A polylactic acid bicomponent composite fiber and a degradable absorbable core prepared by the same

Abstract

The application discloses a kind of polylactic acid bicomponent composite fibers, including the core of cross section is cross-shaped and the skin of cross section is cross-shaped and is covered in core layer outside;Core is high melting point polylactic acid, and skin is low melting point polylactic acid;Also disclosed is the polylactic acid bicomponent composite fiber including degradable absorbable core body;Degradable absorbable core body includes surface layer, intermediate layer and bottom layer;Surface layer and bottom layer are single-component polylactic acid fiber nonwoven fabric;Intermediate layer includes cross-section polylactic acid bicomponent composite fiber, high curl high elasticity polylactic acid bicomponent fiber and high water absorption resin.Crisscross polylactic acid bicomponent fiber better hygroscopicity, wet conductivity and good dispersibility, can quickly absorb liquid, surface layer is polylactic acid hot air nonwoven fabric, bottom layer is polylactic acid spunbond nonwoven fabric, and a large number of cross-section polylactic acid bicomponent composite fibers are used in intermediate layer, and there is good effect to absorb peculiar smell, natural antibacterial property and peculiar smell removal performance more increase the health and comfort of user.

Description

Technical Field

[0001] This invention relates to a polylactic acid bicomponent composite fiber and the biodegradable absorbent core prepared therefrom, belonging to the technical field of polylactic acid fiber and its products. Background Technology

[0002] There are generally three types of absorbent materials used in disposable sanitary napkins: pure wood pulp absorbent material, a mixture of wood pulp and superabsorbent polymer (SAP) absorbent material, and 100% SAP + fluffy cotton absorbent material. While pure wood pulp absorbent material is 100% natural and 100% biodegradable, its absorbency is low, and the wood pulp becomes very damp after saturation, easily breeding bacteria; therefore, it can only be used in regular sanitary napkins. The second type, a mixture of wood pulp and SAP, uses wood pulp fibers as a channeling material, quickly channeling liquid to the surrounding SAP. However, when saturated with handwashing liquid, the presence of a large amount of wood pulp makes the absorbent material very damp. Furthermore, hot melt adhesive is needed to fix the wood pulp and SAP, which hinders further absorption, thus limiting its application. The first type of absorbent material is non-degradable due to the presence of superabsorbent resin. The second type uses 100% superabsorbent resin plus fluffy cotton, with fluffy cotton serving as an insulating layer to accommodate more superabsorbent resin. However, the fluffy cotton only acts as an insulating layer and cannot contain or encapsulate the superabsorbent resin, nor can it provide sufficient space for the superabsorbent resin to swell. Therefore, after the superabsorbent resin becomes saturated, it is very easy to cause local stagnation, hindering further absorption of the liquid. As a result, the utilization rate of the superabsorbent resin is not high. In addition, a large amount of hot melt adhesive needs to be sprayed to fix the fluffy cotton and superabsorbent resin, which further hinders the full utilization of the superabsorbent resin. The fluffy cotton used in this absorbent material is 100% PE / PP and PE / PET fiber, while the superabsorbent resin is an acrylic material, both of which are non-degradable.

[0003] The problem to be solved is how to prepare a biodegradable polylactic acid bicomponent composite fiber and the biodegradable absorbent core prepared therefrom. Summary of the Invention

[0004] One of the objectives of this invention is to provide a polylactic acid bicomponent composite fiber with a cross-shaped cross section and good moisture-wicking properties.

[0005] Another objective of this invention is to provide a biodegradable absorbent core that is both biodegradable and highly absorbent.

[0006] To solve the above-mentioned technical problems, the objective of this invention is achieved as follows:

[0007] The present invention relates to a polylactic acid bicomponent composite fiber, comprising a core with a cross-shaped cross section and a sheath covering the outside of the core layer with a cross-shaped cross section; the core is high-melting-point polylactic acid, and the sheath is low-melting-point polylactic acid;

[0008] The preparation process of the polylactic acid bicomponent composite fiber is as follows:

[0009] 1) First, use drying equipment to dry the high-melting-point polylactic acid (PLA) chips and low-melting-point PLA chips until the moisture content of the high-melting-point PLA chips and low-melting-point PLA chips is 0.008-0.015%;

[0010] 2) The dried high-melting-point polylactic acid (PLA) chips and low-melting-point PLA chips are respectively fed into the twin screws of the composite twin-screw spinning machine for melt extrusion; the screw extrusion temperature of the low-melting-point PLA component is 170-190℃, and the screw extrusion temperature of the high-melting-point PLA component is 200-230℃; after metering and filtration, they are fed into the composite spinning assembly of the spinning machine;

[0011] The spinning parameters are as follows: spinning temperature controlled at 215-245℃, spinning speed controlled at 600-1000m / min, side blowing temperature controlled at 20-24℃, side blowing speed controlled at 0.8-1.2m / s, and pre-draw ratio controlled at 1.3-1.8. Then, the fibers undergo an oiling process, employing a two-stage oiling procedure. The first oiling uses an oil bath, controlling the oiling rate at 0.18-0.25%. Following this, the fibers enter a stretching process, with a stretch ratio controlled at 1.5-2.0. Next, they undergo tension heat setting at 55-65℃. A second oiling process is then performed using an oil roller or spray method, controlling the oiling rate at 0.1-0.2%. Finally, a second heat setting is conducted at 90-110℃. After winding and cutting, high- and low-melting-point bicomponent polylactic acid composite fibers with a cross-shaped cross-section are obtained.

[0012] Based on the above scheme and as a preferred embodiment of the above scheme: the drying equipment is a rotary drum drying equipment; the low melting point polylactic acid component has a melt index of 18 g / 10 min; the high melting point polylactic acid component has a melt index of 23 g / 10 min.

[0013] Based on the above scheme and as a preferred embodiment of the above scheme: the polylactic acid bicomponent composite fiber has a fiber fineness of 1.5-6 dtex, a crimp number of 2-5 / 2.5 mm, and a crimp angle of 80-100 degrees; and the cross-shaped aspect ratio of the polylactic acid bicomponent composite fiber is 3-7:1, and the fiber length is 3-20 mm.

[0014] Based on the above scheme and as a preferred embodiment of the above scheme: the volume ratio of the high-melting-point polylactic acid chips to the low-melting-point polylactic acid components is 60-80:20-40.

[0015] The present invention also relates to a biodegradable absorbent core, comprising the aforementioned polylactic acid bicomponent composite fiber;

[0016] The biodegradable absorbent core comprises a surface layer, a middle layer, and a bottom layer; the surface layer and the bottom layer are single-component polylactic acid fiber nonwoven fabric; the middle layer comprises polylactic acid bicomponent composite fiber with a cross-shaped cross section, highly crimped and highly elastic polylactic acid bicomponent fiber, and superabsorbent resin.

