One-way moisture-conducting biodegradable non-woven fabric and preparation method thereof

Abstract

The present invention discloses a unidirectional moisture-conducting biodegradable non-woven fabric and a preparation method thereof. The present invention grafts hydrazide compounds to lignin through an acylation reaction and obtains a lignin nanoparticle nucleating agent through a nanoprecipitation method. The crystallization behavior of the biodegradable resin is changed through the lignin nanoparticles, the crystallization rate is accelerated, and the cooling and molding cycle is shortened, thereby improving its spinnability. Furthermore, the surface of the biodegradable non-woven fabric is hydrophilically and hydrophobically modified by low-temperature plasma technology to prepare a biodegradable non-woven fabric with a unidirectional moisture-conducting function. The present invention solves the problem of poor spinnability of biodegradable plastics such as PBAT and PBS, prepares a bio-based nucleating agent to replace traditional small molecule organic nucleating agents, and solves the problem that traditional organic nucleating agents are difficult to biodegrade and easy to precipitate. The prepared unidirectional moisture-conducting biodegradable non-woven fabric has good directional infusion performance and can be widely used in sanitary napkins, diapers, masks, shoes and clothing and other fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmentally friendly materials, and in particular relates to a unidirectional moisture-conducting biodegradable non-woven fabric and a preparation method thereof. Background Art

[0002] Nonwoven fabrics, also known as non-woven fabrics, are a new type of fiber product made from short or filament fibers using various web-forming methods and consolidation techniques. They are soft, breathable, and have a flat structure. They are currently widely used in textile industries such as clothing and sanitary products. Traditional nonwoven fabrics are primarily made from fibers such as polypropylene (PP) and polyethylene terephthalate (PET). These materials are difficult to biodegrade in the natural environment and, after use, generate "white pollution" and microplastic pollution. Therefore, replacing traditional plastics with biodegradable plastics is considered the best way to fundamentally address the problem of plastic pollution.

[0003] Most biodegradable plastics contain functional groups such as ester and amide groups in their molecular chains, which are easily decomposed by bacteria, fungi, and other organisms in nature, and eventually turn into carbon dioxide and water and enter the natural cycle. However, most biodegradable plastics have problems such as poor heat resistance and poor crystallization performance during processing. During the spinning process, fiber bonding and filament breakage are prone to occur, resulting in the inability to properly stretch and lay the web. To improve the above situation, methods such as reducing the molecular weight of the plastic, rapid cooling at the outlet, and adding nucleating agents are usually used for modification. By adding nucleating agents for modification, the original homogeneous nucleation is transformed into heterogeneous nucleation in the molten state, which can significantly shorten the crystallization induction period and molding cycle, significantly improve the heat resistance and crystallization performance of the biodegradable plastic, and thus improve the spinnability.

[0004] Traditional inorganic nucleating agents have small particle size, high specific surface energy, and poor dispersibility, resulting in low nucleation rates. Small molecule organic nucleating agents have good dispersibility but are prone to precipitation and are biotoxic. Lignin, the second most abundant biomass on Earth, has been widely used in industry. As a natural plastic nucleating agent, lignin has a certain effect on promoting crystallization, but when used alone, it tends to agglomerate and has a poor nucleation effect. Furthermore, lignin's molecular structure contains a large number of hydrophilic functional groups such as hydroxyl groups, which have poor compatibility in plastics, limiting its further application in biodegradable plastics. Lignin nanoparticles have excellent hydrophobic properties, good compatibility with biodegradable plastics, and are also biodegradable. The addition of lignin nanoparticles can improve the crystallization properties and spinnability of biodegradable plastics such as polybutylene adipate / terephthalate (PBAT).

[0005] In addition, medical, textile, and sanitary non-woven fabrics are usually required to have one-sided hydrophilic properties. For example, the surface non-woven fabric of diapers needs to be hydrophilically modified to improve its liquid conduction ability. One-way moisture conduction has become an essential property of high-performance non-woven fabrics, and is particularly important for the application of non-woven fabrics in high-end fields. At present, the preparation methods of one-way moisture-conducting non-woven fabrics mainly include coating with hydrophilic additives, coating lamination, surface modification, etc. The hydrophilic coating gives the non-woven fabric better moisture conduction ability, but it affects its breathability. Patent CN205467700U discloses a method for preparing a one-way moisture-conducting non-woven fabric. The one-way moisture-conducting non-woven fabric uses polypropylene as raw material, and the hydrophilic spunbond layer on the outer surface and the hydrophobic spunbond layer on the inner surface are superimposed on each other by hot pressing, so that it has a one-way moisture-conducting function. Regardless of whether the coating or hot pressing method is used, the breathability of the non-woven fabric will be affected, and the preparation process is relatively complicated.

