A warm-insulating biodegradable PLA napped composite yarn and its preparation method

Abstract

This invention relates to the field of new yarn materials technology, and more particularly to a thermally insulating biodegradable PLA napped composite yarn and its preparation method. The yarn uses core-sheath structure PLA filaments as the base yarn, with a core layer of PLA and a sheath layer of low-melting-point PLA or copolymer PLA. The monofilament cross-section is irregular and / or hollow. Air blowing is used to form loop / arc loop pile structures on the surface of the base yarn. Subsequently, under restricted shrinkage conditions, the pile is locked and shaped, with the locking temperature controlled above the sheath softening temperature and below the core melting peak, causing the sheath to soften locally at the contact points to form point-bonding locking points to fix the pile. The pile height quantile, coefficient of variation, and bulk index are detected online, and the airflow, feed difference, and shaping parameters are adjusted in a closed loop to achieve structural and performance stability during continuous production. This solution combines high bulk, high warmth retention, washability retention, and batch consistency.

Description

Technical Field

[0001] This invention relates to the field of new yarn materials technology, and in particular to a heat-insulating biodegradable PLA napped composite yarn and its preparation method. Background Technology

[0002] With the advancement of the "dual-carbon" strategy and the trend of green consumption, the demand for biodegradable fiber materials in clothing, home textiles, and thermal insulation functional textiles continues to grow. Polylactic acid (PLA) has become one of the representative materials due to its renewable, biodegradable, and well-suited processing characteristics. However, PLA fibers still face multiple engineering challenges in achieving the "high loft, low thermal conductivity, washability, abrasion resistance, and batch stability" required for thermal insulation fabrics. On the one hand, thermal insulation performance often relies on the formation and maintenance of a stable static air layer in the yarn / fabric. Common methods include "volume reduction" techniques such as forming loop structures and pile structures with hollow / irregularly shaped cross-section fibers and surfaces. On the other hand, PLA itself has a relatively narrow thermal window, and its heat shrinkage and structural retention are significantly affected by the process. If only the loop structure formed by traditional interlacing or air weaving is relied upon, problems such as pile collapse, insufficient volume rebound after washing, and large fluctuations in loft can easily occur, resulting in insufficient consistency between thermal insulation effect and hand feel, thus limiting its promotion in high-end thermal insulation textiles.

[0003] In existing technologies, to achieve a fluffy or "cotton-like" feel, the industry widely employs air-jet texturing or steam-jet texturing. This allows filaments to form three-dimensional structures such as loops, arcs, and curls under the action of high-speed airflow, thereby improving volume and coverage. European patent EP0119044A2 discloses an air-jet texturing system: the woven yarn enters a steam chamber, and then a set of draft / traction rollers controls the yarn speed, tension, and linear shrinkage rate to obtain more uniform woven yarn in continuous production and then wind and collect it. The key technical points of this solution are: achieving stabilization and uniformity of the textured structure through "air-jet texturing, saturated steam treatment, and roller group control of tension and linear shrinkage." However, from the perspective of the demand for warm "pile / fluff" fabrics, the above-mentioned technologies mainly focus on the uniformity and general volume of the woven yarn, and still have at least three shortcomings: First, the loop structure formed on the yarn surface mostly relies on interlacing and mechanical entanglement to maintain its shape, and is prone to loosening or collapsing after repeated washing, friction and stretching cycles; Second, although steam treatment and restricted shrinkage control can improve uniformity, the quantitative control of "fluff height, density and distribution" usually still relies on empirical parameters, making it difficult to guarantee batch-to-batch consistency; Third, this type of technology has not established a "fluff-locking window" for the heat-sensitive characteristics of PLA materials. If it is directly transferred to the PLA system, problems such as insufficient heat setting leading to structural shrinkage or overheating leading to performance degradation may occur.

