JPH09272187A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an appropriate initial tack and to avoid increase in tack with time by forming a pressure-sensitive adhesive layer wherein the main ingredient consists of a hydrogenated resin of a specified styrene random copolymer and an ethylene-α-olefin copolymer on one face of a base material film consisting of a polyolefin resin. SOLUTION: A surface protective film is prepd. by forming an pressure- sensitive adhesive layer on one face of a base material film consisting of a polyolefin resin. The main ingredient of the pressure-sensitive adhesive layer is formed of a hydrogenated resin of a styrene random copolymer and an ethylene-α-olefin copolymer and the content of the hydrogenated resin of the styrene random copolymer is 30-60wt.% in the pressure-sensitive adhesive. In addition, when it is less than 30wt.%, tack to a body to be adhered with unevenness is not exhibited and temp. dependency of the tack tends to become too large in such a way that even when an appropriate tack is exhibited at ambient temp., the adhered film is peeled off at low outer temp. in winter season and when it exceeds 60wt.%, the tack becomes too strong.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a surface protection film suitable for surface protection of metal plates such as stainless steel plates and aluminum plates, painted metal plates, synthetic resin plates, glass plates, vinyl chloride laminated steel plates, and the like. The present invention relates to a surface protection film that protects a surface having irregularities that has been subjected to hairline processing, embossing processing, mat processing, and painting processing.

[0002]

2. Description of the Related Art Conventionally, as a surface protection film, polyvinyl chloride has been used to prevent scratches on the surface during cutting, transportation and transportation of metal plates, synthetic resin plates, decorative plates, etc.
A surface protective film in which a base film made of polyethylene, polypropylene or the like or an adhesive layer containing ethylene / vinyl acetate copolymer, acrylic resin, natural rubber or the like as a main component is provided on one side of paper is often used.

[0003] Further, for a metal plate or a resin plate having one or both surfaces such as a metal plate, a synthetic resin plate, a decorative plate, etc., coated, hairline-processed, matte-processed, or embossed and having an uneven surface, As a pressure-sensitive adhesive that is easily plastically deformed at room temperature, a surface protection film is used in which a natural rubber or the like, which is called gluing, and a tackifier are dissolved in a solvent and applied to a base film by bar coating or the like.

By the way, it has an appropriate adhesive force to a surface having irregularities having different surface roughness, and is exposed to a high temperature,
Even if it is applied for a long period of time, the adhesive strength does not change with time, it can be easily peeled off when not needed, there is no adhesive residue, the base material does not break, or chlorine gas is not released even when incinerated, or A surface protection film that does not use a solvent has been desired.

Therefore, in order to solve the above problems, Japanese Patent Publication No. 58-30911 and Japanese Patent Laid-Open No. 61-103975.
On one side of the base film such as polyolefin,
A block copolymer of the general formula AB (wherein A represents a styrene polymer block, B represents a butadiene polymer block, an isoprene polymer block, or an ethylene / butylene copolymer block) and a tackifier resin. There is disclosed a surface protective film having a pressure-sensitive adhesive layer formed by mixing and.

However, when a pressure-sensitive adhesive layer composed of a block copolymer and a tackifying resin is adhered to the above-mentioned surface protective film, since the content of the block copolymer in the pressure-sensitive adhesive composition is large, the pressure-sensitive adhesive after adhesion is adhered. The strength is already high, and there is a problem that the adhesive strength further increases and it becomes difficult to peel off when it changes with time in transportation and storage, when adherends are stacked, and when it is left at a high temperature of about 40 ° C. It was

As a method of improving them, Japanese Patent Laid-Open No. 6-
No. 240216 discloses that an ethylene-α-olefin copolymer and / or a propylene-α-olefin copolymer, a block-type styrene-based copolymer, and a pressure-sensitive adhesive layer containing a tackifying resin as a main component are exposed to a high temperature, A surface protective film is disclosed in which the adhesive strength does not increase with time even when applied for a long period of time.

Further, in Japanese Patent Laid-Open No. 7-24196,
Styrene-based random copolymer hydrogenated resin 60% by weight
By the above and the adhesive layer having a composition of 40% by weight or less of polyolefin, there is disclosed a surface protective film which has good adhesion to a coated steel sheet and the like and excellent stain resistance of an adherend.

