Treated clay product, methods of making and using and products therefrom

An improved finely divided rubber-reinforcing clay mineral composition can be produced by employing a hydrous kaolin clay surface treated with a functional silane, a methylene donor compound such as hexamethylenetetramine, and a multifunctional methylene acceptor such as resorcinol. A novel process of preparation is provided. The improved reinforcing, treated clay filler can be combined with natural or synthetic elastomer compositions which can be cured to elastomer products which have improved physical properties, such as modulus, tensile, tear, wear resistance and/or resistance to heat build-up.

FIELD OF THE INVENTION 
The present invention is directed to surface treated clays that contain a 
multi-component treatment modification consisting of a functional silane, 
a methylene donor and a methylene acceptor for use in natural or synthetic 
rubber systems as a reinforcing filler or extender. 
BACKGROUND ART 
In the prior art, the use of surface treated clays, such as silane treated 
kaolin clays, as reinforcing fillers for polymers or elastomerics is 
known. Typically, silane treated clays employing sulfur functional silanes 
are utilized in sulfur cured elastomeric systems requiring properties such 
as high tensile strength, high modulus or the like. Organo-functional 
silane treatments used on clays or other mineral fillers are often used 
alone or sometimes in combination with other silanes, such as 
alkylsilanes, but generally not in combination with other non-silicon 
based reinforcement additives. For example, U.S. Pat. Nos. 4,810,578 and 
5,116,886 describe the pre-treatment of hydrous kaolin clays and oxide or 
silicate fillers with a sulfur-functional silane for use as a reinforcing 
filler in elastomers. Sulfur cured elastomers containing reinforcing 
fillers are often found in automotive applications such as tires (e.g., 
carcass, innerliner, tire tread and white sidewalls), belts, hoses or the 
like. 
Outside the scope of treated clay fillers, it is also well known to use 
resorcinol-formaldehyde (R-F) resins or combinations of resorcinol (a 
methylene acceptor) and hexamethylenetetramine (a methylene donor that 
will hereinafter be referred to as hexa) as direct chemical additives to 
rubber compounds to promote good adhesion properties, particularly in 
connection with adhering cords of fabric to rubber stock. The technology 
of building reinforcing cords of fabric into rubber articles is an 
essential aspect of many modern rubber applications. In particular, the 
use of R-F type resins (or its resorcinol/hexa precursors) along with the 
addition of silica fillers has found utility in many elastomeric 
applications for adhesion promotion as described in U.S. Pat. Nos. 
3,738,948 and 4,782,106. 
In U.S. Pat. No. 3,738,948 to Dunnom, a fiber reinforced rubber composition 
employing a vulcanization product comprising a finely-divided reinforcing 
siliceous filler, a methylene donor compound such as 
hexamethylenetetramine, a multifunctional phenol such as resorcinol and a 
compatible metal soap such as calcium stearate is disclosed. This patent 
recognizes that fiber reinforcement such as textile mats can be made to 
adhere to rubber compositions and particularly rubber tires by the use of 
an adhesive mixture comprising a finely-divided precipitated siliceous 
filler, a methylene donor compound and a polyfunctional phenol. One of the 
problems with these mixtures is the degradation of the hexamethylene 
compound to reaction products which attack the fibers of the textile mats. 
The Dunnom patent overcomes this problem by incorporating a metal soap 
into the rubber matrix. 
U.S. Pat. No. 4,782,106 to Fricke, et. al. is another example of a rubber 
adhesive mixture using an adhesive system of 
resorcinol/hexamethylenetetramine with a carbon black filler. This patent 
does not teach nor suggest a treated clay composition comprising these 
chemical additives in combination with a functional silane as a 
reinforcing filler nor the unexpected benefits associated therewith. 
With ever increasing competition in the elastomer industry, more and more 
applications are being developed which need high levels of reinforcement, 
either in terms of modulus, tensile strength, tear or compression set. To 
date, silica or carbon black fillers have been the only types of fillers 
which could provide the desired level of reinforcement in elastomers. For 
example, rubber formulations commonly referred to as "green tire" 
formulations have been developed for fabricating tire tread. These tire 
tread formulations, as described in U.S. Pat. No. 5,227,425 have greatly 
improved physical properties and offer low rolling resistance but require 
large amounts of silica and carbon black. 
Although carbon black and silica offer high levels of reinforcement in 
elastomers, both of these filler systems are not without their 
disadvantages. Carbon black generally cannot be used in applications 
wherein the elastomer compound needs to be pigmented (i.e., white or 
non-black). In addition, a very fine particle size carbon black is needed 
to provide high levels of reinforcement and these carbon blacks can be 
extremely expensive. Further, in many tire related applications carbon 
blacks are known to contribute to higher heat build-up properties, as 
compared to clays, which can have deleterious effects on the service life 
of the tire. 
Using a precipitated or fumed silica as a filler also contributes greatly 
to the cost of the compound since these silicas are often extremely 
expensive on a per pound basis. Moreover, they are difficult to process in 
elastomeric systems. Since silica fillers have extremely high surface 
areas, they are highly absorptive. When mixed with a given elastomeric 
compound, the silicas tend to absorb the oils, plasticizers or the like in 
the compound and make it difficult to mix the compound. This 
characteristic can often lead to poor filler dispersion thereby reducing 
expected physical properties. The use of high levels of precipitated 
silica in tire tread compounds provides excellent rolling resistance and 
good traction properties, but it is also known to cause the build-up of 
undesirable static charge such that they require the co-use of other 
semi-conductive fillers. Ideally, these replacement fillers should have 
virtually no deleterious effects on rolling resistance and rubber physical 
properties as compared to silica. Nevertheless, if one were seeking to 
produce a non-black filled elastomeric compound having a high level of 
reinforcement, silica and its attendant disadvantages has historically 
been the only filler choice. 
In addition to the combined use of silicas and R-F systems in rubber for 
adhesion, silicas have been used with or pre-treated with silanes for 
application in elastomer systems. For example, U.S. Pat. No. 5,008,305 
describes a reinforcing silica for use in silicone elastomers. The 
reinforcing silica is prepared by treating the dry silica with a 
combination of both phenylalkoxysilane and vinylalkoxysilane. This 
combination of surface treatment improves compression set and heat aging 
in silicone elastomers. This prior art differs from the present invention 
in the use of a treated silica as the reinforcing agent (as opposed to a 
treated hydrous clay) and that both phenyl and vinyl functional silanes 
are added to the silica in pure form rather than as emulsions. 
Furthermore, a blend of silanes was required in this prior art composition 
as opposed to the use of our 3 component surface treatment package 
consisting of a single functional silane, a methylene donor and a 
methylene acceptor. Similarly, U.S. Pat. No. 4,714,733 describes a rubber 
composition containing an ethylene-propylene rubber, an organopolysiloxane 
having at least two alkenyl groups per molecule, a silica filler, an 
alkoxysilane, and a thiocarbamyl-containing organosilane. This prior art 
composition exhibits improved compression set and heat aging, but does not 
use the unique surface treatment combination of the present invention. 
Heretofore, silane treated clays have had limited utility in elastomeric 
applications requiring high performance because of their relatively low 
reinforcing benefits. Their ability to replace or extend high performance 
fillers, such as carbon black or silica, has been modest at best. Known 
silane treated clays for use in elastomer systems not requiring high 
performance include the Nucap.RTM. and Nulok.RTM. clays manufactured by J. 
M. Huber Corporation of Macon, Ga. The Nucap.RTM. silane treated clays use 
a sulfur functional silane in treatment levels up to about 0.5% by weight 
of the silane based on dry clay. Exemplary of these sulfur functional 
silanes include a mercapto-silane, a thiocyanato-silane or a bridging 
tetrasulfane silane. The Nucap.RTM. treated clays are therefore mainly 
targeted for use in sulfur-cured rubber systems. In comparison, the 
Nulok.RTM. treated clays utilize various amino functional silanes in 
treatment levels up to about 1.0% by weight and these fillers are used in 
both sulfur-cured and peroxide-cured compounds although more predominantly 
in the latter. These Nucap.RTM. and Nulok.RTM. products, and their 
competitive counterparts, can be based on kaolin clay substrates ranging 
from fine particle size waterwashed clays, to waterwashed delaminated 
clays of relatively coarse particle size to various air-float clays. 
Up to the present, it was well recognized that increasing the amount of 
sulfur functional silanes on the clay did not necessarily increase the 
various performance properties of a given elastomeric system in a 
proportional manner. Diminishing incremental performance benefits are 
provided as silane treatment levels are increased. Thus, the silane 
treatments have been held to the levels noted above, e.g., about 0.5% by 
weight and below based on cost/performance considerations. 
Besides the inability to provide a high level of performance in elastomeric 
systems, clay or current treated clays have also presented a problem in 
regards to their inherent higher specific gravity than that of silica or 
carbon black. The specific gravity of kaolin clay is 2.6 whereas the 
specific gravity of silica is about 2.0 to 2.2. Carbon black's specific 
gravity is about 1.8. In rubber compounds where density is critical, a 
treated clay cannot be substituted for carbon black or silica on a one to 
one weight basis while still meeting the density requirements. In other 
words, less clay must be used than a given phr amount of carbon black or 
silica to meet the density requirement. In addition, the reduced weight 
amount of clay must still be able to impart the same filler performance 
characteristics as the carbon black or silica. Conversely, if the filled 
rubber compounds are to be formulated to yield equal hardness then about 
1.6 parts of clay or treated clay are normally required to replace every 1 
part of carbon black while needing to still maintain other physical 
properties like modulus, tensile strength and tear. At a weight ratio of 
1.6/1, this puts treated clays at a cost/performance disadvantage as 
extenders for larger particle size carbon blacks, i.e., soft carbon 
blacks, unless the treated clays provide a very high level of performance. 
In view of the disadvantages noted above with presently available treated 
clay products as well as the limitations of silica and carbon black as 
fillers in elastomeric systems, a need has developed to provide a treated 
clay product which can be used as a highly effective reinforcement for 
elastomeric systems. 
The present invention solves this need by providing a method of making a 
surface treated clay consisting of a three component surface treatment 
system comprising a functional silane, a methylene donor, and a methylene 
acceptor, and the product therefrom and, in one preferred embodiment, the 
use of an emulsified functional silane. The treated product resulting 
therefrom can be used as a reinforcing filler or extender in elastomeric 
systems to achieve high performance characteristics. 
It should be noted that silanes have been used in dispersed or emulsified 
form in applications other than those employing clays. Patent JP-06285363 
describes the production of hydrophobic fine particles of an inorganic 
compound (more specifically particles of TiO2 pigment) by combining an 
aqueous dispersion of the inorganic compound with surfactant and 
alkylsilane for the purpose of obtaining a silicone polymer coating on the 
surface of fine powders. While the above patent describes a hydrophobic 
inorganic fine particle composition and a process to produce such a 
composition, the compositions of this present invention differ from the 
above by our demonstrated examples of unexpectedly high gains in cured 
elastomer reinforcing properties using significantly lower levels of 
silane treatments which are outside the scope of this prior art. In 
addition, the focus of this prior art was on the use of non-functionalized 
alkylsilanes as opposed to the functional silanes utilized in the present 
invention. 
The technique of using an amino functional silane emulsion to treat an 
aqueous mineral slurry is described in U.S. Pat. No. 4,525,281. The 
treated mineral has improved dewatering properties. As with the current 
invention, a mineral is treated with a silane emulsion. However, the 
effective silanes of this present invention are sulfur as well as amino 
functional silanes which are required to chemically interact with both the 
kaolin clay and the elastomer. The unexpectedly high elastomer 
reinforcement benefits of the current invention could not have been 
predicted from the dewatering benefit described by the prior art. 
A silane emulsion is described in U.S. Pat. No. 4,937,104 which is useful 
for making building material surfaces hydrophobic. The emulsion consists 
of an alkyltrialkoxysilane in aqueous alcohol. Although this prior art and 
the current invention use silane emulsions for surface treatment, the 
current invention requires functional silanes to achieve the reinforcing 
properties in elastomers. Further, the observed hydrophobicity benefit in 
the prior art is unrelated to the reinforcing properties observed in the 
current invention. 
