Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/12—Powdering or granulating
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
  • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones

Definitions

• This invention relates to polyester particles and in particular to a process for producing such particles by agglomerating finer particles laid down in microbiological cells.
• Such polyester is hereinafter referred to as PHA.
• GB application 9215791.6 filed 24 July 1992 and published as WO 94/02622 describes a process of agglomerating PHA particles in suspension in water optionally containing at least partly chemically degraded non-PHA microbial cell matter (NPCM) by maintaining the suspension at a relatively high temperature, for example over 100°C, but at least 30°C below the peak melting point of the PHA (as determined by differential scanning calorimetry).
• NPCM non-PHA microbial cell matter
• GB application 9307674.3 filed 14 April 1993 and published as WO 94/24302 discloses recovery of PHA particles by solubilising NPCM with an oxidizing agent in the presence of a chelating agent.
• the effect of the chelating agent is that the oxidizing treatment can be applied to a PHA suspension that has not been subjected to separation and re-suspension and thus contains heavy metal ions present as trace elements in the microbiological fermentation and which now would catalyze decomposition of the oxidizing agent if not chelated.
• a process for producing R-stereospecific PHA comprises microbiological fermentation, harvesting PHA particles by solubilising NPCM and agglomerating them by heating the aqueous suspension thereof, and is characterized by the succession of steps: (a) partly solubilising NPCM by the action of for example one or more of proteolytic enzyme, hydrolase lysozyme, homogenization and heat-shock;
• step (e) is defined below.
• step (a) can be carried out by methods well established in industry and research, for example as described in EP-A- 145233.
• Step (b) can be applied to the whole product of step (a) or to that product after subjection to minor procedures such as concentration but short of separation and re-suspension.
• Oxidative step (b) is preferably carried out by the action of a peroxide (especially hydrogen peroxide); preferably in presence of a chelator.
• a peroxide especially hydrogen peroxide
• a chelator preferably the process of WO 94/24302 is used.
• the PHA content is in the range 60-250 g/l .
• the pH is suitably in the range 5 to 9 and the temperature in the range 60-180°C.
• Suitable chelators are ethylene diamine tetra- acetic acid, nitrilo triacetic acid, citric acid and diethylenediamine penta-methylenephosphonic acid.
• monomeric water soluble surfactant a compound containing in its molecule a small number of hydrophobic groups which are C 6+ aliphatic hydrocarbon chains (especially 1 or 2 such chains) and a small number of hydrophilic groups (especially 1 or 2 such groups).
• the said chains and groups may be connected by direct links or through for example at least one of oxygen, ester, amide or aromatic hydrocarbon.
• the hydrophilic group(s) may be: anionic, for example, carboxylate, sulphonate, sulphate, phosphonate or phosphate; or cationic, for example quaternary ammonium; or non-ionic, for example polyalkyleneoxy, poly glycerol, glycoside or amine oxide; or a combination of two or more of these.
• Such surfactants are generally characterized by micelle formation in aqueous solution and they decrease the surface tension of water markedly. It may be that their hydrophobic groups are capable of wetting the surface of the PHA granules but not of penetrating such granules. Such wetting may be less favored as the granules agglomerate and crystallize.
• surfactants having a negative temperature coefficient of water solubility are preferable. Good results have been obtained using non-ionic surfactants, especially those having a C 10 . 20 hydrophobic group and 6 to 100 ethylene oxide units.
• the process is especially applicable to suspension initially free of such surfactant, especially those formed by subjecting a fermentation biomass at temperatures in the range 100- 200°C and/or to the action of proteolytic enzymes, in each case without addition of surfactant.
• first surfactant a surfactant
• steps (b) and (c) at least partly overlap.
• the same surfactant may suffice for the agglomeration step, or the content of surfactant may be substantially increased or a different surfactant added.
• the first surfactant is not removed or inactivated and replaced by another; but this is not excluded.
• the surfactant can, in general, thus be introduced at any convenient stage, provided that it is present in step (d).
• the content of surfactant required depends on the detailed operating conditions, in particular: extent of prior decomposition of NPCM; concentration of solubilised NPCM (which in turn depends on the content of PHA in the microorganism cells); type of surfactant and balance of hydrophobic and hydrophilic groups; extent of further NPCM (adsorbed or solubilised) decomposition; extent of agglomeration required; time available; temperature.
• Step (d) can be carried out in presence of polymer processing additives such as pigments, nucleants and plasticisers, such that co-agglomeration takes place.
