U.S. patent application number 15/630192 was filed with the patent office on 2017-10-05 for profiled protective tape for rotor blades of wind turbine generators.
This patent application is currently assigned to 3M INNOVATIVE PROPERTIES COMPANY. The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to CHRISTIAN CLAUS, JAN D. FORSTER, BERND KUEHNEWEG, STEFFEN TRASER.
Application Number | 20170283659 15/630192 |
Document ID | / |
Family ID | 46614641 |
Filed Date | 2017-10-05 |
United States Patent
Application |
20170283659 |
Kind Code |
A1 |
TRASER; STEFFEN ; et
al. |
October 5, 2017 |
PROFILED PROTECTIVE TAPE FOR ROTOR BLADES OF WIND TURBINE
GENERATORS
Abstract
A multilayer protective tape (1) for rotor blades of wind energy
turbines said tape (1) having a protective top layer (2) comprising
a polymer film and an adhesive bottom layer (3), wherein the top
layer (2) has a continuous surface (S) that is outwardly curved or
outwardly trapezoidal surface such that the tape (1) has a
cross-sectional profile having an inner section between two lateral
sections and wherein the inner section has a thickness (T1) made up
by the thickness of the top layer (2) and adhesive bottom layer (3)
that is greater than the thickness of at least one of the lateral
sections (T1,T2) made up by the thickness of the top layer (2) and
adhesive bottom layer (3) and wherein the thickness (T1 or T2) of
at least one lateral section is at most 600 .mu.m and the thickness
of the inner section (T1) is at least 330 .mu.m. Also provided are
processes for making profiled tapes and methods for applying the
tapes to rotor blades and blades containing protective tapes.
Inventors: |
TRASER; STEFFEN; (DARMSTADT,
DE) ; KUEHNEWEG; BERND; (DUESSELDORF, DE) ;
CLAUS; CHRISTIAN; (DUESSELDORF, DE) ; FORSTER; JAN
D.; (AACHEN, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
SAINT PAUL |
MN |
US |
|
|
Assignee: |
3M INNOVATIVE PROPERTIES
COMPANY
SAINT PAUL
MN
|
Family ID: |
46614641 |
Appl. No.: |
15/630192 |
Filed: |
June 22, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14235542 |
Jan 29, 2014 |
9718992 |
|
|
PCT/US2012/048219 |
Jul 26, 2012 |
|
|
|
15630192 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09J 7/385 20180101;
Y02E 10/72 20130101; Y10T 428/24496 20150115; Y10T 428/24612
20150115; B32B 37/24 20130101; C09J 5/08 20130101; F03D 1/0675
20130101; Y10T 156/10 20150115; Y10T 428/24521 20150115; C09J
2301/208 20200801; C09J 7/20 20180101; C09J 2475/006 20130101; C09J
2301/204 20200801 |
International
Class: |
C09J 5/08 20060101
C09J005/08; B32B 37/24 20060101 B32B037/24; F03D 1/06 20060101
F03D001/06; C09J 7/02 20060101 C09J007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2011 |
EP |
11176051 |
Claims
1. A multilayer protective tape (1) for rotor blades of wind energy
turbines said tape (1) having a protective top layer (2) comprising
a polymer film and an adhesive bottom layer (3), wherein the top
layer (2) has a continuous surface (S) that is outwardly curved or
outwardly trapezoidal such that the tape (1) has a cross-sectional
profile having an inner section between two lateral sections and
wherein the inner section has a thickness (T1) made up by the
thickness of the top layer (2) and adhesive bottom layer (3) that
is greater than the thickness of at least one of the lateral
sections (T1,T2) made up by the thickness of the top layer (2) and
adhesive bottom layer (3) and wherein the thickness (T1 or T2) of
at least one lateral section is at most 600 .mu.m and the thickness
of the inner section (T1) is at least 330 .mu.m.
2. The tape (1) according to claim 1 wherein the inner section
comprises up to 95% of the width of the tape.
3. The tape (1) according to claim 1, wherein the cross-sectional
profile of the tape is symmetric or non symmetric.
4. The tape (1) according to claim 1, wherein the adhesive bottom
layer (3) has an upper surface facing the top layer (2) and a
bottom surface opposite thereto and wherein the bottom surface is
patterned to comprise a plurality of grooves or dots.
5. The tape (1) according to claim 1, wherein the adhesive bottom
layer (3) comprises across its thickness at least two adhesive
layers of which one adhesive layer comprises a foam adhesive.
6. The tape (1) according to claim 1, wherein the adhesive layer
(3) is prepared by a wet-in-wet coating process.
7. The tape (1) according to claim 1, wherein the top layer (2) is
of uniform thickness.
8. The tape (1) according to claim 1, wherein the top layer (2) is
outwardly curved.
9. The tape (1) according to claim 1, having a thickness at its
inner section (T1) of from 400 .mu.m up to 5,000 .mu.m and a
thickness at least one, preferably both lateral sections (T1, T2)
of up to 350 .mu.m.
10. The tape (1) according to claim 1, wherein the adhesive layer
(3) comprises an acrylic adhesive.
11. The tape (1) according to claim 1, wherein the top layer (2)
comprises a polyurethane.
12. Method of protecting a rotor blade of a wind turbine from
erosion comprising providing a protective tape (1) according to
claim 1, and adhering it to the rotor blade.
13. Method of protecting a rotor blade from erosion comprising: (i)
providing a protective tape (1) according to claim 1, wherein the
adhesive bottom layer (3) has an upper surface facing the top layer
(2) and a bottom surface opposite thereto and wherein the bottom
surface is patterned to comprise a plurality of grooves or dots;
(ii) applying a liquid adhesive to the rotor blade, to the
patterned bottom surface of the tape or both, and (iii) attaching
the tape to the rotor blade.
14. A rotor blade comprising around its leading edge a protective
tape (1) according to claim 1, wherein the lateral sides of the
tape face the trailing edge of the blade.
15. Process of forming a multilayer tape (1) comprising: (i)
providing a substrate (4); (ii) providing in a coating chamber (6)
a coating knife (300) having a profiled recess (301) at its lower
end facing the substrate (4) and which forms a gap (401) normal to
the surface of the substrate (4); (iii) moving the substrate (4)
relative to the coating knive (300) in a downstream direction; (iv)
providing to the upstream side of the coating knife (300) a curable
adhesive thereby coating an adhesive layer (3) onto the substrate
(4) through the gap (401); (v) providing a polymer film (2) to the
upstream side of the coating knife (300) and feeding the film (2)
simultaneously with the adhesive layer (3) through the recess (301)
of the coating knife (300), wherein the film (2) is positioned
between the recess (301) and the adhesive layer (3); (vi) curing
the adhesive of the multilayer tape thus obtained, wherein the
profiled recess (301) of the coating knife (300) and the size of
the gap (400) between the coating knife (300) and the substrate (4)
define the cross-sectional profile of the tape (1).
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14,235542, filed Jan. 29, 2014,which is a
national stage filing under 35 U.S.C. 371 of PCT/US2012/048219,
filed Jul. 26, 2012, which claims priority to European Patent
Application No. 11176051.8, filed Jul. 29, 2011. The disclosures of
all three applications mentioned above are incorporated by
reference in their entirety herein.
FIELD
[0002] The present disclosure relates to a protective tape for a
rotor blade of a wind turbine generator. The tape has a non-uniform
thickness profile in a widthwise direction.
BACKGROUND
[0003] Rotor blades of wind energy power plants are made of
composite materials, typically glass-fiber composites. The
materials can be damaged by rain, sand, ice, and hailstones, a
process which is commonly referred to as "erosion". Protective
tapes can be applied to the rotor blades to protect them from
erosion. Typically, the tapes are wrapped around the leading edge
of the rotor blade and adhered to the blade by an adhesive.
