Abstract:
A flat textile material ( 10 ) has an upper side and an underside and is used, in particular, as a clothing fabric. For the purpose of controlling the permeability of the textile material ( 10 ), control elements ( 34, 36; 16, 18 ) are provided which are deformable by an environmental parameter. Media whose permeation is controlled thus are, for example, fluids or light. Possible environmental parameters are, for example, the temperature or the air humidity. It is thus possible to make, for example, textile materials whose breathing activity increases with the body temperature of the user.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns a flat textile material as will be described further herein. 
     In respect of permeability, textile materials can be divided into three groups, namely, permeable, impermeable and selectively permeable materials. A fluid is selected in this case as an example of a medium whose passage through a textile material is to be considered. Both textile materials which are permeable to fluid (normal fabric) and textile materials which are impermeable to fluid (fabric with closed pores) have been known for a long time. An example of a textile material which is selectively permeable to fluid is cotton or corresponding mixed fabrics coated with PTFE, known by the brand name of Gore-Tex. 
     The permeability of known textile materials is dependent on environmental parameters such as temperature and air humidity. This prevents an adjustment of the permeability as a result of a variation of such an environmental parameter. For example, the pore size of a Gore-Tex fabric, which is not dependent on environmental parameters, results in a compromise between the wind-tightness and the water vapour permeability of this material. If the outside temperature is low, however, it is desirable to have a wind-tight textile material, i.e., with more closed pores, whereas if the outside temperature is higher it is desirable to have a more actively breathing textile material which is permeable to water vapour, with larger, more open pores. 
     The object of the present invention is to develop a textile material according to the the claims in such a way that its permeability is variable in dependence on environmental parameters. 
     BRIEF SUMMARY OF THE INVENTION 
     This object is achieved, according to the invention, by a textile material with the features stated in the claims. 
     The elements which control the permeability of the textile material define openings or pores in the textile material according to the invention whose inside width varies in dependence on environmental parameters. For example, if the environmental parameter is the temperature, then textile materials can be made in such a way that, for example, their permeability increases either with increasing temperature or with decreasing temperature. Permeability which increases with increasing temperature is desired in the case of clothing, for example, particularly in sports and leisure clothing. When the body temperature of the wearer increases, as a result of either the wearer&#39;s own exertion or increasing outside temperature, the enlarging openings can increase the breathing activity of the clothing made from such a textile material. A reduction in the permeability of an item of clothing at increased temperature can be used, for example, for therapeutic purposes. 
     If the permeability of the textile material in respect of light is considered as a further example, a textile material whose light transmission decreases with increased temperature (or intensified insolation) can be used for beach clothing or sun screens, or also as a textile material which can be used for covering greenhouses. 
     For certain applications, it can also be advantageous that, starting from a predefined temperature, the permeability of the textile material increases or decreases in the case of both an increase and a decrease in the temperature, relative to the predefined temperature. Such textile materials can be used, for example, as covers for industrial installations. A textile material with a permeability which, starting from a predefined temperature, decreases in the case of both an increase and a decrease in the temperature can, for example, prevent the emergence of vapours or other fluids which develop in the case of a temperature deviation from a predefined process temperature. The reverse effect, in which the permeability of the textile material increases in the case of both a temperature increase and a temperature decrease in relation to a predefined temperature, can be used, for example, as a controllable filter in chemical fractionation. 
     The use of control element pairs according to the claims permits the attainment of passage openings of defined sizes, resulting in a defined permeability characteristic. Such a textile material is used, for example, if complete impermeability, e.g. water-tightness, is required in the presence of certain environmental parameters, so that all pores or openings can be closed in a defined manner, down to a passage width of zero. 
     In the case of a textile material according to the claims, use is made of the fact that the control elements, which are of different material, respond differently to one or more environmental parameters. An example of this is the use of control elements made form materials with differing temperature expansion coefficients. Materials with differing swelling behaviour, i.e., differing volume expansion in dependence on the air humidity, for example, can also be used. 
