Page 161 - CW E-Magazine (27-5-2025)

Free to Die

able. More than an hour is needed, 30,000. Someone thought the additional the world and urge them to take up this
besides very heavy machinery, which is double bonds formed by the breakdown challenge. The annual world synthetic
expensive because of the rugged con- of the chains would help crosslinking rubber production is about 16-mt, while
struction. Since a large quantity of car- reactions. But this argument had no sub- that of natural rubber is about 10-mt. So
bon black is required to be dispersed in stance because there are residual double there is a challenge for polymer chemists
rubber, the latter needs to be of suffi - bonds from the diene and are quite abun- to save 70-billion kWh of electrical
ciently low viscosity to be able to mix dant because the unit molecular weight energy annually and for biochemical
effi ciently. Additives like oils, resins, of the diene is just about 60-70 in most engineers to genetically modify the natu-
antioxidants help to reduce viscosity cases. ral rubber plant so that the molecular

further. weight of the rubber from the latex is
On my return I had to fi gure out the
I suggested to the client that if we reasons for manufacture of a million reduced to about 30,000 from the present
can use AMS dimer to regulate the mole- molecular weight rubber. For any poly- 5-6 million. This could be a great green
initiative.
cular weight of rubber, we may be able mer chemist, it is very easy to change
to save signifi cant amount of electri- the molecular weight by adjusting the Substantial savings
city in rubber processing. They liked the process parameters – initiator concentra- As I said earlier, for polymer chemists
idea and asked me to give a proposal. tion, reaction temperature, chain transfer this would be a relatively simpler
Since the process would have involved agent, etc. Polymer chemistry at the time job – increase reaction temperature,
emulsion polymerisation of styrene and of the Second World War was developed increase catalyst concentration and add
butadiene, facilities to handle gaseous enough to achieve any desired molecular a chain transfer agent. Molecular weight
monomers would be required. UDCT’s weight. of about 30,000 would be easily achiev-

Polymer Department did not have these India was once the primary source able for the standard SBR composition.
facilities. So, the proposal ran into a of natural rubber in the world (it was SNR, polyisobutylene, nitrile, chloro-
few lakhs of Rupees, as high pressure even called India Rubber). Other Asian prene, and EPDM could all follow. The
reactors, and equipment for recovery countries like Thailand, Indonesia and cost of tyres manufactured from this
of unused monomers would have to be Vietnam also supplied natural rubber. rubber will be lower to the extent of
installed. The client unfortunately During Second World War, the need saving in electricity, as well as labour
thought the cost was high and I did not for rubber tyres increased many folds. in the operation and maintenance of the
get the project. heavy machinery. These could easily
Availability from India became diffi cult
Why high molecular weight rubbers because India was a British colony. amount to about 20% of the tyre cost.

in the fi rst place? Substitutes were urgently required and India uses about 2-mt of rubber an-
But the question remained unan- that is when SBR was born in early nually currently. Of this, about 90% is
swered in my mind. Regulating mole- 1940s in United States. used for tyre manufacture. A 20% sav-

cular weight of synthetic rubbers like SBR, The manufacturing process of rubber ing could signifi cantly contribute to the
NBR, SNR, and polychloroprene, which tyres was well established. Process steps profi ts of tyre manufacturing compa-
are manufactured by emulsion tech- like mastication and mixing with other nies. With increasing cost of electricity
niques at low temperature using special ingredients was the norm. The US (recently my electricity bill went up by
initiators is not diffi cult. Why then did administration might have wanted to 20%) it would be a great advantage to
everyone produce a million molecular substitute one-for-one so that the produc- the manufacturing sector.
weight rubber in the fi rst place? The tion process could continue unhindered.
answer was not easy to fi nd. I spoke to If the workers were using X quantity India has only three synthetic rubber
several rubber technologist known to of natural rubber, they would use same manufacturers. They might initiate the
me. No one had any satisfactory answers. quantity of synthetic rubber and produce development, but very likely they would
I happened to visit USA in 2003 and met tyres of all description. Such might have not be the fi rst to do this, as Indian entre-
scientists of a large multinational. All been the urgency of the war. By the preneurs are very good followers.

of them sounded very knowledgeable time the war ended, this had become an This development may not be
about the subject of rubber compound- established procedure. So, no one has patentable, as I have disclosed enough to
ing but were clueless as to why the fi rst questioned it in last 85 years. be cited as prior knowledge.
synthetic rubber was manufactured with
a million molecular weight when the de- Today, I am throwing open this idea Still, I wish good luck to the local rub-
sirable molecular weight was only about to the synthetic rubber manufacturers of ber manufacturing industry. V.C. Malshe

Chemical Weekly May 27, 2025 161

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