A biodegradable waterproof and breathable membrane and its preparation method

Abstract

This invention discloses a biodegradable waterproof and breathable membrane and its preparation method. The steps include: preparing a biodegradable membrane-forming liquid and obtaining a base membrane; stretching and shaping the base membrane to obtain a porous base membrane; taking cattail fibers and modifying them to obtain modified cattail fiber powder; taking a double-layer porous base membrane, uniformly spreading the modified cattail fiber powder between the double-layer porous base membrane, and using hot pressing to fuse the double-layer porous base membrane together, with the modified cattail fiber powder dispersed and filled into the interlayer surface and pores of the double-layer porous base membrane. This waterproof and breathable membrane is made of biodegradable materials, which can effectively avoid environmental pollution. Furthermore, the first use of a structure with fused double-layer porous base membranes and interlayer filling with modified cattail fiber powder reduces the requirements for the pore size of the base membrane, thereby reducing process difficulty and production costs. Simultaneously, the use of fiber powder optimizes the membrane pore structure, ensuring that the membrane material possesses excellent breathability and waterproofness.

Description

Technical Field

[0001] This invention relates to the field of waterproof and breathable membrane technology, specifically to a biodegradable waterproof and breathable membrane and its preparation method. Background Technology

[0002] Waterproof and breathable membranes are a new type of polymer waterproof material, now widely used in clothing, construction, medical, and industrial production. Currently, the most common waterproof and breathable membranes on the market are microporous membranes, made from polyvinyl chloride, polyethylene, and polypropylene. Through specific processing techniques, they are manufactured with a certain number and size of micropores, typically between 0.1-20 μm in diameter. This size allows water vapor or other gases to pass through while effectively preventing water droplets from passing through. However, the strict requirements on the size and number of these membranes lead to complex processing and high costs. Furthermore, most current waterproof and breathable membranes are made of or contain non-degradable materials, which, if not properly disposed of after use, can cause environmental pollution. Summary of the Invention

[0003] The purpose of this invention is to provide a biodegradable waterproof and breathable membrane and its preparation method, which solves the problems of high process requirements, high production costs, and environmental pollution caused by non-degradability of existing waterproof and breathable membranes.

[0004] The present invention achieves the above objectives through the following technical solutions:

[0005] A method for preparing a biodegradable waterproof and breathable membrane, comprising the following steps:

[0006] S1. Prepare a biodegradable film-forming solution and obtain a substrate membrane through a film-forming process;

[0007] S2. The substrate membrane is stretched and shaped to obtain a porous substrate membrane;

[0008] S3. Take cattail fibers and modify them to obtain modified cattail fiber powder.

[0009] S4. Take a double-layer porous substrate membrane, evenly spread the modified velvet fiber powder between the double-layer porous substrate membrane, and perform hot pressing to fuse the double-layer porous substrate membrane together, and disperse and fill the interlayer surface and pores of the double-layer porous substrate membrane to obtain the biodegradable waterproof and breathable membrane.

[0010] A further improvement is that, in step S1, the raw materials of the biodegradable film-forming liquid, by weight, include 40-80 parts of biodegradable polyester, 20-50 parts of starch, 10-15 parts of sorbitol, 10-50 parts of inorganic filler, and 1-3 parts of crosslinking agent. All raw materials are homogenized, gelatinized, emulsified, and defoamed to obtain the biodegradable film-forming liquid.

[0011] A further improvement is that the biodegradable polyester is selected from one or more of polybutylene adipate / terephthalate, polylactic acid, polybutylene succinate, and polypropylene carbonate.

[0012] A further improvement is that the inorganic filler is selected from one or more of kaolin, montmorillonite, talc, and calcium carbonate.

[0013] A further improvement is that the crosslinking agent is selected from one or more of glycerol, transglutaminase, and sodium tripolyphosphate.

[0014] A further improvement is that, in step S2, the specific operation of the stretching and shaping process is as follows: first, longitudinal stretching is performed at a temperature of 320-350℃, a stretching speed of 150-250m / s, and a stretching ratio of 6-8 times; after longitudinal stretching, relaxation is performed with a relaxation ratio controlled at 80-90%; then, transverse stretching is performed at a temperature of 220-260℃, a stretching speed of 10-15m / s, and a stretching ratio of 10-12 times; finally, heat setting is performed at 100-110℃.

[0015] A further improvement is that, in step S3, the specific operation of the modification treatment is as follows: after drying the cotton fiber to a constant weight, it is pulverized to obtain fiber powder of 1500-5000 mesh. The fiber powder is soaked in organic acid for 6-10 hours. After filtering out the liquid, the fiber powder is kept at a nitrogen atmosphere of 150-250℃ for 10-30 minutes. Then, 0.5-2% of methionine by weight of the fiber powder is added to the fiber powder, and it is stirred at 60-80℃ for 0.5-2 hours to obtain modified cotton fiber powder.

