JPS5850164B2 - Surface protection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to transportation of metal plates such as stainless steel plates and aluminum plates, painted metal plates, decorative plates, glass plates, etc.
This method relates to a temporary surface protection method to prevent scratches during processing, and involves applying a surface protection adhesive film coated with a photocurable adhesive onto the adherend to be protected. The present invention relates to a surface protection method characterized by irradiating ultraviolet rays to harden the adhesive before peeling off the useless surface protection film after the body has been transported, processed, etc.

Conventionally, adhesive films have been used as temporary surface protection materials, which are made by coating a base material such as paper, cloth, or plastic film with an adhesive containing natural rubber, synthetic rubber, or the like as a main component.

Although this adhesive film is widely used because of its ease of lamination, it has the following drawbacks because the adhesive is extremely unstable and is a material that easily undergoes plastic deformation.

1) After being attached to an adherend, the adhesive material flows well into the fine grooves on the surface of the adherend and increases the contact area, so the adhesive force becomes too large in a short period of time, making it difficult to peel off.

2) Since the cohesive force is small, when the adhesive layer is peeled off, the adhesive layer is likely to break and be transferred onto the adherend.

3) When processing such as bending or drawing is performed, adhesion is particularly likely to occur in areas where pressure or shear stress is concentrated.

To address these drawbacks of adhesive films, proposals have been made to suppress the plastic deformation of the adhesive to some extent or increase its cohesive strength by crosslinking the adhesive or using high molecular weight rubber. The above-mentioned drawbacks have basically not been solved under the condition that the adhesive can be easily attached to an adherend at room temperature.

In general, when an adhesive film is applied industrially to an adherend, the adhesive force required is 50 g / 25 mm or more when peeled in a 180° direction at a speed of 300 mw for 1 minute, even for simple protection during transportation. , 200g/25mm or more, preferably when performing processing such as bending or drawing.
300g/25mm or more is required.

On the other hand, from the point of view of peeling workability, a lower value is preferable, and if it exceeds 200 g/25 mrIL, peeling work becomes difficult.

The adhesive strength of the adhesive film is set by setting the minimum adhesive strength required at the time of application, but since the time from processing to peeling goes through various process routes, it takes a long time, and the time required for peeling is The adhesive strength is usually much higher than during processing, making the peeling process more difficult and making it easier for the adhesive to transfer onto the adherend.

The present invention was developed in consideration of these drawbacks of conventional surface protection adhesive films, and its purpose is to provide a film that is easy to apply to adherends and maintains strong adhesion during storage, transportation, and processing. Another object of the present invention is to provide a surface protection method that reduces the adhesive strength to facilitate the peeling operation when the adhesive is to be peeled off after use, and also prevents the adhesive from transferring to the adherend.

According to the present invention, an adhesive film made of a transparent plastic substrate coated with a photocurable adhesive is attached to an adherend, and after use, the surface of the film substrate is exposed to ultraviolet rays. This can be carried out by crosslinking and curing the adhesive by irradiation.

As the base film of the adhesive film used in the present invention, a transparent plastic film such as polyvinyl chloride, polyethylene, polypropylene, polyester, etc., through which ultraviolet rays can pass, is used.

The photocurable adhesive has two or more photoreactive unsaturated bonds per molecule in the sensitizer and (1) the polymer that is the main component of the adhesive.

Alternatively, (2) it can be achieved by mixing a low-molecular compound such as a photosensitive monomer into an ordinary adhesive.

Regarding (1), acrylic acid or methacrylic acid coexisting in an acrylic ester or methacrylic ester copolymer may be reacted with glycidyl (meth)acrylate, or β-hydroxyethyl (β-hydroxyethyl) having a hydroxyl group in the copolymer may be used. Double bonds can be introduced into the polymer by a method such as reacting polyisocyanate with half-urethane, which is a compound of a monomer having a hydroxyl group, in the presence of a monomer such as meth)acrylate.

Method (2) is an efficient method in that ordinary rubber-based or acrylic-based adhesives can be used as they are.

That is, a mixture of 1 part to 50 parts of a low-molecular compound such as a photosensitive monomer in a conventional adhesive is used.

The photosensitive monomer is an acrylic ester or methacrylic ester containing 1 to 4 polymerizable double bonds in the molecule, preferably a polyfunctional monomer with 2 or more double bonds, for example 1.4. -Butylene glycol diacrylate, 1.6-
Examples include hexane glycol diacrylate, neopentyl glycol diacrylate, (poly)ethylene glycol diacrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethanetetraacrylate.

