Patent Publication Number: US-2021162711-A1

Title: Breathable waterproof membrane capable of being heat-bonded, and method for manufacturing same

Description:
TECHNICAL FIELD 
     The present invention relates to a breathable waterproof membrane used in preparation of a functional fabric for outdoor use and a method of preparing the same, and more particularly, to a thermally-bondable, breathable waterproof membrane and a method of preparing the same, the membrane being attached to a fabric substrate such as a woven fabric by applying heat and pressure on one side of the fabric substrate, thereby having excellent breathability and waterproofing properties and allowing a simple manufacture of a functional fabric for outdoor clothing. 
     BACKGROUND ART 
     Generally, breathable waterproof fabrics refer to fabric materials that allow water vapor such as sweat inside the clothing to pass through to the outside and block moisture such as rain from the outside not to seep into the clothing, and thus the fabrics are prepared not to be wet by rain or snow (waterproof) and to discharge sweat (breathable) to help controlling body temperature and maintaining comfortable feeling of the wearer. 
     The breathable waterproof fabric has a dense structure and flexible pores which allows the fabric to have a windproof function as well. When the wearer is sweating due to increased activity in cold environments, the fabric serves as a medium controlling the transfer of heat and moisture between the human body and the environment, and thus prevents condensation of the sweat or decrease in the body temperature. 
     In recent years, with increasing interest in health and leisure activities, the breathable waterproof fabric has been applied to various fields, and these functionalities have been further emphasized in line with the boom for luxury and well-being. In addition, the breathable waterproof fabric has been widely used in outdoor clothing, mountaineering clothing, outdoor wear, and sleeping bags. 
     Also, with the introduction of a 52-hour work per week, the leisure time has increased, and the lifestyle that emphasizes a comfortable and relaxed life has become a trend, and thus outdoor clothing industries have posted high sales growth every year. 
     Techniques for manufacturing the breathable waterproof fabric may be a wet method, a dry method, and a laminating method, and the laminating method prepares a breathable waterproof fabric by separately preparing a membrane having a breathable waterproof property and then bonding the membrane with a fabric using an adhesive. 
     The prior arts of a membrane for preparing a breathable waterproof fabric using the laminating method may include Korean Patent Publication No. 2017-0127760 (Nov. 22, 2017), which discloses a unidirectional breathable waterproof multilayer membrane and a method of preparing the same, the membrane including a first porous layer including first nanofibers formed of a hydrophobic polymer; a non-porous layer; and a second porous layer including second nanofibers containing or coated with an absorptive material, and Korean Patent Publication No. 2010-0126940 (Dec. 3, 2010), which discloses a breathable waterproof membrane with excellent breathability and moisture permeability and a process for preparing the same, the method including laminating polyurethane beads in the cross-linked state on a releasing paper and forming a number of fine pores between the polyurethane beads to prepare the membrane. Also, Korean Patent Publication No. 2017-0068984 (Jun. 20, 2017) discloses a breathable waterproof fabric and a preparing method therefor, the fabric including a fabric substrate; a surface-modified layer formed on a bonding surface of the fabric substrate; a dot adhesive member transferred to the surface-modified layer; and a membrane bonded to the fabric substrate by the dot adhesive member. 
     However, the membranes for preparing a breathable waterproof fabric according to the prior arts may result in uneven coating distribution of a liquid adhesive when bonding the membrane to a fabric, and this may cause problems such as uneven breathing efficiency and degrading breathability as the liquid adhesive seeps into the fabric. In addition, the membrane attached to the fabric substrate may be poor in peeling durability or abrasion durability, and as a surface of the breathable waterproof membrane contacts moisture such as sweat, a swelling phenomenon in which a volume of the surface of the membrane expands, may occur, which may result in poor appearance of clothing. 
