MATERIALS CONTAINING CELLULOSE NANOFIBERS

Abstract

A material containing cellulose nanofibres, the material comprising a gel material comprising cellulose nanofibres in an aqueous medium, the cellulose nanofibres having 10% or more by weight hemicellulose. The cellulose nanofibres have a diameter of less than 100 nm, or less than 50 nm, or less than 20 nm. The gel material can be used as an adhesive to make laminates or to make paper by dewatering the gel material.

Claims

1. A material containing cellulose nanofibres, the material comprising a gel material comprising cellulose nanofibres in an aqueous medium, the cellulose nanofibres having 10% or more by weight hemicellulose.

2. A material as claimed in claim 1 wherein the cellulose nanofibres have a diameter of less than 100 nm, or less than 50 nm, or less than 20 nm.

3. A material as claimed in claim 1 wherein the cellulose nanofibres have 15% or more by weight hemicellulose, or the cellulose nanofibres have 20% or more by weight hemicellulose, or the cellulose nanofibres have 25% or more by weight hemicellulose, or the cellulose nanofibres have 30% or more by weight hemicellulose.

4. A material as claimed in claim 1 wherein the cellulose nanofibres include cellulose, hemicellulose, lignin and extractives.

5. A material as claimed in claim 4 wherein the cellulose nanofibres comprise from 10 to 25%, by weight, lignin, 35 to 70% by weight cellulose and 2 to 10%, or 2 to 8% extractives.

6. A material as claimed in claim 1 wherein the gel contains from 2 mg/ml (w/V) cellulose nanofibres to 20% w/V cellulose nanofibres, or from 2 mg/ml (w/V) to 15% w/V cellulose nanofibers.

7. A material as claimed in any claim 1 wherein the gel material has rheology modifiers added to the gel in order to effect or controlled the rheology of the gel.

8. A material as claimed in claim 1 wherein the aqueous medium comprises water.

9. A material as claimed in claim 1 wherein the aqueous medium comprises water and an alkali.

10. A material as claimed in claim 9 wherein the aqueous medium has a pH of greater than 7.

11. A material as claimed in claim 1 wherein the aqueous medium comprises an aqueous medium remaining with the cellulose nanofibres following treatment of a plant material to form the cellulose nanofibres following a mild alkali treatment, the mild alkali treatment including treating the plant material with an alkali solution having an alkalinity equivalent to 2% to 15% NaOH, or 2% to 14%, or 2% to 10%, or 2% to 7%, or 2% to 5% NaOH.

12. A method for forming the material as claimed in claim 1 any one of the preceding claims comprising treating plant material with a mild alkali treatment, followed by mechanical processing to form the cellulose nanofibres.

13. A method as claimed in claim 12 wherein the plant material is washed with water following the mild alkali treatment to remove dissolved material from the plant material, subjecting a pulp containing the alkali treated plant material and water to mechanical processing selected from shear mixing, high-energy ball milling, passing the pulp through an extruder, such as a twin screw extruder, high-pressure homogenisation to cause mechanical disintegration of the plant material into microfibrillated cellulose or cellulose nanofibres and form a product comprising a material containing water and cellulose nanofibres and optionally removing part of the water removed therefrom to form the gel material.

14. A method as claimed in claim 12 wherein a pulp resulting from the mechanical processing is dried to recover the cellulose nanofibres and the gel material is formed by subsequently adding an aqueous medium to the dried fibres.

15. Paper made from cellulose nanofibres, characterised in that the cellulose nanofibres have a hemicellulose content of at least 10% by weight.

16. A method for making the paper of claim 15 by dewatering a pulp or gel material as claimed in containing the cellulose nanofibres.

17. A product having a first component adhered to a second component, characterised in that gel material comprising cellulose nanofibres having 10% or more, by weight, hemicellulose in an aqueous medium is used as an adhesive to adhere the first component to the second component.

18. A product as claimed in claim 17 comprising a laminate having a first sheet and a second sheet adhered to the first sheet, with the gel layer adhering the first sheet to the second sheet.

19. A product as claimed in claim 18 wherein the laminate comprises a plurality of sheets, with a gel layer being located between each sheet in order to adhere the gel layer to each sheet.

