CA1155265A - Oriented, semi-crystalline polymer product and method and apparatus for producing such product - Google Patents

Abstract

AN ORIENTED, SEMI-CRYSTALLINE POLYMER PRODUCT AND METHOD AND APPARATUS FOR PRODUCING SUCH PRODUCT Abstract of the Disclosure A thick-walled, seamless, rigid conduit having a substantially uniform wall thickness which is not less than about 0.5 percent of the outside diameter consisting essen-tially of an oriented crystalline thermoplastic polymer characterized by a structure comprised of radially compressed discrete, platelet-like spherulitic crystalline aggregates and having a combination of good ultimate tensile strength and low temperature tensile impact strength is described. The conduit is fabricated by solid state hydro-static extrusion of a substantially non-oriented semi-crystalline thermoplastic polymer preform which may contain up to about 60 weight percent filler. The polymer is sub-stantially simultaneously elongated in both circumferential and axial directions by compressive forces with the circum-ferential elongation being at least 100 percent. The apparatus used to produce the product is a hydrostatic extrusion press which includes an annular orifice in which the thermoplastic polymer is elongated substantially simultaneously circumferentially and axially with the circum-ferential elongation being at least 100 percent. Means for maintaining the rigidity of tooling and the hydrostatic extrusion fluid pressure while providing a film of the fluid on the preform for lubricity are provided in the apparatus. -1-A sheet substantially uniform in thickness and having substantially the microstructure and properties of the conduit and excellent drawability may be made from the conduit. An article of manufacture may be made by solid state deformation processing of the conduit or the sheet. -2-

Description

1 155~

Thls inventlon relates to a thick-walled, seamless, rlgid condult conslsting essentlally of an oriented crystalllne thermoplastic polymer havlng lmproved propertles; to a sheet made thererrom and to an artlcle of manufacture made from the conduit or sheet.
The condult is fabricated by solld sta~e hydro-statlc extrusion of the polymer in an apparatus including an annular orlfice having a diametricallJ diverglng geometry and converging walls and~orlfice area whereby the polymer-ls substantially simultaneously elongated clrcumrerentially and axlally. ~ ~
It ls well known that the physical and mechanlcal properties of semi-crystalline thermoplastic polymers can be lmproved by orienting their struckures. Polymer processlng ~lS methods, such as drawing, blow molding, in~ectlon molding and the ll~e have all been used to rabricate articles of thermoplastic polymers having oriented structures.
In recent years, extensive study has been dlrected I
to methods of de~orming the t~ermoplastic polymers in a ~; 20 ~ ` solid s~tate. In khese methods,~the polymer is~mechanically :
` de~ormed to obtain a deslred uniaxial or biaxlal molecular ~ ~ ~ 3 ~
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orlentatlon. The polymer may be drawn, extruded or processed at temperatures within the range from the glass transltion temperature to temperatures ~ust below the crys~alline melt temperatures of the polymers. In the case of stereoregular polypropylene, the polymer may be processed at temperatures as low as 0C (32F). Products such as strlp~ tubes, rods and shapes, usually havln~ predominantly unidirectlonal orienta-tion, have been fabricated by such processing methods. The extrusion methods and apparatus used for processing the poIymers are similar to those used in the metal industry.
Short tubular artlcles with high axial elongation and low circumferentlal elongation, for example shotgun shells, have been produced by solid s~tate extrusion.
One method for processlng a polymer ls described by Robert A. Covlngton, Jr. et al in U. S. Patent No.~
3,205,290 entitled "Method O:r Making Tubing for Cartrldge easings and the Like." In the method, a molten polymer, ror example polyethylene or polypropylene, is ~ormed lnto a thick-walled tubular prerorm or billet. The billet is processed ln a two-step process into a short~ thlck-waIled tubular article having one closed end.~ Initially, the ~ billet ls expanded circumferentially by an average of about ;~ 40~ to~50 percent Oy rorcing lt onto a solid mandrel.
Circumferentlal elon~atlon re~ers to the expanslon o~ the medlan circum~erence of the billet. The expanded blllet on the solid mandrel ls then forced through a drawing dle to elongate the expanded billet ln an axlal direction while the circum~erentlal elon~atlon remains constant The axial elongatlon can be as much as 350 percent resulting ln a predominantly axial orlentation.

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1 ~52~5 The Covington et al method does not allow a clrcumrerential expansion Or at least 100 percent. If such large circumferential expansions were a~tempted, the blllet would buckle or collapse in an effort to push lt over the mandrel. If large circumrerential deformations Or 100 percent or more could be made by Covington et al, the deformations would be tensile ln nature because the billet would be drawn over the mandrel. Drawing the blllet over the mandrel would result in non-homogeneous deformation of the polymer structure.
U. S. Patent No. 3,198,866 to R. A. Covington et al entitled "Method and Apparatus for producing Plastic Tubular Members" ls directed to a contlnuous method ror producl~g tubular members. In the method, thlck-walled, bored slugs of a thermoplastic polymer, polyethylene having a crystallinity o~ 60 to 85 percent, are rorced over a mandrel b~ ram pressure.
The patent contends that the molecular structure of the polymer is orlented both longitudinally and trans-versely. However, the apparatus o~ Covington et al lsdesigned to prevent any slgniflcant increase ln the outsids diameter Or the slug, l.e. the polymer ls not expanded circumferentially into a conduit having a larger outside diameter than the outside diameter o~ the slug.~ Slnce, the !

slug is lncreased ln length and the wall thickness is decreased but;the outside diameter is not increased~ the polymer ls highly orlented in the longitudlnal directlon but L~ . I

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I 15526~ 1 is not hiKhly orlented in the clrcum~erential directlon.
There is little median clrcumferential elongation there~ore there ls little, lf any, improvement of the average propertles in the circumferential direction.
Another process used to produce orlented shotshells is described by Donald Urquhart Flndla~ et al in U,S. Patent No. 3,929,960 entitled "Method for Producing 0riented Plastic Shotshells." The method is directed to making an ; orlented polyo~lerinic shotshell with an axial tenslle strength between about 1400 and 2100 kilograms of ~orce per square centimeter (20,000 and 30,000 pounds per square inch) and a circumferential tensile~strength between about 387 and 600 kilograms of ~orce per square centimeter (5,500 and 8,500 pounds~per square inch).~ A polyole~inic blank which , ~ is 2.54 centlmete~rs (1 inchj in length and having a wall thlckness or l.06 centimeters (0.42 lnch) is heated to a temperature between 27C and 115C (80F and 240F) and ls placed on a solidlmovable mandrel. The blank 1~ moved into a die cavity. A ram forces the blank over the mandrel in a back extrusi.on to reduce the blank wall with very llttle, ir i any, expansion Or the outside diameter o~ the blank.
The method~o~ Findlay et al limits the clrcum-ferential expansio n Or the polymer, hence limlts the cir-cumrerential~derormation~ o~ the polymer structure. Since the axlal elongatlon is hleh, the molecular structure is hlghly oriented ln the axial dlrection, The structure, ~comprised of spherulltic crystalllne aggregates, is highly L~

