A kind of highly water-absorbent polyvinyl alcohol fiber nonwoven fabric and preparation method thereof

Abstract

A method for preparing a highly absorbent polyvinyl alcohol fiber non-woven fabric comprises the following steps: placing a polyvinyl alcohol spinning solution formed by dissolving a polyvinyl alcohol raw material into a barrel of a wet spinning device, standing and degassing, and then extruding the solution into a coagulation bath through a spinneret to obtain spun fibers; winding and collecting the spun fibers after stretching to obtain uncrosslinked polyvinyl alcohol fibers, and then performing freeze-thaw cycles in an environment of 50 to 2°C and 20 to 45°C for multiple times, and drying to obtain low-crosslinked highly absorbent polyvinyl alcohol fibers; finally, cutting the fibers into short pieces and mixing them with hydrophobic fibers to form a web to obtain a non-woven fabric. The polyvinyl alcohol fibers of the present invention are stretched by only one nozzle and then freeze-thawed to form a low cross-linking density network, so that the polyvinyl alcohol fibers are well formed and highly absorbent. The method is simple and efficient, and the high absorbency and long-lasting water-locking ability of the non-woven fabric are achieved by regulating the fiber structure and the entanglement of the non-woven fabric.

Description

Technical Field

[0001] The present invention relates to the technical field of non-woven fabric preparation, and in particular to a highly water-absorbent polyvinyl alcohol fiber non-woven fabric and a preparation method thereof. Background Art

[0002] Currently, superabsorbent fibers are functional fibers developed from superabsorbent resins, offering improved processability and formability. Domestic research on superabsorbent fibers has been very active in recent years, with wet-spun polyacrylonitrile copolymer superabsorbent fibers and polyacrylic acid superabsorbent fibers achieving promising results. These fibers can then be processed into nonwoven fabrics for use in medical, agricultural, industrial, and sanitary applications. Currently, the pursuit of ultra-high water absorption is not simply about achieving ultra-high water absorption; balanced moisture permeability and long-lasting moisture retention are also becoming market demands.

[0003] For polyvinyl alcohol fibers, the numerous hydrogen bonds formed within the molecules prevent water molecules from penetrating into and between them, resulting in almost no water absorption. To address this issue and make polyvinyl alcohol fibers highly absorbent, Chinese patent CN 101260570A uses dry spinning to prepare polyvinyl alcohol fibers containing a crosslinker. Heat treatment then yields highly absorbent polyvinyl alcohol fibers with an absorption rate of 160 times. Chinese patent CN 1276134C introduces a crosslinking component capable of forming hydrogen, ester, or ether bonds with polyvinyl alcohol into polyvinyl alcohol fibers to produce water-absorbing polyvinyl alcohol fibers. Traditional nonwovens have high water absorption, but the free water in their structure evaporates quickly, resulting in insufficient long-term water retention. Furthermore, their ability to conduct liquid and maintain moisture is weak, potentially leading to accumulation of liquid on the surface of the nonwoven fabric. To address these issues and ensure nonwovens have both high water absorption and good moisture permeability, Swedish company Molnlycke's "Mepilex" product focuses on this issue.

[0004] The above-mentioned method for producing highly absorbent polyvinyl alcohol fiber non-woven fabrics, the maximum absorption capacity of which is mainly affected by the porosity of the non-woven fabric and the wettability of the absorbent fiber, currently still has deficiencies in terms of cost, process flow, and fiber physical properties. In order to be more suitable for large-scale industrial production, it is urgent to solve such problems and obtain non-woven fabrics that are highly absorbent and can retain liquid for a long time. Summary of the Invention

[0005] Based on this, the present invention provides a highly absorbent polyvinyl alcohol fiber non-woven fabric and a preparation method thereof to solve the technical problems of the prior art such as complex preparation process, high cost, limited absorption performance and liquid retention time of highly absorbent polyvinyl alcohol fiber non-woven fabric.

