Synthesis of o-carborane silane coupling agent and application of o-carborane silane coupling agent in high-temperature-resistant silicone rubber

Abstract

The invention belongs to the field of high polymer materials, and provides synthesis of an o-carborane silane coupling agent and application of the o-carborane silane coupling agent in high-temperature-resistant silicone rubber, the synthesis of the o-carborane silane coupling agent adopts a Heck reaction with a high atom utilization rate, the reaction controllability is good, the yield is high, and as a novel high-temperature-resistant silane coupling agent, the yield is high. Under the condition of not changing the existing silicone rubber preparation process, the mechanical property of the silicone rubber at high temperature is improved by a simple mixing mode. Besides, the o-carborane silane coupling agent is introduced into a silicone rubber cross-linked network in a chemical bonding mode, and compared with an o-carborane physical blending mode, the o-carborane silane coupling agent is good in compatibility with a silicone rubber matrix, high in universality and suitable for the field of preparation of high-temperature-resistant silicone rubber.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature resistant silicone rubber preparation, and particularly relates to the synthesis of an o-carborane silane coupling agent and its application in high-temperature resistant silicone rubber. Background Art

[0002] Disclosing the information of this background art section is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or any form of implication that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Due to its special Si-O main chain structure, silicone rubber has better temperature resistance than carbon chain polymer materials and is widely used in fields such as aerospace sealing materials, electronic device packaging, and high-temperature environment thermal protection. However, the mechanical property attenuation and thermal-oxidative aging problems of traditional silicone rubber under high-temperature (>300 °C) conditions seriously restrict its long-term service reliability. Existing modification methods (such as adding heat-resistant fillers, metal oxides, fibers, etc.) are difficult to balance mechanical properties and thermal stability, and a high filler content easily leads to poor compatibility, deteriorated processing performance, and increased material hardness. Through the modification technology of silicone molecules on the main chain or side chain, introducing heteroatoms or large rigid groups (phenyl, POSS, etc.) is a key research direction for improving the heat resistance of silicone rubber. By reasonably designing the type, position, and content of rigid groups, an optimized balance between high-temperature resistance performance and comprehensive mechanical properties can be achieved. However, the complex synthesis steps of silicone macromolecules and harsh reaction conditions, such as Grignard reaction, limit their large-scale promotion and application. In addition, different vulcanization cross-linking methods of silicone rubber also affect the high-temperature resistance performance, such as free radical cross-linking, polycondensation cross-linking, hydrosilylation cross-linking, etc. In the former two, the generation of small molecules during the cross-linking process will affect the high-temperature resistance performance of silicone rubber, while the hydrosilylation cross-linking method does not generate small molecules, and the presence of platinum catalyst is beneficial to the high-temperature performance of silicone rubber.

[0004] Carborane is often used as an additive to improve the high-temperature resistance performance of silicone rubber, but due to problems such as the compatibility between carborane and raw rubber during the direct addition process, the improvement effect on high-temperature mechanical properties still needs to be enhanced.

[0005] Some studies have prepared carborane-containing silane coupling agents by connecting silane coupling agents to carborane, greatly improving the reaction activity of carborane with the surface and matrix of polymer materials and enhancing the high-temperature resistance performance of silicone resin. However, its improvement effect on the high-temperature mechanical properties of addition-cured high-temperature resistant silicone rubber still needs to be enhanced.

[0006] In summary, although there are various methods for modifying / coupling carborane in the current industry, the high-temperature mechanical properties of the prepared carborane-containing silicone rubber still need to be enhanced. Summary of the Invention

[0007] To solve the above problems, the present invention provides a synthesis of an o-carborane silane coupling agent and its application in high-temperature resistant silicone rubber. The synthesis of the o-carborane silane coupling agent of the present invention adopts the Heck reaction with high atomic utilization rate, good reaction controllability and high yield. As a silane coupling agent in the addition-cured high-temperature resistant silicone rubber formulation, it can improve the mechanical properties of silicone rubber at high temperature without changing the existing silicone rubber preparation process.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] In the first aspect of the present invention, a synthesis method of an o-carborane silane coupling agent is provided, including:

[0010] Using o-carborane bromide and vinyltrimethoxysilane as raw materials, in the presence of a palladium acetate / triphenylphosphine catalyst and an acid absorbent, a Heck reaction is carried out to obtain the o-carborane silane coupling agent.

