Preparation method of low-density addition type flame-retardant liquid silicone rubber

Abstract

The invention belongs to the technical field of silicone rubber, and particularly relates to a preparation method of low-density addition type flame-retardant liquid silicone rubber, which comprises the following steps: putting vinyl silicone oil and fumed silica into a vacuum kneading machine, mixing at constant temperature for 1-3 hours, and then heating and mixing for 2-3 hours to obtain a component A; adding a low-density flame retardant into the component A, and mixing at constant temperature for 2-4 hours to obtain a component B; and uniformly stirring the component B, hydrogen-containing silicone oil, a platinum catalyst and 1-ethynyl-1-cyclohexanol, and carrying out vulcanization molding to obtain the low-density addition type flame-retardant liquid silicone rubber. The problem that the mechanical property of an existing flame retardant becomes poor is solved, by means of the porous silica structure contained in the flame retardant, the physical clamping and fixing effect is achieved, and physical and chemical connection of the flame retardant in the whole system is achieved by means of the silicon hydroxyl activity of the silica structure.

Description

Technical Field

[0001] The invention belongs to the technical field of silicone rubber, and in particular relates to a method for preparing low-density addition-type flame-retardant liquid silicone rubber. Background Art

[0002] Addition-type liquid silicone rubber has been widely used in industrial, medical and daily necessities due to its advantages such as non-toxicity, odorlessness, good transparency and strong processability. However, addition-type liquid silicone rubber is a type of silicone material that can be cross-linked and vulcanized at room temperature or under heating under the action of platinum catalyst, which is composed of vinyl-containing polyorganosiloxane as the base polymer and Si-H bond-containing polyorganosiloxane as the cross-linking agent. The molecular chain contains a large amount of carbon and hydrogen, which will smolder when exposed to open flames, which greatly limits its application in high-end precision fields such as aerospace, electronics and power. Therefore, the flame retardant research of addition-type liquid silicone rubber has become a new direction for silicone rubber.

[0003] At present, the flame retardant of addition-type liquid silicone rubber is mainly inorganic flame retardant silicone rubber and peroxide-cured silicone rubber. Inorganic flame retardant silicone rubber improves the flame retardancy of silicone rubber by adding inorganic flame retardants, but the surface inertness of the flame retardant itself leads to poor connection performance within the silicone rubber, resulting in a decrease in mechanical properties. Peroxide-cured silicone rubber contains a large amount of flame retardants, which has the problem of large addition amount and high cost.

[0004] Therefore, it is of great significance to study an addition-type liquid silicone rubber with excellent flame retardant properties. Summary of the invention

[0005] In view of the problems in the prior art, the present invention provides a method for preparing a low-density addition-type flame-retardant liquid silicone rubber, which solves the problem of deterioration of mechanical properties caused by existing flame retardants. The porous silicon-oxygen structure contained in the flame retardant itself is utilized to not only achieve a physical clamping and fixing effect, but also utilizes the silanol activity of the silicon-oxygen structure to achieve physical and chemical connection of the flame retardant in the entire system.

[0006] In order to achieve the above technical objectives, the technical solution of the present invention is:

[0007] A method for preparing a low-density addition-type flame-retardant liquid silicone rubber comprises the following steps:

[0008] Step 1, putting vinyl silicone oil and fumed silica into a vacuum kneader, mixing at a constant temperature for 1-3 hours, and then heating and mixing for 2-3 hours to obtain component A; the vinyl silicone oil adopts terminal vinyl polydimethylsiloxane; the viscosity of the vinyl silicone oil is 1000-10000mPa·s; the mass content of vinyl groups in the vinyl silicone oil is 0.13-0.3%; the amount of the fumed silica added is 20-30% of the mass of the vinyl silicone oil, the particle size of the fumed silica is 100-400nm, and the specific surface area is 150-300m 2 / g, the constant temperature mixing temperature is 30-35°C, and the temperature of the temperature-raising mixing temperature is 140-160°C;

[0009] Step 2, adding a low-density flame retardant to component A, and kneading at a constant temperature for 2-4 hours to obtain a combination B, wherein the constant temperature kneading temperature is 30-50° C.; the amount of the low-density flame retardant added is 30-50% of the mass of white carbon black, and the low-density flame retardant adopts closed-cell silica particles, and the surface of the closed-cell silica particles has a porous structure;

[0010] Step 3, component B, hydrogen-containing silicone oil, platinum catalyst and 1-ethynyl-1-cyclohexanol are stirred evenly, and vulcanized to obtain a low-density addition-type flame-retardant liquid silicone rubber, wherein the amount of hydrogen-containing silicone oil added is 8-10% of the mass of vinyl silicone oil, the amount of platinum catalyst added is 0.03-0.07% of the mass of vinyl silicone oil, and the platinum catalyst adopts platinum-vinylsiloxane complex, and the Pt content in the platinum catalyst is 500-1000ppm. The stirring speed for stirring evenly is 100-400r / min, the temperature is 25-35°C, and the temperature of vulcanization molding is 120-160°C.

