Method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolysate

Abstract

The invention provides a method for synthesizing dimethyl silicone oil by using dimethyldichlorosilane hydrolysate as a raw material, which comprises the following steps: by using dimethyldichlorosilane hydrolysate as a raw material, adding an end-capping reagent and a phosphonitrile chloride catalyst, and reacting at 60-80 DEG C under negative pressure for 1-3 hours to obtain a prepolymer; and then adding a solid acid catalyst to react at normal pressure for 1-3 hours to obtain a polymerization intermediate, and removing the low-temperature to obtain a finished product. According to the method, the dimethyldichlorosilane hydrolysate is directly used as a raw material, compared with a traditional line or ring process, the step of loop line separation of the hydrolysate is omitted, the yield is higher than that of the ring process, a catalyst quenching agent does not need to be additionally added in the reaction, neutralization salt is avoided, and compared with the traditional process, the production process is simple, and the obvious cost advantage is achieved.

Description

Technical Field

[0001] The invention relates to a method for directly synthesizing dimethyl silicone oil by using dimethyldichlorosilane hydrolyzate, belonging to the technical field of polysiloxane synthesis. Background Art

[0002] Dimethyl silicone oil has excellent physical and chemical properties such as good heat resistance, weather resistance, high and low temperature resistance, physiological inertness, chemical stability, electrical insulation, compression resistance, shear resistance, low viscosity-temperature coefficient, low surface tension, etc. Depending on the molecular weight, methyl silicone oil can be a low-viscosity flowing liquid or an ultra-high-viscosity paste, and is widely used in cosmetics, pharmaceuticals, machinery, electrical, textile printing and dyeing, coatings and other fields.

[0003] At present, there are two main processes for preparing dimethyl silicone oil. One is to use dimethylsiloxane mixed ring body (DMC) or octamethylcyclotetrasiloxane (D4) as raw materials, and use tetramethylammonium hydroxide, potassium hydroxide, sulfuric acid and other acidic or alkaline equilibrium catalysts for ring-opening equilibrium reaction. The yield of this process is generally 80-87%; the other process is to use hydroxyl-terminated polydimethylsiloxane (linear body) as raw material and catalyze the preparation with non-equilibrium catalyst chlorophosphazene. The yield of this process is generally >90%. Both processes have certain disadvantages. (1) The raw material ring body or linear body used in both processes is obtained by ring-line separation of dimethyldichlorosilane hydrolyzate, and the raw material cost is high; (2) The production process using the ring body as raw material has a low conversion rate; (3) The linear body production process has a high conversion rate, but the catalyst needs to be additionally added with a neutralizer to quench the catalyst, which inevitably introduces impurities into the product. Summary of the invention

[0004] In view of the problems and shortcomings of the prior art, the present invention provides a method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolyzate, wherein dimethyldichlorosilane hydrolyzate is used as a raw material, a linear chlorophosphazene catalyst and a capping agent are added to obtain a prepolymer, and a solid acid catalyst is further added to react to prepare dimethyl silicone oil. The method has the advantages of simple process, easy availability of raw materials and high conversion rate, and has obvious cost advantages compared with traditional processes.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolyzate comprises the following steps: (1) adding dimethyldichlorosilane hydrolyzate, a capping agent and a chlorophosphazene catalyst into a reaction vessel, and reacting under negative pressure to obtain a prepolymer; (2) After returning to normal pressure, a solid acid catalyst is added to continue the reaction, and the polymerization intermediate is obtained by filtration, and further desulfurization is performed to obtain the finished product dimethyl silicone oil.

[0006] The dimethyldichlorosilane hydrolyzate in step (1) is a mixture of linear polysiloxane and cyclic polysiloxane, and the mass ratio of the linear body to the cyclic body is 7:3-5:5.

[0007] The end-capping agent in step (1) is linear polydimethylsiloxane MDnM, preferably one or more mixtures of hexamethyldisiloxane MM, octamethyltrisiloxane MDM, decamethyltetrasiloxane MDDM or dimethyl silicone oil with a viscosity lower than 20 cSt, more preferably dimethyl silicone oil with a viscosity of 5 cSt or 10 cSt.

[0008] The catalyst in step (1) is linear phosphazene chloride or a linear phosphazene chloride solution, and its structural formula is: ; The solvent of the linear phosphazene chloride solution is one or more of ethyl acetate, toluene, tetrachloroethane or dimethyl silicone oil with a viscosity of 50 cSt to 200 cSt.

