Preparation method of high-molecular-weight fluorosilicone copolymerized raw rubber

Abstract

The preparation method is characterized by comprising the following steps: adding D3F and D4 into a polymerization reaction kettle together for dehydration, introducing vinyl by adopting a self-made cross-linking comonomer, adding a vinyl double-end-capping agent for end capping, adding tetramethylammonium hydroxide and an accelerant DMSO (Dimethylsulfoxide), and carrying out polymerization reaction at 120 DEG C for 1-2 hours in a normal-pressure nitrogen environment, so as to obtain the high-molecular-weight fluorosilicone copolymerized raw rubber. And raising the temperature to inactivate the catalyst, and removing the low temperature to obtain the fluorosilicone copolymerized raw rubber. According to the invention, D3F and dimethyl siloxane ring body are copolymerized, so that the cost is saved, vinyl-containing trifluoropropyl siloxane ring body is prepared, vinyl can be effectively connected into the fluorosilicone polymer, the distribution uniformity of vinyl in the main chain of the fluorosilicone polymer is improved, the vulcanization performance is improved, the chain back-bite phenomenon in the polymerization process can be effectively inhibited by adding the accelerant, and the service life of the fluorosilicone polymer is prolonged. The tetramethylammonium hydroxide catalyst is adopted, so that the neutralization step is omitted, polymerization and low molecule removal by heating are carried out in one reaction kettle, the operation is simple, and production and popularization are easier.

Description

Technical Field

[0001] The present invention belongs to the field of fluorosilicone rubber, and specifically relates to a method for preparing a high-molecular-weight fluorosilicone copolymer rubber, and more particularly to a method for preparing a high-temperature stable fluorosilicone copolymer rubber suitable for the fields of aerospace, automotive industry, electronic appliances, petrochemical industry, medical and health care, etc. Background Art

[0002] Organofluorosilicone, a hybrid of organosilicon and organofluorine, combines the properties of both, boasting low surface tension, solvent resistance, and chemical resistance. Fluorosilicone rubber, a further processed form of organosilicon, exhibits excellent resistance to high and low temperatures, oil, insulation, weathering, and aging. Currently, it is the only elastomer capable of stable operation in fuel-fired media at temperatures ranging from -68°C to 230°C. Since its development, fluorosilicone rubber has been widely used in the aerospace industry as a key material for components used in extreme high and low temperature environments, such as aircraft seals, fuel hoses, and hydraulic system seals. It also has widespread applications in the automotive industry, electronics, petrochemicals, healthcare, and other civilian sectors.

[0003] Fluorosilicone rubber is a modified silicone rubber. Trifluoropropyl functional groups (-CH2CH2CF3) replace the methyl side chains on the backbone of conventional silicone materials. Fluorosilicone rubber is synthesized through anionic ring-opening condensation polymerization using 3,3,3-trifluoropropylmethylcyclotrisiloxane (DF3). However, the high price of fluorosilicone rubber is a major obstacle to its entry into the civilian market. Fluorosilicone rubber, produced by copolymerizing dimethylsiloxane rings (D3, D4, etc.) with 3,3,3-trifluoropropylmethylcyclotrisiloxane (DF3), not only reduces costs but also further improves its high and low temperature resistance.

[0004] The D3F ring has high tension, making it easy to undergo ring-opening polymerization. However, ring-opening polymerization of the dimethylsiloxane ring is relatively difficult and requires a highly active catalyst for ring opening. Tetramethylammonium hydroxide is a highly effective catalyst for the copolymerization of D3F and dimethylsiloxane. The copolymerization of D3F and dimethylsiloxane is a balanced ring-opening polymerization reaction. Alkaline catalysts act as both polymerization catalysts for the D3F and dimethylsiloxane rings and depolymerization catalysts for the copolymer. Therefore, the catalyst must be removed in the later stages of the polymerization reaction to prevent polymer degradation during processing and use. When using tetramethylammonium hydroxide as a catalyst, increasing the temperature to 150°C in the later stages of the reaction can decompose the tetramethylammonium hydroxide, making catalyst removal easier. For example, Application No. 200510026689.6 discloses a method for preparing high-molecular-weight fluorosilicone polymers. Using sodium silanol as a catalyst, a series of fluorosilicone polymers were prepared. However, the catalyst was not neutralized during the preparation process, which would affect the thermal stability of the raw rubber.

