JPS6042835B2 - How to improve the initial adhesion of plywood adhesives - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving the initial adhesion of plywood adhesives.

That is, in plywood adhesives such as urea resins and melamine resins, fillers, crosslinking catalysts, and thickeners are used in addition to the main synthetic resin. Granular CMC (hereinafter abbreviated as granular CMC) is present as partially dissolved particles in a swollen or semi-dissolved state, which dissolves over time after application of the adhesive and increases the viscosity of the adhesive, thereby significantly improving the initial adhesion of plywood. This invention relates to a method for improving the initial adhesion of plywood adhesives. Conventionally, it is known that the initial adhesion of plywood can be improved by mixing CMC as a thickener to the main synthetic resin in plywood adhesives, but in the conventional method, CMC is not added to the adhesive. Since it is completely dissolved, the initial buildup of the adhesive is large, making it difficult to apply it to the plywood.

Therefore, there were problems such as partial adhesion failure occurred during the initial adhesion after cold pressing, peeling phenomenon between the plywood sheets was observed, and main adhesion work by hot pressing became extremely difficult. Furthermore, the amount of CMC used in the adhesive is quite large, several percent relative to the synthetic resin, and plywood with a high moisture content requires a pre-drying process, resulting in a considerable increase in cost. As a result of intensive research aimed at improving these drawbacks, the present invention has found that granular CMC particles are present in the adhesive as a thickener in a swollen or semi-dissolved state and partially dissolved when the adhesive is applied. The present invention was achieved based on the discovery that this method has a remarkable effect on the initial adhesion of . In detail, synthetic resins such as urea resin and melamine resin, which are the main components of plywood adhesive, are mixed with an extender such as wheat flour, rice flour, etc., a crosslinking catalyst such as ammonium chloride, and water, and then immediately before applying this adhesive. When granular CMC is mixed as an adhesive, the initial buildup of the adhesive is reduced (the viscosity at the time of adjustment is approximately 15-25
After application, the CMC particles that are swollen or semi-dissolved due to the moisture contained in the adhesive dissolve over time, and the viscosity of the adhesive increases rapidly (approximately 30 ~40 poise is desirable), is an improved method that can significantly improve the initial adhesion of plywood. In the present invention, partially dissolved granular CMC particles are particles in which the surface of the granular CMC particles is partially dissolved due to the water content in the adhesive being small compared to the total amount of compounded ingredients. However, this means that the core remains completely undissolved. The amount of granular CMC used in the adhesive of the present invention is approximately 0.00 parts per 10 parts of synthetic resin.
Up to about 5% by weight is sufficient, and it is desirable that about 20 to 50% of the granular MC particles remain in the adhesive in a swollen or semi-dissolved form.

In this case, the remaining granular CMC particles differ depending on the type of synthetic resin. That is, the urea resin preferably has a content of 10 to
60%, more preferably 20-60%, melamine resin preferably 10-60%, even more preferably 50-60%
%. The particle size of the granular QMC is not particularly limited, but is preferably 10 to 80 mesh, more preferably 3 mesh.
0 to 60 mesh. Next, the present invention will be explained with reference to Examples and Comparative Examples.

Note that the number of parts indicates parts by weight. Example 1 1 (1) part of urea resin (#815 manufactured by Ohshika Shinko Co., Ltd.), 2 parts of wheat flour, 1 part of ammonium chloride, and 1 part of water were mixed.

Add 0.5 part of granular CMC (Daicel Corporation Ii 1262, etherification degree 0.92) to this mixed adhesive, stir and mix with a mixer for about 2 minutes, and blow steam into
The temperature was raised to C, and the viscosity of the adhesive at this time was maintained at about 20 poise, and the viscosity was adjusted with flour to 30 to 40 poise after 1 hour. Apply this adhesive to a veneer with a moisture content of approximately 27% (3
Approximately 30y was applied to 0c7n x 30C7TL x 0.4C7, and the veneers were laminated from above and below to form a plywood. Granular C at this time
Approximately 20% of the MC particles remained. After this plywood was cold-pressed (10k91d120 minutes), it was further allowed to stand at normal pressure for a period of time, and then the peeling status of the veneer was evaluated. That is, the time required for the front and back veneers to start peeling from the middle veneer was measured. ．． As a result, no peeling phenomenon was observed even after 3 coats, and it was found that the initial adhesion was extremely excellent.
*8 Also, use the adhesive in this example to make a large plywood size 90cm x 1
A similar test was conducted using 80α, and the initial adhesion was sufficient, and the hot press work for main adhesion was also successfully carried out. Example 2
Melamine resin (PWP-8 manufactured by Oshika Shinko Co., Ltd.) 1 (
1) Wheat flour, ammonium chloride and water were mixed in the same manner as in Example 1, and 0.5 part of granular CMC (#1262 manufactured by Daicel Corporation, degree of etherification 0.90) was added. It was mixed in the same way.

The viscosity of the adhesive was maintained at about 22 poise, and the viscosity after 1 hour was adjusted with flour to about 35 poise. When this adhesive was applied to a veneer with a moisture content of about 25% in the same manner as in Example 1, the residual particles of granular QMC were about 50%. The initial adhesion of this plywood after cold pressing was found to be extremely excellent, with no peeling observed even with 3 powders. Also, using the adhesive of this example, 90C77! ×180c
There was no problem with hot pressing work on m-plywood.
Comparative Example 1 The viscosity of the adhesive blended in Example 1 excluding granular CMC was about 13 poise, and the viscosity after 1 hour was adjusted with flour to 35 poise.

This adhesive was applied to a veneer in the same manner as in Example 1, and initial adhesion was evaluated. As a result, peeling of the veneer was observed in 10 minutes. Also, like Example 1, it is 90cm x 180CT! Although it was applied to plywood, the initial adhesion was poor and hot pressing was extremely difficult. The following Table 1 shows experimental results when the amount of granular CMC remaining in the compounded adhesive immediately before coating on the veneer was varied in Examples 1 and 2 above.

Claims (1)

[Claims] 1 As a thickener for plywood adhesives, granular carboxymethyl cellulose particles are partially dissolved and present at the time of adhesive application, and when bonding veneers, the moisture in the adhesive increases the viscosity over time, thereby improving the initial adhesion of veneers. A method for improving the initial adhesion of a plywood adhesive, characterized by improving the initial adhesion of a plywood adhesive.