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Oriented thermoplastic elastomer film and process for producing the sameRelated Patent Categories: Synthetic Resins Or Natural Rubbers -- Part Of The Class 520 Series, Natural Rubber Compositions Having Nonreactive Materials (dnrm) Other Than: Carbon, Silicon Dioxide, Glass Titanium Dioxide, Water, Hydrocarbon, Halohydrocarbon, Ethylenically Unsaturated Reactant Admixed With A Preformed Reaction Product Derived From: (a) At Least One Polycarboxylic Acid, Ester, Or Anhydride; (b) At Least One Polyhydroxy Compound; And (c) At Least One Fatty Acid Glycerol Ester, Or A Fatty Acid Or Salt Derived From A Naturally Occurring Glyceride, Tall Oil, Or A Tall Oil Fatty Acid, At Least One Solid Polymer Derived From Ethylenic Reactants Only, With A Polycarboxylic Acid Or Derivative And A Polyamine Or The Corresponding Salt Thereof; Or With A Lactam; Or With An Aminocarboxylic Acid; Or With The Corresponding Polymers; And Wherein The Monomer Or Polymer Was Derived From At Least One Saturated ReactantOriented thermoplastic elastomer film and process for producing the same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060241244, Oriented thermoplastic elastomer film and process for producing the same. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to an oriented thermoplastic elastomer film having reduced permeability and improved fatigue resistance and also to a method of preparing the same. More particularly, the present invention relates to a process for producing a thermoplastic elastomer film composition with enhanced planar orientation for reduction in gas permeability and a process for producing a pneumatic tire using the same. BACKGROUND ART [0002] EP722850B1 disclosed a low-permeability thermoplastic elastomer composition that is superior as a gas-barrier layer in pneumatic tires. This thermoplastic composition comprises a low-permeability thermoplastic matrix such as polyamides or blends of polyamides, in which a low-permeability rubber such as brominated poly(isobutylene-co-p-methylstyrene) (i.e., or BIMS) is dispersed. Subsequently, in both EP857761A1 and EP969039A1, viscosity ratio between the thermoplastic matrix and the rubber dispersion was specified in order to achieve phase continuity in thermoplastic and fine rubber dispersions. Criticality of smaller rubber dispersions was recognized in EP969039A1 in these thermoplastic elastomers for delivering acceptable durability especially for their usage as innerliners in pneumatic tires. [0003] Further improvement in impermeability of these low-permeability thermoplastic elastomers could be achieved by imposing planar orientation. In WO 0214410, introduction of orientation into a thermoplastic elastomer film for property enhancement and for permeability reduction was disclosed conceptually. No experimental data were provided in this patent application. Further, the process specified in this application involves bi-axial orientation of cast film through drafting, tentering, and heatsetting by assuming the film in discussion has the strain hardening characteristics and suitable stretching dynamics. In the present invention, the planar orientation in a thermoplastic elastomer cast film is imposed simply by the film casting and/or film blowing process and film blowning for the improvement in film properties. This thermoplastic elastomer film does not have the suitable stretching dynamics for it to be oriented by a sequential bi-axial orientation process. SUMMARY OF INVENTION [0004] The objects of the present invention are to provide an oriented thermoplastic elastomer film having a reduced gas permeability and improved fatigue resistance and also to provide a method of preparing the same. [0005] In accordance with the present invention, there is provided an oriented thermoplastic elastomer film having reduced permeability and improved fatigue resistance comprising a dynamically vulcanized polymer blend of (A) a halogenated isobutylene elastomer and (B) polyamide, the film is produced by casting or blowing the above polymer blend under the condition such that a shear rate at a die lip for casting or blowing is regulated to control the molecular arrangement in the film, whereby the planar birefringence (PBR) of the resultant film becomes greater or equal to 0.002, preferably the PBR is 0.004 or more. DISCLOSURE OF INVENTION [0006] In this specification and in the claims which follow, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. [0007] The present invention relates to an oriented thermoplastic elastomer film having reduced permeability and improved fatigue resistance and to a method of preparing the same. [0008] More particular, the present invention relates to film casting and blowing processes for producing a thermoplastic elastomer film with enhanced planar orientation and a process for producing a pneumatic tire using the