[0011] To improve the high-temperature resistance and mechanical properties of silicone rubber, the present invention proposes an efficient synthesis method of an o-carborane silane coupling agent. While solving the compatibility between o-carborane and organosilicon-based rubber, the steric hindrance effect and chemical stability of its large-volume rigid groups are utilized to inhibit the high-temperature cyclization degradation of the silicone oxygen main chain and the side-chain oxidation decomposition reaction, and improve the mechanical properties of silicone rubber under high-temperature conditions.

[0012] In the second aspect of the present invention, the o-carborane silane coupling agent synthesized by the above method is provided.

[0013] In the third aspect of the present invention, a high-temperature resistant silicone rubber is provided, which is composed of the following raw materials in parts by weight: 100 parts of methyl vinyl-based rubber, 3 - 6 parts of hydrogen-containing silicone oil, 30 - 40 parts of white carbon black, 3 - 6 parts of iron(III) oxide, 5 - 50 ppm of platinum catalyst (calculated as Pt), 0.1 - 10 parts of octavinylsilsesquioxane, and 0.1 - 10 parts of o-carborane silane coupling agent.

[0014] In the fourth aspect of the present invention, a preparation method of a high-temperature resistant silicone rubber is provided, including:

[0015] Mix methyl vinyl-based rubber, hydrogen-containing silicone oil, white carbon black, and iron(III) oxide evenly and knead.

[0016] Then add octavinylsilsesquioxane, o-carborane silane coupling agent, and platinum catalyst, and hot press to obtain.

[0017] Advantages of the present invention

[0018] (1) The o-carborane silane coupling agent of the present invention, as a novel high-temperature resistant silane coupling agent, is synthesized by the traditional Heck reaction, with high atomic utilization rate and efficient synthesis method.

[0019] (2) The o-carborane silane coupling agent of the present invention can improve the high-temperature resistance of silicone rubber by a simple addition method without changing the existing silicone rubber formula and preparation process.

[0020] (3) The o-carborane silane coupling agent of the present invention is introduced into the silicone rubber crosslinking network by chemical bonding, and has better compatibility with the silicone rubber matrix compared with the physical blending method of o-carborane.

[0021] (4) The o-carborane silane coupling agent of the present invention has a simple usage method, is easy to operate, is applicable to the field of preparing high-temperature resistant silicone rubber, and has strong universality.

[0022] (5) In the high-temperature resistant silicone rubber of the o-carborane silane coupling agent of the present invention, when vinyl POSS is added as a centralized crosslinking agent to provide the crosslinking density of silicone rubber, the introduction of the large-volume functional groups of POSS will also improve the high-temperature resistance of silicone rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0024] Figure 1 is the synthesis reaction equation of brominated o-carborane of the present invention.

[0025] Figure 2 is the synthesis reaction equation of o-carborane silane coupling agent of the present invention.

[0026] Figure 3 is of brominated o-carborane and o-carborane silane coupling agent of the present invention 11 B spectrum and 1 H spectrum.

[0027] Figure 4 is the tensile curve graph of the addition-cured silicone rubber prepared in Example 1 of the present invention.

[0028] Figure 5 is the tensile curve graph of the addition-cured silicone rubber prepared in Example 2 of the present invention.

[0029] Figure 6 is the tensile curve graph of the addition-cured silicone rubber prepared in Example 3 of the present invention.

[0030] Figure 7 is the tensile curve graph of the addition-cured silicone rubber prepared in Example 4 of the present invention.

[0031] Figure 8 It is the tensile curve graph of the addition-cured silicone rubber prepared in Comparative Example 1 of the present invention.

[0032] Figure 9 It is the tensile graph after high-temperature aging of the addition-cured silicone rubber prepared in Example 1 of the present invention.

[0033] Figure 10 It is the tensile graph after high-temperature aging of the addition-cured silicone rubber prepared in Example 2 of the present invention.

[0034] Figure 11 It is the tensile graph after high-temperature aging of the addition-cured silicone rubber prepared in Example 3 of the present invention.

[0035] Figure 12 It is the tensile graph after high-temperature aging of the addition-cured silicone rubber prepared in Example 4 of the present invention.

[0036] Figure 13 It is the tensile graph after high-temperature aging of the addition-cured silicone rubber prepared in Comparative Example 1 of the present invention.

