Note: Descriptions are shown in the official language in which they were submitted.
103SZ7S
This invention is concerned with a process
for producing a laminated safety glass, a heat reflective
laminated glass or a heat reflective laminated safety glass.
It is particularly well adapted to a continuous process.
Thls invention is concerned also with the product of such
process.
The normal procedure in prior art processes
has involved the use of high temperatures to cure the adhesive
which joins the glass laminates or secures the plastic
interlayer to the sheets of glass with which it is laminated
and usually high pressure to drive out air so as to develop
a product having satisfactory optical properties. Autoclaves
and hot presses have commonly been used and these are costly
and provide a limitation on the rate of production, as they
are in the nature of a batch process.
An object of this invention is to provide a ~ -
process which utilizes moderate temperatures and pressures -~;
so as to be adaptable to a continuous process on a conveyor.
A further object of this invention is to provide
a method of removing air from within the laminate without the
necessity of subjecting the laminate to high temperatures and
- pressures or vacuum. In particular, an object is to solve
the difficult problem of satisfactorily removing air bubbles
from the adhesive layer between a glass sheet or a glass sheet
to which an interlayer has been applied such as a plastic film
or heat reflective coating and a second glass sheet applied
to the adhesive layer. -
In accordance with one aspect of this invention
a method is provided for producing a laminated glass having
an interlayer comprising the steps of applying to the
inwardly facing surface of a first or second sheet of glass
an interlayer of plastic film, heat reflective coating or both
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plastic film and heat reflective coating, conveying said first
sheet of glass to an adhesive application zone, in said ad-
hesive application zone applying a solvent free adhesive which
is capable of anaerobic curing under ambient conditions, applying
to said adhesive a second sheet of glass in registration with
the first sheet of glass, said interlayer being between the
first and second sheets of glass, conveying the assembly of
the first and second sheets of glass and interposed interlayer
to a pressing zone, the dwell time and temperature conditions
from the adhesive application zone to the pressing zone being
such that the adhesive has not gelled or is at the stage of
incipient gellation, in said pressing zone applying moderate
roller pressure under conditions such that the second glass
sheet is caused to delaminate from the underlying surface at
the input side of the roller to permit air to be released and
to cause an interface to form, extending across the glass sheet
between an area which is free from air bubbles and an area where
there are air bubbles in said adhesive and at least partially
curing the adhesive under moderate temperature and pressure
conditions whereby a laminated glass is provided which is sub-
stantially free from visible air bubbles without the use of an
autoclave.
In accordance with another aspect of this invention
a method is provided for producing a laminated safety glass
comprising the steps of conveying a first sheet of glass having ~-
a film of plastic adhered to its upper surface to an adhesive
application zone, in said adhesive application zone applying .
to the outer surface of said plastic film a solvent free
adhesive which is capable of anaerobic curing under ambient
conditions, applying to said film a second sheet of glass in
registra~ion with the first sheet of glass, conveying the
assembly of the first and second sheets of glass and interposed
plastic film to a pressing zone, the dwell time and temperature
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conditions from the adhesive application zone to the pressing
zone being such that the adhesive has not gelled or is at
the stage of incipient gellation, in said pressing zone applying
moderate roller pressure under conditions such that the second
glass sheet is caused to delaminate from the underlying plastic
film at the input side of the roller to permit air to be released
and to cause an interface to form, extending across the glass
sheet, between an area which is free from air bubbles and an
area where there are air bubbles between the plastic film and the ~ .
