Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1995-02-13
1996-05-14
Hoke, Veronica P.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C08K 511
Patent
active
055168256
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION relates to a polymer composition, in particular comprising a polyhydroxyalkanoic acid which is preferably biodegradable and a plasticiser.
Biodegradable polyesters for example the microbiologically produced polyhydroxyalkanoates can be adapted by the use of plasticiser compounds for applications where improved impact strength and decreased stiffness are important. Since such compounds should preferably also be biodegradable, many of the plasticisers used in synthetic polymer processing are not suitable for biodegradable polymers. Most commonly the glyceryl ester triacetin is used, but it is more volatile than could be desired during melt processing or storage at high ambient temperatures.
The invention provides a composition comprising a polyhydroxyalkanoate and a plasticising quantity of at least one doubly esterified hydroxycarboxylic acid having at least 3 ester groups in its molecule.
"Doubly esterified" means that at least some of the hydroxy groups of the hydroxycarboxylic acid are esterified with a carboxylic acid and at least some of the carboxy groups thereof are esterified with a phenol or preferably an alcohol. Preferably at least 90% molar, more preferably substantially 100% molar of both such groups are so esterified.
In principle it is relatively difficult to plasticise stereospecific polyesters of high crystallinity. Surprisingly we have found that the plasticiser of this invention are remarkably effective in plasticising such polymers. The polyhydroxyalkanoate component is especially capable of a relatively high level of crystallinity, for example over 30% especially 50-90%, in the absence of plasticiser. Suitably it is or includes at least one polyester which is suitably microbiologically produced-having units of formula I: ##STR1## where m is in the range 1-11 and n is 2m or (when m is at least 2)2m-2. In very suitable polyesters m is 1 or 2, n is 2m and especially there are units with m=1 and m=2 copolymerised together. Particular polyesters contain a preponderance of m=1 units, especially with 70 to 98 mol % of such units, the balance being units in which m=2. The molecular weight of the polymer is preferably over 100000, especially over 300000. They suitably have the D (-) configuration.
The polyhydroxyalkanoate is Conveniently a blend of two or more polymers differing in the value of m. A particular example contains units have m=2, the rest m=1; and (b) polymer consisting essentially of Formula I units in which 5-30 mol % of units have m=2, the rest m=1. an average m=2 content in the range 4-18 mol %.
The polyhydroxyalkanoate is preferably a fermentation product, especially of a microbiological process in which a microorganism lays down polyhydroxyalkanoate during normal growth or is caused to do so by cultivation in the absence of one or more nutrients necessary for cell multiplication. The microorganism may be wild or mutated or may have the necessary genetic material introduced into it.
Examples of suitable microbiological processes are the following:
The polymer can be extracted from the formulation product cells by means of an organic solvent, or the cellular protein material may be decomposed leaving granules of polymer. For specialised end uses the cellular protein may be partly or wholly allowed to remain with the polymer, but preferably subjected to cell breakage.
Alternately the PHA can be a product of synthetic chemistry using processes known in the art. PHB can be prepared according to Bloembergen, S. and Holden, D. A., Macromolecules. 1989, Vol 22, p1656-1663. PHBV can be prepared according to Bloembergen, Holden, Bluhm, Hamer and Marchessault, Macromolecules. 1989, Vol 22, p1663-1669.
The hydroxycarboxylic acid from which the ester is derived is preferably aliphatic or cycloaliphatic. Its backbone structure (that is, apart from carboxy groups) preferably contains 2-6 carbon atoms. It contains preferably 2-4 carboxy groups and 1-3 hydroxy groups; and preferably the number of carboxy groups exceeds the number of hydroxy groups.
The groups with which the carb
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Patent Abstracts of Japan, vol. 16, No. 369, (C-972) (5412) & JP, A, 41 017 432.
Montador Henry J.
Webb Andrew
Hoke Veronica P.
Zeneca Limited
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