JPH0820202A - Pneumatic tire - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] A rubber composition containing ethylene-propylene-diene rubber as the main component, which is excellent in weather resistance and heat resistance as well as in crack growth resistance and wear resistance, is used for tire sidewalls. By doing so, not only the appearance is dramatically improved, but also the retread life of a large tire is remarkably improved. [Structure] Ethylene-propylene as a main component, (1) glass transition temperature measured by DSC is -50 ° C or lower, (2) iodine value is 10 to 34, (3) weight average molecular weight is 220,000 or more, ( 4) Ethylene content is 68-85m
ol%, (5) molecular weight distribution of 3.0 or more, (6) 95 ≦
1.5 × (iodine value) + (ethylene content) ≦ 120,
(7) 90 ≦ (weight average molecular weight) × 10 ⁻⁴ + (ethylene content) ≦ 110, 20 parts or more of rubber satisfying all the conditions, 100 parts or more of rubber component, 10 parts or more of isoprene-based rubber, process Contains 10 parts or more of oil and 20 to 100 parts of inorganic filler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition containing ethylene-propylene-diene rubber as a main component and having excellent weather resistance and heat resistance as well as crack growth resistance and abrasion resistance. Further, by using this rubber composition for tire sidewalls, not only the appearance is dramatically improved, but especially for pneumatic tires having significantly improved rehabilitation life of large tires, and further by using for tire treads. The present invention relates to a pneumatic tire having not only a dramatic improvement in appearance but also a remarkable improvement in groove crack resistance.

[0002]

2. Description of the Related Art Conventionally, a rubber containing ethylene or propylene as a main component is copolymerized with a third component such as dicyclopentadiene, ethylidene norbornene or 1.4-hexadiene in order to allow crosslinking with sulfur. Technology is being developed. The rubber made by this method is
Since it has no double bond in the main chain, it has excellent weather resistance and heat resistance because the main chain is not broken by a chemical mechanism due to ozone or the like. However, in terms of crack growth resistance and wear resistance, they are several steps inferior to diene rubbers, and their co-vulcanizability with diene rubbers is poor, and their application to rubber products has been limited.

In the field of pneumatic tires, conventionally, rubber compositions for tire sidewalls have often been composed of a blend of natural rubber, BR and SBR. However, the tendency has changed a little recently, and the number of cases in which BR, which is excellent in bending durability, is frequently used is increasing. In the world, the blend of natural rubber and BR is dominant, and the blending ratio of BR is more than 50% in many cases. However, a rubber composition composed only of the above-mentioned diene rubber is essentially easily oxidized by oxygen and ozone, and is usually oxidized by blending a strong amine-based antioxidant and paraffin wax. To prevent it.

While the tire is new, this is not a problem from the viewpoint of weather resistance, but if it is used at the end of use or for a long period of time by rehabilitating the tread portion, the anti-aging agent in the rubber composition may The effective amount has decreased and ozone cracks etc. have occurred. As the performance of tires has improved dramatically as in recent years, this problem has been highlighted as an even greater problem.

As a method of preventing this, a method of increasing the amount of amine anti-aging agent, a method of using a long-life anti-aging agent, a reactive anti-aging method in which the anti-aging agent does not come out to the outside in response to the main chain of rubber Although a method of using an agent can be considered, the method of increasing the amount of the amine anti-aging agent has a small improvement effect from the viewpoint of sustainability, and the long-life anti-aging agent and the reactive anti-aging agent have an anti-aging effect. It had the drawback of being small.

[0006] On the other hand, research has also been conducted to use a non-diene rubber having no double bond in the main chain, which does not require the use of an antioxidant. Examples include EPDM, halogenated butyl rubber, chloroprene rubber,
Compared to diene rubber, flex durability and crack growth resistance are extremely inferior, so very few cases are currently in practical use.

Further, in addition to the above-mentioned problem concerning durability, recently, there is a great demand for improving the appearance of the tire itself. That is, as described above, the rubber composition for tire sidewall contains a large amount of amine-based antioxidant and paraffin-based wax, which blooms on the rubber surface to form a protective layer. Although it has an anti-aging effect, there is a phenomenon that when this layer is exposed to ultraviolet rays, the amine-based anti-aging agent discolors to brown, resulting in a very poor appearance. Particularly in passenger car tires, research to prevent this has been carried out from both aspects of improvement of antiaging agents and non-diene rubbers, but the present situation is that no effective method has been found yet.

Conventionally, rubber compositions for tire tread fields have often been composed of a blend of natural rubber, BR and SBR. The tread of large queer has a large pressure per unit area on the tread surface, and naturally the calorific value of the rubber is also large, so that the rubber composition is mainly composed of natural rubber having a small breaking heat and a large breaking strength. On the other hand, in the case of tires for passenger cars, the pressure on the tread is smaller than that of large tires, and the amount of heat generated is naturally small. Since the tread gauge is thin, it is less likely to accumulate heat. Therefore, the rubber composition is mainly composed of SBR in order to increase the coefficient of friction during high traction, especially when wet.

Important properties in the tread portion are gripping property (especially when wet) and abrasion resistance, and many improvements have been made. However, the abrasion resistance is improved and it does not pose a problem so far. Weather resistance and crack growth resistance are becoming problems. Specifically, it is a crack (groove crack) generated at the groove bottom of the tread portion.
This phenomenon is a phenomenon that is noticeable in tires at the end of running, where most of the amine-based antioxidants that are usually added to rubber compositions are consumed, especially in areas with high temperatures where the consumption of antioxidants is high. It's a big problem.