20. A product as claimed in claim 19 wherein the sheets comprise paper sheets, sheets of hemp, sheets of flax, fibreglass sheets, cardboard sheets, cloth sheets, fabrics sheets, woven sheets, non-woven sheets, polymeric materials or biodegradable polymeric materials.

21. A product as claimed in claim 19 wherein the laminate is used as a packaging material.

22. A product as claimed in claim 18 wherein biodegradable thermoplastics and/or fire retardants are added to the laminate.

23. A product as claimed in claim 22 wherein the biodegradable thermoplastics and/or fire retardants are added to the gel layer or the fire retardants are present in the sheet material.

24. A process for producing an article in which a first component is adhered to a second component, the process comprising applying a layer of the gel material as claimed in claim 1, placing at least part of the second component in contact with the gel material and dewatering the gel material such that the first component adheres to the second component.

25. A method as claimed in claim 24 wherein the first component, gel material and second component are pressed together.

26. A method as claimed in claim 25 wherein the first component, gel material and second component are hot pressed together.

27. A method as claimed in claim 24 wherein the article is heated in order to remove water from the gel layer.

28. A method as claimed in claim 24 wherein the first component and the second component comprise a first sheet and a second sheet and the article comprises a laminate and the laminate is formed into a shaped product by placing the first sheet, the gel layer and the second sheet into a mould and pressing the further sheet, gel layer and second sheet into the mould.

29. A composite material comprising a matrix made from cellulose nanofibres having a hemicellulose content of at least 10% by weight, the composite material including one or more property modifying agents.

30. A composite material as claimed in claim 29 wherein the one or properly modifying agents comprise a reinforcing agent.

31. A composite material as claimed in claim 30 wherein the reinforcing agent comprises glass fibre, carbon fibre, graphene, metal fibres, flake material, or platelet-shaped material.

32. A composite material as claimed in claim 29 wherein the one or more property modifying agents are dispersed throughout the matrix made from the cellulose nanofibres.

33. A composite material as claimed in claim 29 wherein the composite material comprises at least 60% by weight, or at least 70% by weight, or at least 80% by weight, or at least 85% by weight, or at least 90% by weight, or at least 95% by weight, or at least 97% by weight, or at least 98% by weight, or at least 99% by weight, of the matrix made from cellulose nanofibres and the one or more property modifying agents comprise less than 40% by weight, or less than 30% by weight, or less than 20% by weight, or less than 50% by weight, or less than 10% by weight, with 5% by weight, or less than 3% by weight, or less than 2% by weight, or less than 1% by weight, of the composite material.

34. A material as claimed in claim 1 wherein the cellulose nano fibres are derived from a grass species having C4-leaf anatomy, or the cellulose nanofibres are derived from plant material is derived from a drought-tolerant grass species, or an arid grass species, or from Australian native arid grass known as “spinifex” of genera which include Triodia, Monodia, and Symplectrodia or from T. pungens, T. shinzii or T. basedowii, T. longiceps.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0057] Various embodiments of the invention will be described with reference to the following drawings, in which:

[0058] FIG. 1 shows a schematic side view of a moulded article in accordance with the present invention.

DESCRIPTION OF EMBODIMENTS

[0059] In FIG. 1, a mould has a female portion 10 and a male portion 12. The mould portions 10, 12 have holes or perforations 14 to allow excess water to be squeezed out as the male portion 12 mould is closed and pressed towards the female mould portion 10. A plurality of alternating layers of sheets of material, such as paper, hemp mat, flax mat, fibreglass sheets, etc and layers of a gel material comprising cellulose nanofibres having at least 10% hemicellulose content in an aqueous medium are placed in the female mould portion 10. In some of the experimental work conducted to date, the hemicellulose content was around 23%. The male mould portion 12 is then closed and pressed towards the female mould portion 10, which compresses the alternating layers of sheets and gel material. This results in water being squeezed out from the material and the alternating layers of sheets and gel material being compressed together. The mould may be heated to assist in the cellulose nanofibres adhering to the sheets. The mould may then be opened and the formed article removed.

[0060] In another embodiment, “laying up” of the composite material may occur by laying down a first sheet and spraying the CNF gel layer onto the first sheet, followed by applying a second sheet to the gel layer, and so forth. The spraying step could assist in removing some of the excess water, in which case these breaks that may comprise a pseudo-spray drying step.

