Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/10009—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the number, the constitution or treatment of glass sheets
  • B32B17/10036—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the number, the constitution or treatment of glass sheets comprising two outer glass sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/1055—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer
  • B32B17/10743—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer containing acrylate (co)polymers or salts thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/1055—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer
  • B32B17/10761—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer containing vinyl acetal
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/91—Product with molecular orientation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
  • Y10T428/2495—Thickness [relative or absolute]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
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  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
  • Y10T428/2495—Thickness [relative or absolute]
  • Y10T428/24967—Absolute thicknesses specified
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
  • Y10T428/266—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension of base or substrate
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
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  • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
  • Y10T428/269—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension including synthetic resin or polymer layer or component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31551—Of polyamidoester [polyurethane, polyisocyanate, polycarbamate, etc.]
  • Y10T428/31616—Next to polyester [e.g., alkyd]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
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  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31551—Of polyamidoester [polyurethane, polyisocyanate, polycarbamate, etc.]
  • Y10T428/31627—Next to aldehyde or ketone condensation product
  • Y10T428/3163—Next to acetal of polymerized unsaturated alcohol [e.g., formal butyral, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31786—Of polyester [e.g., alkyd, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31786—Of polyester [e.g., alkyd, etc.]
  • Y10T428/31797—Next to addition polymer from unsaturated monomers

Definitions

• an energy absorbing interlayer of plasticized polyvinyl butyral (PVB) with one or more rigid layers such as glass in a safety glazing is usually prepared by interposing the PVB layer between glass sheets while eliminating air from between the engaging surfaces and then subjecting the assembly to elevated temperature and pressure in an autoclave to fusion bond the PVB and glass and form an optically clear structure.
• PVB plasticized polyvinyl butyral
• These glazings are used in windows such as the front, side and rear windows in motor vehicles, particularly windshields, where the interlayer can absorb a blow from the head of an occupant without penetration of the windshield.
• ком ⁇ онент are usually deposited on or adhered to a carrier layer which is different from the low modulus, elastomeric PVB which is unsuitable as a carrier.
• a carrier layer should have good clarity, be relatively uniform in thickness and strong having high modulus to facilitate ease of handling and processing during association with the performance layer(s).
• biaxially oriented polyethylene terephthalate is used as noted, for example, in U.S. Pat. No. 4,465,736.
• PET in glass laminates offers many advantages.
• U.S. Pat. No. 5,024,895, to Kavanagh et al., and U.S. Pat. No. 5,091,258, to Moran disclose, PET can be biaxially stretched to improve strength and can be heat stabilized to provide low shrinkage characteristics when subjected to elevated temperatures.
• the tensile modulus, a desired property of glass laminate interlayers and an indication of the stiffness of the interlayer, at 21° C.-25° C. of PET is about 10 10 Pa as compared with about 10 7 Pa for PVB of the type used in safety glazings. This increased stiffness of PET is a desirable property for use in glass laminates.
• PET Many applications of PET involve a layer of PET being used as a carrier for the aforementioned functional layers, such as solar radiation blockers, antennas or heat strips.
• U.S. Pat. No. 5,979,932 to Jourdaine et al., U.S. Pat. No. 5,091,258, to Moran, and U.S. Pat. No. 5,932,329, to Frost et al. disclose a PET layer between two PVB layers wherein the PET layer is provided with an infrared-reflective coating.
• This invention provides a composite laminate interlayer for use in manufacturing intrusion resistant glass laminates having a higher laminate stiffness.
• Such laminates of the present invention comprise an interlayer having two outside layers of PVB, and two inside layers of bonded optical grade PET.
• To increase the stiffness in the laminate it has been found that using two pieces of optical grade PET improves the stiffness of the laminate but does not significantly reduce the optical clarity of the laminate. This contrasts common practice which recognizes that as the thickness of a single layer of PET increases, its optical clarity is reduced.
• Optical grade PET with haze levels less than ⁇ 1.0% is limited to about 0.175 mm (7 mil) or less.
