LAMINATED SAFETY GLASS

Abstract: Laminated articles, particularly safety glass (12), comprising a lamina of ionomer resin film (14) laminated to a sheet of glass (12). The ionomer resin film is preferably an ionically crosslinked ethylene-methacrylic acid copolymer. The laminated articles may also comprise a sheet of polycarbonate (36) laminated to the ionomer resin film (34) opposite the glass (32). The laminated articles may further comprise an ionomer resin film (56) sandwiched between two sheets of glass (52, 54). The laminated articles may still further comprise a sheet of polycarbonate (62) or other plastics sandwiched between sheets of ionomer resin film (64, 66), which are in turn sandwiched between sheets of glass (68, 70).

Description: LAMINATED SAFETY GLASS BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to the field of reinforced glass structures in general, and in particular, to laminated safety glass reinforced with ionomer resin films and/or polycarbonates. Laminates of glass, ioncmsr resin and metal are also contemplated in the invention. 2.Description of Prior Art Safety glass can be reinforced by lamination with an inner layer of polycarbonate. The resulting lamination, however, is impractical for two principal reasons. One reason is insufficient bond strength when the polycarbonate is bonded directly to the glass. A second, and even more iirportant reason stems from polycarbonate and glass having different co¬ efficients of thermal expansion. Safety glass laminates made by bonding polycarbonate directly to glass will crack and craze on cooling from the temperature necessary to bond the two together, due to the different thermal expansion co-efficients of the components. Initial attempts to solve these problems involved interposing additional interlayers of polyvinyl butyral between the polycarbonate and the glass. Adhesion between the polycarbonate and the glass proved insufficient unless a plasticizer was also used. However, when a plasticizer was used, the plasticizer often caused the polycarbonate to develop stress cracks, and accordingly, to have low light transmission properties. The initial problems appear to have been solved in the laminated safety glass described in U.S. Patent No. 3,888,032, which has achieved wide cαrmercial success. The laminate comprises polycarbonate reinforced glass wherein the polycarbonate and glass are bonded to one another by an interlayer of polyurethane. Polyurethane provides sufficient adhesion to glass and to the polycarbonate, and no stress cracking or cloudiness develops in the product. Despite the ccmπercial success of the polyurethane laminated product, there has been a continuing effort to develop less expensive products, particularly as polyurethane is an expensive component. This invention provides new glass laminates, with and without layers of polycarbonates, and other reinforcing transparent plastics, which are considerably less expensive than the polyurethane laminates, yet which at the same time are ° every bit as satisfactory, if not more so, with regard to adhesion, strength and clarity. Laminates according to this invention coπprise at least one layer of glass laminated with an ioriomer resin film. In the specification and claims the terms "ioncmer" or "ionomer resin" mean an extru able resin comprising ionically crosslinked ethylene-m≥thacrylic acid copolymers; and more particularly, sodium or zinc crosslinked ethylene-methacrylic acid copolymers. Properties which distinguish ionomer resins from other polyolefin heat-seal polymers are high clarity, melt strength, solid-state toughness and resistance to oil/fat permeation. Ionomer resins are generally available as either a sodium or a zinc ionomer, and are available in a wide variety of grades. A ine iσnomers are also produced. Although all grades of ionomer resins generally exhibit the properties noted above when compared to other heat- sealed polymers, sodium ionomers are known for exceptional toughness and resistance to fats and oils, while zinc ionomers exhibit outstanding adhesion to unprimed foil and possess excellent chemical resistance. Sodium ionomers have proved to provide the best clarity, the zinc ionomers proving hazy at times. ^ Various grades of ionomer resins are available for extrusion coating and film extrusion. It is also known that ionomer resins can be co¬ extruded with other plastic resins and exhibit adhesion to other polyolefins, nylon resins and coextrudable adhesive resins often used as bonding layers in multi-ply coextruded structures. A very wide variety of ionomer resins are manufactured by E.I. DuPont de Nemours