A waterproof and breathable material and its preparation method

Abstract

The present invention discloses a preparation method of a waterproof and breathable material, which comprises the following steps: preparing a core layer spinning solution and a skin layer spinning solution respectively, and forming microfibers by using a coaxial meltblown spinning process with the core layer spinning solution and the skin layer spinning solution and covering the surface of a base fabric; the core layer spinning solution contains a thermoplastic polyurethane elastomer, and the skin layer spinning solution contains polyvinylpyrrolidone and a thermoplastic polyurethane elastomer; dipping the side of the base fabric covered with microfibers into a precipitation solution, and polyvinylpyrrolidone precipitates from the thermoplastic polyurethane elastomer, so that primary pores are formed on the surface of the microfibers; performing drying treatment by using hot air drying and cylinder drying in sequence to obtain the waterproof and breathable material. The preparation method of the waterproof and breathable material of the present invention forms two-level pores in the skin layer of a single fiber, and the prepared waterproof and breathable material can simultaneously achieve better waterproof and breathable functions.

Description

Technical Field

[0001] The present invention relates to the technical field of textiles, and particularly relates to a preparation method of a waterproof and breathable material and a waterproof and breathable material prepared by using the preparation method. Background Art

[0002] Waterproof and breathable materials originated in European and American countries and were first designed for use in the production of military uniforms and protective clothing, so that soldiers can still maintain a light and comfortable combat-ready state in harsh rain and snow environments. With the development of modern textile post-treatment technology, waterproof and breathable materials that can prevent water droplets from penetrating while allowing gases or water vapor to pass through have been widely used in daily life, such as shower curtains and functional wall papers in home life, the surface layers of windbreakers and down jackets in clothing, and raincoats and sleeping bags in outdoor products. Generally speaking, waterproof and breathable materials can be prepared by using PE, PU, and PTFE as the main raw materials and other functional auxiliaries as supplements through the formation of high-density weaving, coating, or laminating.

[0003] Currently, for the preparation of waterproof and breathable fabrics or films, there is Chinese Utility Model Patent CN202021205387.1, a waterproof and moisture-permeable polyester-cotton composite fabric TPU composite fabric, which discloses a polyester-cotton composite fabric composed of multiple layers, including a layer of channel fabric layer. Although it is beneficial for the passage of water vapor, it is difficult to be discharged from the fabric as soon as possible due to the influence of the outer layer of TPU, and the existence of the channel increases the overall thickness of the fabric; there is also Chinese Invention Patent CN202010184494.9, which discloses a preparation method of a waterproof and moisture-permeable TPU hot melt adhesive film. In its waterproof and breathable film, a foaming agent and TPU are mixed, and drying and shaping are carried out on a release paper. Due to the thermoplasticity of TPU and the flowability of the auxiliaries, the film cannot maintain the same double-sided properties of the material when used alone. Under the action of hot pressing, if a thinner waterproof and breathable fabric is prepared, it is difficult to control the expansion diameter of its micropores. There is also Chinese Invention Patent CN201811591407.0, which discloses a preparation method of a laminated waterproof fabric, using PTFE as the film raw material. However, compared with the relatively high raw material cost and special performance characteristics of PTFE, TPU has a more economical advantage and is also more widely used in the current textile finishing feeding process.

[0004] It can be seen that the waterproof and breathable materials or films disclosed in the prior art tend to carry out interlayer design on the fabric structure, using a hydrophobic film or a special structure to achieve the waterproof and breathable function, but it is difficult to solve the problem that the air permeability is greatly reduced due to the coating or high-density structure covered for waterproofing on the outermost layer. Summary of the Invention

[0005] In view of this, in order to overcome the defects of the prior art, the purpose of the present invention is to provide an improved method for preparing a waterproof and breathable material, and the prepared waterproof and breathable material can simultaneously achieve better waterproof and breathable functions.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A method for preparing a waterproof and breathable material, comprising the following steps:

[0008] Prepare a core layer spinning solution and a skin layer spinning solution respectively, and form microfibers by coaxial meltblown spinning process and cover them on the surface of the base fabric; the core layer spinning solution contains thermoplastic polyurethane elastomer, and the skin layer spinning solution contains polyvinylpyrrolidone and thermoplastic polyurethane elastomer;

[0009] When the spinning solution is in a molten state after forming fibers and has not completely cooled and solidified, immerse the side of the base fabric covered with microfibers into the precipitation solution, and polyvinylpyrrolidone precipitates from the thermoplastic polyurethane elastomer, so that pores are formed in the skin layer of the microfibers;

[0010] Perform drying treatment by hot air drying and cylinder drying in sequence to obtain the waterproof and breathable material.

[0011] According to some preferred embodiments of the present invention, the mass fraction of polyvinylpyrrolidone in the skin layer spinning solution is 10-25% to control the porosity and the diameter of the pores, and the mass fraction of thermoplastic polyurethane elastomer is 65-86%; the mass fraction of thermoplastic polyurethane elastomer in the core layer spinning solution is 85-96%.