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elongated axlally but with very llttle elongatlon clrcum-ferentially. The structure, thererore, is not comprised of platelet or wafer-like, radially compressed spherulltlc crystalline aggregates nor are the circumferential properties improved signi~lcantly.
The indirect extrusion method Or Findlay et al limits the expansion of the outside dlameter o~ the blank to below 25 percent which is well below the minimum circum-~erential expansion achleved in the method Or the invention hereinafter described.
As noted by Robert Shaw in U.S. Patent No. 3,714,320 entltled "Cold Extrusion Process", polymers, particularly stereoregular polypropylene, can be fabricated by various methods such as rolling, ~orging, swaging and peening at temperatures below the crystalline melt temperature. Shaw teaches that cold extrusion o~ polymers has limited appllca-~lon because excessive heat i9 generated during large defor-matlons thereby increasing the temperature of the polymer to lts melting temperature. Shaw attempts to overcome the problem Or extruding polymers by cooling them to temperatures as low as OC (32F). I~ necessary, the extrusion apparatus can also be cooIed to low temperatures. Forward extruslon results ln the conversion of rod-like shapes into rod-like extrudates of various cross-sectlonal shapes having a ~enerally reduced cross-sectional area. It is apparent that Shaw does not envision ma}cing circum~erentlally elongated pipes and conduit by extruslon since he teaches that tubes .

. - , 11552B~ , or plpes may be formed by a known manner similar to the so-called Mannesmann method in which a mandrel is placed lnside a tube and a rolllng or hammering force is applied to the outside surface. Back extrusion can be used to produce cup-like shapes.
Shaw's teaching is dlametrically opposed to an extrusion process in which a thermoplastic polymer is heated to a temperature which ls between lts 4.64 kilo~rams force ; per square centimeter (66 pounds per square inch) heat derlection temperature and lts crystalline melt temperature for extrusion through a die conflgura~ion whlch will substan-tially slmultaneously elongate the polymer circumferentially and axlally.
In the limited appllcation of Shaw's process to extrusion in which he teaches that the polymer must be cooled to low temperatures, it would requlre exoessively high pressures, on the order of lO times as great as those required to warm extrude the polymer, in order to extrude the cooled polymer into a tube comprised of highly orlented polymer. The use of excessively high pressures applied to a relatively strong msterial would result in stlck-slip, high strain rate, high energy extrusion and perlodic generation o~ hlgh temperatures at whlch the polymer would melt. When a polymer melts, the crystalllnity and orientatlon ln the polymer are adversely af~ected and the product is damaged beyond use. There~ore, a polymer processed accordlng to Shaw could not possibly have a structure comprlsed Or platelst or :

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wafer-llke, radially compressed spherulitlc crystalline aggregates oriented both clrcumferentially and axially and having improved circumferentlal propert~es.
The use of the Mannesmann method wherein a har~er-ing or rolling pressure is applled locally to the surface of a tube or a mandrel to produce an elongated tube would not produce homogeneously deformed spherulitic crystalllne aggregates, since lar~e localized shear strain gradients would be induced in the polymer resulting in non-homogeneous deformation of the spherulites. Non-homogeneous deformation results in damage to the spherulitic crystalline aggregates ~nd to the ~ormatlon Or~ microvids and the enlargement of existing microvoids. The density of a polymer so worked is less than the denslty of the original blllet. Thls non-homogeneous deformation would also adversely affect the lowtemperature tenslle impact strength and the density related properties of the polymer.
Long, thick-walled high strength tubular polymer products, such as high pressure hoses, tubes and pipes have been produced by plasticatlng extrusion Or riber reinrorced plastics and medlum pressure tubes by ~lasticati~g extrusion methods.
One such method for producing medlum pressure thermoplastic pipe having a diameter as lar~e as 152.4 centimeters (6Q inches) and a wall khickness of over 5 . o8 centimeters (2 inches) is described in UOS. Patent No.
3,907,961 to Guy E. Carrow entitled "Flexlble Cylinder ~or Cooling an Extruded Pipe." The pipe can be made by either 1 1552~ ~

screw extrusion or impact extrusion. In either case, the thermoplastlc polymer is heated to a molten state and is extruded through a conical shape passag~ onto a flexlble mandrel. A coolln~ medium is provided to cool the surfaces of the pipe to a solldiried state. The polymer is extruded in the molten state and the resultant pipe has an unoriented structure.
A method for producing high pressure plpe is described in U. S. Patent No. 4,056,591 to Lloyd A. Goet~ler et al which is directed to a process for controlling~the orientation of dlscontinuous fiber in a flber reinforced product produced by melt or plasticatlng extrusion. The flber-fllled matrix is extruded through a dlverglng die having a generally constant channel. The walls Or the dle may taper sllghtly so that the area Or the outlet Or the die is larger than the area of the inlet of the dle. The amounk Or orientation of the fibers in the hoop direction ls directly related to the area expansion of the channel rrom the inlet to the outlet Or the channel. The product produced is a reinforced hose contai~ing flbers which are oriented in the circumferential direction to improve the circumferential properties. While the fibers may be oriented, the polymer is unoriented since it is processed in a molten state.
Since the fiber reinforced polymer is processed in a molten state, the structure is not comprised of platelet or wafer-like, radially compressed spherulitic crystalllne aggregates highly oriented both circumferentially and axially, although the fibers added to the polymer may be oriented circumferentlally.

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1 ~S52~5 Blaxially orlented contalners, such as bo~tles used ln the sort drink lndustry are made by a melt extrusion-stretching or in~ection molding-blowing expandln~ process.
One such process in which a biaxially oriented hollow artlcle ha~ing good transparency and strength and made from polypropylene is processed by the method described ln U.S. Patent No. 3,923,943 to Fumio Iriko et al entltled "Method for Molding Synthetic Resin Hollow Artlcles." In the method, the lnitial step is the production of a parlson by in~ection molding. The parison is expanded by stretching in contradistinction to belng expanded by compressive ~orcec therefore the structure is non-homogeneously deformed and ls susceptlble to the formation o~ microvoids thereby decreasing - the density of the polymer typically about 0.5 percent.
A second method employed to produce a biaxially oriented container is described by Fred E. Wlley et al in U.S. Pat,ent No. 3,896,200 entitled "Method Or Moldlng Biaxially Oriented Hollow Articles." A parison is held in constant ten9ion and ls stretched in the axlal direction be~ore or as it is expanded radially lnto a cavity. i, , Stlll another method ror producln~ containers ;
which have clarlty ls descrlbed in U.S. Patent No. 4,002,709 to Larry P. Mozer entitled "Controlled Air in Polyester Tube Extrusion rOr Clear Sealable Parison." In the process a polyester, for example polyethylene terephthalate, is melt extruded into a clear thlck-w~lled tublng which ls then heated and blown into a container. The polyester is in an amorphous state as evldenced by the clarit~ o~ the tublng.

