Coupling agent composition

A solid coupling agent for use in a vulcanizable rubber compound containing siliceous filler. The coupling agent includes an organosilane, a powderizing agent, and a fatty acid dispersion aid including fatty acid and a salt-forming agent.

BACKGROUND OF THE INVENTION 
This invention relates to additives for rubber compounds and in particular 
to organosilane coupling agents for rubber compounds containing siliceous 
fillers used in tire building. 
A rubber compound, such as for use in a tire, typically includes natural 
and/or synthetic rubber, process aids, reinforcing filler, and a 
vulcanizing agent, such as sulfur. The process aids are used to decrease 
viscosity, disperse filler, reduce shrinkage, and/or provide lubrication. 
The reinforcing filler is used to increase the strength, hardness, and 
abrasion resistance of the rubber compound. The reinforcing filler is 
typically comprised of carbon black and/or a siliceous material, typically 
silica. 
Carbon black is typically used as the predominant reinforcing filler in a 
rubber compound, especially in a tire component, such as a tread. It has 
been recognized, however, that using a siliceous material as the 
predominant reinforcing filler in a tire tread provides benefits, 
including improved rolling resistance and traction. 
A siliceous material is hydrophilic and, thus, is not as compatible with 
rubber as carbon black. Coupling agents, however, have been developed to 
increase the compatibility between a siliceous material and rubber. 
Nonetheless, rubber compounds that are highly filled with a siliceous 
material tend to be viscous and stiff, and therefore difficult to process. 
Organosilane compounds are often used as coupling agents. 
Trialkoxyorganosilane polysulfide compounds have been found to be 
particularly suitable for use as coupling agents, especially 
bis(3-triethoxysilylpropyl)-tetrasulfane (hereinafter referred to as 
"TESPT"). TESPT and other organosilane compounds, however, are liquids at 
room temperature, which is undesirable. In large scale industrial 
processes, liquid compounds are difficult to store, weigh, and otherwise 
handle. 
In order to improve handling characteristics, liquid organosilane compounds 
have been combined with carriers to create coupling agents in powder and 
granulate forms. An example of such a coupling agent and a method of 
forming the same is disclosed in U.S. Pat. No. 4,128,438 to Wolff et al., 
which is incorporated herein by reference. Wolff et al. discloses mixing 
TESPT with carbon black in order to obtain a granulate coupling agent. 
Such a granulate, however, does not substantially improve the processing 
characteristics of rubber compounds that are highly filled with a 
siliceous material. 
Based upon the foregoing, there is a need in the art for an organosilane 
coupling agent in granulate or powder form that improves the processing 
characteristics of rubber compounds that are highly filled with a 
siliceous material. The present invention is directed to such a coupling 
agent. 
SUMMARY OF THE INVENTION 
It therefore would be desirable, and is an advantage of the present 
invention, to provide a coupling agent composition and a siliceous rubber 
compound containing the same, wherein the coupling agent composition is 
solid and improves the processing characteristics of the siliceous rubber 
compound. In accordance with the present invention, the coupling agent 
composition includes about 20-85 weight percent of an organosilane and 
about 9-70 weight percent of a fatty acid dispersion aid. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
It should be noted that parts are parts by weight and percents are weight 
percents unless otherwise indicated or apparent. In addition, when a 
preferred range such as 5-25 is given, this means preferably at least 5 
and preferably not more than 25. 
The coupling agent of the present invention is solid and is free, or 
substantially free, of carbon black. As used herein, the term "solid" 
shall mean not a liquid or a gas and specifically including powders, 
granulates, pellets, and larger masses of material. The coupling agent is 
preferably for addition to a vulcanizable rubber compound comprising 
rubber and a siliceous filler. The coupling agent has a preferred 
formulation (Formulation 1) of: 50 weight % (less preferably 30-60 weight 
%, less preferably 20-70 weight %, less preferably 20-85 weight %) 
organosilane, 20 weight % (less preferably 15-30 weight %, less preferably 
10-40 weight %) powderizing agent, and 30 weight % (less preferably 23-45 
weight %, less preferably 15-60 weight %, less preferably 9-70 weight %) 
fatty acid dispersion aid. Formulation 1 in tabular summary form is as 
follows: 
______________________________________ 
Weight Percent 
Component Preferred 
Less Preferred 
Less Preferred 
______________________________________ 
1. Organosilane 50 30-60 20-85 
2. Powderizing Agent 20 15-30 10-40 
3. Fatty Acid 30 23-45 9-70 
Dispersion Aid 
______________________________________ 
The organosilane component of the present invention contains one or more 
organosilanes having a silica-philic constituent, or moiety, capable of 
associating with the siliceous filler, and a rubber-philic constituent, or 
moiety, capable of associating with the rubber. In this manner, the 
organosilane component acts as a connecting bridge between the siliceous 
filler and the rubber and thereby enhances the rubber reinforcement aspect 
of the siliceous filler. 
