JPH10120828A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent gelation of a rubber in high-temp. kneading and thus obtain a rubber compsn. improved in workability, etc., by compounding a natural rubber and/or a synthetic diene rubber with silica, a specific silane coupling agent, and amine compd. SOLUTION: A natural or a synthetic rubber is used alone or as a blend. The objective rubber compsn. is prepd. by compounding 100 pts.wt. rubber with 10-85 pts.wt. synthetic silica produced by the precipitation method, 1-20wt.% (based on the silica) silane coupling agent represented by formula I (wherein n is 1-3; m is 1-9; and l is 1 or higher) of which the distribution of -Si- in formula I satisfies the relation represented by formula II, 1-15wt.% (based on the silca) tert. amine compd. represented by formula III (wherein R<a> to R<c> are each methyl, 8-36C alkyl, 8-36C alkenyl, cyclohexyl, or benzyl), up to 80 pts.wt. carbon black as the reinforcement, and if necessary, a softener, an antioxidant, a vulcanizing agent, etc., and kneading the resultant compsn. at 150-180 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition blended with silica using a silane coupling agent, and more particularly, to suppress gelation of a polymer by a silane coupling agent during high-temperature kneading at 150 ° C. or higher. The present invention relates to a rubber composition capable of efficiently reacting silica and a silane coupling agent without lowering workability, and further improving low heat generation and abrasion resistance.

[0002]

2. Description of the Related Art Conventionally, rubber reinforcing fillers include:
Carbon black is used. This is because carbon black has higher reinforcing properties and better abrasion resistance than other fillers. However, in recent years, under the social demands for energy saving and resource saving, fuel consumption of automobiles has been reduced. Therefore, it has been required at the same time to reduce the heat generation of the compound rubber.

In order to reduce the heat generation of a compound rubber by carbon black, a small amount of carbon black must be filled,
Alternatively, use of a large particle size carbon black is conceivable, but it is well known that in any of the methods, the reduction in heat generation has a trade-off relationship with the reinforcing property and the wear resistance.

On the other hand, silica is known as a filler for lowering the heat generation of the compound rubber, and many patents have been filed, such as JP-A-3-252431.

However, silica particles tend to agglomerate due to hydrogen bonds of silanol groups, which are surface functional groups. To improve the dispersibility of silica particles in rubber, the kneading time must be increased. There is a need. In addition, if the dispersion of the silica particles in the rubber is insufficient, the Mooney viscosity of the rubber composition becomes high, causing problems such as poor processability such as extrusion.

Further, since the surface of the silica particles is acidic, when vulcanizing the rubber composition, it absorbs a basic substance used as a vulcanization accelerator, and vulcanization is not sufficiently performed, and There was also a problem that the rate did not increase.

[0007] In order to solve these problems, various silane coupling agents have been developed.
No. 29741 describes that a silica coupling agent is used as a reinforcing material. However, even this silica-coupling-agent-based reinforcing material is still insufficient to bring the breaking properties, workability and processability of the rubber composition to a high level. Further, Japanese Patent Publication No. 51-20208 discloses a rubber composition using a silica-silane coupling agent as a reinforcing material. According to such a silica-silane coupling agent-based reinforcement, the reinforcing property of the compounded rubber can be remarkably improved, and the breaking characteristics can be improved. Further, there is a disadvantage that the workability is reduced.

The disadvantages of the prior art due to the use of such a silane coupling agent are caused by the following mechanism.
That is, when the rubber kneading temperature is low, the silanol group on the silica surface does not sufficiently react with the silane coupling agent, and as a result, the reinforcing effect cannot be obtained. Further, the silica is poorly dispersed in the rubber, resulting in deterioration of low heat build-up, which is an advantage of the silica compounded rubber. Furthermore, the alcohol produced by partially reacting between the silanol group on the silica surface and the silane coupling agent does not volatilize completely due to the low kneading temperature,
Alcohol remaining in the rubber in the extrusion process is vaporized, and blisters are generated.

