Color changeable aqueous adhesive systems

The invention describes both a method for bonding at least two elastomeric substrates together, wherein one of the substrates is a tire casing and another substrate is a tire tread, and an aqueous color changeable adhesive for effecting the bonding. The method includes the steps of buffing at least one surface of at least one of the substrates to an RMA 2 or RMA 3, applying the color changeable aqueous adhesive to the at least one surface, drying the adhesive for at least a period of time to permit an initial light grey color of the adhesive as applied to change to a flat black, and contacting the substrates under pressure to bond the substrates together. The color changeable aqueous adhesive includes at least a rubber latex emulsion, a tackifier, a pH adjustment agent, and a carbon black emulsion, wherein the carbon black functions both as a reinforcing agent and a visible color indicia means for evaluating the degree of dryness of the adhesive, which correlates to the degree of tack of the adhesive. The carbon black is a lampblack.

TECHNICAL FIELD 
The invention described herein pertains generally to an aqueous adhesive 
system with color indicia subsystem for visually measuring the degree of 
tackiness of a retread cement. 
BACKGROUND OF THE INVENTION 
With increasing environmental awareness, the use of retread cements which 
contain volatile organic compounds (VOCs) is rapidly decreasing while the 
switch to aqueous based retread cements is increasing. Solvent containing 
adhesives are commonly used in the tire manufacturing industry, because 
they are easy to work, particularly at low temperature, and generally 
provide a good quick bonding capacity and good adhesive strengths. 
However, a serious disadvantage of the solvent containing adhesives is the 
large quantity of organic solvents they contain. These are released by 
evaporation during working and thus, result in a considerable odor, which 
in some circumstances may lead to a health risk for the operator. 
Additionally, due to the volatile nature of these adhesives, explosive 
solvent/air mixtures may be produced. 
While aqueous compositions have been used prior in the prior art, there is 
no teaching which shows the use of an aqueous based adhesive with a color 
indicia which indicates the degree of dryness of the adhesive. U.S. Pat. 
No. 5,425,824 to Marwick, published Jun. 20, 1995, teaches the use of an 
adhesive composition which is a mixture of a one-part heat-curable 
adhesive and a substantially water-insoluble indicator material which is 
substantially unreactive with the components of the one-part heat-curable 
adhesive, but which has the ability to produce a color change in the 
composition on curing of the adhesive. Preferably, the adhesive is a 
one-part heat-curable epoxy adhesive system whereas the indicator 
materials are ones that will not react substantially at room temperature 
with any of the components of the resin, the curing agent and the 
accelerator, if present. 
The indicator materials respond only to the reactor within the adhesive 
during thermally-induced curing by changing color. Chemical indicators 
which were used must be substantially insoluble in water and would include 
bromocresol purpole, and color formers of the type described in the 
Journal of the Society of Dyers and Colorists, 105, April 1989, 171-172, 
an example of which is Reaktred 448, a fluoran color former produced by 
Badische Anilin and Soda Fabrik AG, and 1-2-benzo-6-diethylamine-fluoran. 
The above reference however, fails to suggest that something as 
commercially prevalent as a particular form of carbon black, i.e., 
lampblack, may act in a similar capacity to the above exotic and expensive 
color indicator materials shown above. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided an aqueous 
based color indicia system for visually measuring the degree of tackiness 
of a curable retread cement. More specifically, it relates to an adhesive 
system wherein the drying time of the adhesive and its resulting degree of 
tack, can be visually measured for use by an operator in applying a tire 
tread to a tire casing without resorting to measuring moisture levels in 
the adhesive or a timing device. 
The color indicia system is essentially a water-insoluble indicator 
material which is substantially unreactive with the adhesive, but which 
has the ability to produce a visual color change in the composition upon 
drying of the adhesive. 
These and other objects of this invention will be evident when viewed in 
light of the drawings, detailed description, and appended claims. 