and Company under the registered trademark "SURLYN". Ionomer resins have been suggested for use primarily in the area of packaging, for foods, liquids and pharmaceuticals, as well as certain industrial applications including lightweight sails, bonded cable sheath, roof underlayment and flame retardant products. In most applications, ionomer resins are offered as a superior substitute for polyethylene. In none of the literature or prior art is there any suggestion that ionomer resins should or could be used for reinforcing glass layers or for bonding layeirs of glass to polycarbonate or other plastic layers, in order to form a laminated safety glass. Moreover, there is no suggestion in the literature or prior art indicating that ionomer resins could or should be substituted generally for polyurethanes. Layers of ionomer resins can be formed by casting or extrusion, the latter being preferred. Once formed there are no significant differences between cast and extruded layers. When the ionomer resin layers are sufficiently thick, polycarbonate layers can be eliminated altogether. Ionomer resins have several advantages over polyurethane. Polyurethane is difficult to manufacture and hard to fabricate. It is frequently not clear enough for use in windshields and the like. By contrast, ionomer resin films can be easily extruded to desired thicknesses, and at about one-half the material cost of polyurethane. Ionomer resins have demonstrated better adhesion characteristics to polycarbonates, as well as better resistance to lower temperatures. In preferred embodiments, the surface to which the ionomer resin is adhered may be primed to get good adhesion, as is the case with polyruethane. Silane coupling agents are suitable primers. With regard to optical properties, ionomer resins demonstrate better clarity than polyurethanes. Moreover, the ionomer resins are more hydrolytically stable to water, acids and bases, are more resistant to degradation from ultraviolet light, and overall, are less likely to weaken with time. This greatly enhances the useful life of laminates made in accord with the present invention. Summary of the Invention It is an object of this invention to provide a laminated article based on laminates of glass and ioncmer resins, and depending upon application, laminates of glass, ionomer resin and polycarbonate or other transparent plastics as well. The laminated articles have all of the advantages and positive features of laminates of glass and polyurethane, but are significantly less expensive to produce and have other enhanced features such as increased clarity and greater useful life. It is another object of this invention to provide a larrdnated article of glass, ionomer resin and polycarbonate which has good adhesion and which is transparent and resistant to breakage. It is still another object of this invention to provide a laminated ' article of glass, ionomer resin and polycarbonate which has good strength properties over a wide temperature range. These and other objects of this invention are accomplished by articles comprising a lamina of ionomer resin film laminated to a sheet of glass. The ionomer resin film is preferably an ionically crosslinked ethylene-methacrylic acid copolymer. The laminated articles may also comprise a sheet of polycarbonate laminated to the ionomer resin film opposite the glass. The laminated articles may further comprise an ionomer resin film sandwiched between two sheets of glass. The laminated articles may still further comprise a sheet of polycarbonate sandwiched between sheets of ionomer resin film, which are in turn sandwiched between sheets of glass. The laminated articles may still further comprise an ioncmer resin film sandwiched between a sheet of glass and a sheet of acrylic plastic and an ionomer resin film sandwiched between a sheet of glass and a sheet of metal. The laminated articles may also comprise any number of lamina of glass sandwiched with a lamina of ioncmer resin, the resultant laminate having glass as the outer lamina. BRIEF DESCRIPTION OF THE DRAWING The Figures illustrate cross-section views through portions of laminated articles made in accordance with this invention, wherein: Fig. 1 is a glass/ionomer resin laminate; Fig. 2 is a glass/ionomer resin laminate having a hard coat on the otherwise exposed surface of the ionomer resin layer; Fig. 3 is a glass/ionomer resin/polycarbonate laminate; Fig. 4 is a glass/ionomer resin/polycarbonate laminate having a hard coat on the otherwise exposed surface of the polycarbonate layer; Fig. 5 is a glass/ionomer resin/glass laminate; Fig. 6 is a glass/ionomer