However, in the former case, a metal plate,
It is effective for synthetic resin plates, mirror plates such as decorative plates, or for comparatively smooth surfaces with a small center line average surface roughness (for example, less than 1 μm), but the surfaces are painted, hairline processed, and matte processed. , A metal plate having embossed unevenness, a resin plate (for example, center line average surface roughness (JI
S-B0601) having an Ra of 1 to 3 μm) has a problem that it is difficult to stick. In the latter, when the pressure-sensitive adhesive layer has a composition of 60% by weight or more of a hydrogenated resin of a styrene-based random copolymer, it can adhere even to an adherend having the above-mentioned unevenness, but the adhesive force is too strong,
There was a problem that the adhesive strength could not be controlled.

[0010]

The object of the present invention, as a result of intensive studies for the purpose of solving the above-mentioned drawbacks, is that an appropriate initial adhesive force (100 to 4) is applied to an adherend having irregularities.
00 g / 50 mm), the adhesive strength does not increase with time even when exposed to high temperatures or applied for a long period of time, and
An object of the present invention is to provide a surface protective film that can be easily peeled off when not needed, has no adhesive residue on the adherend, and does not cause breakage of the substrate.

[0011]

In order to solve the above-mentioned problems, the surface protective film of the present invention comprises a base film made of a polyolefin resin and a pressure-sensitive adhesive layer formed on one side of the base film.
The main component of the pressure-sensitive adhesive layer consists of a hydrogenated resin of a styrene-based random copolymer and an ethylene-α-olefin copolymer, and the content of the hydrogenated resin of the styrene-based random copolymer in the pressure-sensitive adhesive is 30. .About.60% by weight.

In the above surface protective film, it is preferable that the hydrogenated resin of the styrene-based random copolymer in the pressure-sensitive adhesive layer comprises 7 to 45% by weight of styrene monomer and 93 to 55% by weight of butadiene. Further, the melt flow rate of the hydrogenated resin of the styrene random copolymer of the pressure-sensitive adhesive layer is 4 to 20 g / 1 at 230 ° C. and 2.16 kg.
It is preferably 0 minutes.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as the polyolefin resin forming the base film, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene (LLD-PE), ethylene-
α-olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-
Methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, polypropylene and the like can be used, and a mixture of two or more of these polyolefin resins may be used.

The hydrogenated resin of the styrenic random copolymer used in the pressure-sensitive adhesive layer of the present invention is 7 to 45% by weight of styrene monomer, preferably 7 to 35% by weight and 93 to 55% by weight of butadiene. Preferred is a copolymer hydrogenated resin with 93 to 65% by weight. When the amount of the styrene-based monomer is less than 7% by weight, the handleability as a resin is deteriorated, and when the amount of the styrene-based monomer exceeds 45% by weight, the resin becomes hard. Furthermore, the hydrogenation rate of the copolymer is 95%
Or more, preferably 97% or more. Further, these resins include a block type and a random type depending on the polymerization method,
The random type is preferable from the viewpoint of exhibiting adhesiveness to an adherend having irregularities.

The block type of the styrene-based copolymer hydrogenated resin is a hydrogenated block copolymer of styrene or α-methylstyrene and butadiene.
Hydrogenated block copolymers of styrene and butadiene are commonly called SEBS (styrene / ethylene / butadiene / styrene) resins. Further, the random type of the hydrogenated resin of the styrene-based copolymer means a block (a) of polystyrene or α-methyl polystyrene and a random copolymer block (b) of styrene or α-methylstyrene and butadiene, if necessary. Is a block copolymer composed of a tapered block (c) of styrene or α-methylstyrene and butadiene, and these are block-bonded.

The difference between the random type and the block type of the styrene copolymer hydrogenated resin is that the block type has a glass transition temperature near 100 ° C. corresponding to the block (a) of polystyrene or α-methyl polystyrene. In contrast to the detection, the random type does not detect the glass transition temperature corresponding to (a).

The content of the hydrogenated resin in the styrene random copolymer of the pressure-sensitive adhesive layer of the present invention is 30 to 60 in the pressure-sensitive adhesive.
% By weight. If it is less than 30% by weight, the adhesive force to an adherend having irregularities may not be exhibited, or at room temperature (23 ° C)
However, even if it has an appropriate adhesive strength, the temperature dependence of the adhesive strength is likely to become strong such that the film attached to the adherend having irregularities is peeled off at a low outdoor temperature such as winter. On the other hand, if it exceeds 60% by weight, the adhesive strength becomes too strong, so that it is limited to 30 to 60% by weight.

