JPH1160809A - Rubber composition and heavy duty tire therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber compsn. and a heavy duty pneumatic tire therewith which are excellent in low rolling resistance, anti-wear property, and anti-tear cracking characteristic. SOLUTION: This rubber compsn. consists of a tread rubber comprising 40-55 parts total quantity of carbon black and silica, wherein silica content is 5-25 parts, the carbon content/silica content is not less than 1, the carbon black has a nitrogen adsorption specific surface area (N2 SA) of 70-170 m<2> /g and a dibutylphthalate(DBP) oil absorption of 100-200 cm<3> /100 g, and the silica has a nitrogen adsorption specific surface area (N2 SA) of 120-240 m<2> /g and a DBP oil absorption of 170-250 cm<3> /100 g, to 100 parts rubber component comprising 10-100 parts natural rubber and 90-0 parts diene rubber, and also 3-30% silane coupling agent represented by the formula (wherein (n) is an integer of 1-3; (m) is an integer of 1-9; and (y) is an average no. of sulfur atoms in a polysulfide, and is a positive no., satisfying 2.0<y<=3.5) to the silica content.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition and a heavy-duty pneumatic tire using the same, and more particularly to a low rolling resistance, that is, a low heat generation, a wear resistance, and a tear resistance.
The present invention relates to a rubber composition having excellent cracking properties and a heavy-duty pneumatic tire using the same.

[0002]

2. Description of the Related Art From the viewpoints of global warming and effective use of energy, vehicles are required to have improved fuel efficiency, and in order to meet the demand, tires are required to have low rolling resistance (low heat generation). . At the same time, from the standpoint of global environmental protection, tires are strongly demanded to have an improved life (durability) from the viewpoint of effective use of resources and improvement of the recycling rate. Tire life improvement is governed by the wear resistance factor, and the tear and crack resistance factor of truck and bus tires, which are used for heavy loads, which are severer in use than passenger car tires, and are greatly influenced by both factors . That is, a heavy-duty pneumatic tire is required to have both low rolling resistance and improved life (wear resistance, tear and crack resistance).

However, conventionally, if the tread rubber satisfies the low rolling resistance, the abrasion resistance and the tear cracking resistance are inferior. If the abrasion resistance and the tear cracking resistance are improved, the low rolling resistance is not satisfied. It is well known that both characteristics have a trade-off relationship, and it is not easy to achieve both characteristics.

On the other hand, various rubber compositions for tire treads have been studied. For example, in a rubber composition for a tire tread having a cap / base structure, a predetermined amount of a rubber component is determined for each of the two-layer structure of the cap and the base. By using a diene rubber such as natural rubber, a specific amount of specific silica and carbon black as a filler, and a normal silane coupling agent, it is possible to obtain a tire that suppresses heat generation during traveling and maintains abrasion resistance. Such proposals are known.

However, by using silica and carbon black in combination and using an ordinary silane coupling agent,
Low heat build-up (generally 10-20% less heat build-up compared to carbon blacks used) and increased tear elongation due to increased elongation at break, but wear resistance is higher than normal carbon blacks 5-10% lower than
Not enough.

In addition, when silica is compounded, it is difficult to secure dispersion in rubber due to its small particle size. For this reason, the silica blending system has a large Banbury kneading load,
In fact, power consumption during the production of the rubber composition is increased, which is not preferable from the viewpoint of ecology, and the production cost is increased.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and an object of the present invention is to achieve a high balance between low rolling resistance (low heat generation), abrasion resistance and tear crack resistance. And a heavy duty pneumatic tire using the same.

[0008]

Means for Solving the Problems The present inventor paid attention to the rubber composition of the tire tread, and as a result of diligent studies, found that the following means could solve the problem and completed the present invention.

That is, (1) The rubber composition of the present invention comprises:
10-100 parts by weight of natural rubber and other diene rubber 90
100 parts by weight of a rubber component consisting of 0 to 0 parts by weight, the total amount of carbon black and silica is 40 to 55 parts by weight, of which the amount of silica is 5 to 25 parts by weight, The mixing ratio of black amount / silica amount is 1
Above, and the said carbon black has a nitrogen adsorption specific surface area ^{_{(N 2 SA) 70~170m 2 /}} g, and a dibutyl phthalate (DBP) oil absorption of 100~200cm ^3/100
g, and the silica is N ₂ SA 120-240 m
² / g, and DBP oil absorption amount 170~250cm ^3/10
It is characterized by comprising a tread rubber having a characteristic of 0 g and containing a silane coupling agent represented by the following general formula (I) in an amount of 3 to 30% by weight, preferably 5 to 15% by weight of the amount of silica. I do.

