JP2002105424A - Surface protection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protection film that furnishes adequate adhesion and initial-stage adhesive force even at a low ambient temperature and even when the centerline surface roughness of an object to be protected is >=1 μm, shows no increase in adhesive force with the passage of time, has excellent peeling properties after use, and shows excellent interlayer adhesion even when it is laminated with a base material layer made of a polyethylene resin that is inexpensive. SOLUTION: This surface protection film is obtained by laminating an adhesive layer on one of the surfaces of a base material layer made of a polyethylene resin. The adhesive layer is made of a resin composition comprising 100 pts.wt. of a hydrogenated styrene type elastomer (1) and 5-100 pts.wt. of a hydrogenated styrene type elastomer (2), wherein elastomer (1) is an elastomer having, as a main skeleton, a block copolymer comprising a styrene polymer block and a random copolymer block made from styrene and a conjugated diene, and elastomer (2) is an elastomer comprising 50-95 wt.% of a conjugated diene polymer block and 5-50 wt.% of a styrene polymer block or a random copolymer block made from styrene and a conjugated diene, both based on the total weight of the elastomer.

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 suitable for protecting the surface of various materials such as a metal plate, a coated steel plate, a synthetic resin plate and a glass plate. In addition, the surface protection film referred to in the present invention includes a surface protection sheet and a surface protection tape.

[0002]

2. Description of the Related Art Conventionally, the surface of various materials (protected bodies) such as a metal plate such as a steel plate, a stainless steel plate, and an aluminum plate, and a coated steel plate, a synthetic resin plate, and a glass plate are protected by a so-called surface protection film. In addition, it is widely practiced to prevent damage that tends to occur during transportation and construction.

As a general surface protective film, for example, a film or paper made of a thermoplastic resin such as a polyolefin resin is used as a base layer, and a rubber (elastomer) -based adhesive or A surface protection film formed by laminating an adhesive layer made of an acrylic adhesive or the like is exemplified.

[0004] When the above surface protective film is used,
By temporarily attaching the pressure-sensitive adhesive layer of the surface protection film to the surface of the protected object, the surface of the protected object is protected, and a function of preventing damage, adhesion of dust, and the like is exhibited. When the protected object is used, the used surface protection film which has been used is peeled off from the surface of the protected object. Therefore, the surface protective film must have an appropriate level of tackiness and initial tackiness that can be easily temporarily attached to the surface of the protected object, have a small increase in tackiness with the passage of time (time), and have an excellent re-coating property. It is required to have a releasability and not to cause a phenomenon that a part of the pressure-sensitive adhesive layer remains on the surface of the protected object at the time of re-peeling, that is, a so-called “adhesive phenomenon”.

Various attempts have been made to meet such demands. For example, Japanese Patent Application Laid-Open No. 7-241960 discloses that 1 to 50% by weight of styrene and
A layer (adhesive layer) composed of a composition of 60% by weight or more of a hydrogenated random copolymer consisting of 9 to 50% by weight and 40% by weight or less of a polyolefin, 1 to 50% by weight of styrene and 99 of a diene hydrocarbon; There is disclosed a surface protective film formed by laminating a layer (substrate layer) having a composition of less than 60% by weight of a hydrogenated product of a random copolymer of less than 50% by weight and a composition of a polyolefin of more than 40% by weight.

However, in the composition of the pressure-sensitive adhesive layer constituting the surface protective film disclosed in the above publication, a metal plate such as a stainless steel plate or an aluminum plate, an acrylic paint, a fluorine paint, a polyester paint or the like is applied. When adhered to a protected object such as a painted steel plate, good adhesion is exhibited in an environment where the ambient temperature is high, but in an environment where the ambient temperature is low, the adhesive layer becomes hard and the adhesion decreases. ,
There is a problem that the surface of the object to be protected is lifted up and cannot exhibit the basic performance as a surface protection film. In the pressure-sensitive adhesive layer, the center line surface roughness (R
There is also a problem that an appropriate degree of tackiness or initial tackiness is not exhibited for a protected body having a) of 1 μm or more, and a sufficient surface protection function cannot be obtained.