Many studies have been conducted to solve this problem. For example, a method of increasing an amine anti-aging agent, a method of using a non-diene rubber composition in a tread,
There is a method of installing a thin and weather resistant rubber sheet on the very surface of the tread (This is a method that uses the fact that the surface of the tread will be worn away and will be lost, but the group part will remain as it is at the end of running) . The method of increasing the amount of amine anti-aging agent seems to be an immediate effect method, but it is actually very effective in terms of weather resistance at the beginning of driving, but it is an effect of improving weather resistance at the end of driving. Is extremely small. This is because the amine-based anti-aging agent has an excellent effect as an anti-aging agent for improving weather resistance, because it blooms on the rubber surface very quickly to form a layer.
This is because even if the amount of addition is increased, the duration itself cannot be lengthened simply by increasing the thickness of this layer.

The conventional non-diene rubbers (butyl rubber, halogenated butyl rubber, FPDM, chlorosulfonated polyethylene rubber, etc.) have a significantly poor wear resistance because of the use of the non-diene rubber composition in the tread. Development has not progressed in that it is difficult to use it as a tread rubber composition in which the property is an important factor.

In the method of installing a thin and weatherproof rubber sheet on the very surface of the tread, it is effective to use a non-diene rubber having no double bond in the main chain as the weatherproof rubber sheet. Adhesion with diene rubber (co-vulcanization) is poor, and even if it looks like adhesion in a static test, there is a problem that peeling occurs due to dynamic deformation during tire running. There are almost no cases that have been done.

[0013]

SUMMARY OF THE INVENTION The present invention controls the microstructure of a rubber containing ethylene-propylene as a main component, which is a non-diene rubber, so as to prevent the iodine value from being extremely increased, and to prevent the EPDM rubber from a conventional EPDM rubber. The present invention provides a rubber composition having significantly improved crack growth resistance and abrasion resistance in comparison with the composition. Using this rubber, the crack growth resistance and weather resistance are greatly improved, and at the same time, amine-based aging prevention is provided. It is an object of the present invention to provide a pneumatic tire in which the appearance is dramatically improved because almost no agent or paraffin wax is used or no wax is used at all.

[0014]

The present invention is directed to ethylene-
Propylene is the main component, and (1) the glass transition temperature measured by DSC is -50 ° C or lower, and (2) the iodine value is 10.
To 34, (3) weight average molecular weight of 220,000 or more, (4) ethylene content of 68 to 85 mol%, (5) molecular weight distribution of 3.0 or more, (6) 95 ≦ 1.5 × (iodine value) +
20 parts by weight or more of rubber satisfying all the conditions of (ethylene content) ≤ 120, (7) 90 ≤ (weight average molecular weight) x 10 ^-4 + (ethylene content) ≤ 110 per 100 parts by weight of the rubber component. A rubber composition that can be vulcanized by containing 20 to 150 parts by weight of an inorganic filler, and configures the sidewall portion in a pneumatic tire including a tread portion, a sidewall portion, and a bead portion. As the rubber composition, 20 parts by weight or more of the rubber containing ethylene-propylene as a main component based on 100 parts by weight of the rubber component, 10 parts by weight or more of isoprene-based rubber, 10 parts by weight or more of process oil, and an inorganic filler are used. A pneumatic tire comprising a rubber composition containing 20 to 100 parts by weight, further comprising a tread part, a side wall part and a bead part. In the pneumatic tire, as a rubber composition constituting the tread portion, the rubber containing ethylene-propylene as a main component is 20 parts by weight or more, the process oil is 10 parts by weight or more, and the inorganic is inorganic. A pneumatic tire comprising a rubber composition containing 50 to 150 parts by weight of a filler.

In the present invention, the rubber containing ethylene-propylene as the main component of the present invention is limited to 20 parts by weight or more.
This is because if it is less than 20 parts by weight, sufficient weather resistance and heat deterioration resistance cannot be obtained. The reason why the rubber containing ethylene-propylene as the main component of the present invention is not clear, but is characterized in that the weather resistance and heat deterioration resistance are rapidly improved from about 26 to 30 parts by weight as the blending amount is increased. It is preferably 30 parts by weight or more. If the amount of the inorganic filler is less than 20 parts by weight, the breaking strength (strength at break, elongation at break) after vulcanizing the rubber composition is not sufficient,
If the amount is more than 150 parts by weight, the workability before vulcanization becomes insufficient.

The glass transition temperature of the rubber containing ethylene-propylene as a main component as measured by DSC at a temperature rising rate of 10 ° C./min is limited to −50 ° C. or lower at −50 ° C.
If it is higher than the above values, sufficient crack growth resistance and bending durability cannot be obtained. The iodine value is limited to 10 to 34 because if it is less than 10, sufficient co-vulcanizability with diene rubber, crack growth resistance, strength at break, and elongation at break cannot be obtained. If it is larger than this, the effect of greatly improving crack growth resistance, strength at break, and elongation at break cannot be expected, and wear resistance after heat deterioration is also reduced, which is not preferable. In addition, the third component copolymerized to increase the iodine value is generally expensive, and as a rubber composition used for rubber products, the amount of the third component is suppressed as much as possible, and the rubber with the best performance among them is used. This is because the production of rubber is also an essential problem for a rubber containing ethylene-propylene as a main component.

The weight average molecular weight of the rubber containing ethylene-propylene as the main component is limited to 220,000 or more.
This is because the effect of improving crack growth resistance and abrasion resistance is remarkable at a molecular weight of 20,000 or more, and surprisingly, the adhesive strength with diene rubber is also greatly improved.

