JPS61268502A - High performance tire - Google Patents

Abstract

PURPOSE:To improve wear resistance and gripping property by forming a tread rubber from a compound of specified composition consisting of an isobutylene group high polymer, and a diene group rubber, which has a specified molar ratio of diene unit to isobutylene unit and a viscosity-average molecular weight. CONSTITUTION:A composition rubber formed by compounding a 30-10pts.wt. of isobutylene group high polymer, a 70-90pts.wt. of diene group rubber, a 90-180pts.wt. of inorganic filler, and a 40-120pts.wt. of process oil, which has a 0-0.01 molar ratio of diene unit to isobutylene unit and a 750,000 or more of viscosity-average molecular weight, is used as a tread rubber. In this case, the weight ratio of the process oil to the inorganic filler is specified as 0.3-1.0. By this formation, wear resistance and gripping property can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to high performance tires, particularly high performance tires with improved wear resistance and grip performance.

<Prior art> Conventionally, high-performance tires are required to have maximum grip performance with the road surface, so rubber compositions with low elastic modulus and high energy loss have been used as tread rubber compositions for these tires. I've been

Specifically, a styrene-butadiene copolymer rubber with a high styrene content is used, but as the styrene content increases beyond a certain value, the styrene begins to enter the polymer main chain in the form of blocks. , and the grip performance actually deteriorates. Therefore, this method has already reached its limit in improving grip performance. In addition to this, many improvement methods have been proposed, but at present none are sufficient.

(Problems to be Solved by the Invention) The present invention utilizes an isobutylene-based high polymer to improve wear resistance and grip performance without achieving the improvement by mainly increasing the styrene content as described above. This is what we are trying to solve. In this case, tires using conventional butyl rubber have poor abrasion resistance and tensile strength.
It has drawbacks such as insufficient adhesion with diene rubber and slow vulcanization rate, and as a result, it has not been able to exhibit effects in improving wear resistance and grip performance. The present invention aims to solve the above problems by using a special isobutylene-based high polymer.

(Means for Solving the Problems) As a result of intensive research to improve the above-mentioned drawbacks, the present inventors have discovered a butyl rubber having a molecular weight of 750,000 or more and having almost no or no double bonds in the main chain. When you blend the
The present invention was achieved by confirming that this material is completely different from conventional butyl rubber in that it has significantly improved wear resistance and a significantly improved coefficient of friction with the road surface.

That is, the present invention provides a pneumatic tire comprising a tread portion, a pair of sidewall portions connected to the tread portion at both shoulders of the tread portion, and a pair of bead portions formed on the inner periphery of the sidewall portion, respectively. The tread rubber composition has a molar ratio of diene units to isobutylene units of 0.
~0.01 and a viscosity average molecular weight of 750,000 or more, 30 to 10 parts by weight of an isobutylene-based high polymer, 70 to 90 parts by weight of diene rubber, 90 to 180 parts by weight of an inorganic filler, and 40 to 40 parts by weight of process oil. 120 parts by weight, and the weight ratio of process oil to inorganic filler is 0.
3 to 1.0.

Conventionally, butyl rubber has a high coefficient of friction with the road surface (particularly with the coefficient of friction with the road surface when wet), so much research has been conducted on it as a rubber composition for tire treads, but it has the following drawbacks: , the actual example used is:
Very few.

(1) Extremely poor wear resistance. When butyl rubber is blended with diene rubber, wear resistance rapidly decreases.

(2) Tensile strength decreases. As butyl rubber is blended, the tensile strength rapidly decreases.

(3) Insufficient adhesion with other diene rubbers. (Rubber...
・Rubber adhesion) (4) Vulcanization speed is slow. (Crosslinking reaction due to sulfur) One of the major causes of these drawbacks is that the vulcanization rate is slow. Since the vulcanization rate is slow compared to other diene rubbers, the interfacial adhesion between the diene rubber and butyl rubber is insufficient, resulting in reduced abrasion resistance and tensile strength. In order to improve this, halogenated butyl rubbers such as chlorobutyl rubber and bromobutyl rubber have been developed, but they are still not sufficient.

