JPH0688377B2 - Veneer manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for obtaining a decorative board by impregnating wood with a specific photocurable resin and photocuring the wood.

[Conventional technology]

Conventionally, there have been attempts to impregnate wood with a photocurable resin and cure it only by light irradiation, but because the resin impregnated inside the wood is poor in photocurability, it is necessary to use an organic oxide together with the surface. The case where the inside was cured by heating after photo-curing was good.

However, such a method has a drawback in that the curing is quick and the man-hours for manufacturing the decorative plate can be significantly reduced, and the merit of using the photocuring system is lacking.

[Problems to be solved by the invention]

The inventors of the present invention not only apply to the surface layer by impregnating with a photocurable resin and irradiate with light without using other troubles, but also to the resin impregnated into the wood, which has been considered difficult until now. The present invention has been completed by discovering that the objective can be achieved by specifying the structure and composition of the photocurable resin, although it has also been cured to cure the decorative board having excellent physical properties. I was able to do it.

[Means for solving problems]

That is, the present invention is (1) obtained by reacting an epoxy resin having two or more epoxy groups in one molecule with acrylic acid and / or methacrylic acid (hereinafter referred to as (meth) acrylic acid), Epoxy-acrylate resin without epoxy group (hereinafter simply referred to as epoxy-acrylate resin) 20-
90% by weight, (2) General formula Or (However, R ₁ is hydrogen or an alkyl group, an aralkyl group,
An aryl group, R ₂ and R ₃ are hydrogen or a methyl group, and m is an integer of 1 or 2) and have an aromatic structure. Monoacrylate or monomethacrylate (hereinafter, aromatic mono (meth)) 80)
10% by weight, and (3) Using a photo-curable resin that is used in combination with 0.1% or more of a photoreaction initiator, the thin wood plate is completely impregnated to the inside, and then light irradiation is performed to make the inside uniform. It is made to cure.

[Work]

 The reason why the composition is specified in the present invention is as follows.

Epoxy-acrylate resins are excellent in photocurability, and even resins impregnated into the interior of wood can be cured, but they have high viscosity and, in practice, it is necessary to use a diluting monomer together.

Conventionally, acrylic acid esters of polyhydric alcohols such as trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and triethylene glycol diacrylate have been used together as the diluting monomer. .

However, it has been found that when the photocurable resin in which these acrylates of polyhydric alcohols are used together is impregnated into wood and cured, cracks occur along the grain of wood due to repeated cold and heat.

On the other hand, as described in the literature, the existing monofunctional monomers have some drawbacks and are not practical.

A few of these examples are styrene, and methacrylates, including methyl methacrylate,
When used in combination with an epoxy-acrylate resin, the photocurability is significantly slowed, the part impregnated inside the wood is not cured, and practically no useful decorative board is given.

Acrylonitrile and the like are problematic in terms of volatility and toxicity, and vinylpyrrolidone is water-soluble and cannot be entirely used in terms of curability. Further, acrylic acid esters are poor in practical use due to various drawbacks such as odor, skin irritation and softness.

The present inventors have studied a monomer to be used in combination because it has a low viscosity and is easily impregnated into the interior of wood, and the resin impregnated into the interior of the wood is hardened, and has a low odor and is easy to handle.
The above general formula Or The present invention could be completed by recognizing that the aromatic mono (meth) acrylate represented by (wherein R ₁ , R ₂ , R ₃ and m are as described above) meets the purpose.

The epoxy-acrylate resin used in the present invention is synthesized from an epoxy resin and (meth) acrylic acid.

As the epoxy resin, various commercially available products such as bisphenol A diglycidyl ether type,
Examples thereof include bisphenal F diglycidyl ether type, novolac polyglycidyl ether type, cycloaliphatic type obtained by oxidizing double bond with peracetic acid, and glycidyl ester type. All of them are raw materials of the epoxy-acrylate resin of the present invention. It can be used.

