Preparation method of water hyacinth bio-based degradable material and insole

Abstract

The application discloses a preparation method of a water hyacinth bio-based degradable material and an insole, and the preparation method comprises the following steps: taking the main resin component containing 60-75 parts of polybutylene adipate terephthalate copolymer, 10-25 parts of ethylene-vinyl acetate copolymer, 10-25 parts of polyolefin elastomer and 3-8 parts of ethylene-propylene rubber by weight, melting and shearing the main resin component together with an auxiliary agent, 0.5-1.2 parts of dry water hyacinth leaf material and 0.2-0.6 parts of ethylene-maleic anhydride polymer, then adding a peroxide crosslinking agent and a chemical foaming agent, and finally obtaining the material through opening and sheeting, mold foaming, drying treatment and cold pressing forming; wherein the dry water hyacinth leaf material is subjected to melting and shearing together with the ethylene-maleic anhydride polymer before crosslinking and foaming. The material prepared by the method has the advantages of good resilience and compression performance retention and the water hyacinth particles are not easy to fall off.

Description

Technical Field

[0001] This invention relates to the field of shoe material manufacturing technology, and in particular to a method for preparing a biodegradable water hyacinth-based material and an insole. Background Technology

[0002] Ethylene-vinyl acetate copolymer foam has long been used in insoles and soles due to its low density, wide processing window, and good foot feel. To improve the environmental friendliness of this type of foamed shoe material, existing technologies propose adding plant powders. These solutions typically use ethylene-vinyl acetate copolymer or other elastomers as the main material, increasing the plant source content or creating a plant granule appearance by adding lignocellulose powder, bamboo fiber, or other plant-derived fillers. However, adding plant powders can damage the inherent properties of the copolymer foam, leading to decreased resilience and compression performance. Furthermore, the added plant powders are prone to particle shedding. Summary of the Invention

[0003] The purpose of this invention is to overcome the defects of the prior art described in the background section and to provide a method for preparing a biodegradable water hyacinth-based material and an insole. The material prepared by this method has the advantages of good resilience and compression performance retention, and the water hyacinth particles are not easily detached.

[0004] The applicant discovered that when poly(butylene adipate / terephthalate) copolyester is co-blended with ethylene-vinyl acetate copolymer, polyolefin elastomer, and EPDM rubber, the resin components exhibit differences in softening temperature, melt viscosity, and shear response. When dried water hyacinth leaf particles or fragments enter this system, insufficient interfacial contact can easily lead to particle detachment during compression molding and cold pressing. Furthermore, excessively low amounts of water hyacinth leaf material make it difficult to form observable spot-like or granular distributions in the finished product, while excessively high amounts increase the risk of cell defects and decreased compressibility.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a biodegradable material based on water hyacinth. The preparation method includes: S10, by weight, melting and shearing 60 to 75 parts of poly(adipate-butylene terephthalate) copolyester, 10 to 25 parts of ethylene-vinyl acetate copolymer, 10 to 25 parts of polyolefin elastomer, 3 to 8 parts of ethylene propylene diene monomer (EPDM) rubber, 1 to 5 parts of inorganic filler, 0.3 to 0.6 parts of stearic acid, 0.5 to 1.0 parts of zinc stearate, 1.0 to 2.0 parts of zinc oxide, 0.5 to 1.2 parts of dried water hyacinth leaves, and 0.2 to 0.6 parts of ethylene-maleic anhydride polymer to obtain a first compound; S20, adding 0.55 to 0.70 parts of... Parts of peroxide crosslinking agent and 5.0 to 6.0 parts of chemical foaming agent are further mixed and then extruded to obtain foamed sheets; S30, the foamed sheets are placed in a mold and molded to obtain a foamed preform; S40, the foamed preform is dried and then cold-pressed to obtain the water hyacinth bio-based biodegradable material; wherein, the dried water hyacinth leaf material is dried water hyacinth leaf granules, water hyacinth leaf fragments or a combination thereof; the ethylene-maleic anhydride polymer is an ethylene-maleic anhydride copolymer, an ethylene-maleic anhydride graft or a combination thereof; the dried water hyacinth leaf material and the ethylene-maleic anhydride polymer are jointly melt-sheared before the addition of the peroxide crosslinking agent and the chemical foaming agent.

[0006] After the above components are combined, a higher amount of poly(adipic acid) / butylene terephthalate copolyester forms a foam matrix with a high polyester content. When the dried water hyacinth leaf material is controlled at 0.5 to 1.2 parts, it can be distributed in the material in the form of a small amount of particles or fragments, forming an observable water hyacinth particle appearance and reducing the impact on the cell structure and foam elasticity. In particular, this invention causes the dried water hyacinth leaf material and the ethylene-maleic anhydride polymer to undergo melt shearing together before the addition of the peroxide crosslinking agent and chemical foaming agent. Water hyacinth leaf material is a plant-derived particle, and its edges and surfaces easily form particle boundaries with the polyester, ethylene-vinyl acetate copolymer, and olefin elastic components. This invention completes the melt shearing of the water hyacinth leaf material, ethylene-maleic anhydride polymer, and main resin before the crosslinking and foaming reaction begins, so that the leaf particles or fragments form sufficient interfacial contact with the surrounding resin before foaming. During compression molding, expansion and stretching occur, and during cold pressing, the particle boundaries are supported by the surrounding matrix, thus mitigating issues such as particle boundary cracking, loosening, and detachment during subsequent foaming and cold pressing. Furthermore, the peroxide crosslinking agent and chemical foaming agent are added after the first compound is formed, ensuring that the initial mixing stage primarily focuses on resin plasticization, leaf material dispersion, and the establishment of the interfacial state around the particles. Subsequent crosslinking and foaming then form a foamed preform, which helps reduce interference from premature crosslinking or foaming reactions on leaf material dispersion. The foamed preform then undergoes drying and cold pressing, achieving final shaping during the pressure cooling process. The interfacial state around the particles formed in the initial stage continues to play a role in this post-processing, resulting in more stable retention of the water hyacinth particles in the finished product. Therefore, this preparation method enables low-volume dried water hyacinth leaf material to remain in a granular or fragmented state in a chemically foamed material with a high content of poly(adipic acid) / butylene terephthalate copolyester, reducing the risk of particle shedding, cell disturbance, and decreased compression performance after foaming and cold pressing. At the same time, the combination of ethylene-vinyl acetate copolymer, polyolefin elastomer, and EPDM rubber ensures that the resulting material is lightweight, resilient, and retains compression well.

