MEDICAL APPARATUS

Abstract: There is described a method of manufacturing flexible elastomeric articles, such as gloves, which comprises stretching, e.g. a glove form comprising hand and cuff portions and finger and thumb stumps.

Description: MEDICAL APPARATUS This invention relates to flexible elastomeric articles, for example, gloves and condoms, processes for their manufacture and formers for use in the manufacturing processes. The manufacture of elastomeric gloves by vacuum moulding is known from US Patent No.3124807. The methods described therein comprise the vacuum moulding and heat sealing of two sheets of a thermoplastic 10 elastomeric material. However, gloves made from this method will generally possess one or more seams which may be a source of rupture or leakage. More conventional methods of manufacturing -- • synthetic elastomeric gloves which overcomes the problem of having seams comprises solvent dipping of an appropriately shaped former into a suitable polymer solvent mix, withdrawing the polymer coated former and then drying off the solvent before stripping the glove 0 • therefrom. There are a number of disadvantages with this method, in particular the use of large amounts of solvent is undesirable. Equally, the method of dipping is both time consuming and costly since it is necessary to have a series of formers for dipping which cannot be j - rapidly reused. Additionally, gloves produced by this method are likely to have residual solvent in them which is toxic and therefore an unacceptable containment. 0 Blow moulding of rigid plastic articles is known, eg. in the manufacture of rigid plastics bottles. However, such techniques have not been used with thin walled flexible elastomeric articles. SUBSTITUTE SHEET The present invention seeks to overcome the abovementioned disadvantages by providing flexible elastomeric articles, especially thin walled articles, a method of manufacturing an article body and then stretching the article body in order to produce a flexible elastomeric article. According to the invention we provide a flexible elastomeric body comprising a flexible elastomeric 1 0 material which body is adapted to be stretched beyond the yield point of the flexible elastomeric material to produce a flexible elastomeric article. By the term article we include, inter alia, -*- ° • gloves and condoms. According to a further feature of the invention we provide a flexible elastomeric body according to claim 1 comprising a glove form comprising hand and 20. cuff portions wherein the finger and thumb portions are stumps which stumps are adapted to be stretched beyond the yield point of the flexible elastomeric material to produce a glove. 25. ith reference to gloves, the finger and thumb stumps may be stretched by applying stretching means. Such stretching means may be mechanical means, such as a system of mechanical plungers which stretch the finger and thumb stumps to form the fingers and thumb 50 • of the glove or alternatively a system of clamps which pull the finger and thumb stumps may be used. Preferably, since the finger and thumb stumps have inner and outer surfaces, they may be stretched by SUBSTITUTESHEET creating a pressure differential between the inner surface and outer surface of the stumps. That is stretching may be carried out either by applying a pressure, eg. blow moulding, to the inner surface, or by applying a vacuum, eg. vacuum moulding, to the outer surface of the stumps. It is particularly preferable to apply pressure or vacuum to the glove form. Conventional moulding techniques may be used in 10 the manufacture of the flexible elastomeric body, ie. moulding a flexible elastomeric material into an appropriately shaped mould. Moulding techniques such as blow mouldin, eg. of a parison of a flexible elastomeric material or injection moulding may be used. 15- Conventional conditions known per se could be used in the manufacture of a flexible elastomeric body. The glove form as hereinbefore described may be manufactured by conventional methods known per se, such 20 • as methods described in Handbook of Thermoplastic Elastomers edited by Benjamin M Walker, which is incorporated herein by reference. Preferably the glove form is manufactured by blow moulding a parison of plastics material to produce a glove form comprising -- ■ ' hand and cuff portions wherein the finger and thumb portions are stumps. A condom body may be manufactured by techniques analogous to those used for glove manufacture. 