[0012] According to some preferred embodiments of the present invention, immerse it in the precipitation solution within 5 minutes after meltblowing to avoid the rapid solidification of the fibers, resulting in limited precipitation of PVP; the immersion precipitation and drying processes are carried out in a closed space to reduce the pollution of the material. Preferably, immerse it in the precipitation solution within 1 minute.

[0013] According to some preferred embodiments of the present invention, the relative molecular weight of polyvinylpyrrolidone PVP is 30000-100000.

[0014] According to some preferred embodiments of the present invention, the intrinsic viscosity ratio of the skin layer spinning solution and the core layer spinning solution is [η] 皮层 :[η] 芯层 =1:0.45-0.65; used to control the skin-core layer structure. On the one hand, the skin-core layer structure requires a certain thickness of the skin layer to generate pores, and on the other hand, it requires a core layer with a certain thickness to bear mechanical deformation; the skin-core layer corresponding to the spinning solution with this intrinsic viscosity ratio is more stable, can form pores and has stable mechanical properties

[0015] According to some preferred implementation aspects of the present invention, the intrinsic viscosity of the skin spinning solution is 0.65 to 0.8 dL / g. The skin spinning solution needs to be melted for spinning and, at the same time, needs to be precipitated subsequently. Therefore, the viscosity of the skin spinning solution cannot be too high, otherwise it is not conducive to subsequent precipitation.

[0016] According to some preferred implementation aspects of the present invention, the holes include primary holes and secondary holes; the diameter of the primary holes is 100 - 800 nm, and the diameter of the secondary holes is 20 - 200 nm; the total porosity of the entire microfiber is 50 - 88%. The pore diameter of the primary holes is larger than that of the secondary holes. If the pore diameter is too large, water will seep through and the waterproof effect cannot be achieved. If the pore diameter is small, the air permeability is not good.

[0017] When the coated base fabric is immersed in the precipitation solution, the skin PVP precipitates from the skin and forms holes in the TPU on the surface of the base fabric. The principle of forming two - stage holes is as follows: when the fiber enters the precipitation solution, the fiber is not completely cured. The low - molecular - weight PVP near the outer layer is first easily dissolved in the precipitation solution, so pores with a larger diameter, namely primary holes, will appear at the position near the outer surface of the fiber. When the radial distance increases and the internal low - molecular - weight PVP contacts the precipitation solution, the curing degree of the fiber is higher, and the precipitation effect of the internal PVP becomes weaker due to the barrier generated by the gradual change of the spinning solution from the molten state to the solid state. Therefore, the pore diameter of the inner layer becomes small and dense, namely secondary holes.

[0018] According to some preferred implementation aspects of the present invention, the core spinning solution and the skin spinning solution contain 4 - 10% by mass of an auxiliary agent; the auxiliary agent is one or more selected from plasticizers, softeners, color fixatives, flame retardants, and anti - shrinkage agents.

[0019] According to some preferred implementation aspects of the present invention, the hot air drying temperature is 95 - 120 °C, and the temperature of the cylinder drying is 25 - 80 °C. The cylinder drying includes multiple cylinders, and the temperature of the cylinders decreases sequentially along the advancing direction of the fabric. For example, the heating temperature of the first cylinder is 65 - 80 °C, the heating temperature of the second cylinder is 45 - 60 °C, the heating temperature of the third cylinder is 30 - 50 °C, and the heating temperature of the fourth cylinder is 25 - 40 °C. During the two drying processes: hot air drying can remove most of the moisture, cylinder drying can dry out the remaining moisture hidden in the pores, and at the same time, cylinder drying can improve the roughness of the surface of the fiber membrane.

[0020] According to some preferred implementation aspects of the present invention, the precipitation solution is water and / or ethanol, the temperature of the precipitation solution is 25 - 45 °C, and the impregnation time is 20 - 120 s to dissolve the PVP. Preferably, the precipitation solution is a mixed solution composed of water and ethanol in a volume ratio of 6 - 8:2 - 4.

[0021] According to some preferred embodiments of the present invention, the melt spinning temperature of the coaxial meltblown spinning process is 160 to 200 °C; the inner diameter of the spinning orifice of the spinneret corresponding to the core layer spinning solution is 40 to 180 μm, and the inner diameter of the spinning orifice of the spinneret corresponding to the skin layer spinning solution is 120 to 350 μm.

[0022] According to some preferred embodiments of the present invention, the thickness of the microfibers on the surface of the base fabric is 0.7 - 1.5 mm, and the diameter of a single microfiber is 20 - 180 μm.

[0023] In some embodiments, the preparation method of the waterproof and breathable material specifically includes the following steps:

[0024] Step 1, prepare the core layer spinning solution and the skin layer spinning solution respectively

[0025] Step 2, coaxial meltblown spinning

[0026] Inject the two spinning solutions into the corresponding skin layer spinneret and core layer spinneret respectively. After the coaxial microfibers are ejected, they are spun on the surface of one side of the base fabric to be treated with a certain thickness under the action of wind force.

[0027] Step 3, immersion precipitation

[0028] Within 5 minutes after meltblowing, the side of the base fabric covered with coaxial microfibers is immersed in the precipitation solution at the lower surface of the heating roller, and PVP precipitates from the TPU solution to form two-stage pores and dissolves in the precipitation solution.

