U.S. patent application number 14/613583 was filed with the patent office on 2015-06-04 for flexible laminate structure.
The applicant listed for this patent is Stern & Stern Industries, Inc.. Invention is credited to Arthur Russell Nelson, Peter B. Thornton.
Application Number | 20150151521 14/613583 |
Document ID | / |
Family ID | 48325900 |
Filed Date | 2015-06-04 |
United States Patent
Application |
20150151521 |
Kind Code |
A1 |
Thornton; Peter B. ; et
al. |
June 4, 2015 |
FLEXIBLE LAMINATE STRUCTURE
Abstract
A flexible non-porous laminate film structure is provided
comprising a textile substrate having a fluorinated film laminated
thereto, which is laminated at a temperature lower than the
softening point of the predominant polymeric component of the
fluoropolymer fiber. The resulting product is resistant to
delamination.
Inventors: |
Thornton; Peter B.;
(Bronxville, NY) ; Nelson; Arthur Russell;
(Decatur, AL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stern & Stern Industries, Inc. |
Hornell |
NY |
US |
|
|
Family ID: |
48325900 |
Appl. No.: |
14/613583 |
Filed: |
February 4, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13867004 |
Apr 19, 2013 |
8975197 |
|
|
14613583 |
|
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|
|
61635721 |
Apr 19, 2012 |
|
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61635521 |
Apr 19, 2012 |
|
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Current U.S.
Class: |
428/36.1 ;
442/289; 442/304 |
Current CPC
Class: |
B32B 2307/546 20130101;
Y10T 442/681 20150401; B32B 38/18 20130101; Y10T 442/674 20150401;
Y10T 442/3878 20150401; F16L 11/02 20130101; Y10T 442/40 20150401;
B32B 2433/02 20130101; F16J 15/108 20130101; Y10T 442/696 20150401;
B32B 2307/308 20130101; B32B 2260/021 20130101; B32B 27/12
20130101; B32B 2597/00 20130101; B32B 5/04 20130101; Y10T 428/2915
20150115; B65G 15/32 20130101; C08L 27/18 20130101; B32B 2262/02
20130101; Y10T 403/21 20150115; Y10T 442/697 20150401; B32B 5/08
20130101; B32B 2260/046 20130101; Y10T 428/1362 20150115; B32B
5/026 20130101; B32B 37/06 20130101; F16J 15/102 20130101; B32B
37/182 20130101; Y10T 442/3854 20150401; F16L 59/029 20130101; B32B
7/04 20130101; B32B 27/322 20130101; B32B 5/024 20130101 |
International
Class: |
B32B 27/12 20060101
B32B027/12; B32B 27/32 20060101 B32B027/32; B32B 7/04 20060101
B32B007/04 |
Claims
1. A flexible, non-porous laminate film structure comprising a
woven or knit textile substrate formed of fluoropolymer fibers, and
at least one fluoropolymer film layer, wherein the fluoropolymer
film layer is intimately bonded to the textile substrate and
material from the fluoropolymer film layer fills voids between at
least some of the fibers of the substrate.
2. The laminate film structure as in claim 1 wherein the film wets
out during the lamination process.
3. The laminate film structure as in claim 1 wherein material from
the fluoropolymer film layer within voids between fibers of the
substrate is visible under SEM magnification.
4. The laminate film structure as in claim 1 wherein the fibers of
the textile substrate initially have a round cross-section, and
wherein the fibers of the textile substrate are transfused into an
amorphous mass and the round cross-sections of the fibers are
morphed into geometries suitable for filling interstitial voids in
the textile structure, as is visible under SEM magnification.
5. The laminate film structure as in claim 1 that is prepared
without surface etching of the film.
6. The laminate film structure as in claim 1 that is prepared
without intermediary dispersions or glues, fibrils or nodes, or
similar interconnecting paths on or in the surface of the
fluoropolymer film conventionally used to create strong adhesion
between substrate and film.
7. The laminate film structure as in claim 1 that is prepared in
the absence of fillers.
8. The laminate film structure as in claim 1 that is prepared in
the absence of cooling processing steps other than ambient to
fixate the lamination for dimensional stability.
9. The laminate film structure of claim 1 that is laminated at a
temperature lower than the softening point of the predominant
polymeric component of the fluoropolymer fiber.
10. The laminate film structure of claim 1 that is laminated
between 310.degree. C. and 325.degree. C., under steady pressure of
at least 20 bars at a speed of 0.5 m/min to 6.5 m/min.
