Preparation process of composite waterproof sports shoes

Abstract

The application relates to the technical field of shoe manufacturing, and discloses a preparation process of a composite waterproof sports shoe, which comprises the following steps: stirring and adsorbing a natural tree bark condensed tannin extract aqueous solution and natural diatomite, filtering and drying, and preparing a tannin-diatomic waterproof functional carrier; filling the natural rubber with waste EVA foaming powder to prepare upper rubber material, compounding the tannin-diatomic waterproof functional carrier and zinc stearate with the natural rubber and reclaimed rubber to prepare middle rubber material, and reinforcing the natural rubber and reclaimed rubber with carbon black to prepare bottom rubber material; once-molded vulcanization of the three-layer rubber sheet to prepare a composite waterproof outsole; and binding, bonding and hot-melt waterproof adhesive tape sealing to prepare a finished product; the application inhibits the oxidation loss of active polyphenol hydroxyl under high temperature of the internal mixer, makes the tannin-zinc waterproof compound generate in sufficient amount and be uniformly fixed in the middle rubber matrix, and the waterproof durability is obviously superior to that of the prior art; the waste EVA foaming powder and waste rubber powder are used in high value.

Description

Technical Field

[0001] This invention relates to the field of footwear manufacturing technology, and more specifically, to a manufacturing process for a composite waterproof athletic shoe. Background Technology

[0002] Current waterproof athletic shoe outsoles are made primarily from natural rubber, with zinc stearate as a waterproofing agent. The process involves intensive mixing, open milling, and then compression molding and vulcanization. Under heating conditions during molding, zinc stearate migrates to the outsole surface, forming a hydrophobic soap film, with its waterproofing effect mainly concentrated on the outsole surface. However, the powder obtained from grinding waste athletic shoe sole rubber (hereinafter referred to as "waste rubber powder") and waste athletic shoe midsole EVA foam material (hereinafter referred to as "waste EVA foam powder") is difficult to effectively recycle without reducing the outsole's waterproof and mechanical properties using existing technologies, resulting in solid waste accumulation and high raw material costs. Natural tree bark tannin extracts are a class of natural compounds containing polyphenolic hydroxyl groups. These polyphenolic hydroxyl groups can combine with zinc ions (Zn²⁺) to form tannin-zinc waterproofing complexes with a hydrophobic carbon chain skeleton. When these complexes are uniformly distributed within the rubber matrix, they can block hydrophilic channels within the rubber phase, demonstrating potential value as an internal waterproofing agent for outsoles. However, if tannin extracts are directly added to a mixer in free form, the polyphenolic ring structure of tannins is highly susceptible to oxidative polymerization under the high-temperature conditions (150–180 °C), resulting in the significant consumption of active polyphenolic hydroxyl groups. Simultaneously, because tannin molecules contain hydrophilic polyphenolic hydroxyl groups and a hydrophobic benzene ring skeleton, they are driven by their amphiphilic nature to segregate towards the rubber / air interface in non-polar rubber matrices, leading to extremely uneven tannin distribution within the rubber matrix. These two major obstacles have prevented tannin extracts from being directly used in the preparation of rubber outsoles to date.

[0003] In existing technologies, the waterproofing effect of zinc stearate relies entirely on the hydrophobic soap film formed on the outsole surface, lacking an effective water-blocking structure inside the outsole. During repeated bending, the surface soap film gradually fails due to physical wear, with weak points easily appearing in the bending areas, resulting in severely insufficient waterproofing durability. Furthermore, in existing single-layer homogeneous outsole formulations, lightweighting, internal waterproofing, and abrasion resistance are difficult to achieve simultaneously due to the interplay of formulation components. Therefore, overcoming the dual obstacles of high-temperature oxidative degradation of tannin extracts during rubber mixing and their uneven distribution within the rubber matrix, and achieving sufficient and uniform formation of the tannin-zinc waterproofing complex in the middle layer of the outsole rubber matrix, thereby constructing a durable waterproofing system primarily based on internal waterproofing, is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0004] This invention provides a manufacturing process for composite waterproof sports shoes, solving the technical problems in related technologies where tannin extracts cannot be used in outsole preparation due to degradation by high-temperature oxidation during intensive mixing and uneven distribution in the rubber matrix, and where the waterproof durability of the soap salt film on the surface of zinc stearate is insufficient.

[0005] This invention provides a manufacturing process for composite waterproof sports shoes, comprising the steps of introducing waterproofing additives into a rubber outsole formulation and preparing the outsole through intensive mixing, open mixing, and compression molding vulcanization, including: Aqueous solutions of condensed tannin extract from natural tree bark were mixed with natural diatomaceous earth, allowing the tannin polyphenol hydroxyl groups and diatomaceous earth silanol groups to be adsorbed and immobilized through hydrogen bonding. After filtration and drying, a tannin-diatomaceous earth waterproof functional carrier was obtained. The tannin-diatomaceous earth waterproof functional carrier is compounded with zinc stearate, natural rubber, and recycled rubber through intensive mixing. The Zn in the molten zinc stearate... 2+ Ligand exchange occurs between the tannin polyphenol hydroxyl groups immobilized within the diatomaceous earth channels and the tannin polyphenol hydroxyl groups, which then replace stearate and Zn. 2+ Coordination is achieved by in-situ generation of tannin-zinc waterproofing complexes in the rubber matrix to produce the middle layer film; The upper layer of rubber is made by filling natural rubber with waste EVA foaming powder and mixing it in an intensive process; the lower layer of rubber is made by mixing natural rubber and recycled rubber with carbon black and mixing them in an intensive process. The bottom layer film, middle layer film, and top layer film are stacked in sequence and placed into a mold for one-time molding and vulcanization. Co-vulcanization and cross-linking occur between the three layers to obtain a composite waterproof outsole. The composite waterproof outsole is bonded to the shoe upper, and hot-melt waterproof tape is applied to the joint edge and pressed to seal it, thus producing a composite waterproof sports shoe.