[0037] Figure 14 It is the thermogravimetric curve graph of the addition-cured silicone rubber prepared in Example 3 of the present invention.

[0038] Figure 15 It is the thermogravimetric curve graph of the addition-cured silicone rubber prepared in Example 2 of the present invention.

[0039] Figure 16 It is the thermogravimetric curve graph of the addition-cured silicone rubber prepared in Example 3 of the present invention.

[0040] Figure 17 It is the thermogravimetric curve graph of the addition-cured silicone rubber prepared in Example 4 of the present invention.

[0041] Figure 18 It is the thermogravimetric curve graph of the addition-cured silicone rubber prepared in Comparative Example 1 of the present invention. Detailed Description of the Invention

[0042] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0043] The present invention provides a simple and efficient o-carborane silane coupling agent and its application in high-temperature resistant silicone rubber. The steps are as follows: o-carborane bromide reacts with vinyltrimethoxysilane through Heck reaction to generate o-carborane silane coupling agent, which is added to the silicone rubber formula during the mixing process, and high-temperature resistant silicone rubber is prepared by hydrosilylation vulcanization.

[0044] In some embodiments, the molar ratio of o-carborane bromide to vinyltrimethoxysilane is 1:1 - 1.1, preferably 1:1.

[0045] In some embodiments, the temperature of the Heck reaction is 120 - 130 °C and the reaction time is 20 - 24 h. Preferably, the temperature of the Heck reaction is 120 °C and the reaction time is 24 h.

[0046] In some embodiments, the mass ratio of palladium acetate, triphenylphosphine catalyst, and acid absorbent is 0.01 - 0.02:0.1 - 0.2:0.95 - 1.9. Preferably, the mass ratio of palladium acetate, triphenylphosphine catalyst, and acid absorbent is 0.01:0.1:0.95.

[0047] In some embodiments, the acid absorbent is sodium bicarbonate.

[0048] In some embodiments, the synthesis steps of the o-carborane silane coupling agent are as follows: Under N2 protection, equimolar amounts of o-carborane bromide and vinyltrimethoxysilane are dissolved in a solvent and added to a three-necked flask. Then, a quantitative amount of palladium acetate / triphenylphosphine catalyst and acid absorbent are added. The temperature is raised, the reaction is carried out, and then vacuum distillation and filtration are performed to obtain the product. Further, the synthesis of the o-carborane silane coupling agent adopts traditional Heck reaction conditions, and the synthesis conditions are not specifically limited.

[0049] In some embodiments, the synthesis steps of o-carborane bromide are as follows: Equimolar amounts of o-carborane and N-bromosuccinimide are placed in a three-necked flask, dissolved in hexafluoroisopropanol solvent, trifluoromethanesulfonic acid is added, and the mixture is stirred and reacted. After the solvent is recovered by heating, o-carborane bromide is obtained. Further, the synthesis method of o-carborane bromide is not limited.

[0050] In some embodiments, the molar ratio of o-carborane to N-bromosuccinimide is 1:1.

[0051] In some embodiments, the molar ratio or mass ratio of o-carborane to trifluoromethanesulfonic acid is 0.1% - 0.5%.

[0052] In some embodiments, the formulation and preparation process of the silicone rubber are not specifically limited. The silicone rubber formulation of the present invention includes vinyl-based rubber, hydrogen-containing silicone oil, fumed silica, iron(III) oxide, vinyl POSS crosslinking agent, and platinum catalyst, and the silicone rubber is prepared by hydrosilylation vulcanization.

[0053] In some embodiments, the amount of the o-carborane silane coupling agent used is 0 - 10 parts, and further preferably, the amount of the o-carborane silane coupling agent used is 1 - 3 parts.

[0054] In some embodiments, the amount of the vinyl POSS is 0 to 10 parts, and further preferably, the amount of the o-carborane silane coupling agent is 0.5 to 1.5 parts.

[0055] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention rather than limitations.

[0056] In the following examples and comparative examples, all the test methods are common methods in the industry, and no special description will be given in this application.

[0057] In the following examples, the platinum catalyst: Karstedt catalyst, Wuhan Kemic Biopharmaceutical Technology Co., Ltd.

[0058] The phenyl hydrogen-containing silicone oil is PH212, commercially available, industrial grade.

