Macromolecular branching agent, star-branched polymer, preparation method and application thereof

Abstract

The present invention relates to the field of polymer compound preparation, and in particular to a macromolecular branching agent, a star-branched polymer, and a preparation method and application thereof, wherein the macromolecular branching agent comprises a white carbon black carrier; the outer surface of the white carbon black carrier is chemically coupled with a coupling agent; and the coupling agent is grafted with a telechelic polymer segment containing a double bond. The present application uses a coupling agent to improve the dispersibility of white carbon black, and fixes it as a reaction site for grafting with a telechelic polymer. This method can more simply and effectively prepare a star-shaped polymer with better performance on the basis of achieving a good dispersion of white carbon black to achieve a reinforcement effect.

Description

Technical Field

[0001] The present invention relates to the field of polymer compound preparation, and in particular to a macromolecular branching agent, a star-branched polymer, and a preparation method and application thereof Background Art

[0002] Black carbon black and white carbon black are important fillers for rubber reinforcement. Compared with black carbon black, white carbon black has a smaller particle size and a larger specific surface area, so it can obtain higher tensile strength, tear strength and wear resistance when filling vulcanized rubber. However, white carbon black has poor compatibility with hydrocarbon rubber, which increases the viscosity of the rubber filled with a large amount of white carbon black, and the processing performance deteriorates with the extension of storage time. In addition, the rubber after storage is prone to hardening, difficulty in extrusion, and poor molding viscosity, and the filled rubber is also prone to accumulate static electricity, resulting in poor processing performance, which limits its application in the rubber industry.

[0003] The reason why silica-filled rubber has the above problems is that there are hydrophilic silanol groups on the surface of silica, and silica forms filler-filler interactions through hydrogen bonding, which easily agglomerates to form a filler network. Therefore, in non-polar rubber, silica has poor dispersibility, resulting in poor performance.

[0004] On the other hand, star-branched polymers have smaller atomic spatial arrangement size, spherical symmetric structure, and no entanglement inside and outside the molecule, which results in smaller intermolecular interactions. Compared with linear polymers with the same molecular weight, star-branched polymers have unique properties such as lower diffusion coefficient, melt viscosity, and smaller hydrodynamic volume. However, due to the complex and tedious nucleation process of star-branched polymers, further exploration of their preparation methods is needed.

[0005] For example, the method for preparing a bimodal star-branched butyl rubber by a slurry method with application number 201910475292.7 adopts anionic polymerization technology to synthesize poly(styrene-conjugated diene) block polymer, and obtains a four-arm star-shaped block polymer by coupling with silicon tetrachloride; after dissolving the copolymer, HCl gas is continuously introduced at -20-0°C for 3-12 hours to obtain a functionalized four-arm star-shaped branching agent containing silicon and chlorine; the functionalized four-arm star-shaped branching agent containing silicon and chlorine is dissolved in a solvent, isobutylene and isoprene are added, the temperature is lowered to below -60°C, the main initiator and the co-initiator are mixed and aged, and then added to the system, polymerized for 3-30 minutes under stirring, a terminator is added to terminate the reaction, and the sample is vacuum-dried to obtain a bimodal star-shaped branched butyl rubber sample. Compared with the prior art, the bimodal star-shaped branched butyl rubber provided by the invention has lower Mooney stress relaxation and intrinsic viscosity, and has better processing performance.

[0006] Therefore, how to disperse silica well to achieve a reinforcement effect and more effectively prepare star-branched polymers with better performance has become an urgent problem to be solved. Summary of the invention

[0007] The present invention aims to overcome the defects in the prior art that the preparation method of star-branched polymer is complicated and it is difficult to compound it with white carbon black reinforcing material, resulting in limited application of it in the rubber industry. Therefore, the present invention provides a macromolecular branching agent, a star-branched polymer and its preparation method and application to overcome the above defects.

[0008] To achieve the above-mentioned purpose, the present invention is implemented by the following technical solutions:

[0009] In a first aspect, the present invention first provides a macromolecular branching agent,

[0010] including a white carbon black carrier;

[0011] The outer surface of the white carbon black carrier is chemically coupled with a coupling agent;

[0012] The coupling agent is grafted with a telechelic polymer segment containing a double bond.

