Room-temperature vulcanized deacidified silicone rubber and preparation method thereof

Abstract

The invention relates to the technical field of organic silicon rubber preparation, in particular to room-temperature vulcanized deacidified silicon rubber and a preparation method thereof.The silicon rubber is prepared from 100-150 parts of vinyl-terminated silicone oil, 10-30 parts of hydrophilic vapor-phase white carbon black, 1-6 parts of hexamethyldisilazane, 1-10 ppm of platinum catalyst, 1-5 parts of triacetoxyhydrosilane, 1-5 parts of acidic cross-linking agent, 0.2-2 parts of coupling agent and 0.1-3 parts of catalyst. According to the room-temperature vulcanized deacidified silicon rubber, methoxysilane is subjected to acylation oxidation, triacetoxyhydrosilane is synthesized in advance, then the LSR technology and the RTV technology are combined through the triacetoxyhydrosilane, the physical property of addition type silicon rubber and the adhesive strength of condensed type silicon rubber are considered, hydroxyl deep treatment is conducted on base rubber of high-filling-rate fumed silica, and the room-temperature vulcanized deacidified silicon rubber has the advantages of high-filling-rate fumed silica, high-filling-rate fumed silica and high-filling-rate fumed silica and high-filling-rate fumed silica. The strength of the silicone rubber body after contacting with moisture and curing can reach more than 4MPa, and the elongation is more than or equal to 200%.

Description

Technical Field

[0001] The invention relates to the technical field of organic silicone rubber preparation, and in particular to room temperature vulcanized deacidified silicone rubber and a preparation method thereof. Background Art

[0002] Liquid silicone rubber uses low-viscosity polysiloxane as the base polymer. It does not require the use of complex adhesive molding and processing equipment. It can be vulcanized into an elastomer at room temperature or under slight heating by contact with moisture or mixing with a crosslinking agent. According to the crosslinking mechanism, it can be divided into two types: addition-vulcanized silicone rubber and condensation-vulcanized silicone rubber. Addition-vulcanized silicone rubber is a platinum-catalyzed addition vulcanization of silicone polymers containing vinyl functional groups and hydrogen-containing polysiloxanes. It can be vulcanized quickly at room temperature or with slight heating, so it is also called low-temperature vulcanized (LSR) silicone rubber. Condensation-vulcanized silicone rubber can be crosslinked at room temperature by contacting moisture in the air, and small molecules such as acids, oximes, alcohols, and acetone can be removed to vulcanize into elastomers, so it is also called room temperature vulcanized (RTV) silicone rubber.

[0003] LSR silicone rubber has a flexible formula, high body strength after vulcanization, and easy adjustment of physical parameters such as hardness, modulus, and elongation. However, the resulting elastomer is a highly saturated non-polar rubber, with a main chain composed of silicon atoms and oxygen atoms, and a layer of non-polar organic groups arranged on the outside of the main chain, and low molecular surface energy; therefore, the adhesion to the base material is low. In order to improve the adhesion, a tackifier needs to be added, and it needs to be cured at above 100°C, or the base material needs to be primed before gluing.

[0004] When RTV silicone rubber is vulcanized in contact with moisture, it can react with the surface of the substrate to form covalent bonds, thereby bonding well to various substrates, and has therefore been widely studied. The most common RTV silicone rubber preparation process is to mix 107 glue, i.e. α, ω-dihydroxy polydimethylsiloxane, with reinforcing fillers, and then add a crosslinking agent and a catalyst to vulcanize at room temperature moisture. A typical example is the preparation process of deacidified one-component room temperature vulcanizing (RTV-1) glue.

[0005] The typical formula of deacidified one-component room temperature vulcanizing (RTV-1) adhesive is 100 parts of 107 adhesive; 14 parts of reinforcing filler, such as white carbon black, calcium carbonate, and silica powder; 5 parts of cross-linking agent, such as tetraacetoxysilane, methyltriacetoxysilane, ethyltriacetoxysilane, vinyltriacetoxysilane, and propyltriacetoxysilane; 0.2 parts of coupling agent; and 0.03 parts of catalyst, such as organic tin or organic titanium.

[0006] At room temperature, when exposed to moisture in the air, the following cross-linking reaction occurs, vulcanization is completed, an elastomer is formed, and adhesion to most substrates is formed.

[0007]

[0008] Wherein, n = 100 ~ 2000;

[0009] R is methyl, ethyl, vinyl or propyl, etc.