However, when the molecular weight is increased, there is a drawback that the viscosity sharply increases and the workability before vulcanization is remarkably lowered. Therefore, it is preferable to extend the oil in the region where the weight average molecular weight exceeds 240,000. However, if the weight average molecular weight exceeds 300,000, the amount of oil required for processability increases excessively and the physical properties after vulcanization, for example, abrasion resistance, are greatly reduced, which is not preferable. Paraffinic oil is preferred as the oil type for oil extension.

The ethylene content of the rubber containing ethylene-propylene as a main component is limited to 68 to 85 mol% unless the ethylene content is within this range, sufficient crack growth resistance, strength at break, and strength at break. This is because the growth cannot be obtained. More specifically, the ethylene content is 68 mol
If it is less than 80%, even if the iodine value is 10 or more, the effect of improving crack growth resistance, strength at break, and elongation at break is very small. This is because the time elongation becomes small and the elastic modulus becomes high, so that it becomes difficult to industrially use it as a rubber.

In the present invention, the molecular weight distribution of the rubber containing ethylene-propylene as the main component is limited to 3.0 or more. When the molecular weight distribution is lower than 3.0, the roll workability is poor and the rubber composition is industrially used. It is difficult to use.

If "1.5 × (iodine value) + (ethylene content)" is less than 95, sufficient crack growth resistance,
Strength at break and elongation at break cannot be obtained, and if it exceeds 120, heat deterioration resistance (including wear resistance after heat deterioration) is lowered.

On the other hand, “(weight average molecular weight) × 10 ⁻⁴ +
If the (ethylene content) ”is less than 90, co-vulcanizability with diene rubber and crack growth resistance cannot be sufficiently obtained, and 1
If it exceeds 10, not only the processability (dispersion of carbon black, roll workability) deteriorates, but also the elastic modulus of the rubber composition becomes too high, which makes it difficult to use industrially.

As described above, the reasons for the individual limiting conditions can be explained.
The characteristics of the rubber containing propylene as a main component are satisfied within the range specified in the claims. In other words, it means that the effect of the present invention cannot be obtained unless all the conditions of physical property requirements (1) to (7) are satisfied at the same time. This is because there are some previously unknown synergistic effects between each condition.

In order to obtain a rubber containing ethylene-propylene as a main component in the present invention, there is a method of blending several rubbers containing ethylene-propylene as a main component, but it shows a fairly good physical property. Of course, although it belongs to the category of the present invention, a rubber composition using a rubber that satisfies the conditions shown in the claims at one time by polymerization from the beginning has better physical properties (crack growth resistance, Abrasion resistance, strength at break, elongation at break, etc.).

In the present invention, ethylidene norbornene is preferable as the third component other than ethylene and propylene of the rubber containing ethylene-propylene as the main component of the present invention,
This is because other commonly used third components such as dicyclopentadiene and 1.4-hexadiene cannot be expected to have sufficient improvement effects on crack growth resistance, strength at break, and elongation at break.

In the present invention, the oil-extended amount of the rubber containing ethylene-propylene as a main component of the present invention is preferably 40 parts by weight or more, but this is a weight average molecular weight in order to sufficiently bring out the effect of the present invention. Is preferably 250,000 or more, and if the amount of oil extension is not 40 parts by weight or more, workability is poor and industrial use becomes difficult.

The rubber composition of the present invention preferably contains 10 parts by weight or more, more preferably 20 parts by weight or more of isoprene-based rubber, but if it is less than 10 parts by weight, the kneading workability will be improved. This is because, depending on the compounding formulation, it becomes difficult to obtain sufficient physical properties at the time of vulcanized rubber. Also, from the viewpoint of ensuring the strength at break, it is industrially more efficient to use isoprene rubber than to use other diene rubber. Here, the isoprene-based rubber refers to natural rubber or synthetic polyisoprene rubber.

Carbon black is most suitable as the inorganic filler to be used in the rubber composition of the present invention, but in addition, silicon dioxide (silica), calcium carbonate, titanium dioxide, white luster and the like can be used. The carbon black for the rubber composition constituting the sidewall portion of the present invention preferably has an iodine adsorption amount of 35 to 100 mg / g and a DBP oil absorption amount of 70 to 140 ml / 100 g. If it is lower than 35 mg / g, it becomes difficult to obtain the desired strength at break, and conversely 100 mg / g.
This is because if it exceeds g, the bending durability is reduced. DBP
If the oil absorption is lower than 70 ml / 100 g, the dispersion of carbon black will not be sufficient, and conversely 140 ml / 100
This is because if it is larger than g, the hardness after vulcanization becomes too large and the bending durability is lowered.

The carbon black of the rubber composition constituting the tread portion of the present invention has an iodine adsorption amount of 85-85.
200 mg / g, DBP oil absorption 100-180 ml / 1
It is preferably 00 g. In order to secure abrasion resistance, iodine adsorption of 85 mg / g or more, DBP oil absorption of 10
The amount is preferably 0 ml / 100 g or more, and in order to ensure the dispersion of carbon black in the rubber composition, the iodine adsorption amount is 200 mg / g or less and the DBP oil absorption amount is 180 m.
It is preferably 1/100 g or less.