     The control elements according to the claims are designed in such a way that a variation of environmental parameters likewise produces different effects on the different control element types, which in turn affects the permeability of the material. If the control elements are of differing geometry, the textile material can also be made from a single material only, which simplifies production. 
     In the case of the embodiment of the textile material according to the claims, use is made of an effect similar to a bimetallic behaviour. The environmental parameter operating range of the textile material can be predefined through the choice of the value of the environmental parameter at which the layers of material dependent on the environmental parameter are jointed together. 
     In the case of the textile material designed according to the claims, the volume variation of the capsules/micro-capsules can be used for closing passage channels or openings in the textile material. Preferably, in this case a fluid with a high vapour pressure is used for the filing and a material with good elasticity is used for the elastic enclosure. A material with good elasticity in this case is a material which, when sued as an enclosure for a capsule/microcapsule, permits an enlargement of the diameter of such a capsule/micro-capsule by, for example, a factor of 2 for a temperature increase of 100° C. The permeability characteristic of the textile material can then be adapted to given requirements, depending on the substances selected for the enclosure and the filing. 
     Preferably, a textile material according to the claims is used, since, in the temperature range which is relevant to the clothing, the vapour pressure is then highly dependent on the temperature and, consequently, the diameter of the capsule/micro-capsule is varied greatly by the temperature. 
     A sufficiently secure and cost-effective bond between the capsules/micro-capsules and the fibres is achieved by the design of the textile material according to the claims. 
     In the case of a textile material according to the claims, the permeability can be varied greatly in dependence on an environmental parameter, since the size and the density of the openings can be varied within wide limits. 
     The design according to the claims results in a closing force which tends to lay the layers of material against one another and which must be overcome by the capsules/micro-capsules which expand in dependence on an environmental parameter. Such a closing force provides for a reversible control of the permeability of the textile material. In addition, the layers of material are securely joined together. 
     A preferred embodiment of the textile material is that according to the claims. The recesses provided for the capsules/micro-capsules enable the layer of material to lie on one another in a sealing manner when the capsules/micro-capsules have reduced in size, in dependence on an environmental parameter, in such a way that they lie completely in the recesses. 
     The design of the textile material according to the claims offers the possibility of producing a basic fabric using a conventional manufacturing method and subsequently inserting the capsules/micro-capsules, which then create the permeability, dependent on environmental parameters, of the textile material. In this case, likewise, depending on the thickness of the textile material used and beyond a certain density and size of the capsules/micro-capsules, on average a virtually complete impermeability is achieved if desired. 
     The design according to the claims can also result in the permeability being highly dependent on one or more environmental parameters. In this case, likewise, the above-mentioned bimetal effect can be exploited in combination with the fabric tongues. 
     The design according to the clams enables textile material which is controllably permeable to fluid to be produced relatively cheaply. In this case, the main layer of material, apart from the openings in it, is substantially impermeable to fluid. The control thread can then expand in dependence on, for example, temperature or can swell in dependence on air humidity in order to close the openings. 
     The control element design according to the claims means that the diameter of the control threads varies greatly in dependence on environmental parameters. A fabric can also be made exclusively from such control threads. The gaps between the control threads are then closed or opened by the variation in their diameter, the permeability of the textile material being varied as a result. Alternatively, it is possible, for example, for such a control thread to be inserted through openings of a main material layer, so that these openings are then opened or closed in dependence on environmental parameters. 
     In the case of the threads being designed according to the claims, the bimetal effect is again used to deform threads. 
     The design accordingly to the claims does not exploit any special property of environmental parameter dependence of the lacquer coating, but rather its shielding effect in combination with a behaviour of the threads which is dependent on environmental parameters. A range of other materials is therefore available which impart to a thread a deformation which is dependent on environmental parameters. 
     The embodiment according to the claims can be produced with conventional weaving technology and another embodiment according to the claims with conventional knitting technology. In the case of known knitting machines, some of the supplied threads, e.g. half, can consist of threads which are dependent on environmental parameters and the remainder of threads made from material which is substantially non-dependent on environmental parameters. 
