CA1143497A - Glazing laminates - Google Patents

Abstract

ABSTRACT

An integument which contributes to the maintenance of surface integrity is disclosed, particularly a sheet for use in preparing laminates, such as vehicle windshields, in which an energy absorbing ply, for example, a ply of poly(vinyl) butyral), is sandwiched between two glass plies, the sheet of this invention being applied to an exposed surface of one of the glass plies and having one surface layer comprising a thermoplastic polyurethane capable of adhering to a glass or plastic substrate and the other surface layer comprising a thermoset polyurethane having anti-lacerative, self-healing and anti-ablative properties; there is further disclosed the manufacture and application of such a sheet as a ply facing the interior of a vehicle, thereby forming a windshield the inwardly exposed surface of which comprises a thermoset polyurethane which protects the vehicle occupants from facial laceration caused by windshield impact and which has self-healing properties.

Description

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, -2- ~.
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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 . .
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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.

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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.

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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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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, 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, '~

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 ~4~

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.
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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.

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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 ~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 ~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.

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.

.~,,, ., 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 ~ ~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-~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 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 ~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 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.

Claims (55)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A glazing laminate comprising as a substrate a glass or plastic ply and adhered thereto a preformed polymeric sheet, one surface of said sheet comprising a thermoplastic material capable of adhering to a ply of said laminate and the other surface of said sheet comprising a thermoset material which imparts desired properties to said laminate.

2. The glazing laminate of claim 1, wherein said substrate is a glass ply.

3. The glazing laminate of claim 1, wherein said substrate is a plastic ply.

4. The laminate according to claim 3, wherein said plastic ply is a polycarbonate.

5. The laminate according to claim 3, wherein said plastic ply is an acrylic resin.

6. The laminate of claim 1, wherein said thermoset material imparts anti-lacerative and self-healing properties to said laminate.

7. The laminate of claim 6, wherein said thermoplastic material is formed of a thermoplastic polyurethane resin and wherein said thermoset material is formed of a thermoset polyurethane resin.

8. The laminate of claim 7, wherein said thermoplastic polyurethane resin is formed from an aliphatic diisocyanate and a diol of an aliphatic diacid polyester or diol of a polyglycol ether, each of said diols having a molecular weight of about 500 to about 4000.

9. The laminate of claim 7, wherein said preformed polymeric sheet includes films of each of said thermoplastic and thermoset material adhered to each other, the surface of said thermoplastic polyurethane resin film being substantially non-tacky at room temperature and capable of adhering to glass at a temperature of about 40°C or more, and said sheet being transparent and exhibiting excellent optical properties in a glazing laminate formed therefrom.

10. The laminate of claim 9, wherein said thermoplastic polyurethane is prepared by reacting an aliphatic diiso-cyanate with a diol of an aliphatic diacid polyester or with a diol of a polyglycol ether, each of said diols having a molecular weight within the range of about 500 to about 4000, and wherein the thickness of said thermoplastic polyurethane resin film and said thermoset polyurethane resin film are respectively about 0.01 to about 0.8 mm and about 0.2 to about 0.8 mm, and wherein each of said thermoplastic and thermoset films has a modulus of elasticity of below about 2000 daN/cm2 and an elongation in excess of 60%, the plastic deformation of said thermoset film being less than 2% and wherein said thermoplastic film is capable of being adhered to glass or plastic at a temperature of about 50 to about 80°C, and wherein said sheet is capable of being wound into a roll and unwound without adverse effect on the optical properties thereof.

11. The laminate of claim 10, wherein the thermoset film has a modulus of elasticity within the range of about 25 to about 200 daN/cm2 and an elongation of about 100 to about 200% with less than 1% plastic deformation, and wherein the modulus of elasticity of said thermoplastic film is no greater than about 200 daN/cm2 and its elongation is in excess of about 200%

12. The laminate of claim 11, wherein said thermoset film is the reaction product of: (a) a polyglycol ether resulting from the condensation of 1,2-propylene oxide with 2,2-bis(hydroxymethyl)1-butanol and containing about 10.5-12% by weight free hydroxyls; and (b) a biuret of 1,6-hexane diisocyanate having about 21-22% by weight isocyanate groups, the weight of said biuret being between about 0.9 and 1.1 times the weight of said polyglycol ether.

