Asymmetric branched polyethylene-propylene-isoamylene rubber, preparation method thereof and application of asymmetric branched polyethylene-propylene-isoamylene rubber in inner tube

Abstract

The invention discloses asymmetric branched polyethylene-propylene-isoamylene rubber, a preparation method thereof and application of the asymmetric branched polyethylene-propylene-isoamylene rubber in an inner tube. The asymmetric branched polyethylene-propylene-isoamylene rubber has the following molecular structure: x, y, m and n are polymerization degrees, (m + n) / (x + y + m + n) is equal to 0.0065-0.0085, and (x + m) / (x + y + m + n) is greater than or equal to 0.6; y is a branched node, and the number of the branched nodes is 2-6. The asymmetric branched polyethylene-propylene-isoamylene rubber and IIR are matched for mixing, vulcanization and molding, and the obtained vulcanized rubber has the characteristics of good air tightness, lasting resistance, excellent physical and mechanical properties, good heat resistance, no softening, no stickiness, no swelling, easiness in processing and molding and the like in the later use period.

Description

Technical Field

[0001] This invention relates to a polyethylene-propylene-isoprene rubber, specifically to an asymmetric branched, highly hydrogenated polyisoprene rubber, as well as its preparation method and its application as an inner tube for automobiles and passenger vehicles, belonging to the field of synthetic rubber technology. Background Technology

[0002] Literally, polyethylene-propylene-isopentene copolymers can be copolymerized from ethylene, propylene, and 3-methyl-1-butene (α-isopentene). Existing polyethylene-1-butene elastomers (EBT) are copolymerized from ethylene and 1-butene, with 10-30% 1-butene in their molecular structure. The presence of 1-butene segments disrupts the regularity of the polyethylene chains in the EBT molecule, giving the copolymer elasticity. At room temperature, the crystallization of the polyethylene chains acts as physical crosslinking points, endowing the copolymer with plasticity, high tensile strength, and impact resistance. However, its disadvantages include high modulus, high hardness, and high crystallinity, making it unsuitable for use as inner tubes in tires.

[0003] Existing ethylene propylene diene monomer (EPDM) rubbers are copolymerized from the third monomer, ethylene-1,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,3-bis(2,4-bis(2,5-bis(2,6 ...

[0004] EPDM and IIR rubber can complement each other in terms of performance, improve processing, and reduce costs. However, due to the varying affinity of different compounding agents for different polymers, and the fact that co-vulcanization depends on the crosslinking efficiency of each polymer, it is impossible to achieve molecular-level compatibility when blending different polymers, resulting in uneven phase separation. This uneven distribution of compounding agents has a significant impact on the performance of EPDM-IIR blends. EPDM and IIR have good compatibility and co-vulcanization properties. The physical and mechanical properties of the two rubbers are additive. IIR can improve the air tightness, tear resistance, and sound insulation of EPDM; while EPDM improves the ozone resistance and aging resistance of IIR, improves the surface gloss of IIR extrusion, and enhances the deformation resistance of semi-finished products during storage. EPDM and IIR are both hydrocarbon rubbers, and they have good compatibility. Typically, 30% EPDM is added to formulations that use IIR as the main component to make inner tubes, which can complement each other and improve processing performance, such as reducing IIR sticking to rollers.