[0010] For example, in order to improve the stability of silicone rubber after aging, a Chinese patent application (application publication number CN 116836679A) discloses a high-displacement aging-resistant deacidification type room temperature vulcanized silicone rubber and a preparation method thereof, in which a reactive plasticizer and a chain extender are introduced into the formula.

[0011] In order to improve the mechanical properties and low-temperature resistance of the product, a Chinese patent application (application publication number CN104194347A) discloses a method for preparing a low-temperature resistant deacidified room-temperature vulcanized silicone rubber. α, ω-dihydroxypolydimethyl diethylsiloxane is used instead of the commonly used 107 rubber. The glass transition temperature of the silicone oil with diethyl structure is lower, so the product can withstand low temperatures of -70°C.

[0012] In order to improve the hydrophobicity and chemical resistance of organic silicone products, a Chinese patent application (application publication number CN113881392A) discloses a method for preparing a deacidified organic silicone adhesive, which introduces fluorine-containing groups into the molecular chain of 107 glue.

[0013] No matter how the formula is improved to enhance the performance of the product, reinforcing fillers cannot be avoided. The body strength of RTV-1 without reinforcing fillers is difficult to exceed 0.5MPa, and the body strength of RTV-1 glue used for building sealing and caulking often needs to be around 1MPa. The most commonly used reinforcing fillers are fumed silica, precipitated silica, nano-calcium carbonate, silica powder, etc., among which fumed silica is the only choice for transparent reinforcement. However, the amount of fumed silica is limited due to its unique nano-chain amorphous particle structure. When the fumed silica in the formula reaches a certain proportion, a sharp thickening effect will occur, resulting in problems such as the glue being too viscous and difficult to mix, and the colloid being too hard, thereby losing extrudability and being unable to be constructed and losing practicality.

[0014] LSR silicone rubber can easily break through the bulk strength of more than 5MPa because the base glue of addition-type silicone rubber is made by using terminal vinyl silicone oil and white carbon black or other reinforcing fillers, which react under the action of hydrophobic treatment agent to treat the moisture and hydroxyl groups on the surface of the inorganic filler to obtain LSR glue with high proportion of white carbon black and good fluidity.

[0015] The LSR process cannot be directly used for the synthesis of RTV because the hexamethyldisilazane or trimethylchlorosilane used in the LSR treatment of the base rubber can act on the silanol groups on the surface of the filler and the silanol groups at both ends of the RTV main polymer 107 rubber at the same time, causing the silicone rubber to form an inert trimethyl end cap and lose its vulcanization reaction activity. The reaction equation is as follows:

[0016]

[0017] As the Chinese patent application (application publication number CN 111269578 A) discloses a storage-stable high-strength room temperature vulcanized silicone rubber and its preparation method, an addition-type base rubber and trimethoxysilane are directly formulated, supplemented with other additives to obtain a high-strength, storage-stable demethanol product. The product produces methanol during the curing process when it comes into contact with moisture, which has an anesthetic effect on the optic nerve and cannot be used in the medical and food industries. At the same time, the trimethoxysilane used in the formula is a chemical substance that needs to be stored in a cylinder, is volatile, has a flash point of -20.7°C, and is highly toxic, highly irritating, and lethal by inhalation. Adding it in the formulation process stage has high safety and environmental risks. Summary of the invention

[0018] In order to overcome the above technical problems, the present invention provides a room temperature vulcanized deacidified silicone rubber, which has the advantages of safety and non-toxicity, strong bonding strength, mild curing conditions, and convenient construction and operation. The room temperature vulcanized deacidified silicone rubber has good bonding strength to various polar plastics, inorganic non-metallic materials such as glass, ceramics, cement, etc., and can be used not only for bonding and molding medical catheters, silicone baby products, silicone medical products, silicone health products, silicone miscellaneous products, silicone tableware, etc., but also for sealing and caulking in buildings.

[0019] The technical solutions to the above technical problems are as follows:

[0020] A room temperature vulcanized deacidified silicone rubber, comprising, by parts by mass:

[0021] 100-150 parts of vinyl-terminated silicone oil, 10-30 parts of hydrophilic fumed silica, 1-6 parts of hexamethyldisilazane, 1-10 ppm of platinum catalyst, 1-5 parts of triacetoxyhydrosilane, 1-5 parts of acidic crosslinking agent, 0.2-2 parts of tackifying coupling agent, and 0.1-3 parts of catalyst;

[0022] Triacetoxyhydrogensilane was synthesized as follows:

