JPH08295859A - Surface-protecting film - Google Patents

Abstract

PURPOSE: To obtain a surface-protecting film having a tacky adhesive layer having a specific composition on a thermoplastic resin layer, to be pasted especially to a plywood resin board to be heat-treated at a high temperature and exhibiting peelability (peeling easiness). CONSTITUTION: This surface-protecting film is composed of (A) a thermoplastic resin layer (e.g. a low-density polyethylene) and (B) a tacky adhesive layer formed on the layer A and composed of a composition containing (i) an ethylene- vinyl acetate copolymer, (ii) a polyethylenimine having an introduced higher alkyl group and (iii) an organic compound exhibiting liquid state at normal temperature (e.g. octyl epoxystearate). The surface-protecting film is produced e.g. by mixing 100 pts.wt. of the component (i) with 0.05 pts.wt. of the component (ii) and 1.0 pt.wt. of the component (iii) to form a tacky adhesive composition and forming the tacky adhesive layer having a thickness of 20μm on the layer of the component A having a thickness of 40μm by an inflation double- layer co-extrusion method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective film which protects the surface of a synthetic resin plate or the like so that it is temporarily attached to the surface of the synthetic resin plate or the like and does not get scratched or soiled. The present invention relates to a technique which is applied to a synthetic resin plate to be treated and is effectively applied to a surface protective film having removability (easy peeling).

[0002]

2. Description of the Related Art Generally, in a surface protective film, not only the physical properties of the entire film that govern the quality of the surface protective action but also the characteristics of the adhesive layer are particularly important. That is, the surface protection film attached during the manufacturing of the synthetic resin plate (adherend) or the like must be securely bonded so as not to come off during handling of the adherend such as transportation, processing and inventory. . Then, when it is finally unnecessary, it is necessary to easily peel it off. The surface protective film has good adhesiveness at the initial stage of application, but when placed in a high temperature environment, the adhesive force tends to increase rapidly, which makes it extremely difficult to peel from the adherend after use. Or adhesive residue (adhesive remains) occurs.

Particularly, in the case of a synthetic resin plate, in order to prevent the synthetic resin plate from being scratched and dust from adhering, various kinds of processing are performed with the surface protective film attached, but at that time, at a relatively high temperature. Often accompanied by heat treatment. For example,
The polycarbonate plate is subjected to a printing process or a vacuum forming process after attaching the surface protection film. In the printing process, a heating process is performed at 90 ° C. for about 30 minutes to dry the ink, and in the vacuum forming process, the heat treatment is performed at 16 ° C.
Heat treatment is performed at 0 ° C. for 30 minutes. In the surface protection film that has undergone such heat treatment, the adhesive force of the pressure-sensitive adhesive layer is greatly increased, and it becomes difficult to peel it from the adherend.

In recent years, low adhesive strength after heat treatment is required,
The demand is increasing from within 50 g / 25 mm to around 10 g / 25 mm. Therefore, in order to meet such a requirement, the pressure-sensitive adhesive layer formed on the thermoplastic resin layer has a temperature of 100 ° C to 2 ° C.
A surface protective film to which an organic compound which is liquid at room temperature and which bleeds from the adhesive layer when heated to 00 ° C. is added is disclosed in, for example, JP-A-59-75974.

In addition, the adhesive layer formed on the thermoplastic resin layer is a high-grade adhesive layer formed on the ethylene-vinyl acetate copolymer at high temperature for a long time (100 ° C. or more and 3 minutes or more), where bleeding from the adhesive layer increases. A surface protective film obtained by adding polyethyleneimine having an alkyl group introduced therein is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-198383.

[0006]

However, the present inventor has found that the above-mentioned surface protective film has the following problems. Japanese Patent Laid-Open No. 59-759
In the surface protection film of Japanese Patent Publication No. 74, when the high temperature heat treatment is performed, the resistance of the adhesive force after heating becomes large. If the addition amount of the organic compound that is liquid at room temperature is increased in order to suppress the resistance of the adhesive force in the high-temperature heat treatment, the initial adhesive force decreases and the adhesive compound floats at the time of attachment.

