Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-05-05
1997-07-08
Yoon, Tae
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 5421, 525411, 525415, 528300, 528354, 528357, 528358, 528361, 523124, C08L 6704, C08G 6306
Patent
active
056462174
DESCRIPTION:
BRIEF SUMMARY
POLYESTERS
This invention relates to polyesters and in particular to compositions comprising polyesters and inorganic oxygen containing compounds.
It is a common problem that some polyesters are not mutually compatible and the blends thereof have inferior properties to the separate polyesters.
It has now been found that transesterification catalysts used in such blends increase compatibility and hence improve physical properties. Such catalysts may maintain or increase the molecular weight of polyester or blend of different polyesters or to increase the resulting melt viscosity of blends of polyesters whose individual components have widely differing melt viscosities.
According to the invention a polymer composition comprises a first component which is a microbiologically produced polyhydroxyalkanoate (PHA) and a second component which is a different microbiologically produced PHA or is a synthetic polyester, and at least one transesterification catalyst which is an oxy compound of a metal from Group IIA or IIIA or IVA of the Periodic Table, or of a metalloid having a valency of at least 3 from a B Group of the Periodic Table.
(The Periodic Table referred to is as in "Abridgements of Patent Specifications" published by the British Patent Office").
The first polyester component is preferably capable of a relatively high level of crystallinity, for example over 30%, especially 50-90%, in the absence of plasticiser.
Suitable PHAs will be or include at least one having units of formula I: Typically C.sub.m H.sub.n contains 2-5 carbon atoms in the polymer chain and the remainder (if any) in a side chain. In very suitable polyesters n is 2 m and especially there are units with m=3 and m=4 copolymerised and with respectively a C.sub.1 and C.sub.2 side chain on the carbon next to oxygen in the chain. Particular polyesters contain a preponderance of m=3 units, especially with 70-95 mol % of such units, the balance being units in which m=4. The molecular weight M.sub.w of the PHA is for example over 50000, especially over 100000, up to eg 2.times.10.sup.6.
In PHAs having units with m=3 and m=4 there may be very small, typically fractional, percentages of units having higher values of m. PHA consisting essentially of m=3 units is poly-3-(R)-hydroxybutyrate (PHB), and PHA consisting of m=3 and 4 units is polyhydroxybutyrate-co-valerate (PHBV).
The PHA can be a product of fermentation, especially of a microbiological process in which a microorganism lays down PHA during normal growth or is caused to do so by cultivation in starvation 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. Alternatively the necessary genetic material may be harboured by an eukariote, to effect the microbiological process.
Examples of suitable microbiological processes are the following: for Formula I material with m=3 or m=partly 3, partly 4:
EP-A-69497 (Alcaligenes eutrophus)
for Formula I materials with m=3:
U.S. Pat. No. 4101533 (A. eutrophus H-16)
EP-A-144017 (A. latus);
for Formula I material with m=7-13:
EP-A-0392687 (various Pseudomonas).
The PHA can be extracted from the fermentation product cells by means of an organic solvent, or the cellular protein material may be decomposed leaving microscopic granules of PHA. For specialised end uses the cellular protein may be partly or wholly allowed to remain with the PHA, but preferably subjected to cell breakage.
Second component PHA may be synthesised by chemical 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 second polymer component may be for example one or more of different manufacturer or a different source, for example re-work or recycled or naturally occurring material; substantially stoichiometric head-to-head tail-to-tail polyester. acyl reactivity;
REFERENCES:
patent: 5124371 (1992-06-01), Tokiwa et al.
patent: 5191016 (1993-03-01), Yalpani
patent: 5252701 (1993-10-01), Jarrett et al.
patent: 5281691 (1994-01-01), Hubbs et al.
patent: 5439985 (1995-08-01), Gross et al.
Yoon Tae
Zeneca Limited
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