Commercial tapes are usually planar and comprise a polymer film as
protective layer and an adhesive layer for attachment to the rotor
blade. Typical tapes are up to 400 .mu.m thick of which the
adhesive layer typically has a thickness of less than 100 .mu.m to
avoid making an impact on the aerodynamic profile of the blade. The
tapes may be prepared by extruding the protective resin through a
rectangular die of the required dimension to define thickness and
width of the tape and coating the adhesive onto the extruded film.
The adhesive layer is typically covered on its external surface by
a release liner and the tapes are wound up into rolls for storage
and handling.
[0004] Rotor blade manufacturers apply the protective tapes after
removal of the release liner to the rotor blade. After application
of the tape the rotor blades are transported to the wind farms
where they are installed. The tapes may also be applied to the
blades after they had been installed in the wind farm.
[0005] Rotor blades for wind turbine generators are becoming
increasingly longer and typically may now have a span of greater
than 40 m, e.g. 60 m. Furthermore, wind turbine generators are
increasingly set up off-shore subjecting the protective tape to
greater forces and harsher erosion conditions. This means that
protective tapes have to face stronger forces, for example during
transportation to the off-shore power plant and/or to harsher
erosion conditions.
[0006] Therefore, there is a need to provide alternative protective
tapes that may appropriately meet the above described
challenges.
SUMMARY
[0007] In the following there is provided in one aspect a
multilayer protective tape (1) for rotor blades of wind energy
turbines said tape (1) having a protective top layer (2) comprising
a polymer film and an adhesive bottom layer (3), wherein the top
layer (2) has a continuous surface (S) that is outwardly curved or
outwardly trapezoidal such that the tape (1) has a cross-sectional
profile having an inner section between two lateral sections and
wherein the inner section has a thickness (T1) made up by the
thickness of the top layer (2) and adhesive bottom layer (3) that
is greater than the thickness of at least one of the lateral
sections (T1,T2) made up by the thickness of the top layer (2) and
adhesive bottom layer (3) and wherein the thickness (T1 or T2) of
at least one lateral section is at most 600 .mu.m and the thickness
of the inner section (T1) is at least 330 .mu.m.
[0008] In another aspect there is provided a method of protecting a
rotor blade of a wind turbine from erosion comprising providing the
protective tape (1) above and adhering it to the rotor blade.
[0009] In a further aspect there is provided a method of protecting
a rotor blade from erosion comprising:
[0010] (i) providing the protective tape (1) above wherein the
adhesive bottom layer (3) has an upper surface facing the top layer
(2) and a bottom surface opposite thereto and wherein the bottom
surface is patterned to comprise a plurality of grooves or
dots;
[0011] (ii) applying a liquid adhesive to the rotor blade, to the
patterned bottom surface of the tape or both, and
[0012] (iii) attaching the tape to the rotor blade.
[0013] In yet another aspect there is provided a rotor blade
comprising around its leading edge a protective tape (1) wherein
the lateral sides of the tape face the trailing edge of the
blade.
[0014] In yet a further aspect there is provided a process of
forming a multilayer protective tape (1) comprising: [0015] (i)
providing a substrate (4); [0016] (ii) providing in a coating
chamber (6) a coating knife (300) having a profiled recess (301) at
its lower end facing the substrate (4) and which forms a gap (401)
normal to the surface of the substrate (4); [0017] (iii) moving the
substrate (4) relative to the coating knive (300) in a downstream
direction; [0018] (iv) providing to the upstream side of the
coating knife (300) a curable adhesive thereby coating an adhesive
layer (3) onto the substrate (4) through the gap (401); [0019] (v)
providing a polymer film (2) to the upstream side of the coating
knife (300) and feeding the film (2) simultaneously with the
adhesive layer (3) through the recess (301) of the coating knife
(300), wherein the film (2) is positioned between the recess (301)
and the adhesive layer (3); [0020] (vi) curing the adhesive of the
multilayer tape thus obtained, wherein the profiled recess (301) of
the coating knife (300) and the size of the gap (400) between the
coating knife (300) and the substrate (4) define the
cross-sectional profile of the tape (1).
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The disclosure may be more completely understood in
consideration of the following detailed description of various
embodiments of the disclosure in connection with the accompanying
drawings.
[0022] FIG. 1A is a schematic perspective representation of a
protective tape according to the present disclosure round up to a
roll.
[0023] FIG. 1B is an enlarged cross-sectional representation of a
section of the protective tape of FIG. 1A.
[0024] FIG. 2A is a schematic cross-sectional representation of the
protective tape according to the present disclosure having a
trapezoidal surface.
[0025] FIG. 2B is a schematic cross-sectional representation of the
protective tape according to the present disclosure having a
trapezoidal surface.
[0026] FIG. 3 is a schematic cross-sectional representation of an
embodiment of the protective tape according to the present
disclosure having a patterned adhesive layer.
[0027] FIG. 4 is a schematic representation of wet-in-wet coating
process of example 1.
[0028] FIG. 5A is a schematic cross-sectional representation of the
profiled recess of the downstream coating knife used in example
1.
[0029] FIG. 5B is the cross-sectional profile of the tape produced
in example 1.
[0030] FIG. 6 is a perspective cross-sectional schematic view of a
rotor blade for wind turbines.
DETAILED DESCRIPTION
[0031] Reference will now be made in detail to embodiments of the
disclosure, one or more examples of which are illustrated in the
drawings. Features illustrated or described as part of one
embodiment can be used with other embodiments to yield still a
third embodiment. It is intended that the present disclosure
include these and other modifications and variations.
[0032] Protective Tape:
[0033] A perspective view of an exemplary protective tape having a
cross-sectional profile according to the present disclosure is
illustrated in FIG. 1A, which shows the tape wound up to a roll.
The protective tape (1) has a length (L), a width (W) and a
thickness (T). The length of the tape is its longest dimension
followed by its width, wherein the length of the tape is always
greater than its width. The width of the tape is always greater
than its thickness. Typically, the tape has a width of at least 150
mm. Typically, the tape has a length of at least 50 cm.
[0034] The tape (1) has a profiled cross-section. The surface (S)
of the tape has a cross-sectional profile such that the tape,
across its width, has an inner part between two lateral parts
wherein the inner part has a thickness (T1) and the lateral parts
have a thickness T1 and T2. The thickness of the inner part (T1) is
greater than the thickness of at least one, preferably both lateral
parts (T1, T2) of the tape. The thickness at the inner section of
the tape (T1) may be the maximum thickness of the tape. The surface
(S) of the tape is shaped to provide the cross-sectional profile
described above. The surface (S) may be outwardly curved, for
example to describe a convex shape (as represented in FIG. 1lA and
1B) or it may be angled to describe a trapezoidal shape (as
represented in FIG. 2A and 2B). Therefore, the tape has a thickness
at its inner section (across its width or cross-section) that is
greater than at its lateral sections or its edges.
[0035] FIG. 1 B shows the layered-construction of the tape (1). The
tape (1) comprises a protective top layer (2) and an adhesive
bottom layer (3). The adhesive bottom layer (3) contains the
adhesive for attachment to the rotor blade. The top layer (2) and
the adhesive bottom layer (3) are arranged parallel to each other.
The adhesive layer (3) may contact the top layer (2) directly, in
which case top layer (2) and adhesive layer (3) are superimposed or
abutting layers or they may be separated from each other by one or
more intermediate layers, which are not shown in FIG.1B. In a
preferred embodiment of the present disclosure, the tape does not
contain intermediate layers between top layer and adhesive layers,
i.e. the top layer abuts the adhesive layer.
[0036] The adhesive layer (3) has an internal surface facing the
top layer (2) and opposite thereto an external surface. The
external surface of the bottom layer faces the rotor blade when
applied to the blade. Prior to application to the blade, for
example, during manufacturing, storage and transportation of the
tape the external surface of the adhesive layer (3) may be covered
by a release liner (4).
