JPS6061312A - Radial tire for passenger vehicle - Google Patents

Abstract

PURPOSE:To enhance the mobility on a slipable road surface, heating, low fuel consumption of a tire having a two layer structure tread, by tread ratio of the outer surface rubber layer, and as well specifying the post-vulcanization characteristics of the inner surface rubber layer. CONSTITUTION:An outer surface rubber 1 having a tread ratio of 0.5-0.9, a complex elastic modulus 3-8MPa at 70 deg.C and a loss tangent 0.1-0.5, is formed with the use of 10-70pts.wt. of natural rubber and/or synthetic polyisoprene rubber, 10-50pts.wt. of poly butadiene rubber including 5pts.wt. of polybutadiene rubber in which the 1, 2 vinyle coupling content is less than 20wt% and more than one atomic groups having predetermined formulae are coupled to molecular chains, less than 60pts.wt. of styrene butadiene rubber containing 10-30wt% of styrene, 30-80pts.wt. of stretching oil having a viscosity gravity constant of 0.80-0.93, and 60-110 of carbon black. Further, the above-mentioned characteristics values of an inner surface rubber 2 is set at values of 2-7MPa and 0.04- 0.15, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial tire for a passenger car that has excellent driving performance, generates little heat in the tire tresode portion during driving, and has excellent fuel efficiency.

The road surface on which an automobile travels changes in various ways depending on weather conditions, such as dry, wet due to precipitation or melting snow, covered with snow, or frozen. The frictional characteristics between tires and the road surface change depending on the condition of the road surface. On a dry road surface, the frictional resistance is sufficiently large so there is no problem, but when the road surface is wet, snowy, or icy, the frictional resistance increases in this order. This causes problems with the vehicle's driving performance, such as braking performance and maneuverability. Regarding the frictional resistance between the tire and the road surface, the polymer used in the rubber that makes up the tresode part, which is the part of the tire that comes into contact with the road surface, plays an important role. That is, on a wet road surface, the use of a polymer with a high glass transition temperature, such as styrene-butadiene copolymer rubber (SBR), increases frictional resistance. On the other hand, on snowy or icy road surfaces, the frictional resistance is abnormally low, and the effective contact area between the tread rubber and the road surface is determined by how much the tread rubber can follow and deform due to subtle irregularities on the road surface. This is a factor that determines frictional resistance. Naturally, the softer the tread rubber, the larger the effective contact area. Therefore, we use polymers with low glass transition temperatures, such as natural rubber (NR) and polybutadiene rubber (BR), which do not harden even in low temperatures, which is a necessary condition for realizing snowy or icy road surfaces, as the tread rubber. When used, frictional resistance increases. In other words, a tread rubber made of a polymer with a high glass transition temperature such as SBR has low frictional resistance on snowy or icy roads, whereas a tread rubber made with a polymer with a low glass transition temperature such as NR or BR has low frictional resistance on snowy or icy roads. The partial comb has low frictional resistance on wet road surfaces. As described above, depending on the type of polymer, the frictional performance of the tresode comb against the road surface is greatly influenced, but at present, no polymer is known that exhibits a large frictional resistance on any road surface.

Therefore, general tires with SBR as the main component of the tread rubber are used when wet roads are the most slippery, such as in summer or in warm regions, and general tires are used when roads are covered in snow or ice in cold regions. So-called snow tires, which are intended for vehicles, must be replaced and used depending on the frequency of each road surface condition. However, even in areas where it is necessary to use snow tires in the winter, it is rare for roads to be covered with snow or ice all the time, so it is necessary to drive on wet roads with snow tires. In many cases, they are forced to take the risk of having to do something. It's outside.
Nowadays, with highly developed road networks, cars often travel between warm regions where snow tires are not needed and regions where roads are covered with snow or ice. There is a demand for tires that have high maneuverability even on snowy or icy roads.

Conventionally, in order to improve driving performance on wet roads, snowy and icy roads, SBR, which has a high frictional resistance on wet roads, and NR and BR, which have a high frictional resistance on snowy and icy roads, have been blended. It was used as trend part rubber. Carbon black was also incorporated into this blend as a reinforcing agent. However, the tread rubber made from these blends has significantly lower frictional resistance on wet roads than the tread rubber of general tires, and also has significantly lower frictional resistance on snowy and icy roads than the tread rubber of snow tires. The resistance is significantly reduced, and only a friction characteristic intermediate between the two can be obtained.

