Low-density 3d knitted mesh material based on modified yarns, process for the preparation thereof and mesh

Abstract

The application relates to the fields of textile materials and high polymer coating technology, and discloses a low-density 3D knitted mesh material based on modified yarn and a preparation process and a mesh of the low-density 3D knitted mesh material. The low-density 3D knitted mesh material comprises PET monofilament as spacer yarn and a coating composition coated on the surface of the PET monofilament. The coating composition comprises polycaprolactone, sebacic acid, active zinc oxide, polyvinyl alcohol, an aqueous thermoplastic copolyester dispersion and glycerol triglycidyl ether. The preparation process melts polycaprolactone to embed sebacic acid and active zinc oxide, cools, crushes and sand grinds to obtain a microparticle dispersion liquid; the copolyester dispersion and glycerol triglycidyl ether are mixed to prepare a slurry; the PET monofilament is sized and heat treated, then woven into a fabric, and then subjected to segmented heat setting. The application improves the normal-temperature stability of the slurry and the weaving adaptability of the monofilament, and improves the anti-top-breaking performance and compression durability of the low-density mesh.

Description

Technical Field

[0001] This invention relates to the field of textile materials and polymer coating technology, specifically to low-density 3D knitted mesh fabric based on modified yarns, its preparation process, and the mesh fabric. Background Technology

[0002] 3D knitted mesh fabrics are typically formed by interlacing upper and lower layers with interlacing spacer yarns connecting the two layers. They offer breathability, elastic cushioning, and some thickness-direction support, and can be used in mattresses, car seats, medical protective gear, and other fields. With the increasing demand for lightweighting, reducing the weave density of 3D knitted mesh fabrics has become a direction in product design.

[0003] However, with reduced weaving density, the number of support points for the interlayer spacer yarns decreases, which can easily lead to a decline in the compressive strength, compression recovery, and dimensional retention under long-term loads of the mesh. In particular, when using finer PET monofilaments as spacer yarns, although it is beneficial to reduce the surface density of the mesh, it also reduces the support stability of the monofilament interlacing areas, thereby affecting the load-bearing durability of low-density 3D knitted mesh.

[0004] To address these issues, existing technologies typically employ resin finishing, coating treatments, or hot-melt bonding to reinforce yarns or fabrics. Traditional reinforcement systems, such as solvent-based polyurethanes, reactive polyurethanes, or coating materials containing isocyanates, suffer from problems like volatile organic compound emissions and stringent operational safety requirements during coating and high-temperature processing. If ordinary water-based coating systems are used as alternatives, they are easily limited by factors such as insufficient wetting and adhesion to the PET fiber surface, and the difficulty in simultaneously achieving the desired sizing stability and thermosetting reactivity. This results in coatings that, at lower adhesion levels, struggle to simultaneously meet the requirements for weaving adaptability, interlayer bond strength, and long-term compression recovery.

[0005] Therefore, this invention proposes a low-density 3D knitted mesh material based on modified yarn, its preparation process, and the mesh itself, to address the shortcomings of existing technologies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a low-density 3D knitted mesh material based on modified yarn, its preparation process, and the mesh itself. This solves the problems of insufficient interlayer bonding strength, compressive support, and compression durability of low-density 3D knitted mesh after reducing its surface density, as well as the difficulty in simultaneously achieving storage stability and thermosetting reactivity of conventional water-based coating slurries.

[0007] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a low-density 3D knitted mesh fabric material based on modified yarn, employing the following technical solution: A low-density 3D knitted mesh material based on modified yarn includes PET monofilaments as spacer yarns and a coating composition coating the surface of the PET monofilaments; the coating composition is made from raw materials comprising the following parts by weight: Polycaprolactone: 21-34 parts; Sebacic acid: 12-16 parts; Active zinc oxide: 0.3–0.8 parts; Polyvinyl alcohol: 0.3–0.6 parts; Waterborne thermoplastic copolyester dispersion: 87.5–94.3 parts; Glyceryl triglycidyl ether: 24-30 parts; The solid content of the aqueous thermoplastic copolyester dispersion is 30wt% to 40wt%, and the weight parts of the aqueous thermoplastic copolyester dispersion are based on the total mass of the dispersion.

[0008] By employing the above technical solution, the waterborne thermoplastic copolyester dispersion can form a continuous coating on the surface of PET monofilaments. Glyceryl triglycidyl ether provides reactive epoxy groups, while polycaprolactone, sebacic acid, and active zinc oxide together constitute the thermoresponsive reaction component. When used in combination, these components improve the adhesion, curing degree, and durability of the coating on the PET monofilament surface, thereby enhancing the interlayer bonding strength, burst resistance, and compression recovery properties of low-density 3D knitted mesh fabrics.

[0009] During heat treatment, the aqueous thermoplastic copolyester dispersion, after film formation, exhibits good compatibility and wetting adhesion with the PET monofilament surface, forming a basic coating structure. As the subsequent heating temperature increases, the epoxy groups in the glycerol triglycidyl ether can undergo ring-opening reactions with the carboxyl and hydroxyl groups in the system, forming a cured structure containing ether or ester bonds. The corresponding reaction can be represented as: R-COOH+R'-CH(O)CH2→R-COO-CH2-CH(OH)-R'; R-OH+R'-CH(O)CH2→RO-CH2-CH(OH)-R'.

[0010] When the system temperature reaches the corresponding thermal transition temperature range of polycaprolactone and sebacic acid, polycaprolactone softens or melts, increasing the contact between sebacic acid and glycerol triglycidyl ether. The terminal carboxyl group of sebacic acid further participates in the epoxy ring-opening reaction. Simultaneously, active zinc oxide can form zinc carboxylates or related coordination structures with sebacic acid and the carboxyl components in the system. The resulting covalent cross-linked structure and coordination structure jointly improve the coating's solvent extraction resistance, washability, and mechanical stability, allowing PET monofilaments to maintain good weaving adaptability and mesh support performance even with low coating adhesion.

[0011] Preferably, the polycaprolactone is a mixture of polycaprolactone with a number average molecular weight of 1800-2200 and polycaprolactone with a number average molecular weight of 3800-4200.

[0012] By employing the above technical solution, the combined use of two polycaprolactones with different molecular weights can balance the thermal response fluidity of the coating and the stability of the film after cooling. Polycaprolactones with a number-average molecular weight of 1800–2200 exhibit better fluidity upon heating, which is beneficial for the dispersion and release of sebacic acid and active zinc oxide in the coating system. Polycaprolactones with a number-average molecular weight of 3800–4200 are beneficial for improving the cohesive strength and anti-dust properties of the film after cooling, thereby improving the unwinding stability and weaving permeability of the modified PET monofilament.

[0013] Preferably, the parameters of the raw material meet the following limitations: The BET specific surface area of ​​the active zinc oxide is 30 m². 2 / g~50m 2 / g; The epoxy equivalent of the glycerol triglycidyl ether is 140 g / eq to 160 g / eq; The aqueous thermoplastic copolyester dispersion is prepared by polymerization reaction of terephthalic acid, isophthalic acid, adipic acid, monosodium 5-sulfoisophthalate, 1,4-butanediol and ethylene glycol, and the solid content of the aqueous thermoplastic copolyester dispersion is 30wt% to 40wt%.

[0014] By adopting the above technical solution, the BET specific surface area of ​​active zinc oxide is controlled at 30m². 2 / g~50m 2 The / g content facilitates contact with carboxyl components during heat treatment, enabling catalytic or coordination effects, while reducing the risk of increased slurry viscosity due to excessively high powder surface activity. Controlling the epoxy equivalent of glycerol triglycidyl ether at 140g / eq to 160g / eq helps obtain a suitable epoxy content, allowing the coating to form a cured structure with a certain degree of cross-linking after heat treatment. Introducing 5-sulfoisophthalic acid monosodium salt monomer into the waterborne thermoplastic copolyester dispersion improves the dispersion stability of the copolyester in the aqueous phase; controlling its solid content at 30wt% to 40wt% helps balance operational stability during storage, solution preparation, and continuous sizing.

[0015] Preferably, the coating composition contains composite particles in the coating slurry before sizing. The composite particles are composed of a solid continuous phase formed by blending polycaprolactone and sebacic acid and active zinc oxide dispersed in the solid continuous phase. The particle size D90 of the composite particles is 2μm to 5μm.

