JPH108014A - Plywood adhesive composition - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce formaldehyde release from plywood, improve water resistance, and suppress the viscosity of compounded glue with time. SOLUTION: An amino resin or a phenol resin,
An acrylic emulsion resin having a functional group capable of crosslinking with the amino resin or phenol resin is contained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an adhesive composition for plywood. More specifically, the present invention relates to an adhesive composition for plywood that maintains the water resistance of the plywood, reduces formalin release from the plywood, and takes into account the stability and workability of the compounded paste during plywood production.

[0002]

2. Description of the Related Art Conventionally, amino resins (urea resins, melamine resins, urea-melamine co-condensation resins) or phenol resins have been mainly used as plywood adhesives.
Formaldehyde is used as a part of the raw material for these adhesives, and unreacted formaldehyde remains in the plate when cured by heat and pressure, and the cured product liberates formaldehyde through the progress of hydrolysis and condensation reactions. I do. These formaldehyde move to the surface of the plywood and are released from the surface of the plywood or from the wood. This is the so-called formalin odor, which causes irritation and discomfort. In order to reduce the formaldehyde emission from the plywood, various measures for reducing the formaldehyde of the amino resin or the phenol resin have been studied. However, it is difficult to balance plywood release formaldehyde with performance aspects such as adhesive strength and water resistance, and it is not perfect. Reduce the amount of formaldehyde emission by storing plywood in a well-ventilated place and spreading it over time, using plywood surface with additives that absorb formaldehyde such as ammonia and urea, and applying paint finishing. There is a method to do this, but it is difficult in practical terms and is not a fundamental solution. It is also 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 the resin as a general-purpose resin in practice, and this will significantly increase the cost.

Further, when an amino resin or a phenol resin is used as an adhesive for plywood, a filler such as flour and rice flour, a hardening agent, water and the like are usually added and used as a glue paste. Viscosity of the glue over time is severe, which hinders the work and is a serious problem in practical use.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the problem that formaldehyde released from plywood can be reduced by using an amino resin or a phenol resin which is a formaldehyde resin, the water resistance can be improved, and the viscosity of the compounded glue with time can be suppressed. Things.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an adhesive composition for plywood which has solved the above-mentioned problems of the prior art by adding a specific acrylic emulsion resin to an amino resin or a phenol resin. by doing,
The present inventors have found that formaldehyde emission from plywood can be reduced, water resistance can be improved, and the viscosity of compounded paste can be prevented from increasing over time, and the present invention has been completed.

That is, the present invention relates to an adhesive composition for plywood comprising an amino resin or a phenol resin and an acrylic emulsion resin having a functional group capable of crosslinking with the amino resin or the phenol resin.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The amino resin used in the present invention includes urea-formaldehyde resin (hereinafter, urea resin), melamine-formaldehyde resin (hereinafter, melamine resin) and urea melamine-
It is a formaldehyde co-condensation resin (hereinafter, urea melamine co-condensation resin) or a phenol resin. As the phenol resin, a water-soluble resol type phenol resin is used. Any of these is preferably manufactured by a known method. Among the above resins, the urea resin can be obtained by adding an alkali catalyst and, if necessary, an acid catalyst at a ratio of 1 to 3 moles of formaldehyde to 1 mole of urea and reacting them. The melamine resin is melamine 1
It is obtained by reacting formaldehyde at a ratio of 1 to 6 moles with respect to the moles. At the time of the reaction, an alkaline compound (alkali catalyst) such as sodium hydroxide, potassium hydroxide, sodium carbonate, aqueous ammonia, etc. Accordingly, an acid (acid catalyst) such as hydrochloric acid or acetic acid is added.

Further, the urea melamine co-condensation resin contains urea in an amount of 0.01 to 0.99 per mole of formaldehyde.
And melamine at a ratio of 0.01 to 0.16 mol, and a reaction at a ratio of the total mol number of melamine and urea not more than 1 mol to 1 mol of formaldehyde.

