Conjugated diene-vinyl aromatic copolymers and methods for making the same

Abstract

The invention provides a conjugated diene and vinyl aromatic hydrocarbon copolymer and a method of making the same. The copolymer of the invention comprises a homopolymer segment comprised of a conjugated diene, and a copolymer segment comprised of the conjugated diene and a vinyl aromatic hydrocarbon connected to the homopolymer segment. The copolymer has a first glass transition temperature between -10°C and -50°C and a second glass transition temperature between -45°C and -85°C, the first glass transition temperature is higher than the second glass transition temperature, and a vinyl aromatic hydrocarbon microblock content of the copolymer is between 1.0% and 10.0% of the total vinyl aromatic hydrocarbon content of the copolymer, wherein the vinyl aromatic hydrocarbon microblock refers to a microblock having at least four consecutive vinyl aromatic hydrocarbon units.

Description

Technical Field

[0001] This invention relates to a conjugated diene-vinyl aromatic hydrocarbon copolymer, particularly a conjugated diene-vinyl aromatic hydrocarbon copolymer containing homopolymer segments and copolymer segments, and a method for manufacturing the same. Background Technology

[0002] Solution-polymerized styrene-butadiene rubber (SSBR) is a copolymer rubber material formed by polymerizing styrene and butadiene in an organic solvent. Compared to emulsion-polymerized SBR, SSBR typically offers better controllability of its molecular structure, such as the ability to adjust the styrene content and the microstructure of the butadiene. This allows for further adjustment of the material's glass transition temperature (Tg) and viscoelastic behavior, as well as improvement of its dynamic mechanical properties. Based on these characteristics, SSBR is commonly used in tire-related applications, particularly in the formulation design of tread compounds.

[0003] In recent years, the development of high-performance tire tread compounds has often needed to simultaneously achieve low rolling resistance (to reduce energy loss and improve fuel efficiency) and wet grip (to improve braking and handling safety on wet roads), while maintaining good wear resistance as much as possible. Existing technologies, such as solution-polymerized styrene-butadiene rubber disclosed in patent documents such as US4843120, JP2008231197A, and CN103958600B, all claim to have various properties. However, several issues still exist that require improvement in practical applications. Summary of the Invention

[0004] The problem the invention aims to solve

[0005] The technical problem this invention aims to solve is that, in response to the demands of energy conservation and driving safety, tire tread materials should simultaneously achieve (i) improved wet grip to enhance braking and handling stability on wet roads, (ii) reduced rolling resistance to reduce energy loss and improve fuel efficiency, and (iii) sufficient wear resistance to extend service life. However, existing conjugated diene-vinyl aromatic copolymers often fail to simultaneously meet these multiple performance requirements in their formulation or structural design, resulting in insufficient performance balance. Therefore, this invention provides an improved conjugated diene-vinyl aromatic copolymer to achieve better overall performance in terms of wet grip, wear resistance, and low rolling resistance.

[0006] Problem-solving methods

[0007] On one hand, to improve the wet grip of tire tread rubber, the inventors of this case have meticulously designed a conjugated diene-vinyl aromatic hydrocarbon copolymer with double glass transition temperatures (double Tg), and this copolymer contains vinyl aromatic hydrocarbon microblocks, aiming to significantly enhance wet grip performance through this specific structural configuration. On the other hand, the inventors have further set and controlled the proportion (SB%) of this vinyl aromatic hydrocarbon microblock within the range of 1.0% to 10.0%, so that the copolymer can maintain good rolling resistance performance while improving wet grip. Furthermore, for conjugated diene-vinyl aromatic hydrocarbon copolymers with modified ends, the modified ends are directly connected to the copolymer segment rather than the homopolymer segment, which is more conducive to forming the double Tg characteristic.

[0008] The present invention also includes other aspects and various embodiments to address other problems. These and other aspects are disclosed in detail in the embodiments. Detailed Implementation

[0009] To ensure a full understanding of the present invention and its claimed scope, preferred embodiments of the invention will be demonstrated below. To avoid obscuring the scope of the invention, known components, related materials, and related processing techniques are omitted from the following description.