[0006] Plasma surface treatment technology is easy to operate and environmentally friendly, making it a common technology for semiconductor surface treatment. Using plasma to treat the surface of nonwoven fabrics does not alter the material structure, maintaining good breathability. Furthermore, this process is simple to operate and environmentally friendly, making it a green alternative for nonwoven surface treatment. This technology uses a variety of high-energy active ions, such as ions, excited states, and free radicals, to etch the material surface and introduce specific surface functional groups, thereby altering the material's surface wettability. Summary of the Invention

[0007] To address the poor spinnability and moisture conductivity of biodegradable materials such as PBAT, PBS, and PBST, the present invention provides a unidirectional moisture-conducting biodegradable nonwoven fabric and its preparation method. Hydrazide compounds are first grafted onto lignin, and a lignin nanoparticle nucleating agent is prepared via a nanoprecipitation method. This is then blended with biodegradable plastics to improve their crystallization properties, resulting in a series of biodegradable nonwoven fabrics. Furthermore, plasma hydrophilic and hydrophobic modifications impart asymmetric wettability and unidirectional moisture conductivity to the nonwoven fabric.

[0008] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is:

[0009] A method for preparing a unidirectional moisture-conducting biodegradable non-woven fabric comprises the following steps:

[0010] (1) Preparation of lignin nanoparticle nucleating agent: Filter the pulping black liquor, acidify, wash with water, and dry to obtain purified lignin, dissolve the purified lignin in a sodium hydroxide solution with a pH of 10-12, heat to 50-70°C, add a hydrazide compound and a catalyst, and react for 1-4 hours to obtain grafted modified lignin; dissolve the grafted modified lignin in ethylene glycol, and then add dropwise to a hydrochloric acid solution with a pH of 4, wash with water, and then spray-dry to obtain a lignin nanoparticle nucleating agent;

[0011] (2) Preparation of biodegradable non-woven fabrics: weigh 88-98.3 parts of biodegradable polyester, 0.5-5 parts of lignin nanoparticle nucleating agent, 0.1-1 parts of dispersant, 1-5 parts of bio-based plasticizer, and 0.1-1 parts of anti-ultraviolet aging additive, stir and mix for 5-10 minutes, and then obtain biodegradable modified particles by melt blending, water-cooling pelletizing, and drying. Add the biodegradable modified material to a spunbond non-woven fabric machine, set the spinning temperature, blowing power, induced draft power, winding rate, traction rate, and pressure roller temperature to make biodegradable non-woven fabrics;

[0012] (3) Preparation of unidirectional moisture-conducting biodegradable non-woven fabric: Low-temperature plasma technology is used to perform hydrophilic and hydrophobic modifications on both sides of the biodegradable non-woven fabric to obtain a biodegradable non-woven fabric with unidirectional moisture-conducting function.

[0013] Furthermore, the pulping black liquor in step (1) is obtained from one or more of poplar, eucalyptus, masson pine, birch, rice straw, wheat straw, reed, bagasse, and bamboo through a caustic soda process, a sulfate process, or a sulfite process, and the lignin content in the pulping black liquor is 10-48%, and the density is 1.02-1.45 g / mL.

[0014] Furthermore, the hydrazide compound in step (1) is one of acetohydrazide, phenylacetohydrazide, p-methylphenylacetohydrazide, dimethylhydrazide, and nonanoic acid hydrazide, and the mass ratio of the hydrazide compound to the purified lignin is 1:5-10.

[0015] Furthermore, the catalyst in step (1) is one of benzyltriethylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium chloride, and the mass ratio of the catalyst to the purified lignin is 1:5-10.

[0016] Furthermore, the lignin nanoparticle nucleating agent prepared in step (1) has a particle size of 100-500 nm, a water contact angle of 135-155°, and a thermal decomposition temperature of 260-270°C.

[0017] Furthermore, the biodegradable polyester in step (2) is one or more of polybutylene succinate (PBS), polybutylene succinate-co-butylene terephthalate (PBST), and polybutylene adipate / terephthalate (PBAT).

[0018] Furthermore, the dispersant in step (2) is one or more of barium stearate, polyethylene wax and polyethylene glycol; the bio-based plasticizer is one or more of epoxy soybean oil, dioctyl succinate, acetyl tributyl citrate and dioctyl sorbate; and the anti-ultraviolet aging additive is one or more of 2-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, methyl phenyl salicylate, Tinuvin 770, Tinuvin 783 and Chimassorb 944.

[0019] Furthermore, in step (2), the spinning temperature is 180-230° C., the blowing power is 50-60 Hz, the induced draft power is 40-50 Hz, the winding rate is 5-6 Hz, and the pulling rate is 3-4 Hz.

[0020] Furthermore, the hydrophilic modified gas in step (3) is any one of O2, N2, CO, CO2, and NH3, the modification power is 60~120W, and the modification time is 1~5min; the hydrophobic modified gas is one or more of CF4, C2F6, trimethylchlorosilane, hexamethyldisilazane, fluorosilane, and ethyl orthosilicate.

[0021] The present invention also provides the use of the one-way moisture-conducting biodegradable non-woven fabric prepared by the above preparation method in sanitary napkins, diapers, masks, shoes and clothing.

[0022] Principle of the present invention:

[0023] In order to solve the problem that traditional small molecule organic nucleating agents such as hydrazide compounds are easy to precipitate and difficult to biodegrade, small molecule hydrazide compounds are grafted onto lignin to solve the precipitation problem and improve its biodegradability, while also improving the compatibility of lignin nanoparticle nucleating agents with biodegradable resins.

