Title:  High-strength degradable materials and molded articles for implantation into human and animal organisms

United States Patent:  6,166,159

Assignee:  Merck Patent GmbH (Darmstadt, DE)

Filed:  May 26, 1993

PCT NO:  PCT/EP91/02169

102(e) Date:  May 26, 1993

PCT PUB. Date:  June 11, 1992

Foreign Application Priority Data:  Nov 26, 1990[DE] (40 37 516)

Described are high-strength materials which are degradable and resorbable in the human and animal organisms and shaped articles manufactured therefrom, such as implants, based on cured (meth)acrylic acid esters of polyfunctionally hydroxyl-terminated oligomers of lower hydroxycarboxylic acids {polyfunctional (meth)acrylic acid esters}. The invention is characterized in that said materials and/or shaped articles have been three-dimensionally cross-linked by radiation-curing and/or any other, however boron-free, free radical-initiated polymerization of the polyfunctional (meth)acrylic acid esters and exhibit a tensile strength under standard conditions of at least 10 N/mm².

DESCRIPTION OF THE INVENTION

The teaching of the present invention provides a new material for the indicated field of use, which material is distinguished by its extremely high and, moreover, even controllable material strength and utilizes the per se known class of oligohydroxycarboxylic acid poly(meth)acrylates, but does not employ initiator systems based on organoboron compounds.

Accordingly, the present invention relates to high-strength materials which are degradable and resorbable in the human and animal organisms and to molded articles manufactured therefrom, such as implants, based on cured (meth)acrylic acid esters of polyfunctionally hydroxyl-terminated oligomers of lower hydroxycarboxylic acids (hereinbelow designated as polyfunctional (meth)acrylic acid esters). Here the term (meth)acrylic acid esters is understood to include the corresponding esters of both acrylic acid and methacrylic acid, while also mixtures of these two ethylenically unsaturated acid components may be present in the same molecule.

The teaching according to the present invention is characterized in that both the materials and the molded articles manufactured therefrom for implantation into the living organism have been three-dimensionally cross-linked by radiation-curing and/or any other, however boron-free, free radical-initiated polymerization of the polyfunctional (meth)acrylic acid esters and exhibit a tensile strength of at least 10 N/mm².

It is preferred that the molded plastics articles have a tensile strength of at least 15 N/mm² and especially have respective values of at least 30 N/mm². Typical materials or molded articles within the scope of the invention have tensile strength values within the range of from about 40 to 60 N/mm² . Thus, the tensile strength values are clearly higher than the typical strength values of healthy human bones. A method suitable for the determination of the tensile strength values will be described hereinbelow.

In addition, in a further embodiment of acting according to the invention it is possible to provide materials and/or molded articles of the type described, which with respect to kind and amount are free from physiologically questionable reaction aids and/or other additives from the production of the materials (hereinbelow designated as active contaminant) so that physiologically undesirable side-effects in the course of the physiological processes of the degradation and resorption of these implants in the body will not have to be suspected. In this embodiment, the invention, more specifically, makes allowance for the mini-constituents and traces of substances present in the final product in comparably concentrations which are introduced into the living organism upon implantation of the plastics-made member. One important cornerstone to be featured in greater detail hereinbelow of the invention is constituted by the parameters concretely selected for the production of the new materials and/or molded articles. Here, more particularly, t he invention provides an adjustment between the inhibitors of the polyfunctional (meth)acrylic acid esters, on the one hand, and the conditions for initiating the reaction of cross-linking these polyfunctional (meth)acrylic acid esters, on the other hand. This adjustment, effected in response to the kinds and amounts of the reactant auxiliary materials, results in that the auxiliary materials used in the production process, which materials inevitably remain incorporated in the solid material upon completion of the reaction, may be released and resorbed by the body without giving rise to doubts.

Claim 1 of 57 Claims

What is claimed is:

1. A composition of matter useful as a high-strength material which is degradable and resorbable in the human and animal organisms comprising cured (meth)acrylic acid esters of polyfunctionally hydroxyl-terminated oligomers of lower hydroxycarboxylic acids, wherein said (meth)acrylic acid esters of polyfunctionally hydroxyl-terminated oligomers of lower hydroxycarboxylic acids have been prepared under solvent-free conditions in the steps of the production of the oligomer(s), the conversion thereof to the polyfunctional (meth)acrylic acid esters and the curing-shaving thereof, and three-dimensionally cross-linked by boron-free, free radical-initiated polymerization and exhibit a tensile strength of at least 10 N/mm².

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