JPH09324003A - Modified rubber and carbon-black-filled tire rubber composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon-black-filled rubber composition which can give tires reduced in rolling resistance without detriment to wet grip performances by using a modified rubber prepared by aminating the chain of a rubber molecule with a specified compound. SOLUTION: A rubber is modified by using a compound represented by formula I (wherein R<1> and R<2> , which are independent of each other, are H atoms or 1-3C alkyl groups; and X<1> is a 1-12C hydrocarbon group) and/or a compound represented by formula II (wherein R<3> , R<4> , R<5> and R<6> , which are independent of each other, are H atoms or 1-3C alkyl groups; X<2> and X<3> , which are independent of each other, are 1-12C hydrocarbon groups; and (n) is an integer of 1-12). A tire rubber composition is obtained desirably by compounding 100 pts.wt. rubber component containing 20-100wt.% above modified rubber with 20-150 pts.wt. carbon black having a nitrogen adsorption specific surface area of 50-250m<2> /g and a DBP absorption of 60-150ml/100g.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a modified rubber suitable for reducing the hysteresis loss of a carbon black-containing rubber composition for a tire, and a rubber composition for a tire containing the modified rubber and carbon black. .

[0002]

2. Description of the Related Art In recent years, the demand for low fuel consumption for automobiles has been increasing. Since the characteristics of tires have an important effect on fuel economy, a carbon black-containing rubber composition for tires containing carbon black as a reinforcing agent and having excellent fuel economy, that is, having low rolling resistance is required. ing. Further, from the viewpoint of running safety, it is desirable to use a carbon black-containing rubber composition for tires which has a large grip on wet road surfaces (hereinafter referred to as wet grip).

By the way, generally, in order to reduce the rolling resistance, a hysteresis loss (tan) of around 70 ° C.
It is necessary to reduce δ), whereas in order to improve the wet grip property, it is necessary to increase the hysteresis loss at around −10 ° C., and both have a contradictory relationship.

Therefore, the present inventors have used a specific coupling agent for carbon black to combine rubber molecules and carbon black in a rubber composition in order to reduce the rolling resistance without lowering the wet grip property. A method of improving the dispersibility of carbon black by chemically bonding was reached (Japanese Patent Application No. 7-1464).
No. 54), but there is still room for improvement in scorch resistance from the processed surface.

Further, in order to improve the dispersibility of carbon black, there is known a method of modifying the rubber by modifying the rubber molecule terminal by introducing a functional group that allows the carbon black and the rubber to interact with each other. Has been. For example, in JP-A-7-102117, the end of a rubber molecule is modified by emulsion polymerization of butadiene or styrene and a polymerizable monomer containing a tertiary amino group, and the interaction between carbon black and rubber. There is disclosed a method for modifying a rubber that imparts active points that improve the rubber composition. However, from a practical point of view, there is a limit in controlling the molecular weight and the microstructure of the obtained modified rubber, and there is a limit in the molecular design. Further, in order to enhance the interaction with carbon black, it is preferable to use an amino group having a small steric hindrance, but the publication does not disclose modification of the rubber molecule terminal with a primary and / or secondary amino group. .

[0006]

Therefore, in view of the above problems, an object of the present invention is to provide a rubber by introducing an amino group, particularly a primary and / or secondary amino group into the molecular chain of the rubber molecule. Another object of the present invention is to provide a rubber composition containing carbon black which is modified and has a small energy loss. Still another object of the present invention is a carbon black-containing rubber composition for a tire, which is composed of the modified rubber and carbon black and has excellent scorch resistance, and reduces rolling resistance without lowering wet grip properties. Another object of the present invention is to provide a rubber composition containing carbon black.

[0007]

According to the present invention, there is provided a compound of formula (I):

[0008]

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(However, R ¹ and R ² are independently H or an alkyl group having 1 to 3 carbon atoms, and X ¹ is 1 to 12 carbon atoms.
A hydrocarbon group) and / or formula (II):

[0010]

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(However, R ³ , R ⁴ , R ⁵ and R ⁶ are independently H or an alkyl group having 1 to 3 carbon atoms, and X ² and X ³ are independently hydrocarbon groups having 1 to 12 carbon atoms. , N is 1
An integer of 12).

