Warm-keeping type PLA yarn and preparation process thereof

Abstract

The invention relates to the technical field of textile, in particular to a warm-keeping type PLA yarn which comprises a PLA fiber base material and ET velvet reinforcing components, the PLA fiber base material is at least one of special-shaped section PLA fibers and hollow PLA fibers, the ET velvet reinforcing components are evenly distributed in gaps of the PLA fiber base material, the diameter of ET velvet in the ET velvet reinforcing components is 0.5-3 mm, and the diameter of the ET velvet in the ET velvet reinforcing components is 0.5-3 mm. The mass of the PLA fiber base material accounts for 15-30% of the total mass, the mass of the ET velvet reinforcing component accounts for 15-30% of the total mass, the PLA fiber base material and the ET velvet reinforcing component are tightly combined through fiber cohesive force, the PLA fiber base material and the ET velvet reinforcing component form a fluffy and porous yarn structure, and the porosity is 40-60%. The defect that a single PLA yarn is insufficient in heat preservation is overcome, and the double requirements for environmental protection and heat preservation are met.

Description

Technical Field

[0001] This invention relates to the field of textile technology, specifically to a thermal insulation PLA yarn and its preparation process. Background Technology

[0002] In the field of thermal insulation yarn, there has long been a persistent industry challenge: the difficulty of balancing environmental friendliness and warmth. Traditional thermal insulation yarns and single-material PLA yarns each suffer from different performance limitations. To achieve ideal warmth, traditional thermal insulation yarns generally rely on synthetic fiber fleece and animal fibers to construct their core insulation structure. These components, by forming a loose and porous structure, effectively trap stagnant air, reducing heat conduction and loss, thus achieving excellent warmth and becoming a common choice in cold environments. However, the core weakness of these yarns lies in their lack of environmental performance. Synthetic fiber fleece is essentially a non-biodegradable polymer, and animal fibers are also difficult to decompose quickly in the natural environment. Large quantities of these yarns accumulate in the environment over a long period after disposal, not only occupying land resources but also potentially generating pollutants such as microplastics through weathering and decomposition, causing continuous damage to soil, water bodies, and ecosystems, contradicting the current green and environmentally friendly development philosophy.

[0003] In contrast, single-PLA yarns, thanks to the natural properties of polylactic acid, possess excellent biodegradability. After disposal, they can be broken down into harmless substances by microorganisms in the natural environment, causing no environmental pollution and perfectly meeting environmental protection requirements. However, due to its structural design, single-PLA yarns have significantly insufficient warmth retention. PLA fibers themselves are mostly dense, solid structures with extremely low internal porosity, lacking effective space to trap still air. Since still air is a key medium for warmth retention, single-PLA yarns cannot form an effective thermal barrier like traditional thermal yarns. Heat is easily lost through rapid conduction, significantly reducing their warmth retention. In cold environments, these yarns struggle to block the intrusion of low temperatures, failing to provide sufficient warmth and failing to meet the needs of winter wear and use in frigid regions. Both types of yarns prioritize a single performance aspect, consistently failing to simultaneously address the dual core requirements of environmental friendliness and warmth retention, becoming a significant bottleneck restricting the upgrading of the thermal yarn industry. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a thermal insulation PLA yarn and its preparation process to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a thermally insulating PLA yarn comprising a PLA fiber substrate and an ET fleece reinforcement component. The PLA fiber substrate is at least one of shaped cross-section PLA fibers and hollow PLA fibers. The ET fleece reinforcement component is uniformly distributed in the gaps of the PLA fiber substrate. The diameter of the ET fleece clusters in the ET fleece reinforcement component is 0.5-3 mm, and the mass of the ET fleece reinforcement component accounts for 15%-30% of the total mass. The PLA fiber substrate and the ET fleece reinforcement component are tightly bonded by fiber cohesion, forming a fluffy and porous yarn structure with a porosity of 40%-60%, which can effectively trap still air and improve thermal insulation performance. By combining PLA fiber substrate with ET fleece reinforcement, a core structure that combines warmth and environmental protection is constructed. The PLA fiber substrate is selected with irregular cross-section or hollow type, and combined with the uniform distribution of ET fleece in the fiber gaps, a fluffy porous structure with a porosity of 40%-60% is formed, which can effectively trap still air and solve the problem of insufficient warmth due to the dense structure of single PLA yarn. At the same time, with biodegradable PLA and ET fleece as the core components, the environmental protection shortcomings of traditional thermal insulation yarns that rely on difficult-to-degrade chemical fiber fleece are avoided. The basic requirements of warmth without sacrificing environmental protection and environmental protection without compromising warmth are achieved, laying the structural foundation for subsequent functional upgrades.

[0006] Specifically, it also includes functional additives, which are uniformly dispersed within the PLA fiber matrix, accounting for 0.5%-5% of the total yarn mass. These functional additives are at least one of antibacterial agents, UV stabilizers, or antistatic agents. Antibacterial agents include nano-silver, zinc oxide, or plant extracts (such as tea polyphenols or artemisia extract). UV stabilizers are benzotriazole or benzophenone compounds, and antistatic agents are quaternary ammonium salt compounds. The particle size of the functional additives is 50-500 nm. They are mixed with polylactic acid resin through melt blending to ensure uniform distribution within the yarn, thus imparting the corresponding functional properties to the yarn. By introducing antibacterial, UV-resistant, and antistatic functional additives through melt blending, and controlling the additive particle size to 50-500 nm, uniform dispersion within the PLA matrix is ​​ensured, allowing the yarn to acquire diverse functions without additional finishing processes. Antibacterial agents inhibit the growth of microorganisms, making them suitable for close-fitting clothing; UV protectants block harmful ultraviolet rays, meeting the needs of outdoor use; and antistatic agents reduce static electricity buildup, improving comfort. This design breaks through the limitations of traditional single-function thermal yarns, allowing the yarn to simultaneously possess warmth, environmental friendliness, and specialized functions, significantly expanding application scenarios and enhancing product competitiveness.

