NO133364B - - Google Patents

Description

The present invention relates to laminated glass objects and more particularly to laminates in the form of a safety glass which consists of a layer of polyester-urethane, attached to at least one layer of glass.

Safety glass is a well-known term for a glass assembly that consists of an intermediate layer that binds two sheets of glass together so that breakage in the glass results in a mini-mal dispersion of fragments of broken glass. These laminated glasses are used extensively in cars, and must have a number of properties, among which should be mentioned: (1) a high level of impact energy absorption to minimize brain damage; (2) a cutting and wear resistance sufficient to prevent abrading from the broken glass; (3) adequate adhesion to the glass to prevent tearing and to prevent pieces of broken glass from scattering and injuring nearby persons; and (4) it must have good optical transparency.

A difficulty with today's windshields is that it

if broken, sharp glass edges develop which can result in serious injuries. To prevent this type of damage, the glass laminates must have improved penetration resistance,

but this resistance must not be so great that it can cause brain damage. Furthermore, safety glass must have these properties in a wide temperature range in which these materials are used.

From US patent no. 3,620,905, a polyester-based polyurethane is known which is indicated as usable in safety glass laminates. Here, however, a polyester diol is used which melts below 40°C" and in order to obtain a polyester with this physical property, it is necessary to use mixtures of glycols and/or mixtures of diacids. However, this polyester-urethane gives a laminate which is brittle at -17.8°C, and this must be considered a significant shortcoming as a laminate which is brittle has little resistance to penetration by impact or shock at the indicated temperature.

Thus, the present invention relates to an optically clear, energy-absorbing laminate, comprising at least one glass plate bonded to a sheet of thermoplastic transparent polyurethane which is virtually free of unreacted cyanate and preferably placed between two glass plates, and the invention is characterized

certified in that the polyurethane is one obtained by reaction in a step of

a) a polyester with hydroxy end groups and with an average molecular weight of between 500 and ^,000 and which

melts above 50°C,

b) an aliphatic or cycloaliphatic hydrocarbon diisocyanate and c) an aliphatic diol with from 2-15 carbon atoms and with a molecular weight of less than 250, where

the molar ratio between (c) and (a) is from 0.5:1 to 10:1 and increases with increasing molecular weight for (a), and where the isocyanate groups in (b)

essentially, the numerical equivalent is the sum of active hydrogen and hydroxyl groups in (c) and (a), and where the molar ratio between (c) and (a) to obtain a polyester urethane which is approximately free of unreacted isocyanate groups is placed within the given area so that a rigid, clamped laminate made from an approximately 7.62 mm thick sheet of said polyester-urethane placed between two 30.5 cm x 30>5 cm x 3>!7 w® glass plates is not brittle at -17.8°C and further exhibits penetration at average speeds of at least 32.18 km/h at laminate temperatures of -17.8°C, +21.1°C and 48.9°C when the laminate is struck with a 2, 26 kg heavy free-falling steel ball.

It has further been found that several factors are important and interdependent for the usability and effectiveness of the polyester-urethanes as interlayers for safety glass applications. Thus, it is noted that the chemical composition of the polyurethane is essential, as well as the connection between the polymer compounds. In many cases, as will be described in more detail below, the factors are interdependent. Polyester urethanes that come into consideration are produced e.g. from polyesters with hydroxy end groups of .molecular weights usually in the range of 1000 and up, rarely exceeding $ 000 or less than 750> determined by hydroxyl end group analysis and by the formula: Molecular weight = ( <p>functionality of the dvol) ( 56, 1) ( 1,000)

hydroxyl number

It is noted that with such polyurethanes and more particularly with polyurethanes such as those formed from poly(1,4-butylene adipate) with a molecular weight of from 1000 to 4000, the best interlayer compositions are obtained when the proportion of polyesters used in relation to the proportion of compound with a pair of active hydrogen groups (e.g. 1,4-butanediol), is regulated within a special range. Furthermore, it has been found that the proportions are dependent on the average molecular weight of the poly(1,4-butylene adipate); i.e. that the ratio for the polyurethane compounds is not necessarily the same with polybutylene adipates of different molecular weights. Intermediate layers made of poly(1,4-butylene azelate) such as polyester also show excellent properties, but for simplicity the following description will be directed to poly(1,4-butylene adipate), while it is understood that the two polyesters are interchangeable in many cases.

To achieve the best results should at least

some of the reactants contain aromatic or cycloaliphatic molecular parts. Usually the isocyanate is cyclic and the reactant with hydroxyl end groups aliphatic, but this is not necessary.

The interdependence noted with respect to the proportions of the polyurethane compounds may be illustrated by reference to a particular class of preferred polyester urethanes. Thus, it has been found particularly advantageous according to the invention to obtain particularly effective safety glass intermediate layer compositions to use polyurethanes of poly(1,4-butylene adipate) with hydroxy end groups and an average molecular weight of from 1000 to 4000, 1,4-butanediol and 4,4'-methylene-bis(cyclohexyl isocyanate) in a stereoisomer content of 19 to 21% trans, trans, 17 to 18% cis, cis, and 62 to 64% cis, trans. The diisocyanate may also contain a smaller and unavoidable amount of monoisocyanate, e.g. between 0.27 °g 0>4-0%> and should have a total acidity, (as HC1) of between about 0.001 and 0.002 weight percent and an isocyanate content of about 99 > 8 fo of the theoretical. Such a product is commercially available under the trade name "Hylene W". For intermediate layers with the best impact energy absorption level, it is important to make the polyurethane from suitable proportions of these substituents. Other things being equal, it has been discovered that the best interlayer materials are obtained when the ratio of 1,4-butanediol to poly(1,4-butylene adipate) is controlled within particular limits, which limits are noted to vary depending on the molecular weight of the poly(l, 4-butylene adipate).

Thus, if the poly(1,4-butylene adipate) has a molecular weight of about 1,000, superior intermediate layer compositions are obtained by using between 0.9 and 1.2 mol of 1,4-butanediol per moles of poly(1,4-butylene adipate). If the ratio here between butanediol and poly(1,4-butylene adipate) exceeds 1.2:1, a loss of optimal performance for safety glass applications is noted when the laminate is at a temperature of -17.8°C, as the interlayer becomes brittle . Brittle interlayers are undesirable due to the small diaphragm effect when the laminate is crushed, which increases the likelihood of brain damage, lacerations or penetration injuries. Within the aforementioned conditions, the compositions are superior to all known interlayer compositions, as the penetration resistance is superior over a wide temperature range of from -17.8 to 48.9°C. In the past, it has only been possible to produce laminates that were effective at a particular temperature, and when variations were made with a view to another temperature, the properties of the laminate at the first temperature were damaged. However, it is possible, with the preferred superior compositions of the invention, to adjust the proportions so that the laminate is unusually effective at a particular temperature. If it is thus e.g. is desirable with a laminate with particularly good properties at -17.8°C, the ratio between 1,4-butanediol and poly(1,4-butylene adipate) with a molecular weight of 1000 can be reduced to 0.5 or less. While this is desirable for laminates to be used at -17.8°C, it is not usually desirable for windscreens, where good properties in a wide temperature range are desirable. If it is desired to produce a laminate with high temperature properties, the ratio between 1,4-butanediol and poly(1,4-butylene adipate)

with a molecular weight of 1000, be as high as 6 or more. In order to achieve performance over a wide temperature range, however, it is seen that the ratio of the components lies within rather narrow limits.

However, it is very surprising to find that

if poly(l,4-butylene adipate) has a molecular weight of 2000, then

the ratio between the constituents can be expanded considerably and still superior compositions can be achieved. For example, the ratio of 1,4-butanediol to poly(1,4-butylene adipate)

with a molecular weight of 2000 be between about 2:1 and about 5:1, and the laminate has superior properties over a wide temperature range. If the ratio exceeds 5>1:1, however, the intermediate layers become brittle at -17>8°C. However, if high temperature properties are desired, the ratio may be as high as about 10 or more, and if low temperature properties are desired, the ratio of 1,4-butanediol to poly(1,4-butylene adipate) may be 1:1 or 0.5 or less. The urethanes can be produced using a mixture of the two aforementioned poly(1,4-butylene adipates) with different molecular weights, and it is assumed that the best intermediate layers are produced from poly(1,4-butylene adipates) with a total average molecular weight of between around 1000 and around 4000. With these poly(1,4-butylene adipates) of preferred molecular weight, an intermediate layer with superior impact properties over a wide temperature range can be produced when the ratio between 1,4-butanediol and poly(1,4-butylene adipate) is between 1 :1 and 6:1 or more. If, however, superior properties are desired at a particular temperature, the conditions can be varied further.

The interdependence is shown by means of the data set out in Table I.

The urethanes were prepared by the general method and under the conditions indicated in Example 1 except that no catalyst was used and the laminates were prepared by the method indicated on page 33*

From the data given in Table I, it can be seen that the intermediate layers became brittle at -17.8°C if only 1.58 mol of 1,4-butanediol per mol of low molecular weight polyester, while irethanes formed from higher molecular weight polyesters did not become brittle until

5>8 mol of butanediol per moles of polyester. Thus forward-

it is possible that the higher molecular weight polyesters allow the proportions of the constituents to be varied within a wide range without the energy absorption properties being reduced, over a wide temperature range. The average penetration speed of the bullet is not stated

for the brittle samples because it is assumed to be misleading as there was very little diaphragm action in the brittle samples. These brittle compositions are, however, usable in applications where properties for the middle or high temperature range are desired, or in applications other than as safety glass. The molar ratio of superior interlayer compositions for wide temperature ranges is also shown in the accompanying drawing. There is the molar ratio of 1,4-butanediol to poly(1,4-butylene adipate)

with a molecular weight of 1000 to 2000 plotted graphically. It appears that the range of the proportions, while it is significant for the lower molecular weight polyesters, is sufficiently wide for the higher molecular weight polyesters that many excellent compositions can be produced.' In general, the most preferred compositions using poly(1,4-butylene adipate) with a molecular weight of 1000 to 2000, and 1,4-butanediol as the active hydrogen compound will have a molar ratio between 1,4-butanediol and polyester that is less than the line BH and generally superior compositions can be prepared when the molar ratio of 1,4-butanediol to poly(1,4-butylene adipate) having a molecular weight of 1000 to 2000 lies between the lines BH and AD (see drawing). When a mixture of polyesters is used

these limits can be exceeded without loss of properties. The ratio can be further expanded with higher molecular weight poly(1,4-butylene adipates) and this is applicable to other polyesters even if the exact molar ratios will vary from those indicated.