In the case of the surface protection film disclosed in Japanese Patent Laid-Open No. 4-198383, when the heat treatment is carried out at a high temperature for a short time, the amount of bleeding is small and the adhesion resistance is increased. If the addition amount of polyethyleneimine having a higher alkyl group introduced is increased in order to suppress the adhesive force resistance of the heat treatment at a high temperature for a short time, the initial adhesive force will be lowered and the adhesive will float at the time of sticking. In view of the above-mentioned problems, an object of the present invention is to provide a surface protective film having excellent removability, in which the adhesive force does not progress during high temperature heat treatment. The above and other objects and novel features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

[0008]

The outline of the present invention will be briefly described as follows. The surface protective film of the present invention is a surface protective film having a pressure-sensitive adhesive layer formed on a thermoplastic resin layer, wherein the pressure-sensitive adhesive layer is ethylene-
It is composed of a composition containing a vinyl acetate copolymer, a higher alkyl group-introduced polyethyleneimine, and an organic compound which is liquid at room temperature.

[0009]

[Operation] According to the above-mentioned means, polyethyleneimine having a higher alkyl group introduced therein has a large amount of bleeding from the pressure-sensitive adhesive layer at a high temperature for a long time (100 ° C. or more and 3 minutes or more).
The organic compound that is liquid at room temperature bleeds from the pressure-sensitive adhesive layer when heated to 100 ° C to 200 ° C. Therefore, even when subjected to a high-temperature heat treatment for a long time and a short time, a higher alkyl group-introduced polyethyleneimine or an organic liquid compound at room temperature bleeds from the pressure-sensitive adhesive layer to fill the interface between the surface protective film and the adherend, Adhesive strength is suppressed.

[0010]

EXAMPLES Examples of the present invention will be described in detail below. [Example 1] The thermoplastic resin layer was formed by using low-density polyethylene, and the adhesive layer was composed of 100 parts by weight of ethylene-vinyl acetate copolymer and 0.05 parts by weight of polyethyleneimine introduced with a higher alkyl group. Formed by mixing 1.0 part by weight of octyl epoxystearate, which is an epoxy-based plasticizer, as an organic compound that is liquid at room temperature, and a thickness of 20 μm on a thermoplastic resin layer having a thickness of 40 μm by an inflation two-layer coextrusion method. The surface protection film which laminated | stacked the adhesive layer of was manufactured.

Then, the obtained surface protective film was attached to a polycarbonate plate having a thickness of 2 mm by a laminator, left at 23 ° C. for 30 minutes, and then peeled off at a width of 25 mm.
The initial adhesion was measured by a 180 ° peel test. Further, the surface protection film is attached to a polycarbonate plate having a thickness of 2 mm by a laminator, left for 1 minute in a hot air circulation type oven preheated to 160 ° C., and then taken out. Then, the surface protective film was allowed to cool to room temperature, allowed to stand at 23 ° C. for 30 minutes, and then the adhesive strength was measured by a 180 ° peel test with a peel width of 25 mm.

The surface protection film is attached to a polycarbonate plate having a thickness of 2 mm by a laminator, and 1
3 in a hot air circulation oven preheated to 60 ° C
After leaving it for a minute, take it out. Then, the surface protective film was allowed to cool to room temperature, allowed to stand at 23 ° C. for 30 minutes, and then the adhesive strength was measured by a 180 ° peel test with a peel width of 25 mm.

The surface protection film is attached to a polycarbonate plate having a thickness of 2 mm by a laminator, and 1
3 in a hot air circulation oven preheated to 60 ° C
After leaving for 0 minutes, this is taken out. Then, the surface protective film was allowed to cool to room temperature, allowed to stand at 23 ° C. for 30 minutes, and then the adhesive strength was measured by a 180 ° peel test with a peel width of 25 mm.

