Skin care bicomponent sheath-core structure fiber and method of making same

Abstract

This invention relates to a skin-care two-component core-skin structure fiber and its preparation method. The fiber includes a skin layer and a core layer, with the core layer completely encapsulating the skin layer. The skin layer is composed of 20%-80% PLA, 20%-80% HDPE, and 5%-20% compatibility modifier by weight percentage. The core layer raw material is either PET or PLA. The compatibility modifier is either maleic anhydride-modified PLA or maleic anhydride-grafted modified PE. This invention uses a blend of PLA, HDPE, and maleic anhydride modifiers as the outer layer, and PET or PLA as the core layer. This structure can fully utilize the advantages of each raw material. The outer layer, with PLA as the core, not only takes into account biocompatibility, flexibility, and skin-friendly properties, but also utilizes PLA's own weak acidity and mild antibacterial properties to create a healthy protective environment for the skin. The core layer ensures the mechanical strength and hot-air bonding stability of the fibers. At the same time, the whole structure is compatible with the melt bonding and web forming process of hot-air nonwoven fabrics, solving the problems of insufficient skin-friendly properties and imbalance between processing and use performance of existing hot-air nonwoven fibers.

Description

Technical Field

[0001] This invention relates to a skin-care two-component core-skin structure fiber and its preparation method. Background Technology

[0002] With the improvement of people's living standards and the enhancement of health awareness, the requirements for personal care and beauty products that come into direct contact with the skin, such as diapers, sanitary napkins, and face masks, are no longer limited to basic breathability and moisture absorption. Functional fibers that combine gentle skincare, non-irritating properties, environmental friendliness, biodegradability, and compatibility with hot-air nonwoven fabric processing technology have become the industry trend. Current technology faces the following bottlenecks: (1) Currently, the fibers used in hot air nonwoven fabrics on the market focus on processing performance, while skin care fibers are mostly achieved through surface coating or the addition of fillers. This results in problems such as easy shedding of skin care ingredients, decreased fiber mechanical properties, poor raw material compatibility, and difficulty in adapting to the high-speed web formation and thermal bonding molding process of hot air nonwoven fabrics. These problems cannot meet the comprehensive requirements of personal care and mask products for the skin-friendliness, strength, and softness of fibers. (2) Polylactic acid (PLA) is a biodegradable polymer material derived from renewable plant resources. It has excellent biocompatibility and is non-toxic. Its degradation product is lactic acid, which is required for human metabolism and does not irritate the skin. At the same time, the surface of PLA is weakly acidic due to the presence of free radical lactic acid monomers, which is highly compatible with the weakly acidic environment of healthy human skin. It can also inhibit the growth of microorganisms through the weakly acidic environment, and has natural and mild antibacterial properties. It is an ideal base material for skin care fibers, but it has problems such as insufficient toughness, poor heat resistance, and poor compatibility with other polymers. High-density polyethylene (HDPE) has good flexibility and processing stability, but its interfacial adhesion with PLA is weak. Direct blending is prone to delamination, making it difficult to form composite materials with uniform performance. Summary of the Invention

[0003] The present invention addresses the problems existing in the prior art. Specifically, the technical problem to be solved by the present invention is to provide a high-performance skin-care bicomponent core-skin structure fiber that is compatible with hot-air nonwoven fabrics and its preparation method.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a skin-care dual-component core-skin structure fiber, wherein the fiber comprises a skin layer and a core layer, the core layer being completely enclosed within the skin layer; the skin layer is composed of 20%-80% PLA, 20%-80% HDPE, and 5%-20% compatibility modifier by mass percentage; the core layer raw material is either PET or PLA; and the compatibility modifier is either maleic anhydride-modified PLA or maleic anhydride-grafted modified PE.

[0005] Furthermore, the mass ratio of the cortex to the core layer is 2:8-7:3.

[0006] Furthermore, the fiber monofilament has a linear density of 1.5 dtex-5.0 dtex, a breaking strength ≥2.0 cN / dtex, a breaking elongation of 20%-90%, and a thermal bonding temperature range of 120℃-160℃.

[0007] Furthermore, the PLA has a melting point of 115℃-145℃ and a melt flow rate of 10-25g / 10min; the HDPE has a melting point of 120℃-140℃ and a melt flow rate of 10-25g / 10min.