[0004] On the other hand, to improve the bonding and forming capabilities of biodegradable fibers, existing technologies have proposed low-melting-point sheath-core PLA composite fibers. Chinese patent CN105133082A discloses a low-melting-point sheath-core polylactic acid composite fiber and its preparation method: it uses low-melting-point PLA as the sheath and spinning-grade PLA as the core layer, with the sheath completely enveloping the core layer, and provides structural design and preparation processes such as the sheath ratio. This type of fiber can be used for thermal bonding, for example, in nonwoven materials where bonding is achieved by first softening the sheath, thereby improving bulkiness and elastic recovery. However, the typical application scenarios for this type of low-melting-point sheath-core PLA fiber are mainly concentrated in nonwoven or thermally bonded structures, and its technical effects are more reflected in the bonding and forming of sheet / mesh structures and their bulkiness and elasticity. If used for warm-insulating pile composite yarns, the "thermally bondable" nature at the material level is insufficient to solve the key problems at the yarn level: such as "how the pile is formed, how to stably fix it on the yarn surface for a long time, and how to consistently control the pile size distribution during continuous processing." In other words, existing technologies emphasize "material bonding" but lack a design for a down-locking mechanism coupled with air-blown / weaving processes and a process control framework oriented towards warmth retention indicators.

[0005] Furthermore, to improve the consistency and controllability of yarn processing, existing technologies have proposed introducing online sensing and closed-loop control during yarn weaving / texturing. Patent WO1993016218A1 discloses a control method for yarn weaving manufacturing, which uses closed-loop adjustment of process conditions and feedback control based on the output of directly acting yarn texture / texture sensors. The sensors can sense parameters such as yarn speed, temperature, yarn bulk, or tension, and adjust heating energy supply, twisting speed, or feeding speed accordingly to compensate for deviations caused by tension and shrinkage changes, achieving product consistency close to the desired state. The aforementioned closed-loop control concept provides important insights for improving consistency, but it primarily targets objectives such as "dyeability, heat flux, bulk, and tension stability" in texturing / false-twist weaving scenarios. For warm-insulating pile composite yarns, the key to final warmth and hand feel is often not a single bulk or tension, but rather indicators closer to the structure, such as "pile height percentile, pile density, bonding point distribution, and retention rate after washing." Without a defined linkage with "blowing into pile, locking and shaping window, and the formation mechanism of bonding point", even with the introduction of closed-loop control, problems such as "bulk stability but pile instability" and "average outer diameter stability but local pile collapse" may still occur, making it difficult to fundamentally solve the structural integrity and batch-to-batch consistency of thermal insulation yarn in actual use conditions.

[0006] In summary, existing technologies offer solutions from the perspectives of (1) air-jet weaving and steam treatment to stabilize the structure, (2) low-melting-point sheath-core PLA composite fibers to provide a thermally bondable material base, and (3) online detection and closed-loop control of the yarn weaving process to improve consistency. However, these solutions still have common shortcomings in the field of thermally insulating biodegradable pile composite yarns: they lack a pile-locking mechanism and parameter window for "long-term stability of pile structure," lack a structured design method that couples "material thermal bonding characteristics" with "blown pile process," and lack a systematic control strategy that incorporates "pile structure indicators" into online detection and closed-loop adjustment. Therefore, there is an urgent need for a thermally insulating pile composite yarn and its preparation method that can achieve controllable formation, reliable locking, and batch consistency of pile structure under a PLA biodegradable system, so as to better meet the comprehensive requirements of thermal textiles for bulkiness, warmth, washability, abrasion resistance, and consistency. Summary of the Invention

[0007] The technical objective of this invention is to provide a warm, retractable, pile-forming composite yarn and its preparation method. By using air blowing to form controllable pile clusters on a PLA sheath-core structure base yarn, and achieving point adhesion and pile locking of the sheath layer under limited shrinkage conditions within a specific temperature window, combined with online detection and closed-loop control to stabilize the pile structure and loft index, this invention solves the problems of easy pile collapse, poor retention after washing, and insufficient batch consistency in existing PLA pile yarns, achieving stable production that combines high loft, high warmth, and biodegradability.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A thermally insulating biodegradable PLA napped composite yarn, comprising a PLA base yarn and a nap layer;

[0010] The PLA base yarn is a core-sheath composite filament, wherein the core layer is polylactic acid (PLA) and the sheath layer is low-melting-point polylactic acid or copolymer polylactic acid, and the monofilament cross-section of the PLA base yarn is an irregular cross-section and / or a hollow cross-section.

[0011] The pile layer is composed of loop-shaped and / or arc-shaped pile structures formed by the air blowing action of pile filaments on the outer surface of the PLA base yarn;

[0012] The composite yarn undergoes restricted shrinkage locking and setting after blown yarn blowing, with the locking and setting temperature being... satisfy:

[0013] ,in This refers to the softening temperature or melting initiation temperature of the skin layer. The melting peak temperature of the core layer; the linear shrinkage rate of the yarn during the fabric setting process. And make the skin layer form a point-adhesive bonding point at the contact position between the fleece and the PLA base yarn;

[0014] The point-locking and tack bonding points are distributed at intervals along the yarn length direction, with an average spacing of 2 to 20 mm, and the coverage rate of the tack bonding points on the filament-base yarn contact points is 3% to 25%.

