JPS6348344A - High-speed endurable pneumatic tire - Google Patents

Abstract

PURPOSE:To enhance greatly the heat resistance of a pneumatic tire and to improve greatly the high-speed running durability, by using a rubber compsn. obtd. by blending a rubber blend consisting of a specified EPDM rubber and a solution-polymerized SBR with process oil and an inorg. filler as a material for the tread of a pneumatic tire. CONSTITUTION:The following rubber compsn. is used as a material for the tread of a pneumatic tire provided with treads, sidewalls and beads. Namely, a rubber compsn. obtd. by blending 100pts.wt. rubber contg. a rubber blend consisting of 10-70pts.wt. ethylene/propylene/diolefin terpolymer rubber (EPDM rubber) and 30-90pts.wt. solution-polymerized SBR with not less than 40pts.wt. process oil and 70-200pts.wt. inorg. filler. EPDM rubber having characteristics meeting all of the following requirements are preferred. Namely, (A) a glass transition temp. (measured DSC) of not higher than -50 deg.C, (B) an iodine value of 10-34, (C) a weight-average MW of not lower than 220,000, (D) an ethylene content of 68-85mol%, (E) an MW distribution (MW/MN) of not lower than 3.0, and others.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention uses a rubber composition with significantly improved heat resistance in a tire tread, thereby increasing high-speed durability while maintaining other high-speed running performance. This relates to a pneumatic tire that has been dramatically improved.

(Prior art) Tires for which high-speed running performance is important include competition tires for automobiles and motorcycles, aircraft tires, and high-performance tires for passenger cars. 1. Excellent grip performance is required to transmit the power of the powerful engine to the road surface. For this reason, the rubber compositions for the treads of these tires are formulated mainly of SBR with a high content of bound styrene and have a high coefficient of friction with the road surface.

(Problems to be Solved by the Invention) Although SBR with a high content of bound styrene certainly has a high coefficient of friction with the road surface, it is more likely to generate heat.

When a tire runs at high speed, the number of times the tire is subjected to strain per unit time also increases proportionally, so naturally the amount of heat generated by the rubber also increases. However, since the heat diffusion rate does not increase proportionally, the degree of corrosion inside the rubber composition that makes up the tire increases, and eventually, due to this heat, the three-dimensional network formed by vulcanization becomes partially It is destroyed and a void is created in that part. When these voids occur, cracks form and grow around these voids, resulting in destruction of the tire.

In addition, SBR, which has a high content of bound styrene, is a rubber that is particularly prone to heat generation, and therefore tires inherently have a hump in terms of failure due to this heat. In order to improve this shortcoming,
Many studies have been carried out, and it is known that among SBR-based rubbers, solution polymerization type SBR, especially the type in which the amount of vinyl bond in the butadiene moiety is in a row, is favorable. Although the performance of road vehicles has improved rapidly, this method has reached a level that is unsatisfactory for current high-speed tires.

(Means for solving problems) In order to improve this, we conducted studies from two directions.

One method is to develop rubber that does not easily generate heat, and the other method is to improve heat resistance by making it difficult to generate voids.

As a result, increasing grip strength and decreasing heat generation are essentially antinomy phenomena, and it is impossible to satisfy both, making it difficult to improve with the first method! -I found out that Managoto. Next, we investigated the latter method by blending vulcanized rubbers whose fracture strength does not change much even at high temperatures.

EPDM rubber is considered to have a high possibility of this, but when we actually examine it, we find that increasing the amount of EPDM rubber blended causes a significant decrease in strength at break and wear resistance. It is difficult to put it into practical use, and the reason for this is E.
It was also found that this was caused by poor compatibility (co-vulcanization) between the PDM rubber and the diene rubber.

Based on the above knowledge, the present inventors conducted extensive research and examination, and as a result, developed EPDM rubber with specific structural characteristics and solution polymerization SDR.
The inventors of the present invention found that the heat resistance of a tread rubber can be significantly improved by using a composition containing a blend of the same as a rubber component as a rubber component.

