Orthopedic tool made of a plastic material

Abstract

The present invention relates to an orthopedic tool made of plastic material (M) comprising at least one semi-aromatic polyamide (P) comprising more than 50 mole % of recurring units obtained by the polycondensation reaction between at least one aliphatic diacid or derivative thereof and at least one aromatic diamine. In particular, hip rasp consisting essentially of at least one plastic material comprising at least one PMXDA polymer.

Claims

1. An orthopedic tool comprising: at least one part consisting essentially of at least one plastic material (M), wherein the plastic material (M) includes at least one semi-aromatic polyamide (P) including more than 50 mole % of recurring units obtained by a polycondensation reaction between at least one aliphatic diacid or derivative thereof and at least one aromatic diamine, and glass fiber, in an amount of from 40 to 60 wt. %, based on a total weight of the plastic material (M), the glass fiber having a diameter ranging from 5 to 40 m, and wherein the semi-aromatic polyamide (P) is contained in the plastic material (M) in an amount of from 25 to 80 wt. %, based on the total weight of the plastic material (M), and wherein the plastic material (M) further comprises an aliphatic polyamide (P*) selected from the group consisting of nylon 6, nylon 66 and nylon 12, in an amount of from 3 to 15 wt. %, based on a weight of the semi-aromatic polyamide (P).

2. The orthopedic tool according to claim 1, wherein the orthopedic tool is an instrument or ancillary used to remove bones for hip or knee prosthetic surgery.

3. The orthopedic tool according to claim 2, wherein the orthopedic tool is a hip rasp.

4. The orthopedic tool according to claim 1, wherein the semi-aromatic polyamide (P) is a PMXDA polymer.

5. The orthopedic tool according to claim 1, wherein the plastic material (M) further comprises a pigment.

6. The orthopedic tool according to claim 1, wherein the glass fiber has a diameter ranging from 5 to 15 m.

Description

DETAILED DESCRIPTION

The Semi-Aromatic Polyamide (P)

(1) An essential feature of the present invention lies in the chemical nature of the plastic material (M), namely it comprises the semi-aromatic polyamide (P).

(2) A polyamide is intended to denote any polymer of which more than 50 mole % of the recurring units comprise an amide moiety of formula (I):

(3) ##STR00001##

(4) Typically, polyamides are formed by reacting a mixture comprising one or more diamine and one or more diacid monomer units, and/or by polymerizing an amino carboxylic acid or lactam.

(5) The polyamide (P) is aromatic. An aromatic polyamide is intended to denote any polymer of which more than 50 mole % of the recurring units comprise at least one aromatic group and an amide moiety of formula (I) (aromatic recurring units, hereinafter). The aromaticity of the aromatic recurring units of an aromatic polyamide can come notably from the diacid (or derivative thereof) and/or from the diamine and/or from the aminoacid used in the polycondensation reaction. Non limitative examples of aromatic diacids are phthalic acids and naphthalenedicarboxylic acids. Metaxylylenediamine is an example of aromatic diamine.

(6) More precisely, the polyamide (P) is semi-aromatic, that is to say that it is an aromatic polyamide as above defined which comprises recurring units derived from the polycondensation reaction between at least one non-aromatic diacid (or derivatives thereof) and an aromatic or non-aromatic diamine, and/or recurring units derived from the polycondensation reaction between an aromatic or non-aromatic diacid (or derivatives thereof) and at least one non-aromatic diamine, and/or recurring units derived from the polycondensation reaction of at least one non-aromatic amino-carboxylic acid (or derivatives thereof). A diacid (or derivative thereof) or a diamine is considered for the purpose of this invention as aromatic when it comprises one or more than one aromatic group. A diacid (or derivative thereof) or a diamine or an amino-carboxylic acid (or derivative thereof) is considered for the purpose of this invention as non-aromatic when it is free from aromatic group.

(7) Still more precisely, the polyamide (P) is a semi-aromatic polyamide comprising recurring units derived from an aromatic diamine and an aliphatic diacid (or derivatives thereof) and/or recurring units derived from an aromatic diacid (or derivatives thereof) and an aliphatic diamine.