     DETAILED DESCRIPTION OF INVENTION 
     Technical Problem 
     Provided are a breathable waterproof membrane  100  capable of being thermally-bonded to a fabric substrate  15  using a hot-melt adhesive that is dot-coated on the surface thereof, and a method of preparing the breathable waterproof membrane  100 . Provided are a thermally-bondable, breathable waterproof membrane  100  and a method of preparing the same, the membrane  100  being applied to the preparation of outdoor clothing, thereby capable of giving excellent breathability and waterproof properties to the outdoor clothing and simplifying a manufacturing process of the outdoor clothing. However, the technical problems to be resolved by the present invention are not limited to the above-described problems, and other problems which not described above may be clearly understood by those skilled in the art through the following description. 
     Solution to Problem 
     According to an aspect of the present invention, a thermally-bondable, breathable waterproof membrane  100  includes a membrane layer  50 ; a release layer  70  formed on a lower portion of the membrane layer  50 ; a base layer  25  transferred in the form of dots on an upper portion of the membrane layer  50 ; and a hot-melt adhesive layer  30  formed on an upper portion of the base layer  25 . Also, a moisture permeability of the thermally-bondable, breathable waterproof membrane  100  may be in a range of 1,000 g/m2/24 h to 50,000 g/m2/24 h, and a protective layer  10  may be preferably formed on the membrane layer  50 . 
     The hot-melt adhesive layer  30  may be preferably formed of one selected from a polyamide-based resin, a polyurethane-based resin, an ethylene vinyl acetate (EVA) resin, and a polyester-based resin, the base layer  25  may be preferably formed of one selected from an acryl-based resin, a polyurethane-based resin, a polyamide-based resin, a polyester-based resin, a polyolefin-based resin, a PVC resin, and an EVA resin; and the membrane layer  50  may be preferably formed of one selected from a polyurethane, a polyester, a polyamide, and polytetrafluoroethylene. 
     The dots of the base layer  25  may be preferably transferred in the form of dots at a density in a range of 1 dot/cm 2  to 220 dots/cm 2  on the membrane layer  50 , and a thickness of the membrane layer  50  may be preferably in a range of 0.15 mm to 0.30 mm. 
     Also, the thermally-bondable, breathable waterproof membrane  100  for preparing a breathable waterproof fabric may be thermally-bonded with a fabric substrate  15  to prepare a breathable waterproof fabric. 
     According to another aspect of the present invention, a method of preparing a thermally-bondable, breathable waterproof membrane  100  may include a first step of preparing a membrane layer  50  with a release layer  70  formed on a lower portion of the membrane layer; a second step of transferring a base layer  25  in the form of dots on an upper portion of the membrane layer  50 ; a third step of scattering hot-melt adhesive powders  35  on an upper portion of the base layer  25 ; a fourth step of removing by suction the hot-melt adhesive powders  35  other than the hot-melt adhesive powders  35  settled on an upper portion of the base layer  25 ; a fifth step of heat-fixing the hot-melt adhesive powders  35  settled on an upper portion of the base layer  25  to form a hot-melt adhesive layer  30 ; and a sixth step of cooling the base layer  25  and the hot-melt adhesive layer  30 . In particular, the method may preferably include adding a protective layer  10  on the membrane layer  50 . 
     Advantageous Effects of Invention 
     According to the present invention, a thermally-bondable, breathable waterproof membrane  100  may be thermally-bonded to a fabric substrate  15  for preparing clothing using a flat press or a roll press and thus facilitates preparation of a functional fabric having a breathable waterproof property. Also, when the membrane  100  is used, a breathable waterproof functional fabric may be prepared by a laminating process, which reduces steps of a sewing process for preparing outdoor clothing, and thus price competitiveness of the final product may increase. In addition, the thermally-bondable, breathable waterproof membrane  100  according to the present invention does not use a solvent, which makes the method eco-friendly compared to a conventional method that applies an adhesive on a fabric and then attaches a membrane to the fabric by bonding the membrane and the fabric, and increases the design completeness of outdoor clothing. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of a thermally-bondable, breathable waterproof membrane  100  according to a first embodiment of the present invention; 
         FIG. 2  is a cross-sectional view of a thermally-bondable, breathable waterproof membrane  100  according to a second embodiment of the present invention; 
         FIG. 3  is a cross-sectional schematic view of a breathable waterproof fabric to which the thermally-bondable, breathable waterproof membrane  100  according to the second embodiment of the present invention is applied; 
         FIG. 4  is a top view of a thermally-bondable, breathable waterproof membrane  100  according to an embodiment of the present invention; 
         FIG. 5  is a preparing process diagram of the thermally-bondable, breathable waterproof membrane  100  according to an embodiment of the present invention; and 
         FIG. 6  is a schematic view of an upper screen roll  100  used in a coating process of a base resin according to an embodiment of the present invention. 
