Note: Descriptions are shown in the official language in which they were submitted.
IMP~O~EMENTS IN GLAZING LAMINATES
IELD oF_THE INVENTION
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This invention relates to articles of manufacture
u~eful in the assemblage of plural laminate structures, partic-
ularly glazing laminates, that is, plural-ply transparent or
translucent glass and/or plastic articles, such as, for example,
windshields, vehicle side windows, building lights, e~ye glasses
of various types, including safety and sun glasses, visors and
lenses. In addition, this inve~tion relates to tne method of
producing the articles of manufacture according to this invention,
to the composition of ~hich such articles are composed and to
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the production of laminates from said articles. Since the
invention is particularly advantageously embodied i.n vehicle
windshields, the invention is hereafter described in connection
with and as an improvement in laminated windshields of the
type now widely used. It should be understood tha~ the in-
vention can be utilized in applications involving other types
o-f laminates, as will be described in detail below.
The type of laminated windshield used most widely in
automobil~s at the present time comprises a sheet of poly
10 . ~vinyl butyral), a high energy-absorbing material, sandwiched
between and adhered to two plies o:E glass. Improvements to
windshields of this type are described in French Patent No.
2,1&7,719 an~ U.S. ~atent No. 3,979,548 to Schafer and
Radisch, eachh assigned to the same assignee as the present
invention. These.patents disclose the application to the inner
surface of the glass ply of a plastic material, for example,
a crosslinked or..thermoset polyurethane which imparts to the
windshield important and highly desired properties.
Upon impact by the head of an occupant, the plastic mat-
erial resists teari.ng and protects the occupant from being cutby the shattered edges of the inner glass ply. Further, the
occupant is protected from being cut by flying splinters of
glass in the event of impac-t :Erom outside the vehicle against
the exterior of the windshield, for example, by a stone
thrown accidentally by the tire of another vehicle. More
succinctly, the plastic material has anti-lacerative properties.
In addition, the plastic material has autorestorative or self-
healing properties, in that surface deformation such as local
indentations tend to heal or disappear relatively quickly,
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~L43~7
often even within several minutes~ or somewhat longer,
depending on the nature of the indentation and the temperature
of the plastic material. Such characteristics of the
thermoset polyurethane apparently result from a type of solid
state plastic memory.
Another important characteristic of the polyurethane
plastic sheet material is that it is sufficiently yielding
so that it doès not cause appreciable impact injury to the
human head when a collision causes an individual to strike
the windshield.
This invention relates to improved means by which a ther-
moset plastlc material of the aforementioned type is adhered
to a glass substrate or to a plastic substrate in a laminate
such as, for example, a windshield, including the type
described above.
REPORTED DEVELOP~ENTS
Various ways have been proposed to adhere thermoset
plastic materials of the aforementioned type to glass sub-
strates As will be seen from the disc~lsslon which follows,
various problems have been encountered with adhering methods
heretofore proposed.
Aforementioned Prench Patent No. 2,187,719 discloses that
the adhesive properties of crosslinked polyurethanes (hereafter
referred to as "thermoset polyurethanes" for convenience) which
have anti-lacerative and self-healing properties are such that
a sheet of this plastic material can be bonded to glass without
. .
~ -3-
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the use of an adhesive, ~ut experience has shown that certain
polyurethanes of this type, includ.ing polyuréthanes described
in aforèmentioned U.S. Patent No. 3,979,5~, do not adhere
well to glass over extended periods o-f time and that the bond
between the thermoset polyurethane and the glass is weakened
when exposed to moisture. By way of example, it is noted that
when a monome~ric liquid mix~ure which forms a thermoset poly-
urethane of the type described ln sai`d Patent No. 3,979,548
is c-ast directly onto a glass surface, the resulting thermoset
9heet exhibits excellent initial adhesion tb the glass, but
the bond is weakened when the glass/plastic laminate is sub-
iected to moisture.
.
I~t is noted further that when a monomer.ic liquid mixture
is cast directly onto a curved sllbstrate, for example, a curved
glass ply of a windshielcl, lt is virtually impossible to form
a film: having a uniform thickness. A film which is not uniform
in thickness le.ads to optical defects in the glazing laminate
and other undesirable problems.
Aforementionecl French Patent No. ~,lg7,719 discloses also
that the thermoset polyurethane can be made in the form of a
sheet ~hich is adhered to the glass substrate by an adhesive.
~arious techniques to effect this type of bonding method lead
to problems. Por example, when using a liquid solution o-f an
adhesive material di.ssolved in solvent, substantial difficul-
ties are encountered in removing the solvent after the sheet
and substrate have been brought together. This applies with
respect to any type of bonding method utilizing a liquid
adhesive ~hich contains an ln~redient which must eventually
be ~emovecl.
:;~
:,.~,.
In general, when using any type of liquid adhesive, even
those which do not contain a solvent or other material whih
nust be removed, it is di~Eicult to form a film of the adhesive
of uni-form thickness, even when the substrate is flat. ~As
mentioned above,' casting a uniform liquid film on a curved sub-
strate is virtually impossible.) Moreover, even when an ad-
hesive film of uniform thickness is initially formed, portions
are apt to be spread and rendered uneven when the thermoset
sheet is applied to the :Eilm on the glass substrate. Very
small dif$erences in the thickness of the adilesive layer,
e~en those which are scarcely visible, can cause substantial
optical clefects in the laminate such as streaks which create
optical distortions and thereore adversely affect the view
through the windshield. For windshields which require par-
ticularly good optical qualities, such defects can render them
unacceptable.
Although U.S. Patent No. 3,960,627 discloses that a
thermoset sheet of the aforementioned type can be first coated
with a coating which is rendered adhesive in character by the
use of heat and/or pressure, there is no disclosure in the
patent respect:ing the composition or character o-f coatings to
be used. It is an object o-f the present invention to provide
improved techniques for laminating a thermoset plastic sheet
to a glass or plastic ply and to provide an improved adhesive
comljosition for effecting the lamination.
