JP2000345117A - Surface protection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a surface protection film having excellent initial stickiness, sparingly causing the increase of stickiness even when placed under a high temperature condition and enabling separation of the film itself from an object to be protected to be easily performed by forming a pressure sensitive adhesive layer with a specific tetra-block copolymer. SOLUTION: This surface protection film is obtained by the coextruding of a thermoplastic polyolefin-based resin as (i) a substrate layer together with a pressure sensitive adhesive to form (ii) a pressure sensitive adhesive layer on the layer (i). The layer (ii) is composed of a tetra-block copolymer expressed by the formula A-B-A1-B1 (wherein A and A1 are each a styrene polymer block and; B and B1 are each a butadiene polymer block or a polymer block obtained by the hydrogenation of an isoprene polymer block). The component (ii) preferably comprises 100 pts.wt. tetra-block copolymer expressed by the above formula and 5-100 pts.wt. α-methylstyrene resin.

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, and more particularly, to an adherend such as a synthetic resin plate, a metal plate, a decorative plywood, a coated coated steel plate, and various nameplates, particularly a coated steel plate and a coated resin plate of an automobile. The present invention relates to a surface protection film that is temporarily attached to a surface during storage or transportation of the product.

[0002]

2. Description of the Related Art Conventionally, when storing, processing, or transporting synthetic resin plates, metal plates, decorative plywood, various nameplates, and the like (hereinafter, referred to as "protected objects"), dirt adheres or scratches on these surfaces. Various surface protective films have been used to prevent sticking. In the above surface protection film,
Generally, a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate or the like or a mixture thereof is used in which a pressure-sensitive adhesive layer is formed on one surface of a substrate layer.

[0003] Such a surface protective film is required to have an initial adhesiveness sufficient to adhere to various protected object surfaces. If the surface protection film is not sufficiently adhered to the object to be protected after being subjected to processing such as shearing, punching, and bending while the surface protection film is adhered to the object to be protected, dust may be applied to the surface protection film and the object to be protected. , And the commercial value of the protected object may be significantly reduced. Therefore,
Even after the various processing steps are performed, it is necessary to adhere to the object to be protected.

[0004] When the object to be protected is used, the surface protective film is peeled off. Such peeling is usually performed after severe conditions such as storage under high temperature conditions in the summer and processing steps, and in a surface protection film using a general adhesive, such a peeling is often performed. Adhesive strength is too strong under severe conditions. If the adhesive strength becomes too strong, there is a problem that the film is broken or cannot be peeled when the surface protective film is peeled.

Conventionally, these surface protective films have been prepared by dissolving a pressure-sensitive adhesive composition mainly composed of an acrylic pressure-sensitive adhesive, natural rubber, or the like in a solvent, coating the substrate with an appropriate undercoating treatment or the like, It is manufactured by removing the solvent in a drying process. However, since such a manufacturing process uses a solvent, there is a problem from the viewpoint of fire and environmental pollution, and further, there is a problem that the manufacturing process is complicated due to the recovery of the solvent.

On the other hand, in recent years, a method has been practiced in which a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate and the like and a pressure-sensitive adhesive composition are hot-melted and co-extruded in multiple layers to produce a surface protective film. However, the adhesive used in this method is ethylene-
Either an ethylene copolymer alone such as a vinyl acetate copolymer or a mixture of a small amount of an additive such as a tackifier in the ethylene copolymer is mainly used, so that sufficient adhesion was not obtained. .

Further, Japanese Patent Publication No. 6-89312 discloses that
A block copolymer represented by the general formula ABA alone or a block copolymer represented by the general formula ABA and A ′
A mixture with a block copolymer represented by the formula -B '
A and A 'represent styrene blocks or styrene homologous blocks, and B and B' represent conjugated diene blocks). A pressure-sensitive adhesive composition for surface protection comprising a hydrogenated block copolymer as a main component has been disclosed. I have.

Japanese Patent Application Laid-Open No. 55-142069 discloses a compound represented by the general formula (AB) _n or (AB) _n -A (wherein
A represents a monovinyl aromatic hydrocarbon block such as styrene, and B represents a conjugated diene block. n represents an integer of 2 to 10), and a pressure-sensitive adhesive composition in which a tackifier resin and a cross-linking reactive tackifier resin are blended with a block copolymer represented by the formula (JP-B-49-330) is disclosed. In
Formula (BA) _n or (BA) _n -B ( _where A,
B and n are the same as described above).

