Abstract: An apparatus and process for expanding polymeric tubing including a bubble of trapped gas within the polymeric tubing. The tubing is expanded by creating a pressure differential between the inside and outside of the tubing such that the pressure inside the tubing is greater than the pressure outside the tubing, thereby causing the tubing to expand. It is possible with the present invention to compensate for loss of gas pressure, thereby increasing the amount of tubing which can be expanded without ceasing production and restarting the process.

Abstract: In a method for forming a cellulose tube suitable for use as a food casing, in which a solution of nonderivatized cellulose, tertiary amine N-oxide and water is extruded through a die gap and the extruded tube is downwardly drawn through an air gap while being internally cooled and then is passed into a water bath, the tube transverse direction tensile strength being increased by drawing the extruded tube through an air length of at least about five inches and exposing the exterior surface of the extruded tube to cooling air in the air gap.

Abstract: A method for making a film which is useful in the packaging of newly formed blocks of cheese and demonstrates flexibility, extensibility, and improved sealing strength comprises extruding an ethylene vinyl acetate/very low density polyethylene sealing layer. In addition to barrier properties, flexibility and extensibility are, preferably, also provided by coextruding a core layer of ethylene vinyl alcohol copolymer containing at least 32% by weight of ethylene with the sealing layer.

Abstract: The present invention is directed to melt blown polyolefin film which is produced cheaply by melt blowing polyolefin resins which contain 25 to 60 wt % fillers selected from the fillers including an inorganic carbonate, synthetic carbonates, nepheline syenite, talc, magnesium hydroxide, aluminum trihydrate, diatomaceous earth, mica, natural or synthetic silicas and calcined clays or mixtures thereof, having a particle size less than 150 mesh.A further aspect of the present invention is directed to polyolefin resins, especially polyethylene, which are chemically degradable by the incorporation of the combination of the above group of fillers and a metal carboxylate. The metal carboxylates of the present invention are inclusive of a large number of metals, such as cerium, cobalt, iron, and magnesium.

Abstract: The present invention relates to an apparatus for automatically blowing a bubble in the production of tubular biaxially stretch oriented thermoplastic flexible film by the "bubble" method comprising a high flow fluid conduit having a proximal end for introducing a high flow fluid, and a distal end substantially perpendicular to said proximal end, and having attached to said distal end a bullet mounted proximate to the distal end of the high fluid flow conduit through which the high flow fluid may pass into the tubular thermoplastic film; a cutting device located on said high flow fluid conduit and in line with the bullet, said high flow fluid conduit, bullet, and cutting device disposed downstream from a first and second pair of rolls defining the bubble; and an automatic bubble blowing control system means comprising means for controlling the flow of fluid into the interior of the tape, and means for controlling the speed of a driven set of squeeze rolls located downstream from the high flow fluid conduit.

Abstract: A method and apparatus for blown film extrusion is described. An annular die receives a molten material and extrudes a film tube. At least one cooling ring is positioned adjacent the annular die for passing an air stream along a particular surface of the film tube. A blower entrains and supplies air to the cooling ring. A flow sensor is positioned in an air flow path intermediate the at least one cooling ring and the blower. It provides a mass air flow signal which is a measure of air mass flow per unit time. An adjustable air flow attribute modifier is placed in communication with the air flow path and operates to selectively modify the air mass flow per time unit. A controller member is in communication with the flow sensor and the adjustable air flow attribute modifier, for receiving the mass air flow signal and for controlling the adjustable air flow attribute modifier to provide a preselected value of air flow in terms of air mass flow per unit time.

Abstract: An apparatus for the manufacturing of plastic pipes has half shells of which two at a time combine as a pair to form a mold. It is provided with a temperature-regulating bell. Supply lines are formed as flexible supply hoses of temperature-resistant plastic material. A line conduit accommodating them is provided with a protecting tube, which accommodates the supply hoses and which is provided with a heat insulation towards an injection head.