Furthermore, the l-renodo rubber made from these blends is
Since it contains a large amount of Car Pump Sick, there is a drawback that heat generation due to repeated deformation during driving increases significantly. Due to heat generation, the tread rubber ages and is exposed to conditions where it is likely to harden. If the aging rate or hardening rate of trend part rubber increases, not only will the performance on snowy and icy roads be lost in a short period of time, but the permanent center of the rubber block that forms the red pattern will increase. As a result, overall athletic performance deteriorates in a short period of time. Furthermore, heat generation worsens the fuel efficiency of automobiles, going against the recent social demand for resource and energy conservation.

By the way, as the tire rotates, the rubber material that makes up the tire undergoes repeated deformation. During this repeated deformation, part of the deformation energy is released (hysteresis loss) and accumulated in the comb, causing a heat generation phenomenon.

The magnitude of this repeated deformation is approximately 1 to 30 inches in terms of strain, and the rubber compounded with carbon black under this dynamic strain exhibits an abnormally large hysteresis loss. This phenomenon is known as the Payne effect, and is said to be caused by solid friction of the carbon blank in the rubber. Therefore, in order to reduce hysteresis loss and heat generation at this dynamic strain level, it is important to disperse the aggregates of the car 5s/fibers into a single column so that they do not come into contact with each other. In order to microscopically disperse carbon black in rubber, when the polymer and carbon blank are mechanically mixed, a large amount of so-called carbon gel, which is a state in which the polymer and carbon blank are bonded, is generated. An effective method is to transmit strong force to carbon blank aggregates suspended in a polymer matrix. As such a method, a two-stage kneading method has been proposed in which a master kneader obtained by mechanically kneading Moon 61Jmer and carbon black at a very high concentration is diluted with a pot mixer. Publication No. 55-104343). However, with this method, it is difficult to mechanically knead the masterbatch uniformly, so there is a need for a method that can more easily generate a large amount of carbon gel and reduce the Payne effect.

The present invention was developed in view of these circumstances, and is capable of maintaining a high level of maneuverability on wet road surfaces and snowy/icy road surfaces, as well as reducing the heat generation of the tire tread portion during driving. The purpose of the present invention is to provide a radial tire for passenger cars with improved characteristics.

To this end, the present inventors have conducted intensive studies on a method to easily generate a large amount of carbon gel when mechanically kneading a polymer and carbon black, and to reduce hysteresis loss in rubber due to the Payne effect. did. As a result,
By using a specific polybutane rubber having a specific functional group introduced into its molecular chain, it is possible to effectively reduce hysteresis loss due to the Payne effect without causing any difficulty in crosstalk, and the introduction of the functional group. It was discovered that this has no effect on the frictional properties of rubber, and this led to the present invention.

Therefore, the present invention provides a pneumatic tire in which the tread portion is composed of at least two layers, an outer surface rubber layer and an inner surface rubber layer, in which the outer surface rubber layer is made of (1) natural rubber and/or synthetic polyinoprene. Rubber (I) lo ~ 70 parts by weight, 1,2-bonding unit content 20 parts by weight, polyfridiene rubber (II) 10-50 parts by weight, styrene content crab 10-30 parts by weight. It consists of 60 parts by weight or less of the polyphridiene copolymer (III), with a total of 100 parts by weight, and at least 5 parts by weight of the polyphridiene rubber (II) has the following formula (in the formula, R1 and R2 represent hydrogen or a substituent, m and n represent integers) at least one of the atomic groups represented by
is a polyfridiene rubber with a weight of 20% of 1,2-bonded gold, in which 1,2-bonds are bonded to the molecular chain by carbon-carbon bonds,
(2) 30 to 8 parts of extender oil per 100 parts by weight of raw material comb
The extension oil contains 0 parts by weight of rough carbon, rough carbon and aromatic carbon percentages respectively.