[0015] Preferably, the irregular cross-section is any one or more of the following: trilobal, cross-shaped, flat, C-shaped, H-shaped, or multi-lobed.

[0016] Preferably, the hollow cross-section is a single hollow or multi-hollow structure, with a hollow ratio of 10% to 45%.

[0017] Preferably, the pile structure index includes statistical values ​​of pile height measured online. and / or coefficient of variation of pile height ,in The 95th percentile value of the pile height; the preset target interval satisfies: 0.3–1.5 mm and / or .

[0018] Preferably, the loft index From online outer diameter With linear density The calculation results show that the relationship is as follows:

[0019] ;

[0020] And the preset target interval is At target value Within the range.

[0021] Preferably, the filaments are continuous filaments and / or short fibers, and the material is selected from one or more of polyester, polyamide, polyolefin or biodegradable polyester.

[0022] Furthermore, this application also provides a method for preparing the composite yarn, comprising:

[0023] S1. Spinning: Prepare core-sheath structure PLA composite filaments as PLA base yarn, with the core layer being PLA and the sheath layer being low-melting-point PLA or copolymer PLA, and make the cross-section of the single filaments irregular and / or hollow through a spinneret.

[0024] S2, blown down into pile: The PLA base yarn and pile filaments are fed into the blown down device together, and the pile filaments are formed into ring-shaped and / or arc-shaped pile structures on the outer surface of the PLA base yarn under the action of airflow.

[0025] S3. Restricted Shrinkage Finishing: The composite yarn after step S2 is finished by finishing with pile, and the finishing temperature is controlled. satisfy And limit the linear shrinkage rate during the shaping process. This creates a point-adhesive bonding point between the fleece filaments and the base yarn at the contact point between the fleece filaments and the base yarn.

[0026] S4. Online detection and closed-loop control: Online acquisition of fluff structure index and fluffiness index, and closed-loop adjustment of process parameters in step S2 and / or step S3 based on deviation output control quantity to stabilize the index within the preset target range.

[0027] S5. Winding: Winding the composite yarn after it has been locked in place into shape.

[0028] Preferably, the process parameters in step S2 include at least one or more of the following: base yarn to filament feed difference, airflow pressure / flow rate, nozzle structure parameters, and yarn tension; the closed-loop control adjusts at least one of the airflow pressure and feed difference.

[0029] And / or, the fabric setting in step S3 employs restricted shrinkage steam setting and / or hot air setting, and is achieved through tension control or linear velocity matching. ;

[0030] And / or, in step S4, the online detection employs one or more of machine vision, laser displacement, and outer diameter sensing, wherein machine vision and / or laser displacement are used to acquire... and The outer diameter sensor is used to obtain To calculate .

[0031] Furthermore, this application also provides a system for preparing pile-forming composite yarn for implementing the method, comprising a spinning assembly, a blowing assembly, a pile-forming and setting assembly, an online detection assembly, a controller, and a winding assembly connected in sequence; the online detection assembly outputs pile structure and bulkiness indices to the controller, and the controller outputs adjustment commands for airflow pressure and / or feed difference to the blowing assembly and / or to the pile-forming and setting assembly based on the deviation of the indices from a preset target range. Regulation instructions for restricted contraction control.

[0032] Preferably, the controller employs PID control and / or model predictive control to achieve [the desired control]. , and / or Multivariable collaborative closed-loop control.

[0033] This invention, by employing the aforementioned technical solutions, achieves unexpected comprehensive technical effects within a biodegradable PLA system: Firstly, by utilizing the irregular shape and / or hollow cross-section of the PLA base yarn to form a stable, static air layer, and constructing loop / arc loop pile structures on the yarn surface, the yarn bulk density is reduced and the loft is significantly increased, thereby effectively improving the fabric's thermal resistance and warmth retention performance; Secondly, within a window where the pile-locking and setting temperature is higher than the softening temperature of the sheath layer and lower than the melting temperature of the core layer, coupled with limited linear shrinkage, the sheath layer softens only locally at the contact points of the pile fibers, forming point-bonding and pile-locking bonding points. This achieves reliable fixation of the pile while avoiding overall melting. The bonding and adhesion can lead to a stiff hand feel or a decrease in yarn strength. This significantly improves the retention rate and resilience of the pile structure after repeated washing, friction, and stretching cycles. Thirdly, by acquiring the pile height quantile value, coefficient of variation, and bulk index calculated from the outer diameter and linear density online, and by implementing closed-loop linkage adjustment of key quantities such as airflow pressure, feed difference, tension, and setting temperature, the pile size distribution and bulk are stabilized within the target range during continuous production. This significantly reduces batch-to-batch fluctuations and process dependence, thereby obtaining a high-warmth, durable, consistent-feel, and mass-producible warm pile composite yarn product while ensuring biodegradability and environmental protection properties. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0035] I. Terminology Explanation and Parameter Definition

