Rubber compositions and pneumatic tires using the same

Rubber compositions and pneumatic tires in which the rubber compositions are used. In the rubber compositions, per 100 parts by weight of natural rubber and a conjugated diene-base synthetic rubber such as a butadiene-styrene copolymer rubber, is compounded 30 to 120 parts by weight of a carbon black having both a characteristic (concentration of >C.dbd.O functional groups)/N.sub.2 SA.gtoreq.4.0.times.10.sup.-4 and a characteristic (concentration of >C.dbd.O functional groups).gtoreq.(concentration of --OH functional groups).sup.2 -0.1.times.(concentration of --OH functional groups)+0.03, or is compounded 30 to 120 parts by weight of a carbon black having the characteristic (concentration of >C.dbd.O functional groups)/N.sub.2 SA.gtoreq.4.0.times.10.sup.-4 and 0.05 to 5.0 parts by weight of at least one of a silane coupling agent, a hydrazide compound and a thiadiazole compound. The rubber compositions of the present invention and pneumatic tires using the rubber compositions excel in low rolling resistance and wet skid resistance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to rubber compositions, and more specifically 
to rubber compositions having excellent low hysteresis loss and a high 
level of wet skid resistance. Further, the present invention relates to 
pneumatic tires in which these rubber compositions are used in the tire 
tread, and more specifically, to pneumatic tires whose low rolling 
resistance performance (low fuel consumption) is greatly improved and 
whose wet skid resistance performance is also excellent. 
2. Description of the Prior Art 
In recent years, as stability and low fuel consumption have been desired of 
automobiles, the strong need has developed for rubber materials for tires 
to simultaneously have good wet skid resistance and low hysteresis loss 
(and thus for tires to have low rolling resistance and low fuel 
consumption). It is known that, generally, these characteristics are 
related inversely. More specifically, if the low hysteresis loss (low 
rolling resistance performance) is improved, the wet skid resistance 
deteriorates, whereas if the wet skid resistance is improved, the low 
hysteresis loss deteriorates. 
In the conventional art, in order to solve the aforementioned problem, 
rubber compositions for tires have been improved from both the standpoint 
of the polymer and the standpoint of the carbon black. 
Many techniques are known as methods of improving the rubber composition by 
the carbon black, and the following are examples of such methods. It is 
known that if the particle diameter of the carbon black is increased, the 
rubber composition has low hysteresis loss but the wet skid resistance 
thereof deteriorates. Here, discussion will be limited to chemical 
characteristics of the surface of the carbon blacks and the effects of the 
rubber compositions for a tire (and therefore pneumatic tires using these 
rubber compositions). JP-A No. 64-20246 discloses a rubber composition 
having improved heat build-up and an improved reinforcing property at high 
temperatures by mainly using a carbon black whose pit value and total acid 
group concentration are specified. JP-A No. 2-105836 discloses a rubber 
composition having excellent wet skid resistance, low rolling resistance, 
and reinforcing property at high temperatures by mainly using a carbon 
black for which the number of oxygen-containing functional groups are 
specified. JP-A No. 2-105837 discloses a rubber composition which has 
excellent low rolling resistance and reinforcing property at high 
temperatures by mainly using a carbon black whose concentration of 
oxygen-containing functional groups is specified. JP-A No. 4-130144 
discloses a rubber composition which has excellent low rolling resistance 
and wear resistance by mainly using a carbon black in which the 
relationship between the amount of functional groups which participate in 
an acetylating reaction with acetic anhydride and the amount of functional 
groups which produce oxime when reacted with hydroxylamine is specified. 
JP-A No. 4-189845 discloses a rubber composition which has excellent low 
rolling resistance and reinforcing property at high temperatures by mainly 
using a carbon black in which the concentration of --OH functional groups 
which participate in an acetylating reaction with acetic anhydride is 
specified. JP-A No. 6-25472 discloses a rubber composition having 
excellent low rolling resistance and traction by mainly using an oxidized 
carbon black. JP-A No. 6-107863 discloses a rubber composition which has 
an excellent reinforcing property by mainly using a carbon black in which 
the quinone group concentration determined by an oximization method and 
the total acidity determined by an NaOH neutralization method are 
specified. 
Many of these prior art aimed to achieve a different object than that of 
the present invention by a rubber composition containing a carbon black 
having the above-described characteristics, and in some cases a modified 
rubber, and in some cases various types of compounding agents. Among these 
prior art, some attempted to achieve the same object as the present 
invention, but sufficient effects were not achieved. Namely, there has not 
been known a rubber composition and pneumatic tire in which the low 
hysteresis loss (low rolling resistance performance) is markedly improved 
and at the same time the wet skid resistance is high level. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a rubber composition which 
excels in low hysteresis loss and wet skid resistance. Another object of 
the present invention is to provide a pneumatic tire in which the low 
rolling resistance performance and wet skid resistance performance are 
both improved. 
In order to solve the above-described drawbacks, the present inventors 
diligently studied the chemical structure, chemical characteristics and 
physical characteristics of the surface of carbon black as well as the 
molecular structures of various types of rubber additives and rubber base 
materials. As a result, the present inventors found that the 
aforementioned desirable properties could be achieved simultaneously by 
the following means by using a specific carbon black or by using a 
specific carbon black together with specific additives, and thus, the 
inventors arrived at the present invention. 
A rubber composition of the present invention comprises: a rubber component 
consisting of at least one rubber selected from the group consisting of 
conjugated diene-base synthetic rubbers and natural rubber; and a carbon 
black in an amount of 30 to 120 parts by weight per 100 parts by weight of 
the rubber component, wherein the carbon black has both of the 
characteristics represented by following equation (I) and equation (II): 
Equation (I) 
EQU (concentration of &gt;C.dbd.O functional groups)/N.sub.2 
SA.gtoreq.4.0.times.10.sub.-4 
Equation (II) 
EQU (concentration of &gt;C.dbd.O functional groups).gtoreq.(concentration of --OH 
functional groups).sup.2 -0.1.times.(concentration of --OH functional 
groups)+0.03 
wherein (concentration of &gt;C.dbd.O functional groups) expresses the 
concentration (meq/g) of functional groups which react with hydroxylamine 
and produce oxime; N.sup.2 SA expresses the nitrogen absorption specific 
surface area (m.sub.2 /g); and (concentration of --OH functional groups) 
expresses the concentration (meq/g) of functional groups which participate 
in an acetylating reaction with acetic anhydride. 
A pneumatic tire of the present invention has a tread portion, sidewall 
portions and bead portions, and used in the tread portion is a rubber 
composition comprising: a rubber component consisting of at least one 
rubber selected from the group consisting of conjugated diene-base 
synthetic rubbers and natural rubber; and a carbon black having both of 
the characteristics represented by above equation (I) and equation (II), 
in an amount of 30 to 120 parts by weight per 100 parts by weight of the 
rubber component. 
A rubber composition of the present invention comprises: a rubber component 
consisting of at least one rubber selected from the group consisting of 
conjugated diene-base synthetic rubbers and natural rubber; 30 to 120 
parts by weight, per 100 parts by weight of the rubber component, of a 
carbon black having the characteristic represented by following equation 
(I); and 0.05 to 5.0 parts by weight, per 100 parts by weight of the 
rubber component, of at least one of: a silane coupling agent selected 
from the group consisting of compounds represented by following general 
formulae (III) and (IV), a hydrazide compound selected from the group 
consisting of compounds represented by following general formulae (V), 
(VI) and (VII), and a thiadiazole compound selected from the group 
consisting of compounds represented by following general formula (VIII). 
Equation (I) 
EQU (concentration of &gt;C.dbd.O functional groups)/N.sub.2 
SA.gtoreq.4.0.times.10.sup.-4 
wherein (concentration of &gt;C.dbd.O functional groups) expresses the 
concentration (meq/g) of functional groups which react with hydroxylamine 
and produce oxime; and N.sub.2 SA expresses the nitrogen absorption 
specific surface area (m.sup.2 /g). 
