Spunlaced non-woven fabric for surface layer of one-way moisture-conducting paper diaper and preparation method thereof

Abstract

The invention relates to a non-manufactured spunlace fabric for a one-way moisture-conducting paper diaper surface layer, which comprises a first fiber web layer and a second fiber web layer which are entangled in a spunlace mode, and the first fiber web layer is composed of modified polypropylene fibers of a cross-shaped structure; the second fiber net layer is composed of bamboo pulp fibers; the modified polypropylene is prepared by carrying out melt co-grafting on polypropylene through polyether diallyl ester and hydroxyl-containing acrylamide and then reacting with a picolinyl chloride derivative; the number-average molecular weight of a polyether segment in the polyether diallyl ester is 1500 to 3000. The first fiber net layer and the second fiber net layer are reinforced through the spunlace process to obtain the spunlace non-manufactured cloth with the one-way moisture conduction function for the paper diaper surface layer. The hydrophilic and hydrophobic difference of the fiber net layers on the two sides is large enough, the differential capillary effect is formed, and the one-way moisture conduction is achieved, and meanwhile the fabric is soft, skin-friendly, resistant to abrasion, free of fluffing and free of chip falling.

Description

Technical Field

[0001] The present invention belongs to the technical field of nonwoven fabrics, and in particular relates to a unidirectional moisture-conducting diaper surface layer spunlace nonwoven fabric and a preparation method thereof. Background Art

[0002] As people's living standards improve, the demand for sanitary products is increasing, and the performance requirements are also getting higher and higher. For example, diapers are required to have not only good absorption capacity and breathability, but also skin-friendly. Diapers are generally composed of four parts: surface layer, diversion layer, absorbent core and bottom layer. To meet the above performance, the surface material of diapers must be soft, skin-friendly, and have excellent water permeability but not water storage. It can quickly guide the liquid into the diversion layer or absorbent core below, and prevent the liquid from back-seeping back to the surface of the diaper, keeping the human skin surface as dry as possible, that is, the surface material of the diaper must have a one-way moisture conduction function. Spunlace nonwovens have the characteristics of soft feel, good fluffiness, not easy to pilling, no chemical mixture, no irritation to the skin, etc., and are widely used in the surface materials of diapers. At present, the surface materials of spunlace nonwovens used in diapers are mainly cotton and viscose fibers. Cotton and viscose fibers are soft and skin-friendly, but because cotton and viscose fibers themselves have good water absorption, when used in diapers, the amount of re-seepage after absorbing liquid is large, and the surface becomes very wet. They do not have excellent one-way moisture conduction function, resulting in poor comfort.

[0003] Polypropylene fiber is widely used in the field of nonwoven fabrics due to its good chemical resistance and wear resistance. However, polypropylene has a regular structure, no polar groups on the surface, good hydrophobicity, and good unidirectional moisture conductivity when used as upper and lower composite nonwoven fabrics with hydrophilic fibers, but poor skin affinity and softness, which limits its application in diaper surface materials. Chinese patent CN202211120117.4 discloses a soft and dry spunlace nonwoven fabric and a preparation method thereof, which includes cotton fiber nonwoven fabric, modified polypropylene nonwoven fabric and viscose fiber nonwoven fabric from the inside to the outside; cotton fiber nonwoven fabric has a certain hygroscopicity, and modified phosphazene is introduced into the viscose fiber nonwoven fabric, so that the viscose fiber nonwoven fabric has stronger hygroscopicity than cotton fiber nonwoven fabric, so that the spunlace nonwoven fabric has moisture conductivity. Although the unidirectional moisture conductivity of the nonwoven fabric for the surface layer of the diaper is good, the introduction of modifiers such as silicon and phosphorus will reduce skin affinity.

[0004] The method to improve the skin-friendly and soft properties of polypropylene is generally to introduce flexible groups, but this often leads to a decrease in mechanical properties, making it easy to fluff and shed. Using modified polypropylene and polypropylene for composite spinning is a good strategy, such as using modified polypropylene as the skin layer and polypropylene as the core layer for composite spinning to form a skin-core structured two-component fiber. The fiber obtained in this way ensures both mechanical properties and good skin-friendly and soft properties. However, the spinning technology requirements for two-component fibers are relatively high, and the process control is difficult.