Abstract: Method of manufacturing a dental aspirator by extruding a continuous tube with a bellows portion. The tube is angled to form a number of folds, each of which consists of two cup-shaped portions having concave surfaces facing each other. One cup-shaped portion is made smaller than the other, allowing them to be snapped together. The bellows are formed from the tube wall by chilled mold chains. At the same time, the tube is profiled to form an end portion at the suction end of the finished aspirator.

Abstract: A process for producing an oriented blown film of a thermoplastic resin by blown film extrusion, carried out by blowing air into an extruded bubble of the resin extruded from a ring die to expand the bubble and cooling the expanded bubble with air from a cooling air ring, wherein blown film extrusion is carried out under such conditions that the ratio of (b) the final diameter of the expanded bubble to (a) the diameter of the bubble at the crystallizing temperature of the thermoplastic resin ((b)/(a)) ranges from 1.5 to 10. The process provides an oriented blown film excellent in strength, appearance, and heat shrinkage characteristics.

Abstract: A method for producing polymeric tubing which is resistant to permeation by organic material contained therein which has at least one region defined by a plurality of outwardly extending annular ridges. In this method, tubular polymeric material having a first outer diameter and composed of at least three overlying polymeric layers is introduced into a mold device upon exit of the tubular polymeric material from a suitable extrusion device, the surface of the mold device having at least one region defined by an annular depression in an essentially cylindrical surface. Once the tubular material is introduced, it is expanded to a second outer diameter such that the tubular material deformably contacts the mold surface. The corrugated tubular material then exits from the die device after completion of the expansion step.

Abstract: The present invention is directed to melt blown polyolefin film which is produced cheaply by melt blowing polyolefin resins which contain 25 to 60 wt% fillers selected from the fillers including an inorganic carbonate, synthetic carbonates, nepheline syenite, talc, magnesium hydroxide, aluminum trihydrate, diatomaceous earth, mica, natural or synthetic silicas and calcined clays or mixtures thereof, having a particle size less than 150 mesh.A further aspect of the present invention is directed to polyolefin resins, especially polyethylene, which are chemically degradable by the incorporation of the combination of the above group of fillers and a metal carboxylate. The metal carboxylates of the present invention are inclusive of a large number of metals, such as cerium, cobalt, iron, and magnesium.

Abstract: A method and apparatus for molding an inflation film even from a thermoplastic resin having a small melt tension, in which a melt resin bubble extruded from an extruder is molded, while controlling a resin temperature of the bubble to a certain temperature range by an air ring provided with a plurality of annular slits for blowing cooling air in a take-up direction of the melt resin bubble and provided at a position at which the melt resin bubble is remarkably expanded, after (a) cooling air is blown to a melt resin bubble from a first air ring provided at the proximity of a die outlet to cool said melt resin bubble; and, then, the bubble is either (i) brought into contact, on the inner surface thereof, with the surface of a stabilizer provided on a die surface, or (ii) is supported in a non-contact state through an air layer, while being taken up.

Abstract: Annularly or helically ribbed or corrugated semi-rigid thermoplastic pipe is modified to have a smooth outer wall. The ribbed or corrugated pipe is passed through a heated sleeve to squash and smooth the outer profile of corrugated pipe or bend over ribs of ribbed pipe and mold a smooth outer skin of the pipe. Apparatus for forming the modified pipe includes a travelling mold tunnel for the production of ribbed or corrugated pipe and a smoothing sleeve downstream thereof. The smoothing sleeve has a heater to heat it sufficiently to mold the smoother outer skin.

Abstract: In a blown 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: A method producing deformed pipe liners from continuously extruded thermoplastic material by collapsing and bending deformable portions of the tube toward a back-up portion thereof and without elongation to maintain diameter and wall thickness, and apparatus to carry out said method and characterized by at least one back-up roller and at least one shaping roller folding the deformable portion along a line of symmetry and juxtaposing a fold of the tube to the back-up portion, all at raised temperature followed by reduced temperature on a rail conforming to the deformed tube configuration.