resin/polycarbonate/ionomer resin/glass laminate; Fig. 7 is a glass/ionomer resin/arcylic plastic laminate; Fig. 8 is a glass/ionomer resin/metal laminate; and Fig. 9 is a glass/ioncmer resin/glass/ionomer resin/glass/ionomer resin/ glass laminate. OMPI DETATFT. DESCRIPTION OF THE PREFERRED EMBODIMEETΓS The basic laminated safety glass article according to this invention is shown in Figure 1. The laminate 10_ comprises a sheet of glass 12 laminated to an ionomer resin layer _. The ioncmer resin layer 14_ is thicker in the basic laminated article than in articles including a layer of polycarbonate or a second layer of glass. A second embodiment of a laminated safety glass article according to this invention is shewn in Figure 2. The laminate 20_ comprises a sheet of glass 22_ and an ionomer resin layer 24, similar to the laminate ^2. of Figure 1. However, the embodiment of Figure 2 is further provided with a hard coat 2_6_ on the otherwise exposed surface of the ionomer resin film, in order to protect the ionomer resin film form scratching, abrasion and other similar damage. A "hard coat" provides abrasion resistant, optically transparent coatings which serve to protect the surface and render the laminate more resistant to scratching and the like.. Useful "hard coat" compositions are described in U.S. Letters Patent No. 4,027,073 and U.S. Patent Application Serial No. 473,790, filed March 10, 1983, and assigned to the owner of this application. A third embodiment of a laminated safety glass article according to this invention is shewn in Figure 3. The laminate 30_ comprises a sheet of glass 3_ laminated to an ionomer resin film 34_, which is in turn laminated to a polycarbonate layer 36. As additional strength is provided by the polycarbonate layer 36_, the ioncmer resin layer 3 may be thinner than the ionomer resin layer 4 in the embodiment shown in Figure 1. A fourth embodiment of a laminated safety glass article according to this invention is shewn in Figure 4. The laminate 4£ is similar to that of Figure 3, in comprising a glass sheet ^2_, an ionomer resin layer 44_ and a polycarbonate layer 46_. Although polycarbonate is used to provide additional strength to the laminate, polycarbonates are usually too soft, and therefore subject to scratches and abrasion. Accordingly, the laminate 40_ is provided with a hard coat layer 4_ for protecting the otherwise exposed surface of the polycarbonate layer 46_. A fifth embodiment of a laminated safety glass article according to this invention is shown in Figure 5. The laminate 50_ comprises two sheets of glass 52, 54 joined by an ionomer resin layer 56. As no soft surfaces are exposed, no hard coat layer is necessary. A sixth eπfc diment of a laminated .safety glass article acco__ding to this invention is shown in Figure 6. The laminate j50_ cαrprises first a polycarbonate layer 6 sandwiched between two ionomer resin layers j>4_, 66. The ionomer resin/polycarbonate/ionomer resin laminate is itself sandwiched between two glass sheets 68_ and 7C As might be expected, the thicker and more complex laminate 60_ shown in Figure 6 is more expensive to produce than the laminates shown in Figures 1-5, but it exhibits the greatest strength and resistance to shattering and spalling. A seventh embodiment of a laminated safety glass article according to this invention is shewn in Figure 7. The laminate 70_ comprises a sheet of glass 72_ and a sheet of acrylic plastic 76_ joined by an ioncmer resin film layer 74. The acrylic plastic layer 76_ may or may not be coated with an appropriate hard coat. An eighth embodiment of a laminated safety glass article according to this invention is shown in Figure 8. The. laminated article j30_ comprises a sheet of glass 82. and a sheet of metal J36_ joined by an ionomer resin film layer 84. The metal layer j36_ may be any metal such as aluminum, silver, iron and copper. A ninth embodiment of a laminated safety glass article according to this invention is shown in Figure 9. The laminated article 90. comprises sheets of glass 9 , 96_, 100 and 104 sandwiched by ionomer resin film layers 9 , 98_ and 102. A nurrber of transparent laminates were prepared for a first series of tests, using a 2.5 millimeter thick sheet of float glass, a 1/8 inch sheet of polycarbonate and a 30 mil thick layer of an ionomer resin film. The ionomer resin film incorporated in the laminate is formulated by melting the ioncπer resin pellets, preferably under an inert atmosphere, such as may be provided by nitrogen, at about 380° F, and extruding the molten resin through a die in accordance with procedures well known in the art. Films varying in