a 5UB430BA finished stainless steel plate with two rubber rollers, 20'CX6
The contact area was calculated after storage in 5% R,H for 30 minutes.

Adhesive strength: Attach the sample to a stainless steel plate finished with SUB 430BA using a rubber roller and heat it at 20°C.
After storage in ×65% R,H for 30 minutes and at 40° C. for 30 days, 1801i peel adhesion was measured by pulling at a rate of 300 ions/min. The unit is 1/2
0 shield.

Example 2 A toluenesulfonyl hydrazide derivative as a blowing agent was added to 100 parts of a pressure-sensitive adhesive composition consisting of 100 parts of wired natural rubber, 50 parts of a polyterpene resin with a softening point of 115° C., and 2 parts of sulfur powder. A 20% by weight toluene solution of the surface protection composition added as shown in the table was added to a thickness of 110 mm.
The thickness after drying is 1 μm soft polyvinyl chloride film.
Opm layered, dried at 150°C, and dried at 150°C.
A surface protection film having a foamed pressure-sensitive adhesive layer having fine cells of 1 to 18 m was obtained.

Claims (1)

[Claims] 1) A surface protection film comprising a foamed pressure-sensitive adhesive layer provided on the surface of a thin sheet material. 2) The surface protection film according to claim 1, wherein the foamed pressure-sensitive adhesive layer has a foaming ratio of not more than 2.7 times. 3) The surface protection film according to any one of claims 1 to 2, which has a contact area of at least 50% when adhered to the surface of an adherend via a foamed pressure-sensitive adhesive layer.