AU2013322383A1 - Furniture - Google Patents

Abstract

The present invention concerns chairs comprising a thermoplastic polymer material and an antimicrobial agent, and methods for producing the same.

Description

WO 2014/049315 PCT/GB2013/000403 Furniture Field of the Invention The present invention relates to antimicrobial furniture. In particular, though not exclusively, 5 it concerns seating units comprising an antimicrobial agent. Background to the Invention 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 10 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. Given that bacteria can double in population on unprotected surfaces every twenty minutes, 15 there is obviously 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. Of particular importance are items employed in environments having a high throughput of 20 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. 25 In addition, microbes may also be responsible for a wide range of undesirable effects such as product deterioration, malodour, and discolouration. In relation to furniture, previous solutions to prevent the spread of microbes have included 30 providing covers, veneers or films impregnated with an antimicrobial agent, or attaching plates comprising an antimicrobial agent.

WO 2014/049315 PCT/GB2013/000403 2 For example, patent publication JP9143854 describes a method for manufacturing a chair having antibacterial and antifungal properties by including powder of a soluble glass containing silver ions in a constituent fibre and/or adhesive component of a non-woven fabric, and sandwiching the fabric between a face fabric and cushioning part. The soluble glass 5 powder is kneaded into the constituent fibre, the mixture is spun by melt-spinning and the obtained short fibres are formed in the form of a sheet and hot-pressed with a calendar role to obtain the objective non-woven fabric. Patent publication CN201282832 describes an antibacterial chair in which the surface of the 10 chair is made of plates having a bactericidal effect. Patent publication CN202021888 describes an antibacterial heat-seal polyester film suitable for the decoration of furniture. The polyester film comprises a crystalline polyester antibacterial layer, a crystalline polyester pearly-lustre core layer and an non-crystalline 15 polyester heat-seal layer, wherein the crystalline polyester antibacterial layer and the non crystalline polyester heat-seal layer are respectively arranged on the upper surface and the lower surface of the crystalline polyester pearly-lustre core layer in a coextru-lamination manner. 20 Patent publication CN101886342 describes a method for manufacturing antibacterial and mould-proof polyurethane synthetic leather, which is suitable for sofa furniture. Such products have antibacterial and mould-proof properties by selecting a base fabric with a single-sided fleece or double-sided fleece and a resin, and a functional antibacterial and mould-proof auxiliary agent. 25 Patent publication CN101733983 discloses a method for manufacturing an inorganic nano silver mildew-proof antibacterial decorative veneer suitable for furniture. The decorative veneer can resist invasion of mildew caused by dampness of the base material to the surface of the decorative veneer, and ensures that sheet materials can achieve the effect of mildew 30 proofing and bacteria resistance.

WO 2014/049315 PCT/GB2013/000403 3 Patent publications US2012/0322903, EP1486523, and W02004/007595 disclose polyurethane foams comprising antimicrobial materials. Patent publications EP0431981 and EP0822116 disclose seating cushions comprising polyurethane. 5 However, the items of the prior art still suffer from problems associated with loss of antimicrobial properties through degradation/fatigue of the antimicrobial cover or surface, and/or insufficient longevity of the antimicrobial agent. In addition, the prior art does not address the problem of preventing microbial spread in school and healthcare environments, where people (particularly children) do not necessarily have the aptitude to personally control 10 levels of hygiene. It is an object of the invention, therefore, to provide a chair which is both durable and possesses long-lasting antimicrobial properties, even in the event of superficial damage to the chair's surface. In particular, it is an object of the invention to provide a chair for long-term 15 use in schools and healthcare environments, which has the ability to eradicate any microbes that it comes into contact with. Summary of the Invention According to the invention, there is provided a chair comprising a thermoplastic polymer 20 material and an antimicrobial agent. Any form of chair arrangement is envisaged by the present invention, including armchairs, benches, swivel chairs, stools, saddles, reclining chairs, side chairs, beam seating and couches. A preferred embodiment nevertheless relates to a chair comprising a seating unit, a pair of 25 front legs and a pair of back legs. Such a chair may further comprise supports which link one or more legs to each other, and may also include one or more arms. The antimicrobial agent may be more specifically an antibacterial and/or antifungal agent. 30 In particular, the chair of the invention is for use in a school environment, including nursery, primary and secondary schools. Therefore, the size of the chair is suited to children of up to 18 years of age. Preferably, the chair is for use in nursery and primary schools, for children up to 11 years of age, in accordance with the standards set out in BS EN 1729:1.

