A method for preparing a three-dimensional integrated lumbar support cushion

Abstract

This invention discloses a method for preparing a three-dimensional integrated lumbar support cushion. The raw materials of the lumbar support cushion include: ethylene-vinyl acetate copolymer, polyether-type thermoplastic polyurethane elastomer, physically foamed microspheres, azodicarbonamide, caprolactam-blocked 4,4'-diphenylmethane diisocyanate, surface-modified copper nanowires, and silver-loaded silicone composite components. The preparation process is as follows: the matrix resin and modified copper nanowires are melt-blended at high temperature, and then mixed with the foaming system, crosslinking agent, and composite components at low temperature to obtain a blended base material; the blended base material is injection molded, followed by static differential temperature field for pressure holding and curing, and finally cooled and demolded. This invention utilizes copper nanowires to construct a thermally conductive network, which, combined with the external temperature difference, forms a continuous foaming ratio and crosslinking density gradient inside, eliminating the physical phase interface of traditional multi-material splicing, significantly improving the tear resistance and fatigue life of the transition zone; and utilizes cooling phase separation to form an anti-slip and antibacterial skin layer.

Description

Technical Field

[0001] This invention relates to the field of seat cushion technology, specifically to a method for preparing a three-dimensional integrated lumbar support seat cushion. Background Technology

[0002] A lumbar support cushion is an ergonomic assistive product that combines hip support and lumbar spine support. When a person is sitting, the hip area needs flexible materials to provide cushioning to distribute the pressure on the ischial tuberosities, while the lumbar area needs materials with higher rigidity to provide support to maintain the normal physiological curvature of the spine. The mechanical performance requirements of a lumbar support cushion vary significantly in different spatial locations.

[0003] In existing manufacturing industries, to meet the differentiated mechanical requirements within the same product, a production method of physical assembly of multiple components is commonly adopted. The processing usually involves first using soft polyurethane foam or low-density foamed resin to separately mold the flexible components of the seat cushion area, then using materials such as high-density foam board or rigid polypropylene support board to mold the rigid components of the lumbar support area, and finally applying adhesive to the reserved contact surfaces to bond and assemble the prefabricated components of different moduli into the finished lumbar support seat cushion.

[0004] This multi-material physical splicing process results in structural defects within the product. The low-modulus soft cushioning component and the high-modulus rigid support component exhibit abrupt changes in mechanical modulus at their interface, forming a discontinuous physical phase interface. When the lumbar support cushion is subjected to alternating bending loads from the human body during actual use, the deformation stress cannot be smoothly transferred between the two materials, causing a large concentration of stress at the splicing interface. Under continuous stress concentration, the interface bonding layer is prone to adhesive peeling and substrate tearing, resulting in low tear resistance in the transition area and a short overall bending fatigue life. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a three-dimensional integrated lumbar support cushion. The technical problem solved by this invention is that traditional multi-functional lumbar support cushions typically employ a multi-material physical splicing process, bonding low-modulus soft sponge for the cushion area with high-modulus rigid materials (such as high-density foam board or polypropylene support board) for the lumbar support area using adhesives. This physical splicing structure results in a significant difference in mechanical modulus at the interface between the two materials, forming a physical phase interface. During use, especially under alternating bending loads, stress cannot be smoothly transferred between materials of different moduli, easily leading to stress concentration at the splicing interface, resulting in adhesive peeling, material tearing, and fatigue failure of the support structure.

[0006] To achieve the above objectives, the present invention provides the following technical solution: Firstly, the present invention provides a three-dimensional integrated lumbar support cushion, comprising the following technical solution: the lumbar support cushion is made from raw materials comprising the following parts by weight: 65.0–80.0 parts of ethylene-vinyl acetate copolymer; 20.0–35.0 parts of polyether-type thermoplastic polyurethane elastomer; 2.0–5.0 parts of physically foamed microspheres; 1.5–3.5 parts of azodicarbonamide; 4.0–8.0 parts of caprolactam-blocked 4,4'-diphenylmethane diisocyanate; 0.8–2.5 parts of surface-modified copper nanowires; and 1.5–4.5 parts of silver-loaded silicone composite component.

[0007] By adopting the above technical solution, the following effects are achieved: This invention forms a basic continuous phase with both flexibility and structural strength by mixing ethylene-vinyl acetate copolymer and polyether-type thermoplastic polyurethane elastomer. Surface-modified copper nanowires form a thermally conductive percolation network in the polymer matrix, reducing the thermal resistance of the polymer phase and establishing a physical channel for spatial heat conduction during subsequent molding. Azodicarbonamide, as a chemical foaming agent, forms a thermosensitive reaction system with caprolactam-blocked 4,4'-diphenylmethane diisocyanate (latent crosslinking agent). Under the action of a specific spatial temperature field, this formulation system can generate different degrees of foaming expansion and chemical crosslinking within a single material, thereby achieving a spatially continuous distribution of the material's macroscopic mechanical modulus without introducing any physical splicing interfaces. The silver-loaded silicone composite component, as a functional dispersed phase, utilizes the thermodynamic state changes in the later stages of molding to impart anti-slip and antibacterial properties to the surface of the part.

[0008] Preferably, the characteristic parameters of the raw materials meet the following conditions: in the ethylene-vinyl acetate copolymer, the mass fraction of vinyl acetate is 18%–28%, and the melt flow rate is 2.0–4.0 g / 10 min; the Shore A hardness of the polyether-type thermoplastic polyurethane elastomer is 80–90. The initial expansion temperature of the physically foamed microspheres is 85–95°C; the thermal decomposition temperature of the azodicarbonamide is 165–175°C; and the unblocking temperature range of the caprolactam-blocked 4,4'-diphenylmethane diisocyanate under purely thermodynamic conditions is 175–185°C. By adopting the above technical solution, the reaction temperature range of each reactive component is defined. Setting the expansion temperature of the physically foamed microspheres at 85–95°C ensures that they can provide basic microfoaming weight reduction effects even in the low-temperature support region. The decomposition temperature of azodicarbonamide and the unblocking temperature of the crosslinking agent are matched, so that the reaction process of the two produces synergy in the high-temperature range, providing a thermodynamic basis for the formation of the crosslinking gradient.

