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
1999-07-27
2001-05-01
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...
C525S528000
Reexamination Certificate
active
06225417
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a one-pack type epoxy resin composition. More particularly, the present invention relates to a one-pack type epoxy resin composition which has high storage stability, which can be made into a film, which is curable at relatively low temperatures, and which has high adhesivity.
2. Description of the Prior Art
The epoxy resin composition used mainly as an adhesive or, in some cases, as a molding material includes (1) a two-pack type epoxy resin composition wherein an epoxy resin (a main component) and a curing agent are prepared separately and, when the composition is used, are mixed and (2) a one-pack type epoxy resin composition which is a mixture of an epoxy resin (a main component) and a curing agent.
In the two-pack type epoxy resin composition, the epoxy resin (a main component) and the curing agent must be accurately measured and mixed when the composition is used; therefore, a measurement error is apt to occur, and the quick reaction between the epoxy resin and the curing agent allows no storage after mixing of the two components.
Meanwhile, in the one-pack type epoxy resin composition which is a mixture of an epoxy resin (a main component) and a curing agent, there are no problems such as mentioned above; however, commencement of a reaction of the epoxy resin with the curing agent and subsequent curing, and resultant reduction in the storage stability of the composition are anticipated. Therefore, various proposals have been made to suppress the reaction of the epoxy resin with the curing agent when the composition is in storage.
As one-pack type epoxy resin compositions having high storage stability, there is generally known a one-pack type epoxy resin composition using dicyandiamide as the curing agent; and there is also known a one-pack type epoxy resin composition using an imidazole as the curing agent.
Also, as one-pack type epoxy resin compositions having good storage stability, there are known, for example, a composition comprising an epoxy resin and a phenol having at least two functional groups (JP-A-8-183835); a composition comprising an epoxy resin and a carbodiimide (JP-A-5-320611); and a composition comprising an epoxy resin, a curing agent (e.g. dicyandiamide, phenol or acid anhydride) and guanidine as a curing accelerator (JP-A-60-28424).
The above proposals, however, have respective problems. The dicyandiamide has a high melting point of 200° C. or higher and therefore must be dispersed in an epoxy resin in a solid state, and the resulting epoxy resin composition inevitably gives rise to nonuniform curing; when the dicyandiamide is used by being dissolved in a solvent, the resulting composition gives rise to uniform curing but has inferior storage stability.
The imidazole has high reactivity and gives an epoxy resin composition of very low storage stability when having a low melting point and, when having a high melting point, gives a composition of improved but still insufficient storage stability and moreover has the same problems as the dicyandiamide does.
Meanwhile, the one-pack type epoxy resin composition comprising an epoxy resin and a phenol and the one-pack type epoxy resin composition comprising an epoxy resin and a carbodiimide have good storage stability as mentioned in the above-mentioned literatures but require a relatively high temperature of 180° C. for curing.
Further, the one-pack type epoxy resin composition comprising an epoxy resin, a curing agent (e.g. Dicyandiamide and the like) and guanidine as a curing accelerator, similarly to the above compositions comprising a phenol or a carbodiimide, requires a relatively high temperature for curing; moreover, the composition has no film-formability and cannot be handled as a film-shaped composition.
SUMMARY OF THE INVENTION
The present invention aims at alleviating the above-mentioned problems of the prior art and providing a one-pack type epoxy resin composition which has high storage stability, which can be made into a film, which can be cured at relatively low temperatures, and which has high adhesivity.
According to the present invention, there is provided a one-pack type epoxy resin composition comprising an epoxy resin having at least two epoxy groups in the molecule and a polyguanidine.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is hereinafter described in detail.
AS the epoxy resin used in the present invention, there can be mentioned epoxy resins having at least two epoxy groups in the molecule, such as glycidyl ether type epoxy resins (e.g. bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic novolac type epoxy resin and cresol novolac type epoxy resin), alicyclic epoxy resins, glycidyl ester type epoxy resins, heterocyclic epoxy resins, liquid rubber-modified epoxy resins and the like. They can be used singly or in admixture thereof. Preferred are a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a phenolic novolac type epoxy resin and a cresol novolac type epoxy resin. The epoxy resin used in the present invention is not restricted thereto and can be any epoxy resin known generally.
The polyguanidine used in the present invention is a polymer having, in the molecule, a plurality of guanidine groups represented by the following formula:
As the polyguanidine used in the present invention, a polyguanidine obtained by modifying a polycarbodiimide with an amine is preferred particularly.
As the polyguanidine obtained by modifying a polycarbodiimide with an amine, there can be mentioned, for example, a polyguanidine represented by the following formula:
In the above formula, R
1
and R
2
are derived from the amine used for modification of polycarbodiimide and are each preferably a straight chain or branched chain alkyl group of 4 or more carbon atoms. Therefore, the amine used for modification of polycarbodiimide is preferably a dialkylamine having two straight chain or branched chain alkyl groups each of 4 or more carbon atoms. Incidentally, R
1
and R
2
are not necessarily the same and may be different from each other when different dialkylamines are used.
Above dialkylamine having two straight chain or branched chain alkyl groups each of 4 or more carbon atoms is exemplified by dibutylamine, dicyclohexylamine, dioctylamine and the like.
In the above formula, R is a bivalent organic group which is derived from the skeleton of the polycarbodiimide.
The polycarbodiimide used for obtaining the polyguanidine has a molecular weight of preferably 5,000 to 100,000. Naturally, therefore, the molecular weight of the polyguanidine is larger than the above-mentioned molecular weight of the polycarbodiimide by the amount of the amine added to the polycarbodiimide group. In the above formula, n is preferably an integer of 30 or more although it varies depending upon the skeleton of the polycarbodiimide used.
When the molecular weight of the polyguanidine used in the present invention is far smaller than 5,000, the resulting epoxy resin composition is difficult to handle when made into a film shape for use as a film-shaped adhesive and, more-over, has low stability in a solution state. When the molecular weight is far larger than 100,000, synthesis of the polycarbodiimide used for production of polyguanidine is difficult, making polyguanidine production difficult.
The polyguanidine used in the present invention can easily be synthesized by, for example, adding the dialkylamine to a solution of the polycarbodiimide so that the two components are the same equivalent, reacting the two components in an ambient temperature or under heating.
The one-pack type epoxy resin composition of the present invention comprises an epoxy resin having at least two epoxy groups in the molecule and a polyguanidine. The amount proportions of the two components can be, for example, 1 equivalent (epoxy resin) and 0.8 to 1.2 equivalents (polyguanidine).
When the amount of the polyguanidine is far smaller than 0.8 equivalent per equivalent of the epoxy resin, the crosslinking reaction
Imashiro Yasuo
Ito Takahiko
Nakamura Norimasa
Tomita Hideshi
Kubovcik & Kubovcik
Nisshinbo Industries Inc.
Sellers Robert E. L.
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