SU~MARY OF THE JNVENTION
In accordance'with this invention, there is provided a
pre-formed sheet'for use in preparing a laminate, such as
windshield or other glazing laminate, the surface layer at
3~ one side of said sheet comprising a thermoplastic material
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~34~
capable of adhering to a ply of said laminate, and the surface
layer at the other side of said sheet comprising a thermoset
material which, :Eor example, has anti-lacerative and self-
healing properties, or the thermoset material may be o-~ a
type which imparts other desired properties to the laminate.
The pre-formed sheet is formed independently of the lam-
inate which is formed subsequently from the sheet and one or
more of the other plies comprising the laminate. The term
"sheet" as used herein includes within its meaning a composite
of the thermoplastic and thermoset materials of indefinite
length and also composite pieces~ for example, pieces of the
general slze and shape of the glazing làminate incorporating
the composlte.
In pre:ferred form, the invention provides a pre-formed
multi~layer sheet, o~e surface layer of which is a thermo-
pl~stic polyurethane capable of adhering to glass or plastic,
for example, polycarbonate, and the other surface layer of
which CQmprises a thermoset polyurethane having anti-lacerative
and self-healing properties.
Other aspects of the invention, including preferred mat-
erials comprising the sheet, preparation o the sheet and the
application of the sheet to a ply or substrate comprising a
glazing laminate are described in detail below. It is noted
further that a very important aspect of the present invention
is the provision of a thermoplastic adhesive, described in
cletail below, which has excellent optical qualities and other
properties which facilitate manufacturing and handling of the
sheet of the present invention and also fabrication of glazing
laminates comprising the sheet.
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BRIEP DESCRIPTION 0~ TH~ DRA~rINGS
Figure 1 is a cross~sectional view of a glazing laminate
prepared from a pre-formed sheet of the present invention.
Figure 2 is a cross-sectional view of another type of
glazing ldminate prepared from a pre-formed sheet of the
present invention.
~TAILED DESCRIPTION OF THE INVENTION
~ n a preferred ernbodiment, the sheet of the present in-
vention comprises: (A) a film o-f pol~urethane of three-dim-
ensional network, that is, a crosslinked or thermoset poly-
urethane, having self-healing and anti-lacerative properties,
and joined thereto (~) a film of polyurethane of linear chains,
that is, a thermoplastic polyurethane, having the ability to
adhere to glass or plastic, for example, pQlycarbonate. The
ilm$ of thermoplastic and thermoset polyurethane can be
joined by physical surface adhesion or, as will be described
in detail below, the joining of the films can include chemical
bonding.
In a preferred form, the surface of the thermoplastic
film, as well as that of the thermoset film, is substantially
non tacky at room temperature (for example, about 15C to about
35C) that is, at temperatures likely to be encountered in a
facility in which the sheet is manu:Eactured, stored, and/or
used in preparing a glazing laminate. At temperatures in e~-
cess of about 35C, the thermplastic material is softened to
the extent that when the sheet is pressed to a glass or plastic
substrate, the thermoplastic material is capable o:E flowing
and adhering to the substrate to an extent that the sheet does
not slip or slide on the surface of the substrate. In this
preferred form, important processing advantages are realized,
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3~7
as will be described below.
~ s to exemplary thickness of the ~ilms comprising the
sheet of the invention, the film of thermoset material can have
a tllickness of about 0.2 to about 0.8 mm, and preEerably from
about 0.~ mm to about 0.6 mm, and the thermoplastic film can
have a thickness of about 0.01 to about 0.8 mm, and preferably
about O.OZ to about 0.6 mm. Accordingly, the tllickncss of the
sheet can be, for example, about 0.21 mm to about 1.~ mm.
Sheets ha~ing film thicknesses within the aforementioned ranges
llave b~een used to excellent ad~antage in preparing windshields
of the type in which an energy absorbing sheet such as poly
(vinyl butyral) is sandwiched between two glass plies. It
$hould be understood that ~or other applications, each of the
~ilms may have a thickness outside of the aEorementioned ranges,
including a thickness in excess of 1 mm.
The following are exemplary monomers that can be used
to prepare the thermoset polyurethane: aliphatic bifunctional
isQcyanates such as 1,6-hexanediisocyanate, 2,2,4-and 2,4,4-
trilnethyl-1,6-hexanediisocyanate, 1,3-bis(isocyanatomethyl)
benzene, bis~4-isocyanatocyclohexyl)methane, bis(3-methyl-4-
isocyanatocyclohexyl)methane, 2,2-bis(4-isocyanatocyclohexyl)
propane~ and 3 isocyanatomethyl-3,5,5~trimethylcyclohexyliso-
cyanate, or their tri- or higher functional biurets, isocyanur-
ates, and prepolymers thereo~; and poly~unctional polyols ob-
tained by the reaction o~ polyfunctional alcohols such as,
~or example, 1,2,3-propane triol (glycerol), 2,2-bis(hydroxy-
methyl) l-propanol (trimethylol ethane), 2,2-bis (hydroxy-
methyl) l-butanol (trimethylol propane), 1,2,4-butane triol,
1,2,6-hexane triol, 2,2-bis(hydroxymethyl) 1,3-propane diol
(pentaerythritol) 1,Z,3,4,5,6-hexane hexol (sorbitol), with
aliphatic diacids such as, ~or example, ethylene oxide,
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1,2-propylene oxide, and tetrahydrofuran. The molecular
weights of the branched polyols desirably fall within the
range of about 250 to about ~000, and pre-ferably about 450
to about 2000. Mixtures of di-fferent polydsocyanate and poly-
ol ~onomers can be used. A particularly preferred thermoset
polyurethane is described in aforementioned U.S. Patent No.
3,979,54~.
