Green manufacturing method of waterproof and moisture-permeable polylactic acid fiber fabric

Abstract

This invention discloses a green manufacturing method for waterproof and breathable polylactic acid (PLA) fiber fabrics. First, waste PLA products are recycled and chemically degraded to obtain low-molecular-weight PLA. The low-molecular-weight PLA is dissolved in ethyl acetate, then dodecylamine, polycaprolactone polyol, diphenylmethane diisocyanate, and dimethylolpropionic acid are added, and the mixture is reacted for a period of time. Next, an aqueous solution of ethylenediamine and triethylamine is added to obtain a PLA-polyurethane emulsion. An appropriate amount of ultra-high molecular weight polyacrylic acid is added to the emulsion, and electrospinning is performed. Finally, the resulting fabric is immersed in an ethanol solution containing hexadecyltrimethylammonium chloride to obtain a waterproof and breathable PLA fabric. This invention uses waste PLA products as raw materials and employs a method of electrospinning followed by immersion, effectively solving the problems of recycling and reusing waste PLA materials and the poor waterproof performance of electrospun PLA fabrics. Furthermore, the preparation process is green and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the technical field of waterproof and breathable membrane materials, specifically relating to a green manufacturing method for waterproof and breathable polylactic acid fiber fabrics. Background Technology

[0002] As people's living standards continue to improve, their demands for clothing comfort are increasing. Waterproof and breathable fabrics are functional fabrics with multiple advantages, including waterproofing, breathability, windproofing, and warmth. Under many extreme conditions, waterproof and breathable fabrics, when used as outerwear, can protect the body from the effects of wind, rain, and other external environmental factors, while also allowing water vapor to pass through and quickly transfer internal sweat to the outside, thus improving wearing comfort.

[0003] Currently, waterproof and breathable membranes are mainly divided into two categories: non-porous hydrophilic membranes and microporous hydrophobic membranes. Polyurethane membranes are typical non-porous hydrophilic membranes. For example, CN104788712A discloses a pore-filled polyurethane waterproof and breathable membrane and its preparation method. This method uses a copolymerized hydrophilic polymer formed by in-situ crosslinking polymerization of hydrophilic and hydrophobic monomers under the action of a crosslinking agent as a pore-filling material. This pore-filling material is then introduced into the micropores of the polyurethane base membrane to prepare a pore-filled polyurethane waterproof and breathable membrane. It has strong resistance to liquid water, but the non-porous structure limits the membrane's permeability. Microporous hydrophobic membranes, on the other hand, have pore sizes larger than liquid water molecules but smaller than water vapor droplets. Therefore, they can resist liquid water penetration while facilitating the transport of air and water vapor. Polytetrafluoroethylene (PTFE) membranes, as widely used microporous hydrophobic membranes, exhibit good hydrophobic and breathable properties. CN101135115B discloses a method for preparing a waterproof and breathable polytetrafluoroethylene (PTFE) fabric. This method involves adding a small amount of natural plant powder to a polyurethane coating solution. After the solvent evaporates, the powder remains in the PTFE film. The resulting PTFE waterproof and breathable membrane exhibits high moisture permeability and strong water pressure resistance. However, fluorinated polymers are typically expensive and environmentally harmful. Furthermore, the preparation of PTFE membranes is complex and requires significant energy consumption.

[0004] Electrospinning is a widely used and easy-to-operate technology for preparing micro and nanofibers. Products prepared by electrospinning have characteristics such as high porosity, large specific surface area, uniform and diverse distribution, and uniform morphology, and have broad application value in biomedicine, environmental engineering, and textiles. It forms ultrafine fiber nonwoven fabrics by stacking micro and nano-scale fibers layer by layer. Due to the microporous structure formed between the fibers, it can achieve the moisture permeability of polytetrafluoroethylene (PTFE) microporous membranes, and to a certain extent replace PTFE membranes. CN110438659A discloses a method for preparing waterproof and breathable nanofiber composite membranes by electrospinning. Polyacrylonitrile, polyvinylidene fluoride (PVDF), and polyurethane are added to N,N-dimethylformamide, and polydimethylsiloxane and modified nano-silica are added to the polymer solution. The spinning solution is obtained by ultrasonic treatment, and a nanofiber membrane with good waterproof and breathable properties is obtained using an electrospinning device. However, due to insufficient bonding force between the fiber layers, its water pressure resistance is not effectively improved.

