Patent Publication Number: US-2022218070-A1

Title: Composite membrane and method of making a composite membrane

Description:
TECHNICAL SECTOR 
     The present invention relates to a composite membrane and a method of making a composite membrane. The composite membrane according to the present invention is particularly suitable for the manufacture of accessories for garments or accessories for wearable items, especially hygienic insoles for footwear. 
     PRIOR ART 
     In the sector for the production of accessories for garments or more generally accessories for wearable items to be used during the practice of a sport or a dynamic activity, owing to their impact-cushioning properties for some time it has been known to use membranes of varying thickness and/or density made using expanded polymeric materials. In fact, these membranes are particularly suitable for the manufacture, for example, of padding, linings, foot supports, insoles and upper supports. 
     Membranes made using expanded polymeric materials have, in addition to their impact-cushioning properties, further mechanical characteristics, including lightness and thermo-formability, which make them particularly suitable for use in this application sector. Other characteristics of the membranes made of expanded polymeric materials are the high thermal insulation capacity. 
     In addition to the impact-cushioning capacity, in order to ensure a high degree of comfort for the user when used, one of the most important requirements in the sector for the production of garment accessories or wearable item accessories to be used during the practice of a sport or a dynamic activity is that of allowing the removal, from the user&#39;s body, of the moisture or heat produced during sweating and consequently helping maintain a comfortable body temperature. This requirement is important in particular in the production of arch supports, insoles, upper supports and padding for protective helmets. 
     In order to obtain the breathability of such membranes it is known nowadays to make them using open-cell polymeric materials. 
     These materials, however, have a short working life in particular when used to make arch supports and insoles. 
     In fact, the hydrolytic action of the moisture which permeates said materials, during and following use, causes the deterioration thereof. 
     Moreover, this type of material tends to become impregnated and to promote the spread of bacteria and, consequently, the formation of bad odors. 
     Furthermore, the use of closed-cell expanded polymeric materials is able to obtain products which are generally more durable, kept more easily clean and have improved impact-cushioning properties, but which are impermeable and therefore unable to dissipate the moisture generated by the user&#39;s body. 
     Therefore, there exists still nowadays a very important need for composite membranes which are able to provide an increasingly higher impact-cushioning capacity and, at the same time, have a suitable capacity to dissipate the heat and/or moisture produced by the user&#39;s body. 
     SUMMARY 
     Therefore, the technical problem underlying the present invention is that of meeting this requirement, namely that of providing a membrane able to ensure the removal from the user&#39;s body of the moisture and the heat produced during sweating. 
     In order to solve this problem, a composite membrane, an accessory for garments or for wearable items, and a method of making the aforementioned membrane are provided, as described in the respective independent claims. 
     Secondary characteristics of the subject of the present invention are defined in the dependent claims. Said claims, as filed, are incorporated herein, for the purposes of specific reference. 
     The membrane according to the present invention is a composite membrane for garment accessories or accessories for wearable items which may comprise:
         a first layer having a first side and a second side opposite to one another and crossed by a plurality of through-holes extending between said first side and said second side;   a first plurality of fibers made of a thermo-conductive material and configured to convey moisture;       

     wherein said through-holes are engaged by first fibers of said first plurality of fibers so as to form channels suitable for conveying a liquid from said first side to said second side. 
     The composite membrane according to the present invention may be able to convey the moisture inside the fibers of thermo-conductive material configured to absorb and attract moisture. In this way, therefore, the heat and sweat generated by the user&#39;s body are captured by the first fibers present inside the holes in the first layer of the membrane. Namely the first fibers attract inside the holes in the first layer of the membrane the heat and moisture produced by a user and convey them across the first layer; consequently, the surface of the membrane in the vicinity of the body of a user or in contact with the latter will be drier and more comfortable compared to conventional membranes. 
