By HAWTHORNE HILL.
The complaint of high prices of India rubber is as old as the rubber
industry, one result of which has been an unceasing effort to discover
a practical substitute. Never was the secret of the transmutation of
metals sought more persistently by ancient philosophers than the
secret of an artificial rubber has been by modern chemists, but, thus
far, the one search has been hardly more successful than the other.
One discovery has been made, however, by which our rubber supplies
have been so far conserved that, for the want of it, we might be
obliged now to pay double the current prices for new rubber. This is
the reclaiming of rubber from worn-out goods, in a condition fit for
use again in almost every class of products of the rubber factory.
Soon after the vulcanization of rubber became fully established,
attempts began to be made to "devulcanize" the scrap and cuttings of
rubber which accumulated in the factories. So extensive were these
accumulations that one company are reported to have built a road with
rubber scrap through a swamp adjacent to their factory, while most
other manufacturers were unable to find even so profitable a use for
their wastes. As time advanced there came to be large stocks, also, of
worn-out rubber goods, such as car springs and the like, all of which
appealed to a practical mind here and there as being of possible
value, since the price of new rubber kept climbing up all the while.
No fewer than nineteen patents were granted in the United States for
"improvements in devulcanizing India rubber," or "restoring waste
vulcanized rubber," beginning in 1855, or eleven years after the date
of Goodyear's patent for the vulcanization process. In that year
Francis Baschnagel obtained a patent for restoring vulcanized rubber
to a soft, plastic, workable state, by treating it with alcohol
absolutus and carbon bisulphuratum, in a closed vessel, without the
application of heat. Later he obtained a patent for accomplishing the
same result by "boiling waste rubber in water, after it has been
reduced to a finely divided state;" and still later, one for treating
the waste to the direct action of steam.
Patents were granted in 1858 to Hiram L. Hall, for the treatment of
waste rubber by boiling in water; also, by subjecting it to steam; and
again, by combining various resinous and other substances with it. The
two inventors named assigned their patents to the Beverly Rubber
Company, of Beverly, Mass., controlled then by the proprietors of the
New York Belting and Packing Company, and their processes became the
basis of an important business in rubber clothing.
The low cost of the devulcanized rubber, as compared with new rubber,
alone gave them a great advantage over other manufacturers, in
addition to which they escaped the payment of a license to work under
the Goodyear patents.
Many army blankets, made for the government during the civil war, were
waterproofed with Hall's devulcanized rubber, and from that period
little new rubber has been used in the manufacture of heavy rubber
coats. The other patents in this class do not deserve special mention.
It having been established that rubber is rubber, no matter where
found, manufacturers gradually turned their attention beyond the
scraps and cuttings which remained after making up their goods. There
was beginning to be a good demand for ground-up rubber car springs,
wringer rolls, tubing and other rubber goods free from fiber, after it
had been so treated as to remove the sulphur contents and restore the
gum to a workable condition. But this left out of account rubber
footwear, belting, and hose, not to mention the later heavy production
of bicycle tires. There were only a few uses to which rubber waste
containing fibrous material could be put when ground up and
devulcanized without the removal of the fiber. It could be put into a
cheap grade of steam packing or mixed in a powdered form with new
rubber for the heels of rubber boots and shoes. There was an early
patent for a process for "combining fibrous materials with waste
vulcanized rubber, rendered soft and plastic." But all the other
patents which come within the scope of this article had for their
object the separation of fibers from the rubber.
An important advance was marked by the Hayward patent (No. 40,407),
granted in 1868, for "boiling waste rags of fibrous material and
rubber in an acid or alkali, for the purpose of destroying the
tenacity of the fibers of the rags, so that the rubber may be
reground." But this process extended only to the weakening of the
fibers, and not their complete destruction. A later patent, in the
same year, provided for exposing the ground rubber waste to the direct
action of flames of gas or inflammable liquids, by which the foreign
matters would be consumed and the rubber rendered plastic and
cohesive, but it is not on record that this process received any
particular application.
