Molecular weight distribution optimization additive for production of molecular weight polyisobutene in n-hexane solvent system and preparation method of molecular weight distribution optimization additive

Abstract

The invention relates to the technical field of preparation of high polymer materials, in particular to a molecular weight distribution optimization additive for production of molecular weight polyisobutene in an n-hexane solvent system and a preparation method of the molecular weight distribution optimization additive. 10%-30% of a nitrogen-containing chain transfer inhibitor; 1%-10% of a stabilizer; the polar solvent conditioning agent is selected from at least one of dichloromethane, chloroform and 1, 2-dichloroethane. The function is to stabilize the cation active center by moderately increasing the polarity of the reaction system. Through compounding of the polar solvent regulator, the nitrogen-containing chain transfer inhibitor and the stabilizer, a synergistic effect is generated. The polar solvent regulator stabilizes the active center, the nitrogen-containing chain transfer inhibitor selectively inhibits the side reaction of chain transfer, and the polymerization reaction is more controllable under the combined action of the polar solvent regulator and the nitrogen-containing chain transfer inhibitor, so that the molecular weight distribution of the product can be remarkably narrowed, and Mw / Mn can be stably controlled below 2.5.

Description

Technical Field

[0001] This invention belongs to the field of polymer material preparation technology, specifically relating to a molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system and its preparation method. Background Technology

[0002] Polyisobutylene (PIB) is an important synthetic rubber and chemical raw material. Medium molecular weight PIB, with a number average molecular weight (Mn) between 10,000 and 100,000, is widely used in lubricant additives, adhesives, sealing materials, and food-grade packaging materials due to its excellent weather resistance, chemical stability, hydrophobicity, and viscoelasticity. Molecular weight distribution (MWD) is one of the key parameters determining the processing and performance properties of PIB. A narrower molecular weight distribution (usually measured by the molecular weight distribution index Mw / Mn) means a more uniform polymer chain length, imparting more stable and consistent physicochemical properties to the material, such as more stable viscosity-temperature characteristics, lower volatility, and better mechanical strength. Industrially, medium- and high molecular weight PIBs are mainly prepared through low-temperature cationic polymerization of isobutylene. Commonly used initiators include Lewis acids such as boron trifluoride and aluminum trichloride, while solvents often include alkanes (such as n-hexane) or chloroalkanes or mixtures thereof. Hexane is a commonly used industrial solvent due to its relatively low toxicity, moderate cost, and moderate polymer solubility. However, in polymerization systems using nonpolar or weakly polar alkanes like hexane as solvents, the highly active cationic centers have short lifespans and are prone to chain transfer reactions to monomers. This side reaction is the main reason for the resulting polymers having a wide molecular weight distribution (Mw / Mn typically greater than 3.0) and a high content of oligomers, severely impacting the high-end application performance of the products. In existing technologies, narrowing the molecular weight distribution often requires using more polar solvents (such as chloroalkanes) or significantly reducing the reaction temperature. However, this leads to increased costs, higher energy consumption, stringent equipment requirements, and potential impacts on the polymerization rate, making it difficult to implement directly and economically on existing hexane-based industrial plants. Therefore, developing an additive that can effectively narrow the molecular weight distribution of polyisobutylene without altering the core conditions of existing hexane-based industrial polymerization processes has significant industrial value. Summary of the Invention

[0003] The primary objective of this invention is to overcome the shortcomings of existing technologies and provide a molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system. This additive is a pre-formulated composite solution that can be directly added to existing polymerization production lines. Through multiple synergistic mechanisms, it effectively regulates the polymerization process and significantly narrows the molecular weight distribution of the product.

[0004] A second objective of this invention is to provide a method for preparing the above-mentioned additive.

[0005] A third objective of this invention is to provide the application of the above-mentioned additives in optimizing the molecular weight distribution of polyisobutylene.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system, comprising the following components by mass percentage: Polar solvent modifier: 40%~70%; Nitrogen chain transfer inhibitors: 10%~30%; Stabilizer: 1%~10%; The balance is n-hexane solvent.