     According to one aspect of the present invention, the composite membrane may also comprise a second layer and a third layer which are thermo-conductive and configured to diffuse vapor or a liquid through them. The first layer may have the first side covered by said second layer and said second side may be covered by said third layer; where said second layer, said third layer and said first fibers may be configured and mutually positioned in such a way that a first end of said first fibers is in contact with said second layer and a second end of said first fibers is in contact with said third layer to form a thermal bridge and to convey moisture and/or liquid between said third layer and said second layer. In particular, the second layer may comprise second fibers of said first plurality of fibers or consist of said second fibers. 
     The third layer may also comprise third fibers of said first plurality of fibers or consist of said third fibers. 
     Moreover, according to another aspect, the second layer may comprise second fibers of said first plurality of fibers or consist of said second fibers and/or, similarly, said third layer comprises third fibers of said first plurality of fibers or consist of said third fibers. Namely, at least partially, the second layer and/or third layer may be made of the same material from which the first fibers present inside the holes in the first layer are made. 
     According to a further aspect, the second layer may have a content of second fibers greater than the content of third fibers of said third layer and than the content of first fibers engaging the through-holes, for generating an attraction of liquid towards said second layer. Advantageously, in this way a gradient for the capacity of attraction of the liquid and the heat is generated such that the liquid and heat are attracted by the third layer which, during use, will be suitably directed towards the user and from here, transferred to the second layer, through the first fibers present in the plurality of holes. By arranging, during use, said third layer in the vicinity of or in contact with the user&#39;s body it is therefore possible to improve the sensation of comfort, in particular so that there is a perception of dryness and a pleasant temperature is maintained. 
     Other aspects of the present invention may concern the materials from which said layers are made. In particular, the first layer is preferably made of closed-cell expanded polymeric material; while the second and third fibers, from which the second layer and third layer are respectively made, as well as the first fibers included inside the plurality of holes, may comprise polymeric fibers and/or polymeric fibers with added thermo-conductive active particles configured to attract moisture, such as volcanic sand or active carbons. 
     The present invention also relates to an accessory for garments or wearable items comprising such a composite membrane. Examples of accessories for garments or for wearable items which may be made with the composite membrane according to the present invention are insoles for footwear, padding and linings. 
     Finally, the present invention relates to a method of making said composite membrane. The method comprises the steps of: forming a first layer, having a first side and a second side opposite to one another and made of a closed-cell expanded polymeric material; making a plurality of through-holes through the first layer; and engaging said through-holes with first fibers made of a thermo-conductive material configured to convey moisture. 
     It can be understood how the formation of through-holes through the first layer and engaging said through-holes with the first fibers may be performed at the same time, for example by means of a needle-punching process, or on successive occasions. According to one aspect of the present method, a step may be provided for forming a second layer of second fibers made of a thermo-conductive material configured to convey moisture, and a step of covering the first side of the first layer with said second layer. 
     In particular, according to this aspect, the steps of forming a plurality of through-holes in the first layer and engaging said through-holes with said first fibers may be performed by needle-punching the second layer onto the first layer. Following needle-punching of the second layer onto the first layer, a third layer of third fibers made of thermo-conductive material configured to attract moisture in contact with the second side of the first layer may be formed. Advantageously the plurality of holes in the first layer and the third layer of the composite membrane may be made at the same time by means of the single needle-punching operation. 
     Further advantages, characteristic features and modes of use forming the subject of the present invention will become clear from the following detailed description of examples of embodiment thereof, provided by way of a non-limiting example. 
    
    
     
       BRIEF DESCRIPTON OF THE DRAWINGS 
       An embodiment of the composite membrane according to the present invention is shown in the attached sets of drawings, in which: 
         FIG. 1  shows a schematic, cross-sectioned and partially exploded view of a composite membrane according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     With particular reference to the attached figure, in said  figures 100  denotes overall a composite membrane for garment accessories or wearable item accessories according to the present invention. 
     “Composite membrane” is understood, in the context of the present invention, as meaning a membrane made of different materials, each of which is designed to perform a specific function. 
