JPS61157567A - Adhesive for plywood - Google Patents

Abstract

PURPOSE:To provide a plywood adhesive capable of remarkably improving the initial bond adhesion of plywood, by adding a specific carboxymethylcellulose to a plywood adhesive as a thickener. CONSTITUTION:The objective adhesive contains an alkali metal salt of carboxymethylcellulose having an etherification degree of >=1.5 as a thickener. Concretely, the objective adhesive is produced preferably by compounding 100 pts.(wt.) of a synthetic resin with 10-50pts. of wheat flour or other thickener, 0.1-3.0pt. of above carboxymethylcellulose, 10-30pts. of water and 0.1-3.0pt. of ammonium chloride.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a plywood adhesive for improving the initial adhesion of a plywood adhesive.

(Prior art) In plywood adhesives such as urea resins, melamine resins, and phenolic resins, fillers, crosslinking catalysts, and thickeners are used in addition to the main synthetic resin. The use of carboxymethylcellulose is known (for example, JP-A-55-90572).

(Problems to be Solved by the Invention) In the production of plywood, it is known that the productivity and quality of the product are greatly affected by the quality of the initial adhesion of the plywood after cold pressing. In other words, plywood with poor initial adhesion significantly reduces the efficiency of pressing operations, and is also a source of defects such as peeling, blistering, and misalignment. However, improving the initial adhesion of plywood is a very difficult problem, and especially in winter and at low temperatures such as in the morning, the number of defective products that are thought to be caused by poor initial adhesion increases significantly.

In addition, South Sea materials such as Merabi and Kapor, which are said to have poor initial adhesion, and domestic materials such as Chinese china and plastic also cause similar problems, and a solution to this problem has been desired.

(Means for Solving the Problems) As a result of intensive research to solve these difficulties, the present inventor has found that by using a special CMC as a thickener in plywood adhesives, the initial adhesive layer of plywood The present invention has been completed based on the discovery that this significantly improves the performance of the present invention.

That is, the present invention is a plywood adhesive characterized by containing an alkali metal salt of carboxymethylcellulose (abbreviated as FCMC) having a degree of etherification of 1.5 or more as a thickener.

The plywood adhesive of the present invention is composed of a synthetic resin as a main component such as urea resin, urea-formalin resin, melamine resin, or phenol resin, an extender such as wheat flour or rice flour, and a crosslinking catalyst such as ammonium chloride. It is manufactured by adding CMC completely dissolved in water and mixing and stirring with a glue mixer.

The composition ratio of the adhesive is usually 100 parts by weight of synthetic resin, 10 to 50 parts of wheat flour or other bulking agent, 0.1 to 3.0 parts of CMC of the present invention, 10 to 30 parts of water, and chloride. Although ammonium is blended in a proportion of 0.1 to 3.0 parts, it is not particularly limited to this range and can be changed as appropriate depending on the adhesive workability and the physical properties after adhesion.

In addition, appropriate amounts of urotropin, aqueous ammonia, melamine,
There is no problem in using gelling modifiers, thickeners, and waterproofing agents such as polyvinyl alcohol, gum arabic, alginic acid, methylcellulose, hydroxyethylcellulose, and paraffin.

Furthermore, the objects of the present invention can be more effectively achieved by adding soybean protein, casein, albumin, gelatin, etc.

The CMC used in the present invention has a degree of etherification (DS) of 1.5 or more, which is expressed as the average degree of substitution by carboxymethyl groups per anhydroglucose unit of cellulose. Highly substituted CMC with a DS of 1.5 or more was not well known until now, partly because it was difficult to produce. In recent years, JP-A-58-45201 and JP-A-58-176
An efficient multi-stage manufacturing method, as described in Japanese Patent No. 202, has been developed and industrial production has become possible. Conventional commercially available C with DS of 1.5 or less
MC does not provide a sufficient improvement in initial adhesion.

The viscosity of the CMC of the present invention is 90 to 9,000 cp as a 1% aqueous solution (BL viscometer, 60 rpm, 25°C).
A range of s is preferred.

CMC with a viscosity lower than this cannot provide a sufficient thickening effect, and one with a high viscosity exceeding 9.000 cps reduces workability and is unsuitable as a thickener for plywood adhesives.

Furthermore, the CMC of the present invention includes sodium salt, potassium salt,
Any alkali metal salt such as lithium salt may be used, but
It is industrially manufactured. The use of thorium salts is preferred.