However, any of the pressure-sensitive adhesive compositions disclosed in the above publications has a good initial tackiness and a small rise in tackiness after being placed at a high temperature.
The two characteristics could not be satisfied at the same time.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and has a good initial tackiness and a small increase in tackiness even under high temperature. An object of the present invention is to provide a surface protective film that can be easily peeled off and does not cause stains, adhesive residue, or sticking marks on an object to be protected.

[0011]

Means for Solving the Problems The surface protective film according to the invention described in claim 1 of the present application (hereinafter, referred to as a first invention) comprises:
A surface protective film obtained by co-extruding a thermoplastic polyolefin-based resin as a base material layer and an adhesive layer on one surface thereof together with the base material layer, wherein the adhesive layer has a general formula of AB-A ¹ -B
It is characterized by comprising a tetrablock copolymer represented by ¹ .

The surface protection film according to the second aspect of the present invention (hereinafter referred to as the second invention) comprises a thermoplastic polyolefin-based resin as a base layer, and a pressure-sensitive adhesive layer on one side thereof, together with a base layer, being co-extruded. a surface protecting film obtained, the adhesive layer, contains a general formula a-B-a ¹ tetra block copolymer represented by -B ¹ polymer 100 parts by weight of α- methyl styrene resin 5 to 100 parts by weight It is characterized by doing.

The invention described in claim 3 of the present application (hereinafter referred to as the third invention)
Surface protective film is a thermoplastic polyolefin
A fin-based resin as the base material layer, and an adhesive layer on one side
A surface protection film obtained by co-extrusion with a layer.
The pressure-sensitive adhesive layer has a general formula of ABA¹-B¹Represented by
100 parts by weight of tetrablock copolymer and general formula A^Two-B
^Two-A^TwoTriblock copolymer 20 to 100 represented by
It is characterized by containing parts by weight.

Hereinafter, the first invention will be described.

[0015] The pressure sensitive adhesive of the surface protective film of the first invention, tetra-block copolymer represented by the general formula A-B-A ¹ -B ¹ is used. In the formula, A and A ¹ represent a styrene polymer block, and B and B ¹ represent a polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block.

The above-mentioned tetrablock copolymer has one terminal composed of a styrene-based polymer block and the other terminal composed of a polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block.

Instead of the tetrablock copolymer represented by ABA ¹ -B ¹ , ABA ¹ or AB
-A ¹ -B ¹ -A ² (A ² represents a butadiene polymer block) and a pressure-sensitive adhesive composed of styrene-based copolymer blocks at both ends, such as a block copolymer (JP-A-5
With the use of JP-A-5-142069, a sufficient cohesive force can be obtained at a high temperature, and an increase in adhesive force at a high temperature is small, but an initial strong adhesive force cannot be obtained.

Further, instead of the tetrablock copolymer represented by the above-mentioned ABA ¹ -B ¹ , BAB ¹ or BAB ¹ -A ¹ -B ² (B ² Is a polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block), buta butadiene polymer block at both ends, such as a block copolymer represented by
The use of an isoprene polymer block or a pressure-sensitive adhesive composed of a polymer block obtained by hydrogenating these polymer blocks (Japanese Patent Publication No. 59-330) enables the initial strong tackiness to be obtained. The increase in adhesive strength underneath is large.

The polymer blocks A and A ¹ in the above tetrablock copolymer have a number average molecular weight of 12,0.
Those having a glass transition temperature of 20 ° C. or higher and a range of 00 to 100,000 are preferable. Further, the polymer block B, as the B ^1, the number-average molecular weight of 10,00
Those having a range of 0 to 300,000 and a glass transition temperature of −20 ° C. or less are preferred.

In the above tetrablock copolymer,
The weight ratio between (A + A ¹ ) and (B + B ¹ ) is (A + A ¹ ):
(B + B ¹ ) = 5: 95 to 50:50 is preferable, and 10:90 to 30:70 is more preferable.

A tackifier may be added to the above tetrablock copolymer. The compounding amount of the tackifier is
It is preferably 100 parts by weight or less based on 100 parts by weight of the tetrablock copolymer. If the amount exceeds 100 parts by weight, the cohesive strength of the pressure-sensitive adhesive layer is reduced. As the tackifier, for example, an aliphatic hydrocarbon resin, a terpene resin, a coumarone-indene resin, an aromatic hydrocarbon resin, a rosin resin, and the like are used.

