Process for producing a nonwoven fabric having low hydrophilicity and low water permeability

Abstract

The present application relates to a kind of weakly hydrophilic low back permeable non-woven fabric preparation method, mainly including the following sequentially performed steps: (1) preparation of hydrophobic modified viscose fiber: dissolved pulp with coniferous wood and broadleaf wood dissolved pulp is prepared viscose staple fiber;Again, through water-repellent finishing and other processes, obtain hydrophobic modified viscose fiber;(2) preparation of weakly hydrophilic low back permeable non-woven fabric: hydrophobic modified viscose fiber is sequentially subjected to opening, carding and water jet processing steps, then through hydrophilic finishing and drying, weakly hydrophilic low back permeable non-woven fabric is obtained.The present application solves the shortcomings that existing non-woven fabric is difficult to simultaneously meet the liquid rapid infiltration and low back permeation amount, by using the preferred water-repellent finishing liquid to hydrophobically modify the viscose fiber first, then using the preferred hydrophilic finishing liquid to hydrophilically modify, weakly hydrophilic low back permeable non-woven fabric is obtained, which has the characteristics of biodegradable, can make liquid rapid infiltration and low back permeation amount.

Description

Technical Field

[0001] This invention relates to a method for preparing a weakly hydrophilic, low-reweave nonwoven fabric, which is applied in the field of nonwoven fabric processing. Background Technology

[0002] The surface layer is a crucial component of disposable hygiene products such as diapers and sanitary napkins, coming into direct contact with human skin and requiring dryness, comfort, softness, and breathability. To address the dryness issue encountered in the use of surface layers in diapers and other hygiene products, patent ZL201911051405.7 discloses a nonwoven fabric that allows liquid to quickly seep down and inhibits backflow; however, the ES fibers used in this fabric are difficult to biodegrade, thus posing an environmental pollution problem. Patent application CN202011286077.1 discloses a method for preparing a hydrophilic low-backflow nonwoven fabric, comprising a hydrophobic layer, an absorbent layer, and a hydrophilic layer; its structure is complex, and the nonwoven fibers used in the hydrophobic layer are any one or a combination of several of polyester, nylon, spandex, polypropylene, chlorofiber, and acrylic fibers, thus posing a problem of difficult biodegradability and environmental pollution. Patent application CN 202011395132.0 discloses a hydrophilic nonwoven fabric for hygiene products and its preparation method. It uses concave embossing and perforation design to solve problems such as surface dryness and liquid seepage. The nonwoven fabric body includes an integrated upper nonwoven fabric and a lower nonwoven fabric. The upper nonwoven fabric is a weakly hydrophilic fiber nonwoven fabric, and the lower nonwoven fabric is a single hydrophilic fiber nonwoven fabric. It also describes the beneficial effects of using the weakly hydrophilic nonwoven fabric, namely, good vertical liquid seepage effect, no lateral diffusion on the surface, relatively low backflow, and relatively dry surface. However, this patent application does not disclose the fiber composition used in the weakly hydrophilic nonwoven fabric or its preparation method.

[0003] Patent ZL202110676881.9 discloses a method for preparing hydrophobic cellulose nonwoven fabric for medical and health purposes. The preparation method is as follows: after hydrophobic modification of cellulose fibers, the cellulose fibers are combed into a web, and the nonwoven fabric is made by hydroentangling reinforcement process of cellulose nonwoven fabric, thus obtaining hydrophobic cellulose nonwoven fabric for medical and health purposes. The hydrophobic modification process is as follows: after mixing cellulose fibers with isocyanate solution, the mixture is heated to 60-90℃ and kept at that temperature for 5-20 minutes. However, if the isocyanate solution is directly added to the oiling process of viscose fibers, there are problems with the compatibility of isocyanate and spinning oil or chemical reaction. Moreover, this hydrophobic modification technology is difficult to apply to the existing viscose fiber post-processing process where the fiber water-repellent finishing time does not exceed 3 minutes and the fiber drying time does not exceed 0.5 hours. Furthermore, as can be seen from the embodiments and Figure 1 in the patent specification, the fabric sample still exhibits good hydrophobic properties. Therefore, if this fabric sample is applied to the surface material of disposable hygiene products such as diapers and sanitary napkins, there is a problem that it is difficult for liquids to quickly seep through. Patent application CN202111567669.5 discloses a hydrophobically modified viscose fiber and its preparation method, which solves the compatibility problem of mixing polyurethane hydrophobic agents and oil agents. However, it does not involve the preparation technology of low-rewetting fabric samples, and because it uses a silicon-containing hydrophobic agent, it is easy to cause the ash content of the hydrophobically modified fiber to be too high.

