FIELD OF INVENTION
The present invention relates to a process for spreading water based adhesive in tyre retreading.
More particularly the present invention relates to a process for spreading water based adhesive
via using spray gun process in tyre retreading.
BACK GROUND OF THE INVENTION
Retreading business has been boost up in tyre technology since last 20 years. Retreading
technology is classical technology in Rubber industries. Retreading process applied on used tyre
(whose tread abraded).
At present solvent based adhesive is commonly used in retreading process. The main
drawback of the conventional process is that it involves high solvent usage which is injurious to
health and environment and is very expensive as compare to water. Water based adhesive has
been tried in past but no success has been achieved so far to obtain a desired properties in the end
product. Since in water based adhesive there is around 70% water and so high drying time is
required. The spreading of water based adhesive in tyre retreading has been a challenge by
maintaining less drying time along with desired end properties.
Using brush method for spreading in retreading process is an old classical method, and is
commonly used for solvent based adhesives. However, when brush method is used for water
based adhesives in retreading process leads to lower durability & tack properties.
So there is a need of developing a process where water based adhesives can be used and spread
in tyre retreading without compromising the durability & tack properties in end application.
Hence, a new improved process of spreading water based adhesive via using spray gun is
developed for tyre retreading.
OBJECTIVES OF THE INVENTION
The primary objective of the invention is to develop a spreading process for water based
adhesive in tyre retreading.
3
Another objective of the invention is to provide a process for spreading water based adhesive in
tyre retreading without compromising the durability & tack properties of the end product.
Yet another objective of the present invention is to overcome the drawback of more drying time
as compared to conventional method.
Another objective of the invention is to provide a retreaded tyre having improved adhesion
between tread and buffed tyre, and improved durability.
BRIEF DESCRIPTION OF FIGURES
Figure 1: Brush process adhesion between substrate to substrate (corresponds to Table 2/S No 1)
Figure 2: Brush process adhesion between substrate to substrate (corresponds to Table 2/S No 2)
Figure 3: Spray process adhesion between substrate to substrate (corresponds to Table 2/S No 3)
Figure 4: Spray process adhesion between substrate to substrate (corresponds to Table 2/S No 4)
Figure 5: Brush process adhesion between substrate to substrate (corresponds to Table 3/ S No 1)
Figure 6: Spray process adhesion between substrate to substrate (corresponds to Table 3/ S No 2)
Figure 7: Brush process adhesion between substrate to substrate (corresponds to Table 4/ S No 1)
Figure 8: Spray process adhesion between substrate to substrate (corresponds to Table 4/ S No 2)
Figure 9: Brush process adhesion between substrate to substrate along with Vulgum (corresponds
to Table 4/ S No 1)
Figure 10: Spray process adhesion between substrate to substrate along with Vulgum-
(corresponds to Table 4/ S No 2)
Figure 11: Brush process adhesion between substrate to substrate (corresponds to Table 5/ S No
1)
Figure 12: Brush process adhesion between substrate to substrate along with Vulgum
(corresponds to Table 5/ S No 1)
4
Figure 13: Spray process adhesion between substrate to substrate (corresponds to Table 5/ S No
2)
Figure 14: Spray process adhesion between substrate to substrate along with Vulgum
(corresponds to Table 5/ S No 2)
DETAILED DESCRIPTION OF THE INVENTION
While the invention is susceptible to various modifications and alternative forms, specific aspects
thereof have been shown by way of example. It should be understood, however that it is not intended
to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover
all modifications, equivalents, and alternative falling within the spirit and the scope of the invention.
It is to be noted that a person skilled in the art can be motivated from the present invention and
modify the various constituents or components of jute composition. However, such modification
should be construed within the scope and spirit of the invention. Accordingly, the examples are
showing only those specific details that are pertinent to understanding the aspects of the present
invention so as not to obscure the disclosure with details that will be readily apparent to those of
ordinary skill in the art having benefit of the description herein.
While preferred aspects and example configurations have been shown and described, it is to be
understood that various further modifications and additional configurations will be apparent to
those skilled in the art. It is intended that the specific embodiments and configurations herein
disclosed are illustrative of the preferred nature of the invention, and should not be interpreted as
limitations on the scope of the invention.
