This invention relate to coatings.

It is well-known to provide parts with coatings to address various problems. For example, parts may be provided with coatings to protect an underlying substrate, for example a metal substrate, from corrosion. Alternatively and/or additionally, parts may be coated to improve their visual appearance and/or wear properties. In the case of cooking utensils, coatings are selected to provide "non-stick" properties, to prevent food sticking to inside or outside surfaces of the utensils.

Examples of coatings systems having anti-adhesive or nonstick properties are described in US6382454 (Seb) and US6596380 (Seb) . The former document describes the use of the polyetheretherketone, oxy-1, 4-phenylene-oxy-l, 4- phenylene-carbonyl-1, 4-phenylene as a primary or undercoat. The document envisages the undercoat to consist essentially of the polyetheretherketone and this is then overcoated with fluorocarbon resin-containing layers to provide a non-stick outer coating. The latter document describes a non-stick coating with improved scratch resistance comprising an undercoat which comprises at least 50wt% of polyetheretherketone, with the remainder of the undercoat comprising other polymers and/or inert fillers. Again, the undercoat is overcoated with fluorocarbon resin-containing layers to provide a non- stick coating.

The aforementioned US Patents acknowledge that the polyetheretherketone undercoat is discontinuous. This

suggests that if the polyetheretherketone alone was used to coat a substrate, the coating would be discontinuous or non-smooth, leading to pin holes through which moisture or corrosive materials could readily penetrate to attack the underlying substrate. Clearly, the thinner the coating of polyetheretherketone, the more likely it is for pin holes to be present in the coating. Since polyetheretherketone is costly it is desirable to provide the thinnest coatings possible; however, coating have to have a certain thickness to reduce the risk if penetration of fluids etc. through pin holds. It is an object of the present invention to address this problem.

Additionally, whilst polyetheretherketone adheres reasonably well to metal substrates, it is generally desirable to optimise adhesion of a coating to a substrate since failure of a coating to substrate bond will result in delamination of the entire coating and complete failure of it. It is an object of the present invention to address this problem.

Another problem, related to the aforementioned problems, is that if polyetheretherketone is used to form an outer coating (or only) layer on a substrate, there is a tendency for the polyetheretherketone to be relatively rough and/or it may have the appearance of "orange-peel" especially for relatively thin coatings. This may be aesthetically and/or technically unacceptable.

This invention is based on the discovery that a polyaryletherketone polymer, closely related to polyetheretherketone described above, has properties which

surpass those of polyetheretherketone and which allow the above described problems to be advantageously addressed.

According to a first aspect of the invention, there is provided a coated part which comprises a substrate and a coating layer over the substrate wherein said coating layer (hereinafter referred to as "layer A") comprises a first polymeric material which consists essentially of a repeat unit of formula

A coating layer as described in accordance with said first aspect has been found to be smoother than a corresponding layer made using polyetheretherketone instead of said first polymeric material. Accordingly, it may more readily be used in a single coating layer and/or as an outer coating layer of a coated part. Also, thinner layers may be used compared to corresponding polyetheretherketone based coatings. Furthermore, said layer in accordance with the first aspect has been found to adhere better to substrate materials compared to a corresponding polyetheretherketone layer; and the wear properties of said layer of the first aspect are improved.

Said first polymeric material may have a melt viscosity (MV) in the range 0.05 to 0.7 kNsm ^"2 , preferably in the range 0.06 to 0.7 kNsm ^"2 , more preferably in the range 0.2 to 0.5 kNsm ^"2 , especially in the range 0.3 to 0.5 kNsm ^"2 .

MV is suitably measured using capillary rheometry operating at 400°C at a shear rate of 1000s ^"1 using a tungsten carbide die, 0.5 x 3.175mm.

Layer A suitably covers an area of at least lcm ² , preferably at least 5cm ² , more preferably at least 10cm ² . It may cover an area of less than Im ² , preferably less than 0.5m ² .

Layer A may have a coat weight of at least 1.0mg/cm ² , preferably at least 1.2mg/cm ² . The coat weight may be less than 20mg/cm ² ' In one embodiment (e.g. where a process using powders is utilised to prepare the coating) the coat weight may be at least 5mg/cm ² .

Layer A may include at least l.Omg, preferably at least 1.2mg of said first polymeric material per cm ² of said layer A. Layer A may include less than 20mg of said first polymeric material per cm ² of said layer A.

