U.S. patent application number 14/277428 was filed with the patent office on 2014-09-04 for membrane with surface structure.
This patent application is currently assigned to SIKA TECHNOLOGY AG. The applicant listed for this patent is SIKA TECHNOLOGY AG. Invention is credited to Peter HUBSCHER, Jean-Claude RUDOLF.
Application Number | 20140248466 14/277428 |
Document ID | / |
Family ID | 47216245 |
Filed Date | 2014-09-04 |
United States Patent
Application |
20140248466 |
Kind Code |
A1 |
RUDOLF; Jean-Claude ; et
al. |
September 4, 2014 |
MEMBRANE WITH SURFACE STRUCTURE
Abstract
A waterproof membrane, a method for sealing substructures, and a
system for reflecting sunlight are disclosed. The waterproof member
can include a barrier layer, which contains a thermoplastic
material, and wherein an upper face of the barrier layer has an
arithmetic mean roughness value R.sub.a in accordance with DIN EN
ISO 4287: 1998-10 of about 0.01-0.8 .mu.m.
Inventors: |
RUDOLF; Jean-Claude; (Horw,
CH) ; HUBSCHER; Peter; (Obernau, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SIKA TECHNOLOGY AG |
Baar |
|
CH |
|
|
Assignee: |
SIKA TECHNOLOGY AG
Baar
CH
|
Family ID: |
47216245 |
Appl. No.: |
14/277428 |
Filed: |
May 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2012/072625 |
Nov 14, 2012 |
|
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14277428 |
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Current U.S.
Class: |
428/141 ;
156/60 |
Current CPC
Class: |
B32B 27/32 20130101;
E04D 5/08 20130101; B32B 2307/4026 20130101; B32B 2307/746
20130101; B32B 2307/7265 20130101; E04D 5/10 20130101; Y10T 156/10
20150115; B32B 2264/102 20130101; Y02E 10/52 20130101; H01L 31/0547
20141201; B32B 2419/06 20130101; Y02B 10/10 20130101; B32B 27/304
20130101; E04B 1/665 20130101; B32B 2307/538 20130101; B32B
2307/712 20130101; B32B 2307/416 20130101; Y10T 428/24355 20150115;
E04D 5/12 20130101; E04D 5/06 20130101; B32B 27/12 20130101; B32B
3/30 20130101; B32B 2307/754 20130101; B32B 2250/02 20130101; B32B
27/20 20130101; B32B 2307/718 20130101 |
Class at
Publication: |
428/141 ;
156/60 |
International
Class: |
E04D 5/12 20060101
E04D005/12; E04D 5/08 20060101 E04D005/08; E04B 1/66 20060101
E04B001/66; E04D 5/06 20060101 E04D005/06; E04D 5/10 20060101
E04D005/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2011 |
EP |
11189212.1 |
Claims
1. A waterproof membrane comprising: a barrier layer, wherein the
barrier layer includes a thermoplastic material; and wherein an
upper face of the barrier layer has an arithmetic mean roughness
value R.sub.a in accordance with DIN EN ISO 4287: 1998-10 of about
0.01-0.8 .mu.m.
2. The waterproof membrane according to claim 1, wherein the
thermoplastic material is thermoplastic polyolefins or polyvinyl
chloride (PVC).
3. The waterproof membrane according to claim 1, wherein the
barrier layer has the arithmetic mean roughness value R.sub.a in
accordance with DIN EN ISO 4287: 1998-10 of the barrier layer of
about 0.025-0.5 .mu.m.
4. The waterproof membrane according to claim 1, wherein the upper
face of the barrier layer comprises: an embossed pattern.
5. The waterproof membrane according to claim 1, wherein a color of
the upper face of the barrier layer is such that proportions of
cyan, magenta, yellow and black on the upper face of the barrier do
not exceed about 5% in a CMYK color model.
6. The waterproof membrane according to claim 1, comprising:
pigments in the barrier layer, and wherein a ratio of the pigments
to a total weight of the barrier layer is about 1-40 wt/%.