WO 2014/049315 PCT/GB2013/000403 4 In another preferred embodiment, the chair is for use in a healthcare environment. For example, hospitals, doctor's and dentist's surgeries, nursing homes, and clinics. The size of chair for this use is not limited and may be produced in a number of different sizes depending 5 on the ultimate environment in which the chair is to be used, e.g. on an adult or child ward in a hospital. Further provided is a method of producing a chair according to the invention, comprising the steps of: (i) combining a masterbatch or powder dispersion of a thermoplastic polymer 10 material and an antimicrobial agent to form a mixture; (ii) heating the mixture so as to form a melt; (iii) introducing the melt into a mould of the desired shape; and (iv) allowing the melt to cool. The thermoplastic polymer material and antimicrobial agent may be thoroughly mixed 15 together before heating so as to ensure that there is an even distribution of the antimicrobial agent throughout the thermoplastic polymer material. This allows the chair to retain antimicrobial properties throughout the chair structure, even where accidental damage has resulted in superficial recesses in the surface of the chair. 20 Detailed Description of the Invention 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 25 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. Any thermoplastic polymer material is suitable for use in the invention, provided there is 30 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 WO 2014/049315 PCT/GB2013/000403 5 (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. 5 A preferred subgroup of such polymers includes polypropylene (PP), ethylene vinyl acetate (EVA), polyethylene (PE), and polyvinyl chloride (PVC). Particularly preferred is polypropylene. Polypropylene, or more specifically high impact polypropylene, provides the chair with an optimal level of durability. This material is also easily processed and exhibits a favourable level of compatibility with a range of antimicrobial agents. The use of 10 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 chair, and makes the surface easier to clean. In a particularly preferred embodiment of the invention, the seating unit and the legs consist of 15 at least one polymer selected from the above list, preferably at least one selected from polypropylene (PP), ethylene vinyl acetate (EVA), polyethylene (PE), and polyvinyl chloride (PVC). It may be desirable that the seating unit of the chair comprises a thermoplastic polymer 20 material and an antibacterial agent whilst the legs comprise another material. For example, the legs may comprise a metal or alloy, such as steel, and may be affixed to the seating unit in a suitably secure manner. Alternatively, the seating unit and legs may comprise the same or different thermoplastic polymer materials and antibacterial agents. It is preferable nonetheless that the seating unit and legs comprise the same thermoplastic polymer material and the same 25 antibacterial agent. In this way, the method of manufacture is greatly simplified and the overall cost is reduced. It is also preferable that where supports linking one or more legs to each other are present, and/or where one or more arms are present, the supports and/or arms comprise the same 30 thermoplastic polymer material and the same antimicrobial agent as the seating unit and/or legs.