[0006] Preferably, the total polyphenol content of the natural bark condensed tannin extract is not less than 60%, calculated as tannic acid; and the mass fraction of the aqueous solution is 5% to 20%.

[0007] Preferably, the particle size of the natural diatomaceous earth is 10-30 μm, and the specific surface area is not less than 20 m² / g; the mass ratio of the condensed tannin extract to the natural diatomaceous earth is 1:3 to 1:8, and the mixture is stirred at room temperature for 30-120 min.

[0008] Preferably, in the filtration and drying process, the drying temperature is 60-80 ℃, and the drying is carried out until the moisture content is less than 3%.

[0009] Preferably, the formulation of the upper layer film is based on 100 parts by weight of natural rubber, including: 100 parts by weight of natural rubber, 20-40 parts by weight of waste EVA foaming powder, 1.5-3 parts by weight of sulfur, and 0.5-1.5 parts by weight of accelerator CBS (N-cyclohexyl-2-benzothiazole sulfenamide); the waste EVA foaming powder is peroxide cross-linked EVA foaming powder obtained by grinding waste sports shoe midsoles, with a particle size of 20-60 mesh and a density of 0.05-0.15 g / cm³.

[0010] Preferably, the formulation of the middle layer film is based on 100 parts by weight of total rubber usage, including: 40-60 parts by weight of natural rubber, 40-60 parts by weight of reclaimed rubber, 10-20 parts by weight of waste rubber powder, 10-20 parts by weight of tannin-diatomaceous earth waterproof functional carrier, 3-6 parts by weight of zinc stearate, 1.5-3 parts by weight of sulfur, and 0.5-1.5 parts by weight of CBS; the Mooney viscosity ML(1+4) of the reclaimed rubber at 100 °C is 50-80; the waste rubber powder is obtained by grinding waste sports shoe soles, with a particle size of 40-80 mesh.

[0011] Preferably, the formulation of the bottom layer film is based on 100 parts by weight of total rubber, including: 50-70 parts by weight of natural rubber, 30-50 parts by weight of reclaimed rubber, 20-40 parts by weight of N330 carbon black, 1.5-3 parts by weight of sulfur, and 0.5-1.5 parts by weight of CBS; the Mooney viscosity ML(1+4) of the reclaimed rubber at 100 °C is 50-80; and the iodine adsorption value of the N330 carbon black is 75-95 mg / g.

[0012] Preferably, the mixing temperature of each layer of film, including the top layer, middle layer, and bottom layer, is 120–150 °C.

[0013] Preferably, the conditions for the primary molding vulcanization are: temperature 150–170 °C, pressure 10–15 MPa, and time 10–20 min.

[0014] Preferably, the natural diatomaceous earth is natural-grade diatomaceous earth that has not undergone forced calcination treatment.

[0015] The beneficial effects of this invention are as follows: by pre-immobilizing tannin extract in the pores of natural diatomaceous earth, and utilizing the dual protection of physical shielding of the pores and low-temperature intensive mixing (120-150 °C), the oxidation and consumption of tannin active polyphenol hydroxyl groups at high temperatures during intensive mixing are significantly inhibited. At the same time, the mechanical shear force of intensive mixing drives the diatomaceous earth particles to be forcibly and uniformly dispersed in the rubber matrix, overcoming the problem of spontaneous agglomeration of free tannins in non-polar rubber, and ensuring the sufficient, uniform, and stable formation of tannin-zinc waterproofing complex in the middle layer rubber matrix. The outsole waterproofing method has been upgraded from a single surface waterproofing that relies on a surface soap salt film to a durable internal waterproofing based on a tannin-zinc waterproofing compound in the middle layer. The tannin-zinc compound is evenly fixed in the middle layer rubber matrix and will not fall off with bending and wear, greatly improving the waterproofing durability. The EVA foam powder from the midsole of discarded sports shoes and the rubber powder from discarded outsoles are introduced into the upper and middle layers respectively. This achieves high-value recycling of waste materials without reducing the overall performance of the outsole, thereby reducing raw material costs and solid waste. The three layers are laminated and co-vulcanized in one molding process, forming chemical bonds between the layers. This gives the outsole three functional zones: lightweight (upper layer), internal waterproof (middle layer), and wear-resistant grounding (bottom layer). At the same time, it ensures that each layer does not separate during bending and use, and the waterproof effect remains stable. Attached Figure Description

[0016] Figure 1 This is a bar chart comparing the retention rates of tannin active polyphenol hydroxyl groups in each group after intensive mixing in Experiment 1 of this invention. Figure 2 This is a comparison diagram of the T-shaped peeling force-displacement curves at the interface between the bottom and middle layers in Experiment 2 of this invention; Figure 3 This is a comparison chart showing the change in hydrostatic pressure resistance of the outsole with the number of bends after the bending durability test in Experiment 3 of this invention. Detailed Implementation

[0017] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0018] Example 1 This embodiment discloses a manufacturing process for a composite waterproof sports shoe, which includes the following steps: Step 1: Preparation of Tannin-Diatomite Waterproofing Carrier A natural bark condensed tannin extract with a total polyphenol content of 62% (calculated as tannic acid) was prepared into a 10% (w / w) tannin aqueous solution by adding water and stirring until completely dissolved. Natural-grade diatomaceous earth (untreated by forced calcination) with a particle size of 15 μm and a specific surface area of ​​25 m² / g was added to the above tannin aqueous solution at a tannin extract to diatomaceous earth mass ratio of 1:5. The mixture was stirred at room temperature for 60 min to allow the tannin polyphenol hydroxyl groups and the diatomaceous earth silanol groups (-SiOH) to be adsorbed and immobilized through hydrogen bonding, thus immobilizing the tannin in the porous structure of the diatomaceous earth. The suspension was filtered to obtain a wet diatomaceous earth filter cake containing tannin, which was dried at 70 °C until the moisture content was below 3%, yielding a tannin-diatomaceous earth waterproof functional carrier for later use.

