JPH07329507A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To lighten a tire by arranging a carcass ply, wherein the arranged body of a carcass cord, wherein prescribed coating is applied to a filament bound by given adhesive without twisting, is embedded in a prescribed rubber composition, facing a tire inner cavity. CONSTITUTION:A carcass cord 9 is bound by adhesive 10 containing at least urethane and epoxy groups without twisting plural single fiber filament (f) with each other. The surface of the carcass cord 9 is coated with coating 11 containing at least resorcinol, formaldehyde, and rubber latex, and a carcass ply, wherein an arranged body of the carcass cord 9 is embedded in a rubber composition, wherein butyl rubber or butyl rubber halide is contained in a range of 60-100% in compound rubber, is arranged facing a tire inner cavity. Consequently, airtightness keeping performance in the tire inner cavity can be combined by a carcass to remove an inner linear layer to lighten a tire and reduce rolling resistance, improving productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire capable of reducing tire weight.

[0002]

2. Description of the Related Art In recent years, various lightweight fuel-efficient tires having a smaller rolling resistance have been developed for the purpose of energy saving and efficiency improvement as part of the improvement of the global environment. Generally, as one method for reducing the weight of a tire, each ply of a tire constituent element such as a carcass layer, a belt layer, and a breaker layer, which consists of a plurality of plies, is conventionally used such as 3 to 2 pieces or 2 to 1 pieces. There is a so-called less ply to reduce the ply from the above, and a less denier to reduce the thickness of the ply by using a small diameter cord on the ply.

[0003]

It is a major premise that the above-described res-plying and res-deniering should be performed while maintaining the performance of the tire components that are originally necessary. The less-ply method is nothing more than removing the flesh to the limit while leaving the tire components left, and naturally there is a limit to the weight reduction of the tire.

On the other hand, as another method for reducing the weight of the tire, it is possible to replace the constituent elements of the tire with other lightweight materials. Above all, the inner liner layer, which occupies a relatively large proportion in the weight of the tire, is made air. Substitutes such as sealing films with low permeability have been proposed, but in reality, production is difficult, airtightness is poor, and basic tire required performance cannot be obtained, so it is still practically successful. It hasn't arrived yet.

The present inventor has conducted extensive studies in view of the above problems, and as a result, combines the two constituent elements of the tire into one, that is, seals the air in the tire inner cavity of the inner liner layer. The present invention has been completed by finding out that the inner liner layer provided separately from the conventional carcass layer can be omitted by providing the carcass layer with the basic performance of retaining.

Therefore, the present invention is based on the use of a carcass ply in which a carcass cord is embedded in a rubber composition using butyl rubber or halogenated butyl rubber having low air permeability, and the carcass ply also serves as an inner liner. Therefore, it is an object of the present invention to provide a pneumatic radial tire capable of reducing the tire weight.

[0007]

SUMMARY OF THE INVENTION According to the present invention, at least one carcass having both ends locked by folding back around a bead core of a bead portion from a tread portion to a sidewall portion and radially arranging carcass cords. A pneumatic radial tire comprising a carcass made of ply and a belt layer extending radially outside of the carcass and inward of a tread portion, wherein the carcass cord has a plurality of filaments at least a urethane group and an epoxy group. An adhesive containing and is bound together without twisting, and the surface is coated with a coating agent containing at least resorcinol, formaldecht, and rubber latex. Butyl rubber or halogenated butyl rubber to 60% or more and 100% or less A pneumatic radial tire characterized by a carcass ply embedded in the rubber composition containing a range of arranged facing the lumen of the tire.

[0008]

According to the present invention, a rubber composition containing a butyl rubber or a halogenated butyl rubber having a low gas permeability in a compounded rubber in an amount of 60% or more and 100% or less is used as a carcass cord. By using the carcass ply in which the aligning body is embedded, the carcass ply itself can exhibit the airtight performance capable of preventing the permeation of the air in the tire cavity, and thus the carcass ply can be arranged facing the tire cavity. Therefore, it is possible to omit the inner liner layer, which has been conventionally arranged in the tire cavity separately from the carcass ply,
The tire weight can be greatly reduced, and the productivity of the tire can be improved by reducing the number of components.

The rubber composition contains butyl rubber and halogenated butyl rubber (hereinafter referred to as "butyl rubber") in an amount of 60% or more and 100% or less, more preferably 60% or more and 85% or less. Is desirable. If the content of butyl rubber in the rubber composition is less than 60%, the air permeability of the carcass ply cannot be reduced, the airtightness maintaining performance of the tire inner cavity is poor, and if it exceeds 85%, The above range is preferable because it tends to be inferior in adhesiveness to the diene rubber.