thickness from 1 mil to 100 mils may be used in the laminates of the invention. The ioncmer resin film may be rolled and stored, preferably in a bag or other container to protect it from dust, dirt or other contaminates. The ioncmer resin pellets may also be melted and poured into a mold to produce cast sheets of ioncmer resin for use in preparing the desired laminates. The sheets and layers were approximately 4 inches by 5 inches in size to facilitate handling and processing. In particular, the ionomer resin film was "SU LYN" 1601, manufactured by the Polymer Products Department of the DuPont Cαrpany. The melt index of "SURLYN" 1601 is 1.3 dg/min, ASTM D-1238. The ion type is sodium and the density is 0.94 g/cc. A data information sheet on "SURLYN" 1601 icno er resin (for flexible packaging) is available under the number E-29173 (7/81) . The information of this technical release, including the rheology curves, is incorporated herein by reference. SURLYN type 1707 is also a preferred sodium ionomer resin for use in this invention. Organic amines may be combined with the ioncmer resin in an amount of from about 0.5 to about 7%, by weight, based on the weight of the resin. It has been found that the presence of an organic amine in the ionomer resin may serve to maintain the optical clarity of the laminates produced in the invention. Useful organic amines include aliphatic diamines or triamines or related compounds such as diethanolamine or diethylenetriamine. The ccmmerically available organic amines are simply combined with the ionomer resin pellets and extruded or cast as desired. Likewise, a mixture of sodium and zinc ioncmer resins may be used to prepare the ionomer resin film useful in the invention. The sodium and zinc ionomer resins may be combined in a ratio of 95:5 to 5:95. • For purposes of simplifying the test, the sandwich was constructed with one outer layer of glass, one inner layer of ionomer resin and one outer layer of polycarbonate. A three layer laminate as tested can be fully expected to perform in the same manner as a five layer lamination such as that shown in the drawing with regard to adhesion, if not overall strength. The sandwiched laminates were assembled in a vacuum bag and placed in an autoclave. The samples were heated to a teπperature of from about 200°F to about 275°F over a 45 minute period; were held at the elevated temperature for about 15 minutes, and were then cooled to room temperature, approximately 65°F-70°F. After cooling, the laminates were immersed in boiling water in an effort to promote premature and unwanted delamination. Throughout all of the examples herein, the same basic procedure, involving vacuum bag? autoclave, heating up, sustained heating and cooling were followed unless otherwise noted. The tests were conducted with and without certain primers to promote adhesion between the ionomer resin and the glass and polycarbonate respectively. Primers suitable for glass, and the glass/ionomer resin interface in particular, were found to include silanes, such as those produced under the registered trademarks "Z-6040" and "Z-6020" by Dow Chemical Company. Other primers suitable for the polycarbσnate/ionσmer resin interface in particular, were found to include organic amines, usually in a diluted solution with an inert solvent (unlikely to attack the polycarbonate, e.g. alkanes and alcohols), such as aliphatic or polyethylene amines or ethanolamines, and specifically diethylenetriiamine. Other specific primers include diisocyanates (toluene diisccyanate) and polyacrylic acid (produced under the registered trademarks "ACRYLOID" and "ACRYSOL" by the Rohm and Haas Company). EXAMPLE 1 • A laminate of glass and ionomer, the glass surface to be laminated to the ionomer resin having been primed with Dow Z-6020 was formed following the procedure set forth above. The laminate did not undergo delamination in boiling water. EXAMPLE 2 A 30cm by 30cm laminate comprising a 3ιtm thick clear polycarbonate sheet sandwiched betaken two 0.7ιm. thick ioncmer resin films made from SURLYN 1601 which in turn are sandwiched between 2.5ι ι thick sheets of chemically strengthened glass was prepared following the procedure set forth above. The glass and polycarbonate coitponents were throughly cleaned and treated with a silane primer to enhance adhesion. The • coπponents were dried, and free of residual solvents and moisture prior to forming the sandwich. The sandwiched laminate was bagged and autoclaved at a temperature of 205° to 255°F under 10 atmospheres of pressure for a period of about 90 minutes. The laminate was cooled quickly to room temperature. The