• Combining two pieces of optical grade PET, for example two 7-mil pieces improves the laminate's resistance to breaking and pullout/push-in as a single layer of PET of the same combined thickness would, without significantly sacrificing the optical clarity of the laminate.
• Another aspect of this invention provides a composite laminate interlayer comprising two layers of PET between layers of plasticized PVB adhesive where at least one of the PVB layers exhibits enhanced stiffness.
• high stiffness in plasticized PVB is provided by reducing the level of plasticizer in the PVB. This is indicated by a rise in glass transition temperature (Tg) of the plasticized PVB, e.g. about 2 to 3° C. above typical values for a commercial application. For instance, for automotive applications, where plasticized PVB sheet typically has a Tg of about 30-33° C., high stiffness PVB of this invention will have a Tg of at least 35° C.
• Another aspect of this invention provides interlayer composites with other functional layers, e.g. sound dampening elastomer layers or radiation blocking layers.
• glass transition temperature (Tg) of plasticized PVB is determined by rheometric dynamic analysis using the following procedure.
• Plasticized PVB sheet is molded into a sample disc of 25 millimeters (mm) in diameter.
• the PVB sample disc is placed between two 25-mm diameter parallel plate test fixtures of a Rheometrics Dynamic Spectrometer II.
• the PVB sample disc is tested in shear mode at an oscillation frequency of 1 Hertz as the temperature of the PVB sample is increased from ⁇ 20 to 70° C. at a rate of 2° C./minute.
• the method is reproducible to within +/ ⁇ 1° C.
• Commercially used PVB typically has a Tg in the range of 30-33° C.
• the units of “mils, “mm” and “inch” will be used in describing the thickness of a glass laminate interlayer. The relationship of these units is illustrated as such: 0.25 mm is roughly equivalent to 10 mils and 0.01 inch.
• the preferred embodiment of the present invention is a glass laminate in which two bonded PET sheets are placed between two standard sheets of PVB. It has been found that increasing the thickness of the PET layer greatly enhances the stiffness of the glass laminate, thus improving the strength of the glass laminate after breaking.
• Optical quality of PET film particularly visual haze, though, is a problem above thicknesses of about 7 mil, whereas PET of about 7 mil or less exhibits acceptable haze of 1% or less.
• typical haze levels for 10 mil Mylar film produced by E. I. du Pont de Nemours is 2% and above that thickness the haze levels are much higher.
• the high haze of the PET layers greater than about 7 mil prohibits the use of these thick layers in combination with PVB for use as automotive glazings, where optical clarity is essential.
• a key advantage of the present invention involves the inherent nature of layers of PET over 10 mils having unacceptable haze characteristics. It has been found that using two layers of PET with acceptable haze characteristics (less than about 1% haze) in combination have the desired and required optical clarity for use in glass laminates. Thus, for instance, providing two 7 mil layers of PET for a total PET layer thickness of 14 mil gives the laminate improved stiffness qualities, without significantly diminishing the optical clarity of the laminate. Providing two layers of PET with acceptable optical clarity between two layers of PVB provides many advantages, including a laminate with increased stiffness (when compared to a conventional laminate) without sacrificing the optical clarity of the laminate.
• two optical grade PET sheets are used in place of a thicker PET sheet.
• the most preferred embodiment employs two PET sheets of about 7-mil thickness each bonded together between two PVB layers. The application of the PET in this manner significantly reduces the haze problem otherwise associated when a single, 14 mil thick PET layer is used.
• the two PET layers are bonded with an adhesive.
• a layer of plasticized PVB, polyurethane 2-component reactive cure, pressure sensitive acrylic resins, and other known adhesives can all be used so long as the chosen adhesive does not substantially increase the haze of glass laminate of this invention.
• the chosen adhesive used with the composite interlayer of the present invention preferably should not substantially differ in sound attenuating performance from that of a laminated glass made with standard PVB. Laminated glass having high sound attenuation will most likely have decreased intrusion resistance, which is not a desired property of the present invention.
• One preferred adhesive is a pressure sensitive acrylic resin. This class of adhesives exhibits the preferred clarity that is a desired component of this invention.