When CN and CA, V, G, C, = 0.00743 Cp + 0.0
0925 CN +0.0110 The viscosity specific gravity constant (V, G, C,) determined by CA is 0.80-0.93, and (3) carbon black is added as a reinforcing agent to 100 parts by weight of raw rubber. (4) The rubber after vulcanization of the outer surface side rubber layer has a complex modulus of elasticity of 3 to 8 MPa at 70°C.

The loss tangent (Ianδ) is 1.0 to 0.5, (5)
The ratio of the outer surface side rubber layer is 0.5 to o9 of the entire tread part.
Furthermore, the complex modulus of elasticity at 70″C after vulcanization of the inner side rubber layer is 2 to 7 MPa, and the loss tangent (tan δ)
The gist of this article is a radial tire for passenger cars in which the tire diameter is 004 to 0.15.

Hereinafter, the configuration of the present invention will be explained in detail.

The figure is an explanatory diagram of a calf half cross section of an example of the tire of the present invention. In the figure, T is the tread portion, which includes a camp layer (outer surface rubber layer) 1 and an under layer (inner surface rubber layer) 2.
It consists of

6 is a carcass mounted between the pair of left and right bead portions 4, 4, and in the tread T, a belt reinforcing layer 5 is arranged so as to surround the outer periphery of this carcass 6. 6 is a tread groove, and 7 is a side portion.

In the present invention, in the cap layer 1, at least one atomic group represented by the following formula is bonded to a molecular chain through a carbon-carbon bond, and the 1,2-bond content is 20 parts by weight or less.
(hereinafter referred to as modified BR).

In the atomic group represented by formula (1) above, R+, R
2 is hydrogen or a substituent, respectively. This substituent is not specified, but includes, for example, an amine group, an alkylamino group, and a dialkylamino group. It's a size, m,
n is an integer.

BR in which at least one of such atomic groups is bonded to a molecular chain with a carbon-carbon bond and the content of 1,2-bonds is 20% by weight or less, that is, modified BR, can be obtained by, for example, using an alkali metal catalyst. It is produced by polymerizing butadiene and adding benzophenones to the butadiene rubber solution obtained after the polymerization reaction is completed. In this case, the alkali metal-based catalyst used is one that exploits each of the metal elements lithium, sodium, rubidium, and senrum.

Furthermore, on average, the number of benzophenones introduced into the polybutane rubber is one or more per rubber molecular chain (
That is, 100 parts by weight of rubber and 0.05 to 10 parts by weight).

As the benzene/siphenones, benzophenones having at least one amine group, alkylamino group, or dialkylamino group in one or both benzene rings in the formula (1) are particularly preferred. Examples of the benzophenone include Eva, 4,4'-bis(dimethylamine)-benzophenone, 4.4'-bis(diethylamino)-benzophenone, 4.4'-bis(/butylamino)-benzophenone, and 4.4'-bis(dimethylamine)-benzophenone. '-diaminobencyphenone and 4-dimethylaminobenzophenone/.

The modified BR obtained as described above has a stronger interaction with carbon black than normal BR that is not treated with benzophenone. This is because: 'When the amount of bound rubber is measured in an unvulcanized product of rubber blended with this modified BR, it is about twice as much as that of normal rubber. This is because the amount of bound rubber increased due to the benzophenone treatment, and it is therefore considered that modified BRO bonds more strongly with carbon black than normal BR. Vulcanized rubber containing modified BR has a higher tan than vulcanized rubber containing ordinary BR.
Low δ and low calorific value.

In the present invention, the cap layer 1 is made of natural rubber and/or
or synthetic poly-1 noprene rubber (IHO~70 parts by weight, 1
, 2-polybutadiene rubber (II) with a bonding unit content of 20 parts by weight or less, 10 to 50 parts by weight, inherited butadiene copolymer rubber (IJI) with a styrene content of 10 to 30 parts by weight, 60 parts by weight The total rubber content is 10.
0 parts by weight, and at least 5 parts by weight or more of the polybutadiene rubber (II) is replaced with modified BR. Here, in the microstructures of BR (II) and modified BR, the amount of 1.2 bond metal is 20 parts by weight or less. 1
, 2. If the content of the alloy exceeds 20 parts by weight, the performance on snowy or icy roads will deteriorate. Also, SBR(I
II) has a styrene content of 10 to 30 parts by weight.

