A method for preparing shoe insoles using recycled thermoplastic elastomer materials

Abstract

This invention provides a method for preparing shoe insoles using recycled thermoplastic elastomer materials, comprising the following steps: cryogenically pulverizing recycled thermoplastic elastomer foam to obtain a granular mixture, adding a polyurethane compatibilizer and mixing; heating and then transferring the mixture into a flatbed mold for pressing into a sheet; coating the surface of the sheet with a moisture-reactive polyurethane hot melt adhesive, and then bonding a mesh fabric; and finally, after static curing, punching out the shoe insole. The shoe insole prepared by this method can provide good structural strength while retaining the appearance of the crushed particles.

Description

Technical Field

[0001] This invention relates to the field of insole manufacturing technology, and specifically to a method for manufacturing insoles using recycled thermoplastic elastomer materials. Background Technology

[0002] In existing technologies, insoles are typically produced by directly foaming raw materials or molding them in molds. This conventional production process is energy-intensive and environmentally unfriendly. To meet increasingly stringent environmental requirements, a production process using recycled insole scraps has emerged. This conventional recycling process usually involves crushing foamed waste materials, mixing them with new virgin raw materials in a certain proportion, adding adhesive, and then hot-pressing or foaming the mixture in a mold. However, current recycled materials are usually only added as a portion of the raw materials, making it difficult to achieve complete recycling of waste materials. The reconstituted insoles look no different from ordinary insoles, with a smooth surface and lacking the visible physical form of crushed particles that recycled materials should have. Consumers cannot intuitively identify the product's environmental attributes. On the other hand, to demonstrate crushed particles, the proportion of recycled materials needs to be increased, resulting in a loose and easily torn finished product. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned defects or problems in the prior art and to provide a method for preparing insoles using recycled thermoplastic elastomer materials. The insoles prepared by this method can provide good structural strength while retaining the appearance of broken particles.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: Technical Solution 1: A method for preparing shoe insoles using recycled thermoplastic elastomer materials, comprising the following steps: S10: placing the recycled thermoplastic elastomer foam material into a cryogenic pulverizer for pulverization, collecting all the pulverized materials, and obtaining a mixture of unscreened particles containing different particle sizes; S20: adding 4 to 6 parts by weight of polyurethane compatibilizer to the particle mixture at a ratio of 100 parts by weight of the particle mixture, and stirring and mixing; S30: heating the particle mixture containing polyurethane compatibilizer outside the mold until the temperature of the particle mixture reaches between 160°C and 170°C; S40: transferring the particle mixture at a temperature between 160°C and 170°C into a flat-press mold at room temperature and spreading it flat, controlling the flat-press mold to close and applying a pressure of 90 kPa to 110 kPa, maintaining this pressure for 280 s to 320 s, opening the flat-press mold and removing the formed sheet; S50: Apply moisture-reactive polyurethane hot melt adhesive to one side of the sheet, controlling the application temperature of the moisture-reactive polyurethane hot melt adhesive between 80°C and 90°C. Lay the mesh fabric flat on the surface coated with the moisture-reactive polyurethane hot melt adhesive and apply pressure to bond it together. S60: Lay the sheet with the mesh fabric bonded flat and let it stand to cure. After curing, use a punch to cut out the insole from the sheet.

[0005] Technical Solution 2, based on Technical Solution 1: The hardness of the thermoplastic elastomer foamed recycled material is between 11 Asker C and 17 Asker C, and the density is between 0.12 g / cm³ and 0.18 g / cm³.

[0006] Technical Solution 3 based on Technical Solution 1: Before step S10, it further includes: washing and drying the recycled thermoplastic elastomer foam in water, and then cutting it into strips in a cutting machine.

[0007] Technical Solution 4 based on Technical Solution 1: In step S10, the internal operating temperature of the cryogenic pulverizer is set between -95℃ and -85℃, and the pulverizing speed of the internal blades of the cryogenic pulverizer is set between 45Hz and 55Hz.

[0008] Technical Solution 5, based on Technical Solution 1: The chemical composition of the recycled thermoplastic elastomer foam contains tetraphenylethylene.

[0009] Technical Solution Six based on Technical Solution One: The polyurethane compatibilizer in step S20 includes a single-component polyurethane prepolymer.

[0010] Technical solution seven based on technical solution one: In step S40, the length of the forming cavity inside the flat pressing mold is limited to between 140cm and 160cm, and the width is limited to between 120cm and 140cm.

[0011] Technical solution eight based on technical solution one: In step S60, the static curing environment temperature of the sheet with the mesh attached is between 20°C and 30°C.

[0012] Technical Solution Nine based on Technical Solution One: In step S60, the static curing time is between 20h and 28h.

