A spunlace nonwoven fabric for a one-way wetness paper diaper cover layer and a method for manufacturing the same

Abstract

The present application relates to a kind of spunlace nonwoven fabrics for one-way wet paper diaper cover, including the first fiber web layer and the second fiber web layer of spunlace entanglement, the first fiber web layer is composed of the modified polypropylene fiber of cross structure;The second fiber web layer is composed of bamboo pulp fiber;The modified polypropylene is polypropylene, after polyether dipropyl ester, hydroxyl-containing acrylamide melt co-grafting, again with pyridine acyl chloride derivative reaction preparation;The number average molecular weight of polyether segment in the polyether dipropyl ester is 1500~3000.The first fiber web layer and the second fiber web layer are reinforced by spunlace process to obtain the spunlace nonwoven fabric for one-way wet paper diaper cover;The hydrophilic-hydrophobic difference of two fiber web layers is large enough, differential capillary effect is formed, one-way wet is realized, and soft skin-friendly nature is simultaneously provided with wear resistance, not hair, not shedding.

Description

Technical Field

[0001] This invention belongs to the field of nonwoven fabric technology, specifically relating to a unidirectional moisture-wicking diaper surface layer made of spunlace nonwoven fabric and its preparation method. Background Technology

[0002] As people's living standards improve, the demand for hygiene products is increasing, and the performance requirements are also becoming more stringent. For example, diapers not only need to have good absorbency and breathability, but also be skin-friendly. Diapers generally consist of four parts: the top layer, the distribution layer, the absorbent core, and the bottom layer. To meet these performance requirements, the top layer material must be soft, skin-friendly, and have excellent water permeability without retaining water. It should be able to quickly guide liquid into the distribution layer or absorbent core below, and prevent liquid from seeping back to the diaper surface, keeping the skin as dry as possible. In other words, the top layer material of the diaper must have one-way moisture-wicking function. Spunlace nonwoven fabric has a soft feel, good bulkiness, is not prone to pilling, does not contain chemical additives, and is non-irritating to the skin, making it widely used in the top layer materials of diapers. Currently, the spunlace nonwoven fabric surface material of diapers is mainly made of cotton and viscose fiber. Cotton and viscose fibers have good softness and skin-friendliness. However, because cotton and viscose fibers have good water absorption, when used in diapers, the amount of backflow after absorbing liquid is large, and the surface will become very damp. They do not have excellent one-way moisture-wicking function, resulting in poor comfort.

[0003] Polypropylene fibers are widely used in the nonwoven fabric field due to their good chemical resistance and abrasion resistance. However, polypropylene has a regular structure, no polar groups on its surface, and good hydrophobicity. When used in composite nonwoven fabrics with hydrophilic fibers, it exhibits good unidirectional moisture wicking properties, but its skin-friendliness and softness are lacking, thus limiting its application in diaper surface materials. Chinese patent CN202211120117.4 discloses a soft and dry spunlace nonwoven fabric and its preparation method, comprising cotton fiber nonwoven fabric, modified polypropylene nonwoven fabric, and viscose fiber nonwoven fabric from the inside out. The cotton fiber nonwoven fabric has a certain degree of moisture absorption. By introducing modified phosphazene into the viscose fiber nonwoven fabric, the moisture absorption of the viscose fiber nonwoven fabric is stronger than that of the cotton fiber nonwoven fabric, giving the spunlace nonwoven fabric moisture-wicking ability. Although the unidirectional moisture wicking properties of this diaper surface nonwoven fabric are good, the introduction of modifiers such as silicon and phosphorus reduces skin-friendliness.

[0004] The common method to improve the skin-friendly softness of polypropylene is to introduce flexible groups, but this often leads to a decrease in mechanical properties, making it prone to fuzzing and shedding. Using modified polypropylene and polypropylene for composite spinning is a good strategy. For example, modified polypropylene can be used as the sheath layer and polypropylene as the core layer to form a bicomponent fiber with a sheath-core structure. This produces fibers that maintain both mechanical properties and good skin-friendly softness. However, the spinning technology for bicomponent fibers is quite demanding, and process control is difficult.

