Abstract: A method is described in which the operative condition of the cooling sections of a slot die for making flat films of thermoplastic material, or of an annular die of a blow molding extruder for making tubular films from synthetic thermoplastics, is tested. The cooling sections are provided with lines for supplying and discharging cooling air and the lines for supplying cooling air are connected, as required, to a central cooling air feed line, which is under superatmospheric pressure, by solenoid valves controlled by an electronic computer. In one embodiment of the invention, a testing program is performed in which the cooling air feed line is disconnected by a shut-off valve from the branch lines leading to respective solenoid valves when the latter are closed.

Abstract: In a blow film extrusion system in which film is extruded as a tube from an annular die and then pulled along a predetermined path, an apparatus is provided for gauging and controlling the circumference of the extruded film tube. At least one transducer, preferably ultrasonic, is mounted adjacent the extruded film tube for transmitting and receiving interrogating pulses along paths normal to the extruded film tube, and for producing a current position signal corresponding to the circumference of the extruded film tube. The current position signal is continuously compared with at least one previous position signal, preferably with a computer program resident in a controller memory. If at least one preselected condition is violated, the current position signal is disregarded in favor of an estimated position signal.

Abstract: Underground pipelines that carry wastewater water, natural gas and industrial fluids deteriorate with age. Shown is a process and apparatus for installing a thermoplastic liner in such existing pipelines to accomplish in situ rehabilitation. It involves extruding a tube of thermoplastic liner material within the interior of a pipeline in situ, said tube having an outside diameter smaller than the inside diameter of said pipeline. The tube is next expanded so that the outside diameter of said tube is essentially equal to the inside diameter of said pipeline. The expanded tube is then cooled and hardened in a liner configuration.

Abstract: A process of producing a transparent resin film includes inflation molding in an upward direction a resin composition which having 100 parts by weight of a polybutylene terephthalate resin having an intrinsic viscosity IV.sub.a of at least 1.0, and between 15 to 45 parts by weight of a polycarbonate resin having an intrinsic viscosity IV.sub.b of at least 0.4. The polybutylene terephthalate and polycarbonate resins are present such that the ratio .eta..sub.A /.eta..sub.B is between 0.35 to 1.5, wherein .eta..sub.A is the melt viscosity of the polybutylene terephthalate resin at a shear rate of 100.sup.-1 at 260.degree. C., and .eta..sub.B is the melt viscosity of the polycarbonate resin at a shear rate of 100.sup.-1 at 260.degree. C. During inflation molding, the resin composition is extruded at an extrusion temperature T(.degree.C.) which satisfies the equation:240.degree. C..ltoreq.T(.degree.C.).ltoreq.(MP-26)+(53.times.IV.sub.

Abstract: The invention relates to processes for producing biaxially oriented single-layered and multilayered films. The biaxially oriented single-layered film receives stresses in the range of 500 kg/cm.sup.2 to 1500 kg/cm.sup.2 each in the machine and transverse directions of the film. The multilayered film receives stresses in the range of 300 kg/cm.sup.2 to 1250 kg/cm.sup.2 each in the machine and transverse directions of the film. Thus, the molding stability in biaxial orientation of a nylon film is improved and the thickness accuracy of a resulting film is improved.

Abstract: A wholly aromatic polyester film, (A) which is made of a wholly aromatic polyester consisting essentially of the following recurring units I and II ##STR1## wherein the aromatic ring may be optionally substituted with at least one substituent selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom and a phenyl group, said wholly aromatic polyester comprising 10 to 90 mol % of the recurring unit I and 90 to 10 mol % of the recurring unit II, being capable of forming an optically anisotropic melt phase, and having a melt strength at a temperature 20.degree. C. higher than its transition temperature to liquid crystal of at least 2.0 g/mm.sup.2 ; (B) said film having an oxygen permeability of not more than 1.0 cc.20.mu./m.sup.2.day.atm at a temperature 20.degree. C.

Abstract: A method for continuously controlling the pressure in a bubble formed of a continuously extruded seamless blown thermoplastic film tubing which is being conducted generally upwardly through a cooling water bath. More particularly, the method contemplates controlling the internal bubble pressure through the intermediary of a Photohelic pressure controller which is utilized to monitor the differential prevailing between the internal bubble pressure and that of the water bath encompassing the bubble. The invention also relates to an apparatus for controlling the internal pressure of a bubble constituted from a seamless blown thermoplastic film which is extruded and conducted through an external cooling water bath, employing the method pursuant to the invention.