[0016] A further improvement is that the organic acid is selected from oxalic acid or tartaric acid.

[0017] A further improvement is that, in step S4, the amount of modified cattail fiber powder applied is 100-200 g / m³. 2 The specific operation of the hot pressing treatment is as follows: hot pressing for 5-8 minutes at a temperature of 150-180℃ and a pressure of 0.8-1.2MPa, so that the thickness of the double-layer porous substrate membrane after fusion becomes 40-60% of the initial total thickness.

[0018] The present invention also provides a biodegradable waterproof and breathable membrane, which is prepared by the above-described preparation method.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The waterproof and breathable membrane is made of biodegradable materials, which can effectively avoid environmental pollution and increase its application areas;

[0021] (2) This waterproof and breathable membrane adopts a structure of double-layer porous matrix membrane fusion and interlayer filling with modified cotton fiber powder for the first time. It can reduce the requirements for the pore size of the matrix membrane, thereby reducing the process difficulty and production cost. At the same time, the fiber powder is used to optimize the pore structure of the membrane layer to ensure that the membrane material has excellent breathability and waterproofness.

[0022] (3) The modified cattail fiber powder filled in the waterproof and breathable membrane interlayer is the first time that cattail fiber has been applied to waterproof and breathable membrane. At the same time, the cattail fiber is first soaked in organic acid and heat-insulated to improve the surface microstructure of the fiber powder, reduce the adverse factors of its excessive adsorption performance, and improve the problem of poor water resistance caused by the expansion of the fiber powder due to water absorption. Then, it is surface modified with methionine to eliminate the internal porous structure, increase the compatibility between the fiber powder and the matrix membrane, and ensure that the membrane material has excellent mechanical properties. Detailed Implementation

[0023] The present application will be further described in detail below with reference to the embodiments. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0024] Example 1

[0025] A method for preparing a biodegradable waterproof and breathable membrane, comprising the following steps:

[0026] S1. Prepare a biodegradable film-forming solution and obtain a base film through a conventional casting process; by weight, the raw materials of the biodegradable film-forming solution include 40 parts of poly(butylene adipate / terephthalate), 50 parts of starch, 10 parts of sorbitol, 50 parts of kaolin and 3 parts of glycerol. All raw materials are subjected to homogenization (homogenization pressure 30 MPa, homogenization cycle 3 times, the same below), gelatinization (gelatinization temperature 80℃, time 60 min, the same below), emulsification (emulsification shear rate 5000 rpm, time 10 min, the same below) and defoaming (vacuum defoaming, temperature 60℃, vacuum degree 80 KPa, time 30 min, the same below) to obtain the biodegradable film-forming solution.

[0027] S2. The substrate membrane is stretched and shaped to obtain a porous substrate membrane. The specific operation of the stretching and shaping process is as follows: first, longitudinal stretching is performed at a temperature of 320°C, a stretching speed of 150 m / s, and a stretching ratio of 6 times; after longitudinal stretching, relaxation is performed with a relaxation ratio controlled at 80%; then, transverse stretching is performed at a temperature of 220°C, a stretching speed of 10 m / s, and a stretching ratio of 10 times; finally, heat setting is performed at 100°C.

[0028] S3. Take cattail fibers and modify them to obtain modified cattail fiber powder. The specific operation of the modification process is as follows: after drying the cattail fibers to constant weight, crush them to obtain 1500 mesh fiber powder. Soak the fiber powder in oxalic acid for 6 hours. After filtering out the liquid, place the fiber powder in a nitrogen atmosphere at 150℃ for 30 minutes. Then add 0.5% methionine by weight of the fiber powder to the fiber powder and stir at 60℃ for 2 hours to obtain modified cattail fiber powder.

[0029] S4. Take a double-layer porous substrate membrane and evenly spread the modified cotton fiber powder between the double-layer porous substrate membrane, with a spreading amount of 100g / m². 2 Then, hot pressing is performed at a temperature of 150℃ and a pressure of 0.8MPa for 8 minutes, so that the thickness of the fused double-layer porous matrix membrane becomes 42% of the initial total thickness. This allows the double-layer porous matrix membrane to fuse together, and the modified cotton fiber powder is dispersed and filled into the interlayer surface and pores of the double-layer porous matrix membrane, thus obtaining the biodegradable waterproof and breathable membrane.

