JP3059499B2 - Conjugated diene rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conjugated diene rubber comprising a specific conjugated diene rubber, a specific amount of a phenolic stabilizer or a phosphorus stabilizer, and a sulfur-containing phenolic compound having a specific structure. The present invention relates to a rubber composition. In particular, the present invention is excellent in high-temperature heat stability and shear insulation stability, and very little gel generation and discoloration,
The present invention relates to a conjugated diene-based rubber composition suitable for resin modification, automobile tires, industrial products, and the like.

[0002]

2. Description of the Related Art Hitherto, diene polymers have been widely used for resin modification, automobile tires and various industrial products. Among them, a diene polymer having a branched structure coupled with a polyfunctional coupling agent has features such as improvement in processability, mechanical strength, and the like. However, the coupled rubber has a relatively high molecular weight and therefore a high Mooney viscosity in order to improve its properties, and has a coupling residue such as a metal or an oxygen atom. As a result, in a rubber production factory, a processing factory, or the like, problems such as generation of a gel or discoloration occur when, for example, a processing operation is performed at a high temperature or a thermal shear stress is applied.

[0003] In order to solve these problems, phenol-based stabilizers, phosphorus-based stabilizers, sulfur-based stabilizers and combinations thereof have been used as stabilizers for preventing gelation. Among them, phenolic stabilizers, particularly 2,6-di-tert-butyl-4-methylphenol (hereinafter abbreviated as BHT), have been widely used.

[0004]

However, although BHT has a thermal stability effect for a short time, its sublimation temperature is low, so that the residual ratio to rubber is reduced, and the thermal stabilization effect is reduced. There are problems such as yellowing of rubber due to dimerization reaction and the like, and improvement thereof is demanded. Further, when used in a large amount, the phosphorus-based stabilizer has a problem in that it reacts with water to generate phosphoric acid, corrodes metals and the like, causes rust, and has a contamination property. Most of the sulfur-based stabilizers have a problem of odor, particularly at high temperatures, and have large rubber coloring. A diene rubber composition containing a large amount of such a stabilizer in order to increase its effect may have deteriorated vulcanization properties or crosslinking properties, or may have reduced tensile strength and rebound resilience of a molded article. Not preferred. In addition, depending on the use of a large amount of a stabilizer, it may be colored or exhibit a remarkable coloration particularly at high temperatures, without deteriorating the preferable properties of the coupled conjugated diene rubber, without causing heat stability and shearing at high temperatures. It has been difficult to improve thermal stability.

[0005]

Means for Solving the Problems The present inventors have solved the problems such as coloring and gel formation at high temperatures and heat shearing without impairing the properties of such coupled conjugated diene rubbers. High Mooney viscosity (ML _{1 + 4,}
100 ° C: hereinafter, abbreviated as Mooney viscosity) or gel permeation chromatograph (hereinafter, abbreviated as GPC), weight average molecular weight in terms of polystyrene measured by

Embedded image As a result of intensive studies on the coupled conjugated diene rubber and various stabilizers, the coupled conjugated diene rubber, a specific amount of at least one phenolic stabilizer or phosphorus-based stabilizer, A conjugated diene rubber composition comprising a sulfur phenolic compound has excellent heat stability at high temperature and shear heat insulation stability by suppressing gel generation and coloring, and the composition is easily vulcanized and crosslinked. Yes, they found that the molded product had good tensile strength and rebound resilience, etc., and completed the present invention.

That is, the present invention relates to at least one kind of a polymer having a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 20 to 180 or a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography of 200,000 to 1,000,000. 100 parts by weight of a conjugated diene rubber comprising a conjugated diene or a conjugated diene and at least one monovinyl aromatic compound, and coupled with a polyfunctional coupling agent, and represented by the following general formulas (1) to (4).
That at least one stabilizer 0.1 to 2.0 parts by weight of the phenolic stabilizer and the phosphorus stabilizer, the following general formula
(5) A conjugated diene rubber composition having excellent thermal stability, comprising at least one kind of sulfur-containing phenolic compound represented by the formula (5) 0.01 to 0.20 part by weight. .

