Long-chain alkane silicone oil and method for preparing the same

Abstract

The application relates to the technical field of silicone oil, and provides long-chain alkane silicone oil and a preparation method thereof. The preparation method comprises the following steps: pretreating hydrogen-containing polysiloxane and non-reactive low-molecular siloxane to obtain pretreated hydrogen-containing polysiloxane; adding long-chain alpha-olefins and a platinum catalyst into the pretreated hydrogen-containing polysiloxane to perform addition reaction, so that long-chain hydrocarbon groups are introduced into polysiloxane segments, and a long-chain hydrocarbon group modified silicone oil intermediate is obtained; adding short-chain alpha-olefins into the long-chain hydrocarbon group modified silicone oil intermediate to perform passivation treatment, and then sequentially performing adsorption filtration treatment and devolatilization treatment to obtain long-chain alkane silicone oil. Before the addition reaction of long-chain alpha-olefins, the hydrogen-containing polysiloxane is pretreated by using non-reactive low-molecular siloxane, so that the Si-H active sites cannot be competitively consumed in the reaction process, the initial viscosity of the reaction system is reduced, and the dispersion state after the long-chain alpha-olefins are added is improved.

Description

Technical Field

[0001] This invention relates to the field of silicone oil technology, and more specifically, to a long-chain alkane silicone oil and its preparation method. Background Technology

[0002] Long-chain alkane-structured silicone oils are a class of modified silicone oils in which long-chain saturated hydrocarbon groups are introduced into the polysiloxane molecular chain. Due to the high molecular weight and low polarity of long-chain hydrocarbon groups, their introduction into the polysiloxane structure can reduce the migration tendency of low-molecular-weight components in the silicone oil and improve the compatibility between the silicone oil and organic polymer materials. Therefore, long-chain alkane-structured silicone oils are widely used in lubricating materials, interface modifiers, and high-stability liquid media. Currently, long-chain alkane-structured silicone oils are typically prepared by hydrosilylation reaction of hydrogen-containing polysiloxanes and long-chain olefins under the action of a platinum catalyst. Through the addition reaction between Si-H bonds and carbon-carbon double bonds, the long-chain hydrocarbon group structure is introduced into the polysiloxane molecular chain, thereby obtaining a modified silicone oil with long-chain hydrocarbon group characteristics.

[0003] However, in actual preparation processes, due to the long chains of long-chain olefins and their strong intermolecular interactions, the mixing uniformity between them and the hydrogen-containing polysiloxane system is limited. When long-chain olefins are directly added to the reaction system, local concentration differences in long-chain olefins can easily occur, causing rapid hydrosilylation of Si-H groups in some regions while other regions react less. This results in uneven distribution of long-chain hydrocarbon groups on the polysiloxane segments, which in turn affects the viscosity stability, volatility, and long-term performance of the resulting long-chain alkane-structured silicone oil. Furthermore, current preparation methods typically aim to improve the conversion rate of long-chain olefins. However, due to steric hindrance and mass transfer differences in the reaction system, a small amount of unreacted Si-H groups remain after the reaction. These groups continue to react during long-term storage or high-temperature cycling, altering the molecular structure of the silicone oil and affecting the material's performance stability.

[0004] Therefore, how to improve the uniformity of the long-chain hydrocarbon group introduction process while maintaining the low volatility and good compatibility of long-chain alkane silicone oil is a problem that needs to be solved in the preparation of long-chain alkane silicone oil. Summary of the Invention

[0005] The present invention aims to provide a long-chain alkane silicone oil and its preparation method.

[0006] To address the above problems, this invention provides a method for preparing long-chain alkane silicone oil, comprising the following steps: S100. The hydrogen-containing polysiloxane is pretreated with a non-reactive low-molecular-weight siloxane to obtain a pretreated hydrogen-containing polysiloxane. S200. Add long-chain α-olefin and platinum catalyst to pretreated hydrogen-containing polysiloxane to carry out an addition reaction, so that the long-chain hydrocarbon structure is introduced into the polysiloxane chain segment to obtain a long-chain hydrocarbon modified silicone oil intermediate. S300: Short-chain α-olefins are added to long-chain hydrocarbon-modified silicone oil intermediates for passivation treatment. After passivation treatment, adsorption filtration treatment and devolatilization treatment are performed sequentially to obtain long-chain alkane silicone oil.

[0007] In the above technical solution, the dynamic viscosity of the hydrogen-containing polysiloxane at 25°C is 150-250 mPa·s, the Si-H content is 0.05-0.5 wt%, and the moisture content is not higher than 500 ppm; and / or the amount of non-reactive low molecular weight siloxane is 10-50 wt. of the hydrogen-containing polysiloxane.

[0008] In any of the above technical solutions, the general structural formula of the non-reactive low-molecular-weight siloxane is shown in formula (I): (CH3)3SiO[Si(CH3)2O] n Si(CH3)3 Equation (I); where n is an integer from 0 to 2.

[0009] In any of the above technical solutions, the pretreatment includes mixing hydrogen-containing polysiloxane and non-reactive low-molecular-weight siloxane under a nitrogen atmosphere; the mixing temperature is 35-55℃, the speed is 200-400 r / min, and the time is 45-90 min.

[0010] In any of the above technical solutions, S200 includes: S210. Divide the long-chain α-olefin into two parts. Add the first part of the long-chain α-olefin and platinum catalyst to the pretreated hydrogen-containing polysiloxane and carry out an addition reaction at 70-90℃ for 1-3 hours to obtain a partially long-chain alkylated hydrogen-containing polysiloxane intermediate. S220. Add a second part of long-chain α-olefin to a partially long-chain hydrocarbon-modified hydrogen-containing polysiloxane intermediate, and continue the reaction at 100-130℃ for 2-5 hours to obtain a long-chain hydrocarbon-modified silicone oil intermediate. The mass ratio of the first long-chain α-olefin to the second long-chain α-olefin is 1:(1-2.7).