     
    
    
     BEST MODE 
     It will be understood that the terms “include,” “comprise,” or “have” when used in this specification, specify the presence of stated features, numbers, steps, elements, components, or combinations thereof but do not preclude possibility of the presence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof. 
     Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Hereinafter, a thermally-bondable, breathable waterproof membrane  100  and a method of preparing the membrane  100  according to the present invention will be described in detail with reference to the accompanying drawings.  FIG. 1  is a cross-sectional view of a thermally-bondable, breathable waterproof membrane  100  according to a first embodiment of the present invention,  FIG. 2  is a cross-sectional view of a thermally-bondable, breathable waterproof membrane  100  according to a second embodiment of the present invention;  FIG. 3  is a cross-sectional schematic view of a breathable waterproof fabric to which the thermally-bondable, breathable waterproof membrane  100  according to the second embodiment of the present invention is applied;  FIG. 4  is a top view of a thermally-bondable, breathable waterproof membrane  100  according to an embodiment of the present invention;  FIG. 5  is a preparing process diagram of the thermally-bondable, breathable waterproof membrane  100  according to an embodiment of the present invention; and  FIG. 6  is a schematic view of an upper screen roll  100  used in a coating process of a base resin according to an embodiment of the present invention. 
     The thermally-bondable, breathable waterproof membrane  100  according to an embodiment of the present invention provides breathability and waterproofing properties to a fabric substrate  15  by being attached to the fabric substrate  15  during preparation of outdoor clothing, etc. The thermally-bondable, breathable waterproof membrane  100  according to an embodiment of the present invention, as shown in  FIG. 1 , includes a membrane layer  50 ; a release layer  70  provided on a lower portion of the membrane layer  50 ; a base layer  25  transferred in the form of dots on an upper portion of the membrane layer  50 ; and a hot-melt adhesive layer  30  formed on an upper portion of the base layer  25 . The hot-melt adhesive layer  30  is formed in the form of dots on the base layer  25  formed in the form of dots to form a double dot layer  60 . 
     That is, according to a first embodiment of the present invention, the membrane layer  50  that forms a basal layer is first needed to prepare the thermally-bondable, breathable waterproof membrane  100  of the present invention. To prepare outdoor clothing, the membrane layer  50  provides breathability and waterproofing properties to the fabric substrate  15  by being attached to the fabric substrate  15 . 
     That is, the membrane layer  50  is a thin film having a microporous structure formed of fine pores and may be prepared using polytetrafluoroethylene, a polyurethane, a polyester, or a polyamide, etc. 
     That is, polytetrafluoroethylene may uniformly form fine pores in a membrane which may thus exhibit excellent moisture permeability, a polyurethane may facilitate size control of pores formed in a membrane, and a polyester may provide excellent tactile feel and durability at the same time providing excellent moisture permeability and waterproofness, and outstanding appearance. Also, a polyamide has excellent corrosion resistance, abrasion resistance, chemical resistance, and insulating property and thus is widely used in preparation of a breathable waterproof membrane. 
     In addition, a thickness of the membrane layer  50  used herein is preferably in a range of 0.15 mm to 0.30 mm. When the thickness of the membrane layer  50  is within this range, clothing prepared using the membrane layer  50  may have excellent air permeability and water resistance, and outdoor clothing having excellent windproof and light weight as well as a breathable waterproof property may be prepared. Also, flexibility of the outdoor clothing may not be deteriorated, and thus activities performed while wearing the outdoor clothing may be easy, which allows manufacture of a variety of functional clothing products. 
     In addition, the thermally-bondable, breathable waterproof membrane  100  of the present invention has a release layer  70  on a lower portion of the membrane layer  50 . 
