A method for preparing a bio-based membrane with high-efficiency waterproof and moisture-permeable properties

Abstract

The present invention provides a method for preparing a bio-based membrane with high-efficiency waterproof and breathable properties, comprising: a) mixing polyurethane, a polymer, and a mixed solvent to obtain a mixed solution; the polymer being selected from one or more of PVA, PVA-co-PE, and chitosan; b) stirring the mixed solution and allowing it to stand for degassing; c) electrospinning the obtained spinning solution; d) grafting silica particles onto the surface of the obtained PU nanofiber membrane using a hydrothermal-assisted sol-gel process, heat-treating the membrane, soaking the membrane, removing the membrane, and then continuing the heat treatment; e) soaking the obtained PU nanofiber membrane with the surface grafted with SiO2 particles in an ethanol solution containing ethyl orthosilicate, removing the membrane, and heat-treating the membrane; f) drying the obtained waterproof and breathable membrane with a multi-level pore structure, and cooling the membrane to obtain a bio-based membrane with high-efficiency waterproof and breathable properties. The bio-based membrane prepared by the above method has high-efficiency waterproof and breathable properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of bio-based membranes, and in particular relates to a method for preparing a bio-based membrane with high-efficiency waterproof and moisture-permeable properties. Background Art

[0002] With increasing environmental awareness, the preparation technology of bio-based materials is gaining increasing attention. Bio-based materials refer to materials prepared from biomass through chemical, physical, or biological methods, and have the advantages of being renewable and biodegradable. Among them, electrospinning technology is a new nanofiber preparation technology that can produce nanofiber membranes with high specific surface area and high porosity, which are widely used in filtration, protection, biomedicine and other fields. Waterproof and breathable membranes are an important type of functional membrane, mainly used in outdoor clothing, medical equipment, etc., and require excellent waterproof properties while maintaining a certain degree of moisture permeability to maintain human comfort.

[0003] Existing waterproof and breathable membranes are mainly prepared using microporous membrane technology. By controlling the microporous structure of the membrane, a balance between waterproofness and breathability can be achieved. However, existing waterproof and breathable membranes still have some problems in practical applications. First, it is often difficult to simultaneously meet the waterproof and breathable properties of microporous membranes. Either the waterproof performance is good but the breathable performance is poor, or the breathable performance is good but the waterproof performance is poor. Traditional waterproof coating preparation methods often require the use of organic solvents, such as DMF (dimethylformamide). These solvents are not only harmful to the environment, but also have a certain impact on human health. In addition, most existing waterproof and breathable membranes use petroleum-based raw materials, which are not environmentally friendly and non-degradable, putting pressure on the environment. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a method for preparing a bio-based membrane with high-efficiency waterproof and moisture-permeable properties, wherein the bio-based membrane prepared by the method has excellent air permeability and waterproofness.

[0005] The present invention provides a method for preparing a bio-based membrane with high-efficiency waterproof and moisture-permeable properties, comprising the following steps:

[0006] a) mixing polyurethane, a polymer and a mixed solvent to obtain a mixed solution; wherein the polymer is selected from one or more of PVA, PVA-co-PE and chitosan;

[0007] b) stirring the mixed solution and allowing it to stand for degassing to obtain a spinning solution;

[0008] c) electrospinning the spinning solution to obtain a PU nanofiber membrane;

[0009] d) grafting silica particles onto the surface of the PU nanofiber membrane using a hydrothermal-assisted sol-gel process, heat-treating, soaking, and then removing and continuing the heat treatment to obtain a PU nanofiber membrane with SiO2 particles grafted onto the surface;

[0010] e) soaking the PU nanofiber membrane with SiO2 particles grafted onto its surface in an ethanol solution containing ethyl orthosilicate, taking it out and performing heat treatment to obtain a waterproof and permeable membrane with a multi-level pore structure;

[0011] f) drying and cooling the waterproof and permeable membrane with the multi-level porous structure to obtain a bio-based membrane with high-efficiency waterproof and moisture permeability.