[0037] The surface (S) is typically made up by the top layer (2) of
the tape, i.e. the surface of the tape is typically also the
surface of the top layer (2). The top layer (2) has an outwardly
profiled surface (S) such that the tape has a thickness at its
inner part (T1) that is greater than its thickness at its lateral
parts (T1, T2) as shown in FIG. 1B.
[0038] The thickness at its inner part (T1) may be greater than 350
.mu.m or greater than 400 .mu.m and preferably is greater than 500
.mu.m. The tape may have a thickness at its inner part of up to
5,000 .mu.m, or up to 2,000 .mu.m or up to 1,000 .mu.m, or up to
745 .mu.m. The inner thickness T1 and the lateral thicknesses T1,
T2 are understood to be the sum of the respective thicknesses of
the top layer (2) and the adhesive layer (3) which includes the
thickness of any intermediate layer(s) between them but excludes
the thickness of any release liner if present. The inner part of
the cross-section of the tape may extend to more than 30%, more
than 50% or even more than 90% or more than 95% or even more than
99% of the width of the tape but is less than 100% of its
width.
[0039] The lateral parts of the tape (1) may have a thickness T1,
T2 of at most 600 .mu.m, or up to 590 .mu.m, or less than 450
.mu.m, less than 400 .mu.m or less than 300 .mu.m, provided the
thickness at the inner part (T1) is greater than the thickness of
at least one, preferably both lateral parts (or edges) of the tape
(1).
[0040] Typically the tape (1) has a cross-sectional profile such
that it has a thickness of at least one at its lateral parts (T1 or
T2), preferably at both of its lateral parts (T1 and T2) of up to
600 .mu.m and an increasing thickness towards its inner part from
its lateral parts to reach a thickness of greater than 700 .mu.m,
greater than 1,000 .mu.m, or 2,000 .mu.m or greater, or up to 5,000
.mu.m. Typically the thickness increases, preferably continuously,
from the lateral parts of the tape towards the central part of the
tape to reach a maximum thickness of up to about 5,000 .mu.m, up to
about 2,125 .mu.m, up to about 1,200 .mu.m or up to about 1,090
.mu.m. Again these thickness ranges are understood to comprise the
thickness of top (2) and adhesive layer (3) including the thickness
of optional intermediate layers but excluding the thickness of
release liners (4) if present.
[0041] The thickness profile of the tape (1) increases in thickness
from the lateral edges towards the inner part to reach a maximum.
Such a profile can be generated by a curved or angular surface (S),
which in case of the tape (1) represented in FIG. 1A and FIG. 1B is
an outwardly curved surface. "Outwardly" as used herein above and
below means a direction across the thickness of the tape starting
from the adhesive bottom layer towards the top layer, i.e. in the
direction towards the weather exposed part of the tape. Preferably,
the increase in thickness is continuous, for example by an
outwardly curved shape (as represented in FIG. 1A and FIG. 1B) or a
shape having angular sides (as represented in FIG. 2A and FIG. 2B).
The maximum thickness may be the apex of a curve or it may be a
plateau. The cross-sectional profile may be symmetric. It may also
be non symmetric, i.e. the increase in thickness from one lateral
part towards the inner part may be greater than the increase of the
other side. Alternatively, the thickness at the lateral sides of
the tape, i.e. T1 or T2 may not be equal. For example, T1 may be
greater than T2. The maximum thickness may be in the middle of the
tape (across its width) or offset from it.
[0042] The cross-sectional profile of the tape (1) is continuous.
This means the profile is not interrupted by a pattern of gaps and
grooves. Preferably, the entire surface of the tape (in widthwise
and lengthwise direction) is continuous. The external surface of
the tape preferably is smooth. However, it is to be understood that
some unevenness may be present due to manufacturing constraints,
i.e. the surface may have a surface roughness. Generally the
surface has a surface roughness (Rz), (DIN EN ISO 4287), of equal
or less than 150 .mu.m, preferably, equal or less than 100
.mu.m.
[0043] Top Layer:
[0044] The top layer (2) contains a polymer film. The polymer
typically is a thermoplast or an elastomeric thermoplast. The
polymer may be cross-linked or not-cross-linked. The top layer (2)
is typically an extruded polymer film but may also be a coated
polymer layer. Polymers that can be used to make the top layer (2)
or that form the top layer (2) include polyurethanes,
polycarbonates, fluoropolymers, epoxy-polymers, silicones,
polester, polyether, and combinations thereof and co-polymers or
graft-polymers thereof. Preferably, the top layer (2) contains a
polyurethane (PU) polymer which may be a polyurethane homo-or
copolymer, more preferably, an extruded polyurethane polymer. The
extruded polyurethane may be a thermoplastic elastomeric
polyurethane. Thermoplastic elastomeric polyurethanes are known in
the art under the abbreviation "TPU". TPU's are formed by the
reaction of: diisocyanates with short-chain diols (so-called chain
extenders) and diisocyanates with long-chain bifunctional diols
(known as polyols). TPU's are commercially available, for example,
under the trade designations DESMOPAN, TEXIN, UTECHLLAN from Bayer
AG, Germany. TPU tapes are also commercially available from 3M
Company, St. Paul, USA. The polymer film may contain additives to
improve the performance of the polymer composition, for example,
but not limited to, anti-oxidation agents, UV-stabilizer,
processing additives, fillers and the like.
[0045] In one embodiment the top layer (2) has a profiled surface
(S) as described above but is itself of uniform thickness. This
embodiment is represented in FIG. 2B, showing a trapezoidal top
layer (2) over a profiled (trapezoidal) adhesive layer (3) on a
release liner (4). Such tape constructions can be obtained by
providing an adhesive layer (3) that is already profiled and has a
cross-sectional profile as described above and onto which the top
layer (2) is adhered. Adhesion between the top layer (2) and the
profiled adhesive layer (3) beneath it forces the top layer (2) to
take up the profile of the pre-shaped adhesive layer (3). The top
layer of this embodiment preferably has a thickness of at least 50
.mu.m and up to 1,500 .mu.m or from at least 100 .mu.m up to about
500 .mu.m.
[0046] A profiled adhesive layer (3) may be generated by feeding a
curable adhesive precursor through a coating knife having an
appropriately shaped recess to create the desired profile and
feeding the top layer, preferably provided as a flexible film
between the curable adhesive around the profiled recess of the
coating knife and curing the adhesive.
[0047] Instead of providing the top layer material as a film it is
also contemplated by this disclosure to provide the top layer
material as a curable polymer composition which can be cured to
form a non-adhesive cross-linked polymer and feeding it around the
profiled knife and curing the adhesive precursor and simultaneously
or subsequently curing the polymer material to form the multi-layer
tape (1). Suitable curable polymer compositions include those that
are not adhesive after curing and include but are not limited to
epoxy compositions, polyurethane compositions or combinations
thereof.
[0048] In another embodiment the top layer (2) is of non-uniform
thickness, i.e. it has a greater thickness at its inner section
than at its lateral sections. This embodiment is represented in
FIG. 1B for tapes having a convex shape and in FIG. 2A for tapes
having a trapezoidal shape. The top layer (2) of such embodiment
may have a thickness at its lateral sections of not more than 400
.mu.m, or not more than 300 .mu.m, or not more than 200 .mu.m. The
top layer (2) has a thickness at its inner part (across its width)
of more than 550 .mu.m, or at least 610 .mu.m or at least 1.520
.mu.m. The maximum thickness of the top layer (2) may be up to
5,000 .mu.m or up to 1,600 .mu.m. In this embodiment the
cross-sectional profile of the tape (1) is generated by the shape
of the top layer (2). Tapes according to this embodiment may be
made, for example, by extruding the material for making up the top
layer of the tape through appropriately shaped (profiled) dies and
attaching the extruded top layer onto the adhesive layer by
coating, laminating or other techniques known in the art, or by the
wet-in-wet coating process described herein using appropriately
shaped coating knives with appropriate gaps between knife and
substrate.
