Tire reinforcing member and reinforced pneumatic tire

ES 2 249 392 T3

DESCRIPTION

Reinforcing element of a tire and a reinforced pneumatic tire

Background of the invention

1. Scope of the invention

The present invention relates to a reinforcing element of a tire and to a pneumatic tire reinforced therewith, and in particular to an element that serves to reinforce a tire and comprises a laminated element comprising a composite layer and a layer of a mixture of rubber and various other ingredients, such as a rubber of the type used to make rubber sweepers, laminated on the composite layer, and to a pneumatic tire whose fatigue resistance has been improved by the tire reinforcing element.

two. Description of the state of the art

In general, a pneumatic tire is reinforced with steel wires by constructing, for example, a carcass layer comprising at least one fabric, a belt layer comprising at least one fabric, or a layer forming a band. stabilizer and comprises at least one fabric made from an element composed of a mixture of rubber and various other ingredients and steel wire. A rubber is also conventionally used which is of the type of the so-called rubbers that are used to make rubber sweepers to increase the resistance to fatigue of the layer containing the threads by laminating a rubber of this type between the layers or fabrics. , thereby improving the fatigue resistance of a pneumatic tire.

Since the adhesion failure that occurs between the rubber mixture and various other ingredients that is used as a coating and the steel wires in the covering rubber and steel wire composite element due to heat generation during operation of the tire causes a fatal failure of the tire, there has been a demand that the adherence of the rubber to the steel wire be further increased. To meet this demand, in general, a cobalt salt of organic acid has been incorporated into the mixture of rubber and various other ingredients that is used as a coating as an adhesion promoter to increase the adhesion to the steel wires.

The coating rubber is surrounded by rubber elements of different chemical compositions. During long-term tire operation, various additive components from the surrounding rubber elements migrate into the coating rubber. Some of the components that migrate appear to adversely affect the adhesion of the rubber to the steel cord. However, this problem has not been sufficiently considered in the state of the art.

The Printed Copy of the Parts of the Japanese Patent Application Distributed to the Public N ° 2000-17115 assigned to the same assignee of this application proposes to deactivate the metal salt of organic acid by mixing a specific water resistant acid acceptor with a coating rubber in which steel wires are embedded, thereby increasing the resistance to fatigue of the adhesion of the rubber to the steel wire. However, it turned out that the acid acceptor, when used in considerable amounts, also captured sulfur and a vulcanization promoter in the rubber mixture and various other ingredients that is used as a coating during vulcanization, thereby failing to improve. sufficiently both the initial adhesion and the resistance to loss of adhesion.

Brief presentation of the invention

In view of the aforementioned problems that occur in the state of the art, an object of the present invention is to provide an element that serves as a reinforcement for a tire and is capable of greatly improving the fatigue resistance of a tire. pneumatic tire dramatically increased resistance to loss of adhesion of the steel wire to the coating rubber without affecting the initial adhesion, and that of providing a pneumatic tire whose resistance to fatigue has been improved by the reinforcing element of the tire.

Consequently, the present invention provides an element that serves to reinforce a cover and comprises:

(a) at least one composite layer (4) comprising a mixture (2) of rubber and various other ingredients that is used as a coating and steel wires (1), and (b) at least one layer (3) of a mixture of rubber and other various ingredients which is of the type used to make rubber sweepers, said layer comprising a mixture of rubber and various other ingredients and said layer being contiguous to the composite layer (4), being a basic inorganic filler incorporated into the mixture of rubber and various other ingredients that is of the type used to make rubber sweepers.

ES 2 249 392 T3

Brief description of the drawings

Fig. 1a is a cross-sectional view of one embodiment of the laminated roof reinforcing element of the present invention;

Fig. 1b is a cross-sectional view of another embodiment of the laminated roof reinforcing element of the present invention; and Fig. 1c is a cross-sectional view of yet another embodiment of the laminated roof reinforcing element of the present invention.

