A fumed silica regenerated PET matte yarn and a preparation method thereof

Abstract

This invention discloses a method for preparing fumed silica-regenerated PET matte yarn. The method first prepares furan-functionalized nano-silica and maleimide-terminated PET prepolymer. A reversible covalent bond interface layer is constructed between the nano-silica and the PET matrix using a Diels-Alder dynamic reversible reaction. During twin-screw extrusion, a temperature gradient process of "high-temperature dispersion-low-temperature reconstruction" is employed. This allows the DA bonds to dissociate in the high-temperature region to reduce viscosity and achieve ultra-uniform dispersion of nanoparticles, while rebonding in the low-temperature region to complete in-situ interface anchoring. Finally, melt spinning and heat setting treatments are performed to obtain regenerated PET matte yarn with self-healing interface capabilities. The resulting product has a breakage rate of less than 1.8%, a breaking strength of over 4.4 cN / dtex, a breaking elongation exceeding 35%, and an adjustable gloss level within the range of 13-22 GU. The production qualification rate exceeds 95%.

Description

Technical Field

[0001] This invention relates to the field of plastic waste recycling technology, and in particular to a fumed silica-regenerated PET matte filament and its preparation method. Background Technology

[0002] Polyethylene terephthalate (PET), as one of the most widely used thermoplastic polyester materials globally, occupies an important position in textiles, packaging, and other fields due to its excellent mechanical strength and thermal stability. Global annual demand exceeded 70 million tons by the end of 2024. However, a large number of PET products are discarded after a single use. Currently in my country, approximately 68% of waste PET is disposed of through landfill or incineration, which not only wastes resources but also causes environmental problems such as microplastic pollution of soil.

[0003] Although physical recycling can achieve material regeneration through melt extrusion, repeated processing leads to molecular chain degradation, causing recycled PET's mechanical properties to decrease by 10%-15% compared to virgin materials. Poor spinning stability severely restricts its high-value applications. In the field of matte yarn preparation, traditional techniques follow the modification approach of virgin PET, using high-volume fillers such as micron-sized titanium dioxide or barium sulfate for physical blending. However, residual impurities and short molecular chain characteristics in recycled materials make filler dispersion extremely difficult. Aggregates clog the spinneret, resulting in a breakage rate as high as 8%-12%. Simultaneously, the introduction of a large number of inorganic particles further disrupts the matrix continuity, reducing the breaking strength of the finished yarn by more than 20%. Furthermore, while existing silane coupling agent modification can improve the compatibility between fillers and the matrix, the permanent covalent bond interface formed lacks reversible controllability, making it difficult to solve the problems of thermal oxidation yellowing and interface damage accumulation during recycled PET processing. The resulting matte yarns generally suffer from uneven gloss and insufficient abrasion resistance, failing to meet the stringent requirements of high-end textile industries for material durability and appearance. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a fumed silica-based recycled PET matte filament and its preparation method, solving the issues of poor dispersibility and high breakage rate of traditional matting agents in the recycled matrix. By employing a low-dosage amount of hydrophobic fumed silica, a stable matte effect is achieved while maximizing the preservation of the mechanical properties of recycled PET, improving the filament's appearance quality and weather resistance. Furthermore, this invention simplifies the production process, reduces processing losses, and promotes the high-value recycling of broken PET waste from water bottles.