DETAILED DESCRIPTION OF THE INVENTION 
The aqueous based color indicia system for visually measuring the degree of 
dryness which is directly correlatable to the tackiness of a retread 
cement comprises an elastomer, water, pH adjuster, and an optically 
visible color-change dryness indicator which co-functions as a reinforcing 
agent e.g., lampblack, and a tackifier. 
Any natural or synthetic rubber may be employed in the adhesive 
compositions of this invention. A non-limiting exemplary list of candidate 
rubbers would include natural rubber and synthetic rubbers, e.g., 
polyisoprene, acrylonitrile-butadiene rubbers, styrene-butadiene rubbers, 
neoprene, butyl rubber, polybutadienes and ethylene-propylene-diene 
rubbery polymers. The diene used in the ethylene-propylene-diene polymer 
is usually a non-conjugated diene such as any of the one or more of those 
generally known in the art, e.g, 1,4-hexadiene, ethylidene norbornene or 
dicyclopentadiene. Rubbery or elastomeric ethylene-propylene-diene 
polymers and methods for preparing them are described in, for example, 
Rubber Chemistry and Technology, 45(1), March 1972. Mixtures of the above 
rubbers are also envisioned within the scope of this invention. 
A preferred elastomer for use in this invention is Kagetex 2003 LATZ CAS 
9003-31-0 for the polymer! as sold by The Ore & Chemical Corporation, 
Virginia. This elastomer is a concentrated, centrifuged, low ammonia grade 
of natural latex, containing a secondary preservative system of 
tetramethylthiuramdisulfide and zinc oxide, which is used to prevent 
bacterial growth and to stabilize the latex. The total solids content is 
61.5% with a dry rubber content of 60.0%. The alkalinity-ammonia content 
is between 0.5-0.75% on the water phase and 0.29% maximum on the latex 
phase. The viscosity at 60% total solids content is between 80-100 cps. 
The KOH number is between 0.55-0.65 and the pH ranges from 9.6 to 10.2. 
The mineral content ranges from 2-4 ppm Cu, 0.1-0.4 ppm Mn, and 5-5 ppm 
Mg. The volatile fatty acids number ranges from 0.01-0.05. The shelf life 
of the latex is 6-12 months. Another preferred elastomer is low ammonia 
centrifuged natural latex GNL 150 sold commercially by The Goodyear Tire & 
Rubber Co. 
Accelerators and/or stabilizers and/or preservatives which may be employed 
in the adhesive compositions are compounds such as thiuram disulfide, 
selenium diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc 
diethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc 
2,2'-dithiobisbenzothiazole, tetramethylthiuram monosulfide, 
diphenylguanidine, N-cyclohexyl-2-benzothiazole sulfenamide, 
N-tert-butyl-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole and 
benzothiazyl disulfide. 
One key aspect of this invention involves the addition of a rubber 
reinforcing agent which coacts as a dryness indicator. An example of such 
a co-functional ingredient is lampblack. The amount of lampblack added is 
typically from approximately 0.5 to 5% by weight. The lampblack is 
typically purchased as an aqueous paste. The preferred lampblack known to 
date is E8678 carbon black as sold by Akrochem, Akron, Ohio. This form of 
carbon black as a particle size of approximately 75 nm, with a DBP 
(dibutyl phthalate) absorption of 63 cm.sup.3 /100 gm. A pH of 8.0 is 
typical with 1% volatiles maximum. The tint strength is 64 (ASTM D 3265) 
and specific gravity is 1.8. 
While lampblack is generally referred to as a form of carbon black, it has 
properties which are markedly different from carbon blacks in general. It 
is made by burning low-grade heavy oils or similar carbonaceous materials 
with insufficient air, and in a closed system such that the soot can be 
collected in settling chambers. Lampblack is strongly hydrophobic and is 
nonflammable. Other, more typical forms of carbon black include channel 
black (also called impingement black), furnace black and thermal black. 
