FIELD OF THE INVENTION

[0001] The present invention relates to a door pull handle having an antimicrobial agent.

BACKGROUND OF THE INVENTION

[0002] Door handles have the potential to harbour unwanted microbes on their surfaces and in any recesses that are present. Even in the most sanitary of environments it is a constant challenge to ensure that such items do not facilitate the propagation of organisms potentially hazardous to human health.

[0003] Given that bacteria can double in population on unprotected surfaces every twenty minutes, there is a need to inhibit the growth of such organisms on frequently used items. It is also desirable to prevent the growth of mould, mildew and other fungi, which can escalate if not adequately controlled.

[0004] Of particular importance are items employed in environments having a high throughput of human traffic, where the risk of contamination and spread is most prevalent. Such environments include, but are by no means limited to, schools, hospitals, doctor's surgeries, clinics, museums, community centres, airports, and other workplaces in general. Indeed, acquired infections in hospitals, including methicillin- resistant Staphylococcus aureus (MRSA), can prove to be fatal.

[0005] In addition, microbes may also be responsible for a wide range of undesirable effects such as product deterioration, malodour, and discolouration.

[0006] Previous solutions to prevent the spread of microbes have included providing polymer sleeves impregnated with an antimicrobial agent over metallic door handle pull bars and backing plates, and metallic pull bars and backing plates made from antimicrobial copper or other metals treated with an antimicrobial finish. However, the sleeves have a limited lifespan, particularly in high use environments such as hospitals and schools, and are subject to cracking and degradation, or become quickly ineffective when the surface is grazed due to normal wear and tear. All current antimicrobial door handles are also expensive to manufacture. The junction between the pull bar and the backing plate, and fixing holes for securing the backing plate to the door may all still provide a haven for dirt ingress upon which unwanted microbes can thrive.

SUMMARY OF THE INVENTION

[0007] A first aspect of the invention provides a door pull handle comprising a pull bar and a backplate, wherein the pull bar and the backplate are integrally formed as a unitary item which comprises a thermoplastic polymer material and an antimicrobial agent dispersed within the thermoplastic polymer material.

[0008] As used, the term "thermoplastic polymer" refers to a polymer that becomes pliable or mouldable above a specific temperature, and returns to a solid state upon cooling. Thermoplastics have molecular chains which associate through intermolecular forces, thereby allowing them to be remoulded because the intermolecular interactions spontaneously reform upon cooling. In this way, thermoplastics differ from thermosetting polymers, since thermosetting polymers form irreversible chemical bonds during the curing process, i.e. the polymer structure breaks down upon melting and does not reform upon cooling.

[0009] The invention is advantageous in that the pull bar and the backing plate are produced as a unitary item. As a result, the overall strength of the door handle is improved, since there are no joining sections of the pull bar and backing plate which may be susceptible to failure or loosening. The absence of joins in the structure also reduces the ability of bacteria and fungi to accumulate in recesses that are relatively inaccessible to everyday cleaning.

[0010] Any thermoplastic polymer material is suitable for use in the invention, provided there is sufficient compatibility with the antimicrobial agent. Suitable examples of thermoplastic polymer include acrylonitrile butadiene styrene (ABS), polyoxymethylene (POM), acrylate, ethylene vinyl acetate (EVA), general purpose polystyrene (GPPS), high impact polystyrene (HIPS), nylon, polyethylene (PE), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), polysulfone (PSU), polyurethane (PU), and polyvinyl chloride (PVC). Preferably, the thermoplastic polymer material comprises at least one polymer from the above list.

[0011] Preferably the thermoplastic polymer material is polypropylene (PP). This material is easily processed and exhibits a favourable level of compatibility with a range of antimicrobial agents. The use of polypropylene is also preferred since it provides a non-porous surface finish. This reduces the ability of microbes to penetrate and embed themselves under the surface of the door handle, and makes the surface easier to clean.

[0012] The term "antimicrobial agent" is used to refer to a substance that kills or inhibits the growth of microorganisms, such as bacteria, fungi, or protozoans. Antimicrobial agents either kill microbes (microbiocidal) or prevent the growth of microbes (microbiostatic).