[0005] This invention can be achieved through the following technical solutions: A method for preparing fumed silica recycled PET matte filament includes the following steps: Step 1: Disperse nano-sized fumed silica with a specific surface area of ​​180-220 m² / g and a particle size of 15-25 nm in xylene, add γ-aminopropyltriethoxysilane (KH550), and reflux at 90-110 °C for 4-8 h to obtain amino-modified silica; then, esterify the amino-modified silica with furanylcarbohydrate in the presence of N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine at 0-25 °C for 12-24 h, centrifuge, wash, and vacuum dry to obtain furan-functionalized nano-silica (Fu-SiO2). Step 2: Mix PET bottle crushed material with intrinsic viscosity of 0.65-0.75 dL / g with ethylene glycol at a mass ratio of 1:(3-6), add an alcoholysis catalyst, and react at 190-220℃ for 2-4 hours under nitrogen protection. Dehydrate under vacuum until the water content is 300-500ppm. Add isophorone diisocyanate dropwise at 70-90℃ with an NCO / OH molar ratio of (1.8-2.2):1. Add catalyst and react for 2-3 hours. Cool to 60-80℃ and add N-hydroxyethyl maleimide with an NCO / OH molar ratio of 1:(1-1.1). Continue the reaction for 1-2 hours. After precipitation, washing, and drying, obtain maleimide-terminated PET prepolymer (MI-PET). Step 3: By weight, take 0.5-3.0 parts of Fu-SiO2, 100 parts of MI-PET, 0.2-1.0 parts of chain extender, 0.05-0.2 parts of polycondensation catalyst, and 0.1-0.5 parts of antioxidant. Mix them evenly and add them to a twin-screw extruder. The material is extruded, cooled with water, and pelletized to obtain recycled PET composite chips. Step 4: Vacuum dry the composite chips at 100-120℃ for 8-12 hours until the moisture content is 40-50ppm. Add the chips to a spinning machine at a spinning temperature of 265-280℃, a spinneret orifice diameter of 0.25-0.35mm, and a spinning speed of 700-900m / min. Cool the filaments with side blowing air and then enter a drawing machine for a two-stage drawing process. After drawing, heat set the filaments at 110-125℃ for 10-30 minutes. Finally, wind the filaments through a winding machine to obtain fumed silica recycled PET matte filaments.

[0006] Preferably, in step 1, the mass ratio of amino-modified silica, furanoic acid, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 1:(0.5-2):(1.2-2):(0.05-0.2).

[0007] Preferably, the vacuum drying conditions in step 1 are 40-60℃ for 24-48 hours.

[0008] Preferably, in step 2, the alcoholysis catalyst is zinc acetate (Zn(Ac)2), and the amount added is 0.5%-1.0% of the mass of PET; the catalyst is dibutyltin dilaurate, and the amount added is 0.05%-0.1% of the total mass of the reactants.

[0009] Preferably, in step 3, the chain extender is pyromellitic dianhydride (PMDA); the polycondensation catalyst is antimony trioxide; and the antioxidant is a compound of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1.

[0010] Preferably, in step 3, the temperature of the twin-screw extruder is 230-275℃, the screw speed is 220-280 r / min, and the feeding speed is 25-35 kg / h.

[0011] Preferably, the two-stage drawing process in step 4 is as follows: the first stage drawing temperature is 75-85℃, and the drawing ratio is 2.0-2.5 times; the second stage drawing temperature is 90-100℃, and the total drawing ratio is 4.0-5.0 times.

[0012] Preferably, the winding speed in step 4 is 2800-3200 m / min.

[0013] The beneficial effects of this invention are: This invention introduces Diels-Alder dynamic covalent bonds into the preparation system of recycled PET matte filaments, constructing a smart interface that can be reversibly controlled during processing. The method first prepares furan-functionalized nano-silica and maleimide-terminated PET prepolymers. Utilizing the reversible DA reaction between the furan ring and maleimide, a chemically bonded interface layer with dynamic characteristics is constructed between the nano-silica and the PET matrix. During twin-screw extrusion, a temperature gradient design allows the DA bonds to dissociate at high temperatures to reduce system viscosity and achieve ultra-uniform dispersion of the nano-silica; rebonding occurs at low temperatures, completing in-situ anchoring of the interface. This unique "high-temperature dispersion-low-temperature reconstruction" process perfectly matches the characteristics of dynamic bonds, enabling nanoparticles to be stably anchored in the matrix in a monodisperse state, solving the aggregation problem that is difficult to overcome with traditional physical blending and permanent covalent bond modification. The resulting recycled PET matte filaments exhibit a breakage rate as low as 1.6% and a tensile strength of 4.4 cN / dtex, representing an improvement of over 50% compared to unmodified recycled PET. Simultaneously, the elongation at break remains above 35%, achieving a dual effect of strengthening and toughening. More notably, the reversible DA bonds endow the material with self-healing interfacial capabilities. After heat setting, the mechanical property recovery rate reaches 88%, the yellowing index is controlled below 1.0, the abrasion resistance exceeds 600 cycles, the product qualification rate reaches over 97%, and the added value increases by nearly 40%. This invention, while achieving an excellent matte finish, endows recycled PET materials with unprecedented interfacial reversibility and self-healing functions, opening up a new avenue for the high-performance and high-value utilization of broken PET waste from water bottles. Attached Figure Description

[0014] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 The breakage rate and gloss of recycled PET matte yarn; Figure 2 The breaking strength retention rate and breaking elongation rate of recycled PET matte yarn; Figure 3 Yellowing index and abrasion resistance of recycled PET matte yarn; Figure 4 To improve the production qualification rate and added value of recycled PET matte yarn. Detailed Implementation

[0015] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions.