The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a
non-exclusive inclusion, such that a setup, device that comprises a list of components does not
include only those components but may include other components not expressly listed or
inherent to such setup or device.
The term “room temperature” is intended to cover the temperature of room between 35 to 45 oC.
The term “ratio of substrate area to drying time” is the ratio of substrate area to drying time and
have the units in sq. cm. per minute. For eg. if the substrate are is 1750 sq. cm. and it took 5
5
minutes to dry (refer to Table 1, S.No. 3), accordingly the ratio of substrate area to drying time is
350 sq. cm. per minute (1750/5).
Accordingly, the present invention relates to a process for spreading water based adhesive in tyre
retreading. More particularly the present invention relates to a process for spreading water based
adhesive via using spray gun process in tyre retreading. New/used tread is applied with the help
of adhesive formulation & bonding gum (vulgum or bonding agent) keeping whole system at 3T
(Time, temperature, tension/pressure) process as per defined specification.
Water based adhesive composition comprising 100 parts rubber latex, 0.5-6.5 parts
Colouring/u.v. stabilizer, 0.01-4.0 parts silica, 0.1-1.5 parts antioxidant, 1.0-3.5 parts stearic acid,
0.2-2.5 parts curatives, 0.1-2.0 parts accelerator, l.0-11.0 parts surfactant and 10-400 parts water
mixed together homogenously. Generally, it is desired to have water based adhesive composition
which comprises solid content of about 20 to 22% w/w and water content of about 78 to 80 %.
The exemplary water based composition is provided below. Formulation I comprising water
based adhesive having composition as mentioned in below table but not limited to this.
Formulation I (Water based Adhesive):
S.No. INGREDIENTS WEIGHT (Kg)
MIXING OF CONC. IN ATTRIOTOR MILL (MIXING TIME 12 HOURS)
1 DISPERSOL – F (Surfactant) 2.50
2 SOLUBLE SULPHUR 0.480
3 VE-950/Alphox-200
(Anionic surfactant)
0.382
4 PF-RESINE
(Phenol formaldehyde Resin)
0.243
5 MBTS (Dibenzothiazole disulfide) 0.121
6 VN-3 (Precipitated Silica) 0.121
7 ZNO (Zinc oxide) 0.610
8 N-330 CARBON (High abrasion
Furnance carbon)
0.728
6
When a tyre has exhausted its intended service life, the worn tread surface is removed and a fresh
new tread is attached (called as tyre retreading). This enables the tyre to be reused instead of
being scrapped, thus extending its usable life.
In one embodiment of present invention, a method of retreading a substrate comprising:
a) buffing the substrate to obtain buffed substrate,
b) spraying the water based adhesive composition through spray gun on the buffed
substrate of step a) to obtain an adhesive coated buffed substrate, wherein the air pressure
applied while spraying is in the range of 7 to 15 psi,
c) drying the adhesive coated buffed substrate of step b) under room temperature to
obtain a dried adhesive coated buffed substrate, wherein the dried adhesive coated buffed
substrate has improved tack properties,
d) applying tread to the dried adhesive coated buffed substrate of step c) to obtain
retreaded substrate.
In another embodiment of present invention, water based adhesive composition comprises a solid
content in the range of 20 to 30 % w/w and water content in the range of 70 to 80 % w/w.
In yet another embodiment of present invention, water based adhesive composition comprises a
solid content in the range of 20 to 22% w/w and water content in the range of 78 to 80 % w/w.
9 TDQ (1,2-Dihydro 2,2,4- trimethyl
quinoline)
0.121
10 WATER 4.70
11 TOTAL CONCENTRATE 10.006
AGITATOR BLENDING OF LATEX & CONCENTRATE
12 CONCENTRATE TAKEN 7.53
13 LATEX (60% Dry Rubber
Content)
19.380
14 WATER 43.0
15 TOTAL 70.0
7
In yet another embodiment of present invention, water based adhesive composition is
formulation I comprising dibenzothiazole disulfide, 1,2-dihydro 2,2,4- trimethyl quinoline,
precipitated silica, zinc oxide, latex and at least one surfactant.