Further, the phenolic resin can be obtained by reacting formaldehyde in an amount of 1 to 4 moles per mole of phenol using an alkali catalyst.
All of these reactions are performed at a temperature of 60 to 100 ° C. The amino resin or phenol resin thus obtained preferably has a solid content of 40 to 70% by weight.

On the other hand, the acrylic emulsion resin used in the present invention can be obtained by a known emulsion polymerization method.
That is, an acrylic main monomer and a functional monomer capable of crosslinking with an amino resin or a phenol resin described below are added dropwise to an appropriate amount of water to which a small amount of an emulsifier and a polymerization initiator have been added, and the acrylic monomer is emulsion-polymerized.

The acrylic main monomer used in the present invention includes (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and stearyl (meth) acrylate. Acrylic acid alkyl esters, 2-hydroxyethyl (meth) acrylate, 2-
(Meth) such as hydroxypropyl (meth) acrylate
Acrylic acid hydroxy esters, (meth) acrylic acid, unsaturated monobasic acids such as crotonic acid and salts thereof,
Polyhydric vinyl compounds such as ethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and trimethylolpropane tri (meth) acrylate; and acrylonitrile. One or more of these are used. You.

The above (meth) acryl means acryl and methacryl. Further, as a functional monomer capable of crosslinking with an amino resin or a phenol resin,
Acrylic acid, methacrylic acid, itaconic acid, maleic acid,
Carboxy compounds such as fumaric acid, amide compounds such as acrylamide and methacrylamide, hydroxy compounds such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate and methylol acrylamide, glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether And the like, and one or more of these are used.

The content of the functional monomer capable of crosslinking with the amino resin or the phenol resin is 0.01 to 0.1 with respect to 1 mol of the main monomer of the acrylic emulsion resin.
50 mol is preferred, and more preferably 0.02 to 0.2 mol.
30 moles are preferred. If the amount is less than 0.01 mol, the crosslinking density with the amino resin becomes small, and strong adhesion cannot be obtained. On the other hand, if it exceeds 0.50 mol, it is not preferable because a sufficient side chain of the functional monomer to the main chain of the acrylic polymer cannot be obtained and a stable acrylic emulsion resin cannot be obtained.

The emulsifier used in the emulsion polymerization of the acrylic monomer includes sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyoxyethylene nonylphenol ether, and polyoxyethylene-
Known compounds such as a polypropylene block copolymer are exemplified.

As the polymerization initiator, potassium persulfate, ammonium persulfate, azobisisobutylnitrile, benzoyl peroxide and the like are used. The molecular weight of the acrylic monomer can be adjusted by adding a small amount of a known and conventional chain transfer agent of an organic thiol compound such as dodecyl mercaptan or lauryl mercaptan, or an organic halogen compound such as chloroform or carbon tetrachloride in advance. It is preferred. Incidentally, the emulsion polymerization is carried out by a method in which the acrylic monomer is dropped into water to which a small amount of an emulsifier and a polymerization initiator are added as described above.
A range of 30 ° C. is preferred.

In the present invention, the solid content of the acrylic emulsion resin is set to 40 to 60 in order to easily carry out emulsion polymerization.
% By weight is preferred. The content of the solid component can be adjusted with the above-mentioned water amount at the time of emulsion polymerization.

The adhesive composition for plywood of the present invention is obtained by uniformly mixing at least one of the amino resin or phenolic resin obtained by the above method and one or more of the acrylic emulsion resin obtained by the above method. Although it is obtained, the mixing ratio is preferably 10 to 900 parts by weight, more preferably 50 to 500 parts by weight, of the acrylic emulsion resin as a solid part, based on 100 parts by weight of the solid part of the amino resin or phenol resin. Parts are preferred. If the proportion of the acrylic emulsion resin is less than 10 parts by weight, the effects of reducing formaldehyde released from the plywood and suppressing the increase in the viscosity of the compounded paste with time are not preferred. Conversely, if it exceeds 900 parts by weight, the adhesive strength of the plywood decreases, the fluidity of the compounded paste deteriorates, and the workability of laminating veneers during handling and production of plywood becomes inconvenient. Is also inferior.