The organosilane component may be comprised of one or more organosilanes 
containing a mercaptan for the rubber-philic constituent. For example the 
organosilane component may include 3-mercapto propyltriethoxysilane 
(C.sub.9 H.sub.22 SSio.sub.3). More preferably, however, the organosilane 
component is comprised of one or more organosilanes having a polysulfide 
for the rubber-philic constituent. Still more preferably, the organosilane 
component is comprised of one or more organosilanes having the formula: 
##STR1## 
where R.sup.1 is an alkyl group with 1 to 3 carbon atoms; 
R.sup.2 is an alkyl or alkoxy group with 1 to 3 carbon atoms; 
R is an alkylene group with 1 to 5 carbon atoms; and 
x has a value from 2 to 6. 
Examples of such organosilanes that may be used as the organosilane 
component of the present invention include the following: 
3,3'-bis(trimethoxysilylpropyl) disulfide, 
3,3'-bis(triethoxysilylpropyl) tetrasulfide, 
3,3'-bis(trimethoxysilylpropyl) tetrasulfide, 
2,2'-bis(triethoxysilylethyl) tetrasulfide, 
3,3'-bis(trimethoxysilylpropyl) trisulfide, 
3,3'-bis(triethoxysilylpropyl)trisulfide, 
3,3'-bis(trimethoxysilylpropyl) hexasulfide, 
2,2'-bis(methoxydiethoxysilylethyl) tetrasulfide, 
2,2'-bis(tripropoxysilylethyl) pentasulfide, 
bis(trimethoxysilylmethyl) tetrasulfide, 
2,2'-bis(methyldimethoxysilylethyl) trisulfide, 
2,2'-bis(methylethoxypropoxysilylethyl) tetrasulfide, 
5,5'-bis(dimethoxymethylsilylpentyl) trisulfide, 
3,3'-bis(trimethoxysilyl-2-methoxypropyl) tetrasulfide 
5,5'-bis(triethoxysilylpentyl) tetrasulfide, 
4,4'-bis(triethoxysilylbutyl) tetrasulfide, 
3,3'-bis(diethoxymethylsilylpropyl) trisulfide, and 
bis(triethoxysilylmethyl) tetrasulfide. 
Still more preferably, the organosilane component is comprised of one or 
more organosilanes having the formula: 
EQU (C.sub.2 H.sub.5 O).sub.3 Si--R.sub.3 --Sx.sub.1 --R.sub.3 --Si (OC.sub.2 
H.sub.5).sub.3 
where R.sub.3 is an alkylene having one to four carbon atoms and X.sub.1 
has a value of 2 to 4. Still more preferably, the organosilane component 
is comprised of TESPT, having CAS No. 40372-72-3. A suitable TESPT is sold 
by the Degussa Corporation under the tradename Si-69. 
As used herein, the term "powderizing agent" shall mean a material that 
operates as an inert carrier to render a liquid into a solid. The 
powderizing agent of the present invention renders the coupling agent into 
solid form. Preferably, the powderizing agent component is synthetic 
calcium silicate, such as is sold by the Celite Corporation under the 
tradename Micro-Cel E. Less preferably, the powderizing agent component is 
precipitated hydrated amorphous silica, such as is sold by PPG Industries 
under the tradename Hi-Sil ABS. Less preferably, other absorbents or 
powderizing agents can be used. 