[0005] Therefore, it is necessary to develop a nonwoven fabric for diaper surface layer that is skin-friendly and soft, has fast one-way moisture wicking, and is not prone to pilling or shedding, using polypropylene as raw material. Summary of the Invention

[0006] Given that existing nonwoven fabrics for diaper surface layers made from polypropylene cannot simultaneously achieve skin-friendly softness, rapid unidirectional moisture wicking, and resistance to lint and shedding, this invention provides a unidirectional moisture-wicking diaper surface layer made of spunlace nonwoven fabric and its preparation method. This invention uses modified polypropylene spinning to obtain a skin-friendly, soft, hydrophobic, and abrasion-resistant first fiber web layer; it uses bamboo pulp fiber with excellent moisture absorption as a hydrophilic second fiber web layer; and then reinforces the first and second fiber web layers through a hydroentangling process to obtain a unidirectional moisture-wicking diaper surface layer made of spunlace nonwoven fabric. The difference in hydrophilicity and hydrophobicity between the two fiber web layers is sufficiently large, forming a differential capillary effect, achieving unidirectional moisture wicking while maintaining softness, skin-friendliness, abrasion resistance, and preventing lint and shedding.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A one-way moisture-wicking diaper surface layer is made of spunlace non-woven fabric, comprising a first fiber web layer and a second fiber web layer entangled by spunlace. The first fiber web layer is composed of modified polypropylene fibers with a cross-shaped structure; the second fiber web layer is composed of bamboo pulp fibers. The modified polypropylene is prepared by melt co-grafting polypropylene with polyether diallyl ester and hydroxyl-containing acrylamide, followed by reaction with a pyridine chloride derivative. The number average molecular weight of the polyether segment in the polyether diallyl ester is 1500-3000.

[0009] Further, the amount of polyether dipropylene ester used is 10-20 wt% of polypropylene; the mass ratio of polyether dipropylene ester, hydroxyl-containing acrylamide, and pyridine chloride derivative is 1:(0.15-0.3)(0.1-0.25).

[0010] Furthermore, the melt index of the polypropylene is 25–40 g / 10 min.

[0011] Polyether diacrylate is a linear polyether macromolecule with acrylate groups at both ends. Grafting it onto polypropylene can improve its flexibility. If its molecular weight is too low, the required flexibility cannot be achieved. If its molecular weight is higher, the grafted molecular chain is longer, and the flexibility is improved better. However, if the molecular weight is too high, the strength performance will be reduced. In this invention, the polyether diacrylate can be selected from at least one of polyethylene glycol (1500) diacrylate, polyethylene glycol (2000) diacrylate, polyethylene glycol (2500) diacrylate, polypropylene glycol (1500) diacrylate, polypropylene glycol (2000) diacrylate, and polypropylene glycol (2500) diacrylate.

[0012] Furthermore, the hydroxyl-containing acrylamide is selected from at least one of N-hydroxyethylacrylamide, N-hydroxymethylacrylamide, and N-[tris(hydroxymethyl)methyl]acrylamide.

[0013] Furthermore, the pyridine chloride derivative is at least one of 2-pyridinecarboxyl chloride, 3-pyridinecarboxyl chloride, 2-pyridineacetyl chloride, and 3-pyridineacetyl chloride. The pyridine chloride derivative is a small-molecule rigid substance that reacts with the hydroxyl groups of polyether diacrylamide to form a locally cross-linked structure in the flexible grafted chain, thereby compensating for the strength reduction caused by the flexible chain during polypropylene grafting.

[0014] Furthermore, the modified polypropylene is prepared by a method comprising the following steps:

[0015] (L1) Polypropylene chips, polyether diacrylate, hydroxyl-containing acrylamide and initiator are mixed evenly and then melt-co-grafted to obtain grafted polypropylene;

[0016] (L2) The grafted polypropylene was dissolved in an organic solvent, and a pyridine chloride derivative and an acid-binding agent were added. The reaction was carried out under controlled temperature. After the reaction was completed, the polypropylene was obtained by rotary evaporation and drying.

