GB2444128A

GB2444128A - Biocidal cover

Info

Publication number: GB2444128A
Application number: GB0711221A
Authority: GB
Inventors: Philip Reed
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-11-27
Filing date: 2007-06-11
Publication date: 2008-05-28
Also published as: GB0711221D0

Abstract

A biocidal cover, e.g. for a door handle 3, incorporates a biocidal substance in the form of a hydrolysable glass matrix which releases silver (Ag+) ions. The cover 4 is formed of a sleeve of extruded heat-shrink material which is applied by means of heat, e.g. using a hot air gun 5. The method of covering the door handle 3 with the biocidal cover is disclosed.

Description

BIOCIDAL COVER

TECHNICAL FIELD OF THE INVENTION

This invention relates to the problem of reducing the everyday risk of cross-infection by micro-organisms.

BACKGROUND

Controlling the spread of diseases caused by bacteria and fungal infections is a major problem in hospitals, and indeed, in other areas to which people have access. The emergence of bacteria which are resistant to most known antibiotics is a serious problem worldwide. Many bacterial diseases such as MRSA, clostridium difficile and certain strains of e. coil can prove to be fatal, and are easily acquired by direct skin contact with surfaces contaminated with these micro-organisms. C. difficile causes a range of diseases from antibiotic-associated diarrhoea to a life-threatening colon disease called pseudomembranous colitis, and presents a particular problem for healthcare professionals because it can only be treated with two antibiotics, metronidazole and vancomycin, and there is concern that these too will soon become ineffective. Such diseases are easily acquired by direct skin contact with surfaces contaminated with the bacteria, and a wide variety of fungal diseases can also be propagated in a similar manner.

Common hygiene advice aimed at reducing the spread of such diseases is to practice frequent hand washing, preferably using disinfecting solutions, but although this remains good practice it can never be completely effective no matter how diligently it is carried out. For example, if someone goes to the toilet in a restaurant and washes their hands as advised they can easily pick up new infections as they leave the toilet area. Cross-infection can also take place by sharing common items such as pens.

The addition of various bioactive agents to moulded thermoplastic articles in order to combat the growth of micro-organisms on the thermoplastic surfaces is known. For example, US 200410137075 Al discloses the use of a bloactive glass as an additive for polymers, which does not contain any heavy metals. Non-specific biocidal polymers are also used in various injection moulded plastic items, well known examples being 2,4,4'-trichloro-2'-hydroxydiphenol ether, or 5-chloro-2-phenol (2,4 dichiorophenoxy) as sold under the trademark Micro ban, by Microban Products Company, Huntersville, N.C. However, many such agents require regular surface activation (e.g washing with water) to maintain their effectiveness, and show a marked reduction in antibacterial activity with time.

GB 2 375 766 A discloses an extrudable PVC composition having biocidal properties, and GB 2 297 552 A discloses a sprayable powder coating composition which can be used to coat door handles. JP 7 331 072 A discloses a shrinkable silicone rubber composition having antibacterial properties which contains an antimicrobial ceramic.

It is widely known that silver, in the form of metallic silver or silver salts, is toxic to micro-organisms. WO 2003 060 003 Al discloses an antimicrobial solid surface material containing a chitosan-silver complex JP 9 059 523 A and JP 2000302 616 A both disclose antibacterial resin compositions containing silver.

Resins and other solid materials having biocidal properties can only be incorporated during manufacture of the article, and such materials are not generally suitable for post-treatment of articles which may already be in service. Furthermore, the post-application of surface coatings such as sprays or paints is not always convenient, e.g. where the articles are already in use in a busy environment such as a hospital, and may incur significant additional costs.

The present invention seeks to provide a new and inventive way of reducing the spread of infections through hand transmission, which is quick and easy to apply to existing articles, and which is highly effect,ve against antibiotic-resistant bacteria for a long period.

SUMMARY OF THE INVENTION

The present invention proposes a method of providing an article having an elongate gripping portion with effective biocidal properties) which comprises: -sliding a sleeve over the elongate gripping portion, the sleeve being formed of thermoplastic material which incorporates a biocidal substance which releases silver ions (Ag+); and -applying sufficient heat to the sleeve to cause it to shrink onto and tightly engage the elongate gripping portion.

