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
  • B32B27/36—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
  • 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
• • 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
  • B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
• • 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
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • 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
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/514—Oriented
  • B32B2307/518—Oriented bi-axially
• • 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
  • B32B2457/00—Electrical equipment
  • B32B2457/12—Photovoltaic modules

Definitions

• Polymeric films are used extensively in applications where the film is exposed to intense electromagnetic radiation, particularly in the infra-red, visible, and ultraviolet range. In some cases the film is used to transmit such radiation, while in others the film may be a substrate for coatings designed to reflect bands of incident radiation.
• One common film material polyethylene terephthalate (PET)
• PET polyethylene terephthalate
• PET has excellent mechanical strength and clarity, but tends to degrade due to radiation absorption in the ultraviolet range. Thus, when this film is exposed for long periods to direct sunlight, it degrades and becomes useless. Under some conditions, such degradation may occur after only a few months of exposure.
• Some radiation protection can be obtained by addition of ultraviolet stabilizers.
• such stabilizers may induce color formation in the film that makes the product less desirable for certain applications.
• Another problem with such additives is that they tend to be unstable under conditions present during film extrusion. This results in loss of effectiveness and forming of hazardous vapors.
• Some stabilizers may exude from the crystalline polymer film during further processing.
• inherently UV stable polymers for example fully aromatic polyesters such as the copolyester of bisphenol A with isophthalic and terephtha ⁇ c acid or the copolyester of p-hydroxybenzoic acid with 2-hydroxy-6-naphtha! ⁇ c acid .
• films of such polymers are either mechanically weak and subject to chemical attack when amorphous or are opaque when "liquid crystalline” .
• U.S. Patent No. 3,008,934 discloses copolyesters containing as acid derived units 4,4'-bibenzoate and a host of other dicarboxylates including 2,6- naphthalic dicarboxylate. It also discloses oriented fibers and films prepared from these copolyesters, however, biaxially oriented PENBB films are not disclosed or envisioned. In particular, those films with improved stiffness (tensile modulus) and tensile strength in both MD and TD as well as thermostability, UV stability, hydrophobicity, dimensional stability and impermeability toward gases in comparison to PET film are not disclosed in U.S. Patent No. 3,008,934.
• An inherently UV resistant film with mechanical properties similar to PET film would offer real advantage to such markets as architectural and automotive glazing, solar collection devices, solar control devices, sign constructions, architectural fabric laminates, and the like. Colorless, highly transparent, stiff and strong and flexible film with extended life in high intensity solar environments are required .
• optical end-uses for plastic films utilize the film as the base for optically active coatings, the need is for high strength combined with selective optical effects.
• Reflective coatings may be applied which reflect infrared light, but have little or no effect on ultraviolet or invisible radiation.
• the present invention provides a biaxially oriented polymeric film containing at least one layer of PENBB copolyester resin with excellent optical properties and ultraviolet light resistance, and optical, glazing, and weathera- ble products made therefrom.
• Copolyesters of PENBB can be processed into film and sheet using processing equipment similar to that used for polyethylene terephthalate sheet to give clear transparent biaxially oriented film.
• PENBB as mentioned herein is a copolyester containing acid-derived units of which at least 25 mole percent are bibenzoate units. The remainder of the acid-derived units are difunctional units such as 2,6-dicarboxy naphthalate, terephthalate, isophthalate, 5-sodium sulfoisophthalate, adipic acid or poly functional units such as trimellitic acid, pyromellitic acid, and p- hydroxy benzoic acid.
• the diol units of the copolyester may be chosen from ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, 1 ,4 cyclohexane dimethanol, and p-xylene glycol.
• the preferred PENBB copolyester film contains 40 - 60 mole percent of 4,4'-bibenzoate (BB)
• the copolyester is obtained by polycondensation of the corresponding diacid or lower dialkyl diester and the corresponding diol. Both components should normally be employed in equimolar ratios. It may, however, be advantageous to employ one of the components -- especially the diol -- in excess, for instance in order to influence the reaction kinetics or to serve as a solvent.