[0036] 1. PLA base yarn: refers to continuous filaments formed by melt spinning of polylactic acid (PLA). Preferably, it has a core-sheath composite structure, where the core layer is high-melting-point PLA and the sheath layer is low-melting-point PLA or copolymer PLA. The sheath layer's function is to initiate localized softening / melting during subsequent pile setting, forming "point-bonded pile bonding points," thereby achieving reliable fixation of the pile structure.

[0037] 2. Irregular cross-section / hollow cross-section: Irregular cross-sections can be trilobed, cross-shaped, C-shaped, H-shaped, multi-lobed, etc.; hollow cross-sections can be single hollow or multi-hollow, used to form a static air layer inside the yarn, improving the basic thermal insulation performance and enhancing the volumetric fluffiness.

[0038] 3. Pile and Cluster Structure: Pile can be continuous filaments, short fibers, or a combination of both. Cluster structure refers to the ring-shaped and / or arc-shaped protruding structures formed on the outer surface of the PLA base yarn under air blowing action. The stability of the cluster is not only related to the blowing formation, but more importantly, to the point bonding points formed by the pile locking and shaping, as well as the conditions for restricted shrinkage.

[0039] 4. Cloth-locking and setting temperature window: The cloth-locking and setting temperature is denoted as... The softening temperature or melting initiation temperature of the cortex is denoted as . The peak melting temperature of the core layer is denoted as The preferred fit for the velvet setting is:

[0040] ;

[0041] in: : The softening temperature or melting initiation temperature of the skin material; : Peak melting temperature of the core material; : Effective temperature of the yarn setting zone (the actual temperature reached by the yarn under the action of steam / hot air / hot rollers).

[0042] 5. Limited shrinkage conditions: The linear shrinkage rate of the yarn during the pile setting stage is denoted as... Preferred to satisfy The linear shrinkage rate is defined as:

[0043] ;

[0044] in: The gauge length under specified tension before shaping. It refers to the gauge length after shaping under the same specified tension.

[0045] 6. Dotted Velcro Fitting Point Parameters: The dotted velcro fitting points are distributed at intervals along the yarn length direction, with an average spacing of... Preferably 2–20 mm; the coverage of the bonding point on the contact point between the filament and the base yarn. The preferred coverage is 3% to 25%. The coverage rate can be obtained by counting the "total number of contact points" and the "number of contact points where point adhesion occurs" within a unit length using microscopy / machine vision.

[0046] 7. Pile structure index and loft index

[0047] (1) Percentile value of pile height : Statistical analysis was performed on the sample of pile height within a unit length, and the 95th percentile value was taken as the "representative value of tall pile".

[0048] (2) Coefficient of variation of pile height :

[0049] ;

[0050] in This represents the average height of the down clusters. This represents the standard deviation of the pile height.

[0051] (3) Apparent density With fluffiness index Online outer diameter With linear density calculate:

[0052] ;

[0053] in: The online outer diameter (mm converted to a consistent unit) Linear density (g / 1000 m). The apparent density of the yarn. The larger the size, the fluffier it is.

[0054] II. System Structure and Implementation Approach

[0055] 1. System Structure

[0056] The system of the present invention includes at least:

[0057] Spinning components: screw extruder, metering pump, composite spinning box (skin-core), spinneret (shaped / hollow), side blowing and oiling device, drawing roller assembly, winding / pre-orientation device.

[0058] Winding / Yarn Feeding Assembly: Stably supplies PLA base yarn in package to subsequent blown yarn.

[0059] The blown-down assembly includes an air-jet blown-down nozzle, a mixing guide structure, a feed roller group (to achieve differential feeding), and a tension control guide roller. The blown-down nozzle can adopt a venturi structure or a multi-hole annular nozzle to generate a stable vortex zone to facilitate the formation of loops / arcs in the fibers.