[0011] Furthermore, the fumed silica is modified fumed silica, the molecular formula of which is SiO2, and it is a white fluffy powder with a porous structure. At the same time, the fumed silica itself has a certain chemical inertness, which not only plays a good reinforcing role, but also can be used as a filler. At the same time, with the extension of the use time and the aging of the silicone rubber, the stability of the fumed silica gradually decreases, and there are problems such as powder falling and easy breakage. To address this problem, the fumed silica is modified to improve the surface group activity, and the active group ensures the connection temperature of the fumed silica in the silicone rubber. At the same time, the fumed silica itself is a nano-scale filling material, which can be quickly filled into the pores of the silicone rubber to form a stable connection structure and a dense structure. The fumed silica is a silica base material with good flame retardancy, which effectively improves the flame retardancy, wear resistance and strength of the silicone rubber. The modified fumed silica is silanol-modified silica; and the preparation method of the silanol-modified silica comprises: a1, adding fumed silica to ether and ultrasonicating for 20-30 minutes, then spraying it into an acid solution at a constant temperature and stirring for 0.5-1h, and spray drying to obtain acid-modified fumed silica, wherein the concentration of the fumed silica in ether is 100-500 g / L, the ultrasonic temperature is 5-10°C, the ultrasonic frequency is 70-90kHz, the constant temperature spraying temperature is 40-50°C, the spraying speed is 5-8mL / min, and the area is 100-200cm 2, the acid solution is a hydrochloric acid solution with a pH of 4-5, the stirring speed is 300-500r / min, and the temperature of the spray drying is 110-140°C; this step uses ether as a cleaning agent, combined with ultrasonic high-frequency vibration, to clean the surface of the fumed silica, not only to clean the impurities on the surface of the fumed silica, but also to completely open the porous structure of the fumed silica by high-frequency vibration, thereby increasing the exposed area of ​​the fumed silica; the cleaned fumed silica is stirred in an acidic solution to form an acid-modified fumed silica, and the acid-modified fumed silica is formed during spray drying; a2, the three Chloromethylsilane and ethyl cellulose are added to ether and stirred evenly, then acid-modified fumed silica is added and ultrasonicated for 20-30 minutes, filtered and then blow-dried to obtain prefabricated modified fumed silica, the mass ratio of trichloromethylsilane to ethyl cellulose is 2-3:2, the mass ratio of trichloromethylsilane to ether is 1:15-20, the stirring speed for uniform stirring is 400-1000r / min, the mass ratio of acid-modified fumed silica to ether is 1:10-12, the ultrasonic temperature is 5-10°C, the ultrasonic frequency is 60-90kHz, and the blowing and spray drying is to extract The filtered precipitate is sprayed into a reaction kettle and dried at a blowing speed of 10-20 g / min. The atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 10-12:1. The drying temperature is 50-60° C. In this step, a homogeneous dispersion solution is formed by utilizing the solubility of trichloromethylsilane and ethyl cellulose in ether. The acid-modified fumed silica is dispersed in the entire homogeneous dispersion solution in ultrasound. After suction filtration and blowing drying, a surface deposition is first formed on the basis of in-situ hydrolysis of trichloromethylsilane, that is, a thin film is formed on the surface of the fumed silica. The thin film is trihydroxymethylsilane. Alkane condensation polymer and ethyl cellulose are the main components; a3, prefabricated modified fumed silica is placed in ethanol for ultrasonic dispersion for 20-30 minutes, filtered and dried to obtain modified fumed silica, the concentration of the prefabricated modified fumed silica in ethanol is 100-300g / L, the ultrasonic frequency of ultrasonic dispersion is 70-90kHz, the temperature is 5-10°C, and the drying temperature is 50-70°C; this step utilizes the solubility of ethyl cellulose in ether, in conjunction with the effect of ultrasonic dispersion, to dissolve and remove the ethyl cellulose in the prefabricated modified fumed silica, thereby forming a porous structure on the surface of the fumed silica. The porous film containing trihydroxymethylsilane condensation polymer on the surface of the modified fumed silica prepared by this process not only contains a large amount of silanol groups, but also the porous film itself has a porous structure, forming a physical and chemical dual connection structure from the perspective of chemical bonding and physical clamping; the method provided by this process is not only stable and reproducible, but also has strong controllability of pore structure.