[0005] Furthermore, to fully vulcanize fluorosilicone rubber, it is often necessary to introduce vulcanization-active groups, such as vinyl groups, into the raw rubber. For example, patent CN101250266A discloses a method for preparing fluorosilicone copolymer rubber. However, the significant difference in the anionic ring-opening activity of D3F and methylvinylcyclosiloxane results in uneven distribution of vinyl groups along the polymer backbone, making effective vinyl introduction difficult and thus affecting the properties of the vulcanized rubber. Summary of the Invention

[0006] To solve the problems existing in the prior art, the present invention provides a method for preparing a high molecular weight fluorosilicone copolymer rubber, which has high molecular weight, uniform vinyl distribution, good appearance, and reduced cost, making it more suitable for the civilian market.

[0007] To solve the above problems, the technical solutions of the present invention are as follows: 1. Preparation of vinyl-containing trifluoropropylsiloxane ring: Add a surfactant to a hydrochloric acid solution, heat it to a certain temperature, slowly add trifluoropropyl methyldichlorosilane and methylvinyldichlorosilane dropwise, wash and separate the liquid, and distill under reduced pressure to obtain a vinyl-containing trifluoropropylsiloxane ring. Its structure is as follows;

[0008] Among them, 3≤m+n≤5, m≤n-1.

[0009] 2. Polymerization: D3F and dimethylsiloxane ring body were added to the polymerization reactor separately for dehydration, and the homemade ring body, end-capping agent, catalyst and accelerator were added in sequence under a nitrogen environment. The nitrogen environment was maintained and stirred continuously for a period of time for polymerization reaction. The mass fraction of D3F was 50-99% and the mass fraction of dimethylsiloxane was 1-49%.

[0010] 3. Deactivation of the catalyst: After step 2, the reactor is heated to deactivate the catalyst, and then the pressure is reduced to remove low molecular weight substances, and the material is discharged after cooling.

[0011] According to the present invention, preferably, in step 1, the concentration of the hydrochloric acid solution is 10-50%, more preferably 20%, and the surfactant is preferably an anionic surfactant, and the amount used is 1-2% of the weight of the hydrolyzate.

[0012] The molar ratio of trifluoropropylmethyldichlorosilane to methylvinyldichlorosilane is 1:1-0.2, the reaction temperature is 30-60°C, and the reduced pressure temperature is 160-180°C. In the present invention, the molar ratio of trifluoropropylmethyldichlorosilane to methylvinyldichlorosilane should be controlled within the range of 1:1-0.2. Excessive amounts of trifluoropropylmethyldichlorosilane, such as 1.2:0.2, can lead to unstable vinyl content in the prepared raw rubber.

[0013] The anionic surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium octylsulfonate, sodium lauryl sulfate, and sodium fatty alcohol polyoxyethylene ether sulfate.

[0014] Preferably, in step 2, the dimethylsiloxane ring body is octamethylcyclotetrasiloxane (D4), the dehydration conditions are -0.009~-0.01MPa, 60~80℃, 0.5~2h, the polymerization reaction temperature is 60~120℃, the polymerization time is 1~2h, and the self-made ring body is 0.01~2% of the mass of D3F and D4.

[0015] Preferably, the end-capping agent is a vinyl double end-capping agent, and the amount used is 0.01-2% of the mass of D3F and D4.

[0016] Preferably, the catalyst is tetramethylammonium hydroxide alkali glue, with an alkali content of 0.3-0.5%, and an amount of 0.1-5% of the mass of D3F and D4.

[0017] Preferably, the accelerator is one of THF, DMF, DMSO, and Bu3PO4, more preferably DMSO, and the amount used is 0.1-1% of the mass of D3F and D4.

[0018] Preferably, in step 3, the reactor is heated to an inactivation temperature of 150° C., and the conditions for removing low-molecular weight molecules under reduced pressure are 150-200° C. and -0.009-0.01 MPa.

[0019] The beneficial effects of the present invention are as follows: (1) The use of trifluoropropylsiloxane ring containing vinyl groups reduces the difference in ring-opening activity with D3F, allowing the vinyl groups to be effectively connected to the fluorosilicone polymer, improving the uniformity of the vinyl group distribution in the fluorosilicone polymer main chain and improving the vulcanization performance.

[0020] (2) The present invention adopts D3F and dimethylsiloxane ring copolymerization, which saves costs and makes it easier to enter the civilian market.

[0021] (3) The present invention adopts the method of adding a accelerator during the polymerization process, which can effectively suppress the "chain backbiting" phenomenon during the polymerization process and stably obtain high molecular weight fluorosilicone raw rubber.

[0022] (4) The present invention uses tetramethylammonium hydroxide as a catalyst, and the catalyst can be removed by heating at a later stage, thus saving the neutralization step.