[0004] Therefore, it has become an urgent task to provide a method for preparing a biodegradable nonwoven fabric that is weakly hydrophilic and has low backflow, which can simultaneously satisfy the requirements of rapid liquid infiltration and low backflow. Summary of the Invention

[0005] To address the problem that existing nonwoven fabrics cannot simultaneously achieve rapid liquid penetration and low backflow, this invention provides a method for preparing a weakly hydrophilic, low-backflow nonwoven fabric. The method involves first hydrophobically modifying viscose fibers with a water-repellent finishing liquid prepared from a fluorine-free, silicone-free hydrophobic agent (or waterproofing agent), and then hydrophilically modifying the hydrophobically modified nonwoven fabric prepared using the same liquid with a hydrophilic finishing liquid. This results in a weakly hydrophilic, low-backflow nonwoven fabric that is biodegradable, allows for rapid liquid penetration, and has low backflow. The weakly hydrophilic, low-backflow nonwoven fabric described here refers to a nonwoven fabric after hydrophilic modification that meets the following requirements: first absorption rate ≤ 30s, second absorption rate ≤ 50s, backflow ≤ 2.5g, and droplet diffusion area not exceeding half that of a nonwoven fabric made from ordinary viscose fibers (i.e., a blank sample, such as the fabric sample prepared in Comparative Example 1).

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a weakly hydrophilic, low-rewetting nonwoven fabric mainly includes the following steps performed in sequence:

[0008] (I) Preparation of hydrophobically modified viscose fibers:

[0009] Softwood dissolving pulp and hardwood dissolving pulp with whiteness ≥89% and methyl cellulose content ≥90% are selected. The softwood dissolving pulp and hardwood dissolving pulp are mixed at a mass ratio of 6-7:100. Then, viscose spinning dope is prepared by impregnation, pressing, crushing, aging, xanthation, dissolving and maturation. Viscose staple fiber is obtained by spinning with this viscose spinning dope. The viscose staple fiber is then fed into a scouring machine and undergoes a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, water-repellent finishing and drying to obtain hydrophobic modified viscose fiber.

[0010] The water-repellent finishing step involves spraying a water-repellent finishing liquid onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the underlying layers, and then removing excess liquid by rollers. This results in the viscose staple fiber adsorbing an appropriate amount of the water-repellent finishing liquid. The mass ratio of viscose staple fiber to water-repellent finishing liquid is 1:5-1:10. The water-repellent finishing liquid is prepared by the following steps:

[0011] ① Heat water to 55-65℃, and add fiber oiling agent to the water while stirring to prepare an oil bath solution with a fiber oiling agent concentration of 3-3.5 g / L. The fiber oiling agent is anionic.

[0012] ② First, add sulfuric acid to the oil bath obtained in step ① to adjust the pH value of the oil bath to 3.5-4.0. Then add hydrogen peroxide to make the concentration of hydrogen peroxide in the oil bath 0.4-0.8 g / L. Mix well to obtain a mixed solution.

[0013] ③ Heat the mixture obtained in step ② to 73-77℃, then add a dispersant at a concentration of 1-2 g / L and mix for 10-15 minutes; then add a hydrophobic agent at a concentration of 5-15 g / L and mix for 10-15 minutes; then add a crosslinking agent at a mass ratio of 1:10-1:20 to the hydrophobic agent and mix thoroughly to obtain the water-repellent finishing solution.

[0014] The hydrophobic agent is an acrylate hydrophobic agent (or waterproofing agent, which can be purchased externally); the crosslinking agent is a polyurethane resin crosslinking agent (or crosslinking agent, which can be purchased externally).

[0015] (II) Preparation of weakly hydrophilic, low-re-permeability nonwoven fabric:

[0016] The hydrophobic modified viscose fiber obtained in step (1) is sequentially processed through opening, carding and hydroentangling to form a hydrophobic modified nonwoven fabric. Then, it is sequentially processed through hydrophilic finishing and drying to obtain the weakly hydrophilic and low-rebleed nonwoven fabric.

[0017] The hydrophilic finishing step involves impregnating the hydrophobic modified nonwoven fabric with a hydrophilic finishing solution. The mass ratio of the hydrophobic modified nonwoven fabric to the hydrophilic finishing solution is 1:5 to 1:10. The hydrophilic finishing solution is prepared by diluting the hydrophilic finishing agent with water at a volume ratio of 1:50 to 1:100. The hydrophilic finishing agent contains a thermally reactive nonionic waterborne polyurethane.

[0018] The method for preparing the weakly hydrophilic, low-reweave nonwoven fabric of this application involves first modifying viscose fibers with a hydrophobic finishing liquid containing a fluorine-free and silicone-free hydrophobic agent to obtain hydrophobically modified viscose fibers; then, using a preferred hydrophilic finishing liquid, modifying the hydrophobically modified nonwoven fabric with hydrophilicity to obtain a weakly hydrophilic, low-reweave nonwoven fabric. This weakly hydrophilic, low-reweave nonwoven fabric is biodegradable, allows liquids to quickly penetrate, and has a low reweave amount.

