Warp yarn for window decoration and preparation process of warp yarn

Abstract

The invention relates to the technical field of continuous fiber reinforced composite materials, in particular to warp yarn for window decoration and a preparation process of the warp yarn. According to the invention, the problems of poor mechanical property and poor antibacterial property of traditional warp yarns for window decoration are solved. The preparation method comprises the following steps: mixing Bio-EG and Petrol-EG according to a ratio, reacting with terephthalic acid, precisely controlling the temperature, and adding a phosphorus stabilizer to obtain a high-performance polyester core material; chitin is modified by DMAA, nano silicon dioxide is modified by KH-560, and the chitin and the nano silicon dioxide are subjected to melt blending with a PLA matrix to form a reinforced sheath material; the sizing agent is composed of WPU, amino silicone oil microemulsion and other substances, and a protective film is formed on the surface of the fiber after the process is optimized; through core-sheath composite spinning and post-treatment processes such as segmented cooling, drafting and heat setting, the prepared warp yarn has high strength, high elongation, wear resistance, resilience and good antibacterial functions.

Description

Technical Field

[0001] This invention relates to the field of continuous fiber reinforced composite materials technology, specifically to a warp yarn for window coverings and its preparation process. Background Technology

[0002] Window coverings play a vital role in residential and commercial spaces, not only providing privacy and light control but also influencing the aesthetics and ambiance of the interior. As the longitudinal foundation of the woven window covering fabric, the warp yarns are crucial to the fabric's structural integrity, drape, and overall performance. The warp yarns bear the primary tension during weaving, and their strength and durability directly determine the quality and lifespan of the final product. With consumers' increasing demands for the functionality of textiles, in addition to basic light control and privacy protection, there is a growing demand for window coverings with enhanced functions such as antibacterial properties. Antibacterial properties can inhibit the growth of odor-causing bacteria, prevent stains, and contribute to a healthier indoor environment.

[0003] Window covering warp yarns must possess excellent mechanical properties, such as high tensile strength, abrasion resistance, and durability, to withstand various stresses during the manufacturing process, including weaving, installation, and daily use. Continuous fiber reinforced composites are superior materials for making window covering warp yarns due to their excellent strength-to-weight ratio, high stiffness, and durability. Continuous fiber reinforced composites are made by combining reinforcing materials (such as glass fibers, carbon fibers, or aramid fibers) with resin polymers; this significantly improves the stiffness and strength of the final material.

[0004] In existing technologies, coating the fiber surface with a large number of nanoparticles hardens the fiber, reducing its flexibility and thus the fabric's drape. Adding excessive substances to the fiber surface to achieve antibacterial effects restricts the fiber's natural bending. Furthermore, the addition of certain antibacterial agents can reduce the strength and abrasion resistance of the matrix fibers over time, especially under prolonged exposure to environmental factors such as ultraviolet radiation. Ultraviolet radiation triggers photochemical reactions, causing the CN bonds of quaternary ammonium salt antibacterial agents to break, generating volatile amines, while simultaneously accelerating the carbonylation degradation of the fiber matrix; the antibacterial properties gradually detach or even disappear during repeated washing or friction. Therefore, developing a warp yarn for window coverings that simultaneously satisfies good mechanical properties and antibacterial properties is an important research direction in the current textile field.

[0005] To address this, a warp yarn for window decoration and its preparation process are proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a warp yarn for window coverings and its preparation process. The process involves mixing Bio-EG and Petro-EG in a specific ratio and reacting them with terephthalic acid, while precisely controlling the temperature and adding a phosphorus-based stabilizer to obtain a high-performance polyester core material. Chitosan is modified using DMAA, and nano-silica is modified with KH-560. These two materials are then melt-blended with a PLA matrix to form a reinforcing sheath material. The sizing agent consists of WPU and amino silicone oil microemulsion, and after process optimization, a protective film is formed on the fiber surface. Through core-sheath composite spinning and post-treatment processes such as segmented cooling, stretching, and heat setting, the prepared warp yarn possesses high strength, high elongation, abrasion resistance, resilience, and good antibacterial properties.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a process for preparing warp yarns for window coverings, the process of which is as follows: 70-85 parts of core material and 15-30 parts of sheath material are placed in a spinning box at 295-310℃ and spun to obtain composite fibers. The composite fibers are cooled and oiled in sections. The oiled composite fibers are stretched in sections at low roller temperature and then heat-set. They are impregnated in a sizing agent and subjected to two dips and two pads. After impregnation and padding, they are pre-dried, baked, and wound to obtain warp yarns for window coverings. The core material is obtained by melt extrusion of a melt obtained from the reaction of terephthalic acid, ethylene glycol, esterification catalyst, and phosphorus stabilizer, followed by water cooling and pelletizing. The sheath material is obtained by melt blending, cooling, and pelletizing of polylactic acid, modified chitin powder, and modified silica powder. The sizing agent is prepared by antistatic agent, nonionic surfactant, auxiliary film-forming agent, waterborne polyurethane emulsion, and amino silicone oil microemulsion.

[0008] Preferably, the specific preparation process of the warp yarn for window coverings is as follows: The core material and sheath material are placed in a spinning box (the spinneret is trilobal with a diameter of 0.25mm; the sheath material is sprayed on the outer edge; the core material is sprayed on the inner edge) at a spinneret temperature of 295-310℃ to obtain composite fibers. The composite fibers are then cooled in stages at a wind speed of 0.7m / s, with the upper stage cooling temperature at 30℃ and the lower stage cooling temperature at 15℃. After cooling, the cooled composite fibers are oiled using polyoxyethylene ether-modified polydimethylsiloxane, with the oiling rate controlled at 0.5-0.8%. The oiled composite fibers are then stretched using staged roller temperature control to obtain stretched composite fibers. The fiber was heat-set at 180°C. Then, the heat-set composite fiber was impregnated in a sizing agent diluted to 5 wt% (low VOC sizing agent) and subjected to two impregnation and two-padding treatments. After impregnation and padding, it was pre-dried at 120°C for 3 minutes and then baked at 150°C for 2 minutes to obtain the composite fiber. The composite fiber was wound at 3800 m / min and a winding tension of 0.15-0.25 cN / dtex to obtain the warp yarn for window coverings. The core material to sheath material ratio was 70-85:15-30.

[0009] Preferably, the spinneret of the spinning box is trilobed with a diameter of 0.25 mm; the front roller temperature of the segmented roller is 90-110℃, and the rear roller temperature is 140-160℃; the initial roller speed of the drafting is 1000-1300 m / min, and the final roller speed is 4000-4500 m / min; the two-dip and two-roll processing is carried out at 45℃ and the roller pressure is 0.2-0.3 MPa, with each immersion time being 15-20 s.

[0010] Preferably, the specific preparation process of the sizing agent is as follows: 700 parts of distilled water are injected into a stirred tank, the temperature is controlled at 25-35℃, and the stirring speed is 80-120 rpm; 1-3 parts of antistatic agent lauryl dimethyl benzyl ammonium chloride (lauryl dimethyl benzyl ammonium chloride is dissolved in a small amount of distilled water beforehand), 3-5 parts of nonionic surfactant isomeric tridecyl alcohol polyoxyethylene ether (9EO), and 8-10 parts of auxiliary film-forming agent cationic starch are added sequentially, and the mixture is stirred for 10 min after each addition; 220 parts of waterborne polyurethane (WPU) emulsion are added at a rate of 5-10 parts / min, and the mixture is stirred for 25 min; then 10 parts of amino silicone oil microemulsion are added, and the mixture is stirred for 15 min. The pH is then adjusted to 7.0-7.5 with 25% ammonia water; distilled water is added to a total of 1000 parts, and the mixture is stirred for 20 min. The mixture is then filtered through a 150-300 mesh filter, stored in a sealed container away from light, and the sizing agent is obtained.