Further, in the carcass cord, a plurality of filaments are bound together with an adhesive liquid containing at least urethane groups and epoxy groups without being twisted together. Therefore, the carcass cord of the present invention can improve strength and elastic modulus as compared with a cord in which filaments are twisted together, and as a result, the cord diameter can be reduced, and the carcass can be achieved at the same time as the less denier. Helps to reduce the gas permeability by eliminating all gaps in the cord. In addition,
In the present application, "carcass cords are bound together without twisting a plurality of filaments with each other" means that the plurality of filaments are bound in parallel with each other, and the carcass cords are not said to be substantially twisted with each other. 1
It should be understood as meaning that the number of twists per 0 cm is less than 1.

Moreover, since the respective filaments of the carcass cord are bound together by using an adhesive liquid without being twisted with each other, when compared with a twisted yarn cord formed by twisting the same number of filaments of the same material, the unit length of the cord is The weight per unit is reduced, the amount of cord used is reduced, and the weight of the tire is reduced.

At least the surface of the filaments bound with the adhesive liquid is at least resorcin, formaldehyde,
By coating with a coating liquid containing a rubber latex, the adhesiveness when embedded in the rubber composition mainly containing butyl rubber can be improved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The pneumatic radial tire 1 of the present invention is folded back from the main body portion 6A extending from the tread portion 2 through the sidewall portion 3 to the bead portion 4 and around the bead core 5 in this example from the inner side to the outer side in the tire axial direction. Carcass 6 consisting of a carcass ply 6a whose both ends are locked by a portion 6B
And a belt layer 7 extending outside of the carcass 6 in the tire radial direction and inside the tread portion 2,
It has a bead apex 8 made of hard rubber extending from the bead core 5 to the outside in the radial direction of the tire and is mainly used as a radial tire for passenger cars.

The carcass ply 6a has a radial structure in which the carcass cords are arranged in the rubber composition at an angle of 60 ° to 90 ° with respect to the tire equator C, and at least 1
Although the structure of one sheet is illustrated in this example, two or more sheets may be provided. The upper edge height h1 of the folded-back portion 6B of the carcass ply 6a is from the bead base line BL to a position of about 45% which is the height from the bead base line BL to the upper surface of the tread when a prescribed internal pressure is filled. The one launched is illustrated.

As shown in FIG. 2, the carcass cord 9 is formed by binding a plurality of monofilament filaments f into one cord by using an adhesive 10 without twisting them.

The stress-strain curve of the cord obtained by binding the filaments f without twisting them together is shown by the solid line in FIG. 40x40T / 10cm (carcass cord 10cm) filaments of approximately the same diameter and the same material
It means the number of times of under-twisting times the number of times of over-twisting. ) Shows the stress-strain curve of the cords twisted together with each other by a chain line. As is clear from the figure, the carcass cord 9 of the present embodiment, which is not twisted, is
The breaking strength is improved by about 20%, and comparing the elastic moduli, it can be understood that the cord 9 of this example is excellent at about 1.5 times the twisted cord.

Therefore, the carcass cord 9 can be made smaller in diameter to achieve less denier at the same time, and the ply thickness, the thickness of the bead apex in the tire axial direction, and the like can be reduced. By making almost no gap inside the carcass cord, gas permeability can be made smaller than that of the twisted cord.

In addition, in the cord formed by twisting the filaments f, when the cord is cut into a unit length, the length per filament is larger than the unit length of the cord by the amount that the filament has a spiral shape. However, since the filament f of this embodiment is not twisted with each other, the unit length of the cord and the length per filament are substantially equal, and the amount of filament used is large. This also contributes to the weight reduction of the tire in this respect as well.

An organic fiber material can be preferably used for the filament f, and in the present embodiment, one made of polyester is shown, and the adhesive 10 contains at least a urethane group and an epoxy group. preferable.

In the carcass cord 9, the surface of one cord obtained by bundling the filaments f with the adhesive 10 is coated with a coating agent 11 capable of improving the adhesive force with the butyl rubber. The coating material 11 contains at least resorcin, formaldehyde, and rubber latex in its components.

Further, the carcass ply 6a is formed by embedding the above-mentioned carcass cords 9 in parallel with each other to form a carcass cord aligning body in a combed weave shape and embedding it in a rubber composition containing butyl rubber. .

In the rubber composition, the butyl rubber is contained in the compounded rubber in an amount of 60% or more and 100% or less, preferably 60%.
The gas permeability of the carcass ply 6a is made small by containing it in the range of not less than 85% and more preferably not less than 60% and not more than 70%.

