Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF MANUFACTURING MULTIPLE-PANE WINDOW UNITS
CoNTAINING INTERMEDIATE PLASTIC FILMS
This invention relates to multiple-pane window
units of insulated glass and the manufacture thereof.
Insulating glass units for windows or doors commonly
comprise two or more parallel glass panes that are separated
from one another by spacers along their edges. Various
multiple-pane configurations are known in the art. Certain
of these configurations have employed plastic sheets in a
parallel spaced relation to the glass panes.
If a multiple pane glass unit is assembled with a
plastic sheet held in spaced relationship between two glass
panes, the unit is usually manufactured by applying a
marginal spacer along the edges of one glass pane, the
spacer extending away from the plane of the pane, by
adhering a heat-shrinkable film to the spacer and by then
heat-shrinking the film to draw the film taut and wrinkle-
free. The second pane, also provided with a marginal
spacer, is then attached, and said film becomes sandwiched
between the opposed marginal spacers of the two panes.
In another embodiment, the film may be grasped by
small springs that are held by, or form a part of, the
spacers separating the two glass panes from one another.
Generally, unbreakable mirrors are formed by adhering a
marginal spacer about the periphery of a sheet of plywood or
like structural element, then adhering a heat-shrinkable,
silvered, plastic film to the spacers, and thereafter heat-
shrinking said film so it becomes taut amd wrinkle-free to
provide a mirrored surface.
In the above embodiments using a heat-shrinkable
plastic film, the film is stretched over spacers held at the
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edge of a stiff pane or structural element and the plastic
film is then heated directly, typically by hot air flow.
For multiple-pane glass units, wherein the plastic film is
deployed as an internal sheet between parallel glass panes,
the above manufacturing methods are difficult and time
consuming. Also, these methods necessitate piecemeal
construction methods.
U.S. Patent 4,335,166 describes manufacture of
multiple-pane glass units by supporting a flexible, heat-
shrinkable plastic sheet between parallel, spaced apart
glass panes, which are spaced from one another and from the
plastic sheet (film) by means of spacers arranged about the
edges of the glass panes. The panes are sealed to one
another along their edges by the spacers and by a sealant
adhered to edges of the plastic sheet to provide, with the
heat-shrinkable plastic sheet, a sealed and integral unit.
The unit itself is then heated for a sufficient time, and at
a sufficient temperature, to cause the plastic sheet to
shrink and become taut and wrinkle-free. Upon cooling, the
resulting integral unit requires no further manufacturing
steps, and is directly insertable into an appropriate window
frame as an insulating glass unit.
Further evaluation of the above patent found that
successful construction was dependent upon the sealant
materials used. For example, the edge sealant utilized
therein was a two-part, room-temperature vulcanizable (RTV)
resin, identified as GE3204TM (manufactured by General
Electric Company, U.S.A.). While the necessary adhesion to
hold the glass panes together along with the spacers was
provided, our efforts found that the plastic sheet became
wrinkled in a short time after manufacture. In addition to
GE3204TM, various silicone sealants were tried by us as edge
CA 02209982 1997-07-08
sealants in making window units with an intermediate plastic
sheet. As far as we know, however, no silicone sealant
appeared completely satisfactory.
U.S. Patent 4,613,530 teaches that the edge
sealant should be polyurethane. Although polyurethanes are
useful for the multiple-pane glass units described by U.S.
Patent 4,335,166, they are degraded by exposure to W
radiation if installed without a proper glazing cap to
protect the sealant. Similarly, U.S. Patent 5,308,662
discloses the pros and cons of various kinds of edge
sealants and then proposes a mechanical means to overcome
the degradation effects of W radiation. The silicone
sealants of this latter patent are resistant to light
induced cross-linking and hardening which cause serious
problems in other sealants, but they are also very permeable
to water vapor. The organic sealants, such as polyurethanes
and polysulfides, are damaged by sunlight and their
constructions require a nonreflective dark tape to be
positioned exactly right to overcome the impact of W
radiation on the edge sealant.
