JPS61296001A - Branched random styrene-butadiene copolymer - Google Patents

Abstract

PURPOSE:The titled copolymer, containing styrene units having specific styrene chain distribution in the copolymer chain, having a long-chain branched structure modified with a specific urea derivative and particularly useful as tire treads for low fuel consumption. CONSTITUTION:Styrene is copolymerized with butadiene in the presence of an organolithium compound, e.g. n-propyl lithium, as a polymerization initiator in a hydrocarbon solvent and a urea derivative expressed by the formula (R1 and R2 are 1-4C alkyl or alkoxyalkyl; Y is O or S; n is an integer 2-4), e.g. 1,3-diethyl-2-imidazolidinone, is added to give an Li-terminated modified copolymer, which is then reacted with a polyfunctional coupling agent having >=3 reactive sites to afford the aimed copolymer having 30-150 Mooney viscosity (ML1+4, 100 deg.C), 5-45wt% combined styrene content, >=40wt% styrene single chain having one styrene unit in the combined styrene and <=5wt% long chain having >=8 styrene units. EFFECT:With improved impact resilience and well-balanced wet skid resistance and abrasion resistance and processability.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a copolymer chain in which the styrene units have a specific styrene chain distribution and a long chain branched structure modified with a specific urea derivative. The present invention relates to a branched lantum styrene-butadiene copolymer having the following properties.

[Prior art] Random styrene-butadiene copolymers using organolithium compounds as polymerization initiators have traditionally been used to improve vulcanizate properties such as impact resilience, wet skid resistance (slip resistance on wet road surfaces), and f1 abrasion resistance. However, it is often inferior in terms of rollability and extrusion strength.

Various methods have been proposed to improve these drawbacks. For example, method D of setting a copolymer with a wide molecular f1 distribution or a branched copolymer (Japanese Patent Publication No. 45-8424
Special Publication No. 52-5071, Special Publication No. 49-3H! i
No. 7, Enduring ITI! (59-5266 + Lee-5 Special Public Showa 5
B-17362)'y is available.

On the other hand, recent social demands for resource and energy conservation have led to demands for lower fuel consumption for automatic cars and demands for increased safety during small-distance driving.

Tire properties such as low fuel consumption, handling stability, and abrasion resistance are now required, and rubber for tires has low fuel consumption (l-), high rebound resilience, and handling stability (1-). It is required to have high wet sugirad resistance, excellent cutting tendency-4- and wear resistance.

However, the relationship between rebound resilience and wet skid resistance is contradictory, and the relationship between abrasion resistance and wet skid resistance is also contradictory, so it is necessary to balance these contradictory characteristics f1 and add IT: A number of methods have been proposed to improve M. For example, 41+
How to set up the high morph full volume 11 11. (,4'I
I-opening/closing 57-128807'=3), specific (7)
i Polymer with 5th transition temperature lW; t rubber and low molecule M
Go1, /(/nd)
46 Lee), method of introducing branched components bound by tin and non-tin coupling agents h) method (4￥
Japanese Patent Application No. 59-159123), q (Japanese Patent Application No. 59-159123) and q (Japanese Patent Application No. 59-159123), which highly homogenizes the methane 1/n middle position in a copolymer chain in which the molecule jt molecule +j is importal.

[Problems to be solved by the invention] However, although these methods show some improvement effects, they do not satisfy these contradictory characteristics to a high degree,
Moreover, the addition r'M has not been improved to 1 min.

The present invention has been made in view of point 1-1, and is a combination of branched lanthanum steel l/n-butadiene with significantly improved balance between impact resilience, wet skid resistance, and N abrasion resistance, and with improved addability. ff (aims to provide 6 bodies.

[Means for Solving the Problems and Sakukawa] The present inventors have disclosed in Japanese Patent Application No. 60-82192 that a conjugated compound obtained by the reaction of a J(functional diene) polymer that combines a specific urea derivative with an alkali metal atom, Diene-based polymers have an excellent balance of impact resilience, wet skid resistance, and abrasion resistance.
As a result of further extensive research on the conjugated diene polymer in which a functional group is bonded to the polymer chain disclosed in No. 192, it was surprisingly discovered that the styrene units in the copolymer chain have a specific styrene chain distribution. A branched lantum styrene-butadiene copolymer obtained by reacting a lithium-terminated modified copolymer modified with a specific urea derivative with a polyfunctional coupling agent having at least three reactive sites has impact resilience. , it was found that it has an excellent balance of wet skid resistance and abrasion resistance, and has excellent workability1.
This was done based on the fact that -jj l.

