Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Patent
1997-01-31
2000-07-11
Gorr, Rachel
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
525450, C08G 1842
Patent
active
060874651
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a melt-processible poly(ester urethane), which contains structural units derived from a polyester and structural units derived from a diisocyanate. Such a polymer contains prepolymer-units derived from a polyester and units derived from diisocyanate.
The invention also relates to a prepolymer according used for the preparation of melt-processible poly(ester urethane)s, which is suitable for the preparation of a poly(ester urethane) according to the present invention, and to a process for preparing a poly(ester urethane). According such a process a lower molecular weight polyester-prepolymer is first formed from hydroxy acid monomers, and then the prepolymer is copolymerized with a monomer containing isocyanate groups in order to form a poly(ester urethane).
Numerous solutions for preparing biodegradable polymers from condensation polymers of lactic acid and from isocyanates are known from the patent literature. The isocyanate works as a coupling group, which joins together the chains of the condensation polymer by means of amide and urethane bonds to form a poly(ester urethane).
JP Published Patent Application No. 05148352 discloses a poly(ester urethane) (PEU), which has been prepared from polylactide (100 parts; M.sub.n >4000 g/mol). The polylactide is reacted in melt with a 0.1 to 5 parts of a diisocyanate. Diol- and diacid-based poly(ester urethane)s have been described also in the European Published Patent Application No. 0 488 617. Biodegradable poly(ester urethane)s based on lactic acid are anticipated by JP Published Patent Application No. 04013710, according to which the chain ends of a hydroxyl-terminated condensation polymer are coupled with aliphatic polyisocyanates. A similar coupling process is described in SU Patent Specification No. 1 016 314, in which lactic acid is used as one component of a hydroxyl-terminated prepolymer. In addition to the prepolymer both a diisocyanate and a diol are used for coupling.
FI Patent Application No. 924699 describes a process for preparing a lactic acid-based polyurethane. According to the process the polymer is prepared in two steps by first polymerizing the lactic acid to form an oligomer, and then copolymerizing the oligomer with isocyanate to form a polyurethane.
The known preparation processes are hampered by, for example, the problem that it is not possible to any substantial extent to influence the molar mass distribution, long-chain branching or degree of cross linking. However, these properties are important for improving the processibility of the polymer and for improving the mechanical properties and heat resistance of the polymer.
It is an object of the present invention to solve the problems relating to the prior art and to provide novel biodegradable poly(ester urethane)s, which are melt-processible and which can therefore easily be formed into the desired shape.
The solution according to the invention is based on the concept of preparing a poly(ester urethane) from a hydroxyl-terminated poly(lactic acid)-prepolymer. Said prepolymer is reacted with a diisocyanate in order to provide a polymer, in which the bonds between the prepolymer and the isocyanate are at least mainly (and in practice almost completely) formed by urethane bonds. By continuing polymerization at least for some time after the point of time when principally all free end groups have reacted with the diisocyanate, i.e. when the polymer does not contain any appreciable amounts of free hydroxyl groups and there are isocyanate groups primarily only at the ends of the polymer chains, long-chain branching of the polymer is achieved, which improves the melt-processing properties as well as the mechanical properties of the polymer. Long-chain branching occurs as a result of reactions between the polymer chains, for example as a result of reaction between the urethane bond and the isocyanate group at the end of the polymer chain.
The number average molar mass, M.sub.n, of the novel polymer is at least 10,000 g/mol and its weight average molar mass, M
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H. Fukuyaki et al; Synthesis pf Biodegradable Copoly (Lactic Acid laromatic Hydroxyacids); European Polymer Journal; 1990; vol. 26, N. 12 pp. 1273-1277 (Abstract).
English Language Translation of Japanese Reference 5148352, Jun., 1993.
Chemical Abstracts No. 116:236374 (Jun. 15, 1992).
Harkonen Mika
Hiltunen Kari
Kylma Janne
Malin Minna
Seppala Jukka
Gorr Rachel
Neste Oy
Valtion teknillinen tutkimuskeskus
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