Channel black is generally characterized by lower pH, higher volatile 
content, and less chainlike structure between the particles. It has the 
smallest particle size (largest specific surface area) of any industrial 
material. The particles are in the colloidal range. The surface area runs 
to about 18 acres per pound. Its chief use is as a reinforcing agent for 
rubber (tire treads), and increases both abrasion and oil resistance. 
Thermal black consists of relative coarse particles and is used primarily 
as a pigment. Furnace black produced from natural gas and has an 
intermediate particle size while that produced from oil can be made in a 
wide variety of controlled particles sizes and is particularly suitable 
for reinforcing synthetic rubber. 
Carbon blacks differ from other forms of bulk carbon such as diamond, 
graphite, cokes, and charcoal in that they are particulate, composed of 
aggregates having complex configurations, quasi graphitic in structure, 
and of colloidal dimensions. They differ from other bulk carbons in having 
their origin in the vapor phase through the thermal decomposition and the 
partial combustion of hydrocarbons. 
A number of processes have been used to produce carbon black including the 
oil-furnace, impingement (channel), lampblack, and the thermal 
decomposition of natural gas and acetylene. These processes produce 
different grades of carbon and are referred to by the process by which 
they are made, e.g., oil-furnace black, lampblack, thermal black, 
acetylene black, and channel-type impingement black. The reason for this 
variety of processes, is that there exists a unique link between 
manufacturing process and performance features of the carbon black and not 
all features are attainable by the products which result from each 
process. The different grades from the various processes have certain 
unique characteristics. 
Various classification schemes are used in the categorization of carbon 
blacks. Classification may be by abrasion resistance, i.e., high abrasion 
furnace (HAF), intermediate super abrasion furnace (ISAF), and super 
abrasion furnace (SAF); by reinforcement, i.e., semi-reinforcing furnace 
(SRF); by a vulcanizate property, i.e., high modulus furnace (HMF); by a 
rubber processing property, i.e., fast extrusion furnace (FEF); by 
usefulness, i.e., general purpose furnace (GPF), and all-purpose furnace 
(APF); by "particle" size, i.e., fine furnace (FF) and large particle size 
furnace (LPF); and on electrical conductive properties, i.e., (XPF). 
The obvious inadequacies of this unwieldy classification procedure lead the 
ASTM committee D-24 on carbon black to establish a letter and number 
system. In the ASTM system, the N-series numbers increase as I.sub.2 
absorption values or surface areas decrease. The SAF grades have 
designated numbers from N100-N199; the ISAF grades, N200-N299; the HAF 
grades, N300-N399; the FF and XCF grades, N400-499; the FEF grades, 
N500-599; the HMF, GPF, and APF grades, N600-699; the SRF grades, 
N700-799; fine thermal (FT) has been designated as N880, and medium 
thermal (MT) N990. 
Acetylene Black Process 
The high carbon content of acetylene (92%) makes it attractive for 
conversion to carbon. It decomposes exothermically at high temperatures, a 
property which was the basis of an explosion process initiated by 
electrical discharge. Acetylene black is made by a continuous 
decomposition process at 800.degree.-1000.degree. C. in water-cooled metal 
retorts lined with a refractory. The process is started by burning 
acetylene and air to heat the retort to reaction temperature, followed by 
shutting off the air supply to allow the acetylene to decompose to carbon 
and hydrogen in the absence of air. The large heat release requires water 
cooling in order to maintain a constant reaction temperature. The high 
carbon concentration, high reaction temperature and relatively long 
residence time produce a unique type of carbon black. After separation 
from the gas stream it is very fluffy with a bulk density of only 19 
kg/m.sup.3 (1.2 lb/ft.sup.3). Acetylene black is difficult to compact by 
compression and resists pelletization. Commercial grades are compressed to 
various bulk densities up to a maximum of 200 kg/m.sup.3 (12.5 
lb/ft.sup.3). 