Melt flow rate (ASTM) of hydrogenated resin of styrene random copolymer of the pressure-sensitive adhesive layer of the present invention
-D1238, hereinafter abbreviated as MFR) is 230 ° C,
It is 4 to 20 g / 10 minutes at 2.16 kg. For example, when a polyolefin resin forming a base film and an adhesive composition are laminated by a hot melt coextrusion method to form a film, the MFR of the polyolefin resin is 4 to 20 g / 20.
Since there are many components, the viscosity of the polyolefin-based resin and the pressure-sensitive adhesive composition are well balanced, and the thickness of the pressure-sensitive adhesive layer in the width direction is kept uniform. A MFR of 20 g / 10 min is preferred.

Ethylene used in the pressure-sensitive adhesive layer of the present invention
The α-olefin copolymer has an ethylene content of 30% by weight or more, preferably 40% by weight or more, more preferably 50% by weight or more, and propylene, butene-1, and hexene-.
It is a copolymer with 1,4-methylpentene-1, octene-1 and the like. Among them, a copolymer of propylene, butene-1 and octene-1 may be used alone or as a mixture, but an amorphous or low crystalline copolymer is preferable.

Further, a tackifier can be appropriately added to the pressure-sensitive adhesive layer, if necessary, within a range that does not impair the effects of the present invention. As the tackifier, one that is selectively compatible with the hydrogenated resin of the styrene-based random copolymer and the ethylene-α-olefin copolymer is used. For example, aliphatic hydrocarbon resins, terpene resins, coumarone-indene resins, aromatic hydrocarbon resins, rosin resins and the like are preferably used. A terpene resin is preferable from the viewpoint of good compatibility with a hydrogenated resin of a styrene-based random copolymer and development of adhesiveness to an adherend having irregularities. The addition amount of the tackifier is preferably as small as possible from the viewpoint of contamination to the adherend, and is preferably 0 to 10% by weight.

The surface protective film of the present invention is produced by co-extruding a polyolefin resin forming a base film and a pressure-sensitive adhesive composition, or by forming a film of the base film and then laminating the pressure-sensitive adhesive composition by lamination. Can be membrane. As a film forming method, a method such as an inflation method or a T-die method can be used. Regarding the laminating method, any method may be adopted, for example, a method of dissolving the above-mentioned pressure-sensitive adhesive composition in a solvent and applying it to a base film by bar coating or the like to laminate it, or a polyolefin forming a base film From the viewpoint of cost, a method of hot-melt coextruding the resin and the pressure-sensitive adhesive composition and laminating them is preferable.

The respective addition amounts of the hydrogenated resin and the polyolefin resin of the styrene random copolymer of the pressure-sensitive adhesive layer of the present invention should be appropriately determined for adherends having different center line average surface roughness. You can For example, for an adherend having a large center line average surface roughness (Ra), the addition amount of the ethylene-α-olefin copolymer may be reduced, or the tackifier described above may be added to obtain an appropriate amount. It can have a sufficient adhesive strength (100 to 400 g / 50 mm).

The thickness of the base film and the pressure-sensitive adhesive layer constituting the surface protective film is appropriately determined depending on the application, but the thickness of the base film is 10 to 100 μm, and the thickness of the pressure-sensitive adhesive layer is 5 to 50 μm. Is preferred.

An antiblocking agent may be added to the polyolefin resin forming the base film, if necessary, within a range not impairing the effects of the present invention. As the anti-blocking agent, liquid or solid paraffin, waxes such as synthetic wax, polyethylene wax, natural wax and the like, organic lubricants such as silicone and fatty acid amide and talc (talc), diatomaceous earth, kaolin (ceramic clay), silicon oxide Inorganic lubricants such as aluminum oxide, titanium oxide, magnesium oxide, zinc oxide, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, and zeolite can be used. Further, the hydrogenated resin of the styrene random copolymer used for the pressure-sensitive adhesive and the ethylene-α-olefin copolymer can be added within a range that does not impair the effects of the present invention. In addition, if necessary, it may be added to a usual resin such as a softener, an ultraviolet absorber, a heat stabilizer, an antioxidant, a weather stabilizer, an antistatic agent, a slip agent, a pigment, a dye, and an inorganic / organic filler. It can be used in combination with the additives used.

