JPH11228652A - Latent curing agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject curing agent capable of solving a delay in curing due to a reduction in formaldehyde of an amino resin or a phenol resin by using a specific compound as the curing agent for the amino resin or phenol resin. SOLUTION: This curing agent is obtained by using (A) a compound producing an acidic compound by decomposition and, as necessary, (B) an ammonium phosphate as a curing agent for an amino resin or a phenol resin. Persulfuric salts (e.g. ammonium persulate), a peroxide (e.g. a ketone peroxide), an azo compound (e.g. 2,2'-azobisisobutyronitrile), etc., are cited as the component A. Ammonium orthophosphate (e.g. ammonium dihydrogenphosphate), ammonium pyrophosphate (e.g. diammonium dihydrogenpyrophosphate), ammonium metaphosphate, ammonium polyphosphate, etc., are cited as the component B. The curing agent is effective in curing the amino resin, etc., used for bonding plywood, laminated wood, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to plywood, veneer plywood,
The present invention relates to a latent curing agent that is effective for curing an amino resin or a phenol resin used at the time of bonding a laminated wood, a wood fiber board or the like.

[0002]

2. Description of the Related Art Conventionally, plywood, veneer plywood, laminated wood,
When adhesively molding a wood fiber board or the like, an amino resin or a phenol resin such as a urea resin, a melamine resin, or a urea-melamine cocondensation resin is used as a main component, and an ammonium salt is added as a curing accelerator to form an adhesive composition. It is common to apply it to a dressing and use it.

[0003] However, when a formaldehyde-based amino resin or phenol resin is used as a main component, there is a drawback that the curing cannot be promoted even if an ammonium salt is added as a curing accelerator due to the reduction of the emitted formaldehyde.

[0004]

SUMMARY OF THE INVENTION The present invention solves the retardation of curing of an amino resin or a phenol resin by reducing formaldehyde.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a specific compound is added to solve the curing delay caused by reducing formaldehyde of an amino resin or a phenol resin.
The inventors have found that curing is accelerated, and have completed the present invention.

That is, the present invention relates to a compound in which a curing agent used in an amino resin or a phenol resin generates an acidic compound by decomposition, or a compound in which a curing agent used in an amino resin or a phenol resin generates an acidic compound by decomposition, and phosphoric acid It relates to a latent curing agent comprising an ammonium salt.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. Conventionally, when adhesively molding plywood, veneer plywood, glued laminated wood, wood fiber board, etc., the main component is an urea resin, a melamine resin, an amino resin such as a urea-melamine co-condensation resin or a phenol resin, and an extender such as flour. In general, water is added and mixed well, and an ammonium salt is further added as a curing accelerator to form an adhesive composition, which is generally applied to an adherend and used.

However, plywood, veneer plywood, laminated wood, wood fiberboard, and the like using an adhesive composition containing a formaldehyde-based amino resin or phenol resin as a main component, use formaldehyde as a part of the raw material. In addition, unreacted formaldehyde remains in plywood, veneer plywood, laminated wood, and wood fiberboard when cured by hot pressure, and also releases formaldehyde after curing due to the progress of hydrolysis and condensation reactions. These formaldehyde move to the surface and are released from the plate surface or side surface. This is the so-called formalin odor, which causes irritation and discomfort. In recent years, particularly, formaldehyde to be released has become a serious social problem, and various measures for reducing formaldehyde in resin have been studied in order to solve these problems of formaldehyde emission. Therefore, it is conceivable to use a urethane resin containing no formaldehyde at all, an aqueous vinyl urethane resin, or the like, but it is obviously difficult to use it as a general-purpose resin in practice, and the cost is greatly increased.

[0009] Therefore, an adhesive composition containing as a main component a resin obtained by reducing formaldehyde of an amino resin or a phenol resin, which is a general-purpose resin, has been studied. However, in this adhesive composition, formaldehyde remaining in the composition and ammonium chloride, which is generally used as a curing agent, lowers the pH by hydrochloric acid generated by the reaction, and is cured. For this reason, amino or phenolic resins that meet the formaldehyde emission test F1 standard prescribed in Japanese Agricultural Standards and Normal Plywood are short of formaldehyde and do not generate a sufficient amount of hydrochloric acid. There is an unsatisfactory problem. Further, in order to obtain a sufficient adhesive strength, the time for hot pressing must be extended, which is disadvantageous in terms of productivity.

Further, the obtained plywood, veneer plywood, laminated wood,
Since chlorinated hydrochloric acid generated by the reaction between ammonium chloride and formaldehyde remains on the wood fiber board, there is a concern about environmental problems when it is burned and discarded.

Further, there is a method in which an acid substance such as hydrochloric acid or sulfuric acid is used as a pH adjuster in order to accelerate the curing of the adhesive composition and satisfy the adhesive strength.
No effect can be obtained and sufficient adhesive strength cannot be satisfied. Under conditions where the amount of addition is large, sufficient adhesive strength can be satisfied, but there is a problem that the viscosity of the resin composition increases sharply with the passage of time and the pot life, which is the actual use time, is short. There are also problems such as a narrow range for obtaining an appropriate amount of addition.