[0008] Furthermore, in the maleic anhydride-modified PLA, the maleic anhydride grafting rate is 1.0%-5.0%, the melting point is 135℃-170℃, and the melt flow rate is 12-30g / 10min.

[0009] Furthermore, in the maleic anhydride-grafted modified PE, the maleic anhydride grafting rate is 0.5%-5.0%, the melting point is 115℃-150℃, and the melt flow rate is 10-25g / 10min.

[0010] Furthermore, the cross-section of the fiber is concentric or eccentric.

[0011] Furthermore, the skin layer has a double-layer gradient structure, comprising an inner layer close to the core layer and an outer layer located outside the inner layer. The inner layer consists of 20%-30% compatibility modifier, 40%-50% HDPE, and 20%-40% PLA by mass percentage; the outer layer consists of 70%-80% PLA, 10%-20% HDPE, and 5%-10% compatibility modifier by mass percentage.

[0012] Another technical solution adopted in this invention is: a method for preparing a skin-care bicomponent core-skin structure fiber, comprising the following steps: Step (1), raw material pretreatment: dry the skin layer raw material and core layer raw material to a moisture content of <0.05%, and premix the compatibility modifier with PLA and HDPE; Step (2), core-sheath composite spinning: the sheath material and the core material are extruded through a two-component spinning machine, composited through a core-sheath spinneret, and cooled by side blowing air; Step (3): Stretching and heat setting: Stretch ratio 3-5 times, heat setting temperature 80-120℃; Step (4), winding and shaping.

[0013] Compared with existing technologies, the present invention has the following advantages: The present invention is rationally designed, using PLA, HDPE and maleic anhydride modified material as the outer layer, and PET or PLA as the core layer. This structure can give full play to the advantages of each raw material. The outer layer, with PLA as the core, not only takes into account biocompatibility, flexibility and skin-friendly properties, but also utilizes PLA's own weak acidity and mild antibacterial properties to create a healthy protective environment for the skin. The core layer ensures the mechanical strength and hot air bonding stability of the fibers. At the same time, the whole structure is adapted to the melt bonding and web forming process of hot air nonwoven fabrics, solving the problems of insufficient skin care properties of existing hot air nonwoven fibers and imbalance between processing and use performance, which can significantly improve the user experience of personal care and mask products. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to specific embodiments.

[0016] This invention discloses a skin-care bicomponent core-sheath structure fiber. By optimizing the raw material formulation and structural design of the sheath and core layers, this fiber fully leverages the advantages of PLA's weak acidity, mild antibacterial properties, and biocompatibility. It also possesses excellent skin-care properties, mechanical properties, and compatibility with hot-air nonwoven fabric processing. Furthermore, some raw materials are biodegradable, making it environmentally friendly. This fiber is specifically designed for the preparation of hot-air nonwoven fabrics, ultimately meeting the production needs of personal care and beauty products such as diapers, sanitary napkins, and facial masks. The fiber specifically includes a sheath and a core layer, with the core layer completely encased within the sheath. The sheath is composed of 20%-80% PLA (polylactic acid), 20%-80% HDPE (high-density polyethylene), and 5%-20% compatibility modifier by weight percentage. The core layer raw material is either PET (melting point 200℃-270℃, high strength, heat resistance) or PLA (biodegradable). The compatibility modifier is either maleic anhydride-modified PLA (MA-modified PLA) or maleic anhydride-grafted modified PE (MA-g-PE).

[0017] The principle behind setting the percentage of raw materials in the dermis of this fiber structure is as follows: PLA is the core material (contributing to biocompatibility, weakly acidic skin-care properties, and mild antibacterial properties), HDPE supplements flexibility (improving the insufficient toughness of PLA), and a compatibility modifier (maleic anhydride-modified PLA / MA-g-PE) overcomes the interfacial incompatibility between PLA and HDPE through polar groups (-COOH). The proportion range aims to balance "skin-care function - flexibility - compatibility": too low a PLA proportion will weaken skin-care properties, while too high a proportion will make the fiber too stiff; the HDPE proportion needs to work synergistically with PLA to avoid stratification; the compatibility modifier is strictly limited to 5%-20% to prevent excessive amounts from leaving unreacted monomers. Through this design, three major functions of "core skin-care + compatibility optimization + flexibility supplementation" are achieved synergistically, avoiding the defects of a single component. The resulting technical effects are: the dermis combines skin-friendly skin-care properties, flexibility, and uniformity; it solves the industry problem of stratification in PLA and HDPE blends; and it ensures that the fiber is safely compatible with personal care products (without irritating residues).

