JPS6161875B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming a surface protective layer on the surface of an adherend, and more specifically, the present invention relates to a method for forming a surface protective layer on the surface of an adherend, and more specifically, the present invention relates to a method for forming a surface protective layer on the surface of an adherend, and more specifically, the present invention relates to a method for forming a surface protective layer on the surface of an adherend. The present invention provides a method for forming a surface protective layer to semi-permanently prevent damage. Conventionally, surface protection of adherends such as plate-shaped articles has been carried out by temporarily attaching a surface protective adhesive film before processing, and then applying paint after processing. is common. These series of steps begin with pasting the film onto a plate-shaped article, followed by bending, drawing, and
The process involves processing such as punching, followed by film peeling, surface cleaning, painting, and drying, which is not only complicated, but also requires safety because the cleaning fluid and paint contain large amounts of organic solvents. There were also various hygiene problems. Therefore, a first object of the present invention is to provide a method for forming a surface protective layer that can easily carry out the process from protecting the surface of a plate-shaped article before processing to protecting the surface after processing. A second object of the present invention is to provide a method for forming a surface protective layer by a simple operation without using an organic solvent during construction. Furthermore, a third object of the present invention is to form a surface protective layer with excellent adhesion to an adherend. That is, the present invention provides an acrylic copolymer obtained by copolymerizing an acrylic unsaturated monomer and a photosensitizer having a polymerizable unsaturated group, and at least one (meth)acryloyl group in the molecule. A photocurable adhesive composition made of a photopolymerizable compound having the following properties is coated on the surface of a self-supporting sheet (or film), and a composite sheet (or film) formed by forming a photocurable adhesive layer is applied on the surface of the adherend. are bonded together via the photo-curable adhesive layer and irradiated with backlight to cure the photo-curable adhesive layer, then only the self-supporting sheet (or film) is peeled off, and the surface of the adherend is polymerized and cured. The present invention relates to a method for forming a surface protective layer, which is characterized by forming a surface protective layer made of a material. According to the method of this invention, damage to the surface of the adherend consisting of a plate-like article before and during processing can be prevented by pasting the composite sheet, and after processing, it can be prevented from being damaged by light irradiation. Since the surface of the adherend is protected by the surface protective layer formed by polymerizing and curing the photocurable adhesive layer, the surface of the adherend will not be damaged. Furthermore, since no organic solvents are used during construction, there are no safety or hygiene issues. Additionally, photosensitizers such as benzophenone and benzoin generally have poor compatibility with acrylic copolymers, and when a composition containing these and a photopolymerizable compound is photocured, the curing will be uneven; Although the adhesion to the adherend may decrease, in the method of this invention, the photosensitizing group is introduced into the acrylic copolymer in the photocurable adhesive composition in advance, so the adhesiveness is reduced during photocuring. Curing is uniform and a surface protective layer with excellent adhesion to the adherend can be formed. Moreover, since the acrylic copolymer and the photopolymerizable compound are bonded via the photosensitizing group during curing, the surface protective layer also has good solvent resistance. The acrylic unsaturated monomer used to obtain the acrylic copolymer in the method of this invention is:
Examples include acrylic acid alkyl esters and methacrylic acid alkyl esters in which the alkyl group has 1 to 12 carbon atoms, and one or more of these may be used. In addition, along with these (meth)acrylic acid alkyl esters, 40
One or more other unsaturated monomers copolymerizable with these may be used in combination in a proportion of not more than % by weight. Other unsaturated monomers include vinyl acetate, vinyl propionate, (meth)acrylonitrile, (meth)acrylamide, diacetone acrylamide, unsaturated monomers such as styrene, (meth)acrylic acid, maleic acid, and fumaric acid. Acid, carboxyl group-containing monomers such as itaconic acid and allyl acetic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, allyl alcohol, monoester of polyethylene glycol and (meth)acrylic acid, pentaerythritol monoacrylate , hydroxyl group-containing monomers such as triglycerol monoacrylate, ethylene glycol or polyethylene glycol monovinyl ether, propylene glycol or polypropylene glycol monovinyl ether, epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, N-methylol (meth) ) N-methylol group- or N-alkoxymethyl group-containing monomers such as acrylamide and Nn-butoxymethylacrylamide. Examples of the photosensitizer having a polymerizable unsaturated group used for copolymerizing with such an acrylic unsaturated monomer to obtain an acrylic copolymer include benzoin, benzoin methyl ether, and benzoin ethyl. ether, benzoin isopropyl ether, benzoins such as α-methylbenzoin, anthraquinones such as 1-chloroanthraquinone, 2-chloroanthraquinone, benzophenones such as benzophenone, p-chlorobenzophenone, p-dimethylaminobenzophenone, Using a (meth)acrylic acid alkyl ester with an alkyl group having 1 to 12 carbon atoms to a benzyl group such as benzyl dimethyl ketal,
Obtained by introducing a (meth)acryloyl group. Specific examples of this photosensitizer include, for example, 4-