[0016] Example 1: A method for preparing fumed silica recycled PET matte filament, comprising the following steps: Step 1: Disperse 50g of nano-fumed silica (Degussa AEROSIL R974) with a specific surface area of ​​180m² / g and a particle size of 15nm in 300mL of anhydrous xylene. Add 12.5g of γ-aminopropyltriethoxysilane (KH550) and reflux at 90℃ for 8h to obtain amino-modified silica. Then, take 50g of amino-modified silica, add 400mL of anhydrous N,N-dimethylformamide, 25g of furanylformic acid, 60g of N,N'-dicyclohexylcarbodiimide and 2.5g of 4-dimethylaminopyridine, and carry out esterification reaction at 0℃ for 24h. After centrifugation (8000rpm, 15min), washing twice with deionized water, and vacuum drying at 40℃ for 48h, obtain furan-functionalized nano-silica (Fu-SiO2). Step 2: Take 200g of cleaned and dried PET bottle crushed material (intrinsic viscosity 0.65 dL / g), 600mL of ethylene glycol, and add 1g of zinc acetate (0.5% of the PET mass). React at 190℃ for 4 hours under nitrogen protection. After the reaction is complete, cool to room temperature and pour the reaction solution into 5... The precipitate was collected in cold water, filtered, and the filter cake was washed three times with deionized water. 600 mL of anhydrous xylene was added, and the mixture was heated to 80°C. Under vacuum, the mixture was dehydrated to a water content of 300 ppm. 122.4 g of isophorone diisocyanate (NCO / OH molar ratio 1.8:1) was added dropwise at 70°C, followed by 0.1375 g of dibutyltin dilaurate (0.05% of the total reactant mass). The reaction was continued for 3 hours, then cooled to 60°C. 42.72 g of N-hydroxyethyl maleimide (NCO / OH molar ratio 1:1) was added, and the reaction continued for 1 hour. After the reaction was complete, the reaction solution was slowly poured into 5 L of anhydrous ethanol to precipitate. The precipitate was filtered, and the filter cake was washed three times with anhydrous ethanol and once with anhydrous diethyl ether. The mixture was then vacuum dried at 40°C for 24 hours to obtain maleimide-terminated PET prepolymer (MI-PET). Step 3: By weight, take 1.5 parts of Fu-SiO2, 100 parts of MI-PET, 0.2 parts of pyromellitic dianhydride, 0.05 parts of antimony trioxide, and 0.1 parts of antioxidant (a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1). Mix them evenly and add them to a twin-screw extruder (the temperature of each section of the twin-screw extruder is 230℃, 245℃, 260℃, 275℃, and 265℃, the screw speed is 220r / min, and the feeding speed is 25kg / h). The material is extruded, water-cooled, and pelletized to obtain recycled PET composite chips. Step 4: Vacuum dry the composite slices at 100℃ for 12 hours until the moisture content is 40ppm. Add the slices to the spinning machine at a spinning temperature of 265℃, a spinneret orifice diameter of 0.25mm, and a spinning speed of 700m / min. Cool the filaments with side blowing air and then enter the drawing machine for a two-stage drawing process (first stage drawing temperature 75℃, drawing ratio 2.0 times; second stage drawing temperature 90℃, total drawing ratio 4.0 times). After drawing, heat set the filaments at 110℃ for 30 minutes. Finally, wind the filaments through a winding machine (winding speed 2800m / min) to obtain fumed silica recycled PET matte filaments.

