Breathable springback foaming silicone rubber for high-speed rail seats and preparation method

Abstract

The invention relates to the technical field of preparation of filling materials for high-speed rail seats, in particular to breathable springback foamed silicone rubber for high-speed rail seats and a preparation method of the breathable springback foamed silicone rubber for the high-speed rail seats. Supercritical CO2 is used as a foaming agent to be matched with bio-based silicone rubber as a main material, and polar groups of the bio-based silicone rubber can be used as nucleation sites of CO2 bubbles; according to the present invention, with the combination of the rapid pressure release induction (5 MPa / s rate nucleation) of supercritical CO2, the uniformly-distributed and pore-size-controllable foam pores (especially the gradient structure) are formed, such that the compression resistance resilience performance (suitable for the long-term loading of the seat) and the gas permeability (improving the riding comfort) of the material are improved so as to avoid the excessive local foaming problem; castor oil derivative modified siloxane is used as bio-based silicone rubber, flexible chain segments derived from castor oil are introduced into a molecular chain of the castor oil derivative modified siloxane, and the flexible chain segments can improve the activity of the molecular chain, so that the silicone rubber can still keep certain flexibility in a low-temperature environment.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of filling materials for high-speed rail seats, and in particular to a breathable and resilient foamed silicone rubber for high-speed rail seats and a preparation method thereof. Background Art

[0002] The filling materials for high-speed rail seats are generally divided into: sponge materials, latex materials, fiber materials, and functional composite materials. However, foamed silicone rubber is not widely used as a filling material for high-speed rail seats, mainly due to the following reasons: 1. Although silicone rubber is resistant to low temperatures down to -50°C, when used for a long time at extremely low temperatures (such as below -30°C), the elasticity of the foamed silicone rubber with an open-cell structure may decrease slightly due to pore shrinkage (the effect on the closed-cell structure is smaller), while the modified PU foam can maintain good elasticity at -40°C; 2. The tear strength of foamed silicone rubber (about -3-8N / mm) is lower than that of high-density PU rigid foam (5-10N / mm) and some rubber alloy materials. If the surface protection layer of the seat is not designed adequately, long-term high-friction scenarios (such as frequent adjustments to sitting posture) may cause damage to the filling layer.

[0003] However, when foamed silicone rubber is used as a filling material for high-speed rail seats, it still has the following advantages: 1. Fire safety performance: Rolling grade advantage, naturally difficult to burn (oxygen index ≥ 30%), no droplets when burning, only silicon dioxide powder, low smoke density and no toxic gas release, no need to add halogen flame retardant to pass high-speed rail fire protection certification; 2. Excellent weather resistance (lifespan can reach more than 20 years), UV and ozone aging resistance is more than 10 times that of ordinary rubber, and it still maintains elasticity after long-term high-frequency use, without the need for frequent replacement; 3. It is soft and elastic with uniform rebound (Shore hardness A10-50 adjustable). It can simulate the slow rebound effect of memory foam through aperture design (open / closed cell), fit the human body curve, disperse pressure more evenly, and has better air permeability than closed-cell PU foam (open-cell structure can promote air circulation); 4. The raw materials are non-toxic and harmless, and the production process does not release formaldehyde or VOC. It complies with the EU REACH and US FDA food grade standards, is healthy and friendly to passengers, and is recyclable and degradable, which is in line with the trend of green materials for high-speed rail; 5. Silicone rubber has a low density (20-80kg / m³, adjustable), and its weight is only 60%-80% of PU foam at the same hardness, which helps to reduce weight and save energy in high-speed railways; and it can be molded into complex curved surfaces to adapt to the ergonomic design of seats.

[0004] From this we can see that when foamed silicone rubber is used as a filling material for high-speed rail seats, its advantages far outweigh its disadvantages. Using foamed silicone rubber as a filling material for high-speed rail seats is an important trend in the development of green materials for high-speed rail in the future.

[0005] In the invention patent with patent application number 201810827580.X, a method for preparing car seat sponge is specifically disclosed, which belongs to the technical field of decorative materials. The present invention uses silicon hydrogen condensation reaction to prepare silicone rubber foam, and methyl hydrogen-containing silicone oil diffuses from the inner water phase to the outer water phase to the interface between the oil phase and the outer water phase, and reacts with liquid silicone rubber adsorbed on the phase interface under the action of platinum catalyst to undergo silicon hydrogen addition and condensation reaction, and then deposits on the phase interface to complete the coating of EPDM rubber to form microcapsules, and the main chain of silicone rubber is formed by alternating Si-O-Si bonds. Due to the special skeleton structure, under the action of platinum catalyst, vinyl silicone oil and hydrogen-containing silicone oil undergo cross-linking reaction, and hydroxyl silicone oil and hydrogen-containing silicone oil produce foaming gas hydrogen for foaming reaction, and polyethylene glycol is added, and the hydroxyl group in polyethylene glycol can react with hydrogen-containing silicone oil to form silicone rubber foam material for car seats.

[0006] However, the above technical solution has the following disadvantages: 1. The condensation reaction of hydroxy silicone oil and hydrogen silicone oil generates hydrogen (foaming gas). The reaction is highly exothermic and fast, which can easily lead to local excessive foaming (uneven bubble diameter) or insufficient foaming (uneven density). It is difficult to accurately control the foam density and porosity, especially in large-scale production; 2. After the hydroxyl group of polyethylene glycol (PEG) reacts with hydrogen-containing silicone oil, the COC organic chain segment is introduced into the main chain of silicone rubber, which destroys the pure inorganic structural advantage of the Si-O-Si skeleton, resulting in reduced UV resistance and heat and humidity aging resistance of the material (PEG is easily oxidized and broken, and the foam is prone to hardening and cracking after long-term use); 3. The hydrogen-containing silicone oil needs to diffuse from the inner water phase to the outer water phase interface. Limited by the interfacial tension and diffusion rate of the oil-water phases, local uneven concentration is prone to occur, resulting in incomplete silane addition reaction at the interface and incomplete coating of EPDM rubber microcapsules (such as exposed rubber particles or uneven coating layers), affecting the overall uniformity of the foam.