[0024] To address the issue of decreased air permeability in unidirectional moisture-conducting nonwovens, a low-temperature plasma modification process was used instead of a coating process to create a biodegradable, unidirectional moisture-conducting nonwoven with asymmetric wettability. This approach addresses the issue of decreased air permeability due to surface modification, while also avoiding the environmental pollution caused by solvents during hydrophilic and hydrophobic finishing.

[0025] Compared with the prior art, the present invention has the following advantages and positive effects:

[0026] (1) Improving spinnability: The present invention prepares a lignin nanoparticle nucleating agent, which improves the crystallization behavior of biodegradable plastics such as PBAT, PBS, and PBST, shortens the molding temperature, increases the crystallinity, and enhances the spinnability of the material. The improvement in nucleating effect is mainly attributed to the lignin nanoparticles acting as crystal nuclei to change the crystallization of the material and the hydrazide compounds inducing crystallization, which work together to improve the crystallization performance of the material. In addition, the lignin nanoparticle nucleating agent is a bio-based material with complete biodegradability, is not easily precipitated during use, and does not pose an environmental pollution risk.

[0027] (2) Excellent unidirectional moisture conduction performance: The present invention uses plasma modification to make the surface layer of the non-woven fabric have good liquid conduction ability (hydrophilicity), and plasma hydrophobic modification to make the bottom layer of the non-woven fabric have anti-rewet performance. Since the prepared non-woven fabric has asymmetric wettability, it has unidirectional moisture conduction performance.

[0028] (3) The one-way moisture-conducting biodegradable non-woven fabric prepared by the present invention has an environmentally friendly modification process and is flexible and simple to operate. The modified one-way moisture-conducting biodegradable non-woven fabric can still maintain its original breathability and comfort, and can be used in sanitary napkins, diapers, masks, shoes and clothing and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The DSC graphs of the biodegradable non-woven fabrics in Examples 1 and 2 and Comparative Example 2 are shown.

[0030] Figure 2 It is the water contact angle of the unidirectional moisture-conducting biodegradable non-woven fabric in Example 4.

[0031] Figure 3 Scanning electron micrographs of the biodegradable nonwoven fabric in Example 3: (a) before O2 modification and (b) after O2 modification.

[0032] Figure 4 This is the infrared spectrum of the biodegradable non-woven fabric in Example 3. DETAILED DESCRIPTION

[0033] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments based on the above content of the present invention, which still fall within the scope of protection of the present invention.

[0034] The instruments and devices used in this invention are also conventional in the art. The pulping black liquor (Massonia pine black liquor, birch pulping black liquor, eucalyptus pulping black liquor, and Massonia pine pulping black liquor) in this invention is sourced from a papermaking enterprise in Fujian. The water vapor transmission coefficient test method used in this invention is as follows: The water vapor transmission rate of non-woven fabrics is measured using a W3 / 031 water vapor transmission rate tester in accordance with GB / T 12704.1-2009. The test temperature is 38°C and the humidity is 90% RH. Five replicates are tested per sample group. The mechanical properties test method used in this invention is as follows: The mechanical properties of non-woven fabrics are measured using an XQ-1C tensile strength tester in accordance with GB / T 24218.3-2010. Samples are cut into strips 300 mm long (test length 200 mm) and 50 mm wide. The tensile speed is 100 mm / min. Five replicates are tested per sample group.

[0035] Example 1

[0036] 1000 g of Masson pine black liquor (lignin content 46%, density 1.38 g / mL) obtained by soda pulping was dissolved in 2000 g of deionized water, stirred thoroughly, and filtered to remove impurities. A 30% (v / v) hydrochloric acid solution was then added dropwise to the filtrate to adjust the pH to 2 to obtain purified lignin. The precipitate was washed three times with deionized water, filtered, and dried in a vacuum at 60°C to obtain purified lignin. 100 g of the purified lignin was dissolved in 500 ml of sodium hydroxide solution (pH = 10). The temperature was raised to 55°C, and 10 g of tetrabutylammonium chloride and 20 g of p-methylphenylacetylhydrazine were slowly added. The mixture was stirred, refluxed, and reacted for 3 h. After cooling, the mixture was washed with deionized water, filtered, and dried in a vacuum at 60°C to obtain grafted modified lignin. The grafted modified lignin was dissolved in ethylene glycol and added dropwise to a pH = 4 hydrochloric acid solution via a peristaltic pump. After washing with water, the mixture was spray-dried to obtain a lignin nanoparticle nucleating agent. The lignin nanoparticle nucleating agent prepared according to the above steps has a particle size of 125 nm, a water contact angle of 138° C., and a thermal decomposition temperature of 265° C.