Detailed description of the invention

The reinforcing element of a roof according to the present invention is a laminated element comprising:

(a) at least one composite layer (4) comprising a mixture (2) of rubber and various other ingredients that is used as a coating and steel wires (1), and (b) at least one layer (3) of a mixture of rubber and other various ingredients which is of the type used to make rubber sweepers, said layer comprising a mixture of rubber and various other ingredients and said layer being contiguous to the composite layer (4), being a basic inorganic filler incorporated into the mixture of rubber and various other ingredients that is of the type used to make rubber sweepers.

The reinforcing element of a cover according to the invention is preferably applied to a truck / bus cover or to a large-sized cover for cross country. The reinforcing element of the cover is preferably used to make at least one fabric from among any of the members of the group consisting of the carcass layer, a belt layer or a layer that constitutes a stabilizing band of the cover. .

The laminated roof reinforcing element may include only one composite layer, or it may include two or more composite layers that are arranged either directly on top of each other or with a gap for each rubber composite layer. They are shown in Figs. 1a to 1c the basic structures of the laminated element for reinforcing a roof made according to the present invention. In the laminated element of Fig. 1a a layer 3 of a mixture of rubber and various other ingredients which is of the type used to make rubber sweepers is arranged on one of the outer surfaces of a composite layer 4 comprising steel wires 1 and a mixture 2 of rubber and other various ingredients that is used as a coating. Alternatively, as shown in Fig. 1b, the laminated element can be made by providing layer 3 with a mixture of rubber and various other ingredients which is of the type used to make rubber sweeps on one of the outer surfaces of a laminate comprising two composite layers 4 which they are laminated directly one on another. As shown in Fig. 1c, a layer 3 of a mixture of rubber and various other ingredients may also be interposed between two adjacent composite layers 4 which is of the type used to make rubber sweepers. In addition, two or more of any of these laminated elements can be laminated.

In the present invention, at least one of the outermost layers of the roof reinforcing laminate element is preferably a layer 3 of a mixture of rubber and various other ingredients which is of the type used to make sweepers. of rubber.

The thickness of each layer of the reinforcing element is not particularly limited and is selected according to the dimensions and the type of the cover to which the element is applied, and said thickness can be the same or different from layer to layer.

It is decisive in the present invention to incorporate a basic inorganic filler to at least the mixture of rubber and various other ingredients which is of the type used to make rubber sweepers.

The basic inorganic filler can include a metal oxide such as MgO, CaO, and Al₂OR₃, a metallic carbonate such as MgCO₃ and CaCO₃, and a basic compound salt such as talc, kaolin, and the mineral called hydrotalcite. Of the aforementioned basic inorganic fillers, a mineral called hydrotalcite is preferred and represented by the following Formula I and its calcined product:

[(M₁²⁺) (1-x) (M2³⁺) x (OH-) 2]^{x +} · [(TO^n-)_{x / n} Mll-Op (I) where M₁²⁺ is a divalent metal cation, M₂³⁺ is a trivalent metal cation, Aⁿ is an n-valent anion, x is a number that satisfies the condition that 0 <x <0.5, and m is zero or a positive number.

More specifically, M₁²+ is a divalent metal cation such as Mg²+, Mn²+, Faith²+, Co²+, Ni²+, Cu²+ and Zn²+, and Mg is particularly preferable²+. M₂³+ is a trivalent metal cation such as Al³+, Faith³+, Cr³+, Co³+ and In³+. TO^n- it is

ES 2 249 392 T3 an n-valent anion such as OH, F, Cl, Br, NO₃ , CO₃² , SO4² , Fe (CN) 6³ , CH₃COOO, an oxalate ion and a salicylate ion, and CO is particularly preferable₃^{2 -}.

The mineral called hydrotalcite, such as Mg₄,₃To the₂(OH)₁₂,₆CO₃-m'H₂O (x is 0.315 in Formula I), and its calcined product from which the water of crystallization has been removed are commercially available from Kyowa Chemical Industry, Co., Ltd.

The amount of the basic filler that is incorporated into the mixture is not particularly limited and can be chosen according to the use.