     A control element according to the claims has a temperature and humidity-dependent expansion which differs from multifilament threads, while having the same dimension. 
     A textile material according to the claims is characterized by a good wearing comfort. If only one material is used, this also both simplifies the product of the textile material and reduces the problem of the occurrence of electrostatic charge. 
     The invention is described more fully below using embodiment examples, with reference to the drawing, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a greatly enlarged top-view of a piece of a textile fabric web, into which there are cut fabric tongues; 
     FIG. 2 shows a section along line II—II of FIG. 1; 
     FIG. 3 shows a top-view of the fabric web of FIG. 1, after it has been subjected to an increased temperature; 
     FIG. 4 shows a section along line IV—IV of FIG. 3; 
     FIG. 5 shows a representation, similar to FIGS. 2 and 4, of a fabric web similar to the fabric web of FIGS. 1 to  4 ; 
     FIG. 6 shows a greatly enlarged top-view of a piece of a textile fabric web according to a further embodiment of the invention; 
     FIG. 7 shows a section through the fabric web of FIG. 6 in a centre plane which runs parallel to the surface of the fabric web; 
     FIG. 8 shows a section as in FIG. 7, in which the fabric web of FIGS. 6 and 7 has been brought to an increased temperature; 
     FIG. 9 shows a schematic and greatly enlarged sectional view perpendicular to the surface of a textile fabric web according to a further embodiment of the invention; 
     FIG. 10 shows a greatly enlarged and partially exploded top-view of a piece of a textile fabric web according to a further embodiment of the invention; 
     FIG. 11 shows a section along line XI—XI of FIG. 10; 
     FIG. 12 shows a section as in FIG. 11, in which the fabric web of FIGS. 10 and 11 has been brought to an increased temperature; 
     FIG. 13 shows greatly enlarged view of a thread for the production of a fabric; 
     FIG. 14 shows a view of the thread according to FIG. 13, at a lower temperature; 
     FIG. 15 shows a further enlarged view of a portion of a single fibre which is part of the fibre bundle of FIGS. 13 and 14; 
     FIG. 16 shows a portion of a fibre according to a further embodiment of the invention; 
     FIG. 17 shows a greatly enlarged top-view of a piece of a textile fabric web according to a further embodiment of the invention; 
     FIG. 18 shows a top-view of the fabric web of FIG. 17 after it has been subjected to an increased temperature; and 
     FIG. 19 shows a section through FIG. 18 along line XIX—XIX of FIG.  18 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The textile fabric web having the general reference number  10  in the drawing is a flat structure made from a textile material which has a low permeability to fluids, particularly water and water vapour. Such substantially fluid-tight textile materials are, for example, textile fabrics whose pores are closed with an appropriate filling material, e.g. boiled linseed oil, acrylic polymers, ammoniacal copper oxide, caoutchouc or resins. 
     The fabric web of both this and also the following embodiment examples can be produced, if the production method is not stated explicitly, both by a knitting and a weaving method. Alternatively, the fabric web can also be a non-woven fabric material, i.e., for example, a felt, fleece, textile composite or even a foil. 
     The textile material shown in FIGS. 1 to  4  is constituted so that when temperature is increased it bends under the action of a mechanical stress induced by the temperature increase. Such a mechanical stress is achieved, for example, by analogy with a bimetal, by a composite construction of the fabric web  10  from two layers of materials  11   a,    11   b  joined flatly together (cf. the section enlargement of FIG. 4) with differing temperature expansion coefficients. 