On the other hand, when kneading at a high kneading temperature of 150 ° C. or higher, the silanol groups on the silica surface react sufficiently with the silane coupling agent, and as a result, the reinforcing property is improved.
Also, the dispersion of silica in the rubber is improved, and a kneaded rubber with low heat generation can be obtained, and the generation of blisters in the extrusion step can be suppressed. However, in this temperature range, the gelation of the polymer derived from the silane coupling agent occurs at the same time, and the Mooney viscosity increases significantly, making it impossible to actually perform processing in a subsequent step.

Therefore, when a silane coupling agent is used in combination with silica, it is necessary to perform low-temperature kneading at a temperature lower than 150 ° C. in multiple stages, and at present, a remarkable decrease in productivity cannot be avoided.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and suppresses gelation of a polymer by a silane coupling agent during high-temperature kneading at 150 ° C. or more, thereby reducing workability. It is an object of the present invention to provide a rubber composition which efficiently performs reaction between silica and a silane coupling agent without causing the heat generation, and further improves low heat generation and abrasion resistance.

[0012]

Means for Solving the Problems The present inventors have conducted intensive studies on rubber compositions containing silica in order to solve the above-mentioned problems, and as a result, have determined the distribution of bound sulfur of various compounds in a silane coupling agent. Thus, it has been found that even at a high temperature kneading of 150 ° C. or more, an increase in the Mooney viscosity of the compound rubber is suppressed, and a rubber composition excellent in workability and low in heat generation can be obtained. Furthermore, by mixing a specific tertiary amine compound into silica in a specific amount, the dispersibility of silica in rubber is greatly improved, and a rubber composition having low heat generation characteristics and high wear resistance can be obtained. And completed the present invention.

That is, the present invention is as follows. (1) With respect to 100 parts by weight of natural rubber and / or diene-based synthetic rubber, 10 to 85 parts by weight of silica and the following general formula: (Wherein, n is an integer of 1-3, m is an integer of 1-9, l is 1
A silane coupling agent represented by the following formula (having a distribution represented by the above integers), wherein -S ₁ -distribution in the above formula is represented by the following formula: (S ₁ + S ₂ + S ₃ + S ₄ ) / (S ₅ + S ₆₎ + S ₇ + S
₈ + S ₉ ) ≧ 0.85, a silane coupling agent satisfying the relationship represented by the following formula: (Wherein, R ^a , R ^b and R ^c each represent any one of a methyl group, an alkyl group having 8 to 36 carbon atoms, an alkenyl group having 8 to 36 carbon atoms, a cyclohexyl group and a benzyl group) The amine compound represented by 1 to the amount of silica
It is a rubber composition characterized by being blended in an amount of up to 15% by weight.

(2) In the rubber composition according to the above (1), the -S ₁ -distribution in the above formula is as follows: (S ₁ + S ₂ + S ₃ ) / (S ₄ or more components) ≧ 0.45 satisfies the relation expressed, and a rubber composition S ₃ component is 20% or more.

(3) In the rubber composition as described in (1) above, the -S ₁ -distribution in the above formula is as follows: (S ₁ + S ₂ + S ₃ ) / (S ₄ or more component) ≧ 0.55 satisfies represented by relationships, and a rubber composition S ₃ component is 30% or more.

(4) In the rubber composition according to any one of the above (1) to (3), as a reinforcing filler,
Further, the rubber composition is obtained by blending carbon black in an amount of 80 parts by weight or less based on 100 parts by weight of the rubber component.

(5) The rubber composition according to any one of the above (1) to (3), wherein anhydrous sodium sulfide (Na ₂ S) and sulfur (S) are mixed in a polar solvent under an inert gas atmosphere. In a molar ratio of 1: 1 to 1: 2.5 in order to obtain sodium polysulfide, which is then reacted with the following general formula: (Wherein, R ¹ and R ² are each an alkyl group having 1 to ³ carbon atoms, R ³ is a divalent hydrocarbon group having 1 to 9 carbon atoms, X is a halogen atom, and k is an integer of 1 to 3) The compound obtained is a rubber composition used as the silane coupling agent by adding a halogenoalkoxysilane and reacting the mixture under an inert gas atmosphere.

