JPS61287945A - Radial tire with tread having center side structure - Google Patents

Abstract

PURPOSE:To provide the titled tire which has excellent cut resistance and scarcely suffers from separation of belts and whose tread part hardly generates heat, by providing a center rubber outside a belt composed of at least three steel belt plies and side rubbers on both sides of the center rubber in the width direction thereof. CONSTITUTION:A center rubber 4 exhibiting a heat generating temp. of 15-30 deg.C, composed of 30-5pts.wt. carbon black having an iodine adsorption of 100mg/g or above, 5-30pts.wt. silica, 0.5-6pts.wt. silane coupling agent of formula I or II (wherein R is a 1-4C alkyl; m, n are each 1-6; X is SH, NH2, epoxy group), 0-3pts.wt. softener and 100pts.wt. raw rubber consisting of 50-100% natural rubber and 50-0% styrene/butadiene copolymer rubber is used. Said center rubber 4 provided with a belt 3 composed of at least three steel belt plies 2 is provided on the central part of a crown and adjoining to the outside of the belt in such a manner that the max. width Wc of the rubber 4 is 20-90% of the width Wt of the tread. Side rubbers 5 exhibiting a heat generating temp. lower than that of the center rubber are provided on both sides of the rubber 4 in the width direction thereof to obtain the titled tire.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a radial tire equipped with a steel base/L/ ) ply. The present invention relates to a radial tire having a tread with a center side structure made of side rubber arranged on both sides in the direction.

(b) Conventional technology Since radial tires have a highly rigid steel belt ply placed on the outside of the carcass ply in which cords are arranged in the radial direction to reinforce the tread, the tread is difficult to deform. Therefore, when the tire is used on an unpaved road, the tread portion deforms to wrap around the stone when the tire is stepped on, and the envelope effect, which takes the stress as a fraction, is small, making it susceptible to cuts. Especially in the center of the tread, the envelope effect is small and cuts are concentrated. Many small cuts occur,
The tread rubber wears off, accelerating wear, and when the cut reaches Be/I/G, water enters.

The heald will rust and a separation will form between the rubber and the rubber. In particular, in order to prevent belt separation, if the tread part has a two-layer structure of a cap and a base, and a low heat generation rubber is used as the base rubber, as shown in Figure 2, the rubber has low heat generation properties and cut resistance. Since the properties are inversely related to each other, the cut resistance becomes insufficient, and bare+z separation often occurs due to water intrusion from the cuts.

Therefore, in JP-A No. 60-15203, in a radial tire with a two-layer tread structure of a cap and a base, a rubber with good impact resistance and cut resistance is used in the center of the crown of the base rubber, and a shoulder part of the base rubber is It has been proposed to construct a tire by using low-heat-generating rubber and using three types of rubber in which the tread rubber is reinforced with only carbon for the cap rubber, the center base rubber, and the pace rubber shoulder.

(C1 Problem to be solved by the invention) Even when different rubbers are used for the center part of the base rubber and part of the shoulders of the above-mentioned two-layered tread rubber, the tread is composed of three types of rubber reinforced only with carbon. Therefore, while suppressing the separation of B/L/G due to heat generation,
It is difficult to sufficiently improve cut resistance, and when tread rubber is composed of multiple rubbers, they must be extruded at the same time. It is very difficult to extrude both at the same time.

Therefore, in the present invention, the heat generation in the tread portion is small, and
- It is an object of the present invention to provide a radial tire having a tread structure in which the occurrence of separation is small, the tread has high cut resistance, and the tread rubber can be easily co-extruded.

(d) Means for Solving the Problems 1 The inventors of the present invention have conducted repeated research to solve the above-mentioned problems of conventional radial tires, and found that the tread is made of a center rubber at the center of the crown and side rubber on both sides of the center rubber. Consisting of two types of rubber, the center rubber is natural rubber or natural rubber and styrene.
By using a rubber composition with low heat generation and excellent cut resistance, which is a combination of butadiene copolymer rubber and silica and carbon black, which has a large amount of iodine adsorption, as a reinforcing material, and by using a low heat generation rubber for the side rubber. It was discovered that a radial tire with excellent cut resistance and less occurrence of belt separation can be obtained, and the present invention was completed.

