Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Extrusion molding
Patent
1993-12-07
1996-03-19
Kuhns, Allan R.
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Extrusion molding
264 451, 264 53, 264131, 26421112, 2643281, 264236, 264478, 602 5, 602 6, B29C 3502
Patent
active
055001637
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a thermoplastic polymer material to be applied for orthopaedical, surgical and veterinary use, shaped as splints, artificial parts, prothesis, bandages and dressings.
The material ought to be used in suitable shapes for said practices as a supporting gird or splint and it shall comply with special requirements, which are not claimed for other plastic articles.
Polymer plastic materials have been proposed already for similar purposes, in order to forestall the disadvantages of gypsum splints.
In U.S. Pat. No. 3,692,023 polymers or mixtures of poly-.epsilon.-caprolactone and polyvinylethylether are described, which can be put upon fabric or gauze. This material was to be wrapped, in a warmed condition, around broken limbs, and after cooling down it formed a relatively hard supporting means, which could be removed again manually by warming up same.
In U.S. Pat. No. 4,175,177 orthopaedical bandages were described, consisting of copolymers of .epsilon.-caprolactone and acrylates.
Now more suitable materials have been sought in order to control the flexibility, bending strength, reciprocal elasticity and tensile strength in a reproducible manner.
The materials, which are already known, have been studied and compared with each other.
From these investigations it became apparent, that the following requirements should be met merely in an accurate way:
The phenomena of elasticity and resistance to elongation, as well as the compression strength, depend from the degree of crystallinity, the cross-linking index and the shape of the molecular chains.
A suitable material for surgical and orthopaedical practice, consisting of a composite of layers of poly-.epsilon.-caprolactone and a polyester with an upper layer of polyurethane foam with open cells has been described in European patent 0 263 552 of applicant.
A novel mixture of improved copolymers with a plasticizer has now been developed.
Hereby use was made of insight and further reflections on the structure of materials obtained by fundamental research. The structure of the materials is shown on page 5.
The process to obtain the present material according to the invention is characterized by a copolymerization by heating equimolecular weight-quantities of .epsilon.-caprolactone, polyurethane of polyoxypropylene-glycol and toluene-di-isocyanate with ethylene-butylene-styrene-copolymer, while during the formation of this mixed copolymer triallyl-cyanurate in an amount of 0.3 to 3.5% wt./wt., related to the total mass, and about 1% wt./wt. of oleic acid imide as a plasticizer are added, and the product, cast in shapes of block sections or sheeting is then irradiated by Gammaradiation up to 2.5 Megarad during a short period.
By this method a material is obtained, which by its partial cross-linking of bundles of macromolecular chains with an isotactic structure and its partial crystallinity of 5-10% can be processed successfully in injection moulds with an inner coating of polytetrafluorethylene, to obtain desired shapes for practical surgery and orthopaedy.
To a small part of the above raw materials during the last step some water can be added, such that a soft foamed layer with open cells is formed, which at the elevated temperature is attaching to the surface of the shapes in a thickness of 0.5 to 1.0 mm.
The temperature of the copolymerization reaction is ranging from 45.degree. to 180.degree. C., depending from the plasticizer contents.
The elasticity, crystallinity and stretch properties depend from the enthalpy of deformation. A measure for this quantity has been developed by Mooney and Rivlin, described in "Journal of Applied Physics", Vol. II, (1940), pages 582 a.f.
A review of the evaluation of similar materials is represented in "Elasticity and Structure of Polyurethane Networks", Dissertation of R. Blokland, Delft Technical University, 1968.
A stretched elastomeric copolymer of the type of the present material has properties in accordance with the formula of Mooney and Rivlin: .multidot.C.sub.2).multidot.(.lambda.-.lambda..sup
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Drucker William A.
Kuhns Allan R.
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