[0013] Technical Solution 10 based on Technical Solution 1: In step S30, a hot air circulation heating device or an infrared radiation heating device is used to perform non-contact heating on the particulate mixture containing polyurethane compatibilizer. As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing shoe insoles using recycled thermoplastic elastomer materials. To retain random particle shapes of varying sizes on the finished product surface, this method involves directly collecting an unscreened mixture of particles of different sizes for pressing. This method leads to difficulties in fully bonding the irregular particles during pressing, resulting in a loose and easily torn finished product. Furthermore, the thinness of the insole exacerbates this problem, further causing the material to lose its foaming elasticity after compaction. Therefore, this method involves adding a polyurethane compatibilizer and then externally heating the material to 160°C to 170°C before it enters the mold. Within this specific temperature range, the heat only causes the outer surface of each particle in the mixture to reach a slightly molten state, thereby activating the chemical cross-linking activity of the polyurethane compatibilizer. Since the heating process is carried out without pressure outside the mold, heat conduction in the internal core of each particle is limited, maintaining a solid, porous foam structure. The particle mixture in a slightly molten state is then rapidly transferred into a flat-press mold at room temperature and held under pressure of 90 kPa to 110 kPa for shaping. The room-temperature mold can rapidly absorb heat from the particle surface, causing the surface micro-melted layer to cool, solidify, and cross-link under appropriate pressure, thus achieving a strong bond between the particles. The set pressure range ensures a tight fit between the particle interfaces without damaging the solid microporous foam skeleton inside the particles. Compared to conventional methods that force material fusion by increasing molding temperature or significantly increasing pressure, resulting in the complete compaction of the soft foam, this solution uses preheating to activate surface viscosity combined with moderate cold pressing and shaping in a room-temperature mold. This ensures that the finished product retains the appearance characteristics of broken particles while preserving the internal micropores, maintaining its original low density and high resilience.

[0014] Furthermore, the cold-pressed sheet material retains a large number of unmelted solid porous foam structures and irregularly sized particle interfaces, making its physical state extremely sensitive to thermal stress. In the art, conventional high-temperature hot-melt bonding processes are typically used when bonding mesh fabric to insoles to ensure peel strength. However, due to the inherent thermal shrinkage characteristics of thermoplastic elastomers, applying conventional high temperatures to the surface of such cold-pressed porous sheets not only causes secondary melting of the particle surface but also triggers a violent release of residual cold-pressing stress within the sheet. This conventional bonding method results in severe thermal shrinkage and warping deformation of the sheet, and the three-dimensional, fragmented particle texture and internal microporous foam skeleton originally preserved through cold pressing will collapse and become distorted over a large area due to thermal deformation. To address this related problem caused by the cold-pressed porous substrate, this solution changes the conventional thermal bonding path in the bonding process, selecting a moisture-reactive polyurethane hot-melt adhesive and strictly limiting the application temperature to between 80°C and 90°C. The application temperature range is below the thermal deformation critical point of the thermoplastic elastomer foam skeleton, ensuring that the liquid adhesive does not trigger thermal shrinkage of the substrate during contact with the sheet surface. Unlike conventional hot melt adhesives that rely on continuous high-temperature melting and physical cooling for setting, the curing mechanism of moisture-reactive polyurethane hot melt adhesives depends on the chemical cross-linking reaction between the polyurethane prepolymer and water molecules in the environment. During the flat, stationary process, the relatively low-temperature adhesive fluid can fully penetrate into the uneven particle gaps on the sheet surface under gravity, gradually undergoing an irreversible curing reaction without introducing additional thermal stress or mechanical tensile force. This room-temperature chemical cross-linking curing method not only meets the physical requirement of avoiding thermal shrinkage in flexible foam materials but also establishes extremely high interfacial peel strength between the rough particle surface and the mesh. The flat, stationary process allows the internal stress of the sheet to be fully released and stabilized at room temperature, preventing damage to the geometric dimensions due to internal tension. After the sheet structure has been left to stand and fully stabilize and cross-link, it is then punched and shaped using a punch cutter. This ensures that the final insole does not shrink or deform in terms of edge contour and physical flatness. While giving the insole a firm covering surface, it fully presents the visual characteristics of the broken particles in the bottom layer and ensures the high resilience mechanical properties of the porous structure.

[0015] In technical solution two, the hardness and density range of the thermoplastic elastomer foamed recycled material are limited to ensure that the thermoplastic elastomer recycled material used as raw material has the characteristics of being soft, highly elastic, and low in density. Furthermore, the recycled material within this hardness and density range can better adapt to the preparation process of this solution, so that the final insole product has sufficient rebound and shock absorption performance.

[0016] In technical solution three, washing, drying, and cutting into strips are added before the crushing process. The washing and drying steps remove physical barriers and eliminate uncontrollable interference from moisture in the subsequent reaction system. Pre-cutting irregular scraps into strips provides a relatively uniform feeding standard for subsequent cryogenic crushing, avoiding crusher jamming or extremely large particles due to significant differences in feed size. This provides a foundation for subsequent pressing of sheets with uniform thickness.

