Composite structure paper diaper surface layer spunlace nonwoven fabric and preparation method thereof

Abstract

The present application relates to a kind of composite structure's paper diaper surface layer with spunlace nonwoven fabric, including the first fiber web and the second fiber web of spunlace entanglement, the first fiber web is high shrinkage polyester (HSPET) / modified polypropylene side-by-side structure's bicomponent fiber, the second fiber web is bamboo pulp fiber;The modified polypropylene is maleimide grafting modified polypropylene.The first fiber web layer and the second fiber web layer are reinforced by spunlace process to obtain the spunlace nonwoven fabric of paper diaper surface layer;The hydrophilic-hydrophobic difference of two fiber web layers is large enough, differential capillary effect is formed, and the material of one-way water guide is realized with soft, skin-friendly.

Description

Technical Field

[0001] This invention belongs to the field of nonwoven fabrics, specifically relating to a composite structure of diaper surface layer spunlace nonwoven fabric and its preparation method. Background Technology

[0002] Disposable diapers generally consist of four parts: the top layer, the distribution layer, the absorbent core, and the bottom layer. The top layer material of a diaper must be soft, skin-friendly, and have excellent permeability without trapping water. It must quickly absorb liquid and guide it into the distribution layer or absorbent core below, preventing liquid from seeping back to the diaper surface and keeping the skin as dry as possible; in other words, the top layer material must have one-way moisture-wicking functionality. Spunlace nonwoven fabric is widely used in diaper top layer materials due to its soft feel, good bulkiness, resistance to pilling, absence of chemical additives, and non-irritating properties. Currently, spunlace nonwoven fabric top layer materials for diapers are mostly made of cotton and viscose fibers. While cotton and viscose fibers have good softness and skin-friendliness, their inherent absorbency leads to significant backflow after absorption, making the surface very damp and lacking excellent one-way moisture-wicking functionality, resulting in poor comfort.

[0003] Chinese patent CN202211120117.4 discloses a soft and dry spunlace nonwoven fabric and its preparation method, which includes 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 moisture absorption, and the introduction of modified phosphazene into the viscose fiber nonwoven fabric makes the moisture absorption of the viscose fiber nonwoven fabric stronger than that of the cotton fiber nonwoven fabric, so that the spunlace nonwoven fabric has moisture wicking ability.

[0004] Chinese patent CN202311083826.4 discloses a composite structure spunlace nonwoven fabric for the surface layer of diapers and its preparation method. The fabric includes a first and second spunlace entangled fiber web layer. The first fiber web layer comprises polyester fibers and a first modified viscose fiber. The second fiber web layer comprises a second modified viscose fiber and kapok fibers. The modifier for the first modified viscose fiber is an alkyl silane coupling agent, and the modifier for the second modified viscose fiber is a quaternary ammonium salt silane coupling agent. The amount of alkyl silane coupling agent in the first modified viscose fiber is 10-20 wt% of the viscose fiber, and the amount of quaternary ammonium salt silane coupling agent in the second modified viscose fiber is 1-5 wt% of the viscose fiber. The nonwoven fabric prepared by combining the first modified viscose fiber with polyester fiber as the first fiber web layer and the second modified viscose fiber with kapok fiber as the second fiber web layer is less prone to backflow, is moisture-loving but not absorbent, and can quickly allow water to pass through.

[0005] While the aforementioned nonwoven fabrics for diaper top layers exhibit good unidirectional moisture wicking properties, the introduction of modifiers such as silicon and phosphorus reduces their skin-friendliness. Polypropylene, due to its regular structure and lack of polar groups on its surface, has good hydrophobicity and good unidirectional moisture wicking properties when combined with hydrophilic fibers in composite nonwoven fabrics. However, its skin-friendliness and softness are inferior, thus limiting its application in diaper top layer materials. Therefore, it is necessary to develop a nonwoven fabric for diaper top layers that possesses both skin-friendliness and softness while also providing rapid unidirectional moisture wicking. Summary of the Invention