[0005] Chinese Patent (CN108395584A) discloses a formulation for automobile tire inner tubes and its preparation method, comprising natural rubber, solution-polymerized styrene-butadiene rubber, butyl reclaimed rubber, fillers, reinforcing agents, softeners, activators, antioxidants, and vulcanizing / accelerators. By combining natural rubber, solution-polymerized styrene-butadiene rubber, and butyl reclaimed rubber, the mechanical and physical-mechanical properties of the inner tube are improved, giving the tire excellent heat resistance, cold resistance, pressure resistance, wear resistance, and flexural strength, meeting the requirements of daily automobile tire use and extending tire lifespan. Chinese patent (CN108395634A) discloses a novel automobile inner tube and its preparation method. It mainly consists of polyurethane (PU), butyl rubber, EPDM rubber, CaSO4 whiskers, carbon fiber, glass fiber, accelerator CZ, antioxidant 6PPD, antioxidant TMQ, stabilizer HS-80, vulcanized rubber, vulcanization accelerator, compound intercalation modified powder, and physical plasticizer WP-1. It has advantages such as good elasticity, good comfort, improved pressure resistance and various mechanical strengths. The formula for a rubber composite material for tire inner tubes disclosed in Chinese Patent (CN105462013A) is as follows: 60-80 parts reclaimed rubber, 5-10 parts polyurethane resin, 2-4 parts rosin glycerol ester, 10-15 parts coal gangue powder, 20-30 parts montmorillonite, 6-8 parts rosin, 2-4 parts butyl acrylate, 0.15-0.25 parts potassium persulfate, 1-2 parts hydroxyethyl cellulose, 0.15-0.25 parts sodium dodecyl sulfate, 1-2 parts zinc stearate, 1-2 parts sodium petroleum sulfonate, 5-10 parts composite additives, and 1-2 parts sulfur. However, the mechanical properties of inner tubes produced by this method cannot be theoretically guaranteed. Chinese Patent (CN103819819A) discloses an ethylene propylene rubber / montmorillonite nanocomposite material, which is composed of ethylene propylene rubber, nano-montmorillonite, and dicumyl peroxide mixed in a weight ratio of 100:1-10:2-5.

[0006] In (“Research on Butyl Rubber / EPDM Inner Tubes and Their Lightweighting Achievement,” Synthetic Rubber Industry, No. 6, 1993) and (“Manufacturing Inner Tubes Using EPDM and Butyl Rubber,”

[0007] The journal *Tire Industry* (Issue 004, 1994) studied the use of butyl rubber and an appropriate amount of EPDM rubber in the manufacture of inner tubes. This method maintained the inner tube's durable physical and mechanical properties and excellent airtightness while solving the problems of butyl rubber softening, stickiness, and swelling in the later stages of use, achieving good economic and social benefits for enterprises. Meanwhile, the journal *Rubber Technology* (Issue 008, 2012) studied the application of 27.2 parts EPDM recycled rubber in inner tube rubber, which significantly improved joint strength and processing performance, alleviated the softening problem in the later stages of use of finished inner tubes, improved the aging resistance of finished inner tubes, and reduced production costs.

[0008] In summary, the materials currently used in inner tube manufacturing are mainly IIR, EPDM and filler composites, while there are no literature reports on polyethylene-propylene-isoprene rubber and inner tube manufacturing technology used in tires. Summary of the Invention

[0009] The existing technology mainly uses IIR rubber for inner tubes. However, IIR alone has problems such as sticking to rollers and difficulty in sheeting during processing and mixing. When EPDM is added to the inner tube formulation to improve its processing performance, the low propylene content and few side methyl units in the molecular chain of EPDM result in less molecular resistance during thermal motion, leading to problems such as decreased air tightness and easy crystallization. In addition, the vulcanization rate of the side alkenyl groups in the existing EPDM molecule is much higher than that of the double bonds in the main chain of the IIR molecule, resulting in a mismatch in the co-vulcanization rate or uneven crosslinking density, which leads to defects such as poor strength and heat aging resistance.

[0010] The first objective of this invention is to provide an asymmetric branched polyethylene-propylene-isoprene rubber, which contains a high proportion of side alkyl groups (including side methyl and side isopropyl groups and a small amount of side isopropyl groups). The steric hindrance effect of the side groups can hinder the thermal motion of the molecular chains, giving it excellent airtightness. It also has the characteristics of non-crystallization, low deformation and high resilience. Moreover, the double bonds in the molecular chain mainly exist as straight chains and side branches, which can co-vulcanize with the straight double bonds in the IIR molecular chain to form a stable and uniform vulcanization network. The vulcanized rubber has excellent comprehensive physical and mechanical properties, and it also has excellent anti-aging properties after vulcanization. The aging mechanism is a coexistence of degradation aging and cross-linking aging, and its hardness shows a slow upward trend. This makes up for the shortcomings of existing IIR rubbers, such as softening, stickiness and swelling during the later aging process. It is particularly suitable for use in inner tube rubber compounds.

[0011] The second objective of this invention is to provide a method for preparing asymmetric branched polyethylene-propylene-isoprene rubber. This method is simple, low-cost, can be produced using existing mature processes, and is easy to control and industrialize.

