JP7115802B2 - Rubber composition and tire - Google Patents

Description

The present invention relates to rubber compositions and tires.

Pneumatic tires for large vehicles and heavy loads are required to improve wear resistance without impairing low heat build-up from the viewpoint of fuel efficiency and tire life. The fracture resistance of the steel is also an important characteristic.
In order to solve the problem of low heat build-up, for example, Patent Document 1 discloses that a thermally conductive rubber composition having a thermal conductivity of 0.3 Kcal/mh°C or higher is used in the surface side of the shoulder portion, and A method is disclosed in which narrow grooves with a width of 0.5 to 3.0 mm are formed in the shoulder at a pitch of 0.5 to 3.0 mm to improve the cooling performance of the shoulder and prevent heat from accumulating in the shoulder. .

Further, Patent Document 2 discloses a rubber composition in which thermal conductivity is improved while maintaining low heat build-up by using pulverized vapor-grown carbon fibers.

JP 2011-255835 A JP 2009-144131 A

However, even if acetylene black, which is a highly thermally conductive filler, is applied to general rubber compounding, heat dissipation is improved but heat buildup is worsened, so it has been difficult to achieve both.

An object of the present invention is to provide a rubber composition exhibiting low heat build-up and good heat dissipation. Another object of the present invention is to provide a tire in which the durability of the bead portion is particularly improved by using the rubber composition.

<1> A rubber composition comprising a rubber component, a filler, a thiuram compound and a hydrazide compound, wherein the filler comprises silica and acetylene black.
<2> With respect to 100 parts by mass of the rubber component, the content of the silica is 5 parts by mass or more and 50 parts by mass or less, and the content of the thiuram compound is 0.1 parts by mass or more and 2.0 parts by mass or less. The rubber composition according to <1>, wherein the content of the hydrazide compound is 0.1 parts by mass or more and 5.0 parts by mass or less.
<3> The rubber composition according to <1> or <2>, wherein the content of the acetylene black is 4 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber component.
<4> A tire using the rubber composition according to any one of <1> to <3> as an internal structural member.

According to the present invention, a rubber composition exhibiting low heat build-up and good heat dissipation can be obtained. Moreover, by using the rubber composition, it is possible to obtain a tire with improved durability of the bead portion in particular.

1 is a schematic cross-sectional view in the width direction of a tire according to an embodiment of the present invention; FIG. 1 is a schematic enlarged cross-sectional view of the vicinity of a belt end portion of a tire according to an embodiment of the present invention; FIG. 1 is a schematic enlarged cross-sectional view of the vicinity of a bead portion of a tire according to an embodiment of the present invention; FIG.

[Rubber composition]
The rubber composition of the present invention contains a rubber component, a filler, a thiuram compound and a hydrazide compound, the filler containing silica and acetylene black.

Thus, by adding silica, a thiuram compound and a hydrazide compound to the rubber component, it is possible to obtain a rubber composition that exhibits excellent low heat build-up when vulcanized. Furthermore, by adding acetylene black as a filler to the above rubber composition, the thermal conductivity of the rubber composition can be improved, and a rubber composition having excellent heat dissipation properties can be obtained.

<Rubber component>
The type of rubber used in the rubber composition of the present invention is not particularly limited. For example, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), butyl rubber (IIR), ethylene-propylene-diene copolymer (EPDM), acrylonitrile -butadiene copolymer (NBR), and rubber combining these. Among the above rubber components, it is preferable to include at least one type of diene rubber such as NR, BR, and SBR.

<Filler>
The rubber composition of the present invention contains silica and acetylene black as fillers. The rubber composition of the present invention may further contain carbon black produced by other methods.

(silica)
Silica is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among them, wet silica is preferred.
As the silica, it is preferable to use one having a BET specific surface area of 80 m ² /g or more. By using such silica, it is possible to obtain a rubber composition having excellent low heat build-up when made into a vulcanized rubber. The BET specific surface area of silica is more preferably 170 m ² /g or more, still more preferably 180 m ² /g or more, and particularly preferably 190 m ² /g or more. Also, the BET specific surface area is preferably 250 m ² /g or less, more preferably 240 m ² /g or less.

