IL72359A

IL72359A - Laminated safety glass pane with polyurethane layer

Info

Publication number: IL72359A
Application number: IL7235984A
Authority: IL
Original assignee: Saint Gobain Vitrage
Priority date: 1983-07-11
Filing date: 1984-07-10
Publication date: 1994-01-25
Also published as: DK337084A; DK162976B; EP0132198A1; EP0132198B1; ES534171A0; NO161968C; SU1517756A3; MX168250B; FI842765A0; IN161465B; FR2549036B1; FI842765A; IL72359A0; YU43578B; PT78882A; HU194789B; YU120784A; NZ208856A; DK162976C; HUT40384A

Abstract

1. A laminated pane comprising a glass sheet, a transparent intermediate layer based on polyurethane having energy-absorbing properties, and a transparent coating layer of self-healing plastics material, notably based on a thermosetting polyurethane, characterised in that the intermediate layer based on polyurethane having energy-absorbing properties is formed essentially of a polyurethane obtained by reactive casting on a flat horizontal support of a reaction mixture of an isocyanate component of viscosity less than 5 Pas at 40 degrees C and a polyol component, the isocyanate component comprising at least one aliphatic or cycloaliphatic di-isocyanate or an isocyanate prepolymer, the isocyanate component containing urea functions, the content of urea being up to 10% of the total weight of isocyanate component, the content of urea preferably being from 5 to 7%, the polyol component comprising at least one long difunctional polyol of molecular weight from 500 to 4000 and at least one short diol as a chain lengthening agent, the ratio of isocyanate group equivalents to hydroxyl group equivalents is about 1, the proportions of the different polyols are selected such that the number of hydroxyl group equivalents due to the short polyol represents from 20 to 70% of the total hydroxyl groups, and this layer having at a thickness of about 0.5 mm, a flow stress sigma y at -20 degrees C not exceeding 3 daN/mm**2 , a rupture stress sigma R at 40 degrees C of at least 2 daN/mm**2 , a lengthening at rupture vepsiln R at + 20 degrees C from 250 to 500%, and a tear resistance Ra at + 20 degrees C of at least 9 daN/mm.

Description

72359/2 imiN> io miv oy rrnn^n nm>oa m Laminated safety glass pane with polyurethane layer SAINT-GOBAIN VITRAGE C: 65105/9 Laminated Safety Pane The invention relates to laminated panes especially windscreens for vehicles comprising a transparent rigid support of silicate glass, a layer of transparent plastics material having properties of absorption of energy (A E layer) and a transparent covering layer of plastics material resistant to scratching and abrasion known as a self-healing layer or sometimes as an internal protection layer (P I layer), as it is oriented towards the interior of the vehicle in the case of a windscreen.

Laminated panes of this type are known. For example, in French Publication 2 13^ 255, there is described a laminated pane comprising a glass sheet, a layer of a plastics material having properties of absorption of energy, notably a layer of plasticised polyvinylbutyral ,and a relatively soft protective layer based on aliphatic polyurethane . Such a laminated pane has not been entirely satisfactory as after a lapse of time which may vary from several days to a few months, there is produced a loss in adhesive properties, notably between the glass and the intermediate layer causing unsticking of the elements of the laminated pane and also a loss of optical properties of the pane with formation of cloudy zones. These losses are apparently due to take-up of humidity by the plasticised polyvinylbutyral layer.

There is also known from French Patent Publication 2 398 606 a laminated pane of the type described above in which the intermediate layer having properties of absorption of energy is a thermoplastic polyurethane obtained from at least one aliphatic diisocyanate and at least one polyesterdiol or polyetherdiol, the ratio between NCO group equivalents to OH group equivalents preferably being from 0.8 to 0.9· This pane retains good optical properties and the adhesion between the elements remains good under very variable conditions of temperature and humidity, but the bio-mechanical properties of the pane and especially its resistance to shock are not entirely satisfactory.

There is also known from European Patent Publication OO5449I a laminated pane having the structure described above and in which the intermediate layer of plastics material having properties of absorption of energy is based on a polyurethane polyurea having a linear structure and a content of urea groups of the order of 1 to 20% by weight, this polyurethane polyurea being the reaction product of a prepolymer obtained from a polyol component and an isocyanate component used in excess with at least one diamine. This intermediate layer is made by extrusion of a polyurethane polyurea resin or by casting of a solution of said resin and evaporation of the solvents which in one case like the other requires a plurality of successive operations.