It is the purest form of carbon black with a carbon content of 99.7%, and a 
hydrogen content of 0.1%. It has the highest aggregation with a DBPA value 
of 250 cm.sup.3 /100 g. X-ray analysis indicates that it is the most 
crystalline or graphitic of the commercial blacks. These features result 
in a product with low surface activity, low moisture adsorption, high 
liquid adsorption, and high electrical and thermal conductivities. 
A major use for acetylene black is in dry cell batteries because it 
contributes low electrical resistance and high capacity. In rubber it 
gives electrically conductive properties to heater pads, heater tapes, 
antistatic belt drives, conveyor belts, and shoe soles. It is also used in 
electrically conductive plastics. Some applications of acetylene black in 
rubber depend on its contribution to improved thermal conductivity, such 
as rubber curing bags for tire manufacture. 
Lampblack Process 
The lampblack process has the distinction of being the oldest and most 
primitive carbon black process still being practiced. The ancient 
Egyptians and Chinese employed techniques similar to modern methods 
collecting the lampblack by deposition on cool surfaces. Basically, the 
process consists of burning various liquid or molten raw materials in 
large, open, shallow pans 0.5 to 2 m in diameter and 16 cm deep under 
brick-lined flue enclosures with a restricted air supply. The smoke from 
the burning pans passes through low velocity settling chambers from which 
the carbon black is cleared by motor-driven ploughs. In more modern 
installations the black is separated by cyclones and filters. By varying 
the size of the burner pans and the amount of combustion air, the particle 
size and surface area can be controlled within narrow limits. Lampblacks 
have similar properties to the low area oil-furnace blacks. A typical 
lampblack has an average particle diameter of 65 nm, a surface area of 22 
m.sup.2 /g, and a DBPA of 130 mL/100 g. Its main use is in paints, as a 
tinting pigment where blue tone is desired. 
Channel Black Process 
The channel black process has had a long and successful history, beginning 
in 1872 and ending in the United States in 1976. Small quantities are 
still produced in a few scattered plants operating in Germany 
(roller-process using oil), Eastern Europe, and Japan. Rising natural gas 
prices, smoke-pollution, low yield, and the rapid development of furnace 
process grades caused the termination of channel black production in the 
United States. 
The name channel black came from the use of steel channel irons whose flat 
side was used to collect carbon black deposited from many small flames in 
contact with its surface. The collecting channels and thousands of flames 
issuing from ceramic tips were housed in sheet metal buildings, each 35-45 
m long, 3-4 m wide, and about 3 m high. The air supply came from the base 
of these buildings, the waste gases, containing large quantities of 
undeposited product, were vented to the atmosphere as a black smoke. 
Carbon black was removed from the channels by scrapers and fell into 
hoppers beneath the channels. Yields were very low, in the range of 1-5%. 
The blackest pigment grades had the lowest yields. The product was 
conveyed from the hot houses to a processing unit where grit, magnetic 
scale, coke, and other foreign material were removed. From an initial bulk 
density of 80 kg/m.sup.3 (5 lb/ft.sup.3) it was compacted and pelletized 
to over 400 kg/m.sup.3 (25 lb/ft.sup.3) for use in rubber. Lower bulk 
densities were used for pigment applications. 
Channel blacks are surface oxidized as a result of their exposure to air at 
elevated temperatures on the channel irons. Due to surface oxidation, the 
particles are slightly porous. These features influence performance in 
most applications. 
Oil-Furnace Process 
The feedstocks for the oil-furnace process are essentially hydrocarbon 
oils. They are specified to be free of coke and other gritty materials, 
possess high aromaticity, and contain low levels of asphalt, sulfur, and 
alkali metals. The oil-furnace process involves a partial combustion of 
the hydrocarbon feed, followed by quenching to reduce the temperatures 
rapidly from 1300.degree.-1600.degree. C. to 1000.degree. C., which 
protects the newly formed carbon black aggregates. The product passes 
through heaters, where the combustion air is preheated, and is quenched 
again at 270.degree. C. prior to collection of the carbon black in glass 
bag filters. The carbon black is ground or micropulverized and stored. 