[0010] Analytical methods

[0011] Vinyl aromatic hydrocarbon microblock content: The vinyl aromatic hydrocarbon microblock referred to in this invention is defined as a microblock having at least four consecutive vinyl aromatic hydrocarbon units. The analytical method, using styrene as an example: 20 mg of sample was dissolved in 2.0 mL of CDCl3 and analyzed using a Bruker 500 MHz NMR instrument. 1 H NMR scan; 1 The integral value of 6.2–7.0 ppm in the H NMR spectrum is defined as a, and the value obtained by subtracting the integral of CDCl3 from the integral value of 7.0 to 7.8 ppm is defined as b. Then, the content of styrene microblocks in the copolymer to which the sample belongs is calculated as [a / (a+b)] × 100% of the total styrene content.

[0012] Rolling resistance (RR): The rolling resistance (RR) of the copolymer compound after it has been made into rubber (tread compound) is evaluated using the loss tangent (tanδ) at 60°C. The storage modulus of the test specimen was measured using a TA Instruments ARES-G2 rheometer under strain sweep conditions. With loss modulus and according to The tanδ value was calculated. The sample temperature was 60℃ during the scan, the strain scan range was 0.1% to 10%, and the tanδ value at 5.0% strain was taken.

[0013] Wet Grip (WG): The loss tangent (tanδ) at 0°C is used as an indicator to evaluate the wet grip of the copolymer compound after it is made into rubber (tread compound). The storage modulus of the test specimens was measured using a TAInstruments ARES-G2 rheometer under strain sweep conditions. With loss modulus and according to The tanδ value was calculated. The sample temperature was 0℃ during scanning, the strain scanning range was 0.1% to 10%, and the tanδ value at 5.0% strain was taken as the indicator for evaluating wet grip.

[0014] Abrasion test (DIN): Measured using the GT-7012-DN model according to ASTM D5963 standard.

[0015] Glass transition temperature (Tg, °C): Primary method: Tg was measured using Dynamic Mechanical Analysis (DMA). Neat Polymer strips were measured according to ASTM E1640 using a rheometer (TA Instruments, trade name "RSA-G2"). An air-cooled system (TA Instruments, trade name "ACS-3") was used during testing, with nitrogen flowing at 50 mL / min, and the temperature was increased from -85 °C at a rate of 2 °C / min. The changes in storage modulus E' and loss modulus E'' were recorded simultaneously. The peak temperature of the loss tangent tanδ (tanδ = E'' / E') was taken as Tg. Special note: The embodiments and comparative examples of this invention use this method to determine the glass transition temperature, and this method is the preferred method. However, if two glass transition temperatures are too close to be clearly distinguished by this method, the following secondary methods can be used.

[0016] Glass transition temperature (Tg, °C): Secondary method: Determined using a Differential Scanning Calorimeter (DSC) (model Q200, TA Instruments) according to ASTM E1356 standard. Specific test conditions were as follows: under nitrogen flow rate of 50 ml / min, the temperature was increased from -90 °C to 100 °C at a heating rate of 20 °C / min, and the heat flow curve was recorded. The glass transition temperature (Tg) is defined as the characteristic peak corresponding to the first derivative peak of the heat flow curve with respect to temperature. By analyzing the characteristic peak of the first derivative curve, glass transition points with weaker signal intensity in the original heat flow curve can be effectively identified, thereby determining the glass transition temperature of the material in a multiphase structure.

[0017] Vinyl aromatic hydrocarbon bond content and vinyl content of the copolymer: The relevant measurement method described in Chinese patent CN103476815B was used. The NMR was performed by a Bruker AV-500 (500MHz) NMR spectrometer with a 5mm dual probe and an automatic frequency tuning device. The NMR software used was TOPSPIN, and the solvent used was deuterated chloroform / tetramethylsilane (CDCl3 / TMS).