[0017] Based on the above scheme and as a preferred embodiment of the above scheme: the high-crimp, high-elasticity polylactic acid bicomponent fiber is in a parallel configuration, comprising a low-viscosity component and a high-viscosity component, wherein the melt index of the low-viscosity component is 23 g / 10min, and the melt index of the high-viscosity component is 6 g / 10min; the fiber fineness of the high-crimp, high-elasticity polylactic acid bicomponent fiber is 1.5-6 dtex, the number of crimps is 8-12 / 2.5 mm, and the fiber length is 10-25 mm.

[0018] Based on the above scheme and as a preferred embodiment of the above scheme, the preparation process of the intermediate layer is as follows:

[0019] 1) Fiber blending: Mixing cross-shaped polylactic acid bicomponent composite fibers and highly crimped and highly elastic polylactic acid bicomponent fibers to form a fiber blend;

[0020] 2) Mixing: The fiber mixture is mixed with superabsorbent resin to prepare the first fiber resin mixture, the second fiber resin mixture and the third fiber resin mixture;

[0021] In the first fiber resin mixture, the ratio of fiber mixture to superabsorbent resin is 0-2:8-10, wherein the particle size of the superabsorbent resin used is 100-120 mesh;

[0022] In the second fiber resin mixture, the ratio of fiber mixture to superabsorbent resin is 4-6:4-6, wherein the particle size of the superabsorbent resin used is 80-100 mesh.

[0023] The fiber-to-superabsorbent resin ratio in the third fiber resin mixture is 7-9:1-3, wherein the particle size of the superabsorbent resin used is 40-70 mesh.

[0024] Based on the above scheme and as a preferred embodiment of the above scheme: the mixing ratio of the polylactic acid bicomponent composite fiber and the highly crimped and highly elastic polylactic acid bicomponent fiber is 50-70:50-30.

[0025] Based on the above scheme and as a preferred embodiment of the above scheme: the preparation process of the biodegradable absorbent core uses a nonwoven fabric composite machine with three spray heads, and the specific preparation process is as follows:

[0026] 1) Preparation before lamination: Adjust the height between the first spray head and the laminating machine table to 10-13cm, the height between the second spray head and the laminating machine table to 12-14cm, and the height between the third spray head and the laminating machine table to 13-15cm.

[0027] 2) Unwind the polylactic acid spunbond nonwoven fabric used as the bottom layer and send it to the nonwoven fabric composite machine for lamination. The selected polylactic acid spunbond nonwoven fabric has a specification of 15-20g / m2.

[0028] 3) When the polylactic acid spunbond nonwoven fabric reaches the first spray head, the first spray head sprays the first fiber resin mixture onto it at a rate of 120-180 g / m², and the vibration frequency of the first spray head during spraying is 20-30 Hz.

[0029] 4) When the polylactic acid spunbond nonwoven fabric reaches the second spray head, the second spray head sprays the second fiber resin mixture onto it at a rate of 60-100 grams per square meter. The vibration frequency of the second spray head during spraying is 28-38 Hz.

[0030] 5) When the polylactic acid spunbond nonwoven fabric reaches the third spray head, the third spray head sprays the third fiber resin mixture onto it at a rate of 40-70 grams per square meter. The vibration frequency of the third spray head during spraying is 35-45 Hz.

[0031] 6) Unwind the polylactic acid hot air nonwoven fabric used on the surface and stack it on top of the sprayed third fiber resin mixture to form a polylactic acid spunbond nonwoven fabric at the bottom, a three-layer cross-shaped polylactic acid bicomponent fiber + high-curvature, high-elasticity polylactic acid bicomponent fiber and high-absorbency resin mixture in the middle, and a five-layer composite structure of polylactic acid hot air nonwoven fabric on the top.

[0032] The composite structure is then placed in an oven for shaping. The hot air penetration temperature in the oven is 115-140℃, and the running speed is 15-20 meters / minute. After exiting the oven, a five-layer composite absorbent material is obtained with a weight of 300-460 grams per square meter.

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

[0034] 1. It has good moisture absorption and wicking properties.

[0035] Polylactic acid (PLA) fiber is a man-made natural fiber derived from plants. PLA fiber has a weakly acidic surface and natural antibacterial properties. It has good moisture wicking, low moisture regain, and good surface dryness. More importantly, PLA fiber is 100% biodegradable, and therefore it will inevitably become the future development direction of disposable hygiene materials.

[0036] This invention utilizes a rational spinning process for cross-shaped bicomponent polylactic acid (PLA) fibers, particularly employing a two-stage oiling process, to impart superior hygroscopicity, moisture-wicking properties, and excellent dispersibility to the cross-shaped PLA fibers. This allows for rapid liquid absorption and transfer of the liquid to the surrounding superabsorbent polymer (SAP). Furthermore, the protruding blades of the cross-shaped PLA fibers can wrap around the SAP in a semi-elliptical shape, fixing the SAP while isolating it from each other, providing space for swelling and preventing excessive SAP from crowding together and causing absorption saturation and blockage. On the other hand, the composite absorbent material of this invention does not use hot melt adhesive to fix the SAP. Instead, the blades of the cross-shaped fibers and the highly crimped elliptical shape wrapping around the SAP increase the specific surface area of ​​the exposed SAP, providing more swelling space for better absorption, improving the core's absorption capacity and liquid-locking ability, reducing the amount of SAP used, and thus lowering production costs.

[0037] 2. Biodegradable.

[0038] The composite absorbent material prepared in this invention uses polylactic acid spunbond nonwoven fabric as the bottom layer, a middle layer of cross-shaped polylactic acid bicomponent composite fiber + high-curvature and high-elasticity polylactic acid bicomponent fiber and superabsorbent resin, and a surface layer of porous polylactic acid hot-air nonwoven fabric. The polylactic acid used is 100% biodegradable fiber, and the superabsorbent resin selected is Formosa Plastics Corporation's biodegradable superabsorbent resin BC706, which has a biodegradation rate of 66% (180 days). According to the evaluation standards of EN 13432 and GB / T 20197, the composting degradation rate or biodegradation rate of bio-based care products is ≥60%, which meets the degradation standard requirements.

[0039] 3. Gradient absorption effect.

