Siloxane modified solution polymerized diene rubber polymer and preparation method thereof

Abstract

The present invention relates to a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The preparation method comprises the following steps in sequence: 1) in the presence of an organic lithium compound, a conjugated diene compound and an aromatic vinyl compound are subjected to polymerization reaction; 2) after the polymerization reaction is completed, a siloxane modifier is added to perform a first modification treatment; 3) a siloxane modifier is added to perform a second modification treatment; 4) a halogenated silicon terminator is added to terminate the active end of the polymer product; 5) the polymer product is steam-condensed at low temperature and negative pressure to obtain the diene rubber polymer, wherein the 2-branch component in the structure reaches less than 25%, and the multi-branch component reaches less than 20%. The technical scheme of the present invention can obtain a siloxane-modified solution-polymerized diene rubber polymer with a lower coupling rate, and the rubber composition formed therefrom has excellent processability, and the vulcanized rubber has excellent rolling resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic rubber, and in particular relates to a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. Background Art

[0002] According to literature reports, silica-mixed rubber compositions are effective for low fuel efficiency tires. In order to improve the rebound resilience or tanδ of rubber as a laboratory index or viscoelasticity test, siloxane modification of solution polymerized diene rubber using an alkoxysilane compound that can effectively disperse silica is beneficial to improving the rebound resilience or viscoelasticity of the rubber.

[0003] For example, the Chinese patent document with publication number CN105837751 A discloses a type of multifunctional solution-polymerized styrene-butadiene rubber containing siloxy groups at the chain ends, which is a terpolymer of butadiene, styrene, and a 1,1-diphenylethylene derivative containing a single siloxy group monomer; the invention improves the dispersibility of carbon black and white carbon black in the rubber matrix, effectively controls the movement and friction heat generated by the active polymer chain ends, reduces the heat generated by the internal friction of the tire, and improves the reinforcement effect of carbon black and white carbon black. However, the invention uses a 1,1-diphenylethylene derivative containing a single siloxy group monomer as one of the monomers, which is not an easily available monomer. For companies that do not have the ability to produce such compounds, this will lead to an increase in polymer costs and make it difficult to industrialize the product. The Chinese patent document with publication number CN106565904A discloses a difunctional styrene-butadiene polymer, the general formula of which is: (ArCH2SR1PR2) m Si(OR3) n , wherein Ar is an aryl or arylalkyl group having 6-20 carbon atoms, R1 is an aryl or arylalkyl group having 1-10 carbon atoms, R2 is an alkyl group having 1-10 carbon atoms, R3 is an alkyl group having 1-5 carbon atoms, m=1-3, n=4-m, and P is a copolymer of butadiene and styrene. Compared with the solution-polymerized styrene-butadiene rubber without double-end functionalization, the sulfur- and siloxane-terminated styrene-butadiene polymer has enhanced mechanical properties, reduced rolling resistance, and enhanced wet skid resistance, and is a high-performance energy-saving rubber with excellent comprehensive performance. The Chinese patent document with publication number CN102712214A discloses a method for terminal functionalized polymers containing at least one sulfur atom and at least one silicon or tin atom, which is used to reduce the rolling resistance of tread rubber and improve wet skid resistance. The method reacts a cyclic compound containing at least one S, Si, Sn atom with a terminal active polymer to obtain a polymer with terminal functionality.

[0004] However, the Si-OR groups contained in the siloxane-modified solution-polymerized diene rubber undergo dehydration condensation reaction during the stripping process, which consumes Si-OR and reduces the number of groups that can react with white carbon black during the mixing process, resulting in a decrease in the resilience and rolling resistance of the rubber product. In addition, the current silane modification technology mostly involves multi-siloxane group modification and the limitation of the type and amount of modifiers, but the multi-siloxane group-modified solution-polymerized styrene-butadiene rubber produces molecular chain coupling in the steam-heated water environment, and the molecular chain coupling has a potential impact on the siloxane groups at the end of the solution-polymerized styrene-butadiene rubber, which will lead to a decrease in the dynamic properties of the final polymer (for example, rolling resistance and anti-slip performance). Summary of the invention

[0005] In view of this, the present invention provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof, wherein after the anionic polymerization reaction of the solution-polymerized diene rubber polymer is completed, a siloxane modifier is added twice to allow the siloxane group to fully react with the polymer terminal, thereby improving the modification rate of the polymer; and by using a low-boiling hydrocarbon solvent (for example, cyclopentane), the stripping temperature of the synthetic product is reduced, thereby reducing the increase in coupling rate caused by the loss of functional groups in the purification process of the synthetic product, and ultimately improving the dynamic performance of the synthetic product.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions.

[0007] In a first aspect, the present invention provides a method for preparing a siloxane-modified solution-polymerized diene rubber polymer, the preparation method comprising the following steps:

[0008] 1) In the presence of an organic lithium compound, a conjugated diene compound and an aromatic vinyl compound are polymerized in an organic hydrocarbon solvent;

[0009] 2) After the polymerization reaction is completed, a siloxane modifier is added to carry out the first modification treatment, so that the polymerization product undergoes a first modification component;

[0010] 3) Adding a siloxane modifier to perform a second modification treatment to produce a secondary modified component in the polymer product;

[0011] 4) Adding a halogenated silicon terminator to treat the polymer product to reduce the multi-branched component to less than 20%;

[0012] 5) The polymerized product obtained in step 4) is steam condensed and dried under low temperature and negative pressure conditions to obtain the siloxane-modified solution-polymerized diene rubber polymer.

[0013] In the above method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 1), the organic lithium compound includes n-butyl lithium.

[0014] In the above method for preparing the siloxane-modified solution-polymerized diene rubber polymer, in the step 1), the conjugated diene compound includes at least one of 1,3-butadiene and 1,3-pentadiene.

[0015] In the above method for preparing the siloxane-modified solution-polymerized diene rubber polymer, in the step 1), the aromatic vinyl compound includes at least one of styrene and methylstyrene.

[0016] In the above method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 1), the organic hydrocarbon solvent is a low-boiling point organic hydrocarbon solvent.

[0017] In the above-mentioned method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 1), the amount of low-boiling hydrocarbon solvent added accounts for 70% to 90% of the total mass of the conjugated diene compound, the aromatic vinyl compound and the organic hydrocarbon solvent.

[0018] In the above method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 1), the low-boiling point organic hydrocarbon solvent is cyclopentane.

[0019] In the above-mentioned method for preparing a siloxane-modified solution-polymerized diene rubber polymer, the siloxane modifier has a structure as shown in the following formula (1):

[0020] (R2O) m -Si-(R3) 4-m Formula (1); where

[0021] R2 is an alkyl group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms containing a nitrogen atom;

[0022] R3 is an alkyl group having 1 to 12 carbon atoms or a halogenated alkyl group containing 1 to 2 halogen elements, wherein the halogen elements include at least one of iodine, bromine and chlorine;

[0023] m is an integer of 2-4.