[0019] Step 2: Preparation of adhesives for each functional layer Upper layer rubber compound: The formula consists of 100 parts by weight of natural rubber, 30 parts by weight of peroxide crosslinked EVA foam powder (particle size 35 mesh, density 0.10 g / cm³) obtained by grinding waste sports shoe midsoles, 2 parts by weight of sulfur, and 1 part by weight of CBS. All components are put into an internal mixer and mixed at 135 ℃ until uniformly mixed. The mixture is then rolled into sheets using a two-roll mill to produce the upper layer rubber sheet for later use.

[0020] Intermediate layer rubber compound: The formula consists of 50 parts by weight of natural rubber, 50 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 65), 15 parts by weight of waste rubber powder (particle size 60 mesh) obtained from grinding waste sports shoe soles, 15 parts by weight of tannin-diatomaceous earth waterproof functional carrier prepared in step one, 4.5 parts by weight of zinc stearate, 2 parts by weight of sulfur, and 1 part by weight of CBS. All components are put into an internal mixer and mixed at 135 ℃ until uniformly mixed. The mixture is then rolled into sheets using a two-roll mill to produce intermediate layer rubber sheets for later use.

[0021] Base layer rubber compound: The formula consists of 60 parts by weight of natural rubber, 40 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 65), 30 parts by weight of N330 carbon black (iodine adsorption value 85 mg / g), 2 parts by weight of sulfur, and 1 part by weight of CBS. All components are put into an internal mixer and mixed at 135 ℃ until uniformly mixed. The mixture is then rolled into sheets using a two-roll mill to produce the base layer rubber sheet for later use.

[0022] Step 3: Three layers are stacked and molded in one step. The bottom layer of rubber is placed at the bottom of the outsole mold (corresponding to the ground side), the middle layer of rubber is stacked on top of the bottom layer of rubber, and the top layer of rubber is stacked on top of the middle layer of rubber (corresponding to the insole side facing the inside of the shoe). After the three layers of rubber are aligned, they are placed into the outsole mold and molded and vulcanized at 160 ℃ and 12 MPa for 15 min. Co-vulcanization crosslinking occurs between the three layers to obtain a composite waterproof outsole.

[0023] Step 4: Overall Preparation of Sports Shoes The composite waterproof outsole obtained in step three is placed with the upper layer facing the inside of the shoe upper. After stretching and gluing, hot melt waterproof tape is applied to the joint edge between the outsole and the shoe upper and then heated and pressed to seal. After shaping and finishing, the finished composite waterproof sports shoe is obtained.

[0024] Example 2 This embodiment discloses a manufacturing process for a composite waterproof sports shoe, which includes the following steps: Step 1: Preparation of Tannin-Diatomite Waterproofing Carrier A natural bark condensed tannin extract with a total polyphenol content of 60% (calculated as tannic acid) was prepared into a 5% (w / w) tannin aqueous solution by adding water and stirring until completely dissolved. Natural-grade diatomaceous earth (untreated by forced calcination) with a particle size of 10 μm and a specific surface area of ​​22 m² / g was added to the above tannin aqueous solution at a tannin extract to diatomaceous earth mass ratio of 1:3. The mixture was stirred at room temperature for 30 min to allow the tannin polyphenol hydroxyl groups and diatomaceous earth silanol groups to be adsorbed and immobilized through hydrogen bonding. The suspension was filtered and dried at 60 °C until the moisture content was below 3%, yielding a tannin-diatomaceous earth waterproof functional carrier for later use.

[0025] Step 2: Preparation of adhesives for each functional layer Upper layer rubber compound: The formula consists of 100 parts by weight of natural rubber, 20 parts by weight of waste EVA foaming powder (particle size 25 mesh, density 0.10 g / cm³), 1.5 parts by weight of sulfur, and 0.5 parts by weight of CBS. The mixture is thoroughly mixed at 120 ℃, then rolled into sheets to form the upper layer rubber sheet for later use.

[0026] Intermediate layer rubber compound: The formula consists of 40 parts by weight of natural rubber, 60 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 50), 10 parts by weight of waste rubber powder (particle size 45 mesh), 10 parts by weight of tannin-diatomaceous earth waterproof functional carrier, 3 parts by weight of zinc stearate, 1.5 parts by weight of sulfur, and 0.5 parts by weight of CBS. The mixture is thoroughly mixed at 120 ℃, then rolled into sheets to form the intermediate layer rubber sheet for later use.

[0027] Base layer rubber compound: The formula consists of 50 parts by weight of natural rubber, 50 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 50), 20 parts by weight of N330 carbon black (iodine adsorption value 75 mg / g), 1.5 parts by weight of sulfur, and 0.5 parts by weight of CBS. The mixture is thoroughly mixed at 120℃, then rolled into sheets to form the base layer rubber sheet for later use.

[0028] Step 3: Three layers are stacked and molded in one step. The three layers of film are stacked in the order of bottom layer, middle layer and top layer and placed into the outsole mold. They are then molded and vulcanized at 150 ℃ and 10 MPa for 10 min. Co-vulcanization and cross-linking occur between the three layers to obtain a composite waterproof outsole.

[0029] Step 4: Overall Preparation of Sports Shoes The composite waterproof outsole obtained in step three is placed with the upper layer facing the inside of the shoe upper. After stretching and gluing, hot melt waterproof tape is applied to the joint edge between the outsole and the shoe upper and then heated and pressed to seal. After shaping and finishing, the finished composite waterproof sports shoe is obtained.

[0030] Example 3 This embodiment discloses a manufacturing process for a composite waterproof sports shoe, which includes the following steps: Step 1: Preparation of Tannin-Diatomite Waterproofing Carrier A natural bark condensed tannin extract with a total polyphenol content of 78% (calculated as tannic acid) was prepared into a 20% (w / w) tannin aqueous solution by adding water and stirring until completely dissolved. Natural-grade diatomaceous earth (untreated by forced calcination) with a particle size of 28 μm and a specific surface area of ​​28 m² / g was added to the above tannin aqueous solution at a tannin extract to diatomaceous earth mass ratio of 1:8. The mixture was stirred at room temperature for 120 min to allow the tannin polyphenol hydroxyl groups and diatomaceous earth silanol groups to be adsorbed and immobilized through hydrogen bonding. The suspension was filtered and dried at 80 °C until the moisture content was below 3%, yielding a tannin-diatomaceous earth waterproof functional carrier for later use.