[0037] 3000g of PBS was placed in a vacuum drying oven and dried at 70°C for 12h; 35g of lignin nanoparticle nucleating agent, 20g of barium stearate, 35g of epoxy soybean oil and 20g of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole were weighed and mixed with PBS resin in a mixer for 5min, melt-blended and water-cooled pelletized through a twin-screw extruder, and dried in a vacuum drying oven at 70°C for 12h to obtain PBS modified particles, which were then made into PBS biodegradable non-woven fabrics using a spunbond non-woven fabric machine.

[0038] The granulation working parameters are as follows: the temperatures of the first 7 zones of the twin-screw extruder are 110°C, 125°C, 135°C, 145°C, 150°C, 145°C, and 135°C, the die temperature is 130°C, and the screw speed is 300 rpm / min.

[0039] The temperatures in each zone of the spunbond nonwoven fabric testing machine are 130°C, 170°C, 200°C, 215°C, and 215°C, the die head temperature is 215°C, the blast power is 40HZ, the induced draft power is 50HZ, the traction frequency is 3HZ, the winding frequency is 4.8HZ, and the pressure roller temperature is 85°C.

[0040] PBS biodegradable non-woven fabric was attached to a flat plate, placed in a low-temperature plasma device, and vacuumed to 10 -3 ~10 -4 , CO was introduced for hydrophilic modification, the modification power was set to 80W, and the time was 1.5min. The hydrophilic modified surface layer was covered and placed in a low-temperature plasma device, and the vacuum degree of the cavity was evacuated to 10 -3 ~10 -4 , C2F6 was introduced for hydrophobic modification, the modification power was set to 90W, the time was 1.0min, and after modification, PBS biodegradable non-woven fabric with unidirectional moisture conduction function was obtained.

[0041] The PBS biodegradable nonwoven fabric prepared according to the above steps has a water contact angle of 150.0° on the hydrophobic modified side and 35.8° on the hydrophilic modified side. It has a thickness of 0.18 mm, a water pressure resistance of 10.62 KPa, and a water permeability of 5957 g / m 2 •d, the elongation at break is 46.23%, and the breaking strength is 12.28N.

[0042] Example 2

[0043] 1000 g of birch pulping black liquor (lignin content 38%, density 1.23 g / mL) obtained by soda pulping was dissolved in 2000 g of deionized water, stirred thoroughly, and filtered to remove impurities. 25% (v / v) sulfuric acid solution was then added dropwise to the filtrate, and the pH of the filtrate was adjusted to 2 to obtain purified lignin. The precipitate was washed three times with deionized water, filtered, and dried in a vacuum at 60°C to obtain purified lignin. 100 g of the purified lignin was dissolved in 500 ml of sodium hydroxide solution (pH 10). The temperature was raised to 55°C, and 10 g of benzyltriethylammonium chloride and 20 g of phenylacetic acid hydrazide were slowly added. The mixture was stirred and refluxed for 2.5 h. After cooling, the mixture was washed with deionized water, filtered, and dried in a vacuum at 60°C to obtain grafted modified lignin. The grafted modified lignin was dissolved in ethylene glycol and added dropwise to a hydrochloric acid solution (pH 4) via a peristaltic pump. After washing with water, the mixture was spray-dried to obtain a lignin nanoparticle nucleating agent. The lignin nanoparticle nucleating agent prepared according to the above steps has a particle size of 135 nm, a water contact angle of 140° C., and a thermal decomposition temperature of 266° C.

[0044] 3000g of PBS was placed in a vacuum drying oven and dried at 70°C for 12h; 30g of lignin-based nucleating agent, 25g of polyethylene wax, 35g of acetyl tributyl citrate and 20g of phenyl salicylate were added respectively, mixed with PBS resin in a mixer for 5min, melt-blended through a twin-screw extruder, water-cooled and pelletized, and then dried in a vacuum drying oven at 70°C for 12h to obtain PBS modified particles, which were then made into PBS biodegradable non-woven fabrics using a spunbond non-woven fabric machine.

[0045] The granulation working parameters are as follows: the temperatures of the first 7 zones of the twin-screw extruder are 110°C, 125°C, 135°C, 145°C, 150°C, 145°C, and 135°C, the die temperature is 130°C, and the screw speed is 300 rpm / min.

[0046] The temperatures in each zone of the spunbond nonwoven fabric testing machine are 130°C, 170°C, 205°C, 220°C, and 220°C, the die head temperature is 220°C, the blast power is 40HZ, the induced draft power is 50HZ, the traction frequency is 3HZ, the winding frequency is 4.8HZ, and the pressure roller temperature is 85°C.

[0047] PBS biodegradable non-woven fabric was attached to a flat plate, placed in a low-temperature plasma device, and vacuumed to 10 -3 ~10 -4 , use N2 to perform hydrophilic modification, set the modification power to 85W, and the time to 1.0min. Cover the hydrophilic modified surface layer, put it into the low-temperature plasma equipment, and evacuate to 10 -3 ~10 -4, C2F6 was introduced for hydrophobic modification, the modification power was set to 80W, the time was 1.5min, and after modification, PBS biodegradable non-woven fabric with unidirectional moisture conduction function was obtained.