[0005] Therefore, it is necessary to develop a nonwoven fabric for the surface layer of diapers using polypropylene as raw material, which has skin-friendly softness, fast one-way moisture conduction, and is not easy to pilling and lint. Summary of the invention

[0006] In view of the problem that the nonwoven fabric for the surface layer of diapers made of polypropylene as raw material in the prior art cannot take into account the skin-friendly softness, rapid unidirectional moisture conduction and non-pilling, the present invention provides a unidirectional moisture conduction diaper surface layer water-spunlace nonwoven fabric and its preparation method. The present invention uses modified polypropylene spinning to prepare a first fiber mesh layer that is skin-friendly, soft, hydrophobic and wear-resistant; uses bamboo pulp fiber with excellent hygroscopicity as a hydrophilic second fiber mesh layer; and then reinforces the first fiber mesh layer and the second fiber mesh layer through a water-spunlace process to obtain a unidirectional moisture conduction diaper surface layer water-spunlace nonwoven fabric; the hydrophilic and hydrophobic difference of the two fiber mesh layers is large enough to form a differential capillary effect, achieving unidirectional moisture conduction while maintaining softness, skin-friendlyness, wear resistance and non-pilling.

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

[0008] A unidirectional moisture-conducting diaper surface layer is made of a spunlace non-woven fabric, comprising a first fiber web layer and a second fiber web layer entangled by spunlace, wherein the first fiber web layer is composed of modified polypropylene fibers with a cross 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, and then reacting with a pyridinyl chloride derivative; the number average molecular weight of the polyether segment in the polyether diacrylate is 1500-3000.

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

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

[0011] Polyether diacrylate is a linear polyether macromolecule containing acrylate groups at both ends, which can improve the softness of polypropylene by grafting. If its molecular weight is too low, the required softness performance cannot be achieved. The larger its molecular weight, the longer the grafted molecular chain, the better the softness improvement, but too large a molecular weight will reduce the strength performance. In the present 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-hydroxyethyl acrylamide, N-hydroxymethyl acrylamide and N-[tris(hydroxymethyl)methyl]acrylamide.

[0013] Furthermore, the pyridinyl chloride derivative is at least one of 2-pyridinyl chloride, 3-pyridinyl chloride, 2-pyridinyl acetyl chloride and 3-pyridinyl acetyl chloride. The pyridinyl chloride derivative is a small molecule rigid substance, which reacts with the hydroxyl group of polyether diacrylamide to form a local cross-linking structure in the flexible grafted chain to compensate for the strength loss caused by the flexible chain grafting to polypropylene.

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

[0015] (L1) uniformly mixing polypropylene chips, polyether diacrylate, hydroxyl-containing acrylamide and an initiator, and melt-co-grafting to obtain grafted polypropylene;

[0016] (L2) dissolving the grafted polypropylene in an organic solvent, adding a pyridoyl chloride derivative and an acid binding agent, and reacting under controlled temperature. After the reaction is completed, performing rotary evaporation and drying to obtain modified polypropylene.

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

[0018] Furthermore, 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 pyridoyl chloride derivative; the temperature control temperature is 0 to 10° C., and the reaction time is 3 to 5 hours.

[0019] Furthermore, the surface density of the first fiber mesh layer and the second fiber mesh layer is independently 8 to 15 g / m2 .

[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] In a second aspect, the present invention provides a method for preparing the above-mentioned unidirectional moisture-conducting diaper surface layer spunlace non-woven fabric, comprising the following steps:

[0022] (S1) melt spinning: the modified polypropylene chips are sent into a screw extruder for heating and melting, and enter the spinning die head through a melt filter, a melt delivery pipeline, and a metering pump, and are evenly distributed to a cross-shaped spinning assembly; spinning is performed at the outlet, and after cooling, stretching, winding, and cutting, a cross-shaped modified polypropylene fiber is produced;

[0023] (S2) preparing a first fiber web layer: opening the cross-shaped modified polypropylene fibers, feeding the fibers into a first carding machine, and laying the fibers in parallel to form a first fiber web layer;

[0024] (S3) preparing a second fiber web layer: opening the bamboo pulp fibers, feeding the fibers into a second carding machine, and laying the fibers in parallel to form a second fiber web layer;

[0025] (S4) Hydroentanglement: The first fiber web layer and the second fiber web layer are composited and stacked, and simultaneously sent to the hydroentanglement high-pressure jet zone for hydroentanglement reinforcement, drying, and rolling to obtain a hydroentangled non-woven fabric for the surface layer of a one-way moisture-conducting diaper.

[0026] Furthermore, in step (S1), the process conditions of melt spinning are: spinning temperature 250-280°C, setting temperature 140-160°C, POY spinning speed 2400-2800m / min, POY drafting multiple 2-3 times, FDY spinning speed 3800-4200m / min, FDY drafting multiple 2.5-3.5 times, winding speed 2700-3200r / min.

