Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Patent
1997-12-18
1999-05-18
Marquis, Melvyn I.
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
2643281, 523445, 528 94, 528110, 528112, 528117, C08J5/00
Patent
active
059048883
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a two part system for producing a curable epoxy resin composition.
Epoxy resin systemis used for making cast products are conventionally supplied as 1-, 2-, 3- or even 4- part compositions which are mixed immediately before use. The most popular systems are 2-part systems, one part containing the epoxy resin and the other part containing the hardener.
Various types of hardener are known, but when making moulded products, it is useful if the mixture of the two parts do not cure immediately, but had a useful life at the mixing temperature.
When processing to make a cast article, the resin is usually first pre-heated in an oven at 40.degree. C. to 100.degree. C., e.g. about 90.degree. C. The hardener is then added and the mixture is then mixed under vacuum to de-aerate it. Typically the mixture will have a temperature of 65.degree. C. and when using an acid anhydride hardener, have a useable life of about 3 hours at 65.degree. C.
A typical epoxy resin/anhydride casting resin system comprises about 30-45% by volume of epoxy resin, 25-35% by volume of anhydride hardener, and 30-45% by volume of mineral filler, together with minor amounts of cure accelerator and other additives.
For technical and cost reasons it is desirable to maximise the level of mineral filler in the system. However, the achievement of high loadings by the caster is complicated for various reasons.
The handling of mineral fillers presents health hazards and requires the skills and equipment available in a resin manufacturer's or formulator's plant but not normally in a casting plant.
Anhydride casting resin systems intended for rapid curing at 100.degree.-200.degree. C. do not usually have sufficient stability at ambient temperatures to permit manufacture and supply as filled single part products. Supply and storage at low temperatures might overcome this problem but incurs additional costs.
With the normal basic resin: hardener mixing ratio being close to 1:1 it is not possible to accommodate the high level of total filler in the resin alone; such a mixture would be too intractable to process. The resin can accommodate only about half as much filler as can the overall resin-hardener mixture.
Whereas manufacture and supply of a resin-filler premix is a simple and commonly adopted technique, prefilled anhydride hardeners are subject to sever filler settlement and hard packing because of the low viscosity of the anhydride itself. Furthermore the separate filling of both resin and hardener is inefficient because it involves an additional processing step with concomitant costs. Moreover, if the caster requires numerous colour variants then economies of scale in the manufacture of pre-filled resins are sacrificed. The cost is increased further if the resins are to be handled in bulk since a number of storage containers will be needed.
It is apparent from the above that great efficiencies could be achieved if the epoxy resin system could be supplied in the form of a two part composition wherein one part constituted less than 25% and preferably less than 10% of the final composition and incorporated the variable elements, principally the colour.
We have now developed such a system wherein both parts display adequate stability for storage and transport at normal ambient temperatures.
Accordingly the present invention provides a two-component system for producing two or more different curable mixtures in which the first component A is common to and comprises 75 to 99.8% by volume of each mixture and comprises: mixture is selected from two or more different components B, each of which comprises:
Either one or both of components A and B may also contain other minor additives.
Component A may be made by mixing the components in any order and at any temperature subject to two criteria, namely that the mixture viscosity can be accommodated by the mixer and that the temperature is substantially below the temperature of onset of the cure reaction. A margin of 50.degree. C. is widely regarded as a desirable margin of safety i
REFERENCES:
patent: 4043969 (1977-08-01), Sporck
patent: 4107353 (1978-08-01), Karoly et al.
patent: 4324713 (1982-04-01), Kita et al.
patent: 4444924 (1984-04-01), Grimmer
Hayes Barry James
Willis Philip David
Wombwell Paul Terrence
Aylward D.
Ciba Specialty Chemicals Corporation
Crichton David R.
Kovaleski Michele A.
Marquis Melvyn I.
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