[0017] In technical solution four, the temperature and grinding speed of the cryogenic pulverizer are limited. The low-temperature environment causes the extremely soft thermoplastic elastomer to cool instantly below its glass transition temperature, entering a completely brittle state. The specific grinding speed then allows the brittle material to be instantly broken down with a very small fracture surface, leaving sharp broken edges and naturally forming a mixture of different particle sizes. This combination of process parameters avoids over-pulverizing the material into powder while preserving the microporous framework structure within the material to the greatest extent possible from compression damage.

[0018] In technical solution five, the chemical composition of the recycled thermoplastic elastomer foam material is limited to include tetraphenylethylene. The tetraphenylethylene molecule contains a double bond system, which, under thermal stimulation and the chemical intervention of the polyurethane compatibilizer, can undergo moderate chain breakage and recombination. This provides chemical bonding anchors, in addition to physical adhesion, between adjacent particles that are only in a slightly molten state on the surface. Macroscopically, this means that even if the particle core does not melt, the particle contact interface can still achieve extremely high tear strength, thus further consolidating the overall structural stability of the finished product in conjunction with the temperature-controlled cold pressing step.

[0019] In technical solution six, the composition of the polyurethane compatibilizer is specified to include a one-component polyurethane prepolymer. This one-component polyurethane prepolymer contains active isocyanate groups. When the particulate mixture is heated to a specified temperature outside the mold, these groups are rapidly activated and chemically bond quickly to the polar sites on the surface of the thermoplastic elastomer. Since its cross-linking and curing process can rely on trace amounts of moisture in the environment, it does not require maintaining a continuous high-temperature environment inside the mold to drive the curing reaction. Combined with the room-temperature mold cold-pressing and shaping process in this solution, it avoids the problem of foam micropore collapse caused by the need for high-temperature curing inside the mold.

[0020] In technical solution seven, the size of the forming cavity inside the flat-press mold is limited, which avoids the problem of loosening of the edge area and collapse of the center area caused by the pressure transmission attenuation of non-uniform particles under large area. This ensures that constant pressure can evenly cover all particles and solves the problem of tolerance loss when irregular recycled materials are formed in large area.

[0021] In technical solution eight, the static curing environment temperature of the sheet with the mesh fabric is limited, so that the fluid adhesive has a sufficient time window before cross-linking and curing, and can slowly penetrate into the micro-pits formed on the surface of the sheet due to the different particle sizes under the influence of gravity. At the same time, the room temperature environment is below the thermal deformation critical temperature of the thermoplastic elastomer foam substrate, which can avoid inducing material shrinkage.

[0022] In technical solution nine, the settling time is limited. Since the cold pressing and shaping in the early stage will accumulate a certain mechanical internal stress inside the porous particles, the limited settling time ensures that the bonding and peel strength between the adhesive and the particle surface reaches the expected value and can effectively release residual stress.

[0023] In technical solution ten, non-contact heating is used, which can concentrate heat on the outer skin of irregular particles, thereby achieving micro-melting of the skin while the core remains in a solid state. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments are briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The insole is prepared by the insole preparation method using recycled thermoplastic elastomer material according to Embodiment 1 of the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] In the claims, description and accompanying drawings of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0028] This invention relates to a method for preparing shoe insoles using recycled thermoplastic elastomer materials, comprising the following steps: S10: Place the recycled thermoplastic elastomer foam material into a cryogenic pulverizer for pulverization, collect all the pulverized materials, and obtain a mixture of unscreened particles containing different particle sizes; S20: Add the polyurethane compatibilizer to the granular mixture at a ratio of 4 to 6 parts by weight per 100 parts by weight of the granular mixture and stir to mix. S30: The particulate mixture containing the polyurethane compatibilizer is heated outside the mold until the temperature of the particulate mixture reaches between 160°C and 170°C. S40: Transfer the particle mixture with a temperature between 160°C and 170°C into a flat die at room temperature and spread it out. Control the flat die to close and apply a pressure of 90 kPa to 110 kPa. Maintain this pressure for 280 s to 320 s. Open the flat die and take out the formed sheet. S50: Apply moisture-reactive polyurethane hot melt adhesive to one side of the sheet, control the application temperature of the moisture-reactive polyurethane hot melt adhesive between 80°C and 90°C, lay the mesh fabric flat on the surface coated with moisture-reactive polyurethane hot melt adhesive and apply pressure to bond them together. S60: Lay the sheet with the mesh attached flat and let it cure. After curing, use a punch to cut out the insole from the sheet.

[0029] The above steps will be explained in detail below.

[0030] In step S10, firstly, recycled thermoplastic elastomer foam that meets the parameter requirements is selected as the raw material. The selected recycled thermoplastic elastomer foam contains tetraphenylethylene in its chemical composition, with a physical hardness between 11 Asker C and 17 Asker C, and a density between 0.12 g / cm³ and 0.18 g / cm³. The prepared recycled thermoplastic elastomer foam is placed in water in a cleaning device for physical washing, and then the washed raw material is transferred to a drying device for thorough drying. The dried recycled thermoplastic elastomer foam is placed on the working platform of a cutting machine, and the cutting machine is started to cut it into strips of uniform width. The resulting strips are collected for later use.