[0013] The branching agent commonly used in the preparation process of the star-branched polymer in the prior art is a small molecule branching agent. Since the small molecule branching agent has a relatively small size and a relatively fixed number of branch arms, the reactive groups in the small molecule branching agent are arranged relatively more closely, resulting in that a part of the reactive groups of the small molecule branching agent participating in the polymerization reaction are easily shielded by the surrounding segments during the growth of the polymer chain segments, thereby stopping the growth, and further resulting in the branching degree of the prepared star-branched polymer cannot be further improved, thereby further affecting the performance of the star-branched polymer.

[0014] The macromolecular branching agent in the present application uses a white carbon black carrier as a carrier. Since the structural size of white carbon black is larger than that of the existing branching agents, multiple telechelic polymer segments containing double bonds can be grafted with it, thereby greatly increasing the number of branch arms of this type of macromolecular branching agent provided in the present invention. At the same time, after multiple telechelic polymer segments containing double bonds are grafted onto the surface of white carbon black, since the interval between the double bonds in adjacent telechelic polymer segments is large, it is not easy to be shielded by the surrounding segments during the polymerization reaction. Therefore, each telechelic polymer segment can play the role of growing a branched segment of a high molecular weight star-branched polymer. This macromolecular structure can improve the physical properties of the polymer, such as tensile strength, heat resistance and chemical resistance. At the same time, the macromolecular structure can also increase the intermolecular crosslinking of the polymer and improve the stability and durability of the polymer. Based on the above effects, the star-branched polymer prepared by this type of macromolecular branching agent provided in the present invention has a higher degree of branching and a higher molecular weight, so that the star-branched polymer has more excellent performance.

[0015] In addition, in the prior art, white carbon black is usually used as a reinforcing material. White carbon black is an inorganic material with high surface area and high adsorption performance, and has good dispersibility and adsorption capacity. Using white carbon black as a carrier can increase the load and dispersibility of the star-shaped branching agent, and improve its dispersion stability and processing performance in the polymer. In addition, white carbon black can also increase the strength and hardness of the polymer and improve the mechanical properties of the polymer. However, as described in the background technology, the surface of white carbon black contains hydrophilic silanol groups, resulting in poor compatibility with the rubber. In the prior art, in order to improve the compatibility between white carbon black and the rubber, white carbon black is usually surface modified (for example, surface modified using a silane coupling agent), and this type of method is simple and effective and can effectively improve the compatibility between white carbon black and the rubber. However, the reinforcement principle of this type of white carbon black is mainly based on the adsorption effect, filling effect and physical electrostatic cross-linking effect of physical principles, but the upper limit of the reinforcement effect of this type of reinforcement based on physical principles is relatively low. In the present application, silica is connected to the interior of the macromolecular branching agent as a carrier. Therefore, after the macromolecular branching agent is polymerized with the polymer monomer to form a star-branched polymer, the silica enters the interior of the star-branched polymer in a chemically bonded manner. Compared with traditional reinforcement effects, this type of chemical reinforcement in the present application can effectively improve the various properties of the star-branched polymer.

[0016] In summary, this macromolecular star-shaped branching agent containing a silica carrier, a coupling agent and a telechelic polymer segment has multiple advantages, including improving the physical properties and chemical stability of the polymer, increasing the dispersibility and compatibility of the star-shaped branching agent, and achieving further functionalization and regulation. This innovative material has broad application prospects in the field of polymers and can be used in plastics, coatings, adhesives, polymer composites and other fields.

[0017] In a second aspect, the present invention also provides a method for preparing the macromolecular branching agent as described above, comprising the following steps:

[0018] (1) using white carbon black as a carrier and chemically coupling the white carbon black with a coupling agent;

[0019] (2) Use telechelic polymers to graft them and convert the ends into double bond groups to obtain macromolecular branching agents.

[0020] The present invention adopts simple chemical reaction steps, including chemical coupling of white carbon black and grafting of telechelic polymer. These reaction steps are relatively easy to implement, do not require complex synthesis conditions and equipment, are widely applicable, and can be carried out in laboratories or industrial production. The method uses white carbon black as a carrier, which has a high surface area and adsorption performance, and can increase the loading amount and dispersibility of the branching agent. Through chemical coupling and grafting reactions, white carbon black can be firmly fixed on the surface of the branching agent, thereby improving the binding force between the carrier and the branching agent. This efficient carrier fixing method can realize the preparation of low-cost and high-load macromolecular branching agents.

