A process for the preparation of a high-vinyl liquid polybutadiene rubber

Abstract

The application relates to a preparation method of high-vinyl liquid polybutadiene rubber, solvent oil is added into a polymerization reactor under the protection of inert gas, 1,3-butadiene, a structure regulator and an organic lithium initiator are added, polymerization is carried out after mixing, a reaction mixture containing polybutadiene is obtained, and liquid butadiene products are separated; the structure regulator is 2,2-di(2-tetrahydrofuran) propane. The application can realize the control of high-vinyl content of liquid polybutadiene rubber by using a structure regulator, the structure regulator can be removed in the solvent stripping process, in addition, the prepared liquid polybutadiene rubber not only has high-vinyl content, but also has narrow molecular weight distribution, suitable molecular weight and dynamic viscosity, and can be applied to the fields of electronic coating, electronic insulation and potting, resin modification and the like.

Description

Technical Field

[0001] This invention belongs to the field of synthetic rubber technology and relates to a method for preparing high vinyl liquid polybutadiene rubber. Background Technology

[0002] Liquid polybutadiene rubber is a viscous, flowable polymer with a number average molecular weight of 500-10000. Based on the vinyl content, it can be divided into medium-vinyl liquid polybutadiene and high-vinyl liquid polybutadiene. High-vinyl liquid polybutadiene refers to liquid polybutadiene with a 1,2-structure content of more than 65% (by weight). High-vinyl liquid polybutadiene is generally prepared using iron-based, cobalt-based, and molybdenum-based catalysts. However, the above catalyst systems have the disadvantages of making it difficult to prepare low-molecular-weight liquid polybutadiene, and the molecular weight distribution is wide. At the same time, the catalysts contain variable-valence metals and have poor stability.

[0003] Chinese patent application CN 113698520 A discloses a method for preparing liquid polybutadiene with high vinyl content and narrow molecular weight distribution. Although it is prepared by anionic polymerization, the use of more than two structure modifiers makes it difficult to regulate the reaction, especially hindering industrial production.

[0004] Chinese patent application CN1089272A discloses a method for controlling the vinyl content in butadiene homopolymers and copolymers. It also uses two regulators to control the vinyl content in polybutadiene rubber. Moreover, the regulator A described in this patent is a hydrophilic compound that is not easily soluble in organic solvents, which can easily cause clogging of filters in industrial equipment pipelines. Furthermore, regulator A is easily adsorbed by molecular sieves in industrial equipment, resulting in unstable regulator concentration, which is even more detrimental to regulation during the production process.

[0005] In addition, Chinese patent application CN113461837A provides a method for preparing low-cis, high-vinyl-terminated hydroxyl polybutadiene rubber. The structure modifier added in this patent is a mixture of tetrahydrofuran and N,N-dimethylformamide, a mixture of tetrahydrofuran and tetramethylethylenediamine, a mixture of tetrahydrofuran and 2,2-di(2-tetrahydrofuranyl)propane, or a mixture of 2,2-di(2-tetrahydrofuranyl)propane and tetrahydrofurfuryl ethyl ether. This patent has two advantages: first, it uses tetrahydrofuran for compounding, whose boiling point is close to that of solvent oil, making it difficult to separate and remove from solvent oil; second, the vinyl content of the synthesized polybutadiene is relatively low, reaching a maximum of only 72.5%. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing high vinyl liquid polybutadiene rubber. A structure modifier can be used to control the high vinyl content of the liquid polybutadiene rubber. At the same time, the structure modifier can be removed during solvent stripping and the solvent can be recycled after purification.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for preparing high-vinyl liquid polybutadiene rubber involves adding solvent oil to a polymerization reactor under inert gas protection, followed by the addition of 1,3-butadiene, a structure modifier, and an organolithium initiator. After mixing, a polymerization reaction is carried out to obtain a reaction mixture containing polybutadiene. The liquid butadiene product is then separated, which is the target product. The structure modifier is 2,2-bis(2-tetrahydrofuranyl)propane.

[0009] Furthermore, the organolithium initiator is selected from one or more of ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, phenyl lithium, 2-naphthyl lithium, 4-butylphenyl lithium, 4-tolyl lithium, cyclohexyl lithium, and 4-butylcyclohexyl lithium. Preferably, the organolithium initiator is n-butyl lithium and / or sec-butyl lithium. More preferably, the organolithium initiator is n-butyl lithium.