[0007] Specifically, the raw material of the PLA fiber substrate is polylactic acid resin, and the number average molecular weight of the polylactic acid resin is 80,000-150,000; the cross-sectional shape of the irregularly shaped PLA fiber is triangular, star-shaped, or multi-lobed; the hollow PLA fiber has a hollowness of 20%-40%; the monofilament diameter of the irregularly shaped PLA fiber is 1-5 μm; the monofilament diameter of the hollow PLA fiber is 2-8 μm; and the surface of the monofilament has a textured surface with a texture depth of 0.1-0.5 μm, which can enhance the cohesion with the ET fleece reinforcing component; the ET fleece reinforcing component is polyester ET fleece, with a fiber fineness of 0.1-1.0 dtex and a length of 3-10 mm, and the surface is treated with hydrophilic modification. The modifier is polyethylene glycol or glycerol fatty acid ester, and the amount of modifier is 1%-5% of the mass of the ET fleece reinforcing component, which can improve the compatibility with the PLA fiber substrate. The textured surface of PLA monofilaments works in conjunction with the hydrophilically modified ET fleece to enhance the cohesion between fibers and prevent the separation of composite components. The irregular cross-sections (triangular, star-shaped, etc.) and hollow structure of PLA fibers not only increase their own bulkiness but also provide a stable attachment space for ET fleece. Precise raw material parameters (number-average molecular weight of polylactic acid, fineness and length of ET fleece) ensure consistent production, while the use of modifiers improves the compatibility of the two components. This allows the yarn to maintain high warmth and environmental friendliness while possessing superior structural stability and durability, reducing performance degradation during use.

[0008] Specifically, the PLA fiber substrate and ET fleece reinforcement component form the core layer of the yarn, which is composed of PLA fiber substrate and the sheath layer of ET fleece reinforcement component. The core layer diameter accounts for 60%-80% of the total yarn diameter, and the sheath layer thickness is 5-20 μm. The PLA fiber substrate in the core layer is arranged in parallel, while the ET fleece reinforcement component in the sheath layer is distributed radially. The fleece clusters in the ET fleece reinforcement component protrude from the yarn surface, forming a fleece structure. The core layer accounts for 60%-80%, providing sufficient mechanical support for the yarn, ensuring tensile strength and structural stability, and preventing the yarn from easily breaking or deforming. The ET fleece in the sheath layer is distributed radially and partially protrudes from the surface, forming a soft fleece structure, improving tactile comfort and heat insulation. This layered design solves the problems of traditional composite yarns being either stiff or prone to shedding, allowing the yarn to have both reliable strength and a skin-friendly, warm wearing experience, adapting to the needs of various end products such as clothing and home textiles.

[0009] A process for preparing a thermal insulation PLA yarn includes the following steps: (S01) Dry polylactic acid resin to a moisture content ≤0.5% at a drying temperature of 60-80℃ for 4-8 hours; the ET fluff reinforcing component is opened and impurity removed at an opening machine speed of 500-1000 r / min, with an impurity removal rate ≥95%; (S02) The dried polylactic acid resin is added to the spinning machine barrel. The barrel temperature is 160-190℃. The melt is extruded through the spinneret. The spinneret orifice diameter is 0.1-0.5mm. The extrusion pressure is 5-10MPa. The cooling air temperature is 15-30℃ and the air velocity is 0.5-2m / s to obtain shaped cross-section or hollow PLA nascent fibers. (S03) Stretch the PLA nascent fibers at a temperature of 60-90℃ and a stretching ratio of 2-5 times, and then set them at 100-120℃ for 5-30 seconds to improve fiber strength and stability. (S04) The shaped PLA fibers and the treated ET fibers are fed into a mixer. The mixer speed is 300-600 r / min and the mixing time is 5-15 min. At the same time, a high-pressure airflow is blown into the mixed fibers through a blown fiber device. The airflow pressure is 0.3-0.8 MPa, so that the ET fibers are evenly dispersed and attached to the surface and gaps of the PLA fibers. (S05) The mixed blown fibers are wound into shape by a winding machine at a winding speed of 500-1500m / min and a winding tension of 5-20cN to obtain a warm PLA yarn.

[0010] Raw material drying reduces the impact of moisture on spinning, stretching and setting improve PLA fiber strength, high-pressure blowing ensures uniform dispersion of ET fibers, and standardized operation throughout the process avoids human error. This ensures that the core properties of each batch of yarn, such as porosity, warmth retention, and environmental friendliness, are highly consistent during mass production, reducing the scrap rate and improving production efficiency and product reliability.