[0040] The absorbent material of this invention employs a five-layer structure. The middle layer utilizes cross-shaped polylactic acid (PLA) bicomponent composite fibers, which exhibit excellent moisture absorption and wicking properties due to their unique groove effect. Highly crimped and elastic PLA bicomponent fibers, with their unique three-dimensional crimp and elasticity, are used to fix and encapsulate superabsorbent resin, thus eliminating the need for conventional core materials that use hot melt adhesives to fix the superabsorbent resin, thereby reducing the superabsorbent resin's absorption capacity. Finally, a gradient absorption effect is achieved through different mixing ratios of cross-shaped PLA bicomponent composite fibers, highly crimped and elastic PLA bicomponent fibers, and superabsorbent resin, as well as the rational selection of the superabsorbent resin's mesh size. The top layer of the three-layer material uses a high proportion of polylactic acid (PLA) fibers and a large-mesh superabsorbent polymer (SAP) to initially absorb and channel liquid. The second layer, with a medium proportion of PLA fibers and a medium-mesh SAP, primarily absorbs liquid and also channels it to some extent. The third layer, with a very low proportion of PLA fibers and a small-mesh SAP, primarily absorbs liquid. The cross-shaped PLA bicomponent composite fibers only serve to fix and micro-channel the SAP. This gradient absorption effect allows liquid to be quickly channeled to the SAP, preventing aggregation and clogging after saturation. It boasts high utilization and excellent absorption capacity. Furthermore, because PLA fibers have a moisture regain of only 0.4-0.6%, the absorbent material maintains excellent dryness while efficiently absorbing water.

[0041] 4. Naturally weakly acidic and antibacterial.

[0042] The absorbent material of this invention adopts a five-layer structure, wherein the top and bottom layers are non-woven fabrics made of polylactic acid fibers, and the middle layer uses cross-shaped polylactic acid bicomponent composite fibers. Since the surface of polylactic acid fibers is weakly acidic, consistent with the pH value of human skin, it creates a weakly acidic microenvironment during use. In particular, since the core layer is polylactic acid hot-air non-woven fabric, the bottom layer is polylactic acid spunbond non-woven fabric, and a large amount of cross-shaped polylactic acid bicomponent composite fibers are used in the middle layer, it has a good effect on absorbing odors. The natural antibacterial and odor-removing properties created further enhance the health and comfort of users. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the cross-sectional structure of the polylactic acid bicomponent composite fiber involved in this invention;

[0044] Figure 2 This is a cross-sectional view of the polylactic acid bicomponent composite fiber involved in this invention;

[0045] Figure 3 This is a longitudinal view of the polylactic acid bicomponent composite fiber involved in this invention;

[0046] Figure 4This is a cross-sectional view of parallel-type highly crimped and highly elastic polylactic acid bicomponent fibers;

[0047] Figure 5 This is an image of a parallel-type, highly crimped, highly elastic polylactic acid bicomponent fiber.

[0048] Figure 6 This is a schematic diagram of the structure of the absorbable core involved in this invention;

[0049] Figure 7 This is a side view of the absorbable core involved in this invention.

[0050] The markings in the diagram are explained as follows: 1-core; 2-skin; 10-surface layer; 20-middle layer; 30-bottom layer; 21-first fiber resin mixture; 22-second fiber resin mixture; 23-third fiber resin mixture. Detailed Implementation

[0051] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0052] Example 1

[0053] This embodiment involves a polylactic acid bicomponent composite fiber, such as... Figure 1 and Figure 2 As shown, it includes a core with a cross-shaped cross section and a skin covering the outside of the core layer with a cross-shaped cross section; the core is high-melting-point polylactic acid, and the skin is low-melting-point polylactic acid.

[0054] The preparation process of the polylactic acid bicomponent composite fiber is as follows:

[0055] First, high-melting-point polylactic acid (PLA) chips are dried at 100℃ for 4-6 hours using a rotary drum dryer, and low-melting-point PLA chips are dried at 40℃ for 22-24 hours using the same dryer. This removes moisture, increases the softening point, and prevents oxidation and degradation during spinning, which would reduce the strength of the PLA composite fiber. The low-melting-point PLA component is from Luminy® PLA resin model LX930, with a melt index of 18 g / 10min (210℃ / 2.16kg); the high-melting-point PLA component is from Luminy® PLA resin model LX130, with a melt index of 23 g / 10min (210℃ / 2.16kg), resulting in a moisture content of 0.008-0.015% for both high- and low-melting-point PLA chips.

[0056] The dried polylactic acid (PLA) chips with high and low melting points were separately fed into the twin screws of a composite twin-screw spinning machine for melt extrusion. The screw extrusion temperature for the low-melting-point PLA component was 170℃, and the screw extrusion temperature for the high-melting-point PLA component was 200℃. After metering and filtration, the PLA components were fed into the composite spinning assembly of the spinning machine. The volume ratio of the high-melting-point PLA components was 60:40. Due to the significant difference in melting points between the high and low-melting-point PLA components, to avoid yarn breakage and yarn ejection during spinning, the successful spinning parameters were: spinning temperature controlled at (215℃), spinning speed controlled at 1000 m / min, side-blowing air temperature controlled at 20℃, side-blowing air speed controlled at 0.8 m / s, and pre-drawing ratio controlled at (1.3). Then, the PLA underwent an oiling process using a two-stage oiling procedure. The first oiling was done using an oil bath oiling method, employing short fiber oiling agent 6214-TS from Takemoto Oils & Fats Co., Ltd. of Japan, with the oiling rate controlled at 0.18%. Afterwards, it enters the stretching process, with the stretching ratio controlled at (1.5), followed by tension heat setting at (55℃). Then, it undergoes a second oiling process, using an oil roller or spraying method, employing Goulston's multi-stage hydrophilic oiling agent Lurol PP-14160, with the oiling rate controlled at 0.1%. It then enters the second heat setting process at (90℃), and after winding and cutting, it obtains a cross-shaped high- and low-melting-point bicomponent polylactic acid composite fiber with a fiber fineness of 1.5 dtex, a crimp count of 5 / 2.5 mm, a crimp angle of 100°, a cross-shaped aspect ratio of 7:1, and a fiber length of 10 mm.

[0057] The biodegradable absorbent core involved in this embodiment includes the aforementioned polylactic acid bicomponent composite fiber; the biodegradable absorbent core includes a surface layer 10, a middle layer 20, and a bottom layer 30; the surface layer 10 and the bottom layer 30 are single-component polylactic acid fiber nonwoven fabrics; the middle layer includes polylactic acid bicomponent composite fiber with a cross-shaped cross section, highly crimped and highly elastic polylactic acid bicomponent fiber, and superabsorbent resin.

