JPS6147712B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for processing a curved surface of a melamine decorative board processed with a surface protective coating coating having excellent heat resistance and excellent releasability at room temperature. Melamine decorative boards, which are made by integrating a surface layer made of paper impregnated with a melamine resin and a back layer made of paper impregnated with a phenol resin, are laminated together under heat and pressure, and are used in many fields as a surface decoration material, but as a highly processed product. Bending melamine decorative board post-form products are used as decorative surface materials for counters, handrails, sinks, bathroom vanities, etc. Conventionally, in the curved surface processing method for melamine decorative boards, the surface of the curved part is heated to a heat deformation temperature (usually 140 to 180°C), so the surface of the melamine decorative board may be scratched by the bending machine, or it may be damaged for a long time. In the case of heating, the surface appearance, which is the life of the decorative board, was damaged by burning, discoloration, or swelling. Therefore, a protective coating or film was applied to the surface of the decorative board and a heat-pressure curved surface was processed. On the other hand, the performance required of a surface protective coating or film is that it has appropriate adhesion and is easy to peel off after use. Furthermore, for decorative boards, transparency is also required so that the hue of the pattern can be seen. Conventional surface protective film coatings include vinyl acetate-vinyl chloride copolymer solutions, polyurethane resin solutions, and other types in which low polymerization degree resins are dissolved in organic solvents, as well as polyvinyl alcohol (Poval) aqueous solutions, which are coated and dried to form a film. Alternatively, films made of these resins were bonded together via an adhesive. However, coatings or films formed by applying thermoplastic resins such as vinyl acetate and vinyl chloride have poor heat resistance, and when heated to the heat deformation temperature required for curved melamine decorative boards, they melt or soften and cannot be used. Nakatsuta. In addition, thermoplastic resins or films with excellent heat resistance, such as nylon, have poor adhesion, so they must be bonded together using adhesives such as acrylic or rubber, and are not put into practical use due to the poor heat resistance of adhesives. do not have. On this point, Poval has a melting point of 230℃ and has good heat resistance and can be applied as an aqueous solution, so it is used as a surface protective coating for melamine decorative boards that are bonded at room temperature.
Publication No. 15010). However, since POVAL aqueous solution is applied with a low resin content and high viscosity, it is easy to form a film containing bubbles, and even if an antifoaming agent is added to form a film without bubbles, the adhesion is poor even at room temperature. Moreover, the moisture in the film, which acts as a plasticizer, evaporates due to heating, and the film after cooling lacks flexibility and breaks when peeled, making it difficult to peel. In addition, the antifoaming agent precipitated and damaged the appearance of the decorative board. For these reasons, a film made only of POVAL had problems as a surface protective film for a melamine decorative board for post-form processing. The purpose of the present invention is to develop a surface protective coating coating with excellent heat resistance to solve the above-mentioned problems, and to create a melamine decorative coating in which a melamine decorative board coated with a surface protective coating coated with the coating and dried is heated and pressurized to form a curved surface. An object of the present invention is to provide a method for post-forming a board. In the present invention, a resin obtained by adding glyoxal and propylene glycol to a polyvinyl aqueous solution and acetalizing and etherifying the resin using an acid catalyst is applied to the surface of a melamine decorative board, dried, and then heated to a core material. This is a post-form processing method for melamine decorative boards, which is characterized by bonding by pressing and processing the curved surface at the same time. The method for producing the surface protective coating coating applied to melamine decorative boards, which plays an important role in the present invention, is to add glyoxal, which is a dialdehyde, and propylene glycol to a known poval, preferably a poval made of a completely saponified product with a high degree of polymerization. It can be obtained by acetalizing and etherifying with an acid such as para-toluenesulfonic acid, and adding an antifoaming agent such as a silicone type, if necessary. This paint has poval cross-linked with glyoxal, so it has excellent water resistance, heat resistance, and toughness, and is hydrophilic with a boiling point of 187°C.
Because it is plasticized with propylene glycol, it is flexible and at the same time has an antifoaming effect, and because the paint has a low viscosity and high solids content, it can be applied thickly and does not break. Because propylene glycol retains residual moisture and promotes the plasticizing effect of the film,