[0018] The core material selection principle in this fiber structure is as follows: the core layer needs to provide mechanical support and thermal stability. PET (melting point 200-270℃) has high strength and good heat resistance, suitable for scenarios requiring high durability; PLA (biodegradable) maintains skin-friendly properties, suitable for overall environmental protection needs. The selection logic is based on the "strength-degradability" trade-off of the application scenario. This design compensates for the shortcomings of the outer layer PLA in terms of "insufficient toughness and poor heat resistance"; optional PLA can achieve "fully degradable" environmental upgrade, resulting in the following technical effects: the fiber has both high strength (breaking strength ≥2.0cN / dtex) and good thermal adhesion (no decomposition at 120-160℃); if PLA is selected, the product's compost degradation rate is ≥60% after 6 months, reducing white pollution.

[0019] Specifically, the mass ratio of the outer layer to the core layer is 2:8-7:3. The outer layer accounts for 20%-70%, ensuring sufficient skin contact area and sufficient core layer support for the nonwoven fabric structure. This design avoids extreme situations where "too little outer layer leads to insufficient skin care" or "too much outer layer leads to insufficient strength." The resulting technical effect is that the hot-air nonwoven fabric made of fibers is both soft and skin-friendly (PLA outer layer in contact with the skin) and not easily damaged or deformed (PET / PLA core layer for support), meeting the needs of diaper drainage and mask base fabric for carrying essence.

[0020] Specifically, the fiber monofilament linear density is 1.5dtex-5.0dtex, which is suitable for the fineness of the hot air nonwoven fabric web (too fine and the filaments are easy to break, too coarse and the softness is affected). The resulting nonwoven fabric has a delicate touch, is breathable and moisture-wicking, and is highly comfortable against the skin.

[0021] Specifically, the tensile strength of the fiber is ≥2.0 cN / dtex, ensuring the tensile strength of the nonwoven fabric. Tensile strength is the core indicator of a fiber's resistance to breakage. ≥2.0 cN / dtex is the lower limit for ensuring the tensile strength of the nonwoven fabric (below this value, it is prone to breakage), ensuring the durability of the nonwoven fabric after it is made from the fiber. This allows the nonwoven fabric to withstand external forces such as friction from diapers and stretching from sanitary napkins, and is not easily torn.

[0022] Specifically, the fiber's elongation at break is 20%-90%, balancing elasticity and processability. Elongation at break reflects fiber elasticity; 20%-90% balances "elastic recovery" and "processing stability" (too low makes it too stiff, too high makes it prone to deformation), taking into account both the fiber's flexibility and adaptability to hot air processing. Nonwoven fabrics made from this fiber are less likely to feel tight against the skin and are less prone to fiber breakage during processing.

[0023] Specifically, the thermal bonding temperature range of the fibers is 120℃-160℃, matching the hot air process and avoiding the thermal decomposition of PLA. Hot air nonwoven fabric achieves bonding by heating the outer layer, with the temperature matching the melting point of the PLA outer layer (115-145℃) (slightly higher to ensure melting) while being lower than the melting point of the PET core layer (200-270℃) (to avoid softening the core layer). If the core layer is PLA, the temperature also needs to be controlled within the 115-145℃ range. By designing this temperature, it adapts to the high-speed web formation and thermal bonding molding process of hot air nonwoven fabric; avoids the thermal decomposition of PLA (which is easily degraded at >160℃), allows the fibers to be stably used in hot air processing, and results in nonwoven fabric with strong adhesion and dimensional stability.

[0024] The fibers, through the above parameter settings, are adapted to the high-speed web forming and thermal bonding processing technology of hot air nonwoven fabric; the resulting hot air nonwoven fabric is not only soft and skin-friendly and meets the strength requirements, but also adapts to the physiological environment of human skin and inhibits the growth of harmful microorganisms by taking advantage of the weak acidity and mild antibacterial properties of the PLA skin layer. It can be directly used as the surface / channel layer of diapers and sanitary napkins or the base fabric of face masks.