13. A windshield comprising.
(a) an outer glass ply having a thickness of about 1 to about 3 mm;
(b) an inter-layer of an energy absorbing material and having a thickness of about 0.5 to about 1 mm;
(c) an inner glass ply having a thickness of about 0.5 to about 3 mm; and (d) a pre-formed polymeric sheet, one surface of which comprises a thermoplastic material capable of adhering to said inner glass ply and the other surface of which comprises a thermoset material which imparts desired properties to the windshield, the thermoplastic material of which has a thickness of about 0.02 to about 0.6 mm and the thermoset material of which has a thickness of about 0.4 to about 0.6 mm, said sheet being adhered to said inner glass ply by said thermoplastic material.

14. A windshield according to claim 13, wherein said energy absorbing material is poly(vinyl butyral).

15. The glazing laminate of claim 1 including a thermoplastic material adhered to the other surface of said thermoset material.

16. The glazing laminate of claim 15, wherein the thermoplastic materials adhered to said thermoset surfaces are like materials.

17. The glazing laminate of claim 15 or 16, wherein the surfaces of each of said thermoplastic materials are adhered to a ply comprising said laminate.

18. The glazing laminate of claim 1, 4 or 5, wherein said thermoplastic material includes a levelling agent, an adhesion promoter or a mixture thereof.

19. A laminate comprising a substrate and a preformed multi-layer sheet, one surface layer of said sheet being presented toward and adhesively bonded to said substrate and comprising thermoplastic polymeric material having tack free surface characteristics at room temperature, but having adhesive surface characteristics with respect to said substrate at a laminating temperature above room temperature, and the surface layer of said sheet presented away from the substrate comprising a thermoset polymeric material having high plastic memory characteristics.

20. A laminate according to claim 19 in which the surface of said other surface layer of the sheet is exposed and manifests anti-lacerative and self-healing properties.

21. A laminate according to claim 19 wherein the surface layer comprising said thermoset polymeric material has adhered thereto a surface layer comprising said thermoplastic material and to which is bonded another lamina.

22. A windshield comprising a glass ply having adhered to one surface thereof a preformed polymeric sheet, one surface of said sheet comprising a thermoplastic material capable of adhering to said glass ply of said windshield and the other surface of said sheet comprising a thermoset material which imparts desired properties to said windshield, said sheet adhered to said glass surface by said thermoplastic material, the other surface of said glass ply and said thermoset material being exposed, said sheet being on that surface of the glass ply which faces the interior of a vehicle.

23. The windshield according to claim 22, wherein the thickness of said thermoplastic material is at least 0.5 mm.

24. The windshield according to claim 23, wherein the thickness of said sheet is not greater than about 1 mm.

25. The windshield according to claim 22, 23 or 24, wherein said thermoplastic material is a highly amorphous thermoplastic polyurethane capable of being formed into a highly transparent film comprising the reaction product of: (a) one or more of the following aliphatic diisocyanates: (i) a branched chain alicyclic diisocyanate; (ii) a non-branched alicyclic diisocyanate;
and (iii) a branched chain non-cyclic diisocyanate; and (b) a branched chain polyester diol or branched chain polyether diol or mixture thereof; and wherein when reactant (a) comprises 85 to 100% of said non-branched alicyclic diisocyanate and reactant (b) comprises said polyester diol, then said polyester diol is prepared from at least two different diols which result in chain branching in said polyester diol.

26. A process for preparing a glazing laminate which includes a glass or plastic ply and a thermoset ply which imparts desired properties to said laminate comprising applying to said glass or plastic ply a preformed polymeric sheet, one surface of said sheet comprising a thermoplastic material capable of adhering to said glass or plastic ply and the other surface of said sheet comprising a thermoset material which imparts desired properties to said laminate, and adhering said preformed sheet to said plastic or glass ply with said thermoplastic material of said sheet.

27. A process according to claim 26 wherein said thermoplastic material is non-tacky at room temperature and capable of adhering to glass at moderately elevated temperatures and including heating said ply to a temperature of about 40°C or more and applying to said heated ply said preformed sheet and adhering it to said ply by pressure.

28. A process according to claim 27 wherein said ply is heated to a temperature of about 50 to about 80°C.

29. A process according to claim 26, 27 or 28 including firmly bonding said preformed sheet to said ply by subjecting a laminate thereof to autoclaving conditions.