In yet another embodiment of present invention, the substrate is tyre.
In yet another embodiment of present invention, room temperature is selected from 35 to 45 oC.
In yet another embodiment of present invention, the ratio range of substrate area to drying time is
in the range of 10:1 to 450:1 sq. cm. per minute in step c).
In yet another embodiment of present invention, air pressure applied while spraying is in the
range of 9 to 12 psi.
In yet another embodiment of present invention, air pressure applied while spraying is 10 psi.
In yet another embodiment of present invention, wherein the drying time is lower in comparison
with brush process.
In yet another embodiment of present invention, a retreaded substrate obtained from the method,
characterized by improved adhesion between tread and buffed tyre.
In yet another embodiment of present invention, a retreaded substrate is characterized by
improved durability.
EXPERIMENTAL DATA
Study and comparison analysis of water based tyre retreading adhesive via brush process and
spray process on end application process is provided herein in detail.
EXAMPLE 1
Processing of water based adhesive composition via brush process and spray process
Water based adhesive composition (Formulation I) is more suitable by spray process as compare
to brush process because:
8
1) Since brush process is manual, so variation in film layer occurs and accordingly, drying
time is high, affecting the product durability. However, no such problems occurred in
application of water based adhesive composition through spray process. Using spray gun
process the film layer formation and drying time is uniform and less respectively.
2) Tack properties is found to be significantly better in spray process as compared to brush
process.
EXAMPLE 2
The drying time and tack of water based adhesive composition applied via brush & spray process
Example 2 reflects the laboratory data for a substrate (having a substrate area and weight) acting
as buffed tyre is taken. The water based adhesive composition (Formulation I) is applied through
brush process and spray process as shown in Tables 1 to 3 below. Thereafter, the tyre is allowed
to dry under room temperature. The spray process yields better results in terms of shortening of
drying time significantly along with improved tack properties, in comparison with brush process.
Further, the adhesion value between substrate to substrate is calculated so as to evaluate the
bonding potential of water based adhesives. It is found that substrate to substrate bonding is
found to be significantly higher in spray process in absence of vulgum, in comparison with Brush
process.
Table: 1 (Room Temp: 41 °C)
S.No. Substrate
area
Substrate
wt. (gm)
Process
method
Drying time
(min.)
Substrate wt.
after drying
(gm)
Tack feeling
1 1750 sq.cm 590 Brush 7’ 595 Good
2 1750 sq. cm 590 Brush 8’ 595 Good
3 1750 sq. cm 590 Spray 5’ 592 Very Good
4 1750 sq. cm 590 Spray 4’ 592 Very Good
9
This is to note that a very thin layer of water based adhesive about 0.10~0.12 gram per square
meter (GSM) is required for fast drying and good tack development. Large amount of said
adhesive i.e. more than 0.15 GSM on substrate took longer time for drying & tack development
is also not good due to thick layer during drying & moisture entrapped inside this layer.
Table: 2 (Room Temp: 43°C)
S.No. Substrate
area
Substrate
wt. (gm)
Process
method
Drying
time(min.)
Substrate
wt. after
drying
(gm)
Tack
feeling
Adhesion value
between subs. to
subs.
(147X10’)
1 116sq.cm 47.80 Brush 6.5’ 47.89 Good 9.30 lbs/inch
2 116 sq. cm 48 Spray 3’ 48.5 V.Good 9.75 lbs/inch
3 120 sq. cm 50.69 Brush 7.5’ 50.80 Good 8.25 lbs/inch
4 120 sq. cm 50 Spray 3’ 50.2 V.Good 11.20 lbs/inch
From the above Table 2, we can conclude that substrate to substrate adhesion with adhesive
spreading is better in spray gun process rather than brush process, in absence of bonding gum.
This is because of atomized form of adhesive spreading on substrate with spray gum. This
uniform spreading of adhesive with spray gun provides uniform thin layer of adhesive film after
drying. Adhesion Value between substrate to substrate is found to be high in spray process in
absence of vulgum, compared to brush process.
