JPH07216340A - Production of water-based adhesive - Google Patents

Abstract

PURPOSE:To produce a water-based adhesive which has sufficient tackiness at normal temperature and becomes releasable when heated. CONSTITUTION:A urethane prepolymer prepared by reacting a mixture comprising a polyol compound, a functional compound having at least two active hydrogen atoms reactive with an isocyanate group and at least one hydrophilic group selected between carboxyl and sulfonyl in the molecule, a polyisocyanate compound and an inorganic filler is reacted with a diamine compound in water to obtain an aqueous dispersion of a urethane polymer containing the inorganic filler. The inorganic filler dispersed in the aqueous dispersion can be kept in a stably dispersed state. A film obtained by drying this dispersion has a high film strength and an improved cohesive force because of the uniformly dispersed inorganic filler particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyurethane-based water-based adhesive having excellent adhesive strength at room temperature and water resistance and excellent adhesive strength at high temperature.

[0002]

2. Description of the Related Art Urethane-based adhesives are used in many applications because they have excellent adhesion to a wide range of adherends, but they do not pose a risk of toxicity or fire. However, it is well known that the conversion from organic solvent type adhesives to water-based adhesives has been vigorously carried out for reasons such as economical advantage (for example, JP-A-3-21).
626).

Further, for the purpose of increasing the adhesive strength of the above-mentioned water-based adhesive, a method of improving the adhesive strength by mixing silica-based particles as a filler in an aqueous dispersion of a urethane polymer has been reported (special feature. (Kaihei 4-20933).

[0004]

However, in the adhesive described in JP-A-4-20933, once the water dispersion of the urethane-based polymer is prepared, the silica-based particles are mixed in the water dispersion. Therefore, a stable solution of the silica-based particles and the aqueous dispersion of the polymer could not be obtained. Moreover, since the silica-based particles are not uniformly filled in the polymer aqueous dispersion particles, the film strength is insufficient even when used as an adhesive, and sufficient adhesive strength cannot be obtained.

The present invention has been made in view of the above problems, and an object of the present invention is to allow a urethane polymer containing an inorganic filler to be kept in a stable state as an aqueous dispersion, and also as an adhesive. An object of the present invention is to provide a method for producing a water-based adhesive containing a urethane polymer as a main component, which has excellent adhesive strength.

[0006]

The polyol compound (A) used in the present invention is a compound having two or more hydroxyl groups in the molecule, such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-
Hexanediol, polyhydric alcohols such as trimethylolpropane and glycerin, and dicarboxylic acids such as adipic acid, sebacic acid, itaconic acid, maleic anhydride, terephthalic acid and isophthalic acid, and ethylene glycol,
Triethylene glycol, 1,4-butanediol,
Examples thereof include polyester polyols obtained by reaction with glycols such as 1,6-hexanediol, tripropylene glycol and neopentyl glycol, polycaprolactone polyols, polytetramethylene ether glycols, polybutadiene polyols and polyacrylate ester polyols.

The functional compound (B) used in the present invention is composed of two or more active hydrogens capable of reacting with an isocyanate group in the molecule, and one or more hydrophilic groups selected from a carboxyl group and a sulfonyl group. Is a compound having Examples of the compound having a carboxyl group and two or more active hydrogens capable of reacting with an isocyanate group in the molecule as the functional compound (B) include dimethylol lactic acid, dimethylol propionic acid, and dimethylol butyric acid. The compound having two or more active hydrogens capable of reacting with an isocyanate group in the molecule and a sulfonyl group is, for example, 3,4-diaminobutanesulfonic acid, 3,
6-diamino-2, toluenesulfonic acid and the like can be mentioned. The above compounds may be used alone or in combination of two or more.