[0058] In the preparation of the biodegradable absorbent core, the materials used are: prepared polylactic acid (PLA) bicomponent composite fibers with a cross-shaped cross section, highly crimped and highly elastic PLA bicomponent fibers, and PLA fiber nonwoven fabric, with PLA spunbond nonwoven fabric being preferred. The highly crimped PLA bicomponent fiber is a biodegradable, highly crimped fiber with a parallel cross section developed by Suzhou Jinquan New Material Co., Ltd. One low-viscosity component is Luminy® PLA resin model LX530, with a melt index of 23 g / 10min (210℃ / 2.16kg); the high-viscosity PLA component is Luminy® PLA resin model LX175, with a melt index of 6 g / 10min (210℃ / 2.16kg). The highly crimped PLA bicomponent fiber has a fineness of 6 dtex, a crimp count of 12 / 2.5mm, and a fiber length of 25 mm.

[0059] Fiber blending: A three-dimensional motion mixer is used to blend cross-shaped polylactic acid bicomponent fibers and high-cribability, high-elasticity polylactic acid bicomponent fibers, with a ratio of 50:50 for the cross-shaped polylactic acid bicomponent fibers and the high-cribability, high-elasticity polylactic acid bicomponent fibers.

[0060] Mixing: The fiber mixture and superabsorbent resin are mixed in different weight ratios to prepare the first fiber resin mixture 21, the second fiber resin mixture 22, and the third fiber resin mixture 3, which are respectively:

[0061] 1) Cross-shaped polylactic acid bicomponent fiber + highly crimped and elastic polylactic acid bicomponent fiber: superabsorbent resin: 0:10, wherein the superabsorbent resin used has a particle size of 100 mesh; the mixing speed of the mixer is 10 rpm, and the mixing time is 30 minutes. Then the mixed material is poured out for later use, which is the first fiber resin mixture. The mixer used is a three-dimensional motion mixer, model SBH300, manufactured by Jiangsu Guibao.

[0062] 2) Cross-shaped polylactic acid bicomponent fiber + highly crimped and elastic polylactic acid bicomponent fiber: superabsorbent resin: 4:6, where the superabsorbent resin used has a particle size of 100 mesh. The mixer speed is 10 rpm, and the mixing time is 30 minutes. The mixed material is then poured out for later use; this is the second fiber resin mixture. The mixer used is a three-dimensional motion mixer, model SBH300, manufactured by Jiangsu Guibao.

[0063] 3) Cross-shaped polylactic acid bicomponent fiber + highly crimped and elastic polylactic acid bicomponent fiber: superabsorbent resin: 7:3, where the superabsorbent resin used has a particle size of 40 mesh. The mixer speed is 12 rpm, and the mixing time is 35 minutes. The mixed material is then poured out for later use; this is the third fiber resin mixture. The mixer used is a three-dimensional motion mixer, model SBH300, manufactured by Jiangsu Guibao.

[0064] In the preparation of the biodegradable absorbent core, a nonwoven fabric laminating machine with three spray heads, manufactured by Jiangsu Gaoqi Machinery Co., Ltd., model GQ-1600, was selected. The preparation process of the biodegradable absorbent core is as follows:

[0065] 1) Preparations before lamination: Adjust the height between the first spray head and the laminating machine table to 10cm, the height between the second spray head and the laminating machine table to 12cm, and the height between the third spray head and the laminating machine table to 13cm.

[0066] 2) Unwind the polylactic acid spunbond nonwoven fabric and feed it to a nonwoven fabric laminating machine for lamination. The selected specification is 15g / m². 2 Polylactic acid spunbond nonwoven fabric.

[0067] 3) When the polylactic acid spunbond nonwoven fabric reaches the first spray head, the first spray head sprays a mixture of cross-shaped polylactic acid bicomponent fibers, high-curvature and high-elasticity polylactic acid bicomponent fibers, and superabsorbent resin onto it. The selected ratio is cross-shaped polylactic acid bicomponent fibers + high-curvature and high-elasticity polylactic acid bicomponent fibers : superabsorbent resin : 0 : 10, which is the first fiber resin mixture. The spraying amount is 180 g / m², and the vibration frequency of the first spray head during spraying is 20 Hz.

[0068] 4) When the polylactic acid spunbond nonwoven fabric reaches the second spray head, the second spray head sprays a mixture of cross-shaped polylactic acid bicomponent fibers, high-curvature and high-elasticity polylactic acid bicomponent fibers, and superabsorbent resin onto it. The selected ratio is cross-shaped polylactic acid bicomponent fibers + high-curvature and high-elasticity polylactic acid bicomponent fibers : superabsorbent resin : 4 : 6, i.e., the second fiber resin mixture. The spraying amount is 100 g / m², and the vibration frequency of the second spray head during spraying is 28 Hz.

[0069] 5) When the polylactic acid spunbond nonwoven fabric reaches the third spray head, the third spray head sprays a mixture of cross-shaped polylactic acid bicomponent fibers, high-curvature and high-elasticity polylactic acid bicomponent fibers, and superabsorbent resin onto it. The selected ratio is cross-shaped polylactic acid bicomponent fibers + high-curvature and high-elasticity polylactic acid bicomponent fibers : superabsorbent resin : 7 : 3, i.e., the third fiber resin mixture. The spraying amount is 70 grams per square meter, and the vibration frequency of the third spray head during spraying is 35 Hz.

[0070] 6) Polylactic acid (PLA) hot-air nonwoven fabric is unwound (PLA hot-air nonwoven fabric specification is 15g / m2) and layered on top of a cross-shaped PLA bicomponent fiber + high-curvature, high-elasticity PLA bicomponent fiber and superabsorbent resin mixture, forming a five-layer composite structure: PLA spunbond nonwoven fabric at the bottom, three layers of cross-shaped PLA bicomponent fiber + high-curvature, high-elasticity PLA bicomponent fiber and superabsorbent resin mixture in the middle, and PLA hot-air nonwoven fabric on top. This composite structure is then placed in an oven for setting. The hot air penetration temperature in the oven is 115℃, and the running speed is 15 meters / minute. After exiting the oven, a five-layer composite absorbent material is obtained with a basis weight of 410 g / m². This core can be used as the absorbent layer in disposable hygiene materials such as diapers, sanitary napkins, and nursing pads.

[0071] Example 2

[0072] This embodiment involves a polylactic acid bicomponent composite fiber, such as... Figure 1 and Figure 2 As shown, it includes a core with a cross-shaped cross section and a skin covering the outside of the core layer with a cross-shaped cross section; the core is high-melting-point polylactic acid, and the skin is low-melting-point polylactic acid.