[0018] Copolymers of conjugated dienes and vinyl aromatic hydrocarbons

[0019] This invention provides a copolymer of a conjugated diene and a vinyl aromatic hydrocarbon, comprising: a homopolymer segment composed of a conjugated diene, and a copolymer segment composed of the conjugated diene and the vinyl aromatic hydrocarbon; wherein the copolymer segment is connected to the homopolymer segment. The copolymer has two glass transition temperatures (Tg): a first glass transition temperature between -10°C and -50°C, and a second glass transition temperature between -45°C and -85°C, wherein the first glass transition temperature is higher than the second glass transition temperature; and the vinyl aromatic hydrocarbon microblocks in the copolymer account for 1.0% to 10.0% of the total vinyl aromatic hydrocarbon content of the copolymer. In a preferred embodiment, the first glass transition temperature is between -12°C and -40°C, and the second glass transition temperature is between -50°C and -60°C. In another preferred embodiment, the vinyl aromatic hydrocarbon microblocks in the copolymer account for 1.0% to 8.0% of the total vinyl aromatic hydrocarbon content of the copolymer. In a preferred embodiment, the conjugated diene content of the homopolymer segment accounts for more than 60 wt% of the total content of the copolymer, preferably 60 wt% to 90 wt%, and more preferably 65 wt% to 73 wt%. In a preferred embodiment, the vinyl aromatic hydrocarbon bond content of the copolymer is 10 wt% to 20 wt%, preferably 12 wt% to 16 wt%. In a preferred embodiment, the vinyl content of the copolymer (based on the total conjugated diene content) is 30 wt% to 40 wt%, preferably 31 wt% to 36 wt%. In a preferred embodiment, the copolymer does not have any glass transition temperature other than the aforementioned first and second glass transition temperatures. In a preferred embodiment, the copolymer further has a modified end, and the modified end is connected to the copolymer segment, such that the copolymer segment is disposed between the homopolymer segment and the modified end. In a preferred embodiment, the modified end contains silicon. In a preferred embodiment, the copolymer is an unhydrogenated copolymer.

[0020] The conjugated diene monomers applicable to this invention are conjugated dienes containing 4 to 12 carbon atoms, and specific examples include 1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 2-methyl-1,3-butadiene (isopentadiene), 2-methyl-1,3-pentadiene, 2-hexyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 2-phenyl-1,3-pentadiene, 2-p-tolyl-1,3-butadiene, 2-benzyl-1,3-butadiene, 3-methyl-1,3-pentadiene, and 3-methyl-1,3-hexadiene. 3-Butyl-1,3-octadiene, 3-phenyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 1,4-diphenyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2,3-dimethyl-1,3-pentadiene, 2,3-dibenzyl-1,3-butadiene, 4,5-diethyl-1,3-octadiene, myrcene, and any combination thereof, wherein 1,3-butadiene is the preferred choice. All butadiene referred to herein is 1,3-butadiene.

[0021] Specific examples of vinyl aromatic hydrocarbon monomers applicable to this invention include styrene, methylstyrene and all its isomers, ethylstyrene and all its isomers, tert-butylstyrene and all its isomers, dimethylstyrene and all its isomers, methoxystyrene and all its isomers, cyclohexylstyrene and all its isomers, vinylbiphenyl, 1-vinyl-5-hexylnaphthalene, vinylnaphthalene, vinylanthracene, 2,4-diisopropylstyrene, 5-tert-butyl-2-methylstyrene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, 4-propylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, N-4-vinylphenyl-N,N-dimethylamine, (4-vinylphenyl)dimethylaminoethyl ether, N,N-dimethylaminomethylstyrene, N,N-dimethylaminoethylstyrene, N, N-Diethylaminomethylstyrene, N,N-Diethylaminoethylstyrene, vinylxylene, vinylpyridine, diphenylethylene, 2,4,6-trimethylstyrene, α-methyl-2,6-dimethylstyrene, α-methyl-2,4-dimethylstyrene, β-methyl-2,6-dimethylstyrene, β-methyl-2,4-dimethylstyrene, indene, diphenylethylene containing a tertiary amino group, such as l-(4-N,N-dimethylaminophenyl)-1-phenylethylene, and any combination thereof, wherein styrene is a preferred choice.