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

[0028] In the present invention, the surface layer of the one-way moisture-conducting diaper can be perforated with a spunlace non-woven fabric to further improve the one-way moisture-conducting property.

[0029] The mechanism of the present invention is described as follows:

[0030] Polypropylene has a regular structure, no polar groups on the surface, and good water permeability, but poor skin affinity and softness. Polyether diacrylate is a linear polyether macromolecule with acrylate groups at both ends. Its grafting to polypropylene can improve its softness; if its molecular weight is too low, it cannot achieve the required softness; the larger its molecular weight, the longer the grafted molecular chain, and the better the softness improvement, but too large a molecular weight will reduce the strength performance. Therefore, the molecular weight of the polyether segment of the polyether macromolecular monomer used for grafting modified polypropylene in the prior art generally does not exceed 1500. The present invention melt-co-grafts polypropylene with polyether diacrylate having a molecular weight of 1500 to 3000 and hydroxyl-containing acrylamide, and then reacts with pyridinyl chloride derivatives to graft flexible long molecular chains on the polypropylene macromolecular chains, thereby significantly improving the softness and skin-friendliness; at the same time, the pyridinyl chloride derivatives are small molecular rigid substances, and their acyl chloride groups react with the hydroxyl groups of hydroxyl-containing acrylamide to form a local rigid cross-linking structure in the flexible long grafted chains, which can compensate for the strength reduction caused by the long flexible chains grafted to the polypropylene; in addition, the hydroxyl-containing acrylamide can also form intermolecular hydrogen bonds with the polyether segments. Therefore, the modified polypropylene obtained by the above modification has improved softness and skin-friendliness, while its mechanical strength will not be significantly reduced.

[0031] The fiber surface of the cross-shaped structure has many grooves distributed longitudinally, and its specific surface area is large. At the same time, the presence of the grooves will increase the pores inside the fiber, which can form a capillary effect, so that the fiber can quickly transport water. The modified polypropylene combined with the shape design of the cross-shaped spinneret micropores can be spun into a fiber that is skin-friendly, soft and can quickly transport water. Using it as the first fiber mesh layer has excellent skin-friendly softness, hydrophobicity, rapid water transport, and good strength performance.

[0032] Bamboo pulp fiber has excellent moisture absorption capacity. It is used as the second fiber web layer and composited with the first fiber web with good hydrophobicity and skin-friendliness formed by the above-mentioned modified polypropylene to form a non-woven fabric with a composite structure of a hydrophobic layer and a hydrophilic layer. Its differential capillary effect and wetting gradient effect cause the non-woven fabric to form an additional pressure difference in the thickness direction, thereby achieving unidirectional moisture conduction while maintaining good skin-friendliness, softness, wear resistance and no chipping.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] After polypropylene is melt-co-grafted with polyether diacrylate with a number average molecular weight of 1500-3000 and hydroxyl-containing acrylamide, it is reacted with pyridinyl chloride derivatives to obtain modified polypropylene. Combined with the shape design of the cross-shaped spinneret micropores, the first fiber mesh layer is made that is skin-friendly, soft, fast in water transport and has good strength performance. Bamboo pulp fiber with excellent hygroscopicity is used as the hydrophilic second fiber mesh layer. The first fiber mesh layer and the second fiber mesh layer are reinforced by a hydroentanglement process to obtain a unidirectional moisture-conducting diaper surface layer made of hydroentangled non-manufactured cloth; the hydrophilic and hydrophobic differences of the two fiber mesh layers are large enough to form a differential capillary effect, which achieves unidirectional moisture conduction while being soft and skin-friendly and wear-resistant, non-pilling and non-shedding. DETAILED DESCRIPTION

[0035] To make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be described in detail below. The following examples are convenient for better understanding of the present invention, but are not intended to limit the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified.

[0036] In the embodiments of the present invention, "parts" are parts by mass unless otherwise specified, and "%" are percentages by mass unless otherwise specified.

[0037] Polypropylene chips were purchased from Beijing Yanshan Petrochemical Corporation, model s2040, with a melt index of 38±1g / 10min.

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

[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 Materials 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 uniformly, and then melt co-grafted in a torque rheometer at 210°C; the screw speed was 70r / min; the reaction product was extruded, cooled in a cooling water tank, and pelletized by a pelletizer to obtain grafted polypropylene.