[0012] Furthermore, the low-density flame retardant adopts a silicone material with closed cells inside and porous outside. The silicone material has a porous structure both inside and outside, and the inside and outside are divided by a barrier material, forming a closed porous structure inside. The barrier material completely seals the internal porous structure, which can effectively reduce the density of the flame retardant. At the same time, the external porous structure is mainly silicone material. The porous physical structure has a good physical fixing effect, which effectively improves the stability of the flame retardant in silicone rubber. The silicone material with an external porous structure and the barrier material are rich in active groups of the hydroxyl system, which can be chemically bonded in the entire system, thereby achieving a good connection mechanism. Both white carbon black and the low-density flame retardant are mainly silicone system, forming a stable silicone connection structure, and have a good composite flame retardant system. The preparation method of the low-density flame retardant comprises the following steps: b1, adding trichloromethylsilane and ethyl cellulose to ether and stirring evenly to form a dissolving solution, and then granulating and standing to obtain prefabricated particles; the mass ratio of trichloromethylsilane to ethyl cellulose is 1:0.5-3, the mass ratio of trichloromethylsilane to ether is 1:5-7, the stirring speed for uniform stirring is 300-500r / min, the granulation temperature is 50-60°C, the standing atmosphere is a mixed atmosphere of nitrogen and water vapor, the volume ratio of nitrogen to water vapor is 8-10:1, and the temperature is 50-80°C; this step Step 1: using the solubility of trichloromethylsilane and ethyl cellulose in ether to form a viscous liquid, during the granulation process, the ether is evaporated and removed to form a particle structure, the particles undergo an in-situ hydrolysis reaction during standing, trichloromethylsilane is converted into trihydroxymethylsilane, and in combination with the influence of temperature, an in-situ condensation reaction is formed; b2: adding aluminum isopropoxide to isopropanol, stirring evenly, and spraying it on the surface of the prefabricated particles, then standing at a constant temperature for 10-20 minutes, and sintering at a constant temperature for 0.5-1h to obtain coated particles, wherein the mass ratio of aluminum isopropoxide to isopropanol is 1:2-3, and the spraying area is 1-2mL / cm 2 , the temperature is 85-90℃, the temperature of the constant temperature standing is 120-130℃, the sintering atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8-10:1, the sintering heating rate is 2-5℃, and the constant temperature sintering temperature is 250-280℃; this step uses the isopropyl aluminum solution to spray on the prefabricated particles, and liquefies the isopropyl aluminum during the constant temperature standing to form a homogeneous liquid film, and hydrolyzes the isopropyl aluminum in situ to form aluminum hydroxide during the sintering process, and forms an active alumina structure at the sintering temperature; b3, spray trichloromethylsilane ether solution on the surface of the coated particles, and stand in situ for 2-3h to obtain secondary coated particles; the mass ratio of trichloromethylsilane to ether in the trichloromethylsilane ether solution is 1:3-4, and the spray volume is 2-4mL / cm 2, the in-situ standing temperature is 60-80°C, the atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 10-12:1. This step utilizes the solubility and in-situ hydrolysis characteristics of trichloromethylsilane to form trihydroxymethylsilane on the surface of the coated particles, thereby achieving the effect of secondary coating. At the same time, trihydroxymethylsilane and activated alumina can form a stable closed barrier structure to seal the internal silicon oxide porous structure; b4, trichloromethylsilane and ethyl cellulose are added to ether and stirred evenly to form a dissolved solution, and then the dissolved solution is sprayed on the surface of the secondary coated particles, and sintered after standing to obtain a low-density flame retardant. The mass ratio of trichloromethylsilane to ethyl cellulose is 1:0.5-2, and the mass ratio of trichloromethylsilane to ether is 1:3-4. The stirring speed for uniform stirring is 300-500r / min, and the spraying amount is 1-3mL / cm 2 , the static atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8-9:1, and the sintering temperature is 250-280℃; this step uses the solubility of ethyl cellulose and trichloromethylsilane in ether to form a dissolving solution, and sprays and deposits it on the surface of the secondary coating particles, and forms a surface film of trihydroxymethylsilane and ethyl cellulose by in-situ hydrolysis, and removes the in-situ polycondensation of ethyl cellulose and trihydroxymethylsilane by sintering to obtain a low-density flame retardant. The flame retardant prepared by this process contains an internal porous silicon oxide structure and has good low-density characteristics; the silicon oxide layer and the aluminum oxide layer arranged in sequence can not only be tightly structured in the internal silicon oxide structure and the external silicon oxide structure, but also the silicon oxide layer is located outside the aluminum oxide layer, which effectively eliminates the problem of heat conduction of the silicon oxide layer; the outer structure and silicon oxide layer of the flame retardant are formed by hydrolysis and polycondensation of trichloromethylsilane, and contain a lot of silanol groups, which can react with the active groups in the silicone rubber, and the external porous structure still has a good physical fixation effect. The low-density flame retardant prepared by this process uses silicon oxide material as the main framework and aluminum oxide material as the auxiliary structure, forming good mechanical support performance, while effectively improving the connection stability and pore controllability of the flame retardant in the entire system.

[0013] It can be seen from the above description that the present invention has the following advantages:

[0014] 1. The present invention solves the problem of deterioration of mechanical properties caused by existing flame retardants. It utilizes the porous silicon-oxygen structure contained in the flame retardant itself to not only achieve a physical clamping and fixing effect, but also utilizes the silanol activity of the silicon-oxygen structure to achieve physical and chemical connection of the flame retardant in the entire system.

[0015] 2. The present invention utilizes a silicone material with an internal closed structure to form an internal closed pore structure, which effectively reduces the density of the flame retardant, thereby achieving the low-density characteristics of silicone rubber. At the same time, the support formed by the silicone structure ensures mechanical stability.

[0016] 3. The present invention utilizes the porous structure both inside and outside of the silica material, which is divided by a barrier material to form a closed porous structure inside. It not only has good flame retardant properties of its own material, but also the coverage of the silica material is combined with fumed silica to form a porous system of flame retardant filler connection system. DETAILED DESCRIPTION

[0017] The present invention is described in detail with reference to the embodiments, but no limitation is imposed on the claims of the present invention.

[0018] Example 1

[0019] A method for preparing a low-density addition-type flame-retardant liquid silicone rubber comprises the following steps:

[0020] Step 1, putting vinyl silicone oil and fumed silica into a vacuum kneader, mixing at a constant temperature for 1 hour, and then heating and mixing for 2 hours to obtain component A; the vinyl silicone oil adopts terminal vinyl polydimethylsiloxane; the viscosity of the vinyl silicone oil is 1000-10000mPa·s; the mass content of vinyl groups in the vinyl silicone oil is 0.13-0.3%; the amount of the fumed silica added is 20% of the mass of the vinyl silicone oil, the particle size of the fumed silica is 100-400nm, and the specific surface area is 150-300m 2 / g, the constant temperature mixing temperature is 30°C, and the temperature of the temperature-raising mixing temperature is 140°C;

[0021] Step 2, adding a low-density flame retardant to component A, mixing at a constant temperature for 2 hours, to obtain a combination B, wherein the constant temperature mixing temperature is 30° C.; the amount of the low-density flame retardant added is 30% of the mass of white carbon black, and the low-density flame retardant adopts closed-cell silica particles, and the surface of the closed-cell silica particles has a porous structure;

[0022] Step 3, component B, hydrogen-containing silicone oil, platinum catalyst and 1-ethynyl-1-cyclohexanol are stirred evenly, and vulcanized to obtain a low-density addition-type flame-retardant liquid silicone rubber, wherein the amount of hydrogen-containing silicone oil added is 8% of the mass of vinyl silicone oil, the amount of platinum catalyst added is 0.03% of the mass of vinyl silicone oil, and the platinum catalyst adopts platinum-vinylsiloxane complex, and the Pt content in the platinum catalyst is 500-1000ppm. The stirring speed for stirring evenly is 100r / min, the temperature is 25°C, and the vulcanization molding temperature is 120°C.