     The piece of the fabric web  10  shown in FIG. 1 has four fabric tongues  12 ,  14 ,  16 ,  18 . The fabric tongue  16 , which is described here as representative of the other fabric tongues  12 ,  14  and  18 , which are of the same construction, is a rectangular portion of fabric which is joined, at its upper end in FIG. 1, to a main fabric layer  20  of the fabric web  10 . The three remaining sides of the fabric tongue  16  are delimited by cut edges  22 ,  24  and  26 . The fabric tongue  16  has been produced by a substantially rectangular cut or punching process, performed in the main fabric layer  20 , which has produced the cut edges  22  to  26  in the fabric tongue  16  and a rectangular U-shaped cut edge, denoted in general by the reference  27 , in the main fabric layer  20 . 
     As can be seen in combination with FIG. 2, the cut edge  24  projects from the surface of the fabric web  10  defined by the main fabric layer  20 . 
     Such a projection is caused by the fact that, in the case of fabric tongues beyond a certain dimensional ratio between the thickness and typical expansion of the fabric tongue in a relatively stiff textile material, for steric reasons, once the fabric tongue  12  has been raised out of the main fabric layer  20  it can no longer slide back into the main fabric layer. In addition, in the case of the above-mentioned cut or punching process, the fabric tongue  12  can lengthen somewhat due to temporary adhesion to the cutting or stamping tool, which likewise impedes or prevents the fabric tongue  12  from sliding back into the main layer  20 . 
     In the position shown in FIGS. 1 and 2, the cut edge  24  of the fabric tongue  12 , with the cut edges  22 ,  26  and the underside  28  of the fabric tongue  16 , sit substantially close to the regions of the main fabric layer  20  which are adjacent to them. Consequently, in this depicted position of the fabric tongues  12  to  18 , the fabric web  10  is substantially fluid-tight. In this case, openings  30  to  36  are closed. The opening  34  is described here as representative of the openings  30 ,  32  and  36 , which are of the same construction. It is delimited by the cut edge  27  of the main fabric layer  20  and by the underside  28  of the fabric tongue  16 . 
     FIGS. 3 and 4 depict the fabric web  10  of FIGS. 1 and 2 at increased temperature. 
     When the temperature of the textile material of the fabric web  10  is increased, the material layer  11   a  of the composite structure of the fabric web  10  (cf. FIG. 5) expands more than the material layer  11   b.  This causes bending of the fabric tongues  12  to  18 , which constitute a first type of control element for controlling the fluid permeability in the fabric web  10 . The openings  30  to  36  of the main fabric layer  20 , which scarcely bends even at increased temperature due to a bordering, not depicted, of the edge of the fabric web  10  and due to additional forces having a stabilizing effect on the main fabric layer  20 , form a second type of control element in the fabric web  10 . 
     As a result of the temperature increase, all of the fabric tongues  12  to  18  bend and the cut edge  24  lifts away from the main fabric layer  20 , as can be seen from FIG.  4 . Depending on the magnitude of the temperature increase, the fabric tongues  12  to  18  then uncover the openings  30  to  36  to a greater or lesser extent. 
     The uncovering of the openings  30  to  36  has the effect of enabling fluid to pass through the fabric web  10 . 
     A further embodiment example, which is similar to that of FIGS. 1 to  4 , is now described with reference to FIG.  5 . The constitution of the textile material and the dimensions of the fabric tongues are selected so that the fabric tongues  12  to  18  can move into the main fabric layer  20 . 
     Elements which correspond to those of FIGS. 1 and 2 have the same reference numbers in FIG.  5  and do not need to be described again in detail. 
     The fabric tongues  16 ,  18  of the fabric web  10  of FIG. 5 have been produced, like those of FIGS. 1 to  4 , by substantially rectangular U-shaped cuts in the main fabric layer  20 . Unlike the fabric web  10  of FIGS. 1 and 2, the fabric tongues  16 ,  18  lie in such a way in the main fabric layer  20 , in a temperature range in which no mechanical stresses or other thermally induced forces operate, that the upper sides and undersides of the fabric tongues  16 ,  18  are flush with those of the main fabric layer  20 . The cut edges  22  to  26  of the fabric tongues  16 ,  18  lie, substantially, closely opposite the cut edge  27  of the main fabric layer  20 . 
