POLYMER COMPOSITION

Abstract

A method of impregnating a polymer composition with an active compound or composition using liquid carbon dioxide, in order for the active compound or composition to be later released from the polymer composition gradually over a period of time. The polymer composition may comprise polybutylene succinate and pores and/or cavities into which the active compound or composition can be introduced by the method. The method involves exposing the polymer composition to carbon dioxide and the active compound or composition under increased pressure. The polymer composition may be used to form an article for use in repelling or attracting insects, for example wearable insect repellent articles or lures for insect traps. Polymer compositions suitable for use in the method, and articles comprising said polymer compositions and active compounds or compositions are also described. A method of attracting or repelling insects is also described.

Claims

1. A method of impregnating an article with an active compound or composition, wherein the article is formed from a polymer composition comprising polybutylene succinate, the method comprising the steps of: a) placing the article in a pressurisable vessel, b) adding carbon dioxide to the pressurisable vessel, c) increasing the pressure in the pressurisable vessel to above ambient pressure, d) adding the active compound or composition to the pressurisable vessel, e) depressurising the reactor and removing the article from the pressurisable vessel.

2. The method of claim 1, wherein in step c) the pressure in the pressurisable vessel is increased to above the critical pressure of carbon dioxide and the temperature in the pressurisable vessel is increased to above the critical temperature of carbon dioxide.

3. The method according to claim 1, wherein the polymer composition comprises polylactic acid.

4. The method according to claim 1, wherein the active compound or composition comprises an essential oil derived from a plant.

5. The method according to claim 1, wherein the active compound or composition is an insect repellent.

6. The method according to claim 1, wherein the active compound or composition comprises lavandin oil, geranium oil and citriodiol.

7. The method according to claim 1, wherein the article is a wearable article for repelling insects from a human or animal.

8. The method according to claim 1, wherein the active compound or composition is an insect attractant.

9. The method according to claim 8, wherein the active compound or composition comprises α-pinene and/or β-pinene.

10. The method according to claim 8, wherein the article is a lure for an insect trap.

11. The method according to claim 1, wherein after step d) and before step e), the pressurisable vessel is kept under the increased pressure of carbon dioxide for at least 10 minutes.

12. A polymer composition comprising polybutylene succinate and a structure-modifying additive.

13. The polymer composition according to claim 12, wherein the structure-modifying additive is selected from any one or more of: polyvinyl acetate, a polysaccharide, calcium carbonate and talc.

14. An article for attracting or repelling insects, wherein the article is formed from a polymer composition comprising polybutylene succinate and wherein the polymer composition is impregnated with an active compound or composition.

15. A method of attracting or repelling insects, the method comprising the steps of: 1) forming an article from a polymer composition comprising polybutylene succinate; 2) impregnating the article with an insect attractant or repellent compound or composition according to the method of claim 1; 3) placing the article at a location where insects are to be attracted to or repelled from.

Description

EXAMPLE SET 1—PREPARATION OF POLYMER COMPOSITIONS

[0097] Each of the polymer compositions described below in Table 1 were formed using standard compounding and extruding equipment by adding the specified components to the compounder, mixing and heating to 145° C. in the compounder and extruding the polymer composition into films. The type of structure-modifying additive used in each polymer composition is noted in Table 1.

TABLE-US-00001 TABLE 1 Polymer PBS PLA Additive composition (wt %) (wt %) type - wt % HDT WPL 011 45 35 Vinnex 2504 - 20 HDT WPL 012 50 30 Chitosan - 20 HDT WPL 013 45 30 Luzenactalc - 25 HDT WPL 014 75 0 Oysterlean - 25 HDT WPL 015 87.5 0 Smartfill - 12.5 HDT WPL 016 40 40 Chitosan - 20 HDT WPL 017 50 30 Polycarb 60S - 20

Examples—Heat Deflection Testing (HDT)

[0098] Heat deflection testing was carried out on the polymer compositions HDT WPL 011-017 shown in Table 1 using the standard procedure of ASTM D648.

[0099] The samples were machined into rectangular bars of 127 mm×13 mm×3 mm ready for HDT testing.