The pressure-sensitive adhesive layer may contain low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene (LLD-PE), ethyl acrylate copolymer as long as the effect of the present invention is not impaired. Polyolefin resin such as ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, polypropylene
It is also possible to add one species or two or more species. If necessary, softeners, UV absorbers, heat stabilizers, antioxidants, weathering stabilizers, antistatic agents, antiblocking agents, slip agents, pigments, dyes, ordinary resins such as inorganic / organic fillers. Can be used in combination with the additive used in addition to.

In the surface protective film of the present invention, the main component of the pressure-sensitive adhesive layer is a resin composition comprising 30 to 60% by weight of a hydrogenated resin of a styrene random copolymer and an ethylene-α-olefin copolymer. Since it is formed from a material, it exhibits appropriate adhesive force to the adherend such as embossed plate, mat plate, painted metal plate having unevenness, good removability, adhesive residue on the adhered surface, heating It is also excellent in aging and weather resistance.

[Characteristic Measuring Method and Evaluation Criteria] (1) Uniformity of Thickness of Adhesive Layer in Width Direction A surface protection film having a width of 40 cm was cut out at 5 cm intervals to cut 9 sections of the film and 50 using an optical microscope. The thickness was doubled to measure the thickness of the adhesive layer, and the uniformity was determined as follows. ○, ± 2 if the thickness range is within ± 20%
Those exceeding 0% and less than ± 50% were evaluated as Δ, and those exceeding ± 50% were evaluated as x.

(2) Adhesive strength An embossed plate (center line average surface roughness J
IS-B0601: Ra = 2.1 μm) and SUS3
04 Hairline (HL) processing board (Ra = 0.03μ
It was adhered to the surface of m) at 23 ° C. using a pressure bonding roller of 2 kg, and the adhesive force in each case of 23 ° C. × 30 minutes and 60 ° C. × 7 days was measured according to JIS-Z0237.

(3) Contamination property of adherend surface The surface protection film is embossed (Ra = 2.1 μm).
m), SUS304HL processed plate (same Ra = 0.03μ)
It was attached to the surface of m) using a pressure roller of 2 kg at 23 ° C., and the contamination of the mat plate after peeling was visually determined in each case of 23 ° C. × 30 minutes and 60 ° C. × 7 days. Those that were not contaminated at all were evaluated as ◯, stains were slightly visible, but those that were practical were rated as Δ, and those that were visible and impractical were rated as x.

(4) Weather resistance A carbon arc type weather meter was used to evaluate the readhesion force and the stain resistance after irradiation for 24 hours. Re-adhesion and stain resistance are unchanged ○, re-adhesion is slightly reduced and stains are slightly visible, but practical use is △, re-adhesion is degraded, stains are visible and impractical Was evaluated as x.

[0031]

Next, the effects of the present invention will be described with reference to examples. (1) Preparation of pressure-sensitive adhesive composition Example 1, Examples 3 to 4, Comparative Examples 1 to 3 In the pressure-sensitive adhesive layer, as a hydrogenated resin of a styrene-based random copolymer, MFR = 8.5 g / 10 min. "Dyalon 1321P" manufactured by Nippon Synthetic Rubber Co., Ltd., an ethylene-octene-1 copolymer (MFR = 5 g / 10 min "ENG" manufactured by Dow Chemical Co., Ltd., as an ethylene-α olefin copolymer.
AGE EG8200 ″) was used. The addition amount of each is shown in Table 1. 1.0 part by weight of “IRGANOX 1010” manufactured by Ciba-Gaigi Co., Ltd. as an antioxidant, and “Tinuvin 327” 0.5 manufactured by Ciba-Gaigi Co., Ltd. as an ultraviolet absorber. An adhesive composition was prepared by blending parts by weight.

Example 2 As an ethylene-α-olefin copolymer, ethylene-1
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the butene copolymer (MFR = 7 g / 10 min, "TAFUMA A4085" manufactured by Mitsui Petrochemical Co., Ltd.) was 50% by weight.

