FIELD OF THE INVENTION

[0001] The present invention relates to a masterbatch for using in plastics manufacturing, the masterbatch including an antimicrobial agent. The invention also relates to products including the masterbatch and methods for their manufacture.

BACKGROUND OF THE INVENTION

[0002] It is well known that many everyday items, such as chairs, tables, door handles, and kitchen utensils, 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] 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.

[0004] Polymer compositions including dispersed antibacterial agents have recently been used to form solid products that have been shown to be particularly effective against e-coli, MRSA and Salmonella, for example, and have been used in door handles.

[0005] One of the biggest challenges facing the healthcare community at present however is Norovirus. Norovirus is the most common cause of viral gastroenteritis in humans. The virus is highly contagious and readily transmitted by contact with contaminated surfaces. Globally, norovirus is estimated to be the most common cause of acute gastroenteritis. It is responsible for 685 million cases every year, 200 million of these cases are among children younger than 5 years old. This leads to an estimated 50,000 child deaths every year. Although most deaths occur in developing countries, norovirus is a problem in both low and high income countries. Every year Norovirus is estimated to cost $60 billion, these costs are mainly due to healthcare costs (money spent to treat complications from norovirus) and lost productivity (people not being able to work because they are sick).

[0006] The spread of Norovirus is typically combatted using chlorine-based disinfectants, but the virus is less susceptible to alcohols and detergents. In a healthcare environment, such as a hospital, tackling a Norovirus outbreak can require a complete shutdown of a ward or entire hospital wing at huge cost and disruption.

[0007] Currently available products proven to be effective against Norovirus are all in liquid formulations.

SUMMARY OF THE INVENTION

[0008] A first aspect of the invention provides a masterbatch for mixing with a raw polymer material during plastics manufacturing, the masterbatch comprising a thermoplastic polymer material and an antimcrobial agent, wherein the antimicrobial agent is dispersed within the thermoplastic polymer material, wherein the antimicrobial agent is present at a level of 20% to 30% by weight of the thermoplastic polymer material.

[0009] It has been surprisingly found that where the antimicrobial agent is present in the masterbatch at a level of 20% to 30%, it becomes possible to produce plastics products, by combing the masterbatch with raw polymer material, that are effective against norovirus.

[0010] In particular it has been surprisingly found that where the antimicrobial agent is present in the masterbatch at a level below approximately 20%, the ratio of masterbatch to raw material typically used during plastics manufacturing produces a finished product with insufficient antimicrobial agent to be effective against norovirus. It has also been found that where the antimicrobial agent is present in the masterbatch at a level above approximately 30%, the finished plastics product is brittle and unfit for many purposes.

[0011] A masterbatch is a concentrated solid or liquid mixture containing a resin and a one or more additives, such as colour pigment or other additive for imparting properties to plastics, for mixing with a raw polymer during plastics manufacturing.

[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; or that destroys a virus. Some antimicrobial agents may kill microbes (microbiocidal) or prevent the growth of microbes (microbiostatic). The antimicrobial agent may be more specifically an antibacterial and/or antifungal agent and/or antiviral agent.

[0013] 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.

[0014] 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).

[0015] In particular, the thermoplastic polymer material is a polyamide nylon, such as PA 6. [0016] 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 is cleaned, touched or the microbe is lost to the environment.

[0017] 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).

[0018] 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.

[0019] 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 chair 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. [0020] The masterbatch may further comprise a colour pigment.

[0021] The masterbatch preferably is a solid, e.g. is in granular form, such as strand cut pellets for example.

[0022] The level of antimicrobial agent in the masterbatch is preferably present at a level of approximately 22% to 28% by weight of the thermoplastic polymer material; more preferably 23% to 27%, even more preferably 24 to 28%, most preferably approximately 25% by weight of the thermoplastic polymer material. In particular, it is advantageous if the antimicrobial agent is evenly dispersed within the thermoplastic polymer material.

[0023] A second aspect of the invention provides an antimicrobial plastics product obtainable by moulding a mixture comprising a masterbatch according to the first aspect and a raw polymer material, wherein the masterbatch is present at a level of 1% to 5% by weight of the mixture.

[0024] The mixture of masterbatch with raw polymer material may be done to ensure the antimicrobial agent is dispersed within the thermoplastic polymer material so as to fix the agent in place and ensure that the entire polymer structure exhibits the desired antimicrobial properties. As such, it does not matter if the finished plastics product 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.

[0025] The mixture preferably comprises 4% masterbatch and 96% raw polymer material by weight of the mixture.

[0026] The mixture may consist substantially or exclusively of the masterbatch and the raw polymer material.

[0027] The raw polymer material may be a thermoplastic polymer material of the same type as present the masterbatch. For example, the resin in the masterbatch and the raw polymer material may both be nylon, preferably a polyamide nylon, most preferably PA 6.

[0028] The antimicrobial agent may be present at a level of 0.2% to 1% by weight of the product.

[0029] The antimicrobial plastics product may be obtainable by injection moulding the mixture. The employment of such a method is especially suitable in the case of a product formed as a unitary element, since the entire product 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.

[0030] The antimicrobial plastics product may, for example, be a door handle, preferably a single piece solid moulded door pull bar with integrated backplate. Since the pull bar and the backing plate are produced as a unitary item, the overall strength of the door handle is improved, and 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 and viruses, such as norovirus to accumulate in recesses that are relatively inaccessible for cleaning.

[0031] 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 or viruses. [0032] Preferably the door pull handle consists exclusively of the pull bar and backplate and has no other parts.

[0033] 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.

[0034] 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.

[0035] The door pull handle is preferably devoid of coatings.