[0023] (5) The dehydration, polymerization, and heating to remove low molecular weight products of the present invention are all carried out in one reactor, which is simple to operate and easier to produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the gas chromatogram of trifluoropropylsiloxane ring containing vinyl. DETAILED DESCRIPTION

[0025] The present invention is further described below with reference to specific examples. However, the scope of protection claimed in the present invention is not limited to the scope described in the examples. The raw materials used in the examples can be purchased commercially or prepared by conventional methods. 3,3,3-Trifluoropropylmethylcyclotrisiloxane and trifluoropropylmethyldichlorosilane can be purchased from Weihai Xinyuan Chemical Co., Ltd., methylvinyldichlorosilane, tetramethylammonium hydroxide, vinyl double head capping agent, and DMSO are all purchased from Sinopharm Group, and dimethylsiloxane ring body is provided by Hubei Xingrui Silicon Materials Co., Ltd.

[0026] Example 1 The vinyl-containing trifluoropropylsiloxane ring used in the examples was prepared by adding the surfactant sodium dodecylbenzenesulfonate to a 20% hydrochloric acid solution, heating the solution to 45-50°C, and slowly adding a 2:1 molar ratio mixture of trifluoropropylmethyldichlorosilane and methylvinyldichlorosilane dropwise. The addition rate was controlled to complete the addition over approximately 30 minutes, followed by a 30-60 minute reaction. The mixture was then washed with warm water three to four times, separated, and distilled at 160°C. The structure is as follows:

[0027] Among them, 3≤m+n≤5, m≤n-1.

[0028] 500g of D3F and 500g of D4 were added to a reactor, heated to 60°C, and vacuum-dehydrated under nitrogen bubbling for 1 hour. The temperature was then raised to 120°C, followed by the addition of 2g of the aforementioned vinyl-containing trifluoropropylsiloxane ring and 0.5g of a vinyl double-capping agent. After stirring and mixing thoroughly, 1.8g of tetramethylammonium hydroxide (TMAH) gel catalyst was added. Immediately after polymerization began, 0.1g of DMSO (DMSO) accelerator was added. Dry nitrogen was continuously purged throughout the polymerization process to remove trace amounts of water vapor generated. After the viscosity of the system increased, the stirring speed of the reactor was slowly reduced and the reaction was continued for 1 hour. After the polymerization was completed, the reactor temperature was raised to 150°C to decompose the TMAH and quench the catalyst. The temperature was further raised to 180°C, and low-molecular-weight products were removed under a pressure of -0.009 to -0.01 MPa. The product was then cooled and discharged.

[0029] Example 2 500g of D3F and 500g of D4 were added to a reactor, heated to 60°C, and vacuum-dehydrated under nitrogen bubbling for 1 hour. The reaction mixture was then heated to 120°C. 2g of a self-made vinyl-containing trifluoropropylsiloxane ring (prepared using the method of Example 1, with a molar ratio of 5:1 between trifluoropropylmethyldichlorosilane and methylvinyldichlorosilane) and 0.8g of a vinyl double-capping agent were added. After stirring and mixing thoroughly, 1.8g of tetramethylammonium hydroxide (TMAH) gel catalyst was added. Immediately after polymerization began, 0.1g of DMSO (accelerator) was added. Dry nitrogen was continuously flowed throughout the polymerization process to remove trace amounts of water vapor generated. After the viscosity of the system increased, the stirring speed of the reactor was slowly reduced and the reaction was continued for 1 hour. After the polymerization reaction was completed, the reactor temperature was raised to 150°C to decompose the TMAH and quench the catalyst. The temperature was further raised to 180°C, and low-molecular-weight products were removed under a pressure of -0.009 to -0.01 MPa. The product was then cooled and discharged.

[0030] Example 3 500g of D3F and 500g of D4 were added to a reactor, heated to 60°C, and vacuum-dehydrated under nitrogen bubbling for 1 hour. The reaction mixture was then heated to 120°C, and 1.5g of a self-produced vinyl-containing trifluoropropylsiloxane ring (prepared using the method of Example 1) and 0.5g of a vinyl double-capping agent were added. After stirring and mixing thoroughly, 1.8g of tetramethylammonium hydroxide (TMAH) alkali gel catalyst was added. Immediately after polymerization began, 0.1g of DMSO (accelerator) was added. Dry nitrogen was continuously purged during the polymerization process to remove trace amounts of water vapor generated. After the viscosity of the system increased, the stirring speed of the reactor was slowly reduced, and the reaction mixture was allowed to react for 1 hour. After the polymerization reaction was completed, the reactor temperature was raised to 150°C to decompose the TMAH and quench the catalyst. The temperature was further raised to 180°C, and low-molecular-weight products were removed under a pressure of -0.009 to -0.01 MPa. The product was then cooled and discharged.