[0031] Turn on the cryogenic pulverizer and inject liquid nitrogen into its refrigeration system. Adjust the temperature control system to lower and stabilize the internal operating temperature of the cryogenic pulverizer between -95℃ and -85℃. Using the control panel, set the pulverizing speed of the internal blades to between 45 Hz and 55 Hz. Once the internal temperature and speed have reached and stabilized the set parameters, uniformly feed the pre-prepared strip-shaped thermoplastic elastomer foamed recycled material into the inlet of the cryogenic pulverizer for physical pulverization. Place a collection container at the outlet of the cryogenic pulverizer to directly collect all the material discharged after being crushed by the internal blades. During the material collection process and subsequent flow to the next process, no sieving or grading is performed on the discharged material; the unscreened mixture containing particles of different sizes is directly obtained.

[0032] In step S20, the unscreened particle mixture containing different particle sizes obtained in step S10 is transferred to a weighing device for weighing, and the total weight of the particle mixture is recorded. A polyurethane compatibilizer is prepared, and its chemical composition includes a single-component polyurethane prepolymer. Based on the total weight of the weighed particle mixture, the corresponding weight of polyurethane compatibilizer is accurately weighed according to the baseline ratio of 4 to 6 parts by weight of polyurethane compatibilizer per 100 parts by weight of the particle mixture. The weighed particle mixture is transferred and poured into the mixing cylinder at room temperature. The mixing machine is turned on, and with the internal paddles running, the prepared polyurethane compatibilizer containing the single-component polyurethane prepolymer is poured uniformly into the mixing cylinder through the feed port. The mixing machine is kept running, and a specific mixing time is set. Through the continuous tumbling and physical friction of the equipment paddles, the added polyurethane compatibilizer is evenly distributed on the surface of all particles of different sizes. After the mixing process reaches the set time, the mixer is turned off, and the granular mixture containing polyurethane compatibilizer is completely discharged from the cylinder and collected and transferred to a transfer container for later use.

[0033] In step S30, the granular mixture containing the polyurethane compatibilizer is spread evenly on a conveyor belt or heat-resistant tray and transported to a heating device independent of the pressing mold. The device is started, and the granular mixture is heated non-contactly using either hot air circulation heating or infrared radiation heating. During the heating operation, the surface temperature of the granular mixture is monitored in real time using a temperature monitoring instrument. Non-contact heating continues until the temperature of the granular mixture reaches between 160°C and 170°C. This non-contact heating process causes the outer surface of each particle in the granular mixture to be in a slightly molten state, while the internal core of each particle maintains a solid, porous, foamed structure. Once the target temperature is reached, the granular mixture is removed from the heating device.

[0034] In step S40, prepare a flat-pressing device at room temperature without any heating source turned on. This device is equipped with a flat-pressing mold, the length of which is limited to 140cm to 160cm, and the width to 120cm to 140cm. Quickly transfer the granular mixture, with a temperature between 160°C and 170°C, into the forming cavity of the flat-pressing mold, and use a spreading tool to evenly spread it at the bottom of the cavity. Operate the control system to fully close the flat-pressing mold, and drive the hydraulic or pneumatic system to apply a constant pressure of 90kPa to 110kPa to the mold. Maintain this pressure for 280s to 320s at room temperature. After the preset holding time is reached, control the flat-pressing mold to depressurize and open, and completely remove the pressed sheet from the forming cavity.

[0035] In step S50, the removed sheet is placed on the adhesive coating platform. The melting tank of the hot melt adhesive coating equipment is turned on, and the moisture-reactive polyurethane hot melt adhesive is placed into the melting tank for heating and melting. The application temperature of the moisture-reactive polyurethane hot melt adhesive is strictly controlled between 80°C and 90°C by the temperature control module. The coating mechanism is operated to evenly coat one side surface of the sheet with the moisture-reactive polyurethane hot melt adhesive at a temperature between 80°C and 90°C. Then, a mesh fabric that meets the size requirements is selected and completely laid flat on the surface of the sheet coated with moisture-reactive polyurethane hot melt adhesive. The bonding roller device is started, and the roller is controlled to roll at a uniform speed on the surface with the mesh fabric, applying downward physical pressure to the mesh fabric surface for bonding.

[0036] In step S60, the sheet with the mesh fabric attached is transferred to a dedicated curing chamber, and the sheet is laid flat on a horizontal rack inside. The air conditioning temperature control system of the curing chamber is adjusted to maintain a stable curing temperature between 20°C and 30°C. At this temperature, the sheet is kept flat for curing, the start time is recorded, and the total curing time is controlled between 20 hours and 28 hours. After the set curing time is completed and the material is fully cross-linked and cured, the sheet is transferred to the worktable of the punching machine. According to the corresponding size, punches are installed on the punching machine, the punching equipment is started, and the punches are used to punch out finished insoles one by one from the sheet and collect them into the warehouse.