[0021] The macromolecular branching agent prepared by this method has many advantages, such as enhancing the physical properties of polymers, improving the thermal stability and mechanical properties of polymers, and improving the dispersibility and compatibility of polymers. This macromolecular branching agent has wide application potential in the fields of plastics, coatings, adhesives, polymer composites, etc.

[0022] Preferably, the coupling agent comprises a silane coupling agent containing an amino group.

[0023] The present invention uses a silane coupling agent containing an amino group as a preferred coupling agent in the method for preparing a macromolecular branching agent, which has the following advantages: the amino functional group can react with a polymer chain segment or other functional monomers, thereby further improving the dispersibility of the branching agent in the polymer. By interacting with the polymer, better compatibility and dispersion stability can be achieved, and the processing performance and mechanical properties of the polymer can be improved.

[0024] Further preferably, the coupling agent is any one or more combinations of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, aminoethylaminoethylaminopropyltrimethoxysilane, and aminophenyltrimethoxysilane.

[0025] Preferably, the mass ratio of the white carbon black to the silane coupling agent containing an amino group is 1:(0.1-10).

[0026] The mass ratio of white carbon black to silane coupling agent is preferably controlled within the range of 1:(0.1-10), which can achieve uniform dispersion of white carbon black in the silane coupling agent and avoid agglomeration and precipitation. This good dispersibility can improve the dispersion stability and processing performance of the branching agent in the polymer.

[0027] By controlling the mass ratio of white carbon black to silane coupling agent, the appropriate carrier content can be achieved. Increasing the carrier loading can increase the loading capacity of the branching agent and enhance its dispersibility and compatibility in the polymer. This is of great significance for improving the performance and function of polymer materials.

[0028] As a carrier, white carbon black has a high surface area and adsorption performance, which can adsorb and fix the silane coupling agent. By adjusting the mass ratio, the degree of combination between the carrier and the branching agent can be controlled, thereby adjusting the structure and performance of the branching agent. This adjustment ability can be used to design and adjust the performance and function of the macromolecular branching agent according to specific application requirements. At the same time, through a reasonable ratio, the reaction efficiency can be improved and the preparation efficiency of the macromolecular branching agent can be improved.

[0029] In summary, controlling the mass ratio of white carbon black to silane coupling agent in the range of 1:(0.1-10) as a preferred choice can achieve good dispersibility, increase the carrier loading, adjust the structure and performance of the branching agent, and maintain an economical and efficient preparation process. This choice can improve the preparation efficiency and performance of macromolecular branching agents and provide more possibilities for the development and application of polymer materials.

[0030] Preferably, the coupling agent may further include diisocyanate.

[0031] Preferably, the diisocyanate includes any one or more combinations of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane-4,4′-diisocyanate, polyether-modified MDI, carbodiimide-modified MDI, polymethylene polyphenyl polyisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, naphthalene-1,5-diisocyanate, methylcyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

[0032] Preferably, the telechelic polymer is a telechelic polyisobutylene as shown in formula (I) or a telechelic polybutadiene as shown in formula (II);

[0033] The structural formulas of the telechelic polyisobutylene and telechelic polybutadiene are as follows:

[0034]

[0035] Wherein, in the formula (I) and formula (II), n is selected from 5-5000.

[0036] In a third aspect, the present invention also provides a method for preparing a star-branched polymer, comprising the following steps: in the presence of an initiator system, initiating a cationic polymerization reaction of the macromolecular branching agent and a monomer, thereby obtaining a star-branched polymer.

[0037] By initiating cationic polymerization with an initiator system, a high degree of control over the polymerization process can be achieved. The selection and control of the initiator can adjust parameters such as polymerization rate, degree of polymerization and molecular weight distribution, thereby achieving precise control over the molecular structure of the star-branched polymer. This highly controlled molecular structure helps to adjust the properties and functions of the polymer.

[0038] In addition, through cationic polymerization, a variety of monomers can be used to prepare star-branched polymers. Different monomers can give polymers different chemical properties and physical properties, thereby expanding the application areas of polymers. This diverse selection of monomers allows the prepared star-branched polymers to have more design freedom.

