Insole rubber composite modified material and preparation method thereof

Abstract

The present application relates to the technical field of high polymer materials, in particular to a kind of insole rubber composite modified material and preparation method thereof.The insole rubber composite modified material of the present application is prepared by natural rubber, styrene-butadiene rubber, zinc oxide, stearic acid, antioxidant, filler and halloysite nanotube loaded with blowing agent etc. through banburying process;The halloysite nanotube loaded with blowing agent is obtained by chlorination of halloysite nanotube first, then reacting with dimethylallylamine and 4-(dimethylamino) benzenesulfonic acid, and finally loading blowing agent.The present application realizes the stable crosslinking network of modified nanotube and rubber matrix through the synergistic effect of chemical bonding and electrostatic adsorption, and realizes the site loading of blowing agent, solves the technical problem that traditional insole material cannot consider high toughness and breathable comfort.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a rubber composite modified material for shoe insoles and its preparation method. Background Technology

[0002] Insoles are an essential part of wearing shoes. They have a certain shock absorption function and can reduce the impact of the ground on the human body when running, thus reducing the damage to muscles and bones.

[0003] As a key component for foot support and cushioning, the performance of insoles directly affects wearing comfort and sports protection. Currently, there are many types of insoles on the market, such as breathable, odor-resistant, antibacterial, health-promoting, and sweat-wicking types. Their elastomeric foam layers mainly use polyurethane and ethylene-vinyl acetate copolymer as the foaming material matrix. Polyurethane foam is highly toxic, volatile, and causes air pollution, and is also relatively expensive. While ethylene-vinyl acetate copolymer is cheaper, prolonged use leads to severe wear on the forefoot and heel, where the foot experiences the most pressure, resulting in poor performance. Compared to polyurethane and ethylene-vinyl acetate copolymer foam, rubber foam has superior tensile, tear, abrasion, compression, and aging resistance properties.

[0004] Patent document CN110713641B discloses a method for preparing a soft, shock-absorbing, and tear-resistant sports shoe insole material. This invention involves thoroughly mixing styrene-butadiene rubber / silicone rubber / ethylene-vinyl acetate with silica, solid paraffin, zinc oxide, and stearic acid in a Banbury mixer. Then, a foaming agent, a crosslinking agent (diisopropylbenzene peroxide), and sulfur are added to the Banbury mixer, and the mixture is further mixed. This mixture is then pressed into sheets on an open two-roll mill, placed in a flat vulcanizing apparatus, and subjected to compression molding, crosslinking, and foaming to produce sheets. After cooling, a soft, shock-absorbing, and tear-resistant sports shoe insole material is obtained, characterized by low hardness, low resilience, lightweight, and high elongation at break and tear strength.

[0005] However, the addition of reinforcing materials often affects the mechanical strength of the matrix, and the compensating materials may block certain pores, thus affecting the breathability and moisture permeability of the insole.

[0006] Therefore, there is an urgent need to develop a new rubber composite material for insoles to solve the problem that insole materials cannot simultaneously possess high mechanical strength and high breathability and moisture permeability. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a rubber composite modified material for insoles and its preparation method, so as to solve the problem that traditional rubber materials for insoles cannot simultaneously possess high mechanical strength and high breathability and moisture permeability.

[0008] To achieve the above objectives, the present invention provides a rubber composite modified material for shoe insoles, which is prepared from the following raw materials in parts by weight: 70-75 parts natural rubber, 25-30 parts styrene-butadiene rubber, 5-6 parts zinc oxide, 1-2 parts stearic acid, 1-2 parts antioxidant, 5-10 parts filler, 10-15 parts halloysite nanotubes loaded with foaming agent, 1.8-2 parts vulcanizing agent, and 0.5-1 part vulcanization accelerator;

[0009] The preparation steps of the halloysite nanotubes loaded with the foaming agent are as follows:

[0010] S1: Halloysite nanotubes and chloropropyltriethoxysilane are hydrolyzed-condensed in a solvent to obtain halloysite nanotubes with chloride.

[0011] S2: Under a nitrogen atmosphere, halloysite nanotubes, dimethylallylamine, and 4-(dimethylamino)benzenesulfonic acid are reacted in tetrahydrofuran to obtain multi-modified halloysite nanotubes.