[0023] Add trimethoxyhydrogensilane to a reaction vessel equipped with a temperature control device, a stirring device and a distillation device, then add a catalyst and stir for at least 5 minutes, then add acetic anhydride to the reaction vessel so that the molar ratio of acetic anhydride to trimethoxyhydrogensilane is 3:1, and the catalyst is a cationic resin; control the temperature of the reaction system to 60-65°C, the boiling point of methyl acetate generated during the reaction is 57.8°C, control the material temperature, continuously remove the by-product methyl acetate, so that the reaction proceeds to the right, and react for 4-5 hours; filter to remove the catalyst, and then remove small molecules by reduced pressure distillation to obtain triacetoxyhydrogensilane;

[0024] The synthetic reaction formula is as follows:

[0025]

[0026] Specifically, the viscosity of the vinyl-terminated silicone oil is 1000 to 100000 cp, preferably 20000 to 50000 cp.

[0027] Furthermore, the specific surface area of ​​hydrophilic fumed silica is 100 to 300 m 2 / g.

[0028] Specifically, the platinum catalyst is a Karstedt-type platinum catalyst or a Speier-type platinum catalyst; preferably a Karstedt-type platinum catalyst.

[0029] Specifically, the acidic crosslinking agent is one or a mixture of methyltriacetoxysilane, ethyltriacetoxysilane, and vinyltriacetoxysilane.

[0030] Specifically, the adhesion-enhancing coupling agent is one or a mixture of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, and di-tert-butoxydiacetoxysilane.

[0031] Furthermore, the catalyst is one of dibutyltin dilaurate, dibutyltin diacetate, chelated tin, n-butyl titanate, isopropyl titanate or bismuth cyclohexaneate; preferably bismuth cyclohexaneate.

[0032] Another object of the present invention is to provide a method for preparing such room temperature vulcanized deacidified silicone rubber, which can take into account the physical properties of addition-type silicone rubber and the bonding strength of condensation-type silicone rubber. The room temperature vulcanized deacidified silicone rubber is subjected to a hydroxyl deep treatment on a base rubber of high-filling rate fumed silica, so that the strength of the silicone rubber body can reach more than 4MPa after contact with moisture and curing, and the elongation is ≥200%.

[0033] The following steps are involved:

[0034] S1: According to the formula, add the vinyl-terminated silicone oil to the kneader, add the hydrophilic fumed silica and hexamethyldisilazane to the kneader in batches, stir until the fumed silica is evenly powdered, then control the material temperature at 60-70°C for kneading for 3-4 hours, increase the temperature to 90-100°C for kneading for 2 hours, then add distilled water to the system to hydrolyze the residual hexamethylsilazane into siloxane and amine; finally, heat the material to 180°C, remove ammonia and other small molecules under reduced pressure; cool the material and obtain a uniformly kneaded base rubber containing vinyl silicone oil and silica;

[0035] S2: The temperature of the base rubber obtained in S1 is controlled at 80-120°C, and a platinum catalyst and triacetoxyhydrogensilane are added to react for 2-4 hours to end-cap the vinyl silicone oil in the base rubber to form a triacetoxy-end-capped prepolymer; the synthetic reaction formula is as follows:

[0036]

[0037] S3: After the triacyloxy-terminated prepolymer obtained in S2 is cooled to room temperature, an acidic crosslinking agent, a tackifying coupling agent, and a catalyst are added according to the process of deacidified RTV-1, and stirred evenly to obtain room temperature vulcanized deacidified silicone rubber.

[0038] The beneficial effects of the present invention are:

[0039] The present invention first synthesizes triacetoxyhydrogensilane in advance by acylating methoxysilane, and then combines the LSR and RTV processes through triacetoxyhydrogensilane, that is, according to the LSR process, the base rubber is wet-processed with vinyl silicone oil and white carbon black; then the triacetoxyhydrogensilane is used to condense the LSR rubber containing vinyl silicone oil and white carbon black to complete the triacyloxy end-capping; the addition-type LSR base rubber is converted into a deacidified RTV rubber, and a new formula and new process for room temperature vulcanized deacidified silicone rubber are obtained. Taking into account the physical properties of addition-type silicone rubber and the bonding strength of condensation-type silicone rubber, the room temperature vulcanized deacidified silicone rubber performs a hydroxyl deep treatment on the base rubber of high filling rate fumed white carbon black, so that the strength of the silicone rubber body can reach more than 4MPa after contact with moisture and curing, and the elongation is ≥200%.

[0040] This room temperature vulcanized deacidified silicone rubber has the advantages of safety, non-toxicity, strong bonding, mild curing conditions, and convenient construction and operation. It can achieve 100% cohesive failure for bonding of various polar plastics, inorganic non-metallic materials such as glass, ceramics, cement and other substrates. It can not only be used for bonding and molding of medical catheters, silicone baby products, silicone medical products, silicone health products, silicone miscellaneous products, silicone tableware, etc., but also for building sealing and caulking.

