CN111051591A

CN111051591A - Waterproof and breathable sheet and manufacturing method thereof

Info

Publication number: CN111051591A
Application number: CN201880057777.8A
Authority: CN
Inventors: 金喆基; 金成镇; 白智淑; 吴兴烈
Original assignee: Kelong Material Co
Current assignee: Kolon Industries Inc
Priority date: 2017-09-06
Filing date: 2018-05-18
Publication date: 2020-04-21
Anticipated expiration: 2038-05-18
Also published as: WO2019050127A1; CN111051591B

Abstract

The present invention relates to a waterproof and breathable sheet material and a method for manufacturing the same, the waterproof and breathable sheet material including: a nano film in which nano fibers are laminated in a non-woven fabric form including a plurality of pores; and the supporting body is used for supporting the nano membrane, and the air permeability is more than 1000mL/min under the pressure of 1 PSI. The waterproof breathable sheet is excellent in both waterproofness and breathability by suppressing the interlayer peeling phenomenon of a nanofilm made of nanofibers to greatly maintain the adhesion between the nanofilm and an adhesive layer, and preventing the decrease in breathability due to pressure when laminating the nanofilm and a support.

Description

Waterproof and breathable sheet and manufacturing method thereof

Technical Field

The present invention relates to a waterproof and breathable sheet and a method for manufacturing the same, and more particularly, to a waterproof and breathable sheet and a method for manufacturing the same, which can suppress a delamination phenomenon of a nano-film made of nanofibers, maintain a strong adhesive force between the nano-film and an adhesive layer, and prevent a decrease in breathability due to pressure when the nano-film and a support are laminated, thereby having excellent waterproofness and breathability.

Background

In various electronic devices such as mobile devices, electronic devices such as hearing aids, communication devices such as interphones, and automotive headlamps, a waterproof performance (waterproof) for preventing water and liquid from penetrating into the electronic devices and a dustproof performance (dustprof) for preventing contamination and dust from penetrating into the electronic devices are required, while maintaining a pressure balance inside and outside the electronic devices by providing air permeability to the electronic devices. Therefore, the electronic apparatus includes a waterproof breathable sheet having both waterproof/dustproof property and air permeability.

The conventional waterproof and breathable sheet is mainly produced using a porous Polytetrafluoroethylene (PTFE) film. The porous PTFE film is melt extruded or calendered PTFE fine powder and is uniaxially or biaxially stretched to achieve microporosity. At this time, the size of the pores or the air permeability may be adjusted according to the conditions of the extrusion and stretching process.

However, since the porous film is made thin for air permeability, it is easily damaged by external force, and therefore, it is difficult to directly use the porous film as a waterproof and air-permeable sheet. The support may be a woven fabric or a knitted fabric, and a nonwoven fabric is mainly used for maximizing air permeability.

However, when the porous film is laminated with the support, although the water repellency can be maximized, there is a problem that the air permeability is lowered.

Disclosure of Invention

Technical problem

The present invention has an object to provide a waterproof and breathable sheet material having excellent waterproof and breathable properties, which is capable of suppressing the interlayer peeling phenomenon of a nanomembrane made of nanofibers, thereby greatly maintaining the adhesion between the nanomembrane and an adhesive layer, and preventing the decrease in breathable properties due to pressure when laminating the nanomembrane and a support.

Another object of the present invention is to provide a method for producing the waterproof and breathable sheet.

Means for solving the problems

According to an embodiment of the present invention, there is provided a waterproof and breathable sheet including: a nano film in which nano fibers are laminated in a non-woven fabric form including a plurality of pores; and the supporting body is used for supporting the nano membrane, and the air permeability is more than 1000mL/min under the pressure of 1 PSI.

The nano film is formed by stacking 2 to 10 layers of the nano fibers, and the interlayer peel strength of the nano fibers can be 100gf/25mm to 500gf/25 mm.

The first and second layers of the nanofibers adjacent to each other in the nanomembrane may include fusion-bonded portions where the nanofibers of the first layer and the nanofibers of the second layer are fused and bonded to each other.

The peel strength of the nanomembrane and the support may be 500gf/25mm to 2000gf/25 mm.

The waterproof breathable sheet further comprises a moisture-curable hot-melt adhesive for bonding the nanomembrane and the support between the nanomembrane and the support, the adhesive having a pattern of dot or mesh morphology, and the coating amount of the adhesive may be 6g/m2 or less.

The waterproof breathable sheet material further comprises a soluble hot-melt adhesive for adhering the nano-film and the support between the nano-film and the support, the adhesive has irregularly scattered dot shapes, and the coating amount of the adhesive can be 6g/m²The following.

The nanomembrane may include a fusion-bonded portion where the nanofibers are fusion-bonded to the support.

The support is a heat bonding non-woven fabric, and the support can be positioned on two sides of the nano film.

The nano film has air permeability of 1-20 CFM (cubic Fe er minute), and the nano film has water pressure resistance of 3000mmH₂O or more.

The waterproof breathable sheet has a rupture strength of 0.5kgf/cm2 to 7kgf/cm2, an air permeability of 0.5CFM to 9CFM, and a water pressure resistance of 3000mmH₂O to 12000mmH₂And O, the waterproof grade of the waterproof and breathable sheet is at least 4, and the water pressure and the waterproofness of the waterproof and breathable sheet can be water-tight for 30 minutes or more under a water pressure of 1.5m or more under normal temperature conditions (20 ℃ +/-5 ℃), low temperature conditions (measured after being held at a temperature of-20 ℃ for 72 hours), high temperature/high humidity conditions (measured after being held at a temperature of 50 ℃ and a humidity of 95% for 72 hours), and thermal shock conditions (measured after being held at a temperature of-40 ℃ and a temperature of 85 ℃ for 1 hour for 30 cycles of repeated cycles).

The nanofibers may be formed from polyvinylidene fluoride (PVdF).

The support may be a polyester spunbonded nonwoven or a thermally bonded nonwoven.

The waterproof breathable sheet may further include an adhesive on one side of the nanomembrane.

According to another embodiment of the present invention, there is provided a method of manufacturing a waterproof and breathable sheet, including: a step of producing an electrospinning solution; a step of electrospinning the produced electrospinning solution to produce a nanofilm in which nanofibers are accumulated in a nonwoven fabric form including a plurality of pores; and a step of laminating the support with the nanomembrane, wherein the waterproof breathable sheet has an air permeability of 1000mL/min or more under a pressure of 1 PSI.

A step of heat-treating the nanomembrane at a temperature above a melting start temperature of the nanofibers may be further included between the step of manufacturing the nanomembrane and the step of laminating the support.

In the heat treatment step, the heat treatment temperature may be 110 ℃ to 170 ℃.

The step of laminating the support may be accomplished by coating a moisture-curable hot-melt adhesive on the nanomembrane or the support using a gravure coater.

The step of laminating the support may be achieved by spraying a soluble hot melt adhesive on the nanomembrane or the support.

The step of laminating the support may be melt-bonding the nanofibers of the nanomembrane at a temperature between the melt initiation temperature of the nanomembrane and the glass transition temperature of the support.

The step of laminating the support may be performed by disposing a so-called thermal bonding nonwoven fabric of a support on both sides of the nanomembrane and then thermally bonding the support.

ADVANTAGEOUS EFFECTS OF INVENTION

The waterproof breathable sheet material of the present invention is excellent in both waterproofness and breathability by suppressing the interlayer peeling phenomenon of a nanomembrane made of nanofibers to maintain the adhesion between the nanomembrane and an adhesive layer to a great extent, and preventing the decrease in breathability due to pressure when laminating the nanomembrane and a support.

Drawings

Fig. 1 is a perspective view schematically showing an embodiment of a waterproof and breathable sheet according to the present invention.

Fig. 2 is a perspective view schematically showing a jig used in the water pressure resistance measuring instrument for measuring water pressure waterproofness.

Fig. 3 is a schematic view of a nozzle-type electrospinning apparatus.

Fig. 4 is a Scanning Electron Microscope (SEM) photograph of the nanomembrane manufactured in example 1.