The thermoplastic polymer :Eor use in preparing the sheet
of the present invention is preferably a polyurethane which,
lnstead of being prepared from monomers which form a three-
dimensional crosslinked network, react to form linear chains
o~ macromolecules. Exemplary diols that can be used are
aliphatic polyesters s-uch as those formed from one or more
cliacids, such as, for example, malonic acid, succinic acid,
glutaric acicl, adiplc acid, suberic acid and sebacic acid
and diols such as, for example, 1,2-ethanediol ~ethylene
glycol), 1,2 propanediol, 1,3-propanediol, 1,2-butanediol,
1,3 butanediol, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol
~neopentyl glycol), 1~6-hexanediol, 2-methyl-2,4-pentanediol~
20 3-methyl=2,4~pentanediol, 2-ethyl-1,3-hexanediol, 2,2,4-tri-
~ethyl-1,3-pentanediol, diethylene glycol, triethylene glycol,
polyethylene glycols, dipropylene glycol, tripropylene glycol,
polypropylene glycols or 2,2-bis~4-hydroxycyclo}lexyl)propane
and mixtures thereof. In preparing the polyester diol, the
addition of lactones, such as gamma-butyrolactone, gamma-
valerolactone, delta-valerolactone, and epsilon-caprolactone,
can be useful. The molecular wei~ght of the polyester is
desirably within the range of about 500 to about 4000, and
preferably about 1000 to about 2000.
The thermoplastic polyurethane can also be prepared from
linear polyethers having a molecular weight within the afore-
g
.. .~ ~,
~L143~g7
mentioned ranges ancl prepared from the following exemplary
compounds: ethylene o~ide, 1,2-propylene oxide and tetra-
hydrofuran.
Examples of dlfunctional aliphatic isocyanates which can
be reacted with the aforementioned diols (the polyesters and/or
polyethers) to produce the thermoplastic polyurethane are:
1,6-hexanediisocyanate, 2,2,4-and 2,4,4-trimethyl-1,6-hexane-
diisocyananate, 1,3-bis(isocyanatomethyl)benzene, bis~4-iso-
cyanatocyclohexyl)methane, bis~3-methyl-4-isocyanatocyclohexyl)
methane, 2,2-bis(~-isocyanatocyclohexyl)propane, and 3-isocyan-
atomethyl-3,5,5-trimethylcyclohexylisocyanate.
Turning now to the drawings, and :first to Figure 1, there
is shown therein a glazing laminate within the scope of the
present invention and prepared from a pre-formed sheet of the
present in~éntion. The safety glazing laminate of Figure l
co~prises a glass sheet 1, for example, ordinary silicate
glass such as made by the float process, or tempered or chem-
; ically tQughened silicate glass, and a pre-formed plastic sheet
2 adhered to glass sheet 1 by the thermoplastic polyurethane
adhesive layer 2a of pre-formed plastic sheet 2. Adhesive
layer 2a forms a firm, long-lasting bond with the surface of
gl~ss sheet 1 by the use of heat and pressure. The thermo-
plastic polyurethane adhesive layer 2a, which has a thickness
of a~out 0.05 mm, is joined to the thermoset polyurethane layer
2b, which has a thickness of about 0.5 mm, and which has
properties which permit it to undergo large deformations,
without plastic deformation even when deflected substantially.
Thermoset polyurethane layer 2b has self-healing and anti-
lacerati-ve properties. Accordingly, plastic sheet 2 prevents
contact wlth sharp edges of pieces of glass upon the breakage
of glass sheet 1. An exemplary use of the glazing laminate
~10-
. .
sho~n in Figure l is an eye piece, for example, in gogxles,
safety or sun glasses` and visors.
Turning now to Figure 2, there is shown therein a glazing
laminate incorporating a pre-formed sheet of the present in-
vention and a laminate which can be used as a windshield.
The pre--Eormed plastic sheet 2 is of the same type as the
plastic sheet 2 of Figure 1~ It is adhered to the glass sheet
5 ~hich in turn is adhered to glass sheet 3 by plastic inter-
layer 4, for exa~ple, poly(vinyl butyral), which functions
also as an energy absorber. In ~ffect, ~igure 2 shows the
use Q~ the sheet of the present invention to modify and improve
laminated windshields of the type no~r widely used.
Plastic sheet 2 can be adhered to the surface of glass
sheet 5 in thc same laminating step used to join glass sheets
3 and 5 and inter-layer 4. Alternatively, plastic sheet 2
can be adhered to glass sheet 5 in a separate process step.
The glazing laminates of Figures 1 and 2 show the sheet
of the present inYention adhered to a glass ply of the laminate.
Glazing lamlnates in which the sheet of the present invention
is adhered to a plastic ply can be prepared also. Examples of
plastics which can be used are polycarbonates, polyacrylics,
poly(v~nyl chloride), polystyrene and cellulose esters, ~or
example, the acetic, propionic and butyric esters.
In preparing a glazing laminate from a pre-formed sheet
of the present invention, the thermoplastic side of the sheet
` is applied to a glass or plastic substrate or ply of the
laminate and adhered theretG under suitable conditions, for
example, by the use of heat and/or pressure. Apparatus and
techniques of the type described in U.S. Patent Nos. 3,806,387
and 3,960,627 and in German Patent No. 2,424,085 and in
published German Patent Application DT-OS 2,531,501 can be used.
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In a preferred form7 a sheet having a non-tacky thermo-
plastic surface at room temperature is pressed onto a substrate
or laminate ply which has been heated to a moderately elevated
temperature (for example, ~bout 50C to about 80C), at which
the thermoplastic material softens, flows and adheres to the
extent that the sheet does not slip or slide from the surface
of the substrate or ply, even when handled at room temperature.
Exemplary pressure that can be used are about 0.5 to about
2 bars above atmospheric pressure. Bonds so formed from
thermplastic materials within the scope of the present in-
vention are sufficiently firm to permit satisfactory handling
of the laminate and they can be made still firmer and stronger
by subjecting the laminate to hiaher temperatures and pressures.