The coating is likely to peel off at room temperature after heat processing. In addition, compared to conventional paints that mainly contain only POVAL, antifoaming agents are not required or are added in small amounts, so antifoaming agent bleeds especially when heated.
It also has the effect of preventing changes in the appearance of the decorative board. That is, as mentioned above, the coating after drying of the surface protective coating paint for the melamine decorative board used as an essential component in the present invention has a thermal deterioration point of 230°C or higher and a tear strength.
It has excellent heat resistance and toughness with an elongation rate of 40 to 80 kg/mm and 200 to 300%, and does not contain air bubbles, and has a direct plasticizing effect due to propylene glycol and an indirect plasticizing effect due to water retention. Since the film is flexible at room temperature after secondary processing by heating, it does not break and is easily peeled off.
A surface protective coating 1 having such characteristics is applied to the surface of the melamine decorative board 2 to be subjected to post-form processing to a thickness of 20 to 70 microns in terms of solid content, and a rubber-based coating is applied to the back surface of the decorative board 2 using a known method. Or, apply adhesive 3 such as hot melt type and attach it to wood, plywood,
A rubber-based or hot-melt adhesive 3 is applied to the convex or concave parts of the core material 4 such as particle board, and the surface of the decorative board is heated to 140 to 180°C using a heating device 5 such as a sheathed heater. By pressing the melamine decorative board 2 onto the core material 4 through the surface protective coating 1 with a pressing machine 6 while heating, the melamine decorative board 2 is curved bonded to the core material 4 with the adhesive 3 (post-form). processing). The melamine decorative board that has been post-formed in this way is treated with a surface protective coating that has the characteristics described above, so it does not get scratches from the bending machine, and it does not burn, discolor, or swell even when heated for a long time. In addition, since the surface protective coating can be easily peeled off after cooling to room temperature, the melamine decorative board can be post-formed without damaging its appearance. Next, the present invention will be explained by examples. Parts represent parts by weight. Example 1 20 parts of propylene glycol was added to 210 parts of water, and 27 parts of completely saponified poval was gradually added while stirring, heated to 95°C and turned into an aqueous solution over 60 minutes, and then cooled to 80°C. , 10 parts of glyoxal and 3 parts of paratoluenesulfonic acid were added, stirred and mixed for 30 minutes, poval was acetalized with glyoxal and etherified with propylene glycol, and 1 part of a silicone antifoaming agent was added and mixed with stirring. ,
The surface protective coating paint of Example 1 had a solid content of 22% and a viscosity of 1000 cps/40°C. Comparative Example 1 Add 1 part of glycerin to 210 parts of water, and gradually add 26 parts of completely saponified poval while stirring.
℃ for 60 minutes to form an aqueous solution. After cooling to room temperature, 1 part of a silicone antifoaming agent as an antifoaming agent and 2 parts of liquid paraffin as a mold release agent were added and mixed with stirring, and the solid content was 12.1 Comparative example 1 with % viscosity 1500cps/40℃
It was used as a surface protective film paint. Next, the surface protective film paints of Example 1 and Comparative Example 1 were applied at a rate of 200 g/m ² to the surface of a melamine decorative board for post-form processing with a thickness of 0.8 mm using a flow coater, and heated at 120°C for 3 minutes. The appearance of the film after drying (number of bubbles), and the core material made of particle board was processed into a convex curved surface with a radius of 15 mm, and a rubber adhesive was applied to the back surface of the melamine decorative board and the convex curved surface of the core material, respectively, and the surface of the decorative board was (surface protective coating surface) with a sheathed heater at 164℃ for 6 seconds,
After processing the melamine decorative board into a post-form (Pf) by pressing it with a mm metal pressing tool for 60 seconds and cooling it to room temperature, the state of the bubbles (number and size) of the surface protective coating and the peelability ( (difficult) and the presence or absence of coating tear. The measured values are shown in Table 1. 【table】

[Brief explanation of the drawing]

FIG. 1 is an enlarged side view of a melamine decorative board treated with a surface protective coating according to the present invention, and FIG. 2 is a side view showing one embodiment of the present invention. 1...Surface protection film, 2...Melamine decorative board,
3... Adhesive, 4... Core material, 5... Heating device, 6
...pressing machine.

Claims (1)

[Claims] 1 A resin obtained by adding glyoxal and propylene glycol to a polyvinyl alcohol aqueous solution and acetalizing and etherifying it with an acid catalyst is applied to the surface of the melamine decorative board, and the surface protective coating treated melamine decorative board is dried and then heated to the core material. A post-form processing method for melamine decorative board, which is characterized by pressing and adhering and simultaneously processing the curved surface.