The aromatic mono (meth) acrylate represented by the above general formula of the present invention is synthesized by reacting phenols with epihalohydrin, particularly epichlorohydrin, and further esterifying the reaction product with (meth) acrylic acid. It

Phenols and substituted phenols are used as the phenols. The substituent is an alkyl group having 1 to 12 carbon atoms, an aralkyl group and an aryl group, and examples of the phenols include phenol, o-cresol, m-cresol, p-cresol, and a mixture thereof, 2, Examples thereof include 3-xylenol, 2,4-xylenol, 3,5-xylenol, 2,6-xylenol, paratertiary butylphenol, paraphenylphenol and paracumylphenol.

It can also be synthesized by esterifying commercially available phenyl glycidyl ether, cresyl glycidyl ether, paratertiary butyl phenyl glycidyl ether, and styrene oxide with acrylic acid or methacrylic acid.

The composition ratio of the mixture of the epoxy-acrylate resin and the aromatic mono (meth) acrylate (hereinafter sometimes referred to as vinyl ester resin) is the epoxy-acrylate resin.
20-90% by weight, aromatic mono (meth) acrylate 10-80
% By weight, preferably epoxy to acrylate resin 40 to 70
% By weight, aromatic mono (meth) acrylate 30-60% by weight
Is. The optimum viscosity is 1-15 poise.

It is necessary to add a photoreaction initiator of 0.1 (%) or more to this mixture to prepare a photocurable resin.

Various initiators are generally commercially available for this purpose, for example, Darocur # 1173 by Merck, Irgacure # 651 by Ciba, benzophenone, etc., and if necessary, Michler's ketone, dimethylaminoethanol, etc. It is also possible to use a promoter of the above.

The wood impregnated with the photocurable resin according to the present invention is not particularly limited. For example, as a kind, any of coniferous trees such as cedar, cypress, pine, bay pine, beihi, and taihi, and broad-leaved trees such as sen, taro, oak, elm, zelkova, hippopotamus, and beech can be used.

The thickness of the thin plate is not particularly limited, but a thickness of 0.2 to 1 mm is suitable for industrial production in view of the relationship between UV transmittance and curing rate. The water content of the thin plate is preferably 20% or less.

One of the features of using the photocurable resin according to the present invention is impregnation,
After curing, it is difficult to generate cracks along the wood grain, which is a disadvantage of this type of decorative board. Practical hardness is sufficient.

The photocurable resin according to the present invention can be freely colored as required. Also, when impregnating wood with resin, decompression,
It is also possible to freely take measures such as pressurization.

〔Example〕

Next, in order to help understanding of the present invention, examples will be shown below.

Reference Example 1 In a one-separable flask equipped with a stirrer, a reflux condenser, and a thermometer, 370 g of Epicoat 827 from Yuka Shell Epoxy Co., 144 g of acrylic acid, 1.5 g of trimethylbenzylammonium chloride, and 0.25 g of hydroquinone were used as epoxy resins. After charging and reacting at 120-130 ℃ for 3 hours,
An epoxy-acrylate resin with an acid value of 6.1 was obtained.

Example 1 410 g of the epoxy-acrylate resin obtained in Reference Example 1
The following structure was obtained by esterifying phenyl glycidyl ether with acrylic acid by a conventional method. A vinyl ester resin (A) was synthesized by adding 465 g of an acrylic ester having

It had a viscosity of 4.7 poise and a yellowish brown liquid.

To 100 parts by weight of the vinyl ester resin (A), 2 parts of Darocur # 1173 manufactured by Merck Ltd. was added as a photoinitiator to obtain a photocurable resin (B).

75 mm x 150 mm rice sliced to a thickness of 0.8 mm is impregnated with a photocurable resin (B) under a reduced pressure of 3 to 5 mmHg, and then the excess resin is removed, and a 25μ thick polyester film is used. High pressure UV lamp (80W / cm) with 2kW output, covering both sides
10 cm under the lamp was passed at a speed of 2 m / min, inverted, and subjected to the same treatment.

The treated wood from which the film was peeled off was completely hardened to the inside and had a surface hardness of 2H.

Comparative Example 1 60 parts by weight of the epoxy-acrylate resin produced in Reference Example 1, 30 parts of methyl methacrylate, 10 parts of styrene, and 2 parts of Darocur # 1173 were added to prepare a photocurable resin (C).

