Negative oxygen ion TPE three-layer plastic uptake foot pad and preparation method thereof

Abstract

The invention relates to the field of polymer functional composite materials, and particularly discloses a negative oxygen ion TPE three-layer plastic uptake foot pad and a preparation method thereof. The foot pad comprises a surface layer, a foam layer and a supporting layer which are sequentially arranged from top to bottom, the surface layer is composed of a modified TPE base body, the foam layer is a micro-foaming TPE elastic layer with the density being 0.4-0.7 g / cm < 3 >, and the supporting layer is a high-hardness TPE material layer with the Shore A hardness being 70-90. The modified TPE matrix is composed of TPE resin, negative oxygen ion composite master batch, 2, 4, 6-trihydroxymethyl phenol, a flexibilizer, an antioxidant, a light stabilizer, a dispersant and an inorganic filler, and the negative oxygen ion composite master batch is prepared by compounding tourmaline powder and a chitosan-organic silicon coupling graft. Through the twin-screw melt blending and three-layer co-extrusion plastic uptake molding process, the foot pad can be stable in structure, layered combination is firm, and negative oxygen ions are continuously released. The foot pad has excellent negative oxygen ion release performance, wear resistance, compression resilience and interlayer bonding strength, and is suitable for the field of automotive interiors and healthy and environment-friendly foot pads.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer materials and automotive interior products, specifically relating to a negative oxygen ion TPE three-layer thermoformed floor mat and its preparation method. Background Technology

[0002] With the development of the automotive industry and the increasing demands for in-vehicle air quality, traditional thermoplastic elastomer (TPE) floor mats have become widely used due to their good softness and high wear resistance. However, existing TPE floor mats mainly meet the requirements of anti-slip, anti-fouling, and wear resistance, but have a weak ability to purify the air in the in-vehicle environment and cannot effectively release negative oxygen ions to improve air quality.

[0003] Some companies are attempting to incorporate tourmaline powder, bamboo charcoal powder, or rare earth minerals into the TPE matrix to generate negative oxygen ions, but the following problems exist: First, the mineral powder has poor dispersibility in TPE, resulting in low and unstable ion release; second, the mineral structure is easily damaged during high-temperature processing, leading to a decrease in negative ion activity; and third, additives can easily cause material hardening or delamination, affecting the overall mechanical properties and molding quality of the foot pads.

[0004] Furthermore, most existing door pads are single-layered or double-layered, lacking a systematic mechanical zoning design, making it difficult to balance support and cushioning. Especially during the vacuum forming process, a single layer of material cannot simultaneously provide surface wear resistance and middle layer cushioning performance, causing the door pads to easily collapse, deform, or develop odors after long-term use.

[0005] Therefore, there is an urgent need for a TPE thermoforming pad material system that can achieve continuous release of negative oxygen ions, has a three-layer structural support design, and combines flexibility and wear resistance, in order to solve the problems of unstable ion release and insufficient structural performance in the existing technology. Summary of the Invention

[0006] To overcome the problems of low negative ion release efficiency, poor material dispersion, and insufficient structural support in the aforementioned technologies, the present invention aims to provide a three-layer thermoformed TPE foot pad with negative ion properties and its preparation method. The present invention prepares a negative ion composite masterbatch from tourmaline powder modified by chitosan-organosilicon coupling, and then blends and modifies it with TPE resin, 2,4,6-tris(hydroxymethyl)phenol, and various additives to form a modified TPE matrix with stable electroactivity. A three-layer co-extrusion thermoforming process is then used to construct a partitioned structure of surface layer, foam layer, and support layer, achieving integrated foot pad molding with a wear-resistant surface layer, cushioning foam layer, and stable support layer. The present invention can continuously release negative ions during use, significantly improving in-vehicle air quality; the material has excellent overall flexibility and compressive strength, and does not deform after long-term use; it has good environmental protection and application value.