30. A method for preparing a laminate comprising bringing into surface contact with one surface of one lamina a multi-layer preformed sheet, the surface layer of the sheet presented toward said one surface of said lamina comprising thermoplastic polymeric material having tack free surface characteristics at room temperature but having adhesive surface characteristics with respect to said one surface of the lamina at a temperature above room temperature, the surface layer of the other side of the sheet comprising a thermoset polymeric material having high plastic memory characteristics, and heating the sheet while in surface contact with said lamina.

31. A process for preparing a preformed polymeric sheet for use in preparing a glazing laminate, one surface of said sheet comprising a thermoplastic material capable of adhering to a ply of said laminate and the other surface of said sheet comprising a thermoset material which imparts desired properties to said laminate, said process comprising: (a) forming on a horizontal support a liquid film comprising a mixture of monomers from which said thermoset material is formed; (b) polymerizing said monomers to form a solid film of said thermoset material; and (c) forming on said solid film a solid film of said thermoplastic material.

32, A process according to claim 31, wherein said solid film of thermoplastic material is formed by depositing on said solid film of thermoset material a liquid, solvent-free mixture of monomers from which said thermoplastic material is formed and polymerizing said monomers.

33. A process according to claim 31, wherein said solid film of thermoplastic material is formed by depositing on said solid film of thermoset material a film of a liquid solution containing said thermoplastic material dissolved in a solvent and evaporating said solvent.

34. A process according to claim 31, 32 or 33, wherein said thermoset and thermoplastic materials contain reactive groups which react to chemically bond said thermoset and thermoplastic materials.

35. A process according to claim 31, 32 or 33, wherein said support is a glass support.

36. A solution having a viscosity of no greater than about 100 cp at room temperature and having dissolved therein a normally solid polyurethane capable of being formed into a highly transparent film comprising the reaction product of: (a) one or more of the following aliphatic diisocyanates: (i) a branched chain alicyclic diisocyanate; (ii) a non-branched alicyclic diisocyanate;

and (iii) a branched chain non-cyclic diisocyanate; and (b) a branched chain polyester diol or branched chain polyether diol or mixture thereof; and wherein when reactant (a) comprises 85 to 100% of said non-branched alicyclic diisocyanate and reactant (b) comprises said polyester diol, then said polyester diol is prepared from at least two different diols which result in chain branching in said polyester diol, the solvent for said polyurethane comprising a low boiling solvent and said solution also including an evaporation- and viscosity-control agent which is a non-solvent for the polyurethane, but which is miscible in said solution and has a high boiling point.

37. A solution according to claim 36 including also a medium boiling point material which is miscible in said solution and which is not a solvent for the polyurethane, but which is capable of swelling it.

38. A solution according to claim 36, wherein said solvent is tetrahydrofuran and said control agent is xylene.

39. A solution according to claim 37 or 38 including methylethylketone as a medium boiling point material.

40. A solution according to claim 36, 37 or 38, wherein the non-solid portions of the solution are present is about equal amounts.

41. A solution according to claim 36, 37 or 38, wherein said viscosity is no greater than about 50-60 cp.

42. A transparent flexible film comprised of a thermo-plastic polyurethane that is the reaction product of:
(a) one or more of the following aliphatic diisocyanates:
(i) a branched chain alicyclic diisocyanate; (ii) a non-branched alicyclic diisocyanate; (iii) a branched chain non-cyclic diisocyanate; and (b) a branched chain polyester diol or branched chain polyether diol or mixture thereof;
and wherein when reactant (a) comprises 85 to 100% of said non-branched alicyclic diisocyanate and reactant (b) comprises said polyester diol, then said polyester diol is prepared from at least two different diols which result in chain branching in said polyester diol.

43. A process for preparing a solid flexible thermo-plastic film for use in a glazing laminate comprising casting a liquid solution of thermoplastic resin onto a moving substrate to form a liquid film thereon, said solution comprising a low boiling solvent for said resin and accelerating the evaporation of said solvent by subjecting said film to heat, controlling the rate of evaporation of said solvent, thereby avoiding the formation of defects in the film, by including in said solution a high boiling material which is a non-solvent for said thermoplastic, but which is miscible in said solution, and evaporating from said film substantially all of said solvent and said high boiling material thereby forming said solid film.

