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FIELD OF APPLICATION
The present invention relates to a rubber formulation for rubber covering rolls
used in steel industry, particular!/ in alkaline cleaning and cremate treatment
operations,
BACKGROUND OF THE INVENTION
The existing rubber covering rolls used in alkaline cleaning operation in steel
industry has a short service fife of only 10 to 12 days. During this period, the
tolls develop a change m surface hardness and separation of layers within the
rubber covering is observed. The rolls also develop edge cuts and cut marks
with groove formation.
Similar problems are also encountered with rubber covering rolls used in the
chromate operation. Formation of surface cracks and slippages are also
observed.
Existing formulations used for rubber covering rolls in the absence of balanced
properties result in the defects and associated low service life.
There was therefore, a need to develop a lubber formulation fOR rubber coveting
rolls used in the steel industry which can overcome the problems encountered
with known rubber covering rolls.

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SUMMARY OF THE INVENTION
The main object of the present Invention therefore, is to provide a rubber
formulation having a unique blend af compounding ingredients to give balance of
properties required to extend the service life of the rubber covering used in
alkaline cleaning and chormate operations in steel industry.
DETAILED DESCRIPTION
The present invention can now be described with the help of photooraphs of the
rubber coveting rails.
For the rubber covering rolls for the alkaline section nital and neopfene rubber
are exclusively used. For the chromate section ESP rubber is used. The edge
cuts and groove marks developed in existing rubber covering rolls are shown in
Figures l{a) and l(b). Figures 2 and 3 show the alkali section where neoprene
based rubher covering rolfs are being used, The development of edge tuts and
groove marks are shown in Figure 4(b). Layer separation, possibly because of
liquid peneration through pin holes, is shown in Figure 4(c). Other mechanical
defects developed during use can be seen in Figure 4(d).
Figures 5 and & show in enlarged view the development of edge cute and cut
marks in the rubber covering rolls.
Table 1 and Table 2 show the data on the existing roll life in the alkali section
and Table 3 gives the data sheet for the chromate section.

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Table 1


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Table 2


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Table 3


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In order to meet the conflicting demands of the working environments,different
formulations were tried. A special rubber covering composition with unique
blend of compounding ingredients providing balance of properties was developed
for each of the two areas of operation.
The composition of the formulations of the present invention for the two
operations are shown below.
COMPOSITION FOR
ALKALI SECTION
Code NBR based rubber covering compound
Ingredients
NBR 100
Sulphur 1
ZnO 15
Steraic acid 1.5
HS/TQ 1.5
MB 1.5
CI Resin 4
PF Resin 10
HAF 30
SRF 15
T90 3
DOP 4
PVI 0.5
CBS 1.5

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COMPOSITION FOR
CHROMATE SECTION
Code Hypalon based rubber
covering compound
Ingredients
Hypalgn 100
Epoxy 10
NBC 1
SRF 30
CI Resin 3
IQ 2
PEG 1
DOP 8
Spmdle Oil 6
Ivamol 4
MBTS 0.5
Tetron A 0.75
DOTG 0.5
Sulphur 1
As shown in Figure 7, no cut or edge mark was observed after 34 days of use.
The severity of groove formation after 34 days of use was negligible. After
taking out for continued run beyond 34 days, rolls were regrinded for removing
very fine formation af grooves at the two ends, as shown in Figure 8.
At the hot rinsing section, occurrence of slippage was observed due to alkali
sediment covering the roll. After use for 34 days very fine groove formation was
observed and the roll was regrinded and reinstalled (Figure 9).
Thus, by using concentrated PF resin in the rubber composition for the alkaline
section and by incorporation epoxy resin the polymer for the chromate section a
balance of properties can be provided resulting in improved surface life.

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The extension of service life of the rubber covering rolls will also yield othet
benefits like shorter breakdown time, reduced shutdown frequency,
uninterrupted production and reduction in cost due to reduced consumption of
rubbet tolls. Reduction in maintenance cost and (ejections on account of quality
may be considered as other benefits accruing from the present invention.

The main object of the present invention therefore, is to provide a rubber formulation having a unique blend of compounding ingredients to give balance of properties required to extend the service life of the rubber covering used in alkaline cleaning and chromate operations in steel industry.