Therefore, it is conceivable to remove polyolefin from the pressure-sensitive adhesive layer. If such a pressure-sensitive adhesive layer is laminated on a base layer made of a polyolefin-based resin alone, particularly a polyethylene resin alone, by co-extrusion, an interlayer between the two is obtained. A new problem of poor adhesion was found.

[0008]

SUMMARY OF THE INVENTION In view of the above-mentioned requirements and problems, an object of the present invention is to provide a suitable protective film even in an environment having a low ambient temperature or a center line surface roughness (Ra) of 1 μm or more. Develops adhesiveness and initial adhesive strength, with little increase in adhesive strength with time, excellent removability after use, and interlayer adhesion even when laminated on a cheap polyethylene resin base layer It is to provide a surface protective film excellent in the above.

[0009]

According to a first aspect of the present invention, there is provided a surface protective film comprising a substrate layer made of polyethylene resin and an adhesive layer laminated on one surface of the substrate layer. The layer is composed of a resin composition in which 5 to 100 parts by weight of a hydrogenated product of the following styrene-based elastomer (II) is blended with 100 parts by weight of a hydrogenated product of the following styrene-based elastomer (I). Surface protection film. Styrene-based elastomer (I): Elastomer having block copolymer composed of styrene polymer block (A) and random copolymer block of styrene and conjugated diene (B) as main skeleton Styrene-based elastomer (II): Conjugate An elastomer wherein the weight fraction of the diene polymer block is 50 to 95% by weight, and the weight fraction of the styrene polymer block or the random copolymer block of styrene and conjugated diene is 5 to 50% by weight.

The substrate layer constituting the surface protective film of the present invention is made of a polyethylene resin film (including a polyethylene resin sheet).

As the polyethylene resin, for example,
Examples include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene.
These polyethylene resins may be used alone or in combination of two or more.

Further, other polyolefin-based resins may be blended in the base layer. For example, blending of a polypropylene resin, an ethylene-vinyl acetate copolymer, etc. improves the interlayer adhesion with the pressure-sensitive adhesive layer. It is effective for

The resin composition used for forming the pressure-sensitive adhesive layer constituting the surface protective film of the present invention includes a hydrogenated styrene-based elastomer (I) (hereinafter simply referred to as “hydrogenated styrene-based elastomer (I) ) ").

The styrene elastomer (I) is, for example, an elastomer having a main skeleton of a block copolymer comprising a styrene polymer block (A) and a random copolymer block (B) of styrene and a conjugated diene. Yes, specifically, one in which each block of A and B is combined:
AB type block copolymer, random copolymer block of styrene and conjugated diene, containing a taper copolymer block (C) in which styrene gradually increases: ABC
Block copolymer, tapered copolymer block (C)
Containing a styrene polymer block (A) instead of
-BA-type block copolymers, those obtained by repeating or coupling these: (AB) n (AB) mX-type block copolymers, (ABC) mX-type block copolymers , (ABA) mX type block copolymer and the like. These styrene elastomers (I) may be used alone or in combination of two or more. Note that n represents an integer of 1 or more, m represents an integer of 2 or more, and X represents a coupling agent residue.

In the styrene-based elastomer (I), the content of styrene and conjugated diene as constituents thereof is preferably from 5:95 to 60:40, more preferably from 7:93 to 40:40 by weight. 40:60. When the styrene content is less than 5% by weight, the cohesive force of the pressure-sensitive adhesive layer becomes insufficient, and adhesive residue may be left on the surface of the protected object when the obtained surface protective film is peeled off after use. Conversely, if it exceeds 60% by weight, the adhesiveness and initial adhesive strength of the pressure-sensitive adhesive layer become insufficient, and it may be difficult to attach the obtained surface protective film to the surface of the protected object.