Fig. 5 is a Scanning Electron Microscope (SEM) photograph of the nano-film manufactured in comparative example 1.

Detailed Description

Preferred embodiments of the present invention will be described below. However, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

According to an embodiment of the present invention, a waterproof breathable sheet includes: a nano-film in which nano-fibers are accumulated in a non-woven fabric form including a plurality of pores; and the supporting body is used for supporting the nano membrane, and the air permeability is more than 1000mL/min under the pressure of 1 PSI.

Fig. 1 is a perspective view schematically showing an embodiment of a waterproof and breathable sheet according to the present invention. The waterproof and breathable sheet will be described with reference to fig. 1.

According to said figure 1, said waterproof breathable sheet 100 comprises: a nanomembrane 10 in which nanofibers are accumulated in a non-woven fabric form including a plurality of pores; and a support 20 for supporting the nanomembrane 10, and optionally, an adhesive layer 30 may be further included on one side of the nanomembrane 10.

The waterproof and breathable sheet 100 of fig. 1 is illustrated as being circular, but the present invention is not limited thereto, and the waterproof and breathable sheet 100 may be circular, oval, rectangular, rounded-corner rectangular, polygonal, P-shaped, and the like.

In addition, although fig. 1 shows that the adhesive layer 30 is located on only one side of the nanomembrane 10, the present invention is not limited thereto, and the adhesive layer 30 may be located on both sides of the nanomembrane 10.

The nanomembrane 10 prevents water/liquid and contaminants/dust, etc. from penetrating into the inside of an electronic device through a porous structure formed by the nanofibers, and at the same time, may impart breathability to the electronic device to maintain the internal/external pressure balance of the electronic device.

For this, the nanomembrane 10 may be formed of a polymer having excellent water resistance, chemical resistance, heat resistance and processing characteristics, and specifically, may be formed of a polyolefin such as polyamide, polyester, polyethylene or polypropylene, a fluoropolymer such as polyvinylidene fluoride, tetrafluoroethylene hexafluoropropylene copolymer (FEP), fluoroethylene (perfluoroacrylic acid) vinyl ether copolymer (PFA) or Polytetrafluoroethylene (PTFE), a polyimide polymer such as Polyimide (PI), Polyetherimide (PEI), Polyamideimide (PAI), etc., Polyethersulfone (PES), Polyacrylonitrile (PAN), etc.

Conventionally, the waterproof and breathable sheet 100 is mainly produced using a porous PTFE sheet. Specifically, the porous PTFE sheet is produced by producing a kneaded product of the PTFE fine powder and the molding aid into a sheet by extrusion molding and rolling, removing the molding aid to obtain a sheet-like body of a molded body, and then stretching the sheet body. However, since the porous PTFE sheet is likely to shrink with the passage of time or heat, the waterproof and breathable sheet 100 has a problem in that the adhesive layer 30 is exposed due to shrinkage.

Therefore, the nanomembrane 10 is more preferably a nanomesh manufactured by electrospinning the polyvinylidene fluoride. Since the polyvinylidene fluoride has excellent water resistance, chemical resistance, and heat resistance, the nano-film 10 manufactured by electrospinning may have excellent hydraulic water resistance and air permeability.

However, the nano-web manufactured by electrospinning the polyvinylidene fluoride can be formed by laminating 2 to 10 layers of the nanofibers, but there is a disadvantage in that the interlayer peel strength of the nanofibers is weak due to the interval between the nozzles or spinnerets of the electrospinning process. When the interlayer peel strength of the nanofibers is weak, not only the strength of the nanomembrane 10 itself is weak, but also the adhesive force between the nanomembrane 10 and the adhesive layer 30 cannot be maintained.

In order to eliminate the interlayer peeling between the nanofibers, there are methods of reducing the ratio of solid components in the composition of the electrospinning solution, reducing the temperature under the electrospinning conditions, or reducing the spinning distance between the nozzle or spinneret and the accumulating portion. However, in this case, the solvent is not smoothly volatilized, so that the manufactured nanomembrane 10 is fabricated in a film shape rather than a fiber shape, resulting in a decrease in air permeability.

In order to solve such problems, the waterproof breathable sheet 100 according to one embodiment of the present invention is formed by laminating 2 to 10 layers of the nanofibers of the nanofilm 10, wherein the nanofibers have an interlayer peel strength of 100gf/25mm to 500gf/25mm, and an air permeability of 1000mL/min or more under a pressure of 1 PST. That is, the interlayer peel strength of the nanofibers may be improved by performing a heat treatment at the melting point starting temperature of the nanofiber polymer or higher, and the adhesive force between the nanomembrane 10 and the adhesive layer 30 may be greatly maintained. Therefore, the first and second layers of the nanofibers adjacent to each other in the nanomembrane 10 may include fusion-bonded portions where the nanofibers of the first layer and the nanofibers of the second layer are fused and bonded to each other.

The thickness reduction rate of the nanomembrane 10 may be 20% to 40% according to the melting degree of the nanofibers. If the thickness reduction rate of the nano-film 10 is less than 20%, interlayer peeling of nano-fibers occurs, and the waterproof performance is lowered, and if the thickness reduction rate is more than 40%, the melted portions of nano-fibers are thinned, and the air permeability is lowered. The thickness reduction rate can be calculated by the following mathematical formula 1.

Mathematical formula 1

Thickness reduction ratio (%) - (h-h')/hX 100

h: thickness of the nanomembrane before formation of the welded joint

h': thickness of the nanomembrane after formation (heat treatment) of the welded joint

The nano-film 10 is formed by stacking 2 to 10 layers of the nano-fibers, and if the number of the nano-fibers is less than 2, the nano-film 10 cannot have a waterproof property due to its thin thickness, and if the number of the nano-fibers is more than 10, the nano-film 10 becomes thick, thereby reducing air permeability. The number of the nanofibers may be measured by confirming the number of the nanofibers on the side cross section of the nano film 10 by a cross-sectional photograph of a scanning electron microscope, or by confirming the number of the nanofibers by peeling off after an adhesive tape is attached to the nano film 10.

The interlayer peel strength of the nanofibers in the nanomembrane 10 of the present invention is 100gf/25mm to 500gf/25mm, and specifically, may be 150gf/25mm to 250gf/25 mm. The interlaminar peel strength of the nanofibers can be measured by 180 degree peel strength measurement of adhesive tapes and adhesive sheets, so-called peel tester (PEEL TESTER) satisfying ASTM D3330 (AR-1000, Chem Instruments) under conditions of width 25mm, length 200mm, and speed 300 mm/min. When the interlayer peel strength of the nanofiber is less than 100gf/25mm, the waterproof performance may be reduced, and, when it is more than 500gf/25mm, the air permeability may be reduced.

In addition, the peel strength of the nanomembrane 10 and the support 20 is reinforced together with the reinforcement of the interlayer peel strength of the nanofibers in the nanomembrane 10, and thus, the peel strength of the nanomembrane 10 and the support 20 may be 500gf/25mm to 2000gf/25mm, and specifically, may be 700gf/25mm to 1100gf/25 mm. The peel strength of the nanomembrane 10 and the support 20 can be measured by a 180 degree peel strength measurement method using an adhesive tape or an adhesive sheet, so-called peel tester (PEEL TESTER) (AR-1000, Chem instruments) satisfying ASTM D3330, under conditions of a width of 25mm, a length of 200mm, and a speed of 300 mm/min. When the peel strength of the nanomembrane 10 and the support 20 is less than 500gf/25mm, the nanomembrane 10 and the support 20 may be separated by impact during punching for manufacturing the waterproof breathable sheet 100, and when it is more than 2000gf/25mm, air permeability may be reduced.

In one aspect, the nanomembrane 10 maximizes the gas permeability of the nanomembrane 10 by adjusting the electrospinning conditions when electrospinning the polyvinylidene fluoride to produce a nanomesh.

