A NEW AND USEFUL METHOD OF MANUFACTURING THE VULCANIZED COMPOUNDS OF VULCANIZABLE GUMS
Year: 1859

page_text: LETTERS PATENT to George Tomlinson Bousfield; of Loughborough
Park, Brixton, in the County of Surrey, for the Invention of "A NEW
AND USEFUL METHOD OF MANUFACTURING THE VULCANIZED COMPOUNDS OF
VULCANIZABLE GUMS."--A communication from abroad by John Murphy,
of the City, County, and State of New York.
Scaled the 27th October 1859, and dated the 9th August 1859.
COMPLETE SPECIFICATION filed by the said George Tomlinson Bousfield
at the Office of the Commissioners of Patents, with his Petition and
Declaration, on the 9th August 1859, pursuant to the 9th Section of the
Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
TOMLINSON BOUSFIELD, of Loughborough Park, Brixton, in the County of
Surrey, do hereby declare the nature of the Invention for "A NEW AND
USEFUL METHOD OF MANUFACTURING THE VULCANIZED COMPOUNDS OF VULCANIZABLE
GUMS," (communicated to me from abroad by John Murphy, of the City,
County, and State of New York,) and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement thereof, that is to say :-

page_text: Some varieties of the vulcanizable gums, as, for example, the poorer kinds
of gutta percha, are of such a character that they swell and blister in the
process of vulcanization, so that when they are compounded with sulphur alone
in the ordinary way and vulcanized, the product is practically valueless; gums
of this quality have gradually accumulated in the market, and are sold at
extremely low prices, from the fact that heretofore they could not be made
available for vulcanization by any known process. On the other hand great
difficulty has been experienced in the manufacture of thick slabs, blocks, and
large masses of hard vulcanized compounds from gums even of the best
quality on account of the softening, blistering, and running of the compound
during the process of vulcanization, and although attempts have been made to
overcome this difficulty by the admixture with the gum of earthy substances,
as, for example, the silicate of magnesia and the carbonates of lead and zinc,
their employment is attended with the disadvantage that the hard compound
produced is not susceptible of as high a polish as that made by the use of gum
and sulphur alone, and is also deficient in strength, so that it cannot be used
with advantage for a variety of purposes to which it would otherwise be
applicable. The object of the Invention is to enable the poorer varieties
of the vulcanizable gums to be used with advantage, and to permit solid
slabs, blocks, and masses of hard compounds to be formed of any desirable
size and thickness without the employment of any other elementary substances
than gum and sulphur. The Inventiou also furnishes a profitable ineans of
working up the scraps produced in the manufacture of finished articles from
slabs, blocks, and masses of the hard compounds of vulcanizable, gums; such
scraps have gradually accumulated and are accumulating in large quantities at
the manufactories, from the want of some practical means of using them to
advantage.
The Invention consists in a mode of manufacture, or process, comprising
the following operations, viz. :-First, the manufacture of hard stock out of a
vulcanizable gum by compounding or blending it with sulphuror its equivalent,
and vulcanizing the compound until it is hard. Second, the reducing of the
hard stock to powder by grinding it in a heated state between rollers, or by
any other means which will produce this result. Third, the compounding of
the ground hard stock with a quantity of raw gum (by which I mean gum
that has never been vulcanized), by which operation a new vulcanizable com-
pound is produced that may be formed into sheets, blocks, and masses of any
desired form and size. Fourth, the vulcanization of the new compound thus
formed. The proportions in which the sulphur and gum are blended in

page_text: carrying out the Invention may be varied as circumstances may render
expedient, as may also the proportion of the hard stock used in the third
operation; the machinery for blending and grinding, and the means for com-
pleting the vulcanization, may also be varied. I prefer, however, to use the
ordinary grinding mill consisting of two hot horizontal rollers, revolving with
different velocities both for blending and grinding, and to effect the change
commonly called vulcanization, by heating the vulcanizable compounds in an
ordinary steam heater, as these means are well known in the art to which this
Invention appertains. I do not deem it necessary to describe them in detail
in this Specification. In manufacturing hard stock from raw gum, whether of
good or inferior quality, I take the gum after it has been cleansed from foreign
matters in the usual way, and grind or knead the same in a heated state with
sulphur until the two are thoroughly blended and formed into a putty-like
mass.
The proportions in which the two materials are used are thirty pounds of
gum and from fifteen to forty pounds of sulphur, as may be found necessary
according to circumstances, the larger quantity of sulphur being employed
when the hard stock produced is to be blended at the third operation with
a larger proportion of raw gum without additional sulphur; or when the
vulcanized compound is required to possess great hardness, the putty-like
mass produced by the operation of the mill is formed either by hand or by the
assistance of suitable machinery into sheets, slabs, or masses of any desirable
form and size that may be most convenient for vulcanizing, and these are then
vulcanized, which operation is readily accomplished by placing them in the
tanks of a steam heater, covering them with water, and submitting them to
the action of steam in the usual manner. The steam heat is maintained
until the compound is vulcanized so as to be sufficiently hard, which I find
takes place from four to eight hours when steam of a temperature of 290°.
Fahrenheit's thermometer is used, the length of time varying with the
proportion of sulphur on the compound, the compounds containing smaller
proportions of sulphur requiring more time to vulcanize them than those
containing larger proportionate quantities of sulphur. After the vulcanization
is completed the hard stock produced is ready for the second operation or step
of the process. The best mode with which I am acquainted of accomplishing
the second step of the process is to break the hard stock into fruginents by
hand or other means, to heat them after being broken, and to grind them in
a hot roller mill. A convenient means of heating the fragments is to place
them upon an ordinary steam table or heater, and to place a cover over them