[0016] By adopting the above technical solution, polycaprolactone, as the hydrophobic waxy continuous phase, physically encapsulates sebacic acid and active zinc oxide, which helps reduce the direct contact between sebacic acid, active zinc oxide, and glyceryl triglycidyl ether in the aqueous phase at room temperature, thereby improving the room temperature stability of the working sizing agent. Controlling the particle size D90 of the composite particles within 2μm to 5μm facilitates their stable dispersion in the aqueous sizing agent and reduces particle exposure and weaving dust during sizing.

[0017] Secondly, the present invention provides a preparation process for a low-density 3D knitted mesh material based on modified yarn, using the following technical solution: A process for preparing a low-density 3D knitted mesh material based on modified yarn includes the following steps: S1. The polycaprolactone is heated and melted, and then sebacic acid and active zinc oxide are added, mixed evenly, cooled into a solid state, and pulverized to obtain composite coarse particles. S2. Dissolve the polyvinyl alcohol in deionized water, add the composite coarse particles obtained in step S1, and perform a circulating sand milling to obtain a composite particle dispersion. S3. Add the aqueous thermoplastic copolyester dispersion to the composite particle dispersion obtained in step S2, add ammonia to adjust the pH value, and add deionized water to make up the volume to obtain component A. S4. Add the glycerol triglycidyl ether to component A obtained in step S3, and mix with deionized water to obtain a coating slurry. S5. The PET monofilament is sized by passing it through the coating slurry obtained in step S4, and then passed through the hot air channel and the cold air channel in sequence to obtain the modified yarn. S6. The modified yarn obtained in step S5 is used as the spacer yarn to weave a 3D spacer fabric, and the 3D spacer fabric is continuously fed into a tenter frame for setting.

[0018] By adopting the above technical solution, polycaprolactone, sebacic acid, and active zinc oxide are first made into composite particles, which are then dispersed in an aqueous phase containing polyvinyl alcohol. Glyceryl triglycidyl ether is added before sizing, thus forming a process route where component A and the crosslinking agent are mixed immediately before use. This process can reduce the direct contact of active components during storage and improve the room temperature stability of the working sizing agent. After sizing, a hot air channel is used to remove moisture and form a preliminary coating, while a cold air channel is used to reduce the surface stickiness of the coating and improve the unwinding stability of the yarn. The woven 3D spaced fabric is then subjected to segmented heat setting, causing the heat-responsive components in the coating to undergo softening, melting, and curing reactions sequentially, thereby improving the interlayer bonding strength and durability of the mesh fabric.

[0019] Preferably, in step S1, the polycaprolactone is heated to 70°C to 75°C, the sebacic acid and the active zinc oxide are added and stirred for 15 min to 25 min, cooled to solid and pulverized to obtain composite coarse particles with a particle size D90 of 300 μm to 500 μm. In step S2, the temperature of the circulating sand mill is 13℃~25℃, and the particle size D90 of the composite particles obtained after the circulating sand mill is 2μm~5μm.

[0020] By adopting the above technical solution, a heating temperature of 70℃~75℃ can soften or melt polycaprolactone into a stirable waxy liquid, allowing sebacic acid and active zinc oxide to disperse in the polycaprolactone wax phase. First, pulverizing the cooled material to a D90 of 300μm~500μm helps reduce the load on subsequent sand milling. Controlling the circulating sand milling temperature at 13℃~25℃ helps reduce the risk of polycaprolactone softening and agglomerating due to frictional heating during sand milling; sand milling to a D90 of 2μm~5μm further improves the dispersion stability of the composite particles in the sizing system.

[0021] Preferably, in step S3, ammonia is added to adjust the pH value to 7.0–7.4; The material temperature when obtaining the coating slurry in step S4 is 15℃~30℃, and the effective non-volatile matter mass fraction of the coating slurry is 12wt%~18wt%.

[0022] By adopting the above technical solutions, controlling the pH value to 7.0–7.4 is beneficial for maintaining the stability of the aqueous thermoplastic copolyester dispersion and the composite particle dispersion. Controlling the material temperature at 15℃–30℃ when adding glycerol triglycidyl ether helps reduce the premature reaction of epoxy groups in the aqueous phase. Controlling the effective non-volatile content of the coating slurry to 12wt%–18wt% is beneficial for obtaining a viscosity and effective coating amount suitable for continuous sizing of PET monofilaments.

[0023] Preferably, in step S5, the wet strip liquid rate of the PET monofilament sizing is controlled to be 3.0 wt% to 6.0 wt%. The temperature of the hot air channel is 75℃~85℃, and the residence time of the PET monofilament in the hot air channel is 10s~40s; The temperature of the cold air channel is 20℃~35℃, and the residence time of the PET monofilament in the cold air channel is 10s~30s.

[0024] By adopting the above technical solution, the wet liquid ratio is controlled at 3.0wt% to 6.0wt%, which is beneficial for controlling the dry weight gain and coating continuity of the PET monofilament surface. The hot air channel at 75℃ to 85℃ allows the moisture in the sizing agent to evaporate and promotes the spreading of coating components on the PET monofilament surface; this temperature range is lower than the melting temperature of sebacic acid, reducing the degree to which sebacic acid participates in the reaction during the sizing and drying stage. The cold air channel at 20℃ to 35℃ allows the polycaprolactone phase to re-solidify, reducing the surface adhesion tendency of the sized monofilaments and improving the stability of subsequent unwinding and weaving processes.

[0025] Preferably, in step S6, the shaping process includes sequentially passing through three heating zones at different temperatures: The temperature of the first heating zone is 105℃~125℃, and the residence time of the 3D spaced fabric in the first heating zone is 20s~40s; The temperature of the second heating zone is 135℃~155℃, and the residence time of the 3D spaced fabric in the second heating zone is 30s~90s; The temperature of the third heating zone is 175℃~190℃, and the residence time of the 3D spaced fabric in the third heating zone is 90s~150s.

[0026] By employing the above technical solution, the first heating zone is used to keep the polycaprolactone phase in the coating in a softened or molten state, providing conditions for subsequent component contact; the second heating zone is used to melt sebacic acid and promote the contact between sebacic acid and active zinc oxide; the third heating zone is used to promote the ring-opening reaction of glycerol triglycidyl ether with carboxyl and hydroxyl groups in the system, and to complete the heat setting treatment of the 3D spacer fabric. Through the above segmented heating treatment, the controllability of the coating curing process can be improved, and the interlayer bonding strength, burst resistance, and dimensional retention performance after cyclic compression of the finished mesh fabric can be enhanced.

[0027] Thirdly, the present invention provides a low-density 3D knitted mesh fabric based on modified yarn, using the following technical solution: A low-density 3D knitted mesh fabric based on modified yarn is prepared by the above-mentioned preparation process of low-density 3D knitted mesh fabric material based on modified yarn.

[0028] This invention provides a low-density 3D knitted mesh material based on modified yarn, its preparation process, and the mesh fabric. It has the following beneficial effects: 1. This invention employs an aqueous thermoplastic copolyester dispersion, glycerol triglycidyl ether, sebacic acid, and active zinc oxide to form a reactive coating system. During heat setting, the epoxy groups in the glycerol triglycidyl ether can undergo ring-opening reactions with the carboxyl and hydroxyl groups in the system, while the active zinc oxide can form zinc carboxylates or related coordination structures with the carboxyl components. These covalent crosslinking and coordination effects jointly improve the curing degree and durability of the coating, which is beneficial for enhancing the bonding stability between PET spacer filaments, resulting in better interlayer bonding strength, burst resistance, and compression recovery properties in low-density 3D knitted mesh fabric.

[0029] 2. This invention utilizes polycaprolactone to melt-embed sebacic acid and active zinc oxide, followed by low-temperature sand milling to form micron-sized composite particles. During the room-temperature solution preparation and sizing stages, the polycaprolactone wax phase reduces the direct contact between sebacic acid, active zinc oxide, and glyceryl triglycidyl ether in the aqueous phase, thereby improving the storage stability of the working slurry. In the subsequent heat-setting stage, the polycaprolactone softens or melts, allowing the embedded components to gradually participate in the reaction. This method achieves process coordination between slurry storage stability and the heat-setting curing reaction.