The polyisocyanate compound (C) used in the present invention is a compound having two or more isocyanate groups in the molecule, such as 1,4-tetramethylene diisocyanate and 1,6-hexamethylene diisocyanate. 2,2,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 3-isocyanate methyl-3,
5,5-trimethylcyclohexyl isocyanate, dicyclohexylmethane-4,4'-diisocyanate,
Methylcyclohexyl 2,4-diisocyanate, methylcyclohexyl 2,6-diisocyanate, xylylene diisocyanate, 1,3-bis (isocyanate)
Aliphatic diisocyanates such as methylcyclohexane, tetramethylxylylene diisocyanate, transcyclohexane-1,4-diisocyanate, 2,4-toluylene diisocyanate, 2,6-toluylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 1 , 5-naphthene diisocyanate, tolidine diisocyanate, diphenylmethylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 4,4′-dibenzyl diisocyanate, 1,3
-Aromatic diisocyanates such as phenylene diisocyanate and lysine diisocyanate, lysine ester triisocyanate, triphenylmethane triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4,4-isocyanate methyl octane , 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate and the like. These polyisocyanates may be used alone or in combination of two or more.

The inorganic filler (D) improves the film strength as an adhesive, and is made of, for example, silica, alumina, titania, zirconia, zinc oxide, magnesium oxide, antimony trioxide, iron oxide or dolomite. Oxides, carbonates such as magnesium carbonate, calcium carbonate, zinc carbonate, aluminum silicate, magnesium silicate,
Calcium silicate, zircon silicate, kaolin, clay, bentonite, talc, mica, zeolite, asbestos, silicates such as sericite, aluminum hydroxide, hydroxides such as magnesium hydroxide, calcium sulfate, barium sulfate, natural gypsum, sulfite Calcium, titanates such as barium titanate, water glass, dawsonite,
Particles of carbon black, silicon carbide, molybdenum disulfide, etc. may be mentioned.

The average particle size of the inorganic filler is 0.
005 to 50 μm, more preferably 0.01 to 10 μm. This is because it is difficult to produce the inorganic particles having a particle size of less than 0.005 μm, and when the particle size exceeds 50 μm, the inorganic filler is liable to settle out without being contained in the water dispersion of the urethane polymer.

The above-mentioned inorganic filler is preferable in that the surface is subjected to a hydrophobic treatment so that the dispersibility of the filler is further improved.

In the present invention, a urethane prepolymer is obtained by reacting a mixture of the polyol compound (A), the functional compound (B), the polyisocyanate compound (C) and the inorganic filler (D). The compounding ratio of the above compound [polyisocyanate compound (C) / polyol compound (A) and functional compound (B)] is functional with the isocyanate group in the polyisocyanate compound (C) and the hydroxyl group in the polyol compound (A). The equivalent ratio of the total amount of active hydrogen groups in the organic compound (B) is at least 1 or more, preferably in the range of 1.1 to 2.0, when the prepolymer produced is chain-extended with a diamine compound, the degree of polymerization is Is preferable because it can improve

The hydrophilic group content is preferably 0.1 to 2 mmol per 1 g of the prepolymer obtained. If it is less than 0.1 mmol, the hydrophilicity of the prepolymer is insufficient, and the dispersibility in water is stably lowered. Again 2
When it exceeds the millimolar level, the water resistance of the water-based adhesive obtained thereafter becomes poor.

The blending amount of the above-mentioned inorganic filler is
1 to 10 relative to 100 parts by weight of urethane prepolymer
The amount is preferably 0 part by weight, more preferably 5 to 50 parts by weight. This is because if the amount is less than 1 part by weight, the coating strength of the adhesive is unlikely to be exhibited, and if it exceeds 100 parts by weight, it is difficult to uniformly disperse all the inorganic fillers in the urethane polymer aqueous dispersion.

Examples of the method for polymerizing the above-mentioned prepolymer include bulk polymerization and solution polymerization, but solution polymerization is preferred from the viewpoint of easy reaction control. As the solvent that can be used in the case of solution polymerization, those that are inert to isocyanate groups, have high compatibility with water, and have a boiling point of 100 ° C. or lower are preferable. This is because when a solvent having a boiling point higher than 100 ° C. is used, it becomes difficult to remove the solvent from the obtained dispersion in the step after water dispersion. As such an organic solvent, for example, acetone,
Methyl ethyl ketone, tetrahydrofuran, methyl acetate and the like can be mentioned.