If it is less than 10% by weight, the maneuverability on wet roads will decrease, and 3
If it exceeds 0 parts by weight, performance on snowy or icy roads will deteriorate. Note that 5BR (III) can be partially or entirely replaced with modified SBR that has been modified in the same manner as in modified BR. NR and/or I
The amount of R (synthetic polyisoprene rubber) used is 10 to 70
Parts by weight. If it is less than 10 parts by weight, the performance on snowy/icy roads will be insufficient, and if it exceeds 70 parts by weight, the performance on wet roads will be poor. The amount of BR used should be 10 to 50 parts by weight; if it is less than 10 parts by weight, the performance on snowy/icy roads will be insufficient, and if it exceeds 50 parts by weight, the performance on wet roads will be reduced. The amount of SBH used is 60 parts by weight or less; if it exceeds 60 parts by weight, the driving performance on snowy and icy roads will deteriorate. Indeed, the amount of modified BR used is at least 5 parts by weight of the BR. If it is less than 5 parts by weight, the effect of suppressing heat generation when the tire runs is low.

Further, in the present invention, the gap layer 1 contains extender oil. This extension oil has a viscosity specific gravity constant (V, G
, C,) 0.80 to 0.93.

When the V, G, and C values are less than 080, the performance on wet roads is reduced, and when they exceed 0.93, the performance on snowy and icy roads is reduced. The amount of extender oil to be used is 30 to 80 parts by weight per 100 parts by weight of the raw rubber. If it is less than 30 parts by weight, it will not be possible to sufficiently improve the maneuverability on snowy or icy roads, and if it is less than 80 parts by weight, If it exceeds this, it becomes difficult to maintain the strength required for the trend rubber, and wear resistance and chipping resistance deteriorate.

Furthermore, the cap layer 1 contains carbon black as a reinforcing agent. This carbon black is not particularly limited as long as it is normally used for tread parts. The amount of carbon blank used is 10
The amount is 60 to 110 parts by weight relative to 0 parts by weight, and if it is less than 60 parts by weight, the driving performance on a wet road surface cannot be sufficiently improved, and if it exceeds 110 parts by weight, heat generation during running of the tire will increase.

In the present invention, 70% of the rubber after vulcanization of the cap layer 1 is
The complex modulus of elasticity (E') at °C is 3 to 8 MPa; if it is less than 3 MPa, the rigidity of the tread part will be low and the deformation during running will be large, resulting in significant heat generation; if it exceeds 8 MPa, the temperature will be low. The tires become too hard, resulting in insufficient maneuverability on snowy and icy roads and poor ride comfort. Also,
The vulcanized rubber of camp layer 1 has a loss tangent (Δ) of 01 to 0.5 at 70°C. l;+11δ
In order to make the value less than 01, it is necessary to reduce the amount of carbon black used or use a carbon blank with less reinforcing properties, resulting in insufficient maneuverability and wear resistance on wet road surfaces. When L811δ exceeds 0.5, heat generation during driving increases.

Further, the ratio of the cap layer 1 is 0.5 of the entire tread portion.
~0.9. That is, the ratio of the cap layer (5) to the underlayer (B) is 0.5<A/(A+B)<0.
It is 9. If the ratio of the cap layer 1 is less than 0.5, the ratio of the underlayer, which is weak in strength, will be high, reducing the rigidity of the tread, and making it easy for the tread to chunk out.
Maneuvering stability at high speeds is insufficient. If it exceeds 09, it becomes difficult to reduce the heat generation of the tire.

Furthermore, in the present invention, El of the rubber after vulcanization of the underlayer 2 is 2 to 7 MPa, and Ωδ is 0.04 to 0.15.
It is. When E is less than 2 MPa, the rigidity of the underlayer 2 is low and deformation tends to concentrate on the underlayer 2, resulting in increased heat generation and a significant decrease in durability due to tread separation/yong. When E7 exceeds 7 MP, it leads to a decrease in strength due to an increase in vulcanization density, or a deterioration in exothermic property due to the use of carbon black with a small particle size or a large amount of carbon black. 1. If l-In6 is less than 0.04, the degree of reinforcement by carbon black will decrease, and if it exceeds 0.15, heat generation will increase.

In the radial tire for a passenger car of the present invention, a vulcanized rubber having physical properties suitable for the purpose can be used except for the trend portion.