In the case of extrusion it is necessary to carry out a previous synthesis of the resin to be able to extrude it.

Further, to obtain the optical quality necessary for the application envisaged it is necessary to "re-pass" the sheet. The optical quality obtained is not generally maintained with time as the plastics material retains in its memory its method of manufacture and the properties retained on "re-passage" are diminished with time.

Further, the extrusion of the layer having the properties of absorption of energy gives an assembly problem with the self-healing layer, In the case of casting of a solution it is also necessary to carry out a previous synthesis of the resin. It is then necessary to dissolve the latter in a solvent and cast the solution and evaporate the solvent in a repetitive manner to obtain a layer of thickness compatible with the desired character of absorbtion of energy. The evaporation of the solvent further constitutes a source of nuisance.

The invention avoids the disadvantages mentioned and suggests a safety pane useful notably as a windscreen for a vehicle which has good optical and biomechanical properties and which conserves them under variable conditions of temperature and humidity.

The pane according to the invention comprises, like the known panes mentioned above, a glass sheet, a sheet of plastics material having properties of absorption of energy and a self-healing coated layer resistant to scratching and abrasion, its originality residing in the choice of the layer of plastics material having properties of absorption of energy.

This layer is, according to the invention, formed in a continuous process by reactive casting on a horizontal flat support from which it may be detached, of a reaction mixture of an isocyanate component and a component having active hydrogens, notably a polyol component, the isocyanate component comprising at least one aliphatic diisocyanate , cycloaliphatic diioscyanate or a diisocyanate prepolymer, this component having a viscosity less than about 5000 centipoises at 40°C, the polyol component comprising at least one long difunctional polyol of molecular weight from 500 to 4000 and at least one short diol as a chain lengthening agent. By reactive casting is meant casting in the form of a layer or a film of a liquid mixture of the components in the monomeric or prepolymer state, followed by polymerisation of this mixture under heat. This reactive casting which gives the layer good mechanical and optical properties will be described more completely in the description which follows.

The proportions of polyurethane components are chosen to obtain preferably a balanced stoichiometric system, that is to say that the ratio of NCO group equivalents supplied by the diisocyanate component to OH group equivalents supplied by the polyol component, that is to say the long polyol or polyols and the short diol or diols is of the order of 1. When the ratio NCO/OH is less than 1 the more it decreases the more the desired mechanical properties for the application become rapidly less satisfactory. When all the components of the polyurethane are difunctional the lower limit of the ratio NCO/OH for obtaining satisfactory mechanical properties is about 0.9. When at least on one of the components is trifunctional , this low limit may be lowered to about 0.8. When the ratio NCO/OH is greater than 1, the more it increases the more certain mechanical properties of the layer obtained by reactive casting are increased, for example the layer becomes more rigid, but given the higher cost of the isocyanate component relative to that of the polyol component, the choice of ratio NCO/OH substantially equal to 1 is a good compromise between the properties obtained and the cost.

The proportions between the long polyol and the short diol may vary as a function of the desired properties and also the ratio of the group equivalents, the number of OH group equivalents due to the short diol however representing generally from 20 to 70% of the total group equivalents of the mixture forming the polyol component in the case when the ratio of the NCO group equivalents to the OH groups is of the order of 1. When the proportion of short diol is increased the layer is hardened and its modulus is generally increased. 72359/2 -5- 0£* ¾¾ Suitable diisocyanates which may be used in the invention are chosen notably from the following aliphatic difunctional isocyanates: hexamethylenediisocyanate (HMDI), 2,2,4-trimethyl-1 , 6-hexanedi isocynate (TMDI), bis 4-isocyanatocyclohexylmethane (Hylene W) , bis 3-methyl-4-isocyanatocyclohexylmethane ,2,2 bis ( 4-isocyanatocyclohexyl ) propane , 3-isocyanatomethyl-3, 5 ,5 t imethylcyclohexyl-isocyanate (IPDI), m-xylylenediisocyanate (XDI), m- and p-tetramethylxylylenediisocyanate (m- and p-TMXDI ) , trans-cyclohexane- 1 , 4 diisocyanate (CHDI), and 1,3 (diisocyanato-methyl)-cyclohexane (XDI hydrogenated ) .

IPDI is preferably used notably for reasons of cost.