The inventor of the present invention has conducted intensive research to apply the property that butyl rubber has a very high coefficient of friction with the road surface (particularly the coefficient of friction when wet) compared to diene rubber to tire treads. However, by increasing the molecular weight of butyl rubber to a higher molecular weight than normal butyl rubber and microdispersing it in a diene rubber composition, this disadvantage can be overcome. I was able to overcome this for the first time.

The isobutylene-based polymer of the present invention differs greatly from the conventional use of butyl rubber in that by increasing the molecular weight of butyl rubber, there is no need for crosslinking, and by increasing the molecular weight, The shape of the interface with the diene rubber becomes complex, the area of the interface increases,
Furthermore, due to the addition of an anchor effect, the adhesive strength increases, resulting in very little decline in wear resistance and tensile strength, and the entire system is actively controlled to be a heterogeneous system. It is.

As described above, the pneumatic tire of the present invention is manufactured by utilizing the characteristics that butyl rubber has a large coefficient of friction with the road surface (particularly a coefficient of friction when wet), has excellent wear resistance, and has a glass transition temperature as low as that of natural rubber. now available.

Examples of the isobutylene-based high polymer include Opanol B80, Opanol B100, Opanol B120,
Opanor B150, Opanor Ro 200 (both B
The viscosity average molecular weight of each grade is as shown in Table 1.

Table 1 Table 1 also includes Obanor B 50 manufactured by BASF Corporation.
is also shown, but this is an isobutylene-based high polymer that is not included in the isobutylene-based high polymer of the present invention. In addition,
The viscosity average molecular weight Mv of the Obanol 8 series polymers in Table 1 is calculated by the formula %. Jo is the intrinsic viscosity measured in isooctane at 20°C.

The molar ratio of diene units to isobutylene units is 0 to 0.01.
The reason for this limitation is that there is no need to copolymerize isoprene monomers in the present invention. In other words, the reason why the commonly used butyl rubber is copolymerized with isoprene in addition to isobutylene is to introduce a double bond into the main chain so that it can be easily crosslinked with sulfur etc. in the same way as diene rubber. It is for this purpose.

However, in the present invention, the need for crosslinking is eliminated by significantly increasing the molecular weight of the isobutylene-based high polymer, so there is no need to introduce double bonds into the rubber main chain. On the other hand, if a diene such as isoprene is copolymerized, it becomes difficult to obtain a high molecular weight rubber. For these reasons, the molar ratio of diene units to isobutylene units was limited to 0 to 0.01.

In the present invention, the viscosity average molecular weight is limited to 750,000 or more because if the molecular weight is less than 750,000, it will flow unless it is crosslinked and used like ordinary rubber, resulting in large permanent deformation. This is because it cannot be done. Furthermore, the effect of complicating the interface with the diene rubber, increasing adhesive strength, and making it difficult to cause adhesive fatigue is still insufficient at around 750,000, so it is preferable to set it at 1,400,000 or more.

The reason why the amount of the isobutylene-based high polymer of the present invention is limited to 10 to 30 parts by weight is that if it is less than 10 parts by weight, there is no effect.
This is because if the amount exceeds 30 parts by weight, poor dispersion of the isobutylene-based polymer will occur.

In the present invention, the amount of inorganic filler is limited to 90 to 180 parts by weight because a large amount of process oil is used to satisfy the grip of the tread, so if the amount of inorganic filler is less than 90 parts by weight, Workability during machining is significantly reduced, sufficient wear resistance cannot be ensured, and 180
This is because if the amount exceeds 1 part by weight, the workability during processing will not be sufficient and it will be of no industrial value.

In the present invention, the amount of process oil is limited to 40 to 120 parts by weight because if the acid amount is less than 40 parts by weight, the effect of improving the grip performance of the tread portion is insufficient.
This is because if the amount exceeds parts by weight, the improvement effect will no longer increase significantly, and on the contrary, the adverse effect on workability during processing will become significant.

In addition, in the present invention, the weight ratio of process oil to inorganic filler is limited to 0.3 to 1.0 because if it is less than 0.3, the amount of process oil is too small and workability during processing is poor. <, If it exceeds 1.0, it becomes too sticky and the workability during processing is also poor.

