mprovements in the Manufacture of Waterproof Material more particularly intended for Roofing and Insulating purposes.
Year: 1898

page_text: Date of Application, 30th Mar., 1898-Accepted, 20th May, 1898
COMPLETE DE
mprovements in the Manufacture of Waterproof Material more
particularly intended for Roofing and Insulating purposes.
I, LUDWIG HATSCHEK, of Vöcklabruck, in the Empire of Austria, Manufacturer, do
ereby declare the nature of this invention and in what manner the same is
o be performed, to be particularly described and ascertained in and by the
ollowing statement :-
Roofing felts as hitherto in use, are manufactured, as is well known, by saturating
or impregnating a felt made from any suitable fibrous material with tar, asphalt-tar,
or the like, such impregnating substances being readily absorbed by the raw felt.
These said substances however contain numerous liquid constituents which escape
in a comparatively short time by evaporation, only the less valuable constituents
remaining in the felt. It consequently becomes necessary to again impregnate the
felt, which impregnation can, at the best, be only inefficiently effected by giving it
a coating of the said substance.
Owing to the evaporation above referred to, numerous small pores are formed,
which, by reason of the greater surface thereby exposed, facilitate both the speedy
evaporation of the liquid constituent parts, and the commencement of atmospheric
action. In order to prevent or lessen this, it is of course desirable to impregnate
the felt with a substance having as great a resistance to deterioration as possible
and one which will not readily evaporate. For such a purpose pure bitumen or
asphalt is eminently suitable, but owing to its consistency it is incapable of
absorption by any kind of felt, whilst even when boiled with the same only a layer
All attempts to impregnate
of greater or less thickness is formed upon the felt.
felt with bitumen have hitherto been frustrated by this circumstance.
The object of this invention is to overcome the above mentioned difficulty and to
produce a felt which is flexible and water-proof in a greater or less degree according
to the proportion of asphalt employed; and which is therefore specially adapted
for roofing purposes and also for use as an insulating material, for pipes for cable
conductors, and the like.
In accordance with my invention, pure asphalt (that is to say, asphalt such as
is obtained from the island of Trinidad, and not asphalt-tar) is used in the form of
O powder, and it is essential that the pulverisation should be carried as far as possible.
This powder is placed with the fibrous material in a mixing apparatus, which may
consist of a well known form of cylindrical mill or a mixing vat of the kind em-
ployed in paper manufacture, both of which apparatus are well adapted for the
After an extremely intimate mixing has been effected, the mass is
purpose.
5 formed into sheets in precisely the same manner as that now employed for making
felt from the usual pulp. It then undergoes a drying process upon heated
calendering cylinders. During this operation the bitumen, which becomes more
'or less liquefied according to the degree of heat employed, spreads uniformly
through the fibrous material. This calendering of the felt has also the additional
10 great advantage over the absorption or impregnation process hitherto employed
that the separate constituent parts of the felt are strongly compressed
and its resistance to wear and deterioration is therefore considerably greater

page_text: than is the case with felts which have been impregnated, as in this latter
process they swell considerably and assume a spongy structure. In addition to
being absolutely water-proof my improved felt has the further important advantage
that the manufacture of the same consists in a continuous process, whilst hitherto
two distinct processes have been necessary, that is to say, the manufacture of the
raw felt and its conversion into tarred or asphalted felt, which material, as
previously stated, when employed for roofing purposes has in addition to be
specially impregnated, this being quite unnecessary with my improved process.
In the manufacture of felts, with a relatively small proportion of bitumen, it is
necessary to heat the calendering cylinders to an increased degree as the asphalt
must be completely liquefied, in order that it may, become uniformly distributed..
In such cases I find it advantageous to employ asbestos as the fibrous material for
the reason that all other fibrous materials hitherto used for making tarred felt
would be destroyed by such a high temperature. In addition to this, asbestos
possesses the further important advantage of not being liable to decomposition or
decay as are all vegetable fibrous substances.
Having now particularly described and ascertained the nature. of my, said inven-
tion and in what manner the same is, to be performed, I declare that what I
claim is :-
1. The process of manufacturing water-proof roofing, insulating, and like felts
or material, characterised by the fact that fibrous material; more. particularly.
asbestos, is intimately mixed with pulverised asphalt and the product resulting
from the manufacture of this mixture into sheets heated until a partial melting. of
the incorporated asphalt takes place.
2. As a new commercial product, roofing and insulating. material provided, by
means of the process described in Claim 1, with a layer or admixture. of asphalt
permeating the fibrous material substantially as described: