RECYCLED MIXED TEXTILE COMPRISING CELLULOSE AND SYNTHETIC PLASTIC

Abstract

A recycled mixed textile having cellulosic fibers and synthetic fibers, wherein the synthetic fibers comprise at least two synthetic plastics, a first synthetic plastic of the two synthetic plastics is selectively depleted from the mixed textile and a second synthetic plastic of the two synthetic plastics is partially retained in the mixed textile, and the mixed textile is further processed to comprise the cellulose fibers and the synthetic fibers are the second synthetic plastic.

Claims

1. A recycled mixed textile comprising: cellulosic fibers and synthetic fibers, wherein the synthetic fibers comprise at least two synthetic plastics; wherein a first synthetic plastic of the two synthetic plastics is selectively depleted from the mixed textile and a second synthetic plastic of the two synthetic plastics is partially retained in the mixed textile; and wherein the mixed textile is further processed to comprise the cellulose fibers and the synthetic fibers are the second synthetic plastic.

2. The mixed textile of claim 1, wherein the first synthetic plastic and/or the second synthetic plastic is at least one of the group consisting of polyester, polyamide, polyurethane, polyether, and elastane.

3. The mixed textile of claim 1, wherein the cellulosic fibers are a form of cotton.

4. The mixed textile of claim 1, wherein the mixed textile completely or partially comprises remains from a clothing manufacture and/or used clothes.

5. The mixed textile of claim 1, wherein the cellulose fibers are cleaned after the first synthetic plastic is selectively depleted and before the mixed textile is further processed.

6. The mixed textile of claim 1, wherein the first synthetic plastic comprises at least one of polyamide, polyester, polypropylene, polyurethane, or elastane.

7. The mixed textile of claim 1, wherein the second synthetic plastic comprises at least one of polyamide, polyester, polyurethane, or elastane.

8. The mixed textile of claim 1, wherein the first synthetic plastic is polyamide and/or polyurethane; wherein the second synthetic plastic is polyethylene terephthalate, PET, and/or polypropylene; and wherein the first synthetic plastic is depleted to a first concentration value and the second synthetic plastic is depleted to a second concentration value, and wherein the first concentration value is different from the second concentration value.

9. The mixed textile of claim 1, further comprising: at least one further mixed textile which comprises cellulosic fibers and synthetic plastic fibers, wherein a portion of the synthetic plastic fibers in the mixed textile and in the further mixed textile is different, such that an obtained plastic-composition comprises at least one predetermined property.

10. The mixed textile of claim 1, wherein a regenerated cellulosic molded body selected from a group comprising a filament, a fiber, a foil, a microsphere, or a bead is manufactured from the depleted and processed mixed textile.

11. The mixed textile of claim 10, wherein the regenerated cellulosic molded body comprises less than 0.5% polyethylene terephtalate, PET, and/or more than 1% polyurethane, PUR, and/or polyamide, PA.

12. The mixed textile of claim 10, wherein the regenerated cellulosic molded body has at least 2% synthetic plastic fibers.

13. The mixed textile of claim 10, wherein the regenerated cellulosic molded body has a reduced tendency to fibrillation in comparison to a conventional lyocell-fiber.

14. A regenerated cellulosic molded body manufactured from a mixed textile comprising: cellulosic fibers and synthetic fibers, wherein the synthetic fibers comprise at least two synthetic plastics; wherein a first synthetic plastic of the two synthetic plastics is selectively depleted from a mixed textile and a second synthetic plastic of the two synthetic plastics is partially retained in the mixed textile; and wherein the mixed textile is further processed to comprise the cellulose fibers and the synthetic fibers are the second synthetic plastic of the regenerated cellulosic molded body; wherein the depleted and processed mixed textile is further processed by a lyocell-method or a viscose-method; wherein the regenerated cellulosic molded body is selected from a group which comprises a filament, a fiber, a foil, a microsphere, or a bead; and wherein the regenerated cellulosic molded body comprises at least one of the following features: the regenerated cellulosic molded body comprises less than 0.5% polyethylene terephtalate, PET, and/or more than 1% polyurethane, PUR, and/or polyamide, PA; the regenerated cellulosic molded body has at least 2% synthetic plastic fibers; the regenerated cellulosic molded body has a reduced tendency to fibrillation in comparison to a conventional lyocell-fiber.