[0006] In view of the shortcomings of existing nonwoven fabrics for diaper surface layers, which cannot simultaneously achieve rapid unidirectional moisture wicking and comfort, this invention provides a composite structure diaper surface layer spunlace nonwoven fabric and its preparation method. This invention uses high-shrinkage polyester (HSPET) and modified polypropylene (PP) in a parallel structure for bicomponent spinning to obtain a soft, skin-friendly, and hydrophobic first fiber web layer; bamboo pulp fiber with excellent moisture absorption is used as a hydrophilic second fiber web layer; the first and second fiber web layers are then reinforced by a hydroentangling process to obtain the diaper surface layer 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 water wicking while maintaining skin-friendliness. The composite hydrowoven fabric can also be perforated to further improve unidirectional moisture wicking.

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

[0008] A composite diaper surface layer is made of spunlace nonwoven fabric, comprising a first fiber web and a second fiber web entangled by hydroentanglement. The first fiber web is a bicomponent fiber with a high-shrinkage polyester (HSPET) / modified polypropylene parallel structure, and the second fiber web is bamboo pulp fiber. The modified polypropylene is maleimide-grafted modified polypropylene.

[0009] High shrinkage polyester (HSPET) is a differentiated polyester with high shrinkage rate. It is generally prepared by copolymerization modification of polyester. The intrinsic viscosity of HSPET for spinning is 0.690±0.025dl / g and the melting point is 225±3℃.

[0010] Furthermore, in the HSPET / modified polypropylene parallel structure bicomponent fiber, the mass ratio of HSPET to modified polypropylene is 10-30:90-70. The preparation steps of the parallel structure bicomponent fiber are as follows: HSPET chips are fed into an extruder for heating and melting, then pass through a melt filter, melt delivery pipe, and metering pump into the spinning die, where they are evenly distributed to the first spinning assembly; modified polypropylene chips are fed into an extruder for heating and melting, filtered, extruded, and then passed through a metering pump into the spinning die, where they are evenly distributed to the second spinning assembly; composite spinning is performed at the outlet, followed by cooling, stretching, winding, and cutting to produce the bicomponent fiber.

[0011] Furthermore, the modified polypropylene is maleimide-grafted modified polypropylene, and the mass percentage of maleimide is 2-4 wt% of polypropylene.

[0012] Furthermore, the modified polypropylene is prepared by a method including the following steps: mixing dried polypropylene chips, maleimide and initiator evenly, and then melt-grafting to obtain modified polypropylene.

[0013] Furthermore, the drying of polypropylene chips and maleimide is carried out in an oven at 60-80℃ for 10-15 hours; the initiator is selected from at least one of ditert-butyl peroxide and dicumyl peroxide, and the amount of initiator is 0.1-0.2 wt% of the polypropylene chips; the melt 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 is completed, the product is cooled and granulated.

[0014] The inventors discovered that grafting maleimide onto polypropylene did not significantly improve the fluffiness and softness of the spunlace nonwoven fabric in the diaper surface layer of the composite structure of the present invention. They speculated that the reaction between the imino groups in maleimide and the hydroxyl groups in HSPET improved the interfacial compatibility and stability of the composite fibers, further enhancing softness and skin-friendliness.

[0015] Furthermore, the areal density of the first and second fiber webs is independently 15-25 g / m². 2 .

[0016] Furthermore, the fineness of the first fiber is 1.5-2.5 dtex and the length is 30-40 mm, and the fineness of the second fiber is 1.0-1.5 dtex and the length is 30-40 mm.

[0017] Polypropylene has a regular structure, no polar groups on its surface, and good water permeability, but its skin-friendliness and softness are poor. Bamboo pulp fiber, on the other hand, has low crystallinity, an irregular circular cross-section, a hollow interior, and numerous longitudinally distributed grooves on its surface. These grooves increase the internal porosity of the fiber, creating capillary action, resulting in strong moisture absorption, softness, and good skin-friendliness. Therefore, combining the good hydrophobicity of polypropylene with the excellent moisture absorption of bamboo pulp fiber to form a composite nonwoven fabric with a hydrophobic-hydrophilic layer creates an additional pressure difference in the thickness direction due to differential capillary effect and wetting gradient effect, achieving unidirectional water conduction and reducing backflow. However, polypropylene's poor skin-friendliness necessitates modification.

