JPS5825355B2 - Thailand - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-resistant adhesive composition suitable for bonding wood such as plywood. Our goal is to provide a good adhesive.

Conventionally, phenol-modified amine resins have been used as molding materials and laminated materials, but because of their poor dispersibility in water, they have not been widely used as adhesives for wood.

However, in recent years, with the increasing demand for special structural plywood, adhesives with a high degree of boiling water resistance have become required, and phenol-modified amine resins, which are superior in workability and cost efficiency compared to phenolic resin adhesives, have become necessary. Adhesives have been attracting a lot of attention as adhesives that have a high degree of boiling water resistance.

However, it is difficult to solve the problem of water dispersibility with phenol-modified amine resin adhesives, and therefore, when washing equipment such as glue mixers and spreaders using phenol-modified amine resin adhesives, After using the adhesive, a method is used in which a urea resin adhesive with good water dispersibility is used and the water dispersibility is aided with a urea resin liquid.

In addition, phenol-modified amine resin adhesives have extremely poor water dispersibility when the degree of condensation of the phenol resin increases.
Since it tends to separate easily during use, it is necessary to suppress the degree of condensation of the phenol resin to a certain level.
Therefore, the adhesive tends to penetrate excessively into the wood, resulting in poor adhesion due to lack of glue, and contamination of the wood surface such as plywood. This creates constraints such as the need to keep the moisture content of the wood low by excessively drying the wood.

In order to solve the problems of the conventional methods of phenol-modified amine resin adhesives, the present inventors have conducted various studies and found that they emulsified a phenol resin and mixed it with a known urea resin adhesive. It was discovered that an adhesive having a high degree of boiling water resistance and excellent water dispersibility could be obtained by this method, and the present invention was completed.

In the present invention, the phenolic resin emulsion to be mixed with the known urea resin adhesive contains 1 to 4 moles of formaldehyde per mole of phenol and a known protective colloid substance (for example, fibers such as methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose). elementary derivatives,
acrylamide, polyvinyl alcohol, etc.) or (and) in the presence of surfactants, metal oxides,
or metal hydroxide, or metal salt, ammonia,
It can be obtained by adding one or more catalysts such as amines to cause a reaction and lowering the pH of the reaction system when a desired degree of condensation is reached, or by proceeding the reaction to a high degree of condensation and making it emulsified. It is something.

At this time, if the molar ratio of formaldehyde to 1 mole of phenol is less than 1 mole, the curing speed of the resulting phenol-modified urea resin adhesive will be slow, resulting in a decrease in workability, while on the other hand, if the formaldehyde content is 4 moles or more, The formaldehyde odor of the phenol-modified urea resin adhesive becomes strong, which not only worsens the working environment but also reduces the shelf life of the adhesive, which is not suitable.

Phenol resin emulsion is made by replacing part of the phenol with melamine,
urea, cresol, xylenol, resorcinol,
Even if a modified phenolic resin emulsion substituted with lignin, tannin, etc. is used, the effects of the present invention will not be diminished.

Further, a known urea resin adhesive uses a urea resin adhesive obtained by condensing urea alone and formaldehyde.

The mixing ratio of the urea resin adhesive and the phenolic resin emulsion can be any desired ratio, but the urea resin adhesive 100%
It is desirable to mix within a range of about 10 to 300 parts by weight of the phenol resin emulsion.

The phenol-modified urea resin adhesive obtained by the method of the present invention can be effectively used not only for adhesion of plywood but also for a wide range of wood adhesives, such as adhesion of particle boards, veneer boards, and flash panels.

Next, examples of the present invention will be shown.

Example 1 To a mixed solution of 1 mole of phenol and 2.5 moles of formaldehyde, 2 parts by weight of zinc acetate and 10 parts by weight of polyvinyl alcohol (Poval 1178, manufactured by KK Kuraray) were added to each part of the phenol. The pH was adjusted to 8.6 with a heavy weight caustic soda aqueous solution and reacted at 90°C for 4 hours. When it became cloudy, it was cooled, and para-toluenesulfonic acid was gradually added to adjust the pH to 7.0 to obtain a phenol resin emulsion. .

A water-resistant adhesive of the present invention was obtained by mixing 100 parts by weight of this phenol resin emulsion with 100 parts by weight of a commercially available urea resin adhesive (UL-002, manufactured by Hounen Oil Co., Ltd.).

The water resistance and water dispersibility of the adhesive according to the present invention were measured by the following method.

A glue solution was prepared by blending 200 g of the adhesive of the present invention obtained by the above method with 50 g of wheat flour (Akahana, manufactured by Nisshin Seifun KK), 20 g of water, and 1 g of ammonium chloride powder.

Take 10g of this glue solution in a beaker and put it at room temperature (28~30°
After being left to stand for 3 hours in C), 100 g of water was added and stirred, and the water dispersibility was observed. The size liquid was uniformly dispersed, showing good water dispersibility.

As a control, we used a phenol-modified urea resin adhesive obtained by mixing 100 parts by weight of a known urea resin adhesive and 50 parts by weight of a resol-type phenolic resin initial condensate, and made a size liquid with the same composition. When the water dispersibility was examined in the same manner, the paste became gummy and precipitated.

On the other hand, the adhesive size liquid of the present invention obtained by the above method was applied to both sides of a 2.5 mm thick lauan veneer at a rate of 40 g/900 d, and then a lauan veneer with a thickness of 2.5 mm was coated. It was piled up on the earthwork and cold-pressed for 20 minutes at a pressure of 10 kg/ffl.

Next, this plywood was heat-pressed for 3 minutes at a pressure of 10 ky/i using a hot press kept at a temperature of 120° C. to produce a structural plywood.

The adhesive strength of this plywood was measured according to JAS standards, and the results shown in the table below were obtained.

From the above measurement results, it can be seen that the adhesive of the present invention has excellent water dispersibility and high boiling water resistance that meets the JAS special relatives standard.

Claims (1)

[Claims] 1 (a) A urea resin adhesive obtained by condensing simple urea and formaldehyde, and (b) 1.0 to 4.0 mol of formaldehyde per 1 mol of phenol to methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, acrylamide. , a phenolic resin emulsion obtained by reacting and emulsifying in the presence of a protective colloid substance such as polyvinyl alcohol or (and) a surfactant.