• the polycondensation is carried out according to known processes used, e.g., in the production of polyethylene terephthalate (PET) .
• Useful stabilizers and catalysts can be polyphosphates, triorganyl phosphates, antimony trioxide or tetraalkoxy titanate(IV) or mixtures of triphenylphosphate and antimony trioxide.
• a preferred process for the production of such copolyesters is described in U.S. Patent Application Serial No. 07/735,553 which is incorporated herein by reference.
• a further increase in molecular weight can be achieved by solid phase polycondensation at a temperature just below the melting point, under vacuum, or in a stream of dry air or inert gas.
• the IV value inherent viscosity, as measured in a 1 : 1 weight-ratio mixture of pentafluorophenol and hexafluoroisopropanol at a concentration of 0.2 g/dl and a temperature of 25 °C
• the IV value of the PENBB polymer after extrusion be > 0.5 dl/g and preferably > 0.55 dl/g.
• the polymer melt is extruded through a die onto a chill roll where it solidifies, is then biaxially oriented, heat set, optionally post treated, and then wound on a roll.
• the solidified film as extruded on the chill roll should be obtained in a mainly amorphous state.
• the melt film must be pinned to the chill roll by a known method such as electrostatic pinning or vacuum, air knife or the like.
• the biaxial orientation of the film is achieved by stretching the film at elevated temperature in the machine direction (MD) and transverse direction (TD). This stretching can be either simultaneous or sequential. In the case of sequential stretching the first stretching step can be in either MD or TD, followed by stretching in the other direction.
• the orientation in MD can also be achieved in several steps, either one after another prior to stretching in TD, or before and after the TD stretching.
• Preferred temperatures for stretching lie between the glass transition temperature and about 30 °C above the cold crystallization temperature of the PENBB copolymer composition in use (both temperatures can easily be measured on amorphous films by DSC).
• Suitable total stretch ratios in MD and TD lie between 1 to 2 and 1 to 10, preferably between 1 to 2.5 and 1 to 5.
• the product of the MD and TD total stretch ratios should be between 1 to 30 preferably between 5 to 20.
• Biaxial drawing is performed such that the birefringeance is ⁇ 0.2, preferably ⁇ 0.1 to ensure adequate isotropic properties. For some optical applications, it may be preferable to biaxially orient the film such that the birefringeance is close to
• Birefringeance as mentioned herein . is the absolute value of the difference between the maximum and minimum refractive indices in the plane of the film, as measured on common instruments such as Abbe refractometer, optical bench or compensators.
• relaxation steps can be included in the orientation and heat setting processes.
• the heat setting takes place at a temperature between the cold crystallization temperature and the melt temperature of the copolymer composition.
• PENBB film has excellent UV stability. Thin cross-sections of the PENBB polymer, as well as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), were exposed to ultraviolet light radiation in a UV weathering tester (QUV weatherometer) wherein the samples were alternately exposed to 4 hours of UV radiation and 4 hours of moisture. Samples were removed at 1 , 2, 5, 10 and 20 day intervals and then tested for tensile properties. After 20 days the PENBB samples retained 96 percent of their break strength. The polyethylene terephthalate samples had lost 94 percent of their strength in the same test.
• UV weathering tester UV weathering tester
• PEN samples showed 20 percent loss in the same period. It has been demonstrated by I. Ouchi et al (J. Applied Polymer Science ( 1 976), Vol. 20, p. 1 983) that PEN has substantially better outdoor life than PET indicating the relationship between laboratory data and outdoor environmental effects. Thus, based on the laboratory data, the PENBB film would be expected to have greater retention of properties when exposed to outdoor environments for extended periods of time.
• Films according to the present invention have an excellent combination of properties, including transparency, UV radiation stability, strength, and colorlessness. Such films are well suited for optical, glazing, and weathering applications.