7. The waterproof membrane according to claim 6, wherein the ratio
of the pigments to the total weight of the barrier layer is about
10-30 wt/%.
8. The waterproof membrane according to claim 6, wherein the
pigments are selected from the group consisting of: barium sulfate,
zinc oxide, magnesium oxide, zirconium oxide and titanium
oxide,
9. The waterproof membrane according to claim 1, wherein a
thickness of the membrane is about 20-100% of a thickness of the
barrier layer.
10. The waterproof membrane according to claim 9, wherein the
thickness of the barrier layer is about 0.1-5 mm.
11. The waterproof membrane according to claim 9, wherein the
thickness of the membrane is about 0.1 to 5 mm.
12. The waterproof membrane according to claim 1, wherein the
membrane comprises: a fibrous material.
13. The waterproof membrane according to claim 12, wherein the
fibrous material comprises: a woven fabric, a non-crimp fabric, or
a non-woven fabric.
14. A method for sealing substructures, the method comprising:
applying a waterproof membrane to a substructure, the waterproof
membrane having a barrier layer, wherein the barrier layer includes
a thermoplastic material, and wherein an upper face of the barrier
layer has an arithmetic mean roughness value R.sub.a in accordance
with DIN EN ISO 4287: 1998-10 of about 0.01-0.8 .mu.m; and
directing the upper face of the waterproof membrane away from the
substructure.
15. The method according to claim 14, wherein the substructure is a
roof of a building.
16. A system for reflecting sunlight, the system comprising: a
structure; and a waterproof membrane applied to the structure, the
waterproof membrane having a barrier layer, wherein the barrier
layer includes a thermoplastic material; and wherein an upper face
of the barrier layer has an arithmetic mean roughness value R.sub.a
in accordance with DIN EN ISO 4287: 1998-10 of about 0.01-0.8
.mu.m.
17. The system according to claim 16, wherein the upper face of the
waterproof membrane is directed away from the structure.
18. The system according to claim 16, wherein the thermoplastic
material is thermoplastic polyolefins or polyvinyl chloride
(PVC).
19. The system according to claim 16, wherein the barrier layer has
the arithmetic mean roughness value R.sub.a in accordance with DIN
EN ISO 4287: 1998-10 of the barrier layer is about 0.025-0.5
.mu.m.
20. The system according to claim 16, wherein the upper face of the
barrier layer comprises: an embossed pattern.
Description
RELATED APPLICATION(S)
[0001] This application claims priority as a continuation
application under 35 U.S.C. .sctn.120 to PCT/EP2012/072625, which
was filed as an International Application on Nov. 14, 2012,
designating the U.S., and claiming priority to European Application
No. 11189212.1 filed in Europe on Nov. 15, 2011. The entire
contents of these applications are hereby incorporated herein by
reference in their entireties.
FIELD
[0002] The disclosure relates to a membrane, for example, a
waterproof membrane, and methods for sealing substructures and
increasing the energy output of bifacial or multifacial
photovoltaic elements.
BACKGROUND INFORMATION
[0003] It is known, for example, for (flat) roofs, to use membranes
that can reflect sunlight in order to help prevent buildings from
becoming overheated. As a result of the reflectivity of these
roofing materials, the absorption of solar radiation and the
conversion thereof to heat can be reduced. In recent years,
photovoltaic systems, so-called bifacial or multifacial
photovoltaic elements, have become available, in which an active
cell can also be located on the reverse side, which can allow the
electromagnetic radiation that is reflected from the roof to also
be converted to electrical energy.
[0004] It is known that (flat) roofs can become soiled over their
service life. This soiling can occur as the roof is being laid, for
example, or can be caused over the service life of the roof by
particles such as soot, humus, sand and leaves.
[0005] Such soiling not only results in unsightly surfaces, for
example, in the case of white or colored surfaces, but can also
diminish the reflective capacity of these roofing materials.
