FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention: TREAD-WEAR INDICATOR COMPOSITION, PROCESS OF
PREPARATION THEREOF, AND A TIRE TREAD
2. Applicant(s)
NAME NATIONALITY ADDRESS
CEAT LIMITED Indian RPG HOUSE, 463, Dr. Annie Besant Road, Worli, Mumbai, 400 030, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

FIELD OF INVENTION
[001] The present disclosure broadly relates to an elastomeric composition used as a tread-wear indicator and particularly refers to a visually observable tread-wear indicator composition for use in a tire tread.
BACKGROUND OF INVENTION
[002] Tread portion of a tire refers to the pattern of grooves, tread blocks, ribs and sipes present on the outer circumference of a tire. It is the part that comes in contact with the road and provides appropriate traction necessary to facilitate a safe and smooth drive under a variety of driving conditions. However, under continuous usage over the time, the tread of the tire wears away and its ability to grip with the road, halt and accelerate diminishes. According to Bureau of Indian Standards (IS 15633: 2005 Automotive Vehicles – Pneumatic Tyres for Passenger Car Vehicles – Diagonal and Radial Ply – Specification), a pneumatic tire becomes unsafe to use when the worn skid depth reaches to a minimum value of 1.6mm.
[003] The sculpture (tread comprising raised and hollow elements) of a tire gives a top view of circumferential ribs, continuously running over the entire circumference of a tire, separated by hollow recesses called as grooves. The height of the ribs is higher than the grooves from the bottom of the tread which provide the tread, essential friction and rolling resistance with the ground surface. The ribs come in contact with the road and undergo a decrease in thickness. In order to indicate to the user that the tire treads have worn out to the extent that they require urgent attention, tread wear indicators are embedded as projections at specific locations inside the tread grooves or tread ribs at adequate depth, height and numbers. By measuring the relative height of the grooves or ribs, a visual indication of the degree of wear of the tire is estimated that is mostly evaluated by a vehicle mechanic or tire vendors. Thus, tread wear indicators hold utmost significance in issuing improved road safety by helping to monitor the stage of tire wear and decreasing the number of road accidents caused due to tire failures.
[004] Various tread wear indicators have been formulated and reported in the literature. For instance, US20060090558A1 discloses a tire wear sensor comprising

a wire, a radio frequency identification device, and a microprocessor. Despite all the research already established in this field, the present state of the art lacks development of a tread wear indicator composition that is easy to locate for an unskilled individual, does not interfere with the tire tread elements performance and is also economical for the manufacturer. Thus, there is a dire need to develop a tread wear indicator formulation that is more commercially advantageous over conventionally used formulations.
SUMMARY OF THE INVENTION
[005] In a first aspect of the present disclosure, there is provided a tread-wear
indicator composition comprising: (a) at least one synthetic rubber; (b) at least one
natural rubber; (c) 5 to 40 phr of at least one filler; (d) 0.5 to 15 phr of at least one
antiozonant; (e) 2 to 10 phr of at least one fluorescent agent; and (f) 20 to 50 phr of
at least one white indicator compound.
[006] In a second aspect of the present disclosure, there is provided a process of
preparing the tread-wear indicator composition as described herein, the process
comprising: (a) contacting the at least one synthetic rubber, the at least one natural
rubber, 5 to 40 phr of the at least one filler, 0.5 to 15 phr of the at least one
antiozonant, 2 to 10 phr of the at least one fluorescent agent, 20 to 50 phr of the at
least one white indicator compound, and 0.5 to 35 phr of the activator to obtain a
first mixture; and (b) curing the first mixture with 1 to 8 phr of the cross-linking
agent, and 0.5 to 2.0 phr of the accelerator to obtain the tread-wear indicator
composition.
[007] In a third aspect of the present disclosure, there is provided a tire tread
comprising the tread-wear indicator composition comprising: (a) at least one
synthetic rubber; (b) at least one natural rubber; (c) 5 to 40 phr of at least one filler;
(d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent
agent; and (f) 20 to 50 phr of at least one white indicator compound.
[008] These and other features, aspects, and advantages of the present subject
matter will be better understood with reference to the following description and
appended claims. This summary is provided to introduce a selection of concepts in a

simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[009] The following drawings form a part of the present specification and are
included to further illustrate aspects of the present disclosure. The disclosure may be
better understood by reference to the drawings in combination with the detailed
description of the specific embodiments presented herein.
[0010] Figure 1 depicts a vertical section of a tire tread through a line such that the
sipe with the greatest depth is visible, in accordance with an embodiment of the present
disclosure.
[0011] Figure 2 depicts a vertical section of a 4-rib tire tread indicating the position
of the tread-wear indicator composition, in accordance with an embodiment of the
present disclosure.
[0012] Figure 3 depicts a vertical section of a 5-rib tire tread indicating the position
of the tread-wear indicator composition, in accordance with an embodiment of the
present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps, features, compositions, and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any or more of such steps or features. Definitions
[0014] For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are delineated here. These definitions should be read in the light of the remainder of the disclosure and

understood as by a person of skill in the art. The terms used herein have the meanings
recognized and known to those of skill in the art, however, for convenience and
completeness, particular terms and their meanings are set forth below.
[0015] The articles “a”, “an” and “the” are used to refer to one or to more than one
(i.e., to at least one) of the grammatical object of the article.
[0016] The terms “comprise” and “comprising” are used in the inclusive, open sense,
meaning that additional elements may be included. It is not intended to be construed
as “consists of only”.
[0017] Throughout this specification, unless the context requires otherwise the word
“comprise”, and variations such as “comprises” and “comprising”, will be
understood to imply the inclusion of a stated element or step or group of element or
steps but not the exclusion of any other element or step or group of element or steps.
[0018] The term “including” is used to mean “including but not limited to”.
“Including” and “including but not limited to” are used interchangeably.
[0019] Ratios, concentrations, amounts, and other numerical data may be presented
herein in a range format. It is to be understood that such range format is used merely
for convenience and brevity and should be interpreted flexibly to include not only
the numerical values explicitly recited as the limits of the range, but also to include
all the individual numerical values or sub-ranges encompassed within that range as
if each numerical value and sub-range is explicitly recited. For example, a
concentration range of about 5 to 40 phr should be interpreted to include not only the
explicitly recited limits of about 5 phr to about 40 phr, but also to include sub-ranges,
such as 10 to 35 phr, 15 to 38 phr, and so forth, as well as individual amounts,
including fractional amounts, within the specified ranges, such as 5.8 phr, and 5.851
phr, for example.
[0020] The term “accelerator” used herein refers to a compounding material used
with a cross-linking agent to increase the speed of vulcanization of rubber.
[0021] The term “activator” used herein refers to products that have a strong
activation effect of increasing the vulcanization speed in the cross-linking reaction
of rubbers. Activators are required to achieve the desired vulcanization and end-user
properties.

[0022] The term “cross-linking agent” used herein refers to substances that can form
chemical bonds between two molecular chains by a chemical reaction. Cross-linking
is important because it provides the substance, mechanical strength and resistance to
heat, wear and attack by solvents.
[0023] The term “filler” used herein refers to a substance added to resins or binders
in order to reduce cost and modify physical, thermal, mechanical and electrical
properties such as bulk, strength, viscosity, weight, opacity, etc. Examples include
silica, carbon black and others.
[0024] The term “natural rubber” used herein refers to an elastic substance obtained
naturally from the bark of trees. It majorly comprises of isoprene units and water
along with some other impurities. Examples include ribbed smoked sheet,
technically specified rubber, and others.
[0025] The term “white indicator compound” used herein refers to a chemical
substance used to impart white base color to the rubber composition. The role of the
white indicator compound is to bring a desired change in the overall appearance of
the colored rubber composition. Examples include, but are not limited to, titanium
dioxide.
[0026] The term “styrene butadiene rubber” used herein refers to a family of
synthetic rubbers obtained from copolymerization of styrene and butadiene
monomers. For the purpose of present disclosure, the styrene content is present in
the range of 10 to 40% with respect to total content of styrene butadiene rubber in
the tread-wear indicator composition.
[0027] The term “emulsion styrene butadiene rubber” used herein refers to styrene
butadiene rubber prepared by emulsion polymerization of styrene and butadiene
monomers initiated by free radical initiators.
[0028] The term “solution styrene butadiene rubber” used herein refers to styrene
butadiene rubber prepared by a homogenous process of anionic polymerization of
styrene and butadiene.
[0029] The term “polybutadiene rubber” used herein refers to rubber obtained from
polymerization of butadiene monomers in the presence of nickel, cobalt or
neodymium metal catalyst. For the purpose of present disclosure, the polybutadiene