WO 2014/049315 PCT/GB2013/000403 6 Also with a view to simplifying the manufacturing process, the chair may be produced as a unitary element. Thus, the seating unit and legs may be integrally formed. As a result, the overall strength of the chair is improved, since there are no joining sections of the seating unit and legs which may be susceptible to failure. The absence of joins in the structure also 5 reduces the ability of bacteria and fungi to accumulate in natural recesses that are relatively inaccessible to everyday cleaning. 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 10 microbes (microbiocidal) or prevent the growth of microbes (microbiostatic). 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 15 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, sat on or the microbe is lost to the environment. Suitable organic additives may comprise siloxane-based polymeric antimicrobials, such as 20 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). 25 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 30 any way, such as by being accidentally scratched or knocked. Suitable examples of silver-based additives include colloidal silver, silver salts, and nanosilver. A particularly preferred antimicrobial agent comprises silver ions, such as the WO 2014/049315 PCT/GB2013/000403 7 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 5 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. 10 The level of antimicrobial agent in the chair is not limited, although for reasons of economy it is desirable that the chair 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 15 antimicrobial agent is dispersed within the thermoplastic polymer material. This allows both components to be easily combined and processed into the desired shape of chair. The antimicrobial agent may also be used to cover as a coating one or more legs comprising a metal or alloy, e.g. by being mixed into a paint, lacquer or powder coat finish. 20 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 chair suffers from any structural damage, since the same properties are maintained throughout. This 25 is unlike a product having a cover or outer film, because these elements may lose their antimicrobial properties over time or when damaged. The surface of the seating unit and/or legs may be smooth in nature or textured with a particular pattern. A textured pattern may be employed, for example, to impart frictional 30 properties to the surface, as a means to prevent slippage. The seating unit and/or legs may have a continuous, non-porous surface with no gaps or breaks on the upper seating surface, and may have rounded edges. The lower seat (underside of the seating unit) may also have a continuous surface with connections to edges, legs and arms, where present, that have smooth WO 2014/049315 PCT/GB2013/000403 8 radius joins. Preferably, all corners and edges of the chair are rounded to allow easy cleaning and to prevent the build up of microbes. Where the chair has arms, the arms preferably flow directly into the legs and/or seating unit in 5 order to eliminate gaps at connection points. The arms may form an integral part of the chair, where the chair is a unitary element, or may be clipped into place as separate components. Preferably, the arms are formed of the same thermoplastic polymer material and the same antimicrobial agent as the seating unit and/or legs. 10 The seating unit may further comprise a seating pad. The seating pad may be in the form of a shaped injection moulded, non-porous, flexible thermoplastic polymer or foam. It may also be formed as a unitary element. For example, the thermoplastic polymer or foam may be polyurethane (PU) or ethylene-vinyl acetate (EVA). The polymer or foam may incorporate the antimicrobial agent of the invention, preferably the same antimicrobial agent as the seating 15 unit and/or legs. This is to ensure antimicrobial protection throughout the seating pad, even in the event of superficial damage. In an alternative embodiment, the seating pad may comprise a traditional foam (e.g. polyurethane, expanded polyurethane, polyether or urethane) with a wooden or hardboard 20 base, fully encased within a non-porous polymer cover. The cover may or may not comprise an antimicrobial additive. Preferably, the cover comprises an antimicrobial additive, such as the same antimicrobial agent as the seating unit and/or legs. The cover may be heat sealed to avoid the use of a seal line that could be penetrated by dirt. The cover may also have an entrance to enable the contents of the cover, e.g. a foam cushion and/or wooden or hardboard 25 base, to be accessed. The entrance may be overlapped using a flap (preferably comprising an antimicrobial agent), such as a fabric flap, and may be sealed with a zip. The base of the seating pad may be moulded to the shape of the upper surface of the seat, and may remain in place by way of friction. This may be due to the properties of the seating pad 30 material and/or