JPH08120244A - Amino resin adhesive composition - Google Patents

Abstract

PURPOSE: To obtain an amino resin adhesive composition excellent in water resistance by mixing an amino resin with a modified PVA containing a specified amount of 4C or lower α-olefin units. CONSTITUTION: A vinyl ester (e.g. vinyl acetate) is copolymerized with a 4C or lower α-olefin (e.g. ethylene) to form a copolymer containing 1-10mol% α- olefin units, and this copolymer is hydrolyzed to obtain a PVA modified with the 4C or lower α-olefin and having a degree of polymerization of about 100-8000 and a degree of hydrolysis of about 50mol% or above. This PVA is mixed with an aldehyde (e.g. formaldehyde), water and at least one amino compound selected from among urea, melamine, dicyandiamide, etc., and further mixed with about 0.1-15wt.%, based on the amino resin component, above modified PVA, and the resulting mixture is mixed with an aqueous NaOH solution to adjust its pH and condensed under heating to form an amino resin. This resin is mixed with a filler and a thickener to obtain an amino resin adhesive composition excellent in water resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amino-based resin adhesive composition, and more specifically, to the water resistance, initial adhesion, aging resistance, viscosity stability and water washability required for bonding wood such as plywood. The present invention relates to an excellent amino resin adhesive composition.

[0002]

2. Description of the Related Art Conventionally, amino resin initial condensates represented by urea resins, melamine resins, aniline aldehyde resins and the like are inexpensive and have relatively high water resistance at the time of adhesion, and thus are mainly used for plywood, furniture and the like. Known as an excellent adhesive for wood products. For these amino resins, there is an increasing demand for workability as well as adhesion performance after adhesion. Generally, an amino resin is used as an aqueous solution in the state of an initial condensate, so that the viscosity is generally low and there is a problem in workability that temporary adhesiveness is lacking. A method of modifying a urea resin by adding a water-soluble polymer such as carboxymethyl cellulose or polyvinyl alcohol (hereinafter simply referred to as PVA) to a reaction system in the condensation reaction of urea and formaldehyde for the purpose of imparting initial adhesive strength is It is known. However, this method improves the temporary adhesion, aging resistance, and water washability of the amino resin, but shortens the pot life due to the decrease in the stability of the resin liquid, and further increases the viscosity and the adhesive strength after long-term storage. However, there was a drawback that it happened and it was not completely satisfactory.

[Problems to be Solved by the Invention]

The present invention solves the drawbacks of conventional amino resin adhesives and provides an amino resin adhesive composition excellent in water resistance, initial adhesion, aging resistance, viscosity stability and water washability. With the goal.

[Means for Solving the Problems]

The present inventors have conducted various studies in order to solve the drawbacks of conventional amino resin adhesives, and as a result, modified amino acid resins and 1 to 10 mol% of α-olefin units having 4 or less carbon atoms. The inventors have found that an adhesive composition made of polyvinyl alcohol satisfies all of water resistance, initial adhesion, aging resistance, viscosity stability and water washability, and has completed the present invention. That is, the present invention provides an amino resin and a carbon number of 4
An adhesive composition comprising a modified polyvinyl alcohol containing 1 to 10 mol% of the following α-olefin unit is provided.

The modified polyvinyl alcohol containing 1 to 10 mol% of an α-olefin unit having 4 or less carbon atoms, which constitutes the amino resin adhesive of the present invention, is a vinyl ester and an α.
-It can be obtained by saponifying a copolymer with an olefin. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like, and vinyl acetate is preferable from the economical point of view. The α-olefin of the present invention has a carbon number of 4 or less, and examples thereof include ethylene, propylene, n-butene, and isobutene, and the water resistance of the resulting amino resin adhesive,
Ethylene is preferable in terms of viscosity stability and water washability. α
-The content of the olefin needs to be 1 to 10 mol%, preferably 2 to 8 mol%. When the content of α-olefin is less than 1 mol%, the above-mentioned remarkable effects cannot be obtained, and when it exceeds 10 mol%, initial adhesiveness and water washability are deteriorated and the above-mentioned effects are obtained. I will not be able to.

The modified polyvinyl alcohol containing an α-olefin unit having 4 or less carbon atoms of the present invention is obtained by copolymerizing an ethylenically unsaturated monomer which is copolymerizable within a range not impairing the effects of the present invention. But good. Examples of such an ethylenically unsaturated monomer include acrylic acid, methacrylic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid,
(Anhydrous) itaconic acid, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, trimethyl- (3-acrylamido-3-dimethylpropyl)-
Ammonium chloride, acrylamido-2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, vinyl Examples thereof include sodium sulfonate and sodium allyl sulfonate. In the presence of a thiol compound such as thiolacetic acid and mercaptopropionic acid,
A vinyl ester monomer such as vinyl acetate has 4 carbon atoms.
A terminal modified product obtained by copolymerizing the following α-olefin and saponifying it may also be used.