[0030] 3. This invention uses an aqueous thermoplastic copolyester dispersion containing sulfonate hydrophilic monomers as the film-forming component, without using solvent-based resin systems, free amine curing agents, or free isocyanate curing agents. This helps reduce volatile organic compound emissions and operational safety during the preparation process. Simultaneously, combined with low-liquidity sizing, hot air drying, cold air recrystallization, and segmented heat setting processes, a low-adhesion continuous modified coating can be formed on the PET monofilament surface, reducing the risk of localized resin buildup and mesh blockage, and improving the unwinding stability and weaving permeability of the modified monofilament. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0032] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available industrial products, chemically pure, analytically pure or higher grade products.

[0033] Polycaprolactone (low molecular weight grade), CAS number 24980-41-4, is a hydroxyl-terminated poly-ε-caprolactone, a linear homopolymer obtained by ring-opening polymerization of lactone, with a number average molecular weight between 1800 and 2200. It is a waxy solid at room temperature, and its melting or softening temperature is between 45°C and 62°C.

[0034] Polycaprolactone (PCV) of medium molecular weight, CAS number 24980-41-4, is a hydroxyl-terminated poly-ε-caprolactone. It is a linear homopolymer obtained by ring-opening polymerization of lactone, with a number average molecular weight between 3800 and 4200. It is a waxy solid at room temperature, and its melting or softening temperature is between 55°C and 62°C.

[0035] Glyceryl triglycidyl ether, CAS No. 13236-02-7, is an aliphatic multifunctional epoxy crosslinking agent containing three reactive epoxy groups, with an epoxy equivalent between 140 g / eq and 160 g / eq, and a dynamic viscosity between 100 mPa·s and 200 mPa·s at 25°C.

[0036] Active zinc oxide, CAS number 1314-13-2, purity ≥99.0%, BET specific surface area between 30m² 2 / g to 50m 2 Between / g.

[0037] Polyvinyl alcohol, CAS number 9002-89-5, is a linear water-soluble polymer obtained by alcoholysis of polyvinyl acetate, with a degree of alcoholysis between 87.0% and 89.0% and a degree of polymerization between 1700 and 1800.

[0038] Sebacic acid, CAS number 111-20-6, purity ≥99.0%, is a white crystalline powder at room temperature with a melting point between 131℃ and 136℃.

[0039] Sodium 5-sulfoisophthalate, CAS No. 6362-79-4, purity ≥98.0%.

[0040] PET fine denier monofilament is a commercially available polyester monofilament with a diameter of 0.12mm, used as the spacer yarn in 3D spacer mesh fabric.

[0041] All raw materials used in this invention are commercially available industrial raw materials, and no free amine curing agents, free isocyanate curing agents, or organic solvent-based resin systems are used. During the preparation and use process, by controlling dust, maintaining ventilation, and adopting conventional personal protective measures, the operation can be carried out in accordance with the conventional safety requirements of textile sizing and heat setting processes.

[0042] Preparation Example 1: This preparation example provides a method for preparing an aqueous thermoplastic copolyester dispersion, including the following steps: (1) In a reactor equipped with a fractionating column and a mechanical stirrer, add 664.5g of terephthalic acid, 332.3g of isophthalic acid, 511.5g of adipic acid and 134.1g of 5-sulfoisophthalic acid monosodium salt. The total amount of 1,4-butanediol is 585.8g, of which 575.8g is added to the reactor and 10.0g is reserved for preparing the catalyst dilution solution. At the same time, add 403.4g of ethylene glycol to the reactor.

[0043] (2) After purging the air in the reactor three times with nitrogen, the reactor is heated to 220°C at a heating rate of 3°C / min under nitrogen protection and held at this temperature for esterification. The stirring speed is maintained at 150 rpm, and the distilled water is continuously collected. When the amount of water produced by the system reaches 85% of the theoretical amount, 1.05 g of tetrabutyl titanate is pre-dissolved in 10.0 g of reserved 1,4-butanediol to form a diluent, which is then added dropwise to the reactor. The reaction continues until the amount of water produced reaches 96% of the theoretical amount, at which point the esterification reaction is terminated. The theoretical amount of water produced is calculated based on the complete esterification of the carboxyl groups in the diacid to produce water.

[0044] (3) Subsequently, the pressure inside the reactor was gradually evacuated to an absolute pressure of 80 Pa within 40 minutes, while the system temperature was raised to 260 °C to carry out the polycondensation reaction. The reaction was carried out under constant temperature and pressure for 120 minutes. Samples were taken according to GB / T 14190 standard. The intrinsic viscosity of the system was measured at 25 °C using a mixed solvent of phenol / 1,1,2,2-tetrachloroethane with a mass ratio of 60 / 40. After the intrinsic viscosity reached 0.52 dL / g, the vacuum was released.

[0045] (4) Cool the melt in the reactor to 160°C and inject it into 3800g of deionized water preheated to 85°C in a thin stream. Disperse the mixture using a high-shear disperser at 2500rpm for 45 minutes, maintaining the system temperature between 80°C and 90°C. After dispersion, allow it to cool naturally to room temperature and filter it through a 200-mesh filter to obtain an aqueous thermoplastic copolyester dispersion with a solid content of 35wt%.

[0046] Preparation Example 2: This preparation example provides a method for preparing an aqueous thermoplastic copolyester dispersion, including the following steps: (1) In a reactor equipped with a fractionating column and a mechanical stirrer, add 747.6g of terephthalic acid, 282.4g of isophthalic acid, 511.5g of adipic acid and 80.5g of 5-sulfoisophthalic acid monosodium salt. The total amount of 1,4-butanediol is 721.0g, of which 711.0g is added to the reactor and 10.0g is reserved for preparing the catalyst dilution solution. At the same time, add 248.3g of ethylene glycol to the reactor.

[0047] (2) After purging the air in the reactor three times with nitrogen, the reactor is heated to 200°C at a heating rate of 2°C / min under nitrogen protection and held at this temperature for esterification reaction. The stirring speed is maintained at 150 rpm, and the distilled water is continuously collected. When the amount of water produced by the system reaches 85% of the theoretical amount, 0.78 g of tetrabutyl titanate is dissolved in the reserved 10.0 g of 1,4-butanediol and added to the reactor. The reaction continues until the amount of water produced reaches 95% of the theoretical amount, at which point the esterification reaction is terminated. The theoretical amount of water produced is calculated based on the complete esterification of the carboxyl groups in the diacid to produce water.

[0048] (3) Subsequently, the pressure inside the reactor was gradually evacuated to an absolute pressure of 50 Pa within 30 minutes, while the system temperature was raised to 250 °C to carry out the polycondensation reaction. The reaction was carried out under constant temperature and pressure for 150 minutes. Samples were taken according to GB / T 14190 standard. The intrinsic viscosity of the system was measured at 25 °C using a mixed solvent of phenol / 1,1,2,2-tetrachloroethane with a mass ratio of 60 / 40. After the intrinsic viscosity reached 0.45 dL / g, the vacuum was released.

[0049] (4) Cool the melt in the reactor to 150°C and inject it into 4800g of deionized water preheated to 80°C in a thin stream. Disperse the mixture using a high-shear disperser at 2000rpm for 60 minutes, maintaining the system temperature between 80°C and 90°C. After dispersion, allow it to cool naturally to room temperature and filter it through a 200-mesh filter to obtain an aqueous thermoplastic copolyester dispersion with a solid content of 30wt%.

[0050] Preparation Example 3: This preparation example provides a method for preparing an aqueous thermoplastic copolyester dispersion, including the following steps: (1) In a reactor equipped with a fractionating column and a mechanical stirrer, add 614.7g of terephthalic acid, 332.3g of isophthalic acid, 511.5g of adipic acid and 214.5g of 5-sulfoisophthalic acid monosodium salt, and add 540.7g of 1,4-butanediol to the reactor; the total amount of ethylene glycol is 558.6g, of which 548.6g is added to the reactor and 10.0g is reserved for preparing the catalyst dilution solution.