The compounds preferably have only primary and / or secondary amino groups. Further, X ¹ , X ² and X ³ are preferably chain or cyclic saturated hydrocarbons.

The present invention also relates to a carbon black-containing rubber composition comprising the modified rubber and carbon black. In this case, carbon black has a nitrogen adsorption specific surface area of 50 to 250 m ² / g and a DBP oil absorption of 60 to 15
The modified rubber 2 is preferably 0 ml / 100 g.
It is preferable to add 20 to 150 parts by weight of the carbon black to 100 parts by weight of the rubber component containing 0 to 100% by weight.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, it is preferable to introduce a primary and / or secondary amino group from the viewpoint of excellent reactivity with an amino group or carbon black in the molecular chain of a rubber molecule. A point is given, and the rubber molecule in the rubber composition is chemically bonded to the acidic functional group portion of carbon black at the active point, so that the dispersibility of carbon black is improved. That is, the modification means imparting active sites in the rubber molecular chain. The molecular chain referred to here is the main chain and / or side chain in the rubber molecule in which the double bond portion is present.

The amino group introduced into the molecular chain of the rubber molecule in order to obtain the modified rubber in the present invention is provided by the compounds represented by the above formulas (I) and (II), and these compounds have the sulfur atom The part chemically bonds with the double bond part in the molecular chain of the rubber molecule.

Specific examples of the compound represented by the formula (I) include cysteamine, 4-aminobutanethiol, 6-
Aminohexanethiol, 4-aminocyclohexylthiol, 2-dimethylaminoethanethiol, 2-methylaminoethanethiol, 4-methylaminobutanethiol, 4-methylaminocyclohexylthiol, aminothiophenol and the like are mentioned, and the stereo group of the amino group is included. Primary amino groups such as cysteamine, 4-aminobutanethiol, and 4-aminocyclohexylthiol are preferred from the viewpoint that the smaller the hindrance, the better the bondability to carbon black, and X ¹ is a linear hydrocarbon group. Cysteamine and 4-aminobutanethiol are particularly preferable in that they are preferable.

Specific examples of the compound represented by the formula (II) include bis (2-aminoethyl) disulfide (cystamine), bis (2-dimethylaminoethyl) disulfide, bis (3-aminopropyl) tetrasulfide and bis. (Aminophenyl disulfide) and the like, and bis (2-aminoethyl) disulfide or bis (3-aminopropyl) tetrasulfide is preferred from the viewpoint that the smaller the steric hindrance of the amino group, the better the bondability with carbon black. Bis (3-aminopropyl) tetrasulfide is particularly preferable because it is preferable that it has a higher reactivity with rubber.

Of these, from the viewpoint of having high reactivity with carbon black, small steric hindrance, and having two active hydrogens which make it difficult to harden the obtained rubber composition,
Primary amines such as cysteamine, 4-aminobutanethiol and 4-aminocyclohexylthiol, 2-dimethylaminoethanethiol, 4-methylaminobutanethiol, 4-methylamino from the viewpoint of having one active hydrogen similar to the above. 2 such as cyclohexyl thiol
It is preferable to use a primary amine.

In the present invention, the compounds represented by the formulas (I) and (II) can be used in the form of salts.

The rubber which can be modified with the compound of the above formulas (I) and / or (II) includes primary and / or secondary amino groups provided by the compound at its terminal and / or side chain. Any rubber that can be incorporated into natural rubber (NR), isoprene rubber (I
R), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber,
Examples thereof include butyl rubber, halogenated butyl rubber, ethylene-propylene-diene rubber, epichlorohydrin rubber, acrylic rubber, and chloroprene. Natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, and acrylonitrile-butadiene are preferred because diene rubber is preferable. Rubber is preferable, and natural rubber, isoprene rubber, butadiene rubber and styrene-butadiene rubber are particularly preferable when used as a rubber composition for tires.