rubber has cis butadiene monomers in the range of 30 to 98% of the total
polybutadiene rubber content in the tread-wear indicator composition.
[0030] The term “zinc oxide” used herein refers to powder form of zinc oxide that
can be used as white seal form, yellow seal form or as a combination of both.
[0031] The term “TiO2” used herein refers to titanium dioxide that can be used in
white colored rutile form and/or anastase form.
[0032] The term “ribbed smoked sheet” used herein refers to natural rubber in the
form the sheets. It is abbreviated as RSS and available in various grades such as
RSS1, RSS2, RSS3, etc., based on percentage of particles in the rubber sheet.
[0033] The term “technically specified rubber” used herein refers to block natural
rubber. It is abbreviated as TSR and available in various grades such as TSR 10, TSR
20, etc., based on various parameters such as ash content, dirt content, nitrogen
content, etc.
[0034] The term “300% modulus” used herein refers to the force required for 300%
elongation of a material. It is measured in units of pressure as MPa or kg/cm2.
[0035] The term “tensile strength” used herein refers to the maximum load a material
can withstand before fracture, breaking, tearing, etc. It is measured in the units of
pressure as MPa or kg/cm2.
[0036] The term “elongation at break %” used herein refers to the percentage change
in elongation of a material at the instant of break.
[0037] The term “hardness shore A” used herein refers to the resistance of a material
to indentation. It is measured using a device called shore durometer. There are
several scales of a durometer out of which two most common scales are A and D.
Scale A is used for measuring the hardness of soft materials, such as polymers,
elastomers and rubber.
[0038] The term “rpm” used herein refers to a unit well used in the field of rubber
technology to define the speed of any rotating part of the machine in terms of
rotations/revolutions per minute.
[0039] The term “phr” used herein refers to parts per hundred resin. It is a unit well
defined in the field of rubber technology to describe the amount of ingredients used.

[0040] The term “at least one” is used to mean one or more and thus includes individual components as well as mixtures/combinations.
[0041] The term “rib” used herein refers to a continuous strip or rubber extending around a tire’s circumference. One of its edges is defined by at least circumferential groove while the second edge may be defined by either second circumferential groove or a lateral edge of the tread.
[0042] The term “groove” used herein refers to a deep elongated void area extending circumferentially and/or laterally in a tire tread. The tire grooves facilitate the expulsion of water by allowing it to flow through the tread design which contributes to the wet traction of a tire.
[0043] As discussed in the background of the present disclosure, tread wear indicators play an important role in warning the user about the wear state of the tire and provides knowledge as to when the tire needs to be replaced. Existing wear indicators are difficult for customers to understand as they are not effectively visible. Thus, they end up using the tire even after the end of life of tire. This is directly linked to the safety of the customer as performance parameters are compromised. In view of this, a variety of colored tread wear indicators have been formulated. However, a majority of currently available colored tread wear indicators are associated with issues related to locating them inside the tread pattern, hence creating a huge dependency for the user on the availability of a vehicle mechanic as he is the one skilled in measuring the tread height and locating the wear indicators in the grooves. Moreover, many existing wear indicators interfere with the flow of water through the groove that affects the performance of the tread.
[0044] To address the problems mentioned above, the present disclosure provides a tread-wear indicator composition comprising colouring agents that makes the composition different in colour from the tire tread colour. The coloured tread wear indicator as described herein, tackles the major problem of visibility associated with wear indicators.
[0045] The present disclosure discloses a tread-wear indicator composition comprising a combination of base rubbers, filler, antiozonant, white indicator compound and a fluorescent agent. Incorporating a fluorescent colouring agent in the

present tread-wear indicator composition provides it with superior advantage of improved visibility from distance and even at night. This aspect also enables the customer to evaluate the wear state of the tire on his own by gauging the level of the colored indicator with respect to the tread. The present disclosure also discloses the dimensions of the tread-wear indicator composition in terms of its thickness and width, suitable for multi-ribbed tire treads. Further disclosed is the specific position of placing the tread-wear indication composition so as to provide a convenient visual alert about the wear stage of the tire. Thus, the tread-wear indicator composition of the present disclosure may be successfully used to substitute the conventionally used tread-wear indicators.
[0046] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.
[0047] The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of exemplification only. Functionally-equivalent products, compositions, and methods are clearly within the scope of the disclosure, as described herein.
[0048] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one natural rubber; (c) 5 to 40 phr of at least one filler; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent; and (f) 20 to 50 phr of at least one white indicator compound. In another embodiment of the present disclosure, a tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one natural rubber; (c) 6 to 38 phr of at least one filler; (d) 0.7 to 13 phr of at least one antiozonant; (e) 2.5 to 9.5 phr of at least one fluorescent agent; and (f) 22 to 48 phr of at least one white indicator compound.
[0049] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) at least one synthetic rubber selected from the