According to one embodiment of the invention, there is used an isocyanate component containing urea functions. These urea functions improve certain mechanical properties of the layer. The content of urea may represent 2 to 10% of the total weight of isocyanate component having urea functions. Preferably the content of urea is from between 5 and 1% of the total weight of said component. For the reason mentioned above there is preferably used 3-isocyanatomethyl-3, ,5 t imethylcyclohexylisocyanate comprising the urea functions (IPDI and derivatives).

The long polyols which are suitable are chosen from polyetherdiols or polyesterdiols of molecular weight 500-4000; the polyesterdiols being products of ester ification of a diacid such as adipic, succinic, palmitic, azelaic, sebacic, orthophthalic acid, and a diol such as ethyleneglycol , propanediol - 1 , 3 , butanediol - 1 , ,hexanediol-1 ,6 and polyetherdiols of general formula H { 0 (CH2)n m 0H wherein n = 2 to 6; m is such that the molecular weight is from 500-4000, or the polyetherdiols of general formula CH_ H - OCH - CH~ - m OH where m is such that the total of the molecular weight is from 500-4000. It is also possible to use polycaprolactonediols .

There is preferably used polytetramethyleneglycol (n = 4) of molecular weight 1000.

The lengthening agents for the chains which may be used include short diols of molecular weight less than about 300 and preferably less than 150, such as: ethyleneglycol , 1 ,2-propanediol , 1 , 3-propanediol , 1,2, -1,3 or -1,4 butane-diol, dimethyl-2,2 propanediol 1,3 (neopentylglycol) , 1 , -pentanediol, 1 , 6-hexanediol , 1,8-octanediol, 1 , 10-decanediol , 1 , 12-dodecanediol , cyclohexanedimethanol, bisphenol A, methyl-2 pentanediol-2,4, methyl-3 pentanediol- 2,4, ethyl-2 hexanediol-1 , 3 , trimethyl-2,2,4-pentanediol-1 ,3, diethyleneglycol , tri-ethyleneglycol , tetraethyleneglycol , butyne-2-diol- 1 , 4- butanediol- 1 , 4 and decynediol which are substituted and/or etherified, hydroquinone-bis-hydroxyethylether , bisphenol A etherified by two or four propylene oxide groups, and dimethylolpropanic acid. In general the shorter the diol the harder the layer obtained.

Preferably there is used 1 , 4-butanediol which is a good compromise between obtaining a layer which is not too hard or too flexible which is desired for this type of application as an energy absorber.

One of the characteristics of the layer having the properties of absorption of energy is that it is obtained by reactive casting on a planar horizontal support. This reactive casting of which a form is already described for example in French Patent Publication 2 442 128 to obtain a layer of thermohardening polyurethane from a mixture of trifunctional components provides in surprising manner according to the invention in the case of starting components which are difunctional a layer which is not entirely thermoplastic when the ratio of NCO/OH groups is substantially equal to 1.

Reactive casting implies a rapid polymerisation reaction for the layer to be formed in a time compatible with industrial application. This requires a high temperature of the order of about 80 to 140°C, approximately, a temperature at which the secondary linking reactions are produced creating for example allophanate and/or biuret groups between the urethane chains such as: R - NH - CO - 0 - R1 - 0 - OCN - R - NCO R - NH - CO - 0 - R' - 0 - R N - CO 7 0 - R' - 0 i' £o allophanate ',ΝΗ \ \ ' * R ' v. - " NH I CO \ R - N - CO - R' - 0 - R" - NH - CO - NH - R" OCN - R - NCO R" - NH - CO - NH - R" A-.

R" - CO - NH V R" , - ' biuret R" - CO - NH - R" 72359/2 -8- In these operating conditions, even with difunctional components, when the ratio NCO/OH is substantially equal to 1 as indicated previously, the product obtained is not completely thermoplastic, in fact it is infusible and insoluble in the majority of solvents for polyurethanes such as tetrahydrofuran and dimethylformamide . This does not present any disadvantage as the film or sheet is already formed; on the other hand, advantage is taken of the improved mechanical properties of the equal formulation with respect to an equivalent system polymerised at low temperature when only a linear polycondensation is produced.

When the ratio NCO/OH is less than 1 and of the order of 0.8 to 0.9, a crosslinking of the type described above is not produced to any significant extent.

