Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-12-29
2002-09-17
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S068000, C528S073000, C528S118000, C528S121000, C528S122000, C528S123000, C528S124000
Reexamination Certificate
active
06451931
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a curing agent composition for an epoxy resin and a curing epoxy resin composition. More particularly, it relates to a curing agent composition which is combined with a polyepoxy compound to provide a one-pack type heat-curable epoxy resin composition which is excellent in storage stability, curability and adhesion and of which a cured product has excellent physical properties; and a one-pack type heat-curable epoxy resin composition comprising the curing agent composition and a polyepoxy compound.
2. Description of Related Art
An epoxy resin exhibits excellent adhesion to various substrates. A cured epoxy resin is relatively excellent in heat resistance, chemical resistance, electrical characteristics and mechanical characteristics and has been in general use in broad applications, particularly in the field of coatings and adhesives.
Two-pack type epoxy resin compositions, which require addition of a curing agent or a cure accelerator immediately before use, have prevailed. A two-pack system is characterized by curability at ambient or low temperature but involves measuring and mixing immediately before use. Besides, once mixed, the curing composition has a short pot life and has difficulty in applying to automated machinery. A one-pack type curing epoxy resin composition free from such restrictions of use has been demanded.
A curing agent which does not react at room temperature but commences reacting on heat application, i.e., a latent curing agent is indispensable for formulating a one-pack type curing resin composition. Latent curing agents proposed to date include dicyandiamide, dibasic acid dihydrazides, boron trifluoride-amine complex salts, guanamines, melamine, and imidazoles. A mixture of an epoxy resin and dicyandiamide, melamine or a guanamine compound has satisfactory storage stability but requires a high curing temperature (150° C. or higher) and a long curing time. A combined use of a cure accelerator has been introduced widely to shorten the curing time, which results in considerable reduction of storage stability. A mixture of an epoxy resin and a dibasic acid dihydrazide or an imidazole compound is curable in relatively low temperatures but poor in storage stability. Although a mixture of an epoxy resin and a boron trifluoride-amine complex salt has high storage stability and needs a shorter curing time, the cured product has poor water resistance and corrodes metal.
In order to overcome these problems, it has been proposed to use, as a curing agent for an epoxy resin, a reaction product between a dialkylamine and an epoxide (see Japanese Patent Laid-Open Nos. 56-155222 and 57-100127) or a reaction product between a tertiary amino-containing alcohol or phenol and a polyepoxide (see Japanese Patent Laid-Open No. 59-53526). The curing compositions containing these curing agents, however, still have insufficient storage stability, and their cured products are unsatisfactory in physical properties.
Japanese Patent Laid-Open No. 3-296525 teaches use of a curing agent obtained by heat reaction of an N,N-dialkylaminoalkylamine, a cyclic amine, and a diisocyanate. The storage stability achieved with this curing agent is still unsatisfactory however.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a one-pack type curing epoxy resin composition excellent in storage stability, curing properties, and adhesive properties and capable of providing a cured product with excellent physical properties.
The present inventors have conducted extensive investigation and have found, as a result, that a curing epoxy resin composition meeting the above object can be obtained by using a latent curing agent prepared from an N,N-dialkylaminoalkylamine, a dicarboxylic acid dihydrazide, and an organic polyisocyanate.
The present invention provides a curing agent composition for an epoxy resin, which comprises (B) a reaction product obtained by allowing to react (a) a monoamine compound comprising an amine compound represented by formula (I):
wherein R
1
and R
2
each represent an alkyl group having 1 to 8 carbon atoms, or R
1
and R
2
are connected together to form an alkylene group which may contain an oxygen atom or a nitrogen atom; and n represents 1 to 6, (b) a polyamine compound comprising a dicarboxylic acid dihydrazide, (c) an organic polyisocyanate, and, if desired, (d) an epoxy compound.
The present invention also provides a curing agent composition for an epoxy resin, which comprises (B) the above-described reaction product and (C) an epoxy adduct of an amine compound.
The present invention also provides a one-pack type heat-curing epoxy resin composition comprising (A) a polyepoxy compound and (B) the above-described reaction product.
The present invention further provides a one-pack type heat-curing epoxy resin composition comprising (A) a polyepoxy compound, (B) the above-described reaction product, and (C) an epoxy adduct of an amine compound.
The epoxy resin composition according to the present invention is a one-pack type curing system which is excellent in storage stability as well as curing properties, adhesive properties, and cured resin physical properties.
DETAILED DESCRIPTION OF THE INVENTION
The monoamine compound as component (a) which can be used in the present invention comprises an N,N-dialkylaminoalkylamine represented by formula (I):
wherein R
1
and R
2
each represent an alkyl group having 1 to 8 carbon atoms, or R
1
and R
2
are connected together to form an alkylene group which may contain an oxygen atom or a nitrogen atom; and n represents 1 to 6.
The monoamine compound (a) can further comprise other monoamine compounds, such as benzylamine and cyclohexylamine.
In formula (I), the alkyl group as represented by R
1
or R
2
includes methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl groups. When taken together, R
1
and R
2
can represent an alkylene group which may contain an oxygen atom or a nitrogen atom. For example, R
1
and R
2
can be taken together with the nitrogen atom to which they are bonded to form a heterocyclic ring, such as a morpholine ring, a piperidine ring or a piperazine ring.
The N,N-dialkylaminoalkylamine of formula (I) includes N,N-dimethylaminopropylamine, N,N-diethylaminopropylamine, N,N-dipropylaminopropylamine, N,N-dibutylaminopropylamine, N,N-dimethylaminoethylamine, N,N-diethylaminoethylamine, N,N-dimethylaminobutylamine, aminopropylmorpholine, aminoethylpiperidine, and 1-(2-aminoethyl)-4-methylpiperazine.
The polyamine compound as component (b) which can be used in the present invention comprises a dicarboxylic acid dihydrazide. The dicarboxylic acid dihydrazide includes oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, and phthalic acid dihydrazide.
The polyamine compound as compound (b) can further comprise other polyamine compounds, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,2-diaminopropane, 1,2-diaminocyclohexane, 1,4-diamino-3,6-diethylcyclohexane, isophoronediamine, m-xylylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, and piperazine.
In using the dicarboxylic acid dihydrazide in combination with other polyamine compounds as component (b), the amount of the other polyamine compound(s) is preferably not more than 5 mol, particularly not more than 3 mol, per mole of the dicarboxylic acid dihydrazide. Use of more than 5 mol of the other polyamine compounds is apt to reduce the storage stability.
A molar ratio of components (b) to (a) is 0.01 to 5, preferably 0.1 to 3. Outside this range, there is possibility that the storage stability or other properties such as curability and adhesion may be reduced.
The organic polyisocyanate which can be used in the present invention as component (c) includes aliphatic, alicyclic or aromatic polyisocyanate compounds. Examples of useful component (c) are 1,3-
Abe Manabu
Ogawa Akio
Asahi Denki Kogyo Kabushiki Kaisha
Sellers Robert E. L.
Young & Thompson
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