[0031] Step 2: Preparation of adhesives for each functional layer Upper layer rubber compound: The formula consists of 100 parts by weight of natural rubber, 40 parts by weight of waste EVA foaming powder (particle size 40 mesh, density 0.08 g / cm³), 3 parts by weight of sulfur, and 1.5 parts by weight of CBS. The mixture is thoroughly mixed at 150 ℃, then rolled into sheets to form the upper layer rubber sheet for later use.

[0032] Intermediate layer rubber compound: The formula consists of 60 parts by weight of natural rubber, 40 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 80), 20 parts by weight of waste rubber powder (particle size 75 mesh), 20 parts by weight of tannin-diatomaceous earth waterproof functional carrier, 6 parts by weight of zinc stearate, 3 parts by weight of sulfur, and 1.5 parts by weight of CBS. The mixture is thoroughly mixed at 150 ℃, then rolled into sheets to form intermediate layer rubber sheets for later use.

[0033] Base layer rubber compound: The formula consists of 70 parts by weight of natural rubber, 30 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 80), 40 parts by weight of N330 carbon black (iodine adsorption value 95 mg / g), 3 parts by weight of sulfur, and 1.5 parts by weight of CBS. The mixture is thoroughly mixed at 150 ℃, then rolled into sheets to form the base layer rubber sheet for later use.

[0034] Step 3: Three layers are stacked and molded in one step. Three layers of film are stacked in the order of bottom layer, middle layer and top layer and placed into the outsole mold. The mold is then subjected to compression molding and vulcanization at 170 ℃ and 15 MPa for 20 min. Co-vulcanization and cross-linking occur between the three layers to obtain a composite waterproof outsole.

[0035] Step 4: Overall Preparation of Sports Shoes The composite waterproof outsole obtained in step three is placed with the upper layer facing the inside of the shoe upper. After stretching and gluing, hot melt waterproof tape is applied to the joint edge between the outsole and the shoe upper and then heated and pressed to seal. After shaping and finishing, the finished composite waterproof sports shoe is obtained.

[0036] Example 4 This embodiment discloses a manufacturing process for a composite waterproof sports shoe, which includes the following steps: Step 1: Preparation of Tannin-Diatomite Waterproofing Carrier A natural bark condensed tannin extract with a total polyphenol content of 70% (calculated as tannic acid) was prepared into a 15% (w / w) tannin aqueous solution by adding water and stirring until completely dissolved. Natural-grade diatomaceous earth (untreated by forced calcination) with a particle size of 20 μm and a specific surface area of ​​26 m² / g was added to the above tannin aqueous solution at a tannin extract to diatomaceous earth mass ratio of 1:6. The mixture was stirred at room temperature for 90 min to allow the tannin polyphenol hydroxyl groups and diatomaceous earth silanol groups to be adsorbed and immobilized through hydrogen bonding. The suspension was filtered and dried at 75 °C until the moisture content was below 3%, yielding a tannin-diatomaceous earth waterproof functional carrier for later use.

[0037] Step 2: Preparation of adhesives for each functional layer Upper layer rubber compound: The formula consists of 100 parts by weight of natural rubber, 35 parts by weight of waste EVA foaming powder (particle size 30 mesh, density 0.08 g / cm³), 2.5 parts by weight of sulfur, and 1.2 parts by weight of CBS. The mixture is thoroughly mixed at 142 ℃, then rolled into sheets to form the upper layer rubber sheet for later use.

[0038] Intermediate layer rubber compound: The formula consists of 55 parts by weight of natural rubber, 45 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 70), 18 parts by weight of waste rubber powder (particle size 50 mesh), 12 parts by weight of tannin-diatomaceous earth waterproof functional carrier, 5 parts by weight of zinc stearate, 2.5 parts by weight of sulfur, and 1.2 parts by weight of CBS. The mixture is thoroughly mixed at 142 ℃, then rolled into sheets to form intermediate layer rubber sheets for later use.

[0039] Base layer rubber compound: The formula consists of 65 parts by weight of natural rubber, 35 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 70), 35 parts by weight of N330 carbon black (iodine adsorption value 88 mg / g), 2.5 parts by weight of sulfur, and 1.2 parts by weight of CBS. The mixture is thoroughly mixed at 142℃, then rolled into sheets to form the base layer rubber sheet for later use.

[0040] Step 3: Three layers are stacked and molded in one step. The three layers of film are stacked in the order of bottom layer, middle layer and top layer and placed into the outsole mold. They are then molded and vulcanized at 163 ℃ and 13 MPa for 17 min. Co-vulcanization crosslinking occurs between the three layers to obtain a composite waterproof outsole.

[0041] Step 4: Overall Preparation of Sports Shoes The composite waterproof outsole obtained in step three is placed with the upper layer facing the inside of the shoe upper. After stretching and gluing, hot melt waterproof tape is applied to the joint edge between the outsole and the shoe upper and then heated and pressed to seal. After shaping and finishing, the finished composite waterproof sports shoe is obtained.

[0042] Example 5 This embodiment discloses a manufacturing process for a composite waterproof sports shoe, which includes the following steps: Step 1: Preparation of Tannin-Diatomite Waterproofing Carrier This step involves pre-adsorbing and immobilizing tannin extracts into the porous structure of natural diatomaceous earth to prepare a tannin-diatomaceous earth waterproof functional carrier.

[0043] A natural bark condensed tannin extract with a total polyphenol content of 62% (calculated as tannic acid) was prepared by adding water to a 10% (w / w) tannin aqueous solution and stirring until completely dissolved. This example uses a condensed tannin extract, whose polyphenolic hydroxyl units are directly linked by C-C bonds and do not contain ester bonds that can be hydrolyzed at high temperatures. Under intensive high-temperature mixing conditions, its thermal stability is significantly better than that of hydrolyzed tannins containing ester bonds.

