JPH07117195A - Surface protective film - Google Patents

Abstract

PURPOSE:To prevent the surface of a coated article from being stained even through it is allowed to stand for a long period by employing for an adhesive layer a composite consisting mainly of butyl rubber and liquid polyisobutylene. CONSTITUTION:The surface protective film is such that an adhesive layer is formed on one surface of a base material layer consisting of polyolefin resin layer, e.g. polyethylene, polyolefin, and these copolymeric substances. The adhesive layer consists of isobutylene-isoprene copolymer and a composite consisting mainly of liquid polyisobutylene. Also, the isobutylene-isoprene copolymer used for an adhesive layer substantially belongs to butyl rubber, and is a copolymer having isoprene at a rate of 0.5-3wt.% and 200,000-500,000 at Flory viscosity mean molecular weight. In addition, the amounts of isobutylene-isoprene copolymer and liquid ployisobutylene are preferably determined so that the latter is 20-200 pts.wt. relative to 100 pts.wt. in the former.

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 used for the purpose of preventing contamination and external damage of a coated steel plate, a synthetic resin molded product, or an automobile.

[0002]

2. Description of the Related Art Conventionally, polyester resin, vinyl chloride resin, polyethylene resin, etc. have been used as a base material for protecting painted steel plates, machine parts, metal household products, synthetic resin molded products, etc. from contamination and external damage. A laminate coated with a releasable rubber-based or acrylic-based pressure-sensitive adhesive is used as a surface protective film. In addition, in the case of automobiles for export, paraffin wax or the like is spray-coated to protect the exterior from contamination and scratches.

[0003]

[Problems to be Solved by the Invention] Painted steel sheets, synthetic resin molded products, automobiles for export, etc.
Temporary storage (usually 2 to 12 months) is often performed indoors or outdoors. However, when the above-mentioned laminate is used as a surface protective film, a difference occurs in the coating surface state between the part that is in close contact and the part that is not (portion containing bubbles) during temporary storage, and There is a problem that after the protective film is peeled off, a pattern having different gloss appears. Therefore, various improvements have been made in the pressure-sensitive adhesive composition and the like, but at present, they are not satisfactory. Also, in the case of paraffin wax, etc., since there is no film forming performance,
At the time of peeling, it is removed by physical scraping or washing with an organic solvent such as kerosene, and a great deal of labor is currently required for drainage treatment and environmental pollution prevention.

[0004]

Means for Solving the Problems As a result of intensive studies to overcome the above-mentioned problems, the present inventors have found that even if they are left for a long period of time, they do not affect the coated surface of an adherend, and We have developed a surface protection film that does not require a scraping or washing process. Thus, the gist of the present invention is that on one surface of the base material layer made of a polyolefin resin,
In the surface protection film formed by the pressure-sensitive adhesive layer,
The surface protective film is characterized in that the pressure-sensitive adhesive layer is a composition containing an isobutylene-isoprene copolymer and liquid polyisobutylene as main components.

The present invention will be described in detail below. The base material layer made of a polyolefin resin is polyethylene,
Films of polypropylene, polyethylene / polypropylene block copolymer, ethylene / vinyl acetate copolymer, etc. are used. The thickness of the film may be appropriately determined depending on the content and the application, but is usually about 20 to 150 μm. If it is 20 μm or less, the resistance to external damage may be poor, and if it is 150 μm or more, the lapping property may be poor and the economy may be poor.

The isobutylene-isoprene copolymer used in the pressure-sensitive adhesive layer is a so-called butyl rubber copolymer having a proportion of isoprene of 0.5 to 3% by weight and a Flory viscosity average molecular weight of 200,000 to 500,000. And especially the Flory viscosity average molecular weight of 350,000-
The range of 450,000 is preferable. 200,00
When it is 0 or less, the cohesive force becomes weak and the removability may be poor, and when it is 500,000 or more, the solubility may be poor. The liquid polyisobutylene has a Flory viscosity average molecular weight of 30,000 to 100,000.
It is preferably 0, particularly 40,000 to 70,000. If it is less than 30,000, the cohesive force will be weakened and the removability will be deteriorated, which will cause adhesive residue.
If it is more than 100,000, the adhesive strength will be weakened, and it may peel off before it reaches the consumer.

The amount of liquid polyisobutylene 20 is based on 100 parts by weight of the isobutylene-isoprene copolymer.
Parts by weight to 200 parts by weight, preferably 50 parts by weight to 100
Parts by weight. If it is 20 parts by weight or less, the adhesive strength may be poor, and if it is 200 parts by weight or more, the removability may be poor, which is not preferable. Incidentally, in the case of temporary storage outdoors, known additives such as ultraviolet absorbers and antioxidants are added to the base material layer and / or the pressure-sensitive adhesive layer within a range that does not impair the object of the present invention. Can be blended. Further, the surface protective film of the present invention may be formed of three or more layers by providing an intermediate layer depending on the purpose and application in addition to the base material layer and the pressure-sensitive adhesive layer.

In order to produce the surface protective film of the present invention, an isobutylene-isoprene copolymer as a pressure-sensitive adhesive and liquid polyisobutylene are dissolved in a solvent such as toluene on a base material layer made of a polyolefin resin film. The dissolved coating solution may be applied onto the substrate by a usual method such as a reverse coating method and dried.