U.S. Patent 5,156,894 provides suitable edge
sealants for multiple-pane glass units that are manufactured
from curable, high modulus, low-creep, low-moisture, low-
vapor transmitting sealants, such as polyurethanes, for
example, the two-component polyurethanes marketed by Bostik,
such as Bostik~ 3180-HM or 3190-HM. U.S. Patent 4,853,264
claims the same kind of edge sealants for use on curved
triple-pane glazing in which a plastic sheet is positioned
intermediate between two glass panes. This plastic sheet is
anchored along the parallel curved edges but is not attached
to the other edges. Further, the plastic sheet heat shrinks
in the direction that it is anchored.
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.
It is an object of our inventiOn to provide a
multiple-pane glass unit containing a heat-shrunk flexible
plastic sheet made with a silicone sealant as an edge
sealant. It is also our object to provide a method of
manufacturing such a unit.
This invention is a sealed insulating glass unit
comprising at least one flexible, heat-shrunk plastic sheet
positioned between parallel, spaced panes. Therein, each
sheet is parallel to, but spaced apart from, confronting
surfaces of the panes or another plastic sheet; and each
sheet is fixed at its edges with respect to edges of the
panes. A silicone edge sealant is used between adjacent
edges of said panes to provide an integral sealed unit, at
least two opposing edges of said unit having each plastic
sheet embedded into the silicone edge sealant. An essential
feature therein is a silicone edge sealant that exhibits a
sheet creep of less than 0.018 cm after 500 hours at 71~C.
This invention also provides a method of
manufacturing a multiple-pane insulating glass unit
comprising
(a) forming a sealed integral unit comprising
supporting at least one flexible, heat-shrinkable plastic
sheet between parallel, spaced apart glass panes, the sheet
being substantially parallel to, but spaced apart from,
confronting surfaces of the panes and being fixed at its
edges with respect to edges of the panes;
(b) applying a curable silicone edge sealant
composition between adjacent edges of the panes to provide
an integral sealed unit and embedding into said curable
silicone edge sealant composition at least two opposing
edges of each flexible, heat-shrinkable plastic sheet;
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(c) curing the silicone edge sealant composition;
and then
(d) heating the unit to cause each plastic sheet
to shrink and become taut or wrinkle-free between the panes,
where said silicone edge sealant exhibits a sheet creep of
less than 0.018 cm after 500 hours at 71~C.
FIG. 1 is a perspective view, partly broken away
and in section, of a window unit.
FIG. 2 is an exploded cross-sectional view showing
elements of the window unit ready for assembling.
FIG. 3 is a cross-sectional view similar to that
of FIG. 2 but showing the window elements assembled.
FIG. 4 is a cross-sectional view similar to that
of FIG. 3 and showing the window unit after the heating
step.
FIG. 5 is a cross-sectional view similar to FIG. 4
but enlarged to show the constructional relationships more
clearly.
FIG. 6 is an enlarged, fragmentary cross-sectional
view of a window unit showing an embodiment in which an
electrical lead is electrically coupled to the plastic sheet
and ground.
FIG. 7 and FIG. 8 are cross-sections of
alternative configurations for single seal, triple glazed
sealed units incorporating a plastic inner sheet.
FIG. 9 is a cross-section of a quad glazed window
unit incorporating two plastic inner sheets.
FIG. 10 is a perspective illustration showing a
curved glazing structure in use in a greenhouse.
FIG. 11 is a cross-sectional view of a curved
glazing structure taken parallel to the straight sides of
the structure of FIG. 10.
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FIG. 12 is a cross-sectional view of a glazing
panel taken parallel to the curved side of the structure of
FIG. 10.
FIG. 13 is a perspective view of the sheet creep
test assembly.
FIG. 14 is a side sectional view of the sheet
creep test assembly showing the dimensions.
FIG. 15 is a front sectional view of the sheet
creep test assembly showing the ~;men~ions.
