JP2002205506A - Tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a tire. SOLUTION: This tire is formed using a complex made of rubber composition having bismaleimide or further trans-polybutadiene, and of a steel cord formed by twisting steel filaments containing a specific amount of Cu, Co, and Ni in a brass plating in a distribution in the specific depth direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire using a rubber-steel cord composite, and more particularly to a technique for improving a coating rubber of a plated steel cord and a plating portion of the steel cord.

[0002]

2. Description of the Related Art For example, a rubber composition applied as a coating rubber to a belt layer reinforced with a steel cord is an important rubber involved in the durability of a tire. The performance required of this rubber composition includes (1) hardness,
(2) Low heat generation, (3) Adhesion to steel cord,
(4) Deterioration resistance and the like. Among them, the above (1)
Increasing the hardness of the tire is an effective means for suppressing the shear strain between the belt layers and improving the durability of the tire.

In order to increase the hardness, conventionally,
(A) increasing the amount of filler such as carbon black, (b) adding a resin or the like, (c) increasing the amount of crosslinking agent such as sulfur, (d) the amount of vulcanization accelerator There is a method such as increasing.

[0004]

However, the above (a),
When the amount of the filler (b) is increased or the resin is added, the hardness certainly increases, but the low heat build-up is lowered and the heat durability is deteriorated. Further, the increase in the compounding amount of sulfur in the above (c) is that even when the tire is left in the state of unvulcanized rubber, the sulfur blooms, the workability is remarkably reduced, and even if the tire is formed,
Since the deterioration resistance of the rubber is reduced, the durability of the tire may be reduced.

[0005] Further, there is no problem in workability, low heat generation and deterioration resistance up to a certain extent in the increase of the amount of the vulcanization accelerator (d). There is a problem that the performance is reduced. Therefore, an object of the present invention is to improve a rubber-steel cord composite to provide a tire having excellent durability.

[0006]

Means for Solving the Problems In order to achieve the above object, the present inventor has made the following findings as a result of intensive studies and has completed the present invention. That is, since bismaleimide is directly crosslinked between polymers such as natural rubber without passing through sulfur, the hardness of the rubber can be increased without impairing the low heat build-up and deterioration resistance of the rubber. Conceivable. In addition, although bismaleimide alone is effective, it has been found that when transpolybutadiene is added together, reversion which is increased by bismaleimide can be suppressed, and the hardness and heat generation can be further improved.
Furthermore, it was found that the adhesion between the rubber and the steel cord was improved by using bismaleimide alone or in combination with bismaleimide and trans polybutadiene.

On the other hand, the cobalt salt acts as an adhesion promoter in the adhesion of the rubber-steel cord, so that it is necessary for promoting the adhesion, but at the same time, the cobalt salt also has an effect of deteriorating the deterioration resistance of the rubber. Thus, the use of bismaleimide alone or in combination with bismaleimide and transpolybutadiene has made it possible to reduce the blending amount of the cobalt salt. Furthermore, it was found that the adhesiveness could be further improved by combining the rubber composition with the novel steel cord of the present invention.

The configuration of the present invention is as follows. (1) A tire using a rubber-steel cord composite comprising a rubber composition in which bismaleimide is blended with a rubber component comprising at least one of natural rubber and a diene-based synthetic rubber, and a steel cord, wherein the rubber Ingredient 1
It is characterized in that 0.1 to 5 parts by weight of the bismaleimide is added to 00 parts by weight. (2) Trans-polybutadiene is further added to the rubber composition in an amount of 0.1 to 15 parts by weight based on 100 parts by weight of the rubber component.
It is characterized by being blended by weight. (3) The rubber component is characterized by containing 50% by weight or more of natural rubber. (4) The bismaleimide is a bismaleimide represented by the following general formula [Formula 2].