[0060] The fabric-locking and shaping assembly includes a restricted shrinkage steam shaping box and / or a hot air shaping box and / or a hot roller shaping zone; and is equipped with inlet / outlet traction roller sets to achieve linear speed matching and tension control of the shaping section, thereby meeting the requirements. .

[0061] Online detection components include at least an outer diameter sensor (laser diameter measurement / capacitive diameter measurement), a pile height sensor (laser displacement / line scan camera vision), a linear density estimation unit (calculated by length measurement, offline weighing calibration or online mass sensing), a tension sensor, and a temperature sensor (infrared temperature measurement / thermocouple).

[0062] Controller: Acquisition , , Signals such as tension and temperature are used to output control commands to adjust: blown air pressure / flow rate, feed differential, yarn tension, etc. The speed difference in the shaping section, etc., form a closed-loop control. The control algorithm can be PID or multivariable model predictive control (MPC), and the "main control index" should be given priority in implementation. Auxiliary control indicators Constraint indicators The collaborative strategy of "".

[0063] Winding assembly: stably winds the composite yarn after it has been locked in place into shape.

[0064] 2. Process Flow

[0065] The overall process can be summarized as follows: S1 spinning and forming → S2 winding and yarn feeding → S3 blowing and forming → S4 restricted shrinkage and setting → S5 online detection and closed-loop control → S6 winding.

[0066] III. Feasibility and Detailed Implementation of Key Process Steps

[0067] S1: Sheath-core PLA base yarn spinning forming (irregular / hollow)

[0068] 1. Raw material preparation:

[0069] Core PLA: Spinning-grade PLA chips, dried to a moisture content that meets melt spinning requirements (e.g., ≤0.03%).

[0070] Low-melting-point PLA / copolymer PLA in the cortex: Drying method as above. The cortex can be copolymerized to lower the melting point / softening point to form a fur-locking window.

[0071] 2. Composite spinning:

[0072] The core-sheath composite spinning assembly is adopted, with the sheath completely covering the core layer, and the sheath-core ratio is optional (e.g., sheath mass fraction of 10% to 40%).

[0073] Spinneret selection: irregularly shaped nozzles (such as trilobal or cross-shaped nozzles) and / or hollow nozzles (single hollow / multiple hollow). The hollow ratio can be adjusted from 10% to 45% by adjusting the nozzle structure and drawing conditions.

[0074] 3. Stretching and oiling:

[0075] Orientation and tensile strength are controlled by the drafting roller group to obtain a base yarn structure suitable for blown yarn (ensuring both strength and the formation of bonding points on the surface).

[0076] 4. Winding: Obtain PLA base yarn rolls.

[0077] Note: This invention does not limit the base yarn to FDY or POY, but preferably it is a continuous filament state that facilitates subsequent air blowing and pile locking.

[0078] S2: Winding and Yarn Supply

[0079] The PLA base yarn is wound to control the package formation and tension consistency; constant tension is set during yarn feeding to reduce fluctuations in the blown yarn section.

[0080] S3: Blow-drying to form pile (forming loops / arc-shaped pile clusters)

[0081] Component feeding: PLA base yarn and pile filaments enter the blown head nozzle area simultaneously. The pile filaments can be continuous filaments or short fiber bundles, and the short fibers can be fed into the airflow mixing zone through a bundler.

[0082] Feed difference and tension: By setting the feed difference (overfeed / underfeed) between the filament and the base yarn through the feed roller group, the filament forms an outward protruding ring / arc in the nozzle vortex zone.

[0083] Airflow conditions: The nozzle airflow pressure / flow rate is controlled by the compressed air pressure regulating valve and flow valve to ensure the pile height reaches the target range, while simultaneously controlling... To avoid "localized areas of excessive focus / localized areas of no focus".

[0084] Initial entanglement: After blown down, initial entanglement can be formed through weak entanglement segments to ensure that the structure is not straightened before entering the lock-down shaping segment.

[0085] S4: Restricted shrinkage locking and shaping (point bonding point formation)

[0086] This is the key step in achieving "washable and wear-resistant, with no collapse of the pile" in this invention.

[0087] 1. Temperature window control: The effective temperature of the shaping zone is controlled within a specified range. ,satisfy: The cortex undergoes localized softening or melting initiation, while the core layer retains its skeletal strength.