[0007]

Embedded image ( Wherein R ₆ , R ₇ and R ₈ are alkyl having 1 to 12 carbons)
Group, allyl group, cycloalkyl group, phenyl group, alcohol
Represents a xy group or the like. )

Embedded image

[0008]

Embedded image (In the formula, R _1, R ₃ represents _{-CH 2 -S-R 5, R} 5
Represents an alkyl group having 20 or less carbon atoms, and R ₂ and R ₄ represent a hydrogen atom or an alkyl group having 15 or less carbon atoms. )

Hereinafter, the present invention will be described in detail. The coupled conjugated diene rubber used in the present invention is, for example, tetrahydrofuran or N, N, N ′, N′- in an inert hydrocarbon solvent such as n-hexane or cyclohexane.
In the presence or absence of a Lewis base such as tetramethylethylenediamine, at least one conjugated diene such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, , 3
An organic lithium compound having one or more lithium atoms in a molecule thereof, such as heptadiene or the like or the conjugated diene and at least one monovinyl aromatic compound such as styrene, α-methylstyrene, 1-vinylnaphthalene, etc., for example, n-butyllithium Or sec-butyllithium, or JP-A-58-136603 or JP-A-57-40.
No. 513, a conjugated diene system obtained by polymerization using a polyfunctional organic lithium catalyst or the like as a polymerization initiator and coupling with a polyfunctional coupling agent after or during polymerization. It is rubber.

Examples of the polyfunctional coupling agent include polyhalogen compounds, polyepoxy compounds, esters, and other generally known compounds. Examples thereof include tin tetrachloride, germanium tetrachloride, silicon tetrachloride, carbon tetrachloride, and epoxidized compounds. Examples include soybean oil, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, dimethyl adipate, carboxylic acid diester, divinylbenzene, and the like. It is necessary that the conjugated diene rubber treated with these coupling agents contains at least 20% by weight or more of a branched component due to coupling.
The processability and mechanical strength of the obtained conjugated diene rubber composition are reduced.

In the conjugated diene rubber used in the present invention, the distribution of monovinyl aromatic compounds such as styrene and the distribution of 1,2-vinyl bonds of the diene may be random or block, or may be gradually reduced along the molecular chain. May be changed. The binding amount of the monovinyl aromatic compound is 7
0% by weight or less, preferably 50% by weight or less.

The Mooney viscosity of the conjugated diene rubber used in the present invention is preferably in the range of 20 to 180. If the Mooney viscosity is lower than 20, the tensile strength and rebound resilience of the obtained conjugated diene rubber composition are lowered, If it becomes higher, the processability of the obtained conjugated diene rubber composition deteriorates.

Embedded image The conjugated diene rubber composition of the present invention may contain less than 80% by weight of natural rubber or other synthetic rubber,
When the above content is contained, various thermal stability which is a feature of the present invention is deteriorated.

The phenolic stabilizer used in the present invention comprises:
It is represented by the following general formula (1) to (4).

Embedded image (In the formula, R ₆ , R ₇ , and R ₈ represent an alkyl group having 1 to 12 carbon atoms, an allyl group, a cycloalkyl group, a phenyl group, an alkoxy group, and the like.)

[0014]

Embedded image

The compounds represented by the general formula (1) include, for example, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 6-di-tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-
i- butylphenol, 2-tert-butyl-4,6
- dimethyl phenol, 2,4,6-tricyclohexylphenol, 2,6-di -tert- butyl-4-methoxyphenol, 2,6-di - include phenyl-4-octadecyloxyphenol.