The sleeve may be applied to any article having an elongate gripping portion such as door handle or a pen.

The biocidal substance preferably comprises a hydrolysable matrix which releases silver ions (Ag+).

Heavy metal ions such as silver interfere with, and may block the cellular transport mechanisms of bacteria and other micro-organisms, resulting in their rapid destruction. The ions may also cause similar effects in many yeasts and fungi, although their effect on the tissue cells of higher organisms such as humans is benign.

The hydrolysable matrix may be added to the thermoplastic polymer in a particulate form. A particularly effective form of hydrolysable matrix comprises particles of glass. Such a matrix is extremely stable to temperatures beyond 500 C, and can withstand extreme acid or alkaline conditions without significantly reducing the release of the silver ions. The use of a hydrolysable glass matrix also enables a high concentration of silver ions in a highly active form to be maintained at the surface of the thermoplastic polymer For optimum effect against known pathogenic bacteria the silver-containing matrix is preferably added to the thermoplastic in a proportion of between 2% and 10% by weight, the preferred proportion being about 6% by weight.

The invention also provides an article having an elongate gripping portion which is provided with a sleeve of heat-shrink material which is heat-shrunk onto the article to tightly engage the elongate gripping portion, the sleeve being formed of thermoplastic material incorporating a biocidal substance which releases silver (Ag+) ions.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Figure 1 is a general view of a door having a biocidal cover in accordance with the invention; FiQure 2 is a side view of the cover during application to the door handle; and FiQure 3 is a side view of a writing implement having a biocidal cover in accordance with the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. I shows one side of a door I which is hung in a doorway through which people can pass. By way of example, the invention may be applied to a toilet door, although it will be appreciated that the invention may advantageously be applied to any door, whether in a public building, in commercial premises, in the home, on board a ship, etc. It should also be noted that although only one side of the door is shown and described the invention may advantageously be applied to both sides of the door.

The door I is hung on hinges 2 and may be opened and closed in known manner using a door handle 3. In this example the handle is of the lever type, although the invention could also be applied to other kinds of handle having an elongate gripping portion, for example pull-type handles which are releasably secured to the door at both ends, It has been found that when using a door, hand contact is most frequently made directly with the door handle 3 during opening and closing of the door. In the present invention, a biocidal cover 4 is applied to the door handle 3. As shown in Fig. 2, the cover is of tubular form and comprises a length of extruded heat-shrink thermoplastic sleeve such as a polyolefin or PVC, which preferably has a shrink temperature of about 100 C, although sleeve with higher shrink temperatures can be used depending on the application.

The sleeve incorporates a biocidal additive such as Bactiglas. In its unshrunk state the cover 4 is large enough to pass easily over the lever portion of the handle 3 and is of a length which is sufficient to cover most of the length of the handle. With some kinds of handle it may be necessary to remove the handle from the door before the sleeve is applied. When the cover is in place a hot air gun 5 or other heat source capable of producing a temperature of at least 100 C is used to heat the cover, e.g. working from one end to the other as shown, so that the cover shrinks in diameter and tightly grips the handle, When anyone grips the cover 4 when using the handle 3 any bacteria, viruses or fungi transferred to the handle are rendered inactive.

The cover has an active biocidal life of several years. When required, the cover may easily be removed by slitting the cover along its length using a sharp knife, and a new biocidal cover may then be applied. Alternatively, the new cover may simply be heat-shrunk over the old one.

Fig. 3 shows another use of biocidal covers in accordance with the invention. In this case the cover is applied to a disposable writing implement such as a ball point or fibre tip pen, having an elongate body and a writing tip 11. The tubular cover 12 comprises a length of extruded heat-shrink thermoplastic sleeve having a shrink temperature of about 100 C, which incorporates a biocidal additive such as Bactiglas In its unshrunk state the cover 12 can be slid over the body 10 to cover most of its length. A hot air gun or other heat source is used to heat the cover so that the cover shrinks in diameter and tightly grips the pen. When anyone uses the pen any bacteria, viruses or fungi transferred to the cover 12 are destroyed. The active biocidal life of the cover exceeds the normal life of a disposable writing implement The biocidal sleeve can be produced in different diameters for application to articles of different sizes.