[0007] The objective of this invention can be achieved through the following technical solutions: A three-layer thermoformed car mat containing negative oxygen ions, comprising a surface layer, a foam layer, and a support layer arranged sequentially from top to bottom. The surface layer is composed of a modified TPE matrix. The foam layer is a micro-foamed TPE elastic layer with a density of 0.4–0.7 g / cm³, used to provide rebound and cushioning support. The support layer is a high-hardness TPE material layer with a Shore A hardness of 70–90, used to enhance the overall structural stability. The car mat is made by three-layer co-extrusion thermoforming and has the characteristics of continuously releasing negative oxygen ions, improving in-vehicle air quality, and excellent wear resistance and pressure resistance.

[0008] Optionally, the modified TPE matrix comprises the following raw materials by weight: 80-120 parts TPE resin, 15-25 parts negative oxygen ion composite masterbatch, 2-6 parts 2,4,6-tris(hydroxymethyl)phenol, 3-5 parts toughening agent, 0.2-0.5 parts antioxidant, 0.3-0.8 parts light stabilizer, 0.5-1.0 parts dispersant, and 5-10 parts inorganic filler.

[0009] Optionally, the negative oxygen ion composite masterbatch is composed of tourmaline powder, chitosan-organosilicon coupling graft and inorganic carrier powder, with the mass ratio of tourmaline powder to chitosan-organosilicon coupling graft being 3 to 5:1.

[0010] Optionally, the toughening agent is a maleic anhydride-grafted polyolefin elastomer; the antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a mass ratio of 1 to 2:1, wherein the hindered phenolic antioxidant is antioxidant 1010 and the phosphite antioxidant is antioxidant 168; the light stabilizer is a hindered amine light stabilizer, wherein the hindered amine light stabilizer is light stabilizer 770; the dispersant is a mixture of stearic acid and polyethylene glycol in a mass ratio of 1 to 3:1; the inorganic filler is a combination of talc and calcium carbonate in a mass ratio of 1 to 2:1.

[0011] Optionally, the preparation method of the modified TPE matrix includes the following steps: (1) Tourmaline powder, chitosan and 3-propyltriethoxysilane were mixed and ethanol was added as a reaction medium. The mixture was stirred under heating conditions to generate chitosan-organosilicon coupling grafts. The grafts were ball-milled and dispersed with inorganic carrier powder, dried and mixed with TPE resin particles. The mixture was then extruded and granulated by twin screw extruder to obtain negative oxygen ion composite masterbatch. (2) Add TPE resin, negative oxygen ion composite masterbatch, 2,4,6-tris(hydroxymethyl)phenol, toughening agent, antioxidant, light stabilizer, dispersant and inorganic filler into a mixer and mix evenly; feed the mixture into a twin-screw extruder and melt blend and granulate at a set temperature and shear rate to obtain modified TPE matrix particles; (3) Collect the extruded granules after cooling and drying for later use.

[0012] Optionally, the reaction conditions in step (1) are: reaction temperature of 80-90℃, reaction time of 2-3 hours, pH value of system controlled at 6.5-7.5, stirring speed of 200-300 rpm; ball milling time of 1-2 hours, drying temperature of 100-120℃, and extrusion granulation temperature controlled at 160-180℃.

[0013] Optionally, the blending modification conditions in step (2) are: blending temperature controlled at 160-190℃, screw speed at 150-250rpm, and melt shearing time at 3-5 minutes.

[0014] Optionally, in step (3), the cooling method is water cooling circulation, the cooling temperature is 20-30℃, the drying temperature is 80-100℃, and the drying time is 2-4 hours, so as to ensure that the obtained modified TPE matrix particles are evenly dispersed and have good thermal stability.