The pressure-sensitive adhesive layer may further include, if necessary,
An antioxidant, an ultraviolet absorber and the like may be blended.

The thermoplastic polyolefin resin used for the base layer is not particularly limited, and may be, for example, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene,
α-olefin copolymer, propylene-α-olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, Examples thereof include propylene homopolymers, random copolymers, block copolymers, and the like, and these may be used alone or in combination of two or more.

The surface protective film of the present invention is obtained by laminating and integrating a pressure-sensitive adhesive layer comprising the above-mentioned pressure-sensitive adhesive composition and a base material layer comprising a thermoplastic polyolefin resin by coextrusion. As a manufacturing method, any of a multilayer inflation method and a multilayer T-die method may be used. It is not always necessary to provide two layers, and one or more intermediate layers may be provided between the base material layer and the pressure-sensitive adhesive layer.

The total thickness of the surface protective film is not particularly limited as long as it can prevent scratches and stains on the object to be protected, and is preferably 30 to 200 μm.

Next, the second invention will be described.

As the pressure-sensitive adhesive for the surface protection film of the second invention, a tetrablock copolymer represented by the general formula AB-A ¹ -B ¹ and an α-methylstyrene resin are used.

[0028] tetra-block copolymers represented by A-B-A ¹ -B ¹ is the same as the first invention is used.

The α-methylstyrene resin is compatible with the blocks A and A ¹ of the tetrablock copolymer, strengthens the cohesive force of the styrene domain in a pseudo crosslinked state, and applies a force at a high speed. In this case, plastic deformation can be prevented, and as a result, it can be lightly peeled off at a higher speed than the object to be protected.

The amount of the α-methylstyrene resin is as follows:
Made with 5-100 parts by weight relative to tetra-block copolymer 100 parts by weight of the general formula ^{A-B-A 1 -B 1} . If the compounding amount is less than 5 parts by weight, it cannot be peeled off lightly at high speed, and if it exceeds 100 parts by weight, the effect of strengthening the cohesive force of the styrene domain becomes too strong and sufficient initial tackiness cannot be obtained. .

The pressure-sensitive adhesive composition may contain the same tackifier, antioxidant, ultraviolet absorber and the like as in the first invention. The amount of the tackifier is preferably 100 parts by weight or less based on 100 parts by weight of the tetrablock copolymer for the same reason as in the first invention.

The surface protective film of the second invention can be obtained by co-extruding the base material layer and the pressure-sensitive adhesive layer in the same manner as in the first invention. For the base material layer, the same thermoplastic polyolefin resin as in the first invention is used.

Next, the third invention will be described.

The pressure-sensitive adhesive for the surface protective film of the third invention includes a tetrablock copolymer represented by the general formula ABA ¹ -B ¹ and a tetrablock copolymer represented by the general formula A ² -B ² -A ^2. Triblock copolymer is used. In the formula, A ² represents a styrene polymer block, and B ² represents a polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block.

[0035] tetra-block copolymers represented by A-B-A ¹ -B ¹ is the same as the first invention is used.

[0036] As the A ² in the triblock copolymer represented by the general formula A ² -B ² -A ^2, in the range of the weight average molecular weight of 12,000～100,000, glass transition temperature 20 ° C. Those described above are preferred. Also,
Examples of the polymer block B ^2, the weight-average molecular weight of 1
Those having a glass transition temperature of −20 ° C. or lower, which are in the range of 000 to 300,000, are preferred.

In the above triblock copolymer, A ²
The weight ratio of the B ^{2 are, A 2: B 2 = 5} : 95~50: 5
0 is preferable, and 10:90 to 30:70 is more preferable.
It is.

In the above tetrablock copolymer, the styrene blocks A and / or A ¹ are in a pseudo-crosslinked state,
The styrene block A and / or A ¹ is mixed with the styrene block A ² of the triblock copolymer to enhance cohesion and prevent plastic deformation when high pressure is applied. An increase in adhesive strength can be suppressed.

The compounding amount of the triblock copolymer represented by the above general formula A ² -B ² -A ² is determined by the following formula: ABA ^1-
Made with 20 to 100 parts by weight relative to tetra-block copolymer 100 parts by weight expressed as B ^1. The blending amount is 20
If the amount is less than 10 parts by weight, the effect of suppressing the increase in adhesive force under high pressure is not sufficient, and if it exceeds 100 parts by weight, the effect of strengthening the cohesive force of the styrene block in a pseudo cross-linked state becomes too strong, and is insufficient. Initial tack cannot be obtained.

