SINGLE-USE MEDICAL NEEDLE

Abstract: A hypodermic needle or other needle for medical use is provided, which can easily be made unusable by means of heat or by mechanical means. The needle consists at least partly of a liquid crystal polymer, especially a thermotropic LCP such as an aromatic polyester.

Description: Single-use medical needle. The present invention relates to an needle suitable for medical and health care applications, which can easily be made unusable. Needles for injection purposes and other applications, for example in health care, are typically made out of metal, since metals, such as stainless steel, have favourable properties for such applications, such as a high strength and relatively low price. It is often desirable, however, that hypodermic needles and other needles cannot he used again after being used once, since any reuse im¬ plies the risk of infection. The need for single-use needles is espe- cially pressing in order to prevent the spread of infection diseases, such as human immune system disorders (AIDS). One can only make sure that hypodermic and other needles are not being used again, by irrepa¬ rably destroying the needle. With metal needles, such a destruction cannot be brought about easily. An additional disadvantage of metal needles, apart from the danger of infection, is the- risk of injuries caused by their sharp points, even after partial destruction. Therefo¬ re, bending or breaking of the needle does not offer a solution. Making metal needles completely harmless requires complicated measures, such as casting a number of needles in a thermosetting resin. However, hypo- dermic needles and other needles for medical use are also often used in places of the world, where such facilities are not available. Consequently there is a need for needles, for example for health care purposes, which share the advantages of metal needles (high.ben¬ ding strength, sharpness, sterilisability and the like), and which, in addition, can easily be made unsuitable for reuse. It has been surprisingly found now, that needles having the requi¬ red properties can be made permamently unusable in a simple way, when the needle consists at least partly of a liquid crystal polymer. Because the rigid molecular chains of the liquid crystal polymer have been uniaxially directed during the forming process, the needle according to the invention has a high bending stiffness (self-reinfor- cement). The sharpness of the point required for in ection and suture operations can also be easily provided. Further advantages of the needle according to the invention are its chemical and biological inertness and its satisfactory dimensioned stability. The material of the needle is resistent to elevated temperatures, allowing the needle to be simply sterilized. The strength across the needle is lower than the longitudinal strength, but it is still high enough to avoid any risk of bending or breaking during use. By exerting a greater force in the transversal di- rection than occurring in normal use, the needle can be broken, cracked or crushed, readily rendering it unfit for further use. A very simple and effective way of making the needle unusable is the use of a flame (match, lighter, gas flame). This is preferably effected at a tempera¬ ture around or above the melting temperature or the degradation tempe- rature of the liquid crystal polymer. As a result of the melting and/or degrading, the molecules loose their unidirectional orientation causing the material to deform, the needle point to loose its sharpness perma¬ nently and the hollow space in the needle to be lost. The known liquid crystal polymers (LCP's) commercially available are suitable as a material for the needle according to the invention. In general, these are polymers, wherein so called mesogenic or "rigid" groups are present in the main chain or in the side chain. Such mesoge¬ nic groups are constituted of aromatic systems, such as phenylene, naphthylene, biphenylene, pyrazinylene and benzoxazolylene groups and the like, linked by groups susceptible to conjugation, such as carho- nyl, ester, amide, imine, azo groups and the like. In the preferably used polymers, the mesogenic groups are situated in the main chain. Suitable LCP's have liquid crystal behaviour in the melt (thermotropic) or in solution (lyotropic). Examples of thermotropic LCP's are aromatic polyesters and examples of lyotropic LCP's are aromatic polyamides (aramides). Thermotropic LCP's are preferred because they can be pro¬ cessed more conveniently (through the melt). The stiffness and melt be¬ haviour of the LCP's can be varied in a known way by changing the ratio between mesogenic (rigid) groups and flexible groups, such as alkylene groups, or by incorporating angle forming groups such as meta substitu¬ ted aromatic groups and the like. The polyesters can be based for exam¬ ple on terephthalic-.acid, aromatic diols and hydroxy substituted carbo- xylic acids. Examples of commercially available thermotropic LCP's are Vectra (Celanese-Hoechεt) , Ultrax (BASF), Xydar (Dartco), X7G (Idimitsu) and Victrex (ICI). Satisfactory results are obtained using Vectra, as this polyester exhibits less fibrillation. Other suitable thermotropic LCP's are described in European Patent Application 284.726. Lyotropic LCP's such as Kevlar (DuPont) and Twaroπ (Akzo) can be processed in solution. If a particularly high stiffness is required for a special appli¬ cation, the LCP can be blended with reinforcement fibres, such as glass fibres, carbon fibres etc. If on the other hand high flexibility is de¬ sired, such as for infusion purposes, the LCP can be mixed with a ther- moplast polymer. Coating with a biocompatible polymer is another possi- bility .contemplated according to the invention. The needle according to the invention, which can be solid or hol¬ low, can be shaped as desired in any convenient way known in itself, whereby the required uniaxial orientation is obtained (elongational flow). If necessary, a final stretching can be performed for obtaining an even stronger orientation. A solid needle can be shaped for example by injection moulding. Solid needles are suitable, for example for sur¬ gical applications (sutures and the like) and can have any convenient shape (straight, curved etc.) and size: the diameter can be for instan¬ ce 0.2 to 3 mm, depending on the length. The needle according to the invention is preferably hollow and therefore suitable for hypodermic injection of liquids. The hollow needle can also be shaped by injection moulding, but in this case extrusion or fibre spinning offers proces¬ sing advantages. The hollow needle can be combined with conventional needle holders and liquid containers to provide syringes-, infusions etc. The combined needle, needle holder and possibly the liquid contai¬ ner can be manufactured as a single integrated product by means of in¬ jection moulding. The hollow needle can have any desired size. The dia¬ meter of the needle is for example 0.2-3 mm and the wall thickness can be for example 0.05-0.5 mm depending on the length. The needle can be bevelled in a known way, for example by grinding or cutting. The quan¬ tity of material needed for the needle according to the invention is very small; for example, for a hypodermic needle it is usually conside¬ rably less than 100 mg; the cost price per disposable needle is thus very low, so that the use of the somewhat expensive LCP's does not rai- se any economical drawbacks.

Claims: C L A I M S 1. Needle, suitable for medical and health care use, which can easily be made unusable, characterized in that it consists at least partly of a liquid crystal polymer.. 2. Needle according to claim 1, characterized in that it is hollow and suitable for injection of liquids. 3. Needle according to claim 1 or 2, characterized in that the liquid crystal polymer is thermotropic. 4. Needle according to any of claims 1-3, characterized in that the liquid crystal polymer comprises an aromatic polyester. 5. Process of making a needle according to any of claims 1-4 un¬ usable, characterized in that it is exposed to a temperature around or above the melting or degrading temperature of the liquid crystal poly¬ mer for a short period of time.

Inventors: PEETERS JOHANNES HENDRICUS ALP, REIJSENBACH DE HAAN FREDERIK K, PEETERS, JOHANNES, HENDRICUS, ALPHONSUS, REIJSENBACH DE HAAN, FREDERIK, KAREL
Applicants: TNO, NEDERLANDSE ORGANISATIE VOOR TOEGEPAST-NATUURWETEN
Application year: 1989
Main classification: C08G63
IPC codes: A61L31, A61M5, C08G63