same. [0009] The preferred planar birefringence of the oriented thermoplastic elastomer film is greater or equal to 0.002. The orientation could be imposed by either increasing wind-up speed during casting and blowing or increasing the blow-up ratio during film blowing. BRIEF DESCRIPTION OF THE DRAWINGS [0010] The present invention will be better understood from the description set forth below with reference to the accompanying drawing of FIG. 1, which shows the correlation between the planar orientation of the film and the permeability thereof. [0011] The thermoplastic elastomer composition is a blend of a halogenated isobutylene elastomer and a polyamide, which is subjected to dynamic vulcanization. [0012] The term "dynamic vulcanization" is used herein to connote a vulcanization process in which the engineering resin and a vulcanizable elastomer are vulcanized under conditions of high shear. As a result, the vulcanizable elastomer is simultaneously crosslinked and dispersed as fine particles of a "micro gel" within the engineering resin matrix. [0013] Dynamic vulcanization is effected by mixing the ingredients at a temperature which is at or above the curing temperature of the elastomer in equipment such as roll mills, Banbury.RTM. mixers, continuous mixers, kneaders or mixing extruders, e.g., twin screw extruders. The unique characteristic of the dynamically cured compositions is that, notwithstanding the fact that the elastomer component may be fully cured, the compositions can be processed and reprocessed by conventional rubber processing techniques such as extrusion, injection molding, compression molding, etc. Scrap or flashing can be salvaged and reprocessed. [0014] In a preferred embodiment the halogenated isobutylene elastomer component include copolymers of isobutylene and para-alkylstyrene, such as described in European Patent Application 0 344 021. The copolymers preferably have a substantially homogeneous compositional distribution. Preferred alkyl groups for the para-alkyl styrene moiety include alkyl groups having from 1 to 5 carbon atoms, primary haloalkyl, secondary haloalkyl having from 1 to 5 carbon atoms and mixtures thereof. A preferred copolymer comprises isobutylene and para-methylstyrene. [0015] Suitable halogenated isobutylene elastomer components include copolymers (such as brominated isobutylene-paramethylstyrene copolymers) having a number average molecular weight Mn of at least about 25,000, preferably at least about 50,000, preferably at least about 75,000, preferably at least about 100,000, preferably at least about 150,000. The copolymers may also have a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), i.e., Mw/Mn of less than about 6, preferably less than about 4, more preferably less than about 2.5, most preferably less than about 2.0. In another embodiment, suitable halogenated isobutylene elastomer components include copolymers (such as brominated isobutylene-paramethylstyrene copolymers) having a Mooney viscosity (1+4) at 125.degree. C. (as measured by ASTM D 1646-99) of 25 or more, preferably 30 or more, more preferably 40 or more. [0016] Preferred brominated copolymers of isobutylene and para-methylstyrene include those having 5 to 12 weight % para-methylstyrene, 0.3 to 1.8 mol % brominated para-methylstyrene, and a Mooney viscosity of 30 to 65(1+4) at 125.degree. C. (as measured by ASTM D 1646-99). [0017] The halogenated isobutylene elastomer component (A) according to the present invention can be prepared from isobutylene and about 0.5 to 25% by weight, preferably about 2 to 20% by weight, based upon the total amount of the comonomers, of p-alkylstyrene, preferably p-methylstyrene, followed by the halogenation. The content of the halogen (e.g., Br and/or Cl, preferably Br) is preferably less than about 10% by weight, more preferably about 0.1 to about 7% by weight, based upon the total amount of the copolymer. [0018] The copolymerization can be carried out in a known manner as described in, for example, European Patent Publication No. EP-34402/A published Nov. 29, 1989 and the halogenation can be carried out in a known method as described in, for example, U.S. Pat. No. 4548995. [0019] The halogenated isobutylene elastomer preferably has the number-average molecular weight (Mn) of at least about 25,000, more preferably at least about 100,000 and a ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn), i.e., Mw/Mn of preferably less than about 10, more preferably less than about 8. Continue reading about Oriented thermoplastic elastomer film and process for producing the same... Full patent description for Oriented thermoplastic elastomer film and process for producing the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Oriented thermoplastic elastomer film and process for producing the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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