As used herein, the term "fatty acid dispersion aid" means a composition 
having a fatty acid component and a salt-forming agent. The fatty acid 
dispersion aid of the present invention preferably has 2.73 parts, less 
preferably 1.9 to 3.5 parts, less preferably 1.2 to 8.6 parts by weight of 
the fatty acid component per 1 part by weight of the salt-forming agent. 
When combined together, the fatty acid component and the salt-forming 
agent form a metallic soap or salt. The fatty acid dispersion aid of the 
present invention renders the coupling agent into solid form, disperses 
the organosilane component in the rubber, disperses the siliceous filler 
in the rubber, reduces the viscosity of the vulcanizable rubber compound, 
and otherwise improves the processing characteristics of the vulcanizable 
rubber compound. 
Preferably, the fatty acid component is comprised of one or more fatty 
acids having 7-22 carbon atoms, more preferably 14-20 carbon atoms. Still 
more preferably, the fatty acid component is comprised of one or more 
fatty acids selected from the group consisting of tall oil fatty acid, 
oleic acid, palmitic acid, and stearic acid. It has been found that tall 
oil fatty acid reacts best with the salt-forming agent. Tall oil fatty 
acid, however, is dark, which is undesirable in some applications. 
Accordingly, it is preferred to lighten the color of tall oil fatty acid 
with stearic acid to preferably yield a light tan color. Thus, it is more 
preferred that the fatty acid component is a combination of 33%, less 
preferably 20-45%, less preferably 15-60% tall oil fatty acid, and 67%, 
less preferably 55-75%, less preferably 40-85% stearic acid. A suitable 
tall oil fatty acid is sold by Arizona Chemical under the tradename FA-3, 
while a suitable stearic acid is sold by Chemical Associates. 
Preferably, the salt-forming agent is comprised of one or more metallic 
compounds. The salt-forming agent is more preferably comprised of one or 
more metallic compounds containing calcium, zinc, aluminum, or magnesium, 
or less preferably, cadmium, barium, potassium, or sodium. Still more 
preferably, the salt-forming agent is comprised of 100% zinc oxide, or 
100% calcium carbonate. Still more preferably, the salt-forming agent is a 
combination of 51%, less preferably 40-60%, less preferably 21-79%, 
calcium carbonate, and 49%, less preferably 40-60%, less preferably 21-79% 
zinc oxide. A suitable calcium carbonate is sold by Akrochem under the 
tradename A-1 Whiting, while a suitable zinc oxide is sold by North 
American Oxides. 
In addition to the fatty acid component and the salt-forming agent, the 
fatty acid dispersion aid may also optionally include a wax component 
and/or an antioxidant component. 
When the wax component is included in the fatty acid dispersion aid, the 
fatty acid dispersion aid preferably has 11.44 parts, less preferably 9 to 
20 parts, less preferably 7 to 32 parts by weight of the fatty acid 
component and the salt-forming agent per 1 part by weight of the wax 
component. The wax component increases the lubricity of the vulcanizable 
rubber compound and is comprised of one or more petroleum waxes. 
Preferably, the wax component is petrolatum, such as is sold by C.P. Hall 
under the tradename Petrolatum SR-172. Less preferably, the wax component 
is comprised of one or more low-melting point paraffin waxes having a 
melting point in a range of 125-157.degree. F., such as are sold by C.P. 
Hall. 
When the antioxidant component is included in the fatty acid dispersion 
aid, the fatty acid dispersion aid preferably has 183 parts, less 
preferably 113 to 285 parts, less preferably 43 to 387 parts by weight of 
the fatty acid component and the salt-forming agent per 1 part by weight 
of the antioxidant component. The antioxidant component retards the 
oxidation of the vulcanizable rubber compound. Preferably, the antioxidant 
component is butylated hydroxy toluene (C.sub.5 H.sub.4 O), which is 
available from Akrochem. Less preferably, the antioxidant component is a 
mixture of octylated diphenylamines, such as is sold by R.T. Vanderbilt 
under the tradename AgeRite Stalite. 
When the wax component and antioxidant component are included in the fatty 
acid dispersion aid, the fatty acid dispersion aid has the following 
preferred formulation (Formulation 2). 