That is, the present invention provides: (1) A pneumatic tire comprising a tread portion, a sidewall portion, and a bead portion, in which the tread portion is provided with ethylene-propylene-diolefin terpolymer rubber (EPD).
10 to 70 parts by weight of M Co9 and solution polymerization SBR30 to 9
0. ! The rubber composition is characterized by using a rubber composition obtained by blending 40 parts or more of process oil and 70 to 200 parts by weight of an inorganic filler to 100 parts by weight of rubber containing a blended rubber consisting of part i. The invention relates to a pneumatic tire with improved high-speed durability, more preferably (2).
) The EPDM rubber satisfies all of the following conditions.

A, glass transition temperature (DSC: ff, 11 constant); -5O
Below ℃.

B. Iodine value: 10-34 C0 weight average molecular weight: 220,000 or more.

D, ethylene content n: 68-85 mol%.

E3 molecular weight distribution (Mw/Mn): 3.0 or more.

F, 95≦1.5X (iodine value) + (ethylene content)
≦120G, 90≦(weight average molecule ff1X10-”(
etele/Town town total) ≦120 and its solution polymerization SBR is
The present invention relates to a pneumatic tire having a structure in which the content of bound styrene in the polymer is 30 to 60% by weight and the vinyl content of the butadiene moiety is 20 to 80% by mole of the butadiene unit.

The present invention will be explained in detail below.

First, the rubber component will be explained.

As a result of evaluating various EPDM rubbers with various structural properties changed in order to improve the above-mentioned drawbacks, the EPDM rubber that met all of the following requirements was found to have significantly improved wear resistance and adhesion with diene rubber, and was found to be rubber for tire treads. It has been discovered that the heat resistance mentioned above is significantly improved at the same time that the composition reaches a level that can be used satisfactorily as a composition.

A. Glass transition temperature (DSC measurement): -50°C or lower.

B, iodine value; 10-34 C1 weight average molecular weight: 220,000 or more.

P, f and y content: 68 to 85 mol%.

E0 molecular weight distribution (Mw/Mn): 3.0 or more.

F, 95≦1.5X (iodine value) + (ethylene content)
≦120G, 90≦Saliva weight average molecular color Xl0-4+ (ethylene content)≦120 The amount of this EPDM rubber used is 1
0 to 70 parts by weight is preferred. This means that if it is less than 10ii parts, sufficient heat resistance cannot be obtained;
This is because if the weight exceeds the weight part, sufficient grip performance cannot be obtained.

Next, the necessary structural conditions for this EPDM rubber will be described.

The glass transition temperature of this rubber measured by DSC is -50℃
The following are preferred. This is because if the temperature is higher than -50°C, sufficient crack growth resistance and bending resistance are not provided. Note that the temperature increase rate during this measurement was 10° C./min.

Next, the iodine value of this rubber is preferably 10 to 34.If it is less than 10, sufficient crack growth resistance, strength at break, and wear resistance cannot be obtained, and if it is higher than 34, it will not run properly when heated. This is because the subsequent abrasion resistance is undesirable. The diolefin component, which is the basis of the iodine value, is generally expensive, so it is important to keep this amount as low as possible in rubber compositions used in rubber products, and to produce the rubber with the best performance among them. This is an important issue for this rubber from an industrial standpoint.

Further, the weight average molecular weight of this rubber is preferably 220,000 or more. That is, when the molecular weight is 220,000 or more, the effect of improving crack growth resistance and abrasion resistance is remarkable, and, unexpectedly, the adhesive strength with tsene rubber is also significantly improved.

On the other hand, when the molecular weight is increased, the viscosity of the rubber increases rapidly, resulting in a disadvantage that the processability of the unvulcanized rubber is significantly reduced. As a countermeasure against this problem, it is preferable to use the rubber as an oil-extended rubber in the range where the weight average molecular weight exceeds 240,000. So, the weight average molecular weight of this column is 4.
If it exceeds 0,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 is exceeded, the amount of oil required to maintain workability is extremely large, which is not preferable because physical properties after vulcanization, such as wear resistance, are significantly reduced. As the oil for oil expansion, /A'Roughinnick oil is preferred.

Moreover, the ethylene content of the rubber is preferably 68 to 85 mol%. If the ethylene content is as low as 68 morpho, even if the iodine value is increased to more than 34, the effect of improving crack growth resistance, strength at break, and wear resistance will be very small; If the molar percentage is high, it becomes close to polyethylene resin, so the elongation at break becomes small and the elastic modulus becomes high, making it difficult to use it industrially as a rubber.