[0041] The present invention is further described in detail below in conjunction with specific implementation modes. DETAILED DESCRIPTION

[0042] Preparation of triacetoxyhydrogensilane:

[0043] 122.2 g of commercially available trimethoxyhydrogensilane (1 mol) was added to a reaction vessel equipped with a temperature control device, a stirring device and a distillation device, and then 5 g of a cationic resin was added and stirred for 5 minutes. Then, 306.27 g of acetic anhydride (3 mol) was added to the reaction vessel, and the temperature of the reaction system was controlled to be 60-65° C. The boiling point of methyl acetate generated during the reaction was 57.8° C. The material temperature was controlled, and the by-product methyl acetate was continuously removed so that the reaction proceeded to the right. The reaction was carried out for 4-5 hours; the cationic resin was filtered out, and then the small molecules were removed by reduced pressure distillation to obtain about 200 g of triacetoxyhydrogensilane.

[0044] Embodiment 1:

[0045] S1: Wet treatment of vinyl-terminated silicone oil and hydrophilic fumed silica:

[0046] 100 parts by weight of vinyl-terminated silicone oil with a viscosity of 1000 cp and 20 parts by weight of a 2 / g of hydrophilic fumed silica is weighed into a kneader and 4 parts by weight of hexamethyldisilazane is added. The material temperature is controlled at 60°C for low-temperature kneading for 4 hours. Then, it is kneaded at 90°C for 2 hours, and 2 parts by weight of distilled water are added to hydrolyze the residual hexamethylsilazane into siloxane and amine. Finally, the material is heated to 180°C and ammonia and other small molecules are removed under reduced pressure. The material is cooled and discharged to obtain a uniformly kneaded base rubber containing ethylene silicone oil and silica;

[0047] S2: At 100°C, add 10 ppm of Karstedt platinum catalyst and 5 parts by weight of triacetoxyhydrosilane to the total rubber compound and react for 3 hours to end-cap the vinyl silicone oil in the base rubber to form a triacetoxy-terminated prepolymer;

[0048] S3: The triacyloxy-terminated prepolymer obtained in S2 is cooled to room temperature, 1 part by weight of methyltriacetoxysilane, 0.2 parts by weight of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.05 parts by weight of dibutyltin dilaurate and 0.05 parts by weight of dibutyltin dilaurate are added, stirred evenly, and packaged to obtain a transparent deacidified RTV-1 finished product.

[0049] Embodiment 2:

[0050] S1: Wet treatment of vinyl-terminated silicone oil and hydrophilic fumed silica:

[0051] 100 parts by weight of a vinyl-terminated silicone oil with a viscosity of 3000 cp and 20 parts by weight of a silicone oil with a specific surface area of ​​150 m 2 / g of hydrophilic fumed silica is weighed into a kneader and 4 parts by weight of hexamethyldisilazane is added. The material temperature is controlled at 70°C for low-temperature kneading for 3 hours. Then, it is kneaded at 95°C for 2 hours, and 2 parts by weight of distilled water are added to hydrolyze the residual hexamethylsilazane into siloxane and amine. Finally, the material is heated to 180°C and ammonia and other small molecules are removed under reduced pressure. The material is cooled and discharged to obtain a uniformly kneaded base rubber containing ethylene silicone oil and silica;

[0052] S2: At 80°C, add 8 ppm of Karstedt platinum catalyst and 2.9 parts by weight of triacetoxyhydrosilane to the total rubber compound and react for 3 hours to end-cap the vinyl silicone oil in the base rubber to form a triacetoxy-terminated prepolymer;

[0053] S3: The triacyloxy-terminated prepolymer obtained in S2 is cooled to room temperature, 2 parts by weight of ethyltriacetoxysilane, 0.5 parts by weight of 3-(methacryloyloxy)propyltrimethoxysilane, and 2 parts by weight of n-butyl titanate are added, stirred evenly, and packaged to obtain a transparent deacidified RTV-1 finished product.