[0023] The fumed silica is modified fumed silica, and the modified fumed silica is silanol-modified silica. The preparation method of the silanol-modified silica comprises: a1, adding fumed silica to ether and ultrasonicating for 20 minutes, then spraying it into an acid solution at a constant temperature and stirring for 0.5 hours, and spray drying to obtain acid-modified fumed silica, wherein the concentration of the fumed silica in ether is 100 g / L, the ultrasonic temperature is 5°C, the ultrasonic frequency is 70 kHz, the constant temperature spraying temperature is 40°C, the spraying speed is 5 mL / min, and the area is 100 cm 2 , the acid solution is a hydrochloric acid solution with a pH of 4, the stirring speed is 300r / min, and the spray drying temperature is 110°C; a2, trichloromethylsilane and ethyl cellulose are added to ether and stirred evenly, and then acid-modified fumed silica is added and ultrasonicated for 20 minutes, and then filtered and blown and dried to obtain prefabricated modified fumed silica, the mass ratio of trichloromethylsilane to ethyl cellulose is 1:1, the mass ratio of trichloromethylsilane to ether is 1:15, the stirring speed is 400r / min, the mass ratio of acid-modified fumed silica to ether is 1:10, and the ultrasonic The temperature is 5°C, the ultrasonic frequency is 60kHz, the blowing and drying is to spray the precipitate after suction filtration into the reactor and dry it, the blowing speed is 10g / min, the atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 10:1, and the drying temperature is 50°C; a3, the preformed modified fumed silica is placed in ethanol and ultrasonically dispersed for 20 minutes, filtered and then dried to obtain modified fumed silica, the concentration of the preformed modified fumed silica in ethanol is 100g / L, the ultrasonic frequency of ultrasonic dispersion is 70kHz, the temperature is 5°C, and the drying temperature is 50°C.

[0024] The low-density flame retardant adopts a silicon oxide material with closed inner pores and porous outer pores. The preparation method of the low-density flame retardant includes the following steps: b1, adding trichloromethylsilane and ethyl cellulose to ether and stirring evenly to form a dissolving solution, and then granulating and standing to obtain prefabricated particles; the mass ratio of trichloromethylsilane to ethyl cellulose is 1:0.5, the mass ratio of trichloromethylsilane to ether is 1:5, the stirring speed for uniform stirring is 300r / min, the granulation temperature is 50°C, the standing atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8:1, and the temperature is 50°C; b2, adding aluminum isopropoxide to isopropanol and stirring evenly, and spraying it on the surface of the prefabricated particles, and then standing at a constant temperature for 10 minutes, and sintering at a constant temperature for 0.5 hours to obtain coated particles, the mass ratio of aluminum isopropoxide to isopropanol is 1:2, and the spraying area is 1mL / cm 2, the temperature is 85°C, the constant temperature standing temperature is 120°C, the sintering atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8:1, the sintering heating rate is 2°C, and the constant temperature sintering temperature is 250°C; b3, spray trichloromethylsilane ether liquid on the surface of the coated particles, and let it stand in situ for 2h to obtain secondary coated particles; the mass ratio of trichloromethylsilane to ether in the trichloromethylsilane ether liquid is 1:3, and the spray volume is 2mL / cm 2 , the in-situ standing temperature is 60°C, the atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 10:1; b4, trichloromethylsilane and ethyl cellulose are added to ether and stirred evenly to form a dissolving solution, and then the dissolving solution is sprayed on the surface of the secondary coating particles, and sintered after standing to obtain a low-density flame retardant, the mass ratio of trichloromethylsilane to ethyl cellulose is 1:0.5, the mass ratio of trichloromethylsilane to ether is 1:3-4, the stirring speed for uniform stirring is 300r / min, and the spraying amount is 1mL / cm 2 The static atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8:1. The sintering temperature is 250°C.

[0025] Example 2

[0026] A method for preparing a low-density addition-type flame-retardant liquid silicone rubber comprises the following steps:

[0027] Step 1, putting vinyl silicone oil and fumed silica into a vacuum kneader, mixing at a constant temperature for 3 hours, and then heating and mixing for 3 hours to obtain component A; the vinyl silicone oil adopts terminal vinyl polydimethylsiloxane; the viscosity of the vinyl silicone oil is 1000-10000mPa·s; the mass content of vinyl groups in the vinyl silicone oil is 0.13-0.3%; the amount of the fumed silica added is 30% of the mass of the vinyl silicone oil, the particle size of the fumed silica is 100-400nm, and the specific surface area is 150-300m 2 / g, the constant temperature mixing temperature is 35°C, and the temperature of the temperature-raising mixing temperature is 160°C;

[0028] Step 2, adding a low-density flame retardant to component A, mixing at a constant temperature for 4 hours, to obtain a combination B, wherein the constant temperature mixing temperature is 50° C.; the amount of the low-density flame retardant added is 50% of the mass of the white carbon black, and the low-density flame retardant adopts closed-cell silica particles, and the surface of the closed-cell silica particles has a porous structure;

[0029] Step 3, component B, hydrogen-containing silicone oil, platinum catalyst and 1-ethynyl-1-cyclohexanol are stirred evenly, and vulcanized to obtain a low-density addition-type flame-retardant liquid silicone rubber, wherein the amount of hydrogen-containing silicone oil added is 10% of the mass of vinyl silicone oil, the amount of platinum catalyst added is 0.07% of the mass of vinyl silicone oil, and the platinum catalyst adopts platinum-vinylsiloxane complex, and the Pt content in the platinum catalyst is 500-1000ppm. The stirring speed for stirring evenly is 400r / min, the temperature is 35°C, and the vulcanization molding temperature is 160°C.