[0018]

Embodiments of the present invention will be described below in detail. As the rubber component in the present invention, natural rubber (NR) or synthetic rubber can be used alone or as a blend thereof. Examples of the synthetic rubber include synthetic polyisoprene rubber, polybutadiene rubber (BR), styrene butadiene rubber (SBR), butyl rubber, and butyl halide.

The silica used in the present invention is a synthetic silica prepared by a precipitation method. Specifically, Nip Seal AQ manufactured by Nippon Silica Kogyo Co., Ltd.
ULTRASIL VN3, BV3370GR, RP1165MP, Zeosil 165GR, Zeosil 175MP, manufactured by Rhone Poulin
Examples include Hisil 233, Hisil 210, Hisil 255 and the like (all trade names) manufactured by PPG, but are not particularly limited.

The amount of the silica is determined according to the above rubber component 1
10 to 85 parts by weight, preferably 20 parts by weight, per 100 parts by weight
６５65 parts by weight. If the compounding amount of silica is less than 10 parts by weight, the reinforcing property cannot be obtained, while if it exceeds 85 parts by weight, workability such as hot extrusion is deteriorated, which is not preferable. In terms of low heat generation and workability, the amount of silica is 20
~ 65 parts by weight are preferred.

The silane coupling agent used in the present invention has the following general formula: (Where n is an integer of 1 to 3, m is an integer of 1 to 9, l is 1
The silane coupling agent is represented by the following formula (having a distribution represented by the above integer), and the -S ₁ -distribution in the above formula is represented by the following formula: (S ₁ + S ₂ + S ₃ + S ₄ ) / (S ₅ + S ₆ + S) ₇ + S
₈ + _{S 9)} ≧ 0.85, preferably the following _{formula, (S 1 + S 2 +} S 3 + S 4) / (S 5 + S 6 + S 7 + S
₈ + S ₉ ) ≧ 1.0. When the distribution ratio is less than 0.85, the effect of suppressing the gelation of the polymer cannot be obtained in high-temperature kneading at 150 ° C. or more,
The Mooney viscosity is greatly increased, resulting in poor productivity. Here, the value of (S ₁ + S ₂ + S ₃ ) / (component of S ₄ or more) in the −S ₁ − distribution in the above expression is preferably 0.4.
5 above, and _{S 3} component is more than 20%, more preferably the value of _{(S 1 + S 2 + S} 3) / (S 4 or more component) 0.5
5 above, and is _{S 3} component is more than 30%. If the value of the above formula is less than 0.45, the effect of suppressing the gelation of the polymer cannot be sufficiently obtained at a high temperature kneading at 150 ° C. or more, and the Mooney viscosity increases, resulting in poor productivity. Also, S ₃
When the amount of the component is 20% or more, the amount of the S ₁ and S ₂ components having no coupling action is relatively reduced, and does not hinder the improvement of abrasion resistance derived from a tertiary amine described below.

The amount of the silane coupling agent is 1 to 20% by weight, preferably 3 to 15% by weight based on the weight of silica. If the amount of the silane coupling agent is less than 1% by weight, the coupling effect is small, while if it exceeds 20% by weight, gelation of the polymer is caused, which is not preferable.

Specific examples of the tertiary amine compound represented by the above general formula used in the present invention include trioctylamine, trilaurylamine, dimethylstearylamine, dimethyldecylamine, dimethylmyristylamine, dilaurylmonomethylamine, dimethyloctaamine. Decenylamine,
Dimethylhexadecenylamine and the like.

The amount of the tertiary amine compound is 1 to 15% by weight, preferably 3 to 10% by weight, based on silica. If the amount of the tertiary amine compound is less than 1% by weight, the desired improvement in dispersibility, low heat build-up and abrasion resistance cannot be exhibited.
Since the effect of improving the dispersion of silica is saturated and the tertiary amine compound functions as a plasticizer, the abrasion resistance is lowered, which is not preferable.