Generally, however, the molar ratio of active hydrogen compound with a molecular weight of less than about 250 to polyesters can be from about 0.5:1 to 7:1 to produce a polyurethane sheet capable of exhibiting an average penetration rate of at least 38 .6 km/h for a 2.27 kS free-falling ball when the laminate is at a temperature of -17.8°C, 21.1°C and 48.9°C, and the urethane is attached and bonded between two sheets of glass with a dimension of 30"4 x 3°>4 cm and with a thickness of 3.17 mm" so that a laminate appears, and the laminate is held firmly and the polyurethane sheet has a thickness of about 0.762 mm. To achieve the best results, the molar ratio of low molecular weight active hydrogen compound to polyester is between about 0.9 '• 1 and about 5 : 1 and preferably between about 0.9 and about 1.2 for polyester with a molecular weight of 1000 and between about 2 : 1 and about 5 : 1 ?or e* polyester with a molecular weight of 2000. The ratio will vary, however, depending on the composition of the reactants, the reaction temperature, the mixing temperature, the configuration of the laminate and other variables mentioned herein. Generally, higher ratios of low molecular weight active hydrogen compound to polyester can be used when the resulting polyester-urethane is attached to a single sheet of glass in a two-layer configuration, without suffering from optimal properties.

Commercial polyesters contain a minor amount of free low molecular weight diol, e.g. not more than 1% by weight for polyesters with a molecular weight of 1000, and not more than 0.5% by weight for polyesters with a molecular weight of 2000. Larger amounts of free diol will give the polyurethane a greater stiffness, and as a consequence of this the conditions as herein are mentioned based on the use of polyesters with small amounts of free diol.

Another important criterion for a good intermediate layer composition is that it must be transparent, at least when it is in the form of a thin plate as used in safety glass. It has been discovered that clear or cloud-free intermediate layers are produced when the urethane reactants are homogenized and reacted at a temperature above about 100°C and preferably above about 120°C. In many cases, however, additional steps are necessary to obtain clear polymers that are free of cloudy sites. For example, certain compositions made from high molecular weight polyesters, such as e.g. poly(1,4-butylene adipate) with a molecular weight of 4000, translucent, if the reaction rates of the reactants are not regulated to achieve a more random distribution, e.g. by using a catalyst or by mixing and/or carrying out the reaction at a higher temperature. Some urethanes are also translucent when made with 4,4,-methylene-bis(cyclohexyl isocyanate) in a stereoisomeric ratio of 70% trans and 30% cis. One method of getting these polymers ready is to heat the polymers to a temperature of between about 160 and about 187.8°C, e.g. by extrusion, and then quenching in water, although in some cases polymers can return to their translucent state upon ageing. In the case of 4>4'-methylene_bis(cyclohexyl isocyanate)

with the above stereoisomeric ratio, the reason the resulting urethanes are often translucent is believed to be due to the fact that the greater amount of the more reactive trans isomer results in blocks of regular segments causing opacity or translucency. A third way of obtaining clear polymers with these above-mentioned diisocyanates is to use a branched structure or unsymmetrical low molecular weight diols as active hydrogen compounds, such as 1,3-butanediol or 1,4-cyclohexane-dimethanol (mixture of cis and trans isomers ). Very surprisingly, it has been found that when 4>4,_methylene-bis (cyclohexyl isocyanate) is used with a stereoisomer ratio of 55 f° trans and 45 i° cis, then the most preferred 1,4-butanediol can be used as active hydrogen compound. The preferred diisocyanates are those where a similar reaction rate can be achieved with each of the other urethane components at the desired reaction temperature and especially the aliphatic and cycloaliphatic diisocyanates which have close to the same reaction rate with both polyesters and low molecular weight aliphatic diols. Most preferred are the cycloaliphatic diisocyanates, such as 4>4'-methylene-bis-(cyclohexyl isocyanate) (eg "Hylene W") which are liquid at room temperature (30°C).

The polyester urethanes which are made from aliphatic

and cycloaliphatic diisocyanates in particular are not adversely affected by ultraviolet light nor are they adversely affected by ordinary processing temperatures. For example, the most preferred polyurethanes, prepared from poly(1,4-butylene adipate), 1,4-butanediol and 4>4'-methylene-bis(cyclohexyl isocyanate) ("Hylene W") were processed in a "DuPont" thermogravimetric analyzer and

these showed no decomposition after 12 hours at a temperature of 200°C, and at a temperature of 250°C in the same period of time the polyurethane decomposed at a rate of only 1.2%

per hour. Thus, the most preferred polyurethanes can be treated at temperatures up to 270°C or above for several minutes without adverse effects.

Without wishing to be bound by any particular explanation, it is believed that the unusual energy absorption properties and transparency are not only dependent on the urethane ingredients and proportions, but also on the method of manufacture. More particularly, it is believed that the presence of regular block segments of polyurethane has an adverse effect on the polyurethane transparency and energy absorption level and thus it is believed that an arbitrary polymer is necessary for optimal results. However, whether or not the urethane contains arbitrary or regular block segments depends on the particular reagents and their relative reactivity as well as the reaction conditions. Generally speaking, the diisocyanate is believed to be more reactive with butanediol than the polyesters with hydroxy end groups, and thus care is taken to inhibit the preferred reaction between the butanediol and the diisocyanate, e.g. by rapidly adding the diisocyanate to an intimate mixture of the butanediol and polyesters with vigorous stirring, preferably at a temperature of at least about 80°C if no catalyst is used, and then maintaining the reaction temperature at at least about 120°C after the exothermic reaction has given up. If a catalyst is used, the mixing temperature will usually be lower, e.g. around 65°C so that the exothermic reaction does not bring the temperature of the mixture significantly above the desired reaction temperature. However, since the polyurethanes are thermally stable, the reaction temperature can reach up to 200°C, especially for the most preferred polyester urethanes; and they can also be as low as down to 70°C. If a catalyst is used, the reaction temperatures can be lower, as the catalyst accelerates the reaction. A preferred temperature range is between about 80°C and about 100°C. If no catalyst is used, the reaction temperature should ideally be between around 120°C and 150°C after the heat generation has subsided.

It is also important to quickly reach the reaction temperatures after a homogeneous mixture has been obtained, when a catalyst is not used, so that the product does not become cloudy. For example, it has been found that when the preferred poly(1,4-butylene adipates), 1,4-butanediol and cycloaliphatic diisocyanates such as 4>4'-methylene-bis-(cyclohexyl-i-diisocyanate") are used, the mixture becomes cloudy after about 103 minutes at a temperature of 65° C. However, if the temperature is raised to 80° C, the mixture becomes cloudy after about 47 minutes and if the temperature of the mixture is slowly raised from 57 to 100° C over a 20 minute period and then held at 100 °C, the mixture becomes cloudy after only 16 minutes at 100 °C. Thus, it is important either by using a catalyst or by adding the reactants at the reaction temperature, e.g. by using a mixing head, to quickly reach the reaction temperature such as e.g. . the above stated 120°C, so that the polymers do not become cloudy. As for the high molecular weight polyesters, their high viscosities require more intense agitation and/or higher temperatures to obtain a homogeneous mixture and the resulting transparent polyurethanes.

The urethane components are preferably mixed in a moisture-free atmosphere, e.g. a nitrogen atmosphere, to prevent moisture contamination. When the reaction is carried out without a catalyst, an oxygen-free atmosphere is also preferred to prevent any surface discoloration of the urethane.

These preferred urethanes are preferably prepared by the one-step mass polymerization method which produces a flexible polymer with a more random distribution of the segments. The total number of hydroxyl groups or labile hydrogen atoms should be approximately equivalent to the number of isocyanate groups, and preferably a slight excess of hydroxyl groups of up to about 5% is used, although rarely an excess of up to 10% may be possible.

The isocyanate reaction is preferably carried out under water-free conditions such as e.g. in a nitrogen atmosphere under atmospheric pressure and at a temperature of between about 70 and about 180°C until the polymer formation is essentially complete, and the product is virtually free of isocyanate groups, i.e. has less than 0.6% by weight of isocyanate groups. The isocyanate content in polymers should ideally be less than about 0.3% by weight. Polyesters and other water absorbing reactants should not have a water content of more than 0.06 fo when the NC0/0H ratio is 0.99. To achieve the desired randomness and a clear tough polymer, the active hydrogen compound is added, e.g. 1,4-butanediol, preferably to the polyester under a nitrogen atmosphere, to exclude moisture, and the temperature is kept sufficiently high so that no phase separation occurs and so that a homogeneous mixture is obtained. The diisocyanate, e.g. 4 >4l_methylene-bis(cyclohexyl-isocyanate), is preferably added quickly, and the temperature of the mixture is kept above about 65°C, although higher temperatures may be necessary for substances that are only slightly soluble, so that no phase separation and so that the mixture remains homogeneous. The mixture is then degassed preferably with agitation for a period of about 3 minutes, during which time the pressure is reduced from atmospheric to about 3 mm of mercury. The pressure reduction facilitates the removal of dissolved gases such as nitrogen and carbon dioxide, and the components are preferably reacted at a boiler temperature of between about 120 and 150°C (e.g. 143°C) if the reaction takes place in the presence of a catalyst, and the reaction is continued for at least about 1/2 hour until essentially no more isocyanate groups are present. If no catalyst is used, the reaction can be carried out

for at least about 10 hours, preferably under a nitrogen atmosphere.