• the acrylic resin preferably comprises polyacrylate esters of varying molecular weights and ester functionalities.
• the acrylic resin may also contain functional monomers which are used to provide a means for crosslinking of polymer molecules to increase the creep resistance or shear strength.
• the most preferred adhesive is commercially available from Solutia, Inc. as Gelva multi-polymer solution adhesive (GMS 263).
• PVB resin is produced by known aqueous or solvent acetalization processes reacting PVOH with butyraldehyde in the presence of acid catalyst, followed by neutralization of the catalyst, separation, stabilization and drying of the resin. It is commercially available from Solutia, Inc. as Butvar® resin. PVB resin typically has a weight average molecular weight greater than 70,000, preferably about 100,000 to 250,000, as measured by size exclusion chromatography using low angle laser light scattering. On a weight basis PVB typically comprises less than 22%, preferably about 17 to 19% hydroxyl groups calculated as polyvinyl alcohol (PVOH); up to 10%, preferably 0 to 3% residual ester groups, calculated as polyvinyl ester, e.g.
• PVOH polyvinyl alcohol
• acetal preferably butyraldehyde acetal, but optionally including a minor amount of acetal groups other than butyral, for example 2-ethyl hexanal as disclosed in U.S. Pat. No. 5,137,954.
• the PVB resin of the sheet is typically plasticized with about 20 to 80 and more commonly 25 to 45 parts plasticizer per hundred parts of resin.
• Plasticizers commonly employed are esters of a polybasic acid or a polyhydric alcohol. Suitable plasticizers are triethylene glycol di-(2-ethylbutyrate), triethyleneglycol di-(2-ethylhexanoate), tetraethyleneglycol diheptanoate, dihexyl adipate, dioctyl adipate, mixtures of heptyl and nonyl adipates, dibutyl sebacate, polymeric plasticizers such as the oil-modified sebacic alkyds, and mixtures of phosphates and adipates such as disclosed in U.S.
• the amount of plasticizer used is a convenient means to modifying and controlling the stiffness of the PVB.
• a useful surrogate property for stiffness is Tg which is directly related to the level of plasticizer.
• the plasticized PVB sheet used in the laminates of the preferred embodiment though, have normal Tg values of about 33° C. or less.
• Some embodiments of this invention can have a Tg of at least 35° C. or higher by modifying the plasticizer content of the PVB.
• PVB sheet may contain other performance-enhancing additives such as pigments or dyes for coloring all or part of the sheet, antioxidants and the like.
• PVB sheet is prepared by mixing combined plasticizer and other additives (e.g. UV-absorber, adhesion control agent and the like) with PVB resin and forcing the mixture under pressure through a die opening to form a sheet. Thickness of the PVB sheet can range from about 0.1 to 2 mm (about 4-80 mil) thick, typically about 0.375 to about 1.5 mm (about 15-60 mils) thick to provide the desired performance in the glass laminate.
• the PET sheets for use in the composite interlayer of this invention are preferably biaxially stretched to improve strength and been heat stabilized to provide low shrinkage characteristics when subjected to elevated temperatures (i.e. less than 2% shrinkage in both directions after 30 min. exposure at 150° C.).
• the tensile modulus (at 21-25° C.) of polyethylene terephthalate is about 10 10 Pa as compared with about 10 7 Pa for a plasticized polyvinyl butyral of the type used in safety glazings.
• any known coating and/or surface treatment may be applied to the PET.
• plasma treatment of biaxially stretched polyester to improve adhesion as disclosed in European Patent 157030 B1, and U.S. Pat. No.
• Another method for treating the surface of PET film includes deposition of a thin layer of carbon by vacuum sputtering as disclosed by Kittler in U.S. Pat. No. 4,865,711 (incorporated herein by reference).
