CN117702366A - Composite structure water-jet nonwoven fabric for sanitary towel surface layer and preparation method thereof - Google Patents

Abstract

The invention relates to a spunlaced non-woven fabric of a sanitary towel surface layer with a composite structure, which comprises a first fiber net layer and a second fiber net layer which are hydraulically entangled, wherein the first fiber net layer is composed of bicomponent fibers with a sheath-core structure, the sheath layer of the bicomponent fibers is modified polypropylene, and the core layer is polypropylene; the second fiber web layer is composed of hydrophilic polyester fibers with a cross-shaped structure; the modified polypropylene is polyether acrylate grafted modified polypropylene, and the hydrophilic polyester is modified copolyester by an in-situ polymerization method. The first fiber web layer and the second fiber web layer are reinforced by a hydroentangled process to obtain a hydroentangled non-woven fabric of the sanitary towel surface layer; the two fiber net layers have large hydrophilic-hydrophobic difference, form differential capillary effect, realize one-way water guiding of the material and simultaneously have softness and skin affinity.

Description

Composite structure water-jet nonwoven fabric for sanitary towel surface layer and preparation method thereof

Technical Field

The invention belongs to the field of non-woven fabrics, and particularly relates to a spunlaced non-woven fabric with a composite structure for a sanitary towel surface layer and a preparation method thereof.

Background

Sanitary napkins generally consist of a top layer, an absorbent layer and a bottom layer. As a facing material of a sanitary napkin, it is required to have softness, skin-friendly property, excellent water permeability, and ability to rapidly absorb and transfer menstrual blood into an absorbent layer and to prevent liquid from reversely penetrating back to the surface of the sanitary napkin, i.e., the facing material of the sanitary napkin is required to have skin-friendly property and unidirectional moisture-conducting function. Compared with spun-bonded non-woven fabrics, the spun-bonded non-woven fabrics have the characteristics of soft hand feeling, good fluffiness, difficult fuzzing, no stimulation to skin and the like, and are widely used in surface layer materials of sanitary napkins. The spunlaced non-woven fabric surface layer material for the sanitary towel at present mainly comprises cotton or viscose fiber raw materials, and the cotton and viscose fibers have good softness and skin-friendly property, but because the cotton and viscose fibers have good water absorbability, the rewet amount after imbibition is large when the spunlaced non-woven fabric surface layer material is applied to the sanitary towel, the surface can become very moist, and the excellent unidirectional moisture-conducting function is not achieved, so that the comfort is poor. The polypropylene has regular structure, no polar group on the surface, better hydrophobicity, better unidirectional moisture permeability when being used as an upper layer and a lower layer of composite non-woven fabric with fibers having good hydrophilicity, but poor skin-friendly property and softness, thus limiting the application of the polypropylene in sanitary towel surface layer materials.

Chinese patent CN202211120117.4 discloses a soft, dry and comfortable spunlaced nonwoven fabric and a preparation method thereof, comprising cotton fiber nonwoven fabric, modified polypropylene nonwoven fabric and viscose nonwoven fabric from inside to outside; the cotton fiber non-woven fabric has certain hygroscopicity, and the modified phosphazene is introduced into the viscose fiber non-woven fabric, so that the hygroscopicity of the viscose fiber non-woven fabric is stronger than that of the cotton fiber non-woven fabric, and the spun-laced non-woven fabric has moisture conductivity. Although the unidirectional moisture permeability of the nonwoven fabric is good, the inclusion of modifiers such as silicon and phosphorus reduces the skin-friendly property.

There is a need for a spunlaced nonwoven for a sanitary napkin facing that has both skin-friendly, soft and rapid unidirectional moisture transfer.