[0022] The modifier used for the modified end of the present invention is preferably an organosilane compound. Preferred organosilane compounds include compounds represented by Formula 1:

[0023] Formula 1

[0024] R 1 R 2 It is a C1-C12 alkyl, C6-C18 aromatic, or allyl group; R 3 It is a C1-C12 alkyl group or a C6-C18 aromatic group; R 4 It is a C1-C12 alkoxy, C1-C12 alkyl, C6-C18 aromatic, or allyl group; Y is a functional group containing O and / or N and / or P atoms, preferably Y is an epoxy alkyl, tertiary amino, secondary or primary amino, ester, aldehyde, ketone, acrylic acid, acrylate, imidazoline, morpholine, or any combination thereof. Preferred organosilane compounds are 4-{3-[dimethoxy(methyl)silyl]propyl}morpholine, 3-(trimethoxysilyl)-N,N-dimethylpropan-1-amine, or diethyl[2-(triethoxysilyl)ethyl]phosphonate.

[0025] Method for manufacturing copolymers of conjugated dienes and vinyl aromatic hydrocarbons

[0026] The copolymers of the present invention can be manufactured by various suitable methods. In a preferred embodiment, the manufacturing method of the present invention includes step (1): providing an initiator; step (2): forming a homopolymer segment composed of the conjugated diene by anionic polymerization using the initiator under conditions containing cyclic ethers and diether compounds; and step (3): forming a copolymer segment composed of the conjugated diene and the vinyl aromatic hydrocarbon and attached to the homopolymer segment after step (2), wherein the vinyl aromatic hydrocarbon and the conjugated diene are added simultaneously to the polymerization reactor in step (3), and the addition rate of the vinyl aromatic hydrocarbon is different from the addition rate of the conjugated diene. In a preferred embodiment, the method further includes step (4): forming a modified end attached to the copolymer segment after step (3), wherein the copolymer segment is located between the homopolymer segment and the modified end.

[0027] Initiator

[0028] Anionic polymerization refers to the process of using an initiator to form an activated carbocation, which, upon addition, reacts with the monomer to form a polymer with negatively charged chain ends. In a preferred embodiment, this invention uses an organoalkali metal as the initiator for anionic polymerization. In another preferred embodiment, this invention uses a multi-terminal initiator as the initiator for anionic polymerization. In yet another preferred embodiment, the multi-terminal initiator is obtained by reacting a divinyl aromatic hydrocarbon-like compound with an organoalkali metal.

[0029] Preferred divinyl aromatic hydrocarbon compounds include compounds represented by Formula 2:

[0030] Formula 2

[0031] A and B are C n H 2n+1 Or an aromatic ring, n is 0~5, A and B may be the same or different, and Q is an aromatic ring. In divinyl aromatic hydrocarbon compounds, substituents A, B and / or Q may be aromatic rings, including substituted or unsubstituted monocyclic, polycyclic or fused polycyclic rings, for example, independently selected from the group consisting of: substituted or unsubstituted benzene, naphthalene, anthracene, phenanthrene, fluorene, tetraphenyl, pyrene, biphenyl, terphenyl, tetraphenyl, β-, triphenylene, perylene, indene and any combination or combination of the above fused rings. Among them, benzene is preferred. Divinyl aromatic compounds, for example, may be independently selected from the group consisting of: m-divinylbenzene, p-divinylbenzene, 1,2-diisopropenylbenzene, 1,3-diisopropenylbenzene, 1,4-diisopropenylbenzene, 1,3-divinylnaphthalene, 1,8-divinylnaphthalene, 1,4-divinylnaphthalene, 1,5-divinylnaphthalene, 2,3-divinylnaphthalene, 2,7-divinylnaphthalene, 2,6-divinylnaphthalene, 4,4'-divinylbiphenyl, 4,3'-divinylbiphenyl, 4,2'-divinylbiphenyl, 3,2'-divinylbiphenyl, 3,3'-divinylbiphenyl, 2,2'-divinylbiphenyl, 2,4-divinylbiphenyl, 1,2-divinyl-3,4-dimethylbenzene, 1,3-divinyl-4,5,8-tributylnaphthalene, 2,2'-divinyl-4-ethyl-4'-propylbiphenyl, and any combination thereof. Among them, 1,3-diisopropenylbenzene is preferred (the diisopropenylbenzene referred to in this article refers to 1,3-diisopropenylbenzene).

[0032] Specific examples of organoalkali metals include monoorganic lithium compounds such as methyl lithium, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, isobutyl lithium, n-pentyl lithium, n-hexyl lithium, benzyl lithium, phenyl lithium, tolyl lithium and all its isomers, naphthyl lithium, and stilbenelithium. These polymerization initiators can be used alone or in combination of two or more, with lithium compounds being a preferred choice. Among these, n-butyl lithium is particularly preferred.