[0017] Example 2: A method for preparing fumed silica recycled PET matte filament, comprising the following steps: Step 1: Disperse 50g of nano-fumed silica (Degussa AEROSIL R974) with a specific surface area of ​​200m² / g and a particle size of 20nm in 300mL of anhydrous xylene. Add 12.5g of γ-aminopropyltriethoxysilane (KH550) and reflux at 100℃ for 6h to obtain amino-modified silica. Then, take 50g of amino-modified silica, add 400mL of anhydrous N,N-dimethylformamide, 62.5g of furanylformic acid, 80g of N,N'-dicyclohexylcarbodiimide, and 6.25g of 4-dimethylaminopyridine, and carry out esterification reaction at 12.5℃ for 18h. After centrifugation (8000rpm, 15min), washing twice with deionized water, and vacuum drying at 50℃ for 36h, obtain furan-functionalized nano-silica (Fu-SiO2). Step 2: Take 200g of cleaned and dried PET bottle fragments (intrinsic viscosity 0.70 dL / g), 900mL of ethylene glycol, and add 1.6g of zinc acetate (0.8% of the PET mass). React at 205℃ for 3 hours under nitrogen protection. After the reaction is complete, cool to room temperature and pour the reaction solution into 5... The precipitate was collected in cold water, filtered, and the filter cake was washed three times with deionized water. 600 mL of anhydrous xylene was added, and the mixture was heated to 80°C. Under vacuum, the mixture was dehydrated to a water content of 400 ppm. 136 g of isophorone diisocyanate (NCO / OH molar ratio 2.0:1) was added dropwise at 80°C, followed by 0.22 g of dibutyltin dilaurate (0.08% of the total reactant mass). The reaction was continued for 2.5 h, then cooled to 70°C. 44 g of N-hydroxyethyl maleimide (NCO / OH molar ratio 1:1.03) was added, and the reaction continued for another 1.5 h. After the reaction was complete, the reaction solution was slowly poured into 5 L of anhydrous ethanol to precipitate. The precipitate was filtered, and the filter cake was washed three times with anhydrous ethanol and once with anhydrous diethyl ether. The mixture was then vacuum dried at 40°C for 24 h to obtain maleimide-terminated PET prepolymer (MI-PET). Step 3: By weight, take 2.25 parts of Fu-SiO2, 100 parts of MI-PET, 0.6 parts of pyromellitic dianhydride, 0.125 parts of antimony trioxide, and 0.3 parts of antioxidant (a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1). Mix them evenly and add them to a twin-screw extruder (the temperature of each section of the twin-screw extruder is 230℃, 245℃, 260℃, 275℃, and 265℃, the screw speed is 250 r / min, and the feeding speed is 30 kg / h). The material is extruded, water-cooled, and pelletized to obtain recycled PET composite chips. Step 4: Vacuum dry the composite slices at 110℃ for 10 hours until the moisture content is 45ppm. Add the slices to the spinning machine at a spinning temperature of 275℃, a spinneret orifice diameter of 0.30mm, and a spinning speed of 800m / min. Cool the filaments with side blowing and then enter the drawing machine for a two-stage drawing process (first stage drawing temperature 80℃, drawing ratio 2.25 times; second stage drawing temperature 95℃, total drawing ratio 4.5 times). After drawing, heat set the filaments at 120℃ for 20 minutes. Finally, wind the filaments through a winding machine (winding speed 3000m / min) to obtain fumed silica recycled PET matte filaments.