[0017] Furthermore, the initiator in step (L1) is selected from at least one of dicumyl peroxide and ditert-butyl peroxide, and the amount of initiator is 0.1 to 0.2 wt% of the polypropylene chips; the melt grafting is carried out in a torque rheometer at a reaction temperature of 200 to 220°C and a rotation speed of 70 to 80 r / min; after the reaction is completed, the product is cooled and granulated.

[0018] Furthermore, the organic solvent in step (L2) is at least one of toluene and xylene; the acid-binding agent is selected from at least one of triethylamine and pyridine, and the mass of the acid-binding agent is 1.5 to 2.0 times that of the pyridine chloride derivative; the temperature is 0 to 10°C, and the reaction time is 3 to 5 hours.

[0019] Furthermore, the areal density of the first fiber web layer and the second fiber web layer is independently 8–15 g / m².2 .

[0020] Furthermore, the first fiber has a fineness of 1.5 to 2.5 dtex and a length of 30 to 50 mm; the second fiber has a fineness of 1.0 to 1.5 dtex and a length of 30 to 50 mm.

[0021] Secondly, the present invention provides a method for preparing the surface layer of the above-mentioned unidirectional moisture-wicking diaper using spunlace non-manufactured fabric, comprising the following steps:

[0022] (S1) Melt spinning: Modified polypropylene chips are fed into a screw extruder for heating and melting, and then enter the spinning die through a melt filter, melt conveying pipeline and metering pump. The chips are evenly distributed to the cross-shaped spinning assembly. Spinning is performed at the outlet, and after cooling, stretching, winding and cutting, cross-shaped modified polypropylene fibers are produced.

[0023] (S2) Preparation of the first fiber web layer: The cross-shaped modified polypropylene fibers are opened, fed into the first carding machine, and laid in parallel to form the first fiber web layer;

[0024] (S3) Preparation of the second fiber web layer: bamboo pulp fibers are opened, fed into the second carding machine, and laid in parallel to form the second fiber web layer;

[0025] (S4) Hydroentangling reinforcement: The first fiber web layer and the second fiber web layer are composited and stacked, and simultaneously fed into the hydroentangling high-pressure jet zone for hydroentangling reinforcement, drying, and rolling to obtain a unidirectional moisture-wicking diaper surface layer made of hydroentangling non-woven fabric.

[0026] Further, in step (S1), the process conditions for melt spinning are as follows: spinning temperature 250-280℃, setting temperature 140-160℃, POY spinning speed 2400-2800m / min, POY draw ratio 2-3 times, FDY spinning speed 3800-4200m / min, FDY draw ratio 2.5-3.5 times, and winding speed 2700-3200r / min.

[0027] Furthermore, in step (S4), the hydroentangling pressure is 4-10 MPa, the number of hydroentangling channels is 4-6, and the drying temperature is 100-150°C.

[0028] In this invention, the surface layer of the one-way moisture-wicking diaper can also be perforated with spunlace nonwoven fabric to further improve its one-way moisture-wicking properties.

[0029] The mechanism of this invention is explained as follows:

[0030] Polypropylene has a regular structure, no polar groups on its surface, and good water permeability, but its skin affinity and softness are poor. Polyether diacrylate is a linear polyether macromolecule with acrylate groups at both ends. Grafting it onto polypropylene can improve its softness; if its molecular weight is too low, the required flexibility will not be achieved; if its molecular weight is higher, the grafted molecular chain will be longer, and the flexibility will be better improved, but if the molecular weight is too high, the strength properties will be reduced. Therefore, in the existing technology, the molecular weight of the polyether macromonomer used in graft-modified polypropylene is generally no more than 1500. This invention involves melt-grafting polypropylene with polyether diacrylate (molecular weight of 1500-3000) and hydroxyl-containing acrylamide, followed by reaction with a pyridine chloride derivative. This grafting of flexible long molecular chains onto the polypropylene macromolecular chain significantly improves its softness and skin-friendliness. Simultaneously, the pyridine chloride derivative, being a small-molecule rigid substance, reacts with the hydroxyl groups of the hydroxyl-containing acrylamide to form a locally rigid cross-linked structure within the flexible long grafted chain, compensating for the strength reduction caused by the long flexible chain grafting. Furthermore, the hydroxyl-containing acrylamide can also form intermolecular hydrogen bonds with the polyether segment. Therefore, the modified polypropylene obtained through this modification exhibits improved softness and skin-friendliness without a significant decrease in mechanical strength.

