JP2001115129A - One-component moisture-curing adhesive and sealant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a one-component moisture-curing adhesive and a sealant which exert excellent adhesion to various adherends, allow no decrease in adhesion strength over time even under conditions such as immersion in water, repetitive wetting and drying, substantially inhibit staining on the surface of a cured product caused by bleedout of low-molecular weight components and exert physical properties suitable for both an adhesive and a sealant. SOLUTION: The one-component moisture-curing adhesive or the sealant essentially comprises a urethane prepolymer having isocyanate groups at both molecular ends, which is obtained by allowing a polyisocyanate compound to react with an acrylic polymer-containing polyol obtained by polymerizing an acrylic monomer in a polyol having a number average molecular weight of from 1,000 to 20,000 using a polymerization initiator having an active hydrogen group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a one-part moisture-curable urethane-based adhesive and sealant.

[0002]

2. Description of the Related Art Conventional one-part moisture-curable urethane adhesives and sealants generally comprise a urethane prepolymer having isocyanate groups at both ends obtained from a polyether polyol and an excess of a polyisocyanate compound. And various additives are blended therein.

However, such one-component moisture-curable urethane-based adhesives and sealants are susceptible to deterioration due to sunlight irradiation because the main chain has a polyether structure. Since the interaction with the interface is weak and the adhesiveness is insufficient, there is a problem that the adhesive strength decreases with time under conditions such as immersion in water and repeated wet and dry.

Further, in order to impart characteristics such as low modulus and high elongation for sealants, a large amount of a low molecular weight compound such as a plasticizer had to be compounded. There is also a problem that the low-molecular weight compound bleeds out and foreign matter such as dust adheres to the compound to significantly impair the appearance.

Various studies have been made to address such problems. For example, in Japanese Patent Application Laid-Open No. H11-50045, "Acrylic acid in a polyoxyalkylene ether type polyol having a number average molecular weight of 3,000 to 20,000" is used. A one-pack moisture-curable sealant containing an isocyanate group-terminated urethane prepolymer and a polyethylene glycol diester obtained by reacting an acrylic polymer-containing polyol obtained by polymerizing an acid C _2-6 alkyl ester with a polyisocyanate; ing.

However, since the one-part moisture-curable sealant disclosed in the above disclosure contains polyethylene glycol diester as an unreacted component, it can be said that it does not easily bleed out as compared with a low molecular weight compound such as a plasticizer. However, there is still a problem that bleed-out remains.

[0007] Further, in applications where bonding and sealing are performed simultaneously, such as in the case of joint application of exterior wall tiles, it is necessary to impart appropriate elasticity to the cured product. In the case of a curable sealant, it is difficult to freely control the elastic modulus, and thus there is a problem that it is difficult to apply the curable sealant as an adhesive and sealant.

[0008]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide excellent adhesion to various adherends, and to reduce the adhesive strength with time even under conditions such as immersion in water and repeated drying and drying. To provide a one-part moisture-curable adhesive and a sealant that can exhibit suitable physical properties as an adhesive / sealant, which causes less bleeding and hardly contaminates the surface of the cured product due to bleed-out of low molecular weight components. It is in.

[0009]

The one-part moisture-curable adhesive and sealant according to claim 1 have a number average molecular weight of 1,000 to 200 using a polymerization initiator having an active hydrogen group.
A urethane prepolymer having isocyanate groups at both molecular terminals obtained by reacting an acrylic polymer-containing polyol obtained by polymerizing an acrylic monomer in a polyol of No. 00 with a polyisocyanate compound (hereinafter simply referred to as “urethane prepolymer”). ") As the main component.

In the present invention, the polyol used for obtaining the acrylic polymer-containing polyol includes:
For example, propylene oxide, ethylene oxide,
Polyoxyalkylene ether type polyol obtained by ring-opening polymerization such as tetrahydrofuran; dicarboxylic acid such as adipic acid, orthophthalic acid, isophthalic acid, terephthalic acid, sebacic acid, itaconic acid, maleic anhydride and ethylene glycol, diethylene glycol, triethylene glycol Polyester polyols obtained by dehydration condensation with glycols such as tripropylene glycol, butanediol, hexanediol and neopentyl glycol; and polymer polyols comprising polymers such as butanediol and acrylic acid esters.
Among them, a polyoxyalkylene ether type polyol is preferably used. These polyols may be used alone or in combination of two or more.