The styrene elastomer (I)
In the above, the styrene content is such that the styrene bond content in the styrene polymer block (A) and the taper copolymer block (C) in all the monomers is 3 to 50% by weight.
And more preferably 5 to 40% by weight.
And more preferably 5 to 25% by weight. If the styrene bond content is less than 3% by weight, the cohesive force of the pressure-sensitive adhesive layer becomes insufficient, and adhesive residue may be left on the surface of the protected object when the obtained surface protective film is peeled off after use. On the contrary, if it exceeds 50% by weight, the tackiness and initial tackiness of the pressure-sensitive adhesive layer become insufficient, and it may be difficult to attach the obtained surface protective film to the surface of the protected object.

Further, in the styrene-based elastomer (I), the vinyl bond content of the conjugated diene portion in the random copolymer block (B) and the tapered copolymer block (C) of styrene and conjugated diene is 60% of the total monomers. Preferably, the amount is greater than weight%,
It is more preferably at least 70% by weight, and even more preferably at least 80% by weight. When the vinyl bond content is 60% by weight or less, the adhesiveness and initial adhesive strength of the adhesive layer may be insufficient. Here, the vinyl bond means a monomer unit in which a conjugated diene is polymerized by a double bond at a 1,2- or 3,4-bond position.

The hydrogenated styrene elastomer (I) used in the present invention refers to the styrene elastomer (I)
The double bond derived from the conjugated diene is partially or completely saturated by hydrogenation. The degree of saturation is preferably at least 80 mol%, more preferably at least 90 mol%, even more preferably at least 95 mol%.
１００100 mol%. If the saturation is less than 80 mol%, the heat resistance and weather resistance of the pressure-sensitive adhesive layer may be insufficient.

The weight-average molecular weight of the hydrogenated styrene elastomer (I) is preferably from 50,000 to 400,000 in terms of polystyrene by GPC analysis, more preferably from 80,000 to 200,000. If the weight-average molecular weight of the hydrogenated styrene-based elastomer (I) is less than 50,000, the cohesive force of the pressure-sensitive adhesive layer becomes insufficient and the surface of the material to be protected when the obtained surface protective film is removed again after use. In some cases, adhesive residue may be generated, and when it exceeds 400,000, the fluidity of the resin composition may deteriorate, or the adhesiveness and initial adhesive strength of the adhesive layer may be insufficient.

The resin composition used to form the pressure-sensitive adhesive layer constituting the surface protective film of the present invention has a weight fraction of the conjugated diene polymer block of 50 to 95% by weight and a styrene polymer block. Or the weight fraction of the random copolymer block of styrene and conjugated diene is 5 to 5
0% by weight of a hydrogenated styrene elastomer (II) (hereinafter simply referred to as “hydrogenated styrene elastomer (I)
I) ").

The styrene-based elastomer (II) is, for example, an ADA type block copolymer comprising a styrene polymer block (A) and a conjugated diene polymer block (D), or a styrene polymer. A-A comprising a block (A), a conjugated diene polymer block (E) having a vinyl bond content of 30 to 70% by weight and a conjugated diene polymer block (F) having a vinyl bond content of less than 30% by weight.
Examples include an EF type block copolymer and (AEF) oX type block copolymer. These styrenic elastomers (II) may be used alone or in combination of two or more. Here, o represents an integer of 2 to 4, and X represents a coupling agent residue. The site to be coupled may be any of the polymer blocks A, E, and F.

When the weight fraction of the conjugated diene polymer block in the styrenic elastomer (II) is less than 50% by weight, the anchoring property of the pressure-sensitive adhesive layer to the polyethylene resin film forming the base material layer is insufficient. As a result, the resulting surface protective film is likely to peel off between the base layer and the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer may remain on the surface of the protected body when peeled off after use, and conversely, the weight When the fraction exceeds 95% by weight, the cohesive force of the pressure-sensitive adhesive layer becomes insufficient, and adhesive residue may be left on the surface of the protected object when the obtained surface protective film is peeled off after use.