[0011] Preferably, the core material preparation process is as follows: 100 parts of terephthalic acid (fiber-grade PTA), bio-based ethylene glycol (Bio-EG), petroleum-based ethylene glycol (Petro-EG), and the esterification catalyst antimony trioxide (Sb₂O₃) are mixed evenly in a slurry mixing tank at 100°C to obtain a slurry; the slurry is reacted at 250-265°C and 0.1-0.4 MPa pressure for 3 hours to obtain oligomers; the oligomers are transferred to a pre-polymerization reactor, and the temperature is increased from 260°C to 280°C at a heating rate of 10°C / h under 3.0 kPa pressure to obtain a pre-polymerization product; a phosphorus-based stabilizer is added to the pre-polymerization product, and the reaction is carried out at 280-290°C and 0.16 kPa for 2-5 hours to obtain a viscosity of 0.60-0.68 dL·g. -1 The melt was extruded at 275-285℃; after being cooled to <50℃ in a water-cooling tank, it was pelletized to obtain core particles with a particle size of 2.0nm; after vacuum drying, the core material was obtained.

[0012] Preferably, the ratio of bio-based ethylene glycol (Bio-EG) to petroleum-based ethylene glycol (Petro-EG) is 12-15:30-34.

[0013] Preferably, the phosphorus stabilizer is any one of phosphoric acid (H3PO4), triethyl phosphite (TEP), and triphenyl phosphite (TPPi).

[0014] Preferably, the specific preparation process of the sheath material is as follows: 100 parts of dry polylactic acid, 8-15 parts of modified chitin powder, and 1-3 parts of modified silica powder are added to a mixer and premixed at 500 rpm for 12 min to obtain a premix; the premix is ​​placed in a twin-screw extruder, and the temperature of the twin-screw extruder from the feed port to the die is set to 175℃, 190℃, 200℃, 205℃, and 200℃, and the screw speed is 150-250 rpm; the extruded strip is cooled to 25-40℃ in a water bath and granulated to obtain 3.0 mm sheath particles; vacuum dried at 80-95℃ for 12 h to obtain the sheath material.

[0015] Preferably, the specific preparation process of modified chitosan powder is as follows: 20-24 parts of acrylamide monomer N,N-dimethylacrylamide (DMAA) are dissolved in distilled water to obtain an acrylamide solution; 0.65-0.95 parts of potassium persulfate are dissolved in distilled water to obtain an initiator solution; after purging with nitrogen for 30 min, 20 parts of dried chitosan powder are added to the reaction vessel, followed by 200 parts of distilled water, and stirred at room temperature and 200 rpm for 60 min to form a suspension; the mixture is then subjected to nitrogen at a flow rate of 0.5-1.0 L / min (reaction pressure is high). Under a nitrogen atmosphere throughout the process, acrylamide solution was added to a reactor and stirred until homogeneous. Then, an initiator solution was added dropwise at a rate of 0.12-0.15 parts / min. After the addition was complete, the mixture was stirred for 15 minutes to obtain a final solution. The reactor was heated to 50-80℃ and reacted at 300 rpm for 5 hours to obtain a copolymer. The copolymer was cooled to room temperature and filtered to obtain solid product one. The product was washed five times with distilled water, and filtered after each wash. After filtration, the product was vacuum dried at 80℃ for 12 hours to obtain modified chitosan powder. The preferred preparation process of modified silica powder is as follows: 5 parts of dried 20-50 nm nano-silica are added to anhydrous ethanol and ultrasonically dispersed at 400 W for 50 min to form a silica suspension; 0.25 parts of silane coupling agent KH-560 are dissolved in 1.0 part of anhydrous ethanol, 0.05 parts of distilled water are added, and acetic acid is added dropwise to adjust the pH to 4-5. The mixture is stirred at room temperature for 30 min to obtain a pre-hydrolyzed coupling agent; the pre-hydrolyzed coupling agent is added dropwise to the silica suspension, stirred for 5 min, and then heated to 80℃ (usually near the reflux temperature of ethanol, about 78°C) and reacted for 4 h; the mixture is centrifuged at 10000 rpm for 20 min to obtain solid product II; after washing three times with anhydrous ethanol, the mixture is dried in a vacuum oven at 110℃ for 10 min to obtain modified silica powder.

[0016] In another aspect, the present invention provides a warp yarn for window coverings, which is prepared by any of the preparation processes described above.

[0017] Unless otherwise specified, the term "parts" in this invention refers to "parts by weight"; and the term "parts ratio" refers to "parts by weight".

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Regarding raw materials, Bio-EG and Petro-EG are mixed in a certain proportion and then esterified with terephthalic acid. The unique structure of Bio-EG and the flexible segments of Petro-EG work together to achieve a balance between the crystallinity and toughness of the amorphous region of the polymer under specific conditions. During the esterification reaction stage, precise control of temperature and pressure ensures high reaction efficiency, producing oligomers with controllable end groups and concentrated molecular weight distribution. The pre-condensation process focuses on removing small molecule byproducts, and before the subsequent high-temperature, high-vacuum condensation reaction, a phosphorus-based stabilizer is added to weaken the activity of the residual esterification catalyst Sb2O3, preventing thermal degradation and etherification of the polyester chain under high-temperature conditions, and helping the molecular chain to "grow" stably within the specified time. From optimizing the raw material ratio to ensuring the orderly connection of each stage of the reaction and the precise control of process parameters, the comprehensive synergistic effect reduces polymer molecular chain defects, creates high molecular weight and well-structured polyester core material, enhances intermolecular forces and chain entanglement, and thus endows the warp yarns for window coverings with excellent tensile strength and elongation at break, laying a solid foundation for improving their mechanical properties.

[0019] 2. On the one hand, chitin powder is grafted and copolymerized, with DMAA grafted onto the chitin molecular chain under the action of an initiator. The modified chitin, due to the introduction of segments containing quaternary ammonium salt groups, exhibits enhanced antibacterial activity and improved dispersibility and compatibility within the PLA matrix. On the other hand, nano-silica is surface-chemically modified using the silane coupling agent KH-560. The coupling agent hydrolyzes and condenses to form organic functional groups on the surface of the nano-silica, which then interact with the PLA matrix, enhancing interfacial bonding and thus improving the overall mechanical properties of the sheath material. During the preparation process, modified chitin powder, modified silica powder, and the PLA matrix are melt-blended in a twin-screw extruder to ensure uniform distribution of components within the sheath material, avoid agglomeration stress concentration, and improve the fine-grained structure of the PLA. Through the synergy of chemical modification and process, the antibacterial and mechanical properties of the sheath material are unified, laying the foundation for subsequent bonding with the core material to generate stable composite fibers.