In the present invention, the above-mentioned polyol needs to have a number average molecular weight of 1,000 to 20,000, preferably 1,500 to 1,2000, particularly preferably 2,000 to 6,000.

The above polyol has a number average molecular weight of 1,000.
If it is less than 1, the viscosity of the obtained urethane prepolymer becomes too high and the workability may be reduced. Conversely, if the number average molecular weight of the polyol exceeds 20,000, the obtained one-pack moisture-curable adhesive and sealant may be obtained. The heat resistance of the cured product may be insufficient.

In the present invention, although not particularly limited, the average number of hydroxyl groups of the polyol is 2 to 2.
It is preferably 3. By using a polyol having an average number of hydroxyl groups of 2 to 3, it becomes possible to obtain an acrylic polymer-containing polyol or a urethane prepolymer having excellent balance characteristics.

In the present invention, the acrylic monomer used to obtain the acrylic polymer-containing polyol includes, for example, methyl acrylate, ethyl acrylate,
Examples thereof include alkyl acrylates such as isopropyl acrylate and n-butyl acrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate, and isobornyl acrylate. These acrylic monomers may be used alone or in combination of two or more.

In the present invention, the number average molecular weight is 1
In order to polymerize the acrylic monomer in a polyol of 2,000 to 20,000, it is necessary to use a polymerization initiator having an active hydrogen group.

By using a polymerization initiator having an active hydrogen group, it is possible to effectively reduce the amount of unreacted polyol and the amount of acrylic monomer (remaining mono amount),
As a result, it is possible to effectively suppress the bleed out of the low molecular weight compound to the surface of the cured product of the one-part moisture-curable adhesive and sealant obtained.

Examples of the polymerization initiator having an active hydrogen group include, for example, 2,2'-azobis {2-methyl-N-
[1,1-bis (hydroxymethyl) ethyl] propionamide}, 2,2′-azobis [2-methyl-N-
(2-hydroxyethyl) propionamide], 2,
2′-azobis [2- (hydroxymethyl) propionitrile] and the like.
An azobis compound having four is preferably used. These polymerization initiators having an active hydrogen group may be used alone or in combination of two or more.

The method for polymerizing the acrylic monomer in the polyol having a number average molecular weight of 1,000 to 20,000 using the polymerization initiator having an active hydrogen group is not particularly limited. By performing a polymerization reaction at a temperature of about 70 to 130 ° C. for about 2 to 8 hours,
A desired acrylic polymer-containing polyol can be obtained.

The ratio between the polyol and the acrylic polymer in the acrylic polymer-containing polyol thus obtained is not particularly limited, but the weight ratio of the acrylic polymer to the polyol is from 10 to 200.
And more preferably 30 to 100.

The ratio (weight ratio) of the acrylic polymer to the polyol 100 is less than 10;
If it exceeds 0, the light resistance and the adhesion to the adherend of the obtained one-pack moisture-curable adhesive and sealant may be insufficient.

In the present invention, the above-mentioned acrylic polymer-containing polyol is reacted with a polyisocyanate compound to synthesize a urethane prepolymer which is a main component of the one-part moisture-curable adhesive and sealant of the present invention.

Examples of the polyisocyanate compound used for synthesizing the urethane prepolymer include toluene diisocyanate, diphenylmethane diisocyanate (purified MDI), a mixture of MDI and another compound (crude MDI), isophorone diisocyanate, hexamethylene diisocyanate, and the like. Polyisocyanate compounds generally used for synthesizing urethane-based compounds such as these derivatives and the like can be mentioned. Among them, purified MDI and crude MDI which are excellent in reactivity, safety and the like are preferably used. These polyisocyanate compounds may be used alone or in combination of two or more.

In the synthesis of the urethane prepolymer, the reaction ratio between the acrylic polymer-containing polyol and the polyisocyanate compound is not particularly limited, but the ratio of the hydroxyl group (OH) in the acrylic polymer-containing polyol to the polyisocyanate compound is not limited. Has a molar ratio (NCO / OH) of isocyanate groups (NCO) of 1.
It is preferably from 3 to 8.0, more preferably 1.
5 to 3.0.

When the NCO / OH (molar ratio) is less than 1.3, the viscosity of the obtained urethane prepolymer becomes too high, and the workability may be reduced.
When CO / OH (molar ratio) exceeds 8.0, the crosslinked density of the cured product of the one-part moisture-curable adhesive and sealant obtained becomes too high, and the elasticity and elongation may be poor.