[0039] Cationic polymerization is highly reactive and can be carried out under relatively mild conditions. This helps to improve the efficiency and yield of the reaction and reduce the occurrence of side reactions. High reactivity can also achieve shorter reaction times and increase the speed of preparing star-branched polymers.

[0040] Preferably, the initiator system comprises a main initiator and a co-initiator; wherein,

[0041] The main initiator includes one or more combinations of water, hydrogen chloride gas, 2-chloro-2,4,4-trimethylpentane, cumyl chloride, dicumyl chloride, 5-tert-butyl-1,3-dicumyl chloride, and 5-tert-butyl-1,3-bis(1-methyl-1-methoxyethyl)benzene;

[0042] The co-initiator includes a combination of one or more of titanium tetrachloride, ferric chloride, boron trifluoride, boron trichloride, aluminum chloride, ethylaluminum dichloride and triethylaluminum trichloride.

[0043] The present invention uses a combination of a main initiator and a co-initiator as an initiator system, which has the following advantages:

[0044] (1) The combination of the main initiator and the co-initiator can promote each other and improve the activity of the initiator system. The co-initiator can enhance the initiation effect of the main initiator and accelerate the polymerization reaction. This helps to increase the reaction rate and yield and shorten the reaction time.

[0045] (2) At the same time, different combinations of primary initiators and co-initiators can be applied to different types of monomers. This makes the initiator system have a wider range of applications and can be used to initiate polymerization reactions of monomers with different chemical properties. This flexibility and diversity helps to achieve precise control of the molecular structure and properties of star-branched polymers.

[0046] (3) The selection and ratio of the main initiator and the co-initiator can adjust the properties of the polymerization reaction. Different initiator combinations will affect parameters such as the molecular weight, molecular weight distribution and degree of polymerization of the polymer. By rationally selecting and controlling the initiator system, the reaction process and product of the star-branched polymer can be regulated.

[0047] Preferably, the molar ratio of the main initiator to the co-initiator is 1:(1-30).

[0048] Preferably, the polymerization temperature of the cationic polymerization reaction is -90°C to -50°C.

[0049] In a fourth aspect, the present invention also provides the use of the star-branched polymer prepared by the method described above in sidewall rubber, airtight layer rubber and inner tube rubber.

[0050] Therefore, the present invention has the following beneficial effects:

[0051] (1) A coupling agent is used to improve the dispersibility of silica and fix it as a reaction site for grafting with a telechelic polymer. This method can achieve a good dispersion of silica to achieve a reinforcing effect, and more simply and effectively prepare a star-shaped polymer with better performance;

[0052] (2) This grafted product is a star-shaped polymer itself, and can also be used as a macromolecular branching agent to carry out cationic polymerization in an initiator system, thereby realizing the preparation of a high-level star-shaped branched polymer. The proportion of molecular chains involved in branching can reach more than 40%; (3) Compared with linear polymers with the same molecular weight, the high-level star-shaped branched polymer prepared by this invention has unique properties such as lower diffusion coefficient, melt viscosity, and smaller fluid dynamic volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The graph is a curve of the mean square radius of rotation and molecular weight of the star-branched polymer and linear polyisobutylene prepared in the present invention.

[0054] Figure 2This is a graph showing the detection results of the star-branched polymer prepared in Example 1 of the present invention under a multi-angle laser light scattering / ultraviolet / online viscosity detector.

[0055] Figure 3 This is the infrared spectrum of the star-branched polymer prepared in Example 1 of the present invention.

[0056] Figure 4 This is a DSC test chart of the linear polyisobutylene prepared in Comparative Example 1 of the present invention.

[0057] Figure 5 This is the DSC test graph of the star-branched polymer prepared in Example 1.

[0058] Figure 6 This is a TGA test chart of the linear polyisobutylene prepared in Comparative Example 1 of the present invention.

[0059] Figure 7 This is the TGA test chart of the star-branched polymer prepared in Example 1.

[0060] Figure 8 This is the H-NMR spectrum of the star-branched polymer prepared in Example 1. DETAILED DESCRIPTION

[0061] The present invention is further described below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0062] Unless otherwise stated, the instruments and reagents used in the following examples are commercially available.