(Example) The present invention will be explained in further detail by showing Examples below, but the present invention is not limited thereto. Note that parts in the examples indicate parts by weight.

Example 1゜The degree of etherification is 2.1, and the viscosity of a 1% aqueous solution (BL viscometer, 60 rpm, 25°C or less) is 370.
c)'s CMC0.5m was added to 20 volumes of water to completely dissolve it to prepare a CMC aqueous solution. Urea resin (S-C50
%, viscosity 150 cps, 25°C) to 100 parts of this C
After adding the MC aqueous solution and uniformly mixing and stirring using a glue mixer, 30 parts of wheat flour and 1 part of ammonium chloride were added and further mixing and stirring to obtain a uniform adhesive. The viscosity of the adhesive at this time was 65 voids.

This adhesive is applied to a lauan wood veneer with a moisture content of approximately 15% (30L:
MLx 3o (:IrLxo, 4cm) was coated on both sides with a coating amount of 28g/shaku2, and a lauan wood veneer (30cIrLx 30cnLxO) was applied from the top and bottom.
, 2cIIL) were laminated to form 3 plies to make plywood. This plywood is cold pressed (10 kg/ca, 15
After the test was carried out for 10 minutes at normal pressure, the state of peeling of the veneer was measured. As a result, no peeling phenomenon of the plywood was observed even after 30 minutes had passed, and it was found that the initial adhesion was extremely excellent. A similar test was conducted using the adhesive of this example on a large plywood board of 9oCrrL x 180crrL, and the initial adhesion was sufficient and hot pressing work was also successfully carried out.

Example 2゜The degree of etherification is 2.6, and the viscosity of the 1% aqueous solution is 130.
C)) 0.5 parts of CMC of S was added to 20 parts of water and completely dissolved to prepare a CMC aqueous solution. Urea resin (S-C50%,
This CMC aqueous solution was added to 100 parts (viscosity: 150 cps, 25°C), mixed and stirred uniformly with a glue mixer, then 30 parts of wheat flour and 1 part of ammonium chloride were added, and further mixed and stirred to form a uniform adhesive. . The viscosity of this adhesive was 57 voids.

Example 1 This adhesive was applied to a lauan wood veneer with a moisture content of approximately 20%.
It was coated in the same manner as above, and the peeling state was measured. As a result, no peeling was observed at all even after 30 minutes of initial adhesion, and it was found that the initial adhesion was extremely excellent. Further, hot pressing work was carried out on plywood of 90z x 180z in the same manner as in Example 1 using the adhesive of this example, but there was no problem.

Example 3゜The degree of etherification is 1.6, and the viscosity of the 1% water bath liquid is 3.56.
0c+)s CM CO, 5 parts was added to 20 parts of water to completely dissolve it to prepare a CMC aqueous solution. Urea resin (S-C5
0%, viscosity 150 cps, 25°C) to 100 parts of this C
An aqueous MC solution was added to prepare a uniform adhesive in the same manner as in Example 1. The viscosity of this adhesive was 69 voids.

Example 1 This adhesive was applied to a lauan wood veneer with a moisture content of about 15%.
The coating was applied in the same manner as above, and the state of peeling was measured. As a result, some peeling of the initial adhesion was observed after 30 minutes, but this was not a problem.

Also, using the adhesive of this example, 9 Qm
Hot pressing work was carried out on xl 80CIrL plywood, but there were no problems.

Comparative Example 1゜The degree of etherification is 0.65, and the viscosity of a 1% aqueous solution is 3.9.
0.5 parts of 80 cps CM CO was added to 20 parts of water and completely dissolved to prepare a CMC aqueous solution.

Urea resin (S-C50%, viscosity 150 cps, 25'
c) Add this CMC water bath solution to the i o o part,
A uniform adhesive was prepared in the same manner as in Example 1. The viscosity of this adhesive was 71 voids.

This adhesive was applied to a lauan wood veneer with a moisture content of approximately 15% in the same manner as in Example 1, and the peeling state was measured. As a result, the initial adhesion was found to be defective as the entire surface peeled off after 30 minutes.

Claims (1)

[Claims] A plywood adhesive characterized by containing an alkali metal salt of carboxymethyl cellulose having a degree of etherification of 1.5 or more as a thickener.