Soft SMS non-woven fabric and preparation method thereof

Abstract

The invention relates to the technical field of non-woven fabrics, and particularly discloses a soft SMS non-woven fabric and a preparation method thereof. The soft SMS non-woven fabric comprises a spunbond layer and a melt-blown layer, and the spunbond layer comprises the following raw materials in parts by weight: 65-80 parts of spunbond PP, 5-10 parts of a PE / PP copolymer, 2-4 parts of PP-g-MAH, 4-6 parts of a dopamine grafted hyperbranched polymer and 7-11 parts of mineralized nanocellulose. The soft SMS non-woven fabric can be used in the fields of medical protection, hygienic product materials, industrial filtration and the like, and is comfortable in hand feeling and excellent in softness.

Description

Technical Field

[0001] The present application relates to the technical field of non-woven fabrics, and more specifically, to a soft SMS non-woven fabric and a preparation method thereof. Background Art

[0002] SMS (Spunbond-Meltblown-Spunbond) non-woven fabric is a multi-layer non-woven material composed of a spunbond layer and a meltblown layer. Its composite structure provides mechanical support through the spunbond layer and realizes micron-level filtration through the meltblown layer, combining excellent mechanical strength, high-efficiency filtration and good barrier properties. Therefore, it is widely used in fields such as medical protection, hygiene product materials, and industrial filtration.

[0003] However, it is found in practical applications that in order to ensure the mechanical properties and filtration performance of the existing SMS non-woven fabric, a high-grammage meltblown layer and a strong consolidation process are usually adopted to increase the rigidity of the fibers and the hot rolling pressure, which directly leads to the densification of the material structure, the decrease of the fiber flexibility and fluffiness, and irreversibly sacrifices the softness of the material. The finished products generally have the problems of being too hard to touch and poor comfort, which limits the comfort when directly contacting the human skin. Especially in scenarios such as medical surgical gowns, protective clothing and baby care products, the defect of softness is more significant.

[0004] In view of the above related technologies, the inventor found that in the prior art, in order to improve the softness of SMS non-woven fabric, the main methods are to adjust the fiber fineness and the interlayer composite structure, such as using an ultra-fine fiber spunbond layer or reducing the grammage of the meltblown layer to reduce the material rigidity, or by introducing chemical additives or post-treatment processes, such as adding softeners, lubricants or performing surface softening treatment. However, the above methods often sacrifice the mechanical strength and filtration efficiency when improving the softness of SMS non-woven fabric, and it is difficult to meet the comprehensive market requirements of high strength, high filtration efficiency and lasting softness. Summary of the Invention

[0005] In order to improve the softness of SMS non-woven fabric, enhance the use comfort of SMS non-woven fabric, and ensure the mechanical properties and filtration efficiency of SMS non-woven fabric, the present application provides a soft SMS non-woven fabric and a preparation method thereof.

[0006] In a first aspect, the present application provides a soft SMS non-woven fabric, adopting the following technical solution: A soft SMS non-woven fabric includes a spunbond layer and a meltblown layer. By weight, the raw materials of the spunbond layer include 65-80 parts of spunbond PP, 5-10 parts of PE / PP copolymer, 2-4 parts of PP-g-MAH, 4-6 parts of dopamine-grafted hyperbranched polymer, and 7-11 parts of mineralized nano-cellulose.

[0007] The inventors found that nanocellulose itself has a high aspect ratio and flexibility. When the mineralized nanocellulose is applied to the preparation of the spunbond layer of non-woven fabric, it can improve the agglomeration phenomenon of nanocellulose, and at the same time reduce the impact of softness improvement on the mechanical properties of the material. In addition, the mineralized layer on the surface of the mineralized nanocellulose makes the surface structure of the nanocellulose more fluffy, which helps to improve the air permeability of the non-woven fabric while maintaining the filtration efficiency of the non-woven fabric.

[0008] Hyperbranched polymers have a highly branched three-dimensional dendritic structure, with less entanglement between molecular chains and low melt viscosity. They can act as molecular-level lubricants in the spunbond layer, reduce internal friction, significantly reduce the bending stiffness of the non-woven fabric, and increase the flexibility and fluffiness of the non-woven fabric.

[0009] Furthermore, the inventors introduced catechol groups into the hyperbranched polymer by dopamine grafting, endowing the hyperbranched polymer with a flexible skeleton and a polar lubricating layer. The dopamine-grafted hyperbranched polymer can act as a molecular bridge inside the spunbond layer, enhancing the compatibility between the mineralized nanocellulose and the spunbond PP matrix through the interaction between the catechol groups and the ions on the surface of the mineralized nanocellulose. At the same time, the thermal stability of the dopamine-grafted hyperbranched polyester and the mineralized nanocellulose is improved, and they can maintain a stable structure during the subsequent melting process.

