JPS6216702B2 - - 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, the 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 etc. after processing. It is common for there to be. 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. That is, the present invention covers a composite sheet (or film) consisting of a self-supporting sheet (or film) and a heat-activatable and photocurable adhesive layer provided on the sheet (or film). After bonding with heat and pressure on the adherend surface via this adhesive layer, the adhesive layer is cured by irradiation with light, and then only the self-supporting sheet (or film) is peeled off to form the adhesive layer. A surface protective layer forming method for forming a surface protective layer made of a polymerized cured product on an adherend surface, the adhesive layer comprising a monomer having an ethylenic double bond and a copolymerizable monomer having a functional group. 100 parts by weight of a copolymer with the body, 30 to 200 parts by weight of a hot-melt resin with a melting point of 50°C or higher,
Relating to a method for forming a surface protective layer, comprising an adhesive composition with heat activation and photocurability, containing 5 to 300 parts by weight of a photoreactive vinyl compound and 0.05 to 30 parts by weight of a photosensitizer. It is something. The adhesive layer in the above composite sheet (or film) is rapidly melted or softened by heating to a viscosity comparable to or lower than that of ordinary pressure-sensitive adhesives, and is cured or three-dimensional by heat activation and light irradiation. Because it has photo-curable properties that create a structure, the adhesive layer exhibits sufficient wettability and adheres well when the composite sheet (or film) is heat-pressed onto an adherend. When irradiated with light, the adhesive layer loses its initial heat-activation activity and becomes a cured product that has good adhesion not only at room temperature but also at high temperatures. According to the method of the present invention using the above-mentioned composite sheet, damage to the surface of the adherend consisting of a plate-like article before and during processing can be prevented by heat-pressing and pasting the composite sheet. After processing, it is protected by a surface protective layer with good adhesion, which is formed by polymerizing and curing the above-mentioned heat-activated and photo-curable adhesive layer by irradiating it with light. No damage to the body surface. In other words, according to the method of the present invention, a surface protective layer that can perform from surface protection before processing to surface protection after processing is formed by pasting a composite sheet (or film), irradiating light, and forming a self-supporting sheet (or film). It can be formed by a simple process of peeling. Furthermore, according to the method of the present invention, the above-mentioned composite sheet (or film) does not contain any organic solvent, and furthermore, no organic solvent is used during the above-mentioned series of operations, so there are no health and safety problems. The self-supporting sheet (or film) constituting the composite sheet (or film) used in the method of this invention is usually a plastic sheet (or film) having a transmittance of about 10% or more for light with a wavelength of 200 to 500 nm. Materials for this sheet (or film) include polyvinyl chloride, polyolefin (including ethylene-vinyl acetate copolymer and saponified products thereof), and polyester. Note that the thickness of this sheet (or film) is usually preferably 10 to 300 μm. The heat-activatable and photocurable adhesive layer provided on the self-supporting sheet (or film) is formed using an adhesive composition containing the above-mentioned components. Preferred specific examples of the monomer having an ethylenic double bond used to obtain the copolymer in this adhesive composition include those in which the alkyl group has 1 to 1 carbon atoms.
12 (meth)acrylic acid alkyl esters, vinyl alkyl esters in which the alkyl group has 1 to 12 carbon atoms, vinyl alkyl ethers in which the alkyl group has 1 to 12 carbon atoms, dimethylaminoethyl (meth)acrylate, ( meta) acrylonitrile,
One or more types such as vinylpyridine may be used. Examples of copolymerizable monomers having functional groups to be copolymerized with these monomers include copolymerizable monomers having carboxyl groups, hydroxyl groups, glycidyl groups, amide groups, etc. as functional groups. Examples include (meth)acrylic acid, maleic acid, itaconic acid, crotonic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycidyl methacrylate, (meth)acrylamide, N-methylol (meth) Examples include one or more of acrylamide and the like. These copolymerizable monomers with functional groups are components that improve compatibility with adherends such as metal plates, and also impart photoreactive polymerizable carbon-carbon double bonds to the copolymer described later. It is a convenient thing to do. A monomer having an ethylenic double bond and a copolymerizable monomer having a functional group are usually used in a ratio of 100 parts by weight of the former monomer to 100 parts by weight of the latter monomer.