That is, in the present invention, styrene and butadiene are co-laminated using an organolithium compound as a polymerization initiator in a hydrocarbon solvent, and then the following formula is obtained: A lithium-terminated modified copolymer prepared by adding a urea derivative represented by an alkyl group or an alkoxyalkyl group, Y represents an oxygen atom f- or a sulfur atom f, and □ represents an integer from 2 to 4) and a polyfunctional coupling agent having at least three reactive sites.
It is a butadiene copolymer with a 1 muni viscosity (ML+
, 4.100℃) is 30-150, bonded styrene is 5-150
45% by weight, 1 styrene chain with 1 styrene middle is 1% or more of bonded styrene, and 1 styrene
The present invention relates to a branched random styrene-ptadiene copolymer characterized in that long chains of styrene consisting of 8 or more f-1 positions account for 5 or more percent f of bonded styrene.

The branched random styrene-butadiene copolymer of the present invention exhibits excellent vulcanizate properties and processability, and is used for various rubber applications, and is useful for tire applications such as tire treads and sidewalls.

The present invention will be explained in detail below.

The urea derivative used in the present invention has a specific hydrocarbon group on each nitrogen atom and fcH? in is bonded to the general formula (wherein R1 and R2 each independently represent an alkyl group of 01 to C4 or an alkoxyalkyl group, Y represents an oxygen atom or a sulfur atom, and 0 represents an integer of 2 to 4. It is necessary to have a cyclic structure shown in the following.

This has an extremely important meaning in achieving the present invention. Normally, in a stoichiometric reaction between a urea derivative having an acyclic structure and a copolymer in which a lithium element f is bonded to the end of the copolymer in a hydrocarbon solvent, the bond between the carbonyl group and the amino group is cleaved and the copolymer is copolymerized. Functional groups cannot be effectively introduced into the polymer, and even if a polyfunctional coupling agent is subsequently added to the reaction system, the coupling reaction hardly occurs. On the other hand, in the stoichiometric reaction of a urea derivative with a cyclic structure and a copolymer in which a lithium atom is bonded to the end of the copolymer chain in a hydrocarbon solvent, it is necessary to reliably introduce a functional group into the copolymer. A coupling reaction occurs in the reaction between the lithium-terminated modified copolymer obtained in the second reaction and the polyfunctional coupling agent, and a branched copolymer having a long chain branched structure is modified with a urea derivative. Causes coalescence. The copolymer of the present invention thus obtained exhibits excellent processability, and the vulcanizate thereof exhibits excellent impact resilience, wet skid resistance, and abrasion resistance.

Mooney viscosity (ML, .4°100 of the copolymer of the present invention)
°C) is 30-150. Preferably it is 50 to 120 degrees. If the Mooney viscosity is less than 30, the effect of improving impact resilience and abrasion resistance is not sufficient. When the Mooney viscosity exceeds 150, problems remain in the processability and extrusion processability of the blend.

The bound styrene content of the copolymers of the present invention is from 5 to 45% by weight, preferably from 10 to 40% by weight. If the bound styrene content is less than 5% by weight, the wet skid resistance will deteriorate, which is undesirable. On the other hand, if the amount of bound styrene exceeds 45% by weight, impact resilience and abrasion resistance will decrease, which is not preferable.

Single styrene chain 111 (hereinafter referred to as S1) having one styrene unit of the copolymer of the present invention is 40% by weight of the bound styrene.
The above, preferably 55% by weight or more, a long styrene chain consisting of 8 or more carbon styrene units (hereinafter referred to as S8~)
is less than 5.0% by weight of the bound styrene, preferably 2.5% by weight of the bound styrene.
Must be less than % by weight. Even if Sl is less than 40% by weight of the bound styrene, or if 58% to 58% by weight exceeds 5% by weight, impact resilience, abrasion resistance, and wet skid resistance are undesirably reduced.