[0049] The top layer (2) of the protective tapes (1) may have a
flat continuous internal surface (i.e., the surface facing the
adhesive layer (3)) but may also have a non flat and/or non
continuous surface, for example a patterned internal surface.
[0050] Adhesive Layer:
[0051] The adhesive layer (3) of the tapes (1) according to the
present disclosure may be made of known adhesive materials.
Preferably, the adhesive is a pressure sensitive adhesive (PSA).
Pressure sensitive adhesives can be applied to a surface using
manual force, which is sufficient to bond the adhesive to the
surface. PSA's may not require setting (i.e. hardening through
solvent evaporation), chemical or thermal treatment for adhering
the adhesive to the substrate. Suitable adhesive materials, in
particular but not limited to pressure sensitive adhesive
materials, include, for example, acrylic based adhesives, vinyl
ether based adhesives, natural or synthetic rubber-based adhesives,
poly (alpha-olefins) based adhesives and silicone based adhesives
and combinations thereof, which are all known in the art. Specific
examples are disclosed in U. S. Pat. Nos. 4,925,671, 4,693,776,
3,930,102, 4,599,265, 5,116,676, 6,045,922, and 6,048,431. The
adhesives may be obtained by curing from curable adhesive
precursors. This means the adhesives obtain their adhesive
properties by curing them, for example by a thermal curing
reaction, or by irradiation curing, e.g. by actinic irradiation,
gamma- or UV-irradiation or e-beam treatment. An example of
UV-curable adhesive precursors includes acrylic adhesives
precursors. Those precursors are typically liquid materials which
harden or solidify or at least increase in viscosity upon
cross-linking (curing), which typically involves UV curing.
[0052] The adhesive bottom layer (3) of the present disclosure may
also contain non-pressure sensitive adhesive materials. Examples of
such materials are described in U. S. Pat. Nos. 5,851,664 and WO
99/50902. In addition, the adhesive layer of the present invention
may be a non tacky adhesive as described in U. S. Pat. No.
5,316,846.
[0053] Typically, the adhesives of adhesive bottom layer (3) may
have a viscosity of at least 2,000, or at least 10,000 or from
about 18,000 to about 60,000 mPas or greater that 60,000 mPas at
room temperature.
[0054] In particular embodiments the adhesives may be used in
combination with settable adhesives or curable liquid adhesives as
will be described in greater detail below.
[0055] Preferably, the adhesive bottom layer (3) comprises at least
one acrylic-based adhesive.
[0056] The adhesive materials used in the adhesive bottom layer (3)
may also include additives. Such additives may include, for
example, pigments, dyes, plasticizers, tackifiers, rheology
modifiers, fillers, stabilizers, UV radiation absorbers,
antioxidants, processing oils, and the like. The amount of
additive(s) used can vary from 0.1 to 50 weight percent of the
adhesive material, depending on the end use desired. The adhesive
layer may also contain particles, in particular hollow particles or
agents that expand upon exposure to heat (e.g. blowing agents) to
generate a foam adhesive. Also a combination a different adhesives
can be used to combine them into a single adhesive mixture. The
adhesive bottom layers (3) provided herein may contain a single
adhesive layer or two or more than two adhesive layers, preferably
superimposed or abutting layers across its thickness. In a
preferred embodiment, the tape (1) contains an adhesive layer (3)
containing at least two abutting adhesive layers and one of them
being a foam adhesive layer. A foam adhesive comprises adhesives
containing solid or hollow particles, like but not limited to solid
or hollow glass particles or hollow organic polymer particles,
gas-filled (other than air) particles or air- or gas-filled
cavities. Preferably, the foam adhesive layer is placed underneath
the top layer (2), preferably abutting the top layer (2). Foam
adhesives may increase the elasticity of the tape which may be
beneficial to the impact dampening properties of the tape.
[0057] The adhesive bottom layer (3) may typically have a thickness
of from about 20 to 120 .mu.m at its lateral sections. In case of a
flat, i.e. non-profiled adhesive bottom layer (3) the thickness at
its lateral sides is the same as at its inner section. In case of a
profiled adhesive bottom layer (3) the bottom layer may have a
thickness at its inner part of at 120 .mu.m or at least 400
.mu.m.
[0058] Adhesive Layers with Patterned External Surface
[0059] In particular embodiments, the adhesive bottom layer (3) may
have a patterned external surface. An embodiment of this type is
represented in FIG. 3. The external surface of the adhesive bottom
layer (3) is the surface that faces the rotor blade (when applied
to the blade). For example, the adhesive bottom layer (3) may
contain at its external surface a pattern of grooves as shown for
the adhesive bottom layer (3) in FIG. 3. In the embodiment
represented in FIG. 3 the adhesive bottom layer (3) is also shaped
to generate the profiled surface of the top layer (2) of the tape
(1) but is to be understood that this embodiment can have any top
layer (2) as described herein and a non-profiled adhesive layer.
The grooves may extend over the entire width and/or length of the
external surface of the adhesive layer (3) or only over parts or
separated sections of it. Preferably the pattern is such that the
grooves allow an uninterrupted path for a liquid to travel across
the width of the tape. The pattern may be symmetric or
non-symmetric. The grooves may be parallel to each other or they
may be interconnected with each other. The grooves may be linear or
non-linear. Instead of grooves also a dotted pattern, preferably a
dotted pattern interconnected by grooves may be used. The grooves
may have a width of from about 5 .mu.m to 5,000 .mu.m (in case of
dots the diameter replaces the width). They may have a depth of
from about 5 .mu.m to 500 .mu.m and in fact penetrate the entire
thickness of the adhesive layer, exposing the top layer (2) or
intermediate layer(s) underneath it--if present. In one embodiment
the grooves have a depth that is equal to the thickness of the
adhesive bottom layer (3). In another embodiment, the grooves have
a depth that is less than the thickness of the adhesive bottom
layer (3).
[0060] The grooves or dots may cover from 20 to 80% of the surface
of the adhesive bottom layer (3).
[0061] An advantage of a patterned external surface of the adhesive
is that it allows the tape to be easier repositioned and/or to be
applied without entrapping air-bubbles. Another advantage is that
such a tape may be used in combination with a separate adhesive to
provide stronger adhesion to the rotor blade.
[0062] In a specific but less preferred embodiment of this
disclosure the tape contains a patterned external surface of the
adhesive bottom layer (3) as described above but a non-profiled,
e.g. a planar top layer wherein the non-profiled top layer is made
of the materials as described above. In this less preferred
embodiment the tape has no cross-sectional profile. In this
particular embodiment the top layer preferably has a thickness of
more than 50 .mu.m and less than 5,000 .mu.m. The tape according to
this embodiment may also contain an adhesive foam layer as
described above. Such embodiments can be prepared by extrusion
through ordinarily (non-profiled dies) and coated or laminated onto
the adhesive layer. Tapes according to the embodiment may be
applied and used as described herein above and below for the
profiled tapes.
[0063] Protective tapes (1) as provided herein having an adhesive
layer (3) with a patterned external surface may be used in
connection with one or more liquid adhesives. The liquid adhesive
may be curable, which provides a bond by curing it, for example by
thermal curing, or irradiation curing as described above. The
adhesive may also be a settable adhesive, which provides a bond by
setting, for example a hot-melt adhesive or a solvent-based
adhesive or a two component (2K) adhesive, which contains two
reactive components which cross-link when combined providing an
adhesive, moisture curable adhesives which set upon exposure to
ambient moisture or a combination of curable and settable
adhesives. The liquid adhesives may be painted or sprayed onto the
rotor blade. The liquid adhesives may be applied to the rotor
blade, to the tape or both prior to attaching the tape to the rotor
blade. The liquid adhesive enters the grooves of the tape and is
allowed to set or is cured to bond the tape to the rotor blade. The
dimension of the grooves and their spatial arrangement with respect
to each other can be adapted to the type of liquid adhesive used
for achieving maximum adhesion and most convenient application.