[0006] To achieve the above object, the present invention provides a method for preparing a highly water-absorbent polyvinyl alcohol fiber nonwoven fabric, which comprises the following steps:

[0007] Step (1), dissolving a polyvinyl alcohol raw material having a degree of polymerization of 1500-2200 and a degree of alcoholysis of 78-99% in a solvent to obtain a polyvinyl alcohol spinning solution;

[0008] Step (2), placing the polyvinyl alcohol spinning solution in a barrel of a wet spinning device, standing at a temperature of 90 to 98° C. under normal pressure for degassing, and then extruding the solution through a spinneret with a pore size of 0.05 to 0.1 mm at a speed of 6 to 15 m / min into a coagulation bath to obtain spun fibers;

[0009] Step (3), stretching the spun fibers and collecting them through a winding device to obtain uncrosslinked polyvinyl alcohol fibers;

[0010] Step (4), freezing and thawing the uncrosslinked polyvinyl alcohol fiber in an environment of -50 to -2°C and 20 to 45°C for multiple times, and drying the uncrosslinked polyvinyl alcohol fiber to obtain a low-crosslinked highly absorbent polyvinyl alcohol fiber;

[0011] (5) Cutting the highly absorbent polyvinyl alcohol fibers into short fibers, cross-laying the short highly absorbent polyvinyl alcohol fibers with hydrophobic fibers at a content of 5 to 40% to obtain a web with a porosity of 300 to 1500 g·m -2 24h -1 Highly absorbent polyvinyl alcohol fiber non-woven fabric.

[0012] As a further preferred technical solution of the present invention, in step (1), the polyvinyl alcohol raw material is first washed and dehydrated and then dissolved, wherein the washing and dehydration treatment is: swelling the polyvinyl alcohol raw material in 55-65°C distilled water for 2-3 hours, and then drying, and this cycle is repeated 1-3 times to wash away impurities in the polyvinyl alcohol raw material.

[0013] As a further preferred technical solution of the present invention, the dissolution of the polyvinyl alcohol raw material in step (1) is: after the polyvinyl alcohol raw material is swelled in water at 60°C for 1 to 2 hours, it is dissolved at 90 to 98°C for 2 to 8 hours to obtain a transparent and stable polyvinyl alcohol spinning solution, and the solid content of the polyvinyl alcohol spinning solution is 15 to 25 wt%.

[0014] As a further preferred technical solution of the present invention, the coagulation bath in step (2) adopts a saturated Na2SO4 solution with a bath ratio of 60 to 80 and a temperature of 42 to 47°C; in step (3), the spun fibers are stretched with a nozzle stretching ratio of 1.0 to 1.5, and the stretching temperature of the spun fibers is kept consistent with the temperature of the coagulation bath.

[0015] As a further preferred technical solution of the present invention, the freeze-thaw cycle in step (4) is: freezing in an environment of -50 to -2°C for 12 to 24 hours, and thawing in an environment of 20 to 45°C for 12 to 24 hours, with the number of cycles being 1 to 5. Preferably, the number of freeze-thaw cycles is 3 to 5.

[0016] As a further preferred technical solution of the present invention, the drying treatment temperature in step (4) is not higher than 42°C.

[0017] As a further preferred technical solution of the present invention, in step (5), the length of the short super absorbent polyvinyl alcohol fibers is 0.2 to 3 cm, and the thickness of the mixed layer of the short super absorbent polyvinyl alcohol fibers and the hydrophobic fibers is 1 to 10 mm.

[0018] As a further preferred technical solution of the present invention, the water absorption rate of the highly absorbent polyvinyl alcohol fiber non-woven fabric is 10 to 200 times its own weight, and the moisturizing time at room temperature is 12 to 48 hours, so that the highly absorbent polyvinyl alcohol fiber non-woven fabric has the characteristics of high absorption and long-term liquid retention capacity.

[0019] According to another aspect of the present invention, the present invention also provides a highly water-absorbent polyvinyl alcohol fiber non-woven fabric, which is prepared by the above method.