[0012] The present invention forms a wear-resistant and waterproof coating by spinning a mixed solution of PU and PVA or PVA-co-PE or chitosan, and grafting silica (SiO2) particles on the surface of PU nanofibers. The prepared waterproof and breathable membrane has excellent waterproof performance and can effectively prevent water intrusion. Compared with traditional coatings, the durability is improved.

[0013] In step a) of the present invention, the mass ratio of polyurethane (PU) and polymer is 1:0.8~1.2; the mixed solvent is a mixture of water, ethanol and isopropyl tone (or acetone) in a mass ratio of 2:0.8~1.2:0.8~1.2; in a specific embodiment, the mixed solvent is a mixture of water, ethanol and acetone in a mass ratio of 2:1:1. In a specific embodiment, the mass ratio of PU and PVA is 1:1; the mass ratio of PU and PVA-co-PE is 1:1; the mass ratio of PU and chitosan is 1:1. The mixed solvent is water, ethanol and acetone in a mass ratio of 2:1:1. The mass ratio of polyurethane and polymer to the mixed solvent is 1:8.5~9.5, preferably 1:9. The mixed solution prepared by the present invention has good hydrophilicity and improves the moisture permeability effect. At the same time, the hydroxyl groups in PU, PVA and chitosan provide more reaction sites, which are easy to react with the waterproof coating.

[0014] In step a) of the present invention, the number average molecular weight of the polyurethane is 75,000 to 85,000; the number average molecular weight of the PVA is 9,500 to 11,000; the number average molecular weight of the PVA-co-PE is 20,000 to 77,000; and the number average molecular weight of the chitosan is 50,000 to 90,000. In a specific embodiment, the number average molecular weight of the PU is 80,000, the number average molecular weight of the PVA is 10,000, the number average molecular weight of the PVA-co-PE is 20,000, and the number average molecular weight of the chitosan is 50,000. The present invention uses bio-based raw materials to prepare a waterproof and breathable bio-based membrane, which has the advantages of being renewable and degradable. The use of an environmentally friendly solvent instead of DMF solvent meets environmental protection requirements, reduces pressure on the environment, and reduces potential harm to human health.

[0015] In step b) of the present invention, the stirring temperature is 55-65° C. for 1.5-2.5 hours, and the standing and degassing time is 11-13 hours. In a specific embodiment, the stirring temperature is 60° C. for 2 hours, and the standing and degassing time is 12 hours.

[0016] The spinning solution is electrospun to obtain a PU nanofiber membrane. The present invention utilizes an electrospinning process to obtain a nanofiber membrane with high porosity, thereby improving the membrane's waterproof and moisture permeability. The electrospinning voltage in step c) of the present invention is 20-30 kV, and the receiving distance is 14.5-15.5 cm. The humidity during electrospinning is 20-80%. In a specific embodiment, the electrospinning voltage is 20 kV, and the receiving distance is 15 cm.

[0017] The present invention utilizes a hydrothermal-assisted sol-gel process to graft silica particles onto the surface of a PU nanofiber membrane, followed by heat treatment, soaking, and subsequent removal and subsequent heat treatment to obtain a PU nanofiber membrane with surface-grafted SiO2 particles. The heat treatment temperature in step d) of the present invention is 85-95°C for 30-60 minutes; in a specific embodiment, the heat treatment temperature is 90°C for 30 minutes. The soaking solution used in step d) of the present invention comprises a diisocyanate, a silane coupling agent, and ethanol in a mass ratio of 1:1:2; the diisocyanate is selected from toluene diisocyanate or diphenylmethane diisocyanate (MDI); the silane coupling agent is selected from KH-550 or LT-560; and the soaking time is 24 hours. After soaking, the membrane is removed and subjected to further heat treatment at a temperature of 55-65°C for 30-60 minutes; in a specific embodiment, the heat treatment temperature is 60°C for 30 minutes.