Since the rubber composition of the present invention has overwhelmingly superior weather resistance and heat resistance as compared with commonly used diene rubber compositions, it does not require an amine anti-aging agent or paraffin wax. However, when the amount of the rubber of the present invention containing ethylene-propylene as a main component is small, for example, 2
In the case of 0 parts by weight, a small amount may be added in some cases. It is preferable to use 0.3 parts by weight or less of the amine thread anti-aging agent and 0.5 parts by weight or less of the paraffin wax. Of course, both may be used in combination.

In order to obtain the rubber containing ethylene-propylene as the main component in the present invention, there is a method of blending several rubbers containing ethylene-propylene as the main component, but it shows a fairly good physical property. Of course, although it belongs to the category of the present invention, a rubber composition using a rubber that satisfies the conditions shown in the claims at one time by polymerization from the beginning has better physical properties (crack growth resistance, Abrasion resistance, strength at break, elongation at break, etc.).

Hardness (JIS spring hardness [A type]) of the rubber composition constituting the side wall portion of the present invention
It is more preferable to set the ratio to 30 to 60 in terms of bending durability and crack growth resistance because the side wall portion undergoes constant strain deformation. In addition, the hardness (JIS spring hardness [A type]) of the rubber composition constituting the tread portion of the present invention is 5
More preferably, it is set to 5 to 70. When it is less than 55, the steering stability and crack growth resistance of the tire are deteriorated, and when it exceeds 70, not only the rib tear resistance and bending durability of the tire tread are deteriorated, but also the grip performance is deteriorated. This is because it becomes difficult to secure the braking performance.

Next, a method for producing a rubber containing ethylene-propylene as a main component used in the present invention will be described. The rubber containing ethylene-propylene as a main component in the present invention is, for example, in a hydrocarbon solvent, (a) a soluble vanadium compound [VO (OR) _n X _3-n : R is a hydrocarbon, X is a halogen, and 0 ≦ n ≦ 3] or a vanadium compound represented by VX ₄ , (b) R ′ _m AlX ′ _3-m [R ′ is a hydrocarbon,
X ′ is a halogen, and in the presence of a catalyst formed from an organoaluminum compound represented by 0 ≦ m ≦ 3, ethylene, propylene and, as a third component, for example, ethylidene norbornene is adjusted to have a desired composition and randomly It may be copolymerized.

The following are specific examples of the vanadium compound represented by the above general formula. That is, VO
_{(OCH 3) Cl 2, VO} (OCH 3) 2 Cl, VO
(OCH ₃ ) ₃ , VO (OC ₂ H ₅ ) Cl ₂ , VO (O
C ₂ H ₅ ) ₂ Cl, VO (OC ₂ H ₅ ) ₃ , VO (OC
₂ H ₅ ) _1.5 Br _1.5 , VO (OC ₃ H ₇ ) C
l ₂ , VO (OC ₃ H ₇ ) _1.5 Cl _1.5 , VO (O
_{C 3 H 7) 2 Cl,} VO (OC 3 H 7) 3, VO (On
_{-C 4 H 9) Cl 2,} VO (On-C 4 H 9) 2 Cl,
_{VO (O iso -C 4 H 9} ) Cl 2, VO (O sec -
_{C 4 H 9) 3, VO} (OC 5 H 11) 1.5 C
1 _1.5 , VOCl ₃ , VCl ₄ or a mixture thereof. Among these, VO (OC ₂ H ₅ ) Cl
₂ , VOCl ₃ is particularly preferred.

The following are specific examples of the organoaluminum compound. (CH ₃ ) ₂ AlC
_{l, (CH 3) 1.5 AlCl} 1.5, (CH 3) Al
Cl ₂ , (C ₂ H ₅ ) ₂ AlCl, (C ₂ H ₅ ) _1.5
AlCl _1.5 , (C ₂ H ₅ ) AlCl ₂ , (C
₃ H ₇ ) ₂ AlCl, (C ₃ H ₇ ) _1.5 AlCl
_{1.5, (C 3 H 7)} AlCl 2, (C 6 H 13)
_1.5 AlCl _1.5 , (C ₆ H ₁₃ ) Al ₂ Cl,
(C ₆ H ₁₃ ) AlCl ₂ or a mixture thereof. The use ratio of the organic aluminum and the vanadium compound is 2 to 50, particularly 5 to 30 as Al / V (atomic ratio).
Is preferred.

The copolymerization can be carried out in a hydrocarbon solvent. For example, hexane, heptane, octane, an aliphatic hydrocarbon such as kerosene, an aromatic hydrocarbon such as benzene, toluene, xylene can be used alone or in a mixture as a solvent. In the copolymerization, the vanadium compound content in the reaction medium is 0.01 to 5 m · mol / l, preferably 0.1 to 2 m · mol / l. The ethylene content can be changed by controlling the supply amount at the time of copolymerization, but it is industrially difficult to set it to 85 mol% or more (the yield can be reduced in the laboratory).
The polymerization temperature is maintained at 0 to 100 ° C., preferably 20 to 80 ° C., and the polymerization pressure is maintained at 0 to 50 kg / cm ² . Hydrogen is used to control the molecular weight.

[0037]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded. (Production Example) The rubber containing ethylene-propylene as the main component in the present invention was produced as follows. Copolymerization of ethylene, propylene and ethylidene norbornene was continuously carried out using a 15 (1) stainless steel polymerization vessel equipped with a stirrer. Hexane as a polymerization solvent was continuously supplied from the upper part of the polymerization vessel at a rate of 5 (1) per hour. on the other hand,
The polymerization liquid was withdrawn from the lower part of the polymerization device so that the polymerization liquid in the polymerization device was always 5 (1). As a catalyst, (a) VO (O
C ₂ H ₅ ) Cl ₂ is adjusted to (b) (C ₂ H 5) so that the concentration of vanadium atoms in the polymerization vessel becomes 0.28 m · mol / l.
₅ ) and _1.5 AlCl _1.5 were continuously fed into the polymerization reactor from the upper part of the polymerization reactor so that the concentration of aluminum atoms in the polymerization reactor was 1.85 m · mol / l.