Said layer A may have a minimum thickness (measured across its whole extent) of 5μm, preferably of at least 8μm.

Said layer A may have a maximum thickness (measured across its whole extent) of less than 150μm.

Said layer A may have an average thickness measured over its whole extent in the range 10 to 150μm.

Said miniumum/maximum thicknesses may be measured using a Sheen Eco Test Plus BFN Coating Thickness Gauge Type 121- 17-00 from Sheen Instruments Ltd.

Layer A may have a total weight of at least lmg, preferably at least 5mg, more preferably at least lOmg, especially at least Ig.

Layer A may include at least lmg, preferably at least lOmg, especially at least Ig of said first polymeric material .

The coated part may include at least lOmg, preferably at least 500mg, especially at least Ig of said first polymeric material.

In one embodiment, layer A may include greater than 90wt%, preferably greater than 95wt%, more preferably greater than 98wt% of said first polymeric material. Such a layer A may have excellent chemical and physical properties and be in the form of a relatively smooth pin hole free surface .

Properties of layer A may be adjusted by including materials in it in addition to said first polymeric material .

Said layer A may include a second polymeric material. A said second polymeric material may be selected from a fluorocarbon resin or a polyether resin. When said second polymeric material comprises a fluorocarbon resin, said resin may comprise perfluoroalkoxy tetrafluoroethylene

(PFA), polytetrafluoroethylene (PTFE) or tetrafluoroethylene-hexafluoropropylene copolymer resin

(FEP) .

A perfluoroalkoxy polymer (herein referred to as PFA) may be represented by the following general formula:

wherein Rf is a fluoroalkyl group (so -O-Rf is a perfluoroalkoxy group) . PFA has a melting point of from 302 to 31O ⁰ C, exhibits melt fluidity at temperatures above the melting point thereof, has high heat resistance and chemical resistance, has a continuous services temperature of 260°C, and is little affected by the usual acids, alkalis, oxidation-reduction agents, halogens, and organic solvents .

PFA is sold under the trade name of Teflon PFA by E . I . Du Pont de Nemours & Co., Inc., U.S.A. and Mitsui Fluorochemicals Co., Ltd., Japan.

A tetrafluoroethylene/hexafluoropropylene copolymer (herein referred to as FEP) may be represented by the following general formula:

FEP has a melting point of from 250 to 290°C, exhibits melt fluidity at temperatures more than the melting point

thereof, has high heat resistance and chemical resistance, and has a continuous service temperature of 200°C.

FEP is commercially available from E.I. Du Pont de Nemours & Co., Inc., U.S.A. (trade mark: Teflon FEP) and Daikin Kogyo Co., Ltd. (trade name: Neofuron) . Among commercially available FEPs, those copolymers having a hexafluoropropylene content of from 18 to 25% by weight are preferably used.

When said second polymeric material comprises a polyether resin, said resin may be a polyaryletherketone or polarylether sulphone. Preferred polyether resins are polyetheretherketone and polyethersulphone, with the former being especially preferred. Blends of said first polymeric material and a polyether resin, especially polyetheretherketone, may be used to produce coatings having properties between those of the two materials. For example, it may be that a layer A comprising said first polymer material is too smooth (or not rough enough) for a particular application. In this case, polyetheretherketone may be included in layer A to increase the roughness of the layer, whilst not affecting detrimentally many other important physical and chemical properties afforded to layer A by said first polymeric material. For example use of polyetheretherketone and said first polymeric material allow roughness to be adjusted whilst maintaining solvent or heat resistance of layer A.

Preferably, layer A includes 0 to 95wt% of said second polymeric material. When the second polymeric material is a polyaryletheretherketone, for example

polyetheretherketone, layer A may include up to 95wt% of such polaryletherketone . If said second polymeric material is a polysulphone it may include up to 60wt% of polysulphone. If said second polymeric material is a fluorocarbon resin it may include up to 80wt%

(particularly if layer A is a top coat) or up to 30wt%

(particularly if layer A is not a top coat) of fluorocarbon resin.

Said layer A may include a filler means. Said filler means may be particulate and/or may comprise nano fibres, nano tubes or other nano fillers. Examples of fillers include glass particles, ceramic particles, metallic particle, mineral particle and pigments. Specific examples include glass beads or microspheres, silica particles, carbon black, titanium dioxide particles, barium titanate particles, molybdenum disulphide and mica.