Carbon blacks are pelletized by dry or wet methods to provide a low 
dusting or nondusting product. 
Thermal Process 
This process is similar to that described previously for the acetylene 
process, with the exception of the feedstock used, hydrocarbons rather 
than acetylene. 
TABLE 1 
______________________________________ 
Carbon Black 
Furnace Thermal Thermal Channel 
HAF MT FT EPC Lamp 
Property 
N330 N990 N880 Acetylene 
S300 black 
______________________________________ 
avg. particle 
28 500 180 40 28 65 
dia. (nm) 
surface area 
75 47 13 65 115 22 
(BET) m.sup.2 /g 
DBPA 103 36 33 250 100 130 
mL/100g 
tinting 210 35 65 108 180 90 
strength 
% SRF 
benzene 0.06% 0.30% 0.80% 0.10% 0.00% 0.20% 
extract 
pH 7.5 8.5 9.0 4.8 3.8 3.0 
volatiles 
1.00% 0.50% 0.50% 0.30% 5.00% 1.50% 
% ash 0.40% 0.30% 0.10% 0.00% 0.02% 0.02% 
% C 97.90% 99.30% 99.20% 
99.70% 95.60% 
98.00% 
% H 0.40% 0.30% 0.50% 0.10% 0.60% 0.20% 
% S 0.60% 0.01% 0.01% 0.02% 0.20% 0.80% 
% O 0.70% 0.10% 0.30% 0.20% 3.50% 0.80% 
______________________________________ 
Selection of a carbon black depends on the black's performance 
characteristics, which are governed by particle size, surface area, 
structure or morphology, chemical composition, and surface chemistry. 
Carbon blacks are intermediate in crystallinity between the crystalline 
graphite and the amorphous structure of coal. Carbon blacks have surface 
areas of 6-1100 m.sup.2 /g and particle sizes of 10-500 nm. With carbon 
black the term particle does not refer to an individual, discrete 
particle, but to a group of particles which are fused together and form a 
primary aggregate. The structure of carbon black is controlled during 
manufacture and is characterized as low, medium, or high; these 
designations refer to the size and configuration of the primary 
aggregates. High structure carbon blacks consist of relatively large, 
highly branched aggregates, whereas low structure blacks are composed of 
compact aggregates. 
Typical properties of carbon black pigments as they relate to particle size 
and structure are listed in Table 1. Carbon blacks have a density of 1.8 
g/cm.sup.3. Oil-absorption values differ. One method which is employed to 
measure oil absorption is the use of a Brabender/Cabot absorptometer by 
which the dibutyl phthalate (DBP) absorption number is determined. Some 
typical DBP absorption values are acetylene black, 250 mL/100 g solvent; 
thermal black, 33 mL/100 g, lamp black, 130 mL/100 g; furnace black, 103 
mL/100 g and channel black, 100 mL/100 g. 
Other conventional components which may be included in the adhesive 
composition are vulcanizing agents, such as elemental sulfur and 
sulfur-containing compounds. Other vulcanizing agents which may be 
employed are organic peroxides, metallic oxides, selenium and tellurium. 
Generally, the amount of vulcanizing agent present in the adhesive 
composition will vary somewhat with the amount or rubber. Preferably, no 
supplemental vulcanizing agents are added to the commercially purchasable 
rubbers. 
Examples of other compounding ingredients which may be employed in the 
adhesive composition are zinc oxide, magnesium oxide and fatty acids 
having from 10 to 22 carbon atoms, such as lauric acid, palmitic acid and 
stearic acid. Mixtures of fatty acids may also be used as accelerators in 
the adhesive compositions. Typically, these components are already present 
in the commercially purchased rubbers, but may be added in incremental 
amounts to the composition for specialized applications. 
