A discoloration-resistant degradable polyester upper material and processing technology

Abstract

This invention relates to the field of polymer material processing and footwear manufacturing technology, specifically to a colorfast and biodegradable polyester upper material and its processing technology, including the following steps: S100, raw material pretreatment: the biodegradable polyester matrix is ​​dehydrated and dried, and the composite wear-resistant reinforcing phase and coupling agent are surface-modified and premixed; S200, first-stage reactive extrusion: the dried biodegradable polyester matrix, the premixed composite wear-resistant reinforcing phase, and the reactive toughening end-capping agent are added to the main feed port of a twin-screw extruder. This invention utilizes a specific segmented rheological processing technology and a chemical formulation system to synergistically couple the epoxy functional groups of the reactive toughening end-capping agent with the free end carboxyl groups generated by polyester chain scission in the first high-temperature zone of the extruder to undergo an in-situ ring-opening addition reaction, thereby forcibly cutting off the protonic acid autocatalytic degradation pathway that leads to molecular weight decay and structural yellowing from the source of chemical kinetics.

Description

Technical Field

[0001] This invention relates to the fields of polymer material processing and footwear manufacturing technology, specifically to a colorfast and biodegradable polyester upper material and its processing technology. Background Technology

[0002] In recent years, with increasingly stringent environmental regulations and the promotion of sustainable development concepts, the use of biodegradable polyesters (such as polylactic acid PLA, polybutylene succinate PBS, and polybutylene adipate / terephthalate terephthalate PBAT) to replace traditional non-degradable petroleum-based polyesters (such as PET) in the preparation of environmentally friendly shoe upper materials has become a key development direction in the footwear materials industry. However, due to the large number of aliphatic ester bonds in their macromolecular backbone, biodegradable polyesters suffer from serious defects in colorfastness and thermomechanical stability when processed into shoe upper materials for industrial applications.

[0003] Specifically, the core technical problem in this field lies in the "autocatalytic degradation of terminal carboxyl groups" and the accompanying structural yellowing of biodegradable polyesters under high-temperature flow field processing and service environments. During the melt extrusion, granulation, and subsequent secondary high-temperature melt spinning or casting of biodegradable polyesters, the polyester matrix is ​​subjected to high-temperature enthalpy and strong mechanical shear forces, making the ester bonds on its molecular chains highly susceptible to thermo-oxidative chain scission and hydrolytic chain scission induced by trace amounts of moisture. After the ester bonds break, a large number of free terminal carboxyl groups (-COOH) are released. These free terminal carboxyl groups exhibit significant protic acid characteristics in the system, acting as a catalytic medium to further accelerate the cleavage of unbroken ester bonds, thus forming a vicious cycle of autocatalytic degradation. This reaction directly leads to a sharp decrease in the weight-average molecular weight of the polyester, macroscopically manifested as material embrittlement and a significant reduction in abrasion resistance and tensile strength. Meanwhile, excessive degradation of molecular chains and oxidation and recombination of end groups can generate conjugated double bonds or chromophores, causing the material to show a yellowish background when it comes off the production line. Furthermore, the yellowing index will increase exponentially when exposed to ultraviolet radiation and sweat during subsequent service.

[0004] To address the aforementioned discoloration and degradation issues, existing conventional solutions typically involve directly adding antioxidants or light stabilizers during the initial stage of polyester melt blending for physical blending. However, in such conventional processing, highly active antioxidants and anti-yellowing auxiliaries must undergo a long-term, high-temperature, high-shear extrusion process with the polyester matrix. Under prolonged thermomechanical coupling, heat-sensitive auxiliary molecules are prone to premature thermal decomposition, losing their free radical capturing and quenching activity; some degraded auxiliaries may even transform into chromophores, triggering the negative effect of "auxiliary-induced yellowing." Furthermore, simple physical antioxidants cannot eliminate the autocatalytic activity of the generated terminal carboxyl groups at the source of chemical kinetics, making it difficult for the final biodegradable shoe upper material to simultaneously achieve high processing rheological stability, long-term resistance to UV yellowing, and excellent mechanical retention. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a processing technology for a colorfast and biodegradable polyester shoe upper material. The processing technology employs segmented side feeding and in-situ reactive extrusion, and specifically includes the following steps:

[0007] S100, Raw material pretreatment: The biodegradable polyester matrix is ​​dehydrated and dried, and the composite wear-resistant reinforcing phase and coupling agent are surface-modified and premixed;

[0008] S200, First-stage reactive extrusion: The dried biodegradable polyester matrix, the premixed composite abrasion-resistant reinforcing phase and the reactive toughening end-capping agent are added to the main feed port of a twin-screw extruder and melt-blended in the first temperature range, so that the reactive toughening end-capping agent and the end carboxyl groups of the polyester melt undergo an in-situ end-capping reaction.

[0009] S300, Second-stage side feeding: In the middle and downstream section of the twin-screw extruder, a multidimensional anti-discoloration synergistic factor is added through a side feeder to carry out short-range melt blending in a second temperature range lower than the first temperature range;

[0010] S400, Exhaust Granulation: The blended melt after the second-stage side feeding is subjected to vacuum exhaust treatment, and then extruded, drawn, cooled and granulated to obtain modified polyester granules.

[0011] S500, Upper Molding: The modified polyester granules are melt-processed to prepare the colorfast and biodegradable polyester upper material.

[0012] Furthermore, the biodegradable polyester matrix is ​​composed of polylactic acid and flexible blended polyester in a mass ratio of 2:1 to 4:1;

[0013] The flexible blended polyester is selected from polybutylene succinate or polybutylene adipate / terephthalate.

[0014] In step S100, the process parameters for the dehydration and drying treatment include: controlling the drying temperature at 80°C to 90°C and the drying time at 8 to 12 hours under a vacuum of ≤-0.08MPa, and ensuring that the moisture content of the biodegradable polyester matrix after treatment is less than 0.02%.