Disclosure of Invention

In view of the defect that the nonwoven fabric of the sanitary towel surface layer in the prior art cannot have both rapid unidirectional moisture permeability and skin affinity, the invention provides the spunlaced nonwoven fabric of the sanitary towel surface layer with a composite structure and a preparation method thereof. The invention uses modified Polypropylene and Polypropylene (PP) to carry out double-component spinning in a skin-core structure to prepare a soft skin-friendly hydrophobic first fiber web layer; spinning with hydrophilic modified polyester through special-shaped spinneret holes to obtain a hydrophilic second fiber web layer; then the first fiber web layer and the second fiber web layer are reinforced by a water needling process to obtain a composite water needling non-woven fabric for the sanitary towel surface layer; the two fiber net layers have large hydrophilic-hydrophobic difference, so that a differential capillary effect is formed, and the unidirectional water guide of the material is realized while the skin-friendly property and softness are maintained.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

the water-jet nonwoven fabric comprises a first fiber web layer and a second fiber web layer which are entangled by water jet, wherein the first fiber web layer is composed of bicomponent fibers with a sheath-core structure, the sheath layer of the bicomponent fibers is modified polypropylene, the core layer is polypropylene, and the second fiber web layer is composed of hydrophilic polyester fibers with a cross-shaped structure; the modified polypropylene is polyether acrylate grafted modified polypropylene; the hydrophilic polyester is modified copolyester by an in-situ polymerization method.

Further, the areal density of the first and second web layers is independently from 8 to 15g/m ² 。

Further, the first fiber has a fineness of 1.5-2.5dtex and a length of 30-50mm, and the second fiber has a fineness of 1.0-1.5dtex and a length of 30-50mm.

In the bicomponent fiber with the sheath-core structure, the mass ratio of the modified polypropylene to the polypropylene is 10-30:90-70.

The modified polypropylene is polyether acrylate grafted modified polypropylene, and the dosage of the polyether acrylate is 10-25wt% of the polypropylene.

Preferably, the number average molecular weight of the polyether acrylate is 300-800, for example, at least one of methoxy polyethylene glycol (400) acrylate, methoxy polyethylene glycol (600) acrylate, polyethylene glycol (400) diacrylate and polyethylene glycol (600) diacrylate is selected. Too long a grafted molecular chain can affect flowability and strength properties, and too short a molecular chain can not achieve the required flexibility properties.

Further, the modified polypropylene is prepared by a preparation method comprising the following steps: and uniformly mixing the dried polypropylene slices, polyether acrylate and an initiator, and performing melt grafting to obtain the modified polypropylene.

Further, drying the polypropylene slices and polyether acrylate in an oven, and drying at 60-80 ℃ for 5-15 hours; the initiator is at least one of ditert-butyl peroxide and dicumyl peroxide, and the dosage of the initiator is 0.1-0.2wt% of the polypropylene slice; the melt grafting is carried out in a torque rheometer, the reaction temperature is 200-220 ℃, and the rotating speed is 70-80r/min; after the reaction is finished, the product is cooled and granulated.

The hydrophilic polyester is formed by copolymerizing terephthalic acid, isophthalic acid, ethylene glycol, dimethyl isophthalate-5-sodium sulfonate and polyethylene glycol under the action of a catalyst and a stabilizer; the dosage of the isophthalic acid is 5-10wt% of terephthalic acid, the dosage of the dimethyl isophthalate-5-sodium sulfonate is 5-15wt% of terephthalic acid, the molecular weight of the polyethylene glycol is 1000-2000, and the dosage is 5-10wt% of terephthalic acid; the catalyst is antimony trioxide or antimony acetate, and the dosage is 0.03-0.04wt% of terephthalic acid; the stabilizer is trimethyl phosphate and the amount of stabilizer is 0.01-0.02wt% of terephthalic acid.

The hydrophilic polyester is prepared by a preparation method comprising the following steps:

(1) Adding terephthalic acid, ethylene glycol and isophthalic acid into a pulping kettle under a stirring state, controlling the molar ratio of the ethylene glycol to the acid to be 1.2-1.5, and adding a catalyst and a stabilizer to obtain a slurry after uniform mixing;

(2) The slurry is led into an esterification kettle with stirring for esterification reaction at 245-255 ℃, the column top temperature of a fractionating column is controlled to be not more than 110 ℃, dimethyl isophthalate-5-sodium sulfonate and polyethylene glycol are added after esterification, and the mixture is led into a polycondensation kettle with stirring when the kettle temperature is increased to 230-250 ℃.

(3) Under the action of a vacuum pump, the pressure in the polycondensation kettle is kept below 50Pa to carry out polycondensation reaction, and the kettle temperature is controlled to be 270-280 ℃ to carry out reaction for 3-4 hours.