As the carbon black used as the reinforcing filler in the present invention, SAF, ISAF, and HAF grades can be preferably used, but are not particularly limited.

The amount of the carbon black is preferably 80 parts by weight or less based on 100 parts by weight of the rubber component. When the amount of the carbon black is more than 80 parts by weight, the low heat build-up is significantly deteriorated. 25 to 60 parts by weight is preferable from the viewpoint of reinforcing properties and low heat generation.

In the rubber composition of the present invention, in addition to the above rubber component, silica, silane coupling agent, tertiary amine compound and carbon black, if necessary,
Compounding agents usually used in the rubber industry, such as a softening agent, an antioxidant, a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerator, can be appropriately compounded.

In utilizing the properties of the rubber composition of the present invention,
The kneading temperature is preferably from 150 ° C to 180 ° C. If the kneading temperature is lower than 150 ° C., the silane coupling agent does not react sufficiently and blisters are generated at the time of extrusion. On the other hand, if the kneading temperature is higher than 180 ° C., the gelation of the polymer also occurs, and the Mooney viscosity increases, resulting in processing. This is not preferred.

In the rubber composition of the present invention, why 150
The action mechanism of whether the polymer does not gel even at a kneading temperature of not less than ° C and the low heat build-up property is improved will be described below based on speculations and examination results. Silane coupling agents commonly used in the tire industry (trade name: Si
69, manufactured by Degussa Deutschland GmbH) in an oven at 150 ° C. for 2 hours. After cooling, the mixture was analyzed by high-performance liquid chromatography. As a result, a component having -S ₆ -or more long-chain sulfur in the molecule was obtained. It is reduced compared to the original product, free sulfur and -S 4 _- component having the short chain sulfur has been confirmed to increase. That is, by receiving high-temperature heat history, -S 6 in the molecule _- components having more long chain sulfur is considered to have decomposed. At the time of such decomposition, it is expected that the polymer is gelled in the high-temperature kneading because radicals are generated or the decomposition product functions as a sulfur supplier.
Therefore, the results of intensive studies based on the presumption that if the component containing long-chain sulfur in the molecule contained in the silane coupling agent is reduced in advance, the gelation of the polymer is suppressed in high-temperature kneading at 150 ° C or higher. When the proportion of the short-chain sulfur component in the component having various lengths of chain sulfur in the molecule is set to a predetermined value or more, the gelation of the polymer is actually suppressed, and the silanol on the silica surface is kneaded at a high temperature. It was found that the reaction between the group and the silane coupling agent was sufficiently caused to improve the dispersibility of the silica in the rubber, resulting in low heat generation. Further, it is considered that the nitrogen atom of the amine has a high ability to form a hydrogen bond with the silanol group on the silica surface and the aggregation of the silica particles is prevented by the masking effect of the silanol group on the silica surface. Since this reaction is chemisorption, this effect is exerted even in a low temperature region around room temperature. Accordingly, from the low temperature range at the initial stage of rubber kneading, there is an effect of preventing aggregation of silica particles. As a result, the rubber composition of the present invention has an effect of greatly improving the dispersion of silica in rubber, and has a low heat generation. It is assumed that the properties and abrasion resistance are improved.

[0030]

The present invention will be described more specifically with reference to the following examples. Various rubber compositions were prepared with the basic compounding ratios shown in Table 2 below and the compounding contents shown in Tables 3 and 4 below. In addition, the various silane coupling agents used in such a formulation are represented by the following formula: (C ₂ H ₅ O) ₃ Si (CH ₂ ) ₃ -S _1- (CH ₂ )
₃ Si is represented by _{(C 2 H 5 O) 3} , -S l in the formula - are in the distribution relationship shown in Table 1 below. Each chain sulfur components shown in Table 1 _(-S l -)
Was calculated from a peak area (%) determined by a high performance liquid chromatography (HPLC) analysis method specifically shown below.