• the PENBB copolyester film may be produced in a single layer, or in multilayers by well known techniques, such as coextrusion. When multilayer film is produced, each layer may be the same PENBB copolyester composition or formulation. More likely, each layer of the PENBB copolyester would vary in formulation-. In a preferred case, one layer of a two layer coextrusion is substantially thinner than the other layer, and said layers contain particulate matter designed to improve slip characteristics of the film. The size, distribution and concentration of the particulate would be sufficient to achieve desirable slip properties without negatively impacting the excellent optical transparency or brilliance of the film structure.
• a similar embodiment is a three layer coextrusion wherein both outer layers would be a PENBB copolyester formulation that contains the particulate matter. Such outer layers are each 10 percent or less of the total film thickness.
• a further embodiment of the coextrusion concept includes the use of other polymers or copolymers as alternative layers.
• polymers or copolymers such as polyethylene terephthalate, polyethylene isophthalate, or copolyesters containing these polyesters plus 2,6-dinaphthoic acid, p-hydroxybenzoic acid, etc., may be used .
• Such materials may also contain slip control agents or other additives.
• the PENBB copolyester film or coextruded films containing the PENBB copolyester may subsequently have coatings or surface depositions made thereon, designed to optimize optical performance of the film.
• Typical coatings or depositions may include silver, gold, aluminum, or other vacuum deposited metals or combinations of metals, metallic oxides, metallic nitrides, silica deposits, carbon (amorphous or crystalline), organic polymers, optically or electrically active liquid crystalline materials, such as used in "Liquid Crystal Displays" (LCDs), and the like.
• Such coatings or depositions may be designed to selectively absorb, transmit, or reflect portions of the electromagnetic spectrum. Such coatings may, for example, selectively reflect infrared radiation and be useful for window constructions used to control interior building temperatures. Other such coatings may selectively absorb infrared radiation for solar energy devices. Such coatings may also reduce UV transmission, thus increasing performance life of the substrate film. These coatings may be applied by conventional coating techniques or by vacuum deposition techniques, such as resistance heated vacuum deposition, induction heated vacuum deposition, sputtering, reactive plasma deposition, and the like. A further substantial advantage of uncoated film products produced from PENBB copolyesters is their excellent optical transmission and brilliance. These properties are especially important for automotive and architectural glazing applications.
• the residual melt was granulated.
• the granules were white, opaque and crystalline.
• An IV value of 0.56 dl/g was determined for the granules (measured at a concentration of 0.1 g/ml in pentafluorophenol/hexafluoroi- sopropanol (weight ratio 1 : 1 ) at 25 ° C) .
• the granules were further condensed for 20 hours at 240 ° C under vacuum in the solid phase. After this treatment the IV value was 1 .1 dl/g.
• T g or T cc was discernable in the DSC recording for the crystalline granules condensed in the solid phase; the melting point (T m ) was 281 " C.
• the PENBB granules having a melting point of 281 ° C were melted in a single screw extruder at temperatures of 280 to 320 ° C and extruded through a sheet die onto a cooling roll temperature controlled at 30 ° C.
• a 120 ⁇ m thick pre-film was obtained which was clear and transparent. Its density was 1 .31 2 g/cm 3 .
• the PENBB pre-film was sequentially biaxially oriented (first transversely then longitudinally: 3.5 x 3.5) at 140 ° C on a film stretching device. An 8 ⁇ m thick, clear film was obtained . The film was clamped in a tenter frame and heat treated at 260 ° C for 10 minutes. Its density was 1 .343 g/cm 3 .
• the mechanical properties were:

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• 1992
  • 1992-12-09 EP EP93901468A patent/EP0674584A4/de not_active Withdrawn
  • 1992-12-09 WO PCT/US1992/010707 patent/WO1994013478A1/en not_active Application Discontinuation
  • 1992-12-09 JP JP6514086A patent/JPH08504386A/ja active Pending

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