Latex modified SiO2 dispersed foamed silicone rubber material and preparation method thereof

Abstract

The invention relates to the technical field of polymer compositions, and particularly discloses a latex modified SiO2 dispersive foamed silicone rubber material and a preparation method thereof, the latex modified SiO2 dispersive foamed silicone rubber material comprises methyl vinyl silicone rubber, latex modified SiO2, a vulcanizing agent and a foaming agent, and the latex modified SiO2 is obtained by coating and modifying SiO2 particles with liquid latex. The preparation method comprises the following steps: S1, diluting liquid latex with a diluent, spraying the diluted liquid latex on the surfaces of SiO2 particles, and heating to volatilize the diluent to obtain modified SiO2; and S2, mixing methyl vinyl silicone rubber with the modified SiO2, then mixing with a vulcanizing agent and a foaming agent, and carrying out vulcanization foaming, which comprises the steps of pre-vulcanization and main vulcanization foaming. The dispersity of SiO2 in silicone rubber is improved through latex coating, foaming and vulcanization processes are regulated and controlled by adopting a double-vulcanization system process, and the filler dispersion effect and the mechanical property of the material are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer composition, in particular to a latex modified SiO2 dispersion foamed silicone rubber material and a preparation method thereof. BACKGROUND

[0002] Foamed silicone rubber material is a combination of the characteristics of silicone rubber and foam material. By adding fillers for reinforcement, it can be widely used in many fields such as electronic products, construction, automobiles, aerospace, new energy, medicine and packaging. Although the performance of silicone rubber can be improved by adding fillers, the uneven dispersion of high filler content also easily leads to a significant increase in material brittleness. Therefore, improving the uneven dispersion of fillers has always been a research topic for researchers.

[0003] CN120349559A discloses a silane coupling agent modified SiO2 to improve the dispersion in foamed silicone rubber material and its preparation method. The hydroxyl groups on the surface of SiO2 are removed by silane coupling agent to improve the dispersion of SiO2 in silicone rubber, and the mechanical properties of foamed silicone rubber material are enhanced. However, the process of silane coupling agent modified SiO2 is complicated, while the process of latex modified SiO2 is simplified. Moreover, latex and methyl vinyl silicone rubber have excellent compatibility. In the realization of uniform dispersion of SiO2, the latex layer can diffuse and dissolve with the matrix through molecular chains to form a continuous network of "SiO2-latex-matrix". There is no clear chemical bond boundary at the interface, and the stress transfer is more uniform, avoiding the interface stress concentration caused by "chemical bond rigid connection" in the modification of silane coupling agent.

[0004] Therefore, it is of great research significance and application value to develop a foamed silicone rubber material with shorter cycle and better compatibility, so that the modified filler of the material is uniformly dispersed and has excellent mechanical properties, and further to prepare a foamed silicone rubber material with excellent cell structure. SUMMARY

[0005] In view of the technical defects in the background art, the present application provides a latex modified SiO2 dispersion foamed silicone rubber material and a preparation method thereof, which solves the above technical problems and meets the actual needs. The specific technical scheme is as follows: A latex modified SiO2 dispersion foamed silicone rubber material, in terms of weight percentage, comprises the following components: methyl vinyl silicone rubber 94-100 parts, SiO2 microparticles 35-45 parts, liquid latex 5.2-6.8 parts, vulcanizing agent 0.1-2 parts, and foaming agent 14 parts. The SiO2 microparticles are modified by coating with the liquid latex, and the average particle size of the SiO2 microparticles is 1 μm. The average molecular weight of the liquid latex is 40-400 thousand g / mol; the liquid latex is selected from any one of silicone rubber latex, natural rubber latex, styrene-butadiene rubber latex or butadiene-acrylonitrile rubber latex.

[0006] As a further technical solution of the present application, the average molecular weight of the silicone rubber latex is 40-100 thousand g / mol, the average molecular weight of the natural rubber latex is 300-400 thousand g / mol, the average molecular weight of the styrene-butadiene rubber latex is 100-300 thousand g / mol, and the average molecular weight of the butadiene-acrylonitrile rubber latex is 100-200 thousand g / mol.

[0007] As a further technical solution of the present application, the average molecular weight of the methyl vinyl silicone rubber is 450-850 thousand g / mol, and the average vinyl content is 0.13-0.18%.