As such silica, commercially available products such as Tosoh Silica Co., Ltd., trade name "Nipsil AQ" and "Nipsil KQ", and Evonik Co., Ltd., trade name "Ultrasil VN3" can be used. One type of silica may be used alone, or two or more types may be used in combination.
A silane coupling agent may be added to the rubber composition of the present invention in order to improve the dispersibility of silica.

In the present invention, the content of silica in the rubber composition is preferably 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the rubber component. When the content of silica is within the above range, a vulcanized rubber with excellent low heat build-up can be obtained. More preferably, the content of silica is 10 parts by mass or more. The viscosity of the rubber composition tends to increase as the silica content increases. Considering the balance between low heat build-up and workability, the silica content is more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, and particularly preferably 20 parts by mass or less. .

(Carbon black)
The present invention requires the inclusion of acetylene black among carbon blacks. Acetylene black is not particularly limited, but preferably has an average particle size of 20 to 60 nm, a specific surface area of 40 to 150 m ² /g, and an iodine adsorption amount of 50 to 200 g/kg. For example, a commercially available product such as "DENKA BLACK" manufactured by Denka Co., Ltd. can be used.

The content of acetylene black is preferably 4 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber component. By setting it as the said range, the thermal conductivity when it is set as vulcanized rubber can be improved. The content of acetylene black is more preferably 7 parts by mass or more, still more preferably 10 parts by mass or more, relative to 100 parts by mass of the rubber component. Also, the content of acetylene black is more preferably 50 parts by mass or less, still more preferably 40 parts by mass or less, relative to 100 parts by mass of the rubber component.

Also, considering the balance between low heat build-up and thermal conductivity, the ratio (S/A) of the silica content (S) to the acetylene black content (A) is 0.08 or more and 12.5 or less. , more preferably 0.1 or more and 4 or less, and even more preferably 0.2 or more and 0.3 or less.

The rubber composition of the present invention may contain carbon black other than acetylene black. Such carbon blacks include furnace black, thermal black, channel black, graphite and the like. Also, various grades of carbon black such as SAF, HAF, ISAF, FEF and GPF can be used. Among them, those having an iodine absorption of 35 to 90 g/kg can be preferably used.
The viscosity of the rubber composition tends to increase as the total content of carbon black including acetylene black increases. Considering workability, the total content of carbon black is preferably 70 parts by mass or less, more preferably 40 parts by mass or less, based on 100 parts by mass of the rubber composition.

The total content of fillers in the rubber composition of the present invention is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, relative to 100 parts by mass of the rubber component. By setting the filler content to 100 parts by mass or less, it is possible to obtain a vulcanized rubber that achieves both low heat build-up and good heat dissipation. Furthermore, an increase in viscosity of the rubber composition can be suppressed, and a rubber composition having excellent processability can be obtained. The total content of fillers is more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more.

<Thiuram compound>
The rubber composition of the present invention contains a thiuram compound. The thiuram compound functions as a vulcanization accelerator.
Thiuram compounds that can be used in the rubber composition of the present invention include tetramethylthiuram monosulfide (TS), tetramethylthiuram disulfide (TT), tetraethylthiuram disulfide (TET), dipentamethylenethiuram hexasulfide (TRA), tetrabutylthiuram disulfide (TBT), tetrakis(2-ethylhexyl)thiuram disulfide (TOT), tetrabenzylthiuram disulfide (TBZTD) and the like. In the rubber composition of the present invention, one of these thiuram compounds may be used alone, or two or more of them may be used in combination.