[0073] The preparation process of the polylactic acid bicomponent composite fiber is as follows:

[0074] First, high-melting-point polylactic acid (PLA) chips are dried at 100°C for 4-6 hours using a rotary drum dryer. Then, low-melting-point PLA chips are dried at 40°C for 22-24 hours using the same dryer to remove moisture, increase the softening point, and prevent oxidation and degradation during spinning, which would reduce the strength of the PLA composite fiber.

[0075] The low-melting-point polylactic acid (PLA) component is derived from Luminy® PLA resin model LX930, with a melt index of 18 g / 10min (210℃ / 2.16kg); the high-melting-point PLA component is derived from Luminy® PLA resin model LX130, with a melt index of 23 g / 10min (210℃ / 2.16kg), resulting in a moisture content of 0.008-0.015% for both high- and low-melting-point PLA chips.

[0076] 2) The dried high- and low-melting-point polylactic acid (PLA) chips were separately fed into the twin screws of a composite twin-screw spinning machine for melt extrusion. The screw extrusion temperature for the low-melting-point PLA component was 190℃, and the screw extrusion temperature for the high-melting-point PLA component was 230℃. After metering and filtration, the PLA components were fed into the composite spinning assembly of the spinning machine. The volume ratio of the high- and low-melting-point PLA components was 80:20. Due to the significant difference in melting points between the high- and low-melting-point PLA components, to avoid yarn breakage and yarn ejection during spinning, the successful spinning parameters were: spinning temperature controlled at 245℃, spinning speed controlled at 600 m / min, and side... The blowing temperature is controlled at 24℃, the side blowing speed is controlled at 1.2m / s, and the pre-stretch ratio is controlled at (1.8). Then, after oiling, a two-stage oiling process is adopted. The first oiling is done by oil bath oiling, using short fiber oiling agent 6214-TS from Takemoto Oils Co., Ltd. of Japan, with the oiling rate controlled at 0.25%. After that, it enters the stretching process, with the stretch ratio controlled at (2.0). Then, it undergoes tension heat setting, with the heat setting temperature controlled at (65℃). Then, a second oiling is performed, using an oil roller or spraying method, using Lurol, a multi-stage hydrophilic oiling agent from Goulston. PP-14160, with the oiling rate controlled at 0.2%, enters the secondary heat setting stage at a temperature of 110℃. After winding and cutting, a cross-shaped section is obtained, which is a high- and low-melting-point bicomponent polylactic acid composite fiber. The fiber fineness is 5.5 dtex, the number of crimps is 2 / 2.5 mm, the crimp angle is 80°, the cross-shaped aspect ratio of the composite fiber is 3:1, and the fiber length is 2 mm.

[0077] The biodegradable absorbent core involved in this embodiment includes the aforementioned polylactic acid bicomponent composite fiber; the biodegradable absorbent core includes a surface layer 10, a middle layer 20, and a bottom layer 30; the surface layer 10 and the bottom layer 30 are single-component polylactic acid fiber nonwoven fabrics; the middle layer includes polylactic acid bicomponent composite fiber with a cross-shaped cross section, highly crimped and highly elastic polylactic acid bicomponent fiber, and superabsorbent resin.

[0078] In the preparation of the biodegradable absorbent core, the following materials are used: prepared cross-shaped polylactic acid (PLA) bicomponent fibers, highly crimped and highly elastic PLA bicomponent fibers, and PLA fiber nonwoven fabric, with PLA spunbond nonwoven fabric being the preferred choice. The highly crimped PLA bicomponent fiber is a biodegradable, highly crimped fiber with a parallel cross-section, specially developed by Suzhou Jinquan New Material Co., Ltd. One low-viscosity component is Luminy® PLA resin model LX530, with a melt index of 23 g / 10min (210℃ / 2.16kg); the high-viscosity PLA component is from Luminy® PLA resin model LX175, with a melt index of 6 g / 10min (210℃ / 2.16kg). The highly crimped PLA bicomponent fiber has a fineness of 3 dtex, a crimp count of 10 / 2.5mm, and a fiber length of 15mm.

[0079] Fiber blending: A three-dimensional motion mixer is used to blend cross-shaped polylactic acid bicomponent fibers and high-cribability, high-elasticity polylactic acid bicomponent fibers, with a ratio of 60:40.

[0080] Mixing: The fiber mixture and superabsorbent resin are mixed in different weight ratios to prepare the first fiber resin mixture 21, the second fiber resin mixture 22, and the third fiber resin mixture 3, which are respectively:

[0081] 1) Cross-shaped polylactic acid bicomponent fiber + highly crimped and elastic polylactic acid bicomponent fiber: superabsorbent resin: 2:10, wherein the superabsorbent resin used has a particle size of 120 mesh; the mixing speed of the mixer is 14 rpm, and the mixing time is 40 minutes. Then the mixed material is poured out for later use, which is the first fiber resin mixture. The mixer used is a three-dimensional motion mixer, model SBH300, manufactured by Jiangsu Guibao.

[0082] 2) Cross-shaped polylactic acid bicomponent fiber + highly crimped, highly elastic polylactic acid bicomponent fiber: superabsorbent resin: 6:4, where the superabsorbent resin particle size is 100 mesh. The mixer speed is 15 rpm, and the mixing time is 50 minutes. The mixed material is then poured out for later use; this is the second fiber resin mixture. The mixer used is a three-dimensional motion mixer, model SBH300, manufactured by Jiangsu Guibao.

[0083] 3) Cross-shaped polylactic acid bicomponent fiber + highly crimped and elastic polylactic acid bicomponent fiber: superabsorbent resin: 9:1, where the superabsorbent resin particle size is 70 mesh. The mixer speed is 15 rpm, and the mixing time is 50 minutes. The mixed material is then poured out for later use; this is the third fiber resin mixture. The mixer used is a three-dimensional motion mixer, model SBH300, manufactured by Jiangsu Guibao.

[0084] In the preparation of the biodegradable absorbent core, a nonwoven fabric laminating machine with three spray heads, manufactured by Jiangsu Gaoqi Machinery Co., Ltd., model GQ-1600, was selected. The preparation process of the biodegradable absorbent core is as follows:

[0085] 1) Preparations before lamination: Adjust the height between the first spray head and the laminating machine table to 13cm, the height between the second spray head and the laminating machine table to 14cm, and the height between the third spray head and the laminating machine table to 15cm.

[0086] 2) Unwind the polylactic acid spunbond nonwoven fabric and send it to the nonwoven fabric laminating machine for lamination. The selected polylactic acid spunbond nonwoven fabric has a specification of 20g / m2.