[0024] In the above-mentioned method for preparing a siloxane-modified solution-polymerized diene rubber polymer, in the step 4), the halogenated silicon terminator has a structure shown in the following formula (2):

[0025] (R1) n -Si-(X) 4-n Formula (2); where

[0026] R1 is an alkyl group having 1 to 12 carbon atoms,

[0027] X is one of iodine, bromine and chlorine,

[0028] n is 0 or 1.

[0029] In the method for preparing the siloxane-modified solution-polymerized diene rubber polymer, the polymerization in steps 1) to 5) is initiated in the presence of an organic lithium compound.

[0030] In the above-mentioned method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 2), the mass amount of the siloxane modifier added in the first modification treatment is 45% to 55% of the total amount of the siloxane modifier added.

[0031] In the above-mentioned method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 2), the mass amount of the siloxane modifier added in the first modification treatment is 50% of the total amount of the siloxane modifier added.

[0032] In the above-mentioned method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 2), the temperature of the first modification treatment is determined according to the polymerization peak temperature. Optionally, the temperature of the first modification treatment is 80-100°C.

[0033] In the above-mentioned method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 2), the time of the first modification treatment is 4 to 6 minutes.

[0034] In the above-mentioned method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 3), in the second modification treatment, the mass amount of the siloxane modifier added is 55% to 45% of the total amount of the siloxane modifier added.

[0035] In the above-mentioned method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 3), in the second modification treatment, the mass amount of the siloxane modifier added is 50% of the total amount of the siloxane modifier added.

[0036] In the above-mentioned method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 3), the time of the second modification treatment is 4 to 6 minutes.

[0037] In the process of siloxane modification, it is inevitable that the polymer ends are not fully reacted with the siloxane modifier. In the present invention, a silicon halide terminator is used to terminate the polymerization reaction in order to prevent the residual active ends in the polymer from reacting with water and oxygen impurities to generate unpredictable products, thereby affecting the polymer properties.

[0038] The present invention adopts a two-stage addition of the siloxane modifier, the purpose of which is to fully connect the polymer terminal with the siloxane group. The halogenated silicon terminator can be used in a small amount and the production cost can be saved.

[0039] In the method for preparing the siloxane-modified solution-polymerized diene rubber polymer, the molar ratio of the total amount of the siloxane modifier added to the organic lithium compound is 1 to 2:1.

[0040] In the method for preparing the siloxane-modified solution-polymerized diene rubber polymer, the molar ratio of the silicon halide terminator to the organic lithium compound is 0.25 to 1:1.

[0041] The active end of the polymer is terminated by using a silane modifier. In conventional methods, the siloxane modifier is generally added all at once. The present invention adds the siloxane modifier in stages to fully connect the polymer end with the siloxane group. Therefore, after adding the halogenated silicon terminator, no redundant multi-branched components are generated during the polymerization stage.

[0042] The method of the present invention can obtain a polymer product structure in which the content of dibranched chains is less than 25% and the content of multi-branched chains is 5-20%.

[0043] In the above method for preparing siloxane-modified solution-polymerized diene rubber polymer, in step 5), the pressure of steam condensation is -30 kPa to -70 kPa.

[0044] In the above method for preparing siloxane-modified solution-polymerized diene rubber polymer, in step 5), the temperature of steam condensation is 60-70°C.

[0045] Compared with the general steam condensation method, the parameters provided by the present invention are applied to siloxane-modified polymers to reduce the loss of siloxane groups at the polymer ends due to hydrolysis coupling reactions, that is, to reduce the 2-branch component in the polymer structure to less than 25%.

[0046] In a second aspect, the present invention provides a siloxane-modified solution-polymerized diene rubber polymer, wherein the siloxane-modified solution-polymerized diene rubber polymer is prepared by any of the above-mentioned methods for preparing the siloxane-modified solution-polymerized diene rubber polymer.

[0047] The above-mentioned siloxane-modified solution-polymerized diene rubber polymer has a general structural formula of: (P) a Si[(OR2) b1 (R3) b2 ];in,

[0048] R2 is an alkyl group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms containing a nitrogen atom;

[0049] R3 is an alkyl group having 1 to 12 carbon atoms or a halogenated alkyl group containing 1 to 2 halogen elements, wherein the halogen elements include at least one of iodine, bromine and chlorine;

[0050] The alkoxy group formed by OR2 and R3 are both connected to the silicon atom.

[0051] P represents a copolymer of butadiene and styrene;

[0052] b1≥1, and b1+b2=1~3;

[0053] a= 4 - (b1+b2).

[0054] The above-mentioned siloxane-modified solution-polymerized diene rubber polymer has a structure in which the bi-branched component is less than 25%, the multi-branched component is 5-20%, and the single chain component is 55%-95%.

[0055] In the present invention, the above technical features can be freely combined to form a new technical solution without conflicting with each other.

[0056] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0057] (1) The present invention performs two-stage siloxane modification on the solution-polymerized diene rubber, which is beneficial for the siloxane modifier to fully react with the polymer terminal during polymerization, and is beneficial for controlling the multi-branch content in the structure of the final polymer product; thereby, it is beneficial for improving the rolling resistance of the rubber composition;

[0058] (2) The present invention adopts a low-boiling point organic hydrocarbon solvent and a negative pressure low-temperature steam condensation method to obtain a solution-polymerized diene rubber polymer, which is beneficial to controlling the content of the 2-branch component of the siloxane-modified solution-polymerized diene rubber, and further helps to improve the rolling resistance of the rubber composition by preventing the consumption of the hydrolysis coupling of the siloxane group to the greatest extent in the steam condensation unit;

[0059] (3) The technical solution of the present invention can be used to obtain a siloxane-modified solution-polymerized diene rubber with a low coupling rate. The rubber composition obtained by blending the siloxane-modified solution-polymerized diene rubber with other additives has excellent processability, and the vulcanized rubber thereof has excellent rolling resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0061] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0062] Figure 1 This is the GPC spectrum of the siloxane-modified solution-polymerized diene rubber polymer prepared in Example 1 of the present invention;

[0063] Figure 2 This is the GPC spectrum of the siloxane-modified solution-polymerized diene rubber polymer prepared in Example 2 of the present invention;

[0064] Figure 3 This is the GPC spectrum of the siloxane-modified solution-polymerized diene rubber polymer prepared in Example 3 of the present invention;

[0065] Figure 4 This is the GPC spectrum of the siloxane-modified solution-polymerized diene rubber polymer prepared in Comparative Example 1 of the present invention;

[0066] Figure 5 This is the GPC spectrum of the siloxane-modified solution-polymerized diene rubber polymer prepared in Comparative Example 2 of the present invention;

[0067] Figure 6 This is the GPC spectrum of the siloxane-modified solution-polymerized diene rubber polymer prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0068] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0069] Some embodiments of the first aspect of the present invention provide a method for preparing a siloxane-modified solution-polymerized diene rubber polymer, the preparation method comprising the following steps:

[0070] 1) In the presence of an organic lithium compound, a conjugated diene compound and an aromatic vinyl compound are polymerized in an organic hydrocarbon solvent;

[0071] 2) After the polymerization reaction is completed, a siloxane modifier is added to perform the first modification treatment so that the polymer product has less than 10% of 2-branch components;

[0072] 3) Adding a siloxane modifier for a second modification treatment to reduce the 2-branch component of the polymer product to less than 25%;

[0073] 4) Adding a halogenated silicon terminator to treat the polymer product to reduce the multi-branched component to less than 20%;

[0074] 5) The polymerized product obtained in step 4) is steam condensed and dried under low temperature and negative pressure conditions to obtain the siloxane-modified solution-polymerized diene rubber polymer.