[0031] The cross-shaped fiber surface features numerous longitudinally distributed grooves, resulting in a large specific surface area. These grooves also increase the internal porosity of the fiber, creating capillary action and enabling rapid water transport. By combining the modified polypropylene with the micropore design of the cross-shaped spinneret, fibers that are skin-friendly, soft, and capable of rapid water transport can be spun. Using this as the first fiber web layer provides excellent skin-friendly softness, hydrophobicity, rapid water transport, and good strength properties.

[0032] Bamboo pulp fiber has excellent moisture absorption capacity. It is used as the second fiber web layer and combined with the first fiber web formed by the above-mentioned modified polypropylene, which has good hydrophobicity and skin-friendly properties, to form a nonwoven fabric with a composite structure of hydrophobic layer and hydrophilic layer. Its differential capillary effect and wetting gradient effect create an additional pressure difference in the thickness direction of the nonwoven fabric, which can achieve unidirectional moisture conduction while maintaining good skin-friendly softness and wear resistance without shedding.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] Polypropylene is melt-grafted with polyether diallyl (polyether segments with a number-average molecular weight of 1500-3000) and hydroxyl-containing acrylamide, and then reacted with pyridine chloride derivatives to obtain modified polypropylene. Combined with the cross-shaped spinneret micropore design, a first fiber web layer is produced that is skin-friendly, soft, rapidly absorbent, and possesses good strength. A hydrophilic second fiber web layer is made using bamboo pulp fiber with excellent moisture absorption. The first and second fiber web layers are reinforced by a hydroentangling process to obtain a unidirectional moisture-wicking diaper surface layer made of spunlace nonwoven fabric. The sufficiently large difference in hydrophilicity and hydrophobicity between the two fiber web layers creates a differential capillary effect, achieving unidirectional moisture wicking while maintaining softness, skin-friendliness, abrasion resistance, and preventing lint and shedding. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. The following embodiments are provided to better understand this invention, but do not limit the invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods.

[0036] Unless otherwise specified, "parts" in the embodiments of the present invention refers to parts by mass, and "%" refers to percentage by mass unless otherwise specified.

[0037] The polypropylene chips were purchased from Beijing Yanshan Petrochemical Corporation, model S2040, with a melt flow index of 38±1g / 10min.

[0038] The bamboo pulp fiber was purchased from Shandong Jiumian Textile Co., Ltd., and it measures 1.33 dtex × 38 mm.

[0039] Polyethylene glycol (600) diacrylate (DA-PEG600-DA), polyethylene glycol (1500) diacrylate (DA-PEG1500-DA), and polyethylene glycol (3000) diacrylate (DA-PEG3000-DA) were all purchased from Guangzhou Haoyi New Material Technology Co., Ltd.

[0040] Preparation of modified polypropylene

[0041] Preparation Example 1: 10%, 1:0.22:0.18

[0042] (L1) 100 parts of polypropylene chips, 10 parts of polyethylene glycol (1500) diacrylate (DA-PEG1500-DA), 2.2 parts of N-hydroxyethyl acrylamide and 0.1 parts of di-tert-butyl peroxide (DTBP) were mixed evenly and then melt-grafted in a torque rheometer at 210°C; the screw speed was 70 r / min; the reaction product was extruded, cooled in a cooling water tank and pelletized by a pelletizer to obtain grafted polypropylene.

