JPH06336577A - Surface-protecting film - Google Patents

Abstract

PURPOSE:To prepare a surface-protecting film which, when applied to the surface of a soft coating layer of a soft and colored steel sheet, hardly causes change in gloss of the coating layer due to deformation, hardly leaves behind traces of film-lamination work such as traces of air bubbles or parting hardly undergoes change in adhesive power with time, and exhibits an excellent releasability. CONSTITUTION:This surface-protecting film is obtd. by coating an olefinic polymer film substrate with a self-adhesive which comprises 100 pts.wt. at least one polymer selected from the group consisting of polyisobutylene, a butyl rubber, and polybutene and having a number average mo.wt. of 150,000 or lower and a ratio of wt. average to number average mol.wt. of 10 or lower as a main component and 0.1-10 pts.wt. release agent added thereto.

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 protecting a coating film such as a soft color steel plate.

[0002]

2. Description of the Related Art Recently, there has been a strong tendency for household appliances, inner walls and outer walls of buildings to be subjected to complicated processing in order to increase added value, and coating films such as colored steel sheets used for this purpose. In order to improve workability, the number of flexible pencil hardnesses of HB or less has been increasing. Furthermore, the consumer preference has shifted from glossy to satin-like, and the flatness of the coating has changed from smooth to rough. Processing of colored steel sheets,
Although an adhesive film is used for surface protection during transportation, storage, etc., due to the softening of the coating film for the above-mentioned reasons, even slight pressure deforms due to temperature and application time, Changes in roughness due to changes in roughness, bubbles that tend to be stressed, and film sticking traces due to deformation at edge parts such as parting-off parts were more likely to occur.

[0003]

As the surface protection film, paper or plastic film coated with an adhesive is generally used. Since this pressure-sensitive adhesive is a viscoelastic body also called a pressure-sensitive adhesive, it is affected by pressure and temperature and deforms with time. Further, the surface of the adherend usually has irregularities of several microns to several tens of microns. On the other hand, since the surface protection film is attached under momentary pressure such as roll pressing, the contact with the adherend is not perfect when viewed microscopically. The contact area increases and the adhesive strength increases. Further, the adhesive force also increases due to intermolecular force such as hydrogen bond between the pressure-sensitive adhesive and the adherend or the formation of a primary bond. Therefore, when peeling off the used surface protection film, if the increase in adhesive strength is too great, peeling becomes difficult, the film is cut,
Adhesive residue occurs. This phenomenon is particularly likely to occur because the surface is rough, and countermeasures have been strongly desired. An object of the present invention is to provide a surface protection film that solves the above problems.

[0004]

The present inventors have arrived at the present invention as a result of intensive research on the above problems. The present invention comprises 100 parts by weight of a main component which is made of any one or more of polyisobutylene, butyl rubber and polybutene and has a number average molecular weight of 150,000 or less and a ratio of the weight average molecular weight to the number average molecular weight of 10 or less. On the other hand, the present invention relates to a surface protective film obtained by applying an adhesive containing 0.1 to 10 parts by weight of a release agent onto a support of an olefin film.

The olefinic film used as the support here is an α, such as ethylene, propylene or butene.
-Olefin homopolymers and copolymers, and also copolymers of monomers such as vinyl acetate and methyl methacrylate. Of these, polyethylene is preferable from the viewpoint of price. Further, for the purpose of improving the weather resistance, heat resistance, processability and workability of the support, an antioxidant, an ultraviolet absorber,
A lubricant, a plasticizer or the like may be added. Polyisobutylene used as the main component of the pressure-sensitive adhesive is a polymer of isobutylene, butyl rubber is a copolymer of isobutylene and isoprene, and polybutene is a structural isomer such as isobutylene and 1-butene, n-butene. And a chlorinated product of a monomer having a crosslinkable functional group such as a carboxylic acid group or a hydroxyl group. One or a mixture of these is used.

The molecular weight can be measured by a high performance liquid chromatographic method, a viscosity method, an ultracentrifugation method, a light scattering method, a membrane osmotic pressure method, a boiling point elevation method, etc., but the high performance liquid chromatography method is simple and generally used. Is widely used as a new method. The number average molecular weight (Mn) can be represented by the following formula (1), and the weight average molecular weight (Mw) can be represented by the following formula (2). In the formula,
Mi represents the molecular weight and Ni represents the number of molecules.

[0007]

[Equation 1] Mn = ΣMi · Ni / ΣNi ………… (1)

[0008]

[Math 2] Mw = ΣMi ² · Ni / ΣMi · Ni (2) If the number average molecular weight exceeds 150,000, traces of sticking of the protective film tend to occur, and even if it is 150,000 or less, the weight average The ratio between the molecular weight and the number average molecular weight is 10
If it exceeds, sticking marks are likely to occur.

As the release agent, vegetable oils and fats, aliphatic soaps,
Examples thereof include silicone polymers, fluororesins, waxes, and long-chain alkyl group-containing substances such as alkyl carbamates. In particular, a silicone polymer is preferable because it has a great effect of suppressing the generation of film sticking marks and the increase in the adhesive force with time.
The silicone polymer has various molecular weights and modifications having a siloxane bond represented by (Si-O-Si) as a skeleton, and is a straight silicone oil such as dimethyl silicone or methylphenyl silicone oil, and polyoxyalkylene. Examples thereof include copolymers, modified silicone oils such as amino-modified silicone, and emulsions thereof. The addition amount is 0.1 to 10 parts by weight with respect to 100 parts by weight of the main component. If the amount is less than 0.1 parts by weight, the film sticking traces remain and the effect of suppressing the increase in the adhesive force with time cannot be obtained, and if it exceeds 10 parts by weight, the adhesive force is significantly reduced or transferred by the release agent, which is preferable. Absent.

