JPS599590B2 - surface protection film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-sensitive adhesive surface protection film that has excellent transparency, heat resistance, oil resistance, and chemical resistance, and is stain-free.

Conventionally, in adhesive films for surface protection of metal plates, resin plates, plywood, etc., in order to obtain sufficient bonding strength between the base film and the adhesive, the film surface is physically or chemically oxidized or corona treated. Efforts such as undercoating with polyurethane compounds have been exhausted.

Strengthening These treatment methods are all aimed at activating the surface of the polyolefin base film, which has poor chemical activity, and adhesives that can obtain good bonding strength through such treatment include: Various acrylic ester polymers,
Pressure-sensitive adhesives containing vinyl ether polymers as a main component are known, and surface protection adhesive films of this type are currently on the market, but they have the following drawbacks.

In other words, since the above-mentioned adhesives are themselves chemically active and reactive, they may contaminate the surface of the adherend, whose surface is highly susceptible to change, or the adhesive may remain after the protective film is used. Problems may arise, such as the protective film becoming unremovable. On the other hand, pressure-sensitive adhesives mainly made of polyisobutylene rubber are extremely chemically inert and non-reactive due to their molecular structure, so they can contaminate the surface of the adherend or leave adhesive residue. Although it maintains useful performance as a pressure-sensitive adhesive for protective films, without modification for the purpose of activating the pressure-sensitive adhesive,
The above-mentioned method of treating the surface of a polyolefin film does not provide sufficient bonding strength with the film.

Therefore, in addition to activating the surface of the film as a method of measuring the adhesion of the pressure-sensitive adhesive mainly composed of rubber to the base film, changing the resin composition of the film base material, i.e., changing the resin composition of the film base material, i.e., changing the composition of polypropylene and polyethylene. It has been proposed to melt-form a film from a mixed resin.

For example, Japanese Patent Publication No. 50-14667 states that when the polyethylene/polypropylene ratio is 85-25/15-75, a strong bonding force with the adhesive can be obtained.

However, this protective film has the following drawbacks. 11. Since polyethylene is mixed, the original strength of polypropylene is reduced.

2. Polypropylene's inherent chemical resistance and oil resistance are reduced because polyethylene is mixed.

3. Since polyethylene is mixed, the inherent heat resistance of polypropylene is reduced.

4. Since polyethylene is mixed, the original transparency and gloss of polypropylene are lost.

5. Due to the mixing of polyethylene, unevenness is formed on the surface of the film, and if the protective film is left unrolled, the adhesive will dig into the recesses on the back surface over time, making it difficult to unwind.

6. If the amount of polypropylene is large, the adhesion between the adhesive mainly composed of polyisobutylene rubber and the base film is insufficient, resulting in adhesive residue, that is, adhesive residue.

As mentioned above, the present inventors have developed a good surface protection film by applying an adhesive mainly composed of polyisobutylene rubber, which is useful as an adhesive for surface protection films, to a polypropylene film without activating it. As a result of extensive experimental research, we have found that chlorine is used as an undercoat between an unstretched or stretched film containing 80% or more of polypropylene as a base film and an adhesive mainly composed of polyisobutylene rubber. By using a mixture of polypropylene and polyisobutylene rubber (or butyl rubber), it has excellent transparency, gloss, and oil resistance.
It has been discovered that a new surface protection film that exhibits excellent heat resistance and chemical resistance can be obtained.

Thus, the present invention provides a film containing 80% or more polypropylene with a chlorine content of 15 to 40% by weight. The present invention provides a surface protection film characterized in that a pressure-sensitive adhesive mainly made of polyisobutylene nonpolar rubber is applied via an undercoat containing chlorinated polypropylene and polyisobutylene rubber and/or butyl rubber. be.

To explain the present invention in more detail, the film base material used in the present invention is made of a resin having a polypropylene content of 80% or more and having a thickness of 0.02 to 0.1511, and has desired physical properties such as transparency, chemical resistance, and heat resistance. The content is preferably 90% or more in order to fully utilize the inherent performance of polypropylene.

Of course, a propylene homopolymer film is also preferred. When the polypropylene content is less than 80%, it is difficult to obtain any of the various desired performances. Further, it is preferable to use a stretched polypropylene film as the base material because even higher levels of strength, transparency, heat resistance, and chemical resistance can be obtained. The component used together with 80% or more of polypropylene is polyolefin such as polyethylene, ethylene monovinyl acetate copolymer, or a copolymer or mixture containing olefin as a main component. For example, by adding about 20% or less of polyethylene, which does not impair the inherent performance of propylene, workability during film molding can be improved and appropriate flexibility can be imparted to the film. The primer used in the present invention was proposed by the present inventors, and has a chlorine content of 1
5-40% (wt%) chlorinated polypropylene 5-80
part and polyisobutylene rubber and/or butyl rubber 20
An undercoat prepared by dissolving 0.1 to 15% of the main component in a solvent such as toluene or n-hexane is well used.

A tackifier as described below can be added to this primer. Both components of the primer must be included; for example, chlorinated polypropylene alone cannot be used well as a surface protection film because adhesive remains when it is peeled off, resulting in contamination of the adhesive surface.

