Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-06-28
2001-07-17
Yoon, Tae (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S495000, C152S151000, C152S209120
Reexamination Certificate
active
06262158
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rubber composition for a tyre read having low fuel consumption.
Recently low fuel consumption of vehicles has been socially demanded, and a tyre for low fuel consumption has been widely developed which decreases rolling resistance. In order to decrease the rolling resistance, it is conventional to lower the hysteresis of the rubber composition for tyre tread.
As one of the methods for solving the above issues, is effective to decrease the amount of carbon black in a rubber composition for a tyre tread or to employ silica as a reinforcing agent.
However, it is undesirable to decrease the amount of carbon black particularly in tread for a truck or bus tyre, since the abrasion resistance becomes remarkably low with a decreasing of the amount of carbon black. Another problem is caused by employing silica which causes an inferior abrasion property under a severe running condition test with heavy load.
Therefore, Japanese Examined Patent Publication No. 62093/1995, for example, discloses a rubber composition excellent in properties such as tread cut resistance without decreasing the abrasion property, which is obtained by the particular mixing ratio of sulfur and a vulcanization accelerator. But the rubber composition obtained by the technology still has a problem of high rolling resistance and low abrasion property.
SUMMARY OF THE INVENTION
To solve the above problems, it has been sought out to obtain a rubber composition for tyre tread, of which rolling resistance is decreased without decreasing abrasion resistance by the careful investigations of the mixing ratio between sulfur and a vulcanization accelerator. Therefore, the object of the present invention is to provide a rubber composition for tyre tread, of which rolling resistance is decreased without decreasing abrasion resistance.
Namely, the present invention relates to a rubber composition for tyre tread which is obtained by mixing 100 parts by weight of a rubber component, 0.5 to 1 part by weight of N,N-bis(2-methyl-2-nitropropyl)-1,6-hexane-diamine, 1 to 1.5 parts by weight of sulfur and 1 to 3 parts by weight of a vulcanization accelerator based on 100 parts by weight of the rubber component, and wherein an amount X of sulfur and an amount Y of a vulcanization accelerator satisfy the equation: 2X−1≦Y≦2X.
In this case it is preferable that the composition further comprises 25 to 60 parts by weight of carbon black.
DETAILED DESCRIPTION
There is no particular limitation for the rubber component employed in the present invention, as long as it has been conventionally employed in tyre tread. Examples thereof are a natural rubber, a butadiene rubber, an isoprene rubber, and a styrene-butadiene rubber having a little inferior effect. These can be employed solely or in a combination use of two or more thereof.
In the present invention 0.5 to 1 part by weight of N,N′-bis(2-methyl-2-nitropropyl)-1,6-hexane-diamine based on 100 parts by weight of the rubber component is mixed in order to control increase of loss tangent and to decrease heating. From the viewpoint of lowering cost, 0.5 to 0.8 part by weight thereof is preferably mixed.
In the present invention 1 to 1.5 parts by weight of sulfur based on 100 parts by weight of the rubber component is mixed in order to provide necessary cross-linking points and to prevent blooming occurred on the surface of the rubber in the presence of unnecessary sulfur. If there are many polysulfide bonds in a rubber composition after vulcanization, they change to monosulfide bonds due to heat of running, and changes of physical properties such as hardness of the obtained tread are promoted. Therefore, 1 to 1.4 parts by weight thereof is preferably mixed in order to improve durability of a tyre.
There is no particular limitation for a vulcanization accelerator. Examples thereof are, for instance, sulfenamides, thiazoles, thiurams, guanidines, dithiocarbamate salts and the like.
In the present invention 1 to 3 parts by weight of the vulcanization accelerator based on 100 parts by weight of the rubber component is mixed from the viewpoint of controlling physical property change and achieving low fuel consumption. From the viewpoint of balance of the above-mentioned properties, 1.5 to 2.5 parts by weight thereof is preferably mixed.
In this case if the amount of the vulcanization accelerator is too small, the physical property change becomes large. On the other hand, if the amount is too large, abrasion property and tread cut resistance become small. From the viewpoint of these reasons, sulfur and a vulcanization accelerator are mixed under the condition that an amount of sulfur X parts by weight and an amount of a vulcanization accelerator Y parts by weight satisfy the following equation: 2X−1≦Y≦2X.
In the rubber composition of the present invention, carbon black is preferably mixed from the viewpoint of abrasion resistance, reinforcement and low cost.
There is no particular limitation for the kind of carbon black, as long as it has been conventionally employed in tyre field. Preferably a specific surface area for nitrogen adsorption thereof is 30 to 200 and an adsorption amount of compressed dibutyl phthalate (DBP) is 30 to 150 ml/100 g. If the specific surface area for nitrogen adsorption is below 30 m
2
/g or the adsorption amount of compressed DBP is below 30 ml/100 ml, it is inferior in dispersion property and reinforcement of carbon black to a rubber composition. On the other hand, if the specific surface area for nitrogen adsorption is above 200 m
2
/g or the adsorption amount of compressed DBP is above 150 ml/100 g, it is inferior in dispersion property of carbon black to a rubber composition and a heat amount thereof becomes large.
Examples of the kind of carbon black are, for instance, HAF, ISAF and SAF, but there is no particular limitation for it.
An amount of carbon black is preferably 25 to 60 parts by weight from the viewpoint of balance between reinforcement (abrasion resistance) and low fuel consumption. And it is more preferably 30 to 50 parts by weight from the viewpoint of low fuel consumption.
To the rubber composition of the present invention, there can be suitably added, except for the above-mentioned components, for instance, filler, an additive such as process oil, an anti-oxidant, stearic acid or zinc oxide in the range of preventing from losing the object of the present invention. There is no particular limitation for filler. Examples thereof are, for instance, silica, clay, calcium carbonate, aluminum hydroxide and the like. There is no particular limitation for process oil. Examples thereof are, for instance, aromatic oil, naphthene oil, paraffin oil, castor oil and the like. There is no particular limitation for an anti-oxidant. Examples thereof are, for instance, reaction products of aldehyde, ketone and amine, amines, derivatives of amines, imidazoles, phenoles and the like.
The rubber composition for tyre tread of the present invention obtained therefrom can be applied to tyre tread by the conventional method.
REFERENCES:
patent: 5002829 (1991-03-01), Shibahara
patent: 5387631 (1995-02-01), Kawakami et al.
patent: 5830930 (1998-11-01), Mahmud et al.
patent: 0345594 A2 (1989-12-01), None
patent: 12-47437 (1989-10-01), None
patent: 13-11141 (1989-12-01), None
patent: 04214748 (1992-08-01), None
patent: 8-73657 (1996-03-01), None
Matsuo Toshiro
Mizuno Yoichi
Birch & Stewart Kolasch & Birch, LLP
Sumitomo Rubber Industries Ltd.
Yoon Tae
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