[0010] Furthermore, the solvent oil is an inert organic hydrocarbon solvent during the polymerization reaction of 1,3-butadiene. Even further, the solvent oil is a C5-C8 alkane, or a C5-C8 cycloalkanes, or a mixture of C5-C8 alkanes and C5-C8 cycloalkanes, providing a favorable reaction environment for the polymerization reaction of butadiene. It should be noted that the present invention does not strictly limit the amount of hydrocarbon solvent added, and can determine it based on the conventional amount of hydrocarbon solvent added in the current preparation process of liquid butadiene rubber.

[0011] At the same time, the present invention does not impose any particular limitation on the amount of butadiene added, which can be determined according to the conventional amount of butadiene added in the current liquid butadiene rubber preparation process.

[0012] Furthermore, the polymerization process of butadiene described above should be carried out in an inert environment to prevent the generated active polymer from reacting with oxygen in the air, which would affect the reaction progress and the properties of the reaction products. An inert environment can be achieved by introducing an inert gas into the reactor; specifically, high-purity nitrogen can be introduced into the reaction vessel to isolate it from air.

[0013] Furthermore, the structure modifier does not participate in the actual copolymerization reaction during the preparation of liquid polybutadiene rubber. In actual industrial production of liquid polybutadiene rubber, the structure modifier is easily separated from the solvent oil, which can be recycled. This invention uses a system of organolithium and a structure modifier to initiate the anionic polymerization reaction of butadiene. By rationally setting the proportions of each component in this system, especially the ratio of the structure modifier to n-butyllithium, the vinyl content in the polybutadiene structure can be precisely controlled. In specific implementation, the molar ratio of the structure modifier to the organolithium initiator is 1~5:1, where the organolithium initiator is calculated as elemental lithium. When the molar ratio of the structure modifier to the organolithium initiator is greater than 5:1, the vinyl content remains essentially unchanged.

[0014] Furthermore, this invention does not impose a particular limitation on the order of adding the components before the polymerization reaction; the order can be reasonably set according to the conventional liquid polybutadiene rubber preparation process. Typically, the hydrocarbon solvent (i.e., solvent oil), butadiene, and the structure modifier (i.e., all raw materials except the organolithium initiator) are first mixed evenly. Then, the system is heated to the initiation temperature of the organolithium initiator (e.g., the initiation temperature of n-butyllithium is around 20°C). Finally, the organolithium initiator is added to initiate the butadiene polymerization reaction. Since the butadiene polymerization reaction is exothermic, the temperature of the reaction system increases as the polymerization continues. In the specific implementation of this invention, controlling the temperature of the reaction system between 5 and 40°C and the reaction time (from the addition of the organolithium initiator to the termination of the reaction) to be more than 1 hour is considered sufficient to complete the butadiene polymerization reaction.

[0015] Furthermore, after the polymerization reaction is complete, a terminator is added to terminate the reaction. Specifically, the terminator can be a solvent such as ethanol, methanol, hydrochloric acid, water, or isopropanol.

[0016] Furthermore, the separation process is as follows: water and acid are added to the reaction mixture containing polybutadiene, the mixture is stirred and allowed to stand to separate into layers, and the aqueous phase and oil phase are separated. The oil phase is then subjected to vacuum distillation to complete the separation.

[0017] Furthermore, the high vinyl liquid polybutadiene rubber prepared by the present invention has a number average molecular weight of 500-5000, a molecular weight distribution index of 1.0-1.1, and a vinyl content of 65-95%.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) Using a structure modifier to control the vinyl content is beneficial for industrial regulation, and the structure modifier used is easy to separate from the solvent oil, which is beneficial for the recycling of the solvent oil.

[0020] (2) The liquid polybutadiene rubber prepared according to the present invention not only has a high vinyl content, but also a narrow molecular weight distribution, and suitable molecular weight and dynamic viscosity, and can be applied to fields such as electronic coating, electronic insulation and potting, and resin modification. Attached Figure Description

[0021] Figure 1 The NMR spectrum of the liquid polybutadiene product obtained in Example 9 is shown. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the following embodiments, the butadiene used is 1,3-butadiene, the structure modifier used is 2,2-bis(2-tetrahydrofuranyl)propane (DTHFP), and the catalyst used is n-butyllithium.

[0025] Unless otherwise specified, all other raw materials or processing techniques are commercially available materials or conventional processing techniques in the field.

[0026] Example 1

[0027] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 200mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 5℃, and then 200mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 5℃ for 60 minutes.