[0008] As a further technical solution of the present application, the vulcanizing agent is 2,5-dimethyl-2,5-bis-(tert-butyl peroxy) hexane and dibenzoyl peroxide; and the foaming agent is selected from any one of sodium bicarbonate and azodicarbonamide.

[0009] A preparation method of a foamed silicone rubber material, comprising the following steps: S1, first diluting and dissolving the liquid latex at 60℃ with a diluent to obtain a diluted latex, then spraying the diluted latex on the surface of SiO2 microparticles through a spraying device, and then heating at a corresponding volatilization temperature of the diluent and volatilizing the diluent to obtain modified SiO2; S2, mixing the methyl vinyl silicone rubber and the modified SiO2, and then uniformly mixing the mixed rubber with 2,5-dimethyl-2,5-bis-(tert-butyl peroxy) hexane, dibenzoyl peroxide and a foaming agent to vulcanize and foam to obtain the foamed silicone rubber material.

[0010] As a further technical solution of the present application, in step S1, when preparing the latex modified SiO2, the weight ratio of the SiO2 microparticles, the liquid latex and the diluent is 40:6:12.

[0011] As a further technical solution of the present application, in step S1, the diluent and the volatilization temperature of the diluent are as follows: (1) the diluent is xylene, and the volatilization temperature is 130℃; (2) the diluent is cyclohexane, and the volatilization temperature is 90℃; (3) the diluent is D-limonene, and the volatilization temperature is 150℃; (4) the diluent is L-ethyl lactate, and the volatilization temperature is 160℃.

[0012] As a further technical scheme of the present application, in step S2, the methyl vinyl silicone rubber and modified SiO2 are mixed at 150 DEG C for 10 min, and the mixed rubber is mixed with vulcanizing agent and foaming agent on an open mill through cooling circulating water at normal temperature.

[0013] As a further technical scheme of the present application, in step S2, the mixed rubber is first pre-vulcanized by dibenzoyl peroxide at 110 DEG C for 10 min and 10 MPa, and then vulcanized and foamed by 2,5-dimethyl-2,5-bis-(tert-butylperoxide) hexane and foaming agent at 170 DEG C for 10 min and 4 MPa.

[0014] As a further technical scheme of the present application, in step S1, the SiO2 particles are pretreated before being sprayed with the diluted latex, and the pretreatment method comprises: (1) mixing SiO2 particles with NaOH solution with a concentration of 0.2-0.4 mol / L at a mass ratio of 1:100-150, refluxing at 70-90 DEG C for 1-2 h, washing and drying to obtain activated SiO2 particles; (2) configuring silane coupling agent and 95% ethanol at a mass ratio of (1-5):(95-100) into a silane coupling agent solution, mixing the activated SiO2 particles with the silane coupling agent solution at a mass ratio of 1:(20-50), stirring and reacting for 5-6 h, washing and drying to obtain pretreated SiO2 particles; The silane coupling agent is selected from any one of gamma-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane and vinyltrimethoxysilane.

[0015] The present application has the beneficial effect that methyl vinyl silicone rubber is used as the main raw material, latex with better compatibility is used to coat the filler SiO2, a filler network with uniform distribution of SiO2 is constructed, and a double vulcanization system process is used, BPO is used at 110 DEG C to pre-vulcanize, so that the silicone rubber has a certain crosslinked network to lock the cell expansion, and DBPMH and the foaming agent are simultaneously decomposed at 170 DEG C to realize precise control of the foaming reaction and vulcanization process. The present application improves the dispersion of SiO2 by using latex, and the latex and the silicone rubber matrix have good compatibility, and under the control of the double vulcanization system process, the dispersion effect of the filler and the mechanical properties of the foamed silicone rubber material are improved. DETAILED DESCRIPTION

[0016] The embodiments of the present application are described below in conjunction with relevant examples, and the embodiments of the present application are not limited to the following examples, and the present application relates to relevant necessary knowledge in the technical field, which should be regarded as the known technology in the technical field and can be known and mastered by the person skilled in the art, and the experimental methods not specified in the following example embodiments are generally in accordance with the conventional conditions in the field or in accordance with the recommended conditions of the manufacturer; the raw materials, reagents and the like used, if not specifically stated, are all raw materials and reagents that can be obtained through commercial channels in the conventional market. Any non-essential change and replacement made by the person skilled in the art on the basis of the present application shall fall within the scope of the present application.