[0100] A calibrated United Instruments HDT/Vicat tester, equipped with three sample stages was used to determine the heat deflection temperature of the samples. The tests were performed according to ASTM D648 applying fibre stresses of σ=0.45 MPa for all samples. The samples were mounted on the HDT tester stages in the edgewise direction. The stages with the samples were then immersed in a heat transfer oil bath. The appropriate total mass, including the mass of the loading rod and press head (˜75 g) was added to each sample to achieve the desired stress (σ) of 0.45 MPa calculated using the equation dictated in the ASTM D648. The distance between the support stands was adjusted to 100 mm.

[0101] A schematic of the test arrangement is shown in FIG. 1 together with the sample geometry. The equation used to calculate the load applied is given below:

[0102] The HDT results are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Polymer Individual HDT test Average HDT result composition results (° C.)* (° C.) HDT WPL 011 96.8, 100.4, 101.0 99 HDT WPL 012 97.2, 96.0 97 HDT WPL 013 93.7, 95.8, 94.7 95 HDT WPL 014 99.7, 98.4 99 HDT WPL 015 100.9, 101.1 101 HDT WPL 016 94.7, 94.3, 95.3 95 HDT WPL 017 97.8, 94.9, 94.4 96 *Only for the samples in which the HDT values between the first two samples was greater than 1.4° C., was a third sample tested and an average of the three reported.

[0103] Each of the samples HDT WPL 011-017 showed a heat deflection test result which indicates the polymer compositions would be suitable for use outdoors in relatively high ambient temperatures. For example, each polymer composition may be suitable for use in a wearable insect repellent articles or insect traps which are both intended for use in hot climates.

Examples—Impregnation of Polymer Compositions with Insect Repellents

[0104] A roll of film formed from polymer composition HDT WPL 011 was impregnated with an essential oil blend that contains lavandin oil, rose geranium oil and nepeta cataria oil.

[0105] Supercritical carbon dioxide (scCO.sub.2) was used in a method for impregnating essential oils to the polymers as it may act as a low viscosity and highly diffusive carrier. Two different methods of impregnating essential oils using scCO.sub.2 were used and then release profiles of the essential oils over time were studied.

[0106] Raw materials: Lavandin oil (Grosso), Rose Geranium oil (Pelargonium graveo/ens) and Catnip oil (Nepeta cataria) were purchased from Elixarome Ltd. A comparative polymer film formed from PLA was provided.

[0107] Sample preparation: polymer film of composition HDT WPL 011 and the comparative polymer film was divided into sections of 13.5 cm×2 cm for all trials. An essential oil blend was prepared by mixing lavandin oil, rose geranium oil and catnip oil at a 1:1:1 ratio.

[0108] Extraction trials: Extraction trial was carried out using a Thar SFC-1000 laboratory plant fitted with a 100 ml extractor and a 250 ml separator. Two independent methods were used to impregnate each sample of the polymer composition and the methods are described below:

[0109] Method 1—Continuous Flow Method

[0110] 23 strips of the polymer film HDT WPL 011 (39.03 g) (called “red sheet” in the following data) or 5 strips of comparative polymer film (41.12 g) (called “collar” in the following data) were packed into a 100 ml extractor and the vessel was pressurised to 100 bar, 40° C. with a CO.sub.2 flow at 5 g/m in. Once the extraction vessel reached 100 bar, 5% (0.25 g/min) of the essential oil blend was continuously introduced into the extractor for 60 minutes. After 60 minutes, the flow of the essential oil blend ceased and neat scCO.sub.2 was passed through the extraction vessel for 15 minutes to remove any free (not impregnated into the polymer film) essential oil. Thereafter, the extractor was depressurized at 1 bar per 5 seconds and the polymer sample was retrieved and stored in heat sealed aluminium laminated bags.