Abstract: An oriented multilayer film comprising a barrier layer, a first layer on one side of said barrier layer and a second layer on the opposite side of said barrier layer is provided for use in food packaging applications. The first and second layers have melting points of at least about 115.degree. C. The barrier layer comprises amorphous nylon having a glass transition temperature greater than the higher of the two melting points or higher than the melting point of the first and second layers. The barrier layer is substantially impermeable to oxygen, while the first and second layers may comprise certain polyethylene resins. The oxygen barrier properties of the film do not deteriorate as the barrier layer gradually absorbs moisture. A process for making such multilayer films is also provided.

Abstract: A process for extrusion, which requires:(i) Blending low density polyethylene having a density equal to or less than about 0.915 gram per cubic centimeter with a liquid hydrocarbon oil in an amount of about 5 to about 30 parts by weight of oil per 100 parts by weight of low density polyethylene; and(ii) extruding the blend.

Abstract: The present invention is directed toward a film comprising a vinylidene chloride interpolymer, wherein the vinylidene chloride interpolymer having polymerized herein vinylidene chloride in an amount of from about 75 to about 95 percent by weight of interpolymer and from about 25 to about 5 percent by weight of interpolymer of at least one monomer copolymerized therewith, is prepared by extruding said interpolymer through an extrusion die to form an extrudate; passing the extrudate through a cooling means; blowing a blown tubular bubble by expanding the cooled extrudate sheet around a trapped gaseous medium, said bubble having an effective blow-up ratio before deflation such that the bubble after deflation has a desired final blow-up ratio; and conveying the tubular bubble through a deflator means to collapse the bubble into a two-layer film, wherein the film has a final blow-up ratio of between about 2.5 to about 3.

Abstract: In inserting a rigid plastic tube through a pipe while paying out the tube from a drum having the tube wound thereon in a flat form, a heating fluid is supplied into the plastic tube to pass the fluid from its one end toward the other end thereof and thereby heat and soften the plastic tube over the entire inner peripheral surface of the tube. The plastic tube as wound on the drum can be heated and softened uniformly at every portion over the entire length thereof and can further be held so softened also during the insertion of the tube through the pipe. The tube can be easily passed through an intermediate bent pipe portion, if any, and efficiently inserted through the pipe.

Abstract: A process for making a film including forming a composite material of a thermoplastic film into an annular original film having at least two thick portions according to the inflation process, making the annular original film into a flat shape such that the thick portions are located at substantially opposite ends thereof, and stretching the flat annular original film by clamping the thick portions.

Abstract: A composition is provided which is suitable for extrusion blowing to form an elastomeric film. The film produced from this composition has a very low modulus, high elongation and excellent elastic recovery. The composition includes: two hydrogenated block copolymers each including at least two blocks containing predominantly polymerized alkene arene monomer units and at least one block containing predominantly polymerized conjugated diene monomer units, the first hydrogenated block copolymer having a molecular weight between about 55,000 and about 200,000 and the second hydrogenated block copolymer having a molecular weight between about 15,000 and about 85,000, the ratio of the molecular weight of the first to the second being greater than 1.

Abstract: A process for producing tubular film from a thermoplastic molten material, including supplying an annular stream of thermoplastic material through a passageway substantially free of flow interurptions having a plurality of axially aligned-annularly spaced feed ports, funneling and recombining the annular stream of thermoplastic material after being supplied through the feed ports to evenly recombine the thermoplastic material, and forming a tubular stream of thermoplastic film having a substantially uniform thickness throughout.

Abstract: The present invention is a process for forming an extruded article containing a copolymer of vinylidene chloride and at least one other ethylenically-unsaturated comonomer, said process comprising the step of extruding the copolymer in the presence of (1) at least one gas which is inert with respect to the copolymer and does not plasticize the copolymer; and (2) essentially no gases which are not inert with respect to the copolymer. Vinylidene chloride copolymers extruded according to the process of the present invention have lower metal adhesion and less tendency to contain specks of carbon than do vinylidene chloride copolymer copolymers extruded under an air atmosphere.