(4) Stopping stirring after the reaction, removing vacuum with high-purity nitrogen, increasing the pressure to 0.2-0.5MPa, casting strips from the casting belt head, granulating with a granulator after cooling water, and obtaining hydrophilic polyester chips.

The second object of the invention is to provide a method for preparing the water-jet cloth for the sanitary towel surface layer with the composite structure, which comprises the following steps:

(S1) a first web layer: conveying the modified polypropylene slices into an extruder for heating and melting, and conveying the modified polypropylene slices into a spinning die head through a melt filter, a melt conveying pipeline and a metering pump, and uniformly distributing the modified polypropylene slices to a first spinning assembly through the spinning die head; feeding the polypropylene slices into an extruder for heating and melting, and feeding the polypropylene slices into a spinning die head through a filter, extrusion and a metering pump for uniform distribution to a second spinning component; carrying out composite spinning at an outlet, and cooling, stretching, winding and cutting to prepare the bicomponent fiber with a sheath-core structure, wherein the sheath layer is modified polypropylene, and the core layer is polypropylene; the bicomponent fibers are opened and carded to form a first web layer.

(S2) a second web layer: feeding hydrophilic polyester chips into an extruder for heating and melting, and feeding the hydrophilic polyester chips into a spinning die head through a filter, extrusion and a metering pump to be uniformly distributed to a cross-shaped spinning component; carrying out composite spinning at an outlet, and preparing the cross-shaped hydrophilic polyester fiber through cooling, stretching, winding and cutting; and opening and carding the hydrophilic polyester fiber with the cross-shaped structure to form a second fiber web layer.

(S3) water-jet nonwoven fabric: and compounding the first fiber web layer and the second fiber web layer, and carrying out hydroentanglement reinforcement, drying and rolling to obtain the composite hydroentangled non-woven fabric for the sanitary towel surface layer.

And (3) selecting one of cross lapping or parallel lapping in a compound mode in the step (S3), wherein the water jet pressure is 4-10MPa, and the number of water jet channels is 3-6.

The mechanism of the invention is explained as follows:

the two-component fiber of the sheath-core structure is a composite fiber with two components distributed in the sheath-core mode, is formed by compounding two polymers with different properties or structures by surrounding one component with the other component along the fiber axial direction, and has the characteristics of the two fibers. The polypropylene has regular structure, no polar group on the surface and good water permeability, but has poor skin-friendly property and flexibility, and the flexible long molecular chain is grafted on the polypropylene macromolecular chain through melt grafting reaction, so that the introduction of the flexible long molecular chain breaks the structural regularity of polypropylene, the flexibility is improved, but the modified polypropylene fiber has high cost, and the introduction of too much flexible long molecular chain also reduces the strength. Then carrying out composite spinning on the modified polypropylene and the polypropylene in a sheath-core structure; the polypropylene is used as a core layer, so that higher breaking strength is provided; the modified polypropylene is used as a skin layer, is in direct contact with the skin, keeps good hydrophobicity and provides good softness. Meanwhile, due to the difference of the heat shrinkage performance of the modified polypropylene and the unmodified polypropylene, the modified polypropylene can shrink to different degrees in the spinning process to generate three-dimensional spiral curling, so that the fluffiness and the softness are further improved, namely, the required fluffiness and softness can be achieved even if less flexible long molecular chains are introduced. Therefore, the first fiber net prepared by composite spinning and net laying of the sheath-core structure of the modified polypropylene/polypropylene has excellent skin-friendly property, hydrophobicity and strength performance, and is contacted with skin, so that the comfort level is high.

The polyester has good mechanical property and chemical resistance and low cost, but has better crystallinity and lacks hydrophilic groups, so that the water absorption is poor. The surface of the fiber of the cross structure is longitudinally provided with more grooves, the specific surface area is large, and the existence of the grooves can enlarge the pores in the fiber, so that capillary action can be formed, and the fiber can quickly absorb and transport water. The polyester and the monomer containing hydrophilic groups are copolymerized and modified, and the fiber with rapid water absorption and water delivery can be spun by combining the shape design of the spinneret plate micropores, so that the fiber has good hygroscopicity as the second fiber web of the lower layer.