Typically, the liquid adhesive has a viscosity at the temperature
at which it is applied, preferably room temperature (25.degree. C.)
of less than 18,000 mPas or less than 10,000 mPas or less than
5,000 mPas, typically from 50 to 16,000 mPas. In this embodiment,
where the patterned tape is used with separate liquid adhesives,
the adhesive used in the patterned adhesive layer (3) of the tape
has a viscosity at room temperature (25.degree. C.) that is equal
or greater than the viscosity of the liquid adhesive. Typically,
the adhesive of the patterned adhesive layer (3) has a viscosity of
at least 2,000, or at least 10,000 or from about 18,000 to about
60,000 mPas or greater that 60,000 mPas at room temperature.
[0064] The liquid adhesives may be of the same chemical class (e.g.
acrylic based adhesives) as the adhesive of the patterned adhesive
layer (3) but may have a different, preferably lower viscosity such
that it flows into the grooves of the patterned bottom. Also
suitable are liquid adhesives that belong to a different chemical
class than the adhesives used in the patterned adhesive layer (3).
In one embodiment the adhesive used in the patterned layer
comprises an acrylate containing adhesive and the liquid adhesive
is selected from acrylate and/or urethane comprising adhesives or
from silicone adhesives or from epoxy-based adhesives.
[0065] The adhesive bottom layer (3) may also contain a pattern as
described above on its internal surface facing the top layer if
improvement of the adhesion between top layer (2) or intermediate
layers (if present) and the adhesive layer (3) is required.
[0066] The pattern on the adhesive bottom layer (3) may be
generated by known methods. For example, the grooves in the
adhesive layer of the present disclosure may be made as described
in WO 98/29516, which is incorporated herein by reference. The
topography may be created in the adhesive by any contacting
technique, such as casting, coating or compressing. The topography
may be made by at least one of: (1) casting the adhesive layer on a
tool with an embossed pattern, (2) coating the adhesive layer onto
a release liner with an embossed pattern, or (3) passing the
adhesive layer through a nip roll to compress the adhesive against
a release liner with an embossed pattern. The adhesive may be
cross-linked to provide a permanent topography. The topography of
the tool used to create the embossed pattern may be made using any
known technique, such as, for example, chemical etching, mechanical
etching, laser ablation, photolithography, stereolithography,
micromachining, knurling, cutting or scoring. The pattern may also
be imparted to the adhesive layer by using an appropriately
patterned release liner.
[0067] The adhesive bottom layer (3) may be a single adhesive layer
which may be patterned as described above or non-patterned or it
may contain multiple adhesive layers of different adhesives or of
adhesives of the same chemical class of adhesives (e.g. acrylic
based adhesives, urethane adhesives, silicone adhesives, rubber
adhesives and the like) but having different physical properties
like, but not limited to adhesive strength, tack, elasticity and/or
viscosity.
[0068] Tape constructions containing several abutting layers can be
prepared by preparing films and laminating them to create a
multi-layered tape. In a specific embodiment the tape (1) contains
at least two superimposed adhesive layers making up the adhesive
bottom layer (3). Such layers may be prepared, for example, by a
wet-in-wet coating process. In the wet-in-wet coating process a
first layer of a curable adhesive precursor is coated onto a
substrate (e.g. a release liner). The coated substrate is then
subjected to a second coating step where a second curable adhesive
precursor is coated on top. The adhesive precursors are typically
liquids and are provided in substantially uncured form. For
example, they may have a polymerization degree of less than 50% or
less than 25% or even less than 10%. The curable adhesive
precursors may have a viscosity which keeps them separated from
each other for the time they are in the coating unit prior to
subjecting them to curing. The adhesive precursor layers are then
cured. It is believed that interfacial diffusion occurs between the
adhesive layers leading to a stronger interfacial adhesion upon
curing such that the resulting multi-layer product is more
resistant to delamination. This wet-in-wet coating process can also
be used for making profiled adhesive layers in which case the most
downstream coating knife, i.e the coating knife that is arranged at
the end of the coating line, has a recess in the shape of the
desired profile of the final tape. The coating knives leave a gap
between the substrate (and coated substrate respectively) and the
lower end of the coating knife through which the adhesive layers
and in some embodiments also an extruded protective film will be
fed. The size of the gap between the lower ends of the coating
knifes and the substrate and the profile of the recess of the most
downstream (or last) coating knife determine the thickness and
profile of the tape.
[0069] Therefore, the disclosure provides a process for making a
profiled tape (1) having a profile as described above, the process
comprises: [0070] (i) providing a substrate (4); [0071] (ii)
providing in a coating chamber (6) a coating knife (300) having a
profiled recess (301) at its end facing the substrate (4) and which
forms a gap (401) between its profiled lower edge (301) and the
substrate (4) [0072] (iii) moving the substrate (4) relative to the
coating knife (300) through the coating unit (downstream
direction), [0073] (iv) providing to the upstream side of the
coating knife (300) a curable adhesive precursor thereby coating an
adhesive layer (3) onto the substrate (4); [0074] (v) providing an
extruded polymeric film (2) to the upstream side of the coating
knife (300) and feeding the film (2) simultaneously with the coated
adhesive layer (3) through the profiled recess (301) of the coating
knife (300), wherein the film (2) is positioned between the
profiled recess (301) of the coating knife (300) and the adhesive
layer (3); [0075] (vi) curing the adhesive of the multilayer tape
thus obtained, wherein the profile of the coating knife (300) and
the size of the gap (401) between the coating knife (300) and the
substrate (4) define the cross-sectional profile of the tape
(1).
[0076] The process as described above may contain one or more
further coating knives arranged in front of the coating knife
(300), i.e. in an upstream position with respect to knife (300),
through which further adhesive precursors may be fed. The knives
are arranged such that they leave a gap between the substrate (4)
and their lower edges for the adhesive or a coated layer to pass
through. This way, multiple layers of adhesives may be formed. Such
a process is referred to as a wet-in-wet process because the
curable adhesive precursors are typically liquid compositions.
These coating knives may have a profiled recess at their lower edge
or may have a flat lower edge. For example a further coating knife
(200) may be positioned upstream to the coating knife (300) and
leaving a gap between coating knife (200) and substrate (4). On the
upstream side of the coating knife (200) a first adhesive precursor
is fed around the edge of the coating knife (200) thereby coating a
first adhesive layer (7) onto the substrate (4) which is then fed
through the coating chamber (6) towards the downstream coating
knife (300) described above. The gap of coating knife (300) is
chosen such that the second adhesive precursor introduced in
chamber (6) and the protective liner (2) can be coated onto the
layer already formed on the substrate to form the multilayer tape
(1). The coating knife (300) having the profiled recess is the most
downstream coating knife, i.e. it is positioned at the end of the
coating line before the tape reaches the curing unit.
[0077] The curable adhesive precursors used in this process may
become adhesive or fully adhesive only upon curing. The adhesives
may be fed through the coating knife under ambient pressure or an
over-pressure, at room temperature or at increased temperatures,
i.e. temperatures above room temperature. Preferably, the adhesive
precursors are used in this process, i.e. curable adhesives, more
preferably UV-curable adhesives. Preferably, the adhesives have a
degree of polymerization of less than 50%, or less than 25% or less
than 10%. Instead of one coating chamber, more than one coating
chambers, preferably abutting each other, may be used.
[0078] The adhesives used to make the tape according to the above
described process may be of different chemical classes or of the
same chemical class but of different physical properties. For
example at least one adhesive, preferably the one adjacent to the
top layer (2), may be an adhesive foam material. It may contain
solid or hollow particles, it may contain expendable particles, in
particular pentane filled expendable microspheres, gaseous
cavities, or combinations thereof The adhesives and/or their
precursors of the above described process typically have
viscosities that prevent them from quickly mixing which each other.