[0010] By adopting the above technical solutions, compared with the traditional method for improving the softness of SMS non-woven fabric, the present application uses dopamine-grafted hyperbranched polymer and mineralized nanocellulose as soft functional components, significantly improving the softness of the non-woven fabric while ensuring that the mechanical properties and filtration efficiency of the non-woven fabric are not affected.

[0011] Optionally, the dopamine-grafted hyperbranched polymer is dopamine-grafted carboxyl-terminated hyperbranched polyester.

[0012] By adopting the above technical solutions, the hyperbranched polyester has good compatibility with the spunbond layer matrix, and the carboxyl terminus provides active sites for dopamine grafting. The dopamine-grafted carboxyl-terminated hyperbranched polyester combines the adhesion of dopamine and the toughening effect of the hyperbranched polyester, which helps to form a more compact network structure in the spunbond layer, improving the softness of the non-woven fabric while ensuring the filtration efficiency.

[0013] Optionally, the preparation method of the dopamine-grafted carboxyl-terminated hyperbranched polyester includes the following steps: S1: Dissolve the carboxyl-terminated hyperbranched polyester in water, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide under the protection of an inert gas, stir and activate, then add dopamine hydrochloride, adjust the pH to alkaline, and react in the dark to obtain a reaction solution; S2: Add the reaction solution to ether for precipitation, collect the crude product after centrifugation, and obtain the product after dialysis and drying.

[0014] Optionally, the method for preparing the mineralized nanocellulose includes the following steps: Disperse the nanocellulose in water and ultrasonically treat it to form a suspension; Mix the suspension with a CaCl2 solution, stir, filter, and wash. Then disperse the washed nanocellulose in a Na2HPO4 solution, adjust the pH to alkaline, stir, filter, and wash. Repeat the above alternating deposition steps of CaCl2 and Na2HPO4, and obtain the product after filtration, washing, and drying.

[0015] By adopting the above technical solution, the alternating deposition of CaCl2 / Na2HPO4 forms a mineralized layer containing calcium ions and phosphate groups on the surface of the nanocellulose. The calcium phosphate nanoparticles are embedded in the nanocellulose network as rigid fillers, which can significantly improve the mechanical properties of the nanocellulose, improve the dispersion uniformity of the nanocellulose in the spunbond layer, and increase the fluffiness without significantly affecting the mechanical properties of the non-woven fabric, making the non-woven fabric softer and more comfortable.

[0016] Furthermore, the negatively charged phosphate groups can form chemical adsorption sites on the surface of the nanocellulose, enhancing the interception efficiency of external biological particles such as bacteria and viruses through electrostatic attraction. In addition, the high specific surface area of calcium phosphate effectively increases the physical interception ability of the non-woven fabric for pollutants such as proteins in droplets, which helps to improve the filtration efficiency of the SMS non-woven fabric.

[0017] Optionally, the following pretreatment is carried out on the nanocellulose: Add NaIO4 to the nanocellulose suspension, heat and react under dark conditions to obtain an aldehyde-functionalized nanocellulose suspension; then adjust the pH of the aldehyde-functionalized nanocellulose suspension to alkaline, introduce a gas containing ozone for oxidation, and then centrifuge, wash, and dry to obtain the pretreated nanocellulose.

[0018] By adopting the above technical solution, through aldehyde group and carboxyl group treatment, on the one hand, it can break the original intermolecular hydrogen bonds of the nanocellulose during the oxidation process, effectively improve the dispersion of the nanocellulose, reduce the agglomeration phenomenon of the nanocellulose, and form a more fluffy network structure, further improving the softness and air permeability of the material. On the other hand, the carboxyl group treatment introduces carboxyl groups on the surface of the nanocellulose, significantly increasing the 2+ chelation sites of Ca, promoting the formation of the mineralized layer on the surface of the nanocellulose.

[0019] Optionally, the melt index of the spunbond PP is 40 - 45 g / min, and the melt index of the meltblown PP is 1200 - 1500 g / min.

[0020] By adopting the above technical solution, the meltblown layer prepared from high melt index PP can form finer meltblown fibers, increase the number of fibers per unit area of the non-woven fabric, form a denser filtration network, and maintain high filtration efficiency at low gram weight.