The above-mentioned pressure-sensitive adhesive composition may contain the same tackifier, antioxidant, ultraviolet absorber and the like as in the first invention. As the amount of the tackifier increases, the cohesive strength of the pressure-sensitive adhesive layer decreases.
It is preferably 200 parts by weight or less based on parts by weight.

The surface protection film of the third invention can be obtained by co-extruding the base material layer and the pressure-sensitive adhesive layer in the same manner as in the first invention. For the base material layer, the same thermoplastic polyolefin resin as in the first invention is used.

(Function) The surface protective film of the first invention is
By the A-B-A ¹ tetra block copolymer represented by -B ¹ polymer adhesive layer, thereby demonstrating a good initial adhesion to the protected object, further increase in the adhesive strength at high temperatures Is small, it can be peeled off cleanly when it is peeled off from the object to be protected.

The surface protective film according to the second invention is characterized in that AB-
By what a tetra-block copolymer alpha-methylstyrene resin represented by A ¹ -B ¹ were blended in a specific ratio and the pressure-sensitive adhesive layer, alpha-methyl styrene resins, the tetra-block copolymer Compatible with the blocks A and A ^{1 of the above} , the cohesive force of the styrene domain in a pseudo cross-linked state is strengthened, so that plastic deformation when force is applied at high speed is prevented, and the speed is higher than that of the protected object. When peeling off, it can be peeled off lightly.

[0044] The surface protective film of the third invention comprises AB-
A ² tetra block copolymer represented by A ¹ -B ¹ -
By forming a triblock copolymer represented by B ² -A ² at a specific ratio as a pressure-sensitive adhesive layer, the styrene block A and / or
Or, A ¹ is in a pseudo-crosslinked state, and the styrene block A ² of the triblock copolymer is compatible with the styrene block A and / or A ¹ to enhance cohesion, and the plasticity when high pressure is applied As a result of preventing deformation, it is possible to suppress an increase in adhesive force under high pressure.

[0045]

Embodiments of the present invention will be described below.

[0046] (Example 1) as a tetra-block copolymer represented by the general formula ^{A-B-A 1 -B 1} , styrene - ethylene propylene tetramer block copolymer [manufactured by Shell Chemical "Kraton G1730M" ( (Trade name)] and a base layer (60 μm thickness) made of low-density polyethylene [“Milason 16” (trade name) manufactured by Mitsui Chemicals, Inc.] from a T-die. A surface protective film was obtained.

[0047] (Example 2) tetra block copolymer represented by the general formula ^{A-B-A 1 -B 1} , styrene - ethylene propylene tetramer block copolymer [manufactured by Shell Chemical "Kraton G1730M" ( (Product name)] 100
A pressure-sensitive adhesive layer (20 μm thick) composed of a pressure-sensitive adhesive composition containing 10 parts by weight of a tackifier [Arukawa Chemical Co., Ltd. “Alcon P-100” (trade name)], and a low-density polyethylene [ "Mirason 16" (trade name) manufactured by Mitsui Chemicals, Inc.]
Was co-extruded with a T-die from a T-die to obtain a surface protective film.

Example 3 The amount of the tackifier was 100
A surface protective film was obtained in the same manner as in Example 2 except that the amount was changed to parts by weight.

(Comparative Example 1) As a triblock copolymer represented by the general formula A ² -B ² -A ² , a styrene-ethylene / propylene triblock copolymer [“Septon 2043” (trade name, manufactured by Kuraray Co., Ltd.) )]) (20)
μm thickness) and a base layer (60 μm thickness) composed of low-density polyethylene [“Mirason 16” (trade name) manufactured by Mitsui Chemicals, Inc.]
Were co-extruded from a T-die to obtain a surface protective film.

Comparative Example 2 As a triblock copolymer represented by the general formula A ² -B ² -A ² , a styrene-ethylene / propylene triblock copolymer [“Septon 2043” (trade name, manufactured by Kuraray Co., Ltd.) )] For 100 parts by weight,
A pressure-sensitive adhesive layer (20 μm thick) composed of a pressure-sensitive adhesive composition containing 100 parts by weight of a tackifier [Alcon P-100 (trade name) manufactured by Arakawa Chemical Co., Ltd.] and a low-density polyethylene [Milason manufactured by Mitsui Chemicals, Inc. 16 "(trade name)] was coextruded from a T-die to obtain a surface protective film.