[0051] (2) After purging the air in the reactor three times with nitrogen, the reactor is heated to 240°C at a heating rate of 4°C / min under nitrogen protection and held at this temperature for esterification. The stirring speed is maintained at 150 rpm, and the distilled water is continuously collected. When the amount of water produced by the system reaches 85% of the theoretical amount, 1.39 g of tetrabutyl titanate is dissolved in the reserved 10.0 g of ethylene glycol and added to the reactor. The reaction continues until the amount of water produced reaches 98% of the theoretical amount, at which point the esterification reaction is terminated. The theoretical amount of water produced is calculated based on the complete esterification of the carboxyl groups in the diacid to produce water.

[0052] (3) Subsequently, the pressure inside the reactor was gradually evacuated to an absolute pressure of 95 Pa within 60 minutes, while the system temperature was raised to 270 °C to carry out the polycondensation reaction. The reaction was carried out under constant temperature and pressure for 90 minutes. Samples were taken according to GB / T 14190 standard. The intrinsic viscosity of the system was measured at 25 °C using a mixed solvent of phenol / 1,1,2,2-tetrachloroethane with a mass ratio of 60 / 40. After the intrinsic viscosity reached 0.60 dL / g, the vacuum was released.

[0053] (4) Cool the melt in the reactor to 170°C and inject it into 3100g of deionized water preheated to 90°C in a thin stream. Disperse the mixture using a high-shear disperser at 3000rpm for 30 minutes, maintaining the system temperature between 80°C and 95°C. After dispersion, allow it to cool naturally to room temperature and filter it through a 200-mesh filter to obtain an aqueous thermoplastic copolyester dispersion with a solid content of 40wt%.

[0054] Example 1: This embodiment provides a process for preparing a low-density 3D knitted mesh material based on modified yarn, including the following steps: (1) 1.85 kg of polycaprolactone with a number average molecular weight between 1800 and 2200 and 0.90 kg of polycaprolactone with a number average molecular weight between 3800 and 4200 were added to a stirred reactor with a heating jacket. The jacket heating was controlled to raise the temperature of the material in the reactor to 72°C at a heating rate of 2°C / min. The temperature was maintained until the polymer softened and formed a stirable waxy liquid. At a stirring speed of 150 rpm, 1.40 kg of sebacic acid and 0.05 kg of active zinc oxide were added to the reactor and the mixture was stirred continuously for 20 minutes.

[0055] (2) The suspended melt in the reactor is released into a water-cooled tray and allowed to cool naturally at room temperature for 2 hours until the material temperature reaches 25°C and forms a solid plate. The solid plate is then crushed into particles with a diameter between 1 mm and 3 mm using a crusher. These particles are then fed into a toothed disc pulverizer with an inlet air temperature controlled at 10°C for further pulverization. The particles with a diameter D are collected. 90 The composite particles are 400 μm in size.

[0056] (3) Add 0.04 kg of polyvinyl alcohol to 10.0 kg of deionized water, heat to 85 °C at a heating rate of 3 °C / min and stir at 200 rpm until completely dissolved, then cool to 12 °C using jacketed circulating cooling water at a cooling rate of 2 °C / min. Add the collected composite particles to the polyvinyl alcohol aqueous solution and stir at 300 rpm for 25 minutes to form a coarse suspension. Pump the coarse suspension into a horizontal jacketed sand mill filled with 0.8 mm zirconia beads for circulating grinding. Control the material temperature in the grinding chamber to 20 °C ± 2 °C by adjusting the flow rate of the jacketed cooling water until the particles are D 90 Discharge material when the particle size is 3μm.

[0057] (4) Under stirring at 150 rpm, 8.86 kg of the aqueous thermoplastic copolyester dispersion obtained in Preparation Example 1 was added to the discharge liquid. Ammonia water with a mass fraction of 10% was continuously added at a flow rate of 50 mL / min to adjust the pH value of the material to 7.2. Finally, deionized water was added to make up the volume so that the effective non-volatile matter mass fraction of the system was 28 wt%, and component A was obtained.

[0058] (5) Pump component A into the working slurry tank, add 2.70 kg of industrial grade glycerol triglycidyl ether at a material temperature of 25°C, add deionized water and stir at 400 rpm for 12 minutes to prepare a working slurry with an effective non-volatile content of 15 wt%.

[0059] (6) The PET fine denier monofilaments were immersed in a fatty alcohol polyoxyethylene ether aqueous solution at a temperature of 55°C and a concentration of 0.3 g / L for water washing and degreasing, followed by rinsing with deionized water and hot air drying. The dried PET fine denier monofilaments were continuously passed through a coating tank containing the above working slurry, and the roller pressure was adjusted so that the wet liquid content of the monofilaments was 4.5 wt%. After exiting the tank, the monofilaments passed through a hot air channel at a temperature of 80°C for 25 seconds, and then immediately entered a cold air channel at a temperature of 25°C for 20 seconds. The dry weight gain of the monofilaments was measured to be 0.68 wt%.

[0060] (7) The monofilament is threaded into a double needle bed warp knitting machine as a spacer yarn to weave a 3D spacer fabric. The fabric is continuously fed into a multi-temperature zone tenter frame and passed through three heating zones in sequence: the temperature of the first zone is set at 115°C and the dwell time is 30 seconds; the temperature of the second zone is set at 145°C and the dwell time is 60 seconds; the temperature of the third zone is set at 185°C and the dwell time is 120 seconds. The finished product is then obtained by winding.

[0061] Example 2: This embodiment provides a process for preparing a low-density 3D knitted mesh material based on modified yarn, including the following steps: (1) Add 1.50 kg of polycaprolactone with a number average molecular weight between 1800 and 2200 and 0.60 kg of polycaprolactone with a number average molecular weight between 3800 and 4200 to a stirred reactor with a heating jacket. Heat the reactor to 70°C at a heating rate of 2°C / min and keep it at that temperature until the polymer softens and forms a stirable waxy liquid. Add 1.20 kg of sebacic acid and 0.03 kg of active zinc oxide at a speed of 100 rpm and stir for 15 minutes.

[0062] (2) The suspended melt is released into a water-cooled tray and allowed to cool naturally to 20°C at room temperature to form a solid plate. After being crushed into particles of 1mm to 3mm, it is further crushed in a toothed disc pulverizer with the inlet air temperature controlled at 8°C, and the particles with a diameter D are collected. 90The composite particles are 300 μm in size.

[0063] (3) Add 0.03 kg of polyvinyl alcohol to 10.0 kg of deionized water, heat to 85 °C at 3 °C / min and stir until dissolved, then cool to 10 °C using circulating water at a rate of 2 °C / min. Add the composite particles to the aqueous solution and stir at 200 rpm for 20 minutes. Pump the mixture into a horizontal jacketed sand mill filled with 0.8 mm zirconia beads for circulating grinding, controlling the material temperature in the grinding chamber to be 15 °C ± 2 °C, and grind until the particles are D 90 The material is discharged when the particle size is 2μm.

[0064] (4) While stirring at 100 rpm, add 9.33 kg of the aqueous thermoplastic copolyester dispersion obtained in Preparation Example 2 to the discharge liquid, add 10% ammonia water at a flow rate of 50 mL / min to adjust the pH value to 7.0, add deionized water to make up to 20 wt% effective non-volatile matter, and obtain component A.

[0065] (5) Transfer component A to the slurry tank, add 2.40 kg of industrial grade glycerol triglycidyl ether when the material temperature is 15℃, add deionized water and stir at 300 rpm for 10 minutes to prepare a working slurry with an effective non-volatile matter mass fraction of 12 wt%.

[0066] (6) The PET fine denier monofilaments were immersed in a 50°C, 0.2 g / L fatty alcohol polyoxyethylene ether aqueous solution for degreasing, rinsed with deionized water, and then dried. The dried PET fine denier monofilaments were passed through a working slurry tank, and the rollers were adjusted to achieve a wet liquid ratio of 3.0 wt%. The monofilaments were passed through a 75°C hot air channel for 10 seconds, and then through a 20°C cold air channel for 10 seconds. The dry weight gain was measured to be 0.36 wt%.

[0067] (7) The monofilaments are woven into 3D spaced fabric. The fabric is fed into a tenter frame: the temperature of the first zone is 105℃, and the holding time is 20 seconds; the temperature of the second zone is 135℃, and the holding time is 30 seconds; the temperature of the third zone is 175℃, and the holding time is 90 seconds. The finished product is then obtained by winding.

