Synthesis method of POE (Polyolefin Elastomer) reinforced room temperature vulcanized silicone rubber

Abstract

The invention relates to the technical field of production of room-temperature vulcanized silicone rubber, and particularly discloses a synthesis method of POE (Polyolefin Elastomer) reinforced room-temperature vulcanized silicone rubber, which comprises the following steps: adding the following raw materials in parts by mass into mixing equipment: 100 parts of base rubber, 5-10 parts of a reinforcing agent and 5-10 parts of fumed silica; the preparation method comprises the following steps: taking base rubber, a reinforcing agent and fumed silica as main raw materials, heating and stirring in mixing equipment, heating to 120 + / -3 DEG C, vacuumizing and keeping for 2 hours, then cooling the mixing equipment, adding a cross-linking agent and stirring for 30 minutes when the temperature is cooled to room temperature, and then adding a catalyst and stirring for 10 minutes to obtain the room-temperature vulcanized silicone rubber. Wherein the reinforcing agent is set to be POE or silane functionalized POE, the interaction between a molecular chain of the POE and a resin molecule is enhanced through mutual winding of the molecular chain of the POE and the resin molecule, and the crosslinking density of the silicone rubber is improved by utilizing a hydrolysis crosslinking reaction between an end group of the silane functionalized POE and a base rubber, the process is simple, and the mechanical strength of the silicone rubber is effectively enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of room temperature vulcanized silicone rubber production, and particularly relates to a method for synthesizing POE reinforced room temperature vulcanized silicone rubber. Background Art

[0002] Room temperature vulcanized silicone rubber (RTV) is an elastomer made from hydroxyl-terminated polydimethylsiloxane, crosslinked by a trifunctional silane compound, and catalytically cured with an organometallic compound. Dealcoholized RTV silicone rubber releases alcohols during the curing process, resulting in low odor, excellent adhesion, and rapid surface drying, making it suitable for a wide range of applications.

[0003] The main chain of the room temperature vulcanized silicone rubber molecules currently on the market is a silicon-oxygen bond, with small intermolecular forces and low mechanical strength. For example, unreinforced RTV silicone rubber shows low breaking strength in tensile tests, making it difficult to withstand large tensile forces and prone to breaking under small stresses. In situations where it needs to withstand tensile loads, silicone rubber may fail due to insufficient tensile strength, resulting in reduced sealing performance or structural damage. Therefore, we need to propose a synthesis method for POE-reinforced room temperature vulcanized silicone rubber to solve the above-mentioned problems, so that it can effectively improve the mechanical strength of room temperature vulcanized silicone rubber. Summary of the Invention

[0004] The object of the present invention is to provide a method for synthesizing POE-reinforced room temperature vulcanized silicone rubber, which can effectively improve the mechanical strength of room temperature vulcanized silicone rubber and solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for synthesizing POE-reinforced room temperature vulcanized silicone rubber comprises the following steps:

[0007] S1. Add the following raw materials in a mixing device according to mass ratio: 100 parts of base rubber, 5-10 parts of reinforcing agent, and 5-10 parts of fumed silica, wherein the reinforcing agent is set to POE or silane-functionalized POE;

[0008] S2. Heat the mixing equipment to 120°C ± 3°C while stirring and maintain vacuum for 2 hours;

[0009] S3. Cool the mixing equipment, add a cross-linking agent and stir for 30 minutes when the temperature drops to room temperature, then add a catalyst and stir for 10 minutes to obtain a mixture, which is room temperature vulcanized silicone rubber.

[0010] Preferably, in step S1, the following raw materials are added to the mixing equipment according to the mass ratio: 100 parts of base rubber, 5 parts of reinforcing agent, and 5 parts of fumed silica.

[0011] Preferably, the base glue is set to be α,ω-dihydroxy polydimethylsiloxane or alkoxy-terminated dimethylsiloxane, and the viscosity of the base glue is set to be 5000 cps-20000 cps.