11. The laminate film structure of claim 1 that is laminated
between 310.degree. C. and 325.degree. C., under steady pressure of
at 30-50 bars for approximately 10 seconds.
12. The laminate film structure of claim 1, wherein the textile
substrate comprises fluoropolymer fibers that are at least 75% by
weight poytetrafluoroethylene and 25% by weight
polyfluoroalkoxy.
13. The laminate film structure of claim 12, wherein the ratio of
poytetrafluoroethylene to polyfluoroalkoxy is 3 to 1.
14. The laminate film structure of claim 12, wherein the film is
wholly or predominately polyfluoroalkoxy or
poytetrafluoroethylene.
15. The laminate film structure of claim 1 in which the film is
laminated on one or both sides of the substrate.
16. The laminate film structure of claim 1 wherein the textile
substrate is a woven or knit fabric.
17. A conveyor belt composed of the laminate film structure of
claim 1.
18. A flexible duct composed of the laminate film structure of
claim 1.
19. An expansion joint composed of the laminate film structure of
claim 1.
20. The laminate film structure of claim 1 wherein the textile
substrate is formed from fluoroploymer fibers comprising a blend of
poytetrafluoroethylene material and polyfluoroalkoxy material.
21. The laminate film structure of claim 20 wherein the
fluoroploymer fibers provide two softening points.
22. The laminate film structure of claim 21 wherein the two
softening points include one at about 305.degree. C. for the
polyfluoroalkoxy material and another at about 330.degree. C. for
the poytetrafluoroethylene material.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/867,004 filed Apr. 19, 2013, which claims
the benefit of U.S. Provisional Patent Application No. 61/635,721
filed Apr. 19, 2012 entitled "Flexible Laminate Structure," and
U.S. Provisional Patent Application No. 61/635,521 entitled
"Dispersion Spun Fluoropolymer Fiber Prepared from
Non-Melt-Processible Polytetrafluroethylene and Perfluroalkoxy,"
the disclosures of which are hereby incorporated by reference in
their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to flexible laminate structures, and
in particular to flexible, fluid resistant laminate structures that
can withstand a wide range of temperatures and pH values.
[0004] 2. Description of Related Art
[0005] Flexible, fluid resistant materials that can withstand a
wide range of temperatures and pHs are required for food processing
belts and for expansion joints in factories and power plants. Ever
increasingly harsher industrial environments require more robust
materials than have heretofore been available.
[0006] Methods for continuously processing food products are known
and typically have conveyors for transporting food products through
a heating process. In some continuous heating conveyor ovens,
radiant heat is provided by heated platens over which the belts
travel. Such belt materials typically must resist continuous use
temperatures of 500.degree. F.-550.degree. F., with infrequent
excursions to 600.degree. F.
[0007] Productivity is lost if the conveyer system uses belts that
degrade quickly. Replacement of conveyer belts and calibration of
conveyer systems are time consuming and costly. Downtime is
extremely expensive in terms of lost manufacturing yield and may
necessitate additional backup lines.
[0008] Conveyor belts used for processing food must meet certain
FDA standards, including CFR 177.1550, which prohibit the contact
of the prepared food with certain materials such as fiberglass.
Unfortunately, the conventional conveyor belt used for processing
such food is a composite of a brittle woven fiberglass substrate
that is dip-coated and saturated in a protective fluoropolymer of
PTFE. Scanning electron microscopy (SEM) images of such composite
structures provide visual evidence of poor adhesion between the
glass rod-like filaments and the PTFE polymer saturating the
interior of the composite (FIGS. 1 and 2). Cross-sectional analysis
under SEM magnification show that the glass fibers readily separate
from the PTFE and easily fracture.
[0009] The oft-called PTFE-coated fiberglass belts are routinely
scrapped prematurely due to surface rupture or weak tear
resistance, resulting in the exposure of fiberglass to food.
Conveyor belts made from PTFE-coated fiberglass last only about a
week or two in normal production. The root cause of failure in all
instances is the presence of fiberglass.
[0010] The woven fiberglass substrate is composed of an industry
standard, Style 1528 or 7628 fiberglass fabric with a tear strength
(tongue) of about 13 lbs per inch, using ASTM D2261-07. However,
the belts are customarily tensioned to at least 1 lbs per inch,
which means that over a typical 45 inch wide belt, the total web
tension would be 45 lbs. If some or all of that total load is
concentrated at a point of tear, it greatly exceeds the tear
strength of the fiberglass fabric and the substrate routinely
fails.