[0030] Furthermore, the fumed silica is modified fumed silica, the modified fumed silica is silanol-modified silica, and the preparation method of the silanol-modified silica comprises: a1, adding fumed silica to ether and ultrasonicating for 30 minutes, then spraying it into an acid solution at a constant temperature and stirring for 1 hour, and spray drying to obtain acid-modified fumed silica, wherein the concentration of the fumed silica in ether is 500 g / L, the ultrasonic temperature is 10°C, the ultrasonic frequency is 90 kHz, the constant temperature spraying temperature is 50°C, the spraying speed is 8 mL / min, and the area is 200 cm 2 , the acid solution is hydrochloric acid solution with a pH of 5, the stirring speed is 500r / min, and the spray drying temperature is 140°C; a2, trichloromethylsilane and ethyl cellulose are added to ether and stirred evenly, and then acid-modified fumed silica is placed in ultrasonic for 30 minutes, and after suction filtration, the preformed modified fumed silica is obtained by spray drying. The mass ratio of trichloromethylsilane to ethyl cellulose is 3:2, and the mass ratio of trichloromethylsilane to ether is 1:20. The stirring speed for uniform stirring is 1000r / min, the mass ratio of acid-modified fumed silica to ether is 1:12, and the ultrasonic temperature is 200°C. The temperature of the prefabricated modified fumed silica is 10°C, the ultrasonic frequency is 90kHz, the blowing and spraying drying is to spray the precipitate after suction filtration into the reactor and dry it, the blowing and spraying speed is 20g / min, the atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 12:1, and the drying temperature is 60°C; a3, the prefabricated modified fumed silica is ultrasonically dispersed in ethanol for 30min, filtered and then dried to obtain modified fumed silica, the concentration of the prefabricated modified fumed silica in ethanol is 300g / L, the ultrasonic frequency of the ultrasonic dispersion is 90kHz, the temperature is 10°C, and the drying temperature is 70°C.

[0031] The low-density flame retardant adopts a silicon oxide material with closed inner pores and porous outer pores. The preparation method of the low-density flame retardant comprises the following steps: b1, adding trichloromethylsilane and ethyl cellulose to ether and stirring evenly to form a dissolving solution, then granulating and standing to obtain prefabricated particles; the mass ratio of trichloromethylsilane to ethyl cellulose is 1:3, the mass ratio of trichloromethylsilane to ether is 1:7, the stirring speed for uniform stirring is 500r / min, the granulation temperature is 60°C, the standing atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 10:1, and the temperature is 80°C; b2, adding aluminum isopropoxide to isopropanol and stirring evenly, and spraying it on the surface of the prefabricated particles, then standing at a constant temperature for 20 minutes, and sintering at a constant temperature for 1 hour to obtain coated particles, the mass ratio of aluminum isopropoxide to isopropanol is 1:3, and the spraying area is 2mL / cm 2 , the temperature is 90°C, the constant temperature standing temperature is 130°C, the sintering atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 10:1, the sintering heating rate is 5°C, and the constant temperature sintering temperature is 280°C; b3, spray trichloromethylsilane ether liquid on the surface of the coated particles, and let it stand in situ for 3h to obtain secondary coated particles; the mass ratio of trichloromethylsilane to ether in the trichloromethylsilane ether liquid is 1:4, and the spray volume is 4mL / cm 2 , the in-situ standing temperature is 80°C, the atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 12:1; b4, trichloromethylsilane and ethyl cellulose are added to ether and stirred evenly to form a dissolving solution, and then the dissolving solution is sprayed on the surface of the secondary coating particles, and sintered after standing to obtain a low-density flame retardant, the mass ratio of trichloromethylsilane to ethyl cellulose is 1:2, the mass ratio of trichloromethylsilane to ether is 1:4, the stirring speed for uniform stirring is 500r / min, and the spraying amount is 3mL / cm 2 The static atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 9:1. The sintering temperature is 280°C.

[0032] Example 3

[0033] A method for preparing a low-density addition-type flame-retardant liquid silicone rubber comprises the following steps:

[0034] Step 1, putting vinyl silicone oil and fumed silica into a vacuum kneader, mixing at a constant temperature for 2 hours, and then heating and mixing for 2 hours to obtain component A; the vinyl silicone oil adopts terminal vinyl polydimethylsiloxane; the viscosity of the vinyl silicone oil is 1000-10000mPa·s; the mass content of vinyl groups in the vinyl silicone oil is 0.13-0.3%; the amount of the fumed silica added is 25% of the mass of the vinyl silicone oil, the particle size of the fumed silica is 100-400nm, and the specific surface area is 150-300m 2 / g, the constant temperature mixing temperature is 33°C, and the temperature of the temperature-raising mixing temperature is 150°C;

