JP2000034447A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a surface protective film excellent in initial tack at low temperatures and peelability. SOLUTION: In a protective film having a pressure-sensitive adhesive layer laminated on one side of a base film, the pressure-sensitive adhesive layer has a density of not less than 0.870 g/cm3 and is composed of 77-94 wt.% straight chain low density polyethylene having a density of less than 0.910 g/cm3; 1-3 wt.% pentaerythritol ester resin of a hydrogenated rosin; and 5-20 wt.% ethylene/α-olefin copolymer having a Vicat softening point prescribed in ASTM D-1525 of not higher than 65 deg.C.

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 for protecting the surface of a synthetic resin plate or the like from scratches and dirt, and more particularly, to a method for treating the surface of a synthetic resin plate under high-temperature heating while keeping the surface protective film bonded. The present invention relates to a surface protective film suitable for use on an acrylic resin plate or the like whose surface is coated.

[0002]

2. Description of the Related Art Surface protective films in which an adhesive layer is formed on one side of a substrate film are widely known, and are used for protecting the surface of synthetic resin plates such as acrylic resin plates and metal plates such as stainless steel plates. I have. As a surface protection film of this type, an adhesive layer containing a tackifying resin is laminated on one surface of a base film such as polyethylene, using an ethylene-vinyl acetate copolymer or a linear low-density polyethylene as a base resin. Is known (for example, see Japanese Unexamined Patent Application Publication
No. 157598). Also, JP-A-9-3100
No. 51 discloses a surface protection film using a pressure-sensitive adhesive layer composed of a linear low-density polyethylene and a completely hydrogenated rosin pentaerythritol ester resin.

[0003] The thing described in the above-mentioned Japanese Patent Application Laid-Open No. 9-157598 can provide a good initial tackiness when affixed to a resin plate or a metal plate. There is a problem that the low molecular weight material bleeds to the surface to reduce the adhesive strength and floats when attached to the adherend without adhering.

According to Japanese Unexamined Patent Publication No. 9-310051, it has excellent initial adhesiveness and releasability, but requires higher initial adhesiveness in a low-temperature environment.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface protective film which is not satisfactory with the above-mentioned conventional surface protective film and which has both excellent initial adhesive strength and releasability at a low temperature. .

[0006]

The surface protective film of the present invention is a surface protective film having a pressure-sensitive adhesive layer laminated on one surface of a base film, wherein the pressure-sensitive adhesive layer has a density of 0.870 g.
/ Cm ³ or more and less than 0.910 g / cm ³ , 77 to 94% by weight of linear low-density polyethylene, 1 to 3% by weight of pentaerythritol ester resin of hydrogenated rosin, and ASTM D-1525. Ethylene-α-olefin copolymer 5 having a Vicat softening point of 65 ° C. or less
-20% by weight.

The substrate film used in the present invention is not particularly limited, but is preferably obtained by coextrusion molding with the above-mentioned pressure-sensitive adhesive layer, and is mainly composed of an olefin resin such as polyethylene or polypropylene. Is preferably used. The base film may be a single-layer film or a laminate of two or more layers.

A light stabilizer, an antioxidant, an ultraviolet absorber, a silane-based lubricant, a filler such as talc, calcium carbonate, mica, and titanium oxide, a coloring agent, and the like may be added to the base film. .

In the present invention, the linear low-density polyethylene, which is the main component of the pressure-sensitive adhesive layer, has α as a comonomer.
It is preferable that the olefin is 4-methyl-1-pentene or that the polymer is polymerized using a metallocene compound as a catalyst, because low-molecular-weight products are reduced and contamination of the adherend is suppressed even at a low density. .

The linear low density polyethylene has a density of 0.8
70-0.940 g / cm^ThreeAre commercially available,
Density range 0.870 to 0.920 g / cm^ThreeThe ones
It can be pasted and used at room temperature (10 ° C or higher).
The linear low-density polyethylene used in the literature has a density of 0.3.
870 g / cm^Three0.910 g / cm ^Three
Less than

When the density is 0.910 g / cm ³ or more, the surface of the formed pressure-sensitive adhesive layer becomes rough, and the initial pressure-sensitive adhesive force is small even at room temperature, causing the surface protection film to float or peel off from the adherend. There is a possibility that it will no longer stick to the adherend at low temperatures. The density is 0.870 g /
If it is less than ³ cm ³ , the smoothness of the surface will be improved, and the initial adhesive strength at low temperature will be improved, but stickiness will appear and the sticking workability will deteriorate.

The pentaerythritol ester resin of hydrogenated rosin is pentaerythritol ester of tetrahydroabietic acid, and commercially available products such as "Foral 105" manufactured by Rika Hercules Co., Ltd.

The addition amount of the hydrogenated rosin pentaerythritol ester resin is preferably 1 to 3% by weight. If the addition amount is larger than this, the adhesive strength after the heat treatment is high, and if the addition amount is smaller than this, the initial adhesive strength and the adhesive strength after the heat treatment decrease.

Vicat softening point (ASTM D-152)
Examples of commercially available ethylene-α-olefin copolymers having 5) of 65 ° C. or lower include, for example, “Tuffmer A-4085” manufactured by Mitsui Chemicals, Inc.