Acryloyloxyethyloxy-4'-chlorobenzophenone, 4-methacryloyloxypropyloxy-4'-chlorobenzophenone, 4-acryloyloxybutyloxy-4'-chlorobenzophenone, benzoincarbonylmethyl methacrylate, (2 -benzoyl-4-methoxy) phenoxycarbomethyl methacrylate, p-nitroanilinocarbonylmethyl methacrylate, 4-
Examples include nitro-1-naphthylaminocarbonylmethyl methacrylate. In order to copolymerize the acrylic unsaturated monomer and the photosensitizer having a polymerizable unsaturated group, known polymerization methods such as emulsion polymerization, solution polymerization, and bulk polymerization may be used. The blending ratio during this copolymerization is usually 1 to 10 parts by weight of the photosensitizer to 100 parts by weight of the acrylic unsaturated monomer. If the amount of this photosensitizer is too small, curing of the photocurable adhesive layer will be insufficient, which is not preferable. Moreover, if the amount is too large, the surface of the photocured product will easily peel off, and the cured product will be colored, which is not preferable. A photopolymerizable compound having at least one (meth)acryloyl group in the molecule that constitutes the photocurable adhesive composition together with the acrylic copolymer obtained in this way refers to a photopolymerizable compound having at least one (meth)acryloyl group in the molecule. Polyfunctional ones having at least one, preferably two or more methacryloyl groups or acryloyl groups as a bond, such as 1,4-butylene glycol di(meth)acrylate, 1,6-
Hexane glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate,
Polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethanetetra(meth)
Examples include monomers such as acrylates, and oligomers such as epoxy acrylates, urethane-modified acrylates, and oligoester acrylates, and two or more of these may be used in combination as necessary. The blending ratio (weight ratio) of this photopolymerizable compound and the above-mentioned acrylic copolymer in the photocurable adhesive composition is 80:20 to 10:90, preferably 70:30 to 30: It is better to set it to 70,
If the amount of the photopolymerizable compound is too large, the cohesiveness of the photocurable adhesive layer before irradiation with light will be poor, and the adhesive may ooze out to the side surfaces, which is not preferable. Furthermore, if the amount is too small, the photocurable adhesive layer will not be sufficiently cured by light irradiation, which is not preferable. Appropriate amounts of other compounding agents may be added to the photocurable pressure-sensitive adhesive composition of the present invention thus obtained, depending on the purpose. Examples of compounding agents include polymerization inhibitors that prevent thermal polymerization during production and reactions during storage, such as hydroquinone, hydroquinone monomethyl ether, tert-butylcatechol, p-benzoquinone, 2,5-tert-butylhydroquinone,
Pigments such as zinc white, yellow lead, and red iron for the purpose of coloring or decoration, such as phenothiazine;
Dyes such as toluidine red, phthalocyanine blue, phthalocyanine green, other metal powders,
Examples include glass beads, glass powder, glass flakes, and tackifying resins such as xylene resin and coumaron resin for the purpose of improving adhesive strength to the adherend surface. In the method of the present invention, the photocurable adhesive composition configured as described above is formed into a colored or colorless transparent self-supporting sheet (or film) that transmits light, such as a polyvinyl chloride sheet or film, or a polyolefin sheet. Or a film (including a sheet or film made of ethylene-vinyl acetate copolymer and its saponified product), a polyester sheet or film (thickness preferably 10 to 300 μm), etc. with a thickness of about 1 to 100 μm after drying on one side. It is coated or transferred to form a photocurable adhesive layer. A composite sheet (or film) composed of a self-supporting sheet (or film) and a photocurable adhesive layer configured in this way can be used as a plate-shaped article made of a metal plate, glass plate, wood board, decorative board, plastic board, etc. etc., through an adhesive layer. In order to polymerize and harden the adhesive layer, a light source such as a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a carbon arc lamp, a xenon lamp, etc. is used.
Light irradiation is performed for 0.3 seconds or more, preferably 3 seconds or more.
Note that the timing of the light irradiation may be before or after processing the adherend depending on the purpose. After light irradiation, self-supporting sheet (or film)
By peeling off the adhesive, a surface protective layer made of a cured polymer is formed on the surface of the adherend. Since the plastic fluidity of the adhesive layer is lost due to curing, the sheet (or film) can be easily peeled off. As described above, according to the method of the present invention, by irradiating the composite sheet used for surface protection of the adherend surface with light and peeling off the self-supporting sheet, the surface can be protected semi-permanently. A protective layer can be formed. Of course, the method of the present invention can also be used simply to form a surface protective layer on the surface of an article, regardless of the processing of the adherend. Next, examples of this invention will be shown. In the following, parts mean parts by weight. Example 1 Ethyl methacrylate 80 parts Methyl methacrylate 20 parts 4-acryloyloxyethyloxy-4'-chlorobenzophenone 10 parts Acrylic acid 5 parts Sodium dodecylbenzenesulfonate 3 parts Ion-exchanged water 100 parts The above compounded composition Pour into a 500ml flask,
After heating and stirring at 70℃ for 1 hour under inert gas, 0.05
of ammonium persulfate was added, and the mixture was reacted at 70°C for 5 hours to obtain an aqueous dispersion of an acrylic copolymer. Next, for 100 parts of this water dispersion (solid content),
Tetraethylene glycol dimethacrylate 50
part is gradually added dropwise to the water dispersion while stirring rapidly to mix uniformly to obtain a water-dispersible photocurable adhesive composition,
This was applied to one side of a 60 μm thick polyethylene sheet so that the thickness after drying was 10 μm.