[0063]

Preparation of macromolecular branching agent

[0064] Preparation Example 1:

[0065] 1g of white carbon black and 10g of γ-aminopropyltriethoxysilane coupling agent were mixed and stirred at high speed for 60 minutes, and then kept at 60°C for one hour and naturally cooled to obtain a coupling product. Then, it was dissolved in 100ml of n-hexane solution, and 100g of isotopic telechelic polyisobutylene was added to undergo condensation reaction to obtain a macromolecular branching agent A.

[0066] Preparation Example 2:

[0067] 1g of white carbon black and 5g of γ-aminopropyl triethoxysilane coupling agent were mixed and stirred at high speed for 30 minutes, and then 7.5g of 2,4-toluene diisocyanate was added and continued to be mixed and stirred at high speed for 30 minutes, and then kept at 60°C for one hour and naturally cooled to obtain a coupling product. Then it was dissolved in 100ml of n-hexane solution, and 100g of isotopic telechelic polyisobutylene was added to undergo condensation reaction to obtain a macromolecular branching agent B.

[0068] Preparation Example 3:

[0069] 1g of white carbon black, 0.1g of γ-aminopropyl triethoxysilane coupling agent and 10g of 4-toluene diisocyanate were mixed and stirred at high speed for 60min, and then kept at 60℃ for one hour and naturally cooled to obtain a coupling product. Then it was dissolved in 100ml of n-hexane solution, and 100g of isotopic telechelic polybutadiene was added to undergo condensation reaction to obtain a macromolecular branching agent C.

[0070] Preparation of advanced star polymers:

[0071] Embodiment 1:

[0072] A 4-liter low-temperature polymerization kettle was used, which was refrigerated to -90°C after baking, vacuuming, and nitrogen filling, and 1300 g of dichloromethane, 540 g of isobutylene, and 5 g of the macromolecular branching agent A prepared in Preparation Example 1 were added. A 0.01M aqueous solution was added as the main initiator, and 0.1M trichlorotriethylaluminum was added as the co-initiator, and the mixture was configured to form an initiation system. Nitrogen was then pressed into the reactor to initiate polymerization, and finally a small amount of methanol was added to terminate the reaction. The product was then freed from the solvent and dried to constant weight.

[0073] Embodiment 2:

[0074] A 4-liter low-temperature polymerization kettle was used, which was refrigerated to -90°C after baking, vacuuming, and nitrogen filling, and 1300 g of dichloromethane, 540 g of isobutylene, 16 g of isoprene, and 10 g of the macromolecular branching agent A prepared in Preparation Example 1 were added. A 0.01 M aqueous solution was added as the main initiator, and 0.1 M trichlorotriethylaluminum was added as the co-initiator, and the mixture was configured to form an initiation system. Nitrogen was then pressed into the reactor to initiate polymerization, and finally a small amount of methanol was added to terminate the reaction. The product was then freed from the solvent and dried to constant weight.

[0075] Embodiment 3:

[0076] A 4-liter low-temperature polymerization kettle was used, which was baked, vacuumed, and filled with nitrogen and then cooled to -80°C, and 1300 g of methyl chloride, 540 g of isobutylene, and 2 g of the macromolecular branching agent A prepared in Preparation Example 1 were added. A 0.01 M aqueous solution was added as the main initiator, and 0.15 M titanium tetrachloride was added as the co-initiator, and the mixture was mixed to form an initiation system, and then nitrogen was pressed into the reactor to initiate polymerization, and finally a small amount of methanol was added to terminate the reaction, and the product was then freed from the solvent and dried to constant weight.

[0077] Embodiment 4:

[0078] A 4-liter low-temperature polymerization kettle was used, which was baked, vacuumed, and filled with nitrogen and then cooled to -60°C, and 1300 g of methyl chloride, 540 g of isobutylene, and 1.5 g of the macromolecular branching agent A prepared in Preparation Example 1 were added. A 0.01 M aqueous solution was added as the main initiator, and 0.15 M aluminum chloride was added as the co-initiator, and the mixture was configured into an initiation system. Nitrogen was then pressed into the reactor to initiate polymerization, and finally a small amount of methanol was added to terminate the reaction. The product was then freed from the solvent and dried to constant weight.