[0009]

Embedded image

Wherein R is an aromatic group having 6 to 18 carbon atoms;
Alternatively, it represents an alkyl aromatic group having 7 to 24 carbon atoms, and x and y each independently represent an integer of 0 to 3. (5) The steel cord has a peripheral surface with a copper concentration of 15 to 45 atomic% of the outermost layer in a surface region from a surface of a brass-plated steel filament to a depth of 15 nm inward in a radial direction of the filament. It is a monofilament steel cord made of one of the brass-plated filaments containing at least one of cobalt atoms and nickel atoms, or a multifilament steel cord obtained by twisting these steel filaments. Here, the “outermost layer” is a minimum unit length that can be measured by the device, and is about 1 nm to 2 nm by X-ray photoelectron spectroscopy.

(6) The total amount of cobalt atoms and nickel atoms contained in the surface layer region is not less than 0.1 atomic% and not more than the copper atom content of the surface layer region. (7) The total amount of cobalt atoms and nickel atoms contained in the surface region is 0.5 to 5.0 atomic%. (8) In the surface region, cobalt atoms and nickel atoms not contained in the oxide are 50 atomic% of the total amount of cobalt atoms and nickel atoms contained in the surface region.
It is characterized by the above. (9) The average thickness of the brass plating is 0.13 to 0.30 μm. (10) The diameter of the filament is 0.40 mm or less.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail. The tire of the present invention is provided with a rubber-steel cord composite comprising a steel cord and a specific rubber composition (coating rubber). The rubber component of the coating rubber is composed of at least one of natural rubber and diene-based synthetic rubber,
It is preferable to contain 50% by weight or more of natural rubber. 5
If the amount is less than 0% by weight, the adhesive property and the rubber breaking property may be deteriorated. The synthetic rubber that forms the balance of the rubber component is styrene-butadiene rubber (S
BR), butadiene rubber (BR), butyl rubber (II
R), a halogenated butyl rubber (X-IIR), preferably a brominated butyl rubber (Br-IIR), a butyl rubber having a paramethylstyrene group (specifically, a copolymer of isobutylene and p-halogenated methylstyrene) etc),
Examples include ethylene propylene diene rubber (EPDM) and isoprene rubber (IR).

In the case of SBR, the butadiene moiety has a vinyl bond content of 35 to 85%, and the amount of bound styrene is 3%.
The solution-polymerized SBR is preferably 0% by weight or less, but it can improve the heat aging resistance of the rubber by setting the vinyl bond amount to 35% or more, and can improve the rubber's heat-resistant aging by 85% or less. This is because the breaking characteristics can be maintained. Further, by setting the amount of bound styrene to 30% by weight or less, a decrease in adhesiveness can be suppressed.

In the present invention, the bismaleimide is used in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the rubber component for both bismaleimide and a combination of bismaleimide and transpolybutadiene. If the amount is less than 0.1 part by weight, the compounding effect is not exerted. If the amount is more than 5 parts by weight, reversion becomes large, and the heat build-up deteriorates. The bismaleimides suitable in the present invention include N, N'-1,2-phenylenebismaleimide, N, N'-1,3-phenylenebismaleimide, N, N'-1,4-phenylenebismaleimide, N , N '-(4,4'-diphenylmethane) bismaleimide, 2,2-bis [4- (4-maleimidophenoxy) phenyl] propane, bis (3-ethyl-5
-Methyl-4-maleimidophenyl] methane and the like, and particularly preferred is N, N '-(4,4'-diphenylmethane) bismaleimide. In the rubber composition,
One or more of these may be included. In the general formula of bismaleimide, if x or y is 4 or more, the molecular weight increases, and the desired effect of increasing the dynamic storage elastic modulus cannot be obtained for the compounding amount, which is not preferable.

The rubber composition used in the tire of the present invention includes:
In order to further improve the fracture resistance, it is preferable to incorporate trans polybutadiene. The trans polybutadiene preferably has a trans bond content of 82% to 98%, and more preferably 86% to 98% from the viewpoint of the effect. Further, its weight average molecular weight is 30,00.
When it is 0 to 200,000, the processability in the unvulcanized state can be improved, and the fracture resistance of the vulcanized rubber can be maintained. The amount of trans polybutadiene is determined from the viewpoints of compatibility with the rubber component and the fracture resistance of the vulcanized rubber.
The amount is preferably 0.1 to 15 parts by weight per 100 parts by weight of the rubber component. Further, when 3 to 15 parts by weight, particularly 4 to 12 parts by weight is added, the effect is large.