[0007] Preferably, the dried water hyacinth leaf material is obtained by drying and crushing water hyacinth leaves; based on the state before feeding, the equivalent particle size of the particles or fragments accounting for 80% to 100% of the mass of the dried water hyacinth leaf material is 0.3 to 3.0 mm, the maximum length is 0.5 to 5.0 mm, and the moisture content is 1% to 8%. The equivalent particle size is the diameter of the circle with equal area corresponding to the planar projected area of ​​the particles or fragments.

[0008] When the particles or fragments are too fine, the leaf material tends to resemble ordinary powder, and the observable particle characteristics are weakened; when the size is too large, it is easy to form local weak interfaces in the foamed matrix. Limiting most particles or fragments to the above range and controlling the moisture content can maintain a more appropriate particle boundary and moisture state for water hyacinth leaf material during melt shearing, molding foaming, and cold pressing, which is conducive to the formation of spot-like or granular distribution and reduces the risk of cell disturbance and particle shedding.

[0009] Preferably, in step S10, the poly(adipate / butylene terephthalate) copolyester, the ethylene-vinyl acetate copolymer, the polyolefin elastomer, and the ethylene propylene diene monomer (EPDM) rubber are first heated and softened to form a molten material. Then, the dried water hyacinth leaf material and the ethylene-maleic anhydride polymer are added to the molten material for further melting and shearing. The melting and shearing temperature in step S10 is 110 to 125°C, and the melting and shearing time is 10 to 15 minutes.

[0010] When the above feeding sequence is adopted, the main resin and rubber components are softened by heat first, and the subsequently added dried water hyacinth leaf material and ethylene-maleic anhydride polymer can continue to be sheared in the composite matrix that has already formed a thermoplastic flow state. As a result, the ethylene-maleic anhydride polymer is more easily distributed between the leaf material particles, polyester components and olefin phase, which is beneficial to maintaining the interfacial state around the particles and reducing the impact of premature crosslinking or foaming processes on the interfacial state.

[0011] Preferably, in step S20, after the peroxide crosslinking agent and the chemical foaming agent are added, they are further mixed until dispersed in the first mixture, and then the foamed sheet is obtained by open milling; the temperature of open milling is 115 to 120°C.

[0012] The peroxide crosslinking agent and chemical foaming agent are added after the first mixture is formed, allowing the dried water hyacinth leaves and ethylene-maleic anhydride polymer to undergo melt shearing before entering the crosslinking and foaming stage. This sequential step reduces the interference of the crosslinking or foaming reaction in the pretreatment on the dispersion of the leaves and the interfacial state around the particles, resulting in a more stable feeding and sheet state for the foamed sheets before entering the molding and foaming process.

[0013] Preferably, before step S10, the process further includes preparing a premix; in preparing the premix, poly(adipate / butylene terephthalate) copolyester, ethylene-vinyl acetate copolymer with a vinyl acetate structural unit content of 30% to 36%, ethylene-maleic anhydride polymer, and stearic acid are melt-sheared and extruded into sheets to obtain the premix; in step S10, the premix serves as at least a portion of the poly(adipate / butylene terephthalate) copolyester and ethylene-vinyl acetate copolymer. When preparing the premix, the melt shear temperature is 110 to 120°C, the melt shear time is 10 to 15 minutes, and the open mill sheeting temperature is 115 to 120°C; or, the raw materials used to prepare the premix are subjected to twin-screw melt shearing treatment, wherein the temperature of the first and second sections of the twin-screw is 130 to 140°C, the temperature of the third and fourth sections is 135 to 145°C, and the temperature of the fifth and sixth sections is 140 to 150°C.

[0014] This premix is ​​pre-melted and sheared from poly(butylene adipate / terephthalate) copolyester, ethylene-vinyl acetate copolymer with a high vinyl acetate structural unit content, and ethylene-maleic anhydride polymer. The polyester component and the ethylene-maleic anhydride polymer have undergone a thermoplastic shearing process before entering the subsequent foaming formulation, thus serving as a source of the poly(butylene adipate / terephthalate) copolyester and ethylene-vinyl acetate copolymer in subsequent S10, providing an optional process route for the compounding and foaming of systems with high polyester content.