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,-The containers ln the above processes are produced by stretching the polymer, typically over 250 percent. Such large stretchlng deformatlons result in non-homogeneous derormation of the structure thereby damaging the spherulitic ', crystalline aggregates, causing the formation of microvolds ; and the enlargement of microvoids already present in the polymer. Th0 density of the polymer is decreased and the mlcrostructural sensltlve properties, such as stress whitenlng and low temperature brittleness are not eliminated.
It is desired to provlde a deformation method which ~s compressive in nature whereby the problems of non-homogeneous deformation and the associated defects are suppressed and an oriented spherulitic crystalllne aggregate structure substantially free rrom such defects ls produced.
The prior art processes described above, by which tubular products consisting essentially vr thermoplastlc polymers are produced are lncapable o~ and cannot be adapted to expand a polymer by at least 100 percent in the cir- j cumferential direction in a compresslon-type deformatlon.
Prlor art processes ~or producing hoses or elongated tubular products are directed to melt or plasticating extrusion processes whlch result ln the production Or non-oriented products. Prior art processes for produclng large diameter containers are directed to stretching or tensioning processes in which a polymer is expanded at least 100 percent ln the circumrerential direction. Stretching or tensioning causes non-homogeneous de~ormation o~ the spherulltic crystalline aggregates in the polymer structure. The spherulites are L~

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11~5~5 ruptured and kllted. Microvolds, microribrils and eventually - fibrils are ~ormed. Defects, such as microvoids already present in the polymer are enlarged. The resultlng products are hlghly oriente~ in a circumferentlal directlon, but have defects formed ln the structure. None of the prior art processes desoribed above produces a conduit conslsting essentially of a crystalline thermoplastic polymer which ls expanded at least 100 percent in the clrcumferential direction and is expanded at least 50 percent ln the axial direct~on and has a structure consisting essentially of dlscrete platelet or wafer-like, radially compressed spherulitic crystalline aggregates which are oriented ln both the clrcu~erential and axial directions, which is substantially devold of process induced defects, such as mlcroVOidS and has a density which is the same as or h~gher than the same polymer processed into a conduit by prlor art processes and whlch has improved circumferential tensile ' impact strength and ls less susceptible to ~urther micro-; skructural damage on subsequent stretching.
Neither do the prlor (~rt rererences produce a sheet from a conduit~, which~sheet retalns the unique morphology and propertles of the conduitS nor an artlcle Or manufacture whlch is made ~rom the conduit or sheet, whlch article will retain the microstructure and properties of the condult or sheet in at least a portion thereof : ' The prior art re~erences also do not produce a conduit, sheet or article of manufacture from a substan-tlally non-oriented seml-crystalline thermoplastic polymer , ~ 13 "

1 ~52~

which contains a rlller and whlch has a matrix comprlsed of the unlque oriented microstructure and properties hereinafter described.
It ls an ob~ect of thls invention to provide a conduit consisting essentially of a crystalline thermo-! plastic polymer which ls substantially ~ree from defects caused by non-homogeneous deformation o~ the polymer, is orlented in both a circumrerent1al direction and an axial ; dlrection, and has particularly improved circumferential tensile impact strength over the ambient to low temperature range, and retains the density of the polymer from which it ls p.rocessed.
It is a rurther ob~ect of thls invention to provide a commercially feasible process by which said conduit is produced from a substantially non-oriented semi-crystalline thermoplastic polymer.
It ls a ~urther ob~ect of this invention to produce a ~heet ~rom the condult by solid state heat-~lattenin~
techniques and which is characterized by retaining substan-tially the same morpholo~y and properties o~ the conduit and having a substantially uniform thickness and excellent formability.
It is a ~urther ob~ect o~ this invention to produce an article Or manufacture ~rom the conduit or sheet by known solid state processing techniques whereby the article will retaln the unique morphology and properties of the conduit or sheet in at least a portion thererore.

-14_ ~ ~lS52~5 Broadly stated, the invention is a hydrostat1c extrusion press provided with means for apply;ng extrusion pressure to extrude a generally cylindrical semi-crystalline thermoplastic polymer preform having an outer surface and a bore surface whereby the preform is forced to pass in a solid state through an annular orifice defined by the surface of a d;e section in spaced relationsh;p w;th the surface of a mandrel-head supported by a mandrel and means for ri.gi:dly aligning the press during ; extrusion. The press comprises: (a) an outer support means having two ends, (b) a container means aligned within one end of the outer support means and including a shell having an outer surface and an inner surface and two end surfaces, a plug and piston assemblage closing one end of the shell, (c) the die sect;on being a continuous surface with respect to one end of the inner surface of the shell of the container means and including : a converging first section, a first generally cylindrical land surface axially aligned with respect to the apparatus, a second generally cy-lindrical land surface larger in diameter than the first generally cylindrical land surface and parallel thereto and a diverging conical surface connecting the first and second generally cylindrical parallel land surfaces and forming an angle ~ of between 15 and 45 with the axis of the apparatus, (d) an extrudate receiving means aligned wlthin the other end of the outer support means and including a shell having an outer surface and an inner surface and two end surfaces, a mandrel having two ends coaxially aligned within the outer shell and generally in spaced relationship to the inner surface thereof, (e) a generally conical mandrel-head suppo.rted on the::other end of the mandrel and in spaced relation : with the surfaces of the die section, having a recessed base surface, a generally cylindrical tapering upper portion which forms an angle of between 20 and 50 with the axis of the apparatus and a generally cylindrical nose portlon, (f) an annular orifice ~ormed by surfaces of - 14a -..
: ' 1 1~5265 the mandrel-head and the die section comprised o~: (;) a generally converging conical entrance, (ii) a generally cyllndrical sealing zone, (iii) a generally con;cally shaped expanding zone h~v~ng a generally converging cross-sectional area and a d;:ametrically diverging geometry, (iv) a generally cylindrical s;zi'ng zone parallel to the seali'ng zone and having a smaller cross-secti'onal area and a median diame-ter which is at least 100 percent larger than the median diameter of the sealing zone, and (v) transition zones of desired radi'i and smooth surfaces between any two of the zones whereby the billet is substantially simultaneously expanded circumferentially at least 100 percent and axially elongated at least 50 percent, and (g) sealing means formed by the surfaces oF the mandrel-head in contact with the inner surface of the billet and the die surfaces in contact with the outer surface of the billet in the container assembly whereby leakage of fluid ;s prevented during loading and prior to extrusion and a film of the hydrostatic fluid is formed on the surfaces of the billet during extrusion, (h) a first pressurizing means disposed adjacent one of the two ends of the outer support means and contiguous with the plug and piston assembly and one end surface of the container assembly of-(d) whereby pressure for extrusion is applied to the preform, and (i) a second pressurizing means disposed adjacent the opposite end of the outer support means and contiguous with one end of the extrudate receiving means and co-acting with the first pressurizi'ng means to rigidly align the extrusion press.