[0017] A foamed silicone rubber material for modifying the dispersion of SiO2 in latex, comprising the following components in parts by weight: methyl vinyl silicone rubber 94-100 parts, SiO2 microparticles 35-45 parts, liquid latex 5.2-6.8 parts, vulcanizing agent 0.1-2 parts, foaming agent 14 parts; The SiO2 microparticles are modified by coating with the liquid latex, and the average particle size of the SiO2 microparticles is 1 μm. The average molecular weight of the liquid latex is 40-400 thousand g / mol, and the liquid latex is selected from any one of silicone rubber latex, natural latex, styrene-butadiene latex or butadiene-acrylonitrile latex.

[0018] The present application effectively improves the dispersion of SiO2 in the silicone rubber matrix through the synergistic effect between the components. The SiO2 microparticles are coated with liquid latex using methyl vinyl silicone rubber as the matrix, and the latex has good compatibility with the silicone rubber matrix, which can avoid the agglomeration of SiO2 and build a uniformly distributed filler network. At the same time, the activity of the SiO2 microparticles is improved after pretreatment, which further enhances the coating effect of the latex and the interfacial bonding force with the matrix, ensuring the synergistic stability of the filler network and the matrix structure.

[0019] The synergistic cooperation of the dual vulcanizing agent and the foaming agent realizes the regulation of the vulcanization and foaming processes. The dibenzoyl peroxide pre-vulcanizes to form a preliminary crosslinking network at a low temperature stage, which can lock the cell expansion and avoid cell rupture. The 2,5-dimethyl-2,5-bis-(tert-butyl peroxy) hexane acts synchronously with the foaming agent at a high temperature stage, and cooperates with the mixing and vulcanization foaming process, finally obtaining a foamed silicone rubber material with uniform and dense cell structure, which effectively improves the mechanical properties of the material.

[0020] As one of the preferred embodiments of the present application, the average molecular weight of the silicone rubber latex is 40-100 thousand g / mol, the average molecular weight of the natural latex is 300-400 thousand g / mol, the average molecular weight of the styrene-butadiene latex is 100-300 thousand g / mol, and the average molecular weight of the butadiene-acrylonitrile latex is 100-200 thousand g / mol.

[0021] The four liquid latices selected by the present application: silicone rubber latex, natural rubber latex, styrene-butadiene rubber latex or butadiene-acrylonitrile rubber latex, contain carbon-carbon double bonds in the backbone structure or side chains, which can cross-link with the vinyl groups in the methyl vinyl silicone rubber matrix, effectively improving the compatibility of the latex and the methyl vinyl silicone rubber matrix, and enhancing the interfacial bonding force between the modified SiO2 and the methyl vinyl silicone rubber matrix, avoiding the agglomeration of fillers in the matrix.

[0022] The four liquid latices described above all have a large average molecular weight range, among which the silicone rubber latex is 40-100 kg / mol, the butadiene-acrylonitrile rubber latex is 100-200 kg / mol, the styrene-butadiene rubber latex is 100-300 kg / mol, and the natural rubber latex is 300-400 kg / mol. The large average molecular weight makes the liquid latex have suitable viscosity and film-forming property, which is beneficial to the formation of a continuous and stable coating layer on the surface of SiO2 particles, ensuring the uniformity and integrity of the coating modification.

[0023] It should be noted that the four liquid latices selected by the present application are solvent-based glue, with a concentration of 10-30%, which are formed by dissolving silicone rubber, natural rubber, styrene-butadiene rubber and butadiene-acrylonitrile rubber in organic solvents. The specific purchase can be made according to the needs, because the diluents used in the preparation process (xylene, cyclohexane, etc.) are all water-insoluble organic solvents. If water-based glue is selected, it will cause demulsification due to the incompatibility of oil and water, resulting in coating failure.

[0024] As one of the preferred embodiments of the present application, the average molecular weight of the methyl vinyl silicone rubber is 450-850 kg / mol, and the average vinyl content is 0.13-0.18%.

