JPS58177702A - Steel radial tire improving durable life - Google Patents

Abstract

PURPOSE:To infiltrate rubber into the inside of a cord and improve adhesive force, by blending the liquid state rubber having an active radical in a fixed amount of embedded rubber. CONSTITUTION:The steel cord of a carcase and/or a belt layer is of compound twist or layer twist construction consisting of three layers of core and intermediate and external layers or two layers of core and external layer, and an open twist steel cord with 5-30% free space factor of the core and 5-15% free space factor of the intermediate and external layers, while embedded rubber of the carcass and/or the belt layer contains liquid state rubber having 2-30pts.wt. active radical in the ingredients of rubber. A free space factor of the core is defined as the percentage of a sum of lengths l1-l3 in parts not occupied by a filament on a circle C1 containing center shafts 01-03 of the filaments 2 of a core strand 1 for a circumferential length L.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a highly durable heavy-duty belt using a ply in which a steel cord having a layered structure and a free space ratio above a certain level is embedded in a rubber composition containing liquid rubber in the belt layer. Regarding radial tires for vehicles.

In general, belt cords for radial tires for passenger cars, carcass cords for tires for heavy vehicles, and belt cords are required to have basic properties such as high elastic modulus, strength, and dimensional stability. is frequently used. The steel cord used for the belt layer or carcass has a so-called layered structure in which several strands of 5 to 5 filaments are twisted together, or a layered structure in which multiple filaments are twisted in concentric rows. There are so-called layer-twisted structures, but when used in tires for heavy vehicles, particularly high strength is required, so multi-layer or layer-twisted structures consisting of a large number of filaments are used. A belt ply is created by pulling this cord parallel to each other and placing it in a piece of rubber. Therefore, since a conventional steel cord has a plurality of filaments twisted together in a close-packed state in its cross section, voids that are difficult for rubber to penetrate are inevitably formed inside the cord. When such a steel cord is used for the belt layer or carcass, if the belt layer or carcass is damaged by a cut, rainwater will enter from that part, reach the void in the cord, and flow inside the void in the longitudinal direction of the cord. The corrosion of the steel cord also spreads along with it. As a result, the fatigue resistance of the cord and the adhesion strength between the cord and the rubber decrease, which significantly impairs the durability of the tire.Recently, the gap between the filaments has been widened to allow the embedded rubber to penetrate inside the steel cord. Open-stranded steel cords that can easily penetrate into voids have been proposed, and the following are particularly available as open-stranded steel cords with a multilayer structure.

(1) Structure to increase the diameter of the core (Utility Model Opening No. 56-105093)
, Utility Model Publication No. 56-103092) [211Xm +n +J + 1 (here m = 2
~4. n=0 or 9. For n±0, 6≦1≦8, n==
9 (12≦I≦14)
-50640. JP-A-54-67901) (3) Method of imparting force to the core strand to make one turn (U.S. Pat. No. 56-95598) In all of the above-mentioned prior art, the core has a free space ratio of 0 or 334. Middle layer, outer layer is 9-2
5 Defined as arrogant. However, the free space ratio of the core is 0
In the cord having the structure No. 4, the rubber does not penetrate into the core, and the effect of preventing water from penetrating into the coat, which is one of the original characteristics of an open twisted steel coat, is not sufficient. On the other hand, if the free space ratio is too large, the structure will exhibit high elongation in the longitudinal direction, but the effect will be impaired, and the core or intermediate layer will protrude from the cord during the steel cord twisting process, or the cord untwisting rate will decrease. from this point of view, it is preferable that the free space ratio of the cord be as small as possible.

However, according to the inventor's experiments, as long as the conventional rubber composition is used for the embedded rubber of the steel cord, the core, intermediate layer,
It has been confirmed that unless the free space ratio of any of the outer layers is at least 114, rubber hardly penetrates into the inside of the cord. Conventionally, as a solution to the problem of rubber intrusion in steel cords with a relatively small free space ratio, the steel cords are treated with a rubber injection liquid in which unvulcanized rubber is dissolved in a solvent that is compatible with rubber before being rubberized with a calender. There is a method of processing (Japanese Unexamined Patent Publication No. 15488/1988), but it has the disadvantage that the process is very complicated. There are also ways to lower the viscosity by increasing the amount of softeners, plasticizers, etc., or decreasing the amount of carbon black, but this will reduce the basic physical properties of the rubber and the adhesive strength with the steel cord. Undesirable. Therefore, the inventor conducted repeated research to improve rubber penetration and adhesion with rubber for steel cords with a free space ratio below a certain level.As a result, the inventor mixed a certain amount of liquid rubber with active groups into the embedded rubber. It was found that by doing so, it was possible to achieve the penetration of rubber into the interior of the cord and the improvement of adhesive strength without deteriorating the physical properties of the rubber, leading to the present invention.