[0018] The parallel-structure bicomponent fiber uses two fibers side-by-side, with continuous and distinct single-component regions or interfaces along the fiber axis. Modified polypropylene and high-shrinkage polyester fiber (HSPET) are combined and spun in parallel. The significant difference in heat shrinkage properties between polypropylene and HSPET causes varying degrees of shrinkage during spinning, resulting in helical curls that make the fiber web fluffy, soft, and elastic, thus imparting excellent bulk and skin-friendliness to the first fiber web. The modified polypropylene is grafted with maleamide. The introduction of maleimide disrupts the structural regularity of polypropylene, improving its softness. Simultaneously, imino groups are introduced into the modified polypropylene, which is then combined with HSPET in a parallel-structure composite spinning process. The imino groups in the modified polypropylene can also react with the hydroxyl groups in HSPET, improving the interfacial compatibility and stability of the composite fiber. The fiber produced through this polypropylene grafting modification and parallel-structure composite spinning process is hydrophobic and skin-friendly, providing high comfort when used as the upper first fiber web in contact with the skin. The first fiber web is combined with bamboo pulp fiber with excellent moisture absorption to form a composite nonwoven fabric with a hydrophobic layer and a hydrophilic layer, which achieves unidirectional water conduction while maintaining good skin-friendliness.

[0019] Preferably, the diaper surface layer of the composite structure of the present invention can also be perforated with spunlace nonwoven fabric. The perforation process is well known to those skilled in the art, such as using laser perforation to form a funnel-shaped hole structure.

[0020] The second objective of this invention is to provide a method for preparing the above-mentioned composite spunlace fabric for the surface layer of diapers, comprising the following steps:

[0021] (S1) The two-component fibers with the parallel structure of HSPET / modified polypropylene are opened and combed to form the first fiber web.

[0022] (S2) Loosen and comb the bamboo pulp fibers to form a second fiber web.

[0023] (S3) The first fiber web and the second fiber web are combined, reinforced by hydroentanglement, dried and rolled to obtain the composite hydroentangled nonwoven fabric for the diaper surface layer.

[0024] In step (S3), the composite method is selected from either cross-laying or parallel-laying, and the hydroentanglement pressure is 4-10 MPa, with 3-6 hydroentanglement channels.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] Polyimide grafted to modify polypropylene is then spun in a parallel structure with high-shrinkage polyester (HSPET) to produce a soft, skin-friendly, and hydrophobic first fiber web layer. A hydrophilic second fiber web layer is made using bamboo pulp fiber with excellent moisture absorption. The first and second fiber web layers are then reinforced by a hydroentangling process to obtain a composite diaper surface layer made of hydroentangled nonwoven fabric. The hydrophilic and hydrophobic differences between the two fiber web layers are large enough to form a differential capillary effect, achieving unidirectional hydrophilicity while maintaining softness and skin-friendliness. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] HSPET chips are sourced from Zhejiang Hengyi High-Tech Materials Co., Ltd., with an intrinsic viscosity of 0.690±0.013 dl / g and a melting point of 225±2℃.

[0030] Bamboo pulp fiber was purchased from Shandong Jiumian Textile Co., Ltd., 1.33dtex×38mm.

[0031] Polypropylene chips were purchased from Beijing Yanshan Petrochemical Corporation, model S2040, with a melt flow rate of 38±1g / 10min and a density of 0.905±0.01g / cm3.

[0032] Polylactic acid (PLA) chips were purchased from Ningbo Huanqiu Biotechnology Co., Ltd., with an intrinsic viscosity of 1.40±0.02 dl / g and a melting point of 170±2℃.

[0033] Preparation of modified polypropylene

[0034] Preparation example a1

[0035] Preparation steps: 100 parts of polypropylene chips and 2 parts of maleimide were dried in a drying oven for 5 hours respectively; the dried polypropylene chips, maleimide and 0.1 parts of ditert-butyl peroxide (DTBP) were mixed evenly and then melt-grafted in a torque rheometer at 200℃; the screw speed was 70 rpm; the reaction extrudate was cooled in a cooling water bath and cut into maleimide-grafted modified polypropylene chips of a certain shape using a pelletizer.