[0009]

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 A polypropylene film (thickness: 50 μm, PF341, manufactured by Mitsubishi Kasei Co., Ltd.) was used as a base material, and an isobutylene-isoprene copolymer (Flory viscosity average molecular weight 350,000, Exxon Chemical Co., Ltd.) was used on the base material. Exxon-butyl-065) 10 parts by weight, liquid polyisobutylene (Flory viscosity average molecular weight 35,000, Exxon Chemical Co., Ltd., Vistanex LM-MS) 5 parts by weight, and an adhesive coating liquid consisting of 60 parts by weight of toluene. Was coated by a reverse coating method at 15 g / m ² (solid content) and dried by holding it in an oven at 100 ° C. for 2 minutes to obtain a surface protective film. With respect to the obtained surface protection film, initial adhesive strength, removability and paint surface stain resistance after peeling were evaluated, and the results are shown in Table 1. The evaluation method is as follows.

(1) Initial Adhesion Strength The obtained surface protection film was attached to a coated steel plate (paint; acrylic-melamine resin and several other types), and JIS K68 was used.
According to No. 54, the 180 ° peel strength was evaluated.

(2) Removability and paint surface contamination after peeling a) Indoor exposure 6 months b) Outdoor exposure 6 months c) Accelerated heat resistance test 80 ° C x 10 hours d) Accelerated weather resistance test Sunshine weather meter 300
Time A surface protective film was attached to a coated steel sheet, exposed to the conditions of a) to d), and then a peeling operation was performed to evaluate the removability at that time and the contamination on the coated surface. The evaluation criteria are as follows.

[0012]

[Table 1] Removability ○ ・ ・ ・ Good △ ・ ・ ・ Slight adhesive residue × ・ ・ ・ Cohesive failure (complete adhesive residue) Coating surface contamination ○ ・ ・ ・ Good △ ・ ・ ・ Small appearance change × ・..Significant change in appearance --- Unable to evaluate due to adhesive residue

Example 2 A polypropylene film (thickness: 50 μm) in which known ultraviolet absorbers and light stabilizers were blended and the ultraviolet region (380 nm or less) was cut was used as a substrate, and Example 1 was formed on this substrate. A pressure-sensitive adhesive layer similar to the above was formed by the same method to obtain a surface protection film. The obtained film was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 Isobutylene-on a substrate similar to that used in Example 2
Isoprene copolymer (Flory viscosity average molecular weight 45
50,000, manufactured by Exxon Chemical Co., Ltd., Exxon Butyl-
268) 10 parts by weight, liquid polyisobutylene (Flory viscosity average molecular weight 46,000, Exxon Chemical Co., Ltd.)
Manufactured by Vistanex LM-MH), 3 parts by weight, 0.1 part by weight of antioxidant, and 60 parts by weight of toluene to form a pressure-sensitive adhesive layer in the same manner as in Example 1,
A surface protection film was obtained. The obtained film was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 An acrylic re-peelable pressure-sensitive adhesive (manufactured by Toyo Ink Kogyo Co., Ltd., Olivene BP) on a substrate similar to that used in Example 1.
S-3180-3A) was applied at 15 g / m ² (solid content) to obtain a surface protection film. This film was evaluated in the same manner as in Example 1, and the results are shown in Table-1.

COMPARATIVE EXAMPLE 2 Isobutylene-on a substrate similar to that used in Example 1
10 parts by weight of isoprene copolymer (manufactured by Exxon Chemical Co., Ltd., exon butyl-268), aromatic modified terpene hydrocarbon resin (molecular weight 600, Yasuhara Chemical Co., Ltd.)
Manufactured by YS Resin TO105) and 60 parts by weight of toluene to form an adhesive coating solution in the same manner as in Example 1 to obtain a surface protective film. The obtained film was evaluated in the same manner as in Example 1, and the results are shown in Table-1.

Comparative Example 3 A surface protective film was obtained by forming the same pressure-sensitive adhesive layer as in Comparative Example 1 on the same substrate as that used in Example 2 by the same method. The obtained film was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 4 A surface protective film was obtained by forming the same pressure-sensitive adhesive layer as in Comparative Example 2 on the same substrate as that used in Example 2 by the same method. The obtained film was evaluated in the same manner as in Example 1, and the results are shown in Table-1.

Comparative Example 5 10 parts by weight of natural rubber (Pale crepe, Mooney viscosity ML60 ± 5) on the same substrate as used in Example 2,
A pressure-sensitive adhesive coating liquid comprising 7 parts by weight of a terpene phenol resin (molecular weight 600, YS Polystar T115 manufactured by Yasuhara Chemical Co., Ltd.), 0.2 parts by weight of an antioxidant, and 60 parts by weight of heptane was formed in the same manner as in Example 1. A surface protective film was obtained. The obtained film was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0020]

[Table 2]

[0021]

The surface protective film of the present invention does not contaminate the coated surface of an adherend even if it is left for a long period of time,
It is extremely useful as a coated steel plate, synthetic resin molded product, or surface protection film for automobiles.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C09J 7/02 JLF // C09J 123/22 JBZ

Claims (2)

[Claims] 1. A surface protective film having a pressure-sensitive adhesive layer formed on one surface of a base material layer made of a polyolefin resin, wherein the pressure-sensitive adhesive layer has an isobutylene-isoprene copolymer and liquid polyisobutylene as main components. A surface protective film characterized by being a thing. 2. The compounding amount of isobutylene-isoprene copolymer and liquid polyisobutylene in the pressure-sensitive adhesive layer is 100
The latter is 20 to 200 parts by weight with respect to parts by weight.
The surface protection film described.