due to a textured finish on the seating unit and/or seating pad. Alternatively, a high grip silicone pad may be employed between the seating unit and seating pad. A shaped, injection moulded, unitary, seating pad may also be held in place by flaps which go around the edge of the seating unit to the underside of the seating unit. Alternatively, the seating pad may WO 2014/049315 PCT/GB2013/000403 9 be held in place using bolts or screws. Preferably, the seating pad is held in place by way of friction, since this allows easy removal for quick and thorough cleaning of the seating pad and/or underneath the seating pad. 5 The seating unit may also comprise a back pad, i.e. a pad which provides cushioning to the back and is affixed to the upper part of the seating unit, which comes into contact with the user's back. Such a pad may have any of the features mentioned herein in relation to the seating pad. 10 The chair may further comprise a linking clip which allows the chair to be temporarily connected to at least one further chair. The clip may be permanently attached to the chair by a suitable fixing means or may be detachable (preferably detachable). The clip may function by providing a biased connection around the legs or seating unit of the chair (preferably the legs). In a preferred embodiment, the linking clip is formed of the same thermoplastic polymer 15 material and the same antimicrobial agent as the seating unit and/or legs. The upper part of the legs may extend underneath the seating unit and connect with the leg on the opposite side, to provide strengthening ribbing underneath the seating unit. The strengthening ribbing underneath the seating unit is preferably closed/solid and merged into 20 the underside of the seating unit, with radius joins to enable a smooth, wipeable surface with no gaps. Such ribbing may have a rounded peak shape to provide strength and also to prevent a shrink mark on the top of the seating unit, following formation thereof. The legs may also have a substantially circular or oval shape to provide a continuous radius 25 which is easy to clean. In addition, there may be a smooth edge that runs around the rim of the seating unit to provide strength that enlarges at the top of the back to form a handle/grip area. The shape or configuration of the chair is not particularly limited, although it is preferable that the chair possesses a shape which allows it to be stacked one on top of the other in a plurality 30 of integers. For example, in stacks of up to 10, 12 or 15, without suffering from a reduction in stack stability. The legs are preferably offset by at least 5 mm (preferably at least 10 mm) in relation to the seating unit, i.e. initially extend laterally from the seating unit before extending toward the ground, to enable stacking and to provide a generous space to clean between the WO 2014/049315 PCT/GB2013/000403 10 legs and seating unit. This arrangement also facilitates easy manufacture by aiding removal of the chair or seating unit from the mould. The chair may be produced in a variety of different sizes depending on the nature of the end 5 user (according to the British and European Furniture Standards BS EN 1729:1, BS EN 16139:2013, and BS EN 1335). Where the chair is for use in a school, as is particularly envisaged by the present invention, it is desirable that the total seat height of the chair is less than 520 mm or 500 mm. Smaller sizes may also be applicable for a given age of child. For example, the total seat height of the chair may be less than 450 mm, 400 mm, 350 mm, 325 10 mm or 300 mm. In an especially preferred aspect of the invention, there is provided a chair comprising a seating unit, a pair of front legs, and a pair of back legs, in which the seating unit and the legs consist of a thermoplastic polymer material impregnated with an antimicrobial agent 15 comprising silver ions. In this embodiment, the thermoplastic polymer material is preferably polypropylene and the antimicrobial agent is preferably dispersed evenly throughout the thermoplastic polymer material. Furthermore, the antimicrobial agent is preferably present in a level of 4 to 6% by weight of the thermoplastic polymer material. 20 The chair may be obtainable by injection moulding. The employment of such a method is especially suitable in the case of a chair formed as a unitary element, since the entire chair 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. 25 The method of producing a chair according to the invention, comprises the steps of: (i) combining a masterbatch or powder dispersion of a thermoplastic polymer material and an antimicrobial agent to form a mixture; (ii) heating the mixture so as to form a melt; (iii) introducing the melt into a mould of the desired shape; and (iv) allowing the melt to cool. The 30 method may be used to produce the entire chair as a unitary element (i.e. seating unit and legs) or may be used to produce seating units to which separate legs may be affixed.