[0018] This invention uses a hydrothermal-assisted sol-gel process to graft silica (SiO2) particles onto the surface of PU nanofibers. This not only creates a rough surface for the fiber membrane but also reduces the fiber surface energy, further improving the waterproof performance of the PU nanofiber membrane. Furthermore, the membrane exhibits excellent abrasion resistance, ensuring that the waterproof and breathable membrane retains its excellent waterproof properties even after multiple washes, thereby extending its service life.

[0019] The PU nanofiber membrane with SiO2 particles grafted onto its surface is immersed in an ethanol solution containing ethyl orthosilicate, removed, and then heat-treated to produce a waterproof and breathable membrane with a multi-layered pore structure. The present invention forms a waterproof and breathable membrane with a multi-layered pore structure, with the pores decreasing from the inside to the outside. This utilizes a siphon effect to facilitate the discharge of internal sweat and prevent external water from entering, thereby improving the breathability, comfort, and waterproof performance of the waterproof and breathable membrane. The post-heat treatment in step e) is performed at a temperature of 55-65°C for 30-60 minutes.

[0020] The drying in step f) of the present invention is vacuum drying or oven drying; the vacuum drying temperature is 55-65° C. and the time is 11-13 hours; the oven drying temperature is 75-85° C. and the time is 1-2 hours.

[0021] The cooling temperature in step f) of the present invention is 15-25° C. and the cooling time is 20-40 minutes. In a specific embodiment, the cooling temperature is 20° C. and the cooling time is 30 minutes.

[0022] The preparation process provided by the present invention utilizes environmentally friendly solvents, such as a mixture of water, ethanol, and isopropyl alcohol, to reduce the use of organic solvents, thereby minimizing environmental pollution and impacts on human health. The preparation process conserves energy and resources, aligning with the concept of green development. For example, high-efficiency spinning equipment and energy-saving drying equipment are used, along with a rational production process design, to reduce energy consumption and waste.

[0023] The bio-based membrane with high-efficiency waterproof and moisture-permeable performance provided by the present invention is mainly used in outdoor jackets, which can provide good waterproof performance while ensuring a certain moisture permeability, maintaining human comfort, and improving the safety and comfort of outdoor activities.

[0024] The present invention provides a method for preparing a bio-based membrane with high-efficiency waterproof and moisture-permeable properties, comprising the following steps: a) mixing polyurethane, a polymer, and a mixed solvent to obtain a mixed solution; the polymer being selected from one or more of PVA, PVA-co-PE, and chitosan; b) stirring the mixed solution and allowing it to stand for degassing to obtain a spinning solution; c) electrospinning the spinning solution to obtain a PU nanofiber membrane; d) grafting silica particles onto the surface of the PU nanofiber membrane using a hydrothermal-assisted sol-gel process, heat-treating the membrane, soaking the membrane, removing the membrane, and continuing the heat treatment to obtain a PU nanofiber membrane with surface-grafted SiO2 particles; e) soaking the PU nanofiber membrane with surface-grafted SiO2 particles in an ethanol solution containing ethyl orthosilicate, removing the membrane, and heat-treating the membrane to obtain a waterproof and moisture-permeable membrane with a multi-level pore structure; f) drying the waterproof and moisture-permeable membrane with a multi-level pore structure and cooling the membrane to obtain a bio-based membrane with high-efficiency waterproof and moisture-permeable properties. The bio-based membrane prepared by the above method has high-efficiency waterproof and moisture-permeable properties. DETAILED DESCRIPTION

[0025] To further illustrate the present invention, the preparation method of a bio-based membrane with high-efficiency waterproof and moisture-permeable properties provided by the present invention is described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present invention.

[0026] In the following examples, the molecular weight of PU is 80,000, the molecular weight of PVA is 10,000, the molecular weight of PVA-co-PE is 20,000, and the molecular weight of chitosan is 50,000.