[0010]

Embedded image

(Wherein, n is an integer of 1 to 3, m is an integer of 1 to 9, y is the average number of sulfur atoms in the polysulfide moiety, and 2.0 <y ≦ 3.5, preferably 2. (It represents a positive number of 5 ≦ y ≦ 3.) (2) In the above item (1), it is preferable that the natural rubber contains at least 30% by weight of technically rated natural rubber (TSR) in 100% by weight of the natural rubber.

(3) In the above item (1), the rubber composition may further contain a tertiary amine compound represented by the following general formula (II) in an amount of 0.1 to 20% by weight based on the amount of silica. preferable.

[0013]

Embedded image

(Wherein R ¹ , R ² and R ³ each independently represent a methyl group, an alkyl group having 8 to 36 carbon atoms,
(4) In the above item (3), R ¹ and R ^{2 in} the general formula (II) described in the item (3) are methyl groups; ³ has 12 carbon atoms
It is preferably an alkyl group of ~ 36. (5) In the above item (3), the tertiary amine compound is preferably dimethylstearylamine. (6) A heavy duty pneumatic tire using the rubber composition according to any one of the above (1) to (5) as a tread rubber.

The rubber composition for a heavy duty tire according to the present invention comprises:
As described above, the type and amount of the rubber component are specified, and the characteristics, total amount, and compounding amount (mixing ratio) of the carbon black and silica as the reinforcing filler are specified. In particular, the type and amount of the silane coupling agent are specified. It is characterized by using a specific tertiary amine compound as a silica dispersion improver, if necessary.

In the rubber composition of the present invention, the rubber component is mainly composed of natural rubber, and an appropriate amount of butadiene rubber is used.
A high level of balance between low rolling resistance, abrasion resistance, and tear cracking resistance, and preferably by using TSR and, if necessary, using a specific tertiary amine to obtain silica rubber Improve dispersibility inside,
By further improving low rolling resistance (low heat generation) and tear and crack resistance, and by specifying each property of carbon black and silica, abrasion resistance is maintained by maintaining reinforcement and tear resistance is maintained by maintaining elongation at break. Crack resistance is maintained at a high level, and by specifying the total amount of both reinforcing fillers, abrasion resistance is maintained, tear and crack resistance is maintained by maintaining elongation at break, and further, low heat generation (low rolling resistance) Is also maintained, and by specifying each blending amount (mixing ratio) of both reinforcing fillers, low heat build-up, elongation at break, and decrease in wear resistance are suppressed,
More particularly, through the use of specific silane coupling agents,
The abrasion resistance is improved, and the low heat build-up is further improved.

As described above, a new finding that the problem can be solved by optimizing the rubber composition has been obtained.
Here, a rubber composition and a heavy-duty pneumatic tire using the rubber composition, which simultaneously have low rolling resistance, abrasion resistance, and tear crack resistance, are obtained.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the present invention comprises:
Natural rubber (NR) 10-1 in 100 parts by weight of all rubber components
00 parts by weight, preferably 40 to 100 parts by weight, and 90 to 0 parts by weight of another diene rubber, preferably 60 to 0 parts by weight. Other diene rubbers include synthetic isoprene rubber, butadiene rubber (BR) such as high cis 1,4-polybutadiene, and emulsion polymerized styrene butadiene rubber (SB).
R) and SBR such as solution polymerization SBR. Among them, BR is preferably used. When a blend system of NR and BR is used, the mixing ratio of NR / BR is 100 /
0 to 40/60 is preferable, and 80/20 to 50/50 is more preferable. When the NR is less than 40 parts by weight based on 100 parts by weight of all the blend components, the tear crack resistance is poor,
When BR exceeds 60 parts by weight, the abrasion resistance and low heat generation are improved, but the merit of tear crack resistance due to the extended crystallinity of NR is lost. Various natural rubbers are used as the natural rubber, for example, sheet rubber such as RSS No. 3, technical grade rubber (TSR) and the like. Among them, TSR is preferably used from the viewpoint of improving the dispersibility of silica.
When SR is used, the compounding amount of TSR is natural rubber 10
It is 30% by weight or more, preferably 60% by weight or more in 0% by weight. When the content is less than 30% by weight, poor dispersion of silica occurs, and tear crack resistance is reduced.

When only natural rubber is used as the rubber component, the compounding amount of TSR is based on 100 parts by weight of natural rubber.
50 to 100 parts by weight are preferred.