[0015] Optionally, a method for preparing a negative oxygen ion TPE three-layer thermoformed foot pad includes the following steps: S1, the modified TPE matrix particles, micro-foamed TPE particles and high-hardness TPE particles are dried separately. S2, the dried modified TPE matrix particles, micro-foamed TPE particles and high-hardness TPE particles are respectively fed into the upper, middle and lower feeding channels of the three-layer co-extrusion thermoforming equipment; S3, start the co-extrusion system, heat and melt the three layers of material at the same time, and use a vacuum forming mold to simultaneously adsorb and form the three layers of material into a single structure; S4. After the molded foot pads are cooled, trimmed, and finished, the finished product of negative oxygen ion TPE three-layer thermoformed foot pads is obtained.

[0016] Optionally, the drying conditions in step S1 are a temperature of 80–100°C and a time of 2–4 hours; the feeding rate in step S2 is 20–40 kg / h per layer; the melting temperature in step S3 is 180–200°C, the thermoforming pressure is 0.08–0.10 MPa, and the vacuum degree is −0.09 MPa; and the cooling temperature in step S4 is 20–30°C and the cooling time is 1–3 minutes.

[0017] The beneficial effects of this invention are: This invention constructs a negative oxygen ion composite masterbatch by introducing chitosan-organosilicon-coupled modified tourmaline powder into a TPE matrix, and forming a hydrogen-bonded stable network with 2,4,6-tris(hydroxymethyl)phenol, thereby maintaining the electroactivity of the tourmaline surface for a long time, thus achieving continuous release and high release output of negative oxygen ions. This composite system overcomes the problems of uneven dispersion and rapid ion decay of traditional mineral fillers in TPE, forming a microphase structure with charge migration channels, and achieving stable air purification function. At the same time, the three-layer co-extrusion structure design forms a stable interface bond between the modified TPE surface layer and the foam layer, ensuring the synergistic integration of functionality and structural performance. Attached Figure Description

[0018] The invention will now be further described with reference to the accompanying drawings.

[0019] Figure 1 A comparison of the infrared spectra of TPE matrix particles and modified TPE matrix particles; Figure 2 This is a comparison chart of the test results for the release of negative oxygen ions from samples with different ratios. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit and essence of the present invention should also be considered to fall within the protection scope of the present invention.

[0021] Example 1 The purpose of this embodiment is to verify the maximum effect of negative oxygen ion release performance and material structure stability of the foot pad when each raw material component is taken at the upper limit of the claim range.

[0022] S1. Tourmaline powder, chitosan, and 3-propyltriethoxysilane were mixed, and ethanol was added as a reaction medium. The mixture was stirred at 90°C for 3 hours, and the pH of the system was controlled at 7.0 to obtain a chitosan-organosilicon coupling graft. The graft was ball-milled with inorganic carrier powder for 2 hours and dried at 120°C. Then it was mixed with TPE resin and granulated by a twin-screw extruder (temperature 180°C, speed 250 rpm) to obtain an ion-reducing composite masterbatch. 120 parts of TPE resin, 25 parts of ion-reducing composite masterbatch, 6 parts of 2,4,6-tris(hydroxymethyl)phenol, 5 parts of toughening agent, 0.5 parts of antioxidant, 0.8 parts of light stabilizer, 1.0 part of dispersant, and 10 parts of inorganic filler were mixed evenly and fed into a twin-screw extruder. The mixture was melt-blended and granulated at 190°C. After cooling and drying, the modified TPE matrix particles were collected. S2, after drying the modified TPE matrix particles, micro-foamed TPE particles and high-hardness TPE particles for 4 hours, they are fed into the upper, middle and lower feeding channels of the three-layer co-extrusion thermoforming equipment; the feeding rate of each layer is set to 40kg / h, and the three-layer melt co-extrusion is carried out at 200℃; S3 is vacuum-formed under vacuum conditions of -0.09MPa and vacuum forming pressure of 0.10MPa; the cooling temperature is 30℃ and the time is 3 minutes. After trimming and finishing, the finished foot pad is obtained.

[0023] Example 2 The purpose of this embodiment is to verify the overall balance between negative oxygen ion release and mechanical properties of the foot pad when the raw materials are at a median ratio.

