GB2263114A

GB2263114A - Biocidal rubber latex products and methods of making same

Info

Publication number: GB2263114A
Application number: GB9126933A
Authority: GB
Inventors: Raymond William Winter; Nigel Barker; Alan Colin Dixon
Original assignee: YAD HYGIENE PRODUCTS Ltd
Current assignee: YAD HYGIENE PRODUCTS Ltd
Priority date: 1991-12-19
Filing date: 1991-12-19
Publication date: 1993-07-14
Also published as: GB9126933D0

Abstract

A method of forming a latex product comprises providing a latex formulation or latex article, providing a solution including a biocide, and contacting the formulation or article and the solution so that the biocide becomes incorporated in the latex formulation or article to provide a latex product with biocidal properties. The biocide is preferably a biguanide. In other aspects, the invention relates to a rubber latex product incorporating a biocide, and to a coagulating solution for a natural or synthetic rubber latex formulation which comprises a biocide. The coagulating solution may comprise a solution of a biguanide and a calcium salt in water and/or an alcohol. The biguanide may be a salt of the monomeric form, e.g. chlorhexidine acetate, or of the polymeric form.

Description

BIOCIDAL RUBBER LATEX PRODUCTS AND METHODS OF MAKING SAME Technical Field of the Invention The invention relates to products made from natural and synthetic rubber latex having bacteriocidal. antiseptic, disinfectant and/or fungicidal effect.

Background Art Rubber products or goods are relatively easily made by processes involving dipping, casting or spreading. These goods find application in many areas inter alia as condoms or more particularly in surgical use as catheters, tubing or gloves. Gloves, condoms and related wear are used to confine and contain e.g. microorganisms: spermatozoa, and pathogenic bacteria. Such rubber goods do not of themselves have bacteriostatic or bactericidal action. Failure of the rubber membranes to confine microorganisms by reason of, for example, pin holes, accidental scalpel damage, mishandling may release the organisms with disadvantageous effects.

A suitable biocide is chlorhexidine acetate. However, neither this biocide nor other salts of chlorhexidine nor its polymeric derivatives e.g. Vantocil can be incorporated in significant amounts into a latex since instability and precipitation of the rubber occurs rendering dipping, casting and spreading, operations difficult unless a chelating agent is added.

The chelating agent. however. may adversely affect the properties of the rubber goods.

Latexes are colloidal suspensions of polymer particles in water as distinguished from solid rubbers or plastics of solutions thereof.

Natural rubber latex is a product of the Hevea brasiliensis tree. Svnthetic latexes are polymerised in solution and emulsified bv dispersion techniques: alternatively they may be prepared by emulsion polymerisation.

Some of the materials used in latexes may, serve as fungal and bacterial nutrients. This is especiallv true of natural latex and latexes compounded with natural products such as casein but is also true to a lesser degree with all latexes. Preservatives often used in the latex are often added to protect the substrate (as in carpets) as well as the polymer. Such fungicide, however, may not be acceptable in surgical formulations.

It is an object of the invention to reduce microbial transfer on surgical and other rubber goods to an acceptably low level without creating harmful or unwanted side effects.

It is also an object of the invention to prevent or hinder unwanted organisms being transmitted from one site to another by the inclusion of a biocide. The site may be associated with living body tissue or may be associated with handling bacteria or viruses in hospitals or laboratories.

According to one aspect of the invention there is provided a method of forming a latex product comprising providing a latex formulation or latex particle. providing a solution including a biocide. and contacting the formulation or article and the solution so that the biocide becomes incorporated in the latex formulation or article to provide a latex product with biocidal properties.

According to a second aspect of the invention there is provided a rubber latex product whenever formed by a method as hereinbefore defined.

According to a third aspect of the invention there is provided a coagulating solution for a natural or synthetic rubber latex formulation, comprising a biocide.

To be effective, the biocide or mixture of biocides should preferably possess a broad spectrum of anti-biocidal activity yet be recognised as safe to handle according to normal practice.

A suitable biocide is based on a salt of a monomeric biguanide e.g. 1,6 di (chlorophenyl diguanido) hexane, 'chlorhexidine' (available from ICI plc) or a salt of the polymeric form e.g. Vantocil (also available from ICI plc). The activity is enhanced when an iodophor such as Isostat is used in combination with chlorhexidine.

The activity of chlorhexidine is quoted in Principles of Practice of Disinfection, Preservation and Sterilisation by A.D. Russell, W.B. Hugo and G.A.J. Aycliffe, Blackwell Scientific Publications, Oxford 1982.

In addition, chlorhexidine has been shown to be effective against a virus, herpes hominus (A. Bailey, M. Longson, J. Clin. Path. 19972 25 76-78).

Vantocil has also been shown to be effective against a wide variety of microorganisms as quoted in ICI literature, Technical Information B13.80 1981.

Latexes can be converted to rubber goods or products bv straight dipping, coagulant dipping or heat-sensitive dipping, dipped products subsequently being dried, and vulcanized in hot air ovens at about 100"C.

Thus using the invention it is possible to use a guanide as a biocide in latex formulations combined with the method of incorporating the biocide, more particularly as described in Example 1 where the biocide itself is used as a cocoagulating agent supporting the use of a calcium salt which is the normal coagulating agent.