The hydrogenated styrene elastomer (II) used in the present invention refers to the styrene elastomer (I)
The double bond derived from the conjugated diene in I) is partially or completely saturated by hydrogenation.
The degree of saturation is preferably 80 mol% or more, more preferably 90 mol% or more, and further preferably 95 to 100 mol%. If the saturation is less than 80 mol%, the heat resistance and weather resistance of the pressure-sensitive adhesive layer may be insufficient.

The weight average molecular weight of the hydrogenated styrene elastomer (II) is preferably 50,000 to 400,000, more preferably 80,000 to 200,000 in terms of polystyrene by GPC analysis. If the weight-average molecular weight of the hydrogenated styrene-based elastomer (II) is less than 50,000, the cohesive force of the pressure-sensitive adhesive layer becomes insufficient, and the surface of the material to be protected when the obtained surface protective film is removed again after use. May cause glue residue, and if it exceeds 400,000,
The fluidity of the resin composition may deteriorate, or the adhesiveness and initial adhesive strength of the adhesive layer may be insufficient.

The resin composition used in the present invention is based on 100 parts by weight of the hydrogenated styrene elastomer (I).
It is necessary that 5 to 100 parts by weight of the hydrogenated styrene-based elastomer (II) is blended.

Hydrogenated styrene elastomer (I) 100
If the amount of the hydrogenated styrene-based elastomer (II) is less than 5 parts by weight, the anchoring of the pressure-sensitive adhesive layer to the polyethylene resin film forming the base material layer becomes insufficient, and the resulting surface protection The film is likely to peel off between the base layer and the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer may remain on the surface of the protected object when peeled off after use,
Conversely, if it exceeds 100 parts by weight, the center line surface roughness (Ra)
May have insufficient adhesion or initial adhesion to a protected object having a particle size of 1 μm or more, causing floating and spontaneous peeling.

The resin composition used in the present invention may contain, if necessary, a tackifying resin, an adhesion promoter, an antioxidant, an ultraviolet absorber, and a stabilizer within a range that does not impair the achievement of the object of the present invention. One or more of various additives such as a filler, a softener, a plasticizer, a surfactant, a coupling agent, a coloring agent, an antistatic agent, and a flame retardant may be blended.

Examples of the tackifying resin include an aliphatic petroleum resin, an alicyclic petroleum resin, an aromatic petroleum resin, a rosin resin, a terpene resin, a phenol resin, and a cumarone / indene resin. And these may be hydrogenated as necessary. These tackifying resins may be used alone or in combination of two or more.

The amount of the tackifying resin is not particularly limited, but may be a hydrogenated styrene elastomer (I).
It is preferably 100 parts by weight or less based on 100 parts by weight. When the compounding amount of the tackifying resin with respect to 100 parts by weight of the hydrogenated styrene-based elastomer (I) exceeds 100 parts by weight, the cohesive force of the pressure-sensitive adhesive layer may be insufficient.

Examples of the adhesion promotion inhibitor include fatty acid amides, long-chain alkyl grafts of polyethyleneimine, soybean oil-modified alkyd resins, tall oil-modified alkyd resins and the like. These adhesion promotion inhibitors may be used alone or in combination of two or more.

Examples of the antioxidant include phenol-based (monophenol-based, bisphenol-based, polymer-type phenol-based, etc.) antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like, and commercially available products thereof Examples include the “Irganox” series manufactured by Ciba Specialty Chemicals. These antioxidants may be used alone or in combination of two or more.

Examples of the ultraviolet absorber include salicylic acid-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers. Commercially available products include, for example, trade names of Ciba Specialty Chemicals Co., Ltd. "Tinuvin" series and the like. These ultraviolet absorbers may be used alone or 2
More than one type may be used in combination.