The physical properties of the copolymer of the present invention change significantly by changing the microstructure of the butadiene moiety, and also change depending on the styrene composition distribution in the copolymer chain.

Regarding the relationship between the microstructure and physical properties of the butadiene moiety, in particular, the relationship between the 1,2 vinyl content and physical properties is known. For example, increasing the 1.2 vinyl content increases the wet skid resistance of the polymer and decreases its abrasion resistance (Rubber Age).

VoR104, 55 (1972)).

Furthermore, as the 1,2-vinyl content increases, heat resistance and reversion are improved. H. Nordsiekr.
Paper J to the 19711 International Rubber Conference
Presented to the Int, Rub
ber Conf, +979).

The relationship between the 1.2 vinyl content and physical properties is already known, and in the present invention, the 1.2 vinyl content is not particularly limited, but from the viewpoint of impact resilience and abrasion resistance, the 1.2 vinyl content is 10 30%, while from the viewpoint of wet skid resistance, the 1.2 vinyl content is preferably 30 to 80%. In any case, the 1,2 vinyl content h1 should be determined depending on the purpose of use O.

Furthermore, regarding the distribution of 1 and 2 vinyl in the polymer chain, even if it is uniform in the polymer chain,
It may be one that changes gradually along the polymer chain as shown in No. 75, or it may be distributed in blocks (USP-3301840), and in short, it is good to decide depending on the purpose of use.

Furthermore, the styrene component 4j in the styrene-butadiene copolymer chain may be uniformly distributed in the copolymer chain, or may be non-uniformly distributed in the copolymer chain (Japanese Patent Application No. 1983).
-4108) may be used, and used for stars [1] It is better to decide according to the target.

Processability of the copolymer of the present invention changes greatly by changing the molecular weight 4i. The relationship between the molecule-integral 11T and workability is well known, and in the present invention, the relationship between the weight 1 gate 1 average molecular thread (MV+) and the number) i equal molecule 1: (Mn
) and the molecular −&+ distribution (Mn/M
Although h) is not particularly limited, it is preferably 1.2 to 3.5 in consideration of the balance between physical properties and additivity. Minutes (-j-f
Regarding the shape of the part 71J, it may be a mono-thousand or a polymotor t/ of a pi-thousand.

The branched rank styrene-butadiene conjugate of the present invention is produced by method l) described below. - For copolymerizing styrene and 1,3-butadiene in a hydrocarbon solvent using a lithium compound as a polymerization initiator, British Pat.
-140211 Lee and JP-A-58-143209
As described in No. 1, styrene in the polymerization system and 1,
Copolymerization S is carried out by continuously or intermittently supplying 1,3-butadiene or a mixture of 1,3-butadiene and styrene so that the styrene monomer content in the monomer composition ratio of 3-butadiene falls within a specific concentration range. After copolymerization Vr, -
・Represented by the general formula (wherein R1 and R2 each independently represent an alkyl group or an alkoxyalkyl group of 01 to C4, Y represents an oxygen atom or a sulfur atom -r, and represents an integer from 2 to 4) A predetermined amount of a polyfunctional coupling agent having at least three reactive sites is added to a lithium-terminated modified copolymer obtained by adding a predetermined amount of a urea derivative.

Another method is to copolymerize styrene and 1,3-butadiene in a hydrocarbon solvent using an organolithium compound as an initiator at a rate slower than the copolymerization rate as described in Japanese Patent Publication No. 38-231!4. A mixture of styrene and 1,3-butadiene is added to copolymerize, and in the copolymer chain,
It is represented by the general formula (wherein R1 and R2 each independently represent an alkyl group or an alkoxyalkyl group of 01 to C4, Y represents an oxygen atom f- or a sulfur atom r, and 1. represents an integer from 2 to 4) It is obtained by adding a predetermined amount of a polyfunctional coupling agent having at least three reactive sites to a lithium-terminated modified copolymer obtained by adding a predetermined amount of a urea derivative.