Table: 3 (Room Temp: 38°C)
S.No. Substrate
area
Substrate
wt. (gm)
Process
method
Drying
time(min.)
Substrate
wt. after
drying
(gm)
Tack
feeling
Adhesion value
between subs. to
subs.
(147X5’)
1 655 sq.cm 277 Brush 3’ 277.5 Good 7.7 lbs/inch
2 683.5 sq.cm. 288 Spray 3’ 289 V.Good 10.2 lbs/inch
10
From above Table 3, we can conclude that adhesion value between substrate to substrate without
bonding agent (vulgum) is more in spray gun process rather than brush process. The mechanism
is same that is uniform pressure, uniform layer formation & uniform spreading. Adhesion Value
between substrate to substrate is found to be high in spray process in absence of vulgum,
compared to brush process.
EXAMPLE 3
Adhesion value between substrate to substrate, with or without vulgum when water based
adhesive is applied via brush & spray process:
Example 3 reflects the laboratory data for a substrate (having a substrate area and weight) acting
as buffed tyre is taken. The water based adhesive composition (Formulation I) is applied through
brush process and spray process as shown in various tables below. Thereafter, the tyre is allowed
to dry under room temperature. The spray process yields better results in terms of shortening of
drying time significantly along with improved tack properties, in comparison with brush process.
Further, the adhesion value between substrate to substrate is calculated so as to evaluate the
bonding potential of water based adhesives, with or without vulgum.
Vulgum (cushion gum or bonding gum) is an uncured/unvulcanized rubber calendared in a
specified width & thickness i.e. 115~120 mm width & 1.10 ~1.15 mm thickness as per tyre
norms. This unvulcanized rubber works as bonding agent between buffed tyre & new applied
tread. This unvulcanized rubber after retreading is vulcanized under specified time, temperature
& pressure & make permanent chemical bonds with cured tyre and cured tread.
It is found that substrate to substrate bonding (adhesion value) is found to be significantly higher
in spray process with or without vulgum, in comparison with brush process.
Table: 4 (Room Temp: 40°C)
S.No Substrate
area (Sq.
cm.)
Substrate
wt. (gm)
Process
method
Drying
time
(min.)
Substrate
wt. after
drying
(gm)
Tack
feeling
Adhesion value
between subs.
to subs.
(147X5’)
Adhesion value
between subs. to
subs. with vulgum
(147X20’)
1 726.75 287 Brush 3’ 287.5 Good 22 lbs/inch 130 lbs/inch
11
2 742.5 306 Spray 2.5’ 307 V.Good 32 lbs/inch 150lbs/inch
(slippage)
Table:5 (Room Temp: 40°C)
S.N
o
Substrate
area (Sq.
cm.)
Substrate
wt. (gm)
Process
method
Drying
time
(min.)
Substrate
wt. after
drying
(gm)
Tack
feeling
Adhesion value
between subs.
to subs.
(147X5’)
Adhesion value
between subs. to
subs. with vulgum
(147X20’)
1 84.96 184.5 Brush 7’ 185.30 Good 7.4 lbs/inch 47 lbs/inch
2 85.55 177.7 Spray 6’ 178.50 V.Good 10.2 lbs/inch 70 lbs/inch
EXAMPLE 4
Dynamic field trial on tyre:
Example 4 refers to actual field trial performed for evaluating the retreading capability of spray
process over brush process.
Retreading of tyre from water based adhesive via spray & brush process: Two Maruti van tyre of
Size 145X70R12 (MRF 3815) and 145X70R12 (MRF 0415) & Two tyre of TATA 407 of size
8.25X16 (CEAT 43064313) and 8.25X16 (CEAT 43064375) have been selected for the field trial
study.
Inspection of tyre has been done manually & buffing has been done through buffing machine and
the cleaning via air. Buffing operation time is 5 minutes for each tyre.
After buffing and cleaning with air, water based adhesive is applied on buffed tyre via brush
process and spray process. Thereafter, drying is performed at room temperature. Further, filling
of tyre may be required after drying. The following table 6 summarizes the drying time and tack
development in brush and spray process.