[0025] Specifically, in the skin layer material, the PLA has a melting point of 115℃-145℃ to ensure controllability during thermal bonding; the melt flow rate is 10-25g / 10min (test conditions: 2.16kg, 210℃); by setting this parameter, the processability of PLA in spinning and thermal bonding is guaranteed; the melting point is adapted to the weakly acidic environment of skin contact, achieving the following effects: smooth spinning and uniform melting during thermal bonding; the skin layer PLA maintains the "weakly acidic antibacterial" properties (inhibiting Staphylococcus aureus ≥90%, Escherichia coli ≥85%). The HDPE has a melting point of 120℃-140℃, which is slightly higher than that of PLA (120-140℃), ensuring synchronous melting when compounded with PLA; the melt flow rate is 10-25g / 10min (test conditions: 2.16g, 190℃); by setting this parameter, it can synergistically improve the flexibility of the skin layer with PLA; the melting point is adapted to the overall thermal bonding temperature of the skin layer, and the resulting effect is: the skin layer is softer to the touch after compounding, and there is no delamination during spinning; it melts synchronously with PLA during thermal bonding, and the interface bonding is tighter.

[0026] Specifically, in the maleic anhydride-modified PLA, the maleic anhydride grafting rate is 1.0%-5.0%, the melting point is 135℃-170℃, and the melt flow rate is 12-30g / 10min (test conditions: 2.16kg, 210℃). A grafting rate of 1.0%-5.0% balances compatibility and safety (too low a rate fails to improve adhesion, while too high a rate easily leaves residual maleic anhydride monomers that irritate the skin); the melting point is slightly higher than PLA to ensure blend compatibility; and the MFR matches PLA. By setting these parameters, chemical bonds are formed between the polar groups and PLA / HDPE, significantly improving interfacial adhesion and solving the problem of layering in PLA and HDPE blends; there are no unreacted monomer residues, making it safe for sensitive skin.

[0027] Specifically, in the maleic anhydride-grafted modified PE, the maleic anhydride grafting rate is 0.5%-5.0% (too low a grafting rate cannot guarantee compatibility), the melting point is 115℃-150℃, and the melt flow rate is 10-25g / 10min (test conditions: 2.16kg, 190℃). By setting the above parameters, polar groups are introduced to improve the interfacial compatibility between PLA and HDPE, enhance the mechanical properties of the blend system, and avoid excessive polarity that could irritate the skin.

[0028] Specifically, the cross-section of the fiber is concentric or eccentric. Concentricity is preferred to ensure uniform stress on the core layer, uniform melting during hot air bonding, and sufficient contact between the outer layer and the skin, thereby improving the comfort of the final personal care and mask products.

[0029] The preparation method of this skincare bicomponent core-skin structure fiber includes the following steps: Step (1), raw material pretreatment: Dry the skin and core materials at 80-100℃ for 4-6 hours until the moisture content is <0.05% to avoid spinning bubbles (PLA / HDPE / PET are easy to absorb water, and too high moisture content will cause spinning bubbles) and ensure smooth spinning; then premix the compatibility modifier (MA-modified PLA / MA-g-PE) with PLA and HDPE in proportion, and stir at low speed for 10 minutes at 50-100 rpm (to ensure that the compatibility modifier and PLA / HDPE are mixed evenly and to avoid high-speed stirring that breaks the particles); Step (2), core-sheath composite spinning: The sheath material and the core material are extruded through a two-component spinning machine. The sheath material (PLA+HDPE+compatibility modifier) ​​is extruded through screw 1 (temperature 180-220℃), and the core material (PET / PLA) is extruded through screw 2 (temperature 240-280℃, PET requires a higher temperature). Then, the core-sheath filaments are formed by combining the core-sheath filaments through a core-sheath spinneret (spinneret orifice diameter 0.2-0.4mm). The core-sheath filaments are cooled by side blowing (side blowing speed 0.3-0.8m / s, temperature 15-25℃ to cool and form the filaments, avoid sudden cooling internal stress, ensure uniform fiber structure, and prevent filament breakage). Step (3): Stretching and heat setting: Stretch ratio 3-5 times (speed 800-1500m / min) to improve fiber orientation; heat setting temperature 80-120℃ (below the melting point of the dermis PLA) to eliminate internal stress and stabilize dimensions; Step (4), winding and shaping.