group consisting of styrene butadiene rubber, emulsion styrene butadiene rubber, solution styrene butadiene rubber, polybutadiene rubber; (b) at least one natural rubber; (c) 5 to 40 phr of at least one filler; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent; and (f) 20 to 50 phr of at least one white indicator compound.
[0050] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one natural rubber selected from the group consisting of ribbed smoked sheet, and technically specified rubber (TSR); (c) 5 to 40 phr of at least one filler; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent; and (f) 20 to 50 phr of at least one white indicator compound.
[0051] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one natural rubber; (c) 5 to 40 phr of at least one filler selected from the group consisting of china clay, kaolin clay, silica, and calcium carbonate; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent; and (f) 20 to 50 phr of at least one white indicator compound.
[0052] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one natural rubber; (c) 5 to 40 phr of at least one filler; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent; and (f) 20 to 50 phr of at least one white indicator compound, wherein the at least one antiozonant is micro-crystalline wax.
[0053] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one natural rubber; (c) 5 to 40 phr of at least one filler; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent selected from the group consisting of ultramarine blue, colored organic pigments, and colored inorganic pigments; and (f) 20 to 50 phr of at least one white indicator compound. [0054] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one

natural rubber; (c) 5 to 40 phr of at least one filler; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent; and (f) 20 to 50 phr of at least one white indicator compound, wherein the at least one white indicator compound is titanium dioxide (TiO2).
[0055] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) at least one synthetic rubber selected from the group consisting of styrene butadiene rubber, emulsion styrene butadiene rubber, solution styrene butadiene rubber, polybutadiene rubber; (b) at least one natural rubber selected from the group consisting of ribbed smoked sheet, and technically specified rubber (TSR); (c) 5 to 40 phr of at least one filler selected from the group consisting of china clay, kaolin clay, silica, and calcium carbonate; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent selected from the group consisting of ultramarine blue, colored organic pigments, and colored inorganic pigments; and (f) 20 to 50 phr of at least one white indicator compound, wherein the at least one antiozonant is micro-crystalline wax, and the at least one white indicator compound is titanium dioxide (TiO2).
[0056] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) a combination of emulsion styrene butadiene rubber and polybutadiene synthetic rubbers; (b) ribbed smoked sheet natural rubber; (c) 5 to 40 phr of a combination of china clay and calcium carbonate filler; (d) 0.5 to 15 phr of micro-crystalline wax antiozonant; (e) 2 to 10 phr of a combination of ultramarine blue and colored organic pigments fluorescent agent; and (f) 20 to 50 phr of titanium dioxide (TiO2) white indicator compound. In another embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) a combination of emulsion styrene butadiene rubber and polybutadiene synthetic rubbers; (b) ribbed smoked sheet natural rubber; (c) 6 to 38 phr of a combination of china clay and calcium carbonate filler; (d) 0.7 to 13 phr of micro-crystalline wax antiozonant; (e) 2.5 to 9.5 phr of a combination of ultramarine blue and colored organic pigments fluorescent agent; and (f) 22 to 48 phr of titanium dioxide (TiO2) white indicator compound.

[0057] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition as described herein, wherein the tread-wear indicator compound further comprises at least one additive selected from the group consisting of cross-linking agent in the concentration range of 1 to 8 phr, an accelerator in the concentration range of 0.5 to 2.0 phr, an activator in the concentration range of 0.5 to 35 phr. In another embodiment of the present disclosure, the tread-wear indicator compound further comprises at least one additive selected from the group consisting of cross-linking agent in the concentration range of 1.5 to 6 phr, an accelerator in the concentration range of 0.8 to 1.7 phr, an activator in the concentration range of 0.8 to 32 phr.
[0058] In an embodiment of the present disclosure, there is provided a tread-wear
indicator composition as described herein, wherein the tread-wear indicator
compound further comprises at least one additive selected from the group consisting
of a sulfur cross-linking agent in the concentration range of 1 to 8 phr, an accelerator
in the concentration range of 0.5 to 2.0 phr selected from the group consisting of n-
cyclohexyl -2-benzothiazole sulfenamide(CBS), N-tert-butyl-benzothiazole
sulfonamide(TBBS), diphenyl guanidine, 2-mercaptobenzothiazole, benzothiazole
disulfide, zinc dibenzyl dithiocarbamate, tetrabenzylthiuram disulfide, and
combinations thereof, an activator in the concentration range of 0.5 to 35 phr selected
from the group consisting of zinc oxide, stearic acid, and combinations thereof.
[0059] In an embodiment of the present disclosure, there is provided a tread-wear
indicator composition as described herein, wherein the tread-wear indicator
compound further comprises at least one additive selected from the group consisting
of sulfur cross-linking agent in the concentration range of 1 to 8 phr, a CBS
accelerator in the concentration range of 0.5 to 2.0 phr, a combination of zinc oxide
and stearic acid activator in the concentration range of 0.5 to 35 phr. In another
embodiment of the present disclosure, there is provided a tread-wear indicator
composition as described herein, wherein the tread-wear indicator compound further
comprises at least one additive selected from the group consisting of sulfur cross-
linking agent in the concentration range of 1.5 to 6 phr, a CBS accelerator in the