[0030] Example 2

[0031] A method for preparing a biodegradable waterproof and breathable membrane, comprising the following steps:

[0032] S1. Prepare a biodegradable film-forming solution and obtain a base film through a conventional casting process; by weight, the raw materials of the biodegradable film-forming solution include 60 parts of polybutylene succinate, 30 parts of starch, 12 parts of sorbitol, 35 parts of talc and 2 parts of sodium trimetaphosphate. All raw materials are homogenized, gelatinized, emulsified and defoamed to obtain the biodegradable film-forming solution.

[0033] S2. The substrate membrane is subjected to stretching and shaping treatment to obtain a porous substrate membrane. The specific operation of the stretching and shaping treatment is as follows: first, longitudinal stretching is performed at a temperature of 330℃, a stretching speed of 200m / s, and a stretching ratio of 7 times; after longitudinal stretching, relaxation is performed with a relaxation ratio controlled at 85%; then, transverse stretching is performed at a temperature of 2400℃, a stretching speed of 12m / s, and a stretching ratio of 11 times; finally, heat setting is performed at 105℃.

[0034] S3. Take cattail fibers and modify them to obtain modified cattail fiber powder. The specific operation of the modification process is as follows: dry the cattail fibers to constant weight and then crush them to obtain 3000 mesh fiber powder. Soak the fiber powder in oxalic acid for 8 hours. After filtering out the liquid, place the fiber powder in a nitrogen atmosphere at 200℃ for 20 minutes. Then add 1% methionine by weight of the fiber powder to the fiber powder and stir at 70℃ for 1 hour to obtain modified cattail fiber powder.

[0035] S4. Take a double-layer porous substrate membrane and evenly spread the modified cotton fiber powder between the double-layer porous substrate membrane at a spreading amount of 150 g / m². 2 Then, hot pressing is performed at a temperature of 160℃ and a pressure of 1MPa for 6 minutes, so that the thickness of the fused double-layer porous matrix membrane becomes 50.6% of the initial total thickness. This allows the double-layer porous matrix membrane to fuse together, and the modified cotton fiber powder is dispersed and filled into the interlayer surface and pores of the double-layer porous matrix membrane, thus obtaining the biodegradable waterproof and breathable membrane.

[0036] Example 3

[0037] A method for preparing a biodegradable waterproof and breathable membrane, comprising the following steps:

[0038] S1. Prepare a biodegradable film-forming solution and obtain a base film through a conventional blow molding process; by weight, the raw materials of the biodegradable film-forming solution include 80 parts polylactic acid, 20 parts starch, 15 parts sorbitol, 10 parts calcium carbonate and 1 part glycerol. All raw materials are homogenized, gelatinized, emulsified and defoamed to obtain the biodegradable film-forming solution.

[0039] S2. The substrate membrane is subjected to stretching and shaping treatment to obtain a porous substrate membrane. The specific operation of the stretching and shaping treatment is as follows: first, longitudinal stretching is performed at a temperature of 350°C, a stretching speed of 250 m / s, and a stretching ratio of 8 times; after longitudinal stretching, relaxation is performed with a relaxation ratio controlled at 90%; then, transverse stretching is performed at a temperature of 260°C, a stretching speed of 15 m / s, and a stretching ratio of 12 times; finally, heat setting is performed at 110°C.

[0040] S3. Take cattail fibers and modify them to obtain modified cattail fiber powder. The specific operation of the modification process is as follows: dry the cattail fibers to constant weight and then crush them to obtain 5000 mesh fiber powder. Soak the fiber powder in tartaric acid for 10 hours. After filtering out the liquid, place the fiber powder in a nitrogen atmosphere at 250℃ for 10 minutes. Then add 2% methionine by weight of the fiber powder to the fiber powder and stir at 80℃ for 0.5 hours to obtain modified cattail fiber powder.

[0041] S4. Take a double-layer porous substrate membrane and evenly spread the modified cotton fiber powder between the double-layer porous substrate membrane, with a spreading amount of 200g / m². 2 Then, hot pressing is performed at a temperature of 180℃ and a pressure of 1.2MPa for 5 minutes, so that the thickness of the fused double-layer porous matrix membrane becomes 59.5% of the initial total thickness. This allows the double-layer porous matrix membrane to fuse together, and the modified cotton fiber powder is dispersed and filled into the interlayer surface and pores of the double-layer porous matrix membrane, thus obtaining the biodegradable waterproof and breathable membrane.