[0015] Furthermore, the composite wear-resistant reinforcing phase is nanocellulose and / or modified biomass lignin, the coupling agent is a silane coupling agent containing epoxy groups, and the mass ratio of the composite wear-resistant reinforcing phase to the coupling agent is 100:1.5 to 100:3.0;

[0016] The surface modification premixing is performed under the following conditions: using a high-speed mixing device, the temperature is raised to 85°C~95°C by relying on the dynamic friction between the materials, and the mixture is maintained at this temperature range for 10~15 minutes to complete the surface coating of the composite wear-resistant reinforcing phase.

[0017] Furthermore, in step S200, the addition ratio of each raw material component is as follows by weight:

[0018] The biodegradable polyester matrix is ​​70-85 parts;

[0019] The composite wear-resistant reinforcing phase consists of 2 to 6 parts;

[0020] The reactive toughening end-capping agent is 3-8 parts;

[0021] The reactive toughening end-capping agent is selected from styrene-acrylate copolymer oligomers containing multiple epoxy functional groups or copolymers containing oxazoline groups.

[0022] The in-situ end-capping reaction specifically involves the epoxy group or oxazoline group in the reactive toughening end-capping agent undergoing a ring-opening addition reaction with the terminal carboxyl group generated by the chain scission of the biodegradable polyester matrix under the action of melt shear force, thereby blocking the autocatalytic degradation pathway of the polyester material by the terminal carboxyl group.

[0023] In step S200, the first temperature range adopts a progressive stepped temperature control arrangement, specifically set as follows:

[0024] The temperature of the feeding zone of the twin-screw extruder is 160°C~170°C;

[0025] The temperature of the melt reaction zone of the twin-screw extruder is 185°C to 195°C, and the residence time of the material in the melt reaction zone is 60 to 120 seconds to ensure the conversion rate of the in-situ end-capping reaction.

[0026] Further, in step S300, relative to the total weight of the raw materials added in step S200, the amount of the multidimensional anti-discoloration synergistic factor added is 1.5 to 4 parts by weight.

[0027] The multidimensional anti-color change synergistic factor is composed of hindered amine light stabilizer, reactive ultraviolet absorber and phosphite antioxidant in a mass ratio of 2:1:1.

[0028] The reactive ultraviolet absorber is a benzotriazole acrylate containing hydroxyl groups;

[0029] The mechanism of action of the multidimensional anti-color change synergistic factor is as follows: the phosphite antioxidant helps to capture free radicals generated during polyester thermal processing, and combined with the long-term free radical quenching effect of the hindered amine light stabilizer and the ultraviolet shielding effect of the reactive ultraviolet absorber, a multidimensional anti-ultraviolet and anti-hydrolysis synergistic protection network is formed inside the polyester matrix.

[0030] Furthermore, in step S300, the temperature of the second temperature range is set to 180°C~185°C;

[0031] The side feeder is positioned at the rear 1 / 3 to 1 / 4 of the length-to-diameter ratio of the main barrel of the twin-screw extruder, so that the melt blending time of the multidimensional anti-discoloration synergistic factor is shorter than the in-situ end-capping reaction time in step S200, thereby avoiding the early thermal decomposition of the multidimensional anti-discoloration synergistic factor under long-range high-temperature shear.

[0032] Furthermore, in step S400, the vacuum degree of the vacuum exhaust treatment is strictly controlled between -0.08MPa and -0.095MPa, which is used to forcibly remove the low molecular weight byproducts, free monomers and residual trace moisture generated in the in-situ end-capping reaction in step S200, so as to prevent the blended melt from undergoing micro-foaming and secondary hydrolysis degradation at the extrusion die.

[0033] Furthermore, the specific process conditions for cooling and pelletizing are as follows:

[0034] The blended melt is extruded into a continuous strip through an extrusion die and then drawn into a constant temperature water cooling tank for flexible curing. The temperature of the constant temperature water cooling tank is maintained at 25°C~35°C.

[0035] After the cured material strip is thoroughly blown away by a high-pressure air knife to remove the surface moisture, it is fed into a pelletizer to cut the modified polyester pellets, and the cutting length is controlled to be 2.5mm~3.5mm.

[0036] Furthermore, in step S500, the upper forming specifically adopts a melt spinning weaving process or an extrusion casting composite process;

[0037] When using the melt spinning weaving process, the specific operation is as follows:

[0038] The modified polyester granules are dried and fed into a spinning box, where they are melt-extruded at a spinning temperature of 190°C to 200°C. They are then sequentially cooled by side blowing, oiled, subjected to multi-stage stretching and heat setting, and wound to obtain high-strength polyester filaments.

[0039] Finally, the high-strength polyester filaments are 3D woven using a computerized flat knitting machine to create a one-piece knit upper.

[0040] When the extrusion casting composite process is used, the specific operation is as follows:

[0041] The modified polyester granules are extruded into a continuous polymer film through a casting die at 185°C~195°C;

[0042] In the roll bonding stage, the polymer film in a semi-molten state is hot-pressed and laminated with a biodegradable base fabric, and after cooling, non-woven shoe upper leather is obtained.

[0043] On the other hand, a colorfast and biodegradable polyester shoe upper material, by weight, comprises the following raw material components:

[0044] Biodegradable polyester matrix: 70-85 parts;

[0045] Reactive toughening end-capping agent: 3-8 parts;

[0046] Composite wear-resistant reinforcing phase: 2-6 parts;

[0047] Multidimensional anti-discoloration synergistic factor: 1.5~4 parts;

[0048] The reactive toughening end-capping agent can undergo an in-situ end-capping reaction with the end carboxyl groups of the biodegradable polyester matrix;

[0049] The multidimensional anti-color change synergistic factor is composed of hindered amine light stabilizers, reactive ultraviolet absorbers, and phosphite antioxidants.