The polyisobutylene nonpolar rubber used in the adhesive of the present invention is, for example, a polymer of isobutylene, a random copolymer of isobutylene and normal butylene, a copolymer of isobutylene and isoprene, or a vulcanized product thereof. . In the present invention, these are toluene, xylene, benzene, n-
3-3 in an organic solvent such as hexane (toluene is the most suitable)
A solution of 0%, preferably 5 to 20% is used. The adhesive mainly composed of polyisobutylene rubber used in the present invention can be applied to polypropylene without adding other polar rubbers or polar tackifiers like ordinary pressure-sensitive adhesives. Adheres well to the film base material.
However, in order to adjust the adhesive strength, it may be preferable to add a tackifier such as polybutene, rosin, terpene resin, pine oil, etc. to the adhesive. Furthermore, when using the protective film, if light unwinding is preferred, a known release agent may be provided on the back surface of the base film. The present invention will be described below with reference to Examples, but the present invention is not limited by the Examples. Example 1 The above mixed solution was used as a primer to coat one side of a 0.05 mm thick unstretched homopolypropylene film with a thickness of 0.005 mm.
After coating and drying, 10 parts of polyisobutylene (Vistanecs MML-120) and 5 parts of polybutene (
1 made of Idemitsu Polybutene 300H manufactured by Idemitsu Petrochemical Co., Ltd.
The thickness of the 5% toluene solution after drying is 0.01m77! The surface protection film of the present invention was obtained by applying the following coating.

When this surface protection film is attached to the exterior of an electrolytically colored stainless steel bathtub, its excellent transparency not only makes it possible to distinguish the attached pattern and color, but also the excellent gloss of the film base material makes it possible to identify the product. It was possible to increase the value.

I removed the protective film after 3 months, but the peel resistance was 2009.
/25 mm, and had good performance as a protective film, with no abnormality such as discoloration due to glue residue. Comparative example 1 polyethylene 0.07m7! Corona treatment was applied to one side of L thickness, and a 20% toluene solution consisting of 100 parts of a commercially available acrylic rubber adhesive and 5 parts of a commercially available polyurethane crosslinking agent was applied to this treated surface so that the thickness after drying was 0.01 mm. This was applied to prepare an adhesive film.

The adhesive films of Example 1 and Comparative Example 1 were bonded to the surface of the name plate, and a commercially available thermal adhesive film was bonded to the back surface. We attempted to heat-bond this name plate to a plastic molded product using a hot press. The crimping conditions are temperature 15
0℃ pressure 3kg/c! l time is 60 seconds. During thermocompression bonding, the polyethylene-based adhesive tape melted under heat and could not be peeled off, but the surface protection film of Example 1 did not melt and could be peeled off without any glue residue. In recent years, the method of fixing name plates has been shifting from double-sided adhesive tapes to thermal adhesive films, so the effectiveness of the protective film of the present invention is clear compared to the conventional protective film of Comparative Example 1. Example 2 After applying the primer of Example 1 to stretched polypropylene with a thickness of 0.05 nm, a 20% toluene solution consisting of 10 parts of polyisobutylene and 10 parts of polybutene was dried to a thickness of 0.011 nm.
1 to obtain a surface protection film of the present invention.

After degreasing a 1m1 thick brass plate with ethyl acetate, applying Example 2 and Comparative Example 1, immersing it in the following chemicals at 60°C for 10 minutes, washing with water, and observing the plate.

The test results are shown in Table 1.

Evaluation ◎ No liquid seepage, no change ○ Slight seepage Δ A lot of liquid seepage, discoloration of the board × Film peels From the above test results, the surface protection film of the present invention has chemical resistance. It can be seen that it can be used for special purposes such as protecting the back (untreated) part of copper plates and other metal plates from chemical baths during various plating processes and chemical polishing processes.

Example 3 10 parts of polyethylene resin and 90 parts of polypropylene resin were mixed and extruded using a hot melt extruder to obtain a film of 0.05 ml.

After applying the primer of Example 1 to this film, the adhesive of Example 1 was applied and dried to obtain a surface protection film. Comparative example
2 Polyethylene 0.05m1! Corona treatment was applied to one side of the thickness, and a 20% toluene solution of 100 parts of a commercially available acrylic adhesive for surface protection sheets and 5 parts of a commercially available crosslinking agent was added to this treated side so that the thickness after drying was 0.0111. to prepare an adhesive film.

Example 3 and Comparative Example 2 were bonded to a 511 transparent acrylic plate and a heating aging acceleration test was conducted. The test results are shown in Table 2.

Evaluation ○ No peelability or board surface abnormality × Peeling impossible As shown in Table 2, the surface protection film of the present invention was compared to Comparative Example 2.
Compared to the above, the increase in adhesive strength over time is small, and good removability can be obtained even after the protective film is used.

Claims (1)

[Claims] 1. On a plastic film containing 80% or more of polypropylene, a chlorinated polypropylene with a chlorine content of 15 to 40% by weight and an undercoat containing polyisobutylene rubber and/or butyl rubber are applied, and a polyisobutylene-based nonpolar rubber material is applied as the main material. A surface protection film characterized by being equipped with a pressure-sensitive adhesive.