- 14 b -1 ~52~

~IGURE 1 is a diagrammatic representation Or the extrusion Or a thermoplastic polymer preform lnto a conduit and the formation of a sheet product rrom the condult and showing a plctorlal representation Or the structure formed in the prerorm and the conduit.
~IGURE lA is a test coupon cut from the thermo-- plast~c polymer preform shown in Figure 1.
FIGURE lB is a test coupon cut from the conduit shown in Figure 1.
FIGURE 2 is an elevation vlew ln cross-section Or a vertical batch extrusion apparatus, which may be used ln the method of the lnvention, showing a substantlally non-orlented seml-crystalllne heated thermoplastic polymer ~ prerorm in posltlon at the start Or the hydrostatlc extrusion process.
FIGURE 3 shows the apparatus o~' FIGURF, 2 arter the preform has been ex~ruded.
FIGU~E 4 is a top vlew or a slotted washer used in the apparatus o~ the inventlon.
FIGURE 5 ls a top view Or a grooved washer used in the apparatus Or the lnvention.
FIGUR~ 6 is~a schematic vlew in cross-sectlon of a second embodiment of an apparatus which may be used in a semi-contlnuous process for~hydrostatlcally ex~ruding a semi-crystalllne thermoplastic polymer prerorm.
~ICURE 7 shows the apparatus Or FIGURE 6 arter the thermoplastic polymer pre~orm has been extruded.

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FIGURE 8 shows a cross-sect~onal v;ew of a portion of a heating tank which ~s used in the apparatus shown in FIGURE 6.
FI.GURE 9 is an isometric view of a frozen food container made from the sheet of the invention.
FIGURE 10 is an isometric vi.ew of a re~ri:gerator door liner which can be made ~rom a sheet of the ;nvention.

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In accordance wlth this lnvention~ there is provided a thick-walled, seamless, rigid conduit havlng a wall thickne~s from about 0.5 percent to about 6.25 percent of the outside diameter, conslsting essentially of an oriented crystalline thermoplastlc polymer characterlzed by a density which is at least equal to the denslty Or the unoriented polymer and by a memory urglng the polymer back to its unoriented state when sub~ected to heating in an unconstralned state for a time ~ust below lts crystalline melt temperature. The polymer has a structure which is substantially free from process induced defects and is comprised of discrete, platelet or wafer-like, radlally compressed spherulltic crystalline aggregates which are oriented in the plane of the conduit wall. The circumfer-ential ultimate tensile strength of the conduit is at least one and three quarters as great as that of the polymer in a substantially non-orlented state and the circumrerenkial tensile lmpact strength is at least five times as great as that o~ the polymer in the substantially non-orierlted state at 24C (75F). The polymer retains at least 20 percen~ of such clrcumferentlal tensile impact strength at -45C (-50F).
~: The ratlo of the tensile impact strength (TIS) to the ultimate tensile strength (UTS) as determined by ASTM D1822 S-type specimens is at least 50% greater than that ratio determlned ~or the same polymer composition wh~ch is biaxlally oriented .

, 11~S~65 , to the same ultimate tenslle ~trength level by conventional solld state de~ormatlon processes, ~or example blow moldlng or thermoforming or tentering. The conduit ls less susceptlble to mlcrostructural damage on subsequent solid state derormatlon processing than conduits comprised of non-oriented thermo-plastic polymers.
In a second embodiment of ~he invention, a conduit of thls invention in which the clrcumferential and axial i orientations are substantially equal is slit and heat flattened under pressure to produce sheet which ls formable at temperatures below the crystalllne melt temperature, i.e., in a solid state by methods, such as hot stamping, thermoforming, pressing and the like, into usable products such as luggage,` automotive hoods, trunk lids, front panels 15~ and the like. Suoh sheets retain the morphology and properties of the conduit and are less permeable than oriented sheets prepared by conventional drawing and stretching process.
In a third embodiment, a conduit Or this lnvention is prepared ~rom a filled seml-crystalline thermoplastlc hornopolymer3 for example lsotactic polypropylene. The conduit is sllt and heat flattened to produce a fllled polymer sheet having a matrix comprised of an oriented microstructure.
In a fourth embodiment o~ the invention the ~illed orlented sheet can be processed by solid state processes into articles Or manufacture such as refrigerator accessories, such as door linersg chiller trays, ve~etable and frult , . I, , 1 ~5~5 trays, gaskets; automotive parts, such as hoods, and trunk lids; deep contalners, such as garbage pails, storage drums, water buckets; luggage, etc.
The conduit of the lnvention ls produced by solid state hydrostatic extrusion of a substantially non-oriented semi-crystalline thermoplastlc polymer. The polymer is preferably heated to a temperature whlch is ln a range between about its 4.64 kilograms of force per square centi-meter (66 pounds per square inch) deflection temperature and 8C (14F) below the crystalline melt temperature. Sufficient pressure is applled through a hydrostatic fluld to extrude the polymer through an annular orifice having converging walls, a converging cross-sectional area and a diametrically diverglng geometry~ The polymer ls elongated substantially slmultaneously in both the clrcumferential and axlal ¦ directions. The pressure required for extrusion ls maintalned ; ln the rluid by a sealing means which allows a thin film of the rluid to be extruded wlth the preform and to act as a lubricant for the polymer during extrusion. The extrudate i 20 is lubrlcated and cooled by a second fluid as it passes over a mandrel surface. Cooling ~lxes the polymer and reduces the lnherent tendency of the polymer to spring back and recover its shape.
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The polymer ls extruded in a hydrostatlc extrusion press. The press is~comprised o~ a hydraulic pressurizlng means coactlng with a contalner assembly and an extrudate ; . receiving assembly. A die and a ~andrel-head posltioned in the contalner assembly form an annular oriflce through whlch li,~ .

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the polymer 15 extrude~. The mandrel-hea~ 1~ conkiguous and aligned with a mandrel in the extrudate receivlng assembly.
A pressurized force surflcient to extrude the thermoplastic polymer is applled to a polymer preform by a pressurlzlng means. The sealing means in the contalner assembly prevents leakage of hydrostatlc-fluld thereby maintalnlng extrusion pressure ln the fluld while allowing a fllm Or the fluid to be extruded wlth the preform to provlde lubricity durlng extrusion. The annular orifice has an axially allgned inlet or sealing zone, an expanding and elongating 20ne having converging walls, a converging cross-sectlonal area and a diametrlcally diverging geometry and an outlet or slzing zone. The sizlng zone ls smaller~in cross-sectional area ~ and has larger outside and lnslde dlameters than the seallng zone.
~ ~ ~ The polymer is extruded into an extrudate receivlng;~ assembly axla`lly allgned and contl~uous wlth the container assembly. The mandrel in the extrudate containing assembly i5 con~lguous and allgned with the ~ase Or the nlan~rel-head.
A clamping force is applied to the mandrel to provide rlgidlty to the apparatus and to prevent lateral and axial movement of~the mandrel-head during extrusion. Means for lntroducing and e~xhausting a lubricating and/or coollng fluid into the extrudate contalning assembly are also provided.
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This inventlon ls dlrected to an oriented crystal-llne thermoplastic polymer product produced by solid state de~ormatlon processes o~ a substantially non-oriented semi-crystalllne thermoplastic polymer which may contaln up to 60 weight percent additlve. The final product may be a conduit, a sheet or an article Or manuracture made by solld state deformatlon processlng of the condult or sheet. At least a portlon of the final product ls characterized by having a microstructure comprised Or spherulltic crystalline a~gregates whlch are compressed transversely to the plane Or the product and are biaxlally orlented ln the plane Or the product. The product is substantially devold of any process induced microvoids and mlcrofibrils. The product is also characterlzed by havlng ln at least a portlon thereor an lmproved comblnation Or tensile impact strength and ultlmate tensile strength at amblent and low temperatures; the ratlo Or the tensile impact strength to ultimate tensile strength ) belng at least 50 percent greaSer than that ratlo determined ~or the same polymer compositlon which is biaxlally orlented to the same ultlmate tenslle strength level by .