SUMMARY
[0006] A waterproof membrane is disclosed comprising: a barrier
layer, wherein the barrier layer includes a thermoplastic material;
and wherein an upper face of the barrier layer has an arithmetic
mean roughness value R.sub.a in accordance with DIN EN ISO 4287:
1998-10 of about 0.01-0.8 .mu.m.
[0007] A method for sealing substructures is disclosed, the method
comprising: applying a waterproof membrane to a substructure, the
waterproof membrane having a barrier layer, wherein the barrier
layer includes a thermoplastic material, and wherein an upper face
of the barrier layer has an arithmetic mean roughness value R.sub.a
in accordance with DIN EN ISO 4287: 1998-10 of about 0.01-0.8
.mu.m; and directing the upper face of the waterproof membrane away
from the substructure.
[0008] A system for reflecting sunlight is disclosed, the system
comprising: a structure; and a waterproof membrane applied to the
structure, the waterproof membrane having a barrier layer, wherein
the barrier layer includes a thermoplastic material; and wherein an
upper face of the barrier layer has an arithmetic mean roughness
value R.sub.a in accordance with DIN EN ISO 4287: 1998-10 of about
0.01-0.8 .mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The disclosure will now be further explained by way of an
exemplary embodiment and with reference to the accompanying
drawings, in which:
[0010] FIG. 1 shows a cross-section of an exemplary membrane
according to the disclosure;
[0011] FIG. 2 shows a cross-section of an exemplary membrane
according to the disclosure;
[0012] FIG. 3 shows a cross-section of an exemplary membrane
according to the disclosure;
[0013] FIG. 4 shows a bifacial or multifacial photovoltaic element
situated on an exemplary membrane according to the disclosure;
[0014] FIG. 5 shows measurements of unrolling forces after storage
at various temperatures; and
[0015] FIG. 6 shows measurements of reflection in a soiling
experiment according to an exemplary embodiment.
DETAILED DESCRIPTION
[0016] The disclosure relates to a waterproof membrane having a
barrier layer, with the barrier layer including a thermoplastic
material. In accordance with an exemplary embodiment, the barrier
layer can have an arithmetic mean roughness value R.sub.a of
0.01-0.8 .mu.m in accordance with DIN EN ISO 4287: 1998-10.
[0017] In accordance with an exemplary embodiment, membranes of
this type offer can have a diminished susceptibility to soiling and
are easier to clean. Moreover, the force to unroll such membranes
when they are in the rolled-up state can also be reduced, for
example, after the membranes have been stored at temperatures above
60.degree. C.
[0018] In accordance with an exemplary embodiment, the present
disclosure relates to a waterproof membrane 1, which can include a
barrier layer 2, wherein the barrier layer contains a thermoplastic
material, for example, thermoplastic polyolefins or polyvinyl
chloride (PVC), for example, polypropylene (PP) or polyethylene
(PE). The upper face 3 of the barrier layer 2 can have an
arithmetic mean roughness value R.sub.a of 0.01-0.8 .mu.m, for
example, 0.025-0.5 .mu.m, for example, 0.05-0.2 .mu.m, in
accordance with DIN EN ISO 4287: 1998-10.
[0019] FIG. 1 shows an exemplary membrane 1 in accordance with the
disclosure. In accordance with an exemplary embodiment, the term
"membrane" can include flexible, flat plastics having a thickness
of 0.1 to 5 mm, for example, of 0.5 to 4 mm, which can be rolled
up. In addition to films, which can have a thickness of less than 1
mm, membranes can also include sealing webs, such as are used for
sealing roofs or terraces, for example, in thicknesses of 1 to 3
mm, and in some cases having a thicknesses of as much as 5 mm. In
accordance with an exemplary embodiment, membranes of this type can
be produced by coating, pouring, calendering or extrusion, and can
be commercially available in the form of rolls, or are produced on
site. The membranes can be single-layered or multilayered in
structure. In addition, the membranes as disclosed herein, can also
contain other accessory agents and processing agents, such as
filler materials, UV stabilizers and heat stabilizers, softeners,
release agents, biocides, fire retardants and antioxidants. For
example, in accordance with an exemplary embodiment, membrane 1
according to the disclosure can be a roofing membrane.