[0011] Likewise for expansion joints, the material of choice has
similarly been PTFE coated fiberglass. By definition, expansion
joints require flexibility and oftentimes vibration resistance, so
fiberglass offers a very limited lifetime because the fiberglass
cuts itself to pieces internally. This is visually apparent in
FIGS. 3 and 4, where (as a consequence of preparation of the sample
for SEM analysis) the cross sectional view displays a jumble of
brittle glass fibers, some fractured and the rest left unprotected
from grating upon each other during flexure.
[0012] Certainly fluoropolymers have previously been applied to
PTFE substrates (see, e.g., Bragaw U.S. Pat. No. 4,877,683, Denny
U.S. Pat. No. 4,025,679, Fagan U.S. Pat. No. 4,324,574, Griffin
U.S. Pat. No. 6,517,919, Kelmartin U.S. Pat. No. 6,770,577, Sassa
U.S. Pat. No. 4,983,434), but these have created porous laminates
involving porous films and adhesives. PTFE films have been
laminated to other films (Tippett, U.S. Pat. No. 7,087,136, Bragaw
U.S. Pat. No. 4,877,683), and PTFE film has been shown to be
laminated to PTFE coated fiberglass (Tippett, U.S. Pat. No.
7,087,136, Matthiessen US Pat. Pub. 2005/0164581) or suggestively
laminated to PTFE woven substrates (Matthiessen US Pat. Pub.
2005/0164581), but at temperatures so high above the melt point of
PTFE as to make the material totally inflexible.
[0013] The concept of laminating PTFE film to a PTFE substrate to
create a flexible, non-porous structure has not been previously
revealed for good reason. The PTFE fiber-based substrate is
generally not considered a good candidate for the presently
envisioned laminate because of the seeming impossibility of
laminating it to a fluorocarbon film and achieving a good result.
Notwithstanding the lamination difficulties, it is also understood
that without proper heat stabilization throughout each process, the
fluoropolymer substrate would undergo 20-25% shrinkage when exposed
to the 500.degree. F.-550.degree. F. operating temperatures of a
food processing belt, resulting in uneven shrinkage within the
laminate itself and tracking problems as the belt is driven and
rotated.
[0014] Therefore, for uses including but not limited to food
conveyor belts and expansion joints, a need exists for robust
materials that can resist a wide range of temperatures and pH
values, and that are tear resistant, fluid resistant, and highly
flexible.
SUMMARY OF THE DISCLOSURE
[0015] In accordance with one or more embodiments, a flexible,
non-porous laminate film structure is provided comprising a textile
substrate having a fluorinated film laminated thereto, which is
laminated at a temperature lower than the softening point of the
predominant polymeric component of the fluoropolymer fiber. The
resulting product is resistant to delamination.
[0016] In accordance with one or more embodiments, a laminate film
structure is provided comprising one or more fluoropolymer films
laminated to a flexible, tear-resistant fluoropolymer textile
substrate. Material from the fluoropolymer film fills voids between
at least some of the fibers of the substrate thereby forming a
hybrid laminate material that is more tear resistant, impact
resistant, and flexible as compared to conventional PTFE coated
fiberglass composite materials.
[0017] In accordance with one or more embodiments, a laminate film
structure is provided comprising a fluoropolymer film laminated to
a surface of a textile substrate that includes fluoropolymer
fibers.
[0018] In accordance with one or more embodiments, a laminate film
structure is provided comprising fluoropolymer films laminated to
opposing surfaces of a textile substrate that is comprised of
fluoropolymer fibers.
[0019] Still other aspects, embodiments, and advantages of these
exemplary aspects and embodiments, are discussed in detail below.
Moreover, it is to be understood that both the foregoing
information and the following detailed description are merely
illustrative examples of various aspects and embodiments, and are
intended to provide an overview or framework for understanding the
nature and character of the aspects and embodiments to be claimed.
The accompanying drawings are included to provide illustration and
a further understanding of the various aspects and embodiments, and
are incorporated in and constitute a part of this specification.
The drawings, together with the remainder of the specification,
serve to explain principles of the described laminate structure and
aspects and embodiments which are to be claimed.