[0087] 3) When the polylactic acid spunbond nonwoven fabric reaches the first spray head, the first spray head sprays a mixture of cross-shaped polylactic acid bicomponent fibers, high-curvature and high-elasticity polylactic acid bicomponent fibers, and superabsorbent resin onto it. The selected ratio is cross-shaped polylactic acid bicomponent fibers + high-curvature and high-elasticity polylactic acid bicomponent fibers : superabsorbent resin : 2 : 10, which is the first fiber resin mixture. The spraying amount is 120 grams per square meter, and the vibration frequency of the first spray head during spraying is 30 Hz.

[0088] 4) When the polylactic acid spunbond nonwoven fabric reaches the second spray head, the second spray head sprays a mixture of cross-shaped polylactic acid bicomponent fibers, high-curvature and high-elasticity polylactic acid bicomponent fibers, and superabsorbent resin onto it. The selected ratio is cross-shaped polylactic acid bicomponent fibers + high-curvature and high-elasticity polylactic acid bicomponent fibers : superabsorbent resin : 6 : 4, which is the second fiber resin mixture. The spraying amount is 60 grams per square meter, and the vibration frequency of the second spray head during spraying is 38 Hz.

[0089] 5) When the polylactic acid spunbond nonwoven fabric reaches the third spray head, the third spray head sprays a mixture of cross-shaped polylactic acid bicomponent fibers, high-curvature and high-elasticity polylactic acid bicomponent fibers, and superabsorbent resin onto it. The selected ratio is cross-shaped polylactic acid bicomponent fibers + high-curvature and high-elasticity polylactic acid bicomponent fibers : superabsorbent resin : 9 : 1, which is the third fiber resin mixture. The spraying amount is 40 grams per square meter, and the vibration frequency of the third spray head during spraying is 45 Hz.

[0090] 6) Polylactic acid (PLA) hot-air nonwoven fabric is unwound (PLA hot-air nonwoven fabric specification is 20g / m2) and layered on top of a cross-shaped PLA bicomponent fiber + high-curvature, high-elasticity PLA bicomponent fiber and superabsorbent resin mixture, forming a five-layer composite structure: PLA spunbond nonwoven fabric at the bottom, three layers of cross-shaped PLA bicomponent fiber + high-curvature, high-elasticity PLA bicomponent fiber and superabsorbent resin mixture in the middle, and PLA hot-air nonwoven fabric on top. This composite structure is then placed in an oven for setting. The hot air penetration temperature in the oven is 140℃, and the running speed is 20 meters / minute. After exiting the oven, a five-layer composite absorbent material is obtained with a basis weight of 260 g / m². This core can be used as the absorbent layer in disposable hygiene materials such as diapers, sanitary napkins, and nursing pads.

[0091] Example 3

[0092] This embodiment involves a polylactic acid bicomponent composite fiber, such as... Figure 1 and Figure 2 As shown, it includes a core with a cross-shaped cross section and a skin covering the outside of the core layer with a cross-shaped cross section; the core is high-melting-point polylactic acid, and the skin is low-melting-point polylactic acid.

[0093] The preparation process of the polylactic acid bicomponent composite fiber is as follows:

[0094] 1) First, use a drum dryer to dry high-melting-point polylactic acid chips at 100℃ for 4-6 hours, and use a drum dryer to dry low-melting-point polylactic acid chips at 40℃ for 22-24 hours to remove moisture, increase softening point, and avoid oxidation and degradation during spinning, thereby reducing the strength of polylactic acid composite fibers.

[0095] The low-melting-point polylactic acid (PLA) component is derived from Luminy® PLA resin model LX930, with a melt index of 18 g / 10min (210℃ / 2.16kg); the high-melting-point PLA component is derived from Luminy® PLA resin model LX130, with a melt index of 23 g / 10min (210℃ / 2.16kg), resulting in a moisture content of 0.008-0.015% for both high- and low-melting-point PLA chips.

[0096] 2) The dried high- and low-melting-point polylactic acid (PLA) chips were separately fed into the twin screws of a composite twin-screw spinning machine for melt extrusion. The screw extrusion temperature for the low-melting-point PLA component was 180℃, and the screw extrusion temperature for the high-melting-point PLA component was 210℃. After metering and filtration, the PLA components were fed into the composite spinning assembly of the spinning machine. The volume ratio of the high- and low-melting-point PLA components was 70:30. Due to the significant difference in melting points between the high- and low-melting-point PLA components, to avoid yarn breakage and yarn ejection during spinning, the successful spinning parameters were: spinning temperature controlled at 230℃, spinning speed controlled at 800 m / min, side-blowing air temperature controlled at 22℃, and side-blowing air speed controlled at 1... m / s, the pre-stretch ratio is controlled at (1.5), and then it is oiled. The oiling process is carried out in two stages. The first oiling is done by oil bath oiling, using short fiber oiling agent 6214-TS from Takemoto Oils Co., Ltd. of Japan, and the oiling rate is controlled at 0.2%. Then it enters the stretching process, and the stretch ratio is controlled at (1.8). Then it is subjected to tension heat setting, and the heat setting temperature is controlled at (60℃). Then it is oiled again, using oil roller or spraying method, using Lurol PP-14160, a multi-layer hydrophilic oiling agent from Goulston, and the oiling rate is controlled at 0.15%. Then it enters the second heat setting, and the temperature is controlled at (100℃). After winding and cutting, high and low melting point bicomponent polylactic acid composite fiber with a cross-shaped cross section is obtained. The fiber fineness is 3.5dtex, the number of crimps is 4 / 2.5mm, the crimp angle is 100°, the cross length-to-width ratio of the composite fiber is 5:1, and the fiber length is 5mm.

[0097] The biodegradable absorbent core involved in this embodiment includes the aforementioned polylactic acid bicomponent composite fiber; the biodegradable absorbent core includes a surface layer 10, a middle layer 20, and a bottom layer 30; the surface layer 10 and the bottom layer 30 are single-component polylactic acid fiber nonwoven fabrics; the middle layer includes polylactic acid bicomponent composite fiber with a cross-shaped cross section, highly crimped and highly elastic polylactic acid bicomponent fiber, and superabsorbent resin.

[0098] In the preparation of the biodegradable absorbent core, the following materials are used: prepared cross-shaped polylactic acid (PLA) bicomponent fibers, highly crimped and elastic PLA bicomponent fibers, and PLA fiber nonwoven fabric, with PLA spunbond nonwoven fabric being the preferred choice. The highly crimped PLA bicomponent fiber is a biodegradable, highly crimped fiber with a parallel cross-section, specially developed by Suzhou Jinquan New Material Co., Ltd. One low-viscosity component is Luminy® PLA resin model LX530, with a melt index of 23 g / 10min (210℃ / 2.16kg); the high-viscosity PLA component is from Luminy® PLA resin model LX175, with a melt index of 6 g / 10min (210℃ / 2.16kg). The highly crimped PLA bicomponent fiber has a fineness of 1.5 dtex, a crimp count of 8 / 2.5mm, and a fiber length of 10mm.

