A high-temperature stable silicone oil and its preparation method

Abstract

This invention relates to a high-temperature stable silicone oil and its preparation method, belonging to the field of silicone oil technology. The silicone oil comprises the following components: 100 parts silicone oil, 8-12 parts N-vinylimidazolium, and 1.5-3.0 parts zinc octanoate; wherein the imidazole group is covalently attached to the side chain. This invention utilizes a hydrosilylation reaction to covalently attach N-vinylimidazolium to the silicone oil side chain, followed by a reaction with zinc octanoate to form an imidazole-zinc coordination complex, anchoring zinc ions to the silicone oil molecule. The resulting product exhibits excellent high-temperature stability. Furthermore, this invention can add antioxidants to the system to form a dual protection mechanism, further improving stability in aerobic environments. The preparation process of this invention is simple, the raw materials are readily available, and the cost is controllable, making it widely applicable in high-temperature lubricants, heat transfer oils, electrical insulation materials, and sealing materials.

Description

Technical Field

[0001] This invention belongs to the field of silicone oil technology and relates to a high-temperature stable silicone oil and its preparation method. Background Technology

[0002] Silicone oil refers to a polysiloxane fluid composed of siloxane chains, the most typical example being dimethyl silicone oil (polydimethylsiloxane, PDMS), a linear polymer with Si-O-Si as the main chain and methyl groups as side groups. Dimethyl silicone oil possesses excellent high and low temperature resistance, low surface tension, physiological inertness, good electrical insulation, and hydrophobicity, allowing for long-term use at temperatures ranging from -50℃ to 200℃. It is widely used in lubricants, heat transfer oils, electrical insulation materials, defoamers, fabric finishing agents, and personal care products.

[0003] However, when the temperature exceeds 200℃, silicone oil undergoes two different types of degradation reactions: one is "biting-back degradation" in an oxygen-free or oxygen-limited environment, where the terminal oxygen atoms nucleophilically attack the main chain silicon atoms to generate small cyclic molecules such as hexamethylcyclotrisiloxane (D3) and octamethylcyclotetrasiloxane (D4), leading to a decrease in silicone oil viscosity and an increase in volatile matter; the other is an oxidative crosslinking reaction in an aerobic environment, where the side chain methyl groups are attacked by free radicals to generate peroxides, which then trigger a chain reaction to form a crosslinked network, leading to an increase in silicone oil viscosity until it gels. These two degradation reactions severely limit the application of silicone oil in high-temperature fields.

[0004] To address the aforementioned issues, researchers both domestically and internationally have conducted extensive research. Existing technologies for improving the high-temperature stability of silicone oils mainly fall into three categories: First, adding aromatic phenolic antioxidants (such as US2389804 and US2389805) to inhibit oxidative cross-linking by capturing free radicals. However, these antioxidants are consumable additives, easily volatilizing or migrating at high temperatures, resulting in insufficient long-term stability. Second, blending organometallic salts (such as US2445567 and CN113388118A) to utilize the catalytic effect of metal ions such as iron, cobalt, and cerium to decompose peroxides. However, these metal salts exist in a free state in the silicone oil, easily migrating, agglomerating, and deactivating at high temperatures, and may introduce problems such as excessive acid values. Third, introducing phenyl side chains to prepare phenyl silicone oils, improving thermal stability through the large volume and conjugation effect of phenyl groups. However, phenyl silicone oils are 3-5 times more expensive than ordinary silicone oils, and their low-temperature performance deteriorates, making them unsuitable for large-scale industrial applications.

[0005] In summary, existing technologies have not yet been able to effectively solve the problem of silicone oil migration and deactivation at high temperatures. Summary of the Invention

[0006] The purpose of this invention is to provide a high-temperature stable silicone oil and its preparation method, the product having high-temperature stability.

[0007] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a high-temperature stable silicone oil comprising the following components: 100 parts silicone oil; 8-12 parts of N-vinylimidazole; Zinc octanoate 1.5-3.0 parts; In the silicone oil, the imidazole group is covalently attached to the side chain.

[0008] As used herein, the term "silicone oil" refers to a polysiloxane primarily composed of dimethylsiloxane linkages. In this invention, the silicone oil is preferably a hydrogen-containing silicone oil, which refers to a silicone oil containing Si-H bonds on its molecular side chains or main chain, with a hydrogen content of 0.1-0.2 mol%.