[0013] The antimicrobial agent may be an organic additive. These additives function by having an organic compound within the polymer material that migrates to the surface over a short space of time to create a film on the surface of the polymer. When the surface of the polymer is cleaned and the surface film is wiped off, a fresh layer of film spontaneously regenerates. This process is repeated every time the plastic door handle is cleaned, touched or the microbe is lost to the environment.

[0014] Suitable organic additives may comprise siloxane-based polymeric antimicrobials, such as Biosafe HM-1400 (a cationic quaternary ammonim salt), triclosan (a polychloro phenoxy phenol, IUPAC name: 5-chloro-2-(2,4- dichlorophenoxy)phenol), zinc pyrithione (IUPAC name: bis(2-pyridylthio)zinc 1, 1'- dioxide), and/or folpet (IUPAC name: N-(trichloromethylthio)phthalimide). [0015] Alternatively, the antimicrobial agent may be an inorganic additive. These additives function by utilising metal ions as their active agent (e.g. silver ions), whereby the metal ions are stored within the plastic and remain effective therein throughout the lifetime of the product. Given that such inorganic additives are present throughout the entire polymer material, the product maintains its antimicrobial properties even if the outer surface of the plastic is compromised in any way, such as by being accidentally scratched or knocked.

[0016] Suitable examples of silver-based additives include colloidal silver, silver salts, and nanosilver. A particularly preferred antimicrobial agent comprises silver ions, such as the known silver additive manufactured under the code SHT-860. When such an inorganic additive is employed, a more stable and safe product is obtained. The resulting product exhibits a lifetime of greater than 10 years whilst constantly maintaining an appropriate level of antimicrobial properties. In addition, the antimicrobial agent is not affected or diminished by heat and/or steam treatment when cleaned in such a manner, thus allowing the door handle to be easily and effectively washed. Products made from such materials can therefore be used safely in a wide variety of environments, and can be subjected to long periods of non-use, such as when placed in storage or exported to distant marketplaces.

[0017] The level of antimicrobial agent in the door handle is not limited, although for reasons of economy it is desirable that the door handle contains between 0.5 and 15% antimicrobial agent by weight of the thermoplastic polymer material. Preferably, the antimicrobial agent is present at a level of 1 to 10%, more preferably 2 to 8%, even more preferably 3 to 7%, most preferably 4 to 6% by weight of the thermoplastic polymer material. In particular, it is advantageous if the antimicrobial agent is dispersed within the thermoplastic polymer material. This allows both components to be easily combined and processed into the desired shape of door handle.

[0018] Having the antimicrobial agent dispersed within the thermoplastic polymer material is a significant advantage because it fixes the agent in place and ensures that the entire polymer structure exhibits the desired antimicrobial properties. As such, it does not matter if the door handle suffers from any structural damage, since the same properties are maintained throughout. This is unlike a product having a cover or outer film, because these elements may lose their antimicrobial properties over time or when damaged.

[0019] The surface of the pull bar and/or backing plate may be smooth in nature or textured with a particular pattern. A textured pattern may be employed, for example, to impart frictional properties to the surface, as a means to prevent slippage. The pull bar and/or backing plate may have a continuous, non-porous surface with no gaps or breaks on the outer surface, and may have rounded edges. The pull bar and backing plate may have smooth radius joins, e.g. the door pull handle may have smooth radius corners where the pull bar meets the backplate. This allows for easy cleaning and prevents the build-up of unwanted microbes where the pull bar meets the backplate. Preferably, all corners and edges of the door handle are rounded to allow easy cleaning and to prevent the build-up of microbes.

[0020] Preferably the door pull handle consists exclusively of the pull bar and backplate and has no other parts. The door pull handle may be obtainable by injection moulding. The employment of such a method is especially since the entire door handle may be efficiently produced in a single process. Injection moulding (including air- assisted injection moulding) is particularly advantageous because it leads to smooth surfaces with fewer connection points.