[0021] In a second aspect, the present application provides a method for preparing a soft SMS non-woven fabric, adopting the following technical solution: A method for preparing a soft SMS non-woven fabric, comprising the following steps: Mix the spunbond layer raw materials according to the ratio, extrude and melt them through a screw, spin, cold air draw, and lay the web to obtain the spunbond layer; mix the meltblown layer raw materials according to the ratio, extrude and melt them through a screw, spin, hot air draw, cool, and lay the web to obtain the meltblown layer; use the meltblown layer as the intermediate layer, lay the spunbond layer on both sides of the meltblown layer respectively, and then perform hot pressing and bonding to obtain the product.

[0022] By adopting the above technical solution, compared with the traditional strong consolidation process, the preparation method of the present application multi-dimensionally improves the softness of the non-woven fabric through the co-blending modification of polymer materials and the strengthening of nano-materials, etc., and effectively improves the bulkiness and softness of the material on the premise of ensuring the interlayer bonding strength.

[0023] Optionally, when preparing the spunbond layer and the meltblown layer by screw extrusion melting, the screw temperature is 210-230 °C, and when preparing the meltblown layer by hot air draw, the hot air temperature is 230-250 °C.

[0024] In summary, the present application has the following beneficial effects: 1. By using a PE / PP blend, dopamine-grafted hyperbranched polymer, and mineralized nano-cellulose as flexible components, and utilizing the highly branched three-dimensional dendritic structure of the hyperbranched polymer and the flexibility of nano-cellulose, the softness of the SMS non-woven fabric is significantly improved. The dopamine-grafted hyperbranched polymer plays the role of a molecular bridge in the spunbond layer. On the one hand, it is covalently connected to the anhydride groups of PP-g-MAH and anchored in the PP matrix. On the other hand, it forms a hydrogen bond network with the calcium phosphate mineralized layer on the surface of the mineralized nano-cellulose, uniformly dispersing the mineralized nano-cellulose in the PP matrix to form a uniform and dense network structure, ensuring that the mechanical properties and filtration efficiency of the non-woven fabric are not affected.

[0025] 2. The present application introduces inorganic fillers into the SMS non-woven fabric by alternately depositing CaCl2 and Na2HPO4 on the surface of nano-cellulose to form an inorganic mineralized layer, enhancing the dispersibility of nano-cellulose in the spunbond layer, reducing the agglomeration of nano-cellulose, and at the same time promoting the dispersion uniformity of inorganic fillers in the spunbond layer and the compatibility with organic raw materials, effectively improving the softness of the SMS non-woven fabric while ensuring that the excellent mechanical properties of the non-woven fabric are not affected.

[0026] 3. The mineralized nanocellulose formed by alternately depositing CaCl2 and Na2HPO4 can enhance the interception efficiency of external biological particles such as bacteria and viruses through electrostatic adsorption. The high specific surface area of calcium phosphate also strengthens the physical interception of external pollutant particles by the non-woven fabric, which can ensure the filtration efficiency of the non-woven fabric while improving its air permeability. Specific Embodiments

[0027] The present application will be further described in detail below with reference to examples and comparative examples. Raw Materials

[0028] Unless otherwise specified, the raw materials used in the preparation examples, examples and comparative examples of the present application are all commercially available products, specifically: Spunbonded PP, with a melt index of 40 - 45 g / min; PE / PP copolymer, with a PE content of 14 - 16 wt% and a density of 0.9 g / cm 3 ; PP-g-MAH, selected from Exxon, PO1020; Carboxyl-terminated hyperbranched polyester, with a molecular weight of 6400 g / mol and 24 carboxyl groups per mole; Dopamine hydrochloride, selected from Hefei Bomei Biotechnology Co., Ltd., DD5109; Nanocellulose, with a diameter of 5 - 8 nm and an aspect ratio of (8 - 10):1; Meltblown PP, with a melt index of 1200 - 1500 g / min for meltblown PP; Polyethylene wax, selected from Honeywell, AC-6A.

[0029] Preparation Example 1.1 of Dopamine-Grafted Carboxyl-Terminated Hyperbranched Polyester The preparation method of dopamine-grafted carboxyl-terminated hyperbranched polyester includes the following steps: S1: Place 5 g of carboxyl-terminated hyperbranched polyester in a 250 mL three-necked flask, add 100 mL of deionized water, introduce nitrogen protection, stir magnetically at 300 rpm until completely dissolved, then add 3.6 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 2.1 g of N-hydroxysuccinimide, adjust the pH to 4.5 - 5, and stir and activate for 1.5 h at 300 rpm to obtain a blend; S2: Add 7.2 g of dopamine hydrochloride to the blend, continue stirring, slowly adjust the pH to 8 - 9 with 1 mol / L NaOH solution, and react in the dark for 16 h to obtain a reaction solution; S3: The reaction solution was added to 800 mL of pre-cooled diethyl ether under stirring for precipitation. After centrifugation, the crude product was collected, dissolved in deionized water, transferred to a dialysis bag, and dialyzed for 48 h. The outer dialysis solution was changed every 8 h to remove unreacted small molecules, and then it was dried to obtain the product. Preparation Examples 2.1 - 2.3 of Mineralized Nanocellulose