[0020] The membrane can have a thickness of 0.1 to 5 mm, for
example, 0.5 to 4 mm, and for example, 1 to 3 mm.
[0021] The upper face 3 of the barrier layer 2 can have an
arithmetic mean roughness value (arithmetic mean of profile
ordinates) R.sub.a of 0.01-0.8 .mu.m, for example, 0.025-0.5 .mu.m,
in accordance with DIN EN ISO 4287: 1998-10. In accordance with an
exemplary embodiment, the arithmetic mean roughness value R.sub.a
in accordance with DIN EN ISO 4287: 1998-10 can be 0.05-0.2
.mu.m.
[0022] An arithmetic mean roughness value R.sub.a in accordance
with DIN EN ISO 4287: 1998-10 of 0.01-0.8 .mu.m can decrease
susceptibility to soiling. In addition, such surfaces can be easier
to clean.
[0023] The force that is used to unroll such membranes when they
are in the rolled-up state can be decreased in relation to
membranes that have an arithmetic mean roughness value R.sub.a in
accordance with DIN EN ISO 4287: 1998-10 of more than 0.8 .mu.m,
for example, of more than 3 .mu.m, for example, after such
membranes have been stored at temperatures above 60.degree. C.
[0024] In accordance with an exemplary embodiment, the total
surface area of the upper face 3 has an arithmetic mean roughness
value R.sub.a in accordance with DIN EN ISO 4287: 1998-10 of for
example, .gtoreq.50%, for example, .gtoreq.80%, and for example,
.gtoreq.98%.
[0025] The upper face 3 of the barrier layer 2 can have an embossed
pattern 4, which can result in the abovementioned arithmetic mean
roughness value R.sub.a in accordance with DIN EN ISO 4287:
1998-10.
[0026] The embossed pattern 4 can be a uniform embossed
pattern.
[0027] In accordance with an exemplary embodiment, the color of the
upper face 3 of the barrier layer 2 can be such that the relevant
proportions of cyan, magenta, yellow and black on the upper face 3
of the barrier layer 2 do not exceed 5% in the CMYK color model.
For example, the color can be white. In accordance with an
exemplary embodiment, for example, the entire upper face 3 can be
white.
[0028] For example, if the upper face is bright, for example, in
the case of a color for which the respective percentages of cyan,
magenta, yellow and black do not exceed 5% in the CMYK color model,
a low susceptibility to soiling can be obtained because the soiling
of bright surfaces can be perceived as objectionable and/or the
reflective capacity of electromagnetic radiation, for example, of
sunlight, can be reduced.
[0029] The barrier layer 2 can contain pigments 5, with the
proportion of the pigments being 1-40 wt/%, for example, 10-30
wt/%, referred to the total weight of the barrier layer.
[0030] The pigments 5 can have an SRI (Solar Reflectance Index
according to ASTM E 1980) of .gtoreq.70, for example,
.gtoreq.78.
[0031] The pigments 5 can be selected from the group including of
barium sulfate, zinc oxide, magnesium oxide, zirconium oxide and
titanium oxide, for example, titanium oxide.
[0032] In accordance with an exemplary embodiment, the presence of
pigments 5 in the barrier layer 2 can cause electromagnetic solar
radiation to be reflected by the membrane 1, which can increase the
energy output of bifacial or multifacial photovoltaic elements, for
example, and/or decreasing the amount of thermal energy that is
absorbed by buildings. The presences of pigments can also
decreasing the susceptibility to soiling.
[0033] The waterproof membrane 1 can include a barrier layer 2. The
barrier layer 2 can be made of materials that can provide water
tightness at high fluid pressures.
[0034] In accordance with an exemplary embodiment, the barrier
layer 2 can be highly resistant to water pressure and weather, and
can achieve high scores in tear propagation tests and perforation
tests, which can be desirable with respect to mechanical loads that
are exerted on building sites. A resistance to sustained mechanical
loads, for example wind, can also be desirable. The material of the
barrier layer can be a flexible material.