The basic inorganic filler is incorporated into the mixture of rubber and other various ingredients, which is of the type used to make rubber sweepers and constitutes the layer (3) of the mixture of rubber and other various ingredients that is contiguous to the layer. compound (4), the preferable mixing amount being 0.1 to 20 parts by weight based on 100 parts by weight of the rubber component of the rubber mixture and various other ingredients. When the amount is less than 0.1 part by weight, a sufficient improvement in the resistance to loss of adhesion which is caused for example by the heat that is generated during the operation of the cover cannot be obtained. An amount of more than 20 parts by weight is likely to reduce the breaking strength, the fatigue resistance of the vulcanized mixture of rubber and various other ingredients, and the workability of the unvulcanized mixture of rubber and various other ingredients. A more preferred amount of the basic inorganic filler is 0.5 to 10 parts by weight in view of the resistance to loss of adhesion, the fatigue resistance of the vulcanized mixture of rubber and various other ingredients, and the workability of the unvulcanized mixture of rubber and various other ingredients.

On the other hand, when the basic inorganic filler is incorporated into the mixture of rubber and various other ingredients that is used as a coating in the composite layer of the tire reinforcing element, the amount of the basic inorganic filler that is incorporated into the mixture is preferably 0.1 to 5 parts, and more preferably 0.1 to 2 parts, by weight based on 100 parts by weight of the rubber component of the mixture of rubber and various other ingredients that is used as a coating in order to increase the fatigue resistance of the tire.

The rubber component for the mixture of rubber and various other ingredients of the tire reinforcing element can be natural rubber and / or synthetic rubber. The synthetic rubber that can be used in the present invention is, for example, butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butyl rubber (IIR), halogenated butyl rubber, which it is preferably brominated butyl rubber, p-methylstyrene functionalized butyl rubber (copolymer of isobutylene and p-halomethylstyrene), ethylene-propylene-diene rubber (EPDM), etc.

Natural rubber and synthetic rubber according to the previous enumeration can be used alone or in combination of two or more depending on the rubber article to which the laminated element is applied and the degree of reinforcement provided. It is more preferable in view of obtaining a sufficient adhesion of the rubber to the steel cord and a sufficient resistance to breakage of the vulcanized mixture of rubber and various other ingredients a rubber component containing natural rubber and / or a rubber of synthetic isoprene in an amount of 50% by weight or more.

The mixture of rubber and various other ingredients that is used as a coating may further contain an adhesion promoter commonly used in known rubber adhesive blends and various other ingredients for steel wires. The adhesion promoter is for example a metal salt of an organic acid, and preferably a cobalt salt of an organic acid. The organic acid can be saturated or unsaturated and linear or branched. Examples of the organic acid include a naphthenic acid such as cyclohexanecarboxylic acid and an alkylcyclopentane having a fatty acid residue; a saturated fatty acid such as hexanoic acid, octanoic acid, decanoic acid including branched isomers such as neodecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid and octadecanoic acid; an unsaturated fatty acid such as methacrylic acid, oleic acid, linoleic acid, and linolenic acid; and resin acid such as rosin, tall oil acid, and abietic acid. The metal element of the metal organic acid salt can be partially substituted with boron, boric acid or an aluminum-containing compound. The amount of the organic acid metal salt to be incorporated, based on the metal element, is 0.1 to 0.3 part by weight based on 100 parts by weight of the rubber component. Also, the adhesion promoter can be incorporated into the rubber and various other ingredient blend layer that is contiguous with the coating rubber-steel cord composite layer.

The mixture of rubber and various other ingredients constituting the reinforcing element of a tire according to the present invention usually contains sulfur preferably in an amount of 3 to 8 parts by weight per 100 parts by weight of the rubber component. When the amount of sulfur is less than 3 parts by weight, the adhesion of the rubber to the steel cord may become insufficient due to the fact that the amount of sulfur decreases for the formation of Cu._xS (formed by the reaction of sulfur and copper in the brassing layer of the steel wires), which contributes to the adherence of the rubber to the steel wire. The use of an amount of more than 8 parts by weight can cause excessive Cu formation._xS, which can lead to occasional failure of cohesion where the amount of Cu has increased_xS, thereby reducing the adhesion of the rubber to the steel wire. Additionally, the resistance to hot aging of the mixture of rubber and various other ingredients tends to be reduced.