[0012] Preferably, the silane-functionalized POE is obtained by introducing silane into POE for modification, wherein the silane is set to one or more of vinyltrimethoxysilane, vinyltriethoxysilane and vinyltri(2-methoxyethoxy)silane.

[0013] Preferably, the fumed silica is a hydrophobic fumed silica of model R812S or model R972.

[0014] Preferably, in step S2, the mixing device is evacuated to a vacuum degree of 0.08 MPa at 120°C, and the mixing device is configured as a vacuum power mixer.

[0015] Preferably, in step S3, the cross-linking agent is set to be one of methyltrimethoxysilane, vinyltrimethoxysilane and tetraethyl orthosilicate.

[0016] Preferably, the catalyst is one of dibutyltin dilaurate, stannous octoate, tetrabutyl titanate and di(ethyl acetoacetate)diisopropyltitanium.

[0017] Preferably, the mixing device is provided with a pipeline interface for adding a crosslinking agent and a catalyst, the mass ratio of the crosslinking agent to the base rubber is 1:10, and the mass ratio of the crosslinking agent to the catalyst is 100:3.

[0018] Preferably, the mixture is poured into a tetrafluoroethylene mold, cured at room temperature for 7 days, and then demoulded to obtain a room temperature vulcanized silicone rubber solid.

[0019] The synthesis method of POE-reinforced room temperature vulcanized silicone rubber proposed in the present invention has the following advantages compared with the prior art:

[0020] 1. The present invention uses base rubber, reinforcing agent and fumed silica as main raw materials, heats and stirs in a mixing device, and when the temperature rises to 120°C±3°C and is vacuumed and maintained for 2 hours, the mixing device is then cooled. When it drops to room temperature, a cross-linking agent is first added and stirred for 30 minutes, and then a catalyst is added and stirred for 10 minutes to obtain room temperature vulcanized silicone rubber, wherein the reinforcing agent is set to POE or silane-functionalized POE, and the molecular chain of POE is entangled with the resin molecules to enhance the interaction between the two, and the hydrolysis cross-linking reaction of the end group of the silane-functionalized POE with the base rubber is utilized to improve the cross-linking density of the silicone rubber. The process is simple and the mechanical strength of the silicone rubber is effectively enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flowchart of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] The present invention provides Figure 1 A method for synthesizing POE-reinforced room temperature vulcanized silicone rubber is shown, comprising the following steps:

[0024] S1. Add the following raw materials in a mixing device according to mass ratio: 100 parts of base rubber, 5-10 parts of reinforcing agent, and 5-10 parts of fumed silica, wherein the reinforcing agent is set to POE or silane-functionalized POE. POE or silane-functionalized POE improves the toughness of silicone rubber through physical blending or chemical bonding. Silane groups (such as vinyltrimethoxysilane) can react with hydroxyl groups in the base rubber to form chemical crosslinks and enhance interfacial bonding.

[0025] The silane-functionalized POE is obtained by introducing silane into POE for modification, wherein the silane is set to be one or more of vinyltrimethoxysilane, vinyltriethoxysilane and vinyltri(2-methoxyethoxy)silane.

[0026] The base glue is set to α,ω-dihydroxy polydimethylsiloxane or alkoxy-terminated dimethylsiloxane, and the viscosity of the base glue is set to 5000cps-20000cps. The selection of α,ω-dihydroxy polydimethylsiloxane or alkoxy-terminated dimethylsiloxane has a viscosity range (5000cps-20000cps) that affects processing performance and mechanical properties after vulcanization. Too high viscosity will lead to poor fluidity, while too low viscosity will affect the strength after vulcanization.