[0009] Preferably, the surface-modified copper nanowires are prepared by the following method: 4.0–6.0 mmol of copper chloride dihydrate and 12.0–30.0 mmol of hexadecylamine are added to water and stirred at 65°C for 45 min to form a complex solution; 20.0–40.0 mmol of ascorbic acid aqueous solution is added dropwise to the complex solution at a rate of 3 mL / min, and then the mixture is kept at 105–125°C for 6–14 h; after the reaction, the precipitate is collected by centrifugation, washed, and dried to obtain the surface-modified copper nanowires. By adopting the above technical solution, hexadecylamine is used as a morphology control agent to guide the anisotropic growth of copper atoms along a one-dimensional direction under specific stoichiometric ratios and hydrothermal conditions. The hexadecylamine coating layer on the surface prevents the oxidation of the copper nanowires, while reducing the interfacial energy between the inorganic nanowires and the organic polymer matrix, improving their dispersion uniformity in the blend system, and ensuring the continuity of the internal heat transfer network.

[0010] Preferably, the silver-loaded silica gel composite component is prepared by the following method: hydroxyl-terminated polydimethylsiloxane and octamethylcyclotetrasiloxane are mixed uniformly at a mass ratio of 3:1 to obtain a siloxane mixture; 2% by mass of silver-loaded zirconium phosphate composite antibacterial powder is added to the siloxane mixture, and the mixture is ultrasonically dispersed to obtain the silver-loaded silica gel composite component. By adopting the above technical solution, the low molecular weight octamethylcyclotetrasiloxane is used as a diluent and carrier to reduce the viscosity of the system, promoting the uniform suspension of the silver-loaded zirconium phosphate powder in the polydimethylsiloxane. This composite structure provides material conditions for surface migration in the subsequent molding and cooling stage.

[0011] Secondly, the present invention provides a method for preparing a three-dimensional integrated lumbar support cushion, which adopts the following technical solution: A method for preparing a three-dimensional integrated lumbar support cushion includes the following steps: S1: Ethylene-vinyl acetate copolymer, polyether-type thermoplastic polyurethane elastomer and surface-modified copper nanowires are melt-blended at high temperature according to the formula, and then extruded and granulated to obtain a thermally conductive alloy masterbatch; S2: The thermally conductive alloy masterbatch is softened and wrapped on a two-roll mill, and physically foamed microspheres, azodicarbonamide, caprolactam-blocked 4,4'-diphenylmethane diisocyanate and silver-loaded silicone composite components are added in sequence for low-temperature mixing, and sheeting is performed to obtain a blended base material; S3: The blended base material is plasticized and injected into a pre-closed mold cavity for integrated molding of the lumbar support cushion; S4: In the pressure holding and curing stage, a static differential temperature field is applied to different spatial areas of the closed mold using an independent temperature control circuit to perform gradient thermal field curing; S5: After the thermal field curing is completed, the temperature is cooled down, and the mold is opened to eject the product.

[0012] By adopting the above technical solution, the preparation method of this invention changes the conventional isothermal foaming molding process. Through the synergistic regulation of two-stage mixing and gradient thermal field curing, the microstructure of the material undergoes a directional gradient change within a single mold cavity. The specific reaction and structural evolution process is as follows: Step 1: In the S1 high-temperature melting stage, the polymer matrix is ​​fully melted and mixed, and the surface-modified copper nanowires are uniformly dispersed under strong shear force, constructing a heat-conducting physical network that runs through the polymer phase. This step does not introduce heat-sensitive foaming agents and crosslinking agents, avoiding premature reaction of the material under high-temperature shear. Step 2: After entering the S4 pressure holding and curing stage, the mold applies a static temperature difference to different areas of the material. The copper nanowire network converts the external temperature difference at both ends of the mold into a continuous temperature gradient inside the material. Step 3: The internal temperature field controls the local reaction process. In the high-temperature region, azodicarbonamide decomposes in large quantities under heat, generating gas that causes the matrix to expand at a high rate; at the same time, the decomposition of azodicarbonamide is accompanied by the generation of ammonia byproducts. The localized high concentration of ammonia gas alters the desealing reaction pathway of caprolactam-blocked isocyanates, lowering their desealing activation energy. The desealed isocyanate groups rapidly cross-link with the matrix molecular chains. As the temperature field transitions to lower temperatures, the decomposition of azodicarbonamide decreases, the ammonia yield decreases, the catalytic desealing effect weakens, and the degree of cross-linking in the matrix decreases axially. In the low-temperature region, both chemical foaming and chemical cross-linking are suppressed, and the matrix maintains an uncross-linked, high-modulus, micro-foamed thermoplastic state. Step Four: Through the above synergistic reactions, a continuously decreasing cross-linking density gradient and foaming ratio gradient are formed within the molded product. The high-cross-linked, low-density high-temperature region exhibits low hardness, providing flexible cushioning for the seat cushion; the uncross-linked, high-density low-temperature region exhibits high hardness, providing rigid support for the lumbar support. This continuous gradual change in microstructure avoids physical interfaces, allowing for uniform stress distribution under stress, and improving the tear resistance and flexural fatigue life of the material interface area. Step 5: During the S5 cooling stage, the rapid drop in ambient temperature reduces the compatibility of hydroxyl-terminated polydimethylsiloxane in the matrix resin, resulting in thermodynamic phase separation. The small-molecule octamethylcyclotetrasiloxane carries the large-molecule siloxane and suspended silver-loaded antibacterial powder to the lower-temperature inner wall interface of the mold, where they migrate and accumulate. After molding and demolding, a dense silver-loaded silicone skin layer forms on the outer surface of the part. The siloxane provides a high static friction coefficient for anti-slip properties, while free silver ions provide continuous antibacterial activity, achieving integrated molding of the material's surface functions.

[0013] Preferably, the temperature control parameters for each step are as follows: In step S1, the high-temperature melt blending temperature is 160–180°C; in step S2, the actual material temperature is controlled below 85°C during the mixing process; in step S3, the temperatures of the injection molding machine's barrel feeding section, compression section, and metering section are set between 70–85°C. In step S4, the temperature of the mold corresponding to the seat cushion area is heated and maintained at 165–175°C, while the temperature of the mold corresponding to the lumbar support area is heated and maintained at 95–105°C, with the gradient thermal field maintained for 12–18 minutes. In step S5, cooling water at 10–15°C is introduced into the mold's cooling water channel, and the temperature is lowered to 35–40°C at a cooling rate of 10–15°C / min. By adopting the above technical solution, the process parameters for each stage of the material from plasticization to curing are defined. 160–180°C ensures that the polyurethane and vinyl acetate copolymer form a homogeneous alloy; low-temperature mixing below 85°C prevents the volume expansion of physical microspheres and the decomposition of chemical foaming agents. A high-temperature field of 165–175℃ matches the reaction range of the chemical foaming agent and crosslinking agent, while a low-temperature field of 95–105℃ only excites physically foamed microspheres to reduce the local specific gravity of the material without triggering crosslinking. A forced cooling rate of 10–15℃ / min increases the temperature gradient driving force of the polymer system, promotes the phase separation process of the system, and thus accelerates the migration of the siloxane composite components to the interface, ensuring the stability of the self-skin thickness and the anti-slip and antibacterial effects.