laminate was used as a target and a 45 calibre bullet from a handgun was fired at the laminate three times. No delamination occurred although the glass shattered. The ionomer resin film remained laminated to the polycarbonate and glass surfaces. EXAMPLE 3 Laminates 75mm square were prepared following the procedure and using like components -Specified in Exairple 2 were prepared. The resultant laminates were placed in boiling water. The laminates did not lose integrity after two hours in boiling water. Small bubbles did develop about the perimeter the laminates; however, visibility was only marginally impaired around the perimeter. On the basis of the foregoing examples, ionomer resin films may be substituted for polyurethane and polyvinyl butyral in laminated safety glass, at a substantial savings in cost. The best primer for the polycarbonate/iono er resin interface is Dow Z-6020. Other primers could prove satisfactory. EXAMPLE 4 A 30cm by 30cm laminate comprising an 0.25mm thick ionomer resin film sandwiched between 1mm thick chemically strengthened glass and a m thick aluminized steel sheet following the procedure set forth in Exarrple 2. The laminate was cycled between -20°F to 160°F, 10 times and did not undergo delamination. EXAMPLE 5 A 30cm by 30cm laminate comprising a 3mm thick clean acrylic sheet sandwiched between two 1.4rrm thick ionomer resin films made from SURLYN 1707 which in turn are sandwiched between 3ιrm thick sheets of chemically strengthened glass was prepared following the procedure of Exarrple 2. A long 22 caliber rifle bullet was fired at the resulting laminate from a distance of 35 feet, and no penetration resulted. EXAMPLE 6 A 30cm by 30cm laminate comprising chemically strengthened glass and ioncmer resin film made frcm SURLYN 1707 sandwiched in the order shown in Figure 9 was prepared following the procedure of Example 2. The lamina was laid up in the following order, starting with the target side: a 2.5mm thick lamina of chanically strengthened glass, a 5mm thick lamina of ionomer resin film, or 12nm thick lamina of chemically strengthened glass, a 5mm thick lamina of ionomer resin film, a 12rrm thick lamina of chanically strengthened glass, a 5_rm thick lamina of ionomer resin film and a Iran thick lamina of chemically strengthened glass. All surfaces were cleaned and treated with a silane primer to enhance adhesion. In this instance, the laminate was autoclaved under vacuum at a teπperature between 205°F and 285°F at 10 atmosphere pressure for a 2.5 hours. After cooling quickly, the resulting laminate was clear and used as a target with the mass of glass facing in the direction of fire. A .357 magnum handgun using 158 grain metal painted anmunition of Remington was fired at the laminate. No penetration occurred after three shots were fired in a triangular pattern. The lirca thick glass sheet did splinter but remained laminated. This exarrple was repeated substituting 6irm thick cast sheets of ionomer resin for the 5mm thick ioncmer resin lamina and in place of the Iran thick glass spall sheet. The resultant laminate was not penetrated when fired on as above, and only a slight bulge appeared on the spall sheet. It is to be understood that the foregoing examples are given for the purpose of illustration and that any other suitable glass, ionomer resin, reinforcing plastic or the like could be used provided that the teachings of this disclosure are followed. The basic building block of this invention, namely a laminate comprising a sheet of glass laminated to an ionomer resin film, may be used in multiples to achieve nearly any desired strength. This is illustrated in Figure 9, wherein lamina of varying thickness of glass are sandwiched with lamina of varying thickness of ionomer resin film. By varying the number and the thickness of the lamina of glass and ionomer resin film, always, however, laminating in the alternative order shown in the Figure, it is possible to produce laminates having resistance to exception-ally large force. The principles of this invention may also be applied to curved laminated articles, such as windshields and face masks. The laminates shown in Figures 1-9 are flat merely for purposes of facilitating illustration. Where transparency is not critical, the bonding techniques taught herein may be used for laminating metal as well as glass such as illustrated in Figure 8. This invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and accordingly, reference should be made to the appended claims, rather than to the foregoing specification,, as indicating the scope of the invention. Having thus described the invention.