The first fiber web with good hydrophobicity and skin-friendly property and the second fiber web with good hygroscopicity are compounded to form the non-woven fabric with the composite structure of the hydrophobic layer and the hydrophilic layer, and the differential capillary effect and the wetting gradient effect enable the non-woven fabric to form additional pressure difference in the thickness direction, so that the non-woven fabric can realize unidirectional water guiding and simultaneously maintain good skin-friendly property. Further preferably, the first fiber web layer adopts polyether acrylate modified polypropylene as a skin layer, and the polyether acrylate chain segment has good compatibility with hydrophilic polyester of the second fiber web layer, so that when the polyether acrylate chain segment and the hydrophilic polyester are contacted, water of the first fiber web layer is more beneficial to be introduced into the second fiber web layer.

Compared with the prior art, the invention has the beneficial effects that:

the spun-laced non-woven fabric comprises a first fiber web and a second fiber web, wherein the first fiber web is modified polypropylene/polypropylene bicomponent fiber with a sheath-core structure, the sheath-modified polypropylene provides softness and hydrophobicity, the core-layer polypropylene provides higher breaking strength, and when the sheath-core structure is used for spinning, the sheath-core structure and the core-layer polypropylene shrink to different degrees to generate three-dimensional spiral curl in the spinning process, so that the spun-laced non-woven fabric is fluffy and soft, and the prepared first fiber web is skin-friendly and hydrophobic; the second fiber web is hydrophilic polyester fiber with a cross structure, hydrophilic groups are introduced into the second fiber web through an in-situ polymerization method to prepare hydrophilic polyester, and the cross spinneret orifice design is combined, so that the first fiber web is endowed with excellent water absorption and hydrophobicity; reinforcing the first fiber net layer and the second fiber net layer through a hydro-entangled process to obtain a hydro-entangled non-woven fabric of the sanitary towel surface layer; the two fiber net layers have large hydrophilic-hydrophobic difference, form differential capillary effect, realize one-way water guiding of the material and simultaneously have softness and skin affinity.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. The following examples facilitate a better understanding of the present invention, but are not intended to limit the same. The experimental methods in the following examples are conventional methods unless otherwise specified.

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

Polypropylene chips were purchased from Peking Yanshan petrochemistry Co., ltd., model s2040, melt flow rate 38.+ -. 1g/10min, density 0.905.+ -. 0.01g/cm3.

Methoxy polyethylene glycol (400) acrylate and methoxy polyethylene glycol (600) acrylate are purchased from Guangzhou-shao new material science and technology Co., ltd, and are respectively of the type MPEG400A, MPEG A.

Dimethyl isophthalate-5-sodium sulfonate is purchased from Shandong Jinsheng New Material technology Co., ltd, the acid value is less than or equal to 0.6mgKOH/g, and the moisture is less than or equal to 0.35%.

Polyethylene glycol PEG-1000, hydroxyl value 102-125 mgKOH/g, water content less than or equal to 1.0%.

Preparation of modified Polypropylene

Preparation example a1

Drying 100 parts of polypropylene slices and 10 parts of methoxy polyethylene glycol (400) acrylic ester in a drying oven at 70 ℃ for 5 hours respectively; uniformly mixing the dried polypropylene slices, methoxy polyethylene glycol (400) acrylic ester and 0.1 part of ditert butyl peroxide (DTBP), and then carrying out melt grafting in a torque rheometer at 200 ℃; the rotating speed of the screw is 70 revolutions per minute; the reaction extrudate is cooled by a cooling water tank and cut into methoxy polyethylene glycol acrylate grafted modified polypropylene slices according to a certain shape by a granulator.

Preparation example a2

The rest is the same as in preparation example 1, except that the raw material components are: 100 parts of polypropylene slice, 25 parts of methoxy polyethylene glycol (600) acrylate and 0.2 part of ditert-butyl peroxide (DTBP).

Preparation example a3

The other components were the same as in preparation example 1 except that methoxypolyethylene glycol (400) acrylate was used in an amount of 5 parts.