[0036] The antimicrobial plastics product preferably contains the masterbatch according to the first aspect so as to be effective against surface contact with one or more of: viruses, human noroviruses, human norovirus surrogates, calciliviruses, Feline calcilivirus.

[0037] The antimicrobial plastics product is preferably sufficiently effective against Feline calcilivirus to achieve an antimicrobial efficacy of at least 99% over a contact time of 8 hours +/- 1 hour under the ISO 22196 method. Further preferably, the antimicrobial plastics product is sufficiently effective against Feline calcilivirus to achieve an antimicrobial efficacy of at least 99.5% over a contact time of 12 hours +/- 1 hour under the ISO 22196 method.

[0038] A yet further aspect of the invention provides a method of producing an antimicrobial plastics product, comprising the steps of: i) providing a masterbatch according to the first aspect of the invention; ii) combining the masterbatch with a raw polymer material to form a mixture, wherein the masterbatch is present at a level of 1% to 4% by weight of the mixture iii) heating the mixture so as to form a melt; iv) introducing the melt into a mould of the desired shape; and v) allowing the melt to cool.

[0039] The melt may be injection moulded. 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.

[0040] 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.

[0041] 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.

[0042] The antibacterial plastics products may also be produced in a variety of different colours, as appropriate for the specific end use. Colouring of the masterbatch may be achieved by adding a colour pigment at a level of 1 to 6% by weight of the masterbatch. For school and healthcare environments it may be advantageous to colour code products, e.g. the door handles, to a particular location, such as a classroom, ward, waiting room, etc.

[0043] The mixture preferably comprises 4% masterbatch and 96% raw polymer material by weight of the mixture.

[0044] The mixture preferably consists substantially or exclusively of the masterbatch and the raw polymer material.

[0045] The raw polymer material may be a thermoplastic polymer material of the same type as present the masterbatch.

[0046] The thermoplastic polymer material may be nylon, preferably a polyamide nylon, most preferably PA 6.

[0047] The antimicrobial agent may be present at a level of 0.2% to 1% by weight of the finished product.

[0048] A yet further aspect of the invention provides am antimicrobial plastics product according to the second aspect of the invention for use in the prevention of i) infection, or ii) infection by virus, or iii) infection by human norovirus.

[0049] A yet further aspect of the invention provides a method for reducing the spread of infection, the method comprising providing an antimicrobial plastics product according to the second aspect of the invention in place of an equivalent non- antimicrobial plastics product.

[0050] The antimicrobial plastics product may be provided in areas of i) high human contact, and/or ii) high risk of faecal contamination, and/or iii) high risk of human bodily fluid contamination.

[0051] The infection may be a viral infection or a norovirus infection. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0053] Figures la and lb are plan and side views of a door handle according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODFMENT(S)

[0054] 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.

[0055] 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.

[0056] 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. EXAMPLES

Example 1 - Process & Composition

[0057] The door handle 1 was produced by injection moulding into a single mould a 96wt% raw PA 6 nylon material and 4wt% masterbatch; the masterbatch comprising PA6 nylon material, colour pigment, and inorganic antimicrobial agent comprising silver ions (SHT-860) added at 25wt%. The masterbatch and the raw PA 6 nylon material were mixed prior to injection into the tool. Mixing of the raw plastic and masterbatch both prior to injection into the tool and during injection 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.

Example 2 - Antiviral Testing

[0058] A sample of plastic door handle according to Example 1 was tested for antimicrobial activity according to ISO 22196:2011 (E) method specification (Measurement of antibacterial activity on plastics and other non-porous surfaces) modified for viruses (Protocol PI 570).

[0059] One microorganism was tested to determine the antimicrobial efficacy of the test sample: Feline calicivirus, Strain F-9, ATCC VR-782 (U.S. EPA- Approved Human Norovirus Surrogate).

[0060] The antimicrobial efficacy of the test sample was demonstrated at contact times of 8 hours and 12 hours.

[0061] The Spearman-Karber Method was used to calculate the Plate Recovery Control titer (TCID50), the viral titer following test substance exposure (TCLD50), and the titer of host cell cultures exhibiting cytoxicity following test substance exposure (TCCDso).

[0062] The TCID50 (Tissue Culture Infectivity Dose) represented the endpoint dilution where 50% of the cell cultures exhibited cytopathic effects due to infection by the test vims. The dose required to kill 50% of the test viruses after the given exposure time was referred to as the Tissue Culture Lethal Dose (TCLD50), and the endpoint dilution at which 50% of the host cell monolayers exhibited cytoxicity was termed the Tissue Culture Cytoxicity Dose (TCCD50). The TCID50, TCLD50, and TCCD50 were determined according to the method of Spearman-Karber as follows:

[-Log of 1st dilustion inoculated - [(Sum of % mortality at each dilution / 1000 - 0.5 x logarithm of dilution)]

[0063] The calculation of virus inactivation due to test substance exposure is:

Mean Plate Recovery Control Logio TCID50 - Mean Virus-Test Substance Film Logio TCLD50 = Logio Reduction of Virus Due to Inactivation by Test Substance

[0064] After incubation for the first selected contact time (8 hours +/- 1 hour) at ambient conditions, the test surface demonstrated an average 2.08 logio (99.17%) reduction against Feline calicivirus, Strain F-9, ATCC VR-782 when compared to the control surface.

[0065] After incubation for the second selected contact time (12 hours +/- 1 hour) at ambient conditions, the test surface demonstrated an average 2.59 logio (99.74%) reduction against Feline calicivirus, Strain F-9, ATCC VR-782 when compared to the control surface.

[0066] These results therefore clearly show that the antimicrobial plastic door handle according to Example 1 demonstrated excellent antimicrobial activity against Feline calicivirus (U.S. EPA- Approved Human Norovirus Surrogate).

[0067] 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.