Platinum vulcanized flame-retardant silicone rubber and preparation method thereof

Abstract

The invention relates to platinum vulcanized flame-retardant silicone rubber and a preparation method thereof, and belongs to the technical field of silicone rubber. The preparation method comprises the following steps: modifying fumed silica with a silane coupling agent and a self-made bacteriostatic agent to obtain a modified filler, and curing the modified filler and a zinc borate flame retardant under the action of a platinum catalyst to obtain the platinum vulcanized flame-retardant silicone rubber. Double bonds in the modified filler can participate in a silica gel vulcanization reaction, so that the filler is connected with silica gel through covalent bonds, and structural damage caused by high temperature can be effectively reduced; the phosphate group can inhibit gas-phase combustion from forming a carbon layer and has a synergistic effect with the zinc borate flame retardant, so that the flame retardance of the material is enhanced; the quaternary ammonium salt structure can destroy cell integrity and hinder medium permeation. Meanwhile, compared with unmodified fumed silica, the modified filler has better compatibility with silica gel, and the mechanical property, heat resistance, flame retardance and antibacterial property of the platinum vulcanized flame-retardant silicone rubber are greatly improved under the action of multiple structures.

Description

Technical Field

[0001] This invention belongs to the field of silicone rubber technology, specifically, it relates to a platinum vulcanized flame-retardant silicone rubber and its preparation method. Background Technology

[0002] Ordinary silicone is a flammable or combustible material, burning and releasing smoke when exposed to open flames. This limits its application in environments requiring strict flame retardancy. Therefore, improving the flame retardant properties of silicone has become an urgent need for industry development. Fumed silica, as a core reinforcing filler for silicone rubber, can significantly improve the mechanical properties of silicone. However, unmodified fumed silica fillers are rich in silanol groups on their surface, making them prone to agglomeration and uneven dispersion in silicone rubber, which severely affects the processing performance of silicone rubber. Therefore, surface modification of fumed silica has become a key strategy. By grafting functional groups, fumed silica can be transformed from a simple reinforcing filler into a functional reinforcing flame-retardant filler.

[0003] Based on this, the present invention provides a platinum vulcanized flame-retardant silicone rubber and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a platinum vulcanized flame-retardant silicone rubber and its preparation method, in order to solve the problems mentioned in the background art.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing platinum-cured flame-retardant silicone rubber includes the following steps:

[0007] Step 1: Add 3,4-dihydroxypyridine, phosphorus oxychloride, acid binder, magnesium chloride and acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 55-65℃ for 2-3 hours. After cooling to room temperature, filter out the solid. Remove the solvent from the remaining filtrate by rotary evaporation and then elute by column chromatography to obtain the flame retardant.

[0008] Step 2: Add haloolefin, flame retardant and acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 50-70℃ for 20-30 hours. After the reaction is completed, rotary evaporate, wash with ether and filter. The obtained solid is dried to obtain the antibacterial agent.

[0009] The third step is to add the silane coupling agent and ethanol solution to a three-necked flask, attach a condenser and thermometer, turn on the magnetic stirrer, and react at room temperature for 20-30 minutes. Then add fumed silica, raise the system temperature to 70-80°C, and react at 70-80°C for 8-12 hours. After cooling to room temperature, filter out the solid and dry the obtained solid to obtain fumed silica loaded with silane coupling agent.

[0010] Step 4: Add the antibacterial agent, fumed silica loaded with silane coupling agent, acid binder and acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on the magnetic stirrer, and react at 65-75℃ for 7-9 hours. After the reaction is completed, filter out the solid, wash the obtained solid with anhydrous ethanol and deionized water in sequence, and then dry to obtain the modified filler.

[0011] Step 5: Add methyl vinyl silicone rubber, hydrogen-containing silicone oil, and modified filler to a mixing tank and stir at room temperature for 20-30 minutes. Then add platinum catalyst, inhibitor, and zinc borate and stir under vacuum for 10-20 minutes. Transfer to a mold and place in an oven to cure at 80-120°C for 10-30 minutes. After cooling, package into cans to obtain platinum vulcanized flame-retardant silicone rubber.