[0061] In other embodiments, water may be removed from the gel by heating, such as by the use of microwaves, steam drying, superheated steam, infrared radiation or the like. Heating is anticipated to be especially useful where manufacturing processes require the rapid removal of water from the gel.

Example—Preparation of Cellulose Nanofibers

[0062] Spinifex grass (Triodia pungens) was collected from Camooweal in Queensland, Australia. NaOH flake (98% purity) was purchased from Alfa Aesar. Calcofluor white was obtained from Sigma-Aldrich. Reverse osmosis (RO) purified water was used throughout.

[0063] Grass was pre-screened and the leaves were selected and cut-off from the woody stem. Thus pre-screened material is referred to as the “tips”. The tips were then cut to about 5 cm with a guillotine, washed three times with water at 85° C. at approximately 1:35 grass to water ratio in a 100 L tank and dried at room temperature over 3 days. The tips were then ground to <0.5 mm. The material was pre-soaked in water and treated with a 2% (w/v) aqueous NaOH solution using a grass-to-liquid ratio of 1:10 for 2 h at 80° C. in a 50 L jacketed stainless steel tank. The mixture was vigorously stirred to ensure uniform mixing. Subsequently, the NaOH-treated pulp was washed with hot water (approximately 60° C.) to remove dissolved material, until the effluent was neutral. The pulp was stored at 4° C.

[0064] The chemical composition analysis of the spinifex grass was performed to evaluate the effectiveness of the alkaline treatment process prior to mechanical processing. The treatment is aimed to reduce the issue of clogging and energy consumption of the machines by removal of lignin and extractives, and softening material. The results are presented in Table 1. The data revealed a significant (p=0.003) reduction of lignin from 18.4% (total amount of acid soluble and insoluble lignin) to 12.7% after alkaline pulping as compared to hot water-washed grass. The treatment resulted in a twofold increase in the ratio of cellulose to lignin in the pulp (Table 1). The reduction in the amount of lignin is attributed to the solubilization of lignin due to its depolymerization and formation of free phenolic groups. Use of aqueous alkali solutions at elevated temperatures is commonly applied for this purpose. Lignin provides stiffness, and rigidity of the plant as well as it repulses water from the cell wall volume. Therefore, chemical removal of this component can be related to reduction of stiffness of the fibers, which can improve efficiency of mechanical fibrillation by lower cohesion between the cell wall bundles. Non-wood lignocellulosic resources are generally easier to fibrillate than wood due to usually lower amount of lignin in their cell wall. Consequently, in the case of non-wood material, alkali hydrolysis can be typically milder and more effective. The alkaline pulping also removed a significant (p=0.006) amount of extractives (Table 1). Spinifex T. pungens is a resinous species therefore, the extractives could be attributed to this remnant resin trapped in the leaves, unable to be removed with only hot water washing. The resin makes the material sticky, which could cause adhesion to the machinery parts, hence its removal is important prior to processing. Since lignin and resin are relatively hydrophobic components of spinifex, their presence can hinder swelling of cellulose and impede the subsequent fractionation process. Use of alkali solution can also influence the susceptible carbohydrates. As can be seen in Table 1 the ratio of cellulose to hemicellulose increased after NaOH treatment. It is possible that at high temperature and pH the structure of cellulose was affected. However, it is more likely that the more readily accessible hemicelluloses undergo degradation and/or dissolution in the alkaline medium. A similar reduction in hemicellulose content attributed to its degradation was earlier shown during mild NaOH pretreatment. Previously, researchers were not able to fractionate wood biomass treated at even harsher conditions with NaOH, followed by extrusion processing. However, in the current study, we show that the alkaline pulping allowed easy processing of the material without any clogging issues.

