High-temperature-resistant polydimethylsiloxane composition and preparation method thereof

Abstract

The invention relates to the technical field of polysiloxane, and discloses a high-temperature-resistant polydimethylsiloxane composition and a preparation method thereof.The high-temperature-resistant polydimethylsiloxane composition is prepared from, by mass, polydimethylsiloxane, an additive A accounting for 0.002-1% of the mass of the polydimethylsiloxane and an additive B accounting for 0.01-5% of the mass of the polydimethylsiloxane; the additive A comprises one or more of organic compounds containing variable valence metals; and the additive B comprises one or more of compounds containing hindered amine or arylamine structures. By adding the additive A and the additive B with synergistic oxidation resistance, the high temperature resistance and oxidation resistance of the polydimethylsiloxane can be better improved, so that the gelation time of the polydimethylsiloxane composition is greatly prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of polysiloxanes, and in particular to a high-temperature resistant polydimethylsiloxane composition and a preparation method thereof. Background Art

[0002] Polydimethylsiloxane is an ideal high-temperature lubricating heat transfer material. How to better improve the thermal oxidation stability of polysiloxane so that it can be used for a long time at a higher temperature without gelling is a problem that technical workers often consider.

[0003] There are generally two methods currently adopted. The first method is to improve the molecular structure of silicone oil, and the second method is to use an effective thermal oxidation stabilizer. Adding a small amount of thermal oxidation stabilizer to silicone oil is an economical and effective method. The thermal oxidation stabilizer can improve the thermal oxidation stability of silicone oil without adverse effects. For example, the invention patent with publication number CN1117124C discloses an oxidation-resistant polysiloxane composition, the components and contents of the polysiloxane composition are as follows (parts by weight): 100 polysiloxane rubber, 0.1-15 Fe-containing polysilazane; the polysiloxane rubber is silicone oil, silicone grease, silicone rubber rubber, and various commercial mixed rubbers or silicone resins; the silicone rubber rubber has the following components and contents (parts by weight): 100 silicone rubber raw rubber, 0.1-15 Fe-containing polysilazane; 2 10-40, precipitation method SiO 2 0-60, catalyst 0-2, crosslinking agent or vulcanizing agent 0.3-6; the general formula of the Fe-containing polysilazane is (A) and (B): R1, R2 = CH 3 , Ph, may be the same or different; n = 3-600; R3 = CH 3 , Ph, H or x=1-3; (A) R1, R2=CH 3 , Ph, may be the same or different; R3=CH 3 , Ph, H or x=1-3. The composition uses an Fe-containing polysilazane as an additive, thereby improving the thermal oxidation resistance of polysiloxane, and various commercial silicone oils, silicone rubbers and silicone resins can be used to replace the polysiloxane rubber of the formula to improve their high temperature resistance in the air. However, the structure of the Fe-containing polysilazane added in the patent is relatively complex, and in addition to adding the Fe-containing polysilazane as an antioxidant, a variety of additives are also added to the polysiloxane rubber, which increases the difficulty and cost of the preparation process. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a high temperature resistant polydimethylsiloxane composition and a preparation method thereof. By optimizing the formula of the combined additives, the polydimethylsiloxane composition has a higher operating temperature and better antioxidant performance, thereby improving the stability of polydimethylsiloxane at high temperatures. In addition, the preparation process is relatively simple to operate and the use effect is excellent.

[0005] The purpose of the present invention is achieved through the following technical solutions: In the first aspect, the present invention provides a high temperature resistant polydimethylsiloxane composition, comprising the following components: polydimethylsiloxane and an additive A accounting for 0.002-1% of the mass of the polydimethylsiloxane, and an additive B accounting for 0.01-5% of the mass of the polydimethylsiloxane; the additive A comprises one or more organic compounds containing variable valence metals; the additive B comprises one or more compounds containing hindered amine or aromatic amine structures.

[0006] Under high-temperature oxidation conditions, antioxidant additives will have an antioxidant effect and be continuously consumed, resulting in a decreasing performance trend of the oil after oxidation. The present invention improves the high-temperature antioxidant performance of polydimethylsiloxane by adding a synergistic antioxidant.