It was photocured under the same conditions as in Example 1, but the surface was only gelled and the interior was not cured at all.

Comparative Example 2 50 parts by weight of the epoxy-acrylate resin produced in Example 1 was added with 50 parts of trimethylolpropane triacrylate,
A photocurable resin (D) was prepared by adding 2 parts of Darocur # 1173.

The hardened wood treated in the same manner as in Example 1 had been hardened to the inside and had a hardness of 2 to 3H.

After leaving at −20 ° C. for 1 hour and then at room temperature for 1 hour, and further at 80 ° C. for 1 hour, a cold heat repeated test was carried out, and the decorative board produced in Comparative Example 2 had a wood grain in 1 cycle. Along the entire surface, cracks occurred.

However, the decorative board manufactured in Example 1 did not crack in the test up to 3 cycles.

Example 2 410 g of the epoxy-acrylate resin obtained in Reference Example 1
The following structure obtained by esterifying o-cresyl glycidyl ether with methacrylic acid by a conventional method (510 g) of a methacrylic acid ester having a vinyl ester was added to synthesize a vinyl ester resin (B).

It had a viscosity of 3.9 poise and a yellowish brown liquid.

To 100 parts of vinyl ester resin (B), 3 parts of "Irgacure # 651" manufactured by Ciba Co., Ltd. was added as an initiator to prepare a photocurable resin.

A 7.5 mm × 15 cm cypress, which was cut to 0.7 mm, was impregnated with the vinyl ester resin (B) under a reduced pressure of 3 to 5 mmHg, and then photocured in the same manner as in Example 1. The hardness of the obtained decorative board is
In the 2H, cold heat repeated test, no cracks were found in 3 cycles.

Reference Example 2 As a polyvalent carboxylic acid type epoxy resin, 350 g of "Epiclone # 200" from Dainippon Ink and Chemicals, Inc., 144 g of acrylic acid, 1.5 g of triphenylphosphine, hydroquinone.
Using an apparatus similar to that of Example 1, 25 g was reacted at 120 to 130 ° C. for 4 hours to obtain an epoxy-acrylate resin having an acid value of 11.4.

It was yellowish brown and syrupy.

Example 3 The following structure obtained by esterifying styrene oxide with 450 parts by weight of the epoxy-acrylate resin obtained in Reference Example 2 with acrylic acid by a conventional method A vinyl ester resin (C) was synthesized by adding 360 g of acrylic acid ester of.

It had a viscosity of 5.4 poise and a yellowish brown liquid.

To 100 parts of the vinyl ester resin (C), 3 parts of "Irgacure # 651" manufactured by Ciba Co., Ltd. was added as an initiator to prepare a photocurable resin.

A 75 mm × 150 mm cypress, which was cut to 0.7 mm, was impregnated with the vinyl ester resin (C) under a reduced pressure of 3 to 5 mmHg, and then photocured in the same manner as in Example 1. The hardness of the obtained decorative board is
In the 2H, cold heat repeated test, no cracks were found in 3 cycles.

〔The invention's effect〕

The decorative board obtained by the method of the present invention has a short curing cycle and is economical because it is produced only by photo-curing, and it does not cause cracks along the wood grain pattern due to the cold heat repeated test, and has high hardness. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Takagi 1-1126-8 Fukunari, Okayama-shi, Okayama (72) Masayuki Oshima 4-82-23 Tai, Tamano-shi, Okayama

Claims (1)

[Claims] (1) An epoxy-acrylate resin having substantially no epoxy group, which is obtained by reacting an epoxy resin having two or more epoxy groups in one molecule with acrylic acid and / or methacrylic acid. 20-90% by weight, (2) General formula Or (However, R ₁ is hydrogen or an alkyl group, an aralkyl group,
An aryl group, R ₂ and R ₃ are hydrogen or a methyl group, and m is an integer of 1 or 2, and the aromatic structure-containing monoacrylate or monomethacrylate 80 to 10% by weight, and ( 3) A method for producing a decorative board, which comprises impregnating a wood thin plate with a photocurable resin obtained by using 0.1% or more of a photoreaction initiator in combination and photocuring.