[0019] Traditional methods of preparing spunlace nonwoven fabrics using hydrophobically modified viscose fibers result in poor surface dryness because the fabric samples only possess hydrophobic properties and lack hydrophilic properties, making it difficult for liquids to penetrate quickly. This invention further modifies the hydrophobic fabric samples to facilitate rapid liquid penetration, incorporating appropriate amounts of hydrophilic groups into the fabric surface, thereby improving the surface's wetting properties and facilitating liquid penetration through the fabric's mesh openings. Furthermore, the preferred use of acrylate hydrophobic agents and polyurethane resin crosslinking agents in this application results in hydrophobically modified viscose fibers with superior hydrophobic properties and a certain degree of wash resistance, making them suitable for both textile and nonwoven applications. The preparation of the water-repellent finishing solution involves adding the dispersant first, followed by the hydrophobic agent, avoiding the agglomeration problem that easily occurs when mixing hydrophobic agents and oils. However, the amount of dispersant should not be too high, otherwise it will affect the fiber's hydrophobic properties. This application first prepares hydrophobically modified viscose fibers, and then performs hydrophilic modification on fabric samples prepared with these fibers. This helps ensure the stability of the final nonwoven fabric performance and avoids the fluctuations in the permeability of nonwoven fabrics caused by fluctuations in the concentration of hydrophobic agents, which exists in existing methods for hydrophobically modifying fabric samples prepared with ordinary viscose fibers. To allow liquids to quickly permeate the surface layer of hygiene products such as diapers, the surface layer needs to have a certain degree of hydrophilicity. However, if too much hydrophilic agent is added during the nonwoven fabric production process, the amount of backflow will increase. Conversely, if too little hydrophilic agent is added, it will be difficult for the liquid to permeate quickly. Only when the content of hydrophilic agent adsorbed on the surface of the hydrophobically modified viscose fibers in this application reaches an appropriate level can both rapid liquid permeation and effective inhibition of backflow be achieved. The preferred proportion of hydrophilic finishing liquid in this application effectively ensures that the nonwoven fabric meets the performance requirements for surface materials used in hygiene products. In this application, a preferred crosslinking agent is a polyurethane resin crosslinking agent. Adding a small amount of crosslinking agent is beneficial for improving the hydrophobicity and washability of the fiber, reducing the amount of hydrophobic agent used, and lowering production costs. The preferred thermally reactive nonionic waterborne polyurethane in this application has reactive groups and nonionic hydrophilic segments. At high temperatures, it can react with active groups such as amino and hydroxyl groups on the hydrophobically modified viscose fiber. The polyurethane itself can also undergo a crosslinking reaction, thereby forming a three-dimensional network structure that is fixed on the surface of the nonwoven fabric, giving the fabric made of hydrophobic fibers a certain degree of hydrophilicity.

[0020] The hydrophobic modified viscose fiber obtained in step (I) meets the following standards (testing methods refer to industry standard FZT 54032): fineness 1.65~1.75dtex; length 40mm; dry breaking strength ≥2.1cN / dtex; dry breaking elongation 18%~22%; whiteness ≥86%; water absorption time ≥1800s. The weakly hydrophilic, low-rewetting nonwoven fabric finally obtained in this case meets the following standards: nonwoven fabric basis weight 38-45g / m², first absorption rate ≤30s, second absorption rate ≤50s, rewetting amount ≤2.5g, and the drip diffusion area does not exceed half of the nonwoven fabric made of ordinary viscose fiber (i.e., blank sample, such as the fabric sample prepared in Comparative Example 1).

[0021] The dispersant (or anti-precipitation dispersant, which can be purchased externally) is a cationic surfactant.

[0022] The preferred dispersant has better dispersing and anti-settling effects, which is more conducive to ensuring the stability of the oil bath.

[0023] The spinning speed in step (1) is 56-59 m / min, and the drying temperature is 135-145℃.

[0024] If the drying temperature is too low, it is difficult to ensure the binding effect of the hydrophobic agent with the fiber; if the drying temperature is too high, the fiber is easily oxidized and turns yellow. If the spinning speed is too low, the cost will be high; if the spinning speed is too high, it is difficult to ensure that the moisture regain of the fiber meets the requirements.

[0025] The drying temperature mentioned in step (ii) is 135-145℃.

[0026] If the drying temperature is too low, it will be difficult to ensure the bonding effect between the hydrophilic agent and the fabric sample; if the drying temperature is too high, the fabric sample will easily be oxidized and turn yellow.

[0027] Compared with the prior art, this invention application has the following advantages:

[0028] The method for preparing a weakly hydrophilic, low-reflow nonwoven fabric of this application involves first modifying viscose fibers with a hydrophobic finishing liquid prepared by using a preferred hydrophobic agent and a crosslinking agent, and then modifying them with a preferred hydrophilic finishing liquid to obtain a weakly hydrophilic, low-reflow nonwoven fabric, which has the characteristics of allowing liquid to penetrate quickly and having a low reflow rate. Detailed Implementation

[0029] The technical solution of the present invention will be described in detail below with reference to the various embodiments in the specification.

[0030] Example 1

[0031] The method for preparing a weakly hydrophilic, low-re-permeability nonwoven fabric according to the present invention mainly includes the following steps performed in sequence:

[0032] (I) Preparation of hydrophobically modified viscose fibers:

[0033] Softwood dissolving pulp and hardwood dissolving pulp with a whiteness of ≥89% and a methyl cellulose content of ≥90% were selected. The softwood dissolving pulp and hardwood dissolving pulp were mixed at a mass ratio of 6:100. Then, viscose spinning dope was prepared by sequentially impregnating, pressing, crushing, aging, xanthation, dissolving, and maturing. Viscose staple fiber was obtained by spinning with this viscose spinning dope. The viscose staple fiber was then fed into a refining machine and sequentially subjected to washing, desulfurization, washing, bleaching, washing, final washing, water-repellent finishing, and drying processes to obtain hydrophobic modified viscose fiber. The spinning speed was 56 m / min, and the drying temperature was 135℃.