This can be effected in an autoclave, for example, at tem-
per~tures and pressures within the ranges respectively of
about lOO~C to about 140C and about 3 to about 15 bars above
at~ospheric pressure, depending on the nature of the materials
comprising the plies of the laminate.
~ number of processing advantages are realized by the
provision of a sheet which has a non-tacky surface at room tem-
perature. Such a sheet can be rolled, stored and handled con-
veniently ~hen there is a lapse of time between the formation
of the sheet and its use in forming the glazing laminate.
~ nother highly important advantage of such a sheet is
that dust and other foreign particles and materials ~o not
tightly adhere to the non-tacky surface and can be removed
readily therefrom. The presence of undue amounts of such for-
eign materials tends to ¢reate optical defects in the glazing
laminate and to render the laminate unsatisfactory for use in
applications where the optical standards of the laminate are
high. Such problems are greatly mitigated by the provision
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of a sheet having a non-tacky surface at room temperature.
It is noted also that the thermoplastic ]ayer upon being
heated has the ability, in contrast to a thermoset layer, to
absorb dust particles and other foreign materials on its
surface or the surface to which it is adhered. In effect,
such materials are embedded within the thermplastic layer.
This reduces the tendency of such foreign ma~erials to cause
optical defects in the laminate. ~ith a thermoset surface,
dust partlcles ~nd the like are not absorbed~ but they are
adsorbed on the surface which they distort, thereby forming
in the laminate lenses which create optical distortions.
Qpe~atlng ad~antages are also realized by the provision
of a thermoplastic resinous layer which at moderately elevated
temperatures ~dheres well enough to the glass or plastic sur-
face t~ permit the laminaté to be safely handled and stored.
Thus, when there is a lapse of time between the application
of the sheet to the ~lass or plastic surface and -final and
firmer bQnding in an autoclave, the laminate can be safely
transported and handled.
The pre-~ormed sheet of the present invention can be formed
in yarious ways. A mixture of the liquid ~monomers Erom which
the thermoset material is -formed can be cast onto a solid
:Eilm of the thermop~astic adhesive material and polymerized
to form a solid thermoset layer adhered to the underlying
thermoplastic film. The sheet of thermoplastic adhesive
material can be formed in any suitab:Le way, for example, by
a casting or extrusion operation.
The pre-formed sheet can also be prepared by asting mono-
meric mixtures of the reactants which form the respective
3~ thermoset and thermoplastic materials one on top o-f the other
at appropriate time intervals, and onto a suitable substrate,
:~r.
1, ~.
inclucling a glass substrate, coated with a release agent,
.f
necessary.
The follow;ng method has been -used advantageously
in forming a pre--formed sheet according to the present in-
vention. A monomeric mixture of the reactants which form the
desired thermqset polyuret]lane are cast onto a mo-ving glass
support, coated with a release agent, by a casting head having
a narrow elongated slot. Preferred apparatus for use in such
a castlng operation~is described in Iranian Patent No. 19873,
issued ~lay 16, 1977. After the monomers have polymerized
~accelerated by heat) to form a solid thermoset polyurethane
film, a solution CQmpriSing the thermoplastic polyurethane
dissolyed in a suitable solvent is cast in a similar manner
onto the previously formed film of thermoset polyurethane. As
the solvent is evaporated, aided b~ heat, there is formed a
solid film of the thermoplastic polyurethane firmly bonded to
the underlying thermoset film.
A modified form of this method includes casting a solvent-
free monomeric mixture of the reactants which form the thermo-
plastic film onto the film of thermoset polyurethane. ThismethQd is advantageous in that a solvent removal step is
avoided,
On the other hand, the method which includes the use of
a solution of resin dissolved in solvent generally permits the
user to exercise better control over the resin in that it is
pre~formed, whereas the reaction of monomers while supported
on the thermoset film can result in polyurethanes of dif-ferent
chain lengths. This can lead to the production of films
having varying properties.
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Any of the aforementioned methods can be utilized to
form pre formed sheets of continuous length.
The nature of the interface between the thermoset and
thermoplastic portions oE the sheet can vary, depending on how
the sheet is made and the constituents used. For example, if
a solution of resin dissolved in solvent is applied to a
solid film of the thermoset material, the solvent may swell
the surface of the thermoset film in which event, the solid
thermoplastic film which forms as the solvent evaporates tends
to merge with the surface of the thermoset film. I-E reactive
groups are present in the thermoset and thermoplastic materials
when they are brought into contact, the bonding o:E the mat-
erials can lnclude chemlcal bonding at the interEace. Also
the materials may be joined by physical surface adhesion.
.
ExAMpLEs
Examples which follow are illustrative of the present in-
vention~ Each of the examples shows the use of a preferred
thermoset polyurethane having anti-lacerative and sel-healing
properties. Preerred thermoset polyurethanes for use in the
practice o the present invention are described in U.S. Patent
No~ 3~979,548.
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Example No. 1
A thermoset polyurethane o-f the aforementioned type was
prepared from the -followi.ng monomers which were first degassed
by stirring under reduced pressure to avoid the formation of
bubbles in the film formed from the polyurethane:
~A) 1000 g of a polyether having a molecular weight
of about 450 and obtained by the condensation of
1,2-propylene oxide with 2,2-bis(hydroxymethyl)l-
butanol and having a percentage of free OH groups
of about 10.5 to about 12% (for example, the pro-
duct sold under the trademark DES~OPHF.N 550 U
of the Bayer AG), and
(B) 1000 g of a biuret of 1,6-hexanediisocyanate
containlng about 21 - 22% of free NCO groups ~for
example, the product sold under the trademark
DESMODUR N/100 of the Bayer AG).