Blending 0.01 to 15 parts by weight, emulsion polymerization method,
By copolymerizing by various known polymerization methods such as solution polymerization and bulk polymerization, a copolymer having an average molecular weight of about 10,000 or more is preferably obtained. The above-mentioned copolymer is a component in the adhesive layer that imparts desired tackiness and adhesion after photocuring when the composite sheet (or film) is bonded by heat and pressure to an adherend. By introducing at least one photoreactive polymerizable carbon-carbon double bond into each molecule on average, the photocuring properties of the adhesive layer can be further improved.
As a means for this, for example, light containing a polymerizable carbon-carbon double bond having a group that can react directly or indirectly with a functional group such as a carboxyl group, a hydroxyl group, or a glycidyl group present in the above-mentioned copolymer. A modified copolymer may be obtained by reacting 0.01 to 15 parts by weight of a reactive monomer with 100 parts by weight of the copolymer. Examples of such photoreactive monomers include monomers that can react with hydroxyl groups such as N-methylolacrylamide, N-butoxymethylacrylamide, (meth)acrylic acid chloride, (meth)acrylic acid bromide, etc. Glycidyl (meth)acrylate and the like are examples of monomers that can react with groups and hydroxyl groups. Another means of introducing a photoreactive polymerizable carbon-carbon double bond into a copolymer is to use a polyene monomer having two or more ethylenic double bonds as a copolymerizable monomer when obtaining the copolymer. Examples of the polyene monomer include polyethylene glycol di(meth)acrylate and pentaerythritol tri(meth)acrylate. The hot-melt resin in the adhesive composition provides the adhesive layer with sufficient thermal adhesion and wettability to the adherend when the composite sheet (or film) is heated and pressed onto the adherend, and is also photocurable. It is a component that also contributes to the subsequent improvement of adhesion, and it is desirable that it has a melting point of 50°C or higher, preferably in the range of 70 to 150°C, and that has excellent compatibility with the copolymer, especially the copolymer. Those having at least one photoreactive polymerizable carbon-carbon double bond in the molecule that can react with the photoreactive polymerizable carbon-carbon double bond in the molecule through a photosensitizer are preferred. suitable. Preferred specific examples of such hot-melt resins include xylene resin, novolak or resol type phenolic resin, rosin, rosin-modified phenolic resin, hydrogenated rosin, hydrogenated rosin ester, terpene-modified phenolic resin, and maleic anhydride-modified resin. Examples include phenolic resins, coumaron indene resins, terpene resins, aromatic petroleum resins, styrene resins, aliphatic hydrocarbon resins, and two or more types may be used in combination. These hot melt resins are used in an amount of 30 to 200 parts by weight, preferably 50 to 150 parts by weight, based on 100 parts by weight of the copolymer.