[0043] (L2) Dissolve all of the above-mentioned grafted polypropylene in dichloromethane, add 1.8 parts of 2-pyridinecarboxyl chloride and 3 parts of triethylamine, react at 5±1℃ for 4h, and after the reaction is completed, rotary evaporate and dry to obtain modified polypropylene a.

[0044] Preparation Example 2: 10%, 1:0.15:0.1

[0045] The rest is the same as in Preparation Example 1, except that the raw material composition is: 100 parts polypropylene chips, 10 parts polyethylene glycol (1500) diacrylate (DA-PEG1500-DA), 1.5 parts N-hydroxyethyl acrylamide, 0.1 parts di-tert-butyl peroxide (DTBP), 1 part 2-pyridinecarboxyl chloride, and 1.5 parts triethylamine. Modified polypropylene b was finally obtained.

[0046] Preparation Example 3: 10%, 1:0.3:0.25

[0047] The rest is the same as in Preparation Example 1, except that the raw material composition is: 100 parts polypropylene chips, 10 parts polyethylene glycol (1500) diacrylate (DA-PEG1500-DA), 3 parts N-hydroxyethyl acrylamide, 0.1 parts di-tert-butyl peroxide (DTBP), 2.5 parts 2-pyridinecarboxyl chloride, and 4 parts triethylamine. Modified polypropylene c was finally obtained.

[0048] Preparation Example 4: 20%, 1:0.22:0.18

[0049] The rest of the preparation was the same as in Preparation Example 1, except that in step (L1), 20 parts of polyethylene glycol (2000) diacrylate (DA-PEG3000-DA) were used instead of 10 parts of polyethylene glycol (1500) diacrylate (DA-PEG1500-DA), and N-hydroxymethylacrylamide was used instead of N-hydroxyethylacrylamide; in step (L2), 2-pyridineacetyl chloride was used instead of 2-pyridineformyl chloride. Modified polypropylene d was finally obtained.

[0050] Comparative Preparation Example 1

[0051] The rest is the same as in Preparation Example 1, except that step (L2) is omitted, i.e., the reaction between 2-pyridinecarboxyl chloride and grafted polypropylene is not carried out. Modified polypropylene e is finally obtained.

[0052] Comparative Preparation Example 2

[0053] The rest is the same as in Preparation Example 1, except that N-hydroxyethylacrylamide is not added in step (L1), and the modified polypropylene f is finally obtained.

[0054] Comparative preparation example 3

[0055] The rest was the same as in Preparation Example 1, except that polyethylene glycol (600) diacrylate (DA-PEG600-DA) was used instead of polyethylene glycol (1500) diacrylate (DA-PEG1500-DA). Modified polypropylene g was finally obtained.

[0056] Example 1

[0057] (S1) Melt spinning: The modified polypropylene a obtained in Preparation Example 1 is fed into an extruder for heating and melting. It then enters the spinning die through a melt filter, melt delivery pipeline, and metering pump, and is evenly distributed to the cross-shaped spinning assembly. Spinning is performed at the outlet, followed by cooling, stretching, and cutting to produce cross-shaped modified polypropylene fibers with a fineness of 2.0 dtex and a length of 30 mm. The melt spinning process is as follows: spinning temperature 260℃, setting temperature 140℃, POY spinning speed 2500 m / min, POY draw ratio 2, FDY spinning speed 4000 m / min, FDY draw ratio 3, and winding speed 2800 r / min.

[0058] (S2) Preparation of the first fiber web layer: The cross-shaped modified polypropylene fibers are opened, fed into the first carding machine, and laid in parallel to form the first fiber web layer;

[0059] (S2) Preparation of the second fiber web layer: bamboo pulp fibers are opened, fed into the second carding machine, and laid in parallel to form the second fiber web layer;

[0060] (S3) Hydroentangling reinforcement: The first fiber web layer and the second fiber web layer are composited and stacked, and simultaneously fed into the hydroentangling high-pressure jet zone for hydroentangling reinforcement at 8 MPa. The number of hydroentangling passes is 5. Then, it is dried at 120°C and rolled into a roll to obtain the unidirectional moisture-wicking diaper surface layer made of hydroentangling non-woven fabric.