[0012] S3: Disperse multiple modified halloysite nanotubes and a foaming agent in deionized water, and after ultrasonic treatment, obtain halloysite nanotubes loaded with foaming agent.

[0013] Preferably, the weight ratio of halloysite nanotubes, chloropropyltriethoxysilane, and solvent in step S1 is 10-15g:1-1.5g:100g.

[0014] Preferably, the halloysite nanotubes described in step S1 have an outer diameter of 40-150 nm, an inner diameter of 10-25 nm, and a length of 100-2000 nm.

[0015] Preferably, the solvent in step S1 is a mixture of deionized water and anhydrous ethanol in a weight ratio of 30-40g:60-70g.

[0016] Preferably, the weight ratio of halloysite nanotubes, dimethylallylamine, 4-(dimethylamino)benzenesulfonic acid, and tetrahydrofuran in step S2 is 10-15g:0.5-0.75g:1-1.5g:100-200g.

[0017] Preferably, the weight ratio of the multiple modified halloysite nanotubes, foaming agent, and deionized water in step S3 is 10-15g:5-10g:100-200g.

[0018] The foaming agent mentioned in step S3 is 4,4'-oxobisbenzenesulfonylhydrazine.

[0019] Preferably, the main component of the natural rubber is a natural polymer compound, of which 91%-94% is rubber hydrocarbon, and the remainder is non-rubber substances such as protein, fatty acid, ash and sugar.

[0020] Preferably, the styrene monomer unit content of the styrene-butadiene rubber is 22%-25%.

[0021] Preferably, the antioxidant is one of antioxidant AW and antioxidant 4020.

[0022] Preferably, the filler is one of carbon black N330, E250G, N110 and N234.

[0023] Preferably, the vulcanizing agent is sulfur.

[0024] Preferably, the vulcanization accelerator is accelerator CZ.

[0025] Furthermore, the present invention also provides a method for preparing a rubber composite modified material for shoe insoles, comprising the following steps:

[0026] Natural rubber and styrene-butadiene rubber are added to a mixer and plasticized at 100-110℃ for 5 minutes. Then, zinc oxide, stearic acid, antioxidant and filler are added in sequence and mixed at 120-130℃ for 8-10 minutes to obtain a primary rubber compound. Then, halloysite nanotubes loaded with foaming agent and the primary rubber compound are added to the mixer and mixed at 150-160℃ for 6-9 minutes. Then, vulcanizing agent and accelerator are added and mixed for another 5-6 minutes. The rubber compound is discharged and cooled to room temperature to obtain a rubber composite modified material for shoe insoles.

[0027] The beneficial effects of this invention are:

[0028] This invention modifies halloysite nanotubes to construct a crosslinked network on their surface, with quaternary ammonium salt segments and alkenyl and benzenesulfonic acid end caps. The alkenyl groups can participate in subsequent vulcanization crosslinking, resulting in good interfacial bonding between the multi-modified halloysite nanotubes and the rubber matrix. At the same time, the quaternary ammonium salts and benzenesulfonic acid on the surface have good hydrophilicity, which can enhance its moisture permeability, giving the insole rubber composite material good mechanical properties and moisture permeability.

[0029] This invention modifies halloysite nanotubes, enabling the foaming agent to be loaded onto the surface of the halloysite nanotubes through electrostatic and hydrogen bonding interactions. During the subsequent foaming process, this results in point-to-point foaming and a more regular hierarchical pore structure, which ensures rapid transport of gas and water vapor while avoiding the strength loss problem common in traditional porous materials.

[0030] Compared to a simple system of mixing multiple modified halloysite nanotubes and a foaming agent, the halloysite nanotubes loaded with a foaming agent utilize a loading method. Through the loading, the foaming agent is confined between the lumen and surface active sites of the halloysite nanotubes, resulting in a more uniformly distributed microporous structure during vulcanization. This maintains the integrity of the material while forming effective air permeability channels, leading to superior overall performance in terms of mechanical properties, wear resistance, and air and moisture permeability. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] The properties or sources of the raw materials used in the embodiments and comparative examples of this invention are as follows:

[0033] Natural rubber: 91%-94% is rubber hydrocarbon, the remainder is non-rubber substances such as protein, fatty acid, ash and sugar; Styrene-butadiene rubber: styrene monomer content is 22%-25%; Halloysite nanotubes: outer diameter is 40-150nm, inner diameter is 10-25nm, and length is 100-2000nm.