[0029] Under the continuous replacement action of the precipitation solution, due to the existence of pores that are small and dense in the TPU layer on the surface of the base fabric, a waterproof and breathable coaxial meltblown film is formed.

[0030] Step 4, hot air drying

[0031] During the hot air drying process, the moisture that has not had time to escape due to the water tension in the skin layer of the microfibers further emerges; and the moisture on the waterproof and breathable material is initially dried.

[0032] Step 5, drying with a drying cylinder

[0033] Use a drying cylinder to further dry the moisture in the waterproof and breathable material. At the same time, the smooth surface of the high-temperature drying cylinder finishes the rough surface generated by the escape of moisture from the waterproof and breathable material, and finally obtains the waterproof and breathable material.

[0034] Among them, the temperature of the heating roller is 110 - 130 °C, the temperature of the hot air drying is 95 - 120 °C, and the temperature of the drying with a drying cylinder is 25 - 80 °C.

[0035] The present invention also provides a waterproof and breathable material prepared by the preparation method as described above.

[0036] Due to the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: In the preparation method of the waterproof and breathable material of the present invention, a core-shell structure microfiber membrane spun from coaxial melt spinning is formed on the surface of the base fabric. Through the design of the composition and method, channels are formed between the fibers, and pores are formed within the cortex of a single fiber. The pores of the pores are small, which can hinder the passage of water molecules, and TPU is a hydrophobic material, which can achieve the waterproof effect. Different from the polymer waterproof film, in this application, not only the channels between the fibers ensure a certain air permeability, but at the same time, due to the formation of pores in a single fiber, the mechanical properties of the fiber will be reduced; therefore, in this application, the fiber is core-shell layered. On the one hand, the cortex can form pores to enhance air permeability, and on the other hand, it can maintain the mechanical properties of the fiber layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0038] Figure 1 It is a process flow chart of the preparation of the waterproof and breathable material in the preferred embodiment of the present invention;

[0039] Figure 2 It is a schematic structural diagram of the waterproof and breathable material in the preferred embodiment of the present invention;

[0040] Figure 3 It is a schematic cross-sectional view of the microfiber prepared in the preferred embodiment of the present invention;

[0041] Figure 4 It is a scanning electron microscope image of the microfiber prepared in the preferred embodiment of the present invention;

[0042] In the drawings, 1, receiving device; 2, coaxial meltblowing device; 3, heating roller; 4, precipitation liquid; 5, hot air drying device; 6, dehumidifying exhaust port; 7, first drying cylinder; 8, light roller; 9, second drying cylinder; 10, third drying cylinder; 11, fourth drying cylinder; 21, waterproof and breathable layer; 22, base fabric layer; 31, core layer; 32, cortex; 33, pores. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] To enable those skilled in the art to better understand the technical solution of the present invention, the following will clearly and completely describe the technical solution in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0044] The models and manufacturers of some reagents used in this embodiment are as follows:

[0045] Polyvinylpyrrolidone (PVP) (Model: PVP-K30; Company: Shanghai Qifuqing Materials Technology Co., Ltd.);

[0046] Thermoplastic polyurethane (TPU) (Model: HF-3398AX; Company: Shenzhen Chuangda Plastic Raw Materials Co., Ltd.);

[0047] Fixing agent (Model: Feylorfix 50; Company: Jiangsu Fumiao Technology Co., Ltd.);

[0048] Softening agent (Model: 6030; Company: Jinan Xinglongda Chemical Co., Ltd.);

[0049] Shrink-proof agent (Model: NG-3206; Company: Nanjing Guojue Textile Technology Co., Ltd.);

[0050] Plasticizer (Model: DOA; Company: Nanjing Rongji Chemical Co., Ltd.);

[0051] Polyester woven fabric (Model: 20221209; Company: Taian Dingfeng Engineering Materials Co., Ltd.).

[0052] The reason why the microfiltration membrane can achieve waterproof and breathable is that there is a difference in the diameters of water molecules and gas molecules. Generally, when the membrane pore diameter is less than 10 μm, it can not only block the penetration of water but also allow gas to pass through. Although the diameter of water vapor molecules is much smaller than that of water molecules, due to the existence of surface tension, it is very difficult for them to pass through the porous channels. Based on this, the present invention designs a waterproof and breathable membrane composed of micron fibers, which not only realizes gas passage through the pores formed by the entanglement between multiple fibers but also designs a porous structure on a single fiber, which not only further hinders the passage of water vapor molecules but also increases the passage path of ordinary gases.

[0053] In order to replace the ordinary film with a fiber membrane, the present invention adopts a melt spinning process. When the molten spinning solution is extruded, under the action of wind force, the molten polymer is further stretched in a small diameter state and finally forms fibers on the micron scale and aggregates on the base fabric. At the same time, when the environmental temperature cools immediately, the molten polymer will quickly turn into a solid state, which can help the fiber membrane to form. At the same time, in this process, the "pore-forming agent" low molecular weight PVP can also complete the process of "melting-swelling-dissolving" of the polymer in a short time. Finally, PVP is replaced by liquid, and a porous structure is formed after drying.