[0088] 2. Restricted shrinkage: Linear shrinkage is controlled by the speed difference and tension of the inlet / outlet traction rollers. The purpose is to: 1) prevent the pile from shrinking and collapsing as a whole under heat; 2) make the softening of the skin occur at the "contact point" rather than the whole coating and adhesion, so as to avoid the yarn from hardening or losing its fluffiness.

[0089] 3. Point bonding formation: Within the softening window of the cortex, point bonding points are formed at the contact points between the fleece and the base yarn. These bonding points form a certain density and coverage along the length direction (e.g., , ).

[0090] 4. Cooling and shaping: After shaping, a cooling zone is set up to quickly solidify the skin layer's point-bonded structure and stabilize the shape of the fluff.

[0091] S5: Online detection and closed-loop control (ensuring batch consistency)

[0092] 1. Inspection: Outer diameter The diameter is obtained online by laser diameter measurement; the height of the pile is obtained by laser displacement or visual line scanning to obtain the pile outline, and then calculated. and Linear density It can be calculated through offline calibration and online length measurement, or by configuring an online quality sensor.

[0093] 2. Indicator Calculation: and with master controller, For auxiliary control, For constraints.

[0094] 3. Closed-loop parameter tuning logic:

[0095] like Too low: Increase the blowing air pressure or increase the pile feed difference, or slightly reduce the tension of the lock pile section;

[0096] like High and Increase: Reduce air pressure and fine-tune the feed differential, while increasing the restriction of the down-locking section to suppress bursting;

[0097] like Too low (not fluffy enough): without causing Improving the volumetric efficiency of blown fabric under deteriorating conditions may... Adjust to the windowed average and optimize the sticky coverage;

[0098] If hardening occurs: reduce the spot adhesion coverage (by reducing...) (Or shorten the setting time), making the dermal dots more "dot-like" rather than surface-like.

[0099] S6: Winding

[0100] Control the winding tension and speed to keep them stable and avoid secondary straightening of the already formed pile structure.

[0101] IV. Testing Methods and Evaluation Criteria

[0102] To ensure data repeatability, this implementation method provides the following testing method:

[0103] 1. Plum height and The sampling length is 10 m. At least 10,000 down cluster height samples are obtained online or offline using laser displacement / visual line scanning, and the 95th percentile is calculated. With coefficient of variation .

[0104] 2. Looseness Index :

[0105] outer diameter Online laser diameter measurement requires a stable sampling period of at least 60 seconds.

[0106] Linear density The weight and length are obtained by sampling, weighing and counting according to GB / T or enterprise standards (or calculated by online quality sensing).

[0107] Substitute: in Conversion to ( ) is required A consistent unit system.

[0108] 3. Thermal insulation performance (thermal resistance / insulation rate):

[0109] The yarn is woven into a knitted or woven fabric (or non-woven filling layer) of a specified weight, and the thermal resistance is measured according to the textile thermal resistance test standard. Or the heat preservation rate index; all samples use the same tissue and weight to ensure comparability.

[0110] 4. Washability retention rate:

[0111] Test the results after washing 10 and 20 times according to the family washing program. and Calculate the retention rate:

[0112] ;

[0113] in , Data before washing, , This is the data after washing.

[0114] 4. Feel and risk of hardening (auxiliary indicator):

[0115] Fabric bending stiffness / compression resilience tests can be used, or the "compression work / resilience rate under the same areal density" can be used for quantitative characterization; if only for comparison, expert scoring can also be used, but it is recommended to use at least one instrument indicator.

[0116] V. Examples and Comparative Examples

[0117] (I) Example 1:

[0118] 1. Base yarn preparation (S1):

[0119] Core layer: PLA (melting peak) (approximately 170℃)

[0120] Skin: Low-melting-point copolymer PLA (softening / melting) (approximately 135℃)

[0121] Cortex-to-core ratio: cortex approximately 25%, core approximately 75%;

[0122] Spinneret: Tri-lobe irregular nozzle;

[0123] The spinning and drawing process yields PLA base yarn packages (linear density of approximately 110 dtex, which can be adjusted according to the target specifications).

[0124] 2. Blow-drying to form pile (S3):

[0125] Pile yarn: Continuous polyester filament (or biodegradable polyester filament) is fed together with the base yarn; the air pressure of the blown nozzle is set to a medium level, and the feed difference is set to stably form loops / arcs; the initial interlacing section is lightly interlaced to ensure that the structure is not straightened when it enters the shaping section.