Comparative Example 4 Adhesion was carried out in the same manner as in Example 1 except that 60% by weight of "Tuftec H1052" manufactured by Asahi Kasei Kogyo Co., Ltd. was used instead of the hydrogenated resin of the styrene random copolymer, with MFR = 12 g / 10 min. An agent composition was prepared.

Comparative Example 5 Example 1 except that "Dyalon 1320P" manufactured by Japan Synthetic Rubber Co., Ltd., MFR = 3.5 g / 10 min, was used as a hydrogenated resin for a styrene-based random copolymer in the adhesive layer. An adhesive composition was prepared in the same manner as in.

(2) Preparation of surface protection film High-density polyethylene (Showflex "F6080" manufactured by Showa Denko KK) / low-density polyethylene (Sumitomo Chemical Co., Ltd.) for the above-mentioned pressure-sensitive adhesive composition and substrate layer Sumikasen "L705") = 50/50 was mixed with 0.2 part by weight of "fatty acid amide E" manufactured by Kao Corporation as an anti-blocking agent, and hot melt extrusion was performed by a two-layer coextrusion method to form a base layer. A surface protective film having a thickness of 50 μm and a thickness of 60 μm was prepared so that the pressure-sensitive adhesive layer had a thickness of 10 μm. The obtained surface protective film was attached to adherends having different center line average surface roughness Ra, and the characteristics of the film were evaluated. The results were as shown in Table 1.

[0036]

[Table 1]

As can be seen from Table 1, Examples 1 to 4 have a suitable adhesive force (100
~ 400g / 50mm), and high temperature (6
The change with time due to (0 ° C.) was small, there was no contamination of the surface of the adherend after sticking to or peeling from the adherend, and no deterioration in adhesive performance due to ultraviolet rays was observed.

On the other hand, in Comparative Examples 1 and 2, although the surface of the adherend after being adhered to and removed from the adherend and the deterioration of the adhesive performance due to ultraviolet rays were not observed, the adherence having unevenness was observed. The adhesive force was too strong for the body, and in Comparative Examples 3 and 4, the adhesive force was insufficient for the adherends having irregularities. Comparative Example 5 using a hydrogenated resin of a styrene-based random copolymer having a small MFR (melt flow rate) has a moderate adhesive force, but the thickness of the film and the adhesive layer in the width direction is not uniform, There was a large variation in adhesive strength to the body.

The surface protective film of the present invention, as shown in the above examples, is excellent in the uniformity of the thickness in the width direction of the film,
It has an appropriate adhesive force to the adherend with irregularities, does not increase in adhesive force due to temperature and changes over time, and there is no adhesive residue on the surface of the adherend, and also the adhesive performance is deteriorated by ultraviolet rays. It turns out that it is remarkably excellent by not having it.

[0040]

The surface protective film according to the present invention comprises a hydrogenated resin of styrene-based random copolymer and ethylene-α.
A film obtained by hot-melt extruding a pressure-sensitive adhesive layer containing an olefin copolymer as a main component and a base material layer by a two-layer coextrusion method, which is excellent in uniformity of thickness in the width direction of the film, and has a coating treatment, It has an appropriate initial adhesive force to adherends such as metal plates and synthetic resin plates that have irregularities such as hairline processing, matting processing, embossing processing, even if exposed to high temperature or applied for a long time , The adhesive strength does not increase over time,
It has excellent weather resistance, and can be easily peeled off at the time of peeling, leaving no adhesive residue on the adherend and not breaking the base film.

Claims (3)

[Claims] 1. A pressure-sensitive adhesive layer is formed on one side of a base film made of a polyolefin-based resin, and the main components of the pressure-sensitive adhesive layer are a hydrogenated resin of a styrene-based random copolymer and an ethylene-α-olefin copolymer. And the content of the hydrogenated resin of the styrene-based random copolymer in the adhesive is 3
A surface protective film, which is 0 to 60% by weight. 2. The styrene-based random copolymer hydrogenated resin of the pressure-sensitive adhesive layer is 7 to 45% by weight of a styrene-based monomer.
The surface protection film according to claim 1, wherein the surface protection film comprises 93 to 55% by weight of butadiene. 3. The melt flow rate of the hydrogenated resin of the styrene-based random copolymer of the pressure-sensitive adhesive layer is 230 ° C.,
3. The surface protective film according to claim 1, wherein the surface protection film has a weight of 4 to 20 g / 10 minutes at 2.16 kg.