[0020] 3. In the sizing agent preparation process, the soft and hard segment structure of the WPU molecular chain enables it to form a film layer with both strength and flexibility on the surface of the composite fiber. Its polar groups can form hydrogen bonds with the ester or cellulose groups in the composite fiber, providing good adhesion and elasticity. Amino silicone oil microemulsion utilizes the low surface energy and flexibility of the siloxane backbone and the activity of the amino side chains to spread on the surface of the composite fiber, forming a low-friction, soft, and smooth protective layer, reducing friction between fibers and with equipment. Simultaneously, the amino groups in the amino silicone oil microemulsion can interact with the composite fiber or WPU components, enhancing the film layer bonding. Antistatic agents, nonionic surfactants, and auxiliary film-forming agents synergistically stabilize the emulsion system, improve wetting and spreading, and enhance the cohesive strength and adhesion of the film layer. Specific feeding sequences and mild reaction conditions ensure stable dispersion of each component, avoiding WPU particle aggregation or demulsification, and preventing changes or degradation of the properties of active components such as amino silicone oil and cationic starch. Through chemical synergy between components and optimization of the preparation process, the sizing agent is ensured to form a uniform, dense, tough and low-friction protective film on the surface of the composite fiber, thereby effectively improving the elastic recovery rate and abrasion resistance of the warp yarn.

[0021] 4. In core-sheath composite spinning, the core and sheath materials are co-extruded at a suitable temperature to form a core-sheath structure, laying the foundation for bonding. Segmented cooling controls fiber solidification and crystallization; appropriate oiling lubricates the composite fibers and forms a protective layer, buffering interfacial stress; segmented roller temperature drafting ensures consistent orientation of the core and sheath molecular chains, improving the strength and modulus of the composite fiber; temperature gradients ensure coordinated deformation and promote interfacial bonding. Heat setting relaxes internal stress, stabilizes orientation and crystallization, and enhances interfacial bonding; sizing treatment allows the active components of the sizing agent to penetrate and solidify at the composite fiber interface. Throughout the entire process, the parameters of each step are optimized and coordinated, from raw material selection to structural design, drafting, heat treatment, and sizing, ensuring that the prepared warp yarn possesses antibacterial properties while also exhibiting excellent comprehensive mechanical properties. Attached Figure Description

[0022] Figure 1 The figures show the test results of the nuclear sheath interface binding strength in Examples 15-17 and Comparative Examples 19-23 of this invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figure 1 This invention provides a warp yarn for window decoration and its preparation process, the technical solution of which is as follows: The material information involved in this invention is as follows: 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide CAS No.: 174899-82-2; Bio-based ethylene glycol (Bio-EG, purity 99.9%) was purchased from Zhongke Baiyijin (Zhengzhou) New Energy Technology Co., Ltd.; Terephthalic acid (cellulose grade PTA) was purchased from Tongkun Group Co., Ltd.; Chitosan powder (100-200 mesh); The preparation method of cationic starch HTCC is based on patent CN102076741A; WPU emulsion (aliphatic polyether anionic aqueous polyurethane dispersion) is Impranil® DL 1068 purchased from Covestro; amino silicone oil microemulsion was purchased from Yangzhou Chenhua New Material Co., Ltd.

[0025] Example 1 100 parts of terephthalic acid (cellulose-grade PTA), 15 parts of bio-based ethylene glycol (Bio-EG), 30 parts of petroleum-based ethylene glycol (Petro-EG), and 0.04 parts of antimony trioxide (Sb₂O₃) esterification catalyst were mixed evenly in a slurry mixing tank at 100°C to obtain a slurry. The slurry was reacted at 250°C and 0.4 MPa for 3 hours to obtain oligomers. The oligomers were transferred to a prepolymerization reactor and heated from 260°C to 280°C at a heating rate of 10°C / h under a pressure of 3.0 kPa to obtain a prepolymerization product. Phosphoric acid (H₃PO₄) was added to the prepolymerization product, and the reaction was carried out at 290°C and 0.16 kPa for 3 hours to obtain a product with a viscosity of 0.61 dL·g. -1 The melt was extruded at 275-285℃; after being cooled to <50℃ in a water-cooling tank, it was pelletized to obtain core particles with a particle size of 2.0nm; after vacuum drying, the core material was obtained.

[0026] 24 parts of N,N-dimethylacrylamide (DMAA) were dissolved in 80 parts of distilled water to obtain an acrylamide solution; 0.65 parts of potassium persulfate were dissolved in distilled water to obtain an initiator solution; after purging with nitrogen for 30 min, 20 parts of dried chitin powder were added to the reactor, followed by 200 parts of distilled water, and stirred at room temperature and 200 rpm for 60 min to form a suspension; under a nitrogen flow rate of 0.5 L / min (maintaining a nitrogen atmosphere throughout the reaction), the acrylamide solution was added to the reactor, and after stirring and mixing evenly, the initiator solution was added dropwise at a rate of 0.15 parts / min; after the dropwise addition was completed, the mixture was stirred for 15 min to obtain a mixed solution; the reactor was heated to 70℃ and reacted at 300 rpm for 5 h to obtain a copolymer; cooled to room temperature, and filtered to obtain solid product one; washed 5 times with distilled water, and filtered after each wash; after filtration, dried under vacuum at 80℃ for 12 h to obtain modified chitin powder.

[0027] Five parts of dried 30nm nano-silica were added to 20 parts of anhydrous ethanol and ultrasonically dispersed at 400W for 50 min to form a silica suspension. 0.25 parts of silane coupling agent KH-560 were dissolved in 1.0 part of anhydrous ethanol, and 0.05 parts of distilled water were added. Acetic acid was added dropwise to adjust the pH to 5, and the mixture was stirred at room temperature for 30 min to obtain a pre-hydrolyzed coupling agent. The pre-hydrolyzed coupling agent was added dropwise to the silica suspension, stirred for 5 min, and then heated to 80℃ (ethanol reflux temperature) and refluxed for 4 h. The mixture was centrifuged at 10000 rpm for 20 min to obtain solid product II. After washing three times with anhydrous ethanol, the product was dried in a vacuum oven at 110℃ for 10 min to obtain modified silica powder.

[0028] 100 parts of dried polylactic acid (PLA), 15 parts of modified chitin powder, and 3 parts of modified silica powder were added to a mixer and premixed at 500 rpm for 12 min to obtain a premix. The premix was then placed in a twin-screw extruder, with the temperature from the feed port to the die set to 175℃, 190℃, 200℃, 205℃, and 200℃, and the screw speed set to 250 rpm. The extruded strip was cooled to 25℃ in a water bath and then pelletized to obtain 3.0 mm sheath pellets. The pellets were then vacuum dried at 80-95℃ for 12 h to obtain the sheath material.

[0029] 700 parts of distilled water were injected into a stirred tank, and the temperature was controlled at 25℃ with a stirring speed of 120 rpm. Then, 3 parts of antistatic agent lauryl dimethyl benzyl ammonium chloride (3 parts of lauryl dimethyl benzyl ammonium chloride were pre-dissolved in 10 parts of distilled water), 5 parts of nonionic surfactant isomeric tridecyl alcohol polyoxyethylene ether (9EO), and 10 parts of auxiliary film-forming agent cationic starch HTCC were added sequentially, stirring for 10 min after each addition. 220 parts of waterborne polyurethane (WPU) emulsion were added at a rate of 5 parts / min and stirred for 25 min. Then, 10 parts of amino silicone oil microemulsion were added and stirred for 15 min. The pH was adjusted to 7.0 with 25% ammonia water. Distilled water was added to bring the total volume to 1000 parts, and the mixture was stirred for 20 min. The mixture was then filtered through a 150-mesh filter, stored in a light-proof and sealed container to obtain a sizing agent (low VOC sizing agent).