     The composite membrane  100  comprises a first layer  10 , having a first side  101 , or first surface, and a second side, or second surface  102 , opposite one another. Said first layer  10  may be crossed by a plurality of through-holes  11 , namely holes extending between the first side  101  and the second side  102  of the first layer  10 . In other words, the first layer  10  may be a perforated layer in which one end of each hole  11  is located on the first side  101  and the other end of each hole  11  is located on the second side  102 . 
     The composite membrane  110  may further comprise a first plurality of fibers  21  made of a thermo-conductive material and configured to convey moisture. 
     First fibers  21   a  of said first plurality of fibers  21  are contained inside the through-holes  11  of the first layer  10 . Namely, said first fibers  21   a  of said first plurality of fibers  24  may engage or occupy the through-holes in the first layer  10 , crossing therefore the first layer  10  from the first side  101  to the second side  102 , so as to form channels designed to convey a liquid from said first side  101  to said second side  102 , for example by means of capillarity. Expressed in other words, the holes  11  of the first layer  10  together with the first fibers  21   a  contained inside them may form channels for transferring a liquid for promoting the transmission of heat and/or moisture from the first side  101  to the second side  102  of the first layer  10 . 
     Therefore, the heat and the sweat produced by a user when performing an activity, in particular a dynamic activity, are substantially attracted and channeled inside the holes  11  of the first layer  10  and consequently conveyed away from the surface of the first layer  10  which is placed in contact with, or in the proximity of, the user&#39;s body. 
     The composite membrane  100  may have a multilayer structure. In addition to the aforementioned first layer  10 , the membrane  100  may further comprise a second layer  20  and a third layer  30 . The first layer  10  is located in between the second layer  20  and the third layer  30 ; the first side  101  of the first layer  10  may be completely or partially covered by the second layer  20  which may be in contact substantially with the whole of the first side  101  or with a portion thereof, so as to diffuse onto it heat and/or moisture. 
     The second side  102  may be completely or partially covered by the third layer  30  which may be in contact substantially with the whole of the second side  101  or with a portion thereof, so as to diffuse onto it heat and/or moisture. 
     The second layer  20  and/or third layer  30 , preferably both of them, may be thermo-conductive layers and configured to spread vapor or liquids through them. In particular, said second layer  20 , said third layer  30  and said first fibers  21   a  may be configured and mutually positioned in such a way that a first end of said first fibers  21   a  is in contact with the second layer  20  and a second end of said first fibers  21   a  is in contact with the third layer  30 . More specifically, the contact between the first fibers  21  and the second layer  21  and third layer  30  may be such as to facilitate the transfer of liquid between the second layer  20  and the third layer  30  and the formation of a thermal bridge between the latter, namely generate a region of the membrane  100  in which the thermal flow between the second layer  20  and the third layer  30  is facilitated. 
     The second layer  20  may comprise second fibers  21   b  of said first plurality of fibers  21 , or may consist of said second fibers  21   b,  and/or similarly the third layer  30  may comprise third fibers  21   c  of said first plurality of fibers  21  or consist of said third fibers  21   c.  Therefore, both the second layer  20  and the third layer  30  may be made at least partially of the same thermo-conductive material and configured to convey moisture from or towards the first fibers  21   a  contained inside the holes  11  of the first layer  10 . Preferably, a part of the second fibers  21   b  of the second layer  20  is braided or intertwined with or twisted onto a part of the first fibers  21   a  contained inside the holes  11  and/or a part of the third fibers  21   c  of the third layer  30  is braided or intertwined with a part of the first fibers  21   a  contained inside the holes  11 . Alternatively, the second fibers  21   b  of the second layer  20  and/or the third fibers  21   c  of the third layer  30  are integral with the first fibers  21   a.  The intertwining or the integrality between the third fibers  21   c  of the third layer  30  and the first fibers  21   a  contained inside the holes  11  and/or the intertwining or the integrality of the latter with the second fibers  21   b  of the second layer  20  favors further transfer of the moisture, for example by means capillarity, between the third layer  30  and the second layer  20 . 
     In this connection, the second layer  20  is more hygroscopic than said third layer  30 . 