Preferably layer A includes 0 to 40wt% % of filler means.

Said layer A could include additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, a lubricant, a releasing agent, a coloring agent (e.g., a dye and a pigment) , a flame retardant, an auxiliary flame retardant, and a antistatic agent, or suitably reinforcing agent and fillers. The additives can be used alone or in combination of two or more thereof.

The sum of the amount of said second polymeric material and filler means in layer A may be in the range 0 to 90wt%, preferably 0 to 70wt%, more preferably 0 to 50wt%, especially 0 to 30wt%.

Suitably, even when said layer A includes materials in addition to said first polymeric material, said layer A includes at least 40wt%, preferably at least 50wt%, more preferably at least 60wt% of said first polymeric material.

Said substrate may comprise a metal which may be selected from steel (including stainless steel) , aluminium, copper and iron, including cast versions of any of the aforesaid.

Said coated part may be for an item of cookware, bakeware, domestic appliance, industrial apparatus or automotive application. It may be a sealing gasket, piston ring, valve, impeller, seal (or the like) .

The coated part may have a weight of at least Ig, preferably at least 5g, more preferably at least 1Og. The weight may be less than 10kg, preferably less than lkg.

A layer A as described may be provided on internal or external surfaces of a said coated part. For example in the case of a receptacle, for example for cookware, it may coat internal and external surfaces thereof. Given the potentially improved aesthetics (e.g. reduction in pin holes and "orange-peel" effect) of layer A compared to corresponding polyetheretherketone coatings, a relatively thin layer A may be aesthetically acceptable even on highly visible outer surfaces of parts.

Said layer A may be in direct contact with a base surface of a part to be coated, for example a metal surface. Alternatively, said layer A may be remote from such a base surface. It may be between the base surface and an outer

layer of the coated part or it may form part of the outer layer .

Said coated part may include a layer A and a layer B which may be over layer A and is suitably closer to an outer surface of the coated part than layer A. Optionally layers A and B are in direct contact with one another. Layer B may have any feature of layer A described herein. Layer A may comprise more of said first polymeric material than layer B. For example, layer B may be outside layer A and may include a wt% of said first polymeric material which is less than the wt% of said first polymeric material in layer A. Layer B may include more of a fluororesin than in layer A.

Said coated part may include a multiplicity of layers each of which may include a first polymeric material as described. Each of said layers may independently have any feature of layer A described herein. The coated part may include other coating layers which do not include said first polymeric material.

According to a second aspect of the invention, there is provided apparatus which incorporates a coated part according to said first aspect, wherein, in use, said coated part is subject to a temperature of at least 15O ⁰ C or even at least 200°C or 225°C. It may be subject to such a temperature for a continuous period of at least five minutes, or even at least one hour, in use.

According to a third aspect of the invention, there is provided a method of manufacturing a coated part according to said first aspect, the method comprising contacting a

substrate of a part to be coated with a first polymeric material as described according to said first aspect to form a layer (herein referred to as "layer A") over said substrate wherein layer A comprises said first polymeric material .

Said substrate may comprise an uncoated part, for example made out of metal (in which case, said first polymeric material may be contacted with a base surface (e.g. metal surface) of said uncoated part; or said substrate may comprise a part which has already been coated to some extent. Advantageously, said method may involve contacting said first polymeric material with a substantially uncoated part, for example with a metal surface.

Said first polymeric material may have a D ₅₀ of less than lOOμm, suitably less than 60μm, preferably less than 40μm, more preferably less than 20μm, especially less than lOμm The D ₅₀ may be greater than lμm.

Said first polymeric material may have a D ₉₀ of less than 50μm, preferably less than 40μm, more preferably less than 30μm, especially less than 20μm.

Said first polymeric material may have a D ₉₉ of less than 60μm, preferably less than 50μm, more preferably less than 40μm, especially less than 30μm.

D ₅₀ , D ₉₀ and D ₉₉ referred to herein may be measured by laser diffraction, for example using a Sympatece Helos (HO476) RODOS Analyser with Windocs Software from Sympatece GmbH, Germany.