[0044] The tannin extract was mixed with natural diatomaceous earth (particle size 15 μm, specific surface area not less than 20 m² / g, natural grade diatomaceous earth without forced calcination) at a mass ratio of 1:5. The diatomaceous earth was added to the tannin aqueous solution and stirred at room temperature for 60 min. This allowed the polyphenolic hydroxyl groups of the tannin molecules to bond with the silanol hydroxyl groups (-SiOH) on the surface and inner walls of the pores of the diatomaceous earth particles through hydrogen bonds, thus adsorbing and immobilizing the tannin within the porous structure of the diatomaceous earth. The resulting suspension was filtered to remove excess liquid, yielding a wet diatomaceous earth filter cake containing tannin. The filter cake was then dried at 70 °C until the moisture content was less than 3%, yielding a tannin-diatomaceous earth waterproof functional carrier for later use.

[0045] The core function of step one is: (1) After the tannin is fixed on the inner wall of the diatomite channel, the channel wall forms a physical shield for the tannin, reducing the contact between the tannin and oxygen in the mixing system. Combined with the dual protection of low temperature mixing (135 ℃), it synergistically inhibits the oxidation consumption of the active polyphenol hydroxyl groups of tannin; (2) It is put into the mixing machine in the form of solid particle carrier. Under the forced action of the mechanical shear force of the mixing machine rotor, the diatomite particles are evenly dispersed in various parts of the rubber matrix, and the tannin in its channel is simultaneously evenly distributed, overcoming the problem that free tannin molecules spontaneously agglomerate to the rubber / air interface driven by their own amphiphilicity.

[0046] Step 2: Preparation of adhesives for each functional layer This step introduces waste EVA foaming powder and waste rubber powder into different functional layer formulations, and uses the tannin-diatomite waterproof functional carrier obtained in step one together with zinc stearate in the intermediate waterproof formulation.

[0047] The upper layer rubber compound is formulated with 100 parts by weight of natural rubber, 30 parts by weight of peroxide-crosslinked EVA foam powder (particle size 35 mesh, density 0.10 g / cm³) obtained from grinding waste sports shoe midsoles, 2 parts by weight of sulfur, and 1 part by weight of CBS. All components are added to an internal mixer and mixed at 135 ℃ until homogeneous. The mixture is then pressed into sheets using a two-roll mill to produce the upper layer rubber sheet for later use. The waste EVA foam powder is obtained by grinding and crushing waste sports shoe midsoles (peroxide-crosslinked EVA foam). The EVA molecular chains are interconnected by chemical crosslinking bonds, forming a thermosetting network structure. At the molding temperature (160 ℃), the crosslinked EVA particles only soften without melting, preserving the cell skeleton structure and ensuring the lightweight effect persists in the final outsole.

[0048] Intermediate layer rubber compound: The formula consists of 50 parts by weight of natural rubber, 50 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 65), 15 parts by weight of waste rubber powder (particle size 60 mesh) obtained from grinding waste sports shoe soles, 15 parts by weight of tannin-diatomaceous earth waterproof functional carrier prepared in step one, 4.5 parts by weight of zinc stearate, 2 parts by weight of sulfur, and 1 part by weight of CBS. All components are put into an internal mixer and mixed at 135 ℃ until uniformly mixed. The mixture is then rolled into sheets using a two-roll mill to produce intermediate layer rubber sheets for later use. During the mixing process, zinc stearate is heated and melted (melting point approximately 130 ℃). The Zn²⁺ in the molten zinc stearate comes into direct contact with the active polyphenolic hydroxyl groups of tannins immobilized in the pores of diatomaceous earth, resulting in ligand exchange. The polyphenolic hydroxyl groups of tannins replace stearate groups and coordinate with Zn²⁺ due to their multidentate chelating advantage, generating tannin-zinc waterproof complexes and free stearic acid in situ in the rubber matrix.

[0049] Base layer rubber compound: The formula consists of 60 parts by weight of natural rubber, 40 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 100 ℃ is 65), 30 parts by weight of N330 carbon black (iodine adsorption value 85 mg / g), 2 parts by weight of sulfur, and 1 part by weight of CBS. All components are put into an internal mixer and mixed at 135 ℃ until uniformly mixed. The mixture is then rolled into sheets using a two-roll mill to produce the base layer rubber sheet for later use.

[0050] Step 3: Three layers are stacked and molded in one step. This step involves stacking the three layers of film obtained in step two according to their functional zones, and then molding and vulcanizing them once to produce a composite waterproof outsole with a three-layer functional zone structure.

[0051] The bottom layer of rubber is placed at the bottom of the outsole mold (corresponding to the side of the outsole that touches the ground), the middle layer of rubber is stacked on top of the bottom layer, and the top layer of rubber is stacked on top of the middle layer (corresponding to the side of the outsole facing the insole). After aligning the three layers of rubber, they are placed into the outsole mold and molded and vulcanized at 160 ℃ and 12 MPa for 15 min to obtain a composite waterproof outsole. During the molding process, co-vulcanization crosslinking occurs between adjacent layers of rubber at the interface, and interlayer chemical bonds are formed between the layers. At the same time, the molding temperature (160 ℃) is higher than the mixing temperature (135 ℃). The remaining zinc stearate in the middle layer of rubber that has not yet completed ligand exchange during the mixing stage continues to undergo ligand exchange with the active polyphenol hydroxyl groups of tannins under the high temperature of molding, making the formation of the tannin-zinc waterproof complex more complete.

[0052] The outsole has three functional zones: the top layer (facing the midsole) is a natural rubber layer filled with waste EVA foam powder, giving the outsole low-density characteristics; the middle layer (interlayer) is the main waterproof layer containing tannin-zinc waterproofing compound, which seals the hydrophilic channels inside the rubber matrix; and the bottom layer (grounding side) is a rubber layer filled with high carbon black, providing excellent grounding and abrasion resistance.