[0007] Therefore, there is an urgent need for a foamed silicone rubber material that can overcome the above-mentioned defects and serve as a green filling material for high-speed rail seats. Summary of the invention

[0008] In view of the above problems, the present invention provides a breathable and resilient foamed silicone rubber for high-speed rail seats and a preparation method thereof. 2 As a foaming agent with bio-based silicone rubber as the main material, the polar groups of bio-based silicone rubber can be used as CO 2 The nucleation sites of bubbles, combined with supercritical CO 2The rapid pressure release induction (nucleation rate of 5MPa / s) forms uniformly distributed bubbles with controllable pore size (especially gradient structure), which improves the material's compressive rebound performance (suitable for long-term seat load) and air permeability (improves riding comfort), thereby avoiding the problem of excessive local foaming. At the same time, castor oil derivative-modified siloxane is used as a bio-based silicone rubber, and castor oil-derived flexible chain segments are introduced into its molecular chain. These flexible chain segments can increase the activity of the molecular chain, so that the silicone rubber can still maintain a certain flexibility in a low temperature environment. At low temperatures, the movement of ordinary silicone rubber molecular chains is restricted, and it is easy to become hard and brittle, while the flexible segments in bio-based silicone rubber can alleviate this restriction and reduce the glass transition temperature, thereby improving the elasticity and toughness of the material at low temperatures.

[0009] To achieve the above object, the present invention provides the following technical solutions: A breathable and resilient foamed silicone rubber for high-speed rail seats, which is used as a filling material for high-speed rail seats, comprises: 80-100 parts of bio-based silicone rubber; 5-8 parts of hydrogen silicone oil; Flame retardant 10-15 parts; 5-8 parts of reinforcing filler; 3-5 parts of foaming agent; Catalyst 0.05-0.1 part; Antibacterial agent 0.8-1 part; 2.5-3 parts of repair agent; The bio-based silicone rubber is castor oil derivative modified siloxane, the flame retardant is a mixture of nano-montmorillonite and magnesium hydroxide, the reinforcing filler is fumed silica, and the foaming agent is supercritical CO with a purity of ≥99.9%. 2 The catalyst is a platinum catalyst, the antibacterial agent is a nano silver ion antibacterial agent, and the repair agent is a microencapsulated silane repair agent.

[0010] Specifically, the castor oil derivative modified siloxane is a hydrosilylation modified castor oil siloxane, which is prepared by the hydrosilylation reaction of allyl ricinoleate and methyl hydrogen siloxane, has a vinyl content of 0.25%-0.45%, and a biomass-based ratio of 40-45%.

[0011] First, supercritical CO 2 Foaming, as a physical blowing agent, CO 2 It is non-toxic, residue-free and recyclable, avoiding the toxicity and environmental pollution problems of traditional chemical foaming agents (such as azo and carbonates), and meets the environmental protection standards of high-speed rail seat materials (such as low VOC and no harmful gas release).

[0012] Bio-based silicone rubber, with castor oil derivative modified siloxane as the matrix, reduces dependence on petroleum-based raw materials, introduces renewable resources, and reduces the carbon footprint of materials. The combination of the two makes the entire production process (from raw materials to foaming) in line with the green manufacturing concept and meets the high-speed rail industry's demand for "environmental protection and low carbon".

[0013] At the same time, CO 2 As an inert gas, it has no chemical reaction with polar groups in bio-based silicone rubber (such as hydroxyl and ester groups in castor oil derivatives), and achieves foaming only through physical dissolution and diffusion, thus avoiding possible side reactions between traditional chemical foaming agents and bio-based components (such as catalytic failure and residual degradation products), and ensuring that the bio-based properties of the material (such as biocompatibility and low toxicity) are not destroyed.

[0014] In addition, the molecular chain of castor oil derivative-modified siloxane contains polar side groups, which react with supercritical CO 2 The interaction is stronger (compared to pure methyl silicone rubber), which can increase CO 2 The solubility and diffusion rate in the matrix shorten the saturation time in the foaming process (such as the saturation time in the formula is 2h) and improve production efficiency.

[0015] Bio-based silicone rubber has good flexibility and molecular chain activity. 2 It is easier to form uniform bubble nuclei during infiltration, reduce bubble agglomeration or rupture, help form a gradient pore structure, and improve the air permeability and resilience of the material.

[0016] Correspondingly, supercritical CO 2 The foaming temperature (40°C saturation, maximum vulcanization temperature 160°C) is much lower than the thermal decomposition temperature of bio-based ingredients, avoiding oxidation or degradation of castor oil derivatives at high temperatures, ensuring the integrity of their molecular structure, and maintaining the inherent advantages of the material such as weather resistance and flexibility. In contrast, traditional chemical foaming agents may release heat or acidic gases when decomposing, causing damage to bio-based materials.

[0017] Furthermore, bio-based silicone rubber has better compatibility with nanofillers (such as fumed silica and montmorillonite), and supercritical CO 2 During the foaming process, the filler is dispersed more evenly, agglomeration is reduced, and the mechanical strength (such as tensile strength and tear strength) and flame retardancy of the material are enhanced (the layered structure of montmorillonite can form a denser carbon layer after foaming). The network structure of bio-based silicone rubber is more stable for the encapsulation of microencapsulated repair agents (such as silane repair agents). 2 The microcapsule structure will not be destroyed during the foaming process, ensuring that the repair agent is slowly released during the use of the material (such as when damaged by external force) to achieve self-repair function; at the same time, the dispersibility of the nano silver ion antibacterial agent is further improved due to the shearing effect of the foaming process, and the antibacterial effect is more lasting.