     In the case of a temperature increase, the fabric tongues  16 ,  18  of FIG. 5 bend away from the surface of the main fabric layer  20 . The fabric web  10  is then more permeable. 
     Through the choice of the temperature at which the material layers  11   a,    11   b  are joined together (joining temperature), it is possible to achieve a fluid permeability characteristic of the fabric web  10  at which the fluid permeability of the fabric web  10  increases both towards higher and towards lower temperatures. In the case of cooling below the joining temperature, the fabric tongues  12  to  18  are raised in the direction opposite to that shown in FIGS. 2 and 4 in the case of the temperature increase. In this case, likewise, the openings  30  to  36  are uncovered, so that fluid can penetrate the fabric web  10 . 
     If such a permeability characteristic with an increase of the permeability below the joining temperature is not desired, such a low value is selected for the latter that, when the textile is worn, the temperature of the material does not fall below the joining temperature to such an extent that the permeability is increased even in the case of temperatures lower than the joining temperature. 
     Alteratively, bending of the fabric tongue towards the second side (to the left in FIG. 5) can be prevented by stops provided for each fabric tongue in the main fabric layer  20 . Such a stop can already be provided by, for example, the cut edge  27 , as shown in FIGS. 1 to  4 . 
     Further embodiment examples are described in FIGS. 6 to  18 . Here again, elements which correspond to those of the embodiments already described are denoted by the same reference numbers. 
     The piece of a fabric web  10  shown in FIG. 6 has a main fabric layer  20  of a fluid-tight material with a relatively low thermal expansion coefficient. The piece shown has four holes  38  to  44 . There is a control thread  46  drawn through the holes  38  to  44 , in a manner similar to a zig-zag seam, in such a way that it passes once though each hole  38  to  44 . 
     The control thread  46  is produced from a material which has a low permeability to fluid or is impermeable to fluid and, by comparison with the main fabric layer  20 , it has a high thermal expansion coefficient. In this embodiment example, the control thread  46  and the openings  38  to  44  form the two types of control elements which define the fluid permeability of the fabric web  10 . 
     The sectional representation of FIG. 7 shows a section through the centre plane of the fabric web of FIG.  6 . In the case of the fabric web  10  represented in FIGS. 6 and 7, the diameter of the control thread  46  is smaller than the diameter of the holes  38  to  44 . A substantially circular gap therefore remains in each case between the edges of the holes  38  to  44  and the outer face of the control thread  46 . This distance between the control thread  46  and the edges of the holes  38  to  44  is sufficiently large to enable fluid, e.g. water or water vapour, to pass through the gap. 
     FIG. 8 depicts the fabric web  10  of FIGS. 6 and 7 at increased temperature. Under the influence of the increased temperature, the control thread  46  has expanded so that, in particular, its diameter has become larger. As a result, the outer circumferential surface  48  of the control yarn  46  now lies close against the edges of the openings  38  to  44 , so that the latter are closed in a substantially fluid-tight manner. 
     A further embodiment is shown in FIG.  9 . This depicts a schematic, greatly enlarged section perpendicular to the plane of a fabric web  10  with fabric fibres  50  made from a fluid-tight textile material with a low thermal expansion coefficient. The upper portion of the sectional representation shows the fabric web  10  at approximately 25° C. 
     As can be seen particularly from the enlarged section in FIG. 9, there is adhering to the outer face  52  of the fabric fibres  50 , by means of a bonding medium  53 , a plurality of micro-capsules  54 . The latter are blown, when the bonding medium  53  is moist, on to the fabric fibres  50  coated with the bonding medium. 
     The micro-capsules  54  each comprise an enclosure  56  of an elastic material and a filling  58  of fluid and vapour of an alcohol/water mixture. The enclosure is impermeable to the content of the capsule. 