• Composite interlayers according to this invention are prepared by known procedures. See for instance, U.S. Pat. Nos. 4,973,511, 5,024,895 and 5,091,258 (incorporated herein by reference) for methods for laminating plasticized PVB to surface-treated PET sheet. Because final bonding conditions will be experienced when the interlayer is bonded to glass, the degree of bonding of PVB to PET in the composite interlayer is not critical. If a layer of plasticized PVB in the composite interlayers of this invention has a Tg higher than convention, a person of ordinary skill in the art will appreciate a need to raise the processing temperature of the PVB sheet by an amount corresponding to the elevation in Tg. Suitable temperatures for bonding PVB to PET will typically be in the range of 50 to 120° C.
• the PET/PVB composites can be pressed, e.g. in a nip roller, to improve adhesion.
• Glass laminates using sheets of the invention are prepared by known procedures, e.g. as disclosed in U.S. Pat. Nos. 5,024,895; 5,091,258; 5,145,744; 5,189,551; 5,264,058 and 5,529,654 (all of which are incorporated herein by reference).
• the composite interlayer is placed between two sheets of glass and heated under vacuum to a temperature in the range of about 85 to 120° C. for about 10 to 30 minutes, depending on temperature, to remove air from between the layers of the laminate and to seal the laminate edge prior to autoclave lamination.
• the laminate is preferably heated in an autoclave at elevated temperature (about 90 to 165° C.) and pressure (about 1000 to 2000 kPa) for sufficient time to firmly bond the layers of the laminate.
• elevated temperature about 90 to 165° C.
• pressure about 1000 to 2000 kPa
• Non-autoclave methods as disclosed in U.S. Pat. No. 5,536,347 may are also useful, e.g. for plasticized PVB having only moderate increases in Tg.
• a typical glass laminate of the current invention contains glass sheets that are usually float glass, heat strengthened glass or tempered glass typically in the range of 1 to 10 millimeters (mm) thick, preferably in the range of 1-5 mm thick.
• a composite interlayer comprising two PET sheets between layers of plasticized PVB adhesive.
• Each PVB sheet is preferably about 0.76 mm thick, and each PET sheet is biaxially-oriented and can be in the range of about 0.025 to 0.25 mm thick (1 to 10 mils), preferably about 0.175 mm thick (7 mils) thick, for a total preferred PET thickness of 0.350 mm (14 mils).
• the optical clarity of each PET layer must exhibit acceptable optical clarity characteristics, preferably below 1% haze.
• the PET layers are bonded together, preferably with a pressure sensitive acrylic resin.
• the surface of the PET is preferably modified, such as by roughening of the surface or by chemical modification of the material at the surface.
• modification can be effected by flame treatment, chemical oxidation, corona discharge, carbon sputtering, plasma treatment in vacuum or in air or other treatments well known to those of ordinary skill in the art.
• the PVB is plasticized, most preferably with triethylene glycol di-(2-ethylhexanoate).
• the plasticizer can be added, alternatively, in an amount to provide a Tg of at least 35° C.
• the PVB layers can be similar, e.g. both PVB layers having a Tg of at least 35° C. or, having a conventional Tg value, with the preferred embodiment encompassing similar layers of conventional PVB.
• the two layers can be different, e.g. one plasticized PVB layer having a conventional Tg of about 30 to 33° C. and the other PVB layer being stiffened by having a Tg of at least 35° C.
• a further embodiment of the present invention is a glass laminate containing an additional functional layer.
• This layer can be, e.g., a sound attenuating elastomer layer as disclosed in U.S. Pat. No. 5,796,055 (incorporated herein by reference) or a radiation blocking layer, e.g. comprising a composite of one or more layers of metal or metal oxide deposited onto either PET layer as disclosed in any of U.S. Pat. Nos. 5,024,895, 5,091,258 or 5,932,329 (the disclosures of all four patents being incorporated herein by reference). If a sound attenuating layer is used, it should be added to the glass laminate of the present invention by replacing one of the two PVB layers.
• An alternative embodiment to the present invention is the use of multiple layers of optical grade PET, limited only by the haze characteristics of the final glass laminate. For instance, using two 5-mil sheets and one 2-mil sheet of optical grade PET could be used to improve the stiffness of the glass laminate without reducing its optical clarity. It is within the scope of this invention to use multiple thinner, optical grade PET sheets in place of an equivalent thicker sheet of PET, the total number of sheets used being limited only to having an acceptable optical clarity.