     According to one aspect of the present invention, the second layer  20  may have a content of second fibers  21   b  greater than the content of the third fibers  21   c  of said third layer  30  and than the content of first fibers  21   a  engaging the through-holes  11 . The different content of fibers  21  between the different layers of the membrane  100  generates a gradient for the capacity to transmit heat and absorb and convey liquid from the layer with lesser fiber content to the layer with a greater fiber content, passing via the first fibers  21   a  contained inside the through-holes  11 . 
     As a result, during use, the heat and the liquid from the third layer  30  flow towards the second layer  20 . The layer with a lesser fiber content, namely the third layer  30 , will be suitably directed towards or placed in contact with the user&#39;s body. 
     In this way, said third layer  30  exerts an action which removes the moisture and heat from the user&#39;s body, resulting in a pleasing sensation of freshness and dryness for the user. 
     In detail, the moisture produced by the user&#39;s body will tend gradually to be diffused through the third layer  30  which, in particular, may be configured to promote this diffusion effect. 
     Equally well, the third fibers  21   c  of the third layer  30  will diffuse the heat through the said third layer. 
     In this way, heat and moisture will be diffused in particular towards the first fibers  21   a  and, from these, will be diffused into the second layer  20 , through the first layer  10 . 
     The heat and the moisture flow through the channels formed by the holes  11  comprising the first fibers  21   a  towards the layer with a greater content of fibers, namely the second layer  20 , which is coupled with the first side  102  of the first layer  10 , opposite to the second side  102  of the first layer  10 , with which instead said third layer  30  is coupled. In other words, there is a tendency to move the heat and moisture away from the user&#39;s body, favoring therefore the sensation of freshness and dryness. 
     The first layer  10  may be made of closed-cell or open-cell expanded polymeric material. 
     A closed-cell material will be chosen in those embodiments of the present invention where the main requirement is that of heat insulation and impact cushioning, durability or impermeability as opposed to breathability. 
     On the other hand, where the main requirement is that of optimizing the breathability, the first layer may be made of an open-cell expanded polymeric material, the intrinsic breathability of which will be greatly increased by the presence of the holes  11  engaged by the first fibers  21   a.    
     Also, where a high degree of softness and/or elasticity of the composite membrane is required, in any case combined with durability and capacity to prevent the formation of bad odors, the first layer may be made of an open-cell expanded polymeric material where the first side  101  and/or the second side  102  may be lined with an impermeable film. 
     It can be understood how a composite membrane, according to the present invention, may be composed of a plurality of first layers as described above, each chosen so as to provide the manufactured item with the aforementioned properties depending on its structure. 
     The choice of a closed-cell expanded polymeric material for the first layer  10  also results in a high thermo-formability, which facilitates and reduces the cost of the manufacture of accessories for garments and wearable items with complex and ergonomic forms, and lightness, which makes the wearing of the garment or the article comprising an accessory made using the membrane according to the present invention more comfortable. The first layer  10  may be made of a polyolefinic crosslinked expanded foam, such as a crosslinked expanded foam based on polyethylene, polypropylene or a mixture based on ethylene vinyl acetate (EVA). In one embodiment, the first layer  10  may be made of crosslinked expanded polyethylene foam and has a density of between 20 kg/m 3  and 800 kg/m 3  or between 25 kg/m 3  and 600 kg/m 3  or between 30 kg/m 3  and 180 kg/m 3  or between 50 and 130 kg/m 3 . 
     These densities are suitable for the manufacture of insoles for footwear, but also for padding, for example for the shoulders, elbows and knees. More specifically, a density of 115 kg/m 3  is preferable, in particular for the production of hygienic insoles for footwear. 
     Irrespective as to the type of material used for the manufacture of the first layer  10 , it may have in particular a thickness of between 0.2 mm and 20 mm or between 2 mm and 8 mm, in particular a thickness of 5 mm. In this way, the accessory, such a padding or insole for footwear, made using the composite membrane  100  according to the present invention, occupies a small volume and may be removed or extracted from the garment or wearable item in a simple manner, thus facilitating the operations of cleaning the accessory itself and/or the garment or wearable item, of which it forms part. 
