JPS58193130A - Post form-working process for melamine-decorative board - Google Patents

Abstract

PURPOSE:To achieve the post form-working process for a melamine decorative board without injuring its external appearance by the curved surface-work for said decorative board coated with the mixture of specifically defined hemiacetal resin and water-soluble polyvinyl acetal resin as the coating material for protecting surface. CONSTITUTION:Hemiacetal resin is prepared by mixing glyoxal and glycol group (glycerin is preferable) is added to polyvinyl alcohol solution and is acetalized by acid catalyst, and the water-soluble polyvinyl acetal resin acetalized by acetaldehyde. The surface 2 of a melamine decorative board is coated with this mixture as coating material 1 for protecting the surface and is dried. Said decorative board processed by coating treatment is made to adhere under heating and pressure to a core material and simultaneously its curved surface is worked and the post form-work is achieved. EFFECT:As the coating material for protecting a surface is excellent in heat resistance, and exfoliating property under room temperature, the decorative board may be worked without injuring its appearance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for processing a curved surface of a 1'-coated melamine board coated with a surface protective coating coating having excellent heat resistance and excellent removability 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 phenolic resin by heat-pressure lamination, are used in many fields as a surface decoration material, but as a highly processed surface 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 of melamine decorative board, the surface of the curved surface processed part is heated to a heat deformation temperature (usually 140 to 180 degrees Celsius), so the surface of the melamine decorative board is scratched by the bending machine. In the case of long-term heating, the surface appearance, which is the life of the decorative board, was damaged due to 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, which are seemingly contradictory properties. 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 coating thermoplastic resins such as vinyl acetate and vinyl chloride have poor heat resistance;
When the melamine decorative board was heated to the heat distortion temperature required for processing the curved surface, it melted or softened and could not be used. Also,
Thermoplastic resins or films with excellent heat resistance, such as nylon, have poor adhesion, so they must be bonded through an acrylic or rubber adhesive, and are not put into practical use due to the adhesive's poor heat resistance. . On that point, Poval has a melting point of 2
It has a good heat resistance of 30° C. 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 (Japanese Utility Model Publication No. 15010/1983). 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 may tear during peeling, making peeling work difficult. In addition, the antifoaming agent bled out, damaging the appearance of the decorative board.

For these reasons, a film made only of poval has 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 mixture of a hemiacetal resin obtained by adding glyoxal and glycols to an aqueous polyvinyl alcohol solution and acetalized with an acid catalyst, and a water-soluble polyvinyl acetal resin acetalized with acetaldehyde is applied to the surface of a melamine decorative board. This is a post-form processing method for melamine decorative boards, in which a melamine decorative board with a surface protective coating that has been dried is bonded to a core material by heat and pressure, and at the same time a curved surface is processed.

The method for producing the surface protective coating paint applied to the melamine decorative board, which plays an important role in the present invention, is to add a well-known aqueous poval solution to the melamine decorative board.
Preferably, glyoxal and glycols are added to an aqueous solution of Poval, which is a completely saponified product with a high degree of polymerization, and preferably the glycol is glycerin, and the added amount is polyvinyl alcohol and water-soluble polyvinyl acetal resin to form a solid resin. A water-soluble polyvinyl acetal resin that has been diacetalized with acetaldehyde is mixed with a hemiacetal resin that has been added in an amount of 15 to 45% in terms of weight and acetalized with an acid such as para-toluenesulfonic acid. It can be obtained by adding antifoaming agents such as silicone type.

The surface protective coating paint produced in this way has better water resistance and toughness than POVAL because POVAL is partially cross-linked with glyoxal, a dialdehyde, to form a hemiacetal resin. . In addition, since glycols are added, it has a plasticizing (flexibility) effect and an antifoaming effect.Furthermore, the paint has a low viscosity and high solid content, so even with the same amount applied, the dry film is thick and does not cause film breakage. The membrane becomes tougher and its tear strength improves. Furthermore, since glycols retain residual moisture and promote the plasticizing action of the film, the film is likely to peel off at room temperature after heating and pressurizing.