[0054] Embodiment 3:

[0055] S1: Wet treatment of vinyl-terminated silicone oil and hydrophilic fumed silica:

[0056] 100 parts by weight of vinyl-terminated silicone oil with a viscosity of 20,000 cp and 20 parts by weight of a silicone rubber with a specific surface area of ​​150 m 2 / g of hydrophilic fumed silica is weighed into a kneader, and 5 parts by weight of hexamethyldisilazane is added. The material temperature is controlled at 65°C for low-temperature kneading for 3.5 hours. Then, knead at 100°C for 2 hours, and 2.5 parts by weight of distilled water are added to hydrolyze the residual hexamethylsilazane into siloxane and amine. Finally, the material is heated to 180°C and ammonia and other small molecules are removed under reduced pressure. The material is cooled and discharged to obtain a uniformly kneaded base rubber containing ethylene silicone oil and silica;

[0057] S2: At 120°C, add 5 ppm of Speier platinum catalyst and 1.5 parts by weight of triacetoxyhydrosilane to the total rubber concentration, and react for 4 hours to end-cap the vinyl silicone oil in the base rubber to form a triacetoxy-terminated prepolymer;

[0058] S3: The triacyloxy-terminated prepolymer obtained in S2 is cooled to room temperature, 3 parts by weight of vinyl triacetoxysilane, 1.0 parts by weight of di-tert-butoxy diacetoxysilane, and 0.2 parts by weight of chelated tin are added, stirred evenly, and packaged to obtain a transparent deacidified RTV-1 finished product.

[0059] Embodiment 4:

[0060] S1: Wet treatment of vinyl-terminated silicone oil and hydrophilic fumed silica:

[0061] 100 parts by weight of a vinyl-terminated silicone oil with a viscosity of 50,000 cp and 25 parts by weight of a silicone oil with a specific surface area of ​​150 m 2 / g of hydrophilic fumed silica is weighed into a kneader and 5 parts by weight of hexamethyldisilazane is added. The material temperature is controlled at 60°C for low-temperature kneading for 4 hours. Then, it is kneaded at 95°C for 2 hours, and 2.5 parts by weight of distilled water are added to hydrolyze the residual hexamethylsilazane into siloxane and amine. Finally, the material is heated to 180°C and ammonia and other small molecules are removed under reduced pressure. The material is cooled and discharged to obtain a uniformly kneaded base rubber containing ethylene silicone oil and silica;

[0062] S2: At 80°C, add 5 ppm of Speier platinum catalyst and 1.2 parts by weight of triacetoxyhydrosilane to the total rubber concentration, and react for 2 hours to end-cap the vinyl silicone oil in the base rubber to form a triacetoxy-terminated prepolymer;

[0063] S3: The triacyloxy-terminated prepolymer obtained in S2 is cooled to room temperature, 4 parts by weight of ethyltriacetoxysilane, 1.5 parts by weight of di-tert-butoxydiacetoxysilane, and 0.5 parts by weight of bismuth cyclohexaneate are added, stirred evenly, and packaged to obtain a transparent deacidified RTV-1 finished product.

[0064] Embodiment 5:

[0065] S1: Wet treatment of vinyl-terminated silicone oil and hydrophilic fumed silica:

[0066] 100 parts by weight of a vinyl-terminated silicone oil with a viscosity of 50,000 cp and 25 parts by weight of a silicone oil with a specific surface area of ​​200 m 2 / g of hydrophilic fumed silica is weighed into a kneader and 5 parts by weight of hexamethyldisilazane is added. The material temperature is controlled at 70°C for low-temperature kneading for 3 hours. Then, it is kneaded at 100°C for 2 hours, and 2.5 parts by weight of distilled water are added to hydrolyze the residual hexamethylsilazane into siloxane and amine. Finally, the material is heated to 180°C and ammonia and other small molecules are removed under reduced pressure. The material is cooled and discharged to obtain a uniformly kneaded base rubber containing ethylene silicone oil and silica;

[0067] S2: At 90°C, add 3 ppm of Karstedt platinum catalyst and 1.2 parts by weight of triacetoxyhydrosilane to the total rubber concentration, and react for 3 hours to end-cap the vinyl silicone oil in the base rubber to form a triacetoxy-terminated prepolymer;

[0068] S3: The triacyloxy-terminated prepolymer obtained in S2 is cooled to room temperature, 5 parts by weight of vinyl triacetoxysilane, 1 part by weight of di-tert-butoxy diacetoxysilane, 1 part by weight of 3-(methacryloyloxy)propyl trimethoxysilane, and 3 parts by weight of bismuth cyclohexane are added, stirred evenly, and packaged to obtain a transparent deacidified RTV-1 finished product.