[0030] 75 parts of core material and 25 parts of sheath material were placed in a spinning box (spinneret orifice is trilobal, diameter is 0.25mm) with a spinneret temperature of 310℃ to obtain composite fiber. The composite fiber was cooled in stages at an air velocity of 0.7m / s, with the upper cooling temperature at 30℃ and the lower cooling temperature at 15℃. After cooling, polyoxyethylene ether modified polydimethylsiloxane was used to oil the cooled composite fiber, with the oiling rate controlled at 0.5%. The oiled composite fiber was stretched at a front roller temperature of 90℃ and a rear roller temperature of 160℃, with an initial roller speed of 1000m / min and a final roller speed of 4500m / min. The drawn composite fiber was obtained by speeding up the flow rate to 180°C. The drawn composite fiber was then heat-set at 180°C. Next, the heat-set composite fiber was immersed in a sizing agent diluted to 5 wt%, and subjected to two dips and two pads at 45°C and a roll pressure of 0.2 MPa, with each dip lasting 15 seconds. After padding, the fiber was pre-dried at 120°C for 3 minutes, followed by baking at 150°C for 2 minutes to obtain the composite fiber. The composite fiber was then wound at 4500 m / min and a winding tension of 0.15 cN / dtex to obtain the final warp yarn for window coverings.

[0031] Examples 2-7 The preparation method and parameters of Example 1 are as follows, with specific differences shown in Table 1; in Table 1, Bio-EG refers to bio-based ethylene glycol; Petro-EG refers to petroleum-based ethylene glycol; Temperature 1 and Pressure 2 refer to Temperature 1 and Pressure 3 during oligomer preparation; Temperature 2 and Polycondensation Time 3 refer to the temperature and time of the polycondensation reaction after adding phosphorus-based stabilizers to the pre-polymerization product; H3PO4 refers to phosphoric acid; TEP refers to triethyl phosphite; TPPi refers to triphenyl phosphite.

[0032] Comparative Example 1 The preparation method and parameters are the same as in Example 7, except that the ratio of Bio-EG to Petro-EG is 5:41.

[0033] Comparative Example 2 The preparation method and parameters of Example 7 were used, except that the slurry was reacted at 200°C (esterification reaction temperature) for 3 hours to obtain oligomers.

[0034] Comparative Example 3 The preparation method and parameters of Example 7 were used, except that the slurry was reacted at 300°C (esterification reaction temperature) for 3 hours to obtain oligomers.

[0035] Comparative Example 4 The preparation method and parameters are the same as in Example 7, except that the temperature of temperature two (condensation reaction) is 250°C.

[0036] Comparative Example 5 The preparation method and parameters are the same as in Example 7, except that the temperature of temperature two (condensation reaction) is 330°C.

[0037] Comparative Example 6 The preparation method and parameters are the same as in Example 7, except that the polycondensation time is 1 hour.

[0038] Comparative Example 7 The preparation method and parameters of Example 7 are the same, except that no phosphorus stabilizer is added to the prepolymerization product, thus obtaining the melt.

[0039] Test Example 1: Mechanical Property Test Five yarn samples (single yarns) with a length of 250 mm were cut from the prepared warp yarns for window coverings. A 100 mm long area was marked in the middle of the sample as the effective test length. The two ends of the sample were fixed to the clamps of the testing machine, ensuring an initial clamping length of 100 mm. The tensile speed of the testing machine was set to 100 mm / min. The testing machine was started, and the maximum tensile force and the elongation of the sample at fracture were recorded. The tensile strength and elongation at break of the sample were tested using an electronic universal testing machine, and the average value of the test results was taken. The formula for calculating the tensile strength is: The formula for calculating elongation at break is: The specific test results are shown in Table 2.

[0040] Table 1. Parameters and conditions for Examples 1-7 and Comparative Examples 1-7

[0041] Table 2 Mechanical property tests of Examples 1-7 and Comparative Examples 1-7

[0042] As shown in Table 2, the tensile strength of Examples 1-7 is greater than 22 N, and the elongation at break is greater than 11.0%; this indicates that the prepared core material gives the warp yarns for window coverings good mechanical properties. In Comparative Example 1, the ratio of Bio-EG to Petro-EG is 5:41, which severely disrupts the regularity and compatibility of the polyester molecular chain. The cyclic carbonate groups in the Bio-EG molecule can form a stronger hydrogen bond network when reacting with PTA, while the straight-chain alkyl structure of Petro-EG is more conducive to chain segment movement. A specific ratio (12-15:30-34) is required to balance the crystallization rate and the toughness of the amorphous region. When the proportion of Bio-EG is too low, the crystallinity of the system increases abnormally, leading to an increase in stress concentration points. At the same time, TPPi is difficult to disperse uniformly in a low-polarity environment, and cannot effectively suppress oxidative chain scission during high-temperature polycondensation. While the esterification temperature of 265℃ met conventional requirements, the imbalance in the raw material ratio resulted in an esterification rate of less than 92%. Residual monomers interfered with the subsequent polycondensation kinetics, leading to a melt viscosity of only 0.55 dL / g. Ultimately, microporous defects formed inside the core material, reducing the interfacial bonding strength with the sheath material by 30%, causing the tensile strength of the warp yarns used in window coverings to decrease from 28N to 21N.

[0043] In Comparative Example 2, the esterification reaction temperature was too low, leading to a significant decrease in the reaction rate and the formation of oligomers with low molecular weights and containing a large number of micro-reacting monomers or terminal carboxyl groups. These low molecular weight compounds and high acid values ​​severely affect subsequent polycondensation reactions, making it difficult to form high molecular weight polyesters. In Comparative Example 3, the esterification reaction temperature was too high, which exacerbated side reactions and accelerated the etherification of ethylene glycol to form diethylene glycol. The introduction of diethylene glycol disrupts the regularity of the oligomer chains, lowers their melting point and crystallinity, and exacerbates the thermal and oxidative degradation of the oligomers. Low molecular weight, high diethylene glycol content, and molecular chain degradation all lead to reduced molecular chain entanglement within the oligomers, weakened intermolecular forces, and increased structural defects, resulting in a significant decrease in the tensile strength and elongation at break of the prepared core material and warp yarns for window coverings.

[0044] Polycondensation is a process under vacuum and low pressure that further increases the molecular weight of a polymer through transesterification or end-group reactions. The reaction temperature is equally important in this process. In Comparative Example 4, the polycondensation temperature was too low, resulting in excessively high melt viscosity. This hindered the movement of molecular chain segments, restricted reactant diffusion, and made it difficult to remove small molecules, leading to an extremely slow polycondensation rate that could not reach the melt viscosity of Examples 1-7. In Comparative Example 5, the polycondensation temperature was too high, causing severe thermal and oxidative degradation of the polyester, resulting in extensive molecular chain breakage and the formation of small molecules and cross-linked structures. Simultaneously, it exacerbated side reactions (forming diethylene glycol, enol esters, etc.). This not only reduced the polymer molecular weight but also caused the polymer to yellow and become brittle. Insufficient molecular weight (too low polycondensation temperature) and severe degradation (too high polycondensation temperature) both lead to a sharp decrease in the strength and toughness of the core material, manifested as a significant reduction in the tensile strength and elongation at break of the warp yarns used in window coverings.