[0011] In any of the above technical solutions, the molar ratio of carbon-carbon double bonds in the long-chain α-olefin to the molar ratio of Si-H groups in the hydrogen-containing polysiloxane is (0.95-1):1; the long-chain α-olefin includes at least one or a combination of 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene and 1-octadecene; the platinum catalyst includes caster platinum catalyst or chloroplatinic acid catalyst; the amount of platinum catalyst, calculated as platinum element, is 5-30 ppm.

[0012] In any of the above technical solutions, the short-chain α-olefin includes at least one or a combination of 1-butene, 1-hexene, and 1-octene; and / or the passivation treatment temperature is 80-110℃ and the time is 1-3h.

[0013] In any of the above technical solutions, the adsorption filtration process includes: adding an adsorbent to the passivated product for adsorption treatment and then filtering; the adsorbent includes at least one or a combination of activated alumina, silica gel and molecular sieve.

[0014] In any of the above technical solutions, the devolatilization process includes a first devolatilization process and a second devolatilization process; the temperature of the first devolatilization process is 80-100℃ and the pressure is 5-20kPa; the temperature of the second devolatilization process is 120-150℃ and the pressure is less than 1kPa.

[0015] The present invention also provides a long-chain alkane silicone oil, which is prepared by any of the preparation methods described above.

[0016] Beneficial effects This invention provides a long-chain alkane silicone oil and its preparation method. Before the hydrosilylation reaction of the long-chain α-olefin, a non-reactive low-molecular-weight siloxane is used to pretreat the hydrogen-containing polysiloxane. The non-reactive low-molecular-weight siloxane does not compete for Si-H active sites during the reaction, and simultaneously reduces the initial viscosity of the reaction system, improves the dispersion state and mass transfer conditions after the addition of the long-chain α-olefin, and allows the long-chain hydrocarbon groups to be introduced into the polysiloxane segments more uniformly, thus improving the structural uniformity of the resulting long-chain alkane silicone oil. The long-chain α-olefin is added to the pretreated hydrogen-containing polysiloxane in stages for the addition reaction, transforming the formation process of the long-chain hydrocarbon group structure from a single concentrated reaction to a gradual introduction process, thereby reducing the initial reaction pressure. The reaction rate differences caused by excessively high local concentrations of long-chain α-olefins allow Si-H groups at different positions to participate in the reaction more evenly, reducing local over-substitution or under-substitution and improving the uniformity of long-chain hydrocarbon group distribution on the polysiloxane molecular chain. After the long-chain hydrocarbon group structure is formed, short-chain α-olefins with smaller molecular size and lower steric hindrance are used to passivate the residual Si-H groups, making it easier to access the incompletely reacted Si-H active sites and complete hydrosilylation under milder conditions. This reduces the residual Si-H content in the final product, reduces the risk of performance changes in long-chain alkane silicone oils due to continued reactions of active groups during storage or long-term use, and improves molecular structure stability. Detailed Implementation

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, a detailed description of specific embodiments of the present invention will be provided below.

[0018] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available. Experimental methods in the following examples that do not specify particular conditions should be performed according to conventional methods and conditions, or as selected in the product instructions.

[0019] The long-chain alkane silicone oil in this invention refers to a modified silicone oil formed by the hydrosilylation reaction of long-chain α-olefins with Si-H groups in hydrogen-containing polysiloxanes, thereby introducing long-chain alkyl structures into the siloxane molecular chain.

[0020] Long-chain alkane silicone oils introduce long-chain hydrocarbon groups into the polysiloxane chain via hydrosilylation, which can reduce low-molecular-weight migration and improve compatibility. However, the mixing uniformity of long-chain olefins and hydrogen-containing polysiloxanes is poor, and direct addition can easily lead to excessively high local concentrations, resulting in rapid consumption of Si-H in some areas and uneven distribution of long-chain hydrocarbon groups, affecting the viscosity stability and long-term performance of the product. Furthermore, due to steric hindrance and mass transfer differences, a small amount of Si-H often remains after the reaction, which continues to react during long-term storage or high-temperature cycling, causing changes in molecular structure and impairing performance stability.

[0021] This invention provides a long-chain alkane silicone oil and its preparation method. First, hydrogen-containing polysiloxanes are pretreated with non-reactive low-molecular-weight siloxanes to improve the mixing and mass transfer state of the reaction system. Then, long-chain α-olefins are added in stages for hydrosilylation to improve the uniformity of long-chain hydrocarbon group introduction. Next, short-chain α-olefins are used to consume residual Si-H groups. Low-molecular-weight and migratable components are removed through devolatilization and adsorption filtration, thereby improving the long-term stability of the long-chain alkane silicone oil.

[0022] Specifically, the present invention provides a method for preparing long-chain alkane silicone oil, comprising the following steps: S100. The hydrogen-containing polysiloxane is pretreated with a non-reactive low-molecular-weight siloxane to obtain a pretreated hydrogen-containing polysiloxane. S200. Add long-chain α-olefin and platinum catalyst to pretreated hydrogen-containing polysiloxane to carry out an addition reaction, so that the long-chain hydrocarbon structure is introduced into the polysiloxane chain segment to obtain a long-chain hydrocarbon modified silicone oil intermediate. S300: Short-chain α-olefins are added to long-chain hydrocarbon-modified silicone oil intermediates for passivation treatment. After passivation treatment, adsorption filtration treatment and devolatilization treatment are performed sequentially to obtain long-chain alkane silicone oil.