[0020] The present invention combines the polyvinyl alcohol fiber forming process with the construction of the polyvinyl alcohol gel cross-linking structure. It induces crystallization between molecular chains to form cross-linking points through cyclic freeze-thaw technology, and at the same time regulates the cross-linking degree by controlling the number of freeze-thaw cycles. A gel network with low cross-linking density is constructed in the primary fiber, which not only achieves fiber forming but also has high water absorption of the gel.

[0021] The present invention uses polyvinyl alcohol fibers as absorbent fibers and cross-spreads them with conventional hydrophobic fibers on the market to form a non-woven fabric, resulting in high absorption and long-term liquid retention. The high water absorption is due to the capillary action between the hydrophobic fibers, which allows a large amount of water to enter the fiber pores, playing a major role in water absorption. A small amount of water is retained inside the absorbent fibers or hydrogen-bonded to the fiber surface, playing a major role in moisturizing. Moisture-retention durability is achieved by, on the one hand, regulating the cross-linking degree of the absorbent fibers and increasing bound water by controlling the number of freeze-thaw cycles; on the other hand, by regulating the porosity during the hot air (needle punching or hydroentanglement) process for preparing the non-woven fabric, and by varying the absorbent fiber content, thereby ensuring long-term moisture retention from two aspects.

[0022] The highly water-absorbent polyvinyl alcohol fiber nonwoven fabric and its preparation method of the present invention can achieve the following beneficial effects by adopting the above technical solution:

[0023] 1) The polyvinyl alcohol fiber of the present invention is subjected to only one nozzle stretching, followed by cyclic freeze-thaw cycles, to construct a low cross-linking density network, so that the polyvinyl alcohol fiber is well formed and has high water absorbency. The method is simple and efficient, and there is no complicated heat treatment process in the entire preparation process, which simplifies the process and is conducive to large-scale production;

[0024] 2) The present invention realizes the continuous preparation of highly absorbent polyvinyl alcohol fibers through wet spinning. The resulting non-woven fabric has high absorbency and long-lasting moisturizing effect, with a water absorption rate of up to 200 times and a room temperature moisturizing time (60% weight reduction) of up to 48 hours;

[0025] 3) The highly absorbent polyvinyl alcohol fiber non-woven fabric prepared by the present invention through low-crosslinking spinning and non-woven fabric entanglement control has a water absorption rate of up to 10 to 200 times and can be used in highly absorbent medical wound dressings, etc.

[0026] 4) The polyvinyl alcohol fiber nonwoven fabric of the present invention is cross-laid with polyvinyl alcohol staple fibers and hydrophobic fibers by needle punching, hydroentanglement or hot air process, and has high water absorption and long-lasting wetting ability. The moisture retention time at room temperature is 12 to 24 hours. It is applied to wound treatment to effectively promote wound recovery.

[0027] 5) The polyvinyl alcohol fiber nonwoven fabric of the present invention forms a siphon phenomenon through the pores between the hydrophobic fibers, which can quickly guide away the liquid while locking some free water, achieving a moisture permeability balance and creating a dry environment at the contact surface between the nonwoven fabric and the skin. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Figure 1 Microscope images of the polyvinyl alcohol fibers prepared in Example 1 (A: dry state; B: swollen state);

[0030] Figure 2 Microscope images of the polyvinyl alcohol fibers prepared in Example 3 (C: dry state; D: swollen state);

[0031] Figure 3 Microscope images of the polyvinyl alcohol fibers prepared in Example 5 (E: dry state; F: swollen state);

[0032] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0033] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0034] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.

[0035] Example 1

[0036] This embodiment provides a method for preparing a highly absorbent polyvinyl alcohol fiber nonwoven fabric, the materials of which include: polyvinyl alcohol with a degree of polymerization of 1500 and a degree of alcoholysis of 92%; distilled water; and a coagulation bath of saturated sodium sulfate solution.