The principal activity of invention in the field of reclaiming rubber
dates from 1870, since which year 37 patents have been granted for
processes more or less distinctive from those which had for their
object only the devulcanization of rubber. Prior to that time the use
of rubber reclaimed from fibrous wastes had been confined practically
to one large factory in Boston and one near New York. One concern, for
a while, bought old rubber shoes and sent them to women in the
country, whom they paid so much a pound for the rubber stripped off--a
very expensive process. There were several claimants for priority in
the matter of reclaiming rubber by the processes which finally became
standard, and some conflicting interests were brought together under
the head of the Chemical Rubber Company. This corporation controlled
the leading patents for the "acid" process, licensing various parties
to work under them, and bringing suits against concerns who reclaimed
rubber without their license. In 1895 the United States courts decided
in favor of the defendants, practically rendering the patents invalid,
on the ground that the inventions claimed under them had been
disclosed by the Hall patents of 1858 and the Hayward patent of 1863.
The two patents upon which the suits for infringement rested
principally were No. 249,970, granted to N.C. Mitchell, in 1881, and
No. 300,720, granted to the same, in 1884. About the same time the
Rubber Reclaiming Company, formed in 1890 by the combination of five
leading rubber reclaiming plants, and working under license from the
company above named, was resolved into the original elements. There
were about that time five other rubber reclaiming plants in the United
States, operating either the "acid" or the "mechanical" process,
besides nine general rubber factories producing their own reclaimed
rubber by the "acid" process. While several of the latter--rubber shoe
concerns controlled by the United States Rubber Company--have been
consolidated, there has been an increase in the number of rubber
manufacturers reclaiming their own rubber, since the end of the patent
litigation, so that the total number of reclaiming plants now probably
is twenty.
The first step in any process for reclaiming rubber is the grinding of
the waste, for which purpose several machines have been designed
specially, an early patent for disintegrating rubber scrap by
"subjecting it to the abrading action of grindstones" having failed to
meet with favor. The most usual chemical treatment is a bath in a
solution of sulphuric acid in lead-lined tanks. Generally heat is
employed to hasten the process, through the medium of steam, in which
case the tanks are tightly closed. The next step is the washing of the
scrap, to free it of acid and dirt, after which it is sheeted by being
run between iron rollers and hung in drying rooms. As soon as it has
become dry it is ready for sale.
In the extended litigation over the acid process patents, the points
at issue related to the strength of the acid named in the various
specifications and also to the methods of applying steam. Prof.
Charles F. Chandler, called as an expert in one case, testified that
the effects of acids, such as sulphuric or hydrochloric, upon rubber
and rubber compounds, under varying strength and temperature, had been
known at a period antedating all the patents then the basis of suits
for infringement; also that their effect upon cotton and woolen
fabrics had been equally well known. They had the same effect upon
fibers, whether the latter were combined with rubber or not, but very
strong acids would affect the rubber injuriously. The line of defense
in this case was that "no invention was required in selecting the
strength of acid; only the common sense of the manufacturer, aided by
his skill and experience, was necessary to bring about the proper
results." In support of this a factory superintendent testified that
varied stocks required skill and judgment in their treatment and more
or less variation as to the strength of acid, temperature, etc.
As to the use of steam, Prof. Henry B. Cornwall, of Princeton College,
called as an expert in another case, testified that, having put to a
test the specifications in all the patents involved, he had found it
necessary in no case to inject live steam into the mixtures of acid
and rubber scrap in order to effect the decomposition and removal of
either woolen or cotton fiber. The use of the acids specified was
sufficient for this, and the various high temperatures called for were
not essential for the destruction of the fibers. He neglected to
mention, however, that the steam served an equally important purpose
in devulcanizing the rubber.
It appeared that the practice in different factories had included the
use of sulphuric acid varying from a 2½ per cent. solution to the
full commercial strength of the acid, but one of the defendant
companies based their case upon their use of acid of the strength of
28° to 30° Baumé, whereas the patent they were charged with infringing
specified a strength of 66°. Their tanks were lead-lined and provided
on the interior with steam pipes running down the sides and along the
bottom, the sections at the bottom being perforated and the steam
admitted at a pressure of 75 to 80 pounds. The chemical treatment
lasted from 2½ to 4 hours.
The sulphuric acid treatment, however, is confined mainly to scrap
containing cotton fiber. Where woolen fibers occur, which is much less
frequently, their disintegration is accomplished generally by the use
of caustic soda.
