U.S. patent number 3,864,157 [Application Number 05/207,800] was granted by the patent office on 1975-02-04 for impervious barrier comprising polyolefin fabric, asphalt and asbestos.
This patent grant is currently assigned to Phillips Petroleum Company. Invention is credited to Clarence R. Bresson, Forrest D. Spaulding.
United States Patent |
3,864,157 |
Bresson , et al. |
February 4, 1975 |
IMPERVIOUS BARRIER COMPRISING POLYOLEFIN FABRIC, ASPHALT AND
ASBESTOS
Abstract
An impervious cover structure is produced by laying a polyolefin
fabric fused on one side only, fused side against the surface to be
covered and the unfused side is coated with a mixture containing
asphalt and asbestos fibers.
Inventors: |
Bresson; Clarence R.
(Bartlesville, OK), Spaulding; Forrest D. (Bartlesville,
OK) |
Assignee: |
Phillips Petroleum Company
(Bartlesville, OK)
|
Family
ID: |
22772049 |
Appl.
No.: |
05/207,800 |
Filed: |
December 14, 1971 |
Current U.S.
Class: |
427/202; 106/282;
156/148; 428/489 |
Current CPC
Class: |
B32B
17/02 (20130101); B32B 5/022 (20130101); E02B
3/126 (20130101); E04B 1/66 (20130101); B32B
2262/0253 (20130101); Y10T 428/31815 (20150401) |
Current International
Class: |
E02B
3/12 (20060101); E04B 1/66 (20060101); B32b
027/00 () |
Field of
Search: |
;161/81,82,151,154,155,156,164,170,205 ;156/148 ;117/138.8E,168
;106/282 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Van Balen; William J.
Assistant Examiner: Bell; James J.
Claims
We claim:
1. A method of providing a surface covering comprising a non-woven
polyolefin fabric, mat or web, fused externally on one side and
having unfused fiber on the other external side, which method
comprises placing said polyolefin fabric, mat or web, which can be
needle-punched, against a surface to be rendered impervious to
fluids, the side of the fabric placed against the surface to be
covered having been fused and then coating the other side of the
fabric which presents unfused fibers with a mixture containing
asphalt and asbestos fibers.
2. A method according to claim 1 wherein the fabric is
polypropylene fabric made by needle punching together a mass of
non-woven fibers and wherein the asphalt-asbestos mixture is
cut-back with a sufficient amount of a solvent or oil to make the
resultant blend applicable to said other external side by hot
application at a temperature below that which will adversely melt
said polyolefin fabric, mat or web, and the cut-back
asphalt-asbestos mixture is applied to said other side at the rate
of approximately 3-5 pounds per square yard of the fabric of the
asphaltic mixture, and the mixture applied to said other side is
allowed to cure in air at ambient temperature.
Description
This invention relates to an impervious cover structure. In one of
its aspects, it relates to a cover structure comprising a
polyolefin fabric, asphalt and asbestos fibers. In another of its
aspects, the invention comprises a surface or object to which has
been applied an impervious cover structure comprising a polyolefin,
for example, a non-woven polyolefin fabric, mat, or web, the
polyolefin being impregnated with a mixture containing asphalt and
asbestos fibers. It also relates to a method for producing covers
or coatings as described herein. Further, in a specific aspect, the
invention relates to a reservoir or pond or other container which
is rendered fluid retentive by applying thereto an impervious cover
structure according to the invention.
In one of its concepts the invention provides a cover structure
which is produced by fusing externally on one side, or at least on
one side, a polyolefin fabric, mat, or web, laying said fabric,
mat, or web with its fused side against an object surface or ground
to be rendered impervious and then coating said fabric, mat, or web
on a provided unfused external side with a mixture containing
asphalt and asbestos fibers.
In another of its concepts the invention provides a reservoir,
container or pond having a liner or structure applied to the
surface thereof as herein described.
Various liners have been provided for covering objects or surfaces
or the ground to render these impervious to fluids, for example, to
water, or other liquids. In places at which the fluid or liquid
exerts considerable pressure against the covering structure or
liner, leakage is often observed. The leakage occurs at so-called
pin hole openings in the coating or covering structure. These leaks
have been observed, particularly with non-woven fabrics which have
been coated with various sealants. Thus, in fairly deep pond liner
applications, it has been observed that asphalt sealed non-woven
polypropylene fabric can develop pin hole leaks which may be due to
cold flow.