     Generally, the release layer  70  is formed of a film, etc. having a so-called release property that does not adhere well to an adhesive component or a pressure sensitive adhesive component. The release layer  70  protects the membrane layer  50  by being attached to the membrane layer  50  and may be used to prevent the membrane layer  50  from contamination by dusts or foreign matters. Also, when the preparation of clothing is completed, the release layer  70  may be easily removed using an easy peel-off property. 
     In addition, the thermally-bondable, breathable waterproof membrane  100  of the present invention includes a base layer  25  transferred in the form of dots on an upper portion of the membrane layer  50 . The base layer  25  may preferably be included to prevent attachment of the membrane layer  50  with another fabric and prevent sagging of the membrane layer  50  by gravity during preparation of the thermally-bondable, breathable waterproof membrane  100  of the present invention, and thus processability may be improved and a problem of workability deterioration may be prevented. 
     The base layer  25  may be formed using one selected from an acrylic-based resin, a polyurethane-based resin, a polyamide-based resin, a polyester-based resin, a polyolefin-based resin, a polyvinylchloride resin, and an ethylene-vinyl acetate copolymer (EVA) resin. In the present invention, the base layer  25  may preferably be transferred in the form of dots on an upper portion of the membrane layer  50  as shown in  FIGS. 1 and 2 . 
     Also, a hot-melt adhesive layer  30  may be formed on the base layer  25 . The hot-melt adhesive layer  30  is a part for attaching the membrane layer  50  to the fabric substrate  15  for preparing clothing, wherein, after preparing the thermally-bondable, breathable waterproof membrane  100  of the present invention, the hot-melt adhesive layer  30  may be melted by applying heat to the thermally-bondable, breathable waterproof membrane  100  and then pressed to be thermally-bonded to the fabric substrate  15 . 
     The hot-melt adhesive refer to a heat-melting adhesive that uses a nonvolatile and nonflammable thermoplastic resin in a solid phase at room temperature without using water or a solvent and is melted in a liquid phase by applying heat thereto, and then is applied to a subject to be attached, and then exhibits adhesive strength as the adhesive cools and solidifies. 
     In the present invention, the base layer  25  and the hot-melt adhesive layer  30  formed on the base layer  25  may form a double dot layer  60  as shown in  FIGS. 1 and 2 . 
     A density of the double dot layer  60  formed on the membrane layer  50  of the present invention may be appropriately chosen and implemented. 
     That is,  FIG. 4  is a top view of the thermally-bondable, breathable waterproof membrane  100  of the present invention having the double dot layer  60 . As shown in  FIG. 4 , a formation density of the double dot layer  60  may be represented by the number of dots of the double dot layer  60  formed in 1 cm 2  of a surface of the thermally-bondable, breathable waterproof membrane  100 , i.e., a unit density. In other words, in the present invention, a unit density of the double dot layer  60  may be preferably in a range of 1 dot/cm 2  to 220 dots/cm 2 . 
     Also, as shown in  FIG. 4 , the formation density of the double dot layer  60  may be represented by the number of dots of the double dot layer  60  formed in a line on a  1 -inch long line, i.e., a linear density. In the present invention, a linear density of the double dot layer  60  may be preferably in a range of 7 dots to 40 dots. 
     When the double dot layer  60  is formed within these unit density range and linear density range, a moisture permeability of the thermally-bondable, breathable waterproof membrane  100  of the present invention may be maintained in a range of 1,000 g/m2/24 h to 50,000 g/m2/24 h, which does not result in significant deterioration of the moisture permeability, and thus the thermally-bondable, breathable waterproof membrane  100  may have an excellent moisture permeability. Also, since the hot-melt adhesive layer  30  has the most excellent adhesive strength, the membrane layer  50  may have excellent peeling durability and abrasion durability. 