[0037] The aforementioned insole preparation method, in order to retain the random particle morphology of varying sizes on the surface of the finished product, directly uses a mixture of unscreened particles containing different particle sizes for pressing. This method leads to problems with the irregular particles not being able to fully bond during pressing, resulting in a loose and easily torn structure in the finished product. Furthermore, because the insole is relatively thin, this problem is further exacerbated, leading to a loss of foam elasticity after compaction. Therefore, after adding a polyurethane compatibilizer, the material is externally heated to 160°C to 170°C before entering the mold. At this specific temperature range, the heat only causes the outer surface of each particle in the particle mixture to reach a slightly molten state, thereby activating the chemical cross-linking activity of the polyurethane compatibilizer. Since the heating process is carried out under no-pressure conditions outside the mold, the heat conduction in the internal core of each particle is limited, maintaining a solid, porous foam structure. The particle mixture in a slightly molten state is then rapidly transferred into a flat-press mold at room temperature and held under pressure of 90 kPa to 110 kPa for shaping. The room-temperature mold can rapidly absorb heat from the particle surface, causing the surface micro-melt layer to cool, solidify, and cross-link under appropriate pressure, thus achieving a strong bond between the particles. The set pressure range ensures a tight fit between the particle interfaces without damaging the solid microporous foam skeleton inside the particles. Compared to the conventional method of forcibly fusing materials by increasing molding temperature or significantly increasing pressure, which leads to the complete compaction of the soft foam, the preheating to activate surface viscosity combined with moderate cold pressing and shaping in a room-temperature mold ensures that the finished product retains the appearance characteristics of broken particles while preserving the internal micropores, maintaining its original low density and high resilience.

[0038] Furthermore, the cold-pressed sheet material retains a large number of unmelted solid porous foam structures and irregularly sized particle interfaces, making its physical state extremely sensitive to thermal stress. In the art, conventional high-temperature hot-melt bonding processes are typically used when bonding mesh fabric to insoles to ensure peel strength. However, due to the inherent thermal shrinkage characteristics of thermoplastic elastomers, applying conventional high temperatures to the surface of such cold-pressed porous sheets not only causes secondary melting of the particle surface but also triggers a violent release of residual stress from the cold pressing process. This conventional bonding method results in severe thermal shrinkage and warping deformation of the sheet, and the three-dimensional, fragmented particle texture and internal microporous foam skeleton originally preserved through cold pressing will collapse and become distorted over a large area due to thermal deformation. To address this related problem caused by the cold-pressed porous substrate, the conventional thermal bonding path was changed in the bonding process. A moisture-reactive polyurethane hot-melt adhesive was selected, and the application temperature was strictly limited to between 80°C and 90°C. The application temperature range is below the thermal deformation critical point of the thermoplastic elastomer foam skeleton, ensuring that the liquid adhesive does not trigger thermal shrinkage of the substrate during contact with the sheet surface. Unlike conventional hot melt adhesives that rely on continuous high-temperature melting and physical cooling for setting, the curing mechanism of moisture-reactive polyurethane hot melt adhesives depends on the chemical cross-linking reaction between the polyurethane prepolymer and water molecules in the environment. During the flat, static curing process, the relatively low-temperature adhesive fluid can fully penetrate into the uneven particle gaps on the sheet surface under gravity, and gradually undergoes an irreversible curing reaction without introducing additional thermal stress or mechanical tensile force. This room-temperature chemical cross-linking curing method not only meets the physical requirement of avoiding thermal shrinkage in flexible foam materials but also builds extremely high interfacial peel strength between the rough particle surface and the mesh. The flat, static curing process allows the internal stress of the sheet to be fully released and stabilized at room temperature, preventing damage to the geometric dimensions caused by internal tension. After the sheet structure has been left to stand and fully stabilize and cross-link, it is then punched and shaped using a punch cutter. This ensures that the final insole does not shrink or deform in terms of edge contour and physical flatness. While giving the insole a firm covering surface, it fully presents the visual characteristics of the broken particles in the bottom layer and ensures the high resilience mechanical properties of the porous structure.

[0039] To further illustrate the technical effects of the insole preparation method using recycled thermoplastic elastomer materials provided by the present invention, the following embodiments and comparative examples are provided.

[0040] The specific information of the raw materials used in the following embodiments and comparative examples is as follows: Thermoplastic elastomer foam recycled material: Thermoplastic elastomer (TPE) scraps of grade Prime Touch are selected. Its main chemical components include tetraphenylethylene, its physical hardness is 14 Asker C, its initial density is 0.15 g / cm³, and its initial resilience is 56%.

[0041] Polyurethane compatibilizer: HY-912 single-component polyurethane prepolymer compatibilizer is selected.

[0042] Moisture-reactive polyurethane hot melt adhesive: PUR hot melt adhesive model Z-8590 is selected.