[0075] The present invention does not specifically limit the organic lithium compound, and those skilled in the art may select conventional organic lithium initiators in the art.

[0076] In some embodiments, in step 1), the organic lithium compound includes n-butyl lithium.

[0077] In the above-mentioned method for preparing siloxane-modified solution-polymerized diene rubber polymer, in the step 1), the conjugated diene compound includes at least one of 1,3-butadiene and 1,3-pentadiene; and the aromatic vinyl compound includes at least one of styrene and methyl styrene.

[0078] In some embodiments, in step 1), the organic hydrocarbon solvent is a low boiling point organic hydrocarbon solvent.

[0079] In some embodiments, in step 1), the amount of low-boiling-point hydrocarbon solvent added accounts for 70% to 90% (eg, 75%, 80% or 85%) of the total mass of the conjugated diene compound, the aromatic vinyl compound and the organic hydrocarbon solvent.

[0080] In some embodiments, in step 1), the low boiling point organic hydrocarbon solvent is cyclopentane.

[0081] In some embodiments, the siloxane modifier has a structure as shown in the following formula (1):

[0082] (R2O) m -Si-(R3) 4-m Formula (1); where

[0083] R2 is an alkyl group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms containing a nitrogen atom;

[0084] R3 is an alkyl group having 1 to 12 carbon atoms or a halogenated alkyl group containing 1 to 2 halogen elements, wherein the halogen elements include at least one of iodine, bromine and chlorine;

[0085] m is an integer of 2-4.

[0086] In some embodiments, in step 4), the silicon halide terminator has a structure shown in the following formula (2):

[0087] (R1) n -Si-(X) 4-n Formula (2); where

[0088] R1 is an alkyl group having 1 to 12 carbon atoms,

[0089] X is one of iodine, bromine and chlorine,

[0090] n is 0 or 1.

[0091] In some embodiments, the polymerization of step 1) to step 5) is initiated in the presence of an organic lithium compound.

[0092] In some embodiments, in the step 2), the mass amount of the siloxane modifier added in the first modification treatment is 45% to 55% of the total amount of the siloxane modifier added; in the step 3), the mass amount of the siloxane modifier added in the second modification treatment is 55% to 45% of the total amount of the siloxane modifier added.

[0093] In some embodiments, in the step 2), the mass amount of the siloxane modifier added in the first modification treatment is 50% of the total amount of the siloxane modifier added, and in the step 3), the mass amount of the siloxane modifier added in the second modification treatment is 50% of the total amount of the siloxane modifier added.

[0094] In the present invention, the siloxane modifier is added twice, each time adding 45% to 55% (for example, 50%) of the total amount, and the reaction is carried out for a certain time after the first addition of the siloxane modifier, or the reaction is carried out for a certain time after the second addition of the siloxane modifier and then entering the next process.

[0095] In some embodiments, in step 2), the temperature of the first modification treatment is determined according to the polymerization peak temperature. Optionally, the temperature of the first modification treatment is 80-100° C. (eg, 85° C., 90° C. or 95° C.).

[0096] In the present invention, the timing of the first modification treatment is determined according to the peak temperature of the polymerization reaction. That is, after the temperature of the polymerization reaction reaches the peak and the temperature of the polymerization reaction system begins to decline, the first modification treatment is performed; optionally, the temperature of the first modification treatment is 80-100°C.

[0097] Specifically, in the step 2), after the temperature of the polymerization reaction reaches a peak value, a siloxane modifier is added to perform the first modification treatment.

[0098] The present invention does not specifically limit the reaction time after adding the siloxane modifier, and those skilled in the art can select a suitable reaction time according to specific experimental results.

[0099] In some embodiments, in step 2), the time of the first modification treatment is 4 to 6 min (eg, 5 min); the time of the second modification treatment is 4 to 6 min (eg, 5 min).

[0100] In some embodiments, the molar ratio of the total amount of the siloxane modifier added to the organic lithium compound is 1 to 2:1 (eg, 1.2:1, 1.5:1, 1.7:1, or 1.9:1).

[0101] In some embodiments, the molar ratio of the silicon halide terminator to the organolithium compound is 0.25 to 1:1 (eg, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, or 0.9:1).

[0102] In some embodiments, after the second siloxane modifier reaction is completed, a silicon halide terminator is added to react for a certain time before entering the next process. The present invention does not specifically limit the reaction time after adding the silicon halide terminator, and those skilled in the art can select a suitable reaction time according to specific experimental results.

[0103] Generally, a silane modifier is used to terminate the active end of the polymer. In conventional methods, the siloxane modifier is generally added all at once. The present invention adds the siloxane modifier in stages to fully connect the polymer end with the siloxane group. Therefore, after adding the halogenated silicon terminator, the polymerization no longer generates redundant multi-branched coupling structures.

[0104] In the process of siloxane modification, it is inevitable that the polymer ends are not fully reacted with the siloxane modifier. In the present invention, a silicon halide terminator is used to terminate the polymerization reaction in order to prevent the residual active ends in the polymer from reacting with water and oxygen impurities to generate unpredictable products, thereby affecting the polymer properties.

[0105] The present invention adopts a two-stage addition of the siloxane modifier, the purpose of which is to fully connect the polymer terminal with the siloxane group. The halogenated silicon terminator can be used in a small amount and the production cost is saved.

[0106] In the structure of the polymer product obtained by the preparation method of the present invention, the component of two branches is less than 25%, and the component of multiple branches is 5-20%.

[0107] In some embodiments, in step 5), the pressure at which the steam is condensed is -30 kPa to -70 kPa (eg, -40 kPa, -50 kPa, -60 kPa, or -65 kPa).

[0108] In some embodiments, in step 5), the temperature at which the steam is condensed is 60-70° C. (eg, 62° C., 65° C., or 68° C.).

[0109] In the prior art, the steam condensation temperature of the siloxane-modified solution-polymerized diene rubber polymer is generally 84-120°C, and the steam condensation pressure is 30 kPa-50 kPa. Under such high temperature and pressure steam condensation conditions, the Si-OR groups contained in the siloxane-modified solution-polymerized diene rubber undergo dehydration condensation reaction during the steam stripping process, consuming Si-OR, thereby reducing the number of groups that can react with white carbon black during the mixing process, resulting in a decrease in the resilience and rolling resistance of the rubber product. Alternatively, the polysiloxane group-modified solution-polymerized styrene-butadiene rubber produces molecular chain coupling in a steam-heated water environment, and the molecular chain coupling has a potential impact on the siloxane groups at the end of the solution-polymerized styrene-butadiene rubber, which will lead to a decrease in the dynamic properties of the final polymer (for example, rolling resistance and anti-slip performance).

[0110] In the present invention, after the low-temperature negative pressure steam condensation in step 5), the structure of the polymer product does not change, and its 2-branch component is less than 25%; the multi-branch component is 5% to 20%; and the single chain component is 55% to 95%.

[0111] The present invention adopts a two-stage modification method of a siloxane modifier, firstly, the siloxane modifier is used to perform a termination reaction of a solution-polymerized diene rubber twice, then a halogenated silicon terminator is used to terminate all active species, and finally, the solution-polymerized diene rubber polymerization product is steam condensed (i.e., stripped) under negative pressure (-70 kPa to -30 kPa) and low temperature (60 to 70°C), thereby reducing the coupling rate of the solution-polymerized diene rubber polymer product to the greatest extent, which is beneficial to improving the rolling resistance performance of the rubber composition.

[0112] The siloxane-modified solution-polymerized diene rubber polymer prepared by the preparation method of the present invention has excellent rolling resistance, structural stability and low coupling rate, and has excellent processability during mixing. Compared with general siloxane-modified solution-polymerized diene rubber, the rolling resistance and wear resistance of the rubber obtained by the preparation method are improved. When used for tire rubber, it is most suitable for automobile tires with good processability and excellent low fuel efficiency.

[0113] Some embodiments of the second aspect of the present invention provide a siloxane-modified solution-polymerized diene rubber polymer, wherein the siloxane-modified solution-polymerized diene rubber polymer is prepared by any of the above-mentioned methods for preparing a siloxane-modified solution-polymerized diene rubber polymer.

[0114] In some embodiments, the solution polymerized diene rubber has the general structural formula: (P) a Si[(OR2) b1 (R3) b2 ];in,

[0115] R2 is an alkyl group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms containing a nitrogen atom;

[0116] R3 is an alkyl group having 1 to 12 carbon atoms or a halogenated alkyl group containing 1 to 2 halogen elements, wherein the halogen elements include at least one of iodine, bromine and chlorine;

[0117] The alkoxy group formed by OR2 and R3 are both connected to the silicon atom.

[0118] P represents a copolymer of butadiene and styrene;

[0119] b1≥1, and b1+b2=1~3;

[0120] a= 4 - (b1+b2).

[0121] In some embodiments, in the structure of the solution-polymerized diene rubber, the content of 2-chain branches is less than 25% (e.g., 5%, 10%, 15% or 20%); the content of multiple branches is 5-20% (e.g., 7%, 10%, 15% or 18%); and the content of single chains is 55%-95% (e.g., 60%, 65%, 70%, 75%, 80%, 85% or 90%).

[0122] The present invention adopts a two-stage modification method of a siloxane modifier, firstly, the siloxane modifier is used to perform a termination reaction of a solution-polymerized diene rubber twice, then a halogenated silicon terminator is used to terminate all active species, and finally, the solution-polymerized diene rubber polymerization product is steam condensed (i.e., stripped) under negative pressure (-70 kPa to -30 kPa) and low temperature (60 to 70°C), thereby reducing the coupling rate of the solution-polymerized diene rubber polymer product to the greatest extent, which is beneficial to improving the rolling resistance performance of the rubber composition.

[0123] Based on the fact that siloxane-modified solution-polymerized diene rubber has excellent rolling resistance, structural stability and low coupling rate, and the rubber polymer obtained when mixed has excellent processability, the present invention conducts in-depth research on the preparation method of siloxane-modified solution-polymerized diene rubber, and develops a method in which a conjugated diene compound and an aromatic vinyl compound are polymerized in a (low-boiling-point) alkane (preferably low-boiling-point cyclopentane) in the presence of an organic lithium compound as an initiator, a specific siloxane modifier is added in a specific proportion after the polymerization is completed, a halogenated silicon terminator is further added under specific conditions, and then the siloxane group is protected from being hydrolyzed and destroyed by condensation of negative pressure low-temperature steam, thereby forming more coupling structures, thereby manufacturing a siloxane-modified solution-polymerized diene rubber with excellent rolling resistance, low coupling rate, and excellent processability when mixed with white carbon black.

[0124] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0125] The experimental methods in the following examples without specifying specific conditions are usually measured according to national standards. If there are no corresponding national standards, they are carried out according to the general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0126] It should be noted that in the following embodiments and comparative examples of the present invention, the molecular weight and molecular weight distribution of the siloxane-modified solution-polymerized diene rubber polymer product were measured by gel permeation chromatography according to ISO11344-2016 gel chromatography. The dynamic properties (tanδ, 0° and tanδ, 60°) of the compound rubber obtained by the siloxane-modified solution-polymerized diene rubber polymer prepared in each embodiment and comparative example were tested according to GB / T 9870.1-2006.

[0127] Example 1

[0128] A siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof, comprising the following steps:

[0129] A polymerization kettle with a volume of 125 L was fully replaced with dry nitrogen. According to the proportion of cyclopentane in the total material (i.e., the total mass of styrene, 1,3-butadiene and cyclopentane) of 90%, 63 kg of cyclopentane was added. According to the molar ratio of DTHFP to butyl lithium of 6:1, 50 g of structure regulator 2,2-di(2-tetrahydrofuranyl)propane (DTHFP), 1.96 kg of styrene, and 5.04 kg of 1,3-butadiene were added to the polymerization kettle. After the material temperature was adjusted to 15°C, butyl lithium was added to the polymerization kettle to start the reaction. The highest temperature during the polymerization process reached 90°C. At this time, the siloxane modifier methyltri[2-(dimethylamino)ethoxy]silane was added in two stages using a sequential control program. Specifically, in the first stage of the addition of the siloxane modifier, 63 g of siloxane modifier was added according to the molar ratio of the siloxane modifier to butyl lithium of 0.5:1. Methyltri[2-(dimethylamino)ethoxy]silane, wait for 5 minutes before adding the second stage siloxane modifier; during the addition of the second stage siloxane modifier, 63 g of methyltri[2-(dimethylamino)ethoxy]silane was added according to a molar ratio of siloxane modifier to butyl lithium of 0.5:1, and silicon tetrachloride was used to terminate the reaction after waiting for 5 minutes; specifically, 125 g of silicon tetrachloride was added according to a molar ratio of silicon tetrachloride to butyl lithium of 0.25:1; after reacting for 30 minutes, the discharge valve was opened, and the glue liquid was pressurized into the condensation kettle through a screw pump and a nozzle for low-temperature and low-pressure steam condensation; specifically, by controlling the pressure of the oil-water stratification tank, the amount of water vapor added, and the amount of glue sprayed, the temperature of the No. 1 stripping kettle was controlled at 68°C and the pressure was controlled at -30 kPa, the rubber liquid forms rubber particles under the action of dispersant (for example, TAMOL™731A, calcium chloride) and stirring of the stripping kettle, and enters the No. 2 stripping kettle through the overflow inclined pipe. The temperature of the No. 2 stripping kettle is controlled at 70℃ and the pressure is controlled at -30 kPa. After the rubber particles are stripped continuously for 1 hour, dry rubber is prepared, namely, siloxane-modified solution-polymerized diene rubber.