     When the temperature of the textile material is increased, e.g. through an increase of the ambient temperature to 35° C., the vapour pressure of the filling  58  increases so that the elastic enclosure  56  is expanded, in a manner similar to an air balloon, thus enlarging the diameter of the micro-capsule  54 . Due to the elasticity of the enclosure  56 , the enlargement, or reduction, of the size of the micro-capsules  54 , which is dependent on the vapour pressure of the filling  58 , is reversible. 
     In the upper representation of FIG. 9, the diameter of the micro-capsule  54  is small in relation to the typical distance between the fabric fibres  50 . Fluid can therefore pass through the gaps remaining between the fabric fibres  50  and, consequently, through the fabric web  10 . 
     The lower part of FIG. 9 shows a piece of the fabric web  10  at increased temperature. Whereas the fabric fibres  50  and also the gaps formed between them have not altered substantially in their extent, the diameter of the micro-capsules  54  has increased significantly under the influence of the temperature (by a factor of 3 in the representation). Consequently, the diameter of the micro-capsules  54  is now of the order of magnitude of the gaps between the fabric fibres  50 . The connecting channels between the surfaces of the fabric web  10  which run through these gaps are therefore reduced by the micro-capsules  54 . As a result, as the temperature increases there is an ever-decreasing amount of the fabric web  10  that is permeable to fluid. 
     A further embodiment of the invention is depicted in FIGS. 10 to  12 . Here, the fabric web  10  is constructed from two fabric web layers  10   a,    10   b  lying flat on one another, with main fabric layers  20   a,    20   b,  regions of the upper fabric web  10   a  being broken away so that the fabric web  10   b  under them is uncovered. 
     The main fabric layers  20   a,    20   b  are composed of a material which is impermeable to fluid, with preferably a low thermal expansion coefficient, and are welded together at the edges by means of weld seams which are not depicted in the drawing. By this means, and by gravity, a force is exerted on the fabric webs  10   a,    10   b,  acting perpendicularly to their surfaces, so that in the absence of further influences they lie flat on one another, as shown in FIG.  11 . 
     The fabric web layer  10   b  comprises hemispherical recesses  60 , disposed in a square matrix, which can be produced by, for example, stamping with an appropriately shaped stamping cylinder. In these recesses, micro-capsules  54  adhere by means of a bonding medium  61  applied to the surface of the recesses  60 , the micro-capsules  54  having been blown on to the moist bonding medium. The conditions at the boundary layer between a micro-capsule  54  and the surface of a recess  60  are comparable to those depicted in the enlarged section of the embodiment example shown in FIG.  9 . 
     At the relatively low temperature of FIG. 11, the micro-capsules  54  lie fully within the recesses  60 . 
     FIG. 12 depicts the fabric web  10  at a temperature which has been increased by comparison with FIG.  11 . Under the influence of the temperature increase, the diameter of the micro-capsules  54  has approximately tripled due to the increased vapour pressure of its gas filling. The thus enlarged micro-capsules  54  now project out over the surface of the fabric web layer  10   b  and force the two fabric web layers  10   a,    10   b  apart from one another, by a distance  62 . 
     As can be seen from FIG. 10, the fabric web layers  10   a,    10   b  comprise passage openings  64   a,    64   b.  The passage openings  64   a  of the fabric web  10   a  are offset in relation to the passage openings  64   b  of the fabric web  10   b  so that they do not overlap, as evident from the top-view shown in FIG.  10 . The recesses  60  are disposed equidistantly around the circumference of the passage openings  64   b,  in a square matrix. 
     The fabric web  10  of FIGS. 10 to  12  with controllable permeability functions as follows: 
     When the micro-capsules  54  are enlarged by a temperature increase so that they force the fabric web layers  10   a,    10   b  apart from one another (e.g. distance  62  in FIG.  12 ), a plurality of passage channels is produced in the fabric web  10 , due to the fact that the passage openings  64   a,    64   b  which are offset in relation to one another now interconnect via the fabric web layers  10   a,    10   b  which are separated from one another. Fluid can then penetrate the fabric web  10 , through the channels that are produced. 