Furthermore, adhesion is improved by adding water-soluble polyvinyl acetal resin diacetalized with acetaldehyde. In addition, compared to conventional paints that mainly contain only POVAL, since antifoaming agents are not required or are added in small amounts, the luster of the decorative board is reduced due to bleeding of antifoaming agents caused by heating. It also has the effect of preventing change. That is, the dried coating of the surface protective coating for 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 of 40 to 80 cuts - 1 elongation of 200 to 300, as described above.
%, has excellent heat resistance and toughness, does not contain bubbles, and has a plasticizing effect both directly by glycols (e.g. glycerin) and indirectly by water retention, so it can be used at room temperature after secondary processing by heating. The surface protection film (1) having such characteristics is applied to the surface of the melamine decorative board (2) to be subjected to post-form processing using a flow coater. Using an applicator such as the following, apply the adhesive to a thickness of 20 to 70 microns in terms of solid content, and apply a rubber-based or hot-melt adhesive (3) to the back side of the decorative board (2) using a known method. Coat it with a core material such as wood, plywood, particle board (4
A rubber-based or hot melt-based adhesive (3) is also applied to the convex or concave processed portions and the horizontal surface of the adhesive (3).

Next, the melamine decorative board is heated to 140 to 180°C with a heating device (5) such as a sheathed heater, and the melamine decorative board is heated through the surface protection film (1) with a pressing machine (6). This is a method of processing the melamine decorative board (2) into a core material (4) into a curved surface (post-form processing) using an adhesive (3) by pressing (2) onto the core material.

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 cause marks or scratches on the surface of the bending press without any special processing. Even when heated for a long time, the surface of the melamine decorative board will not burn, discolor, swell, or bleed, and the surface protective film can be easily peeled off after cooling to room temperature, so the melamine decorative board can be used without damaging its appearance. The board can be postformed.

Next, the present invention will be explained by examples. Parts represent parts by weight.

Example 1 60 parts of glycerin was added to 864 parts of water, 114 parts of poval was gradually added while stirring, and heated to 95°C.
After cooling to 80°C, 4.2 parts of silicone antifoaming agent was added, 17 parts of glyoxal and 3 parts of para-toluenesulfonic acid were added, and the mixture was stirred and mixed for 30 minutes. , Poval is hemiacetalized with glyoxal and glycerin is etherified. Next, 40 parts of a 25% aqueous solution of a water-soluble polyvinyl acetal resin acetalized with acetaldehyde was added and mixed with stirring.
Solid content 17.4*, viscosity [1000ePI/40℃
(7) Example 111ta The surface protective coating paint of Example 1 was obtained.

Comparative Example 1 1 part of glycerin was added to 210 parts of water, and 26 parts of poval was gradually added while stirring.The mixture was heated to 95°C and turned into an aqueous solution for 60 minutes. After cooling to room temperature, silicone-based 1 part of an antifoaming agent and 2 parts of liquid paraffin as a mold release agent were added and mixed with stirring, resulting in a solid content of 12.1 inches and a viscosity of 150009117.
Comparative Example 10 surface protective coating paint was obtained at 40°C.

Next, the surface protective coating paints of Example 1 and Comparative Example 1 were applied at a rate of 200 f/d to the surface of a 0.8 part m thick melamine decorative board for post-form processing using a flow coater, and heated at 120°C. The appearance of the film after drying for 3 minutes (number of bubbles/cd) and the core material made of particle board with a radius of 1
Processed into a 55m+ convex curved surface, a rubber adhesive was applied to the back surface of the melamine decorative board and the convex curved surface of the core material, and the surface of the decorative board (surface protection coating surface) was heated at 164°C for 6 seconds with a sheathed heater. After applying post-form (PF) processing to the melamine decorative board by crimping it for 60 seconds using a metal pressing tool with a diameter of 10 wg, the state of the bubbles in the surface protective coating after cooling to room temperature (the number of bubbles; pcs/-1 bubble size;-ψ
, removability: difficult, and film tearing: presence/absence). The measured values are shown in Table 1.

Table 1 Performance of surface protective film

[Brief explanation of drawings]

FIG. 1 is an enlarged side sectional view of a melamine decorative board treated with a surface protective coating used in the present invention, and FIG. 2 is a side sectional 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 patent applicant Aikani Gyo Co., Ltd. No. 1L, ] No. 21, J 15

Claims (1)

[Scope of Claims] 1. A mixture of a hemiacetal resin obtained by adding glyoxal and glycols to an aqueous polyvinyl alcohol solution and acetalized with an acid catalyst, and a water-soluble polyvinyl acetal resin acetalized with acetaldehyde, to form a melamine decorative board. A post-form processing method for a melamine decorative board, characterized in that a melamine decorative board processed with a surface protective coating applied to the surface and dried is bonded to a core material by heating and pressure, and at the same time, a curved surface is processed. 2. The melamine decorative board according to claim 1, wherein the glycol is glycerin and the amount added is 15 to 45% in terms of resin solid weight including polyvinyl alcohol, water, and soluble polyvinyl acetal resin. Post 7 ohm processing method.