In one embodiment of polyurethane layer having properties of absorbtion of energy, the polyol component may contain a small proportion of at least one polyol of functionality greater than 2 in a proportion of about 5 to 30% by weight of the total weight of the polyol component and especially monomeric aliphatic triols such as glycerol, trimethylolpropane , triols having polyether chains, triols of polycaprolactone , the molecular weight of the triols being generally from 90 to 1000, mixed polyether/polyester polyols of functionality greater than 2, for example functionality between 2 and 3· The addition of a polyol of functionality greater than 2 creates additional bridging linkages between the polyurethane chains and may thus improve the cohesion of the layer.

The proportions between the long polyol, the short diol and possibly the polyol of functionality greater than 2 may vary according' to the desired properties. There are generally chosen proportions such that for hydroxyl equivalent, the long polyol represents about 0.3 to 0.M5 equivalent, the short diol about 0.2 to 0.7 equivalent and 72359/2 the polyol of functionality greater than 2 about 0 to 0.35 equivalent. Under these conditions, the layer has the following mechanical characteristics measured according to standards AFNOR NFT 46.002, 1.034 and 54.108: - a stress at the start of flow (Ty at -20°C not 2 exceeding 3 daN/mm , - a stress at rupture (T~R at +40°C not less than 2 daN/mm^ , - an elongation at rupture £R at +20°C from 250 to 500%, - resistance to start of tearing Ra at + 20°C greater than or equal to 9 daN/mm thickness.

According to another embodiment of the AE layer of the invention, the isocyanate component may contain limited proportions for example less than 15% of NCO equivalents of at least one triisocyanate such as a biuret of an isocyanate or a tr iisocyanurate .

According to one aspect of the invention, a part of the polyol component may be replaced by a product having different active hydrogens such as an amine.

Although reactive pouring is an essential feature of the present invention, particularly for obtaining crosslinking bonds, it is not satisfactory. It is also necessary to select the starting components of the reaction mixture to be moulded or poured. The invention proposes three possibilities, which are neither described, nor mentioned in US-A-4,103,070. 1. These consist of choosing bifunctional components, which form biurets by using for this purpose a diisocyanate containing urea functions, at a rate of 2 to 10% by weight of the isocyanate component. This isocyanate type is neither described, nor suggested in the citation. - 1 2. The second possibility consists of adding a polyol with a functionality higher than 2, at a rate of 5 to 30% by weight of the total weight of the polyol component. The addition of a polyol with a functionality higher than 2 is a secondary option of the citations. The U.S. patent given no information on the polyol type or the quantity to be used. 3. The third possibility is the combination of the two above variants.

An important advantage of the AE layer used according to the invention is that it may be formed by reactive casting on a first layer of plastics material which is already polymerised, thus finishing its polymerisation, notably the layer of self-healing plastics material without it being necessary to treat the support layer.

The self-healing covering layer resistant to scratching of plastics material which is designated in this application as an interior protection layer (PI layer) is for example described in French Patent Publications 2 187 719 and 2 251 608. This self-healing layer has under normal conditions of temperature a high capacity for elastic deformation, a small modulus in elasticity less than 2000 -10- 2 ? dN/cm and preferably less than 200 daN/cm , and a lengthening at rupture of more than 60% with less than 2% of plastic deformation and preferably a lengthening at rupture of more than 100? with less than 1$ plastic deformation. Preferred layers of this type are thermohardening polyurethanes having a modulus of elasticity of about 25 to 200 daN/cm and a lengthening of about 100 to 200$ with less than 1ί of plastic deformation.

Examples of monomers which are suitable for preparation of these thermohardened polyurethanes are on the one hand aliphatic difunctional isocyanates such as 1, 6-hexanediisocyanate ,2,2, 4-trimethyl-1 , 6-hexanediisocyanate, 2,4 ,4-trimethyl-1 , 6-hexanediisocyanate , 1 ,3-bis(isocyanatomethyl) benzene, bis (4-isocyanatocyclohexyl) methane, bis (3-methyl-4-isocyanatocyclohexyl )methane , 2 , 2-bis ( 4-isocyanatocyclohexyDpropane and 3- socyanatomethyl-3)5,5-trimethylcyclohexylisocyanate, as well as the biurets isocyanurates and prepolymers of these components having a functionality of 3 or more and on the other hand polyfunctional polyols such as branched polyols such as the polyesterpolyols and polyetherpolyols obtained by reaction of polyfunctional alcohols, notably 1,2,3-propanetriol (glycerol), 2,2- bis (hydroxymethyD-1-propanol (trimethylolethane) , 2,2- bis (hydroxymethyD-1-butanol ( trimethylolpropane) 1 ,2,4-butane-triol, 1,2,6- hexane-triol, 2,2-bis(hydroxymethyl)-1 , 3-propane-diol (pentaerythritol) and 1 ,2,3,4,5,6-hexane-hexol (sorbitol), with the aliphatic diacids such as malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, and sebacic acid or with the cyclic ethers, such as ethylene oxide, 1 ,2-propylene oxide and tetrahydrofuran .

