Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-03-07
2003-05-06
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C525S403000, C525S523000, C525S535000, C528S073000, C528S377000, C528S378000, C528S380000, C548S110000, C548S215000
Reexamination Certificate
active
06559269
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a curable resin composition, and more specifically, to a curable resin composition which exhibits excellent curability and storage stability.
This invention also relates to a novel compound which is well adapted for use as a latent curing agent for epoxy resin and/or thiirane resin, and also, to a curable resin composition containing such compound.
It has been known to use ketimine as a latent curing agent in one part curable resin composition containing an epoxy resin. The curable resin composition produced by using ketimine, however, suffered from the problem of low storage stability. In view of such situation, attempts have been made to improve the storage stability by converting the ketimine used as the latent curing agent with the type which is sterically hindered to a considerable degree to thereby provide a one part curable epoxy resin composition which exhibits improved storage stability without detracting from curability (JP 11-21532 A, JP 2000-178343 A, etc.).
Such use of the sterically hindered ketimine, however, did not fully improve the storage stability of the one part curable epoxy resin composition, and in particular, the resin composition still suffered from the problem of poor storage stability under the condition where the resin composition only contained the resin component and the latent curing agent as its only components, namely, in the absence of a filler, a plasticizer, a thixotropic agent, or other additives. When the storage stability under the condition that the resin composition only contains the resin component and the latent curing agent is low, reaction (i.e. increase in the molecular weight of the resin composition) proceeds during the storage, and this results in the increased viscosity and poor working convenience after blending with other agents and being made into a commodity, as well as reduced performance including the poor adhesion to the object on which the resin composition is applied because of poor contact.
In the case of thiirane resin which is more reactive than the epoxy resin, the problem of the poor storage stability under the condition where the resin composition only contains the resin component and the latent curing agent is more serious.
SUMMARY OF THE INVENTION
In view of the situation as described above, first object of the present invention is to provide a curable resin composition which has excellent curability and storage stability, and in particular, which has improved storage stability under the condition where the resin composition only contains the resin component and the latent curing agent.
Second object of the present invention is to provide a novel composition which can be used as a latent curing agent for an epoxy resin and/or a thiirane resin; and a curable resin composition which comprises the epoxy resin and/or the thiirane resin as its main polymer and the novel compound as the latent curing agent, and which has improved storage stability under the condition where the resin composition only contains the resin component and the latent curing agent.
In order to achieve the first object, there is provided as the first aspect of the present invention a curable resin composition (hereinafter also referred to as the “first composition of the present invention”) comprising
a resin component having oxirane ring and thiirane ring at a ratio (oxirane ring/thiirane ring) of 95/5 to 1/100; and
a resin component having oxirane ring and thiirane ring at a ratio (oxirane ring/thiirane ring) of 95/5 to 1/100; and
an oxazolidine compound represented by the following formula (1):
wherein R
1
represents a hydrocarbon group having 1 to 6 carbon atoms, and
R
2
and R
3
independently represent hydrogen atom or a monovalent hydrocarbon group having 1 to 15 carbon atoms, or together form an alicyclic ring or an aromatic ring.
In the oxazolidine compound represented by the formula (1), R
1
is preferably methyl group or ethyl group, and R
2
is preferably a hydrocarbon group wherein the carbon at the first position is a branched carbon or a ring member carbon.
The oxazolidine compound represented by the formula (1) undergoes ring opening reaction through hydrolysis in the curable resin composition in the presence of moisture (water content), and it functions as a latent curing agent by reacting with the oxirane ring or the thiirane ring. This oxazolidine compound exhibits excellent curability, and also, improved storage stability since it has a substituent, and to be more specific, a bulky substituent around the nitrogen atom in the heterocycle and this results in the reduced reactivity with the moisture compared to conventional ketimine.
In addition, the resin component in the first composition of the present invention has thiirane ring. In contrast to the oxirane ring which easily reacts with both acidic and basic groups, thiirane ring has a nature that it is reactive with a basic group while it is relatively less reactive with an acidic group. The oxazolidine compound represented by the formula (1) exhibits only a weak basicity since a bulky group is present around the nitrogen atom in the amino group, and it also has a hydroxy group (—OH) which is an acidic group, and as a consequence, this oxazolidine compound is relatively reactive with the oxirane ring while it is relatively less reactive with the thiirane ring. Accordingly, the thiirane compound wherein a part or all of the oxirane ring has been substituted with the thiirane ring is less reactive with the oxazolidine compound represented by the formula (1) during the storage compared to the epoxy compounds including only the oxirane ring, and the first composition of the present invention exhibits improved storage stability compared to the composition comprising the epoxy compound including only the oxirane ring.
The first composition of the present invention which contains a thiirane compound having the thiirane ring as the resin component, and an oxazolidine compound as the latent curing agent exhibits both excellent curability and improved storage stability, and such composition is quite useful. To be more specific, this composition can be used with no practical problem even if it was not diluted with a filler or a plasticizer since it has significantly improved storage stability under the condition where it only comprises the resin component and the latent curing agent.
This invention also provides the first composition of the present invention which further comprises an isocyanate compound having at least two isocyanate groups in one molecule. This composition also exhibits both excellent curability and improved storage stability, and in particular, an improved storage stability under the condition where it only comprises the resin component and the latent curing agent.
In order to achieve the first object, there is also provided as the second aspect of the present invention a curable resin composition (hereinafter also referred to as the “second composition of the present invention”) comprising a resin compound having isocyanate group and thiirane ring, and an oxazolidine compound represented by the formula (1). This second composition also exhibits excellent curability and improved storage stability, and in particular, a storage stability under the condition where the resin composition only contains the resin component and the latent curing agent.
In order to achieve the second object, there is provided as the third aspect of the present invention a compound (hereinafter also referred to as the “compound of the present invention”) obtained from an oxazolidine compound represented by the formula (1) and a compound having at least one functional group selected from the group consisting of alkoxysilyl group, isocyanate group, vinylether group, and carboxy group through addition or condensation between hydroxy group of the oxazolidine compound and the functional group of the compound having at least one functional group.
In the compound of the present invention, the hydroxy group in the oxazolidine compound of the
Okuhira Hiroyuki
Suga Kazuo
Aylward D.
Dawson Robert
Rader & Fishman & Grauer, PLLC
The Yokohama Rubber Co. Ltd.
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