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
1997-11-24
1999-11-02
Yoon, Tae
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...
528361, 527202, 427391, C08L 6704, C08G 6306, C08H 500, C12P 762
Patent
active
059772506
DESCRIPTION:
BRIEF SUMMARY
This invention relates to particulate polyester, to polyhydroxyalkanoate (PHA) in preferred forms and processes for making it, and to a structure having PHA as coating or binder.
PHA, the general formula of which is set out below, is accumulated by many micro-organisms, particularly bacteria, for example of the genera Alcaligenes, Athiorhodium, Azotobacter, Bacillus, Nocardia, Pseudomonas, Rhizobium, and Spirillium, as an energy reserve material. It is conveniently prepared by cultivating the micro-organism in an aqueous medium on an energy and carbon source. At least part of the cultivation is preferably conducted under limitation of a nutrient essential for growth but not required for PHA accumulation. Examples of suitable processes are described in EP-A-15669 and 46344.
Such PHAs containing both 3-hydroxybutyrate (HB) units alone or with 3-hydroxyvalerate (HV) units are available commercially. Such PHAs containing larger repeating units have been described.
In the paper by Marchessault et al. (Report of NATO Advanced Research Workshop at Sitges, Spain 26-31 May 1990, `Novel biodegradable microbial polymers; ed. Dawes, publ. Kluwer) there is disclosed a latex of a PHA, namely polyhydroxybutyrate-co-valerate (PHBV 21% V) supplied by a predecessor of the present applicant in which x-ray diffraction shows some crystalline diffraction in the PHB lattice. Further relevant work by this author along with various co-authors is described in other publications, including Polymer 1992, 33(A), 823-827; FEMS Microbiology Reviews 1992, 103, 299-310; TAPPI Journal 1993 May, 76(5), 71-77. From these it appears that the PHA, whether in the commercially obtained 21% or 27% V latex or in latex made by the hypochlorite route, was 95% pure and the latex particles invariably comprised an amorphous core within a crystalline shell. Experiments using the latex in making films are described and the suggestion is made to use it as a binder, coating material or barrier for paper or non-wovens. In patent application WO 91/13207 (corresponding U.S. Pat. No. 5,451,456) of the same author along with co-inventors the use of the 21% V latex in the production of the film and coated paper is described in more detail and a content of amorphous polymer is designated as essential.
Co-pending application WO 95/15260 describes a composite film made by applying partly amorphous, for example 34% crystalline, PHBV as latex to preformed cellulose film.
Co-pending application WO 94/07940 describes the preparation of a PHA suspension containing NPCM (non PHA cell material) decomposition products and surfactant, in which 60% of the PHA particles are amorphous (density 1.176) and 30% are crystalline (density 1.231), the remainder being non resolved in caesium chloride gradient solution. No means of removing the dissolved materials from the suspension is disclosed.
In each of the above prior documents the PHA may be `virgin`, that is, the product of solubilising and removing NPCM leaving the PHA particles as laid down in microorganism cells or as agglomerates thereof. (Whereas it is possible to make a latex by dissolving PHA in a volatile liquid such as chloroform, emulsifying the solution in water and removing the volatile liquid e.g. by evaporation, the PHA particles of such a latex are not virgin).
We have now prepared latex in which the suspended particles are of higher amorphous content. Such a latex has interesting properties for example substantial advantages when used in conjunction with film, paper or non-wovens, the advantages lying in the quality of the products and/or the convenience of the procedure used in making them.
The invention in its first aspect provides an aqueous latex of microobiologically produced PHA comprising virgin disperse phase particles of which fewer than 30, especially fewer than 20, especially fewer than 1, % w/w are crystalline.
Percentage crystallinity is as measured by density, X-ray diffraction or small or wide angle x-ray scattering (SAXS or WAXS). The percentages are by weight and are believed to represent: ##EQU
REFERENCES:
patent: 5451456 (1995-09-01), Marchessault et al.
STN Iternational, Derwent Information, Ltd., WPIDS accession No. 95-157857, Denki Kagaku Kogyo KK: "Isolation and purificn. of poly hydroxy-alkanoate used as coating agent--from microorganisms, using surfactant to control poly hydroxy-alkanoate in amorphous condition."
Koning, G.J.M., et al., "Biosynthesis of Poly-(R)-3-hyudroxyalkanoate: An Emulsion Polymerization," 1:223-226, 1993.
George Neil
Hammond Timothy
Liddell John Macdonald
Satgurunathan Rajasingham
Turner Peter Deryk
Bond Gary M.
Monsanto Company
Yoon Tae
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