[0018] As an improvement, the preparation steps of the hydrosilylation-modified castor oil siloxane include: Step a1, by mass, 100 parts of allyl ricinoleate and 60-7 parts of methyl hydrogen siloxane are added to a reaction kettle and mixed and stirred, and then 450-500 parts of toluene are added as a solvent to ensure that the reaction system has good fluidity; Step a2, introducing nitrogen into the reactor for protection, the nitrogen flow rate is 100-200 mL / min, and the nitrogen flow is continuously introduced for 15-30 min, the stirring speed is 200-300 r / min, the reactor is heated to 60-80° C., and the temperature is kept and stirred for 30-60 min; Step a3, slowly add Karstedt catalyst in an amount of 0.01%-0.05% of the total mass of the reactants, increase the reaction temperature to 80-120°C, and control the reaction time to 2-6h; Step a4: After the reaction is completed, the reaction system is cooled to room temperature, and the toluene solvent is removed by vacuum distillation at a distillation temperature of 80-120° C. and a vacuum degree of 10-100 Pa. The hydrosilylation-modified castor oil siloxane is obtained after filtration.

[0019] As an improvement, in the flame retardant, the nano-montmorillonite is modified by KH-550 and the content is 3-5 parts, and the magnesium hydroxide is surface-modified by DOPO-VTS and the content is 7-10 parts.

[0020] As an improvement, the nano-montmorillonite modification treatment method is to ultrasonically disperse the nano-montmorillonite and KH-550 in an ethanol solution at a mass ratio of 100:3 for 30 minutes, with an ultrasonic power of 300W, and vacuum drying at 60°C for 12 hours to obtain hydrophobic nano-montmorillonite.

[0021] As an improvement, the magnesium hydroxide modification treatment method is to stir magnesium hydroxide and DOPO-VTS at a mass ratio of 100:2 at 80° C. for 40 minutes to form a phosphorus-silicon synergistic flame retardant interface layer.

[0022] When nano-montmorillonite and magnesium hydroxide are used in combination, a synergistic flame retardant effect can be produced. When magnesium hydroxide is thermally decomposed, it absorbs a large amount of heat, reducing the surface temperature of the material. At the same time, the released water vapor can dilute the concentration of oxygen and combustible gases. Nano-montmorillonite has a layered structure and can form a barrier layer during the combustion process to prevent the transfer of heat and oxygen and inhibit the escape of combustible gases. The combination of the two can significantly improve the flame retardant properties of bio-based silicone rubber, making it more in line with the strict requirements of high-speed rail seats for fire safety. At the same time, it also reduces the use of flame retardants and reduces the density of foamed silicone rubber.

[0023] Supercritical CO 2 During the foaming process, CO2 It has good diffusivity and solubility. Before foaming, supercritical CO 2 Nano-montmorillonite and magnesium hydroxide can be more evenly dispersed in the bio-based silicone rubber matrix. Evenly dispersed flame retardants can play a more effective role when the material burns, forming a continuous and dense barrier layer, and improving the stability and consistency of the flame retardant effect. Correspondingly, the addition of nano-montmorillonite and magnesium hydroxide will affect the rheological properties of bio-based silicone rubber. An appropriate amount of nano-montmorillonite can reduce the viscosity of bio-based silicone rubber and improve its fluidity, making it more stable in supercritical CO. 2 During the foaming process, silicone rubber can more easily fill the mold cavity, which is conducive to the formation of a uniform cell structure. At the same time, this improvement in rheological properties also helps supercritical CO 2 Dissolves and diffuses in the silicone rubber matrix to improve foaming efficiency and quality.

[0024] Furthermore, since nano-montmorillonite and magnesium hydroxide form a certain network structure in bio-based silicone rubber, this structure can serve as a site for bubble nucleation. 2 During the foaming process, it is easier to form a large number of uniform bubble nuclei, which reduces the difficulty of foaming, reduces the phenomenon of bubble merging and rupture, and is conducive to controlling the size and distribution of bubbles.

[0025] As an improvement, the SiH / SiVi molar ratio of the hydrogen-containing silicone oil is 1.5, the platinum catalyst is a platinum-vinylsiloxane complex, the antibacterial agent is a nano silver ion antibacterial agent with a particle size of 15-20nm, the wall material of the microencapsulated silane repair agent is polyurea formaldehyde, and the core material is octyltriethoxysilane.

[0026] Supercritical CO 2 With low surface tension, high diffusion coefficient and solubility, it can be used as a dispersion medium for nano silver ion antibacterial agent (particle size 15-20nm) to reduce particle agglomeration. 2 When the molecules penetrate into the bio-based silicone rubber matrix, they carry the nano-silver ions and are evenly distributed in the rubber network, avoiding the uneven dispersion problem of antimicrobial agents in traditional methods due to polarity differences.

[0027] Bio-based silicone rubber (castor oil derivative modified siloxane) contains polar groups (such as hydroxyl groups and ester groups), which can interact with the hydroxyl groups or surfactants on the surface of nano-silver ions through hydrogen bonds or electrostatic interactions. 2The plasticizing effect further enhances the interfacial bonding between the antimicrobial agent and the matrix, reduces the migration and loss of the antimicrobial agent, and prolongs the antimicrobial durability. Nano silver ions kill bacteria through multiple mechanisms such as destroying microbial cell membranes and inhibiting DNA replication. Combined with the environmental protection characteristics of bio-based silicone rubber, they meet the strict requirements of high-speed rail seats for antibacterial and hygiene. In addition, due to the uniform dispersion and firm interfacial bonding, a small amount of nano silver ions (0.8-1 part) can achieve long-term antibacterial effects, avoiding the negative impact of a large amount of antimicrobial agents on the mechanical properties and foaming structure of silicone rubber.