[0037] The specific preparation steps are as follows: polyvinyl alcohol and distilled water are dissolved in a weight ratio of 3:17 to prepare a spinning solution with a solid content of 15wt%. The polyvinyl alcohol is first swelled in 60℃ water for 1 hour, and then dissolved at 90℃ for 4 hours to prepare the spinning solution. The temperature is controlled to be constant at 90℃ and allowed to stand for degassing for 6 hours. The spinning solution is extruded from a spinneret into a coagulation bath with a spinneret aperture of 0.05mm and an extrusion speed of 6m / min to obtain nascent fibers. The nascent fibers are stretched by a nozzle and then wound to obtain uncrosslinked polyvinyl alcohol fibers. The nozzle stretch ratio is 1.0, maintaining the temperature at 45°C; then freezing the obtained fiber at -25°C for 24 hours, and then thawing the frozen fiber at 25°C for 24 hours, and performing this freeze-thaw cycle three times to obtain polyvinyl alcohol fiber with a low degree of cross-linking, which was then dried at 60°C; the dried polyvinyl alcohol fiber was cut into short strands with a length of 0.2 cm; the short polyvinyl alcohol fiber was used as the water-absorbing fiber, and the water-absorbing fiber and the hydrophobic fiber were cross-spread into a non-woven fabric with a thickness of 5 mm by a hot air process, and the porosity was set to 1500 g·m -2 24h -1 , the water-absorbent fiber content is 10%.

[0038] The dry and wet morphologies of PVA fibers were observed under a microscope. Figure 1 shown.

[0039] In the non-woven fabric water absorption test, when the water-absorbing fiber content is 10%, the water absorption rate of the polyvinyl alcohol fiber non-woven fabric reaches 150 times; in the non-woven fabric moisturizing test, the polyvinyl alcohol fiber non-woven fabric after absorbing water is left to stand at room temperature and pressure, and the time required for it to reduce 60% of its weight is 30 hours.

[0040] Example 2

[0041] As a comparative experiment of Example 1, this example provides a method for preparing a highly absorbent polyvinyl alcohol fiber nonwoven fabric, wherein the materials include: polyvinyl alcohol with a degree of polymerization of 1500 and a degree of alcoholysis of 92%; distilled water; and a coagulation bath of saturated sodium sulfate solution.

[0042] The specific preparation steps are as follows: polyvinyl alcohol and distilled water are dissolved in a weight ratio of 3:17 to prepare a spinning solution with a solid content of 15 wt%. The operation of Example 1 is repeated, and the dried polyvinyl alcohol fibers are then cut into short strands with a length of 0.2 cm. The short polyvinyl alcohol fibers are used as water-absorbing fibers, and the water-absorbing fibers and hydrophobic fibers are cross-stretched into a non-woven fabric with a thickness of 5 mm and a porosity of 1500 g·m -2 24h -1 The preparation process is different from that of Example 1 except for the content of the water-absorbing fiber.

[0043] In the non-woven fabric water absorption test, when the water-absorbing fiber content is 30%, the water absorption rate of the polyvinyl alcohol fiber non-woven fabric reaches 200 times; in the non-woven fabric moisturizing test, the polyvinyl alcohol fiber non-woven fabric after absorbing water is left to stand at room temperature and pressure, and the time required for it to reduce 60% of its weight is 40 hours.

[0044] Comparative analysis shows that the long-term wetting ability of non-woven fabrics increases with the content of polyvinyl alcohol fibers in the non-woven fabric. However, when the content of water-absorbing fibers is too high, the water absorption and expansion will block the pores of the non-woven fabric, which is not conducive to the liquid conduction and moisture permeability of the non-woven fabric, and may cause liquid accumulation on the surface of the material. The preferred content of polyvinyl alcohol fibers in non-woven fabrics is 10-40%.