15. The regenerated cellulosic molded body of claim 14, wherein the first synthetic plastic and/or the second synthetic plastic is at least one of the group consisting of polyester, polyamide, polyurethane, polyether, and elastane.

16. The regenerated cellulosic molded body of claim 14, wherein the cellulosic fibers are a form of cotton.

17. The regenerated cellulosic molded body of claim 14, wherein the mixed textile completely or partially comprises remains from a clothing manufacture and/or used clothes.

18. The regenerated cellulosic molded body of claim 14, wherein the first synthetic plastic is polyamide and/or polyurethane; wherein the second synthetic plastic is polyethylene terephthalate, PET, and/or polypropylene; and wherein the first synthetic plastic is depleted to a first concentration value and the second synthetic plastic is depleted to a second concentration value, and wherein the first concentration value is different from the second concentration value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] In the following, exemplary embodiments of the present invention are described in detail with reference to the following figures.

[0081] FIG. 1 shows a flow diagram of a method of recycling a mixed textile, wherein a regenerated cellulosic molded body is manufactured, according to an exemplary embodiment of the invention.

[0082] FIG. 2 shows a device for manufacturing a regenerated cellulosic molded body by a lyocell-method according to an exemplary embodiment of the invention.

[0083] FIG. 3 shows a cellulose fiber which is manufactured by a lyocell-method.

[0084] FIG. 4 shows a cellulose fiber which is manufactured by a viscose-method.

[0085] FIG. 5 shows a natural cellulose fiber of a cotton plant.

DETAILED DESCRIPTION

[0086] Same or similar components in different figures are provided with the same reference numbers.

[0087] Before, referring to the figures, exemplary embodiments are described, some basic considerations shall be summarized based on which exemplary embodiments of the invention have been derived.

[0088] According to an exemplary embodiment of the invention, a selective depleting of thermoplastic additives in mixed textiles is performed, such that they can be reused for the manufacture of a (lyocell-) molded body. PET-portions are highly reduced and PUR-portions are slightly reduced. The circumstance is used, that residual constituents of PUR in the context of the lyocell-method may serve as positive property-changers.

[0089] According to a further exemplary embodiment of the invention, a recycling of cellulose from mixed tissues (mixed textiles) with polymer-portions is performed by selectively solving and depositing the polymer-portions in a solvent which does not attack the cellulose.

[0090] According to a further exemplary embodiment of the invention, by the recovery of cellulose, a new solution concept is suggested, which is based on a typically lower (<50%) polymer-portion in a starting material (mixed textile). The execution of the invention is optimal, e.g. when it is a matter to deplete polymer-portions below 30% to values in the single-digit percentage range (at the most per mill range). This is in particular especially advantageous, since, in contrast to the known methods, the focus is not on the recycling of the plastics, but on the recycling of the non-polymeric residual constituents, in particular cellulose. On the contrary, previously known methods are based on the fact that the substances to be recycled comprise a high to very high plastic-portion. From an exemplary high plastic-portion of 80 to 90%, a significant part of polymers can be recovered. In the residual material which is typically thermically further processed, would then still be up to 50% residual polymer portion.

[0091] According to a further exemplary embodiment of the invention, residual polymers from starting materials are used as adhesion promoter between cellulose fibers or as thermoplastic properties promoter within a lyocell-molded body. They stay substantially inert until the completion of a certain step in the production process. In particular, a belated reinforcement of a tissue by heat (analog to melting adhesive) may thus be achieved (e.g. non-iron shirts, pleating, etc.). For manufacturing tissues which have the property of a high dimensional stability (e.g. non-iron), an elaborate method is typically used. For example, this may be the combination of highly elaborate chemical methods. It makes the shirt look like a new one for a long term. The so-called humid cross-linking is also possible, wherein between the molecules of cotton cellulose, an elastic bridge is built. This bridge pulls the textile back in form after washing.

[0092] By the targeted control of the portion of residual polymers (e.g. polyurethane from the elastane from mixed textiles), according to an embodiment, a certain thermoplasticity in a lyocell fiber can be obtained, which re-supplies the corresponding portion of residual polymers from a starting material back into a lyocell-molded body via the depleting process, according to an embodiment of the invention, via a lyocell-method.