The adhesives and/or their precursors may have identical or
different viscosities. Typically, one adhesive and/or its precursor
has a viscosity of at least 1,000 mPas at 25.degree. C. and up to
30,000 mPas or up to 10,900 mPas at 25.degree. C. and the other
adhesive and/or its precursor, preferably being a foam adhesive,
has the same viscosity or a viscosity of from about 2,000 to 12,000
mPas at 25.degree. C., in particular from 2,500 to 9,000 mPas at
25.degree. C.
[0079] The substrate used in this process typically is a release
liner but may also be an intermediate layer. The release liner may
be structured to provide a patterned adhesive bottom layer (3).
[0080] Release Liner
[0081] The adhesive bottom layer (3) may be covered on its external
surface by a release liner (4) for convenient handling and storage.
The release liner (4) may be structured on the side facing the
adhesive to impart a pattern as described above to the adhesive.
The release liner (4) may be any release liner or transfer liner
known to those skilled in the art. In case of providing a patterned
external surface of the adhesive layer the release liner may be
embossed. Typical release liners include polymer coated paper with
a silicone release coating, a polyethylene coated polyethylene
terepthalate (PET) film with silicone release coatings, or a cast
polypropylene film with a silicone release coating. The release
liner (4) typically has a thickness of between 50 and 500
.mu.m.
[0082] Application of the Tape
[0083] A typical rotor blade is shown in FIG. 6. As shown in FIG. 6
the blade (11) has a leading edge (12) and a trailing edge (11).
The leading edge of the rotor blade is the side that predominantly
faces the wind. The tape (1) may be applied to the rotor blade by
removing the release liner and wrapping the tape around the rotor
blade, typically around the leading edge of the rotor blade and
bonding the tape to the blade. The tape (1) is preferably attached
to the blade such that it covers the leading edge with its thicker
part and the thinner sides of the tape directed towards the
trailing edge of the blade.
[0084] In a particular embodiment of the present disclosure a tape
(1) having a patterned bottom adhesive layer (3) as described above
is provided. A liquid adhesive as described above is provided and
applied to the blade on the parts to be covered by the tape (1) or
on the adhesive side of the tape (1) or both. The tape (1) is then
attached to the blade and the liquid adhesive is cured (UV-curing
or thermal curing in case the adhesives is UV-curable or thermally
curable), or the adhesive is allowed to set in case the liquid
adhesive obtains its adhesive strength by setting (e.g. by
evaporation of solvent, moisture curing or reaction curing in case
of a 2K system). The tape (1) according to this embodiment is
attached to the blade by an adhesive bond formed between the liquid
adhesive and the patterned adhesive bottom layer (3) of the
protective tape (1).
[0085] The disclosure will now be described by way of examples and
lists of specific embodiments for illustrative purposes only. It is
not intended to limit the disclosure to the examples and the
specific embodiments.
List of Specific Embodiments
[0086] 1. A multilayer protective tape (1) for rotor blades of wind
energy turbines said tape (1) having a protective top layer (2)
comprising a polymer film and an adhesive bottom layer (3), wherein
the top layer (2) has a continuous surface (S) that is outwardly
curved or outwardly trapezoidal such that the tape (1) has a
cross-sectional profile having an inner section between two lateral
sections and wherein the inner section has a thickness (T1) made up
by the thickness of the top layer (2) and adhesive bottom layer (3)
that is greater than the thickness of at least one of the lateral
sections (T1,T2) made up by the thickness of the top layer (2) and
adhesive bottom layer (3) and wherein the thickness (T1 or T2) of
at least one lateral section is at most 600 .mu.m and the thickness
of the inner section (T1) is at least 330 .mu.m.
[0087] 2. The tape (1) according to embodiment 1 wherein the inner
section comprises up to 90%, up to 95% or even up to 99% of the
width of the tape.
[0088] 3. The tape (1) according to any one of the preceding
embodiment wherein the cross-sectional profile of the tape is
symmetric.
[0089] 4. The tape (1) according to any one of the preceding
embodiments wherein the adhesive bottom layer (3) has an upper
surface facing the top layer (2) and a bottom surface opposite
thereto and wherein the bottom surface is patterned to comprise a
plurality of grooves or dots.
[0090] 5. The tape (1) according to any one of the preceding
embodiments wherein the adhesive bottom layer (3) comprises across
its thickness at least two adhesive layers of which one adhesive
layer comprises a foam adhesive.
[0091] 6. The tape (1) according to embodiment 5 wherein the
adhesive layer (3) is prepared by a wet-in-wet coating process.
[0092] 7. The tape (1) according to any one of the preceding
embodiments wherein the top layer (2) has a uniform thickness.
[0093] 8. The tape (1) according to any one of the preceding
embodiments wherein the top layer (2) is outwardly curved.
[0094] 9. The tape (1) according to any one of the preceding
embodiments wherein the top layer (2) is outwardly convex.
[0095] 10. The tape (1) according to any one of embodiments 1 to 9
having a thickness at its inner section (T1) of from 400 .mu.m up
to 5,000 .mu.m and a thickness at the sections (T1, T2) of up to350
.mu.m.
[0096] 11. The tape (1) according to any one of the preceding
embodiments wherein the adhesive layer (3) comprises an acrylic
adhesive.
[0097] 12. The tape (1) according to any one of the preceding
embodiments wherein the top layer (2) comprises a polyurethane.
[0098] 13. The tape (1) according to embodiment 1 or 2, wherein the
cross-sectional profile is not symmetric.
[0099] 14. The tape (1) according to embodiment 13, wherein the
thickness (T1, T2) at the lateral sections of the tape (1) is not
equal.
[0100] 15. The tape (1) according to any one of the preceding
embodiments 13 to 14 wherein the adhesive bottom layer (3) has an
upper surface facing the top layer (2) and a bottom surface
opposite thereto and wherein the bottom surface is patterned to
comprise a plurality of grooves or dots.
[0101] 16. The tape (1) according to any one of the preceding
embodiments 13 to 15 wherein the adhesive bottom layer (3)
comprises across its thickness at least two adhesive layers of
which one adhesive layer comprises a foam adhesive.
[0102] 17. The tape (1) according to embodiment 16 wherein the
adhesive layer (3) is prepared by a wet-in-wet coating process.
[0103] 18. The tape (1) according to any one of the preceding
embodiments 13 to 17 wherein the top layer (2) has a uniform
thickness.
[0104] 19. The tape (1) according to any one of the preceding
embodiments 13 to 18 wherein the top layer (2) is outwardly
curved.
[0105] 20. The tape (1) according to any one of the preceding
embodiments 13 to 19 wherein the top layer (2) is outwardly
convex.
[0106] 21. The tape (1) according to any one of embodiments 13 to
20 having a thickness at its inner section (T1) of from 400 .mu.m
up to 5,000 .mu.m and a thickness at one of it lateral sections
(T1) of up to 350 .mu.m.
[0107] 22. The tape (1) according to any one of the preceding
embodiments 13 to 21 wherein the adhesive layer (3) comprises an
acrylic adhesive.
[0108] 23. The tape (1) according to any one of the preceding
embodiments 13 to 22 wherein the top layer (2) comprises a
polyurethane.
[0109] 24. The tape (1) according to any one of the preceding
embodiments 1 to 7, and 10 to 12 having an outwardly trapezoidal
cross-sectional profile.
[0110] 25. The tape (1) according to any one of the preceding
embodiments 12 to 18 and 21 to 23 having an outwardly trapezoidal
cross-sectional profile.
[0111] 26. A multilayer protective tape (1) for rotor blades of
wind energy turbines said tape (1) having a protective top layer
(2) comprising a polymer film and an adhesive bottom layer (3),
wherein the top layer (2) has a continuous surface, and wherein the
adhesive bottom layer (3) has an upper surface facing the top layer
(2) and a bottom surface opposite thereto and wherein the bottom
surface is patterned to comprise a plurality of grooves or dots,
and wherein the tape has a thickness (combined thickness of layers
(2) and (3) of more than 250 .mu.m.