The saponification degree of a modified polyvinyl alcohol (hereinafter abbreviated as PVA) containing 1 to 10 mol% of an α-olefin having 4 or less carbon atoms, which constitutes the amino resin adhesive of the present invention, depends on the α-olefin content. 50 mol% depending on
The above is preferable, and 80 mol% or more is more preferable. When the saponification degree of the modified PVA is lower than 50 mol%, the detergency with water, water resistance and initial adhesive strength cannot be balanced. The degree of polymerization of the modified PVA is preferably in the range of 100 to 8000, more preferably 300 to 2000. When the degree of polymerization of the modified PVA is less than 100, the initial adhesiveness is difficult to develop, and when the degree of polymerization exceeds 8000, the viscosity stability deteriorates.

1 to 10 mol% of α-olefin having 4 or less carbon atoms used in the amino resin adhesive composition of the present invention
The modified PVA contained is 0.1 to 15% by weight based on the amino resin component before the condensation reaction of the amino compound and the aldehyde, the system during the reaction, or after the reaction.
Added. If the amount added is less than 0.1% by weight, the effect intended by the present invention will not be sufficiently exhibited, while if it exceeds 15% by weight, not only will it be economically disadvantageous, but the amino resin solution The viscosity stability becomes poor, the workability is lowered, and the water resistance of the adhesive is also lowered, which is not preferable.

The amino resin constituting the amino resin composition of the present invention is obtained by a condensation reaction of an amino compound and an aldehyde. Examples of the amino compound used for the condensation reaction include melamine, urea, thiourea, dicyandiamide, benzoguanamine and acetoguanamine, and these can be used alone or in admixture of two or more. As the aldehyde, formaldehyde is used in the form of an aqueous solution or an alcohol solution,
In addition, a compound capable of generating formaldehyde under condensation reaction conditions, such as paraformaldehyde, is also used.

The amino resin adhesive composition of the present invention comprises:
Conventionally known clay, pigments such as calcium carbonate, titanium oxide, aluminum hydroxide, calcium sulfate and zinc oxide, wood flour, flour, extenders and fillers such as corn starch, carboxymethyl cellulose, sodium alginate, polyethylene oxide, polyacrylic acid. Alternatively, a thickener such as a salt thereof may be added.

In the amino resin adhesive composition of the present invention, the object of adhesion is not particularly limited, but it is particularly suitable for wood adhesives. By wood is meant for plywood splinter fittings, furniture, trucks and other woodworking products.

[0012]

The present invention will be described in more detail with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples, "part" and "%" mean weight basis unless otherwise specified.

Example 1 Formalin (35.52%) (268 g) and water (45 g) were mixed with ethylene-modified PVA (ethylene 4.5 mol% modified, polymerization degree 1400, saponification degree 98.5 mol%) 3 g, and further urotrobin 1 g. , Urea 100 g, and the system was adjusted to pH 7. with sodium hydroxide aqueous solution (10%) at room temperature.
After adjusting to 5, the mixture was heated and heated to 90 ° C. to start the condensation reaction. The degree of condensation was estimated by adding a part of the system to water at 40 ° C. and observing its cloudiness. A white turbidity point was observed by the white turbidity method in water 50 minutes after the temperature was raised to 90 ° C.
An aqueous sodium hydroxide solution was added to 4) to adjust the pH to 7.5 and then cooled to room temperature to obtain a resin solution for adhesive. The adhesive performance is shown in Table 1.

Comparative Example 1 Instead of the ethylene-modified PVA of Example 1, unmodified PVA
An adhesive resin liquid was obtained in the same manner as in Example 1 except that the polymerization degree was 1400 and the saponification degree was 98.5 mol%. The performance is shown in Table 1.

Comparative Example 2 Instead of the ethylene-modified PVA of Example 1, unmodified PVA was used.
A resin liquid for adhesives was obtained in the same manner as in Example 1 except that the polymerization degree was 1400 and the saponification degree was 88.0 mol%. The performance is shown in Table 1.

Comparative Example 3 Instead of the ethylene-modified PVA of Example 1, ethylene-modified PVA was used.
PVA (Ethylene 11.0 mol% modified, degree of polymerization 140
0, saponification degree 98.5 mol%)
A resin solution for adhesive was obtained in the same manner as in. The performance is shown in Table 1.