The amount of the above copolymer is preferably in the range of 5 to 20% by weight. If it is more than 20% by weight, the adhesive strength is too high, and if it is less than 5% by weight, the initial adhesive strength is insufficient. It may float without it.

The thickness of the surface protective film of the present invention is not limited as long as it can exert the function of protecting the object to be protected from scratches and dirt.
The thickness is from 0 to 70 μm and the thickness of the pressure-sensitive adhesive layer is from 10 to 30 μm, and preferably about 40 to 100 μm in total thickness.

In order to produce the surface protective film of the present invention, a method in which a substrate film and a pressure-sensitive adhesive layer resin are separately molded by a molding method such as a T-die method or an inflation method, and then subjected to heat lamination, It is possible to employ either a method in which the pressure-sensitive adhesive layer resin is laminated on the base film by extrusion lamination, or a multi-layer coextrusion method in which the substrate film and the pressure-sensitive adhesive layer resin are laminated while simultaneously extruding.

[0018]

Embodiments of the present invention will be described below. (Example 1) Linear low-density polyethylene (density 0.905 g / cm ³ , manufactured by Mitsui Chemicals, trade name “Evolue SP0540”) in which an α-olefin as a copolymerization monomer is polymerized with a metallocene catalyst. 94% by weight
And hydrogenated rosin pentaerythritol ester resin (Rika Hercules Co., Ltd., trade name "Foral 10
5 ") 1% by weight and 5% by weight of an ethylene-α-olefin copolymer (Vicat softening point 55 ° C., manufactured by Mitsui Chemicals, Inc., trade name“ Toughmer A-4085 ”); Density polyethylene (made by Asahi Kasei Corporation, trade name "S-
360 ”and a density of 0.960 g / cm ³ ) by co-extrusion using an inflation method to obtain a base film having a thickness of 40
μm, a surface protective film having a pressure-sensitive adhesive layer thickness of 20 μm was produced.

(Examples 2, 3 and Comparative Examples 1 to 3) The compounding ratio of linear low-density polyethylene, the compounding ratio of pentaerythritol ester resin of hydrogenated rosin, and ethylene-α
A surface protective film having the same thickness was produced in the same manner as in Example 1 except that the mixing ratio of the olefin copolymer was changed as shown in Table 1.

Comparative Example 4 The procedure of Example 1 was repeated except that the pressure-sensitive adhesive layer was changed to an ethylene-vinyl acetate copolymer (trade name “Evaflex P-1407” manufactured by DuPont-Mitsui Polychemicals). To produce a surface protective film having the same thickness.

Performance Evaluation The surface protective films obtained in the above Examples and Comparative Examples were evaluated according to the following items, and the results are shown in Table 1. (1) Initial adhesive strength The surface protective film was 25 mm in width and was attached to an acrylic resin plate having a thickness of 2 mm at each of the temperatures shown in Table 1 with a laminator. The peeling force at 180 ° peeling at a speed of 300 mm / min at a temperature was measured and defined as the initial adhesive strength. (2) Adhesion promoting property The surface protective film was 25 mm in width, was attached to an acrylic resin plate having a thickness of 2 mm at each temperature shown in Table 1 with a laminator, and was heated at 180 ° C. for 10 minutes in a hot-air circulating oven and then at room temperature. After cooling, the sample was allowed to stand in an environment of 23 ° C. and 65% RH for 30 minutes.
The peeling force at the time of 180 ° peeling at a speed of / min was measured and defined as an enhanced adhesive force. (3) Adhesive force after 6 months After the roll of the surface protective film was manufactured, it was left in a warehouse for 6 months and stuck to a 2-mm thick acrylic resin plate at a temperature of 5 ° C with a laminator. In an environment of 5 ° C, 3
After leaving for 0 minutes, the peeling force was measured when the film was peeled at 180 ° at the same temperature and at a speed of 300 mm / min. (4) Occurrence of Floating After Adhesion In (3) above, the state of the surface protection film when it was adhered to the acrylic resin plate with a laminator was visually observed. The result was indicated by x.

[0022]

[Table 1]

As is clear from Table 1, all of Examples 1 to 3 according to the present invention have improved initial adhesion at a low temperature (5 ° C.) to an acrylic resin plate. Also, no floating occurred after pasting even after long-term storage as a roll. Furthermore, even if heat treatment was carried out in a state of being adhered to the adherend, the adhesive strength was rather lowered, so that it could be easily peeled off from the surface of the protected object.

[0024]

Since the surface protective film of the present invention has the above constitution, it has excellent initial adhesive strength even under a low temperature condition and after being stored as a roll for a long period of time. It is easy to peel off from the adherend and is suitable for high temperature heating applications.

Claims (1)

[Claims] 1. A surface protective film having a pressure-sensitive adhesive layer laminated on one surface of a base film, wherein the pressure-sensitive adhesive layer has a density of 0.3.
870 g / cm ³ or more and 0.910 g / cm ³
Less than 77-94% by weight of linear low density polyethylene
And hydrogenated rosin pentaerythritol ester resin 1
A surface protective film comprising: 〜3% by weight and 5-20% by weight of an ethylene-α-olefin copolymer having a Vicat softening point specified by ASTM D-1525 of 65 ° C. or lower.