______________________________________ 
Weight Percent 
Component Preferred 
Less Preferred 
Less Preferred 
______________________________________ 
1. Fatty Acid 67 46-76 25-86 
2. Wax 8 6-10 3-12 
3. Salt-Forming Agent 24.5 17-32 10-40 
4. Antioxidant .5 .38-1.25 .25-2 
______________________________________ 
The fatty acid dispersion aid may be prepared and then stored until it is 
used in the preparation of the coupling agent. When the wax component and 
antioxidant component are included in the fatty acid dispersion aid and 
the preferred constituency of components is used, the fatty acid 
dispersion aid is preferably prepared in advance as follows. 
A mixing reactor vessel with a suitable capacity and a mixing device is 
selected. The reactor vessel is pre-heated to a temperature of about 
280.degree. to 300.degree. F. The tall oil fatty acid is added to the 
reactor vessel and is mixed at a speed of about 80 rpm until the tall oil 
fatty acid reaches the temperature of the reactor vessel. The stearic acid 
is then added to the reactor vessel and blended with the tall oil fatty 
acid, while the temperature is maintained above 260.degree. F. The zinc 
oxide is slowly added to the reactor vessel and mixed with the fatty acids 
for about 1 hour. Afterwards, the wax component is added to the reactor 
vessel and blended with the other components for about 10 minutes. The 
antioxidant component is added and blended for about 10 minutes, and then 
the calcium carbonate is added and blended for about 45 minutes. The 
resulting mixture of components is then preferably pastillated, i.e., 
extruded in small droplets, onto a cooling belt to complete the formation 
of the fatty acid dispersion aid. Alternately, the mixture of components 
can be pelletized under water, or flaked. The mixing and subsequent 
pastillating, pelletizing, or flaking of the components can be done in a 
continuous system such as a mixing extruder, or other continuous system 
known in the art. 
When formed in the manner described above using Formulation 2, the fatty 
acid dispersion aid is a light tan to light brown in color, and is in the 
form of flakes. The fatty acid dispersion aid has a softening point around 
230.degree. F., less preferably 225.degree.-235.degree., an ash content of 
about 20%, less preferably 19-21%, and a specific gravity of about 1.20, 
less preferably 1.15-1.25. 
The coupling agent of the present invention is preferably formed as 
follows. A mixing reactor vessel with a suitable capacity and a mixing 
device is selected. The reactor vessel is pre-heated to a temperature of 
about 200.degree. to 230.degree. F. The fatty acid dispersion aid is added 
to the reactor vessel and allowed to heat. Once the fatty acid dispersion 
aid has softened, the mixing device is activated so as to mix the 
dispersion aid at about 70-80 rpm. The organosilane component is then 
slowly added to the reactor vessel and mixed for about fifteen minutes. 
Afterwards, the mixture of the fatty acid dispersion aid and the 
organosilane component is allowed to cool. 
Once the mixture of the fatty acid dispersion aid and the organosilane 
component has cooled to the ambient temperature, the mixture is placed in 
a double blade mixer adapted for blending powders or pastes. Preferably, 
the double blade mixer is a sigma-type mixer. The powderizing agent is 
added to the double blade mixer and is mixed at a speed of about 60 rpm 
until a uniform, non-dusting powder is obtained, which generally takes 
about 5 minutes. At this point, the formation of the coupling agent is 
complete. 
When formed in the manner described above, using Formulation 1, and with 
the preferred constituency of components, the coupling agent is a light 
gray powder. The coupling agent preferably has an ash content of about 
20%, less preferably 19-21%, and a specific gravity of preferably about 
1.15, less preferably about 1.11 to 1.19. 
Preferably, the vulcanizable rubber compound to which the coupling agent is 
added includes rubber selected from the group consisting of natural 
rubbers, synthetic rubbers, and mixtures thereof. The synthetic rubbers 
are preferably styrene-butadiene rubber, isobutylene-based rubbers such as 
butyl rubber, halobutyl rubber, and isobutylene-paramethylstyrene 
copolymer rubber, polychloroprene rubber, polybutadiene rubber, 
polyisoprene rubber, EPDM rubber, and nitrile rubber. Less preferably, the 
synthetic rubbers are acrylic, chlorinated polyethylene, epichlorohydrin, 
ethylene/acrylic, EPM, isoprene-acrylonitrile, polyisobutylene, 
polynorbornene, and styrene-isoprene. 