[0030] Preparation Example 2.1 A method for preparing mineralized nanocellulose includes the following steps: S1: The nanocellulose was dispersed in water and ultrasonically dispersed for 30 min to form a 3% suspension; S2: Under stirring conditions, NaIO4 was added to the nanocellulose suspension. The mass ratio of NaIO4 to nanocellulose in the suspension was 0.3:1. It was heated to 55 °C and reacted for 4 h in the dark to obtain an aldehyde-functionalized nanocellulose suspension; S3: The pH of the aldehyde-functionalized nanocellulose suspension obtained in step S2 was adjusted to 9 - 10 with 1 mol / L NaOH solution, and then it was oxidized by introducing an ozone-containing gas in the dark. The inlet gas flow rate and ozone inlet concentration were 1.8 NL / min and 2.5 wt% respectively, and the gas injection time was 12 min. After centrifugation and washing until neutral, it was dried to obtain pretreated nanocellulose; S4: The pretreated nanocellulose was redispersed in water, ultrasonically dispersed for 20 min to form a 3% suspension, and then mixed with a 3% CaCl2 solution in a volume ratio of 1:1 and stirred for 20 min to allow Ca 2+ to be adsorbed on the surface of nanocellulose through electrostatic interaction. After that, it was filtered and washed to remove unadsorbed Ca 2+ , and then the washed nanocellulose was dispersed in a 2% Na2HPO4 solution with the same volume as the CaCl2 solution, the pH was adjusted to 7.5 - 8.5, stirred for 25 min, filtered, washed, and the above alternating deposition steps of CaCl2 and Na2HPO4 were repeated 5 times, and then it was filtered, washed and dried to obtain the product.

[0031] Preparation Example 2.2 A method for preparing mineralized nanocellulose includes the following steps: S1: The nanocellulose was dispersed in water and ultrasonically dispersed for 30 min to form a 4% suspension; S2: Under stirring conditions, NaIO4 was added to the nanocellulose suspension. The mass ratio of NaIO4 to nanocellulose in the suspension was 0.35:1. It was heated to 55 °C and reacted for 4 h in the dark to obtain an aldehyde-functionalized nanocellulose suspension; S3: Adjust the pH of the aldehyde-functionalized nanocellulose suspension obtained in step S2 to 9 - 10 with 1 mol / L NaOH solution, and then oxidize it by introducing ozone-containing gas under light-shielded conditions. The inlet gas flow rate and ozone inlet concentration are 1.8 NL / min and 2.5 wt% respectively, and the gas ventilation time is 16 min. Then, centrifuge, wash until neutral, and dry to obtain pretreated nanocellulose; S4: Redisperse the pretreated nanocellulose in water, form a 4% suspension after ultrasonic treatment for 20 min, and then mix it with 2% CaCl2 solution at a volume ratio of 1:1, and stir for 20 min to make Ca 2+ adsorb on the surface of nanocellulose through electrostatic interaction, and then filter and wash to remove the unadsorbed Ca 2+ , and then disperse the washed nanocellulose in 1% Na2HPO4 solution with the same volume as the CaCl2 solution, adjust the pH to 7.5 - 8.5, stir for 25 min, then filter, wash, and repeat the above alternating deposition steps of CaCl2 and Na2HPO4 4 times, and obtain the product after filtration, washing, and drying.

[0032] Preparation Example 2.3 A method for preparing mineralized nanocellulose, comprising the following steps: S1: Disperse nanocellulose in water and form a 5% suspension after ultrasonic dispersion for 30 min; S2: Add NaIO4 to the nanocellulose suspension under stirring conditions, and the mass ratio of NaIO4 to nanocellulose in the suspension is 0.4:1. Heat it to 55 °C and react for 4 h under light-shielded conditions to obtain an aldehyde-functionalized nanocellulose suspension; S3: Adjust the pH of the aldehyde-functionalized nanocellulose suspension obtained in step S2 to 9 - 10 with 1 mol / L NaOH solution, and then oxidize it by introducing ozone-containing gas under light-shielded conditions. The inlet gas flow rate and ozone inlet concentration are 1.8 NL / min and 2.5 wt% respectively, and the gas ventilation time is 15 min. Then, centrifuge, wash until neutral, and dry to obtain pretreated nanocellulose; S4: Redisperse the pretreated nanocellulose in water, form a 5% suspension after ultrasonic treatment for 20 min, and then mix it with 4% CaCl2 solution at a volume ratio of 1:1, and stir for 20 min to make Ca 2+ adsorb on the surface of nanocellulose through electrostatic interaction, and then filter and wash to remove the unadsorbed Ca 2+ , and then disperse the washed nanocellulose in 3% Na2HPO4 solution with the same volume as the CaCl2 solution, adjust the pH to 7.5 - 8.5, stir for 25 min, then filter, wash, and repeat the above alternating deposition steps of CaCl2 and Na2HPO4 3 times, and obtain the product after filtration, washing, and drying.