While the prior art recognizes the use of methylene donors and acceptors as 
adhesion promoters in rubber formulations, it does not teach nor suggest 
their use in clay surface treatment systems (particularly not in the 
presence of a functional silane treatment). The closest related art to the 
present invention is that disclosed by Pochert, et. al. in U.S. Pat. No. 
3,957,718. This patent teaches that adding an organosilane to a silica 
containing mixture can improve the adhesion of vulcanizable mixtures of 
natural and/or synthetic rubber to reinforcing fillers or supports of 
textiles and/or metallic fabrics after vulcanization. This adhesion 
benefit can be provided by a mixture which substantially consists of a 
synthetic silica or silicate filler of high BET surface area of about 50 
to 500 m.sup.2 /g, a combination of resin forming components such as 
phenols plus formaldehyde donors and at least one sulfur-functional 
silane. In a further aspect of Pochert et al., it is also disclosed that 
the resin forming components can be pre-bound to the fillers by absorption 
prior to being mixed into the elastomer which reportedly yields 
substantially better distribution of these reactants and further increases 
adhesion. While this prior art composition utilizes a combination of 
silica, a methylene donor, a methylene acceptor and a sulfur-functional 
silane, it does not teach the pre-treatment of a silicate filler with all 
three chemical additives nor does it teach the utilization of a kaolin 
clay. Pochert et al. does not teach nor suggest that a combination of 
resorcinol, hexa and silane with a low surface area clay are particularly 
useful for improving rubber reinforcement properties such as modulus, 
tensile strength or tear but are instead useful for improving adhesion 
properties. One of the principal objects of the present invention was to 
provide a treated clay filler that provides a high level of modulus 
reinforcement comparable to that provided by soft carbon blacks and 
silicas. 
In summary, the prior art does not teach the use of methylene donors and 
acceptors in clay systems. Furthermore, the prior art does not teach the 
unexpected improvements obtained when these compounds are used in 
conjunction with a functional silane as a three component clay surface 
treatment system in terms of providing modulus, tear and improved dynamic 
properties such as rolling resistance and lower heat build-up. The prior 
art also fails to recognize the improvements achieved according to the 
invention in terms of how the form of the reagents and methods of 
treatment determine treated clay stability and performance thereof. 
SUMMARY OF THE INVENTION 
Accordingly, it is a first object of the present invention to provide a 
clay product surface treated with a functional silane, a methylene donor 
and a methylene acceptor which can be used as a reinforcing filler or 
extender for elastomeric systems. The treated clay of the present 
invention is especially well suited to use as a reinforcing filler for 
natural and synthetic rubbers because the available pendant functional 
group (an amine or sulfur containing group) on the treated clay chemically 
reacts with the polymer backbone during the curing process to yield 
cross-linking between the clay and the polymer. Synthetic rubber, isoprene 
rubber (IR), nitrile butadiene rubber (NBR), ethylene-propylene rubber 
(EPDM), styrene butadiene rubber (SBR), neoprene (CR) and polybutadiene 
rubber (BR) are examples of different elastomers that can be reinforced 
with the inventive treated clay. The elastomeric systems can be sulfur 
cured, peroxide cured or metal oxide cured, but are preferably sulfur 
cured. 
Another object of the present invention is to provide treated clay products 
that yield superior filler reinforcement properties in rubber relative to 
conventional treated clays (like the various Nucap.RTM. and Nulok.RTM. 
clays) The performance benefits to be provided include higher tensile 
strength, modulus and tear properties, lower rolling resistance, lower 
heat build- up or improved compression set depending on the particular 
clay/silane combination used with a given natural or synthetic rubber 
polymer. Hence, a further object of the invention is to provide high 
performance treated clays having the ability to totally or partially 
replace soft carbon black or silica fillers in various elastomeric 
applications on a cost/performance basis. The ability to provide carbon 
black-like performance properties in white or non-black rubber 
applications is greatly desired. Yet another object of the invention is to 
provide treated clay products of high performance for use in sulfur cured 
and in metal oxide cured elastomer systems. 
Another object of the present invention is to provide a method of making a 
multi-component surface treated clay product that is useful for high 
performance elastomeric systems. 
A still further object of the present invention is an enhancement of the 
treatment of the clay using the methylene acceptors and donors and silane 
by using the minimal amount of a dispersant so as to affect caly slurry 
fluidity for processing while also maintaining a more positive overall 
surface charge value. 
One further object of the invention is to provide a rubber formulation, 
particularly a tire carcass, a tire wire belt coat, a tire apex, radiator 
hose, V-belt, innertube, or tire tread formulation, using the treated clay 
product of the invention. 
The clay starting material can be in the form of an aqueous slurry, a dry 
clay or a wet crude clay for multi-component treatment. For slurry 
treatment, it is preferred that the clay be in the form of a dispersed 
filter cake slurry of essentially neutral pH when treated with the three 
reagents of this invention. Preferably, at least the desired silane is in 
the form of an aqueous emulsion when added to the clay slurry to insure 
proper dispersion upon mixing with the clay so as to yield good surface 
treatment uniformity. For dry clays, it is preferred that the dry clay be 
charged to a solids/liquid mixer followed by addition of the three surface 
reagents under vigorous mixing conditions. For wet crude clays having a 
moisture content of about 20%, it is preferred that the crude clay is 
first pulverized to a small aggregate size and then conveyed into a mixer 
such as a pin mixer for combining with the three surface reagents prior to 
drying, milling and air classifying to a finished product. In both cases, 
at least the silane is again preferably in the form of an aqueous emulsion 
when mixed with the clay (dry or wet crude form) to insure proper wetting 
of the clay's surface with the treatment agent so as to yield good surface 
treatment uniformity. Finally, the ability to homogeneously treat 
waterwashed kaolin clays in slurry or dry clay form with such silane 
emulsions and the methylene donors and acceptors is another object of this 
invention. 
Other objects and advantages of the present invention will become apparent 
as a description thereof proceeds. 
In satisfaction of the foregoing objects and advantages, the present 
invention, in its broadest embodiment, comprises a hydrous kaolin clay 
surface treated with a functional silane in an amount between 0.1 and 5.0% 
by weight based on dry clay, a methylene donor in an amount between about 
0.1 and 5.0% by weight based on dry clay and a methylene acceptor in an 
amount between about 0.1 and 5.0% by weight based on dry clay. Preferably, 
the functional silane is a sulfur functional silane. The hydrous kaolin 
clay is one of a waterwashed kaolin clay having a fine particle size, or 
an air-float fine particle size clay. 
The methylene acceptor is preferably resorcinol with the methylene donor 
being preferably hexamethylenetetramine. 
In one method aspect of the invention, a hydrous kaolin clay slurry feed 
stock is prepared for the surface treatment with the functional silane, 
methylene donor and methylene acceptor by the steps of first obtaining a 
crude clay, preferably a crude kaolin clay. The crude clay is formed into 
a clay slurry via high shear blunging wherein a dispersant is utilized, 
preferably an inorganic dispersant. The dispersant amount is 
minimized/controlled to obtain a more positive zeta potential, e.g. 
preferably more positive than -22 millivolts, and more preferably, more 
positive than -16 millivolts when measured at a pH of 7 using zeta 
potential determination methods. In this way, the clay of the slurry has 
improved performance when treated according to the invention and used with 
elastomeric compounds. The inorganic dispersant is preferably sodium 
silicate, tetrasodium pyrophosphate, sodium tripolyphosphate, or sodium 
hexametaphosphate and ranges between 0 and 1.0% by weight based on dry 
clay. The clay slurry can be further beneficated to a dry form, e.g. 
degritted and fractionated and surface treated with the functional silane, 
methylene donor and methylene acceptor to form the treated clay product. 
Other known techniques can be used to prepare the clay for treatment. 
In another method aspect of the invention, the treated clay product is made 
by the steps of providing a crude clay and beneficating the crude clay to 
form a fine particle size clay. The fine particle size clay is surface 
treated by combining it with a functional silane, methylene donor and 
methylene acceptor to form the treated clay product. The surface treating 
step can comprise combining the functional silane, methylene donor and 
methylene acceptor with either a dry fine particle size clay or a slurry 
of the fine particle size clay. 
The functional silane, methylene donor and methylene acceptor can be in the 
form of a solution, an emulsion or neat prior to the combining step. 
The combining step can entail adding the functional silane, methylene donor 
and methylene acceptor to the dry clay in a liquid/solids mixer or to the 
clay slurry. In either case, the treated clay is then dried, preferably 
dried at sufficiently low temperatures and short residence times so as not 
to adversely affect the surface treatment on the clay. The surface 
treatment can be adversely affected by either partial volatilization of at 
least one of the three surface treatment reagents or by premature polymer 
forming reactions between the methylene donor and methylene acceptor. 
Polymer forming reactions are indicated by darkening of the treated clay 
color and/or fouling of the process equipment. 
In a preferred embodiment, the functional silane and methylene donor are 
combined together and kept separate from the methylene acceptor prior to 
their contact with the clay. Separation of the acceptor and donor avoid 
the possibility of premature reaction therebetween. More preferably, the 
fine particle size clay, in a slurry or a dry form, is treated with the 
methylene acceptor and an aqueous emulsion containing both a functional 
silane and methylene donor. 
The treated clays are preferred for use in elastomeric systems requiring 
high levels of crosslink density (e.g. tensile strength or high modulus). 
The treated clays can be used as a total or partial replacement for fillers 
such as silica or carbon black in elastomeric systems. The amount of 
treated clay filler employed in a compound will depend on the desired 
system characteristics such as density, hardness, modulus at 300%, tensile 
strength, tear, compression set, rolling resistance, heat build-up or the 
like; however, useful filler loadings for these treated clays in natural 
or synthetic rubbers typically range from 10-225 parts by weight of 
treated clay with respect to 100 parts by weight of rubber polymer (i.e., 
10-225 phr).

PREFERRED EMBODIMENTS OF THE INVENTION 
In its broadest embodiment, the method of making the inventive treated clay 
product involves chemically treating the surfaces of the clay mineral 
particles. This chemical treatment can be performed in a number of ways. 
The methods of chemical treatment involve both the form of the reagents, 
i.e., the silane, the methylene acceptor(s) and the methylene donor(s) as 
well as their order of addition. Further, two reagents can be combined so 
that only two process streams are required. The form of the clay can also 
be selected from a dry form, wet crude clay form, or a slurry. 
More specifically, the surface treating reagents can be combined in either 
neat, as a solution, or as an aqueous emulsion to a clay slurry followed 
by subsequent drying of the mixture to form a powder. Alternatively, the 
surface treating reagents can be added either neat, as a solution or as an 
aqueous emulsion to dry clay or wet crude clay in a mixer such as a 
fluidized bed mixer or a pin mixer followed by subsequent drying as needed 
to form dry powder. The preferred method of mixing the particular reagent 
and the clay is one which gives the most uniform coating, is amenable to 
large-scale processing and is environmentally and economically acceptable. 
The following outlines more preferred process conditions which can be 
utilized with the method described above. 
It was found that the preferred method of addition of the functional silane 
in this invention is to add the silane as an aqueous emulsion to either 
the dry clay powder followed by oven or fluidized bed drying, or to the 
clay slurry then spray drying. The silane emulsion yields a uniform clay 
coating, it is amenable to large-scale processing, and the water diluent 
is environmentally acceptable. 
It was unexpectedly discovered in this invention that clays surface treated 
with reagents other than silane, such as methylene donors and methylene 
acceptors, should not be excessively heated as can occur by spray drying 
the treated clay. For example, when either of these reagents is coated on 
a clay surface and exposed to excessive heat they can be partially removed 
from the clay by sublimation, giving low and uncontrollable treatment 
levels as well as producing undesirable environmental emissions. Also, 
fouling and discoloring of the equipment can occur when a clay slurry 
containing a methylene donor and/or methylene acceptor is spray dried at 
excessive temperatures. 
It was found that solutions of methylene donors and acceptors such as 
hexamethylenetetramine (hereinafter hexa) and resorcinol should not be 
combined since they are unstable with respect to polymerization. Only the 
silane and the hexa can be combined to yield emulsions that are stable for 
extended periods. 
Absorbed product moisture in combination with methylene donors and 
acceptors can yield highly colored treated clay powders which is 
intensified with heat. Therefore, moisture should be avoided. It was 
further unexpectedly found that improved aging stability could be obtained 
by adding the silane and hexa as an aqueous solution or emulsion while 
adding resorcinol as a dry powder to the clay powder. 
