Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1998-03-27
2000-08-29
Dawson, Robert
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523442, 525107, 525121, 528 94, C08K 910
Patent
active
061109932
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a thermosetting epoxy resin composition. In particular, the present invention relates to a thermosetting epoxy resin composition comprising an epoxy resin and a curing agent that is surface treated by a specific method and is in the solid state at room temperature, which composition is useful as an adhesive, a sealant, a coating material, a paint, a potting material, and a molding material, and copes with both the storage stability in a sealed container and curing properties at a low temperature.
BACKGROUND ART
Epoxy resins are used in the fields of adhesives, sealants, coating materials, paints, potting materials, molding materials and the like, and most of them are two-pack types. However, since storage or handling of the two-pack type compositions are troublesome, and their pot life is limited, many restrictions are imposed on their application conditions, and they may not be used effectively.
Thus, some one-pack type epoxy resin compositions have been proposed. The known one-pack type compositions are mainly thermosetting ones, and contain BF.sub.3 -amine complexes, dicyandiamide, dibasic acid hydrazide, imidazole compounds and the like, as latent curing agents. Among such latent curing agents, those having good storage stability in sealed containers (in particular at 40.degree. C.) require high temperature (generally from 150 to 215.degree. C.) for curing, while those which can be cured at a relatively low temperature, for example, from 60 to 120.degree. C., have low storage stability. Thus, only few compositions satisfy the storage stability and curing properties at a low temperature at a practical level.
To overcome such drawbacks, following compositions have been proposed:
i) a composition comprising an amine-adduct curing agent,
ii) a composition comprising a curing agent in the form of microcapsules which are dispersed in an epoxy resin,
iii) a composition comprising a curing agent which is adsorbed on molecular sieves for preventing the contact of the curing agent with an epoxy resin.
These one-pack compositions i), ii) and iii) still have technical problems for practically using them, apart from the costs. For example, with the composition i), when the amine-adduct curing agent is solely used, the composition has low adhesion strength, and thus it is not suitable as a one-pack type composition. With the composition ii), the stability of capsules is insufficient. With the composition iii), the composition is unstable against water, and does not have sufficient storage stability.
Accordingly, it has been highly desired to provide a latent curing agent which can cope with both good storage stability, and quick curing properties (in the range between several minutes and 2 hours) at a low temperature (for example, 60 to 120.degree. C.), and which is suitable for a one-pack type epoxy resin composition. That is, the storage stability is important for determining the commercial value of the composition, while the curing properties at a low temperature are valuable properties for saving energy and natural resources. Therefore, it is highly desired to cope with both these properties.
DESCRIPTION OF THE INVENTION
The present inventors have made studies for solving such problems, and found that, when the specific amount of a fine powder having a specific center particle size is adhered to the surface of a curing agent which is in the solid state at room temperature for hiding active sites on the surface, the curing agent can be easily dispersed in epoxy resins in a stable state, and achieve good storage stability of the composition, and further the curing agent the surface of which is covered with the fine powder melts under low temperature conditions, for example, at a temperature of between 60 and 120.degree. C. for several minutes to 2 hours, so that the active sites are exposed for inducing the curing of the resin. Thus, the present invention has been completed.
Accordingly, the present invention provides a thermosetting curable epoxy resi
REFERENCES:
patent: 5218015 (1993-06-01), Yasuda et al.
Okuno Tatsuya
Saito Atsushi
Aylward D.
Dawson Robert
Sunstar Giken Kabushiki Kaisha
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