The method for synthesizing the urethane prepolymer is not particularly limited. For example, a predetermined amount of the acrylic polymer-containing polyol and a predetermined amount of the polyisocyanate compound may be obtained under a stream of an inert gas such as nitrogen gas or under reduced pressure. Is reacted at a temperature of about 80 to 100 ° C. for about 3 to 6 hours to obtain a desired urethane prepolymer.

The isocyanate group content in the urethane prepolymer thus obtained is not particularly limited, but is preferably 0.5 to 10% by weight, more preferably 1.5 to 5% by weight. is there.

When the isocyanate group content in the urethane prepolymer is less than 0.5% by weight, the crosslink density of the cured product of the one-part moisture-curable adhesive and the sealant becomes low, and sufficient adhesive strength and When the cohesive strength may not be obtained, and when the isocyanate group content in the urethane prepolymer exceeds 10% by weight, the obtained one-part moisture-curable adhesive and sealant are easily foamed during moisture curing, Adhesive strength and cohesive strength may decrease.

The one-part moisture-curable adhesive and sealant of the present invention may further contain, in addition to the urethane prepolymer as a main component, an inorganic or organic filler, if necessary, as long as the object of the present invention is not hindered. Tackifier resin, coupling agent, high molecular weight softener (including high molecular weight plasticizer), thixotropic agent, curing acceleration catalyst, antioxidant (antiaging agent), heat stabilizer, light stabilizer, ultraviolet absorber One or more of various additives such as a coloring agent, an antistatic agent, a flame retardant, and an organic solvent may be added.

The method for producing the one-part moisture-curable adhesive and sealant of the present invention is not particularly limited. For example, a predetermined amount of the urethane prepolymer as a main component and the above-mentioned urethane prepolymer to be added as necessary. One or two or more of each of the various additives is weighed with a predetermined amount, and after premixing using a stirring mixer such as a mixer or a kneader, dehydration at room temperature or under heat is performed under reduced pressure. For example, the desired one-component moisture-curable adhesive and sealant can be obtained by uniformly kneading using the above-mentioned stirring mixer or three rolls. In addition, various additives may be dehydrated in advance.

The one-part moisture-curable adhesive and sealant of the present invention thus obtained include, for example, building sealants,
It is suitably used for various purposes as an adhesive, a sealant, or an adhesive and sealant, such as a sealant for waterproofing base treatment, an adhesive for construction, an adhesive sealant for automobiles and ships, and various types of adhesive bonding.

[0031]

The one-part moisture-curable adhesive and sealant of the present invention are acrylic polymers obtained by polymerizing an acrylic monomer in a polyol having a specific number average molecular weight during the synthesis of a urethane prepolymer as a main component. Since the containing polyol is used, the adhesiveness to various adherends is excellent as compared with the case where a normal polyether type polyol is used. Therefore, even under conditions such as immersion in water or repeated drying and drying, the adhesive strength hardly decreases over time.

Since a polymerization initiator having an active hydrogen group is used at the time of polymerization of the acrylic monomer, the amount of unreacted acrylic monomer (remaining monomer amount) is as small as possible. Further, since the low molecular weight component is not contained in the one-component moisture-curable adhesive and sealant, contamination of the surface of the cured product due to bleed-out of residual materials and low molecular weight components hardly occurs.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” means “parts by weight”.

Example 1 450 parts of polypropylene glycol (trade name "Preminol 4002", manufactured by Asahi Glass Co., Ltd.) having a number-average molecular weight of 4,000 which had been subjected to a vacuum dehydration treatment at 130 ° C. for 1 hour, and 250 parts of ethyl acrylate The mixture was charged in a four-neck separable flask and heated to 80 ° C. while stirring under a nitrogen stream. Next, using a dropping device, 2,2′-azobis [2- (hydroxymethyl) propionitrile] is used as a polymerization initiator having an active hydrogen group.
3 parts and polypropylene glycol "Preminol 400"
2) A mixture with 50 parts was dropped in three portions every hour, and the temperature was raised to 90 ° C., and the mixture was reacted for 2 hours to prepare an acrylic polymer-containing polyol.

Next, 100 parts of the acrylic polymer-containing polyol obtained above and 30 parts of crude diphenylmethane diisocyanate (crude MDI) containing 50% by weight of purified diphenylmethane diisocyanate (purified MDI) were mixed with 80 parts of nitrogen under a nitrogen stream. The mixture was reacted at 5 ° C. for 5 hours to synthesize a urethane prepolymer having isocyanate groups at both molecular terminals.