[0033] Preparation Example 2.4 A method for preparing mineralized nanocellulose, comprising the following steps: S1: Disperse nanocellulose in water and ultrasonically disperse for 30 min to form a 3% suspension; S2: Mix the suspension with a 3% CaCl2 solution in a volume ratio of 1:1, stir for 20 min to allow Ca 2+ to be adsorbed on the surface of nanocellulose through electrostatic interaction, and then filter and wash to remove the unadsorbed Ca 2+ After that, disperse the washed nanocellulose in a 2% Na2HPO4 solution with the same volume as the CaCl2 solution, adjust the pH to 7.5 - 8.5, stir for 25 min, then filter, wash, and repeat the above alternating deposition steps of CaCl2 and Na2HPO4 5 times. After filtering, washing, and drying, the product is obtained. Example Example 1

[0034] A soft SMS non-woven fabric, comprising a spunbond layer and a meltblown layer. The raw materials and their dosages of the spunbond layer are shown in Table 1. The dopamine-grafted hyperbranched polymer is dopamine-grafted carboxyl-terminated hyperbranched polyester, obtained from Preparation Example 1.1, and the mineralized nanocellulose is obtained from Preparation Example 2.1.

[0035] Table 1

[0036] The method for preparing the above soft SMS non-woven fabric, comprising the following steps: S1: Mix the spunbond PP, PE / PP copolymer, PP-g-MAH, dopamine-grafted hyperbranched polymer, mineralized nanocellulose, and antioxidant 1010 according to the ratio, extrude and melt at 210 °C with a screw extruder, then filter the melt, meter the melt, and transport it to the spinning box. Extrude at an extrusion pressure of 6.5 MPa, cool by air at 12 °C, and obtain the spunbond layer after drawing and laying the web; S2: Mix 50 parts by weight of meltblown PP and 1.5 parts by weight of polyethylene wax, extrude and melt at 210 °C with a screw extruder, then filter the melt, meter the melt, and transport it to the spinning box. Extrude at an extrusion pressure of 6.5 MPa, draw by hot air at 230 °C, cool by air at 20 °C, and evenly lay it on a high-speed running mesh belt to form the meltblown layer; S3: Use the meltblown layer as the intermediate layer, lay the spunbond layer on both sides of the meltblown layer respectively, and perform hot pressing and bonding treatment. The temperature of the hot rolling machine is 145 °C and the pressure is 50 Kpa to obtain an SMS non-woven fabric with a basis weight of 30.7 gsm, wherein the mass ratio of the meltblown layer accounts for 10.5% of the entire SMS non-woven fabric. Example 2

[0037] A soft SMS non-woven fabric, which is different from that of Example 1 in that the raw materials and their dosages of the spunbond layer are shown in Table 1. The specific preparation method includes the following steps: S1: Mix the spunbond PP, PE / PP copolymer, PP-g-MAH, dopamine-grafted hyperbranched polymer, mineralized nanocellulose, and antioxidant 1010 according to the ratio, extrude and melt them at 230 °C with a screw extruder, then after melt filtration and melt metering, transport them to the spinning box, extrude at an extrusion pressure of 6.5 MPa, cool down by air cooling at 12 °C, and obtain the spunbond layer after stretching and laying; S2: Mix 50 parts by weight of meltblown PP and 1.4 parts by weight of polyethylene wax, extrude and melt them at 230 °C with a screw extruder, then after melt filtration and melt metering, transport them to the spinning box, extrude at an extrusion pressure of 6.5 MPa, perform hot air stretching at 250 °C, cool down by air cooling at 20 °C, and evenly lay them on a high-speed running mesh belt to form a meltblown layer; S3: Use the meltblown layer as the middle layer, lay the spunbond layers on both sides of the meltblown layer respectively, and perform hot pressing and bonding treatment. The temperature of the hot rolling machine is 140 °C and the pressure is 55 Kpa to obtain an SMS non-woven fabric with a gram weight of 29.9 gsm, where the mass ratio of the meltblown layer accounts for 9.6% of the entire SMS non-woven fabric. Example 3