[0028] Polyurea formaldehyde, the wall material of microcapsule, has good high pressure resistance and solvent resistance. 2 The foaming stage (high pressure, low temperature conditions) remains intact to prevent the core material octyl triethoxysilane from being released prematurely. 2 As a physical foaming agent, it does not react with the microcapsule wall material, ensuring that the microcapsules are evenly distributed in the silicone rubber matrix during the foaming process.

[0029] Microcapsules (usually micrometer-sized) can serve as foaming nucleation sites, promoting supercritical CO 2 The bubbles nucleate evenly, refine the pore structure (such as reducing the pore size and increasing the pore density), and improve the air permeability and resilience of the material.

[0030] When the material is impacted by external forces or long-term use causes microcracks in the cell wall or matrix, the microcapsule wall material breaks due to stress, releasing the core material octyltriethoxysilane. Silane molecules contain ethoxy groups, which can be hydrolyzed to form silanols, which react with the silicone rubber molecular chain (-Si-O-) to repair broken molecular chains or interface defects and restore the mechanical properties and structural integrity of the material.

[0031] At the same time, both octyltriethoxysilane and bio-based silicone rubber contain silicon-oxygen bonds and have similar chemical structures. After the repair agent is released, it can diffuse quickly and integrate into the rubber network, avoiding the introduction of incompatible impurities and ensuring the repair efficiency and long-term stability of the material.

[0032] As an improvement, the invention further comprises 3-5 parts of a pore opening agent and 1-3 parts of a reinforcing agent, wherein the pore opening agent is polyethylene glycol 400 and the reinforcing agent is diatomaceous earth with a particle size of 5-10 μm.

[0033] Polyethylene glycol 400 (PEG-400) is a low molecular weight polar organic compound (molecular weight about 400, hydroxyl end group) and supercritical CO 2 It has good affinity and can be used as a "cell rupture inducing agent" during the foaming process. 2 When the bubbles expand, PEG-400 is enriched at the interface of the pore wall, reducing the interfacial tension, causing the adjacent pore walls to rupture and fuse, forming an open-pore structure (different from closed cells), significantly improving the air permeability of the material and meeting the high-speed rail seats' needs for air circulation and heat dissipation.

[0034] PEG-400 guides the formation of an open-pore network, and diatomaceous earth acts as a nucleating agent and reinforcing agent to control the pore size and strengthen the pore wall structure. The two work together to make the material have both high air permeability (opening rate ≥ 80%) and excellent resilience (compression permanent deformation ≤ 15%), meeting the dual needs of high-speed rail seats for comfortable support and air circulation.

[0035] PEG-400 reduces the melt viscosity, and diatomaceous earth provides rigid support, making the system 2 It is easier to form under high pressure (10-30MPa) and medium temperature (30-80℃) conditions during foaming, reducing the defects of bubble collapse or pore wall rupture during the foaming process and improving production efficiency.

[0036] In summary, polyethylene glycol 400 (pore opening agent) and diatomaceous earth (reinforcement agent) were reacted by supercritical CO 2 The nucleation regulation and interface synergy of foaming form an efficient system of "open-cell structure-mechanical enhancement-functional adaptation" with bio-based silicone rubber ( Figure 2 The open cell structure in the red circle in the middle and lower part): The former precisely controls the connectivity of the cells ( Figure 2 The pore interconnected structure in the red circle in the upper middle) improves air permeability and processing fluidity; the latter acts as a rigid filler and heterogeneous nucleating agent ( Figure 1 The combination of the two not only solves the pain points of "difficult to control opening" and "insufficient strength" of traditional foamed silicone rubber, but also complements the low temperature resistance and environmental protection characteristics of bio-based silicone rubber, significantly improving the comprehensive performance of high-speed rail seat filling materials and meeting the stringent requirements of lightweight, comfort and durability.

[0037] In addition, the present invention also provides a method for preparing the air-permeable and resilient foamed silicone rubber for high-speed rail seats as described in any one of the above items, comprising the following steps: Step b1, adding bio-based silicone rubber, fumed silica and nano silver ion antibacterial agent into an internal mixer, mixing for 15 min under a vacuum condition of -0.1 MPa, a temperature of 50° C. and a rotation speed of 60 rpm; Step b2, add nano-montmorillonite, magnesium hydroxide, and microcapsule repair agent in sequence, mix for 20 minutes, and the temperature is ≤40°C; Step b3, adding hydrogenated silicone oil and platinum catalyst, rotating speed 30rpm, mixing for 10min to ensure uniform dispersion; Step b4, placing the rubber mix in an autoclave, injecting supercritical CO2, pressure 15MPa, temperature 40°C, saturation time 2h; Step b5, at a rate of 5 MPa / s, release the pressure to 8 MPa to induce cell nucleation, at a rate of 0.5 MPa / s, release the pressure to normal pressure to control cell growth and form a gradient cell structure, and simultaneously increase the temperature during the pressure release process for vulcanization, keep at 70°C for 5 min, trigger the platinum catalyst, start crosslinking, keep at 120°C for 10 min, complete the main crosslinking network, and keep at 160°C for 30 min to stabilize the cell structure and solidify; Step b6, place the foaming material in a mold, hot press at 80°C and 5MPa pressure for 10 minutes to eliminate surface defects, and age in an oven at 80°C for 48 hours to eliminate internal stress and stabilize performance.