[0012] Furthermore, the acid-binding agent in the first step is at least one of triethylamine, 4-dimethylaminopyridine, and N,N-diisopropylethylamine.

[0013] Furthermore, in the first step, the mass fractions of 3,4-dihydroxypyridine, phosphorus oxychloride, acid binder, magnesium chloride, and acetonitrile are 11–13: 18.5–21.5: 25–30: 0.9–2.8: 250–290.

[0014] Furthermore, the general structural formula of the haloolefin in the second step is: X is either chlorine or bromine.

[0015] Furthermore, in the second step, the mass ratio of halogenated olefins, flame retardants, and acetonitrile is 10–12:14–17:120–160.

[0016] Furthermore, the silane coupling agent in the third step is at least one of 3-hydroxypropyltrimethoxysilane and 3-hydroxypropyltriethoxysilane.

[0017] Furthermore, the ethanol solution in the third step has a mass fraction of 80–95%.

[0018] Furthermore, in the third step, the mass ratio of silane coupling agent, ethanol solution, and fumed silica is 12–16:180–250:36–48.

[0019] Furthermore, in the fourth step, the mass ratio of the antibacterial agent, fumed silica loaded with silane coupling agent, acid binder, and acetonitrile is 18–20: 23–25: 8–9: 200–220.

[0020] Furthermore, the vacuum condition in step five is a vacuum degree of 0.09–0.098 MPa.

[0021] Furthermore, the inhibitor in step five is at least one of methylbutynol, ethynylcyclohexanol, and propynol.

[0022] Furthermore, in step five, the mass ratio of methyl vinyl silicone rubber, hydrogen-containing silicone oil, modified filler, platinum catalyst, inhibitor, and zinc borate is 40–60: 20–30: 25–45: 0.1–0.5: 0.5–2.5: 0.5–2.5.

[0023] A platinum-cured flame-retardant silicone rubber is prepared by any of the above preparation steps.

[0024] The beneficial effects of this invention are:

[0025] 1) This invention uses 3,4-dihydroxypyridine and phosphorus oxychloride as raw materials to carry out a phosphoric acid esterification reaction to obtain a flame retardant, and uses the flame retardant and halogenated olefins as raw materials to carry out a quaternary ammonium salt reaction to obtain an antibacterial agent, grafting a silane coupling agent onto fumed silica to obtain fumed silica loaded with a silane coupling agent, and then grafting the antibacterial agent onto fumed silica loaded with a silane coupling agent to obtain a modified filler, and finally curing with methyl vinyl silicone rubber, hydrogen-containing silicone oil and modified filler as raw materials under the action of a platinum catalyst to obtain platinum vulcanized flame retardant silicone rubber.

[0026] 2) The double bonds present in the modified filler grafted with the antibacterial agent of this invention can directly participate in the platinum-catalyzed vulcanization crosslinking reaction of silica gel. Through chemical bonding into the crosslinking network, the filler is covalently linked to the silica gel, inhibiting structural damage at high temperatures. This enhances the thermal stability of the material and the interfacial bonding between the filler and silica gel. Compared to unmodified fumed silica, the modified filler exhibits better compatibility with silica gel, thereby enhancing the heat resistance and mechanical properties of platinum-cured flame-retardant silicone rubber.

[0027] 3) The phosphate ester group in the modified filler of this invention is a highly efficient flame retardant component. During combustion, it can form a phosphorus oxide carbon layer, which isolates oxygen and inhibits the volatilization of combustibles. At the same time, phosphorus can capture free radicals generated during combustion, interrupt the combustion chain reaction, and can also have a synergistic effect with the zinc borate flame retardant in the system to improve the overall flame retardant efficiency, thus significantly improving the flame retardant performance of the material.