The resulting semi-solid polymer is then preferably cut while hot, granulated, extruded and/or ground and calendered into sheets and assembled into laminates.

Polymers with the desired random distribution can also be produced by the prepolymerization method whereby polyesters are first treated with a diisocyanate in excess of what is necessary to bind the ends, i.e. with more than two moles per moles of polyester. Usually around 3 mol of diisocyanate per mol polyester necessary, preferably 4 mol or more. The active hydrogen compound is then reacted with prepolymers.

In addition to the preferred polyesters prepared from adipic and azelaic acid, and 1,4-butanediol, other preferred aliphatic polyesters can be used, which can be prepared by an esterification reaction of an aliphatic dibasic acid or an anhydride thereof with a diol, preferably an aliphatic diol. Suitable aliphatic dicarboxylic acids can be described by the formula:

H00C - R - C00H

where R is an alkylene radical with from 2 to 12, preferably 4 to 8 carbon atoms, e.g. adipic acid, succinic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and the like, or their anhydrides

or unsaturated acids such as maleic acid and fumaric acid, and acetylenic dicarboxylic acids can also be used. In addition to 1,4-butanediol, other aliphatic diols with from 2 to 15 carbon atoms can be used to form polyesters, e.g. ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, ethylene/propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, and unsaturated diols such as 2 -butene-1,4-diol and 2-butyne-1,4-diol and the like, which diols preferably contain the hydroxyl groups in the terminal position. Other preferred polyesters are polycaprolactones such as e.g. prepared from epsilon-caprolactone or•polypivalolactone.

Although several polyesters with hydroxy end groups can be used, particularly good results are achieved when polyesters with a melting point of around 50°C are used, exemplified by the following polyesters:

In addition to the preferred 4>4'-methylenebis-(cyclohexyl isocyanate) other dinuclear cyclic aliphatic diisocyanates are preferred, which are connected through an alkylene group with from 1 to 3 carbon atoms, and which can be substituted with nitro, chlorine, alkyl, alkoxy and other groups which are not reactive with hydroxyl groups (or active hydrogen groups), provided that they are not placed so as to make the isocyanate group non-reactive. Examples of preferred dinuclear cyclic aliphatic diisocyanates are 4>4'-isopropylidene-bis(cyclohexyl isocyanate). Mononuclear cycloaliphatic diisocyanates are also useful,

such as 1,4-cyclohexyl diisocyanate.

In addition to the most preferred 1,4-butanediol, other preferred aliphatic diols with from 2 to 15 carbon atoms can be used as active hydrogen compounds, of which mention should be made: ethylene glycol, 1,3-propanediol, ethylene/propylene glycol, 1,3-Propandiol , 1,3-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol and unsaturated diols such as 2-butene-1,4-diol and 2-butyne-1,4-diol and the like , which diols preferably contain the hydroxyl group in the terminal position. These preferred diols do not have ether, carboxyl, ester or other non-hydrocarbon linkages. Generally, the preferred active hydrogen compounds are essentially difunctional hydrocarbons with terminal hydroxyl groups.

Although the best interlayer polyester urethanes are made from aliphatic polyesters with molecular weights between 1000 and about 4000, good results can be obtained with polyesters with molecular weights between about 750 and 5000. If polyesters have a low molecular weight of about 500, it is to achieve the desired flexibility and optical clarity required that the amount of active hydrogen compound be reduced to less than 1 mol per mol polyester, e.g. to a quarter mole to half a mole per moles of polyester. The exact amount used will, however, depend on the particular components and their molecular weight.

As the substances have different refractive indices, in order to obtain a product with good optical clarity, it is necessary that polyesters make up a large proportion of polymers, so that the other segments are present in quantities that are small in relation to the wavelength of visible light, so that the amount of light that is split is small, resulting in a highly transparent sample. Thus, the polyester proportion should make up at least about 40 percent by weight of polymers and preferably between about 50 and about 70%. Generally, the polyesters will have an average molecular weight of between about 750 and 4000, the diisocyanates between about 172 and about 300 and the active hydrogen compound between about 62 and about 250. If the substances are used within the above-mentioned molecular weight ranges, the resulting polyurethane will contain (calculated from the weight proportion of the components) between about 40 and about 80 percent by weight, preferably between about 50 and 70 percent by weight of polyester and between about 10 and about 60 percent by weight, preferably between about 20 and about 40 weight percent diisocyanate and, if at all, from between about 3 to about 25 and preferably between about 5 and about 15 weight percent active hydrogen compound.

The preferred urethanes are thermoplastic and

thus are essentially linear, difunctional constitu-

parts preferred, although trifunctional components can be used in smaller amounts of less than about 1 percent by weight of the reactive groups, and a thermoplastic urethane will still be obtained. Generally, these plastomeric urethanes are characterized by being substantially free of cross-linking due to branching. They are plastomers because they are made essentially of difunctional reactants. Thus, polyesters, the diisocyanate and the active hydrogen compound (e.g. diol) are ideal as the only polyfunctional reactants used in the production of the polyurethane.

The polyesters used in the production of the urethanes according to the invention preferably have hydroxyl end groups,

and thus a molar ratio of more than 1 mol diol per mol of acid to obtain linear chains that have a predominance of terminal hydroxyl groups. A catalyst, if this is used for the polyester production, is only used in a small amount so as not to influence the subsequent urethane reaction. If desired, special precautions can be taken to remove the catalyst from the polyester before the polyurethane formation. Useful polyesters are commercially available or they can be readily prepared by methods reported in the literature.

The urethanes used in the laminates according to the invention are preferably made according to a one-step mass polymerization method so that a random block polymer is obtained and because this is the easiest and cheapest method.

In addition to the preferred aliphatic polyesters, polyesters formed from other compounds can be used. Aromatic dicarboxylic acids which can be used include the mononuclear dibasic acids and especially terephthalic acid and isophthalic acid as well as the dinuclear acids which are preferably linked by means of an alkyl group, e.g. such as the following: 4>4'-isopropylidenedibenzoic acid, 4>4'-(2,2-butylidene)dibenzoic acid, 4>4'-(l>l>2,2-tetramethylethylene)dibenzoic acid, 4 > 4'-(1 >1>2,2-tetramethylene)benzoic acid , 4,4'-(1,1,2,2-tetrapropylethylene)dibenzoic acid, 4,4f<->(1,1,2,2-tetrabutylethylene)dibenzoic acid, 3 > 3*-isopropylidenedibenzoic acid, 2,2f-isopropylidenebenzoic acid, 4,4'-(1,2-diethyl-1,2-dimethylethylene)-dibenzoic acid, 2,2'-(1,1,2,2-tetraethylethylene) )dibenzoic acid, 2,2'-(1,1,2,2-tetrabutylethylene)dibenzoic acid, 4>4'-(2,2-butylidene)di-benzoic acid, 3>3'-(2,2-butylidene)dibenzoic acid , 2,2'-(2,2-butylidene)-dibenzoic acid, 4>4'-(2,2-pentylidene)dibenzoic acid, 3,3'-(2,2-pentylidene)dibenzoic acid, 2,2' -(2,2-pentylidene)dibenzoic acid, 4>4'-(3>3-pentylidene)dibenzoic acid, 3> 3'—13>3-pentylidene)dibenzoic acid, 2,2'-(3>3-Pentylidene)dibenzoic acid , 4>4'-(2,2-hexylidene)dibenzoic acid,

3,3'-(2,2-hexylidene)dibenzoic acid, 2,2'-(2,2-hexylidene)dibenzoic acid, 4,4'-(3,3-hexylidene)dibenzoic acid, 4>4' -(3> 3_neptylidene)dibenzoic acid, 3 > 3'-(3>3-peptylidene)dibenzoic acid, 4>4'-(4>4-heptylidene)dibenzoic acid, 4,4'-(4>4-°ctylidene)dibenzoic acid, 3 > 3 '-(4>4_octylidene)dibenzoic acid,

2,2'-(4,4-octylidene)dibenzoic acid, 4 > 4* -(5 >5-nonylidene)dibenzoic acid, 3»31-(5 >5_nonylidene)dibenzoic acid, 2,2'-(5,5-nonylidene) )dibenzoic acid,

The diols which are reacted with the aforementioned aromatic acids are aliphatic diols such as those mentioned above, and especially 1,4-butanediol.

In addition to the most preferred cyclic aliphatic diisocyanates, straight chain aliphatic diisocyanates such as 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate and 1,10-decamethylene diisocyanate can be used.

In addition, sterically hindered types can also do so

such as 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl diisocyanate (IPDI) in which the two isocyanate groups are very different with regard to reactivity, are also used. In addition, the corresponding cycloaliphatic diisocyanates, produced by hydrogenation of aromatic compounds, can be used, such as e.g. hydrogenated toluene diisocyanate.

The polyurethanes for the laminates according to the invention

can be produced in different ways. The prepolymer process provides selective control of the polymerization step. In this method, polyesters are first reacted with an excess of diisocyanate to give an adduct or prepolymer with a lower molecular weight. Prepolymers can then be polymerized (chain extended) with glycols, diamines or other active hydrogen compounds. A thermosetting or a cross-linked material can be achieved by using some triol or other trifunctional substances in the curing step, or cross-linking can be achieved by regulating the ratio between prepolymer and active hydrogen compound so that a slight excess of NCO is present.