On the other hand, the amino resin or phenol resin exceeding the formaldehyde emission test F3 standard specified in Japanese Agricultural and Forestry Standards, which contain a lot of formaldehyde, and ordinary plywood, or more than this, has sufficient formaldehyde and satisfactory adhesive strength. The formaldehyde odor generated in the above process is intensified, resulting in a problem that the working environment is deteriorated and the amount of emitted formaldehyde is large.

By using the latent curing agent of the present invention, the curability of the resin is remarkably improved, and the problem of curing delay due to the reduction of formaldehyde in the amino resin or phenol resin can be solved. Everything can be solved. The latent curing agent that generates an acidic compound by decomposition according to the present invention means a compound that decomposes by heat or the like to release an acidic compound.

Unlike the commonly used ammonium chloride, the compound of the present invention which decomposes by heat or the like to decompose by heat or the like to generate an acidic compound irrespective of the amount of formaldehyde in the resin, unlike ammonium chloride, is used. The curing acceleration effect can be exerted even with a resin having a reduced amount.
In addition, the acidic compound generated by the decomposition of the latent curing agent lowers the pH of the adhesive composition and accelerates the curing of the resin. Therefore, a compound having a larger amount of protons generated by the decomposition has a greater effect of accelerating the curing.

Examples of the compound which releases an acidic compound upon decomposition according to the present invention include persulfates, peroxides, azo compounds and the like. Examples of persulfates include ammonium persulfate, potassium persulfate, sodium persulfate, barium persulfate and the like. Examples of the peroxide include ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxyester, and peroxydicarbonate.

Further, as the azo compound, 2,2'-
Azobisisobutyronitrile, 2,2′-azobis (4
-Methoxy-2,4-dimethylpentanenitrile),
Azonitrile type such as 2,2′-azobis (2,4-dimethylpentanenitrile) and 2,2′-azobis (2-methylbutanenitrile), azoamidine type [V-50
Wako Pure Chemical Industries K. K, 2,2'-azobis (2-amidinopropane) hydrochloride], azodicarbonamide, 2,2'-azobis (azoamides such as 2-methylpropanimidamide, 2,2'-azobis (2-
The azoalkyl type of acetoxypropane can be listed.
One or more of these persulfates, peroxides and azo compounds may be used.

The term "ammonium phosphate salt" means an ammonium salt of a phosphoric acid compound such as orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid and polyphosphoric acid. Examples include ammonium dihydrogen phosphate, ammonium orthophosphate exemplified by diammonium phosphate, ammonium pyrophosphate exemplified by diammonium pyrophosphate, ammonium metaphosphate, ammonium polyphosphate, and the like. More than one species may be used.

In the present invention, the ammonium phosphate having a higher proton release amount has a higher curability improving effect.
It is desirable to use an ammonium phosphate salt having a small amount of replacement of OH with ammonia. In the present invention, the stability is improved by using a compound which generates an acidic compound by decomposition together with an ammonium phosphate salt. Also, a flame retardant effect can be provided.

In the present invention, the compound capable of generating an acidic compound and the ammonium phosphate salt can be used in any ratio. These may be mixed in advance with a ball mill or a V blender and added to the resin, or each may be separately added. May be added to the resin.

By adding the latent curing agent of the present invention to an amino resin or a phenol resin, the curability of the resin can be significantly improved as compared with conventional ammonium salts. With the amino resin of the present invention, urea, thiourea, melamine, benzoguanamine, one or more compounds having an amino group in the molecule such as dicyandiamide,
An oligomer and / or polymer obtained by reacting with an aldehyde such as formaldehyde.

In particular, by mixing melamine with an amino resin to impart water resistance to form an amino-melamine resin, a decrease in strength in a high humidity environment can be avoided. Further, in order to impart various properties at the time of amino resin production, polyvinyl alcohol, may be mixed with other polymers such as cellulose derivatives, or, if necessary, in use,
You may mix and use with a water-producing agent, a flame retardant, an insect repellent, a preservative, etc.

The production method and properties of the amino resin used in the present invention are not particularly limited, and a production method generally applied may be used. Amino resin uses a catalyst or forms a cured product that is polymerized by heating and partially cross-linked to form a high-hardness adhesive layer.The bending strength and rigidity of plywood, veneer plywood, glulam, and wood fiber board are obtained. Higher is desirable.

The phenolic resin of the present invention is usually phenol, resorcinol, cresol, xylenol,
An oligomer and / or polymer obtained by reacting one or more phenols such as bisphenol A with an aldehyde such as formaldehyde. Also,
In order to impart various properties at the time of phenol resin production, it may be mixed with other polymers such as polyvinyl alcohol and cellulose derivatives, and when necessary, as necessary, with a water generating agent, a flame retardant, an insect repellent, an antiseptic, etc. You may mix and use.