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Table:6 (Room Temp: 40°C)
Tyre No. Tyre size Tread
area
(sq.
cm.)
Consumption
of adhesive
(gm) in
mentioned
process
Drying
time
(min.)
Processing
time via
both
process
(minutes)
Tack
feeling
Cushion
type
Tread type
3815 145X70
R12
MRF
1884 42
(BRUSH)
30 3 Good Vulgum BRYR/127
0145 145X70
R12
MRF
1884 36
(SPRAY)
25 2 V.Good Vulgum BRYR/127
4306437
5
8.25X16
CEAT
4238.5 117
(BRUSH)
40 5 Good Vulgum HWR/171
4306431
3
8.25X16
CEAT
4238.5 117
(SPRAY)
28 5 V. Good Vulgum HWR/171
Simultaneously, during drying of the water based adhesive on buffed tyre, application of vulgum
is done on the new tread. Further, on each tyre, application of vulgum has been performed on
sides of the buffed tyre.
Tread specification of a Maruti tyre as provided below:
o Weight of tread along with cushion =2.40 Kg
o Length of tread = 155 cm
o Width of tread = 12.7 cm
o Rib depth = 1cm
Tread specification of TATA 407 Tyre as below:
o Weight of tread along with cushion = 7.15 Kg
o Length of tread = 250 cm
o Width of tread = 17 cm
o Rib depth = 1cm
Finally, the new tread is applied on the buffed tyre and mechanical pressure is applied to seal the
tyre with new tread. Assembly of retreaded tyre is performed in auto clave for curing. Assembly
required envelops, tube & metal fixture same as rim.
13
Curing in auto clave:
 Auto clave chamber pressure 85 psi
 Tyre pressure = 110 psi
 Cushion type = Vulgum
 Curing time = 220 minutes
 Curing temperature = 104oC to 105 oC
Both the tyre has been successfully cured and fitted in vehicle and running for dynamical
durability response.
ADVANTAGES:
Spray process showed significantly better results compared to brush process that lead to better
durability, drying time and tack properties in the end product (retreaded tyre).
The advantages of the present spray process is to provide an ecofriendly, economical tyre
retreading process.

We claim:
1. A method of retreading a substrate comprising:
a) buffing the substrate to obtain buffed substrate,
b) spraying the water based adhesive composition through spray gun on the buffed
substrate of step a) to obtain an adhesive coated buffed substrate, wherein the air pressure
applied while spraying is in the range of 7 to 15 psi,
c) drying the adhesive coated buffed substrate of step b) under room temperature to
obtain a dried adhesive coated buffed substrate, wherein the dried adhesive coated buffed
substrate has improved tack properties,
d) applying tread to the dried adhesive coated buffed substrate of step c) to obtain
retreaded substrate.
2. The method as claimed in claim 1, wherein water based adhesive composition comprises a
solid content in the range of 20 to 30 % w/w and water content in the range of 70 to 80 % w/w.
3. The method as claimed in claim 1, wherein water based adhesive composition comprises a
solid content in the range of 20 to 22% w/w and water content in the range of 78 to 80 % w/w.
4. The method as claimed in claim 1, wherein water based adhesive composition is of
formulation I comprising dibenzothiazole disulfide, 1,2-dihydro 2,2,4- trimethyl quinoline,
precipitated silica, zinc oxide, latex and at least one surfactant.
5. The method as claimed in claim 1, wherein the substrate is tyre.
6. The method as claimed in claim 1, wherein room temperature is selected from 35 to 45 oC.
7. The method as claimed in claim 1, wherein the ratio range of substrate area to drying time is in
the range of 10:1 to 450:1 sq. cm. per minute in step c).
8. The method as claimed in claim 1, wherein air pressure applied while spraying is in the range
of 9 to 12 psi.
15
9. The method as claimed in claim 1, wherein air pressure applied while spraying is 10 psi.
10. The method as claimed in claim 1, wherein the drying time is lower in comparison with
brush process.
11. A retreaded substrate obtained from the method as claimed in claim 1, characterized by
improved adhesion between tread and buffed tyre.
12. The retreaded substrate as claimed in preceding claims, having improved durability.