[0068] Example 3: This embodiment provides a process for preparing a low-density 3D knitted mesh material based on modified yarn, including the following steps: (1) Add 2.20 kg of polycaprolactone with a number average molecular weight between 1800 and 2200 and 1.20 kg of polycaprolactone with a number average molecular weight between 3800 and 4200 to a stirred reactor with a heating jacket. Heat the reactor to 75°C at a heating rate of 3°C / min and keep it at this temperature until the polymer forms a stirable waxy liquid. Add 1.60 kg of sebacic acid and 0.08 kg of active zinc oxide at a stirring speed of 200 rpm and stir for 25 minutes.

[0069] (2) Feed the material and allow it to cool naturally to 25°C to form a solid plate. After crushing, grind it in a toothed disc pulverizer with the inlet air temperature controlled at 10°C, and collect the particles with a diameter D. 90 The composite particles are 500 μm in size.

[0070] (3) Add 0.06 kg of polyvinyl alcohol to 10.0 kg of deionized water, heat to 90 °C and stir to dissolve, then cool to 15 °C at a rate of 3 °C / min. Add the composite particles and stir at 400 rpm for 30 minutes. Pump the mixture into a horizontal jacketed sand mill filled with 0.8 mm zirconia beads for circulating grinding, controlling the material temperature in the grinding chamber to be below 25 °C, and grind until the particle size is D. 90 Discharge material when the particle size is 5μm.

[0071] (4) Add 8.75 kg of the aqueous thermoplastic copolyester dispersion obtained in Preparation Example 3 under stirring at 200 rpm, add 10% ammonia water at a flow rate of 60 mL / min to adjust the pH value to 7.4, add deionized water to make up to 35 wt% effective non-volatile matter, and obtain component A.

[0072] (5) When the material temperature is 30℃, add 3.00 kg of industrial grade glycerol triglycidyl ether to component A, add deionized water, stir at 500 rpm for 15 minutes, and prepare a working slurry with an effective non-volatile mass fraction of 18 wt%.

[0073] (6) The PET fine denier monofilaments were immersed in a 60℃, 0.5 g / L fatty alcohol polyoxyethylene ether aqueous solution for degreasing, rinsed with deionized water, and then dried. The dried PET fine denier monofilaments were passed through a working slurry tank, and the wet liquid ratio was adjusted to 6.0 wt%. The monofilaments were passed through an 85℃ hot air channel for 40 seconds and through a 35℃ cold air channel for 30 seconds. The dry weight gain was measured to be 1.08 wt%.

[0074] (7) The monofilament is woven into a 3D spaced fabric by a double needle bed warp knitting machine. It is fed into a setting machine: the temperature of the first zone is 125℃, and the holding time is 40 seconds; the temperature of the second zone is 155℃, and the holding time is 90 seconds; the temperature of the third zone is 190℃, and the holding time is 150 seconds. The finished product is then obtained by winding.

[0075] Example 4: This embodiment provides a process for preparing a low-density 3D knitted mesh material based on modified yarn, including the following steps: (1) Add 2.00 kg of polycaprolactone with a number average molecular weight between 1800 and 2200 and 0.80 kg of polycaprolactone with a number average molecular weight between 3800 and 4200 to a stirred reactor with a heating jacket. Heat the reactor to 73°C at 2°C / min and keep it at that temperature until the polymer forms a stirable waxy liquid. Add 1.50 kg of sebacic acid and 0.06 kg of active zinc oxide at 150 rpm and stir for 20 minutes.

[0076] (2) Feed the material and allow it to cool naturally to 22°C to form a solid plate. After crushing, grind it in a toothed disc pulverizer with the inlet air temperature controlled at 10°C, and collect the particles with a diameter D. 90 The composite particles are 350 μm in size.

[0077] (3) Add 0.05 kg of polyvinyl alcohol to 10.0 kg of deionized water, heat to 85 °C and stir to dissolve, then cool to 13 °C at a rate of 2 °C / min. Add the composite particles and stir at 300 rpm for 25 minutes. Pump the mixture into a horizontal jacketed sand mill filled with 0.8 mm zirconia beads for circulating grinding, maintaining the material temperature at 22 °C ± 2 °C, and grind until the particle size is D. 90 Discharge material when the particle size is 4μm.

[0078] (4) Add 9.43 kg of the aqueous thermoplastic copolyester dispersion obtained in Example 1, add 10% ammonia water at a flow rate of 50 mL / min to adjust the pH value to 7.3, add deionized water to make up to 30 wt% effective non-volatile matter, and obtain component A.

[0079] (5) Add 2.80 kg of industrial grade glycerol triglycidyl ether at a material temperature of 20°C, add deionized water, stir at 400 rpm for 12 minutes, and prepare a working slurry with an effective non-volatile matter mass fraction of 16 wt%.

[0080] (6) The PET fine denier monofilaments were immersed in a 55℃, 0.4 g / L fatty alcohol polyoxyethylene ether aqueous solution for degreasing, rinsed with deionized water, and then dried. The dried PET fine denier monofilaments were then passed through a working sizing tank for sizing, and the wet liquid ratio was adjusted to 5.0 wt%. After passing through an 82℃ hot air channel for 30 seconds and a 28℃ cold air channel for 25 seconds, the dry weight gain was measured to be 0.80 wt%.

[0081] (7) The monofilament is woven into a 3D spaced fabric by a double needle bed warp knitting machine. It is fed into a setting machine: the temperature of the first zone is 120℃, and the holding time is 35 seconds; the temperature of the second zone is 150℃, and the holding time is 70 seconds; the temperature of the third zone is 180℃, and the holding time is 100 seconds. The finished product is then obtained by winding.

[0082] Comparative Example 1: Compared to Example 1, the difference lies in that: the steps of melt mixing, cooling and slab formation, and pre-pulverization of polycaprolactone, sebacic acid, and active zinc oxide are omitted; the pre-pulverization is directly carried out to D... 90 Polycaprolactone particles weighing 1.85 kg with a number average molecular weight between 1800 and 2200 and a diameter not exceeding 400 μm, pre-crushed to D... 90 0.90 kg of polycaprolactone particles with a size not exceeding 400 μm and a number-average molecular weight between 3800 and 4200, 1.40 kg of sebacic acid powder, and 0.05 kg of activated zinc oxide powder were added to a polyvinyl alcohol aqueous solution cooled to 12°C. The mixture was stirred at 300 rpm for 25 minutes to form a coarse suspension, which was then pumped into a horizontal jacketed sand mill filled with 0.8 mm zirconia beads for circulating grinding. The material temperature in the grinding chamber was controlled at 20°C ± 2°C until the particle size reached D... 90 The material was discharged when the particle size was 3μm; all other aspects were the same as in Example 1.

[0083] Comparative Example 2: Compared with Example 1, the difference is that the forced cooling step of the cold air channel is removed; after the monofilament exits the groove, it passes through a hot air channel with a temperature of 80°C and a passage dwell time of 25 seconds, and is directly wound up after exiting the hot air channel, and is naturally cooled at an ambient temperature of 25°C, without entering the cold air channel with a temperature of 25°C for passage dwell before winding up; the rest is the same as Example 1.

[0084] Comparative Example 3: Compared with Example 1, the difference is that the heating parameters of the multi-temperature zone tenter frame are changed, and the three-stage stepped heating trigger is not performed; the temperature of all heating zones of the tenter frame is set to 185°C, and the total passing time of the fabric in the tenter frame is set to 210 seconds; the rest are the same as Example 1.

[0085] Comparative Example 4: Compared with Example 1, the differences are as follows: no active zinc oxide was added to the formulation; when preparing the suspension melt in the stirred reactor, 1.40 kg of sebacic acid was added to the softened or molten polycaprolactone and then stirred continuously for 20 minutes without adding active zinc oxide; in the preparation stage of component A and working slurry, by reducing the amount of deionized water replenishment, the effective non-volatile matter mass fractions of component A and working slurry were controlled to be 28 wt% and 15 wt%, respectively, while the roller pressure was adjusted to maintain the wet strip liquid ratio at 4.5 wt% and the monofilament dry weight gain at 0.68 wt%; the rest were the same as in Example 1.