A mixed gas of ethylene and propylene (45 mol% ethylene, 55 m propylene) was fed from the upper part of the polymerization vessel.
ol%) was fed at a rate of 450 (1) per hour, and ethylidene norbornene was fed from the upper part of the polymerization vessel at a rate of 25 g / h. As the molecular weight regulator, hydrogen gas is 3.2 per hour.
It was supplied at the rate of (1).

The polymerization temperature was controlled at 41 ° C. by a jacket attached outside the polymerization vessel. The pressure inside the polymerization vessel was 4.8 kg / cm ² . The polymerization liquid taken out from the lower part of the polymerization vessel was subjected to steam stripping, dried at 80 ° C. for one day and then vacuum dried.
The rubber containing ethylene-propylene as the main component is 26 per hour.
Obtained at a rate of 5 g.

The weight average molecular weight and the molecular weight distribution were measured by the GPC method. The weight average molecular weight was determined in terms of polystyrene. The obtained sample was designated as Prototype-1, and Prototypes 2 to 11 were also produced by appropriately changing the amount of ethylene, the amount of the third component, the catalyst amount ratio, the polymerization temperature, the polymerization time, and the like. Table 1 and Table 2 show the details of the obtained rubber samples containing ethylene-propylene as a main component.

[0041]

[Table 1]

[0042]

[Table 2]

Here, EP33 and EP43 are EPDM manufactured by Nippon Synthetic Rubber Co., Ltd., EBN is ethylidene norbornene, and DCP is dicyclopentadiene.
Paraffinic oil (non-contaminated) manufactured by Idemitsu Petrochemical Co., Ltd. was used as the oil-extended oil.

(Examples 1 and 2) Five kinds of rubber compositions were prepared by a Banbury mixer according to the formulation shown in Table 3 and vulcanized at 145 ° C for 30 minutes. The physical properties of the obtained vulcanized rubber sample were evaluated. Aroma take oil manufactured by Fuji Kosan Co., Ltd. was used as the aroma take oil. The results are shown in Table 3.

The evaluation test methods in the examples are based on the following. (1) Crack growth resistance A test piece of 60 mm x 100 mm x 1.0 mm has a center of 0.
3mm scratch, vibration frequency 300 cycles / min, strain 50
The elongation strain was given under the condition of%, and the time required for the elongation strain to grow to 20 mm was evaluated. Index = (control time / test sample time) × 100 The larger this value, the better the crack growth resistance.

(2) Abrasion resistance after heat deterioration Evaluation was made by the abrasion resistance ratio between the original sample and the sample left in a constant temperature bath at 120 ° C. for 24 hours.・ Acron wear (load 6 Lbs, angle 15 °, main slide 10
(00 times) Index = (wear amount ratio of test sample / wear amount ratio of control) × 100 wear amount ratio = original wear amount / wear amount of sample after thermal deterioration

(3) Resistance to heat deterioration Evaluation was made by the ratio of strength at break between the original sample and the sample left in a constant temperature bath at 120 ° C. for 24 hours. Index = (strength ratio at break of test sample / strength ratio at break of control) × 100 strength ratio at break = strength at break of sample after thermal deterioration / original strength at break Test piece: 150 mm × 150 mm × 2.0 mm vulcanized rubber sheet

(4) Strength at break, elongation at break Measured according to JIS K6301. JIS No. 3 was used as the sample shape.

(5) Weather resistance A test piece of rubber plate of 20 mm × 100 mm × 1.0 mm was used.
The sample was left to stand in a constant temperature oven having an ozone concentration of 50 pphm at 40 ° C. with 0% elongation and evaluated by the time until cracks could be visually confirmed. Index = (time of test sample / time of control) × 100 The larger this value, the better the weather resistance.

From Examples 1 and 2, the rubber composition of the present invention has a crack growth resistance, a heat deterioration resistance, a strength at break as compared with a rubber composition using a conventional rubber containing ethylene-propylene as a main component. It is understood that there is a dramatic improvement in elongation at break. In Table 3, Santoflex 13 is an antioxidant N-1.3-dimethyl-butyl-N'-phenyl-p-phenylenediamine, CZ is an accelerator N-cyclohexyl-2-benzothiazylsulfenamide, TS
Is the accelerator tetramethylthiuram monosulfide.

[0051]

[Table 3]

Examples 3 to 4 Compositions containing rubber sample trials 2 to 10 containing ethylene-propylene as a main component and having different structures and characteristics according to the formulations shown in Table 4 and compositions not containing them Ten kinds of physical objects were blended with a Banbury mixer and vulcanized at 145 ° C. for 30 minutes. Physical properties of the obtained vulcanized rubber samples were evaluated in the same manner as in Examples 1 and 2. Roll workability was based on visual inspection. The results are shown in Table 4. The paraffinic oil used was the same as the oil extending oil. In Comparative Example 11, the elastic modulus of the composition increased, and the crack growth resistance, strength at break, and elongation at break decreased. As is clear from Table 4, it is understood that the effects intended by the present invention cannot be obtained unless the structural and physical property conditions (1) to (7) of the ethylene-propylene rubber are simultaneously satisfied.