[0045] Example 3

[0046] This embodiment provides a method for preparing a highly absorbent polyvinyl alcohol fiber nonwoven fabric, wherein the materials include: polyvinyl alcohol with a degree of polymerization of 2200 and a degree of alcoholysis of 78%; distilled water; a coagulation bath of saturated sodium sulfate solution;

[0047] The specific preparation steps are as follows: polyvinyl alcohol and distilled water are dissolved in a weight ratio of 1:3 to prepare a spinning solution with a solid content of 25wt%. The polyvinyl alcohol is first swelled in water at 60℃ for 1 hour, then dissolved at 98℃ for 2 hours to prepare the spinning solution. The temperature is kept constant at 98℃ and allowed to stand for 6 hours for degassing. The spinning solution is extruded from a spinneret with an aperture of 0.06mm at an extrusion speed of 15m / min. The spun fiber is stretched by a nozzle and then wound to obtain uncrosslinked polyvinyl alcohol fiber. The nozzle stretch ratio is 1. 0; freezing the obtained fiber at -25°C for 24 hours, then thawing the frozen fiber at 25°C for 24 hours, repeating the cycle twice to obtain polyvinyl alcohol fiber with a low degree of crosslinking, and then drying at 50°C; chopping the polyvinyl alcohol fiber into short strands with a length of 0.2 cm; using the short polyvinyl alcohol fiber as the water-absorbing fiber, cross-spreading the water-absorbing fiber and the hydrophobic fiber into a 5 mm thick non-woven fabric through a hot air process (or a needle punching or hydroentanglement process), with a porosity of 500 g·m -2 24h-1 , the water-absorbent fiber content is 20%.

[0048] The dry and wet morphologies of PVA fibers were observed under a microscope. Figure 2 shown.

[0049] The non-woven fabric water absorption test showed that after 2 freeze-thaw cycles, the water absorption rate of the polyvinyl alcohol fiber non-woven fabric reached 10 times; the moisturizing test showed that the time required for the non-woven polyvinyl alcohol fiber non-woven fabric to reduce 60% of its weight was 10 hours.

[0050] Example 4

[0051] As a comparative experiment of Example 3, this example provides a method for preparing a highly absorbent polyvinyl alcohol fiber nonwoven fabric, wherein the materials include: polyvinyl alcohol having a degree of polymerization of 2200 and a degree of alcoholysis of 78%; distilled water; and a coagulation bath of saturated sodium sulfate solution.

[0052] The specific preparation steps are as follows: polyvinyl alcohol and distilled water are dissolved in a weight ratio of 1:3 to prepare a spinning solution with a solid content of 25 wt%. The operation of Example 2 is repeated, and the obtained fiber is frozen at -25°C for 24 hours, and then the frozen fiber is thawed at 25°C for 24 hours. This cycle is repeated five times to obtain polyvinyl alcohol fiber with a low degree of cross-linking, and then dried at 50°C. The polyvinyl alcohol fiber is cut into short strands with a length of 0.2 cm. The short polyvinyl alcohol fiber is used as the water-absorbing fiber, and the water-absorbing fiber and the hydrophobic fiber are cross-spread into a non-woven fabric with a thickness of 5 mm by a hot air process, and the porosity is set to 500 g·m -2 24h -1 The preparation process is different from that of Example 2 except for the number of freeze-thaw cycles.

[0053] In the non-woven fabric water absorption test, after 5 freeze-thaw cycles, the water absorption rate of the polyvinyl alcohol fiber non-woven fabric reached 80 times; in the non-woven fabric moisturizing test, the polyvinyl alcohol fiber non-woven fabric after absorbing water was left to stand at room temperature and pressure, and the time required for it to reduce 60% of its weight was 24 hours.

[0054] Comparative analysis shows that cyclic freeze-thaw cycles can improve fiber water absorption by creating a low-crosslink network. The number and duration of freeze-thaw cycles affect the density of crosslinks between molecular chains. Too low a crosslink density is detrimental to fiber formation and water binding capacity, while conversely, it is detrimental to fiber swelling. The optimal freeze-thaw cycle is 2 to 5 times.