Carbon used in the rubber composition of the present invention
Black is the nitrogen adsorption specific surface area (N_TwoSA) is 70-17
0m^Two/ G, and dibutyl phthalate (DBP) oil absorption
But 100-200cm^Three/ 100g characteristics
Is used. N_TwoSA is 70m^TwoLess than / g
Is insufficient, wear resistance becomes insufficient, and 170m^Two/ G
If it exceeds, the dispersion in the rubber decreases, which is not preferable. Also,
DBP oil absorption 100cm^ThreeLess than / 100g reinforcement
Is insufficient, wear resistance is not enough, 200cm ^Three/ 10
If it exceeds 0 g, elongation at break decreases, and tear and crack resistance
Is not good and is not preferable. This carbon black and
For example, ISAF, SAF, etc. satisfying the above characteristics
Can be mentioned.

The silica used in the rubber composition of the present invention is
N_TwoSA is 120-240m^Two/ G, preferably 160
~ 200m^Two/ G and DBP oil absorption of 170 to 250
cm ^Three/ 100g, preferably 170-220cm^Three/
Those having a characteristic of 100 g are used. N_TwoSA
120m^Two/ G does not provide sufficient reinforcement and wear resistance
Inferior, 240m^Two/ G, the dispersion in rubber decreases
And is not preferred. DBP oil absorption 170cm^Three/ 10
If it is less than 0 g, the reinforcing property is poor, the wear resistance is reduced,
250cm^Three/ 100g, elongation at break decreases,
The tear and crack resistance becomes poor, which is not preferable.

As the silica, a synthetic silica prepared by a precipitation method is used. Specifically, Nip Seal AQ manufactured by Nippon Silica Co., Ltd., ULTRASIL manufactured by Degussa, Germany
VN3, BV3370GR, RP1165MP, Zeosil165GR, Zeos from Rhone-Poulenc
il 175VP, Hisil 233 from PPG,
Hisil 210, Hisil 255 and the like (both are trade names) may be mentioned, but they are not particularly limited as long as the above properties are satisfied.

The filler used in the present invention comprises carbon black and silica as described above. The total compounding amount of carbon black and silica is 40 to 55 parts by weight with respect to 100 parts by weight of the rubber component.
The silica is 5 to 25 parts by weight, and the mixing ratio of the amount of carbon black / the amount of silica is 1 or more. If the total amount is less than 40 parts by weight, the abrasion resistance decreases. If the total amount exceeds 55 parts by weight, poor dispersion of the reinforcing filler occurs, so that the abrasion resistance and elongation at break (tear crack resistance) are reduced, and Exothermicity, that is, low rolling resistance is unpreferably increased. On the other hand, if the amount of silica is too small, the advantages of low heat build-up (low rolling resistance) and elongation at break (tear crack resistance) of the silica compounded system cannot be fully utilized. If the amount of silica is too large, poor dispersion in rubber occurs, and the above advantages cannot be exhibited. The mixing ratio of the amount of carbon black / the amount of silica is less than 1, that is, the silica ratio in all the fillers is 50%.
When the ratio exceeds 1, the silica system has a disadvantage that the wear resistance is poor, but the wear resistance is further deteriorated.

In the coupling agent used in the present invention, since the physical bond between the silica and the rubber component is weaker than the bond between the carbon black and the rubber component, the wear resistance of the tire is reduced. Used to strengthen bonding and ensure wear resistance.

In the present invention, a silane coupling agent represented by the general formula (II) is used as the coupling agent. In the formula, n represents an integer of 1 to 3, m represents an integer of 1 to 9, and preferably an integer of 2 to 5.

Further, y in the polysulfide portion Sy represents the average number of sulfur atoms, and is a positive number satisfying 2.0 <y ≦ 3.5, preferably a positive number satisfying 2.5 ≦ y ≦ 3.
The average number of sulfur atoms means that the polysulfide portion is S _{1 to} S
Having a distribution of different numbers of sulfur atoms, such as ₉ , means the average number of this distribution. When the average number y of sulfur atoms is 2 or less, that is, S ₁ and S ₂ , the coupling effect is not exhibited, and thus the reinforcing property is deteriorated. Is likely to occur, and the Mooney viscosity is greatly increased, resulting in poor productivity.

As the silane coupling agent, for example, the alkoxy group of bis (trialkoxysilylalkyl) polysulfide of the general formula (II) is, for example, a methoxy group, an ethoxy group, a propoxy group; -Propyl group, isopropyl group, n-
Butyl group, isobutyl group, t-butyl group, pentyl group,
Hexyl group; a compound in which the polysulfide group -Sy- is a group having the above average number of sulfur atoms is used.