Examples of the diene rubber of the present invention include natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, α-methylstyrene-butadiene copolymer rubber, and butadiene-isoprene copolymer rubber. At least one type of diene rubber selected from the group consisting of:

The diene rubber is preferably a vinyl aromatic-butadiene copolymer rubber containing 30% by weight or more of styrene units and/or α-methylstyrene units, and the upper limit of the content of the units is 50% by weight or less. is preferable, because when it is within the above range, it is easy to obtain a large grip in a rubber composition containing a large amount of process oil and carbon black. The vinyl aromatic-butadiene copolymer rubber has heat resistance that the vinyl structure content of the butadiene moiety is 40% by weight or more of the butadiene moiety, and that the glass transition temperature of the copolymer rubber is 145°C or higher. It is preferable in that it is excellent. In addition, the diene rubber is polyisoprene rubber, isoprene-styrene copolymer rubber, or isoprene-α- rubber whose isoprene portion has a 3.4 vinyl structure content of 40% or more and a glass transition temperature of 145°C or more.
Also preferred is methylstyrene copolymer rubber.

The isobutylene-based polymer of the present invention is preferably incompatible with diene-based rubber and forms an independent layer (island phase) in the diene-based rubber (sea phase); This is because if it is not a solvent-based rubber, the properties of polyisobutylene rubber (the coefficient of friction with the road surface, especially the coefficient of friction with the road surface when wet is high) cannot be fully demonstrated.

In the present invention, the average diameter of the isobutylene-based high polymer independent layer is preferably 10 μm or less, because if it exceeds 10 μm, the tensile strength will decrease considerably. In order to fully demonstrate the properties of the isobutylene-based polymer and maintain tensile strength, the average diameter of the independent layers should be 0.3.
˜3.0 μm is most preferred.

In the present invention, the average diameter is determined by preparing an ultrathin section from the sample, magnifying it 10,000 times with an electron microscope, measuring the longest diameter of the independent layer and the diameter in the direction perpendicular to it, and adding both. 2
The value divided by 300 randomly selected independent layers was simply averaged.

In the rubber composition according to the present invention, in addition to the compounding agents, rubber compounding agents such as anti-aging agents, vulcanization accelerators, vulcanization accelerators such as stearic acid and zinc white, and vulcanizing agents are added. It can be blended into rubber within the usual range.

In the present invention, the glass transition temperature of the polymer was measured using a differential scanning calorimeter, PerkinElmer's DSC-2, at a heating rate of 10° C./min.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

In addition, as part of tire testing, wear resistance and grip performance (
Shown in braking distance. ) and rolling resistance were measured according to the following methods.

Wear resistance: The test tire was driven 15,000 km in a passenger car together with the control tire, and the frame gauge was measured.
Expressed as an index relative to control. The larger the index, the better.

Braking distance: Four test tires were mounted on a passenger car, the vehicle was driven on a dry road at 50 km/hr, sudden braking was applied, and the braking distance until it came to a complete stop was evaluated. It is expressed as an index compared to the control, and the larger the index, the better.

In addition, if the tire temperature at the time of measurement is 18℃, the braking distance (
Unless otherwise specified, the evaluation was performed at room temperature.

The tensile strength of the rubber composition after vulcanization is determined by JIS,
Measurement was performed using a JIS No. 3 dumbbell type sample in accordance with K63 old.

It is expressed as an index relative to the control, and a larger value indicates greater tensile strength.

Example 1 Comparative Examples 1-2 Example 1 shows that the high performance tire of the present invention has significantly improved grip performance and wear resistance compared to conventional high performance tires.

Three types of rubber compositions were prepared according to the formulations shown in Table 2, and radial tires of size 175SR14 were prepared using these as tread rubber, and the braking distance (
The coefficient of friction with the road surface) and wear resistance were evaluated. The results are shown in Table 3.

Table 2 Pass Styrene content 35%, Vinyl content 45%, Glass transition temperature -43°C 02 Manufactured by Japan Synthetic Rubber Co., Ltd. Butyl rubber Product name:
Viscosity average molecular weight 540,000, isoprene/isobutylene (mole ratio) 0.0152 $3 Antioxidant Table 3 Examples 2 to 6 Comparative Examples 3 to 4 In Examples 2 to 6, the diene of the isobutylene-based high polymer of the present invention The molar ratio of units to isobutylene units is 0 to 0.01
, the viscosity average molecular weight is limited to 750,000 or more,
More preferably, it is 1.4 million or more.