General Formula (III) 
EQU Y.sup.1.sub.a Y.sup.2.sub.b --Si--C.sub.n H.sub.2n S.sub.m C.sub.n H.sub.2n 
Si--Y.sup.1.sub.a Y.sub.2.sub.b 
or 
EQU Y.sup.1.sub.a Y.sup.2.sub.b --SiC.sub.n H.sub.2n --X.sup.1 
wherein X.sup.1 represents a nitroso group, a mercapto group, an amino 
group, an epoxy group, a vinyl group, a chlorine atom, or an imide group; 
Y.sup.1 represents an alkoxy group having from 1 to 4 carbon atoms or a 
chlorine atom; Y.sup.2 represents an alkyl group having from 1 to 4 carbon 
atoms; a is an integer from 1 to 3, b is an integer from 0 to 2, and 
a+b=3; and n and m are respectively integers from 1 to 6. 
General Formula (IV) 
EQU Y.sup.1.sub.a Y.sup.2.sub.b --SiC.sub.n H.sub.2n S.sub.m --X.sup.2 
wherein X.sup.2 is represented by the following formula: 
##STR1## 
wherein Y.sup.1 represents an alkoxy group having from 1 to 4 carbon atoms 
or a chlorine atom; Y.sup.2 represents an alkyl group having from 1 to 4 
carbon atoms; a is an integer from to 3, b is an integer from 0 to 2, and 
a+b=3; and n and m are respectively integers from 1 to 6. 
##STR2## 
wherein A represents an aromatic ring, a saturated or unsaturated 
hydantoin ring, or a linear saturated or unsaturated alkyl group having 
from 1 to 18 carbon atoms; n is 0 or 1; B represents an aromatic ring; Z 
represents a hydroxyl group or an amino group; and L represents a pyridyl 
group or a hydrazino group. 
##STR3## 
wherein R.sup.1 represents a mercapto group; and R.sup.2 represents a 
mercapto group, an amino group or a trifluoromethyl group. 
A pneumatic tire of the present invention has a tread portion, sidewall 
portions and bead portions, and used in the tread portion is a rubber 
composition comprising: a rubber component consisting of at least one 
rubber selected from the group consisting of conjugated diene-base 
synthetic rubbers and natural rubber; 30 to 120 parts by weight, per 100 
parts by weight of the rubber component, of a carbon black having the 
characteristic represented by above equation (I); and 0.05 to 0.5 parts by 
weight, per 100 parts by weight of the rubber component, of at least one 
of: a silane coupling agent selected from the group consisting of 
compounds represented by above general formulae (III) and (IV), a 
hydrazide compound selected from the group consisting of compounds 
represented by above general formulae (V), (VI) and (VII), and a 
thiadiazole compound selected from the group consisting of compounds 
represented by above general formula (VIII). 
In one embodiment, the carbon black compounded in the rubber composition of 
the present invention must have the following two characteristics: 
(concentration (meq/g) of &gt;C.dbd.O functional groups)/N.sub.2 SA (m.sup.2 
/g).gtoreq.4.0.times.10.sup.-4 (which is referred to hereinafter as 
characteristic X), and (concentration of &gt;C.dbd.O functional 
groups).gtoreq.(concentration of --OH functional groups).sup.2 
-0.1.times.(concentration of --OH functional groups)+0.03 (hereinafter 
referred to as characteristic Y). Various functional groups exist on the 
carbon black surface, and the carbon black is specified by using various 
characteristics based on these functional groups as in the above 
description of the prior art. In the present invention, in one embodiment, 
a carbon black is used which is specified by characteristic X and 
characteristic Y which are related to the concentration of &gt;C.dbd.O 
functional groups and/or the concentration of --OH functional groups. The 
carbon black of the present invention is a carbon black of new 
specifications that has not been known conventionally. Characteristic X 
expresses the necessary concentration of &gt;C.dbd.O functional groups, and 
characteristic Y expresses the relative difference in concentrations of 
the &gt;C.dbd.O functional groups and the --OH functional groups. By using a 
carbon black which exhibits both characteristic X and characteristic Y, 
the rubber composition exhibits a low hysteresis loss effect and a wet 
skid resistance effect. If the carbon black lacks either of these 
characteristics, it is difficult for both of these effects to be exhibited 
simultaneously. A carbon black in which the value is less than 
4.0.times.10.sup.-4 in characteristic X and the inequality is not 
satisfied in characteristic Y will not exhibit these effects to a 
sufficient degree. 
In another embodiment, in a case in which the carbon black compounded in 
the rubber composition off the present invention is used together with at 
least one specific additive, it suffices for the carbon black to satisfy 
aforementioned characteristic X. Various functional groups exist on the 
carbon black surface, and the carbon black is specified by using various 
characteristics based on these functional groups as in the above 
description of the prior art. In this embodiment of the present invention, 
a carbon black is used which is specified by characteristic X which is 
related to the concentration of &gt;C.dbd.O functional groups. Characteristic 
X expresses the necessary concentration of &gt;C.dbd.O functional groups. By 
using a carbon black which exhibits characteristic X and specific 
additives as will be described hereinafter, the rubber composition 
exhibits improved low hysteresis loss property and wet skid resistance. If 
either the carbon black or the specific additives are missing, it is 
difficult for both of these effects to be exhibited simultaneously. A 
carbon black having a value of less than 4.0.times.10.sup.-4 (meq/m.sup.2) 
in characteristic X will not sufficiently exhibit these effects. 
The carbon black used in the present invention is not particularly limited 
provided that it satisfies both characteristic X and characteristic Y or 
that it satisfies characteristic X if at least one specific additive is 
used, and the carbon black may be a commercially available product, may be 
produced by treating a commercially available product, or may be a novel 
carbon black. Examples of the carbon black used in the present invention 
include (1) gas furnace black, (2) channel-type carbon black, (3) a carbon 
black obtained by oxidizing furnace black (including oil furnace black and 
gas furnace black) or channel-type carbon black by an oxidizing agent such 
as HNO.sub.3, H.sub.2 O.sub.2, O.sub.3, or dichromate, (4) a carbon black 
obtained by heating gas furnace black or channel-type carbon black at 
temperatures of 100.degree. to 900.degree. C., and (5) a carbon black 
obtained by subjecting the oxidized carbon black of above (3) to heat 
processing at temperatures of 100.degree. to 900.degree. C. Among these, 
the carbon blacks (3) and (5) are preferable from the standpoint of the 
effects which are achieved. 
The compounded amount of the carbon black used in the rubber composition of 
the present invention is 80 to 120 parts by weight, and preferably 35 to 
100 parts by weight, per 100 parts by weight of the rubber component. If 
the compounded amount is less than 30 parts by weight, a rubber 
composition having a sufficient modulus of elasticity cannot be obtained, 
and the reinforcing property cannot be ensured. If the compounded amount 
exceeds 120 parts by weight, sufficient carbon dispersion cannot be 
obtained, and the reinforcing effect deteriorates. 
The rubber component used in the rubber composition of the present 
invention is at least one rubber selected from the group of conjugated 
diene-base synthetic rubbers and natural rubber. 
The conjugated diene-base synthetic rubber may be (1) a rubber obtained by 
polymerizing a conjugated diene monomer, (2) a rubber obtained by 
copolymerizing a conjugated diene monomer and a vinyl aromatic hydrocarbon 
monomer, or (3) a rubber obtained by modifying the conjugated diene rubber 
end of above (1) or the conjugated diene/vinyl aromatic hydrocarbon 
copolymer rubber end of above (2) by a functional group selected from the 
group of tin-containing groups and nitrogen-containing groups. Among 
these, above rubber (3) is preferable from the standpoint of improving low 
hysteresis loss and wet skid resistance. These synthetic rubbers may be 
used singly, or two or more may be used together. Further, a blend of 
natural rubber and one or more of these synthetic rubbers is also 
preferably used. In this case, the synthetic rubber/natural rubber weight 
ratio is preferably around 90/10 to 30/70. 
Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 
2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and 1,3-hexadiene, as well as 
mixtures thereof. Among these, 1,3-butadiene and isoprene are preferable. 