Although natural rubber has some tack, the strength developed is inadequate 
for many uses. Most of the commercially available forms of synthetic 
elastomers have little tack either for themselves or other surfaces. 
Tackifiers are added to these systems to increase tack, a measure of the 
degree of bonding between the tire carcass and the tire tread. An 
exemplary list of tackifiers includes modified wood rosins, derivatives of 
wood rosin and modified rosin, polyterpene resins, coumarone-indene resins 
and phenolic-modified coumarone-indene resins. One preferred example of a 
tackifying agent is Aquatac, a rosin ester emulsion (CAS 133874-92-7), a 
complex combination derived from tall oil. It is composed primarily of 
tricyclic monocarboxylic acids, mainly abietic and dehydroabietic acids, 
and includes tall-oil rosin stabilized by catalytic disproportionation. 
Thickening agents are also typically added to the adhesive formulation to 
control the sprayability thereof. One preferred example of this type of 
agent is Alcogum, a sodium polyacrylate, (methacrylic acid-ethyl acrylate 
copolymer).

In the following description, reference will be made to the invention as it 
applies to the bonding of a tire tread to a tire casing. However, it is to 
be understood that the invention is not limited to that particular 
application, and may be employed in the fabrication of other laminated 
elastomeric articles, such as for example, conveyor belts, hoses, and the 
like. 
The tire casing and tread substrates which are to be used are formed from 
rubber compounds which have been cured according to conventional 
techniques. Such rubber compounds contain olefinic unsaturation in their 
polymer chains and include natural rubber, synthetic polyisoprene, 
polybutadiene, butadiene-isoprene copolymers, rubbery copolymers of 
butadiene and styrene, rubbery copolymers of butadiene and acrylonitrile, 
rubbery copolymers of isoprene and isobutylene, polychloroprene, 
ethylene-propylene rubbers, and the like. 
The term "natural rubber" as used herein means an elastomeric substance 
obtained from various trees and plants which generally grow in the tropics 
or desert portions of the world. Natural rubber contains a very high 
cis-content, typically in excess of 90% or more of cis-1,4-polyisoprene. 
Prior to subjecting the tire casing to the priming treatment, the casing is 
allowed to equilibrate at ambient indoor temperature and humidity for a 
period of time, typically from about several minutes to 15 hours. Visible 
moisture on the casing is removed and holes or other damage to the casing 
are repaired. 
Since the adhesive is an aquous based adhesive, it is important that the 
adhesive not come into direct contact with steel cables or body plies, 
which would have the potential of rusting. Repair cements as supplemented 
as necessary with filler extruder rope or caulking gum should be applied 
to the affected areas. 
The surface of the casing onto which the tread is to be bonded is then 
subjected to a conventional buffing procedure in order to clean the 
surface and provide a roughened surface to enhance bonding with the tread. 
The buffing is carried out using conventional tire buffing equipment. 
Buffing of the casing is carried out until the desired buffing depth and 
casing surface radius are obtained, in accordance with predetermined tire 
specifications, which generally mean to a texture of RMA 2 (Rubber 
Manufacturers Association Standard) or RMA 3. When the buffing is too 
rigorous, i.e., RMA 4 or RMA 5, then the adhesive puddles, leading to 
improper drying and poor adhesion. 
The tire tread may optionally be subjected to buffing to clean the surface 
of any contaminants and to roughen the surface. The term "tire tread" as 
used herein is intended to include not only conventional tire tread 
provided with grooves and/or lugs, but also "build-up". Build-up is a 
strip of cured rubber which does not have any tread thereon and is 
designed to provide a thickened surface on the tire casing prior to the 
application of the tire tread. 