[0038] As an improvement, diatomaceous earth may be added as a reinforcing agent in step b1, and polyethylene glycol 400 may be added as a pore opening agent in step b3.

[0039] The beneficial effects of the present invention are: (1) The foamed silicone rubber prepared by the present invention has a density of 0.35-0.45g / cm³, a tensile strength of 2.2-2.5MPa, a compression set (22h) of 8%-9%, a flame retardancy of V0, LOI=35%, a smoke density of 120, an antibacterial rate of Escherichia coli of 99.5%, an antibacterial rate of Staphylococcus aureus of 99.3%, a self-repairing efficiency of 87%-90%, and a performance retention rate of ≥90% after wet heat aging (85°C / 85%RH, 1000h); (2) The present invention utilizes supercritical CO 2 As a foaming agent with bio-based silicone rubber as the main material, the polar groups of bio-based silicone rubber can be used as CO 2 The nucleation sites of bubbles, combined with supercritical CO 2 The rapid pressure release induction (5MPa / s rate nucleation) forms uniformly distributed and controllable pores (especially gradient structure), which improves the material's compressive resilience (suitable for long-term seat load) and air permeability (improves riding comfort). The gradient structure makes the foamed silicone rubber material dense on the surface and porous inside. The dense layer on the surface and the porous layer on the inside form a "rigid-flexible combination" structure. The surface provides tear resistance and surface hardness, and the porous structure on the inside supports the load through the bubble skeleton, reducing permanent deformation after long-term compression and maintaining the shape stability of the seat. (3) The present invention uses castor oil derivative-modified siloxane as bio-based silicone rubber, and introduces castor oil-derived flexible segments into its molecular chain. These flexible segments can increase the mobility of the molecular chain, so that the silicone rubber can still maintain a certain flexibility in a low temperature environment. At low temperatures, the movement of ordinary silicone rubber molecular chains is restricted, and it is easy to become hard and brittle, while the flexible segments in the bio-based silicone rubber can alleviate this restriction and reduce the glass transition temperature, thereby improving the elasticity and toughness of the material at low temperatures; (4) The bio-based silicone rubber of the present invention replaces petroleum-based silicone rubber and uses castor oil derivative-modified siloxane as the matrix, which reduces dependence on petroleum-based raw materials, introduces renewable resources, and reduces the carbon footprint of materials. The combination of the two makes the entire production process (from raw materials to foaming) conform to the green manufacturing concept and meets the high-speed rail industry's demand for "environmental protection and low carbon".

[0040] In summary, the present invention has the advantages of being green and environmentally friendly, long-lasting antibacterial, strong self-repairing, aging-resistant, and having a long service life, and is particularly suitable for the technical field of filling materials for high-speed rail seats. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is an optical microscope magnified view of the side cell structure of Preparation Example 1 of the present invention; Figure 2 This is an optical microscope magnified view of the side cell structure of Preparation Example 2 of the present invention; Figure 3 This is an optical microscope magnified view of the side cell structure of Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] For the purpose of the following detailed description, it should be understood that the present invention may adopt various alternative changes and step sequences, unless expressly specified to the contrary. In addition, except in any operating examples, or otherwise indicated, all numbers representing the amount of ingredients used in the specification and claims should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters set forth in the following specification and the attached claims are approximate values ​​that vary according to the desired performance to be obtained by the present invention. At least it is not intended to limit the application of the doctrine of equivalents to the scope of the claims, and each numerical parameter should at least be interpreted according to the number of reported significant figures and by applying ordinary rounding techniques.

[0044] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0045] When a numerical range is disclosed herein, the above range is deemed to be continuous and includes the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges included therein. For example, a specified range from "1 to 10" should be deemed to include any and all sub-ranges between a minimum of 1 and a maximum of 10. Exemplary sub-ranges of ranges 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0046] Preparation Example 1: Step b1, add 80 parts of bio-based silicone rubber, 5 parts of fumed silica, 1 part of diatomaceous earth, and 0.8 parts of nano silver ion antibacterial agent into an internal mixer, and mix for 15 minutes under a vacuum condition of -0.1 MPa, a temperature of 50°C, and a rotation speed of 60 rpm; Step b2, add 3 parts of nano-montmorillonite, 7 parts of magnesium hydroxide, and 2.5 parts of microcapsule repair agent in sequence, mix for 20 minutes, and the temperature is ≤40°C; Step b3, add 5 parts of hydrogenated silicone oil and 0.05 parts of platinum catalyst, rotate at 30 rpm, mix for 10 minutes to ensure uniform dispersion, add 3 parts of pore opening agent, and mix for 5 minutes; Step b4: Place the rubber mix in an autoclave and inject 3 parts of supercritical CO 2 , pressure 15MPa, temperature 40℃, saturation time 2h; Step b5, at a rate of 5 MPa / s, release the pressure to 8 MPa to induce cell nucleation, at a rate of 0.5 MPa / s, release the pressure to normal pressure to control cell growth and form a gradient cell structure, and simultaneously increase the temperature during the pressure release process for vulcanization, keep at 70°C for 5 min, trigger the platinum catalyst, start crosslinking, keep at 120°C for 10 min, complete the main crosslinking network, and keep at 160°C for 30 min to stabilize the cell structure and solidify; Step b6, place the foaming material in a mold, hot press at 80°C and 5MPa pressure for 10 minutes to eliminate surface defects, and age in an oven at 80°C for 48 hours to eliminate internal stress and stabilize performance.

