U.S. patent application number 11/874828 was filed with the patent office on 2009-04-23 for self repairing roof membrane.
This patent application is currently assigned to CARLISLE INTANGIBLE COMPANY. Invention is credited to Thierry Timothy Trial.
Application Number | 20090100775 11/874828 |
Document ID | / |
Family ID | 40560125 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090100775 |
Kind Code |
A1 |
Trial; Thierry Timothy |
April 23, 2009 |
SELF REPAIRING ROOF MEMBRANE
Abstract
A self repairing roof membrane includes a water impervious layer
such as EPDM covering a layer including a water swellable polymer.
Preferably, the water swellable polymer is bound to a nonwoven web.
If a tear is formed through the membrane, water that passes through
the tear will be absorbed by the water swellable polymer, which
will form a hydrogel and plug the tear.
Inventors: |
Trial; Thierry Timothy;
(Carlisle, PA) |
Correspondence
Address: |
WOOD, HERRON & EVANS, LLP
2700 CAREW TOWER, 441 VINE STREET
CINCINNATI
OH
45202
US
|
Assignee: |
CARLISLE INTANGIBLE COMPANY
Syracuse
NY
|
Family ID: |
40560125 |
Appl. No.: |
11/874828 |
Filed: |
October 18, 2007 |
Current U.S.
Class: |
52/408 ;
52/309.1 |
Current CPC
Class: |
B32B 27/304 20130101;
E04D 5/10 20130101; B32B 2274/00 20130101; B32B 2419/06 20130101;
B32B 25/14 20130101; B32B 11/10 20130101; B32B 25/10 20130101; B32B
27/32 20130101; B32B 2307/7265 20130101 |
Class at
Publication: |
52/408 ;
52/309.1 |
International
Class: |
E04D 5/10 20060101
E04D005/10 |
Claims
1. A roof structure comprising a roof surface covered with a water
impervious membrane said membrane having an exposed waterproof
layer and an inner layer including a water swellable polymer.
2. The roof structure claimed in claim 1 wherein said inner layer
comprises a web impregnated with said water swellable polymer.
3. The roof structure claimed in claim 1 wherein said inner layer
is adjacent said roof surface.
4. The roof structure claimed in claim 1 wherein said inner layer
is located between upper and lower waterproof membrane layers.
5. The roof structure claimed in claim 4 wherein said upper
waterproof membrane layer comprises a thin layer of a polymer
selected from the group consisting of polyethylene and
polypropylene, polyvinyl chloride and modified bitumen.
6. The roof structure claimed in claim 4 wherein said waterproof
membrane layers comprise ethylene propylene diene monomer
rubber.
7. The roof structure claimed in claim 1 wherein said inner layer
is adhered to a bottom surface of said waterproof layer.
8. The roof structure claimed in claim 1 wherein said waterproof
layer is selected from the group consisting of ethylene propylene
diene rubber, polyvinyl chloride, thermoplastic olefin and modified
bitumen.
9. A water impervious composite roofing membrane having an upper
water impervious layer and an inner layer comprising a water
swellable polymer layer.
10. The roofing membrane claimed in claim 9 wherein said water
swellable polymer layer includes a nonwoven web impregnated with a
water swellable polymer.
11. The roofing membrane claimed in claim 10 wherein said water
swellable polymer layer is adhered to a bottom surface of said
waterproof membrane.
12. A built up roof structure having at least one layer of roofing
felt and an outer water impervious coating and further including a
water swellable polymer layer between a roof deck and said water
impervious coat.
13. The built up roof claimed in claim 12 wherein said water
swellable polymer layer comprises water swellable polymer bound to
a nonwoven web.
Description
BACKGROUND OF THE INVENTION
[0001] Single ply membrane roofing utilizes a polymeric sheet as
the exterior surface of a roof structure. The sheets, which can be
7-50 feet in width, are positioned on the roof. In order to cover
the entire roof, multiple sheets are positioned side by side, and
the overlapped edges are adhered together to form a seam. This
forms a continuous membrane, covering the entire roof.