[0043] Example 1 The above-mentioned recycled thermoplastic elastomer foam was washed in water and dried, then cut into strips using a cutting machine. The strips were then fed into a cryogenic pulverizer with an internal operating temperature of -90℃ and an internal blade crushing speed of 50 Hz for cryogenic brittle pulverization. All discharged material was collected, yielding 100 kg of unscreened granular mixture containing particles of different sizes. This 100 kg granular mixture was poured into a mixer, and 5 kg of HY-912 polyurethane compatibilizer was added. The mixer was then turned on to mix thoroughly. The mixed material was spread evenly on a heat-resistant tray and placed in a separate hot air circulation heating device for non-contact heating. Temperature sensors monitored the temperature in real time. When the surface temperature of the granular mixture reached 165℃, heating was stopped and the material was removed. At this point, the outer surface of the particles was in a slightly molten state, while the internal core remained a solid porous foam structure. The material at 165℃ was quickly transferred into a flat-press mold at room temperature (25℃), with an internal molding cavity length of 150 cm and a width of 130 cm, and then spread evenly. Control the closing of the flat-press mold, apply a constant pressure of 100 kPa, and maintain this pressure for 300 s. Open the flat-press mold and remove the cold-pressed sheet. Coat one side of the sheet with moisture-reactive polyurethane hot melt adhesive (model Z-8590), controlling the application temperature at 85℃. Lay the mesh fabric flat on the adhesive-coated surface and apply pressure using a roller to bond them together. Place the sheet with the mesh fabric bonded flat in a curing chamber at an ambient temperature of 25℃ and allow it to cure for 24 hours. After curing, use a punch to cut out the finished insole.

[0044] Example 2 The above-mentioned recycled thermoplastic elastomer foam was washed in water and dried, then cut into strips using a cutting machine. The strips were then fed into a cryogenic pulverizer with an internal operating temperature of -95℃ and an internal blade pulverizing speed of 45 Hz for cryogenic brittle pulverization. All discharged material was collected, yielding 100 kg of unscreened granular mixture containing different particle sizes. This 100 kg granular mixture was poured into a mixer, and 4 kg of HY-912 polyurethane compatibilizer was added. The mixer was then turned on to mix thoroughly. The mixed material was spread evenly on a heat-resistant tray and placed in a separate hot air circulation heating device for non-contact heating. Heating was stopped and the material removed when the surface temperature of the granular mixture reached 160℃, monitored in real time by a temperature sensor. The material at 160℃ was quickly transferred into a flat-press mold with an internal molding cavity length of 140 cm and a width of 120 cm, operating at 25℃. The flat-press mold was closed, and a constant pressure of 90 kPa was applied and maintained for 280 s. Open the flatbed mold and remove the cold-pressed sheet. Apply moisture-reactive polyurethane hot melt adhesive (model Z-8590) to one side of the sheet, controlling the application temperature to 80℃. Lay the mesh fabric flat on the adhesive-coated surface and apply pressure using a roller. Place the sheet with the mesh fabric attached flat in a curing chamber at an ambient temperature of 20℃ and allow it to cure for 20 hours. After curing, use a punch to cut out the finished insole.

[0045] Example 3 The above-mentioned recycled thermoplastic elastomer foam was washed in water and dried, then cut into strips using a cutting machine. The strips were then fed into a cryogenic pulverizer with an internal operating temperature of -85℃ and an internal blade pulverizing speed of 55 Hz for cryogenic brittle pulverization. All discharged material was collected, yielding 100 kg of unscreened granular mixture containing particles of different sizes. This 100 kg granular mixture was poured into a mixer, and 6 kg of HY-912 polyurethane compatibilizer was added. The mixer was then turned on to mix thoroughly. The mixed material was spread evenly on a heat-resistant tray and placed in a separate hot air circulation heating device for non-contact heating. Heating was stopped and the material removed when the surface temperature of the granular mixture reached 170℃, monitored in real time by a temperature sensor. The material at 170℃ was quickly transferred into a flat-press mold with an internal molding cavity length of 160 cm and a width of 140 cm, operating at 25℃. The flat-press mold was closed, and a constant pressure of 110 kPa was applied and maintained for 320 s. Open the flatbed mold and remove the cold-pressed sheet. Apply moisture-reactive polyurethane hot melt adhesive (model Z-8590) to one side of the sheet, controlling the application temperature to 90℃. Lay the mesh fabric flat on the adhesive-coated surface and apply pressure using a roller. Place the sheet with the mesh fabric attached flat in a curing chamber at an ambient temperature of 30℃ and allow it to cure for 28 hours. After curing, use a punch to cut out the finished insole.

[0046] Comparative Example 1 This comparative example uses the exact same raw materials and proportions as Example 1. The main difference lies in the molding process, which does not employ the disconnect between external preheating and room-temperature cold pressing. Instead, it uses a conventional hot press mold. Specifically, 100 kg of the granular mixture is added to 5 kg of polyurethane compatibilizer (HY-912) and stirred. After mixing, the external heating step is skipped, and the mixture is directly poured into a hot press mold heated to 165°C. The hot press mold is kept closed, and a constant pressure of 100 kPa is applied. The mold is held under pressure for 300 seconds while continuously heated. The hot press mold is then opened, the sheet is removed, and cooled. Subsequent steps of applying adhesive, attaching fabric, static curing, and die-cutting are exactly the same as in Example 1.