[0018] Example 3: A method for preparing fumed silica recycled PET matte filament, comprising the following steps: Step 1: Disperse 50g of nano-fumed silica (Degussa AEROSIL R974) with a specific surface area of ​​220m² / g and a particle size of 25nm in 300mL of anhydrous xylene. Add 12.5g of γ-aminopropyltriethoxysilane (KH550) and reflux at 110℃ for 4h to obtain amino-modified silica. Then, take 50g of amino-modified silica, add 400mL of anhydrous N,N-dimethylformamide, 100g of furanylformic acid, 100g of N,N'-dicyclohexylcarbodiimide and 10g of 4-dimethylaminopyridine, and carry out esterification reaction at 25℃ for 12h. After centrifugation (8000rpm, 15min), washing twice with deionized water, and vacuum drying at 60℃ for 24h, obtain furan-functionalized nano-silica (Fu-SiO2). Step 2: Take 200g of cleaned and dried PET bottle fragments (intrinsic viscosity 0.75 dL / g), 1200mL of ethylene glycol, and add 2g of zinc acetate (1.0% of the PET mass). React at 220℃ for 2 hours under nitrogen protection. After the reaction is complete, cool to room temperature and pour the reaction solution into 5... The precipitate was collected in cold water, filtered, and the filter cake was washed three times with deionized water. 600 mL of anhydrous xylene was added, and the mixture was heated to 80°C. Under vacuum, the mixture was dehydrated to a water content of 500 ppm. 149.6 g of isophorone diisocyanate (NCO / OH molar ratio 2.2:1) was added dropwise at 90°C, followed by 0.275 g of dibutyltin dilaurate (0.1% of the total reactant mass). The reaction was continued for 2 hours, then cooled to 80°C. 42.72-47.0 g of N-hydroxyethyl maleimide (NCO / OH molar ratio 1:1.1) was added, and the reaction continued for 1 hour. After the reaction was complete, the reaction solution was slowly poured into 5 L of anhydrous ethanol to precipitate. The precipitate was filtered, and the filter cake was washed three times with anhydrous ethanol and once with anhydrous diethyl ether. The mixture was then vacuum dried at 40°C for 24 hours to obtain maleimide-terminated PET prepolymer (MI-PET). Step 3: By weight, take 3.0 parts of Fu-SiO2, 100 parts of MI-PET, 1.0 part of pyromellitic dianhydride, 0.2 parts of antimony trioxide, and 0.5 parts of antioxidant (a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1). Mix them evenly and add them to a twin-screw extruder (the temperature of each section of the twin-screw extruder is 230℃, 245℃, 260℃, 275℃, and 265℃, the screw speed is 280r / min, and the feeding speed is 35kg / h). The material is extruded, water-cooled, and pelletized to obtain recycled PET composite chips. Step 4: Vacuum dry the composite slices at 120℃ for 8 hours until the moisture content is 50ppm. Add the slices to the spinning machine at a spinning temperature of 280℃, a spinneret orifice diameter of 0.35mm, and a spinning speed of 900m / min. Cool the filaments with side blowing air and then enter the drawing machine for a two-stage drawing process (first stage drawing temperature 85℃, drawing ratio 2.5 times; second stage drawing temperature 100℃, total drawing ratio 5.0 times). After drawing, heat set the filaments at 125℃ for 10 minutes. Finally, wind the filaments through a winding machine (winding speed 3200m / min) to obtain fumed silica recycled PET matte filaments.

[0019] Comparative Example 1: The difference between this comparative example and Example 1 is that it uses a conventional silane coupling agent to modify nano-silica.

[0020] A method for preparing fumed silica recycled PET matte filament includes the following steps: Step 1: Take 50g of nano-fumed silica (Degussa AEROSIL R974) with a specific surface area of ​​180m² / g and a particle size of 15nm and disperse it in 300mL of anhydrous xylene. Add 12.5g of γ-aminopropyltriethoxysilane (KH550) and reflux at 90℃ for 8h to obtain amino-modified silica. Dry it under vacuum at 40℃ for 48h to obtain KH550-modified nano-silica (KH550-SiO2). Step 2: Take 200g of cleaned and dried PET bottle crushed material (intrinsic viscosity 0.65 dL / g), 600mL of ethylene glycol, and add 1g of zinc acetate (0.5% of the PET mass). React at 190℃ for 4 hours under nitrogen protection. After the reaction is complete, cool to room temperature and pour the reaction solution into 5... The precipitate was collected in cold water, filtered, and the filter cake was washed three times with deionized water. 600 mL of anhydrous xylene was added, and the mixture was heated to 80°C. Under vacuum, the mixture was dehydrated to a water content of 300 ppm. 122.4 g of isophorone diisocyanate (NCO / OH molar ratio 1.8:1) was added dropwise at 70°C, followed by 0.1375 g of dibutyltin dilaurate (0.05% of the total reactant mass). The reaction was continued for 3 hours, then cooled to 60°C. 42.72 g of N-hydroxyethyl maleimide (NCO / OH molar ratio 1:1) was added, and the reaction continued for 1 hour. After the reaction was complete, the reaction solution was slowly poured into 5 L of anhydrous ethanol to precipitate. The precipitate was filtered, and the filter cake was washed three times with anhydrous ethanol and once with anhydrous diethyl ether. The mixture was then vacuum dried at 40°C for 24 hours to obtain maleimide-terminated PET prepolymer (MI-PET). Step 3: By weight, take 0.5 parts of KH550-SiO2, 100 parts of MI-PET, 0.2 parts of pyromellitic dianhydride, 0.05 parts of antimony trioxide, and 0.1 parts of antioxidant (a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1). Mix them evenly and add them to a twin-screw extruder (the temperature of each section of the twin-screw extruder is 230℃, 245℃, 260℃, 275℃, and 265℃, the screw speed is 220r / min, and the feeding speed is 25kg / h). The material is extruded, water-cooled, and pelletized to obtain recycled PET composite chips. Step 4: Vacuum dry the composite slices at 100℃ for 12 hours until the moisture content is 40ppm. Add the slices to the spinning machine at a spinning temperature of 265℃, a spinneret orifice diameter of 0.25mm, and a spinning speed of 700m / min. Cool the filaments with side blowing air and then enter the drawing machine for a two-stage drawing process (first stage drawing temperature 75℃, drawing ratio 2.0 times; second stage drawing temperature 90℃, total drawing ratio 4.0 times). After drawing, heat set the filaments at 110℃ for 30 minutes. Finally, wind the filaments through a winding machine (winding speed 2800m / min) to obtain fumed silica recycled PET matte filaments.