Therefore, in the nano-film 10, the diameter of the nano-fiber is 50nm to 3000n m, specifically, may be 100nm to 2000nm, the thickness of the nano-film 10 is 3 μm to 40 μm, specifically, may be 5 μm to 35 μm, the pore size of the nano-film 10 is 0.1 μm to 5 μm, specifically, may be 0.1 μm to 4 μm, the porosity is 40% to 90%, specifically, may be 60% to 90%, and the grammage of the nano-film 10 is 0.5g/m²To 20g/m²And may be, in particular, 1g/m²To 15g/m²。

The pore size of the nanomembrane 10 can be measured using a capillary flow pore size analyzer (CFP) specified by ASTM F316 as the pore size of the narrowest region, that is, the average pore in the diameter of the limiting pores and the size distribution of the pores. The thickness of the nanomembrane 10 may be measured by a thickness measurement method specified in KS K0506 or KS K ISO 9073-2, ISO 4593. The grammage of the nanomembrane 10 can be determined using KS K0514 or ASTM D3776. The porosity of the nanomembrane 10 may be calculated by a ratio of an air volume to the total volume of the nanomembrane 10 according to the following equation 2. In this case, the total volume is calculated by preparing a sample in a rectangular shape and measuring the length, width, and thickness, and the air volume is obtained by subtracting the polymer volume inversely calculated from the density from the total volume after measuring the weight of the sample.

Mathematical formula 2

Porosity (%) [1- (a/B) ] × 100 ═ 1- [ (C/D)/B ] } × 100

(in the mathematical formula 2, A is the density of the nano-film, B is the density of the polymer of the nano-film, C is the weight of the nano-film, and D is the volume of the nano-film)

In addition, since the nanomembrane 10 includes a channelThe nano-mesh made of the polyvinylidene fluoride is electrospun, and thus, the nano-film 10 has a gas permeability of 1CFM to 20CFM (cubic fe per minute), and more particularly, may be 3CFM to 7 CFM. The air permeability of the nanomembrane 10 can be measured by measuring the air permeability of the fabric by the method of ASTM D737 in an area of 38cm²The measurement under the condition of 125Pa is carried out by an Air Permeability Tester (Air Permeability Tester) (FX 3300, textile Instruments) satisfying ASTM D737. When the air permeability of the nanomembrane 10 is less than 1CFM, although the water pressure resistance is increased, the air permeability of the waterproof and breathable sheet 100 is decreased, and when it is more than 20CFM, the water pressure resistance is decreased, and the adhesive is oozed from the inside of the nanomembrane 10 in the lamination process with the support 20, so that the lamination is not easy.

Further, as the nanomembrane 10 includes a nanomesh manufactured by electrospinning the polyvinylidene fluoride, the water pressure resistance of the nanomembrane 10 is 3000mmH₂O or more, specifically, the water pressure resistance may be 5000mmH₂O to 12000mmH₂And O. The water pressure resistance of the nano-film 10 was measured by applying IS O811 to an area of 100cm2 at a low water pressure of 600mmH₂O/min was pressurized to measure the pressure at the position where 3 spots were generated in the water droplets. When the water pressure resistance of the nano-film 10 is less than 3000mmH₂O, the waterproof breathable sheet 100 including the nanomembrane 10 may not satisfy the waterproof property.

In addition, as the nanomembrane 10 includes a nanomesh manufactured by electrospinning polyvinylidene fluoride, the nanomembrane 10 may have a waterproof rating of 4 or more, and specifically, the waterproof rating may be 4 to 5. The water repellency rating of the nanofilm 10 can be measured by the method specified by KS K0590. When the waterproofing grade of the nanomembrane 10 is less than grade 4, the waterproofing performance may be degraded.

When the waterproof breathable sheet 100 includes the nanomembrane 10, the rupture strength is 0.5kgf/cm²To 7kgf/cm²Specifically, it may be 2kgf/cm²To 4.5kgf/cm². The rupture strength of the waterproof breathable sheet 100 can be measured by a Mullen type bursting strength tester (Mullen type bursting strength) satisfying ASTM D3786ester). The waterproof breathable sheet 100 has a rupture strength of less than 0.5kgf/cm²In the case, since the assembling and disassembling process, the impact at the time of actual use, the environmental change, and the like are performed by evaluating the waterproofness of the waterproof and breathable sheet 100, the performance of the waterproof and breathable sheet 100 is lowered to more than 7kgf/cm²In this case, the punching property of the waterproof and breathable sheet is lowered.

The air permeability of the waterproof and breathable sheet 100 is 1000mL/min or more, and specifically, may be 1500mL/min to 3000 mL/min. The air permeability of the waterproof and breathable sheet 100 can measure the flow rate of air passing through a circular area of 1mm in diameter for 1 minute by a Gas permeation method (Gas permeability method) under a pressure of 1PSI with a Capillary flow pore size analyzer (CFP). When the air permeability of the waterproof and breathable sheet 100 is less than 1000mL/min, the pressure balance ability of the waterproof and breathable sheet is reduced.

The waterproof air-permeable sheet 100 has an air permeability of 0.5CFM to 9CFM, and specifically, may have an air permeability of 3CFM to 7 CFM. The breathability of the waterproof breathable sheet 100 can be measured at 38cm by the method of measuring the breathability of the fabric, ASTM D737²Area of (b) and a pressure condition of 125Pa, and measured by using an air permeability Tester (AirPermeability Tester) (FX 3300, textile Instruments) satisfying ASTM D737. When the air permeability of the waterproof breathable sheet 100 is less than 0.5CFM, there is a problem in that the pressure balance capability is reduced due to the reduction of air permeability, and when the air permeability is more than 9CFM, there is a problem in that waterproofness cannot be maintained.

The waterproof and breathable sheet 100 has a water pressure resistance of 3000mmH₂O or more, specifically, the water pressure resistance may be 3000mmH₂O to 12000mmH₂And O. The water pressure resistance of the waterproof and breathable sheet 100 is 100cm by applying ISO 811 low water pressure method²Area of (2) is 600mmH₂O/m in was pressurized to measure the pressure at the position where 3 dots were generated in the water droplet. When the water pressure resistance of the waterproof breathable sheet material 100 is less than 3000mmH₂O, there is a problem that the water repellency cannot be maintained, and when it exceeds 12000mmH₂O, although excellent in water resistance,but has a problem of reduced air permeability.

The water pressure waterproof property of the waterproof breathable sheet 100 can be measured using a water pressure resistance measuring instrument used in KS K ISO 811 that is pressurized at a predetermined time with a predetermined water pressure of a depth of 0m to 20 m. In this case, a jig may be used in the water pressure resistance measuring instrument to measure the water pressure and water resistance of the waterproof and breathable sheet 100.

Fig. 2 is a perspective view schematically showing an embodiment of a jig used for measuring the water pressure and water repellency of the water-repellent breathable sheet 100 in the water pressure resistance measuring instrument. Referring to fig. 2, in a state where the waterproof and breathable sheet 100 is fixed or bonded by the jig 200, the hydraulic waterproofness can be evaluated by applying a predetermined water pressure at a water pressure portion 210 for a predetermined time using a water pressure resistance meter. In fig. 2, the number of the hydraulic pressure parts 210 is 19, but the present invention is not limited thereto, and the number of the hydraulic pressure parts 210 may be adjusted to 1, 3, 5, 9, 20, or the like, for example. The size of the perforations of the water pressing portion 210 is preferably smaller than the opening area of the waterproof and breathable sheet 100. This can be appropriately adjusted according to the size of the waterproof breathable sheet 100.

In order to confirm the water-repellent performance in various environments, the hydraulic water repellency was evaluated after pretreatment under low-temperature, high-temperature/high-humidity, thermal shock conditions. In the case of low temperature, the evaluation was performed after pretreatment at a temperature of-20 ℃ for 72 hours, the evaluation was performed after pretreatment at a temperature of 50 ℃ and a humidity of 95% for 72 hours under high temperature/high humidity conditions, and the evaluation was performed after repeating 30 cycles of maintaining a temperature of-40 ℃ and a temperature of 85 ℃ for 1 hour under thermal shock conditions.