A more preferred method for treating a clay powder with these surface 
reagents is to add an aqueous emulsion of combined silane and hexa, and 
separately add resorcinol as an aqueous solution or as a solid powder into 
a fluidized bed of the clay powder followed by moderately low temperature 
and/or short duration drying. 
Referring now to FIG. 1, an exemplary mode of the inventive method is 
schematically illustrated. This flow sheet describes the inventive process 
from the source of mined crude clay to the finally packaged treated clay. 
More specifically, the mined crude clay is blunged into a slurry wherein 
it is combined with an inorganic dispersant. As will be described in more 
detail hereinafter, the selection of the inorganic dispersant controls the 
surface charge of the crude clay which itself controls the performance of 
the treated clay in its final dry form when used as a reinforcing filler 
in a rubber composition. The dispersed clay is then degritted and 
centrifuged to produce the fine overflow clay. The grit from the 
degritting step is disposed of and the underflow from the centrifuge is 
recycled. 
The fine overflow clay is then degritted again through a 325 mesh screen 
and spray dried to form a beneficiated dry clay. The beneficiated clay is 
then introduced into a liquid/powder mixer where it is combined with a two 
stream reagent flow. One reagent flow combines the silane, prepared in 
emulsified form with a surfactant, and the methylene donor as a blend. The 
methylene acceptor is separately added as an aqueous solution. The 
silane/methylene donor blend and aqueous solution of methylene acceptor 
are intimately mixed with the beneficiated dry clay and subsequently dried 
and milled to form the treated clay. FIG. 1 also shows using a fine 
particle size air-float clay as the dry clay feedstock to the mixer. It 
should be understood that FIG. 1 is a preferred mode of the invention and 
the manner in which the silane, methylene donor and methylene acceptor are 
combined with the clay can vary. 
Table 1 details the intermediate and final physical properties of a fine 
particle size, Tertiary clay processed in accordance with FIG. 1. The 
beneficiated kaolin clay described in Table 1 is a particularly well 
suited feedstock for producing the treated clay products of the present 
invention and will herein after be referred to as Clay A. Other types of 
clays described below will be designated in a similar manner, e.g. Clay B, 
Clay C, etc. 
TABLE 1 
______________________________________ 
Kaolin Clay Physical Properties 
Crude Centrifuged 
Sample Tertiary Overflow Beneficiated 
Treated 
Description: 
Clay Clay Dry Clay 
Dry Clay.sup.1 
______________________________________ 
Sp. Gr. of 2.60 2.60 2.60 2.60 
PIGMENT 
Malvern Part. 
2.32 1.70 1.25 -- 
Size (med.), .mu. 
Malvern Sp. S.A., 
2.9756 3.5574 3.9349 -- 
M.sup.2 /GM 
Malvern Pres. # 
0907 0907 0907 -- 
& mm Lens; 45 mm 45 mm 45 mm 
Dispersion Method: 
sodium sodium sodium 
silicate silicate silicate 
% TiO.sub.2 
1.83 1.80 -- -- 
% Fe.sub.2 O.sub.3 
1.10 1.10 -- -- 
% Al.sub.2 O.sub.3 
38.70 38.51 -- -- 
% SiO.sub.2 
45.52 45.28 -- -- 
% Na.sub.2 O 
0.204 0.107 -- -- 
% K.sub.2 O 
0.209 0.203 -- -- 
% CaO 0.024 0.024 -- -- 
BET S.A., m.sup.2 /g 
21.63 22.13 23.95 24.11 
@ 130.degree. 
BF Visc. (20 rpm), 
32.5 21.5 N.A. N.A. 
cps @ as-is % 
Solids 
Hercules visc., 
0.4/1100 0.4/1100 N.A. N.A. 
Dynes/RPMs 
Sedigraph particle 
1.0 0.9 0.9 
size, % +10.mu. 
% +5.mu. 1.9 1.6 1.7 
% -2.mu. 93.8 93.4 93.6 
% -1.mu. 88.0 88.4 88.8 
% -0.5.mu. 77.1 77.6 80.0 
Slurry % Solids 
59.93 37.5 N.A. N.A. 
Brightness 80.30 73.73 74.26 71.50 
Residue, % +325 
24.4 0.014 .004 0.0042 
Mesh 
pH at as-is % Solids 
7.10 5.2 5.8 8.6 
______________________________________ 
.sup.1 Particle size analyses are not report for the treated clay since 
the treatment interferes with the analyses. 
The functional silanes intended for use with the inventive method are 
silicon-containing compounds which include, within a single molecule, one 
or more hydrolytic groups which generate silanol groups which can form 
covalent bonds with the surface hydroxyls of the kaolin clay by means of 
condensation, and a functional group which can form bonds with surrounding 
organic matrices. The above-mentioned hydrolytic group can be a methoxyl 
group, an ethoxyl group or the like. Typically, the functional silanes of 
greatest utility in this invention will contain 2 or 3 alkoxy type groups. 
These alkoxy groups are hydrolytically decomposed in the presence of 
water, (e.g., water contained in the kaolin clay slurry or moisture 
adhering to the surface of the kaolin clay) thereby forming silanol groups 
and liberating the corresponding alcohol. The functional silanes modify 
the surface of the kaolin clay by means of chemical bonds which these 
silanol groups form with the surface hydroxyls of the kaolin clay. The 
above-mentioned functional group can be an amino group, a mercapto group, 
a thiocyanato group, a bridging tetrasulfane group, or other sulfur 
functional groups. Additionally, the silane may have an alkyl group such 
as a methyl group, an ethyl group or a propyl group. 
Silanes which contain at least an amine group or a sulfur atom, such as 
mercaptosilane, thiocyanatosilane, and disilyl tetrasulfane are preferable 
for use in the production method of the present invention. After the 
silane has been mixed into the kaolin clay, a silane-treated clay is 
obtained when the resulting silanol groups reach the kaolin silicate layer 
to undergo a chemical reaction with the surface hydroxyls of the kaolin 
clay. Then, pendant amino groups, mercapto groups, thiocyanate groups, or 
tetrasulfane groups provided on the surface of the silane-treated clay are 
able to form a bridging, cross-linking reaction with rubber and the like 
when cured. Consequently, the treated clay has a good affinity towards 
rubber, thus having exceptional strength with respect to rubber and the 
like. 
Examples of functional silanes for use with the invention are the 
mercaptosilane and thiocyanatosilane types represented by the following 
Formula 1, the disilyl tetrasulfane type represented by the following 
Formula 2, and the aminosilane type represented by the following formula 3 
: 
EQU (RO).sub.2 R'--Si--X (1) 
(wherein R represents a methyl group or an ethyl group, 
R' represents a methyl group, an ethyl group, a methoxyl group or an 
ethoxyl group, and X represents a 3-mercaptopropyl group or a 
3-thiocyanatopropyl group) 
EQU (RO).sub.3 --Si--(CH.sub.2).sub.3 --SSSS--(CH.sub.2).sub.3 
--Si--(OR).sub.3(2) 
(wherein R represents a methyl group or an ethyl group) 
EQU (RO).sub.2 R'--Si--Y (3) 
wherein R represents a methyl group or an ethyl group, R' represents a 
methyl group, an ethyl group, a methoxyl group or an ethoxyl group, and Y 
represents a 3-aminopropyl group or a 3-aminopropyl-2-aminoethyl group. 
A specific example of a suitable mercaptosilane is 
3-mercaptopropyltrimethoxysilane, a specific example of a suitable 
thiocyanatosilane is 3-thiocyanatopropyl-triethoxysilane; specific 
examples of suitable aminosilanes are 3-aminopropyltriethoxysilane and 
N-3-(trimethoxysilyl)propyl!ethylenediamine, and a specific example of a 
disilyltetrasulfane is bis(3-triethoxysilylpropyl)tetrasulfane. 
Many silanes, particularly the above-mentioned thiocyanato and tetrasulfane 
silanes, are generally difficult to dissolve or disperse in water because 
of their organophilic nature. As a result, it is preferred to emulsify 
these silanes in water by means of high speed dispersion with surfactants 
and then mix the emulsified silanes with kaolin clay, the silanes can 
therefore be more intimately mixed with the clay particles and made to 
uniformly coat and adhere to the surface of the kaolin clay for subsequent 
bonding upon drying (the clay particles themselves being inherently 
hydrophilic in nature). As a result, the surface of the kaolin clay is 
uniformly surface-treated, so that the treated clay product has 
exceptional quality and uniformity. 
With the present invention, the silanes are preferably high speed dispersed 
in water with the aid of surfactants and then mixed with the clay in this 
state, either with or without a methylene donor. The silanes are 
emulsified into water containing surfactants, which behave as wetting 
agents and emulsifiers. As surfactants for use in this case, it is 
preferable that the surfactants have HLB (hydrophilic/lipophilic balance) 
values of 8-18. Non-ionic surfactants are especially preferable for 
producing these emulsions. Non-ionic surfactants allow silanes to be 
easily dispersed in water and form particularly stable silane emulsions 
wherein it is believed that the functional silane is in a partially 
hydrolyzed form. The formation of stable silane emulsions is particularly 
advantageous because premature self-condensation of the partially 
hydrolyzed functional silane into silicone-like oligomers has been 
frequently noted to decrease the expected reinforcing benefits of the 
silane treatment. It should also be noted that the pH at which the 
silane/non-ionic surfactant emulsion was prepared is very important to 
resultant silane emulsion stability as the hydrolysis of alkoxy based 
silanes are well known to be acid or base promoted. Additionally, the 
presence of residual non-ionic surfactants in the finished treated clay 
product will not affect the processability or quality of the rubber. 
Non-ionic surfactants include ether-types and ester types which have 
polyoxyethylene or polyhydric alcohols and the like as their hydrophilic 
groups. Examples of non-ionic surfactants are polyoxyethylene alkyl 
ethers, polyoxyethylene fatty acid esters, polyoxyethylene alkylphenyl 
ethers, polyhydric alcohol fatty acid esters, and polyoxyethylene 
polyhydric alcohol fatty acid esters. 
More specific examples of suitable non-ionic surfactants are 
polyoxyethylene alkyl ethers such as ethoxylated tridecyl alcohol, 
polyoxyethylene alkylphenyl ethers such as 9-EO ethoxylated nonylphenol, 
15-EO ethoxylated nonylphenol, 20-EO ethoxylated nonylphenol and 20-EO 
ethoxylated octylphenol; polyoxyethylene polyhydric alcohol fatty acid 
esters such as 5-EO ethoxylated sorbitol mono-oleate and PEG-20 sorbitol 
monolaurate, PEG-12 dioleate, and PEG-16 hydrogenated castor oil. These 
non-ionic surfactants have HLB values of 8-18. 
These non-ionic surfactant compounds which have oxyethylene bonds 
(--CH.sub.2 CH.sub.2 O--) as hydrophilic groups leave residues of 
approximately 10 ppm-5000 ppm in the finished treated clay. These 
surfactant amounts are small enough not to influence the quality of the 
clay filled rubber compositions. Typically, the amount of non-ionic 
surfactant used to prepare a 50% active emulsion of an organosilane is 
about 5% by weight of the total silane content. With regard to the present 
invention, compounds having oxyethylene bonds refer to non-ionic 
surfactants having oxyethylene bonds or reactants of these non-ionic 
surfactants with silanes. 
The methylene donor can be any known type in the art such as 
hexamethylenetretramine, paraformaldehyde, trioxane, 
2-methyl-2-nitro-1-propanal, substituted melamine and glycoluril cross 
linking agents or butylated urea-formaldehyde resin cross linking agents. 
The more preferred methylene donor is hexamethylenetetramine. 
The methylene acceptor can also be any known type in the art. Examples of 
these includes resorcinol, catechol, hydroquinone, pyrogallol, 
phloroglucinol, 1-naphthol, 2-naphthol and resorcinol-formaldehyde resins. 
The more preferred methylene acceptor is resorcinol. 
In combining the functional silane, methylene donor and methylene acceptor, 
it is preferred to use the treatment amounts shown in Table B which are 
based on a weight percentage of the reagent in terms of dry clay. 