[0034] Example 1: A rubber composite modified material for shoe insoles, the specific preparation steps are as follows:

[0035] (1) Add 10g halloysite nanotubes to 30g deionized water and 60g anhydrous ethanol, sonicate for 30min, then add 1g chloropropyltriethoxysilane, heat to 50℃, stir for 6h, centrifuge after the reaction is completed, and obtain chlorinated halloysite nanotubes after washing and drying.

[0036] (2) Under a nitrogen atmosphere, 10g of halloysite nanotubes, 0.5g of dimethylallylamine and 1g of 4-(dimethylamino)benzenesulfonic acid were added to 100g of tetrahydrofuran, heated to 50℃, and stirred for 48h. After the reaction was completed, the mixture was centrifuged, and the resulting precipitate was washed and dried to obtain multi-modified halloysite nanotubes.

[0037] (3) Disperse 10g of multimodified halloysite nanotubes in 100g of deionized water, sonicate for 20min, add 5g of foaming agent 4,4'-oxobisbenzenesulfonylhydrazine, stir continuously for 2h, then centrifuge and vacuum dry at 60℃ for 12h to obtain halloysite nanotubes loaded with foaming agent.

[0038] (4) Add 70g of natural rubber and 0g of styrene-butadiene rubber to a mixer and plasticize at 100°C for 5 minutes. Then add 5g of zinc oxide, 1g of stearic acid, 1g of antioxidant 4020 and 5g of carbon black N330 in sequence and mix at 120°C for 8 minutes to obtain the initial mixed rubber compound.

[0039] (5) Add 10g of halloysite nanotubes loaded with foaming agent into a mixer and mix with the initial mixed rubber at 150°C for 6 minutes. Then add 1.8g of sulfur and 0.5g of accelerator CZ and continue mixing for 5 minutes until the torque is stable. Discharge the rubber and cool it to room temperature to obtain the insole rubber composite modified material.

[0040] Example 2: A rubber composite modified material for shoe insoles, the specific preparation steps are as follows:

[0041] (1) Add 13g halloysite nanotubes to 35g deionized water and 65g anhydrous ethanol, sonicate for 30min, then add 1.3g chloropropyltriethoxysilane, heat to 55℃, stir for 6h, centrifuge after the reaction is completed, and obtain chlorinated halloysite nanotubes after washing and drying.

[0042] (2) Under a nitrogen atmosphere, 13g of halloysite nanotubes, 0.65g of dimethylallylamine and 1.3g of 4-(dimethylamino)benzenesulfonic acid were added to 150g of tetrahydrofuran, heated to 53℃, and stirred for 48h. After the reaction was completed, the mixture was centrifuged, and the resulting precipitate was washed and dried to obtain multi-modified halloysite nanotubes.

[0043] (3) 13g of multimodified halloysite nanotubes were dispersed in 150g of deionized water, sonicated for 20min, and then 8g of foaming agent 4,4'-oxobisbenzenesulfonylhydrazine was added. The mixture was stirred for 2h, and then centrifuged and vacuum dried at 60℃ for 12h to obtain halloysite nanotubes loaded with foaming agent.

[0044] (4) Add 73g of natural rubber and 27g of styrene-butadiene rubber to a mixer and plasticize at 105°C for 5 minutes. Then add 5.5g of zinc oxide, 1.5g of stearic acid, 1.5g of antioxidant 4020 and 8g of carbon black N330 in sequence and mix at 125°C for 9 minutes to obtain the initial mixed rubber compound.

[0045] (5) Add 13g of halloysite nanotubes loaded with foaming agent into a mixer and mix with the initial mixed rubber at 155°C for 8 minutes. Then add 1.9g of sulfur and 0.8g of accelerator CZ and continue mixing for 6 minutes until the torque is stable. Discharge the rubber and cool it to room temperature to obtain the insole rubber composite modified material.