The present invention provides a radial tire comprising a carcass with a radial structure and a belt layer which is constructed of a braai in which steel cords are embedded in rubber and is arranged around the outer periphery of the crown portion of the carcass, in which the steel cords of the carcass and/or the belt layer are provided. has a core-averse, layer-twisted structure or layer-twisted structure consisting of three layers, an intermediate layer and an outer layer, or two layers, a core and an outer edge, and the free space ratio of the core is 5 to 304, and the free space ratio of the middle layer and the outer layer is 5. 154, wherein the embedded rubber in the carcass and/or belt layer contains liquid rubber having 2 to Sot parts of active groups in the rubber component. It is.

The steel cord used in the present invention has a core free space ratio of 5 to 304. Free space ratio of middle layer and outer layer is 5~
15! It is. Here, the free space ratio of the core is as shown in Figure 1.
It is defined as the percentage of the total circumferential length IJtn of the length of the portion not occupied by the filaments It 1215) on a circle (cl) including 0,C203). In addition, the free space ratio of the middle layer and the outer layer is a circle (C2) including the center 4 (A1 to A6) of the outer layer (or middle layer) (61 strands (or filaments) H4) as shown in Figure 2.
It is defined as the percentage of the total circumferential length Dlt of the lengths d1 to d6) of the portion not occupied by the upper strand (4). If the free space ratio of the core, intermediate layer, and outer layer is smaller than the above range, the quality will be the same as that of conventional steel cord, and the empty space inside the cord will cause the rubber to penetrate and cause rust. Furthermore, if the free space ratio exceeds the above range, it becomes difficult to produce a uniform twisted cord, and the twist at the ends of the cord becomes uneven, impairing the uniformity of the tire.

The twist pitch of the steel cord is usually in the range of 3 to 20 squares, but if it is smaller than 3fi, the strength and productivity of the cord will decrease significantly, while if it exceeds 20 squares, the bending fatigue and bundle properties of the cord will deteriorate. This is because it decreases. Also, the filament that makes up the steel cord usually has a diameter of α10~
The strand is manufactured by twisting 2 to 5 strands together at 0°40-. Furthermore, brass-plated steel cords are generally used, but copper-plated steel cords are used in consideration of drawability and adhesion.
It is preferable to use a ternary alloy plating of zinc-cobalt/L'coat having a composition of, for example, copper 55-74% by weight, zinc 16-42% by weight, and cobalt 0.4% S12% by weight.

Next, in the present invention, the embedded rubber in the ply of the belt 1 or carcass is a liquid rubber made of low molecular weight polybutadiene or low molecular weight polyisoprene having active groups, such as carboxyl groups and hydroxyl groups. 2 to 50 parts per portion. By mixing this liquid rubber with other diene-based rubbers, the viscosity of the buried rubber is reduced, allowing it to smoothly penetrate into the voids inside the steel cord during the vulcanization process, and co-vulcanizing with other rubber base materials. The basic characteristics of vulcanized rubber are further improved. Moreover, since the polymer molecules have active groups such as hydroxyl groups or carboxyl groups, the affinity between the steel cord surface and the rubber is increased, the adhesive interface is expanded, and the chemical bond between the rubber and the steel cord is strengthened. As a result, the problem of rubber peeling that often occurred at the end of the belt layer can be effectively prevented.
If the amount is more than 1 part by weight, the workability and physical properties of the vulcanized rubber will deteriorate, while if it is less than 2 parts by weight, a sufficient reduction in viscosity cannot be expected. In addition, the viscosity average molecular weight of liquid rubber is 500 from the viewpoint of workability, penetration of the rubber into the inside of the vulcanized rubber physical property code, etc.
~50,000. Furthermore, it is desirable that the liquid rubber contains 1 to 15 active groups per molecule in consideration of affinity with steel cords and compatibility with other diene rubber base materials. In other words, the greater the number of active groups per molecule, the higher the affinity with steel cord, but the worse the compatibility with diene rubber (as a result, improvements in physical properties through co-vulcanization cannot be achieved. Belt layer or carcass ply) Diene rubber components used in buried rubber include natural rubber, synthetic polyisoprene rubber, polybutadiene rubber,
Styrene-butadiene rubber copolymer rubber or this Ftb
There are mixtures of two or more types of
From the viewpoint of heat generation properties, natural rubber or synthetic polyisoprene rubber is preferable.

In addition, this embedded rubber contains compound fillers that are usually used,
A vulcanizing agent and the like are suitably combined with N.

Examples of the present invention will be described below.

Example 1 Various types of steel cords having the twisted structure shown in Table 1 were embedded in rubber having the shape shown in Table 2, and a tire size 1
A trial tire was manufactured using the belt layer and carcass layer of a 000R20 whole steel radial tire for trucks and buses.