TABLE-US-00001 TABLE 1 Chemical composition of T. pungens grass washed and treated with 2% NaOH for 2 h at 80° C. Acid Cellulose: Man/Ara/ Klason soluble Ex- Not Hemi- Cellulose: Glucan Xylan Gal/Rha lignin lignin tractives Ash quantified cellulose Lignin Sample (%) (%) (%) (%) (%) (%) (%) (%) ratio ratio Grass 37.8 ± 0.2 23.34 ± 0.03 3.87 ± 0.03 15.5 ± 0.2 2.89 ± 0.01 6.5 ± 0.2 2.30 ± 0.03 7.7 1.4 2.1 washed Alkali 52.6 ± 0.2 22.42 ± 0.08 3.48 ± 0.02 11.4 ± 0.3 1.26 ± 0.01 2.17 ± 0.01 1.54 ± 0.04 5.2 2.0 4.2 delignified pulp

[0065] Mechanical processing of the pulp was carried out using a twin screw extruder (TSE), high energy ball milling (HEBM) and high-pressure homogenisers and (HPH). The TSE processing was performed on a HAAKE PolyLab OS (Thermo Scientific, England) co-rotating twin-screw extruder with a screw diameter of 16 mm and a barrel length to diameter ratio (L/D) of 40:1. The material was hand-fed into the extruder at approximately 15% solid content and the screw speed was kept at 90 rpm, using between 1 and 10 passes. The die was removed from the end of the extruder to ease pulp outflow. No external heating was applied in the extruder barrel. The torque applied on the screws was recorded with the PolyLab OS software and the data is presented as an average and standard deviation. The extruded samples are denoted as X-followed by a number of times the material was passed through e.g. X-1 for the sample extruded once.

[0066] The HEBM processing was performed on a laboratory agitator bead mill LabStar (Netzch, Germany). The pulp was diluted to approximately 0.7% (w/v) with water and processed in a continuous mode for 20 or 40 minutes per liter of dispersion. The mill was packed with smooth-surface, 1 mm zirconium oxide beads ZetaBeads® Plus (Netzch, Germany) and was operated at 1000 rpm for the duration of the process. The feed pump speed was set to 60 rpm. The samples prepared with the use of the bead mill are denoted as M-, followed by the time of milling per 1 liter of suspension e.g. M-20 for the sample milled for 20 min L.sup.−1. The samples extruded and then milled follow the notation for the extrusion and milling, as described above.

[0067] High pressure homogenization (HPH) was performed on Panther NS3006L pilot-scale high pressure homogenizer (GEA Niro Soavi, Italy) at a solid content of approximately 0.6% (w/v). Material was passed through the homogenizer at 400 bar, 700 bar and subsequently three times at 1100 bar. The sample prepared accordingly is denoted as H.

[0068] To evaluate the morphology of the fibers after mechanical treatments, CLSM and TEM were used. Here, we propose that confocal microscopy can be employed to observe the overall sample appearance on a micro-scale, which can be a good indication of nanofibrillation efficiency. In the literature, usually optical microscopy is used to evaluate pulp macro-scale dimensions (Rol et al. 2017) however, it does not provide good contrast between fibers and the background, which makes it difficult to image fibers and fiber bundles. The advantage of CLSM is that it allows for visualization of both large fibers, and smaller fiber bundles, when the material has been dyed with a fluorescent dye. Moreover, the sample can be reconstructed in a three-dimensional image. For the purpose of this work, four representative samples prepared via different mechanical treatments are shown. All samples show fibers of a few hundred micrometers in length, irrespective of the mechanical process used. The long (>200 nm) fibers are present even for the samples processed by homogenization (H), extrusion combined with milling (X-M), and milling alone (M). Nevertheless, in the case of samples H, X-3-M-20 and M-20, in between the relatively large, distinct fibers of a few hundreds of micrometers length, there appear to be a dense network of nano-fibrillated material observed in the confocal images. This is not the case of the sample X-3, which was processed by extrusion only, as well as the other extruded-only samples (data not shown). For the X-3 sample, the space in between the large fibers is relatively clear, without traces of fine, fluorescent material.

[0069] To evaluate the material morphology on the nano-scale, TEM was employed. It was found that all samples included at least some proportion of nanosized fibers, including the extruded-only material. The average diameter of the individual nanofibers were 8±2 nm, 11±3 nm, 10±3 nm and 10±3 nm for the H, X-3, X-3-M-20 and M-20 samples, respectively. According to the statistical analysis, sample H showed a significantly smaller (p<<0.05) diameter to the other samples. The size distribution of the fiber diameters presented in FIG. 3 indicates that most of the fibers of sample H are within the 7-8 nm bin range whereas, for the X-3, X-3-M-20 and M-20 samples most of the fibers are 9-10 nm in diameter. Moreover, for sample H only 1% of the fibers are within the largest measured diameter (15-16 nm) whereas, for the other samples around 7% (X-3-M-20) and 11-12% (X-3 and M-20) of fibers are within the largest measured diameter (15-20 nm). This shows that high pressure homogenization produces fibers with overall smallest diameter and the remaining methods produce fibers with similar average diameter and similar size distribution. This can be correlated to the high shear and impact forces utilized in the homogenization process, which results in higher fibrillation efficiency. The presence of nanofibers, as indicated by TEM, in the extruded-only pulp indicates that even this low-energy processing is able to produce CNF. However, the CNF quantity in the H, X-M and M samples seems to be higher than that of X samples based on the network density in the overall CLSM images