[0112] 27. The tape (1) according to embodiment 26 wherein the
adhesive bottom layer (3) comprises across its thickness at least
two adhesive layers of which one adhesive layer comprises a foam
adhesive.
[0113] 28. The tape (1) according to embodiments 26 or 27 wherein
the adhesive layer (3) is prepared by a wet-in-wet coating
process.
[0114] 29. The tape (1) according to any one of the preceding
embodiments 26 to 28 wherein the top layer (2) has a uniform
thickness.
[0115] 30. The tape (1) according to any one of the preceding
embodiments 26 to 29 wherein the adhesive layer (3) comprises an
acrylic adhesive.
[0116] 31. The tape (1) according to any one of the preceding
embodiments 26 to 30 wherein the top layer (2) comprises a
polyurethane.
[0117] 32. The tape (1) according to any one of embodiments 26 to
31, wherein the tape has cross-sectional profile that is not
symmetric or is symmetric.
[0118] 33. The tape according to any one of embodiments 26 to 32,
wherein the tape has a surface (S) that is outwardly curved or
outwardly trapezoidal such that the tape (1) has a cross-sectional
profile having an inner section between two lateral sections and
wherein the inner section has a thickness (T1) made up by the
thickness of the top layer (2) and adhesive bottom layer (3) that
is greater than the thickness of at least one of the lateral
sections (T1,T2) made up by the thickness of the top layer (2) and
adhesive bottom layer (3) and wherein the thickness (T1 or T2) of
at least one lateral section is at most 600 .mu.m and the thickness
of the inner section (T1) is at least 330 .mu.m.
[0119] 34. The tape (1) according to embodiment 33 wherein the
inner section comprises up to 90%, up to 95% or even up to 99% of
the width of the tape.
[0120] 35. The tape (1) according to any one of the preceding
embodiments 33 and 34 wherein the top layer (2) is outwardly
convex.
[0121] 36. The tape (1) according to any one of embodiments 33 to
35 having a thickness at its inner section (T1) of from 400 .mu.m
up to 5,000 .mu.m and a thickness at the sections (T1, T2) of up to
350 .mu.m.
[0122] 37. The tape (1) according to any one of embodiment 33 to 36
wherein the thickness (T1, T2) at the lateral sections of the tape
(1) is equal or not equal.
[0123] 38. The tape (1) according to any one of the preceding
embodiments 26 to 37 wherein the plurality of grooves or dots has a
depth that is equal or less than equal than the thickness of the
adhesive bottom layer (3).
[0124] 39. The tape (1) according to any one of embodiments 33 to
37 having a thickness at its inner section (T1) of from 400 .mu.m
up to 5,000 .mu.m and a thickness at one of it lateral sections
(T1) of up to 350 .mu.m.
[0125] 40. The tape (1) according to any one of the preceding
embodiments 33 to 39 having an outwardly trapezoidal
cross-sectional profile.
[0126] 41. Use of a tape according to any one of embodiments 1 to
40 for protecting a rotor blade of a wind turbine from erosion.
[0127] 42. Method of protecting a rotor blade of a wind turbine
from erosion comprising providing a protective tape (1) according
to any one of embodiments 1 to 40 and adhering it to the rotor
blade.
[0128] 43. Method of protecting a rotor blade from erosion
comprising [0129] (i) providing a protective tape (1) according to
any one of embodiments 26 to 40; [0130] (ii) applying a liquid
adhesive to the rotor blade, to the patterned bottom surface of the
tape or both, and [0131] (iii) attaching the tape to the rotor
blade.
[0132] 44. The method according to embodiment 43 wherein the liquid
adhesive has a viscosity of less than 20,000 mPas.
[0133] 45. The method according to embodiment 43 wherein the liquid
adhesive has a viscosity of less than 20,000 mPas and the adhesive
of the patterned bottom layer has a viscosity of at least 20,000
mPas.
[0134] 46. The method according to embodiments 43 to 45 wherein the
liquid adhesive is sprayed onto the rotor blade.
[0135] 47. A rotor blade comprising around its leading edge a
protective tape (1) according to any one of embodiments 1 to 40,
wherein the lateral sides of the tape face the trailing edge of the
blade.
[0136] 48. Process of forming a multilayer tape (1) according to
any one of embodiments 1 to 40 comprising: [0137] (i) providing a
substrate (4); [0138] (ii) providing in a coating chamber (6) a
coating knife (300) having a profiled recess (301) at its lower end
facing the substrate (4) and which forms a gap (401) normal to the
surface of the substrate (4); [0139] (iii) moving the substrate (4)
relative to the coating knive (300) in a downstream direction;
[0140] (iv) providing to the upstream side of the coating knife
(300) a curable adhesive thereby coating an adhesive layer (3) onto
the substrate (4) through the gap (401); [0141] (v) providing a
polymer film (2) to the upstream side of the coating knife (300)
and feeding the film (2) simultaneously with the adhesive layer (3)
through the recess (301) of the coating knife (300), wherein the
film (2) is positioned between the recess (301) and the adhesive
layer (3); [0142] (vi) curing the adhesive of the multilayer tape
thus obtained, wherein the profiled recess (301) of the coating
knife (300) and the size of the gap (400) between the coating knife
(300) and the substrate (4) define the cross-sectional profile of
the tape (1).
[0143] 49. The process according to embodiment 48, wherein the
substrate (4) is a structured release liner.
Methods
Viscosity:
[0144] The viscosity referred to in the general description of this
disclosure and the viscosity of the materials used in the example
section is Brookfield viscosity, measured at 25.degree. C., unless
specified otherwise. Measurements were carried out according to DIN
EN ISO 2555:1999 at 25.degree. C. using spindle 3, at 12 rpm in a
Brookfield Digital Viscosimeter DV-II commercially available from
Brookfield Engineering Laboratories, Inc.
Surface Roughness (Rz):
[0145] The surface roughness (Rz; average maximum height of surface
profile) can be determined according to DIN EN ISO 4287 using the
method according to DIN EN ISO 4288.
[0146] Materials:
[0147] AA: Acrylic acid from BASF AG, Germany;
[0148] 2-EHA: 2-ethylhexylacrylate from BASF AG, Germany;
[0149] IOA: Isooctyl acrylate, ester of isooctyl alcohol and
acrylic acid, from Sartomer Company, Cray Valley, France;
[0150] HDDA: 1,6-Hexanedioldiacrylate (cross-linker) from Sartomer
Company, Cray Valley, France;
[0151] Aerosil 972: fumed silica, filler, commercially available
from Evonik Industries GmbH, Germany;
[0152] Glass bubbles K15: low density hollow glass microspheres
(density 0.15 g/cm.sup.3), foam material, from 3M Company, USA;
[0153] Omnirad BDK: 2,2-Dimethoxy-2-phenylacetophenone,
UV-initiator, from iGm resins, Waalwijk, Netherlands;
[0154] Release liner: HOSTAPHAN 2 SLK, siliconized polyester, 75
.mu.m thickness from Mitsubishi, Wiesbaden, Germany.
EXAMPLES
[0155] Preparation of Liquid Adhesive Precursor I:
[0156] The liquid adhesive precursor was prepared by combining 90%
of ISO with 10% AA and 0.04 pph (parts per hundred based on the sum
of IOA and AA) of Omnirad BDK in a glass vessel under stirring for
30 minutes. The mixture was partially polymerized under a
mitrogen-rich atmosphere by UV irradiation to a degree of
polymerization of approximately 8% giving a Brookfield viscosity of
approximately 3,000 mPas at 25.degree. C. Subsequent to the curing
0.12 pph of HDDA and 0.16 pph of Omnirad BDK were added and the
resulting mixture was thoroughly stirred for 30 minutes giving a
material having a viscosity of 3,500 mPas.