[0002] The membrane can be attached to the roof in a variety of
different ways. Adhesive can be used, as well as ballast, i.e.,
gravel, as well as various types of mechanical fastening systems.
The obvious purpose of the membrane is to prevent water from
entering the building. If the membrane is damaged, and a tear forms
through the membrane, water can leak into the building. Therefore,
such tears must be repaired.
SUMMARY OF THE INVENTION
[0003] The present invention is based on the concept that damage to
a roofing membrane can be repaired in-situ by the incorporation of
a water swellable polymer layer in the membrane structure. The
water swellable polymer, or, super absorbent polymer forms a
hydrogel when in contact with water. If a tear in the membrane
forms, and water enters through the tear, and is absorbed by the
water swellable polymer forming a hydrogel which expands and seals
the tear, preventing water from entering the building.
[0004] The water swellable layer can be formed between two layers
of the membrane sheeting, or, it can be adhered to the bottom
surface of the membrane sheeting, as well as other locations, as
long as it is not exposed to weather absent a tear in the
membrane.
[0005] The objects and advantages of the present invention will be
further appreciated in light of the following detailed description
and drawings in which
DESCRIPTION OF THE INVENTION
[0006] FIG. 1 is a cross sectional view of the present
invention;
[0007] FIG. 2 is a cross sectional view of an alternate embodiment
of the present invention; and
[0008] FIG. 3 is a cross sectional view of a second alternate
embodiment of the present invention.
[0009] FIG. 4 is a cross sectional view of a third alternate
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0010] A self repairing membrane roofing material 10, as shown in
FIG. 1, includes an uppermost layer of a water insoluble polymeric
sheeting 12 and a lower layer 14 which includes a water swellable,
or super absorbent polymer. As shown, layer 14 is adhered to layer
12 by an adhesive layer 16.
[0011] Membrane 12 can be any polymeric membrane typically used on
a membrane roof. Typical membrane roofs are formed from, for
example, ethylene propylene diene monomer rubber (EPDM), polyvinyl
chloride (PVC), thermoplastic olefins (TPO), modified bitumen
membranes, epichlorohydrin, as well as other polymers. Typically,
when such membranes are formed, two plies of polymer are formed and
laminated together to form the membrane 12. This minimizes the
possibility that a membrane will be formed with a perforation. For
purposes of the present invention, the membrane 12 will preferably
be a clean sheet. In other words, the surface 17 of membrane 12
will not include any talc or any other release agent. Thermoplastic
sheeting is normally formed without talc or release agents.
Thermoset sheeting such as EPDM is usually formed with talc. A
method of forming the clean EPDM sheet is disclosed, for example,
in Venable U.S. Pat. No. 5,643,399, the disclosure of which is
hereby incorporated by reference.
[0012] Water swellable polymers are not typically adhesive in
nature. Therefore, the layer 14 may incorporate additional
structure to bind the water swellable polymer. The water swellable
polymer layer can incorporate a thermoplastic adhesive layer to
bind the water swellable polymer particles to the surface of a
thermoset membrane. If the membrane is a thermoplastic, such as PVC
or TPO, water swellable polymer particles can be pressed into the
molten surface of the thermoplastic membrane as it is being
manufactured. Alternately, a layer of a nonwoven web, or other
fabric material, that physically incorporates the water swellable
polymer can be adhesively bonded to the roofing membrane.
[0013] Typically, the water swellable polymers are polyacrylates,
polyacrylamides, polyvinyl alcohols, copolymers of polyacrylate and
polyacrylamide, hydrolyzed starch, poly(acrylonitrile), sodium
carboxymethylcellulose, sodium alginate, copolymers of polyacrylate
and polyvinyl alcohol, copolymers of polyacryamide and polyvinyl
alcohol, and combinations thereof. These are partially cross-linked
so that they are not water soluble, but merely water absorbent,
forming a hydrogel when combined with water.