[0027] α,ω-dihydroxypolydimethylsiloxane is typically a colorless, transparent, viscous liquid that can flow or form a viscous paste. The cured silicone rubber maintains over 90% of its tensile strength in a -60°C low-temperature impact test. After 1000 hours of heat aging at 250°C, its mass loss is less than 0.5%. It exhibits properties such as aging resistance, corrosion resistance, water and moisture resistance, non-toxicity, insulation, and shock resistance. Its surface cure time is less than 2 hours, its brittle temperature is -60°C, its hardness (A°) is greater than 20, its volume resistivity is ≥110, its tensile strength (3.5kg / m2) is greater than 3.5, its dielectric constant (1mHz) is ≤3.2, its elongation (%) is 100, and its breakdown voltage (kV / mm) is ≥13. Under a field strength of 30kV / mm, its volume resistivity remains on the order of 1×10^15Ω·cm. Its corona resistance life reaches 8000 hours at 3kV / mm, a three-order-of-magnitude improvement over conventional rubber materials.

[0028] Alkoxy-terminated dimethylsiloxane is a colorless or slightly yellow transparent liquid with customizable viscosity. It has good high-temperature resistance and can be used above 300°C. It also has good chemical stability: good oxidation resistance and is not easily oxidized and decomposed in the air; good weather resistance and is not easily cracked or discolored by ultraviolet rays and chemicals; it has electrical properties and can be used in insulating materials, remaining stable under high voltage and high temperature; it is chemically resistant and is not affected by acids, alkalis and other chemicals. As a raw material for organosilanol-type vulcanized silicone rubber, it has moisture-curing properties and is terminated with single, double, di / trialkoxy groups.

[0029] The fumed silica is configured as a hydrophobic fumed silica of model R812S or model R972. Both R812S and R972 are hydrophobic fumed silicas prepared by a chemical reaction between hydrophilic fumed silica and active silane. They are hydrophobic (water-repellent) and cannot be dispersed in water. They have low hygroscopicity, which enables them to maintain stable performance in a humid environment. They are also easily dispersed in organic media and can form a uniform system. They also have rheology adjustment capabilities and can function even in polar systems, helping to control the viscosity and fluidity of the system. Hydrophobic fumed silica prevents particle agglomeration through a steric hindrance effect, thereby improving dispersibility. R812S has a high specific surface area and a more significant reinforcement effect; R972 balances reinforcement and processability.

[0030] The three-dimensional network structure is formed by evenly dispersed reinforcing agents and base rubber, which improves the tensile strength, tear strength and hardness of silicone rubber.

[0031] S2. Heat the mixing equipment to 120℃±3℃ while stirring and keep it in vacuum for 2 hours to remove moisture and low molecular weight volatiles from the raw materials and prevent bubbles from forming during the vulcanization process, which may affect the density of the material.

[0032] The mixing equipment is evacuated to a vacuum degree of 0.08 MPa at 120° C. The mixing equipment is configured as a vacuum power mixer to ensure that the raw materials are fully devolatilized, while avoiding degradation of the base rubber at high temperatures, thereby improving the physical properties (such as tensile strength and elongation at break) and aging resistance of the vulcanized material.

[0033] S3. Cool the mixing equipment, add a cross-linking agent and stir for 30 minutes when the temperature drops to room temperature, then add a catalyst and stir for 10 minutes to obtain a mixture, which is room temperature vulcanized silicone rubber.

[0034] The cross-linking agent is set to be one of methyltrimethoxysilane, vinyltrimethoxysilane and ethyl orthosilicate. Methyltrimethoxysilane is a colorless, transparent liquid with a pungent odor. It is soluble in many organic solvents, such as alcohols, ethers and ketones. It will hydrolyze and cross-link in water to produce methanol.

[0035] Vinyltrimethoxysilane is a colorless, transparent liquid with an ester smell. It is insoluble in water and can be slowly hydrolyzed in water to generate the corresponding silanol. It is miscible with organic solvents such as alcohol, ether, and benzene.

[0036] Tetraethyl orthosilicate is a colorless liquid with a slight odor. It is slightly soluble in water and soluble in organic solvents such as ethanol and ether. It gradually becomes turbid in humid air and silicic acid precipitates after standing. Methyltrimethoxysilane, vinyltrimethoxysilane or tetraethyl orthosilicate reacts with the hydroxyl groups in the base rubber to form Si-O-Si cross-linking bonds and construct a three-dimensional network structure.

