JPS6243402A - Novel random styrene-butadiene copolymer - Google Patents

Abstract

PURPOSE:A novel copolymer useful as rubber for tire having improved balance of impact resilience, wet skid resistance and wear resistance, wherein a styrene unit in a copolymer chain is modified with a specific amide compound. CONSTITUTION:A copolymer containing Li end obtained by copolymerizing styrene with butadiene by the use of an organolithium compound (e.g., n- propyllithium, dilithiomethane, etc.,) as a polymerization initiator is reacted with an amide compound shown by the formula (R1 is 1-6C alkyl, cycloalkyl or alkoxyalkyl; Y is O or S; n is 3 or 4) or an amide compound wherein one or more hydrogens of -(CH2)2 in the formula is replaced with 1-6C alkyl, to give a copolymer having 30-150 Mooney viscosity (ML1+4, 100 deg.C), 5-45wt% bonded styrene, >=40% based on bonded styrene of styrene single chain of one styrene unit and <=5% styrene long chains of >=8 chains of styrene units.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a novel random styrene-butadiene copolymer in which the styrene units in the copolymer chain are modified with a specific amide compound having a specific styrene chain distribution. It's about merging.

[Prior art] Random styrene-butadiene copolymers have traditionally been widely used as rubber for tires, but in recent years, due to social demands for resource and energy conservation, there has been a demand for lower fuel consumption for automobiles and cars, and for automobiles when driving. With the demand for improved safety, tire characteristics such as fuel efficiency, handling stability,
There is a growing demand for products with excellent durability, and GOL for tires has high rebound resilience and low fuel consumption.
It is required that the steering stability property is 11, the wet skid resistance is 7+1, and the durability property is 12, and the abrasion resistance is excellent.

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, and in order to balance these contradictory characteristics, it is necessary to Various methods have been proposed. For example, a method of improving impact resilience without impairing wet skid resistance by introducing a functional group into a diene polymer (Japanese Unexamined Patent Publication No. 1983-IEi2G
No. 04, JP-A No. 11 ((60-137913)),
Furthermore, a method has been proposed for improving impact resilience, wet skid resistance, and abrasion resistance by controlling the styrene distribution in the styrene-butadiene copolymer chain.

For example, there is a method of greatly increasing the styrene distribution width at the terminal end of a copolymer chain (Japanese Patent Application Laid-Open No. 143209/1989), and a method of blowing one type of copolymer with different styrene contents in the same copolymer. , method of converting into
No. 5, JP-A-57-200413 R5), a method for highly homogenizing styrene units in copolymer chains (JP-A-57-200413 R5);
7-100112).

[Problems to be Solved by the Invention] However, although these copolymers show some improvement effects, they have not yet reached a high level of repulsion, wet skid resistance, and abrasion resistance. .

The present invention was made in view of the above points, and an object thereof is to provide a random styrene-butadiene copolymer having a highly improved balance of impact resilience, wet skid resistance, and abrasion resistance. .

[Means and effects for solving the problems] The present invention is based on a thorough investigation on the chain distribution of styrene in the styrene-butadiene copolymer chain in which a functional group is bonded to the copolymer chain. As a result, a lanthanum styrene-butadiene copolymer modified with a specific amide compound in which the styrene center in the copolymer chain has a specific styrene linkage 4j exhibits high repulsion properties, wet skid resistance, and This was based on the discovery that the wear resistance was highly balanced.

That is, the present invention relates to a lithium-terminated copolymer obtained by copolymerizing styrene and butadiene in a hydrocarbon solvent using an organolithium compound as a polymerization initiator (a lithium-terminated copolymer having a lithium atom bonded to the end of the copolymer chain). tamstyrene-butadiene copolymer) and the general formula (wherein, R1 is an alkyl group, cycloalkyl group, or alkoxyalkyl group of 01 to C6, Y is an oxygen source f or a sulfur source f-, and n is 3 to (represents an integer of 4) or an amide compound represented by the above general formula (f
cH2. 1 of the hydrogen atom of the polymethylene chain represented by
A styrene-butadiene copolymer obtained by reacting an amide compound in which at least one of C1 to C6 argyl groups is substituted, and has a Mooney viscosity (MLl, 4°C and 100°C) of 30
-150. 5-45% of bonded styrene, 40% by weight of bonded styrene with single styrene chain with one styrene center
The present invention relates to a random styrene-butadiene copolymer having the above characteristics and characterized in that long styrene chains having eight or more styrene centers are 5% by weight or less of the bonded styrene.