(Comparative Example 3) As a triblock copolymer represented by the general formula A ² -B ² -A ² , a styrene-ethylene / butylene triblock copolymer [“Clayton G1657” (product of Shell Chemical Co., Ltd.) Name)] to 100 parts by weight of a tackifier [Arukawa Chemical Co., Ltd. “ALCON P-10
0 "(trade name)] and a base layer composed of a pressure-sensitive adhesive composition (20 μm thick) mixed with 100 parts by weight, and a low-density polyethylene [Milason 16 (trade name) manufactured by Mitsui Chemicals, Inc.] (Thickness: 60 μm) was co-extruded from a T-die to obtain a surface protective film.

The above-mentioned surface protective film was evaluated for the following properties, and the results are shown in Table 1. (1) Adhesive strength 1 hour after application (initial adhesive strength) A surface protective film is made of color steel plate (surface gloss = 10%)
The 180-degree peel strength after 1 hour of the sample adhered to the sample was measured at a peel rate of 30 in accordance with JIS Z 0237.
It was measured at 0 mm / min.

(2) Adhesive force after 2 weeks at 60 ° C. Surface protective film was coated with a color steel plate (surface gloss = 10%)
Was placed in a circulating gear oven at 60 ° C., left for 2 weeks, and then taken out. The 180 ° peel strength was measured at a peel speed of 300 mm /
Measured in minutes.

[0054]

[Table 1]

In Examples 1 to 3, the adhesive strength one hour after application was good, and the increase in adhesive strength after standing at 60 ° C. for two weeks was small. In contrast, in Comparative Examples 1 and 3, the adhesive strength after one hour was small, and in Comparative Examples 1 to 3, the adhesive strength after standing at 60 ° C. for 2 weeks was large.

[0056] (Example 4) as a tetra-block copolymer represented by the general formula ^{A-B-A 1 -B 1} , styrene - ethylene propylene tetramer block copolymer [manufactured by Shell Chemical "Kraton G1730M" ( (Product name)] 100
Pressure-sensitive adhesive layer (20 μm thick) composed of a pressure-sensitive adhesive composition in which 5 parts by weight of an α-methylstyrene resin (“Endex 155” (trade name) manufactured by Hercules) is blended with respect to parts by weight.
And low-density polyethylene [Mirason 1 manufactured by Mitsui Chemicals, Inc.
6 ”(trade name)] and a base layer (60 μm thick)
Co-extrusion from a die gave a surface protection film.

[0057] (Example 5) tetra block copolymer represented by the general formula ^{A-B-A 1 -B 1} , styrene - ethylene propylene tetramer block copolymer [manufactured by Shell Chemical "Kraton G1730M" ( (Product name)] 100
10 parts by weight of a tackifier [Alcon P-100 (trade name) manufactured by Arakawa Chemical Co., Ltd.] and α-methylstyrene resin [Endex 155 manufactured by Hercules Co., Ltd.]
(Trade name)] A pressure-sensitive adhesive layer (20 μm thick) composed of a pressure-sensitive adhesive composition containing 5 parts by weight, and a base layer (60 μm) made of low-density polyethylene [“Mirason 16” (trade name) manufactured by Mitsui Chemicals, Inc.] Was co-extruded from a T-die to obtain a surface protective film.

Example 6 The amount of the tackifier was 100
A surface protective film was obtained in the same manner as in Example 5, except that the amount was changed to parts by weight.

Example 7 A surface protective film was obtained in the same manner as in Example 5, except that the amount of the α-methylstyrene resin was changed to 100 parts by weight.

[0060] Instead of (Comparative Example 4) tetra block copolymer represented by the general formula ^{A-B-A 1 -B 1} , the general formula A
Styrene-ethylene propylene triblock copolymer represented by ^2- B ² -A ² [Septon 20 manufactured by Kuraray Co., Ltd.
43 "(trade name)], and a surface protective film was obtained in the same manner as in Example 4.

[0061] Instead of (Comparative Example 5) tetra block copolymer represented by the general formula ^{A-B-A 1 -B 1} , the general formula A
-B-A styrene-ethylene / butylene triblock copolymer [Clayton G16 manufactured by Shell Chemical Co., Ltd.]
57 "(trade name)], and a surface protective film was obtained in the same manner as in Example 4.