[0021] Comparative Example 2: The difference between this comparative example and Example 1 is that it uses unmodified ordinary PET crushed material.

[0022] A method for preparing fumed silica recycled PET matte filament includes the following steps: Step 1: Disperse 50g of nano-fumed silica (Degussa AEROSIL R974) with a specific surface area of ​​180m² / g and a particle size of 15nm in 300mL of anhydrous xylene. Add 12.5g of γ-aminopropyltriethoxysilane (KH550) and reflux at 90℃ for 8h to obtain amino-modified silica. Then, take 50g of amino-modified silica, add 400mL of anhydrous N,N-dimethylformamide, 25g of furanylformic acid, 60g of N,N'-dicyclohexylcarbodiimide and 2.5g of 4-dimethylaminopyridine, and carry out esterification reaction at 0℃ for 24h. After centrifugation (8000rpm, 15min), washing twice with deionized water, and vacuum drying at 40℃ for 48h, obtain furan-functionalized nano-silica (Fu-SiO2). Step 2: By weight, take 0.5 parts of Fu-SiO2, 100 parts of PET water bottle crushed material (intrinsic viscosity of 0.65 dL / g), 0.2 parts of pyromellitic dianhydride, 0.05 parts of antimony trioxide, and 0.1 parts of antioxidant (a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1). Mix them evenly and add them to a twin-screw extruder (the temperature of each section of the twin-screw extruder is 230℃, 245℃, 260℃, 275℃, and 265℃, the screw speed is 220 r / min, and the feeding speed is 25 kg / h). The material is extruded, water-cooled, and pelletized to obtain recycled PET composite chips. Step 3: Vacuum dry the composite slices at 100℃ for 12 hours until the moisture content is 40ppm. Add the slices to the spinning machine at a spinning temperature of 265℃, a spinneret orifice diameter of 0.25mm, and a spinning speed of 700m / min. Cool the filaments with side blowing air and then enter the drawing machine for a two-stage drawing process (first stage drawing temperature 75℃, drawing ratio 2.0 times; second stage drawing temperature 90℃, total drawing ratio 4.0 times). After drawing, heat set the filaments at 110℃ for 30 minutes. Finally, wind the filaments through a winding machine (winding speed 2800m / min) to obtain fumed silica recycled PET matte filaments.

[0023] Performance testing 1. Broken wire rate test The operating data of the continuous spinning process over 8 hours was collected. The number of spinneret breaks and the total number of spinning heads were counted. The breakage rate (%) was calculated as (number of breaks / total number of spinning heads) × 100%, where the total number of spinning heads is the product of the number of spinneret holes and the operating time. Each sample was tested three times, and the arithmetic mean was taken.

[0024] 2 Gloss The gloss of recycled PET matte yarn was tested in accordance with the GB / T 8807-1988 standard.