[0050] Beneficial effects

[0051] This invention utilizes a specific segmented rheological processing technology and a chemical formulation system for synergistic coupling. In the first high-temperature zone of the extruder, the epoxy functional groups of the reactive toughening end-capping agent undergo an in-situ ring-opening addition reaction with the free end carboxyl groups generated by polyester chain scission. This forcibly severs the protic acid autocatalytic degradation pathway that leads to molecular weight decay and structural yellowing from the source of chemical kinetics. Simultaneously, in the second cooling zone, the aspect ratio spatial delay is used to achieve lateral short-range feeding, seamlessly introducing a multidimensional anti-coloring synergistic factor composed of hindered amines, reactive UV absorbers, and phosphites into the polyester matrix. This avoids the early thermal decomposition and deactivation of functional additives under long-range high temperature and high shear conditions, constructing a three-dimensional protective network against UV and hydrolysis within the material. Combined with the micro-crosslinking directional distribution of the composite wear-resistant reinforcing phase in the rheological field and the end-flexible water-cooling curing mechanism, while maintaining the excellent biodegradability of the polyester material, the yellowing effect of the matrix under secondary thermoforming and long-term photothermal exposure is effectively suppressed, and the micro-compatibility, tensile strength, and dynamic fatigue resistance of the final molded shoe upper are significantly improved. Attached Figure Description

[0052] Figure 1 This is a flowchart of the processing technology of the present invention;

[0053] Figure 2 This is a cross-sectional view of the multilayer composite material of the shoe upper of the present invention. Detailed Implementation

[0054] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0055] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but includes other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0056] The present invention will now be described in further detail with reference to the accompanying drawings:

[0057] Example 1:

[0058] like Figure 1 As shown, a processing technology for a colorfast and biodegradable polyester shoe upper material is employed, which utilizes segmented side feeding and in-situ reactive extrusion technology. The specific steps include:

[0059] S100, Raw material pretreatment: The biodegradable polyester matrix is ​​dehydrated and dried, and the composite wear-resistant reinforcing phase and coupling agent are surface-modified and premixed;

[0060] S200, First-stage reactive extrusion: The dried biodegradable polyester matrix, the premixed composite abrasion-resistant reinforcing phase and the reactive toughening end-capping agent are added to the main feed port of the twin-screw extruder and melt-blended in the first temperature range, so that the reactive toughening end-capping agent and the end carboxyl groups of the polyester melt undergo an in-situ end-capping reaction.

[0061] S300, Second-stage side feeding: In the middle and downstream section of the twin-screw extruder, a multidimensional anti-discoloration synergistic factor is added through a side feeder to carry out short-range melt blending in a second temperature range lower than the first temperature range;

[0062] S400, Exhaust Granulation: The blended melt after two-stage side feeding is subjected to vacuum exhaust treatment, and then extruded, drawn, cooled and granulated to obtain modified polyester granules.

[0063] S500, Upper Molding: Modified polyester granules are melt-processed to prepare a colorfast and biodegradable polyester upper material.

[0064] Furthermore, the specific implementation process of step S100 is as follows:

[0065] The raw material pretreatment process in step S100 is divided into a dehydration and drying step of the matrix resin and a surface chemical grafting step of the reinforcing phase. The two are processed in parallel using independent equipment.

[0066] Dehydration and drying process of biodegradable polyester matrix:

[0067] Polylactic acid (PLA) with a weight-average molecular weight of 120,000 and polybutylene adipate terephthalate (PBAT) with a weight-average molecular weight of 90,000 were dry-mixed at a mass ratio of 3:1 to construct a biodegradable polyester matrix. The mixed resin particles were fed into a double-cone rotary vacuum dryer. A water ring vacuum pump and a Roots vacuum pump unit, operating in series, were used to extract and maintain the operating system pressure inside the dryer within a constant absolute vacuum range of -0.085 MPa to -0.090 MPa. Simultaneously, the heat transfer oil circulation heating system of the dryer jacket was activated, and the jacket heating temperature was set and controlled at 85°C. The dryer cylinder continuously rotated and tumbled at a speed of 15 rpm, causing the resin particles to form a continuous sliding microbed inside the cylinder. Under the set temperature and negative pressure gradient, bound water and free water molecules inside the resin particles overcame capillary resistance and diffused to the particle surface, then rapidly vaporized and were extracted by the vacuum flow field. The above dynamic vacuum thermodynamic state was maintained for 10 hours. A polyester matrix sample was extracted and Karl Fischer moisture titration was performed to confirm that the final absolute moisture content of the system was strictly reduced to an extremely low threshold of 0.015%. Subsequently, the vacuum was released and high-purity nitrogen was introduced for micro-positive pressure sealing and pressure maintenance to prevent secondary contact with ambient moisture.

[0068] Surface modification premixing process of composite wear-resistant reinforcing phase:

[0069] 100 parts by weight of nanocellulose (average radial dimension 20-50 nm, aspect ratio greater than 50) were weighed and added to the homogenization chamber of a high-speed mixer with a jacketed cooling structure. The main drive shaft of the mixer was started and its speed was set to 1500 rpm. The high-speed shearing of the blades caused the nanocellulose powder to overcome van der Waals forces and form a highly dispersed fluidized turbulent flow field within the chamber. Subsequently, 2.5 parts by weight of a silane coupling agent containing epoxy groups (specifically γ-(2,3-epoxypropoxy)propyltrimethoxysilane, brand name KH-560) was continuously sprayed into the fluidized powder through a pneumatic atomizing nozzle at a feed rate of 5 ml / min. During the spraying and mixing process, the coupling agent droplets collided with the nanocellulose particles at high frequency, and strong dynamic mechanical friction and shearing forces were generated between the powder particles, between the particles and the blades and the chamber wall. The work done by the machine is directly converted into the system's internal frictional heat, causing the material system temperature to rise at a rate of 3°C to 5°C per minute.

[0070] When the internal sensor detects that the core temperature of the material reaches 90°C, the main drive shaft speed is finely adjusted to maintain a constant system thermal balance, locking the temperature at 90°C and continuing isothermal mixing for 12 minutes. During this isothermal high-shear stage, the methoxy groups at the ends of the silane coupling agent molecules undergo a hydrolysis ring-opening reaction using trace amounts of bound water adsorbed on the surface of nanocellulose, generating a silanol intermediate structure in situ. The free silanol then undergoes a dehydration condensation reaction with the hydroxyl active sites on the surface of nanocellulose, forming a stable Si-OC covalent bond. The unreacted methanol byproduct overflows in gaseous form through the exhaust valve at the top of the mixer. This process completes the high-density monolayer chemical grafting coating of epoxy functional groups on the surface of nanocellulose, producing a pre-treated composite wear-resistant reinforcing phase, which is then sealed and left to stand for later use.