[0014] The method of forming the water swellable
polymer-impregnated fabrics, as well as the method of forming
adhesive coatings incorporating the water swellable polymers, are
well known and are disclosed, for example, in Anton et al. U.S.
Pat. No. 4,837,077; Fairgrieve U.S. Pat. No. 5,925,461; Fairgrieve
U.S. Pat. No. 6,348,236; Bahlmann et al. U.S. Pat. No. 6,899,776;
and Gruhn et al. U.S. Pat. No. 6,284,267, the disclosures of which
are hereby incorporated by reference.
[0015] According to the preferred embodiment of the present
invention, the layer 14 is a nonwoven web impregnated with the
water swellable polymer. Such a material can be obtained from
Neptco, Inc. This layer is adhered to surface 17 of membrane 12
with, for example, an adhesive layer 16. A polyethylene
thermoplastic adhesive is suitable. If the membrane is a
thermoplastic, a separate adhesive layer may not be required.
[0016] The amount of water swellable polymer loaded onto the
surface will determine the amount of hydrogel formed and, thereby,
determine the size of the tear that can be repaired with the
hydrogel. Generally, the loading of the dry polymer onto the
substrate will be from about 10 to about 50 g/m.sup.2.
[0017] To form a roof, the membrane sheeting 10 is applied over a
roof structure 20, as indicated, with the water swellable polymer
layer 14, adjacent the roof surface 20 protected by water by the
membrane 12. The roof surface may be metal, wood, concrete, or
insulation. The membrane 10 can be attached to the roof structure
20 by a variety of well known application methods, such as ballast,
mechanical fasteners or an adhesive layer 18, as shown in FIG.
1.
[0018] As will be explained below, if the membrane 10 is damaged,
water will pass through layer 12 and be absorbed by the water
swellable polymer in layer 14. The water swellable polymer will
expand, sealing or closing the tear and preventing further water
from passing though the damaged area. Even after drying, the
polymer in layer 14 will maintain its ability to absorb water and
expand, thus providing a long term repair.
[0019] An alternate embodiment of the present invention is shown in
FIG. 2. As shown in FIG. 2, the membrane structure 22 includes
first and second plies or layers 26,28 of a water insoluble
membrane, such as EPDM, with an inner layer 30 of the water
swellable polymer. In this embodiment, the water swellable polymer
is impregnated into a nonwoven web. The nonwoven web is
incorporated into the membrane structure 22 by locating layer 30
between uncured EPDM layers 26 and 28 and compressing these
together. The structure is then heat cured, forming the composite
structure 22. This can be applied to a roof surface by using an
adhesive, ballast or a mechanical fastening system. Layers 26 and
28 can also be thermoplastic plies which are compressed together
when in a partially molten state. Again, if damage forms through
membrane 22, water will be absorbed by the water swellable polymer
in layer 30 and act to seal the hole. This will reduce or eliminate
any water leaking through the tear.
[0020] A third embodiment of the present invention, as shown in
FIG. 3, is a composite 32 which includes a water insoluble barrier
layer such as EPDM 34 adhered by adhesive layer 36 to a layer 38
which includes a water swellable polymer. The exterior surface of
layer 38 is covered with a thin layer of water insoluble polymer
40. This can be, for example, polyethylene, or polypropylene, or
the like. In this embodiment, the layer 34 of water insoluble
polymer, i.e., EPDM, would be attached directly to the roof surface
with the layer 40 exposed to the surface. In this embodiment, the
layer 40 protects the water swellable polymer from water, unless a
tear forms.
[0021] The present invention can also be incorporated into a
built-up roof. As shown in FIG. 4, a built-up roof 50 includes a
roof deck surface 52 covered with a roofing felt layer 54, in turn
covered with a bituminous material or tar layer 56 and an optional
gravel ballast layer 58. Incorporated with the structure in this
embodiment, between the roof deck 52 and the roofing felt 54 is a
layer of a water swellable polymer 60. In this embodiment, the
water swellable polymer layer 60 is preferably a nonwoven web
impregnated with the water swellable polymer, similar to the layer
30 in FIG. 2. The roof structure itself is formed in the same
manner as any built-up roof with the layer 60 applied on the roof
deck or between any layers of the roofing structure, i.e., between
layers of roofing felt. Thus, if any penetration is formed through
the outer surfaces, allowing water to contact the layer 60, the
water swellable polymer will absorb water and seal the
penetration.