Since the waterproof breathable sheet 100 includes the nanomembrane 10, it may have hydraulic waterproofness as follows. That is, the water-tightness under the conditions of normal temperature (20 ℃ C. + -5 ℃ C.) and water pressure of 1.5m or more for 30 minutes or more, specifically, the water-tightness under the conditions of water pressure of 1.5m to 6m for 30 minutes or more, in the case of low temperature (measured after being maintained for 72 hours under the temperature condition of-20 ℃ C.), the water-tightness under the conditions of water pressure of 1.5m or more for 30 minutes or more, specifically, the water-tightness under the conditions of water pressure of 1.5m to 6m for 30 minutes or more, in the case of high temperature/high humidity (measured after being maintained for 72 hours under the conditions of 50 ℃ C. and 95% humidity), the water-tightness under the conditions of water pressure of 1.5m or more for 30 minutes or more, specifically, the water-tightness under the conditions of water pressure of 1.5m to 6m for 30 minutes or more, and in the case of thermal shock (measured after repeating one cycle of 30 cycles of maintaining the temperature of-40 ℃ C. and the temperature of 85 ℃ C, the water-tight structure is water-tight under a water pressure of 1.5m or more for 30 minutes or more, specifically, water-tight under a water pressure of 1.5m to 6m for 30 minutes or more. The water pressure waterproofness of the waterproof breathable sheet 100 cannot be satisfied when the water pressure waterproofness is less than 30 minutes under the conditions of normal temperature (20 ℃ ± 5 ℃), water pressure of 1.5m or more, low water pressure of 1.5m or more, high temperature/high humidity water pressure of 1.5m or more, and thermal shock water pressure of 1.5m or more.

For reference, the water pressure at the predetermined depth may be calculated by the following equation 3, and in the ocean, the water pressure is generally increased by 1 atmosphere whenever the water depth is increased by 10 m.

Mathematical formula 3

Water pressure (p) pgz

(in the mathematical formula 3, p is the density of seawater (about 1.03 g/cm)³) G is 980cm/sec²And z is depth of water (cm) below sea surface)

In addition, the waterproof breathable sheet 100 further includes a support 20 for enhancing the strength of the nanomembrane 10.

The support 20 has pores having a size larger than that of the nanomembrane 10, and a material having excellent air permeability and strength, such as woven fabric, nonwoven fabric, mesh, net, sponge, foam, porous metal material, metal mesh, or the like, may be used. When heat resistance is required, the support 20 made of polyester, polyamide, aramid resin, polyimide, fluororesin, ultra-high molecular weight polyethylene, metal, or the like can be used.

Specifically, when the support 20 is the nonwoven fabric formed of a plurality of randomly oriented fibers, the nonwoven fabric is sandwiched (interlaid), but the nonwoven fabric is a sheet having a structure of individual fibers or filaments unlike a woven fabric. The nonwoven fabric may be manufactured by one method selected from the group consisting of carding (carding), opening (garneting), air-laying (air-laying), wet-laying (wet-laying), melt-blowing (melt-blowing), spunbonding (spunbonding), thermal bonding (thermal bonding), and stitch-bonding (stich bonding). The fibers forming the nonwoven fabric may contain one or more polymer materials, and in general, any polymer material may be used as long as it is used as a fiber-forming polymer material, and specifically, a hydrocarbon fiber-forming polymer material may be used. For example, the fiber-forming polymer material includes one selected from the group consisting of polyolefins such as polybutylene, polypropylene and polyethylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides (nylon-6 and nylon-6, 6), polyurethanes, polybutylene, polylactic acid, polyvinyl alcohol, polyphenylene sulfide, polysulfone, liquid crystal polymers, polyvinyl acetate, polyacrylonitrile, cyclic polyolefins, polyoxymethylene, polyolefin-based thermoplastic elastomers, and combinations thereof, but is not limited thereto.

More specifically, it is most preferable to use a polyester spunbonded or thermally bonded nonwoven fabric as the support 20, and it is advantageous in that the air permeability is high and the deformation is small under severe environmental conditions when the polyester spunbonded or thermally bonded nonwoven fabric is used. Further, the support 20 may be a nonwoven fabric obtained by cis-or blend-spinning of polymers having different melting points of the polyester, and the nonwoven fabric may have a non-embossed form, which is advantageous in terms of air permeability. The fibers of the embossed portion of the embossed nonwoven fabric are fused to block the pores, which results in a large variation in air permeability of the waterproof and breathable sheet 100. In the waterproof breathable sheet 100 according to another embodiment of the present invention, the peel strength of the nanomembrane and the support is 500gf/25mm to 2000gf/25mm, and the breathability is 1000mL/min or more under a pressure of 1 PSI.

The nanomembrane 10 and the support 20 may be laminated with or without an adhesive. At this time, pressure may be minimized during the lamination of the nanomembrane 10 made of the nanofibers and the support 30, and the permeability of the nanomembrane 10 sensitive to pressure may be prevented from being lowered.

As an example, the waterproof breathable sheet 100 may include a moisture-curable hot-melt adhesive that bonds the nanomembrane 10 and the support 20 between the nanomembrane 10 and the support 20.

The moisture-curable hot-melt adhesive may be, for example, polyurethanes, acrylics, silicones, and the like.

The binder may have a pattern of dots or mesh morphology. When the adhesive is applied to the front surface without the pattern of the dot or mesh form, the adhesive is excessively adhered and bleeds out from the pores of the nanomembrane 10, thereby reducing air permeability, and the adhesive and the nanomembrane 10 are damaged, thereby reducing water pressure resistance.

The pattern of dot or mesh morphology may be formed around the surface of the nanomembrane at intervals of a ratio of 5% to 25% of the surface circumference of the nanomembrane in order to reduce the air permeability of the nanomembrane 10. When the pattern is less than 5% of the surface circumference of the nanomembrane, the problem of lowering the adhesion between the nanomembrane and the support is caused, and when the pattern is more than 25%, the problem of lowering the waterproof property and the air permeability is caused by the adhesive.

In order to prevent the decrease of the permeability of the nanomembrane 10, the coating amount of the binder is 6g/m²Hereinafter, it may be specifically 1g/m²To 3g/m². If the coating weight of the binder is more than 6g/m²The air permeability of the waterproof air-permeable sheet is lowered, and when the air permeability is less than 1g/m²When the binder is used, the binder cannot be uniformly applied.

As another example, the waterproof and breathable sheet 100 may further include a soluble hot melt adhesive for bonding the nanomembrane 10 and the supporter 20 between the nanomembrane 10 and the supporter 20.

The soluble hot melt adhesive may be, for example, polyurethane, polyester, polyamide, or the like.

Since the adhesive is applied with a sprayer, it may have irregularly scattered spots. Since the adhesive has irregularly scattered dot shapes, it is possible to solve the problem that the air permeability is reduced due to the phenomenon that the adhesive leaks between the pores of the nanomembrane 10, and the water pressure drop is reduced due to the nanomembrane 10 being damaged by the adhesive.

Specifically, the coating amount of the binder is 6g/m in order to prevent the decrease in the air permeability of the nanomembrane 10²Hereinafter, it may be specifically 1g/m²To 3g/m². When the coating weight of the binder is more than 6g/m²When less than 1g/m, the air permeability of the waterproof breathable sheet is lowered²In this case, the binder may not be uniformly applied.

As another example, the nanomembrane 10 may include a fusion bonded portion where the nanofibers are fusion bonded to the support 20. That is, the nanomembrane 10 and the support 20 are bonded by being melted and bonded to the support 20 without the binder and then cured again. In this manner, when the nanomembrane 10 and the support 20 are bonded without an adhesive, it is possible to solve a problem that the pores of the nanomembrane 10 are clogged by the adhesive, resulting in a decrease in the air permeability of the nanomembrane 10. Accordingly, the nanofibers of the nanomembrane 10, which are bonded to the support 20, may be fusion bonded to the fusion bonded portion of the support 20.

The thickness reduction rate of the nanomembrane may be 20% to 40% according to the melting degree of the nanofibers. When the thickness reduction rate of the nano-film is less than 20%, interlayer peeling of the nano-fibers may occur, resulting in a reduction in waterproof property, and when the thickness reduction rate is greater than 40%, the melted portions of the nano-fibers are formed into a film, resulting in a reduction in air permeability. The thickness reduction rate can be calculated by the mathematical formula 1.