Further, in order to improve the adhesion of the pressure-sensitive adhesive, it is preferable to previously coat the support with a primer comprising an ethylene-vinyl acetate copolymer and / or a chlorinated polyolefin resin. The ethylene-vinyl acetate copolymer may be copolymerized with a monomer having a double bond, a carboxylic acid group, a crosslinkable functional group such as a hydroxyl group, in addition to the usual one. Examples of the chlorinated polyolefin include chlorinated polyethylene and chlorinated polypropylene, and a monomer having a double bond or a crosslinkable functional group such as a carboxylic acid group and a hydroxyl group may be copolymerized. In addition to the above components, the pressure-sensitive adhesive used in the present invention may contain a commonly-used compounding agent such as a tackifier, a softening agent, a weather resistance improver and a colorant.

[0011]

[Function] Since polyisobutylene, butyl rubber and polybutene have low polarity and are chemically stable structure, the adhesive force is difficult to increase and they have good characteristics. However, this alone is still insufficient to suppress the increase in the adhesive strength, and the addition of a release agent can realize a surface protective film with a small increase in the adhesive strength and good peelability. Further, the number average molecular weight of the main component is set to 150,000 or less, and the adhesive is made flexible to suppress the occurrence of sticking marks. Further, the addition of a release agent increases the displacement of the interface between the pressure-sensitive adhesive and the adherend, and suppresses mutual mass transfer due to the difference in polarity, which is also a factor in suppressing the occurrence of sticking marks. Further, by using the ethylene-vinyl acetate copolymer and / or the chlorinated polyolefin resin, sufficient anchoring force can be obtained even for an olefin film, so that an inexpensive adhesive film can be provided.

[0012]

EXAMPLES Examples of the present invention will now be described, but the present invention is not limited to these examples. Example 1 An ethylene-vinyl acetate copolymer (EV-550, was added to a 60 μm-thick polyethylene film subjected to corona treatment.
A primer comprising 50 parts by weight of Mitsui Polychemical, 50 parts by weight of a reactive ethylene-vinyl acetate copolymer (VR-103, manufactured by Mitsui Polychemical), and 1 part by weight of isocyanate (Sumijour N, manufactured by Sumitomo Biurethane). It is applied to a thickness of 0.1 μm, and polyisobutylene (Opanol B50, Mn 86000, Mn / Mw) is applied to this.
2.8, made by BASF) 100 parts by weight of silicone oil (KF96, viscosity 1000 cSt, made by Shin-Etsu Silicone) 1
A pressure-sensitive adhesive to which parts by weight were added was applied so as to have a thickness of 5 μm to prepare a surface protection film. The test results are shown in Table 1.

Example 2 A surface protective film was produced in the same manner as in Example 1 except that the amount of silicone oil was increased to 5 parts by weight. The test results are shown in Table 1. Comparative Example 1 A surface protective film was produced in the same manner as in Example 2 except that polyisobutylene having Mn of 658000 and Mn / Mw of 1.7 was used. The test results are shown in Table 1. Comparative Example 2 A surface protective film was produced in the same manner as in Example 2 except that polyisobutylene of Mn92000 and Mn / Mw150 was used. The test results are shown in Table 1.

Comparative Example 3 A surface protective film was produced in the same manner as in Example 1 except that the amount of silicone oil was increased to 20 parts by weight. The test results are shown in Table 1. Comparative Example 4 A surface protective film was produced in the same manner as in Example 1 except that silicone oil was not used. The test results are shown in Table 1.

Test conditions Polyester color steel sheet (made by Nippon Steel Tube, pencil hardness:
The surface protective films obtained in Examples and Comparative Examples were applied to B), and then heat-treated at 80 ° C. for 1 day. The adhesive force was measured immediately after application and after heat treatment. That is, room temperature 20 ° C, humidity 6
At 5%, the edge of the film having a width of 25 mm was folded back in the direction of 180 degrees, and the load (g) when peeled by pulling at a speed of 300 mm per minute was obtained.

[0016]

[Table 1] Note) Surface condition after heating is ◯: Good, A: Adhesive film sticking marks occur, B: Cloudy (extent: large), C:
Cloudy weather (degree: small).

Table 1 shows that the example has a smaller difference in the adhesive force before and after the deposition (the change in the adhesive force is smaller) than that of the comparative example, and is excellent in peelability.

[0018]

EFFECTS OF THE INVENTION The surface protective film of the present invention is less likely to cause a gloss change caused by the deformation of a coating film or a film sticking mark such as a bubble mark or a cut-off mark, and has a small change in adhesive force with time. It has excellent releasability.

Claims (3)

[Claims] 1. A main component of 100 parts by weight which is composed of one or more of polyisobutylene, butyl rubber and polybutene and has a number average molecular weight of 150,000 or less and a ratio of the weight average molecular weight to the number average molecular weight of 10 or less. To 10 parts by weight of the pressure-sensitive adhesive containing a release agent of 0.1 to 10 parts by weight,
A surface protection film formed by coating an olefin film support. 2. The surface protective film according to claim 1, wherein the release agent comprises silicone. 3. The surface protective film according to claim 1, wherein the olefin-based film is polyethylene, and an ethylene-vinyl acetate copolymer and / or a chlorinated polyolefin resin is used as a primer.