A preferred substituent of R _{10 in} the general formula (2) is an octadecyl group or the like. As the compound, for example,
n-octadecyl-3- (3 ', 5'-di-tert-
Butyl-4-hydroxyphenyl) propionate. Further, as the compound represented by the general formula (3),
For example, tetrakis- [methylene-3- (3 ′, 5′-
Di-tert-butyl-4'-hydroxy-phenyl)
Propionate] -methane and the like. General formula
As the compound represented by (4), for example, 1,3,5-
Trimethyl-2,4,6-tris (3,5-di-ter
(t-butyl-4-hydroxybenzyl) benzene and the like.

Examples of the phosphorus-based stabilizer include tris (nonylphenyl) phosphite, cyclic neopentanetetraylbis (octadecylphosphite), and tris (2,4-di-tert-butylphenyl) phosphite. And the like.

The content of at least one of these phenolic stabilizers or phosphorus stabilizers represented by the general formulas (1) to (5) is based on 100 parts by weight of the conjugated diene rubber.
0.1 to 2.0 parts by weight, preferably 0.1 to 1.
0 parts by weight. In this case , if the amount is less than 0.1 part by weight, the effect of improving the thermal stability is small, and if the amount is more than 2.0 parts by weight, the vulcanization / crosslinking time becomes longer, and the tensile strength and rebound resilience of the molded product are reduced. Getting worse.

The sulfur-containing phenolic compound used in the present invention has the general formula (5):

Embedded image (In the formula, R _1, R ₃ represents _{-CH 2 -S-R 5, R} 5
Represents an alkyl group having 20 or less carbon atoms, and R ₂ and R ₄ represent a hydrogen atom or an alkyl group having 15 or less carbon atoms. )

For example, 2,4-bis (n-octylthiomethyl) -6-methylphenol, 2,4-bis (2 ', 3'-di-hydroxypropylthiomethyl)-
3,6-di-methylphenol, 2,4-bis (2′-
Acetyloxyethylthiomethyl) -3,6-dimethylphenol is preferred.

[0021] The content of the sulfur-containing phenolic compound used in the present invention is 100 parts by weight of the conjugated diene rubber.
The amount is 0.01 to 0.20 part by weight, preferably 0.01 to 0.05 part by weight based on part by weight. In this case, 0.01
If the amount is less than parts by weight, the thermal stability will deteriorate. Also, 0.2
When the amount is more than 0 parts by weight, the thermal stability during shearing is good, but the rubber composition is markedly colored and odor is generated, which is not preferable. At the same time, the vulcanization behavior, the tensile strength of the molded product, the rebound resilience, and the like deteriorate.

The conjugated diene rubber composition of the present invention may contain 0.05 to 1.0 part by weight of at least one other sulfur stabilizer based on 100 parts by weight of the conjugated diene rubber. Examples of the sulfur-based stabilizer include pentaerythritol-tetrakis- (β-lauryl-thio-propionate), dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, and distearyl. -3,3'-thiodipropionate and the like are listed. The sulfur-based stabilizer can effectively improve the color tone and thermal stability of the composition by adding an appropriate amount.

The method for preparing the conjugated diene-based rubber composition of the present invention is not particularly limited. For example, a phenol-based stabilizer or a phosphorus-based stabilizer may be dissolved in a state in which the conjugated diene-based rubber is dissolved in an organic solvent. At least one desired amount;
At least one desired amount of a specific sulfur-containing phenolic compound and, if necessary, the sulfur-based stabilizer are blended in a preferred order or at the same time, and then mixed with a solvent by a known method, for example, a steam stripping method or a hot roll. Or it may be directly mixed with dry rubber and mixed by a known method, for example, a roll, a Banbury, an extruder, or the like. Alternatively, it is also possible to mix simultaneously when adding and mixing other compounding agents, and in short, it can be prepared by any known compounding method.

[0024]

Hereinafter, the present invention will be described with reference to examples.
These examples do not limit the invention. In addition, the measurement of various characteristics was implemented by the following methods. Mooney viscosity was measured at 100 ° C. and 2 rpm using an L rotor according to the method of JIS-K6300.