[0055] Example 5

[0056] This embodiment provides a method for preparing a highly absorbent polyvinyl alcohol fiber nonwoven fabric, wherein the materials include: polyvinyl alcohol with a degree of polymerization of 1800 and a degree of alcoholysis of 85%; distilled water; a coagulation bath of saturated sodium sulfate solution;

[0057] The specific preparation steps are as follows: polyvinyl alcohol and distilled water are dissolved in a weight ratio of 1:4 to prepare a spinning solution with a solid content of 20wt%. The polyvinyl alcohol is first swelled in water at 60℃ for 1 hour, then dissolved at 94℃ for 3 hours to prepare the spinning solution. The temperature is kept constant at 94℃ and allowed to stand for 6 hours for degassing. The spinning solution is extruded from a spinneret with an aperture of 0.08mm at an extrusion speed of 10m / min. The spun fiber is stretched by a nozzle and then wound to obtain uncrosslinked polyvinyl alcohol fiber. The nozzle stretch ratio is 1. 0; the obtained fiber is frozen at -25°C for 24 hours, and then the frozen fiber is thawed at 25°C for 24 hours, and the cycle is repeated three times to obtain polyvinyl alcohol fiber with a low cross-linking degree, and then dried at 55°C; the polyvinyl alcohol fiber is cut into short strands with a length of 0.2 cm; the short polyvinyl alcohol fiber is used as the water-absorbing fiber, and the water-absorbing fiber and the hydrophobic fiber are cross-spread into a non-woven fabric with a thickness of 5 mm and a porosity of 800 g·m -2 24h -1 , the water-absorbent fiber content is 30%.

[0058] The dry and wet morphologies of PVA fibers were observed under a microscope. Figure 3 shown.

[0059] In the non-woven fabric water absorption test, the water absorption rate of the polyvinyl alcohol fiber non-woven fabric reached 100 times; in the non-woven fabric moisturizing test, the polyvinyl alcohol fiber non-woven fabric after absorbing water was left to stand at room temperature and pressure, and the time required for it to reduce 60% of its weight was 15 hours.

[0060] Example 6

[0061] As a comparative experiment of Example 5, this example provides a method for preparing a highly absorbent polyvinyl alcohol fiber nonwoven fabric, wherein the materials include: polyvinyl alcohol with a degree of polymerization of 1800 and a degree of alcoholysis of 85%; distilled water; and a saturated sodium sulfate solution as a coagulation bath.

[0062] Polyvinyl alcohol and distilled water were dissolved in a weight ratio of 1:4 to prepare a spinning solution with a solid content of 20 wt%. The operation of Example 3 was repeated, and the obtained fibers were frozen at -25°C for 24 hours, and then the frozen fibers were thawed at 25°C for 24 hours. This cycle was repeated three times to obtain polyvinyl alcohol fibers with a low degree of crosslinking, which were then dried at 55°C. The polyvinyl alcohol fibers were chopped into short strands with a length of 0.2 cm. The chopped polyvinyl alcohol fibers were used as water-absorbing fibers, and the water-absorbing fibers and hydrophobic fibers were cross-spread into a 5 mm thick non-woven fabric using a hot air process, with a porosity of 1200 g·m -2 24h -1The water-absorbing fiber content is 30%. The preparation process is different from that of Example 3, except for the size of the porosity of the non-woven fabric.

[0063] In the non-woven fabric water absorption test, the water absorption rate of the polyvinyl alcohol fiber non-woven fabric reached 150 times; in the non-woven fabric moisturizing test, the polyvinyl alcohol fiber non-woven fabric after absorbing water was left to stand at room temperature and pressure, and the time required for it to reduce 60% of its weight was 20 hours.

[0064] Comparative analysis shows that polyvinyl alcohol fiber nonwoven fabric is a porous material that can absorb a large amount of water through capillary action. The greater the porosity, the greater the structural absorption capacity. The porosity is adjusted by entanglement of the nonwoven fabric to enable the nonwoven fabric to reach its maximum absorption capacity. The porosity of the highly absorbent polyvinyl alcohol fiber nonwoven fabric is preferably 300-1500g·m -2 24h -1 .