It is preferable to mix within the range of parts by weight. This amount is
If it is less than 30 parts by weight, the melt viscosity of the adhesive layer during heating will be high, resulting in insufficient wettability to the adherend, and the adhesive strength after photo-curing will be reduced, and if it exceeds 200 parts by weight, the copolymer will The proportion of the adhesive in the adhesive layer is too low, and its function is not fully exhibited. The photoreactive vinyl compound in the adhesive composition has at least one methacryloyl group or acryloyl group, preferably two or more, as a polymerizable carbon-carbon double bond that is activated by light irradiation to undergo a photopolymerization reaction. It is multifunctional,
For example, 1,4-butylene glycol di(meth)
Acrylate, 1,6-hexane glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylol Examples include monomers such as methane tetra(meth)acrylate, and oligomers such as epoxy acrylate, urethane-modified acrylate, and oligoester acrylate, and two or more of these may be used in combination as necessary. This photoreactive vinyl compound is the copolymer 100
5 to 300 parts by weight, preferably 10 to 300 parts by weight
It is best to mix within the range of 200 parts by weight; if this amount is less than 5 parts by weight, the degree of curing of the adhesive layer by light irradiation will be insufficient and the cohesive force and adhesive strength will decrease; If it is exceeded, the adhesive layer becomes too hard, resulting in a decrease in adhesive strength. The photosensitizer to be included in the adhesive composition may be one that promotes the photopolymerization reaction of the photoreactive vinyl compound, and specific examples thereof include benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl. ether, benzoins such as α-methylbenzoin,
Contains anthraquinones such as 1-chloroanthraquinone and 2-chloroanthraquinone, benzophenones such as benzophenone, p-chlorobenzophenone, and p-dimethylaminobenzophenone, diphenyl disulfide, and tetramethylthiuram disulfide. Examples include sulfur compounds. Such photosensitizers are preferably used in the range of 0.05 to 30 parts by weight per 100 parts by weight of the copolymer; if it is less than 0.05 parts by weight, the effect of promoting the photopolymerization reaction is insufficient; If the amount exceeds 1 part by weight, the promoting effect cannot be further increased, which is economically disadvantageous. The adhesive composition contains each of the above-mentioned components as essential components, and appropriate amounts of other compounding agents can be added depending on the purpose. Examples of formulations 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, and phenothiazine. may be added in an amount of 5 to 1000 ppm to the photoreactive vinyl compound.
Additionally, pigments such as zinc white, yellow lead, and red iron oxide, dyes such as toluidine red, phthalocyanine blue, and phthalocyanine green, and other metal powders, glass beads, glass powder, and glass flakes may be added for the purpose of coloring or decoration. You may. In order to form a heat-activatable and photocurable adhesive layer using the adhesive composition configured as described above, this composition is applied to one side of the self-supporting sheet (or film) as described above. It may be coated or transferred to a thickness of about 1 to 100 μm. A composite sheet (or film) consisting of a self-supporting sheet (or film) configured in this manner and an adhesive layer having heat activation and photocurability.
is applied to the adherend surface of plate-shaped articles made of metal plates, glass plates, wood plates, decorative plates, plastic plates, etc.
A temperature at which the adhesive layer can be melted or softened to a viscosity that exhibits sufficient wettability even on the rough surface of the adherend through the adhesive layer;
Usually, the material is heated to about 50 to 180°C and pressed to achieve good adhesion. 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 irradiation with light, only the self-supporting sheet (or film) is peeled off to form a surface protective layer made of a polymerized cured product on the surface of the adherend. As described above, according to the method of the present invention, by irradiating the composite sheet (or film) used for surface protection of the adherend surface with light and peeling off the self-supporting sheet (or film), semi-permanent protection can be achieved. A surface protective layer capable of protecting the surface 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. Parts below mean parts by weight. Example 1 2-Ethylhexyl acrylate 50 parts Methyl methacrylate 50 parts Methacrylic acid 6 parts Benzoyl peroxide 0.2 parts Ethyl acetate 100 parts A mixture of the above components was placed in flask 1, and the temperature of the reaction system was maintained at 65°C while stirring. After polymerizing for about 15 hours, the temperature of the reaction system was raised to 80°C and held for 2 hours to completely polymerize the remaining monomers ^.
A polymerization product containing an acrylic copolymer was obtained. To this polymerization product, 150 parts of rosin ester (melting point 60°C), 40 parts of pentaerythritol trimethacrylate, 3 parts of benzoin isopropyl ether, 0.01 part of hydroquinone monomethyl ether, and 300 parts of ethyl acetate were blended into the polymerized product, based on 100 parts of its solid content. A solution containing a heat-activatable and photocurable adhesive composition was obtained by uniformly mixing the adhesive composition. This composition solution was applied to one side of a polypropylene sheet with a thickness of 60 μm so that the thickness after drying would be 20 μm, and dried at 80° C. for 5 minutes to form an adhesive layer having heat activation and photocurability. , a composite sheet was obtained. This composite sheet is made of BA finished stainless steel plate.