[0007] Preferably, the polar solvent modifier is selected from at least one of dichloromethane, chloroform, and 1,2-dichloroethane. Its function is to moderately increase the polarity of the reaction system, stabilize the cationic active center, and suppress side reactions caused by its excessive activity.

[0008] Preferably, the nitrogen-containing chain transfer inhibitor is selected from at least one of 2,6-di-tert-butylpyridine (DtBP), triphenylamine (TPA), melamine derivatives, or sterically hindered alkylated aniline. Its function is to selectively inhibit side reactions such as chain transfer to monomers by utilizing the weak interaction between the lone pair electrons of the nitrogen atom and the Lewis acid or active center.

[0009] Preferably, the stabilizer is selected from at least one of hindered phenolic antioxidants (such as antioxidant 1010, antioxidant 1076) and phosphite antioxidants (such as antioxidant 168). Its function is to prevent oxidation of components during additive storage and polymerization, ensuring the stability of additive performance.

[0010] Preparation method of additives The preparation method of the above-mentioned molecular weight distribution optimized additive includes the following steps: Under the protection of an inert gas (such as nitrogen or argon), metered amounts of polar solvent modifier, nitrogen-containing chain transfer inhibitor, and stabilizer are added sequentially to metered amounts of n-hexane. The mixture is stirred and mixed at 10°C-40°C for 0.5-2 hours until all components are completely dissolved, forming a homogeneous and transparent solution.

[0011] Application of additives The above-mentioned molecular weight distribution optimizing additive is used in optimizing the molecular weight distribution of polyisobutylene. The application is to add the additive to an isobutylene cationic polymerization system with hexane as the main solvent and Lewis acid as the initiator.

[0012] Preferably, the number-average molecular weight (Mn) of the polyisobutylene is in the range of 10,000 to 100,000.

[0013] Preferably, the Lewis acid initiator is boron trifluoride or its complex, or aluminum trichloride.

[0014] Preferably, the additive is added in the following manner: before the polymerization reaction is initiated, it is added to the monomer solvent mixture, or it is continuously added dropwise to the reaction system in the early stage after the polymerization reaction is initiated.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. Synergistic effect, significantly narrowing the molecular weight distribution: This invention achieves a synergistic effect through the combination of a polar solvent regulator, a nitrogen-containing chain transfer inhibitor, and a stabilizer. The polar solvent regulator stabilizes the active center, while the nitrogen-containing chain transfer inhibitor selectively inhibits chain transfer side reactions. The combined effect of these two agents makes the polymerization reaction more controllable, thereby significantly narrowing the molecular weight distribution of the product and allowing Mw / Mn to be stably controlled below 2.5.

[0016] 2. Strong process compatibility and easy industrialization: The additive is in liquid form and can be directly added to existing industrial polymerization equipment using n-hexane as a solvent without changing the core initiation system or significantly adjusting the reaction temperature. It is convenient to use and easy to achieve continuous production.

[0017] 3. Maintaining high conversion rate and target molecular weight: While effectively narrowing the molecular weight distribution, this additive does not significantly inhibit the main reaction, maintains a high monomer conversion rate, and ensures that the product reaches the target molecular weight range.

[0018] 4. Improved product quality: Polyisobutylene produced using the additives of this invention has a more uniform chain structure, and its uniformity, stability and subsequent application performance (such as viscosity-temperature characteristics and mechanical strength) are effectively improved. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is the ingredient list for the additives of this invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0022] Please see Figure 1 and Figure 2 The present invention provides a technical solution: Example 1: Preparation of Additives Under nitrogen protection, 500g of n-hexane, 200g of dichloromethane (polar solvent regulator), 50g of ~2,6-di-tert-butylpyridine (containing nitrogen chain transfer inhibitor), and 5g of antioxidant 1010 (stabilizer) were added sequentially to a dry reaction flask equipped with a stirrer. The mixture was stirred continuously at 25°C for 1 hour until the solid was completely dissolved, yielding a homogeneous and transparent composite additive solution.