[0009] The amount of catalyst added in step (1) is 1 ppm to 20 ppm, preferably 5 ppm, based on linear chlorophosphazene.

[0010] The reaction system pressure of step (1) is -80 kPa to -90 kPa; the reaction temperature is 60-80°C, preferably 70°C; and the reaction time is 1-3 h, preferably 1.5 h.

[0011] The solid acid catalyst in step (2) is any one of perfluorosulfonic acid type ion exchange resin, D61 macroporous strong acid cation exchange resin, acidic clay or styrene-divinylbenzene type strong acid cation exchange resin.

[0012] In the step (2), the reaction temperature is 60-80°C, preferably 70°C; the reaction time is 1-3h, preferably 1.5h.

[0013] The viscosity of the finished dimethyl silicone oil in step (2) is 50cp~1000cp.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The raw material used in the present invention is a direct product of the hydrolysis of dimethyldichlorosilane, and there is no need to remove the cyclosiloxane step. Compared with the raw materials DMC, D4 or filaments used in the traditional process, it has obvious cost advantages.

[0015] (2) The solid acid catalyst added in the present invention not only promotes the ring-opening polymerization, but also has the function of adsorbing the chlorophosphazene catalyst. Therefore, the present invention does not need to use a catalyst quencher, and the product purity is high.

[0016] (3) After the solid acid catalyst is used to adsorb the chlorophosphazene catalyst, the synergistic effect of the two enhances the resin ring-opening activity, thereby improving the conversion rate and raw material utilization rate. DETAILED DESCRIPTION

[0017] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0018] Preparation method of linear chlorophosphonitrile catalyst: 20.5 g of phosphorus pentachloride, 2.6 g of ammonium chloride and 100 mL of tetrachloroethane were added to a 250 ml three-necked flask, and refluxed at 150 ° C for 6 h. After the reaction was completed, it was cooled to room temperature and the reaction solution was injected into 100 ml of petroleum ether to precipitate. After the precipitate was washed with petroleum ether, the residual petroleum ether was removed under reduced pressure to obtain a linear chlorophosphazene catalyst.

[0019] In the dimethyldichlorosilane hydrolyzate used in the examples and comparative examples mentioned in the present application, the mass ratio of linear polysiloxane to cyclosiloxane is 6:4.

[0020] The method for evaluating whether there is any residual chlorophosphonitrile catalyst in the finished product in the embodiments and comparative examples mentioned in the present application is: the finished product is heated at 180°C for 12 hours, and the changes in viscosity and volatile matter (detection method: 200 degrees / 15 minutes) are detected. If there is no change, it means that there is no residual catalyst. If the viscosity becomes higher and the volatile matter increases, it means that there is residual catalyst, resulting in cracking of the finished product.

[0021] Example 1 3000g of dimethyldichlorosilane hydrolyzate, 195g of 5cSt dimethyl silicone oil, and 5ppm of chlorophosphazene catalyst were added to a three-necked flask, stirred and heated to 70°C, kept warm for 1.5h at -90kpa to obtain a prepolymer, then restored to normal pressure, maintained the temperature of the reaction system at 70°C, added 5wt% of styrene-divinylbenzene type strong acid cation exchange resin, continued to react for 1.5h, filtered to obtain a polymer intermediate, heated the intermediate to 180°C to degas, cooled and filtered to obtain a finished product. The finished product has a transparent appearance, a conversion rate of 91%, a viscosity of 367cP, and a volatile matter of 0.5%. The finished product has no change in viscosity and volatile matter when heated at 200°C for 12h.

[0022] Example 2 3000g of dimethyldichlorosilane hydrolyzate, 140g of 5cSt dimethyl silicone oil, and 5ppm of chlorophosphazene catalyst were added to a three-necked flask, stirred and heated to 70°C, kept warm for 1.5h at -90kpa to obtain a prepolymer, then restored to normal pressure, maintained the temperature of the reaction system at 70°C, added 5wt% of styrene-divinylbenzene type strong acid cation exchange resin, continued to react for 1.5h, filtered to obtain a polymer intermediate, heated the intermediate to 180°C to degas, cooled and filtered to obtain a finished product. The finished product has a transparent appearance, a conversion rate of 92%, a viscosity of 471cP, and a volatile matter of 0.43%. The finished product has no change in viscosity and volatile matter when heated at 200°C for 12h.