[0054] In the process of forming the porous structure, due to the difference in the time sequence when the single fiber contacts the precipitation liquid in the radial direction of the fiber, the contact time points of the PVP on the surface layer and the inner layer with the solvent are different, thus forming hierarchical holes with different sizes. Figure 4 As shown in the figure, the PVP near the surface layer can more easily contact the precipitation liquid first. At this time, the fiber has not completely cooled and solidified. The PVP near the surface layer contacts the precipitation liquid more fully, and thus can form primary holes with larger pore diameters. As time goes by, the precipitation liquid penetrates inward, and the PVP near the inside of the fiber can only contact the precipitation liquid. At this time, the fiber is more cooled and solidified, making the PVP in the inner layer not as fully and directly in contact with the liquid as the PVP on the surface layer, and thus forming secondary holes with smaller pore diameters.

[0055] Specifically, as Figure 1 shown, the preparation method of the waterproof and breathable material in this embodiment includes the following steps:

[0056] Step 1: Prepare the core layer spinning solution and the skin layer spinning solution respectively

[0057] The mass fraction of polyvinylpyrrolidone in the skin layer spinning solution is 10-25%, and the mass fraction of thermoplastic polyurethane elastomer is 65-86%; the mass fraction of thermoplastic polyurethane elastomer in the core layer spinning solution is 85-96%. The core layer spinning solution and the skin layer spinning solution contain 4-10% of additives by mass; the additives are one or more selected from plasticizers, softeners, color fixatives, flame retardants and anti-shrinking agents. Specifically, in this embodiment:

[0058] By mass percentage, the raw materials of the skin layer spinning solution contain: 10-25% PVP, 65-86% TPU, 1-5% color fixative and 1-5% softener. The relative molecular weight of polyvinylpyrrolidone PVP is 30000-100000.

[0059] By mass percentage, the raw materials of the core layer spinning solution contain: 85-96% TPU, 1-8% anti-shrinking agent and 1-8% plasticizer.

[0060] The intrinsic viscosity of the skin spinning solution obtained after melting and mixing the skin spinning solution raw materials is 0.65 to 0.8 dL / g. The ratio of the intrinsic viscosities of the skin spinning solution and the core spinning solution is [η] 皮层 :[η] 芯层 = 1:0.45 to 0.65.

[0061] Step 2, coaxial meltblown spinning

[0062] Add the skin spinning solution raw materials and the core spinning solution raw materials in the above ratios to the screw extruder respectively, melt them at a temperature of 160 to 200 °C and mix them evenly respectively, and spray them out through a coaxial melt spinning plate to form microfibers and spin them on the surface of the base fabric - polyester woven fabric with a certain thickness under the action of wind. As Figure 1 shown, the coaxial meltblown device 2 is arranged above the receiving device 1, and the base fabric 22 passes between the receiving device 1 and the coaxial meltblown device 2.

[0063] The inner diameter of the spinning hole of the spinning plate corresponding to the core spinning solution is 40 to 180 μm, and the inner diameter of the spinning hole of the spinning plate corresponding to the skin spinning solution is 120 to 350 μm. The thickness of the microfibers on the surface of the base fabric is 0.7 - 1.5 mm, and the diameter of a single microfiber is 20 to 180 μm.

[0064] Step 3, immersion precipitation

[0065] One side of the base fabric covered with coaxial microfibers is immersed in the precipitation liquid 4 at the lower surface of the heating roller 3, and PVP in the skin layer precipitates from the TPU to form two-stage pores and dissolves in the precipitation liquid. The temperature of the heating roller is 110 to 130 °C, which further effectively increases the bonding between the microfibers and the base fabric. Preferably, a guiding roller (not shown) is also arranged below the heating roller to prevent the bottom of the heating roller from contacting the liquid surface and causing loss of the precipitation liquid, and at the same time, the lower surface of the base fabric can be immersed in the precipitation liquid.

[0066] The precipitation liquid is water and / or ethanol, the temperature of the precipitation liquid is 25 - 45 °C, and the impregnation time is 20 to 120 s. Under the continuous replacement action of the precipitation liquid, due to the existence of pores with small and dense holes in the skin layer of the microfibers on the surface of the base fabric, a waterproof and breathable coaxial meltblown film is formed.

[0067] Immerse in the precipitation liquid within 5 minutes after meltblowing to avoid the rapid solidification of the fibers, resulting in limited precipitation of PVP. The immersion precipitation and drying processes are carried out in a closed space to reduce material contamination. Preferably, immerse in the precipitation liquid within 1 minute.

[0068] Step 4, hot air drying

[0069] Hot air drying is carried out by using the hot air drying device 5, and the hot air drying device 5 is provided with a dehumidifying exhaust port 6. During the hot air drying process, the moisture that has not had time to escape due to the water tension in the cortex of the waterproof and breathable material further emerges; and the moisture on the waterproof and breathable material is initially dried.

[0070] Step 5: Cylinder drying

[0071] The cylinder is used to further dry the moisture in the waterproof and breathable material. At the same time, the smooth surface of the high-temperature cylinder sorts out the rough surface generated by the escape of moisture from the waterproof and breathable material, and finally the waterproof and breathable material is obtained.