As a method for producing the surface protective film of the present invention, for example, a resin composition for forming an adhesive layer is coated on one side of a base layer made of a polyethylene resin film prepared in advance by an ordinary film forming method. A method of applying (directly applying) a pressure-sensitive adhesive layer by applying directly to the working thickness and, if necessary, through steps such as drying, crosslinking, and cooling (direct coating method), release paper and release. A method of forming a pressure-sensitive adhesive layer on the release-treated surface of a film in the same manner as described above, and then laminating this pressure-sensitive adhesive layer on one side of a previously prepared base material layer by a transfer method (transfer method); A method of co-extrusion of a polyethylene resin for use with a resin composition for forming an adhesive layer to form an integral body (co-extrusion method), and the like, but in view of productivity, the co-extrusion method is preferable. When a surface protective film is manufactured by a direct coating method or a transfer method, in order to further improve the adhesion between the base material layer and the pressure-sensitive adhesive layer, a corona discharge is previously applied to the surface of the base material layer on which the pressure-sensitive adhesive layer is laminated. Pretreatment such as treatment or primer coating may be performed.

In the surface protective film of the present invention, the thickness of the substrate layer may be appropriately set according to the use and purpose of use of the surface protective film, and is not particularly limited. When considered, typically 15-100
μm is preferred. Also, the thickness of the adhesive layer,
The surface protection film may be appropriately set according to the use or purpose of use, and is not particularly limited. However, in consideration of adhesive performance, cost, and the like, it is generally preferably 3 to 50 μm.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" means "parts by weight", and "%" means "% by weight" unless otherwise specified.

In this example, the following raw materials were used. 1. Polyethylene resin for base layer Product name "Mirason 16" @ melt flow rate (190
C): 3.7 g / 10 minutes, manufactured by Mitsui Chemicals, Inc. Hydrogenated styrene-based elastomer for pressure-sensitive adhesive layer (I) A-BC type block copolymer hydrogenated product (total styrene content: 10%, bound styrene content in blocks A and C: 4.5%, 2. The vinyl bond content of the conjugated diene portion in the block B: 80%, weight average molecular weight: 250,000) Hydrogenated styrenic elastomer (II) for pressure-sensitive adhesive layer (1) Hydrogenated block copolymer (a) Hydrogenated product of ADA type block copolymer (weight fraction of styrene polymer block: 20 %, Weight fraction of conjugated diene polymer block: 80%, weight average molecular weight: 90,000) (2) hydrogenated block copolymer (b) hydrogenated product of AEF type block copolymer (styrene Weight fraction of polymer block: 27.7%, weight fraction of block E: 50.3%, vinyl bond content of block E:
53%, weight fraction of block F: 22.0%, vinyl bond content of block F: 12%, weight average molecular weight: 16
10,000) Tackifying resin: trade name “YS Resin Px1150” (softening point: 115
C, manufactured by Yashara Chemical Co.) Adhesion increase inhibitor Soybean oil-modified alkyd resin (trade name "Arachid 25
1 ", Arakawa Chemical Industries, Ltd.) Antioxidant Product name "Irganox 1010" (manufactured by Ciba Specialty Chemicals)

Example 1 For the pressure-sensitive adhesive layer, 5 parts of a hydrogenated block copolymer (a), 20 parts of a tackifying resin and 20 parts of an antioxidant 1 were added to 100 parts of a hydrogenated styrene elastomer (I). A resin composition was prepared in which parts were blended. Then
Co-extrusion of the polyethylene resin for the base material layer and the resin composition for the pressure-sensitive adhesive layer was performed by a two-layer co-extrusion method to obtain a thickness of 5%.
A surface protective film was prepared by laminating a 10 μm thick adhesive layer on one side of a 0 μm base layer.

(Examples 2 to 5) and (Comparative Example 1)
And Comparative Example 2) A surface protective film was produced in the same manner as in Example 1 except that the resin composition for the pressure-sensitive adhesive layer was changed to the compounding composition shown in Table 1.

The performances (initial adhesive strength, adhesive strength over time, removability, interlayer strength, sticking property) of the surface protective films obtained in Examples 1 to 5 and Comparative Examples 1 and 2 are as follows. Was evaluated. In addition, SUS304 plate (No. 280 polishing) and acrylic coated steel plate (Ra: 1.3 μm) were used as the protection target. The performance evaluation results are shown in Table 1.

