JP2002338739A - Rubber composition for tire cord coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for tire cord covering capable of sufficiently controlling the change of elasticity of rubber by curing while fully keeping the fracture toughness of the rubber under a condition receiving thermal oxidation. SOLUTION: This rubber composition is prepared by adding following (A) to (F) to 100 pts.wt. rubber component comprising at least either one of a natural rubber and a diene synthetic rubber. (A) 0.1-10 pts.wt. p-phenylenediamine antioxidant, a quinoline antioxidant, a phenol antioxidant or other proton donor antioxidant, or any combination of them, (B) 0.1-5 pts.wt. peroxide decomposer comprising a phosphorus containing organic compound, (C) 20-200 pts.wt. filler for rubber reinforcement, (D) 1-10 pts.wt. sulfur, (E) 0.1-10 pts.wt. phenolic resin obtained by condensing a phenolic compound with formaldehyde or a phenol compound, and (F) 0.2-20 pts.wt. hexamethylenetetramine or a melamine derivative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition for coating a tire cord for coating a steel cord.

[0002]

2. Description of the Related Art Various reinforcing materials are used in tires of automobiles and the like. In particular, a steel cord excellent in strength and rigidity is widely used for a belt portion and the like of a tire.
Steel cord is usually brass (brass), bronze (Bron
It is used after being plated with a copper alloy such as z) or zinc.

[0003] Before embedding and reinforcing a steel cord in a tire component such as a belt, a steel cord is previously coated with a rubber composition having adhesiveness or the like.

[0004] When the coated rubber covering the steel cord is deteriorated by oxygen, heat, or the like, the fracture toughness and strength of the rubber are reduced, and the generation and growth of cracks in the rubber layer are promoted. For this reason, it is necessary to impart necessary deterioration resistance performance to the coating rubber for the tire cord.

[0005] In particular, in recent years, as the speed of vehicles and the output of engines have been improved, durability under high heat generation conditions has been required, and the life of tires has been extended from the viewpoint of environmental considerations. Therefore, durability under long-term heat history conditions is required.

[0006] As a deterioration inhibitor for improving the durability of the coated rubber for a tire cord, an amine-based antioxidant, particularly a p- (para) phenylenediamine-based antioxidant is used. The amine-based antioxidant, like the phenol-based antioxidant, stabilizes the radical with hydrogen that easily reacts with the radical. That is, the radical is trapped by a proton donating mechanism. By cutting off the radical chain reaction in this manner, deterioration of the rubber is prevented.

On the other hand, it has been practiced to improve the antioxidant effect by using a peroxide decomposer together with such a proton donating type antioxidant, that is, a radical chain inhibitor that captures radicals. The peroxide decomposers used in the tire cord coating rubber include thiodicarboxylates, thioureas, thiocarbamates, thiophosphates, hexavalent molybdates, phosphites, thiophosphites, thiophosphates, and thiophosphates. Phenol compounds containing sulfur or phosphorus in the chain are mentioned (JP-A-11-189679).

In general, when the required level of durability is increased, or particularly for applications where the required durability is strict, the amount of the antioxidant added is increased.

[0009]

However, as the added amount of the antioxidant is increased, over a certain added amount region,
The improvement in the anti-deterioration performance due to the increased amount of addition becomes extremely slow. When such a large amount is added,
In addition to the increase in cost, problems such as a decrease in rubber elasticity and contamination due to blooming of the antioxidant occur.

Further, even when a large amount of an antioxidant is added, under relatively severe deterioration conditions, rubber crosslinking often progresses and the elastic modulus often increases significantly.
When the elastic modulus becomes extremely high, the deformation in the rubber layer proceeds due to the deformation received during use of the tire.

The inventors of the present application have conducted intensive studies in view of the above problems, and as a result, have added an appropriate amount of a proton-donating antioxidant and a peroxide decomposer composed of a phosphorus-containing organic compound, and a phenolic compound of formalin. It has been found that it is effective to simultaneously add a condensate (phenolic resin) and a hexamethylenetetramine or melamine derivative.

According to the present invention, in a rubber composition for coating a tire cord, a change in elastic modulus due to curing of rubber can be sufficiently suppressed while sufficiently maintaining fracture toughness under conditions where rubber is subjected to thermal oxidation. Provide things.

[0013]

The rubber composition for coating a tire cord according to the present invention comprises a rubber component 10 comprising a diene rubber.
It is characterized by adding the following (A) to (F) to 0 parts by weight.