page_text: to retain the heat. The grinding is then readily effected by passing the hot
fragments between the hot rollers of a roller mill, such as is commonly used
for grinding india-rubber and gutta percha, with and without sulphur and
other materials. This grinding constitutes the second step of the process, and
although the ordinary roller mill may be used for the purpose it is expedient
to employ a mill of double the usual strength, so that the operation may be
performed with rapidity. In accomplishing the third step of the process a new
vulcanizable compound is formed by blending the ground stock resulting from
the second operation with raw gum. The proportious in which the materials
are blended may be varied according to their qualities or the nature of the
product required, or both, it being understood that the hard stock that
contains the largest proportion of sulphur can be blended with the largest
proportion of raw gum. Agood mixture for producing hard vulcanized com-
pound for general use consists of three parts by weight of ground hard stock
formed of equal quantities of gum and sulphur with one part of raw gum; if
the compound to be produced is to be soft or elastic, the proportion of ground
stock should be diminished, and if hard compound ivory-like in its properties
is to be produced, the proportion of ground stock should be increased; the
materials should be thoroughly blended, which may be done efficiently by means
of the ordinary hot cylinder mill. The putty-like mass produced may be formed
into blocks, sheets, or slabs, or may be moulded into any desirable forms by the
methods employed in the manufacture of the vulcanizable compounds of the
vulcanizable gums. In whatever forms it is put, care should be taken to expel
all the air from the mass, so as to prevent blistering in the subsequent step of
the process. The fourth step of the process consists in heating the compound
produced by the third operation in such manner as to produce the change
commonly called vulcanization. The best means of effecting this operation
with which I am acquainted is to place the articles formed of the compound
in the tanks of a steam heater, to cover them with water, and to subject them
to the action of high steam while closed up in the heater. The steam should
be admitted into the heater at a temperature of from 280° to 300° of Fahren-
heit's thermometer, the operation being continued from four to eight hours
according to circumstances, it being understood that the compounds which
contain the lowest proportions of sulphur require the longest time to produce
the change, and that with equal heats the compounds that contain most
sulphur will vulcanize the hardest, also that the longer the operation is con-
tinued the greater will be the hardness of the product. As a general rule I
find that an exposure to a steam heat of 290° of Fahrenheit's for five hours

page_text: will produce a proper vulcanization of the hard compound, having the pro-
portions particularly specified in the foregoing description of the third operation
of the process.
Having thus described a practical means of carrying out the Invention into
effect, I wish it to be understood that it is not confined to any particular
incans or method of accomplishing any one of its separate steps, as these may
be varied as circumstances render expedient; neither is it confined to the
employment of hard stock prepared specially for the purpose out of raw gum,
as the scraps produced in the manufacture of articles from the ordinary hard
compounds of the vulcanizable gums may be employed in place of such stock,
for they have already undergone the first step of the process, and are ready for
the subsequent operations. The Invention also is not limited to the employ-
ment at the third operation of ground hard stock and raw gum alone to the
exclusion of other materials, as circumstances arise in the course of manu-
facture in which an admixture of one other material may be necessary; thus,
if but a small proportion of ground stock is to be combined with a large
proportion of raw gum, an additional quantity of sulphur should be blended
with them sufficient to ensure the vulcanization of the raw gum, and on the
other hand, if, for any reason, the hard stock has been manufactured with
just sufficient sulphur to produce its vulcanization, an additional quantity of
sulphur is required at the third step of the process in order that the product
obtained at the fourth step may be sufficiently hard. Various earthy materials
may also be incorporated with the compound in the process of manufacture,
but the employmeut of such materials is objectionable for the reasons before
mentioned. What I claim as the Invention, and desire to secure by Letters
Patent is the process herein described for manufacturing the vulcanizable
compounds of vulcanizable gums, consisting of the following operations,
viz. :-
First, the manufacture of hard stock of the vulcanizable gum by blending
it with sulphur or its equivalent, and vulcanizing the compound until it is
hard.
Second, the reduction of the hard stock to powder.
Third, the formation of a compound of the ground stock and raw gum by
blending the two together.
Fourth, the vulcanization of the compound formed by the preceding
operations; the several operations constituting the process being effected in
the order herein stated.
And I claim the foregoing, whether the materials be so proportioned and

page_text: the vulcanization be so conducted as to produce hard compound for hard
goods or soft compound for soft or very flexible goods.
In witness whereof, I, the said George Tomlinson Bousfield, have
hereunto set my hand and seal, this Eighth day of August, in the year
of our Lord One thousand eight hundred and fifty-nine.
GEO. T. BOUSFIELD. (L.S.)
Witness,
W. S. HARRISON,
New Court, St. Swithin's Lane.