[0014] This invention provides a method for preparing a three-dimensional integrated lumbar support cushion. It has the following beneficial effects: 1. This invention mixes a blended polymer matrix with physically foamed microspheres, azodicarbonamide, and a latent crosslinking agent, and applies a static differentiated temperature field to different spatial regions of the molding die. This creates a dual gradient of crosslinking density and foaming ratio within the material, which smoothly decreases from the seat cushion to the lumbar support area. This eliminates the defects of abrupt changes in physical phase interfaces and mechanical modulus in traditional multi-material splicing processes. It allows the stress to be evenly diffused when the material is subjected to alternating loads to avoid stress concentration, thereby improving the tear resistance of the transition boundary area and the overall bending fatigue life.

[0015] 2. This invention introduces surface-modified copper nanowires coated with hexadecylamine into a polymer blend matrix, which reduces the interfacial energy between inorganic fillers and organic resins to promote dispersion. A three-dimensional thermal conductivity physical network is constructed in the polymer phase that runs through the entire material, so that the static differential temperature field applied at both ends of the mold can be transformed into a linearly and gradually decaying temperature gradient field inside the material. This allows for precise control of the local decomposition gas generation of the foaming agent and the desealing reaction rate of the crosslinking agent, and achieves stable control of the spatial gradual transformation process of the microstructure inside a single material.

[0016] 3. This invention adds hydroxyl-terminated polydimethylsiloxane with octamethylcyclotetrasiloxane as a carrier and silver-loaded zirconium phosphate composite antibacterial powder to the blended material. The cooling process after pressure curing drives the polymer system to undergo thermodynamic phase separation, causing the siloxane macromolecules to carry the antibacterial components to migrate and accumulate to the interface of the mold inner wall at a lower temperature. This forms a dense silver-loaded silicone skin layer on the outer surface of the part, which is intertwined with the molecular chains of the internal matrix. This avoids the defects of secondary dispensing or easy peeling of spraying, and realizes the molding integration of anti-slip function and antibacterial function of the cushion surface. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see the appendix Figure 1 This invention provides a method for preparing a three-dimensional integrated lumbar support cushion.

[0020] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0021] The ethylene-vinyl acetate copolymer has a vinyl acetate mass fraction of 18%~28%, a melt flow rate of 2.0~4.0 g / 10 min (190℃, 2.16 kg), and a crystallinity of 15%~25%.

[0022] The polyether-type thermoplastic polyurethane elastomer is polymerized from polytetrahydrofuran ether diol and diisocyanate. The soft segment mass fraction in the microphase-separated structure is 60%~70%, and the Shore A hardness is 80~90.

[0023] Azodicarbonamide, with a purity ≥98%, has a thermal decomposition temperature of 165℃~175℃ and a decomposition gas production of 220~240mL / g.

[0024] Physically foamed microspheres are core-shell structured expandable microspheres with liquid isopentane encapsulated inside a commercially available thermoplastic polyvinylidene chloride-acrylonitrile copolymer polymer shell. Their initial expansion temperature is 85℃~95℃, the maximum expansion temperature is 135℃~145℃, and the average particle size is 10~20μm.

[0025] Caprolactam-blocked 4,4'-diphenylmethane diisocyanate is a latent crosslinking agent prepared by reacting 4,4'-diphenylmethane diisocyanate with ε-caprolactam. The effective isocyanate group mass fraction is 11%~13%, and the deblocking temperature range under purely thermodynamic conditions is 175℃~185℃.

[0026] Hydroxyl-terminated polydimethylsiloxane with a molecular weight distribution coefficient of 1.5 to 2.0 and a kinematic viscosity of 1000 to 5000 cSt.

[0027] Octamethylcyclotetrasiloxane, purity ≥99%.

[0028] Silver-loaded zirconium phosphate composite antibacterial powder is prepared by ion-exchange loading silver ions onto a zirconium phosphate carrier, with an average particle size of 0.5~1.5μm and a silver mass content of 3%~5%. Copper chloride dihydrate, hexadecylamine, and ascorbic acid were all commercially available analytical grade reagents with a purity of ≥98%.

[0029] Preparation example: Preparation Example 1: A method for preparing surface-modified copper nanowires includes the following steps: 5.0 mmol (approximately 0.85 g) of copper chloride dihydrate and 20.0 mmol (approximately 4.83 g) of hexadecylamine are added to 40 mL of deionized water and magnetically stirred at 65 °C for 45 min to form a deep blue complex solution. 30.0 mmol (approximately 5.28 g) of ascorbic acid is dissolved in 20 mL of deionized water to prepare a reducing solution, which is slowly added dropwise to the complex solution at a rate of 3 mL / min. After the addition is complete, the total volume of the mixed solution (approximately 60 mL) is transferred to a 100 mL polytetrafluoroethylene-lined reactor and reacted at 115 °C for 10 h. After the reaction, the mixture is allowed to cool naturally to room temperature, and the reaction solution is centrifuged at 6000 rpm for 15 min, collecting the deep red precipitate at the bottom. The precipitate was ultrasonically washed three times each with anhydrous ethanol and n-hexane, and then placed in a vacuum drying oven and dried at 45°C for 12 hours to obtain surface-modified copper nanowires.

[0030] Preparation Example 2: A method for preparing surface-modified copper nanowires includes the following steps: 4.0 mmol (approximately 0.68 g) of copper chloride dihydrate and 12.0 mmol (approximately 2.90 g) of hexadecylamine are added to 40 mL of deionized water and magnetically stirred at 65 °C for 45 min to form a complex solution. 20.0 mmol (approximately 3.52 g) of ascorbic acid is dissolved in 20 mL of deionized water to prepare a reducing solution, which is slowly added dropwise to the complex solution at a rate of 3 mL / min. After the addition is complete, the mixed solution is transferred to a polytetrafluoroethylene-lined reactor and reacted at 105 °C for 6 h. After the reaction, the solution is naturally cooled to room temperature, and post-treatment is performed under the same centrifugation, washing, and drying conditions as in Preparation Example 1 to obtain surface-modified copper nanowires.