[0048] The PBS biodegradable non-woven fabric prepared according to the above steps has a water contact angle of 145.0° on the hydrophobic modified side and 36.2° on the hydrophilic modified side. It has a thickness of 0.25 mm, a water pressure resistance of 10.68 KPa, and a water permeability of 5414 g / m 2 •d, the elongation at break is 46.71%, and the breaking strength is 30.40N.

[0049] Example 3

[0050] 1000 g of eucalyptus pulping black liquor (lignin content 40%, density 1.27 g / mL) obtained by soda pulping was dissolved in 2000 g of deionized water, stirred thoroughly, and filtered to remove impurities. 30% (v / v) sulfuric acid solution was then added dropwise to the filtrate, and the pH of the filtrate was adjusted to 2 to obtain purified lignin. The precipitate was washed three times with deionized water, filtered, and dried in a vacuum at 60°C to obtain purified lignin. 100 g of the purified lignin was dissolved in 500 ml of sodium hydroxide solution (pH 10). The temperature was raised to 55°C, and 10 g of tetrabutylammonium bromide and 20 g of dimethylhydrazide were slowly added. The mixture was stirred and refluxed for 4 h. After cooling, the mixture was washed with deionized water, filtered, and dried in a vacuum at 60°C to obtain grafted modified lignin. The grafted modified lignin was dissolved in ethylene glycol and added dropwise to a hydrochloric acid solution (pH 4) via a peristaltic pump. The mixture was washed with water and spray-dried to obtain a lignin nanoparticle nucleating agent. The lignin nanoparticle nucleating agent prepared according to the above steps has a particle size of 140 nm, a water contact angle of 135° C., and a thermal decomposition temperature of 268° C.

[0051] 3000g of PBST was placed in a vacuum drying oven and dried at 70°C for 12 hours; 40g of lignin nanoparticle nucleating agent, 25g of polyethylene glycol, 40g of dioctyl sorbate and 25g of 2-hydroxybenzophenone were added respectively, mixed with PBST resin in a mixer for 5 minutes, melt-blended through a twin-screw extruder, water-cooled and pelletized, and then dried in a vacuum drying oven at 70°C for 12 hours to obtain PBST modified particles, which were then made into PBST biodegradable non-woven fabrics using a spunbond non-woven fabric machine.

[0052] The granulation working parameters are as follows: the temperatures of the first 7 zones of the twin-screw extruder are 150°C, 165°C, 175°C, 185°C, 180°C, 175°C, and 170°C, the die temperature is 170°C, and the screw speed is 300 rpm / min.

[0053] The temperatures in each zone of the spunbond nonwoven fabric testing machine are 160°C, 180°C, 210°C, 225°C, and 225°C, the die head temperature is 225°C, the blast power is 40HZ, the induced draft power is 50HZ, the traction frequency is 3HZ, the winding frequency is 4.8HZ, and the pressure roller temperature is 95°C.

[0054] PBST biodegradable non-woven fabric was attached to a flat plate, placed in a low-temperature plasma device, and vacuumed to 10 -3 ~10 -4 , use O2 for hydrophilic modification, set the modification power to 100W, time 1.0min. Cover the hydrophilic modified surface layer, put it into the low temperature plasma equipment, and evacuate to 10 -3 ~10 -4 , CHF3 was introduced for hydrophobic modification, the modification power was set to 80W, the time was 2.0min, and after modification, PBST biodegradable non-woven fabric with unidirectional moisture conduction function was obtained.

[0055] The PBST biodegradable non-woven fabric prepared according to the above steps has a water contact angle of 150.3° on the hydrophobic modified side and 38.5° on the hydrophilic modified side. It has a thickness of 0.18 mm, a water pressure resistance of 11.47 KPa, and a water permeability of 5979 g / m 2 •d, the elongation at break is 50.81%, and the breaking strength is 35.45N.

[0056] Example 4

[0057] 1000 g of Masson pine pulping black liquor (lignin content 46%, density 1.38 g / mL) obtained by soda pulping was dissolved in 2000 g of deionized water, stirred thoroughly, and filtered to remove impurities. A 20% (v / v) sulfuric acid solution was then added dropwise to the filtrate, and the pH of the filtrate was adjusted to 2 to obtain purified lignin. The precipitate was washed three times with deionized water, filtered, and dried in a vacuum at 60°C to obtain purified lignin. 100 g of the purified lignin was dissolved in 500 ml of sodium hydroxide solution (pH 10). The temperature was raised to 65°C, and 10 g of benzyltriethylammonium chloride and 20 g of phenylacetic acid hydrazide were slowly added. The mixture was stirred and refluxed for 4 h. The mixture was then cooled, washed with deionized water, filtered, and dried in a vacuum at 60°C to obtain grafted modified lignin. The grafted modified lignin was dissolved in ethylene glycol and added dropwise to a pH 4 hydrochloric acid solution via a peristaltic pump. The mixture was washed with water and spray-dried to obtain a lignin nanoparticle nucleating agent. The lignin nanoparticle nucleating agent prepared according to the above steps has a particle size of 125 nm, a water contact angle of 137° C., and a thermal decomposition temperature of 266° C.

