Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Patent
1997-07-07
1999-09-14
Teskin, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
528361, 528481, 528487, 528490, 528499, 528502F, 435135, 435136, 435146, C08G 6389, C08G 6306
Patent
active
059524600
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION relates to the production of polymers of hydroxyalkanoic acid.
It is known, for example from European patents 69497 and 52460 to produce polymers of hydroxyalkanoic acids (PHA) especially polymers and copolymers of hydroxybutyric acid by microbial fermentation. European patent 145233 discloses a process in which microorganisms produced may be treated by heat and reagents in one or more stages to liberate PHA particles contained in them giving a suspension of the particles in an aqueous phase which particles may be separated for example by centrifuging. It may be desirable to resuspend the particles in water in order to carry out further purification.
According to this invention a process of recovering PHA from a suspension which comprises particles of PHA in a liquid comprises maintaining the suspension at a temperature at which the PHA melts and substantial coalescence of PHA particles occurs thereby at least partly forming a layer of molten PHA from the liquid and separating the layer of PHA of the layer from the liquid optionally after cooling to form a solid.
If the process starts from a microbiologically produced PHA suspension, any one or a mixture of the following can be used: diluted; (1); enzyme; in presence of a chelator and/or surfactant.
For each of such suspensions there may be a step of concentration or dilution or solubles separation before the melt-separation step. 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.
The layer of PHA and the layer of the liquid may be formed by permitting the PHA to settle in a molten condition either under normal gravity or under an enhanced gravitational field. Suitably the layers are subject to little or no turbulence during the settling process.
It is preferred that the temperature at which the layers are formed should not greatly exceed the melting point of the PHA. It may for example be up to 25.degree. C. above the said melting point. The temperature and residence time of the PRA should be such that during the period of exposure to the said temperature the molecular weight of the PHA is not reduced below 200,000 and preferably is not reduced below 400,000.
The PHA is preferably a polymer or copolymer of hydroxybutyric acid, for example a copolymer thereof with another hydroxyalkanoic acid preferably having 3 to 10 carbon atoms, for example hydroxyvaleric acid.
Suitably the liquid comprises water.
The layers may be formed in the presence of materials which are soluble in water. Such materials may include the degradation products of non PHA cellular material of microorganisms in which the PHA is formed, reagents used to degrade or solubilise such materials, for example proteases, surfactants or peroxy compounds, for example hydrogen peroxide and decomposition products thereof and nutrients for microorganisms for example carbon nutrients e.g glucose and inorganic nutrients. If desired materials may be added to improve the formation of the layers by for example by reducing the surface activity of other materials which tend to stabilise the suspension.
If a component of the liquid boils at a temperature lower than the melting point of the PHA the process is suitably carried out under pressure in order to avoid turbulence resulting from boiling.
In general temperatures employed in forming the layers are above 100.degree. C., for example 140 to 200.degree. C.; if the liquid comprises water operation under pressure is therefore usually desirable.
In a preferred form of the process a suspension of PHA containing microorganisms in water which may contain nutrients for the microorganisms is contacted with hydrogen peroxide in the presence of a complexing agent which may comprise ethylene diamine tetra acetic acid or ethylene diamine tetra (methylene phosphonic acid) at a temperature sufficient to solubilise non PHA materials and maintained at a temperature sufficient to permit a layer of PHA and an aqueous layer to form and separating the layer
REFERENCES:
patent: 3107172 (1963-10-01), Baptist et al.
patent: 3746688 (1973-07-01), Berkau
patent: 5798440 (1998-08-01), Liddell et al.
Database WPI, Section Ch, Week 9042, Derwent Publications Ltd., London, GB: Class A92 AN 90-317488 & JP 02 227 438 (Chuko Kasei Kogyo K), Sep. 10, 1990.
George Neil
Hall Alan
Liddell John Macdonald
Bond Gary M.
Monsanto Company
Teskin Fred
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