[0042] Comparative Example 1

[0043] A method for preparing a biodegradable waterproof and breathable membrane, comprising the following steps:

[0044] S1. Prepare a biodegradable film-forming solution and obtain a base film through a conventional casting process; by weight, the raw materials of the biodegradable film-forming solution include 40 parts of poly(butylene adipate / terephthalate), 50 parts of starch, 10 parts of sorbitol, 50 parts of kaolin and 3 parts of glycerol. All raw materials are homogenized, gelatinized, emulsified and defoamed to obtain the biodegradable film-forming solution.

[0045] S2. The substrate membrane is stretched and shaped to obtain a porous substrate membrane. The specific operation of the stretching and shaping process is as follows: first, longitudinal stretching is performed at a temperature of 320°C, a stretching speed of 150 m / s, and a stretching ratio of 6 times; after longitudinal stretching, relaxation is performed with a relaxation ratio controlled at 80%; then, transverse stretching is performed at a temperature of 220°C, a stretching speed of 10 m / s, and a stretching ratio of 10 times; finally, heat setting is performed at 100°C.

[0046] S3. Take cattail fiber, dry the cattail fiber to constant weight, and then crush it to obtain 1500 mesh fiber powder.

[0047] S4. Take a double-layer porous substrate membrane and evenly spread the fiber powder between the double-layer porous substrate membrane at a spreading amount of 100 g / m². 2 Then, hot pressing is performed at a temperature of 150℃ and a pressure of 0.8MPa for 8 minutes, so that the thickness of the fused double-layer porous matrix membrane becomes 42% of the initial total thickness. This allows the double-layer porous matrix membrane to fuse together, and the fiber powder is dispersed and filled into the interlayer surface and pores of the double-layer porous matrix membrane, thus obtaining the biodegradable waterproof and breathable membrane.

[0048] Comparative Example 2

[0049] A method for preparing a biodegradable waterproof and breathable membrane, comprising the following steps:

[0050] S1. Prepare a biodegradable film-forming solution and obtain a base film through a conventional casting process; by weight, the raw materials of the biodegradable film-forming solution include 40 parts of poly(butylene adipate / terephthalate), 50 parts of starch, 10 parts of sorbitol, 50 parts of kaolin and 3 parts of glycerol. All raw materials are subjected to homogenization (homogenization pressure 30 MPa, homogenization cycle 3 times, the same below), gelatinization (gelatinization temperature 80℃, time 60 min, the same below), emulsification (emulsification shear rate 5000 rpm, time 10 min, the same below) and defoaming (vacuum defoaming, temperature 60℃, vacuum degree 80 KPa, time 30 min, the same below) to obtain the biodegradable film-forming solution.

[0051] S2. The substrate membrane is stretched and shaped to obtain a porous substrate membrane. The specific operation of the stretching and shaping process is as follows: first, longitudinal stretching is performed at a temperature of 320°C, a stretching speed of 150 m / s, and a stretching ratio of 6 times; after longitudinal stretching, relaxation is performed with a relaxation ratio controlled at 80%; then, transverse stretching is performed at a temperature of 220°C, a stretching speed of 10 m / s, and a stretching ratio of 10 times; finally, heat setting is performed at 100°C.

[0052] S3. Take the double-layer porous substrate membrane and perform hot pressing treatment. Hot pressing is carried out at a temperature of 150℃ and a pressure of 0.8MPa for 6.5 minutes, so that the thickness of the double-layer porous substrate membrane after fusion becomes 42% of the initial total thickness, thereby fusing the double-layer porous substrate membrane to obtain the biodegradable waterproof and breathable membrane.

[0053] Biodegradable waterproof and breathable membrane samples prepared in Examples 1-3 and Comparative Examples 1-2 were taken respectively, and their performance was tested, including:

[0054] (1) Mechanical Properties: Stress-strain tests were performed on the samples using a Q800 Dynamic Mechanical Analyzer (DMA, TA Instruments, Inc., USA) to determine the sample strength and elastic modulus. The samples were cut into strips of 30×10mm and placed in a tensile fixture, with one end fixed and the other end movable with the fixture. The temperature was maintained at 20℃, the frequency was set to 1Hz, and the applied stress was gradually increased from 0 at a rate of 5MPa / s. The strain change of the sample was recorded until the sample fractured. The stress at the fracture point was taken as the tensile strength of the sample, and the ratio of stress to strain at the fracture point was taken as the elastic modulus of the sample.

[0055] (2) Air permeability: The water vapor transmission rate of the breathable membrane was tested according to the method specified in GB / T 1037.

[0056] (3) Water resistance: The hydrostatic pressure resistance of the breathable membrane shall be tested in accordance with the method specified in GB / T 4744.