[0130] The dried gel was sampled and recorded as sample 1, and subjected to gel permeation chromatography (GPC) analysis. Figure 1 The GPC spectrum of the siloxane-modified solution-polymerized diene rubber sample prepared in this example is shown. In the structure of the siloxane-modified solution-polymerized diene rubber, the content of di-branching is 24%, the content of multi-branching is 15%, and the content of single chain is 61%.

[0131] Example 2

[0132] A siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof, comprising the following steps:

[0133] A polymerization kettle with a volume of 125 L was fully replaced with dry nitrogen. According to the proportion of cyclopentane in the total material (i.e., the total mass of styrene, 1,3-butadiene and cyclopentane) of 70%, 16 kg of cyclopentane was added, and 50 g of structure regulator 2,2-di(2-tetrahydrofuranyl)propane (DTHFP), 2 kg of styrene, and 5 kg of 1,3-butadiene were added to the polymerization kettle. After the material temperature was adjusted to 15°C, butyl lithium was added to the polymerization kettle to start the reaction. The highest temperature during the polymerization process reached 105°C. At this time, the siloxane modifier methyltri[2-(dimethylamino)ethoxy]silane was added in two stages using a sequential control program. Specifically, in the first stage of the addition of the siloxane modifier, 63 g of butyl lithium was added according to the molar ratio of the siloxane modifier to butyl lithium of 0.5:1. Methyltri[2-(dimethylamino)ethoxy]silane, wait for 5 minutes before adding the second stage siloxane modifier; during the addition of the second stage siloxane modifier, 63 g of methyltri[2-(dimethylamino)ethoxy]silane was added according to a molar ratio of siloxane modifier to butyl lithium of 0.5:1, and silicon tetrachloride was used to terminate the reaction after waiting for 5 minutes; specifically, 125 g of silicon tetrachloride was added according to a molar ratio of silicon tetrachloride to butyl lithium of 0.25:1; after reacting for 30 minutes, the discharge valve was opened, and the glue liquid was pressurized into the condensation kettle through a screw pump and a nozzle for low-temperature and low-pressure steam condensation; specifically, by controlling the pressure of the oil-water stratification tank, the amount of water vapor added, and the amount of glue sprayed, the temperature of the No. 1 stripping kettle was controlled at 60°C and the pressure was controlled at -70 kPa, the rubber liquid forms rubber particles under the action of dispersant and stirring of the stripping kettle, and enters the No. 2 stripping kettle through the overflow inclined tube. The temperature of the No. 2 stripping kettle is controlled at 65℃, and the pressure is controlled at -55 kPa. After the rubber particles are continuously stripped for 1 hour, dry rubber is prepared, namely, siloxane-modified solution-polymerized diene rubber.

[0134] The dried rubber was sampled and recorded as sample 2, and subjected to GPC analysis. Figure 2 The GPC spectrum of the siloxane-modified solution-polymerized diene rubber prepared in this example is shown. In the structure of the siloxane-modified solution-polymerized diene rubber, the content of di-chains is 24%, the content of multi-chains is 5%, and the content of single chains is 71%.

[0135] Example 3

[0136] A siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof, comprising the following steps:

[0137] A polymerization kettle with a volume of 125 L was fully replaced with dry nitrogen. According to the proportion of cyclopentane in the total material (i.e., the total mass of styrene, 1,3-butadiene and cyclopentane) of 83%, 35 kg of cyclopentane was added, and 50 g of structure regulator 2,2-di(2-tetrahydrofuranyl)propane (DTHFP), 2 kg of styrene, and 5 kg of 1,3-butadiene were added to the polymerization kettle. After the material temperature was adjusted to 15°C, butyl lithium was added to the polymerization kettle to start the reaction. The highest temperature during the polymerization process reached 95°C. At this time, the siloxane modifier methyltri[2-(dimethylamino)ethoxy]silane was added in one step using a sequential control program. Specifically, according to the molar ratio of the siloxane modifier to butyl lithium of 0.5:1, 63 g Methyltri[2-(dimethylamino)ethoxy]silane, wait for 5 minutes before adding the second stage siloxane modifier; during the addition of the second stage siloxane modifier, 63 g of methyltri[2-(dimethylamino)ethoxy]silane was added according to a molar ratio of siloxane modifier to butyl lithium of 0.5:1, and silicon tetrachloride was used to terminate the reaction after waiting for 5 minutes; specifically, 125 g of silicon tetrachloride was added according to a molar ratio of silicon tetrachloride to butyl lithium of 0.25:1; after reacting for 30 minutes, the discharge valve was opened, and the glue liquid was pressurized into the condensation kettle through a screw pump and a nozzle for low-temperature and low-pressure steam condensation; specifically, by controlling the pressure of the oil-water stratification tank, the amount of water vapor added, and the amount of glue sprayed, the temperature of the No. 1 stripping kettle was controlled at 65°C and the pressure was controlled at -50 kPa, the rubber liquid forms rubber particles under the action of dispersant and stirring of the stripping kettle, and enters the No. 2 stripping kettle through the overflow inclined tube. The temperature of the No. 2 stripping kettle is controlled at 68℃, and the pressure is controlled at -50 kPa. After the rubber particles are continuously stripped for 1 hour, dry rubber is prepared, namely siloxane-modified solution-polymerized diene rubber.

[0138] The dried rubber was sampled and recorded as sample 3, and subjected to GPC analysis. Figure 3 The GPC spectrum of the siloxane-modified solution-polymerized diene rubber prepared in this example is shown. In the structure of the siloxane-modified solution-polymerized diene rubber, the content of di-branching is 25%, the content of multi-branching is 12%, and the content of single chain is 63%.

[0139] Example 4

[0140] This embodiment provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the structure regulator DTHFP in embodiment 1 is replaced by diethylenetetrahydrofurfuryl ether (ETE), and ETE is added to the polymerization system at a molar ratio of ETE to butyl lithium of 5:1.

[0141] In the structure of the siloxane-modified solution-polymerized diene rubber polymer prepared in this example, the di-branched polymer accounts for 23%, the multi-branched polymer accounts for 20%, and the single-chain polymer accounts for 57%.

[0142] Example 5

[0143] This embodiment provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the methyltri[2-(dimethylamino)ethoxy]silane in embodiment 1 is replaced by chloropropyltrimethoxysilane and added into the polymerization system.

[0144] In the structure of the siloxane-modified solution-polymerized diene rubber polymer prepared in this example, the di-branched polymer accounts for 21%, the multi-branched polymer accounts for 18%, and the single-chain polymer accounts for 61%.