(Comparative Example 6) In place of the tetrablock copolymer represented by the general formula AB-A ¹ -B ¹ ,
² -B ² styrene represented by -A ² - except for using ethylene-butylene triblock copolymer [manufactured by Shell Chemical "Kraton G1657" (trade name)], in the same manner as in Example 5 surface A protective film was obtained.

Comparative Example 7 A surface protective film was obtained in the same manner as in Example 4, except that the amount of the α-methylstyrene resin was changed to 120 parts by weight.

With respect to the surface protective films of Examples 4 to 7 and Comparative Examples 4 to 7, "Adhesive force 1 hour after application (initial adhesive force)" and "6
The performance was evaluated for “adhesive strength at 0 ° C. after 2 weeks”, and the results are shown in Table 2. The "adhesive strength after 2 weeks at 60 ° C." was measured at a peeling speed of 300 mm / min and 20 m / min, respectively.

[0065]

[Table 2]

In Examples 4 to 7, the adhesive strength after one hour of application is good, the increase in adhesive strength after standing at 60 ° C. for 2 weeks is small, and the peeling can be performed with a small force when peeling at high speed. On the other hand, in Comparative Examples 4 to 6, since the adhesive strength after standing at 60 ° C. for 2 weeks is large, a large peeling force is required for high-speed peeling. In Comparative Example 7, the adhesive strength one hour after application was small.

[0067] As tetra block copolymer represented by (Example 8) In formula ^{A-B-A 1 -B 1} , styrene - ethylene propylene tetramer block copolymer [manufactured by Shell Chemical "Kraton G1730M" ( (Product name)] 100
Adhesion in which 20 parts by weight of a styrene-ethylene-propylene triblock copolymer [“Septon 2043” (trade name) manufactured by Kuraray Co., Ltd.] represented by the general formula A ² -B ² -A ² is blended with respect to parts by weight. Pressure sensitive adhesive layer (20μ)
m) and a base layer (60 μm thick) made of low-density polyethylene [Milason 16 (trade name) manufactured by Mitsui Chemicals, Inc.] were co-extruded from a T-die to obtain a surface protective film.

[0068] As tetra block copolymer represented by (Example 9) In formula ^{A-B-A 1 -B 1} , styrene - ethylene propylene tetramer block copolymer [manufactured by Shell Chemical "Kraton G1730M" ( (Product name)] 100
20 parts by weight of a styrene-ethylene-propylene triblock copolymer represented by the general formula A ² -B ² -A ² [“Septon 2043” (trade name) manufactured by Kuraray Co., Ltd.] and a tackifier [Arakawa Chemical Co., Ltd. "Alcon P-10"
0 "(trade name)] A pressure-sensitive adhesive layer (20 μm thick) composed of a pressure-sensitive adhesive composition containing 10 parts by weight, and a base layer composed of low-density polyethylene [Milason 16 (trade name) manufactured by Mitsui Chemicals, Inc.] (Thickness: 60 μm) was co-extruded from a T-die to obtain a surface protective film.

Example 10 Styrene-ethylene propylene triblock copolymer [Septon 20 manufactured by Kuraray Co., Ltd.]
43 "(trade name)] was obtained in the same manner as in Example 9 except that the blending amount was 100 parts by weight.

Example 11 The amount of the tackifier was 100
A surface protective film was obtained in the same manner as in Example 9 except that the amount was changed to parts by weight.

[0071] As tetra block copolymer represented by (Example 12) In formula ^{A-B-A 1 -B 1} , styrene - ethylene propylene tetramer block copolymer [manufactured by Shell Chemical "Kraton G1730M" ( (Product name)] 100
Styrene-ethylene / butylene triblock copolymer represented by the general formula A ² -B ² -A ² [“Clayton G1657” (trade name) manufactured by Shell Chemical Co., Ltd.) based on parts by weight
0 part by weight of the pressure-sensitive adhesive layer (2)
(Thickness of 0 μm) and a base layer (60 μm) made of low-density polyethylene (“Mirason 16” (trade name) manufactured by Mitsui Chemicals, Inc.)
Was co-extruded from a T-die to obtain a surface protective film.

Example 13 The compounding amount of the tackifier was 200
A surface protective film was obtained in the same manner as in Example 10 except that the amount was changed to parts by weight.