Preparation example a4

The remainder was the same as in preparation example 1, except that methoxypolyethylene glycol (200) acrylate was used instead of methoxypolyethylene glycol (200) acrylate.

Comparative preparation a1

The remainder was the same as in preparation example 1 except that 2.47 parts of maleic anhydride was used instead of 10 parts of methoxypolyethylene glycol (400) acrylate. (i.e., molar ratio of maleic anhydride to methoxypolyethylene glycol (400) acrylate)

Preparation of hydrophilic polyesters

Preparation example b1

(1) Adding 100 parts of terephthalic acid, 50 parts of ethylene glycol, 10 parts of isophthalic acid, 0.04 part of catalyst antimony trioxide and 0.02 part of stabilizer trimethyl phosphate into a beating kettle under a stirring state, and uniformly stirring and mixing to obtain slurry;

(2) The slurry is led into an esterification kettle with stirring for esterification reaction at 250 ℃, the column top temperature of a fractionating column is controlled to be 100-105 ℃, 10 parts of dimethyl isophthalate-5-sodium sulfonate and 6 parts of polyethylene glycol PEG-1000 are added after esterification, and the kettle temperature is raised to be led into a polycondensation kettle with stirring at 240 ℃.

(3) Under the action of a vacuum pump, the pressure in the polycondensation kettle is kept below 50Pa to carry out polycondensation reaction, and the kettle temperature is controlled to carry out reaction for 3-4 hours at 270 ℃.

(4) Stopping stirring after the reaction, removing vacuum with high-purity nitrogen, increasing the pressure to 0.25MPa, casting the strip from the casting belt head, granulating with a granulator after cooling water, and obtaining hydrophilic polyester chips.

Preparation example b2

The remainder was the same as in preparation example 1 except that the raw material components: 100 parts of terephthalic acid, 50 parts of ethylene glycol, 8 parts of isophthalic acid, 0.04 part of catalyst antimonous oxide, 0.02 part of stabilizer trimethyl phosphate, 6 parts of dimethyl isophthalate-5-sodium sulfonate and 10 parts of polyethylene glycol PEG-1000.

Example 1

(S1) a first web: 10 parts of modified polypropylene slices prepared in preparation example a1 are sent into an extruder for heating and melting, enter a spinning die head through a melt filter, a melt conveying pipeline and a metering pump, and are uniformly distributed to a first spinning component through the spinning die head; feeding 90 parts of polypropylene slices into an extruder for heating and melting, and feeding the polypropylene slices into a spinning die head through a filter, extrusion and metering pump to be uniformly distributed to a second spinning component; carrying out composite spinning at an outlet, and cooling, stretching and cutting to prepare modified polypropylene/polypropylene bicomponent fiber with a fiber number of 2.0dtex and a sheath-core structure with a length of 30 mm; the melt spinning process is that the spinning temperature is 280 ℃, the shaping temperature is 150 ℃, the POY spinning speed is 2600m/min, the POY drafting multiple is 2 times, the FDY spinning speed is 4200m/min, the FDY drafting multiple is 3 times, and the winding speed is 3000r/min; the bicomponent fibers are opened and carded to form a first web.

(S2) a second web: feeding the hydrophilic polyester chips obtained in the preparation example b1 into an extruder for heating and melting, filtering, extruding, feeding into a spinning die head through a metering pump, and uniformly distributing to a cross-shaped spinning component; carrying out composite spinning at an outlet, and preparing the cross-shaped hydrophilic polyester fiber with fineness of 1.5dtex and length of 30mm through cooling, stretching, winding and cutting, wherein the melt spinning process comprises the steps of spinning temperature 280 ℃, shaping temperature 120 ℃ and POY spinning speed: 2200m/min, POY draft multiple 2 times, FDY spinning speed 3800m/min, FDY draft multiple 3 times, winding speed 3000r/min; opening and carding the cross-shaped hydrophilic polyester fiber to form a second fiber web.

(S3) water-jet nonwoven fabric: and compounding the first fiber web and the second fiber web, and carrying out hydroentanglement reinforcement, drying and rolling to obtain the hydroentangled non-woven fabric of the sanitary towel with the composite structure.