[0007] The specific antioxidant mechanism is: Additive A (metal-containing organic antioxidant) has a strong ability to scavenge free radicals, which can significantly improve the antioxidant property. Since polydimethylsiloxane is easily oxidized to form compounds such as aldehydes, ketones and acids under high temperature conditions, the antioxidant capacity of additive A will be reduced. When additive A is compounded with additive B (amine antioxidant), the active hydrogen in additive A can be transferred to the amine antioxidant, thereby regenerating the amine antioxidant. There is a synergistic effect between the two, which can better inhibit the oxidation of oil products. Further, when the organic amine antioxidant is specifically an aniline structure antioxidant, aniline will also react with free radicals in the system to form amine radicals, alkanes and hydroperoxides. Among them, the peroxy radicals in the hydroperoxide will be converted to form nitroxide radicals, which will then react with alkoxy radicals, and aniline can be re-formed by generating ketone compounds. At the same time, N-hydroxyaniline will be generated to continue to react with peroxy radicals to produce hydroperoxides and nitroxide radicals. This cycle is repeated continuously, and the high temperature resistance and antioxidant efficiency are greatly improved by continuously consuming free radicals in the system.

[0008] Preferably, the high temperature resistant polydimethylsiloxane composition comprises the following components: polydimethylsiloxane, an additive A accounting for 0.01-1% by weight of the polydimethylsiloxane, and an additive B accounting for 0.02-5% by weight of the polydimethylsiloxane.

[0009] Preferably, the polydimethylsiloxane is methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methylphenyl silicone oil or fluorine-containing silicone oil.

[0010] Preferably, the kinematic viscosity of the polydimethylsiloxane at 25°C is 5-1000 mm 2 / s; More preferably, the kinematic viscosity of the polydimethylsiloxane at 25°C is 5-500mm 2 / s.

[0011] Preferably, the acid value of the polydimethylsiloxane is less than 0.05 mg KOH / g, and the content of volatile small molecules therein is less than 0.3%.

[0012] The volatile small molecule content in polydimethylsiloxane was detected after being stored in an oven at 150°C for 3 h.

[0013] Preferably, the variable-valent metal in the additive A is one or more of iron, copper, chromium, platinum, cerium, silver and molybdenum.

[0014] Preferably, the additive A is one or more of cerium acetylacetonate, iron acetylacetonate, platinum acetylacetonate, ferrocene, cerium 2-ethylhexanoate, silver 2-ethylhexanoate, cerium trifluoromethanesulfonate and dialkyl molybdenum dithiophosphate.

[0015] Preferably, the additive B is one or more of tetracarboxamide, benzimidazole, dihydroquinoline, 4-oxy-TEMPO and N-cyclohexylthiophthalimide.

[0016] The additives A and B in the present invention have good solubility in polydimethylsiloxane and can be evenly dispersed therein for a long time, thereby further ensuring that the polydimethylsiloxane composition has good stability.

[0017] Preferably, the added mass of the additive A is less than the added mass of the additive B.

[0018] Preferably, the mass ratio of the additive A to the additive B is 1:2-50.

[0019] In a second aspect, the present invention also provides a method for preparing a high temperature resistant polydimethylsiloxane composition, comprising the following steps: (1) pre-treating octamethylcyclotetrasiloxane (D4) or dimethylsiloxane mixed ring (DMC); (2) using the treated octamethylcyclotetrasiloxane or dimethylsiloxane mixed ring to synthesize polydimethylsiloxane; (3) Under the protection of inert gas, polydimethylsiloxane, additive A and additive B are stirred and mixed and heated to react, and then cooled to room temperature to obtain a high temperature resistant polydimethylsiloxane composition.

[0020] Preferably, the pretreatment comprises adsorption treatment and reduced pressure distillation treatment performed sequentially.

[0021] Preferably, the adsorption treatment is: adding 0.01-5.0wt% (relative to the mass of D4 or DMC) of adsorbent to D4 or DMC, stirring for adsorption and filtering after adsorption. The adsorbent includes one or more of zeolite powder, activated carbon fiber felt, polyvinyl alcohol and crown ether.

[0022] Preferably, the vacuum distillation treatment is: heating the adsorbed D4 or DMC to 80-90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5-10wt% of D4 or DMC and then stopping the vacuum distillation, at which time the water content in D4 or DMC is below 50ppm.

[0023] The metal ion and chloride ion impurities in D4 or DMC are removed by adsorption treatment, the water content in D4 or DMC is reduced by reduced pressure distillation treatment, and the pretreatment of polydimethylsiloxane can help additives A and additive B to exert their effectiveness, further improving high temperature resistance and antioxidant properties.

[0024] Preferably, the inert gas is nitrogen or argon.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) Additive A and Additive B have synergistic antioxidant properties and can better improve the high-temperature antioxidant properties of polydimethylsiloxane; (2) By controlling the addition ratio of additive A and additive B, a better synergistic antioxidant effect can be achieved. In addition, by pre-treating the polydimethylsiloxane, the gel time of the polydimethylsiloxane composition can be greatly prolonged. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] Example 1 The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (cerium acetylacetonate) 0.2wt%; Additive B (dihydroquinoline) 0.4 wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0028] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0029] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0030] (3) Under the protection of inert gas, 0.2 wt% of cerium acetylacetonate and 0.4 wt% of dihydroquinoline were added to polydimethylsiloxane, and the mixture was heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and the mixture was filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0031] Example 2 Additive A was changed to 0.015 wt % of platinum acetylacetonate, and the rest was the same as in Example 1.