     On cooling, the micro-capsules  54  diminish in size due to the diminishing vapour pressure. The micro-capsules  54  then become smaller, the distance between the fabric web layers  10   a,    10   b  and, consequently, the permeability of the fabric web  10  also being reduced. When the micro-capsules  54  have retracted back into the recesses  60  the fabric webs  10   a,    10   b  again lie close and flat on one another. 
     FIG. 14 shows a thread  66  which can serve as a starting material for a fabric with a permeability which can be controlled by temperature or also as an alternative to the control thread  46  in the embodiment of FIGS. 6 to  8 . The thread  66  is constructed from a plurality of individual short fibres  68 , which can be specially modified composite natural fibres or composite fibres produced from impermeable synthetic material. 
     FIG. 15 shows a detail view of such a fibre  68 . It comprises a main fibre  70  and a control fibre  72 , shown as thinner in this case. The main fibre  70  and the control fibre  72  are bonded together longitudinally. 
     The control fibre  72  has a greater temperature expansion coefficient than the main fibre  70 . At the temperature at which the main fibre  70  and the control fibre  72  were bonded together, they do not exert on one another any forces resulting from thermal longitudinal deformation, so that the overall result is a substantially straight fibre  60 . The substantially straight fibres  68  form the substantially smooth thread  66  of FIG.  14 . 
     The inside diameter of the thread  66  is smaller than that of the thread  66  depicted in FIG. 13, the temperature of which is increased relative to that of the thread  66  of FIG.  14 . The control thread  72  has expanded more, particularly in the longitudinal direction, than the main thread  70 , so that the fibres  68  have developed a curvature, in a manner similar to the case of a bimetal. The result is the unravelling of the thread  66  shown in FIG. 13, with an enlargement of the inside diameter. 
     When unravelled in such a manner, the thread  66  in a fabric closes to a greater extent the gaps remaining between the weft and warp or, if it is used as a control thread  46  according to FIGS. 6 to  8 , it closes to a greater extent the openings  38  to  44  present in the fabric web  10 , so that a fabric web  10  which previously had good fluid permeability becomes less permeable to fluid. 
     In the case of a temperature which is reduced in relation to the bonding temperature, the control fibre  72  contracts more than the main fibre  70 , likewise resulting in bending of the fibres  68  and unravelling, as depicted in FIG.  13 . 
     Thus, through the choice of the temperature at which the main fibre  70  and the control fibre  72  are bonded together, within a predefined temperature operating range it is possible to achieve, analogous to the permeability characteristic of the joined material layers  11   a,    11   b  of FIGS. 1 to  5 , in the case of an increase of temperature, either an increase or decrease of the fluid permeability of a fabric web  10  according to FIGS. 6 to  8  comprising such threads  66 , depending on whether the bonding temperature is below or above the temperature operating range. 
     A further embodiment of a fibre  68  is shown in FIG.  16 . Here, the fibre  68  comprises a main fibre  70  which is provided with a lacquer coating  74  extending over only a portion of the circumference of the fibre. 
     The material of the lacquer coating  74  can differ from the material of the main fibre  70  in respect of its thermal expansion coefficient. A structure similar to a bimetal is then achieved which responds to temperature variations. The material can also differ from the material of the main fibre  70  in respect of its capacity to swell in a humid environment. A structure similar to a bimetal is then achieved which responds to humidity variations. The material of the lacquer coating  74  can also effect only direct blocking of moisture, so that humidity variations in the environment have less effect in the covered regions of the fibre that in the non-covered regions, so that again moisture-induced deformations of the main fibre  70  are achieved. 
     The above-mentioned effects can also be used in combination in order to achieve a fabric web permeability which is dependent on both the temperature and the humidity. 
     Alternatively, the lacquer coating  74  can also be applied so that it is distributed with a layer thickness which varies over the circumference of the main fibre  70 . This results, likewise, in a temperature- or humidity-dependent bimetal effect, as described in connection with the fibre  68  in FIGS. 13 to  15 . The lacquer coating  74  in this case assumes the role of the control fibre  72 . 