The polymerization reaction temperature is preferably in the range of 50 to 150 ° C. Below 50 ° C, the polymerization reaction is slow and 1
This is because at 50 ° C. or higher, gelation occurs during the polymerization reaction.

The hydrophilic group in the prepolymer produced by the above method is ionized with a neutralizing agent to obtain a stable dispersed state in water. Preferable examples of the neutralizing agent used for such a purpose include ammonia and triethylamine.

In the present invention, a urethane polymer aqueous dispersion containing an inorganic filler (D) is obtained by reacting the above prepolymer with a diamine compound in water.
Examples of the diamine compound include ethylenediamine, 1,4-diaminobutane, 1,6-hexamethylenediamine, and 3-aminomethyl-3,5,5-trimethylcyclohexylamine.

As a method for obtaining the above aqueous dispersion, a method of dispersing a prepolymer in water and adding a diamine compound, or a method of dispersing the prepolymer in an aqueous solution of diamine can obtain a uniform aqueous dispersion. Therefore, it is preferable.

In addition to the above diamine compounds, glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol and polyethylene glycol may be used together as a means for chain extension.

[0021]

In the method for producing an aqueous adhesive of the present invention, a polyol compound (A), a functional compound (B), a polyisocyanate compound (C) and an inorganic filler (D) are used as a mixture.
Since the urethane prepolymer is produced by polymerization in the presence of the inorganic filler, the inorganic filler is uniformly dispersed and contained in the aqueous dispersion of the urethane polymer obtained thereafter.

[0022]

EXAMPLES Examples of the present invention will be described below.
In the following, "parts" means "parts by weight". (Example 1) Polypropylene glycol [OH value: 5
5, trade name "PLACCEL-L220AL", manufactured by Daicel Chemical Industries, Ltd.] 100 parts, isophorone diisocyanate 41.8 parts and dimethylolpropionic acid 5.96.
Parts, hydrophilic silica particles (average particle diameter 0.016 μm: trade name “Aerosil 130”, manufactured by Nippon Aerosil Co., Ltd.) 1
4.8 parts and 37 parts of methyl ethyl ketone (MEK) were stirred to make a homogeneous mixture. The homogeneous mixture was subjected to boiling point polymerization until the isocyanate content became 4.3% by weight or less to obtain a urethane prepolymer solution. To the above urethane prepolymer solution, 4.6 parts of triethylamine was added, and after stirring for about 20 minutes, the mixture was cooled to room temperature to obtain a neutralized solution of the urethane prepolymer. Next, after adding the neutralization solution of the urethane prepolymer to 437 parts of a 1.23% by weight ethylenediamine aqueous solution over 1 minute, the mixture is stirred at 40 ° C., depressurized to remove the solvent, and an inorganic filler is contained. An aqueous dispersion of urethane polymer was obtained.

Example 2 Instead of the hydrophilic silica particles used in Example 1, hydrophobic silica particles (average particle size 0.0
16 μm: A urethane polymer aqueous dispersion containing an inorganic filler was obtained in the same manner as in Example 1 except that the product name “Aerosil R972”, manufactured by Nippon Aerosil Co., Ltd. was used.

(Example 3) Instead of the hydrophilic silica particles used in Example 1, titania particles treated with an organic substance (average particle size 0.26 μm: trade name "Typpure R-1") are used.
00 ”manufactured by DuPont Japan Co., Ltd. was used, and an aqueous dispersion of a urethane polymer containing an inorganic filler was obtained in the same manner as in Example 1.