In addition to the prepolymer method where the reaction between isocyanate and polyester is finished before the active hydrogen compound (herein alternatively called the "curing agent") is added, all components can preferably be mixed simultaneously in a so-called one-step process as described earlier with the most preferred compositions. This method is usually satisfactory, when all active hydrogen reacts at approximately the same rate, such as e.g. when all contain hydroxyl groups as the only reactive sites.

Catalysts are usually not necessary for the relatively stable aliphatic diisocyanates.

The treatment conditions used and the properties

in the finished polymer will determine the choice of curing agent.

When the prepolymerization method is used, prepolymers are preferably heated to a temperature that is above the melting point of the curing agent and which reduces the prepolymer viscosity to a few hundred or at most a few thousand cP in order to support mixing in this way and prevent the curing agent from becoming solid. The curing agent is also usually heated above its melting point. The mixing of prepolymers with curing agent is an important step and the agitation should be excellent.

Corresponding or better results can be obtained with the one-step method if the heat generation is carefully regulated and if the relative reaction rates for all components are adjusted to be close to the same. If not, a catalyst must be used.

The properties of the polyurethanes are determined by several characteristic features such as molecular weight, cross-linking, inter-molecular forces, the stiffness of the chain units, the rotatability of the chain segments and the crystallization. However, these variables can be changed to obtain polymers with specific properties. The polyurethane or polyurethaneurea segments formed from the low molecular weight active hydrogen compounds are believed to be present in regions that provide stiffness in polymers, and the polyester and other polyol segments provide flexibility. The structure and length of the hard segment, which is derived from the low molecular weight active hydrogen compound and diisocyanate, can be controlled by the amount of the type of reactants used. In the same way, the structure and length of the flexible segments can be regulated by means of the molecular weight and the type of hydroxyl-containing polyester used.

The ratio between the reactants may vary depending on the substances used and the intended use of urethane, but the total number of labile or active hydrogen atoms should ideally be roughly equivalent to the number of isocyanate groups. The ratio of NCO to active or labile hydrogen atoms should generally be from about 0.97 to about 1.03, preferably between about 0.98 and 1.01.

After the reaction is substantially complete, polymers are transferred directly to an extruder and extruded and/or ground and calendered to the desired thickness, or the partially polymerized material can be further polymerized in the forming equipment. If it is not possible to make a direct transfer from the reaction apparatus to the forming apparatus, the polyurethane substance can be poured into containers or the like and allowed to harden in blocks. The containers are preferably covered with an extruded sheet of the same urethane material so that polymers do not stick to the container, otherwise removal will sometimes be difficult. Suitable covering materials are halogenated hydrocarbons such as "Teflon", or Carbauba wax or a sheet material such as "Tedlar" can be placed first in the vessel. Common granulators, mills and extruders can be used to convert polymers into sheet form. The material is then preferably placed between a non-adherent protective fabric, such as a polyethylene to exclude dust, and preferably sealed in a container to exclude moisture. It may be desirable to coat polymers with a powder such as e.g. sodium bicarbonate to prevent adjacent sheets from sticking to each other. For. use in a laminate, it is desirable to regulate the moisture content in polymers, e.g. by drying in an oven at a temperature of between room temperature and about 48.9°C for a period of time from some. hours and up to 3 days or more. Before lamination, the powder, if used, can be removed in a water bath, after which the sheet is dried. The polyurethane can then be placed together with other materials to form the desired laminate. In some cases, an adhesion promoter may be necessary, e.g. an alkoxysilane. Suitable substances include: gamma-aminopropyltriethoxysilane, commercially available under the name "A-1100" and "Z6020", and N-((3-amino-ethyl)gamma-aminopropyltrimethoxysilane, commercially available under the name "A-1120". -The promoter can incorporated into the urethane reactants, applied externally to the sheet material, or preferably applied to the glass surface. In some cases, an adhesion regulator or inhibitor may be necessary, such as, for example, the alkyl acid phosphates described in Canadian Patent No. 861,469. Particularly preferred is stearyl acid phosphate noted to produce a desired controlled adhesion with excellent diaphragm action and glass retention when a laminate is fractured.

It has been found that when laminates are produced by cast-in-place, an adhesion inhibitor is usually necessary, as this process produces laminates where the urethane bonds rather strongly to the glass. A promoter may or may not be necessary, depending on the polymer used, when the polyurethane is extruded and/or calendered into a sheet such as e.g. when produced by means of the one-step mass polymerization method. The inhibitors are usually added to the urethane reactants, although in

in some cases it can be coated on the sheet material or the glass layer. Only a small amount of adhesion-regulating agent is required, if at all, e.g. from about 0.00001 to about 0.1 fo.

After the desired layers have been installed, air must be removed after which the edges of the laminate are sealed by placing a rubber strip or channel around the edges of the laminate and then applying a vacuum while simultaneously heating the laminate to the polyurethane softening temperature. The sealing can be carried out within 5 to 10 minutes at a temperature of 148.9°C at a pressure of 0.7 to 1.75 kg/cm<2> gauge pressure. The laminate may then be placed in an oil or air autoclave until the laminate is sealed at a temperature of between about 135 and about 176.7°C for a period of between 45 minutes and 2 hours at from 3.5 to 1715 kg/ cm gauge pressure. The autoclave conditions will, however, depend on the particular polymer used. In the absence of an edge seal, and/or if the polyurethane is attached to a single layer of glass and will thus be exposed to the oil in the autoclave, the laminate can be placed in a heat-resistant heat-sealable bag, e.g. a polyethylene-coated <n>Mylar" bag commercially available under the name

"Polymar". The air can then be removed by applying a vacuum which seals the bag, eliminating the edge sealing step.

The following is illustrative of a method by which two-layer laminates with a single glass layer can be produced.

Flat copolymer sheets of rectangular perimeter, large enough to be trimmed to the shape of a windshield, and of substantially uniform thickness are cut and stored to make dual-layer windshields.

A release agent is prepared as follows: a glass resin "OI-65O" is pulverized and 200 g of this pulverized organopolysiloxane is dissolved in 575 cm 3 of anhydrous n-butanol. The mixture is stirred at 200 rpm. minute for about 1 to 1/2 hour at room temperature to complete the dissolution of the organopolysiloxane in n-butanol. The resulting solution is then filtered under vacuum in a Buchner funnel using No. 3 filter paper. This solution contains 30% solids by weight and is stored in a polyethylene bottle.

A pair of glass plates of matching curvature, corresponding to the shape of the desired windscreen, is selected from among those pre-formed. One of the glass panels in the pair is edge-treated to give a beveled edge around the entire periphery. This provides a peripheral passage extending obliquely inward from the edge surface to the convexly curved main surface of the edge-treated glass sheet, and allows easy removal from the second glass sheet.

An adhesive-promoting composition consisting essentially of a solution of gamma-aminopropyltriethoxysilane ("A-1100rt) is dissolved in anhydrous ~n-butanol at a concentration of 0.3 percent by volume. The solution is filtered through a No. 3 filter paper in a Biichner -funnel under vacuum, diluted and poured over the convex surface of one of the glass plates to be used as a mold. The release agent solution with JO% solids which was stored in the polyethylene bottle is diluted with additional n-butanol to a 15% by weight concentration, filtered through a no. 3 filter paper under vacuum, degassed until bubbling ceases and poured over the convex surface of the edge-treated glass plate. The glass plate thus coated is dried for 30 minutes at room temperature and then cured for 24 hours at 121.1°C in a clean oven. After cooling, a strip of poly-tetrafluoroethylene, such as is commercially available under the trade name "Teflon", is applied over the edge surface and over the chamfered portion extending from the edge -of the edge-treated glass sheet, and is folded over a 4"76 mm wide frame near the edge along the opposite surface of the glass sheet.

Another adhesive promoter, consisting essentially of N-(P-aminoethyl)gamma-aminopropyl-trimethoxysilane ("A-1120") is dissolved in a 50% by weight isopropanol/50% by weight water solution to a concentration of J. 1 percent by weight. The solution is applied to the concave surface of the glass plate to be incorporated into the two-layer windscreen and dried for approximately 10 minutes at room temperature. An assembly consisting of the edge-treated glass sheet, the preformed copolymer sheet and the second glass sheet to be laminated to the copolymer sheet is then formed. The whole is oriented so that one surface of the copolymer sheet lies against the surface of the glass plate treated with the adhesive-promoting composition, and the opposite surface of the copolymer sheet lies against the edge-treated coated surface of the mold

which is constituted by the glass plate coated with the "OI-650" glass release resin.

The assembly is wrapped in plastic and the plastic-wrapped assembly is placed in a so-called "polyma;c" bag of the type described in US patent no. 3•3^1•517* The bag consists of an outer layer of polyethylene glycol terephthalate ("Mylar ") and an inner layer of polyethylene bonded to this. The bag is then placed in a second bag of the same material, and the unit is evacuated and sealed. The sealed unit is placed in an oil autoclave and subjected to a pressure of 14 kg/cm<2> at 135°C for 45 minutes. The unit is then cooled to room temperature while the elevated pressure is maintained. The pressure is then reduced.

The assembly is removed from the autoclave and the bags and plastic wrap are removed from the assembly. The resulting assembly is placed concave side up on a support table and a razor blade is inserted into the peripheral passage created by edging the frame of the presheet, between the tape and the copolymer sheet to enlarge the passage. A circular tool similar to a "pizza cutter" is inserted into the opening and the tool is passed around the edge of the assembly along the band to force the peripheral opening around the edge. After finished edge separation to a depth of about 25 mm, the form of the bi-layer assembly is pulled by hand using a vacuum holder to hold the outer layer of the bi-layer windshield.