We have now conceived of an improved cover structure. Thus, we have
conceived that if the non-woven fabric is provided with a fused
external side and a non-fused external side, and is laid fused side
against the object to be covered or fused side down on the ground
as in the lining of a pond and is then covered or coated with
asphalt-containing asbestos fibers, as further described herein,
the resulting structure will not develop leaks.
An object of the invention is to provide a cover structure. A
further object of the invention is to provide a fluid or liquid
impervious cover structure suitable for application to objects to
be protected against fluid or liquid. A further object of the
invention is to provide a liner for liquid storage ponds. A still
further object of the invention is to provide a cover structure of
improved character in that it will withstand liquid pressure of
considerable magnitude, yet not develop leaks. A further object of
the invention is to provide a cover structure comprising a
non-woven fabric covered with asphalt which will not flow, once
cured, due to cold flow through "windows" in the non-woven
fabric.
Other aspects, concepts, objects and the several advantages of the
invention are apparent from this disclosure and the appended
claims.
According to the invention, there is provided an impervious cover
structure which comprises a non-woven polyolefin fabric, mat, or
web, fused externally on one side and having unfused fiber on the
other external side thereof, the fused side being laid against the
material to be covered, the unfused fibrous side being coated with
a mixture containing asphalt and asbestos fibers.
The asphalt-asbestos mixture which is applied is usually applied as
a cut-back asphalt. The cut-back asphalt is prepared from an
air-blown asphaltic material having a penetration of about 20-50,
preferably 25-35, a minimum ductility at 77.degree. F of 5, and a
Ring and Ball softening temperature of 160.degree.-175.degree.
F.
The cut-back solvent used to prepare the cut-back asphalt is
selected from kerosene, cycle oil, Stoddard solvent or, in general
a hydrocarbon based material having an initial boiling point in the
range of 160.degree.-450.degree. F, preferably
200.degree.-300.degree. F.
Sufficient cut-back oil is used to make the resultant blend
applicable to the surface by hot application not exceeding about
250.degree. F (melting point of polypropylene) at a temperature
which will not adversely melt the fabric or by spray or brush
technique at ambient temperatures. Usually about 20-100 parts by
weight of solvent, preferably about 40-70 parts by weight per 100
parts by weight of asphaltic material, are used.
The asbestos fiber is added to the cut-back asphalt in amounts from
about 4-10 parts/100 parts by weight of cut-back asphalt. It can
have a fiber length of about 0.01-0.1 in., preferably about
0.03-0.06 in. While the presence of longer fibers can be tolerated,
the preferred range is more readily handled by the usual equipment
and best improves the desirable properties of the asphalt, such as
the penetration values.
It has been found that using an approximately 4 oz/yd.sup.2 fabric,
an asbestos fiber content of about 6-8, or more, parts/100 parts of
cut-back asphalt is preferred, while for a 5 oz. web a fiber
content of about 5-6 in the cut-back asphalt is sufficient.
The fabric is made from about 2-20 denier, preferably about 3-8
denier crimped staple about one-half to about 3 in. long; a batt of
these fibers is needle punched by conventional means and the needle
punched fabric is then passed through a pair of nip rolls, one of
which is heated above the melting point of the fibers to heat-fuse
the fibers on one side. The amount of fusion is adjusted to give
the final product a tensile strength of from about 10 lbs. to about
75 lbs/inch of width, the strength depending both on the amount of
fusion, weight of fabric and denier of the fiber. The fabric is
about 1-5 mm thick under no compression and ordinarily less than
about 10% of the thickness of the fabric is fused.
The polypropylene fabric should have a weight of at least about
3.5-4 ox/yd.sup.2 and is fused on one side only. A heavier fabric
weighing about 5-6 ox/yd.sup.2 is now preferred. Much heavier
fabrics become uneconomical and heavy to handle.
