JP3354224B2 - Surface protection film - Google Patents

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. More specifically, it is suitable for surface protection of thin metal plates such as stainless steel plates, aluminum plates, copper plates, etc., and particularly for surface protection of thin metal plates when performing multiple drawing, roll forming, bender processing, etc. The present invention relates to a surface protective film that can be used for:

[0002]

2. Description of the Related Art Conventionally, as a protective film for a metal plate such as a stainless steel plate, for example, a film made of polyvinyl chloride, low density polyethylene, polypropylene, or the like has been used as a base material.

[0003] The film made of polyvinyl chloride,
Although it has high mechanical strength and extensibility, it is excellent in workability, but since chlorine is contained in the raw material, it causes problems such as generating harmful gases during incineration and damaging the incinerator. Has the disadvantage that its disposal is difficult.

Further, the film made of the low-density polyethylene does not contain chlorine in the raw material and is easy to dispose of, but has a drawback that the mechanical strength is insufficient and the workability is poor.

On the other hand, a film made of polypropylene is easy to dispose of and at the same time has a certain degree of processability. However, such a film made of polypropylene has a high hardness, so that its processability is insufficient compared with the film made of polyvinyl chloride. Further, since the film made of polypropylene has a property of whitening upon impact, bending, elongation, etc., there is a problem that the aesthetic appearance of the metal plate surface is lost after processing.

[0006] In order to solve the problems in the film made of polypropylene, an ethylene-propylene copolymer (Japanese Patent Publication No.
No. 14,667) and a film imparted with flexibility by blending an ethylene-vinyl acetate copolymer (Japanese Patent Application Laid-Open No. 53-60940) have been proposed. Such whitening properties are not sufficiently improved, and the problem of poor transparency arises.

Attempts have also been made to blend diene rubbers with polypropylene, but the polypropylene and diene rubbers have poor compatibility and are difficult to blend themselves. However, there is a problem that the target strength is insufficient and the transparency is also poor.

[0008]

The inventors of the present invention have conducted intensive studies in view of the above-mentioned prior art, and as a result, obtained by blending a polypropylene resin and a specific styrene-butadiene rubber at a specific ratio. Film has high mechanical strength and flexibility, has excellent workability, does not whiten against impact, bending, elongation, etc., has excellent transparency, and is easy to dispose of. The present invention has been completed.

[0009]

That is, the present invention provides a film base comprising 20 to 85% by weight of a polypropylene resin (A) and 15 to 80% by weight of a styrene-butadiene rubber (B) obtained by adding hydrogen to butadiene. A surface protective film for a metal plate to be drawn which is provided with an adhesive layer and has a 10% modulus of 3 to 7 MPa.
And a surface protective film having a hardness of 81 to 98 .

[0010]

Operation and Examples As described above, the surface protective film of the present invention can be used as a polypropylene resin (A) 20 to 85.
Weight percent and styrene with hydrogen added to butadiene
Butadiene rubber (B) Gold film to be drawn having an adhesive layer provided on a film substrate consisting of 15 to 80% by weight
A surface protection film for a metal plate having a 10% modulus.
3 to 7 MPa and a hardness of 81 to 98 .

The polypropylene resin (A) used for the film substrate is, for example, polypropylene,
Ethylene-propylene random copolymer, ethylene-
Ethylene-propylene copolymer such as propylene block copolymer, ethylene-propylene-butene random terpolymer, ethylene-propylene-butene terpolymer such as ethylene-propylene-butene block terpolymer, propylene-butene copolymer, propylene-maleic anhydride copolymer and the like Examples of the resin include a resin having a propylene content of 50% by weight or more. Among these, polypropylene is preferable because a film substrate having high mechanical strength can be obtained.

When the ethylene-propylene copolymer is used, the flexibility of the obtained surface protective film tends to be further improved. Such an ethylene-propylene copolymer has an ethylene content of 15% by weight.
Hereinafter, it is particularly preferable that the content is 10% by weight or less. When the ethylene content exceeds 15% by weight, the mechanical strength of the obtained surface protective film tends to decrease.