Preferably, the vulcanizable rubber compound to which the coupling agent is 
added also includes siliceous filler selected from the group consisting of 
silicas, silicates, compounds containing silicas, compounds containing 
silicates, and mixtures thereof. Examples of suitable siliceous filler 
include: highly dispersed silica (silicon dioxide); oxide mixtures 
containing silicas and metal oxides, such as alumina, magnesium oxide, 
calcium oxide, barium oxide, zinc oxide, zirconium dioxide, and titanium 
dioxide; synthetic silicates such as aluminum silicate, magnesium 
silicate, and calcium silicate; natural silicates, such as kaolin, 
wallastonite, talc, and asbestos; natural silicas, such as quartz, sand, 
and kieselguhr; glass fibers, glass fiber products such as mats, webs, 
strands, fabrics, and microglass balls. 
Preferably, the vulcanizable rubber compound has about 70 parts, less 
preferably 50-90 parts by weight of the siliceous filler per 100 parts by 
weight of rubber. 
In addition to the coupling agent, the rubber, and the siliceous filler, 
the vulcanizable rubber compound of the present invention may include 
other types of fillers and reinforcing materials, such as carbon black, as 
well as accelerators, retarders, activators, vulcanizers, antioxidants, 
antiozonants, plasticizers, processing aids, stabilizers, tackifiers, 
extenders, blowing agents, lubricants, polymerization materials, and other 
rubber compounding materials known in the art. 
The coupling agent of the present invention is used by adding it to the 
vulcanizable rubber compound the way other known coupling agents are added 
to siliceous rubber compounds, i.e., vulcanizable rubber compounds 
containing siliceous material. Preferably, the coupling agent is added to 
the vulcanizable rubber compound in an amount so there are about 6.25 
parts, less preferably 3-8 parts by weight of the organosilane component 
per 70 parts by weight of the siliceous filler. Thus, there is preferably 
12.5 parts, less preferably 7-15 parts, less preferably 2-17 parts by 
weight of the coupling agent per one hundred parts rubber. 
The coupling agent of the present invention can be used in many different 
types of siliceous rubber compounds. The coupling agent finds particular 
utility in siliceous rubber compounds used for building tires, such as 
tire treads, carcasses, innerliners, sidewalls, and sidewall components. 
The coupling agent is also useful in siliceous rubber compounds for 
coating stocks, hoses, belting, inner tubes, general purpose rubbers, and 
other synthetic and natural elastomers. 
The coupling agent of the present invention provides many advantages. When 
added to the vulcanizable rubber compound, the coupling agent disperses 
the siliceous filler and associates the siliceous filler with the rubber, 
thereby enhancing the rubber reinforcement aspect of the siliceous filler. 
In addition, the coupling agent reduces the viscosity, enhances the mold 
flow properties, and otherwise improves the processing characteristics of 
the vulcanizable rubber compound. 
In addition to improving the characteristics of the vulcanizable rubber 
compound, the coupling agent is in solid form, which provides the coupling 
agent with favorable handling characteristics and makes the coupling agent 
suitable for use in processes utilizing automatic weighing systems. 
The following Examples further illustrate various aspects of the invention. 
Unless otherwise indicated, the ingredients are combined using methods 
known in the art or as described above.

EXAMPLE 1 
A coupling agent was prepared in accordance with the preferred embodiment 
of the present invention by mixing 50 parts TESPT, 20 parts synthetic 
calcium silicate, and 30 parts of the fatty acid dispersion aid (comprised 
of 6.6 parts tall oil fatty acid, 13.5 parts stearic acid, 2.4 parts 
petrolatum, 3.75 parts calcium carbonate, 3.6 parts zinc oxide, and 0.15 
parts butylated hydroxy toluene). The coupling agent with the foregoing 
formulation shall hereinafter be referred to as the "Inventive Compound". 
