Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1994-06-17
1996-02-20
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
528196, 528354, 528355, C08G 6400
Patent
active
054929970
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a copolymer of at least one lactone and at least one cyclic carbonate.
Such a copolymer is known from U.S. Pat. No. 4,705,820, which patent specification discloses a copolymer of glycolide and trimethylene carbonate (TMC).
Such polymers and copolymers are applied, inter alia, in the medical world, where objects on the basis of these materials are implanted in the human or animal body. If the implanted material is to fulfill a (temporary) supporting function, good material-properties, such as toughness and stiffness, are required.
One way of obtaining a good toughness and stiffness is to use semi-crystalline material. Semi-crystalline material can be obtained, for instance, by the use of controlled polymerization conditions or special after-treatments, both as known from literature.
Such polymers and copolymers further are interesting mainly because the material is biodegradable. This implies that the polymer hydrolyzes and disintegrates into its constituent parts under certain biological conditions, such as for instance physiological conditions.
An implanted object based on such polymers or copolymers should not stay in the body for too long so as to avoid any tissue reactions and give the body-specific structure, which the implant was meant to support, the chance to regain its own firmness. This means that rapid degradation and resorption are required as soon as the temporary support function of the implant is no longer needed.
The drawback of copolymers with a high crystallinity is that they disintegrate into high-crystallinity, possibly needle-shaped fragments during degradation, which are resorbed only very slowly, on account of which tissue reactions may occur that are harmful to the patient.
It is the object of the invention to furnish a copolymer that possesses good mechanical properties, has a good resorption velocity and does not cause troublesome complications upon degradation.
According to the invention this is achieved in that the carbonate is polycyclic.
This renders it possible to obtain cross-linked copolymers. The mechanical properties of objects based on these copolymers are significantly better than those of objects on the basis of non-cross-linked copolymers. The material is tough--in particularly the tensile strength is higher--, impact resistant, less crystalline than non-cross-linked copolymer and it is biodegradable.
The degradation velocity under physiological conditions of the copolymer according to the invention is higher than that of non-cross-linked polymers. Because of the lower crystallinity, the fragments formed upon degradation are less harmful. Mostly they are relatively small and thus cause fewer problems in the body. The crystallinity and the crystal dimensions can be derived, inter alia, from the thermal properties.
An added advantage of the copolymer according to the invention is that it may start swelling in a certain environment, so that in principle it is suitable for use as a so-called drug-release system. To this end the object involved is made to swell in a swelling medium, a drug is introduced into the swollen material, and subsequently the object is reduced to its normal proportions by removing the swelling medium or by reducing the swelling-promoting properties of the medium, for instance by adding an amount of non-swelling medium. After this, the object may be implanted.
Cross-linking of copolymers of lactones is disclosed in U.S. Pat. No. 4,379,138, in which an amount of lactone is copolymerized with a polycyclic dilactone. U.S. Pat. No. 4,379,138 does not state that this is possible also with a polycyclic carbonate.
Copolymers of lactones and cyclic carbonates are disclosed in GB-A-2,033,411, but the monocyclic carbonates described therein cannot be cross-linked.
The use of polycyclic carbonates for polyester cross-linking is disclosed in GB-A-1,228,490 which, however, does not disclose the possibility of cross-linking a copolymer on the basis of lactones. The polyesters in GB-A-1,228,490 are polyesters obtained by esterification rea
Grijpma Dirk W.
Kroeze Erik
Nijenhuis Atze J.
Pennings Albertus J.
Fink Edward M.
Michaelson Peter L.
Mosley Terressa
Rijksuniversiteit te Groningen
Seidleck James J.
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