[0069] Embodiment 6:

[0070] S1: Wet treatment of vinyl-terminated silicone oil and hydrophilic fumed silica:

[0071] 150 parts by weight of a vinyl-terminated silicone oil with a viscosity of 70,000 cp and 25 parts by weight of a silicone oil with a specific surface area of ​​200 m 2 / g of hydrophilic fumed silica is weighed into a kneader and 1 part by weight of hexamethyldisilazane is added. The material temperature is controlled at 63°C for low-temperature kneading for 4 hours. Then, it is kneaded at 95°C for 2 hours, and 2.5 parts by weight of distilled water are added to hydrolyze the residual hexamethylsilazane into siloxane and amine. Finally, the material is heated to 180°C and ammonia and other small molecules are removed under reduced pressure. The material is cooled and discharged to obtain a uniformly kneaded base rubber containing ethylene silicone oil and silica;

[0072] S2: At 95°C, add 1 ppm of Karstedt platinum catalyst and 1.2 parts by weight of triacetoxyhydrosilane to the total rubber concentration, and react for 4 hours to end-cap the vinyl silicone oil in the base rubber to form a triacetoxy-terminated prepolymer;

[0073] S3: The triacyloxy-terminated prepolymer obtained in S2 is cooled to room temperature, 4 parts by weight of vinyl triacetoxysilane, 0.35 parts by weight of γ-(2,3-epoxypropoxy)propyl trimethoxysilane, 0.25 parts by weight of 3-(methacryloyloxy)propyl trimethoxysilane, and 2.5 parts by weight of isopropyl titanate are added, stirred evenly, and packaged to obtain a transparent deacidified RTV-1 finished product.

[0074] Embodiment 7:

[0075] S1: Wet treatment of vinyl-terminated silicone oil and hydrophilic fumed silica:

[0076] 120 parts by weight of vinyl-terminated silicone oil with a viscosity of 85,000 cp and 25 parts by weight of a polyvinyl-terminated silicone oil with a specific surface area of ​​250 m 2 / g of hydrophilic fumed silica is weighed into a kneader and 2 parts by weight of hexamethyldisilazane is added. The material temperature is controlled at 68°C for low-temperature kneading for 3 hours. Then, it is kneaded at 100°C for 2 hours, and 2.5 parts by weight of distilled water are added to hydrolyze the residual hexamethylsilazane into siloxane and amine. Finally, the material is heated to 180°C and ammonia and other small molecules are removed under reduced pressure. The material is cooled and discharged to obtain a uniformly kneaded base rubber containing ethylene silicone oil and silica;

[0077] S2: At 110°C, add 2 ppm of Karstedt platinum catalyst and 1 part by weight of triacetoxyhydrosilane to the total rubber concentration, and react for 3 hours to end-cap the vinyl silicone oil in the base rubber to form a triacetoxy-terminated prepolymer;

[0078] S3: The triacyloxy-terminated prepolymer obtained in S2 is cooled to room temperature, 3 parts by weight of vinyl triacetoxysilane, 0.8 parts by weight of di-tert-butoxy diacetoxy silane, 0.3 parts by weight of γ-(2,3-epoxypropoxy)propyl trimethoxy silane, 0.5 parts by weight of bismuth cyclohexane acid and 0.5 parts by weight of isopropyl titanate are added, stirred evenly, and packaged to obtain a transparent deacidified RTV-1 finished product.

[0079] Embodiment 8:

[0080] S1: Wet treatment of vinyl-terminated silicone oil and hydrophilic fumed silica:

[0081] 130 parts by weight of vinyl-terminated silicone oil with a viscosity of 100,000 cp and 25 parts by weight of a specific surface area of ​​300 m 2 / g of hydrophilic fumed silica is weighed into a kneader and 3 parts by weight of hexamethyldisilazane is added. The material temperature is controlled at 65°C for low-temperature kneading for 3 hours. Then, it is kneaded at 100°C for 2 hours, and 2.5 parts by weight of distilled water are added to hydrolyze the residual hexamethylsilazane into siloxane and amine. Finally, the material is heated to 180°C and ammonia and other small molecules are removed under reduced pressure. The material is cooled and discharged to obtain a uniformly kneaded base rubber containing ethylene silicone oil and silica;

[0082] S2: At 120°C, add 4 ppm of Karstedt platinum catalyst and 1 part by weight of triacetoxyhydrosilane to the total rubber concentration, and react for 2.5 hours to end-cap the vinyl silicone oil in the base rubber to form a triacetoxy-terminated prepolymer;

[0083] S3: Cool the triacyloxy-terminated prepolymer obtained in S2 to room temperature, add 1 part by weight of methyltriacetoxysilane, 0.1 part by weight of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.1 part by weight of 3-(methacryloyloxy)propyltrimethoxysilane, and 1.5 parts by weight of bismuth cyclohexaneate, stir evenly, and package to obtain a transparent deacidified RTV-1 finished product.