[0099] Fiber blending: A three-dimensional motion mixer is used to blend cross-shaped polylactic acid bicomponent fibers and high-cribability, high-elasticity polylactic acid bicomponent fibers. The ratio of cross-shaped polylactic acid bicomponent fibers to high-cribability, high-elasticity polylactic acid bicomponent fibers is 70:30.

[0100] In the preparation of the biodegradable absorbent core, a nonwoven fabric laminating machine with three spray heads, manufactured by Jiangsu Gaoqi Machinery Co., Ltd., model GQ-1600, was selected. The preparation process of the biodegradable absorbent core is as follows:

[0101] 1) Preparations before lamination: Adjust the height between the first spray head and the laminating machine table to 12 cm, the height between the second spray head and the laminating machine table to 13 cm, and the height between the third spray head and the laminating machine table to 15 cm.

[0102] 2) Unwind the polylactic acid spunbond nonwoven fabric and send it to the nonwoven fabric laminating machine for lamination. The selected polylactic acid spunbond nonwoven fabric has a specification of 18 g / m2.

[0103] 3) When the polylactic acid spunbond nonwoven fabric reaches the first spray head, the first spray head sprays a mixture of cross-shaped polylactic acid bicomponent fibers, high-curvature and high-elasticity polylactic acid bicomponent fibers, and superabsorbent resin onto it. The selected ratio is cross-shaped polylactic acid bicomponent fibers + high-curvature and high-elasticity polylactic acid bicomponent fibers : superabsorbent resin : 1 : 9, the spraying amount is 140 g / m², and the vibration frequency of the first spray head during spraying is 30 Hz.

[0104] 4) When the polylactic acid spunbond nonwoven fabric reaches the second spray head, the second spray head sprays a mixture of cross-shaped polylactic acid bicomponent fibers, high-curvature and high-elasticity polylactic acid bicomponent fibers, and superabsorbent resin onto it. The selected ratio is cross-shaped polylactic acid bicomponent fibers + high-curvature and high-elasticity polylactic acid bicomponent fibers : superabsorbent resin : 5 : 5, the spraying amount is 80 grams / square meter, and the vibration frequency of the second spray head during spraying is 38 Hz.

[0105] 5) When the polylactic acid spunbond nonwoven fabric reaches the third spray head, the third spray head sprays a mixture of cross-shaped polylactic acid bicomponent fibers, high-curvature and high-elasticity polylactic acid bicomponent fibers, and superabsorbent resin onto it. The selected ratio is cross-shaped polylactic acid bicomponent fibers + high-curvature and high-elasticity polylactic acid bicomponent fibers : superabsorbent resin : 8 : 2, the spraying amount is 50 g / m², and the vibration frequency of the third spray head during spraying is 45 Hz.

[0106] 6) Polylactic acid (PLA) hot-air nonwoven fabric is unwound (PLA hot-air nonwoven fabric specification is 18g / m2) and layered on top of a cross-shaped PLA bicomponent fiber + high-curvature, high-elasticity PLA bicomponent fiber and superabsorbent resin mixture, forming a five-layer composite structure: PLA spunbond nonwoven fabric at the bottom, three layers of cross-shaped PLA bicomponent fiber + high-curvature, high-elasticity PLA bicomponent fiber and superabsorbent resin mixture in the middle, and PLA hot-air nonwoven fabric on top. This composite structure is then placed in an oven for setting. The hot air penetration temperature in the oven is 130℃, and the running speed is 17 m / min. After exiting the oven, a five-layer composite absorbent material is obtained with a basis weight of 306 g / m². This core can be used as the absorbent layer in disposable hygiene materials such as diapers, sanitary napkins, and nursing pads.

[0107] The following performance tests were performed on the embodiments, including:

[0108] (1) Absorption rate

[0109] The test procedure for absorption rate is as follows:

[0110] Prepare a 0.9% physiological saline solution (simulating artificial urine). Cut the composite absorbent material prepared in this invention into strips with a width of 95 mm, flatten and straighten them. Place a standard national standard funnel at the midpoint of the composite absorbent material, and adjust the height of the funnel so that the lowest point of its opening is 5-10 mm away from the surface of the test sample. Measure 80 ml of physiological saline using a graduated cylinder and pour it into the dispensing funnel. Then, quickly open the funnel gate to its maximum to allow the solution to flow freely onto the sample surface, and start timing simultaneously. Stop timing after the liquid has completely penetrated below the surface layer. Record the time as the absorption rate of the test sample.

[0111] (2) Diffusion length and re-infiltration amount

[0112] Diffusion length: Measure 0.9% physiological saline (simulating artificial urine) as the test solution and pour it into a funnel. After equilibration, quickly open the funnel gate to its maximum to allow the liquid to flow freely to the sample surface and start timing. After 5 minutes, inject the same amount of physiological saline again. After 9 minutes, measure the diffusion length of the liquid within the absorbent material using a steel ruler. Diffusion length = the average of the maximum and minimum liquid lengths after the two injections.

[0113] Recirculation rate: Tested according to Appendix A of GB / T 28004-2011.

[0114] (3) Saturation absorption

[0115] Given the wet weight A of the nylon bag and the weight B after spin-drying, a 0.5m length of the absorbent material to be tested is cut and weighed, recorded as C. The absorbent material to be tested is placed into the nylon bag and completely immersed in 0.9% physiological saline solution for 30 minutes. It is then removed and hung on a draining rack. After 10 minutes, the total weight of the absorbent material and the nylon bag is weighed and recorded as D. Saturated absorption capacity = DAC.

[0116] (4) pH value

[0117] Test according to the method specified in Appendix C of GB / T 8939-2008 standard.

[0118] (5) Degradability

[0119] The test was conducted according to the method of GB / T19277-2003 (IDT ISO 14855:1999).

[0120] The test results are shown in Table 1.

[0121] Table 1: Test results of composite absorbent material performance

[0122]

[0123] The degradation results of the absorbent core material of this invention are shown in Table 2.