Claims: What is claimed is: 1. A laminated article comprising a lamina of ionomer resin film laminated to a sheet of glass. 2. Ihe laminated article of claim 1, further comprising a sheet of polycarbonate laminated to said ionomer resin film on the surface thereof opposite said sheet of glass, whereby said ionomer resin film is sandwiched between said sheet of glass and said sheet of polycarbonate. 3. Ωe laminated article of claim 1, further coirprising a second sheet of glass laminated to said ioncmer resin film, said ionomer resin film being sandwiched between said two sheets of glass. 4. The laminated article of claim 1, further coirprising: a sheet of polycarbonate laminated to said ionomer resin film, to the surface thereof opposite the sheet of glass; a second ionomer resin film laminated to said sheet of polycarbonate, said sheet of polycarbonate being sandwiched between said ionomer resin films; and, a second sheet of glass laminated to said second ioncmer resin film, to the surface thereof opposite said sheet of polycarbonate, whereby said sheet of polycarbonate is sandwiched between said ioncmer resin films, which in turn are sandwiched between said sheets of glass. 5. The laminated articles of claims 1, 2, 3 or 4, wherein all surfaces laminated to said ionomer resin films are first primed to promote adhesion. 6. The laminated article of claim 5, wherein the surfaces are primed with a silane coupling agent. 7. A method for forming a laminated glass article, comprising the steps of: priming a glass sheet surface; and, laminating an ionomer resin film to the primed surface of the sheet of glass. 8. The method of claim 7, comprising the step of priming the glass surface with a silane coupling agent. 9. The method of claim 8, further comprising the steps of: heating the resulting laminate to a baking terrperature in the range of arproximately 180°F to approximately 310 β F; maintaining the laminate at the baking terrperature for a period of time in the range of approximately 15 minutes to approximately 1 hour; and, cooling the laminate as rapidly as possible without damaging the laminate. 10. The method of claim 7, further coirprising the step of covering the otherwise exposed surface of the ionomer resin film with a hard coat to reduce damage from scratching and abrasion. 11. The method of claim 7, further comprising the step of laminating a sheet of polycarbonate to the otherwise exposed surface of the ionomer resin film. 12. The method of claim 11, further comprising the step of priming the surfaces of the sheet of polycarbonate to be bonded to the ionomer resin film with a silane coupling agent.. 13. The method of claim 12,.further comprising the step of covering the otherwise exposed surface of the sheet of polycarbonate with a hard coat to resist damage from scratching and abrasion. 14. The method of claim 11, further comprising the steps of: laminating a second ioncmer resin film to the otherwise exposed surface of the sheet of polycarbonate; and, laminating a second sheet of glass to the otherwise exposed surface of said second ionomer resin film. 15. The method of claim 14, further comprising the step of priming all surfaces to be bonded to an ionomer resin film with a silane coupling agent. 16. The method of claim 9, further comprising the step of heating the laminate under a pressure of approximately 150 p.s.i., in an autoclave. OMPI

Inventors: BOLTON NELSON P, SMITH NOVIS W JR, BOLTON, NELSON, P., SMITH, NOVIS, W., JR.
Applicants: BOLTON NELSON P, SMITH NOVIS W JR, BOLTON, NELSON, P., SMITH, NOVIS, W., JR.
Application year: 1984
Main classification: B32B17
IPC codes: B32B15, B32B17, C03C27