After applying heat and pressure bonding to SUS304 through the adhesive layer mentioned above at 100℃, a high pressure mercury lamp (80W/cm/1
The adhesive layer was cured by irradiating it with ultraviolet light for about 5 seconds from a distance of 10 cm, and then only the polypropylene sheet was peeled off to form a surface protective layer made of a cured polymer on the stainless steel plate. Example 2 Ethyl acrylate 85 parts Methyl methacrylate 10 parts Acrylic acid 5 parts Ammonium persulfate 0.2 parts Sodium dodecylbenzenesulfonate 7 parts Ion-exchanged water 100 parts A mixture of the above components was placed in flask 1, and heated with nitrogen for about 30 minutes while stirring. After the substitution, polymerization was carried out under heating at 65°C for 2 hours, and after the polymerization was completed, the reaction system was heated to 75°C and aged for 1 hour to obtain an acrylic copolymer with an average particle size of 0.09 μm and a pH of about 3. I got an emulsion. The weight average molecular weight of this acrylic copolymer was approximately 800,000. Next, while stirring this emulsion, 200 parts of terpene-modified phenolic resin emulsion (melting point 75°C, solid content 50% by weight) was added to 100 parts of the solid content of the acrylic copolymer.
20 parts neopentyl glycol diacrylate 25 parts benzoin ethyl ether 3.5 parts hydroquinone 0.01 part ion-exchanged water 300 parts of each component were blended to obtain an emulsion containing a heat-activatable and photocurable adhesive composition. This composition emulsion was coated on one side of a 25 μm thick polyester sheet so that the thickness after drying would be 20 μm, and dried at 100° C. for 5 minutes to produce a composite sheet. Example 1 using this composite sheet
A surface protective layer was formed on a BA finished stainless steel plate SUS304 in the same manner as above. Example 3 To the polymerization product in Example 2, 3 parts of glycidyl methacrylate and 0.5 parts of triethylamine were added to 100 parts of the acrylic copolymer,
The reaction was carried out at 70° C. for 5 hours to introduce a photoreactive polymerizable carbon-carbon double bond into the copolymer. Each component described in Example 2 was blended with 100 parts of the solid content of this reaction product, and a composite sheet was produced in the same manner as in Example 2. Using this composite sheet, a surface protective layer was formed on a BA finished stainless steel plate SUS304 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 strength, the values when the surface protective 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,
The adhesive strength was measured by peeling off at 180 degrees after applying heat and pressure at 100°C to BA finish stainless steel plate SUS304 and leaving it for 30 minutes (peeling speed: 300 mm/min, 20
℃×65%RH). Self-supporting sheet peeling force: Cut the composite sheet into 25 mm width and apply 100 to BA finish stainless steel plate SUS304.
After applying heat and pressure at ℃ and irradiating it with ultraviolet light for about 5 seconds from a distance of 10 cm using a high-pressure mercury lamp (80 W/cm/lamp), the 180 degree peel adhesive strength of the self-supporting sheet was measured (peeling speed 300mm/min, 20℃×
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 score was expressed as the percentage remaining of the grid pieces. 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. A composite sheet (or film) consisting of a self-supporting sheet (or film) and a heat-activatable and photocurable adhesive layer provided on the sheet (or film). After bonding with heat and pressure on the adherend surface via this adhesive layer, the adhesive layer is cured by irradiation with light, and then only the self-supporting sheet (or film) is peeled off to form the adhesive layer. A surface protective layer forming method for forming a surface protective layer made of a polymerized cured product on the surface of an adherend, the adhesive layer comprising a monomer having an ethylenic double bond and a copolymerizable monomer having a functional group. 100 parts by weight of a copolymer with polymer, 30 to 200 parts by weight of a heat-melting resin with a melting point of 50°C or higher, photoreactive vinyl compound 5
1. A method for forming a surface protective layer, comprising a heat-activatable and photocurable adhesive composition containing ~300 parts by weight and 0.05 to 30 parts by weight of a photosensitizer. 2 A copolymer of a monomer having an ethylenic double bond and a copolymerizable monomer having a functional group has at least one photoreactive carbon-carbon double bond in the molecule on average A method for forming a surface protective layer according to claim 1.