[0035] The barrier layer can contain a thermoplastic material, for
example, thermoplastic polyolefins or polyvinyl chloride (PVC), for
example, polypropylene (PP) or polyethylene (PE), which can result
in a high resistance to environmental factors.
[0036] The barrier layer 2 can be selected from materials from the
group consisting of high-density polyethylene (HDPE),
medium-density polyethylene (MDPE), low-density polyethylene
(LDPE), polyethylene (PE), polyvinyl chloride (PVC), ethylene/vinyl
acetate copolymer (EVA), chlorosulfonated polyethylene,
olefin-based thermoplastic elastomers (TPE-O, TPO) and
polyisobutylene (PIB), and mixtures thereof.
[0037] The barrier layer 2 can consist of 50 to 100 wt/%, for
example, 80 to 90 wt/%, one of the abovementioned materials,
referred to the total weight of the barrier layer.
[0038] The barrier layer 2 can have a thickness of 0.1-5 mm, for
example, 0.5-2.5 mm, for example, 1-2 mm.
[0039] In accordance with an exemplary embodiment, the thickness of
membrane 1 can comprise 20% to 100% of the thickness of the barrier
layer 2.
[0040] The membrane 1 can contain a fibrous material 6, for
example, a woven fabric, a non-crimp fabric or a non-woven fabric.
The fibrous material can be attached to the barrier layer, as shown
in FIG. 2, for example, or can be integrated into the barrier
layer, as shown in FIG. 3. In accordance with an exemplary
embodiment, a fibrous material 6, for example, a woven fabric, a
non-crimp fabric or a non-woven fabric, can be incorporated into
the barrier layer 2.
[0041] In accordance with an exemplary embodiment, the fibrous
material 6 can be a material that is composed of fibers. The fibers
can include or consist of organic, inorganic or synthetic material.
For example, the fibers can be cellulose fibers, cotton fibers,
protein fibers, glass fibers or synthetic fibers. Synthetic fibers
can be fibers made of polyester or of a homopolymer or copolymer of
ethylene and/or propylene or of viscose. These fibers can be short
fibers or long fibers, spun, woven or non-woven fibers or
filaments. Furthermore, the fibers can be directed or stretched
fibers.
[0042] In accordance with an exemplary embodiment, the body
constructed from the fibers can be produced using a very wide range
of methods known to a person skilled in the art. For example, the
bodies that include a woven fabric, a non-crimp fabric or a knitted
fabric can be used.
[0043] In accordance with an exemplary embodiment, a fibrous
material can be a woven fabric, a non-crimp fabric or a non-woven
fabric. In accordance with an exemplary embodiment, the fibrous
materials can have a mesh count (or mesh number), for example, of
5-40 per 10 cm.
[0044] In accordance with an exemplary embodiment, the fibrous
material 6 can be capable of protecting the barrier layer 2 against
mechanical loads. For example, during the installation and mounting
of waterproof membrane 1, heavy mechanical loads can occur, for
example, from installers walking on the waterproof membrane. In
accordance with an exemplary embodiment, the fibrous material 6 can
have a certain base weight, and therefore a certain pressure
resistance to mechanical loads. For example, suitable are fibrous
materials, for example, woven fabrics, non-crimp fabrics or
non-woven fabrics, which can have a base weight of 30-200, for
example, of 50-150 g/m.sup.2.
[0045] In accordance with an exemplary embodiment, the fibrous
material 6 can consist of a thermoplastic material, and the
material can be selected from the group including high-density
polyethylene (HDPE), polyethylene terephthalate (PET), polystyrene
(PS), polypropylene (PP), polyvinyl chloride (PVC), polyamide (PA)
and combinations thereof.
[0046] In accordance with an exemplary embodiment, the fibrous
material 6 can consist of an inorganic material, for example,
glass.