     Such an uneven application of the lacquer coating  74  can be achieved in that, for example, following immersion in a fluid lacquer, the main fibres  70  are dried, freely suspended, in a horizontal orientation, so that under the influence of gravity there is a greater accumulation of the lacquer on that portion of the surface of the main fibre  70  which faces the floor. Following drying of the lacquer coating  74 , a fibre  68  is obtained with a lacquer coating  74  which is thicker on one side. The temperature- or humidity-dependent expansion effects of the thicker lacquer coating side then prevail and result in the bimetal effect described above. 
     In the case of a further embodiment, the fabric tongues  12  to  18  of FIGS. 1 to  5  are also provided with such a lacquer coating, so that instead of or in addition to bending in dependence on temperature, they also bend in dependence on an air humidity variation and thus render the fabric web  10  permeable to fluid. 
     The fabric web  10  of the further embodiment of the invention, depicted in FIGS. 17 and 18, comprises warp threads  80  and weft threads  82 . 
     In the case of a first temperature of the fabric web  10 , depicted in FIG. 17, the warp threads  80  and the weft threads  82  from a fabric which is substantially fluid-tight, the size of the gaps  86 , which in each case remain between two adjacent warp threads  80  and two likewise adjacent weft threads  82  crossing the latter and which in the top-view shown are substantially square, being exaggerated in the depiction in FIGS. 17 and 18. The fabric web  10  of FIG. 17 is thus substantially fluid-tight. 
     The group of the weft threads  82  comprises control weft threads, of which one control weft thread  84  is depicted in FIGS. 17 and 18. This, unlike the other depicted weft threads  82  and warp threads  80 , is made from a material which is substantially uninfluenced by an environmental parameter variation. 
     FIG. 18 depicts the fabric web  10  at a temperature which has been increased in relation to that of FIG.  17 . Due to this temperature increase, the control weft thread  84  has become elongated in relation to the other threads. Consequently, in the weave of the fabric web  10 , between each two warp threads  80  disposed on either side of a third warp thread  80 , the control weft thread  84  forms loops  88  which protrude in the form of a nap from the plane of the fabric web  10 . The sectional representation of FIG. 19 shows that the loops  88  of the elongated control weft thread  84  extend alternately upwards and downwards. Due to the fact that the loops  88  no longer lie directly on the warp threads  80 , a gap remaining instead between the warp thread  80  and the control thread  84  in the region of the loops  88 , the fluid permeability of the fabric web increases in the area around the gaps  86 , in the vicinity of the loops  88 . The fabric web is then permeable to fluid at the temperature as depicted in FIG.  18 . 
     The elongation of the control weft thread  84  can be effected, either alternatively or additionally, by swelling in the case of increased air humidity. 
     The control thread  46 , the fibre  68  or the control thread  84  can be made as monofilament synthetic fibres. Monofilament fibres differ from multifilament fibres in respect of both their temperature behaviour and their swelling behaviour. This difference can obviously also be exploited analogously, in that the control threads are produced from multifilament fibres and the remaining textile material is produced from monofilament fibres. 
     The textile material can also be made as a stretch fabric. Different expansion coefficients, dependent on environmental parameters, can be achieved through the texturing of synthetic fibres or through a corresponding process, e.g. for cotton. 
     If the fabric web  10  is a knit fabric, control threads of the type of the control thread  84  can be knit-in, in that, in the case of a knitting machine which, for example, simultaneously knits 24 threads to produce the knit fabric, some of these 24 threads, for example five, are fashioned as control threads, i.e., they are composed of a material with an expansion coefficient which is dependent on environmental parameters. 
     The controllable permeability of fabric webs described above is fluid permeability. It is understood that this also at the same time includes other permeabilities, e.g. permeability to light. Thus, for example, awnings or suchlike can be produced which afford a predefined brightness under the awning, irrespective of the intensity of the sun.