Examples off preferable conjugated diene rubbers include high 
cis-1,4-polybutadiene, low cis-1,4-polybutadiene and high 
cis-1,4-polyisoprene. 
Examples of the vinyl aromatic hydrocarbon monomer include styrene, 
vinyltoluene, .alpha.-methylstyrene, p-methylstyrene and t-butylstyrenes. 
Among these, styrene is preferable. Preferable conjugated diene/vinyl 
aromatic hydrocarbon copolymer rubbers include styrene-butadiene rubber. 
With regard to the microstructure of the conjugated diene/vinyl aromatic 
hydrocarbon copolymer rubber, e.g., styrene-butadiene rubber, the 
compositional distribution may be random-type, block-type or an 
intermediate-type between random-type and block-type. A random-type 
compositional distribution is preferable. The amount of vinyl linkage of 
the conjugated diene portion is not particularly limited. When 
polymerization is carried out by using a lithium compound initiator 
system, the amount of vinyl linkage is usually around 20 to 80%. The 
styrene/butadiene weight ratio is not particularly limited and is usually 
within the range of 10/90 to 60/40. As a random-type styrene-butadiene 
rubber, a rubber obtained by emulsion polymerization or solution 
polymerization is preferably used. 
The conjugated diene rubber and the conjugated diene/vinyl aromatic 
hydrocarbon copolymer rubber can respectively be easily obtained by 
polymerizing or copolymerizing a predetermined amount of the 
above-described monomer while using, for example, an organic lithium 
compound as the initiator. The organic lithium compound may be any of 
generally known compounds and is not particularly limited. Examples 
include alkyllithiums such as methyllithium, ethyllithium, propyllithium, 
n-butyllithium, sec-butyllithium, tert-butyllithium, hexyllithium and 
octyllithium: aryllithiums such as phenyllithium, tolyllithium and lithium 
naphthalide: alkenyllithiums such as vinyllithium and propenyllithium; 
alkylenedilithiums such as tetramethylenedilithium, 
pentamethylenedilithium, hexamethylenedilithium, heptamethylenedilithium 
and decamethylenedilithium: and organic lithium compounds containing an 
atom other than a carbon atom or a hydrogen atom. 
The amount of the organic lithium compound is determined in accordance with 
the desired molecular weight of the rubber. Generally, 0.05 to 15 mmol and 
preferably 0.1 to 10 mmol of the organic lithium compound is used per 100 
g of the monomer. When the amount used exceeds 15 mmol, it is difficult to 
obtain a high molecular weight polymer, and when the amount is less than 
0.05 mmol, the polymerization initiator may deactivate due to impurities 
within the polymeric system such that polymerization does not proceed. 
In the case of the conjugated diene rubber or the conjugated diene/vinyl 
aromatic hydrocarbon copolymer rubber, when it is desired to obtain a 
rubber of a desired molecular structure, a randomizer is preferably used 
in the rubber composition of the present invention. Here, "randomizer" is 
intended to mean a compound which controls the microstructure of the 
rubber, e.g., increases the amount of vinyl linkage of the butadiene 
portion of the polybutadiene or the styrene-butadiene rubber and controls 
the compositional distribution of the monomer units of the conjugated 
diene/vinyl aromatic hydrocarbon copolymer rubber, e.g., randomizes the 
butadiene units and the styrene units of the styrene-butadiene rubber. 
The randomizer is not particularly limited, and any generally-known 
randomizer can be used. Examples of the randomizer include ethers such as 
tetrahydrofuran (THF), tetrahydropyran, 1,4-dioxane, monoglycolmethylether 
(monoglyme), diglycolmethylether (diglyme) and triglycolmethylether 
(triglyme); oligomeric oxolanyl alkane compounds such as 
bis(2-oxolanyl)methane, 2,2-bis(2-oxolanyl)propane, 
1,1-bis(2-oxolanyl)ethane and 2,2-bis(5-methyl-2-oxolanyl)propane; and 
tertiary amine compounds such as triethylamine, tripropylamine, 
tributylamine, N,N,N',N'-tetramethylethylenediamine (TMEDA) and 
dipiperidinoethane. 
The amount off the randomizer is in a range of 0.01 to 100 mol per 1 mol of 
the organic lithium compound. 
Polymerization can be carried out at any arbitrary temperature within the 
range of -80.degree. to 150.degree. C., and temperatures off -20.degree. 
to 100.degree. C. are preferable. The polymerization reaction can be 
carried out under a developing pressure, and it is desirable that pressure 
sufficient to maintain the monomer substantially in a liquid phase is 
usually applied. More specifically, the pressure depends on the various 
substances to be polymerized as well as the diluent used and the 
polymerization temperature. If desired, a higher pressure can be used, and 
the pressure can be obtained by an appropriate method such as pressurizing 
the reaction vessel with an inert gas for the polymerization reaction. 
Either bulk polymerization, solution polymerization or emulsion 
polymerization can be used as the method of polymerization. However, using 
solution polymerization in an inert solvent is optimal. It is preferable 
that the solvent is a liquid under usual polymerization reaction 
conditions, and aliphatic, alicyclic or aromatic hydrocarbons may be used. 
Preferable examples of the inert solvent include propane, butane, pentane, 
hexane, heptane, isooctane, cyclopentane, cyclohexane, methylcyclohexane, 
decane, benzene, toluene, xylene, naphthalene and tetrahydronaphthalene. 
These solvents may also be used as a mixture of two or more thereof. 
Generally, it is optimal to remove water, oxygen, carbon dioxide, and 
other catalyst poisons from all of the substances which participate in the 
polymerization process such as the initiator component, the solvent and 
the monomer. 
The following rubbers are two examples of the tin-modified rubber which is 
used in the rubber composition of the present invention: (1) as described 
above, a rubber which is obtained by reacting, for example, a 
tin-containing compound with the active end of a conjugated diene rubber 
obtained by polymerizing a monomer with an organic lithium compound 
initiator, or with the active end of a conjugated diene/vinyl aromatic 
hydrocarbon copolymer rubber obtained by copolymerizing monomers with an 
organic lithium compound initiator; and (2) a rubber obtained by 
polymerizing the above conjugated diene monomer or copolymerizing a 
conjugated diene monomer and a vinyl aromatic hydrocarbon monomer by using 
a tin-containing initiator in the same manner as using the organic lithium 
initiator as described above. 
The tin-containing compound used as a modifier is a compound represented by 
the following general formula: 
EQU SnR.sup.1 pXq 
or 
EQU R.sup.1 pSn--(OCO--R.sup.2).sub.4-p 
wherein R.sup.1 and R.sup.2 are each a substituent group selected from the 
group consisting of alkyl group, alkenyl group, cycloalkyl group, and aryl 
group, and R.sup.1 and R.sup.2 may be the same or different; X is a 
halogen atom; p is an integer from 0 to 3; and p+q=4. Chlorine or bromine 
are preferably used for the halogen atom X. A group having 1 to 20 carbon 
atoms is preferably used for the alkyl group or the alkenyl group used for 
R.sup.1 and R.sup.2, and a group having from 6 to 20 carbon atoms is 
preferably used for the cycloalkyl group or the aryl group used for 
R.sup.l and R.sup.2. 
Specific examples of tin halide compounds expressed by the above general 
formula SnR.sup.1 pXq include tintetrachloride, tintetrabromide, 
methyltintrichloride, butyltintrichloride, octyltintrichloride, 
phenyltintrichloride, phenyltintribromide, tolyltintrichloride, 
dimethyltindichloride, dimethyltindibromide, diethyltindichloride, 
dibutyltindichloride, dioctyltindichloride, diphenyltindichloride, 
diallyltindichloride, dibutenyltindichloride and tributyltinchloride. 