A Control Batch, a Batch A, a Batch B, and a Batch C of tire tread were 
prepared pursuant to identical formulations, except for different amounts 
of the Inventive Compound, X50-S, a Processing Aid, and N-330 carbon 
black. X50-S is sold by the Degussa Corporation and is a mixture of Si69 
(TESPT) and N-330 carbon black in a proportion of 1:1 by weight. The 
Processing Aid is a mixture comprised of (by weight) 22 parts tall oil 
fatty acid, 45 parts stearic acid, 8 parts petrolatum, 12.5 parts calcium 
carbonate, 12 parts zinc oxide, and 0.5 parts butylated hydroxy toluene. 
The Control Batch, Batch A, Batch B, and Batch C were prepared pursuant to 
the following formulation, where the amounts are in parts: 
______________________________________ 
Ingredient Control A B C 
______________________________________ 
SBR D-706 Styrene 
70.00 70.00 70.00 70.00 
Butadiene Rubber 
Budene 1207 30.00 30.00 30.00 30.00 
Polybutadiene Rubber 
N110 Carbon Black 5.00 5.00 5.00 5.00 
Z1165 Silica 70.00 70.00 70.00 70.00 
X50-S 12.50 12.50 0.00 0.00 
Inventive Compound 0.00 0.00 12.50 12.50 
Processing Aid 0.00 3.75 0.00 0.00 
N330 Carbon Black 0.00 0.00 0.00 5.00 
VANOX 1030 1.00 1.00 1.00 1.00 
Antioxidant 
240 Paraffin Wax 1.00 1.00 1.00 1.00 
6PPD Antiozonant 1.50 1.50 1.50 1.50 
Zinc Oxide 3.00 3.00 3.00 3.00 
Stearic Acid 1.00 1.00 1.00 1.00 
PEG-400 Lubricant 2.00 2.00 2.00 2.00 
SUNDEX 790 Aromatic 20.00 20.00 20.00 20.00 
Oil 
DPG Accelerator 2.00 2.00 2.00 2.00 
CBTS Accelerator 1.60 1.60 1.60 1.60 
Sulfur 1.60 1.60 1.60 1.60 
Total Weight 222.20 225.95 222.20 227.20 
______________________________________ 
The Control Batch, Batch A, Batch B, and Batch C were each prepared in a 
laboratory Brabender internal mixer having an initial temperature of 
176.degree. F. In each batch, a rotor speed of 60 rpm was used. Except as 
specifically noted, the following sequential procedure was followed in 
each of the batches. In a first stage, the styrene butadiene rubber, the 
polybutadiene rubber, and the zinc oxide were premasticated for about 1 
minute. The N110 carbon black, 50% of the Z1165 silica, the stearic acid, 
the Sundex 790, and the PEG 400 were then added. In addition, in the 
Control Batch and Batch A, 50% of the X50-S was added, whereas in Batch B 
and Batch C, 50% of the Inventive Compound was added. In Batch A, the 
Processing Aid was also added, while in Batch C, the N330 carbon black was 
also added. The components were then mixed for about 1 minute. The Vanox 
1030, the 240 paraffin wax, the 6PPD antiozonant, the remaining 50% of the 
Z1165 silica, and the remaining 50% of the X50-S in the Control Batch and 
Batch A, and the remaining 50% of the Inventive Compound in Batch B and 
Batch C were added and mixed for about 1 minute. The components were 
observed for silica dispersion and surface quality, and then discharged at 
a temperature in a range of about 266.degree.-284.degree. F. A 40 gram 
sample was taken for viscosity measurement. The components were then 
placed on a two roll mill and cross-cut 5 times in each direction. 
In a second stage, the components were placed back into the Brabender 
internal mixer and mixed until the temperature of the components reached a 
temperature in a range of about 266.degree.-284.degree. F. The components 
were observed for silica dispersion and surface quality, and then 
discharged. Another 40 gram sample was taken for viscosity measurement. 
The components were then placed on a two roll mill and cross-cut 5 times 
in each direction. 
In a third stage, when the components cooled to ambient temperature, the 
components were placed back into the Brabender internal mixer. The sulfur, 
the DPG accelerator, and the CBTS accelerator were then added and all the 
components mixed until the components reached a temperature of about 
230.degree. F. The components were again placed on a two roll mill and 
cross-cut 5 times in each direction. 