[0028] 4) The quaternary ammonium salt structure in the antibacterial agent of this invention generates electrostatic interactions with the negatively charged bacterial cell membrane and cell wall, thereby disrupting the cell membrane integrity and achieving the antibacterial effect. Simultaneously, the strong polarity of the quaternary ammonium salt increases the polarity of the silica gel network, hindering media penetration and improving the material's resistance to swelling. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The raw materials used in this invention are not particularly restricted in terms of their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0031] Example 1

[0032] A method for preparing platinum-cured flame-retardant silicone rubber includes the following steps:

[0033] Step 1: Add 11g of 3,4-dihydroxypyridine, 18.5g of phosphorus oxychloride, 25g of triethylamine, 0.95g of magnesium chloride and 250g of acetonitrile to a three-necked flask, attach a condenser and a thermometer, turn on the magnetic stirrer, and react at 55℃ for 3h. After cooling to room temperature, filter out the solid. Remove the solvent from the remaining filtrate by rotary evaporation and then elute by column chromatography to obtain the flame retardant.

[0034] Step 2: Add 10g of 4-chloro-1-butene, 14g of flame retardant and 120g of acetonitrile to a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 50℃ for 30h. After the reaction is completed, rotary evaporate, wash with ether and filter. The obtained solid is dried to obtain the antibacterial agent.

[0035] Step 3: Add 12g of 3-hydroxypropyltrimethoxysilane and 180g of 95% ethanol to a three-necked flask, attach a condenser and a thermometer, turn on the magnetic stirrer, and react at room temperature for 30 minutes. Then add 36g of fumed silica, raise the system temperature to 70℃, and react at 70℃ for 12 hours. After cooling to room temperature, filter out the solid and dry the obtained solid to obtain fumed silica loaded with silane coupling agent.

[0036] Step 4: Add 18g of antibacterial agent, 23g of fumed silica loaded with silane coupling agent, 8g of N,N-diisopropylethylamine and 200g of acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 65℃ for 9 hours. After the reaction is complete, filter out the solid, wash the obtained solid with anhydrous ethanol and deionized water in sequence, and then dry to obtain the modified filler.

[0037] Step 5: Add 40g of methyl vinyl silicone rubber, 20g of hydrogen-containing silicone oil and 25g of modified filler to a mixing tank and stir at room temperature for 20-30 minutes. Then add 0.1g of platinum catalyst, 0.5g of methylbutyninol and 0.5g of zinc borate and stir for 15 minutes under a vacuum of 0.9MPa. Transfer to a mold and place in an oven to cure at 80℃ for 30 minutes. After cooling, package into cans to obtain platinum vulcanized flame-retardant silicone rubber.

[0038] A platinum-cured flame-retardant silicone rubber is prepared by the above preparation steps.

[0039] Example 2

[0040] A method for preparing platinum-cured flame-retardant silicone rubber includes the following steps:

[0041] Step 1: Add 12g of 3,4-dihydroxypyridine, 20g of phosphorus oxychloride, 27.5g of 4-dimethylaminopyridine, 1.9g of magnesium chloride and 270g of acetonitrile to a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 60℃ for 2.5h. After cooling to room temperature, filter out the solid, remove the solvent by rotary evaporation of the remaining filtrate, and then elute by column chromatography to obtain the flame retardant.

[0042] Step 2: Add 11g of 6-bromo-1-hexene, 15g of flame retardant and 140g of acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 60℃ for 25h. After the reaction is completed, evaporate by rotary evaporation, wash with ether and filter. The obtained solid is dried to obtain the antibacterial agent.

[0043] Step 3: Add 14g of 3-hydroxypropyltriethoxysilane and 215g of 90% ethanol solution to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at room temperature for 25min. Then add 42g of fumed silica, raise the system temperature to 75℃, and react at 75℃ for 8-12h. After cooling to room temperature, filter out the solid and dry the obtained solid to obtain fumed silica loaded with silane coupling agent.