[0011] Specifically, based on the yarn's warmth requirements, the diameter range of ET fluff clusters is set to 0.5-3mm. The degree of ET fluff opening is controlled by adjusting the needle roller speed and spacing of the opening machine. The needle roller speed is 500-1000 r / min, and the spacing is 0.5-2mm. The higher the degree of opening, the smaller the fluff cluster diameter. The airflow pressure and airflow speed of the blowing device are adjusted. The airflow pressure is 0.3-0.8MPa, and the airflow speed is 10-30m / s. The higher the airflow pressure and the faster the speed, the fluffier and larger the fluff clusters. The mixing time of the mixer is 5-15min. Too long a mixing time will cause the fluff clusters to become excessively dispersed and smaller, while too short a mixing time will result in uneven fluff cluster size. The mixing time is adjusted according to the target fluff cluster diameter. The diameter of the ET fluff clusters in the yarn is observed through a microscope. If it does not meet the target range, the opening, blowing, or mixing parameters are readjusted until the fluff cluster diameter reaches the set requirements, thus achieving precise control of the yarn's warmth and fluffiness. By adjusting the parameters of the opening machine, the blowing airflow conditions, and the mixing time, the diameter of the ET pile can be precisely controlled within the range of 0.5-3mm. The coordinated adjustment of the opening degree, airflow pressure, and mixing time allows for flexible acquisition of piles with different lofts, meeting diverse needs from lightweight warmth (small piles) to extreme cold warmth (large piles). Simultaneously, real-time microscopic monitoring and adjustment ensure that the pile diameter meets the set requirements. This allows the yarn to adapt to various application scenarios without changing the core raw materials, simply by adjusting process parameters, improving production flexibility and reducing the R&D and production costs of multi-specification products.

[0012] Specifically, polylactic acid (PLA) resin with a number average molecular weight of 80,000-120,000 is selected to ensure that the resin itself has a good degradation basis. A degradation accelerator, such as citric acid, adipic acid, or polyethylene glycol, is added to the PLA resin at a mass ratio of 0.5%-3% and uniformly dispersed in the resin through melt blending. The spinning machine barrel temperature is controlled at 160-185℃ to avoid high temperatures causing PLA resin degradation or cross-linking, which would affect subsequent biodegradability. The drawing temperature is 60-85℃, the drawing ratio is 2-4 times, the setting temperature is 100-115℃, and the setting time is 10-20 seconds to reduce internal fiber stress and improve degradation uniformity. The wound yarn is placed in an environment of 40-60℃ and 60%-80% humidity for 24-48 hours for conditioning treatment to further improve degradation performance. Testing shows that the yarn treated with this process has a degradation rate of ≥90% in natural environment after 12 months. By selecting polylactic acid resin with a specific number-average molecular weight, and combining it with degradation promoters and dispersing it evenly, a foundation for efficient degradation is provided. Strict control of spinning, drawing, and setting temperatures prevents excessive degradation or cross-linking of polylactic acid resin, ensuring uniform degradation. The conditioning treatment after winding further optimizes degradation performance, ensuring that the yarn has a degradation rate of ≥90% in the natural environment for 12 months. This design solves the problems of low degradation efficiency and uneven degradation in some biodegradable yarns, making the environmental advantages of the yarn more significant, fully in line with the concept of green development, and reducing the environmental burden.

[0013] Specifically, the drawn and shaped PLA fibers are treated with plasma at a power of 50-200W for 1-5 minutes using argon or oxygen as the treatment gas. This process forms active groups on the PLA fiber surface, improving surface roughness. The ET fibers are then soaked in a 1%-5% modifier solution for 10-30 minutes. The modifier is polyethylene glycol, glycerol fatty acid ester, or silane coupling agent. Subsequently, they are dried at 60-80℃ until the moisture content is ≤1%. A stirring paddle is installed in the mixer at a speed of 300-600 r / min, while the temperature introduced is 30-50℃. Hot air, with a wind speed of 0.5-1.5 m / s, promotes the tight bonding between PLA fibers and ET fleece. During the mixing process, a 5%-10% (w / w) binder solution, using water-based polyurethane or starch-based adhesive, is sprayed into the fiber mixture at a rate of 1%-3% of the total fiber mass. The mixture is then dried at 80-100℃ for 5-15 minutes. The dried fibers undergo a second drafting process at 70-90℃ with a draft ratio of 1.2-2 times to further enhance the cohesion between PLA fibers and ET fleece, ensuring the yarn does not shed or unravel during use. Plasma treatment improves the surface roughness and activity of PLA fibers, modifier treatment improves the compatibility with ET fleece, hot air-assisted mixing and binder spraying further strengthen the component bonds, and the second drafting makes the bonding even tighter. These designs fundamentally solve the problems of linting and strand breakage in traditional composite yarns, ensuring that the yarn maintains its structural integrity under various conditions such as wearing, washing, and stress, preventing lint shedding and strand breakage, extending product lifespan, and improving user experience.

[0014] Specifically, based on the yarn's warmth retention requirements, the porosity range is set to 40%-60%. To increase porosity, hollow PLA fibers with a hollowness of 30%-40% are selected; to decrease porosity, PLA fibers with irregular cross-sections or non-hollow PLA fibers are selected. The ET fleece weight percentage is 15%-30%; the higher the amount added, the greater the porosity. The ET fleece addition ratio is adjusted according to the target porosity. The airflow pressure of the blown fabric is 0.3-0.8 MPa; the higher the airflow pressure, the higher the fiber bulk and the greater the porosity. The porosity is precisely controlled by adjusting the airflow pressure. The yarn porosity is tested using mercury intrusion porosimetry or gas adsorption. If the porosity does not reach the target value, the PLA fiber morphology, ET fleece addition amount, or blown fabric airflow parameters are adjusted until the porosity meets the set requirements, ensuring the yarn's warmth retention performance and stability in use. By selecting PLA fibers of different forms (hollow fibers to increase porosity, irregular cross-section fibers or non-hollow fibers to reduce porosity) and adjusting the proportion of ET fleece and the blowing air pressure, the porosity can be stably controlled between 40% and 60%. Porosity is a core factor affecting thermal insulation performance. Precise control ensures stable yarn insulation performance and avoids inconsistent thermal insulation performance due to porosity fluctuations. Combined with mercury intrusion porosimetry or gas adsorption methods for detection and parameter feedback, precise control of thermal insulation performance can be achieved, ensuring that the yarn maintains a stable thermal insulation effect in different production batches and usage scenarios.