TABLE 2 
______________________________________ 
Reagent Treatment Levels on Clay 
More Most 
Preferred Preferred 
Preferred 
Reagent TL TL TL TL 
______________________________________ 
Functional Silane 
0.1-5% 0.2-2% 0.8-1.0% 
0.9% 
Methylene Donor 
0.1-5% 0.2-1% 0.4-0.6% 
0.5% 
(e.g., hexa) 
Methylene Acceptor 
0.1-5% 0.2-1% 0.4-0.6% 
0.5% 
(e.g., Resorcinol) 
______________________________________ 
When added to clay as a solution the methylene acceptor's concentration in 
the solution ranges preferably between 5% and 50%. When adding the 
methylene donor either as a solution, emulsion or combined with silane in 
solution or emulsion form, the concentration of the donor ranges between 
5% and 50%. 
The pure theoretical chemical composition of hydrous kaolin clay can be 
represented by the formula Al.sub.2 O.sub.3. 2SiO.sub.2. 2H.sub.2 O, and 
its specific gravity is approximately 2.60. It should be noted that kaolin 
clay is the mineral kaolinite and being a naturally occurring mineral 
substance it contains other ingredients in small but varying amounts. 
There is no particular restriction on the type of kaolin clay to be used 
in the production method of the present invention. However, it is 
preferable that sedimentary clays such as kaolin clay from the Tertiary 
clay layer in Georgia, or a clay layer in South Carolina be used. These 
kaolin clays result in treated clays which have especially good 
reinforcing effects with respect to rubber. Aside from having specific 
physical properties, these sedimentary clays have excellent particle size 
and shape characteristics and result in highly workable rubber 
compositions. 
Generally, kaolin clays have a unique chemical composition, unique chemical 
properties and unique particle size and morphology depending upon the 
origin thereof. 
Fine particle size waterwashed kaolin clays taken from the Tertiary layer 
in east Georgia can be treated according to the invention. This type of 
clay, herein referred to as Clay B, has a median Malvern particle size of 
0.4-1.0.mu. and a BET surface area of 19-23 m.sup.2 /g. Additionally, a 
Sedigraph particle size analysis shows that the treated clay has a 
particle size distribution such that particles having particle sizes of 
greater than 5.mu. make up less than 3% by weight, particles having 
particle sizes of less than 2.mu. make up over 90% by weight, particles 
having particle sizes of less than 1.mu. make up over 80% by weight, 
particles having particle sizes of less than 0.5.mu. make up over 70% by 
weight, and particles having particle sizes of less than 0.2.mu. make up 
less than 50% by weight of the treated clay. A fine particle size clay is 
usually referred to as one having particle sizes wherein 90% by weight are 
less than 2.mu.. 
Air-float kaolin clay taken from South Carolina crudes can be treated 
according to the invention. This type of clay, herein referred to as Clay 
C, has a median Malvern particle size of 1.9-2.9.mu. and a BET surface 
area of 22-26 m.sup.2 /g. Additionally, a Sedigraph particle size analysis 
shows that the treated clay has a particle size distribution such that 
particles having particle sizes of greater than 5.mu. make up less than 8% 
by weight, particles having particle sizes of less than 2.mu. make up over 
80% by weight, particles having particle sizes of less than 1.mu. make up 
over 70% by weight, particles having particle sizes of less than 0.5.mu. 
make up over 60% by weight, and particles having particle sizes of less 
than 0.2.mu. make up less than 50% by weight of the treated clay. 
The Malvern particle size measurement method is a laser light scattering 
method, wherein the particle size properties of kaolin clay are determined 
on dilute aqueous dispersions and the data is analyzed on the basis of Mie 
scattering and Fraunhofer diffraction theory. The Malvern median particle 
size values reported herein were measured using Malvern's Mastersizer/E 
particle size unit. 
The Sedigraph particle size measurement is a particle sedimentation method 
based on Stokes Law, wherein the particle size properties of kaolin clay 
are determined on dilute aqueous dispersions. The sedimentation data is 
collected and analyzed by a Micromeritics 5100 X-ray Sedigraph particle 
size instrument. 
The kaolin clay feedstock can be processed in any known and conventional 
mineral processing scheme for subsequent coupling with the silanes, 
methylene donors and methylene acceptor disclosed herein. In one instance, 
the kaolin clay feed can be produced from the known waterwashing process 
to form a fine particle size clay of essentially neutral pH. In 
waterwashing, the crude clay is made into a slurry using chemical 
dispersants and then fractionated or classified to remove unwanted 
material and to divide the clay into the desired particle size. The 
fractionated clay slurry is then subjected to any number of chemical 
purification/grinding techniques to remove impurities and increase the 
clay brightness to the desired brightness level. After filtration, the 
beneficiated clay filter cake is redispersed at a neutral pH for 
subsequent product use. Since this waterwashing technique is well 
recognized in the art, a further description thereof is not needed for 
understanding of the invention. Preferably, the kaolin clay feed is 
produced from a waterwash process in accordance with that previously 
disclosed in FIG. 1, whereby the dispersant level is minimized to control 
the surface charge of the clay particles. 
Alternatively, the kaolin clay to be combined with the silane, methylene 
acceptor and methylene donor can be an air-float type. Air-float clay is 
obtained by crushing crude clay, drying it and air classifying it to 
remove unwanted materials and to achieve a particular particle size. 
It should be understood that the kaolin clay starting material for 
treatment can be processed according to the techniques described above or 
any other known techniques in the clay industry. Likewise, although 
specific clay compositions are disclosed herein below, any known kaolin 
clays are deemed usable for the inventive multi-component treatment, 
treatment process and elastomeric applications. 
Although a conventional waterwash process can be used to produce a kaolin 
clay feed stock for clay treatment, it has been discovered that improved 
physical reinforcement properties in a filler-containing rubber 
composition are achieved when the surface charge of the crude clay being 
processed is controlled. Referring again to FIG. 1, the mined crude clay 
is blunged into a slurry. In prior art processes, it is typical to add 
dispersants when producing the blunged slurry to increase the pH to 
achieve neutralization of the charge on the clay. However and contrary to 
that which is known in the art, it has been discovered that improved 
results occur when the charge of the clay is controlled through the use of 
particular dispersant types and/or by minimizing the dispersant amounts 
employed. As determined by zeta potential measurements, clay in its 
natural mined state has an overall net negative surface charge which is 
made up of both positive and negative charges. Depending on the type of 
crude clay, some crudes may have more positive charge on the clay 
particles than others thereby decreasing the overall negativity of the 
surface charge. By minimizing the overall negative charge through control 
of the dispersant type and amount added to the crude clay, more positive 
charges remain on the clay platelets. The increase in positive charges 
results in an overall decrease in the negativity of the surface charge. 
By minimizing the amount and/or the type of the dispersants used during the 
crude clay processing, the clay remains more cationic which contributes to 
the improvements in clay performance when the clay is subsequently surface 
treated according to the invention and used as a reinforcing filler in 
elastomeric systems. Inorganic dispersants are preferred over organic 
dispersants such as sodium polyacrylates. Acceptable inorganic dispersants 
include sodium silicate, tetasodium pyrophosphate, sodium 
tripolyphosphate, sodium hexametaphosphate and similar phosphate salts. 
In order to verify the effect of the dispersant on clay performance in 
rubber, different types of dispersant levels were used during the blunging 
of a crude clay into a slurry. The crude clay was then processed according 
to the invention with functional silane, methylene acceptor and methylene 
donor and used in an isoprene rubber formulation. An in-house screening 
compound comprising a polyisoprene rubber formulation (hereinafter 
designated "Natsyn.TM. 2200") is listed in Table 3 below and is used in 
most all of the experiments conducted to optimize the reagents, treatment 
levels and process of the present invention unless otherwise noted. Rubber 
compounding, sample preparations and sample testing were carried out in 
accordance with ASTM procedures. The rubber compounds whose formulations 
are shown in the tables were singled-passed, laboratory productions, mixed 
in a BR size Banbury.TM. internal mixer with the ingredients added in the 
order shown. The rubber compounds were weighed to fill 75% of the 2.6 lb. 
maximum fill volume of the BR mixer. The rubber compounds were finalized 
on a two roll lab mill. 
Compression molding of the test pieces were carried out at 40 tons pressure 
and 160.degree. C. Cure times were determined by calculating the T90 
optimum cure times which were measured on a Monsanto R-100 rheometer at 
160.degree. C. Cure times were determined by calculating the T90 optimum 
cure times which were measured on a Monsanto R-100 rheometer at 
160.degree. C. and 3.degree. arc. Typically, the inventive treated clay 
products were substituted for carbon black/silica to maintain approximate 
durometer hardness, e.g. 1.6 phr of treated clay for every 1.0 phr of 
carbon black. It should also be understood that the various formulations 
were not optimized in terms of altering/changing various formulation 
components in order to obtain the optimum cure times, etc. Designation of 
the various clays used in the following examples references the type of 
crude clay form used in the following Tables, e.g., the fine particle size 
Tertiary Clay A. The types of functional silanes and their designations as 
used in the Examples are: 3- mercaptopropyltrimethoxysilane (HS--Si); 
3-thiocyanatopropyltriethoxysilane (NCS--Si); bis(3-triethoxysilypropyl) 
tetrasulfane (S.sub.4 --Si); and 3 aminopropyltriethyoxysilane (H.sub.2 
N--Si). In addition, for remaining examples, if not stated, percentages 
are weight percentages on a dry clay basis. 
TABLE 3 
______________________________________ 
Natsyn 2200 Screening Formulation 
INGREDIENT Phr 
______________________________________ 
Unvulcanized IR Rubber 
100.00 
Filler 75.00 
Polyethylene 617A 2.50 
Terpene phenol resin 
2.00 
Stearic Acid 2.00 
Zinc Oxide 5.00 
Sulfur 1.60 
N-tert-butyl-2- 1.60 
benzothiazyl sulfenamide 
Zinc-di-n-butyl- 0.50 
dithiocarbamate 
Diphenylquanidine 0.50 
Benzoic Acid 1.00 
TOTAL 191.70 
______________________________________ 
Table 4 shows a comparison of the treated clay product of FIG. 1 when using 
Clay A as the mined crude clay and when prepared with two different levels 
of an inorganic dispersant and one type and level of an organic 
dispersant. The levels of dispersants are indicated in the tables as wt/wt 
percent on an active basis. Active basis refers to pure dispersant which 
does not include any solvent or diluent. The best performing dispersant 
was the inorganic dispersant, sodium silicate, particularly when used at 
the lower concentration. The sample prepared with 0.32% sodium silicate in 
Table 4 gave the highest tensile, modulus and tear die values as compared 
to the higher concentration sodium silicate sample or the organic sodium 
polyacrylate dispersant. Quite surprisingly, the inorganic dispersant used 
at the lower concentration level led to a better treated clay performance 
than the organic dispersant having a concentration lower than the 
inorganic dispersant. 
TABLE 4 
______________________________________ 
Comparison of Inorganic and Organic Dispersants 
4A. Prepared with 0.32% inorganic sodium silicate 
4B. Prepared with 0.65% inorganic sodium silicate 
4C. Prepared with 0.19% organic sodium polyacrylate 
Natsyn 2200 Screening Formulation 
Compound Identification 
4A 4B 4C 
______________________________________ 
Rheometer (T = 90%) (min.) 
4:56 5:04 5:32 
Durometer (Shore A) (pts) 
64 64 64 
Tensile (psi) 3700 3280 3340 
Elongation, % 430 410 430 
Modulus (psi) 
@ 100% Elongation 730 750 680 
@ 200% Elongation 1630 1560 1440 
@ 300% Elongation 2430 2280 2150 
Tear Die "C" (pli) 
422 407 399 
______________________________________ 
Table 5 compares two inorganic dispersants, sodium silicate and tetrasodium 
pyrophosphate (TSPP). These two inorganic dispersants were further 
evaluated for their effects on rubber performance when used to disperse 
and process Clay A according to FIG. 1. Sodium silicate performed better 
than TSPP as can be seen in the tensile, modulus and tear die values. 
Since tensile strength is often proportional to clay filler particle size, 
the high tensile strength for sodium silicate suggests that this 
dispersant more efficiently disperses Clay A. Also, lower amounts of 
dispersant appear preferable by comparing 4A versus 4B and 4C versus 4D. 