The modified rubber of the present invention contains 0.01 to 100 amino groups provided by the compound of formula (I) and / or (II) per 100 repeating units constituting the rubber.
If the number is 50, too small, the effect is small, and if it is too large, workability and mechanical strength are deteriorated, so that the number is preferably 0.05 to 30, and more preferably 0.1 to 10. .

As a method for producing a modified rubber by modifying the rubber, the rubber and the formula (I) and / or (II) are used.
The compound of (2) is kneaded in a closed kneader such as a twin-screw extruder or a Banbury mixer, preferably in an inert atmosphere such as N ₂ gas. In this case, the kneading temperature is 50 to 200 ° C., and if the temperature is too low, the reaction rate is too slow and it takes too long, and if it is too high, the molecules are cleaved due to oxidation and the like, the molecular weight is lowered and the physical properties are deteriorated. Is preferably 80 to 170 ° C., and the kneading time may be 0.5 to 30 minutes, preferably 1 to 15 minutes.

As another method for producing the modified rubber,
First, the rubber is dissolved in an organic solvent such as xylene or toluene, and then the formula (I) and / or (II) is added thereto.
Of a compound of 80 to 150 ° C., preferably 10 to 150 ° C. under an inert atmosphere such as nitrogen, argon or helium.
Heat at a temperature of 0 to 140 ° C. for 0.2 to 4 hours, preferably 0.5 to 1 hour. Then, after cooling, the rubber is washed with distilled water or the like, precipitated in a large amount of alcohol such as methanol, and dried to obtain the modified rubber of the present invention.

The present invention also relates to a rubber composition comprising a rubber component containing the modified rubber and carbon black (carbon black-containing rubber composition).

In this case, as the rubber component of the rubber composition other than the modified rubber, those usually used in the field of tires such as natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile- are used.
Diene rubbers such as butadiene rubber and chloroprene rubber, butyl rubber, halogenated butyl rubber, ethylene propylene-diene rubber and the like can be used, but natural rubber, isoprene rubber, from the viewpoint of easy modification,
It is preferable to use butadiene rubber or styrene-butadiene rubber.

As for the blending ratio of the modified rubber in the rubber component, it is sufficient that the modified rubber is contained in the rubber component, but it is 20 to 10 from the viewpoint of sufficiently bringing out the modifying effect.
It is preferably 0% by weight, more preferably 30 to 100% by weight from the viewpoint of more practical use.

Next, carbon black that can be used in the rubber composition containing carbon black of the present invention is not particularly limited, but examples thereof include furnace black, acetylene black, thermal black and channel black. Furnace black is particularly preferable from the viewpoint.

The nitrogen adsorption specific surface area of carbon black is such that it does not deteriorate the dispersibility of carbon black in the rubber composition containing carbon black of the present invention and does not deteriorate the wet grip of the rubber composition. Well, 50 to 250 m ² / g, preferably 70 to 230 m ²
/ G is preferable.

The DBP oil absorption of carbon black may be any amount which does not deteriorate the dispersibility of carbon black and the reinforcing property and processability of the rubber composition containing carbon black of the present invention, and is 60 to 150 ml / 10.
It is 0 g, preferably 80 to 140 ml / 100 g.

The blending ratio of carbon black in the rubber composition containing carbon black of the present invention is such that the dispersibility of carbon black and the processability of the rubber composition containing carbon black are not deteriorated and the wet grip property is not deteriorated. It is sufficient that carbon black 20 to 150 is added to 100 parts by weight of the rubber component containing the modified rubber.
The amount is preferably 30 to 80 parts by weight.

Further, as the other components of the rubber composition containing carbon black of the present invention, a reinforcing agent such as silica,
A filler, a vulcanizing agent such as sulfur, a vulcanization accelerator such as ZnO and / or stearic acid, a process oil such as aroma oil, and a compounding agent such as a processing aid are added to disperse carbon black and a rubber containing carbon black. The composition may be appropriately blended to such an extent that the processability of the composition is not deteriorated, the wet grip property is not reduced, and the rolling resistance is not increased.