Reference Numberal Key
multiple-pane window unit
12 spaced pane
13 silicone edge sealant
14 spaced pane
flexible heat shrinkable plastic sheet
16 taut, flexible, heat-shrunk plastic
sheet
17 electrically conductive lead coupling
plastic sheet 16 to ground
18 spacer
spacer
21 foam spacer
22 outer window frame
23 pressure sensitive adhesive
24 gas barrier sealant
gas barrier sheet
26 gas barrier sealant
28 gas filled space
gas filled space
31 curved edge
32 curved edge
33 curved glass pane
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34 curved glass pane
flexible heat shrunk plastic sheet
36 spacer
37 spacer
38 spacer
39 spacer
41 spacer
42 spacer
43 spacer
44 spacer
frame member
46 straight edge
47 straight edge
greenhouse structure
52 flat wall window unit
53 flat roof window unit
54 curved window unit
56 clear float glass panel
57 clear float glass panel
59 test edge sealant
61 aluminum bar
62 aluminum bar
64 screw and nut fastener to clamp
screw and nut fastener to clamp
67 aluminum foil
68 hole for hanging weights
spacer
71 spacer
H1 0.33 cm height
H2 5.08 cm height
H3 2.235 cm height
H4 15.57 cm height
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H5 6.35 cm height
D 0.356 cm diameter
L1 7.09 cm length
L2 5.08 cm length
L3 2.54 cm + 0.038 cm
We have found that certain silicone sealants used
as an edge sealant 13 in a multiple-pane window unit 10
having at least one internal taut, flexible, heat-shrunk
plastic sheet 16, keeps the plastic sheet wrinkle-free for
longer time periods than previously known silicone sealants.
Also, our edge sealant 13 exhibits W stability for longer
time periods than polyurethanes or polysulfides. When
window units 10 are made using our silicone edge sealants 13
which have a sheet creep of less than 0.018 cm after 500
hours at 71~C., preferably less than 0.018 cm after 1,000
hours at 71~C., the heat-shrunk plastic sheet is retained in
a taut condition and is wrinkle-free. In contrast, those
silicone sealants which have a sheet creep of greater than
0.018 cm after 500 hours at 71~C. will fail by exhibit of
wrinkling in the plastic sheet and by the resulting optical
distortions or waves producted therefrom that are
unacceptable to the end user.
Although not bound by the following theory, we
believe that those silicone sealants, having a sheet creep
greater than 0.018 cm after 500 hours at 71~C., do not
contain one or more ingredients that are present in
sufficient quantities, either singly or collectively, to
achieve an acceptable sheet creep property. It is thought
that such ingredients are active after the sealant is cured,
either during the heat shrink step or during the window unit
life, causing said sealant to change properties and yielding
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unacceptable distortions in the plastic sheet. For
instance, some silicone sealants, having a sheet creep
greater than 0.018 cm after 500 hours at 71~C., were found
to contain either a plasticizer or a bond rearranging
ingredient that remained active after the sealant cured; or
said sealants contained both plasticizer and a bond
rearranging ingredient. Our taut, flexible, heat-shrunk
plastic sheet 16 is embedded in our silicone edge sealant 13
to anchor the plastic sheet. If the silicone edge sealant
allows the anchored portion of the plastic sheet 16 to
relax, which is under tension, then the undesirable effect
of wrinkling will occur. Because optical properties are
very sensitive to any distortion, even slight wrinkling or
waves produce unacceptable windows.
Silicone sealant compositions curable under
ambient conditions, such as in atmospheric air at room
temperature, have now been found capable of meeting our low
sheet creep requirements of less than 0.018 cm after 500
hours at 71~C. In particular, these silicone sealants are
known as one-package or two-package RTV silicone sealant
compositions that are characterized by being void of
ingredients that cause sheet creep to increase to greater
than 0.018 cm after 500 hours at 71~C. Two-package RTV
silicone sealant compositions can be used to provide faster
curing products than one-package compositions.
It is believed that ingredients which cause such
an increase in sheet creep include plasticizers and/or
siloxane bond rearranging ingredients that remain active
after the RTV composition has cured to a sealant. Examples
of suitable silicone sealant compositions that are useful as
edge sealants which exhibit a sheet creep of less than 0.018
cm after 500 hours at 71~C are: Dow Corning(R) 3-0117
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Silicone Insulating Glass Sealant (hereinafter DC 3-0117)
comprising a polysiloxane, calcium carbonate and
methyltrimethoxysilane; Dow Corning(R) 3145 RTV MIL-A-46145
Adhesive/Sealant (hereinafter DC 3145) comprising a hydroxy-
terminated dimethylsiloxane, trimethylated silica, titanium
dioxide and methyltrimethoxysilane; and Dow Corning(R) 995
Silicone Structural Adhesive (hereinafter DC 995) comprising
a polysiloxane, calcium carbonate and methyltrimethoxy-
silane. These sealant compositions do not contain
plasticizer or a siloxane bond rearranging ingredient that
rem~;n.~ active after the sealant composition is cured.