A composite sheet having a photocurable adhesive layer formed thereon was obtained by drying at ℃ for 5 minutes. This composite sheet is made of BA finished stainless steel plate.
After pasting it on SUS304 through the adhesive layer, the adhesive layer was cured by irradiating it with ultraviolet light for about 5 seconds from a distance of 10 cm using a high-pressure mercury lamp (1KW), and then only the polyethylene sheet was peeled off and placed on the stainless steel plate. A surface protective layer made of a cured acrylic polymer was formed on the surface. Example 2 Methyl methacrylate 60 parts 4-acryloyloxybutyloxy-4'chlorobenzophenone 40 parts Methacrylic acid 5 parts Sodium dodecylbenzenesulfonate 3 parts Ion-exchanged water 100 parts Using the above composition, Example 1 is as follows. An aqueous dispersion of an acrylic copolymer was obtained in the same manner as above. On the other hand, pentaerythritol triacrylate
60 parts was added to 60 parts of water containing 1 part of sodium dodecylbenzenesulfonate and emulsified by rapid stirring to obtain an aqueous dispersion of a photopolymerizable compound. This water dispersion was mixed with 80 parts (solid content) of the above acrylic copolymer water dispersion to obtain a water-dispersible photocurable adhesive composition. This composition was applied to one side of a 60 μm thick polyethylene sheet so that the thickness after drying would be 10 μm, and dried at 85° C. for 5 minutes to obtain a composite sheet. A surface protective layer was formed using this composite sheet in the same manner as in Example 1. Example 3 Ethyl acrylate 80 Styrene 20 parts 4-methacryloyloxypropyloxy-
4'-chlorobenzophenone 10 parts Azobisisobutyronitrile 0.2 parts Toluene 100 parts The above blended composition was polymerized at 70°C for 4 hours to obtain an acrylic copolymer. Next, 30 parts of tetramethylolmethanetetraacrylate was blended with 70 parts (solid content) of this copolymer, mixed uniformly, and coated on one side of a 120 μm thick polyvinyl chloride sheet to a thickness of 5 μm after drying. The composite sheet was dried at 100°C for 5 minutes to obtain a composite sheet. A surface protective layer was formed using this composite sheet in the same manner as in Example 1. The results of measuring the pencil hardness and adhesion of the surface protective layers obtained in Examples 1 to 3 above are shown in the following table. In addition, regarding the adhesion force, the values when the surface protection layer was formed in the same manner as in Examples 1 to 3 using a copper plate and an acrylic plate as adherends are also shown. In addition, the results of investigating the adhesive strength of the composite sheet before light irradiation (initial adhesive strength) and the adhesive strength when peeling off the self-supporting sheet after light irradiation (self-supporting sheet peeling force) are also listed in the following table.

[Table] The above measurements were performed by the following method. Initial adhesive strength: Cut the composite sheet into 25mm width,
After pasting it on a BA-finished stainless steel plate SUS304 and leaving it for 30 minutes, it was peeled off 180 degrees and its adhesive strength was measured (peeling speed 300 mm/min, 20°C x 65% RH). Self-supporting sheet peeling force: After cutting the composite sheet into 25 mm width and pasting it on a BA finish stainless steel plate SUS304, it was peeled off with a high pressure mercury lamp (80w/cm/1 lamp) for 10 minutes.
After UV irradiation for about 5 seconds from a distance of cm, the 180 degree peel adhesive strength of the self-supporting sheet was measured (peel speed 300 mm/min, 20° C. x 65% RH). Pencil hardness: The hardness of the surface protective layer was measured according to JIS-K-5400. Adhesion: 100 cuts at 1 mm intervals were made in a grid pattern on the surface protective layer, commercially available cellophane adhesive tape was pasted thereon, the tape was then peeled off, and the percentage of remaining grid pieces was expressed. As is clear from the above examples, it can be seen that according to the method of the present invention, a good surface protective layer can be easily formed on an adherend.

Claims (1)

[Claims] 1 Acrylic copolymer obtained by copolymerizing an acrylic unsaturated monomer and a photosensitizer having a polymerizable unsaturated group, and a photopolymerizable copolymer having at least one (meth)acryloyl group in the molecule A photocurable adhesive composition consisting of a compound is coated on the surface of a self-supporting sheet (or film), and a composite sheet (or film) formed by forming a photocurable adhesive layer is applied on the surface of the adherend. The photocurable adhesive layer is cured by bonding through the adhesive layer and irradiated with backlight, and then only the self-supporting sheet (or film) is peeled off, and a surface protection made of a polymerized cured product is applied to the adherend surface. A method for forming a surface protective layer, the method comprising forming a layer.