In addition to the aforementioned additives or components, the mixture of rubber and various other ingredients that is used as a coating and the layer of rubber mixture and various other ingredients that is contiguous therewith may

ES 2 249 392 T3 also contain another mixing additive commonly used in the rubber art in a usual amount.

Such a mixing additive can include a filler, a plasticizer, a vulcanization accelerator, and an antioxidant. The filler includes carbon black, zinc white, silica, etc. The plasticizer includes aromatic extract oil. Examples of the vulcanization accelerator include a guanidine compound such as diphenylguanizine, a thiazole compound such as mercaptobenzothiazole, a sulfenamide compound such as N, N'-dicyclohexyl-2-benzothiazolyl sulfenamide, and a thiouram compound such as tetramethylthiouram disulfide. The antioxidant includes an amino compound such as poly (2,2,4-trimethyl-1,2-dihydroquinoline) and phenyl-α-naphthylamine.

To enhance adhesion to rubber, the steel cords that are used in the reinforcing element of the present invention are preferably electroplated with brass or zinc, each optionally containing nickel or cobalt. Brassing is particularly preferable. To obtain good and stable adhesion, the Cu content in the brass coating is 75% by weight or less, and preferably 55 to 70% by weight. Steel wires can be twisted without a specific limitation with respect to the twisting structure.

The tire of the present invention is a pneumatic tire to which the reinforcing element of a tire that has been described above is applied. The cover element to which the reinforcing element is applied is not particularly limited, but is preferably a carcass fabric and / or a belt fabric. The reinforcing element of the cover comprises (a) at least one layer composed (4) of steel wires (1) coated with a mixture (2) of rubber and various other ingredients that is used as a coating, and (b) when minus one layer (3) of a mixture of rubber and various other ingredients which is of the type used to make rubber sweepers, this last layer being contiguous to the composite layer (4). The roof reinforcing element may have a single composite layer, or two or more composite layers. And preferably the carcass layer has one or two composite layers, and the belt layer has two to six composite layers.

The pneumatic tire of the present invention is preferably used as a truck / bus tire or as a large-sized tire for cross country, such as a tire for a construction vehicle such as a dump truck, a power shovel and a scraper blade, being The resistance to the loss of adhesion of the steel wire to the rubber is very important due to the great thickness of the cover.

The production of the mixture of rubber and various other ingredients, the composite body of steel wire and covering rubber, the reinforcing element of the tire and the pneumatic tire that have been described above does not require a specific process that requires excessive experimentation. , and can be carried out by methods that are known to a person skilled in the art within the field of rubber and tire manufacturing art.

The pneumatic tire of the present invention can be filled with air or with an inert gas such as nitrogen.

The present invention is described in more detail below with reference to the following examples, which are not intended to limit the scope of the present invention thereto.

The initial adhesion and the resistance to loss of adhesion of the test cover were evaluated by the methods indicated below.

(1) Initial Adhesion

A sample of a carcass fabric was cut into a part that forms the link between the sidewall and the tread of a vulcanized tire. Steel wires were then pulled from the sample at -90 ° C. The surface area of ​​the stripped steel wires that was covered with rubber was measured, and the amount of rubber that had remained on the wires (%) was expressed by the ratio of the surface covered with rubber to the total surface of the wires. steel wires. The greater the amount of rubber that remains on the wires, the better is the initial adhesion of the steel wire to the rubber.

(2) Resistance to Loss of Adhesion

The vulcanized tire was stored for 15 days at 100 ° C. Then the amount of rubber remaining on the yarns (%) was determined in the same way as in (1). The greater the amount of rubber that remains on the yarns, the better the resistance to loss of adhesion.