The molecular weight of the branched polyols are advantageously about 250 to 4000 and preferably about 450 to 2000. Mixtures of different polyisocyanates and monomeric polyols may be used. A particularly preferred thermohardening polyurethane is that described in French Patent Publication 2 251 608.

The choice of thickness of the layer having properties of absorbtion of energy (AE layer) and that of the self-healing layer (PI layer) and the ratio between these two thicknesses are important factors. According to the invention the total thickness of the two superposed layers is greater than 0.5mm with a thickness of at least 0.½m for the layer having properties of absorbtion of energy.

Further, the adhesion between this layer and the sheet of glass should be greater than about 2 daN/5cm, a value measured using a peeling test as described below. This force of adhesion should not however be too high, especially when there is used an AE layer of relatively small thickness close to the lower usable limit of about 0.4mm.

The layer having properties of absorption of energy may contain various additives which generally serve to facilitate its manufacture by reactive casting or which may possibly, as the case requires, further improve certain of its properties.

It may contain a catalyst such as a tin catalyst for example dibutyltin dilaurate, tributyltin oxide, tin octoate, or an organomercuric catalyst for example mercury phenyl ester, or an amine catalyst, for example diazabicyclo(2,2,2)-octane, or 1,8 diazabicyclo (5 , 4 , 0 )- 1 decene-7.

The layer may contain a stabiliser such as bis (2,2,6,6- tetramethyl-1! piperidyl) sebacate, or a phenolic antioxidant. -12- The layer may also contain a spreading agent such as a silicone resin, a fluoroalkyl ester, or an acrylic ester.

It is possible to make a sheet having two layers in the following way.

There is first made a first layer which may be either the adhesive layer having properties of absorption of energy (AE layer), or a layer of self-healing plastics material for interior protection (PI layer) formed notably of a thermohardening polyurethane . And on this first layer, there is formed a second layer.

It is thus possible to make first of all a layer of thermohardening polyurethane by casting of a mixture of components on a casting support. After polymerisation of the monomers and formation of a thermohardening layer of thickness which may vary from 0.1 to 0.8mm, the mixture of reaction components of the layer having properties of absorbtion of energy is cast.

It is also possible to proceed in inverse manner, that is to say forming first of all the layer having properties of absorption of energy (AE layer) and then forming the PI layer.

To make the laminated pane, the elements are assembled with the use of pressure, for example by pressing between the rolls of a calender device and by the action of heat, the AE layer always being between the glass and the PI layer.

It is possible to improve the connection of the elements later by subjecting the laminated pane to an autoclave cycle, for example one hour at a temperature of about 100 to 140°C and under a pressure of about 3 to 15 bars, or by a stoving cycle. -13- Examples of manufacture of laminated panes according to the invention are described in the following.

Example 1 On a moving glass support passing in continuous manner, coated with a separation agent which may, for example, be that described in French Patent Publication 2 383 000, that is to say a modified addition product of ethylene oxide, there is cast a homogeneous mixture with the following proportions of: - 1000 g of a polyether of molecular weight of about 450 obtained by condensation of 1 ,2-propylene oxide with 2,2-bis (hydroxymethyl)- 1-butanol and having a content of hydroxy free radicals of about 10.5 to 12% containing 1J& by weight of stabiliser, 0.05% by weight of a catalyst, that is dibutyltin dilaurate and 0.1% by weight of a spreading agent. - 1020 g of a biuret of 1 , 6-hexanediisocyanate having a content of free isocyanate radicals of about 23.2%.

There is used a casting head such as that described in French Patent Publication 2 3 7 170. There is formed a uniform layer which after polymerisation under the effect of heat, for example about 15 minutes at 120°C, has a thickness of about 0.19mm and self-healing properties.