(Comparative Example 1) Polypropylene glycol [OH value: 55, trade name "PLACCEL-L220A"
L ", manufactured by Daicel Chemical Industries, Ltd.] 100 parts, isophorone diisocyanate 41.8 parts and dimethylolpropionic acid 5.96 parts and methyl ethyl ketone (MEK) 3.
7 parts were stirred to make a homogeneous mixture. The above homogeneous mixture,
Boiling point polymerization was carried out until the isocyanate content became 4.3% by weight or less to obtain a urethane prepolymer solution. Triethylamine 4.6 was added to the urethane prepolymer solution.
After adding 20 parts and stirring for about 20 minutes, the mixture was cooled to room temperature to obtain a neutralized solution of the urethane prepolymer. Next, the above-mentioned neutralization solution of urethane prepolymer was added to 437 parts of a 1.23 wt% ethylenediamine aqueous solution over 1 minute, and then the mixture was stirred at 40 ° C. and depressurized to remove the solvent. Got

(Comparative Example 2) Hydrophilic silica particles (trade name "Aerosil 130", manufactured by Nippon Aerosil Co., Ltd.) are added to 200 parts of the urethane polymer aqueous dispersion obtained in Comparative Example 1.
5.24 parts were added and stirred to obtain a mixed dispersion composed of an inorganic filler and an aqueous dispersion of a urethane polymer. The resulting urethane polymer aqueous dispersions containing the inorganic fillers of Examples 1 to 3 and Comparative Examples 1 and 2 and the mixed dispersions of the inorganic filler and urethane polymer aqueous dispersions were heated at 23 ° C.
It was left in a transparent glass closed container for a month and visually evaluated for the presence of sediment. The water dispersion and the mixed dispersion were used as water-based adhesives, and the adhesiveness and water resistance were evaluated by the evaluation methods described below. (Evaluation of Adhesion at Room Temperature) The above water-based adhesive was applied to a canvas and a stainless steel plate (SUS304: width 25 mm, length 125 mm, thickness 2 mm) (coating amount was against the canvas, solid content 0.1 m).
g / cm ² , against stainless steel plate, 0.04 mg / cm
² ) After drying at 80 ° C. in a blast drying oven for 3 minutes, a test piece was prepared at a pressing pressure of 10 kg / cm ² , 5 minutes at 80 ° C. The test piece thus obtained is 23
9 ° C at a pulling speed of 50 mm / min under the condition of ℃
A 0 ° C peel test was performed. (Water resistance evaluation) A test piece prepared by the same method as the room temperature adhesive strength evaluation test was dipped in 40 ° C warm water for 3 days, and then wiped with water, and then the test piece was heated at 23 ° C. A 90 ° C peeling test was performed at a pulling speed of 50 mm / min. The above evaluation results are shown in Table 1.

[0027]

[Table 1]

[0028]

INDUSTRIAL APPLICABILITY In the method for producing an aqueous adhesive of the present invention, a polyol compound, a functional compound, a polyisocyanate compound and an inorganic filler are mixed and polymerized in the presence of the inorganic filler to form a urethane prepolymer. Therefore, the inorganic filler is uniformly dispersed and contained in the subsequently obtained urethane polymer aqueous dispersion. As a result, the inorganic filler dispersed in the water dispersion is dispersed in a stable state without settling. Further, since the inorganic filler is uniformly dispersed in the urethane polymer aqueous dispersion, the strength of the coating film obtained by drying is high and the cohesive force of the adhesive is improved. Furthermore, since the obtained water-based adhesive does not contain a surfactant such as an emulsifier, the water resistance of the adhesive is excellent.

Claims (1)

[Claims] 1. A polyol compound (A), a functional compound (B) having two or more active hydrogens capable of reacting with an isocyanate group in the molecule, and one or more hydrophilic groups selected from a carboxyl group and a sulfonyl group. , A polyisocyanate compound (C) and an inorganic filler (D) are reacted to obtain a urethane prepolymer, and then the urethane prepolymer and a diamine compound are reacted in water to give an inorganic filler (D). A method for producing an aqueous adhesive, which comprises obtaining an aqueous dispersion of a urethane polymer containing