[0031] Preparation Example 3: A method for preparing surface-modified copper nanowires includes the following steps: 6.0 mmol (approximately 1.02 g) of copper chloride dihydrate and 30.0 mmol (approximately 7.24 g) of hexadecylamine are added to 40 mL of deionized water and magnetically stirred at 65 °C for 45 min to form a complex solution. 40.0 mmol (approximately 7.04 g) of ascorbic acid is dissolved in 20 mL of deionized water to prepare a reducing solution, which is slowly added dropwise to the complex solution at a rate of 3 mL / min. After the addition is complete, the mixed solution is transferred to a polytetrafluoroethylene-lined reactor and reacted at 125 °C for 14 h. After the reaction, the solution is naturally cooled to room temperature, and post-treatment is performed under the same centrifugation, washing, and drying conditions as in Preparation Example 1 to obtain surface-modified copper nanowires.

[0032] Preparation Example 4: A method for preparing a silver-loaded silica gel composite component includes the following steps: Hydroxyl-terminated polydimethylsiloxane and octamethylcyclotetrasiloxane are added to a mixing container at a mass ratio of 3:1. The mixture is stirred evenly using a mechanical stirrer at 300 rpm to obtain a siloxane mixture. 2% (by mass) of silver-loaded zirconium phosphate composite antibacterial powder is added to the siloxane mixture. The mixing container is placed in an ultrasonic cell disruptor and ultrasonically dispersed in an ice bath at 300W for 30 minutes to obtain the silver-loaded silica gel composite component.

[0033] Example: Example 1: This embodiment provides a method for preparing a three-dimensional integrated lumbar support cushion, comprising the following steps: 70.0 parts by weight of ethylene-vinyl acetate copolymer, 30.0 parts by weight of polyether-type thermoplastic polyurethane elastomer, and 1.5 parts by weight of surface-modified copper nanowires obtained in Preparation Example 1 are weighed. The above three raw materials are fed into a co-rotating twin-screw extruder for high-temperature melt blending. The temperature of each zone of the extruder is set to 160°C to 175°C. After blending and extrusion, the mixture is granulated underwater and dried to obtain a homogeneous thermally conductive alloy masterbatch. The above thermally conductive alloy masterbatch is fed into a two-roll open mill, and the roll temperature is set to 75°C. After the masterbatch softens and wraps around the rolls, 3.5 parts by weight of physically foamed microspheres, 2.5 parts by weight of azodicarbonamide, 6.0 parts by weight of caprolactam-blocked 4,4'-diphenylmethane diisocyanate, and 3.0 parts by weight of the silver-loaded silicone composite component obtained in Preparation Example 4 are added sequentially. The low-heat mixing time was controlled at 8 minutes, during which the material was continuously turned over in triangular folds to ensure that the actual temperature of the material remained below 85℃. After uniform mixing, the mixture was sheeted and cut to obtain the blended base material. The blended base material was added to an injection molding machine, with the temperatures of the feeding section, compression section, and metering section of the injection molding machine set to 72℃, 78℃, and 82℃, respectively. Under the conditions of an injection pressure of 50MPa and an injection speed of 40mm / s, the plasticized material was injected into the pre-closed mold cavity of the lumbar support cushion in one go, with the filling volume controlled at 65% of the total cavity volume. After injection, the material entered the pressure holding and curing stage, with the holding pressure set at 10MPa. An independent temperature control loop was used to apply a static differential temperature field to different spatial areas of the closed mold, heating and maintaining the temperature of the corresponding cushion area at 170℃, while simultaneously heating and maintaining the temperature of the corresponding lumbar support area at 100℃. The gradient thermal field was maintained for 15 minutes. After the thermal curing is completed, the mold heating system is turned off, and cooling water at 12°C is introduced into the mold cooling water channel to cool the entire mold at a cooling rate of 12°C / min. When the overall temperature of the mold drops to 38°C, the mold is opened and the product is ejected. It is then left to stand and mature for 24 hours to obtain a three-dimensional integrated lumbar support cushion.

[0034] Example 2: This embodiment provides a method for preparing a three-dimensional integrated lumbar support cushion, comprising the following steps: 80.0 parts by weight of ethylene-vinyl acetate copolymer, 20.0 parts by weight of polyether-type thermoplastic polyurethane elastomer, and 0.8 parts by weight of surface-modified copper nanowires obtained in Preparation Example 2 are weighed. The above materials are fed into a twin-screw extruder for high-temperature melt blending. The extruder temperature is set to 160°C to 170°C. After extrusion, pelletizing, and drying, a thermally conductive alloy masterbatch is obtained. The thermally conductive alloy masterbatch is fed into a two-roll mill. The roll temperature is set to 70°C. After softening and wrapping the rolls, 2.0 parts by weight of physically foamed microspheres, 1.5 parts by weight of azodicarbonamide, 4.0 parts by weight of caprolactam-blocked 4,4'-diphenylmethane diisocyanate, and 1.5 parts by weight of the silver-loaded silicone composite component obtained in Preparation Example 4 are added. The mixing time is controlled to 6 minutes, and the actual material temperature is controlled to be below 85°C. After uniform mixing, the mixture is sheeted to obtain the blended base material. The blended base material was added to the injection molding machine, and the temperatures of each section of the barrel were set to 70℃, 75℃, and 80℃, respectively. Injection was carried out under the conditions of an injection pressure of 40MPa and an injection speed of 30mm / s, with the filling volume controlled at 60% of the total cavity volume. After injection, the pressure was held at 5MPa. The temperature of the mold corresponding to the seat cushion area was heated and kept constant at 165℃, and the temperature of the mold corresponding to the lumbar support area was heated and kept constant at 95℃, with the gradient thermal field maintained for 12 minutes. After curing, 10℃ cooling water was introduced into the cooling water channel, and the temperature was lowered at a rate of 10℃ / min. When the mold temperature dropped to 35℃, the mold was opened and ejected, and the mixture was allowed to stand and cure for 24 hours to obtain a three-dimensional integrated lumbar support seat cushion.