[0045] Polycondensation is a gradual process that requires sufficient time for the molecular chains to grow to the target length (i.e., reach the target viscosity). However, in Comparative Example 6, the polycondensation time was too short (1 hour), meaning the reaction terminated prematurely, and a large amount of oligomers and medium-molecular-weight chains did not fully react and grow. This resulted in a melt viscosity far below the target value (0.60-0.68 dL·g). -1 While low-viscosity melts have good fluidity, they are unable to withstand high stretching during subsequent spinning and drawing processes, making them prone to breakage. The resulting polymer has a significantly lower molecular weight, fewer entanglement points between molecular chains, and incomplete crystallization, leading to poor load-bearing capacity of the core material. Consequently, the tensile strength and elongation at break of the prepared window covering warp yarns will decrease significantly. The role of phosphorus-based stabilizers in the polycondensation reaction is to react with the esterification catalyst Sb₂O₃, reducing its activity at high temperatures and inhibiting its catalytic side reactions and degradation reactions. However, in Comparative Example 7, the absence of phosphorus-based stabilizers leads to poorer polymer stability under high-temperature conditions, making it more susceptible to degradation. This results in unstable melt viscosity and poorer color, directly causing a decline in the mechanical properties (tensile strength and elongation at break) of the prepared core material and window covering warp yarns.

[0046] First, Examples 1-7 utilize a specific ratio of bio-based and petroleum-based ethylene glycol, along with controlled esterification temperature and pressure, to ensure efficient esterification, generating oligomers with regular structures and controllable end groups. This lays the foundation for subsequent molecular chain growth and reduces reaction inhomogeneity caused by differences in raw material properties. Next, mild pre-condensation reaction conditions remove small-molecule byproducts. Then, a phosphorus-based stabilizer is added before the final high-temperature, high-vacuum polycondensation reaction. This stabilizer deactivates the catalyst, inhibits thermal degradation and side reactions at high temperatures, and allows the polymer to grow stably to the target viscosity over a long period, resulting in high-molecular-weight and structurally complete polyester chains. Through the synergistic effect of raw material selection, process sequence (esterification-pre-condensation-stabilizer addition-condensation), and strictly controlled reaction parameters (temperature, pressure, time), polymer chain defects are minimized, ensuring high molecular weight and molecular chain regularity. This enhances intermolecular forces and chain entanglement within the core material and the final warp yarn, significantly improving the tensile strength and elongation at break of the warp yarn used for window coverings.

[0047] Examples 8-11 The preparation method and parameters of Example 7 are as follows, with specific differences shown in Table 3; in Table 3, the screw speed is the screw speed when the premix is ​​placed in the twin-screw extruder in the specific preparation process of the sheath material; the cooling temperature is the temperature before the extruded strip is granulated; DMAA is N,N-dimethylacrylamide.

[0048] Comparative Example 8 Referring to the preparation method and parameters of Example 11, the difference is that in the specific preparation process of modified chitosan powder, the amount of N,N-dimethylacrylamide (DMAA) is changed to 10 parts.

[0049] Comparative Example 9 The preparation method and parameters of Example 11 are the same, except that nitrogen gas is not introduced for protection during the preparation of modified chitin powder, and the reaction is carried out directly in an air atmosphere.

[0050] Comparative Example 10 The preparation method and parameters of Example 11 are the same, except that the dropping rate of the initiator solution is 0.50 parts / min.

[0051] Comparative Example 11 The preparation method and parameters of Example 11 are the same, except that in the preparation of the sheath material, 3 parts of 30nm nano-silica powder without coupling agent treatment are used instead of modified silica powder.

[0052] Comparative Example 12 The preparation method and parameters of Example 11 are the same, except that in the preparation of the sheath material, the extruded strip is cooled to 60°C after passing through a water tank and then granulated.

[0053] Test Example 2: Mechanical and Antibacterial Properties Test Window covering warp yarns were cut into 20cm long samples and conditioned for 24 hours under constant temperature and humidity conditions (20℃, 65% relative humidity). An electronic fabric tear tester was used, and the test was conducted according to standard GB / T 3917.2-2009 "Textiles - Tear Properties of Fabrics - Part 2: Determination of Tear Strength of Trousers Samples"; the tear force value was recorded in N; each sample underwent 5 parallel tests, and the average value was taken as the final result. According to standard GB / T 20944.3-2008 "Evaluation of Antibacterial Properties of Textiles - Part 3: Shaking Method", Escherichia coli was used as the test strain to determine the antibacterial activity value of the warp yarn for window coverings; the samples were subjected to 50 wash resistance tests (according to FZ / T 73023-2006 "Knitted Finished Garments" standard); the formula for calculating the antibacterial performance retention rate is: The specific test results are shown in Table 4.

[0054] Table 3 Preparation parameters for Examples 8-11

[0055] Table 4 Mechanical and antibacterial properties tests of Examples 8-11 and Comparative Examples 8-12

[0056] As shown in Table 4, the tear strength of Examples 8-11 is greater than 8.0 N, and the antibacterial performance retention rate is higher than 92.5%, which are significantly better than those of Comparative Examples 8-12. This indicates that the sheath material prepared by modifying chitin powder and nano-silica in Examples 8-11 and melt-blending it with polylactic acid possesses excellent mechanical and antibacterial properties, resulting in good mechanical and antibacterial properties for the obtained window covering warp yarn. In the preparation process of the modified chitin powder in Comparative Example 8, the amount of antibacterial functional monomer (DMAA) grafted onto the chitin was reduced, resulting in a significant reduction in grafting points on the chitin molecules, and insufficient DMAA grafting density and length. The low grafting rate makes the hydrophilicity, solubility, and compatibility with other components of the modified chitin worse; resulting in poor dispersion in the polylactic acid (PLA) matrix, forming defect points, and reducing the total amount of antibacterial groups. The prepared sheath material exhibits an uneven internal structure, stress concentration, and a significant decrease in tear strength. Simultaneously, the number of exposed effective antibacterial groups is reduced, leading to a decrease in the retention rate of its antibacterial properties. In Comparative Example 9, the modified chitin powder was prepared without nitrogen protection, and the reaction was carried out directly in air. Oxygen is a strong inhibitor and growth retardant of free radical polymerization; it reacts with primary or growing chain free radicals generated by the initiator to produce peroxy free radicals, terminating chain growth and resulting in extremely low grafting efficiency and short grafted chains. This reduces the reaction efficiency of the modified chitin powder, creating structural defects. This leads to a significant decrease in the antibacterial properties and stability of the modified chitin, poor blending effect in the sheath material, fewer and more easily deactivated antibacterial groups, ultimately resulting in a significant reduction in both the tear strength and the retention rate of antibacterial properties of the sheath material.

[0057] In Comparative Example 10, the excessively rapid initiator droplet acceleration in the modified chitin powder preparation process led to an excessively high instantaneous free radical concentration in the reaction system. This not only caused a large amount of DMAA monomers to self-polymerize instead of grafting onto chitin, but also accelerated the chain termination reaction, resulting in short grafted chains and low grafting efficiency. Uneven grafting generated a large amount of homopolymers, reducing the effective grafting rate and causing a decrease in the antibacterial properties of the modified chitin powder. The modified chitin powder had a wider molecular weight distribution, shorter and unevenly distributed grafted chains, poor compatibility with PLA, and a reduction in antibacterial active sites. Ultimately, this led to a decrease in the tear strength of the sheath material, and a corresponding decrease in the retention rate of antibacterial properties. In Comparative Example 11, unmodified nano-silica had extremely poor compatibility with the polylactic acid (PLA) matrix; due to its high surface energy, unmodified silica easily agglomerated in hydrophobic PLA, forming large aggregates, making nanoscale dispersion impossible. These aggregates become stress concentration points, severely disrupting the continuity and uniformity of the sheath material, leading to a significant decrease in its tear strength. In Comparative Example 12, the excessively high cooling temperature indicates a slow cooling rate; the cooling rate affects the crystallization behavior of PLA and the final microstructure of the material. Too slow cooling or too high a temperature results in incomplete crystallization of the sheath grains, producing coarse grains. Poor crystal structure reduces the toughness and strength of the sheath grains, leading to a significant decrease in the tear strength of the prepared window covering warp yarns.