[0053] Step 4: Overall Preparation of Sports Shoes With the upper layer of the composite waterproof outsole obtained in step three facing the inside of the upper, the upper is stretched and fixed to the shoe last through a stretching process; shoe adhesive is applied between the upper layer of the outsole and the upper, and the upper and outsole are bonded together by bonding and pressing; hot melt waterproof tape is applied to the edge where the outsole and upper meet and then heated and pressed to seal, eliminating water seepage channels at the joint; after shaping and finishing, the finished composite waterproof sports shoe is obtained.

[0054] Experimental verification Experiment 1: Effect of Tannin-Diatomite Waterproofing Carrier on the Retention of Active Polyphenol Hydroxyl Groups in Tannins During the Intensive Mixing Process 1. Experimental Objective The study verified the effect of the dual protection mechanism of physical shielding of diatomaceous earth channels and low-temperature intensive mixing on improving the retention of hydroxyl groups of tannin active polyphenols, and proved that the tannin-diatomaceous earth waterproof functional carrier can significantly inhibit the oxidative degradation of tannin during the intensive mixing process, thereby ensuring the sufficient generation of subsequent tannin-zinc waterproof complexes.

[0055] 2. Preparation of experimental samples The rubber matrix was based on the formulation of the intermediate layer rubber compound in Example 1, uniformly using 50 parts by weight of natural rubber, 50 parts by weight of reclaimed rubber (Mounney viscosity ML(1+4) 65 at 100℃), 2 parts by weight of sulfur, and 1 part by weight of CBS. The amount of tannin components in each group was uniformly prepared according to a calculated dry tannin content of 2.5 parts by weight (consistent with the tannin content of the 15 parts by weight tannin-diatomaceous earth carrier in Example 1; the tannin extract to diatomaceous earth mass ratio is 1:5, therefore 15 parts of carrier contain 2.5 parts of tannin extract). The three groups of samples were prepared as follows: Control group A (free tannins, high-temperature internal mixing): 2.5 parts by weight of condensed tannin extract dry powder with a total polyphenol content of 62% were directly mixed with the above rubber matrix components, put into an internal mixer, and internally mixed at 150°C for 10 min.

[0056] Control group B (free tannins, low-temperature mixing): Take 2.5 parts by weight of the same amount of free tannin extract dry powder, mix it directly with the above rubber matrix components, put it into a mixer, and mix it at 135℃ for 10 min.

[0057] Experimental group (tannin-diatomaceous earth waterproof functional carrier, low-temperature mixing): Tannin-diatomaceous earth waterproof functional carrier was prepared according to the parameters of step one of Example 1 (10% aqueous solution mass fraction, 62% total polyphenol content, tannin extract to diatomaceous earth mass ratio 1:5, stirring at room temperature for 60 min, drying at 70℃ until the moisture content is less than 3%). 15 parts by mass of the carrier and the above rubber matrix components were put into a mixer and mixed at 135℃ for 10 min.

[0058] 3. Experimental conditions (1) Rotor speed of internal mixer: 60 rpm; (2) Internal mixing time: 10 min for each group; (3) Method for determining polyphenol content: Folin-Ciocalteu colorimetric method (refer to QB / T 2600), wavelength of 760 nm, with gallic acid as standard to draw a standard curve, and the result is expressed as gallic acid equivalent (mg / g); (4) Each group is measured 3 times, the average value is taken, and the standard deviation is calculated.

[0059] 4. Experimental Procedure (1) After the mixing is completed, take about 3 g from each group of rubber compounds, add 30 mL of 70% ethanol solution, and extract by ultrasonication in a water bath at 80℃ for 30 min. Filter and make up to 50 mL of the filtrate as the test solution for each group.

[0060] (2) Take an appropriate amount of raw material condensed tannin extract that has not been refurbished and dissolve it directly in a 70% ethanol solution to prepare an initial control solution with the same concentration as each group, which serves as the baseline for 100% retention.

[0061] (3) The total polyphenol content of each group of test solutions was determined according to the Folin-phenol method specified in QB / T 2600, and the total polyphenol content of each group was converted by the gallic acid standard curve (mg / g, calculated as gallic acid equivalent).

[0062] (4) Calculate the retention rate of active polyphenol hydroxyl groups after intensive mixing (%) = Measured value after intensive mixing / Measured value of initial control × 100%.

[0063] 5. Experimental Results Table 1. Comparison of total tannin polyphenol content and retention rate of active polyphenol hydroxyl groups in each group after intensive refining. (Note: Each value is the average of three parallel measurements ± standard deviation.) Figure 1 Bar chart of hydroxyl group retention rate of active polyphenols after intensive mixing (see attached figure) Figure 1 ) 6. Analysis and Summary The retention rate of active polyphenolic hydroxyl groups in control group A (free tannins, 150℃ internal mixing) was only 28.3%, indicating that free tannins underwent extensive oxidative polymerization under high-temperature internal mixing, resulting in severe loss of active polyphenolic hydroxyl groups. The retention rate in control group B (free tannins, 135℃ internal mixing) increased to 42.7%, demonstrating that lowering the mixing temperature has a certain inhibitory effect on tannin oxidation, but the effect of lowering the temperature alone is limited.

[0064] The retention rate of the experimental group (tannin-diatomaceous earth carrier, 135℃ intensive mixing) reached 68.1%, which was 39.8 percentage points higher than that of the control group A and 25.4 percentage points higher than that of the control group B. This proves that the dual protection mechanism of physical shielding of diatomaceous earth channels and low-temperature intensive mixing significantly reduced the oxidation consumption of active polyphenol hydroxyl groups of tannin, which can effectively guarantee the sufficient generation of tannin-zinc waterproofing complex.

[0065] Experiment 2: Verification of the interlayer bond strength of three-layer composite single-stage molding co-vulcanization crosslinking 1. Experimental Objective By comparing the bonding strength between the bottom and middle layers of the three-layer composite outsole obtained by the co-vulcanization crosslinking process and the traditional physical bonding process, it is verified that the one-time molding co-vulcanization crosslinking method of the present invention can achieve a significantly better interlayer bonding strength than physical bonding, thereby ensuring that the layers do not separate during the bending and use of the outsole.