• a series of glass laminates were made to assess the effects of the inclusion of various PET films on the optical haze. These glass laminate structures were prepared using conventional PVB laminating techniques in combination with two pieces of 2.3-mm thickness clear annealed float glass and various combinations of PET and PVB as described in the table below.
• the 14 mil (0.35 mm) PET component was a composite of two layers of 7 mil (0.18 mm) films bonded together with the Gelva 263 acrylic pressure sensitive adhesive. Haze measurements were made in accordance with ASTM D1003 using Illuminant C (2° observer angle), the results of which are disclosed in TABLE 1.
• a standard glass laminate was prepared for use as a control during the experiments. This control was a sandwich of two pieces of heat-strengthened float glass with a homogeneous interlayer of conventional PVB having a Tg of about 33° C. Each layer of glass typically measured 2.1 mm thick, while the PVB layer was 0.76 mm.
• the standard laminate performed acceptably in blunt-pendulum impact testing, with tests indicating that the standard laminate required 20-30 sec to penetrate, as opposed to less than 2 sec for tempered glass.
• the target of these tests was a front side door, with glass edge engagement of at least 14 mm.
• the standard laminate showed a considerable deformation ( ⁇ 3 cm), suggesting that the standard laminate was on the edge of its ability to pass this test.
• the PVB used in laminates A, C and D was industry standard automotive grade Saflex® PVB made by Solutia Inc. containing normal plasticizer levels.
• the PVB used in laminate B (PVB-A) was an experimental material with increased stiffness, wherein the plasticizer level was adjusted so as to give a PVB layer with a Tg greater than 35° C.
• the PET layers used in laminates A and B comprised a single sheet of optical grade 7 mil (0.18 mm) thickness PET film.
• the PET layer used in laminate C comprised two sheets of optical grade 7 mil (0.18 mm) thickness PET film bonded together with acrylic adhesive. Testing of these trial laminates followed the parameters of BS AU 209, part 4a.
• the pendulum mass used was either 9.5 kg, delivering an impact energy of 65 J, or at 19.5 kg, delivering an impact energy of 134 J. All impacts were made at the center of the laminates instead of toward the top center as specified by BS AU 209, part 4a, and were in a diamond shaped pattern, as in the standard method.
• Test results are summarized in TABLE 5. While standard laminate delivers reasonably good resistance to axehead impact, the PVB composite laminates, particularly the preferred embodiment of the present invention laminate C, revealed exceptionally high resistance to the attack of the cutting tool.
• the stiffness data from TABLE 5 is discussed in Example 8 below.
• each laminate was impacted per the modified BS AU 209, part 4a test at an energy level of 65 J (using the 9.5 kg pendulum).
• Headform pullout/push-in resistance was done with a ram having an 18-cm diameter, hemispherical metal head.
• Pullout/push-in speed was 10 cm/min perpendicular to the impacted side of the laminate.
• Force (load) applied to the laminate vs. the displacement (distance the laminate was pushed in) was recorded.
• the apparent laminate modulus was obtained by dividing the maximum load by the maximum displacement. Maximum laminate modulus was the highest average of the slopes from the pullout force vs. displacement curve over a range of 2-cm displacement. Results are summarized in TABLE 6.
• laminates B and C showed much improved modulus properties over the standard laminate and laminate A.
• This increased resistance to headform pullout/push-in testing represents improved strength of the laminates after being broken with a blunt object.
• This increased laminate modulus or stiffness after glass breakage is a very desirable property in automotive laminates as a deterrent to break-ins.
• the standard laminate loses half of the stiffness after the penetration and is, thus, vulnerable to this type of testing sequence.
• the laminates B and C showed greater resistance to the blunt-head impact at higher energy level, and they had the highest measured stiffness after the penetration. It would take tremendous effort to pull these laminates out of the window frame, even though a 3 to 4 cm diameter hole has been made in each laminate.

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