Abstract: An improved method is provided for extruding ePTFE tube (12) for use in medical applications. A tube (12) of PTFE is extruded, preferably in an extrusion process, using counter-rotated die components (22, 26). The die component (16) is maintained at a constant temperature during processing. The resulting green tube (12) has enhanced fibrous state formation in a direction perpendicular to the direction of extrusion. The PTFE green tube (12) is then subjected to secondary operations such as stretching and expansion to yield medical product. The ePTFE tube (12) structure is defined by nodes interconnected by elongate fibrils. Both the nodes and fibrils are substantially randomly tilted with respect to the longitudinal axis of the tube (12). This particular structure yields a tube (12) which exhibits a high degree of radial tear strength useful in medical applications.

Abstract: A method of and an apparatus for cooling or quenching a tube extruded from a water soluble polymer includes a plurality of cooling rings with bores through which the extruded tube passes. A gaseous cooling medium, such as compressed air, is supplied to each cooling ring and is directed immediately downstream of the bore thereof to impinge upon and cool the tubing passing therethrough. The cooling medium is supplied annularly so as to maintain the just-extruded tubing concentric and keep it centered in the bore.

Abstract: A process for the manufacture of a multilayer, cross-linked, heat shrinkable, polyolefin film, the film having at least one inner layer including a thermoplastic polymer sandwiched between two outer layers including a thermoplastic polymer different from the thermoplastic polymer of the inner layer, including the steps of coextruding the polymers into a tape; cross-linking the tape; and converting the cross-linked tape into a heat shrinkable film by orientation; wherein scrap material produced in the manufacture of the heat shrinkable film is incorporated by recycling the film into the coextrusion step in an amount up to 50% by weight of the total film weight.

Abstract: The present invention is directed to an improved internal mold release system for the production of high density molded SRIM parts, i.e. molded parts having a density of from 1.3 to 2.0 g/cc. In particular, the process involves reacting a reaction mixture comprising an organic polyisocyanate and at least one organic compound containing isocyanate-reactive hydrogens in the presence of a catalyst and an internal mold release agent in a closed mold. The internal mold release agent is a compound corresponding to the formula: ##STR1## wherein R.sup.2 represents hydrogen, the group R.sup.5 --NH--CO--, or a C.sub.1 to C.sub.24 alkyl or substituted alkyl group, a C.sub.3 to C.sub.24 cycloalkyl or substituted cycloalkyl group, a C.sub.2 to C.sub.24 alkenyl or substituted alkenyl group, or a C.sub.6 to C.sub.24 aryl or substituted aryl group, andwherein R.sup.1, R.sup.3, R.sup.4 and R.sup.5 may be the same or different and represent a C.sub.1 to C.sub.24 alkyl or substituted alkyl group, a C.sub.3 to C.sub.

Abstract: A process for improving adhesion of a thermoplastic polymeric resin on a casting surface by using an electrostatic pinning wire in conjunction with a conductive shield. The method includes the steps of extrusion casting a sheet of molten polymer from a die, directing the cast sheet onto a moving, chilled and electrically grounded casting surface to solidify the polymer and extending a conductive wire transverse to a longitudinal axis of the sheet with the sheet between the wire and the chilled surface before the sheet contacts the chilled surface. An elongated conductive uninsulated shield parallel to the wire with the wire between the shield and the sheet is provided and a bias voltage is applied to the wire and the shield. The bias voltage of the wire is in the range of 6 to 15 kV, and the bias voltage of the shield is adjusted to be at least 5 kV lower than the voltage of the wire to maintain a desired current flowing from the wire and the shield to the sheet.

Abstract: A method and charging apparatus for feeding successively individual strips of a deformable material to a calender for calendering under pressure between at least two rotatably driven calender rolls. The strips are produced from a strand of an elongated mass of deformable material provided from an extruder or rolling mill which is then cut into individual strips transported to a roller conveyor which positions them in a common plane successively at a selected or determined position extending transversely of the roller conveyor rollers in a direction parallel to the length direction of the calender rolls.

Abstract: A method of forming a plastic film with at least one closure element utilizes a die having a removable lower die lip with grooves in the shape of the closure elements and a choker bar located in the manifold of the die to control the amount of extrudate to the grooves.

Abstract: A process for producing a phase retarder film or sheet, which comprises subjecting a stretched thermoplastic resin film or sheet to thermal relaxation at a temperature not lower than the glass transition temperature of the thermoplastic resin to shrink the film or sheet in the stretching axis direction while suppressing the expansion of the film or sheet in a direction parallel to the film or sheet surface and perpendicular to the stretching axis.

Abstract: Helical plastic members are formed by rotating an extrusion die while extruding a filament in a generally horizontal direction just above a tank of liquid. The plastic helix so formed is cooled and solidified in the liquid. A mandrel in the liquid can be used to guide the helix downwardly, and the helix is removed from the tank with extraction rollers. As a variation, the tank can rotate relative to a fixed extrusion nozzle which extrudes the plastic horizontally just above the rotating liquid in the tank.