0 In order that the finger and thumb portions of the glove are of smaller thickness to the hand and cuff portions. The finger and thumb stumps in the glove form will generally be of at least equal thickness or SUBSTITUTE SHEET preferably greater thickness than the remainder of the hand and cuff portions of the glove form. During the stretching, the polymer used to produce the gloves undergoes "strain hardening" (the alignment of the long chains of the polymer) , which at a low thickness actually increase the strength of the flexible elastomeric polymer. Thus a glove produced from the glove form may comprise hand and cuff portions of greater thickness than the finger and thumb portions. Preferably the finger and thumb portions are of a thickness less than 50μm and the glove body is of a thickness less than 200μm. As an alternative the cuff portion may be greater in thickness than the hand portion which will be beneficial in the donning of the gloves as the additional thickness provides additional strength and tear resistance to the glove. Whereas in the glove form the hand and cuff portions may generally be of the same thickness as the finger and thumb stumps, ie. less than 200μm. According to yet a further aspect of the present invention there is provided a glove made by the process as hereinbefore described. In particular we provide a glove made from a polyetherester block copolymer such as HYTREL (TM) . A variety of polymers may be used in the manufacture of the articles and flexible elastomeric bodies of the present invention. The material used in the invention may be any thermoplastic elastomer which SUBSTITUTESHEET material may be stretched beyond their yield value to a point such that the material will be permanently deformed, but which still displays elastic properties in the new deformed state. According to the invention we provide a glove form as hereinbefore described comprising a thermoplastic elastomer. By the term thermoplastic elastomer (TPE) we mean compounds which show intermediate behaviour between a thermoplastic and an elastomer. They are provided with crosslinks derived from physical means rather than chemical means as in the case with true rubbers. Consequently they can be processed as thermoplastics, including, eg. blow moulding which is impossible for rubbers. After processing they return to their original state with the crosslinks reforming. There are a number of different types of TPEs and their distinction is typically made on the method of crosslink. They invariably have a two phase system comprising of rubbery matrix, or sort block embedded in which is a stiff phase comprising a glassy or crystalline polymer, or hard block. In particular we prefer thermoplastic elastomers which comprise hard and soft block copolymers, eg. di-block and tri-block copolymers. Typical di- and tri- block copolymers include styrenic di- and tri- block copolymers, eg. styrene-butadiene-styrene and styrene-ethylenebutadiene-styrene. Preferred polymers of this type include those sold by Shell in the UK under the names KRATON and CARIFLEX (Trade Marks) . SUBSTITUTESHEET Other preferred thermoplastic elastomers include polyurethanes where a polyol comprises the soft block and a polyester or polyether glycol the hard block. Polyether polyurethanes are preferred since they tend to be more flexible. Specifically preferred polyurethanes include those available in the UK, ELASTOLLAN (Trade Mark) from BASF, ESTANE (Trade Mark) from BF Goodrich and AVALON (Trade Mark) from ICI. Thermoplastic polyetheresters may also be mentioned. Such copolymers comprise a polyether soft block and a polyester hard block. Preferred polyetheresters include HYTREL (Trade Mark) available from Du Pont. In addition to hard and soft block copolymers, thermoplastics for use in the present invention include alloys and blends. For example, blends of polyurethane and vinyl acetate which are polymerised, eg. having a vinyl acetate content of from 10-30% w/w may be used. Other materials include blends such as polyurethane/ high impact polystyrene (PU/HIPS) and EVA/HIPS, copolyamides, eg. polyether block amides, and silicones. Thus, in particular, hard and soft block copolymers may include those where the soft block may be selected from dienes, eg. alkyldienes such as butadienes, polyols, such as polyether or polyester polyols, polyethers, and vinyl acetates. The hard blocks may be selected from styrenes, glycols, polyesters and polyethylenes. SUBSTITUTESHEET According to the invention we provide the use of a polymer or polymer blend as hereinbefore defined in the manufacture of a flexible elastomeric