The amino resin or phenol resin and the acrylic emulsion resin of the present invention obtain an adhesive composition for plywood as follows. That is, into a vessel equipped with a stirrer suitable for high viscosity, such as a twin-screw mixer or a kneader, put an amino resin or a phenol resin and an acrylic emulsion resin at an arbitrary ratio, and, while stirring this, put the flour, Further, water and a curing agent are gradually added as needed, and the mixture is sufficiently kneaded until a predetermined viscosity is reached.

The wheat flour used preferably contains at least 10% by weight of crude protein, and more preferably at least 13% by weight. If it is less than 10% by weight,
The resulting mixed paste solution has poor viscosity, and the plywood is displaced during veneer bonding. Water is added for viscosity adjustment and economy. The amount of addition is preferably 50 to 400% by weight, more preferably 80 to 300% by weight, of wheat flour and water, based on the total solid content of amino resin or phenol resin and acrylic emulsion resin. . If the amount is less than 50% by weight, a compound having adhesive strength cannot be obtained, which is economically disadvantageous. If the amount exceeds 400% by weight, the fluidity of the compound deteriorates and the applicability in a coating machine is adversely affected. And the adhesive strength and water resistance of the plywood are undesirably reduced.

In order to cure the adhesive composition, ammonium chloride, ammonium nitrate, ammonium phosphate,
A known curing agent such as ammonium sulfate is used. The addition amount is added as needed, but is generally 0.1 to 3% by weight as a solid content with respect to the amino resin or the phenol resin.
Is preferred. The curing agent may be used as an aqueous solution.

The viscosity of the adhesive composition thus obtained is 1
0-100 poise is preferred. If it is less than 10 poise, the permeation of the resin into the veneer becomes large and the adhesiveness is poor, which is not preferable. On the other hand, if it exceeds 100 poise, the coating amount in the coating machine is unstable, and the stability over time deteriorates.

The adhesive for plywood thus obtained is adhered by a conventional method.
0 g / 900 cm ² , and a hot-press temperature of 105 to 180
Sufficient bonding performance is exhibited under the bonding conditions of 10 ° C. and a heat pressure time of 10 to 100 seconds / mm.

The amino resin or phenolic resin and the acrylic emulsion resin obtained by the present invention are used as an adhesive composition for plywood, and can be used as an adhesive for products having extremely low formaldehyde release from plywood and excellent plywood adhesive strength. It is an adhesive having a high practical value with good stability over time of compounding paste, so-called good workability.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless there is a change in the gist. In the following, parts and percentages are by weight unless otherwise specified. Example 1 Based on 100 parts of solid content of urea resin (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name U-701, 192.3 parts, solid content 5)
2%), 100 parts of a solid content of an acrylic emulsion resin (trade name: E-269, 232.M, manufactured by Mitsui Toatsu Chemicals, Inc.)
(6 parts, solid content 43%) were mixed and stirred, and 110 parts of flour (Nippon Flour Mill, Akana), 70 parts of water and 1.0 part of ammonium chloride were added and mixed to obtain an adhesive for plywood. The obtained compounded paste was subjected to a performance test under the following bonding operation conditions. Table 1 shows the test results.

(1) Bonding work conditions Single veneer configuration 1.6 × 3 plies (4.8 mm) Single veneer moisture content 7 to 10% Coating amount 30 g / 900 m ² Cold pressing pressure 12 kg / cm ² Cold pressing time 30 Heat-pressing pressure 8kg / cm ² Hot-pressing time 150sec Hot-pressing temperature 135 ° C