[0084] Detection:

[0085] The glue is applied in a constant temperature and humidity environment of 25°C and 50% RH for room temperature moisture curing.

[0086] According to GB 16776-2005 and GB / T 27570-2011, the surface drying time is measured by scraping 2mm film.

[0087] After curing for 168 h, standard dumbbell-shaped specimens were cut to measure the tensile strength, elongation at break, and glass substrate adhesion test.

[0088] The test results are shown in Table 1 below:

[0089] Table 1 Product performance test data of Examples 1 to 8

[0090] Example 1 2 3 4 5 6 7 8 Surface drying time (min) 13 12 10 9 6 5 5 4 Tensile strength(MPa) 3.27 3.65 4.04 4.52 4.75 4.66 4.86 5.10 Hardness(Shore A) 52 47 35 31 38 35 38 40 Elongation at break (%) 55 120 350 470 430 485 510 460 <![CDATA[Hand-pulling adhesion test (1) > Cohesive failure Cohesive failure Cohesive failure Cohesive failure Cohesive failure Cohesive failure Cohesive failure Cohesive failure

[0091] Note:

[0092] (1) The hand-pull adhesion test is carried out in accordance with GB 16776-2005 on glass. After curing, the adhesive layer is peeled off by hand at 180° to determine the damage form of the adhesive layer.

[0093] It can be seen from the performance test data in Table 1 that the base rubber prepared by the wet process of treating white carbon black with addition-type liquid silicone rubber in the present invention is terminated by catalytic reaction with triacetoxyhydrogensilane. The prepolymer that can be added and vulcanized is converted into a condensation-type prepolymer that can react in contact with moisture, completing the conversion of the reaction activity of LSR-RTV; finally, a crosslinking agent, a silane coupling agent, a metal catalyst, etc. are added to obtain a room temperature moisture-vulcanized high-strength silicone rubber. This technical route avoids the contradiction between the surface treatment of α,ω-dihydroxy polydimethylsiloxane and reinforcing filler in the traditional RTV process, thereby breaking through the shackles of the physical properties of deacidified RTV-1. The room temperature vulcanized deacidified silicone rubber obtained by the new formula and new process of the present invention takes into account the advantages of high bulk strength, high elongation at break of LSR and strong adhesion of RTV. After vulcanization in contact with moisture, the bulk strength of the silicone rubber can reach more than 4MPa, and the elongation is ≥200%.

[0094] It can be seen from the data in Table 1 that with the increase of the viscosity of the vinyl silicone oil, the surface drying time of the RTV base glue in step S1 gradually shortens. This is because as the molecular chain of the vinyl silicone oil becomes larger, the absolute content of acetoxysilane at both ends of the silicone oil decreases, the amount of moisture required for curing is low, and a dense crust is formed on the surface more quickly.

[0095] When the viscosity of vinyl silicone oil is 20000-50000cp, the product has better body strength and elongation performance, because the length of the vinyl silicone oil molecular chain in the base glue directly affects the aggregation degree of the crosslinking points of the moisture-curing colloid, which will affect the strength and elongation of the final product. Therefore, the viscosity of vinyl silicone oil is preferably 20000-50000cp, and the comprehensive performance of the obtained product is better. Further increasing the viscosity of vinyl silicone oil can obtain a higher strength glue, but it will cause the viscosity of the glue to be high before curing, large extrusion resistance, high glue pressure, and inconvenience in construction.

[0096] Comparing the schemes of Example 4 and Example 3, it can be seen that the colloid strength obtained by moisture curing increased by 0.5MPa, but the elongation increased by about 100%. The reason for this is that, on the one hand, it is attributed to the reinforcing effect of hydrophilic fumed silica, and on the other hand, the crosslinking agent is replaced by ethyltriacetoxysilane from methyltriacetoxysilane, which has a large reaction steric hindrance and low hydrolysis reaction activity, and further reduces the crosslinking point density, so the colloid elongation is significantly improved. At the same time, in Example 5, the increase in the specific surface area of ​​hydrophilic fumed silica also has a great influence on the reinforcement effect, and the strength of the colloid body is improved. In Examples 7 and 8, the viscosity of the vinyl silicone oil and the specific surface area of ​​the reinforcing fumed silica are increased at the same time, and the RTV extrusion before curing is difficult, but the obtained colloid strength will be further improved.