[0005] Therefore, there is an urgent need to find a green method for preparing environmentally friendly waterproof and breathable fiber membranes with high water pressure resistance. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this invention provides a green manufacturing method for waterproof and breathable polylactic acid (PLA) fiber fabrics. This invention primarily uses waste PLA products as raw materials, is fluoride-free, environmentally friendly, and turns waste into treasure. The electrospinning method is low-cost, simple to operate, and highly efficient, while also imparting excellent moisture permeability to the fabric. Furthermore, by immersing the electrospun fabric in an ethanol solution containing hexadecyltrimethylammonium chloride, this invention maintains the moisture permeability of the PLA electrospun membrane while simultaneously imparting excellent waterproof properties, demonstrating significant practicality.

[0007] The present invention provides a green manufacturing method for waterproof and breathable polylactic acid fiber fabrics, comprising the following steps:

[0008] Step 1: After cleaning the recycled polylactic acid product, degrade it using alcoholysis; precipitate, wash, filter, and remove impurities from the degradation product to obtain low molecular weight polylactic acid;

[0009] Step 2: Dissolve the obtained low molecular weight polylactic acid in ethyl acetate, add dodecylamine, polycaprolactone polyol, diphenylmethane diisocyanate and dimethylolpropionic acid, and react for a period of time;

[0010] Step 3: Add the polylactic acid solution to deionized water containing ethylenediamine and triethylamine, and stir at high speed to obtain an emulsion;

[0011] Step 4: Add ultra-high molecular weight polyacrylic acid to the emulsion obtained in Step 3, and then electrospin;

[0012] Step 5: After soaking the fabric obtained by electrospinning in an ethanol solution containing hexadecyltrimethylammonium chloride for a period of time, the fabric is removed to obtain a waterproof and breathable polylactic acid fabric.

[0013] In step 1, the polylactic acid products include straws, packaging boxes, tableware, wrapping paper, film bags, etc.

[0014] In step 1, ethylene glycol is used as a solvent, and a microwave-assisted degradation method is employed. The reaction temperature is 250℃, the reaction time is 28 minutes, and the mass ratio of polylactic acid to ethylene glycol is 1:1.8. The molecular weight of the degradation products is controlled to be between 1000-2000 g / mol.

[0015] In step 2, low molecular weight polylactic acid accounts for 32% of the mass fraction of ethyl acetate, and the mass ratio of low molecular weight polylactic acid, polycaprolactone polyol (Mw=2000), diphenylmethane diisocyanate, dimethylolpropionic acid and dodecylamine is 1:1.5:1:0.06:0.06.

[0016] In step 2, the reaction temperature is 80±0.2℃ and the reaction time is 3h.

[0017] In step 3, the mass ratio of ethylenediamine to triethylamine is 1:2.7, with ethylenediamine accounting for 3% of the deionized water mass fraction; the stirring speed is 180 rpm.

[0018] In step 4, the Mw of the ultra-high molecular weight polyacrylic acid is 30 million, and the added mass is 1.2% of the emulsion mass.

[0019] In step 4, the electrospinning voltage is 18-22kV, the receiving distance is 12-15cm, the spinning solution supply rate is 1.5-2.5mL / h, the temperature is 22-28℃, the humidity is 40-60%, and the thickness of the resulting fiber membrane is 80-250μm.

[0020] In step 5, hexadecyltrimethylammonium chloride accounts for 10% of the mass fraction of ethanol, and the fabric is soaked for 0.5 hours.

[0021] The beneficial effects of this invention are reflected in:

[0022] 1. This invention uses waste polylactic acid products as raw materials, turning waste into treasure.

[0023] 2. This invention prepares polylactic acid fabrics using water-based emulsions, which is green and environmentally friendly.

[0024] 3. The electrospun polylactic acid fabric prepared by this invention has excellent waterproof and moisture-permeable properties. Attached Figure Description

[0025] Figure 1This is a diagram showing the water contact angle of the waterproof and breathable polylactic acid fiber fabric prepared according to an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of a mechanical pressure friction test conducted on the waterproof and breathable polylactic acid fiber fabric prepared according to an embodiment of the present invention. Detailed Implementation

[0027] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0028] Example 1:

[0029] 1. The recycled polylactic acid products, including straws, packaging boxes, tableware, wrapping paper, film bags, etc., are cleaned, crushed, and then degraded using ethylene glycol as a solvent via microwave-assisted degradation at a reaction temperature of 250℃ for 28 minutes. The mass ratio of polylactic acid products to ethylene glycol is 1:1.8. The molecular weight of the degradation products is controlled to be between 1000-2000 g / mol.