concentration range of 0.8 to 1.7 phr, a combination of zinc oxide and stearic acid activator in the concentration range of 0.8 to 32 phr.
[0060] In an embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) a combination of emulsion styrene butadiene rubber and polybutadiene synthetic rubbers; (b) ribbed smoked sheet natural rubber; (c) 5 to 40 phr of a combination of china clay and calcium carbonate filler; (d) 0.5 to 15 phr of micro-crystalline wax antiozonant; (e) 2 to 10 phr of a combination of ultramarine blue and colored organic pigments fluorescent agent; (f) 20 to 50 phr of titanium dioxide (TiO2) white indicator compound; (g) sulfur cross-linking agent in the concentration range of 1 to 8 phr; (h) CBS accelerator in the concentration range of 0.5 to 2.0 phr; and (i) a combination of zinc oxide and stearic acid activator in the concentration range of 0.5 to 35 phr. In another embodiment of the present disclosure, there is provided a tread-wear indicator composition comprising: (a) a combination of emulsion styrene butadiene rubber and polybutadiene synthetic rubbers; (b) ribbed smoked sheet natural rubber; (c) 6 to 38 phr of a combination of china clay and calcium carbonate filler; (d) 0.7 to 13 phr of micro-crystalline wax antiozonant; (e) 2.5 to 9.5 phr of a combination of ultramarine blue and colored organic pigments fluorescent agent; (f) 22 to 48 phr of titanium dioxide (TiO2) white indicator compound; (g) sulfur cross-linking agent in the concentration range of 1.5 to 6 phr; (h) CBS accelerator in the concentration range of 0.8 to 1.7 phr; and (i) a combination of zinc oxide and stearic acid activator in the concentration range of 0.8 to 33 phr.
[0061] In an embodiment of the present disclosure, there is provided a process of preparing the tread-wear indicator composition as described herein, the process comprising: a) contacting the at least one synthetic rubber, the at least one natural rubber, 5 to 40 phr of the at least one filler, 0.5 to 15 phr of the at least one antiozonant, 2 to 10 phr of the at least one fluorescent agent, 20 to 50 phr of the at least one white indicator compound, and 0.5 to 35 phr of the activator to obtain a first mixture; and b) curing the first mixture with 1 to 8 phr of the cross-linking agent, and 0.5 to 2.0 phr of the accelerator to obtain the tread-wear indicator composition. In another embodiment of the present disclosure, a process of preparing the tread-

wear indicator composition comprises: a) contacting the at least one synthetic rubber, the at least one natural rubber, 6 to 38 phr of the at least one filler, 0.7 to 13 phr of the at least one antiozonant, 2.5 to 9.5 phr of the at least one fluorescent agent, 22 to 48 phr of the at least one white indicator compound, and 0.8 to 33 phr of the activator to obtain a first mixture; and b) curing the first mixture with 1.5 to 6 phr of the cross-linking agent, and 0.8 to 1.7 phr of the accelerator to obtain the tread-wear indicator composition.
[0062] In an embodiment of the present disclosure, there is provided a tire tread comprising the tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one natural rubber; (c) 5 to 40 phr of at least one filler; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent; and (f) 20 to 50 phr of at least one white indicator compound. In another embodiment of the present disclosure, a tire tread comprising the tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one natural rubber; (c) 6 to 38 phr of at least one filler; (d) 0.7 to 13 phr of at least one antiozonant; (e) 2.5 to 9.5 phr of at least one fluorescent agent; and (f) 22 to 48 phr of at least one white indicator compound.
[0063] In an embodiment of the present disclosure, there is provided a tire tread comprising the tread-wear indicator composition comprising: (a) at least one synthetic rubber; (b) at least one natural rubber; (c) 5 to 40 phr of at least one filler; (d) 0.5 to 15 phr of at least one antiozonant; (e) 2 to 10 phr of at least one fluorescent agent; and (f) 20 to 50 phr of at least one white indicator compound, wherein the tread-wear indicator composition has a color different from the color of the tire tread. [0064] In an embodiment of the present disclosure, there is provided a tire tread comprising the tread-wear indicator composition prepared by a process comprising: a) contacting the at least one synthetic rubber, the at least one natural rubber, 5 to 40 phr of the at least one filler, 0.5 to 15 phr of the at least one antiozonant, 2 to 10 phr of the at least one fluorescent agent, 20 to 50 phr of the at least one white indicator compound, and 0.5 to 35 phr of the activator to obtain a first mixture; and b) curing the first mixture with 1 to 8 phr of the cross-linking agent, and 0.5 to 2.0 phr of the accelerator to obtain the tread-wear indicator composition.