100 parts of butyl rubber is added to the rubber composition.
When it is contained in%, halogenated butyl rubber such as chlorinated butyl rubber and brominated butyl rubber can be preferably used because it can maintain the adhesive force with other rubbers. When the butyl rubber content does not reach 100%, the rubber is mixed with a reinforcing agent such as carbon black, a tackifier, and a softening agent such as paraffin oil in addition to natural rubber and butadiene rubber. It is preferable to improve the adhesiveness and strength of the composition.

The carcass ply 6a using such a rubber composition having a low gas permeability is disposed facing the tire inner cavity 12 and maintains airtightness, so that
It may be possible to remove the inner liner layer, which was provided separately from the carcass ply.

The belt layer 7 on the outer side in the tire radial direction of the carcass 6 is made of various belt cords made of organic, inorganic, steel or the like, preferably cords made of a lighter weight aramid fiber, at 0 ° to 30 ° to the tire equator. Two belt plies 7A and 7B arranged at a small angle of ° are arranged so that the belt cords cross each other, and the inner belt ply 7A is made wider than the outer belt ply 7B, and both ends are cut ends. It has a structure.

Further, on the outer side of the belt layer 7 in the radial direction of the tire, a belt-shaped ply of a small width or the like, to which one cord or a plurality of organic fiber cords are topped in parallel in order to prevent lifting of the belt layer, is formed on the entire belt layer. A band layer 8 spirally wound over the width is provided.

(Specific example) Tire size is 185 / 70R
Radial tires for passenger cars having the construction shown in Fig. 1 and 14 were prototyped, and the tire weight and rolling resistance were measured. In addition, a conventional product including a conventional inner liner layer was also tested. The test conditions are as follows.

A) Tire weight The weight per tire was measured and expressed as an index with the conventional product as 100. The smaller the value, the lighter the weight.

(B) Rolling resistance It was measured using a rolling resistance tester and indicated by an index with the conventional product being 100. The smaller the value, the smaller the rolling resistance and the better. The test results are shown in Table 1.

[0030]

[Table 1]

As a result of the test, it was confirmed that the tires of the examples reduced the weight of the tires as compared with the conventional products and had a low rolling resistance.

Next, the adhesion between the carcass cord of this example and various rubber compositions was confirmed. The rubber composition includes natural rubber (NR), styrene-butadiene rubber (S
BR) blend, natural rubber (NR), butadiene rubber (B
R) and butyl rubber (IIR), natural rubber (N
R) and butyl rubber (IIR) were mixed, and a conventional twisted carcass cord was also tested. The test method is as follows.

C) Pull-through test A carcass cord 1 is obtained by extracting a test piece from the carcass ply.
A tensile load was applied to the book in the axial direction, and the load value when the carcass cord was pulled out from the ply was measured, and it was shown by an index with the load of the conventional carcass cord being 100 in various rubbers. The larger the index is, the larger the adhesive force of the ply with the rubber composition is, and the better the index is. The test results are shown in Table 2.

[0034]

[Table 2]

It was confirmed that the carcass cord of this example has a larger adhesive force with the butyl rubber than the conventional cord.

Further, the tire of the example was assembled on a specified rim, filled with a specified internal pressure, and placed in an oven at 80 ° C.
The tire internal pressure drop after being left for 5 days was investigated, and it was confirmed that the tires of Examples 1 to 4 all had a decrease rate of 98% or less and passed the airtight performance.

[0037]

INDUSTRIAL APPLICABILITY As described above, the pneumatic radial tire of the present invention removes the inner liner layer which is conventionally provided separately from the carcass ply by providing the carcass with the ability to keep the tire cavity airtight. Therefore, the tire weight can be significantly reduced, the rolling resistance can be reduced, and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a left sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a sectional view for explaining a carcass cord.

FIG. 3 is a stress-strain curve of a carcass cord.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 7 belt layer 9 carcass cord 10 adhesive 11 coating agent 12 tire lumen

Claims (2)

[Claims] 1. A carcass comprising at least one carcass ply in which both ends are locked by folding back around a bead core of a bead part from a tread part to a sidewall part, and the carcass. A pneumatic radial tire comprising a belt layer extending radially outside and inward of the tread portion of the carcass cord, wherein the carcass cord is an adhesive containing at least a plurality of filaments of a urethane group and an epoxy group. The carcass cords are bound together without twisting each other, and the surfaces thereof are coated with a coating agent containing at least resorcinol, formaldehyde and rubber latex. % Or more and 10
A pneumatic radial tire characterized in that a carcass ply embedded in a rubber composition contained in an amount of 0% or less is arranged so as to face the inner cavity of the tire. 2. The pneumatic radial tire according to claim 2, wherein the butyl rubber or halogenated butyl rubber is contained in the compounded rubber in the range of 60% or more and 85% or less.