[0071] Furthermore, the specific implementation process of step S200 is as follows:

[0072] In this embodiment, the first-order reactive extrusion process in step S200 is continuously executed on a co-rotating parallel twin-screw extruder platform with a length-to-diameter ratio of 48:1. The core of this process lies in inducing a highly efficient liquid-phase bulk chemical reaction between polymer chain segments through precise temperature control in the rheological field and the mechanical work of the screw shear configuration.

[0073] Continuous metering and phase transition processes for materials:

[0074] A multi-set loss-in-weight precision feeder system is activated to simultaneously and continuously feed the dehydrated and dried biodegradable polyester matrix (80 parts by weight), the surface-modified composite wear-resistant reinforcing phase (5 parts by weight), and the styrene-acrylate copolymer oligomer reactive toughening end-capping agent (5 parts by weight, the oligomer main chain side groups containing a high-density epoxy functional group skeleton) obtained in step S100 into the main feed port of the twin-screw extruder according to the reference formula ratio. The main feed section and the first zone of the twin-screw extruder are insulated with cold water circulation, and the feed preheating temperature range of zones two and three is set at 165°C. The material is propelled forward by the axial thrust of the twin-screw forward conveying thread element. The heat conduction of the barrel wall causes the surface temperature of the solid resin particles to cross the glass transition temperature, gradually transitioning to a highly elastic and viscous flow state, avoiding instantaneous torque overload and bridging accumulation at the feed port caused by the friction of the polymer solid phase in the low-temperature section.

[0075] The specific process of the in-situ end-capping addition reaction:

[0076] As the material is conveyed to zones four through six of the extruder, the designated melt reaction zone, the barrel heater stabilizes the ambient temperature gradient in this zone at 190°C. The screw configuration in this zone features multiple sets of interlocking kneading block elements with staggered angles of 45 degrees and 90 degrees. Under the dual coupling of thermodynamic and strong mechanical shear flow fields, the polyester matrix undergoes a phase transformation, completely disintegrating the crystalline structure and forming a homogeneous viscoelastic melt. Inside the melt, the polyester molecular chains undergo conformational disentanglement and chain segment extension under shear stress, fully exposing the free terminal carboxyl groups (-COOH) active sites exposed at the ends of the polyester macromolecules due to prior thermodynamic degradation or hydrolytic chain scission to the reaction field.

[0077] In this fluid state, styrene-acrylate copolymer oligomer molecules are highly dispersed along with melt convection. The epoxy groups on the oligomer segments act as electrophiles, undergoing high-frequency collisions with dissociated protons in the terminal carboxyl groups of the polyester under the activation energy of 190°C, thus crossing the reaction energy barrier and initiating a typical nucleophilic ring-opening addition chemical reaction. The oxygen atom of the epoxy group combines with the hydrogen proton of the carboxyl group to form a secondary hydroxyl group, while the epoxy carbon atom bonds with the carboxyl oxygen atom, transforming into an extremely stable ester bond structure. This irreversible chemical bonding process consumes the terminal carboxyl groups with protonic acid catalytic properties in situ, forcibly severing the autocatalytic degradation cycle path that leads to yellowing and a sharp collapse in molecular weight of the degradable polyester at its source.

[0078] Constraints and control of reaction kinetic parameters:

[0079] To ensure the reaction conversion rate of the aforementioned multiphase reaction system while avoiding thermal degradation of the polyester backbone, the spindle speed of the twin-screw extruder was adjusted to 240 rpm, and the total throughput of the feeding system was set accordingly. This forced the full residence time of the blended melt in the 190°C melting reaction zone to be constrained to 90 seconds. This residence period meets the kinetic threshold requirements of the epoxy-carboxyl ring-opening reaction, ensuring that the end-capping reaction conversion rate reaches over 95%, while avoiding the side reactions of polymer backbone lactone exchange that may be caused by prolonged thermal history. After the chemical recombination of micro-molecules is completed, the polymer melt containing the in-situ end-capped structure is smoothly transported to the subsequent mid-to-downstream temperature zone of the extruder, constructing a stable and purified polyester fluid base for the subsequent introduction of secondary materials.

[0080] Furthermore, the specific implementation process of step S300 is as follows:

[0081] In this embodiment, the second-stage lateral feeding process in step S300 utilizes the aspect ratio delay in the spatial layout of the extruder and the stepped cooling of the temperature control field to construct a short-range low-temperature blending microenvironment for the thermosensitive photo-oxidation stabilizer, thereby achieving non-destructive doping and network dispersion of the anti-yellowing functional additive.

[0082] Physical definition and temperature field reconstruction of the second-order feeding space:

[0083] With the completion of the in-situ end-capping reaction in step S200, the polyester blend melt enters the downstream region of the barrel under the propulsion of the twin-screw extruder. The system precisely positions the physical access interface of the side feeder at the boundary of the last 1 / 3 to 1 / 4 of the twin-screw main shaft's length-to-diameter ratio (L / D) (i.e., the seventh temperature zone of the extruder). To protect the highly reactive additives to be introduced, the barrel control system implements an independent forced water cooling and heater-coordinated fine-tuning program for zones seven to nine, forcibly reducing the operating temperature environment of this zone from the previous high-temperature reaction state of 190°C and strictly locking it at 182°C (i.e., within the second temperature range threshold of 180°C to 185°C). This temperature gradient causes a slight increase in the rheological viscosity of the polyester melt within a controllable range, providing the necessary melt back pressure support for the shear dispersion of subsequent additives, while simultaneously preventing the premature thermal degradation of heat-sensitive chemical components by the residual enthalpy in the system.