[0030] 2. Dissolve the obtained low molecular weight polylactic acid in ethyl acetate, add polycaprolactone polyol, diphenylmethane diisocyanate, dimethylolpropionic acid and dodecylamine, the reaction temperature is 80±0.2℃, the reaction time is 3h; the low molecular weight polylactic acid accounts for 32% of the mass fraction of ethyl acetate, and the mass ratio of low molecular weight polylactic acid, polycaprolactone polyol (Mw=2000), diphenylmethane diisocyanate, dimethylolpropionic acid and dodecylamine is 1:1.5:1:0.06:0.06;

[0031] 3. Add the above solution to deionized water containing ethylenediamine and triethylamine, and stir at high speed to obtain an emulsion. The mass ratio of ethylenediamine to triethylamine is 1:2.7, and the mass fraction of ethylenediamine in deionized water is 3%. The stirring speed is 180 rpm.

[0032] 4. Add a small amount of ultra-high molecular weight polyacrylic acid to the emulsion. The added polyacrylic acid has a molecular weight of 30 million and accounts for 1.2% of the emulsion by mass.

[0033] 5. The above emulsion is subjected to electrospinning. The electrospinning conditions are: voltage of 18-22kV, receiving distance of 12-15cm, spinning solution supply rate of 1.5-2.5mL / h, temperature of 22-28℃, humidity of 40-60%, and the thickness of the resulting fiber membrane is 80-250μm.

[0034] 6. The fabric obtained by electrospinning is soaked in an ethanol solution containing hexadecyltrimethylammonium chloride for a period of time and then taken out. The hexadecyltrimethylammonium chloride accounts for 10% of the mass fraction of ethanol, and the soaking time is 0.5h. Finally, a waterproof and breathable polylactic acid fabric is obtained.

[0035] Example 2:

[0036] Compared with Example 1, in step 2 of this example, the mass ratio of low molecular weight polylactic acid, polycaprolactone polyol (Mw=2000), diphenylmethane diisocyanate, dimethylolpropionic acid and dodecylamine is 1:1.5:1:0.06:0, and all other conditions are the same.

[0037] Example 3:

[0038] Compared with Example 1, in step 2 of this example, the mass ratio of low molecular weight polylactic acid, polycaprolactone polyol (Mw=2000), diphenylmethane diisocyanate, dimethylolpropionic acid and dodecylamine is 1:1:1:0.06:0.06, and all other conditions are the same.

[0039] Example 4:

[0040] Compared with Example 1, in this embodiment, the mass ratio of low molecular weight polylactic acid, polycaprolactone polyol (Mw=2000), diphenylmethane diisocyanate, dimethylolpropionic acid and dodecylamine in step 2 is 1:1.5:0.5:0.06:0.06, and all other conditions are the same.

[0041] Example 5:

[0042] Compared with Example 1, the Mw of polyacrylic acid used in step 4 of this example is 30,000, while all other conditions are the same.

[0043] Example 6:

[0044] Compared with Example 1, in this embodiment, the mass of polyacrylic acid added in step 4 is 0.6% of the emulsion mass.

[0045] Example 7:

[0046] Compared with Example 1, in this embodiment, the mass of polyacrylic acid added in step 4 is 1.8% of the emulsion mass.

[0047] Example 8:

[0048] Compared with Example 1, this embodiment omits step 6, in which the spinning membrane is immersed in a hexadecyltrimethylammonium bromide solution, while all other conditions remain the same.

[0049] Example 9:

[0050] Compared with Example 1, this embodiment changes the alcoholysis process in step 1 to an acidolysis process, while all other conditions remain the same.

[0051] Example 10: Test on the relationship between microwave-assisted degradation reaction time and polylactic acid molecular weight

[0052] The microwave-assisted degradation reaction time was changed to degrade waste polylactic acid (PLA) products, while other conditions remained the same as in Example 1. The molecular weight of the obtained PLA was determined by gel permeation chromatography, and the results are shown in the table below:

[0053] Table 1: Effect of microwave-assisted degradation reaction time on the molecular weight of polylactic acid

[0054]

[0055] The table above shows that the molecular weight of polylactic acid (PLA) decreases exponentially with increasing degradation reaction time. For PLA-polyurethane synthesis, selecting a suitable molecular weight of PLA is crucial, as molecular weight directly affects the polymer's molecular structure, condensed-state structure, and mechanical properties. PLA with excessively high molecular weight has fewer terminal hydroxyl groups, resulting in a slower reaction and difficulty in effectively binding to the polyurethane molecular chain. Conversely, PLA with excessively low molecular weight, while easily bound to the polyurethane molecular chain, tends to aggregate and crystallize, leading to an overly rigid PLA-polyurethane. Therefore, PLA with a microwave-assisted degradation reaction time of 28 min and a molecular weight of 1000-2000 g / mol was ultimately selected for further processing.