[0035] Example 3: This embodiment provides a method for preparing a three-dimensional integrated lumbar support cushion, comprising the following steps: 65.0 parts by weight of ethylene-vinyl acetate copolymer, 35.0 parts by weight of polyether-type thermoplastic polyurethane elastomer, and 2.5 parts by weight of surface-modified copper nanowires obtained in Preparation Example 3 are weighed. The above materials are fed into a twin-screw extruder for high-temperature melt blending. The extruder temperature is set to 165°C to 180°C. After extrusion, pelletizing, and drying, a thermally conductive alloy masterbatch is obtained. The thermally conductive alloy masterbatch is fed into a two-roll mill. The roll temperature is set to 80°C. After softening and wrapping the rolls, 5.0 parts by weight of physically foamed microspheres, 3.5 parts by weight of azodicarbonamide, 8.0 parts by weight of caprolactam-blocked 4,4'-diphenylmethane diisocyanate, and 4.5 parts by weight of the silver-loaded silicone composite component obtained in Preparation Example 4 are added. The mixing time is controlled to 10 minutes, and the actual temperature of the materials is strictly controlled not to exceed 85°C. After uniform mixing, the mixture is sheeted to obtain the blended base material. The blended base material was added to the injection molding machine, and the temperatures of each section of the barrel were set to 75℃, 80℃, and 85℃, respectively. Injection was carried out under the conditions of an injection pressure of 60MPa and an injection speed of 50mm / s, with the filling volume controlled at 70% of the total cavity volume. After injection, the pressure was held at 15MPa. The temperature of the mold corresponding to the seat cushion area was heated and kept constant at 175℃, and the temperature of the mold corresponding to the lumbar support area was heated and kept constant at 105℃, with the gradient thermal field maintained for 18 minutes. After curing, 15℃ cooling water was introduced into the cooling water channel, and the temperature was lowered at a rate of 15℃ / min. When the mold temperature dropped to 40℃, the mold was opened and ejected, and the mixture was allowed to stand and cure for 24 hours to obtain the three-dimensional integrated lumbar support seat cushion.

[0036] Comparative example: Comparative Example 1: The difference from Example 1 is that no surface-modified copper nanowires were added in the first stage of high-temperature melt blending; all other aspects are the same.

[0037] Comparative Example 2: Compared with Example 1, the difference is that the azodicarbonamide in the second stage of low-temperature mixing is replaced by 4,4'-oxobisbenzenesulfonyl hydrazine (OBSH chemical foaming agent, which does not produce ammonia byproducts when it is thermally decomposed), while the rest of the formulation and preparation steps are the same.

[0038] Comparative Example 3: Compared with Example 1, the difference is that caprolactam-blocked 4,4'-diphenylmethane diisocyanate was not added in the second stage of low-temperature mixing, while the rest of the formulation and preparation steps are the same.

[0039] Comparative Example 4: Compared with Example 1, the difference is that a static differentiated temperature field was not used in the pressure holding and curing stage. Instead, the seat cushion part and the lumbar support part of the closed mold were heated as a whole and kept constant at 170°C. All other aspects are the same.

[0040] Comparative Example 5: Compared with Example 1, the difference is that no silver-loaded silicone composite component was added in the second stage of low-temperature mixing, while the rest of the formulation and preparation steps are the same.

[0041] Comparative Example 6: Compared with Example 1, the difference is that this comparative example does not use the integrated molding process of blended base materials, but uses the traditional multi-part physical splicing process to prepare the lumbar support cushion: commercially available soft polyurethane foam is used as the cushion area material, commercially available high-density EVA foam board is used as the lumbar support area material, a slot is reserved in the lumbar support area and a rigid polypropylene support board is inserted, and the components are bonded and spliced ​​together with polyurethane adhesive.

[0042] Test Example 1: Internal Temperature Gradient Field Verification Test Temperature was recorded using a multi-channel temperature data acquisition instrument and a 0.5mm diameter K-type thermocouple probe. Six temperature measurement points were equidistantly positioned along the longitudinal axis from the center of the seat area to the center of the lumbar support area within the mold cavity. Starting from the center of the seat area (0cm), the spacing between temperature measurement points was set to 2cm, extending to the center of the lumbar support area (10cm). Thermocouple probes were pre-embedded and fixed at the geometric center of the cavity at each temperature measurement point. Injection molding was performed according to the molding process parameters of each embodiment and comparative example. The mold was closed, and the independent temperature control circuits at both ends were activated to enter the pressure holding and curing stage, at which point the temperature data acquisition instrument was turned on. At the 10-minute mark of the pressure holding and curing stage, the internal temperature data of each temperature measurement point was recorded. Each set of parameters was repeated three times, and the average value was taken.

[0043] Table 1 shows the temperature records of each temperature measuring point on the longitudinal central axis inside the mold during the 10th minute of pressure holding and curing in each embodiment and comparative example.

[0044] Table 1: Spatial distribution data of internal temperature field in each embodiment and comparative example

[0045] According to the data in Table 1, Comparative Example 1, without the addition of surface-modified copper nanowires, had a low thermal conductivity polymer matrix. When 170℃ and 100℃ were applied to both ends of the mold respectively, internal heat conduction was hindered, resulting in a temperature abrupt change of nearly 50℃ in the 4cm to 6cm interface region. This temperature abrupt change leads to a sudden change in the decomposition and conversion rate of the chemical foaming agent, causing a step change in the mechanical modulus and easily inducing stress concentration. Comparative Example 4 used isothermal molding, with the internal temperature kept constant at around 170℃. No temperature gradient was formed, making it impossible to differentiate and control the mechanical properties of different regions.

[0046] The temperature data from Examples 1 to 3 show a continuous decreasing trend. Surface-modified copper nanowires form a percolation network within the polymer matrix, establishing a heat transfer channel between the high-temperature cushion region and the low-temperature lumbar support region, transforming the temperature difference applied externally to the mold into a linear heat flux distribution within the material. The continuously decaying internal temperature field affects the reaction kinetics of the foaming and crosslinking systems. As the temperature transitions from 170°C to 100°C, the decomposition rate of azodicarbonamide decreases gradually, the concentration of ammonia byproducts decreases accordingly, and the deblocking rate and degree of crosslinking reaction of caprolactam-blocked isocyanate continuously decrease along the axial direction. Internal heat conduction achieves a dual gradient transition in foaming ratio and chemical crosslinking density, avoiding physical phase interfaces generated in multi-material splicing processes.