WO 2014/049315 PCT/GB2013/000403 11 In particular, the method may involve an injection moulding process, whereby the antimicrobial agent is 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, 5 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. The injection moulding process may consist of high pressure injection of the raw material into 10 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. Preferably, the mould contains a single cavity in order to produce a chair as a unitary element. 15 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 20 and time are considerably reduced. Many steel moulds are designed to process well over a million parts during their lifetime. The chair 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 25 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 chairs to a particular location, such as a classroom, ward, waiting room, etc. This may further prevent cross-contamination by discouraging the movement of the chairs to alternative locations. 30 In another embodiment of the invention, there is provided a chair assembly comprising a plurality of seating units comprising a thermoplastic polymer material and an antimicrobial agent, a pair of front legs and a pair of back legs. The seating units may have any of the WO 2014/049315 PCT/GB2013/000403 12 features described above in relation to the chair or seating unit of the invention. The number of seating units is not limited, but is preferably 2 to 10, more preferably 2 to 5, such as 2, 3, 4 or 5. Preferably, the seating units are arranged in a row, side by side. The legs may be arranged such that one front leg and one back leg are located at one end of the assembly and 5 the other front leg and the other back leg are located at the other end of the assembly. The legs at each end of the assembly may be connected together by a connection means, and the connection means (e.g. a bar) may provide a base onto which the seating units are fixed. A number of arms may also be present in the assembly and may be located between each seating unit, secured in position by connection to the connection means. Preferably, the seating units 10 comprise a thermoplastic polymer material and an antimicrobial agent and the legs and connection means comprise another material, such as a metal or alloy. Figure 1. A chair according to the invention in which the chair has been formed as a unitary element and both the seating unit and legs comprise a thermoplastic polymer material and an 15 antimicrobial agent: in (a) perspective view, (b) plan view, (c) front view, (d) bottom view, (e) side view, (f) detail of strengthening ribbing and smooth contours between front legs (g) detail of strengthening ribbing and smooth contours between back legs, and (h) perspective view with arms. Figure 2. A chair according to the invention in which the seating unit comprises a 20 thermoplastic polymer material and an antimicrobial agent and the legs comprise another material: in (a) perspective view, (b) plan view, (c) front view, (d) bottom view, (e) side view, and (f) perspective view with linking supports between front and back legs. Figure 3. A chair assembly according to the invention in which the seating units comprise a thermoplastic polymer material and an antimicrobial agent and the legs comprise another 25 material: in (a) perspective view, (b) plan view, (c) front view, (d) bottom view, and (e) side view. The invention will now be described in more detail by way of example only. 30 Examples Example 1 - Process WO 2014/049315 PCT/GB2013/000403 13 A chair according to the invention, having a seating unit, a pair of back legs and a pair of front legs, 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 5 an even distribution. No additional components were added or attached to the chair once the chair had been removed from the injection moulding process. A seating unit according to the invention may be produced by the same injection moulding process and then affixed to a separate set of legs (e.g. steel legs) 10 Example 2 - Compositions Table 1 illustrates a number of different chair structures and compositions. Table 1: Chair structures and compositions Example Seating Unit Legs Structure Additive A Polypropylene + 5% Steel Legs removably Silver antimicrobial additive attached to ions seating unit B Polyethylene + 5% Steel Legs removably Silver antimicrobial additive attached to ions seating unit C Polyvinyl chloride + Steel Legs removably Silver 5% antimicrobial attached to ions additive seating unit D Polypropylene + 5% Polypropylene + 5% Unitary structure Silver antimicrobial additive antimicrobial additive ions E Polyethylene + 5% Polyethylene + 5% Unitary structure Silver antimicrobial additive antimicrobial additive ions F Polyvinyl chloride + Polyvinyl chloride + Unitary structure Silver 5% antimicrobial 5% antimicrobial ions additive additive 15 Example 3 - Antibacterial Testing WO 2014/049315 PCT/GB2013/000403 14 A sample of plastic seating according to Example 1 was tested for antimicrobial activity according to ISO 22196: 2011 (Measurement of antibacterial activity on plastics and other non-porous surfaces, formerly JIS Z 2801: 2000). 5 Replicate test pieces measuring 35 mm x 35 mm were cut from the plastic seating and two separate tests were carried out using the following organisms: (i) Staphylococcus aureus ATCC6538P, and (ii) Escherichia coli ATCC8739. For each test organism, 0.1 ml of a suspension containing approximately 5 x 10 5 cells was 10 placed on the surface of triplicate test pieces and on triplicate samples of polystyrene sheet (used as the control material and known to have no antimicrobial activity). The suspension was held in intimate contact with test and control surfaces using a polyethylene film rectangle, 20 mm x 20 mm in size. 15 To provide a time zero inoculation level, an additional triplicate set of control samples (polystyrene sheet) were inoculated and washed off immediately, each into 10 ml of sterile neutraliser solution, shaken with glass beads, and microbial counts determined to give a time zero count. 20 The remaining replicates were incubated at 35 'C and relative humidity of not less than 90%. After 24 hours incubation, the test pieces were washed off as described above, and microbial counts determined. The microbial counts obtained (represented as a geometric mean), together with the 25 antimicrobial activity (represented as a Logio reduction) and the % kill, are given in Tables 2 and 3. T he antimicrobial activity was calculated as follows: R = [log (B/A) - log (C/A)] = [log (B/C)] where, R = antimicrobial activity; A = mean microbial count on control sample at time zero; 30 B = mean microbial count on control sample after 24 hours; and C = mean microbial count on test piece after 24 hours. Table 2: Antimicrobial activity against S. aureus WO 2014/049315 PCT/GB2013/000403 15 Test Sample Mean count Antimicrobial % Kill Initial count 24 hour count activity Control 5.5 x 10, 2.4 x 10' - Seating <10 > 4.4 > 99.9 Table 3: Antimicrobial activity against E. coli Test Sample Mean count Antimicrobial % Kill Initial count 24 hour count activity Control 5.1 x 10 5 3.7 x 10 5 - Seating <10 > 4.6 > 99.9 These results therefore clearly show that the plastic seating according to the invention 5 demonstrated excellent antimicrobial activity against both S. aureus and E. coli.