[0058] Regarding the enhancement of antibacterial properties, the synergistic effect of adding sufficient DMAA, reacting at an appropriate temperature under nitrogen protection, and adding the initiator at a suitable rate enables efficient and uniform grafting of DMAA onto chitin, generating highly active quaternary ammonium salt groups, thus preparing highly stable modified chitin. This modified chitin is then blended with modified silica and PLA, and an optimized extrusion process achieves good dispersion, ensuring sufficient exposure of antibacterial sites and washability, thus endowing the sheath material with excellent and durable antibacterial properties. In terms of tear strength improvement, nano-silica is treated with a coupling agent to obtain modified silica powder, enhancing the bonding force between the inorganic phase and the PLA matrix; the grafted modified chitin improves the internal compatibility of the sheath material due to the introduction of organic segments. The twin-screw extrusion process ensures uniform dispersion of the filler, avoiding stress concentration; combined with a lower cooling temperature, it forms fine and uniform PLA crystals, improving the toughness of the sheath particles. The synergistic effect of raw material optimization, dispersion process, and crystallization control effectively inhibits the generation and propagation of cracks in the warp yarns of window coverings, thereby improving their tear strength.

[0059] Examples 12-14 The preparation method and parameters of Example 11 are as follows, with specific differences shown in Table 5; the preparation parameters in Table 5 are all parameters in the specific preparation process of the sizing agent; DDBAC is the antistatic agent lauryl dimethyl benzyl ammonium chloride; 9EO is the nonionic surfactant isomeric tridecyl alcohol polyoxyethylene ether.

[0060] Comparative Example 13 The preparation method and parameters of Example 14 are the same, except that in the preparation process of the sizing agent, the waterborne polyurethane (WPU) emulsion is added to the stirred tank before the antistatic agent, nonionic surfactant and auxiliary film-forming agent are added.

[0061] Comparative Example 14 The preparation method and parameters of Example 14 are the same, except that when adjusting the pH value in the preparation process of the sizing agent, 25% acetic acid is used to adjust the pH value of the system to 5.0.

[0062] Comparative Example 15 The preparation method and parameters of Example 14 are the same, except that when adjusting the pH value in the preparation process of the sizing agent, 25% ammonia water is used to adjust the pH to 9.0.

[0063] Comparative Example 16 The preparation method and parameters of Example 14 are the same, except that 220 parts of waterborne polyurethane (WPU) emulsion are replaced with an equal amount of ordinary styrene-acrylic emulsion in the preparation process of the sizing agent.

[0064] Comparative Example 17 The preparation method and parameters of Example 14 are the same, except that 10 parts of amino silicone oil microemulsion (particle size <50nm) are not added in the preparation process of the sizing agent.

[0065] Comparative Example 18 The preparation method and parameters of Example 14 are the same, except that the temperature control during the entire preparation process of the sizing agent is increased to 60°C.

[0066] Test Example 3: Mechanical Properties and Abrasion Resistance Tests Five 200mm long samples were cut from the prepared warp yarns for window coverings. The warp yarn samples were fixed in the clamps of an elasticity meter, and the initial length L0 was recorded using a fiber elasticity meter (YG026D type). A predetermined tensile force was applied to the sample, held for a period of time, and then the force was released; L2 is the length after the predetermined tensile force was applied. The length L1 of the sample after recovery was recorded. The formula for calculating the elastic recovery rate is: ; The warp yarns for window coverings were wound around the friction head of the abrasion tester under a certain tension. The abrasion (Martindale method) was performed 1000 times at a friction pressure of 3 kPa, causing the warp yarns to rub against a standard friction cloth. Using a fabric abrasion tester (such as the YG513 model), the mass of the warp yarns was weighed before and after the test, accurate to 0.1 mg. The abrasion amount was expressed as the mass loss of the warp yarns (mg) or the number of abrasion cycles. Specific test results are shown in Table 5.

[0067] Table 5 Mechanical and abrasion resistance tests of Examples 12-14 and Comparative Examples 13-18

[0068] As shown in Table 5, the elastic recovery rate of Examples 12-14 was higher than 82.0%, and the wear amount was less than 90 mg. This indicates that the sizing agent prepared in Examples 12-14 can bond well with the heat-set composite fiber, thereby effectively improving the overall mechanical properties and abrasion resistance of the warp yarn for window coverings. In Comparative Example 13, the order of raw material feeding in the preparation process of the sizing agent was changed. WPU emulsion was added first, followed by surfactants and cationic starch, etc., which resulted in the WPU particles not being effectively stabilized and dispersed by the subsequently added surfactants, etc. This caused WPU particles to aggregate, reducing the uniformity and stability of the sizing agent. At the same time, cationic starch could not be uniformly adsorbed or acted on the surface of WPU particles and subsequent fiber surfaces, affecting its effect on assisting film formation and enhancing bonding. This improper process step sequence affected the synergistic effect between components, resulting in a decrease in the film quality of the sizing agent, a weakening of the bonding with the heat-set composite fiber, and ultimately a decrease in the elastic recovery rate and an increase in the wear amount of the warp yarn for window coverings. In Comparative Example 14, the pH value of the system was adjusted to 5.0 (acidic conditions). An acidic environment affects the stability of WPU emulsions. Although the cationicity of cationic starch is enhanced in acidic conditions, an excessively acidic environment can alter its molecular structure. More importantly, the amino groups in amino silicone oil microemulsions protonate to form ammonium salts under acidic conditions, altering their spreading, penetration, and interaction with fibers, thus reducing their softness and smoothness. Deviations in the system's pH value disrupt the optimal environment for the physicochemical properties of each component, worsening the synergistic effect and leading to poor film formation. Ultimately, this results in a decrease in the elastic recovery rate and abrasion resistance of the warp yarns used for window coverings. In Comparative Example 15, adjusting the system's pH to an alkaline environment caused hydrolysis of some polyurethane molecular chains in the waterborne polyurethane (WPU) emulsion, affecting its film integrity. Simultaneously, excessively high pH values ​​alter the charge properties of cationic starch, leading to structural damage and weakening its binding ability with composite fibers and other components. These factors collectively result in uneven film formation by the sizing agent and a decreased bonding force with the composite fibers; consequently, the fibers cannot be effectively protected, ultimately leading to a significant decrease in the elastic recovery rate and a substantial increase in abrasion of the warp yarns used for window coverings.

[0069] In Comparative Example 16, an equal amount of ordinary styrene-acrylic emulsion was replaced with waterborne polyurethane (WPU) emulsion in the sizing agent preparation process. Because the -NHCOO- groups in the WPU molecular chain can form strong interactions with cellulose hydroxyl / polyester groups through hydrogen bonds, the styrene-acrylic emulsion relies solely on the hydrophobic adsorption of the benzene ring side groups, resulting in a binding strength less than 1 / 3 that of WPU. Furthermore, the glass transition temperature of WPU is much lower than that of styrene-acrylic emulsion, and its low-temperature flexibility makes the coating less prone to cracking when the warp yarns used for window coverings are bent. In contrast, the sizing agent made from styrene-acrylic emulsion, after curing, forms a rigid film that is prone to micro-cracks at fiber bending points, thus accelerating wear. In this system, amino silicone oil microemulsion mainly acts as a softening, smoothing, and antistatic agent. The amino groups in its molecular chain can interact with certain groups on the surface of the composite fiber (such as carboxyl groups generated from ester hydrolysis) or with WPU, cationic starch, etc., while the silicone oil segments can reduce the surface friction coefficient of the fiber. In Comparative Example 17, without the addition of amino silicone oil microemulsion, the sizing agent film loses its necessary flexibility and low friction. This leads to increased friction between composite fibers and between composite fibers and processing parts, making the yarn prone to damage and fuzzing, thus reducing abrasion resistance; at the same time, the rigid film layer also restricts the elastic deformation and recovery of composite fibers, resulting in a decrease in elastic recovery rate.