In each of the above embodiments the cover incorporates Bactiglas AM 93456 which releases silver (Ag+) ions. The silver ions are held in particles of a hydrolysable glass matrix which is extremely stable to temperatures beyond 500 C and protects the ions during thermal processing of the plastic. The glass particles are thoroughly mixed into the thermoplastic moulding material, in a proportion of about 6% by weight, to achieve a uniform distribution. Once the plastic is set, in the presence of minute amounts of moisture silver ions are released from the surface of the plastic at a continuous but extremely slow rate. The slow release of Ag+ ions acts as a biocide which interrupts the normal membrane functions of bacteria, algae and fungi which come into contact with the surface of the cover, resulting in rapid destruction of the micro-organisms. At the surface of the thermoplastic the released silver ions either complex in solution or loosely combine with the polymer forming active, but highly stable complexes which remain at the surface, holding the silver in an active form.

Tests carried out by a Japanese laboratory have shown that the surfaces of the polymer are better than 99.995% effective at destroying MRSA bacteria1 e.coli and s.aureus, which is considerably more effective than other antibacterial surface treatments, Independent tests have also confirmed that the antibacterial properties are not significantly diminished after a period of eight years.

It wilt be appreciated that the features disclosed herein may be present in any embodiment of the invention in any feasible combination. Whilst the above description places emphasis on those areas which, in combination, are believed to be new, protection is sought for any inventive combination of the features disclosed herein.

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Claims

1. A method of providing an article having an elongate gripping portion with effective biocidal properties, which comprises: -sliding a sleeve over the elongate gripping portion, the sleeve being formed of thermoplastic material which incorporates a biocidal substance which releases silver ions (Ag+); and -applying sufficient heat to the sleeve to cause it to shrink onto and tightly engage the elongate gripping portion.

2. A method according to Claim I in which the sleeve is formed by an extrusion process.

3. A method according to Claim 1 or 2 in which the biocidal substance comprises a hydrolysable matrix which releases the silver ions (Ag+).

4. A method according to Claim 3 in which the hydrotysable matrix is distributed throughout the thermoplastic polymer in a particulate form.

5. A method according to Claim 4 in which the hydrolysable matrix comprises particles of glass.

6. A method according to Claim 5 in which the particles of glass are incorporated into the thermoplastic polymer in a proportion of between 2% and 10% by weight.

7. A method according to Claim 5 in which the particles of glass are incorporated into the thermoplastic polymer in a proportion of substantiauy 6% by weight.

8. A method according to any preceding claim in which the sleeve is formed from a polyolefin.

9. A method according to any of Claims 1 to 7 in which the sleeve is formed from PVC.

10. A method according to any preceding claim in which the article is a door handle.

11. A method according to any preceding claim in which the article is a writing implement.

12. An article having an elongate gripping portion which is provided with a sleeve of heat-shrink material which is heat-shrunk onto the article to tightly engage the elongate gripping portion, the sleeve being formed of thermoplastic material incorporating a biocidal substance which releases silver (Ag+) ions.

13. An article according to Claim 12 in which the sleeve is formed by an extrusion process.

14. An article according to Claim 12 or 13 in which the biocidal substance comprises a hydrolysable matrix which releases the silver ions (Ag+).

15. An article according to Claim 14 in which the hydrolysable matnx is distributed throughout the thermoplastic polymer in a particulate -11 -form.

16. An article according to Claim 15 in which the hydroiysable matrix comprises particles of glass.

17. An article according to Claim 16 in which the particles of glass are incorporated into the thermoplastic polymer in a proportion of between 2% and 10% by weight.

18. An article according to Claim 16 in which the particles of glass are incorporated into the thermoplastic polymer in a proportion of substantially 6% by weight.

19. An article according to any of Claims 12 to 18 in which the sleeve is formed from a polyolefin.

20. An article according to any of Claims 12 to 18 in which the sleeve is formed from PVC.

21. An article according to any of Claims 12 to 20 which comprises a door handle.

22. An article according to any of Claims 12 to 20 which comprises a writing implement,

23. A method of providing an article having an elongate gripping portion with effective biocidal properties which is substantially as described with reference to the drawings.

24. An article which is substantially as described with reference to -12 -the drawings.

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