JPS603436B2 - Adhesive composition for plywood - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and useful adhesive composition for plywood, and more particularly, the present invention relates to a new and useful adhesive composition for plywood, which is composed of a phenolic resin powder and an aqueous dispersion, has a significantly reduced formalin odor, Moreover, it relates to a composition with significantly improved workability.

Generally, as adhesives for this type of plywood, aluminum/resins such as urea formaldehyde resin and melamine-formaldehyde resin and water-curing phenolic resin are used, but they have a formalin odor, {2 } The viscosity of the blended glue increases significantly, [3- There is a limit to the deposition tolerance, {4
) There were various drawbacks such as poor temporary adhesion.

To this end, it has been proposed to improve the formalin odor by lowering the reaction molar ratio of the amino compound and formaldehyde or by increasing the degree of condensation. Methods such as adding amino compounds such as ethylenediamine have also been proposed, and although these methods are effective in reducing free formaldehyde, they also have the disadvantage of prolonging the curing time and making it difficult to clean the formulated glue. Deterioration of physical properties, such as a decrease in physical properties, is observed.

Furthermore, plywood made of urea formaldehyde resin may generate a formalin odor due to decomposition of the resin during storage or use, and the above-mentioned countermeasures cannot be said to be drastic. On the other hand, water-soluble phenolic resins have less formalin odor, but they have a shorter deposition tolerance, and furthermore, the viscosity of the resin decreases due to heating during hot pressing, which causes it to penetrate into the veneer, resulting in poor adhesion performance. It cannot be said to be a perfect adhesive for plywood as it may cause problems with the adhesive itself.

However, as a result of intensive research aimed at reducing formalin odor and improving workability, the present inventors found that by using a mixture of phenolic resin powder and an aqueous dispersion,
The present invention was completed by successfully reducing the formalin odor emitted from plywood, which was a drawback of the conventional technology, and by discovering that it was also possible to significantly improve deposition tolerance, temporary adhesion, and stability of compounded glue. I ended up letting it happen.

That is, the present invention combines phenolic resin powder, synthetic resin emulsion (b-1), and synthetic rubber latex (b-1).
-2) A mixing ratio of at least one aqueous dispersion 'B- selected from the group consisting of: 10/90 to 10/90 per solid weight
The present invention provides an adhesive composition particularly useful for plywood, which contains both components as essential components in a ratio of 90/10.

Here, the typical phenolic resin powders include novolac type and resol type powdered phenolic resins, and there is no major difference in adhesion between novolac type and resol type. but,
Regarding the dispersibility in the aqueous dispersion [B], it can be said that the noporac type is better.

Phenols used to obtain the phenolic resin powder include phenol, cresol, and pt-
Butylphenol, P-SeC-phthylphenol, p
-Octylphenol/Nylphenol or xylenol or bisphenols are typical compounds, but those with a molar ratio of other phenols to phenol of 1:0.3 or less have good curing speed and dispersibility. It is optimal from this point of view.

There are no particular restrictions on the properties required for the phenolic resin powder (1), but in the case of a noporac type phenol resin, the resin must have a free phenol content of 5% by weight or less and a melting point of 90 to 105 qo. More favorable results are obtained as the fluidity of the mixture increases.

In the case of resol type phenolic resin powder, there are no major restrictions as with novolac type, but the softening point is 65~
75 qo and a curing time of 40 to 120 seconds gives the best results in terms of pressing conditions and physical properties of the plywood.

In addition, regarding the particle size of the phenolic resin powder, from the viewpoint of adhesive performance alone, the finer the particle size, the better, but from the viewpoint of workability such as prevention of dust generation and prevention of powder floating when compounding glue. A range of 50 to 60 μm is best.

On the other hand, the above-mentioned aqueous dispersion [B}' is an important component as a dispersion medium for the phenolic resin powder and as a temporary adhesion improver, and is a synthetic resin emulsion (b-1) or a synthetic rubber latex (b-1). 2).