A capped product, i.e., a light fabric fused on both sides, having
a "cap" of 1-2 oz/yd.sup.2 of additional fiber, e.g., nylon,
attached to one side thereof by an added needle punch operation and
having a total weight between about 4.0 and about 5.5 oz/sq yard is
also suitable. The added fiber now acts as does the unfused side of
the fabric which is fused on one side only. Thus, the capped side
is the one to which the cut-back asphalt/asbestos mixture is
applied.
It is obvious that there are a number of variables which coact to
provide an effective leak-proof liner. Under mild conditions, for
example, a shallow, sweet water pit or ditch, an asphalt with
higher penetration can be used and a more fluid cut-back
formulation containing less asbestos can be used. For more severe
conditions, deep water, high temperature and brine, for example, a
lower penetration asphalt is used with a heavier mat and more
asbestos; this more viscous material may have to be applied hot
(v.s.). These and other variables can be determined by mere routine
testing by one skilled in the art in possession of this
disclosure.
It is essential, however, that the asbestos fibers in the mixture
be forced by the flow of the liquid through the mat into immediate
contact with the surface of the mat where they become imbedded in
the unconsolidated top surface of the fabric and lodge in the
interstitial voids present therein.
The bar graphs reflect results obtained without and by using the
invention. These are comparable.
Referring now to the bar graph, these indicate by their lengths the
time in hours at certain pressures required for failure of the
cover structure indicated.
The pressure was applied in a test apparatus into which water was
fed and maintained under pressure against the test covered
structure supported on a screen.
There are six tests shown in the bar graph. Failure or end of test
with failure is indicated by the bars which have smooth or straight
line endings. The cut-away endings in tests 4 and 6 indicate that
the tests were still under way at the indicated time in hours.
The final oven cure for tests 5 and 6 was for 8 and 12 hours at
140.degree. F in an air circulating oven, respectively.
It can be seen that one coat covering with cut-back asphalt
containing asbestos according to the invention yields results which
are far superior to those obtained even with two coats of covering
when the asbestos is only in the second coat. Thus, the tests
demonstrate a coaction between the asbestos in the asphalt and the
fabric to which it is applied.
It will be evident to one skilled in the art in possession of this
disclosure and having studied the same that there must needs be,
according to the invention, loose or unfused fibers on the external
surface of the fabric to which the asphalt-asbestos mixture is
applied. Thus, it is within the scope of the invention to use a
fabric which has been fused on both sides but to which there has
been applied additional fiber in some manner or other as by a
needle punch operation.
The asbestos fiber now preferred is Johns-Manville 7MO2 fibers.
These asbestos fibers were used in the specific tests reported in
the bar graphs. The fabric used was a non-woven polypropylene five
ounce per square yard fabric, heat-fused on one side. This fabric
is now preferred. The mixture of asphalt-asbestos and solvent
should be readily sprayable at temperature of
120.degree.-180.degree. F. and as such can be applied to vertical
surfaces as well as horizontal ones. Applications in addition to
those described are various. Various shaped objects in addition to
ponds can be covered. Inside of tanks of various shapes can be
covered. Rooftops, especially those which may be structured to
accumulate and to retain liquid as a shield against heat can also
be covered. Indeed, though the structure of the invention is
particularly well suited for use under considerable hydrostatic
pressure, it can, of course, be used in all those places where
fabric reinforced asphalt containing coverings are used.
The following examples include data from which the bar graph has
been prepared, as well as other data.
EXAMPLE 1
Polypropylene fibers of staple length, about 6 denier, were carded
and needle-punched to a consolidated fibrous bat. The bat was
subjected to a heating step in which it was passed through a pair
of nip rolls, one of which is heated to about 400.degree. F to fuse
the fibers on that side. The resulting nonwoven fabric has a weight
of about 5 oz/yd.sup.2 and an average thickness of about 2 mm.
PREPARATION OF CUT-BACK ASPHALT/ASBESTOS MIX
The cut-back asphalt was prepared from an air blown asphaltic
material having a penetration of 35, a ductility of 77.degree. F of
5 and a Ring and Ball softening temperature of 165.degree. F. The
asphalt was cut back with naphtha, boiling range
200.degree.-400.degree. F, at a ratio of 100 parts of asphalt and
50 parts of naptha. To this blend were added asbestos fibers with
an average fiber length of about 0.05 in. Sufficient fibers were
added to provide about 5 parts by weight asbestos fibers in 100
parts of cut-back asphalt.