[0038] A soft SMS non-woven fabric, which is different from that of Example 1 in that the raw materials and their dosages of the spunbond layer are shown in Table 1. The specific preparation method includes the following steps: S1: Mix the spunbond PP, PE / PP copolymer, PP-g-MAH, dopamine-grafted hyperbranched polymer, mineralized nanocellulose, and antioxidant 1010 according to the ratio, extrude and melt them at 220 °C with a screw extruder, then after melt filtration and melt metering, transport them to the spinning box, extrude at an extrusion pressure of 6.5 MPa, cool down by air cooling at 12 °C, and obtain the spunbond layer after stretching and laying; S2: Mix 50 parts by weight of meltblown PP and 1.7 parts by weight of polyethylene wax, extrude and melt them at 230 °C with a screw extruder, then after melt filtration and melt metering, transport them to the spinning box, extrude at an extrusion pressure of 6.5 MPa, perform hot air stretching at 240 °C, cool down by air cooling at 20 °C, and evenly lay them on a high-speed running mesh belt to form a meltblown layer; S3: Use the meltblown layer as the middle layer, lay the spunbond layers on both sides of the meltblown layer respectively, and perform hot pressing and bonding treatment. The temperature of the hot rolling machine is 150 °C and the pressure is 45 Kpa to obtain an SMS non-woven fabric with a gram weight of 32.1 gsm, where the mass ratio of the meltblown layer accounts for 9.2% of the entire SMS non-woven fabric. Example 4

[0039] A soft SMS non-woven fabric, which is different from that of Example 1 in that the raw materials and dosages of the spunbond layer are shown in Table 1. The specific preparation method includes the following steps: S1: Mix the spunbond PP, PE / PP copolymer, PP-g-MAH, dopamine-grafted hyperbranched polymer, mineralized nanocellulose, and antioxidant 1010 according to the ratio, extrude and melt them at 210 °C with a screw extruder, then transport them to the spinning box after melt filtration and melt metering, extrude them under an extrusion pressure of 6.5 MPa, and cool them by air cooling at 12 °C. After drawing and web laying, a spunbond layer is obtained; S2: Mix 50 parts by weight of meltblown PP and 1.2 parts by weight of polyethylene wax, extrude and melt them at 220 °C with a screw extruder, then transport them to the spinning box after melt filtration and melt metering, extrude them under an extrusion pressure of 6.5 MPa, draw them with hot air at 230 °C, cool them by air cooling at 20 °C, and evenly lay them on a high-speed moving mesh belt to form a meltblown layer; S3: Use the meltblown layer as the intermediate layer, lay the spunbond layers on both sides of the meltblown layer respectively, and perform hot pressing and bonding treatment. The temperature of the hot rolling machine is 145 °C and the pressure is 50 Kpa to obtain an SMS non-woven fabric with a gram weight of 33.2 gsm. The mass ratio of the meltblown layer accounts for 10.4% of the entire SMS non-woven fabric. Example 5

[0040] A soft SMS non-woven fabric, which is different from that of Example 1 in that the mineralized nanocellulose in the spunbond layer raw material is obtained from Preparation Example 2.2, and other steps are the same as those of Example 1. Example 6

[0041] A soft SMS non-woven fabric, which is different from that of Example 1 in that the mineralized nanocellulose in the spunbond layer raw material is obtained from Preparation Example 2.3, and other steps are the same as those of Example 1. Example 7

[0042] A soft SMS non-woven fabric, which is different from that of Example 1 in that the mineralized nanocellulose in the spunbond layer raw material is obtained from Preparation Example 2.4, and other steps are the same as those of Example 1. Comparative Example

[0043] Comparative Example 1 A soft SMS non-woven fabric, which is different from that of Example 1 in that the dopamine-grafted carboxyl-terminated hyperbranched polyester in the spunbond layer raw material is replaced with an equal mass of carboxyl-terminated hyperbranched polyester, and other steps are the same as those of Example 1.

[0044] Comparative Example 2 A soft SMS non-woven fabric, which is different from that in Example 1 in that no dopamine-grafted hyperbranched polymer is added, and the dopamine-grafted carboxyl-terminated hyperbranched polyester in the spunbond layer raw material is replaced with the same mass of spunbond PP, and other steps are the same as those in Example 1.

[0045] Comparative Example 3 A soft SMS non-woven fabric, which is different from that in Example 1 in that the mineralized nanocellulose in the spunbond layer raw material is replaced with the same mass of non-mineralized nanocellulose, and other steps are the same as those in Example 1.

[0046] Comparative Example 4 A soft SMS non-woven fabric, which is different from that in Example 1 in that no mineralized nanocellulose is added, and the mineralized nanocellulose in the spunbond layer raw material is replaced with the same mass of spunbond PP, and other steps are the same as those in Example 1.