[0086] Comparative Example 5: Compared with Example 1, the difference is that no industrial-grade glycerol triglycidyl ether was added to the working slurry; after component A was pumped into the working slurry tank, under the condition that the material temperature was 25°C, no industrial-grade glycerol triglycidyl ether was added, and the working slurry with an effective non-volatile matter content of 15wt% was prepared by simply adjusting the amount of deionized water and stirring at 400 rpm for 12 minutes. At the same time, the roller pressure was adjusted to keep the wet liquid ratio at 4.5wt% and the monofilament dry weight gain controlled at 0.68wt%; the rest were the same as in Example 1.

[0087] Comparative Example 6: Compared with Example 1, the differences are as follows: the types and amounts of polycaprolactone compounded were changed; when preparing the suspension melt, polycaprolactone with a number average molecular weight between 3800 and 4200 was not added, but 2.75 kg of polycaprolactone with a number average molecular weight between 1800 and 2200 was directly added to a stirred reactor with a heating jacket; the effective non-volatile mass fraction, wet liquid carry-over rate and monofilament dry weight gain of component A and working slurry were controlled in the same way as in Example 1; all other aspects were the same as in Example 1.

[0088] Test Example 1: Test objective: To evaluate the isolation effect of polycaprolactone wax phase embedding structure on sebacic acid and active zinc oxide, to determine the viscosity stability of the working slurry during room temperature storage, and to determine the thermal transition temperature of polycaprolactone and sebacic acid in the freeze-dried powder, so as to provide experimental basis for the temperature setting of the segmented heat setting process.

[0089] The experimental steps are as follows: (1) Take 50 mL of the prepared working slurry of Examples 1 to 4 and Comparative Example 1 respectively, transfer it into the test container, and place it in a constant temperature environment of 25°C.

[0090] (2) The rheological properties of each group of working slurries were tested using a rotational rheometer equipped with a coaxial cylindrical measuring system. The fluid temperature at the measuring gap was controlled at 25℃ using an external water bath circulation device. The shear rate was set to 50 s. -1 The apparent viscosity was measured after the slurry had been left to stand for 0 h, 4 h, 8 h, 12 h and 24 h, and the appearance of the samples was recorded.

[0091] (3) Take 15 mL of each of the working slurry from Examples 1 to 4 and Comparative Example 1 and place them in a sample bottle. Pre-freeze at -40°C for 12 hours, and then transfer them to a vacuum freeze dryer to dry for 48 hours to obtain freeze-dried materials. Lightly grind the freeze-dried materials to obtain dry powder samples.

[0092] (4) Weigh approximately 5.2 mg of each group of dry powder samples, place them in a standard aluminum crucible, seal the crucible, and place it in a differential scanning calorimeter for testing. During the test, high-purity nitrogen gas with a flow rate of 50 mL / min is introduced into the furnace chamber. The initial equilibrium temperature is set at 30 °C, and the temperature is increased to 160 °C at a heating rate of 10 °C / min. The heat flow rate change curve is recorded, and the endothermic transition peak temperature is extracted.

[0093] The experimental results are shown in Table 1: Table 1: Slurry viscosity variation and thermodynamic parameters of dry powder phase transition

[0094] As shown in Table 1, the working slurries of Examples 1 to 4 maintained a low viscosity increase after standing at 25°C for 24 hours, with a viscosity change rate not exceeding 10% in each case, and maintained a uniform flow state. Comparative Example 1, without polycaprolactone melt embedding treatment, had its powder components directly dispersed in the aqueous phase, resulting in a 24-hour viscosity change rate of 705.0% and significant flocculation. These results indicate that the polycaprolactone wax phase composite particles formed through melt embedding and low-temperature milling help reduce the direct contact between sebacic acid, active zinc oxide, and other reactive components in the working slurry in the room-temperature aqueous phase, thereby improving the room-temperature stability of the working slurry.

[0095] Differential scanning calorimetry (DSC) results showed that the lyophilized powders of Examples 1 to 4 all exhibited endothermic melting peaks of polycaprolactone in the range of 61.8℃ to 63.1℃, and endothermic melting peaks of sebacic acid in the range of 133.5℃ to 134.1℃. This indicates that the polycaprolactone and sebacic acid phases in the system have different thermal transition temperature ranges. The melt transition temperature of polycaprolactone is lower than that of sebacic acid, corresponding to the temperature settings in the segmented heat setting process, which involves phase transformation softening followed by diacid melting and subsequent crosslinking and curing. Therefore, the DSC test results provide experimental basis for the segmented heat setting processes of 105℃ to 125℃, 135℃ to 155℃, and 175℃ to 190℃.

[0096] Test Example 2: Test objective: To evaluate the changes in epoxy, carboxyl, and ester group characteristics within the system during segmented heat treatment, and to evaluate the solvent extraction resistance of the heat-set coating through solvent extraction testing.

[0097] The experimental steps are as follows: (1) Take the working slurry from Examples 1 to 4, Comparative Example 4 and Comparative Example 5, and use a film scraper to uniformly coat a wet film with a thickness of about 0.2 mm on a polytetrafluoroethylene plate. Place the wet film in a forced-air drying oven and perform a stepped heat treatment according to the procedure of treating at 80°C for 30 minutes, 155°C for 10 minutes and 185°C for 120 seconds. After each temperature segment, take off a portion of the film sample for later use.

[0098] (2) Film samples from Example 1, after treatment at 80℃, 155℃, and 185℃, were taken and surface scanned using a Fourier transform infrared spectrometer equipped with an attenuated total reflectance accessory. The scanning range was 4000 cm⁻¹. -1 Up to 600cm -1 The resolution is 4cm. -1 A total of 32 scans were performed, extracting 1800 cm⁻¹. -1 Up to 800cm -1 Compare the spectral data of the bands.

[0099] (3) Accurately weigh approximately 1.5 g of each of the dried film samples from Examples 1 to 4, Comparative Example 4 and Comparative Example 5 after treatment at 80 °C and 185 °C respectively. The epoxy value of each sample was determined by hydrochloric acid-acetone titration, and the acid value of each sample was determined by potassium hydroxide-ethanol standard solution titration.

[0100] (4) Take about 5.0g of monofilament samples from Examples 1 to 4, Comparative Example 4 and Comparative Example 5 after the complete process, and cut them into short segments with a length of about 5mm. After wrapping the sample with filter paper, place it in a Soxhlet extractor and extract continuously for 6 hours under reflux with tetrahydrofuran as solvent.

[0101] (5) After extraction, the residue along with the filter paper was transferred to an 80°C vacuum oven and dried to constant weight. The weight was then measured using an analytical balance. Simultaneously, unsized PET monofilaments of the same length and number as the sized sample were taken as blank substrates and subjected to the same extraction and drying treatments to obtain the quality of the corrected substrates.

[0102] The coating gel retention rate is calculated using the following formula: Coating gel retention rate = (m2-m0) / (m1-m0)×100%; In the formula, m0 is the mass of the unsized PET monofilament after the same extraction and drying treatment, m1 is the mass of the sized monofilament sample before extraction, and m2 is the mass of the sized monofilament sample after extraction and drying.

[0103] The experimental results are shown in Table 2: Table 2: Characteristic titration parameters of coating film and test data of final coating gel retention rate

[0104] The ATR-FTIR test results of Example 1 show that the membrane sample treated at 80℃ has a wavelength of 910 cm⁻¹. -1 Nearby, there is epoxy-related absorption; after treatment at 155℃, 910 cm⁻¹ -1 The absorption intensity decreases in the vicinity, 1585cm -1 Changes were observed in the nearby carboxylate-related absorption region; after treatment at 185℃, the absorption rate at 1730 cm⁻¹... -1 Enhancement or peak shape changes were observed in the absorption regions related to the nearby ester carbonyl groups. Since both polycaprolactone and waterborne thermoplastic copolyester in the system contain ester structures, the above infrared changes need to be interpreted in conjunction with titration results.

[0105] As shown in Table 2, after treatment at 185°C, the epoxy value of Example 1 decreased from 0.214 eq / 100g to 0.042 eq / 100g, and the acid value decreased from 38.6 mgKOH / g to 6.3 mgKOH / g. Examples 2 to 4 showed the same trend. These results indicate that under the stated heat treatment conditions, the epoxy and carboxyl groups in the system were consumed through reaction.