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2 6 5 conventional solid state de~ormation processes, for example blow moldlng. The tensile lmpact strength ln at least a portion o~ the product is at least 5 times greater and the ult~mate tensile strength is at least 1-3/4 times greater than that of the unoriented polymer from which the product is made. The product retalns at least the same denslty as the unoriented polymer and ls less permeable than a product made by conventional solid state tensioning processes, such as blow moldin~ from the same polymer composition- -The product or products are made by lnitially extruding a substantially non-oriented semi-crystalline thermoplastic polymer prerorm in the solld state with a hydrostatic fluid through an extrusion zone at a temperature whlch is between the 4.64 kilograms force per square centimeter heat deflection temperature, i.e. maxlmum use temperature,~ and 8C below the crystalline melt temperature of the thermoplastic polymer while expandin~ the preform substantially simultaneously clrcumferentially at least 100 percent and axially at least 50 percent~ The resulting product or intermediate tubular or conduit type product has a substantially uniform wall~thickness which is about 0.5 to 6.5 percent Or the outside dlameter wlth an actual thickness of not less than 0.079 centimeter in conduits havin~ an outside diameter Or between 2.54 centimeters and 152.0 ce~ntimeters~and consists of~at;least one oriented crystalline thermoplastic po~lymer characterlzed by a density which ls at .
least equal to the density Or the unoriented polymer and a mlcrostructure substantially devold Or any microvolds and ~:::: . ~:
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, . . .~ .

~ 1~52~
microl'ibrlls induced durlng processlng and comprlsed o~
radially compressed, dlscrete, platelet-llke spherulitic crystalllne aggregat/es which are orlented in the pl~ne Or the condult, the conduit havlng a tensile impact strength at -45C which ls not less than 20 percent of lts tensile impact strength at 24C and having a tensile impact strength at 24C which is at least five times and a circumrerential ultlmate tensile strength whlch is at least one and three quarters that of the corresponding conduit of the same polymer ln the unorlented state.
The oriented semi-crystalline thermoplastlc condult may contaln up to about 60 weight percent flller material.
It has ln the past been very difrlcult, lf not lmposslble, ~ to orient thermoplastlc material which contains substantial lS ~ filllng materlal. However, when the thermoplastlc polymer , contains a filler and is extruded ln accordance with the present inventlon it is found that the~thermoplastic polymer can be successfully oriented as descrlbed above and will have a tructure unllke previous~products substantlally devoid Or microvoIds and mlcrofibrils and havlng within the thermoplastio polymer discrete, platelet-like spherulitlc crystalllne aggregates oriented in the plane of the conduit.
After the tubular or conduit product Or the invention ls made~the product can be used as a condult or structural member~or~the llke, but more frequently will be spllt and heat rlattened in a solld state into a sheet :
product. The amoun;t Or heat used ln flattenlng ls insufrlcient to afrect the properties or microstructure Or the oriented , '' :

the~mcplastic ~ol~mer and th~ shcet prod~r~ ~hus ha3 ~he same superlor properties as the conduit.
The sheet product ln turn can be used as is for structural or the like purposes, or other uses, but will in many cases be used as a blank to rorm a final product such as, for example, a solid state ~ormed product. Many solid state formed products are so called stretch formed products where the thermoplastic polymer is formed ln a die under - sufflcient heat and pressure to deform the thermoplastic polymer in a solid state. The properties of the flnal solld state stretch-formed product will depend primarily upon the extent of derormatlon. However, it has been found that solid state stretch formed products made from the oriented sheet blanks Or the inventlon have superior properties lS compared with the properties Or similar products made with unoriented thermoplastic polymer. For example, stretch formed products made rrom the oriented thermoplastic polymer sheet blanks of the lnvention will have a more uni~orm cross section. The superior propertles Or the oriented thermo plastic polymer prevent the thermoplastlc polymer ~rom "necklng" down appreciably and the resulting product is thus much more` uniformly stl~ and strong than would otherwise be the case. The actual properties of the stretch formed ;~ product may vary from place to place ln the product ~25 depending upon the amount of work or deformation applied to any given portion of the product. Any flanges on the product, belng substantlally unworked~ will have the same superlor characteristic propertles as the origlnal orlented :

~.

, 5~$

blank. In some products this ls very lmportant as the flanges provide important structural strength and toughness.
The lips or rlanges around the edges Or rerrigerator freezer door liners, freezer food containers, pans or tote boxes are representative o~ this type of product. Likewise any portion of the product which is expanded less than roughly 50% will havè essentially the same property characteristics as the original oriented blank material. Thus the properties of shallow drawn or formed articles are very superior.
Beyond about 50% expansion the characteristic properties of the thermoplastic polymer are progressively changed due to the progressive destruction of the spherulitic crystalline aggregates and the increase in planar orientation as de~ormation continues. Initially, an lncrease in deformation lncreases the ultimate tensile strength while retaining at least the same tensile lmpact properties but at high elon~ation the properties begin to decrease. Thererore, products made ; from the oriented blanks Or the invention will usually have very signirlcant portions which have very superior properties compared to products made from an unoriented thermoplastlc polymer, ~illed or unfilled, of the same composltion.
In a detailed descrip~ion o~ the invention, the product is a thlck-waIled, seamless, conduit (a conduit is a cylindrical member indeterminate in length and includes such forms as a tube, pipe and the like~ consisting essentlally Or an orlented crystalline thermoplastlc polymer. The conduit can have an outside dlameter between about 2.54 centlmeters (l lnch) to 152 centimeters (60 lnches), however -24_ ~ 1~5~6~ ;

a prererred range is about 5 centimeters (2 lnches) to 63.5 centimeters (24 inches) and the most preferred range ls about 20 centimeters (8 inches) to 41 centimeters (16 inches). The thickness of the wall is substantially uniform radially and circumferentially from end to end and will not vary by more than plus or minus 10 percent, and prererably by not more than plus or minus 5 percent and most prererably not more than plus or minus:2.5 percent. The thlckness of the wall is about 0.5 percent to about 6.25~percent, pre~erably about 1.0 to 3.0 percent and most preferably about 1.0 to ~.0 percent, of the outside diameter. However, in conduits which have an outside diameter o~ 2.54 to 7.62 centimeters (1 to 3 inches), the wall thickness is at least ~: 0.074 centimeters (1/32 of an inch). The conduit may be short as about 7.6 centimeters (3 inches) and as long as commercially practical and dictated by machine limltatlons~ ;
however it is preferred to make a conduit which is between about 30 centimeters (12 inches) and 244 centimeters (96 lnches). The condult is dimensionally stable and has at least about one and three quarters the circumferential ultimate tensile strength and not less than five times the circumrerentlal tensile lmpact stren~th at 24C (75F) o~ a similar conduit made from the same substantially non-orlented semi-crystalline thermoplastic polymer by con-ventional methods. The condult retalns at least 20 percent o~ the room ~emperature tenslle impact strength at -45C
(-50F).