Abstract: The heating of the powder of rigid polyvinyl chloride in an extrusion machine of known type presents difficulties and causes burning. According to the invention this is avoided by introducing continuously the raw material in the form of powder after intense mixing with stabilizer and plasticizer in the feed opening of a monoscrew extruder. The said monoscrew extruder has eight different zones: an introduction zone preferably without heating; a slightly heated compression zone; a heated homogenization zone (H); a plasticizing zone; a heated decompression zone (D); a heated degasifying zone (G); a heated compression zone (K.sub.2) and a heated expulsion zone.For the plasticizing there is inserted in the extrusion screw before the decompression zone (D) a ring (3) provided with calibrated bores (4 and 5) which obstruct, that is, delay the flow so as to plasticize it without having to increase the temperature.

Abstract: A method for extrusion of a highly viscous thermosetting or a thermoplastic material comprising extrusion of said material in the presence of substances diminishing external friction of the melt, at a ratio between internal and external friction values of the material melt within the range of from 1.5 to 4.0; the thermosetting material melt viscosity being ranged from 50.times.10.sup.6 to 300.times.10.sup.6 poises, while the thermoplastic material melt index being varied from 0.01 to 0.1 g/10 min.The ratio between internal and external friction values of the material melt is maintained within the above-specified range by way of incorporation, into the starting thermosetting or thermoplastic material, of certain compounds. For thermosetting materials, use is made of, e.g. zinc dialkyldithiophosphate, and for thermoplastic materials barium sulphonate is used as such a compound.

Abstract: Method and apparatus for continuously vulcanizing unsheathed and unvulcanized elastomeric or plastomeric material by passing the material through an enclosure, within which it is subjected to vulcanizing conditions, in the form of a helix, the helix convolutions in part contacting a drive member and idler member and in part being freely suspended. A resilient elastomeric diaphragm is disposed on the surface of one of the said members.

Abstract: Process for the extrusion, followed by cooling with water, of compositions based on alpha-olefin polymers. The composition being extruded comprises a phenolic anti-oxidizing agent, an organic phosphite, and a carbonate of an alkaline-earth metal. The process permits fabricating films, filaments and tubes.

Abstract: A melt extrusion process is taught which employs a saran of the type generally considered suitable for liquid coating.

Abstract: Extruded articles of resinous transparent monovinyl-substituted aromatic compound/conjugated diene block copolymer are subjected to a brief heat treatment which results in a substantial improvement in clarity.

Abstract: There is disclosed a process for preparing shear degradable particle-containing resin powders. This process comprises (a) preparing a first composition comprising shear degradable particles and molten resin in the absence of high shearing forces on the particles, (b) intimately blending the first composition with a second composition comprising molten resin and curing agent to form a shear degradable particle-containing molten resin mixture in the absence of high shearing forces on the shear degradable particles, (c) solidifying this shear degradable particle-containing molten resin mixture, and (d) grinding the solidified mixture to desired particle size. The particles may then be classified according to particle size.The final powder particles contain shear degradable particles or flakes in substantially undegraded form. The powder particles are especially useful in powder coating applications such as in automobile and appliance topcoats.

Abstract: A method for manufacturing carbon-carbon composite bodies consisting essentially exclusively of carbon, of about 20 to about 96 weight percent from carbon fiber, from 0 to about 72 weight percent from a carbonaceous flour, and from about 4 to about 15 weight percent from a carbonized resin, which consists in forming a mat by allowing a mixture of the solid ingredients to settle to equilibrium height by the force of gravity or by centrifugation in a solution of the resin and an appropriate solvent, then pressing the settled solids at up to about 100 psi and removing the excess liquid therefrom. Heating the formed and pressed mat to cure the resin, and then baking and optionally graphitizing the cured mat completes the process.

Abstract: Additions of small amounts of fine particle size specialized monoclinic inorganic crystals to otherwise relatively pure polyalkylene terephthalate molding compounds increases the rate and extent of crystallization and the specific gravity of the polyalkylene terephthalate molded part. Both low and high molecular weight polyalkylene terephthalates are improved with regard to physical properties and dimensional stability through addition of these small quantities of these specialized monoclinic materials. Under controlled conditions of injection and forming, anisotropic properties may be obtained as a consequence of the effect and extent of the crystallization of the polyalkylene terephthalates which has been promoted by these strongly active nucleating agents.

Abstract: The facile extrusion of ethylene oxide resins has been effected by employing water as an extrusion aid.

Abstract: Plastic film is made using a heat transfer liquid circulated through the film extrusion die to control (by either heating or cooling, as required) the temperature of the plastic melt flowing through such die. A plastic bubble emerging at the outlet of the die is inflated and ventilated by continuously circulated gas which is controlled in temperature as it enters and leaves the bubble so that it does not adversely affect the temperature of the melt in the die.