Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1995-05-05
1997-01-14
Acquah, Samuel A.
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
528272, 528294, 528354, 528361, 528363, 528364, 528365, 525437, 525439, 525444, 264239, D02G 300, C08F 2000, B27B 308
Patent
active
055937780
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP94/01489 filed Sep. 8, 1994.
TECHNICAL FIELD
The present invention relates to a novel biodegradable copolyester having a versatility which is applicable to fibers, films, containers and the like and is improved in toughness, degradability, heat resistance and dyeing ability, a molded article having improved mechanical properties such as toughness produced using the copolyester (for example, polylactic acid fibers having a biodegradability and suitable for preparing fibrous structures such as a non-woven fabric, conjugate fibers having a controlled biodegradability or a hydrolyzability in neutral environment, conjugate fibers capable of being divided easily even under neutral or weak alkaline environment and capable of forming into fine fiber, ultrafine fiber or fiber having special section, and fibrous structures prepared using them), and a process for producing the molded article.
BACKGROUND ART
Complete circulation type degradable polymers which are finally degraded into carbon dioxide and water by degradation by means of microorganisms under natural environment and/or by hydrolysis under neutral environment, attract attention recently from the viewpoint of environmental protection.
For example, among such polymers, polyhydroxybutyrate (hereinafter referred to as "PHB"), polycaprolactone (hereinafter referred to as "PCL") and polylactic acid are known as a melt-moldable and biodegradable polymer.
However, not only PHB requires a large energy in recovery and purification of the polymer because of biosynthesis by microorganisms, thus the production cost is too high, but also molding thereof is difficult because it is difficult to control the molecular weight and the crystallinity. Also, it is difficult to control the physical properties of the molded articles such that the molded articles are poor in transparency. Thus, it is the actual circumstances that it is not easy to industrially and inexpensively provide performances and moldability which meet the uses.
Also, PCL has a serious problem and an obstacle in practical use that the creep during use is large since its melting point is as low as 60.degree. C. and, therefore, the articles prepared therefrom are poor in shape stability or the strength is extremely lowered depending on the use temperature.
On the other hand, polylactic acid is relatively inexpensive, and is a thermoplastic resin having a sufficient heat resistance since its melting point is 178.degree. C. Thus, it is melt-moldable and the use as fibers for clothing and industrial purposes is expected. Also, although the polylactic acid is a biodegradable polymer excellent on practical use, it has the problems in production and processing that (1) polylactic acid homopolymer is poor in melt-moldability due to too high crystallinity, and moreover, the molded articles, films, fibers and the like obtained therefrom are not sufficient in toughness, and also are fragile and low in impact strength (having a rigid crystal structure), (2) the dye affinity is poor, (3) the molecular weight of polylactic acid cannot be sufficiently raised, (4) if polylactic acid is heated, the molecular weight is decreased, resulting in deterioration of strength and the like of the final products, and in addition, a technique to produce practical fibers for clothing and for industrial use from polylactic acid has not yet been established, (5) it is behind technical development for commercialization as fiber products.
For such a reason, a very limited use such as thread for suture utilizing the biocompatibility is only hitherto known.
Also, Japanese Patent Publication Kokai No. 1-163135 discloses a drug sustained release base material for releasing drug into living body, which is obtained by reacting a polymer or copolymer of lactic acid having a molecular weight of 300 to 10,000 with a polyoxyethylene glycol (hereinafter referred to as "PEG") having a molecular weight of 150 to 10,000 in an equivalent ratio of PEG to the polylactic acid of 0.3 to 5.0 (30 to 500%).
However, the obt
REFERENCES:
patent: 4826945 (1989-05-01), Cohn et al.
Supplementary Partial European Search Report for Appln. No. EP 94 92 6374 Piero Cerrai et al., "Block copolymers from L-lactide and poly(ethylene glycol) through a non-catalyzed route", Die Makromol. Chem., Rapid Commun., vol. 14, No. 9, 1993, pp. 529-538.
Hans R. Kricheldorf et al., "ABA triblock copolymers of L-lactide and poly(ethylene glycol), Die Makromol. Chem", vol. 194, Feb. 93, pp. 715-725.
Zbigniew Jedlinski et al., "Synthesis of ethylene glycol-L-lactide block copolymers" Die Makromol. Chem., vol. 194, Jun. 1993, pp. 1681-1689.
Fujii Yasuhiro
Kajiyama Hiroshi
Kondo Yoshikazu
Matsui Masao
Osaki Takuji
Acquah Samuel A.
Kanebo Ltd.
Shimadzu Corporation
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