Abstract: A heat-shrinkable, tubular foam can be produced from a composition which comprises 100 parts by weight of an ethylene-.alpha.-olefin-nonconjugated diene copolymer, 1 to 20 parts by weight of a foaming agent, 5 to 100 parts by weight of a thermoplastic resin having a vicat softening point of 50.degree. to 200.degree. C., and up to 10 parts by weight of a crosslinking agent, by shaping the composition into a tube, crosslinking and foaming the tube and pressurizing the tube in the interior to inflate it. This heat-shrinkable, tubular foam is best suited for jacketing pipes, hoses, and the like.

Abstract: A method of producing an oxygen barrier film, and the resulting film, includes the coextrusion of a multi-layer extrudate having an outside ethylene vinyl alcohol copolymer layer which has been passed through a hot water system to soften and wet the ethylene vinyl alcohol copolymer. The wetted film can be more easily oriented to produce a shrinkable film.

Abstract: This invention relates to a process for the production of shrinkable sheet products from copolyamides with good processing properties. The copolyamides consist of .epsilon.-caprolactam and equimolar quantities of dimeric fatty acids and diamines.

Abstract: The extruded sleeve is cooled at the end of the die by a circulation of a refrigerant fluid whose temperature To satisfies the relationship: ##EQU1## G being equal to: ##EQU2## Tm and V being the mean temperature of the resin at the exit of the die and its mean extrusion velocity,Tc is a temperature characteristic of the extruded resin,.rho., Cp and .lambda. are the density, the specific heat and the thermal conductivity of the resin,H is the height of the die gap in the refrigerated zone,L is the length of the refrigerated zone.

Abstract: An extrusion die for producing a fastener profile having a male profile portion and an alignment rib spaced on each side thereof has a first peripheral slot to produce the male profile portion and second and third slots to produce the ribs. By inclining the axes of the second and third slots relative to the first slot, preferably at respective different angles, one can remove the tendency for the male profile portion to tilt or roll and reduce lateral stresses set up during the extrusion process. The thermoplastic material is fed to each of the three slots separately, and preferably at a pressure to the second and third slots which is greater than to the first slot.

Abstract: A process for preparing a heat shrinkable film which is made from a copolymer of ethylene and 0.5 to 10% by mole of an .alpha.-olefin having 4 to 12 carbon atoms, the copolymer having a g* value (i.e., intrinsic viscosity of the copolymer/intrinsic viscosity of a linear polyethylene having the same molecular weight) of 0.3 to 0.7, a melt index of 0.3 to 2.0 g/10 min., and a density at 25.degree. C. of 0.86 to 0.92 g/cm.sup.3, wherein a tubular film of the copolymer is stretched under the following conditions:(A) the film surface temperature at the starting point of expansion being within the range of 20.degree. to 30.degree. C.

Abstract: This invention relates to a tubular stretching method for producing a stretched film by passing a tubular thermoplastic resin film between pairs of nip rolls having mutually different peripheral speeds and by inflating the tubular film with internal pressure under heating and a stretching apparatus to be employed therefor. The pairs of nip rolls include at least three pairs of nip rolls. Pressurized air is admitted into a stretched bubble situated between the first and second rolls through a slit-like air injecting nozzle, and the bubble formed by the supplied pressurized air is inflated and stretched under heating. In this stage, if desired, the amount of injected pressurized air is controlled by manual or automatic control by detecting the diameter of the bubble so as to keep the bubble's diameter constant. After stretching, the tubular film is collapsed and is introduced to the second nip rolls. Both side ends of the collapsed film are cut open with film cutting knives to make two sheets of flat films.

Abstract: The present invention relates to a method of and an apparatus for manufacturing biaxially oriented film. A tubular original film which has been extruded by an extruding die is biaxially oriented by heat and air injected to the inside portion thereof being conveyed to nip rolls each having an individual circumferential speed. The temperature of heat to be applied to the film is controlled on the basis of the detected film thickness for the purpose of obtaining a uniform film thickness distribution. Furthermore, the film can be made uniform by adjusting the outer diameter of the bubble-shaped oriented film by adjusting the distance between two sets of nip rolls on the basis of the measured width of the film. In addition, when the thus-oriented film is subjected to a heat treatment, temperature of heat is arranged to be a predetermined temperature as to prevent adhesion of the films.

Abstract: This invention relates in general to the formation of thick films having a biaxial molecular orientation. Such films are prepared in accordance with the present invention from rod-like extended chain aromatic-heterocyclic ordered polymers. Such films have high tensile strength, modulus, and environmental resistance characteristics. A preferred ordered polymer for use in the present invention is poly (para--phenylenebenzo bisthiazole), (PBT), a compound having the structure: ##STR1## The present invention is also directed to methods and apparatus suitable for producing biaxially oriented films, coatings, and like materials from ordered polymers, preferably PBT.