[0036] Preparation Example a2

[0037] The rest is the same as in Preparation Example 1, except that the raw materials are changed to: 100 parts polypropylene chips, 4 parts maleimide, and 0.2 parts ditert-butyl peroxide (DTBP).

[0038] Comparative preparation example a1

[0039] The rest is the same as in Preparation Example 1, except that maleic imine is replaced with an equal mass of maleic anhydride.

[0040] Preparation Example b1

[0041] Ten parts of HSPET chips were fed into an extruder for heating and melting. The melt was then passed through a melt filter, melt delivery pipe, and metering pump into the spinning die, where it was evenly distributed to the first spinning assembly. Ninety parts of the modified polypropylene chips from Preparation Example a1 were fed into an extruder for heating and melting. The chips were then filtered, extruded, and pumped through a metering pump into the spinning die, where they were evenly distributed to the second spinning assembly. Composite spinning was performed at the outlet, followed by cooling, stretching, and cutting to produce short fibers with a fineness of 2.0 dtex and a length of 25 mm. The melt spinning process was as follows: spinning temperature 300℃, setting temperature 150℃, POY spinning speed 2600 m / min, POY draw ratio 2, FDY spinning speed 4200 m / min, FDY draw ratio 3, and winding speed 3000 r / min.

[0042] Preparation Example b2

[0043] The rest is the same as in preparation example b1, except that the raw materials are changed to: 30 parts of HSPET chips and 70 parts of modified polypropylene chips from preparation example a1.

[0044] Preparation Example b3

[0045] The rest is the same as in preparation example b1, except that the raw materials are changed to: 20 parts of HSPET chips and 80 parts of modified polypropylene chips from preparation example a2.

[0046] Comparative preparation example b1

[0047] The rest is the same as in preparation example b1, except that the modified polypropylene chips in preparation example b1 are replaced with the modified polypropylene chips in comparative preparation example a1.

[0048] Comparative preparation example b2

[0049] The rest is the same as in Preparation Example b1, except that HSPET is not added, and only the modified polypropylene chips from Preparation Example a1 are used to prepare the first fiber of a single component.

[0050] Comparative preparation example b3

[0051] The rest is the same as in preparation example b1, except that HSPET in preparation example b1 is replaced with polylactic acid.

[0052] Example 1

[0053] The HSPET / modified polypropylene parallel structure bicomponent fibers obtained in Preparation Example b1 were opened and combed to form a first fiber web; bamboo pulp fibers were opened and combed to form a second fiber web; the injection amount was controlled so that the areal density of the first fiber web was 20 g / m². 2 The areal density of the second fiber web is 20 g / m². 2 The first and second fiber webs are cross-laid and reinforced with three hydroentangling processes. The water pressure of the first hydroentangling process is 4.5 MPa, the water pressure of the second hydroentangling process is 7.5 MPa, and the water pressure of the third hydroentangling process is 4.5 MPa. After drying and rolling, the composite hydroentangled nonwoven fabric for the diaper surface layer is obtained.

[0054] Example 2

[0055] The rest is the same as in Example 1, except that the first fiber web is made using the parallel structure bicomponent fibers of Preparation Example b2.

[0056] Example 3

[0057] The rest is the same as in Example 1, except that the first fiber web is made using the side-by-side bicomponent fibers of Preparation Example b3.

[0058] Comparative Example 1

[0059] The rest is the same as in Example 1, except that the first fiber web is prepared using the parallel structure bicomponent fibers of b1 prepared in the comparative example.

[0060] Comparative Example 2

[0061] The rest is the same as in Example 1, except that the first fiber web is made using the modified polypropylene fiber of Comparative Preparation Example b2.

[0062] Comparative Example 3

[0063] The rest is the same as in Example 1, except that the first fiber web was prepared using the modified polypropylene fiber of Comparative Preparation Example b3.