In the mechanical process of reclaiming rubber, the rubber is
separated from the fiber, after the whole has been finely ground, by
means of an air blast, the method being not unlike that practiced by
furriers for separating hair and fur from bits of pelt after skins
have been finely divided. As the powdered waste comes from the blower,
the rubber falls in a heap near the machine, while the particles of
fiber, being lighter, are carried far enough away to make the
separation complete. Devulcanization in this case is effected by
exposure to live steam at a high temperature. No oil is used in the
process, the sheeting of the product being facilitated by means of hot
friction rollers.
The cost of reclaiming rubber by the acid process is less than by
mechanical means, for which reason the former is now much more
generally used. But some manufacturers are willing to pay more per
pound for mechanically-reclaimed rubber, either (1) because it can be
"compounded" more heavily than the acid product, or (2) because of
certain inherent disadvantages of the latter. It is the testimony of
these manufacturers that the action of sulphuric acid upon whiting
(one of the most common adulterants used in rubber shoes) is to turn
it into sulphate of lime--an ingredient which is far from advantageous
in a rubber compound. Again, any acid which may remain in the
reclaimed rubber is liable to rot thin textile fabrics with which it
may be combined in manufacture. Finally, rubber recovered by the
chemical process, it is claimed, is harder than that obtained by any
other; so that it is usual to add, during vulcanization, in order to
soften the product, the residuum obtained from petroleum manufactures,
or palm or other oils. Unvulcanized rubber clippings also have been
used for this purpose. One of the most successful of our rubber
factory superintendents, who formerly made the reclaimed rubber used
by his factory, has stated that his practice was to subject the
material to an alkaline bath after the acid treatment, not only for
the better cleaning of the rubber, but to neutralize any acid which
might remain. Considering all the points involved, it was his opinion
that, when scrap rubber is cheap, the mechanical process is the more
economical, while, if it is high priced, the acid process has the
advantage. Since this expression of opinion, however, prices of rubber
scrap have ranged constantly at higher figures than before, and there
is no indication that we shall have again what was known formerly as
"cheap" scrap. It is not surprising, therefore, that the volume of
mechanical "shoddy" should be placed by the best estimates at not
above one-sixth of the total production of reclaimed rubber in the
United States. And the acid product, with all its admitted
shortcomings, is still superior to any of the so-called rubber
substitutes.
Reclaimed rubber is not to be considered as an adulterant, except in
the same sense as fillings, like whiting, litharge or barytes, the use
of which in rubber compounds often gives to the product desirable
qualities that are unobtainable by the use of "pure gum." It lacks
some of the qualities of good native rubber, and yet it is rubber, and
fills its proper place as acceptably as any raw material of
manufacture. Rubber shoes made of new gum entirely would be too
elastic, and for that reason would draw the feet, besides being too
costly for the ordinary trade. The construction of a rubber shoe, by
the way, is well adapted for the use of different compounds for the
different parts. Rubber enters into twenty-six pieces of a rubber boot
and nine or more pieces of a rubber shoe. Consequently, as many
different compounds may be used, if desired, for the output of a
single factory for rubber footwear. The highest grades of native
rubber may be used for waterproofing the uppers of a fine overshoe,
while reclaimed rubber, of a cheap class even, may be good enough for
the heel, which requires only to be waterproof and durable, without
too much weight, and with no elasticity. Reclaimed rubber goes into
many classes of goods of high grade. The result is that such goods
have been cheapened legitimately, placing them within the reach of
immense numbers of consumers who otherwise would be obliged to do
without.
While the extensive use of reclaimed rubber is a matter of common
knowledge to all who are familiar with the rubber industry, there are
nowhere available any statistics of either the absolute or comparative
volume of its consumption, with the single exception of the official
returns of imports into Canada. There separate accounts are kept of
crude India rubber and of recovered rubber received in each year, and
as only a consuming market exists for these commodities in the
Dominion, the figures given below may be taken to represent closely
the actual consumption by the rubber factories of Ontario and Quebec.
It is interesting to note the heavy growth of the percentage of
recovered rubber shown in the table, all the figures representing
pounds:
Fiscal Crude Recovered Total
Year. Rubber. Rubber. Imports.