[0023] Example 3 3000g of dimethyldichlorosilane hydrolyzate, 90g of 5cSt dimethyl silicone oil, and 5ppm of chlorophosphazene catalyst were added to a three-necked flask, stirred and heated to 70°C, kept warm for 1.5h at -90kpa to obtain a prepolymer, then restored to normal pressure, maintained the temperature of the reaction system at 70°C, added 5wt% of styrene-divinylbenzene type strong acid cation exchange resin, continued to react for 1.5h, filtered to obtain a polymer intermediate, heated the intermediate to 180°C to degas, cooled and filtered to obtain a finished product. The finished product has a transparent appearance, a conversion rate of 91.7%, a viscosity of 945cP, and a volatile matter of 0.3%. The finished product has no change in viscosity and volatile matter when heated at 200°C for 12h.

[0024] Example 4 3000g of dimethyldichlorosilane hydrolyzate, 247g of 5cSt dimethyl silicone oil, and 5ppm of chlorophosphazene catalyst were added to a three-necked flask, stirred and heated to 70°C, kept warm for 1.5h at -90kpa to obtain a prepolymer, then restored to normal pressure, maintained the temperature of the reaction system at 70°C, added 5wt% of styrene-divinylbenzene type strong acid cation exchange resin, continued to react for 1.5h, filtered to obtain a polymer intermediate, heated the intermediate to 180°C to degas, cooled and filtered to obtain a finished product. The finished product has a transparent appearance, a conversion rate of 90.4%, a viscosity of 107cP, and a volatile matter of 0.52%. The finished product has no change in viscosity and volatile matter when heated at 200°C for 12h.

[0025] Example 5 3000g of dimethyldichlorosilane hydrolyzate, 300g of 5cSt dimethyl silicone oil, and 5ppm of chlorophosphazene catalyst were added to a three-necked flask, stirred and heated to 70°C, kept warm for 1.5h at -90kpa to obtain a prepolymer, then restored to normal pressure, maintained the temperature of the reaction system at 70°C, added 5wt% of styrene-divinylbenzene type strong acid cation exchange resin, continued to react for 1.5h, filtered to obtain a polymer intermediate, heated the intermediate to 180°C to degas, cooled and filtered to obtain a finished product. The finished product has a transparent appearance, a conversion rate of 91.2%, a viscosity of 50cP, and a volatile matter of 0.49%. The finished product has no change in viscosity and volatile matter when heated at 200°C for 12h.

[0026] Example 6 Same as Example 1, except that the solid acid catalyst added is a perfluorosulfonic acid type ion exchange resin. The finished product has a transparent appearance, a conversion rate of 92%, a viscosity of 370 cP, and a volatile matter of 0.44%. The finished product has no change in viscosity and volatile matter when heated at 200°C for 12 hours.

[0027] Example 7 Same as Example 1, except that the solid acid catalyst added is acid clay. The finished product has a transparent appearance, a conversion rate of 91.8%, a viscosity of 365 cP, and a volatile matter of 0.36%. The finished product has no change in viscosity and volatile matter when heated at 200°C for 12 hours.

[0028] Example 8 Same as Example 1, except that the solid acid catalyst added is D61 macroporous strong acid cation exchange resin. The finished product has a transparent appearance, a conversion rate of 93.2%, a viscosity of 357 cP, and a volatile matter of 0.32%. The finished product has no change in viscosity and volatile matter when heated at 200°C for 12 hours.

[0029] Comparative Example 1 3000g of dimethyldichlorosilane hydrolyzate, 195g of 5cSt dimethyl silicone oil and 5ppm of chlorophosphazene catalyst were added to a three-necked flask, stirred and heated to 70°C, kept warm for reaction at -90kPa for 3h, and then hexamethyldisilazane was added for neutralization. The conversion rate was 57%, the viscosity was 463cp, and the volatile matter was 0.41%.

[0030] Comparative Example 2 3000g of dimethyldichlorosilane hydrolyzate, 195g of 5cSt dimethyl silicone oil, and 5wt% of styrene-divinylbenzene type strong acid cation exchange resin were reacted at 70°C for 3h and then filtered, with a conversion rate of 24%.