Next, the molecular weight distribution (Mw/Mn) of this rubber is preferably 3.0 or more. The reason is that if this value is lower than 3.0, roll workability is poor and industrial use becomes difficult.

Further, it is preferable that this rubber satisfies the following two formulas.

95≦1.5X (iodine value) + (ethylene content)≦1
2090≦(weight average molecular t) Strength and wear resistance cannot be obtained, and 12
This is because if it exceeds 0, heat deterioration resistance including wear resistance after heat deterioration decreases.

Furthermore, if "(weight average molecule it)
If it exceeds 0, processability such as C/H dispersion and roll workability will deteriorate, and the elastic modulus of the rubber composition will become too high, making it difficult to use industrially. It is.

Although the 1d11 limiting conditions of each structure and their reasons have been explained above, it is necessary to satisfy all of the individual conditions at the same time. This is thought to be due to a) synergistic effect of a previously unknown confounding relationship between the individual conditions.

The diolefin component of this rubber is preferably ethylidene norbornene. This is compatible with other commonly used diolefin components such as dicyclopentadiene and 1,4-
This is because hexadiene cannot exhibit sufficient improvement effects in terms of crack growth resistance, strength at break, and elongation at break.

Next is solution polymerized SBR, which has a structure in which the content of bound styrene in the polymer is 30 to 60% by mass, and the vinyl bond content of the butadiene unit is 20 to 80 mol% of the butadiene unit. It is.

This solution polymerized SBR is used as one component of the blended rubber because this rubber has the best heat resistance as mentioned above among diene rubbers, and also has excellent grip performance. .

In terms of the structure of this rubber, the vinyl bond content of the butadiene moiety is preferably 20 to 80 mol% of the butadiene units. This is because its value decreases below 20 mo/l/%, which is undesirable.

The bound styrene content is 30 to 60% by weight of the polymer.
is preferred. This is because the weight exceeds 30 weight, and it becomes impossible to obtain sufficient grip performance as well.

Next, the inorganic filler is selected from carbon black, silicon dioxide, calcium carbonate, titanium dioxide, and the like.

Among these inorganic fillers, carbon black is preferred, and its iodine adsorption amount is 100 to 300 m9/
9. DBP oil absorption is 100-200d/100g
Particularly preferred is carbon black.

This is because if the amount of iodine adsorbed is lower than 100/9, sufficient wear resistance cannot be obtained.

In addition, if the DI3P oil absorption is lower than 100 m/10 (l), carbon black will not be sufficiently dispersed and sufficient wear resistance will not be obtained.
In either case, exceeding the upper limit causes poor carbon dispersion, which is undesirable.

The amount of inorganic filler used is preferably 70 to 200 parts by weight, and the amount of process oil used is preferably 40 parts by weight or more.

That is, in the tread of this type of tire that requires high-speed performance, carbon black and process oil are used in a larger amount than in the tread rubber composition of a normal tire to ensure excellent grip performance. On the other hand, if the amount exceeds 200 parts by weight, it is necessary to add a correspondingly large amount of process oil/l, which results in a relative decrease in the concentration of the polymer in the rubber composition, resulting in sufficient wear resistance. This is because you will not be able to have sex.

In addition, when 70 parts by weight or more of an inorganic filler is added, it is preferable to use 40 parts by weight or more of process oil as the oil for extending the oil in the rubber.

The rubber composition of the present invention has extremely excellent weather resistance and heat resistance compared to commonly used didine rubber compositions, so it is particularly important to add amine anti-aging agents, paraffin wax, etc. do not need.

Furthermore, when the amount of EPDM rubber used is small, such as 20 parts by weight, adding a small amount may result in a dry coating.

Even in this case, if it is an amine-based anti-aging agent, it should be 0.3 parts by weight or less, and if it is a nosorafuin-based wax, it should be less than 0.3 parts by weight.

It is sufficient to use less than 0.5 parts. Of course, there is no problem in using both of them together.

The hardness of the rubber composition of the present invention after vulcanization (JIS hardened type A) is preferably 20 to 80.