The production method and properties of the phenol resin used in the present invention are not particularly limited, and a production method generally applied may be used. Plywood obtained from the use of a phenolic resin or a catalyst to form a cured product that is polymerized by heating and partially crosslinked to form a high-hardness adhesive layer,
The bending strength and rigidity of veneer plywood, glulam, and wood fiber board are increased, which is desirable.

The amount of the latent curing agent used in the adhesive composition is based on 100 parts by weight (in terms of solid content) of the amino resin or phenol resin used in the resin composition.
It is preferably 0.05 to 20.0 parts by weight, more preferably 0.2 to 10.0 parts by weight, most preferably 0.3 to 10.0 parts by weight.
~ 7.0 parts by weight are preferred. If the addition amount is less than 0.1 part by weight, hardening of the resin hardly improves, so that
Not preferred. If the amount exceeds 5.0 parts by weight, the effect of improving the curability of the resin hardly changes, which is not preferable.

[0026]

Hereinafter, the present invention will be described in detail with reference to Examples.
The present invention is not limited to these examples. Parts and% represent parts by weight or% by weight unless otherwise specified. Example 1 A reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer was charged with 750 parts of a 48% formaldehyde aqueous solution, the pH was adjusted to 8.0, and then 360 parts of primary urea was added. And reacted at 85 ° C. for 30 minutes. Thereafter, the pH was readjusted to 5.8, reacted for 15 minutes, and further adjusted to pH 7.5.
And 150 parts of powdered melamine were added and reacted for 30 minutes. Thereafter, the resultant was cooled to obtain an amino resin (hereinafter abbreviated as a1). For a1, the molar ratio (F / U) of formaldehyde (F) to urea (U) was 1.20. The nonvolatile content was adjusted to 50.0%. Next, using a1, the curing time of the resin was measured by the method described below. 100 parts of the resin was weighed into a glass beaker, and the latent curing agent and the amount of addition shown in Table 1 were added to the amino resin, followed by mixing and stirring for 5 minutes to obtain a sample. Further, 5 g of the sample was weighed in a test tube, immersed in boiling water at 100 ° C., and the time required for curing was measured. Table 1 shows the results. Next, a1 was used as a latent curing agent in the adhesive composition shown below, and ammonium persulfate 1.0 was used as a latent curing agent.
The plywood was prepared under the following plywood manufacturing conditions using the parts, and an adhesion test was performed using a JAS ordinary plywood and hot and cold water immersion test. Table 1 shows the evaluation results.

(Adhesive composition blending) a1 resin 100 parts Wheat flour (Nisshin Flour Milling Co., Ltd., red flower) 25 parts Water (tap water) 20 parts Latent curing agent (ammonium persulfate) 1 part (Plywood production conditions) Single plate configuration: 0.6 mm + 1.2 mm + 0.6 mm (2.
4 mm, 3-ply) veneer moisture content: 8% to 10% adhesive composition coated amount: 26 g / scale ² deposition time: 15 minutes Cold pressure pressure-Time: 10 Kg / ^cm 2 · 20 min heat-pressure pressure and time: 10 Kg / ^cm 2 · 30 seconds

Examples 2 to 13 The same procedures as in Example 1 were carried out except that the latent curing agents or curing accelerators shown in Table 1 and the amounts added were used. Table 1 shows the evaluation results.

Comparative Example 1 The procedure of Example 1 was repeated except that the a1 resin was used and the latent curing agent was changed to 1 part of ammonium chloride. Table 1 shows the evaluation results.

Comparative Example 2 The procedure of Example 1 was repeated except that the a1 resin was used and the latent curing agent was changed to 3 parts of ammonium chloride. Table 1 shows the evaluation results.

[0031]

[Table 1]

[0032]

The present invention solves the curing delay caused by using an amino resin or a phenol resin with reduced formaldehyde. That is, the comparative example of the present invention has a long curing time and a low adhesive strength. In contrast, the embodiment of the present invention satisfies all of them.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Tanaka 7-1-1, Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Prefecture Inside Mitsui Chemicals, Inc. (72) Inventor Nobuhiko Kotan 7-chome, Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Prefecture No. 1 in Mitsui Chemicals, Inc.

Claims (4)

[Claims] 1. A latent curing agent in which a curing agent used for an amino resin or a phenol resin is a compound that generates an acidic compound by decomposition. 2. A latent curing agent in which a curing agent used for an amino resin or a phenol resin comprises a compound which generates an acidic compound by decomposition and an ammonium phosphate salt. 3. The latent curing agent according to claim 1, wherein the compound that generates an acidic compound by decomposition is a persulfate, a peroxide, or an azo compound. 4. The latent curing agent according to claim 2, wherein the ammonium phosphate salt is ammonium orthophosphate, ammonium pyrophosphate, ammonium metaphosphate, or ammonium polyphosphate.