[0093] According to a further exemplary embodiment of the invention, the proper integrating behavior of certain synthetic plastics may be described by a compatibility between cellulose and further synthetic plastic, such as elastane, polyamide, or polyester. The polyethylene glycol (PEG)-portion in elastane may be responsible for the proper compatibility with the glycan ether-bond of the cellulose, due to its typical ether-structure. Thus, between the substances, a proper homogenization/mixing occurs. A corresponding integrating process, according to an embodiment, may additionally be highly dependent from the temperature of the respective method.

[0094] FIG. 1 shows a flow diagram 50 of a method of manufacturing a regenerated cellulosic molded body 102 (compare FIG. 2) from a mixed textile 110 according to an exemplary embodiment of the invention.

[0095] In the following, at first a depleting method for the mixed textile 110 is described by the blocks 52, 54, 56, and 58. The depleted and processed, respectively, mixed textile 60 may then be supplied to a lyocell-method 78. Moreover, subsequently the lyocell-method is described by the blocks 62, 64, 66, 70, 72, and 74, in order to manufacture a regenerated cellulosic molded body 102 from the depleted and processed, respectively, mixed textile 60 as starting material 110. According to a preferred embodiment, the depleted mixed textile 60 comprises substantially only cellulose. According to a further embodiment, the depleted mixed textile 60 comprises cellulose and synthetic plastic.

[0096] The mixed textile 110 comprises cellulosic fibers and fibers of at least one synthetic plastic and is present in form of old clothes and/or remains from a clothing manufacture.

[0097] As illustrated by the block 48, a mixed textile 110, in the case of old clothes, may be used by a consumer, for example as item of clothing. When the consumer disposes the item of clothing, it can be processed as post-consumer and then be used as starting material for a subsequent lyocell-method or viscose-method, wherein the former is described in more detail in the following.

[0098] Alternatively or in addition, it is also possible to use a pre-consumer mixed textile, for example offcut remains from the clothing manufacture.

[0099] At first, according to the block 52, the mixed textile 110 is supplied to the depleting process. Now, depleting 54 the mixed textile takes place, wherein at least one synthetic plastic is at least partially depleted. This may include hydrolyzing or derivatizing. Especially preferred, a solvent is used which does not degrade the cellulose. In this way, e.g. a polyester, such as PET, can be depleted from the cellulose. Between depleting 54 and the following further processing 58 of the mixed textile 110, a cleaning 56 may take place. Thereby, the cellulose can be cleaned from excessive plastic or other foreign matters. The further processing 58 in particular comprises supplying the depleted mixed textile 60 as starting material 110 to a lyocell-method.

[0100] In the following, it is described, how on basis of the depleted mixed textile 60, a molded body 102 made of cellulose according to an embodiment of the invention can be manufactured. For this purpose, the depleted mixed textile 60 is supplied to a device 100 (see FIG. 2) for performing a lyocell-method, compare reference sign 78. In the following, the depleted mixed textile 60 is denoted as starting material 110 (compare FIG. 2) for the lyocell-method.

[0101] There, first a mechanical comminuting 62 of the starting material 110 is performed by shredding. Thereby, mainly large non-cellulosic impurities may be removed from the starting material 110, for example buttons, seams and prints of the old clothes, which have been at least partially used for generating the starting material 110. By mechanically comminuting 62, the starting material 110 can be separated into single fibers, for example. It should be noted that the described mechanically comminuting 62 according to a further embodiment may also be performed during the depleting process, in particular before depleting 54.

[0102] It is also possible (see block 64) to utilize the starting material 110 which is comprising cellulose commonly with other materials which are comprising cellulose, for the subsequent lyocell-method. Thus, the starting material 110 can be mixed with a further starting material which comprises cellulose and at least one synthetic plastic, see block 64. This supplied further starting material comprises a portion of synthetic plastics, which is different from the portion of synthetic plastic in the starting material 110. Generating the regenerated cellulosic molded body can now be performed based on the starting material 110 and the further starting material, such that the regenerated cellulosic molded body 102 contains a predetermined portion of synthetic plastic. Alternatively or in addition, the further starting material may comprise remains from a clothing manufacture. Preferably, the further starting material is also a mixed textile. According to a further exemplary embodiment, the further mixed textile may be also supplied during the depleting process, in particular substantially at the same time with supplying 52 the mixed textile 110.