[0034] The water-repellent finishing step involves spraying a water-repellent finishing liquid onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the underlying layers, and then rolling off excess liquid with rollers. This results in the viscose staple fiber adsorbing an appropriate amount of the water-repellent finishing liquid. The mass ratio of the viscose staple fiber to the water-repellent finishing liquid is 1:5. The water-repellent finishing liquid is prepared by the following steps:

[0035] ① Heat water to 55℃, and add fiber oiling agent to the water while stirring to prepare an oil bath solution with a fiber oiling agent concentration of 3.5g / L. The fiber oiling agent is anionic.

[0036] ② First, add sulfuric acid to the oil bath obtained in step ① to adjust the pH value of the oil bath to 3.8, then add hydrogen peroxide to make the concentration of hydrogen peroxide in the oil bath 0.4g / L, mix evenly to obtain a mixed solution;

[0037] ③ Heat the mixture obtained in step ② to 73°C, then add a dispersant at a concentration of 1 g / L and mix for 10 minutes; then add a hydrophobic agent at a concentration of 5 g / L and mix for 10 minutes; then add a crosslinking agent at a mass ratio of 1:10 to the hydrophobic agent and mix thoroughly to obtain the water-repellent finishing solution.

[0038] The dispersant is a cationic surfactant; the hydrophobic agent is an acrylate waterproofing agent; and the crosslinking agent is a polyurethane resin crosslinking agent.

[0039] The technical parameters of the hydrophobic modified viscose fiber obtained by the above steps are as follows: fineness 1.65 dtex; length 40 mm; dry breaking strength 2.2 cN / dtex; dry breaking elongation 18%; whiteness 87%; water absorption time ≥1800 s.

[0040] (II) Preparation of weakly hydrophilic, low-re-permeability nonwoven fabric:

[0041] The hydrophobic modified viscose fiber obtained in step (1) is sequentially processed through opening, carding and hydroentangling to form a hydrophobic modified nonwoven fabric. Then, it is sequentially processed through hydrophilic finishing and drying to obtain the weakly hydrophilic and low-reweave nonwoven fabric with a basis weight of 38 g / m². The drying temperature is 135°C.

[0042] The hydrophilic finishing step involves impregnating the hydrophobic modified nonwoven fabric with a hydrophilic finishing solution. The mass ratio of the hydrophobic modified nonwoven fabric to the hydrophilic finishing solution is 1:5. The hydrophilic finishing solution is prepared by diluting the hydrophilic finishing agent and water at a volume ratio of 1:100. The hydrophilic finishing agent contains a thermally reactive nonionic waterborne polyurethane.

[0043] Example 2

[0044] The method for preparing a weakly hydrophilic, low-re-permeability nonwoven fabric according to the present invention mainly includes the following steps performed in sequence:

[0045] (I) Preparation of hydrophobically modified viscose fibers:

[0046] Softwood dissolving pulp and hardwood dissolving pulp with a whiteness of ≥89% and a methyl cellulose content of ≥90% were selected. The softwood dissolving pulp and hardwood dissolving pulp were mixed at a mass ratio of 7:100. Then, viscose spinning dope was prepared by impregnation, pressing, crushing, aging, xanthation, dissolution and maturation. Viscose staple fiber was obtained by spinning with this viscose spinning dope. The viscose staple fiber was then fed into a refining machine and subjected to a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, water-repellent finishing and drying to obtain hydrophobic modified viscose fiber. The spinning speed was 59 m / min and the drying temperature was 145℃.

[0047] The water-repellent finishing step involves spraying a water-repellent finishing liquid onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the underlying layers, and then rolling off excess liquid with rollers. This results in the viscose staple fiber adsorbing an appropriate amount of the water-repellent finishing liquid. The mass ratio of the viscose staple fiber to the water-repellent finishing liquid is 1:10. The water-repellent finishing liquid is prepared by the following steps:

[0048] ① Heat water to 65℃, and add fiber oiling agent to the water while stirring to prepare an oil bath solution with a fiber oiling agent concentration of 3g / L. The ionic nature of the fiber oiling agent is anionic.

[0049] ② First, add sulfuric acid to the oil bath obtained in step ① to adjust the pH value of the oil bath to 3.5, then add hydrogen peroxide to make the concentration of hydrogen peroxide in the oil bath 0.8g / L, mix evenly to obtain a mixed solution;

[0050] ③ Heat the mixture obtained in step ② to 77°C, then add a dispersant at a concentration of 2 g / L and mix for 12 minutes; then add a hydrophobic agent at a concentration of 15 g / L and mix for 12 minutes; then add a crosslinking agent at a mass ratio of 1:20 to the hydrophobic agent and mix thoroughly to obtain the water-repellent finishing solution.