In the rubber composition of the present invention, in addition to the above components, if necessary, reinforcing fillers, silane coupling agents, vulcanizing agents, vulcanization accelerators, A sulfur promoting accelerator, an antioxidant, an ozone deterioration inhibitor, an antioxidant, a process oil, zinc white (ZnO), stearic acid and the like can be appropriately blended.

The brass-plated steel cord of the present invention will be described below. By the way, the present inventor has determined that the brass plating applied to the generally used brass-plated filament in order to clarify the relationship between the component composition in the depth direction and the initial adhesiveness of the brass plating applied to the peripheral surface of the filament. Co ion implantation was performed to examine the adhesion to the coated rubber with the adhesion promoter reduced or not added. That is, using the ion plantation technique, the relationship between the ion implantation time and the Co content of the brass plating surface, and the relationship between the ionization rate of Co to be implanted and the depth distribution of the Co content shown in FIG. After grasping in advance, the Co content of the plating surface layer was variously controlled, and the relationship with the initial adhesion was investigated.

As a result, it has been newly found that the inclusion of Co to a depth of 15 nm from the plating surface is most effective for improving the initial adhesiveness, and the present invention has been completed. That is, the initial adhesion was evaluated by expanding the Co-containing region in the depth direction from the plating surface and evaluating the initial adhesion at various stages of the enlarging process of the region. As the Co-containing region was expanded in the depth direction, the initial adhesion increased. Although it was improved, it was found that even if the Co-containing region was expanded to a depth exceeding 15 nm, the initial adhesiveness was not further improved, and the effect was saturated at a depth of 15 nm. did.

On the other hand, when the initial adhesion was similarly evaluated by increasing the Co content only on the plating surface, if Co was not diffused to a certain depth, the effect of improving the initial adhesion was small, It was also found that the initial adhesion to the coated rubber with reduced or no added metal salt was not at a level that would ensure it. Therefore, the surface area is set to 15 nm. As described above, this is the main area that affects the improvement of the adhesiveness.

Further, when the Co content in the surface layer region from the plating surface to a depth of 15 nm was examined, if the content was less than 0.1 atomic%, the effect of improving the initial adhesion was poor, while the effect of the surface region was poor. When the Cu content is exceeded, the effect of improving the initial adhesiveness is saturated.
It is preferable that the content be in the range of 0.1 atomic% or more and Cu content of the surface layer region or less. More preferably, 0.5 to
It is recommended to be in the range of 5.0 atomic%.

When Co is contained only in the surface layer up to a depth of 15 nm from the plating surface, if ion implantation is used, as shown in FIG. It will show a concentration gradient that gradually decreases in the direction. In this case, as described below, the Co content in the surface layer region is determined by creating a depth profile as shown in FIG. 3 by using X-ray photoelectron spectroscopy (XPS) to obtain Cu, Zn, and Co in the entire surface region. C for all atomic quantities
o It is obtained by calculating the atomic% amount. The same applies to the Ni content.

Here, the reason that the initial adhesion is improved by containing Co in the surface layer region up to a depth of 15 nm from the plating surface is only when the Co diffuses from the plating surface to a depth of 15 nm. This is because effective diffusion of Cu inside the plating can be realized. Further, even if Co diffuses into a region exceeding this depth during plating, it is clear that the effect is saturated, and this leads to an increase in cost due to an increase in Co. The above findings were not limited to Co, but were similar for Ni.