The content of the thiuram compound is preferably 0.1 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the rubber component. By setting the content within the above range, an effect of improving low heat build-up is obtained, and scorch is less likely to occur. More preferably, the content of the thiuram compound is 0.2 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

<Hydrazide compound>
The rubber composition of the present invention contains a hydrazide compound.
Examples of hydrazide compounds used in the rubber composition of the present invention include isophthalic acid dihydrazide, adipic acid dihydrazide, isophthalic acid di(1,3-dimethylpropylidene)hydrazide, 2-naphthalene acid-3-hydroxy(1,3- dimethylpropylidene) hydrazide, 2-naphthalenoic acid-3-hydroxy(1,3-dimethylbutylidene) hydrazide, salicylic acid (1,3-dimethylpropylidene) hydrazide, isonicotinic acid hydrazide, isonicotinic acid (1,3- dimethylpropylidene) hydrazide, salicylic acid hydrazide, 2-naphthalene acid-3-hydroxyhydrazide, salicylic acid (1-methylethylidene) hydrazide, 2-naphthalene acid-3-hydroxy(1-methylethylidene) hydrazide, salicylic acid (1-methylpropylidene) (1,3-dimethylpropylidene)hydrazide, 2-naphthalenoic acid-3-hydroxy(1-methylpropylidene)hydrazide, salicylic acid (1,3-dimethylpropylidene)hydrazide, 2-naphthalenoic acid-3-hydroxy(1,3-dimethylpropylidene)hydrazide hydrazide, salicylic acid (1-phenylethylidene) hydrazide, 2-naphthalene acid-3-hydroxy(1-phenylethylidene) hydrazide isonicotinic acid hydrazide, isonicotinic acid (1-methylethylidene) hydrazide, isonicotinic acid (1-methylpropionate) (1,3-dimethylpropylidene)hydrazide, isonicotinic acid (1,3-dimethylpropylidene)hydrazide, and isonicotinic acid (1-phenylethylidene)hydrazide. In addition, in the rubber composition of the present invention, these hydrazide compounds may be used singly or in combination of two or more.

The content of the hydrazide compound is preferably 0.1 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the rubber component. By setting it as the said range, the low heat build-up improvement effect is acquired. The content of the hydrazide compound is more preferably 0.5 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

<Various ingredients>
In addition to the components described above, the rubber composition of the present invention contains various components commonly used in the rubber industry, such as vulcanizing agents, vulcanization accelerators, zinc white, stearic acid, antioxidants, and waxes. , can be appropriately selected and blended within a range that does not impair the object of the present invention. Commercially available products can be suitably used as these various components.

Examples of the vulcanizing agent include sulfur and the like, and the compounding amount thereof is preferably 0.1 to 10.0 parts by mass, more preferably 1.0 to 5.0 parts by mass as a sulfur content, per 100 parts by mass of the rubber component. Department.

Examples of vulcanization accelerators include, but are not limited to, M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), CZ (N-cyclohexyl-2-benzothiazylsulfenamide). and guanidine-based vulcanization accelerators such as DPG (diphenylguanidine). The blending amount is preferably 0.1 to 5.0 parts by mass, more preferably 0.2 to 3.0 parts by mass, per 100 parts by mass of the rubber component.

As the softening agent, process oils can be used, and examples thereof include process oils such as paraffinic, naphthenic, and aromatic oils. For example, aromatic type is used for applications where tensile strength and wear resistance are important, and naphthenic or paraffin type is used for applications where hysteresis loss and low temperature properties are important. The amount is preferably 0 to 100 parts by mass with respect to 100 parts by mass of the rubber component, and if it is 100 parts by mass or less, it suppresses the deterioration of the tensile strength and low heat build-up (fuel efficiency) of the vulcanized rubber. can do.

Examples of anti-aging agents include 3C (N-isopropyl-N'-phenyl-p-phenylenediamine, 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine), AW ( 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline), a high-temperature condensate of diphenylamine and acetone, etc. The amount to be blended is 0.5 parts per 100 parts by mass of the rubber component. It is preferably 1 to 5.0 parts by mass, more preferably 0.3 to 3.0 parts by mass.

The rubber composition of the present invention is obtained by kneading using a kneader such as an open kneader such as a roll or a closed kneader such as a Banbury mixer, and vulcanized after molding to produce various rubbers. Applicable to products. The use of the rubber composition of the present invention is not particularly limited, but it is used for soft stiffeners of heavy-duty pneumatic tires, belt end inserts, sidewall fillers, etc., due to its excellent low heat build-up and crack growth resistance. It can also be used as a base rubber.