HPLC Analysis Conditions HPLC: Tosoh HLC-8020 UV Detector: Tosoh UV-8010 (254)
nm) Recorder: Super System Controller SC-8010 manufactured by Tosoh Corporation Column: TSKgel ODS- manufactured by Tosoh Corporation
80T _M CTR (inner diameter: 4.6 mm, length: 10 cm) Measurement temperature: 25 ° C. Sample concentration: 6 mg / 10 cc acetonitrile solution Sample injection amount: 20 μl Elution condition: flow rate 1 cc / min acetonitrile: water = 1: 1 mixed solution And eluted with a gradient over 18 minutes so that acetonitrile became 100%.

Analysis of the silane coupling agent (Si69, Degussa, Germany) of Sample A in Table 1 under the above conditions showed that the free sulfur was reduced to about 17.5 minutes in peak time, and 1
9.5, 20.6, 21.7, 22.8, 24.0, 2
-S near 5.4, 27.1 and 29.0 minutes respectively
_{2 -, - S 3 -,} - S 4 -, - S 5 -, - S 6 -, - S
_{7 -, - S 8 -,} - S 9 - peak of was isolated. Each peak area was _{measured, (S 1 + S 2 +} S 3 + S 4) values and _{(S 5 + S 6 + S} 7 + S 8 + S 9) value is calculated, further _{(S 1 + S 2 + S} 3 + S 4) / ( S ₅ + S ₆ + S ₇
+ S ₈ + S ₉ ) was 0.73. Also, the value of (S ₁ + S ₂ + S ₃ ) and the value of (S ₄ + S ₅₎
+ S ₆ + S ₇ + S ₈ + S ₉ ), and further calculates (S <sub>1
+ S 2 + S 3) /</sub> (S 4 + S 5 + S 6 + S 7 + S 8 + S
₉ ) was 0.225. Each value was similarly obtained for Samples B to D in Table 1.

[0033]

[Table 1] * 1 Si69 manufactured by Degussa of Germany * 2 Sample B to D prototype

Preparation of Samples B and C According to the method described in JP-A-7-228588, anhydrous sodium sulfide and sulfur were synthesized at the following molar ratios. Sample B 1: 2.5 Sample C 1: 1.5

Preparation of Sample D The compound was synthesized by oxidizing γ-mercaptopropyltriethoxysilane using manganese dioxide as a catalyst according to the method described in EP 0 732 362 A1.

The obtained rubber composition was evaluated for abrasion resistance, Mooney viscosity, hysteresis loss characteristics (heat generation), and presence or absence of blisters by the following evaluation methods.

(1) Abrasion resistance The abrasion resistance index indicating the abrasion resistance was measured using a Lambourn abrasion tester, using BS (British Standard) standard 903 (part A).
It was measured at a contact pressure of 5 kg / cm ² and a slip ratio of 40% by a method according to Method D, and calculated by the following equation. Abrasion resistance index = (weight loss of control / weight loss of test specimen) × 100 The larger the index, the better the wear resistance.

(2) Mooney viscosity According to JIS K6301, preheating 1 minute, measurement 4 minutes,
It was measured at a temperature of 130 ° C. and expressed as an index relative to the control. The smaller the index value, the lower the Mooney viscosity and the better the processability.

(3) Measurement of hysteresis loss characteristics (exothermicity) The internal loss (tan δ) was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the conditions of dynamic tensile strain of 1%, frequency of 50 Hz and 60 ° C. Was measured. The test piece was a slab sheet with a thickness of about 2 mm and a width of 5 mm.
The initial load was set to 160 g with the inter-use distance of 2 cm. The value of tan δ was expressed as an index relative to the control. The smaller the index value, the smaller the hysteresis loss and the lower the heat generation.

