JP2772387B2 - Radial tire for heavy-duty vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) In the present invention, a rubber reinforcing layer excellent in cut resistance, adhesiveness and low heat generation is disposed between a tread and a belt, especially in the center of the tread. The present invention relates to a radial tire for a heavy load vehicle having excellent durability and suitable for use on an unpaved road.

(Prior Art) Radial tires have a longer wear life than bias tires, so there is a case where separation occurs at a belt portion or the like, so that the tire cannot be used even though a tread remains.

As a method of improvement, use of a rubber composition with low heat generation on the tread, especially a base tread using a rubber composition with low heat generation at the side adjacent to the belt at the expense of abrasion resistance and excellent wear resistance on the outside thereof Tires with cap-based structure with cap-treads or treads, or rubber compositions with adhesives such as cobalt salts of organic acids, oxybenzoic acid, and resorcinol to increase the adhesion to steel cords are used for rubber embedded steel cords There were tires, but none of them were perfect.

Even in tires that use a rubber composition that shows high adhesion in steel cord adhesion tests as embedded rubber for belt cords, the tires that show extremely low values when measured for adhesion after use have a low incidence rate But it can be seen. Of course, it is important that the adhesive strength between the steel cord and the buried rubber is large, but it is also important that the decrease in the adhesive strength during use is small.

The following can be considered as a cause of the decrease in the adhesive strength of the steel cord to the rubber during use of the tire.

1.While the tire is running, there are many small cuts that reach the inner surface of the tread by stepping on stones and the like, and the air and moisture that penetrate through it promote aging and fatigue of the buried rubber, while rusting the steel cord, As a result, the adhesive strength is reduced.

2. During vulcanization or use, the adhesion improver incorporated into the steel cord embedded rubber diffuses and migrates toward the tread rubber, lowering the concentration in the embedded rubber and weakening its effect.

3. Conversely, the softener compounded in the tread migrates to the steel cord embedded rubber, and the adhesive strength of the embedded rubber is weakened.

(Problems to be Solved by the Invention) An object of the present invention is to provide a radial tire for a heavy-duty vehicle, which has a large adhesive force between a steel cord and an embedded rubber and a small decrease in the adhesive force during use of the tire. .

Another object of the present invention is to provide a radial tire for a heavy load vehicle which is excellent in cut resistance and separation resistance.

(Means for Solving the Problems) The present invention relates to a tire in which a belt reinforced with a steel cord is disposed between a carcass and a tread of a radial tire structure, and in addition to carbon black and silica, resorcin or a resorcin derivative is used as a reinforcing agent in rubber 100. A rubber composition containing 0.5 to 3 parts by weight of hexamethylenetetramine or a melamine derivative as a methylene donor and resorcinol or 0.8 to 2 times by weight of the resorcinol derivative with respect to parts by weight, the width of which is at least one-half of the tread width. The rubber reinforcing layer 4 is arranged along the inner surface of the tread so as to extend from the center to the end, and at the same time, the dynamic elastic modulus of the rubber reinforcing layer is E '(MPa) and the thickness is d (mm). When represented by The present invention relates to a radial tire for a heavy load vehicle, wherein the reinforcement coefficient indicated by is in the range of 3.3 to 5.3.

FIGS. 1 and 2 show sectional views of an example of the radial tire of the present invention. FIG. 1 shows a case where the rubber reinforcing layer 3 is lined over the entire width of the inner surface of the tread 1, and FIG. 2 shows a case where the rubber reinforcing layer 3 is lined at a part of the inner surface of the tread 1. In the figure, WR indicates the width of the rubber reinforcing layer 3, and WT indicates the width of the tread 1. Reference numeral 2 denotes a belt, 4 denotes a carcass, 5 denotes a side wall, 6 denotes a pad rubber, and 7 denotes a skirt sheet.

In the present invention, a reinforcement made of a rubber composition which has a large dynamic elastic modulus E 'between the belt and the tread, particularly at the center of the tread where the probability of receiving a cut is large, but which has a relatively low heat generation between the belt and the tread. The layers are placed as thick as possible without causing other major problems to increase resistance to microcuts. At the same time, as a compounding agent for increasing the dynamic elastic modulus E ', a substance having a property of preventing a decrease in adhesive strength with steel cord and not increasing heat generation is used. The steel cord is kept high in adhesive strength until the tire is used by adding the effect of preventing the transfer of the substance causing the decrease and increasing the adhesive strength of the adhesive modifier.