[0058] 3000g of PBAT was placed in a vacuum drying oven and dried at 70°C for 12h; 40g of lignin nanoparticle nucleating agent, 20g of barium stearate, 35g of dioctyl succinate and 30g of Tinuvin 783 were added respectively, mixed with the PBAT resin in a mixer for 5min, melt-blended through a twin-screw extruder, water-cooled and pelletized, and then dried in a vacuum drying oven at 70°C for 12h to obtain PBAT modified particles, which were then made into PBAT biodegradable non-woven fabrics using a spunbond non-woven fabric machine.

[0059] The granulation working parameters are as follows: the temperatures of the first 7 zones of the twin-screw extruder are 130°C, 135°C, 145°C, 155°C, 150°C, 145°C, and 140°C, the die temperature is 140°C, and the screw speed is 300 rpm / min.

[0060] The temperatures in each zone of the spunbond nonwoven fabric testing machine are 150°C, 190°C, 210°C, 215°C, and 215°C, the die head temperature is 215°C, the blast power is 45HZ, the induced draft power is 60HZ, the traction frequency is 3HZ, the winding frequency is 4.8HZ, and the pressure roller temperature is 80°C.

[0061] PBAT biodegradable non-woven fabric was pasted on a flat plate, placed in a low-temperature plasma device, and vacuumed to 10 -3 ~10 -4 , NH3 was introduced for hydrophilic modification, the modification parameters were: power 100W, time 1.0min, the modification parameters were: power 80W, time 1min. The hydrophilic modified surface layer was covered and placed in a low temperature plasma device, and vacuumed to 10 -3 ~10 -4 SF3 was introduced for hydrophobic modification, with the modification power set at 90W and the time being 1 minute. After modification, a PBAT biodegradable nonwoven fabric with unidirectional moisture conduction function was obtained.

[0062] The PBAT biodegradable non-woven fabric prepared according to the above steps has a water contact angle of 152.1° on the hydrophobically modified side and 39.2° on the hydrophilically modified side. The thickness is 0.15 mm, the water pressure resistance is 10.69 KPa, and the moisture permeability is 5554 g / m 2 •d, the elongation at break is 230.6%, and the breaking strength is 10.31N.

[0063] Comparative Example 1

[0064] 1000 g of Masson pine pulping black liquor (lignin content 46%, density 1.38 g / mL) obtained by the soda pulping process was dissolved in 2000 g of deionized water, stirred evenly, and filtered to remove impurities. 28% (v / v) hydrochloric acid solution was then added dropwise to the filtrate to adjust the pH to 2 to obtain purified lignin. The precipitate was washed three times with deionized water, filtered, and dried in a vacuum at 60°C to obtain purified lignin. 100 g of the purified lignin was dissolved in 500 ml of sodium hydroxide solution (pH 10), heated to 65°C, and then 10 g of benzyltriethylammonium chloride and 20 g of dimethylhydrazide were slowly added. The mixture was refluxed with stirring for 3 h, cooled, washed with deionized water, filtered, and dried in a vacuum at 65°C to obtain grafted modified lignin. The grafted modified lignin was dissolved in ethylene glycol and added dropwise to a hydrochloric acid solution at pH 4 using a peristaltic pump. The product was washed with water and then spray-dried to obtain a lignin nanoparticle nucleating agent. The lignin nanoparticle nucleating agent prepared according to the above steps had a particle size of 130 nm, a water contact angle of 140°C, and a thermal decomposition temperature of 266°C.

[0065] 3000g of PBS was placed in a vacuum drying oven at 70°C and dried for 12h; 35g of lignin nanoparticle nucleating agent, 20g of polyethylene glycol, 35g of dioctyl succinate and 20g of 2-hydroxybenzophenone were added respectively, mixed with PBS resin in a mixer for 5min, melt-blended through a twin-screw extruder, water-cooled and pelletized, and then dried in a vacuum drying oven at 70°C for 12h to obtain PBS modified particles, which were then made into PBS biodegradable non-woven fabrics using a spunbond non-woven fabric machine.

[0066] The granulation working parameters are as follows: the temperatures of the first 7 zones of the twin-screw extruder are 110°C, 125°C, 135°C, 145°C, 150°C, 145°C, and 135°C, the die temperature is 130°C, and the screw speed is 300 rpm / min.

[0067] The temperatures in each zone of the spunbond nonwoven fabric testing machine are 130°C, 170°C, 200°C, 215°C, and 215°C, the die head temperature is 215°C, the blast power is 45HZ, the induced draft power is 60HZ, the traction frequency is 3HZ, the winding frequency is 4.8HZ, and the pressure roller temperature is 80°C.

[0068] The PBS biodegradable non-woven fabric prepared according to the above steps has water contact angles of 125.1° and 125.3° on both sides, a thickness of 0.18 mm, a water pressure resistance of 9.62 KPa, and a water vapor permeability of 2865 g / m 2 •d, the elongation at break is 48.34%, and the breaking strength is 11.35N.