In the above evaluations, Comparative Example 1 was used in Examples 1 to 9 and Comparative Examples 1 to 4, Comparative Example 5 was used in Example 10 and Comparative Examples 5 to 7, and Example 11 was used.
In Comparative Examples 8 to 12, the rubber compositions of Comparative Example 8 were used as controls.

(4) Presence or absence of blister generation Rheograp manufactured by GOTTFERT
h) Measured at 2000. Extrusion opening is 9mm x 2mm
The measurement was performed at 120 ° C. using a rectangular die having a thickness of 2 mm. Remaining heat time 3 minutes, piston extrusion speed 1
The extruded product was extruded at 0 mm / sec, and whether or not blisters were generated in the extruded product was visually determined.

[0042]

[Table 2] * 1 N-phenyl-N'-isopropyl-P-phenylenediamine * 2 N-oxydiethylene-2-benzothiazolesulfenamide

[0043]

[Table 3] * 1 Nippon Synthetic Rubber Co., Ltd. * 2 Nippon Silica Industry Co., Ltd. * 3 Tokai Carbon Co., Ltd.

[0044]

[Table 4] * 1 Nippon Synthetic Rubber Co., Ltd. * 2 Nippon Silica Industry Co., Ltd. * 3 Tokai Carbon Co., Ltd.

[0045]

As described above, according to the present invention, at the time of high-temperature kneading at 150 ° C. or more, the occurrence of blisters in the extrusion step is suppressed, and at the same time, the gelation of the polymer by the silane coupling agent is suppressed. The reaction between the silica and the silane coupling agent is carried out efficiently without lowering the workability, and the dispersibility of the silica in the rubber is improved, thereby exhibiting excellent effects on abrasion resistance and low heat generation. .

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 7/00 C08L 7/00

Claims (5)

[Claims] 1. Natural rubber and / or diene synthetic rubber 1
With respect to 00 parts by weight, 10 to 85 parts by weight of silica and the following general formula: (Wherein, n is an integer of 1-3, m is an integer of 1-9, l is 1
A silane coupling agent represented by the following formula (having a distribution represented by the above integers), wherein -S ₁ -distribution in the above formula is represented by the following formula: (S ₁ + S ₂ + S ₃ + S ₄ ) / (S ₅ + S ₆₎ + S ₇ + S
₈ + S ₉ ) ≧ 0.85, a silane coupling agent satisfying the relationship represented by the following formula: (Wherein, R ^a , R ^b and R ^c each represent any one of a methyl group, an alkyl group having 8 to 36 carbon atoms, an alkenyl group having 8 to 36 carbon atoms, a cyclohexyl group and a benzyl group) The amine compound represented by 1 to the amount of silica
1 to 15% by weight of a rubber composition. 2. The -S ₁ -distribution in the above expression satisfies the following expression: (S ₁ + S ₂ + S ₃ ) / (S ₄ or more components) ≧ 0.45, and S ₃ component Is 20% or more. 3. The -S ₁ -distribution in the above expression satisfies the following expression: (S ₁ + S ₂ + S ₃ ) / (S ₄ or more components) ≧ 0.55 and S ₃ component Is 30% or more. 4. The rubber composition according to claim 1, wherein the reinforcing filler further comprises carbon black in an amount of 80 parts by weight or less based on 100 parts by weight of the rubber component. 5. A sodium polysulfide obtained by reacting anhydrous sodium sulfide (Na ₂ S) and sulfur (S) in a polar solvent in an inert gas atmosphere at a molar ratio of 1: 1 to 1: 2.5. And then this sodium polysulfide is represented by the following general formula: (Wherein, R ¹ and R ² are each an alkyl group having 1 to ³ carbon atoms, R ³ is a divalent hydrocarbon group having 1 to 9 carbon atoms, X is a halogen atom, and k is an integer of 1 to 3) The rubber composition according to any one of claims 1 to 3, wherein the halogenoalkoxysilane represented by the formula (1) is added and reacted under an inert gas atmosphere, and the obtained compound is used as the silane coupling agent. Stuff.