[0015] The beneficial effects of this invention are: PLA fiber substrate adopts irregular cross-section or hollow structure, combined with ET fleece reinforcement component evenly distributed in the fiber gaps, forming a fluffy structure with a porosity of 40%-60%, which can effectively trap still air and reduce heat conduction and loss. The fleece part of the ET fleece reinforcement component protrudes from the yarn surface to form a fleece structure, further enhancing the heat insulation effect, making the yarn's warmth performance comparable to traditional warmth yarn, solving the shortcomings of insufficient warmth of single PLA yarn, and achieving the dual goals of environmental protection and warmth.

[0016] The yarn uses PLA fiber as the base material. Polylactic acid resin itself has good biodegradability. Combined with biodegradable ET fleece reinforcement components and degradation promoters, it ensures that the yarn can be quickly decomposed by microorganisms in the natural environment after disposal, leaving no pollutant residue. This solves the environmental problem of traditional thermal insulation yarns being difficult to degrade. At the same time, the process ensures the uniformity of yarn degradation through precise control of spinning temperature, humidity conditioning and other processes. The degradation rate is excellent in 12 months, perfectly meeting the needs of green development. Detailed Implementation

[0017] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0018] This invention provides a technical solution: a warm PLA yarn, comprising a PLA fiber substrate, an ET fleece reinforcing component, and functional additives. The raw material of the PLA fiber substrate is polylactic acid resin, with a number-average molecular weight of 80,000-150,000. The PLA fiber substrate is at least one of shaped cross-section PLA fiber and hollow PLA fiber. The cross-sectional shape of the shaped cross-section PLA fiber is triangular, star-shaped, or multi-lobed. The hollow rate of the hollow PLA fiber is 20%-40%. The ET fleece reinforcing component is uniformly distributed in the gaps of the PLA fiber substrate. The diameter of the ET fleece clusters in the ET fleece reinforcing component is 0.5-3 mm. The mass of the ET fleece reinforcing component accounts for 15%-30% of the total mass. The PLA fiber substrate and the ET fleece reinforcing component are tightly bonded by fiber cohesion, forming a fluffy and porous yarn structure with a porosity of 40%-60%.

[0019] The functional additives are uniformly dispersed within the PLA fiber matrix, accounting for 0.5%-5% of the total yarn mass. The functional additives are at least one of antibacterial agents, UV stabilizers, or antistatic agents. The antibacterial agents are nano-silver, zinc oxide, or plant extracts (such as tea polyphenols or artemisia extract). The UV stabilizers are benzotriazole or benzophenone compounds. The antistatic agents are quaternary ammonium salt compounds. The particle size of the functional additives is 50-500 nm. They are mixed with polylactic acid resin through melt blending to ensure uniform distribution in the yarn and impart corresponding functional properties to the yarn.

[0020] The monofilament diameter of the irregularly shaped PLA fiber is 1-5μm, and the monofilament diameter of the hollow PLA fiber is 2-8μm. The surface of the monofilament has a textured surface with a texture depth of 0.1-0.5μm, which can enhance the cohesion with the ET fleece reinforcing component. The ET fleece reinforcing component is polyester ET fleece with a fiber fineness of 0.1-1.0dtex and a length of 3-10mm. The surface is treated with hydrophilic modification. The modifier is polyethylene glycol or glycerol fatty acid ester. The amount of modifier is 1%-5% of the mass of the ET fleece reinforcing component, which can improve the compatibility with the PLA fiber substrate.

[0021] The core layer of the yarn formed by the PLA fiber matrix and the ET fluff reinforcement component is PLA fiber matrix, and the sheath layer is ET fluff reinforcement component. The core layer diameter accounts for 60%-80% of the total yarn diameter, and the sheath layer thickness is 5-20μm. The PLA fiber matrix in the core layer is arranged in parallel, and the ET fluff reinforcement component in the sheath layer is distributed radially. The fluff clusters in the ET fluff reinforcement component protrude from the yarn surface, forming a fluffy structure.

[0022] A process for preparing a thermal insulation PLA yarn, characterized by the following steps: (S01) Dry polylactic acid resin to a moisture content ≤0.5% at a drying temperature of 60-80℃ for 4-8 hours; the ET fluff reinforcing component is opened and impurity removed at an opening machine speed of 500-1000 r / min, with an impurity removal rate ≥95%; (S02) The dried polylactic acid resin is added to the spinning machine barrel. The barrel temperature is 160-190℃. The melt is extruded through the spinneret. The spinneret orifice diameter is 0.1-0.5mm. The extrusion pressure is 5-10MPa. The cooling air temperature is 15-30℃ and the air velocity is 0.5-2m / s to obtain shaped cross-section or hollow PLA nascent fibers. (S03) Stretch the PLA nascent fibers at a temperature of 60-90℃ and a stretching ratio of 2-5 times, and then set them at 100-120℃ for 5-30 seconds to improve fiber strength and stability. (S04) The shaped PLA fibers and the treated ET fibers are fed into a mixer. The mixer speed is 300-600 r / min and the mixing time is 5-15 min. At the same time, a high-pressure airflow is blown into the mixed fibers through a blown fiber device. The airflow pressure is 0.3-0.8 MPa, so that the ET fibers are evenly dispersed and attached to the surface and gaps of the PLA fibers. (S05) The mixed blown fibers are wound into shape by a winding machine at a winding speed of 500-1500m / min and a winding tension of 5-20cN to obtain a warm PLA yarn.