[0103] Directly after the mechanical comminuting 62 and directly after the mixing 64, respectively, directly solving 68 of the (pure and mixed, respectively) starting material 110 in a further solvent 116 (for example tertiary amine oxides, such as N-methylmorpholine-N-oxide (NMMO)) can be performed without chemical pretreatment in an advantageous manner. In more detail, the mechanically comminuted (and optionally mixed) starting material 110 may be directly transferred in solution, in particular without chemical cleaning and without adjusting the viscosity. In this way, the manufacturing method and recycling method, respectively, can be performed in an extraordinary simple and fast and ecological manner. It has surprisingly turned out that after mechanically comminuting 62, certain synthetic plastics (e.g. elastane, polyamide) as remaining foreign matter in the starting material 110 do not disturb the lyocell-method and do not negatively influence the quality of the recovered lyocell-cellulose. In contrast, certain amounts of certain synthetic plastics may remain in the manufactured cellulose fibers without deteriorating their properties, but to even improve them. Also certain amounts of remaining polyester do not disturb the obtained product, but may even strengthen the mechanical integrity of the molded body 102 to be manufactured.

[0104] Alternatively, the method may comprise an optional chemical cleaning 66 of the starting material 110 after mechanically comminuting 62 (or after mixing 64) and before solving 68. Such an optional cleaning 66 may comprise at least partially removing colorants by bleaching, for example. Therefore, it is possible to completely or partially discolor the starting material 110 before subsequently solving 68 the starting material 110 in solvent 116, for example in order to manufacture white or gray molded bodies 102. Alternatively or in addition, it is also possible that, in the context of the optional chemical cleaning 66, the starting material 110 (before or after solving 68 it) is at least partially freed from cross-linkers which are cross-linking fibers of the starting material 110. In applications in which such cross-linkers between the fibers of the starting material 110 are present, the starting material 110 may be completely or partially freed from these cross-linkers by means of an alkaline or acid pretreatment, for example. This additionally improves the solubility of the starting material 110. By means of cleaning 66, optionally at least a part of the synthetic plastic may be removed, if desired. For example, in this way the portion of synthetic plastic in the molded body 102 to be manufactured can be adjusted and influenced, respectively. According to a further exemplary embodiment, cleaning 56 during the depleting process may be performed in the same way. Moreover, a cleaning 66 may get unnecessary, when a cleaning 56 was already performed during the depleting process.

[0105] After solving 68 the starting material 110 in solvent (preferably NMMO), the obtained lyocell-spinning solution 104 may be pressed through one or more spinning nozzles, whereby threads and filaments, respectively, with a honey-like viscosity are generated (see block 70 concerning this spinning).

[0106] During and/or after the falling of these threads and filaments, respectively, these are brought in operational connection with an aqueous environment and are therefore diluted. Thereby, the concentration of the solvent 116 of the threads and filaments, respectively, is reduced in an aqueous fog and an aqueous liquid bath, respectively, to such an extent that the lyocell-spinning solution is transferred to a solid phase made of cellulose-filaments. In other words, a precipitating, depositing or coagulating of the cellulose-filaments occurs, see reference sign 72. Therefore, a pre-form of the molded body 102 is obtained.

[0107] Generating 80 the regenerated cellulosic molded body 102, in particular solving 68, spinning 70 and subsequently precipitating 72, by means of a lyocell-method, is thus performed based on a depleted mixed textile 60 as starting material 110 which itself comprises cellulose and optionally synthetic plastic.

[0108] Furthermore, the method may comprise a postprocessing 74 of the precipitated lyocell-cellulose for obtaining the molded body 102 from the preform of the molded body 102. Such a postprocessing may encompass a drying, impregnating and/or reshaping of the obtained filaments to the final molded body 102, for example. For example, the molded body 102 may be processed by means of the described manufacturing method to fibers, a foil, a tissue, a fleece, a sphere, a porous sponge, or beads and may then be supplied to a further use (see reference sign 76).

[0109] With advantage, after using the molded body 102, its cellulose (and optionally its synthetic plastic) may be again recovered by performing a further method corresponding to the process steps between reference signs 48 and 74 and between 78 and 74 (see block 80). Alternatively, the cellulose and optional further synthetic plastic of the molded body 102 may be recovered in a further method (see further block 80), for example a viscose method. This multiple repeatability of the recycling by means of repeated process stages is enabled by the knowledge that cellulose from a mixed textile, by means of at least partially, selectively depleting of plastic-portions, can be especially efficiently used in a recycling-method.