[0035] Step 2, adding a low-density flame retardant to component A, mixing at a constant temperature for 3 hours, to obtain a combination B, wherein the constant temperature mixing temperature is 40° C.; the amount of the low-density flame retardant added is 40% of the mass of white carbon black, and the low-density flame retardant adopts closed-cell silica particles, and the surface of the closed-cell silica particles has a porous structure;

[0036] Step 3, component B, hydrogen-containing silicone oil, platinum catalyst and 1-ethynyl-1-cyclohexanol are stirred evenly, and vulcanized to obtain a low-density addition-type flame-retardant liquid silicone rubber, wherein the amount of hydrogen-containing silicone oil added is 9% of the mass of vinyl silicone oil, the amount of platinum catalyst added is 0.05% of the mass of vinyl silicone oil, and the platinum catalyst adopts platinum-vinylsiloxane complex, and the Pt content in the platinum catalyst is 500-1000ppm. The stirring speed for stirring evenly is 300r / min, the temperature is 30°C, and the vulcanization molding temperature is 150°C.

[0037] Furthermore, the fumed silica is modified fumed silica, the modified fumed silica is silanol-modified silica, and the preparation method of the silanol-modified silica comprises: a1, adding fumed silica to ether and ultrasonicating for 25 minutes, then spraying it into an acid solution at a constant temperature and stirring for 1 hour, and spray drying to obtain acid-modified fumed silica, wherein the concentration of the fumed silica in ether is 300 g / L, the ultrasonic temperature is 8°C, the ultrasonic frequency is 80 kHz, the constant temperature spraying temperature is 45°C, the spraying speed is 7 mL / min, and the area is 150 cm 2, the acid solution is hydrochloric acid solution with a pH of 5, the stirring speed is 400r / min, and the spray drying temperature is 130°C; a2, trichloromethylsilane and ethyl cellulose are added to ether and stirred evenly, and then acid-modified fumed silica is added and ultrasonicated for 25 minutes, and then filtered and blown and dried to obtain prefabricated modified fumed silica, the mass ratio of trichloromethylsilane to ethyl cellulose is 3:2, the mass ratio of trichloromethylsilane to ether is 1:18, the stirring speed for uniform stirring is 800r / min, the mass ratio of acid-modified fumed silica to ether is 1:11, and the ultrasonic The temperature is 8°C, the ultrasonic frequency is 70kHz, the blowing and drying is to spray the precipitate after suction filtration into the reactor and dry it, the blowing speed is 15g / min, the atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 11:1, and the drying temperature is 55°C; a3, the preformed modified fumed silica is placed in ethanol and ultrasonically dispersed for 25 minutes, filtered and then dried to obtain modified fumed silica, the concentration of the preformed modified fumed silica in ethanol is 200g / L, the ultrasonic frequency of ultrasonic dispersion is 80kHz, the temperature is 8°C, and the drying temperature is 60°C.

[0038] The low-density flame retardant adopts a silicon oxide material with closed inner pores and porous outer pores. The silicon oxide material has porous structures both inside and outside, and the inside and outside are divided by a barrier material to form a closed porous structure inside. The preparation method of the low-density flame retardant comprises the following steps: b1, adding trichloromethylsilane and ethyl cellulose to ether and stirring evenly to form a dissolving solution, then granulating and standing to obtain prefabricated particles; the mass ratio of trichloromethylsilane to ethyl cellulose is 1:2, the mass ratio of trichloromethylsilane to ether is 1:6, the stirring speed for uniform stirring is 400r / min, the granulation temperature is 55°C, the standing atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 9:1, and the temperature is 70°C; b2, adding aluminum isopropoxide to isopropanol and stirring evenly, and spraying it on the surface of the prefabricated particles, then standing at a constant temperature for 15 minutes, and sintering at a constant temperature for 1 hour to obtain coated particles, the mass ratio of aluminum isopropoxide to isopropanol is 1:2, and the spraying area is 2mL / cm 2 , the temperature is 90°C, the constant temperature standing temperature is 125°C, the sintering atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 9:1, the sintering heating rate is 4°C, and the constant temperature sintering temperature is 270°C; b3, spray trichloromethylsilane ether liquid on the surface of the coated particles, and let it stand in situ for 2h to obtain secondary coated particles; the mass ratio of trichloromethylsilane to ether in the trichloromethylsilane ether liquid is 1:4, and the spray volume is 3mL / cm 2, the in-situ standing temperature is 70°C, the atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 11:1; b4, trichloromethylsilane and ethyl cellulose are added to ether and stirred evenly to form a dissolving solution, and then the dissolving solution is sprayed on the surface of the secondary coating particles, and sintered after standing to obtain a low-density flame retardant, the mass ratio of trichloromethylsilane to ethyl cellulose is 1:1, the mass ratio of trichloromethylsilane to ether is 1:4, the stirring speed for uniform stirring is 400r / min, and the spraying amount is 2mL / cm 2 The static atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8:1. The sintering temperature is 270°C.