(A) a p-phenylenediamine antioxidant, a quinoline antioxidant, a phenolic antioxidant,
Or another proton-donating antioxidant or any combination thereof 0.1 to 10 parts by weight, (B) a peroxide decomposing agent comprising a phosphorus-containing organic compound, that is, an organic compound containing a phosphorus atom 0.1 to 5 Parts by weight, (C) filler for reinforcing rubber 20 to 200 parts by weight, (D) sulfur 1 to 1
0 parts by weight, (E) a phenolic resin or a phenolic compound obtained by condensing a phenolic compound with formalin
0.1 to 10 parts by weight, and (F) hexamethylenetetramine or melamine derivative 0.2 to 20 parts by weight.

According to the above configuration, a change in the elastic modulus due to the curing of the rubber can be sufficiently suppressed while sufficiently maintaining the fracture toughness under the condition that the rubber is subjected to thermal oxidation.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the rubber composition for coating a tire cord of the present invention is a diene rubber.

As the diene rubber, natural rubber (N
R), isoprene rubber (IR), butadiene rubber (B
R), styrene-butadiene rubber (SBR), and halogenated butyl rubber. A rubber blend in which a plurality of these are selected and combined may be used. Preferred rubber components are, for example, natural rubber alone or a rubber blend with a diene-based synthetic rubber mainly composed of natural rubber.

The rubber composition for coating a tire cord of the present invention contains a proton-donating antioxidant (radical chain inhibitor or primary antioxidant) as a deterioration inhibitor for preventing thermal oxidation deterioration. Peroxide decomposer (secondary anti-aging agent) comprising 10 to 10 parts by weight and a phosphorus-containing organic compound
-5 parts by weight.

The proton-donating antioxidants include paraphenylenediamine and its derivatives, styrenated diphenylamine and other aromatic secondary amines, quinoline compounds, and monophenol-type, bisphenol-type and polyphenol-type antioxidants. Agent included.

As a peroxide decomposer comprising a phosphorus-containing organic compound, tris (2,4-dibutyl-t-t-
(Butylphenyl) phosphite, cyclic neopentanetetraylbisnonylphenyl phosphite, trisnonylphenyl phosphite, and other trisphenyl phosphite derivatives. However, the peroxide decomposer may be a phosphate containing a phenyl group unit or the like.

The amount of the proton-donating antioxidant added is
Preferably it is 0.3-5 weight part, More preferably, it is 0.5-3 weight part. The amount of the peroxide decomposer added is preferably 0.3 to 3 parts by weight, more preferably 0.5 to 2 parts by weight.

If the amount of the proton-donating antioxidant is less than 0.1 part by weight, a sufficient effect of preventing deterioration cannot be obtained, and thermal oxidation deterioration of the rubber and embrittlement due to progress of crosslinking progress. I will. On the other hand, if the addition amount of the antioxidant exceeds 10 parts by weight, not only the cost is increased, but also problems such as excessive decrease in the elastic modulus of the rubber and contamination by blooming of the antioxidant are caused.

Further, even if a large amount of an antioxidant is added, under relatively severe deterioration conditions, rubber crosslinking often progresses, and the elastic modulus often increases significantly.
When the elastic modulus becomes extremely high, the deformation in the rubber layer proceeds due to the deformation received during use of the tire.

On the other hand, if the added amount of the peroxide decomposing agent is less than 0.1 part by weight, a sufficient deterioration preventing effect cannot be obtained. On the other hand, if the amount of the peroxide decomposing agent exceeds 5 parts, the cost will increase without further improving the antioxidant effect, and similarly, there will be problems such as a decrease in the elastic modulus of the rubber and contamination. Occurs.

In the rubber composition for coating a tire cord of the present invention, a rubber reinforcing filler is added in an amount of 20 to 200 parts by weight based on 100 parts by weight of the rubber component. In general, carbon black or silica is used as a reinforcing filler, and these can be used as a mixture. Carbon black alone can be added in the range of 10 to 200 parts by weight. When silica is added alone or together with carbon black, the amount of silica can be appropriately selected in the range of 10 to 100 parts by weight.

In some cases, a short fibrous filler composed of synthetic fibers such as polyester or inorganic fibers such as carbon fiber can be used together with the particulate filler.

As a crosslinking agent for the diene rubber, 1 to 10 parts by weight of sulfur is added to 100 parts by weight of the rubber component. When the diene rubber is 100% natural rubber, preferably 3 to 8 parts by weight of sulfur is added. Adequate crosslinking is achieved with an appropriate amount of sulfur. If the amount of sulfur is less than 1 part by weight, sufficient crosslinking density and rubber elasticity due to this cannot be obtained, or sufficient crosslinking is not easy. On the other hand, if the amount of sulfur exceeds 10 parts by weight, problems such as blooming also occur.