[0145] Example 6

[0146] This embodiment provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the methyltri[2-(dimethylamino)ethoxy]silane in embodiment 1 is replaced by N,N-diethyl-3-aminopropyltrimethoxysilane and added to the polymerization system.

[0147] In the structure of the siloxane-modified solution-polymerized diene rubber polymer prepared in this example, the di-branched polymer accounts for 25%, the multi-branched polymer accounts for 10%, and the single-chain polymer accounts for 65%.

[0148] Example 7

[0149] This embodiment provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between this embodiment and embodiment 1 is that methyltri[2-(dimethylamino)ethoxy]silane in embodiment 1 is replaced by chloropropyltriethoxysilane and added into the polymerization system.

[0150] In the structure of the siloxane-modified solution-polymerized diene rubber polymer prepared in this example, the di-branched polymer accounts for 15%, the multi-branched polymer accounts for 13%, and the single-chain polymer accounts for 72%.

[0151] Example 8

[0152] This embodiment provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof, which differs from Embodiment 1 in that methyltri[2-(dimethylamino)ethoxy]silane in Embodiment 1 is replaced with isocyanatepropyltrimethoxysilane and added to the polymerization system.

[0153] In the structure of the siloxane-modified solution-polymerized diene rubber polymer prepared in this example, the di-branched polymer accounts for 24%, the multi-branched polymer accounts for 19%, and the single-chain polymer accounts for 57%.

[0154] Example 9

[0155] This embodiment provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the molar ratio of methyltri[2-(dimethylamino)ethoxy]silane to butyl lithium in embodiment 1 is changed to 2:1 and added to the polymerization system.

[0156] In the structure of the siloxane-modified solution-polymerized diene rubber polymer prepared in this example, the di-branched polymer accounts for 18%, the multi-branched polymer accounts for 10%, and the single-chain polymer accounts for 72%.

[0157] Example 10

[0158] This embodiment provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the molar ratio of methyltri[2-(dimethylamino)ethoxy]silane to butyl lithium in embodiment 1 is changed to 0.8:1 and added into the polymerization system.

[0159] In the structure of the siloxane-modified solution-polymerized diene rubber polymer prepared in this example, the di-branched polymer accounts for 25%, the multi-branched polymer accounts for 20%, and the single-chain polymer accounts for 55%.

[0160] Embodiment 11

[0161] This embodiment provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the molar ratio of silicon tetrachloride to butyl lithium in embodiment 1 is changed to 0.5:1 and added into the polymerization system.

[0162] In the structure of the siloxane-modified solution-polymerized diene rubber polymer prepared in this example, the di-branched polymer accounts for 23%, the multi-branched polymer accounts for 20%, and the single-chain polymer accounts for 57%.

[0163] Example 12

[0164] This embodiment provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the molar ratio of silicon tetrachloride to butyl lithium in embodiment 1 is changed to 1:1 and added into the polymerization system.

[0165] In the structure of the siloxane-modified solution-polymerized diene rubber polymer prepared in this example, the di-branched polymer accounts for 22%, the multi-branched polymer accounts for 18%, and the single-chain polymer accounts for 60%.

[0166] Comparative Example 1

[0167] The present comparative example provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between the comparative example and Example 1 is that the temperature of the No. 1 stripping kettle is controlled at 84°C and the pressure is controlled at 30 kPa. The rubber liquid forms rubber particles under the action of the dispersant and the stirring of the stripping kettle, and enters the No. 2 stripping kettle through the overflow inclined pipe. The temperature of the No. 2 stripping kettle is controlled at 105°C and the pressure is controlled at 30 kPa. After the rubber particles are continuously stripped for 1 hour, dry rubber, i.e., siloxane-modified solution-polymerized diene rubber, is prepared.

[0168] The dried rubber was sampled and recorded as sample 4, and subjected to GPC analysis. Figure 4 The GPC spectrum of the siloxane-modified solution-polymerized diene rubber prepared in this example is shown. In the structure of the siloxane-modified solution-polymerized diene rubber, the content of di-chains is 35%, the content of multi-chains is 20%, and the content of single chains is 45%.

[0169] Comparative Example 2

[0170] The present comparative example provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between the comparative example and Example 2 is that the temperature of the No. 1 stripping kettle is controlled at 95°C and the pressure is controlled at 50 kPa. The rubber liquid forms rubber particles under the action of the dispersant and the stripping kettle stirring. The No. 2 stripping kettle is carried out through an overflow inclined pipe. The temperature of the No. 2 stripping kettle is controlled at 110°C and the pressure is controlled at 50 kPa. After the rubber particles are continuously stripped for 1 hour, a dry rubber is prepared, namely, the siloxane-modified solution-polymerized diene rubber.

[0171] The dried rubber was sampled and recorded as sample 5, and subjected to GPC analysis. Figure 5 The GPC spectrum of the siloxane-modified solution-polymerized diene rubber prepared in this example is shown. In the structure of the siloxane-modified solution-polymerized diene rubber, the content of di-branching is 35%, the content of multi-branching is 45%, and the content of single chain is 20%.

[0172] Comparative Example 3

[0173] The present comparative example provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between the comparative example and the embodiment 1 is that the cyclopentane in the embodiment 1 is replaced by cyclohexane and added to the polymerization system; after the material temperature is adjusted to 15°C, butyl lithium is added to the polymerization kettle to start the reaction, and the highest temperature during the polymerization process reaches 101°C; after the reaction for 30 minutes, the discharge valve is opened, and the glue liquid is pressurized by the screw pump and the nozzle to enter the condensation kettle for low-temperature and low-pressure steam condensation; specifically, the temperature and pressure of the No. 1 stripping kettle are controlled by controlling the pressure of the oil-water delamination tank, the amount of water vapor added, and the amount of glue sprayed, so that the glue liquid forms glue particles under the action of the dispersant and the stripping kettle stirring; since the boiling point of the cyclohexane solvent is above 80°C, the temperature of the No. 1 stripping kettle is relatively maintained at 75°C and the pressure is -30°C. kPa, the rubber liquid forms rubber particles under the action of dispersant and stirring of the stripping kettle, and enters the No. 2 stripping kettle through the overflow inclined pipe. The temperature of the No. 2 stripping kettle is 85℃. After the rubber particles are stripped continuously for 1 hour, dry rubber is prepared, namely siloxane-modified solution-polymerized diene rubber.

[0174] The dried rubber was sampled and recorded as sample 6, and subjected to GPC analysis. Figure 6 The GPC spectrum of the siloxane-modified solution-polymerized diene rubber prepared in this comparative example is shown. In the structure of the siloxane-modified solution-polymerized diene rubber, the content of di-chains is 30%, the content of multi-chains is 30%, and the content of single chains is 40%.

[0175] Compared with the siloxane-modified solution-polymerized diene rubber polymer prepared in Example 1, the coupling rate of the polymer prepared in this comparative example is significantly higher, and more siloxane groups are lost. Obviously, the polymer rolling resistance performance is poor.