Examples of the tin carboxylate compound represented by the above general 
formula R.sup.1 pSn--(OCO--R.sup.2).sub.4-p include methyltintristearate, 
ethyltintristearate, butyltintrioctanoate, butyltintristearate, 
octyltintristearate, butyltintrilaurate, dibutyltindioctanoate, 
dibutyltindistearate, dibutyltindilaurate, dimethyltindistearate, 
diethyltindilaurate, dioctyltindistearate, trimethyltinlaurate, 
trimethyltinstearate, tributyltinoctanoate, tributyltinstearate, 
tributyltinlaurate, trioctyltinstearate, phenyltintristearate, 
phenyltintrioctanoate, phenyltintrilaurate, diphenyltindistearate, 
diphenyltindioctanoate, diphenyltindilaurate, triphenyltinstearate, 
triphenyltinoctanoate, triphenyltinlaurate, cyelohexyltintristearate, 
dicyclohexyltindistearate, tricyclohexyltinstearate, tributyltinacetate, 
dibutyltindiacetate, and butyltintriacetate. 
The reaction of the tin-containing compound and the active end of the 
rubber is usually carried out at 30.degree. to 120.degree. C. for 0.5 
minutes to 1 hour. 
The amount of the tin-containing compound used is, per 1 mol equivalent of 
the lithium in the end, 0.4 to 1.5 mol equivalent based on the halogen 
atom in a case in which a tin halide compound is used. Further, in a case 
in which a tin carboxylate compound is used, 0.2 to 3.0 mol equivalent of 
carboxyl groups is used per 1 mol equivalent of the lithium, and 
preferably 0.4 to 1.5 mol equivalent of carboxyl groups is used per 1 mol 
equivalent of the lithium. If the amount of the tin halide compound is 
less than 0.4 mol equivalent or the amount of the tin carboxylate compound 
is less than 0.2 mol equivalent, the low hysteresis loss property of a 
vulcanizate of the obtained rubber tends to deteriorate. If the amount of 
the tin halide compound exceeds 1.5 mol equivalent or the amount of the 
tin carboxylate compound exceeds 3.0 mol equivalent, a gel-like polymer is 
formed, and the low hysteresis loss property of a vulcanizate thereof 
tends to deteriorate. 
The tin-containing initiator may be obtained, for example, by reacting a 
lithium metal with an organic tin halide compound having the general 
formula R.sup.3.sub.3 SnX. In this formula, R.sup.3 is selected from the 
group consisting of an alkyl group having 1 to 20 carbon atoms, a 
cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 
carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. Examples 
of the alkyl group include n-butyl, sec-butyl, methyl, ethyl and 
isopropyl. Examples of the cycloalkyl group include cyclohexyl and 
menthyl. Examples of the aryl group and the aralkyl group include phenyl, 
benzyl and naphthyl. In the Formula, X is preferably a chlorine atom or a 
bromine atom. 
Another example of tin-containing initiators may be obtained by, for 
example, reacting a lithium metal with an organic tin compound containing 
a tin-tin bond and expressed by general formula R.sup.4.sub.3 
SnSnR.sup.4.sub.3 (where R.sup.4 has the same definition as R.sup.3). An 
optimal organic tin compound or this type has 6 to 120 carbon atoms, and 
an example thereof is (C.sub.4 H.sub.9).sub.3 SnSn(C.sub.4 H.sub.9).sub.3. 
The tin-containing initiator is preferably R.sup.3.sub.3 SnLi (wherein 
R.sup.3 is as defined above) which is obtained by reacting a lithium metal 
with an organic tin halide compound. Tributyltinlithium is an example 
thereof. 
The Following two rubbers are examples of the nitrogen-containing rubber 
used in the rubber composition of the present invention: (1) as described 
previously, a rubber obtained by reacting, for example, an isocyanate 
compound, a dialkylamino-substituted aromatic compound or a 
nitrogen-containing heteroaromatic compound with the active end of a 
conjugated diene rubber obtained by polymerizing a monomer by using an 
organic lithium compound initiator, or with the active end of a conjugated 
diene/vinyl aromatic hydrocarbon copolymer rubber obtained by 
copolymerizing monomers by using an organic lithium compound initiator; 
and (2) a rubber obtained by polymerizing the above conjugated diene 
monomer or by copolymerizing a conjugated diene monomer and a vinyl 
aromatic hydrocarbon monomer by using a nitrogen-containing organic 
lithium initiator in the same way as described above, wherein the 
initiator here is prepared in advance or prepared in situ in the presence 
of the monomer. 
Examples of the isocyanate compound include 2,4-toluenediisocyanate, 
2,6-tolylenediisocyanate, diphenylmethanediisocyanate, 
naphthalenediisocyanate, tolidinediisocyanate, 
triphenylmethanetriisocyanate, p-phenylenediisocyanate, 
tris(isocyanatephenyl)thiophosphate, xylyleneisocyanate, 
benzene-1,2,4-triisocyanate, naphthalene-1,2,5,7-tetraisocyanate, 
naphthalene-1,3,7-triisocyanate, phenylisocyanate, 
hexamethylenediisocyanate and methylcyclohexanediisocyanate. Preferably 
used are aromatic diisocyanates, aromatic triisocyanates, dimers and 
trimers of aromatic isocyanate compounds, and adducts of the 
aforementioned aromatic isocyanates and polyol or polyamine. Aromatic 
polyisocyanate compounds such as 2,4-tolylenediisocyanate, 
diphenylmethanediisocyanate and naphthalenediisocyanate are more 
preferably used. 
Examples of the dialkylamino-substituted aromatic compound include 
N,N'-dimethylaminobenzophenone, N,N'-diethylaminobenzophenone, 
N-dimethylaminobenzaldehyde, N-diethylaminobenzaldehyde, 
N-dimethylaminobenzoylchloride, methylester of N-dimethylaminobenzoic 
acid, p-diethylaminostyrene, p-dimethylaminostyrene, 
p-dimethylamino-.alpha.-methylstyrene and 
1-(N-dimethylamino)-4-chlorobenzene. 
Examples of the nitrogen-containing heteroaromatic compound include 
4-vinylpyridine, 2-vinylpyridine, bis(2-pyridyl)ketone and 
bis(4-pyridyl)ketone. 
1 to 10 mol equivalent, and preferably 0.2 to 3 mol equivalent of these 
compounds as the reaction group are used per 1 mol equivalent of the 
lithium atoms at the active end of the rubber. If the amount of the 
compound is less than 0.1 mol equivalent, the reactivity with the carbon 
black is insufficient, and the reinforcing property tends to deteriorate. 
Further, even if more than 10 mol equivalent of the compound is used, the 
improvement has reached its saturation point and no further improvements 
can be obtained by the addition of more of the compound. Consequently, 
amounts in excess of 10 mol equivalent are disadvantageous from an 
economic standpoint. 
The coupling reaction of the active end of the rubber and the 
above-described compounds may be carried out at 0.degree. C. to 
150.degree. C. A constant temperature may be maintained throughout the 
coupling reaction, or the temperature may be raised throughout the course 
of the coupling reaction. 
The lithium amide initiator is prepared by reacting an above-described 
organic lithium compound with a secondary amine compound which is an amine 
compound or an imine compound. Examples of the amine compound include 
dimethylamine, diethylamine, dipropylamine, di-n-butylamine, 
diisobutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, 
diallylamine, dicyclohexylamine, butylisopropylamine, dibenzylamine, 
methylbenzylamine, methylhexylamine and ethylhexylamine. Examples of the 
imine compound include trimethyleneimine, pyrrolidine, piperidine, 
2-methylpiperidine, 3-methylpiperidine, 4-methylpiperidine, 
3,5-dimethylpiperidine, 2-ethylpiperidine, hexamethyleneimine, 
heptamethyleneimine, morpholine, N-methylpiperazine, N-ethylpiperazine, 
N-methylimidazolidine, N-ethylimidazolidine, oxazine, pyrroline, pyrrole 
and azepine. 