[0069] Comparative Example 2

[0070] 3000g of PBS was dried in a 70°C vacuum drying oven for 12 hours. 25g of polyethylene wax, 35g of acetyl tributyl citrate, and 20g of methyl phenyl salicylate were added and mixed in a mixer for 5 minutes. The mixture was then melt-blended in a twin-screw extruder, cooled with water, pelletized, and dried in a 70°C vacuum drying oven for 12 hours to obtain PBS-modified particles. PBS biodegradable nonwoven fabric was then produced using a spunbond nonwoven fabric machine.

[0071] The granulation working parameters are as follows: the temperatures of the first 7 zones of the twin-screw extruder are 110°C, 125°C, 135°C, 145°C, 150°C, 145°C, and 135°C, the die temperature is 130°C, and the screw speed is 300 rpm / min.

[0072] The temperatures in each zone of the spunbond nonwoven fabric testing machine are 130°C, 170°C, 205°C, 220°C, and 220°C, the die head temperature is 220°C, the blast power is 40HZ, the induced draft power is 50HZ, the traction frequency is 3HZ, the winding frequency is 4.8HZ, and the pressure roller temperature is 85°C.

[0073] PBS biodegradable non-woven fabric was attached to a flat plate, placed in a low-temperature plasma device, and vacuumed to 10 -3 ~10 -4 , use N2 to perform hydrophilic modification, set the modification power to 85W, and the time to 1.0min. Cover the hydrophilic modified surface layer, put it into the low-temperature plasma equipment, and evacuate to 10 -3 ~10 -4 , C2F6 was introduced for hydrophobic modification, the modification power was set to 80W, the time was 1.5min, and after modification, PBS biodegradable non-woven fabric with unidirectional moisture conduction function was obtained.

[0074] The PBS biodegradable nonwoven fabric prepared according to the above steps is prone to breakage and other problems. The water contact angle of the hydrophobic modified side is 140.4°, the water contact angle of the hydrophilic modified side is 45.2°, the thickness is 0.25mm, the water pressure resistance is: 8.09KPa, and the moisture permeability is 4370g / m 2 •d, the elongation at break is 43.22%, and the breaking strength is 21.34N.

[0075] Table 1 Application of lignin nanoparticle nucleating agents prepared in Examples 1-4 in the field of biodegradable plastics

[0076]

[0077] The results in Table 1 show that the biodegradable nonwoven fabrics of Examples 1-4 of the present invention, after undergoing plasma hydrophilic and hydrophobic modification, construct a biodegradable nonwoven fabric with asymmetric wettability, significantly improving its moisture permeability. In Comparative Example 1, the biodegradable nonwoven fabric that was not plasma-modified had almost identical wettability on both sides, thus lacking asymmetric wettability, resulting in a lower moisture permeability. In Comparative Example 2, the biodegradable nonwoven fabric without the addition of a lignin nanoparticle nucleating agent exhibited poorer spinnability than that of Example 2, and the difference in water contact angles on both sides of the nonwoven fabric was lower. This demonstrates that the lignin nanoparticle nucleating agent can effectively improve the spinnability of biodegradable plastics and further optimize their unidirectional moisture conduction properties.

[0078] Figure 1 The DSC graphs of the PBS biodegradable nonwoven fabrics prepared in Examples 1 and 2 and Comparative Example 2 are shown. The crystallization temperature of the PBS biodegradable nonwoven fabric with the addition of lignin nanoparticles increased from 58.8°C to 87.1°C, indicating that the addition of lignin nanoparticles can significantly shorten the crystallization induction period and molding cycle, thereby significantly improving the spinnability of the biodegradable plastic.

[0079] Figure 2 The unidirectional moisture-conducting biodegradable nonwoven fabric prepared in Example 4 was measured using a contact angle meter to measure the change in its contact angle over time. The unmodified PBAT biodegradable nonwoven fabric exhibited hydrophobicity, but over time, the water droplet gradually penetrated the interior of the biodegradable nonwoven fabric, causing the contact angle to decrease from 125.0° to 115.6°. The surface contact angle of the PBAT biodegradable nonwoven fabric in Example 4 increased to 152.1° after SF3 plasma hydrophobic modification, with no significant change within one minute. This is primarily due to the presence of hydrophobic fluorinated groups on the modified surface, which effectively inhibited water droplet penetration. However, after NH3 plasma hydrophilic modification, the contact angle decreased from 89.3° to 38.5°. This is primarily due to the increase in surface oxygen-containing functional groups after hydrophilic modification, which transformed the surface from hydrophobic to hydrophilic. Therefore, plasma modification successfully constructed a biodegradable nonwoven fabric with significant wettability differences.

[0080] Figure 3 This is a scanning electron microscope image of the biodegradable nonwoven fabric prepared in Example 3. Figure 3 a is before O2 modification. Scanning electron microscopy shows that the fiber surface of the biodegradable non-woven fabric is smooth and has good morphology before modification. The fiber morphology does not change much after modification, with only a few scale-like protrusions on the surface ( Figure 3 b). The fiber morphology on the surface of the modified nonwoven fabric remained intact, and the internal fiber morphology changed slightly. This indicates that the modification occurred only on the fiber surface and did not significantly affect the mechanical properties of the nonwoven fabric.