[0059] In the following examples, the preparation method of the o-carborane silane coupling agent is as follows:

[0060] (1) Equimolar amounts of o-carborane and N-bromosuccinimide (0.2 mmol) were placed in a three-necked flask, dissolved in hexafluoroisopropanol solvent, and 0.3% of trifluoromethanesulfonic acid based on the amount of o-carborane was added, and the mixture was stirred and reacted for 0.8 h. After heating to recover the solvent, brominated o-carborane was obtained.

[0061] (2) Under N2 protection, equimolar amounts of brominated o-carborane and vinyltrimethoxysilane (4.0 mmol) were dissolved in a solvent and added to a three-necked flask. Then, 0.03 g of palladium acetate, 0.3 g of triphenylphosphine catalyst, and 285 mg of acid absorbent (sodium bicarbonate) were added. The temperature was raised to 120 °C and the reaction was carried out for 24 h. After vacuum distillation and filtration, the product was obtained.

[0062] Example 1

[0063] Using PDMS as the base rubber (100 parts), 30 parts of SiO2, 3 parts of Fe2O3, and 3 parts of phenyl hydrogen-containing silicone oil were added and uniformly kneaded. Then, 1.5 parts of octavinylsilsesquioxane and 1.5 parts of o-carborane silane coupling agent were added, and 20 ppm of platinum catalyst (calculated as Pt) was added. Under 55 °C and 10 MPa pressure, the addition-cured silicone rubber TB1 was prepared by hot pressing.

[0064] Example 2

[0065] Using PDMS as the base rubber (100 parts), 30 parts of SiO2, 3 parts of Fe2O3, and 3 parts of phenyl hydrogen-containing silicone oil were added and uniformly kneaded. Then, 1.5 parts of octavinylsilsesquioxane and 0.5 parts of o-carborane silane coupling agent were added, and 20 ppm of platinum catalyst (calculated as Pt) was added. Under 55 °C and 10 MPa pressure, the addition-cured silicone rubber TB2 was prepared by hot pressing.

[0066] Example 3

[0067] Using PDMS as the base rubber (100 parts), adding 30 parts of SiO2, 3 parts of Fe2O3, and 3 parts of phenylhydrogen silicone oil. After uniform mixing, 1.5 parts of o-carborane silane coupling agent are added, and then 20 ppm of platinum catalyst (calculated as Pt) is added. Under the conditions of 55 °C and 10 MPa pressure, an addition-cured silicone rubber TB3 is prepared by hot pressing.

[0068] Example 4

[0069] Using PDMS as the base rubber (100 parts), adding 30 parts of SiO2, 3 parts of Fe2O3, and 3 parts of phenylhydrogen silicone oil. After uniform mixing, 0.5 parts of o-carborane silane coupling agent are added, and then 20 ppm of platinum catalyst (calculated as Pt) is added. Under the conditions of 55 °C and 10 MPa pressure, an addition-cured silicone rubber TB4 is prepared by hot pressing.

[0070] Comparative Example 1

[0071] Using PDMS as the base rubber (100 parts), adding 30 parts of SiO2, 3 parts of Fe2O3, and 3 parts of phenylhydrogen silicone oil. After uniform mixing, 20 ppm of platinum catalyst (calculated as Pt) is added. Under the conditions of 55 °C and 10 MPa pressure, an addition-cured silicone rubber TB0 is prepared by hot pressing.

[0072] Comparative Example 2

[0073] It is different from Example 3 in that vinyltrimethoxysilane is used to replace the o-carborane silane coupling agent.

[0074] The test results show that the tensile strength of the silicone rubber at room temperature is 3.9 MPa and the elongation at break is 380%. However, it becomes brittle and loses its mechanical properties after aging at 350 °C for 24 h.

[0075] Performance Test

[0076] 1) The mechanism diagram for preparing Br-CB in Example 1 is as shown in 10 H 11 as follows. Figure 1 shown.

[0077] 2) The mechanism diagram for preparing BTPW in Example 2 is as shown in Figure 2 shown.