〔tire〕
A tire of the present invention will be described with reference to the drawings. The tire of the present invention is preferably a pneumatic tire for heavy loads.
FIG. 1 is a schematic cross-sectional view in the width direction of a tire according to one embodiment of the present invention. The illustrated tire 20 has a pair of bead portions 1, a pair of sidewall portions 2, and a tread portion 3, and a carcass 5 extending like a toroid between bead cores 4 embedded in the bead portions 1 respectively. , a belt 6 composed of a plurality of belt layers arranged outside in the tire radial direction at the crown portion of the carcass 5, and a bead filler 7 arranged outside the bead core 4 in the tire radial direction.

The rubber composition of the present invention is preferably used for internal structural members, that is, rubber used inside the tire that does not appear on the tire surface layer. FIG. 2 is a schematic enlarged cross-sectional view of the vicinity of the belt end of the tire according to one embodiment. The rubber composition of the present invention includes, for example, belt end rubbers 8a to 8e that cover the ends of the belt layers 6a to 6e, end cushion rubbers 9 disposed in the gaps between the upper and lower belt layers at the ends of the belt layers, belt It can be suitably used for coating rubber of steel cords constituting carcass.
Moreover, FIG. 3 is a schematic enlarged cross-sectional view of the vicinity of the bead portion of the tire according to one embodiment of the present invention. The rubber composition of the present invention is used, for example, as a soft stiffener 10 arranged between the main body of the carcass 5a and the folded portion 5b of the carcass 5, or as a sidewall filler 11 arranged outside the carcass folded portion 5b in the tire width direction. It can be used preferably. The rubber composition of the present invention can also be used as a base rubber for the tread portion.

The rubber composition of the present invention is more effective in inner layer members of tires where the gauge thickness of the tread portion is 70 mm or more and vulcanization is excessively performed. For example, in large tires for industrial use, the gauge thickness of the tread is as large as 70 mm or more. In order to allow vulcanization to proceed to the inside of such a tire, vulcanization is performed under conditions such that vulcanization is excessively performed as compared with general passenger car tires and the like, and the degree of vulcanization is increased. Under such conditions, the rubber composition for an inner layer member of the present invention contains a rubber component, silica, a hydrazide compound, and a thiuram compound, so that a rubber for an inner layer member having low heat build-up and excellent thermal conductivity can be obtained. can get. The gauge thickness of the tread portion is the thickness from the outer surface of the outermost reinforcing layer in the tire radial direction to the outer surface of the tire, and means the value at the thinnest position.

In addition, in the tire 20 of the present invention, members other than the members made of the rubber composition of the present invention are not particularly limited, and known members can be used. Moreover, as the gas to be filled in the tire 20 of the present invention, in addition to normal air or air with an adjusted oxygen partial pressure, an inert gas such as nitrogen, argon, or helium can be used.

[Examples 1 to 6, Comparative Examples 1 to 3]
<Preparation of rubber composition>
Each component was kneaded according to the compounding composition shown in Table 1 below to prepare a rubber composition.
The details of the components in the table are as follows.