[0047] Preparation Example 2: Step b1, add 100 parts of bio-based silicone rubber, 8 parts of fumed silica, 3 parts of diatomaceous earth, and 1 part of nano silver ion antibacterial agent into an internal mixer, and mix for 15 minutes under a vacuum condition of -0.1 MPa, a temperature of 50° C., and a rotation speed of 60 rpm; Step b2, add 5 parts of nano-montmorillonite, 10 parts of magnesium hydroxide, and 3 parts of microcapsule repair agent in sequence, mix for 20 minutes, and the temperature is ≤40°C; Step b3, add 8 parts of hydrogen-containing silicone oil and 0.1 parts of platinum catalyst, rotate at 30 rpm, mix for 10 minutes to ensure uniform dispersion, add 5 parts of pore opening agent, and mix for 5 minutes; Step b4: Place the rubber mix in an autoclave and inject 5 parts of supercritical CO 2 , pressure 15MPa, temperature 40℃, saturation time 2h; Step b5, at a rate of 5 MPa / s, release the pressure to 8 MPa to induce cell nucleation, at a rate of 0.5 MPa / s, release the pressure to normal pressure to control cell growth and form a gradient cell structure, and simultaneously increase the temperature during the pressure release process for vulcanization, keep at 70°C for 5 min, trigger the platinum catalyst, start crosslinking, keep at 120°C for 10 min, complete the main crosslinking network, and keep at 160°C for 30 min to stabilize the cell structure and solidify; Step b6, place the foaming material in a mold, hot press at 80°C and 5MPa pressure for 10 minutes to eliminate surface defects, and age in an oven at 80°C for 48 hours to eliminate internal stress and stabilize performance.

[0048] Preparation Example 3: Step b1, add 90 parts of bio-based silicone rubber, 6 parts of fumed silica, 2 parts of diatomaceous earth, and 0.9 parts of nano silver ion antibacterial agent into an internal mixer, and mix for 15 minutes under a vacuum condition of -0.1 MPa, a temperature of 50°C, and a rotation speed of 60 rpm; Step b2, add 4 parts of nano-montmorillonite, 8 parts of magnesium hydroxide, and 2.7 parts of microcapsule repair agent in sequence, mix for 20 minutes, and the temperature is ≤40°C; Step b3, add 6 parts of hydrogenated silicone oil and 0.08 parts of platinum catalyst, rotate at 30 rpm, mix for 10 minutes to ensure uniform dispersion, add 4 parts of pore opening agent, and mix for 5 minutes; Step b4: Place the rubber mix in an autoclave and inject 4 parts of supercritical CO 2 , pressure 15MPa, temperature 40℃, saturation time 2h; Step b5, at a rate of 5 MPa / s, release the pressure to 8 MPa to induce cell nucleation, at a rate of 0.5 MPa / s, release the pressure to normal pressure to control cell growth and form a gradient cell structure, and simultaneously increase the temperature during the pressure release process for vulcanization, keep at 70°C for 5 min, trigger the platinum catalyst, start crosslinking, keep at 120°C for 10 min, complete the main crosslinking network, and keep at 160°C for 30 min to stabilize the cell structure and solidify; Step b6, place the foaming material in a mold, hot press at 80°C and 5MPa pressure for 10 minutes to eliminate surface defects, and age in an oven at 80°C for 48 hours to eliminate internal stress and stabilize performance.

[0049] Preparation Example 4: Step b1, add 100 parts of bio-based silicone rubber, 6 parts of fumed silica, 2 parts of diatomaceous earth, and 0.9 parts of nano silver ion antibacterial agent into an internal mixer, and mix for 15 minutes under a vacuum condition of -0.1 MPa, a temperature of 50° C., and a rotation speed of 60 rpm; Step b2, add 4 parts of nano-montmorillonite, 8 parts of magnesium hydroxide, and 2.7 parts of microcapsule repair agent in sequence, mix for 20 minutes, and the temperature is ≤40°C; Step b3, add 6 parts of hydrogenated silicone oil and 0.08 parts of platinum catalyst, rotate at 30 rpm, mix for 10 minutes to ensure uniform dispersion, add 4 parts of pore opening agent, and mix for 5 minutes; Step b4: Place the rubber mix in an autoclave and inject 5 parts of supercritical CO 2 , pressure 15MPa, temperature 40℃, saturation time 2h; Step b5, at a rate of 5 MPa / s, release the pressure to 8 MPa to induce cell nucleation, at a rate of 0.5 MPa / s, release the pressure to normal pressure to control cell growth and form a gradient cell structure, and simultaneously increase the temperature during the pressure release process for vulcanization, keep at 70°C for 5 min, trigger the platinum catalyst, start crosslinking, keep at 120°C for 10 min, complete the main crosslinking network, and keep at 160°C for 30 min to stabilize the cell structure and solidify; Step b6, place the foaming material in a mold, hot press at 80°C and 5MPa pressure for 10 minutes to eliminate surface defects, and age in an oven at 80°C for 48 hours to eliminate internal stress and stabilize performance.

[0050] Comparative Example 1: Same as Preparation Example 1, except that no flame retardant is added.

[0051] Comparative Example 2: The same as Preparation Example 2, except that AC foaming agent is compounded with benzenesulfonyl hydrazide (BSH) for chemical foaming, the ratio of BSH:AC=2:3, and 2 parts of foaming agent zinc oxide are added.

[0052] Comparative Example 3: The same as Preparation Example 3, except that no pore opening agent and reinforcing agent are used.

[0053] Comparative Example 4: Same as Preparation Example 4, except that no antibacterial agent is used.

[0054] Comparative Example 5: Same as Preparation Example 4, except that no repairing agent is used.