[0051] The dispersant is a cationic surfactant; the hydrophobic agent is an acrylate waterproofing agent; and the crosslinking agent is a polyurethane resin crosslinking agent.

[0052] The technical parameters of the hydrophobically modified viscose fiber obtained by the above steps are as follows: fineness 1.75 dtex; length 40 mm; dry breaking strength 2.1 cN / dtex; dry breaking elongation 22%; whiteness 86%; water absorption time ≥3600s.

[0053] (II) Preparation of weakly hydrophilic, low-re-permeability nonwoven fabric:

[0054] The hydrophobic modified viscose fiber obtained in step (I) is sequentially processed through opening, carding and hydroentangling to form a hydrophobic modified nonwoven fabric. Then, it is sequentially processed through hydrophilic finishing and drying to obtain the weakly hydrophilic and low-reweave nonwoven fabric with a basis weight of 45 g / m². The drying temperature is 145°C.

[0055] The hydrophilic finishing step involves impregnating the hydrophobic modified nonwoven fabric with a hydrophilic finishing solution. The mass ratio of the hydrophobic modified nonwoven fabric to the hydrophilic finishing solution is 1:10. The hydrophilic finishing solution is prepared by diluting the hydrophilic finishing agent and water at a volume ratio of 1:50. The hydrophilic finishing agent contains a thermally reactive nonionic waterborne polyurethane.

[0056] Example 3

[0057] The method for preparing a weakly hydrophilic, low-re-permeability nonwoven fabric according to the present invention mainly includes the following steps performed in sequence:

[0058] (I) Preparation of hydrophobically modified viscose fibers:

[0059] Softwood dissolving pulp and hardwood dissolving pulp with a whiteness of ≥89% and a methyl cellulose content of ≥90% were selected. The softwood dissolving pulp and hardwood dissolving pulp were mixed at a mass ratio of 6.5:100. Then, viscose spinning dope was prepared by impregnation, pressing, crushing, aging, xanthation, dissolving and maturation. Viscose staple fiber was obtained by spinning with this viscose spinning dope. The viscose staple fiber was then fed into a scouring machine and subjected to a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, water-repellent finishing and drying to obtain hydrophobic modified viscose fiber. The spinning speed was 57 m / min and the drying temperature was 140℃.

[0060] The water-repellent finishing step involves spraying a water-repellent finishing liquid onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the underlying layers, and then rolling off excess liquid with rollers. This results in the viscose staple fiber adsorbing an appropriate amount of the water-repellent finishing liquid. The mass ratio of the viscose staple fiber to the water-repellent finishing liquid is 1:8. The water-repellent finishing liquid is prepared by the following steps:

[0061] The water-repellent finishing step involves spraying a water-repellent finishing liquid onto the surface of the viscose staple fiber, allowing the liquid to penetrate into the lower layer of the fiber, and then removing excess liquid by rollers, thereby enabling the viscose staple fiber to absorb an appropriate amount of the water-repellent finishing liquid. The mass ratio of the viscose staple fiber to the water-repellent finishing liquid is 1:8. The water-repellent finishing liquid is prepared by the following steps:

[0062] ① Heat water to 60℃, and add fiber oiling agent to the water while stirring to prepare an oil bath solution with a fiber oiling agent concentration of 3.2g / L. The fiber oiling agent is anionic.

[0063] ② First, add sulfuric acid to the oil bath obtained in step ① to adjust the pH value of the oil bath to 4.0. Then add hydrogen peroxide to make the concentration of hydrogen peroxide in the oil bath 0.5g / L. Mix well to obtain a mixed solution.

[0064] ③ Heat the mixture obtained in step ② to 75°C, then add a dispersant at a concentration of 1.2 g / L and mix for 15 minutes; then add a hydrophobic agent at a concentration of 8 g / L and mix for 15 minutes; then add a crosslinking agent at a mass ratio of 1:12 to the hydrophobic agent and mix thoroughly to obtain the water-repellent finishing solution.

[0065] The dispersant is a cationic surfactant; the hydrophobic agent is an acrylate waterproofing agent; and the crosslinking agent is a polyurethane resin crosslinking agent.

[0066] The technical parameters of the hydrophobically modified viscose fiber obtained by the above steps are as follows: fineness 1.7 dtex; length 40 mm; dry breaking strength 2.25 cN / dtex; dry breaking elongation 20%; whiteness 87%; water absorption time ≥4800s.

[0067] (II) Preparation of weakly hydrophilic, low-re-permeability nonwoven fabric:

[0068] The hydrophobic modified viscose fiber obtained in step (1) is sequentially processed through opening, carding and hydroentangling to form a hydrophobic modified nonwoven fabric. Then, it is sequentially processed through hydrophilic finishing and drying to obtain the weakly hydrophilic and low-reweave nonwoven fabric with a basis weight of 40 g / m². The drying temperature is 140°C.

[0069] The hydrophilic finishing step involves impregnating the hydrophobic modified nonwoven fabric with a hydrophilic finishing solution. The mass ratio of the hydrophobic modified nonwoven fabric to the hydrophilic finishing solution is 1:7. The hydrophilic finishing solution is prepared by diluting the hydrophilic finishing agent and water at a volume ratio of 1:80. The hydrophilic finishing agent contains a thermally reactive nonionic waterborne polyurethane.