Abstract: Annularly or helically ribbed or corrugated semi-rigid thermoplastic pipe is modified to have a smooth outer wall. The ribbed or corrugated pipe is passed through a heated sleeve to squash and smooth the outer profile of corrugated pipe or bend over ribs of ribbed pipe and mold a smooth outer skin of the pipe. Apparatus for forming the modified pipe includes a travelling mold tunnel for the production of ribbed or corrugated pipe and a smoothing sleeve downstream thereof. The smoothing sleeve has a heater to heat it sufficiently to mold the smoother outer skin.

Abstract: A storage or shipping carton for automotive parts or the like has disposed therewithin layers of resilient tubular dunnage having part configured cut outs in the side walls. The dunnage extends transversely of the carton between two of the side walls while the parts extend transversely of the dunnage between the other two side walls. The tubular dunnage is preferably formed of low density polyethylene and the notches in the dunnage are formed by flattening the dunnage and severing the side walls thereof while in the flattened condition and then reopening the dunnage to its normal configuration.

Abstract: The invention concerns a cooling plug for sizing the interior surface of thermoplastic extruded pipe. Vacuum and/or pneumatic pressure is applied at the surface of the plug. The pneumatic pressure may cause the inner wall to balloon outwardly to form bells within a mold or within an outer wall, to fit into corrugations of an outer corrugated tube, etc. The vacuum may be used to pull the inner wall back to the surface of the plug after application of pneumatic pressure.

Abstract: A method for improving the internal surface of a gas-barrier, when required heat-shrinkable, multi-layer plastics film laminate in the form of a seamless tube having the innermost layer of olefin resin, the method including applying corona discharge employing at least two pairs of electrodes to the innermost layer from the outside of the tube having a gas sealed therein and pressed to a flat state avoiding the contact of opposed surface areas of innermost olefin resin layer with each other, the two pairs of electrodes being arranged such that one electrode of each pair is in contact with the outermost layer of the tube and the other of the same pair out of contact therewith while one electrode of one pair is kept in contact with the outermost layer of the tube with which one electrode of another pair is kept out of contact on the same side of the tube, so that the wetting tension of the innermost layer surface is increased to at least 35 dyne/cm by the corona discharge treatment.

Abstract: A blend for blown film which exhibits improved MD/TD tear balance. The blend is a bimodal molecular weight ethylene resin containing two fractions of different molecular weight. The weight fraction of a higher molecular weight component of the blend is about 0.35 to 0.75.

Abstract: A method for producing film having high tensile impact and dart drop properties by introducing a very low density ethylene alpha olefin copolymer having a melt index of less than 0.1 gm/10 min. a melt flow ratio of about 14-18 and a dispersity greater than 10 into a stalk extrusion apparatus and thereafter forming a film from said resin.

Abstract: A process of expanding plastics film is disclosed, together with an apparatus for performing that process, in which expansion of the plastics film is performed under the control of a liquid providing a stable hydraulic mass, by the downward extrusion and drawing of the plastics film, and the final expansion thereof, exclusively under the influence of the static and dynamic pressure of a hydraulic mass, at a position spaced downwardly of the extrusion head, the hydraulic mass being one that remains in a liquid phase at all temperatures encountered during the step of lateral stretching of the plastics film, to the exclusion of vaporization of the hydraulic mass.

Abstract: An improved blown-film extrusion process with particular application for high modulus thermoplastic resins. A cylinder is mounted above the cooling air ring. The film bubble passes through this cylinder, which has a diameter approximating the final diameter of the bubble. The frost line remains at or slightly higher than the top of the cylinder, leaving a small gap between the top of the cylinder bubble. The improvement enhances bubble cooling and stability and results in wrinkle-free film.

Abstract: A method of creating a score in a pouch formed from a thermoplastic film is described. Ultrasonic energy is used to create the score in a film that is later formed into a pouch. The score can be used to open the pouch by pulling opposite sides of the scored area. The ultrasonic force is applied to the film as a part of a downstream process in a blown film manufacturing line to produce the pouch.