[0033] To adjust the vinyl content of the copolymer, a polar modifier that improves solvent polarity is preferably added during the reaction. In one specific example, a cyclic ether compound and / or a diether compound may be added. The cyclic ether compound may be a monocyclic ether compound or a bicyclic ether compound. For example, the monocyclic ether compound may be independently selected from the group consisting of: tetrahydrofuran, furan, tetrahydropyran, 2-methyl-tetrahydropyran, 3-methyl-tetrahydropyran, crown ethers (such as 12-crown-4 ether, 15-crown-5 ether, or 18-crown-6 ether). The diether compound may be 2,2-bis(2-tetrahydrofuranyl)propane; the diether compound may be independently selected from the group consisting of: diethyl ether, di-n-propyl ether, di-n-butyl ether, ethylene glycol dibutyl ether, ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, methyl-n-propyl ether, diisopropyl ether, terpentylethyl ether, methyl tert-butyl ether or ethyl tert-butyl ether and any combination thereof. Tetrahydrofuran and ethylene glycol diethyl ether are preferred choices.

[0034] Formation of copolymer segment

[0035] In step (3), the distribution of vinyl aromatic hydrocarbon microblocks in the copolymer segment can be adjusted by regulating the difference in the addition rate of monomers. To balance the properties of the rubber composition such as DIN abrasion, rolling resistance (RR), and wet grip (WG), a preferred vinyl aromatic hydrocarbon microblock distribution is that the content of vinyl aromatic hydrocarbon microblocks accounts for 1.0% to 10.0% of the total vinyl aromatic hydrocarbon content in the copolymer. Specifically, when forming the copolymer segment, the vinyl aromatic hydrocarbon and the conjugated diene are added to the polymerization reactor simultaneously, and the addition rate of the vinyl aromatic hydrocarbon is different from the addition rate of the conjugated diene; for example, in terms of mass flow rate, the addition rate of the vinyl aromatic hydrocarbon can be controlled at 70 g / min, and the addition rate of the conjugated diene can be controlled at 11 to 18 g / min, so that the addition rate ratio (vinyl aromatic hydrocarbon / conjugated diene) is controlled at 3.8 to 6.4, thereby achieving the aforementioned control of the vinyl aromatic hydrocarbon microblock distribution.

[0036] Applications of conjugated diene-vinyl aromatic hydrocarbon copolymers

[0037] The conjugated diene-vinyl aromatic hydrocarbon copolymer of the present invention can be mixed with other components to obtain a rubber composition. Specific examples of other components include natural rubber, other conjugated diene polymers different from those of the present invention, ethylene-propylene copolymers, and ethylene-octene copolymers. Furthermore, the rubber composition may also contain additives. Specific examples of additives include vulcanizing agents such as sulfur powder; vulcanization accelerators such as sulfenamide-based vulcanization accelerators and diphenylguanidine co-accelerators; vulcanization activators such as stearic acid or zinc oxide; reinforcing agents such as white smoke or carbon black; fillers such as calcium carbonate or talc; silane coupling agents; filler oils; processing aids; antioxidants; and lubricants, etc.

[0038] The method for mixing the rubber composition of this invention can use, for example, conventional mixers, such as rollers, or a Banbury mixer or internal mixer to knead the components. Regarding mixing conditions, when mixing additives, fillers, white smoke, and / or other reinforcing agents, in addition to vulcanizing agents or vulcanization accelerators, the mixing temperature is generally from 50°C to 200°C, preferably from 80°C to 150°C. When mixing with vulcanizing agents or vulcanization accelerators, the mixing temperature generally does not exceed 100°C, preferably from room temperature to 90°C.

[0039] The conjugated diene-vinyl aromatic hydrocarbon copolymer and its rubber composition of this invention can be applied to tires, shoe soles, flooring materials, and vibration damping materials, with tire applications being particularly suitable. When applied to tire treads, it can reduce rolling resistance and improve wet traction, thereby improving handling stability and reliability in wet conditions. This allows the tire to achieve a better balance between wet grip, wear resistance, and rolling resistance, and also helps improve fuel efficiency.