[Example 2] The thermoplastic resin layer was formed by using low density polyethylene, and the pressure-sensitive adhesive layer contained 100 parts by weight of an ethylene-vinyl acetate copolymer containing polyethyleneimine having a higher alkyl group introduced therein. 5 parts by weight and 2.0 parts by weight of octyl epoxystearate are mixed and formed, and a surface protection is obtained by laminating a pressure-sensitive adhesive layer having a thickness of 20 μm on a thermoplastic resin layer having a thickness of 40 μm by an inflation two-layer coextrusion method. A film was produced. Then, the adhesive strength was measured in the same manner as in Example 1.

Comparative Example 1 The thermoplastic resin layer was formed by using low-density polyethylene, the adhesive layer was formed by ethylene-vinyl acetate copolymer, and a 40 μm-thick heat layer was formed by an inflation two-layer coextrusion method. Thickness 2 on the plastic resin layer
A surface protection film having a 0 μm pressure-sensitive adhesive layer laminated was manufactured. Then, the adhesive strength was measured in the same manner as in Example 1.

[Comparative Example 2] The thermoplastic resin layer was formed by using low density polyethylene, and the pressure-sensitive adhesive layer contained 100 parts by weight of an ethylene-vinyl acetate copolymer with polyethyleneimine having a higher alkyl group introduced therein in an amount of 0. It is formed by mixing 5 parts by weight, and a thickness of 40 μm is obtained by an inflation two-layer coextrusion method.
A 20 μm thick pressure-sensitive adhesive layer was laminated on a thermoplastic resin layer of m to produce a surface protection film. Then, the adhesive strength was measured in the same manner as in Example 1.

[Comparative Example 3] The thermoplastic resin layer was formed by using low density polyethylene, and the pressure-sensitive adhesive layer was prepared by adding polyethyleneimine in which a higher alkyl group was introduced to 100 parts by weight of an ethylene-vinyl acetate copolymer. It is formed by mixing 0 parts by weight, and a thickness of 40 μm is obtained by an inflation two-layer coextrusion method.
A 20 μm thick pressure-sensitive adhesive layer was laminated on a thermoplastic resin layer of m to produce a surface protection film. Then, the adhesive strength was measured in the same manner as in Example 1.

[Comparative Example 4] The thermoplastic resin layer was formed by using low density polyethylene, and the pressure-sensitive adhesive layer contained 100 parts by weight of ethylene-vinyl acetate copolymer and 2 parts of octyl epoxystearate as an epoxy plasticizer. It was formed by mixing 0.0 parts by weight, and a thickness of 4 was obtained by an inflation two-layer coextrusion method.
A surface protection film was prepared by laminating a 20 μm thick adhesive layer on a 0 μm thermoplastic resin layer. Then, the adhesive strength was measured in the same manner as in Example 1. The following table shows the measurement results of Examples 1 and 2 and Comparative Examples 1, 2, 3, and 4 described above.

[0019]

[Table 1]

In the table, A is polyethyleneimine having a higher alkyl group introduced, and B is octyl epoxystearate. Thus, according to this embodiment,
Since the pressure-sensitive adhesive layer was formed by adding ethylene-vinyl acetate copolymer, polyethyleneimine in which a higher alkyl group was introduced, and octyl epoxystearate, as shown in the above table, heating the polycarbonate plate Even under conditions of high-temperature heat treatment during molding, the resistance of the adhesive force is small, the surface protective film can be easily peeled off, and the initial adhesive force is also good.

As described above, the inventions made by the present inventor are
Although the present invention has been specifically described based on the embodiments, it goes without saying that the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention.
Although the thermoplastic resin layer is formed of low density polyethylene in this embodiment, an extrudable material such as polypropylene and polyester may be used.