The amount of the secondary amine is 0.01 to 20 mol equivalent, preferably 
0.1 to 5.0 mol equivalent, and more preferably 0.2 to 1.5 mol equivalent 
per 1 mol equivalent of lithium atom in the organic lithium compound. A 
large amount of the secondary amine leads to an increase in the hysteresis 
loss of the rubber. If the amount of the secondary amine is less than 0.01 
mol equivalent, the efficiency in introducing a tertiary amine to the 
polymer chain deteriorates. When the amount of the secondary amine exceeds 
20 mol equivalent weight, the generated amount of amine-containing 
oligomers, which do not contribute to the improvement of the physical 
properties, becomes large, which is not preferable. 
The above explanation is described as an example of a rubber obtained by 
modifying only one end of a conjugated diene rubber chain or only one end 
of a conjugated diene/vinyl aromatic: hydrocarbon copolymer rubber chain 
by a tin-containing group or a nitrogen-containing group. On the other 
hand, because the tin-containing initiator or the nitrogen-containing 
initiator is a living polymerization initiator, the ends of the resultant 
rubber are active. Therefore, the active end can react with an 
above-described tin-containing compound or nitrogen-containing compound, 
and a rubber having a tin-containing group or a nitrogen-containing group 
at both ends of the chain can be obtained. Accordingly, a rubber can be 
obtained in which a desired tin-containing group or nitrogen-containing 
group is introduced arbitrarily to one end or both ends of the rubber. 
The silane coupling agent used in the rubber composition of the present 
invention is selected from the group of compounds represented by above 
general formulae III and IV. Examples of the compound of general formula 
III include bis-(3-triethoxysilylpropyl)tetrasulfide and 
.gamma.-mercaptopropyltrimethoxysilane. Examples of the compound of 
general formula IV include 
3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 
trimethoxysilylpropyl-mercaptobenzothiazol tetrasulfide, 
triethoxysilylpropylmethacrylate monosulfide and 
dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide. Among 
these, bis-(3-triethoxysilylpropyl)tetrasulfide and 
.gamma.-mercaptopropyltrimethoxysilane are preferable from the point of 
view of the low hysteresis loss effect. 
The hydrazide compound used in the rubber composition of the present 
invention functions as a low hysteresis loss promoting agent and is 
selected from the group of compounds expressed by above general formulae 
V, VI and VII. Examples of the compound of general formula V include 
isophthaloyl dihydrazide, terephthaloyl dihydrazide, azelaoyl dihydrazide, 
azepinoyl dihydrazide, succinoyl dihydrazide, icosanoyl hydrazide, 
7,11-octadecadiene-1,18-dicarbohydrazide and 
1,3-bis(hydrazinocarboethyl)-5-isopropylhydantoin. Examples of the 
compound of general formula VI include 2-hydroxy-3-naphthoyl hydrazide, 
anthraniloyl hydrazide, salicyloyl hydrazide and 4-hydroxybenzoyl 
hydrazide. Examples of the compound of general formula VII include 
carbodihydrazide and isonicotinoyl hydrazide. Among these, 
2-hydroxy-3-naphthoyl hydrazide is preferable from the standpoint of the 
low hysteresis loss effect. 
The thiadiazole compound used in the rubber composition of the present 
invention functions as a low hysteresis loss promoting agent and is 
selected from the group of compounds represented by above general formula 
VIII. Examples of the compound of formula VIII include 
2,5-dimercapto-1,3,4-thiadiazole, 2-amino-5-mercapto-1,3,4-thiadiazole and 
2-amino-5-trifluoromethyl-1,3,4-thiadiazole. Among these, 
2,5-dimercapto-1,3,4-thiadiazole is preferable from the standpoint of low 
hysteresis loss effect. 
The compounding amounts of the compounds expressed by general formulae III 
through VIII are, per 100 parts by weight of the rubber component, 0.05 
through 5.0 parts by weight, and preferably 0.1 to 1.0 parts by weight. If 
the compounding amount is less than 0.05 parts by weight, sufficient 
effects are not achieved. A compounding amount exceeding 5.0 parts by 
weight is not preferable from the standpoint of the balance with the other 
physical properties of the rubber. 
In the rubber composition of one embodiment of the present invention, a 
conjugated diene-base synthetic rubber and a carbon black specified by 
characteristic X and characteristic Y interact, and the low hysteresis 
loss property is improved. Due to the reinforcing effects caused by the 
interaction, the wet skid resistance is also improved. Further, the 
effects of the rubber composition of the present invention are enhanced 
even more when a tin-containing or nitrogen-containing conjugated diene 
rubber or conjugated diene/vinyl aromatic hydrocarbon copolymer rubber is 
used as the conjugated diene-base synthetic rubber. This is most likely 
due to the interaction between the modifying group of the rubber and the 
specified functional group of the surface of the carbon black. 
In another embodiment, one functional group of a coupling agent and/or a 
low hysteresis loss promoting agent reacts with a functional group of a 
carbon black specified by characteristic X. Respective another ends of 
these additives interact with a conjugated diene-base synthetic rubber, 
and the low hysteresis loss property is improved. Due to the reinforcing 
effects caused by the interaction, the wet skid resistance is also 
improved. 
Compounding agents used ordinarily in the rubber industry, such as other 
reinforcing fillers, non-reinforcing inorganic fillers, vulcanizing 
agents, stearic acid, zinc oxide, vulcanizing accelerators, anti-oxidants 
and softeners, can be compounded appropriately in the rubber composition 
of the present invention. 
The rubber composition of the present invention is preferably used as the 
tread rubber for a tire and the sidewall rubber for a tire, and especially 
as the tread rubber. The rubber composition is also used for other rubber 
products of which low hysteresis loss property is required, such as belts 
and shock absorbers.

EXAMPLES 
The present invention will be concretely described hereinafter by the 
following Examples. It is to be noted that the present invention is not 
limited to the following Examples, and other embodiments are possible 
within the scope off the invention. 
Various measurements were taken as follows. 
*Measurement of N.sub.2 SA (Nitrogen Absorption Specific Surface Area) 
In accordance with ASTM D3037, the specific surface area (m.sup.2) per 1 g 
of carbon black was determined from the absorbed amount of nitrogen 
(N.sub.2). 
*Measurement of &gt;C.dbd.O Functional Group Concentration 
1) Preparation of Oximized Carbon Black 
About 1.5 g of carbon black was placed into two Erlenmeyer flasks, 
respectively. A solution in which 1 g of hydroxylamine hydrochlorate had 
been dissolved in 20 ml of pyridine was added to one of the flasks, 
whereas 20 ml of pyridine was added to the other flask. A condenser was 
attached to the upper portion of the Erlenmeyer flask, and a calcium 
chloride tube and a deoxigenating apparatus were connected to the 
condenser. A stream of nitrogen gas was passed through the entire 
apparatus to displace the air such that a nitrogen atmosphere was 
obtained. 
The flasks were placed in an oil bath maintained at 100.degree. C., and the 
reaction was carried out for 16 hours at that temperature. After the 
reaction was completed, while the reactants were cooling, 50 ml of 3 
normal hydrochloric acid was added and the excess hydroxylamine was 
neutralized. The contents were suction filtered, and the oximized carbon 
black was separated and rinsed with about 300 ml of distilled water. The 
rinsed oximized carbon black was transferred onto a No. 5B filter paper 
and again rinsed with 300 ml of distilled water. 
After rinsing, the oximized carbon black was placed in a drying apparatus 
maintained at 105.degree. C. and was dried until a constant weight was 
reached, and the oximized carbon black was thus prepared. (The same 
operations were also carried out for the blank.) 
2) Quantitative Determination of Nitrogen 
1 Preparation of the Sample for Quantitative Determination 
About 0.2 grams of the oximized carbon black and about 0.2 grams of a 
control carbon black were accurately measured and placed into respective 
semi-micro-Kjeldahl decomposition bins. 2.5 g of calcium sulfate and 0.02 
g of mercury (II), and lastly, 4 ml of concentrated sulfuric acid were 
added to each bin. 