[0023] This method first pretreats hydrogen-containing polysiloxanes with non-reactive low-molecular-weight siloxanes to create a more uniform liquid environment in the reaction system before entering the addition stage, thereby reducing local concentration differences during the subsequent addition of long-chain olefins. Then, a staged addition of long-chain α-olefins is employed to gradually introduce long-chain hydrocarbon structures into the polysiloxane segments, avoiding the problem of excessively large reaction rate differences caused by adding a large amount of olefins at once, and improving the uniformity of long-chain hydrocarbon distribution. After completing the main structure construction, short-chain α-olefins are used to passivate residual Si-H, effectively consuming active sites in the reaction system that are difficult to fully react with long-chain olefins, reducing the risk of structural changes during subsequent storage or use. Finally, low-molecular-weight components, unreacted substances, and trace impurities introduced during the reaction are removed through devolatilization and filtration, reducing the impact of migratable components on the final product performance.

[0024] Preferably, in step S100, the hydrogen-containing polysiloxane is pretreated with a non-reactive low-molecular-weight siloxane, the general structural formula of which is shown in formula (I): (CH3)3SiO[Si(CH3)2O] n Si(CH3)3 Formula (I); Where n is an integer between 0 and 2.

[0025] When n=0, the non-reactive low-molecular-weight siloxane is hexamethyldisiloxane; when n=1, it is octamethyltrisiloxane; and when n=2, it is decamethyltetrasiloxane. These types of non-reactive low-molecular-weight siloxanes all possess a siloxane structure primarily based on Si-O-Si, with both ends of the molecular chain capped by trimethylsilyl groups. They do not contain Si-H groups or carbon-carbon double bonds. Therefore, they will not participate as reactants in the subsequent platinum-catalyzed hydrosilylation reaction to introduce long-chain hydrocarbon groups, nor will they compete for the Si-H active sites in hydrogen-containing polysiloxanes. Furthermore, because their molecular structure has a similar siloxane skeleton to that of hydrogen-containing polysiloxanes, they can be well dispersed in hydrogen-containing polysiloxane systems. This allows for the adjustment of the system viscosity and mixing state before the reaction, improving the mass transfer uniformity after the addition of long-chain α-olefins. If the amount of non-reactive low-molecular-weight siloxane is too small, the improvement on the viscosity and mass transfer state of the system is limited, and it is difficult to give full play to the pretreatment effect. If the amount is too high, although it can further reduce the viscosity of the system, it will increase the subsequent devolatilization burden and reduce the concentration of effective reactive components per unit volume. Therefore, the amount of non-reactive low-molecular-weight siloxane should be 10-50 wt.% of hydrogen-containing polysiloxane.

[0026] Preferably, the hydrogen-containing polysiloxane has a dynamic viscosity of 150-250 mPa·s at 25°C. This ensures sufficient molecular chain length to guarantee the basic stability of the final long-chain alkane silicone oil while avoiding excessively high initial viscosity that could restrict the diffusion of long-chain α-olefins in the reaction system. The Si-H content is 0.05-0.5 wt%, ensuring sufficient reaction sites for the introduction of long-chain hydrocarbon groups, while avoiding excessively high Si-H content that could lead to excessively rapid local addition rates and increase the risk of structural inhomogeneity. Since moisture can react with the Si-H groups in the hydrogen-containing polysiloxane, affecting the catalytic environment of the subsequent platinum catalyst, controlling the moisture content of the hydrogen-containing polysiloxane to no more than 500 ppm can improve the stability of the subsequent addition reaction process. Furthermore, since non-reactive low-molecular-weight siloxanes directly participate in the pretreatment, their purity affects the stability of the catalytic system. Therefore, reactive low-molecular-weight siloxanes with low levels of trace active impurities such as silanol groups are preferred to reduce the possibility of interaction with Si-H groups or the platinum catalyst. This allows long-chain α-olefins to complete subsequent addition reactions in a more stable catalytic environment, reducing the problem of uneven introduction of long-chain hydrocarbon groups caused by side reactions or fluctuations in catalytic activity.

[0027] Furthermore, the pretreatment includes mixing hydrogen-containing polysiloxanes with non-reactive low-molecular-weight siloxanes under a nitrogen atmosphere. At this stage, no platinum catalyst or long-chain α-olefins have been added. The main process involves mixing and viscosity homogenization between the low-viscosity siloxanes and the hydrogen-containing polysiloxanes, without prematurely consuming large amounts of Si-H. The mixing temperature is 35-55℃, the speed is 200-400 r / min, and the time is 45-90 min. This reduces the flow resistance of the hydrogen-containing polysiloxanes without significantly increasing the ineffective volatilization loss of the low-molecular-weight siloxanes, which is beneficial for obtaining uniform pretreated hydrogen-containing polysiloxanes.

[0028] Preferably, in step S200, by adding a long-chain α-olefin and a platinum catalyst to the pretreated hydrogen-containing polysiloxane, the carbon-carbon double bonds in the long-chain α-olefin undergo a hydrosilylation reaction with the Si-H groups in the hydrogen-containing polysiloxane, thereby introducing the long-chain hydrocarbon structure into the polysiloxane segment. Since the long-chain hydrocarbon group has a large molecular chain structure, introducing it into the siloxane skeleton can increase the degree of organic integration of the molecular chain segment, reduce the migration tendency of low-molecular-weight components in the siloxane segment, improve the interaction between silicone oil and organic materials, and make it have a more stable compositional state during long-term use. Using a long-chain α-olefin and introducing it via platinum-catalyzed hydrosilylation can avoid problems such as chain segment breakage, cross-linking side reactions, and uncontrollable structure that may occur during traditional free radical grafting, allowing the long-chain hydrocarbon group to be connected to the polysiloxane segment in a more defined chemical bond form, thus improving the stability of the modified structure.