Prior to mixing the monomers, monomer (A) was first mixed with
23 g o-~ an antioxidant, namely, 2,6-cli(tert.butyl)4-methyl-
phenol (~or example, the product sold under the trademark
IONPI. by Shell) and 1.5 g of a catalyst, namely, dibutyltin
dilaurate.
The homogenous mixture obtained by mixing the aforementioned
was cast onto a glass plate coated with a release agent. The
monomers poly~erized under the influence of heat and formed a
solid thermoset polyurethane film having anti-lacerative
and self healing properties.
1~-
~3~7
A thermoplastic polyurethane was formed from the
following monomers which were first degassed by stirring under
reduced pressure to avoid the -Cormation of air bu~bles in the
film formed from the polyurethane
(A) ~0 g of a linear polyether having a mean
molecular ~eight of about 2000 and prepared from
1,2-propane diol and 1,2-propylene oxide and
having about 1.6 - 1.8% of free hyclroxyl groups
~for example, the product sold under the trademark
DE~MOPHEN 3600 by Barer) and
(~) 110 g of 3-isocyanatomethyl-3J;5,5-trimethylcycl~-
hexylisocyanate having a content of free NCO
groups o-f about 37.5% and sold under the trademark
IPDI by ~eba AG.
Prior to mixing the monomers, monomer ~A) was first mixed with
4 g of an antioxidant, namely, 2,6-di(tert.butyl)4-methylphenol
~IONOL) and 0.1 g of dibutyltin dilaurate catalyst.
The monomeric mixture was cast onto the previously
formed film of thermoset polyurethane and polymerizes thereon
to form a film which is solid at room temperature and which
adheres tightly to the underlying filnl of thermoset polyureth-
ane thereby forming a sheet of the present invention. The
solid flexible plastic sheet formed from the two joined films
of thermoplastic and thermoset polyurethanes was stripped from
the underlying glass support and its non-tacky thermoplastic
surface was appIied to a glass substrate and adhered thereto.
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This was done by pressing the sheet onto the glass substrate
with a rolling pin at room temperature and thereafter placing
the laminate in an autoclave for about 1 h.our at a temperature
of about 135C and a pressure of 6 bars a~ove atmospheric
pressure. The sheet was firmly and uniformly bonded, the
glass and it ha~ excellent transparency properties.
The adherence or bonding of the thermoplastic layer to
the thermoset layer o-f the sheet can include ch.emical bonding
when the monomeric mixture from which the thermoplastic
polyurethane is:formed is applied to the underlying thermo-
sett~ng film prior to the time it is fully cured, that is,
while there are present free OH and NCO groups :Eor;reacting
with reactable groups in the monomeric mixture.
The next example shows the preparation and use of
a thermoplastic polyurethane different from that shown in
Example 1. .
Example No. 2
A thermoplastic polyurethane is prepared from the
following monomers:
~) 1000 g of a linear polyester having a molecular
wei~]lt of 1850 and about 1.8 - 1.9% free OH
groups and prepared from 100 parts of adipic
acid, 56 parts of 1,6-hexa.nediol, 30 parts of
2,2-dimethyl-1,3-propanediol and 7 parts of
1,2-propanediol; and
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~3~17
(~) 128 g o~ bis(4-isocyanatocyclohexyl)methane having
a content oE free MCO groups of about 31.5% (for
example, the product sold under the trademark
HYLENE W by Dupont).
The monomers ~long with catalyst and antioxidant as described
in Example No. 1, are placed into a reactor and polymerizecl
to form a thermoplastic polyurethane in a nitrogenous atmos-
phere. The cooled molten mass is granulated and dissolved
in demethylformamide to form a 10 wt.~ solution. This
solution is cast onto a thermoset polyurethane resinous ~ilm
as described in Fxample 1. The solvent is evaporated, aided
by heat, ~nd there is obtained a solid film of thermoplastic
polyurethane which adheres tightly to the underlying thermoset
polyurethane film, thereby forming a sheet of the present
invention.
The next example shows the preparation of still another
thermoplastic polyurethane which can be used to advantage in
the practice of the present invention.
Exa~ple No. 3
. . .
The linear thermoplastic polyurethane of this example is
prep~red ln a nitrogenous atmosphere by reacting a polyester
and ~iisocyanates. The polyester is prepared in a reactor by
reacting 145 g of adipic acid and 50 g of sebacic acid with
145 g of E-caprolactone, 120 g of 2,2-dimethyl-1,3-propanediol
and 80 g of 1,4-butallediol in the presence of 25 g of xylene
and 0.25 g of dibutyltin dilaurate at a temperature of 180C.
After separating 22.5 g of water fro~n the reaction, there
is added 18 g of a chain extender, namely, 1,4-butanediol,
along ~ith 400 g of xylene. Thereafter, the temperature is
- 1 9 -
~3~7
lowered to 80C and there are added with vigorous agitation,
150 g of bis(4 isocyanatocyclohexyl)methane and then 50 g
of 3-isocyanatomethyl-3,5,5-~trimetllylcyclohexylisocyanate.
After raising the temperature to 100C, the polymerization is
continued until a linear thermoplastic polyurethane resin
having a molecular weight of in excess 40,000 - 50,0~0 is
obtained. After cooling to about 70~C, the mixture is diluted
with about 30nO g of methylethylketone, and then, at a tem-
perature of about 30Cj with about 3000 g of tetrahydrofuran
to give a solution of about 10% by weight of polyurethane resin.
The sol~tion is cast onto a solid film of th~rmoset poly-
urethane as described in Example No. 1. The solvents are
evaporated, aided by heat, and a solid t]lermoplastic poly-
urethane is o~tained.
The next example shows the use of the thermoplastic poly-
urethane resin of Example No. 2 in solution form in preparing
a pre formed sheet according to the present invention.
Example No. 4
-
The thermoplastic polyurethane of Example No. 2 is
2Q dis501yed in a solvent consistlng of equal amounts of tetra-
hydro~uran, methylethylketone and xylene in an amount such
that a 10 wt. % solution of the resin is obtainecL. This sol-
ution is cast onto a film of thermoset polyurethane as described
in Example No. 1. The solvent is evaporated ~rith heating and
there is obtained a thermoplastic polyurethane film adhered
:Eirmly to the underlying thermoset polyurethane film.
-2Q-
With reference to the above examples, .it should be
not~d that the monomers from ~hich the thexmoplastic poly-
urethanes are prepared are selected so that the resulting
polymer has a highly amorphous structure, and thus, excellent
transparency in addition to the other highly desi.rable pro-
perties discussed in detail below. Amorphous thermoplastic
polyurethanes having a combination of highly attractive
properties are made in accordance with the present in~ention
by reacting one or more of the following aliphatic diisocyanates:
(A) br~nched chain alicyclic diisocyanates; (B~ non-branched
alicyclic diisocyanates; and (C) branched chain non-cyclic
aliphatic diisocyanates with a branchèd chain polyester diol
or branched chain polyether diol. Groups.which Eorm the
branched cha.ins include pendant alkyl, aryl, alkaryl and
aralkyl groups. In the case of the polyester diols, the
source of the branching is desirably the diol used in pre-
.
parin~ the polyester. If the diisocyanate reactant comprisesabout 35 to 100% of the non-branched alicyclic type, the
pQlyester diol is prepared from at least two different diols
which result in chain branching in the polyester (see Example
N4. 2 and the use of 2,2-dimethyl-1,3-propanediol and 1,2-
propanediol).
With respect to Example No. 3, it can be seen that the
amorphous thermoplastic polyurethane can also desirably be made
from a polyester diol prepared from at least two different
diols, and at least one of which is alicyclic and/or branched,
preferably branched. In preparing the polyester diol, mixtures
of acid can,.also be used to impart additional irregularity to
the molecular configuration of the polymer, as does also the
addition of epsilon-caprolactone; similarly mixtures of the
isocyanates can also be desirably used.
-21-
.~,,,
.,
97
3~
The amounts of isocyanate and diol used should be such
that preferably the NCO/OH ratio is not greater than 1, for
example, 0.8 to 0.9. If the ratlo is greater than 1, there is
a risk that the available NCO groups will react in an un-
controlled manner.
Depending on the particular thermoplastic polymer used,
the method by which it is formed into a sheet of the present
invention and the partlcular type laminate in which it is used,
various additives may be incorporated into the thermoplastic
~ormulation to improve particular properties. Examples of
such additives include adheslon promo~ers, leveling agents,
tack1fiers which impart a tackine.ss to the resinous surface
at moderately elevated temperatures (for example, 50 - 80~C),
and U.V. stabilizers. ~xamples of such additives are as
follo~s; adhesiorl promoters - trialkoxy silanes containing
1 to about 4 carbon atoms in the alkoxy groups, wuch as
glycidyl oxypropyl trimethoxy silane, gamma-aminopropyl tri-
ethoxy sllane, 3,4-epoxycyclohexylethyl trimethoxy silane and
a~inQethyl trimethoxy silanes; leveling agents - silicon
oils~ urea-formaldehyde resin solutions, phenolic resins,
and cellulose esters; tackifiers - phthalic acid type polyester
re5ins and U.V. stabilizers - benæophenones, salicylates;
cyan~acrylates; and benzotriaols.
When used, the additives should be present in amounts
which do not adversely affect other desired properties of the
thermoplastic polyurethane. Speaking generally, the additives
can be used in amounts within the following ranges, in parts
by weight based on 100 parts of the thermoplastic polyurethane:
About 0.05 to about 2, and preferably about 0.1 to about 0.5
part of adhesion promoter, about 0.1 to about 2 parts of silicon
~ -22-
:
.
3~
oil and for other leveling agents, about 0.5 to about 5 parts;
about 1 to about 20 parts of a tackifier; and about 0.1 to about
3 parts of a U.V. stabili~er.
In the preparation and use of sheets comprising
thermoplastic polyurethanes of the types described in the above
examples~ improvements in adhesive and leveling properties
can be achieved by the use of adhesion promoters and ]eveling
agents of the types mentioned above. Such polyurethane form-
ulations have a combination of properties which make them par-
ticularly suitable for use in glazing laminates re~uiring highoptical standards, such as required in windshields. In this
regard, films of the polyurethane have excellent -transparency
and optlcal properties and are haze-free for extended periods
of time and do not bloom. They also have excellent bondlng
properties to both glass and plastic, including to the anti-
lacerative and self-healing thermoset polyurethane, which
ploperties are maintained for long periods of time under varying
conditions, including exposure of laminates comprising the sheet
to ultra-violet radiation, wide temperature variations (for
example, -5 to 150C, and high humidity (for example, 95%
relative humidity up to S0C).
~ n addition, the degree of adhesion between the a~ore-
mentioned thermoplastic polyurethane and a glass ply is such
that when used in a windshield, upon impact, the adhesive
bond is strong enough to avoid delamination and yet weak enough
to release from the glass to avoid being torn. In this respect,
it meets standard requirements.
It is further noted that the elastic properties of the
aforementioned thermoplastic polyurethane are such that sheets
incorporating them can be formed into rolls without adverse
~ -23-
effect on the optical properties of the resinous film. In
addition, the plastic deformation proper-ties of the poly~
urethane are such -that such rolls can be unwound without
adverse effect on the optical properties of the plastic :Eilm.
Ano-ther important feature of the aforementioned thermo-
plastic polyurethanes is that they have a combination of pro-
perties which renders them compatible for use with materials
conventionally used in commercial windshields and also with
anti-lacerative~self-healing thermoset polvurethanes. In this
connection, it is noted that a~orementioned French Patent No.