[0047] Comparative Example 5 A soft SMS non-woven fabric, which is different from that in Example 1 in that no mineralized nanocellulose and dopamine-grafted hyperbranched polymer are added, and the mineralized nanocellulose and dopamine-grafted hyperbranched polymer in the spunbond layer raw material are replaced with the same mass of spunbond PP, and other steps are the same as those in Example 1. Performance detection test

[0048] The following relevant performance detection tests were carried out on the soft SMS non-woven fabrics obtained in Examples 1-7 and Comparative Examples 1-5. Each group of tests was repeated 3 times, and the average value of the 3 test results was taken as the final result and the final result was recorded in Table 2.

[0049] 1. Tensile strength: Referring to the relevant regulations in GB / T 24218.3-2010 "Textiles - Test methods for non-woven fabrics - Part 3: Determination of tensile strength and elongation at break (strip method)", the tensile strength of the SMS non-woven fabric was detected; 2. Softness: Referring to the relevant regulations in GB / T 8942-2016 "Determination of paper softness", the softness of the SMS non-woven fabric was detected; 3. Air permeability: Referring to the relevant regulations in GB / T 5453 "Determination of fabric air permeability of textiles", a test head of 20 cm 2 was selected, and the air permeability of the SMS non-woven fabric was tested at a pressure difference of 200 Pa; 4. Filtration efficiency: Referring to the medical surgical mask standard YY0469-2011, the test was carried out at a NaCl aerosol flow rate of 28.3 L / min, and the test instrument was a TSI 8130 filtration efficiency detector.

[0050] Table 2

[0051] From the performance test results of Examples 1-6 and Comparative Example 5 in Table 2, it can be seen that the SMS non-woven fabric prepared by using a PE / PP blend, dopamine-grafted hyperbranched polymer, and mineralized nanocellulose as flexible components significantly improves the softness of the non-woven fabric without having an adverse impact on the mechanical properties of the non-woven fabric. Further, by connecting mineralized nanocellulose with other raw materials through a hyperbranched polymer, a more uniform and dense network structure is formed inside the non-woven fabric, which further improves the air permeability of the non-woven fabric on the basis of ensuring the filtration efficiency, and this helps to enhance the use comfort of the non-woven fabric when applied to the fields of medical protection, hygiene products, and industrial filtration.

[0052] From the performance test results of Example 1 and Comparative Examples 3-4, it can be seen that after oxidation and mineralization treatment of nanocellulose, the softness and fluffiness of nanocellulose are further improved, the dispersion uniformity of nanocellulose in the material matrix is promoted, the agglomeration phenomenon of nanocellulose in the material matrix is effectively reduced, and the softness, mechanical properties, and filtration efficiency of the SMS non-woven fabric are significantly improved.

[0053] In Comparative Example 3, nanocellulose was not mineralized and was directly added to the non-woven fabric raw materials. Although it can effectively improve the softness of the non-woven fabric, it significantly sacrifices the mechanical properties of the non-woven fabric. In addition, due to the lack of mineralization treatment, the dispersion uniformity of nanocellulose in the non-woven fabric raw materials decreases, and local agglomeration may occur, and a uniform and dense network structure cannot be formed inside the non-woven fabric, resulting in an impact on the filtration performance of the non-woven fabric.

[0054] In Example 7, nanocellulose was directly mineralized without oxidation modification pretreatment. The adsorption ability of nanocellulose for inorganic particles decreased, and the amount of inorganic particles adsorbed by nanocellulose under the same treatment conditions decreased. Surface mineralization unevenness may occur, resulting in an insignificant strengthening effect of inorganic particles in the non-woven fabric. In addition, the softness of nanocellulose without oxidation modification treatment was further improved compared with the group with oxidation modification treatment.

[0055] From the performance test results of Example 1 and Comparative Examples 1-2, it can be seen that the use of dopamine-grafted carboxyl-terminated hyperbranched polyester not only helps to improve the softness of the non-woven fabric, but also can improve the compatibility between the non-woven fabric raw materials through its molecular bridge effect, thereby improving the mechanical properties and filtration performance of the non-woven fabric.

[0056] In Comparative Example 1, the terminal carboxyl hyperbranched polyester was not grafted with dopamine, and the softness, mechanical properties, and filtration efficiency of the non-woven fabric all decreased. This is because the grafting method of dopamine introduced catechol groups into the hyperbranched polymer, endowing the hyperbranched polymer with a flexible backbone and a polar lubricating layer. The dopamine-grafted hyperbranched polymer can act as a molecular bridge inside the spunbond layer, and enhance the compatibility between the mineralized nanocellulose and the spunbond PP matrix through the interaction between the catechol groups and the ions on the surface of the mineralized nanocellulose, promoting the formation of a more uniform and dense network structure inside the non-woven fabric, thereby ensuring that the filtration efficiency and mechanical properties of the non-woven fabric are stable and not affected.