[0070] Experimental data:

[0071] I. Comparison Sample

[0072] Comparative Example 1 (Blank Sample)

[0073] (1) Preparation of viscose fiber:

[0074] Softwood dissolving pulp and hardwood dissolving pulp with a whiteness of ≥89% and a methyl cellulose content of ≥90% are selected. The softwood dissolving pulp and hardwood dissolving pulp are mixed at a mass ratio of 6.5:100. Then, viscose spinning dope is prepared by impregnation, pressing, crushing, aging, xanthation, dissolving and maturation. Viscose staple fiber is obtained by spinning with this viscose spinning dope. The viscose staple fiber is then fed into a refining machine and undergoes a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying to obtain viscose fiber. The spinning speed is 57 m / min and the drying temperature is 140℃.

[0075] The oiling step involves spraying an oil bath mixture onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the underlying layers. Excess liquid is then removed by rollers, resulting in the viscose staple fiber absorbing an appropriate amount of the oil bath mixture. The mass ratio of viscose staple fiber to oil bath mixture is 1:8. The oil bath mixture is prepared using the following steps:

[0076] ① Heat water to 60℃, and add fiber oiling agent to the water while stirring to prepare an oil bath solution with a fiber oiling agent concentration of 3.2g / L. The fiber oiling agent is anionic.

[0077] ② First, add sulfuric acid to the oil bath obtained in step ① to adjust the pH value of the oil bath to 3.8, then add hydrogen peroxide to make the concentration of hydrogen peroxide in the oil bath 0.5g / L, mix evenly to obtain a mixed solution;

[0078] ③ Heat the mixture obtained in step ② to 75°C to obtain the oil bath mixture.

[0079] The technical parameters of the viscose fiber obtained by the above steps are as follows: fineness 1.7 dtex; length 40 mm; dry breaking strength 2.3 cN / dtex; dry breaking elongation 19.5%; whiteness 88%; water absorption time 4 s.

[0080] (2) Preparation of nonwoven fabric:

[0081] The viscose fibers obtained in step (1) are sequentially processed through opening, carding and hydroentangling, and then dried to produce a nonwoven fabric with a weight of 40 g / m². The drying temperature is 140°C.

[0082] The main difference between Comparative Example 1 and Example 3 is that the viscose fiber was not hydrophobically modified, and the nonwoven fabric was not hydrophilically modified.

[0083] Comparative Example 2

[0084] (1) Preparation of hydrophobic modified viscose fibers:

[0085] Softwood dissolving pulp and hardwood dissolving pulp with a whiteness of ≥89% and a methyl cellulose content of ≥90% were selected. The softwood dissolving pulp and hardwood dissolving pulp were mixed at a mass ratio of 6.5:100. Then, viscose spinning dope was prepared by impregnation, pressing, crushing, aging, xanthation, dissolution and maturation. Viscose staple fiber was obtained by spinning with the viscose spinning dope. The viscose staple fiber was then fed into a scouring machine and subjected to a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, water-repellent finishing and drying to obtain hydrophobic modified viscose fiber. The spinning speed was 57 m / min and the drying temperature was 140℃.

[0086] The water-repellent finishing step involves spraying a water-repellent finishing liquid onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the underlying layers, and then rolling off excess liquid with rollers. This results in the viscose staple fiber adsorbing an appropriate amount of the water-repellent finishing liquid. The mass ratio of the viscose staple fiber to the water-repellent finishing liquid is 1:8. The water-repellent finishing liquid is prepared by the following steps:

[0087] ① Heat water to 60℃, and add fiber oiling agent to the water while stirring to prepare an oil bath solution with a fiber oiling agent concentration of 3.2g / L. The fiber oiling agent is anionic.

[0088] ② First, add sulfuric acid to the oil bath obtained in step ① to adjust the pH value of the oil bath to 3.8, then add hydrogen peroxide to make the concentration of hydrogen peroxide in the oil bath 0.5g / L, mix evenly to obtain a mixed solution;

[0089] ③ Heat the mixture obtained in step ② to 75°C, then add a dispersant at a concentration of 1.2 g / L and mix for 10 minutes; then add a hydrophobic agent at a concentration of 8 g / L and mix for 10 minutes; then add a crosslinking agent at a mass ratio of 1:12 to the hydrophobic agent and mix thoroughly to obtain the water-repellent finishing solution.

[0090] The dispersant is a cationic surfactant; the hydrophobic agent is an acrylate waterproofing agent; and the crosslinking agent is a polyurethane resin crosslinking agent.

[0091] The technical parameters of the hydrophobically modified viscose fiber obtained by the above steps are as follows: fineness 1.7 dtex; length 40 mm; dry breaking strength 2.25 cN / dtex; dry breaking elongation 20%; whiteness 87%; water absorption time ≥4800s.

[0092] (2) Preparation of nonwoven fabric:

[0093] The hydrophobic modified viscose fiber obtained in step (1) is sequentially processed through opening, carding and hydroentangling, and then dried to produce a nonwoven fabric with a weight of 40 g / m²; the drying temperature is 140°C.