As described above, the ion implantation technique was used to contain Co in the depth direction from the plating surface. However, when other methods of inserting Co or Ni into the surface layer region of the brass plating were examined, it was found that the brass plating was After repeating the step of immersing the applied filament in a colloid in which 5 to 10 parts by weight of a cobalt metal salt and an appropriate surfactant are dispersed with respect to 100 parts by weight of water and drying, for example,
The heat treatment at a temperature of 250 ° C. also allowed Co to diffuse to the inside of the plating having a depth of 15 nm. At this time, the cobalt content of the surface layer can be adjusted by controlling at least one of the number of times of dipping the cord in the liquid, the number of times of drying, and the number of times of thermal diffusion. FIG. 2 shows an example of the results of elemental quantification of Cu, Zn, and Co in the plating depth direction of the filament manufactured in this manner using photoelectron spectroscopy, with respect to the Co content. Similarly, when producing a steel cord, in the wire drawing step of the filament, an appropriate amount of a metal salt of Co or Ni as an adhesion promoter is added to a lubricant, and the heat generated during the wire drawing is used to add Co or Ni. Can be diffused into the plating of 15 nm.

Next, the Cu content on the plating surface was studied diligently. That is, the basic composition of plating is
In addition to the initial adhesion, it is necessary to consider adhesion durability such as heat resistance and moisture resistance after rubber vulcanization, and from the viewpoint of adhesion durability, the Cu content on the outermost surface is 45 atomic% or less, preferably Preferably, it is limited to 40 atomic% or less. On the other hand, in order to secure the initial adhesiveness, it is necessary to contain Cu in a certain amount or more, and the Cu content is made 15 atomic% or more, preferably 25 atomic% or more.

FIG. 3 shows a typical example of the concentration distribution of each component in the plating depth direction, including the plating surface layer region, when the basic plating composition and the Co content are regulated according to the present invention. Further, Co and Ni contained in the surface layer region
Means that 50% of their total amount is present as oxides
It is preferably less than atomic%. Because the bond between the metal atom and the oxygen atom is strong, the metal oxide itself is stable, for example, Co or Co
This is because diffusion and movement of ions in the metal become difficult. As a result, the exchange reaction and the substitution reaction between Co and Cu do not proceed sufficiently, and may not sufficiently serve as an adhesion promoter.

The amount of Co or Ni not contained in the oxide contained in the surface layer region is determined based on the result of measuring the plating surface by X-ray photoelectron spectroscopy, for example, as shown in FIG. Can be determined from the area ratio between the oxide and the metal from the abundance ratio of both.

Further, the average thickness of the brass plating is 0.1
Advantageously, it is between 3 and 0.30 μm. That is,
When the average plating thickness is less than 0.13 μm, the portion where the iron base is exposed is increased, and the initial adhesiveness is impaired.
This is because, if it exceeds, the adhesive reaction proceeds excessively due to heat during use of the rubber article, and only weak adhesiveness can be obtained.

It is advantageous that the filament diameter is 0.40 mm or less. Because 0.40mm
When the value exceeds the above, when the used rubber article is repeatedly strained under bending deformation, the surface strain increases and buckling is easily caused.

The amount of Co in the plating is determined by X-ray photoelectron spectroscopy from the plating surface to a depth of 15 nm or more in terms of the etching speed of SiO _2.
While performing argon etching while monitoring characteristic photoelectrons of u, Zn, Co, O, and C, the amount of elements present at each depth i is quantified to obtain Cu _i atomic% and Co _i atomic%, respectively. Further, a depth profile up to 15 nm (see FIG. 3) was created, and the Co atomic% of the surface layer region was calculated from the relative areas of Cu, Zn, and Co in that region. The plating thickness is 0.25 μm
It is.

Here, Cu _i atomic% and Co _i atomic% are Cu _i atomic% = [fcu Cu _in / (fcu Cu _in + fznZn _in + f
coCo _in )] × 100 Co _i atomic% = [fco Co _in / (fcuCu _in + fznZn _in
+ fcoCo _in )] × 100 where fcu, fzn, and fco are sensitivity coefficients of each element,
_in , Zn _in , and Co _in are counts of each element at the position of the depth i, and the unit is count per second.