[0025] Table 1. Broken fiber rate and gloss of recycled PET matte yarn

[0026] As shown in Table 1, the breakage rate of the recycled PET matte filaments prepared in the example group was less than 2.3%, significantly better than that of Comparative Example 1 (4.2%) and Comparative Example 2 (5.7%). This indicates that the use of DA dynamic covalent bond interface design combined with temperature gradient process achieved ultra-uniform dispersion of nano-silica, effectively avoiding the agglomeration problem that is difficult to overcome in traditional physical blending (Comparative Example 2) and permanent covalent bond modification (Comparative Example 1). The gloss of the example group can be flexibly adjusted within the range of 13.6-21.4 GU to meet the matte effect requirements of different application scenarios.

[0027] 3 Mechanical properties The mechanical properties of recycled PET matte yarn were tested in accordance with the GB / T 14344-2022 standard.

[0028] Table 2. Tensile strength and elongation at break of recycled PET matte yarn

[0029] As shown in Table 2, the tensile strength of the example groups all reached over 4.0 cN / dtex, far exceeding the first-grade standard for recycled polyester staple fiber (≥2.2 cN / dtex); the elongation at break remained above 35%, exhibiting both good toughness and processing performance. Comparative Example 1 (permanent covalent bond modification) had a tensile strength of 3.3 cN / dtex, still lower than the example groups; Comparative Example 2 (unmodified physical blend) had a tensile strength of only 2.8 cN / dtex, and a significantly reduced elongation at break. This indicates that the DA dynamic covalent bond interface can not only effectively transfer stress but also dissipate energy through the "sacrifice-reconstruction" mechanism of reversible bonds, achieving a dual effect of strengthening and toughening.

[0030] 4. Yellowing Index and Abrasion Resistance Test (1) Yellowing index: The colorimeter was used for testing. Finished recycled PET matte yarn was taken and tightly wound in parallel on a white standard plate to form a yarn bundle plane with a thickness of not less than 2 mm. Under the conditions of D65 light source and 10° viewing angle, the tristimulus values ​​X, Y and Z of the yarn bundle plane were measured. The yellowing index was calculated according to the following formula: Yellowing index = (1.28X - 1.06Z) / Y × 100. Five test points were randomly selected for each sample and the arithmetic mean was taken.

[0031] (2) Number of abrasion resistance: The number of abrasion resistance of recycled PET matte yarn was tested in accordance with GB / T 21196.2-2007 standard.

[0032] Table 3 Yellowing Index and Abrasion Resistance of Recycled PET Matte Yarn

[0033] As shown in Table 3, the yellowing index of the example groups was below 1.5, meeting the weather resistance requirements of high-quality PET materials (ΔY≤1.5); the number of abrasion cycles all exceeded 550, significantly better than the comparative group. Comparative Example 1 had a yellowing index of 2.1, indicating that although permanent covalent bond modification provided some protection, high-temperature processing still led to partial thermal oxidation; Comparative Example 2 had a yellowing index as high as 3.3 and a number of abrasion cycles of only 340, indicating that nanoparticles in the physical blend system were prone to detachment and could not provide lasting protection. The superior performance of the example groups is attributed to the reversibility of the DA bonds reducing the thermal history during processing, the chemically anchored nano-interface preventing particle migration and detachment, and the synergistic effect of the antioxidant system and dynamic bonds.

[0034] 5 Production Qualification Rate Take the operating data of 8 hours in the continuous spinning production process, count the total output and the output of qualified products, and calculate the production qualification rate (%) = (output of qualified products / total output) × 100%. Among them, qualified products refer to finished yarns that are free of fuzz, broken ends and defects, and whose luster and mechanical properties meet the quality standards.

[0035] 6. Calculation of Added Value Enhancement Rate Based on the market price of ordinary recycled PET glossy yarn of the same specification, the market price of the recycled PET matte yarn of the present invention is calculated, and the added value increase rate (%) is calculated as follows: [(Market price of matte yarn of the present invention - Market price of ordinary recycled PET glossy yarn) / Market price of ordinary recycled PET glossy yarn] × 100%.

[0036] Table 4. Production qualification rate and added value improvement rate of recycled PET matte yarn

[0037] As shown in Table 4, the production qualification rate of the example groups all reached over 95%, significantly higher than that of Comparative Example 1 (89.7%) and Comparative Example 2 (82.3%). The added value improvement rate reached 32.6%-39.1%, far higher than the 8.0%-18.4% of the comparative examples. This proves that the present invention, through DA dynamic covalent bond interface design and temperature gradient process, achieves uniform dispersion and stable anchoring of nanoparticles, significantly reducing the fiber breakage rate and defect rate. At the same time, the improved product performance brings significant market premium, truly realizing the high-value recycling of recycled PET.