     Moreover, it is preferable that the plurality of through-holes  11  of the first layer  10  should have a density of between 10 and 60 holes/cm 2 , so as to not to affect excessively the rigidity and impact-cushioning capacity of the membrane  100 , while providing it with a homogeneous breathability and increasing it where the material from which the first layer  10  is made is already breathable. The plurality of holes  11  may have a density of 37 holes/cm 2 ; this density is particularly recommended for a membrane  100 , according to the present invention, which is designed for the manufacture of hygienic insoles for footwear. Moreover, the holes are preferably distributed uniformly across the first layer  10  so as to favor an equally uniform transfer of the heat and liquid from the third layer  30  to the second layer  20 . 
     It can be understood how, in alternative embodiments of the invention, the holes may be more concentrated in zones where it is required to remove a greater quantity of heat and/or moisture and more spread out where a greater structural strength or a greater impact-cushioning capacity is required. 
     A further aspect of the membrane  100  according to the present invention concerns the composition of the first plurality of fibers  21  which may be made of thermo-conductive material and configured to convey moisture. According to this aspect, said first plurality of fibers  21  may comprise polymeric fibers and/or polymeric fibers with added thermo-conductive active particles configured to attract moisture. In the context of the present invention, “polymeric fibers with added active particles” is understood as meaning that said polymeric fibers are treated so as to retain for a long time inside them, mainly on their outer surface, thermo-conductive active particles designed to attract moisture. 
     The polymeric fibers with added particles may have a porous structure and/or internal channels determined by the presence of the active particles which may also be included or incorporated in the said fibers. 
     More specifically, said particles designed to attract moisture are particles, for example comprising volcanic sand and especially zeolite and/or active carbon, which have an outer surface with a micro porosity inside which molecules of water in liquid or gaseous form are attracted and retained. 
     In one embodiment, said first plurality of fibers  21  may contain polyester fibers which may be present in an amount equal to 50% and fibers added with active particles comprising volcanic sand and/or active carbon which may be present in an amount equal to 50%. Examples of a material which may be used in this way are described in the U.S. Pat. Nos. 7,850,766, 7,247,374, 6,998,155 and 6,844,122. 
     Finally, the composite membrane  100  may also comprise a fourth layer  40  coupled with said third layer  30 . 
     The fourth layer  40  may cover said third layer  30  so that the third layer  30  is arranged between the fourth layer  40  and the first layer  10 . Therefore, when the composite membrane  100  is in use, the fourth layer  40  is located directed towards the user&#39;s body or is located in contact therewith. Like the second layer  20  and the third layer  30 , the fourth layer  40  may consist of a second plurality of fibers  22  made of thermo-conductive material and configured to convey moisture. 
     The second plurality of fibers  22  may also comprise, in turn, polymeric fibers and/or polymeric fibers with added thermo-conductive active particles configured to attract moisture. However, preferably, the fourth layer  40  has a smaller content of polymeric fibers with added particles or generally a smaller content of added particles than the second layer  20  and the third layer  30 . 
     Therefore, between the fourth layer  40  and the third layer  30  there is created a thermal bridge, namely a region of the membrane  100  in which the thermal flow is facilitated, and a gradient for the liquid conveying capacity such as to facilitate the transfer of the liquid from the fourth layer  40  to the third layer  30 . 
     Moreover the fourth layer  40  may have a distribution of the fibers  22  which is more uniform than that of the third layer  30 . Consequently, the heat and vapor are absorbed more uniformly along said fourth layer  40  and transferred to the third layer  30 . 
     The present invention also relates to an accessory for garments or wearable items comprising the composite membrane  100  as described above. Some possible examples of accessories for garments or for wearable items which may be made with the composite membrane according to the present invention are upper portions, insoles for footwear, padding and linings. 