[0024] S1. Tourmaline powder, chitosan, and 3-propyltriethoxysilane were mixed, ethanol was added, and the mixture was reacted at 85°C for 2.5 hours. The pH was adjusted to 7.0, and the stirring speed was 250 rpm to obtain a chitosan-organosilicon coupling graft. The graft was ball-milled with inorganic carrier powder for 1.5 hours and dried at 110°C. The dried powder was mixed with TPE resin and extruded and granulated at 170°C and 200 rpm to obtain a negative oxygen ion composite masterbatch. 100 parts of TPE resin, 20 parts of negative oxygen ion composite masterbatch, 4 parts of 2,4,6-tris(hydroxymethyl)phenol, 4 parts of toughening agent, 0.35 parts of antioxidant, 0.5 parts of light stabilizer, 0.7 parts of dispersant, and 8 parts of inorganic filler were mixed evenly. The mixture was extruded and granulated at 180°C and 200 rpm, and after cooling and drying, modified TPE matrix particles were obtained. Figure 1 The modified TPE matrix showed a significant increase in both the number and intensity of absorption peaks compared to the unmodified matrix. The peaks were clear and distinctive, with a marked increase in intensity at 3400 cm⁻¹, indicating that the chitosan-organosilicon coupling introduced a large number of polar hydroxyl and amino groups. The new peak at 1720 cm⁻¹ corresponds to the C=O stretching vibration, indicating that the silane coupling reaction generates ester bonds. A new NH bending vibration appeared at 1560 cm⁻¹, confirming the formation of amide bonds between chitosan and silane. The Si–O–C peak at 1250 cm⁻¹ and the Si–O–Si peak at 950 cm⁻¹ indicate that the organosilicon structure has formed a cross-linked network. Overall, the modified TPE matrix showed a significant increase in polar groups, silicon-oxygen skeleton, and hydrogen bond structure, proving the successful modification of the tourmaline-chitosan-silane composite. This achieved interfacial chemical bonding and structural stabilization, laying the molecular structural foundation for the continuous release of negative oxygen ions. S2, after drying the three types of granules separately for 3 hours, they are fed into the upper, middle and lower hoppers of the three-layer co-extrusion thermoforming equipment; the feeding speed is 30kg / h, the melting temperature is 190℃, and the three layers are extruded simultaneously to form a composite structure. S3, vacuum degree −0.09MPa, thermoforming pressure 0.09MPa; cooling temperature 25℃, cooling time 2 minutes; after trimming and shaping, the finished product of negative oxygen ion TPE three-layer thermoformed foot pad is obtained.

[0025] Example 3 The purpose of this embodiment is to verify the feasibility of the resulting foot pad in terms of lightweighting and energy consumption control when each component is taken as the lower limit of the scope of the claims.

[0026] S1. Tourmaline powder, chitosan, and 3-propyltriethoxysilane were mixed, ethanol was added, and the mixture was reacted at 80°C for 2 hours at pH 6.5 with a stirring speed of 200 rpm to generate a chitosan-organosilicon coupled graft. The graft was ball-milled with inorganic carrier powder for 1 hour and dried at 100°C. After being mixed with TPE resin, the mixture was extruded and granulated at 160°C and 150 rpm to obtain a negative oxygen ion composite masterbatch. 80 parts of TPE resin, 15 parts of negative oxygen ion composite masterbatch, 2 parts of 2,4,6-tris(hydroxymethyl)phenol, 3 parts of toughening agent, 0.2 parts of antioxidant, 0.3 parts of light stabilizer, 0.5 parts of dispersant, and 5 parts of inorganic filler were mixed evenly. The mixture was melt-blended and extruded and granulated at 170°C and 180 rpm. After cooling and drying, modified TPE matrix particles were obtained. S2, after drying the three types of granules for 2 hours, they are fed into a three-layer co-extrusion thermoforming equipment; the feeding speed of each layer is 20kg / h, the melting temperature is 180℃, and synchronous melting thermoforming is carried out. S3, vacuum degree −0.09MPa, thermoforming pressure 0.08MPa; cooling temperature 20℃, cooling time 1 minute; after trimming and finishing, a lightweight negative oxygen ion TPE three-layer thermoformed foot pad sample was obtained.