In addition, various compounding agents commonly used in the rubber industry can be appropriately selected and used in all parts including the tread part.

EXAMPLES The effects of the present invention will be specifically explained below with reference to Examples.

EXAMPLE A 165 Sl 13 size tire was prepared using a rubber having a composition shown in Table 1 for the cap layer and a rubber shown in Table 2 for the under layer.

The modified BR and modified SBR used for the cap layer were n-
Using butyllithium as a catalyst, active lithium was added to the molecular chain terminals that had been polymerized by solution polymerization. A catalytic amount of 4,4'-bis(dimethylamine)be/siphenone was added to the solution of BR and SBR. Add 1.5 times the mole and stir 1
After the reaction was completed, it was coagulated and dried. Modification B
For comparison of R and modified SBR, BR and SBR were prepared by polymerizing in the same manner, coagulating and drying without adding 4,4'-bis(dimethylamino)benzophenone.
was used. Table 3 shows the characteristics of the synthetic polymer used for the cap tread.

A tire with a two-layer tread structure has a 7-t-shaped underlayer placed on the entire bottom of the trend part in contact with the belt part, and a cap layer placed on the bottom side, with the 85 volume part of the tread part serving as the cap layer. It was designed as such.

(Margins below this page) Table 1 Compound of cap layer rubber 1) See Table 4 for polymer composition 2) N-inoglobin-N'-phenyl-p-phenylenediamine a) ASTM designation, N 220 4) 7-nocol 7-rec y, 115ON: V,
G, C, =: 0.95) N-oxyjetylehapenzothiazyl-26) R8S #3 7) Tuffden 1000 (non-chemical) 8) ASTM indication, N 550 Table 2 Compounding of underlayer rubber and Physical properties 0, Fuji Kosan - Sulfenamide Table 3 Synthetic polymer BR3 used for cap tread
55213 Modified BR355213 SBR25324523 Modified SBR25324523 The tires thus prepared were subjected to a wet road braking test, an icy road climbing test, a rolling resistance test, and a tread rubber aging test by driving on general roads. Each test was conducted in the following manner.

◎Wet road braking test Water was sprinkled on the asphalt pavement surface, the braking distance was measured from 60 km/br, and the index was evaluated based on the standard tire being 100. The larger the index, the better the braking performance.

◎Frozen road pitching test Initial speed 20”/200m on frozen road at temperature 0-5°C
Measure the time required when pitching in hr, and set the standard tire to 1
Evaluated by index when set to 00. The higher the index, the better the pitching performance.

◎Rolling resistance test On an indoor test drum with a diameter of 707 mm, the tire internal pressure was 1.
9 K9kd, load 420Kg, 100”/
After 30 minutes of preliminary driving at a speed of 60 K”
The rolling resistance was measured at a speed of /hr, and the standard tire was
Evaluation is based on the index when it is set to 0. The smaller the index, the lower the rolling resistance.

◎Tread Rubber Aging Test The vehicle was driven on a general road for approximately 20,000 km, and changes in the JIS hardness of the cap layer before and after driving were measured.

In conjunction with the tire test, rubber samples of the cap layer and underlayer were taken from a separately prepared unused tire with the same specifications and subjected to a dynamic viscoelasticity test. The dynamic viscoelasticity test was performed using a viscoelastic spectrometer manufactured by Oiki Seisakusho.
The test was carried out at 0°C under the conditions of a frequency of 20 H2, an initial elongation strain of 10%, and a dynamic elongation strain of ±2. The dynamic viscoelastic properties of the underlayer did not differ significantly depending on the cap layer used, and the average values are shown in Table 2.

Experiment 1 40 parts by weight of natural rubber, 30 parts by weight of BR in Table 3, S in Table 3
A cap layer consisting of a polymer composition of 30 parts by weight of BR, 75 parts by weight of carbon black of N220, 40 parts by weight of extension oil of V, G, C, value 0.90, and BR and SBR.
Table 4 shows the characteristics of tires having a cap layer in which the entire amount of was replaced with modified BR and modified SBR, respectively.