[0012] The third objective of this invention is to provide an application of asymmetric branched polyethylene-propylene-isoprene rubber, which is compounded and vulcanized with IIR to obtain a vulcanized rubber with excellent airtightness, durability, superior physical and mechanical properties, good heat resistance, no softening, no stickiness or swelling in the later stages of use, and easy processing and molding.

[0013] To achieve the above-mentioned technical objectives, the present invention provides an asymmetric branched polyethylene-propylene-isoprene rubber having the following molecular structure:

[0014]

[0015] in,

[0016] x, y, m, and n are the degree of aggregation, (m+n) / (x+y+m+n)=0.0065~0.0085, (x+m) / (x+y+m+n)≥0.6;

[0017] Y represents a branched node, with the number of branched nodes ranging from 2 to 6.

[0018] In the asymmetric branched polyethylene-propylene-isoprene rubber (EPIR) molecular structure provided by this invention, x, y, m, and n represent the degree of polymerization, all of which are not less than 1. x+y is much greater than m+n, and x+y determines the molecular weight of the polymer, while m+n determines the degree of unsaturation (number of double bonds or iodine value). Y represents the number of branching nodes, which are the copolymerization nodes of divinylbenzene. These nodes are linked with multiple polymer chains to produce an asymmetric branched structure. The x, y, m, n, and DVB units in the polymer chain exhibit a random distribution, and the number of homopolymer repeating units or homopolymers of DVB is ≤3.

[0019] This invention provides EPIR, which, compared to EPDM with side methyl groups, has a main chain structure similar to IIR, exhibiting good compatibility. EPIR contains a higher proportion of side isopropyl and methyl groups, resulting in a higher carbon chain number. The two side isopropyl groups provide more internal space for the molecular chain, increasing the main chain's mobility, improving molecular flexibility and low-temperature resistance. Furthermore, its steric hindrance effect effectively hinders the thermal motion of the molecular chain, resulting in excellent gas tightness. The polymer units in the EPIR molecule are randomly distributed, and the individual ethylene and isopropyl groups contribute to the polymer's non-crystallization, low deformation, and high resilience. The small amount of side isopropyl groups and carbon-carbon double bonds in the EPIR molecular chain allow for co-curing with the straight-chain double bonds in the IIR molecular chain, forming a stable and uniform vulcanization network. The resulting vulcanized rubber exhibits excellent comprehensive physical and mechanical properties. Moreover, the co-curing rates of the straight-chain double bonds in the EPIR and IIR molecular chains are matched, resulting in short curing times, good effects, and excellent physical and mechanical properties in the co-cured composite rubber.

[0020] As is well known, the double bonds of existing EPDM are derived from ethylene noradiene. The activity of its double bonds is much higher than that of carbon-carbon double bonds in the main chain of general rubber (such as IIR). The co-curing crosslinking rates of EPDM and IIR under sulfur differ greatly, the co-crosslinking density of EPDM and IIR is uneven, and the heat resistance of the vulcanized rubber does not reach the optimal state.

[0021] The degree of unsaturation in the EPIR molecule provided by this invention should be controlled within an appropriate range. If the unsaturation is too high, the vulcanization rate is fast; if the unsaturation is too low, the vulcanization rate is slow. Typically, the iodine value of IIR is 3–4 g / 100 g, and the double bonds originate from the isoprene polymerization unit. To ensure better coordination between EPIR and IIR and the formation of a common, uniform crosslinking, a hydrogenation degree of 99.15–99.35% for the double bonds in the preferred EPIR raw rubber (IDR) molecule is preferable. That is, the carbon chain unsaturation in the EPIR molecular chain is 0.65–0.85% (iodine value 3–4 g / 100 g).

[0022] The EPIR molecule provided by this invention has a side alkyl content of not less than 60%, mainly to ensure that after EPIR and IIR are vulcanized and crosslinked, there are enough or large side isopropyl groups in the network molecule. This can ensure that the vulcanized rubber has good air tightness and prevent gas molecules from escaping from the inner tube during thermal motion. The large number of side alkyl groups has a shielding effect on the thermal motion of gas molecules, ensuring the air tightness of compressed air in the inner tube.