When similar silicone sealant compositions do
contain plasticizer and/or a siloxane bond rearranging
ingredient, they exhibit a sheet creep of greater than 0.018
cm after 500 hours at 71~C. Such products include Dow
Corning(R) 982 Silicone Insulating Glass Sealant
(hereinafter DC 982) comprising a two-package product of a
base and curing agent, wherein the mixed composition
contains a hydroxy-terminated dimethylsiloxane, calcium
carbonate, tetrapropyl orthosilicate, gamma-aminopropyl-
triethoxysilane, carbon black, polydimethylsiloxane and
dibutyltin dilaurate and where the polydimethylsiloxane acts
as a plasticizer and the dibutyltin dilaurate acts as a
siloxane bond rearranger within the cured sealant; and Dow
Corning(R) 795 Silicone Building Sealant (hereinafter DC
795) which is a one-package sealant composition hydroxy-
terminated dimethylsiloxane, calcium carbonate, amorphous
silica, methyltrimethoxysilane and polydimethylsiloxane,
wherein the polydimethylsiloxane acts as a plasticizer.
Both DC 982 and DC 795 exhibit sheet creep of greater than
0.018 cm after 500 hours at 71~C. Other silicone sealants
in this category include a one-package silicone sealant,
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known as GE SCS 2501~ and a two-package sealant, known as
GE3204~, both from General Electric Company.
When DC 3-0117, DC 3145 and DC 995 were used as a
silicone edge sealant 13, they exhibited a sheet creep of
less than 0.018 cm after 1,000 hours at 71~C. In
comparison, those silicone sealants which failed and
exhibited wrinkling of plastic sheet 16 exhibited sheet
creeps of more than 20 times greater after only 500 hours at
71~C.
The methods of making window units and the
construction of windows for the embodiments of this
invention are similar to those which are described in the
prior art. The principle difference is using our silicone
sealant composition to produce an edge sealant 13 where the
resulting cured silicone sealant exhibits a sheet creep of
less than 0.018 cm after 500 hours at 71~C. A silicone edge
sealant is easily penetrated by water vapor; and thus there
is a requirement to provide a means to prevent egress of the
insulating gas used to fill spaces 28 and 30, and to also
prevent the ingress of water vapor into these spaces 28 and
30. One means to prevent gas egress and water vapor egress
is the use of gas barrier materials as illustrated by gas
barrier sealant 24 and 26 or gas barrier sheet 25. The
phrase "gas barrier sealant" means that neither water vapor
or inert gases will pass through said sealant in any
substantial amount which alters the functioning of the
resulting window construction for the expected lifetime of
consumer use.
FIG. 1 shows a completed multi-pane window unit 10
resulting from a method of this invention comprising at
least a pair of parallel, spaced apart panes 12 and 14 and
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an intermediate flexible, heat-shrunk plastic sheet 16 that
is parallel to said panes, but spaced inwardly from each
pane. Although panes 12 and 14 are referred to as being
glass throughout this description, it is understood that
these panes may be made of other construction materials,
such as rigid plastics like polyacrylic or polycarbonate.
However, glass is the most common material for window
construction and panes are typically referred to as glass
panes. The panes 12 and 14 are provided with opposing
spacers 18 and 20, about their peripheral edges, the spacers
supporting said panes in their spaced, parallel relationship
to our plastic sheet 16. Plastic sheet 16 may be coated or
tinted, as desired, to provide any known window effect used
in the art. The thickness of plastic sheét 16 in FIG. 1 is
slightly exaggerated to merely illustrate the position of
said sheet relative to panes 12 and 14. Window frame 22
illustrates that glass window units are produced with frames
which are well-known in the art and that there is no need
for further details here.