[0037] The catalyst is set to be one of dibutyltin dilaurate, stannous octoate, tetrabutyl titanate and di(ethyl acetoacetate) diisopropyl titanium. Dibutyltin dilaurate is usually a light yellow or colorless oily liquid, which may form white crystals at low temperatures. It is soluble in organic solvents such as benzene, toluene, carbon tetrachloride, ethyl acetate, chloroform, acetone, petroleum ether, and all industrial plasticizers, but is insoluble in water. Dibutyltin dilaurate is an organic tin additive with excellent lubricity, transparency, weather resistance, and good resistance to sulfide pollution.

[0038] Stannous octoate is a white or yellow paste that is insoluble in water but soluble in organic solvents such as petroleum ether and polyols. Stannous octoate is chemically unstable and easily oxidized. It is primarily used as a catalyst in the production of polyurethane foam, room-temperature curing silicone rubber, polyurethane rubber, and polyurethane coatings. It is also used as a catalyst-type curing agent for epoxy resins. During curing, stannous octoate has greater catalytic activity than dibutyltin dilaurate. Combining the two can achieve a balanced reaction speed and curing speed.

[0039] Tetrabutyl titanate is a colorless to pale yellow viscous liquid that is soluble in most organic solvents except ketones. It easily solidifies into transparent flakes when exposed to air, decomposes in water, and is flammable. It is mainly used in transesterification reactions to improve the heat resistance of coatings (heat resistant up to 500°C) and improve the adhesion of coatings, rubber, and plastics to metal surfaces. In addition, it can also be used as a condensation catalyst and cross-linking agent.

[0040] Di(ethyl acetoacetate)diisopropyltitanium is a light red, transparent liquid that is slightly soluble in common organic solvents but readily soluble in isopropyl alcohol, benzene, and toluene. When stored at low temperatures, it can sometimes partially or completely crystallize. IBAY's main component is stable at room temperature in a chelated form. During use, as the solvent evaporates, IBAY can cross-link with active base materials (such as -OH, -COOH, -NH2, OCONH2, and -SH) in substrates and ink and coating binders, forming bridges and increasing molecular weight. This improves properties such as heat resistance, chemical resistance, water resistance, and drying properties. It also enhances the adhesion of inks and coatings to substrates (such as pre-treated plastics, aluminum foil, metal, and glass).

[0041] Dibutyltin dilaurate, stannous octoate, and other agents accelerate the crosslinking reaction and shorten the vulcanization time. Titanate catalysts such as IBAY can increase crosslink density and heat resistance.

[0042] The mixing device is provided with a pipeline interface for adding a cross-linking agent and a catalyst. The mass ratio of the cross-linking agent to the base rubber is 1:10 to ensure sufficient cross-linking and avoid insufficient or excessive cross-linking. The mass ratio of the cross-linking agent to the catalyst is 100:3 to balance the reaction rate and the degree of vulcanization.

[0043] By mixing cross-linking agents and catalysts with raw materials, a dense cross-linking network is formed, which significantly improves the mechanical strength (such as tensile strength, tear strength), hardness and heat resistance of silicone rubber.

[0044] The mixture is poured into a tetrafluoroethylene mold and cured at room temperature for 7 days before demoulding to facilitate the full cross-linking reaction and form a stable network structure to obtain a room temperature vulcanized silicone rubber solid. The tetrafluoroethylene mold is formulated according to the actual shape requirements of the rubber solid, and the material properties of tetrafluoroethylene can prevent adhesion and facilitate demoulding.