[0023] As a preferred embodiment, the number-average molecular weight Mn of the asymmetric branched polyethylene-propylene-isoprene rubber is 14 × 10⁻⁶. 4 ~16×10 4 Molecular weight distribution index M w / M n ≥1.8.

[0024] As a preferred embodiment, the Mooney viscosity ML of the asymmetric branched polyethylene-propylene-isoprene rubber is... 100℃ =40~50.

[0025] The Mooney viscosity ML (100°C) of the EPIR of this invention is 40-50, and the molecular weight distribution index M0 is... w / M n With a content of ≥1.8 and no crystallization, it gives the material good processing performance and high filling performance, which makes up for the shortcomings of stickiness and roller sticking during IIR compounding and is beneficial to the compounding, processing, vulcanization and molding of composite materials.

[0026] This invention also provides a method for preparing asymmetric branched polyethylene-propylene-isoprene rubber. The method involves heating an anionic polymerization system containing a structure modifier to 50-55°C, continuously and uniformly adding an initiator, isoprene, and a branching agent over 50-60 minutes to initiate polymerization. During polymerization, the system temperature is maintained below 65°C. After polymerization, the resulting rubber solution undergoes a catalytic hydrogenation reaction to obtain the final product.

[0027] In the process of preparing polyisoprene polymer, since isoprene tends to 1,4-polymerize at high temperatures, the polymerization temperature should not be too high in order to obtain a high proportion of 3,4-polymer units.

[0028] In the process of preparing polyisoprene polymer, the initiator, isoprene and branching agent are added continuously and uniformly, which ensures that the branching agent is evenly distributed in the polymer chain.

[0029] As a preferred embodiment, the structure modifier is at least one selected from tetrahydrofurfuryl ethyl ether, bis(tetrahydrofurfuryl propane), tetrahydrofurfuryl butyl ether, and tetrahydrofurfuryl ethyl ether. The preferred structure modifier exhibits high moderating ability on the 3,4-polymerization units of isoprene at low temperatures.

[0030] As a preferred embodiment, the amount of the structure modifier is 200–260 mg / kg solvent. The amount of structure modifier affects its modulating ability; at the preferred amount of structure modifier, polyisoprene with a 3,4-polymer unit content of more than 60% can be obtained.

[0031] As a preferred embodiment, the branching agent is divinylbenzene.

[0032] As a preferred embodiment, the amount of the branching agent is 1 / 1.8 to 1 / 2.0 of the molar amount of the initiator. This preferred amount of branching agent ensures that the number of branching nodes in the IDR molecule is between 2 and 6, as shown in the molecular construction models of Equations 1 and 2 below. However, excessive DVB usage results in an excessively large polymer molecular weight, and may also lead to crosslinking and gelation; insufficient usage results in too few branching nodes, failing to achieve the purpose of branching.

[0033]

[0034] In molecular structure models It consists of random segments composed of x, y, m, and n units. The side alkyl groups in the entire molecule exhibit a random and disordered distribution. The EPIR molecule does not have repeating units of polyethylene and has a high degree of hydrogenation, which is beneficial to its resistance to high temperature and good heat aging resistance.

[0035] As a preferred embodiment, the polymerization temperature is maintained at 55-65°C during the polymerization process, and the polymerization time is 20-25 minutes after the feeding is completed.

[0036] As a preferred embodiment, the catalytic hydrogenation reaction conditions are: hydrogen pressure of 13–16 bar, temperature of 70–115 °C, and hydrogenation time of 110 min or more. By controlling the catalytic hydrogenation conditions, the hydrogenation endpoint can be achieved with an unsaturation degree of 0.65%–0.85% in the EPIR molecule and a residual iodine value of 3–4 g / 100 g. The preferred hydrogenation time is 115–120 min.

[0037] As a preferred embodiment, the catalytic hydrogenation employs a nickel-based catalytic system. The catalytic hydrogenation utilizes a nickel-based catalytic system well-known to those skilled in the art, such as the hydrogenation of polystyrene-isoprene block copolymer (SIS) to SEPS, for example, a cyclohexane aging solution of triisobutylaluminum (Al) / nickel isooctanoate (Ni) as the catalyst, with a preferred Al / Ni (mol ratio) of 3–4 and a Ni dosage of 3.5–4.5 mmol / 100g polymer. If dicyclopentadiene titanium dichloride is used as the catalyst, the degree of hydrogenation is lower due to the steric hindrance of the side methyl group in the IDR molecule.