[0029] Furthermore, S200 includes: S210. Divide the long-chain α-olefin into two parts. Add the first part of the long-chain α-olefin and platinum catalyst to the pretreated hydrogen-containing polysiloxane and carry out an addition reaction at 70-90℃ for 1-3 hours to obtain a partially long-chain alkylated hydrogen-containing polysiloxane intermediate. S220. Add a second part of long-chain α-olefin to a partially long-chain hydrocarbon-modified hydrogen-containing polysiloxane intermediate, and continue the reaction at 100-130℃ for 2-5 hours to obtain a long-chain hydrocarbon-modified silicone oil intermediate.

[0030] Preferably, the long-chain α-olefin is divided into two parts. The first part of the long-chain α-olefin and platinum catalyst are added to the pretreated hydrogen-containing polysiloxane and then subjected to an addition reaction at 70-90°C for 1-3 hours. This allows some Si-H to undergo hydrosilylation with the long-chain α-olefin, yielding a partially long-chain alkylated hydrogen-containing polysiloxane intermediate. This step, under relatively mild reaction conditions, forms an intermediate state that has introduced some long-chain hydrocarbon groups while still retaining a significant number of Si-H reaction sites. Since step S100 has reduced the initial system viscosity, the first part of the long-chain α-olefin can diffuse more fully into the continuous phase of the hydrogen-containing polysiloxane. The first-stage olefin concentration is low, and the relatively mild temperature can suppress localized overly rapid reactions, allowing Si-H to be consumed more uniformly throughout the system, reducing the possibility of excessive differences in the degree of substitution of long-chain hydrocarbon groups between the final molecular chains.

[0031] Preferably, in step S220, a second part of long-chain α-olefin is added to the partially long-chain alkylated hydrogen-containing polysiloxane intermediate, and the addition reaction continues at 100-130°C for 2-5 hours. At this point, the first stage has already consumed some of the more reactive or easily accessible Si-H sites, reducing the effective concentration of the remaining Si-H. Simultaneously, the presence of long-chain hydrocarbon groups in the system increases the steric hindrance and mass transfer effects on subsequent reactions. Therefore, appropriately increasing the temperature at this stage can compensate for the decrease in the later hydrosilylation rate, allowing the remaining Si-H to further react with the long-chain α-olefin.

[0032] Preferably, the mass ratio of the first long-chain α-olefin to the second long-chain α-olefin is 1:(1-2.7). In the first stage, an appropriate amount of long-chain α-olefin is added to allow some Si-H groups to undergo hydrosilylation first, establishing a more uniform reaction environment and avoiding localized high concentrations caused by excessive addition of long-chain α-olefin, which could lead to differences in reaction rates. In the second stage, the amount of long-chain α-olefin added is increased to promote further conversion of the remaining Si-H groups and improve the degree of long-chain hydrocarbon introduction. The molar ratio of the carbon-carbon double bond in the long-chain α-olefin to the molar ratio of Si-H groups in the hydrogen-containing polysiloxane is (0.95-1):1, ensuring sufficient introduction of long-chain hydrocarbon groups while avoiding excessive long-chain α-olefin residue. The long-chain α-olefin includes at least one or a combination of 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene, with the carbon-carbon double bond located at the chain end, reducing the steric hindrance and regioselectivity complexity caused by the inner olefin, thus making it more suitable for platinum-catalyzed hydrosilylation with Si-H. Platinum catalysts include caster platinum catalysts or chloroplatinic acid catalysts. The amount of platinum catalyst, calculated as elemental platinum, is 5-30 ppm relative to the total mass of hydrogen-containing polysiloxanes and long-chain α-olefins. This ensures that the target hydrosilylation can proceed smoothly while avoiding excessive platinum that would make the reaction too vigorous and reducing the purification burden of residual catalyst in the subsequent process.

[0033] Preferably, since the S200 step mainly constructs long-chain hydrocarbon structures, a small amount of unreacted Si-H groups may still exist during the actual reaction process due to steric hindrance of the molecular chain and the influence of the local reaction environment. If these Si-H groups remain in the final product for a long time, they may undergo unexpected reactions with trace amounts of moisture, active impurities, etc., during storage or use, leading to changes in the composition and properties of the silicone oil. Therefore, by adding short-chain α-olefins in step S300 to allow them to undergo hydrosilylation with the residual Si-H, the remaining active sites can be effectively consumed, improving the stability of the molecular structure. Short-chain α-olefins include at least one or a combination of 1-butene, 1-hexene, and 1-octene. These short-chain α-olefin molecules have small molecular size and low steric hindrance, making them easier to diffuse to the vicinity of the remaining Si-H at 80-110°C and complete effective conversion within 1-3 hours. Furthermore, the amount of short-chain α-olefins added is controlled based on the molar amount of residual Si-H, preferably 0.95-1.1 times the molar amount of residual Si-H. This modification targets only a small number of unreacted active sites and does not significantly change the proportion of long-chain hydrocarbon groups as the main structure. Thus, while reducing the residual Si-H content and minimizing the risk of structural changes during subsequent storage or use, the original low migration and stability characteristics of long-chain alkane silicone oil are maintained.