• the temperature in step (d) is by 30-80, preferably 40-70, °C lower than the melting point of the PHA as measured by DSC.
• the temperature is over 100°C and agglomeration is carried out under superatmospheric pressure. It will be appreciated that the temperature is stated in terms ofthe DSC melting point of the PHA because the PHA particles at the time of agglomeration are in transition between the amo ⁇ hous state and the crystalline stale, so that their melting point cannot be known.
• the PHA is especially capable of a relatively high level of crystallinity, for example over 30%, especially 50-90%. It typically has units of formula 1 :
• m is in the range 1 -13 and n is 2m or (except when m is unity) 2m-2.
• C m H n contains 2-5 carbon atoms in the polymer chain and the remainder (if any) in a side chain.
• n is 3 or 4
• the molecular weight of the polymer is for example over 50000, especially over 100000, up to eg 2 x 10 .
• a particular example contains:
• the microorganism may lay down PHA during normal growth or may be 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 had the necessary genetic material introduced into it.
• the necessary genetic material may be harboured by a eukariote, to effect the microbiological process.
• the starting PHA particles are typically of weight average diameter in the range
• the process of the invention typically increases this to at least 50, preferably 100- 5000, for example 200-500, ⁇ m.
• Their porosity is then typically at least 0.6, especially 0.7 to 0.8, by volume.
• the filtration rate of the suspension is typically 100 to 10000 times greater than that ofthe starting suspension.
• the agglomerates may be separated from the aqueous phase of the suspension by for example decantation, filtration or centrifugation.
• decantation filtration
• centrifugation there may be one or more steps of resuspension, washing and re-separation, to ensure more complete removal of solubilised NPCM and surfactant from the agglomerates. It is an advantage if using an agglomeration step that such separation and washing can be effected by decantation and/or filtration, without the expense of enhanced-gravity machinery such as centrifuge.
• one or more steps of washing by decantation and/or filtration preferably constitute step (e) ofthe process hereinbefore defined.
• the washing liquid is usually w ⁇ iter.
• other liquids may be used, for example alcohols (especially methanol) to remove liquid components of NPCM and less polar liquids (such as ethers, esters and hydrocarbons).
• the process is capable of producing PHA of better colour, as measured by yellowness index, as a result of low occlusion of impurities by the agglomerates.
• the separated and washed agglomerates are dried.
• they consist substantially of crystalline PHA.
• They are suitable for uses involving melting, such as:
• Injection moulding, injection blow moulding, compression moulding and casting (which usually do not involve post-shaping mechanical treatment causing substantial crystallization); film casting, fiber spinning, each of which commonly is followed by stretching to increase crystallinity towards the maximum possible; fluidized bed coating, as described in WO 93/10308.
• the agglomerates may be used as such (especially if they are large enough to afford good die-fill and avoid serious dusting) or may be extruded to granular feed.
• agglomerates are as carriers foi biochemically active materials such as human medicines, animal medicines and agrochemicals.
• a component may be introduced during the agglomeration step or into the separated agglomerates taking advantage of their porosity. Depending on its chemistry, it may itself act as the surfactant or part of it or may form water-insoluble complex with a surfactant.
• a wide variety of such components can be used with minor risk of decomposition.
• EXAMPLE 1 A fermentation biomass was formed by growing Alcaligenes eutrophus on a nutrient medium containing glucose as carbon source, then accumulating PHA by feeding glucose and propionic acid under phosphate limitation.
• Samples of the product were treated by addition of chelator DEQUEST, (RTM) (diethylene triamine pentamethylenephosphonic acid), hydrogen peroxide, the surfactant Synperonic A-l 1 water soluble C 13 alkyl ethoxylate (1 1 EO) and silicone antifoam and stirred at 80°C for up to 15h. Test samples were removed at 7h and 15h, transferred to a glass tube, sealed, and heated at 140°C for 30 min.
• Synperonic A50 (C 13 alkyl 50 EO), except that using A50 a concentration of 1% was found to be sufficient.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Preparation Of Compounds By Using Micro-Organisms (AREA)
• Polyesters Or Polycarbonates (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Developing Agents For Electrophotography (AREA)

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• 1995
  • 1995-12-16 GB GBGB9525932.1A patent/GB9525932D0/en active Pending
• 1996
  • 1996-12-13 AU AU14626/97A patent/AU1462697A/en not_active Abandoned
  • 1996-12-13 JP JP09522949A patent/JP2000503046A/ja active Pending
  • 1996-12-13 EP EP96945205A patent/EP0866830A1/de not_active Ceased
  • 1996-12-13 WO PCT/US1996/020016 patent/WO1997022654A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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