[0056] Example 11: Performance Testing Experiment

[0057] The polylactic acid-based electrospun nanofiber composite membranes prepared in Examples 1-9 were tested, and the specific tests are as follows:

[0058] Waterproof and moisture-permeable performance test: Referring to GB / T4744-2013 "Test and Evaluation of Waterproof Performance of Textiles - Hydrostatic Pressure Method", the electrospun membrane was tested for hydrostatic resistance using the ISO811-1981 fabric water resistance tester. The pressure increase method was selected, with a pressure increase rate of 6.0 kPa / min ± 0.36 kPa / min. The average value was taken to represent the waterproof performance of the composite membrane. The moisture permeability of the composite membrane was tested using a YG601-1 type computerized fabric moisture permeability meter, referring to standard GB / T12704-91 "Methods for Determination of Moisture Permeability of Fabrics - Permeability Cup Method / Method A - Moisture Absorption Method".

[0059] Tensile properties test: The test was conducted using a CMT4104 electronic universal testing machine in accordance with GB / T3923.1-2013 "Tensive properties of fabrics - Part 1: Determination of breaking strength and elongation at break (strip method)". During the test, the sample was cut into a rectangular strip of 10*50mm, the gauge length was set to 35mm, and the tensile speed was 10mm / min.

[0060] Table 2: Performance test results of Examples 1-5

[0061]

[0062]

[0063] As shown in the table above, the polylactic acid waterproof and breathable membrane of Example 1 exhibits high moisture permeability, water pressure resistance, tensile strength, and elongation at break. This is because electrospinning technology allows polylactic acid fibers to accumulate layer by layer, thereby endowing the polylactic acid fibers with excellent moisture permeability. Immersing the fabric obtained by electrospinning in an ethanol solution containing hexadecyltrimethylammonium chloride effectively improves its waterproof performance and mechanical properties while maintaining the moisture permeability of the polylactic acid fabric fiber structure. However, after removing dodecylamine, the hydrophobicity and hydrolytic tentacles of the electrospun membrane decreased (as in Example 2); when the mass ratio of polylactic acid to polycaprolactone polyol was greater than 1:1.5, the flexibility of the resulting polylactic acid-polyurethane molecular chain decreased, and the molecular chain became too rigid, thus reducing its elongation (as in Example 3); when the mass ratio of polylactic acid to diphenylmethane diisocyanate was greater than 1:1, the polylactic acid and polycaprolactone polyol could not react sufficiently, which also led to a deterioration in the mechanical properties of the material (as in Example 4); using relatively low molecular weight polyacrylic acid could not smoothly carry out emulsion spinning and obtain electrospun membranes (as in Example 5); when the amount of polyacrylic acid added was too small, This can lead to discontinuity in the electrospinning process, making it impossible to obtain a complete electrospun film (as in Example 6); when too much polyacrylic acid is added, it can cause a large amount of entanglement between polymer molecular chains, and even cause needle blockage, which can also prevent normal spinning (as in Example 7); therefore, the final selected amount of polyacrylic acid added is 1.2% of the emulsion mass; omitting the ethanol solution soaking process of hexadecyltrimethylammonium chloride reduces the hydrophobicity and hydrolysis tentacles of the electrospun film (as in Example 8); using the acid hydrolysis process, it is impossible to obtain low molecular weight polylactic acid with the same structure as the alcohol hydrolysis process, and it is impossible to smoothly implement subsequent steps and obtain an electrospun film (as in Example 9).