The rubber reinforcing layer used in the present invention has a width of at least 1/4 of the width of the tread, and is arranged so as to extend from the center to the end along the inner surface of the tread. As the rubber component of the rubber reinforcing layer, natural rubber, isoprene rubber, styrene-butadiene rubber, and butadiene rubber are preferably used. The rubber component is blended with carbon black, silica or the like as a reinforcing agent. In particular, the rubber component contains 0.5 to 3 parts by weight of resorcinol or a resorcinol derivative per 100 parts by weight of the rubber component. It is characterized in that it contains twice as many parts by weight of a hexamethylenetetramine or melamine derivative as a methylene donor. At the same time, the dynamic elastic modulus of the rubber reinforcing layer is E '.
When expressed in (MPa) and thickness is expressed in d (mm) It is also characterized in that the reinforcement coefficient indicated by is in the range of 3.3 to 5.3.

In the above, examples of the resorcinol derivative include a polycondensate of resorcinol and formalin, a molten mixture of a polycondensate of resorcinol and formalin, and an alkylphenol-formaldehyde resin. As the melamine derivative, for example, a partially etherified product of methylol melamine, a compound obtained by methoxylating a reaction product of melamine and formalin with methanol, and the like are used. Among them, the number of bound formalin per molecule of melamine is 4 to 6, and the number of methoxy groups is 4 to 6. Is preferably a mixture of 2 to 6 and a melamine derivative having a monomer content of 60 to 90%.

The tread is also curved in the width direction, so when stepping on the stone at the end of the tread, it is unlikely that the stone will be pushed out to the side and receive a cut, but when stepping on the stone in the center of the tread, it will be You will get more cuts as you get over them. Therefore, it is necessary to reinforce at least the central part of the tread. In the present invention, if the width of the reinforcing layer is less than 1/4 of the width of the tread at the center of the tread, the reinforcing effect is small. Preferably, the belt is covered with a rubber reinforcing layer over the entire width so as to have resistance to the fine cut and to prevent migration of a softener or the like from the tread. The reinforcing rubber layer is tacky when unvulcanized, and its thickness is small and soft, making it difficult to handle. Therefore, in the tread rubber extrusion process, the calendered sheet is directly laminated on the entire back surface of the extruded tread rubber. By doing so, handling becomes easier. It is more preferable that the width is substantially the same as the back surface of the tread rubber, because it can be interposed between the tread rubber and the side wall rubber or the carcass cord burying rubber to increase the adhesive strength therebetween.

If the amount of resorcinol or resorcinol derivative is less than 0.5 part by weight with respect to 100 parts by weight of rubber in the rubber composition, the decrease in adhesion between the steel cord and the embedded rubber during tire running is large and the amount exceeds 3 parts by weight and increases. Even if the amount is increased, that is, a reinforcing effect commensurate with an increase in cost cannot be obtained. If the amount of hexamethylenetetramine or melamine derivative is less than 0.8 parts by weight relative to resorcinol or resorcinol derivative, unreacted resorcinol or resorcinol derivative remains, and if it exceeds 2 parts by weight, even if the amount is further increased, it is met. The effect is not obtained, and disadvantages such as easy scorching occur.

If the reinforcement coefficient is less than 3.3, the cut resistance is inferior and the improvement effect of the rubber reinforcement layer is small, and if it exceeds 5.3, the heat generation increases and the aging and fatigue of the rubber buried in the belt are accelerated, and the separation resistance is reduced. Extremely low. This is apparent from FIG. 3 showing the relationship between the reinforcement coefficient and the belt end separation length (mm).

Among the hard carbons such as HAF-LS carbon black, ISAF-LM carbon black, ISAF-LS and HAF carbon black, the rubber composition used for the reinforcing rubber layer is preferably a carbon having a small amount of iodine adsorption or DBP oil absorption. The amounts of carbon black and silica are preferably 40 to 80 parts by weight and 5 to 40 parts by weight, respectively, based on 100 parts by weight of the rubber component.

In the rubber reinforcing layer of the present invention, in addition to the above components, known vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids, vulcanization retarders, reinforcing agents
Needless to say, a plasticizer, an antioxidant, a tackifier and the like can be added.

The radial tire of the present invention can be manufactured by a generally known method except for using the rubber reinforcing layer. For example, it can be produced by the method described in US Pat.

(Example) Hereinafter, an example and a comparative example will be described. It is to be noted that “parts” simply means “parts by weight”.

EXAMPLES AND COMPARATIVE EXAMPLES The components shown in Table 1 were mixed using a Banbury mixer, one part of which was divided into test pieces, and tested for the items shown in Table 2.

Using the remaining rubber, make a tire with a tire size of 1000R20 whose cross section is shown in Fig. 1 or Fig. 2, attach it to a dump truck, run it until the tread wears, and then disassemble it to reach the belt. The state of No. was observed and evaluated by the four-point method, the belt edge was observed over the entire circumference, and if separation occurred, its length was measured. The results are shown in Table 2.