[0045] According to the above synthesis method, a specific embodiment of the synthesis method of POE reinforced room temperature vulcanized silicone rubber is proposed, which is as follows:

[0046] Example 1:

[0047] Add 500 g of 10,000 cps end-hydroxy polydimethylsiloxane, 25 g of R812S fumed silica and 25 g of POE (8150) into the mixing equipment, raise the temperature to 120°C and evacuate for 2 hours, then cool to room temperature, add 50 g of cross-linking agent methyltrimethoxysilane under vacuum and stir for 30 minutes, then add 1.5 g of catalyst dibutyltin dilaurate and stir for 10 minutes, and seal for storage.

[0048] Example 2:

[0049] Add 500g of 10000cps end-hydroxy polydimethylsiloxane, 25g of R812S fumed silica and 50g of POE (8150) into the mixing equipment, heat to 120°C and keep under vacuum for 2 hours, wait until it drops to room temperature, add 50g of cross-linking agent methyltrimethoxysilane under vacuum and stir for 30 minutes, then add 1.5g of catalyst dibutyltin dilaurate and stir for 10 minutes, and seal for storage.

[0050] Example 3:

[0051] Add 500 g of 10,000 cps hydroxy-terminated polydimethylsiloxane, 25 g of R812S fumed silica, and 25 g of vinyltrimethoxysilane-functionalized POE to a mixing device, raise the temperature to 120°C and evacuate for 2 hours. After cooling to room temperature, add 50 g of methyltrimethoxysilane (a crosslinker) under vacuum and stir for 30 minutes. Then add 1.5 g of dibutyltin dilaurate (a catalyst) and stir for 10 minutes. Seal and store.

[0052] Example 4:

[0053] Add 500 g of 10,000 cps hydroxy-terminated polydimethylsiloxane, 25 g of R812S fumed silica, and 25 g of vinyltriethoxysilane-functionalized POE to a mixing device, raise the temperature to 120°C and evacuate for 2 hours. After cooling to room temperature, add 50 g of methyltrimethoxysilane (a crosslinker) under vacuum and stir for 30 minutes. Then add 1.5 g of dibutyltin dilaurate (a catalyst) and stir for 10 minutes. Seal and store.

[0054] Example 5:

[0055] Add 500 g of 10,000 cps hydroxy-terminated polydimethylsiloxane, 50 g of R972 fumed silica, and 50 g of vinyltriethoxysilane-functionalized POE to a mixing device, raise the temperature to 120°C and evacuate for 2 hours. After cooling to room temperature, add 50 g of crosslinker vinyltrimethoxysilane under vacuum and stir for 30 minutes. Then add 1.5 g of catalyst dibutyltin dilaurate and stir for 10 minutes. Seal and store.

[0056] Example 6:

[0057] Add 500 g of 10,000 cps hydroxy-terminated polydimethylsiloxane, 35 g of R972 fumed silica, and 35 g of vinyltriethoxysilane-functionalized POE to a mixing device, raise the temperature to 120°C and evacuate for 2 hours. After cooling to room temperature, add 50 g of methyltrimethoxysilane (a crosslinker) under vacuum and stir for 30 minutes. Then add 1.5 g of dibutyltin dilaurate (a catalyst) and stir for 10 minutes. Seal and store.

[0058] Comparative Example:

[0059] Add 500 g of 10,000 cps hydroxy-terminated polydimethylsiloxane and 25 g of fumed silica R812S to a mixing device, raise the temperature to 120°C and evacuate for 2 hours. After cooling to room temperature, add 50 g of cross-linking agent methyltrimethoxysilane under vacuum and stir for 30 minutes. Then add 1.5 g of catalyst dibutyltin dilaurate and stir for 10 minutes. Seal and store.

[0060] The mixtures prepared in Examples 1 to 6 and the comparative example were placed in a tetrafluoroethylene mold and cured at room temperature. The tensile strength and elongation at break of the cured solids were tested. The test results are shown in the following table:

[0061]

[0062] It can be concluded from the tabular data that the tensile strength and elongation at break of room temperature vulcanized silicone rubber synthesized using POE reinforcing agent are significantly improved, and the crosslinking density of room temperature vulcanized silicone rubber is increased.