[0110] FIG. 2 shows a device 100 for manufacturing a regenerated cellulosic molded body 102 by means of a lyocell-method on basis of a starting material 110 which is a depleted and processed, respectively, mixed textile 60, according to an exemplary embodiment of the invention which is described with reference to FIG. 1.

[0111] Thus, FIG. 2 shows a device 100 according to an exemplary embodiment of the invention for manufacturing a cellulose-comprising molded body 102 which may be manufactured in form of a fleece (nonwoven), as fiber, foil, sphere, textile tissue, sponge, or in form of beads or flakes, for example. According to FIG. 2, the molded body 102 is manufactured directly from a spinning solution 104. The latter is converted to cellulose fibers 108 as molded body 102 by means of a coagulation-fluid 106 (in particular made of air humidity) and/or a coagulation-bath 191 (for example a water bath which optionally comprises tertiary amine oxides such as N-methylmorpholine-N-oxide (NMMO)). By means of the device 100, a lyocell-method may be performed. In this way, substantially endless filaments or fibers 108 or mixtures of substantially endless filaments and fibers 108 with a discrete length may be manufactured as molded body 102, for example. A plurality of nozzles which respectively have one or more openings 126 (which may be also denoted as spinning holes) are provided for ejecting the lyocell-spinning solution 104.

[0112] As can be taken from FIG. 2, a starting material 110 which is based on cellulose may be supplied to a storage tank 114 via a dosing device 113.

[0113] According to an embodiment, a water ingress in the cellulose-based starting material 110 may be performed by a solvent 116 (in particular NMMO) which is described in more detail below. The cellulose-based starting material 110 itself may also contain a certain residual moisture (dry pulp frequently has a residual moisture of 5 weight percent to 8 weight percent, for example). In particular, according to the described embodiment, the starting material 110 may directly be supplied to a mixture of water and solvent 116 without pre-moistening. An optional water container 112 which is shown in FIG. 2 may then be omitted.

[0114] According to an alternative embodiment, the starting material 110 which is comprising cellulose may be additionally moistened, in order to therefore provide moist cellulose. For this purpose, water from an optional water container 112 may be supplied to the storage tank 114 via the dosing device 113. Therefore, the dosing device 113 which is controlled by a control device 140 may supply adjustable relative amounts of water and starting material 110 to the storage tank 114.

[0115] A suitable solvent 116, preferably tertiary amine oxides, such as N-methylmorpholine-N-oxide (NMMO) and an aqueous mixture of the solvent 116, respectively, for example a 76% solution of NMMO in water, is contained in a solvent container. The concentration of the solvent 116 may be adjusted in a concentrating device 118 either by supplying pure solvent or water. The solvent 116 may then be mixed with the starting material 110 with definable relative amounts in a mixing unit 119. Also the mixing unit 119 may be controlled by the control unit 140. Thereby, the cellulose-comprising starting material 110 is solved in the concentrated solvent 116 in a solving device 120 with adjustable relative amounts, whereby the lyocell-spinning solution 104 is obtained. The relative concentration ranges (also denoted as spinning window) of the components starting material 110, water, and solvent 116 in the spinning solution 104 for manufacturing cellulosic regenerated molded bodies according to the lyocell-method may be suitably adjusted as known to a person skilled in the art.

[0116] The lyocell-spinning solution 104 is supplied to a fiber generating device 124 (which may be configured with a number of spinning beams or jets 122).

[0117] When the lyocell-spinning solution 104 is guided through the openings 126 of the jets 122, it is separated into a plurality of parallel threads made of the lyocell-spinning solution 104. The described process flow transforms the lyocell-spinning solution 104 to increasingly long and thin threads whose properties may be adjusted by a corresponding adjustment of the process conditions, controlled by the control unit 140. Optionally, a gas flow may accelerate the lyocell-spinning solution 104 on its way from the openings 126 to a fiber receiving unit 132.

[0118] After the lyocell-spinning solution 104 has moved through the jets 122 and further downwards, the long and thin threads of the lyocell-spinning solution 104 interact with the coagulation-fluid 106.

[0119] In the interaction with the coagulation-fluid 106 (for example water), the solvent concentration of the lyocell-spinning solution 104 is reduced, such that the cellulose of the starting material 110 at least partially coagulates and precipitates, respectively, as long and thin cellulose fibers 108 (which may still contain residues of solvent and water).