This is because if this value is lower than 20, sufficient steering stability, which is essential for high-speed tires, cannot be obtained;
: If it is exceeded, it will not be possible to obtain sufficient grip performance.

With the above structure, a tire excellent in high-speed durability can be obtained.

Next, a method for producing EPDM rubber used in the present invention will be explained. That is, EPDM rubber is prepared by (a) in a hydrocarbon solvent.
A vanadium compound represented by y□(OR)nXs-n (R is a hydrocarbon residue,
In the presence of a catalyst formed from an organoaluminium compound represented by At'3-m (R' is a hydrocarbon residue, in which a halogen element, 0≦m≦3), ethylene, zolopyrene, and as a third component, for example, ethylidene. Examples of adjusting norbornene to the desired monomer unit composition are:
VO(OCI(3)Cl3.VQ(OCH3)2Ct
.

vO(OCH3)3. ■0(OC2H5)C62, ■0
(OC2H5)2C4゜vO(OC2F■5)3. vO
(OC2H5)4.5Br1゜5. vO(OC3H7)
C42°VO (QC, H,), 5CL, 5. VO(
QC3)I,) 2CL, VO(QC6H,),
.

vo(o-nc4u,)Cl2. vo(o-nc4H
,)2C4°VO(0-taOc4H2)C22,vo
(o-secc4u,)3゜VO(QC5H,1) 1
．． 5CL1,5. Examples include VOCl3, vC44, or a mixture thereof. Among these compounds, vO
(OC2H5)Cl3 and vocz are particularly preferred.

Also, specific examples of organoaluminum compounds include:

(ca3)2Azcz, (CH,)4.5AtCL
,,5. (CH3)AlCl2゜(C2H5)2A
tCt, (C2H5), 5AtcL1.5. (C
2H5) AtCA2゜(C3f(7)2AtC4, (C
3H7) 1.5AAC21,5a (C,)I,)kL
cz2゜(c6H13) 1.5AAC24,51(C
6H13) AA2CL, (C6H4,)AtCA2°, or a mixture thereof.

The usage ratio of the organoaluminum compound and the 4-nadium compound is 2 to 50 as ht compound/V compound (mole ratio).
．． Particularly preferred is a range of 5 to 30.

The concentration of the vanadium compound is 0.01 to 5 mmol/liter, preferably 0.1 to 2.0 mmol/liter.

Examples of hydrocarbon solvents include hexane, hezotane,
Fatty raw coals such as octane or kerosene can be used alone or in mixtures with mizuki and aromatic hydrocarbons such as benzene, toluene or xylene.

The ethylene content in the polymer can be adjusted by controlling the amount of heptamer supplied during copolymerization, but it is industrially difficult to increase the content to 85 mol% or more... Polymerization temperature is 0 to 100°C, preferably 20 to 80°C
1 Polymerization pressure is maintained at 0 to 50 kg/L-rn2.

Furthermore, hydrogen is used to adjust the molecular weight of the EPDM rubber produced.

(Example) The present invention will be explained in more detail with reference to Examples below.

First, the test method used, the type of tire used, and the EPDM
Rubber and solution polymerized SBH will be explained.

Test Method> (1) Heat Resistance: Using a Goodrich Flexomater, the temperature at which a rubber sample generates nitrogen gaps due to heat generation was measured. That is, the temperature of each of the control sample and the test sample is measured and the difference is shown as the difference, and the larger this value is, the better it is.

(2) Grip performance: The vehicle was run 10 times around a cart course (720 m) and evaluated based on the best lap time. The smaller the lap time, the better this performance is. Note that the difference between 1 and 0 has a great meaning in terms of performance.

(3) Wear resistance: Evaluation was made on the appearance of wear after running 10 laps on a cart course (720 m) in three grades: excellent, good, and fair.

(4) Adhesive strength with diene rubber; Unvulcanized rubber sheets of the diene rubber composition and the rubber composition of the present invention each having a thickness of about 2.0 m are laminated together, and a cellophane sheet with a width of 3 m is attached to one end of the unvulcanized rubber sheet. It was used as a grip when performing a beer ring test by sandwiching a piece of paper. The laminated sample was reinforced by laminating canvas on both sides and placed in a 4.0 m thick mold, and vulcanized at 145° C. for 45 minutes.