In our method of manufacturing window units, panes
12 and 14 are provided and are cut to the same length and
width dimensions. To one surface of each of the panes is
adhered a spacer (18 and 20 as shown in FIG. 2), the spacer
extending about the periphery of the pane and spaced
inwardly from the pane edge, as shown in FIG. 5, which is
also enlarged for illustrative purposes. Each spacer
comprises an elongated shape of aluminum, plastic or other
rigid material, the shape desirably having walls formed to
provide hollow interior and flattened, parallel exterior
wall portions. The hollow portion may also contain a
desiccant, such as a silica gel. The spacer is adhered, for
example, to the surface of the glass pane by a gas barrier
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13
sealant (24 and 26) such as polyisobutylene which is capable
of withstanding temperatures of 121~C. without substantial
deterioration.
A flexible heat shrinkable plastic sheet 15 is
drawn across spacers 20 carried by one of the panes and is
pulled as taut as practical, as illustrated by FIG. 2, so
the sheet 15 comes into contact with a sealant, such as the
gas barrier sealant 26, on spacer 20 as shown. The other
pane 12, with its peripheral spacer 18 is oriented with
respect to the first pane 14 so that gas barrier sealant 26
on spacer 18 is opposite to spacer 20 and in a direct
opposed relationship, plastic sheet 15 being captured
between the opposing sealants 26. The plastic sheet 15,
being flexible, ordinarily contains waves and wrinkles at
this stage, as shown diagramatically and in exaggerated form
in FIG. 3. Edge sealant 13 is then applied between the
edges of the glass panes which extend outwardly of the
spacers 18 and 20, such edges forming, with the spacers, a
slight depression or trough in the edge of the assembled
unit. The edges of plastic sheet 15 extend into the
depression as shown in FIG. 3 and FIG. 5. The silicone edge
sealant is then cured in place to adhere the panes together
strongly enough to allow movement of the units. The panes,
the outwardly exposed portions of the spacers, and the edges
of the plastic sheet thus form an integral unit.
Plastic sheet 15 is preferably oriented midway
between the surfaces of confronting panes 12 and 14. It is
understood that the plastic sheet, when shrunk, exerts
inwardly directed forces on the spacers which in turn cause
compressive forces to be exerted on, and in the plane of,
said panes. By having the plastic sheet midway between the
confronting pane surfaces, the compressive load borne by
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14
each pane, although slight, is expected to be approximately
equal.
The integral unit is then heated, such as by
placing it into a forced air oven, for a period sufficient
to cause the heat shrinkable plastic sheet to shrink to the
extent necessary to remove all wrinkles or waves in the
sheet. The sheet is held at its edges by spacers 18 and 20
and silicone edge sealant 13. Edge sealant 13 will resist
softening during the heating step to heat-shrink the plastic
sheet; it will not deteriorate during the heating step; and
the sealant anchors the edges of the sheet and prevents its
movement with respect to the panes. The silicone edge
sealant holds the plastic sheet in position and does not
relax, either during the heating step or thereafter. Such
relaxation or sheet creep will undesirably result in
wrinkles or waves that yield unacceptable optical
distortions. It is important to equalize the gas pressure
between gas filled spaces 28 and 30. This pressure
equalization is accomplished by providing one or more
perforations in the plastic sheet. FIG. 4 illustrates a
multi-pane window unit 10 after the heating step and with
the heat-shrunk plastic sheet 16 in its taut condition.
FIG. 5 illustrates, in an enlarged view, the positioning of
the taut heat-shrunk plastic sheet 16 with respect to panes
12 and 14, the gas barrier sealant 24 and 26, the spacers 18
and 20 and edge sealant 13.
Flexible heat shrinkable plastic sheets 15 are
known in the art and are available commercially. Such
sheets are produced by stretching the sheets in their length
and width dimensions at temperatures below their melting
point to provide molecular orientation in the sheets.
Subsequently heating the sheets reduces the molecular
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orientation thereby causing the sheets to shrink in length
and width dimensions. One preferred plastic for making
these sheets is a polyester known as polyethylene
terephthalate. Common temperatures for causing such
materials to shrink are in the range of 90 to 121~C.