The resulting bilayer windshield has an exposed copolymer surface that is smooth and free of surface scratches on the inside avi.edge along which the "pizza cutter" was used to enlarge the peripheral passage between the mold and the bilayer windshield. Furthermore, the dual-layer windshield has excellent optical properties and is clear and exhibits excellent transmission of visible light.

The preferred urethanes have an intrinsic viscosity at 30°C in 0.5 percent solutions of silica-stabilized chloroform or N-methyl-2-pyrrolidone of between about 0.3 and 30, preferably between about 0.8 and 1, 6 plus-minus 0.1. The most preferred urethanes, prepared from polybutylene adipate, cycloaliphatic diisocyanates and aliphatic diols generally fall within this preferred range.

The polyurethanes can also be characterized by the urethane (HNCOO) concentration. For example, based on 1 mole of any polyol and an NCO:OH ratio of 1, the amount of monomeric diol and diisocyanate can be determined by the formula:

where Wu = percentage by weight of the urethane group.

Polyurethanes which are useful according to the invention will usually have a Wu of between about 14.11 and. about 15»31 percent by weight of polyols with a molecular weight of 1000 and between about 12.07 °6 17 > 2? weight percent with an optimum at around 13.71 weight percent for polyols with a molecular weight of 2000.

The preferred urethanes according to the invention can be characterized as plastomes, i.e. that they are elastoplastic, and thus do not retract like the same elastomers when they are loaded. In addition, they are clear, flexible and essentially non-adhesive at room temperature. They can also be described as tough and usually have a relatively constant Gehman modulus of between about -20 and 50°C of between 10<?> and lo<9>'<5>, log of 3 times the shear modulus in dyne per cm 2 , measured according to "ASTM-D IO53-65". The Gehman modulus should be taken within a few days or no more than 1 month after the polyurethane sheet is formed, as the modulus may change with aging due to the presence of unreacted isocyanate.

The preferred polyurethanes according to the invention will usually have an average molecular weight, calculated from the inherent viscosity, of between about 10,000 and about 100,000 and preferably between about 20,000 and 65,000. In addition, when heated, the optically clear polyurethanes will usually show a low-temperature endotherm at about 70°C (differentiated thermal analysis can be carried out with a "DuPont 900 Thermal Analyzer"), and usually no endotherm or exotherm • occurs between 100 and 170°C , suggesting that polymers are amorphous. Softening points of about 170°C, melting points of about 220°C and decomposition at about 270°C are typical. The preferred compositions, suitable for use in automobile windshields, meet standard requirements for minimum light transmission of " JO % and preferably 86.5 f° or above ("Illument A, tungsten lamp 2,840° K) and less than 2 fo haze on a ground sample ("ANSI Code Z-26.1", 1966, Sample No. l8). Percent light transmission and percent haze can be measured using the Hunter Pivotable Sphere Haze Meter.

A significant advantage of the invention is thus the discovery that special polyurethanes can be used as the only or main intermediate layer between two glass surfaces, or attached to a single layer of glass to obtain a laminate with good optical properties and superior properties with a view to minimizing personal injuries .

A method for producing a three-layer laminate is described in US patent no. 3•5^9*015• In this method, two layers of glass that have been shaped in advance (if desired) are placed on top of each other, and spacers such as tape are placed around the perimeter . The glass layers are thus separated so that the liquid polymer can be poured between the layers in the desired thickness, after which the urethane polymers can be cured. Preferably, however, the compositions according to the invention are extruded to achieve better uniform stress-free plates, but they can be ground and calendered and applied between the glass surfaces in sheet form, followed by a normal heating step to achieve adhesion of the substances. If a two-layer laminate is desired by cast-in-place, one layer of glass may be treated with a release agent such as a poly-siloxane, "Teflon" and the like, and the layer removed after the second layer of glass and the urethane are bonded together. Where the width of the intermediate layer is not significant, a two-layer laminate can be produced by spraying the liquid urethane poly-

more on a single layer of glass, with subsequent heating of the laminate. When it is desirable to produce a two-layer laminate using extruded and/or calendered material,

a three-layer laminate can be produced in which a layer of glass is preferably treated with a release agent as above, and where a sheet of glass is removed. A pressure plate made of glass or similar material can also be used to attach the urethane to a single sheet of glass.

The glass that can be used in the invention can be

of any type, depending on the desired use of the laminate, but should preferably be a clear, slightly colored, transparent

clean glass including soda-lime glass, aluminum silicate, "Pyrex" and "Vycor", tempered glass such as "Herculite II" and "Tuflex", chemically strengthened glass such as "Chemcor", "Z-glass" and "Herculite . II", and tinted glass such as "Solex", etc. The most preferred ; however, glass for use in safety glass laminates is the thinnest

(about 1.-65 w® thick) aforesaid chemically strengthened and tinted glasses.

Of particular interest are those glass emulsions specially formulated for ion exchange techniques. Such glasses are e.g. described in US patent no. 3,357,876. The glass can

be made by a commercially well-known technique, such as e.g. "The Float Process" for the manufacture of glass as described in US Patent No. 3.083.55I, "The Pittsburgh Process", also known as the "Pennvernon Process", for the manufacture of sheet glass as described in US Patent No. 1,833,379, 1,833,380, 1,833,381 and I,833,382, and "The Continuous Plate Process" for the manufacture

of plate glass as described in US Patent No. 2,478,090

and 2.5O5.103.

A soda-lime-silica glass, with the following glass composition, made by "The Float Process" is preferred, as it has the best combination of optical quality paired with economical production costs: Na 2 O, 10-15 wt. percent, K^ O 0-5 percent by weight, CaO 5-15 percent by weight, Si02 65-75 percent by weight, MgO 0-10 percent by weight, B2O^ 0-5 percent by weight, A^O^

0-1 percent by weight and Fe^O^ 0-1 percent by weight.

In addition to vehicle windshields, laminates can be produced for use in shower enclosures, fixed and sliding doors or any boundary, especially where injury to people or animals is possible.

For car or other vehicle windshields, the glass should preferably have a thickness of between about 1.65 mm and 4.57 xm-- When. a three-layer laminate is used, the outer layer can be thicker than the inner layer, but they should ideally have the same thickness, namely around 3>17 mm. Although the thickness of the intermediate layer can vary between about 0.125 mm and 3 mm or more, it is preferred that it be between about 0.375 °S 1>125 mm for in car windshields to achieve maximum transparency, low haze and good diaphragm action in case of impact .

In addition to a special specified printing as mentioned above, the polyurethane should be of essentially uniform thickness over the entire sheet to avoid fractional differences. The thickness variation from edge to edge should not be more than + 0.125 mm» preferably not more than + 0.05 mm. Analogously, but more important than the edge-to-edge change in thickness, is the degree of thickness change. If the polyurethane has a thickness variation and a degree of change of thickness sufficient to give a diopter of 0.006 and above, visible optical dispersion • due to variations, of the refractive index will be noted. Therefore, the edge-to-edge polyurethane should be of substantially uniform thickness with a diopter in each surface portion of less than 0.006.

In addition, the polyurethane should have a sanding resistance. stability, as measured by "A.N.S.I. Code Z 26.1", test ■.' No. l8 for plastic is, of no more than -15$ increase in haze after 100 "Taber" cycles on a "Taber abraser". For flexibility, the polyurethane should have a tensile strength of at least 70 kg/cm<2>, preferably 140 to 350 kg/cm<2>, measured according to "A.S.T.M. D-638-64T". For adhesion purposes, the polyurethane should laminate to the reinforced glass sheet with a bond strength of 1785.8 to 10714.8, preferably 3571.6 to 5357.4 g per linear cm, measured at 90°.' pull-off test according to a slightly modified method according to.;

"ASTM D-I876-6IT". The modification of ASTM «.the sample b.es-tår-of- to--in building /a cloth of stainless steel wire in the .exposed surface of.-

polyurethane. The purpose of the cloth is to prevent the polyurethane from stretching when it is pulled from the surface.

In addition to the fact that the polyurethane, when used between two sheets of glass, has the above-mentioned physical properties, a laminated two-layer structure of reinforced glass and a polyurethane layer should have special physical properties in the combined laminated configuration, especially when the laminate is used as a vehicle closure. Minimum standards for motor vehicle glass are determined according to the procedures specified in "ANSI Code Z 26.1". Therefore, the laminated two-layer structures according to the invention have the following physical properties when tested according to the method indicated in the tests according to "ANSI Code Z 26.1".

Properties of two-layer laminates, prepared

according to the present invention.

The following examples will serve to illustrate the invention and preferred embodiments. All parts and percentages in the given examples are given by weight unless otherwise indicated.