article body, or a glove form according to the invention. We also provide the use of a polyetherester in the manufacture of an article, eg. a glove according to the invention. The mould for use in the manufacture of the glove 10 form according to the invention is also novel per se. Thus, according to yet a further aspect of the present invention there is provided a mould adapted for use in the production of a blow moulded glove form which mould has internal dimensions in the form of glove, hand and ■L D ' cuff portions and with chambers for fingers and thumb stumps. The mould as hereinbefore described preferably comprises two portions which may be separated to 0 • facilitate removal of the glove form. Further there is provided a mould adapted to receive a glove form comprising a hand and cuff portion and finger and thumb stumps which mould is provided ^ • with finger and thumb shaped chambers adapted to correspond with the finger and thumb stumps in the glove form, said finger and thumb chambers also optionally being provided at the end distal from the hand portion with conduits for, eg. evacuation of the 0 finger and thumb chambers. Preferably the mould is a hollow mould in two parts in the shape of a glove form with finger and thumb stumps. Advantageously a second hollow mould is SUBSTITUTESHEET provided in the form of a complete glove with finger cavities in order that a glove produced in the first mould may subsequently be stretched into a complete glove in this second mould. The invention will now be described, but in no way limited, by way of example, with reference to the accompanying drawings, in which: 10 Figure 1 is a sectional view of a mould for the manufacture of a glove form as hereinbefore described; Figure 2 is a sectional view of the mould of Figure 1 illustrating the blow moulding of a glove -^ • form; Figure 3 is a sectional view of a mould for the manufacture of a glove as hereinbefore described illustrating a glove form in position ready to be " • ° • stretched; and Figure 4 is a sectional view of a glove after stretching of the glove form. 3 Referring to Figures 1 and 2, there is illustrated a hollow mould generally designated 10, which hollow mould 10 comprises two halves 12 and 14 respectively. There is also shown in position between the two halves 12 and 14 a parison 9. Each half 12, 14 0 of the mould 10 is internally shaped in the form two halves of a glove form having internal walls 16 and 18 and having finger and thumb stump chambers generally designated 20. SUBSTITUTESHEET The two halves 12 and 14 co-operate with each other in such a manner that in union the walls 16 and 18 of the mould form a space defining a glove hand portion 22, with an opening 24 providing a cuff portion 26 to the glove. A parison transport mounting 28 into which a blowing pin 30 is fitted co-operates with the opening 24 and acts as a seal. In use, a molten parison tube 9, eg. of 10 polyetherester block copolymer such as HYTREL (TM) is placed between the two halves 12 and 14 of the hollow mould 10. The parison tube 9 is produced by a conventional method of pin extrusion known in the field of blow moulding. Once the parison tube 9 is in 1=- position and mounted around the parison transport mounting 28, the two halves of the mould 12 and 14 are clamped together to form a space defining the glove form. As a consequence of the two halves 12 and 14 engaging and being clamped, the parison tube 9 is ■ ' • " • sealed and the waste end of the parison 38 of the tube trimmed away. The blow pin 30 is then placed into the transport mounting 28 and air is injected into the parison tube 9 which expands until it comes into contact with walls 16 and 18 of the hollow mould 10 ^- takes the shape of glove form 21. The mould 10 can then be opened to remove the glove form 21. Figure 3 illustrates a second hollow mould 32 in the form of a complete glove 34 with finger and thumb 0 cavities generally designated 36. The finger and thumb cavities 36 of the glove 34 has its tip remote from the glove form 21 and conduits 39 which form a connection between the fingers 36 of the mould 32 and a means of suction (not illustrated) . SUBSTITUTESHEET The glove form 21 which is still mounted on the transport mounting 28 and which still contains the air injected into it, is then placed in the second hollow mould 32. In position in the mould 32 each of the protrusions 20 correspond with a respective finger cavity 36. In this cold state each of the protrusions 20 are stretched by the use of suction into their respective finger cavities 