[0072] The hot air drying temperature is 95 - 120 °C, and the cylinder drying temperature is 25 - 80 °C. The cylinder drying includes a plurality of cylinders, and the temperature of the cylinders decreases sequentially along the advancing direction of the fabric. For example, the heating temperature of the first cylinder 7 is 65 - 80 °C, the heating temperature of the second cylinder 9 is 45 - 60 °C, the heating temperature of the third cylinder 10 is 30 - 50 °C, and the heating temperature of the fourth cylinder 11 is 25 - 40 °C.

[0073] The prepared waterproof and breathable material includes a base fabric layer 22 and a waterproof and breathable layer 21 covering it. The waterproof and breathable layer 21 is composed of micron fibers formed by coaxial melt spinning. The micron fibers are of a skin-core structure, including a core layer 31 and a cortex layer 32. At the same time, the cortex layer 32 has first-level holes 33 and second-level holes 33 with different sizes. The porosity of the micron fibers is 50 - 88%; the holes include first-level holes and second-level holes. The diameter of the first-level holes is 100 - 800 nm, and the diameter of the second-level holes is 20 - 200 nm.

[0074] Example 1

[0075] The preparation method of the waterproof and breathable material in this example specifically includes the following steps:

[0076] Step 1: Prepare the core layer spinning solution and the cortex layer spinning solution respectively

[0077] By mass percentage, the raw materials of the cortex layer spinning solution contain: 11% PVP, 84% TPU, 3% color fixing agent, and 2% softening agent. The relative molecular weight of polyvinylpyrrolidone PVP is 50000.

[0078] By mass percentage, the raw materials of the core layer spinning solution contain: 96% TPU, 3% shrinkage-proof agent, and 1% plasticizer.

[0079] The intrinsic viscosity of the cortex layer spinning solution obtained after melting and mixing the raw materials of the cortex layer spinning solution is 0.7 dL / g. The intrinsic viscosity of the core layer spinning solution is 0.4 dL / g.

[0080] Step 2: Coaxial melt spinning

[0081] The above-mentioned raw materials of the skin layer spinning solution and the core layer spinning solution are respectively added to a screw extruder, melted at a temperature of 190 °C, and uniformly mixed respectively. Then, they are extruded through a coaxial melt spinning plate to form microfibers, and are spun onto the surface of a base fabric - polyester woven fabric with a certain thickness under the action of wind.

[0082] The inner diameter of the spinning holes of the spinning plate corresponding to the core layer spinning solution is 80 μm, and the inner diameter of the spinning holes of the spinning plate corresponding to the skin layer spinning solution is 270 μm. The thickness of the microfibers on the surface of the base fabric is 0.75 mm, and the diameter of a single microfiber is 138 μm.

[0083] Step 3: Immersion and precipitation

[0084] Within 1 minute, the side of the base fabric covered with coaxial microfibers is immersed in the precipitation solution at the lower surface of the heating roller. The PVP in the skin layer precipitates from the TPU, forming two - stage pores and dissolving in the precipitation solution. The temperature of the heating roller is 115 °C.

[0085] Under the continuous replacement action of the precipitation solution, due to the existence of small and dense pores in the skin layer of the microfibers on the surface of the base fabric, a waterproof and breathable coaxial melt - blown film with pores is formed.

[0086] The precipitation solution is a mixed solution composed of water and ethanol in a volume ratio of 7:3. The temperature of the precipitation solution is 25 °C, and the impregnation time is 100 s. The addition of ethanol can change the surface tension of the precipitation solution and help the precipitation of PVP.

[0087] Step 4: Hot - air drying

[0088] During the hot - air drying process, the water that has not had time to escape from the skin layer of the waterproof and breathable material further emerges, and the water on the waterproof and breathable material is initially dried, obtaining a waterproof and breathable material with two - stage pores. The temperature of the hot - air drying is 120 °C, and the speed is 0.1 m / s.

[0089] Step 5: Cylinder drying

[0090] The cylinder is used to further dry the water in the waterproof and breathable material. At the same time, the smooth surface of the high - temperature cylinder finishes the rough surface of the waterproof and breathable material caused by the escape of water, and finally obtains the waterproof and breathable material.

[0091] The cylinder drying includes multiple cylinders, and the temperature of the cylinders decreases sequentially along the advancing direction of the fabric. The heating temperature of the first cylinder is 75 °C, the heating temperature of the second cylinder is 60 °C, the heating temperature of the third cylinder is 50 °C, and the heating temperature of the fourth cylinder is 40 °C.

[0092] In the microfibers of this embodiment, the diameter of the primary pores is 600 - 800 nm, and the diameter of the secondary pores is 100 - 200 nm; the total porosity of the microfibers is 80%.

[0093] Example 2

[0094] The preparation method of the waterproof and breathable material in this embodiment specifically includes the following steps:

[0095] Step 1: Prepare the core layer spinning solution and the skin layer spinning solution respectively

[0096] By mass percentage, the raw materials of the skin layer spinning solution contain: 18% PVP, 79% TPU, 2% color fixing agent, and 1% softening agent. The relative molecular weight of polyvinylpyrrolidone PVP is 70,000.