This sample was punched out to a width of 1 d at a shop, and after removing the cellophane paper, it was subjected to bee IJing at a speed of 50 brocades/min, and the force at that time was evaluated.

2. As the diene rubber composition, the rubber compositions shown in Table 1 were used.

Table 1 Diene-based rubber compound composition for adhesion evaluation (
5) Roll workability; Roll workability with a 10-inch roll was evaluated, with particular attention paid to buggy performance.

Types of test tires> Florlt, 4.5/10.0-5, Rea
Cart tires of r 7.1/11.0-5 were used.

Table 2 shows the relationship between the names of EPDM rubber samples used for tire treads and their structural properties.

Note that the EPDM rubber of Trial Production-3 in Table 2 was produced as follows. Using a 15-liter stainless steel polymerization vessel equipped with a stirring device, ethylene, propylene, and ethylidenenorbornene were continuously copolymerized by the following method.

Hexane was continuously supplied as a polymerization solvent from the top of the polymerization vessel at a rate of 5 liters per hour. On the other hand, the polymerization liquid was drawn out from the lower part of the polymerization vessel so that the polymerization liquid in the polymerization vessel was always 5 liters. As a catalyst (a) VO(OC2H5)C2
2, the concentration in the polymerization vessel is 0.28 mmol/liter, (
b) The concentration of (C2H5)1.5AtCL4.5 is 1.8
Each was continuously fed from the top of the polymerization vessel at a concentration of 5 mmol/liter. In addition, a mixed gas of 45 mol% ethylene and 55 mol% tocropyrene was supplied from the top of the polymerization reactor at 4 mol% per hour.
Ethylidene norbornene was fed at a rate of 50 liters and 25 g/hour, respectively. Additionally, hydrogen gas was supplied as a molecular weight regulator at a rate of 3.2 liters per hour.

The polymerization temperature was controlled at 41°C by a jacket attached to the outside of the polymerization vessel, and the pressure inside the polymerization vessel was 4.81°C.
v/cm".

The polymerization solution taken out from the lower part of the polymerization vessel was subjected to steam stripping treatment, dried at 80° C. for a day and night, and then dried under vacuum. The yield of EPDM rubber was 2651 per hour. In addition, the 1-weight average molecular weight and Mw/Mn were measured by GPC.

Table 3 shows the relationship between the names of SBH samples used for tire treads, polymerization types, and structural characteristics.

Table 3 5BR-List (Note) (1) Numbers that lack the constitutional conditions of the invention are underlined (2) SBR-B to I; Produced according to the method of 5BR-A (3) SBR-J: (4) Oil for oil extension manufactured by Japan Synthetic Rubber Co., Ltd.; Heavy Aromatic Oil manufactured by Fuji Kosan Co., Ltd. Note that SBR-A was produced by the following method.

100 pp of 1,2-butadiene as monomer into a reactor with an internal volume of 20 liters equipped with a stirrer and a jacket.
1.3-butadiene with a content of m was fed at a rate of 20 g/min, styrene at a rate of 12.9/min, cyclohexane as a solvent at a rate of 150 F/min, and tetrahydrofuran at a rate of 1.5 pumps to bring the temperature of one reactor to 70°C. Controlled 8 polymerizations were carried out. At the top outlet of the reactor, silicon tetrachloride is continuously added at a ratio of 1/4 mole to 1 mole of n-butyllithium, and this is poured into a second reactor connected to the top of the reactor to form a cup. A ring reaction was performed. At the outlet of the second reactor, 0.5 parts by weight of sheet tert-butyl-p-cresol was added to 100 parts by weight of rubber, followed by 37.5 parts by weight of aroma oil.
zOkibeY.

In addition, the solvent was removed and dried in a conventional manner to obtain a polymer.

[Examples 1-2. Comparative Examples 1 to 3] A pneumatic tire made of the material of the present invention and a tire with a tread made of a conventional rubber composition were manufactured, and their performance was evaluated.

The results are shown in Table 4.

According to the results in Table 4, EPDM satisfies the structural conditions of the present invention.
A tire using a rubber composition containing a rubber-solution polymerized SBR blend system as a tire tread rubber.