36. Each protrusion 20 is stretched to a point where the polymer such as HYTREL 10 exhibits a yielding phenomenon whereby the polymer is permanently deformed, but still displays elastic properties in the new deformed state. Referring to Figure 4, as a result of the suction 1= • applied to the finger and thumb stumps are formed. During the stretching, the polymer used to produce the gloves undergoes "strain hardening" (the alignment of the long chains of the polymer) , which at a low thickness actually increase the strength of the 20 • polymer. Having stretched the finger and thumb stumps as illustrated in Figure 3 and 4 a glove 46 is produced which can then be released from the mould 32. 25. 0 SUBSTITUTESHEET

Claims: CLAIMS 1. A flexible elastomeric body comprising a flexible elastomeric material which body is adapted to be stretched beyond the yield point of the flexible elastomeric material to produce a flexible elastomeric article. 2. A flexible elastomeric body according to claim 1 comprising a glove form comprising hand and cuff portions wherein the finger and thumb portions are 10 stumps which stumps are adapted to be stretched beyond the yield point of the flexible elastomeric material to produce a glove. 3. A method of manufacturing a flexible elastomeric !5. body according to claim 1 which comprises moulding a flexible elastomeric material into an appropriately shaped mould. 4. A method according to claim 3 which comprises 0 blow moulding a parison of a flexible elastomeric material into an appropriately shaped mould. 5. A method according to claim 3 which comprises injection moulding a flexible elastomeric material into 5- an appropriately shaped mould. 6. A glove form according to claim 2 wherein the hand and cuff portions are of substantially the same thickness as the finger and thumb stumps. 0 7. A glove form according to claim 2 comprising a thermoplastic elastomer. 8. A method of manufacturing a flexible elastomeric article which comprises stretching a flexible elastomeric body beyond the yield point of the elastomeric material. 9. A method of manufacturing a flexible elastomeric glove which comprises applying stretching means to the stumps according to claim 2 to produce finger and thumb portions. 10. 10. A method according to claim 9 wherein a pressure differential is created between the inner surface and the outer surface of the finger and thumb stumps. 1 ^- 11. A method according to claim 10 wherein the pressure differential is created by applying a vacuum to the outer surface of the finger and thumb stumps. 12. A flexible elastomeric glove comprising hand and 1 0 cuff portions and finger and thumb portions wherein the hand and cuff portions are greater in thickness than the finger and thumb portions. 13. A flexible elastomeric glove according to claim ^- 12 wherein the hand and cuff portions have a thickness of less than 200μm. 14. A flexible elastomeric glove according to claim 12 wherein the finger and thumb portions have a 30. thickness of less than 50μm. 15. A glove made from a polyetherester block copolymers. 16. A mould adapted for use in the manufacture of a flexible elastomeric body according to claim 1. 17. A mould according to claim 16 which has internal dimensions defining a glove form comprising hand and cuff portions and with chambers for finger and thumb stumps. 18. A mould according to claim 16 which has internal 10 dimensions defining the shape of a stumpy condom. 19. A mould according to claim 16 which is a hollow mould in two parts. 15. 20. The use of a thermoplastic elastomer in the manufacture of an article body according to claim 1. 21. The use of a polyetherester in the manufacture of a flexible elastomeric article. 22. A mould adapted for use in the manufacture of a flexible elastomeric glove and adapted to receive a glove form comprising hand and cuff portions and finger and thumb stumps which mould has internal dimensions in ώJ * the form of a glove with hand and cuff portions and finger and thumb portions. 23. A mould according to claim 22 wherein the ends of the finger and thumb chambers distal from the hand portion are provided with conduits. 24. A mould according to claim 23 wherein the conduits are adapted to evacuate the finger and thumb chambers. 10 15. 0 5 0

Inventors: SANDBANK BARRY MICHAEL, SANDBANK, BARRY, MICHAEL
Applicants: SANDBANK BARRY MICHAEL, SMITH & NEPHEW, SANDBANK, BARRY, MICHAEL, SMITH & NEPHEW PLC.
Application year: 1993
Main classification: B29C49
IPC codes: A41D19, A61B19, A61F6, B29B11, B29C45, B29C49, B29C51, B29K67, B29L31