Plastic sheets 15 preferably have thicknesses of from 0.01
to 0.5 mm. These sheets can be coated or tinted with dye to
provide desirable or pleasing window effects. The sheets
may also be coated on one or both sides with coatings which
are highly transmissive of visible light, but are highly
reflective of long wave infrared radiation. For additional
details regarding conventional window construction and the
method of manufacturing window units which contain an
intermediate plastic sheet, see U.S. Patent 4,335,166.
In buildings or enclosures, it is desirable to
provide windows and doors which will allow natural light to
enter said building or enclosure that are also shielded from
electromagnetic radiation, such as microwave radiation.
Yet, these window units should also be heat insulating while
rem~ining transparent to visible light. Such buildings or
enclosures might be used for housing digital computers or
sensitive electronic equipment which are adversely affected
by high or low level radiation in the range from kilohertz
to gigahertz frequencies. There also exists a security need
in many government and military buildings for shielding
interiors thereof to prevent electronic eavesdropping or
espionage. The ability to remotely access information
through electronic monitoring is significantly reduced by
the use of electronic shielding techniques when combined
with properly designed shielded walls, roofs and floors.
U.S. Patent 4,613,530 shows window units
containing a heat-shrunk plastic sheet 16 which is coated
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16
with an electrically conductive coating as a transparent
thermally insulating sheet that also serves as a shield for
electromagnetic radiation. Such electrically conductive
heat-shrunk plastic sheets are made with a metallic coating
deposited to one or both sides of the sheet. These coatings
are produced by vacuum deposition of materials which result
in optically transparent films in the 400 to 700 nm range
(visible region) but which also have electrical conductivity
sufficient to attenuate electromagnetic energy in the longer
wavelength range, 104 to 101~ nm, of radio frequencies.
FIG. 6 illustrates an electrically conductive heat-shrunk
plastic sheet 16 with an electrically conductive lead 17
from said sheet to ground. Thus, it may become necessary to
extend the plastic sheet through the edge sealant to make
such a connection.
This invention includes insulating glass units
which contain one or more intermediate taut, flexible, heat-
shrunk plastic sheets and also other kinds of spacers such
as in U.S. Patent 5,007,217, shows in more detail glass
units with more than one taut plastic sheet, other kinds of
spacers or combinations of spacers, and other methods of
making such glass units. FIG. 7 and FIG. 8 show triple
glazed units with an intermediate plastic sheet 16. As
illustrated in the aforementioned patent, such plastic
sheets are coated with a low-emmissivity coating, such as a
product of Southwall Technologies, Palo Alto, California,
and sold under the name of Heat Mirror~.
FIG. 7 shows a conventional metal T-shaped spacer
18 with a foam spacer 21 that typically contains desiccant.
The flexible or semi-rigid foam spacer 21 is manufactured
from thermoplastic or thermosetting plastics. Suitable
thermosetting plastics include silicone and polyurethane and
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suitable thermoplastics include thermoplastic elastomers
such as Santoprene~. Preferably, the foam is a silicone
because of its advantages, including good durability,
minimal outgassing, low compression set, good resilience,
high temperature stability and cold temperature flexibility.
Silicone foam is also moisture permeable so moisture vapors
can readily reach the desiccant material within the foam.
An assembled metal spacer frame is laid on top of said
plastic sheet and the sheet is adhered to the spacer with a
pressure sensitive adhesive 23. The sheet is then cut to
size in a conventional way so it extends into the groove
created by spacer 18. A foam spacer 21 is then laid on top
of the plastic sheet in line with spacer 18 below and
adhered to said sheet with pressure sensitive adhesive 23.
The plastic sheet 15, spacer 18 and foam spacer 21
combination is then sandwiched between panes 12 and 14. The
outward facing perimeter is next filled with edge sealant
13. This edge sealant composition cures and bonds strongly
to the plastic sheet, glass panes and spacers to hold the
unit in position. Plastic sheet 15 is then heat-shrunk by
exposing the assembled unit to heat by placing it in an air
circulating oven thereby producing a taut, flexible, heat-
shrunk plastic sheet 16 intermediate between panes 12 and
14. A gas barrier sheet 25 is also shown in the unit
construction of FIG. 7.
