GB2505784A

GB2505784A - An antimicrobial chair

Info

Publication number: GB2505784A
Application number: GB201317172A
Authority: GB
Inventors: Paul Richard Cook; Alexander John Worswick
Original assignee: TITAN FURNITURE UK Ltd
Current assignee: TITAN FURNITURE UK Ltd
Priority date: 2012-09-26
Filing date: 2013-09-26
Publication date: 2014-03-12
Anticipated expiration: 2033-09-26
Also published as: WO2014049315A1; AU2013322383A1; GB201217159D0; GB201317172D0; GB2505784B; EP2900107A1

Abstract

A chair comprising a seating unit made of a thermoplastic polymer material with an antimicrobial agent dispersed within the thermoplastic polymer and pairs of front and back legs made of a metal or alloy. The antimicrobial agent may be an antibacterial or antifungal agent and may comprise silver ions or be at a level of 0.5 to 15% by weight of the thermoplastic polymer. The thermoplastic polymer may be acrylonite butadiene styrene, polyoxymethylene, acrylate, ethylene vinyl acetate, general purpose polystyrene, high impact polystyrene, nylon, polyethylene, polyether ether ketone, polyethylene terephthalate, polypropylene, polyphenylene sulphide, polysulfone, polyurethane or polyvinyl chloride. The chair is designed for use in areas with high levels of use such as hospitals, schools and other public places.

Description

Furniture

Field of the Invention

The present invention relates to antimicrobial furniture. In particular, though not exclusively, it concerns seating units comprising an antimicrobial agent.

Background to the Invention

It is welt 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.

Given that bacteria can double in population on unprotected surfaces every twenty minutes, 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 enviromnents 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, 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 providing covers, veneers or films impregnated with an antimicrobial agent, or attaching plates comprising an antimicrobial agent.

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 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 chair is made of plates having a bactericidal effect.

Patent publication CN20202 1888 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 1 5 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-larnination manner.

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.

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 proofing and bacteria resistance.

However, the items of the prior art still suffer from problems associated with loss of antimicrobial properties through degradationlfatigue of the antimicrobial cover or surface, andlor insufficient longevity of the antimicrobial agent. In addition, the prior art does not address the problem of preventing microbial spread in school environments, where children do not necessarily have the aptitude to personally control 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 use in schools, 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 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, and couches. A preferred 1 5 embodiment nevertheless relates to a chair comprising a seating unit, a pair of front legs and a pair of back legs. Such a chair may further comprise supports which link one or more legs to each another, and may also include one or more arms.

The antimicrobial agent may be more specifically an antibacterial and/or antifungal agent.

In particular, the chair of the invention is for usc 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 upto 11 years of age.

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 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 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.

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 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 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.

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.

In a particularly preferred embodiment of the invention, the seating unit and the legs consist of 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 material and an antibacterial agent whilst the legs comprise another material. For example, the legs may comprise a metal or ahoy, such as steel, and may be affixed to the seating unit in a suitably secure maimer. 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 thennoplastic polymer material and the same antibacterial agent. In this way, the method of manufacture is greatly simplified and the overall cost is reduced.

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 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 microbes (microbiocidal) or prevent the growth of microbes (microbiostatic).

The antimicrobial agent may be an organic additive. These additives fi.nction 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, sat on or the microbe is lost to the environment.

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-ch1oro-2(2,4-dichlorophenoxy)phenol), zinc pyrithione (JUPAC name: bis(2-pyridylthio)zinc 1,1 -dioxide), and/or folpet (IUPAC name: N- (trichloromethylthio)phthalimide).

Alternatively, the antimicrobial agent may be an inorganic additive, These additives thnction 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.

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 andlor 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.

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 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.

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 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 properties to the surface, as a means to prevent slippage.

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 of integers. For example, in stacks of up to 10, 12 or 15, without suffering from a reduction in stack stability.

The chair may be produced in a variety of different sizes depending on the nature of the end user (according to the British and European Furniture Standard EN 1729). Where the chair is for use in a school, as is particularly envisaged by the present invention, it is desirable that the total height of the chair is less than 500 mm. Smaller sizes may also be applicable for a given' age of child. For example, the total height of the chair may be less than 450 mm, 400 mm, 350mm,325 mmor300mm.

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 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.

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.

The method of producing a chair according to the invention, comprises the steps of: (i) combining a masterbatch or powder dispersion of a thennoplastic 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.

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, 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 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.

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 axe 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.

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 masterbatch at a level of 1 to 6% by weight of the thermoplastic polymer material to the mixture prior to heating.

The invention will now be described in more detail by way of example only.

Examples

Example I -Process

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 an even distribution. No additional components were added or attached to the chair once the chair had been removed from the injection moulding process.

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 Example 3 -Antibacterial Testing 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 MS Z 2801: 2000).

Replicate test pieces measuring 35 mm x 35 nun were cut from the plastic seating and two separate tests were carried out using the following organisms: (i) Staphylococcus aureus ATCC6S38P, and (ii) Escherichia coli ATCC8739.

For each test organism, 0.1 ml of a suspension containing approximately 5 x 1 o cells was 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, mm x 20 mm in size.

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 neutraliscr solution, shaken with glass beads, and microbial counts determined to give a time zero count.

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 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: It = [log (B/A) -log (C/A)] = [log (B/C)] where, R = antimicrobial activity; A = mean microbial count on control sample at time zero; 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 Test Sample Mean count Antimicrobial % Kill Initial count 24 hour count activity Control 5.5x10 2.4x105 --Seating -<10 >4.4 >99.9 Table 3: Antimicrobial activity against E. coil Test Sample Mean count Antimicrobial % Kill Initial count 24 hour count activity Control 5.1 x io5 3.7 x io5 --Seating -<10 >4.6 >99,9 These results therefore clearly show that the plastic seating according to the invention demonstrated excellent antimicrobial activity against both S. aureus and E. coli.

Claims

Claims 1. A chair comprising a seating unit, a pair of front legs and a pair of back legs, in which the seating unit comprises a thermoplastic polymer material and an antimicrobial agent and the legs comprise a metal or alloy, and in which the antimicrobial agent is dispersed within the thermoplastic polymer material.
2. A chair according to claim 1, in which the antimicrobial agent is an antibacterial and/or antifungal agent.
3. A chair according to claim I or claim 2, in which the thermoplastic polymer material coniprises 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, polyethylene (PE), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), polysulfone (PSU), polyurethane (PU), and polyvinyl chloride (PVC).
4. A chair according to claim 3, in which the thermoplastic polymer material is polypropylene (PP).
5. 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.
6. A chair according to any preceding claim, in which the antimicrobial agent comprises silver ions.
7. 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; 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.
8. A method according to claim 7, in which the melt is injection moulded.Amendments to the claims have been fUed as follows Claims 1. A chair comprising a seating unit, a pair of front legs and a pair of back legs, in which the seating unit comprises a thermoplastic polymer material and an antimicrobial agent and the legs comprise a metal or alloy, in which the antimicrobial agent is dispersed within the thermoplastic polymer material, in which the thermoplastic polymer material is polypropylene (PP), and in which the antimicrobial agent comprises silver ions and is present at a level of 0.5 to 15% by weight of the thermoplastic polymer material.2. A method of producing a chair according to claim 1, comprising 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 I S iv) allowing the melt to cool.3. A method according to claim 2, in which the melt is injection moulded. n..S fl**S * S Sen*5 * * * S..S * S. * S SSSCSS 5.S