[0047] Test Example 2: Crosslinking Gradient Distribution Verification Test The gel ratio of the molded product was determined using Soxhlet extraction to characterize the spatial distribution of cross-linking within the material. 0.5g samples were taken along the longitudinal central axis of the molded product at points 0cm, 2cm, 4cm, 6cm, 8cm from the center of the seat cushion, and 10cm from the center of the lumbar support. The samples were wrapped in a 120-mesh stainless steel wire mesh bag, and the total mass of the sample and bag was weighed. The net mass of the bag was subtracted to obtain the initial mass of the sample. The bag containing the sample was placed in the extraction tube of a Soxhlet extractor, and xylene solvent was added to a round-bottom flask. The mixture was heated under reflux for 24 hours. After extraction, the bag was removed and dried in an 80℃ vacuum drying oven to constant weight. After cooling to room temperature, the remaining insoluble matter was weighed to obtain the mass of the extracted material. The gel ratio was calculated as the percentage of the remaining insoluble matter to the initial mass of the sample. Samples at different locations in each group were tested in triplicate, and the average value was taken.

[0048] The gelation rate test data of each embodiment and comparative example at different spatial locations are shown in Table 2.

[0049] Table 2: Spatial distribution data of gelation rate for each embodiment and comparative example

[0050] Table 2 shows the gel rate data, reflecting the spatial distribution of the cross-linking state within the material. Comparative Example 3, without the addition of a latent cross-linking agent, showed a gel rate of 0% at all test points, maintaining the thermoplastic elastomer state throughout the material. Comparative Example 4, using isothermal molding at 170℃, exhibited a uniform spatial temperature distribution, with the gel rate at each test point remaining above 70%, indicating no cross-linking gradient. Comparative Example 2, by replacing azodicarbonamide with the ammonia-free OBSH chemical foaming agent, showed a gel rate of 12.4% in the cushion area at 170℃, demonstrating that caprolactam-blocked diisocyanate exhibits a low purely thermodynamic deblocking rate at 170℃ under ammonia-free conditions.

[0051] The gelation rates of Examples 1 to 3 exhibit a spatially decaying distribution. The gelation rate is higher in the seat cushion area, indicating cross-linking of the matrix. Extending towards the lumbar support area, the gelation rate gradually decreases, reaching nearly 0% in the central area of ​​the lumbar support, where no significant cross-linking reaction occurs, maintaining a thermoplastic state.

[0052] The crosslinking gradient distribution is controlled by the temperature field. The internal temperature distribution of the mold affects the thermal decomposition rate of azodicarbonamide. In the 170°C region, azodicarbonamide decomposes to produce ammonia, which promotes the deblocking of caprolactam-blocked diisocyanate and its crosslinking reaction with the matrix. As the temperature transitions longitudinally towards 100°C, the amount of azodicarbonamide decomposition decreases, the amount of ammonia generated decreases, and the deblocking reaction of the crosslinking agent weakens. The temperature field, the decomposition products of the foaming agent, and the degree of chemical crosslinking form a cascade relationship, achieving spatial regulation of the crosslinking density within the material.

[0053] Test Example 3: Macroscopic Hardness Continuity Test The hardness distribution on the surface of the molded product was determined using a Shore A hardness tester. A complete lumbar support cushion, cured for 24 hours, was used as the test sample and laid flat on a test table at room temperature (23±2℃). Along the longitudinal centerline of the sample, starting from the geometric center of the cushion area (0cm), test points were marked every 1cm towards the center of the lumbar support area (10cm), for a total of 11 test points. The Shore A hardness tester was vertically pressed into each test point, applying a uniformly distributed load to ensure complete contact between the indenter and the sample surface. The hardness value was read after 3 seconds. Each sample was measured three times at the same parallel cross-section. Three samples from the same batch were selected for repeated testing, and the arithmetic mean was taken after removing outliers.

[0054] The Shore A hardness distribution test data of each embodiment and comparative example at different locations are shown in Table 3.

[0055] Table 3: Spatial distribution data of Shore A hardness in each embodiment and comparative example

[0056] Table 3 shows the hardness data reflecting the spatial variation of the material's macroscopic mechanical modulus. Comparative Example 6 used a physical splicing process; the 0-4cm region was made of soft sponge, and the 6-10cm region was made of high-density EVA board, bonded together at 5cm with adhesive. The results showed a sudden change in hardness from 15.4 to 82.1 at 5cm, indicating a mechanical interface fault, which could easily lead to stress concentration at the interface during bending. Comparative Example 1, without added thermally conductive filler, showed foaming in the 0-4cm region due to high temperature, resulting in a hardness below 33.2; micro-foaming in the 6-10cm region due to low temperature, resulting in a hardness above 81.6; and a near 40-degree drop in hardness at the 5cm interface, indicating a mechanical fault defect.

[0057] The hardness of Examples 1 to 3 increased with distance. In the seat cushion area (0-2cm), the physical and chemical foaming agents were activated at 170°C, causing the matrix to expand and form a low-density structure, with a hardness between 23 and 39. In the lumbar support area (8-10cm), only part of the physical foaming agent was activated at 100°C, the matrix was in a micro-foamed state and no cross-linking occurred, with a hardness reaching 80 to 89. In the transition region of 3-7cm, the heat conduction path constructed by the surface-modified copper nanowire network caused the internal temperature to decrease linearly. The temperature decay limited the expansion ratio and gas production of the foaming agent, resulting in a corresponding decrease in the porosity and macromolecular cross-linking network density of the material. The continuous change in microstructure avoided the formation of physical phase interfaces, achieving a smooth transition in hardness indicators. The structural continuity helped improve the overall fatigue resistance and stress transmission distribution of the material.

[0058] Test Example 4: Tear Resistance Test at the Junction Zone The right-angle tear strength of the transition zone of the molded product was tested using a universal testing machine. Following GB / T 529 standard, specimens were cut from the sample after 24 hours of curing. The sampling location was at the junction of the longitudinal centerline of the sample, between 4 cm and 6 cm. A right-angle specimen without a notch was cut, and the thickness was measured. The specimen was fixed at both ends in the upper and lower clamps of the testing machine, and the tensile speed was set to 500 mm / min. The specimen was stretched until it broke, and the maximum force was recorded. The tear strength was calculated as the ratio of the maximum force to the specimen thickness. Five parallel specimens were cut from each group for testing, the location of fracture was recorded, and the arithmetic mean was calculated.

[0059] The tear strength and fracture location of the samples at the interface of each embodiment and comparative example are shown in Table 4.

[0060] Table 4: Tear strength test data of the boundary zone between each embodiment and comparative example

[0061] Comparative Example 6, using a physical splicing process, had an average tear strength of 11.8 kN / m, with all fractures occurring at the adhesive splicing seams. The soft sponge and high-density EVA board have different mechanical moduli, and their interface relies on adhesive bonding. Under tensile deformation, stress concentrates at the splicing interface, leading to the peeling and failure of the bonding layer.