[0021] The door pull handle is preferably devoid of fixing holes. The backing plate may be adhered to the door thereby avoiding the need to bolt through the door, allowing for simple installation, and replacement. Alternatively, the door pull handle may have screw holes for fixing the door pull handle to a door. The door pull handle is preferably for use on internal doors. For use on internal fire doors it is desirable that the door pull handle is screwed, and not bolted, to the door. In a fire the plastic door pull handle may melt or burn and detach from the door but in the absence of a bolted connection the fire door will remain sealed in its door frame. By contrast a bolted connection may leave a hole through the door between opposing sides of the door. Conventional two-piece metallic door handles require bolting through the door to join the pull bar to the backplate and to the door, but the metal will withstand fires up to a much higher temperature so the through hole in the door is not a problem for fire regulations. The inventors have surprisingly found that the one-piece plastic door pull handle of the invention which, due to its one-piece unitary constructions does not require bolting through the door, may be used on a fire door whilst fully complying with existing fire regulations. The door pull handle may be attached to the door surface by screws passing through screw holes in the backplate.

[0022] The pull bar may comprise a solid body. This is to say, the pull bar has a body that is not tubular and contains no large voids.

[0023] The door pull handle is preferably devoid of coatings.

[0024] A further aspect of the invention provides a method of producing a door pull handle according to any preceding claim, comprising the steps of: combining a masterbatch or powder dispersion of a thermoplastic polymer material and an antimicrobial agent to form a mixture;

heating the mixture so as to form a melt;

introducing the melt into a mould of the desired shape; and

allowing the melt to cool.

[0025] The melt may be injection moulded. In particular, the antimicrobial agent may be added and mixed with the thermoplastic polymer material prior to injection into the moulding tool. This guarantees efficient mixing of the components before they are heated to form a melt. Typical melt temperatures are between 180 and 320 °C, preferably 210 to 290 °C. Once the melt has formed, a ram or screw-type plunger is used to force molten plastic material into a mould cavity, thereby producing a solid or open-ended shape that has conformed to the contour of the mould.

[0026] The injection moulding process may include high pressure injection of the raw material into a mould which shapes the polymer into the desired shape. Moulds can be of a single cavity or multiple cavities. In multiple cavity moulds, each cavity can be identical and form the same parts or can be unique and form multiple different geometries during a single cycle.

[0027] Moulds are generally made from tool steels, but stainless steels and aluminum molds are also suitable for certain applications. Aluminum moulds typically are ill- suited for high volume production or parts with narrow dimensional tolerances as they have inferior mechanical properties and are more prone to wear, damage and deformation during the injection and clamping cycles, but are cost effective in low volume applications as mould fabrication costs and time are considerably reduced. Many steel moulds are designed to process well over a million parts during their lifetime.

[0028] The door handles may also be produced in a variety of different colours, as appropriate for the specific end use. Colouring of the thermoplastic polymer material may be achieved by adding a colour masterbatch at a level of 1 to 6% by weight of the thermoplastic polymer material to the mixture prior to heating. For school and healthcare environments it may be advantageous to colour code the door handles to a particular location, such as a classroom, ward, waiting room, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0030] Figures la and lb are plan and side views of a door handle according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENT(S)

[0031] A door handle 1 according to an embodiment of the invention is shown in Figures la and lb and comprises a pull bar 2 and a backplate 3, wherein the pull bar 2 and the backplate 3 are integrally formed as a unitary item which comprises a thermoplastic polymer material and an antimicrobial agent dispersed within the thermoplastic polymer material. [0032] The door handle 1 was produced by injection moulding into a single mould a 100% polypropylene material and an inorganic antimicrobial agent comprising silver ions (SHT-860), added at 5 wt% and mixed within the plastic prior to injection into the tool. Mixing of the plastic and agent ensured an even distribution. No additional components were added or attached to the door handle once the door handle had been removed from the injection moulding process

[0033] The pull bar 2 has a solid body. The intersection between the pull bar 2 and the backplate 3 includes radiused corners 4. The side edge of the backplate 3 has radiused corners 5.

[0034] The backplate has no fixing holes and the door handle is suitable for fixing to a door with adhesive. In an alternative embodiment (not shown) the backplate includes fixing holes drilled through the back plate for receiving fasteners (e.g. screws) for fixing the door handle to a door. Adhesive on the reverse face of the backplate may additionally be used with the fasteners.

[0035] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.