[0015] Preferably, the vinyl acetate structural unit content in the ethylene-vinyl acetate copolymer is 18% to 36%. Specifically, the ethylene-vinyl acetate copolymer in the main formulation can be a product with a lower vinyl acetate structural unit content, while the ethylene-vinyl acetate copolymer in the premix can be a product with a higher vinyl acetate structural unit content. The polyolefin elastomer is an ethylene-octene copolymer elastomer. The inorganic filler is talc.

[0016] Ethylene-vinyl acetate copolymer, ethylene-octene copolymer elastomer, and EPDM rubber together form an elastic component suitable for footwear foam materials. This elastic component, combined with a high content of poly(adipate / butylene terephthalate) copolyester and a low amount of water hyacinth leaf particles, allows the material to retain the appearance of plant particles while still possessing the flexibility, resilience, and compression retention properties required for footwear materials.

[0017] Preferably, in step S30, the mold temperature for compression molding is 170 to 180°C, the compression molding time is 190 to 480 seconds, and the foaming ratio is 180% to 220%.

[0018] Preferably, in step S40, the drying temperature is 85 to 95°C, the drying time is 6 to 10 minutes, and the cold pressing time is 150 to 210 seconds.

[0019] The foamed sheet is molded to form a pre-foamed preform, which is then dried and cold-pressed with cooling water to achieve final shape during post-processing and pressure cooling. Because the water hyacinth leaf particles or fragments have already undergone melt shearing with the ethylene-maleic anhydride polymer before foaming, the disturbance to the interface around the particles caused by subsequent foaming expansion and cold pressing can be buffered by the interface contact state formed in the previous stage, thus helping to retain a spot-like or granular distribution in the finished product.

[0020] The present invention also provides an insole, which is made of a water hyacinth biodegradable material prepared by the preparation method described in any of the above embodiments.

[0021] The insole is made of a material containing biodegradable polyester and water hyacinth leaf material obtained by the above preparation method. Water hyacinth spots are visible on the surface or cross-section, and the insole has good particle retention and resilience. Attached Figure Description

[0022] The following figures are used to illustrate embodiments of the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0023] Figure 1 This is a schematic diagram of the insole according to an embodiment of the present invention. Detailed Implementation

[0024] The present application will be further described below with reference to the embodiments and accompanying drawings. It should be understood that the following embodiments are used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Where there is no conflict, the technical features in the following embodiments can be combined with each other.

[0025] The method for preparing the water hyacinth-based biodegradable material in this embodiment includes the following steps: S10, by weight, comprises 60 to 75 parts of poly(adipate-butyl terephthalate) copolyester, 10 to 25 parts of ethylene-vinyl acetate copolymer, 10 to 25 parts of polyolefin elastomer, 3 to 8 parts of ethylene propylene diene monomer (EPDM) rubber, 1 to 5 parts of inorganic filler, 0.3 to 0.6 parts of stearic acid, 0.5 to 1.0 parts of zinc stearate, 1.0 to 2.0 parts of zinc oxide, 0.5 to 1.2 parts of dried water hyacinth leaves, and 0.2 to 0.6 parts of ethylene-maleic anhydride polymer, which are melt-sheared to obtain a first compound. S20, add 0.55 to 0.70 parts of peroxide crosslinking agent and 5.0 to 6.0 parts of chemical foaming agent to the first mixture and continue mixing, and then extrude the mixture to obtain a foamed sheet; S30, the foaming sheet is placed in a mold and molded to obtain a foamed preform; S40, the foamed preform is dried and then cold-pressed to obtain the water hyacinth bio-based biodegradable material.

[0026] Specifically, in S10, 60 to 75 parts by weight of poly(adipate / butylene terephthalate) copolyester, 10 to 25 parts of ethylene-vinyl acetate copolymer, 10 to 25 parts of polyolefin elastomer, 3 to 8 parts of ethylene propylene diene monomer (EPDM) rubber, 1 to 5 parts of inorganic filler, 0.3 to 0.6 parts of stearic acid, 0.5 to 1.0 parts of zinc stearate, 1.0 to 2.0 parts of zinc oxide, 0.5 to 1.2 parts of dried water hyacinth leaf material, and 0.2 to 0.6 parts of ethylene-maleic anhydride polymer are weighed out. The ethylene-vinyl acetate copolymer can be an ethylene-vinyl acetate copolymer with a vinyl acetate structural unit content of 18% to 36%; specifically, the ethylene-vinyl acetate copolymer in the main formulation can be a product with a vinyl acetate structural unit content of approximately 18%, and the ethylene-vinyl acetate copolymer in the premix can be a product with a vinyl acetate structural unit content of approximately 33%. The polyolefin elastomer can be an ethylene-octene copolymer elastomer; the inorganic filler can be talc.

[0027] The dried water hyacinth leaf material comprises dried water hyacinth leaf particles, water hyacinth leaf fragments, or a combination of both. When using water hyacinth leaves, the leaves are first dried, then crushed and sieved. Based on the state before feeding, the equivalent particle size of 80% to 100% of the particles or fragments in the dried water hyacinth leaf material is 0.3 to 3.0 mm, the maximum length is 0.5 to 5.0 mm, and the moisture content is 1% to 8%. The equivalent particle size is determined according to the diameter of the circle with equal area corresponding to the planar projected area of ​​the particles or fragments. Before feeding, the dried water hyacinth leaf material is preferably free of obvious wet clumps, obvious agglomerates, or obvious long strips of entanglement.