[0057] In Comparative Example 2, dopamine-grafted terminal carboxyl hyperbranched polyester was not added, and only mineralized nanocellulose was added as a functional component to improve softness. All properties of the non-woven fabric were adversely affected. This is because the hyperbranched polymer has a highly branched three-dimensional dendritic structure with less entanglement between molecular chains and low melt viscosity. It can not only act as a molecular-level lubricant in the spunbond layer, reduce internal friction, significantly reduce the bending stiffness of the non-woven fabric, and increase the flexibility and fluffiness of the non-woven fabric, but also through the molecular bridge effect, on the one hand, covalently connect with the anhydride groups of PP-g-MAH and anchor in the PP matrix, and on the other hand, form a hydrogen bond network with the calcium phosphate mineralized layer on the surface of the mineralized nanocellulose to uniformly disperse the mineralized nanocellulose in the PP matrix, enhancing the compatibility between the mineralized nanocellulose and the spunbond PP matrix and ensuring that the mechanical properties and filtration efficiency of the non-woven fabric are not affected.

[0058] This specific embodiment is only an explanation of the present application and does not limit the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A soft SMS non-woven fabric, comprising a spunbond layer and a meltblown layer, characterized in that, By weight, the raw materials of the spunbond layer include 65-80 parts of spunbond PP, 5-10 parts of PE / PP copolymer, 2-4 parts of PP-g-MAH, 4-6 parts of dopamine-grafted hyperbranched polymer, and 7-11 parts of mineralized nanocellulose.

2. The soft SMS non-woven fabric according to claim 1, wherein The dopamine-grafted hyperbranched polymer is dopamine-grafted carboxyl-terminated hyperbranched polyester.

3. The soft SMS non-woven fabric according to claim 2, characterized in that, The preparation method of the dopamine-grafted carboxyl-terminated hyperbranched polyester includes the following steps: S1: Dissolve the carboxyl-terminated hyperbranched polyester in water, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide under the protection of inert gas for stirring activation, then add dopamine hydrochloride, adjust the pH to alkaline, and obtain a reaction solution after reacting in the dark. S2: Add the reaction solution to ether for precipitation, collect the crude product after centrifugation, and obtain the product after dialysis and drying.

4. The soft SMS non-woven fabric according to claim 1, wherein, The preparation method of the mineralized nanocellulose includes the following steps: Disperse the nanocellulose in water and form a suspension by ultrasonic treatment. Mix the suspension with a CaCl2 solution, stir, filter, and wash. Then disperse the washed nanocellulose in a Na2HPO4 solution, adjust the pH to alkaline, stir, filter, and wash. Repeat the above alternating deposition steps of CaCl2 and Na2HPO4, and obtain the product after filtration, washing, and drying.

5. The soft SMS non-woven fabric according to claim 4, wherein, The following pretreatment is carried out on the nanocellulose: Add NaIO4 to the nanocellulose suspension, heat and react in the dark to obtain an aldehyde-functionalized nanocellulose suspension. Then adjust the pH of the aldehyde-functionalized nanocellulose suspension to alkaline, introduce a gas containing ozone for oxidation, and obtain the pretreated nanocellulose after centrifugation, washing, and drying.

6. The soft SMS non-woven fabric according to claim 1, wherein The raw materials of the meltblown layer include meltblown PP. The melt index of the spunbond PP is 40-45 g / min, and the melt index of the meltblown PP is 1200-1500 g / min.

7. A method for preparing a soft SMS non-woven fabric according to any one of claims 1-6, characterized in that, It includes the following steps: Mix the raw materials of the spunbond layer according to the ratio, and obtain the spunbond layer through screw extrusion melting, spinning, cold air drawing, and web laying; mix the raw materials of the meltblown layer according to the ratio, and obtain the meltblown layer through screw extrusion melting, spinning, hot air drawing, cooling, and web laying; use the meltblown layer as the intermediate layer, lay the spunbond layer on both sides of the meltblown layer respectively, and obtain the product after hot pressing and bonding.

8. The preparation method of a soft SMS non-woven fabric according to claim 7, characterized in that, When preparing the spunbond layer and the meltblown layer by screw extrusion melting, the screw temperature is 210-230 °C. When preparing the meltblown layer by hot air drawing, the hot air temperature is 230-250 °C.

Images