Among these, representative synthetic resin emulsions (b-1) include acrylic resin emulsions, vinyl acetate resin emulsions, vinyl acetate-acrylic copolymer resin emulsions, and ethylene-vinyl acetate copolymer resin emulsions. Rubber latex (b-2)
Typical examples include styrene butadiene rubber latex (SBR), acrylonitrile butadiene rubber latex (NBR), isobutylene isoprene rubber latex (11R), polychloroprene rubber latex (CR), and polybutadiene rubber latex (BR).
), isoprene rubber latex (IR) or butadiene styrene vinyl pyridine latex (VR).

These aqueous dispersions [B-] can be used as long as they are commercially available, but those with a film forming temperature of 30° C. or less, preferably 5 to 10° C. are suitable; In particular, synthetic resin emulsions using polyvinyl alcohol as a protective colloid are optimal in terms of temporary adhesion and adhesive strength.

Note that the emulsion (b-
As for 1), even if it is classified as a dispersion by definition, there is no problem in using it. Although the blending ratio (solid content weight ratio) of each of the resin powders (■) and the aqueous dispersion 'B} described above varies depending on the type of plywood required as the grade of plywood to be applied, in general, /{B)= 10/90 to 90/10, preferably 20/80 to 50/50 in type 1
The ratio is 30/70 to 50/50, and both physical properties and workability are optimized at such a limited blending ratio.

Next, the present invention will be specifically explained using Examples and Comparative Examples.

Examples 1 to 5 and Comparative Examples 1 and 2 Various synthetic adhesives were prepared at the compounding ratios shown in Table 1. Various plywood adhesion tests as described below were conducted on these various adhesives.

Plywood production conditions ■ Veneer configuration 〇, 7 sails + I, 3 sails 〇, 7 sides ■ Veneer moisture content 6-8% by weight ■ Adhesive application amount 300 t/min ■ Cold press 25q○ x 10k9/ground x 30 Minutes Hot press 125 pm C x 10k9' ground x 2 minutes 13500 x 10k9/carp x 2 minutes The results are summarized in Tables 2 to 6. The result of formalin odor is shown (the pressing conditions for this scale are 125℃ x 10kg/
Earth x 2 minutes.

), Table 3 shows the results of the adhesion test with the pressing conditions changed to 135qo x 10k9/x2 minutes,
Table 4 shows the results of examining the deposition time using lauan material as the veneer and pressing conditions of 13yo x 10kg/ground x 2 minutes, and Table 5 shows the test results of temporary adhesion. Table 6 shows the test results for the change in viscosity of the glue over time. Table 1 *The numbers in the table mean "parts by weight."

Note) ``Boncoat W-2520'' Polyvinyl acetate resin manufactured by Dainippon Ink Chemical Co., Ltd. ``Luckstar 7310K'' Same as above SBR latex manufactured by the company ``Luxstar 7310K''
Barkham TD-2097" Same as above. Novolak type phenolic resin powder "Pryochen BA-5"
034" Same as above. Resol type phenolic resin powder "Plyauchen TD--2206" Same as above. Water-soluble phenolic resin "Pryamine TD" as above.
-2940" Same as above Melamine resin manufactured by the same company Table 2 Note) Formalin Table 3 Table 4 Note) Temperature during deposition: 30C Note 5J Note) Measurement procedure: 1800 peeling strength after single-center dopressing.

The size of the test piece at this time was 20×20.
Note) Measurement procedure: Measured at a temperature of 35C using a "Lyon UT-02" viscometer.

Claims (1)

[Scope of Claims] 1. (A) phenolic resin powder and (B) at least one aqueous dispersion selected from the group consisting of synthetic resin emulsion (b-1) and synthetic rubber latex (b-2). An adhesive composition for plywood comprising the above-mentioned powders (A) and dispersion (B) mixed at a mixing ratio of 10/90 to 90/10 based on solid weight.