[0038] The method for preparing EPIR rubber of the present invention includes the following steps:

[0039] 1) Add a cyclohexane solution containing a certain amount of structure modifier to a clean steel polymerization reactor. Then, heat the solution to 50-55°C. Within 50-60 minutes, add the mixed monomer and n-butyllithium (NBL) uniformly and continuously to the polymerization reactor through two separate pipeline inlets. After the monomer and NBL have been added, continue the reaction for another 20-25 minutes to obtain the IDR solution. During this period, if necessary, introduce cooling water to remove the heat of reaction and maintain the polymerization temperature at no higher than 65°C. Finally, pressurize the solution into the hydrogenation reactor with nitrogen.

[0040] 2) After adding a measured amount of Al / Ni aging solution to the hydrogenation reactor containing the IDR gel, hydrogen gas is introduced, maintaining a hydrogen pressure of 13–15 bar and a temperature of 70–115 °C for 110–120 min. By controlling the hydrogenation time to 110–120 min, the hydrogenation endpoint is achieved when the unsaturation degree in the EPIR molecules is 0.65–0.85% and the residual iodine value is 3.0–4.0 g / 100 g, thus obtaining the EPIR gel.

[0041] 3) The EPIR solution is washed with a quantitative amount of citric acid aqueous solution, and the residual catalyst residue in the solution is removed by sedimentation. The clear colorless solution is then removed by water vapor condensation to remove the solvent. After drying and pressing, the EPIR raw rubber is obtained. The solution washing is done by washing the catalyst with a small amount of citric acid aqueous solution. The preferred amount of citric acid is citric acid / Ni (mol ratio) = 1.5 to 1.8.

[0042] The EPIR raw rubber molecules of the present invention contain polyisoprene polymer units with the same molecular structure as the existing IIR molecules, and have the same or small difference in iodine value. Both belong to carbon-hydrogen structure polymers, have good compatibility, and are easy to mix, process, vulcanize and mold with fillers.

[0043] The present invention also provides an application of asymmetric branched polyethylene-propylene-isoprene rubber as a base rubber for inner tube compounds.

[0044] As a preferred embodiment, the inner tube compound comprises asymmetric branched polyethylene-propylene-isoprene rubber and IIR and auxiliary materials.

[0045] As a preferred embodiment, the inner tube compound comprises the following components in parts by weight: 45-50 parts of asymmetric branched polyethylene-propylene-isoprene rubber, 50-60 parts of IIR, 1.0-1.5 parts of stearic acid, 3-5 parts of zinc oxide, 65-70 parts of carbon black, 20-30 parts of rubber oil, 1-2 parts of antioxidant, 2.5 parts of accelerator DM, 1.5 parts of accelerator T, and 1.5-1.7 parts of sulfur.

[0046] As a preferred embodiment, the IIR is at least one of the conventional commercially available halogenated or non-halogenated types such as IIR-268, IIR365, IIR4266, and IIR-1751.

[0047] As a preferred embodiment, the stearic acid, zinc oxide, and sulfur in the inner tube compound are all additives known to those skilled in the art.

[0048] As a preferred embodiment, the rubber oil is a white oil known to those skilled in the art, with naphthenic or paraffinic white oil being the most preferred, such as at least one of commercially available white oils including KN4010, KN4006, 46#, 32#, 400N, and 320#.

[0049] As a preferred embodiment, the carbon black is mainly used as a reinforcing agent, preferably nano-sized such as N330.

[0050] As a preferred embodiment, the antioxidant is an amine-based antioxidant known to those skilled in the art. For example, antioxidant 4020.

[0051] The preparation method of the inner tube rubber compound of the present invention is a conventional method, as follows: EPIR and IIR raw rubber are put into an open mill (or internal mixer), and then the motor is started to break, mix, and roll the raw rubber. Then stearic acid, zinc oxide, carbon black, white oil, antioxidant and accelerator are added in sequence and mixed. After the powder is completely "eaten up", sulfur is added and mixed. Then the rubber is cut three times to the left and right 3 / 4. Then the masterbatch is thinly passed through 6 times and then sheeted.