Abstract: An open tube apparatus and method for continuously producing a rotating elongate strip of material are disclosed. An extrusion die continuously extrudes flowable material to form an open tube with a central longitudinal cavity and a transport mechanism includes a plurality of drive rollers which engage and pull the tube downline. A driver rotates the extrusion die and transport mechanism. A tube cutter, which is offset at an angle with respect to the downline direction and defines the open end of the tube, cuts the tube into a continuous elongate web of the desired width as the tube moves downline. An air seal seals the tube cavity to prevent air from escaping through the open end of the cavity, and a tube pressurizer controls air pressure in the central longitudinal cavity of the tube to expand the tube laterally outwardly.

Abstract: An apparatus and method for the production of polymeric films by a blown film process is disclosed. Polymeric films produced from crystallizable linear polymers are extruded through a die extruder, expanded by the injection of a gas inside the tubular film, cooled at the point of extrusion from the die, and further cooled at the point of maximal expansion or the frost line to produce a film having substantially enhanced optical characteristics.

Abstract: A constraining structure for an open tube apparatus for continuously producing a rotating elongate strip of material is disclosed. The constraining structure controls expansion of an extruded blown film tube to a desired outer diameter range after the tube is formed. The constraining structure includes a casing positionable around the tube, and an annular sleeve in the casing having a generally cylindrical central passageway adapted to receive the tube to permit movement of the tube along its longitudinal axis in a downline direction. The casing and the sleeve walls define a gas chamber with pressurized gas separate from the passageway. The gas layer along the inner surface of the sleeve is at a sufficiently large pressure to constrain the tube to the desired outer diameter while the tube solidifies and to prevent the tube from contacting the sleeve.

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: 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 the extrusion of plastic pipe wherein the pipe is in a self supporting but semi-molten state on exiting a die orifice, the inner surface of the extrudate is cooled by a device which applies a suction for establishing flow of a cooling fluid which contacts the inner surface of the extrudate. In a further embodiment the flow of cooling fluid established for cooling the extrudate additionally cools a cavity within a mandrel of the die orifice.

Abstract: Thermoplastic articles such as fenders, of large cross-sectional dimensions, may be made by extrusion without shrinkage voids by extruding a first stream of theremoplastic as a hollow profile, and extruding a second stream of molten thermoplastic by a second extruder and forcing same under pressure into the hollow profile to till the voids of shrink-age on cooling.

Abstract: Apparatus and methods are disclosed for the rapid generation of high hydrostatic pressures and the concurrent delivery of said pressures to a workpiece. The apparatus and methods comprise the rapid thermal expansion and vaporization of a volatile fluid. The volatile fluid is typically liquid argon and heated typically by means of a controllable electric heater, delivered to the workpiece typically by means of a pressure-rupturable membrane. The disclosed apparatus and methods permit the application of high hydrostatic pressures to commercial-scale workpieces, in an economic manner and with reduced cycle times.

Abstract: An apparatus for highly intensive cooling of biaxially oriented films from high- and medium-molecular weight thermoplastics using a long neck on a blown film line is described, including: a plastics extruder, a die for forming a tube neck from the extruded plastic, means positioned adjacent the die for externally cooling the tube neck, an expansion zone where the tube neck becomes a bubble, a drag mandrel positioned immediately before the expansion zone for internally contacting, stabilizing and guiding the tube neck, means for continuously providing cool air internally of the tube neck at the expansion zone immediately after the contact, the means including a first tube in communication with a cool air source, and means for continuously removing the cool air that has been heated.

Abstract: A method for the molecular orientation of plastic material by expanding a tube of plastic material, includes introducing the tube into a container filled with heated liquid, preferably water of a temperature of 70.degree.-100.degree. C. The tube is expanded by introducing a pressurized liquid into the tube. An apparatus for carrying out the method and a plastic material are also disclosed.

Abstract: Apparatus and methods are disclosed for the rapid generation of high hydrostatic pressures and the concurrent delivery of said pressures to a workpiece. The apparatus and methods comprise the rapid thermal expansion and vaporization of a volatile fluid. The volatile fluid is typically liquid argon and heated typically by way of a controllable electric heater, delivered to the workpiece typically by way of a pressure-rupturable membrane. The disclosed apparatus and methods permit the application of high hydrostatic pressures to commercial-scale workpieces, in an economic manner and with reduced cycle times.