It can be seen that the heat resistance is particularly excellent compared to solution polymerized SBR alone or unsatisfactory blend systems. It is also found that it has good properties that are as good as, but not inferior to, in terms of abrasion resistance and adhesive strength of diene rubber.

[Examples 3-4. Comparative Example 4 to IQ] Tires were produced with various structures of the EPDM rubber constituting the rubber composition of the tire tread, and their performance was evaluated. Note that other conditions were the same as in Example 1.

The results are shown in Table 5. Note that the EPDM rubber types in Table 5 correspond to the EPDM rubber types in Table 2.

From the results in Table 5, it is clear that EPDM satisfies the structural conditions of the present invention.
It can be seen that the rubber is a solution polymerized SBR blend system and has good heat resistance properties.

(2) DPG; Nophenylguanidine (3) manufactured by Daien Shinko Kagaku Kogyo Co., Ltd. DM: 2-benzothiazoyl disulfide manufactured by Daien Shinko Kagaku Kogyo Co., Ltd. [Examples 5 to 7. Comparative Examples 11 to 13] Tires having treads made of rubber compositions with varying amounts of EPDAi rubber were produced and their performance was evaluated.

The results are shown in Table 6.

(Results in Table 5), in order to achieve sufficient effect, EPDM
It has been found that it is necessary to have the amount of rubber within a certain range, namely from 10 to 70 parts by weight.

[Examples 8-11. Comparative Examples 14 to 18] Tires were manufactured by changing the structure of the solution polymerized SBR constituting the rubber composition for tire treads, and their performance was evaluated. The results are shown in Table 7.

Note that the SBRA in Table 7 and the SBR in Table 3 indicate that the structure of the solution polymerized SBR used preferably satisfies the conditions described in the specification.

(Effects of the invention) (1) EPDM rubber with a fixed structure ~ solution polymerization S with a specific structure
By using a rubber composition containing a BR blend system in a tire tread, its heat resistance has been greatly improved, and the high-speed durability of the tire has been dramatically improved.

(2) In terms of performance, this tire also has performance superior to conventional tires in terms of grip, abrasion resistance, and workability such as adhesion with diene rubber, which are essential for high-speed running. It is something.

Shi-Yuko-21

Claims (1)

[Scope of Claims] (1) A pneumatic tire comprising a tread part, a sidewall part, and a bead part, in which the tread part is made of ethylene-propylene-diolefin terpolymer rubber (EPD).
M rubber) 10 to 70 parts by weight and solution polymerization SBR30 to 90
The rubber composition is characterized by using a rubber composition obtained by blending 40 parts by weight or more of process oil and 70 to 200 parts by weight of an inorganic filler with respect to 100 parts by weight of rubber including a blended rubber consisting of parts by weight. , improved pneumatic tires for high speed durability. (2) The pneumatic tire according to claim 1, wherein the EPDM rubber is a rubber that satisfies all of the following conditions. A. Glass transition temperature (DSC measurement): -50°C or lower. B, iodine value: 10-34 C, weight average molecular weight: 220,000 or more. D, ethylene content; 68-85 mol%. E, molecular weight distribution (Mw/Mn); 3.0 or more. F, 95≦1.5×(iodine value) + (ethylene content)
≦120G, 90≦(weight average molecular weight) x 10^-^4
+(Ethylene content)≦120 (3) Solution polymerized SBR has a structure in which the bound styrene content is 30 to 60% by weight of the polymer and the vinyl bond content of the butadiene moiety is 20 to 80 mol% of the butadiene unit. A pneumatic tire according to claim 1, characterized in that the pneumatic tire comprises: (4) The pneumatic tire according to claim 1, wherein the diolefin of the EPDM rubber is ethylidene norbornene. (5) The inorganic filler is carbon black, silicon dioxide,
The pneumatic tire according to claim 1, characterized in that the pneumatic tire is selected from calcium carbonate and titanium dioxide. (6) The iodine adsorption amount of carbon black is 100 to 3
00mg/g, DBP oil absorption 100-200ml/1
6. The pneumatic tire according to claim 5, wherein the pneumatic tire has a weight of 0.00 g. (7) The pneumatic tire according to claim 1, wherein 60% or more of the process oil is an oil for extending EPDM rubber.