[0126] 3. Loose-lined shaping (S4):

[0127] choose Falling within the window value (approximately 150°C equivalent temperature); inlet / outlet roller speed matching limits linear shrinkage. Formation of point bonding points: average spacing of approximately 8 mm, coverage of approximately 12%.

[0128] 4. Online closed loop (S5):

[0129] Target range: Approximately 0.9 mm, , Within ±8% of the target value;

[0130] Control parameters: air pressure, feed difference, down-locking temperature and tension of the shaping section are linked.

[0131] Results: See Table 1.

[0132] (II) Example 2:

[0133] Differences from Example 1:

[0134] The spinneret has a single hollow structure with a hollow rate of approximately 30%; the pile consists of short fiber bundles (e.g., 1.5–2.0 dtex, 38 mm in length, etc.), which are fed into the nozzle mixing zone through a bundler to form pile clusters; pile locking is achieved using hot air setting. The window relationship is still satisfied, and the contraction is limited. The dot-adhesive spacing is approximately 10 mm, with a coverage rate of approximately 9%. The results are shown in Table 1. It achieves essentially the same heat retention and washability as Example 1, and due to the increased hollowness, Slightly higher.

[0135] (III) Example 3:

[0136] Differences from Example 1:

[0137] The base yarn is a cross-shaped irregular shape with multiple hollow sections (the hollow section rate is approximately 20%); online detection uses a dual sensor system of outer diameter laser measurement and visual line scanning, and the main control... auxiliary control ,Will As a constraint, the dot-adhesion spacing was approximately 6 mm, with a coverage of approximately 18%, to improve washability retention. The results are shown in Table 1, regarding batch-to-batch consistency (…). The improvement is more obvious.

[0138] (iv) Comparative Example 1:

[0139] Compared with Example 1, the word " "Point-locking and shaping of the pile within the window" involves only routine low-temperature relaxation or non-amorphous treatment, allowing the pile clusters to be held together primarily by interlacing / entanglement. Result: After washing and rubbing, the pile clusters noticeably collapsed. and Significant decrease.

[0140] (v) Comparative Example 2:

[0141] Compared to Example 1, the base yarn was changed to a single-component PLA filament with the same melting point (without a low-melting-point sheath), and the remaining blowing and setting steps were kept as consistent as possible, even though... and Even with the same control, it is difficult to form stable bonding points. Result: Wash resistance retention is not as good as the example, and there is a risk of hardening or decreased strength due to the possibility of increasing the temperature in pursuit of fixation.

[0142] (vi) Comparative Example 3:

[0143] Compared to Example 1, the fabric locking process still involves heating, but it does not restrict linear shrinkage. This thermal shrinkage causes the pile to be pulled back, resulting in structural collapse. Result: decline, The thermal resistance of the fabric decreases.

[0144] (vii) Comparative Example 4:

[0145] Compared to Example 1, online detection and closed-loop parameter tuning were eliminated, and only fixed air pressure / feed difference / temperature settings were used. Results: Average performance indicators may be similar, but... Increased volume and large batch-to-batch fluctuations, especially when raw material batches / environment fluctuate, consistency deteriorates significantly.

[0146] VI. Data Summary

[0147] Table 1. Comparison of structural properties, thermal insulation, and durability between the examples and comparative examples.

[0148]

[0149] As can be seen from Table 1:

[0150] Comparative Example 1, when lacking a tack loop, after washing and The significant decrease proves that interlocking / entanglement alone is insufficient to maintain washability;

[0151] Comparative Example 2 lacks a low-melting-point skin layer, making it difficult to form stable bonding points at the window temperature. Its retention rate after washing is significantly lower than that of the Example, and the pursuit of fixation may introduce the risk of hardening.

[0152] Comparative Example 3 lacks restricted shrinkage; heat treatment causes structural shrinkage and collapse. and All of these are significantly reduced, thus decreasing thermal resistance;

[0153] Comparative Example 4 lacks an online closed loop, and its average value may be close to that of the Example 1, but... A significant increase indicates insufficient batch consistency and process robustness.

[0154] In summary, this invention achieves high loft, high warmth retention, washability, and consistency through a synergistic effect of "low-melting-point leather point adhesion and velour locking, restricted shrinkage, and online closed-loop."