[0032] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (platinum acetylacetonate) 0.015wt%; Additive B (dihydroquinoline) 0.4 wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0033] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0034] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0035] (3) Under the protection of inert gas, 0.015 wt% of platinum acetylacetonate and 0.4 wt% of dihydroquinoline were added to polydimethylsiloxane, and the mixture was heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and the mixture was filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0036] Example 3 The additive A was changed to 0.02 wt % of silver 2-ethylhexanoate, and the rest was the same as in Example 1.

[0037] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (silver 2-ethylhexanoate) 0.02wt%; Additive B (dihydroquinoline) 0.4 wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0038] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0039] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0040] (3) Under the protection of inert gas, 0.02 wt% of silver 2-ethylhexanoate and 0.4 wt% of dihydroquinoline were added to polydimethylsiloxane, and the mixture was heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and the mixture was filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0041] Example 4 Additive B was changed to 0.4 wt % of N-cyclohexylthiophthalimide, and the rest was the same as in Example 1.

[0042] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (cerium acetylacetonate) 0.2wt%; Additive B (N-cyclohexylthiophthalimide) 0.4wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0043] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0044] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0045] (3) Under the protection of inert gas, 0.2 wt% of cerium acetylacetonate and 0.4 wt% of N-cyclohexylthiophthalimide were added to polydimethylsiloxane, mixed, and heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0046] Example 5 Additive A was changed to 0.05 wt % of cerium 2-ethylhexanoate, and additive B was changed to 0.1 wt % of tetracarboxamide. Others were the same as in Example 1.

[0047] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (cerium 2-ethylhexanoate) 0.05wt%; Additive B (tetracarboxamide) 0.1wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0048] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0049] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0050] (3) Under the protection of inert gas, 0.05 wt% of cerium 2-ethylhexanoate and 0.1 wt% of tetracarboxamide were added to polydimethylsiloxane, mixed, and heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0051] Example 6 Additive A was changed to 0.05 wt % of ferric acetylacetonate, and additive B was changed to 0.1 wt % of dihydroquinoline. The rest was the same as in Example 1.

[0052] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (ferrous acetylacetonate) 0.05wt%; Additive B (dihydroquinoline) 0.1wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0053] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0054] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0055] (3) Under the protection of inert gas, 0.05 wt% of ferric acetylacetonate and 0.1 wt% of dihydroquinoline were added to polydimethylsiloxane, mixed, and heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0056] Example 7 Additive A was changed to 0.1 wt % of cerium trifluoromethanesulfonate, and additive B was changed to 0.25 wt % of 4-oxy-TEMPO. The rest was the same as in Example 1.

[0057] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (cerium trifluoromethanesulfonate) 0.1wt%; Additive B (4-oxy-TEMPO) 0.25 wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0058] (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0059] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0060] (3) Under the protection of inert gas, 0.1 wt% of cerium trifluoromethanesulfonate and 0.25 wt% of 4-oxy-TEMPO were added to polydimethylsiloxane, and the mixture was heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature, and the mixture was filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0061] Example 8 Additive A was changed to 0.05 wt % of dialkyl dithiophosphate molybdenum, and additive B was changed to 0.25 wt % of 4-oxy-TEMPO. The rest was the same as in Example 1.

[0062] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (molybdenum dialkyl dithiophosphate) 0.05wt%; Additive B (4-oxy-TEMPO) 0.25 wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0063] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0064] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0065] (3) Under the protection of inert gas, 0.05 wt% of dialkyl dithiophosphate molybdenum and 0.25 wt% of 4-oxy-TEMPO were added to polydimethylsiloxane, and the mixture was heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature, and the mixture was filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0066] Example 9 Additive A was changed to 0.05 wt % of dialkyl dithiophosphate molybdenum, and additive B was changed to 0.4 wt % of benzimidazole. The rest was the same as in Example 1.

[0067] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (molybdenum dialkyl dithiophosphate) 0.05wt%; Additive B (benzimidazole) 0.4wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0068] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0069] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0070] (3) Under the protection of inert gas, 0.05 wt% of dialkyl dithiophosphate molybdenum and 0.4 wt% of benzimidazole were added to polydimethylsiloxane, and the mixture was heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature, and the mixture was filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0071] Example 10 The additive A was changed to 0.05 wt % of ferrocene, the additive B was changed to 0.1 wt % of tetracarboxamide, and the rest was the same as in Example 1.