[0023] Based on the yarn's warmth requirements, the diameter range of ET fluff clusters is set to 0.5-3mm. The degree of ET fluff opening is controlled by adjusting the needle roller speed and spacing of the opening machine. The needle roller speed is 500-1000 r / min, and the spacing is 0.5-2mm. The higher the degree of opening, the smaller the fluff cluster diameter. The airflow pressure and airflow speed of the blowing device are adjusted. The airflow pressure is 0.3-0.8MPa, and the airflow speed is 10-30m / s. The higher the airflow pressure and the faster the speed, the fluffier and larger the fluff clusters. The mixing time of the mixer is 5-15min. Too long a mixing time will cause the fluff clusters to become excessively dispersed and smaller, while too short a time will result in uneven fluff cluster size. The mixing time is adjusted according to the target fluff cluster diameter. The diameter of the ET fluff clusters in the yarn is observed through a microscope. If it does not meet the target range, the opening, blowing, or mixing parameters are readjusted until the fluff cluster diameter reaches the set requirements, thus achieving precise control of the yarn's warmth and fluffiness.

[0024] A degradation accelerator, such as citric acid, adipic acid, or polyethylene glycol, is added to polylactic acid resin at a mass ratio of 0.5%-3% and uniformly dispersed in the resin through melt blending. The spinning machine barrel temperature is controlled at 160-185℃ to avoid high temperature causing degradation or cross-linking of the polylactic acid resin, which would affect subsequent biodegradability. The drawing temperature is 60-85℃, the drawing ratio is 2-4 times, the setting temperature is 100-115℃, and the setting time is 10-20s to reduce internal fiber stress and improve degradation uniformity. The wound yarn is placed in an environment of 40-60℃ and 60%-80% humidity for 24-48 hours for humidification treatment to further improve degradation performance. After testing, the yarn treated by this process showed a degradation rate of ≥90% in natural environment after 12 months.

[0025] The drawn and shaped PLA fibers are treated with plasma at a power of 50-200W for 1-5 minutes using argon or oxygen as the treatment gas. This process forms active groups on the PLA fiber surface, improving surface roughness. The ET fibers are then soaked in a 1%-5% modifier solution (polyethylene glycol, glycerol fatty acid ester, or silane coupling agent) for 10-30 minutes, followed by drying at 60-80℃ until the moisture content is ≤1%. A stirring paddle is installed in the mixer at a speed of 300-600 r / min, while heat at 30-50℃ is simultaneously introduced. The hot air is 0.5-1.5 m / s to promote the tight bonding between PLA fibers and ET fleece. During the mixing process, a 5%-10% (w / w) binder solution is sprayed into the fiber mixture. The binder is water-based polyurethane or starch-based adhesive, and the spraying amount is 1%-3% of the total fiber mass. Then, it is dried at 80-100℃ for 5-15 minutes. The dried fibers are then subjected to a second stretching at a temperature of 70-90℃ and a stretching ratio of 1.2-2 times to further enhance the cohesion between PLA fibers and ET fleece, ensuring that the yarn does not shed or unravel during use.

[0026] Based on the yarn's warmth requirements, the porosity range is set to 40%-60%. To increase porosity, hollow PLA fibers with a hollowness of 30%-40% are selected; to decrease porosity, PLA fibers with irregular cross-sections or non-hollow PLA fibers are selected. The ET fleece weight percentage is 15%-30%; the higher the addition amount, the greater the porosity. The ET fleece addition ratio is adjusted according to the target porosity. The airflow pressure of the blown fabric is 0.3-0.8 MPa; the higher the airflow pressure, the higher the fiber bulk and the greater the porosity. The porosity is precisely controlled by adjusting the airflow pressure. The yarn porosity is tested using mercury intrusion porosimetry or gas adsorption. If the porosity does not reach the target value, the PLA fiber morphology, ET fleece addition amount, or blown fabric airflow parameters are adjusted until the porosity meets the set requirements, ensuring the yarn's warmth retention performance and stability in use.

[0027] Example 1: Conventional Warm PLA Yarn I. Preparation Parameters PLA fiber substrate: hollow PLA fiber with a hollow rate of 30%, a single filament diameter of 5μm, and a surface texture depth of 0.3μm; polylactic acid resin with a number average molecular weight of 100,000.

[0028] ET fleece reinforcement component: 20% by weight, fiber fineness 0.5dtex, length 6mm, modified with polyethylene glycol (modifier dosage 3%), fleece diameter 1.5mm.

[0029] Preparation process: Resin drying: 70℃, 6h, moisture content 0.3%; ET velvet opener speed 700r / min, impurity removal rate 96%.

[0030] Spinning parameters: barrel temperature 175℃, extrusion pressure 7MPa, spinneret orifice diameter 0.3mm, cooling air temperature 22℃, air velocity 1.2m / s.

[0031] Stretching and setting: Stretching temperature 75℃, stretching ratio 3 times, setting temperature 110℃, time 15s.