[0097] By mass percentage, the raw materials of the core layer spinning solution contain: 97% TPU, 2.5% shrinkage preventer, and 1.5% plasticizer.

[0098] The intrinsic viscosity of the skin layer spinning solution obtained after the raw materials of the skin layer spinning solution are melt - mixed is 0.75 dL / g. The intrinsic viscosity of the core layer spinning solution is 0.45 dL / g.

[0099] Step 2: Coaxial melt - blown spinning

[0100] Add the above - proportioned raw materials of the skin layer spinning solution and the core layer spinning solution into the screw extruder respectively, melt them at a temperature of 200 °C and uniformly mix them respectively, and extrude them through a coaxial melt - blown spinneret to form microfibers, and spin them on the surface of the base fabric - polyester woven fabric with a certain thickness under the action of wind force.

[0101] The inner diameter of the spinneret hole of the spinneret corresponding to the core layer spinning solution is 100 μm, and the inner diameter of the spinneret hole of the spinneret corresponding to the skin layer spinning solution is 290 μm. The thickness of the microfibers on the surface of the base fabric is 1.0 mm, and the diameter of a single microfiber is 143 μm.

[0102] Step 3: Immersion precipitation

[0103] Within 1 minute, immerse the side of the base fabric covered with coaxial microfibers in the precipitation solution at the lower surface of the heating roller, and the PVP in the skin layer precipitates from the TPU to form two - stage pores and dissolve in the precipitation solution. The temperature of the heating roller is 125 °C.

[0104] Under the continuous replacement action of the precipitation solution, due to the existence of small and dense pores in the skin layer of the microfibers on the surface of the base fabric, a waterproof and breathable coaxial melt - blown film with pores is formed.

[0105] The precipitated liquid is a mixed liquid composed of water and ethanol in a volume ratio of 8:2. The temperature of the precipitated liquid is 25°C, and the impregnation time is 100 s. The addition of ethanol can change the surface tension of the precipitated liquid and help the precipitation of PVP.

[0106] Step 4, hot air drying

[0107] During the hot air drying process, the water that has not had time to escape in the skin layer of the waterproof and breathable material further emerges, and the water on the waterproof and breathable material is initially dried, obtaining a waterproof and breathable material with two levels of pores. The temperature of the hot air drying is 115°C, and the speed is 0.1 m / s.

[0108] Step 5, cylinder drying

[0109] The cylinder is used to further dry the water in the waterproof and breathable material. At the same time, the smooth surface of the high-temperature cylinder finishes the rough surface generated by the escape of water from the waterproof and breathable material, and finally obtains the waterproof and breathable material.

[0110] The cylinder drying includes multiple cylinders, and the temperature of the cylinders decreases sequentially along the advancing direction of the fabric. The heating temperature of the first cylinder is 75°C, the heating temperature of the second cylinder is 60°C, the heating temperature of the third cylinder is 50°C, and the heating temperature of the fourth cylinder is 40°C.

[0111] In the microfibers of this embodiment, the diameter of the first-level pores is 600 - 800 nm, and the diameter of the second-level pores is 100 - 200 nm; the total porosity of the microfibers is 87%.

[0112] Example 3

[0113] The preparation method of the waterproof and breathable material in this embodiment specifically includes the following steps:

[0114] Step 1, prepare the core layer spinning solution and the skin layer spinning solution respectively

[0115] By mass percentage, the raw materials of the skin layer spinning solution contain: 10% PVP, 86% TPU, 2% color fixing agent, and 2% softening agent. The relative molecular weight of polyvinylpyrrolidone PVP is 100,000.

[0116] By mass percentage, the raw materials of the core layer spinning solution contain: 96% TPU, 3% shrinkage prevention agent, and 1% plasticizer.

[0117] The intrinsic viscosity of the skin layer spinning solution obtained after melting and mixing the raw materials of the skin layer spinning solution is 0.8 dL / g. The intrinsic viscosity of the core layer spinning solution is 0.4 dL / g.

[0118] Step 2, coaxial meltblown spinning

[0119] The above-mentioned proportion of cortical spinning solution raw material and core spinning solution raw material are respectively added into a screw extruder, melted at a temperature of 190°C, and uniformly mixed respectively. They are ejected through a coaxial melt spinning plate to form microfibers, and are spun onto the surface of a base fabric - polyester woven fabric with a certain thickness under the action of wind force.

[0120] The inner diameter of the spinning orifice of the spinning plate corresponding to the core spinning solution is 130 μm, and the inner diameter of the spinning orifice of the spinning plate corresponding to the cortical spinning solution is 200 μm. The thickness of the microfibers on the surface of the base fabric is 1.5 mm, and the diameter of a single microfiber is 110 μm.

[0121] Step 3: Immersion precipitation

[0122] Within 1 minute, the side of the base fabric covered with coaxial microfibers is immersed in the precipitation liquid at the lower surface of the heating roller. The PVP in the cortex precipitates from the TPU, forming two - stage pores and dissolving in the precipitation liquid. The temperature of the heating roller is 130°C.