Example 1

A poly(1,4-butylene adipate) polyester (785>6 g, 0.400 mol) having a molecular weight of 1965> a hydroxyl number of 57_ and a melting point of 51 and an acid number of 0.5> and a poly(l,4- butylene adipate) polyester (707.4 g> 0.698 mol) having a molecular weight of 1014, a hydroxyl number of 111 and an acid number of 0.5 was dried together with stirring in a glass reactor to remove trace amounts of water by heating to 100-105° C under a pressure of 3 mm of mercury for 3 hours. The pressure was released, while prepurified nitrogen was added, and anhydrous 1,4-butanediol in an amount of 260.6 g (2.892 mol, 0.03 HgO) was added over one minute to the stirred mixture of dried polyesters at 93°C) after which the mixture was heated to 95°C for 15 minutes. The resulting mixture was homogeneous. To this homogeneous mixture, 1046.8 g (3.989 mol) of 4>4'-methylene-bis-(cyclohexyl isocyanate) with a stereoisomer content of 19 to 21% trans, trans, 17 to 18 fo cis, cis, and 62 to 64 fo trans, cis, containing between 0.27 $ °g of 0.40% monoisocyanate ("Hylene W") containing 0.280 g (0.01 $ of the total reactants) of dibutyltin dilaurate catalyst. The butane diols and the diisocyanate had a temperature of 22°C and their additions were made while the reactor was under a nitrogen atmosphere. The resulting mixture was rapidly stirred for about 1 minute during which time the temperature of the mixture rose from 80 to 95°C~« The mixture was poured into a dry "Teflon" coated reactor which was closed and placed in a non-circulating oven which was continuously flushed with nitrogen and which maintained 130°C (the temperature in polymers was approximately 143°C) for approx. 2 hours, until the reaction and polyurethane formation was essentially complete. The NCO content of polymers was 0.07% by weight, determined by infrared spectrometry. The resulting semi-solid polymer was allowed to cool to room temperature, was removed, cut and ground (front roll 82.2°C and main roll 57.2°C) and calendered on a 3 roll mill (top roll 121.1°C, center roll 107.2° C and bottom roll 101.7°C) to sheets with "a thickness of 0.875 "^m °g a width of 35 >5^ cm. The polymer had an intrinsic viscosity at 30°C in a 0.5 percent concentration in N-methyl-2-pyrrolidone of about 1.40 before painting, and an NCO content of 0.07%. The intrinsic viscosity after calendering was approximately the same (1.41)•

Example 2

According to the general procedure and conditions set forth in Example 1, a poly(1,4-butylene adipate) polyester (2.274 mol) with a molecular weight of 1010 and a hydroxyl number of 111.1 was mixed with a poly(1,4 -butylene adipate) (1.295 mol) with a molecular weight of 19&5 °S a hydroxyl number of 57»1 to which agitated mixture of dried polyester was first added 7.23 mol of 1,4-butanediol and then 9»99 m°l 4>4 '-methylene-bis-(cyclohexyl isocyanate) ("Hylene W"), and the mixture was heated to 80°C. However, no catalyst was present and the homogeneous mass was heated to an oven temperature of between 122 and 129°C for 19 hours. The resulting polymer had an intrinsic viscosity at 10°C in a 0.5% concentration in N-methyl-2-pyrrolidone of about 0.79°C and an NCO content of 0.1% by weight. The intrinsic viscosity remained unchanged after calendering. The front roller in the mill had a temperature of 82.2°C and the main roller 57.2°C. The top roll of the calender maintained a temperature of 65.6°C, the middle roll 57>2°C and the bottom roll 5i.7°C.

In examples 3 to 13, polyurethanes were prepared from the specified substances by following the general procedure and under the conditions indicated in example 1, except that no catalyst was used. The intrinsic viscosities of the produced polyurethanes were measured at 30°C in a 0.5 percent concentration in N-methyl-2-pyrrolidone and the NCO content was determined by infrared spectrometry.

Example 3.

1 mol poly(1,4-butylene adipate), molecular weight 1014> hydroxyl number 110.7, acid number 0.5, 0.905 mol 1,4-butanediol, 1.905 mol "Hylene W".

Reaction time: 19 hours at an oven temperature of 130°C, intrinsic viscosity 1.21, NCO content 0.1 fo.

Example 4

1 mol poly(1,4-butylene adipate), molecular weight 1965» hydroxyl number 57.1, acid number 0.5, 3.26 mol 1,4-butanediol,

4.26 mol "Hylene W".

Reaction time: 24 hours at an oven temperature of 130°C, intrinsic

viscosity 0.78, NCO content 0.03

Example 5

1 mol poly(1,4-butylene adipate), molecular weight 1965» hydroxyl number 57>1> acid number 0.5, 2.34 mol 1,4-butanediol,

3.34 mol "Hylene W".

Reaction time: 19 hours at an oven temperature of 130-131°C, intrinsic viscosity 1.03, NCO content 0.07 1°>

Example 6

1 mol poly(1,4-butylene adipate), molecular weight 1965» hydroxyl number 57,<1> acid number 0.5, 3.40 mol 1,4-butanediol,

4.40 mol "Hylene W".

Reaction time: 23 3/4 hours at an oven temperature of 129-130°C> inherent viscosity 1.06, NCO content 0.1 fo.

Example 7

1 mol poly(1,4-butylene adipate), molecular weight 19&5> hydroxyl number 57>1> acid number 0.5> 3>H mol 1,4-butanediol,

4.11 mol "Hylene-W<»>.

Reaction time: 19>5 hours at an oven temperature of 128-130°C, intrinsic viscosity 0.84.

Example 8

1 mol poly(1,4-butylene adipate), molecular weight 19&5> hydroxyl number 57>1> acid number 0.5, 2.71 mol 1,4-butanediol,

3-.71 mol "Hylene W".

Reaction time: 19 hours at an oven temperature of 130-131°C, intrinsic viscosity 0.88.

Example

1 mol poly(1,4-butylene adipate), molecular weight 19^5» hydroxyl number 57.1, acid number 0.5, 3>26 mol 1,4-butanediol,

4.26 mol "Hylene W".

Reaction time: 20 hours at an oven temperature of 130°C, intrinsic viscosity 1.02, NCO content 0.1

Example 10

1 mol poly(1,4-butylene adipate), molecular weight 1965» hydroxyl number 57>1> acid number 0.4, 3>6l mol 1,4-butanediol,

4.61 mol "Hylene W".

Reaction time: 18 hours at an oven temperature of 130°C,

intrinsic viscosity 0.72, NCO content 0.07 fo.

Example 11

1 mol poly(ethylene adipate), molecular weight 1902, hydroxyl number 59O, acid number 0.3, 3.5<1> mol 1,4-butanediol, 4.51

mol "Hylene W", 0.01% dibutyltin dilaurate, 0.6% "Irganox 1093"> commercially available multifunctional hindered phenols.

Reaction time: 43 hours at an oven temperature of 128°C,

intrinsic viscosity 0.84, NCO content 0, 2. fo.

Example 12

1.76 mol poly(1,4-butylene adipate), molecular weight 1010, hydroxyl number 111.1, acid number 0.5, 1 mol poly(1,4-butylene adipate), molecular weight 1965, hydroxyl number 57.1, acid number 0.5,

7.36 moles of 1,3-butanediolj 10.11 moles of "Nacconat H-12", commercially available 4>4,-methylene-bis-(cyclohexyl-isocyanate) in stereoisomeric ratio of 70 $ trans and 30 fo cis.

Reaction time: 17 l/2 hours at an oven temperature of 130°C,

intrinsic viscosity 0.62, NCO content 0.03 1°-

Example 13

1 mol poly(ethylene/propylene adipate), molecular weight 1886, hydroxyl number 59>5> acid number 0.6,

3.49 mol of 1,4-butanediol,

4.49 mol "Hylene W",

0.01% dibutyltin dilaurate,

0.6 fo "Irganox 1093" > commercially available multifunctional ionically hindered phenols.

Reaction time: 21 hours at an oven temperature of 130°C, catalyst dissolved in diisocyanate. Inherent viscosity 0.87, NCO content 0.1%.

The following compositions from Examples 14-22 were heated in a 143°C circulating air oven for 20 hours.

Example 14

1 mol poly(1,4-butylene adipate), molecular weight 2011, hydroxyl number 55.8, acid number 0.48,

I, 784 mol poly(1,4-butylene adipate), molecular weight 1012, hydroxyl number 110.9, acid number 0.51,

8.385 mol of 1,4-butanediol,

II. I69 mol "Hylene W".

Example 15

1 mole of poly(1,4-butylene adipate), molecular weight I9891

hydroxyl number'56.4> acid number 0.38,

1.767 mol poly(1,4-butylene adipate), molecular weight 1012, hydroxyl number 110.9, acid number 0.51,

4.257 mol of 1,4-butanediol,

7.024 mol "Hylene W",

intrinsic viscosity for polymers 0.87 at 0.5 percent concentration in chloroform at '} 0°G.

Example 16

1 mol poly(1,4-butylene adipate), molecular weight 1989» hydroxyl number 56.4, acid number 0.38,

1.767 mol poly(1,4-butylene adipate), molecular weight 1012, hydroxyl number 110.9, acid number 0.51,

5.474 mol 1,4-butanediol,

8.241 mol "Hylene W",

intrinsic viscosity for polymers 1.25 ve^ 0.5 percent concentration in chloroform at J0°G.

Example 17

1 mol poly(1,4-butylene adipate), molecular weight 1989» hydroxyl number 56.4, acid number 0.38.

1.767 mol poly(1,4-butylene adipate), molecular weight 1012, hydroxyl number 110.9, acid number 0.51,

6.291 mol of 1,4-butanediol,

9.058 mol "Hylene W",

intrinsic viscosity for polymers 1.08 at 0.5 percent concentration in chloroform at J0°C.

Example 18

1 mol poly(1,4-butylene adipate), molecular weight 1989» hydroxyl number 56.4, acid number 0.38,

2.737 mol of 1,4-butanediol,

3.737 mol "Hylene W",

intrinsic viscosity for polymers 1.10 at 0.5 percent concentration in chloroform of 30°C.

Example 19

1 mol poly(1,4-butylene adipate), molecular weight 2011, hydroxyl number 55.8, acid number 0.48,

2.150 mol of 1,4-butanediol,

3.150 mol "Hylene W",

intrinsic viscosity for polymers 1.21 at 0.5 percent concentration in chloroform of 30°C,

Example 20

1 mol poly(1,4-butylene adipate), molecular weight 1012, hydroxyl number 110.9, acid number 0.51,

1.205 mo1 1,4-butanediol,

2.205 mol "Hylene W",

intrinsic viscosity for polymers 0.98 at 0.5 percent concentration in chloroform of 30°C.