[0079] Embodiment 5:

[0080] A 4-liter low-temperature polymerization kettle was used, which was baked, vacuumed, and filled with nitrogen and then cooled to -70°C, and 1300 g of dichloromethane, 540 g of isobutylene, and 2.5 g of the macromolecular branching agent A prepared in Preparation Example 1 were added. Hydrogen chloride gas was introduced as the main initiator, and 0.8 M triethylaluminum trichloride aged at low temperature for 10 min was used as the co-initiator. Nitrogen was then pressed into the reactor to initiate polymerization, and finally a small amount of methanol was added to terminate the reaction. The product was then freed from the solvent and dried to constant weight.

[0081] Embodiment 6:

[0082] A 4-liter low-temperature polymerization kettle was used, which was baked, vacuumed, and filled with nitrogen and then cooled to -90°C, and 1300 g of dichloromethane, 540 g of isobutylene, and 5 g of the macromolecular branching agent B prepared in Preparation Example 2 were added. A 0.01M aqueous solution was added as the main initiator, and 0.1M triethylaluminum trichloride was added as the co-initiator, and the mixture was configured to form an initiation system, and then nitrogen was pressed into the reactor to initiate polymerization, and finally a small amount of methanol was added to terminate the reaction, and the product was then freed from the solvent and dried to constant weight.

[0083] Embodiment 7:

[0084] A 4-liter low-temperature polymerization kettle was used, which was refrigerated to -90°C after baking, vacuuming, and nitrogen filling, and 1300 g of dichloromethane, 540 g of isobutylene, and 5 g of the macromolecular branching agent C prepared in Preparation Example 3 were added. A 0.01M aqueous solution was added as the main initiator, and 0.1M trichlorotriethylaluminum was added as the co-initiator, and the mixture was configured to form an initiation system. Nitrogen was then pressed into the reactor to initiate polymerization, and a small amount of methanol was added to terminate the reaction. The product was then freed from the solvent and dried to constant weight.

[0085] Comparative Example 1

[0086] Preparation of linear polymer: A 4-liter low-temperature polymerization kettle was used, which was baked, vacuumed, and filled with nitrogen, then cooled to -90°C, and 1300 g of dichloromethane and 540 g of isobutylene were added. A 0.01 M aqueous solution was added as the main initiator, and 0.1 M trichlorotriethylaluminum was added as the co-initiator, and the mixture was configured into an initiation system. Nitrogen was then pressed into the reactor to initiate polymerization, and a small amount of methanol was added to terminate the reaction. The product was then freed of solvent and dried to constant weight to obtain linear polyisobutylene.

[0087]

Performance test

[0088] Dynamic viscosity test:

[0089] The dynamic viscosity of two liquid rubber products, linear polyisobutylene and star-branched polymer, was tested using DV-1 digital rotational viscometer.

[0090] Water content test:

[0091] The water content of the solvent used in the experiment was determined using a C30S&D0308 micro-moisture analyzer from Mettler-Toledo. After the instrument automatically balanced the electrolyte, a small amount of the solvent to be tested was drawn with a syringe, its mass was accurately weighed, and then the sample was injected into the electrolytic cell for testing. The reagent used in the test was a pyridine-free Karl Fischer reagent.

[0092] Molecular weight and molecular weight distribution test:

[0093] The molecular weight and molecular weight distribution of polymers were determined by a combination of multi-angle laser light scattering / ultraviolet / online viscosity detector, including HPLC pump (Waters 515HPLC pump), ultraviolet detector (UV), interferometer refractometer (RI), multi-angle light scattering detector (LS), and injector. At a column temperature of 35°C, chromatographic grade tetrahydrofuran was used as the mobile phase with a flow rate of 1.0 mL / min, and the results were analyzed using ASTRAsoftware (Wyatt Technology).

[0094] Infrared spectrum test:

[0095] A Nicolet 380 Fourier transform infrared spectrometer was used for polymer structure characterization. The sample was first dissolved in anhydrous dichloromethane to prepare a solution, and then the solution was applied to a potassium bromide sheet for testing, with a scanning range of 4000-400 cm -1 , scanned 64 times, with a resolution of 2cm -1 .