[0066] 2. Preparation of experimental samples Both groups of samples were prepared using the formulation of Example 1 to prepare the top, middle, and bottom layers of film (with parameters completely consistent with Example 1).

[0067] Control group (physical bonding): The three layers of rubber were individually molded and vulcanized at 160℃ and 12 MPa for 15 min. Then, a shoe-grade neoprene rubber adhesive (approximately 100 g / m²) was uniformly applied to the contact surface between the bottom and middle layers. The layers were then pressed together at room temperature for 24 h to obtain the control group three-layer outsole sample.

[0068] Experimental group (co-vulcanization crosslinking, this invention): The three-layer film was stacked in the order of bottom layer, middle layer and top layer and then placed into the mold at once. It was molded and vulcanized at 160°C and 12 MPa for 15 min. Co-vulcanization crosslinking occurred between the three layers at the interface, and the experimental group three-layer outsole sample was obtained, which was completely consistent with step three of Example 1.

[0069] 3. Experimental conditions (1) T-type peel strength test shall be performed in accordance with GB / T 2791; (2) Sample size: 25 mm wide, effective peel length not less than 100 mm; (3) Tensile speed: 100 mm / min; (4) Test interface: the interface between the bottom layer and the middle layer; (5) Prepare 5 samples for each group and take the average value and standard deviation.

[0070] 4. Experimental Procedure (1) Cut each group of three-layer bottom samples into strips 25 mm wide. Carefully pre-peel about 20 mm at the interface between the bottom and middle layers as the clamping end. Clamp the bottom and middle layers into the upper and lower clamps of the universal testing machine respectively. (2) Perform T-shaped peeling at a tensile speed of 100 mm / min and record the peeling force-displacement curve (the effective length of the segment should not be less than 50 mm). (3) Calculate the average value of the effective segment peeling force and divide it by the sample width to obtain the T-shaped peeling strength (N / mm). (4) Record the failure mode (interfacial failure or cohesive failure).

[0071] 5. Experimental Results Table 2 Comparison of T-type peel strength between the bottom and middle layers (Note: Each value is the average of 5 samples ± standard deviation. Cohesive failure indicates that the interlayer chemical bond strength has exceeded the strength of the rubber matrix.) Figure 2 T-shaped peel force-displacement curve at the interface between the bottom and middle layers (see attached figure) Figure 2 ) 6. Analysis and Summary The control group (physical bonding) showed a T-peel strength of only 2.48 N / mm, with failure occurring at the adhesive-rubber interface, indicating that physical bonding has limited effect on improving interlayer bond strength. The experimental group (co-vulcanization crosslinking) achieved a T-peel strength of 8.17 N / mm, an improvement of approximately 229% compared to the control group. Furthermore, the failure mode was cohesive failure within the rubber matrix, indicating that the chemical bond strength formed by interlayer co-vulcanization crosslinking exceeds the strength of the rubber matrix itself, and the interface is the strongest point rather than a weak point. This result demonstrates that the three-layer lamination, one-time molding co-vulcanization crosslinking process can form high-strength interlayer chemical bonds, ensuring that the layers do not separate during bending and stress, and preventing water seepage channels from forming in the middle rubber matrix due to interlayer separation.

[0072] Experiment 3: Verification of the outsole's hydrostatic pressure resistance after bending durability test 1. Experimental Objective By comparing the three-layer composite outsole of this invention (with an internal waterproofing system containing tannin-zinc waterproofing compound in the middle layer) with the existing single-layer homogeneous outsole (which relies solely on the surface zinc stearate migration film for waterproofing) after repeated bending, the durability advantage of the waterproofing system of this invention is verified.

[0073] 2. Preparation of experimental samples Control Group A (Pre-existing single-layer homogeneous outsole): A single-layer homogeneous outsole sample was prepared using a formula of 100 parts by weight of natural rubber, 4.5 parts by weight of zinc stearate, 2 parts by weight of sulfur, and 1 part by weight of CBS. The mixture was thoroughly mixed at 135°C, pressed into sheets, and then molded and vulcanized at 160°C and 12 MPa for 15 min. (Note: This control group represents the existing outsole formula using a single-layer homogeneous natural rubber compound with zinc stearate as the sole waterproofing agent. Its waterproofing mechanism relies entirely on the migration of zinc stearate to the outer surface of the outsole to form a hydrophobic soap film. The zinc stearate content in the control group was 4.5 parts by weight per 100 parts of rubber, consistent with the zinc stearate content in the middle layer of the experimental group. This eliminates the interference of differences in ZnSt content on the experimental results, allowing the comparison of waterproofing performance degradation between the two groups to directly reflect the essential difference in the waterproofing mechanism.) Experimental group (three-layer composite outsole of the present invention): prepared strictly according to steps one to three of Example 1, wherein the middle layer formula contains 15 parts by mass of tannin-diatomite waterproof functional carrier and 4.5 parts by mass of zinc stearate, and a three-layer composite outsole sample is obtained.

[0074] Both sets of samples were cut to standard dimensions (150 mm long, 80 mm wide, and 6 mm thick).

[0075] 3. Experimental conditions (1) Bending test: A reciprocating bending tester was used, with a bending angle of 60° and a frequency of 100 times / min. The samples were taken out after bending for 100, 300 and 500 times respectively. (2) Static water pressure test: The test was performed in accordance with QB / T 2813. The test surface was the bottom surface (outer surface of the bottom layer). The pressure rate was 6 kPa / min. The static water pressure value (kPa) when water seeped out was recorded. (3) After each bending stage, the independent samples of the same batch were subjected to static water pressure test. Three samples were taken for each stage of each group, and the average value was taken.

[0076] 4. Experimental Procedure (1) Take 3 samples from each of the two groups and perform an initial hydrostatic pressure test (QB / T 2813) before bending, and record the initial hydrostatic pressure value; (2) Put the remaining samples into the bending test machine in batches, bend them to 100, 300 and 500 times respectively, and take them out immediately for hydrostatic pressure test; (3) Plot the hydrostatic pressure retention rate (%) of the number of bending times (0, 100, 300 and 500 times) against the initial value, and compare the attenuation trend of the two groups.