[0040] Various examples of conjugated diene-vinyl aromatic hydrocarbon copolymers

[0041] Example 1: In a 5525g cyclohexane solution containing 8.3g of cyclic ether and 0.5g of diether compound, 4.9 mmole of n-butyllithium and 1g of diisopropylbenzene were added, and the mixture was reacted at 50°C for 30 minutes. Then, 1,3-butadiene (65 wt% of the total copolymer) was added for the first stage of polymerization, and the reaction was maintained at the first stage maximum temperature for 10 minutes. Next, the remaining butadiene and styrene (totaling 35 wt% of the total copolymer) were added for the second stage of polymerization. Styrene and butadiene were added simultaneously but at different rates; the styrene microblock content was controlled by adjusting the ratio of their addition rates. The reaction was maintained at the second stage maximum temperature for another 15 minutes. Then, 4.2g of 4-{3-[dimethoxy(methyl)silyl]propyl}morpholine was added and the reaction was maintained at the first stage for 20 minutes. Finally, methanol was added to terminate the reaction.

[0042] The preparation methods of Examples 2 to 7 can be referred to Example 1. In Example 5, only 4.9 mmole of n-butyllithium was added, and diisopropenylbenzene was not added. Other differences are shown in Table 1.

[0043] Comparative Example 1: In a 5525g cyclohexane solution containing 8.3g of cyclic ether and 0.5g of diether compound, 4.9 mmole of n-butyllithium and 1g of diisopropylbenzene were added, and the mixture was reacted at 50°C for 30 minutes. Then, 1,3-butadiene and styrene (totaling 65 wt% of the copolymer) were added for the first stage of polymerization, with styrene and butadiene added simultaneously at different rates. After reaching the maximum temperature of the first stage, the reaction was maintained for 10 minutes. Next, the remaining butadiene (35 wt% of the copolymer) was added for the second stage of polymerization, and the reaction was maintained for another 15 minutes after reaching the maximum temperature of the second stage. Then, 4.2g of 4-{3-[dimethoxy(methyl)silyl]propyl}morpholine was added and the reaction was maintained for 20 minutes. Finally, methanol was added to terminate the reaction. The difference between Comparative Example 1 and the various embodiments is that in Comparative Example 1, a copolymer segment is formed first, and then a homopolymer segment is formed, and the butadiene content of the homopolymer segment accounts for 35 wt% of the total copolymer.

[0044] The preparation method of Comparative Example 2 can be the same as that of Comparative Example 1, with the differences shown in Table 1. The difference between Comparative Example 2 and the other examples is that in Comparative Example 2, the copolymer segment is formed first, and then the homopolymer segment is formed.

[0045] Comparative Example 3: 4.9 mmol of n-butyllithium was added to a 5525 g cyclohexane solution containing 8.3 g of cyclic ether and 0.5 g of diether compound, followed by the addition of 1,3-butadiene (65 wt% of the total copolymer) for the first stage polymerization. The reaction was maintained at the first stage maximum temperature for 10 minutes. Then, the remaining butadiene and styrene (totaling 35 wt% of the total copolymer) were added for the second stage polymerization, with styrene and butadiene added simultaneously at different rates. The reaction was maintained at the second stage maximum temperature for another 15 minutes. Next, 4.2 g of 4-{3-[dimethoxy(methyl)silyl]propyl}morpholine was added and the reaction was maintained at the second stage for 20 minutes. Finally, methanol was added to terminate the reaction. The main difference between Comparative Example 3 and the other examples is that the butadiene addition rate in the second stage polymerization of Comparative Example 3 was lower.