[0032] Mixing and blowing: Mixer speed 450r / min, time 10min, blowing air pressure 0.5MPa.

[0033] Winding speed: 1000m / min, tension: 12cN.

[0034] Performance parameters and testing standards Example 2: High-warmth, multi-functional PLA yarn (suitable for extremely cold outdoor environments) I. Preparation Parameters PLA fiber substrate: Triangular cross-section PLA fiber + hollow PLA fiber (mass ratio 1:1), hollow PLA fiber hollow rate 35%, single filament diameter 6μm, cross-section fiber single filament diameter 3μm, surface texture depth 0.4μm; polylactic acid resin number average molecular weight 120000.

[0035] Functional additive: Nano silver antibacterial agent (particle size 200nm), 2% by mass, is dispersed in PLA substrate by melt blending.

[0036] ET fleece reinforcement component: 28% by weight, fiber fineness 0.3dtex, length 8mm, modified with glycerol fatty acid ester (modifier dosage 4%), fleece diameter 2.5mm.

[0037] Preparation process: Resin drying: 80℃, 7h, moisture content 0.2%; ET velvet opener speed 800r / min, impurity removal rate 97%.

[0038] Spinning parameters: barrel temperature 180℃, extrusion pressure 8MPa, spinneret orifice diameter 0.4mm, cooling air temperature 20℃, air velocity 1.5m / s.

[0039] Stretching and setting: Stretching temperature 85℃, stretching ratio 4 times, setting temperature 115℃, time 20s.

[0040] Mixing and blowing: Mixer speed 500r / min, time 12min, blowing air pressure 0.7MPa; spray 8% water-based polyurethane adhesive (2% spray amount) during mixing, dry at 85℃ for 10min, secondary stretching temperature 80℃, multiple 1.5 times.

[0041] Winding speed: 800 m / min, tension: 15 cN.

[0042] II. Performance Parameters and Testing Basis Example 3: Lightweight and breathable PLA yarn (suitable for spring and autumn seasons) I. Preparation Parameters PLA fiber substrate: Selected star-shaped cross-section PLA fiber with a single filament diameter of 2μm and a surface texture depth of 0.2μm; polylactic acid resin with a number average molecular weight of 80,000.

[0043] Functional additives: Antistatic agent (quaternary ammonium salt, particle size 100nm), 1% by mass, dispersed in PLA substrate by melt blending.

[0044] ET fleece reinforcement component: 16% by weight, fiber fineness 0.8dtex, length 4mm, modified with polyethylene glycol (modifier dosage 2%), fleece diameter 0.8mm.

[0045] Preparation process: Resin drying: 65℃, 5h, moisture content 0.4%; ET velvet opener speed 600r / min, impurity removal rate 95%.

[0046] Spinning parameters: barrel temperature 170℃, extrusion pressure 6MPa, spinneret orifice diameter 0.2mm, cooling air temperature 25℃, air velocity 0.8m / s.

[0047] Stretching and setting: Stretching temperature 65℃, stretching ratio 2.5 times, setting temperature 105℃, setting time 10s.

[0048] Mixing and blowing: Mixer speed 350r / min, time 8min, blowing air pressure 0.4MPa.

[0049] Winding: speed 1200m / min, tension 8cN; after winding, adjust the humidity to 45℃ and 70% for 36 hours. Example 1: Through the composite design of hollow PLA fiber (hollow ratio 30%) and ET fleece (20% by mass), a fluffy structure with a porosity of 50% is formed, achieving a warmth retention rate of 55%. It can effectively trap still air to achieve warmth for daily wear, while avoiding the bulkiness of traditional thermal yarns. With a breaking strength of 3.2cN / dtex and a breaking elongation of 30%, it meets the mechanical requirements of end products such as clothing and home textiles, eliminating concerns about easy breakage and deformation.

[0050] Based on polylactic acid resin with a number average molecular weight of 100,000 and biodegradable ET fleece, the degradation rate reaches 92% in 12 months. After disposal, it can decompose naturally without pollutant residue, solving the environmental problem of traditional chemical fiber thermal insulation yarn being difficult to degrade. Moreover, the preparation process does not contain any additional harmful additives, which meets the environmental standards of daily consumer products and is suitable for the needs of the public who value green living.

[0051] Using standardized spinning (barrel temperature 175℃, extrusion pressure 7MPa), mixing (speed 450r / min), and winding (speed 1000m / min) parameters, no complex post-processing is required. The fiber cohesion of 4.5cN ensures that it is not easy to break apart during production. It has high performance consistency and low scrap rate during mass production, enabling low-cost large-scale supply and meeting the mass production needs of daily scenarios.

[0052] Example 2: By using a composite substrate of triangular irregular PLA fiber and hollow PLA fiber (hollow rate 35%), combined with a high proportion of ET fleece (28%) and a 0.7MPa high-pressure blown fleece process, the porosity is increased to 58%, the warmth retention rate reaches 68%, the fleece diameter is 2.5mm and some protrusions form a fleece surface, further enhancing the heat insulation effect, which can resist the cold outdoors, solve the pain point of insufficient warmth of single PLA yarn in low temperature environment, and is suitable for winter outdoor wear and use in cold regions.

[0053] With the addition of 2% nano-silver antibacterial agent (particle size 200nm), the antibacterial rate reaches 99%, which can inhibit the growth of microorganisms such as Staphylococcus aureus and prevent odor caused by bacteria growing in sweat during long-term outdoor wear, making it suitable for close-fitting outdoor clothing scenarios; at the same time, through adhesive spraying (water-based polyurethane) and secondary stretching process, the fiber cohesion is increased to 6.2cN, ensuring that the yarn does not shed or unravel after frequent outdoor activities and washing, and its durability is significantly better than that of traditional composite yarns.