[0111] Method 2—Stop Flow Method

[0112] 27 strips of red sheet (37.68 g) of 5 strips of collar (39.06 g) were packed into a 100 ml extractor and the vessel was pressurised to 100 bar, 40° C. with a CO.sub.2 flow at 5 g/min. Once the extraction vessel reached 100 bar, 5% (0.25 g/min) of the essential oil blend was continuously introduced into the extraction for 30 minutes. After 30 minutes, the flow of the essential oil blend and CO.sub.2 were ceased and the extraction vessel was isolated so that the polymer sample stood in solution for a further 60 minutes. After 60 minutes, neat scCO.sub.2 was passed through the extraction vessel for 15 minutes to remove any free essential oil. Thereafter, the extractor was depressurized at 1 bar per 5 seconds and the polymer sample was retrieved and stored in heat sealed aluminium laminated bags.

[0113] All samples of polymer were impregnated on the same day to eliminate any process variables that might occur on different days.

[0114] Establishment of release profile of essential oil: 3 strips of impregnated polymers were removed from the heat sealed aluminium bags on the day of analysis and the volatile organic compounds (VOCs) of each strip of polymer were analysed. The profile of VOCs of these samples were denoted as day 1. The strips of polymers were laid on a tray and preserved in a temperature controlled room (27° C.) for a 10 day period. Strips of red sheet were analysed on days 1, 3, 5, 8 and 10. Analysis of three independent strips of impregnated polymer would allow the elimination of any outlier.

[0115] Analysis: Essential oil (as supplied) and as blended were analysed as liquid dilution (2 μl in 1 cm.sup.3 of heptane) and 1 μl of this solution was injected into the GC-MS injector at 250° C. This was carried out to determine the principal components of the essential oil and these components were used as markers to follow the progress of the release profile.

[0116] The relative abundance of VOCs emitted by the polymer sample was analysed by Headspace Solid Phase Microextraction (HS-SPME). The procedure is described as follows.

[0117] Approximately 35 mg of polymer sample was placed into a headspace vial (20 cm.sup.3) and equilibrated for 10 minutes at 40° C. After equilibration, a 5 cm 50/30 μm Divinylbenzene/Carboxen/Polydimethylsiloaxane (DVB/CAR/PDMS) fibre was exposed in the headspace of the vial under the same conditions for a suitable period. After absorption, the fibre was retracted and desorbed for 1 minute in the GC-MS injector (250° C.). This process was carried out manually using accurate timing at all stages. Between extractions, the fibre was conditioned following the manufacturer's instructions, exposing the fibre at 270° C. for 30 minutes in a GC injector under a constant flow of hydrogen.

[0118] The peak area of the principal component of each essential oil was acquired for each sample of polymer and these provided semi-quantitative data to monitor the abundance of the principal component of each essential oil over a 10 day period.

[0119] GC-MS conditions: Analysis was carried out using an Agilent 6890 gas chromatograph coupled to an Agilent 5973 mass spectrometer (EI detector) equipped with a Zebron ZB5-MS column (30 m×0.25 mm×0.25 μm). The GC-MS system was controlled by MSD Chemstationsoftware equipped with NIST/EPA/NIH Mass Spectral Library. The carrier gas was maintained at 1 cm.sup.3.min-1helium, injector temperature was 250° C. and had a split ratio of either 2:1 (for HS-SPME analysis) or 50:1 (for analysis of liquid dilution). Mass spectra were recorded in electron impact (EI) ionization mode, scanning m/z 40 to 600 in 1 second.

[0120] Temperature programme 1—HS-SPME analysis: The temperature program was as follows: 40° C. (2.5 min hold), 5° C./min to 200° C., 10° C./min to 240° C. (5 min hold).

[0121] Temperature programme 2—Analysis of liquid dilution: The temperature program was as follows: 60° C. (1 min hold), 6° C./min to 300° C. (10 min hold).

[0122] Results: The essential oils used in the impregnation trials were analysed individually and as a blend of the three oils using HS-SPME and liquid injections. The analytical response for the principal components of the liquid injection and HS-SPME measures the volatility of the components. Thus β-cineole and linalyl acetate were identified as markers for lavendin oil; citronellol and 8-linalool for geranium oil and nepetalactone and caryophyllene for nepeta oil.