Comparative Example 4 Instead of the ethylene-modified PVA of Example 1, ethylene-modified PVA was used.
PVA (modified with ethylene 0.5 mol%, degree of polymerization 1400,
An adhesive resin solution was obtained in the same manner as in Example 1 except that the saponification degree was 98.5 mol%). The performance is shown in Table 1.

Example 2 Instead of the ethylene modified PVA of Example 1, ethylene modified
PVA (modified with ethylene 3.0 mol%, degree of polymerization 1750,
An adhesive resin liquid was obtained in the same manner as in Example 1 except that the saponification degree was 98.7 mol%). The performance is shown in Table 1.

Comparative Example 5 Instead of the ethylene-modified PVA of Example 1, unmodified PVA was used.
An adhesive resin solution was obtained in the same manner as in Example 1 except that the polymerization degree was 1750 and the saponification degree was 98.6 mol%. The performance is shown in Table 1.

Example 3 Instead of the ethylene-modified PVA of Example 1, ethylene-modified PVA was used.
An adhesive resin solution was obtained in the same manner as in Example 1 except that PVA (modified with 6.0 mol% of ethylene, degree of polymerization 500, degree of saponification 90.0 mol%) was used. The performance is shown in Table 1.

Comparative Example 6 Instead of the ethylene-modified PVA of Example 1, unmodified PVA
A resin liquid for adhesives was obtained in the same manner as in Example 1 except that the polymerization degree was 500 and the saponification degree was 90.0 mol%. The performance is shown in Table 1.

Urea produced according to the above Examples 1 to 3
The performance of the formalin resin adhesive paste solution is shown in Table 1 together with Comparative Examples 1 to 6. The adhesive paste solution was used by mixing 20 parts of wheat flour with 100 parts of the adhesive resin solution, and further adding 5% ammonium chloride aqueous solution in an amount such that the pot life was 3 hours. The storage stability (25 ° C.) was indicated by the number of days required for the viscosity of the condensed resin solution without addition of wheat flour and ammonium chloride to be doubled immediately after production.

Note) Plywood manufacturing conditions for measuring adhesive strength Veneer: South Sea wood (water content 8.33%, 65% RH / 20
℃) 1) Initial adhesive strength Single plate (thickness 0.45 mm, width 25 m
m, length 80 mm), the adhesive was applied at 10 g / 30 cm square (one side), and after 10 minutes cold pressure at 10 kg / cm ² , tensile strength was determined. 2) Equilibrium adhesive strength Single plate thickness Front, back plate 0.45 mm, middle plate 1.7
5 mm size 25 × 80 mm Adhesive coating amount 20 g / 30 cm square (both sides) Cold pressure 10 kg / cm ² for 20 minutes Hot pressure 10 kg / cm ² , 110 ° C. for 3 minutes 65% RH / 20 ° C. after completion of heat pressure After being left for a period of time, the adhesive strength was subjected to a hot and cold water immersion test in accordance with Japanese agricultural and forestry standards. 3) Aging resistance The plywood prepared in 2) above is treated at 25 ° C., 33% RH, and 2
One cycle was allowed to stand at 5 ° C. and 87% RH for 2 weeks, and the adhesive strength after 20 cycles was determined by a hot and cold water immersion test according to the Japanese Agricultural Standards. 4) Washability With water, water was put into a container to which an adhesive had been applied, and the mixture was stirred, and the quality of the washability was judged by visually confirming the degree of emulsification and dispersibility in water.

[0024]

[Table 1]

* 1: Degree of polymerization 1400, degree of saponification 98.5 mol%, modification of ethylene 4.5 mol% * 2: Degree of polymerization 1400, degree of saponification 98.5 mol% * 3: Degree of polymerization 1400, degree of saponification 88.0 mol% * 4: Polymerization degree 1400, saponification degree 98.5 mol%, ethylene 11.0 mol% modified * 5: Polymerization degree 1400, saponification degree 98.5 mol%, ethylene 0.5 mol% modified * 6: Polymerization degree 1750, saponification degree 98. 7 mol%, ethylene 3.0 mol% modified * 7: degree of polymerization 1750, saponification degree 98.6 mol% * 8: degree of polymerization 500, saponification degree 90.0 mol%, ethylene 6.0 mol% modified * 9: degree of polymerization 500, saponification 90.0 mol%

[0026]

The amino resin adhesive of the present invention is excellent in water resistance, initial adhesion, aging resistance, viscosity stability and water washability.

Claims (1)

[Claims] 1. An amino resin adhesive composition comprising an amino resin and a modified polyvinyl alcohol containing 1 to 10 mol% of an α-olefin unit having 4 or less carbon atoms.