[0044] Step 4: Add 19g of antibacterial agent, 24g of fumed silica loaded with silane coupling agent, 8.5g of 4-dimethylaminopyridine and 210g of acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 70℃ for 8h. After the reaction is complete, filter out the solid, wash the obtained solid with anhydrous ethanol and deionized water in sequence, and then dry to obtain the modified filler.

[0045] Step 5: Add 50g of methyl vinyl silicone rubber, 25g of hydrogen-containing silicone oil and 35g of modified filler to a mixing tank and stir at room temperature for 25 minutes. Then add 0.3g of platinum catalyst, 1.5g of ethynylcyclohexanol and 1.5g of zinc borate and stir under a vacuum of 0.094MPa for 15 minutes. Transfer to a mold and place in an oven to cure at 100℃ for 20 minutes. After cooling, package into cans to obtain platinum vulcanized flame-retardant silicone rubber.

[0046] A platinum-cured flame-retardant silicone rubber is prepared by the above preparation steps.

[0047] Example 3

[0048] A method for preparing platinum-cured flame-retardant silicone rubber includes the following steps:

[0049] Step 1: Add 13g of 3,4-dihydroxypyridine, 21.5g of phosphorus oxychloride, 30g of N,N-diisopropylethylamine, 2.8g of magnesium chloride and 290g of acetonitrile to a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 65℃ for 2 hours. After cooling to room temperature, filter out the solid. Remove the solvent from the remaining filtrate by rotary evaporation and then elute by column chromatography to obtain the flame retardant.

[0050] Step 2: Add 12g of 8-chloro-1-octene, 17g of flame retardant and 160g of acetonitrile to a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 70℃ for 20h. After the reaction is completed, rotary evaporate, wash with ether and filter. The obtained solid is dried to obtain the antibacterial agent.

[0051] Step 3: Add 16g of 3-hydroxypropyltrimethoxysilane and 250g of 85% ethanol solution to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at room temperature for 20min. Then add 48g of fumed silica, raise the system temperature to 80℃, and react at 80℃ for 8h. After cooling to room temperature, filter out the solid and dry the obtained solid to obtain fumed silica loaded with silane coupling agent.

[0052] Step 4: Add 20g of antibacterial agent, 25g of fumed silica loaded with silane coupling agent, 9g of triethylamine and 220g of acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 75℃ for 7h. After the reaction is complete, filter out the solid, wash the obtained solid with anhydrous ethanol and deionized water in sequence, and then dry to obtain the modified filler.

[0053] Step 5: Add 60g of methyl vinyl silicone rubber, 30g of hydrogen-containing silicone oil and 45g of modified filler to a mixing tank and stir at room temperature for 20 minutes. Then add 0.5g of platinum catalyst, 2.5g of propynyl alcohol and 2.5g of zinc borate and stir for 10 minutes under a vacuum of 0.098MPa. Transfer to a mold and place in an oven to cure at 120℃ for 10 minutes. After cooling, package into cans to obtain platinum vulcanized flame-retardant silicone rubber.

[0054] A platinum-cured flame-retardant silicone rubber is prepared by the above preparation steps.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Example 2 is that no modification is made to the fumed silica, while the other raw materials and preparation steps remain unchanged.

[0057] Experimental Example 1

[0058] The vulcanized silicone rubbers in Examples 1-3 and Comparative Example 1 were subjected to performance tests. The tensile strength of each group of platinum vulcanized silicone rubbers was tested according to GB / T528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber". The flame retardancy rating of each group of platinum vulcanized silicone rubbers was tested according to GB / T2408-2021 "Determination of Burning Properties of Plastics - Horizontal and Vertical Methods". The heat shrinkage rate of each group of platinum vulcanized silicone rubbers was tested according to GB / T3512-2014 "Accelerated Aging and Heat Resistance Test of Vulcanized Rubber or Thermoplastic Rubber in Hot Air". The antibacterial rate of each group of platinum vulcanized silicone rubbers against Staphylococcus aureus was tested according to GB / T31402-2023 "Determination of Antibacterial Activity of Plastics and Other Non-porous Materials". Comparative Example 1 served as a blank control. The test results are shown in Table 1.