(8) Still still more precisely, the polyamide (P) is a semi-aromatic polyamide comprising more than 50 mole % of recurring units obtained by the polycondensation reaction between at least one aliphatic diacid or derivative thereof and at least one aromatic diamine, preferably more than 75 mole % and more preferably more than 90 mole % of said recurring units are obtained by the polycondensation reaction between at least one aliphatic diacid or derivative thereof and at least one aromatic diamine. Still more preferably, essentially all or even all the recurring units of the semi-aromatic polyamide (P) are obtained by the polycondensation reaction between at least one aliphatic diacid or derivative thereof and at least one aromatic diamine.

(9) The term diacid derivative is intended to encompass acid halogenides, especially chlorides, acid anhydrides, acid salts, acid amides and the like, which can be advantageously used in the polycondensation reaction.

(10) The expression at least one aliphatic diacid or derivative thereof and at least one aromatic diamine are understood to mean that one or more than one aliphatic diacid or derivative thereof and one or more than one aromatic diamine can be made to react as above specified.

(11) Non limitative examples of aromatic diamines are notably m-phenylene diamine (MPD), p-phenylene diamine (PPD), 3,4-diaminodiphenyl ether (3,4-ODA), 4,4-diaminodiphenyl ether (4,4-ODA), metaxylylenediamine (MXDA), as shown below:

(12) ##STR00002##

(13) The aromatic diamine is preferably metaxylylenediamine (MXDA).

(14) Non limitative examples of aliphatic diacids are notably oxalic acid (HOOCCOOH), malonic acid (HOOCCH.sub.2COOH), succinic acid [HOOC(CH.sub.2).sub.2COOH], glutaric acid [HOOC(CH.sub.2).sub.3COOH], 2,2-dimethyl-glutaric acid [HOOCC(CH.sub.3).sub.2(CH.sub.2).sub.2COOH], adipic acid [HOOC(CH.sub.2).sub.4COOH], 2,4,4-trimethyl-adipic acid [HOOCCH(CH.sub.3)CH.sub.2C(CH.sub.3).sub.2CH.sub.2COOH], pimelic acid [HOOC(CH.sub.2).sub.5COOH], suberic acid [HOOC(CH.sub.2).sub.6COOH], azelaic acid [HOOC(CH.sub.2).sub.7COOH], sebacic acid [HOOC(CH.sub.2).sub.8COOH], undecanedioic acid [HOOC(CH.sub.2).sub.9COOH], dodecanedioic acid [HOOC(CH.sub.2).sub.10COOH], tetradecandioic acid [HOOC(CH.sub.2).sub.11COOH].

(15) The aliphatic diacid is preferably adipic acid.

(16) As above mentioned, such aliphatic diacids can be used in the polycondensation reaction notably under the form of free acid and acid chloride.

(17) Good results are obtained when using PMXDA polymers as the semi-aromatic polyamide (P).

(18) For the purpose of the present invention, a PMXDA polymer is intended to denote a semi-aromatic polyamide essentially all, if not all, the recurring units of which are obtained by the polycondensation reaction of adipic acid with meta-xylylene diamine.

(19) PMXDA polymers are notably commercially available as IXEF polyamides from Solvay Advanced Polymers, L.L.C.

(20) The molecular weight of the PMXDA polymer is not particularly limited. The PMXDA has advantageously a number average molecular weight (M.sub.n) of at least 2,500, more preferably of at least 5,000, more preferably of at least 10,000 and still more preferably of at least 20,000. In addition, the PMXDA has advantageously a number average molecular weight (M.sub.n) of at most 60,000, more preferably of at most 50,000 and still more preferably of at most 30,000.

(21) M.sub.n can be calculated according to the following formula:
M.sub.n=210.sup.6/(COOH end groups)+(NH2 end groups)(COOH end groups)=number of acid end groups in equivalents/gram of product resin (titrated with a base)

(22) (NH2 end groups)=number of basic end groups in equivalents/gram of product resin (titrated with an acid).