second glass sheet and at least partially curing the adhesive : -
applied in the second adhesive application zone under moderate
temperature and pressure conditions whereby a laminated glass is ~
provided which is substantially free from visible air bubbles . ~ -
without the use of an autoclave. ~ `
In accordance with another aspect of this invention ~ ~ -
a continuous process is provided for producing a laminated -~
safety glass comprising the steps of: ;
(a) conveying a first series of flat sheets of glass
arranged end to end to a first adhesive application zone;
(b) applying to a surface of each of said sheets in
said first adhesive application zone a solvent free adhesive
which is capable of anaerobic curing under ambient conditions;
(c) conveying each of said sheets of glass to a
film application zone;
(d) in said film application zone applying a film
of flexible plastic to said surface of each of said sheets
of glass; `
(e) conveying each of said sheets of glass to a first
pressing zone, the dwell time during which the sheets are con-
veyed to the pressing zone and the temperature conditions being
such that the adhesive is gelled and tacky, but there is
the possibility of limited relative movement between the
plastic fil~ and said glass sheets;
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(f) in said first pressing zone applying moderate
roller pressure to said plastic film to smooth out any wrinkles
in said plastic film and to expel any air trapped between the
plastic film and the glass sheets;
(g) conveying said sheets to a second adhesive
application zone;
(h) in said second adhesive application zone applying
to the outer surface of said plastic film a solvent free
adhesive which is capable of anaerobic curing under ambient
conditions;
(i) applying to said outer surface of said plastic film
a second series of sheets of glass in registration with the
sheets of said first series;
(j) conveying the assembly of sheets of the first and
second series of sheets of glass and interposed plastic film
'o a second pressing zone, the dwell time and temperature
conditions from the second adhesive application zone to the
second pressing zone being such that the adhesive applied in
the second adhesive application zone has not gelled or is at
the stage of incipient gellation;
(k) in said second pressing zone applying moderate
roller pressure under conditions such that the second glass
sheet is caused to delaminate from the underlying plastic film ~-
at the input side of the roller to permit air to be released
and to cause an interface to be formed, extending across the
glass sheet, between an area which is free from air bubbles and
an area where there are air bubbles between the plastic film and
the second glass sheet;
(1) at least partially curing the adhesive applied in
the second adhesive application zone under moderate temperature
and pressure conditions whereby a laminated glass is provided
which is substantially free from visible air bubbles without the
use of an autoclave.
1038275
This invention also includes a glass laminate
comprising a pair of flat sheets of glass, an interlayer
selected from the group consisting of a film of plastic, a
heat reflec~ive metallic layer and both a film of plastic
and a heat reflective metallic layer laminated between said
sheets of glass and a layer of a solvent free adhesive cured
under anaerobic con~tions at moderate temperature, adhering ~ -
said interlayer to an overlying sheet of glass, said laminate
having been subjected to moderate rolling pressure to remove -
10 air bubbles from said layer of adhesive.
This invention may be applied to produce a safety ~ -
glass laminate without a heat reflective coating, or may be
used to provide a heat reflective safety glass by including
a heat reflective metallic coating or may be used to provide
a heat reflective laminate. , r
In the drawings which illustrate-the preferred -
, embodiment of this invention;
Figure 1 is a diagrammatic elevation view
illustrating the first section of a process in accordance
with this invention;
Figure 2 is a diagrammatic elevation view
- illustrating the second section of a process in accordance
with this invention. Figure 2 represents a continuation of
Figure 1.
Figure 3 is a detail plan view of the rollers
shown in Figure 2.
Figure 4 is a detail elevation view of the rollers
shown in Figure 3.
~eferring now to the drawings, Figures 1 and 2
illustrate a continuous conveyor chain 10 having a driving
sprocket 11 at one end driven by reduction gearing 12 from
motor 13. A second sprocket 14 is at the other end of the
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conveyor and there is a s~ries of intermediate supporting
rollers 15 driven by sprockets at the ends of rollers 15.
For convenience of illustration only some of rollers 15 are shown.
There will be an adequate number to support the glass. Rollers
15 may be fitted with annular rubber rings spread a few inches
apart to provide frictional engagement with the glass.
Flat sheets of glass 16 are transferred in
succession by a suitable means such as suction cups from a
stack (not shown) located close to sprocket 11 so that there
will be a series of sheets of glass lying end to end on the
conveyor as illustrated in Figures 1 and 2. Preferably the
adjacent ends of the sheets of glass are spaced a few inches.