To make the layer having properties of absorption of energy there is first prepared the polyol component by mixing a polytetramethyleneglycol of molecular weight 1000 (for example the product sold commercially under the name Polymeg 1000 -by the QUAKER OATS Company), with 1,4- butanediol, the proportions of the two constituents being such that the polytetramethylenegl-ycol supplies 0.37 equivalents in hydroxyl groups whereas the butanediol-1 ,4 gives 0.63· -14- In the polyol component there is incorporated a stabiliser in an amount of 0.5% by weight of the total weight of the polyol component and the isocyanate component, a spreading agent in an amount of 0,05% by weight calculated in the same way and a catalyst that is dibutyltin dilaurate in an amount of 0.02$ by weight calculated in the same way.

The isocyanate component used is 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (IPDI) having urea functions obtained by partial hydrolysis of the IPDI and having a content of free NCO groups of about 31.5$ by weight .

The components are taken in quantities such that the NC0/0H ratio is 1.

After degassing in vacuum of the components the mixture brought to about 40°C is cast by means of a casting head, as described in French Patent Publication 2 347 170, on the layer of self-healing polyurethane formed previously. There is thus formed a layer of about 0.53mm thickness which is subjected to a polymerisation cycle consisting of 25 minutes heating at about 120°C.

The sheet of two layers is withdrawn from the glass support and it may be manipulated easily, stored and used immediately afterwards for manufacture of laminated panes according to the invention.

To make the pane, there is assembled the sheet having two layers obtained previously with a glass sheet which is heated of 2.6mm thickness. The glass may possibly be hardened or tempered. The assembly as mentioned above may be carried out in two stages, a first stage consisting of preliminary assembly obtained by passage of the elements forming the pane between two rollers of a calendar. For this purpose there may be used for example a device -15-described in European Patent Publication 0 015 209, the AE layer being applied against the internal surface of the glass and a second stage consisting of disposing the laminated product obtained in an autoclave, where, for about an hour it is subjected to a pressure of about 10 bars at a temperature of about 135°C. This autoclave cycle may possibly be replaced by a stoving cycle without increased pressure.

The pane obtained has excellent optical quality and perfect transparency.

The adhesion obtained between the glass sheet and the layer having the properties of absorption of energy is measured for the manufactured pane by a peeling test described below.

There is cut a strip of 5cm width from the covering sheet having two layers. An end of the strip is unstuck and there is applied thereto a pulling force perpendicular to the surface of the glass with a pulling speed of 5cm per minute. The operation is carried out at 20°C. The force of traction necessary for unsticking of the strip is noted. Operating thus there is obtained a traction force of 10 daN/5cm.

Trials for resistance to shock at different temperatures are carried out on the pane made according to this example.

The first trial for resistance to shock is carried out with a steel ball of weight 2.260kg (heavy ball test) which is caused to fall on the central part of a square sample of laminated glass of 30.5cra side, held on a rigid frame. There is determined the approximate height from which 90% of the samples tested at the chosen temperature resist fall of the ball without the ball passing through. -16- For the laminated pane according to the example the value obtained is 8 metres.

Another trial for resistance to shock is carried out with a 5 steel ball of 0.227kg and 38mm diameter. A trial is carried out at a temperature of -20°C, another carried out at a temperature of +40°C. The values obtained are respectively 11 and 13 metres. 10 Taking account of European standard R 43 which is now in force, the desired results are at least 4 metres with the heavy ball, at least 8.5 metres with the light ball at -20°C and at least 9 metres with the light ball at +40°C. ά 15 The PI layer shows surface properties adequate for use in a laminated pane and especially resistance to scratching measured with the ERICHSEN type 413 apparatus greater than 20g and a resistance to abrasion according to European standard R 43 with a difference in haze (Ahaze) less than 20 4$.

A pane according to the example has all the characteristics rendering it suitable as a windscreen for a vehicle. 25 Comparison Example The procedure of Example 1 is followed with the same starting components and the same proportions for manufacture of the AE layer except that this layer is not 30 obtained by reactive casting but by a plurality of successive castings of a solution of polyurethane prepared by synthesis in solution in order to obtain a thickness of 0.53mm. 35 Trials for resistance to shock carried out under the same conditions as Example 1 provide the following values: - 3· 5 metres with a heavy ball, 4 metres and 3 metres with a light ball at respective temperatures of -20°C and -17- The peeling test provides a value of 8 daN/5 cm.

These values are insufficient which shows that the reactive casting used in Example 1 gives the AE layer the desired properties.