[0094] The difference between Comparative Example 2 and Example 3 is that step (2) did not involve hydrophilic finishing.

[0095] Comparative Example 3

[0096] (1) Preparation of viscose fiber:

[0097] Softwood dissolving pulp and hardwood dissolving pulp with a whiteness of ≥89% and a methyl cellulose content of ≥90% are selected. The softwood dissolving pulp and hardwood dissolving pulp are mixed at a mass ratio of 6.5:100. Then, viscose spinning dope is prepared by impregnation, pressing, crushing, aging, xanthation, dissolving and maturation. Viscose staple fiber is obtained by spinning with this viscose spinning dope. The viscose staple fiber is then fed into a refining machine and undergoes a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying to obtain viscose fiber. The spinning speed is 57 m / min and the drying temperature is 140℃.

[0098] The oiling step involves spraying an oil bath mixture onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the underlying layers. Excess liquid is then removed by rollers, allowing the viscose staple fiber to absorb an appropriate amount of the oil bath mixture. The mass ratio of viscose staple fiber to oil bath mixture is 1:8. The oil bath mixture is prepared using the following steps:

[0099] ① Heat water to 60℃, and add fiber oiling agent to the water while stirring to prepare an oil bath solution with a fiber oiling agent concentration of 3.2g / L. The fiber oiling agent is anionic.

[0100] ② First, add sulfuric acid to the oil bath obtained in step ① to adjust the pH value of the oil bath to 3.8, then add hydrogen peroxide to make the concentration of hydrogen peroxide in the oil bath 0.5g / L, mix evenly to obtain a mixed solution;

[0101] ③ Heat the mixture obtained in step ② to 75°C to obtain the oil bath mixture.

[0102] The technical parameters of the viscose fiber obtained by the above steps are as follows: fineness 1.7 dtex; length 40 mm; dry breaking strength 2.3 cN / dtex; dry breaking elongation 19.5%; whiteness 88%; water absorption time 4 s.

[0103] (2) Preparation of nonwoven fabric:

[0104] The viscose fibers obtained in step (1) are sequentially processed through opening, carding and hydroentangling, followed by hydrophobic finishing and drying to produce a nonwoven fabric with a weight of 40 g / m²; the drying temperature is 140°C.

[0105] The hydrophobic finishing agent used is a polyurethane waterproofing agent, with a dosage of 5g / L and a pH value controlled at around 6.

[0106] The main difference between Comparative Sample 3 and Example 3 is that the viscose fiber was not hydrophobically modified, but the nonwoven fabric was moderately hydrophobically modified.

[0107] Comparative Example 4

[0108] (1) Preparation of hydrophobic modified viscose fibers:

[0109] Softwood dissolving pulp and hardwood dissolving pulp with a whiteness of ≥89% and a methyl cellulose content of ≥90% were selected. The softwood dissolving pulp and hardwood dissolving pulp were mixed at a mass ratio of 6.5:100. Then, viscose spinning dope was prepared by impregnation, pressing, crushing, aging, xanthation, dissolving and maturation. Viscose staple fiber was obtained by spinning with this viscose spinning dope. The viscose staple fiber was then fed into a scouring machine and subjected to a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, water-repellent finishing and drying to obtain hydrophobic modified viscose fiber. The spinning speed was 57 m / min and the drying temperature was 140℃.

[0110] The water-repellent finishing step involves spraying a water-repellent finishing liquid onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the underlying layers, and then rolling off excess liquid with rollers. This results in the viscose staple fiber adsorbing an appropriate amount of the water-repellent finishing liquid. The mass ratio of the viscose staple fiber to the water-repellent finishing liquid is 1:8. The water-repellent finishing liquid is prepared by the following steps:

[0111] ① Heat water to 60℃, and add fiber oiling agent to the water while stirring to prepare an oil bath solution with a fiber oiling agent concentration of 3.2g / L. The fiber oiling agent is anionic.

[0112] ② First, add sulfuric acid to the oil bath obtained in step ① to adjust the pH value of the oil bath to 3.8, then add hydrogen peroxide to make the concentration of hydrogen peroxide in the oil bath 0.5g / L, mix evenly to obtain a mixed solution;

[0113] ③ Heat the mixture obtained in step ② to 75°C, then add a dispersant at a concentration of 1.2 g / L and mix for 10 minutes; then add a hydrophobic agent at a concentration of 2.5 g / L and mix for 10 minutes; then add a crosslinking agent at a mass ratio of 1:12 to the hydrophobic agent and mix thoroughly to obtain the water-repellent finishing solution.

[0114] The dispersant is a cationic surfactant; the hydrophobic agent is an acrylate waterproofing agent; and the crosslinking agent is a polyurethane resin crosslinking agent.

[0115] The technical parameters of the hydrophobically modified viscose fiber obtained by the above steps are as follows: fineness 1.7 dtex; length 40 mm; dry breaking strength 2.26 cN / dtex; dry breaking elongation 19.8%; whiteness 87.5%; water absorption time 200 s.