The method for producing the silane coupling agent used in the present invention is not particularly limited.
It can be manufactured as follows according to the method described in JP-A-588-588.

Anhydrous sodium sulfide (Na ₂ S) and sulfur (S) are reacted in an inert gas atmosphere in a polar solvent in an appropriate molar ratio, for example, in the range of 1: 1 to 1: 3 to form sodium polysulfide. And then reacting the sodium polysulfide with an halogenoalkoxysilane under an inert gas atmosphere.

The amount of the coupling agent used in the present invention is 3 to 30% by weight, preferably 5 to 30% by weight based on the amount of silica.
１５15% by weight. If it is less than 3% by weight, the abrasion resistance is reduced, and if it exceeds 30% by weight, no further improvement in the effect is observed, and further increase in the amount is not necessary from an economic viewpoint.

The filler composed of silica and a normal silane coupling agent has a tear and crack resistance due to elongation at break and a low rolling resistance due to low heat generation, as compared with a case where normal carbon black is used in the same amount as silica. There is an advantage of 10 to 20%, but wear resistance is reduced by 5 to 10%. However, in the present invention, the abrasion resistance is maintained at a high level by using a specific silane coupling agent. This unexpected effect is one of the major features of the present invention.

The tertiary amine which can be used in the present invention particularly has a role of improving the dispersion of the filler silica, and by improving the low rolling resistance and the abrasion resistance, in particular, by suppressing the heat generation during tire running, Suppress hardening of tread rubber, maintain high elongation at break, and improve tear and crack resistance.

As the tertiary amine compound, R ¹ , R ² and R ^{3 in} the above formula (II) each independently represent a methyl group, an alkyl group having 8 to 36 carbon atoms, or an alkenyl having 8 to 36 carbon atoms. Group, a cyclohexyl group or a benzyl group. Specifically, preferred examples include trioctylamine, trilaurylamine, dimethylstearylamine, dimethyldecylamine, dimethylmyristylamine, dilaurylmonomethylamine, dimethyloctadecenylamine, and dimethylhexadecenylamine. More preferred are tertiary amine compounds in which R ¹ and R ² are methyl groups and R ³ is an alkyl group having 12 to 36 carbon atoms, and still more preferred are a flash point, low heat build-up, and improved dispersion of the filler. Dimethylstearylamine from the viewpoint of

The tertiary amine compound used in the present invention preferably has a molecular weight of 180 or more. If the molecular weight of the tertiary amine compound is lower than 180, the flash point is 100 ° C.
This is not preferable because there is a risk of ignition in the processing step.

The amount of the tertiary amine compound is 0.1 to 20% by weight, preferably 0.5 to 4% by weight, based on the amount of silica.

The rubber composition of the pneumatic tire for heavy load according to the present invention is composed of zinc oxide, stearic acid, an antioxidant, a wax, a vulcanizing agent and the like, which are commonly used in the rubber industry together with the above-mentioned components. Can be appropriately compounded within a range that does not impair.

Examples of the vulcanizing agent include sulfur and the like, and the amount of sulfur is 0.1 to 5 parts by weight, preferably 1 to 2 parts by weight, based on 100 parts by weight of the rubber component.
If the amount is less than 0.1 part by weight, the breaking strength and abrasion resistance of the vulcanized rubber decrease, and if it exceeds 5 parts by weight, the rubber elasticity tends to be impaired.

The rubber composition for a pneumatic tire of the present invention comprises:
It is obtained by kneading using a kneading machine such as a roll, an internal mixer, a Banbury mixer, and the like, and after forming, vulcanized and used for a tire tread and the like.

[0039]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention.

Various measurements were made according to the following methods. (1) Wear resistance Size TBR1 used at an average contact pressure of 0.8 MPa
1R22.5, a prototype tire with a rib pattern was mounted on all wheels of a 10-ton truck, and after traveling 50,000 km, the amount of wear was measured from the remaining groove depth of the tread rubber pattern, and the reciprocal thereof was used. It was indicated by an index with the value being 100. Therefore, the larger the numerical value, the better the wear resistance.

(2) Tearing and cracking resistance A prototype tire was mounted on all wheels of a 10-ton truck, and 50,000 km
After running, the tire is climbed on the curb at an angle of 45 °, the degree of rib tearing / cracking (the length of tearing / cracking) is measured, and the value of Conventional Example 1 is set to 100 using the reciprocal thereof. The index is shown. Therefore, the larger the numerical value is, the better the tear crack resistance is. (3) Rolling Resistance The resistance of the prototype tire in the traveling direction generated on the tire contact surface during running at 80 km / h was measured by a drum test, and the value of Conventional Example 1 was expressed as an index with 100 as an index. The higher the value, the better the low rolling resistance.