[0046] Comparative Example 4: In a 5525g cyclohexane solution containing 8.3g of cyclic ether and 0.5g of diether compound, 4.9 mmole of n-butyllithium and 1g of diisopropylbenzene were added, and the mixture was reacted at 50°C for 30 minutes. Then, 1,3-butadiene (65 wt% of the total copolymer) was added for the first stage of polymerization, and the reaction was maintained at the first stage maximum temperature for 10 minutes. Next, the remaining butadiene and styrene (totaling 35 wt% of the total copolymer) were added for the second stage of polymerization. In this step, styrene was added first, followed by butadiene 30 seconds later, to allow some styrene to form blocks first, and the addition rate of both styrene and butadiene was 70 g / min. The reaction was maintained at the second stage maximum temperature for another 15 minutes. Then, 4.2g of 4-{3-[dimethoxy(methyl)silyl]propyl}morpholine was added and the reaction was maintained at the first stage for 20 minutes. Finally, methanol was added to terminate the reaction. The difference between Comparative Example 4 and the various embodiments is that butadiene and styrene are not added simultaneously during the second stage polymerization. Instead, styrene is added first for a period of time before butadiene is added, and the addition rates of styrene and butadiene are the same.

[0047] Comparative Example 5: The preparation method of Comparative Example 5 can be the same as that of Comparative Example 4. The difference between Comparative Example 5 and Comparative Example 4 is that when carrying out the second stage polymerization, styrene is added first, and butadiene is added 1 minute later.

[0048] Table 1

[0049]

[0050] Note: Y indicates that it is used, and N indicates that it is not used.

[0051] The copolymers obtained from the aforementioned examples and comparative examples (collectively referred to as solution-polymerized styrene-butadiene rubber (SSBR)) were prepared into rubber compositions according to the mixing formulations described in Table 2, and the results were tested as shown in Tables 3 and 4. For the mixing formulations described in Table 2, an internal mixer was used to knead the components. During the primary mixing, the speed was controlled at 55 rpm and the temperature at 150°C. During the final mixing, the speed was controlled at 45 rpm and the temperature at 100°C.

[0052] Table 2

[0053]

[0054] Table 3

[0055]

[0056] Note: The DIN, RR and WG values ​​shown in Table 3 have been normalized and are relative values ​​rather than absolute values.

[0057] Table 4

[0058]

[0059] Note: The DIN, RR and WG values ​​shown in Table 4 have been normalized and are relative values ​​rather than absolute values.

[0060] Comparative Example 1 first forms a copolymer segment, then a homopolymer segment, and the content of the butadiene homopolymer segment accounts for only 35 wt% of the total copolymer. As can be seen from the data in Tables 3 and 4, Comparative Example 1 exhibits a single Tg phase, and its wet grip is worse than that of the examples exhibiting a dual Tg phase.

[0061] Comparative Example 2 first forms a copolymer segment, and then a homopolymer segment. As can be seen from the data in Tables 3 and 4, Comparative Example 2 not only exhibits a single Tg phase, but also has zero styrene microblocks. Therefore, its wet grip is significantly reduced compared to the examples (and even worse than Comparative Example 1).

[0062] Comparative Example 2 and the copolymers of Examples 1 to 7 are similar in overall structure, with the main difference being the polymerization sequence of the copolymer and homopolymer segments. The copolymer segment of Comparative Example 2 belongs to the first stage of polymerization. Since no polymerization reaction has occurred in the reactor, the environment inside the reactor gradually heats up from a lower temperature as polymerization begins. That is, the copolymer segment of Comparative Example 2 starts polymerization at a lower temperature, making the distribution of styrene units in the chain more random, resulting in a styrene microblock ratio approaching 0. This structural characteristic also affects its glass transition behavior, causing it to exhibit only a single glass transition temperature (Tg) in viscoelastic rheological analysis. In contrast, the copolymer segment of Examples 1 to 7 belongs to the second stage of polymerization. The reactor is already at a high temperature after the first stage of polymerization. That is, the copolymer segment of Examples 1 to 7 polymerizes at a higher temperature, which is more conducive to the formation of styrene microblocks, thus forming a polymer with two glass transition temperatures (double Tg).

[0063] Compared to the examples, the addition rate of butadiene in the second stage of polymerization in Comparative Example 3 was lower. As can be seen from the data in Tables 3 and 4, although Comparative Example 3 exhibits a double Tg phase, its styrene microblocks are relatively low, so its wet grip is still worse than that of the examples.

[0064] In Comparative Examples 4 and 5, styrene was added first, followed by butadiene, during the copolymerization stage. As shown in Tables 3 and 4, both Comparative Examples 4 and 5 exhibited a single Tg phase and had an excessively high styrene microblock ratio; therefore, although they had good wet grip, their rolling resistance was significantly lower.