TABLE 5 
______________________________________ 
Inorganic Dispersants 
5A. 0.2% sodium silicate 
5B. 0.25% sodium silicate 
5C. 0.15% TSPP 
5D. 0.35% TSPP 
Natsyn 2200 Screening Formulation 
5A 5B 5C 5D 
______________________________________ 
Durometer (A) 65 65 64 64 
Tensile (psi) 3670 3530 3050 3060 
Elongation, % 390 400 400 400 
Modulus (psi) 
@ 100% Elongation 
870 830 740 700 
@ 200% Elongation 
1750 1690 1440 1340 
@ 300% Elongation 
2580 2480 2150 2040 
Tear Die "C" (pli) 
371 362 328 325 
______________________________________ 
Referring to FIG. 2, the rubber performance of a treated clay was found to 
be sensitive to the clay's surface charge. FIG. 2 demonstrates that the 
more positive surface charge values, i.e., less negative values, gave 
higher 300% modulus values. The surface charge, itself, is a function of 
the type of clay, the type of dispersant, and the amount of dispersant. 
Clay B in FIG. 2 is an east Georgia waterwashed, fine particle size kaolin 
clay. Clays A1-A3 correspond to Clay A with different dispersants/levels. 
Clay C is a South Carolina fine particle size air-float clay. As is 
clearly evident from FIG. 2, significant improvements are seen in rubber 
modulus when the surface charge of the clay is made less negative (more 
positive) by using less dispersant and/or an inorganic dispersant. 
Preferably, the amount of dispersant is selected so that the clay's 
surface charge is more positive than -22 millivolts as measured at a pH of 
7 by zeta potential determination. The surface charge measurement is made 
after the crude clay is blunged with the dispersant, degritted, 
fractionated and degritted again, see FIG. 1. More preferably, the 
dispersant amount is controlled to obtain a zeta potential more positive 
than -16 millivolts and more preferably -12 millivolts, measured as 
described above. Zeta potentials reported herein were measured using a 
Malvern Zetasizer Model 4. Since zeta potential measurement techniques by 
electrophoretic mobility are well known, a further description thereof is 
not needed. 
When treating slurries of waterwashed kaolin clays, addition of the 
functional silanes is best accomplished by using an aqueous silane 
emulsion. When silane treating an air-float clay, it is preferred to use a 
dry solids/liquid mixing device such as a ribbon blender, pin mixer, 
Littleford blender, etc., to mix the dry clay with the silane emulsion. 
The functional silanes are added to the dry clay solids in emulsified form 
under intimate mixing conditions. The methylene donors and acceptors can 
be combined with the clay and/or the methylene donor can be pre-blended 
with the silane emulsion as described above. The treated clay product can 
then be dried to remove residual moisture and pulverized. 
Typically, waterwashed kaolin clay products have a fine particle size and 
high brightness. Air-float clay products can have a fine particle size but 
are low brightness. 
As stated above, the silanes are preferably high speed dispersed into water 
in the presence of surfactants to form a silane emulsion. In order to 
efficiently and uniformly disperse the silanes into the water, the fluid 
mixture containing silanes, surfactants and water should be agitated 
vigorously. A silane dispersion fluid wherein silanes have been 
pre-dispersed in surfactant-containing water should be prepared prior to 
mixing the silanes with the kaolin clay. The concentration of the silanes 
in the silane dispersion fluid should be 25-60% by weight. Additionally, 
the amount of surfactant used should be 0.5-10 parts by weight, more 
preferably 2.0-5.0 parts by weight with respect to 100 parts by weight of 
the silane. It is preferable that the surfactants employed have HLB 
(hydrophilic/lipophilic balance) values of 8-18 and various non-ionic 
surfactants are especially preferable as the surfactants. The 
above-mentioned silane dispersion fluid is pH-adjusted depending upon the 
type of silane to enhance emulsion stability, prior to mixing with the 
kaolin clay. 
If the pH of a silane dispersion fluid wherein sulfur atom-containing 
mercaptosilanes, thiocyanatosilanes or disilyl tetrasulfanes are dispersed 
in water with a surfactant is adjusted to be alkaline, for example in the 
pH range of 7.5-10, then the sulfur functional silane emulsion can be 
stabilized. That is, if the pH of the silane dispersion fluid is alkaline 
in this way, then the sulfur functional silane can be prevented from being 
lost by means of silanol self-condensation into silicone oligomers or 
polymers before reacting with the surface hydroxyls of the kaolin clay. 
When the methylene donor and acceptors are added separately from the silane 
and each other, the silane dispersion fluid is mixed with a kaolin clay 
powder, or, with a clay slurry wherein the clay has been suspended in 
water. When the silane dispersion fluid, and the kaolin clay slurry are 
combined, two miscible fluids are being mixed, thus making it especially 
easy to uniformly mix together the silane and the kaolin clay. As a 
result, the required mixing time becomes shorter and the silanes are 
distributed uniformly on to the surface of the kaolin clay particles. The 
solids concentration of kaolin clay in the slurry is typically 40-70% by 
weight but more preferably 50-60% by weight as dispersed clay filter cake 
slurries are conveniently used. 
In treating waterwashed kaolin clays, the addition of a silane emulsion and 
separate solutions of the methylene donor and methylene acceptor reagents 
to a clay slurry normally occurs at the dispersed clay filter cake stage. 
The clay slurry at this point in the waterwash beneficiation process is 
typically 50-60% solids and has a pH value falling into the range of 
6.0-8.0. Addition of the silane emulsion, donor solution and acceptor 
solution can be handled in one of several ways so long as they are 
introduced to the dispersed clay slurry under good mixing conditions 
(e.g., via a Cowles mixer or in-line mixer injection). After mixing the 
treated clay slurry for a sufficient time to achieve good treatment 
uniformity, the product is then dried. 
In the case of treating an air-float clay, this is best accomplished 
through the use of a dry solids/liquid mixing device (such as a ribbon 
blender, pin mixer, Littleford blender, etc.). The functional silanes are 
again best applied in emulsified form. The methylene donor and acceptor 
reagents are added as separate reagent solutions or the methylene donor 
can be pre-blended with the silane emulsion. After intimate mixing of the 
clay, silane emulsion, and other liquid reagents, the product is then 
dried to remove residual moisture and pulverized. 
In summary, when producing the treated clays of the present invention, the 
methylene donor can be put in solution and added either directly to the 
clay or added to the silane emulsion prior to combining with the clay. 
Alternatively, the methylene acceptor may be added to the dry clay or clay 
slurry in dry form or as a solution. 
As stated above, the treatment level of the functional silane, methylene 
acceptor and methylene donor can be compromised by both moisture and heat. 
Excessive heat during the drying step can cause a partial loss of the 
reagents on the clay surface which then results in lower filler 
performance levels when the clay is used in a rubber composition. The 
effect of heat on the treatment level of a surface treated clay is shown 
in FIG. 3. Clay A was treated with hexa and placed into a 120.degree. C. 
oven. Samples were removed from the oven at several time intervals and the 
amount of hexa remaining on the clay was determined by carbon analysis. 
Clay A was also treated with resorcinol then heated to 120.degree. C. and 
analyzed in an analogous fashion to the above hexa/Clay A sample. The loss 
of both hexa and resorcinol in the separate experiments can be seen in 
FIG. 3 with the loss of hexa being more severe than that of resorcinol. 
The effect of heat and moisture is shown in FIG. 4. In this figure, the 
change on rubber modulus is plotted for three different treated clay 
samples under three different conditions. 
The treated clays were prepared by three different methods as follows: 1) 
Spray drying a slurry containing all three surface treatment reagents and 
a beneficiated clay (I); 2) Dry blending dry resorcinol powder with spray 
dried hexa/NCS--Si treated beneficiated clay (II); 3) Dry blending both 
dry hexa and dry resorcinol with spray dried NCS--Si treated beneficiated 
clay (III). Each of these samples was then exposed to heat or heat and 
moisture (80% relative humidity) to determine the process that would yield 
the most resilient product. This chart indicates that adding dry 
resorcinol to the spray dried hexa/NCS--Si treated beneficiated clay (II) 
gives the most heat and moisture stable treated product as measured by 
300% modulus values. 
FIGS. 3 and 4 demonstrate that the surface treated clay should not be dried 
at an excessive temperature or time. When surface treating a clay in dry 
form, the preferred maximum drying temperature is believed to be about 
75.degree. C., and more preferably, 60.degree. C. Similarly, when 
spray-drying treated clay slurries, the drying temperature should be such 
that losses due to volatilization of one or more of the surface treatment 
reagents should not exceed about 10% by weight of the total treatment 
amount of the surface reagents as a multi-component system. The drying 
temperature should also be low enough so as not to cause premature polymer 
forming reaction between the methylene donor and the methylene acceptor as 
evidenced by the treated clay product developing an orange-brown hue after 
drying. 
Heat drying the combination of treatment reagents and clay via conventional 
spray drying or flash-drying causes a chemical reaction between the 
hydrolyzed silane and the surface hydroxyls of the kaolin clay, thereby 
resulting in a surface-treated clay by means of a functional silane. 
Furthermore, heat drying this combination causes the silane treated clay 
to become co-modified with a surface coating consisting of a methylene 
donor and a methylene acceptor thereby bringing these two reagents into 
close proximity for subsequent polymer forming reaction when the treated 
clay is compounded into rubber. It is believed that forming said polymer 
at the clay surface interface is particularly advantageous with respect to 
enhancing clay filler reinforcement. Finally, heat drying provides the 
treated clay product in dry powder form. While 10 ppm-5000 ppm of 
surfactants such as non-ionic surfactants may normally remain in the 
treated clay when using the silane emulsion of the invention, the amount 
is sufficiently small as to not have any adverse effects on the physical 
properties of the clay filled rubber compositions. 
While the treated clay of the present invention can be applied to many 
different uses, it is suited for use as a filler for synthetic resins such 
as polyethylene or polypropylene, or as a reinforcing filler or extender 
for natural or synthetic rubbers. The treated clay of the present 
invention is especially suited to use as a reinforcing filler for natural 
and synthetic rubbers because the pendant functional group (an amino or 
sulfur containing group) provided by the silane component present on the 
treated clay chemically reacts with these rubber polymers during the 
curing process to yield reinforcement via cross-linking between the clay 
and the polymer. As examples, synthetic rubber, isoprene rubber (IR), 
nitrile butadiene rubber (NBR), ethylene-propylene rubber (EPDM), styrene 
butadiene rubber (SBR), neoprene (CR) and polybutadiene rubber (BR) can be 
given. By adding 10-225 parts by weight of treated clay with respect to 
100 parts by weight of natural or synthetic rubber, it is possible to 
obtain a compound having exceptional mechanical strength. Rubber 
compositions with this filler loading have excellent physical properties, 
as well as making rubber products more economical. The treated clay of the 
present invention enable the making of color pigmented rubber products. 
A treated clay to be added to rubber for the purpose of enhancing modulus, 
tensile strength or tear properties should preferably be a fine dry powder 
having a clay particle size of at least 90% less than 2.mu. as determined 
by x-ray Sedigraph, and a BET surface area of 19-28 m2/ g. If the particle 
size is small and the surface area is large for a treated clay in this 
way, then it will have good reinforcing strength with respect to rubber. 
The inventive treated clays are particularly adapted as a high performance 
filler in rubber compositions for automotive use, e.g., tire tread 
formulations, tire carcass formulations, tire wire belt coats, tire 
apexes, radiator hoses, V-belt, innertubes, or the like. Quite 
unexpectedly, the uniquely treated kaolin clay of the present invention 
provides rubber compounds with improved processing properties, improved 
rubber physical properties and is more economical than silica or carbon 
black. The inventive treated clay can be processed with rubber 
compositions in shortened mix cycles than that required for silicas. 
Similarly, shorter cure times and improved viscosity are realized using 
the inventive treated clay. Even more unexpectedly, end-use application 
properties like lower rolling resistance and lower heat build-up in the 
final product are realized when using the inventive treated clay. 
Heretofore, the rubber formulation of Table 3 using conventional silane 
treated clays has only achieved modulus values in the vicinity of 
1,500-2,000 psi at 300% elongation. The same rubber formulations using the 
inventive clay, as will be shown below, shows a significant improvement in 
physical properties over those containing non-treated or conventional 
silane treated clays. Furthermore, and equivalent properties are obtained 
when the inventive treated clay is used as a substitute for silica or 
carbon black. 