As another example, the support 20 may be a thermal adhesive nonwoven fabric, and the nanomembrane 10 and the support 20 may be bonded to each other by thermal adhesion of the support 20. In this case, the support 20 is preferably positioned on both sides of the nanomembrane 10.

Specifically, the thermally bonded nonwoven fabric comprises: a first fiber made of high melting point polyethylene terephthalate (PET); and a second fiber made of low-melting polyethylene terephthalate (PET) and obtained by mixing and spinning the first fiber and the second fiber. The high melting point polyethylene terephthalate (PET) may have a melting point of 240 ℃ or more, and the low melting point polyethylene terephthalate (PET) may have a melting point of 120 ℃ to 230 ℃. At this time, the content of the first fibers may be 10 to 90 weight percent, specifically, 30 to 70 weight percent, and the content of the second fibers may be 10 to 90 weight percent, specifically, 30 to 70 weight percent, with respect to the total weight of the heat-bonded nonwoven fabric.

As described above, when the nanomembrane 10 and the support 20 are laminated with or without an adhesive, the peel strength of the nanomembrane 10 and the support 20 may be 500gf/25mm to 2000gf/25mm, and specifically, may be 700gf/25mm to 1100gf/25 mm. The peel strength of the nanomembrane 10 and the support 20 can be measured by a 180 degree peel strength measurement method using an adhesive tape and an adhesive sheet, so-called peel tester (PEEL TESTER) satisfying ASTM D3330 (AR-1000, Chem Instruments Co.) under conditions of a width of 25mm, a length of 200mm, and a speed of 300 mm/min. When the peel strength of the nanomembrane 10 and the support 20 is less than 500gf/25mm, the nanomembrane 10 and the support 20 may be separated by impact during punching for manufacturing the waterproof breathable sheet 100, and when it is more than 2000gf/25mm, air permeability may be reduced.

The adhesive layer 30 is positioned on the surface of the nanomembrane 10, and specifically, the peripheral portion 30a of the adhesive layer 30 is positioned around the surface of the nanomembrane 10, and the central portion 30b of the adhesive layer 30 may have an open frame shape. The nanomembrane 10 is attached to an inner surface of the vent hole of the electronic device case by an adhesive layer 30, and blocks the vent hole of the electronic device case by an opening of a center portion 30b of the adhesive layer 30, thereby providing air permeability and waterproof property to the electronic device.

The shape and size of the opening of the center portion 30b of the adhesive layer 30 may be substantially the same as those of the vent hole of the electronic device case, and specifically, may be in the shape of a circle, an ellipse, a rectangle with rounded corners, a polygon, a P-shape, and the like, but the present invention is not limited thereto.

In this case, the adhesive between the nanomembrane 10 and the support 20 in the region exposed through the opening of the center portion 30b of the adhesive layer 30 may be 3 wt% or less, specifically, 0.5 wt% to 1 wt%, based on the total weight of the adhesive. When the content of the binder is more than 3% by weight in the region exposed through the opening of the center portion 30b of the adhesive layer 30, the air permeability of the waterproof and breathable sheet may be reduced.

Also, as shown in fig. 1, the end of the peripheral portion 30a of the adhesive layer 30 may coincide with the end of the nanomembrane 10, and the end of the peripheral portion 30a of the adhesive layer 30 may extend beyond the segment of the nanomembrane 10 to cover the end of the nanomembrane 10.

The adhesive layer 30 may include a binder selected from the group consisting of polypropylene, polyamide, polyacrylamide, polyester, polyolefin, polyurethane, polysilicon and a mixture thereof, and may be of a liquid type or a solid type, and may be of a thermoplastic type, a heat-distortion type or a reaction-curing type.

In one aspect, the adhesive layer 30 may be a double-sided tape. The double-sided tape may be polyethylene terephthalate (PET) substrate double-sided tape, polypropylene substrate double-sided tape, polyethylene substrate double-sided tape, polyimide substrate double-sided tape, nylon substrate double-sided tape, foam (e.g., polyurethane foam, silicone foam, acrylic foam, polyethylene foam, etc.) substrate double-sided tape, double-sided tape without a substrate, or the like.

On the other hand, the waterproof and breathable sheet 100 may further include a protective substrate (not shown) for protecting the adhesive layer 30 before being attached to an electronic device.

As the protective base material, a rubber or silicone material, a polyester such as polyethylene terephthalate (PET) or polybutylene terephthalate, a polyolefin such as polypropylene, polyethylene, or polymethylpentene, a resin material such as polycarbonate, a paper material such as cellophane, fine paper, coated paper, impregnated paper, or synthetic paper, or a metal foil material such as aluminum or stainless steel can be used.

Further, for the purpose of antistatic, a conductive material may be applied to the protective base material as needed, or a base material in which the protective base material itself is mixed with a conductive material may be used. Thereby, electrification of the waterproof breathable sheet 100 can be prevented. For example, the thickness of the protective substrate may be 10 μm to 100 μm, and specifically, may be 25 μm to 50 μm. In order to improve the adhesion to the adhesive layer 30, the surface of the protective base material may be subjected to corona discharge treatment, plasma treatment, frame plasma treatment, or the like, or may be formed with a primer layer or the like. The primer layer may use a high molecular material (anchor coating agent) selected from the group consisting of polyethylene, polypropylene, styrene copolymer, polyester, polyurethane, polyvinyl alcohol, polyethyleneimine, polyacrylate, polymethacrylate, and a mixture thereof.

On the other hand, in the case where the waterproof and breathable sheet 100 does not further include the adhesive layer 30, when the waterproof and breathable sheet 100 is attached to the housing of an electronic device, the adhesive may be directly applied to the waterproof and breathable sheet 100 or the housing of the electronic device by a method such as screen printing, spray coating, gravure printing, transfer printing, or powder coating, and then attached, and in the case where the adhesive is not present, the waterproof and breathable sheet 100 may be directly attached to the housing of the electronic device by a method such as heat welding or ultrasonic welding.

A method of manufacturing a waterproof breathable sheet according to another embodiment of the present invention includes: a step of producing an electrospinning solution; a step of electrospinning the produced electrospinning solution to produce a nanofilm in which nanofibers are accumulated in a nonwoven fabric form including a plurality of pores; and a step of laminating a support to the nanomembrane. The air permeability of the waterproof and breathable sheet manufactured by the method for manufacturing the waterproof and breathable sheet is 1000mL/min or more under a pressure of 1 PSI.

First, the step of manufacturing the electrospinning solution is to manufacture a solution including a polymer for forming nanofibers by electrospinning, for example, the electrospinning solution may be manufactured by mixing a polymer such as polyvinylidene fluoride (PVdF) with one solvent selected from the group consisting of N, N-dimethylacetamide (N, N-dimethylacetamide), N-dimethylformamide (N, N-dimethylformamide), dimethyl sulfoxide (dimethyl sulfoxide), N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone), triethyl phosphate (triethyl phosphate), methyl ethyl ketone (methylethylketone), tetrahydrofuran (tetrahydrofuran), acetone (acetone), and a mixture thereof.

Then, the produced electrospinning solution is electrospun to produce a nanofilm in which nanofibers are accumulated in the form of a nonwoven fabric having a plurality of pores.

The electrospinning can be performed using the electrospinning apparatus shown in fig. 3. FIG. 3 is a schematic view of a nozzle type electrospinning apparatus. Referring to fig. 3, in the electrospinning process, the electrospinning solution is supplied from a solution tank 1 storing the electrospinning solution to a plurality of nozzles 3 or spinnerets to which a high voltage is applied by a high voltage generator 6 using a metering pump 2, and at this time, the electrospinning solution is transported by forming a jet flow by a difference between electric energy of the nozzles 3 or spinnerets and an electric energy of an accumulation portion 4, that is, a voltage difference. The jet formed is oscillated and stretched by an electric field to be made finer, and the solid fibers are accumulated in the accumulation portion 4 by vaporizing the solvent.