[0096] DSC test:

[0097] The glass transition temperature of the polymer was tested using a DSC Q2000-TA differential scanning calorimeter. Under a nitrogen atmosphere, an appropriate amount of sample was weighed, and the temperature was quickly raised to 120°C for 5 minutes to eliminate the thermal history, then cooled to -90°C, and then heated at a rate of 10°C / min. The test temperature range was -90°C to 20°C.

[0098] TGA test:

[0099] The decomposition temperature of the polymer was tested using a Q500 TGA thermogravimetric analyzer. An appropriate amount of sample was weighed and placed in a crucible, and the temperature was raised from room temperature to 550°C at a heating rate of 10°C / min in a nitrogen atmosphere.

[0100] 1H-NMR analysis:

[0101] 1H-NMR test was performed at room temperature using a German Bruker Vance 400MHZ nuclear magnetic resonance instrument, with deuterated chloroform CDCl3 (DMSO) as the solvent and TMS as the internal standard. The sample concentration was 4-5 mg / mL.

[0102] The test results are shown in Table 1 below.

[0103] Table 1

[0104] Product Name Branching agent dosage Branching ratio Number average molecular weight Test temperature Dynamic viscosity Example 1 5g 53％ 4825g / mol 38℃ 5.7Pa·s Example 2 10g 60％ 6298g / mol 38℃ 4.6Pa·s Example 3 2g 45％ 4703g / mol 38℃ 5.9Pa·s Example 4 1.5g 41％ 4598g / mol 38℃ 6.1Pa·s Example 5 2.5g 48％ 4755g / mol 40℃ 5.9Pa·s Example 6 5g 52％ 4806g / mol 40℃ 6.0Pa·s Example 7 5g 56％ 5346g / mol 40℃ 5.2Pa·s Comparative Example 1 4240g / mol 38℃ 6.4Pa·s .

[0105] It can be seen from the data in the above table that the star-branched polymer prepared by the present invention has a higher branching ratio.

[0106] In addition, linear polyisobutylene liquid rubber is a kind of liquid that has fluidity at room temperature and also exhibits a competitive behavior between viscosity and elastic modulus, so it has the ability of plastic deformation and recovery elasticity. This fluidity and deformation behavior depend on the molecular structure of the liquid rubber and external conditions (ambient temperature and force, etc.). The bulk viscosity of liquid rubber is one of the main parameters that characterize its rheological behavior, and is usually described by dynamic viscosity. It is defined as a physical quantity that is proportional to the density and velocity gradient of the fluid when the liquid is subjected to shear stress. It is usually expressed as the force of the relative velocity difference per unit area, and the unit is Pascal seconds (Pa·s) or millipascal seconds (mPa·s). It can be seen from the data in the above table that the star-branched polymer prepared in the present invention has a lower dynamic viscosity than linear polyisobutylene.

[0107] In addition, the ASTRA software in the multi-angle laser scattering instrument (MALLS) / viscometer / differential refractometer can be used to draw a curve of mean square rotation radius and molecular weight to indicate the branching degree of the molecule. The relationship between the macromolecular rotation radius Rg and the molecular weight M is as follows: Rg = K`M α, when α=0.5-0.6, the polymer chain corresponds to a random coil, and when α<0.33, the polymer chain is spherical. Figure 1 It can be seen that the linear polyisobutylene without branching agent (Comparative Example 1) has an index α=0.52, showing a random coil conformation in the solvent, and the star-branched polymer (Example 1) after adding the branching agent has an index α=0.10, indicating that the polymer molecular chain has been branched and has a spherical conformation in a dilute solution.

[0108] Figure 2 This is a graph showing the test results of the star-branched polymer prepared in Example 1 of the present invention under a multi-angle laser light scattering / ultraviolet / online viscosity detector. Figure 2 It was found that the laser signal showed an obvious double peak and the differential curve showed a shoulder platform, proving that a high molecular weight branched polymer was generated.

[0109] Figure 3 The infrared spectrum of the star-branched polymer prepared in Example 1 of the present invention is shown in the figure. At a wave number of 2950 cm -1 、2890cm -1 The corresponding -CH stretching vibration peak in the polymer has a wave number of 1460 cm -1 、1365cm -1 The corresponding -CH bending vibration peak has a wave number of 1050-1180cm -1 The corresponding position is the stretching vibration of the methoxyl group, with a wave number of 1018 cm -1 Corresponding to silicon-oxygen stretching vibration.