[0009] N-Vinylimidazole is the key modifying monomer in this invention, and its molecular structure contains two parts: a vinyl group and an imidazole ring. The vinyl group can undergo a hydrosilylation reaction with the Si-H bond of the silicone oil side chain under the action of a platinum catalyst, thereby introducing the imidazole ring into the silicone oil side chain through a covalent bond. The nitrogen atom at position 2 on the imidazole ring retains a lone pair of electrons, which can act as a coordinating atom to form a stable coordinate bond with zinc ions.

[0010] Zinc octoate is the source of zinc ions in this invention, and its chemical structure is Zn(C8H2O)2O2. 15 O2)2. The long octanoic acid group in zinc octanoate endows it with good solubility and dispersibility in silicone oil, allowing it to be uniformly distributed in the reaction system. During the reaction, the Zn released from zinc octanoate... 2+ It undergoes a coordination reaction with the imidazole group on the side chain to form a stable imidazole-zinc coordination complex, thereby achieving the anchoring of zinc ions on silicone oil molecules.

[0011] This invention fixes zinc ions onto the side chains of silicone oil through covalent bonding and coordinate bonding. The covalent bonds ensure that the imidazole groups do not detach from the silicone oil molecules, while the coordinate bonds ensure that the zinc ions do not dissociate from the imidazole groups. The synergistic effect of these two mechanisms improves the problems of easy migration and deactivation of metal ions in traditional metal salt blend systems.

[0012] Preferably, the amount of N-vinylimidazole is 9-10 parts, and the amount of zinc octanoate is 2.0-2.5 parts. This ensures a sufficient number of anchoring sites while avoiding excessive metal ions remaining in the system. (Zn) 2+ It typically forms a tetrahedral or octahedral coordination configuration with 2-4 imidazole ligands.

[0013] Preferably, the silicone oil further comprises 0.1-1.0 parts of an antioxidant, wherein the antioxidant is selected from one or more of phenyl-α-naphthylamine, cerium octanoate, and 2,6-di-tert-butyl-p-cresol. The antioxidant's function is to capture free radicals in an aerobic environment, inhibiting the oxidative cross-linking reaction of the silicone oil, and forming a dual protection mechanism of "anchoring + antioxidation" with the imidazole-zinc anchoring system, further improving the high-temperature stability of the silicone oil in an open system.

[0014] Secondly, the present invention provides a method for preparing a high-temperature stable silicone oil, comprising the following steps: (1) Silicone oil and N-vinylimidazolium were subjected to hydrosilylation reaction in the presence of platinum catalyst to obtain modified silicone oil with imidazolium groups in the side chain; Hydrosilylation is an addition reaction that occurs between a compound containing a Si-H bond and a compound containing an unsaturated bond under the action of a catalyst. In this invention, the vinyl group in N-vinylimidazolium undergoes an addition reaction with the Si-H bond to form a Si-C bond, thereby covalently attaching the imidazolium ring to the silicone oil side chain. This reaction exhibits high regioselectivity and stereoselectivity, mild reaction conditions, and high yield.

[0015] (2) React the modified silicone oil obtained in step (1) with zinc octoate, and control the reaction temperature at 50-80℃ for 1-3 hours. This step is a coordination reaction; the nitrogen atom at position ② on the imidazole group of the side chain donates a lone pair of electrons, which react with the Zn released from zinc octanoate. 2+ Coordinate bonds are formed.

[0016] (3) Remove low-boiling substances from the product of step (2) at 150-200℃ and absolute pressure <100Pa for 1-2 hours, filter, and obtain the final product.

[0017] The purpose of the low-boiling point removal process is to remove unreacted monomers, catalyst decomposition products, octanoic acid, and other small molecules remaining in the reaction system, ensuring the purity and stability of the product. Under high temperature and high vacuum conditions, these small molecules are evaporated and removed, ultimately yielding pure, high-temperature stable silicone oil.

[0018] Preferably, the platinum catalyst in step (1) is a chloroplatinic acid-isopropanol solution, and the amount used is 0.025-0.1% of the mass of the silicone oil.

[0019] Preferably, the reaction temperature of the hydrosilylation reaction in step (1) is 80-100℃ and the reaction time is 3-6h.

[0020] Preferably, step (2) further includes adding 0.1-1.0 parts of antioxidant and mixing.