[0025] In the present application, the methyl vinyl silicone rubber has a large average molecular weight of 450-850 kg / mol, which can effectively improve the cohesive energy and mechanical basis of the matrix itself and ensure the formation of a continuous and stable matrix structure during the mixing process, providing support for the subsequent cross-linking reaction and bubble morphology maintenance. The average vinyl content of 0.13-0.18% of the methyl vinyl silicone rubber provides sufficient cross-linking reaction sites for the cross-linking reaction, which can be cross-linked with the carbon-carbon double bonds in the liquid latex under the initiation of the vulcanizing agent, forming a uniform and dense cross-linking network, and finally improving the tensile strength, elongation at break and compression strain strength of the foamed silicone rubber.

[0026] As one of the preferred embodiments of the present application, the vulcanizing agent is 2,5-dimethyl-2,5-bis-(tert-butyl peroxy) hexane and dibenzoyl peroxide; the foaming agent is selected from any one of sodium bicarbonate and azodicarbonamide.

[0027] The application adopts two vulcanizing agents to cooperatively initiate crosslinking, wherein dibenzoyl peroxide (BPO) acts first at 110 DEG C to build an initial crosslinking network through pre-vulcanization, which can effectively lock the cell expansion and avoid cell rupture or combination during foaming process, and 2,5-dimethyl-2,5-bis-(tert-butyl peroxy) hexane (DBPMH) is decomposed synchronously with the selected foaming agent (sodium bicarbonate or azodicarbonamide) at 170 DEG C; DBPMH completes subsequent vulcanization to strengthen the crosslinking network, and the foaming agent releases gas to form cells, so that the vulcanization and foaming processes are cooperatively adapted by the two vulcanizing agents and the foaming agent, and the stability of the mechanical properties and foaming structure of the material is ensured.

[0028] A preparation method of a foamed silicone rubber material, comprising the following steps: S1, first dilute and dissolve the liquid latex at 60 DEG C with a diluent to obtain a diluted latex, then spray the diluted latex on the surface of SiO2 particles through a spraying device, and then heat at a corresponding volatilization temperature of the diluent and volatilize the diluent to obtain modified SiO2; S2, mix the methyl vinyl silicone rubber and the modified SiO2, then uniformly mix the mixed rubber with 2,5-dimethyl-2,5-bis-(tert-butyl peroxy) hexane, dibenzoyl peroxide and a foaming agent, and then vulcanize and foam to obtain the foamed silicone rubber material.

[0029] In the preparation process, in the SiO2 pretreatment link, the two-step method of alkali activation and silane coupling agent modification is adopted to effectively improve the activity and interface bonding capacity of SiO2; in the latex coating stage, the dilution and spraying coating of the diluent are combined with clear volatilization temperature parameters to ensure uniform and dense coating layer and avoid the agglomeration problem easily occurring in the traditional coating process.

[0030] In the mixing process, the targeted mixing at 150 DEG C for 10 min can ensure that the methyl vinyl silicone rubber and the modified SiO2 are fully compatible, and the subsequent cold mixing with the help of cooling circulating water can avoid the premature decomposition of the vulcanizing agent and the foaming agent, and improve the uniformity of the material mixture. In the two-stage vulcanization and foaming stage, the temperature gradient of 110 DEG C pre-vulcanization and 170 DEG C vulcanization and foaming matches the decomposition characteristics of the two vulcanizing agents and the gas production law of the foaming agent, and realizes the synchronous matching of the vulcanization and foaming processes, which not only ensures the uniform and stable cell structure, but also strengthens the crosslinking network.

[0031] As one of the preferred embodiments of the application, in step S1, when preparing the latex modified SiO2, the weight ratio of the SiO2 particles, the liquid latex and the diluent is 40:6:12.

[0032] In the foamed silicone rubber material of the present application, SiO2 microparticles serve as core fillers, and the use amount of 40 parts can meet the demand for mechanical enhancement of the material. 6 parts of liquid latex are just suitable for surface coating of 1 μm particle size SiO2, and neither incomplete coating caused by insufficient latex nor latex agglomeration caused by excessive amount occurs. 12 parts of diluent are used to form a 2:1 ratio with the liquid latex, so as to dilute the latex to a suitable viscosity, ensure uniform coverage of the SiO2 surface during spraying, and form a dense coating layer through subsequent volatilization process. The uniformly coated modified SiO2 can be fully compatible with the matrix, so that the crosslinked network formed by pre-vulcanization at 110℃ is more uniform, and then the modified SiO2 cooperates with DBPMH and foaming agent at 170℃, so as to ensure stable pore structure and improved mechanical properties.