BRIEF DESCRIPTION OF THE DRAWING
[0020] The foregoing summary, as well as the following detailed
description of certain embodiments will be better understood when
read in conjunction with the appended drawings. For the purpose of
illustrating the invention, there are shown in the drawings certain
embodiments, although it should be understood that the invention is
not limited to the precise arrangements and instrumentalities
shown.
[0021] FIGS. 1-4 are scanning electron microscope photographs of
conventional composite structures formed of a woven fiberglass
substrate that is dip-coated and saturated in a protective
fluoropolymer of PTFE;
[0022] FIGS. 5 and 6 are scanning electron microscope photographs
of a flexible laminate film structure described herein, in which
FIG. 6 shows a cross-section at a slight perspective angle;
[0023] FIG. 7 is a scanning electron microscope photograph of PTFE
fibers modified in a laminate film structure described herein;
[0024] FIGS. 8, 9 and 10 are scanning electron microscope
photographs of conventionally laminated structures prone to
delamination; and
[0025] FIG. 11 is a schematic illustration of a double belt press
laminator.
DETAILED DESCRIPTION
[0026] The flexible, non-porous laminate film structure described
herein is useful in the processing of commercial products over a
wide range of viscosities, temperatures, and pHs. For instance, the
laminate film structure is suitable for uses including but not
limited to food preparation conveyor belts, expansion joint
materials, flexible ducting and for the transmission of gaseous
fluids.
[0027] The herein described laminate film structure is useful as a
replacement for conventional PTFE-coated fiberglass composites. The
herein laminate structure is, in certain embodiments, formed of a
woven substrate of a PTFE fluorocarbon fiber or PTFE-PFA hybrid
fluorocarbon fiber that has been heat stabilized at high
temperature which is laminated to a pre-formed PFA film at a
temperature between the melt point of PFA (582.degree. F.,
305.degree. C.), and that of PTFE (627.degree. F., 330.degree. C.).
The roughly 45.degree. F. (25.degree. C.) difference allows for
melting of the PFA in the film and the yarn to occur at a
temperature safely lower than that of the predominant polymer in
the yarn, PTFE. Significantly, the unaffected PTFE retains its
strength and structural flexibility, as does the overall textile
substrate. The melted and re-solidified PFA component after cooling
does not adversely impact the substrate. The softening point of the
PTFE in the substrate is cautiously avoided, lest the substrate
stiffen upon cooling and lose the desired properties of the
finished laminate.
[0028] The term "laminate" as used herein means layers of materials
bonded together, in this case a film to a textile substrate, in
contrast to a "composite" formed by saturation coating of a
polymeric fluidic paste within and throughout a substrate, such as
in dip-coating.
[0029] The term "film" as used herein means a relatively thin
polymeric layer, which can be variously described as a non-cellular
membrane or a non-metallic foil.
[0030] The terms "fluoropolymer" and "fluorocarbon," which may be
used interchangeably, refer to a fluorocarbon-based polymer with
multiple strong carbon-fluorine bonds.
[0031] The term "textile" as used herein means a woven, knit, or
non-woven structure composed of fibers.
[0032] The term "non-porous" as used herein means that the measured
flow rate of air through the laminate is zero cubic feet per minute
per square foot of material area under a pressure drop of 0.5''
H.sub.2O using Test Method ASTM D737.
[0033] The term "flexible" as used herein in relation to describing
the laminate structure means that is it capable of being draped or
rolled over a relatively narrow radius cylindrical rod and returned
to a straight configuration repeatedly without significant change
in the performance of the laminate structure.
[0034] The term "SEM," an acronym for scanning electron microscope,
as used herein means photo micrographs taken under 80.times. or
greater magnification.
[0035] In one embodiment of a process to manufacture the herein
described flexible non-porous laminate structure, a textile is
provided as a substrate and a fluorinated film is laminated to the
textile. The counter-rotating steel belts of a double belt press
laminator pull the textile and the fluorinated film from an
off-wind stand between heated pressure plates where lamination
occurs, optionally through standard cooling plates, and then onto a
re-wind stand. A general diagram of a conventional double belt
press laminator is shown in FIG. 11.
[0036] The fluorinated film is a film formed of resins such as
perfluoroalkoxy copolymer (e.g., commercially available from E. I.
DuPont de Nemours under the trade name Teflon.RTM. PFA resin) or
chemically modified polytetrafluoroethylene (PTFE) polymer (e.g.,
commercially available from E. I. DuPont de Nemours under the trade
name Teflon.RTM. NXT resin).
