View report page

37
1919
(4) Calendering.
The rubber dough or paste is next run into sheets by repeated
passages over a calender machine. A band of calico is
passed between the rollers and on the calico layers of paste are
placed. The " bed " of the machine is heated and as the calico
passes through, the naphtha evaporates, leaving a thin sheet of
rubber on the calico. Subsequent passages increase this layer
until the desired amount has been deposited.
(5) Vulcanization.
Vulcanization is carried out in different ways, but in every
instance the result is the incorporation of a certain amount of
sulphur with the rubber. A physico-chemical combination is
obtained composed of the rubber and sulphur. This compound,
unlike the raw rubber can be utilized for a variety of articles,
because of its pliability and resiliency. It does not become hard
when cooled or sticky when heated, and at these works the articles
made ranged from the inner tubes of motor-car wheels to bathingcaps
and syringes. The various articles required are modelled
and worked from the sulphur-incorporated rubber paste and then
buried in French chalk in trays or boxes, which are then run into
an autoclave, where steam under pressure is turned on for the
requisite period of time. The carbon disulphide process is not
employed in this factory.
The principal nuisance that can arise from the manufacture,
arises from the presence of naphtha in the atmosphere.
The rubber after mastication and mixing, has an unpleasant
odour, but the odour is too slight to be observed unless a portion
of the rubber is handled and sniffed.
It is also stated that a trace of sulphuretted hydrogen is
liberated in the process of vulcanization, but the amount must
be a very minute one, and I was not able to detect its odour during
any of my visits through the works.
Naphtha escapes into the atmosphere in the calendering
process and in the making-up process.
The greatest amount of evaporation occurs in the calender
room, but its effects here are not so noticeable, as there are less
people occupied in the room, the ventilation is more free, and the
vapour therefore accumulated to a less extent.