[0110] Figure 4 This is the DSC test graph of the linear polyisobutylene prepared in Comparative Example 1 of the present invention. Figure 4 It can be seen that the glass transition temperature (Tg) of the linear polyisobutylene is -65.3°C, indicating that the product has excellent low temperature resistance. Figure 5 This is the DSC test graph of the star-branched polymer prepared in Example 1. Figure 5 It can be seen that the glass transition temperature (Tg) of the star-branched polymer is -66.8°C, indicating that the low temperature resistance of the product is improved.

[0111] Figure 6 This is the TGA test chart of the linear polyisobutylene prepared in Comparative Example 1 of the present invention. The thermal gravimetric curve shows that the thermal decomposition temperature of the linear polyisobutylene is 397.8°C, and it can be completely decomposed without residual substances when the temperature continues to rise, which indicates that the material has excellent thermal stability. Figure 7 This is a TGA test chart of the star-branched polymer prepared in Example 1. The thermogravimetric curve shows that the thermal decomposition temperature of the star-branched polymer is 409.1° C., indicating that the thermal stability of the product is improved.

[0112] Figure 8 This is the H NMR spectrum of the star-branched polymer prepared in Example 1, where δ=1.13ppm corresponds to the characteristic peak of -CH3(e) protons in the polymer, δ=1.44ppm corresponds to the characteristic peak of -CH2(d) protons in the polymer, and δ=3.63ppm corresponds to the characteristic peak of (a) protons connected to the hydroxyl group. δ=5.85ppm and δ=5.0ppm correspond to the characteristic peaks f and g of the external olefin double bond, respectively. Based on the above analysis, it can be seen that the star-branched polymer with a clear structure has been successfully synthesized.

[0113] The examples of the present invention are merely illustrative of the technical solutions of the present invention. Any modifications, supplements or equivalent substitutions made by technicians in the field of the present invention on the basis of the examples are within the scope of protection required by the claims of the present invention.

Claims

1. A method for preparing a star-branched polymer, characterized in that: The following steps are involved: In the presence of an initiator system, a cationic polymerization reaction of a macromolecular branching agent and a monomer is initiated to obtain a star-branched polymer; The macromolecular branching agent includes a white carbon black carrier; The outer surface of the white carbon black carrier is chemically coupled with a coupling agent; The coupling agent is grafted with a telechelic polymer segment containing a double bond; The preparation method comprises the following steps: (1) Using white carbon black as a carrier, a coupling agent is used to chemically couple white carbon black; (2) Grafting it with a telechelic polymer to convert the terminal into a double bond group, thereby obtaining a macromolecular branching agent; The coupling agent includes a silane coupling agent containing at least an amino group; The telechelic polymer is a telechelic polyisobutylene as shown in formula (I) or a telechelic polybutadiene as shown in formula (II); The structural formulas of the telechelic polyisobutylene and telechelic polybutadiene are as follows: Formula (I) Formula (II) Wherein, in the formula (I) and formula (II), n is selected from 5-5000; The mass ratio of the white carbon black to the silane coupling agent containing an amino group is 1:(0.1-10); The mass ratio of the white carbon black to the telechelic polymer is 1:

100.

2. The method according to claim 1, characterized in that The initiator system includes a main initiator and a co-initiator; wherein, The main initiator includes one or more combinations of water, hydrogen chloride gas, 2-chloro-2,4,4-trimethylpentane, cumyl chloride, dicumyl chloride, 5-tert-butyl-1,3-dicumyl chloride, and 5-tert-butyl-1,3-bis(1-methyl-1-methoxyethyl)benzene; The co-initiator includes a combination of one or more of titanium tetrachloride, ferric chloride, boron trifluoride, boron trichloride, aluminum chloride, ethylaluminum dichloride and triethylaluminum trichloride.

3. The method according to claim 2, characterized in that The molar ratio of the main initiator to the co-initiator is 1:(1-30).

4. The method according to claim 1, 2 or 3, characterized in that: The polymerization temperature of the cationic polymerization reaction is -90°C to -50°C.

5. Use of the star-branched polymer prepared by the method according to any one of claims 1 to 4 in sidewall rubber, airtight layer rubber and inner tube rubber.

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