[0028] S10 can be carried out in an internal mixer, open mill, or other mixing equipment capable of providing heating and shearing. When using an internal mixer, the mixing chamber is first preheated to 110 to 125°C, and then the poly(butylene adipate / terephthalate) copolyester, ethylene-vinyl acetate copolymer, polyolefin elastomer, and ethylene propylene diene monomer (EPDM) rubber are added, causing the resin and rubber components to soften under shear conditions, forming a continuous molten material. At the end of this stage, the mixture preferably contains no obvious unsoftened resin particles or rubber lumps.

[0029] After the main resin and rubber components form a molten material, inorganic fillers, stearic acid, zinc stearate, and zinc oxide are added, and the process continues with melting and shearing. The powders and additives can be added all at once or in stages depending on the equipment capacity and feed rate. After addition, continue mixing until the powder is completely coated with the molten material, and there are no obvious white lumps, powder accumulations, or agglomerates in the mixture.

[0030] Subsequently, ethylene-maleic anhydride polymer and dried water hyacinth leaf material are added. The ethylene-maleic anhydride polymer is an ethylene-maleic anhydride copolymer, an ethylene-maleic anhydride graft, or a combination of both. When adding, the ethylene-maleic anhydride polymer can be added first, followed by the dried water hyacinth leaf material; alternatively, the ethylene-maleic anhydride polymer and dried water hyacinth leaf material can be pre-dry-mixed before being added to the mixing equipment. After addition, the mixture is further melt-sheared at 110 to 125°C, causing the dried water hyacinth leaf material particles or fragments to tumble and shear with the molten material. The melt-shearing time for S10 is 10 to 15 minutes. At the end of S10, the first mixture is obtained. The first mixture is a lumpy or flaky mixture in a thermoplastic state, containing dried water hyacinth leaf material particles or fragments.

[0031] In some embodiments, a premix can be prepared before step S10. To prepare the premix, poly(adipate / butylene terephthalate) copolyester, ethylene-vinyl acetate copolymer with a vinyl acetate structural unit content of 30% to 36%, ethylene-maleic anhydride polymer, and stearic acid are fed into a mixing apparatus, melt-sheared at 110 to 120°C for 10 to 15 minutes, and then open-milled at 115 to 120°C to obtain sheet-like premix. Alternatively, the above raw materials can be melt-sheared using a twin-screw extruder, with the first and second stages at 130 to 140°C, the third and fourth stages at 135 to 145°C, and the fifth and sixth stages at 140 to 150°C. When using a premix, the premix is ​​used as at least a part of the source of poly(adipate / butylene terephthalate) copolyester and ethylene-vinyl acetate copolymer in S10, and the total amount of S10 is calculated according to the content of each component in the premix.

[0032] In step S20, 0.55 to 0.70 parts of peroxide crosslinking agent and 5.0 to 6.0 parts of chemical foaming agent are added to the first mixture obtained in step S10. The peroxide crosslinking agent and chemical foaming agent are weighed separately before addition and can be mixed before or added sequentially to the first mixture. During the addition process, the first mixture remains in a thermoplasticized state that can be sheared and turned, and the mixing equipment continues to operate to disperse the newly added powdery or granular components in the first mixture.

[0033] After the peroxide crosslinking agent and chemical foaming agent are added, the mixture is continued until they are dispersed in the first mixture. If an open mill is used for this stage, the first mixture can be coated on the rollers, and then the peroxide crosslinking agent and chemical foaming agent can be sprinkled into the gap between the rollers in batches. The next batch can be added after each batch of powder is carried in by the flake material.

[0034] After mixing, the resulting mixture is transferred to an open mill for sheeting. The sheeting temperature is controlled between 115 and 120°C. During open milling, the roller gap is adjusted to allow the mixture to pass repeatedly between the two rollers, and folding, turning, and pressing are performed according to the sheet thickness requirements. The resulting sheet is a foamed material. The foamed sheet is a sheet material containing peroxide crosslinking agent, chemical foaming agent, and dried water hyacinth leaf particles or fragments.

[0035] In step S30, the foaming sheet obtained in step S20 is placed in a mold for compression molding. Before compression molding, the mold cavity is inspected to ensure there are no residues, significant moisture, or foreign objects that could affect mold closure. Based on the shape and size of the material to be prepared, the foaming sheet is cut into sheet units that match the mold cavity, and these sheet units are placed flat inside the mold cavity. When multiple sheets need to be stacked, the edges of each sheet should be aligned.

[0036] After the mold is closed, heating and molding foaming are performed. The mold temperature is controlled at 170 to 180°C, the molding foaming time is 190 to 480 seconds, and the foaming ratio is 180% to 220%. The molding foaming time can be selected within the above range according to the sheet thickness, mold cavity capacity, and target foaming ratio. After the set time is reached, the mold is opened and the foamed preform is removed. The foamed preform is a foam body with the shape of the mold cavity, and water hyacinth leaf particles or fragments are visible on the surface and cross-section.

[0037] In step S40, the foamed preform obtained in step S30 is first dried and then cold-pressed. Before drying, the preform can be visually inspected to remove any obvious burrs or demolding residue. The preform is placed in an oven at 85-95°C for 6-10 minutes. After drying, the preform is placed in a cold-press mold and held under pressure for 150-210 seconds. During cold pressing, cooling water or ice water can be introduced into the mold. Once the cold pressing time reaches the set range, the mold is opened and the material is removed. After removal, trimming, cooling, and visual inspection can be performed. The resulting material is a water hyacinth biodegradable material, its shape corresponding to the cavity of the cold-press mold, with visible water hyacinth leaf particles or fragments on the surface and / or cross-section. The resulting water hyacinth biodegradable material can be further cut, trimmed, or molded into insoles.