[0070] Handsheets from the processed spinifex samples were prepared using an automatic British handsheet maker (Mavis Engineering, England) with a target grammage of 80-85 g m.sup.−2. The mechanically treated pulp was diluted to 0.3% (w/w), vigorously mixed, poured over a Whatman 541 filter paper, and drained. After drainage, the wet cake was pressed between two blotting papers with an automated couching system (sample H) or with 10 kg hand-roll (samples X and M) to remove excess water. Subsequently, the filter paper was removed and the samples were cold-pressed between fresh blotting papers for 5 min at 345 kPa on an L&W Sheet Press (AB Lorentzen & Wettre). The H sample was dried on a drum roll dryer at 105° C. for approximately 15 min. The X and M samples were air dried for 24 h (at 50% RH, 22° C.) on a steel plate, restrained by a metal ring with weight placed on top.

[0071] The mechanical properties of the handsheets allow a good evaluation of the fibrillation efficiency obtained via different processing techniques. The results of the tensile mechanical properties, burst strength, density, and porosity of the sheets are presented in Table 2.

TABLE-US-00002 TABLE 2 Mechanical and physical properties, and energy consumption of handsheets produced with different processing methods. Tensile Strain Burst Energy Index at Tensile Young's Strength con- Sample (kNm break Strength Modulus (kPa Density Porosity Cr sumption name g.sup.−1) (%) (MPa) (GPa) m.sup.2 g.sup.−1) (g cm.sup.−3) (%) I (kWh/t)* X-1   32 ± 4 .sup.d   1.8 ± 0.4 .sup.d   25 ± 3 .sup.d 1.27 ± 0.07 1.9 ± 0.3 .sup.d 0.75 ± 0.05 .sup.b 48 ± 4 .sup.b 74 326 X-3 40 ± 2 2.1 ± 0.3 32 ± 2 1.9 ± 0.2 2.3 ± 0.1   0.82 ± 0.05 .sup.b 44 ± 3 .sup.b 74 476 X-6 40 ± 3 1.8 ± 0.4 36 ± 3 2.1 ± 0.3 2.5 ± 0.2   0.91 ± 0.05 .sup.d 38 ± 4 .sup.d 72 601 X-10 46 ± 8 2.0 ± 0.2 40 ± 7 2.0 ± 0.1 2.6 ± 0.3 .sup.d 0.88 ± 0.06 .sup.d 40 ± 4 .sup.d 73 704 X-3-M-20 77 ± 7 3.2 ± 0.8 83 ± 8 3.6 ± 0.4 5.3 ± 0.6 .sup.a 1.09 ± 0.05 .sup.d 25 ± 4 .sup.d 72 114 761 X-6-M-20 81 ± 5 3.5 ± 0.6 90 ± 6 3.5 ± 0.4 5.3 ± 0.5 .sup.c 1.11 ± 0.06 .sup.d 24 ± 4 .sup.d 70 114 886 X-10-M-20 79 ± 5 3.3 ± 0.5 85 ± 5 3.5 ± 0.4 5.7 ± 0.3 .sup.b 1.08 ± 0.05 .sup.d 26 ± 3 .sup.d 71 114 990 M-20 80 ± 4 3.0 ± 0.3 80 ± 4 2.5 ± 0.4 4.7 ± 0.3 .sup.c 1.0 ± 0.1 .sup.d 31 ± 7 .sup.d 71 114 286 M-40 82 ± 4 2.8 ± 0.5 87 ± 4 2.7 ± 0.4 5.0 ± 0.7 .sup.b 1.07 ± 0.09 .sup.d 26 ± 6 .sup.d 68 228 571 H  84 ± 10 3.1 ± 0.7  84 ± 10 2.9 ± 0.3 6.2 ± 0.4   1.00 ± 0.02 .sup.b 31 ± 2 .sup.b 72 43300 Number of replicates for value, n= .sup.a: 4; .sup.b: 5; .sup.c: 6; .sup.d: 9, n = 10 otherwise. *Value calculated based on a single experiment.