11~52~

The structure o~ the condult is comprised Or spherulltiC crystalline aggregates which are discrete and platelet or wafer-like and have a generally polygonal shape.
The aggregates are radially compressed and circum~erentially and axlally elongated and are planar oriented, that is, are oriented in the plane of the condult wall. The structure is substantlally free of press induced mlcrovoids and mlcrofibrils ln the boundaries between the spherulitic crystalline aggregates and in the spherulitlc crystalllne aggregates.
The startlng thermoplastic polymer which can be used ln this inventlon is a substantially non-oriented semi-crystalllne or crystalline homopolymer or copolymer having a crystallinlty o~ at least 45 percent, a relatlvely sharp crystalline melklng polnt observed by difrerentlal thermal 1~ analy-sis and having a structure contalning long chaln molecules which~solldl~y in the ~orm o~ spherulitic crystal-llne aggregates. The polymer can be sortened and f'ormed by heat or stress and can be molecularly oriented by drawlng and stretching at a temperature between the glass transitlon temperature and the crystalline melting point as shown by ma~or lmprovements in properties, such as ultimate tensile strength and tensile impact strength. The polymer can have a molecular weight between 104 and 106. Such thermoplastlc polymers include orientable polyole~ins, ~or example lsotactic polypropylene, high density polyethylene; polyamides, for example nylon 6,6; polyacetals, for example poly~
oxymethylene; polyesters, ~or example polybutyl~ne terephthalate; and polycarbonates.

By way of example only, a typical structure Or a polymer, whlch in this instance is isotactic polypropylene, processed by the method o~ the inventlon and the structure of the startlng polymer preform are shown pictorially in FIG. l. Test coupons A ln FIGURE lA and A' ln FIGURE lB
were cut from the pre~orm X and conduit Y, respectlvely, as shown. The outer surfaces B and B', and transverse surfaces C and C' and D and D' were polished and etched and were exam~ned at a magnificatlon of lOOx by llght optical micro-scopy. The surfaces were polished in a two-step sequence using a first paste containing .6 micron dlamond dust and a second aqueous paste containlng .3 mlcron alumlnwn oxide partlcles. The surfaces were carefully cleaned of any paste resldue and were etched in a solution containing equal parts of benzene, xylene and chloroform heated to a temperature of about 80C (175F). It required three to four minutes ~o etch the surfaces Or coupon A and five to six mlnutes ~o etch the surfaces of coupon A'. The sur~aces B, C and D Or coupon A
were round to be comprised o~ substantially non-oriented spherulltlc crystalllne aggregates as shown. It is generally recognized that the crystallihe aggregates grow radially from nuclei and are referred to as spherulites.
The spherulitic crystalline aggregates appear as generally polygonal in shape on polished ~aces. While the structure of the polymer is predominantly crystalline in nature, small areas Or non-crystalline or amorphous structures become entrapped in and between the spherulites during their growth.

1 ~55265 i The sur~ace B' shows a structure comprised Or spherulltic crystalline a6gregates whlch are discrete platelets generally polygonal in shape. The sur~aces C' and D' show the aggregates to be radlally compressed into relatively thln lamellae elongated in both the circumrer-ential and axial dlrections and oriented ln the plane of the conduit wall, l.e. oriented circumferentially and axially.
No evidence of microvoids or enlargement of existing microvoids was seen in the conduit.
A coupon of the conduit Y material was notched with a sharp knlfe blade on two transverse surfaces perpen-dicularly to the plane o~ the conduit. The material was then torn circumferentially and axially. Microscoplc examination o~ the tear surfaces at lO0 magnificatlons showed what appeared to be radlally compressed platelet or warer-like spherulitlc crystalline aggregates arranged in an overlapping pattern.
The sheet product E was formed by slitting the ; condult Y along llne a-a as shown in FIGURE l. The slit conduit was heat flattened under pressure at about 129C
(265F) ror five minutes. A test coupon F was cut from the sheet, polished and etched and examined as descrlbed above.
The microstructure appeared to be identicaI to the mlcr~-structure Or the conduit.
Coupons K and H cut from the heavy wall flange areas of the.~reezer food container9 FIGURE 9, and re~rlgerator rreezer door llner, FIGUR~ lO respectively, have mlcrostructure~ comprlsed of radially compressed ~ ~ 55~

dlscrete platelet like spherulitic crystalllne aggregates slmllar to those seen in hydrostatically extruded conduit and sheet made therefrom as seen in coupon B' Or FIGURE lB.
In c,ontrast to the structure formed by the method Or the invention, polypropylene of the same resin batch was compression molded by a conventional process into sheet and thermoformed at 149C (300F) and 2.8 kilograms force per square centimeter (40 pounds per square inch) air pressure, to provlde comparative samples of biaxially streched sheet.
Microscoplc examination by the aforementioned procedure showed substantial spherulite damage at 70 percent, biaxial elongation and the original discrete spherulite st'ructure pattern substantially destroyed by 100 percent biaxial elongation by conventional compression molding techniques.
A tes~ coupon from the sheet was notched on a transverse surface and torn. Mlcroscopic examination Or ~he tear surfaces at 100 magnirications showed the absence of an overlappin~ spherulikic crystalllne aggregate structure.
A coupon G was cut from the conduit. The coupon was placed in an oil bath and was heated to a temperature of 165C ~330F) without any restraining pressure being applied and held at temperature ~or ~ifteen minutes. The section reverted to about 85 percent of the shape, size and structure it would have had it been cut from the preform used in the manuracture of the conduitO The substantially complete recovery of.the spherulitic crystalline aggregate structure indlcates that the strain lnduced in the spherulltlc crystalline aggregate structure by the compressive forces -2~-~ 155~65 employed to elongate the polymer was,homogeneously distrlbuted.
As a result, the polymer retained its memory and density.
The formation of microvoids and the e~largement of existing microvoids was eliminated. It is postulated that the unique spherulitic crystalline ag~regate structure wherein the aggregates are radially compressed and clrcumferentially and axially elongated ls responsible for the lncrease in the clrcumferentlal tensile lmpact strength9 the unusual low temperature tensile impact strength; a ratlo to the tensile impact strength (referred to as TIS) over the ultimate tensile strength (referred to as UTS) determined by ASTM
; D1822 S-type specimens which is at least 50 percent greater than that ratio determined for a thermoplastic polymer Or the same composition whlch has been bia~lally oriented to the same ultimate strength level by conventional solid state deformatlons, such as blow molding, tentering and the like, and the retentlon Or the density and reduced permeability Or ; the polymer in ~he conduit.
The conduit of the invention ls fabri aked by a solid state hydrostatlc extrusion method in which a polymer is heated to a tem~erature between its 4.64 kilograms force per square centlmeter (66 pounds per square inch) heat derlection temperature as determined by ASTM D-648 and about 8G (14F) below its crystalline melt temperature and is extruded by hydrostatic fluid pressure through an annular ori~ice at a.straln rate which does not exceed 20 seconds 1 and pre~erably is less than 10 seconds 1. The polymer is substantially simultaneously elongated ln the axial dlrection & ~ , and expanded in the circumferential direction by forces whlch are compressive in nature. The expansion or elon~ation - in the circumferential direction is at least l00 percent and is preferably at least 200 percent. The elongation in the axial direction may be less than l00 percent but it is preferred that the axial elongation be at least 50 percent and most preferably equal to the circumferential elongation.
The temperature to which the polymer ls heated for extrusion must be such that the crystalline melt temperature will not be exceeded durlng extrusion and excessive extrusion pressures resulting in stick-slip extrusion and its attendant overheating problems are not permitted. Broadly, the polymer may be heated to any temperature within the range o~
lts 4.64 kilograms force per square centimeter l66 pounds per square inch~ heat deflectlon temperature and about 8C
(14F) below the crystalline melt temperature. However, a temperature range between about 50C (90F) and 18C (32F) below the crystalllne melt temperatures is preferred but the most prererred range is betweerl 30C (54F) and 18C (32F) below its crystalline melt temperature. The temperature range is dependent upon the polymer, the e.YtrUSiOn rate and the reduction ratio. By way of example, the broad temperature ranges, the preferred temperature ranges and the most preferred temperature ranges at which some polymers may be extruded in the method of the invention are shown in Table I, below. .