[0106] Comparative Example 4 did not contain active zinc oxide. Its epoxy value after treatment at 185°C was 0.142 eq / 100g, and its acid value was 26.1 mgKOH / g, both higher than the corresponding values ​​in the examples. This indicates that in the absence of active zinc oxide, the system experiences lower consumption of epoxy and carboxyl groups under the same heat treatment conditions. Comparative Example 5 did not contain glycerol triglycidyl ether, and its epoxy value was not detected. Furthermore, its acid value after treatment at 185°C was still 33.8 mgKOH / g, indicating that it did not possess the same epoxy crosslinking reaction basis as the examples.

[0107] Solvent extraction results showed that after 6 hours of Soxhlet extraction with tetrahydrofuran in Examples 1 to 4, the coating gel retention rate was 86.5% to 89.1%; the coating gel retention rate in Comparative Example 4 was 52.3%, and the coating gel retention rate in Comparative Example 5 was 18.7%. These results indicate that the co-existence of active zinc oxide and glyceryl triglycidyl ether helps improve the resistance of the heat-set coating to tetrahydrofuran extraction and supports the formation of a solvent-resistant cured structure after heat treatment.

[0108] Test Example 3: Test objective: To evaluate the dynamic friction coefficient, unwinding tension stability and friction dust resistance of modified PET fine denier monofilaments, so as to characterize their process adaptability in the weaving process.

[0109] The experimental steps are as follows: (1) Modified PET fine denier monofilaments prepared in Examples 1 to 4, Comparative Examples 2 and 6 were selected as test samples. Before the test, each group of yarn packages was placed in a standard environment with a temperature of 20±2℃ and a relative humidity of 65±4% for 24 hours to acclimate.

[0110] (2) The dynamic friction coefficient of each group of monofilaments was determined using a yarn friction coefficient meter. During the test, the monofilament was passed through an alumina ceramic guide post, the wrap angle was 180°, the initial tension was 0.1 cN / dtex, and the yarn feed speed was 100 m / min. Ten monofilament samples at different positions were tested continuously for each group, and the average value was taken as the dynamic friction coefficient of that group.

[0111] (3) The unwinding stability of each group of monofilaments was evaluated using an unwinding tension testing device. The yarn package was installed on the unwinding device and unwound for 5000m at a speed of 200m / min. The 5000m unwinding process was divided into 10 consecutive segments, each 500m long. The maximum and minimum unwinding tensions in each segment were recorded, and the difference between the two was calculated. The average of the differences in the 10 segments was taken as the unwinding tension fluctuation range.

[0112] (4) The friction-resistant powder-shedding performance of the monofilament surface coating was evaluated using a simulated guide wire and needle groove combination device. A continuous 1000m monofilament was passed through the combination device under a set tension. A pre-weighed collection tray was set below the device to collect the debris scattered during the wire feeding process.

[0113] (5) Weigh the collected debris using a micro-analytical balance and measure the initial mass of the 1000m monofilament sample before testing. The dust loss rate is calculated using the following formula: Dust shedding rate = mass of scattered debris / initial mass of monofilament before test × 100%.

[0114] The experimental results are shown in Table 3: Table 3. Test results of monofilament surface friction characteristics and simulated weaving process parameters

[0115] As shown in Table 3, the dynamic friction coefficients of Examples 1 to 4 are all below 0.25, the unwinding tension fluctuation range is not higher than 0.67 cN, and the dust shedding rate is below 0.020%. These results indicate that the modified PET fine denier monofilaments obtained in Examples 1 to 4 have low surface friction resistance, stable unwinding performance, and low coating peeling, which can meet the requirements of continuous weaving processes for yarn passability and surface stability.

[0116] Comparative Example 2, which did not undergo forced cooling before winding, had a dynamic friction coefficient of 0.413 and an unwinding tension fluctuation range of 2.87 cN, both higher than those of Examples 1 to 4. This result indicates that cold air channel treatment after drying is beneficial for improving the surface condition and unwinding stability of the modified monofilament.

[0117] Comparative Example 6 used only polycaprolactone with a number average molecular weight between 1800 and 2200, without adding polycaprolactone with a number average molecular weight between 3800 and 4200. Its powder shedding rate was 0.126%, which was higher than that of Examples 1 to 4. This result indicates that the combination of medium and low molecular weight polycaprolactones is beneficial to reducing the amount of coating peeling during the simulated weaving friction process.

[0118] Test Example 4: Test objective: To evaluate the impact of segmented thermally triggered curing process on the interlayer bonding strength and burst resistance of 3D spacer mesh fabric.

[0119] The experimental steps are as follows: (1) The 3D spacer mesh fabrics prepared in Examples 1 to 4, Comparative Examples 3 and 4 were used as test samples. Each group of samples was prepared using the same specification of basic PET fine denier monofilament, the same double needle bed warp knitting process and the same structure parameters. The difference was in the sizing formula or heat setting procedure. Before testing, each group of samples was placed in a standard environment with a temperature of 20±2℃ and a relative humidity of 65±4% for 24 hours to acclimate.

[0120] (2) Determine the interlayer peel strength of the mesh sample. Cut a strip of sample with a length of 200 mm and a width of 50 mm along the warp direction. Separate the upper and lower surface layers of one end of the sample by about 50 mm beforehand. Fix the separated upper and lower surface layers in the upper and lower clamps of the universal testing machine and peel continuously at a speed of 100 mm / min. Discard the data of the initial peeling stage and the end peeling stage, and take the average force value of the middle stable peeling section as the test result. Test 5 parallel samples in each group and take the arithmetic mean.

[0121] (3) Determine the steel ball bursting strength of the mesh sample. The test was conducted according to GB / T 19976-2005. A circular sample with a diameter of approximately 150 mm was cut and fixed flat in a ring clamp with an inner diameter of 50 mm. A hemispherical polished steel ball with a diameter of 38 mm was used as the push rod, and a normal load was applied to the central area of ​​the sample at a speed of 100 mm / min. The maximum load value at which the sample broke was recorded. Five parallel samples were tested in each group, and the arithmetic mean was taken.

[0122] The experimental results are shown in Table 4: Table 4: Test results of interlayer peel strength and steel ball bursting strength of 3D spacer mesh samples

[0123] Note: The data in Table 4 are the arithmetic mean of 5 parallel samples.

[0124] As shown in Table 4, the interlaminar peel strength of Examples 1 to 4 ranges from 37.9 N / 50 mm to 41.2 N / 50 mm, and the steel ball bursting strength ranges from 1326.4 N to 1385.1 N. The interlaminar peel strength of Comparative Example 3 is 25.3 N / 50 mm, and the steel ball bursting strength is 1154.8 N; the interlaminar peel strength of Comparative Example 4 is 28.7 N / 50 mm, and the steel ball bursting strength is 1192.3 N. These results indicate that the 3D spacer mesh fabrics prepared in Examples 1 to 4 possess high interlaminar bonding strength and bursting resistance.

[0125] Comparative Example 3 employed a single high-temperature heat setting treatment, without the segmented heat setting procedure of Example 1. Compared to Example 1, Comparative Example 3 showed reduced interlaminar peel strength and steel ball bursting strength. This result indicates that a segmented heat setting procedure helps improve the interlaminar bonding strength and bursting resistance of 3D spacer mesh fabrics.

[0126] Comparative Example 4 employed the same segmented heat-setting procedure as Example 1, but without the addition of active zinc oxide. Compared to Example 1, Comparative Example 4 showed reduced interlayer peel strength and steel ball bursting strength. This result indicates that the addition of active zinc oxide helps improve the curing degree of the coating after heat setting and its contribution to the mechanical properties of the mesh.

[0127] Test Example 5: Test objective: To evaluate the interlayer strength retention, thickness retention, and compression recovery of the finished 3D spacer mesh after standard washing and cyclic compression.

[0128] The experimental steps are as follows: (1) The 3D spacer mesh fabrics prepared in Examples 1 to 4 and Comparative Example 5 were selected as test samples. Before the test, each group of samples was placed in a standard environment with a temperature of 20±2℃ and a relative humidity of 65±4% for 24 hours to adjust the humidity.