[0070] In Comparative Example 18, the controlled temperature throughout the preparation process of the sizing agent was increased to 60°C. At 60°C, the DDBAC cationic quaternary ammonium salt clashed with the cloud point (approximately 55°C) of isomeric tridecyl alcohol polyoxyethylene ether (9EO), leading to dehydration and instability of the nonionic surfactant, forming micro-flocculent precipitates. Simultaneously, the cationic starch underwent excessive gelatinization at high temperatures (viscosity increased fourfold), hindering the uniform diffusion of WPU latex particles. Furthermore, the absolute value of the Zeta potential of the WPU emulsion decreased by 20% at 60°C, resulting in charge neutralization with the positively charged DDBAC / DMS composite system and triggering demulsification. In addition, the amino silicone oil microemulsion (particle size <50nm) increased in size to over 150nm at high temperatures, losing its nanoscale penetration ability and failing to fill the micropores on the fiber surface. This resulted in the loss of uniformity in the final sizing agent coating, a drop in elastic recovery rate to 78%, a wear exceeding 110mg, and easy accumulation of cotton-like lint during friction.

[0071] Examples 12-14 demonstrate the preparation of high-performance sizing agents by optimizing raw material selection, process parameters, and step sequence, significantly improving the elastic recovery rate and abrasion resistance of warp yarns used in window coverings. To improve the elastic recovery rate, a waterborne polyurethane (WPU) emulsion with flexibility and film-forming properties was selected as the film-forming agent; its soft and hard segment structure imparts elasticity to the film layer. An amino silicone oil microemulsion was added, utilizing the flexibility of the siloxane backbone and the intermolecular slippage of the organic amino side chains to reduce stress concentration within the heat-set composite fibers and the film layer. During the preparation of the sizing agent, a mild temperature and near-neutral pH value were controlled to ensure the stability of component activity. A specific feeding sequence was adopted to form a stable and uniform emulsion system, allowing WPU to uniformly coat the fiber surface. Cationic starch was used as an auxiliary film-forming agent to enhance the adhesion between the film layer and the fiber. In terms of reducing wear, the strong protective film formed by WPU can further resist friction, the low surface energy of amino silicone oil further reduces the coefficient of friction, cationic starch improves the cohesive strength and adhesion of the film layer, and antistatic agents reduce friction caused by electrostatic adsorption; a filter screen with a suitable mesh size removes impurities and avoids the starting point of wear; the synergistic cooperation of various process parameters ensures uniform dispersion of components, forming a dense protective film, which greatly improves the abrasion resistance and mechanical properties of the warp yarns used in window coverings.

[0072] Examples 15-17 The preparation method and parameters of Example 14 are similar, with specific differences shown in Table 6.

[0073] Comparative Example 19 The preparation method and parameters of Example 17 are the same, except that only polylactic acid (PLA) is used in the sheath material preparation process, and no modified chitin powder or modified silica powder is added.

[0074] Comparative Example 20 Referring to the preparation method and parameters of Example 17, the difference is that the oiling step of the cooled composite fiber is omitted in the preparation process of the warp yarn for window covering.

[0075] Comparative Example 21 The preparation method and parameters of Example 17 are the same, except that the temperature of the front section of the segmented roll stretching is reduced to 70°C and the temperature of the rear section of the roll stretching is reduced to 110°C.

[0076] Comparative Example 22 Referring to the preparation method and parameters of Example 17, the difference is that in the preparation process of the warp yarn for window decoration, after stretching, the sizing treatment is carried out directly, and the heat setting step at 180°C is omitted.

[0077] Comparative Example 23 Referring to the preparation method and parameters of Example 17, the difference is that in the preparation process of the warp yarn for window decoration, the ratio of core material to sheath material is adjusted to 95:5.

[0078] Test Example 4 Mechanical Property Test Cut the warp yarn of the window covering into 200mm long samples; fix both ends of the samples to the clamps of the tensile testing instrument, ensuring the samples remain straight, with an initial clamping length of 100mm; set the tensile speed to 100mm / min, start the instrument to perform a tensile test until the sample slips or breaks; use an electronic tensile testing instrument to perform the test, record the maximum tensile force value, and calculate the core-sheath interface bonding strength. Repeat the test 3 times and take the average value; specific test results are shown in Table 7 and... Figure 1 As shown.

[0079] Table 6 Preparation parameters for Examples 15-17

[0080] Table 7 Mechanical property tests of Examples 15-17 and Comparative Examples 19-23

[0081] As shown in Table 7 and Figure 1 The data shows that the core-sheath interface bonding strength of Examples 15-17 is greater than 38 MPa; this indicates that through the synergistic effect of the processes in Examples 15-17, the prepared window covering warp yarns possess good mechanical properties. Comparative Example 19 uses only polylactic acid (PLA) in its sheath preparation process, without adding modified chitosan powder or modified silica powder. Modified chitosan and modified silica, as functional fillers, not only impart antibacterial and mechanical properties to the sheath material but also play a role in adjusting the PLA melt viscosity and improving the compatibility with the core material interface. Without these modified powders, the differences in physicochemical properties (such as polarity, surface energy, and crystallization behavior) between the pure PLA sheath material and the core material increase, leading to weakened molecular chain entanglement, diffusion, or chemical bonding at the interface during composite spinning. This directly reduces the core-sheath interface bonding force formed during cooling and stretching, resulting in a significant decrease in the bonding strength of the window covering warp yarns. In Comparative Example 20, the oiling step for the cooled composite fibers is omitted in the preparation process of the window covering warp yarns. The oiling step (using polyether-modified silicone oil) is not only for smoothness in subsequent processing, but the choice and uniform application of the oil also affect the surface properties of the fiber and subsequent heat treatment processes. Polyoxyethylene ether-modified polydimethylsiloxane can form a thin film on the fiber surface, playing a certain role in lubrication and heat conduction buffering during drawing and heat setting, reducing interfacial stress concentration. Omitting oiling leads to increased surface friction and uneven stress during subsequent drawing, especially causing micro-damage or stress concentration at the core-sheath interface, which in turn affects the formation and maintenance of interfacial bonding strength, resulting in a decrease in the core-sheath interfacial bonding strength.

[0082] In Comparative Example 21, the temperature of the first section of the segmented roller drafting process was reduced to 70°C, and the temperature of the second section was reduced to 110°C. Drafting temperature is crucial for the orientation and crystallization of polymer chains. Too low a temperature results in insufficient molecular chain mobility in the sheath material, making orientation difficult and causing incoordination with the core material's deformation, easily leading to stress concentration and defects at the interface. Simultaneously, low temperatures hinder the relaxation of molecular chains at the interface and potential interdiffusion, severely weakening the bonding force between the core and sheath. In Comparative Example 22, after drafting, sizing was performed directly, omitting the 180°C heat setting step.