[0027] Example 1

[0028] Step a): A mixture of PU and PVA in a mass ratio of 1:1 is added to a mixed solvent and stirred until completely dissolved to obtain a mixed solution; wherein the mass ratio of the mixture to the mixed solvent is 1:9. The number average molecular weight of PU is 80,000, and the number average molecular weight of PVA is 10,000. The mixed solvent is a mixture of water, ethanol, and acetone in a mass ratio of 2:1:1.

[0029] Step b): the mixed solution was stirred at 60° C. for 2 hours, and then allowed to stand at room temperature for degassing for 12 hours to obtain a spinning solution.

[0030] Step c): electrospinning the spinning solution at a voltage of 20 kV and a receiving distance of 15 cm for 4 h, changing the spinning humidity every hour to 20%, 40%, 60%, and 80%, respectively, to obtain a PU nanofiber membrane with a multi-level pore structure.

[0031] Step d): The resulting PU nanofiber membrane was heat-treated at 90°C for 30 minutes, then immersed in an ethanol solution containing diphenylmethane diisocyanate (MDI) and a silane coupling agent, KH-550, for 24 hours. After removal, the membrane was heat-treated at 60°C for 30 minutes to obtain a PU nanofiber membrane with surface-grafted SiO2 particles. The concentration of the silane coupling agent, KH-550, was 5% by weight, and the concentration of diphenylmethane diisocyanate was 10% by weight.

[0032] Step e): Soak the PU nanofiber membrane with SiO2 particles grafted onto its surface in an ethanol solution containing ethyl orthosilicate for 24 hours, then heat-treat it at 60°C for 30 minutes to obtain a waterproof and breathable membrane with a multi-layered porous structure. The concentration of ethyl orthosilicate was 5 wt%.

[0033] Step f): vacuum drying the obtained waterproof and breathable membrane at 60° C. for 12 hours, and cooling the dried waterproof and breathable membrane at a temperature of 20° C. for 30 minutes to obtain a bio-based membrane with high waterproof and breathable properties.

[0034] Example 2

[0035] Step a): A mixture of PU and PVA-co-PE in a mass ratio of 1:1 is added to a mixed solvent and stirred until completely dissolved to obtain a mixed solution; wherein the mass ratio of the mixture to the mixed solvent is 1:9. The number average molecular weight of PU is 80,000, and the number average molecular weight of PVA-co-PE is 20,000. The mixed solvent is a mixture of water, ethanol, and acetone in a mass ratio of 2:1:1.

[0036] Step b): the mixed solution was stirred at 60° C. for 2 hours, and then allowed to stand at room temperature for degassing for 12 hours to obtain a spinning solution.

[0037] Step c): electrospinning the spinning solution at a voltage of 20 kV and a receiving distance of 15 cm for 4 h, changing the spinning humidity every hour to 20%, 40%, 60%, and 80%, respectively, to obtain a PU nanofiber membrane with a multi-level pore structure.

[0038] Step d): The resulting PU nanofiber membrane was heat-treated at 90°C for 60 minutes, then immersed in an ethanol solution containing diphenylmethane diisocyanate (MDI) and a silane coupling agent, KH-550, for 24 hours. After removal, the membrane was heat-treated at 60°C for 60 minutes to obtain a PU nanofiber membrane with surface-grafted SiO2 particles. The concentration of the silane coupling agent, KH-550, was 5% by weight, and the concentration of diphenylmethane diisocyanate was 10% by weight.

[0039] Step e): Soak the PU nanofiber membrane with SiO2 particles grafted onto its surface in an ethanol solution containing ethyl orthosilicate for 24 hours, then heat-treat it at 60°C for 60 minutes to obtain a waterproof and breathable membrane with a multi-layered porous structure. The concentration of ethyl orthosilicate was 5 wt%.

[0040] Step f): drying the obtained waterproof and breathable membrane at 80° C. for 1 hour, and cooling the dried waterproof and breathable membrane at a cooling temperature of 20° C. for 30 minutes to obtain a bio-based membrane with high waterproof and breathable performance.