As described above, in the method of manufacturing a steel cord according to the present invention, in addition to ion implantation using a dry technique, a brass-plated filament is immersed in a colloid in which a cobalt metal salt and an appropriate surfactant are dispersed. After repeating the drying step, heat treatment is performed at 150 to 250 ° C. to diffuse Co into the plating surface layer region.
The amount of Co can be controlled by the number of times the cord is immersed in the colloid solution, the number of times of drying, and the number of times of thermal diffusion. The same applies to Ni. The tire of the present invention can be filled with an inert gas such as nitrogen, in addition to air.

[0032]

EXAMPLES The present invention will be specifically described. Table 1 and Table 2
Each rubber composition (coating rubber) having the described composition and a rubber-steel cord composite in which a steel cord was embedded were prepared, and the rubber properties and adhesive strength of these were measured by the following methods.

(1) Storage modulus E 'and loss factor tan
δ For the rubber composition vulcanized under vulcanization conditions [160 ° C. × 14 minutes], an initial load of 160 g and a frequency of 5 were measured using a spectrometer (dynamic viscoelasticity measuring tester) manufactured by Toyo Seiki Co., Ltd.
The measurement was performed at 2 Hz, 1% strain, and a measurement temperature of 25 ° C. Comparative Example 1
And 100 as an index. The larger the numerical value, the higher the elastic modulus of the vulcanized rubber is, the better the E is. The lower the heat generation is, the better the tan δ is.

(2) Retention of Elongation at Break Eb after Degradation For the rubber composition vulcanized under the same vulcanization conditions as above (160 ° C. × 14 minutes), the EB before deterioration and the deterioration condition [10
0 ° C. for 24 hours in the air]
B was measured according to JIS K6301-1995 (No. 3 test piece), and the retention was determined by the following equation. Retention rate = 100 × [Eb after deterioration] / [Eb before deterioration] The larger the numerical value, the higher the deterioration resistance and the better.

(3) Bloom property after standing for 3 days The rubber composition vulcanized under the same vulcanization conditions as above (160 ° C. × 14 minutes) was allowed to stand at 25 ° C. for 3 days, and then the rubber surface was visually observed. Then, the whiteness caused by the sulfur bloom was so small as to be negligible, and the one with many white portions was judged as "poor".

(4) Rubber-Cord Adhesive Strength Each of the following brass-plated steel cords (1 ×
5 structures, wire diameter 0.25 mm) were arranged in parallel at an interval of 12.5 mm, and the steel cord was coated from both sides with a rubber composition to prepare a sample. This was applied to vulcanization conditions [16
0 ° C. × 10 minutes], and the ASTM-D
The steel cord was pulled out according to −2229, and the ratio of the surface area of the pulled-out cord covered with rubber was visually determined. The larger the numerical value, the higher the adhesive strength and the better.

[0037]

[Table 1]

[0038]

[Table 2]

(Supplementary Note) Transpolybutadiene: (Synthesis method) According to JP-A-11-158207, [0054]. (That is, 750ml dried in the oven
Was sealed with a butyl liner and a crown.
After cooling the bottle, 223 grams of a dry butadiene / hexane blend (22.3% by weight) were charged.
Lanthanum tris [bis (2-ethylhexyl) phosphate] (0.27 mmol) was added to the monomer solution. This was followed by the addition of n-BuLi (1.08 mmol). The bottle was placed in a 65 ° C. water bath for 2 hours. Next, a white powder was obtained by evaporating the solvent. The isolation yield was 87%. ) Cobalt salt: Cobalt naphthenate Vulcanization accelerator: N, N'-dicyclohexyl-2-benzothiazolylsulfenamide (Noxeller DZ manufactured by Ouchi Shinko Chemical Co., Ltd.) Bismaleimide: N, N '-(4, 4'-diphenylmethane) bismaleimide steel cord [conventional product]: conventional brass plating (Cu
63% by weight, Zn 37% by weight, and plating thickness of at least 15 nm). In addition, Cu of the surface is 15-4.
5 atomic%. Steel cord [invention]: Brass plated with the composition of the present invention. (Cu 63% by weight, Co in the surface layer region
0.5-5.0 atomic%, Cu15-45 of the outermost layer
Atomic%, average plating thickness 0.13-0.3μ
m) Antioxidant: N- (1,3-dimethyl-butyl) -N ′
-Phenyl-p-phenylenediamine (NOCRAC 6C manufactured by Ouchi Shinko Chemical Co., Ltd.)