[0027] Comparative Example 1 The purpose of this comparative example is to verify the effect on negative oxygen ion release and overall mechanical properties when no 2,4,6-tris(hydroxymethyl)phenol is added, while keeping the other conditions consistent with those in Example 2.

[0028] S1. Tourmaline powder, chitosan, and 3-propyltriethoxysilane were mixed, ethanol was added, and the mixture was reacted at 85°C for 2.5 hours. The pH was adjusted to 7.0, and the stirring speed was 250 rpm to obtain a chitosan-organosilicon coupling graft. The graft was ball-milled with inorganic carrier powder for 1.5 hours and dried at 110°C. The dried powder was mixed with TPE resin and extruded and granulated at 170°C and 200 rpm to obtain a negative oxygen ion composite masterbatch. 104 parts of TPE resin, 20 parts of negative oxygen ion composite masterbatch, 4 parts of toughening agent (without 2,4,6-tris(hydroxymethyl)phenol), 0.35 parts of antioxidant, 0.5 parts of light stabilizer, 0.7 parts of dispersant, and 8 parts of inorganic filler were mixed evenly. The mixture was extruded and granulated at 180°C and 200 rpm, and after cooling and drying, modified TPE matrix particles were obtained. S2, after drying the three types of granules separately for 3 hours, they are fed into the upper, middle and lower hoppers of the three-layer co-extrusion thermoforming equipment; the feeding speed is 30kg / h, the melting temperature is 190℃, and the three layers are extruded simultaneously to form a composite structure. S3 vacuum degree −0.09MPa, thermoforming pressure 0.09MPa; cooling temperature 25℃, cooling time 2 minutes; the sample is obtained after trimming and shaping.

[0029] Comparative Example 2 The purpose of this comparative example is to verify the effect of adding only 2,4,6-tris(hydroxymethylphenol) on material properties and negative oxygen ion release without using negative oxygen ion composite masterbatch.

[0030] S1, without the chitosan-organosilicon coupling grafting reaction and masterbatch preparation steps; directly take 120 parts of TPE resin, 4 parts of non-negative oxygen ion composite masterbatch, 4 parts of 2,4,6-tris(hydroxymethyl)phenol, 4 parts of toughening agent, 0.35 parts of antioxidant, 0.5 parts of light stabilizer, 0.7 parts of dispersant, and 8 parts of inorganic filler, mix them evenly; extrude and granulate at 180℃ and 200rpm, and obtain matrix particles after cooling and drying; S2, after drying the matrix particles, micro-foamed TPE particles and high-hardness TPE particles for 3 hours, they are sequentially fed into the upper, middle and lower hoppers; the feeding speed is 30 kg / h, the melting temperature is 190°C, and the three layers are extruded simultaneously to form a composite structure. S3, vacuum degree −0.09MPa, thermoforming pressure 0.09MPa; cooling temperature 25℃, cooling time 2 minutes; the sample is obtained after trimming and shaping.

[0031] Comparative Example 3 The purpose of this comparative example is to verify the difference in effect when only the surface modification method of the masterbatch is changed, the chitosan-organosilicon coupling is removed, and the rest of the formulation and process parameters remain the same.