[0041] Example 3

[0042] Step a): A mixture of PU and chitosan in a mass ratio of 1:1 is added to a mixed solvent and stirred until completely dissolved to obtain a mixed solution; wherein the mass ratio of the mixture to the mixed solvent is 1:9. The number average molecular weight of PU is 80,000, and the number average molecular weight of chitosan is 50,000. The mixed solvent is a mixture of water, isopropyl alcohol, and acetone in a mass ratio of 2:1:1.

[0043] Step b): the mixed solution was stirred at 60° C. for 2 hours, and then allowed to stand at room temperature for degassing for 12 hours to obtain a spinning solution.

[0044] Step c): electrospinning the spinning solution at a voltage of 30 kV and a receiving distance of 15 cm for 4 h, changing the spinning humidity every hour to 20%, 40%, 60%, and 80%, respectively, to obtain a PU nanofiber membrane with a multi-level pore structure.

[0045] Step d): The resulting PU nanofiber membrane was heat-treated at 90°C for 30 minutes, then immersed in an ethanol solution containing diphenylmethane diisocyanate (MDI) and a silane coupling agent, KH-550, for 24 hours. After removal, the membrane was heat-treated at 60°C for 30 minutes to obtain a PU nanofiber membrane with surface-grafted SiO2 particles. The concentration of the silane coupling agent, KH-550, was 5% by weight, and the concentration of diphenylmethane diisocyanate was 10% by weight.

[0046] Step e): Soak the PU nanofiber membrane with SiO2 particles grafted onto its surface in an ethanol solution containing ethyl orthosilicate for 24 hours, then heat-treat it at 60°C for 30 minutes to obtain a waterproof and breathable membrane with a multi-layered porous structure. The concentration of ethyl orthosilicate was 5 wt%.

[0047] Step f): vacuum drying the obtained waterproof and breathable membrane at 60° C. for 12 hours, and cooling the dried waterproof and breathable membrane at a temperature of 20° C. for 30 minutes to obtain a bio-based membrane with high waterproof and breathable properties.

[0048] The porosity of the bio-based membrane was determined using the liquid displacement method, and n-hexane was selected as the displacement liquid (n-hexane can easily penetrate into the fiber and does not cause shrinkage or expansion of the fiber structure);

[0049] The hydrostatic pressure test is carried out in accordance with the national standard GB / T4744 "Hydrostatic pressure test for determination of water seepage resistance";

[0050] The moisture permeability test refers to the second part of GB / T 12704 "Test method for moisture permeability of textile fabrics" to test the permeability of the nanofiber membrane, including method A upright cup method and method B inverted cup method;

[0051] The washing method refers to the national standard GB / T8629 "Household washing and drying procedures for textile testing", the washing procedure is 4N, and wash 5 times.

[0052] The present invention uses the above-mentioned test method to test the performance of the bio-based membranes prepared in Examples 1 to 3. The results are shown in Table 1:

[0053] Table 1 Performance test results of bio-based membranes prepared in Examples 1 to 3

[0054]