1885-86 739,169 19,499 758,668
1886-87 785,040 46,508 831,548
1887-88 1,225,893 88,471 1,314,364
1888-89 1,669,014 221,674 1,890,688
1889-90 1,290,766 147,377 1,438,143
1890-91 1,602,644 8,254 1,610,898
1891-92 2,100,358 106,080 2,206,438
1892-93 2,152,855 195,281 2,348,136
1893-94 2,077,703 529,900 2,607,603
1894-95 1,402,844 611,745 2,014,589
1895-96 2,155,576 643,169 2,798,745
1896-97 2,014,936 1,061,402 3,076,338
Percentage, 1885-86 97.5 2.5 100
" 1896-97 65.5 34.5 100
If it were possible to examine the books of the several rubber
reclaiming plants on this side of the border, including rubber shoe
and mechanical goods factories producing their own reclaimed rubber,
the percentage of this material used, in comparison with the total
rubber consumption, might be found to be as great in the United States
as in Canada. The rubber manufacture in the Dominion, in its
inception, was practically an offshoot from the industry in this
country. Our manufacturers supplied the Canadian demand for rubber
goods until, under the stimulus of heavy protective duties, rubber
works were established beyond the border, since which time, to quote a
leader in the trade in the United States, "the methods of the Dominion
rubber industry have mirrored the best practice in our country." Hence
it seems not unreasonable to conclude that if the Canadians are using
so large a percentage of reclaimed rubber, they are doing no more nor
less than the older and larger concerns here. The most trustworthy
authorities place the consumption of new rubber in the United States
during 1897 at not far from 35,000,000 pounds. Assuming that the rate
of consumption of reclaimed rubber was as great as in Canada, we have
18,435,000 pounds more, or a total of 53,433,000 pounds. But there are
producers of reclaimed rubber who insist that the amount of this
material used in this country equals, pound for pound, the consumption
of new rubber.
The use of reclaimed rubber in Europe is increasing gradually, and
especially in Great Britain. The American product is sold extensively
in that country, and some native reclaiming plants have been started.
The most extensive "galosh" factory in Russia, which is said to be the
largest in the world, is reclaiming rubber according to American
methods. But, as a rule, the Continental rubber manufacturers make
more use of "substitutes," a class of materials which has not found
favor in America. These rubber substitutes belong chiefly to the class
of oxidized oils and may be classed in three divisions: Those obtained
(1) by the action of oxygen or air on linseed oil; (2) by acting on
rape oil with chloride of sulphur; and (3) by the action of sulphur on
rape oil at a high temperature. The first class has little application
to the rubber trade, though its use is universal in the linoleum
industry. In Europe the chemist holds a more important position in the
rubber manufacture than here, one result of which has been cheaper
compounds of rubber and another the satisfactory employment of the
refractory African rubbers long before they were used extensively in
the United States. Hence the cost of raw materials in the rubber
industry has been, on the whole, cheaper abroad. The Europeans have
had an advantage, too, in respect to cheaper labor, which has offset
somewhat our own advantage from the use of reclaimed rubber as a cheap
material.
There are numerous grades of reclaimed rubber, due to differences in
the quality of stock used, and also to the different degrees of care
used in its preparation, according to the requirements of
manufacturers. The declared value of reclaimed rubber exported from
New York during July, 1897, averaged 12.6 cents per pound, while the
value of exports for September averaged only 9.1 cents. The average
value for the eight months ending February 28, 1898, was 10.08 cents
per pound. The total declared value of such exports for the fiscal
year 1896-97 was $119,440, which, at the prices prevailing since,
would represent considerably more than 1,000,000 pounds. Some of the
material sold at home is known to bring less than any prices quoted
above. "Mechanical" stock brings about two cents per pound more than
"acid" stock of corresponding grade.
The collection of old rubber has acquired large proportions as an
adjunct to the trade in junk or rags. Not long ago the estimated
yearly collection of rubber shoes alone amounted to 18,000 tons, and
since that time the business in bicycle tire scrap has also become
very large. During the past ten years the price of old rubber shoes
has ranged between $60 and $120 per ton in carload lots, being at
present about $90 per ton. Some 1,500 tons of rubber scrap are
imported annually by the reclaiming companies in the United States.
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In the Baltic Sea there are more wrecks than in any other place in the
world. The average throughout the year is one each day.
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