[0037] Cross-sectional views under SEM magnification of the
laminate in FIGS. 5 and 6 show that [0038] a. the film has flowed
into the interstitial voids of the woven structure as if it had
been coated; [0039] b. the film has encapsulated the surface and
near-subsurface fibers of the substrate; and [0040] c. the film has
formed a smooth, unbroken surface.
[0041] In addition, the fluoropolymer fibers have partially
softened and merged into a flexible mass between the film layers
(L1 and L2). As is apparent, the film layers are minimally
discernible, for instance when viewed using scanning electron
microscopy. Although the softening point of the predominant
component in the yarn, PTFE, has not been reached, it appears that
it too has softened, when in fact it has not. Examination of the
fibers in the substrate shows a fiber that is more gelatinous and
amorphous in shape than the fiberglass fiber evident in FIGS. 1 and
2 or of a conventional PTFE fiber evident in FIGS. 8-10.
[0042] The resulting laminate in embodiments which are 100%
fluoropolymer provides an additional benefit of being 100%
compatible with CFR 177.1550, a useful benefit if for any reason
the film should rupture and the woven fabric should become exposed
to food. In such a circumstance, the belt remains suitable for use
and need not be immediately taken out of use or scrapped, as is the
case with the conventional PTFE coated fiberglass composite
material based food conveyor belts.
[0043] The hybrid laminate material is more tear resistant, impact
resistant, and flexible than the conventional PTFE coated
fiberglass composite material. In certain embodiments of the
flexible laminate formed according to the present description, the
PFA/PTFE laminated material can last up to, and in certain
embodiments more than, 10 times longer in use than the conventional
material used, e.g., for food processing belts and for flexible
seals and joints.
[0044] Suitable textile substrates include woven, knit, or
non-woven structure comprising fluoropolymer fibers, PTFE
fluorocarbon fibers or combinations thereof. A suitable fiber is
described in related U.S. Provisional Patent Application No.
61/635,521 entitled "Dispersion Spun Fluoropolymer Fiber Prepared
from Non-Melt-Processible Polytetrafluroethylene and
Perfluroalkoxy," the disclosure of which is hereby incorporated by
reference. Dispersion spun fluoroploymer fibers include a blend of
PTFE particles and PFA particles. The fluoroploymer fiber is
prepared by forming an aqueous dispersion of PFA particles and PTFE
particles, mixing the dispersion with an aqueous matrix polymer
solution containing a matrix polymer, extruding the mixture into a
coagulation bath and forming an intermediate fiber structure. The
intermediate fiber structure is sintered to decompose the matrix
polymer and coalesce the PTFE particles and the PFA particles into
a blended fiber. The matrix spinning process of PTFE allows for the
inclusion of an appreciable concentration of PFA in to a fiber
structure that has sufficient tensile properties for normal textile
processing such as knitting and weaving. The inclusion of PFA into
a matrix spun PTFE fiber results in a true biocomponent fiber with
typical thermal capabilities (maximum continuous use temperature)
of PTFE. Further, the inclusion of PFA into the fiber matrix
provides a lower melt component to the fiber. This lower melt
component when in a fabric structure provides a system to which a
PFA film can be laminated at lower temperature and pressures
compared to 100% PTFE. In certain embodiments, the PTFE particles
are non-melt processible, which means that no melt flow is detected
when tested by the standard melt viscosity determining procedure
for melt-processible polymers, e.g., ASTM D-1238-00 or
modifications thereof.
[0045] In one embodiment, a hybrid, multifilament yarn is used to
form the textile substrate that is produced by Toray Fluorofibers
USA in a ratio of 3:1 by weight of PTFE and PFA dispersions, said
hybrid yarn offering two softening points, one at about 305.degree.
C. (582.degree. F.) for the PFA and a higher one at about
330.degree. C. (627.degree. F.) for the predominant PTFE element.
The fiber has the following nominal properties: round
cross-section, 1200 denier, 6.7 denier per filament, 1.2 g.sup.f/d
break tenacity, 50% elongation at the break, and 11.5% shrinkage at
300.degree. C. for 30 minutes, based on standard industry testing
methods for synthetic yarn. Test fiber was woven into a 1.times.2
basket weave with a balanced count of 59.times.59. It was heatset
at 600.degree. F. (315.degree. C.) in a fully tensioned state on a
tenter frame at the rate of 20 yards per minute, using standard
tentering equipment and procedures, to produce a dimensionally
stabilized fabric.