[0053]

[Table 4]

(Examples 5 to 7) Using a rubber sample trial product-1 containing ethylene-propylene as a main component, 5 kinds of compositions were blended by a Banbury mixer in accordance with the blending recipe shown in Table 5, and 145 ° C. and 30 Partial vulcanization was performed. Table 5 shows the results of physical property evaluation after vulcanization. The evaluation test method is based on the above.

In Table 5, Comparative Example 13, Examples 5 and 6
And the amount of the rubber containing ethylene-propylene of the present invention as the main component of trial production-1 (oil-extended rubber: oil-extended amount 30 parts by weight) contained in Nos. 7 and 7 are 15, 25, 40 and 80 parts by weight, respectively. From the evaluation results shown in Table 5, it is understood that by using 20 parts by weight or more of the rubber containing ethylene-propylene as the main component of the present invention, the effect intended by the present invention is exhibited.

Further, according to the formulation shown in Table 5, five kinds of rubber compositions for tires and treads were used by dividing them into tire and tread parts on the tire circumference, and tire size 165SR13 having five kinds of rubber compositions in the tread parts. Produced a radial tire for passenger cars of the above, and the internal pressure of the trial tire was 1.7 kg / c.
After running for 150,000 km on an outdoor drum tester at m ² , JIS 150% load, 65 km / hr, the state of cracking at the groove bottom of the tire was observed to evaluate the weather resistance. The tread rubbers of Comparative Examples 12 and 13 had many cracks at the groove bottom, but the tread rubbers of Examples 5, 6 and 7 had no cracks at the groove bottom.

[0057]

[Table 5]

(Examples 8 to 10) According to the formulation shown in Table 6, the carbon black dispersion, weather resistance and strength at break of five compositions were evaluated in the same manner as above. In Comparative Example 15, the carbon black was poorly dispersed, and thus the physical properties were not evaluated. Less than 20 parts by weight of inorganic filler, or 15
It can be seen that if the amount exceeds 0 parts by weight, it cannot be used.

[0059]

[Table 6]

(Examples 11 to 12) Five kinds of rubber compositions prepared according to the formulations shown in Table 7 were used by dividing the tire side wall into five parts on the tire circumference, and five kinds of rubber compositions were used in the side wall. Size 195/7 with
After making a prototype radial tire for passenger cars of 0HR14, tire performance was evaluated by the following test methods.

[0061]

[Table 7]

(1) Crack Growth Resistance Twenty scratches each having a width of 2 mm and a depth of 1.5 mm were alternately inserted into the tire sidewall at + 45 ° and −45 ° in the radial direction, and the internal pressure was 1.7 kg / cm ² , JIS1
It was run on an indoor drum tester at a load of 00% and 65 km / hr, and evaluated by the time until the length of the scratch became 2.0 cm. Index = (test sample time / control time) × 100 The larger this value, the better the crack growth resistance.

(2) Weather resistance A radial tire for passenger cars having a tire size of 195 / 70HR14 was partially made of 5 kinds of rubber compositions, and (way tire) was subjected to ozone cracking after running for 40,000 km (1 year). The presence or absence was evaluated.

(3) Discoloration of Sidewalls The degree of discoloration before and after running of the tire sidewall portion used for evaluation of weather resistance was evaluated by a color difference meter. Color difference meter: CR100, Minolta Co., Ltd. CR100 is evaluated by an increase in lightness (ΔL), and a larger value indicates a greater degree of discoloration.

(4) Heat deterioration resistance Five rubber compositions having the compounding recipes shown in Table 7 were prepared at 145 ° C.
After vulcanization for 30 minutes, the ratio of the strength at break between the original sample and the sample left for 24 hours in a constant temperature bath at 120 ° C. was evaluated. Index = (strength ratio at break of test sample / strength ratio at break of control) × 100

In Table 7, the antiaging agent Santoflex 13 and the paraffin wax were blended in Comparative Example 16 in fact, although the formulation excluding the Santoflex 13 and paraffin wax from Comparative Example 16 was actually prepared. Evaluation of weather resistance (at 50 pphm ozone concentration,
This is because the tire was not evaluated because the weather resistance was too poor under the condition of 40 ° C. and 20% elongation of strain). From Table 7, the rubber composition containing ethylene-propylene as a main component of the present invention shows superior weather resistance and heat deterioration resistance as compared with the conventional EPDM composition, and at the same time, the crack growth resistance is remarkably improved. You can see that it is done.

(Examples 13 to 14) Ten kinds of rubber compositions prepared according to the formulations shown in Table 8 were used by dividing the tire sidewall into 10 parts on the tire circumference, and using ten kinds of rubber compositions in the sidewall part. Size 10 with
After a trial production of a radial tire for trucks and buses of 00R20, the evaluation was carried out in the same manner as in Examples 11 to 12. However, since it is a large tire, the tire internal pressure is 7.5 kg / cm.
^{It was set to 2} . Table 8 shows the results. The strength at break, elongation at break and roll workability were based on the above-mentioned methods. Physical property condition (1) of the rubber containing ethylene-propylene as a main component of the present invention
When (1) to (7) are satisfied at the same time, the sidewall rubber composition for tires simultaneously satisfies the desired weather resistance, crack growth resistance, heat aging resistance, strength at break and elongation at break, and roll workability. Is good and can be used in industrial manufacture of tires.