[0030] Example 1: Sheet layer PLA / HDPE / MA-g-PE composite, core layer PET Raw material ratio: Sheath (PLA 50%, HDPE 30%, MA-g-PE 20%), core layer PET; sheath-core mass ratio 5:5; Preparation parameters: Screw 1 temperature 200℃, screw 2 temperature 260℃, draw ratio 4 times, heat setting 100℃; Performance testing: monofilament linear density 3.0 dtex, tensile strength 2.5 cN / dtex, elongation at break 50%, thermal bonding temperature 140℃, antibacterial rate (Staphylococcus aureus) 92%.

[0031] Example 2: A composite of PLA / HDPE / MA-modified PLA for the outer layer, and PLA for the core layer. Raw material ratio: Sheath (PLA 60%, HDPE 25%, MA-modified PLA 15%), core layer PLA; sheath-core mass ratio 6:4; Preparation parameters: Screw 1 temperature 210℃, screw 2 temperature 220℃, draw ratio 3.5 times, heat setting 90℃; Performance testing: monofilament linear density 2.5 dtex, tensile strength 2.2 cN / dtex, elongation at break 65%, biodegradability (6 months) 65%.

[0032] The advantages of this invention are: (1) Excellent skin care performance and suitable for skin-friendly scenarios: The skin layer is made of PLA as the main raw material, which not only has excellent biocompatibility and non-toxicity, but also its own weak acidity (pH 5.8±0.3) can match the weak acid physiological environment of healthy human skin, which is gentle and non-irritating. At the same time, it can inhibit harmful microorganisms such as Staphylococcus aureus (antibacterial rate ≥90%) and Escherichia coli (antibacterial rate ≥85%) through the weak acid environment. It can replace the traditional coating solution and effectively reduce the risk of skin allergies, itching and microbial infection when infants, women and other sensitive groups use diapers, sanitary napkins and face masks. The skin-friendly properties of PLA combined with the softness of HDPE make the hot air nonwoven fabric made of fiber delicate to the touch and highly comfortable to the skin, meeting the core needs of personal care and beauty products. The skin-friendly properties of PLA and the softness of HDPE work together to make the contact angle of hot air nonwoven fabric <90° (hydrophilicity improved), and the delicate touch is better than that of single PLA fiber. (2) Good compatibility and safe and controllable raw materials: By adding maleic anhydride modified PLA or maleic anhydride graft modified PE as compatibility modifiers, the interfacial adhesion between PLA and HDPE is effectively improved (by more than 50%), solving the problem of poor compatibility and easy delamination when the two polymers are blended. (3) Mechanical properties and processing performance are compatible: The core layer is made of PET or PLA to provide excellent tensile strength and heat resistance. The skin layer is made of PLA and HDPE to ensure flexibility and thermal bonding performance, so that the fiber has high strength, good elastic recovery and suitable thermal bonding temperature. It can be stably adapted to the high-speed web forming and thermal bonding processing of hot air nonwoven fabric. The nonwoven fabric is not easy to break or deform, and meets the usage requirements of diaper diversion, sanitary napkin seepage prevention, and mask base fabric carrying essence. (4) Environmentally friendly and biodegradable: Both the PLA in the outer layer and the PLA in the core layer (if selected) are biodegradable materials. After the product is used, it can be decomposed by microorganisms in the natural environment, reducing white pollution and conforming to the development trend of green environmental protection. (5) Strong process adaptability and clear application scenarios: The conventional composite spinning equipment is used, the process parameters are easy to control, the production cost is low, and it is suitable for large-scale industrial production; the prepared fibers are specially adapted to hot air nonwoven fabric processing, and can be directly applied to personal care and beauty products such as diapers, sanitary napkins, and facial masks, with broad market application prospects.

[0033] In another embodiment, the skin layer has a double-layer gradient structure, comprising an inner layer close to the core layer and an outer layer outside the inner layer. The inner layer consists of 20%-30% compatibility modifier, 40%-50% HDPE, and 20%-40% PLA by mass, focusing on improving interfacial adhesion with the core layer. The outer layer (in contact with the skin) consists of 70%-80% PLA, 10%-20% HDPE, and 5%-10% compatibility modifier by mass, focusing on enhancing skin-care properties and a skin-friendly feel. The inner layer uses a high proportion of compatibility modifier (such as MA-g-PE) to overcome the interfacial incompatibility between PLA and HDPE, preventing delamination; the outer layer uses a high proportion of PLA to retain its weakly acidic skin-care and antibacterial properties, while a small amount of HDPE adjusts its softness. This gradient design achieves a functional division of "strong adhesion in the inner layer and strong skin care in the outer layer."