[0043] (L2) The grafted polypropylene was completely dissolved in dichloromethane, and 1.8 parts of 2-pyridinecarbonyl chloride and 3 parts of triethylamine were added. The mixture was reacted at 5±1° C. for 4 h. After the reaction was completed, the mixture was subjected to rotary evaporation and dried to obtain modified polypropylene a.

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

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

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

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

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

[0049] The rest is the same as Preparation Example 1, except that: in step (L1), 20 parts of polyethylene glycol (2000) diacrylate (DA-PEG3000-DA) are used to replace 10 parts of polyethylene glycol (1500) diacrylate (DA-PEG1500-DA), and N-hydroxymethyl acrylamide is used to replace N-hydroxyethyl acrylamide; in step (L2), 2-pyridyl acetyl chloride is used to replace 2-pyridylcarbonyl chloride. Finally, modified polypropylene d is obtained.

[0050] Comparative Preparation Example 1

[0051] The rest is the same as Preparation Example 1, except that step (L2), that is, the reaction between 2-pyridinecarbonyl chloride and grafted polypropylene is not performed, to finally obtain modified polypropylene e.

[0052] Comparative Preparation Example 2

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

[0054] Comparative Preparation Example 3

[0055] The rest is the same as Preparation Example 1, except that polyethylene glycol (600) diacrylate (DA-PEG600-DA) is used instead of polyethylene glycol (1500) diacrylate (DA-PEG1500-DA). Finally, modified polypropylene g is 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, and enters a spinning die through a melt filter, a melt delivery pipeline, and a metering pump, and is evenly distributed to a cross-shaped spinning assembly; spinning is performed at the outlet, and after cooling, stretching, and cutting, a cross-shaped modified polypropylene fiber with a fineness of 2.0 dtex and a length of 30 mm is prepared; the melt spinning process is as follows: a spinning temperature of 260° C., a setting temperature of 140° C., a POY spinning speed of 2500 m / min, a POY drafting multiple of 2 times, a FDY spinning speed of 4000 m / min, a FDY drafting multiple of 3 times, and a winding speed of 2800 r / min;

[0058] (S2) preparing a first fiber web layer: opening the cross-shaped modified polypropylene fibers, feeding the fibers into a first carding machine, and laying the fibers in parallel to form a first fiber web layer;

[0059] (S2) preparing a second fiber web layer: opening the bamboo pulp fibers, feeding the fibers into a second carding machine, and laying the fibers in parallel to form a second fiber web layer;

[0060] (S3) Hydroentanglement: The first fiber web layer and the second fiber web layer are composited and stacked, and simultaneously sent into the hydroentanglement high-pressure jet zone for hydroentanglement reinforcement at 8Mpa, with the number of hydroentanglement passes being 5, and then dried at 120°C and rolled to obtain a hydroentangled non-woven fabric for the surface layer of a one-way moisture-conducting diaper.

[0061] Example 2

[0062] The rest is the same as 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 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 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 Example 1, except that the modified polypropylene e prepared in Comparative Preparation Example 1 is used to replace the modified polypropylene slice a prepared in Preparation Example 1.

[0069] Comparative Example 2

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

[0071] Comparative Example 3

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

[0073] Testing and analysis

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

[0075] Liquid penetration time: measured in accordance with standard GB / T 24218 Textiles-Nonwoven fabrics test methods.

[0076] Rewetting amount: measured in accordance with standard GB / T24218 Textiles-Nonwoven fabrics test method.

[0077] Softness: measured in accordance with standard GB-T 8942-2016.

[0078] Abrasion resistance: measured with reference to standard GB / T20991-2007, test conditions: pressure 5 kPa, grinding wheel speed 100 r / min, time 5 min, and visual observation of the surface state of the nonwoven fabric.

[0079] Table 1 Performance test of spunlace nonwovens

[0080]

[0081] As can be seen from Table 1, the spunlace nonwoven fabric used as the surface layer of the one-way moisture-conducting diaper prepared by the present invention has a short liquid penetration time and is not easy to reversely penetrate, indicating that it has good one-way moisture-conducting properties; and it is soft, skin-friendly, and does not lint or shed. Although the spunlace nonwoven fabrics prepared in Comparative Examples 1 and 2 have good one-way moisture-conducting properties and are soft and skin-friendly, they have poor wear resistance. Although the spunlace nonwoven fabric prepared in Comparative Example 3 is wear-resistant, does not lint or shed, it has poor softness and skin-friendliness.