(23) The semi-aromatic polyamide (P) can be amorphous or semi-crystalline. Preferably, it is semi-crystalline.

(24) The semi-aromatic polyamide (P) is contained in the plastic material (M) in an amount of advantageously at least 10 wt. %, preferably at least 25 wt. %, more preferably at least 35 wt. % and still more preferably at least 40 wt. %, based on the total weight of the plastic material (M). Besides, the semi-aromatic polyamide (P) is contained in the plastic material (M) in an amount of advantageously at most 95 wt. %, preferably at most 80 wt. %, more preferably at most 60 wt. % and still more preferably at most 50 wt. %, based on the total weight of the plastic material (M).

(25) Optional Ingredients of the Plastic Material (M)

(26) Preferably, the plastic material (M) further comprises an aliphatic polyamide (P*) of which more than 50 mole % of the recurring units are obtained by the polycondensation reaction between an aliphatic diacid (and/or a derivative thereof) and an aliphatic diamine, and/or by the auto-polycondensation reaction of an amino carboxylic acid, and/or by the auto-polycondensation reaction of a lactam.

(27) More preferably, the aliphatic polyamide (P*) is chosen from nylon 6, nylon 66 and nylon 12.

(28) Still more preferably, the aliphatic polyamide (P*) is nylon 66, i.e. the polyamide obtained by the polycondensation reaction between 1,6-hexamethylenediamine and adipic acid.

(29) The aliphatic polyamide (P*) is contained in the polymer composition in an amount of advantageously at least 3 wt. %, and preferably at least 6 wt. %, based on the weight of the semi-aromatic polaymide (P). Besides, the aliphatic polyamide (P*) is contained in the polymer composition in an amount of advantageously at most 30 wt. %, preferably at most 20 wt. %, and more preferably at most 15 wt. %, based on the weight of the semi-aromatic polyamide (P).

(30) Preferably, the plastic material (M) further comprises a reinforcing fiber (F).

(31) Any reinforcing fiber is in principle desirable. The skilled person will easily recognize the reinforcing fiber which fits best the plastic material (M) contained in the orthopedic tool. Generally, the reinforcing fiber is chosen depending on its chemical nature, its length, diameter, ability to feed nicely in compounding equipment without bridging and surface treatment (notably because good interfacial adhesion between the reinforcing fiber and the semi-aromatic polyamide (P) improves the stiffness and the toughness of the plastic material (M)).

(32) Non limitative examples of suitable reinforcing fibers include glass fibers, asbestos, graphitic carbon fibers (some of them having possibly a graphite content of above 99%), amorphous carbon fibers, pitch-based carbon fibers, PAN-based carbon fibers, synthetic polymeric fibers, aluminum fibers, aluminum silicate fibers, oxide of metals of such aluminum fibers, titanium fibers, magnesium fibers, rock wool fibers, steel fibers, silicon carbide fibers, boron fibers and so on.

(33) Preferably, the reinforcing fiber (F) is chosen from glass fibers and carbon fibers. More preferably, it is glass fiber.

(34) The reinforcing fiber (F), in particular when it is glass fiber, has a diameter preferably below 40 m: the Applicant has observed this resulted in increased reinforcement. More preferably, its diameter is below 20 m, and still more preferably below 15 m. On the other hand, the diameter of the reinforcing fiber, in particular the glass fiber, is preferably above 5 m.

(35) The reinforcing fiber (F), in particular the glass fiber, has a length preferably of below 20 mm, more preferably below 10 mm.

(36) The reinforcing fiber (F) is contained in the polymer composition in an amount of advantageously at least 10 wt. %, preferably at least 20 wt. %, more preferably at least 30 wt. % and still more preferably at least 40 wt. %, based on the weight of the plastic material (M). Besides, the glass fiber (F) is contained in the polymer composition in an amount of advantageously at most 60 wt. %, preferably at most 55 wt. %, and more preferably at most 52 wt. %, based on the weight of the plastic material (M).

(37) Other ingredients may be present in the plastic material (M), including pigments, lubricants and nucleating agents.