[0157] Preparation of Liquid Adhesive Precursor II (Foam
Adhesive):
[0158] The liquid precursor was prepared by combining 90% of 2-EHA
with 10% AA and 0.04 pph (parts per hundred based on the sum of
2-EHA and AA) of Omnirad BDK in a glass vessel under stirring for
30 minutes. The mixture was partially polymerized under a
mitrogen-rich atmosphere by UV irradiation to a degree of
polymerization of approximately 8% giving a Brookfield viscosity of
approximately 2,100 mPas at 25.degree. C. Subsequent to the curing
0.10 pph of HDDA,0.16 pph of Omnirad BDK, 3 pph of filler and 6 pph
of Glasbubbles K15 were added and the resulting mixture was
thoroughly stirred for 30 minutes. The resulting precursor had a
viscosity of about 10,000 mPas.
Example 1
Preparation of Protective Tape Having a Profiled Surface
[0159] A profiled adhesive layer was prepared by the wet-in-wet
coating process in a coating station represented in FIG. 4 to which
will now be referred.
[0160] The coating unit (5) contained a coating chamber (6) made up
by the upstream coating knife (200) at its front and the downstream
coating knife (300) at its back. The lateral walls of the coating
station are not shown. However, it is possible to provide more
coating knives if further layers are to be prepared as described
above. A substrate (4) was fed through the coating unit (5) in
downstream direction as indicated by the straight arrow at a line
speed of 6 m/min to reach first the upstream coating knife (200)
and then the downstream coating knife (300). A position facing the
web direction (downstream direction) is referred to as "upstream
position". The position opposite to the "upstream position" is
referred to as "downstream position". The substrate used in the
example was a release liner (4). Both coating knives were held in a
position that left a gap (400),(401) between the lower ends of the
coating knives (the ends facing the substrate) and the substrate
(4). The upstream coating knife (200) had a flat lower end. The
downstream coating knife (300) was provided at its lower end with a
profiled recess (301) having a trapezoidal shape as is shown in
FIG. 5 A (viewed from the webdirection/downstream direction). The
coating knives (200), (300) were arranged vertically spaced apart
and held independently from each other. The liquid adhesive
precursor (I) was fed on a rolling bead in front of coating knife
(200) (upstream side of the coating knife (200), onto the substrate
and passed through the gap (400) between the lower end of the
coating knife (200) and the substrate (4) thus coating the
substrate to form a layer (7). The coated substrate was fed into
the coating chamber (6) where the second liquid adhesive precursor
(II) was introduced onto to coated substrate (4) under ambient
pressure forming a layer (8) superimposed on layer (7).
[0161] In the coating chamber (6), a solid film (2) in the form of
a TPU liner of 150 .mu.m thickness was conveyed on the upstream
side of the coating knife (300) and fed around the profiled recess
(301) of the coating knife (300) simultaneously with the liquid
precursor II thus forming a multi-layer tape (1) containing an
adhesive layer (3) having separate adhesive layers (7) and (8). The
gap (400) between the first (upstream) coating knife (200) and the
substrate (4) was such that the adhesive layer (7) had a thickness
of about 75 .mu.m. The gap (401) between the flat parts of the
profiled recess of the lower edge of the coating knife (300) and
the coated substrate (4) was about 400 .mu.m and the gap between
the middle of the profiled recess and the substrate was about 1,200
.mu.m. The resulting multilayer tape was then continuously cured in
a 3 meter UV-curing station (2.07 mW/cm.sup.2 during the first 2 m
and 4.27 mW/cm.sup.2 at the last meter) to yield an erosion
protection tape (1) having a profiled thickness. The
cross-sectional profile of the resulting tape is shown in FIG. 5B.
The solid line indicates the thickness profile of the tape
(including the top layer (2), adhesive layer (3) made up of layers
(7) and (8) and the release liner (4). The dotted line indicates
the profile of the profiled adhesive bottom layer (3)--without the
top layer (2).
[0162] Example 1 is provided to demonstrate the construction of a
complex tape having an outwardly curved profile with a uniform
polyurethane film as top layer and an adhesive bottom layer
containing several distinct adhesive layers. It is understood that
also much simpler tape constructions are encompassed by the present
disclosure. For, example, it may be sufficient to provide an
adhesive bottom layer (3) containing just one adhesive layer. Such
less complex tapes can also be prepared in the coating system as
described above but then only the profiled coating knife may be
needed. The adhesive should be chosen such that its viscosity and
adhesive strength allows the tape to maintain its shape. Instead of
using a foam adhesive also plain adhesives with no foam-type
properties may be used. More complex tape constructions could also
be provided. In this case further coating knives may be added for
generating additional layers.
[0163] The complex tape construction provided in example 1 allows
for tapes being prepared having adhesive components fine-tuned to
the desired needs for a protective wind tape. In particular it is
believed that one or more adhesive foam layers may add further
protection to damage through sand or hailstones by providing
elasticity to the tape.
Example 2 (hypothetical)
Protective Profiled Tape with Patterned Adhesive Layer
[0164] The tape prepared in example 1 can be adhered to a tape
containing a structured adhesive layer. Such tapes are commercially
available, for example under the trade designation CONTROLAC 180
from 3M Company, St. Paul, USA. Such tapes contain a PVC top layer
and a bottom layer containing a structured adhesive. The profiled
tape can be adhered with its adhesive bottom layer to the PVC side
of the CONTROLTAC tape giving a protective tape having a structured
adhesive layer at its bottom and an intermediate non adhesive layer
(the PVC layer).
[0165] For making tapes without the intermediate layers that would
result from the hypothetical example above, the adhesive layer of
the multi-layer tape prepared in example 1 can be provided with a
pattern by the methods described in the description, for example,
but not limited to, embossing using a patterned release liner.
Example 3
Adhesion of a Tape with a Patterned Adhesive Bottom Layer to Liquid
Adhesives
[0166] A protective tape having a patterned adhesive layer was
prepared as follows:
[0167] A PVC film having a patterned adhesive layer (CONTROLTAC 180
from 3M Company, St. Paul, USA) was adhered to the adhesive side of
a protective film comprising a polyurethane resin as protective
layer and an adhesive bottom layer (WINDTAPE 8607 from 3M Company).
The protective tape had a uniform profile but the experiment is
provided to demonstrate the interaction of the patterned adhesive
layer with a liquid adhesive on bonding to rotor blades.
[0168] Three different adhesives of different viscosities where
applied to the patterned part of the protective tape, which was
then wrapped around the leading edge of a glass fiber composite
rotor blade and attached by hand wiping from the middle to the
sides to remove air and excess liquid adhesive. The liquid adhesive
was allowed to cure according to the supplier's instructions.
[0169] The following liquid adhesives were used:
[0170] Resin I: SCOTCH-WELD UV 11 from 3M Company, St. Paul, USA
(urethane-acrylate-based adhesive), viscosity 90 m Pas, UV curable
adhesive.
[0171] Resin II: SCOTCH-WELD DP 600 SL polyurethane-based adhesive,
viscosity 2500-4050 mPas. 2K (2 component) adhesive which cures
upon combination of the two reactive components after 24 hours.
[0172] Resin III: SCOTCH-WELD DP 810, acrylate-based adhesive,
viscosity 20,000-40,000 mPas, UV curable adhesive.
[0173] The tapes using liquid adhesives I and II could be easily
applied, repositioned and strongly bonded to the blade. Tapes with
resin III could not be easily attached to the blade.
[0174] To test the strength of the bond, the tapes were removed by
hand from the glass-fiber composite. The test was compared by using
a TPU--tape having a PSA layer at its bottom that was flat, i.e.
not patterned. The tape was attached to the same glass composite
material. The tape was removed from the blade by hand which could
be carried out more easily than the tests done with adhesives I and
II using the patterned material as described above.
* * * * *