[0021] Thirdly, the present invention provides an application of high-temperature stable silicone oil in high-temperature lubricants, heat-conducting oils, electrical insulating materials, or sealing materials.

[0022] Preferably, the application environment is an oxygen-limited or sealed system. In oxygen-limited or sealed systems, the imidazole-zinc anchoring structure of the product of the present invention can fully exert its function of inhibiting backbiting degradation and exhibits optimal high-temperature stability.

[0023] The beneficial effects of this invention are: (1) In this invention, N-vinylimidazolium is covalently added to the side chain of silicone oil via hydrosilylation reaction, and then the nitrogen atom on the imidazolium ring (number ②) is combined with Zn 2+ By forming a stable coordination complex, zinc ions are fixed on silicone oil molecules, which improves the problem of easy migration and deactivation of metal ions in traditional metal salt blend systems.

[0024] (2) The imidazole-zinc coordination structure of the present invention is stable at high temperatures, effectively inhibiting the back-biting degradation of the siloxane backbone. At the same time, the addition of antioxidants can form a dual protection mechanism of "anchoring + anti-oxidation" with the imidazole-zinc anchoring system, which remains stable in the presence of oxygen and can be widely used in high-temperature lubricants, heat transfer oils, electrical insulation materials, sealing materials and other fields. Detailed Implementation

[0025] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with embodiments, is provided below.

[0026] Raw material description: Octamethylcyclotetrasiloxane (D4): Industrial grade, purity ≥99.5% Tetramethyltetrahydrocyclotetrasiloxane (D4H): Industrial grade, purity ≥98%. N-Vinylimidazole: Industrial grade, purity ≥98% Chloroplatinic acid-isopropanol solution: Dissolve chloroplatinic acid (analytical grade) in isopropanol to prepare a solution with a Pt content of 2%. Zinc octanoate: Industrial grade, purity ≥98% Phenylenol-α-naphthylamine: Industrial grade, purity ≥98% Cerium octoate: Industrial grade, purity ≥98% 2,6-Di-tert-butyl-p-cresol (BHT): Industrial grade, purity ≥98% Preparation of hydrogen-containing silicone oil: Octamethylcyclotetrasiloxane is copolymerized with hydrogen-containing cyclic compounds in the presence of a non-equilibrium catalyst to obtain hydrogen-containing silicone oil with a hydrogen content of 0.1-0.2 mol%. For example, under nitrogen protection, 980 g of octamethylcyclotetrasiloxane, 20 g of tetramethyltetrahydrocyclotetrasiloxane, and 0.5 g of tetramethylammonium hydroxide silanolate are added to a reactor, and the mixture is heated to 90 °C for 3 h and then heated to 120 °C for 2 h. The mixture is then neutralized with CO2 and subjected to a reaction at 160 °C and -0.09 MPa for 1 h to remove low-boiling substances, yielding hydrogen-containing silicone oil with a hydrogen content of 0.12 mol%.

[0027] Example 1 A method for preparing a high-temperature stable silicone oil includes the following steps: (1) Take 100 parts of the hydrogen-containing silicone oil prepared in the above steps, add 10 parts of N-vinylimidazolium, add 0.08 parts of chloroplatinic acid-isopropanol solution (Pt content 2%), heat to 90℃ and react for 4h to obtain modified silicone oil with imidazolium group in the side chain.

[0028] (2) Add 2.5 parts of zinc octoate to the modified silicone oil obtained in step (1) and heat to 60°C for 2 hours.

[0029] (3) Remove low-boiling substances from the product of step (2) at 180°C and 50Pa absolute pressure for 1.5h, filter, and obtain a colorless and transparent liquid.

[0030] Example 2 A method for preparing a high-temperature stable silicone oil includes the following steps: The difference from Example 1 is that 0.5 parts of phenyl-α-naphthylamine were added to the product in step (2), and the mixture was stirred evenly. The rest of the operation was the same as in Example 1.

[0031] Example 3 A method for preparing a high-temperature stable silicone oil includes the following steps: The difference from Example 1 is that: in step (2), 0.5 parts of cerium octanoate and 0.5 parts of 2,6-di-tert-butyl-p-cresol are added to the product and stirred evenly. The rest of the operation is the same as in Example 1.

[0032] Example 4 A method for preparing a high-temperature stable silicone oil includes the following steps: The difference from Example 1 is that 8 parts of N-vinylimidazole were added in step (1), and 1.5 parts of zinc octanoate were added in step (2). The rest of the operation is the same as in Example 1.