[0031] Example 4 700g of D3F and 300g of D4 were added to a reactor, heated to 60°C, and vacuum-dehydrated under nitrogen bubbling for 1 hour. The reaction mixture was then heated to 120°C. 2g of a self-made vinyl-containing trifluoropropylsiloxane ring (prepared using the method of Example 1, with a molar ratio of 1:1 between trifluoropropylmethyldichlorosilane and methylvinyldichlorosilane) and 0.5g of a vinyl double-capping agent were added. After stirring and mixing thoroughly, 1.8g of tetramethylammonium hydroxide (TMAH) gel catalyst was added. Immediately after polymerization began, 0.1g of DMSO (accelerator) was added. Dry nitrogen was continuously purged during the polymerization to remove trace amounts of water vapor generated. After the viscosity of the system increased, the stirring speed of the reactor was slowly reduced and the reaction was continued for 1 hour. After the polymerization reaction was completed, the reactor temperature was raised to 150°C to decompose the TMAH and quench the catalyst. The temperature was further raised to 180°C, and low-molecular-weight products were removed under a pressure of -0.009 to -0.01 MPa. The product was then cooled and discharged.

[0032] Comparative Example 1 500g of D3F and 500g of D4 were added to a reactor, heated to 60°C, and vacuum-dehydrated for 1 hour under nitrogen bubbling. The temperature was then raised to 120°C, followed by the addition of 2g of tetramethyltetravinylsiloxane and 0.5g of a vinyl double-capping agent. After stirring and mixing thoroughly, 1.8g of tetramethylammonium hydroxide (TMAH) gel catalyst was added. Immediately after polymerization began, 0.1g of DMSO (accelerator) was added. Dry nitrogen was continuously flowed throughout the polymerization process to remove trace amounts of water vapor generated. After the viscosity of the system increased, the stirring speed of the reactor was slowly reduced and the reaction was continued for 1 hour. After the polymerization was completed, the temperature in the reactor was raised to 150°C to decompose the TMAH and quench the catalyst. The temperature was further raised to 180°C, and low-molecular-weight products were removed under a pressure of -0.009 to -0.01 MPa. The product was then cooled and discharged.

[0033] Comparative Example 2 500g of D3F and 500g of D4 were added to a reactor, heated to 60°C, and vacuum-dehydrated for 1 hour under nitrogen bubbling. The temperature was then raised to 120°C, followed by the addition of 2g of a self-made vinyl-containing trifluoropropylsiloxane ring and 0.5g of a vinyl double-capping agent. After stirring and mixing thoroughly, 1.8g of tetramethylammonium hydroxide (TMAH) alkali gel catalyst was added. Dry nitrogen was continuously flowed throughout the polymerization process to remove trace amounts of water vapor generated. After the viscosity of the system increased, the stirring speed of the reactor was slowly reduced and the reaction was continued for 1 hour. After the polymerization reaction was completed, the temperature in the reactor was raised to 150°C to decompose the TMAH and quench the catalyst. The temperature was further raised to 180°C, and low-molecular-weight compounds were removed under a pressure of -0.009 to -0.01 MPa. The product was then cooled and discharged.

[0034] Comparative Example 3 500g of D3F and 500g of D4 were added to a reactor, heated to 60°C, and vacuum-dehydrated under nitrogen bubbling for 1 hour. The temperature was then raised to 120°C. 2g of a vinyl-containing trifluoropropylsiloxane ring prepared using the above method with a molar ratio of 6:1 between trifluoropropylmethyldichlorosilane and methylvinyldichlorosilane (i.e., a vinyl-containing trifluoropropylsiloxane ring prepared using the above method, with only a molar ratio of 6:1 between trifluoropropylmethyldichlorosilane and methylvinyldichlorosilane) and 0.5g of a vinyl double-capping agent were added. After stirring and mixing thoroughly, 1.8g of tetramethylammonium hydroxide (TMAH) gel catalyst was added. Immediately after polymerization began, 0.1g of DMSO (accelerator) was added. Dry nitrogen was continuously purged during the polymerization to remove trace amounts of water vapor generated. Once the viscosity of the system increased, the stirring speed of the reactor was slowly reduced and the reaction was continued for 1 hour. After the polymerization was completed, the reactor temperature was raised to 150°C to decompose the TMAH and quench the catalyst. The temperature is further raised to 180°C, and low molecular weight molecules in the system are removed under -0.009~-0.01MPa conditions, and the material is discharged after cooling.