Sheets of glass 16 are preferably float glass, as this provides
a particularly smooth surface, bUt good quality plate glass
may also be used. Glass of any standard thickness can be used.
The first step in the process should be to clean -
the glass and this may conveniently be carried out on the same
conveyor as used to form the laminate by providing a cleaning - `
zone. For this purpose polishing brushes 17 rotating about a
vertical axis are employed using a polishing powder such as
cerium oxide, following which a water spray 18 washes off
the polishing powder. Additional polishing ~rushes 19 rotating
about a horizontal axis are then applied to ensure the removal
of any residue of polishing powder. An additional water spray
20 which should use deionized water is then applied, followed
by the application, as illustrated at 21, of a sensitizer
such as stannous chloride to remove fats and oil and, in the
case of float glass, any metallic residue. The sensitizer
treatment is followed by an a~ditional water spray 22 wi~h
deionized water. It will be appreciated that sufficient
~rushes or sprays will be provided to treat the full width
of the glass sheets in the cleaning zone.
1038~qs
Where it is desired that the laminate produced in
accordance with this invention include a metallic heat reflect-
ive layer it will be convenient to include a metallizing zone
to deposit a metallic film on the first series of sheets of
glass. Another possibility is to metallize the sheets of the
second series of sheets of glass prior to their lamination
later in the process. Yet another possibility is to precoat ~ -
the plastic film which will be applied later in the process
with a metallic layer.
The metallizing zone, which as previously indicated
is optional, comprises metallic sprays 23 followed by a spray
of deionized water 24. In the metallizing zone an optical
coating of metal such as silver or copper may be applied using
known techniques.
The next step is to dry the surface of the glass --
using air blowers 25 and 26.
The sheets of glass of the first series are then
passed to an adhesive application zone which includes infra red
lamps 27 which preheat the glass to about 40-50C. to reduce
the gel time of the subsequently applied adhesive and also
complete the drying of the glass. These are followed by a
roller coater 28 which applies a layer of adhesive to the
upper surface of the glass. The adhesive must be capable of
curing under anaerobic conditions and at ambient temperatures.
The gel time should be at least 15 minutes at ambient conditions.
It also must be free from solvent. It must also develop
an adequate bond between the glass and the particular plastic
which will be applied later in the process. The laminate
which is eventually produced should stand up to current
specifications with respect to resistance to boiling water,
fragmentation and impact resistance, such as Canadian Govern-
ment Specification 12-GP-IM dated October 1975. Any adhesive
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which meets these requirements may be used. But the most
satisfactory adhesive is an epoxy adhesive such as the material
sold by Hysol Division of the Dexter Corporation of Olean, New
York, under the trade mark Hysol R8-2038. Hysol R8-2038 is the
condensation product of epichlorhydrin and bisphenol A. A
wide variety of hardeners are available such as primary,
secondary or tertiary amines, acid anhydrides and Lewis acids.
A commercially available suitable hardener also sold by
Hysol Division of the Dexter Corporation is sold under the
designation H-3404 and is used in the proportion of about ~ -~
10:1 epoxy resin to hardener. The viscosity (Brookfield) of
the mix of epoxy and hardener at 25C. is about 500 centipoises. ~ - -
The gel time is about 25 minutes at 25C. and it will cure in ~ -
about 24 hours at 25C. The cure time is shortened to about
2 hours at 60C. Urethane adhesives are self polymerizing and
may be used but are not recommended as the bond is less
satisfactory than that obtained with epoxy adhesives.
The glass of the first series of sheets is then
conveyed to a film application zone 29. The film application
zone 29 comprises a reel of plastic film 30A, tensioning rolls
31 and 32 and applicator roll 33 which causes a film of plastic
30 to be laid down as the sheets of glass 16 of the first
series advance along the conveyor. A rubber pressure roll 33A
is located immediately below applicator roll 33 to provide a
back up roll.