[0064] Application examples

[0065] The spunlace nonwoven fabrics of the above embodiments and comparative examples were subjected to the following performance tests:

[0066] Liquid penetration time: determined according to standard GB / T 24218 Textiles - Nonwovens Test Method.

[0067] Moisture return rate: Determined according to standard GB / T24218 Textiles - Nonwovens Test Methods.

[0068] Softness: Measured according to standard GB-T 8942-2016.

[0069] Table 1

[0070]

[0071] As shown in Table 1, the composite structure diaper surface layer made by the present invention has a short liquid penetration time with spunlace nonwoven fabric, is not prone to backflow, has good one-way water permeability, and is soft and skin-friendly.

Claims

1. A composite structure diaper surface layer made of spunlace nonwoven fabric, characterized in that, It includes a hydroentangled first fiber web and a second fiber web, wherein the first fiber web is a bicomponent fiber with a high-shrinkage polyester / modified polypropylene parallel structure, and the second fiber web is bamboo pulp fiber; The modified polypropylene is maleimide-grafted modified polypropylene; in the first fiber web, the mass ratio of high-shrinkage polyester to modified polypropylene is 10-30:90-70; the modified polypropylene is maleimide-grafted modified polypropylene, and the mass percentage of maleimide is 2-4 wt% of polypropylene.

2. The diaper surface layer of the composite structure according to claim 1 is made of spunlace nonwoven fabric, characterized in that, The intrinsic viscosity of the high-shrinkage polyester is 0.690±0.025 dl / g, and the melting point is 225±3℃.

3. The diaper surface layer of the composite structure according to claim 1 is made of spunlace nonwoven fabric, characterized in that, The modified polypropylene is prepared by a method including the following steps: mixing dried polypropylene chips, maleimide and initiator evenly, and then melt grafting to obtain modified polypropylene.

4. The diaper surface layer of the composite structure according to claim 3 is made of spunlace nonwoven fabric, characterized in that, The drying of polypropylene chips and maleimide was carried out in an oven at 60-80℃ for 10-15 hours. The initiator was selected from at least one of ditert-butyl peroxide and dicumyl peroxide, and the amount of initiator was 0.1-0.2 wt% of the polypropylene chips. The melt grafting was 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 was completed, the product was cooled and granulated.

5. The diaper surface layer of the composite structure according to claim 1 is made of spunlace nonwoven fabric, characterized in that... The areal density of the first and second fiber webs is independently 15-25 g / m². 2 ; The fineness of the first fiber is 1.5-2.5 dtex and the length is 30-40 mm. The fineness of the second fiber is 1.0-1.5 dtex and the length is 30-40 mm.

6. A method for preparing the diaper surface layer of the composite structure according to any one of claims 1-5 using spunlace nonwoven fabric, characterized in that, Includes the following steps: (S1) The high-shrinkage polyester / modified polypropylene bicomponent fibers with parallel structures are opened and combed to form a first fiber web; (S2) Loosen and comb the bamboo pulp fibers to form a second fiber web; (S3) The first fiber web and the second fiber web are combined, reinforced by hydroentanglement, dried and rolled to obtain the composite hydroentangled nonwoven fabric for the diaper surface layer.

7. The method for preparing the composite structure diaper surface layer using spunlace nonwoven fabric according to claim 6, characterized in that, The first fiber web is prepared by a method including the following steps: high-shrinkage polyester chips are fed into an extruder for heating and melting, and then enter the spinning die through a melt filter, melt conveying pipeline, and metering pump, and are evenly distributed to the first spinning assembly through the spinning die; modified polypropylene chips are fed into an extruder for heating and melting, filtered, extruded, and then enter the spinning die through a metering pump, and are evenly distributed to the second spinning assembly; composite spinning is performed at the outlet, and after cooling, stretching, winding, and cutting, bicomponent fibers are produced.

8. The method for preparing the composite structure diaper surface layer using spunlace nonwoven fabric according to claim 6, characterized in that, In step (S3), the composite method is selected from either cross-laying or parallel-laying, and the hydroentanglement pressure is 4-10 MPa, with 3-6 hydroentanglement channels.

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