As a guide for the overall evaluation of tire performance, E rolling resistance index, F wear resistance index, G tear resistance
The arithmetic average of EF and EG of the crackability index was calculated. In each case, the larger the average value, the better the tire performance.

(Examples 1 to 8, Conventional Examples 1 and 2, Comparative Example 1
5) Kneading and blending are performed according to the blending recipes shown in Tables 1 to 4 below, and using this tread rubber composition, the average ground contact pressure of a 4-steel belt, a 1-steel carcass, and a rib pattern as a tire structure is 0.8 MPa. Size TB used in
R11R22.5 tires were prototyped and various tire characteristics were measured. The results are shown in Tables 1 to 4.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

[Table 4]

As shown in Tables 1 to 4, the rubber composition of the present invention and the pneumatic tire for heavy load using the same have a high level of both low rolling resistance, abrasion resistance and tear crack resistance. Has excellent properties.

When the total amount of carbon black and silica exceeds the range according to the present invention (conventional examples 1, 2, comparative example 1)
Has deteriorated low rolling resistance and tear crack resistance,
When the total amount of carbon black and silica is smaller than the range according to the present invention (Comparative Example 2), and when the mixture ratio of carbon black amount / silica amount is smaller than the range according to the present invention (Comparative Example 3), all wear resistance is obtained. When the properties (N ₂ SA) of the silica are out of the range according to the present invention (Comparative Example 4), the low rolling resistance is not sufficient and the tear crack resistance is deteriorated. When no coupling agent is used (Comparative Example 5), the level is low over the entire tire performance. The average value of the rolling resistance index-abrasion resistance index and the average value of the rolling resistance index-tear crack resistance index corresponding to the overall evaluation of the tire performance are significantly larger in the conventional example and the comparative example than in the examples. It turns out that it is inferior.

[0050]

As described above, the rubber composition of the present invention and the pneumatic tire for heavy load using the same have the above-mentioned structure, and thus have a high balance between low rolling resistance, abrasion resistance and tear crack resistance. The effect is excellent.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 9/00 C08L 9/00

Claims (8)

[Claims] 1. A rubber component comprising 10 to 100 parts by weight of natural rubber and 90 to 0 parts by weight of another diene rubber, and a total amount of carbon black and silica of 40 to 55 parts by weight based on 100 parts by weight of the rubber component. In the total amount, the amount of silica is 5 to 25 parts by weight, the mixing ratio of the amount of carbon black / the amount of silica is 1 or more, and the carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of 7;
0 to 170 m ² / g and dibutyl phthalate (DB
P) has the characteristics of oil absorption 100~200cm ³ / 100g, the silica is N ^₂ SA120~240m ₂ / g, and DB
It has characteristics of P oil absorption 170~250cm ³ / 100g, and characterized by comprising the following general formula of the silane coupling agent represented by (I) 3 to 30 wt% of the amount of silica, a tread rubber containing Rubber composition. Embedded image (Wherein, n is an integer of 1 to 3, m is an integer of 1 to 9, y is the average number of sulfur atoms in the polysulfide moiety, and 2.0 <
represents a positive number with y ≦ 3.5) 2. The natural rubber is technically rated natural rubber (T
The rubber composition according to claim 1, wherein the rubber composition contains at least 30% by weight of SR) in 100% by weight of natural rubber. 3. The silane coupling agent according to claim 1, wherein the average number y of sulfur atoms in the polysulfide portion of the silane coupling agent is a positive number satisfying 2.5 ≦ y ≦ 3. The rubber composition according to claim 1, characterized in that: 4. The rubber composition according to claim 1, wherein the amount of the silane coupling agent is 5 to 15% by weight of the silica amount. 5. The rubber composition according to claim 1, wherein the rubber composition further contains a tertiary amine compound represented by the following general formula (II) in an amount of 0.1 to 20% by weight based on the amount of silica. Rubber composition. Embedded image (Wherein, R ¹ , R ² and R ³ each independently represent a methyl group, an alkyl group having 8 to 36 carbon atoms, an alkenyl group having 8 to 36 carbon atoms, a cyclohexyl group or a benzyl group) 6. The method according to claim 5, wherein R ¹ and R ^{2 in} the general formula (II) are methyl groups, and R ³ is an alkyl group having 12 to 36 carbon atoms. The rubber composition as described in the above. 7. The rubber composition according to claim 5, wherein the tertiary amine compound is dimethyl stearylamine. 8. A heavy-duty pneumatic tire using the rubber composition according to any one of claims 1 to 7 as a tread rubber.