The carbon black-containing rubber composition of the present invention may be prepared by physically kneading it using, for example, a roll or a Banbury mixer. The carbon black is dispersed in the carbon black-containing rubber composition. In order to make the composition uniform, it is preferable to add other compounding agents after adding rubber and carbon black.

The composition and production conditions of the carbon black-containing rubber composition of the present invention are as follows.

(Example 1) Modified rubber 100 parts by weight Carbon black 30 to 60 parts by weight Kneading time 3 to 5 minutes Kneading temperature 100 to 170 ° C. This is a dispersion of carbon black in a rubber composition containing carbon black. Can be uniform, 70 ℃
Tan δ at low temperature and tan at −10 ° C.
It has the advantage that δ is high.

(Example 2) Modified rubber 20 to 100 parts by weight Other rubber components (NR, SBR, IR, BR 80 to 0 parts by weight and / or butyl rubber, etc.) Carbon black 30 to 60 parts by weight Kneading time 3 to 5 Minute kneading temperature 100 to 170 ° C. This can make the dispersion of carbon black in the rubber composition containing carbon black uniform, and is 70 ° C.
Tan δ at low temperature and tan at −10 ° C.
Not only does it have the advantage of high δ and there is a cost advantage by reducing the amount of the modified rubber used, but it also has the advantage that the range of compounding design is widened by blending with different types of rubber.

[0036]

EXAMPLES Next, the method for producing the modified rubber and the carbon black-containing rubber composition of the present invention will be explained more specifically based on examples, but the present invention is not limited to these.

Example 1 100 parts by weight of SBR-a and 0.39 parts by weight of cysteamine were mixed by an open roll at 60 ° C.
Modified rubber 1 was obtained by kneading at 145 ° C. for 5 minutes using a Banbury mixer. However, as SBR-a, SBR manufactured by Sumitomo Chemical Co., Ltd. (styrene content 29% by weight, butadiene portion vinyl content 39% by weight) was used.

Example 2 SBR-a (80 g) was dissolved in xylene (1.4 liter), cysteamine (0.31 g) was added, and the mixture was placed under a nitrogen atmosphere.
Heated at 135 ° C. for 2 hours. After cooling down, wash with distilled water,
The modified rubber 2 was obtained by precipitating the rubber in a large amount of methanol and drying it in vacuum.

Example 3 A modified rubber 3 was obtained in the same manner as in Example 2 except that the amount of cysteamine added was 1.23 g.

Example 4 SBR-b (80 g) was dissolved in xylene (1.4 liter), cysteamine (0.62 g) was added, and the mixture was placed under a nitrogen atmosphere.
Heated at 135 ° C. for 2 hours. After cooling down, wash with distilled water,
Modified rubber 4 was obtained by precipitating the rubber in a large amount of methanol and drying it in vacuum. However, SBR-b
SBR1502 manufactured by Sumitomo Chemical Co., Ltd. (styrene content 23.5% by weight, butadiene portion vinyl content 1)
6 wt%) was used.

Example 5 A modified rubber 5 was obtained in the same manner as in Example 4 except that 1.00 g of 4-aminothiophenol was used instead of 0.62 g of cysteamine.

Example 6 A modified rubber 6 was obtained in the same manner as in Example 4 except that 0.90 g of cystamine dihydrochloride was used instead of 0.62 g of cysteamine.

Examples 7 to 9 and Comparative Examples 1 and 2 The modified rubbers 1 to 3 or SBR-a obtained in Examples 1 to 3 were used in the proportions shown in Table 1 using a Banbury mixer.
By kneading at 115 ° C. for 4 minutes, rubber compositions 1 to 3 containing carbon black of the present invention and comparative rubber compositions 1 and 2 were obtained. However, carbon black has a nitrogen adsorption specific surface area of 183 m ² / g and a DBP oil absorption of 120 ml /
A 100 g one was used.

