JPH07126596A - Adhesive for wood materials - Google Patents

Abstract

PURPOSE:To obtain an adhesive for a wooden material which can suppress the released of formaldehyde, can maintain rapid curability, and can keep water resistance of the adhesiveness under the ordinary condition for using an aminoplast resin. CONSTITUTION:This adhesive is prepd. by adding 0.2-20 pts.wt. glyoxal to 100 pts.wt. water-soluble aminoplast resin wherein formaldehyde is a main component. By using this adhesive, a wooden product wherein, even when the content of free formaldehyde in the water-soluble aminoplast resin is reduced to at most 1wt.%, it is unnecessary to prolong the curing time or to sacrifice the productivity, and the physical properties and water resistance can be kept and the amt. of the released aldehyde is small can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive used for manufacturing wood materials such as plywood, particle board and MDF.

[0002]

2. Description of the Related Art Conventionally, water-soluble aminoplast resins such as water-soluble urea resins, melamine resins and phenol resins have been widely used as adhesives for wood materials. However, these resins contain free formaldehyde,
Further formaldehyde may be added to accelerate the curing. Therefore, the formaldehyde odor during use is strong, and free formaldehyde remains in the wood material of the product, so formaldehyde gas is released, and when it is used for indoor board materials, furniture, etc., the formaldehyde odor becomes a problem, From a hygiene standpoint, it doesn't look good.

However, in order to reduce formaldehyde odor during use and free formaldehyde in products,
It is necessary to reduce the amount of residual formaldehyde in the adhesive, but in order to reduce the amount of residual formaldehyde, the amount of formaldehyde with respect to amino groups during aminoplast resin synthesis should be reduced, and formaldehyde such as urea and melamine amine should be captured. The method is to mix the agent with the aminoplast resin.

[0004]

However, when plywood, particle board and MDF are produced by using the aminoplast resin by such means, the curing time of the resin is significantly delayed and the cured product has a low adhesive strength. , The use is limited. Therefore, there has been a demand for an adhesive for wood materials which does not reduce the curing speed of the conventional aminoplast resin, maintains the adhesive water resistance, and has no formaldehyde odor.

[0005]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that the formaldehyde released under the normal use conditions of aminoplast resin is small, and the rapid curing property is maintained so as not to reduce the productivity. It was possible to obtain an adhesive for wood materials that maintains the above-mentioned properties and maintains and improves the adhesive water resistance.

That is, the adhesive for wood materials of the present invention is a water-soluble aminoplast resin 100 containing formaldehyde as a main component.
It is characterized in that 0.2 to 20 parts by weight of glyoxal is added to parts by weight. Conventionally, if an ammonium salt or a strong acid curing agent is used in the aminoplast resin in order to shorten the curing time more than usual, the effect of shortening the gel time is great in the aminoplast resin having residual formaldehyde of 1.0 wt% or more. There was no effect of reducing the amount of formaldehyde released, and there could have been problems with the pregel before molding.

The residual formaldehyde content is 1.0 wt.
% Or less, especially 0.5 wt% or less, it is possible to reduce the aldehyde odor, but even if an ammonium salt or a strong acid curing agent is used more than usual, there is no significant effect of shortening the curing and, at the same time, the adhesive water resistance deteriorates. Therefore, it is difficult to reduce the residual formaldehyde, and therefore the emitted formaldehyde cannot be reduced as expected. However, when glyoxal is added to the resin, the amount of the curing agent does not increase, and the curing agent usually cures rapidly with the amount of the curing agent, and since the amount of the curing agent added is small, there is no pregel before molding. Further, even if the residual formaldehyde is 1.0 wt% or less, it is not necessary to extend the curing time, and the wood properties such as plywood and particle board that retain the physical properties and water resistance without sacrificing the productivity and emit a small amount of formaldehyde. You can get the product.

In the adhesive for wood materials of the present invention, the curing time of the urea resin compounded by changing the addition amount of glyoxal, the adhesive strength when formed into plywood, the released formaldehyde and the released formaldehyde when formed into a particle board, the bending strength, Regarding the water resistance, when comparing the conventional urea resin and the low-odor urea resin, the urea resin in the general-purpose type shows a remarkable shortening effect of the curing time with the addition amount of glyoxal. On the other hand, conventional low odor urea resins such as residual formaldehyde of 0.48% and 0.25% were examined, respectively. When the amount of residual formaldehyde in the original resin was reduced, the curing time tended to increase remarkably and the productivity was reduced. Not only that, the strength and water resistance of plywood are significantly reduced.

However, by adding or partially reacting glyoxal, the curing time is greatly shortened and the productivity is improved. At the same time, the amount of residual formaldehyde in the plywood is reduced and the amount of formaldehyde released is kept low, while the strength and water resistance are kept low. Remarkably improved in sex. This tendency is the same when molding a particle board or MDF. If the addition amount of Glyoxal is less than 0.2 parts by weight, the curing time shortening effect and the flexural strength expression are weak, and if 20 parts by weight or more, the curing time shortening effect and the adhesive strength expression effect are saturated and the cost is high. Hateful.

As the water-soluble aminoplast resin in the present invention, not only a urea resin, a urea / melamine co-condensation resin, a urea resin and a melamine resin mixture, but also a phenol resin may be blended and used. The compounding amount can be up to 30 parts with respect to 100 parts of the aminoplast resin. When these aminoplast resins are used as an adhesive for wood materials, it is also possible to mix and use fillers and extenders that are usually used. As the filler and extender, wheat flour, rice flour, barley flour, defatted soybean flour, defatted corn flour, various cereal powders such as konjac flour, wood flour, talc, use of one or more inorganic powders such as clay, etc. Can be done.