[0065] In an embodiment of the present disclosure, there is provided a tread-wear
indicator composition as described herein, wherein the at least one natural rubber is
ribbed smoked sheet selected from the group consisting of RSS1, RSS2, RSS3,
RSS4, and combinations thereof.
[0066] In an embodiment of the present disclosure, there is provided a tread-wear
indicator composition as described herein, wherein the at least one natural rubber is
technically specified rubber (TSR) selected from TSR 10, TSR 20, or combinations
thereof.
[0067] In embodiment of the present disclosure, there is provided a tire tread
comprising the tread-wear indicator composition having a maximum height in the
range of 3.1 to 6.2 mm from the bottom of a tread rib and a maximum width in the
range of 15 to 50 mm from the center of a tread rib.
[0068] In embodiment of the present disclosure, there is provided a tire tread
comprising the tread-wear indicator composition as described herein, wherein the
tread-wear indicator composition has a maximum height in the range of 3.1 to 6.2
mm from bottom of a tread rib. In another embodiment, tread-wear indicator has a
maximum height in the range of 3.5 to 6.0 mm, or 3.75 to 5.5 mm, or 4 to 5 mm, or
4.2 to 4.8 mm from bottom of a tread rib.
[0069] In embodiment of the present disclosure, there is provided a tire tread
comprising the tread-wear indicator composition as described herein, wherein the
tread-wear indicator composition has a maximum width in the range of 15 to 50 mm
from center of a tread rib. In another embodiment, the tread-wear indicator
composition has a maximum width in the range of 20 to 45 mm, or 22 to 40 mm, or
25 to 35 mm from center of a tread rib.
[0070] Although the subject matter has been described in considerable detail with
reference to certain examples and implementations thereof, other implementations
are possible.
EXAMPLES
[0071] The disclosure will now be illustrated with working examples, which is
intended to illustrate the working of disclosure and not intended to take restrictively

to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may apply.
[0072] The working and non-working examples as depicted in the forthcoming sections highlight the criticality of the working percentages of different components in achieving the tread-wear indicator composition of the present disclosure. It is further specified that the presence of all the components and additives is critical so as to achieve the desired visibility of the tread-wear indicator composition. The absence of any of components or additives specified above or replacement of the same with any other additive substantially affects the applicability of the indicator composition as a tread-wear indicator.
Materials and Methods
[0073] For the purpose of the present disclosure, the fluorescent dye sudafast yellow 132K was obtained from Sudarshan chemical. The ultramarine dye was obtained from DCL Corporation. The mechanical properties of the tread-wear indicator composition were measured using Zwick Roell UTM. Emulsion styrene butadiene rubber 1502 was obtained from Reliance Industries Ltd. Polybutadiene rubber 01 was obtained from Reliance Industries Ltd. Ribbed smoked sheet RSS4 was obtained from Mark Tradelinks.
EXAMPLE 1
Formulation of the tread-wear indicator composition
[0074] Test tread-wear indicator formulations F1, F2 and F3 were compounded as
shown in Table 1, wherein F1, F2 and F3 stand for formulations 1, 2 and 3
respectively. Appropriate concentrations of each of the components was loaded in

order to bring in the desired visibility and mechanical properties in the tread-wear indicator composition of the present disclosure. The formulations were further subjected to investigations for their mechanical properties.
Table 1

Categories Component/additive Formulations/weight in phr

F1 F2 F3
Components Synthetic rubber Emulsion styrene butadiene rubber 1502 15.0 30.0 40.0