(* 1) Carbon black A; HAF-LS (* 2) Carbon black B; ISAF-LS (* 3) Resorcinol derivative; polycondensate of resorcinol and formalin (* 4) Melamine derivative; Partially etherified methylolmelamine ( * 5) Antioxidant (6C); N- (1,3 dimethylbutyl)
-N-phenyl-p-phenylenediamine (* 6) accelerator (DZ); N, N'-dicyclohexyl-2-
Benzothiazolylsulfenamide The melamine derivative of the above (* 4) is shown in Reference Example 1 below.
It was manufactured by

Reference Example 1 (Synthesis of Melamine Derivative) 1 glass 3 with stirrer, thermometer and reflux unit
In a one-necked flask, 259.6 g (3.20 g) of formalin (37%)
Mol), adjust the pH to 9.0 to 9.5 with a small amount of caustic soda, then add 50.5 g (0.40 mol) of melamine, raise the temperature of the content liquid to reflux in an oil bath (about 80 ° C) and keep warm. did. After 60 minutes from the start of reflux, remove the oil bath, cool to room temperature, and add 202.6 g (6.33 mol) of methanol.
Was charged. Further, the pH was lowered to 2-3 with sulfuric acid, and a methoxylation reaction was carried out at about 30 ° C. for 120 minutes. Water and methanol were distilled off from the synthesized reaction solution by distillation under reduced pressure, and the reaction solution was taken out in a heated state.

The monomer content of this melamine derivative is 81%, the number of bound formalin is 5.7 per melamine molecule, and the number of methoxy groups is
It was 4.2.

The monomer content of the melamine derivative, the number of bound formalins and the number of methoxy groups were measured by the following methods.

(Measurement method) Monomer content: Area percentage by GPC (gel permeation chromatography).

Bound formalin amount: After addition of phosphoric acid, formalin was driven out by distillation, and the obtained formalin amount was calculated by iodine-sodium thiosulfate titration.

Number of methoxy groups: Calculated by potassium iodide-sodium thiosulfate titration after adding hydroiodic acid to a phenol / propionic acid solution of a melamine derivative.

Test method (1) Dynamic elastic modulus tester; Viscoelastic spectrometer manufactured by Iwamoto Seisakusho Test conditions: Initial strain 15%, amplitude 1%, frequency 50Hz, temperature
30 ° C (2) Adhesion test A number of steel cords are juxtaposed at intervals of about 1 mm, and the above-mentioned mixed rubber sheet is superimposed on a sample that has been double-sided rubberized with an embedded rubber composition, and vulcanized and molded using a mold. It was removed from the mold and cooled.

Furthermore, after leaving in a hot air at a temperature of 120 ° C. for 4 days for accelerated aging, a peeling test was performed to evaluate the area of the rubber remaining with the cord layer covered, that is, the coverage.

When there was no rubber reinforcing layer and only the embedded rubber (control) was used, tread rubber was used instead of the mixed rubber.

 Tire number 4 is an example and the others are comparative examples.

[Brief description of the drawings]

1 and 2 are cross-sectional views of an example of the radial tire for a heavy load vehicle according to the present invention. FIG. 3 is a graph showing a relationship between a reinforcing coefficient and a belt end separation length (mm).

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Ryo Muramatsu 100, Fujinogi, Tianjin, Itami-shi, Hyogo Tire Technology Center, Toyo Tire & Rubber Co., Ltd. (56) References JP-A-63-49501 (JP, A) JP-A-62-61805 (JP, A) JP-A-61-229602 (JP, A) JP-A-60-234002 (JP, A) JP-A-60-82406 (JP, A) (58) Int.Cl. ⁶ , DB name) B60C 9/18 C08K 5/13 C08K 5/17 C08L 21/00

Claims (1)

(57) [Claims] 1. A tire in which a belt reinforced with a steel cord is arranged between a carcass and a tread having a radial structure, in addition to carbon black and silica, resorcin or a resorcin derivative is used as a reinforcing agent in an amount of 0.5 to 3 parts per 100 parts by weight of rubber. The rubber reinforcing layer comprising a rubber part containing at least 0.8 parts by weight of hexamethylenetetramine or a melamine derivative as a methylene donor and 0.8 to 2 times by weight of the resorcinol derivative as a methylene donor, and having a width at least 1/4 of the width of the tread. When the rubber reinforcing layer is arranged so as to extend from the center to the end along the inner surface of the rubber reinforcing layer, and the dynamic elastic modulus of the rubber reinforcing layer is represented by E '(MPa) and the thickness is represented by d (mm) A radial tire for a heavy-duty vehicle, wherein a reinforcement coefficient indicated by a symbol is in a range of 3.3 to 5.3.