[0176] Comparative Example 4

[0177] The present comparative example provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof, which differs from Example 1 in that the cyclopentane in Example 1 is replaced by cyclohexane, and cyclohexane is added to the polymerization system according to the proportion of 70% in the total material; after the material temperature is adjusted to 15°C, butyl lithium is added to the polymerization kettle to start the reaction, and the highest temperature during the polymerization process reaches 110°C; after the reaction for 30 minutes, the discharge valve is opened, and the glue liquid is pressurized by the screw pump and the nozzle into the condensation kettle for low-temperature and low-pressure steam condensation; specifically, by controlling the pressure of the oil-water delamination tank, the amount of water vapor added, and the amount of glue sprayed, since the boiling point of the cyclohexane solvent of C6 is above 80 degrees Celsius, the temperature of the No. 1 stripping kettle is relatively maintained at 76°C, and the pressure is at -25kPa, the glue liquid forms glue particles under the action of the dispersant and the stirring of the stripping kettle, and enters the No. 2 stripping kettle through the overflow inclined tube. The temperature of the No. 2 stripping kettle is 90°C, and the glue particles are continuously stripped for 1 hour to prepare dry glue, that is, siloxane-modified solution-polymerized diene rubber.

[0178] In the structure of the siloxane-modified solution-polymerized diene rubber prepared in this comparative example, the content of di-chains is 35%, the content of multi-chains is 30%, and the content of single chains is 35%.

[0179] Compared with the siloxane-modified solution-polymerized diene rubber polymer prepared in Example 1, the coupling rate of the polymer prepared in this comparative example is significantly higher, and more siloxane groups are lost. Obviously, the polymer rolling resistance performance is poor.

[0180] Comparative Example 5

[0181] The comparative example provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The comparative example is different from Example 1 in that a conventional stripping (i.e., steam condensation) process is adopted, i.e., after reacting for 30 minutes, the discharge valve is opened, and the rubber liquid is pressurized by a screw pump and a nozzle to enter a condensation kettle for steam condensation. By controlling the amount of water vapor added and the amount of glue sprayed, the temperature of the No. 1 stripping kettle is controlled at 84°C and the pressure is controlled at 50 kPa. The rubber liquid forms rubber particles under the action of the dispersant and the stirring of the stripping kettle, and enters the No. 2 stripping kettle through an overflow inclined pipe. The temperature of the No. 2 stripping kettle is controlled at 98°C and the pressure is controlled at 45 kPa. After the rubber particles are continuously stripped for 1 hour, dry rubber is prepared, i.e., siloxane-modified solution-polymerized diene rubber.

[0182] In the structure of the siloxane-modified solution-polymerized diene rubber prepared in this comparative example, the content of di-chains is 40%, the content of multi-chains is 30%, and the content of single chains is 30%.

[0183] Compared with the siloxane-modified solution-polymerized diene rubber polymer prepared in Example 1, the coupling rate of the polymer prepared in this comparative example is significantly higher, and more siloxane groups are lost. Obviously, the polymer rolling resistance performance is poor.

[0184] Comparative Example 6

[0185] The present comparative example provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof. The difference between the comparative example and Example 1 is that cyclopentane is replaced by cyclohexane, and a conventional stripping process is adopted, that is, after reacting for 30 minutes, the discharge valve is opened, and the rubber liquid is pressurized into a coagulation kettle through a screw pump and a nozzle, and the temperature of the No. 1 stripping kettle is controlled at 98°C and the pressure is 50 kPa by controlling the amount of water vapor added and the amount of glue sprayed, and the rubber liquid forms rubber particles under the action of the dispersant and the stripping kettle, and enters the No. 2 stripping kettle through an overflow inclined pipe, and the temperature of the No. 2 stripping kettle is 110°C and the pressure is 45 kPa. After the rubber particles are continuously stripped for 1 hour, dry rubber is prepared, that is, the siloxane-modified solution-polymerized diene rubber.

[0186] In the structure of the siloxane-modified solution-polymerized diene rubber prepared in this comparative example, the content of di-chains is 40%, the content of multi-chains is 40%, and the content of single chains is 20%.

[0187] Compared with the siloxane-modified solution-polymerized diene rubber polymer prepared in Example 1, the polymer prepared in this comparative example has a significantly higher coupling rate and more lost siloxane groups. Obviously, the polymer has poor rolling resistance.

[0188] Comparative Example 7

[0189] This comparative example provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof, which is different from Example 1 in that silicon tetrachloride terminator is not added.

[0190] In the structure of the siloxane-modified solution-polymerized diene rubber prepared in this comparative example, the content of di-chains is 70%; and the content of single chains is 30%.

[0191] Compared with the siloxane-modified solution-polymerized diene rubber polymer prepared in Example 1, the coupling rate of the polymer prepared in this comparative example is significantly higher, the loss of siloxane groups is more, and the polymer rolling resistance performance is obviously poor.

[0192] Comparative Example 8

[0193] This comparative example provides a siloxane-modified solution-polymerized diene rubber polymer and a preparation method thereof, which is different from Example 1 in that methyltri[2-(dimethylamino)ethoxy]silane is added to the polymerization system all at once (i.e., in one stage).

[0194] In the structure of the siloxane-modified solution-polymerized diene rubber prepared in this comparative example, the di-branched polymer accounts for 25% and the multi-branched polymer accounts for 40%.

[0195] Performance Testing

[0196] The performance of samples 1-2 of the siloxane-modified solution-polymerized diene rubber prepared in Examples 1-2 and samples 4-5 of the siloxane-modified solution-polymerized diene rubber prepared in Comparative Examples 1-2 were tested. The specific testing method is as follows:

[0197] First, the corresponding rubber composition was prepared by adopting the following formula of the rubber composition. Specifically, the formula of the rubber composition was as follows: SSBR 100.0, white carbon black 75.0, carbon black 5.0, silane Si69 12.8, stearic acid 2.0, zinc oxide 3.0, TDAE oil 37.5, sulfur 1.5, TBBS 2.0, DPG 2.0;

[0198] Then, the rubber composition was mixed on a BR1600 internal mixer using a two-end internal mixing method to obtain a mixed rubber; and a vulcanized rubber sample was prepared by vulcanizing at 151° C. for 30 min using a flat vulcanizer.

[0199] Table 1 shows the content of 2-chain and 3-chain branches and total branches of each sample in Examples 1-2 and Comparative Examples 1-2, the corresponding Mooney viscosity and DIN abrasion index of each rubber mix, and the rolling resistance parameter tanδ, 60° and anti-slip parameter tanδ, 0° of the vulcanized rubber.

[0200] Table 1:

[0201]

[0202] As can be seen from Table 1, compared with Sample 4 and Sample 5 prepared by the conventional method (i.e., the preparation method in Comparative Examples 1-2), the rolling resistance parameter tanδ, 60° of the vulcanized rubber corresponding to Sample 1 and Sample 2 prepared by the preparation method of the present invention is significantly smaller, indicating better rolling resistance performance; the anti-skid property parameter tanδ, 0° is significantly larger, indicating better anti-skid property.