[0054] Based on its high warmth retention and antibacterial properties, it maintains a 91% degradation rate after 12 months, without sacrificing environmental friendliness due to the addition of functional ingredients; with a tensile strength of 3.5cN / dtex, its mechanical properties are further improved, enabling it to withstand external forces such as stretching and friction in outdoor wear, achieving the dual advantages of uncompromised performance in harsh scenarios and no loss of environmental attributes.

[0055] Example 3: Using star-shaped PLA fibers (monofilament diameter 2μm) and low-percentage ET fleece (16%), with a porosity of 45% and uniform pore size ensured by gas adsorption method, the air permeability reaches 85mm / s. This avoids the stuffy feeling of dense and non-breathable PLA yarn, and meets the temperature difference requirements of spring and autumn with a 42% warmth retention rate. It achieves a lightweight and non-heavy wearing experience that is warm but not stuffy, and is suitable for spring and autumn T-shirts, light jackets and other products.

[0056] Adding 1% quaternary ammonium salt antistatic agent (particle size 100nm) reduced the surface resistivity to 1.2×10⁻⁶. 8 Ω effectively reduces static electricity buildup in the dry environment of spring and autumn, prevents yarn from absorbing dust and causing static stinging when worn, solves the problem of traditional lightweight yarns being prone to static electricity, and improves the comfort of daily wear.

[0057] With a spinning temperature of 170℃ and a winding speed of 1200m / min, the process energy consumption is lower than that of Example 2. Furthermore, the post-winding moisture conditioning treatment (45℃, 70% humidity) further optimizes the degradation performance, achieving a degradation rate of 93% in 12 months. The breaking elongation of 38% ensures that the yarn is soft and easy to process, making it suitable for lightweight knitted fabrics. This meets the green consumption needs of lightweight textiles in spring and autumn, balancing comfort, environmental protection, and low cost.

[0058] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A type of thermal insulation PLA yarn, characterized in that, The product comprises a PLA fiber substrate and an ET fleece reinforcement component. The PLA fiber substrate is at least one of shaped cross-section PLA fiber and hollow PLA fiber. The ET fleece reinforcement component is uniformly distributed in the gaps of the PLA fiber substrate. The diameter of the ET fleece clusters in the ET fleece reinforcement component is 0.5-3 mm. The mass of the ET fleece reinforcement component accounts for 15%-30% of the total mass. The PLA fiber substrate and the ET fleece reinforcement component are tightly bonded by fiber cohesion, forming a fluffy and porous yarn structure with a porosity of 40%-60%.

2. The thermal insulation PLA yarn according to claim 1, characterized in that: It also includes functional additives, which are uniformly dispersed within the PLA fiber matrix, accounting for 0.5%-5% of the total yarn mass. The functional additives are at least one of antibacterial agents, UV stabilizers, or antistatic agents. The antibacterial agents are nano-silver, zinc oxide, or plant extracts; the UV stabilizers are benzotriazole or benzophenone compounds; and the antistatic agents are quaternary ammonium salt compounds. The particle size of the functional additives is 50-500 nm. They are mixed with polylactic acid resin through melt blending to ensure uniform distribution in the yarn and impart corresponding functional properties to the yarn.

3. The thermal insulation PLA yarn according to claim 2, characterized in that: The raw material of the PLA fiber substrate is polylactic acid resin, with a number average molecular weight of 80,000-150,000. The cross-sectional shape of the irregularly shaped PLA fiber is triangular, star-shaped, or multi-lobed. The hollow PLA fiber has a hollowness of 20%-40%. The monofilament diameter of the irregularly shaped PLA fiber is 1-5 μm, and the monofilament diameter of the hollow PLA fiber is 2-8 μm. The surface of the monofilament has a textured surface with a texture depth of 0.1-0.5 μm, which can enhance the cohesion with the ET fleece reinforcing component. The ET fleece reinforcing component is polyester ET fleece with a fiber fineness of 0.1-1.0 dtex and a length of 3-10 mm. The surface is treated with hydrophilic modification. The modifier is polyethylene glycol or glycerol fatty acid ester. The amount of modifier is 1%-5% of the mass of the ET fleece reinforcing component, which can improve the compatibility with the PLA fiber substrate.

4. The thermal insulation PLA yarn according to claim 3, characterized in that: The core layer of the yarn formed by the PLA fiber substrate and the ET fluff reinforcement component is PLA fiber substrate, and the sheath layer is ET fluff reinforcement component. The core layer diameter accounts for 60%-80% of the total yarn diameter, and the sheath layer thickness is 5-20μm. The PLA fiber substrate in the core layer is arranged in parallel, and the ET fluff reinforcement component in the sheath layer is distributed radially. The fluff clusters in the ET fluff reinforcement component protrude from the yarn surface to form a fluffy structure.