In addition to the inflation method, the surface protective film is preferably manufactured by a multi-layer coextrusion molding method such as a T-die method or laminating. The thickness of the surface protection film is
It is not particularly limited as long as it can prevent scratches and stains on the adherend such as a polycarbonate plate, but usually the thickness of the adhesive layer is 10 μm to 30 μm, and the thickness of the thermoplastic resin layer is 30 μm to 70 μm. , 40 μm to 1 as a whole
It is preferably about 00 μm.

The ethylene-vinyl acetate copolymer of the pressure-sensitive adhesive layer is not particularly limited as long as it can be extruded,
For example, those having a vinyl acetate content of 5 to 20% by weight are preferable. The polyethyleneimine in which the higher alkyl group of the adhesive layer is introduced has an average molecular weight of 1000 to 20.
000 is preferable. The higher alkyl group is preferably introduced in an amount of 0.5 to 1.0 equivalent with respect to the imine group of polyethyleneimine. As the higher alkyl group, an alkyl group having 12 or more carbon atoms is generally preferable, and an octadecyl group is particularly preferable.

The amount of polyethyleneimine having a higher alkyl group introduced is preferably 0.01 to 10.0 parts by weight based on the ethylene-vinyl acetate copolymer. That is, when the amount is less than 0.01 parts by weight, a sufficient effect of suppressing the adhesive force after heating cannot be obtained, and when the heat treatment is applied, the adhesive force advances. If it exceeds 10.0 parts by weight, the effect of suppressing the adhesive force after heating is too large, and after the heat treatment, the adhesive force becomes low and spontaneous peeling occurs. In addition, the initial adhesive strength is reduced, and the adhesive may float when attached.

In the present embodiment, octyl epoxystearate was used as the organic compound of the pressure-sensitive adhesive layer which is liquid at room temperature, but it is preferably liquid at room temperature with a melting point of 20 ° C. or lower, and is phthalic acid-based or polyester-based epoxy-based. Plasticizer,
Epoxy processing aids such as α-olefin oxide,
Examples thereof include phenol-phosphite-based antioxidants, which are uniformly dispersed in the pressure-sensitive adhesive layer at room temperature, and the temperature is 100 ° C to 100 ° C.
At the time of heating at 200 ° C., it is preferable that the adhesive layer bleeds to fill the interface with the adherend.

The addition amount of the organic compound which is liquid at room temperature is as follows.
0.1 to 5.0 parts by weight, preferably 1 by weight of the adhesive layer
~ 2 parts by weight is preferred. If it is less than 0.1 parts by weight, a sufficient effect of suppressing the adhesive force after heating cannot be obtained, and if heat treatment is performed,
This is because the adhesive strength is increased, and when it exceeds 5.0 parts by weight, the initial adhesive strength is reduced and the adhesive material floats when it is attached.

[0027]

The effects obtained by the present invention will be briefly described as follows. According to the present invention, the pressure-sensitive adhesive layer contains the higher alkyl group-introduced polyethyleneimine and the organic compound that is liquid at room temperature, so that the higher alkyl group was introduced even after high-temperature heat treatment for a long time and a short time. Polyethyleneimine or an organic compound that is liquid at room temperature bleeds from the pressure-sensitive adhesive layer to fill the interface between the surface protection film and the adherend and suppresses the resistance of the adhesive force, improving removability after high-temperature heat treatment. can do. Therefore, it is possible to obtain a surface protective film suitable for a synthetic resin plate accompanied by heat treatment such as printing or vacuum forming.

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Claims (1)

[Claims] 1. A surface protective film having a pressure-sensitive adhesive layer formed on a thermoplastic resin layer, wherein the pressure-sensitive adhesive layer comprises an ethylene-vinyl acetate copolymer and polyethyleneimine having a higher alkyl group introduced therein. A surface protective film comprising a composition containing an organic compound that is liquid at room temperature.