[0039] Example 4

[0040] A method for preparing a low-density addition-type flame-retardant liquid silicone rubber comprises the following steps:

[0041] Step 1, putting vinyl silicone oil and fumed silica into a vacuum kneader, mixing at a constant temperature for 2 hours, and then heating and mixing for 2 hours to obtain component A; the vinyl silicone oil adopts terminal vinyl polydimethylsiloxane; the viscosity of the vinyl silicone oil is 1000-10000mPa·s; the mass content of vinyl groups in the vinyl silicone oil is 0.13-0.3%; the amount of the fumed silica added is 25% of the mass of the vinyl silicone oil, the particle size of the fumed silica is 100-400nm, and the specific surface area is 150-300m 2 / g, the constant temperature mixing temperature is 33 ° C, the temperature of the temperature-raising mixing temperature is 150 ° C;

[0042] Step 2, adding a low-density flame retardant to component A, mixing at a constant temperature for 3 hours, to obtain a combination B, wherein the constant temperature mixing temperature is 40° C.; the amount of the low-density flame retardant added is 40% of the mass of white carbon black, and the low-density flame retardant adopts closed-cell silica particles, and the surface of the closed-cell silica particles has a porous structure;

[0043] Step 3, component B, hydrogen-containing silicone oil, platinum catalyst and 1-ethynyl-1-cyclohexanol are stirred evenly, and vulcanized to obtain a low-density addition-type flame-retardant liquid silicone rubber, wherein the amount of hydrogen-containing silicone oil added is 9% of the mass of vinyl silicone oil, the amount of platinum catalyst added is 0.05% of the mass of vinyl silicone oil, and the platinum catalyst adopts platinum-vinylsiloxane complex, and the Pt content in the platinum catalyst is 500-1000ppm. The stirring speed for stirring evenly is 300r / min, the temperature is 30°C, and the vulcanization molding temperature is 150°C.

[0044] The low-density flame retardant is a silicon oxide material with closed inner pores and porous outer pores. The silicon oxide material has porous structures both inside and outside, and the inside and outside are divided by a barrier material to form a closed porous structure inside. The preparation method of the low-density flame retardant comprises the following steps: b1, adding trichloromethylsilane and ethyl cellulose to ether and stirring evenly to form a dissolving solution, then granulating and standing to obtain prefabricated particles; the mass ratio of trichloromethylsilane to ethyl cellulose is 1:2, the mass ratio of trichloromethylsilane to ether is 1:6, the stirring speed for uniform stirring is 400r / min, the granulation temperature is 55°C, the standing atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 9:1, and the temperature is 70°C; b2, adding aluminum isopropoxide to isopropanol and stirring evenly, and spraying it on the surface of the prefabricated particles, then standing at a constant temperature for 15 minutes, and sintering at a constant temperature for 1 hour to obtain coated particles, the mass ratio of aluminum isopropoxide to isopropanol is 1:2, and the spraying area is 2mL / cm 2 , the temperature is 90°C, the constant temperature standing temperature is 125°C, the sintering atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 9:1, the sintering heating rate is 4°C, and the constant temperature sintering temperature is 270°C; b3, spray trichloromethylsilane ether liquid on the surface of the coated particles, and let it stand in situ for 2h to obtain secondary coated particles; the mass ratio of trichloromethylsilane to ether in the trichloromethylsilane ether liquid is 1:4, and the spray volume is 3mL / cm 2 , the in-situ standing temperature is 70°C, the atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 11:1; b4, trichloromethylsilane and ethyl cellulose are added to ether and stirred evenly to form a dissolving solution, and then the dissolving solution is sprayed on the surface of the secondary coating particles, and sintered after standing to obtain a low-density flame retardant, the mass ratio of trichloromethylsilane to ethyl cellulose is 1:1, the mass ratio of trichloromethylsilane to ether is 1:4, the stirring speed for uniform stirring is 400r / min, and the spraying amount is 2mL / cm 2 The static atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8:1. The sintering temperature is 270°C.

[0045] Example 5

[0046] A method for preparing a low-density addition-type flame-retardant liquid silicone rubber comprises the following steps:

[0047] Step 1, putting vinyl silicone oil and fumed silica into a vacuum kneader, mixing at a constant temperature for 2 hours, and then heating and mixing for 2 hours to obtain component A; the vinyl silicone oil adopts terminal vinyl polydimethylsiloxane; the viscosity of the vinyl silicone oil is 1000-10000mPa·s; the mass content of vinyl groups in the vinyl silicone oil is 0.13-0.3%; the amount of the fumed silica added is 25% of the mass of the vinyl silicone oil, the particle size of the fumed silica is 100-400nm, and the specific surface area is 150-300m 2 / g, the constant temperature mixing temperature is 33°C, and the temperature of the temperature-raising mixing temperature is 150°C;

[0048] Step 2, adding a low-density flame retardant to component A, and kneading at a constant temperature for 3 hours to obtain a combination B, wherein the constant temperature kneading temperature is 40° C.; the amount of the low-density flame retardant added is 40% of the mass of white carbon black, and the low-density flame retardant is a silicon-oxygen material, and the silicon-oxygen material is formed by hydrolysis and condensation of trichloromethylsilane;

[0049] Step 3, component B, hydrogen-containing silicone oil, platinum catalyst and 1-ethynyl-1-cyclohexanol are stirred evenly, and vulcanized to obtain a low-density addition-type flame-retardant liquid silicone rubber, wherein the amount of hydrogen-containing silicone oil added is 9% of the mass of vinyl silicone oil, the amount of platinum catalyst added is 0.05% of the mass of vinyl silicone oil, and the platinum catalyst adopts platinum-vinylsiloxane complex, and the Pt content in the platinum catalyst is 500-1000ppm. The stirring speed for stirring evenly is 300r / min, the temperature is 30°C, and the vulcanization molding temperature is 150°C.