As the polypropylene resin (A), for example, a melt flow rate (ASTM D 12
38 (230 ° C., 2.16 kg)) is 0.01 to 50 g.
/ 10 minutes, preferably 0.05 to 15 g / 10 minutes. When the melt flow rate is less than 0.01 g / 10 minutes, the melt viscosity is low, and it tends to be difficult to form a film substrate during extrusion, and when the melt flow rate exceeds 50 g / 10 minutes. Has a high melt viscosity and tends to be difficult to knead during extrusion.

Styrene-butadiene rubber (B) obtained by adding hydrogen to butadiene used for the film substrate
(Hereinafter referred to as rubber (B)) can be easily melted by heating, has excellent extrusion characteristics such as good fluidity, and is easily processed into a film substrate, and is obtained by a solution polymerization method. Block copolymers are preferred.

The styrene content of the rubber (B) is 5-4.
It is preferably 0% by weight, especially 8 to 35% by weight. When the styrene content is less than 5% by weight, the strength of the obtained surface protective film tends to be insufficient, and when it exceeds 40% by weight, the hardness of the surface protective film becomes too large. Therefore, flexibility tends to be low, compatibility with the polypropylene resin (A) is low, and transparency of the surface protective film tends to be low.

In the rubber (B), the residual unsaturation in the butadiene segment is preferably at most 10 mol%, more preferably at most 5 mol%. When the residual unsaturation ratio in such a butadiene segment exceeds 10 mol%, the compatibility with the polypropylene resin (A) and the weather resistance of the obtained surface protective film tend to decrease.

Incidentally, the melt flow rate of the rubber (B) is usually included in the numerical range of the melt flow rate of the polypropylene resin (A).

The method for obtaining a film substrate from the polypropylene resin (A) and the rubber (B) is not particularly limited. For example, a twin-screw extruder is used to obtain a polypropylene resin at a cylinder temperature of about 210 to 230 ° C. (A)
And the rubber (B) are melt-kneaded to produce pellets from the obtained strand-like extrudates, and the pellets are extruded at a die temperature of about 210 to 230 ° C. using a T-die or the like using, for example, a single screw extruder. A method or the like can be adopted.

The mixing ratio of the polypropylene resin (A) and the rubber (B) is such that the polypropylene resin (A) is 20 to 85% by weight, preferably 25 to 80% by weight, more preferably 40 to 75% by weight. That is, the rubber (B) is adjusted to be 15 to 80% by weight, preferably 20 to 75% by weight, and more preferably 25 to 60% by weight.
When the amount of the polypropylene-based resin (A) is less than 20% by weight, the mechanical strength of the obtained film substrate becomes insufficient, and when the amount exceeds 85% by weight, In addition, the hardness of the film base material becomes too large, so that the workability of the surface protective film is reduced, and it is difficult to prevent the surface protective film from whitening due to impact or the like.

The thickness of the film substrate depends on the intended use of the obtained surface protective film and the like, and cannot be unconditionally determined. However, if it is too small, the mechanical strength is insufficient. It tends to be torn and, for example, tends to damage metal plates such as stainless steel plates that are protected, and if it is too large, it tends to be too hard to be processed by drawing, bending, etc. Therefore, it is usually preferably about 30 to 200 μm, particularly preferably about 40 to 150 μm.

The surface protective film of the present invention can be obtained by providing a pressure-sensitive adhesive layer on the film substrate thus obtained.

Examples of the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer include rubbers such as natural rubber, polyisobutylene rubber, butyl rubber, and synthetic rubber such as styrene-isoprene block copolymer rubber; acrylate ester copolymers; Ethers, synthetic resins such as ethylene-vinyl acetate copolymers and the like, whose main component is one or two or more are listed. Among them, those having excellent weather resistance and high cohesive strength are mentioned. From the viewpoint, those having an acrylic ester copolymer as a main component are preferred.

The method for forming the pressure-sensitive adhesive layer on the film substrate is not particularly limited. For example, a method in which the pressure-sensitive adhesive is dissolved in an organic solvent such as toluene, xylene, methyl ethyl ketone or the like and dispersed in water is used. The method of applying and drying on a film substrate, the method of melt-coating an adhesive on the film substrate, the method of co-extruding the film substrate and the adhesive during the production of the film substrate, and the like. It can be appropriately selected and employed depending on the type of the agent and the like.