[0155] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A warm, retractable, pile-forming composite yarn, characterized in that, Including PLA base yarn and pile layer; The PLA base yarn is a core-sheath composite filament, wherein the core layer is polylactic acid (PLA) and the sheath layer is low-melting-point polylactic acid or copolymer polylactic acid, and the monofilament cross-section of the PLA base yarn is an irregular cross-section and / or a hollow cross-section. The pile layer is composed of loop-shaped and / or arc-shaped pile structures formed by the air blowing action of pile filaments on the outer surface of the PLA base yarn; The composite yarn undergoes restricted shrinkage locking and setting after blown yarn blowing, with the locking and setting temperature being... satisfy: ,in This refers to the softening temperature or melting initiation temperature of the skin layer. The melting peak temperature of the core layer; the linear shrinkage rate of the yarn during the fabric setting process. And make the skin layer form a point-adhesive bonding point at the contact position between the fleece and the PLA base yarn; The point-locking and tack bonding points are distributed at intervals along the yarn length direction, with an average spacing of 2 to 20 mm, and the coverage rate of the tack bonding points on the filament-base yarn contact points is 3% to 25%.

2. The composite yarn according to claim 1, characterized in that, The irregular cross-section is any one or more of the following: trilobal, cross-shaped, flat, C-shaped, H-shaped, or multi-lobed.

3. The composite yarn according to claim 1, characterized in that, The hollow section is a single hollow or multiple hollow structure, with a hollow ratio of 10% to 45%.

4. The composite yarn according to claim 1, characterized in that, The down cluster structure index includes the statistical value of down cluster height measured online. and / or coefficient of variation of pile height ,in The 95th percentile value of the pile height; the preset target interval satisfies: 0.3–1.5 mm and / or .

5. The composite yarn according to claim 1, characterized in that, The fluffiness index From online outer diameter With linear density The calculation results show that the relationship is as follows: ； And the preset target interval is At target value Within the range.

6. The composite yarn according to claim 1, characterized in that, The filaments are continuous filaments and / or short fibers, and the material is selected from one or more of polyester, polyamide, polyolefin or biodegradable polyester.

7. A method for preparing the composite yarn according to any one of claims 1 to 6, characterized in that, include: S1. Spinning: Prepare core-sheath structure PLA composite filaments as PLA base yarn, with the core layer being PLA and the sheath layer being low-melting-point PLA or copolymer PLA, and make the cross-section of the single filaments irregular and / or hollow through a spinneret. S2, blown down into pile: The PLA base yarn and pile filaments are fed into the blown down device together, and the pile filaments are formed into ring-shaped and / or arc-shaped pile structures on the outer surface of the PLA base yarn under the action of airflow. S3. Restricted Shrinkage Finishing: The composite yarn after step S2 is finished by finishing with pile, and the finishing temperature is controlled. satisfy And limit the linear shrinkage rate during the shaping process. This creates a point-adhesive bonding point between the fleece filaments and the base yarn at the contact point between the fleece filaments and the base yarn. S4. Online detection and closed-loop control: Online acquisition of fluff structure index and fluffiness index, and closed-loop adjustment of process parameters in step S2 and / or step S3 based on deviation output control quantity to stabilize the index within the preset target range. S5. Winding: Winding the composite yarn after it has been locked in place into shape.

8. The method according to claim 7, characterized in that, The process parameters in step S2 include at least one or more of the following: base yarn to filament feed difference, airflow pressure / flow rate, nozzle structure parameters, and yarn tension; the closed-loop control adjusts at least one of the following: airflow pressure and feed difference. And / or, the fabric setting in step S3 employs restricted shrinkage steam setting and / or hot air setting, and is achieved through tension control or linear velocity matching. ; And / or, in step S4, the online detection employs one or more of machine vision, laser displacement, and outer diameter sensing, wherein machine vision and / or laser displacement are used to acquire... and The outer diameter sensor is used to obtain To calculate .

9. A system for preparing napped composite yarn for implementing the method according to any one of claims 7-8, characterized in that, The assembly includes a spinning component, a blowing component, a pile-locking and shaping component, an online detection component, a controller, and a winding component connected in sequence. The online detection component outputs pile structure and loft indices to the controller. Based on the deviation of these indices from a preset target range, the controller outputs adjustment commands for airflow pressure and / or feed difference to the blowing component, and / or outputs... Regulation instructions for restricted contraction control.

10. The system according to claim 9, characterized in that, The controller employs PID control and / or model predictive control to achieve... , and / or Multivariable collaborative closed-loop control.

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