[0038] To further illustrate the properties of the materials prepared by the method of preparing water hyacinth bio-based biodegradable materials involved in this invention, the following examples and comparative examples are provided.

[0039] In the following examples and comparative examples, the poly(adipate) / butylene terephthalate copolyester can be GOYENCHEM-PBAT102 poly(adipate) / butylene terephthalate copolyester manufactured by GOYEN CHEMICAL INDUSTRIAL CO., LTD. In the main formulations of Examples 1 to 3, the ethylene-vinyl acetate copolymer can be a product with approximately 18% vinyl acetate structural unit content, such as V5110J ethylene-vinyl acetate copolymer manufactured by BASF-YPC Company Limited; in the premixes of Examples 4, Comparative Examples 3 and 4, the ethylene-vinyl acetate copolymer can be a product with approximately 33% vinyl acetate structural unit content, such as EVATANE 33-45 ethylene-vinyl acetate copolymer manufactured by SK Functional Polymer. The polyolefin elastomer can be ENGAGE 8003 or ENGAGE 8150 ethylene-octene polyolefin elastomer manufactured by Dow Chemical Company. The inorganic filler can be commercially available talc. The peroxide crosslinking agent can be a commercially available odorless peroxide crosslinking agent, and the chemical foaming agent can be ACP-H low-temperature foaming agent produced by Fujian Jinlang New Material Technology Co., Ltd. The above-mentioned brand names and manufacturer information are only used to illustrate the sources of raw materials that can be used in the examples and are not intended to limit the scope of protection of this application.

[0040] Example 1 By weight, weigh out 60 parts of poly(adipate / butylene terephthalate) copolyester, 20 parts of ethylene-vinyl acetate copolymer with a vinyl acetate structural unit content of approximately 18%, 12 parts of polyolefin elastomer, 6 parts of ethylene propylene diene monomer (EPDM) rubber, 2 parts of talc, 0.45 parts of stearic acid, 0.75 parts of zinc stearate, 1.49 parts of zinc oxide, 0.6 parts of dried water hyacinth leaf material, and 0.3 parts of ethylene-maleic anhydride polymer.

[0041] The above-mentioned poly(adipateac / butylene terephthalate) copolyester, ethylene-vinyl acetate copolymer, polyolefin elastomer, ethylene propylene diene monomer (EPDM) rubber, talc, stearic acid, zinc stearate, zinc oxide, dried water hyacinth leaf material, and ethylene-maleic anhydride polymer were mixed at 115±5°C for 12 minutes to obtain the first compound. Subsequently, 0.60 parts of peroxide crosslinking agent and 5.4 parts of chemical foaming agent were added and mixing continued. After mixing, the mixture was extruded at approximately 118°C to obtain foamed sheets.

[0042] The foaming sheet was placed into a mold for compression molding and foaming, with a foaming ratio of 200% and the mold temperature controlled at approximately 175℃. After foaming, a foamed preform was obtained. The foamed preform was placed in a 90℃ oven for drying for 8 minutes, and then transferred to a cold pressing mold for cold pressing for 180±30 seconds. Cooling water was circulated during the cold pressing process to obtain a water hyacinth bio-based biodegradable insole.

[0043] Example 2 By weight, weigh 65 parts of poly(adipate / butylene terephthalate) copolyester, 15 parts of ethylene-vinyl acetate copolymer with a vinyl acetate structural unit content of approximately 18%, 15 parts of polyolefin elastomer, 5 parts of ethylene propylene diene monomer (EPDM) rubber, 1.5 parts of talc, 0.45 parts of stearic acid, 0.75 parts of zinc stearate, 1.49 parts of zinc oxide, 0.8 parts of dried water hyacinth leaf material, and 0.4 parts of ethylene-maleic anhydride polymer.

[0044] The above-mentioned poly(adipateac / butylene terephthalate) copolyester, ethylene-vinyl acetate copolymer, polyolefin elastomer, ethylene propylene diene monomer (EPDM) rubber, talc, stearic acid, zinc stearate, zinc oxide, dried water hyacinth leaf material, and ethylene-maleic anhydride polymer were mixed at 115±5°C for 12 minutes to obtain the first compound. Subsequently, 0.62 parts of peroxide crosslinking agent and 5.6 parts of chemical foaming agent were added and mixing continued. After mixing, the mixture was sheeted at approximately 118°C to obtain foamed sheets.

[0045] The foaming sheet is placed into a mold for compression molding. During compression molding, the mold temperature is controlled at approximately 175℃, and the foaming ratio is 200%. After foaming, the sheet is demolded to obtain a pre-foamed material. The pre-foamed material is then dried in a 90℃ oven for 8 minutes. After drying, the pre-foamed material is transferred to a cold pressing mold and cold-pressed for 180±30 seconds, with cooling water flowing through during the cold pressing process. After cold pressing is completed, the material is removed to obtain a water hyacinth bio-based biodegradable insole.

[0046] The insole obtained in this embodiment is shown in Figure 1. The dried water hyacinth leaves are distributed in granular form on the surface and / or cross-section of the insole. The water hyacinth particles have good color and appearance, and no particles fall off.