At this time, the nozzles 3 or the spinnerets are arranged at predetermined intervals in a plurality of stages so as to form a stable electric field and easily volatilize the solvent. The nanomembrane may be formed by stacking 2 to 10 layers of the nanofibers through the interval between the nozzles 3 or spinnerets.

On the other hand, the fine structure of the nanofilm is controlled by adjusting the electrospinning conditions, so that a water-repellent breathable sheet having excellent water pressure water repellency and breathability can be manufactured.

The concentration of the electrospinning solution is 5% to 35%, specifically, may be 5% to 25%. The concentration refers to the percentage concentration, which can be calculated from the percentage of the mass of the solute to the mass of the solution. For example, the concentration can be determined by dividing the mass of the polymer contained in the electrospinning solution by the mass of the solvent and multiplying the result by 100. When the concentration of the electrospinning solution is less than 5%, the polymer content is low, and therefore, fibers cannot be formed and microbeads are sprayed, and when the concentration of the electrospinning solution is more than 35%, the polymer is difficult to dissolve, and therefore, the polymer cannot be discharged or the pressure on the solution transfer line is increased, and leakage or breakage of the solution may occur.

The viscosity of the electrospinning solution is 100cP to 10000cP, and specifically, may be 200cP to 5000 cP. The viscosity of the solution can be measured by the KS M ISO 2555 method at a temperature of 23 ℃. When the viscosity of the electrospinning solution is less than 100cP, fibers cannot be generated due to too low viscosity, and when the viscosity is more than 10000cP, there is a problem in that jet flow cannot be formed or solidification occurs to increase the disadvantages of the nanomembrane during spinning.

In addition, the voltage of the electrospinning condition is 0kV to 100kV, and specifically, may be 20kV to 70 kV. When the voltage is more than 100kV, sparks may be generated at portions easily insulated during spinning, resulting in damage of products or transfer to or peeling from a transfer roller during transfer due to static electricity during transfer.

The discharge amount of the electrospinning conditions may be 0.01mL/min to 100mL/min, and specifically, may be 0.5mL/min to 50 mL/min. When the discharge amount is less than 0.01mL/min, productivity is lowered or delamination occurs due to a small amount of stacked fibers, and when the discharge amount is more than 100mL/min, a phenomenon occurs in which the solvent is not volatilized due to an increase in the saturated concentration of the solvent in the chamber, and finally the product is dissolved again to form a film.

As described above, the nanomembrane may be formed by stacking 2 to 10 layers of the nanofibers by the multistage arrangement of the nozzles 3 or the spinnerets, and thus, interlayer peeling of the nanofibers may occur. Therefore, according to the method for manufacturing the waterproof breathable sheet in one embodiment of the present invention, between the step of manufacturing the nanomembrane and the step of laminating the support to the nanomembrane, the method further includes a step of heat-treating the nanomembrane at a temperature equal to or higher than the melting start temperature of the nanofibers. By performing the heat treatment at the melting point starting temperature of the nanofibers or higher, the interlayer peel strength of the nanofibers can be improved.

However, the nano-mesh manufactured by electrospinning the polyvinylidene fluoride easily damages the surface due to pressure or external scratch, and since the fiber phase shows a tendency to collapse and form a film, a decrease in air permeability easily occurs. Therefore, it is preferable to perform the heat treatment of the nanomembrane in a manner of not applying pressure or minimizing pressure. For example, the surface temperature of a hot roll may be fixed to the melting point starting temperature of the nanofibers and the nanofilm may be continuously passed along the surface of the hot roll.

The heat treatment temperature may be 110 to 170 ℃, and specifically, may be 120 to 150 ℃. When the heat treatment temperature is less than 110 ℃, interlayer peeling easily occurs because interlayer peeling strength of the nanomembrane is not increased, and when it is more than 170 ℃, the fibers of the nanomembrane are melted to block pores, resulting in a decrease in air permeability.

Finally, the support is laminated on the nanomembrane to produce a waterproof and breathable sheet. At this time, the method of manufacturing the waterproof breathable sheet provides a method of preventing the decrease in breathability of the pressure-sensitive nanomembrane by minimizing pressure during the lamination of the nanomembrane made of the nanofibers and the support.

Specifically, according to an embodiment of the method of laminating the support on the nanomembrane, the moisture-curable hot melt adhesive may be coated on the nanomembrane or the support using a gravure coater.

The roll of the gravure coater used in the gravure coater may have dots or a mesh pattern on the surface so as to coat the adhesive to have the dots or the mesh pattern.

The lamination speed of the gravure coater is 1m/min or more, and specifically, may be 5m/min to 10 m/min. When the lamination speed of the gravure coater is less than 1m/min, the transfer of the adhesive is not uniform, and the adhesive in a specific portion of the adhesive pattern is excessive, which may reduce the air permeability of the nanomembrane and the support.

In addition, in order to prevent the adhesive from leaking to one surface of the nanomembrane or the support, the fluidity of the adhesive may be reduced by using another interlayer film or cooling the adhesive before winding. When the adhesive leaks, the nano-film is damaged during inspection to cause a decrease in water pressure resistance, or the waterproof breathable sheet cannot satisfy waterproofness.

Then, in order to cure the moisture of the binder, it may be cured in a curing chamber at a temperature of 30 to 50 ℃ and a humidity of 85% or more for at least one day.

In the method of laminating the support on the nanomembrane according to another example, the coating may be performed by spraying the soluble hot-melt adhesive on the nanomembrane or the support.

In this case, the ejection speed is 5m/min or more, specifically, 7m/min to 10 m/min. When the spray velocity is less than 5m/min, the transfer of the adhesive is not uniform, and the adhesive is excessive at a specific portion of the bonding pattern, and thus, the air permeability of the nanomembrane and the support may be reduced.

The melting temperature of the hot melt adhesive is 90 to 160 ℃, and specifically, may be 100 to 120 ℃. When the melting temperature of the hot-melt adhesive is less than 90 ℃, the adhesive can be melted again at the thermal shock temperature of the waterproof breathable sheet material to block the air holes of the nano film, so that the waterproof performance and the air permeability are reduced, and when the temperature is more than 160 ℃, the nano fibers are melted to block the air holes of the nano film.

Specifically, the soluble hot-melt adhesive is melted, sprayed onto the nanomembrane or the support through a nozzle or a spinneret, and the nanomembrane is supplied and wound on the upper surface of the support in a predetermined manner. In this case, in order to prevent the adhesive from bleeding out, the fluidity of the adhesive may be reduced in a cooling portion on the lower surface of the laminated support before the interlayer film is wound or wound together.

In another example of the method of laminating the support on the nanomembrane, the fusion bonding may be performed at a temperature between a melting start temperature of the nanomembrane and a glass transition temperature of the support. That is, this case is the case where the binder is not used.

Specifically, this is a manner of setting a temperature between the glass transition temperature of the support and the melting start temperature of the nanomembrane and laminating with a minimum pressure by utilizing the thermal characteristics of the nanomembrane and the support. For example, the support comprising low melting PET has a glass transition temperature of 60 ℃ to 70 ℃ and the melting onset temperature of the nanoweb made by electrospinning the polyvinylidene fluoride is 125 ℃. At this time, the surface temperature of the laminated hot roll is fixed between the glass transition temperature of the support and the melting point onset temperature of the nano-mesh produced by electrospinning the polyvinylidene fluoride. When the surface temperature of the hot roll is less than the glass transition temperature (60 to 70 ℃) of the support, bonding may not be performed, and when the surface temperature of the hot roll is greater than the melting start temperature (125 ℃) of the nano-web manufactured by electrospinning the polyvinylidene fluoride, the bonding force is excellent, but the nano-fiber phase of the nano-film collapses and forms a film, and thus, the air permeability may be drastically reduced.

Then, in order to minimize damage to the nano-net produced by electrospinning the polyvinylidene fluoride, it is preferable to set the pressure to 10kgf/cm or less, specifically 1kgf/cm or less. When the pressure is greater than 10kgf/cm, the nano-mesh manufactured by electrospinning the polyvinylidene fluoride collapses and forms a film due to the pressure, and thus, air permeability may be reduced.