[0052] The vulcanization conditions for the inner tube rubber compound of the present invention are: vulcanization temperature of 160°C and vulcanization time of 30 min.

[0053] Compared with existing technologies, the beneficial effects of the technical solution of this invention are as follows:

[0054] In existing technologies, EPDM rubber molecules have low side methyl content, resulting in easy polymer crystallization, large deformation, and poorer airtightness compared to IIR. The fast vulcanization rate of double bonds in the molecular side chains does not match the co-vulcanization rate of straight-chain double bonds in IIR molecular chains, leading to unequal vulcanization rates and long vulcanization times, resulting in poor physical and mechanical properties.

[0055] The EPIR molecular chain provided by this invention mainly consists of straight-chain and side-branched double bonds, which have the same activity as the double bonds of polyisoprene polymer units in IIR molecules. The double bonds exhibit the same vulcanization rate as sulfur, and after co-vulcanization, a stable and uniform vulcanization network density can be formed. The vulcanized rubber exhibits excellent comprehensive physical and mechanical properties. The density of side alkyl groups in the molecular chain is higher than that of side methyl groups in existing EPDM molecules. The steric hindrance effect of the side alkyl groups hinders the thermal motion of the molecules, and its shielding effect is far greater than that of the side methyl groups in EPDM molecules, resulting in superior airtightness. It also possesses non-crystallization, low deformation, and high resilience. EPIR vulcanized rubber also has excellent anti-aging properties. The aging mechanism of EPIR involves both degradation aging and cross-linking aging, with its hardness showing a slow upward trend, thus compensating for the softening, stickiness, and swelling defects that occur during the later aging stages of butyl rubber. In addition, the branched and wide molecular weight distribution of EPIR gives existing IIR good processing performance and high filling performance, making up for the shortcomings of butyl rubber in mixing and roller sticking, and improving the mixing, processing, vulcanization and molding of composite materials.

[0056] The EPIR provided by this invention, as a material for inner tubes, retains the advantages of the original IIR / EPDM composite material. It has good processing performance, excellent physical properties of vulcanized rubber, and is comparable to existing EPDM in terms of heat resistance and anti-aging properties. It avoids various technical deficiencies and drawbacks in the process of preparing inner tubes with existing IIR / EPDM.

[0057] The preparation method of the EPIR and inner tube of the present invention is simple, can be made using existing mature processes, and is easy to control and industrialize. Attached Figure Description

[0058] Figure 1 The GPC spectrum of the hydrogenated polymer IDR-1# is shown.

[0059] Figure 2 H for hydrogenated polymer EPIR-1# 1 -NMR, the absorption peaks in the chemical shift range of 4.7 to 5.2 in the figure represent the hydrogen protons on the unsaturated carbon atoms of the isoprene 1,2-addition, 1,4-addition and 3,4-addition units remaining in the EPIR molecule. Detailed Implementation

[0060] The following examples are intended to further illustrate and describe the content of the present invention, and do not constitute a limitation on the scope of protection of the claims of the present invention.

[0061] In the following examples, the number-average molecular weight and molecular weight distribution index of the polymers were determined using gel permeation chromatography (GPC); H2 was used. 1 - The microstructure of the polymer was quantitatively determined by NMR spectroscopy; the mechanical properties of the vulcanized rubber were tested according to GB / T36089-2018; the Mooney viscosity of the raw rubber was performed according to GB1232; and the air tightness of the inner tube was tested according to GB / T1703-2017.

[0062] Example 1

[0063] Under nitrogen protection, 3500 mL of cyclohexane and 0.85 mL of tetrahydrofurfuryl ethyl ether (ETE) were added to a 5L polymerization reactor. Stirring was started and the material temperature was raised to 55°C. At this time, 5.5 mL of 0.50 mol / L NBL and a mixed monomer consisting of 410 mL of isoprene and 0.3 mL of DVB were continuously added to the polymerization reactor. The continuous addition time for all three was 55 min. After the materials were added, the reaction continued for another 25 min, during which the polymerization temperature was maintained not higher than 65°C.