[0081] Figure 4 This is the infrared spectrum of the biodegradable nonwoven fabric prepared in Example 3. The figure shows that the stretching vibration peaks of the COC and C=O bonds of the biodegradable nonwoven fabric after O2 plasma modification are significantly enhanced, and hydrophilic oxygen-containing functional groups are introduced, turning the surface from hydrophobic to hydrophilic.

[0082] The above description is merely a preferred embodiment of the present invention and therefore cannot be used to limit the scope of the present invention. In other words, equivalent changes and modifications made within the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a unidirectional moisture-conducting biodegradable non-woven fabric, characterized in that: The following steps are involved: (1) Preparation of lignin nanoparticle nucleating agent: Filter the pulping black liquor, acidify, wash with water, and dry to obtain purified lignin, dissolve the purified lignin in a sodium hydroxide solution with a pH of 10-12, heat to 50-70°C, add a hydrazide compound and a catalyst, and react for 1-4 hours to obtain grafted modified lignin; dissolve the grafted modified lignin in ethylene glycol, and then add dropwise to a hydrochloric acid solution with a pH of 4, wash with water, and then spray-dry to obtain a lignin nanoparticle nucleating agent; (2) Preparation of biodegradable non-woven fabrics: weigh 88-98.3 parts of biodegradable polyester, 0.5-5 parts of lignin nanoparticle nucleating agent, 0.1-1 parts of dispersant, 1-5 parts of bio-based plasticizer, and 0.1-1 parts of anti-ultraviolet aging additive, and stir and mix for 5-10 minutes. Then, obtain biodegradable modified particles by melt blending, water-cooled pelletizing, and drying. Add the biodegradable modified material to a spunbond non-woven fabric machine, set the spinning temperature, blowing power, induced draft power, winding rate, traction rate, and pressure roller temperature, and make biodegradable non-woven fabrics. (3) Preparation of unidirectional moisture-conducting biodegradable non-woven fabric: Using low-temperature plasma technology to perform hydrophilic modification and hydrophobic modification on both sides of the biodegradable non-woven fabric to obtain a biodegradable non-woven fabric with unidirectional moisture-conducting function; The pulping black liquor in step (1) is obtained from one or more of poplar, eucalyptus, masson pine, birch, rice straw, wheat straw, reed, bagasse, and bamboo through a caustic soda process, a sulfate process, or a sulfite process, and the lignin content in the pulping black liquor is 10-48%, and the density is 1.02-1.45 g / mL.

2. The method for preparing a unidirectional moisture-conducting biodegradable non-woven fabric according to claim 1, wherein: The hydrazide compound in step (1) is one of acetohydrazide, phenylacetohydrazide, p-methylphenylacetohydrazide, dimethylhydrazide, and nonanoic acid hydrazide, and the mass ratio of the hydrazide compound to the purified lignin is 1:5-10.

3. The method for preparing a unidirectional moisture-conducting biodegradable non-woven fabric according to claim 1, wherein: The catalyst in step (1) is one of benzyltriethylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium chloride, and the mass ratio of the catalyst to the purified lignin is 1:5-10.

4. The method for preparing a unidirectional moisture-conducting biodegradable non-woven fabric according to claim 1, wherein: The lignin nanoparticle nucleating agent prepared in step (1) has a particle size of 100-500 nm, a water contact angle of 135-155°, and a thermal decomposition temperature of 260-270°C.

5. The method for preparing a unidirectional moisture-conducting biodegradable non-woven fabric according to claim 1, wherein: The biodegradable polyester in step (2) is one or more of polybutylene succinate, polybutylene succinate-co-butylene terephthalate, and polybutylene adipate / terephthalate.

6. The method for preparing a unidirectional moisture-conducting biodegradable non-woven fabric according to claim 1, wherein: The dispersant in step (2) is one or more of barium stearate, polyethylene wax and polyethylene glycol; the bio-based plasticizer is one or more of epoxy soybean oil, dioctyl succinate, acetyl tributyl citrate and dioctyl sorbate; the anti-ultraviolet aging additive is one or more of 2-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, methyl phenyl salicylate, Tinuvin 770, Tinuvin 783 and Chimassorb 944.

7. The method for preparing a unidirectional moisture-conducting biodegradable non-woven fabric according to claim 1, wherein: In step (2), the spinning temperature is 180-230° C., the blowing power is 50-60 Hz, the induced draft power is 40-50 Hz, the winding rate is 5-6 Hz, and the pulling rate is 3-4 Hz.

8. The method for preparing a unidirectional moisture-conducting biodegradable non-woven fabric according to claim 1, wherein: The hydrophilic modified gas in step (3) is any one of O2, N2, CO, CO2, and NH3, the modification power is 60~120W, and the modification time is 1~5min; the hydrophobic modified gas is one or more of CF4 and C2F6.

9. Use of the unidirectional moisture-conducting biodegradable non-woven fabric prepared by the preparation method according to any one of claims 1 to 8 in sanitary napkins, diapers, masks, shoes and clothing.

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