[0028] After polymerization, ethanol was added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 2mL of sulfuric acid were added to the mixture, and the mixture was stirred for 20 minutes. After standing and separating the layers, the aqueous phase was separated. The oil phase was then washed twice with 1L of water. The resulting oil phase was then subjected to vacuum distillation to obtain liquid polybutadiene product.

[0029] Example 2

[0030] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 98mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 10℃, and then 65mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 10℃ for 70 minutes.

[0031] After polymerization, ethanol was added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 1mL of sulfuric acid were added to the mixture, and the mixture was stirred for 10 minutes. The mixture was then allowed to stand and separate into layers. The aqueous phase was separated, and the oil phase was washed twice with 1L of water. The resulting oil phase was then subjected to vacuum distillation to obtain liquid polybutadiene product.

[0032] Example 3

[0033] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 120mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 10℃, and then 60mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 15℃ for 90 minutes.

[0034] After polymerization, ethanol is added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 1mL of sulfuric acid are added to the mixture, and the mixture is stirred for 20 minutes. After standing and separating the layers, the aqueous phase is separated, and the oil phase is subjected to vacuum distillation to obtain liquid polybutadiene product.

[0035] Example 4

[0036] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 100mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 15℃, and then 50mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 25℃ for 90 minutes.

[0037] After polymerization, ethanol was added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 1mL of sulfuric acid were added to the mixture, and the mixture was stirred for 20 minutes. After standing and separating the layers, the aqueous phase was separated. The oil phase was then washed twice with 1L of water. The resulting oil phase was then subjected to vacuum distillation to obtain liquid polybutadiene product.

[0038] Example 5

[0039] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 111mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 30℃, and then 37mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 40℃ for 80 minutes.

[0040] After polymerization, ethanol was added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 1mL of sulfuric acid were added to the mixture, and the mixture was stirred for 20 minutes. After standing and separating the layers, the aqueous phase was separated. The oil phase was then washed twice with 1L of water. The resulting oil phase was then subjected to vacuum distillation to obtain liquid polybutadiene product.

[0041] Example 6

[0042] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 116mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 30℃, and then 33mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 40℃ for 90 minutes.

[0043] After polymerization, ethanol was added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 1mL of sulfuric acid were added to the mixture, and the mixture was stirred for 20 minutes. After standing and separating the layers, the aqueous phase was separated. The oil phase was then washed twice with 1L of water. The resulting oil phase was then subjected to vacuum distillation to obtain liquid polybutadiene product.

[0044] Example 7

[0045] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 165mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 5℃, and then 33mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 5℃ for 90 minutes.

[0046] After polymerization, ethanol was added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 1mL of sulfuric acid were added to the mixture, and the mixture was stirred for 20 minutes. After standing and separating the layers, the aqueous phase was separated. The oil phase was then washed twice with 1L of water. The resulting oil phase was then subjected to vacuum distillation to obtain liquid polybutadiene product.

[0047] Example 8

[0048] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 200mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 5℃, and then 25mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 10℃ for 90 minutes.

[0049] After polymerization, ethanol was added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 1mL of sulfuric acid were added to the mixture, and the mixture was stirred for 20 minutes. After standing and separating the layers, the aqueous phase was separated. The oil phase was then washed twice with 1L of water. The resulting oil phase was then subjected to vacuum distillation to obtain liquid polybutadiene product.

[0050] Example 9

[0051] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 120mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 20℃, and then 30mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 30℃ for 90 minutes.

[0052] After polymerization, ethanol was added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 1mL of sulfuric acid were added to the mixture, and the mixture was stirred for 20 minutes. After standing and separating the layers, the aqueous phase was separated. The oil phase was then washed twice with 1L of water. The resulting oil phase was then subjected to vacuum distillation to obtain liquid polybutadiene product.

[0053] Example 10

[0054] Under high-purity nitrogen protection, 9000g of cyclohexane and 100g of butadiene were added to a 2L polymerization reactor, followed by 125mmol of 2,2-bis(2-tetrahydrofuranyl)propane. After stirring for 10 minutes, the reactor temperature was maintained at 15℃, and then 25mmol of n-butyllithium was added. The specific raw material ratios are shown in Table 1. During the polymerization reaction, the temperature was maintained at 20℃ for 90 minutes.

[0055] After polymerization, ethanol was added to terminate the reaction, resulting in a polymerization mixture. 1L of water and 1mL of sulfuric acid were added to the mixture, and the mixture was stirred for 20 minutes. After standing and separating the layers, the aqueous phase was separated. The oil phase was then washed twice with 1L of water. The resulting oil phase was then subjected to vacuum distillation to obtain liquid polybutadiene product.