[0068]

[Table 8]

(Examples 15 to 17) Five types of rubber compositions were prepared according to the formulations shown in Table 9, and Examples 11 to 12 were prepared.
Similarly to the above, a passenger car radial tire having a tire size of 165SR13 having five kinds of rubber compositions in the tire sidewall was experimentally manufactured, and then evaluated by the above method.
The results are shown in Table 9. It is understood that the use of the rubber containing ethylene-propylene as the main component of the present invention in an amount of 20% by weight or more dramatically improves the intended effect of the present invention.

[0070]

[Table 9]

(Examples 18 to 20) Four types of rubber compositions were prepared according to the formulations shown in Table 10, and Examples 1 and 2 were prepared.
In the same manner as in Example 11, carbon black dispersion, weather resistance and strength at break were evaluated, and in the same manner as in Examples 11 to 12, a passenger car radial of tire size 165SR13 having five rubber compositions in the tire sidewall portion. After the tire was prototyped, the crack growth resistance of the tire sidewall was evaluated. The results are shown in Table 10. As is clear from Table 10, the rubber composition of Example 20 is not preferable as a rubber composition for sidewalls that undergoes constant strain deformation, because the crack growth property decreases. Further, Comparative Example 28 having an inorganic filler content of less than 20 parts by weight has low strength at break and poor weather resistance, and therefore cannot be used as a rubber composition for a sidewall.

[0072]

[Table 10]

(Examples 21 to 24) Four types of rubber compositions were prepared according to the formulations shown in Table 11, and Examples 1 and 2 were prepared.
The physical properties were evaluated in the same manner as. The results are shown in Table 11. Table 1
In 1, DOTG represents the accelerator diorthotolyl guanidine, and DM represents dibenzothiazyl disulfide. For reference, iodine adsorption amount of various carbon black and DB
Table 12 shows the values of P oil absorption.

[0074]

[Table 11]

[0075]

[Table 12]

(Examples 25 to 27) Three kinds of sidewall rubber compositions were prepared according to the formulations shown in Table 13 and used for the tire / sidewall part by dividing the tire circumference into three parts. A radial tire for a passenger car having a tire size of 175SR14 having three kinds of rubber compositions was prototyped. These tires are used in Examples 11 to 1
The crack growth resistance was evaluated in the same manner as in 2. The hardness measurement method is JI described in JIS-K-6031.
Based on S spring type hardness [A type].

[0077]

[Table 13]

As disclosed in Table 13, when the hardness of the side wall rubber of the tire compounded with the rubber containing ethylene-propylene as the main component of the present invention exceeds 60, the crack growth resistance is sharply reduced. The rubber composition for walls preferably has a hardness of 60 or less. On the other hand, if the hardness is less than 30, the cut resistance of the side wall portion sharply decreases, which is not preferable.

Examples 28 to 29 Five rubber compositions for tires and treads were blended and adjusted with a Banbury mixer according to the formulation shown in Table 14. These five rubber compositions were used by dividing the tire / tread portion into five on the tire circumference, and a passenger car radial tire having a tire size of 195 / 70HR14 having five rubber compositions in the tread portion was trial-produced to obtain weather resistance and heat resistance. Degradability, crack growth resistance, abrasion resistance and adhesion with diene rubber were evaluated. The heat deterioration resistance was based on the measuring method described in Examples 1-2. For weather resistance, the outdoor drum test described in Examples 5-7 was performed. Other measuring methods will be described below.

(1) Crack growth resistance Five scratches each having a width of 2 mm and a depth of 1.0 mm were put along the groove at the bottom of the tire tread portion, and the internal pressure was 1.7 kg / cm.
^{2. The} test was run on an indoor drum tester at a JIS 100% load and 65 km / hr, and the time until the length of the scratch became 1.5 cm was evaluated. Index = (time of test sample / time of control) × 100 The larger this value, the better the crack growth resistance.

(2) Abrasion resistance A prototype tire was run on a real vehicle for 20,000 km, and the depth of the remaining groove was measured at four points and evaluated as an average value ((initial groove depth-groove depth after running)). The amount of wear was calculated by. Index = (abrasion amount of control / abrasion amount of test sample) × 100 The larger the value, the better.

(3) Adhesion with diene rubber A prototype tire was tested with an internal pressure of 1.7 kg / cm ² , JIS 150%.
After running for 150,000 km on a drum tester with an indoor projection at a load of 65 km / hr, a peeling test between the tire tread rubber and the tire tread base rubber was carried out. Those with smooth interfacial peeling were evaluated as bad, and those without smooth interfacial peeling were rated as good. Table 15 shows the compounding recipe of the tread base rubber.

[0083]

[Table 14]

[0084]

[Table 15]

As is clear from Table 14, the rubber composition containing 20 parts by weight or more of the rubber containing ethylene-propylene as the main component of the present invention is more resistant to cracking than the conventional rubber composition containing the same amount of EPDM. It can be seen that the growth property, abrasion resistance, and adhesion to the diene rubber are remarkably improved.

(Examples 30 to 34) Five rubber compositions for tires and treads according to the formulations shown in Table 16 were used by dividing the tire tread portion into five parts on the tire circumference, and using the five rubber compositions for the tread portion. Size 165SR with objects
13 radial tires for passenger cars were prototyped, and Examples 28-
In the same manner as in No. 29, crack growth resistance and abrasion resistance were evaluated, and roll workability and carbon black dispersion were also evaluated. The results are shown in Table 16.