     In addition, according to a second embodiment of the present invention, a protective layer  10  may be added on the membrane layer  50 . That is, as shown in  FIG. 2 , a thermally-bondable, breathable waterproof membrane  100  according to the second embodiment of the present invention may have the protective layer  10  that protects the membrane layer  50  by being formed on a lower portion of the membrane layer  50 . The protective layer  10  may protect the membrane layer  50  by being attached to the membrane layer  50  as shown in  FIGS. 2 and 3  and thus may protect fine pores formed in the membrane layer  50  or may be laminated on the membrane layer  50  to enhance a surface strength of the membrane layer  50 . The protective layer  10  may be formed of a polyurethane film and may be preferably laminated on the membrane layer  50  as the polyurethane film having a thickness in a range of 1 μm to 2 μm. 
     The thermally-bondable, breathable waterproof membrane  100  of the present invention prepared as described above is then thermally-bonded to the fabric substrate  15 , thereby completing manufacturing a breathable waterproof fabric for preparation of outdoor clothing. 
     Hereinafter, a method of preparing the thermally-bondable, breathable waterproof membrane  100  of the present invention will be described with reference to  FIG. 5 . 
       FIG. 5  is a preparing process diagram that shows preparing processes of the thermally-bondable, breathable waterproof membrane  100  according to the present invention. In the manufacturing process of the thermally-bondable, breathable waterproof membrane  100  according to the present invention, a first step is preparing a membrane layer  50  having a release layer  70  under the membrane layer  50 . The membrane layer  50  having the release layer  70  thereunder is inserted between an upper screen roll  100  and a lower roll  200  and transferred in the direction of the arrow. 
     As a second step, a base layer  25  is formed on an upper portion of the membrane layer  50 . In the second step, a base resin is first melted and transferred in the form of dots using the rotating upper screen roll  100  to form the base layer  25  on an upper portion of the membrane layer  50 . 
     That is, in the second step, after melting the base resin in the upper screen roll  100 , the melted base resin may be transferred in the form of dots on the membrane layer  50  for breathability and waterproofing properties through a doctor blade  150  disposed at one side of the upper screen roll  100  to form the base layer  25 . 
     The second step is preferably performed using the upper screen roll  100 . In particular, when the base resin is transferred in the form of dots using the upper screen roll  100 , the tactile feel and drapability of the membrane layer  50  thus prepared may be excellent. 
     Also, as shown in  FIG. 6 , the upper screen roll  100  may preferably have 30 to 180 outlet holes  15  per an area of 1 cm 2 , wherein the base resin is melted and eluted through the outlet holes  15 , and a diameter of each of the outlet holes  15  may preferably be in a range of 350 μm to 750 μm. 
     When the step of forming the base layer  25  is described in further detail, as shown in  FIG. 5 , the base resin is applied on the membrane layer  50  in the form of dots through the upper screen roll  100 , and thus the base layer  25  is formed. Here, an amount of the base resin transferred in the form of dots on the membrane layer  50  may be preferably in a range of 10 g/m 2  to 30 g/m 2 . When the amount of the base resin applied is greater than 30 g/m 2 , the texture of a fabric may be too hardened, which may degrade the tactile feel of the fabric. When the amount of the base resin applied is less than 10 g/m 2 , the bonding strength may be insufficient, and thus sufficient durability to withstand washing may not be obtained, and as a result, the adhesive strength between the membrane layer  50  and the fabric substrate  15  may decrease. 
     A transfer rate of the base layer  25  may be most preferably in a range of 20 meters to 30 meters per minute. Also, according to an embodiment of the present invention, a melt viscosity of the base resin may be most preferably in a range of 7,000 cps to 45,000 cps. 
     The base layer  25  may be formed by melting one base resin selected from an acryl-based resin, a polyurethane, a polyamide, a polyester, a polyolefin, polyvinylchloride (PVC) and an ethylene-vinyl acetate (EVA) copolymer by applying a suitable temperature to the base resin. 
     Next, a third step is scattering hot-melt adhesive powders  35  on an upper portion of the base layer  25 . 
     The base layer  25  formed in the form of dots in the second step is a melted product that has been produced by applying a suitable temperature to the base resin, where the melted product may be transferred in the form of dots on the membrane layer  50  using the upper screen roll  100 . In the third step, before the melted product of the base resin transferred in the form of dots is cooled and solidified, the hot-melt adhesive powders  35  are scattered on the base layer  25 . 