[0203] Similarly, the sample 3 of the siloxane-modified solution-polymerized diene rubber prepared in Example 3 was compared with the commercially available siloxane-modified product JSR HPR850 as a comparative sample. The preparation of the rubber mix and the vulcanized rubber samples adopts the above-mentioned method for preparing the rubber mix and the vulcanized rubber samples. Table 2 shows the content of various structures of sample 3 and JSR HPR850, the single-chain molecular weight, the Mooney viscosity and DIN wear index of the rubber mix, and the rolling resistance parameter tanδ, 60° and the anti-wet skid parameter tanδ, 0° of the vulcanized rubber.

[0204] Table 2:

[0205]

[0206] It can be seen from Table 2 that, compared with the JSR HPR850 sample, the rolling resistance parameter tanδ,60° of the vulcanized rubber obtained by the siloxane-modified solution-polymerized diene rubber polymer sample 3 prepared by Example 3 of the present invention is significantly smaller, indicating that its rolling resistance performance is better; in addition, the value of its anti-skid parameter tanδ,0° is significantly larger, indicating that its anti-skid property is better.

[0207] In the prior art, the steam condensation temperature of the siloxane-modified solution-polymerized diene rubber polymer is generally 84-120°C, and the steam condensation pressure is 30 kPa-50 kPa. Under such high temperature and pressure steam condensation conditions, the Si-OR groups contained in the siloxane-modified solution-polymerized diene rubber undergo dehydration condensation reaction during the steam stripping process, consuming Si-OR, thereby reducing the number of groups that can react with white carbon black during the mixing process, resulting in a decrease in the resilience and rolling resistance of the rubber product. Alternatively, the polysiloxane group-modified solution-polymerized styrene-butadiene rubber produces molecular chain coupling in a steam-heated water environment, and the molecular chain coupling has a potential impact on the siloxane groups at the end of the solution-polymerized styrene-butadiene rubber, which will lead to a decrease in the dynamic properties of the final polymer (for example, rolling resistance and anti-slip performance).

[0208] In the present invention, after condensation by low-temperature negative pressure steam, the structure of the polymer product does not change, and its bi-branched component is less than 25%, the multi-branched component is 5-20%, and the single chain component is 55%-95%.

[0209] The present invention adopts a two-stage modification method of a siloxane modifier, firstly, the siloxane modifier is used to perform a termination reaction of a solution-polymerized diene rubber twice, then a halogenated silicon terminator is used to terminate all active species, and finally, the solution-polymerized diene rubber polymerization product is steam condensed (i.e., stripped) under negative pressure (-70 kPa to -30 kPa) and low temperature (60 to 70°C), thereby reducing the coupling rate of the solution-polymerized diene rubber polymer product to the greatest extent, which is beneficial to improving the rolling resistance performance of the rubber composition.

[0210] The siloxane-modified solution-polymerized diene rubber polymer prepared by the preparation method of the present invention has excellent rolling resistance, structural stability and low coupling rate, and has excellent processability during mixing. Compared with general siloxane-modified solution-polymerized diene rubber, the rolling resistance and wear resistance of the rubber obtained by the preparation method are improved. When used for tire rubber, it is most suitable for automobile tires with good processability and excellent low fuel efficiency.

[0211] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a siloxane-modified solution-polymerized diene rubber polymer, characterized in that: The preparation method comprises the following steps in sequence: 1) in the presence of an organic lithium compound, a conjugated diene compound and an aromatic vinyl compound are polymerized in an organic hydrocarbon solvent, wherein the organic hydrocarbon solvent is a low boiling point organic hydrocarbon solvent, and the low boiling point organic hydrocarbon solvent is cyclopentane; 2) After the polymerization reaction is completed, a siloxane modifier is added to carry out the first modification treatment for a certain period of time, wherein the mass addition amount of the siloxane modifier is 45% to 55% of the total addition amount of the siloxane modifier; 3) Adding a siloxane modifier to carry out a second modification treatment for a certain period of time, wherein the mass addition amount of the siloxane modifier is 55% to 45% of the total addition amount of the siloxane modifier; 4) Add silicon halide terminator for treatment; 5) Steam condensing and drying the polymerization product obtained in step 4) under low temperature and negative pressure conditions to obtain the siloxane-modified solution-polymerized diene rubber polymer, wherein the di-branched component in the structure is less than 25%, and the multi-branched component is less than 20%, the steam condensation pressure is -30 kPa to -70 kPa, and the temperature is 60 to 70°C.

2. The method for preparing a siloxane-modified solution-polymerized diene rubber polymer according to claim 1, characterized in that: The siloxane modifier has a structure as shown in the following formula (1): (R2O) m -Si-(R3) 4-m Formula (1); where R2 is an alkyl group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms containing a nitrogen atom; R3 is an alkyl group having 1 to 12 carbon atoms or a halogenated alkyl group containing 1 to 2 halogen elements, wherein the halogen elements include at least one of iodine, bromine and chlorine; m is an integer from 2 to 4; The silicon halide terminator has a structure as shown in the following formula (2): (R1) n -Si-(X) 4-n Formula (2); where R1 is an alkyl group having 1 to 12 carbon atoms, X is one of iodine, bromine and chlorine, n is 0 or 1.

3. The method for preparing a siloxane-modified solution-polymerized diene rubber polymer according to claim 2, characterized in that: The added amount of the low-boiling-point hydrocarbon solvent accounts for 70% to 90% of the total mass of the conjugated diene compound, the aromatic vinyl compound and the organic hydrocarbon solvent.

4. The method for preparing a siloxane-modified solution-polymerized diene rubber polymer according to claim 1, 2 or 3, characterized in that: The molar ratio of the total amount of the siloxane modifier added to the organic lithium compound is 1 to 2:1; or The molar ratio of the silicon halide terminator to the organic lithium compound is 0.25 to 1:

1.

5. A siloxane-modified solution-polymerized diene rubber polymer, characterized in that: The method for preparing a siloxane-modified solution-polymerized diene rubber polymer according to any one of claims 1 to 4 is used, wherein the general structural formula of the solution-polymerized diene rubber is: (P) a Si[(OR2) b1 (R3) b2 ];in, R2 is an alkyl group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms containing a nitrogen atom; R3 is an alkyl group having 1 to 12 carbon atoms or a halogenated alkyl group containing 1 to 2 halogen elements, wherein the halogen elements include at least one of iodine, bromine and chlorine; The alkoxy group formed by OR2 and R3 are both connected to the silicon atom. P represents a copolymer of butadiene and styrene; b1≥1, and b1+b2=1~3; a= 4 - (b1+b2).

6. The siloxane-modified solution-polymerized diene rubber polymer according to claim 5, characterized in that: In the structure of the solution polymerized diene rubber, the component of two branches is less than 25%, the component of multiple branches is 5-20%, and the component of single chain is 55-95%.

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