[0072] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (ferrocene) 0.05wt%; Additive B (tetracarboxamide) 0.1wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0073] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0074] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0075] (3) Under the protection of inert gas, 0.05 wt% of ferrocene and 0.1 wt% of tetracarboxamide were added to polydimethylsiloxane, mixed, and heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0076] Embodiment 11 The kinematic viscosity of the polydimethylsiloxane at 25°C is changed to 350 mm 2 / s, and the rest is consistent with Example 1.

[0077] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0078] (2) The pre-treated D4 and 4.5 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, the kinematic viscosity of which at 25°C was 350 mm 2 / s.

[0079] (3) Under the protection of inert gas, 0.2 wt% of cerium acetylacetonate and 0.4 wt% of dihydroquinoline were added to polydimethylsiloxane, and the mixture was heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and the mixture was filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0080] Example 12 The 0.5 wt % activated carbon fiber felt was replaced with 0.2 wt % crown ether, and the rest was the same as in Example 1.

[0081] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.2 wt% of crown ether to D4, stirring for 2 h for adsorption treatment and filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4, and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0082] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0083] (3) Under the protection of inert gas, 0.2 wt% of cerium acetylacetonate and 0.4 wt% of dihydroquinoline were added to polydimethylsiloxane, and the mixture was heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and the mixture was filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0084] Comparative Example 1 The D4 raw material was not subjected to adsorption treatment, and the rest was the same as in Example 1.

[0085] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Octamethylcyclotetrasiloxane (D4) and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0086] (2) Under the protection of inert gas, 0.2 wt% of cerium acetylacetonate and 0.4 wt% of dihydroquinoline were added to polydimethylsiloxane, and the mixture was heated to 120° C. and stirred for reaction for 2 h. After completion, the mixture was cooled to room temperature and the mixture was filtered under reduced pressure to obtain a filtrate, thereby obtaining a high temperature resistant polydimethylsiloxane composition.

[0087] Comparative Example 2 No additive A was added, only 0.6 wt % of additive B was added, and the rest was the same as in Example 1.

[0088] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive B (dihydroquinoline) 0.6wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0089] Comparative Example 3 No additive B was added, only 0.6 wt % of additive A was added, and the rest was the same as in Example 1.

[0090] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (cerium acetylacetonate) 0.6wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0091] Comparative Example 4 The mass ratio of the added additives was adjusted to 0.4 wt % of cerium acetylacetonate and 0.2 wt % of dihydroquinoline, and the others were consistent with Example 1.

[0092] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (cerium acetylacetonate) 0.4wt%; Additive B (dihydroquinoline) 0.2wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0093] Comparative Example 5 The mass ratio of the added additives was adjusted to 0.1 wt % of ferrocene and 0.05 wt % of tetracarboxamide, and the rest was consistent with Example 10.

[0094] The high temperature resistant polydimethylsiloxane composition comprises the following components: Polydimethylsiloxane (kinematic viscosity at 25°C is 100 mm 2 / s); Additive A (ferrocene) 0.1wt%; Additive B (tetracarboxamide) 0.05wt%; The amounts of additive A and additive B added are calculated based on the mass percentage of polydimethylsiloxane.

[0095] Comparative Example 6 D4 was not subjected to adsorption treatment, and additives A and B were not added. The other conditions were the same as those in Example 1.

[0096] The preparation method of polydimethylsiloxane comprises the following steps: Octamethylcyclotetrasiloxane (D4) and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 hours under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0097] Comparative Example 7 Additives A and B were not added, and the rest was the same as in Example 1.

[0098] The preparation method of the high temperature resistant polydimethylsiloxane composition comprises the following steps: (1) Pre-treating octamethylcyclotetrasiloxane (D4): first adding 0.5 wt% of activated carbon fiber felt to D4, stirring for 2 h for adsorption treatment and then filtering; then heating the adsorbed D4 to 90°C for vacuum distillation, collecting the distillate until the mass of the distillate reaches 5 wt% of D4 and then stopping the vacuum distillation, at which time the water content in D4 is below 50 ppm.

[0099] (2) The pre-treated D4 and 8 wt% of methyl-terminated siloxane capping agent (MDM) were subjected to equilibrium reaction at 80°C for 4 h under the catalysis of activated clay, and then filtered and desorbed to synthesize polydimethylsiloxane, which had a kinematic viscosity of 100 mm at 25°C. 2 / s.