Embedded image For the measurement of the coupling ratio, GPC (trade name 204 compact type) manufactured by Waters was used, and the column was Dupo.
nt. ZORBAK-PSM-1000S and 60S
With a solvent of tetrahydrofuran,

Embedded image The coupling amount (% by weight) was determined from the area of the chromatogram.

The 1,2-vinyl bond amount of the butadiene portion was measured with a Perkin Elmer 1710 infrared spectrophotometer and calculated by the Hampton method. The bound styrene was calculated from the absorption based on the phenyl group at 262 nm by the ultraviolet absorption spectrum method. Thermal stability at high temperature was measured by placing a stabilizer-prepared polymer composition sheet having a length and width of 5 cm and a thickness of 0.5 cm into an oven heated to 180 ° C., and testing time: 0.5 hour, 1 hour, 2 hours 3 hours, the coloring degree of each sheet was examined. The degree of coloring was ranked as follows. No discoloration (white) = 0, pale yellow = 1, pale yellow =
2, yellow = 3, brown yellow = 4, brown = 5, brown = 6, dark brown = 7.

The thermal stability during shearing was measured at a test temperature (cylinder temperature) of 100 using a mixer B-75 with Labo Plastomill LPM-2500-200 manufactured by Toyo Seiki Co., Ltd.
At 55 ° C. and 10 rpm of rotor rotation.
After charging for 100 minutes, the pressure was immediately increased to 100 rpm, the torque value gradually decreased, and then the gelation started and the torque began to increase. The lowest point of the torque value at this time was measured as the gelation start time. FIG. 1 shows a lab plast mill kneading test chart. The vulcanization time of the unvulcanized compound of the rubber composition is determined by JS
Test temperature 160 ° C using R type Curastometer II
The time at which 90% (T ₉₀ ) of the maximum torque during vulcanization (T ₁₀₀ ) based on the minimum torque during unvulcanization (T ₀ ) was measured. The unvulcanized compound sample used for the tensile test and the rebound resilience test is 160 ° C.-200 kg / cm ²
Vulcanized for 20 minutes. The tensile strength of the vulcanized product was measured on the above sample according to the method of JIS-K6301. 'The rebound resilience was measured at a test temperature of 70 ° C. using the above sample using a Lupke rebound resilience tester.

[0027]

[Reference Example] Production of conjugated diene rubber. The conjugated diene rubber used in Examples and Comparative Examples of the present invention was prepared by the following method. The coupled conjugated diene rubber was charged with 42 kg of dried cyclohexane, 130 g of tetrahydrofuran, 5.25 kg of 1,3-butadiene, and 1.75 kg of styrene monomer in a nitrogen-substituted 100 L stainless steel autoclave while stirring. 38
After heating to ℃, 78 mmol of n-butyllithium was added for polymerization. After about 25 minutes, the reaction temperature showed a peak temperature of 98 ° C., and 4 minutes later, 9.0 mmol of tin tetrachloride was added and reacted for 10 minutes.

Separately, for comparison, n-butyllithium was 69 mmol, polymerization was carried out under the same conditions (93 ° C. peak temperature), and non-coupling conjugated diene rubber (A) containing no tin tetrachloride was added. A non-coupling conjugated diene rubber (B) prepared by polymerizing n-butyllithium at 60 mmol under the same conditions was also prepared. For each rubber solution,
Active lithium was decomposed by adding methyl alcohol.
The Mooney viscosity of the conjugated diene rubber thus obtained is determined by GPC.

Embedded image Table 1 shows the measurement results such as the total amount of bound styrene and the amount of 1,2-vinyl bond.