Thus, the thickness of the pressure-sensitive adhesive layer provided on the film substrate has a cohesive force and, for example, can adhere to irregularities of a protected metal plate such as a stainless steel plate and adhere to the same. About 5-100 μm, especially about 1
It is preferably from 0 to 50 μm.

As described above, the surface protective film of the present invention has a pressure-sensitive adhesive layer provided on a film substrate. In the present invention, the adhesiveness between the film substrate and the pressure-sensitive adhesive layer is improved. For further improvement, it is preferable to perform a chemical treatment or a physical treatment on the surface of the film substrate in contact with the pressure-sensitive adhesive layer to form an oxidation treatment layer.

As a method for treating the surface of the film substrate for forming the oxidized layer, there are, for example, a chromic acid treatment method using sulfuric acid or hot nitric acid, for example, an ozone exposure treatment method performed at 100 ° C. or higher, and a high-pressure method involving corona discharge. Examples of the method include an electric shock exposure treatment method, for example, an ionizing radiation irradiation treatment method performed at a temperature at which the surface is oxidized, such as 100 ° C. or higher, and a flame exposure treatment method. Among these, the oxidation treatment effect is excellent and the operation is easy. In that
A high-voltage impact exposure treatment method involving corona discharge is preferred.

The shape of the surface protective film of the present invention is not particularly limited, and may be appropriately determined according to the shape of the metal plate to be protected. A flat plate is the most common. Examples thereof include a tape shape and a sheet shape.

Next, the surface protective film of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Polypropylene FM was used as the polypropylene resin (A).
202B (manufactured by Tokuyama Soda Co., Ltd., melt flow rate (2
25 °% by weight at 30 ° C., 2.16 kg) 8 g / 10 min) and DYNARON1320P as rubber (B) (manufactured by Nippon Synthetic Rubber Co., Ltd., styrene content 10% by weight, residual unsaturation ratio in butadiene segment 2 mol%) 75 % By weight into a twin-screw extruder, melt-kneaded at a cylinder temperature of 210 ° C., and cut the extrudate extruded from a round die.
Pellets were made.

The obtained pellets are put into a single screw extruder,
It was extruded at 220 ° C. from a T-die to produce a film substrate having a thickness of 80 μm.

After one surface of the obtained film substrate is subjected to a high-voltage impact exposure treatment with corona discharge to form an oxidation treatment layer, an acrylic pressure-sensitive adhesive (2-ethylhexyl acrylate 80% by weight) is formed on the oxidation treatment layer. , Methyl methacrylate 15% by weight and hydroxyethyl acrylate 5
Polyisocyanate (Coronate L, Nippon Polyurethane Industry Co., Ltd.)
A 30% by weight toluene solution prepared by mixing 3 parts by weight) was applied so that the thickness after drying was 10 μm, and an adhesive layer was provided to obtain a surface protective film.

Example 2 A surface protective film was obtained in the same manner as in Example 1 except that the mixing ratio of the polypropylene FM202B was changed to 50% by weight and the mixing ratio of DYNARON1320P was changed to 50% by weight.

Example 3 A surface protection film was obtained in the same manner as in Example 1, except that the blending ratio of the polypropylene FM202B was changed to 75% by weight and the blending ratio of DYNARON1320P was changed to 25% by weight.

Example 4 In Example 2, DYNARON1 was used as the rubber (B).
Surface protection was carried out in the same manner as in Example 2 except that DYNARON 1910P (manufactured by Nippon Synthetic Rubber Co., Ltd., styrene content 30% by weight, residual unsaturation ratio in butadiene segment 2 mol%) 50% by weight was used instead of 320P. I got the film.

Example 5 In Example 2, an ethylene-propylene copolymer S-131 (manufactured by Sumitomo Chemical Co., Ltd.) was used in place of polypropylene FM202B as the polypropylene resin (A).
Melt flow rate (230 ° C, 2.16 kg) 1.2
g / 10 minutes, ethylene content about 10% by weight) 50% by weight
A surface protective film was obtained in the same manner as in Example 2 except that を was used.

Comparative Example 1 A surface protective film was obtained in the same manner as in Example 1, except that the blending ratio of the polypropylene FM202B was changed to 10% by weight and the blending ratio of DYNARON1320P was changed to 90% by weight.