The styrene-butadiene copolymer of the present invention exhibits excellent properties and is used in various rubber applications, but is particularly useful as a tire tread rubber.

The present invention will be explained in detail below.

In the amide compound used in the present invention, a specific hydrocarbon group is bonded to the nitrogen atom f, and the nitrogen atom f and one father atom are +CH
A general formula (wherein R1 is an alkyl group, a cycloalkyl group, or an alkoxyalkyl group of 01 to C6, Y is an oxygen atom or a sulfur atom, and n is an atom of 3 to 4 It is necessary to have a cyclic structure represented by (representing an integer).

This has an extremely important meaning in achieving the present invention.Normally, in the stoichiometric reaction between an amide compound having an acyclic structure and a lithium-terminated polymer,
As described in No. 24174, the bond between the carbonyl group and the amine 7 group is broken, making it impossible to effectively introduce the amine 7 group into the copolymer, and this reaction product undergoes hydrolysis. This reaction is not preferred from a practical point of view, as it results in a secondary amine that deactivates the catalyst.

The E reaction is shown below (in the formula, P represents a polymer chain).

On the other hand, in the stoichiometric reaction of the amide compound having a 5- or 6-membered ring structure used in the present invention and the lithium-terminated copolymer in a hydrocarbon solvent, secondary amines are liberated. Functional groups such as amine groups can be reliably introduced into the copolymer without any When the thus obtained copolymer is blended with compounding agents such as carbon black and process oil, mixed and kneaded, and vulcanized, the vulcanized product exhibits excellent impact resilience and abrasion resistance.

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 decrease, which is undesirable. On the other hand, if the bound styrene content exceeds 45% by weight, the impact resilience and abrasion resistance will decrease, which is undesirable.

In the copolymer of the present invention, the styrene unit fi (hereinafter referred to as Sl) having one styrene center is 40% by weight or more, preferably 55% by weight or more of the bound styrene, and the styrene unit is 8
The number of long styrene chains (hereinafter referred to as 88 to 88) must be less than 5.0% by weight, preferably less than 2.5% by weight of the bound styrene, even if S+ is less than 40% by weight of the bound styrene. Even when ~ exceeds 5% by weight, impact resilience, abrasion resistance, and wet skid resistance deteriorate, which is not preferable.

Mooney viscosity (ML, .4°100 of the copolymer of the present invention)
C) is 30-150, preferably 50-120.

If the Mooney viscosity is less than 30, the effects of improving impact resilience and abrasion resistance will not be sufficient; if the Mooney viscosity exceeds 150, problems will remain in the calendering processability and extrusion processability of the compound.

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

Regarding the relationship between the microstructure and physical properties of the butadiene moiety, the relationship between the 1.2 vinyl content and physical properties is known. For example, as the 1,2 vinyl content increases, the wet skid resistance of the polymer improves; Wear resistance decreases [Rubber Age” VoR104,5
5 (1972)).

Furthermore, as the 1,2-vinyl content increases, heat resistance and reversion are improved, H. Nordsiek.

r 1979 Report to the International Rubber Conference J (Pape
rPresented to the Ink, Ru
Bber Conf, 1979).

The relationship between the 1.2 vinyl content and physical properties is already known, and in the present invention, the 1.2 vinyl content and the 2 vinyl content are not particularly limited, but from the viewpoint of impact resilience and abrasion resistance, the 1.2 vinyl content is On the other hand, 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 is preferably determined depending on the usage.

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. 5, or it may be distributed in blocks (USP-3301840), and should be determined depending on the purpose of use.