Comparative Example 8 100 parts by weight of a styrene-ethylene / butylene triblock copolymer represented by the general formula A ² -B ² -A ² [Clayton G1657 (trade name) manufactured by Shell Chemical Co., Ltd.] On the other hand, a pressure-sensitive adhesive layer (20 μm thick) made of a pressure-sensitive adhesive composition containing 10 parts by weight of a tackifier [Arukawa Chemical Co., Ltd. “Alcon P-100” (trade name)]
And low-density polyethylene [Mirason 1 manufactured by Mitsui Chemicals, Inc.
6 ”(trade name)] and a base layer (60 μm thick)
Co-extrusion from a die gave a surface protection film.

Comparative Example 9 Styrene-ethylene propylene triblock copolymer represented by the general formula A ² -B ² -A ² [“Septon 2043” (trade name) manufactured by Kuraray Co., Ltd.)
A surface protection film was obtained in the same manner as in Example 8, except that the compounding amount of was 5 parts by weight.

Comparative Example 10 Styrene-ethylene propylene triblock copolymer represented by the general formula A ² -B ² -A ² [“Septon 2043” (trade name) manufactured by Kuraray Co., Ltd.)
Was obtained in the same manner as in Example 8 except that the blending amount of was changed to 150 parts by weight.

Comparative Example 11 The amount of the styrene-ethylene / butylene triblock copolymer represented by the general formula A ² -B ² -A ² [“Clayton G1657” (trade name) manufactured by Shell Chemical Co., Ltd.) was determined. Example 8 except that the amount was 5 parts by weight.
A surface protection film was obtained in the same manner as described above.

With respect to the surface protective films of Examples 8 to 13 and Comparative Examples 8 to 11, “Adhesive force 1 hour after application (initial adhesive force)” and “6
The performance was evaluated for "adhesion after 2 weeks at 0 ° C." and the results are shown in Table 3. The “adhesive strength at 60 ° C. after 2 weeks” was measured after standing for 2 weeks under a pressure of 50 t / m ^{2 with} a vise.

[0078]

[Table 3]

In Examples 8 to 13, the adhesive strength 1 hour after application was good, and the pressure was 50 t / m ² at 60 ° C.
Even after standing for a week, the increase in adhesive strength is small. In contrast, Comparative Examples 8 to 11 show a large increase in adhesive strength after being left at 60 ° C. for 2 weeks under a pressure of 50 t / m ² . Furthermore, in Comparative Examples 9 to 11, the adhesive strength one hour after application was small.

[0080]

The surface protective film of the present invention has the above-mentioned structure, and has good initial adhesion to an object to be protected.
In addition, since the increase in adhesive strength under high pressure is small, the adhesive can be easily peeled off when it is peeled off after application, and no dirt, adhesive residue or traces of application are generated on the adherend surface. Furthermore, since the base layer and the pressure-sensitive adhesive layer are formed by a co-extrusion method, it is possible to simplify the molding process and eliminate the use of a solvent, thereby improving the adhesive strength between the base layer and the pressure-sensitive adhesive layer. Can be done.

Claims (3)

[Claims] 1. A surface protection film obtained by co-extruding a thermoplastic polyolefin-based resin as a base material layer and an adhesive layer on one surface thereof together with the base material layer, wherein the adhesive layer has a general formula A
A surface protective film comprising a tetrablock copolymer represented by -B-A ¹ -B ¹ . (Where
A and A ¹ represent a styrene polymer block, and B and B ¹ represent a polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block. 2. A surface protection film obtained by co-extruding a thermoplastic polyolefin-based resin as a base material layer and a pressure-sensitive adhesive layer on one surface thereof together with the base material layer, wherein the pressure-sensitive adhesive layer has a general formula of AB- A surface protective film comprising 100 parts by weight of a tetrablock copolymer represented by A ¹ -B ¹ and 5 to 100 parts by weight of an α-methylstyrene resin. (Where A and A ¹ represent styrene polymer blocks, and B and B
¹ indicates a polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block) 3. A surface protective film obtained by co-extruding a thermoplastic polyolefin-based resin as a base material layer and a pressure-sensitive adhesive layer on one surface thereof together with the base material layer, wherein the pressure-sensitive adhesive layer has a general formula of AB- It is characterized by containing 100 parts by weight of a tetrablock copolymer represented by A ¹ -B ¹ and 20 to 100 parts by weight of a triblock copolymer represented by a general formula A ² -B ² -A ^2. Surface protection film. (Where A, A ¹ , A ²
Represents a styrene polymer block, and B, B ¹ and B ² represent a polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block.)