[0061] Example 2

[0062] The rest is the same as in Example 1, except that the modified polypropylene b prepared in Preparation Example 2 is used instead of the modified polypropylene slice a prepared in Preparation Example 1.

[0063] Example 3

[0064] The rest is the same as in Example 1, except that the modified polypropylene c prepared in Preparation Example 3 is used instead of the modified polypropylene slice a prepared in Preparation Example 1.

[0065] Example 4

[0066] The rest is the same as in Example 1, except that the modified polypropylene d prepared in Preparation Example 4 is used instead of the modified polypropylene slice a prepared in Preparation Example 1.

[0067] Comparative Example 1

[0068] The rest is the same as in Example 1, except that the modified polypropylene e prepared in Comparative Preparation Example 1 is used instead of the modified polypropylene slice a prepared in Preparation Example 1.

[0069] Comparative Example 2

[0070] The rest is the same as in Example 1, except that the modified polypropylene f prepared in Comparative Preparation Example 2 is used instead of the modified polypropylene slice a prepared in Preparation Example 1.

[0071] Comparative Example 3

[0072] The rest is the same as in Example 1, except that the modified polypropylene g prepared in Comparative Preparation Example 3 is used instead of the modified polypropylene slice a prepared in Preparation Example 1.

[0073] Testing and Analysis

[0074] The spunlace nonwoven fabrics of the above embodiments and comparative examples were subjected to the following performance tests:

[0075] Liquid penetration time: determined according to standard GB / T 24218 Textiles - Nonwovens Test Method.

[0076] Moisture return rate: Determined according to standard GB / T24218 Textiles - Nonwovens Test Methods.

[0077] Softness: Measured according to standard GB-T 8942-2016.

[0078] Abrasion resistance: The test was conducted in accordance with standard GB / T20991-2007. The test conditions were: pressure 5 kPa, grinding wheel speed 100 r / min, time 5 min, and the surface condition of the nonwoven fabric was observed with the naked eye.

[0079] Table 1 Performance Tests of Spunlace Nonwovens

[0080]

[0081] As shown in Table 1, the unidirectional moisture-wicking diaper surface layer prepared by this invention exhibits excellent unidirectional moisture-wicking properties due to its short liquid penetration time and low backflow rate with spunlace nonwoven fabric; it is also soft, skin-friendly, lint-free, and does not shed. While the spunlace nonwoven fabrics prepared in Comparative Examples 1 and 2 exhibit excellent unidirectional moisture-wicking properties and are soft and skin-friendly, they have poor abrasion resistance. Although the spunlace nonwoven fabric prepared in Comparative Example 3 is abrasion-resistant, lint-free, and does not shed, it has poor softness and skin-friendliness.

Claims

1. A unidirectional moisture-wicking diaper surface layer made of spunlace nonwoven fabric, comprising a first fiber web layer and a second fiber web layer entangled by hydroentanglement, characterized in that, The first fiber web layer is composed of modified polypropylene fibers with a cross-shaped structure; the second fiber web layer is composed of bamboo pulp fibers; the modified polypropylene is prepared by melt co-grafting polypropylene with polyether diacrylate and hydroxyl-containing acrylamide, followed by reaction with pyridine chloride derivative; the number average molecular weight of the polyether segment in the polyether diacrylate is 1500~3000; the amount of polyether diacrylate used is 10~20wt% of polypropylene; the mass ratio of polyether diacrylate, hydroxyl-containing acrylamide, and pyridine chloride derivative is 1:(0.15~0.3):(0.1~0.25); The modified polypropylene is prepared by a method comprising the following steps: (L1) Polypropylene chips, polyether diacrylate, hydroxyl-containing acrylamide and initiator are mixed evenly and then melt-co-grafted to obtain grafted polypropylene; (L2) The grafted polypropylene was dissolved in an organic solvent, and a pyridine chloride derivative and an acid-binding agent were added. The reaction was carried out under controlled temperature. After the reaction was completed, the modified polypropylene was obtained by rotary evaporation and drying.