Example 21

1 mol poly(1,4-butylene adipate), molecular weight 1012, hydroxyl number 110.9, acid number 0.51,

0.904 mol of 1,4-butanediol,

1.904 mol "Hylene W",

intrinsic viscosity for polymers 1.03 ve|in 0.5 percent concentration in chloroform of 30°C.

Example 22

1 mol poly(1,4-butylene adipate), molecular weight 1012, hydroxyl number 110.9, acid number 0.51,

0.640 mol of 1,4-butanediol,

1.640 mol "Hylene W".

Example 23

1 mol poly(1,4-butylene adipate), molecular weight 2010, hydroxyl number 55.8, acid number 0.5,

2,354 mol of 1,4-butanediol,

3,356 moles of isopropylidene-bis-(cyclohexyl isocyanate) with a stereoisomeric ratio of 77.5 <$> trans and 22.5 $ cis.

Example 24

1 mol poly(1,4-butylene adipate), molecular weight 4156» hydroxyl number 27, acid number 0.3,

7.174 mol 1,4-butanediol,

8.174 mol "Hylene W",

The reactants were mixed at 130°C and then heated for 20 hours at 143°C.

Example 25

1 mol poly(1,4-butylene adipate), molecular weight 2609, hydroxyl number 43, acid number 1.31,

5.15 mol of 1,4-butanediol,

6.15 mol "Hylene W",

the reactants mixed at 170-180°C, then poured between two glass sheets and heated to 144°C for 24 hours.

Example 26

1 mol poly(ethylene adipate), molecular weight 1603, hydr.oxyl number 70, acid number 0.117,

2.696 mol of 1,4-butanediol,

3.696 mol "Hylene W".

The reactants were mixed at 71°C> then poured between two glass sheets and heated to 143°C for 24 hours.

The Gehman moduli taken two days after molding for some of the preferred compositions are given below and are compared to plasticized polyvinyl butyral.

Log off 3 times the jæremodule in dyne per cm<p>

It appears from these data that the preferred compositions have a relatively constant modulus in the toughness range at different temperatures, while the polyvinyl butyral composition is outside the toughness range at both -20 and 50°C, and is not relatively constant at the other two intermediate temperatures .

The sample compositions meet the minimum light transmission and clarity requirements of "ANSI Code Z-26l" 1966, Test No. 18.

Safety glass laminates were prepared using as an interlayer the compositions of Examples 1-24 and a commercial polyvinyl butyral polymer. The laminates measuring 30.5 x 30.5 cm used glass sheets with a thickness of 3>17 mm and were formed by placing the interlayers (0.75 - 1>15 mm) between two glass sheets and the laminate was subjected to a temperature of from 135-176.7 c °g a pressure of 14 kg/cm for 45 minutes in an autoclave. The laminates were aged for 1 week at room temperature and then subjected to the impact test. In this test, a 2.25 k6 heavy steel ball was dropped onto the laminate from various heights to determine the minimum height and viscosity at which the ball just penetrated or shattered the laminate. Separate laminates were used for each test and several laminates were tested at temperatures of -17.8°C, 21.1°C and 48.9°C. A simple mean penetration rate at a temperature is indicated when all three ball drops produced approximately the same result. The test results are given in Table II.

From this table it can be seen that the compositions according to the invention can be effectively used as an intermediate layer. They are effective over a wide temperature range and are usually superior to the commercial polyvinyl butyral interlayers. Furthermore, it is seen that by varying the concentration of the reactants, a composition for a particular use and a particular temperature can be achieved. The compositions are particularly suitable for use in vehicle windscreens due to their room temperature properties. These are important as a vehicle windshield is usually kept at or near room temperature when using interior heat during the winter and at ambient temperature during the summer.

In order to carry out tests with a view to the extent of the damage, sled tests were carried out (see e.g. "Eleventh STAPP

Car Crash Conference", published by the "Society of Automotive Engineers, Inc., New York," New York (I967, page 143)). These tests consist of throwing a dummy of an average body weight (with a head covered with a double layer of moist suede) at different speeds against a laminated safety glass held at different temperatures, after which the degree of leather tear after the impact is recorded. The windshields are mounted in a frame at an angle! of 70° using adhesive glass similar to most American commercial product assemblies. A damage assessment is carried out using the following procedure. Surface damage to the outer layer of the suede is only indicated as "minor" and gives a damage assessment of 1. Deep cutting through both layers of the suede is considered "severe" and gives a damage assessment of 5" Intermediate degrees of damage on the suede leather are assessed as 2,

3 or 4> depending on the severity of the damage. A factor known as "The Severity Index" has been identified with the relative safety of windshields, as determined by impact testing using a 50th percentile Alderson dummy, covered with two layers of moist suede using the test sled apparatus. "The Severity Index" (S.I.) is calculated according to the formula

where A is the deceleration in gravity units and dt is the time differential in milliseconds between the moment of impact between the dummy's head and the test windshield and the time when a horizontal accelerometer mounted inside the dummy's head indicates a sudden negative gait. This value is determined for each millisecond during the time interval and the value is integrated for the entire time period. In other words, "The Severity Index" is calculated from the area under a curve resulting from an entry of the acceleration acting on the dummy's head raised to the 2.5 power as a function of time. Generally, "The Severity Index" increases with impact speed.

The test results for the windshields using a composition prepared according to the method of Example 18 and for commercial polyvinyl butyral compositions as an interlayer are shown in Table III. The interlayers were about 0.75 111111 and the glass ^, 1^ mai thick. The windshields were heated in an autoclave for 45 minutes at 135°C and 14 kg/cm<2> gauge pressure.

The preferred polyurethanes provide windshields with indices below 1000 when the windshield is not penetrated by the dummy and an outer sheet of glass is struck at a speed of 40>2

km/h of a dummy of average body weight, while the windshield is kept at a temperature of -1.1, 23 >9 °& 43>3°c>°g the total length of polyurethane tear is less than about 12.7 cm>° S damage rating is no more than 3*

From the data given in the table, it can be seen that the composition according to the invention is effective over a wide temperature range and is superior to the PVB interlayer at high impact speeds, as confirmed by the low damage assessments, the limited amount of interlayer tearing and low indices.

In addition to the stated data, the compositions according to the invention are stretched to a considerable extent and thus absorb energy and prevent or minimize brain damage, and they also adhere well to the glass and thus prevent the spread of broken glass particles.

The following examples are illustrative of two-layer laminates where the composition according to the invention is adhered to a single glass layer.

Examples 27- 28- 29

Three polyurethanes, prepared by the method and under the conditions of Example 1, were placed between two glass plates (annealed "float glass" or thermally tempered plate glass as indicated) of which one glass plate was covered at the interface with a release agent of "Tedlar" film with a thickness of 0.025 111111 > °g the other was treated on the surface with an adhesion promoter of a 1% by weight solution of N-(p~aminoethyl)gamma-aminopropyltrimethoxysilane in isopropyl alcohol and water. The solution of the solvent was prepared from 250 ml of isopropanol and 195 ml of water, from which a portion of 99 S °g mixed with 1 g of silane was taken. The adhesion promoter was then sprayed onto the glass slide and allowed to dry. The assembly was then subjected to a temperature of between 135 and 176.7°C and a pressure of 14 kg/cm<2> for 45 minutes in an autoclave. The laminate was then subjected to the sled test on the plastic side, and the results are given in Table IV.

Laminate dextrox. ion testing.

Bullet drop results are usually given in the literature as the height from which the bullet is released. To allow comparison of other results with the average permeation rates stated herein, the following table has been prepared. The table suggests

•the approximate distance from which a bullet must be released to correspond to the number of km per hour as stated herein:

The NCO content of the urethane.

Urethanes, suitable for use in laminates according to the invention, react essentially completely (ie the reaction and polyurethane formation is essentially complete) within the scope of the description and claims, when the urethane components are heated to a temperature of 143°C for 20 hours without a catalyst.

The procedure used to determine the NCO content of the urethane is as follows: a 0.5 g sample of the polyurethane is placed between two pieces of "Tedlar" polyethylene film cut into squares of about 4 cm>°g the composition is placed in. an oven in about 5 minutes at a temperature of between about 160 and 170°C until the urethane sample is softened. The hot composition was then placed between the hot plates of a "Pasadena Hydraulic Inc. Press, Model B-244" and a pressure was applied to the laminate. The urethane sample was then removed from the press and mounted in a "Perkin-Elmer, Model 621, Spectrophotometer", and examined between 2350 cm""1" and 2000 cm""<1>". Then a baseline was drawn across the shoulders of the NCO signal at 2250 cm""'", and the baseline absorbance at 2250 cm<->"'" was subtracted from the absorbance signal of the NCO signal at 2250 cm~^~ to determine the net absorption of the NCO signal The percentage NC0- is then determined from the formula:

0.32 for "Hylene W",

where C = % NC0

a = absorption per 1 fo diisocyanate per mm thickness, or 8.1 for "Hylene W"

A = net absorption for the NCO signal and

D = film thickness.