1. Rubber component (1) natural rubber (NR)
RSS#3
(2) Styrene-butadiene copolymer rubber (SBR)
Manufactured by JSR Corporation, type "1500"
(3) Polybutadiene rubber (BR)
Manufactured by JSR Corporation, variety "BR01"
2. Filler (1) Other carbon black (CB)
N330, manufactured by Asahi Carbon Co., Ltd., trade name "#70"
(2) Acetylene black (AB)
Manufactured by Denka Co., Ltd., trade name “DENKA BLACK Li-100”
(3) Silica manufactured by Tosoh Silica Co., Ltd., trade name “Nipsil AQ” (BET specific surface area = 205 m ² /g)
3. Silane coupling agent Evonik Industries, trade name “Si69”
4. hydrazide compound 3-hydroxy, N'-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide5. Stearic acid Shin Nippon Chemical Co., Ltd., trade name “Stearic acid 50S”
6. Zinc white Manufactured by Hakusui Tech Co., Ltd., product name "No. 3 zinc white"
7. Antiaging agent Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name "Nocrac 6C"
8. Oil Made by Idemitsu Kosan Co., Ltd., petroleum-based hydrocarbon process oil, trade name “DAIHANA PROCESS OIL NS-28”
9. Wax Made by Nippon Seiro Co., Ltd., trade name “Ozoace 701”
10. Sulfur Sulfur: manufactured by Tsurumi Chemical Co., Ltd., trade name “powder sulfur”
11. Vulcanization accelerator (1) Vulcanization accelerator 1
Manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name "Noccellar CZ-G"
(2) Vulcanization accelerator 2 (thiuram compound)
Tetrakis (2-ethylhexyl) thiuram disulfide (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name “Noccellar TOT-N”)

<Evaluation>
The obtained rubber composition is vulcanized under vulcanizing conditions of 160° C. for 20 minutes to prepare a predetermined test piece, and then evaluated for low heat build-up and thermal conductivity according to the following procedure.
1. Using a low heat build-up viscoelasticity measuring device (manufactured by Rheometrics), tan δ is measured at a temperature of 60°C, dynamic strain of 5%, and frequency of 15 Hz. The tan δ of Comparative Example 1 was set to 100 and indicated as an index. A smaller index value indicates a lower heat build-up and a smaller hysteresis loss.

2. Thermal conductivity Using a rapid thermal conductivity meter (model: QTM-500) manufactured by Kyoto Electronics Industry Co., Ltd., temperature: 20 ° C. to 22 ° C., time: 1 minute, current value: 2 A, each heating The thermal conductivity (λ) (W/mK) of sulfur rubber is measured. The thermal conductivity of Comparative Example 1 was set to 100 and indicated as an index. A larger index value indicates higher thermal conductivity.

3. Bead Temperature Tires (tire size 46/90R57 for construction vehicles, hereinafter the same) are produced using the rubber compositions of each example and comparative example. For each tire, the predicted value when measuring the temperature of the bead portion at 100% of the normal load defined by TRA under the normal internal pressure defined by TRA, the speed of 8 km / h, and the drum diameter of 5 m. The temperature of the bead portion is expressed as 100 and displayed as an index. A smaller index value indicates a smaller temperature rise.

All of the vulcanized rubbers using the rubber compositions of Examples show low heat build-up and good thermal conductivity (heat dissipation). As a result, the bead portion temperatures (predicted values) are all lowered.
On the other hand, in the vulcanized rubber using the rubber composition of the comparative example, the use of acetylene black deteriorates heat build-up, resulting in a significant rise in bead temperature.

By using the rubber composition of the present invention, it is possible to obtain a vulcanized rubber that exhibits low heat build-up due to the inclusion of silica, a thiuram compound and a hydrazide compound, and exhibits good heat dissipation due to the inclusion of acetylene black. can. By using the rubber composition of the present invention as an internal structural member of a tire, it is possible to suppress the temperature rise of the bead portion and improve the durability of the bead portion.

1 bead portion 2 sidewall portion 3 tread portion 4 bead core 5 carcass 6 belt 7 bead filler 8a to 8e belt end rubber 9 end cushion rubber 10 soft stiffener 11 sidewall filler 20 tire

Claims (4)

containing a rubber component, a filler, a thiuram compound and a hydrazide compound,
A rubber composition in which the filler comprises silica and acetylene black. For 100 parts by mass of the rubber component,
The silica content is 5 parts by mass or more and 50 parts by mass or less,
The content of the thiuram compound is 0.1 parts by mass or more and 2.0 parts by mass or less,
2. The rubber composition according to claim 1, wherein the content of said hydrazide compound is 0.1 parts by mass or more and 5.0 parts by mass or less. The rubber composition according to claim 1 or 2, wherein the content of said acetylene black is 4 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of said rubber component. A tire using the rubber composition according to any one of claims 1 to 3 as an internal structural member.

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