Said first polymeric material is suitably in particulate form with the particle sizes being suitably as described. Particles of said particulate form (preferably greater than 90wt%, more preferably about 100wt%) preferably consist essentially of a said first polymeric material having a repeat unit of formula I, as described according to the first aspect.

Preferably, at least 1.Og, more preferably at least 1.2g, per cm ² of said first polymeric material is applied in said method to form layer A

The method may be used to prepare a layer A having a total weight of at least lmg, preferably at least 5mg, more preferably at least lOmg.

Preferably, the method involves preparation of a layer A which includes at least lOmg, preferably at least 250 mg of said first polymeric material.

Preferably, the method comprises contacting a substrate with at least 1 gram of said first polymeric material.

The method may comprise forming a layer A which includes at least lmg preferably at least Ig of said first polymeric material per cm ² of said layer A.

Preferably, in the method, a layer A is formed which has a minimum thickness of 5μm, preferably 8μm (after drying) .

Preferably, the method involves contacting the substrate with a spray which comprises said first polymeric material.

The method may involve contacting the substrate with a powder which includes said first polymeric material or contacting the substrate with a liquid which includes said first polymeric material. When a powder is used, it is preferred that the substrate is at a temperature above ambient temperature at the time of contact with said first polymeric material. Suitably, the substrate may be at a temperature of greater than 100 ⁰ C, preferably greater than 200 ⁰ C, more preferably greater than 300 ⁰ C, especially greater than 350°C, at the time of contact with said first polymeric material.

When a liquid is contacted with said substrate, said liquid and/or said substrate may be at a temperature in the range 10°C to 50°C at the time the substrate and first polymeric material are contacted.

In some cases, it may be preferred to use a powder.

Preferably, the method involves subjecting the substrate, after it has been contacted with said first polymeric material, to an environment wherein the temperature is at least 100°C, preferably at least 200°C, more preferably at least 300 ⁰ C, and especially at least 350 ⁰ C. The temperature is suitably selected to cause said first polymeric material to fuse and form a substantially continuous coating over the substrate. The temperature is suitably selected so that said first polymeric material is not degraded or otherwise detrimentally affected.

Suitably, the temperature is less than 500 ⁰ C, more preferably less than 450 ⁰ C.

The method preferably involves selecting at least 10 grams of first polymeric material or a formulation which includes at least 10 grams of said first polymeric material and contacting said substrate with said at least 10 grams to prepare layer A.

Said method may comprising selecting a coating formulation which comprises said first polymeric material and an additive selected from a second polymeric material and a filler means, each suitably being as described according to said first aspect and contacting said substrate of said part with said formulation. Suitably, the coating formulation includes at least lwt%, preferably at least 5wt%, more preferably at least 10wt% of a said second polymeric material described herein, especially a fluorocarbon resin. In the method, suitably, a quantity of said coating formulation is contacted with said substrate and the substrate is subsequently subjected to an environment as described above (e.g. having a temperature of greater than 300 ⁰ C) , to cause fusion of polymeric materials to prepare thereby layer A.

The layer A prepared may be an outer layer of a coated part for use in a finished product or may be a intermediate layer, in which case the method may include contacting layer A with a second coating formulation which is preferably different to the coating formulation used to prepare layer A but which may have any feature of a coating formulation described herein.

The method of the third aspect may be used to manufacture a coated part which is subjected to a temperature of at least 150 ⁰ C or even at least 200°C or 220 ⁰ C for at least 1 minute, or even at least 1 hour in use.

According to a fourth aspect of the invention, there is provided a coating formulation for use in accordance with the first and/or third aspects, the coating formulation comprising a first polymeric material as described according to the first aspect and a second polymeric material as described according the first aspect. Said second polymeric material may be a fluorocarbon resin

(especially selected from PTFE, FEP and PFA) . Said coating formulation suitably includes at least lwt%, preferably at least 5 wt%, more preferably at least 10wt% of said second polymeric material. The formulation may include less than 50wt% of said second polymeric material.

According to a fifth aspect of the invention, there is provided a method of preparing a coating formulation according to the third aspect, the method comprising contacting first and second polymeric materials. Contact may be carried out in the presence of a carrier, for example water.

According to a sixth aspect of the invention, there is provided the use of a first polymeric material as described according to the first aspect for reducing the roughness of a coating layer.

According to a seventh aspect of the present invention, there is provided the use of a first polymeric material as

described according to the first aspect for improving the appearance of a coating layer.