[0123] Observations from the impregnation trials: FIGS. 2A and 2B show the roll of polymer film pre- and post-impregnation. The strips of polymer obtained after the impregnation trial show that during the process, blisters have formed on the surface of the sample of polymer due to the passage of CO.sub.2 that had penetrated through the material (FIG. 2B). After each impregnation trial, neat scCO.sub.2 was passed through the sample of polymer in order to remove the free oil; the mass of free oil obtained in each impregnation trial as shown in Table 3. The data showed that using method 2, the mass of free oil obtained was lower and this indicated that this process had allowed the polymer to capture more essential oil blend. By stopping the CO.sub.2 flow the oil has greater contact with the sample of polymer thus an equilibrium is established. It was noted that there was a loss to the colour of the blend of essential oil that was recovered. Analysis of the oil indicated that there were no compositional changes to the blend of essential oil and the loss of colour was due to pigments binding onto the polymer. This suggests that the oil that was recovered can be recycled for additional trials and the pigment binding is not likely to have a detrimental effect on the polymer.

TABLE-US-00003 TABLE 3 Mass of polymer sample loaded and mass of free oil recovered in each impregnation trial No. of Mass of strips of Mass of free oil Impregnation polymer in sample in recovered in Sample method extractor extractor (g) separator (g) Red film 1 23 39.03 7.82 Red film 2 27 37.68 3.58 Collar 1 1 5 41.12 11.57 Collar 2 2 5 39.06 4.71

Examples—Insect Repellent Release Profiles

[0124] Three individual strips of impregnated polymer were preserved in a temperature controlled room and the volatile organic compounds (VOCs) of these samples were analysed over a 10-day period. The relative abundance of the selected marker compounds for each essential oil over this period was monitored. FIGS. 3-6 shows that from day 1 to day 3, there was a rapid decrease to the abundance of each selected marker compound. From day 3 to day 10, the relative abundance of each marker compounds was stable and no further decline was observed. It was noted that there was only a marginal change in the relative abundance due to a variation of analytical response. This trend was observed for all the VOCs, this was not expected as the boiling points of each VOCs differed and it was expected that some VOCs would have had experienced a greater reduction than others.

[0125] To assess the stability of the VOCs of the impregnated polymers, the strips of impregnated polymer were re-sealed in heat sealed aluminium bags and retained in a temperature controlled room. The relative abundance of the marker compounds in these strips of impregnated polymers (after prolonged storage) were compared with the strips of impregnated polymers at day 1. FIGS. 7 and 8 shows relative abundance of the marker compounds and an insignificant difference was observed. It was not known if the minor variation was due to differences in analytical response or a sample to sample variation during the impregnation trial.

[0126] Conclusions: This work has demonstrated that it was feasible to impregnate essentials oils into polymers using scCO.sub.2. The release profile of the impregnated polymer indicated that the VOCs that were impregnated into the polymers experienced a rapid decline from day 1 to day 3. Subsequently, the abundance of these VOCs remained stable from day 3 to day 10 and shows no further reduction in level of abundance of these VOCs. The stability of the impregnated polymer that was kept in heat seal aluminum bag in a temperature controlled room indicated there was no significant decline to the VOCs and demonstrated that these impregnated polymers have a long shelf life when in suitable packaging.

Examples—Impregnation of Polymer Compositions with Insect Attractant

[0127] A roll of film formed from polymer composition HDT WPL015 (called “red film” in the data below) and pellets of the same polymer composition (called “polymer beads” in the data below) were impregnated with pinene compounds using the following procedure and materials.

[0128] Raw materials: 100 ml of α-pinene was purchased from Sigma Aldrich.

[0129] Extraction trials: An extraction trial was carried out using a Thar SFC-1000 laboratory plant fitted with a 1 L extractor and a 250 ml separator. The samples were packed into a 1 L extractor and the vessel was pressurised to 100 bar, 35° C. with a CO.sub.2 flow at 10 g/min. Once the extraction vessel reached 100 bar, 5% (0.50 g/min) of α-pinene was continuously introduced into the extraction for 90 minutes. After 90 minutes, the flow of essential oil and CO.sub.2 were ceased and the extraction vessel was isolated so that the polymer sample stood in solution for a further 120 minutes. After 120 minutes, neat scCO.sub.2 was passed through the extraction vessel for 30 minutes to remove any free oil. Thereafter, the extractor was depressurised at 1 bar per 10 seconds and the polymer sample was retrieved and stored in sealed aluminium foil pouches.