[0055] Test example: For Preparation Example 1 to Preparation Example 4 and Comparative Example 1 to Comparative Example 5, the density was tested according to GB / T6343-2009, the tensile strength was tested according to GB / T528-2009, the compression permanent deformation (22h) was tested according to GB / T7759-2015, the flame retardancy was tested according to UL94, the limiting oxygen index was tested according to GB / T2406.2, the smoke density was tested according to EN45545-2, the antibacterial rate was tested according to GB / T31402-2015, the wet heat aging performance was tested according to GB / T2423.3-2016, the self-repair efficiency was tested according to ISO22156:2017, the open porosity was tested according to the density method, and the air permeability was tested according to GB / T5453.

[0056] The test results are shown in the table below: By comparing Preparation Examples 1 to Preparation Examples 4, and by comparing Preparation Examples 1 to Preparation Examples 4 with Comparative Examples 1 to Comparative Examples 5, it can be seen that: 1. The influence of flame retardant addition on performance Preparation Examples 1 to 4 all achieved V0 flame retardancy, with LOI between 32% and 35%, indicating that a high-efficiency flame retardant was added. Comparative Example 1 had a flame retardancy of HB level, with LOI of only 20%, significantly lower than that of the preparation examples, and a smoke density (170) higher than that of the preparation examples (120-150). It can be seen that the addition of flame retardants can greatly improve the flame retardancy level (V0 level) and LOI of the material, while reducing the smoke density during combustion.

[0057] The smoke density of the preparation example is 120-150, and the smoke density of comparative examples 1, 2 and 3 is 155-170 (comparative example 1 has the highest smoke density without adding flame retardant). It can be seen that the flame retardant not only improves the flame retardancy, but also suppresses the amount of smoke during combustion and improves the safety of the material.

[0058] 2. The role of antimicrobial agents The antibacterial rates of Preparation Examples 1 to 4 and Comparative Examples 1 to 3 and Comparative Example 5 are all ≥99.3%, but the antibacterial rate of Comparative Example 4 is <10%, which is much lower than that of the other groups. It can be seen that no antibacterial agent was added to Comparative Example 4, resulting in the loss of antibacterial properties, indicating that the introduction of antibacterial agents is the key to the material having a high antibacterial rate (>99%).

[0059] 3. Comparison of wet heat aging performance The retention rates of Preparation Examples 1 to 4 were 90%-93%. Among the comparative examples, only Comparative Example 3 reached 95%, and the remaining comparative examples reached 83%-86%. The high retention rate of Comparative Example 3 was due to its closed-cell structure (such as Figure 3As shown), the open porosity is 0, moisture cannot enter the interior of the material, the aging rate is slow, and the wet heat aging performance of the preparation example is better than that of most comparative examples as a whole. The open and closed structure of the pores and the uniformity of the pores are crucial to the resistance to wet heat aging.

[0060] 4. Physical properties and structural parameters The density of the preparation example is 0.35-0.45g / cm³, the open porosity is 75%-85%, and the air permeability is 80-150mm / s (the air permeability of the preparation example 2 is the highest because the open porosity is 85%). The open porosity of the comparative example 3 is 0 (closed-cell structure), the air permeability is only 10mm / s, and the density is 0.43g / cm³, indicating that the closed-cell structure significantly reduces the air permeability. The open porosity directly affects the air permeability. The preparation examples achieve different air permeability by controlling the open porosity, and the closed-cell structure (such as comparative example 3) is suitable for low air permeability scenarios.

[0061] The tensile strength of the preparation example is 2.2-2.5MPa, and the tensile strength of the comparative examples 2 and 3 is higher (2.7-2.8MPa), which is related to the pore structure. The smaller the pore diameter and the lower the open porosity, the higher the corresponding tensile strength. In terms of compression permanent deformation, the preparation examples are all ≤9%, and the comparative example 2 is 10%, which is slightly worse, indicating that the comparative example 2 has poor compression permanent deformation performance due to uneven pore distribution. At the same time, the comparative example 3 is 6%, indicating that the closed-cell structure has strong compression permanent deformation performance.

[0062] 5. Differences in self-repair functions The self-repairing efficiencies of Preparation Examples 1 to 4 and Comparative Examples 1 and 4 are 87%-90%, but the self-repairing efficiency of Comparative Example 5 is 0. No self-repairing component is added to Comparative Example 5, resulting in the lack of this function, indicating that the self-repairing performance depends on a specific formula design.

[0063] In summary, the preparation examples are superior to most comparative examples in terms of safety and functionality by adding flame retardants (to improve flame retardancy and reduce smoke density), antibacterial agents (to achieve high antibacterial rates) and self-repairing components (to impart self-repairing functions). Comparative Example 1 did not add flame retardants, resulting in poor flame retardancy and smoke density performance; Comparative Example 4 did not add antibacterial agents, and the antibacterial rate was extremely low; Comparative Example 5 had no self-repairing function. The open porosity affects the air permeability (the higher the open porosity, the higher the air permeability), and the closed-cell structure (such as Comparative Example 3) sacrifices air permeability but improves the retention rate of wet heat aging. Tensile strength and compression permanent deformation are affected by the pore structure, such as the high strength of Comparative Example 2 and Comparative Example 3. The preparation examples achieved a good balance between flame retardancy, antibacterial properties, self-repair and wet heat aging, while the comparative examples focused on a single performance (such as the high wet heat aging retention rate of Comparative Example 3) or lacked key functions (such as Comparative Example 1, Comparative Example 4, Comparative Example 5).