As shown in the above table, the coating rubber containing bismaleimide has relatively high hardness, low heat build-up, deterioration resistance, appearance, and adhesion. The coating rubber used in combination with trans-polybutadiene is as follows. The composite with a steel cord having improved high hardness, low heat build-up, and deterioration resistance and further improved plating further improved the adhesiveness.

[0041]

As described above, the tire using the rubber-steel cord composite of the present invention increases the hardness of the rubber, and has low heat build-up, adhesion to the steel cord,
Provide a rubber composition that does not impair the deterioration resistance, and provide a steel cord that can further improve the adhesiveness,
As a result, the durability of pneumatic tires for vehicles and the like can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the distribution of the Co content in the depth direction from the plating surface to the inside when Co is injected into the brass plating surface by ion plantation.

FIG. 2 is a view showing the distribution of the Co content in the depth direction from the plating surface to the inside when the Co is immersed and dried in a colloid containing a cobalt metal salt and thermally diffused at 200 ° C. into the inside of the plating.

FIG. 3 is a diagram showing a concentration distribution in the depth direction of each component in brass plating.

FIG. 4 is a schematic diagram of a spectrum when the state of Co on the surface of the brass plating is diffracted by X-ray photoelectron spectroscopy.

Claims (10)

[Claims] Claims: 1. A tire using a rubber-steel cord composite comprising a rubber composition obtained by blending bismaleimide with a rubber component comprising at least one of natural rubber and a diene-based synthetic rubber, and a steel cord, The bismaleimide is added in an amount of 0. 0 to 100 parts by weight of the rubber component.
A tire comprising 1 to 5 parts by weight. 2. The rubber composition further comprises trans polybutadiene in an amount of 0.1 to 100 parts by weight of the rubber component.
2. The composition according to claim 1, wherein the content is 1 to 15 parts by weight.
The tire described in the above. 3. The tire according to claim 1, wherein the rubber component contains 50% by weight or more of natural rubber. 4. The tire according to claim 1, wherein the bismaleimide is a bismaleimide represented by the following general formula [Formula 1]. Embedded image (Wherein, R represents an aromatic group having 6 to 18 carbon atoms or an alkyl aromatic group having 7 to 24 carbon atoms;
Any integer of 3 is independently represented. ) 5. The steel cord according to claim 1, wherein the steel cord has a peripheral surface in a surface region from the surface of the brass-plated steel filament having a copper concentration of 15 to 45 atomic% to a depth of 15 nm inward in the radial direction of the filament. A monofilament steel cord comprising at least one brass-plated filament containing at least one of cobalt atoms and nickel atoms, or a multifilament steel cord obtained by twisting these steel filaments. The tire according to any one of claims 1 to 4. 6. The method according to claim 1, wherein the total amount of cobalt atoms and nickel atoms contained in the surface layer region is not less than 0.1 atomic% and not more than the copper atom content of the surface layer region. The tire according to the item. 7. The tire according to claim 1, wherein a total amount of cobalt atoms and nickel atoms contained in the surface layer region is 0.5 to 5.0 atomic%. 8. The method according to claim 1, wherein in the surface region, the amount of cobalt atoms and nickel atoms not contained in the oxide is 50 atomic% or more of the total amount of cobalt atoms and nickel atoms contained in the surface region. Item 8. The tire according to any one of items 1 to 7. 9. An average thickness of the brass plating is 0.13 to 0.1.
The tire according to any one of claims 1 to 8, wherein the thickness is 30 µm. 10. The tire according to claim 1, wherein the filament has a diameter of 0.40 mm or less.