While the above-mentioned rubber compositions contain a treated clay and 
natural or synthetic rubber as necessary components, vulcanizing agents, 
cross-linking agents, vulcanization accelerators, age resistors, 
antioxidants, UV absorbents, plasticizers, lubricants, flame retardants, 
or other fillers such as silica, carbon black, talc, calcium carbonate, 
alumina trihydrate, mica, zinc oxide, barium sulfate, magnesium oxide, 
metal silicates, silicas, and combinations thereof and the like can also 
be added if necessary. Other types of known clay fillers could be used in 
combination with the above listed components such as those having a silane 
treatment or untreated clays. Additionally, while there are no 
restrictions to the method of processing the rubber compositions of the 
present invention, the desired product can be obtained through 
calendaring, extrusion molding, compression molding, injection molding or 
the like. 
EXAMPLES 
The present invention will be further explained in detail with the use of 
examples. In the examples, the terms "parts" and "%" always indicate parts 
by weight and % by weight, respectively. 
In order to demonstrate the benefits of combining the functional silane 
NCS--Si (a thiocyanatosilane) with both the methylene donor and methylene 
acceptor, a comparison was made with Clay A of Table 1 and various 
combinations of the reagents. The data in Table 6 show that the use of all 
three reagents yields the highest performing treated clay. For example, 
the highest modulus and tear values are exhibited by sample 6H which 
contains all three reagents. Single reagents or pairs of reagents on the 
clay surface do not perform as well. 
TABLE 6 
__________________________________________________________________________ 
6A. Clay A 
6B. 0.9%/Clay A 
6C. 0.5% hexa/Clay A 
6D. 0.5% resorcinol/Clay A 
6E. 0.9% NCS--Si/0.5% resorcinol/Clay A 
6F. 0.9% NCS--Si/0.5% hexa/Clay A 
6G. 0.5% hexa/0.5% resorcinol/Clay A 
6H. 0.9% NCS--Si/0.5% hexa/0.5% resorcinol/Clay A (Control) 
Netsyn 2200 Screening Formulation 
Compound 
Identification 
6A 6B 6C 6D 6E 6F 6G 6H 
__________________________________________________________________________ 
Rheometer (T-90%) (min.) 
5:05 
5:30 
4:38 
4:14 
4:52 
4:54 
5:10 
5:21 
Durometer (Shore A) (pts) 
59 65 
61 61 65 
65 
62 
65 
Tensile (psi) 
3370 
3630 
3240 
3350 
3610 
3670 
3470 
3460 
Elongation, % 
560 460 
530 550 470 
460 
500 
430 
Modulus (psi) 
@ 100% Elongation 
330 710 
370 370 680 
720 
530 
760 
@ 200% Elongation 
510 1410 
570 580 1360 
1450 
1020 
1590 
@ 300% Elongation 
770 2080 
860 870 2000 
2150 
1550 
2320 
Tear Die "C" (pli.) 
251 395 
256 267 390 
404 
345 
413 
__________________________________________________________________________ 
Table 7 summarizes the study of four chemically different functional 
silanes and their effect on filler performance in regard to the inventive 
treated clay. HS--Si is a mercaptosilane. S.sub.4 --Si is a 
tetrasulfanesilane and H.sub.2 N--Si is an aminosilane. The conclusion is 
that the sulfur containing silanes (7A, 7B, 7C) perform better than the 
amino-silane (7D) in this rubber formulation by having higher durometer 
hardness, modulus, and tear values. The NCS--Si silane performs best of 
all these silanes in these same categories. 
TABLE 7 
______________________________________ 
7A. 0.9% NCS--Si/0.5% hexa/0.5% resorcinol/Clay A 
7B. 0.9% HS--Si/0.5% hexa/0.5% resorcinol/Clay A 
7C. 0.9% S.sub.4 --Si/0.5% hexa/0.5% resorcinol/Clay A 
7D. 0.9% H.sub.2 N--Si/0.5% hexa/0.5% resorcinol/Clay A 
Natsyn 2200 Screening Formulation 
Compound 
Identification 
7A 7B 7C 7D 
______________________________________ 
Rheometer (T- 5:11 5:00 5:22 5:23 
90%) (min.) 
Durometer (Shore 
65 64 64 62 
A) (pts) 
Tensile (psi) 3650 3150 3460 3240 
Elongation, % 440 420 440 470 
Modulus (psi) 
@ 100% Elongation 
740 660 690 530 
@ 200% Elongation 
1580 1390 1460 1050 
@ 300% Elongation 
2340 2080 2160 1630 
Tear Die "C" (pli.) 
414 373 403 345 
______________________________________ 
Table 8 shows the relative efficacies of various methylene acceptors used 
in the inventive clay concept. It was found that two methylene acceptors 
performed particularly well in providing 300% modulus. Both resorcinol 
(8A) and Penacolite R-2200 (8H) were superior to the others with 
resorcinol being the preferred reagent. Herewith the embodiment identified 
as 8A using Clay A and the defined reagents and treatment levels will be 
referred to as Treated Clay A*. 
TABLE 8 
__________________________________________________________________________ 
8A. 0.9% NCS--Si/0.5% hexa/0.5% resorcinol/Clay A (Treated Clay A*) 
8B. 0.9% NCS--Si/0.5% hexa/0.5% catechol/Clay A 
8C. 0.9% NCS--Si/0.5% hexa/0.5% hydroquinone/Clay A 
8D. 0.9% NCS--Si/0.5% hexa/0.57% pyrogallol/Clay A 
8E. 0.9% NCS--Si/0.5% hexa/0.57 phloroglucinol dihydrate/Clay A 
8F. 0.9% NCS--Si/0.5% hexa/0.65% 1-naphthol/Clay A 
8G. 0.9% NCS--Si/0.5% hexa/0.65% 2-naphthol/Clay A 
8H. 0.9% NCS--Si/0.5% hexa/0.9% Penacolite R-2200.sup.1 /Clay A 
Natsyn 2200 Screening Formulation 
Compound 
Identification 
8A 8B 8C 8D 8E 8F 8G 8H 
__________________________________________________________________________ 
Rheometer (T-90%) (min.) 
4:55 
5:54 
4:41 
5:30 
5:47 
4:59 
4:56 
5:37 
Durometer (Shore A) (pts) 
65 
65 
65 
65 64 
64 
64 
64 
Tensile (psi) 
3420 
3260 
3310 
3280 
3060 
3290 
3440 
2980 
Elongation, % 
420 
440 
440 
440 
420 
430 
440 
390 
Modulus (psi) 
@ 100% Elongation 
730 
660 
680 
670 
650 
680 
680 
690 
@ 200% Elongation 
1570 
1350 
1400 
1370 
1370 
1380 
1400 
1500 
@ 300% Elongation 
2320 
2000 
2070 
2030 
2050 
2070 
2100 
2260 
Tear Die "C" (pli.) 
417 
400 
407 
403 
404 
406 
407 
409 
__________________________________________________________________________ 
.sup.1 Penacolite R2200 is a resorcinolformaldehyde resin from Indspec 
Chemical Corp., Pittsburgh, PA. 
A variety of methylene donors and other crosslinking agents were evaluated 
as treatment components in the inventive clay. The rubber performance data 
of Table 9 show that there is almost an even spread of 300% modulus values 
from 1950 to 2400 psi. Among the treatment systems evaluated, hexa (9A) 
and Cymel 370 (9E) yielded the highest modulus values. 
TABLE 9 
__________________________________________________________________________ 
9A. 0.9% NCS--Si/0.5% resorcinol/0.5% hexa/Clay A (Treated Clay A*) 
9B. 0.9% NCS--Si/0.5% resorcinol/0.64% paraformaldehyde/Clay A 
9C. 0.9% NCS--Si/0.5% resorcinol/0.64% trioxane/Clay A 
9D. 0.9% NCS--Si/0.5% resorcinol/0.5% Cymel 3031/Clay A 
9E. 0.9% NCS--Si/0.5% resorcinol/0.5% Cymel 3701/Clay A 
9F. 0.9% NCS--Si/0.5% resorcinol/0.5% Cymel 1172.sup.1 /Clay A 
9G. 0.9% NCS--Si/0.5% resorcinol/0.5% Beetle 80.sup.2 /Clay A 
9H. 0.9% NCS--Si/0.5% resorcinol/0.43% 2-methyl-2-nitro-1-propanol/Clay 
Natsyn 2200 Screening Formulation 
Compound 
Identification 
9A 9B 9C 9D 9E 9F 9G 9H 
__________________________________________________________________________ 
Rheometer (T-90%) (min.) 
4:55 
5:36 
4:49 
5:02 
5:18 
5:01 
4:57 
5:07 
Durometer (Shore A) (pts) 
65 
62 
65 
65 64 
64 
64 
65 
Tensile (psi) 
3420 
3380 
3390 
3360 
3350 
3060 
3370 
3160 
Elongation, % 
420 
430 
460 
420 
410 
390 
430 
430 
Modulus (psi) 
@ 100% Elongation 
730 
650 
660 
710 
730 
690 
710 
700 
@ 200% Elongation 
1570 
1460 
1320 
1450 
1610 
1530 
1530 
1390 
@ 300% Elongation 
2320 
2220 
1950 
2160 
2420 
2300 
2260 
2030 
Tear Die "C" (pli) 
417 
408 
399 
408 
420 
413 
410 
406 
__________________________________________________________________________ 
.sup.1 Cymel resins are substituted melamine and glycoluril crosslinking 
agents from Cytex Industries, West Paterson, NJ. 
.sup.2 Beetle 80 is a butylated ureaformaldehyde resin crosslinking agent 
from Cytec Industries, West Paterson, NJ. 
Hexa Concentration Study 
The concentration of the methylene donor, hexa, on the clay surface was 
varied in the inventive clay composition to establish its preferred 
concentration range. Different hexa treatment concentrations were used in 
combination with 0.9% NCS--Si plus 0.5% resorcinol and the results are 
shown in Table 10. Sample 10B through 10E have virtually equivalent filler 
performance particularly in 300% modulus thereby indicating that hexa has 
a large concentration latitude for yielding high performance. 
TABLE 10 
______________________________________ 
10A. 0.9% NCS--Si/0.5% resorcinol/Clay A 
10B. 0.9% NCS--Si/0.5% resorcinol/0.15% hexa/Clay A 
10C. 0.9% NCS--Si/0.5% resorcinol/0.25% hexa/Clay A 
10D. 0.9% NCS--Si/0.5% resorcinol/0.35% hexa/Clay A 
10E. 0.9% NCS--Si/0.5% resorcinol/0.5% hexa/Clay A 
(Treated Clay A*) 
Natsyn 2200 Screening Formulation 
NCS--Si 
resor- 0.15% 0.25% 0.35% 0.5% 
cinol hexa hexa hexa hexa 
Sample Description 
only added added added added 
______________________________________ 
Compound 10A 10B 10C 10D 10E 
Identification 
Rheometer (T- 
5:13 5:12 5:1O 5:49 5:31 
90%) (min.) 
Durometer (Shore 
66 66 66 66 66 
A) (pts) 
Tensile (psi) 
3270 3380 3390 3300 3140 
Elongation, % 
440 410 410 400 390 
Modulus (psi) 
@ 100% Elongation 
750 790 770 770 780 
@ 200% Elongation 
1450 1680 1670 1670 1660 
@ 300% Elongation 
2060 2460 2450 2460 2400 
Tear Die "C" (pli.) 
398 411 408 410 407 
______________________________________ 
Air-Float Clay Study 
Table 11 shows a comparative filler study using a South Carolina fine 
particle size, air-float kaolin clay (Clay C) which was evaluated as an 
alternate clay feedstock for producing the treated clay of this invention. 
The particle size and surface area properties typical of Clay C have been 
previously disussed. Clay C was surface treated by two different 
processes. In the first process, the air-float clay was dispersed in water 
using 0.2% TSPP as a dispersant, then slurry treated with a 50% aqueous 
emulsion of NCS--Si, and separate solutions of hexa, and resorcinol, then 
spray dried. This treatment process was performed twice using different 
treatment levels of the reagents to give Samples 11B and 11C. 