[0032] S1: Tourmaline powder and inorganic carrier powder are mixed, mechanically stirred until uniform, and then mixed with TPE resin without chitosan-organosilicon coupling grafting reaction or ethanol medium treatment; the mixture is directly extruded and granulated at 170℃ and 200rpm to obtain unmodified tourmaline masterbatch; 100 parts of TPE resin, 20 parts of unmodified tourmaline masterbatch, 4 parts of 2,4,6-tris(hydroxymethyl)phenol, 4 parts of toughening agent, 0.35 parts of antioxidant, 0.5 parts of light stabilizer, 0.7 parts of dispersant, and 8 parts of inorganic filler are mixed evenly; the mixture is extruded and granulated at 180℃ and 200rpm, and then cooled and dried to obtain matrix particles; S2, after drying the three types of granules separately for 3 hours, they are fed into the upper, middle and lower hoppers of the three-layer co-extrusion thermoforming equipment; the feeding speed is 30kg / h, the melting temperature is 190℃, and the three layers are extruded simultaneously to form a composite structure. S3, vacuum degree −0.09MPa, thermoforming pressure 0.09MPa; cooling temperature 25℃, cooling time 2 minutes; the sample is obtained after trimming and shaping.

[0033] Performance testing 1. Negative oxygen ion release test Foot pad samples were cut into 300mm × 300mm pieces and placed face up in the center of a 1m³ sealed test chamber. The test environment was set at 23±2℃ and 50±5% relative humidity. The initial concentration of negative oxygen ions in the air was recorded as a background value before the samples were placed in the chamber. The chamber was then sealed, and the concentration of negative oxygen ions in the air was collected at 5, 10, 20, 30, 45, and 60 minutes. The average value from 30 to 60 minutes was taken as the steady-state release concentration, and the cumulative release from 0 to 60 minutes was calculated. Each group of samples was tested three times, and the average value was taken. The steady-state release concentration and release per unit area were used to characterize the negative oxygen ion release performance.

[0034] 2. Interlayer peel strength test Cut 25mm × 200mm strips along the extrusion direction of the foot pad, and pre-separate 30-40mm along the interlayer interface at the ends to form a peelable area. Fix the sample in a universal testing machine and perform a 180° peel test at a peeling speed of 100mm / min. Record the peel force versus displacement curves, remove the unstable sections at the beginning and end, and take the average value of the stable peel force in the middle section. Test 5 strips in each group, and determine the peel strength of the surface layer / bubble layer and the bubble layer / support layer respectively. Use the average value to characterize the interlayer bonding strength.

[0035] 3. Wear resistance test Take a composite sheet material for the foot pad surface layer, with a thickness of not less than 3mm, and cut it into a sample measuring 16mm × 6mm × actual thickness. Use a DIN-type abrasion tester with 60-grit sandpaper and apply a load of 5N. The test environment is 23±2℃ and 50±5% relative humidity. Measure the initial mass before the test, and the abrasion distance is 40m. After the test, remove dust and weigh the abrasion-affected material, calculating the abrasion volume. Test three samples in each group and take the average value. The abrasion resistance of the surface layer is represented by the abrasion volume; the smaller the value, the better the abrasion resistance.

[0036] 4. Compression and rebound performance test 25mm × 25mm × 12.5mm test blocks were cut from the finished floor mats and equilibrated at 23℃ for 24 hours. Compression performance testing employed a 25% constant deformation method, with one group held at 23℃ for 24 hours and the other at 50℃ for 22 hours. Thickness change was measured after unloading for 30 minutes to obtain the permanent compression deformation. Rebound performance testing was conducted at 23℃ using a rebound meter method. Each sample was tested five times consecutively, and the average value was taken. The data obtained was used to evaluate the elastic recovery performance and structural stability of the floor mats.

[0037] Table 1 Comparison of performance test results between the examples and the comparative samples.

[0038] As shown in Table 1, Examples 1-3 and Comparative Examples 1-3 exhibit significant differences in negative oxygen ion release, interlayer bonding strength, wear resistance, and compression resilience. Among them, Example 2 demonstrates the best overall performance, fully verifying the significant advantages of the synergistic modification of chitosan-organosilicon coupled-grafted tourmaline masterbatch and 2,4,6-tris(hydroxymethyl)phenol.