According to a eighth aspect of the present invention, there is provided the use of a first polymeric material as described according to the first aspect for reducing pin holes in a coating layer.

According to a ninth aspect of the present invention, there is provided the use of a first polymeric material as described according to the first aspect for improving wearability of a coating layer.

According to an tenth aspect of the present invention, there is provided the use of a first polymeric material as described according to the first aspect for improving adhesion of a coating layer to an underlying surface in contact therewith.

According to a eleventh aspect, there is provided a method of reducing the roughness of a coating layer on a coated part, the method comprising:

selecting a first polymeric material as described according to the first aspect;

contacting said first polymeric material with a substrate of a part to be coated; and

causing said first polymeric material to fuse to form said coating layer.

According to a twelfth aspect, there is provided a method of improving the appearance of the coating layer on a coated part, the method comprising:

selecting a first polymeric material as described according to the first aspect;

contacting said first polymeric material with a substrate of a part to be coated; and

causing said first polymeric material to fuse to form said coating layer.

According to a thirteenth aspect, there is provided a method of reducing pin holes in a coating layer on a coated part, the method comprising:

selecting a first polymeric material as described according to the first aspect;

contacting said first polymeric material with a substrate of a part to be coated; and

causing said first polymeric material to fuse to form said coating layer.

According to a fourteenth aspect, there is provided a method of improving wearability of the coating layer on a coated part, the method comprising:

selecting a first polymeric material as described according to the first aspect;

contacting said first polymeric material with a substrate of a part to be coated; and

causing said first polymeric material to fuse to form said coating layer.

According to a fifteenth aspect, there is provided a method of improving adhesion between a coating layer and a surface of substrate, the method comprising:

selecting a first polymeric material as described according to the first aspect;

contacting said first polymeric material with a substrate of a part to be coated; and

causing said first polymeric material to fuse to form said coating layer.

Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention or embodiment described herein mutatis mutandis.

Commercially available fluorocarbon-containing dispersion Greblon 1231 ref 05-1231-L2816 for cookware from Weilburger Schramm Coatings.

PEEK D150UF10 powder - polyetheretherketone having a D ₅₀ of 9.64μm obtained from Victrex pic.

PEEK HT DP22UF10 powder - polyetherketone having a D ₅₀ of lOμm obtained from Victrex pic.

Examples Ia Dispersion of polyetheretherketone using D150

UFlO (Victrex pic) in a commercially available formulation for coating cookware .

A plastic 2000 ml beaker was charged with Greblon 1231 dispersion (0.5kg) and to it was added slowly PEEK D150 UFlO (5Og) and n-methylpyrrolidone (50ml) with stirring until all the PEEK D150UF10 had been dispersed and the mixture was homogeneous. The dispersion was poured into 500ml glass jars and allowed to stand over night.

Examples Ib Dispersion of polyetheretherketone using D150

UFlO (Victrex pic) in a commercially available formulation for coating cookware .

A plastic 2000 ml beaker was charged with Greblon 1231 dispersion (0.5kg) and to it was added slowly PEEK D150 UFlO

(10Og) and n-methylpyrrolidone (80ml) with stirring until all the PEEK D150UF10 had been dispersed and the mixture was homogeneous. The dispersion was poured into 500ml glass jars and allowed to stand over night.

Examples Ic and Ib Dispersion of polyetherketone using DP22UF10 (Victrex pic) in a commercially available formulation for coating cookware.

The procedure of Examples Ia and Ib were repeated except the PEEK D150UF10 was replaced by PEEK DP22UF10.

Examples 2a-d Dispersion Coatings

The coating gun used was a Binks Bullows, type 630, with a tip size of 0.06". Air pressure to the gun was 30 to 40 psi depending on what type of coating was required i.e. wet, dry, thin or thick coating. Substrates for coating were 2mmm thick x 100 x 100mm square mild steel plaques. The plaques were degreased using trichloroethylene vapour and then grit blasted using Aluminum oxide. Excess dust was removed by air blast. Procedure for coating: The dispersions from Examples la-Id were hand mixed with a stirrer rod before pouring into the spray gun reservoir. The plaques were placed in an air extracted spraying cabinet and one wet coat applied. The coated plaques were then placed in an oven for 5 minutes set to 100 ⁰ C to flash off the solvent. The plaques were left for 10 minutes in an oven set to 390°C-420°C to melt and flow the coating. After removal from the oven the plaques were forced cooled with an air gun and cooled to room temperature. The coatings were subsequently visually evaluated for smoothness and defects and details are given in Table 1 below.