[0047] Example 3 By weight, weigh out 75 parts of poly(adipate / butylene terephthalate) copolyester, 10 parts of ethylene-vinyl acetate copolymer with a vinyl acetate structural unit content of about 18%, 10 parts of polyolefin elastomer, 3 parts of ethylene propylene diene monomer (EPDM) rubber, 1 part of talc, 0.6 parts of stearic acid, 1.0 part of zinc stearate, 2.0 parts of zinc oxide, 1.2 parts of dried water hyacinth leaf material, and 0.6 parts of ethylene-maleic anhydride polymer.

[0048] The above-mentioned poly(adipateac / butylene terephthalate) copolyester, ethylene-vinyl acetate copolymer, polyolefin elastomer, ethylene propylene diene monomer (EPDM) rubber, talc, stearic acid, zinc stearate, zinc oxide, dried water hyacinth leaf material, and ethylene-maleic anhydride polymer were mixed at 120°C for 12 minutes to obtain the first compound. Subsequently, 0.70 parts of peroxide crosslinking agent and 6.0 parts of chemical foaming agent were added and mixing continued. After mixing, the mixture was extruded at 120°C to obtain foamed sheets.

[0049] The foaming sheet is placed into a mold for compression molding and foaming, with a foaming ratio of 200% and the mold temperature controlled at 175℃. After foaming, a foamed preform is obtained. The foamed preform is placed in a 90℃ oven for drying for 8 minutes, and then transferred to a cold pressing mold for cold pressing for 180 seconds. Cooling water is circulated during the cold pressing process to obtain a water hyacinth bio-based biodegradable insole.

[0050] Example 4 In this embodiment, a premix with a high polyester content and a relatively high amount of ethylene-maleic anhydride polymer is used as a source of part of the poly(adipate / butylene terephthalate) copolyester and ethylene-vinyl acetate copolymer in S10. By weight, 75 parts of poly(adipate / butylene terephthalate) copolyester, 25 parts of ethylene-vinyl acetate copolymer with approximately 33% vinyl acetate structural units, 1.5 parts of ethylene-maleic anhydride polymer, and 1 part of stearic acid are weighed and mixed at 115±5°C for 12 minutes, and then sheeted at approximately 118°C to obtain the premix.

[0051] Subsequently, the target finished product formulation of Example 2 was recalculated, and the aforementioned premixed material, along with the supplemented poly(adipate / butylene terephthalate) copolyester, ethylene-vinyl acetate copolymer, polyolefin elastomer, EPDM rubber, talc, zinc stearate, zinc oxide, dried water hyacinth leaves, and ethylene-maleic anhydride polymer, were added to a mixing apparatus to ensure that the final main material ratio remained consistent with that of Example 2. The remaining mixing, open milling, molding and foaming, drying, and cold pressing steps were performed according to Example 2 to obtain the water hyacinth bio-based biodegradable insole.

[0052] Comparative Example 1 By weight, the following components are weighed: 25 parts poly(adipateac / butylene terephthalate) copolyester, 45 parts ethylene-vinyl acetate copolymer, 18 parts polyolefin elastomer, 12 parts ethylene propylene diene monomer (EPDM) rubber, 4.5 parts talc, 0.45 parts stearic acid, 0.75 parts zinc stearate, 1.49 parts zinc oxide, and 0.46 parts dried water hyacinth leaf material. This comparative example does not include ethylene-maleic anhydride polymer. The peroxide crosslinking agent is 0.58 parts, and the chemical foaming agent is 5.4 parts.

[0053] The above raw materials were mixed, extruded, molded, foamed, dried, and cold-pressed according to the steps of Example 2 to prepare the comparative insole. Compared with Example 2, the difference in Comparative Example 1 is that the poly(adipate diol) / butylene terephthalate copolyester was 25 parts, the dried water hyacinth leaf material was 0.46 parts, and the ethylene-maleic anhydride polymer was not added.

[0054] Comparative Example 2 By weight, the following components are weighed: 40 parts poly(adipateac / butylene terephthalate) copolyester, 32 parts ethylene-vinyl acetate copolymer, 20 parts polyolefin elastomer, 8 parts ethylene propylene diene monomer (EPDM) rubber, 4.5 parts talc, 0.45 parts stearic acid, 0.75 parts zinc stearate, 1.49 parts zinc oxide, 0.8 parts dried water hyacinth leaf material, and 0.2 parts ethylene-maleic anhydride polymer. The peroxide crosslinking agent is 0.60 parts, and the chemical foaming agent is 5.6 parts.

[0055] The above raw materials were mixed, extruded, molded, foamed, dried, and cold-pressed according to the steps of Example 2 to prepare the comparative insole. Compared with Example 2, the difference in Comparative Example 2 is that the poly(adipate di(2-ethylhexyl) terephthalate) copolyester is 40 parts, the ethylene-maleic anhydride polymer is 0.2 parts, and the amounts of ethylene-vinyl acetate copolymer, polyolefin elastomer, ethylene propylene diene monomer (EPDM) rubber, and talc are adjusted accordingly.

[0056] Comparative Example 3 This comparative example uses a premix with low polyester content and no ethylene-maleic anhydride polymer as a source of some of the poly(adipate / butylene terephthalate) copolyester and ethylene-vinyl acetate copolymer in S10. By weight, 25 parts of poly(adipate / butylene terephthalate) copolyester, 75 parts of ethylene-vinyl acetate copolymer with approximately 33% vinyl acetate structural units, 0.8 parts of KT-25 toughening agent produced by Shenyang Ketong Plastics Co., Ltd., and 1 part of stearic acid were weighed out. Without adding ethylene-maleic anhydride polymer, the mixture was kneaded at 115±5℃ for 12 minutes and then sheeted at approximately 118℃ to obtain the premix. The KT-25 toughening agent is a maleic anhydride-grafted styrene elastomer toughening agent, used only to form a historical premix control and not as a necessary component of the foaming material in this application.