[0084] The compounding and non-destructive forced feeding process of multidimensional anti-discoloration synergistic factors:

[0085] Before the side-feeding action is executed, a multidimensional anti-discoloration synergistic factor is prepared in an external high-speed mixing device. Based on the total weight of the raw materials added in step S200, 2.5 parts by weight of the mixed additive are accurately weighed. This system consists of a macromolecular hindered amine light stabilizer (e.g., light stabilizer 944), an acrylate reactive UV absorber containing a hydroxybenzotriazole structure, and a phosphite auxiliary antioxidant (e.g., antioxidant 168) pre-mixed in a strict mass specification ratio of 2:1:1. This powder composite is loaded into the hopper of a side-feeder equipped with an independent servo motor. The twin screw speed of the side-feeder is set to a synchronous coupling ratio that matches the speed of the main extruder. Utilizing the forced engagement thrust of the side screws, the room-temperature multidimensional anti-discoloration synergistic factor overcomes the radial back pressure of the melt in the main extruder and is instantaneously and continuously forced into the 182°C polyester main melt flow.

[0086] Microscopic construction mechanism of multi-protection networks in short-range shear fields:

[0087] After the multidimensional anti-discoloration synergistic factor enters the barrel, it is subjected to high-frequency shearing and stretching action by the mixing elements distributed by the main screw in the short-range melt blending zone (where the residence time is physically defined within an extremely short period of 20 to 30 seconds). This causes it to melt rapidly and penetrate into the polyester matrix at the nanoscale. During this hydrodynamic process, the three chemical components undergo phase separation and directional arrangement within the free volume of the polyester due to their differences in polarity and molecular weight.

[0088] The specific microscopic mechanism is as follows: Phosphite antioxidants, acting as peroxide decomposers, preferentially capture primary free radicals and hydroperoxides generated by friction in localized high-shear regions of the polyester melt, initiating redox reactions to generate harmless alcohol compounds and severing the initiation source of chain oxidation reactions. Macromolecular hindered amine light stabilizers, utilizing their steric hindrance configuration, uniformly colonize the amorphous regions of the polyester molecular chains, exerting a long-lasting free radical quenching function. Simultaneously, reactive UV absorbers containing hydroxybenzotriazole structures, through the unsaturated double bonds of their acrylate end groups, undergo micro-crosslinking and anchoring with the matrix under the drive of residual heat, thereby forming a spatially layered broadband UV shielding isolation band around the polyester macromolecular backbone. These three components complement each other in terms of steric hindrance distribution and chemical consumption rate, constructing a multidimensional, synergistic physical-chemical composite protective network against UV and hydrolysis within the polyester matrix under the prerequisite of not undergoing high-temperature thermal decomposition. The modified polyester melt, after completing the dispersion of the additives, is then smoothly pushed into the final exhaust and pressure-building zone of the extruder.

[0089] Furthermore, the specific implementation process of step S400 is as follows:

[0090] In this embodiment, the exhaust granulation process in step S400 is the final core engineering step after the polymer melt undergoes complex physical blending and chemical modification, achieving gas-liquid separation, phase solidification, and geometric standardization. The fluid dynamics control and thermodynamic solidification trajectory of this step directly determine the apparent density and molecular weight retention of the final modified polyester granules.

[0091] Vacuum degassing and gas-liquid phase separation devolatilization process of blended melts:

[0092] After undergoing two-stage lateral feeding and short-path blending, the polyester melt enters the vacuum exhaust and pressure build-up zone located at the end of the barrel under axial conveying by a twin-screw extruder. In this section, the screw configuration changes from a mixing element to a large-lead deep-groove conveying element, causing a sudden drop in the melt fill level inside the barrel. The polymer melt is then stretched into a dynamic thin film layer with a huge specific surface area on the screw groove surface. At this point, the high-vacuum pump unit connected to the barrel exhaust port is started, and the absolute value of the negative pressure in the exhaust chamber is strictly locked at -0.090 MPa (compliant with the process constraint range of -0.08 MPa to -0.095 MPa) through a precision proportional valve.

[0093] Driven by the combined coupling of this high vacuum negative pressure field and the residual enthalpy of the melt at 185°C, the gas-phase equilibrium within the system is forcibly disrupted. Trace amounts of methanol byproducts generated from the hydrolysis and condensation of the coupling agent in step S100, low-molecular-weight oligomers that may overflow due to side-chain breakage during the in-situ end-capping reaction in step S200, trace amounts of residual free monomers, and trace amounts of moisture instantly overcome the surface tension and rheological viscous resistance of the polymer melt, resulting in a violent flash phase transition. The vaporized volatiles are rapidly stripped from the barrel by the vacuum suction flow field. This deep forced devolatilization mechanism completely eliminates the latent bubble sources within the melt, eradicating the micro-foaming runaway phenomenon caused by a sudden pressure drop at the extrusion die from a fluid dynamics perspective, and eliminating the potential for secondary hydrolysis and degradation caused by moisture from a chemical thermodynamics perspective.

[0094] Extrusion rheology and flexible curing process for continuous strips:

[0095] After purification and devolatilization, the blended melt is pressurized at the screw end and pushed to the extruder head. After passing through multiple layers of dense stainless steel metal filters (to establish stable extrusion back pressure and filter out gel), it is extruded through a porous die at a constant rheological temperature of 185°C into multiple smooth, dense, continuous polymer fluid strips. Subsequently, under the constant tension of the traction rollers, the strips are immersed at a specific angle into a constant temperature water-cooling bath equipped with a forced water circulation temperature control system.

[0096] The operating water temperature of the water-cooling bath is locked at 30°C by a high-precision heat exchange system (compliant with the process calibration range of 25°C to 35°C). This specific gradient of warm water bath environment performs a "flexible curing" heat treatment on the biodegradable polyester strips. Unlike traditional ice-water quenching, which causes the molecular chain segments to freeze instantly and leaves huge residual thermal shrinkage stress in the amorphous region, the 30°C flexible cooling medium allows the polyester macromolecular chains to undergo microscale stress relaxation and orderly growth of local crystal nuclei within the critical window period of the transition from the viscous flow state to the glassy state. This special phase evolution trajectory significantly reduces the macroscopic brittleness of the strips, endowing them with excellent axial and radial cutting toughness.