5. The preparation process of a thermal insulation PLA yarn according to any one of claims 1-4, characterized in that... Includes the following steps: (S01) Dry polylactic acid resin to a moisture content ≤0.5% at a drying temperature of 60-80℃ for 4-8 hours; the ET fluff reinforcing component is opened and impurity removed at an opening machine speed of 500-1000 r / min, with an impurity removal rate ≥95%; (S02) The dried polylactic acid resin is added to the spinning machine barrel. The barrel temperature is 160-190℃. The melt is extruded through the spinneret. The spinneret orifice diameter is 0.1-0.5mm. The extrusion pressure is 5-10MPa. The cooling air temperature is 15-30℃ and the air velocity is 0.5-2m / s to obtain shaped cross-section or hollow PLA nascent fibers. (S03) Stretch the PLA nascent fibers at a temperature of 60-90℃ and a stretching ratio of 2-5 times, and then set them at 100-120℃ for 5-30 seconds to improve fiber strength and stability. (S04) The shaped PLA fibers and the treated ET fibers are fed into a mixer. The mixer speed is 300-600 r / min and the mixing time is 5-15 min. At the same time, a high-pressure airflow is blown into the mixed fibers through a blown fiber device. The airflow pressure is 0.3-0.8 MPa, so that the ET fibers are evenly dispersed and attached to the surface and gaps of the PLA fibers. (S05) The mixed blown fibers are wound into shape by a winding machine at a winding speed of 500-1500m / min and a winding tension of 5-20cN to obtain a warm PLA yarn.

6. The preparation process of a thermal insulation PLA yarn according to claim 5, characterized in that: Based on the yarn's warmth requirements, the diameter range of ET fluff clusters is set to 0.5-3mm. The degree of ET fluff opening is controlled by adjusting the needle roller speed and spacing of the opening machine. The needle roller speed is 500-1000 r / min, and the spacing is 0.5-2mm. The higher the degree of opening, the smaller the fluff cluster diameter. The airflow pressure and airflow speed of the blowing device are adjusted. The airflow pressure is 0.3-0.8MPa, and the airflow speed is 10-30m / s. The higher the airflow pressure and the faster the speed, the fluffier and larger the fluff clusters. The mixing time of the mixer is 5-15min. Too long a mixing time will cause the fluff clusters to become excessively dispersed and smaller, while too short a time will result in uneven fluff cluster size. The mixing time is adjusted according to the target fluff cluster diameter. The diameter of the ET fluff clusters in the yarn is observed through a microscope. If it does not meet the target range, the opening, blowing, or mixing parameters are readjusted until the fluff cluster diameter reaches the set requirements, thus achieving precise control of the yarn's warmth and fluffiness.

7. The preparation process of a thermal insulation PLA yarn according to claim 5, characterized in that: Polylactic acid (PLA) resin with a number average molecular weight of 80,000-120,000 is selected to ensure that the resin itself has a good degradation basis. A degradation accelerator, such as citric acid, adipic acid, or polyethylene glycol, is added to the PLA resin at a mass ratio of 0.5%-3% and uniformly dispersed in the resin through melt blending. The spinning machine barrel temperature is controlled at 160-185℃ to avoid high temperatures causing PLA resin degradation or cross-linking, which would affect subsequent biodegradability. The drawing temperature is 60-85℃, the drawing ratio is 2-4 times, the setting temperature is 100-115℃, and the setting time is 10-20 seconds to reduce internal fiber stress and improve degradation uniformity. The wound yarn is placed in an environment of 40-60℃ and 60%-80% humidity for 24-48 hours for conditioning treatment to further improve degradation performance. Testing shows that the yarn treated with this process has a degradation rate of ≥90% in natural environment after 12 months.

8. The preparation process of a thermal insulation PLA yarn according to claim 5, characterized in that: The drawn and shaped PLA fibers are treated with plasma at a power of 50-200W for 1-5 minutes using argon or oxygen as the treatment gas. This process forms active groups on the PLA fiber surface, improving surface roughness. The ET fibers are then soaked in a 1%-5% modifier solution (polyethylene glycol, glycerol fatty acid ester, or silane coupling agent) for 10-30 minutes, followed by drying at 60-80℃ until the moisture content is ≤1%. A stirring paddle is installed in the mixer at a speed of 300-600 r / min, while heat at 30-50℃ is simultaneously introduced. The hot air is 0.5-1.5 m / s to promote the tight bonding between PLA fibers and ET fleece. During the mixing process, a 5%-10% (by mass) binder solution is sprayed into the fiber mixture. The binder is water-based polyurethane or starch-based adhesive, and the spraying amount is 1%-3% of the total fiber mass. Then, the mixture is dried at 80-100℃ for 5-15 minutes. The dried fibers are then subjected to a second stretching at a temperature of 70-90℃ and a stretching ratio of 1.2-2 times to further enhance the cohesion between PLA fibers and ET fleece, ensuring that the yarn does not shed or unravel during use.

9. The preparation process of a thermal insulation PLA yarn according to claim 5, characterized in that: Based on the yarn's warmth requirements, the porosity range is set to 40%-60%. To increase porosity, hollow PLA fibers with a hollowness of 30%-40% are selected; to decrease porosity, PLA fibers with irregular cross-sections or non-hollow PLA fibers are selected. The ET fleece weight percentage is 15%-30%; the higher the amount added, the greater the porosity. The ET fleece addition ratio is adjusted according to the target porosity. The airflow pressure of the blown fabric is 0.3-0.8 MPa; the higher the airflow pressure, the higher the fiber bulk and the greater the porosity. The porosity is precisely controlled by adjusting the airflow pressure. The yarn porosity is tested using mercury intrusion porosimetry or gas adsorption. If the porosity does not reach the target value, the PLA fiber morphology, ET fleece addition amount, or blown fabric airflow parameters are adjusted until the porosity meets the set requirements, ensuring the yarn's warmth retention performance and stability in use.