[0023] Example 2: Preparation of Additives Under nitrogen protection, 450 g of n-hexane, 250 g of 1,2-dichloroethane (polar solvent regulator), 80 g of triphenylamine (containing nitrogen chain transfer inhibitor), and 8 g of antioxidant 168 (stabilizer) were added sequentially to a dry reaction flask equipped with a stirrer. The mixture was stirred continuously at 15°C for 1.5 hours to obtain a homogeneous and transparent composite additive solution.

[0024] Example 3: Application of additives in the synthesis of polyisobutylene In a polymerization reactor equipped with a stirring, temperature control, and feeding system, a mixed solution of 10 kg isobutylene monomer and 90 kg n-hexane was added. An additive solution equivalent to 1.5% of the monomer mass prepared in Example 1 was added to the reactor and stirred until homogeneous. The system was cooled to -20°C, and then boron trifluoride gas was introduced as an initiator to begin the polymerization reaction. The reaction continued until the monomer conversion exceeded 95%. After the reaction, post-processing yielded polyisobutylene. Gel permeation chromatography (GPC) analysis showed that the Mn of the obtained polyisobutylene was approximately 45,000, and the molecular weight distribution index (Mw / Mn) was 2.2.

[0025] Comparative Example 1 Except for the absence of the additives of this invention, the operating conditions were exactly the same as in Example 3. The resulting polyisobutylene had a Mn of approximately 48,000, but a molecular weight distribution index (Mw / Mn) of 3.5.

[0026] Comparing the results of Example 3 and Comparative Example 1, it can be seen that the additive of the present invention can significantly narrow the molecular weight distribution of polyisobutylene.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system, characterized in that, It consists of the following components by mass percentage: Polar solvent modifier: 40%~70%; Nitrogen chain transfer inhibitors: 10%~30%; Stabilizer: 1%~10%; The balance is n-hexane solvent.

2. The molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system according to claim 1, characterized in that, The polar solvent modifier is selected from at least one of dichloromethane, chloroform, and 1,2-dichloroethane.

3. The molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system according to claim 1 or 2, characterized in that, The nitrogen-containing chain transfer inhibitor is selected from at least one of 2,6-di-tert-butylpyridine, triphenylamine, melamine derivatives, or sterically hindered alkylated aniline.

4. A molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system according to any one of claims 1 to 3, characterized in that, The stabilizer is selected from at least one of hindered phenolic antioxidants or phosphite antioxidants.

5. A method for preparing a molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system, as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Under inert gas protection, metered amounts of polar solvent modifier, nitrogen-containing chain transfer inhibitor, and stabilizer are sequentially added to metered amounts of n-hexane, and the mixture is stirred and mixed at 10-40°C for 0.5-2 hours to form a homogeneous solution.

6. The application of a molecular weight distribution optimizing additive for the production of polyisobutylene in a hexane solvent system according to any one of claims 1 to 4 in optimizing the molecular weight distribution of polyisobutylene.

7. The application of the molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system according to claim 6, characterized in that, The application involves adding the additive to an isobutylene cationic polymerization system using n-hexane as the main solvent and Lewis acid as the initiator.

8. The application of the molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system according to claim 7, characterized in that, The Lewis acid initiator is boron trifluoride or its complex, or aluminum trichloride.

9. The application of the molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system according to claim 7, characterized in that, The additive is added in the following manner: either by adding it to the monomer solvent mixture before the polymerization reaction is initiated, or by continuously adding it dropwise to the reaction system in the early stage after the polymerization reaction is initiated.

10. The application of the molecular weight distribution optimization additive for the production of polyisobutylene in a hexane solvent system according to claim 6, characterized in that, The polyisobutylene has a number-average molecular weight range of 10,000 to 100,000 and a molecular weight distribution index Mw / Mn ≤ 2.5.

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