The decomposition bin was attached to a semi-micro-Kjeldahl decomposition 
apparatus. A stream of tap water was passed through an exhaust gas suction 
aspirator, and the gas burner was ignited. The intensity of the flame of 
the burner was made weak to the extent that the contents within the 
decomposition bin did not boil at first. When the amount of white smoke 
generated from the decomposition bin decreased such that there was little 
white smoke, the intensity off the flame was then gradually increased to 
the extent that the contents boiled. This high heat was maintained for 1 
hour after the contents of the decomposition bin had become completely 
transparent. The flame was then turned off, and after the bin had cooled 
in air to room temperature, the bin was removed from the decomposition 
apparatus, and approximately 10 ml of distilled water was added to the bin 
portion by portion. The solution of the contents was placed in a sampling 
flask of a semi-micro-Kjeldahl nitrogen distilling apparatus. The 
decomposition bin was washed several times with a small amount of water, 
and the water was added to the solution in the sampling flask. 
2 Quantitative Determination of Nitrogen 
The sampling flask was attached to the distilling apparatus, and a beaker 
containing 5 ml of a 2% boric acid solution was connected to the outlet of 
a condenser mounted onto the distilling apparatus. 25 ml of a sodium 
hydroxide/sodium thiosulfate (50%/5%) solution was injected from the 
alkali injection opening of the distilling apparatus. The injection 
opening and the vapor opening were closed, and distillation was carried 
out for 9 minutes in order to trap the ammonia into the boric acid 
solution. 
The 2% boric acid solution in which ammonia had been dissolved was titrated 
with 1/100 normal hydrochloric acid. 
Using an ammonium sulfate solution with a precisely-known amount of 
nitrogen, the same operations were carried out, and a calibration curve 
was prepared. The milliequivalent of the nitrogen in the sample was 
determined from the titrated amount of the sample and the calibration 
curve, and the milliequivalent of the &gt;C.dbd.O functional groups per 1 g 
of carbon black (meq/g) was calculated according to the following 
equation. 
##EQU1## 
*Measurement of Concentration of --OH Functional Groups 1) Preparation of 
Acetylated Carbon Black 
20 ml of pyridine and 10 ml of acetic anhydride were placed in an 
Erlenmeyer flask containing about 2 g of carbon black. A calcium chloride 
tube was connected to the upper portion of a condenser, and was placed in 
the inlet of the Erlenmeyer flask. A stream of nitrogen gas was passed 
through the apparatus to displace the air such that a nitrogen atmosphere 
was obtained. 
The flask was placed in an oil bath maintained at 120.degree. C., and the 
reaction was carried out for 15 hours at that temperature. After the 
reaction was completed, while the reactants were cooling, 100 ml of 
distilled water was added and the excess acetic anhydride was decomposed. 
Then, the acetylated carbon black was separated by suction filtration, and 
rinsed with about 300 ml of distilled water. 
The rinsed acetylated carbon black was placed in a drying apparatus 
maintained at 105.degree. C. and was dried until a constant weight was 
reached, and the acetylated carbon black was thus prepared. 
2) Quantitative Determination of Acetic Acid 
About 1 g of the acetylated carbon black was accurately measured and placed 
in a beaker. A solution in which 2 g of barium hydroxide had been added to 
20 ml of heated distilled water was added to the beaker. The beaker was 
placed in a 100.degree. C. water bath, and hydrolysis was carried out for 
5 hours. The contents cooled, and were suction filtered by using a 
membrane filter. The beaker and the filter were rinsed with a small amount 
of distilled water. The liquid consisting of the filtrate and the rinsing 
liquid was passed down a column of Umberlite IR120 (trade name; 
manufactured by Organo Corporation) of a cation exchange resin activated 
with hydrochloric acid, so as to liberate the acetic acid. The column was 
rinsed until the acidity off the acetic acid was no longer observed in the 
filtrate. 
All the liquid which had been passed through the column was gathered and 
titrated with a 1/500 normal sodium hydroxide solution by using an 
indicator which was a mixture of methyl red and bromocresol green. 
Before titration, a calibration curve was prepared in advance by using a 
1/500 normal acetic acid standard solution. The amount of acetic acid in 
the sample was determined from the aforementioned titration value by using 
this calibration curve. 
The milliequivalent of the --OH Functional groups per 1 g of carbon black 
(meq/g) was calculated by the following formula. 
##EQU2## 
wherein f is the titer of the acetic acid standard solution. *Measurement 
of Hysteresis Loss Property 
The loss tangent (tang .delta.) was measured at a tensile dynamic 
distortion of 1%, a frequency of 50 Hz, and a temperature off 60.degree. 
C. by using a viscoelasticity spectrometer manufactured by Iwamoto 
Seisakusho Co., Ltd. The test piece was a slab sheet having a thickness of 
about 2 mm and a width off 5 mm. The distance between the positions at 
which the test material was nipped was 2 cm, and the initial load was 160 
g. The values of tan .delta. were expressed as indices with the value for 
Comparative Example 1 being see to 100. Smaller numbers mean a lower 
hysteresis loss, which is preferable. 
*Measurement of Wet Skid Resistance 
The wet skid resistance was evaluated by measuring the skid resistance at 
room temperature on a concrete road surface which had been wet with water, 
by using a Skid Tester manufactured by Stanley London Co. (England). The 
values were expressed as indices with the value for Comparative Example 1 
being set to 100. Here, larger numbers are more preferable. 
*Measurement of Low Rolling Resistance Performance 
The rubber composition was used in the tread of a 195/65R15 size tire for a 
passenger vehicle. The rim 6 JJ tire, which had an internal pressure of 
2.0 kg and a load of 440 kg, was set on a drum having an external diameter 
of 1.7 m. The drum was rotated, and the rolling resistance was calculated 
in accordance with the following formula from a value calculated from the 
moment of inertia at the time the drum was coasting at 80 km/h after the 
speed thereof had been raised to 120 km/h. The numerical values were 
expressed as indices with the value for Comparative Example 1 being set to 
100. Larger numbers are more preferable. 
##EQU3## 
*Measurement of Wet Skid Resistance Performance of Tire 
In accordance with the method stipulated in UTQGS (U.S. Tire Quality and 
Grade Standards), tires were placed on a trailer for testing which was 
then run on a wet, tightly-packed asphalt road surface. The frictional 
resistance at the time the rotation of the tires was locked was measured. 
The numerical values were expressed as indices with the value for 
Comparative Example 1 being set to 100. Larger values are more preferable. 
*Carbon Blacks used in the Comparative Examples and in the Examples 
1) Carbon Blacks used in the Comparative Examples 
Carbon black A (control), B, C, D, E and F were all common furnace blacks, 
and were ASTM code N330, N660, N550, N839, N220 and N110, respectively. 
2) Carbon Blacks used in the Examples 
Carbon black G was prepared by oxidizing carbon black A for three hours at 
room temperature in an ozone atmosphere. 
Carbon black H was prepared by heating carbon black G for 1 hour at 
450.degree. C. in a nitrogen atmosphere. 
Carbon black I was prepared by using the gas furnace method with LPG as the 
raw material. 
Carbon black J was channel-type black CK-3 (trade name off a product 
manufactured by Deggusa AG). 
Carbon black K was prepared by oxidizing carbon black J for three hours at 
room temperature in an ozone atmosphere. 
Carbon black L was prepared by heating carbon black K for 1 hour at 
450.degree. C. in a nitrogen atmosphere. 
Carbon black M was channel-type black Special Black 4A (trade name of a 
product manufactured by Deggusa AG), which is an oxidized channel-type 
black. 
*Rubbers used in the Comparative Examples and in the Examples 
1) SBR was #1500 manufactured by Japan Synthetic Rubber Co., Ltd. 
2) Modified SBR 1 was prepared by copolymerizing 1 kg of styrene and 4 kg 
of butadiene in a cyclohexane solvent for 30 minutes at 10.degree. C. by 
using 48 mmol of n-butyllithium and 250 g of tetrahydrofuran. The obtained 
butadiene-styrene copolymer was coupled with 12 mmol of tin tetrachloride. 
The styrene content of the copolymer before coupling was 20% by weight, 
the vinyl linkage content of the butadiene portion was 60%, and the weight 
average molecular weight was 2.1.times.10.sup.5. 