In order to improve reactivity, sensitizers such as diacetyl, benzyl, benzophenone, benzoin, etc. are added to these formulations.
An adhesive is prepared by mixing about 0.1 to 10% of organic carpol compounds such as ω-bromoacetophenone, chloroacetone, benzoquinone, anthraquinone, 2-ether anthraquinone, benzoin isopropyl ether, and benzoin ether ether.

A pressure-sensitive adhesive film is obtained by applying the pressure-sensitive adhesive having these structures onto a base film using a conventional method.

After applying this adhesive film to the object whose surface is to be protected, transporting it, and before peeling it off after processing, it is irradiated with ultraviolet rays having a wavelength of 2,000 to 4,000 people for 5 seconds or more, preferably 3Q seconds or more using a commercially available ultra-high pressure, high-pressure mercury lamp, etc. The photosensitive groups react, causing polymerization reactions such as polymerization and crosslinking, and the adhesive solidifies, reducing adhesive strength and making it extremely difficult for transfer to occur.

The reason why the adhesive strength decreases as the adhesive hardens is that the adhesive strength of an adhesive film is due to the work of the plastic flow of the adhesive during peeling, as explained in "Adhesive J" (March 1968 issue, Kobunshi Publishing Association). Since the majority of the adhesive is spent on the adhesive, it is thought that the adhesive force decreases because the amount of work due to plastic flow becomes smaller as the adhesive solidifies.

Solidifying the adhesive is significantly effective in preventing transfer, and this is thought to be because the adhesive force decreases and fine particles of the adhesive that have penetrated into the rebus are pulled out without tearing.

In this case, since the ultraviolet rays are irradiated through the base film and oxygen in the air is naturally blocked, the curing reaction proceeds quickly.

Here, the degree of curing can be adjusted in any way depending on the amount and type of photoreactive groups in the adhesive, but the adhesive strength is 50g725
If the adhesive strength is less than mm, the peeling workability will not be affected and there will be almost no transfer, so it is sufficient to aim for an adhesive strength of this level.

This will be explained below using examples.

Example 1 Acrylic adhesive (trade name: Aron S manufactured by Toagosei Chemical Co., Ltd.
100 parts of 1511 Coat it so that it becomes 100605
The mixture was dried for several minutes to produce an adhesive film.

This adhesive film was attached to a stainless steel plate (430BA plate) with a thickness of 0.6 mrn at room temperature, and then left for one month.

Ultraviolet rays were irradiated for 15 seconds on the film surface of this stainless steel plate from a distance of 20 cm using a 2 kW high-pressure mercury lamp.
It was peeled off after 0 minutes.

Table 1 shows the adhesive strength and presence or absence of adhesion at each stage.

note), How to measure adhesive strength Compliant with JIS C-2107.

Adhesive strength to 5US-430BA 20℃1800 peeling, tensile speed Measured under the condition of 300mm/min.

When no ultraviolet rays were irradiated, the adhesive force increased and adhesion occurred, but in the case of the present invention, the adhesive force was small and peeling was easy, and no adhesion occurred.

Comparative Example 1 Trimethylolpropane triacrylate of Example 1,
Table 2 shows the results when an adhesive film coated with an adhesive excluding benzophenone was produced and similarly attached to a stainless steel plate.

Transfer occurred in both the samples that were not irradiated with ultraviolet rays and those that were irradiated with ultraviolet rays.

Example 2 The adhesive film obtained in Example 1 and Comparative Example 1 was made to a thickness of 1.5 m.
Example of applying ultraviolet rays perpendicularly to the plane of the bent product. Irradiation was carried out in the same manner as in 1.

Table 3 shows the state of the transfer at this time.

As described above, a surface protection adhesive film coated with a photocurable adhesive is applied to an adherend by irradiating it with ultraviolet rays to harden the adhesive before being peeled off after transportation and processing. The peelability, which was a drawback of conventional adhesive films, has been significantly improved, and there is almost no adhesive transfer.

Claims (1)

[Claims] 1. An adhesive film made by applying a photocurable adhesive to a transparent plastic film base material is attached to an adherend, and after use, the adhesive is cross-linked by irradiating the surface of the film base material with ultraviolet rays. A surface protection method characterized by curing and peeling.