In the present invention, ethers, tertiary amines, alkali Polar compounds such as metal alkoxides can be used. For example, diethyl ether, ethylene glycol dimethyl ether, ethylene glycol di-n-butyl ether, ethylene glycol n-
Butyl-tert-butyl ether, ethylene glycol di-tert-butyl ether, diethylene glycol dimethyl ether, )・lyeethylene glycol・
Dimethyl ether, tetrahydrofuran, α-methoxymethyltetrahydrofuran, dioxane, 1,2-dimethoxybenzene, triethylamine, N, N, N',
N'-te]-ramethylethylenediamine, potassium-t
These include ert-amyloxy F, potassium-tert-butyl oxide, and the like. These compounds may be used alone or as a mixture of two or more.

The polar compound used in the present invention has an additive M of 0 to 200 mol per mol of the organic lithium compound.

As the organolithium compound that can be used in the present invention, n-
Monoorganolithium compounds such as propyllithium, isopropyllithium, n-butyllithium, 5ea-butyllithium, tert-butyllithium, dilithiomethane, 1.4-dilithiobutane, 1.4-dilithio-2-ethylcyclohexane, 1.2- These include polyfunctional organolithium compounds such as dilithio-1,2-diphenylmethane and 1.3.5-trilithiobenzene. These alone are
Or used in a mixture of two or more. Furthermore, as the polyfunctional organolithium compound used in the present invention, compounds that can be substantially turned into a polyfunctional organolithium compound by reacting the above-mentioned monoorganolithium compound with another compound are also used. . For example, a reaction product of a monoorganolithium compound and a polyvinyl aromatic compound (Japanese Patent Publication No. 15-8852), a reaction product of a monoorganolithium compound and a conjugated diene, and/or a monovinyl aromatic compound, A reaction product obtained by reacting a compound, or a reaction product obtained by simultaneously reacting a monoorganolithium compound, a conjugated diene, and/or a monovinyl aromatic compound, and a polyvinyl compound (West German Patent No. 2003384, etc.).

The amount of these organic lithium compounds used is usually 0.1 to 10 mmol per 00 g of conjugated diene monomer.

As the hydrocarbon solvent used in the present invention, aliphatic, cycloaliphatic and aromatic hydrocarbons can be used. For example, hydrocarbon solvents include propane, imbutane, n
-hexane, isooctane, cyclopentane, cyclohexane, benzene, toluene, etc., and particularly preferred solvents are n-hexane, cyclohexane, and benzene.

These may be used alone or as a mixture of two inserts-1-.

The urea derivative used in the present invention has the general formula (wherein R1 and R2 each independently represent a C1 to C4 alkyl group or an alkoxyalkyl group, Y represents an oxygen atom or a sulfur atom, and ■ represents 2 to 4 (representing an integer of
-imidazolidinone, l,3-dipropyl-2-imidazolidinone, l-methyl-3-ethyl-2-imidazolidinone, l-methyl-3-propyl-2-imidazolidinone, 1-methyl-3 -Butyl-2-imidazolidinone, 1-methyl-3-(2-methoxyethyl-2-imidazolidinone, l-methyl-3-(2-ethoxyethyl)-2-imidazolidinone, 1.3- Examples include di(2-ethoxyethyl)-2-imidazolidinone, 1,3-dimethylethylenethiolea, 1,3-dimethyl-3,4,5,8-tetrahydro-2(IH)-pyrimidinone, etc. However, 1.
3-dimethyl-2-imidazolidinone is preferred.

The amount of the urea derivative used in the present invention is usually 0.7 to 1.3 mol, preferably 0.8 to 1.1 mol, particularly preferably It is 1.0 mol. The reaction between the conjugated diene polymer that binds lithium atoms and the urea derivative occurs immediately upon contact with each other, so the reaction temperature and reaction time can be adjusted over a wide range, but usually the reaction temperature is between 15 and 115°C.
, the reaction time is within the range of 1 second to 3 hours.

The polyfunctional coupling agents used in the present invention include epoxidized soybean oil, epoxidized linseed oil, epoxidized liquid polybutadiene, dimethyl terephthalate, diethyl terephthalate, dimethyl phthalate, dimethyl isophthalate, diethyl adipate, Terephthalic acid dichloride, phthalic acid dichloride, isophthalic acid dichloride, adipic acid dichloride, silicon tetrachloride, methyltrichlorosilane, hexachlorosilane, tetrasilane, carbon tetrachloride, tin chloride, methyltrichlorotin, tin bromide , dodecyltrichlorotin, hexa-(2-methyl-1-aziridinyl)triphospha)・
Examples include riazine, pyromellitic acid anhydride, and polyarylboriisocyanate. Among these, silicon tetrachloride and stannic chloride are preferred. When a polymer coupled with stannic chloride is kneaded with carbon black, process oil, etc., the vulcanizate exhibits excellent impact resilience. On the other hand, copolymers coupled with silicon tetrachloride exhibit desirable processability, particularly excellent extrusion properties. Therefore, a copolymer with better processability is
In this case, it is preferable to use silicon tetrachloride as a coupling agent.