[0065] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a highly water-absorbent polyvinyl alcohol fiber nonwoven fabric, characterized in that: The following steps are involved: (1) dissolving a polyvinyl alcohol raw material having a degree of polymerization of 1500 to 2200 and a degree of alcoholysis of 78 to 99% in a solvent to obtain a polyvinyl alcohol spinning solution; (2) placing the polyvinyl alcohol spinning solution in the barrel of a wet spinning device for degassing, and then extruding it through a spinneret into a coagulation bath to obtain nascent fibers; (3) stretching the spun fibers and collecting them through a winding device to obtain uncrosslinked polyvinyl alcohol fibers; (4) The uncrosslinked polyvinyl alcohol fiber was freeze-thawed multiple times in an environment of -50 ~ -2 ° C and 20 ~ 45 ° C, and then dried to obtain low-crosslinked highly absorbent polyvinyl alcohol fiber; (5) Cut the super absorbent polyvinyl alcohol fibers into short fibers, and cross-lay the short super absorbent polyvinyl alcohol fibers with hydrophobic fibers by hot air process according to the content of super absorbent polyvinyl alcohol fibers of 5-40%, so as to obtain a porosity of 300-1500 g·m -2 24h -1 Highly absorbent polyvinyl alcohol fiber non-woven fabric; The freeze-thaw cycle in step (4) is as follows: alternately freezing in a -50 to -2°C environment for 12 to 24 hours and thawing in a 20 to 45°C environment for 12 to 24 hours, with the number of alternating cycles being 2 to 5 times.

2. The method for preparing a highly water-absorbent polyvinyl alcohol fiber nonwoven fabric according to claim 1, wherein: In step (1), the polyvinyl alcohol raw material is first washed with water and dehydrated, and then dissolved, wherein the washing and dehydration treatment is: the polyvinyl alcohol raw material is swelled in 55-65°C distilled water for 2-3 hours, and then dried, and this cycle is repeated 1-3 times.

3. The method for preparing a highly water-absorbent polyvinyl alcohol fiber nonwoven fabric according to claim 1, wherein: The dissolution of the polyvinyl alcohol raw material in step (1) is as follows: the polyvinyl alcohol raw material is swelled in water at 60°C for 1 to 2 hours, and then dissolved at 90 to 98°C for 2 to 8 hours. The solid content of the obtained polyvinyl alcohol spinning solution is 15 to 25 wt%.

4. The method for preparing a highly water-absorbent polyvinyl alcohol fiber nonwoven fabric according to claim 1, wherein: The coagulation bath in step (2) uses a saturated Na2SO4 solution with a bath ratio of 60 to 80 and a temperature of 42 to 47°C. In step (3), the spun fibers are stretched with a nozzle stretch ratio of 1.0 to 1.5, and the stretching temperature of the spun fibers is kept consistent with the temperature of the coagulation bath.

5. The method for preparing a highly water-absorbent polyvinyl alcohol fiber nonwoven fabric according to claim 1, wherein: In step (2), the polyvinyl alcohol spinning solution is placed in a barrel at a temperature of 90 to 98° C. and at normal pressure to achieve degassing; the aperture of the spinneret is 0.05 to 0.1 mm, and the extrusion speed is 6 to 15 m / min.

6. The method for preparing a highly water-absorbent polyvinyl alcohol fiber nonwoven fabric according to claim 1, wherein: The drying treatment temperature in step (4) is not higher than 42°C.

7. The method for preparing a highly water-absorbent polyvinyl alcohol fiber nonwoven fabric according to claim 1, wherein: In step (5), the length of the short super absorbent polyvinyl alcohol fibers is 0.2 to 3 cm, and the thickness of the mixed paving layer of the short super absorbent polyvinyl alcohol fibers and the hydrophobic fibers is 1 to 10 mm.

8. The method for preparing a highly water-absorbent polyvinyl alcohol fiber nonwoven fabric according to claim 1, wherein: The highly water-absorbent polyvinyl alcohol fiber non-woven fabric has a water absorption rate of 10 to 200 times its own weight and a moisturizing time at room temperature of 12 to 48 hours.

9. A highly water-absorbent polyvinyl alcohol fiber nonwoven fabric, characterized in that: The non-woven fabric is prepared by the method for preparing the highly water-absorbent polyvinyl alcohol fiber non-woven fabric according to any one of claims 1 to 8.

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