[0064] The gel solution was pressurized into a 5L hydrogenation reactor under nitrogen, and 24mL of a cyclohexane aging solution with a nickel content of 0.4mol / L (triisobutylaluminum (Al) / nickel isooctanoate (Ni)) of 3.8 (mol ratio) was added. The mixture was stirred and hydrogenated for 120min at a hydrogen pressure of 14.0 bar and a temperature of 90℃ to obtain the EBIR gel solution. The product was discharged, and 42mL of a 0.5mol / L citric acid aqueous solution was added to the hydrogenated gel solution. The mixture was stirred at room temperature for 30min, and after standing for 60min, the lower green nickel-containing aqueous phase was removed. The upper colorless hydrogenated gel solution was then subjected to steam condensation, extrusion, and drying to obtain the EBIR block gel (labeled EPIR-1#). Its GPC spectrum is shown below. Figure 1 H 1 -NMR spectrum see Figure 2 The characteristic behaviors of the polymers are shown in Table 1.

[0065] Example 2

[0066] The process conditions of Example 1 were kept unchanged, except that 450 mL of isoprene, 0.9 mL of bis(tetrahydrofurfuryl)propane, 5.0 mL of NBL were added, the amount of hydrogenation catalyst was 28 mL, and the hydrogenation time was 115 min.

[0067] The resulting hydrogenated gel was labeled EPIR-2#, and the behavior analysis of the polymer is shown in Table 1.

[0068] Example 3

[0069] The relevant process conditions in Example 2 were kept unchanged, except that 0.75 mL of tetrahydrofurfuryl ether, 6.0 mL of NBL, and 0.25 mL of DVB were added. The hydrogenation unit was set at a hydrogenation pressure of 13 bar and a hydrogenation time of 125 min.

[0070] The resulting raw rubber was labeled EPIR-3#, and the behavior analysis of the polymer is shown in Table 1.

[0071] Example 4

[0072] The relevant process conditions in Example 1 were kept unchanged, except that 6.5 mL of NBL and 0.20 mL of DVB were added, the amount of hydrogenation catalyst was 20 mL, and the hydrogenation time was 130 min.

[0073] The resulting hydrogenated gel was labeled EPIR-4#, and the behavior analysis of the polymer is shown in Table 1.

[0074] Example 5 (Comparative)

[0075] The relevant process conditions in Implementation 1 remain unchanged, except that the monomer and NBL are added to the polymerization reactor at once.

[0076] The resulting hydrogenated gel was labeled EPIR-5#, and the behavior analysis of the polymer is shown in Table 1.

[0077] Example 6 (Comparative)

[0078] The relevant process conditions in step 4 will remain unchanged, except that the DVB is 0.16 mL.

[0079] The resulting hydrogenated gel was labeled EPIR-6#, and the behavior analysis of the polymer is shown in Table 1.

[0080] Example 7 (Comparative)

[0081] The relevant process conditions in Implementation 1 remain unchanged, except that the DVB is 0.32 mL.

[0082] The resulting polymerized gel exhibited a gelation phenomenon.

[0083] Example 8 (Comparative)

[0084] The process conditions of Example 1 were kept unchanged, except that the amount of ETE added in the polymerization section was 0.45 mL, the amount of hydrogenation catalyst added was 33 mL, and the hydrogenation time was 135 min.

[0085] The resulting hydrogenated gel was labeled EPIR-8#, and the behavior analysis of the polymer is shown in Table 1.

[0086] Example 9 (Comparative)

[0087] The relevant process conditions of Example 1 were kept unchanged, except that the amount of hydrogenation catalyst was increased to 16 mL and the hydrogenation time was increased to 110 min.

[0088] The resulting hydrogenated gel was labeled EPIR-9#, and the behavior analysis of the polymer is shown in Table 1.

[0089] Table 1 Characteristic Analysis of EPIR

[0090]

[0091] Inner tube preparation examples

[0092] The raw rubbers #1, #2, #3, #4, #6, #8, #9 from Table 1, and commercially available EPDM3640 (manufactured by Dow Chemical Company, Mooney viscosity 40, propylene mass fraction 45%, iodine value 3.81g / 100g) were mixed and vulcanized on an open mill according to the materials in the inner tube formulation of this invention. The vulcanization conditions were 160℃ / 30min. The formulations of each embodiment are shown in Table 2, and the physical properties are shown in Table 3.