[0047] In accordance with an exemplary embodiment, the disclosure
relates to the use of a waterproof membrane 1 as disclosed herein
for increasing the amount of sunlight that can be reflected off of
buildings, for example, roofs of buildings.
[0048] In accordance with an exemplary embodiment, the disclosure
relates to the use of a waterproof membrane 1 as disclosed herein
for increasing the energy output of bifacial or multifacial
photovoltaic elements 8.
[0049] The energy output of bifacial or multifacial photovoltaic
elements 8 can be increased by using the membrane according to the
disclosure, as a result of which the percentage of electromagnetic
radiation coming from the membrane and striking the photovoltaic
element, referred to the total amount of electromagnetic radiation
that strikes the membrane, can be higher than with membranes of the
known art. The source of the electromagnetic radiation that strikes
the membrane can be the sun. The electromagnetic radiation coming
from the membrane according to the disclosure can include reflected
electromagnetic radiation.
[0050] In accordance with an exemplary embodiment, the disclosure
relates to a structure, for example, a building structure, for
example, a building or a sports arena, including a waterproof
membrane 1 as described above. For example, the membrane 1 can be
mounted on the roof of the structure. In accordance with an
exemplary embodiment, bifacial or multifacial photovoltaic elements
8 can be located on the membrane.
[0051] In an accordance with an exemplary embodiment, the
disclosure relates to a method for sealing substructures 7,
including the following steps: i) applying a waterproof membrane,
such as the membrane disclosed herein, to a substructure 7, with
the upper face 3 of the waterproof membrane 1 being directed away
from the substructure 7.
[0052] The method can also include the step of: ii) of mounting at
least one bifacial or multifacial photovoltaic element 8 on the
upper face 3 of the waterproof membrane 1.
[0053] The membrane can be arranged at a distance of 20-200 cm from
at least one bifacial or multifacial photovoltaic element 8 on a
substructure 7, on which the at least one bifacial or multifacial
photovoltaic element can also be mounted.
[0054] The substructure 7 can be a structure such as a building or
a sports arena. The substructure 7 can be, for example, a part, for
example, the roof, of a structure, for example, a building.
[0055] The membrane 1 can be produced by any method. For example,
the membranes can be produced using commercial machinery. The
membranes can be produced in a single process step as a continuous
product, for example, by extrusion and/or calendering and/or
laminating and/or bonding, and can be rolled up onto reels, for
example. The stock temperature in the extruder or the calender can
range from 120.degree. C.-250.degree. C., for example 130.degree.
C.-220.degree. C., for example 180.degree. C.-220.degree. C., for
example, during extrusion and/or calendering and/or laminating
and/or bonding.
[0056] In accordance with an exemplary embodiment, to help ensure
that the upper face of the barrier layer will have an arithmetic
mean roughness value R.sub.a in accordance with DIN EN ISO 4287:
1998-10 of 0.01-0.8 .mu.m, for example, of 0.025-0.5 .mu.m, an
embossing roller can be used, for example.
[0057] In an accordance with an exemplary embodiment, the
disclosure relates to the use of an arithmetic mean roughness value
R.sub.a in accordance with DIN EN ISO 4287: 1998-10 of 0.01-0.8
.mu.m, for example, of 0.025-0.5 .mu.m, on the upper face 3 of a
barrier layer 2 of a waterproof membrane 1, wherein the barrier
layer contains a thermoplastic material, for example, thermoplastic
polyolefins or polyvinyl chloride (PVC), for the purpose of
reducing the force to unroll the waterproof membrane 1 after heated
storage, at storage temperatures above 60.degree. C., for example,
.gtoreq.70.degree. C.
[0058] In accordance with an exemplary embodiment, the barrier
layer and the waterproof membrane as disclosed herein can have the
arithmetic mean roughness value R.sub.a, for example, involves an
embossed pattern 4, for example, a uniform embossed pattern. For
example, .gtoreq.50%, for example .gtoreq.80%, for example,
.gtoreq.98% of the total area of the upper face 3 can have an
arithmetic mean roughness value R.sub.a in accordance with DIN EN
ISO 4287: 1998-10 as described above.