Initial adhesive strength: 0 ° C. and 2 according to JIS Z-0237 “Testing method for adhesive tape / adhesive sheet”
Under both atmospheres of 3 ° C. and 65% RH, a surface protection film cut to a width of 25 mm was attached to the surface of the SUS304 plate and the surface of the acrylic-coated steel plate at a pressing speed of 300 mm / min using a 2 kg pressing roller, respectively. After standing for minutes, each peel test was performed to measure the 180 degree square peel strength.

Adhesion over time: width 25 in an atmosphere of 23 ° C. and 65% RH according to JIS Z-0237.
mm and attached to the surface of the acrylic coated steel sheet in the same manner as in the case of the acrylic coated steel sheet.
After leaving for 7 days in the state of pressurizing, a peeling test was performed.
The 80 degree square peel strength was measured.

Removability: After performing a peel test on a SUS304 plate and a peel test on an acrylic-coated steel plate, visually observe the surface of each protected object and determine the following criteria. Was evaluated for removability. [Judgment Criteria] ○ ‥‥ No adhesive residue was observed on the surface of the protected object. Δ ‥‥ Partial adhesive residue was observed on the surface of the protected object. X: Adhesive residue was entirely observed on the surface of the protected object.

Interlayer adhesion: After a peel test was performed on the SUS304 plate, and after a peel test was performed on the acrylic-coated steel plate, each of the peeled surface protective films was visually observed, and the following judgment was made. The interlayer adhesion was evaluated based on criteria. [Evaluation Criteria] ○ ‥‥ No delamination was observed at the interface between the base material layer and the pressure-sensitive adhesive layer. × ‥‥ Delamination was observed at the interface between the base material layer and the pressure-sensitive adhesive layer.

Attachment: At the time of measuring the peel strength, the state of attachment of the surface protective film to the surface of the acrylic coated steel sheet was visually observed, and the adherence was evaluated according to the following criteria. [Evaluation Criteria] ○ ‥‥ No lifting or spontaneous peeling of the surface protective film was observed. X: Floating and spontaneous peeling of the surface protective film were partially observed.

[0045]

[Table 1]

[0046]

As described above, the surface protective film of the present invention is provided on one side of the base layer made of polyethylene resin.
Hydrogenated styrene in which the weight fraction of a conjugated diene polymer block and a styrene polymer block or a random copolymer block of styrene and a conjugated diene is in a specific range with respect to a specific amount of the hydrogenated styrene elastomer (I). Since the pressure-sensitive adhesive layer formed from the resin composition containing a specific amount of the elastomer (II) is laminated, the center line surface roughness (Ra) of the protected object is 1 μm in an environment where the ambient temperature is low or in a protected environment.
m or more, while exhibiting appropriate adhesiveness and initial adhesive strength, and having excellent interlayer adhesion between the base material layer and the adhesive layer, with little increase in adhesive strength over time, and thus removability after use. Metal plate, painted steel plate, synthetic resin plate,
It is suitably used for protecting the surface of various materials (protected bodies) such as glass plates indoors and outdoors.

Claims (1)

[Claims] 1. A surface protection film in which an adhesive layer is laminated on one surface of a base layer made of a polyethylene resin, wherein the adhesive layer comprises 100 parts by weight of a hydrogenated product of the following styrene-based elastomer (I). A surface protection film comprising a resin composition containing 5 to 100 parts by weight of a hydrogenated product of the following styrene-based elastomer (II). Styrene-based elastomer (I): Elastomer having block copolymer composed of styrene polymer block (A) and random copolymer block of styrene and conjugated diene (B) as main skeleton Styrene-based elastomer (II): Conjugate An elastomer wherein the weight fraction of the diene polymer block is 50 to 95% by weight, and the weight fraction of the styrene polymer block or the random copolymer block of styrene and conjugated diene is 5 to 50% by weight.