Examples 3a Powder Coatings of PEEK D150UF10

Substrates for coating were 2mmm thick x 100 x 100mm square mild steel plaques. The plaques were degreased using trichloroethylene vapour and then grit blasted using aluminum oxide. Excess dust was removed by air blast. The PEEK D150UF10 powder was dried an oven at 15O ⁰ C for 3 hours before use. The substrate to be spray coated was placed in an oven at 400 ⁰ C for 10 minutes, removed from the oven and quickly sprayed with the powder. The powder melted on contact with the substrate. The coated substrate was placed in the oven at 400 ⁰ C for 10 minutes to melt and

flow the coating. The substrate was removed from the oven and allowed to cool.

The coating was subseguently visually evaluated for smoothness and defects and details are given in Table 1 below.

Examples 3b Powder Coating of PEEK-HT DP22UF10

The procedure of Example 3a was repeated except the PEEK D150UF10 powder was replaced by PEEK DP22UF10 powder.

The coating was subsequently visually evaluated for smoothness and defects and details are given in Table 1 below.

Example 4 Surface Roughness Testing of coatings

Using a Form Talysurf Intra Instrument from Taylor Hobson Precision the surface roughness of each coated substrate was measured over a 25mm trace using a standard Gausian filter and the R _a (i.e. the arithmetic mean of the absolute departures of the roughness profile from the mean) and R _t (i.e. the maximum peak to valley height of the profile in the assessment length) values were recorded. The results are summarized in Table 1 below.

Table 1

Examples 5a-b Abrasion resistance by Taber Abraser

The coated plaques from Examples 2a and 2b were evaluated for their abrasion resistance using a Taber Abraser, Teledyne model 503 following the ASTM D4060-90 Test Method. 100mm square test specimens of the coated plaques 0 from Examples 2a and 2b were prepared, accurately weighed to the nearest 0. lmg and mounted on a rotating turntable.

CSlO abrasion wheels of weight 25Og and lOOOg were applied to duplicate test specimens of each coating composition for 100, 200, 500 and 1000 cycles for the 25Og weight and 1500 and 2000 cycles for the lOOOg weight. On the 5 completion of the required number of cycles loose abradings remaining on the test specimens were removed by light brushing and the test specimens reweighed and the weight loss recorded. The Wear Index, I, for each test specimen was calculated as follows:

10

Wear Index (I) = (A-B) x 1000

C

Where:

A = weight of test specimen before abrasion, mg

15 B = weight of test specimen after abrasion, mg C = Number of cycles of abrasion recorded.

The results are summarized in Table 2 below.

20 Table 2

Examples 6a-f Comparison of adhesion of polyetheretherketone and polyetherketone coatings.

The adhesion of the coatings to the substrates produced in Examples 2a-d and 3a-b were tested following the Cross Hatch Adhesion Test Method as follows:

The coated substrate was laid on a flat firm surface and with a metal ruler, eleven lines 3.75 cm long and 2mm apart and parallel to each other were cut using a sharp, single-edged razor blade. The cuts were clean and penetrated the coating completely through to the substrate. The test piece was rotated through 90° and a second set of eleven lines 3.75cm long and 2mm apart were cut at right angles to the first. The completed cuts formed a grid of 100 squares. Any flakes of coating from the grid were removed. A piece of adhesive tape, 3M Scotch 8953, 15cm long was applied over the grid and firm pressure applied. Within 90 4^ 30 seconds of application the tape was removed by grasping one end and rapidly pulling, without jerking, at a peeling angle of 180°. This procedure with a fresh piece of adhesive tape was repeated a further four times. Using a magnifying glass the grid was inspected for the removal of the coating from the substrate by the tape. The result is reported as the percentage of squares of coating remaining. For example 100% means no coating was removed.

The results for the individual coated substrates from Examples 2a-d and 3a-b are summarised in Table 3 below.

Table 3

The invention is not restricted to the details of the foregoing embodiment ( s ) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , or to any novel one, or any novel combination, of the steps of any method or process so disclosed.