(2) Adhesion performance test (a) Hot and cold water immersion test; JAS ordinary plywood A test piece was immersed in hot water of 60 ° C. ± 3 ° C. for 3 hours.
It is immersed in water at room temperature until it is immersed, and an adhesive strength test is performed in a wet state to determine the shear strength (kg / cm ² ) and the average xylem fracture rate (%). (B) Boiling repetition test: JAS ordinary plywood After immersing the test piece in boiling water for 4 hours, dried at a temperature of 60 ± 3 ° C for 20 hours, further immersed in boiling water for 4 hours, and then immersed in room temperature water at room temperature Immersion until wet, perform an adhesion test in a wet state, and measure the shear strength (kg
/ Cm ² ) and average xylem fracture rate (%). (C) Continuous boiling test; JAS ordinary plywood After immersing a test piece in boiling water for 72 hours, immersing it in room temperature water until it reaches room temperature, performing an adhesion test in a wet state, and performing a shear strength test. (Kg / cm ² ) and average xylem fracture rate (%) are determined. (D) Formaldehyde emission amount test; JAS ordinary plywood 300 m at the bottom of a desiccator 240 mm (up to 9 to 11 L) in size specified in JIS R 3503
A crystal dish having a diameter of 120 mm and a height of 60 mm containing 1 l of distilled water is placed thereon, and a test piece (15 × 5 cm10 pieces) is fixed on a support bracket so that the test pieces do not come into contact with each other,
The sample is allowed to stand at 20 ° C. for 24 hours to absorb formaldehyde which is diffused to make a sample solution, which is then tested with an acetylacetone-ammonium acetate solution. (E) Measurement of viscosity increase of compounded paste over time Immediately after the compounded paste is completed-until 3 hours have passed, 40
Measure the viscosity at room temperature and measure the increase in viscosity of the compounded paste.

Example 2 The procedure of Example 1 was repeated, except that the acrylic emulsion resin, flour and water of Example 1 were changed as shown in Table 1. Table 1 shows the test results.

Examples 3 and 4 The urea resin U-701 was changed to a urea-melamine resin (trade name: U-350, manufactured by Mitsui Toatsu Chemicals Co., Ltd., 181.8 parts, solid content: 55%), and an acrylic emulsion was prepared. The procedure was performed in the same manner as in Example 1 except that the resin, flour and water were changed as shown in Table 1, respectively. Table 1 shows the test results. still,
The adhesion performance test was conducted by repeating the boiling test.

Examples 5 to 6 The urea resin U-701 was changed to a phenolic resin (PL-266, 243.9 parts, trade name: 413.9 parts, manufactured by Mitsui Toatsu Chemicals, Inc., solid content: 41%). Example 1 was repeated except that the flour and water were changed as shown in Table 1. Table 1 shows the test results. The adhesive performance test was a continuous boiling test.

Comparative Example 1 The procedure of Example 1 was repeated except that the flour and water were changed to 80 parts and 70 parts, respectively, except for the acrylic emulsion resin. Table 1 shows the test results. In addition, the adhesion performance test performed the same test as Example 1.

[0031]

[Table 1] In the table ・ Viscosity is poise / ° C ・ Keep water / cold water immersion test, boiling repetition test and continuous boiling test are kg / cm ²・ Plywood release formaldehyde is expressed in ppm

[0032]

According to the present invention, by using a specific acrylic emulsion resin which can be crosslinked with an amino resin or a phenol resin, the formaldehyde release from the plywood is reduced, the thickening of the compounded glue with time is reduced, and the water resistance of the plywood is reduced. The adhesive composition for plywood which did not reduce the property could be obtained.
That is, in Comparative Example 1 in which the acrylic emulsion resin is out of the range of the present invention, the performance is not achieved in the formaldehyde released from the plywood, the thickening of the compounded adhesive with time, and the water resistance of the plywood. However, embodiments of the present invention all have these excellent performances.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Nobuhiko Koto 7-1-1, Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Pref.

Claims (3)

[Claims] 1. An amino resin or a phenol resin,
An adhesive composition for plywood comprising an acrylic emulsion resin having a functional group capable of crosslinking with the amino resin or phenol resin. 2. The adhesive composition for plywood according to claim 1, which comprises 10 to 900 parts by weight of an acrylic emulsion resin based on 100 parts by weight of an amino resin or a phenol resin as a solid component. 3. The adhesive for plywood according to claim 1, wherein the content of the functional group monomer capable of crosslinking with the amino resin or the phenol resin is 0.01 to 0.50 mol per 1 mol of the main monomer of the acrylic emulsion resin. Composition.