[0046] The dimensionally stabilized fabric was then laminated to a
standard 1 or 2 mil PFA extruded film (produced commonly by E. I.
DuPont de Nemours or Saint Gobain), using either isobaric or
isochoric double belt press technology in common use, at
temperatures between 590.degree. F. (310.degree. C.) and
620.degree. F. (327.degree. C.), preferably 600.degree. F.
(315.degree. C.), and at pressures greater than about 20 bar (290
psi), and in certain embodiments between 30 and 50 bar (435-725
psi), at suitable speeds to provide the requisite dwell time, e.g.,
approximately 0.5 meters per minute to 6.5 meters per minute. In
one embodiment a dwell time of about 10 seconds is achieved at a
feed rate of approximately 4 m/min.
[0047] It was unexpectedly found that an appropriate combination of
temperature and pressure results in the laminate structure having
the desired properties of high peel strength, flexibility,
impermeability, and tear resistance. Under the appropriate
combination of temperature and pressure, the film "wets out" and
becomes intimately bonded to the substrate, whereby the term
"wetting out" describes a visual phenomenon in which an opaque or
translucent fabric or film becomes transparent during processing,
e.g., when a woven fiberglass fabric that appears white when dry
becomes transparent when immersed in epoxy resin and using common
industry terminology it "wets out" and appears to dissolve into the
underlying resinous material. PFA film that has been laminated at
too low of a pressure, or at too short of a dwell time such as in a
conventional calendaring operation, does not wet out, bonds weakly
to the substrate, and is easily peeled off by hand. Such a weak
bond is shown in FIGS. 8-10, where the film has not been intimately
bonded to the fiber of the substrate, and appears to float above
the surface of the substrate.
[0048] As indicated in FIGS. 5 and 6, PFA film that has been
laminated at the appropriate temperature, pressure and dwell time
is intimately suffused into the surface of the substrate fiber. It
can be seen in FIG. 7 that the original cross-section of each
fluoropolymer fiber in the woven substrate is no longer round, but
has deformed to fill the voids around it. With the naked eye during
lamination, the film can be seen to have wetted out on the surface.
The bond between surface film and subsurface fibers is so complete
that any attempt to peel one of the film layers from the substrate
is tantamount to rupturing the substrate itself. This is in stark
contrast to laminated fluoropolymers formed by conventional
calendaring, such as shown in FIGS. 8-10, whereby the original
cross-section of each fiber in the woven substrate remains round.
It should be noted that razor cutting for purposed of SEM
cross-sectional photograph may distort the end view of the bundle
of fibers. For instance, in FIG. 9, the stray fiber near the center
of the photograph clearly has a round cross-section.
[0049] Furthermore, the gauge of the laminate structure formed
herein is significantly less than that of the total of the
individual thickness gauges of its components--film and textile.
For instance, in FIGS. 5-7 the laminate shown is composed of 24 mil
(0.024 in) textile sandwiched between about 2 mil (0.002 in) films,
for a total pre-lamination gauge of 0.028 inches. Lamination
reduced the three layers to an average gauge of 0.0177 inches, a
reduction of approximately 40%.
[0050] Note that in certain embodiments, the gauge of the textile
component can be reduced, e.g, to as low as 5 mil using a 200
denier textile fiber. Likewise, a 400 denier textile fiber offers a
textile component having a gauge as low as 8 mil. In these
embodiments, the film component(s) can be 1 mil for a potential
laminate structure gauge of 4 mil or 6 mil, using 200 denier or 400
denier fibers, respectively. The thinner gauge laminate structures
are effective for applications requiring greater flexibility and/or
higher rates of heat transfer.
[0051] Advantageously, the herein laminate structure is effective
for its intended use as a food conveyor belt, expansion joint,
flexible ducting, and for forming passageways for transmission of
gaseous fluids. Notably certain embodiments of the herein laminate
structure require: [0052] a. no surface etching of the film; [0053]
b. no intermediary dispersions or glues, fibrils or nodes, or
similar interconnecting paths on or in the surface of the
fluoropolymer film to create strong adhesion between substrate and
film; [0054] c. no fillers; and [0055] d. no special cooling
features or process steps other than ambient to fixate the
lamination for dimensional stability.
[0056] The method and structure of the present invention have been
described above and in the attached drawings; however,
modifications will be apparent to those of ordinary skill in the
art and the scope of protection for the invention is to be defined
by the claims that follow.
* * * * *