[0057] The performance test results are summarized in the table below:

[0058]

[0059] As can be seen from the table above, the biodegradable waterproof and breathable membranes prepared in Examples 1-3 of this invention exhibit good performance in terms of mechanical properties, water vapor transmission rate, and hydrostatic pressure resistance. Their overall performance meets the requirements for membrane materials in many fields of the market. In particular, compared to Comparative Example 2, the addition of modified cattail fiber powder has a relatively small impact on mechanical properties and water vapor transmission rate, with only a slight decrease. However, it significantly improves hydrostatic pressure resistance by 49.6%, indicating that the fiber powder optimizes the pore structure of the membrane layer. Furthermore, Comparative Example 1, by replacing the modified cattail fiber powder with ordinary cattail fiber powder and lacking the organic acid soaking, heat insulation treatment, and methionine surface modification treatment, suffers from a decrease in mechanical properties. Compared to Example 1, the tensile strength decreases by 18.3%, the elastic modulus decreases by 15.1%, and the hydrostatic pressure resistance also decreases by 20.2%.

[0060] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a biodegradable waterproof and breathable membrane, characterized in that the steps include... include: S1. Prepare a biodegradable film-forming solution and obtain a substrate membrane through a film-forming process; S2. The substrate membrane is stretched and shaped to obtain a porous substrate membrane; S3. Take cattail fibers and modify them to obtain modified cattail fiber powder. The specific operation of the modification treatment is as follows: after drying the cotton fiber to constant weight, it is crushed to obtain fiber powder of 1500-5000 mesh. The fiber powder is soaked in organic acid for 6-10 hours. After filtering out the liquid, the fiber powder is kept at a temperature of 150-250℃ in a nitrogen atmosphere for 10-30 minutes. Then, 0.5-2% of methionine by weight of the fiber powder is added to the fiber powder, and it is stirred at 60-80℃ for 0.5-2 hours to obtain modified cotton fiber powder. S4. Take a double-layer porous substrate membrane, evenly spread the modified velvet fiber powder between the double-layer porous substrate membrane, and perform hot pressing to fuse the double-layer porous substrate membrane together, and disperse and fill the interlayer surface and pores of the double-layer porous substrate membrane to obtain the biodegradable waterproof and breathable membrane.

2. The method for preparing a biodegradable waterproof and breathable membrane according to claim 1, characterized in that, In step S1, the raw materials of the biodegradable film-forming liquid, by weight, include 40-80 parts of biodegradable polyester, 20-50 parts of starch, 10-15 parts of sorbitol, 10-50 parts of inorganic filler and 1-3 parts of crosslinking agent. All raw materials are homogenized, gelatinized, emulsified and defoamed to obtain the biodegradable film-forming liquid.

3. The method for preparing a biodegradable waterproof and breathable membrane according to claim 2, characterized in that, The biodegradable polyester is selected from one or more of polybutylene adipate / terephthalate, polylactic acid, polybutylene succinate, and polypropylene carbonate.

4. The method for preparing a biodegradable waterproof and breathable membrane according to claim 2, characterized in that, The inorganic filler is selected from one or more of kaolin, montmorillonite, talc, and calcium carbonate.

5. The method for preparing a biodegradable waterproof and breathable membrane according to claim 2, characterized in that, The cross-linking agent is selected from one or more of glycerol, transglutaminase, and sodium tripolyphosphate.

6. The method for preparing a biodegradable waterproof and breathable membrane according to claim 1, characterized in that, In step S2, the specific operation of the stretching and shaping process is as follows: first, longitudinal stretching is performed at a temperature of 320-350℃, a stretching speed of 150-250m / s, and a stretching ratio of 6-8 times; after longitudinal stretching, relaxation is performed with a relaxation ratio controlled at 80-90%; then, transverse stretching is performed at a temperature of 220-260℃, a stretching speed of 10-15m / s, and a stretching ratio of 10-12 times; finally, heat setting is performed at 100-110℃.

7. The method for preparing a biodegradable waterproof and breathable membrane according to claim 1, characterized in that, The organic acid is selected from oxalic acid or tartaric acid.

8. The method for preparing a biodegradable waterproof and breathable membrane according to claim 1, characterized in that, In step S4, the amount of modified cattail fiber powder applied is 100-200 g / m³. 2 The specific operation of the hot pressing treatment is as follows: hot pressing for 5-8 minutes at a temperature of 150-180℃ and a pressure of 0.8-1.2MPa, so that the thickness of the double-layer porous substrate membrane after fusion becomes 40-60% of the initial total thickness.

9. A biodegradable waterproof and breathable membrane, characterized in that, The biodegradable waterproof and breathable membrane is prepared by the preparation method described in any one of claims 1-8.

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