Polybutadiene rubber 01 0.0 0.0 10.0

Natural rubber Ribbed smoked sheet RSS4 85.0 70.0 50.0

Filler Calcium carbonate 20.0 25.0 30.0

China clay 30.0 15.0 10.0

Antiozonant Micro-crystalline wax 10.0 6.0 1.0

Fluorescent agent Ultramarine blue 1.0 0.15 0.10

Organic colored Pigment 9.0 6.0 3.0

White
indicator
compound Titanium dioxide 25.0 37.0 45.0
Additives Cross-linking agent Sulfur 5.0 3.5 2.0

Accelerator CBS 1.0 1.25 1.5

Activator Zinc oxide 10.0 20.0 30.0

Stearic acid 5.0 2.0 1.0
EXAMPLE 2
Process of preparing the tread-wear indicator composition
[0075] The tread-wear indicator compositions as formulated in Example 1 were
prepared by mixing the components at one stage. According to the weight
concentrations disclosed in Table 1 above, the components synthetic rubber, natural
rubber, fillers, antiozonant, fluorescent agents, white indicator compound, and
activators, excluding the cross-linking agents and accelerator were kneaded using a
brabender internal mixer at a temperature of 150 °C for 6 minutes to prepare a first

non-crosslinked mixture. Further to this, crosslinking agent and accelerators were added to the first non-crosslinked mixture and mixed at 100oC temperature for 2 minutes to obtain the final tread-wear indicator composition of the present disclosure.
EXAMPLE 3
Measurement of mechanical properties
[0076] The tread-wear indicator compositions as synthesized in Example 2 were
subjected to further investigations for their mechanical properties such as 300%
modulus, tensile strength, % elongation at break and hardness shore (a) The recorded
data is presented in Table 2.
Table 2

Mechanical properties F1 F2 F3
300 % modulus (kg/cm2) 25 29 32
Tensile strength (kg/cm2) 165 167 168
Elongation at break % 695 686 660
Hardness shore A 58 59 62
[0077] The data illustrated in Table 2 indicates that tread-wear indicator formulation F3 comprising 10 phr of polybutadiene rubber showed improved 300% modulus, tensile strength and hardness shore A as compared to compositions F1 and F2. The percentage elongation at break was found to be comparable for all three formulations F1, F2 and F3. Thus, it can be inferred, that the results obtained for mechanical properties of the prepared tread-wear indicator compositions were in agreement with the commercially desirable properties, which further qualifies the tread-wear indicator composition of the present disclosure suitable to be used as a tread wear indicator in pneumatic tires.
EXAMPLE 4
Placement of tread-wear indicator

[0078] Figure 1 illustrates the width of the various layers of a tire tread as C1, C4 and C0 and also indicates the minimum (1) and maximum (4,9) heights of the tread-wear composition placed in a tire tread. Figure 2 and Figure 3 illustrate the positioning of the present tread-wear indicator composition in a 4-ribbed and 5-ribbed tire tread respectively. The 4-ribbed pattern consists of 3 separating grooves while the 5-ribbed pattern consists of 4 separating groves. The 4-rib tread pattern in Figure 2 is characterized by at least one circumferentially extending intermediate rib (4) separated from another rib by a circumferentially extending groove (2). The 5-rib pattern in Figure 3 shows a center rib (1) separated from another circumferentially extending intermediate rib (4) by groove (2). The tread wear indicator is placed on the circumferential cup strip (3) extending horizontally downwards from the rib surface which makes contact with the ground during tire rotation. The maximum height of the tread-wear indicator composition (6) is denoted by (5). When the tire gets worn, the uppermost surface (5) of the tread-wear indicator composition is exposed providing a colored visual indication to the operator. The tread wear indicator (6) has a maximum height or thickness X and maximum width Y from the center of the tread rib (1). Table 3 depicts the maximum as well as the minimum reach (millimeters) of the tread wear indicator (6) profile parameters X (1 in Figure 1) and Y (4,9 in Figure 1). The portion having maximum thickness X is positioned in the middle of the intermediate rib (4) (Figure 2) and the center rib (1) (Figure 3) while the portion with minimum circular thickness 1 (Figure 1) lies just below the groove base (7). The tire is intended to worn-out to an admissible height of X from the base (3), on approach of which, the maximum wear limit of the tire is indicated by (5), which triggers the due replacement of the tire.
Table 3