Example 2 The procedure of Example 1 is carried out except that there are made layers with different thicknesses, that is a self-healing layer (P I) of 0.41mm thickness and an AE layer of 0.29 mm thickness.

The laminated pane obtained has the following characteristics: The peeling test gives a value of 10 daN/5cm. The heavy ball test and the two tests with a light ball give respective values of 3.5, 9 and 9 metres which is insufficient. These poor values are due to the insufficient thickness of the layer having properties of absorption of energy.

Example 3 The procedure of Example. 1 is followed, except that there is made a P I layer of 0.315 mm thickness and an AE layer of 0.415mm thickness.

The peeling test gives the value of 10 daN/5cm. The tests with the heavy ball and the light ball give respective values of 4.5, 10 and 13 metres which is satisfactory.

Example The procedure of Example 1 is carried out except that there is made a PI layer of 0.32mm thickness, an AE layer of 0.42mm thickness and the surface of the glass before assembly is subjected to a known treatment with an adhesion promoter such as a silane to obtain a higher value of adhesion. -18- The peel test gives a value of 20 daN/5cm. The heavy ball test gives a value of 3.5 metres. This value for resistance to shock which is insufficient is due to an adhesion which is too strong of the AE layer to the glass in the case where this layer has a relatively small thickness. This example is to be compared with Example 3» which despite the use of layers of the same thicknesses provides a satisfactory pane owing to a smaller force of adhesion.

Example 5 The procedure of Example 1 is carried out except that there is made a PI layer of 0.46mm thickness and an AE layer of 0.56mm thickness and the glass is treated for assembly as in Example M.

The peeling test provides a value of 20 daN/5cm whereas the tests with the heavy and light ball give respective values of 8, 11.5 and 13 metres.

This example is to be compared with Example 4. It shows that despite a strong adhesion, the use of the AE layer of high thickness provides satisfactory values of mechanical resistance .

Example 6 The procedure of Example 1 is carried out except that the starting polyol component for the AE layer is formed of a mixture of polytetramethyleneglycol of molecular weight 1000, 1 ,4-butanediol and polycaprolactotriol (for example the product sold under the name Niax 301 by UNION CARBIDE), in relative proportions such that for a hydroxyl equivalent there is used 0.35, 0.55 and 0.10 equivalents in the respective polyols. -19- There are made layers of 0.160mm thickness for the PI layer and 0.660mm thickness for the AE layer.

The pane obtained has optical and mechanical characteristics which are completely satisfactory. The values measured for different tests are as follows: an adhesion of 3 daN/5cm, and values of ball tests of 9, 13 and 13 metres .

Example 7 The procedure of Example 6 is followed except that the proportions of different polyols are respectively 0.35 OH equivalents for the Polymeg 1000, 0.45 OH equivalents for the 1 ,4-butanediol and 0.20 OH equivalents for the Niax 301.

There are made layers of 0.31mm thickness for the PI layer and 0.48mm thickness for the AE layer.

The values measured in tests are as follows: an adhesion of 3 daN/5cm, values of 4.5, 10 and 12 metres for balls, which is satisfactory.

Example 8 The procedure of Example 7 is followed except that there are used thicknesses of 0.39mm for the PI layer and 0.39mm for the AE layer.

The values measured are as follows: an adhesion of 4, values of 3, 8 and 8 for the balls, which is insufficient.

This example compared with Example 7 shows that for a same thickness for the sheet having two layers there exists a ratio of thickness between the AE layer and the PI layer which, according to the value, gives a pane which may or may not be satisfactory. -20- Example 9 The procedure of Example 1 is followed except that there is carried out the polymerisation of the AE layer at a temperature of 60°C only for 20 hours.

Trials for resistance to shock carried out under the same conditions as in Example 1 give the following values: - 6 metres with a heavy ball, 6 and 13.5 metres for the light ball at temperatures respectively of -20°C and +40°C.

The value obtained with the small ball at -20°C is insufficient. This trial compared with Example 1 shows the influence of the temperature of polymerisation during the reactive casting.