[0039] Regarding the release performance of negative oxygen ions Figure 2 The steady-state release concentration of Example 2 reached 890 ions / cm³, significantly higher than that of Examples 1 and 3, and far higher than that of the comparative sample. This result indicates that the interfacial electric dipole structure formed by tourmaline powder and chitosan-organosilicon coupling in the composite masterbatch effectively promotes sustained ion release, while the introduction of 2,4,6-tris(hydroxymethyl)phenol further enhances interfacial polarization and charge migration, thereby achieving a high release rate and persistence of negative oxygen ions.

[0040] Regarding interlayer bonding strength, the peel strength of the face / bubble layer and bubble / support layer in Examples 1-3 were all above 2.0 N / mm, with Examples 1 and 2 exhibiting the best interfacial bonding performance. In contrast, the peel strength of Comparative Examples 1 and 2 decreased significantly, indicating that when organic small molecules are used alone or when coupling graft structures are lacking, the interfacial bonding force is insufficient, and delamination or fatigue cracking easily occurs between the three layers.

[0041] Regarding wear resistance, Example 2 exhibited the smallest wear volume at 18.2 mm³, demonstrating the best wear resistance. Example 1 showed slightly higher wear resistance, and Example 3 slightly lower, but both were significantly better than the comparative example. This indicates that the coupling-modified tourmaline filler can form a dense, micro-dispersed phase in the TPE matrix, improving the surface density and friction resistance of the material.

[0042] Regarding compression and resilience, Example 2 exhibited the lowest compression set at 23°C and 50°C, at 9.8% and 13.4% respectively, while displaying the highest resilience at 73.6%. This demonstrates that the modified TPE matrix structure possesses excellent deformation recovery and internal energy release characteristics under external forces. The comparative samples generally showed larger compression set, especially Comparative Example 2, which exceeded 20% at high temperatures, indicating that the material is prone to irreversible compression deformation in the absence of an electroactive network structure.

[0043] A comprehensive comparison shows that Example 2 exhibits the best performance in four aspects: negative oxygen ion release performance, interfacial bonding strength, wear resistance, and compression resilience, demonstrating the structural stability and functional synergy of the synergistic modification system. The chitosan-organosilicon coupling-modified tourmaline masterbatch effectively improves the interfacial compatibility between the inorganic components and the polymer matrix, while 2,4,6-tris(hydroxymethyl)phenol enhances energy transfer and stress relief between polymer chains through intramolecular hydrogen bonding. This results in the negative oxygen ion TPE three-layer thermoformed foot pad being significantly superior to the comparative example in both functionality and durability.

Claims

1. A three-layer thermoformed foot pad containing negative oxygen ions (TPE), characterized in that, The foot pad comprises a surface layer, a foam layer, and a support layer arranged sequentially from top to bottom. The surface layer is composed of a modified TPE matrix. The foam layer is a micro-foamed TPE elastic layer with a density of 0.4–0.7 g / cm³, used to provide rebound and cushioning support. The support layer is a high-hardness TPE material layer with a Shore A hardness of 70–90, used to enhance the overall structural stability. The foot pad is manufactured by three-layer co-extrusion thermoforming.

2. The negative oxygen ion TPE three-layer thermoformed foot pad according to claim 1, characterized in that, The modified TPE matrix comprises the following raw materials by weight: 80-120 parts TPE resin, 15-25 parts negative oxygen ion composite masterbatch, 2-6 parts 2,4,6-tris(hydroxymethyl)phenol, 3-5 parts toughening agent, 0.2-0.5 parts antioxidant, 0.3-0.8 parts light stabilizer, 0.5-1.0 parts dispersant, and 5-10 parts inorganic filler.

3. The negative oxygen ion TPE three-layer thermoformed foot pad according to claim 2, characterized in that, The negative oxygen ion composite masterbatch is composed of tourmaline powder, chitosan-organosilicon coupling graft and inorganic carrier powder, with the mass ratio of tourmaline powder to chitosan-organosilicon coupling graft being 3 to 5:

1.