[0033] As one of the preferred embodiments of the present application, in step S1, the diluent and the volatilization temperature of the diluent are as follows: (1) the diluent is xylene, and the volatilization temperature is 130℃; (2) the diluent is cyclohexane, and the volatilization temperature is 90℃; (3) the diluent is D-limonene, and the volatilization temperature is 150℃; (4) the diluent is L-ethyl lactate, and the volatilization temperature is 160℃.

[0034] In the four kinds of diluents selected in the present application, the volatilization temperature of each diluent is in its reasonable boiling point range, which can ensure rapid and complete volatilization of the diluent, and also can not damage the stability of the liquid latex due to too high temperature, so as to avoid problems such as cracking and falling off of the coating layer. Cyclohexane has a low boiling point and corresponds to a mild volatilization at 90℃, which is suitable for latex systems sensitive to temperature; the volatilization temperatures of xylene, D-limonene and L-ethyl lactate increase in turn, which can adapt to the coating scenarios of latexes with different molecular weights, so as to ensure that the latex can form a uniform and dense coating layer on the surface of SiO2 microparticles while the diluent is completely volatilized.

[0035] As one of the preferred embodiments of the present application, in step S2, the methyl vinyl silicone rubber and the modified SiO2 are mixed at 150℃ for 10 min, and the mixed rubber is opened and rolled with the vulcanizing agent and the foaming agent on an open mill through cooling circulating water.

[0036] Mixing at 150℃ for 10 min can ensure that the trace amount of diluent remaining on the surface of the modified SiO2 is completely volatilized, so as to avoid air bubble defects caused by residual diluent in the subsequent process. On the other hand, the mild temperature and time can ensure that the latex coating layer on the surface of the modified SiO2 is not damaged. The mixed rubber, the vulcanizing agent and the foaming agent are opened and rolled at room temperature with cooling circulating water, which can accurately control the temperature, prevent the vulcanizing agent from decomposing too early, and ensure the uniformity of the material mixing.

[0037] As one of the preferred embodiments of the present application, in step S2, the rubber compound is first pre-vulcanized by dibenzoyl peroxide at 110℃, 10min and 10MPa, and then vulcanized and foamed by 2,5-dimethyl-2,5-bis-(tert-butylperoxy) hexane and a foaming agent at 170℃, 10min and 4MPa.

[0038] The pre-vulcanization is carried out at 110℃, matching the decomposition characteristics of dibenzoyl peroxide, so that the vulcanizing agent can decompose smoothly to generate active species, the 10min time length ensures that the preliminary crosslinking network is fully formed, and the 10MPa pressure can promote the crosslinking structure to be dense, avoiding the rupture or combination of the cells. In the secondary vulcanization stage, the decomposition of 2,5-dimethyl-2,5-bis-(tert-butylperoxy) hexane at 170℃ can trigger the efficient gas production of the foaming agent, and the pressure of 4MPa is lower than that in the pre-vulcanization stage, which can provide sufficient space for the formation of cells and avoid excessive expansion of the cells caused by too low pressure, so that the foamed silicone rubber material with uniform cells and stable mechanical properties is finally obtained.

[0039] As one of the preferred embodiments of the present application, in step S1, the SiO2 particles are pretreated before being sprayed with the diluted latex, and the pretreatment method comprises: (1) mixing the SiO2 particles with a NaOH solution with a concentration of 0.2-0.4mol / L at a mass ratio of 1:100-150, refluxing at 70-90℃ for 1-2h, washing and drying to obtain activated SiO2 particles; (2) configuring a silane coupling agent solution by mixing a silane coupling agent and 95% ethanol at a mass ratio of (1-5):(95-100), mixing the activated SiO2 particles with the silane coupling agent solution at a mass ratio of 1:(20-50), stirring and reacting for 5-6h, washing and drying to obtain pretreated SiO2 particles; The silane coupling agent is selected from any one of γ-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane and vinyltrimethoxysilane.