To the rubber composition for coating a tire cord of the present invention, 0.1 to 10 parts by weight of a phenolic compound or a phenolic resin obtained by condensing a phenolic compound with formalin is added to 100 parts by weight of the rubber component. You. Here, the phenolic resin is an uncured resin and has a liquid or thermal fluidity.

Further, the rubber composition for coating a tire cord of the present invention is added with 0.2 to 20 parts by weight of a hexamethylenetetramine or melamine derivative which plays a role of reacting and curing a phenolic resin or the like. .

The addition amount of the phenolic resin or phenolic compound is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight. When the addition amount of phenolic resin or the like is 1 to 3 parts by weight, the addition amount of hexamethylenetetramine or the like is preferably about 1.5 to 2.5 times the amount.

Here, the phenolic compounds include phenol, resorcinol and their alkyl derivatives. Alkyl derivatives include derivatives of methyl groups such as cresol and xylenol, as well as derivatives of relatively long-chain alkyl groups such as nonylphenol and octylphenol.

The phenolic resin obtained by condensing a phenol compound with formalin includes, for example, a resorcin-formalin resin, a phenol-formalin resin, a cresol-formalin resin, and a formalin resin comprising a plurality of phenol compounds. However, from the viewpoint of compatibility with the rubber component and other components, those containing alkylphenol are preferable, and from the viewpoint of the denseness and reliability of the cured resin, those containing resorcinol or a derivative thereof are preferable. Therefore, a particularly preferred phenolic resin is a resorcinol-alkylphenol co-condensed formalin resin.

When a highly reactive phenol compound such as resorcinol or alkylresorcinol is used, a formalin resin is formed by reacting with formalin derived from hexamethylenetetramine during kneading of the rubber. The same effect as when the adhesive resin is added can be obtained. If the time for kneading and processing of the rubber is sufficiently long, a phenolic compound other than the resorcinol family can be directly added to the rubber component.

If the amount of the phenolic resin is less than 0.1 part by weight, even if it is sufficient to improve the adhesiveness of the surface of the tire cord such as a steel cord, the rubber for covering the tire cord is not used. Physical properties cannot be sufficiently improved. The elastic modulus of the coated rubber significantly changes before and after long-term use or accelerated deterioration, and the fracture toughness cannot be sufficiently maintained. On the other hand, if the amount of the adhesive resin added is 1
If the amount exceeds 0 parts by weight, the elastic modulus of the whole coated rubber becomes large and the whole may become brittle (fragile).

In the rubber composition for coating a tire cord of the present invention, the amount of the hexamethylenetetramine or melamine derivative to be added is at least an amount sufficient to sufficiently react and cure the phenolic resin or phenolic compound. It is. If the added amount is less than 0.2 parts by weight, or if the added amount is less than the amount of the phenolic resin or the like, it is not preferable because sufficient reaction and curing cannot be performed. On the other hand, if the added amount exceeds 20 parts by weight, the physical properties of the coated rubber are rather deteriorated.

An embodiment of the present invention will be described below.

(Test Method) <Kneading> Kneading was performed according to a general method using a Banbury mixer. A prescribed antioxidant, a prescribed phenolic resin or phenolic compound, HAF grade carbon black (CB) 60 per 100 parts by weight of natural rubber
Parts by weight, zinc oxide (ZnO) 8 parts by weight, cobalt metal salt 0.2 parts by weight in terms of metal, vulcanization accelerator (Kawaguchi Chemical D
Z-G) 1 part by weight, 6 parts by weight of insolubilized sulfur, and a predetermined amount of a reaction / curing agent for curing the phenolic resin or phenolic compound were sequentially added in this order.

<Tensile Test> The unvulcanized rubber after completion of kneading was formed into a sheet by a roll, and heated by a hot press at 150 ° C. for 30 minutes to obtain a 2 mm thick vulcanized rubber sheet. A tensile test was performed on a test piece obtained by punching out this sheet with a No. 3 dumbbell using a strograph R manufactured by Toyo Seiki Seisaku-sho, Ltd. These were performed in accordance with JIS K6251.

Further, the test piece for tensile test was left for 192 hours in a constant temperature drier adjusted to 90 ° C., and then the above tensile test was performed. Then, the percentage of the elongation at break and the 100% modulus (Young's modulus at an elongation of 100%) with respect to the value before the accelerated deterioration was calculated and defined as the retention (%).