4. The negative oxygen ion TPE three-layer thermoformed foot pad according to claim 2, characterized in that, The toughening agent is a maleic anhydride-grafted polyolefin elastomer; the antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a mass ratio of 1 to 2:1, wherein the hindered phenolic antioxidant is antioxidant 1010 and the phosphite antioxidant is antioxidant 168; the light stabilizer is a hindered amine light stabilizer, wherein the hindered amine light stabilizer is light stabilizer 770; the dispersant is a mixture of stearic acid and polyethylene glycol in a mass ratio of 1 to 3:1; the inorganic filler is a combination of talc and calcium carbonate in a mass ratio of 1 to 2:

1.

5. A negative oxygen ion TPE three-layer thermoformed foot pad according to any one of claims 1 to 4, characterized in that, The method for preparing the modified TPE matrix includes the following steps: (1) Tourmaline powder, chitosan and 3-propyltriethoxysilane were mixed and ethanol was added as a reaction medium. The mixture was stirred under heating conditions to generate chitosan-organosilicon coupling grafts. The grafts were ball-milled and dispersed with inorganic carrier powder, dried and mixed with TPE resin particles. The mixture was then extruded and granulated by twin screw extruder to obtain negative oxygen ion composite masterbatch. (2) Add TPE resin, negative oxygen ion composite masterbatch, 2,4,6-tris(hydroxymethyl)phenol, toughening agent, antioxidant, light stabilizer, dispersant and inorganic filler into a mixer and mix evenly; feed the mixture into a twin-screw extruder and melt blend and granulate at a set temperature and shear rate to obtain modified TPE matrix particles; (3) Collect the extruded granules after cooling and drying for later use.

6. The negative oxygen ion TPE three-layer thermoformed foot pad according to claim 5, characterized in that, The reaction conditions for step (1) are as follows: reaction temperature is 80-90℃, reaction time is 2-3 hours, pH value of system is controlled at 6.5-7.5, stirring speed is 200-300 rpm; ball milling time is 1-2 hours, drying temperature is 100-120℃, and extrusion granulation temperature is controlled at 160-180℃.

7. The negative oxygen ion TPE three-layer thermoformed foot pad according to claim 5, characterized in that, The blending modification conditions in step (2) are: blending temperature controlled at 160-190℃, screw speed at 150-250rpm, and melt shearing time at 3-5 minutes.

8. The negative oxygen ion TPE three-layer thermoformed foot pad according to claim 5, characterized in that, The cooling method in step (3) is water cooling circulation, the cooling temperature is 20-30℃, the drying temperature is 80-100℃, and the drying time is 2-4 hours.

9. A method for preparing a negative ion TPE three-layer thermoformed foot pad, wherein the negative ion TPE three-layer thermoformed foot pad is as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1, the modified TPE matrix particles, micro-foamed TPE particles and high-hardness TPE particles are dried separately. S2, the dried modified TPE matrix particles, micro-foamed TPE particles and high-hardness TPE particles are respectively fed into the upper, middle and lower feeding channels of the three-layer co-extrusion thermoforming equipment; S3, start the co-extrusion system, heat and melt the three layers of material at the same time, and use a vacuum forming mold to simultaneously adsorb and form the three layers of material into a single structure; S4. After the molded foot pads are cooled, trimmed, and finished, the finished product of negative oxygen ion TPE three-layer thermoformed foot pads is obtained.

10. The method for preparing a negative oxygen ion TPE three-layer thermoformed foot pad according to claim 9, characterized in that, The drying conditions in step S1 are a temperature of 80–100°C and a time of 2–4 hours; the feeding rate in step S2 is 20–40 kg / h per layer; the melting temperature in step S3 is 180–200°C, the thermoforming pressure is 0.08–0.10 MPa, and the vacuum degree is −0.09 MPa; the cooling temperature in step S4 is 20–30°C, and the cooling time is 1–3 minutes.

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