2,1~7~719 discloses that the anti.-lacerative/self-healing film
has a, hlgh capacity for elastic deformation, a low modulus
of elasticity (below 2000 daN/cm2, preferably below 1200 daN/cm~.),
and an elongation to rupture in excess of 60% with less than
2% plastlc deformationr and preferably an elongation to rupture
in excess of 100 wlth less than 1% plastic deformation. Highly
preferred -thermoset polyurethane films of this type, and as
described in the aforementioned examples, have a modulus of
elasticity of about 25 to about 200 daN/cm2 and an elongation
of about 100 to about 200% with less than 1% plastic deform-
ation. In addition to the previously mentioned, highly desired
properties possessed by films of the thermoplastic polyurethane
described above, it is noteworthy that they also possess
pr~perties which are compatible with those properties of the
thermoset polyurethane which contribute to their anti-lacerative
properties. Thus, the aforementioned thermoplastic polyurethanes
have a modulus of elasticity below 200 daN/cm2 and an elong-
ation to rupture in excess of 60%. By way of example, it is
noted that thermoplasti.c polyurethanes of the types described
in the examples can be made to have a modulus of elasticity
of less than 10 daN/cm2 and with an elongation in excess of
-24-
~ ~o~4~7
of 750% at 25 daN/cm .
Another important property of the aforementionedthermoplastic polyurethanes is that sheets incorporating them
can be adhered firmly to a glass surface in an autoclave to
produce a glazing laminate at temperatures which do not ad-
versely affect the anti-lacerative, self-healing film or other
materials conventionally used in laminates, for exampler poly-
(vinyl butyral). This permits laminates containing such
matexials and the sheet of the present invention to be readily
made u-tilizing conditlons which do not cause a degradation of
the properties oE the materials. In general, poly(vinyl butyral)
and thermQset polyurethane films of the aforementioned type
tend to degrade respectively at temperatures within the range
of abQut 135~140~C and about 150-200C, depending on time
of exposure and the speciEic mate~ials involved. Glazing lam-
inates incorporating the aforementioned thermoplastic poly-
urethanes can be satisfactorily formed in an autocla~e at tem-
per~tures below the aforementioned temperatures, for example,
at temperatures of about 115C. Sheets of the type shown in
the examples are transparent prior to and after being subjected
to the heat and pressure laminating conditions. It is noted
.
also that the cohesive properties of thermoplastic and thermoset
materials of said sheets are excellent prior to and after being
sub j ected to autoclaving conditions.
Thusr the amorphous thermoplastic polyurethane is such
that at moderatel~ elevated kemperatures it is a highly viscous
fluid which is capable of well-wetting a surface and flowing
inko khe pores of khe surEace ko thereby provide a good adhesive
bond between the sheet and the substrate, and this chàracteristic
is maintained over a wide temperature range. The melting point
of the thermoplastic polyurethane is in excess of any temper-
-25-
~4L3~
ature likely to be reached in an application in which the sheet
of the present invention is used. Thus, the thermoplastic
polyurethane advantageously sof-tens or is tacky over a wide
temperature range, but does not liquify at temperatures to which
a laminate including the sheet is likely -to be exposed. Thermo-
plastic polyurethanes within the scope of the present invention
can have a melting range in e~cess of 200C.
Still another important property of the thermoplastic
polyurethane film is that if functions in a manner such that
problems that would otherwise be encountered due to the wide
; differences in the coefficients of e~pansion between glass and
the thermoset ~olyurethane are mitigated or avoided. In a
laminate in which a film of the thermoset polyurethane is ad-
hered directl~ to a glass surface or other surface comprising a
material which has a coefficient of expansion substantially dif-
ferent than the thermoset polyurethane, defects in the thermoset
film are formed as it is subjected to stresses and strains
which arise when the laminate is subjected to wide temperature
yariations. Due to the presence of the thermoplastic layer
with its elastic properties and its ability to soften and flow
at elevated temperatures, such defects are mitigated or avoided.
It is noted also that elastic properties of the thermo-
plastic polyurethane contribute to the maintenance of a good ad-
hesive bond between the glass and the sheet at relatively low
temperatures. In contrast, in a laminate in which a thermoset
film is bonded directly to glass surface, the bond is weakened
at lower temperature.
Another aspect of this invention relates to the
formation of a continuous film of the thermoplastic polyurethane
utili2ing selected solvents and evaporation and viscosi-ty control
agents which af~ord the formation of film of high optical
-26-
34~7
quality in a continuous operation. By way of back~xound, it
is noted that when forming a solid thermoplastic polyurethane
continuous film on an industrial scale from a li.quid film
that has been cast onto a moving surface, it is highly ad-
vanta~eous to use or cast a li~uid that has good levelling
properties, that is, a film of the liquid should assume the
.
desired form of -the solid film and a uniform thickness wi'~hin
a short time, for example, within less than one minute and
preferably within about 30 seconds or less. To achieve this,
the viscosity of the li~uid thermoplastic polyurethane~at
room temperature should be no greater than about 100 cp, and
pre~erably no greater than about 50 to 60 cp. Solvents are
added to liquify the normally solid thermoplastic polyurethane,
and leyelling agents of the type described above can be used to
improve the levelling characteris-tics of the resulting solution.
Rursuant to this inventlon, the normally solid thermo-
plastic polyurethane is dlssolved ln a solvent which has a
rela~tiyely low boiling polnt (no greater than about 70C), and
there is included in this solution an evaporation- and viscosity-
contxol agent ~hereafter referred to as "control agent" forconveniénce) consisting of a material which is a non-solvent
for the polyurethane, but which is miscible with said solution,
and which has a relatively high boiling point, that is, in
excess of about 120C, and preferably no greater than about
150qC. The solvent and control agent are combined with the
thermoplastic polyurethane in amounts such that the resulting
solution has the desired viscosity. Such.amounts will depend
on the part.icular materials used, including the polyurethane
and its molecular weight. The solvent should be used in an
amount such that all of the polyurethane is dissolved in the
solution.