[0087]

[Table 16]

(Examples 35 to 37) Three kinds of rubber compositions for tires and treads according to the formulations shown in Table 17 were used by dividing the tires and treads into three parts on the tire circumference, and three kinds of rubber compositions were used in the treads. Size 175SR with objects
14 passenger car radial tires were prototyped and evaluated for hardness and steering stability. Steering stability was evaluated by the driver's feeling when driving the orbital course and slalom course on the test course. The results are shown in Table 1.
7 shows. From the steering stability evaluation results shown in Table 17, it is preferable that the hardness (JIS spring hardness [A type]) after vulcanization of the tread rubber composition is 55 or more because steering stability is better and more preferable. I understand.

[0089]

[Table 17]

[0090]

As shown in the above examples, the physical property conditions (1) to (1) of a rubber containing ethylene-propylene as a main component
The rubber composition of the present invention satisfying all of (7) has crack growth resistance, abrasion resistance, strength at break, and elongation at break as compared with a rubber composition using a conventional rubber containing ethylene-propylene as a main component. Furthermore, it is clear that the adhesiveness with the diene rubber has been dramatically improved.

By using this rubber composition of the present invention in tire sidewalls, the appearance is remarkably improved, and by using it in the tire tread, the appearance and groove crack resistance are remarkably improved, and the retread life of large tires is improved. Can be significantly improved. The rubber composition of the present invention can be used for not only tires but also general rubber products such as industrial belts, hoses, anti-vibration rubbers and fenders.

Incidentally, in order to satisfy the physical property conditions (1) to (7) of the rubber containing ethylene-propylene as the main component of the present invention, some ethylene-propylene rubbers may be blended, but Polymerization of a rubber satisfying all the physical property conditions (1) to (7) for use shows better physical properties due to crack growth resistance, abrasion resistance and the like.

[Procedure amendment]

[Submission date] October 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C08L 23/16 LCY LDD // (C08L 23/16 9:00)

Claims (16)

[Claims] 1. A pneumatic tire comprising a tread portion, a side wall portion and a bead portion, wherein a rubber composition constituting the side wall portion contains ethylene-propylene as a main component, and (1) a glass measured by DSC. Transition temperature is -50 ° C or lower, (2) iodine value is 10 to 34, (3) weight average molecular weight is 220,000 or more, (4) ethylene content is 68 to 85 mol%, (5) molecular weight distribution is 3.0. As described above, (6) 95 ≦ 1.5 × (iodine value) + (ethylene content) ≦ 120, (7) 90 ≦ (weight average molecular weight) × 10 ⁻⁴ + (ethylene content) ≦ 110, 20 parts by weight or more per 100 parts by weight of the rubber component, 10 parts by weight or more of isoprene-based rubber, 10 parts by weight or more of process oil, and 2 parts of inorganic filler with respect to 100 parts by weight of the rubber component.
A pneumatic tire comprising a rubber composition containing 0 to 100 parts by weight. 2. The pneumatic tire according to claim 1, wherein the rubber composition has a hardness (JIS spring hardness [A type]) after vulcanization of 30 to 60. 3. A pneumatic tire having a tread portion, a sidewall portion and a bead portion, wherein the rubber composition constituting the tread portion contains ethylene-propylene as a main component, and (1) a glass transition measured by DSC. Temperature is -50 ° C or lower, (2) Iodine value is 10 to 34, (3) Weight average molecular weight is 220,000 or more, (4) Ethylene content is 68 to 85 mol%, (5) Molecular weight distribution is 3.0 or more , (6) 95 ≦ 1.5 × (iodine value) + (ethylene content) ≦ 120, (7) 90 ≦ (weight average molecular weight) × 10 ⁻⁴ + (ethylene content) ≦ 110, 20 parts by weight or more of the filling rubber with respect to 100 parts by weight of the rubber component, 10 parts by weight or more of the process oil,
A pneumatic tire comprising a rubber composition containing 50 to 150 parts by weight of an inorganic filler. 4. The pneumatic tire according to claim 3, wherein the rubber composition has a hardness (JIS spring hardness [A type]) after vulcanization of 55 to 70. 5. The pneumatic tire according to claim 1, wherein the rubber containing ethylene-propylene as a main component is 30 parts by weight or more. 6. The pneumatic tire according to claim 1 or 3, wherein the main component other than ethylene and propylene is ethylidene norbornene. 7. The pneumatic tire according to claim 1 or 3, wherein the rubber containing ethylene-propylene as a main component is an oil-extended rubber. 8. The pneumatic tire according to claim 1, wherein the inorganic filler is carbon black, silicon dioxide, calcium carbonate, titanium dioxide or the like. 9. The pneumatic queer according to claim 3, wherein the inorganic filler is carbon black, silicon dioxide, calcium carbonate, titanium dioxide or the like. 10. The pneumatic tire according to claim 1, which does not contain an amine-based antioxidant. 11. The pneumatic tire according to claim 1, wherein 60% or more of the process oil contained in the rubber composition is a process oil oil-extended with rubber. 12. The process oil according to claim 1, wherein 60% or more of the process oil contained in the rubber composition is a process oil oil-extended to a rubber containing ethylene and propylene as a main component. Pneumatic tire. 13. The pneumatic tire according to claim 7, wherein the oil used for oil extension is paraffinic oil. 14. The pneumatic tire according to claim 7, wherein the oil extension amount is 20 parts by weight or more. 15. The carbon black has an iodine adsorption amount of 35.
~ 100mg / g, DBP oil absorption 70 ~ 140ml / 1
The pneumatic tire according to claim 8, which is 00 g of carbon black. 16. Carbon black has an iodine adsorption amount of 85.
~ 200mg / g, DBP oil absorption 100 ~ 180ml /
Claim 9 which is 100 g of carbon black
The pneumatic tire according to the item.