Production of a polymer composition

Details Production of a polymer composition Production of a polymer composition

1998-01-06

1999-04-06

Michl, Paul R.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

528361, C08J 302

Patent

active

058919368

DESCRIPTION:

BRIEF SUMMARY
THIS INVENTION relates to the production of a polymer composition containing a polyhydroxyalkanoic acid (PHA), particularly in latex form.
International application PCT/GB95/01925 discloses water by maintaining the suspension at a temperature at which the PHA melts, at least partly forming a layer of molten PHA, and separating the PHA layer; and surfactant and water. Generally the preferred conditions indicated therein are preferred for the present invention so far as relevant.
According to the invention a process of making an aqueous PHA latex comprises contacting a liquid-form solution of such PHA in a water-soluble liquid with water under shear.
The PHA can be derived from ring-opening or other organic synthesis, but preferably it is microbiologically produced. It may be introduced by dissolving solid PHA purified from non-PHA cell material (NPCM) by way of solvent extraction or NPCM solubilisation. More preferably it is introduced as a component of a slurry or suspension produced by microbiological fermentation followed optionally by NPCM solubilisation but possibly without drying. Such a suspension may have been subjected to process (a) of the said International application, so that the melt-separation effects significant purification of PHA from NPCM.
Starting from a microbiologically produced biomass of PHA-containing cells, any one or a mixture of the following microbiological suspensions can be subjected to melt-separation and dissolving the PHA in the water-soluble liquid: diluted; in presence of a chelator and/or surfactant.
Alternatively any of such suspensions may be partly or wholly dried and then contacted with the water-soluble liquid.
For each of such suspensions there may be a step of concentration or dilution or solubles separation before melt-separation. For each of the suspensions made by surfactant treatment in particular, it may be desirable to remove any excess surfactant before the melt-separation step.
If the process starts from solid PHA, it may comprise for example heating an aqueous slurry of solid PHA to above the liquefying point of the PHA in presence of the liquid, or liquefying PHA (eg in an extruder) and injecting it into water at above that point.
The process may be carried out by the steps of: liquid into a zone maintained at a pressure and temperature at which the PHA and water are both in the liquid state; all in liquid form; the solution, surfactant (if present) and water to mixing at a pressure and temperature at which the PHA solution and water are both in the liquid state until a fine dispersion of PHA has formed; and
To limit decrease of PHA molecular weight at the relatively high temperatures involved, the process is preferably carried out continuously.
Suitable PHAs comprise repeating units of formula --O--C.sub.m H.sub.n --CO-- where m is in the range 1-13 and n is 2m or (except when m is unity) 2m-2. 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 PHAs m is 3 or 4, n is 2m and especially there are units with m=3 and m=4 copolymerized together with respectively a C.sub.1 and C.sub.2 side chain on the carbon next to oxygen in the chain. Particular PHAs contain a preponderance of m=3 units, especially with at least 70 mol% of such units, the balance being units in which m=4. The molecular weight of the PHA is for example over 50000, especially over 100000, up to eg 2.times.10.sup.6.
PHA of formula I containing only m=3 units is referred to as PHB; PHA containing m=3 and m=4 units is the co-polymer polyhydroxybutyrate-co-valerate PHBV. PHBV preferably contains 4-20% of m=4 units. The PHA can also be a blend of two or more PHAs differing in the value of m. Correspondingly a mixture of starting suspensions is used. A particular example contains: have m=4, the rest m=3; and units have m=4, the rest m=3. The proportions in such a blend are preferably such as give an average m=4 content in the range 4-20%.
For the PHA-producing microbiological process the microorganism may be wild or

REFERENCES:
patent: 5451456 (1995-09-01), Marchessault

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