[0022] The present invention will be further appreciated in light
of the following detailed example.
EXAMPLE 1
[0023] Samples of various grades of water swellable polymer (WSP)
impregnated on a nonwoven fabric were obtained from Neptco, Inc.
Laboratory samples (about 0.060-0.070 inches) were prepared by
placing the WSP impregnated nonwoven fabric between two pieces of
uncured EPDM rubber, as shown in FIG. 2. Press-cure samples were
obtained after heating at 320.degree. F. for 35 minutes
(2,000-5,000 psi). To simulate a cut in the membrane, a 1-inch gash
was cut through the sample. A 3-inch.times.2-inch cylinder was
positioned over the gash and adhered to the sample with plumbers
putty. The system was tested by dripping 25 ml of water from a
burette over a 1-minute period. After the WSP had swelled, an
additional 150 ml of water was added to the system in the same
manner over a 3-minute period. The amount of water that had passed
through the system was recorded every hour. Using this system,
leakage was slowed by 26.0-93.0%.
EXAMPLE 2
[0024] Samples were prepared by attaching the WSP impregnated
nonwoven fabric to the bottom of a standard 0.045-inch EPDM
membrane using a polyethylene hot melt adhesive (see FIG. 1).
[0025] Samples were damaged by cutting a 1-inch gash through the
entire sample. The test assembly was prepared as previously
described. Samples were tested by dripping 125 ml of water over a
10-minute period. Results were recorded every 15 minutes for one
hour, and then after an additional hour. The results of the
experiment are shown in Table 1.
TABLE-US-00001 TABLE 1 Self Repairing Membrane, WSP nonwoven on
bottom of membrane Time (min) Control 1 2 3 Water through sample
(ml) 15 111 (88.8%) 1 (0.8%) 2 (1.6%) 5 (4%) 30 12 (85%) 0 10 (8%)
9 (7.5%) 45 0 0 17 (15%) 30 (27.5%) 60 0 0 0 0 120 0 0 0 0 Total
123 (98.4%) 1 (0.8%) 29 (23.2%) 39 (31.2%)
[0026] The control leaked about 89% of the water introduced in the
system within the first 15 minutes, and 85% of the remaining water
over the following 15 minutes. In one case, the experimental sample
leaked only 1 ml of water (0.8%) before the system self-repaired.
In the other two cases, self-repairing was somewhat slower, but the
process was completed within 45 minutes. It should be noted that
the samples were not supported, and the water applied did wick
through the WSP material.
[0027] The performance of this system as compared to the system
where the sample was fabricated with the WSP nonwoven between two
cured layers was significantly improved.
EXAMPLE 3
[0028] Samples were prepared by attaching the WSP nonwoven to the
bottom of a membrane as previously described (see FIG. 1). The
membrane and nonwoven composite were adhered to two pieces of
polyisocyanurate insulation with Carlisle Sure-Seal 90-8-30A
Bonding Adhesive. Damage was introduced to the system with two
1/2-inch, 45.degree. cuts into the membrane simulating a tear. In
order to investigate a worst case scenario, the damage was
inflicted over the void space between the two pieces of insulation.
The test assembly was prepared as previously described.
[0029] Water was introduced to the system via a burette at the rate
of 125 ml (volume of about 1.75 in) over a 15-minute period to
simulate a heavy rainstorm. Results were recorded every 15 minutes
for one hour, and then after an additional hour. The results of the
experiment are shown in Table 2.