[0097] After 7 days of room temperature moisture reaction, the colloid gradually solidified and formed a bond to the substrate, which could not be completely peeled off from the glass. If it was forcibly peeled off, damage would occur from within the adhesive layer, and the bond to the substrate could reach 100% cohesive failure.

[0098] This room temperature vulcanized deacidified silicone rubber has the advantages of safety, non-toxicity, strong bonding, mild curing conditions, and convenient construction and operation. It has good bonding to a variety of polar plastics, inorganic non-metallic materials such as glass, ceramics, cement and other substrates. It can not only be used for bonding and molding medical catheters, silicone baby products, silicone medical products, silicone health products, silicone miscellaneous products, silicone tableware, etc., but also for building sealing and caulking.

[0099] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A room temperature vulcanized deacidified silicone rubber, characterized in that: In parts by mass, including: 100-150 parts of vinyl-terminated silicone oil, 10-30 parts of hydrophilic fumed silica, 1-6 parts of hexamethyldisilazane, 1-10 ppm of platinum catalyst, 1-5 parts of triacetoxyhydrosilane, 1-5 parts of acidic crosslinking agent, 0.2-2 parts of tackifying coupling agent, and 0.1-3 parts of catalyst; The triacetoxyhydrogensilane is synthesized according to the following steps: Add trimethoxyhydrogensilane to a reaction vessel equipped with a temperature control device, a stirring device and a distillation device, then add a catalyst and stir for at least 5 minutes, then add acetic anhydride to the reaction vessel so that the molar ratio of acetic anhydride to trimethoxyhydrogensilane is 3:1, and the catalyst is a cationic resin; control the temperature of the reaction system to 60-65°C, continuously remove the by-product methyl acetate during the reaction so that the reaction proceeds to the right, and react for 4-5 hours; filter to remove the catalyst, and then remove small molecules by reduced pressure distillation to obtain triacetoxyhydrogensilane; The synthetic reaction formula is as follows:

2. The room temperature vulcanized deacidified silicone rubber according to claim 1, characterized in that: The viscosity of the vinyl-terminated silicone oil is 1000-100000cp.

3. The room temperature vulcanized deacidified silicone rubber according to claim 2, characterized in that: The viscosity of the vinyl-terminated silicone oil is 20,000-50,000 cp.

4. The room temperature vulcanized deacidified silicone rubber according to claim 1, characterized in that: The specific surface area of ​​the hydrophilic fumed silica is 100 to 300 m 2 / g.

5. The room temperature vulcanized deacidified silicone rubber according to claim 1, characterized in that: The platinum catalyst is a Karstedt-type platinum catalyst or a Speier-type platinum catalyst.

6. The room temperature vulcanized deacidified silicone rubber according to claim 1, characterized in that: The acidic crosslinking agent is one or a mixture of methyl triacetoxysilane, ethyl triacetoxysilane and vinyl triacetoxysilane.

7. The room temperature vulcanized deacidified silicone rubber according to claim 1, characterized in that: The adhesion-enhancing coupling agent is one or a mixture of gamma-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane and di-tert-butoxydiacetoxysilane.

8. The room temperature vulcanized deacidified silicone rubber according to claim 1, characterized in that: The catalyst is one of dibutyltin dilaurate, dibutyltin diacetate, chelated tin, n-butyl titanate, isopropyl titanate or bismuth cyclohexaneate.

9. A method for preparing room temperature vulcanized deacidified silicone rubber according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: According to the formula, add the vinyl-terminated silicone oil to the kneader, add the hydrophilic fumed silica and hexamethyldisilazane to the kneader in batches, stir until the fumed silica is evenly powdered, then control the material temperature at 60-70°C for kneading for 3-4 hours, increase the temperature to 90-100°C for kneading for 2 hours, then add distilled water to the system to hydrolyze the residual hexamethylsilazane into siloxane and amine; finally, heat the material to 180°C, remove ammonia and other small molecules under reduced pressure; cool the material and obtain a uniformly kneaded base rubber containing vinyl silicone oil and silica; S2: synthesizing triacetoxyhydrogensilane according to the method of claim 1; controlling the temperature of the base rubber obtained in S1 at 80-120°C, adding a platinum catalyst and triacetoxyhydrogensilane, reacting for 2-4 hours, completing the end-capping of the vinyl silicone oil in the base rubber to form a triacyloxy-terminated prepolymer; the synthetic reaction formula is as follows: S3: After cooling the triacyloxy-terminated prepolymer obtained in S2 to room temperature, an acidic crosslinking agent, a tackifying coupling agent, and a catalyst are added, and stirred evenly to obtain room temperature vulcanized deacidified silicone rubber.

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