FIELD OF THE INVENTION
The present invention relates a method of plating for improving adhesion of motor
tyre bead wires with rubber. More particularly the invention relates to bead wire
coated with small amount of plating materials used for the reinforcing in the tyre.
BACKGROUND OF THE INVENTION
Steel cords have been extensively used as a reinforcement material in tyres by
manufacturers for decades. Since superior bonding of the copper plated steel wires
with rubber is obtained therefore copper plated steel wires are exclusively used as
reinforcing material. The pure copper is not plated on the wires rather depending
on the end usages in the tire reinforcement plating is either in form of brass or
bronze. The tyre bead wires are high carbon steel wires of diameter around 1 mm,
which are immersion plated in aqueous bath of CUSO4 and SnSO4 to obtain a very
thin coating on the wires. These plated wires are further coated with organic
compound to prevent its oxidation. Motor tyre bead acts as reinforcement of tyre
for getting a proper grip of the tyre on the rim. The copper in the plating reacts
with the sulfur of the rubber

forming copper sulfide (CuxS) at the steel rubber interface. This CuxS is responsible to
cause its adhesion with rubber. This layer then helps mechanical interlocking of the
rubber compound, resulting in a very strong bond. The rubber penetrates into the
dendritically structured CuxS layer initially when it is in the liquid state and then it gets
crosslinked later by the delayed-action accelerator, giving a very firm interlocked
rubber network adhered tightly to the copper sulfide layer on steel cord. For better
performance of tyres, an optimum formation of the copper sulfide layer is necessary
to increase the strength of this bonding.
Several attempts have been made in the past to improve adhesion of the bead wires;
however none of them could significantly affect the same. The adequate adhesion of
bead wire with the rubber is major quality criteria set by the tyre manufacturer.
Therefore it is extremely important for the bead wire manufacturer to achieve
sustainable improvement in the adhesion of bead wire with rubber.
The schematic of the prior art process has been shown in Figure 1. The arrows in the
process represent direction of the wire being processed. The wires of 0.965 mm
diameter are stressed relived in lead bath maintained at 430°C. These wires are
passed in the sand bath for leap wiping followed by alkali cleaning and water
quenching. Now these wires are again alkali cleaned, rinsed and pickled in two
different tanks of H2SO4. In order to take care of acid carriage, these wires are rinsed
alkali cleaned and rinsed again. Now wires are ready to be plated which is carried out

by dipping in the two different baths of CuSO4, SnSO4 and H2SO4. The
concentration of CuSO4, SnSO4 and H2SO4 in both plating baths are mutually
different. After plating these wires are rinsed, dried and cumuor coated. Now the
product bead wire is ready for the winding and packing.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention is to propose a method of plating
for improving adhesion of motor tyre bead wires with rubber which eliminates the
disadvantages of prior art.
Another object of the present invention is to propose a method of plating for
improving adhesion of motor tyre bead wires with rubber which increase the life of
motor tyre.
A further object of the present invention is to propose a method of plating for
improving adhesion of motor tyre bead wires with rubber which increases the load
carrying capacity of motor tyre.
A still further object of the invention is to propose a method of plating for
improving adhesion of motor tyre bead wires with rubber which is eco friendly.

A still further object of the present invention is to propose an improved plating
process for improving adhesion of motor tyre bead wire with rubber which is eco-
friendly.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.l - shows a process flow chart as per prior art
Fig.2 - shows an improved process flow chart as per new invention
Fig.3 - shows a comparative plot of average adhesion. The comparisons have been
made between wires plated from existing plating process and new improved plating
process for three different quality of rubbers. ,
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in Fig.2, the wires of 0.965 mm diameter (1) are stress relived in lead bath
(2) maintained at 430-450°C. These wires are passed in sand bath for leap wiping (3)
followed by alkali cleaning (4) and water quenching (5). Now these wires are again
alkali cleaned (6), rinsed (7) and pickled in two different tanks of H2SO4 (8,9). In
order to take care of acid carriage, these wires are again rinsed (10) and further
cleaning with NaOH at 60-70 gm/litre and applying a current per wire 40-50 Amp (11)

and rinsed (12) again. Now these wires are ready to be plated which is carried out by
dipping in the two different plating bath. Plating-I bath (13) contains CuSO4 at 5-10
gm/litre, H2SO4 at 25-30 gm/litre and SnSO4 at 0.5-1.0 gm/litre and Plating-II bath
(14) contains CuSO4 at 28-30 gm/litre, H2SO4 at 25-30 gm/litre and SnSO4 at 0.4-0.7
gm/litre and allowing a wire speed at 350-375 meter/min. After plating these wires
are rinsed (15,16) dried in oven (17) and cumuor coated (18). Now these product
wire is ready for winding and packing (19).

Table 2: The new process parameters for improving adhesion
The new improved process for improving adhesion of the bead wire are listed in
Table-2. The laboratory experiments and plant trials with new improved process were
taken and adhesions of these samples were measured.
The laboratory experiments and plant trial with above mentioned parameters (Table
2) were taken and adhesions of these samples were measured. The adhesion of

sample obtained from above mentioned plating parameters has been compared with
adhesion of the samples from existing plating parameters (Table 1) in the Figure 2.
The adhesion has been measured with three different qualities of rubbers
(Bridgestone, JK and MRF) and improvement was observed in all three different
rubbers.

WE CLAIM
1. A method of plating for improving adhesion of motor tyre bead
wires with rubber comprising the steps.
- steel wire (1) having diameter 0.965mm are subjected to stress
relieving at 430-450°C
- sand bathing (3) the steel wires for lead wiping
- cleaning the steel wires in alkali solution (4)
- quenching in water the steel wires for cleaning (5)
- cleaning the steel wires in alkali solution (5% NaOH) (6)
- rinsing the steel wires (7) ,
- pickling the steel wires twice subsequently in two picking baths
(8,9) containing H2SO4 at 70 gm/lit.
- rinsing the steel wires (10)
- plating the steel wires in 1st stage (13) in a Plating Tank I
containing a mixture of CuSO4 at 5-10 gm/lit, H2SO4 at 27-30
gm/lit and SnSO4 at 0.5-1.0 gm/lit maintaining a wire speed
350-375 meter/min.
- plating the steel wires in 2nd stage (14) in a Plating Tank II
containing a mixture of at CuSO4 at 28-30 gm/lit, H2SO4 at
25-30 gm/lit and SnSO4 at 0.4-0.7 gm/lit maintaining wire
speed 300-375 meter/min
- rinsing the steel wires (15)
- rinsing further the steel wires is not water (16)
- drying the steel wire in a drying oven (17)
- cumuor coating the steel wires (18)

- winding and packing the steel wires (19)
Characterized in that the steel wires being plated twice subsequently in
two plating baths having different composition of constituents wherein
the speed of wires at variance, improves adhesion of rubber.
2. The plating process as claimed in claim 1 where all kinds of rubber
can be used.

ABSTRACT

A METHOD OF PLATING FOR IMPROVING THE ADHESION OF
MOTOR TYRE BEAD WIRES WITH RUBBER
The invention relates to a method of plating for improving the adhesion
of motor tyre bead wires with rubber. More particularly it relates to bead
wire coated with small amount of plating material used for reinforcing
the tyre. The preplating and plating processes include lead bathing for
stress relieving, sand bathing for lead wiping, quenching, rinsing with the
exception of setting an improved process parameters during cleaning
with NaOH solution followed by plating in two different plating tanks
having different concentrations where the wire speed is maintained.