TABLE-US-00002 TABLE 2 Prototype testing - Simulated Tear Results
Time (min) Control 1 2 3 Water through sample (ml) 15 125 1 5 15 30
-- 0.5 0 16 45 -- 0.5 0 15 60 -- 0.5 0 120 -- 1 0 Total 125 (100%)
2.5 (2%) 5 (4%) 75 (60%)
[0030] As can be seen from the results, two of the three
experimental samples exhibited excellent self-repairing
characteristics. Although leakage was observed in the third sample,
it significantly outperformed the control. (It should be noted that
the third sample was tested immediately after preparation.) In the
case of the first two samples, they were allowed to sit overnight
before testing was commenced. This behavior could be a result of an
interaction between the WSP material and residual solvents from the
bonding adhesive and has been observed with other samples tested
immediately after preparation.
EXAMPLE 4
[0031] In order to examine the reversibility of the system, the
samples were placed in an oven at 100.degree. C. to dry overnight
and retested the next day. The testing procedure was identical to
that described above. The results of the experiment are shown in
Table 3.
TABLE-US-00003 TABLE 3 Prototype Testing - Simulated Tear -
Reversibility demonstration Time (min) Control 1 2 3 Water through
sample (ml) 15 125 0 1 3 30 -- 0 0 0 45 -- 0 0 0.5 60 -- 0 0.5 0
120 -- 0 0 0 Total 125 (100%) 0 (0%) 1.5 (1.2%) 3.5 (2.8%)
[0032] The results demonstrate the reversibility of the system.
Additionally, the self repairing ability of the third sample
improved dramatically. The results suggest that if there is an
interaction between residual solvent from the bonding adhesive and
the WSP material, it does not permanently affect the self repairing
characteristics of the system after the system has completely
dried.
EXAMPLE 5
[0033] In order to test the ability of the system to repair a cut
in the membrane, a 2-inch cut was made to the membrane system. The
test assembly was prepared and tested as previously described. The
results of the simulated cut damage are reported in Table 4.
TABLE-US-00004 TABLE 4 Prototype testing - Simulated cut Time (min)
Control 1 2 3 Water through sample (ml) 15 125 0 3 0 30 -- 0 0.5
0.5 45 -- 0 0 0 60 -- 0 0.5 0 120 -- 0 0 0 Total 125 (100%) 0 (0%)
3.5 (1.2%) .5 (0.4%)
[0034] As the results indicate, the system is capable of
self-repair when subjected to damage of this type. The
reversibility of the system was also investigated. The samples were
dried as before, and tested the next day. The results are shown in
Table 5.
TABLE-US-00005 TABLE 5 Prototype Testing - Simulated Cut -
Reversibility demonstration Time (min) Control 1 2 3 Water through
sample (ml) 15 125 8 0 0 30 -- 3 0 0 45 -- 0.5 0 0 60 -- 2 0 0 120
-- 0.5 0 0 Total 125 (100%) 14 (11.2%) 0 (0%) 0 (0%)
[0035] One experimental sample exhibited minor leakage. Initial
leakage within the first few minutes is expected when the rate of
water flowing into the system is greater than the rate of the WSP
particles absorbing water and swelling to fill and repair the
membrane damage. As can be seen from the results, the volume of
water through the system decreased over time. The other two samples
were observed to completely self-repair.
EXAMPLE 6
[0036] In order to determine the effects of heat aging on the
ability to self-repair, samples were prepared and attached to
insulation as previously described. The samples were aged for 14
days at 70.degree. C. After 14 days the samples were damaged using
the simulated tear technique, and then tested. After testing, the
samples were returned to the 70.degree. C. oven and tested weekly.
The results of this study are summarized in Table 6 and Table
6A.