Since the adhesive is an aqueous based system, mixing of the adhesive is 
critical in that after short storage times, the adhesive will separate, 
with a low or thin viscosity material at the bottom and a higher, thick 
viscosity material at the top. Proper mixing insures a homogeneous 
viscosity throughout the product. One specialized form of equipment which 
is particularly suited for use with this adhesive and in the tire retread 
business is a spray applicator. 
This applicator typically uses air pressure to atomize the adhesive through 
a spray gun. In order to minimize any chance of contamination, oil filters 
and moisture traps are typically placed on the inlet air side of the 
equipment. A fluid pressure of about 20 psi is maintained in the liquid 
while an atomizing pressure of 50-55 psi is generally used for the spray 
gun. Prior to the use of the adhesive, it should be mixed for at least 2 
minutes and checked. Adhesive which has been exposed to temperatures below 
38.degree. F. or greater than 140.degree. F. will tend to gel or separate 
and will not be effective for the intended application. 
Prior to each use, the adhesive should be mixed for about 10 minutes and 
the spray nozzle flushed for about 2 minutes to remove any cleaning 
solution which may have been used previously to clean the nozzle. The 
adhesive should always be remixed for 2 minutes after about 4 hours of use 
time. 
Application of the adhesive is typically via spraying with an 8-10" spray 
pattern desired. A spray gun is typically held about 8-10" away from the 
buffed rotating tire carcass and a light even application of adhesive is 
applied with 4-5 slow revolutions of the tire. In a preferred embodiment, 
the application of adhesive is performed so as to minimize overspraying 
adhesive onto other tires to which adhesive has previously been applied. 
The applied adhesive is allowed to dry for a period of about 20-40 minutes, 
preferably 20-30 minutes, although this time will be a function of the 
quantity of adhesive applied. The adhesive as applied is a light grey, and 
upon proper drying and resulting desired degree of tack, the color of the 
adhesive will change to a flat black. This distinct visual indicator of 
dryness and tack, is achievable by the use of lampblack as the color 
indicia. Other forms of carbon blacks do not produce this distinct color 
change, the adhesive going on as a dark grey to begin, with the final 
color being an even darker grey. This makes it visually difficult for an 
operator to determine when the proper degree of tack has been developed. 
In a preferred embodiment of this invention, the color change described for 
this invention, i.e., light grey to dull black, can be measured with 
reference to Federal Standard Colors, Federal Standard 595B (1989), 
wherein non-limiting exemplary light greys would include 16099, 26118, 
26099, 26008, 36118 and 36099. Similarly, non-limiting exemplary dull 
blacks would include 27040, 37030 and 37031. Of course, it is recognized 
that the color perceived is often dependent upon viewing angle. Thought of 
in another way, using the RGB color value standard wherein each color 
value for each color ranges from 0 to 255, a color of grey is only 
achieved when all three values for red, green and blue are essentially 
equal, with some minor variations between the numeric color values being 
permitted. The shade of grey (i.e., greyscale) is then determined by the 
HSL values for hue, saturation and luminosity (or brightness), the values 
ranging from 0 to 239 for hue, and 0-240 for saturation and luminosity. 
With the color of grey, the value for hue is relatively insensitive to 
various changes in greyscale color, saturation values are essentially zero 
and the most sensitive parameter is luminosity, ranging from 239 (light 
grey) to 0 (black). It is not possible for the H and S values to be zero 
and the L value to equal 240 and still achieve a grey color, this 
combination leading to white. Therefore, in its simplest form, the 
invention relates to a greyscale color change wherein the RGB values are 
essentially equal and the brightness change is at least 5%, preferably 
10%, and more preferably, 30% or more as measured against the total value 
of the scale. 
An exemplary grey to black color change under the RGB/HSB system would have 
values as follows in Table 2. 
TABLE 2 
______________________________________ 
R G B H S L 
Red Green Blue Hue Saturation 
Luminosity 
Color 
(0-255) (0-255) (0-255) 
(0-239) 
(0-240) 
(0-240) 
______________________________________ 
Light 
65 65 65 0 0 123 
Grey 
Black 
65 65 65 0 0 61 
______________________________________ 
Alternatively, acceptable color changes would also be visible with the 
following numeric values of the above parameters as shown in Table 3. 