[0062] Comparative Example 1, without the addition of surface-modified copper nanowires, exhibited an average tear strength of 17.0 kN / m, with fracture concentrated at the abrupt hardness change cross-section. A temperature fault existed in the 4 cm to 6 cm region of the material, causing a step change in the foaming ratio and crosslinking density within this range. Tensile stress could not be uniformly transmitted internally, leading to fracture failure at the modulus abrupt change cross-section.

[0063] The average tear strength of Examples 1 to 3 ranged from 31.2 kN / m to 38.6 kN / m, with the fracture location within the sample matrix, exhibiting random tearing extension. The surface-modified copper nanowire network established heat transfer channels within the matrix, transforming the spatial temperature difference applied by the mold into a continuous internal temperature field. This temperature field modulated the foaming kinetics and ammonia yield of azodicarbonamide, thereby affecting the deblocking and crosslinking reaction of caprolactam-blocked diisocyanate. The porosity and crosslinking density within the matrix exhibited gradient changes with spatial location, avoiding abrupt changes in the physical phase interface and mechanical properties at the rigid-flexible interface. Under stress, stress diffused through the gradient structure, alleviating stress concentration and improving the tear resistance of the interface region.

[0064] Test Example 5: Bending Fatigue Life Test Dynamic bending fatigue testing was conducted on lumbar support area specimens using a bending endurance testing machine. Long strip specimens were cut from the lumbar support area of ​​the molded product (within 8-10 cm of the seat center). Both ends of the specimen were fixed in the moving and stationary clamps of the testing machine, respectively. The bending angle was set to 90 degrees, and the bending test frequency was 60 cycles / minute. Alternating bending tests were performed at room temperature. The machine was stopped every 10,000 cycles to observe changes in specimen morphology. The cumulative number of bends at which the first crack appeared on the specimen surface, and the cumulative number of bends at which the specimen fractured or lost its support stiffness leading to functional failure, were recorded. Five parallel specimens were cut from each group for testing, and the arithmetic mean was calculated after removing outliers.

[0065] The bending fatigue test data of the lumbar support area specimens of each embodiment and comparative example are shown in Table 5.

[0066] Table 5: Bending fatigue life test data of the lumbar support area in each embodiment and comparative example

[0067] Comparative Example 6 employed a physical splicing structure with a rigid polypropylene support plate embedded within a foamed matrix. Initial surface cracking occurred at 38,640 cycles, and support failure occurred at 51,480 cycles. The polypropylene support plate, due to its high hardness, was prone to fatigue cracking under repeated bending. The deformation difference between the rigid support plate and the flexible foam matrix led to friction and relative sliding at the contact surface due to alternating stress. The discontinuity of the internal structure accelerated stress concentration towards the edges of the support plate, triggering internal failure.

[0068] Comparative Example 1 did not establish a spatial temperature gradient, and the material contained abruptly different layers of foaming ratio and crosslinking density. During alternating bending, stress could not be smoothly transmitted within the matrix, resulting in stress concentration points at the interface of modulus abrupt change. The matrix developed cracks after 84,260 bends, and its fatigue resistance was limited by internal mechanical faulting.

[0069] The support failure cycles in Examples 1 to 3 all exceeded 190,000. The lumbar support area was in a 100°C environment during the molding stage, preventing thermal decomposition of the azodicarbonamide and maintaining the inertness of the latent crosslinking agent. The polyether-type thermoplastic polyurethane and ethylene-vinyl acetate copolymer matrix maintained a pure thermoplastic elastomer state, without forming a crosslinked network, thus preserving chain segment mobility and bulk toughness. Microfoaming occurred in the material, forming a self-supporting microporous structure. Under alternating bending loads, there was no modulus difference or physical interface between the support plate and the matrix. Bending stress was dissipated to the surroundings through the homogeneous microporous thermoplastic elastomer network, avoiding localized stress concentration. The continuous gradient field eliminated abrupt changes in the microstructure cross-section, maintaining the structural integrity of the material under dynamic deformation cycles.

[0070] Test Example 6: Surface Anti-slip and Antibacterial Performance Test The surface anti-slip ability and antibacterial activity of the molded products were evaluated using a static friction coefficient tester and a film application method.

[0071] The static friction coefficient of the surface was determined according to GB / T 10006 standard. A square specimen with a side length of 80 mm was cut from a flat area of ​​the sample's seat cushion and conditioned for 24 hours at 23±2℃ and 50±5% relative humidity. The specimen was laid flat and fixed on the test platform, with its surface in contact with a 200g standard stainless steel slider. The measuring instrument was started to allow relative sliding between the contact surfaces, and the initial maximum static friction force was recorded. The static friction coefficient was calculated. Five specimens were taken from each group for testing, and the arithmetic mean was calculated.

[0072] The antibacterial rate was determined according to GB / T 31402 standard. A square slice with a side length of 50 mm was cut from the sample surface. The test bacteria were *Escherichia coli* (ATCC 8739) and *Staphylococcus aureus* (ATCC 6538). A concentration of 1.0 × 10⁻⁶ was used. 5 CFU / mL up to 5.0 × 10⁻⁶ 5 A CFU / mL bacterial suspension was dropped onto the test surface of the sample and covered with a 40mm square polyethylene film to ensure uniform contact between the bacterial suspension and the sample surface. The sample was then incubated in a constant temperature and humidity incubator at 35±1℃ and a relative humidity of over 90% for 24 hours. After incubation, surviving bacteria were washed off from the sample and film and counted using the agar plate pour method. The inhibition rate was calculated based on the difference in the logarithmic number of viable bacteria between the control and test samples after 24 hours of incubation. Each group of samples was tested in triplicate, and the average value was taken.

[0073] The surface static friction coefficient and antibacterial rate test data of each embodiment and comparative sample are shown in Table 6.

[0074] Table 6: Test data of surface static friction coefficient and antibacterial rate for each embodiment and comparative example

[0075] Table 6 shows the migration and enrichment of the silicone composite component at the material interface and its impact on surface properties. Comparative Example 5, without the addition of the silver-loaded silicone composite component, had a static friction coefficient of 0.32, which is typical for blends. The inhibition rates against both *E. coli* and *Staphylococcus aureus* were below 17%, indicating no antibacterial activity on the surface. Comparative Example 6, using a physical splicing process and undergoing secondary silicone dotting and antibacterial spraying on the finished product, had a static friction coefficient of 0.67, and the initial antibacterial rate of the applied antibacterial coating ranged from 91.25% to 92.41%. The secondary processing adds steps, and the coating adhesion is affected by substrate deformation, posing a risk of peeling over long-term use.