Although the best results are found when urethane is prepared by reacting polyesters with a diisocyanate and a low molecular weight compound containing active hydrogen, such as an aliphatic diol, it is possible to prepare compositions without using the low molecular weight active hydrogen compound by using a polyester"with lower average molecular weight. Thus, for example, a polymer expert can produce a polyester which will have the same average molecular weight as a polyester produced from a high molecular weight polyester and a low molecular weight active hydrogen compound, which polyester is then reacted with a diisocyanate. Urethanes used in laminates according to the present invention invention can also be prepared by other methods. For example, phosgene can be reacted with polyesters with hydroxyl end groups and low molecular weight diols to produce bis(chloroformates), after which these can be reacted with a diamine, such as the diisocyanate precursor. Alternatively, carbamoyl chlorides can be reacted tes with polyesters with hydroxy end groups and low molecular weight diols. These methods are more precisely described in US Patent No. 3,215,668.

Particularly important laminate configurations according to the invention are the two-layer and three-layer laminates. The three-layer laminate in which the polyester urethane is molded between two sheets of glass or formed into a sheet and mounted between two sheets of glass and heated at a temperature and under pressure to attach polyester urethanes to the sheets of glass is particularly suitable for car windshields. This is because the polyester urethane intermediate layer is not usually destroyed in a collision, but is stretched so that brain damage to passengers is minimized. Furthermore, the polyester urethane prevents the scattering of glass, causing the glass to shatter into relatively small particles, reducing injuries to occupants of the vehicle. In the preferred three-layer configuration, the polyester urethane interlayer is the only interlayer material. In addition to the intermediate layer material, there may of course be adhesion regulators present between the glass plates such as adhesion promoters or inhibitors or other chemicals which may include cleaning agents, release agents and the like. Thus, a preferred thin-layer laminate is built up of two sheets of glass spaced apart by means of an intermediate layer made only of the polyester urethane, except for minor amounts of chemical agents such as adhesion regulators, plasticizers and other chemicals present for purposes other than make up the middle layer.

Two-layer configurations with a polyester urethane inner layer are also ideally suited for use as car windshields, as, in addition to the benefits of a three-layer laminate, occupants are less prone to brain injuries and lacerations when thrown against a two-layer laminate. In the two-layer configuration, the polyester urethane adheres to a single sheet of glass and the polyester urethane forms the inner surface of the windshield so that occupants hit the polyester urethane sheet instead of a sheet of glass when impacting the windshield. Furthermore, the inner surface of the polyester urethanes is self-curing, which means that it can be scratched and the smooth surface will be restored after the polyester urethane "cures" within a few minutes. This improves their use as a two-layer or multi-layer laminate when the polyester urethane layer can be equipped with a thin coating to maintain the optical properties, or coated with an anti-static agent to redu-. sere accumulation of dirt. It is also possible to protectively coat the inner surface with a thin layer of a scratch-resistant transparent material, e.g. a thin layer of a melamine resin, or a silicon oxide-based film. Usually these coatings or films will be rather thin, with a thickness of only a few microns. The term "two-layer" - as used herein and as used in the claims - indicates a configuration with as the essential components only a plate of glass with an inner layer made only of the polyester urethane, while next to these main components it may include adhesion promoters and the like

(as indicated for the three-layer configuration)

as well as thin surface layers or films as indicated above.

In addition to these two-layer and three-layer configurations, the use of the polyester urethane as at least an intermediate layer composition in configurations with four or more layers is covered by the present invention. Such configurations are those where the layers are made of glass, polycarbonate, polyvinyl butyral and other materials next to the polyester-urethane layer. For example, a bulletproof glass can be made from many layers, but when

the inner layer is made of polyester urethane, will damage

persons are minimized in the event of a collision. Bulletproof glass is made with from 3 to 25 layers, in which an intermediate layer such as polyvinyl butyral or polycarbonate is placed between the glass layers. The thickness of the glass layers has been from 6.35, 9.52

to even 25.4 n™ thick and polycarbonate interlayers of 3>i7> 4>76 and 6.35 mm have been used, and the plastic materials such as polyvinyl butyral and polyester urethane usually have a thick

thickness from 0.508 to 1.016 mm. The polyester urethanes used in laminates according to the invention can likewise be used in these multilayer laminates with or without other plastic materials such as polyvinyl butyral and polycarbonate.

In the accompanying claims, the use of the expression is indicated

"optically clear" in connection with polyester urethane a polyester

urethane with a minimum light transmission of 70% and less than 2 fo haze on a sanded sample determined in accordance with "ANSI Code Z 26.1", I966, Test No. 18.

"Penetration at medium speeds" like that

is used in the accompanying requirements is the average speed

heat with which a 2.25 kg free-falling steel ball with a diameter of 82.55 111111 would just penetrate a laminate made of a polyester urethane interlayer placed between two sheets of "Float glass" with dimensions of 3^.5 cm x 30.5 cm x 3.17 mm that make up a laminate, when the laminate is held firmly, when the polyester urethane layer is approximately 0.75 ^ thick and the laminate is maintained at a temperature of -17.8, 21.1 or 48.9°C

The term "sheet", as used in the accompanying documents

requirements with reference to the polyurethanes, do not only include pre-

molded polyurethane, but also cast-in-place polyurethane, or a polyurethane layer is obtained in any other way.

Claims (12)

1. Optically clear, energy-absorbing laminate, comprising at least one glass plate bonded to a sheet of thermoplastic transparent polyurethane which is substantially free of unreacted cyanate and preferably placed between two glass plates, characterized in that the polyurethane is one obtained by reaction in one step of a) a polyester with hydroxy end groups and with an average molecular weight of between 500 and 5000 and which melts above 50°C, b) an aliphatic or cycloaliphatic hydrocarbon diisocyanate and c) an aliphatic diol with from 2-15 carbon atoms and with a molecular weight of less than 250, where the molar ratio between (c) and (a) is from 0.5:1 to 10:1 and increases with increasing molecular weight for (a), and where the isocyanate groups in (b) are essentially numerically equivalent to the sum of active hydrogen and hydroxyl groups in (c) and (a), and where the molar ratio between (c) and (a) to obtain a polyester urethane which is approximately free of unreacted isocyanate groups, is placed within the given range so that a rigid, clamped laminate produced from an approximately 7.62 mm thick plate of said polyester urethane placed between two 30.5 cm x 30>5 cm x 3>i7 ^ large glass plates is not brittle at -17.8°C and further exhibits penetration at average velocities of at least J2,lQ km/h at laminate temperatures of -17.8°C, +21.1°C and 48.9°C when the laminate is hit with a 2.26 kg free-falling steel ball. 2. Laminate according to claim 1, characterized in that (c) is a diol almost free of non-hydrocarbon bonds, with a molecular weight of less than 25O, where the molar ratio between (c) and (a) is from 0.5:1 to 7 ;1« 3. Laminate according to claim 1, characterized in that (a) is polyepsilon-caprolactone, preferably with a molecular weight of 1000 to 2000. 4. Laminate according to claim 1, characterized in that (a) is produced from an aliphatic dibasic acid or an anhydride thereof and an aliphatic diol, and that (b) is an optional dinuclear cycloaliphatic diisocyanate and that (c) is an aliphatic diol, preferably 1,4-butanediol. 5. Laminate according to claim 1, characterized in that (a) is poly(1,4-butylene adipate). 6. Laminate according to claim 1, characterized in that (b) is 4,4'-methylene-bis-(cyclohexyl-isocyanate), preferably with a stereoisomer content of 19-21% trans, trans, 17-18% cis, cis and 62-64% cis, trans. 7. Laminate according to claim 1, characterized in that the polyester urethane has an inherent viscosity at 0.5 percent concentration in an N-methyl-2-pyrrolidone of 30°c of between 0.3 and J, 0 preferably between 0.8 and 1 ,6. 8. Laminate according to claim 1, characterized in that (a) is poly(1,4-butylene adipate) with an average molecular weight of about 1000, (b) is 4>4'-methylene-bis(cyclohexyl isocyanate), preferably with a stereoisomer content of about 19-21 fo trans, trans, 17-18 fo cis, cis and 62-64% cis, trans and that (c) is 1,4-butanediol and that the molar ratio between butanediol and polyester is between 0.9 :1 and 1.2:1. 9. Laminate according to claim 1, characterized in that (a) is poly(1,4-butylene adipate) with an average molecular weight of about 2000, (b) is 4,4,-methylene-bis-(cyclohexyl)-isocyanate, preferably with a stereoisomer content of about 19-21 fo trans, trans, 17-18% cis, cis and 62-64% cis, trans and that (c) is 1,4-butanediol, and that the molar ratio between butanediol and polyester is between from 2:1 to 5;1" 10. Laminate according to claim 1, characterized in that (a) is poly(1,4-butylene adipate), (b) is 4'4'-methylene-bis-(cyclohexyl isocyanate), preferably with a stereoisomer content of 19-21% trans , trans, 17-18% cis, cis and 62-64% cis, trans, and (c) is 1,4-butanediol, and that the molar ratio between (c) and (a) lies between lines BH and AD in fig. 1 in the accompanying drawing. 11. Laminate according to claim 1, characterized in that (a), (b) and (c) are reacted at a temperature of over 120°C. 12. Laminate according to claim 1, characterized in that it comprises at least one sheet of glass bonded to a sheet of polyester urethane produced from (a) poly(1,4-butylene adipate) with an average molecular weight of between 1000 and 4000> (b) 4.4 '-methylene-bis-(cyclohexyl isocyanate), preferably with a stereoisomer content of 19-21% trans, trans, 17-18% cis, cis and 62-64% cis, trans and (c) 1,4-butanediol, and that the polyester urethane is produced by rapid addition of diisocyanate to an intimate mixture of butanediol and polyester under vigorous stirring at a temperature of at least 80°C, possibly at least 65°C in the presence of a catalyst, so that the reaction temperature is quickly reached and maintained at at least 130°C. 13• Laminate according to claim 1, characterized in that the polyester is poly(1,4-butylene acelate) with a molecular weight from 1000 to 2000.