[0057] Subsequently, the components other than the ethylene-maleic anhydride polymer in the target finished product formulation of Example 2 were recalculated. The aforementioned premix, along with the supplemented poly(adipate / butylene terephthalate) copolyester, ethylene-vinyl acetate copolymer, polyolefin elastomer, EPDM rubber, talc, stearic acid, zinc stearate, zinc oxide, and dried water hyacinth leaf material, were added to the internal mixing equipment. The amounts of poly(adipate / butylene terephthalate) copolyester, ethylene-vinyl acetate copolymer, polyolefin elastomer, EPDM rubber, talc, and dried water hyacinth leaf material in the final system were the same as in Example 2, while the ethylene-maleic anhydride polymer content was 0 parts. Then, 0.62 parts of peroxide crosslinking agent and 5.6 parts of chemical foaming agent were added, and the open milling, molding, foaming, drying, and cold pressing steps of Example 2 were followed to obtain the comparative insole.

[0058] Comparative Example 4 This comparative example uses a premix with increased polyester content and containing ethylene-maleic anhydride polymer as a source of some of the poly(adipate / butylene terephthalate) copolyester and ethylene-vinyl acetate copolymer in S10. By weight, 50 parts of poly(adipate / butylene terephthalate) copolyester, 50 parts of ethylene-vinyl acetate copolymer with approximately 33% vinyl acetate structural units, 0.8 parts of ethylene-maleic anhydride polymer, and 1 part of stearic acid were weighed and mixed at 115±5℃ for 12 minutes, and then sheeted at approximately 118℃ to obtain the premix.

[0059] Subsequently, using this premixed material as a partial resin source, it was added together with supplemented poly(butylene adipate / terephthalate) copolyester, ethylene-vinyl acetate copolymer, polyolefin elastomer, ethylene propylene diene monomer (EPDM) rubber, talc, stearic acid, zinc stearate, zinc oxide, dried water hyacinth leaf material, and ethylene-maleic anhydride polymer into a mixing unit. This resulted in the final product containing 50 parts of poly(butylene adipate / terephthalate) copolyester, 30 parts of ethylene-vinyl acetate copolymer, 12 parts of polyolefin elastomer, 8 parts of EPDM rubber, 4.5 parts of talc, 0.45 parts of stearic acid, 0.75 parts of zinc stearate, 1.49 parts of zinc oxide, 0.8 parts of dried water hyacinth leaf material, and 0.8 parts of ethylene-maleic anhydride polymer. Subsequently, 0.60 parts of peroxide crosslinking agent and 5.6 parts of chemical foaming agent were added, and the process of open milling, molding foaming, drying and cold pressing was carried out according to the steps of Example 2 to obtain the comparative insole.

[0060] Performance tests were conducted on the finished insoles obtained in the examples and comparative examples. The performance tests included hardness, density, resilience, static compression, mesh bonding strength, aging resistance, light fastness, and water hyacinth spot effect.

[0061] For finished insole samples, the test piece dimensions were 220 mm × 150 mm × 10 mm. Hardness was measured using an Asker C hardness tester by sampling points on the test piece surface. Density was expressed in g / cm³ and calculated by weighing the test piece and measuring its volume. Rebound rate was measured under the same impact or compression recovery conditions and expressed as a percentage; a higher value indicates better elastic recovery. Static compression testing involved holding the test piece under the same compression conditions for 2 hours and 24 hours, respectively, and measuring the compression set after release; the percentage was expressed as a percentage, with a lower value indicating better compression retention. The mesh bonding strength was obtained by peeling the bonded mesh / foam material interface and measuring the peel force per unit width, expressed in N / cm. Aging resistance and light fastness were assessed using the same batch of samples under the same conditions; a higher grade indicates better appearance retention after testing. The water hyacinth spot effect was determined by observing the particle color, particle distribution, and particle shedding on the insole surface and / or cross-section.

[0062] The test results are shown in Table 1, which lists the test results of the finished insoles of Examples 1 to 4 and Comparative Examples 1 to 4.

[0063] Table 1. Test results of finished insoles from the examples and comparative examples.

[0064] As shown in Table 1, the densities of Examples 1 to 4 were 0.105 to 0.110 g / cm³, the resilience was 64% to 66%, the static compression after 24 hours was 16% to 18%, the mesh adhesive strength was 18.0 to 18.5 N / cm, and the dried water hyacinth leaf particles or fragments remained visible in the insoles without significant particle shedding. Compared with Comparative Examples 1 to 4, Examples 1 to 4 exhibited better overall performance in terms of density, static compression, mesh adhesive strength, and particle retention.

