Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1993-05-03
1995-08-08
Krass, Frederick
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525507, 528 98, 528 91, 549517, 549559, 549560, 428413, C08G 812, C08G 828, C08G 832, C08G 836
Patent
active
054399890
DESCRIPTION:
BRIEF SUMMARY
The invention relates to epoxy group-containing macrocyclic compounds suitable for use as epoxy resins which when formulated and cured give polymer matrices having high glass transition temperatures.
In this specification the term "epoxy resin" is used to denote a mixture of chemical compounds containing on average one or more epoxy groups per molecule. Epoxy resins are commonly reacted with curing agents (hardeners) usually in the presence of other additives such as catalysts, toughening agents, reinforcing fibres or fillers, to produce crosslinked cured resin composites which are useful for structural purposes. Such mixtures of ingredients before reaction occurs are referred to as curable epoxy resin formulations; all ingredients may be combined in one container (one-pack formulation) or the epoxy resin and curing agents may be in separate containers (two pack formulation). In the latter case the two parts Of the formulation are mixed immediately before curing.
Epoxy resins based on phenols form a significant portion of the thermosetting resins in commercial use. Of these epoxy resins, the diglycidyl ethers of bisphenol A (DGEBA) and their analogues are the most important for use in composite materials and adhesives. Other epoxy resins based on phenol/formaldehyde Novolac resins are also used and offer advantages in some applications. Existing resins of this latter type are glycidyl derivatives of linear oligomers made from various phenols and formaldehyde.
The glycidyl ether type epoxy resins known in the art, when cured, tend to have glass transition temperatures (T.sub.g) which are too low for high temperature use, for example, as matrices in composite materials for use in advanced aerospace and automotive applications. A low T.sub.g of the matrix material leads to an early fall-off in mechanical properties of a laminate with rise in temperature.
Epoxy resins of a different type in which the glycidyl ether groups are replaced by N-glycidyl substituents have been developed which show limited improvement in T.sub.g. These are used extensively in the advanced composites industry at the present time. However, they have the disadvantage of being based on highly toxic bisarylamines such as methylene dianiline and have different cure characteristics to the glycidyl ether-type resins which can lead to a problem of differential curing and deterioriation in mechanical properties in compositions containing both types.
The present invention provides an alternative to this latter approach which uses glycidyl ether-type epoxy resins based on more rigid macrocyclic structures built up from simple, cheap phenols of low toxicity. The cured resin formulations have better high temperature performance than those based on existing glycidyl ethers. Moreover, the formulations can also contain the diglycidyl bisphenol A type resins without significant detriment to T.sub.g.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, reference will be made to the accompanying drawings, in which:
FIG. 1 is a diagrammatic representation of a calixarene; and
FIG. 2 is a plan view of an upper rim epoxy calixarene.
Macrocyclic structures can be synthesized by reaction of specific phenols with aldehydes under special conditions. These are well defined chemical compounds with Zinke and Zeigler, 1944, Ber., 77, 264; Niederl and Vogel. 1940, J. Am. Chem. Soc, 62, 2512, Cornforth et al., 1955, Br. J. Pharmacol., 10, 73 making early contributions to their synthesis and structural elucidation. More recently, Gutsche (Gutsche and Muthukrishnan, 1978, J. Org. Chem., 43,4905) has assigned such compounds the collective name "Calixarenes" because they often adopt a conformation in which the aryl rings are arranged to form the sides of an urn or calix as shown in FIG. 1. It is compounds of this type that form the precursors of the resins of the present invention.
So far, calixarenes have found only limited use in polymer chemistry. A recent summary of such applications can be found in the article by Perrin and Harris (Topics in Inclusion Science, Vi
REFERENCES:
patent: 4259464 (1981-03-01), Buriks et al.
patent: 5218060 (1983-06-01), Rolfe et al.
Patent Abstracts of Japan, C-742, p. 118, JP A 2-123126, 10 May 1990.
Journal of Organic Chemistry, vol. 50, issued 1985, Washington, D.C., Gutsche et al., 5802-5806.
Journal of the American Chemical Society, vol. 103, issued 1981, Washington, D.C., Gutsche et al., 3782-3792.
Journal of Organic Chemistry, vol. 43, No. 25, issued 1978, Washington, D.C., Gutsche et al., 4905-4906.
British Journal of Pharmacology, vol. 10, issued 1955, Cornforth et al. 73-86.
Dao Buu N.
Hodgkin Jonathan H.
Morton Trevor C.
Commonwealth Scientific & Industrial Research Organisation
Krass Frederick
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