[0031] Comparative Example 3 3000g of dimethyldichlorosilane hydrolyzate, 195g of 5cSt dimethyl silicone oil, and 5wt% of styrene-divinylbenzene type strong acid cation exchange resin were mixed, reacted at 70℃ for 1.5h under normal pressure, and the prepolymer was obtained after filtering out the resin; 5ppm of chlorophosphazene catalyst was added to the prepolymer, and the reaction was kept warm for 1.5h at -90kpa and 70℃ to obtain a polymerization intermediate, and hexamethyldisilazane was finally added to deactivate the catalyst, and the temperature was finally raised to 180℃ for degassing, and the finished product was obtained by cooling and filtering. The finished product has a transparent appearance, a conversion rate of 65%, a viscosity of 421cp, and a volatile matter of 0.58%. The finished product has no change in viscosity and volatile matter when heated at 200℃ for 12h.

[0032] Comparative Example 4 The same as Example 1, except that the solid acid catalyst added was vanadium pentoxide resin. The finished product had a conversion rate of 75%, a viscosity of 405 cp, and a volatile matter of 0.46%; after the finished product was heated at 200° C. for 12 hours, the viscosity was 501 cp and the volatile matter was 2.5%, indicating that the vanadium pentoxide resin could not completely adsorb the chlorophosphazene catalyst.

[0033] The above data show that, by adopting the order of adding chlorophosphazene first and then adding the solid acid catalyst, the solid acid catalyst can not only have a catalytic effect, but also play a role in adsorbing chlorophosphazene, thereby avoiding the addition of chlorophosphazene quencher affecting the purity of the product. In the present invention, chlorophosphazene is used as a catalyst for the reaction of linear polysiloxanes, and the solid acid catalyst is used as a catalyst for the reaction of cyclosiloxanes. It can be seen from the data of Example 1 and Comparative Example 3 that the solid acid catalyst can significantly improve the finished product conversion rate while adsorbing chlorophosphazene, which indicates that the solid acid catalyst can further improve its catalytic effect by adsorbing chlorophosphazene.

[0034] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolyzate, characterized in that: The following steps are involved: (1) adding dimethyldichlorosilane hydrolyzate, a capping agent and a chlorophosphazene catalyst into a reaction vessel, and reacting under negative pressure to obtain a prepolymer; (2) After returning to normal pressure, a solid acid catalyst is added to continue the reaction, and the polymerization intermediate is obtained by filtration, and further desulfurization is performed to obtain the finished product dimethyl silicone oil.

2. A method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolyzate according to claim 1, characterized in that: The dimethyldichlorosilane hydrolyzate in step (1) is a mixture of linear polysiloxane and cyclic polysiloxane, and the mass ratio of the linear body to the cyclic body is 7:3-5:

5.

3. A method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolyzate according to claim 1, characterized in that: The end-capping agent in step (1) is linear polydimethylsiloxane MDnM, preferably one or more mixtures of hexamethyldisiloxane MM, octamethyltrisiloxane MDM, decamethyltetrasiloxane MDDM or dimethyl silicone oil with a viscosity lower than 20 cSt, more preferably dimethyl silicone oil with a viscosity of 5 cSt or 10 cSt.

4. A method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolyzate according to claim 1, characterized in that: The catalyst in step (1) is linear phosphazene chloride or a linear phosphazene chloride solution, and its structural formula is: ； The solvent of the linear phosphazene chloride solution is one or more of ethyl acetate, toluene, tetrachloroethane or dimethyl silicone oil with a viscosity of 50 cSt to 200 cSt.

5. A method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolyzate according to claim 1, characterized in that: The amount of catalyst added in step (1) is 1 ppm to 20 ppm, preferably 5 ppm, based on linear chlorophosphazene.

6. A method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolyzate according to claim 1, characterized in that: The reaction system pressure of step (1) is -80 kPa to -90 kPa; the reaction temperature is 60-80°C, preferably 70°C; and the reaction time is 1-3 h, preferably 1.5 h.

7. A method for directly synthesizing dimethyl silicone oil from dimethyldichlorosilane hydrolyzate according to claim 1, characterized in that: The solid acid catalyst in step (2) is any one of perfluorosulfonic acid type ion exchange resin, D61 macroporous strong acid cation exchange resin, acidic clay or styrene-divinylbenzene type strong acid cation exchange resin.

8. A method for directly synthesizing dimethyl silicone oil from hydrolyzate according to claim 1, characterized in that: In the step (2), the reaction temperature is 60-80°C, preferably 70°C; the reaction time is 1-3h, preferably 1.5h.

9. A method for directly synthesizing dimethyl silicone oil from hydrolyzate according to claim 1, characterized in that: The viscosity of the finished dimethyl silicone oil in step (2) is 50cp~1000cp.

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