2 ~ 5 a) ~ ~ ~
b~ t~ O
J O O U~
~) N tr7 J J
~; ~
t~ C~ t~ C~
~V 0~ N t-- N
tl) o Ir~ O (r~
h ~ ~ ~ c~
L.
tl~
. ~ ,~
tl) ~ 1~
h O o o o 1~
N ~Jt~ 3 U~ ~ V
0 3 ~~
O N QO ~1 ~l N

~ ,_ ~
~ ¢ 4 ~ ' ~ O

3 0 0 U-\
Q) N t''l ~ 3 bl ~ C~
~a G~ N ~-- N
~ O - ~ O
U~ ~ ,1 h tl~
S~ ~ ~ ~ _~
h li~
t~ a1 O ~O O O
H 5~ ~
tl) tL) ~ N trl 3 . ~ h .
O ~ ~
Z O r~l N 3 r-l E-l ~ O L~ N
kl ~:
h Is~ 3 t~
~O N N
X N tfl 3 3 t~ t~ C~
~( a~ N t-- N
C~ N
~:: r-l ~ N N

~ ~4 ~ ~ ~ . ' 1 O O ~ O O
~1 a~ r-l N tr~ 3 r--l N 3 ~1 ~ O U~ t~J
- r-l ~i N
.
tl) S: tL~
tl~
J
~1 ~ h ~
tL~ tl~ O ~ ~D
~; O :~ ~ O
O O ~, m a. ~ ~

, .

~ 5 The thermoplastlc polymer preform is ~abrlcated on a hydrostatic extrusion press. The press may be a batch, semi-continuous or contlnuous press. In any event, the press is comprlsed of a supporting structure and ~oollng.
The tooling is comprised of a pressure means which provides the extruslon pressure; clamping means ~or maintaining alignment of the tooling; a contalner assembly in which a polymer preform is placed ~or extruslon which assembly includes a die, a mandrel-head and sealing means to retain the extrusion pressure; and a receiving assembly ln which the extrudate is recei~ed, lubricated and cooled a~ter extrusion, which assembly includes a mandrel and means ror lubrlcatlng and cooling the extrudate.
The die and mandrel-head are spatially and coaxially aligned wlthin the container assembly. The sur~ace o~ the die and the sur~ace of the mandrel-head form the walls Or an annular ori~ice having a converging conlcal entrance; a cylindrlcal inlet or 9ealing zone; an expansion zon~ having converging walls, a conver~lng cross-sectlonal area and a dlverging geometry and a cylindrical outlet or sizing zone.
The sealing zone has an outside diameter which ls smaller than the outside diameter Or the preform. As the preform is extruded, inltially the cross-sectional area o~ lts wall is reduced by about 5 percent and axial elongation begins. The preform enters the expansion zone and is circumrerentially elongated, i.e. the outslde and inside diameters o~ the preform are increased. At the same time, because of the converging walls and the converging cross-sectlonal area of the orifice, t~.e wall o~ the preform continues to be reducéd . ' ' ' ' in cross-sectional area untll lt passes through the exlt Or the expanslon zone into the sizing zone. The extruded preform or extrudate in the slzlng zone is cooled to prevent recovery and shrlnkage of the polymer. The extrudate is lubricated and cooled as it passes into the receiv1ng assembly. The lubrication and cooling assures the production of a condult having wall surfaces which are smooth and substantially wrlnkle-free. The wall is concentric and of ; substantially uniform thickness.
In the hydrostatic extrusion of the thermoplastic polymer in the sol~d state whereby an elongated, expanded, concentric, substantially unlform thick-walied conduit ls produced, lt is necessary to maintain sufriclent constant extruslon pressure in the container assembly and to prevent lateral and axial movement of the tooling. To maintaln the constant extruslon pressure~ it is necessary to e~ectlvely seal the hydrostatic rluid in the container assembly while allowlng a f.tlm o~ the hydrostakic rluid to be extruded along the preform surfaces to provide the lubrlclty needed for extruslon. An effective seal is obtained by providing a preform havlng a cross-sectional area Or the wall which is about 5 percent greater than the cross-sectional area of the sealing zone ln the annular orifice and a converging conical entrance to the sealing zone. When extrusion begins, the outside sur~ace o~ the preform contacts the surface o~ the outside wall Or annular orifice as lt enters the conical entrance and is guided into the sealing zone. The outslde surface Or the prerorm remalns in contact wlth the surface -34~

1 ~526S

Or the outslde wall of the annular orifice thereby making an efrectlve seal which prevents leakage Or hydrostatlc rlu~d from the container assembly and at the same time allows a rllm Or the fluid to be extruded on the surfaces Or the prerorm to provlde lubricity between the surfaces Or the preform and the walls of the orlrlce.
The extrudate is lubricated and cooled by a second ~luid~ such as air, ln the receiving assembly. The fluid is applied to the inner surface o~ the extrudate and acts as a 0 CUs~liOn ~et~!eel: the extrudate and the tooling ln the receiving assem~ly thereby preventing damage to the sur~aces ~r t}le extrudate due to frictlon. The fluid also prevents wrinkllng of a thin-walled extrudate and undue thickening or a heavy-walled extrudate due to the elimination Or frictlonal drag.
l~ Ir deslred, additional fluld may be applied to the outer surrace Or the extrudate ror cooling.
A hydrostatic fluld blow-out, caused when one slde Or the prerorm contlnues to rlow while an acl~acent section Or the pre~orm does not ~low as well causln~ uneven extruslon and introduclng a derect in the extrudate, can occur near the end Or the extrusion Or the prerorm. The blow-out can be prevented by termlnating the extrusion Or the preform before the rear portlon Or the preform enters the seallng zone, inserting a second pre~orm lnto the press with its front end contlguous wlth the rear portion of the orlginal preform and continuing the extruslon. T~e extrudate can be removed concurrently wlth the lnsertion Or a n-w billet.

