JPS5884875A - Adhesive composition for plywood - Google Patents

Abstract

PURPOSE:To obtain titled composition with markedly reduced formalin ordor, having improved assembly time toleranece, interim adhesiveness, and the stability of compounded glue, comprising a phenolic resin powder and an aqueous dispersion such as a synthetic resin emulsion in a specific proportion. CONSTITUTION:The objective composition comprising (A) a phenolic resin powder (pref. a novolak-type one with a fre phenol content <=5wt%; a melting point 90-105 deg.C; a particle size 50-60mu) and (B) an aqueous dispersion selected from (i) synthetic resik emulsions such as of acrylic resin, vinyl acetate resin, and (ii) synthetic rubber latexes such as of styrene-butadiene, acrylonitrile-butadiene, with a solid weight ratio (A)/(B) being 10/90-90/10.

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 comprises a phenolic resin powder and an aqueous dispersion, and which has a significantly reduced formalin odor. Moreover, it is related to the composition, which has a wide range of workability and other aspects.

Generally, urea-formaldehyde resin, melamine-formaldehyde-like amino resin, and water-bathable phenolic resin are used as adhesives for plywood in this building, but 1) they have a formalin odor, and 2) they are compounded. The viscosity of the glue has increased or it is thicker, 6) There is a limit to the deposition FfF Tanie, 4
) It had some drawbacks, such as poor temporary adhesion.

To this end, it has been proposed to improve the formalin odor by lowering the molar ratio of the reaction between the amino compound and formaldehyde or by increasing the degree of condensation. Some methods have been proposed, such as adding amine compounds such as ethylenediamine, but are these methods effective in reducing free formaldehyde? There is a deterioration in the physical properties, such as a decrease in the area.
With plywood made of formaldehyde-based fat, a formalin odor is generated due to the decomposition of the resin during storage or current use, so the above-mentioned measures cannot be considered as fundamental.

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 used as 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,
We succeeded in reducing the formalin odor emitted from plywood, which was a drawback of the conventional technology, and also found that the deposition tolerance, temporary adhesiveness, and stability of the mixed glue could be greatly improved, and the present invention was developed. I have completed it.

That is, the present invention utilizes phenol resin powder N, and an aqueous dispersion (B) of a small amount selected from the group consisting of a synthetic resin emulsion (b-1) and a synthetic rubber latex (b-2). Solid content M per lid mixing ratio or 10/9
The present invention provides a adhesive composition 9:J which is particularly useful for plywood and which contains both components as essential components in a ratio of 0 to 90/10.

Here, typical phenolic resin powders N include novolac type and resol type powdered phenol fats, and there is no significant difference in adhesion between the novolac type and the resol type. Can't you?
Regarding the dispersibility in the aqueous dispersion (IEB), it can be said that the novolak type is better.

Phenols used in obtaining the phenol fat powder include phenol, cresol, p-=t
- Typical compounds such as butylphenol, p-11@e-butylphenol, p-octylphenol, nonylphenol or xylenol or bisphenols, but the molar ratio of other phenols to phenol is 1:CL3 or less This is optimal in terms of curing speed and dispersibility.

There are no particular restrictions on the properties required for the powdered phenol fat. In the case of novolac-type phenol fat, the free phenol content must be 5% by weight or less, and the melting point must be within the range of 90 to 105°C. Within this range, preferable results are obtained as the fluidity of the resin increases.

In the case of resol type phenolic resin powder, as with novolak type, are there any major limitations?
What are the pressing conditions and plywood? l! The best results are obtained in terms of one company.

In addition, in terms of the particle size of the phenol fallen rice powder (A), from the viewpoint of adhesive performance alone, the abrasion is fine or good, but
From the viewpoint of workability, such as prevention of dust generation and prevention of powder floating during blending of glue, a range of 50 to 60 μm is best.

On the other hand, the above-mentioned aqueous dispersion mB) is a favorable component as a dispersion medium or a temporary adhesion improver for the phenolic resin powder described in 8TI, and is a component suitable for synthetic resin emulsion (b-1) or synthetic rubber latex (b-2). It is the one that is chosen more.

Among these, representative synthetic residual fat emulsion/(b-1) are acrylic resin emulsion, acetic acid vinyl 111M & emulsion, vinyl acetate-acrylic copolymerization-fat emulsion, or ethylene-vinyl acetate copolymerization side fat emulsion. Synthetic rubber latex (b
Typical examples of -2) include styrene butadiene rubber latex (SBR), acrylonitrile butadiene rubber latex (NBR), inbutin/isoprene rubber latex (IIR), polychloroprene rubber latex (CR), and polybutadiene rubber latex. (BR), isoprene rubber latex (IR) or butadiene styrene vinyl pyridine latex (VP
)and so on.

Any commercially available aqueous dispersion B) can be used, but film forming +
1! Degrees! A temperature below IG°C, preferably within a range of 5 to 10°C is appropriate, and in particular, a type that uses polyvinyl alcohol as a colloid in a synthetic four-sided emulsion is optimal in terms of temporary adhesion and adhesive strength. be. Note that the emulsion (b) used in the present invention
-1) For regular maintenance, even if it is classified as a dispersion, there is no problem in using it.

Then, each of the above-mentioned working fat powder and aqueous dispersion (
Although the blending ratio (solid content Nii ratio) with B) varies depending on the type of plywood required as the grade of plywood to be applied, it is generally &gt;A)/(Bl = 10/90 to 90/1
0, preferably 20/80 to 501 in type ■
50, and 30/70 to 50150 for type (1), and both physical properties and workability become severe in such a limited blending ratio.

Next, the present invention will be specifically celebrated with reference to Examples and Comparative Examples.

Examples 1 to 5 and Comparative Example 1.2 7? at the blending ratio listed in Table 1? ! R types of synthetic adhesives were prepared.

For these various adhesives, the following plywood adhesion test was conducted.

α7wx+t5＋α7關■ Veneer moisture content 6-81% ■ Adhesive application amount 50011/ln'' ■ Cold press 25℃ x 1 o J/cys' x 50 minutes ■ Hot press 125℃ x 10 hours 4-×2 155°C x 10 kpi/lx" x 2 minutes The results are summarized in Table 2. ), Table 6 shows the press conditions at 165°C x 10kl/
Table 4 shows the results of the adhesion test when the pressure was changed to 165℃ x 1-<I/am'' x 2 minutes using lauan material as the veneer and pressing conditions of 165℃ x 1-<I/am'' x 2 minutes. Table 5 shows the results of a study of the deposition time, Table 5 shows the results of a test on temporary gradation, and Table 6 shows the results of a test on changes in the viscosity of the glue over time.

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Claims (1)

[Claims] The essential ingredients include a phenolic resin powder and (B) at least one aqueous dispersion selected from the group consisting of a filtrate emulsion (b-1> and a synthetic rubber latex (b-2)). , the mixing ratio of each of the above powders N and dispersion (B) per solid weight is 10/90 to 90.
An adhesive composition for plywood, which is obtained by mixing the adhesive composition so that the ratio of