[0040] In step (1), the surface of the SiO2 particles is activated by alkali treatment, and the concentration of the 0.2-0.4mol / L NaOH solution, the solid-liquid ratio of 1:100-150 and the refluxing conditions of 70-90℃ for 1-2h can gently etch the surface of SiO2 and increase the number of hydroxyl groups, providing sufficient active sites for the subsequent grafting reaction of the silane coupling agent. In step (2), the selected silane coupling agents all contain carbon-carbon double bonds, and the solution configured by mixing the silane coupling agent with 95% ethanol at a specific ratio can ensure uniform dispersion of the coupling agent. The solid-liquid ratio of 1:(20-50) and the reaction time of 5-6h can promote the reaction of the alkoxyl group of the coupling agent with the hydroxyl group on the surface of SiO2 to achieve stable grafting, and successfully introduce carbon-carbon double bonds to the surface of SiO2.

[0041] After the SiO2 microparticles are subjected to the pretreatment process described above, the carbon-carbon double bonds in the liquid latex can cross-link with the carbon-carbon double bonds of the silane coupling agent and react with the vinyl groups of the methyl vinyl silicone rubber under the action of the vulcanizing agent, thereby forming a stable cross-linked network, effectively enhancing the interfacial bonding force between the SiO2 and the matrix, avoiding filler agglomeration, and improving the mechanical properties of the material.

[0042] The application is further described below by way of examples and comparative examples Examples 1-9 A foamed silicone rubber material is prepared from the following components in parts by weight: methyl vinyl silicone rubber; liquid latex; diluent; SiO2; BPO; DBPMH; and NaHCO3.

[0043] The specific parts by weight of each component are shown in Table 1 below.

[0044] Table 1 Composition of foamed silicone rubber material of each example (in parts by weight)

[0045] The foamed silicone rubber materials of Examples 1-9 above are prepared by the following method: SiO2 microparticles with an average particle size of 1 μm are mixed with a 0.3 mol / L NaOH solution at a mass ratio of 1:125, refluxed at 80°C for 1.5 h, washed, and dried to obtain activated SiO2 microparticles; vinyl triethoxysilane and 95% ethanol are mixed at a mass ratio of 2.5:97.5 to prepare a silane coupling agent solution, and the activated SiO2 microparticles are mixed with the silane coupling agent solution at a mass ratio of 1:35, stirred, and reacted for 5.5 h, washed, and dried to obtain pretreated SiO2 microparticles.

[0046] The liquid latex is first diluted and dissolved with the diluent at 60°C, and then the diluted latex is uniformly sprayed onto the surface of the pretreated SiO2 microparticles using a spray bottle to obtain modified SiO2, and finally the modified SiO2 is volatilized at a temperature corresponding to the volatilization temperature of the diluent to remove the diluent.

[0047] The methyl vinyl silicone rubber and the modified SiO2 are mixed at 150°C for 10 min, and then the mixed rubber is uniformly mixed with DBPMH, BPO, and NaHCO3 for 10 min each time, and the mixed rubber is first pre-vulcanized by BPO at 110°C for 10 min and 10 MPa, and then vulcanized and foamed by DBPMH and a foaming agent at 170°C for 10 min and 4 MPa to obtain the foamed silicone rubber material.

[0048] Comparative Examples 1-3 A foamed silicone rubber material is prepared from the following components by weight parts: methyl vinyl silicone rubber, liquid latex, diluent, SiO2, BPO, DBPMH, NaHCO3.

[0049] The specific weight parts of each component are shown in Table 2 below.

[0050] Table 2 Composition of foamed silicone rubber material of each comparative example (by weight parts)

[0051] The foamed silicone rubber material of the above comparative example is prepared by the following method: First, the liquid latex is diluted and dissolved at 60°C with the diluent, then the diluted latex is uniformly sprayed on the surface of SiO2 to obtain modified SiO2 by a spray bottle, and finally the modified SiO2 is volatilized at the corresponding diluent decomposition temperature to remove the diluent.