In another example of the method of laminating the support to the nanomembrane, the support may be formed by disposing a so-called thermally adhesive nonwoven fabric of the support on both surfaces of the nanomembrane and then performing heat treatment. That is, this case also belongs to the case where no adhesive is used.

Specifically, the heat-bondable nonwoven fabric may be formed by joining the nanomembrane and the support by heat treatment at a temperature equal to or higher than the heat-bonding temperature of the heat-bondable nonwoven fabric, and in this case, it is advantageous to dispose the heat-bondable nonwoven fabric on both surfaces of the nanomembrane to maximize the adhesive strength between the nanomembrane and the nonwoven fabric.

For example, the thermally bonded nonwoven fabric includes: a first fiber formed of high melting point polyethylene terephthalate (PET) having a melting point of 240 ℃ or higher; a second fiber formed of a low melting point polyethylene terephthalate (PET) having a melting point of 120 ℃ to 230 ℃, and when the first fiber and the second fiber are included, the surface temperature of the laminated hot roll may be thermally bonded between the melting point starting temperature of the low melting point polyethylene terephthalate and the melting point starting temperature of the nano-web manufactured by electrospinning the polyvinylidene fluoride. Then, in order to minimize damage to the nano-net produced by electrospinning the polyvinylidene fluoride, it is preferable to set the pressure to 10kgf/cm or less, specifically 1kgf/cm or less. When the pressure is greater than 10kgf/cm, the nano-mesh manufactured by electrospinning the polyvinylidene fluoride has its fiber phase collapsed by the pressure and is formed into a film, and thus, air permeability may be reduced.

Detailed description of the preferred embodiments

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily carry out the present invention. However, the present invention may be embodied in various forms and is not limited to the embodiments described herein.

Preparation example: manufacture of waterproof breathable sheet

Example 1

Polyvinylidene fluoride was dissolved in dimethylacetamide at a concentration of 15% (w/w) to produce an electrospinning solution. The viscosity of the electrospinning solution was 2100 cP.

The electrospinning solution was electrospun using the electrospinning apparatus of fig. 3 at a voltage of 60kV and a discharge rate of 6.5mL/min to produce a nano-film.

The above-mentionedThe prepared nano film has porosity of 78%, air permeability of 6.79CFM and water pressure resistance of 6500mmH₂O, and the nanofibers are stacked in 5 layers.

And (c) heat-treating the manufactured nanofilm by fixing the surface temperature of a hot roll at the melting point starting temperature of the nanofibers at 125 ℃, and continuously passing the nanofilm along the surface of the hot roll.

As a support, a support having a thickness of 50: 50 weight ratio of the heat-bonded nonwoven fabric of the blend of ordinary PET and low-melting PET. The gram weight of the support body is 30g/m²。

The fabricated nanomembrane and the support were laminated by moisture-curing hot-melt adhesive using a gravure coater, and aged for 24 hours in an aging chamber at a temperature of 35 ℃ and a humidity of 85% in order to cure the moisture of the adhesive. In this case, the moisture-curable hot-melt adhesive is polyurethane, the laminating speed of the gravure coater is 5m/min, and the coating amount of the adhesive is 5g/m²The pattern of the roll of the gravure coater is in the form of mesh (mesh).

And continuously feeding the nano film laminated with the support, the double-sided adhesive and the protective substrate, bonding the lower surface of the double-sided adhesive on the upper surface of the nano film, and laminating the protective substrate. Next, the waterproof and breathable sheet is manufactured by pressing in a predetermined size between dies moving at a predetermined pressure and speed.

Example 2

In the example 1, the manufacturing of the waterproof air-permeable sheet was performed in the same manner as the example 1 except that the mesh pattern of the hot melt adhesive was spaced at intervals of a ratio of 5% to 25% of the circumference of the surface of the nanomembrane at predetermined intervals.

Example 3

In the example 1, except that the laminating speed of the gravure coater was changed to 10m/min, the coating amount of the adhesive was changed to 6g/m²Except for this, a waterproof and breathable sheet was produced in the same manner as in example 1.

Example 4

In example 1, the production of a waterproof and breathable sheet was performed in the same manner as in example 1, except that the produced nanomembrane and the support were laminated by spraying a soluble hot melt adhesive.

In this case, the soluble hot melt adhesive is polyester, the spraying speed is 15m/min, and the coating weight of the adhesive is 5g/m²The melting temperature of the hot melt adhesive is 120 ℃.

Example 5

In example 1, the production of a waterproof and breathable sheet was carried out in the same manner as in example 1, except that the nanomembrane and the support were fusion-bonded at a temperature between the melting start temperature of the nanomembrane and the glass transition temperature of the support, and laminated without an adhesive.

At this time, the surface temperature of the hot roll was fixed to 100 ℃ of a temperature between 125 ℃ of the melting start temperature of the nanomembrane and 60 ℃ to 70 ℃ of the glass transition temperature of the support, and a pressure was set to 0.7kgf/cm in order to minimize damage of the nanomembrane.

Example 6

As the support, a support was prepared in which 50: 50 weight ratio of the heat-bonded nonwoven fabric of the blend of ordinary PET and low-melting PET. The gram weight of the support body is 15g/m²。

A waterproof and breathable sheet was produced in the same manner as in example 1, except that the thermal bonding nonwoven fabric was disposed on both sides of the nanomembrane, heat-treated at a temperature equal to or higher than the thermal bonding temperature of the thermal bonding nonwoven fabric, and the nanomembrane and the support were laminated without the binder.

At this time, the surface temperature of the hot roll was 100 ℃, and the pressure was set to 0.7kgf/cm in order to minimize the damage of the nano-film.

Comparative example 1

In the example 1, the manufacturing of the waterproof and breathable sheet was performed in the same manner as in the example 1, except that the nanomembrane was not heat-treated.

Comparative example 2

In the example 1, the manufacturing of the waterproof and breathable sheet was performed in the same manner as in the example 1, except that the hot melt adhesive was randomly coated on the nanomembrane.

Comparative example 3

In the example 1, except that the lamination speed of the gravure coater was 1m/min and the coating amount of the adhesive was 8g/m when the fabricated nanomembrane and the support were laminated by the moisture-curable hot-melt adhesive using the gravure coater²The manufacture of a waterproof and breathable sheet was carried out in the same manner as in example 1, except that the roll of the gravure coater was not patterned.

Experimental example 1: scanning electron microscope observation of nanomembranes

The nano-films produced in example 1 and comparative example 1 were observed by a Scanning Electron Microscope (SEM), and the results are shown in fig. 4 and 5, respectively.

Referring to fig. 4 and 5, it was confirmed that the nano-film manufactured in example 1 formed fusion-bonded portions of the nano-fibers by the heat treatment, but it was confirmed that fusion-bonded portions of the nano-fibers were not formed when the nano-film manufactured in comparative example 1 was not heat-treated.

Experimental example 2: measurement of interlayer Release Property of Nanoplane

The interlayer peel strength of the nano-films manufactured in example 1 and comparative example 1 was measured, and the results thereof are shown in table 1 below.

In the following table 1, the porosity of the nanomembrane was measured according to the equation 2.

By ASTM D737 method with area 38cm²The air permeability was measured under a pressure of 125 Pa.

The water pressure resistance of the nano film is determined by applying ISO 811 low water pressure method at 100cm²Applying 600mmH to the area of₂The pressure at O/min was used to measure the pressure at the point where 3 spots were generated in the water droplet.

The interlayer peel strength was measured by the method of ASTM D3330 under the conditions of a width of 25mm, a length of 200mm, and a speed of 300 mm/min.

TABLE 1

Referring to the table 1, it can be seen that the interlayer peel strength of the nano-film of the example 1 is improved by 10 times or more by the heat treatment.

Experimental example 3: measurement of characteristics of waterproof breathable sheet

The characteristics of the waterproof breathable sheets manufactured in the examples and comparative examples were measured, and the results thereof are shown in tables 2 and 3 below.

In the following table 2, the peel strength of the nanomembrane 10 and the support 20 was measured by the ASTM D3330 method under the conditions of a width of 25mm, a length of 200mm, and a speed of 300 mm/min.