[0038] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing fumed silica recycled PET matte filament, characterized in that, Includes the following steps: Step 1: Disperse nano-sized fumed silica with a specific surface area of ​​180-220 m² / g and a particle size of 15-25 nm in xylene, add γ-aminopropyltriethoxysilane (KH550), and reflux at 90-110 °C for 4-8 h to obtain amino-modified silica; then, esterify the amino-modified silica with furanylcarbohydrate in the presence of N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine at 0-25 °C for 12-24 h, centrifuge, wash, and vacuum dry to obtain furan-functionalized nano-silica (Fu-SiO2). Step 2: Mix PET bottle crushed material with intrinsic viscosity of 0.65-0.75 dL / g with ethylene glycol at a mass ratio of 1:(3-6), add an alcoholysis catalyst, and react at 190-220℃ for 2-4 hours under nitrogen protection. Dehydrate under vacuum until the water content is 300-500ppm. Add isophorone diisocyanate dropwise at 70-90℃ with an NCO / OH molar ratio of (1.8-2.2):

1. Add catalyst and react for 2-3 hours. Cool to 60-80℃ and add N-hydroxyethyl maleimide with an NCO / OH molar ratio of 1:(1-1.1). Continue the reaction for 1-2 hours. After precipitation, washing, and drying, obtain maleimide-terminated PET prepolymer (MI-PET). Step 3: By weight, take 0.5-3.0 parts of Fu-SiO2, 100 parts of MI-PET, 0.2-1.0 parts of chain extender, 0.05-0.2 parts of polycondensation catalyst, and 0.1-0.5 parts of antioxidant. Mix them evenly and add them to a twin-screw extruder. The material is extruded, cooled with water, and pelletized to obtain recycled PET composite chips. Step 4: Vacuum dry the composite chips at 100-120℃ for 8-12 hours until the moisture content is 40-50ppm. Add the chips to a spinning machine at a spinning temperature of 265-280℃, a spinneret orifice diameter of 0.25-0.35mm, and a spinning speed of 700-900m / min. Cool the filaments with side blowing air and then enter a drawing machine for a two-stage drawing process. After drawing, heat set the filaments at 110-125℃ for 10-30 minutes. Finally, wind the filaments through a winding machine to obtain fumed silica recycled PET matte filaments.

2. The method for preparing fumed silica recycled PET matte filament according to claim 1, characterized in that, In step 1, the mass ratio of amino-modified silica, furanoic acid, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 1:(0.5-2):(1.2-2):(0.05-0.2).

3. The method for preparing fumed silica recycled PET matte filament according to claim 1, characterized in that, In step 1, the vacuum drying conditions are 40-60℃ for 24-48 hours.

4. The method for preparing fumed silica recycled PET matte filament according to claim 1, characterized in that, In step 2, the alcoholysis catalyst is zinc acetate (Zn(Ac)2), and the amount added is 0.5%-1.0% of the PET mass; the catalyst is dibutyltin dilaurate, and the amount added is 0.05%-0.1% of the total mass of the reactants.

5. The method for preparing fumed silica recycled PET matte filament according to claim 1, characterized in that, In step 3, the chain extender is pyromellitic dianhydride (PMDA); the polycondensation catalyst is antimony trioxide; and the antioxidant is a compound of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:

1.

6. The method for preparing fumed silica recycled PET matte filament according to claim 1, characterized in that, In step 3, the temperature of the twin-screw extruder is 230-275℃, the screw speed is 220-280 r / min, and the feeding speed is 25-35 kg / h.

7. The method for preparing fumed silica recycled PET matte filament according to claim 1, characterized in that, The two-stage drawing process in step 4 is as follows: the first stage drawing temperature is 75-85℃, and the drawing ratio is 2.0-2.5 times; the second stage drawing temperature is 90-100℃, and the total drawing ratio is 4.0-5.0 times.

8. The method for preparing fumed silica recycled PET matte filament according to claim 1, characterized in that, In step 4, the winding speed is 2800-3200 m / min.

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