[0123] Under the continuous replacement action of the precipitation liquid, due to the existence of small and dense pores in the cortex of the microfibers on the surface of the base fabric, a waterproof and breathable coaxial melt - blown film with pores is formed.

[0124] The precipitation liquid is a mixed liquid composed of water and ethanol in a volume ratio of 6:4. The temperature of the precipitation liquid is 25°C, and the impregnation time is 100 s. The addition of ethanol can change the surface tension of the precipitation liquid and help the precipitation of PVP.

[0125] Step 4: Hot - air drying

[0126] During the hot - air drying process, the water that has not had time to escape from the cortex of the waterproof and breathable material further emerges, and the water on the waterproof and breathable material is initially dried, obtaining a waterproof and breathable material with two - stage pores. The temperature of the hot - air drying is 100°C, and the speed is 0.1 m / s.

[0127] In this embodiment, the diameter of the first - stage pores formed is 600 - 800 nm, the diameter of the second - stage pores is 100 - 200 nm; the total porosity of the microfibers is 75%.

[0128] Step 5: Cylinder drying

[0129] A cylinder is used to further dry the water in the waterproof and breathable material. At the same time, the smooth surface of the high - temperature cylinder finishes the rough surface of the waterproof and breathable material caused by the escape of water, and finally a waterproof and breathable material is obtained.

[0130] The drying process using drying cylinders includes multiple drying cylinders, and the temperature of the drying cylinders decreases successively along the direction in which the fabric advances. The heating temperature of the first drying cylinder is 75 °C, the heating temperature of the second drying cylinder is 60 °C, the heating temperature of the third drying cylinder is 50 °C, and the heating temperature of the fourth drying cylinder is 40 °C.

[0131] In the microfibers of this embodiment, the diameter of the primary pores formed is 600 - 800 nm, and the diameter of the secondary pores is 100 - 200 nm; the total porosity of the microfibers is 76%.

[0132] Comparative Example 1

[0133] The difference between this comparative example and Example 1 is that: in the microfibers of this comparative example, there is no skin layer and core layer, and the coaxial melt - blown film in Example 1 is changed to a uniaxial melt - blown spinning that is consistent with the core layer pore channels. Other steps and parameters are basically the same as those in Example 1.

[0134] Comparative Example 2

[0135] The difference between this comparative example and Example 1 is that: in this comparative example, hot - air drying is not carried out. Other steps and parameters are basically the same as those in Example 1.

[0136] Comparative Example 3

[0137] The difference between this comparative example and Example 1 is that: in this comparative example, drying using drying cylinders is not carried out, and the drying cylinders are not heated. Other steps and parameters are basically the same as those in Example 1.

[0138] Comparative Example 4

[0139] The difference between this comparative example and Example 1 is that: in this comparative example, after the coaxial melt - blown spinning in Step 2, water inlet and precipitation are carried out after 30 minutes in Step 3. Other steps and parameters are basically the same as those in Example 1.

[0140] Testing and Results

[0141] The waterproof and breathable materials prepared in Example 2 and the comparative examples are subjected to relevant tests. The test standards and test results are shown in Table 1 below:

[0142] Table 1 Test Results

[0143]

[0144] Table 1 shows that, based on the original properties of the base fabric, after being treated by the method of the present invention, the fabric of Example 2 not only has good waterproof property, but also its air permeability can be maintained at more than 70% of the original. However, in Comparative Example 1 without a porous skin layer, the reduction of pores affects the air permeability, and the hydrostatic pressure resistance decreases, indicating the decline of the waterproof property. In Comparative Example 2, without hot air drying, the water in the fiber membrane was not removed in time, which not only prolonged the subsequent cylinder drying process, but also affected the pore structure of the membrane layer, resulting in a decrease in the hydrostatic pressure resistance. In the preparation process of Comparative Example 3, the drying cylinder was not heated, resulting in an uneven fabric surface. The rough surface will reduce the water contact angle and cause the waterproof property to decline. In Comparative Example 4, due to the creep phenomenon during 30 minutes of natural placement, the fiber diameter will increase, and since the polyurethane fiber after cooling is morphologically solidified, only a small amount of surface PVP is precipitated when entering the precipitation liquid, thus affecting the formation of pores between fibers, resulting in a significant reduction in the air permeability outside the improvement of the waterproof property.

[0145] The present invention provides a preparation method of a waterproof and breathable material. The material of the waterproof and breathable membrane is mainly composed of a pore-forming agent polyvinylpyrrolidone (PVP) and thermoplastic polyurethane (TPU). Using a coaxial meltblowing process, with TPU as the core and PVP / TPU as the skin, a structure with randomly distributed micro / nano fibers in the waterproof and breathable membrane is given; the base fabric after film coating goes through three processes: immersion precipitation, hot air drying, and cylinder drying. When the film-coated base fabric is immersed in the precipitation liquid, the cortical PVP precipitates from the skin liquid and forms primary pores and secondary pores with different pore diameters in the TPU on the surface of the base fabric, thereby realizing the function of waterproof and breathable on the surface of the base fabric. The present invention designs the meltblowing process as a fabric functional finishing link, realizing the processes of online finishing, drying, and shaping, which can improve production efficiency. The obtained waterproof and breathable material can be used in products such as tents, shoe uppers, and clothing surfaces.