Abstract: This invention relates in general to the formation of multiaxially (e.g., biaxially) oriented films from high molecular weight liquid crystalline thermotropic polymers (homopolymers, copolymers, and the like), wherein due to the processing conditions employed, the films have a controlled molecular orientation. The novel multiaxially oriented films of the present invention are preferably prepared from two commercially available thermotropic polymers, Datrco Manufacturing, Incorporated's XYDAR.RTM. LCP and Hoechst Celanese's VECTRA.RTM. LCP.

Abstract: Disclosed are window envelopes and a method of making wherein the window envelope film from which window patches are made contains an anti-flecking agent in the form of a wax.

Abstract: A 10 to 200 .mu.m thick film comprised of high density polyethylene having a density of 0.935 g/cm.sup.3 or more, the high density polyethylene type film having a film surface roughness of 0.001 to 0.15 .mu.m, a coefficient of C axis orientation of the cyrstals in the film (Fc) of 0.10 to 0.50, a difference .DELTA.n of the birefringence of the amorphous portions and crystalline portions in the film of 0.1000 to 0.1070, and a transparency of a haze of less than 10%. Such a film can be produced by passing an original material film through three heating rolls, designated as, for example, the first heating roll (hereinafter referred to as "R.sub.1 "), the second heating roll (hereinafter referred to as "R.sub.2 "), and the third heating roll (hereinafter referred to as "R.sub.3 "), in accordance with the order of the passage of the original material film, at a temperature of R.sub.2 higher than the temperatures of R.sub.1 and R.sub.3 and a temperature of R.sub.2 of 105.degree. C.

Abstract: A process for substantially eliminating surface melt fracture during extrusion of a thermoplastic polymer such as a molten narrow molecular weight distribution, linear, ethylene copolymer, by using a die having a die land region defining opposing surfaces at least one of which is coated with a composition containing about 80% to 99% nickel and about 1% to 20% phosphorous.

Abstract: This invention relates in general to the formation of thick films having a biaxial molecular orientation. Such films are prepared in accordance with the present invention from rod-like extended chain aromatic-heterocyclic ordered polymers. Such films have high tensile strength, modulus, and environmental resistance characteristics.A preferred ordered polymer for use in the present invention is poly (para - phenylenebenzo bisthiazole), (PBT), a compound having the structure: ##STR1## The present invention is also directed to methods and apparatus suitable for producing biaxially oriented films, coatings, and like materials from ordered polymers, preferably PBT.

Abstract: An apparatus and process for producing tubular film from thermoplastic molten material including a tubular housing having an axially-aligned interior defined inner surface, an elongated member including an outer surface disposed within the inner surface of the housing and spaced therefrom providing a passageway, and an alignment member having a plurality of annularly-spaced feed ports defining an inside surface, the alignment member securely connecting the elongated member to the housing, wherein the inner surface of the housing, the outer surface of the elongated member and the plurality of annularly-spaced feed ports define an annular-axially aligned passageway for allowing a balanced flow of thermoplastic material therethrough.

Abstract: An apparatus for the production of a tubular thermoplastic film, and more particularly, a water bath film cooling apparatus for the rapid quenching of an extruded tubular thermoplastic film so as to enhance the speed of cooling thereof, and increase the strength of the film material. Also disclosed is a method of rapidly cooling a thermoplastic film material through the intermediary of a water bath, utilizing the inventive cooling apparatus. A predetermined internal pressure is maintained within the tube by a gaseous medium, such as air, which is slightly higher than the external pressure imparted to the film tube by the water bath, so as to enhance the speed of cooling of the film materials and increase the strength of the film by minimizing the premature crystallinity thereof upon extrusion of the film and passage through the cooling apparatus.

Abstract: A process of producing a tubular polymeric anticorrosion film which includes extrusion of a mixture of a thermoplastic polymer with a corrosion inhibitor in a liquid phase or with a solution thereof in a plastifying agent employed in an amount exceeding the limit of compatibility with the polymer, blowing this melt into a tubular film upon cooling, application of a layer of an enamel or a varnish incompatible with the thermoplastic polymer onto the external surface of the formed tubular film before the line of crystallization, which layer has a difference of the solubility parameters in respect of said corrosion inhibitor or a solution thereof in a plastifying agent of not more than 8.