TABLE-US-00006 TABLE 6 Prototype Testing - Aging Studies -
Simulated tear Time (min) Control 1 2 3 Water through sample (ml)
15 125 0 1 3 30 -- 0 0 0 45 -- 0 0 0.5 60 -- 0 0.5 0 120 -- 0 0 0
Total 125 (100%) 0 (0%) 1.5 (1.2%) 3.5 (2.8%)
TABLE-US-00007 TABLE 6A Prototype Testing - Simulated Tear - Aging
Studies Control Time 2-5 weeks 2 weeks 3 weeks 4 weeks 5 weeks 6
weeks (min) aging aging aging aging aging aging Water through
sample (ml) 15 125 0 0 0 0 0 30 -- 0 0 0 0 0 45 -- 0 0 0 0 0 60 --
0 0 0 0 0 120 -- 0 0 0 0 0 Total 125 (100%) 0 (0%) 0 (0%) 0 (0%) 0
(0%) 0 (0%)
[0037] The results clearly indicate that heat aging at modest
temperatures does not impact the ability of the system to
self-repair (attempts to age the samples at higher temperatures
resulted in a degradation of the polyisocyanurate insulation and
bonding adhesive). Additionally, the results also demonstrate the
reversibility of the system. In this case, five cycles of
swelling/drying/swelling were demonstrated.
EXAMPLE 7
[0038] Aging studies were also performed on samples with a
simulated cut. Samples were aged, assembled and tested as described
above. The results of this study are shown in Table 7. As with the
simulated tear aging tests, the results indicate that aging has no
effect on the ability of the system to self-repair and regenerate
after drying.
TABLE-US-00008 TABLE 7 Prototype Testing - Aging Studies -
Simulated cut Control Time 2-6 weeks 2 weeks 3 weeks 4 weeks 5
weeks 6 weeks (min) aging aging aging aging aging aging Water
through sample (ml) 15 125 0 0 0 0 0 30 -- 0 0 0 0 0 45 -- 0 0 0 0
0 60 -- 0 0 0 0 0 120 -- 0 0 0 0 0 Total 125 (100%) 0 (0%) 0 (0%) 0
(0%) 0 (0%) 0 (0%)
EXAMPLE 8
[0039] To study the effect of ponding water on the system, an
experimental sample was prepared with a simulated tear as described
above. Water (about 150 ml, 2 inches volume) was introduced into
the system, and the membrane was allowed to self-repair. The test
was checked daily for any signs of leakage. Water was periodically
added to the system in order to replace that lost to evaporation.
The system held 2 inches of water without leakage for a period of
three weeks. Theoretically, the sample should only leak when the
hydrostatic pressure of the water above the damage is sufficient
enough to force the WSP particles from the damaged area.
Preliminary results indicate the simulated cut system can hold in
excess of 12 inches of water without leaking.
EXAMPLE 9
[0040] Ruptures in roofing material can occur during the
installation of heavy equipment on a rooftop. In order to
investigate the ability of the system to repair damage of this
type, a membrane rupture was simulated by the use of a dynamic
puncture device as described in ASTM D 5635. A 3,000 g weight was
used to create an impact energy of 15 J. The test assembly was
prepared as previously described. The samples were aged for 14 days
at 70.degree. C. before being subjected to damage. The samples were
tested as previously described. The amount of water that leaked
through the system was recorded after two hours. The samples were
dried at 70.degree. C. overnight and retested. This cycle was
repeated for 12 testing periods in order to demonstrate the
reversibility of the system. The results of the simulated rupture
are reported in Table 8.
TABLE-US-00009 TABLE 8 Cycle Control Sample 1 Sample 2 Sample 3
Water through sample (ml) Original 79 2 3 2 2 125 5 2 4 3 87 39 3 3
4 125 86 3 3 5 102 10 3 4 6 102 2 3 4 7 125 3 4 3 8 125 3 3 2 9 125
1 2 4 10 125 3 3 3 11 125 6 2 4 12 125 3 2 3
[0041] As shown in the above examples, the present invention
provides a self repairing roofing membrane that provides long term
repairs of minor tears in a membrane structure. This will
substantially reduce the risk of water damage caused by such tears
and reduce and/or eliminate the need for repair of the tear.
Further, many of the tears should be visible. This will allow for a
secondary repair or patch over the tear.
[0042] This has been a description of the present invention along
with the preferred method of practicing the invention. However, the
invention itself should only be defined by the appended claims,
wherein we claim:
* * * * *