[0130] Analysis: The relative abundance of VOCs emitted by the polymer sample was analysed by Headspace Solid Phase Microextraction (HS-SPME). The procedure is described as follows.

[0131] Approximately 60 mg of polymer sample was placed into a headspace vial (20 cm.sup.3) and equilibrated for 10 minutes at 40° C. After equilibration, a 5 cm 50/30 μm divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre was exposed in the headspace of the vial under the same conditions for a suitable period. After absorption, the fibre was retracted and desorbed for 1 minute in the GC-MS injector (250° C.). This process was carried out manually using accurate timing at all stages. Between extractions, the fibre was conditioned following the manufacturer's instructions, exposing the fibre at 270° C. for 30 minutes in a GC injector under a constant flow of hydrogen.

[0132] GC-MS conditions: Analysis was carried out using an Agilent 6890 gas chromatograph coupled to an Agilent 5973 mass spectrometer (EI detector) equipped with a Zebron ZB5-MS column (30 m×0.25 mm×0.25 μm). The GC-MS system was controlled by MSD Chemstation software equipped with NIST/EPA/NIH Mass Spectral Library. The carrier gas was maintained a 1 cm.sup.3.Math.min.sup.−1 helium, injector temperature was 250° C. and had a split ratio of either 2:1 (for HS-SPME analysis) or 50:1 (for analysis of liquid dilution). Mass spectra were recorded in electron impact (EI) ionization mode, scanning m/z 40 to 600 in 1 second. The temperature program was as follows: 40° C. (2.5 min hold), 5° C./min to 200° C., 10° C./min to 240° C. (5 min hold).

[0133] Results: Table 4 shows the mass of polymer samples loaded into a 1 L extraction vessel and the volume of free α-pinene recovered; a lower volume of α-pinene was recovered from the use of polymer beads as the material absorbed a greater volume of α-pinene.

TABLE-US-00004 TABLE 4 Mass of polymer sample loaded and mass of free oil recovered in each impregnation trial Mass of polymer Mass of free packed in the oil recovered from Sample extractor (g) the separator (g) Red film 532.16 21.18 Polymer beads 603.11 13.47

[0134] The physical appearance of the recovered α-pinene after the impregnation trial showed that pigments from the polymers were extracted along with an unknown white solid. The white solid is presumably residual matter retained during the manufacture of the polymers beads, bur there is no justification for the white solids recovered from the red film trial as loose polymeric material should have been absent. The recovered α-pinene can be used for subsequent batches of impregnation trials, but the α-pinene would require filtration to remove the white solids to avoid causing mechanical problems to the delivery pump. It can be noted that if the process is scale-up to the pilot plant or commercial scale, the required treatment of the recovered α-pinene can contribute to elevating the cost of production.

[0135] Red film supplied was coiled into rolls, similar to as shown in FIG. 2, and blisters were formed on the surface of the red film during the impregnation trial as shown in FIG. 3. The formation of the blisters was due to the encapsulation of α-pinene. It was observed that this encapsulation effect was not observed in the polymers beads as the polymer beads remained in its original form after the impregnation trial was completed.

[0136] An equal mass of each individual impregnated polymer samples was analysed using headspace and the chromatogram is shown in FIG. 9. FIG. 9 shows HS-SPME-GC-MS chromatogram of the impregnated red film (top) and impregnated polymer beads (bottom). The data suggested that although the two sources of polymers were impregnated using the identical method, it appeared that the red film had released a higher abundance of α-pinene compared to the polymer beads. This greater release of α-pinene may be due to the encapsulation of the α-pinene within the blisters on the impregnated red film material.

[0137] Conclusions: These tests have demonstrated that α-pinene can be successfully impregnated into two forms of polymer composition HDT WPL015. It was noted that blisters were formed on the red film material due to the encapsulation of α-pinene; this encapsulation effect had enhanced the abundance of the release of α-pinene from the material compared to the polymer beads which did not have the encapsulation effect.