[0129] (2) The washing resistance test was carried out according to the washing procedure specified in GB / T 8629. Each group of samples was placed in a standard washing device and subjected to 20 and 50 standard washing cycles respectively at a washing liquid temperature of 60℃. After completing the specified number of washing cycles, the samples were air-dried and then conditioned again for 24 hours in a standard environment with a temperature of 20±2℃ and a relative humidity of 65±4%.

[0130] (3) Determine the interlayer peel strength of the sample after washing. Cut a strip of sample with a length of 200 mm and a width of 50 mm along the warp direction. After pre-peeling the ends of the sample, fix the upper and lower surfaces in the upper and lower clamps of the universal testing machine, respectively. Perform a tensile test at a speed of 100 mm / min, and take the average force value of the middle stable peeling section as the interlayer peel strength. The strength retention rate after washing is calculated by the following formula: Strength retention rate after washing = interlayer peel strength after washing / interlayer peel strength before washing × 100%.

[0131] (4) Perform cyclic compression fatigue test. Cut a square specimen with a side length of 100 mm and lay it flat on the lower platen of the compression testing machine. Measure the initial thickness h0 before fatigue under a preload of 0.5 kPa. Use a circular upper platen with a diameter of 50 mm to cyclically compress the central area of ​​the specimen. The deformation of a single compression is 50% of the initial thickness, the thickness h1 in the compressed state is 0.5h0, the operating frequency is 1 Hz, and the number of cycles is 20,000.

[0132] (5) After the cyclic compression test, the sample was allowed to stand for 1 hour in a standard environment with a temperature of 20±2℃ and a relative humidity of 65±4%, and the thickness h2 after recovery was measured. The thickness retention rate and compression recovery rate were calculated according to the following formulas: Thickness retention rate = h2 / h0 × 100%; Compression recovery rate = (h2-h1) / (h0-h1)×100%.

[0133] Five parallel samples were tested in each group, and the arithmetic mean was taken.

[0134] The experimental results are shown in Table 5: Table 5: Results of Water Washing and Cyclic Compression Durability Tests for Mesh Fabric Samples

[0135] Note: The data in Table 5 are the arithmetic mean of 5 parallel samples.

[0136] As shown in Table 5, the interlayer peel strength retention rates of Examples 1 to 4 after 20 standard water washes were 87.2% to 91.5%, and after 50 standard water washes were 78.4% to 83.7%. The interlayer peel strength retention rates of Comparative Example 5 after 20 and 50 standard water washes were 58.4% and 41.6%, respectively. These results indicate that the 3D spacer mesh fabrics prepared in Examples 1 to 4 exhibit high interlayer strength retention levels after multiple standard water washes.

[0137] The cyclic compression test results showed that the thickness retention rate of Examples 1 to 4 after 20,000 cycles of compression was 88.5% to 91.8%, and the compression recovery rate was 86.3% to 89.4%. Comparative Example 5, after the same cyclic compression, had a thickness retention rate of 68.7% and a compression recovery rate of 63.5%. These results indicate that the 3D spacer mesh fabrics prepared in Examples 1 to 4 have high thickness retention and compression recovery rates after cyclic compression.

[0138] Comparative Example 5, without the addition of glycerol triglycidyl ether, showed lower strength retention, thickness retention, and compression recovery rates after washing compared to Examples 1 to 4. These results indicate that, under the test conditions, the reaction-cured system formed by introducing glycerol triglycidyl ether and undergoing heat treatment helps improve the wash resistance and dimensional retention of the 3D spacer mesh after cyclic compression.

[0139] 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 low-density 3D knitted mesh fabric material based on modified yarn, characterized in that, The coating comprises PET monofilaments as spacer yarns and a coating composition covering the surface of the PET monofilaments; the coating composition is made from raw materials comprising the following parts by weight: Polycaprolactone: 21-34 parts; Sebacic acid: 12-16 parts; Active zinc oxide: 0.3–0.8 parts; Polyvinyl alcohol: 0.3–0.6 parts; Waterborne thermoplastic copolyester dispersion: 87.5–94.3 parts; Glyceryl triglycidyl ether: 24-30 parts; The aqueous thermoplastic copolyester dispersion is prepared by polymerization reaction of terephthalic acid, isophthalic acid, adipic acid, 5-sulfoisophthalic acid monosodium salt, 1,4-butanediol and ethylene glycol, and the solid content of the aqueous thermoplastic copolyester dispersion is 30wt% to 40wt%, and the weight parts of the aqueous thermoplastic copolyester dispersion are based on the total mass of the dispersion.

2. The low-density 3D knitted mesh material based on modified yarn according to claim 1, characterized in that, The polycaprolactone is a mixture of polycaprolactone with a number average molecular weight of 1800-2200 and polycaprolactone with a number average molecular weight of 3800-4200.

3. The low-density 3D knitted mesh material based on modified yarn according to claim 1, characterized in that, The parameters of the raw materials meet the following limitations: The BET specific surface area of ​​the active zinc oxide is 30 m². 2 / g~50m 2 / g; The epoxy equivalent of the glycerol triglycidyl ether is 140 g / eq to 160 g / eq.

4. The low-density 3D knitted mesh material based on modified yarn according to claim 1, characterized in that, In the coating slurry used to form the coating composition, the polycaprolactone is blended to form a solid continuous phase, and the sebacic acid and the active zinc oxide are dispersed and embedded in the solid continuous phase to form composite particles, wherein the particle size D90 of the composite particles is 2 μm to 5 μm.

5. A process for preparing a low-density 3D knitted mesh fabric material based on modified yarn, used to prepare the low-density 3D knitted mesh fabric material based on modified yarn as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Polycaprolactone is heated and melted, sebacic acid and active zinc oxide are added, mixed evenly, cooled into a solid state, and then pulverized to obtain composite particles. S2. Dissolve polyvinyl alcohol in deionized water, add the composite particles obtained in step S1, and perform a circulating sand milling to obtain a composite particle dispersion. S3. Add aqueous thermoplastic copolyester dispersion to the composite particle dispersion obtained in step S2, add ammonia to adjust the pH value, and add deionized water to make up the volume to obtain a mixed solution. S4. Add glycerol triglycidyl ether to the mixture obtained in step S3, and add deionized water to mix and obtain the coating slurry. S5. The PET monofilament is sized by passing it through the coating slurry obtained in step S4, and then passed through the hot air channel and the cold air channel in sequence to obtain the modified yarn. S6. The modified yarn obtained in step S5 is used as the spacer yarn to weave a 3D spacer fabric, and the 3D spacer fabric is continuously fed into a tenter frame for setting.

6. The preparation process according to claim 5, characterized in that, In step S1, the polycaprolactone is heated to 70℃~75℃, sebacic acid and active zinc oxide are added and stirred for 15min~25min, cooled to solidify and pulverized to obtain composite coarse particles with a particle size D90 of 300μm~500μm. In step S2, the temperature of the circulating sand mill is 13℃~25℃.

7. The preparation process according to claim 5, characterized in that, In step S3, ammonia is added to adjust the pH to 7.0–7.4; The material temperature when obtaining the coating slurry in step S4 is 15℃~30℃, and the effective non-volatile matter mass fraction of the coating slurry is 12wt%~18wt%.

8. The preparation process according to claim 5, characterized in that, In step S5, the wet tape ratio for PET monofilament sizing is controlled to be 3.0 wt%–6.0 wt%. The temperature of the hot air channel is 75℃~85℃, and the residence time of the PET monofilament in the hot air channel is 10s~40s; The temperature of the cold air channel is 20℃~35℃, and the residence time of the PET monofilament in the cold air channel is 10s~30s.

9. The preparation process according to claim 5, characterized in that, In step S6, the shaping process includes sequentially passing through three heating zones at different temperatures: The temperature of the first heating zone is 105℃~125℃, and the residence time of the 3D spaced fabric in the first heating zone is 20s~40s; The temperature of the second heating zone is 135℃~155℃, and the residence time of the 3D spaced fabric in the second heating zone is 30s~90s; The temperature of the third heating zone is 175℃~190℃, and the residence time of the 3D spaced fabric in the third heating zone is 90s~150s.

10. A low-density 3D knitted mesh fabric based on modified yarn, characterized in that, It is prepared by the preparation process described in any one of claims 5 to 9.

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