Abstract: The rate for producing blown films of thermoplastic resins may be increased by using the extrusion and blowing apparatus of the invention, which includes a means of rapidly cooling the blown film at points both above and below the bubble frost line.

Abstract: An apparatus for cooling a tubular polymer film material which is being extruded, and more particularly, an apparatus for extruding tubular thermoplastic films including two tandem spaced air rings for controlling the cooling rate and production speeds of the thermoplastic films during extrusion thereof. Moreover, there is also disclosed a method for the cooling of an extruded tubular thermoplastic film material through the utilization of a tandem air ring cooling structure.

Abstract: A method of lining a passageway comprising pulling a first flexible lining pipe sized to the passageway to be lined into the passageway, the first lining tube comprising at least one resin absorbent layer impregnated with curable synthetic resin, and by the eversion into the first lining tube of a second flexible lining tube sized to the first tube inner diameter, to the inner surface of which a second lining tube before eversion is applied an initiator for the resin impregnating the first lining tube whereby, as the second lining tube everts into and along the first tube when in the passageway, the first tube is pressed against the passageway surface by fluid pressure used to evert the second tube, and also the initiator comes into contact with the resin of the first tube and commences and effects cure of the same.

Abstract: A bubbler stabilizer for a blown film extrusion apparatus has a shaft mounted on an extrusion die of the apparatus, a pair of supporting members mounted on the shaft and spaced a predetermined distance from each other, and a plurality of lengths of coil spring extending between the peripheral portions of the supporting members with the lengths being spaced peripherally at intervals of a predetermined size around the supporting members. The coil spring lengths extend in a skew position relative to the axis of the shaft.

Abstract: A stretching device for stretching a tubular film includes a mandrel including a stretching section, a pair of payoff nip rolls disposed upstream of the mandrel and a pair of take-up nip rolls disposed downstream of the mandrel. The stretching section of the mandrel is comprised of a plurality of rings arranged substantially concentrically in spaced-apart relationship in the travelling direction of the tubular film. The outside diameter of a ring on the downstream side is larger than that of a ring on the upstream side. Each of the rings has a plurality of rotating members mounted rotatably, and the plurality of rotating members define an outer circumferential ring edge which is generally smoothly circular.

Abstract: Apparatus and method are provided for straightening a parison tube (58b) in an apparatus of the type in which thermoplastic tubing (48) is extruded into open halves (24 and 26) of a blow mold (22) and a parison tube (58b) is severed from the thermoplastic tube (48) concurrently with the blow mold being rotated around an axis (28). The present invention orients the curvature of the parison (58b) in a predetermined plane (52) by accelerating the parison tube (58b) transversely to the axis (90) of the parison tube (58b); and then the parison tube (58b) is straightened by applying jets of air (76) against the neck and moil portion (68) of the parison tube (58b), thereby straightening the parison tube (58b), and thereby preventing the neck and moil portion (68) of the parison tube (58b) from being pinched between the mold halves (24 and 26) in the area of the neck and moil cavity (38).

Abstract: The invention refers to a method and apparatus for manufacturing a single-wall pipe, tube or like conduit (9,44) having smooth inner surfaces and a mechanical-strength enhancing pattern of walls, flanges or ridges on the outer surface thereof, the conduit being made of plastics or like extrudable material.

Abstract: Thermoplastic articles such as fenders, of large cross-sectional dimensions, may be made by extrusion without shrinkage voids by extruding a first stream of thermoplastic as a hollow profile, and extruding a second stream of molten thermoplastic by a second extruder and forcing same under pressure into the hollow profile to fill the voids of shrinkage on cooling.

Abstract: The invention provides for the light curing of a synthetic resin which is light curable, and is arranged as a layer upon the surface of a pipeline or passageway. The curing lamps are enabled to be pulled into the pipeline or passageway by virtue of inserting a tubular member into the passageway which is inflatable by fluid pressure so as to hold the resin layer in position. The lamps pass through the inflatable tubular member so that radiation therefrom will fall on the layer of resin and cure or initiate the cure of the same.