TEST PROCEDURE
A sample of the non-woven fabric (5 oz/sq yd) was spray-coated with
the cut-back asphalt containing 5 percent asbestos fibers at a rate
of two-thirds gal/yd.sup.2 and allowed to cure for 12 hours at
140.degree. F in a hot air oven. The fabric had no pin holes and
was an effective hydraulic barrier at 67 ft. at 80.degree. F. The
test was carried out in a static load apparatus in which a sample
fabric is subjected to a static hydraulic load at a controlled
temperature and the time measured to develop a leak. This sample
was tested for 60 hours without failure when the test was
discontinued.
EXAMPLES II - V
Other samples of 5 oz/yd.sup.2 fabric were variously treated and
tested as in Example I.
1. single coats of a cationic asphalt emulsion were applied on 2
consecutive days and then allowed to cure in air at ambient
temperature for 1 week. The sample failed under 10 psi load after
about 6 minutes.
2. Two coats of air-blown, cut-back asphalt (2.0 lbs. asphalt/sq
yd) without asbestos fibers on fabric samples were tested at 30 psi
(67 ft) and failed after 60 minutes.
3. Two coats of air-blown cut-back asphalt were applied, the first
coat without asbestos fibers and after a 1-day cure the second coat
containing 5 parts asbestos fibers/100 parts of cut-back asphalt
(4.0 lbs asphalt/sq yd). This sample failed after 45 minutes (7-day
air cure).
4. One coat air-blown cut-back asphalt with 5 parts asbestos
fibers/100 parts cut-back asphalt (3.08 lbs/sq yd), 7-day air cure.
The sample did not fail after 22 hours at 30 psi (67 ft) when test
was terminated.
EXAMPLE VI
Samples of 4 oz non-woven fabric fused on one side were coated with
a cut-back asphalt containing 5 and 7 parts by weight of asbestos
fibers per 100 parts of cut-back asphalt, respectively, cured and
tested as before.
The 4 oz material coated with the 5/100 mixture failed after 5
hours while with the 7/100 mixture the test was discontinued at 95
hours without failure.
EXAMPLE VII
A non-woven fabric was prepared by carding and needle-punching 6
denier polypropylene staple and the about 1 1/2 oz/sq yd nylon 66
staple was needle-punched into the bat and the polypropylene side
was fused. This nylon capped fabric had an approximate weight of 5
1/2 oz/sq yd.
A sample of this material was coated with two-thirds gal/sq yd of
5/100 asbestos cut-back asphalt mixture and allowed to cure for 8
days. Under hydraulic test at 80.degree. F and 30 psi (67 ft) no
failure occurred after 130 hours when the test was
discontinued.
EXAMPLE VIII
A similar capped coated fabric was prepared, except that 6 denier
polypropylene fiber was substituted for the nylon of Example VII.
One coat of 5/100 asbestos/asphalt (one-half gal/sq yd) mix was
applied as in Example VII and the cured fabric was tested at
80.degree. F and 30 psi (67 ft). No failure had occurred after 25
hours when the test was discontinued.
It is evident from Example I that the spray coated fabric which had
been cured was free from pin holes and was an effective barrier
against hydraulic pressure for a period of 60 hours.
In Examples II - V, it is shown that (1) single coating asphalt
emulsion applied on 2 consecutive days or (2) single coats of
cut-back asphalt applied on 2 consecutive days, failed to provide
an effective barrier under comparative conditions. Also application
of a first coat (3) without and a second coat with asbestos fibers
likewise failed to provide a suitable barrier. A single coating
including asbestos fibers (4) provided such a barrier.
Examples VII and VIII show the use of a capped fabric, that is, a
fabric which has a coating of, say, nylon or polypropylene thereon.
These fabrics also produce excellent test results against hydraulic
pressure.
Reasonable variation and modification are possible within the scope
of the foregoing disclosure and the appended claims of the
invention, the essence of which is that there has been set forth an
impervious cover structure which comprises a non-woven polyolefin
fabric, mat or web fused externally on one side and placed with
that side against a surface or area to be protected or rendered
impervious and then covering the other side on which the surface
fibers are unfused with a mixture containing asphalt and asbestos
fibers, substantially as described.
* * * * *