Next, to 100 parts of the urethane prepolymer obtained above, 50 parts of surface fatty acid-treated calcium carbonate (trade name “Shirayuka CCR”, manufactured by Shiraishi Calcium Co., Ltd.), which had been subjected to a dehydration treatment, was added. After kneading with stirring, 5 parts of xylene was added as a diluent under a nitrogen stream,
The mixture was uniformly stirred and kneaded to produce a one-part moisture-curable adhesive and sealant.

Comparative Example 1 In the synthesis of the urethane prepolymer, polypropylene glycol “Preminol 4” was used instead of 100 parts of the acrylic polymer-containing polyol.
A urethane prepolymer, a one-part moisture-curable adhesive and a sealant were obtained in the same manner as in Example 1 except that 100 parts of “002” were used.

Comparative Example 2 In the preparation of an acrylic polymer-containing polyol, instead of 3 parts of 2,2′-azobis [2- (hydroxymethyl) propionitrile], a polymerization initiator having an active hydrogen group, as a polymerization initiator In the same manner as in Example 1 except that 3 parts of a polymerization initiator 2,2′-azobis (isobutyronitrile) having no active hydrogen group was used, an acrylic polymer-containing polyol, a urethane prepolymer and A one-part moisture-curable adhesive and sealant were obtained.

Performance of three kinds of one-part moisture-curable adhesives and sealants obtained in Example 1 and Comparative Examples 1 and 2 (initial tensile adhesive strength, tensile adhesive strength after repeated drying and immersion in water) , Contamination) were evaluated by the following methods. The results were as shown in Table 1.

Initial tensile bond strength: A wooden cement board coated with acrylic silicone and a ceramic tile are used as the adherend, and the initial tensile bond strength is determined according to JIS A-5548 "Adhesive for Ceramic Tile". (Kg / cm
² ) was measured.

Tensile bond strength after repeated drying and immersion in water: JIS A-5 using a wood cement board coated with acrylic silicone and a ceramic tile as an adherend
The tensile adhesive strength (kg / cm ² ) after repeated drying and immersion in water was measured according to 548.

Contamination: A joint having a width of 20 mm, a depth of 5 mm, and a length of 150 mm was filled with a one-part moisture-curable adhesive and a sealant, cured at 20 ° C. for 4 weeks, and then treated with an acrylic elastic paint (trade name “VINYLOK”). ”, Manufactured by Rock Paint
And then exposed outdoors for 6 months at a 45 degree exposure angle to the outdoor south side. Thereafter, the presence or absence of contamination on the painted surface was visually observed, and the contamination was evaluated according to the following criteria. [Judgment criteria] ○ ‥‥ No contamination was found on the painted surface × ‥‥ Significant contamination was found on the painted surface

[0043]

[Table 1]

As is evident from Table 1, the one-part moisture-curable adhesive and sealant of Example 1 according to the present invention have excellent initial adhesive strength and show no decrease in adhesive strength even after repeated drying and immersion in water. There was no. In addition, no contamination occurred on the cured product surface (painted surface) even after long-term outdoor exposure.

On the other hand, the one-part moisture-curable adhesive and sealant of Comparative Example 1 in which the acrylic polymer-containing polyol was not used at the time of synthesizing the urethane prepolymer were dried and cured.
The adhesive strength after repeated immersion in water was remarkably reduced.

The one-pack moisture-curable adhesive and sealant of Comparative Example 2 in which the polymerization initiator having an active hydrogen group was not used at the time of preparing the acrylic polymer-containing polyol had a cured product surface when exposed outdoors for a long period of time. (Painted surface) was significantly contaminated.

[0047]

As described above, the one-pack moisture-curable adhesives and sealants of the present invention have excellent adhesion to various adherends, and therefore can be used with time even under conditions such as immersion in water or repeated drying and drying. Adhesion strength hardly decreases, and hardly contaminates the cured product surface even when exposed outdoors for a long period of time, for example, adhesives and sealants for construction and civil engineering, such as automobiles and ships It is suitably used for various applications as an adhesive, a sealant, or an adhesive and sealant such as an adhesive sealant.

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Claims (1)

[Claims] 1. An acrylic polymer-containing polyol obtained by polymerizing an acrylic monomer in a polyol having a number average molecular weight of 1,000 to 20,000 using a polymerization initiator having an active hydrogen group, and a polyisocyanate compound A one-part moisture-curable adhesive and sealant comprising, as a main component, a urethane prepolymer having isocyanate groups at both molecular terminals obtained by the reaction.