TABLE 3 
______________________________________ 
R G B H S L 
Red Green Blue Hue Saturation 
Luminosity 
Color 
(0-255) (0-255) (0-255) 
(0-239) 
(0-240) 
(0-240) 
______________________________________ 
Light 
131 126 130 214 4 121 
Grey 
Black 
67 65 66 214 4 62 
______________________________________ 
It is of course that a wide variety of combinations will yield the desired 
color changes as shown above for two examples, the above numeric values 
having been derived by a comparison of the Federal Standard Color swatches 
with the Color Palette in Win-OS/2.RTM. Windows 3.1 running under OS/2 
Warp.RTM., although similar values are obtainable using the same Color 
Palette for computers running DOS.RTM./Windows 3.1.RTM.. The color change 
essentially depends upon the values for RGB as being essentially the same 
and the luminosity varying by at least 5% of the permissible range, more 
preferably 10%, and most preferably 20%. The permissible value for the 
saturation must be kept fairly low, typically 0-10, more preferably 0-5, 
and most preferably 0. 
After application of the adhesive is completed, the tread and casing are 
brought together and the ends of the tread stapled together to hold in 
place on the casing. The tire is "stitched" by applying pressure to the 
tread using rollers or the like. The stitching process more evenly 
distributes the adhesive between the casing and the tread. In general, 
there is a 48 hour window during which the adhesive is effective in 
bonding the tread to the carcass. Longer periods of time lead to surface 
oxidation and contamination leading to bond failure. Preferably, the 
operator will wait no longer than 4 hours prior to applying the tire tread 
to the tire carcass. 
The best mode for carrying out the invention will now be described for the 
purposes of illustrating the best mode known to the applicant at the time. 
The examples are illustrative only and not meant to limit the invention, 
as measured by the scope and spirit of the claims. 
The following components were mixed together in the following proportions. 
TABLE 4 
______________________________________ 
Weight Weight 
Weight Active Other Weight 
Component Formula Ingredients 
Solids.sup.(a) 
Water 
______________________________________ 
Kagetex 2003 LATZ 
55.28% 33.17% 0.83% 21.28% 
Natural Rubber Latex 
Emulsion 
Aquatac 6085 
17.54% 10.00% 0.70% 6.84% 
Rosin Ester Emulsion 
E-8678 2.50% 1.00% 0.30% 1.20% 
Lampblack Emulsion 
Alcogum NLT 2.00% 0.25% 1.75% 
Sodium Polyacryate 
KOH 0.16% 0.07% 0.09% 
Distilled Water 
22.52% 22.52% 
TOTALS 100.00% 44.49% 1.83% 53.68% 
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(a)Consists of surfactants, dispersing agents, emulsifiers, preservatives 
stabilizers and/or unknown ingredients in the above products. 
The percentages listed above are illustrative of the best mode known to the 
applicants at the time of the filing of this application. Envisioned to be 
effective in this invention are a broader range of values for the weight 
percent of the active ingredients. The natural latex rubber emulsion is 
envisioned to be effective between 12-58 weight percent, more preferably 
from 27-43 weight percent, the rosin ester emulsion between 1-20 weight 
percent, more preferably from 5-15 weight percent, the lampblack emulsion 
between 0.1 to 5 weight percent, more preferably from 0.3-1.7 weight 
percent and the pH adjuster between 0.01 to 0.6 weight percent, more 
preferably from 0.02 to 0.2 weight percent. 
The invention has been described with reference to preferred and alternate 
embodiments. Obviously, modifications and alterations will occur to others 
upon the reading and understanding of the specification. It is intended to 
include all such modifications and alterations insofar as they come within 
the scope of the appended claims or the equivalents thereof.