(Blank below) Table 4 +o) Refer to Table 3 +1) Comparative Example] is a standard tire Comparative Example 1 is a conventional tire with a two-layer trend structure, and Comparative Example 2 is a BR used in the cap layer of a conventional tire. and SBR are respectively modified BR and modified SBR.
Example 1 of the present invention is a tire with a single-layer tread structure consisting only of the cap layer replaced by the cap layer, and Example 1 of the present invention is a tire with a 2-layer tread structure using the cap layer of Comparative Example 2.

The cap layer rubbers using the modified BR and modified 5EIR have slightly lower E values and significantly lower tan δ compared to conventional cap layer rubbers. Modified BR and modified SBR have no effect on the wet road braking performance of the tire, but slightly improve the icy road performance. The tire of Comparative Example 2, whose tread portion is composed only of a cap layer using modified BR and modified SBR, has slightly lower rolling resistance than the conventional tire of Comparative Example 1, which has a two-layer tread structure, and has improved running performance. Although the increase in the hardness of the cap tread caused by this change has been slightly reduced, the improvement effect is unsatisfactory. On the other hand, in the tire of Example 1 of the present invention, which uses modified BR and modified SBR in the cap layer and has a two-layer tread structure, the rolling resistance is significantly reduced, and at the same time, the increase in hardness of the cap layer rubber due to running is also significantly small. It is clear that excellent maneuverability can be maintained over a long period of time on snowy and icy roads.

Experiment 2 Polymer composition of 60 parts by weight of natural rubber, 40 parts by weight of BR in Table 3, 85 parts by weight of N220 carbon black, V, G
Table 5 shows the characteristics of a tire having a cap layer made of 60 parts by weight of extender oil having a C value of 090 and a cap layer in which the entire amount of BR was replaced with modified BR.

(Margins below this page) Table 5 12) Comparative Example 3 is a standard tire Compared to the tire of Comparative Example 3 which has a two-layer trend structure, the tire of Inventive Example 2 has improved rolling performance without deteriorating its maneuverability on various road surfaces. It can be seen that resistance is significantly reduced and aging of the cap layer rubber is reduced due to improved heat generation.

The above experiments 1 and 2 showed that the steel radial tire of the present invention, which has a two-layer tread structure using BR and SBR with functional groups introduced into the molecular chain terminals, was blended with a large amount of carbon black, This exemplifies that the tire has improved heat generation, which was a drawback of conventional tires, and has improved maneuverability on icy roads.

[Brief explanation of drawings]

The figure is a meridional half-section explanatory view of an example of the tire of the present invention. T: Tread portion, 1: Cap layer, 2: Underlayer, 6: Carcass, 4: Bead portion, 5: Belt reinforcement layer.

Claims (1)

[Scope of Claims] A pneumatic tire in which the tread portion is composed of at least two layers, an outer surface rubber layer and an inner surface rubber layer, wherein the outer surface rubber layer is made of (1) natural rubber and/or synthetic polyisoprene rubber. (IHO ~ 70 parts by weight, polybutadiene rubber (II) with a 1,2-bond unit content of 20 parts by weight or less 1
The polybutadiene rubber (II ), at least 5 parts by weight of at least one of the atomic groups represented by the following formula (wherein R1 and R2 represent hydrogen or a substituent, and m and n represent integers)
is a polyfridiene rubber in which the 1,2-bond gold content is 20 or less by weight, in which the
(2) 30 to 8 parts of extender oil per 100 parts by weight of raw material comb
The extension oil contains 0 parts by weight of rough carbon, naphthenic carbon and aromatic carbon percentages, respectively. When CN and CA, V, G, C, 20, 00743 Cp + 0.009
25 CN + 0.0110 It has a viscosity specific gravity constant (V, G, C,) of 0.80 to 0.93 determined by CA, and (3) carbon fiber is added as a reinforcing agent to 100 parts by weight of the raw rubber. (4) The rubber after vulcanization of the outfield side comb layer is heated to 70°C.
The complex modulus of elasticity is 3 to 8 MPa, the loss tangent (Ian
δ) is 0.1-0.5, (5) the ratio of the outer surface side rubber layer is 05-0.9 in the entire tread portion, and further,
The complex modulus of elasticity at 70°C after vulcanization of the inner comb layer is 2 to 7 MPa, and the loss tangent (tan δ) is 0.04.
~0.15 Ranal tires for passenger cars.