[0077] 5. Experimental Results Table 3 Comparison of hydrostatic pressure resistance of the outsole at different stages of the bending durability test (Note: Each value is the average of 3 samples ± standard deviation.) Figure 3 Comparison of the effects of bending times on the hydrostatic pressure resistance of the two sets of outsole (see attached figure) Figure 3 ) 6. Analysis and Summary The control group A (single-layer homogeneous outsole with a surface soap salt film for waterproofing) had an initial hydrostatic pressure resistance of 18.2 kPa. After 100 bends, this dropped to 13.8 kPa (75.8% retention rate), and after 500 bends, it was only 3.6 kPa (19.8% retention rate). This indicates that with increasing bends, the zinc stearate soap salt film on the outsole surface gradually detaches due to mechanical wear, leading to a rapid decline in waterproofing performance. The experimental group (three-layer composite outsole with tannin-zinc internal waterproofing) had an initial hydrostatic pressure resistance of 24.8 kPa, and after 500 bends, it maintained 22.9 kPa (92.3% retention rate), showing almost no decrease in waterproofing performance with increasing bends. The difference in hydrostatic pressure resistance between the two groups after 500 bends was 19.3 kPa, fully demonstrating that the uniformly fixed tannin-zinc waterproofing complex within the rubber matrix of this invention does not rely on a surface migration film layer, and its waterproofing function does not fail due to outsole bending and wear. The outsole's waterproofing durability is significantly superior to existing technologies.

[0078] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A manufacturing process for a composite waterproof sports shoe, comprising the steps of introducing a waterproofing additive into a rubber outsole formulation and then preparing the outsole through intensive mixing, open mixing, and compression molding vulcanization, characterized in that, include: Aqueous solutions of condensed tannin extract from natural tree bark were mixed with natural diatomaceous earth, allowing the tannin polyphenol hydroxyl groups and diatomaceous earth silanol groups to be adsorbed and immobilized through hydrogen bonding. After filtration and drying, a tannin-diatomaceous earth waterproof functional carrier was obtained. The tannin-diatomaceous earth waterproof functional carrier is compounded with zinc stearate, natural rubber, and recycled rubber through intensive mixing. The Zn in the molten zinc stearate... 2+ Ligand exchange occurs between the tannin polyphenol hydroxyl groups immobilized within the diatomaceous earth channels and the tannin polyphenol hydroxyl groups, which then replace stearate and Zn. 2+ Coordination is achieved by in-situ generation of tannin-zinc waterproofing complexes in the rubber matrix to produce the middle layer film; The upper layer of rubber is made by filling natural rubber with waste EVA foaming powder and mixing it in an intensive process; the lower layer of rubber is made by mixing natural rubber and recycled rubber with carbon black and mixing them in an intensive process. The bottom layer film, middle layer film, and top layer film are stacked in sequence and placed into a mold for one-time molding and vulcanization. Co-vulcanization and cross-linking occur between the three layers to obtain a composite waterproof outsole. The composite waterproof outsole is bonded to the upper, and hot melt waterproof tape is applied to the joint edge and pressed to seal it, thus producing a composite waterproof sports shoe. The total polyphenol content of the natural bark condensed tannin extract is not less than 60%, calculated as tannic acid; the mass fraction of the aqueous solution is 5% to 20%. The natural diatomaceous earth has a particle size of 10–30 μm and a specific surface area of ​​not less than 20 m². 2 / g; the mass ratio of the condensed tannin extract to natural diatomaceous earth is 1:3 to 1:8, and the mixture is stirred at room temperature for 30 to 120 minutes.

2. The preparation process according to claim 1, characterized in that, In the filtration and drying process, the drying temperature is 60-80℃, and the drying is carried out until the moisture content is less than 3%.

3. The preparation process according to claim 1, characterized in that, The formulation of the upper layer film is based on 100 parts by weight of natural rubber, including: 100 parts by weight of natural rubber, 20-40 parts by weight of waste EVA foam powder, 1.5-3 parts by weight of sulfur, and 0.5-1.5 parts by weight of CBS; the waste EVA foam powder is peroxide cross-linked EVA foam powder obtained by grinding waste sports shoe midsoles, with a particle size of 20-60 mesh and a density of 0.05-0.15 g / cm³. 3 .

4. The preparation process according to claim 1, characterized in that, The formulation of the middle layer film is based on a total rubber content of 100 parts by weight, including: 40-60 parts by weight of natural rubber, 40-60 parts by weight of reclaimed rubber, 10-20 parts by weight of waste rubber powder, 10-20 parts by weight of tannin-diatomaceous earth waterproof functional carrier, 3-6 parts by weight of zinc stearate, 1.5-3 parts by weight of sulfur, and 0.5-1.5 parts by weight of CBS; the Mooney viscosity ML(1+4) of the reclaimed rubber at 100 °C is 50-80; the waste rubber powder is obtained by grinding waste sports shoe soles, with a particle size of 40-80 mesh.

5. The preparation process according to claim 1, characterized in that, The formulation of the bottom film is based on a total rubber content of 100 parts by weight, including: 50-70 parts by weight of natural rubber, 30-50 parts by weight of reclaimed rubber, 20-40 parts by weight of N330 carbon black, 1.5-3 parts by weight of sulfur, and 0.5-1.5 parts by weight of CBS; the Mooney viscosity ML(1+4) of the reclaimed rubber at 100°C is 50-80; and the iodine adsorption value of the N330 carbon black is 75-95 mg / g.

6. The preparation process according to claim 1, characterized in that, The mixing temperature for each layer of film is 120–150 °C.

7. The preparation process according to claim 1, characterized in that, The conditions for the first compression molding vulcanization are: temperature 150-170 ℃, pressure 10-15 MPa, and time 10-20 min.

8. The preparation process according to claim 1, characterized in that, The natural diatomaceous earth is natural-grade diatomaceous earth that has not undergone forced calcination treatment.

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