<Peeling Test> The unvulcanized rubber after completion of kneading was similarly formed into a sheet by a roll, and 1 mm in a cold press.
A thick sheet of unvulcanized rubber was obtained. On the other hand, twelve brass-plated steel cords were aligned at regular intervals in a 25 mm width. This array of steel cords was sandwiched between unvulcanized rubber sheets.
Furthermore, two sheets of this sandwich-like sheet are superimposed and heated at 150 ° C. for 30 minutes by a hot press to have a width of 25 mm.
To obtain a sheet of vulcanized rubber.

Then, a cut was made with a cutter knife so as to be equally divided in the thickness direction, and a strip (strip) -shaped test piece was formed, and a peeling test was performed by an autograph.

Further, the scrambled test piece was heated at 100 ° C.
After leaving for 96 hours in a thermostatic dryer adjusted to the above, the same peel test was performed to evaluate the dry heat resistance. Furthermore, the spiky test piece prepared in the same manner was allowed to stand in an autoclave heated to 105 ° C. and heated to 105 ° C. for 96 hours, and then subjected to the same test to evaluate the wet heat resistance. As for the dry heat resistance and the wet heat resistance, the retention rate (%) with respect to the initial adhesive force was determined in the same manner as in the tensile test.

Tables 1 and 2 below collectively show the test results obtained in Examples and Comparative Examples in which the compositions of the antioxidant and the phenolic resin component were variously changed. In these tables, the results of the peel test are shown in percentage (%) based on the value of Comparative Example 1.

[0044]

[Table 1] Examples

[Table 2] Comparative example As shown in Table 1 above, in Examples 1 to 10, the 100% modulus could be suppressed to 182% or less of the initial value while maintaining the elongation at break of 25% or more. In all examples, sufficient values were obtained for both the initial adhesive force and the adhesive force after accelerated deterioration. At this time, all the breaks occurred in the rubber layer, and it is considered that the adhesion at the interface between the coated rubber and the brass-plated steel cord was sufficient.

In particular, as can be seen from the results of Example 1, even when the total amount of the antioxidant is 2.2 parts by weight, the addition of the phenolic resin composition can sufficiently increase the 100% modulus by thermal oxidation. Could be suppressed.

On the other hand, as can be seen from Comparative Examples 1 to 3 shown in Table 2, when the same phenolic resin composition as in the example was used, when no peroxide decomposing agent was used,
The increase in 0% modulus could not be suppressed. Also, the adhesive strength was relatively low.

As is known from the results of Comparative Example 4, when an organic compound having a sulfur atom was used as the peroxide decomposing agent, the other conditions were exactly the same as in Examples 2-3. Nevertheless, there was no effect on suppressing the increase of the modulus by 100% and improving the adhesive strength. That is, among the peroxide decomposers, the sulfur-based decomposer did not provide any effect, and the effect was obtained only when the phosphorus-based decomposer was used.

As can be seen from the results of Comparative Examples 5 to 8, when the phenolic resin composition was not used, even if the antioxidant was sufficiently added, the increase due to thermal oxidation of 100% modulus was suppressed. I couldn't do that. Also, the value of the adhesive force was considerably low.

As described above, the rubber composition for coating a tire cord according to the embodiment can sufficiently suppress the change in the elastic modulus due to the hardening of the rubber with the fracture toughness. In addition, sufficient adhesion performance to a brass-plated steel cord can be realized.

[0050]

According to the present invention, it is possible to sufficiently suppress the change in the elastic modulus due to the hardening of the rubber while maintaining the fracture toughness sufficiently under the condition that the rubber is subjected to thermal oxidation.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/13 C08K 5/13 5/3477 5/3477 5/49 5/49 C08L 61/04 C08L 61 / 04 (72) Inventor Kentaro Nishioka 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka Toyo Tire & Rubber Co., Ltd. (72) Inventor Takashi Miyasaka 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka Toyo Ind. F term (reference) 4J002 AC011 AC031 AC061 AC081 AC111 CC032 DA038 DA049 DJ018 EJ016 EN076 EU056 EU189 EW067 FD018 FD067 FD076 FD149 GN01

Claims (1)

[Claims] 1. A rubber composition for coating a tire cord, wherein the following components (A) to (F) are added to 100 parts by weight of a rubber component comprising a diene rubber. (A) at least one proton donating antioxidant
0.1 to 10 parts by weight, (B) a peroxide decomposer comprising a phosphorus-containing organic compound 0.1 to 5 parts by weight, (C) a rubber reinforcing filler 20 to 200 parts by weight, (D) sulfur 1 to 1 10 parts by weight, (E) a phenolic resin or a phenolic compound obtained by condensing a phenolic compound with formalin 0.1
And (F) hexamethylenetetramine or melamine derivative 0.2 to 20 parts by weight.