Abstract: The apparatus of the invention provides gauge distribution in extruded plastic tubing, so that a more uniform roll thereof is obtained. The extruded plastic tube, usually blown to increase its diameter and decrease its wall thickness, is collapsed and passed through a diametrical slot in a rotor, which is rotated about a vertical axis so that any non-uniformity in wall thickness of the tube is distributed as much as possible around its periphery. The upwardly-moving tube passes over a skew member which turns it to move horizontally. Two spaced parallel end rollers are provided between one end of the slot and the rotor periphery, and each engages the tube during a respective 180.degree. of rotation to deliver the tube to a fixed roller on the apparatus frame from where it passes to the storage roll. Two deflection rollers are also provided on opposite sides of the slot, and each engages the tube in the rotation of the rotor close to zero and 360.degree.

Abstract: A process for producing a thin-walled cylindrical body of an aromatic polyester, which comprises(A) heating a continuous thick-walled tubular body of an aromatic polyester by introducing it continuously into a heating zone while feeding a pressure fluid into the thick-walled tubular body,(B) expanding the heated thick-walled tubular body into a cylindrical form, and(C) continuously stretching and taking up the resulting cylindrical expanded body, while at least forming a fold-free portion in the expanded body in its longitudinal direction; and a thin-walled cylindrical body of an aromatic polyester characterized by a specific intrinsic viscosity, density, wall thickness, surface roughness (CLA), and difference of its refractive indices in the circumferential direction and in a direction perpendicular to the circumferential direction, and substantial freedom from folded marks which cannot be removed at a temperature of 80.degree. C.

Abstract: Disclosed herein is a cooling/guiding method and a cooling/guiding apparatus that will be used when a film of a thermoplastic synthetic resin or the like is to be produced by the inflation method or the T-die method.According to the invention, a thermoplastic synthetic resin film is continuously passed through a section constituted by a single or a plurality of air-introducing members having air intake ports, the air surrounding said film is vacuumed by said air-introducing members so that the pressure differential imparted to the film is balanced, and the film is guided into a predetermined path under the condition where the film is separated away from the air-introducing members.Therefore, the apparatus cools and guides the film without coming into contact thereto, and without cooling the film irregularly and without marring the film, making it possible to markedly increase the film-forming speed and quality of the film.

Abstract: A take-away device for a plastic tubing produced in a blowing process in which the tubing is flattened by squeeze rollers followed by a pair of take-away rollers. The pair of take-away rollers which have horizontal axes of rotation swivel reversingly about a vertical axis of rotation. The flattened tubing is fed to a stationary wind-up device, whereby two turning rods over which the flattened tubing is guided, are arranged between the take-away rollers and the stationary wind-up device, and swivel reversingly about the vertical axis of rotation of the pair of squeeze rollers. The first turning rod can thereby be swivelled about a first vertical axis which, together with the take-away rollers, swivels about the vertical axis of rotation of the pair of take-away rollers.

Abstract: Apparatus for cooling tubular plastic films extruded from a film blowing head. Air cooling means consisting of co-axial pipes extending axially through the film blowing head supply the cooling and inflating air and withdraw the same from the inflated parison. Vertically inner cooling rings are disposed substantially concentrically to the axis of the parison downstream of the annular extrusion die orifice of the blowing head. The inner cooling rings define nozzle gaps and have air guiding surfaces, which face the wall of the parison and are convexly curved in a longitudinal section of the inner cooling rings and during the operation of the apparatus are swept by the cooling air blown out of said nozzle gaps. An outer cooling air jet concentrically surrounds the extruded parison and serves to blow air in a direction which is approximately parallel to the direction of travel of the parison. The inner cooling rings are concentric to the parison.

Abstract: A method of blown film extrusion of polyolefins having high elongational viscosity which is independent of applied stress, and high melt strength wherein a first air ring is disposed adjacent an extrusion die to assist in the formation and stability of a stalk bubble configuration, and a second air ring is disposed downstream of the first air ring to assist in controlled expansion of the bubble at a point where the bubble has dissipated its melt elasticity.