And (3) selecting one of cross lapping and parallel lapping in the compound mode in the step (S3), wherein the hydroentangling pressure is 8MPa, and the number of hydroentangled channels is 5.

Example 2

The remainder was the same as in example 1 except that the amount of the modified polypropylene produced in production example a1 was 30 parts.

Example 3

The remainder was the same as in example 1, except that the modified polypropylene prepared in preparation example a2 was used instead of the modified polypropylene prepared in preparation example a 1.

Example 4

The rest is the same as in example 1, except that the second web uses the hydrophilic polyester chips of preparation b2 instead of the hydrophilic polyester chips obtained in preparation b 1.

Example 5

The remainder was the same as in example 1, except that the modified polypropylene prepared in preparation example a3 was used instead of the modified polypropylene prepared in preparation example a 1.

Example 6

The remainder was the same as in example 1, except that the modified polypropylene prepared in preparation example a4 was used instead of the modified polypropylene prepared in preparation example a 1.

Comparative example 1

The remainder was the same as in example 1, except that the modified polypropylene prepared in comparative preparation a1 was used instead of the modified polypropylene prepared in preparation a 1.

Comparative example 2

The remainder was the same as in example 1, except that the first web layer was made of only the modified polypropylene of preparation a1 into monocomponent fibers, instead of sheath-core bicomponent fibers.

Comparative example 3

The remainder is the same as in example 1 except that the hydrophilic polyester in the second web is spun by a common circular spin pack, i.e., not a cross-type spin pack.

Application example

The following performance tests were performed on the spunlaced nonwoven fabrics of the above examples and comparative examples:

liquid penetration time: the measurements were made with reference to the standard GB/T24218 textile-nonwoven test method.

Moisture regain: the measurements were made with reference to the standard GB/T24218 textile-nonwoven test method.

Softness: the measurement was carried out with reference to standard GB-T8942-2016.

TABLE 1

As shown in Table 1, the composite structure spunlaced nonwoven fabric prepared by the invention has short liquid penetration time, difficult reverse osmosis, good unidirectional water conductivity, softness and skin friendliness.

Claims (10)

1. The water-jet nonwoven fabric of the sanitary towel surface layer with the composite structure comprises a first fiber net layer and a second fiber net layer which are entangled by water jet, and is characterized in that the first fiber net layer is composed of bicomponent fibers with a sheath-core structure, the sheath layer of the bicomponent fibers is modified polypropylene, and the core layer is polypropylene; the second fiber web layer is composed of hydrophilic polyester fibers with a cross-shaped structure; the modified polypropylene is polyether acrylate grafted modified polypropylene.

2. The composite structural sanitary napkin facing spunlaced nonwoven of claim 1 wherein the areal density of the first and second fibrous web layers independently is from 8 to 15g/m ² The method comprises the steps of carrying out a first treatment on the surface of the The first fiber has a fineness of 1.5-2.5dtex and a length of 30-50mm, and the second fiber has a fineness of 1.0-1.5dtex and a length of 30-50mm.

3. The spunlaced nonwoven fabric of a sanitary napkin having a composite structure according to claim 1, wherein the mass ratio of modified polypropylene to polypropylene in the bicomponent fibers of the sheath-core structure is 10-30:90-70.

4. The water-entangled nonwoven fabric for sanitary towel surface layer according to claim 1, characterized in that the polyether acrylate is used in an amount of 10-25wt% of polypropylene in the raw material for preparing the polyether acrylate graft modified polypropylene.

5. The composite structural sanitary napkin facing spunlaced nonwoven of claim 4 wherein said polyether acrylate has a number average molecular weight of 300 to 800.

6. The composite structured sanitary napkin facing spunlaced nonwoven fabric of claim 1, wherein the modified polypropylene is prepared by a process comprising the steps of: drying polypropylene slices and polyether acrylate, then uniformly mixing with an initiator, and performing melt grafting to obtain modified polypropylene;

preferably, the drying is that the polypropylene slice and the polyether acrylate are dried in a drying oven at 60-80 ℃ for 5-15h; the initiator is at least one of ditert-butyl peroxide and dicumyl peroxide, and the dosage of the initiator is 0.1-0.2wt% of the polypropylene slice; the melt grafting is carried out in a torque rheometer, the reaction temperature is 200-220 ℃, and the rotating speed is 70-80r/min; after the reaction is finished, the product is cooled and granulated.