In order to understand the twistability of the steel cord and the degree of rubber penetration into the steel cord of the prototype tire, we evaluated the air permeability of the cord and the degree of rust on the cord after running in a salt water drum, and the results are shown in Table 1. .

The performance evaluation method is as follows.

(A1 Twisting processability of steel cords The degree of fly susceptibility during twisting process of steel cords was evaluated. Problems were listed as 0 for those with no problems and × for those with problems.

(b) Cord air permeability A steel cord ply is cut out from the belt layer or case of a trial tire and molded and vulcanized into a test piece 01) having the shape shown in FIG. In the figure, 9 is a vulcanized rubber plate, and 10 is a steel cord ply. Therefore, the test piece 11) was inserted into the empty press-in hole 1151 and exhaust hole [1
) in the measuring device section 1. So back pressure 3u/
When a load of d was applied, the volume of air exiting from the exhaust hole I) in one minute was measured. The measured values of Comparative Example 2 are shown as relative values with 100 and -.

(c) Incidence of steel cord rust after running on a salt water drum. Drill holes of 3 mm diameter from the inner surface of the tire at 5 locations in the radial direction in the tread portion of the tire to penetrate through the tread surface.

Assemble the tire to the rim and add 500cc of salt water between the tire and the tube to apply an internal pressure of n7.75#/d.

A drum test was conducted under the conditions of a load of 3645-1 and a speed of 5 ob/h, and after driving for 30,000 km, the tire was disassembled and the
) cut out the ply or carcass ply.

The average value obtained by dividing the length of rust generated along the steel cord around the drill hole by the total length of each cord is defined as the degree of occurrence of steel cord.

Hl bll Breaker Edge Separation After running on the salt water filled drum, the tire is steel cord.Before measuring the degree of rust, the breaker edge is dismantled, and the length of the rubber crack grown from the breaker edge is measured and the test number is determined. The relative value relative to 5 is shown as an index. The larger the index, the smaller the crack growth length and the better.

As is clear from Table 1, the present invention, in which the free space ratio of the cord is in a specific range and is compounded with a liquid rubber having active groups, has excellent air permeability, twistability, degree of cord rust occurrence after running in a salt water drum, and 1.1 breaker resistance. It is recognized that the edge separation property is improved.

Note 1) Core expansion and twisting Note 2) Core, -strand expansion and twisting Note 3) Liquid/reinprene rubber containing no active groups, viscosity average molecular weight 29,000, Clareprene L Engineering R-30
(Clare Isoprene Chemica A/ll) Note 4) Liquid polyisoprene rubber containing about 10 carboxy ρ groups and 71 molecules, viscosity average molecular weight 25,000.
, Clarebrene L Engineering R-410 (manufactured by Clarei Soprene Chemical Co., Ltd.) Note 5) Liquid polybutadiene rubber containing αBsm #/g of hydroxyl groups, number average molecular weight 2,800, R-45HT (
(manufactured by Idemitsu Petrochemical) Note 1) 2.2.4-Trimethyl-1,2-dihydroquinoline Note 2) N-Cyclohex V/I/-2
-Benzothiazyl sulfene aodide (az manufactured by Sumitomo Chemical Co., Ltd.)
)

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram for determining the free space ratio of the core strand, Figure 2 is an explanatory diagram for determining the free space ratio of the intermediate layer or outer layer, and Figure 3 is a schematic diagram of the cord air permeability measuring device. Patent applicant showing each figure: Sumitomo Rubber Industries Co., Ltd. Representative Patent attorney Yoshihira Nakamura Figure 1

Claims (1)

[Claims] (11 Radia) A radial tire comprising a V-structured carcass and a belt m disposed to surround the outer periphery of the crown portion of the carcass, comprising a braai in which a steel cord is embedded in rubber. The steel cord of the carcass and/or belt 1 has a three-layered structure consisting of a core, an intermediate layer, and an outer layer, or a layered structure or a layered structure consisting of 2Nij of a core and an outer layer, and has a core free space ratio of 5 to 334, and an intermediate layer. It is an open twisted steel cord with a free space ratio of 5 to 154 between the inner and outer parts, and the rubber embedded in the carcass and the belt contains 2 to 30 parts of liquid rubber having active groups in the rubber component. The radial tire is characterized in that: (The radial tire according to claim 1, wherein the 21l & shaped rubber is liquid polybutadiene or liquid polyisoprene. (5) The liquid rubber has a viscosity average molecular weight of 15,000 to 5o.
, o o o radial tire according to claim 2. (4) The radial tire according to claim 2 or 3, wherein the active group is a carboxyl group or a hydroxyl group.