FIG. 8 is an alternate construction of a glazed
unit, similar to the one illustrated by FIG. 7, but where
both spacers are foam spacers 21. FIG. 9 shows a quad
glazed unit containing two taut, flexible, heat-shrunk
plastic sheets 16 which are adhered to spacer 18 with
pressure sensitive adhesive 23. On either side of spacer
18, there is a foam spacer 21 typically containing desiccant
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and backed with gas barrier sheet 25. This window unit of
FIG. 9 is constructed using essentially the same method of
manufacturing as described above using foam spacers, except
it incorporates an additional flexible heat shrinkable
plastic sheet 15 and foam spacer 21. The three
interconnected gas filled spaces 28 are then filled with a
very low heat conductive gas such as krypton. This type of
window construction is further illustrated by U.S. Patent
4,831,799, which can be consulted fro more details on
multiple layer insulating glazing units with foam spacers.
Silicone edge sealant 13 of this invention also
finds use in constructing curved glazing structures, such as
those described in U.S. Patent 4,853,264. FIG. 10 shows a
greenhouse structure 50 which is an assembled curved glazing
structure having a frame member 45, flat wall window unit
52, flat roof window unit 53, curved window unit 54,
straight edges 46 and 47, and curved edges 31 and 32. The
two curved edges are parallel to one another and the two
straight edges are parallel to one another.
FIG. 11 is a cross-section taken along lines 11-
11' in FIG. 10 and shows two curved panes 33 and 34 with
flexible heat-shrunk plastic sheet 35. Plastic sheet 35 can
have a heat-reflective layer on its outer side, i.e. the
side facing out of a building. Glass panes 33 and 34, and
plastic sheet 35, are spaced apart from one another by gas
filled spaces 28 and 30 by means of spacers 36, 37, 38 and
39. The spacers together with edge sealant 13 and gas
barrier sealant, grip and adhere plastic sheet 35 into the
structure along curved edges 31 and 32. In contrast, and as
shown in FIG. 12, plastic sheet 35 is not affixed to curved
panes 33 and 34 at the edges parallel to straight sides 46
and 47. At these edges, spacers 41, 42, 43, and 44 serve to
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19
join panes 33 and 34. The spacers 36, 37, 38, 39, 41, 42,
43, and 44 are illustrated as individual components, but in
actual practice can be assembled into cured rectangular open
frames.
Typical spacer materials are plastic extrudates
and aluminum or steel extruded and roll-formed channels,
such as those described U.S. Patents 4,335,166 and
4,853,264. These spacers can be of any cross-section and
the distorted circles shown in FIG. 11 and FIG. 12 are
merely representational since they can also be generally
rectangular or square cross-sections. To achieve a good
parallel relationship among the two panes and the
intermediate plastic sheet, the heat-shrinkable plastic
sheet will shrink, preferentially, perpendicular to the
curved edges to which the plastic sheet is attached. For
example, using a 0.0254 cm polyester as the plastic sheet
and heating at 93 to 104~C., it is possible to obtain an
overall shrinkage in the range of 0.4-0.5~ in one direction
and a shrinkage in the range of only 0.1-0.2~ in the other
direction. Such plastic sheets are typically oriented with
the high-shrink direction being between the two curved
edges. In fabricating such window units, one can use
plastic sheet coated with a dielectric-metal, dielectric-
interference filter or heat and light-reflecting layers,
such as taught by U.S. Patent 4,337,990 which details
plastic sheets containing coatings for various purposes.
Edge sealant 13 as described herein, in a variety
of window constructions containing intermediate taut,
flexible, heat-shrunk plastic sheets, imparts said window
constructions with a longevity of the plastic sheets not
previously observed. The utility of heat-shrunk plastic
sheets depends upon its maintaining its taut condition over
CA 02209982 1997-07-08
the expected life of the window construction without
permitting formation of waves or wrinkles that create
optical or reflective distortions. It is the use of our
silicone edge sealant 13 which provides these advantages in
these window units and the employment of our methods of
manufacturing a variety of constructions.