[0052] The methyl vinyl silicone rubber and the modified SiO2 are mixed at 150°C for 10 min, then the mixed rubber is uniformly mixed with DBPMH, BPO and NaHCO3 for 10 min, and then the mixed rubber is pre-vulcanized by BPO at 110°C for 10 min and 10 MPa, and then vulcanized and foamed by DBPMH and the foaming agent at 170°C for 10 min and 4 MPa, to obtain the foamed silicone rubber material.

[0053] Performance test The performance test method and standard of the foamed silicone rubber material of each embodiment and comparative example of the present application are as follows: (1) Density test: GB / T6343-2009 Test for apparent density of foamed rubber.

[0054] (2) Foaming ratio: GB / T6343 Test for foaming ratio of foamed material.

[0055] (3) Tensile strength test: GB528-2009 Determination of tensile properties of rubber, L0 is 40 mm; the greater the tensile strength, the better the mechanical properties.

[0056] (4) Elongation at break test: GB528-2009 Determination of tensile properties of rubber.

[0057] (5) 50% compression strain strength test: GBT7759.1-2015 Determination of compression properties of rubber; the higher the compression strength, the better the compression resistance of the material.

[0058] The performance test results of the foamed silicone rubber material prepared according to the above-mentioned method for each embodiment and comparative example are shown in Table 3.

[0059] Table 3 Performance test results of each example and comparative example

[0060] From the comparison of the test data of the examples and the comparative examples, it can be seen that the latex modified Si02 process combined with the double vulcanization foaming process is more obvious for improving the comprehensive performance of the foamed silicone rubber material; Comparative Example 1 which is not modified by latex only uses a diluent to treat Si02, and the tensile strength, elongation at break and compression strength are all significantly lower than those of each example, which shows the indispensability of liquid latex coating for improving the dispersibility of Si02; simply adding a diluent cannot solve the agglomeration problem of Si02, and even the residual solvent may interfere with the vulcanization and foaming process, resulting in a decrease in the mechanical properties of the material.

[0061] Comparative Example 2 does not use a diluent, and its performance is better than that of Comparative Example 1, but still significantly lower than that of Examples 2 to 9 which use the complete coating process, which shows that the diluent can effectively adjust the viscosity of the latex to ensure the formation of a uniform and continuous coating layer on the surface of Si02; and an excess of latex or diluent will cause negative effects, such as in Comparative Example 3, too much latex causes part of the latex not to participate in coating and the mechanical properties of the latex itself are weak, and in Comparative Example 4, too much diluent causes re-agglomeration of Si02 and an increase in the amount of residual solvent, both of which cause the reinforcing effect to decrease.

[0062] Among the many examples, Example 3 exhibits the best comprehensive performance, which uses silicone rubber latex and cyclohexane in combination and undergoes a complete pretreatment and coating process; this example achieves the best tensile strength, elongation at break and compression strength while maintaining a low density and a high foaming ratio, which shows the excellent compatibility of silicone rubber latex with the methyl vinyl silicone rubber matrix, and the dense coating layer formed by cyclohexane at a suitable volatilization temperature; the silane coupling agent introduced in the pretreatment step further enhances the interfacial bonding between Si02 and the latex and the matrix, thereby constructing a stable filler network.

[0063] Each example uses a BPO and DBPMH complex vulcanizing agent in combination with sodium bicarbonate or azodicarbonamide foaming agent to achieve the matching of the vulcanization and foaming processes; the preliminary network formed in the prevulcanization stage effectively stabilizes the cell structure, which makes the mechanical properties of all examples better than those of the comparative examples under the premise of similar foaming ratios; in particular, Example 9 uses azodicarbonamide as a foaming agent, and its performance is comparable to that of the examples using sodium bicarbonate, which shows that this process has certain adaptability to different foaming agents.

[0064] In summary, by modifying SiO2 with latex, the dispersibility of the filler in the matrix is significantly improved, and stress concentration caused by agglomeration is avoided; by strictly controlling the component ratio and process, the uniformity and integrity of the coating layer are ensured; and by combining the time sequence synergistic effect of the dual vulcanizing agent and the foaming agent, a foamed silicone rubber material with uniform cell structure and good mechanical properties is finally obtained.