The plastic film is preferably a polyester such as
that known under the trade mark Mylar and which is supplied by
E.I. Dupont of Wilmington, Delaware. With this polyester it
has been found that a film thickness in the range 1-1/2 to 5 mils
may be used which is less than the thickness of polyvinyl butyral
film of about 15 mils normally used for safety glass. A film
which is less than 1-1/2 mils is likely to cause problems of
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103~Z75
wrinklin~. Other plastic films such as polymethyl methacrylate,
polypropylene and polyamide may be used provided that an adequate ~ ~ -
bond is developed with the particular adhesive which is used.
It has been found that, with the preferred epoxy adhesive,
polyvinyl film and cellulose acetate film develop inadequate
bonds, but they might be satisfactory with a different formu-
lation of adhesive. Film such as polyester film is commercially
available having an optical layer of heat reflective metal
deposited on it and such film may be used as an alternative to
providing a metallizing zone where heat reflective properties
are desired.
Following application of the film the sheets of
glass are conveyed to a pressing zone. The dwell time and
spacing on the conveyor should be such that the adhesive has r
become gelled and tacky but not hardened by the time it reaches
pressure roller 35. There is therefore the possibility of
limited movement between the film and the underlying glass.
It will be appreciated that the curing can be
shortened by preheating the glass or by supplying heat after
the adhesive has been applied. With Hysol R8-2038/H-3404
and with preheating of the glass to 40 - 50GC~using infrared
lamps 34 a distance of about 15 feet with a conveyor travelling
18 inches per minute has been found to be suitable. The
precise-combination of conditions of time and temperature
indicated above are not intended to be limiting. A moderate
temperature preferably not in excess of about 50C should
however be used.
In the pressing zone a rubber roller 35 acts
-with back up roll 35A to apply moderate pressure to smooth out
any wrinkles in the plastic film and to expel any air trapped
between the plastic film 30 and the glass sheet 16. A pressure
of the order of magnitude of five pounds for a sheet of glass
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1038Z75
six feet in width and with rolls 6" in diameter has been found
to be satisfactory. Too little pressure will be ineffective
but excessive pressure will squeeze out too much of the
adhesive and may also damage the film. The thickness of the
adhesive after pressing may be approximately 0.025 mm.
A cutting knife 36 may be provided to sever the plastic between
successive sheets of glass.
The next step is to apply a layer of adhesive
to the upper surface of the plastic film and this is achieved
by roller coater 37.
A second series of sheets of glass 3~ is then
successively applied in registration with the first series by
being transferred in a conventional manner such as by the use
of suction cups from a stack (not shown). The inwardly facing
surfaces of sheets of glass 38 should first be cleaned as
described in connection with the first series 16. This may
conveniently be carried out by running the sheets through the
cleaning zone of the conveyor to prepare a stack of clean
sheets for use as the second series. ~- ;
The first and second sheets of glass between which
the plastic film is sandwiched are then advanced to a pressing
zone where rubber roller 39 cooperates with back up roller 40
to apply rolling pressure. As illustrated in Figure 4, the
rolls 39 and 40 are driven at the same rate in opposite
directions of rotation by chain 41. Motor 42 drives chain 41
through drive sprocket 43. A tension sprocket 43A is also
provided.