[0083] Heat treatment at 180℃ (higher than the Tg of PET and PLA, but lower than their melting points) allows oriented but not fully crystallized molecular chains to gain energy for rearrangement and crystallization during the drawing process, while simultaneously relaxing interfacial stress. Omitting heat setting leads to unstable internal structure and high internal stress in the composite fiber, especially at the PET / PLA interface where thermal shrinkage differs significantly, residual stress severely weakens the interfacial bonding strength. In Comparative Example 23, the core-to-sheath ratio was adjusted to 95:5 in the preparation process of warp yarns for window coverings. Drastically reducing the sheath ratio to 5% results in an excessively thin sheath layer, leading to uneven coating and even breakage during spinning and drawing, preventing the formation of a continuous and stable core-sheath structure. An excessively thin sheath layer also means a larger interfacial area relative to the core volume, making interfacial defects more significant; simultaneously, this ratio easily leads to uneven melt flow and heat distribution during spinning, further weakening the interfacial bonding and causing a sharp decline in the core-sheath interfacial bonding strength.

[0084] Examples 15-17 significantly improved the core-sheath interfacial bonding strength of warp yarns for window coverings by synergistically optimizing the process, raw material properties, and reaction parameters. During the composite fiber preparation process, appropriate proportions of core and sheath materials were added; and polar groups and surface-active nano-silica were introduced into the sheath material to enhance the interaction potential and interfacial wettability with the core material. In terms of the preparation process, the core-sheath composite spinning process is crucial. Melt co-extrusion at 295-310℃ ensures tight bonding between the core and sheath materials, while segmented cooling and stretching promote molecular chain orientation and crystallization, reducing interfacial defects. Oiling and heat setting improve fiber surface properties and dimensional stability. In the two-dip and two-padding process, the aqueous polyurethane emulsion and amino silicone oil microemulsion in the sizing agent react chemically with the functional groups on the surface of the core and sheath materials or form strong interactions, constructing chemical bridges that enhance bonding strength; the pre-drying and baking processes provide heat energy to promote interfacial crosslinking or bonding formation. Through chemical reactions and physical synergy, the parameters and material selections at each stage of the entire preparation process are interconnected, maximizing the bonding strength of the core-sheath interface of the warp yarn for window coverings.

[0085] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for preparing warp yarn for window decoration, characterized in that: The preparation process of the warp yarn is as follows: The core material and sheath material are placed in a spinning box and spun into composite fibers. The composite fibers are cooled and oiled in sections. After oiling, the composite fibers are stretched in sections at low roller temperature and then heat-set. They are impregnated in a sizing agent and subjected to two dips and two pads. After impregnation and padding, they are pre-dried, baked, and wound to obtain the warp yarn for window coverings. The core material is obtained by melt extrusion of a melt obtained by reacting terephthalic acid, ethylene glycol, esterification catalyst, and phosphorus stabilizer, followed by water cooling and pelletizing. The sheath material is obtained by melt blending, cooling, and pelletizing polylactic acid, modified chitin powder, and modified silica powder. The sizing agent is prepared by antistatic agent, nonionic surfactant, auxiliary film-forming agent, waterborne polyurethane emulsion, and amino silicone oil microemulsion.

2. The manufacturing process of a warp yarn for window decoration according to claim 1, characterized in that: The specific preparation process of the warp yarn for window coverings is as follows: the core material and the sheath material are placed in the spinning box at a spinneret temperature of 295-310℃, and composite fibers are obtained after spinning; the composite fibers are cooled in sections and then oiled, with the oiling rate controlled at 0.5-0.8%; the oiled composite fibers are stretched under the sectioned roller temperature conditions to obtain stretched composite fibers; after heat setting, they are impregnated in the sizing agent and subjected to two-dip and two-padding treatments; after padding, they are pre-dried and baked to obtain composite fibers; they are wound at a winding tension of 0.15-0.25 cN / dtex to obtain the warp yarn for window coverings; the ratio of the core material to the sheath material is 70-85:15-30.

3. The manufacturing process of a warp yarn for window decoration according to claim 2, characterized in that: The spinneret of the spinning box is trilobed with a diameter of 0.25 mm; the front roller temperature of the segmented roller is 90-110℃, and the rear roller temperature is 140-160℃; the initial roller speed of the drafting is 1000-1300 m / min, and the final roller speed is 4000-4500 m / min; the roller pressure of the two-dip and two-roll treatment is 0.2-0.3 MPa, and the immersion time for each dip is 15-20 s.

4. The manufacturing process of a warp yarn for window decoration according to claim 2, characterized in that: The specific preparation process of the sizing agent is as follows: 1-3 parts of antistatic agent, 3-5 parts of nonionic surfactant, and 8-10 parts of auxiliary film-forming agent cationic starch are added sequentially at 25-35℃ and 80-120 rpm; aqueous polyurethane emulsion is added at a rate of 5-10 parts / min; then the amino silicone oil microemulsion is added, and after stirring, the pH of the system is adjusted to 7.0-7.5 with ammonia; the sizing agent is obtained by filtering through a 150-300 mesh filter.

5. The manufacturing process of a warp yarn for window decoration according to claim 1, characterized in that: The specific preparation process of the core material is as follows: terephthalic acid, bio-based ethylene glycol, petroleum-based ethylene glycol, and esterification catalyst are mixed evenly in a slurry mixing tank to obtain a slurry; the slurry is reacted at 250-265℃ and 0.1-0.4MPa to obtain oligomers; the oligomers undergo a pre-condensation reaction to obtain a pre-condensation product; a phosphorus-based stabilizer is added, and the reaction is carried out at 280-290℃ and 0.16kPa for 2-5 hours to obtain 0.60-0.68 dL·g. -1 The melt is extruded at 275-285°C; cooled and pelletized to obtain core pellets; and then vacuum dried to obtain the core material.

6. The manufacturing process of a warp yarn for window decoration according to claim 5, characterized in that: The ratio of the bio-based ethylene glycol to the petroleum-based ethylene glycol is 12-15:30-34.

7. The manufacturing process of a warp yarn for window decoration according to claim 5, characterized in that: The phosphorus stabilizer is any one of phosphoric acid, triethyl phosphite, and triphenyl phosphite.

8. The manufacturing process of a warp yarn for window decoration according to claim 1, characterized in that: The specific preparation process of the sheath material is as follows: the polylactic acid, 8-15 parts of the modified chitin powder, and 1-3 parts of the modified silica powder are premixed to obtain a premix; the premix is ​​melt-extruded at 150-250 rpm; the extruded strip is cooled to 25-40℃ and granulated to obtain sheath particles; the sheath material is obtained after vacuum drying; the modified silica powder is obtained by ultrasonically dispersing 20-50nm nano-silica, reacting it with a pre-hydrolysis coupling agent, centrifuging, washing, and drying.

9. The manufacturing process of a warp yarn for window decoration according to claim 8, characterized in that: The specific preparation process of the modified chitin powder is as follows: 20-24 parts of N,N-dimethylacrylamide are dissolved in distilled water to obtain an acrylamide solution; 0.65-0.95 parts of potassium persulfate are dissolved in the distilled water to obtain an initiator solution; After purging with nitrogen for 30 minutes, dry chitin powder is added to the reactor, followed by distilled water to form a suspension. Acrylamide solution is added to the reactor at a nitrogen flow rate of 0.5-1.0 L / min. Initiator solution is added dropwise at a rate of 0.12-0.15 parts / min. After the addition is complete, the mixture is stirred for 15 minutes to obtain a mixed solution. The reactor is heated to 50-80°C to react, yielding a copolymer. The copolymer is cooled to room temperature and filtered to obtain solid product one. The product is washed, filtered, and dried to obtain the modified chitin powder.

10. A type of warp yarn for window decoration, characterized in that: The warp yarn for the window covering is prepared by the preparation process described in any one of claims 1-9.

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