7. The water-jet nonwoven fabric of the composite structure sanitary towel surface layer according to claim 1, wherein the hydrophilic polyester is formed by copolymerizing terephthalic acid, isophthalic acid, ethylene glycol, dimethyl isophthalate-5-sodium sulfonate and polyethylene glycol under the action of a catalyst and a stabilizer; the dosage of the isophthalic acid is 5-10wt% of terephthalic acid, the dosage of the dimethyl isophthalate-5-sodium sulfonate is 5-15wt% of terephthalic acid, the molecular weight of the polyethylene glycol is 1000-2000, and the dosage is 5-10wt% of terephthalic acid; the catalyst is antimony trioxide or antimony acetate, and the dosage is 0.03-0.04wt% of terephthalic acid; the stabilizer is trimethyl phosphate and the amount of stabilizer is 0.01-0.02wt% of terephthalic acid.

8. The composite structured sanitary napkin facing spunlaced nonwoven fabric of claim 1, wherein the hydrophilic polyester is prepared by a process comprising the steps of:

(1) Adding terephthalic acid, ethylene glycol and isophthalic acid into a pulping kettle under a stirring state, controlling the molar ratio of the ethylene glycol to the acid to be 1.2-1.5, and adding a catalyst and a stabilizer to obtain a slurry after uniform mixing;

(2) Introducing the slurry into an esterification kettle with stirring for esterification reaction at 245-255 ℃, controlling the column top temperature of a fractionating column to be not more than 110 ℃, adding dimethyl isophthalate-5-sodium sulfonate and polyethylene glycol after esterification, and introducing into a polycondensation kettle with stirring when the kettle temperature is increased to 230-250 ℃;

(3) Under the action of a vacuum pump, keeping the pressure in the polycondensation kettle below 50Pa for polycondensation reaction, and controlling the kettle temperature to react for 3-4 hours at 270-280 ℃;

(4) Stopping stirring after the reaction, removing vacuum with high-purity nitrogen, increasing the pressure to 0.2-0.5MPa, casting strips from the casting belt head, granulating with a granulator after cooling water, and obtaining hydrophilic polyester chips.

9. The method for producing a composite structured spunlaced fabric for a sanitary napkin cover according to any one of claims 1 to 8, comprising the steps of:

(S1) a first web layer: conveying the modified polypropylene slices into an extruder for heating and melting, and conveying the modified polypropylene slices into a spinning die head through a melt filter, a melt conveying pipeline and a metering pump, and uniformly distributing the modified polypropylene slices to a first spinning assembly through the spinning die head; feeding the polypropylene slices into an extruder for heating and melting, and feeding the polypropylene slices into a spinning die head through a filter, extrusion and a metering pump for uniform distribution to a second spinning component; carrying out composite spinning at an outlet, and cooling, stretching, winding and cutting to prepare the bicomponent fiber with a sheath-core structure, wherein the sheath layer is modified polypropylene, and the core layer is polypropylene; opening and carding the bicomponent fiber to form a first fiber web layer;

(S2) a second web layer: feeding hydrophilic polyester chips into an extruder for heating and melting, and feeding the hydrophilic polyester chips into a spinning die head through a filter, extrusion and a metering pump to be uniformly distributed to a cross-shaped spinning component; carrying out composite spinning at an outlet, and preparing the cross-shaped hydrophilic polyester fiber through cooling, stretching, winding and cutting; opening and carding hydrophilic polyester fibers with a cross-shaped structure to form a second fiber web layer;

(S3) water-jet nonwoven fabric: and compounding the first fiber web layer and the second fiber web layer, and carrying out hydroentanglement reinforcement, drying and rolling to obtain the composite hydroentangled non-woven fabric for the sanitary towel surface layer.

10. The composite structure spunlaced fabric for a sanitary towel cover according to claim 9, wherein the composite mode in the step (S3) is one of cross-lapping or parallel lapping, the spunlaced pressure is 4-10MPa, and the number of spunlaced channels is 3-6.