[0076] Examples 1 to 3 show static friction coefficients ranging from 0.58 to 0.71, with antibacterial rates exceeding 98.5%. The material undergoes surface modification during the molding process. This modification utilizes the thermodynamic phase separation principle of polymer melts. During the cooling phase after pressure curing, the compatibility between hydroxyl-terminated polydimethylsiloxane and the matrix resin decreases at low temperatures. Small-molecule octamethylcyclotetrasiloxane acts as a carrier, driving the siloxane macromolecules to migrate towards the mold's inner wall interface. Silver-loaded zirconium phosphate composite antibacterial powder is suspended and dispersed within the siloxane matrix, simultaneously enriching on the surface along with the siloxane components. After the mold cools to room temperature, it is opened, forming a skin layer rich in siloxane and silver ions on the part's surface. The low surface energy and high friction coefficient of polydimethylsiloxane provide anti-slip properties, while the zirconium phosphate carrier releases silver ions that disrupt bacterial cell membranes and bind to enzyme proteins to exert a bactericidal effect. The phase separation forms a skin layer that intertwines with the macromolecular chains within the matrix, resulting in a structural stability higher than that of a secondary adhesive coating. The molding process utilizes phase separation behavior to replace secondary surface processing, achieving simultaneous integration of surface physical and chemical functions.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A three-dimensional integrated lumbar support cushion, characterized in that, The lumbar support cushion is made from raw materials comprising the following parts by weight: 65.0–80.0 parts of ethylene-vinyl acetate copolymer; 20.0–35.0 parts of polyether-type thermoplastic polyurethane elastomer; Physically foamed microspheres, 2.0–5.0 parts; Azodicarbonamide 1.5–3.5 parts; 4.0–8.0 parts of caprolactam-blocked 4,4'-diphenylmethane diisocyanate; 0.8–2.5 parts of surface-modified copper nanowires; The silver-loaded silicone composite component is 1.5 to 4.5 parts.

2. The three-dimensional integrated lumbar support cushion according to claim 1, characterized in that, The characteristic parameters of the raw material satisfy the following conditions: In the ethylene-vinyl acetate copolymer, the mass fraction of vinyl acetate is 18% to 28%, and the melt flow rate is 2.0 to 4.0 g / 10 min; The Shore A hardness of the polyether-type thermoplastic polyurethane elastomer is 80-90.

3. The three-dimensional integrated lumbar support cushion according to claim 1, characterized in that, The specific parameters of the raw material meet the following conditions: The initial expansion temperature of the physically foamed microspheres is 85–95°C; The thermal decomposition temperature of the azodicarbonamide is 165–175°C. The caprolactam-blocked 4,4'-diphenylmethane diisocyanate has a deblocking temperature range of 175–185 °C under purely thermodynamic conditions.

4. The three-dimensional integrated lumbar support cushion according to claim 1, characterized in that, The surface-modified copper nanowires were prepared by the following method: Add 4.0–6.0 mmol of copper chloride dihydrate and 12.0–30.0 mmol of hexadecylamine to water and stir at 65 °C for 45 min to form a complex solution; Add 20.0–40.0 mmol of ascorbic acid aqueous solution dropwise to the complex solution at a rate of 3 mL / min, and then keep the mixture at 105–125 °C for 6–14 h. After the reaction was completed, the precipitate was collected by centrifugation, and then washed and dried to obtain surface-modified copper nanowires.

5. The three-dimensional integrated lumbar support cushion according to claim 1, characterized in that, The silver-loaded silicone composite component was prepared by the following method: Hydroxyl-terminated polydimethylsiloxane and octamethylcyclotetrasiloxane were mixed evenly at a mass ratio of 3:1 to obtain a siloxane mixture; 2% of silver-loaded zirconium phosphate composite antibacterial powder was added to the siloxane mixture, and the mixture was ultrasonically dispersed to obtain a silver-loaded silica gel composite component.

6. The method for preparing the three-dimensional integrated lumbar support cushion according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Ethylene-vinyl acetate copolymer, polyether thermoplastic polyurethane elastomer and surface-modified copper nanowires are melt-blended at high temperature according to the formula, and then extruded and granulated to obtain thermally conductive alloy masterbatch. S2: The thermally conductive alloy masterbatch is softened and wrapped on a two-roll mill, and physically foamed microspheres, azodicarbonamide, caprolactam-blocked 4,4'-diphenylmethane diisocyanate and silver-loaded silica gel composite components are added in sequence for low-temperature mixing, and the resulting sheet is sheeted to obtain the blended base material. S3: After plasticizing the blended base material, inject it into the pre-closed mold cavity of the lumbar support cushion; S4: During the pressure holding and curing stage, an independent temperature control circuit is used to apply a static differentiated temperature field to different spatial areas of the closed mold to perform gradient thermal field curing; S5: After the thermal curing is completed, cool down and eject the product from the mold.

7. The method for preparing the three-dimensional integrated lumbar support cushion according to claim 6, characterized in that, The temperature control parameters for each step are as follows: In step S1, the high-temperature melt blending temperature is 160–180°C; In step S2, the actual temperature of the material is controlled to be below 85°C during the mixing process; In step S3, the temperatures of the feeding section, compression section, and metering section of the injection molding machine barrel are set between 70 and 85°C.

8. The method for preparing the three-dimensional integrated lumbar support cushion according to claim 6, characterized in that, The specific implementation method of step S4 is as follows: The temperature of the mold corresponding to the seat cushion is heated and kept constant at 165-175℃, while the temperature of the mold corresponding to the lumbar support is heated and kept constant at 95-105℃. The gradient thermal field is maintained for 12-18 minutes.

9. The method for preparing the three-dimensional integrated lumbar support cushion according to claim 8, characterized in that, After gradient thermal curing in step S4, a crosslinking density gradient and foaming ratio gradient are formed inside the molded product, which smoothly decrease from the seat cushion part to the lumbar support part. The matrix of the seat cushion part is in a foamed crosslinked state, while the matrix of the lumbar support part is in an uncrosslinked thermoplastic state.

10. The method for preparing the three-dimensional integrated lumbar support cushion according to claim 6, characterized in that, The specific implementation method of step S5 is as follows: Cooling water at 10-15°C is introduced into the mold cooling water channel, and the temperature is reduced to 35-40°C at a cooling rate of 10-15°C / min. After the cooling step, a dense skin layer rich in siloxane and silver-loaded antibacterial powder is formed on the outer surface of the molded product.

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