Claims (25)

1. A chair comprising a thermoplastic polymer material and an antimicrobial agent.

2. A chair according to claim 1, in which the chair comprises a seating unit, a pair of front 5 legs and a pair of back legs.

3. A chair according to claim 1 or claim 2, in which the antimicrobial agent is an antibacterial and/or antifungal agent.

4. A chair according to any preceding claim, in which the thermoplastic polymer material comprises at least one polymer selected from acrylonitrile butadiene styrene (ABS), 10 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). 15

5. A chair according to claim 4, in which the thermoplastic polymer material is polypropylene (PP).

6. A chair according to claim 4, in which the seating unit and the legs consist of at least one polymer selected from polypropylene (PP), ethylene vinyl acetate (EVA), polyethylene (PE), and polyvinyl chloride (PVC). 20

7. A chair according to any of claims 2 to 6, in which the seating unit and the legs comprise the same thermoplastic polymer material and the same antimicrobial agent.

8. A chair according to any of claims 2 to 7, in which the seating unit and the legs are formed as a unitary element.

9. A chair according to any preceding claim, in which the antimicrobial agent is dispersed 25 within the thermoplastic polymer material.

10. A chair according to any preceding claim, in which the antimicrobial agent is present at a level of 0.5 to 15% by weight of the thermoplastic polymer material.

11. A chair according to any preceding claim, in which the antimicrobial agent comprises silver ions. 30

12. A chair according to any preceding claim, in which the total seat height of the chair is less than 500 mm.

13. A chair according to any preceding claim, obtainable by injection moulding. WO 2014/049315 PCT/GB2013/000403 17

14. A chair comprising a seating unit, a pair of front legs, and a pair of back legs, in which the seating unit and the legs consist of a thermoplastic polymer material impregnated with an antimicrobial agent comprising silver ions.

15. A chair according to claim 14, in which the thermoplastic polymer material is 5 polypropylene (PP).

16. A method of producing a chair according to any preceding claim, comprising the steps of: i) combining a masterbatch or powder dispersion of a thermoplastic polymer material and an antimicrobial agent to form a mixture; 10 ii) heating the mixture so as to form a melt; iii) introducing the melt into a mould of the desired shape; and iv) allowing the melt to cool.

17. A method according to claim 16, in which the melt is injection moulded.

18. A method according to claim 16 or claim 17, in which the melt is moulded using a 15 single mould and produces a chair as a unitary element.

19. A chair assembly comprising a plurality of seating units comprising a thermoplastic polymer material and an antimicrobial agent, a pair of front legs and a pair of back legs.

20. A chair assembly according to claim 19, in which the antimicrobial agent is an 20 antibacterial and/or antifungal agent.

21. A chair assembly according to claim 19 or claim 20, in which the thermoplastic polymer material comprises at least one polymer selected from acrylonitrile butadiene styrene (ABS), polyoxymethylene (POM), acrylate, ethylene vinyl acetate (EVA), general purpose polystyrene (GPPS), high impact polystyrene (HIPS), nylon, 25 polyethylene (PE), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), polysulfone (PSU), polyurethane (PU), and polyvinyl chloride (PVC).

22. A chair assembly according to claim 21, in which the thermoplastic polymer material is polypropylene (PP). 30

23. A chair assembly according to any of claims 19 to 22, in which the antimicrobial agent is dispersed within the thermoplastic polymer material.

24. A chair assembly according to any of claims 19 to 23, in which the antimicrobial agent is present at a level of 0.5 to 15% by weight of the thermoplastic polymer material. WO 2014/049315 PCT/GB2013/000403 18

25. A chair assembly according to any of claims 19 to 23, in which the antimicrobial agent comprises silver ions.