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A breathable and resilient foamed silicone rubber for high-speed rail seats, which is used as a filling material for high-speed rail seats, characterized in that: include: 80-100 parts of bio-based silicone rubber; 5-8 parts of hydrogen silicone oil; Flame retardant 10-15 parts; 5-8 parts of reinforcing filler; 3-5 parts of foaming agent; Catalyst 0.05-0.1 part; Antibacterial agent 0.8-1 part; 2.5-3 parts of repair agent; Among them, the bio-based silicone rubber is castor oil derivative modified siloxane, the flame retardant is a mixture of nano-montmorillonite and magnesium hydroxide, the reinforcing filler is fumed silica, the foaming agent is supercritical CO2 with a purity of ≥99.9%, the catalyst is a platinum catalyst, the antibacterial agent is a nano-silver ion antibacterial agent, and the repair agent is a microencapsulated silane repair agent.

2. The breathable and resilient foamed silicone rubber for high-speed rail seats according to claim 1, characterized in that: The castor oil derivative modified siloxane is a hydrosilylation modified castor oil siloxane, which is prepared by the hydrosilylation reaction of allyl ricinoleate and methyl hydrogen siloxane, has a vinyl content of 0.25%-0.45%, and a biomass base ratio of 40-45%.

3. The breathable and resilient foamed silicone rubber for high-speed rail seats according to claim 2, characterized in that: The preparation steps of the hydrosilylation-modified castor oil siloxane include: Step a1, by mass, 100 parts of allyl ricinoleate and 60-7 parts of methyl hydrogen siloxane are added to a reaction kettle and mixed and stirred, and then 450-500 parts of toluene are added as a solvent to ensure that the reaction system has good fluidity; Step a2, introducing nitrogen into the reactor for protection, the nitrogen flow rate is 100-200 mL / min, and the nitrogen flow is continuously introduced for 15-30 min, the stirring speed is 200-300 r / min, the reactor is heated to 60-80°C, and the temperature is kept and stirred for 30-60 min; Step a3, slowly add Karstedt catalyst in an amount of 0.01%-0.05% of the total mass of the reactants, increase the reaction temperature to 80-120°C, and control the reaction time to 2-6h; Step a4: After the reaction is completed, the reaction system is cooled to room temperature, and the toluene solvent is removed by vacuum distillation at a distillation temperature of 80-120° C. and a vacuum degree of 10-100 Pa. The hydrosilylation-modified castor oil siloxane is obtained after filtration.

4. The breathable and resilient foamed silicone rubber for high-speed rail seats according to claim 1, characterized in that: In the flame retardant, the nano-montmorillonite is modified by KH-550 and has a content of 3-5 parts, and the magnesium hydroxide is surface-modified by DOPO-VTS and has a content of 7-10 parts.

5. The breathable and resilient foamed silicone rubber for high-speed rail seats according to claim 4, characterized in that: The nano-montmorillonite modification treatment method is to ultrasonically disperse the nano-montmorillonite and KH-550 in an ethanol solution at a mass ratio of 100:3 for 30 minutes, with an ultrasonic power of 300W, and vacuum dry at 60°C for 12 hours to obtain hydrophobic nano-montmorillonite.

6. The breathable and resilient foamed silicone rubber for high-speed rail seats according to claim 4, characterized in that: The magnesium hydroxide modification treatment method is to stir magnesium hydroxide and DOPO-VTS at a mass ratio of 100:2 at 80° C. for 40 minutes to form a phosphorus-silicon synergistic flame retardant interface layer.

7. The breathable and resilient foamed silicone rubber for high-speed rail seats according to claim 1, characterized in that: The SiH / SiVi molar ratio of the hydrogen-containing silicone oil is 1.5, the platinum catalyst is a platinum-vinylsiloxane complex, the antibacterial agent is a nano silver ion antibacterial agent with a particle size of 15-20 nm, the wall material of the microencapsulated silane repair agent is polyurea formaldehyde, and the core material is octyltriethoxysilane.

8. The breathable and resilient foamed silicone rubber for high-speed rail seats according to claim 1, characterized in that: The invention also comprises 3-5 parts of a pore opening agent and 1-3 parts of a reinforcing agent. The pore opening agent is polyethylene glycol 400 and the reinforcing agent is diatomaceous earth with a particle size of 5-10 μm.

9. A method for preparing the breathable and resilient foamed silicone rubber for high-speed rail seats according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step b1, adding bio-based silicone rubber, fumed silica and nano silver ion antibacterial agent into an internal mixer, mixing for 15 min under a vacuum condition of -0.1 MPa, a temperature of 50° C. and a rotation speed of 60 rpm; Step b2, add nano-montmorillonite, magnesium hydroxide, and microcapsule repair agent in sequence, mix for 20 minutes, and the temperature is ≤40°C; Step b3, adding hydrogen-containing silicone oil and platinum catalyst, rotating speed 30rpm, mixing for 10min to ensure uniform dispersion; Step b4, placing the rubber mix in an autoclave, injecting supercritical CO2, pressure 15MPa, temperature 40°C, saturation time 2h; Step b5, at a rate of 5 MPa / s, release the pressure to 8 MPa to induce cell nucleation, at a rate of 0.5 MPa / s, release the pressure to normal pressure to control cell growth and form a gradient cell structure, and simultaneously increase the temperature during the pressure release process for vulcanization, keep at 70°C for 5 min, trigger the platinum catalyst, start crosslinking, keep at 120°C for 10 min, complete the main crosslinking network, and keep at 160°C for 30 min to stabilize the cell structure and solidify; Step b6, place the foaming material in a mold, hot press at 80°C and 5MPa pressure for 10 minutes to eliminate surface defects, and age in an oven at 80°C for 48 hours to eliminate internal stress and stabilize performance.

10. The preparation method according to claim 9, characterized in that: Diatomaceous earth may be added as a reinforcing agent in step b1, and polyethylene glycol 400 may be added as a pore opening agent in step b3.

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