Note: Descriptions are shown in the official language in which they were submitted.
32C39
`- 63293-2307
This invention relates to a reinforced bituminous
membrane which is particularly suitable for roofing and o~her
water-proo~ing applications, and to the manufacture thereof.
Conventional built-up roofing consists of layers of ~uch
membranes which are successively adhered to the roof substrate and
to each other to form a multi-layer system of, e.g., up to ~ plies
in situ. Hot applied mopping bitumen is u~ed as adhesive in this
system. It is applied using, e.g., a strong mop, the membrane
then being rolled onto the layer of hot mopping bitumen.
In winter applications, in particular, the surface of
the mopping bitumen tends to cool so rapidly that it is not always
possible to obtain a good adhesive bond. This effect is also
noticeable when applying hlgh quality polymer modified bitumen
membranes which are designed as a 2 layer system using
conventional mopping bitumen ~or application.
It has now been found that a layer of mopping bitumen
applied ~o the underside of the membrane during manufacture
results in improved bonding in otherwise marginal tempera~ure
conditlons, when torch applied.
This invention therefore rela~es to a reinforced
bituminous membrane, particularly suitable for roofing, comprising
a sheet containing a bituminous material which compri~es a mixture
of bitumen and a synthetic rubber, having the formula:
A-B-A or A-B (-B-A)
in which A represents a polystyrene block and B a polyconjugated
diene block, and n is an integer from 1 to 5, and a reinforcement,
and furthermore comprising a layer o~ mopping bitumen at the
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~L251~2(~
63293-2307
underside of thi~ sheet. The layer of mopping bitumen pre~erably
contains a carrier.
The layer of mopping bitumen is applied during the
manufacture of the membrane, e.g. by coating the underside of the
sheet containing the bitumlnous materlal and the reinforcement
with the mopping bitumen during or after the membrane's
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manufacture in order to prepare a prefabricated membrane which
is ready for use. This coating can e.g. be carried out by
spraying.
Preferably the present membrane is manufactured by coating,
e.g~ by spraying, a carrier, preferably a fibreglass carrier, on
both sides with the mcpping bitumen. The carrier may also be
impregnated wlth the ~cpping bitumen. The carrier is then cooled
and if desired stored, e.g. in rolls. It is subsequently applied
to the underside of the sheet containing the`bituminous material,
preferably a mixture of bitumen and a synthetic rubber, and the
reinforcement, preferably during the ~anufacture of the latter
at elevated temperatures, e.g. at production ~emperatures of at
least about 138C. m e mcpping bibumen in this case preferably
has a Ring and Ball softening point of 90-98C (ASTM D-3~).
As carrier a fibreglass is preferred to other c æ riers,
such as polyester carriers, because it will not shrink or
distort. Mbreover it is not too thick as ccmpared to conv~ntional
felt carriers.
The untreated fibreglass carrier may have a weight of about
1.85 pcunds per 100 s~uare feat (about 0.09 kg/m7). After
treatment with the ~cpping bitumen its weight is about 40 pounds
per 100 square feet (about 2 kg/m2).
Ihe carrier thickness is about 0.5 mm when untreated and
abcu~ 1.5 to 2 mm after treatment.
Further advantages of the membrane of this invention appear
from the following.
In ex*reme low temperature conditicns, e.g. do~n to -18C,
mopping bitumen loses temperature very rapidly as it is m~pped
out in a thin layer on a rc~f. It has been found that if an open
flame (torch) is applied to the surface of the mcpping bitume~
immediataly in front d the advancing roll of membrane, the
surface of the mcpping bitumen is quickly raised to an acceptably
high temperature. The layer of m~pping bitumen on the underside
of the membrane of the i~vention is heated by heat from the
torch as well. The net effect is an improved initial bond as the
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membran~ is ~olled into the heated mopping bitumen on the roof,
despite low ambient temperature conditions.
Furthenmore, the application of specially thickened bitumi-
nous membranes (torching felts) by torch is well known m the
industry. The torch softens a portion of the bitumen of the
membrane and the softened bitumen acts as an in situ adhesive
without the neEd for separate application of hot mopp mg bitumen
on the roof deck.
If the bituminous material of such a membrane comprises a
mixture o~ bitumen and a synthetic rubber, then the synthetic
rukber can be damaged by the torching method if a conventional
membrane is used. This thermal degradation may occur through
exposure to excessively high flame temperatures, even for short
periods. This degradation may not be noticed at the time of
application but the long tenm performance of the membrane may be
seriously im~aired.
If the underside of the membrane is coated with a layer of
mcpping bitumen, this la~r, especially if it c~ntains a carrier,
provides a protective layer for the thermally sensiti~e rubber
during the torching application, in addition to bonding to the
substrate.
The reinforoement of the membrane may comprise woven or
unwoven fabric, or chopped fibres. Fillers, extenders, plas-
ticizers and pigments may also be present.
The bitNmincus material is preferably a petrol~um bitum~n,
e.g. having a softening point of at least 75~C.
The synthetic rubber may be present in a prcportion of,
e.g., 5-30%w based on the mixture of bitumen and synthetic
rubber. Particularly suitable are thenmoplastic rubbers, in
particular linear, branched, including star-shaped, block
copolymers of styrene and conjugated dienes.
~he linear block copolymer preferably has the formula
A-B-A, in whic~ A represents a polystyrene block having a
molecular weight of~ e.g., 7,500 to 100,000, and B represents a
~:2582(~
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polyconjugated diene block, such as a polyisoprene or poly-
butadiene block. m e molecular weight of block B is, e.g.,
25,000 to 1,000,000.
m e line æ block copolymer may also be partly or completely
hydrogenated, in particular as far as block B is concerned.
The branched block copolymer preferably has ~he formula
A-~--tB-A)n, wherein A and B ha~e the above-mentioned
meaning ana n is an in~eger, suitably from 1 to 5. Also this
block ccpolymer may be partly or ocmpletely hydrogenated, in
particular as far as blocks B are concerned.
In this specification mopping bitumen means bitumen blown
to a softer grade than coating grade blown bitumen and sub-
stantially not con~aining a mineral filler or rubber. m e
penetration of the mopping bitumen (25C, 100 g, 5 s) is prefer-
ably 15-30, more preferably 15-25, 0.1 m~ (ASTM D-5). The Ring
and Ball softening point is preferably 75-98C, more preferably
90-98C, (ASTM D-36).
The thickness of the thin layer of mopping bitumen on the
membrane is preferably 0.5-2.0 mm, more preferably 0.5-1.0 mm.
The coating of mDpping bitumen is preferably applied to all
of the underside of the membrane.
Sticking of the present mEmbranes during storage is avoided
by conventional mEans, e.g., by applying a thin layer of a fine
grade of sand on the coated surface.