[0046] Example 3: A rubber composite modified material for shoe insoles, the specific preparation steps are as follows:

[0047] (1) Add 15g halloysite nanotubes to 40g deionized water and 70g anhydrous ethanol, sonicate for 30min, then add 1.5g chloropropyltriethoxysilane, heat to 60℃, stir for 6h, centrifuge after the reaction is completed, and obtain chlorinated halloysite nanotubes after washing and drying.

[0048] (2) Under a nitrogen atmosphere, 15g of halloysite nanotubes, 0.75g of dimethylallylamine and 1.5g of 4-(dimethylamino)benzenesulfonic acid were added to 200g of tetrahydrofuran, heated to 55℃, and stirred for 48h. After the reaction was completed, the mixture was centrifuged, and the resulting precipitate was washed and dried to obtain multi-modified halloysite nanotubes.

[0049] (3) Disperse 15g of multimodified halloysite nanotubes in 200g of deionized water, sonicate for 20min, add 10g of foaming agent 4,4'-oxobisbenzenesulfonylhydrazine, stir continuously for 3h, then centrifuge and vacuum dry at 60℃ for 12h to obtain halloysite nanotubes loaded with foaming agent.

[0050] (4) Add 75g of natural rubber and 25g of styrene-butadiene rubber to a mixer and plasticize at 110°C for 5 minutes. Then add 6g of zinc oxide, 2g of stearic acid, 2g of antioxidant 4020 and 10g of carbon black N330 in sequence and mix at 130°C for 10 minutes to obtain the initial mixed rubber compound.

[0051] (5) Add 15g of halloysite nanotubes loaded with foaming agent into a mixer and mix with the initial mixed rubber at 160°C for 9min. Then add 2g of sulfur and 1g of accelerator CZ and continue mixing for 6min until the torque is stable. Discharge the rubber and cool it to room temperature to obtain the insole rubber composite modified material.

[0052] Comparative Example 1: The difference from Example 2 is that dimethylallylamine in step (2) is replaced with 4-(dimethylamino)benzenesulfonic acid, and the specific steps are as follows:

[0053] (1) Add 13g halloysite nanotubes to 35g deionized water and 65g anhydrous ethanol, sonicate for 30min, then add 1.3g chloropropyltriethoxysilane, heat to 55℃, stir for 6h, centrifuge after the reaction is completed, and obtain chlorinated halloysite nanotubes after washing and drying.

[0054] (2) Under a nitrogen atmosphere, 13g of halloysite nanotubes and 1.95g of 4-(dimethylamino)benzenesulfonic acid were added to 150g of tetrahydrofuran, heated to 53℃, and stirred for 48h. After the reaction was completed, the mixture was centrifuged, and the resulting precipitate was washed and dried to obtain multi-modified halloysite nanotubes.

[0055] (3) 13g of multimodified halloysite nanotubes were dispersed in 150g of deionized water, sonicated for 20min, and then 8g of foaming agent 4,4'-oxobisbenzenesulfonylhydrazine was added. The mixture was stirred for 2h, and then centrifuged and vacuum dried at 60℃ for 12h to obtain halloysite nanotubes loaded with foaming agent.

[0056] (4) Add 73g of natural rubber and 27g of styrene-butadiene rubber to a mixer and plasticize at 105°C for 5 minutes. Then add 5.5g of zinc oxide, 1.5g of stearic acid, 1.5g of antioxidant 4020 and 8g of carbon black N330 in sequence and mix at 125°C for 9 minutes to obtain the initial mixed rubber compound.

[0057] (5) Add 13g of halloysite nanotubes loaded with foaming agent into a mixer and mix with the initial mixed rubber at 155°C for 8 minutes. Then add 1.9g of sulfur and 0.8g of accelerator CZ and continue mixing for 6 minutes until the torque is stable. Discharge the rubber and cool it to room temperature to obtain the insole rubber composite modified material.

[0058] Comparative Example 2: The difference from Example 2 is that 4-(dimethylamino)benzenesulfonic acid in step (2) is replaced with dimethylallylamine. The specific steps are as follows:

[0059] (1) Add 13g halloysite nanotubes to 35g deionized water and 65g anhydrous ethanol, sonicate for 30min, then add 1.3g chloropropyltriethoxysilane, heat to 55℃, stir for 6h, centrifuge after the reaction is completed, and obtain chlorinated halloysite nanotubes after washing and drying.

[0060] (2) Under a nitrogen atmosphere, 13g of halloysite nanotubes and 1.95g of dimethylallylamine were added to 150g of tetrahydrofuran, heated to 53°C, and stirred for 48h. After the reaction was completed, the mixture was centrifuged, and the resulting precipitate was washed and dried to obtain multi-modified halloysite nanotubes.

[0061] (3) 13g of multimodified halloysite nanotubes were dispersed in 150g of deionized water, sonicated for 20min, and then 8g of foaming agent 4,4'-oxobisbenzenesulfonylhydrazine was added. The mixture was stirred for 2h, and then centrifuged and vacuum dried at 60℃ for 12h to obtain halloysite nanotubes loaded with foaming agent.

[0062] (4) Add 73g of natural rubber and 27g of styrene-butadiene rubber to a mixer and plasticize at 105°C for 5 minutes. Then add 5.5g of zinc oxide, 1.5g of stearic acid, 1.5g of antioxidant 4020 and 8g of carbon black N330 in sequence and mix at 125°C for 9 minutes to obtain the initial mixed rubber compound.

[0063] (5) Add 13g of halloysite nanotubes loaded with foaming agent into a mixer and mix with the initial mixed rubber at 155°C for 8 minutes. Then add 1.9g of sulfur and 0.8g of accelerator CZ and continue mixing for 6 minutes until the torque is stable. Discharge the rubber and cool it to room temperature to obtain the insole rubber composite modified material.

[0064] Comparative Example 3: The difference from Example 2 is that the multiple modified halloysite nanotubes in step (3) are replaced with halloysite nanotubes. The specific steps are as follows:

[0065] (1) Disperse 13g halloysite nanotubes in 150g deionized water, sonicate for 20min, add 8g foaming agent 4,4'-oxobisbenzenesulfonylhydrazine, stir continuously for 2h, then centrifuge and vacuum dry at 60℃ for 12h to obtain halloysite nanotubes loaded with foaming agent.

[0066] (2) Add 73g of natural rubber and 27g of styrene-butadiene rubber to a mixer and plasticize at 105°C for 5 minutes. Then add 5.5g of zinc oxide, 1.5g of stearic acid, 1.5g of antioxidant 4020 and 8g of carbon black N330 in sequence and mix at 125°C for 9 minutes to obtain the initial mixed rubber compound.

[0067] (3) Add 13g of halloysite nanotubes loaded with foaming agent into a mixer and mix with the initial mixed rubber at 155°C for 8 minutes. Then add 1.9g of sulfur and 0.8g of accelerator CZ and continue mixing for 6 minutes until the torque is stable. Discharge the rubber and cool it to room temperature to obtain the insole rubber composite modified material.

[0068] Comparative Example 4: The difference from Example 2 is that the halloysite nanotubes loaded with the foaming agent in step (5) are replaced with multi-modified halloysite nanotubes and the foaming agent. The specific steps are as follows:

[0069] (1) Add 13g halloysite nanotubes to 35g deionized water and 65g anhydrous ethanol, sonicate for 30min, then add 1.3g chloropropyltriethoxysilane, heat to 55℃, stir for 6h, centrifuge after the reaction is completed, and obtain chlorinated halloysite nanotubes after washing and drying.

[0070] (2) Under a nitrogen atmosphere, 13g of halloysite nanotubes, 0.65g of dimethylallylamine and 1.3g of 4-(dimethylamino)benzenesulfonic acid were added to 150g of tetrahydrofuran, heated to 53℃, and stirred for 48h. After the reaction was completed, the mixture was centrifuged, and the resulting precipitate was washed and dried to obtain multi-modified halloysite nanotubes.

[0071] (3) Add 73g of natural rubber and 27g of styrene-butadiene rubber to a mixer and plasticize at 105°C for 5 minutes. Then add 5.5g of zinc oxide, 1.5g of stearic acid, 1.5g of antioxidant 4020 and 8g of carbon black N330 in sequence and mix at 125°C for 9 minutes to obtain the initial mixed rubber compound.

[0072] (4) Add 8.1g of multiple modified halloysite nanotubes and 4.9g of foaming agent 4,4'-oxobisbenzenesulfonylhydrazine to a mixer and mix with the initial mixed rubber at 155°C for 8 minutes. Then add 1.9g of sulfur and 0.8g of accelerator CZ and continue mixing for 6 minutes until the torque is stable. Discharge the rubber and cool it to room temperature to obtain the insole rubber composite modified material.