[0034] Preferably, after passivation, adsorption filtration is performed. This adsorption filtration includes adding an adsorbent to the passivated product for adsorption followed by filtration. This effectively addresses issues such as trace platinum catalyst residue, polar byproducts, and fine insoluble matter. The adsorbent includes at least one or a combination of activated alumina, silica gel, and molecular sieves. Activated alumina, silica gel, or molecular sieves have a large specific surface area and numerous adsorption sites, enabling them to adsorb some catalyst residue, trace polar impurities, and moisture. The adsorbent is then removed by filtration, further improving the purity of the final silicone oil. The amount of adsorbent used is 0.5-3 wt.% of the passivated product, providing sufficient adsorption capacity while avoiding excessive silicone oil loss and filtration difficulties caused by a large amount of solid adsorbent. Filtration and adsorption form a unified process. First, the adsorbent is brought into full contact with residual trace impurities, and then the solid phase carrying these impurities is removed from the system through filtration. The resulting final product simultaneously reduces volatile small molecules, active Si-H, and catalytic activity residues, resulting in a more robust long-term stability compared to long-chain alkane silicone oils that only undergo conventional filtration.

[0035] Preferably, a devolatilization process is performed last, comprising a first-stage devolatilization process and a second-stage devolatilization process. The first-stage devolatilization process is carried out at a temperature of 80-100°C and a pressure of 5-20 kPa, which can preferentially remove short-chain α-olefins, some unreacted long-chain olefins, and volatile low-molecular-weight siloxanes. This reduces the content of light components before the system enters higher temperature and higher vacuum conditions, reducing the possibility of entrainment and foaming caused by the rapid boiling of a large number of light components during direct deep vacuuming, as well as the possibility of unreacted components continuing to undergo side reactions at high temperatures. The second-stage devolatilization process is carried out at a temperature of 120-150°C and a pressure of less than 1 kPa, mainly to remove low-molecular-weight siloxanes and high-boiling-point olefins that are difficult to remove sufficiently in the first stage. As the pressure is further reduced, these components can be removed at a relatively controllable temperature without the need for excessively high temperature and long-term treatment. For target long-chain alkane silicone oils, reducing the residue of low-molecular-weight siloxanes and free olefins can directly reduce evaporation losses and migration precipitation during subsequent use, while also reducing the possibility of free hydrocarbons causing additional swelling of seals, adhesives and other polymer components.

[0036] The present invention also provides a long-chain alkane silicone oil, which is prepared by any of the preparation methods described above.

[0037] Example 1

[0038] This embodiment provides a long-chain alkane silicone oil, the preparation method of which includes the following steps: S100. Add 100 parts by mass of hydrogen-containing polysiloxane to a dry reaction vessel, add 25 parts by mass of octamethyltrisiloxane, and mix at 45°C for 60 minutes with a stirring speed of 300 r / min under nitrogen protection to fully mix the hydrogen-containing polysiloxane and octamethyltrisiloxane to obtain pretreated hydrogen-containing polysiloxane. S210. 40 parts by mass of 1-dodecene were divided into two parts at a mass ratio of 1:1.5. The first part of 1-dodecene and 15 ppm of caster platinum catalyst (calculated as platinum element) were added to the pretreated hydrogen-containing polysiloxane. The reaction was carried out at 80°C for 2 hours to obtain a partially long-chain alkylated hydrogen-containing polysiloxane intermediate. S220. Add a second part of 1-dodecene to a partially long-chain hydrocarbon-modified hydrogen-containing polysiloxane intermediate, and heat to 120°C, and continue the reaction for 4 hours to obtain a long-chain hydrocarbon-modified silicone oil intermediate. S300. The residual Si-H content in the long-chain hydrocarbon-modified silicone oil intermediate was detected. 1-Octenene was added at 1.05 times the molar amount of residual Si-H, and the mixture was reacted at 95℃ for 2 hours to allow 1-octene to undergo an addition reaction with the residual Si-H. After passivation treatment, 1.5 parts by mass of activated alumina were added, and the mixture was stirred at 60℃ for 40 minutes for adsorption treatment. The adsorbent was then removed by filtration. The first stage of devolatilization treatment was carried out at 90℃ and 10kPa for 2 hours, and the second stage of devolatilization treatment was carried out at 135℃ and 0.8kPa for 1.5 hours to obtain long-chain alkane silicone oil. The hydrogen-containing polysiloxane has a dynamic viscosity of 200 mPa·s at 25°C, a Si-H content of 0.25 wt%, a moisture content of 180 ppm, and a molar ratio of carbon-carbon double bonds in the long-chain α-olefin to the molar ratio of Si-H groups in the hydrogen-containing polysiloxane of 0.98:1.

[0039] Example 2

[0040] This embodiment provides a long-chain alkane silicone oil, which differs from Example 1 in that: In S100, the dynamic viscosity of the hydrogen-containing polysiloxane at 25°C is 150 mPa·s, the Si-H content is 0.20 wt%, the moisture content is 150 ppm, 15 parts by mass of octamethyltrisiloxane are added, the mixing temperature is 40°C, the stirring speed is 300 r / min, and the time is 45 min. In S210, the long-chain α-olefin is 1-decene, the mass ratio of the first 1-decene to the second 1-decene is 1:2.3, the molar ratio of the carbon-carbon double bond in the long-chain α-olefin to the molar ratio of the Si-H group in the hydrogen-containing polysiloxane is 0.95:1, the first 1-decene is added, and the reaction is carried out at 75°C for 2 hours.