[0063] In summary, the base rubber, reinforcing agent and fumed silica are used as the main raw materials, and the temperature is heated and stirred in a mixing equipment. When the temperature is raised to 120℃±3℃ and vacuumed for 2 hours, the mixing equipment is then cooled. When it drops to room temperature, a cross-linking agent is first added and stirred for 30 minutes, and then a catalyst is added and stirred for 10 minutes to obtain room temperature vulcanized silicone rubber. The reinforcing agent is set to POE or silane-functionalized POE, and the molecular chain of POE is entangled with the resin molecules to enhance the interaction between the two. The cross-linking density of the silicone rubber is improved by utilizing the hydrolysis cross-linking reaction between the end group of the silane-functionalized POE and the base rubber. The process is simple and effectively enhances the mechanical strength of the silicone rubber.

[0064] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for synthesizing POE-reinforced room temperature vulcanized silicone rubber, characterized in that: The steps include: S1. Add the following raw materials in a mixing device according to mass ratio: 100 parts of base rubber, 5-10 parts of reinforcing agent, and 5-10 parts of fumed silica, wherein the reinforcing agent is set to POE or silane-functionalized POE; S2. Heat the mixing equipment to 120°C ± 3°C while stirring and maintain vacuum for 2 hours; S3. Cool the mixing equipment, add a cross-linking agent and stir for 30 minutes when the temperature drops to room temperature, then add a catalyst and stir for 10 minutes to obtain a mixture, which is room temperature vulcanized silicone rubber.

2. The method for synthesizing POE-enhanced room temperature vulcanized silicone rubber according to claim 1, wherein: In step S1, the following raw materials are added into a mixing device according to the mass ratio: 100 parts of base rubber, 5 parts of reinforcing agent, and 5 parts of fumed silica.

3. The method for synthesizing POE-enhanced room temperature vulcanized silicone rubber according to claim 1, wherein: The base glue is set to be α,ω-dihydroxy polydimethylsiloxane or alkoxy-terminated dimethylsiloxane, and the viscosity of the base glue is set to be 5000cps-20000cps.

4. The method for synthesizing POE-enhanced room temperature vulcanized silicone rubber according to claim 3, wherein: The silane-functionalized POE is obtained by introducing silane into POE for modification, wherein the silane is set to be one or more of vinyltrimethoxysilane, vinyltriethoxysilane and vinyltri(2-methoxyethoxy)silane.

5. The method for synthesizing POE-enhanced room temperature vulcanized silicone rubber according to claim 4, wherein: The fumed silica is set to be a hydrophobic fumed silica of model R812S or model R972.

6. The method for synthesizing POE-reinforced room temperature vulcanized silicone rubber according to claim 5, wherein: In step S2, the mixing device is evacuated to a vacuum degree of 0.08 MPa at 120°C, and the mixing device is configured as a vacuum power mixer.

7. The method for synthesizing POE-reinforced room temperature vulcanized silicone rubber according to claim 6, wherein: In step S3, the cross-linking agent is set to be one of methyltrimethoxysilane, vinyltrimethoxysilane and tetraethyl orthosilicate.

8. The method for synthesizing POE-reinforced room temperature vulcanized silicone rubber according to claim 7, wherein: The catalyst is one of dibutyltin dilaurate, stannous octoate, tetrabutyl titanate and di(ethyl acetoacetate) diisopropyl titanium.

9. The method for synthesizing POE-reinforced room temperature vulcanized silicone rubber according to claim 8, wherein: The mixing device is provided with a pipeline interface for adding a cross-linking agent and a catalyst. The mass ratio of the cross-linking agent to the base rubber is 1:10, and the mass ratio of the cross-linking agent to the catalyst is 100:

3.

10. The method for synthesizing POE-reinforced room temperature vulcanized silicone rubber according to claim 9, wherein: The mixture was poured into a tetrafluoroethylene mold, and then demoulded after curing at room temperature for 7 days to obtain room temperature vulcanized silicone rubber solid.

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