The dwell time between the application of the
adhesive by roller coater 37 and pressing with rollers 39 and
40 is short, represented by about 12 feet of travel on a
conveyor moving 18 inches per minute and preheating is avoided
so that the adhesive will not have gelled or at most will be
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~0;~75
at the sta~e o~ incipient ~ell. Rollers 39 and 40 are spaced
to accommodate the thickness of the sheets of glass together
with the plastic film, the adhesive securing the plastic film
to the underlying sheet of glass and the desired thickness of
adhesive between the upper sheet of glass and the plastic film
after pressing between rollers 39 and 40. A slight excess of
adhesive is applied by roller coater 37 which will result in
moderate pressure of the order of about ten pounds over a six
foot width being developed between rollers39 and 40 as the
assembly advances through the rollers 39 and 40 to squeeze out
the excess adhesive. Most of the excess adhesive flows in
a direction opposite to the direction of rolling. This pressure
of the wedging action of the excess adhesive will cause the
upper sheet of glass to bend upwardly slightly at the input
side of the rollers to delaminate from the surface of the
, underlying plastic 30 as illustrated at 44 in Figure 4. This
will provide for the release of air from between sheet 38 and
plastic film 30. As illustratPd in Figure 3 an interface 45
extending across the width of_the glass sheet will be apparent - --
in plan view between an area 46 which is free from air bubbles
and an area 47 which is clouded with air bubbles. This interface
is normally curved and is preferably spaced some 4" to 6" from
the rollers on the input side of the rollers. ~ -
The pressure exerted by rollers 39 and 40 must
be sufficient for the delamination and interface described
above to occur, but must not be such as to squeeze out an
excessive amount of adhesive. The adhesive applied by roller
coater 37 should be somewhat thicker than the adhesive applied
earlier by roller coater 28 to give a thickness of adhesive
of about 0.05 mm. before application of pressure. The
thickness of the adhesive after the application of pressure is
about .025.
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103~Zq5
The laminate is then advanced to a zone where
infrared lamps 48 raise the temperature to about 40-50C.
to advance the cure of the adhesive applied by roller coater
37 so that the laminate can safely be removed from the conveyor.
It will be appreciat~ that as an alternative the infra red
lamps 48 could be omitted and replaced by an extended dwell
time on the conveyor.
Where the desired product includes a heat reflect-
ive interlayer but safety qualities are not requixed, the process
described above in conjunction with Figures 1 to 4 may be used
employing the metallizing zone 23 but with the omission of the
roller coater 28, the film application zone 29, infra red~ ;
lamps 34 and pressing zone 35.
The nature of a process in accordance with this -
invention and the characteristics of the product will be
additionally illustrated by the following examples:
EXAMPLE I
A pair of sheets of glass 3 m.m. thick and
measuring 6" x 6" were laminated with 1-1/2 mil Mylar sheet
with a heat reflective silver coating using 4 litres of clear
Hysol R8-2038/H-3404 adhesive per 1000 square feet of glass
for the first or lower layer and 6 litres of such adhesive
for the second or upper layer. The procedure described in
detail in connection with Figures 1 to 4, scaled down for
sample preparation, was followed. The resultant product was
a reflective laminated safety glass which was optically
transparent with no visible signs of air bubbles. The sample
was subjected to the following tests:
- immersed vertically on edge in boiling
water for a period of 3 hours, then -
- immersed vertically on edge for a further
period of three hours in a boiling salt
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~03~2qs
water solution, then -
- put in a deep freeze unit with a temperature
of -5C for a further period of 12 hours.
On examination at the completion of this test cycle the subject
sample was found to have no signs of delamination at the edges
or discoloration of the polyester film or adhesive.
EXAMPLE II
The product tested was a laminated glass unit
18" x 24" fabricated from 2 lights of 3mm clear glass laminated
together using a 3 mil polyester film with a heat reflective
silver coating and clear Hysol R8-2038/H-3404 adhesive. It
was free from visible air bubbles. The sample was held in
a manner such that the 24" dimension was vertical and the glass
was struck in the lower centre area with a 10 lb. hammer.
The sample fractured on both sides and held
,together firmly with no delamination. The fracture pattern
of the side struck was a random mixture of small and medium size
pieces. The fracture pattern on the obverse side was fan shaped
with the origin of the fractur~_clearly outlined at the point
of striking. The pattern of fracture was similar to that
experienced when tempered glass is broken.
EXAMPLE III
Similar results to Examples 1 and II will be
obtained where the polyester film is not coated with an optical
layer of heat reflective silver or where a layer of heat
reflective silver is applied to one of the glass sheets.
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