[0041] In S220, a second part of 1-decene was added, and the reaction was continued at 115°C for 5 hours. In S300, 1-hexene is used as a short-chain α-olefin, and the amount added is 1.03 times the molar amount of residual Si-H. The passivation treatment temperature is 100℃ and the time is 1.5h. The devolatilization treatment and adsorption filtration treatment are the same as in Example 1.

[0042] Example 3

[0043] This embodiment provides a long-chain alkane silicone oil, which differs from Example 1 in that: In S100, the hydrogen-containing polysiloxane has a dynamic viscosity of 250 mPa·s at 25°C, a Si-H content of 0.30 wt%, and a moisture content of 200 ppm. 35 parts by mass of decamethyltetrasiloxane are added. The mixing process is carried out at 50°C, with a stirring speed of 400 r / min and a time of 90 min. In S210, the long-chain α-olefin is 1-tetradecene, the mass ratio of the first part of 1-tetradecene to the second part of 1-tetradecene is 1:1, the molar ratio of the carbon-carbon double bond in the long-chain α-olefin to the molar ratio of the Si-H group in the hydrogen-containing polysiloxane is 1:1, the first part of 1-tetradecene is added, and the reaction is carried out at 90°C for 3 hours.

[0044] In S220, a second part of 1-tetradecene was added, and the reaction was carried out at 130°C for 3 hours. In S300, 1-octene was used as a short-chain α-olefin, and the amount added was 1.08 times the molar amount of residual Si-H. The passivation treatment temperature was 110°C, the reaction time was 3 hours, and the remaining steps were the same as in Example 1.

[0045] Example 4

[0046] This embodiment provides a long-chain alkane silicone oil, which is prepared in the same way as in Example 1. The difference from Example 1 is that the water content of the hydrogen-containing polysiloxane is 450 ppm, while the other conditions remain unchanged.

[0047] Example 5

[0048] This embodiment provides a long-chain alkane silicone oil, which is prepared in the same way as in Example 1. The difference from Example 1 is that 15 parts by mass of octamethyltrisiloxane and 10 parts by mass of decamethyltetrasiloxane are used to replace octamethyltrisiloxane in S100, while the other conditions remain unchanged.

[0049] Comparative Example 1 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that S100 is omitted, that is, non-reactive low-molecular-weight siloxanes are not added, and hydrogen-containing polysiloxanes are directly used for the S200 reaction.

[0050] Comparative Example 2 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that 25 parts by mass of isoparaffin are used instead of octamethyltrisiloxane in S100.

[0051] Comparative Example 3 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that 25 parts by mass of isopropanol are used instead of octamethyltrisiloxane in S100.

[0052] Comparative Example 4 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that: in S200, all 1-dodecene is added at once, and after reacting at 80°C for 2 hours, the temperature is raised to 120°C and the reaction continues for 4 hours.

[0053] Comparative Example 5 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that the mass ratio of the first part of 1-dodecene to the second part of 1-dodecene is 1:4.

[0054] Comparative Example 6 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that the short-chain α-olefin passivation step is omitted, and devolatilization and adsorption filtration are performed directly after S200.

[0055] Comparative Example 7 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that 1-dodecene is used instead of 1-octene for passivation in S300.

[0056] Comparative Example 8 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that only the first stage of devolatilization is performed in S300, and the second stage of deep devolatilization is omitted.

[0057] Comparative Example 9 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that the adsorption treatment is eliminated and the product is obtained directly by filtration after the devolatilization is completed.

[0058] Comparative Example 10 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that: after adding 25 parts by mass of octamethyltrisiloxane in S100, it is not mixed at 45°C for 60 minutes, but directly enters S210.

[0059] Comparative Example 11 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that: in S300, a two-stage devolatilization process is performed first, followed by the addition of activated alumina for adsorption and filtration.

[0060] Comparative Example 12 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that: octamethyltrisiloxane is not added in S100, the hydrogen-containing polysiloxane is stirred separately under nitrogen for 60 min, and 25 parts by mass of octamethyltrisiloxane are added after reacting for 30 min in S210. The remaining conditions are the same as in Example 1.

[0061] Comparative Example 13 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that 25 parts by mass of cyclic volatile siloxane are used instead of octamethyltrisiloxane in S100.

[0062] Comparative Example 14 This comparative example provides a long-chain alkane silicone oil, which differs from Example 1 in that: after adding 25 parts by mass of octamethyltrisiloxane in S100, it is mixed at 45°C for 5 minutes and then directly enters S210.

[0063] Performance testing The long-chain alkane silicone oil samples from Examples 1-5 and Comparative Examples 1-14 were subjected to the following tests: Effective grafting rate test of long-chain alkyl groups: using quantitative methods 1 The area of ​​the characteristic methylene peak in the sample was measured by H NMR, and the effective grafting rate of the long-chain alkyl group was calculated based on the integrated area of ​​the characteristic peak of the long-chain alkyl group and the methyl peak of the siloxane. Homogeneity test of long-chain hydrocarbon groups: The long-chain hydrocarbon group signal was analyzed by nuclear magnetic resonance hydrogen spectroscopy, and the dynamic viscosity of different batches of samples at 25℃ was measured at the same time. The relative standard deviation (RSD) of the dynamic viscosity of different batches of samples at 25℃ was calculated. Residual Si-H content test: The residual Si-H content was determined by infrared spectroscopy combined with titration. Thermal cycling stability test: The dynamic viscosity change rate was tested after aging at 150℃ for 500 hours. Volatilization loss rate test: Keep at 150℃ for 24 hours and calculate the mass loss; Low molecular weight migration test: The sample and polytetrafluoroethylene medium were sealed together and aged at 150°C for 240 hours. The weight gain of the medium was then measured. Low molecular weight siloxane residue test: The low molecular weight siloxane residue in the sample was detected by GC-MS; The test results are shown in Table 1-6.