     The present invention relates finally to a method of making a composite membrane  100 , as described in detail hitherto. In the description of this method, elements and materials of the composite membrane  100  involved in the method and having the same function and the same structure as the elements and the materials of the invention as described above retain the same reference number and are not described again in detail. 
     The method of making a membrane  100  according to the present invention comprises the following steps:
         forming a first layer  10  having a first side  101  and a second side  102  opposite to one another and made of a closed-cell expanded polymeric material;   making a plurality of through-holes  11  in the first layer  10 ;   engaging said through-holes  11  with first fibers  21   a  of a first plurality of fibers  21  made of a thermo-conductive material configured to convey moisture; In particular, the method may envisage:   forming a second layer  20  made of a thermo-conductive fibrous material configured to convey moisture; and   covering the first side  101  of the first layer  10  with said second layer  20 .       

     This step of covering the first side  101  may involve the first side  101  of the first layer  10  bring completely or partially covered by the second layer  20  which may therefore be in contact substantially with the whole of the first side  101  or with a portion thereof, so as to diffuse over it heat and/or moisture in a uniform or localized manner, respectively. 
     Even more particularly, the steps of forming a plurality of through-holes  11  in the first layer  10  and engaging said through-holes  11  with first fibers  21   a  of the first plurality of fibers  21  are performed by needle-punching the second layer  20  onto the first layer  10 . 
     According to said embodiment of the method, following needle-punching of the second layer  20  onto the first layer  10 , a third layer  30 , which may be placed in contact with the second side  102  of the first layer  10 , may be formed. 
     The third layer  30  may be made using third fibers  21   c  made of thermo-conductive material configured to convey and attract moisture. 
     It will therefore be understood that, preferably, said first fibers  21   a,  said second fibers  21   b  and said third fibers  21   c  belong to the same first plurality of fibers  21 . 
     The second side  102  may be completely or partially covered by the third layer  30  which may be in contact substantially with the whole of the second side  101  or with a portion thereof, so as to diffuse over it heat and/or moisture. 
     As known per se, needle-punching is a machining technique which consists in interlacing superimposed layers by means of punching with needles which introduce a fibrous material into the holes. The interlacing in fact is performed by means of a plurality of needles which move so as to cross transversely first a layer of fibrous material and then a second layer. 
     In this case, therefore, interlacing is performed by means of a plurality of needles which move firstly through the second layer  20  and then through the first layer  10 . During said step, by means of the penetration of needles through the second layer  20  and the first layer  10 , the plurality of holes  11  is therefore formed in the latter. Moreover, as a result of the action of the needles, some of the second fibers  21   b  of the second layer  20  are conveyed by the same needles so that they penetrate inside the first layer  10  and are bonded together with the latter. In other words, said first fibers  21   a  may form an integral part of said second fibers  21   b.    
     In addition, at least some of the ends of the first fibers  21   a  project from the second side  102  of the first layer  10 . Namely, a part of the second fibers  21   b  of the second layer  20  conveyed by the movement of the needles may be made to project outside the end of the holes in the second side  102  of the first layer  10  so as to form the third layer  30 . 
     The part of the second fibers  21   b  of the second layer  20  conveyed by the movement of the needles which projects from the second side  102  of the first layer  10  may therefore form said third fibers  21   c  in which case the third layer  30  will therefore be formed, at least partly, by the same first fibers  21   a.    
     Preferably, the needle-punching is performed using a density of needles of between 10 and 60 needles/cm 2 , even more preferably with a density equal to 37 needles/cm 2 . 
     Finally, the method of making a membrane  100  according to the present invention may also comprise a step which consists in mounting, on top of the third layer  30 , a fourth layer  40  composed of a second plurality of fibers  24  made of a thermo-conductive material and configured to convey moisture. 
     The fourth layer  40  has the function of attracting heat and moisture and transferring them in a uniform manner to the third layer  30 . 
     The fibers of the second plurality of fibers  24  may be equal to those of the first plurality of fibers  21 . 
     The composite membrane  100  thus obtained may therefore be thermoformed so as to assume the form or shape of an accessory for a garment or a wearable item, such as a hygienic insole.