Comparative Example 2 A surface protective film was obtained in the same manner as in Example 4, except that the mixing ratio of the polypropylene FM202B was changed to 90% by weight and the mixing ratio of DYNARON 1910P was changed to 10% by weight.

Comparative Example 3 100 wt% of polypropylene FM202B was put into a single screw extruder, and extruded at 230 ° C. from a T die to a thickness of 80 μm.
m was prepared.

Using the obtained film substrate, a surface protective film was obtained in the same manner as in Example 1.

Comparative Example 4 A styrene-butadiene rubber in which hydrogen was not added to butadiene instead of DYNARON1320P (JSR SL574, Nippon Synthetic Rubber Co., Ltd.)
Surface protective film was obtained in the same manner as in Example 2 except that 50% by weight of styrene content (15% by weight) was used.

Test Example 1 The surface protective films obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were examined for workability, 10% modulus, hardness and transparency according to the following methods. Table 1 shows the results.

(A) Workability A surface protection film is stuck on a stainless steel plate (SUS 304) having a thickness of 0.5 mm, and after one hour, drawing (one time) using a press (punch diameter 50 mm, drawing depth 15 mm) The surface protection film was visually observed for the state (break, whitening and floating) of the surface protective film as a drawability, and evaluated based on the following evaluation criteria.

(Evaluation criteria for tearing) A: No tearing of the film. B: The film has a slightly torn part,
There is no scratch on the stainless plate. C: The film is slightly torn and the stainless steel plate is slightly damaged. D: The film is torn, and the scratches on the stainless steel plate are conspicuous. E: The film is severely torn and the stainless steel plate is very scratchy.

(Evaluation Criteria for Whitening) A: No whitening is observed. B: Whitening is slightly observed. C: Whitening is remarkable.

(Evaluation Criteria for Floating) A: There is no peeling of the film at the bottom with a drawing depth of 15 mm. B: Peeling of the film is observed around the bottom corner with a drawing depth of 15 mm. C: Peeling of the film is observed over the entire bottom at a drawing depth of 15 mm.

(B) 10% modulus In order to examine the flexibility (extensibility) of the surface protective film,
The 10% modulus (MPa) of the surface protective film was measured according to the test method of JIS K 6732 "Agricultural polyvinyl chloride film".

The smaller the value of the 10% modulus, the better the flexibility (extensibility) of the surface protective film.

(C) Hardness The hardness (JISA) of the surface protective film was measured in accordance with JIS K6301 “Vulcanized Rubber Test Method”.

(D) Transparency The light transmittance of the surface protective film was measured in accordance with ASTM D 1003, and Haze (%) was calculated using the following equation.
I asked.

Haze (%) = (diffuse light transmittance / total light transmittance) × 10
0 The smaller the value of Haze, the better the transparency of the surface protective film.

[0051]

[Table 1]

From the results shown in Table 1, it can be seen that the surface protective films obtained in Examples 1 to 5 were torn even after being drawn, hardly whitened or lifted, had excellent flexibility, and had high hardness. It can be seen that they are excellent in processability and at the same time excellent in transparency.

[0053]

The surface protective film of the present invention is excellent in processability such as drawing and transparency, contains no component that generates harmful gas when incinerated, and can be easily disposed.

Therefore, the surface protective film of the present invention can be suitably used for protecting the surface of a thin metal plate or the like when, for example, drawing is performed many times.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-62-197409 (JP, A) JP-A-3-76744 (JP, A) JP-A-2-305814 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) C09J 7/02 B32B 27/00

Claims (3)

(57) [Claims] 1. A polypropylene resin (A) 20 to 85.
Weight percent and styrene with hydrogen added to butadiene
Butadiene rubber (B) 15 to 80% by weight of a film base, on which a pressure-sensitive adhesive layer is provided, which is subjected to drawing processing
A surface protection film for a metal plate having a 10% modulus.
Surface protection of 3 to 7 MPa and hardness of 81 to 98
Film . 2. A styrene-butadiene rubber (B) obtained by adding hydrogen to butadiene has a styrene content of 5 to 40% by weight.
The surface protective film according to claim 1, wherein 3. The surface protective film according to claim 1, wherein the residual unsaturation ratio in the butadiene segment of the styrene-butadiene rubber (B) obtained by adding hydrogen to butadiene is 10 mol% or less.