[0073] Performance testing

[0074] Tensile strength: According to GB / T 528-2009, the obtained sample was cut into dumbbell-shaped type 1 specimens (thickness 2.0±0.2mm), and the tensile strength was recorded using a universal testing machine at a tensile speed of 500mm / min.

[0075] Abrasion resistance: Abrasion resistance was tested according to GBT1689-2014 "Determination of Abrasion Resistance of Vulcanized Rubber" (Akron Abrasion Tester), and the test time was 1 hour.

[0076] Air permeability: The air permeability of the obtained samples was tested according to GB / T 10655-2003;

[0077] Water vapor transmission rate: According to GB / T 10655-2003, the obtained sample was cut into circular specimens with a diameter of 70 mm (thickness 2.0±0.1 mm). The permeation cup method was used, the test temperature was 38±0.5℃, the relative humidity was a gradient difference of 90% to 50%, the weighing interval was 1 h, and it was continued for 24 h until the mass change was stable. The water vapor transmission rate per unit time and per unit area (g / (m²)) was calculated. 2 The test results are shown in Table 1.

[0078] Table 1 Performance Test Results

[0079]

[0080]

[0081] Data Analysis: As can be seen from the data in Examples 1-3 of Table 1, the modified rubber composite material for insoles prepared in this invention exhibits excellent comprehensive performance. Its high tensile strength indicates excellent mechanical load-bearing capacity, which is likely attributed to the strong interfacial bonding formed between the multi-modified halloysite nanotubes and the rubber matrix. Simultaneously, the low abrasion rate indicates excellent wear resistance on the material surface, possibly due to the three-dimensional network structure formed by the uniform dispersion of nanotubes effectively hindering crack propagation during friction. Furthermore, good air permeability and high water vapor transmission rate indicate that the material possesses open porous channels. This stems from the directional decomposition of the foaming agent within the confined space of the halloysite nanotubes, forming interconnected micropores. Simultaneously, the hydrophilicity of the sulfonic acid groups may promote the adsorption and diffusion of water molecules. These synergistic improvements in performance demonstrate that the material achieves multi-scale control of the reinforcing phase, foaming structure, and matrix in its molecular design, thereby simultaneously meeting the requirements of mechanical performance and wearing comfort.

[0082] As can be seen from the data comparison of Example 2 and Comparative Examples 1 and 2 in Table 1, the present invention, through the synergistic modification of dimethylallylamine and 4-(dimethylamino)benzenesulfonic acid, maintains excellent mechanical properties and wear resistance while preserving the high air permeability and moisture permeability of the material. On the one hand, the alkenyl groups on the modified surface can participate in vulcanization crosslinking, enhancing the interfacial compatibility of nanotubes in the rubber matrix, resulting in more uniform filler dispersion. At the same time, the sulfonic acid groups can enhance the adsorption-diffusion process of water molecules inside the material by interacting with the formed quaternary ammonium salt groups. Furthermore, the foaming agent can be loaded onto the surface of halloysite nanotubes through electrostatic adsorption and hydrogen bonding. On the other hand, the dual modification enables the foaming agent to be uniformly loaded on the surface of the nanotubes, forming a more regular hierarchical pore structure. This unique microstructure ensures rapid transport of gas and water vapor while avoiding the strength loss problem common in traditional porous materials.

[0083] Comparing the performance data of Example 2 and Comparative Example 3, it can be seen that the technical solution using multi-modified halloysite nanotubes loaded with foaming agents exhibits significant advantages in mechanical properties, wear resistance, and air and moisture permeability compared to the unmodified halloysite nanotube system. The introduction of the silane coupling agent enhances the interfacial bonding strength between the nanotubes and the rubber matrix through chemical bonding. Furthermore, the synergistic modification not only improves the dispersibility of the nanotubes, but the resulting zwitterionic structure can adsorb the foaming agent and attach it to the surface of the halloysite nanotubes, achieving a point-to-point foaming effect. This results in a microporous structure with both size uniformity and good connectivity. This optimized hierarchical channel ensures efficient gas and water vapor transport while avoiding the stress concentration problem common in traditional foaming materials. Simultaneously, the hydrophilic properties of the sulfonic acid groups and quaternary ammonium salts on the nanotube surface may promote the adsorption-diffusion process of water molecules within the material. This balanced design allows the material to maintain excellent mechanical properties while still possessing good moisture permeability and comfort.