[0033] Comparative Example 1 Hydrogen-containing silicone oil, without any modification.

[0034] Comparative Example 2 Take 100 parts of hydrogen-containing silicone oil, add 2.5 parts of zinc octanoate, and stir at 60°C for 1 hour to dissolve.

[0035] Comparative Example 3 Imidazole-modified silicone oil was prepared according to step (1) of Example 1, but the zinc complexation reaction in step (2) was not carried out, and the low-boiling point was directly removed.

[0036] Comparative Example 4 Take 100 parts of hydrogen-containing silicone oil, add 0.5 parts of phenyl-α-naphthylamine, and stir well.

[0037] Performance testing: (1) Zinc anchoring strength test: Take 5g of sample, add 50mL of 0.1M EDTA solution, and extract at 60℃ for 24h with stirring. Separate the oil phase, digest it, and determine the zinc content by ICP-MS. Calculate the zinc content residue rate before and after extraction. Zinc residue rate (%) = (zinc content after extraction / zinc content before extraction) × 100%.

[0038] (2) High-temperature aging test: Weigh 40g of sample into a 70mm diameter petri dish and place it in a 250±2℃ forced-air drying oven (cover the petri dish during oxygen-limited environment testing). Remove the sample every 24 hours, cool it to 25℃, and then measure the viscosity using a Bollerfeld rotational viscometer to calculate the viscosity change rate. After all samples have been tested, continue the 250℃ hot air aging experiment, and repeat the above measurement process after 24 hours. This test is used to evaluate the high-temperature stability of the product.

[0039] The test results show that: The high-temperature stable silicone oils prepared in Examples 1-4 of this invention all had a zinc residue rate >96% after EDTA extraction, proving that zinc ions were anchored on the silicone oil side chains. In contrast, the zinc residue rate of Comparative Example 2 (free zinc salt blend) was only 35.2%, proving that free zinc ions are easily extracted and lost.

[0040] After aging in an oxygen-limited environment at 250℃ for 168 hours, the viscosity change rate of Examples 1-4 of this invention is ≤50%, demonstrating excellent high-temperature stability.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high temperature stable silicone oil characterized in that, A high-temperature stable silicone oil comprising the following components: Silicone oil 100 parts; N-vinylimidazole 8-12 parts; Zinc octoate 1.5-3.0 parts; In the silicone oil, imidazole groups are covalently bonded to the side chains.

2. The high temperature stable silicone oil of claim 1, wherein, The amount of N-vinylimidazole is 9-10 parts, and the amount of zinc octoate is 2.0-2.5 parts.

3. The high temperature stable silicone oil of claim 1, wherein, The silicone oil is hydrogen-containing silicone oil.

4. The high temperature stable silicone oil of claim 1, wherein, It also contains 0.1-1.0 parts of an antioxidant selected from one or more of phenyl-α-naphthylamine, cerium octoate, and 2,6-di-tert-butyl-p-cresol.

5. A process for preparing the high temperature stable silicone oil according to any one of claims 1 to 4, characterized in that, The following steps are included: (1) Silicon oil and N-vinylimidazole are subjected to a silicon-hydrogen addition reaction in the presence of a platinum catalyst to obtain modified silicone oil containing imidazole groups in the side chains; (2) The modified silicone oil obtained in step (1) is reacted with zinc octoate, with the reaction temperature controlled at 50-80°C and the reaction time controlled at 1-3 hours; (3) The product of step (2) is subjected to removal of low-boiling substances at 150-200°C and an absolute pressure of <100 Pa for 1-2 hours, filtered, and the final product is obtained.

6. The method of claim 5, wherein, The platinum catalyst in step (1) is chloroplatinic acid-isopropanol solution, and the amount used is 0.025-0.1% of the mass of the silicone oil.

7. The method of claim 5, wherein, The reaction temperature of the silicon-hydrogen addition reaction in step (1) is 80-100°C, and the reaction time is 3-6 hours.

8. The method of claim 5, wherein, After step (2), 0.1-1.0 parts of an antioxidant is added and mixed.

9. Use of the high-temperature stable silicone oil according to any one of claims 1-4 in high-temperature lubricants, heat-conducting oils, electrically insulating materials, or sealing materials.

10. Use according to claim 9, characterized in that, The application environment is an oxygen-limited or sealed system.

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