Silicone edge sealants, suitable for the
construction of window units by our invention and our
methods of manufacturing such window units, must have a
sheet creep of less than 0.018 cm after 500 hours at 71~C.
The sheet creep was determined by a high temperature sealant
creep test which follows:
A 5.08 cm H2 by 5.08 cm L2 cross-section of an
insulating glass test unit was constructed as illustrated by
FIG. 13, FIG. 14 and FIG. 15, where an aluminum strip 67
having a thickness of 0.381 mm, was substituted for a
plastic sheet. A load of 3.6 kg was applied by hanging
weights from hole 68 having a 0.356 cm diameter D for a test
period measured in hours at 71~C + 1~C. A fixed reference
point was used to monitor the relative movement due to
sealant creep (sheet creep). The amount of creep allowed by
the test edge sealant 59 was observed and recorded
identifying the load and length of time of the test. FIG.
13 illustrates the positioning of spacers 70 and 71, test
edge sealant 59, aluminum bars 61 and 62 which were held in
place by screw and nut fasteners 64 and 65 to clamp the
aluminum bars to the aluminum sheet 67 to measure the amount
of creep. Spacers 70 and 71 were 5.08 cm long and 0.8 cm
wide. The glass panes of the test units were 5.08 cm
squares of clear float glass with a 0.3 cm thickness.
Aluminum sheet 67 was 5.08 cm by 15.24 cm by 0.381 mm. The
CA 02209982 1997-07-08
aluminum bars 61 and 62 were 0.635 cm by 0.635 cm by 7.94
cm.
Each edge sealant compositions to be tested were
used to prepare insulating glass test units as described by
FIG. 13, FIG. 14 and FIG. 15, along with the description
provided here. Epoxy resin was used to adhere the spacers
to the glass test panes and the aluminum sheet in the
construction as identified by the drawings. Within one hour
after the epoxy resin was applied, a sealant composition,
mixed if a two package composition, was applied to complete
the glass test unit. Each test unit was cured for at least
21 hours at 21~C. The aluminum bars were attached to the
aluminum sheet and secured with the screw and nut fasteners
as shown. The glass test unit was then mounted along with a
linear displacement measurement device as the reference
point.
Each edge sealant composition was tested at least
three times. Each test unit was placed in a forced-
convection oven at 71~C. where the temperature was
maintained within 1~C. An oven with a transparent door was
used so the movement of the aluminum bar could be observed
without disturbing the test units. It was required that the
fixtures for mounting the glass test units in the oven
evenly supported the two glass panes in each sample and that
the aluminum sheet with attached weights did not touch the
fixture. The fixtures also kept the glass panes parallel to
each other with an allowable deviation from parallel of
0.127 mm m~;mnm. The load on each test unit aluminum sheet
acted along the vertical centerline of the sheet. The
device used to measure the linear displacement of the
all~m;nllm bars had a range of 0 to 2.54 cm with minimum
marked increments of 0.025 mm.
CA 02209982 1997-07-08
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CA 02209982 1997-07-08
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22
Each creep test was started within 72 hours of the
application of the edge sealant composition. The test units
were placed in the test oven, load (weights) was placed on
the aluminum sheet being careful to avoid impact loading.
The measuring device was zeroed between 2 and 5 minutes
after loading the weights. Creep data were recorded daily
by recording the hours from zeroing the measuring device,
the observed displacement and sheet creep. Each edge
sealant composition was at least tested three times and the
average was recorded as shown in the Table. Sheet creep of
less than 0.018 cm after 500 hours at 71~C. was considered
to be acceptable for our silicone edge sealants. Also,
extrapolating the data out to 10 years by observing the rate
of change, was considered an acceptable sheet creep if such
an extrapolation was found to be less than 0.018 cm at the
10 year time.
The sealant compositions tested for sheet creep
were as follows: DC 3-0117, DC 3145, DC 995, DC 982, DC
795, GE SCS 2501, Bostik~ 3180-HM, Novaguard~ 470 and
GE3204. The values for the resulting sheet creep are given
in the Table, except it was observed that GE3204 resulted in
wrinkling of a taut, heat-shrunk plastic sheet in a
relatively short time period.