44. A process according to claim 43 wherein said solution includes also a medium boiling point material which is miscible in said solution and which is not a solvent for said resin, but which is capable of swelling it, and evaporating substantially all of said material from said film.

45. A process according to claim 43 or 44 wherein said thermoplastic material is polyurethane capable of being formed into a transparent solid film.

46. A process according to claim 43, wherein the non-solid constituents of said solution are present in amounts such that the viscosity of the solution at room temperature is no greater than 100 cp.

47. A process according to claim 46, wherein said viscosity is no greater than about 50-60 cp.

48. A process according to claim 43, wherein said resin is a polyurethane capable of being formed into a highly transparent film comprising the reaction product of:
(a) one or more of the following aliphatic diisocyanates:
(i) a branched chain alicyclic diisocyanate; (ii) a non-branched alicyclic diisocyanate; and (iii) a branched chain non-cyclic diisocyanate; and (b) a branched chain polyester diol or branched chain polyether diol or mixture thereof; and wherein when reactant (a) comprises 85 to 100% of said non-branched alicyclic diisocyanate and reactant (b) comprises said polyester diol, then said polyester diol is prepared from at least two different diols which result in chain branching in said polyester diol.

49. A process according to claim 48, wherein the solvent for said polyurethane is tetrahydrofuran and said high boiling material is xylene.

50. A process according to claim 49 including also methyethylketone.

51. A process according to claim 43, wherein said liquid film has levelled within about 60 seconds after it has been cast.

52. A process according to claim 51, wherein said liquid film has levelled within about 30 seconds after it has been cast.

53. A windshield according to claim 13, wherein said pre-formed polymeric sheet includes one surface comprising a thermoplastic polyurethane capable of adhering to said inner glass ply at a temperature of about 40°C or more and being substantially non-tacky at room temperature, and the other surface of said polymeric sheet comprising a thermoset polyurethane which imparts anti-lacerative and self-healing properties to said windshield, and which is the reaction product of:
(a) a polyglycol ether resulting from the condensation of 1,2-propylene oxide with 2,2-bis (hydroxymethyl)-1-butanol and containing about 10.5-12% by weight free hydroxyls; and (b) a biuret of 1,6-hexane diisocyanate having about 21-22% by weight isocyanate groups, the weight of said biuret being between about 0.9 and 1.1 times the weight of said polyglycol ether.

54. A windshield comprising a glass ply having adhered to one surface thereof a pre-formed polymeric sheet having a thickness not greater than about 1 mm, one surface of said sheet comprising a thermoplastic polyurethane having a thickness of at least 0.5 mm, capable of adhering to said glass ply at a temperature of about 40°C or more and being substantially non-tacky at room temperature, and the other surface of said sheet comprising a thermoset polyurethane which imparts anti-lacerative and self-healing properties to said windshield, wherein said thermoplastic polyurethane is highly amorphous and highly transparent and comprises the reaction product of:

(a) one or more of the following aliphatic diiso-cyanates:
(i) a branched chain alicyclic diisocyanate;
(ii) a non-branched alicyclic diisocyanate; and (iii) a branched chain non-cyclic diisocyanate; and (b) a branched chain polyester diol or branched chain polyether diol or mixture thereof; and wherein when reactant (a) comprises 85 to 100% of said non-branched alicyclic diisocyanate and reactant (b) comprises said polyester diol, then said polyester diol is prepared from at least two different diols which result in chain branching in said polyester diol; and wherein said thermoset polyurethane is the reaction product of:
(a) a polyglycol ether resulting from the condensation of 1,2-propylene oxide with 2,2-bis(hydroxymethyl)-1-butanol and containing about 10.5-12% by weight free hydroxyls; and (b) a biuret of 1,6-hexane diisocyanate having about 21-22% by weight isocyanate groups, the weight of said biuret being between about 0.9 and 1.1 times the weight of said polyglycol ether.

55. A method according to claim 30 wherein said thermoset polymeric material imparts anti-lacerative and self-healing properties to said laminate and which is the reaction product of:
(a) a polyglycol ether resulting from the condensation of 1,2-propylene oxide with 2,2-bis(hydroxymethyl)-1-butanol and containing about 10.5-12% by weight free hydroxyls; and (b) a biuret of 1,6-hexane diisocyanate having about 21-22% by weight isocyanate groups, the weight of said biuret being between about 0.9 and 1.1 times the weight of said polyglycol ether.