[0072] Sample H, shows significantly the highest tensile index (p<<0.05) of 89 Nm g.sup.−1 amongst all samples. This was expected, as the homogenization process utilizes high shear and impact forces to push the material through a small orifice, which results in higher fibrillation efficiency. However, the handsheets, which were produced by extrusion and milling (X-M), or only milling (M), demonstrate similarly high tensile indices, in the range between 77-82 Nm g.sup.−1. Moreover, there is no significant difference (p>0.05) in the tensile index values between samples that were processed with milling for 20 min L.sup.−1 and 40 min L.sup.−1. This implies that milling for 20 min L.sup.−1 is sufficient to obtain nanofibrillated material. Previously, researchers observed that after five passes through extruder the tensile strength and elongation of films dropped significantly, presumably due to the degradation of material. In contrast to this, an increasing number of passes through the extruder in this study is associated with a significant increase in the tensile index of the handsheets (p<<0.05), except between three to six passes. However, subsequent additional extrusion passes did not increase the tensile index (p>0.05) if milling was performed as an additional processing method. The high tensile values of H, X-M, and M samples can be explained by their higher density, which is ≥1 g cm.sup.−1 as compared to X samples, <0.9 g cm.sup.−1. This, in turn relates to the lower porosity of the denser films, made from nano- rather than micro-fibrillated material, i.e. the H, X-M, and M. For the latter, the porosity was <31%, while for the extruded samples, which were a mixture of CNF and MFC fractions, the porosity was much higher, over 38%. In some instances the greater porosity of these X samples could be advantageous e.g. in the case of paper-based battery separators, where high-porosity, strong materials are required. The values of strain at break were significantly higher (p>0.05) for the samples processed with HEBM, as compared to extrusion. Surprisingly, the samples processed by milling showed also greater elasticity than the homogenized ones. The exception was sample M-40, which had a strain at break in a similar range to the H sample. The range of strain at break for the milled and extruded samples is between 2.8-3.5% and 1.8-3.2%, respectively. The tensile values obtained in this research are much larger than those previously reported in the literature. Researchers obtained elongation at break in the range of 0.4-0.8% and comparable tensile strength for similarly prepared samples of extruded Eucalyptus bleached pulp. Ball milling of bleached softwood pulp resulted in a 1.7% strain at break and much lower tensile index and strength of less than 30 Nm g.sup.−1 and 12 MPa, respectively, at a 100 times lower throughput than in the current study. Similarly, commercial MFC milled at a throughput approximately three orders of magnitude lower than in our study resulted in a third of the tensile values as compared to M-20. The Young's modulus of the samples shows a similar trend to the tensile strength, with the highest values for the X-M and M samples, followed by H and X.

[0073] Although the sheets made from milled and homogenized samples are composed primarily of nano-sized cellulose fibers, the elastic moduli of these materials was still far from the theoretical modulus of a single cellulose I nanofiber, which is between 110-220 GPa. It should be mentioned however, that the nanofibers or nanofiber bundles are randomly oriented in the sheets therefore, reducing the maximum tensile strength. Furthermore, our spinifex-derived CNF and MFC comprise relatively high levels of residual non-crystalline cell wall polymers such as hemicellulose and lignin, with the hemicellulose in particular contributing towards a less elastic and more viscoelastic property profile (as indicated by the higher strain at break values). Nonetheless, the Young's moduli of the sustainable, spinifex-derived “paper” in the current study is comparable to many engineering polymers of similar density.

[0074] This study shows that the cellulose nanofibres have good adhesion, thereby opening up the possibility that a gel material comprising the cellulose nanofibres dispersed in an aqueous medium provide a good candidate for use as a natural adhesive.

[0075] In the present specification and claims (if any), the word ‘comprising’ and its derivatives including ‘comprises’ and ‘comprise’ include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0076] Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0077] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.