3) Modified SBR 2 was obtained by modifying, with 12 mmol of 
diethylaminobenzophenone, a butadiene/styrene random copolymer obtained in 
the same manner as SBR1. The molecular structure of the polymer before 
modification was the same as that off modified SBR1. 
(Example 1) 
A rubber composition was prepared by using carbon black G, natural rubber, 
and modified SBR 1, in accordance with the compounding formulations of 
Tables 2 and 3. The rubber composition was vulcanized at 150.degree. C. 
for 40 minutes. The results of measurement of the characteristics of 
carbon black G are listed in Table 1. The results of the evaluation of 
physical properties such as the hysteresis loss (tan .delta.) and the wet 
skid resistance of the vulcanitizate are listed in Table 3. Further, the 
results of the evaluation of the performances such as rolling resistance 
performance and wet skid resistance performance of a 195/65R15 size tire 
for a passenger vehicle in whose tread the rubber composition was used are 
listed in Table 4. 
(Examples 2 through 10, Comparative Examples 1 through 7) 
In the same way as in Example 1, rubber compositions and tires were 
obtained by using the various types of carbon black and the various types 
of rubber listed in the tables. The results of the evaluation of the 
characteristics of the carbon blacks are listed in Table 1, the results of 
measuring the physical properties of the vulcanizates are listed in Table 
3, and the results of evaluating the performances of the tires are listed 
in Table 4. 
TABLE 1 
__________________________________________________________________________ 
Characteristics of Carbon Black 
(&gt;CO Concentration)- 
&gt;C.dbd.O/N.sub.2 SA 
(--OH Concentration).sup.2 + 
N.sub.2 SA 
&gt;CO.dbd.O Concentration 
--OH Concentration 
(meq/m.sup.2) 
0.1(--OH Concentration)- 
(m.sup.2 /g) 
(meq/g) (meq/g) (.times.100) 
0.03 (meq/g) 
__________________________________________________________________________ 
Type of 
Carbon Black 
A 77 0.028 0.133 0.036 -0.006 
B 26 0.003 0.084 0.012 -0.026 
C 40 0.007 0.109 0.018 -0.024 
D 92 0.033 0.138 0.036 -0.002 
E 115 0.031 0.192 0.027 -0.017 
F 144 0.044 0.238 0.031 -0.019 
G 80 0.177 0.221 0.222 0.120 
H 81 0.044 0.172 0.054 0.002 
I 130 0.242 0.426 0.186 0.073 
J 96 0.084 0.241 0.087 0.020 
K 93 0.182 0.376 0.195 0.048 
L 104 0.088 0.294 0.085 0.001 
M 179 0.131 0.327 0.073 0.027 
__________________________________________________________________________ 
TABLE 2 
______________________________________ 
Compounding Agent 
Parts By Weight 
______________________________________ 
Rubber 100 
Natural rubber 30 
SBR or modified SBR 
70 
Carbon black 50 
Stearic acid 2 
Zinc white 3 
Antioxidant 810NA.sup.1 
1 
Accelerator CZ.sup.2 
0.6 
Accelerator M.sup.3 
0.6 
Accelerator D.sup.4 
0.4 
Sulfur 1.5 
______________________________________ 
.sup.1 Nphenyl-N-isopropyl-p-phenylenediamine 
.sup.2 Ncyclohexyl-2-benzothiazolylsulfenamide 
.sup.3 2mercaptobenzothiazole 
.sup.4 1,3diphenylguanidine 
TABLE 3 
__________________________________________________________________________ 
Physical Properties of 
Rubber Component (parts by weight) 
Carbon 
Rubber Composition 
Modified 
Modified 
Black 
tan.delta. 60.degree. C. 
Wet Skid 
NR 
SBR 
SBR 1 SBR 2 
Type 
Index Index 
__________________________________________________________________________ 
Comparative 
1 30 
-- 70 -- A 100 100 
Examples 
2 30 
-- 70 -- B 64 97 
3 30 
-- 70 -- C 87 99 
4 30 
-- 70 -- D 104 100 
5 30 
-- 70 -- E 133 102 
6 30 
-- 70 -- F 158 102 
Examples 
1 30 
-- 70 -- G 86 103 
2 30 
-- 70 -- H 71 103 
3 30 
-- 70 -- I 77 103 
4 30 
-- 70 -- J 78 104 
5 30 
-- 70 -- K 69 104 
6 30 
-- 70 -- L 67 105 
7 30 
-- 70 -- M 52 106 
Comparative 
7 30 
70 -- -- A 112 99 
Example 
Examples 
8 30 
70 -- -- J 97 101 
9 30 
-- -- 70 J 70 103 
10 
30 
-- -- 70 M 46 104 
__________________________________________________________________________ 
TABLE 4 
__________________________________________________________________________ 
Tire Performance 
Rubber Component (parts by weight) 
Carbon 
Rolling 
Modified 
Modified 
Black 
Resistance 
Wet Skid 
NR 
SBR 
SBR 1 SBR 2 
Type 
Index 
Index 
__________________________________________________________________________ 
Comparative 
1 30 
-- 70 -- A 100 100 
Examples 
2 30 
-- 70 -- B 105 96 
3 30 
-- 70 -- C 103 98 
4 30 
-- 70 -- D 99 100 
5 30 
-- 70 -- E 95 101 
6 30 
-- 70 -- F 84 102 
Examples 
1 30 
-- 70 -- G 103 103 
2 30 
-- 70 -- H 103 102 
3 30 
-- 70 -- I 103 104 
4 30 
-- 70 -- J 103 105 
5 30 
-- 70 -- K 105 104 
6 30 
-- 70 -- L 105 103 
7 30 
-- 70 -- M 112 107 
Comparative 
7 30 
70 -- -- A 96 98 
Example 
Examples 
8 30 
70 -- -- J 101 101 
9 30 
-- -- 70 J 106 102 
10 
30 
-- -- 70 M 114 104 
__________________________________________________________________________ 
As can be seen from Table 3, the rubber compositions of one embodiment of 
the present invention, in which were used carbon blacks having 
characteristic X and characteristic Y, exhibited excellent low hysteresis 
loss property and at the same time had high levels of wet skid resistance. 
Further, as is clear from Table 4, for pneumatic tires using these rubber 
compositions, the low rolling resistance performance was greatly improved, 
and the wet skid resistance performance was also outstanding. 
As can be seen from Comparative Examples 1 through 7, rubber compositions, 
in which were used carbon blacks not having both of the two claimed 
characteristics of the present invention, were inferior with respect to 
one of low hysteresis loss property and wet skid resistance. Namely, there 
exists an inverse relationship between low hysteresis loss property and 
wet skid resistance. Tires using these rubber compositions similarly 
cannot simultaneously exhibit satisfactory low rolling resistance 
performance and wet skid resistance performance. As can be seen from 
Example 8 (in which ordinary SBR is used) and other Examples (in which 
modified SBR is used), in the present invention, rubber compositions using 
modified SBR as the rubber component and tires using these rubber 
compositions exhibit better effects. 
(Example 11) 
A rubber composition was prepared in accordance with the compounding 
formulations of Table 5 and Table 6 by using carbon black J, natural 
rubber, SBR and silane coupling agent Si69 (trade name of a product 
manufactured by Deggusa AG). The rubber composition was vulcanized for 40 
minutes at 150.degree. C. The results of measuring the characteristics of 
carbon black J are listed in Table 1. The results of the evaluation of 
physical properties such as the hysteresis loss (tan .delta.) and the wet 
skid resistance of the vulcanizate are listed in Table 6. Further, the 
results of the evaluation of the performances such as rolling resistance 
performance and wet skid resistance performance of a 195/65R15 size tire 
for a passenger vehicle in whose tread the rubber composition was used are 
listed in Table 7. 
(Examples 12-20) 
In the same way as in Example 11, rubber compositions and tires were 
obtained by using the various types of carbon black (G through M) and the 
various types of additives listed in the tables. The results of evaluation 
of the characteristics of the carbon blacks are Listed in Table 1, the 
results of measurement of the physical properties of the vulcanizates are 
listed in Table 6, and the results of the evaluation of the performances 
of the tires are listed in Table 7. 