Claims

1. A one-way moisture-conducting diaper surface layer made of spunlace non-woven fabric, comprising a first fiber web layer and a second fiber web layer entangled by spunlace, characterized in that: The first fiber mesh layer is composed of modified polypropylene fibers with a cross structure; the second fiber mesh layer is composed of bamboo pulp fibers; the modified polypropylene is prepared by melt co-grafting polypropylene with polyether bisacrylate and hydroxyl-containing acrylamide, and then reacting with a pyridinyl chloride derivative; the number average molecular weight of the polyether segment in the polyether bisacrylate is 1500-3000.

2. The one-way moisture-conducting diaper surface layer spunlace non-woven fabric according to claim 1, characterized in that: The dosage of the polyether dipropylene ester is 10-20wt% of the polypropylene; the mass ratio of the polyether dipropylene ester, hydroxyl-containing acrylamide and pyridinyl chloride derivative is 1: (0.15-0.3) (0.1-0.25).

3. The one-way moisture-conducting diaper surface layer spunlace non-woven fabric according to claim 1, characterized in that: The melt index of the polypropylene is 25-40 g / 10 min.

4. The one-way moisture-conducting diaper surface layer 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.

5. The one-way moisture-conducting diaper surface layer spunlace non-woven fabric according to claim 1, characterized in that: The pyridinyl chloride derivative is at least one of 2-pyridinylcarbonyl chloride, 3-pyridinylcarbonyl chloride, 2-pyridinylacetyl chloride and 3-pyridinylacetyl chloride.

6. The one-way moisture-conducting diaper surface layer spunlace non-woven fabric according to claim 1, characterized in that: The modified polypropylene is prepared by a preparation method comprising the following steps: (L1) uniformly mixing polypropylene chips, polyether diacrylate, hydroxyl-containing acrylamide and an initiator, and melt-co-grafting to obtain grafted polypropylene; (L2) dissolving the grafted polypropylene in an organic solvent, adding a pyridoyl chloride derivative and an acid binding agent, and reacting under controlled temperature. After the reaction is completed, performing rotary evaporation and drying to obtain modified polypropylene.

7. The preparation method according to claim 6, wherein in step (L1), the initiator is selected from at least one of dicumyl peroxide and di-tert-butyl peroxide, and the amount of the initiator is 0.1-0.2wt% of the polypropylene chips; the melt grafting is carried out in a torque rheometer at a reaction temperature of 200-220°C and a rotation speed of 70-80r / min; after the reaction is completed, the product is cooled and granulated to obtain; and / or In step (L2), all organic solvents are 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 pyridoyl chloride derivative; the temperature control temperature is 0 to 10° C., and the reaction time is 3 to 5 hours.

8. The one-way moisture-conducting diaper surface layer spunlace non-woven fabric according to claim 1, characterized in that: The surface density of the first fiber web layer and the second fiber web layer is independently 8 to 15 g / m 2 ; The fineness of the first fiber is 1.5~2.5dtex, and the length is 30~50mm; the fineness of the second fiber is 1.0~1.5dtex, and the length is 30~50mm.

9. The method for preparing the unidirectional moisture-conducting diaper surface layer spunlace non-woven fabric according to any one of claims 1 to 8, characterized in that: The following steps are involved: (S1) melt spinning: the modified polypropylene chips are sent into a screw extruder for heating and melting, and enter the spinning die head through a melt filter, a melt delivery pipeline, and a metering pump, and are evenly distributed to a cross-shaped spinning assembly; spinning is performed at the outlet, and after cooling, stretching, winding, and cutting, a cross-shaped modified polypropylene fiber is produced; (S2) preparing a first fiber web layer: opening the cross-shaped modified polypropylene fibers, feeding the fibers into a first carding machine, and laying the fibers in parallel to form a first fiber web layer; (S3) preparing a second fiber web layer: opening the bamboo pulp fibers, feeding the fibers into a second carding machine, and laying the fibers in parallel to form a second fiber web layer; (S4) Hydroentanglement: The first fiber web layer and the second fiber web layer are composited and stacked, and simultaneously sent to the hydroentanglement high-pressure jet zone for hydroentanglement reinforcement, drying, and rolling to obtain a hydroentangled non-woven fabric for the surface layer of a one-way moisture-conducting diaper.

10. The preparation method according to claim 9, characterized in that: In step (S1), the process conditions of melt spinning are: spinning temperature 250-280°C, shaping temperature 140-160°C, POY spinning speed 2400-2800m / min, POY drafting multiple 2-3 times, FDY spinning speed 3800-4200m / min, FDY drafting multiple 2.5-3.5 times, winding speed 2700-3200r / min; in step (S4), the water spunlace pressure is 4-10Mpa, the number of water spunlace passes is 4-6 passes; the drying temperature is 100-150°C.

Images