[0059] Table 1

[0060]

[0061] As can be seen from Table 1, Examples 1-3 have higher tensile strength, flame retardancy rating, and antibacterial rate, and lower heat shrinkage rate compared with Comparative Example 1. This indicates that the tensile properties, flame retardancy, heat resistance, and antibacterial properties of Examples 1-3 are all superior to those of Comparative Example 1. Combined with Comparative Example 1, it can be seen that modified fumed silica filler can effectively improve the tensile properties, flame retardancy, heat resistance, and antibacterial properties of platinum vulcanized silicone rubber.

[0062] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the concept and scope of protection of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the design concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for preparing platinum-cured flame-retardant silicone rubber, characterized in that, Includes the following steps: Preparation of antibacterial agents: Flame retardants are obtained by phosphorylation reaction of 3,4-dihydroxypyridine and phosphorus oxychloride under the action of an acid binder, and antibacterial agents are obtained by quaternary ammonium salt reaction of halogenated olefins and flame retardants. Preparation of platinum-cured flame-retardant silicone rubber: A silane coupling agent is grafted onto fumed silica to obtain fumed silica loaded with silane coupling agent. Then, an antibacterial agent is grafted onto fumed silica loaded with silane coupling agent under the action of an acid-binding agent to obtain a modified filler. Under vacuum conditions, methyl vinyl silicone rubber, hydrogen-containing silicone oil, modified filler, inhibitor, and zinc borate are cured under the action of a platinum catalyst to obtain platinum-cured flame-retardant silicone rubber.

2. The method for preparing platinum-cured flame-retardant silicone rubber according to claim 1, characterized in that, The acid-binding agent is at least one of triethylamine, 4-dimethylaminopyridine, and N,N-diisopropylethylamine.

3. The method for preparing platinum-cured flame-retardant silicone rubber according to claim 1, characterized in that, The mass ratio of 3,4-dihydroxypyridine, phosphorus oxychloride, and acid retardant is 11–13:18.5–21.5:25–30, and the mass ratio of halogenated olefin and flame retardant is 10–12:14–17.

4. The method for preparing platinum-cured flame-retardant silicone rubber according to claim 1, characterized in that, The general structural formula of haloalkenes is Where n ranges from 1 to 5, and X is either chlorine or bromine.

5. The method for preparing platinum-cured flame-retardant silicone rubber according to claim 1, characterized in that, The silane coupling agent is at least one of 3-hydroxypropyltrimethoxysilane and 3-hydroxypropyltriethoxysilane.

6. The method for preparing platinum-cured flame-retardant silicone rubber according to claim 1, characterized in that, The mass ratio of silane coupling agent to fumed silica is 12-16:36-48, and the mass ratio of fumed silica loaded with silane coupling agent, antibacterial agent, and acid-binding agent is 23-25:18-20:8-9.

7. The method for preparing platinum-cured flame-retardant silicone rubber according to claim 1, characterized in that, The inhibitor is at least one of methylbutynol, ethynylcyclohexanol, and propynol.

8. The method for preparing platinum-cured flame-retardant silicone rubber according to claim 1, characterized in that, The vacuum conditions are 0.09 to 0.098 MPa.

9. The method for preparing platinum-cured flame-retardant silicone rubber according to claim 1, characterized in that, The mass ratio of methyl vinyl silicone rubber, hydrogen-containing silicone oil, modified filler, platinum catalyst, inhibitor, and zinc borate is 40–60: 20–30: 25–45: 0.1–0.5: 0.5–2.5: 0.5–2.

5.

10. A platinum-cured flame-retardant silicone rubber, characterized in that, Platinum vulcanized flame-retardant silicone rubber is prepared by the preparation method described in any one of claims 1 to 9.

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