Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified... – With substrate layer of specified composition
Reexamination Certificate
1997-10-20
2001-07-31
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
With substrate layer of specified composition
C428S001100, C428S035700, C428S036900, C428S036910, C428S480000, C428S910000, C264S500000, C264S510000, C264S512000, C264S513000, C264S514000, C264S515000, C264S516000, C264S523000, C264S529000, C264S531000, C264S532000, C264S544000, C264S563000, C264S173110, C264S173120, C264S173150, C264S173160, C264S210100, C264S288400, C264S290200
Reexamination Certificate
active
06268026
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to multilayer laminates, including films, sheets, preforms, containers and other articles, comprising at least one layer of a wholly aromatic, amorphous, stretchable liquid crystalline polymer with at least one non-liquid crystalline polyester layer, and methods of producing and stretching such liquid crystalline polymers and such multilayer articles. The disclosures in this application are related to those in copending patent applications, Ser. Nos. 08/954,377, 08/954,378, 08/954,997 and 08/955,000, filed Oct. 20, 1997.
BACKGROUND OF THE INVENTION
Multilayer laminates, containers and other articles have numerous applications in industry, particularly for packaging applications.
Kirk
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Othmer Encyclopedia of Chemical Technology
, Third edition, Volume 10, page 216 (1980), Wiley-lnterscience Publication, John Wiley & Sons, New York, details generally the materials and processes required for making such articles as well as their applications. Another article of interest, for example, is “Films, Multilayer,” by W. Schrenk and E. Veazey,
Encyclopedia of Polymer Science and Engineering
, Vol. 7, 106 (1980). Generally, such articles are prepared by coprocessing individual polymers in injection or extrusion operations or by laminating individually formed layers together or by a combination of these processes. Coprocessing as discussed herein refers to forming and/or subsequently processing at least two layers of polymeric material, each layer comprising a different polymeric material. Common polymers used in these applications include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-methyl acrylate copolymer, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polycarbonate, polystyrene, acrylonitrile copolymers and the like. Desired properties in the laminates, films, sheets and the like, depend on the intended applications but generally include good mechanical properties such as tensile and impact strengths, processability, tear resistance, gas barrier properties, moisture barrier properties, optical properties, thermal and dimensional stability and the like.
U.S. Pat. No. 5,256,351 to Lustig et al and U.S. Pat. No. 5,283,128 to Wilhoit disclose biaxially stretched thermoplastic films from polyethylene and a process to prepare them. U.S. Pat. No. 5,460,861 to Vicik et al also teaches improved multilayer films from polyolefins. U.S. Pat. No. 4,911,963 to Lustig et at discloses an oriented multilayer film from nylon. U.S. Pat. No. 5,004,647 to Shah describes a coextruded multilayer film comprising ethylene-vinyl alcohol copolymer.
Many methods of forming useful articles from combinations of polymers require that all components of the combination be stretched, expanded or extended in one or more directions, or deformed in some other way, such as by folding, creasing and the like. This stretching, extending or other deformation may be carried out concurrently with the process of forming the laminate or individual layers from the melt or may be part of a subsequent forming operation. Deformation can also be a requirement of using the article. Such methods of forming include but are not limited to, uniaxial and biaxially stretching of extruded films, thermoforming of multilayer laminates, blowing of extruded or injection-molded tubes, stretch blow molding of preforms or parisons, creasing or folding of laminates to form boxes, twisting of films to form a wrapper and the like.
Combining layers of different polymers is a method generally used to form a multilayer laminate which takes advantage of the different properties which may be available in the different polymer layers while also minimizing the amount of the more expensive polymer used.
Many methods of container formation require the collapse of a tube or the folding of a multi-layer structure. In such cases, it is desirable to avoid wrinkles, to ensure that the various layers remain bonded to each other and to avoid fracturing or tearing one of the layers. Other methods of container formation require uniform stretching or expansion of the multilayer laminate at temperatures sufficient to stretch any polymeric material present in the laminate. It is advantageous to be able to coprocess the laminate, for example, to fold, stretch, expand or compress it without fracturing, tearing or otherwise destroying the integrity of any layer.
Thermotropic liquid crystal polymers are polymers which are liquid crystalline (i.e., anisotropic) in the melt phase. Other terms, such as “liquid crystal”, “liquid crystalline” and “anisotropic” have been used to describe such polymers. These polymers are thought to possess a parallel ordering of their molecular chains. The state in which the molecules are so ordered is often referred to as either the liquid crystal state or the nematic phase of the liquid crystalline material. These polymers are prepared from monomers which are generally long, flat and fairly rigid along the long axis of the molecule.
Generally, liquid crystal polymers (“LCPs”) have properties that are very desirable, such as excellent chemical resistance, high mechanical strength, and excellent gas, moisture and aroma barrier properties. It can be, however, difficult to heat-bond articles made of LCPs together or to other materials. It also may be difficult to write or print on articles made from LCPs.
LCPs are more expensive than conventional polyesters. Additionally several conventional LCPs even in the form of thin films do not possess high optical clarity. In general LCPs cannot be stretched or deformed more than a few percent unless they are heated to a processing temperature range of from about 200° C. to about 320° C., preferably from about 220° C. to about 300° C. Generally film and bottle formation processes require an excess of 100% elongation. For amorphous LCPs having no measurable melting point, this processing temperature range is referred to as the “molten state”. In addition, in this temperature range where conventional LCPs can be deformed, they have very low melt strength and are weak. Tubes from conventional LCPs cannot be collapsed without wrinkling. Films or laminates containing one or more conventional LCP layers are difficult to fold without delamination and splitting. Preforms or parisons containing conventional LCP layers will have fractures or tears in the LCP layer unless they are heated to or are in the molten state before stretching, which may be far too high a temperature for coprocessing the other layers in the laminate.
U.S. Pat. No. 4,384,016 to Ide et at discloses that when polymers which exhibit anisotropic properties in the melt phase (i.e., thermotropic liquid crystal polymers) are extruded through a slit die and drawn in the melt phase, films and sheets which exhibit high machine direction properties are obtained. However, Ide et at recognizes that such films or sheets possess poor transverse directional properties which may limit their usefulness in certain structural applications and proposes laminating uniaxially oriented sheets at angles to one another to provide a multiaxially oriented sheet.
Stretching or drawing of the laminated, multiaxially oriented sheet proposed by Ide et al is not disclosed.
Another method for producing a multiaxially oriented liquid crystal polymer film is proposed by Harvey et at in U.S. Pat. No. 5,288,529 wherein axially flowing liquid crystal polymer material is subjected to transverse directional forces to strain the axial flow, and then the microscale structural orientation obtained is solidified to achieve a liquid crystal polymer film with nearly isotropic mechanical properties. Harvey et at proposes a process of shear orientation during extrusion to overcome the deficiencies in the mechanical properties of liquid crystal polymer films, which films are disclosed as being inadequate for certain applications because they can not be blown and drawn after extrusion as coil polymers (such as polyethylene terephthalate) can. More specifically, it is di
Cangiano Dominick
Jester Randy D.
Kimmel Robert M.
Penoyer John A.
Wolf Arnold E.
Burns Doane Swecker & Mathis L.L.P.
Chen Vivian
Hoechst Celanese Corporation
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