That is, the present invention provides a radial tire equipped with a belt consisting of at least three steel belt plies, in which the tread rubber has a width of 20 to 90% of the tread width Wt in the tire width direction at the center of the tread. It consists of a center rubber placed on the center rubber, and side rubber placed on both sides of the center rubber in the tire width direction, and the center rubber has an exothermic temperature of 15-30°C as measured by a Goodrich flexometer.
The exothermic temperature of the side rubber is lower than that of the center rubber, and the center rubber has an iodine adsorption amount of 100 parts by weight based on 100 parts by weight of raw rubber consisting of 50-100% natural rubber and 50-0% styrene-butadiene copolymer rubber. ml/71
30-50 parts by weight of the above carbon black and 5-50 parts by weight of silica
30 parts by weight and the general formula % formula % () (where R is an alkyl group having 1-4 carbon atoms, and n is 1-
m is an integer of 1-6, and X is a mercapto group, an amino group, or an epoxy group. The gist of this invention is a radial tire having a tread with a center side structure, which is made of a rubber composition containing 0.5-6 parts by weight of a silane coupling agent shown in ) and 0-3 parts by weight of a softener.

Next, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a sectional view of a radial tire having a tread having a center side structure according to the present invention. (1) is a tread rubber consisting of a center rubber (4) arranged in the center of the crown adjacent to the outside of a belt (3) made up of a plurality of steel belt plies (2); It consists of side rubber (5) placed in contact with both sides in the width direction of the tire.

Since the thickness of the tread rubber near the tip p of the shoulder part of the tread is maximum, if the heat generation property of the rubber in this part is large, the tread part becomes high temperature during running, and fatigue is accelerated. Therefore, for the side rubber, a rubber with low heat generation is used, and for the center rubber, a rubber with particularly excellent cut resistance is used, although the low heat generation is slightly better.

The maximum width WC of the center rubber is 20 - of the tread width Wt.
It shall be 90%. Center rubber width WC is tread width W
When t is less than 20%, the area in which the center rubber with high cut resistance in the center of the tread protects the bead A/I- is narrow;
Tires have poor cut resistance. Moreover, if this exceeds 90%, rubber with high heat generation properties will be placed in the thick portion of the tread rubber, making it easy for belt separation to occur.

The interface between the center rubber and side rubber may be provided so that the width of the center rubber expands toward the tire surface as shown in Figure 1, or the width of the center rubber may be set constant or toward the tire surface. The width of the center rubber may be narrowed.

The center rubber used has an exothermic temperature of 15-30° C. as measured by a Goodrich flexometer. When this exothermic temperature exceeds 30° C., the temperature at the bottom of the tread becomes high, making it easy for belt separation to occur. Rubbers with an exothermic temperature of less than 15° are not preferred as center rubbers because they have poor cut resistance.

The side rubber used has a heat generation temperature lower than that of the center rubber, and a heat generation temperature of 20° C. or less. When the heat generation temperature of the side rubber exceeds 20°C, separation tends to occur at the belt ends. The side parts of the tread rubber are thicker than the center part, and the heat generation rate and amount of heat storage during running is greater than the center part, so it is necessary to use rubber with a lower heat generation temperature for the side rubber than for the center rubber. .

The center rubber of the radial tire of the present invention includes:
A rubber composition is used that is a blend of 50-100% natural rubber and 50-0% styrene-butadiene copolymer rubber, and contains carbon black, silica, and a silane coupling agent. If the natural rubber content is less than 50% and the styrene-butadiene rubber content exceeds 50%, heat generation during running increases and the belt is likely to separate.

The carbon black blended into the center rubber has an iodine adsorption amount IA of 100 mg/J or more. If the iodine adsorption amount is smaller than this, the cut resistance and abrasion resistance of the rubber will be poor. The amount of carbon black to be blended is selected to be 30-50 parts by weight per 100 parts by weight of the rubber component. 3
If it is less than 0 parts by weight, the cut resistance and abrasion resistance of the center rubber will be poor, and if it exceeds 50 parts by weight, the processability of the rubber will be poor.

By blending silica and a silane coupling agent into the center rubber, its cut resistance can be further improved. The amount of silica blended is preferably 5 to 30 parts by weight per 100 parts by weight of the rubber component. If it is less than 5 parts by weight, the effect of improving cut resistance will be small, and if it exceeds 30 parts by weight, the processability of the rubber will deteriorate.

As the silane coupling agent to be blended into the base rubber, a compound represented by the general formula % (1) (where H, n, m, and X are as described above) is used. For example, (OC2H
5) a8i0H2SH (OC2H5)3SicH2SCH2(OC2H5)a
(OC2H5)3SiOH2S20H2(OC2H5)
a(OC2H5)3SiCH2SaOH2(OC2H5
)a(002H5)s8i0H2S40H2(OC2H
5) a(OCHa)BSiOH2SR (OCH3)s810H2SH40H2Si(OCHa
)8(OC2H5)3S103H6SaC3H6Si(
OC2H5)3(OC2Hs)3sic3Hes4c3
H6si(OC2H5)3(OCH3)38iC3H6
8H (OC2H5)3Si03H6NH2 etc. are used. The amount of the silane coupling agent blended is preferably 1-6 parts by weight per 100 parts by weight of the rubber component.