Abstract: An oriented multilayer film comprising a barrier layer, a first layer on one side of said barrier layer and a second layer on the opposite side of said barrier layer is provided for use in food packaging applications. The first and second layers have melting points of at least about 115.degree. C. The barrier layer comprises amorphous nylon having a glass transition temperature greater than the higher of the two melting points or higher than the melting point of the first and second layers. The barrier layer is substantially impermeable to oxygen, while the first and second layers may comprise certain polyethylene resins. The oxygen barrier properties of the film do not deteriorate as the barrier layer gradually absorbs moisture. A process for making such multilayer films is also provided.

Abstract: This invention provides a process for producing a blown film of butene-1 polymer excellent in elasticity, elastic recovery, impact strength and the like which includes extruding a butene-1 polymer having a melt index of 0.3-10 g/10 min in a tubular form from extrusion die at an extrusion temperature of 120.degree.-250.degree. C. and then inflation molding the tubular film under the conditions that frost line height is 38-100 cm, stretch ratio in machine direction is 5 or more and ratio of stretch ratio in machine direction/stretch ratio in transverse direction is 2.5 or more.

Abstract: A polyacetal resin is manufactured by an improvement whereby a polyacetal resin having a melt index (MI) of 0.3.about.5.

Abstract: Polyvinyl alcohol films are provided which are gelled, non-tacky, bubble-free and resistant to water at ambient temperatures. The polyvinyl alcohol film is obtained by plasticizing (fluxing) and melting granules of pure polyvinyl alcohol containing from 25 to 35% by weight of water at a temperature at least 100.degree. C. above the equilibrium melting point of the granules and less than or equal to 220.degree. C., and extruding the melted granules through a die at a temperature at least 5.degree. C. above the equilibrium melting point of the granules and less than or equal to 98.degree. C., optionally followed by monoaxial stretching or biaxial stretching of the unstretched film obtained. The stretched or unstretched film may be heat-treated to improve its properties. The polyvinyl alcohol film can be used to prepare with thermoplastic films composite films or sheets having a high gas impermeability.

Abstract: A polybutylene terephthalate resin film is produced by forming a film of a polybutylene terephthalate resin having an inherent viscosity of more than 1.0 by the inflation molding technique and under the condition of extrusion resin temperatures within a range defined by the following relation:melting point (.degree.C.)<extrusion resintemperature (.degree.C.)<melting point-26+53.times.inherent viscosity (.degree.C.).

Abstract: The present invention relates to a method and an apparatus for tubularly drawing a tubular raw material of thermoplastic resin. Gas for forming a bubble to heatingly draw the tubular raw material is injected into the raw material from a direction opposite to a direction for transferring the raw material through a nozzle. The raw material is cut into a plurality of web-like pieces by cutting blades provided on pinch rolls for taking up the raw material. One of the web-like pieces thus cut is separated from the others and formed with an opening into which the nozzle is inserted to inject the gas.

Abstract: A method for the extrusion of polyethylene resins, especially linear low density polyethylene resins and; more particularly, a method of high shear extrusion through the intermediary of which the frequently encountered melt fracture; for instance, such as the sharkskin melt fracture of linear low density polyethylene can be either reduced or even completely eliminated by effecting the extrustion at a high shear rate or shear stress over the lip section of a tubular or sheet extrusion die.

Abstract: A process for the preparation of highly oriented blown polyethylene film is disclosed. The film is mono-axially oriented and has improved stiffness, tear resistance and tensile strength. In the process, a molten polymer composition is extruded through an annular die gap of at least 2 mm at a melt temperature at the die gap of below 160.degree. C. The process achieves films which exhibit an x-ray diffraction intensity ratio max/min of the 110 retleation band of at least 20 and an angle .alpha. between the average orientation direction of the polymer molecules and film extrusion direction of at most 20.degree..

Abstract: Blown film on the basis of polyethylene with a density below 910 kg/m.sup.3 is prepared by extruding the molten polymer having a melt index of at least 2 dg/min at temperatures of the melt at the die gap of at most 160.degree. C., the die gap width being at least 2 mm, blowing the molten polymer to a balloon, cooling, flattening and rolling it up. Films that have been prepared this way have improved mechanical and optical properties and are highly oriented.