[0029]

[Table 1]

[0030]

Examples 1 to 7 and Comparative Examples 1 to 9 The samples for the thermal stability test were prepared by adding the stabilizer and the stabilizer to the rubber solution of the diene rubber obtained in the Reference Example by the treatment methods shown in Tables 2 and 3 , respectively. The sulfur phenolic compound was blended, and then the solvent was removed with a hot roll to obtain a conjugated diene rubber composition. Storage stability was compared by oven heat stability test. The results are shown in Tables 4 and 5 . Shear insulation stability was also tested by Labo Plastmill. The results are shown in Tables 6 and 7 . The physical properties test of the rubber composition was performed according to the formulation shown in Table 8 by using a small pressure kneader (Moriyama Seisakusho, pressure double arm kneader, D-
The mixture was kneaded and compounded at a cylinder temperature of 100 ° C. for 10 minutes using a 0.5-3 type), and the vulcanization time (T ₉₀ ) of the obtained unvulcanized compound and the tensile strength and rebound resilience of the vulcanized molded product were measured. The results are shown in Tables 9 to 10 .

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

[Table 7]

[0037]

[Table 8]

[0038]

[Table 9]

[0039]

[Table 10]

According to the oven test results in Tables 4 and 5 , the coloring degree of the present invention (Examples 1 to 7) is as good as 2 or less, and Comparative Examples 1 and 3 to 7 show strong coloring. Table 6-
7 Gel time likewise Examples 1-7 also show has a superior results gelation time is slow, but Comparative Example 1 and Comparative Example 3
7 and Comparative Example 8 show that gelation occurs in a short time. Tables 9 to 10 are examples of the physical property test of the conjugated diene rubber composition of the present invention. In Examples, the vulcanization time is good, and the vulcanized molded product has good tensile strength and rebound resilience. It is.

On the other hand, Comparative Example 2 in which a large amount of a stabilizer was blended had good oven heat stability, and Comparative Example 7 had good gelation time, but had extremely poor tensile strength and rebound resilience. Comparative Examples 8 and 9 show relatively good oven heat stability. In particular, Comparative Examples show excellent gelation time, but extremely poor tensile strength and rebound resilience. From the above examples, it can be seen that the conjugated diene rubber composition of the present invention has excellent high-temperature heat stability and shear heat insulation stability, and that the composition has good physical properties.

[0042]

Industrial Applicability The conjugated diene rubber composition of the present invention has extremely excellent thermal stability at high temperatures and heat shear, prevents gel formation, has good discoloration resistance, and has high impact resistance. It is suitable as a rubber for modifying resins such as polystyrene. Also,
It has good vulcanization and cross-linking behavior during processing and molding, and has good tensile strength and rebound resilience, and is suitable for, for example, tire applications, industrial products, and akimono applications, and has great industrial significance.

[Brief description of the drawings]

FIG. 1 is a graph showing a laboplastmill kneading test chart for a conjugated diene rubber composition sample of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-114955 (JP, A) JP-A-59-45338 (JP, A) JP-A-57-200439 (JP, A) JP-A-1- 289857 (JP, A) JP-A 1-284539 (JP, A) JP-A 3-31334 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 15/00 C08K 5 / 13,5 / 36,5 / 524

Claims (1)

(57) [Claims] 1. A Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 20
-180 or a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography of 2
100,000 to 1,000,000 of at least one conjugated diene or 100 parts by weight of a conjugated diene rubber composed of at least one monovinyl aromatic compound and coupled with a polyfunctional coupling agent, and the following general formula ( 1) to at least one of the phenolic stabilizers and phosphorus-based stabilizers represented by (4) 0.1
Conjugated diene-based rubber composition, characterized by comprising: 0.01 to 2.0 parts by weight, and 0.01 to 0.20 parts by weight of at least one sulfur-containing compound represented by the following general formula (5) . . Embedded image ( Wherein R ₆ , R ₇ and R ₈ are alkyl having 1 to 12 carbons)
Group, allyl group, cycloalkyl group, phenyl group, alcohol
Represents a xy group or the like. ) Embedded image (In the formula, R _1, R ₃ represents _{-CH 2 -S-R 5, R} 5
Represents an alkyl group having 20 or less carbon atoms, and R ₂ and R ₄ represent a hydrogen atom or an alkyl group having 15 or less carbon atoms. )