The Control Batch, Batch A, Batch B, and Batch C were cured for 90 minutes 
at about 320.degree. F. and then allowed to sit at room temperature for 
about 24 hours. The batches were then tested in accordance with ASTM 
methods, with the following results. 
______________________________________ 
Physicals 
Control A B C 
______________________________________ 
Durometer (points) 
80 79 79 79 
100% Modulus (psi) 580 565 550 590 
300% Modulus (psi) 2060 2040 2035 2180 
Elongation (%-break) 390 400 405 395 
Tensile (psi) 2863 2840 2800 2905 
Tear C (psi) 330 323 325 323 
______________________________________ 
The Control Batch, Batch A, Batch B, and Batch C were also tested as to how 
well they flowed through a mold during compression molding. The 
measurements were taken 30 minutes after molding to allow for post-mold 
shrinkage. 
______________________________________ 
Mold Flow 
Control A B C 
______________________________________ 
Flow Distance (mm) 
76.5 85.5 88.0 87.0 
______________________________________ 
The viscosities of the samples taken from the Control Batch, Batch A, Batch 
B, and Batch C during stages 1 and 2 were measured after the samples had 
cooled at room temperature for about 1 to about 1.25 hours. The 
viscosities of the finished tire treads of the Control Batch, Batch A, 
Batch B, and Batch C were also measured at an initial period of time, at 
72 hours, and at 168 hours. Values were recorded at an initial peak and at 
four minutes. The viscosities were measured using a rheometer at a 
temperature of 320.degree. F. for 30 minutes. The motor of the rheometer 
had a 100 inch-lb torque range and a 30 arc. 
______________________________________ 
Viscosities 
initial/4 min 
Control A B C 
______________________________________ 
Stage 1 154.5/126.0 
118.0/96.0 
105.0/91.0 
105.5/91.0 
Stage 2 147.5/127.0 84.5/72.5 61.0/51.5 80.0/67.5 
Initial 117.0/79.0 60.0/59.5 50.0/40.0 55.0/44.0 
72 hours 109.0/64.5 68.5/49.0 57.5/45.0 61.0/46.0 
168 hours 108.5/64.5 70.5/49.0 59.0/45.0 61.5/45.5 
Mixing Amps 16.00 14.25 13.00 13.25 
Stage 1 
Mixing Amps 15.50 14.00 12.75 13.00 
Stage 2 
______________________________________ 
As set forth above, the Control Batch, Batch A, Batch B, and Batch C were 
observed after mixing in the first and second stages for silica dispersion 
and surface quality. The batches were visually inspected by two qualified 
laboratory technicians who independently rated each batch on a scale of 
poor "P", fair "F", good "G", or very good "VG". When the ratings of the 
technicians differ, both of their ratings are provided. 
______________________________________ 
Silica Dispersion and Surface Quality 
Control A B C 
______________________________________ 
Dispersion - Stage 1 
P F/G G G 
Dispersion - Stage 2 P/F G G/VG G/VG 
Surf. Qual - Stage 1 P/F F/G G G 
Surf. Qual - Stage 2 P/F G G/VG G/VG 
______________________________________ 
As indicated by the above results, the coupling agent of the present 
invention alone (Batch B) and with the N330 carbon black (Batch C) 
provides better processing characteristics than the X50-S alone (Control 
Batch) and with the Processing Aid (Batch A). More specifically, the 
coupling agent alone and with the N330 carbon black has better silica 
dispersion and surface quality, less viscosity and mixing energy, and 
greater mold flow than the X50-S alone and with the Processing Aid. Thus, 
the coupling agent of the present invention can be used in place of a 
TESPT/carbon black mixture in those formulations where a TESPT/carbon 
black mixture is presently used. These results are surprising and 
unexpected. 
While the invention has been shown and described with respect to particular 
embodiments thereof, those embodiments are for the purpose of illustration 
rather than limitation, and other variations and modifications of the 
specific embodiments herein described will be apparent to those skilled in 
the art, all within the intended spirit and scope of the invention. 
Accordingly, the invention is not to be limited in scope and effect to the 
specific embodiments herein described, nor in any other way that is 
inconsistent with the extent to which the progress in the art has been 
advanced by the invention.