[0097] Surface dehydration and standard geometric pelletizing process:

[0098] The continuous strip, having undergone flexible curing and possessing sufficient mechanical strength, is pulled out of the water and then passed laterally through a high-pressure air knife system equipped with bidirectional slit nozzles. The air knife generates a high-speed airflow wall with an air dynamic pressure of 0.6 MPa. Utilizing the strong momentum and shearing force of the airflow, the attached water film on the surface of the strip and the residual water droplets in the microscopic capillaries are completely peeled off and dried. This ensures that the strip enters the final process in an absolutely dry surface physical state, preventing moisture from causing hydrolysis and deactivation of the material during subsequent storage.

[0099] Absolutely dry continuous strips are fed parallel into a cantilevered rotary pelletizer under the control of guide rollers. The rotational speed of the pelletizer's moving blade roller and the traction linear speed are electrically and rigidly synchronized via a PLC system. During high-speed shearing engagement, the moving blade and the fixed blade precisely cut the continuous strip, which possesses cutting toughness, into standardized cylindrical modified polyester pellets with a length of 3.0 mm and a diameter of approximately 2.5 mm. Thanks to the pre-treatment flexible curing mechanism, the cut cross-section is smooth and flat, without the dusting, chipping, or debris shedding common in brittle materials, ensuring excellent geometric uniformity and volumetric density stability during subsequent shoe upper molding. The final pellets are graded by a vibrating screen and then heat-sealed in vacuum aluminum foil moisture-proof bags.

[0100] Furthermore, the specific implementation process of step S500 is as follows:

[0101] In this embodiment, the upper forming process in step S500 utilizes the thermoplastic rheological characteristics of modified polyester granules to transform them from a microscopic blend system into a macroscopic upper product through a secondary thermal process. To cover different end-use footwear and apparel applications, this embodiment discloses two independent macroscopic forming physical evolution routes: melt spinning and weaving process and extrusion casting composite process.

[0102] The specific physical evolution and mechanical forming steps of the melt spinning and weaving process:

[0103] The modified polyester granules obtained in step S400 were vacuum drum dried to a moisture content of less than 0.005%, and then fed into a spinning-specific single-screw extruder using a closed-loop negative pressure conveying system. The extruder's melting temperature range was set in an increasing gradient from 190°C to 200°C. The granules underwent secondary melting under this temperature field. Thanks to the in-situ end-capping structure and multidimensional UV / hydrolysis synergistic network constructed in previous steps S200 and S300, the polyester melt maintained stable weight-average molecular weight even after undergoing a secondary high-temperature shear process at close to 200°C, without significant segmental thermal degradation, breakage, or yellowing.

[0104] The homogenized polyester melt is conveyed to a spinning box equipped with a heat-conducting oil circulation heating system. After being forcibly distributed at a constant volumetric flow rate by a high-precision gear metering pump, it is extruded into the spinning assembly with a back pressure of 15MPa to 20MPa and ejected from the micron-sized capillaries of the spinneret, forming a continuous melt stream. During its vertical descent, the melt stream is vertically cut into a lateral blowing cooling field with a temperature of 20°C and a wind speed of 0.5 m / s. Under the dual action of heat and mass exchange and traction tension, the polymer chain segments undergo axial high-orientation and freezing at the instant they cross the glass transition temperature, completing the phase transition from a viscous flow state to solid nascent fibers.

[0105] After the nascent fibers are coated with an antistatic oil by an oiling assembly, they are continuously introduced into a multi-stage drawing and heating roller (Godet roller) system. Under the speed difference between the drawing rollers (drawing ratio set to 3.5 to 4.5 times) and in a contact-type heat conduction coupling field of 120°C, the amorphous molecular chains inside the nascent fibers undergo irreversible plastic stretching deformation and forced crystallization. The crystalline regions align along the axial height, thus endowing the fibers with a breaking strength exceeding 6.0 cN / dtex. Subsequently, the fibers undergo stress relaxation on a heat-setting roller at 160°C to eliminate residual internal stress, and are finally formed into high-strength polyester filament bobbins under constant tension by a winding machine. This high-strength polyester filament is then fed into a computer-controlled flat knitting machine with a needle pitch of 14G. Based on a preset CAD three-dimensional digital model of the shoe upper, the spatial three-dimensional structure of the integrated seamless flyknit shoe upper is constructed through the precise coordination of the knitting needles' looping, gathering, and floating yarn mechanical motion mechanisms.

[0106] The specific physical evolution and mechanical forming steps of the extrusion-cast composite process:

[0107] The dried modified polyester granules are fed into a cast single-screw extruder equipped with a static mixer, and the barrel and die temperatures are precisely locked within a control range of 185°C to 195°C. The molten modified polyester fluid enters the coat hanger-type T-die through the connecting neck. Under the hydrodynamic regulation of the manifold channels and chokes inside the die, the cylindrical melt is forced to extend and be extruded along the transverse die lip slit, forming a uniform, wide, and continuous polymer melt network in a semi-molten, highly elastic state.

[0108] At the critical point where the molten network is vertically descending and about to contact the cooling casting roller, the constant tension unwinding mechanism is simultaneously activated. This introduces the pre-prepared biodegradable base fabric (such as polylactic acid nonwoven fabric or plain woven fabric) into the mechanical roller clamping jaws (Nip zone) formed by the cooling casting roller and the rubber compaction roller at a matched linear speed. Under the lateral linear pressure provided by the roller clamping jaws, the semi-molten polyester network, relying on its excellent fluidity, is forced to penetrate and embed itself deep into the three-dimensional micropores of the surface fibers of the biodegradable base fabric.

[0109] The composite material is then pressed tightly against the surface of a casting roller with internal cooling water at 20°C, undergoing a wrap-around angle of approximately 180 degrees. Under the rapid cooling and heat conduction mechanism, the polyester melt network instantly solidifies and shrinks, forming a high-strength physical-mechanical interlocking structure with the base fabric fibers without any chemical adhesives. Simultaneously, the high-cleanliness mirror surface or pre-set micro-nano texture of the casting roller is precisely replicated onto the solidified polyester surface layer, forming a dense "leather-like" outer layer with water-repellent and stain-resistant properties. After cooling and setting, the continuous strip composite material is trimmed of irregular edges by an edge-cutting mechanism and then wound up by a surface friction winding machine, ultimately producing a biodegradable nonwoven shoe upper leather material with excellent resistance to mechanical fatigue and colorfastness.