[0064] Example 12: Cyclic Friction Test under Mechanical Pressure

[0065] like Figure 2As shown, the electrospun polylactic acid waterproof and breathable fabric prepared in Example 1 was subjected to 100 cycles of friction at a rate of 35 freq / min under a load of 100g. This process was defined as one cycle, and five cycles of mechanical pressure friction performance tests were conducted. After each cycle of mechanical pressure friction, the water contact angle and water roll-off angle of the waterproof and breathable fabric were measured. The results are shown in the table below:

[0066] Table 3: Results of Mechanical Pressure Cyclic Friction Test in Example 1

[0067]

[0068] As shown in the table above, after five cycles of mechanical pressure friction resistance test, the electrospun polylactic acid waterproof and breathable fabric prepared in Example 1 still maintains good hydrophobic properties, indicating that the electrospun polylactic acid waterproof and breathable fabric has good friction resistance.

[0069] Example 13: Acid and Alkali Resistance Test

[0070] The waterproof and breathable fabric prepared in Example 1 was immersed in a strong acid (HCl) / strong alkali (NaOH) solution with a pH of 2-10 for 24 hours. The water contact angle and water roll-off angle of the polylactic acid waterproof and breathable membrane were measured, and the results are shown in the table below.

[0071] Table 4: Acid and Alkali Resistance Test Results of Example 1

[0072]

[0073] As shown in the table above, after being soaked in strong acids and alkalis for 24 hours, the electrospun polylactic acid waterproof and breathable fabric prepared in Example 1 still maintains its superhydrophobic properties, indicating that the electrospun polylactic acid waterproof and breathable fabric has excellent acid and alkali resistance.

[0074] The green manufacturing method of waterproof and breathable polylactic acid fiber fabric of the present invention uses waste polylactic acid products as the main raw material, which is green and environmentally friendly and turns waste into treasure; the electrospinning method is low-cost, simple to operate, and highly efficient, and the microporous structure formed between the fibers gives the fabric good moisture permeability; by simply immersing the fabric in an ethanol solution containing hexadecyltrimethylammonium chloride, the problem of poor hydrophobicity of electrospun fabrics is effectively solved, which has excellent practical value.

[0075] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A green manufacturing method for waterproof and breathable polylactic acid fiber fabric, characterized in that... Includes the following steps: Step 1: After cleaning the recycled polylactic acid product, degrade it using alcoholysis. The degradation products were precipitated, washed, filtered, and impurities were removed to obtain low molecular weight polylactic acid. Step 2: Dissolve the obtained low molecular weight polylactic acid in ethyl acetate, add dodecylamine, polycaprolactone polyol, diphenylmethane diisocyanate and dimethylolpropionic acid, and react for a period of time; Step 3: Add the polylactic acid solution to deionized water containing ethylenediamine and triethylamine, and stir at high speed to obtain an emulsion; Step 4: Add ultra-high molecular weight polyacrylic acid to the emulsion obtained in Step 3, and then electrospin; Step 5: After soaking the fabric obtained by electrospinning in an ethanol solution containing hexadecyltrimethylammonium chloride for a period of time, the fabric is removed to obtain waterproof and breathable polylactic acid fabric. In step 1, ethylene glycol was used as a solvent, and a microwave-assisted degradation method was employed. The reaction temperature was 250℃, the reaction time was 28 minutes, and the mass ratio of polylactic acid to ethylene glycol was 1:1.

8. The molecular weight of the degradation products was controlled to be between 1000-2000 g / mol. In step 2, low molecular weight polylactic acid accounts for 32% of the mass fraction of ethyl acetate, and the mass ratio of low molecular weight polylactic acid, polycaprolactone polyol, diphenylmethane diisocyanate, dimethylolpropionic acid and dodecylamine is 1:1.5:1:0.06:0.

06. In step 3, the mass ratio of ethylenediamine to triethylamine is 1:2.7, and ethylenediamine accounts for 3% of the mass fraction of deionized water. In step 4, the Mw of the ultra-high molecular weight polyacrylic acid is 30 million, and the added mass is 1.2% of the emulsion mass; In step 5, hexadecyltrimethylammonium chloride accounts for 10% of the mass fraction of ethanol, and the fabric is soaked for 0.5 h.

2. The method according to claim 1, characterized in that: In step 1, the polylactic acid product includes one or more of the following: straws, packaging boxes, tableware, wrapping paper, and film bags.

3. The method according to claim 1, characterized in that: In step 2, the reaction temperature is 80±0.2℃ and the reaction time is 3 h.

4. The method according to claim 1, characterized in that: In step 4, the electrospinning voltage is 18-22 kV, the receiving distance is 12-15 cm, the spinning solution supply rate is 1.5-2.5 mL / h, the temperature is 22-28℃, the humidity is 40-60%, and the thickness of the resulting fiber membrane is 80-250 μm.

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