Regarding the styrene composition distribution in the styrene-butadiene copolymer chain, it may be uniformly distributed in the copolymer chain, or it may be distributed non-uniformly in the copolymer chain.
o-4108), and should be determined depending on the purpose of use.

Processability of the conjugated diene polymer of the present invention changes greatly by changing the molecular weight distribution.

The relationship between molecular ra distribution and processability is well known, and in the present invention, the fraction 'F expressed as the ratio of weight average molecular weight (Few) to number average molecular weight (MN) is known.
-5 distribution (Mw/Fai+) is not particularly limited, but considering the balance between physical properties and processability, 1.2 to 3.5 is preferable. It may be polymodal of modal or E.

The copolymer of the present invention is produced by the method described below. One method is to copolymerize styrene and 1,3-butadiene in a hydrocarbon solvent using an organolithium compound as a polymerization initiator, as described in British Patent No. 994726 and Japanese Patent Application Laid-open No. 59-198.
As described in No. 40211 and JP-A-56-143209, the styrene monomer content in the 7-mer composition ratio of styrene and 1,3-butadiene in the polymerization system is adjusted to be within a specific concentration range of 1.3-butadiene. A lithium-terminated copolymer obtained by carrying out copolymerization by continuously or intermittently supplying a mixture of -butadiene or 1,3-butadiene and styrene, and a lithium-terminated copolymer having the general formula (1, R1 is C1 to (C6 alkyl group, cycloalkyl group or alkoxyalkyl group, Y represents an oxygen atom I or a sulfur atom, n represents an integer of 3 to 4) or fc in the above general formula
The present invention can be carried out by reacting with an amide compound in which one hydrogen atom of the polymethylene chain represented by H2t= has been converted into 8 with an alkyl group of 01 to C6, and after the reaction is completed, alcohol and Mizukasa are added to the reaction system. This is a method for obtaining a styrene-butadiene copolymer.

Another method is to copolymerize styrene and 1,3-butadiene in a hydrocarbon solvent using an organolithium compound as a polymerization initiator, at a rate slower than the copolymerization rate as described in Japanese Patent Publication No. 38-2394. Copolymerization is carried out by adding a mixture of styrene and 1,3-butadiene, and the resulting lithium-terminated copolymer and the general formula (wherein R1 is an 01 to C6 alkyl group, cycloalkyl group, or alkoxyalkyl group) , Y represents an oxygen atom or a sulfur atom, and n represents an integer of 3 to 4) or +C in the above general formula
The styrene of the present invention is produced by reacting with an amide compound in which one or more hydrogen atoms of the polymethylene chain represented by H2h is substituted with an alkyl group of c, -C6, and after the reaction is completed, alcohol, water, etc. are added to the reaction system. - A method for obtaining a butadiene copolymer.

In the present invention, ethers, tertiary amines, alkali metal alkoxides, etc. 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. , triethylene glycol dimethyl ether, tetrahydrofuran, α-methoxymethyltetrahydrofuran, dioxane, 1,2-dimethoxybenzene, triethylamine.

N, N, N', N'-tetramethylethylenediamine,
potassium-tart-7 miloxide, potassium-te
rt-butyl oxide and the like. These compounds may be used alone or as a mixture of two or more.

The amount of the polar compound used in the present invention is 0 to 200 mol per mol of the organolithium metal compound.

The organolithium compound used in the present invention includes n-
Monoorganolithium compounds such as propyllithium, isopropyllithium, n-butyllithium, 5ec-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 L,3,5-trilithiobenzene. These may be used alone or in a mixture of two or more. Furthermore, as the polyfunctional organolithium compound used in the present invention, compounds that can be substantially converted into a polyfunctional organolithium compound by reacting the above-mentioned monoorganolithium compound with another compound are also used. For example, after reacting a reaction product of a monoorganolithium compound and a polyvinyl aromatic compound (Japanese Patent Publication No. 55-1 [!52]), a monoorganolithium compound and a conjugated diene, and/or a monovinyl aromatic compound, A reaction product obtained by reacting a polyvinyl aromatic compound, or a reaction product obtained by simultaneously reacting a monoorganolithium compound, a conjugated diene, and/or a monovinyl aromatic compound, and the king of polyvinyl compounds (West German patent 2003384, etc.) .