Claims

- 21 - 72359/3 CLAIMS:

1. A laminated pane comprising a glass sheet, a transparent intermediate layer based on a polyurethane having energy-absorbing properties, and a transparent coating layer of self-healing plastics material, notably based on a thermosetting polyurethane, characterised in that the intermediate layer based on polyurethane having energy-absorbing properties is formed essentially of a polyurethane obtained by reactive casting on a flat horizontal support of a reaction mixture of an isocyanate component of viscosity less than 5 Pas at 40°C and a polyol component, the isocyanate component comprising at least one aliphatic or cycloaliphatic di-isocyanate or an isocyanate prepolymer, the isocyanate component containing urea functions, the content of urea being 2 to 10% of the total weight of isocyanate component, the content of urea preferably being from 5 to 7%, the polyol component comprising at least one long difunctional polyol of molecular weight from 500 to 4000 and at least one short diol as a chain lengthening agent, the ratio of isocyanate group equivalents to hydroxyl group equivalents is about 1, the proportions of the different polyols are selected such that the number of hydroxyl group equivalents due to the short polyol represents from 20 to 70% of the total hydroxyl groups, and this layer having at a thickness of about 0.5 mm, a flow stress σγ at -20°C not exceeding 3 daN/mm2, a rupture stress aR at 40°C of at least 2 daN/mm2, a lengthening at rupture cR at +20°C from 250 to 500%, and a tear resistance Ra at +20°C of at least 9 daN/mm.

2. A laminated pane comprising a glass sheet, a transparent intermediate layer based on a polyurethane having energy-absorbing properties, and a transparent coating layer of self-healing plastics material, notably based on a thermosetting polyurethane, characterised in that - 22 - 72359/3 the intermediate layer based on polyurethane having energy-absorbing properties is formed essentially of a polyurethane obtained by reactive casting on a flat horizontal support of a reaction mixture of an isocyanate component having a viscosity less than 5 Pas at 40 °C and a polyol component, the isocyanate component comprising at least one aliphatic or cycloaliphatic di-isocyanate or an isocyanate prepolymer, the polyol component comprising at least one long difunctional polyol of molecular weight from 500 to 4000, at least one short diol as a chain lengthening agent, and at ~ least one polyol of functionality greater than 2, in a proportion of about 5 to 30% by weight of the total weight of the polyol component^,the ratio of isocyanate group equivalents to hydroxyl equivalents is about 1, the proportions of the different polyols are chosen such that the number of hydroxyl group equivalents due to the short diol represents from 20% to 70% of the total of hydroxyl groups, this layer having at a thickness of about 0.5 mm a flow stress σν at -20°C of not more than 3 daN/mm2, a rupture stress CTr at +40 °C of at least 2 daN/mm2, a lengthening at rupture εκ at +20° from 250 to 500% and a tear resistance Ra at +20°C of at least 9 daN/mm.

3. A laminated pane according to claim 1 or 2, characterised in that the isocyanate component comprises 3-isocyanato-methyl-3, 5, 5-trimethylcyclohexylisocyanate.

4. A laminated pane according to one of claims 1 to 3, characterised in that the isocyanate component is formed essentially of 3-isocyanatomethyl-3, 5, 5-trimethylcyclo-hexylisocyanate having urea groups and in that the polyol component is formed essentially of polytetramethyleneglycol of molecular weight about 1000 and 1, 4-butanediol.

5. A laminated pane according to one of claims 2 to 4, characterised in that the polyol of functionality greater than 2 is a triol.

6. A laminated pane according to one of claims 2 to 5 , characterised in . that for one hydroxyl equivalent in total for the polyol component of the polyurethane having - 23 - 72359/2 energy-absorbing properties, the long polyol represents 0.30 to 0.45 equivalent, the short diol 0.2 to 0.7 equivalent and the polyol of functionality greater than 2 0 to 0.35 equivalent.

7. A laminated pane according to one of claims 1 to 6, characterised in that the polyurethane layer having energy-absorbing properties comprises additives, such as a catalyst, a spreading agent and a stabiliser.

8. A laminated pane according to one of claims 1 to 7,~ characterised in that the thickness of the polyurethane ~ layer having energy-absorbing properties increased by the thickness of the coating layer is greater than 0.5 mm, with a thickness of at least 0.4 mm for the layer having energy-absorbing properties.

9. A laminated pane according to any one of claims 1 to 8, characterised in that the adhesion between the layer having energy-absorption properties and the glass sheet is greater than 2 daN/5 cm.

10. A laminated pane according to any one of claims 1 to 9, characterised in that the polyurethane layer, having energy-absorbing properties is obtained by polymerisation at a polymerisation temperature greater than 80°C during reactive casting.

11. A laminated pane according to any one of claims 1 to 10, characterised in that the isocyanate component further comprises at least one tri-isocyanate. 72359/PC/jg