Abstract: A method for forming non-equilibrium and/or metastable metallic or non-metallic powder, foil or fine wire material into a solid body comprises charging the material into a metal container, subjecting the metal container containing the material to rolling at a temperature at which the inherent properties of the material are maintained, and thereafter removing the metal container.

Abstract: Method and apparatus are disclosed for producing various materials and products of a thermoplastic nature. In the method, thermoplastic material is subjected to a high intensity mixing and melting step to form a material which is a non-flowable and self-sustaining mass, having a temperature low enough to prevent it from being readily flowable, in a subsequent step, the method involves placing the material between a fixed rigid surface and a moving rigid surface to force air from the mass and to densify, compress and convert it to a flowable form whereafter it is passed through a restricted opening. There is provided a combination of a high intensity mixer and melter in which the product produced is then fed into a gear-pump where the material is passed between a fixed rigid surface and a moving surface.

Abstract: Process and device for cooling a tubular sleeve produced by hot extrusion-blowing of a thermoplastic material through an annular die. In the process, a stream of primary air is flowed under pressure substantially parallel to and spaced from the tubular sleeve and reaches the tubular sleeve at a second stage. The stream of primary air induces a stream of secondary air which flows substantially parallel and proximate to the tubular sleeve at a first stage and whose flow is substantially laminar over most of its path. The device includes a first cylindrical sleeve member that, in combination with the tubular sleeve, defines a secondary air flow space. A second cyclindrical sleeve member and the first sleeve member define a primary air flow space therebetween. A cylindrical ring disposed proximate to the annular die directs air into the secondary air flow space. A source of pressurized air is in flow communication with the primary air flow space.

Abstract: A process for extrusion comprising extruding, under conditions which will provide a shrink film, a linear low density copolymer of ethylene and at least one alpha-olefin having 3 to 6 carbon atoms, said copolymer having (i) a density in the range of about 0.915 to about 0.932 grams per cubic centimeter; (ii) a weight average molecular weight of at least about 250,000, (iii) a ratio of weight average molecular weight to number average molecular weight of at least about 6; and (iv) a copolymer species with a molecular weight of at least about 500,000 in an amount of at least about 8 percent by weight based on the weight of the copolymer.

Abstract: On extrusion of thermoplastic melts, flow anomalies occurring in the extrusion dies can be decisively reduced when dies are used whose surfaces coming into contact with the melts are provided with a thermally applied spray coating.

Abstract: A method is disclosed for improving the clarity of polyethylene film containing silica or diatomaceous earth as an anti-blocking agent. The method comprises treating the anti-blocking agent with polyethylene glycol such that sufficient polyethylene glycol is deposited on said anti-blocking agents such that at least 10 parts per million of polyethylene glycol is present in the final blend. Next, the treated anti-blocking agent is added to the polyethylene resin and this blend is formed into a film.

Abstract: Blends of a vinylidene chloride polymer, an olefin polymer, and a compatibilizer polymer are successfully fabricated into films using the well-known inflated bubble technique, by using blow-up rates in the range of about 1.5 to 5.0 and a drawn-down ratio upwards of 6, preferably upwards of 8, but not exceeding the critical draw-down ratio of 13. At a draw-down ratio exceeding 13, the physical properties of the polymer blend are seriously diminished.

Abstract: A process of forming biaxially oriented tubular articles by repeatedly performing a cycle of operations which includes engaging a thermoplastic tube by a first clamping member over a first region at a trailing end of the tube and engaging the tube by a second clamping mechanism over a second region at a spacing from the first region so as to define between the clamping mechanisms a portion of the tube to be longitudinally stretched and radially expanded; moving the clamping mechanisms apart to stretch the tube portion therebetween longitudinally; admitting pressure fluid into the tube portion to expand it radially and form a biaxially oriented bubble adjacent the leading end of the tube, and severing a substantial part, but not all, of the bubble from the tube to form the tube with a radially outwardly flared end as the leading end of the tube for the succeeding cycle of operations.

Abstract: A method of biaxially stretching a tubular thermoplastic resin to provide a film, wherein air is blown against a starting point for heating and stretching the tube, from the upstream side of the starting point, at a predetermined angle relative to the feeding direction of the film. An apparatus for achieving this method includes: two pairs of nip rolls being different in circumferential speed between the pairs; a heating-stretching section interposed between the pairs of nip rolls, for heating the tube to a temperature where the tube can be stretched; and an air ring device for blowing air in the feeding direction of the film.