The second treatment process in which Clay C was used as a feedstock is 
shown in FIG. 1 where the dry air-float clay was directly treated with an 
aqueous emulsion of NCS--Si, plus hexa, and a separate solution of 
resorcinol in a liquid/powder mixer, then dried and milled (Sample 11D). 
These three treated air-float clays are compared with the untreated clay 
control (Sample 11A). 
The rubber performance data shown below indicate that the multi-component 
surface treatment of this invention improves the performance of clays 
other than Clay A. Further indicated by these data is that surface 
treatment can be satisfactorily performed by spray drying treated slurries 
under conditions of minimal heat and residence time. Comparison of the 
similar performance values for Samples 11B and 11C indicate that there is 
a broad latitude for the treatment levels of all three reagents which 
yield high performance compared to the base clay, Sample 11A. 
Sample 11D illustrates that undispersed, dry clays, such as air-float 
clays, can be surface treated directly with minimal beneficiation in a 
liquid/powder mixer and still obtain large improvements in rubber 
reinforcement properties over the untreated clay. 
TABLE 11 
______________________________________ 
11A. Clay C 
11B. Clay C/0.5% NCS--Si/1.0% resorcinol/0.75% hexa; slurry 
treated, spray dried 
11C. Clay C/0.9% NCS--Si/0.5%.resorcinol/0.5% hexa; slurry 
treated, spray dried 
11D. Clay C/0.9% NCS--Si/0.5% resorcinol/0.5% hexa; 
liquid/powder mixer, dried 
Natsyn 2200 Screening Formulation 
11A 11B 11C 11D 
______________________________________ 
Durometer (A) 58 63 63 63 
Tensile (psi) 3450 3470 3730 3190 
Elongation, % 490 390 390 420 
Modulus (psi) 
@ 100% Elongation 
340 820 830 670 
@ 200% Elongation 
530 1590 1670 1250 
@ 300% Elongation 
900 2440 2610 1900 
Tear Die "C" (pli) 
215 374 374 310 
______________________________________ 
In this example, the filler performance of the inventive treated clay was 
investigated and compared to conventional, prior art silane treated clays 
and carbon black. The results of this comparison are shown in Table 12 
where all fillers were utilized at a loading of 75 phr. 
Table 12 indicates that Treated Clay A* (see Table 8) has superior 
performance in rubber as compared to the prior art silane treated clays 
identified as Treated Clay B and Hi--Treated Clay B. Clay B is a fine 
particle size, waterwashed kaolin clay produced from a Tertiary east 
Georgia crude whose physical properties have been previously discussed. 
Treated Clay A* has equivalent modulus performance to a soft carbon black 
which is a high cost alternative. 
TABLE 12 
______________________________________ 
Natsyn 2200 Screening Formulation 
Hi- Carbon 
Treated Treated Black Treated 
Sample Description 
Clay B.sup.1 
Clay B.sup.2 
N-660.sup.3 
Clay A* 
______________________________________ 
Rheometer (T = 90%) (min.) 
6:13 5:25 5:27 5:15 
Durometer (Shore A) (pts) 
64 65 75 65 
Tensile (psi) 3310 3620 2710 3390 
Elongation, % 470 450 310 360 
Modulus (psi) 
@ 100% Elongation 
550 700 960 910 
@ 200% Elongation 
1100 1350 2080 1780 
@ 300% Elongation 
1640 2040 2630 2660 
Tear Die "C" (pli) 
319 352 341 367 
______________________________________ 
.sup.1 East Georgia fine particle size, high brightness clay (Clay B) 
treated with 0.4% NCS--Si. 
.sup.2 East Georgia fine particle size, high brightness clay (Clay B) 
treated with 1.0 NCS--Si. 
.sup.3 The carbon black filler level was 75.0 phr. 
Tire Tread Study 
In a further performance comparison, Tables 13 and 14, the inventive 
treated clay product was successfully used as a substitute for a 
substantial portion of either carbon black or silica in a rubber tire 
tread formulation. While these filler studies exemplify substituting as 
much as 80% of the carbon black or silica, depending on the end use 
application, the inventive treated clay product can completely replace the 
carbon black or silica filler. 
The data in Table 14 compare carbon black (C.B., earlier tire technology), 
precipitated silica (Ppt SiO.sub.2, current tire technology), and Treated 
Clay A* for processing performance, general applications performance, and 
filler performance specific to the Michelin tire tread formulation shown 
in Table 13. Treated Clay A* was substituted for 70% of Ppt SiO.sub.2 in 
Sample 14C. 
There is a large processing advantage to using Treated Clay A* in this 
formulation over the earlier technologies. This can be seen in the 
improved values for Banbury mix cycle, rheometer cure time, and Mooney 
viscosity. 
Regarding applications performance, Treated Clay A* also gives superior 
resistance to heat build-up (see Goodrich flexometer), wear resistance and 
rolling resistance (see MTS, DMA data). 
Durometer hardness, tensile strength, compression set, modulus, and tear 
die of Sample 14C is equivalent to Sample 14B which contains all Ppt 
SiO.sub.2. Sample 14C has superior performance in these same properties 
compared to carbon black, Sample 14A. 
In summary, the data indicate that Treated Clay A* can be used to replace 
most of the expensive Ppt SiO.sub.2 in the Michelin tire tread formulation 
to give superior performance as compared to either the pure Ppt SiO.sub.2 
or carbon black compounds where improved processing, wear resistance, 
rolling resistance, and low heat build-up are required. Only abrasion and 
wet traction values were lower which can be rectified by using less clay 
in the clay based formulation. 
TABLE 13 
______________________________________ 
Michelin Tire Tread Formulation 
Ingredients 14A 14B 14C 
______________________________________ 
SBR Solution 75.00 75.00 
SBR Emulsion 65.00 
Polybutadiene 35.00 25.00 25.00 
N-234 C.B. 80.00 
Dispersible Pptd. Silica 80.00 25.00 
Clay A* 55.00 
N-330 C.B. 4.40 
Crossinking agent X 50 S 12.80 4.00 
Aromatic oil 37.50 32.50 7.00 
Stearic Acid 1.00 1.00 1.50 
Antozite 67P 2.00 2.00 2.00 
Sunproof Improved 
1.50 1.50 1.50 
Zinc Oxide 2.50 2.50 2.50 
Suflur 1.35 1.40 1.70 
Santocure CBS 1.35 1.70 1.70 
Diphenyl Guanidine 
1.35 2.00 1.20 
Total 227.20 237.40 208.30 
______________________________________ 
TABLE 14 
______________________________________ 
Compound Identification 
14A 14B 14C 
______________________________________ 
Specific Gravity 1.156 1.196 1.275 
Durometer (Shore A) (pts) 
75 68 67 
Tensile (psi) 2030 2240 2220 
Elongation (%) 400 300 320 
Compression Set: 22 hrs. @ 
46.5% 35.3% 35.8% 
212.degree. F. Deflection (%) 
DeMattia Flexibility 
1,000 5,000 5,000 
(cycles) 
Banbury Mix Cycle Time 
5:30 6:30 5:00 
(min.) 
Rheometer (T-90%) (min.) 
9:55 13:13 9:15 
Mooney Viscosity (1 
195.6 148.0 97.7 
unit = 0.083 Nm) 
Initial Viscosity (units) 
ML 1 + 4 (212.degree. F.) (units) 
99.6 68.8 64.4 
Modulus (psi) 
@ 100% Elongation 420 590 830 
@ 200% Elongation 900 1310 1520 
@ 300% Elongation 1500 2220 2110 
Tear Die "C" (pli.) 
166 318 336 
Goodrich Flexometer 
117.0 31.5 27.0 
.DELTA.Temperature (.degree.F.) 
Static Deflection (%) 
16.73 13.22 11.67 
(stiffness) 
Dynamic Deflection (%) 
30.42 3.15 1.59 
(stiffness) 
Dynamic Compression Set (%) 
13.42 1.09 0.79 
NBS Abrasion (abrasive 
804 762 245 
index) 
Pico Abrasion (Index) 
160 118 61 
MTS Dynamic Testing 
Tan delta @ -20.degree. C. (.uparw.) 
0.3679 0.6399 0.7564 
Tan delta @ 0.degree. C. (.uparw.) 
0.4423 0.5046 0.3824 
Tan delta @ 60.degree. C. (.dwnarw.) 
0.3954 0.1094 0.0882 
DMA Testing 
Tan delta @ -20.degree. C. (.uparw.) 
0.445 0.767 0.941 
Tan delta @ 0.degree. C. (.uparw.) 
0.477 0.513 0.376 
Tan delta @ 60.degree. C. (.dwnarw.) 
0.501 0.160 0.134 
______________________________________ 
Key: MTS and DMA data 
-20.degree. C. = higher the number (.uparw.), the better the wear 
resistance 
0.degree. C. = higher the number (.uparw.), the better the wet traction 
60.degree. C. = lower the number (.dwnarw.), the lower the rolling 
resistance 
Tire Carcass Formulation 
The following example demonstrates the use of alternate sources of clay, 
the effectiveness of the inventive surface treatment in alternate rubber 
formulations, and the ability of these high performance clays to replace 
carbon black in rubber. 
The multi-component surface treatment of this invention was tested on an 
alternate fine particle size, Tertiary east Georgia clay hereinafter 
referred to as Treated Clay D. Treated Clay D is more coarse and has lower 
brightness than Clay B, having been degritted but was not fully 
beneficiated. The Sedigraph particle size distribution of Treated Clay D 
shows that 90% of particles are less than 2.mu.. Treated Clay D, was 
compounded into the tire carcass formulation shown in Table 15. The 
amounts of Treated Clay D and carbon black were adjusted to maintain 
constant durometer hardness. The performance is compared to carbon black 
in Table 16. All of the results of Table 16 show excellent performance, 
equivalent to a soft carbon black, the industry standard, at significantly 
lower cost. Thus, Treated Clay D can almost completely replace carbon 
black at significant cost advantage. 
TABLE 15 
______________________________________ 
Tire Carcass Formulation 
Ingredient 16A 16B 
______________________________________ 
Natural Rubber SMR-L 
75.00 75.00 
SBR 1778 34.40 34.40 
Treated Clay D 64.00 -- 
N-660 Carbon Black 
10.00 50.00 
Circosol 4240 5.00 5.00 
Stearic Acid 1.00 1.00 
Wingstay 100 1.00 1.00 
SP 1068 Resin 3.00 3.00 
Zinc Oxide 5.00 5.00 
Sulfur (Rubber Makers) 
2.50 2.50 
Benzothiazyl disulfide 
0.85 0.85 
Diphenyl Guanidine 
0.15 0.15 
Total 201.90 177.90 
______________________________________ 
TABLE 16 
______________________________________ 
16A. Treated Clay D 
16B. N-660 Carbon Black 
Compound 
Identification 16A 16B 
______________________________________ 
Durometer (A) 53 54 
Tensile (psi) 3510 3240 
Elongation, % 450 430 
Modulus (psi) 
@ 100% Elongation 540 400 
@ 200% Elongation 1220 1080 
@ 300% Elongation 1910 1920 
Tear Die "C" (pli) 350 322 
______________________________________ 
Treated Clays versus Carbon Black Fillers 
The reinforcing performance of Treated Clay B, Hi-Treated Clay B and 
Treated Clay A* were compared to that of five different carbon blacks in a 
rubber compound similar to the Natsyn 2200 screening formulation of Table 
3. Only the filler loadings differed from the standard Natsyn 2200 
formulation wherein the carbon black formulations each contain 50 phr of 
the indicated carbon black while the clay based formulations contain 80 
phr of treated clay to maintain approximate constant hardness. Treated 
Clay B and Hi-Treated Caly B both represent conventional silane-treated 
clays, as previously presented in Table 12. The reinforcing performance 
results are shown in Table 17. 
The treated clay samples exhibited relatively high 300% moduli as compared 
to the carbon black samples. In particular the treated clay of this 
invention, Treated Clay A*, provides the highest level of reinforcement 
among the treated clays and exhibits a 300% modulus well above that of any 
carbon black samples. The carbon black samples' 300% moduli are observed 
to decrease with increasing particle size. All of the treated clay tensile 
values are greater than those of the carbon black samples. Also, the clay 
tear values are greater than any of the carbon black tear values. The 
Treated Caly A* sample was the most resilient of all samples in 
accelerated aging performance. 