[0065] As can be seen from Comparative Examples 3 and 4, the composition of the premix and whether the final formulation falls within the scope of this application affect the overall performance of the insole. Although Comparative Example 3 also used a premix, its premix had a lower polyester content, and the final system did not include ethylene-maleic anhydride polymer, resulting in lower density, static compression, mesh bonding strength, and particle retention in the insole. Comparative Example 4 contained ethylene-maleic anhydride polymer in its premix, but the final product's main ingredients had lower poly(adipic acid / butylene terephthalate) copolyester content than the limits specified in this application, while the ethylene-vinyl acetate copolymer and ethylene-maleic anhydride polymer content were higher. The results were somewhat improved but still lower than Example 4. Example 4 used a premix with a high polyester content and a higher amount of ethylene-maleic anhydride polymer, while ensuring the final product formulation still met the scope of this application corresponding to Example 2. The finished product's density, resilience, static compression, mesh bonding strength, and particle retention were all within the range of Examples 1 to 3. Therefore, when the premixed material is used as a source of some of the poly(adipate / butylene terephthalate) copolyester and ethylene-vinyl acetate copolymer in S10, it can be considered as an optional process route for systems with higher polyester content.

[0066] The above embodiments are used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or improvements made by those skilled in the art to the above embodiments without departing from the concept of the present invention should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a biodegradable material based on water hyacinth, characterized in that, include: S10, by weight, comprises 60 to 75 parts of poly(adipate-butyl terephthalate) copolyester, 10 to 25 parts of ethylene-vinyl acetate copolymer, 10 to 25 parts of polyolefin elastomer, 3 to 8 parts of ethylene propylene diene monomer (EPDM) rubber, 1 to 5 parts of inorganic filler, 0.3 to 0.6 parts of stearic acid, 0.5 to 1.0 parts of zinc stearate, 1.0 to 2.0 parts of zinc oxide, 0.5 to 1.2 parts of dried water hyacinth leaves, and 0.2 to 0.6 parts of ethylene-maleic anhydride polymer, which are melt-sheared to obtain a first compound. S20, add 0.55 to 0.70 parts of peroxide crosslinking agent and 5.0 to 6.0 parts of chemical foaming agent to the first mixture and continue mixing, and then extrude the mixture to obtain a foamed sheet; S30, the foaming sheet is placed in a mold and molded to obtain a foamed preform; S40, the foamed preform is dried and then cold-pressed to obtain the water hyacinth bio-based biodegradable material; The dried water hyacinth leaf material is dried water hyacinth leaf granules, water hyacinth leaf fragments, or a combination thereof; the ethylene-maleic anhydride polymer is an ethylene-maleic anhydride copolymer, an ethylene-maleic anhydride graft, or a combination thereof; the dried water hyacinth leaf material and the ethylene-maleic anhydride polymer are subjected to melt shearing together before the addition of the peroxide crosslinking agent and the chemical foaming agent.

2. The preparation method according to claim 1, characterized in that, The dried water hyacinth leaf material is obtained by drying and crushing water hyacinth leaves; based on the state before feeding, the equivalent particle size of the particles or fragments accounting for 80% to 100% of the mass of the dried water hyacinth leaf material is 0.3 to 3.0 mm, the maximum length is 0.5 to 5.0 mm, and the moisture content is 1% to 8%; the equivalent particle size is the diameter of the circle with equal area corresponding to the planar projected area of ​​the particles or fragments.

3. The preparation method according to claim 1 or 2, characterized in that, In step S10, the poly(adipate / butylene terephthalate) copolyester, the ethylene-vinyl acetate copolymer, the polyolefin elastomer, and the ethylene propylene diene monomer (EPDM) rubber are first heated and softened to form a molten material. Then, the dried water hyacinth leaf material and the ethylene-maleic anhydride polymer are added to the molten material for further melting and shearing. The melting and shearing temperature in step S10 is 110 to 125°C, and the melting and shearing time is 10 to 15 minutes.

4. The preparation method according to claim 1, characterized in that, In step S20, after the peroxide crosslinking agent and the chemical foaming agent are added, they are further mixed until dispersed in the first mixture, and then the foamed sheet is obtained by open milling; the temperature of open milling is 115 to 120°C.

5. The preparation method according to claim 1, characterized in that, Before step S10, the process further includes preparing a premix; in preparing the premix, poly(adipate / butylene terephthalate) copolyester, ethylene-vinyl acetate copolymer with a vinyl acetate structural unit content of 30% to 36%, ethylene-maleic anhydride polymer, and stearic acid are melt-sheared and extruded into sheets to obtain the premix; in step S10, the premix is ​​used as at least a portion of the poly(adipate / butylene terephthalate) copolyester and ethylene-vinyl acetate copolymer.

6. The preparation method according to claim 5, characterized in that, When preparing the premix, the melt shear temperature is 110 to 120°C, the melt shear time is 10 to 15 minutes, and the open mill sheeting temperature is 115 to 120°C; or, the raw materials used to prepare the premix are subjected to twin-screw melt shearing treatment, wherein the temperature of the first and second sections of the twin-screw is 130 to 140°C, the temperature of the third and fourth sections is 135 to 145°C, and the temperature of the fifth and sixth sections is 140 to 150°C.

7. The preparation method according to claim 1, characterized in that, The ethylene-vinyl acetate copolymer contains 18% to 36% vinyl acetate structural units; the polyolefin elastomer is an ethylene-octene copolymer elastomer; and the inorganic filler is talc.

8. The preparation method according to claim 1, characterized in that, In S30, the mold temperature for compression molding is 170 to 180°C, the compression molding time is 190 to 480 seconds, and the foaming ratio is 180% to 220%.

9. The preparation method according to claim 1, characterized in that, In step S40, the drying temperature is 85 to 95°C, the drying time is 6 to 10 minutes, and the cold pressing time is 150 to 210 seconds.

10. An insole, characterized in that, The insole is made of a water hyacinth-based biodegradable material prepared by any one of claims 1 to 9.

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