[0100] 50 grams of the polydimethylsiloxane composition / polydimethylsiloxane in the above Examples 1-12 and Comparative Examples 1-7 were each taken into a beaker and placed in an oven at 250° C. The time for gelation of each sample was recorded and the results are shown in Table 1. It can be seen from Table 1 that the polydimethylsiloxane composition prepared by the method provided by the present invention has obvious high temperature resistance and antioxidant properties.

[0101] Table 1 sample Gel time / day Example 1 68 Example 2 95 Example 3 59 Example 4 84 Example 5 39 Example 6 78 Example 7 64 Example 8 89 Example 9 71 Example 10 45 Embodiment 11 50 Example 12 61 Comparative Example 1 47 Comparative Example 2 34 Comparative Example 3 28 Comparative Example 4 42 Comparative Example 5 23 Comparative Example 6 1 Comparative Example 7 3 As shown in Table 1, the comparison between Examples 1-12 and Comparative Examples 1, 6, and 7 shows that the high-temperature antioxidant performance of the polydimethylsiloxane composition is better by adding additives A and additives B with synergistic antioxidant properties and pre-treating the polydimethylsiloxane. The comparison between Example 1 and Comparative Examples 2-3 shows that the high-temperature antioxidant performance of the polydimethylsiloxane composition obtained by adding additives A and additives B at the same time is better than that of adding additives A or additives B alone, and the gel time is longer. The comparison between Example 1 and Comparative Example 4 and Example 10 and Comparative Example 5 shows that the amount of additive A added must be less than the amount of additive B added to exert a better synergistic antioxidant effect.

[0102] In addition, since high-viscosity polysiloxane has a higher degree of polymerization and a larger molecular structure, heat is easily accumulated inside the molecules after being heated, which accelerates the breakage of the Si-O-Si main chain, resulting in a slightly shorter gel time in Example 11 compared to Example 1.

[0103] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high temperature resistant polydimethylsiloxane composition, characterized in that: The invention comprises the following components: polydimethylsiloxane, additive A accounting for 0.002-1% of the mass of polydimethylsiloxane, and additive B accounting for 0.01-5% of the mass of polydimethylsiloxane; the additive A comprises one or more organic compounds containing variable valence metals; the additive B comprises one or more compounds containing hindered amine or aromatic amine structures.

2. The high temperature resistant polydimethylsiloxane composition according to claim 1, characterized in that: The polydimethylsiloxane is methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methylphenyl silicone oil or fluorine-containing silicone oil.

3. The high temperature resistant polydimethylsiloxane composition according to claim 1, characterized in that: The kinematic viscosity of the polydimethylsiloxane at 25°C is 5-1000 mm 2 / s.

4. The high temperature resistant polydimethylsiloxane composition according to any one of claims 1 to 3, characterized in that: The acid value of the polydimethylsiloxane is less than 0.05 mg KOH / g, and the content of volatile small molecules therein is less than 0.3%.

5. The high temperature resistant polydimethylsiloxane composition according to claim 1, characterized in that: The variable valence metal in the additive A is one or more of iron, copper, chromium, platinum, cerium, silver and molybdenum.

6. The high temperature resistant polydimethylsiloxane composition according to claim 5, characterized in that: The additive A is one or more of cerium acetylacetonate, iron acetylacetonate, platinum acetylacetonate, ferrocene, cerium 2-ethylhexanoate, silver 2-ethylhexanoate, cerium trifluoromethanesulfonate and dialkyl molybdenum dithiophosphate.

7. The high temperature resistant polydimethylsiloxane composition according to claim 1, characterized in that: The additive B is one or more of tetracarboxamide, benzimidazole, dihydroquinoline, 4-oxy-TEMPO and N-cyclohexylthiophthalimide.

8. The high temperature resistant polydimethylsiloxane composition according to claim 1, 5, 6 or 7, characterized in that: The added mass of the additive A is less than the added mass of the additive B.

9. The high temperature resistant polydimethylsiloxane composition according to claim 8, characterized in that: The mass ratio of the additive A to the additive B is 1:2-50.

10. A method for preparing the high temperature resistant polydimethylsiloxane composition according to any one of claims 1 to 9, characterized in that: The steps include: (1) pre-treating octamethylcyclotetrasiloxane or dimethylsiloxane mixed ring; (2) using the treated octamethylcyclotetrasiloxane or dimethylsiloxane mixed ring to synthesize polydimethylsiloxane; (3) Under the protection of an inert gas, the polydimethylsiloxane, the additive A and the additive B are stirred and mixed, and the temperature is raised to react. After the reaction is completed, the temperature is lowered to room temperature to obtain a high temperature resistant polydimethylsiloxane composition.