Parameter Minimum (mm) Maximum (mm)
X 3.1 6.2
Y 15 50

[0079] Overall, the combination of components and additives in the disclosed weight ranges and the optimized parameters of the tread-wear indicator composition, along with its specific positioning inside the tire tread are essential elements to achieve improved visibility and provide an easy indication of the wear state of a tire. Replacing even a single component with another component does not provide the desired effect. Also, deviating from the disclosed weight ranges does not exhibit the desired result. Those skilled in the art will appreciate that more than one tread-wear indicator compositions may be placed in a tire tread which may have multiple continuous or non-continuous ribs and more than one circumferential grooves.
Advantages of the present disclosure
[0080] The above-mentioned implementation examples as described on this subject
matter and its equivalent thereof have many advantages, including those which are
described.
[0081] The present disclosure discloses a tread-wear indicator composition comprising a combination of fluorescent dyes that provides an improved visibility to the tread wear indicator, thus making it convenient for the user to easily identify the extent of wear of the tire with little or no assistance of the tire experts. The tread-wear indicator with appropriate dimensions and placing at disclosed position, depth and height, timely educates the user about any abnormal wear of the tires and warns about possible tire failure. The present disclosure encourages preventive tire replacement and aids in providing improved public safety. Furthermore, the tread-wear indicator composition of the present disclosure with improved mechanical properties qualifies for use at commercial levels in all possible varieties of tires. The raw materials required for the preparation of the composition are abundantly available and the process of preparation of the composition is also quite simple and rapid.
[0082] Although the subject matter has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. As such, the spirit and scope of the disclosure should not be limited to the description of the embodiments contained herein.

I/We Claim:
1) A tread-wear indicator composition comprising:
(a) at least one synthetic rubber;
(b) at least one natural rubber;
(c) 5 to 40 phr of at least one filler;
(d) 0.5 to 15 phr of at least one antiozonant;
(e) 2 to 10 phr of at least one fluorescent agent; and
(f) 20 to 50 phr of at least one white indicator compound.

2) The tread-wear indicator composition as claimed in claim 1 further comprises at least one additive selected from the group consisting of cross-linking agent in the concentration range of 1 to 8 phr, an accelerator in the concentration range of 0.5 to 2.0 phr, an activator in the concentration range of 0.5 to 35 phr.
3) The tread-wear indicator composition as claimed in claim 1, wherein the at least one synthetic rubber is selected from the group consisting of styrene butadiene rubber, emulsion styrene butadiene rubber, solution styrene butadiene rubber, polybutadiene rubber.
4) The tread-wear indicator composition as claimed in claim 1, wherein the at least one natural rubber is selected from the group consisting of ribbed smoked sheet, and technically specified rubber (TSR).
5) The tread-wear indicator composition as claimed in claim 1, wherein the at least one filler is selected from the group consisting of china clay, kaolin clay, silica, and calcium carbonate.
6) The tread-wear indicator composition as claimed in claim 1, wherein the at least one antiozonant is micro-crystalline wax.
7) The tread-wear indicator composition as claimed in claim 1, wherein the at least one fluorescent agent is selected from the group consisting of ultramarine blue, colored organic pigments, and colored inorganic pigments.
8) The tread-wear indicator composition as claimed in claim 1, wherein the at least one white indicator compound is titanium dioxide (TiO2).

9) The tread-wear indicator composition as claimed in claim 2, wherein the accelerator is selected from the group consisting of n-cyclohexyl -2-benzothiazole sulfonamide (CBS), N-tert-butyl-benzothiazole sulfonamide (TBBS), diphenyl guanidine, 2-mercaptobenzothiazole, benzothiazole disulfide, zinc dibenzyl dithiocarbamate, tetrabenzylthiuram disulfide, and combinations thereof, the cross-linking agent is sulfur, the activator is selected from the group consisting of zinc oxide, stearic acid, and combinations thereof.
10) A process of preparing the tread-wear indicator composition as claimed in claim 1, the process comprising:

a) contacting the at least one synthetic rubber, the at least one natural rubber, 5 to 40 phr of the at least one filler, 0.5 to 15 phr of the at least one antiozonant, 2 to 10 phr of the at least one fluorescent agent, 20 to 50 phr of the at least one white indicator compound, and 0.5 to 35 phr of the activator to obtain a first mixture; and
b) curing the first mixture with 1 to 8 phr of the cross-linking agent, and 0.5 to 2.0 phr of the accelerator to obtain the tread-wear indicator composition.

11) A tire tread comprising the tread-wear indicator composition as claimed in any one of the claims 1- 9.
12) The tire tread as claimed in claim 11, wherein the tread-wear indicator composition has a color different from the color of the tire tread.
13) The tire tread as claimed in claim 11, wherein the tread-wear indicator composition has a maximum height in the range of 3.1 to 6.2 mm from the bottom of a tread rib and a maximum width in the range of 15 to 50 mm from the center of a tread rib.