[0056] Comparative Example 1

[0057] Liquid polybutadiene was prepared using the same method as in Example 4, except that the amount of 2,2-bis(2-tetrahydrofuranyl)propane, the structure modifier, was adjusted to 25 mmol.

[0058] Comparative Example 2

[0059] Liquid polybutadiene was prepared using the same method as in Example 6, except that the polymerization temperature was adjusted to 70°C for the reaction.

[0060] Comparative Example 3

[0061] Liquid polybutadiene was prepared using the same method as in Example 10, except that the amount of 125 mmol of the structure modifier 2,2-bis(2-tetrahydrofuranyl)propane added in the polymerization step was adjusted to 150 mmol.

[0062] Comparative Example 4

[0063] Liquid polybutadiene was prepared using the same method as in Example 5, except that a tetrahydrofuran was added as a structure modifier in the polymerization step, and the amount of 2,2-bis(2-tetrahydrofuranyl)propane added was reduced to 56 mmol, while the amount of tetrahydrofuran added was 56 mmol.

[0064] Figure 1 The NMR spectrum of the liquid polybutadiene product obtained in Example 9 is shown.

[0065] The performance data obtained from the tests conducted on Examples 1-9 and Comparative Examples 1-3 are as follows.

[0066] Table 1 Raw material ratio and reaction conditions

[0067]

[0068] Table 2. Microstructure test results of samples from each embodiment.

[0069]

[0070] Compared to Comparative Example 1, Example 4 reduced the amount of structure modifier added, decreasing the molar ratio of structure modifier to n-butyllithium from 2:1 to 0.5:1, and reducing vinyl content from 80.2% to 63.4%. Compared to Comparative Example 2, Example 6 increased the reaction temperature from 40°C to 70°C, reducing vinyl content from 75.9% to 61.2%. Compared to Comparative Example 3, Example 10 increased the amount of modifier added from 125 mmol to 150 mmol, increasing the ether-lithium ratio from 5:1 to 6:1, while maintaining essentially the same vinyl content. From a cost perspective, the optimal ratio of structure modifier to n-butyllithium is 5:1. Although lower temperatures favor higher vinyl content, energy conservation is paramount; temperatures that are too low result in excessive energy consumption.

[0071] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing high-vinyl liquid polybutadiene rubber, characterized in that, Under inert gas protection, solvent oil is added to the polymerization reactor, followed by 1,3-butadiene, a structure modifier, and an organolithium initiator. After mixing, a polymerization reaction is carried out to obtain a reaction mixture containing polybutadiene. The liquid butadiene product is then separated, which is the target product. The structure modifier is 2,2-bis(2-tetrahydrofuranyl)propane. The molar ratio of lithium in the structure modifier to the organolithium initiator is 1~5:1; During the polymerization reaction, the temperature of the reaction system is controlled at 5~40℃.

2. The method for preparing a high-vinyl liquid polybutadiene rubber according to claim 1, characterized in that, The organolithium initiator is selected from one or a combination of several of ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, phenyl lithium, 2-naphthyl lithium, 4-butylphenyl lithium, 4-tolyl lithium, cyclohexyl lithium, and 4-butylcyclohexyl lithium.

3. The method for preparing a high-vinyl liquid polybutadiene rubber according to claim 1, characterized in that, The organolithium initiator is n-butyllithium and / or sec-butyllithium.

4. The method for preparing a high-vinyl liquid polybutadiene rubber according to claim 1, characterized in that, The solvent oil is an organic hydrocarbon solvent that is inert during the polymerization reaction of 1,3-butadiene.

5. The method for preparing a high-vinyl liquid polybutadiene rubber according to claim 4, characterized in that, The solvent oil is a C5-C8 alkane, or a C5-C8 cycloalkanes, or a mixture of C5-C8 alkane and C5-C8 cycloalkanes.

6. The method for preparing a high-vinyl liquid polybutadiene rubber according to claim 1, characterized in that, During the polymerization reaction, the reaction time is more than 1 hour.

7. The method for preparing a high-vinyl liquid polybutadiene rubber according to claim 1, characterized in that, After the polymerization reaction is complete, a terminator is added to terminate the reaction.

8. The method for preparing a high-vinyl liquid polybutadiene rubber according to claim 1, characterized in that, The separation process is as follows: water and acid are added to the reaction mixture containing polybutadiene, the mixture is stirred and allowed to stand to separate into layers, and the aqueous phase and oil phase are separated. The oil phase is then subjected to vacuum distillation to complete the separation.

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