[0065] The above only describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A latex-modified SiO2-dispersible foamed silicone rubber material, characterized in that, By weight, it comprises the following components: 94-100 parts of methyl vinyl silicone rubber, 35-45 parts of SiO2 particles, 5.2-6.8 parts of liquid latex, 0.1-2 parts of vulcanizing agent, and 14 parts of foaming agent; The SiO2 particles are modified by being coated with the liquid latex, and the average particle size of the SiO2 particles is 1 μm. The average molecular weight of the liquid latex is 40,000-400,000 g / mol; the liquid latex is selected from any one of silicone rubber latex, natural latex, styrene-butadiene latex, or butyl rubber latex.

2. The latex-modified SiO2-dispersible foamed silicone rubber material according to claim 1, characterized in that, The average molecular weight of the silicone rubber latex is 40,000-100,000 g / mol, the average molecular weight of the natural latex is 300,000-400,000 g / mol, the average molecular weight of the styrene-butadiene latex is 100,000-300,000 g / mol, and the average molecular weight of the butadiene-pyridine latex is 100,000-200,000 g / mol.

3. The latex-modified SiO2 dispersible foamed silicone rubber material according to claim 1, characterized in that, The methyl vinyl silicone rubber has an average molecular weight of 450,000-850,000 g / mol and an average vinyl content of 0.13-0.18%.

4. The latex-modified SiO2 dispersible foamed silicone rubber material according to claim 1, characterized in that, The vulcanizing agent is 2,5-dimethyl-2,5-bis-(tert-butylperoxide)hexane and benzoyl peroxide; the foaming agent is selected from sodium bicarbonate and azodicarbonamide.

5. The method for preparing foamed silicone rubber material according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. First, dilute and dissolve the liquid latex with a diluent at 60°C to obtain diluted latex. Then, spray the diluted latex onto the surface of SiO2 particles using a spraying device. Then, heat it at the corresponding diluent volatilization temperature to volatilize the diluent and obtain modified SiO2. S2. Methyl vinyl silicone rubber and modified SiO2 are mixed together, and then the mixed rubber is mixed evenly with 2,5-dimethyl-2,5-bis-(tert-butylperoxide)hexane, benzoyl peroxide and foaming agent, and then vulcanized and foamed to obtain foamed silicone rubber material.

6. The method for preparing foamed silicone rubber material according to claim 5, characterized in that, In step S1, when preparing the latex-modified SiO2, the weight ratio of the SiO2 particles, liquid latex and diluent is 40:6:

12.

7. The method for preparing foamed silicone rubber material according to claim 5, characterized in that, In step S1, the diluent and its evaporation temperature are any one of the following: (1) The diluent is xylene, with a volatilization temperature of 130°C; (2) The diluent is cyclohexane with an evaporation temperature of 90°C; (3) The diluent is D-limonene, with a volatilization temperature of 150℃; (4) The diluent is L-ethyl lactate with an evaporation temperature of 160°C.

8. The method for preparing foamed silicone rubber material according to claim 5, characterized in that, In step S2, the methyl vinyl silicone rubber and modified SiO2 are mixed at 150°C for 10 minutes, and the mixed rubber is then mixed with vulcanizing agent and foaming agent at room temperature on a two-roll mill with circulating cooling water.

9. The method for preparing foamed silicone rubber material according to claim 5, characterized in that, In step S2, the compound is first pre-cured with benzoyl peroxide at 110°C, 10 min and 10 MPa, and then vulcanized and foamed with 2,5-dimethyl-2,5-bis-(tert-butyl peroxide)hexane and a foaming agent at 170°C, 10 min and 4 MPa.

10. The method for preparing foamed silicone rubber material according to claim 5, characterized in that, In step S1, the SiO2 particles undergo pretreatment before spraying the diluted latex. The pretreatment method includes: (1) Mix SiO2 particles with NaOH solution with a concentration of 0.2-0.4 mol / L at a mass ratio of 1:100-150, reflux at 70-90℃ for 1-2 h, wash and dry to obtain activated SiO2 particles; (2) Prepare a silane coupling agent solution by mixing silane coupling agent and 95% ethanol at a mass ratio of (1-5):(95-100). Mix activated SiO2 particles with the silane coupling agent solution at a mass ratio of 1:(20-50), stir and react for 5-6 hours, wash and dry to obtain pretreated SiO2 particles. The silane coupling agent is selected from any one of γ-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, and vinyltrimethoxysilane.

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