Example 1 shows the test rubber composition and the production of a radial tire of size 175SR14 using the same as tread rubber.
I followed the instructions. The composition of the rubber composition, the state of the independent layer, etc. are shown in Table 4, and the tire test results are shown in Table 5.

Examples 7-8 Comparative Examples 5-7 Examples 7-8 show that the amount of isobutylene-based high polymer blended is limited to 10-30 parts by weight per 100 parts by weight of rubber. A radial tire of size 175SR14 was prepared according to Example 1 using a rubber composition having the formulation shown in Table 6 for the tread portion, and was tested.

The results are shown in Table 7.

Table 7 In Examples 9 to 14, it is preferable that the independent layer of isobutylene-based polymer exists with an average diameter of 10 μm or less, and it is more preferable that the independent layer exists with an average diameter of 0.3 to 3.0 μm. Show that.

In this example, the composition was the same as that of the rubber composition used in Example 1, only the kneading conditions were changed, and only the dispersion form of the independent layer was changed. During kneading, the smaller the clearance between the rotor of the kneader and the wall surface and the higher the kneading temperature, the smaller the average diameter of the independent layers became. A radial tire of size 175 SR14 was prepared using these rubber compositions for the tread portion and tested. The results are shown in Table 8.

Examples 15-16, Comparative Examples 8-11 In Examples 15-16, the inorganic filler was 90 to 180 parts by weight, the process oil was 40 to 120 parts by weight, and the weight ratio of the inorganic filler to the process oil was 0.3-1.0
Indicates that it is limited within the range of A radial tire of size 175SR14 was prepared using a rubber composition having the formulation shown in Table 9 for the tread portion, and tested. The test results are shown in Table 10. Note that Comparative Example 1 was used as a control.

(Effects of the Invention) The present invention provides a tread rubber composition comprising an isobutylene polymer having a molar ratio of diene units to isobutylene units of 0 to 0.01 and a viscosity average molecular weight of 750,000 or more.
This is a high-performance tire made of a rubber composition made by blending specific amounts of diene rubber, inorganic filler, and process oil. Both abrasion resistance and grip performance could be improved.

Claims (1)

[Claims] 1. A pneumatic tire comprising a tread portion, a pair of sidewall portions connected to the tread portion at both shoulders of the tread portion, and a pair of bead portions formed on the inner periphery of the sidewall portions. , the tread rubber composition has a molar ratio of diene units to isobutylene units of 0 to 0.01,
and 30 to 10 parts by weight of an isobutylene-based high polymer having a viscosity average molecular weight of 750,000 or more, 70 to 90 parts by weight of diene rubber, 90 to 180 parts by weight of an inorganic filler, and 40 to 120 parts by weight of process oil. A high-performance tire characterized by being a rubber composition in which the weight ratio of process oil to inorganic filler is 0.3 to 1.0. 2. The diene rubber is selected from the group consisting of natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, α-methylstyrene-butadiene copolymer rubber, and butadiene-isoprene copolymer rubber. The tire according to claim 1, which is at least one diene rubber. 3. Vinyl aromatic diene rubber containing 30% by weight or more of styrene units and/or α-methylstyrene units.
The tire according to claim 1, which is a butadiene copolymer rubber. 4. A vinyl aromatic-butadiene copolymer rubber in which the vinyl structure content of the butadiene moiety is 40% by weight or more of the butadiene moiety, and the glass transition temperature of the copolymer rubber is -45°C or higher. Tires described in range item 3. 5. The diene rubber is polyisoprene rubber, isoprene-styrene copolymer rubber, or isoprene-α-methylstyrene whose isoprene moiety has a 3,4-vinyl structure content of 40% or more and a glass transition temperature of -45°C or higher. The tire according to claim 1, which is a copolymer rubber. 6. The tire according to claim 1, wherein the isobutylene polymer does not contain a double bond in its molecular main chain and has a viscosity average molecular weight of 750,000 or more, preferably 1,400,000 or more. 7. The tire according to claim 1, wherein the isobutylene copolymer has a viscosity average molecular weight of 750,000 or more, preferably 1,400,000 or more, and is incompatible with the diene rubber and forms an independent layer. . 8. The tire according to claim 7, wherein the independent layer has an average diameter of 10 μm or less. 9. The tire according to claim 7 or 8, wherein the independent layer has an average diameter of 0.3 to 3.0 μm.