[0093] Table 2 Inner Tube Formula (parts by weight)

[0094]

[0095]

[0096] Note: Other fillers and minor ingredients in the formula are: 1 part stearic acid, 5 parts zinc oxide, 70 parts carbon black N330, 2.5 parts accelerator DM, 1.5 parts accelerator T, and 1.5 parts antioxidant 4020.

[0097] Table 3 Physical properties of inner tubes

[0098]

Claims

1. An asymmetric branched polyethylene-propylene-isoprene rubber, characterized in that: It has the following molecular structure: in, x, y, m, and n are the degree of aggregation, (m+n) / (x+y+m+n)=0.0065~0.0085, (x+m) / (x+y+m+n)≥0.6; Y represents a branched node, with the number of branched nodes ranging from 2 to 6.

2. The asymmetric branched polyethylene-propylene-isoprene rubber according to claim 1, characterized in that: The number-average molecular weight Mn of the asymmetric branched polyethylene-propylene-isoprene rubber is 14 × 10⁻⁶. 4 ~16×10 4 Molecular weight distribution index M w / M n ≥1.

8.

3. The asymmetric branched polyethylene-propylene-isoprene rubber according to claim 1, characterized in that: The Mooney viscosity (ML) of the asymmetric branched polyethylene-propylene-isoprene rubber 100℃ =40~50.

4. A method for preparing an asymmetric branched polyethylene-propylene-isoprene rubber according to any one of claims 1 to 3, characterized in that: The anionic polymerization system containing the structure modifier is heated to 50-55°C. The initiator, isoprene, and branching agent are continuously and uniformly added over 50-60 minutes to initiate polymerization. During the polymerization process, the system temperature is maintained below 65°C. After polymerization, the resulting solution is subjected to catalytic hydrogenation to obtain the final product.

5. The method for preparing an asymmetric branched polyethylene-propylene-isoprene rubber according to claim 4, characterized in that: The structure modifier is at least one of tetrahydrofurfuryl ethyl ether, bis(tetrahydrofurfuryl propane), tetrahydrofurfuryl butyl ether, and tetrahydrofurfuryl ethyl ether.

6. The method for preparing an asymmetric branched polyethylene-propylene-isoprene rubber according to claim 4 or 5, characterized in that: The amount of the structure modifier is 200-260 mg / kg solvent.

7. The method for preparing an asymmetric branched polyethylene-propylene-isoprene rubber according to claim 4, characterized in that: The branching agent is divinylbenzene.

8. The method for preparing an asymmetric branched polyethylene-propylene-isoprene rubber according to claim 4 or 7, characterized in that: The amount of the branching agent is 1 / 1.8 to 1 / 2.0 of the molar amount of the initiator.

9. The method for preparing an asymmetric branched polyethylene-propylene-isoprene rubber according to claim 4, characterized in that: The polymerization process is maintained at a polymerization temperature of 55-65°C, and the polymerization time is 20-25 minutes after the feeding is completed.

10. The method for preparing an asymmetric branched polyethylene-propylene-isoprene rubber according to claim 4, characterized in that: The conditions for the catalytic hydrogenation reaction are: hydrogen pressure of 13-16 bar, temperature of 70-115°C, and hydrogenation time of 110 min or more.

11. The method for preparing an asymmetric branched polyethylene-propylene-isoprene rubber according to claim 10, characterized in that: The catalytic hydrogenation uses a nickel-based catalytic system.

12. The application of the asymmetric branched polyethylene-propylene-isoprene rubber according to any one of claims 1 to 3, characterized in that: As a base rubber for inner tubes.

13. The application of the asymmetric branched polyethylene-propylene-isoprene rubber according to claim 12, characterized in that: The inner tube compound includes asymmetric branched polyethylene-propylene-isoprene rubber and IIR and auxiliary materials.

14. The application of the asymmetric branched polyethylene-propylene-isoprene rubber according to claim 12, characterized in that: The inner tube compound comprises the following components by weight: 45-50 parts of asymmetric branched polyethylene-propylene-isoprene rubber, 50-60 parts of IIR, 1.0-1.5 parts of stearic acid, 3-5 parts of zinc oxide, 65-70 parts of carbon black, 20-30 parts of rubber oil, 1-2 parts of antioxidant, 2.5 parts of accelerator DM, 1.5 parts of accelerator T, and 1.5-1.7 parts of sulfur.

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