[0084] Comparing the performance data of Example 2 and Comparative Example 4, it can be seen that halloysite nanotubes using a loaded foaming agent exhibit superior overall performance in terms of mechanical properties, abrasion resistance, and air and moisture permeability compared to the system of simply mixing multiple modified halloysite nanotubes and a foaming agent. In the loading process, the foaming agent generates a more uniformly distributed microporous structure during vulcanization, maintaining the integrity of the material while forming effective air permeability channels. In contrast, the free dispersion of the foaming agent in the simple mixing system (Comparative Example 4) may lead to uneven pore distribution. Furthermore, the regular pore structure formed by the loading process may optimize the transport paths of gas and water vapor, improving air and moisture permeability while maintaining high mechanical strength.

[0085] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A rubber composite modified material for shoe insoles, characterized in that, It is prepared from the following raw materials in parts by weight: 70-75 parts natural rubber, 25-30 parts styrene-butadiene rubber, 5-6 parts zinc oxide, 1-2 parts stearic acid, 1-2 parts antioxidant, 5-10 parts filler, 10-15 parts halloysite nanotubes loaded with foaming agent, 1.8-2 parts vulcanizing agent, and 0.5-1 part vulcanization accelerator; The preparation steps of the halloysite nanotubes loaded with the foaming agent are as follows: S1: Halloysite nanotubes and chloropropyltriethoxysilane are hydrolyzed-condensed in a solvent to obtain halloysite nanotubes with chloride. S2: Under a nitrogen atmosphere, halloysite nanotubes, dimethylallylamine, and 4-(dimethylamino)benzenesulfonic acid are reacted in tetrahydrofuran to obtain multi-modified halloysite nanotubes. S3: Disperse multiple modified halloysite nanotubes and foaming agents in deionized water, and after ultrasonic treatment, obtain halloysite nanotubes loaded with foaming agents. In step S1, the weight ratio of halloysite nanotubes, chloropropyltriethoxysilane, and solvent is 10-15g:1-1.5g:100g; the halloysite nanotubes have an outer diameter of 40-150nm, an inner diameter of 10-25nm, and a length of 100-2000nm. The weight ratio of halloysite nanotubes, dimethylallylamine, 4-(dimethylamino)benzenesulfonic acid, and tetrahydrofuran in step S2 is 10-15g:0.5-0.75g:1-1.5g:100-200g; The weight ratio of the multiple modified halloysite nanotubes, foaming agent, and deionized water in step S3 is 10-15g:5-10g:100-200g.

2. The insole rubber composite modified material according to claim 1, characterized in that, The natural rubber is composed of 91%-94% rubber hydrocarbons.

3. The insole rubber composite modified material according to claim 1, characterized in that, The styrene monomer unit content of the styrene-butadiene rubber is 22%-25%.

4. The insole rubber composite modified material according to claim 1, characterized in that, The antioxidant is one of antioxidant AW and antioxidant 4020.

5. The insole rubber composite modified material according to claim 1, characterized in that, The filler is one of carbon black N330, E250G, N110 and N234.

6. The insole rubber composite modified material according to claim 1, characterized in that, The vulcanizing agent is sulfur, and the vulcanization accelerator is accelerator CZ.

7. A method for preparing a rubber composite modified material for shoe insoles according to any one of claims 1-6, characterized in that, Includes the following steps: Natural rubber and styrene-butadiene rubber are added to a mixer and plasticized at 100-110℃. Then, zinc oxide, stearic acid, antioxidant and filler are added in sequence and the mixture is mixed at 120-130℃ to obtain a primary rubber compound. Then, halloysite nanotubes loaded with foaming agent and the primary rubber compound are added to the mixer and mixed at 150-160℃. Then, vulcanizing agent and accelerator are added and the mixture is mixed again. The rubber compound is discharged and cooled to room temperature to obtain a rubber composite modified material for shoe insoles.

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