Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1991-04-08
1995-01-17
Jagannathan, Vasu S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 63, 525 72, 525 73, 525 77, 525 82, 525263, 525281, 525288, 525291, 525296, 525303, 525305, 525309, 525420, 525445, 525455, C08F28300, C08F28302, C08F28304, C08F25500, C08F25904, C08F, C08F, C08F26504, C08L 5106, C08L 5108
Patent
active
053826337
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the modification of thermoplastic polymers to give thermoplastic polymer adducts which contain residues of modifier molecules bound to the polymeric substrate.
Thermoplastic polymers usually comprise essentially linear molecules or molecules with only relatively short side chains. They do not, as a general rule, contain significant amounts of cross-linking, since cross-linking tends to increase the rigidity of the polymer through formation of a tangled matrix of cross-linked polymer chains. Include within this class of polymers are vinyl polymers and copolymers and substantially linear condensation polymers. Such vinyl polymers and copolymers include, for example, polyolefins, such as polyethylene and polypropylene, polyvinyl chloride, polystyrene, ethylene-propylene co- and ter-polymers, polyacrylates, polymethacrylates, polyacrylonitrile, and acrylonitrile-butadiene-styrene terpolymers, to name but a few. Examples of thermoplastic condensation polymers include polyamides, polyesters, and linear and substantially linear polyurethanes.
There is increasing concern about the migration and loss of additives from thermoplastic polymers. This concern arises from several causes. Firstly, if the additives (for example, antioxidants, stabilisers, plasticisers, antistatic agents, photosensitisers and the like) are lost from the polymer by volatilisation or leaching, then they no longer fulfil their intended purpose. Secondly, when additives are leached into the contacting medium for example by foodstuffs or by other extractants that are subsequently ingested, then they may cause toxicity in the host environment. Thirdly, when polymers are used in medical applications, for example in surgical goods, prostheses or body implants, it is essential that no migration of additives occurs since although polymers are normally biologically inert, low molecular weight additives are generally not so and because they are readily leached into the biosystem, they cause toxicity problems. Traditionally, additives, and particularly stabilisers, have been relatively low molecular weight materials of high volatility and with marginal compatibility with the base polymer.
Recently, it has been proposed to overcome the problem of migration and loss of antioxidants and stabilisers by copolymerising antioxidants containing vinyl groups with a major proportion of conventional monomers to give polymers containing the appropriate antioxidant in polymerised form at the concentration required for use during service. This is an expensive procedure and to overcome this it has been proposed, in, for example, U.S. Pat. No. 4,354,007 to Scott (hereinafter referred to as "the '007 Patent"), that a wide variety of antioxidants and stabilisers may be reacted with preformed polymers in the presence of free radicals to provide a stabilised polymer directly or to make an intermediate, highly concentrated polymer-bound adduct which may be blended with further amounts of a suitable compatible base polymer to give an antioxidant modified polymer suitable for a wide variety of end use applications. The technique is particularly applicable to rubbers in latex form.
The '007 patent describes a wide variety of antioxidant and stabiliser molecules including compounds selected from categories which include chain-breaking or peroxide-decomposing antioxidants, ultraviolet screening agents, triplet quenchers and metal deactivators. In terms of a limitation on the scope of the stabiliser compounds that may be used, perhaps the most significant structural limitation is that it should be capable of being activated by a free radical in the polymer (see col. 1, lines 40-50). In this regard, however, it has been found with regard to the unsaturated or vinyl group-containing stabiliser compounds described in the '007 patent and also as to similar stabiliser compounds which have been suggested by others for grafting to pre-formed polymers in the presence of free radicals, that frequently the reactivity of the stabiliser molecules containing polymeri
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patent: 4032592 (1977-06-01), Ogihara et al.
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patent: 4130534 (1978-12-01), Coran et al.
patent: 4591615 (1986-05-01), Aldred et al.
patent: 4910245 (1990-03-01), Flynn et al.
Al-Malaika Sahar
Scott Gerald
3i Research Exploitation Limited
Jagannathan Vasu S.
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