[0065] Data from Examples 1 to 7 show that the conjugated diene-vinyl aromatic hydrocarbon copolymer of the present invention, through a specific structural design with two glass transition temperatures (a first Tg of -10 to -50°C and a second Tg of -45 to -85°C) and styrene microblock content (SB%) controlled at 1.0% to 10.0%, can significantly improve wet grip (WG). As shown in Examples 1 to 7 in Table 3, expressed as normalized relative values, its wet grip (WG) can reach up to 167, which is significantly better than copolymers with only a single Tg (e.g., Comparative Example 2). At the same time, the present invention can also maintain rolling resistance (RR) at a relative value of 98 to 103, avoiding a significant decrease in the relative value of rolling resistance to 81 due to excessively high styrene microblock content (e.g., 22% in Comparative Example 5). In addition, the abrasion resistance index (DIN) of the present invention can also remain stable, approximately between a relative value of 100 and 110.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the patent application of the present invention; all other equivalent changes or modifications made without departing from the spirit disclosed in the present invention should be included in the scope of the patent application below.

Claims

1. A copolymer of a conjugated diene and a vinyl aromatic hydrocarbon, comprising a homopolymer segment composed of a conjugated diene and a copolymer segment composed of a conjugated diene and a vinyl aromatic hydrocarbon, the copolymer segment being connected to the homopolymer segment, the copolymer having a first glass transition temperature between -10°C and -50°C and a second glass transition temperature between -45°C and -85°C, the first glass transition temperature being higher than the second glass transition temperature, wherein the vinyl aromatic hydrocarbon microblock content in the copolymer accounts for 1.0% to 10.0% of the total vinyl aromatic hydrocarbon content in the copolymer, wherein the vinyl aromatic hydrocarbon microblock refers to a microblock having at least four consecutive vinyl aromatic hydrocarbon units.

2. The copolymer of claim 1, wherein the homopolymer segment contains 60 wt% to 90 wt% of the total content of the copolymer.

3. The copolymer of claim 2, wherein the homopolymer segment contains 65 wt% to 73 wt% of the total content of the copolymer.

4. The copolymer of claim 1, wherein the vinyl aromatic hydrocarbon is styrene and the conjugated diene is 1,3-butadiene.

5. The copolymer of claim 1, wherein the vinyl aromatic hydrocarbon bond content of the copolymer is in the range of 10 wt% to 20 wt%.

6. The copolymer of claim 1, wherein the vinyl content of the copolymer accounts for 30 wt% to 40 wt% of the total conjugated diene content of the copolymer.

7. The copolymer of claim 1, wherein the copolymer has no other glass transition temperature.

8. The copolymer of claim 1, wherein the copolymer further comprises a modified end connecting the copolymer segment, wherein the copolymer segment is located between the homopolymer segment and the modified end.

9. The copolymer of claim 8, wherein the modified end contains silicon.

10. A method for manufacturing a copolymer as described in any one of claims 1 to 7, comprising: step (1): providing an initiator; step (2): forming a homopolymer segment composed of a conjugated diene by anionic polymerization using the initiator under conditions containing cyclic ethers and diether compounds; step (3): forming a copolymer segment composed of a conjugated diene and a vinyl aromatic hydrocarbon after step (2) to connect the homopolymer segment, wherein in step (3), the vinyl aromatic hydrocarbon and the conjugated diene are simultaneously added to the polymerization reactor, wherein the addition rate of the vinyl aromatic hydrocarbon is different from the addition rate of the conjugated diene.

11. The method of claim 10, wherein the initiator is a multi-terminal initiator generated by the reaction of a divinyl aromatic hydrocarbon compound with an organoalkali metal.

12. The method of claim 10, wherein the cyclic ether and the diether compound are tetrahydrofuran and ethylene glycol diethyl ether, respectively.

13. The method of claim 10, wherein in step (3), the ratio of the vinyl aromatic hydrocarbon addition rate to the conjugated diene addition rate is 3.8 to 6.

4.

14. The method of claim 10, wherein the method further comprises step (4): forming a modified end of a connecting copolymer segment after step (3), wherein the copolymer segment is located between the homopolymer segment and the modified end.

Images