Examples—Insect Attractant Release Profiles

[0138] Initial observations have indicated that the polymer film of polymer composition HDT WPL015 release the insect attractant α-pinene over a period of at least 3 months, in an amount sufficient to attract pine weevils and/or pine beetles into an insect trap. Therefore an insect lure formed from HDT WPL015 and impregnated with a pinene compound as described above may be effective in a method of controlling insects which affect tree plantations, during a breeding season of said insects.

[0139] In summary. The present invention provides a method for impregnating a polymer composition with an active compound or composition using liquid carbon dioxide, in order for the active compound or composition to be later released from the polymer composition gradually over a period of time. The polymer composition may comprise polybutylene succinate and pores and/or cavities into which the active compound or composition can be introduced by the method. The method involves exposing the polymer composition to carbon dioxide and the active compound or composition under increased pressure. The polymer composition may be used to form an article for use in repelling or attracting insects, for example wearable insect repellent articles or lures for insect traps. Polymer compositions suitable for use in the method, and articles comprising said polymer compositions and active compounds or compositions are also provided. A method of attracting or repelling insects is also provided.

EXAMPLE SET 2—PREPARATION OF POLYMER COMPOSITIONS

[0140] Each of the polymer compositions described below in Table 4 were formed as described above for Example Set 1. The type of structure-modifying additive used in each polymer composition is noted in the far right-hand column.

TABLE-US-00005 TABLE 4 Polymer PBS PLA Additive composition (wt %) (wt %) type - wt % 2.1 35 45 Vinnex 2504 - 15 and starch - 5 2.2 30 55 Vinnex 2504 - 15 2.3 19 60 Luzenac talc - 7 and Vinnex 2504 - 14 2.4 10 55 Polycarb 60S - 22 and Vinnex 2504 - 13

[0141] These polymer compositions were formed into rolls of film as described above for Example Set 1. The films were impregnated with active compounds as described above for Example Set 1.

[0142] Polymer composition 2.1 was impregnated with a 1:1:1 mixture of lavandin oil, geranium oil and citriodiol. The film was found to provide a suitable release profile for the application of this polymer composition and active composition for repelling mosquitos and/or horsefly from humans or animals.

[0143] Polymer composition 2.2 was impregnated with nootkatone. The film was found to provide a suitable release profile for the application of this polymer composition and active compound composition for repelling ticks from humans or animals.

[0144] Polymer composition 2.3 was impregnated with nonanal and octanal. The film was found to provide a suitable release profile for the application of this polymer composition and active composition for attracting bed bugs, for example into a trap.

[0145] Polymer composition 2.4 was impregnated with a liquid seaweed fertilizer comprising comprises nitrogen, potassium, phosphate and suitably magnesium, as well as plant sugars, growth hormones and other essential minerals. The film was found to provide a suitable release profile for the application of this polymer composition and active composition for feeding plants such as turf, fruit, vegetables and ornamental plants.

[0146] Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

[0147] Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of” or “consists essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention. Typically, when referring to compositions, a composition consisting essentially of a set of components will comprise less than 5% by weight, typically less than 3% by weight, more typically less than 1% by weight of non-specified components.

[0148] The term “consisting of” or “consists of” means including the components specified but excluding addition of other components.

[0149] Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to encompass or include the meaning “consists essentially of” or “consisting essentially of”, and may also be taken to include the meaning “consists of” or “consisting of”.

[0150] For the avoidance of doubt, wherein amounts of components in a composition are described in wt %, this means the weight percentage of the specified component in relation to the whole composition referred to. For example, “the polymer composition comprises from 30 to 90 wt % PBS” means that 30 to 90 wt % of the polymer composition is provided by PBS.

[0151] The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention as set out herein are also to be read as applicable to any other aspect or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each exemplary embodiment of the invention as interchangeable and combinable between different exemplary embodiments.

[0152] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0153] All of the features disclosed in this specification (including any accompanying claims, and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0154] Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0155] 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, and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.