[0050] The low-density flame retardant is a silicon oxide material with closed inner pores and porous outer pores. The silicon oxide material has porous structures both inside and outside, and the inside and outside are divided by a barrier material to form a closed porous structure inside. The preparation method of the low-density flame retardant comprises the following steps: b1, adding trichloromethylsilane and ethyl cellulose to ether and stirring evenly to form a dissolving solution, then granulating and standing to obtain prefabricated particles; the mass ratio of trichloromethylsilane to ethyl cellulose is 1:2, the mass ratio of trichloromethylsilane to ether is 1:6, the stirring speed for uniform stirring is 400r / min, the granulation temperature is 55°C, the standing atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 9:1, and the temperature is 70°C; b2, adding aluminum isopropoxide to isopropanol and stirring evenly, and spraying it on the surface of the prefabricated particles, then standing at a constant temperature for 15 minutes, and sintering at a constant temperature for 1 hour to obtain coated particles, the mass ratio of aluminum isopropoxide to isopropanol is 1:2, and the spraying area is 2mL / cm 2, the temperature is 90°C, the constant temperature standing temperature is 125°C, the sintering atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 9:1, the sintering heating rate is 4°C, and the constant temperature sintering temperature is 270°C; b3, spray trichloromethylsilane ether liquid on the surface of the coated particles, and let it stand in situ for 2h to obtain secondary coated particles; the mass ratio of trichloromethylsilane to ether in the trichloromethylsilane ether liquid is 1:4, and the spray volume is 3mL / cm 2 , the in-situ standing temperature is 70°C, the atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 11:1; b4, trichloromethylsilane and ethyl cellulose are added to ether and stirred evenly to form a dissolving solution, and then the dissolving solution is sprayed on the surface of the secondary coating particles, and sintered after standing to obtain a low-density flame retardant, the mass ratio of trichloromethylsilane to ethyl cellulose is 1:1, the mass ratio of trichloromethylsilane to ether is 1:4, the stirring speed for uniform stirring is 400r / min, and the spraying amount is 2mL / cm 2 The static atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8:1. The sintering temperature is 270°C.

[0051] Performance Testing

[0052] The samples produced in Examples 1-5 were used as test examples to perform performance testing and comparison, and the results are as follows:

[0053] Example 1 Example 2 Example 3 Example 4 Example 5 Hardness A° 50 48 49 53 55 Tensile strength MPa 1.21 1.19 1.21 1.26 1.31 Elongation % 530 620 489 452 301 Tear strength KN / m 25 23 26 28 16 <![CDATA[Specific gravity g / cm 3 > 1.21 1.19 1.20 1.24 1.31 Compression set % 12 13 10 14 19 Flame retardant grade 1VA 1VA 1VA V0 V1

[0054] Example 2 > Example 1 / Example 3 > Example 4 > Example 5

[0055] It is understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the use requirements are met, they are within the protection scope of the present invention.

Claims

1. A method for preparing a low-density addition-type flame-retardant liquid silicone rubber, characterized in that: The steps include: Step 1, putting vinyl silicone oil and fumed silica into a vacuum kneader, mixing at a constant temperature for 1-3 hours, and then heating and mixing for 2-3 hours to obtain component A; Step 2, adding a low-density flame retardant to component A, mixing at a constant temperature for 2-4 hours, to obtain combination B. Step 3, mixing component B, hydrogen-containing silicone oil, platinum catalyst and 1-ethynyl-1-cyclohexanol evenly, and vulcanizing and molding to obtain a low-density addition-type flame-retardant liquid silicone rubber.

2. The method for preparing the low-density addition-type flame-retardant liquid silicone rubber according to claim 1, characterized in that: The vinyl silicone oil in step 1 is vinyl-terminated polydimethylsiloxane; the viscosity of the vinyl silicone oil is 1000-10000 mPa·s; the mass content of vinyl groups in the vinyl silicone oil is 0.13-0.3%.

3. The method for preparing the low-density addition-type flame-retardant liquid silicone rubber according to claim 1, characterized in that: The amount of the fumed silica added in step 1 is 20-30% of the mass of the vinyl silicone oil, the particle size of the fumed silica is 100-400nm, and the specific surface area is 150-300m 2 / g.

4. The method for preparing the low-density addition-type flame-retardant liquid silicone rubber according to claim 3, characterized in that: The fumed silica is modified fumed silica.

5. The method for preparing the low-density addition-type flame-retardant liquid silicone rubber according to claim 1, characterized in that: The temperature of the constant temperature mixing in step 1 is 30-35°C, and the temperature of the temperature-raising mixing is 140-160°C.

6. The method for preparing the low-density addition-type flame-retardant liquid silicone rubber according to claim 1, characterized in that: The temperature of the constant temperature mixing in step 2 is 30-50° C.; the amount of the low-density flame retardant added is 30-50% of the mass of the white carbon black.

7. The method for preparing the low-density addition-type flame-retardant liquid silicone rubber according to claim 1, characterized in that: The low-density flame retardant in step 2 is a closed-cell silica particle, and the surface of the closed-cell silica particle is porous.

8. The method for preparing the low-density addition-type flame-retardant liquid silicone rubber according to claim 7, characterized in that: The low-density flame retardant is a silicon-oxygen material with closed inner pores and porous outer pores.

9. The method for preparing the low-density addition-type flame-retardant liquid silicone rubber according to claim 1, characterized in that: The amount of hydrogenated silicone oil added in step 3 is 8-10% of the mass of vinyl silicone oil, the amount of platinum catalyst added is 0.03-0.07% of the mass of vinyl silicone oil, and the platinum catalyst adopts platinum-vinylsiloxane complex, and the Pt content in the platinum catalyst is 500-1000ppm.

10. The method for preparing the low-density addition-type flame-retardant liquid silicone rubber according to claim 1, characterized in that: The stirring speed for uniform stirring in step 3 is 100-400 r / min, the temperature is 25-35° C., and the temperature for vulcanization molding is 120-160° C.