     That is, the hot-melt adhesive powders  35  having a particle size in a range of 80 μm to 200 μm filled in a hopper  160  are supplied to the membrane layer  50  having the base layer  25  formed thereon using a scattering roll  250 , and here a vibration brush  251  scatters the hot-melt adhesive powders  35  onto the base layer  25 . 
     Here, the hot-melt adhesive powders  35  are scattered on the membrane layer  50  in the powder form and settled on the base layer  25  that is not yet solidified and thus may form a hot-melt adhesive layer  30  in the form of dots. 
     Then, the process may undergo a fourth step, in which the hot-melt adhesive powders  35  scattered on the membrane layer  50  other than the hot-melt adhesive powders  35  settled on the base layer  25  are suctioned and removed using a suction device  300 . 
     Since the base resin forming the base layer  25  is in a state before solidification after being transferred on the membrane layer  50  in the form of dots, the hot-melt adhesive powders  35  settled on the base layer  25  are attached on the base layer  25 . However, the hot-melt adhesive powders  35  that are not settled on the base layer  25  and fell on the membrane layer  50  are suctioned by the suction device  300  and removed from a surface of the membrane layer  50  in the fourth step. 
     Subsequently, the process may undergo a fifth step, in which the membrane layer  50 , from which the hot-melt adhesive powders  35  not settled on the base layer  25  have been removed, passes through a tenter 350, and thus moisture contained in the double dot layer  60  formed on the membrane layer  50  may be evaporated, and the base layer  25  and the hot-melt adhesive layer  30  formed on the base layer  25  are thermally fixed. 
     Here, a temperature condition of the tenter  350  may be appropriately set according to the melting temperature of the hot-melt adhesive. 
     In the fifth step, the hot-melt adhesive powders  35  settled on the base layer  25  form the hot-melt adhesive layer  30  on the base layer  25  in the form of dots at the same time the hot-melt adhesive powders  35  are melt. 
     Here, the hot-melt adhesive layer  30  formed at a rate of 15 g/m 2  to 20 g/m 2  may provide the most excellent adhesive strength after being thermally-bonded to the fabric substrate  15 , and this may allow forming the membrane layer  50  with excellent peeling durability and abrasion durability. 
     After transferring the base layer  25  in the form of dots on the membrane layer  50  as described above, the hot-melt adhesive layer  30  is formed in the form of dots on the base layer  25 , thereby completing formation of the double dot layer  60 . 
     Also, after completing the fifth step, the process may undergo a sixth step, in which the double dot layer  60  consisting of the base layer  25  and the hot-melt adhesive layer  30  is cooled. In the sixth step, the double dot layer  60  is cooled using a cooling roll 400, and thus the double dot layer  60  may be taken up thereafter. 
     Also, according to the second embodiment of the present invention, a step of adding a protective layer  10  on the release layer  70  may further be included in the method. 
     As described above, the protective layer  10  is formed to enhance strength of a surface of the membrane layer  50  while protecting the membrane layer  50  by being laminated on one side of the release layer  70 . The protective layer  10  is formed of a polyurethane film, and a thickness of the polyurethane film may preferably be in a range of 1 μm to 2 μm. The protective layer  10  formed of the polyurethane film may be formed by being laminated between the release layer  70  and the membrane layer  50  using a gravure roll. 
     The thermally-bondable, breathable waterproof membrane  100  of the present invention prepared through these steps described above may be thermally-bonded to a fabric substrate for manufacturing clothing by applying heat and pressure thereto and thus may prepare a functional fabric having breathability and waterproofing properties. Also, a breathable waterproof functional fabric may be prepared by a laminating process in a sewing process, which reduces steps of preparing outdoor clothing, and thus a price competitiveness of the final product may increase. Also, the thermally-bondable, breathable waterproof membrane  100  of the present invention is eco-friendly and has an effect of increasing the design completeness of outdoor clothing. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope of the present invention. It will also be understood by those skilled in the art that those of ordinary skill in the art may readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. Therefore, it should be understood that the embodiments described above are illustrative in all aspects and should not be construed as limiting the scope of the present invention.