[0116] (2) Preparation of nonwoven fabric:

[0117] The hydrophobic modified viscose fiber obtained in step (1) is sequentially processed through opening, carding and hydroentangling, and then dried to obtain a nonwoven fabric with a weight of 40 g / m²; the drying temperature is 140°C.

[0118] The difference between Comparative Sample 4 and Example 3 is that: in step (1), the viscose fiber is moderately hydrophobically modified, while in step (2), no hydrophilic finishing is performed.

[0119] II. Detection Methods:

[0120] Determination of absorption rate and reabsorption rate: Refer to standard GB / T 28004 and its related referenced standards;

[0121] Determination of droplet diffusion area: Place the nonwoven fabric horizontally above the filter paper, take 0.5 ml of colorimetric solution, drop it at a height of 1 cm above the fabric surface, and drop it evenly over 5 seconds. Let it stand for 10 seconds, and then measure the lengths of the longest and widest displacements of the colored area after the fabric sample is wetted by the colorimetric solution (the longest and widest displacements are perpendicular to each other). The product of the two is used to characterize the droplet diffusion area.

[0122] The test data such as absorption rate and reabsorption amount of the above-mentioned embodiments and comparative fabric samples are shown in Table 1.

[0123] Table 1

[0124]

[0125] As can be seen from the table above, the nonwoven fabric prepared by the method of this application, which is weakly hydrophilic and has low backflow, has the advantages of both rapid liquid penetration and low backflow.

[0126] The method for preparing the weakly hydrophilic and low-re-permeability nonwoven fabric described in this invention is not limited to the above embodiments. Any improvements or substitutions based on the principles of this invention should be within the scope of protection of this invention.

Claims

1. A method for preparing a weakly hydrophilic, low-reweave nonwoven fabric, characterized in that: The main steps are as follows, performed in sequence: (I) Preparation of hydrophobically modified viscose fibers: Softwood dissolving pulp and hardwood dissolving pulp with whiteness ≥89% and methyl cellulose content ≥90% are selected. The softwood dissolving pulp and hardwood dissolving pulp are mixed at a mass ratio of 6-7:

100. Then, viscose spinning dope is prepared by impregnation, pressing, crushing, aging, xanthation, dissolving and maturation. Viscose staple fiber is obtained by spinning with this viscose spinning dope. The viscose staple fiber is then fed into a scouring machine and undergoes a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, water-repellent finishing and drying to obtain hydrophobic modified viscose fiber. The water-repellent finishing step involves spraying a water-repellent finishing liquid onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the underlying layers, and then removing excess liquid by rollers. This results in the viscose staple fiber adsorbing an appropriate amount of the water-repellent finishing liquid. The mass ratio of viscose staple fiber to water-repellent finishing liquid is 1:5-1:

10. The water-repellent finishing liquid is prepared by the following steps: ① Heat water to 55-65℃, and add fiber oiling agent to the water while stirring to prepare an oil bath solution with a fiber oiling agent concentration of 3-3.5g / L. The fiber oiling agent is anionic. ② First, add sulfuric acid to the oil bath obtained in step ① to adjust the pH value of the oil bath to 3.5-4.

0. Then add hydrogen peroxide to make the concentration of hydrogen peroxide in the oil bath 0.4-0.8g / L. Mix well to obtain a mixed solution. ③ Heat the mixture obtained in step ② to 73-77℃, then add a dispersant at a dosage of 1-2 g / L and mix for 10-15 minutes; then add a hydrophobic agent at a dosage of 5-15 g / L and mix for 10-15 minutes; then add a crosslinking agent at a mass ratio of 1:10-1:20 to the hydrophobic agent and mix thoroughly to obtain the water-repellent finishing solution. Wherein, the hydrophobic agent is an acrylate hydrophobic agent; the crosslinking agent is a polyurethane resin crosslinking agent; (II) Preparation of weakly hydrophilic, low-re-permeability nonwoven fabric: The hydrophobic modified viscose fiber obtained in step (1) is sequentially processed through opening, carding and hydroentangling to form a hydrophobic modified nonwoven fabric. Then, it is sequentially processed through hydrophilic finishing and drying to obtain the weakly hydrophilic and low-rebleed nonwoven fabric. The hydrophilic finishing step involves impregnating the hydrophobic modified nonwoven fabric with a hydrophilic finishing solution. The mass ratio of the hydrophobic modified nonwoven fabric to the hydrophilic finishing solution is 1:5 to 1:

10. The hydrophilic finishing solution is prepared by diluting the hydrophilic finishing agent with water at a volume ratio of 1:50 to 1:

100. The hydrophilic finishing agent contains a thermally reactive nonionic waterborne polyurethane.

2. The method for preparing the weakly hydrophilic, low-reweave nonwoven fabric according to claim 1, characterized in that: The dispersant is a cationic surfactant.

3. The method for preparing the weakly hydrophilic, low-reweave nonwoven fabric according to claim 1, characterized in that: The spinning speed in step (1) is 56-59 m / min, and the drying temperature is 135-145℃.

4. The method for preparing the weakly hydrophilic, low-reweave nonwoven fabric according to claim 1, characterized in that: The drying temperature mentioned in step (ii) is 135-145℃.

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