The amount used for these multifunctional +11 coupling agents is 0.2 to 1.5 equivalents, preferably 0.5 to 1.0 equivalents, based on the lithium bonded to the copolymer. The reaction between the polyfunctional coupling agent and the lithium-terminated modified copolymer occurs immediately when the respective substances come into contact, so the reaction temperature and reaction time can be adjusted over a wide range, but usually the reaction temperature is 30 to 115°C per reaction time. is within the range of 1 second to 2 hours.

The polymerization method in the present invention may be either a batch polymerization method or a continuous polymerization method. The polymerization temperature is in the range of 20 to 130 °C, and in batch polymerization, polymerization starts at 30 to 87 °C, and it is recommended to perform at 1-y1 temperature so that the maximum temperature reaches 90 to 125 °C. be done.

After completion of the specified reaction, 2,6-tert-butyl-p-
After adding an antioxidant Tl-agent such as Fresol, the resulting copolymer is separated, washed, and subjected to the usual post-treatment in a drying tube.
The desired copolymer can be obtained.

The copolymer of the present invention is mixed with a process oil in a solution state,
After mixing, the solvent may be removed and used as an oil-extended rubber.

The copolymers of the present invention can be used alone or in blends with natural rubber or other synthetic rubbers such as polybutadiene, polyisoprene, emulsion polymerized styrene-butadiene copolymers, and the like. When used in a blend with natural rubber or other synthetic rubber, in order to exhibit the superior properties of the present invention, it is necessary to make sure that at least the 30-fold star shape of the raw material rubber is the copolymer of the present invention. I need.

Further, the copolymer of the present invention is blended with known compounding agents such as carbon black, process oil, etc., and after mixing and vulcanization,
It can be used as a product, for example, in tire applications such as tire treads, carcass, and sidewalls, or in applications such as extruded products, automobile window frames, T-business products, and anti-vibration rubber. It has a good balance of skid resistance and abrasion resistance, and is easy to process, so it can be used particularly as a red for fuel-efficient tires.

[Examples] The present invention will be explained below with reference to Examples, but these Examples do not limit the present invention.

Note that measurements of various characteristics were carried out using the following methods.

The 18-2-viscosity of the U branched conjugated diene polymer was determined by I11 at 100° C. using an L rotor in a conventional manner. Bonded styrene was determined by the ultraviolet absorption spectrum I-L method.
Calculated from absorption based on phenyl group at 62 nm. The microstructure of the butadiene moiety was calculated using an infrared spectrophotometer according to the Hump I-N method. The styrene chain distribution of the copolymer is analyzed by Kölper permeation chromatography (CPC) of the decomposed product obtained by osson cleavage of all the double bonds at the 11-position of butadiene (Polymers Society Proceedings Vol. 29). No. 9, p. 2055). Repulsion resilience was measured using a Tanlop tribometer at a test temperature of 70°C.

Abrasion resistance was determined by Δ11 using a Pico abrasion tester. Wet skid resistance was measured using a device manufactured by the British Road Research Institute. Processability was judged based on the Mooney viscosity of the compound or the roll windability of the compound. Rolling of the compound (
=j The rollability was evaluated using a 6-inch roll and the roll windability of the blend, operability, etc.

Examples 1 to 6, Comparative Examples 1 to 4 Under a nitrogen atmosphere, predetermined amounts of cyclohexane, styrene, and 1.3-'tadiene as shown in Table 1 were placed in a stainless steel polymerization vessel with an internal volume of about 10 tons and equipped with a stirrer. (hereinafter referred to as primary butadiene) and Lewis base, and while stirring the mixture in the polymerization vessel, the mixture was adjusted to a predetermined temperature, and then a predetermined amount of n-butyllithium was added to start the copolymerization. It started.