[0064] Table 1

[0065] As shown in Table 1, Examples 1-5 all achieved high effective grafting rates of long-chain alkyl groups and low residual Si-H content, indicating that the present invention improves the reaction system state through pretreatment with non-reactive low-molecular-weight siloxanes, and, combined with the staged addition of long-chain α-olefins and passivation treatment of short-chain α-olefins, can effectively promote the formation of long-chain alkyl structures and reduce the residual unreacted active groups. Examples 2 and 3 used long-chain α-olefins of different chain lengths for the reaction, and the product performance was basically similar to that of Example 1, indicating that the present invention is applicable to long-chain olefin systems of different chain lengths. In Example 4, the moisture content of the hydrogen-containing polysiloxane was close to the upper limit. Although the residual Si-H content and viscosity change rate increased slightly, they remained at a low level, indicating that controlling the moisture content of the raw materials can reduce the impact of side reactions and ensure that the system still has good reaction stability. Example 5 used different combinations of non-reactive low-molecular-weight siloxanes for pretreatment, and still showed good comprehensive performance, indicating that the pretreatment method is not limited to a single type of low-molecular-weight siloxane.

[0066] Table 2

[0067] As shown in Table 2, Example 1 exhibits a high effective grafting rate of long-chain alkyl groups and a low batch viscosity deviation. In Comparative Example 1, the high initial viscosity of the reaction system restricts the diffusion ability of long-chain α-olefins after entering the system, leading to differences in the degree of Si-H group participation in the reaction in different regions and reducing the uniformity of long-chain alkyl structure formation. Comparative Example 2 uses isoalkanes instead of octamethyltrisiloxane, which reduces system viscosity, but due to its poor compatibility with the siloxane host structure, it cannot effectively improve the mass transfer state during hydrosilylation and increases the risk of residual non-siloxane components in the system, thus its performance is lower than that of Example 1. Comparative Example 3 uses hydroxyl-containing isopropanol as a pretreatment component. Because the hydroxyl groups undergo side reactions with Si-H, consuming some active hydrogen and interfering with the platinum catalytic system, the target hydrosilylation efficiency decreases, resulting in a significantly reduced grafting rate and a high residual activity difference. Comparative Example 10 only adds octamethyltrisiloxane without premixing, resulting in limited improvement. This indicates that the advantages of this invention stem not only from the presence of low-molecular-weight siloxanes but also from their role in pre-improving the reaction system state.

[0068] Table 3

[0069] As shown in Table 3, Example 1 uses a phased addition of long-chain α-olefins, allowing the long-chain olefins to gradually participate in the hydrosilylation reaction under a lower reaction load. This reduces the reaction rate differences caused by excessively high local olefin concentrations in the early stages of the reaction, and allows Si-H groups at different positions to participate in the reaction more evenly. In Comparative Example 4, all long-chain α-olefins are added at once, and the reaction is carried out under the same temperature program. Due to the high initial olefin concentration, the reaction rate in some areas is too fast, while the reaction in other areas is insufficient. Therefore, the effective grafting rate of long-chain alkyl groups is reduced, and the batch viscosity difference increases. In Comparative Example 5, the ratio of long-chain α-olefins in the first and second stages is changed, making it impossible to achieve a balance between the early structure establishment and the later conversion process, thus reducing the overall performance.

[0070] Table 4

[0071] As shown in Table 4, Example 1 passivated the residual Si-H by adding short-chain α-olefins. Due to the smaller molecular size and lower steric hindrance of short-chain α-olefins, they can more easily access the unreacted Si-H sites, thus further reducing the content of residual active groups. In Comparative Example 6, the short-chain passivation step was omitted, and a large amount of residual Si-H remained in the product, which was prone to continue to react during thermal aging, causing an increase in viscosity change. In Comparative Example 7, long-chain α-olefins were used to replace short-chain α-olefins. Due to the larger steric hindrance of the long-chain structure, the reaction efficiency of the residual sites decreased, thus reducing the passivation effect.

[0072] Table 5

[0073] As shown in Table 5, Example 1 effectively reduced the content of low molecular weight components and migratable impurities in the system by combining adsorption filtration with staged devolatilization. Since adsorption treatment first removes some polar impurities and trace byproducts, and then staged devolatilization further removes low-boiling components, the resulting long-chain alkyl silicone oil exhibits lower volatilization loss and migration. Comparative Example 8 omitted the second stage of devolatilization, resulting in some low-boiling components remaining, thus significantly increasing volatilization loss and migration. Comparative Example 9 omitted adsorption treatment, relying solely on devolatilization to remove components, which was insufficient for removing some non-volatile impurities, thus reducing migration performance. Comparative Example 11 changed the adsorption and devolatilization sequence; due to the increased system viscosity after devolatilization, the contact efficiency between the adsorbent and the system decreased, resulting in a lower purification effect than Example 1.