[0078] 3) The 1H spectrum and 10 H 11 11B spectrum of the prepared Br-CB 1 and BTPW are as shown in 11 as follows. Figure 3 shown. Figure 3As shown in (c), the peaks at chemical shifts of -3.79 ppm and -4.92 ppm shift upfield to -2.41 ppm and -3.59 ppm respectively, as Figure 3 shown in (b). In addition, as Figure 3 shown in (b), a new absorption peak with a chemical shift of -0.83 ppm appears in the B spectrum of Br-CB 10 H 11 . This indicates that the original symmetric cage structure of the carborane is broken and the Br substitution reaction has been successfully carried out; the 11 H spectrum of BTPW also proves that the peak integral areas at the double bond peak positions are 1:1. 1

[0079] 4) Tensile tests of the addition-cured silicone rubbers prepared in Test Examples 1, 2, 3, 4 and Comparative Example 1 are shown in Figure 4 , 5, 6, 7, 8. When the content of BTPW increases from 0.5% to 1.5%, the tensile strength of the rubber increases from 4.5 MPa to 5.6 MPa, and the elongation at break increases from 383% to 495%, indicating improved mechanical properties. After adding Vi-POSS, the tensile strength is significantly improved. The tensile stress of the sample of TB1 is 6.8 MPa and the elongation at break is 748%.

[0080] 5) 350 °C aging tests of the addition-cured silicone rubbers prepared in Test Examples 1, 2, 3, 4 and Comparative Example 1 are shown in Figure 9 , 10, 11, 12, 13. After aging for 24 h, the tensile stress of TB4 is 1.2 MPa and the elongation at break is 82%. As the content of BTPW increases from 0.5% to 1.5%, the stress of TB3 increases to 2.3 MPa and the elongation at break increases to 89%. TB1 and TB2 with added Vi-POSS show better tensile properties. After high-temperature aging for 24 h, the stress intensities of TB1 and TB2 are both greater than 3.0 MPa.

[0081] 6) Thermogravimetric tests of the addition-cured silicone rubbers prepared in Test Examples 1, 2, 3, 4 and Comparative Sample 1 are shown in Figure 14 , 15, 16, 17, 18. Under air conditions, the initial decomposition temperature (the temperature corresponding to a 5% weight loss) of the comparative sample TB0 is the lowest at 378 °C. The initial decomposition temperatures (the temperatures corresponding to a 5% weight loss) of the samples in the examples are not very different and are all between 415 °C and 420 °C. Among them, the initial decomposition temperatures of TB1 and TB2 with added Vi-POSS are both higher than those of the TB3 and TB4 samples.

[0082] ​The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for synthesizing an o-carborane silane coupling agent, characterized in that, Comprising: Using brominated o-carborane and vinyltrimethoxysilane as raw materials, under the conditions of palladium acetate / triphenylphosphine catalyst and an acid absorbent, a Heck reaction is carried out to obtain an o-carborane silane coupling agent.

2. The synthesis method of the o-carborane silane coupling agent according to claim 1, characterized in that, The molar ratio of the o-carborane to N-bromosuccinimide is 1:1 - 1.

1.

3. The synthesis method of the o-carborane silane coupling agent according to claim 1, wherein The temperature of the Heck reaction is 120 - 130 °C, and the reaction time is 20 - 24 h.

4. The synthesis method of the o-carborane silane coupling agent according to claim 1, characterized in that, The mass ratio of the palladium acetate, triphenylphosphine catalyst, and acid absorbent is 0.01 - 0.02:0.1 - 0.2:0.95 - 1.

9.

5. The synthesis method of the o-carborane silane coupling agent according to claim 1, characterized in that, The acid absorbent is sodium bicarbonate.

6. The o-carborane silane coupling agent synthesized by the method according to any one of claims 1 - 5.

7. A high-temperature resistant silicone rubber, characterized in that, Composed of the following raw materials in parts by weight: 100 parts of methyl vinyl rubber, 3 - 6 parts of hydrogen-containing silicone oil, 30 - 40 parts of white carbon black, 3 - 6 parts of iron(III) oxide, 5 - 50 ppm of platinum catalyst calculated as Pt, and 0.1 - 10 parts of o-carborane silane coupling agent.

8. The high-temperature resistant silicone rubber according to claim 7, wherein 0.5 - 1.5 parts of octavinylsilsesquioxane are also added.

9. The high-temperature resistant silicone rubber according to claim 7, wherein The dosage of the o-carborane silane coupling agent is 0.5 - 1.5 parts.

10. A preparation method of a high-temperature resistant silicone rubber, characterized in that, Comprising: Mixing methyl vinyl rubber, hydrogen-containing silicone oil, white carbon black, and iron(III) oxide evenly and kneading; Then adding octavinylsilsesquioxane, o-carborane silane coupling agent, and platinum catalyst, and hot pressing to obtain.

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