[0035] Performance testing: 1. Molecular weight test The molecular weight of the copolymerized fluorosilicone rubber was measured using an Ubbelohde viscometer with butyl acetate as the solvent and a temperature of 25°C. The obtained value is the viscosity-average molecular weight.

[0036] 2. Vinyl content test The vinyl content was determined by iodine titration using a trifluorotrichloroethane-butyl acetate solvent system at 25°C.

[0037] 3. Determination of volatile matter Determined according to the national standard GB / T24131-2009 oven method.

[0038] The test results of Examples 1-4 and Comparative Examples 1-3 are listed in Table 1.

[0039] Table 1:

[0040] It should be understood that the above embodiments are only intended to illustrate the present invention and are not intended to limit the scope of protection of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A method for preparing a high molecular weight fluorosilicone copolymer rubber, characterized in that: (1) Preparation of trifluoropropylsiloxane ring containing vinyl group: add surfactant to hydrochloric acid solution, heat to a certain temperature, slowly add trifluoropropyl methyldichlorosilane and methylvinyldichlorosilane dropwise, wash with water, separate the liquid, and distill under reduced pressure to obtain trifluoropropylsiloxane ring containing vinyl group; (2) Polymerization: D3F and dimethylsiloxane ring body are added to the polymerization reactor for dehydration respectively, and vinyl-containing trifluoropropylsiloxane ring body, end-capping agent, catalyst and accelerator are added in sequence under nitrogen environment, and the nitrogen environment is maintained and stirred for a period of time to carry out polymerization reaction; (3) Catalyst inactivation: After the polymerization reaction is completed, the reactor is heated to inactivate the catalyst, and then the pressure is reduced to remove low molecular weight substances, and the material is discharged after cooling.

2. The method for preparing a high molecular weight fluorosilicone copolymer rubber according to claim 1, characterized in that: The concentration of the hydrochloric acid solution described in step (1) is 10-50%, the surfactant is one or more of sodium dodecylbenzenesulfonate, sodium octylsulfonate, sodium lauryl sulfate, and sodium fatty alcohol polyoxyethylene ether sulfate, and the amount used is 1-2% of the mass of the hydrolyzate; the molar ratio of trifluoropropylmethyldichlorosilane to methylvinyldichlorosilane is 1:1-0.

2.

3. The method for preparing a high molecular weight fluorosilicone copolymer rubber according to claim 1, characterized in that: In step (1), the reaction temperature is 30-60°C, and the reduced pressure temperature is 160-180°C.

4. The method for preparing a high molecular weight fluorosilicone copolymer rubber according to claim 1, characterized in that: The dimethylsiloxane ring body described in step (2) is octamethylcyclotetrasiloxane, and the dehydration conditions are -0.009~-0.01MPa, 60~80℃, and dehydration for 0.5~2h; the polymerization reaction temperature is 60~120℃, and the polymerization time is 1~2h.

5. The method for preparing a high molecular weight fluorosilicone copolymer rubber according to claim 4, characterized in that: In step (2), the mass fraction of D3F is 50-99% and the mass fraction of dimethylsiloxane is 1-49%.

6. The method for preparing a high molecular weight fluorosilicone copolymer rubber according to claim 1, characterized in that: The self-made vinyl-containing trifluoropropylsiloxane ring body described in step (2) is 0.01-2% of the total mass of D3F and D4.

7. The method for preparing a high molecular weight fluorosilicone copolymer rubber according to claim 1, characterized in that: The end-capping agent in step (2) is a vinyl double end-capping agent, and the amount used is 0.01-2% of the total mass of D3F and D4.

8. The method for preparing a high molecular weight fluorosilicone copolymer rubber according to claim 1, characterized in that: The catalyst in step (2) is tetramethylammonium hydroxide alkali glue, with an alkali content of 0.3-0.5%, and an amount of 0.1-5% of the total mass of D3F and D4.

9. The method for preparing a high molecular weight fluorosilicone copolymer rubber according to claim 1, characterized in that: The accelerator in step (2) is one of THF, DMF, DMSO, and Bu3PO4, and the amount used is 0.1-1% of the total mass of D3F and D4.

10. The method for preparing a high molecular weight fluorosilicone copolymer rubber according to claim 1, characterized in that: The reactor in step (3) is heated to a temperature of 150°C for inactivation, and the conditions for decompression and removal of low-molecular-weight substances are 150-200°C and -0.009-0.01 MPa.

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