[0110] Example 2:

[0111] like Figure 2 As shown, a colorfast and biodegradable polyester shoe upper material comprises the following raw material components by weight:

[0112] Biodegradable polyester matrix: 70-85 parts;

[0113] Reactive toughening end-capping agent: 3-8 parts;

[0114] Composite wear-resistant reinforcing phase: 2-6 parts;

[0115] Multidimensional anti-discoloration synergistic factor: 1.5~4 parts;

[0116] Reactive toughening end-capping agents can undergo in-situ end-capping reactions with the terminal carboxyl groups of biodegradable polyester matrices;

[0117] The multidimensional anti-color change synergistic factor is composed of hindered amine light stabilizers, reactive ultraviolet absorbers, and phosphite antioxidants.

[0118] Specifically, a colorfast and biodegradable polyester shoe upper material, by weight, has the following precise material composition: 80 parts of biodegradable polyester matrix; 5 parts of reactive toughening end-capping agent; 4 parts of composite abrasion-resistant reinforcing phase; and 2.5 parts of multidimensional colorfast synergistic factor.

[0119] Microscopic characterization of the material's basic framework and the chemical bonding state of its end groups:

[0120] In the microscopic continuous phase of this material, the biodegradable polyester matrix is ​​composed of 60 parts by weight of polylactic acid and 20 parts by weight of polybutylene adipate / terephthalate. Within this matrix network, the hard crystalline regions of polylactic acid and the flexible amorphous regions of polybutylene adipate / terephthalate undergo molecular-level chain segment entanglement. There are no free reactive toughening end-capping agents (in this embodiment, a polyepoxy-functionalized styrene-acrylate copolymer oligomer is specifically used); the end-capping agent component is completely integrated into the polyester backbone network through chemical bonding. Specifically, the epoxy functional groups on the oligomer backbone have completely undergone ring-opening, with their oxygen atoms combining with the hydrogen protons of the free-terminal carboxyl groups at the ends of the polyester macromolecular chains to transform into secondary hydroxyl groups, while the epoxy carbon atoms directly form stable covalent ester bonds with the carboxyl oxygen atoms. This high-density end-group consumption mechanism causes the concentration of protic acid inside the shoe upper material to approach zero, and the polyester molecular chain changes from the original linear end-active structure to a star-shaped or micro-crosslinked passivated topology with locally long branches.

[0121] The dispersion and interfacial bonding state of the composite wear-resistant reinforcing phase in the matrix:

[0122] In the aforementioned continuous polyester phase, a nanoscale dispersed phase, namely a composite wear-resistant reinforcing phase (specifically, a phase using a nanoscale dispersed phase is employed in this embodiment), is uniformly dispersed. (2,3-Epoxypropoxy)propyltrimethoxysilane surface-modified nanocellulose). This dispersed phase did not exhibit the macroscopic agglomeration and phase separation defects commonly found in polymer blends. Through the strong dipole interaction between the surface siloxane covalent bonds and the residual epoxy groups and the polar groups of the polyester matrix, the nanocellulose constructed a dense, physically rigid support framework within the polyester matrix. This framework acts as a microscopic hub for stress transfer, allowing stress to be rapidly transferred along the polyester backbone to the high-modulus nanocellulose nodes and dissipated when the material is subjected to external mechanical friction or high-frequency bending stress.

[0123] Spatial arrangement mechanism of multidimensional UV-resistant and thermo-oxidative degradation-resistant network:

[0124] Within the free volume of the amorphous polyester region of this material, a multidimensional anti-discoloration synergistic factor is in situ implanted, consisting of a hindered amine light stabilizer (1.25 parts by weight), a reactive hydroxybenzotriazole acrylate UV absorber (0.625 parts by weight), and a phosphite antioxidant (0.625 parts by weight). The hindered amine macromolecules and phosphite molecules, relying on polarity matching with the polyester segments, are anchored around the flexible segments prone to thermo-oxidative aging with a single-molecule-level dispersion, forming a short-range chemical protective layer against free radical quenching and peroxide decomposition. In particular, the reactive UV absorber's unsaturated acrylate double bonds at its end groups have undergone micropolymerization or partial grafting reactions with the active hydrogens of the polyester chain under prior thermal field excitation.

[0125] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A processing technology for a colorfast and biodegradable polyester shoe upper material, characterized in that, The processing technology employs segmented side feeding and in-situ reactive extrusion, specifically including the following steps: S100, Raw material pretreatment: The biodegradable polyester matrix is ​​dehydrated and dried, and the composite wear-resistant reinforcing phase and coupling agent are surface-modified and premixed; S200, First-stage reactive extrusion: The dried biodegradable polyester matrix, the premixed composite abrasion-resistant reinforcing phase and the reactive toughening end-capping agent are added to the main feed port of a twin-screw extruder and melt-blended in the first temperature range, so that the reactive toughening end-capping agent and the end carboxyl groups of the polyester melt undergo an in-situ end-capping reaction. S300, Second-stage side feeding: In the middle and downstream section of the twin-screw extruder, a multidimensional anti-discoloration synergistic factor is added through a side feeder to carry out short-range melt blending in a second temperature range lower than the first temperature range; S400, Exhaust Granulation: The blended melt after the second-stage side feeding is subjected to vacuum exhaust treatment, and then extruded, drawn, cooled and granulated to obtain modified polyester granules. S500, Upper Molding: The modified polyester granules are melt-processed to prepare the colorfast and biodegradable polyester upper material.

2. The processing technology of the colorfast and biodegradable polyester shoe upper material according to claim 1, characterized in that, The biodegradable polyester matrix is ​​composed of polylactic acid and flexible blended polyester in a mass ratio of 2:1 to 4:

1. The flexible blended polyester is selected from polybutylene succinate or polybutylene adipate / terephthalate. In step S100, the process parameters for the dehydration and drying treatment include: controlling the drying temperature at 80°C to 90°C and the drying time at 8 to 12 hours under a vacuum of ≤-0.08MPa, and ensuring that the moisture content of the biodegradable polyester matrix after treatment is less than 0.02%.