The Burst strength of the waterproof breathable sheet was measured 5 times with a Mullen-type bursting strength Tester (Mullen-type bursting strength Tester) satisfying ASTM D3786, and an average value thereof was shown.

By ASTM D737 method with area 38cm²The breathability of the waterproof breathable sheet was measured under a pressure of 125 Pa.

The water pressure resistance of the waterproof breathable sheet is 100cm by applying ISO 811 low water pressure method²Applying 600mmH to the area of₂The pressure at O/min was used to measure the pressure at the point where 3 spots were generated in the water droplet.

TABLE 2

In table 3 below, the water pressure waterproof property of the waterproof breathable sheet can be measured using a water pressure resistance meter used in KS K IS O811 pressurized at a prescribed water pressure of a depth of 0m to 20m for a prescribed time. In the case of the low temperature, the evaluation was carried out after pretreatment at a temperature of-20 ℃ for 72 hours, the evaluation was carried out under high temperature/high humidity conditions after pretreatment at a temperature of 50 ℃ and a humidity of 95% for 72 hours, and the evaluation was carried out under conditions of normal temperature (20 ℃. + -. 5 ℃) after thermal shock conditions in which the temperature of-40 ℃ and the temperature of 85 ℃ were maintained for 1 hour for one cycle of 30 cycles. The air permeability of the waterproof air-permeable sheet was measured by a gas permeability method using a Capillary flow pore size analyzer (CFP) under a pressure of 1PSI for air flow through a circular area of 1mm in diameter in one minute.

TABLE 3

Referring to tables 2 and 3, it can be seen that, as in comparative example 3, a non-patterned gravure coater was used, and when the lamination speed of the gravure coater and the coating amount of the adhesive were out of the range of the present invention, the adhesive bleeding phenomenon was caused due to excessive adhesion, which resulted in a decrease in air permeability, and the adhesive damaged the film, which resulted in a decrease in water pressure resistance.

While the embodiments of the present invention have been described in detail, it is apparent that the scope of the claims of the present invention is not limited thereto, and those skilled in the art can make various modifications and variations without departing from the technical spirit of the present invention described in the claims.

Description of reference numerals

1: solution tank

2: constant delivery pump

3: nozzle with a nozzle body

4: accumulation part

6: high voltage generating device

100: waterproof breathable sheet

10: nano-film

20: support body

30: adhesive layer

30 a: peripheral portion 30 b: center part

200: clamp apparatus

210: water pressing part

Industrial applicability

The present invention relates to a waterproof and breathable sheet that suppresses an interlayer peeling phenomenon of a nanomembrane made of nanofibers to greatly maintain an adhesive force between the nanomembrane and an adhesive layer, and prevents a decrease in breathability due to pressure when laminating the nanomembrane and a support, thereby being excellent in both waterproofness and breathability, and a method for manufacturing the same.

The waterproof and breathable sheet is used for various electronic devices such as mobile devices, electronic devices such as hearing aids, communication devices such as interphones, and automotive headlamps, and can impart breathability to the electronic devices to maintain pressure balance inside and outside the electronic devices, and at the same time, can impart waterproof performance (waterproof) for preventing water/liquid from penetrating the inside of the electronic devices, and dustproof performance (dustprof) for preventing contaminants/dust from penetrating the inside of the electronic devices.

Claims

1. A waterproof breathable sheet material, comprising:

a nano film in which nano fibers are laminated in a non-woven fabric form including a plurality of pores; and

a support for supporting the nanomembrane,

the air permeability is above 1000mL/min under the pressure of 1 PSI.

2. The waterproof breathable sheet according to claim 1, wherein the nanomembrane is formed by stacking 2 to 10 layers of the nanofibers, and the nanofibers have an interlayer peel strength of 100gf/25mm to 500gf/25 mm.

3. The waterproof breathable sheet material of claim 2, wherein the first and second layers of nanofibers adjacent to each other in the nanomembrane include fusion-bonded portions where the nanofibers of the first layer and the nanofibers of the second layer are fused to each other to be bonded.

4. The waterproof breathable sheet according to claim 1, wherein the peel strength of the nanomembrane and the support is 500gf/25mm to 2000gf/25 mm.

5. The waterproof breathable sheet according to claim 1, further comprising a moisture-curable hot-melt adhesive for bonding the nanomembrane and the support between the nanomembrane and the support, the adhesive having a pattern of dot or mesh morphology, the amount of the adhesive being 6g/m²The following.

6. The waterproof breathable sheet according to claim 1, further comprising a soluble hot-melt adhesive for bonding the nanomembrane and the support between the nanomembrane and the support, the adhesive having irregularly scattered dots, the adhesive being applied in an amount of 6g/m²The following.

7. The waterproof breathable sheet of claim 1, wherein the nanomembrane comprises a fusion bonded portion where the nanofibers are fusion bonded to the support.

8. The waterproof breathable sheet material of claim 1, wherein the support is a thermally bonded nonwoven fabric, the support being on both sides of the nanomembrane.

9. The waterproof breathable sheet material of claim 1, wherein the nanofilm has a breathability of 1 to 20CFM and a water pressure resistance of 3000mmH₂O or more.

10. The waterproof breathable sheet of claim 1, wherein the waterproof breathable sheet has a burst strength of 0.5kgf/cm²To 7kgf/cm²The waterproof breathable sheet has air permeability of 0.5-9 CFM and water pressure resistance of 3000mmH₂O to 12000mmH₂And O, the waterproof grade of the waterproof breathable sheet is more than grade 4, and the water pressure and the waterproofness of the waterproof breathable sheet are not leaked for more than 30 minutes under the water pressure of more than 1.5m under the normal temperature condition of 20 +/-5 ℃, the low temperature condition measured after being kept for 72 hours at the temperature of-20 ℃, the high temperature and high humidity condition measured after being kept for 72 hours at the temperature of 50 ℃ and the humidity of 95 percent, and the heat shock condition measured after repeating 30 cycles of one cycle of respectively keeping the temperature of-40 ℃ and the temperature of 85 ℃ for 1 hour.

11. The waterproof breathable sheet material of claim 1, wherein the nanofibers are formed from polyvinylidene fluoride.

12. The waterproof breathable sheet material of claim 1, wherein the support is a polyester spunbonded nonwoven or a thermally bonded nonwoven.

13. The waterproof breathable sheet of claim 1, further comprising an adhesive on one side of the nanomembrane.

14. A method for manufacturing a waterproof and breathable sheet, comprising:

a step of producing an electrospinning solution;

a step of electrospinning the produced electrospinning solution to produce a nanofilm in which nanofibers are accumulated in a nonwoven fabric form including a plurality of pores; and

a step of laminating a support to the nanomembrane,

the waterproof breathable sheet has an air permeability of 1000mL/min or more under a pressure of 1 PSI.

15. The method for producing a waterproof breathable sheet material according to claim 14, further comprising a step of heat-treating the nanomembrane at a temperature equal to or higher than a melting start temperature of the nanofibers between the step of producing the nanomembrane and the step of laminating the support.

16. The method for manufacturing a waterproof breathable sheet according to claim 14, wherein in the heat treatment step, the heat treatment temperature is 110 ℃ to 170 ℃.

17. The method of manufacturing a waterproof breathable sheet according to claim 14, wherein the step of laminating the support is performed by applying a moisture-curable hot-melt adhesive to the nanomembrane or the support using a gravure coater.

18. The method of manufacturing a waterproof breathable sheet according to claim 14, wherein the step of laminating the support is achieved by spraying a soluble hot-melt adhesive on the nanomembrane or the support.

19. The method of manufacturing a waterproof breathable sheet according to claim 14, wherein the step of laminating the support is to melt-bond the nanofibers of the nanomembrane at a temperature between a melt initiation temperature of the nanomembrane and a glass transition temperature of the support.

20. The method for producing a waterproof breathable sheet according to claim 14, wherein the step of laminating the support is performed by arranging a so-called thermal bonding nonwoven fabric of a support on both surfaces of the nanomembrane and then thermally bonding the support.