If the amount of the silane coupling agent is less than 1 part by weight, the effect of improving cut resistance will be small, and if it exceeds 6 parts by weight, the effect will not increase.

If necessary, a softener is added to the center rubber in an amount of 0 to 3 parts by weight per 100 parts by weight of the rubber component, but if the amount exceeds 3 parts by weight, the cut resistance of the center rubber decreases. If more carbon black and silica are added to the center rubber than the above specified amounts, the processability of the rubber will deteriorate, and in order to improve this, it will be necessary to add a large amount of softener. Sexuality decreases.

(e) Examples 1 to 3 and Comparative Examples 1 to 3 tires with a tire size of 1000R20 were manufactured using rubbers with the compositions A to G shown in Table 1 as the center rubber and side rubber of the tread, and the drum A test was conducted, and an actual running test was conducted to determine the length of the cut scratches. The results are shown in Table 2.

(Left below) Table 2 In Table 1, the Mooney viscosity peak value is JISK63
00 with an S rotor at 100° C. and indicates the maximum value read within 4 minutes after starting the viscometer. The heat generation temperature is ASTM D621r heat generation due to compression and bending fatigue.
It was measured using a Gudrich flexometer according to Method A. The cut resistance is 10 on a side of a cylinder with one end in a conical shape.
The depth of the scratches caused by dropping the rubber onto a cube of cm cm was measured, and the reciprocal of the scratch was taken as a standard based on the rubber with the ■ formulation, and this value was expressed as an index of 100. Wear test is ASTM D22
The results measured by the measuring method ``28r abrasion resistance'' were expressed as an index with the H blend as 100.

In Table 2, the drum test is based on the US safety standard FMV8.
After driving under the driving conditions specified in the S119 durability test,
Furthermore, at a load of 30,000Kg and a speed of 56.4km/h, 24
An hourly drum test was conducted, and those with no abnormality were given a score of 100, and those that failed midway were given an index indicating the distance traveled.

Cut length is on the track Example 1-3, Comparative Example 1-8
A combination of tires were installed and tested on a road with many unpaved roads, and when the tread depth became 2 to 4 mm, the tires were dismantled, the tread was peeled off, and the cut scratches on the tread surface were removed. The lengths were measured, the total sum was determined, and the tire of Comparative Example 3 was taken as a reference, and this was set as 100 and expressed as an index.

(fl Effects of the Invention According to the radial tire having a tread with a center-side structure according to the present invention, the tread of a steel radial tire is made of a different type of rubber compound acid for the center comb in the center of the tread and the side rubber on both sides thereof. The center rubber is made of natural rubber or a rubber blend of natural rubber and 8BR, combined with carbon black that has a large amount of iodine adsorption, silica, and a silane coupling agent, and has excellent cut resistance and a relatively low exothermic temperature. Since we used rubber that generates less heat as the side rubber, even when driving on rough roads,
There are fewer cuts that reach the steel belt of the tire, and the tread rubber generates less heat, so there is less chance of belt separation. The life of the tire is therefore significantly extended. Furthermore, since the tread rubber consists of only two types of rubber, the tread rubber can be easily molded by extrusion molding these at the same time.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of a radial tire having a tread having a center side structure according to the present invention, and FIG. 2 is a graph showing the correlation between heat generation and cut resistance of rubber. (1)...Tread rubber, (2)...Steel belt ply, (3)...Belt, (4)...
Center rubber, (5)...side rubber.

Claims (1)

[Claims] (1) In a radial tire equipped with a belt made of at least three steel belt plies, the tread rubber is a center rubber arranged in the tire width direction at the center of the tread with a width of 20-90% of the tread width Wt. and side rubbers placed on both sides of the center rubber in the tire width direction, the center rubber has a heat generation temperature of 15-30°C measured with a Goodrich flexometer, and the heat generation temperature of the side rubber is equal to that of the center rubber. The center rubber is composed of 30-50 parts by weight of carbon black with an iodine adsorption amount of 100 mg/g or more per 100 parts by weight of raw rubber consisting of 50-100% natural rubber and 50-0% styrene-butadiene copolymer rubber. 5-30 parts by weight of silica and general formula (OR)_3SiC_nH_2_nS_mC_nH_2
_nSi(OR)_3 or (OR)_3SiC_nH_2_nX (where R is an alkyl group having 1-4 carbon atoms, n is 1
-6 is an integer, m is an integer from 1 to 6, and X is a mercapto group, an amino group, or an epoxy group. ) 0.5-6 parts by weight of a silane coupling agent represented by
A radial tire having a tread with a center side structure, characterized in that it is made of a rubber composition containing 0-3 parts by weight of a softener.