[0034] Designing the dermis as a dual-layer gradient structure offers several advantages: it resolves the contradiction of "difficulty in balancing compatibility and skincare benefits" in a single dermis (the compatibility modifier in the inner layer does not affect the concentration of skincare ingredients in the outer layer); the adhesion between the dermis and the core layer is increased by 30%-40% compared to a single dermis; and the high proportion of PLA in the outer layer makes the weak acidity of the skin contact area more pronounced (pH 5.5-6.0), further enhancing the antibacterial rate.

[0035] If this invention discloses or relates to components or structural parts that are fixedly connected to each other, then, unless otherwise stated, a fixed connection can be understood as: a fixed connection that can be detached (e.g., using bolts or screws), or a fixed connection that cannot be detached (e.g., riveting, welding). Of course, a fixed connection can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0036] In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes include states or shapes that are similar to, close to, or approximate with those states or shapes.

[0037] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A skin-care two-component skin-core structure fiber, the fiber comprising a skin layer and a core layer, the core layer being completely enclosed within the skin layer, characterized in that: The outer layer is composed of 20%-80% PLA, 20%-80% HDPE, and 5%-20% compatibility modifier by weight percentage; the core layer material is either PET or PLA; the compatibility modifier is either maleic anhydride-modified PLA or maleic anhydride-grafted modified PE.

2. The skin-care bicomponent core-sheath structure fiber according to claim 1, characterized in that: The mass ratio of the cortex to the core is 2:8-7:

3.

3. The skin-care bicomponent core-sheath structure fiber according to claim 2, characterized in that: The fiber monofilament has a linear density of 1.5 dtex-5.0 dtex, a breaking strength ≥2.0 cN / dtex, a breaking elongation of 20%-90%, and a thermal bonding temperature range of 120℃-160℃.

4. The skin-care bicomponent core-sheath structure fiber according to claim 1, characterized in that: The PLA has a melting point of 115℃-145℃ and a melt flow rate of 10-25g / 10min; the HDPE has a melting point of 120℃-140℃ and a melt flow rate of 10-25g / 10min.

5. The skin-care bicomponent core-sheath structure fiber according to claim 1, characterized in that: The maleic anhydride-modified PLA has a maleic anhydride grafting rate of 1.0%-5.0%, a melting point of 135℃-170℃, and a melt flow rate of 12-30g / 10min.

6. The skin-care bicomponent core-sheath structure fiber according to claim 1, characterized in that: The maleic anhydride-grafted modified PE has a maleic anhydride grafting rate of 0.5%-5.0%, a melting point of 115℃-150℃, and a melt flow rate of 10-25g / 10min.

7. The skin-care bicomponent core-sheath structure fiber according to claim 1, characterized in that: The cross-section of the fiber is concentric or eccentric.

8. The skin-care bicomponent core-sheath structure fiber according to claim 1, characterized in that: The skin layer has a double-layer gradient structure, comprising an inner layer close to the core layer and an outer layer located outside the inner layer. The inner layer consists of 20%-30% compatibility modifier, 40%-50% HDPE, and 20%-40% PLA by mass percentage; the outer layer consists of 70%-80% PLA, 10%-20% HDPE, and 5%-10% compatibility modifier by mass percentage.

9. A method for preparing skincare bicomponent core-skin structure fibers as described in any one of claims 1-7, characterized in that: Includes the following steps: Step (1), raw material pretreatment: dry the skin layer raw material and core layer raw material to a moisture content of <0.05%, and premix the compatibility modifier with PLA and HDPE; Step (2), core-sheath composite spinning: the sheath material and the core material are extruded through a two-component spinning machine, composited through a core-sheath spinneret, and cooled by side blowing air; Step (3): Stretching and heat setting: Stretch ratio 3-5 times, heat setting temperature 80-120℃; Step (4), winding and shaping.