The amount of these organolithium compounds used is usually 0.1 to 10 mmol per 100 g of conjugated diene monomer.

As hydrocarbon solvents used in the present invention, aliphatic, cycloaliphatic and aromatic hydrocarbons can be used. For example, hydrocarbon solvents include propane, isobutane, 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 or more.

The amide compound used in the present invention has the general formula (wherein R1
represents an alkyl group, cycloalkyl group, or alkoxyalkyl group of 01 to C, Y represents an oxygen atom or a sulfuric acid atom, and n represents an integer of 3 to 4) or +CH2sn in the above general formula One or more of the hydrogen atoms in the polymethylene chain shown is C
An amide compound substituted with a 1 to C6 alkyl group, specific examples of which include l-cyclohexyl-2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, and 1-furopyru-2-pyrrolidone. , l-butyl-2-pyrrolidone, l-isopropyl-2-pyrrolidone, 1,5-dimethyl-2-pyrrolidone, 1-methoxymethyl-2-pyrrolidone, l-methyl-2-piperidone,
1.4-dimethyl-2-piperidone, 1-ethyl-2-
piperidone, l-isopropyl-2-piperidone, 1-
Examples include isopropyl-5,5-dimethyl-2-piperidone, and l-methyl-2-pyrrolidone and 1-methyl-2-piperidone are preferred, with l-methyl-2-pyrrolidone being particularly preferred.

The amount of the amide compound used in the present invention is usually 0.2 to 2.0 mol, preferably 0.5 to 1.5 mol, particularly preferably It is 1.0 mol. The reaction between the lithium-terminated copolymer and the amide compound occurs immediately when they come into contact with each other, so the reaction temperature and reaction time can be adjusted over a wide range, but usually the reaction temperature is 25-115°C and the reaction time is 1 second or more. It is within 3 hours. There are no particular limitations on the method of adding these amide compounds, but there is a method of adding the amide compound after the completion of copolymerization, or a method of adding the amide compound after completion of copolymerization, or
There is a method of adding -butadiene tt and then adding an amide compound, or a method of adding an amide compound of 1.1 during copolymerization so as not to stop the copolymerization. In short, the method of adding the amide compound υ should be determined depending on the purpose of use.

Unreleased 1. ! The iE polymerization format in II is a batch polymerization method,
Or continuous polymerization method may be used. J polymerization temperature is 20 to 1
In the range of 30℃, in the batch polymerization method, the temperature is 30 to 87℃.
It is recommended that the polymerization be carried out at elevated temperatures such that the polymerization starts at 90-125°C and the maximum temperature reaches 90-125°C.

After a given reaction path r, 2,6-tert~butyl-p-
After adding an antioxidant such as Fresol, the resulting Daito coalescence is separated, washed, and subjected to standard post-treatments such as dry smoking.
The desired copolymer can be obtained.

The undeveloped copolymer No. 11 may be used as an oil-extended rubber by mixing it with a process oil in a solution state and removing the solvent after mixing.

The undeveloped 1!1 copolymer can be used by blending Sino-German or natural rubber or other synthetic rubbers such as polybutadiene, polyimprene, emulsion with styrene-butadiene copolymer, etc. . When used in a blend with natural rubber or other synthetic rubber, the copolymer of the present invention must account for at least 30% by weight of the raw rubber in order to exhibit the excellent properties of the present invention.

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,
As a product, for example, tire applications such as tire treads, carcass, sidewalls, extrusion products, automobile window frames, etc. It can be used for products, anti-vibration rubber, etc., and because it has an excellent balance of rebound resilience and wet skid resistance, it can be used particularly as a tread 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 styrene chain distribution of lanthanum styrene-butadiene copolymers is analyzed with a method recently developed by Yamanaka et al. Specifically, the styrene chain distribution is analyzed by gel permeation chromatogram (GPC) of the decomposed product obtained by opening all the single bonds in the middle part of butadiene with ozone. (Vol. 29, No. 9, p. 2055)
, Mooney viscosity was measured at 100° C. using an L rotor in a conventional manner. The bound styrene was calculated from the absorption based on the phenyl group at 2B2 nm using ultraviolet absorption spectroscopy. The microstructure of the butadiene moiety was determined using an infrared spectrophotometer, and the impact resilience was calculated using the Hampton method at a test temperature of 70% using a Tanlop tripunmeter.
Measured at ℃. Abrasion resistance was measured using a Pico abrasion tester. Wet skid resistance was measured using British Road Research Institute bodywork.