[0059] The level of unrolling force (take-off tension) can be
measured using a tension gauge, in which rolls of the waterproof
membranes can be unrolled by means of a take-off device via the
tension gauge, and the level of take-off tension can be determined.
Heated storage, at storage temperatures above 60.degree. C., for
example, .gtoreq.70.degree. C., for example at 70.degree. C. or
80.degree. C., can be carried out in a cabinet dryer for a period
of 24 hours, followed by storage at 23.degree. C. for a period of
24 hours.
[0060] In accordance with an exemplary embodiment, the membrane 1
according to the disclosure can be embodied as a sealing membrane
web, which can consist of a barrier layer 2 made of thermoplastic
polyolefins. For example, the thickness of the barrier layer can be
about 2 mm. The upper face of the barrier layer has can have an
arithmetic mean roughness value R.sub.a in accordance with DIN EN
ISO 4287: 1998-10 of, for example, 0.1 .mu.m.
[0061] In accordance with an exemplary embodiment, the
susceptibility to soiling and the force to unwind a roll of a
membrane (E) according to the disclosure, with a barrier layer
upper face that has an arithmetic mean roughness value R.sub.a in
accordance with DIN EN ISO 4287: 1998-10 of 0.1 .mu.m, has been
compared with the susceptibility to soiling and the force to unwind
a roll of a membrane (V) not according to the disclosure, with a
barrier layer upper face that has an arithmetic mean roughness
value R.sub.a in accordance with DIN EN ISO 4287: 1998-10 of 3
.mu.m. Both membranes had a thickness of 2 mm, and the barrier
layers were made of thermoplastic olefins.
[0062] The reflectance properties of the two membranes E and V were
measured (before experiment) using a Solyndra Albedometer Model H
500, after which the two membranes E and V were walked upon with
street shoes for a period of 45 days, and the reflectance
properties were measured once again (uncleaned after experiment).
Afterward, the two membranes E and V were cleaned using simple
cleansing materials (wet sponge with a small amount of commercial
cleaning agent), and the reflectance properties were measured again
(cleaned after experiment). As is shown in FIG. 6, the membrane (E)
according to the disclosure having a barrier layer that has an
arithmetic mean roughness value R.sub.a in accordance with DIN EN
ISO 4287: 1998-10 of 0.1 .mu.m is less heavily soiled and can be
cleaned more easily than the membrane (V) not according to the
disclosure, which has an arithmetic mean roughness value R.sub.a in
accordance with DIN EN ISO 4287: 1998-10 of 3 .mu.m.
[0063] Rolls of the two membranes E and V, measuring 15 m in length
and 25 cm in width, were stored in a cabinet drier at 60.degree.
C., 70.degree. C. or 80.degree. C. for a period of 24 hours, after
which the two membranes were stored at 23.degree. C. for a period
of 24 hours. These rolls were then unrolled by means of a take-off
device equipped with a tension gauge, and the level of force for
unrolling (take-off tension) was measured. The rolls were stored in
the cabinet drier at different temperatures in order to ascertain
the behavior of the membranes under different storage/transport
conditions. As is shown in FIG. 5, the membranes E according to the
disclosure unexpectedly exhibit substantially lower levels of
unrolling force, for example, when stored at temperatures above
60.degree. C.
[0064] Thus, it will be appreciated by those skilled in the art
that the present invention can be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The presently disclosed embodiments are therefore
considered in all respects to be illustrative and not restricted.
The scope of the invention is indicated by the appended claims
rather than the foregoing description and all changes that come
within the meaning and range and equivalence thereof are intended
to be embraced therein.
LIST OF REFERENCE SIGNS
[0065] 1 Waterproof membrane [0066] 2 Barrier layer [0067] 3 Upper
face of the barrier layer [0068] 4 Embossed pattern [0069] 5
Pigments [0070] 6 Fibrous material [0071] 7 Substructure [0072] 8
Bifacial or multifacial photovoltaic element
* * * * *