[0120] During or after the initial formation of the individual cellulose fibers 108 from the extruded lyocell-spinning solution 104, the cellulose fibers 108 are received at the fiber receiving unit 132. The cellulose fibers 108 may immerse into the coagulation-bath 191 shown in FIG. 2 (for example a water bath optionally comprising a solvent such as NMMO) and may complete their precipitation when interacting with the liquid of the coagulation-bath 191. Depending on the process adjustment of the coagulation, the cellulose may form cellulose fibers 108 (as shown, wherein the cellulose fibers 108 may be made of one substance and integrally merged with each other (merging), respectively, or may be present as separated cellulose fibers 108), or a foil and a film, respectively, made of cellulose may form at the fiber receiving unit 132 (not illustrated in FIG. 2).

[0121] Thus, the cellulose fibers 108 are extruded out of the spinning nozzles of the jets 122 and are guided through the spinning bath and coagulation-bath 191, respectively (for example containing water and NMMO in low concentration for precipitation/coagulation), wherein the cellulose fibers 108 are guided around a respective deflection roll 193 in the coagulation-bath 191 and are supplied to a draw-off godet outside the coagulation-bath 191. The draw-off godet 195 serves for further transport and post-stretching of the cellulose fibers 108, in order to achieve a desired titer. Downstream the draw-off godet 195, the fiber bundle made of the cellulose fibers 108 is washed in a washing unit 180, optionally scrooped and subsequently cut (not shown).

[0122] Although not illustrated in FIG. 2, the solvent 116 of the lyocell-spinning solution 104 which is removed from the cellulose fibers 108 when coagulating and in a subsequent washing in the washing unit 180, may be at least partially recovered and recycled, respectively, and may be transferred back in the storage tank 114 in a subsequent cycle.

[0123] During the transport along the fiber receiving unit 132, the molded body 102 (here in form of the cellulose fibers 108) may be washed by means of the washing unit 180, as the latter supplies a washing liquid for removing solvent residues. Thereafter, the molded body 102 may be dried.

[0124] Moreover, the molded body 102 may be made subject to a posttreatment, see the schematically illustrated posttreatment unit 134. For example, such a posttreatment may comprise a hydro-entangling, a posttreatment, a needle treatment, an impregnation, a steam treatment with a steam which is supplied under pressure and/or a calendaring, etc.

[0125] The fiber receiving unit 132 may supply the molded body 102 to a winding device 136, at which the molded body 102 may be winded. The molded body 102 may then be supplied as rolling freight to an entity which manufactures products such as wipes or textiles on basis of the molded body 102.

[0126] FIG. 3 shows a cellulose fiber 200 which is manufactured by means of a lyocell-method in cross-section. The cellulose fiber 200 which is manufactured by means of a lyocell-method has a smooth round outer surface 202 and is homogenous and free from macroscopic holes, filled with cellulose material. Therefore, it can be unambiguously distinguished from cellulose fibers which are manufactured by means of a viscose-method (see reference sign 204 in FIG. 4) and from cellulose fibers of cotton plants (see reference sign 206 in FIG. 5) by a person skilled in the art.

[0127] FIG. 4 shows a cellulose fiber 204 which is manufactured by means of a viscose-method in cross-section. The cellulose fiber 204 is cloud-shaped and comprises a plurality of arc-shaped structures 208 along its outer circumference.

[0128] FIG. 5 shows a natural cellulose fiber 206 of a cotton plant in cross-section. The cellulose fiber 206 is kidney-shaped and comprises a lumen 210 which is free from material as a fully circumferentially enclosed hollow in an interior.

[0129] By means of the significant geometric and structural, respectively, differences of the fibers according to FIG. 3 to FIG. 5, it is possible for a person skilled in the art to unambiguously determine, for example by means of a microscope, if a cellulose fiber is formed by means of the lyocell-method, by means of the viscose-method, or naturally in a cotton plant.

[0130] In addition, it should be noted that comprising does not exclude other elements or steps and a or an does not exclude a multiplicity. Furthermore, it should be noted that features or steps which are described with reference to one of the above embodiments may also be used in combination with other features or steps of other above described embodiments. Reference signs in the claims should not be construed as a limitation.