As the curing agent for the aminoplast resin, a generally known curing agent can be used. Examples of the curing agent include ammonium salts such as ammonium chloride, hydrochloric acid, acetic acid, paratoluenesulfonic acid, aluminum sulfate, and aluminum chloride.

[0012]

The present invention will be described with reference to the following examples. All parts in the examples are parts by weight. The evaluation test method is based on the method shown in Table 1.

[0013]

[Table 1]

Examples 1, 2, 3, 7, 8 and Comparative Examples 4, 5 A predetermined amount of a portion of urea and a predetermined amount of 37% formalin were charged and dissolved by heating under alkaline conditions, and the primary reaction was carried out at 90 ° C.
After carrying out the reaction for 30 minutes at 80 ° C. under acidic condition, the remaining amount of urea is charged at room temperature and the reaction is carried out for 4 hours. After cooling by neutralization, a predetermined amount of glyoxal is added to neutralize the product. Measure the amount of formaldehyde remaining in the resin before adding glyoxal. The gel time time at 100 ° C. is measured according to test method A for each resin. Next, a compounding paste is prepared by Test Method B to prepare plywood, and the adhesive strength of the plywood and the amount of formaldehyde released are measured. The results are shown in Table 2.

Examples 4, 5 and 6 Corresponding to Examples 1 to 3, similarly, urea and 37% formalin were charged and dissolved by heating in a predetermined amount under alkaline conditions, and the primary reaction was carried out at 90 ° C. for 30 minutes and then under acidic condition. Then, a predetermined amount of urea is charged at 80 ° C. and reacted for 4 hours. Upon cooling, at 60 ° C., a predetermined amount of glyoxal corresponding to Examples 1 to 3 was added, and the mixture was left for 30 minutes and neutralized to obtain a product. Gel time is measured according to Test Method A for each resin. Next, test method B
Make a compounded paste to make a plywood, and measure the adhesive strength of the plywood and the formaldehyde emission. The results are shown in Table 2.

Comparative Examples 1 to 3 In the same manner as in Examples 1 to 3, urea and 37% formalin were charged, and a predetermined amount was heated and dissolved in an alkaline solution to carry out the primary reaction.
After carrying out at 90 ° C. for 30 minutes, a predetermined amount of urea is charged at 80 ° C. under acidic condition and reacted for 4 hours. Cooled product after neutralization. Gel time and residual formaldehyde are measured according to Examples 1 to 3 by the method of Test Method A. Next, a compounding paste is prepared by Test Method B to prepare plywood, and the adhesive strength of the plywood and the amount of formaldehyde released are measured. The results are shown in Table 2.

Example 9 Melamine and 46% formalin in the amounts shown in Table 3 were charged, reacted under alkaline conditions at 90 ° C. for 4 hours, cooled to a solid content of 62 wt% under vacuum, and glyoxal was added as shown after cooling. And Gel time is measured by Test Method C. Next, a particle board was prepared by Test Method D, and the physical properties and the amount of formaldehyde released were measured. The results are shown in Table 3.

Comparative Example 6 Melamine and 46% formalin were added in the amounts shown in Table 3 and reacted under alkaline conditions at 90 ° C. for 4 hours to give a solid content of 60 wt% under vacuum to obtain a cooled product. Test method C, D
Then, the gel time was measured, then a particle board was prepared, and the physical properties, the amount of formaldehyde released, and the physical properties were tested by the same test method. The results are shown in Table 3.

Example 10 70 parts of urea resin of Comparative Example 3 and melamine resin 3 of Comparative Example 4
0 parts are compounded and glyoxal is added in the amount shown in Table 3. Gel time, physical properties, and released formaldehyde were measured by Test Method C and Test Method D. The results are shown in Table 3.

Comparative Example 7 70 parts of the urea resin of Comparative Example 3 and the melamine resin 3 of Comparative Example 4
0 parts are blended, and gel time, physical properties, and released formaldehyde are measured by Test Method C and Test Method D. The results are shown in Table 3.

Example 11 80 parts of the melamine resin of Comparative Example 4 and 15 parts of a phenol resin (Euroid 883P manufactured by Mitsui Toatsu Chemicals Inc.) were mixed and the amount of glyoxal shown in Table 3 was added. In Test Method C and Test Method D, the gel time of the resin, the physical properties of the particle board, and the released formaldehyde were measured. The results are shown in Table 3.

Comparative Example 8 80 parts of the melamine resin of Comparative Example 4 and 20 parts of a phenol resin (Euroid 883P manufactured by Mitsui Toatsu Kagaku Co., Ltd.) were mixed and the gel time of the resin, the physical properties of the particle board and the release were measured by Test Method C and Test Method D. Measure formaldehyde. The results are shown in Table 3.

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

EFFECTS OF THE INVENTION According to the adhesive composition of the present invention, it is possible to improve the productivity by keeping the gel time short while keeping the residual formaldehyde low, and also improve the physical properties such as adhesive strength and bending strength, and also the water resistance. Since it can be maintained, it is extremely beneficial to the industry.

Front page continuation (72) Inventor Hiroyuki Kaigaishi 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemical Co., Ltd.

Claims (3)

[Claims] 1. An adhesive for wood materials, characterized in that 0.2 to 20 parts by weight of glyoxal is added to 100 parts by weight of a water-soluble aminoplast resin containing formaldehyde as a main component. 2. The adhesive for wood materials according to claim 1, wherein the amino compound which is the other main component of the aminoplast resin containing formaldehyde as the main component is urea alone, melamine alone or urea and melamine in combination. 3. The adhesive for wood materials according to claim 1, wherein the content of free formaldehyde contained in the aqueous aminoplast resin is 1 wt% or less.