(Comparative Examples 8 and 13) 
Rubber compositions and tires were obtained by using carbon black A (in 
Comparative Example 8) and carbon black J (in Comparative Example 13) in 
the same way as in Example 11, except that additives were not used in 
either of Comparative Examples 8 and 13. The results of measurement of the 
characteristics of the carbon blacks are listed in Table 1, the results of 
measurement of the physical properties of the vulcanizates are listed in 
Table 6, and the results of the evaluation off the performances of the 
tires are listed in Table 7. 
(Comparative Examples 9 through 12, 14 through 18) 
Rubber compositions and tires were obtained in the same was as in Example 
11 by using various types of carbon blacks (A through F) and various types 
of additives. The results of measurement of the characteristics of the 
carbon blacks are listed in Table 1, the results of measurement of the 
physical properties off the vulcanizates are listed in Table 6, and the 
results off evaluation off the performances of the tires are listed in 
Table 7. 
TABLE 5 
______________________________________ 
Compounding Agent 
Parts By Weight 
______________________________________ 
Rubber 100 
Natural rubber 30 
SBR 70 
Additive See Table 6 
Silane coupling agent 
Hydrazide compound 
Thiadiazole compound 
Carbon black 50 
Stearic acid 2 
Zinc white 3 
Antioxidant 810NA.sup.1 
1 
Accelerator CZ.sup.2 
0.6 
Accelerator M.sup.3 
0.6 
Accelerator D.sup.4 
0.4 
Sulfur 1.5 
______________________________________ 
.sup.1 Nphenyl-N-isopropyl-p-phenylenediamine 
.sup.2 Ncyclohexyl-2-benzothiazolylsulfenamide 
.sup.3 2mercaptobenzothiazole 
.sup.4 1,3diphenylguanidine 
TABLE 6 
__________________________________________________________________________ 
Physical Properties 
Rubber of Rubber 
Component 
Additive Carbon 
Composition 
(parts by weight) 
(parts by weight) 
Black 
tan.delta. 60.degree. C. 
Wet Skid 
NR SBR.sup.1 
C.sup.2 
H1.sup.3 
H2.sup.4 
T.sup.5 
Type 
Index Index 
__________________________________________________________________________ 
Comparative 
8 
30 70 -- 
-- -- -- 
A 128 96 
Examples 
9 
30 70 2 -- -- -- 
A 115 97 
10 
30 70 -- 
0.5 
-- -- 
A 112 96 
11 
30 70 -- 
-- 1 -- 
A 113 96 
12 
30 70 -- 
-- -- 0.5 
A 108 95 
13 
30 70 -- 
-- -- -- 
J 100 100 
Examples 
11 
30 70 2 -- -- -- 
J 87 101 
12 
30 70 -- 
0.5 
-- -- 
J 77 101 
13 
30 70 -- 
-- 1 -- 
J 78 102 
14 
30 70 -- 
-- -- 0.5 
J 73 101 
Comparative 
14 
30 70 -- 
0.5 
-- -- 
B 91 93 
Examples 
15 
30 70 -- 
0.5 
-- -- 
C 104 95 
16 
30 70 -- 
0.5 
-- -- 
D 116 97 
17 
30 70 -- 
0.5 
-- -- 
E 140 98 
18 
30 70 -- 
0.5 
-- -- 
F 163 99 
Examples 
15 
30 70 -- 
0.5 
-- -- 
G 85 101 
16 
30 70 -- 
0.5 
-- -- 
H 70 101 
17 
30 70 -- 
0.5 
-- -- 
I 76 102 
18 
30 70 -- 
0.5 
-- -- 
K 70 101 
19 
30 70 -- 
0.5 
-- -- 
L 66 102 
20 
30 70 -- 
0.5 
-- -- 
M 54 103 
__________________________________________________________________________ 
.sup.1 SBR: #1500 manufactured by Japan Synthetic Rubber Co., Ltd. 
.sup.2 C: silane coupling agent; Si69 (trade namemanufactured by Deggusa 
AG), bis(3-triethoxysilylpropyl) tetrasulfide 
.sup.3 H1: hydrazide compound; IDH, isophthaloyl dihydrazide 
.sup.4 H2: hydrazide compound; HNH, 2hydroxy-3-naphthoyl hydrazide 
.sup.5 T: thiadiazole compound; 2,5dimercapto-1,3,4-thiadiazole 
TABLE 7 
__________________________________________________________________________ 
Tire Performance 
Rubber Component 
Additive Carbon 
Rolling 
(parts by weight) 
(parts by weight) 
Black 
Resistance 
Wet Skid 
NR SBR.sup.1 
C.sup.2 
H1.sup.3 
H2.sup.4 
T.sup.5 
Type 
Index 
Index 
__________________________________________________________________________ 
Comparative 
8 
30 70 -- 
-- -- -- 
A 97 95 
Examples 
9 
30 70 2 -- -- -- 
A 98 96 
10 
30 70 -- 
0.5 
-- -- 
A 99 95 
11 
30 70 -- 
-- 1 -- 
A 98 94 
12 
30 70 -- 
-- -- 0.5 
A 99 95 
13 
30 70 -- 
-- -- -- 
J 100 100 
Examples 
11 
30 70 2 -- -- -- 
J 101 101 
12 
30 70 -- 
0.5 
-- -- 
J 103 102 
13 
30 70 -- 
-- 1 -- 
J 102 103 
14 
30 70 -- 
-- -- 0.5 
J 104 101 
Comparative 
14 
30 70 -- 
0.5 
-- -- 
B 104 91 
Examples 
15 
30 70 -- 
0.5 
-- -- 
C 102 94 
16 
30 70 -- 
0.5 
-- -- 
D 98 96 
17 
30 70 -- 
0.5 
-- -- 
E 95 96 
18 
30 70 -- 
0.5 
-- -- 
F 83 98 
Examples 
15 
30 70 -- 
0.5 
-- -- 
G 103 101 
16 
30 70 -- 
0.5 
-- -- 
H 103 101 
17 
30 70 -- 
0.5 
-- -- 
I 104 102 
18 
30 70 -- 
0.5 
-- -- 
K 105 102 
19 
30 70 -- 
0.5 
-- -- 
L 105 101 
20 
30 70 -- 
0.5 
-- -- 
M 110 104 
__________________________________________________________________________ 
.sup.1 SBR: #1500 manufactured by Japan Synthetic Rubber Co., Ltd. 
.sup.2 C: silane coupling agent; Si69 (trade namemanufactured by Deggusa 
AG), bis(3-triethoxysilylpropyl) tetrasulfide 
.sup.3 H1: hydrazide compound; IDH, isophthaloyl dihydrazide 
.sup.4 H2: hydrazide compound; HNH, 2hydroxy-3-naphthoyl hydrazide 
.sup.5 T: thiadiazole compound; 2,5dimercapto-1,3,4-thiadiazole 
As can be seen from Table 6, the rubber compositions of the present 
invention, in which were used carbon blacks having characteristic X and 
specific additives, exhibited excellent low hysteresis loss property and 
at the same time had high levels of wet skid resistance. Further, as is 
clear from Table 7, for pneumatic tires using these rubber compositions, 
the low rolling resistance performance was greatly improved, and the wet 
skid resistance performance was also outstanding. 
As can be seen from Comparative Examples 8 through 18, rubber compositions 
using carbon blacks falling outside of the scope of the claimed invention 
(Comparative Examples 8 through 12, 14 through 18) were inferior with 
respect to both low hysteresis loss property and wet skid resistance 
regardless of whether the specific additives were used therein. Similarly, 
tires using these rubber compositions could not exhibit both low rolling 
resistance performance and wet skid resistance performance simultaneously. 
Further, in a case in which a carbon black falling within the scope of the 
claimed invention was used but the additives were not used (Comparative 
Example 13), the obtained rubber composition and tire could not exhibit 
the effects of the present invention.