[0124] Table 2: Degradation Experiment Results

[0125]

[0126] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A degradable absorbent core body, characterized in that, Including polylactic acid bicomponent composite fibers; The polylactic acid bicomponent composite fiber includes a core with a cross-shaped cross section and a sheath covering the outside of the core layer with a cross-shaped cross section; the core is high-melting-point polylactic acid, and the sheath is low-melting-point polylactic acid; The preparation process of the polylactic acid bicomponent composite fiber is as follows: 1) First, use drying equipment to dry the high-melting-point polylactic acid (PLA) chips and low-melting-point PLA chips until the moisture content of the high-melting-point PLA chips and low-melting-point PLA chips is 0.008-0.015%; 2) The dried high-melting-point polylactic acid (PLA) chips and low-melting-point PLA chips are respectively fed into the twin screws of the composite twin-screw spinning machine for melt extrusion; the screw extrusion temperature of the low-melting-point PLA component is 170-190℃, and the screw extrusion temperature of the high-melting-point PLA component is 200-230℃; after metering and filtration, they are fed into the composite spinning assembly of the spinning machine; The spinning parameters are as follows: spinning temperature controlled at 215-245℃, spinning speed controlled at 600-1000m / min, side blowing temperature controlled at 20-24℃, side blowing speed controlled at 0.8-1.2m / s, and pre-draw ratio controlled at 1.3-1.

8. Then, the fibers undergo an oiling process, employing a two-stage oiling procedure. The first oiling uses an oil bath, controlling the oiling rate at 0.18-0.25%. Following this, a stretching process is performed, with a stretch ratio controlled at 1.5-2.

0. Next, tension heat setting is carried out at 55-65℃. A second oiling process is then performed using an oil roller or spray method, controlling the oiling rate at 0.1-0.2%. Finally, a second heat setting is performed at 90-110℃. After winding and cutting, high- and low-melting-point bicomponent polylactic acid composite fibers with a cross-shaped cross-section are obtained. The biodegradable absorbent core comprises a surface layer, a middle layer, and a bottom layer; the surface layer and the bottom layer are single-component polylactic acid fiber nonwoven fabric; the middle layer comprises polylactic acid bicomponent composite fiber with a cross-shaped cross section, highly crimped and highly elastic polylactic acid bicomponent fiber, and superabsorbent resin. The preparation process of the intermediate layer is as follows: 1) Fiber blending: Mixing cross-shaped polylactic acid bicomponent composite fibers and highly crimped and highly elastic polylactic acid bicomponent fibers to form a fiber blend; 2) Mixing: The fiber mixture is mixed with superabsorbent resin to prepare the first fiber resin mixture, the second fiber resin mixture and the third fiber resin mixture; In the first fiber resin mixture, the ratio of fiber mixture to superabsorbent resin is 0-2:8-10, wherein the particle size of the superabsorbent resin used is 100-120 mesh; In the second fiber resin mixture, the ratio of fiber mixture to superabsorbent resin is 4-6:4-6, wherein the particle size of the superabsorbent resin used is 80-100 mesh. The fiber-to-superabsorbent resin ratio in the third fiber resin mixture is 7-9:1-3, wherein the particle size of the superabsorbent resin used is 40-70 mesh.

2. The degradable absorbent core body of claim 1, wherein, The highly crimped and highly elastic polylactic acid bicomponent fiber is arranged in a side-by-side configuration, comprising a low-viscosity component and a high-viscosity component. The low-viscosity component has a melt index of 23 g / 10 min, and the high-viscosity component has a melt index of 6 g / 10 min. The fiber fineness of the highly crimped and highly elastic polylactic acid bicomponent fiber is 1.5-6 dtex, the number of crimps is 8-12 / 2.5 mm, and the fiber length is 10-25 mm.

3. The degradable absorbable core body according to claim 1, wherein, The mixing ratio of the polylactic acid bicomponent composite fiber and the highly crimped and highly elastic polylactic acid bicomponent fiber is 50-70:50-30.

4. The degradable absorbable core of claim 1, wherein, The biodegradable absorbent core is prepared using a nonwoven fabric composite machine with three spray heads. The specific preparation process is as follows: 1) Preparation before lamination: Adjust the height between the first spray head and the laminating machine table to 10-13cm, the height between the second spray head and the laminating machine table to 12-14cm, and the height between the third spray head and the laminating machine table to 13-15cm. 2) Unwind the polylactic acid spunbond nonwoven fabric used as the bottom layer and send it to the nonwoven fabric composite machine for lamination. The selected polylactic acid spunbond nonwoven fabric has a specification of 15-20g / m2. 3) When the polylactic acid spunbond nonwoven fabric reaches the first spray head, the first spray head sprays the first fiber resin mixture onto it at a rate of 120-180 g / m², and the vibration frequency of the first spray head during spraying is 20-30 Hz. 4) When the polylactic acid spunbond nonwoven fabric reaches the second spray head, the second spray head sprays the second fiber resin mixture onto it at a rate of 60-100 grams per square meter. The vibration frequency of the second spray head during spraying is 28-38 Hz. 5) When the polylactic acid spunbond nonwoven fabric reaches the third spray head, the third spray head sprays the third fiber resin mixture onto it at a rate of 40-70 grams per square meter. The vibration frequency of the third spray head during spraying is 35-45 Hz. 6) Unwind the polylactic acid hot air nonwoven fabric used on the surface and stack it on top of the sprayed third fiber resin mixture to form a polylactic acid spunbond nonwoven fabric at the bottom, a three-layer cross-shaped polylactic acid bicomponent fiber + high-curvature, high-elasticity polylactic acid bicomponent fiber and high-absorbency resin mixture in the middle, and a five-layer composite structure of polylactic acid hot air nonwoven fabric on the top. The composite structure is then placed in an oven for shaping. The hot air penetration temperature in the oven is 115-140℃, and the running speed is 15-20 meters / minute. After exiting the oven, a five-layer composite absorbent material is obtained with a weight of 300-460 grams per square meter.

5. The biodegradable absorbent core according to claim 1, characterized in that, The drying equipment is a rotary drum dryer; the low-melting-point polylactic acid component has a melt index of 18 g / 10 min; the high-melting-point polylactic acid component has a melt index of 23 g / 10 min.

6. The biodegradable absorbent core according to claim 1, characterized in that, The polylactic acid bicomponent composite fiber has a fiber fineness of 1.5-6 dtex, a crimp number of 2-5 / 2.5 mm, and a crimp angle of 80-100 degrees; and the cross-shaped aspect ratio of the polylactic acid bicomponent composite fiber is 3-7:1, with a fiber length of 3-20 mm.

7. The biodegradable absorbent core according to claim 1, characterized in that, The volume ratio of the high-melting-point polylactic acid chips to the low-melting-point polylactic acid components is 60-80:20-40.

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