[0074] Table 6

[0075] As shown in Table 6, Example 1 showed good overall performance in terms of effective grafting rate of long-chain alkyl groups, residual Si-H content, batch viscosity stability and thermal aging stability. This indicates that premixing with low-molecular-weight linear siloxanes before the reaction can effectively improve the reaction state between the subsequent long-chain α-olefins and hydrogen-containing polysiloxanes, making the hydrosilylation process more complete and uniform. Comparative Example 1, without the addition of octamethyltrisiloxane for premixing, suffered from high initial viscosity, limiting the diffusion of long-chain α-olefins and resulting in insufficient Si-H participation in the reaction. This led to a decrease in grafting rate, an increase in residual Si-H, and a decline in reaction uniformity. During thermal aging, residual active groups continued to react, increasing the viscosity change rate. Comparative Example 2, using isoalkanes instead of octamethyltrisiloxane, reduced system viscosity, but its insufficient compatibility with the siloxane matrix prevented effective improvement of mass transfer within the reaction system. Consequently, grafting rate, thermal stability, and migration performance were lower than in Example 1, indicating that ordinary organic diluents cannot replace the role of low-molecular-weight linear siloxanes. Comparative Example 12, where octamethyltrisiloxane was added only during the long-chain α-olefin reaction, while containing low-molecular-weight siloxanes, lacked sufficient reaction time. The premixing process, which cannot improve the system state in advance, leads to a decrease in grafting uniformity and thermal stability, indicating that the premixing step in S100 is essential and cannot be replaced by simply adding low-molecular-weight siloxanes. Comparative Example 13 uses cyclic volatile siloxanes instead of octamethyltrisiloxane. Due to the different compatibility between the cyclic structure and the linear polysiloxane chain segments, and the greater likelihood of low-molecular-weight residues, it exhibits higher migration and residue levels, indicating that not all low-molecular-weight siloxanes have the same pretreatment effect. Comparative Example 14 shortens the premixing time between octamethyltrisiloxane and hydrogen-containing polysiloxane. Due to the insufficient diffusion of low-molecular-weight siloxanes, the improvement effect is limited, resulting in a decrease in grafting rate, an increase in residual Si-H, and a decrease in thermal aging stability, indicating that sufficient premixing plays an important role in forming a uniform reaction environment.

[0076] Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing a long-chain alkane silicone oil, characterized in that, Includes the following steps: S100. The hydrogen-containing polysiloxane is pretreated with a non-reactive low-molecular-weight siloxane to obtain a pretreated hydrogen-containing polysiloxane. S200. Add long-chain α-olefin and platinum catalyst to the pretreated hydrogen-containing polysiloxane to carry out an addition reaction, so that the long-chain hydrocarbon structure is introduced into the polysiloxane chain segment to obtain a long-chain hydrocarbon modified silicone oil intermediate. S300. Add short-chain α-olefins to the long-chain hydrocarbon-modified silicone oil intermediate for passivation treatment. After the passivation treatment is completed, perform adsorption filtration treatment and devolatilization treatment in sequence to obtain the long-chain alkane silicone oil.

2. The preparation method according to claim 1, characterized in that, The hydrogen-containing polysiloxane has a dynamic viscosity of 150-250 mPa·s at 25°C, a Si-H content of 0.05-0.5 wt%, and a moisture content not exceeding 500 ppm; and / or The amount of the non-reactive low molecular weight siloxane is 10-50 wt. of the hydrogen-containing polysiloxane.

3. The preparation method according to claim 2, characterized in that, The general structural formula of the non-reactive low-molecular-weight siloxane is shown in formula (I): (CH3)3SiO[Si(CH3)2O] n Si(CH3)3 Formula (I); Where n is an integer between 0 and 2.

4. The preparation method according to claim 1, characterized in that, The pretreatment includes mixing hydrogen-containing polysiloxanes and non-reactive low-molecular-weight siloxanes under a nitrogen atmosphere. The mixing process is carried out at a temperature of 35-55℃, a speed of 200-400 r / min, and a time of 45-90 min.

5. The preparation method according to claim 1, characterized in that, S200 includes: S210. The long-chain α-olefin is divided into two parts. The first part of the long-chain α-olefin and the platinum catalyst are added to the pretreated hydrogen-containing polysiloxane. The addition reaction is carried out at 70-90°C for 1-3 hours to obtain a partially long-chain alkylated hydrogen-containing polysiloxane intermediate. S220. Add a second part of the long-chain α-olefin to the partially long-chain hydrocarbon-modified hydrogen-containing polysiloxane intermediate, and continue the reaction at 100-130°C for 2-5 hours to obtain the long-chain hydrocarbon-modified silicone oil intermediate. The mass ratio of the first portion of the long-chain α-olefin to the second portion of the long-chain α-olefin is 1:(1-2.7).

6. The preparation method according to claim 5, characterized in that, The ratio of the molar amount of carbon-carbon double bonds in the long-chain α-olefin to the molar amount of Si-H groups in the hydrogen-containing polysiloxane is (0.95-1):1; The long-chain α-olefins include at least one or a combination of 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene and 1-octadecene; The platinum catalyst includes a caster platinum catalyst or a chloroplatinic acid catalyst. The platinum catalyst, calculated as elemental platinum, is used in an amount of 5-30 ppm.

7. The preparation method according to claim 1, characterized in that, The short-chain α-olefin includes at least one or a combination of 1-butene, 1-hexene, and 1-octene; and / or The passivation treatment is performed at a temperature of 80-110℃ for 1-3 hours.

8. The preparation method according to claim 1, characterized in that, The adsorption filtration process includes: adding an adsorbent to the passivated product for adsorption treatment followed by filtration; The adsorbent includes at least one or a combination of activated alumina, silica gel, and molecular sieve.

9. The preparation method according to claim 1, characterized in that, The devolatilization process includes a first devolatilization process and a second devolatilization process; The temperature of the first stage of devolatilization treatment is 80-100℃, and the pressure is 5-20kPa; The temperature of the second stage of devolatilization treatment is 120-150℃, and the pressure is less than 1kPa.

10. A long-chain alkane silicone oil, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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