Examples 1-6. Comparative Examples 1, 2, 5.6 Under a nitrogen atmosphere, predetermined amounts of cyclohexane, styrene, and 1,3-butadiene (hereinafter referred to as 1 butadiene) and Lewis 11! While stirring the mixture in the polymerization vessel vigorously.

After adjusting this mixture to a predetermined temperature, a predetermined amount of n-butyllithium was added to initiate copolymerization.

Next, as shown in Table 1, 1,3-butadiene (hereinafter referred to as FS2 butadiene) was continuously supplied to the Togane system at a constant rate using a metering pump. After the supply of the second butadiene was finished and the polymerization temperature reached the maximum temperature and the copolymerization was completed, a predetermined amount of the amide compound was added as shown in Table 1, and the reaction was allowed to occur for about 10 minutes. 2,6-sheeter was added as a stabilizer to the copolymer solution thus obtained.
5 g of t-butyl-p-fretool was added and the solvent was removed by heating to obtain a copolymer. However, in Comparative Example 6, the amide compound was changed to 1 g of methanol and copolymerization was carried out. The basic properties of the copolymers thus obtained are shown in Table 3. The vulcanized rubber composition was vulcanized at 145°C, and the physical properties J'+ value were measured.

The measurement results are shown in Table-3.

Comparative Example 3.4 Under a nitrogen atmosphere, a polymer was placed in a polymerization vessel similar to that used in Example 1.
As shown in 1, predetermined amounts of cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene 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 - Butyl lithium was added to start copolymerization. After the polymerization temperature reached the maximum temperature and copolymerization was completed, a predetermined amide compound was added as shown in Table 1 and reacted for about 10 minutes. however,
In Comparative Example 4, 0.059 g of potassium tart-butyl oxide (KTB) was newly added to the polymerization system. A copolymer was obtained from the thus obtained copolymer solution in the same manner as in Example 1. A copolymer was obtained from the thus obtained copolymer solution in the same manner as in Example 1. 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 have an excellent balance of impact resilience, wet skid resistance, and abrasion resistance.

[Effect of the invention] The styrene-butadiene copolymer according to the present invention is obtained by reacting a specific amide compound with a copolymer that binds a lithium atom to the end of the copolymer chain, and Because the styrene units in the copolymer chain have a specific styrene chain distribution, this copolymer has an excellent balance of impact resilience, wet skid resistance, and abrasion resistance, and is useful for tire treads, carcass, sidewalls, etc. It can be used for tires, extruded products, automobile window frames, anti-vibration rubber, industrial products, etc., and has great industrial significance.

Claims (1)

[Claims] A lithium-terminated copolymer obtained by copolymerizing styrene and butadiene using an organolithium compound as a polymerization initiator, and a general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R_1 is (C_1 to C_6 alkyl group, cycloalkyl group, or alkoxyalkyl group, Y represents an oxygen atom or sulfur atom, and n represents an integer of 3 to 4) or -( in the above general formula)
A styrene-butadiene copolymer obtained by reacting an amide compound in which one or more of the hydrogen atoms in the polymethylene chain represented by CH_2)-_n is substituted with an alkyl group of C_1 to C_6, and has a Mooney viscosity (ML_1_+_4, 1
00℃) is 30 to 150, 5 to 45% by weight of bound styrene, 40% by weight or more of the bound styrene single chain with one styrene unit, and long styrene chains with 8 or more styrene units. A random styrene-butadiene copolymer characterized in that the amount of bound styrene is 5% by weight or less.