27~
~L43~
As to the benefits achieved by use of the solyent/
control agent solution described above, it is first noted
that developmental work revealed that dissolving thermoplastic
polyurethanes of the type to which this invention relates in
a low boiling liquid solvent resulted in the formation of a
solid film having defects, for example, an orange peel surface,
when heat was used to accelerate evaporation of -the solvent.
It is desirable to use heat to accelera-te evaporation of
the solvent in order to maintain satisfactory production rates
and to ensure that substantially all of the solvent is removed
from the polyurethane film~ With regard to solvent removal,
good solvents for the thermoplastic polyurethane of the present
invention are polar materials having a high degree of affinity
for the polyurethane. Solvent not removed from the film can
lead to numerous problems during manufacture and use of a
laminate comprising a sheet of this invention.
When using a high boiling solvent for the polyurethane,
as compared to a low boiling solvent, orangé peel surface defects
can be avoided, but-it is most difficult to remove ~rom the film
substantially all of the high boiling solvent. The presence of
solyent in the film can lead to the formation of defects such as,
for example~ bubbles and pinholes during processing of a laminate
comprising the film in an autoclave, or when the laminate is
subjected to elevated temperatures during use. The presence of
solyent can also adversely affect the surface characteristics
of ~he f ilm.
The use of the solvent/control agent solution of the
present invention enables the user to formulate a solution
having desired levelling and viscosity characteristics while
avoiding or mitigating problems of the type described above.
Eleyated temperatures can be used effectively to remove the low
28-
~4,.~9~
boiling solvent~and the high boiling, non-solvent control
agent/ which is non-polar and has little or no a:Efinity for
the polyurethane, but which permits a controlled evaporation
of the low boiling solvent so that surface defects of the orange
peel type are avoided.
~ n preferred form, there is included in the solvent/
contxol agent solution a material which has a medium boiling
point (between about 70QC and about 120~C) and which is not a
solvent for the solid polyurethane, but is capable of swelling
lt. Such materials wh-~ch are polar, but less so than the
solvent, are miscible with the two other ingredients comprising
the solution and aid in further controlling the evaporating
characteristics of the solution.
The numerous variables inherent in removing the non-
solid portion oE the solut~on make it difficult, if not im-
possible, to define -the proportion of the control agent and
medium boiling point material comprising the solution. Exem-
plary o~ such variables are the particular ingredients comprising
the sQlution, the precise boiling points of the non-solids
portion of the solution, the elevated temperatures used to
eyaporate the non-sol;lds portion of the solution, and the time
of heating. In view of this, it ls recommended that for any
particularl application, arbitrary amounts be initially selected
and adjustments be made as needed if defects of the type des-
cribed above are encountered. For guideline purposes, it is
recommended that equal amounts of the non-solid constituents
of the solution be used, and that adjustments be made if nec-
essary.
Suitable materials having the properties mentioned above
can be used to prepare the solution. Preferred organic materials
are as follows: low boiling solvent - tetrahydrofuran (boiling
-29-
9~Y
point of 65C); medium boilin~ materi~l - methylethylkçtone
(boiling point of 80C); and hl~h boiling non-solvent - xylene
(boiling point of 140C).
Solutions of the type described above make it possible
to cast the solution as a liquid film which levels prior to
evaporation of an amount of solvent that would cause the film
to increase in viscosity to the extent that irregularities
are set or frozen therein. It should be understood that sol-
utiQns of the type described can be case directly onto a moving
film of the thermoset material or onto a different type
substrate~ r
In summary, it can be said that the article of the
present invention possesses a number of highly desirable pro-
perties whlch permit it to be used effectively in a variety
~; of applications. Thus, the sheet can be used as a protective
material which contributes to the maintenance of surface in-
tegrety on one or both faces or rigid or flexible glass or plas-
tic suhstrates to form glazing laminates of the type mentioned
above, and also laminates which can be used as windows or
.
transpaxencieS in the building and transport industries, in-
cluding, fox example, side or lateral windows in motor vehicles,
planes and trains~ ~n addition, the sheet can be laminated to
a container such as glass and plastic bottles. For many of
these applications, the sheet of the present invention can be
used efectively with polycarbonates and polyacrylics which
are now widely used in many applications. Tinting may be effected
before or after the sh~et of the present invention is applied.
The sheet of the present invention can also be used to
produce a windshield comprising a single glass ply having adhered
to the glass surface facing the interior of the vehicle the
~30-
thermoplastic surface layer of the sheet. In such an embodi-
ment, the thermoplastic surface layer functions also as an
energy absorber, and for this purpose it should have a thickness
of at least about 5 mm, and preferably not in excess of about
1 mm.
The sheet of the present inventlon can be modified by
ioining to the surface of the thermoset material a thermoplastic
material, for example, of the type comprising the other
surface of the sheet. In this modified form, the sheet can be
used as an in~er-layer bet~een two glass or plastic plies or
between glass and plastic plies which are adhered to the sheet
by the thexmoplastic layers on each side thereof.
It is believed that the sheet will be widely used to
improve ~ehicle windshields of the type now conventionally used
thxoughout the world~ An improved windshield according to the
invention will generally comprise an outer glass ply having a
thickness of about 1 to about 3 mm, an inter-layer of suitable
energy absorbing material such as poly(vinyl butyral) having a
thickness of about 0.5 to about 1 mm, an inner glass ply having
a thickness of about 0.5 to about 3 mm and adhered thereto,
the pre-formed sheet of the present invention comprising a
thermoplastic film having a thickness of about 0.02 to about
0.6 mm and a thermos~t film of anti-lacerative and self-healing
properties having a thickness of about 0.4 to about 0.6 mm.
Such safety windshields should function to effectively mitigate
injuries of the type normally caused by shattered glass to the
face of an individual.
This application is a division of copending Canadian
application Serial No. 281,812, filed June 30, 1977.
-31-