Example 1 A dry test tube was immersed in natural rubber latex and withdrawn slowly so that an even coating was obtained. The latex-coated tube was then dipped into an aqueous solution containing 3chic Vantocil and 20% calcium nitrate.

The coated tube was then immediately removed, rinsed with water, allowed to dry thoroughly and vulcanised at llO"C for 10 minutes in an oven. The rubber latex product was then stripped from the tube. In this example, the biocidal activity was found to be confined to the inner surface and was substantive. Eversion of the product would return the active surface to the outside.

Example 2 A clean test tube was dipped into a solution comprising 5% chlorhexidine acetate and 20cos calcium nitrate in a 50:50 solution of alcohol and water mixture. Prior to complete drying, the coated tube was dipped into rubber latex, withdrawn, dried and vulcanised at 100"C. The product was stripped from the tube. The biocidal activity was confined to the outer surface.

Example 3 A fully cured latex tube open at both ends was removed from its former and completely immersed in 5% chlorhexidine acetate in butvl alcohol and allowed to remain for 20 minutes. the tube was removed, drained optionally washed with butyl alcohol. substantive biocidal activity was observed on both the inside and outside of the tube. In this example the butyl alcohol served to swell the latex slightly to allow the ingress of the biocide.

Example 4 A test tube was dipped into a solution of 5% chlorhexidine acetate and 20% calcium nitrate in a 50:50 solution of alcohol and water mixture. Prior to complete drying the coated tube was dipped into latex, withdrawn and dipped once again into the chlorhexidine acetate solution. After withdrawal, vulcanizing at 100"C and stripping, the biocidal activity remained on both sides.

Example 5 A drv test tube was immersed in latex and slowlv withdrawn. The latex coated tube was partially dried and then dipped into 4% Vantocil in water and left for 10 minutes. Withdrawal followed by optional rinsing with water, drying and vulcanizing at 110 C for 10 minutes and then stripping gave a product with biocidal activity on the inside surface. In this example the biocide was able to diffuse into the onlv partially dried latex.

It is understood that in any of the above procedures the dipping coagulating process may be repeated to increase the thickness of the product and to increase the biocidal activity. The biocidal activity in each case was examined by cutting specimens from a portion of the cured latex and coating the biocide treated surface with flora from the human gut. the rubber samples were incubated and the flora counted. None remained on the samples. In each case, the chlorhexidine or Vantocil had effectively killed the microorganisms whilst no deterioration of the properties of the rubber were noted.

Thus using the invention there is (1) Use of mixtures of guanidine.

(2) Use of Vantocil as a fungicide; and (3) Use of the above singly or in combination as the coagulating electrolyte when combined with the more usual calcium nitrate or chloride.

Claims

1. A method of forming a latex product comprising providing a latex formulation or latex article. providing a solution including a biocide, and contacting the formulation or article and the solution so that the biocide becomes incorporated in the latex formulation or article to provide a latex product with biocidal properlies.

2. A method according to Claim 1. the biocide comprising a biguanide.

3. A method according to Claim 1 or Claim 2, the contacting step comprising immersing the latex formulation coated on a former in the solution whereby the formulation is coagulated.

4. A method according to Claim 1 or Claim 2, the contacting step comprising immersing the solution coated on a former in the latex formulation whereby the formulation is coagulated on the former.

5. A method according to Claim 1 or Claim 2, the contacting step comprising immersing a fully cured latex article in a rubber swelling medium containing a biocide.

6. A method according to Claim 3, comprising partially drying the latex formulation on the former prior to contacting with the solution.

7. A method according to Claim 4, comprising partially drying the solution on the former prior to contacting with the latex formulation.

8. A method according to any preceding Claim, the contacting step comprising a dipping operation.

9. A method according to any of Claims 2 to 8, the solution comprising an aqueous solution of a calcium salt and a monomeric or polymeric biguanide.

10. A method according to any of Claims 2 to 8, the solution comprising a calcium salt and a monomeric or polymeric guanide in alcohol.

11. A method according to any of Claims 2 to 8. the solution comprising an aqueous/alcohol solution of a calcium salt and a monomeric or polymeric biguanide.

12. A method according to any of Claims 9, 10 or 11, the biguanide comprising a salt thereof.

13. A method according to any of Claims 9 to 12, the biocide comprising a mixture of biguanides or salts thereof.

14. A method according to any preceding claim, including vulcanising the latex formulation.

15. A method according to Claim 1, of forming a latex product, substantially as hereinbefore described.

16. A method of forming a latex product, substantially as hereinbefore described in any of the Examples.

17. A method according to any preceding Claim. in which the latex is a natural or synthetic rubber latex.

18. A rubber latex product incorporating a biocide.

19. A rubber latex product whenever product whenever produced by a method according to any one of Claims 1 to 17.

20. A rubber latex product whenever produced as hereinbefore described in any one of the Examples.

21. A coagulating solution for a natural or synthetic rubber latex formulation, comprising a biocide.

22. A solution according to Claim 21, which is an aqueous solution of a calcium salt and a biguanide.

23. A solution according to Claim 21. which is a solution of a calcium salt and a biguanide in alcohol.

24. A solution according to Claim 21, which is a solution of a calcium salt and a guanide in water and alcohol.

25. A solution as hereinbefore described in any one of the Examples.