Next, as shown in Table 1, 1,3-butadiene (hereinafter referred to as secondary butadiene) was continuously supplied to the polymerization system at a constant rate using a pump. After the supply of secondary butadiene is finished and the polymerization temperature reaches the maximum temperature and the copolymerization is completed, a predetermined amount of urea derivative is added as shown in Table 1 and reacted for about 5 minutes. A polyfunctional coupling agent was added and reacted for about 10 minutes. To the thus obtained copolymer solution, 6 g of 2,6-tert-butyl-p-cresol was added as a stabilizer, and the solvent was removed by heating to obtain a copolymer. However, in Comparative Example 1, copolymerization was carried out without adding a polyfunctional coupling agent. Moreover, in Comparative Example 2, copolymerization was carried out by adding a polyfunctional coupling agent without adding a urea derivative. Table 1 shows the basic properties of the copolymer thus obtained.
Shown below. These copolymers were kneaded and mixed in a Banbury mixer according to the formulation shown in Table 2, and the resulting unvulcanized rubber composition was vulcanized at 145°C and evaluated for physical properties. The foot measurement results are shown in Table 3.

Comparative Examples 5 and 6 Table 1 was placed in a polymerization vessel similar to that used in Example 1 under a nitrogen atmosphere.
As shown in 1, predetermined amounts of cyclohexane, styrene, 1
, 3-butadiene, and a Lewis base were charged, and while the mixture in the polymerization vessel was vigorously stirred, the temperature of this mixture was adjusted to a predetermined temperature, and then a predetermined amount of n-butyllithium was added to start copolymerization. . After the polymerization temperature reached the maximum temperature and the copolymerization was completed, a predetermined amount of urea derivative was added and reacted for about 5 minutes as shown in Table 1, and then a predetermined amount of a polyfunctional coupling agent was added. The reaction was allowed to take place for about 10 minutes. However, in Comparative Example 6, 0.082 g of potassium tert-butyl oxide (KTB) was newly added to the polymerization system. 2,6-tert-butyl-p-cresol 6 was added to the copolymer solution thus obtained as a stabilizer.
g was added thereto, and the solvent was removed by heating to obtain a copolymer. The basic properties of the copolymer thus obtained and the properties of the vulcanizate are shown in Table 3.

As can be seen from Table 3, Examples 1 to 6 had an excellent balance of impact resilience, abrasion resistance, and wet skid resistance, and were also excellent in processability.

Table 2 N-cyclohexyl-2-benzothiazylsulfenamide? ) High-temperature reaction product of diphenylamine and acetone [Effect 1 of the invention The branched random styrene-butadiene copolymer according to the present invention has at least three reactivity with the lithium-terminated copolymer modified with a specific urea derivative. It is obtained by reacting a polyfunctional coupling agent having a moiety,
In addition, the styrene units in the copolymer chain have a specific styrene chain distribution, so this copolymer has an excellent balance of impact resilience, wet skid resistance, and abrasion resistance, and has excellent processability. , tire tread,
It can be used for tire applications such as carcass and sidewalls, extruded products, automobile window frames, anti-vibration rubber, and industrial products, and has great industrial significance.

Claims (1)

[Claims] Styrene and butadiene are copolymerized in a hydrocarbon solvent using an organolithium compound as a polymerization initiator, and then the general formula, ▲mathematical formula, chemical formula, table, etc.▼ (in the formula, R_1 and R_2 are Lithium-terminated modified copolymer obtained by adding a urea derivative represented by C_1 to C_4 alkyl groups or alkoxyalkyl groups, Y represents an oxygen atom or a sulfur atom, and n represents an integer of 2 to 4. A styrene-butadiene copolymer obtained by reacting a polymer with a polyfunctional coupling agent having at least three reactive sites, the copolymer having a Mooney viscosity (ML_1_・
_4, 100℃) is 30~150, bound styrene is 5~
45% by weight, a single styrene chain with one styrene unit accounts for 40% by weight or more of the bonded styrene, and a long styrene chain with 8 or more styrene units makes up 5% of the bonded styrene.
% or less by weight of a branched random styrene-butadiene copolymer.