[0044]

[Table 1]

Evaluation Carbon black-containing rubber composition 1 obtained in Examples 4 to 6
~ 3 and Comparative Rubber Composition 1 obtained in Comparative Examples 1 and 2
Hysteresis loss (tan δ) at −10 ° C. and 70 ° C. of No. 2 and No. 2 are VES-II manufactured by Iwamoto Manufacturing Co., Ltd.
It was measured using I under the condition of 10 Hz and an amplitude of ± 0.25%. In addition, WIR, RIR and TIR were calculated by the following formulas. W.I.R. = {Tan δ (-10 ° C.)-Tan δ _c (-10
℃)} / tan δ _c (−10 ℃) R.I.R. = {Tan δ _c (70 ℃) -tan δ (70 ℃)} / t
an δ _c (70 ° C) T.I.R. = W.I.R. + 2 (R.I.R.)

However, tan δ _c (-10 ° C) and t
an δ _c (70 ° C.) is the tan δ at −10 ° C. and 70 ° C. of the rubber composition of Comparative Example 1, that is, the rubber composition composed of the rubber not modified with the compound represented by Formula 1 or Formula 2. In general, the value of tan δ largely depends on the types and amounts of carbon black, softening agents, vulcanizing agents, etc., and these are not only wet grip properties and fuel economy in the conventional technique, but also other properties such as resistance to resistance. It is optimized in consideration of balance with characteristics such as wearability and workability. Therefore, in order to investigate the modifying effect of the compound of formula (I) and / or formula (II),
It is necessary to compare with the rubber composition of Comparative Example 1 used as a control. In addition, the reason that R.I.R. is doubled in the formula of T.I.R. is that it is weighted in consideration of the merit and difficulty of the modification.

Further, using a Mooney viscometer SMV-202 manufactured by Shimadzu Corporation, carbon black-containing rubber compositions 1 to 7 and comparative rubber composition 1 at 130 ° C.
Scorch time (t ₁₀ ) (min) of ˜4 was measured.

The results are shown in Table 2.

[0049]

[Table 2]

Examples 10 to 13 and Comparative Examples 3 and 4 Using the modified rubbers 4 to 6 and SBR-b obtained in Examples 4 to 6 and using the Banbury mixer at the ratios shown in Table 3, 1
The carbon black-containing rubber composition 4 of the present invention was kneaded at 00 ° C. (Banbury set temperature) for 4 minutes.
7, comparative rubber compositions 3 and 4 were obtained. The same carbon black as in Example 7 was used.

[0051]

[Table 3]

Evaluation The carbon black-containing rubber compositions 4 to 7 obtained in Examples 10 to 13 and the comparative rubber compositions 3 and 4 obtained in Comparative Examples 3 and 4 were evaluated in the same manner as in Example 7. However, the rubber composition of Comparative Example 3 was used as a control.

The results are shown in Table 4.

[0054]

[Table 4]

[0055]

According to the present invention, a modified rubber having an amino group in the molecular chain of the rubber molecule can be obtained. When the modified rubber of the present invention is used, it is possible to obtain a carbon black-containing rubber composition for tires having high wet grip properties and low rolling resistance.

Claims (3)

[Claims] 1. Formula (I): (However, R ¹ and R ² are independently H or 1 carbon
To an alkyl group, X ¹ is a hydrocarbon group having 1 to 12 carbon atoms and / or a compound represented by the formula (II): (However, R ³ , R ⁴ , R ⁵ and R ⁶ are independently H or an alkyl group having 1 to 3 carbon atoms, X ² and X ³ are independently hydrocarbon groups having 1 to 12 carbon atoms, and n is A rubber modified with a compound represented by the formula (1 to 12). 2. A rubber composition for a tire comprising a rubber component containing the modified rubber according to claim 1 and carbon black. 3. 100 parts by weight of a rubber component containing 20 to 100% by weight of the modified rubber and a nitrogen adsorption specific surface area of 50 to 2
50m ² / g, DBP oil absorption is 60 ~ 150ml
The rubber composition for a tire according to claim 2, comprising 20 to 150 parts by weight of carbon black of 100 g / 100 g.