[0047] Comparative Example 2 The preparation process of this comparative example is exactly the same as that of Example 1, the main difference being the absence of a specific type of single-component polyurethane compatibilizer. In the mixing step, instead of adding HY-912 polyurethane compatibilizer, an equal amount (5 kg) of commercially available water-based environmentally friendly polyurethane adhesive was used. All other operating parameters for cryogenic pulverization, external heating, room temperature cold pressing, adhesive application, and static curing were completely consistent with those of Example 1.

[0048] Comparative Example 3 The molding process of this comparative example is exactly the same as that of Example 1, the main difference being that conventional high-temperature hot melt adhesive was used in the mesh bonding step. After removing the cold-pressed and shaped sheet, a conventional EVA-based hot melt adhesive sheet was selected and placed between the sheet and the mesh, and then fed into a hot press laminating machine heated to 140°C for high-temperature roller pressing and bonding. The bonded sheet was left to cool at room temperature for 24 hours before being die-cut.

[0049] The samples prepared in the above embodiments and comparative examples were subjected to performance tests, and the test standards are as follows: The rebound rate was tested according to the national standard GB / T 10807-2006 "Determination of elasticity of flexible polyurethane foam".

[0050] The tear strength of the trousers was tested in accordance with the national standard GB / T 529-2008 "Determination of tear strength of vulcanized rubber or thermoplastic rubber".

[0051] Tensile strength was tested in accordance with the national standard GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber".

[0052] Compression deformation was tested under the 3-day test conditions at room temperature according to the chemical industry standard HG / T 2876-2009 "Method for Determination of Compression Fatigue Deformation of Rubber and Plastic Microporous Materials".

[0053] The density of the finished product was tested in accordance with the national standard GB / T 6343-2009 "Determination of apparent density of foamed plastics and rubber".

[0054] Appearance and dimensional stability were assessed by visually evaluating the retention of surface particle fragmentation and by measuring the dimensional shrinkage rate 24 hours after punching.

[0055] The test results are summarized below: Example 1 has a rebound rate of 56%, a trouser tear strength of 4.2 kN / m, a tensile strength of 5.1 MPa, a compression deformation of 28% with no cracks, a finished product density of 0.16 g / cm³, an appearance with obvious three-dimensional broken particles and strong texture, and a dimensional shrinkage rate of <1%.

[0056] Example 2 has a rebound rate of 55%, a trouser tear strength of 3.8 kN / m, a tensile strength of 4.5 MPa, a compression deformation of 29% with no cracks, a finished product density of 0.14 g / cm³, an appearance with obvious three-dimensional broken particles and strong texture, and a dimensional shrinkage rate of <1%.

[0057] Example 3 has a rebound rate of 54%, a trouser tear strength of 4.5 kN / m, a tensile strength of 5.5 MPa, a compression deformation of 27% with no cracks, a finished product density of 0.17 g / cm³, an appearance with obvious three-dimensional broken particles and good texture, and a dimensional shrinkage rate of <1%.

[0058] Comparative Example 1 has a rebound rate of 32%, a trouser tear strength of 4.5 kN / m, a tensile strength of 5.4 MPa, a compression deformation of 45% and hardening and collapse, a finished product density of 0.38 g / cm³, a smooth and dense surface with completely melted particles and no brokenness, and a dimensional shrinkage rate of <1%.

[0059] Comparative Example 2 had a rebound rate of 52%, a trouser tear strength of 1.8 kN / m, a tensile strength of 2.1 MPa, a compression deformation of 35% with surface micro-cracks, a finished product density of 0.15 g / cm³, an appearance with obvious three-dimensional broken granular texture, and a dimensional shrinkage rate of <1%.

[0060] Comparative Example 3 had a rebound rate of 48%, a trouser tear strength of 3.9 kN / m, a tensile strength of 4.6 MPa, a compression deformation of 38% with edge deformation, a finished product density of 0.22 g / cm³, and the appearance of the particles was locally ironed flat and the whole was severely warped and deformed, with a dimensional shrinkage rate of 8.5%.

[0061] The technical data from Examples 1 to 3 show that, while referring to... Figure 1 The insoles prepared in Example 1 shown above, based on the same soft and elastic raw materials, can maintain extremely high resilience and mechanical strength, and the finished product density is stably maintained in a lightweight state, and the appearance of broken particles is preserved. This indicates that the insoles prepared by this method can take into account both the appearance of broken particles and structural strength.

[0062] Comparing Example 1 with Comparative Example 1, when Comparative Example 1 was directly pressed using a conventional hot press mold, the density of the finished product increased dramatically from 0.15 g / cm³ of the raw material to 0.38 g / cm³, the springback rate dropped sharply to 32%, and the appearance completely lost the granular texture characteristic of environmentally friendly materials. This is because conventional hot pressing creates a continuous high-temperature and high-pressure environment inside the mold, causing the extremely soft porous foam skeleton of the thermoplastic elastomer to completely collapse and melt, resulting in the material losing its lightweight and high elasticity characteristics. Example 1 used a non-contact external preheating method at 165°C and then quickly transferred it into a room-temperature mold to apply 100 kPa cold pressing. Test data showed that its density basically maintained the lightweight state of the raw material, the springback rate was as high as 56%, and it retained the three-dimensional broken granular texture of varying sizes.