[0146] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0147] 1. In the present invention, a coaxial meltblowing process is adopted, using micron fibers to replace traditional films. The core layer can maintain the mechanical structure of the fiber membrane. The entanglement between fibers prevents the infiltration of liquids, and the gaps formed between fibers and the two-stage pores precipitated on the skin layer surface can increase the gas permeability, achieving the purpose of waterproof and breathable under a simple structure.

[0148] 2. In this application, two drying processes are adopted. During the hot air drying process, the water that did not have time to escape due to the water tension in the skin layer of the waterproof and breathable material further floats out; and the water on the waterproof and breathable material is initially dried. During the cylinder drying process, its main function is to fully dry the finished fabric. At the same time, due to the escape of small holes in the previous process, there may be small edge protrusions on the fabric surface. After being sorted by the hot pressing cylinder, the fabric surface becomes flat. The existence of the two-stage small holes hinders the infiltration of liquids and further enhances the passage of gases.

[0149] The traditional base fabric itself does not have waterproof effect, but it is desired that the post-treatment does not affect the final breathability of the fabric. Therefore, in this application, a core-shell structured microfiber membrane formed by coaxial melt spinning is formed on the surface of the base fabric. Not only channels are formed between fibers, but also two-stage pores are formed within the cortex of a single fiber. The first stage is pores with relatively larger channels that are easily precipitated on the surface of the skin, and the second stage is small pores that are difficult to precipitate or have not had time to be completely dissolved and precipitated near the center of the single fiber cortex. The two-stage pores formed have small pores, which can hinder the passage of water molecules, and TPU is a hydrophobic material, so the waterproof effect can be achieved. Different from the polymer waterproof film, in this application, not only the channels between fibers ensure a certain breathability, but also the "channels" formed in the two-stage pores are interconnected, which further enhances the breathability of the fabric. At the same time, since pores are generated in a single fiber, the mechanical properties of the fiber will be reduced. Therefore, in this application, the fiber is core-shell layered. On the one hand, the cortex can form pores to enhance breathability, and on the other hand, it can maintain the mechanical properties of the fiber layer.

[0150] The endpoints and any values disclosed in this article for ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article. The equipment and raw materials used, etc. can all be purchased from the market or are commonly used in this field. The methods in the above embodiments, unless otherwise specified, are all conventional methods in this field. The raw materials not specifically mentioned in the examples are obtained through commercial purchase. Operations without specifically mentioning the temperature are carried out at room temperature. The operation methods and conditions not specifically mentioned can adopt the well-known or conventional means and conditions in this field.

[0151] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a waterproof and breathable material, characterized in that, It includes the following steps: Prepare a core layer spinning solution and a skin layer spinning solution respectively, and use a coaxial meltblown spinning process to form microfibers and cover them on the surface of the base fabric; the core layer spinning solution contains thermoplastic polyurethane elastomer, and the skin layer spinning solution contains polyvinylpyrrolidone and thermoplastic polyurethane elastomer; Dip the side of the base fabric covered with microfibers into the precipitation solution within 5 minutes after meltblowing, and polyvinylpyrrolidone precipitates from the thermoplastic polyurethane elastomer, so that pores are formed in the skin layer of the microfibers; Carry out drying treatment by hot air drying and cylinder drying in sequence to obtain the waterproof and breathable material; The intrinsic viscosity ratio of the cortical spinning solution to the core spinning solution is [η] 皮层 :[η] 芯层 = 1: 0.45 to 0.65; The pores include primary pores and secondary pores; the diameter of the primary pores is 100 - 800 nm, the diameter of the secondary pores is 20 - 200 nm, and the total porosity of the microfibers is 50 - 88%; 2. The preparation method according to claim 1, characterized in that, The mass fraction of polyvinylpyrrolidone in the skin layer spinning solution is 10 - 25%, and the mass fraction of thermoplastic polyurethane elastomer is 65 - 86%; the mass fraction of thermoplastic polyurethane elastomer in the core layer spinning solution is 85 - 96%.

3. The preparation method according to claim 1, characterized in that, The intrinsic viscosity of the skin layer spinning solution is 0.65 - 0.8 dL / g.

4. The preparation method according to claim 1, characterized in that, The hot air drying temperature is 95 - 120 °C, and the temperature of cylinder drying is 25 - 80 °C.

5. The preparation method according to claim 1, characterized in that, The precipitation solution is water and / or ethanol, and the temperature of the precipitation solution is 25 - 45 °C.

6. The preparation method according to claim 1, characterized in that, The melt spinning temperature of the coaxial meltblown spinning process is 160 - 200 °C; the inner diameter of the spinning hole of the spinneret corresponding to the core layer spinning solution is 40 - 180 μm, and the inner diameter of the spinning hole of the spinneret corresponding to the skin layer spinning solution is 120 - 350 μm.

7. The preparation method according to claim 1, characterized in that, The thickness of the microfibers on the surface of the base fabric is 0.7 - 1.5 mm, and the diameter of a single microfiber is 20 - 180 μm.

8. A waterproof and breathable material prepared by the preparation method according to any one of claims 1 - 7.

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