Examples 1-6 and Comparative Examples 1-2

A truck / bus cover having dimensions 11R22.5 and four belt ply was prepared by a known method. Brass (Cu: 63% by weight, Zn: 37) were used as reinforcement for the carcass fabric (which had a structure of 3 + 9 + 1 and a diameter of a single wire of 0.23 mm). % in weigh). The carcass fabric was made of a cover reinforcing element that had a composite layer comprising the steel wires coated with a mixture of rubber and various other ingredients that was used as a coating and a layer of rubber and other mixture. various ingredients (the kind used to make sweepers of

ES 2 249 392 T3 rubber) contiguous to the composite layer for Examples 1 to 5 and for Comparative Example 1 and a composite layer comprising the steel wires coated with a mixture of rubber and various other ingredients that was used as a coating for Example 6 and Comparative Example 2.

The mixtures of rubber and various other ingredients A to E were used for the mixture of rubber and various other ingredients that was used as a coating on the composite layer and for the mixture of rubber and various other ingredients of the rubber mixture layer and others. various ingredients of the carcass fabric of a test tire. Mix A of rubber and various other ingredients was prepared by mixing 100 parts by weight of natural rubber, 55 parts by weight of FEF carbon black, 1.0 part by weight of a plasticizer, 2.0 parts by weight of cobalt naphthenate , 6 parts by weight of zinc oxide, 2 parts by weight of N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine (Nocrac 6C, trade name of Ouchi Shinko Kagaku Kogyo Co., Ltd. ) as an antioxidant, 5 parts by weight of sulfur and 0.8 parts by weight of N, N'-dicyclohexyl-2-benzothiazolylsulfenamide (Nocceler DZ, trade name of Ouchi Shinko Kagaku Kogyo Co., Ltd.) as a vulcanization accelerator. The formulation of blend A of rubber and various other ingredients was used as the basic formulation. Each of the mixtures of rubber and various other ingredients B to E was prepared by combining the basic formulation with a predetermined amount of hydrotalcite (KW-2200, trademark of Kyowa Chemical Industry Co., Ltd.) or MgO as filler. basic inorganic, as indicated in Table 1.

TABLE 1

<td rowspan="2">Inorganic charge Basic (parts by weight)</td><td colspan="2">Rubber Blends and Other Various Ingredients</td>

<td>ABC</td><td>FROM</td>

<td>Hydrotalcite</td><td> - 0.5 5</td><td> 10 -</td>

<td>MgO</td><td> ---</td><td> -1</td>

Indicated in Table 2 is the combination of the coating rubber (composite layer) and the rubber of the type that are used to make rubber sweepers (layer of rubber mixture and other various ingredients) that was used in the fabric of the casing of each test cover.

Each test cover thus prepared was examined for initial adhesion and resistance to loss of adhesion in the manner described above. The results are indicated in Table 2.

TABLE 2

Examples

Comparative Examples

2 3 4 5 1 2 3

Shell Fabric

<td>coating rubber</td><td>TO</td><td>TO</td><td>TO</td><td>TO</td><td>B</td><td>B</td><td>TO</td><td>TO</td>

<td>rubber sweeper</td><td>B</td><td>C</td><td>D</td><td>AND</td><td>B</td><td>none</td><td>TO</td><td>none</td>

<td>Initial adherence (%)</td><td> 95</td><td> 95</td><td> 95</td><td> 95</td><td> 90</td><td> 90</td><td> 95</td><td> 95</td>

<td>Resistance to loss of adhesion (%)</td><td> 40</td><td> 55</td><td> 65</td><td> 45</td><td> 50</td><td> 50</td><td> 10</td><td> 10</td>

As seen from Table 2, in the tires of the present invention with the carcass fabric having the mixture of rubber and various other ingredients combined with hydrotalcite, excellent results were obtained both in terms of initial adhesion and in terms of the resistance to loss of adhesion.

The tire reinforcing member according to the present invention greatly increases the resistance to loss of adhesion of the steel cord to the coating rubber without decreasing the initial adhesion of the steel cord to the coating rubber. Consequently, the tire reinforcing element makes it possible to obtain a pneumatic tire in which the fatigue resistance has been dramatically improved.