[0055] It can be seen from the above embodiments that the present invention provides a method for preparing a bio-based membrane with high-efficiency waterproof and moisture-permeable properties, comprising the following steps: a) mixing polyurethane, a polymer and a mixed solvent to obtain a mixed liquid; the polymer is selected from one or more of PVA, PVA-co-PE and chitosan; b) stirring the mixed liquid, standing and degassing to obtain a spinning solution; c) electrospinning the spinning solution to obtain a PU nanofiber membrane; d) using a hydrothermal-assisted sol-gel process to graft silica particles on the surface of the PU nanofiber membrane, heat-treating, soaking, taking out and continuing to heat-treat to obtain a PU nanofiber membrane with SiO2 particles grafted on the surface; e) soaking the PU nanofiber membrane with SiO2 particles grafted on the surface in an ethanol solution containing ethyl orthosilicate, taking out and heat-treating to obtain a waterproof and breathable membrane with a multi-level pore structure; f) drying the waterproof and breathable membrane with a multi-level pore structure, cooling, to obtain a bio-based membrane with high-efficiency waterproof and moisture-permeable properties. The hydrostatic pressure of the bio-based membrane prepared by the above method decreased slightly after washing, which did not affect the overall waterproof effect; the moisture permeability did not change much, and it had high waterproof and moisture permeability. The experimental results showed that the porosity of the bio-based membrane was 91.2-93.3%; the hydrostatic pressure before washing was 104-116 kPa, and the moisture permeability of the positive cup method was 5125-5366 g / (m 2 .24h), the moisture permeability of the inverted cup method is 9560~9757g / (m 2 .24h); the hydrostatic pressure after washing is 97~112kPa, and the moisture permeability of the positive cup method is 4904~5253g / (m 2 .24h), the moisture permeability of the inverted cup method is 9378~9566g / (m 2 .24h).

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a bio-based membrane with high-efficiency waterproof and moisture-permeable properties, comprising the following steps: a) mixing polyurethane, a polymer, and a mixed solvent to obtain a mixed solution; the polymer is selected from one or more of PVA, PVA-co-PE, and chitosan; and the mixed solvent is a mixture of water, ethanol, and acetone in a mass ratio of 2:0.8-1.2:0.8-1.2; b) stirring the mixed solution and allowing it to stand for degassing to obtain a spinning solution; c) electrospinning the spinning solution to obtain a PU nanofiber membrane; d) grafting silica particles onto the surface of the PU nanofiber membrane using a hydrothermal-assisted sol-gel process, heat-treating the membrane at 85-95° C. for 30-60 minutes, soaking the membrane, and then removing the membrane and continuing to heat-treat it at 55-65° C. for 30-60 minutes to obtain a PU nanofiber membrane with SiO2 particles grafted onto the surface; the soaking solution used for the soaking comprises diisocyanate, a silane coupling agent, and ethanol; e) soaking the PU nanofiber membrane with SiO2 particles grafted onto its surface in an ethanol solution containing ethyl orthosilicate, and then heat-treating the membrane at 55-65° C. for 30-60 minutes to obtain a waterproof and permeable membrane with a multi-level porous structure; f) drying and cooling the waterproof and permeable membrane with the multi-level porous structure to obtain a bio-based membrane with high-efficiency waterproof and moisture permeability.

2. The preparation method according to claim 1, characterized in that The mass ratio of polyurethane to polymer in step a) is 1:0.8-1.

2.

3. The preparation method according to claim 1, characterized in that The number average molecular weight of the polyurethane in step a) is 75,000 to 85,000; The number average molecular weight of PVA is 9500~11000; The number average molecular weight of PVA-co-PE is 20,000~77,000; The number average molecular weight of chitosan is 50,000~90,000.

4. The preparation method according to claim 1, characterized in that In step b), the stirring temperature is 55-65° C. and the stirring time is 1.5-2.5 hours; and the standing and degassing time is 11-13 hours.

5. The preparation method according to claim 1, characterized in that In step c), the voltage of electrospinning is 20-30 kV, and the receiving distance is 14.5-15.5 cm.

6. The preparation method according to claim 1, characterized in that The soaking solution used in step d) comprises diisocyanate, silane coupling agent and ethanol in a mass ratio of 1:1:2; The diisocyanate is selected from toluene diisocyanate or diphenylmethane diisocyanate; The silane coupling agent is selected from KH-550 or LT-560.

7. The preparation method according to claim 1, characterized in that In step f), the drying is vacuum drying or oven drying; The vacuum drying temperature is 55-65°C and the time is 11-13 hours; The drying temperature is 75-85° C. and the drying time is 1-2 hours.

8. The preparation method according to claim 1, characterized in that The cooling temperature in step f) is 15-25° C., and the cooling time is 20-40 minutes.

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