3. The processing technology of a colorfast and biodegradable polyester shoe upper material according to claim 2, characterized in that, The composite wear-resistant reinforcing phase is nanocellulose and / or modified biomass lignin, the coupling agent is a silane coupling agent containing epoxy groups, and the mass ratio of the composite wear-resistant reinforcing phase to the coupling agent is 100:1.5 to 100:3.

0. The surface modification premixing is performed under the following conditions: using a high-speed mixing device, the temperature is raised to 85°C~95°C by relying on the dynamic friction between the materials, and the mixture is maintained at this temperature range for 10~15 minutes to complete the surface coating of the composite wear-resistant reinforcing phase.

4. The processing technology of the colorfast and biodegradable polyester shoe upper material according to claim 3, characterized in that, In step S200, the addition ratio of each raw material component is as follows by weight: The biodegradable polyester matrix is ​​70-85 parts; The composite wear-resistant reinforcing phase consists of 2 to 6 parts; The reactive toughening end-capping agent is 3-8 parts; The reactive toughening end-capping agent is selected from styrene-acrylate copolymer oligomers containing multiple epoxy functional groups or copolymers containing oxazoline groups. The in-situ end-capping reaction specifically involves the epoxy group or oxazoline group in the reactive toughening end-capping agent undergoing a ring-opening addition reaction with the terminal carboxyl group generated by the chain scission of the biodegradable polyester matrix under the action of melt shear force, thereby blocking the autocatalytic degradation pathway of the polyester material by the terminal carboxyl group. In step S200, the first temperature range adopts a progressive stepped temperature control arrangement, specifically set as follows: The temperature of the feeding zone of the twin-screw extruder is 160°C~170°C; The temperature of the melt reaction zone of the twin-screw extruder is 185°C to 195°C, and the residence time of the material in the melt reaction zone is 60 to 120 seconds to ensure the conversion rate of the in-situ end-capping reaction.

5. The processing technology of the colorfast and biodegradable polyester shoe upper material according to claim 4, characterized in that, In step S300, relative to the total weight of the raw materials added in step S200, the amount of the multidimensional anti-discoloration synergistic factor added is 1.5 to 4 parts by weight. The multidimensional anti-color change synergistic factor is composed of hindered amine light stabilizer, reactive ultraviolet absorber and phosphite antioxidant in a mass ratio of 2:1:

1. The reactive ultraviolet absorber is a benzotriazole acrylate containing hydroxyl groups; The mechanism of action of the multidimensional anti-color change synergistic factor is as follows: the phosphite antioxidant helps to capture free radicals generated during polyester thermal processing, and combined with the long-term free radical quenching effect of the hindered amine light stabilizer and the ultraviolet shielding effect of the reactive ultraviolet absorber, a multidimensional anti-ultraviolet and anti-hydrolysis synergistic protection network is formed inside the polyester matrix.

6. The processing technology of a colorfast and biodegradable polyester shoe upper material according to claim 5, characterized in that, In step S300, the temperature of the second temperature range is set to 180°C~185°C; The side feeder is positioned at the rear 1 / 3 to 1 / 4 of the length-to-diameter ratio of the main barrel of the twin-screw extruder, so that the melt blending time of the multidimensional anti-discoloration synergistic factor is shorter than the in-situ end-capping reaction time in step S200, thereby avoiding the early thermal decomposition of the multidimensional anti-discoloration synergistic factor under long-range high-temperature shear.

7. The processing technology of a colorfast and biodegradable polyester shoe upper material according to claim 6, characterized in that, In step S400, the vacuum degree of the vacuum exhaust process is strictly controlled between -0.08MPa and -0.095MPa to forcibly remove low molecular weight byproducts, free monomers and residual trace moisture generated in the in-situ end-capping reaction in step S200, so as to prevent micro-foaming and secondary hydrolysis degradation of the blended melt at the extrusion die.

8. The processing technology of a colorfast and biodegradable polyester shoe upper material according to claim 7, characterized in that, The specific process conditions for cooling and pelletizing are as follows: The blended melt is extruded into a continuous strip through an extrusion die and then drawn into a constant temperature water cooling tank for flexible curing. The temperature of the constant temperature water cooling tank is maintained at 25°C~35°C. After the cured material strip is thoroughly blown away by a high-pressure air knife to remove the surface moisture, it is fed into a pelletizer to cut the modified polyester pellets, and the cutting length is controlled to be 2.5mm~3.5mm.

9. The processing technology of a colorfast and biodegradable polyester shoe upper material according to claim 8, characterized in that, In step S500, the shoe upper forming specifically adopts a melt spinning weaving process or an extrusion casting composite process; When using the melt spinning weaving process, the specific operation is as follows: The modified polyester granules are dried and fed into a spinning box, where they are melt-extruded at a spinning temperature of 190°C to 200°C. They are then sequentially cooled by side blowing, oiled, subjected to multi-stage stretching and heat setting, and wound to obtain high-strength polyester filaments. Finally, the high-strength polyester filaments are 3D woven using a computerized flat knitting machine to create a one-piece knit upper. When the extrusion casting composite process is used, the specific operation is as follows: The modified polyester granules are extruded into a continuous polymer film through a casting die at 185°C~195°C; In the roll bonding stage, the polymer film in a semi-molten state is hot-pressed and laminated with a biodegradable base fabric, and after cooling, non-woven shoe upper leather is obtained.

10. A colorfast and biodegradable polyester shoe upper material, characterized in that, By weight, it includes the following raw material components: Biodegradable polyester matrix: 70-85 parts; Reactive toughening end-capping agent: 3-8 parts; Composite wear-resistant reinforcing phase: 2-6 parts; Multidimensional anti-discoloration synergistic factor: 1.5~4 parts; The reactive toughening end-capping agent can undergo an in-situ end-capping reaction with the end carboxyl groups of the biodegradable polyester matrix; The multidimensional anti-color change synergistic factor is composed of hindered amine light stabilizers, reactive ultraviolet absorbers, and phosphite antioxidants.

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