TABLE 17 
______________________________________ 
Carbon Black Samples.sup.1 
______________________________________ 
N-330 N-550 N-660 N-754 N-990 
Sample Description 
C.B. C.B. C.B. C.B. C.B. 
______________________________________ 
Rheometer (T = 90%), 
4:15 4:27 4:58 5:13 5:37 
min. 
Durometer (Shore A) pts 
68 67 62 61 56 
Tensile, (psi) 
3040 3120 3080 3060 2520 
Elongation % 400 440 480 460 540 
Modulus (psi) 
@ 100% Elongation 
490 580 400 400 230 
@ 200% Elongation 
1200 1300 920 920 350 
@ 300% Elongation 
2060 2030 1560 1570 460 
Tear Die "C", pli 
370 369 303 306 182 
______________________________________ 
Clay Samples.sup.2 
______________________________________ 
Treated Hi-Treated 
Treated 
Sample Description 
Clay B Clay B Clay A* 
______________________________________ 
Rheometer (T = 90%), min. 
5:18 5:28 4:50 
Durometer (Shore A) pts 
64 65 67 
Tensile, (psi) 3480 3610 3480 
Elongation % 470 440 400 
Modulus (psi) 
@ 100% Elongation 
590 760 870 
@ 200% Elongation 
1190 1520 1810 
@ 300% Elongation 
1790 2230 2600 
Tear Die "C", pli 
383 418 418 
______________________________________ 
.sup.1 The formulation is that of Table 3, except that carbon black 
loadings are 50 phr. 
.sup.2 The formulation is that of Table 3, except that clay loadings are 
80 phr. 
Truck Tire Wire Belt Coat Compound 
This example demonstrates that Treated Clay A* can completely replace 
carbon black in this rubber application where modulus is a critical 
parameter. A formulation calling for complete substitution of carbon black 
by the treated clays is shown in Table 18 and the physical testing results 
are shown in Table 19. While the prior art, silane-treated clays have 300% 
moduli that are less than that of the N-300 sample, the 300% modulus of 
Treated Clay A* of this invention is radically higher than either the 
prior art clays or the N-330 sample. Treated Clay A* also shows 
significant improvements over the prior art, silane-treated clays in 
tensile and tear and is close to those observed for N-330. 
TABLE 18 
______________________________________ 
Truck Tire Wire Belt Coat Formulation 
Ingredient phr 
______________________________________ 
SMR 5 100.00 
Carbon Black or See Table 19 
Treated Clay 
Antioxidant 35 1.00 
Antozite 67P 1.00 
Stearic Acid 1.00 
Zinc Oxide 6.00 
Cobalt Stearate 1.80 
Insoluble Sulfur 
3.60 
Amax 0.65 
______________________________________ 
TABLE 19 
______________________________________ 
Hi- 
N-330 Treated Treated 
Treated 
C.B. Clay B Clay B Clay A* 
Sample Description.sup.1 
50 phr 80 phr 80 phr 80 phr 
______________________________________ 
Rheometer (T = 90%), mins. 
5:58 8:30 8:08 9:02 
Durometer (Shore A) pts 
66 53 56 59 
Tensile, (psi) 4010 3470 3620 3880 
Elongation, % 560 570 550 460 
Modulus (psi) 
@ 100% Elongation 
380 300 360 590 
@ 200% Elongation 
960 660 810 1360 
@ 300% Elongation 
1750 1120 1350 2190 
Tear Die "C", pli 
401 332 370 389 
______________________________________ 
.sup.1 Clay samples also contain 4.0 phr of N330 C.B. 
Tire Apex Compound 
This example demonstrates the performance of treated clays as compared to a 
carbon black in an SBR formulation on a direct substitution basis without 
any optimization of the formula in terms of curing rate (Table 20). 
Treated Clay A* shows significant improvement over the prior art, silane 
treated clays in modulus though not as high as that provided by N-660 
(Table 21). Further improvements can be obtained by optimizing the treated 
clay compounds to give a tighter cure. All of the treated clay samples 
exhibit comparable tensile to N-660, but considerably higher elongation 
and tear. When the loadings of the treated clays are increased to 160 phr 
to approximate equal durometer hardness, the Treated Clay A* modulus 
increases dramatically to beyond that for carbon black. 
TABLE 20 
______________________________________ 
Tire Apex Compound 
Ingredient Phr 
______________________________________ 
SBR 1500 100.00 
Carbon Black or 100.00 
Treated Clay 
Aromatic oil 5.00 
Rosin oil 5.00 
Vanplast R 2.00 
Stearic Acid 2.00 
Zinc Oxide 4.00 
Agerite Resin D 2.00 
Sulfur 3.50 
N-Cyclohexylbenzo- 
1.00 
thiazole sulfenamide 
Total Parts 224.50 
______________________________________ 
TABLE 21 
______________________________________ 
Hi- 
N-660 Treated Treated 
Treated 
Sample Description.sup.1 
C.B. Clay B Clay B Clay A* 
______________________________________ 
Rheometer (T = 90%) , min 
15:13 22:50 22:25 16:20 
Durometer (Shore A), pts 
78 65 68 69 
Tensile, (psi) 2870 3020 3090 2780 
Elongation, % 300 630 580 440 
Modulus (psi) 
@ 100% Elongation 
1000 500 650 870 
@ 200% Elongation 
2260 930 1220 1620 
@ 300% Elongation 
2870 1190 1530 2090 
Tear Die "C", pli 
296 343 392 357 
______________________________________ 
.sup.1 Clay samples also contain 4.0 phr of N660 C.B. 
Automotive Radiator Hose Compound 
In this example, a radiator hose formulation was chosen to compare the 
performance of N-550 and N-990 carbon blacks to Treated Clay B, Hi-Treated 
Clay B or Treated Clay A* (see Table 22). This compound is an unusual 
formulation in that the clay loading is over three times that of the 
rubber polymer (352 phr). This situation results from formulation 
adjustments to maintain constant hardness when replacing carbon black with 
treated clay. The high clay loading is used to demonstrate the crosslink 
density benefits of Treated Clay A* while not necessarily using an optimum 
formulation. All fillers provided comparable tensile and tear. However, 
the 300% modulus provided by the treated clay of this invention, Treated 
Clay A*, surpasses that of carbon black, as well as that for all of the 
prior art, silane-treated clays. 
TABLE 22 
______________________________________ 
Automotive Radiator Hose Compound 
Ingredients phr 
______________________________________ 
EPDM 1145 100.00 
Carbon Black or Treated Clay 
See Table 23 
Arornatic Oil 120.00 
Stearic Acid 1.00 
Zinc Oxide 5.00 
Sulfur 1.50 
Zinc dimethyldithiocarbamate 
1.25 
Tetramethylthiuram disulfide 
1.25 
2-mercaptobenzothiazole 
.50 
Tellurium 0.80 
diethyldithiocarbamate 
______________________________________ 
TABLE 23 
______________________________________ 
Hi- 
N-550/ Treated Treated 
Treated 
Sample Description.sup.1 
N-990 Clay B Clay B 
Clay A* 
______________________________________ 
Filler Loading, phr 
120.0 352.0 352.0 352.0 
100.0 
Rheometer (T = 90%), min 
11:25 18:47 16:53 18:35 
Durometer (Shore A), pts 
70 71 72 72 
Tensile, (psi) 1150 950 1070 1050 
Elongation, % 540 540 480 420 
Modulus (psi) 
@ 100% Elongation 
400 420 510 490 
@ 200% Elongation 
770 690 830 870 
@ 300% Elongation 
940 810 940 1020 
Tear Die "C", pli 
162 148 160 147 
______________________________________ 
.sup.1 Clay samples contain 5.0 phr N550. 
V-Belt (Tensile Gum) Compound 
In this example, a V-belt compound was examined. As is shown in Table 24, 
this rubber formulation uses polychloroprene, N-550 carbon black, and 
precipitated silica. The curing agent is zinc oxide which is unique among 
the formulations thus shown. Both the carbon black and silica are replaced 
by Treated Clay B, Hi-Treated Clay B, and then Treated Clay A*. 
Table 25 reports the physical testing results. The modulus and abrasion 
properties of this formulation are improved over the prior art, 
silane-treated clays by using the multi-component treatment of Treated 
Clay A*, though they are not as high as those provided by the carbon 
black. Tear properties are particularly critical in V-belt applications 
and the tear value of the Treated Clay A* sample is the highest of all 
samples including the carbon black sample. 
TABLE 24 
______________________________________ 
V - Belt (Tensile Gum) Compound 
Ingredients phr 
______________________________________ 
Polycholorprene GK 100.00 
Carbon Black or see Table 25 
Treated Clay 
Hydrotreated 12.00 
Naphthenic oil 
Dioctylphthalate 6.00 
Stearic Acid 2.50 
Magnesium Oxide 4.00 
Agerite HP-S 2.00 
Agerite Stalite 2.00 
Zinc Oxide 6.00 
______________________________________ 
TABLE 25 
______________________________________ 
N-550 C.B./ 
Treated Hi-Treated 
Treated 
Sample Description.sup.1 
Pptd silica 
Clay B Clay B Clay A 
______________________________________ 
Filler Loading, phr 
50.0/20.0 100.0 100.0 100.0 
Rheometer (T = 90%), min 
19:17 22:25 22:05 19:45 
Durometer (Shore A) pts 
76 63 64 66 
Tensile, (psi) 
2460 2480 2350 1960 
Elongation, % 330 800 730 550 
Modulus (psi) 
@ 100% Elongation 
770 490 620 820 
@ 200% Elongation 
1540 770 1080 1410 
@ 300% Elongation 
2250 900 1270 1630 
Tear Die "C", pli 
367 233 338 420 
NBS Abrasion, cycles 
428 186 237 253 
______________________________________ 
.sup.1 Clay samples contain 4.00 phr N550 C.B. 
Innertube Rubber Compound 
The innertube formulation examined in this example uses EPDM, butyl rubber, 
and N-660 carbon black (Table 26). The carbon black was completely 
replaced by Treated Clay B, Hi-carbon black was completely replaced by 
Treated Clay B, Hi-Treated Clay B and Treated Clay A*. The performance 
data in Table 27 show that two of the treated clay samples have higher 
moduli as compared to carbon black, including Treated Clay A*. The tear 
values of Treated Clay A* and carbon black are essentially equivalent 
whereas the tensile values show an interesting reversal in trend as 
compared to the increasing trend for modulus. 
TABLE 26 
______________________________________ 
Innertube Compound 
Ingredients phr 
______________________________________ 
EPDM 2200 20.00 
Butyl 268 80.00 
Carbon Black or See Table 27 
Treated Clay 
ASTM 104B oil 25.00 
Zinc Oxide 5.00 
Stearic Acid 1.00 
Sulfur 1.00 
Tetramethylthiuram 1.50 
disulfide 
2-Mercapto- 0.50 
benzothiazole 
______________________________________ 
TABLE 27 
______________________________________ 
Hi- 
N-660/ Treated Treated 
Treated 
Sample Description.sup.1 
C.B. Clay B Clay B 
Clay A* 
______________________________________ 
Filler Loading, phr 
70.0 112.0 112.0 112.0 
Rheometer (T = 90%), mins. 
14:15 17:47 15:50 16:08 
Durometer (Shore A), pts 
51 49 51 54 
Tensile, (psi) 1700 1800 1620 1370 
Elongation, % 630 770 650 580 
Modulus (psi) 
@ 100% Elongation 
230 250 310 330 
@ 200% Elongation 
490 450 610 660 
@ 300% Elongation 
740 600 810 870 
Tear Die "C", pli 
191 158 178 188 
______________________________________ 
.sup.1 Clay samples contain 4.00 phr N660 C.B. 
As such, an invention has been disclosed in terms of preferred embodiments 
thereof which fulfill each of the objects of the present invention as set 
forth above and provides a new and improved treated clay product, method 
of making an improved clay feed stock, an improved rubber formulation and 
a method of making the rubber formulation. 
Various changes, modifications and alterations from the teachings of the 
present invention may be contemplated by those skilled in the art without 
departing from the intended spirit and scope thereof. Accordingly, it is 
intended that the present invention only be limited by the terms of the 
appended claims.