[0063] Comparing Example 1 with Comparative Example 2, Comparative Example 2, which did not add a one-component polyurethane prepolymer compatibilizer, showed a sharp drop in tear strength to 1.8 kN / m and tensile strength to only 2.1 MPa. The finished product was extremely prone to breakage and fragmentation at the particle interface under stress. Example 1, on the other hand, achieved tear strength and tensile strength of 4.2 kN / m and 5.1 MPa, respectively. This indicates that the active isocyanate groups in the compatibilizer, under external thermal excitation, formed a strong chemical bond with the double bonds on the surface of the thermoplastic elastomer.

[0064] Comparing Example 1 with Comparative Example 3, Comparative Example 3 used conventional high-temperature hot melt adhesive for the mesh bonding stage. Test data showed that the finished product had a dimensional shrinkage rate as high as 8.5%, and the surface particles were locally flattened, resulting in severe overall warping. This is because the extremely soft porous sheet containing residual stress from cold pressing underwent drastic thermal shrinkage deformation when exposed to secondary high temperatures. Example 1, by using a moisture-reactive polyurethane hot melt adhesive and strictly controlling the application temperature within a low range, combined with room-temperature curing, kept the dimensional shrinkage rate below 1% and prevented any warping.

[0065] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or a portion thereof that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the foregoing embodiments, in conjunction with common knowledge, general technical knowledge, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. A method for preparing shoe insoles using recycled thermoplastic elastomer materials, characterized in that, Includes the following steps: S10: Place the recycled thermoplastic elastomer foam material into a cryogenic pulverizer for pulverization, collect all the pulverized materials, and obtain a mixture of unscreened particles containing different particle sizes; S20: Add the polyurethane compatibilizer to the granular mixture at a ratio of 4 to 6 parts by weight per 100 parts by weight of the granular mixture and stir to mix. S30: The particulate mixture containing the polyurethane compatibilizer is heated outside the mold until the temperature of the particulate mixture reaches between 160°C and 170°C. S40: Transfer the particle mixture with a temperature between 160°C and 170°C into a flat die at room temperature and spread it out. Control the flat die to close and apply a pressure of 90 kPa to 110 kPa. Maintain this pressure for 280 s to 320 s. Open the flat die and take out the formed sheet. S50: Apply moisture-reactive polyurethane hot melt adhesive to one side of the sheet, control the application temperature of the moisture-reactive polyurethane hot melt adhesive between 80°C and 90°C, lay the mesh fabric flat on the surface coated with moisture-reactive polyurethane hot melt adhesive and apply pressure to bond them together. S60: Lay the sheet with the mesh attached flat and let it cure. After curing, use a punch to cut out the insole from the sheet.

2. The method for preparing insoles using recycled thermoplastic elastomer materials as described in claim 1, characterized in that, The hardness of the thermoplastic elastomer foam recycled material is between 11 Asker C and 17 Asker C, and the density is between 0.12 g / cm³ and 0.18 g / cm³.

3. The method for preparing insoles using recycled thermoplastic elastomer materials as described in claim 1, characterized in that, Before step S10, the method further includes: The recycled thermoplastic elastomer foam is washed in water and dried, then cut into strips using a cutting machine.

4. The method for preparing insoles using recycled thermoplastic elastomer materials as described in claim 1, characterized in that, In step S10, the internal operating temperature of the cryogenic pulverizer is set between -95°C and -85°C, and the pulverizing speed of the internal blades of the cryogenic pulverizer is set between 45Hz and 55Hz.

5. The method for preparing insoles using recycled thermoplastic elastomer materials as described in claim 1, characterized in that, The chemical composition of recycled thermoplastic elastomer foam includes tetraphenylethylene.

6. The method for preparing insoles using recycled thermoplastic elastomer materials as described in claim 1, characterized in that, The polyurethane compatibilizer in step S20 comprises a one-component polyurethane prepolymer.

7. The method for preparing insoles using recycled thermoplastic elastomer materials as described in claim 1, characterized in that, In step S40, the length of the forming cavity inside the flat mold is limited to between 140cm and 160cm, and the width is limited to between 120cm and 140cm.

8. The method for preparing insoles using recycled thermoplastic elastomer materials as described in claim 1, characterized in that, In step S60, the static curing environment temperature of the sheet with the mesh attached is between 20°C and 30°C.

9. The method for preparing insoles using recycled thermoplastic elastomer materials as described in claim 1, characterized in that, In step S60, the curing time is between 20 hours and 28 hours.

10. The method for preparing insoles using recycled thermoplastic elastomer materials as described in claim 1, characterized in that, In step S30, a hot air circulation heating device or an infrared radiation heating device is used to heat the particulate mixture containing polyurethane compatibilizer in a non-contact manner.

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