2. The unidirectional moisture-wicking diaper surface layer is made of spunlace non-woven fabric according to claim 1, characterized in that, The melt index of the polypropylene is 25~40 g / 10 min.

3. The unidirectional moisture-wicking diaper surface layer is made of spunlace non-woven fabric according to claim 1, characterized in that, The hydroxyl-containing acrylamide is selected from at least one of N-hydroxyethyl acrylamide, N-hydroxymethyl acrylamide, and N-[tris(hydroxymethyl)methyl]acrylamide.

4. The unidirectional moisture-wicking diaper surface layer according to claim 1 is made of spunlace nonwoven fabric, characterized in that, The pyridine chloride derivative is at least one of 2-pyridinecarboxyl chloride, 3-pyridinecarboxyl chloride, 2-pyridineacetyl chloride, and 3-pyridineacetyl chloride.

5. The unidirectional moisture-wicking diaper surface layer is made of spunlace nonwoven fabric according to claim 1, wherein in step (L1), the initiator is selected from at least one of dicumyl peroxide and ditert-butyl peroxide, and the amount of initiator is 0.1~0.2wt% of polypropylene chips; the melt co-grafting is carried out in a torque rheometer at a reaction temperature of 200~220℃ and a rotation speed of 70~80 r / min; after the reaction, the product is cooled and granulated; and / or In step (L2), the organic solvent is at least one of toluene and xylene; the acid-binding agent is selected from at least one of triethylamine and pyridine, and the mass of the acid-binding agent is 1.5 to 2.0 times that of the pyridine chloride derivative; the temperature is 0 to 10°C, and the reaction time is 3 to 5 hours.

6. The unidirectional moisture-wicking diaper surface layer is made of spunlace non-woven fabric according to claim 1, characterized in that, The areal density of the first fiber web layer and the second fiber web layer is independently 8~15 g / m². 2 The first fiber has a fineness of 1.5~2.5 dtex and a length of 30~50 mm; the second fiber has a fineness of 1.0~1.5 dtex and a length of 30~50 mm.

7. The method for preparing the surface layer of the unidirectional moisture-wicking diaper as described in any one of claims 1-6 using spunlace nonwoven fabric, characterized in that, Includes the following steps: (S1) Melt spinning: Modified polypropylene chips are fed into a screw extruder for heating and melting, and then enter the spinning die through a melt filter, melt delivery pipeline and metering pump. The chips are evenly distributed to the cross-shaped spinning assembly. Spinning is performed at the outlet, and after cooling, stretching, winding and cutting, modified polypropylene fibers with a cross-shaped structure are produced. (S2) Preparation of the first fiber web layer: The modified polypropylene fibers with a cross-shaped structure are opened, fed into the first carding machine, and laid in parallel to form the first fiber web layer; (S3) Preparation of the second fiber web layer: bamboo pulp fibers are opened, fed into the second carding machine, and laid in parallel to form the second fiber web layer; (S4) Hydroentangling reinforcement: The first fiber web layer and the second fiber web layer are composited and stacked, and simultaneously fed into the hydroentangling high-pressure jet zone for hydroentangling reinforcement, drying, and rolling to obtain a unidirectional moisture-wicking diaper surface layer made of hydroentangling non-woven fabric.

8. The preparation method according to claim 7, characterized in that, In step (S1), the melt spinning process conditions are as follows: spinning temperature 250~280℃, setting temperature 140~160℃, POY spinning speed 2400-2800m / min, POY draw ratio 2~3 times, FDY spinning speed 3800-4200m / min, FDY draw ratio 2.5-3.5 times, and winding speed 2700~3200r / min; in step (S4), the hydroentangling pressure is 4~10MPa, the number of hydroentangling passes is 4~6; and the drying temperature is 100~150℃.

Images