-3s-1 ~i$526~ .

It is possible to continuously constrain anneal, 1,e. under su~ricient pressure to suppress recovery of the polymer, and heat stabilize the extrudate ln the press by ; heatin~ the preform to a temperature near the upper llmlt Or the temperature range and extruding the prerorm at a low extrusion rate and by usin~ a long sizlng zone.
A high hydrostatlc compressive stress state may be increased in the deformatlon zone by using a longer sizin~
zone with a higher friction rela~ed pressure drop.
By using the combination o~ the above techniques, it is possible to extrude a split preform to produce a split conduit suitable ror heat flattening into a thermop'lastic polymer sheet. It is also within the scope of this invention to produce thick thermoplastlc polymer sheet by slitting and heat ~lattening the extruded conduit. Any means, such as a heat knlfe or slitter well known in t~e art, can be used to slit the conduit. The slit conduit can'be heat flattened by clamping it in a restralning device such as press platens which are heated to a temperature whlch is between 16C (30F~
~20 and 44C (80F) below lts crystalline melt temperature. A
suitable pressure is applied to the polymer durlng heatlng.
The polymer is held at temperature and pressure for between one to twenty minutes depending upon the initial temperature and thickness o~ the polymer, ~or example a 0.16 centimeter (1~16 inch) thlck polypropylene sheet at a temperature Or 24C (75F) in~erted between the press platens at a temperature o~ 129C (265F) and held at a pressure Or 14.06 kllograms rorce per square centlmeter (200 pounds per square inch) ia -2 ~ 5 heated to 143C (290F) and is held ror flve minutes. The sheet may be cooled in the press or may be removed and cooled between metal plates.
The sheet produced as described above retains substantially the same morphology and propertles Or the condult. The sheet also exhibits excellent drawability.
The polymer sheet may be solld state thermally formed by known technlques, for example stamping or uslng pressurized gas with the use o~ a plug asslst being optional and the like. The temperature to which the polymer is heated must be between lIC (20F) and 44C (80F) and preferably 16C
(30F) to 22C (40F) below the crystalline meit temperature of the polymer.
Products produced by solld state thermal treatment lS are useful articles ln many ~ields, for example rerrigerator door liners, ~reézer food conkainers, stamped aukomobile hoods, luggage, and the like. In any article produced by such processes, the portion Or the article ~hich undergoes a mlnlmum amounk o~ derormation, i.e. less than 50 percent~
will retaln substantia11y the same morphology and properties Or the sheet from whlch it iB produced.i Of course, the `~ ~ portion o~ the~article sub~ected to maximum derormation may ~ not retain the same morphology.
;~ It also has been found that a substantially non~
orlented seml-crystalline~thermoplastic homopolymer whlch contains particles of a flller can be processed into a condult and sheet~and subsequently an article of manufacture by the processus previously described. An article o~

.

1 1~$2B~ I
man~facture produced as described ~bove is n~vel iJI itselI
slnce it wll~ have a matrix which ls an oriented crystalline structure. Heretofore, such orlentation Or the structure : has not been posslble wlth solid state high draw ratio stretch orlentatlon processes, for example, tentering, blow molding and other known stretching processes. Such processes, while orlenting the structure also damage areas Or the thermo-plastic polymer by producing volds in the matrix ad~acent to the particles of the filler or enlarglng exlsting microvoids thereby adversely a~recting the properties of the finished product.
The biaxially oriented filled crystalline thermo-plastlc polymer products produced by the prlor art solid state processes mentioned above do not have a tensile lmpact strength whlch is 5 times and an ultimate tensile strength wh~ch is 1-3/4 t~lmes that of an unorlented polymer Or the :. same composltion. Nor do such products have a ratio Or ; tensile impact strength to ultimate stren~th ~-Tu~s) which is at least 50 percent greater than that ratio determlned f'or a semi-orystalllne thermoplastic polymer Or the same ! composltion which has been biaxlally oriented to the same ultimate tensile strength level by con~entional solid state , deformations, for example blow molding,:tentering and the e~ The voids around the particles of the filler adversely affect the~appearance, stiffness and density of the product.
A hydrostatic fluid suitable for use in the hydro-static extruslon of a thermoplastic polyme:r i:s a fluld which ~: has the requlred high temperature properties to resist `, ' "

, degradatlon at extruslon temperature and which is insoluble in and will not react with the thermoplastic polymers, Such oils can be castor oll, sillcone oils~ synthetlc olls~ and various mineral and vegetable oils. It is presently preferred to use silicone oils.
The thermoplastic polymers processed ln the method of the inventlon may also contaln additlves, such as flame retardants, liquid or solid colorants and fillers, such as talc, mica, silica and the like and elastomerlc particles.
By a ~llled thermoplastic polymer we mean a polymer which contains up to about 60 weight percent of a material inert to the polymer and which is in the form of dlscrete partlcles or short flbers wlth length over diameter ratios not greater than flve and whlch wlll modi~y the propertles o~ the polymer or reduce the materlal and processlng costs of the polymer. The inert materlal can be lnorganlc, for example talc, calclum carbonate, clay, sillca and the like, and includes such materials as colorants and flame retarders, By a substantlally non-oriented semi~crystalllne thermoplastic polymer preform, we mean a solid or hollow billet or plug formed from a polymeric melt which is fabri-.
cated into the deslred shape by a process, such as extrusion, compression molding or in~ectlon molding. A minor amount of ; 25 orientation may occur ln the polymer preform during processing, however the amount Or orientation is insurficlent to cause any substantial lmprovement ln the propertles of the polymer.
As noted previously the polymer can contain a flller.

5S~85 It ls wlthin the scope Or this lnvention to produce slngle-layered and multllayered conduits rrom single-layered and multllayered prerorms produced by conventional plast-icating methods.
The oriented thermoplastic polymer conduit of the inventlon may be produced ln a batch extrusion process using an apparatus as shown, by way Or example only, in FIGURES 2 and 3. FIGURE 2 is a cross-sectional view ln elevatlon of a , vertical hydrostatlc extrusion press 10 sho~n at the start lo of the extrusion process. FIGURE 3 ls a cross-sectional ; view of the extrusion press 10 at the finish of the extrusion process O
~ The hydrostatlc extrus~ion press 10 comprises a cyllndrical outer casing 11 havlng threaded open ends 12 and 13, a first hydraulio pressurizlng means 14 and a second ~ : hydraullc pressurizing means 15~ a billet container assembly .l 16 and an extrudate receiving assembly 17 ali~ned in spaced relationship coaxially within said outer casing 11.
Since pressurizing means 14 and 15 are identical, only means 14 wlll be described. The pressurizing means 14 18 a hydraullc apparatus comprlslng a cylinder 18 definlng an annular chamber~l9 with an axial bore 20. A hollow cyllndrlcal piston 21 is posltioned in chamber l9 whereby force is transmitted to a cylindrical plug 30 in the billet .
contalner assembly 16. Pressure ls applied to the piston 21 from a source (no~ shown) through piping assembly 22.
The assembly 16 lncludes a cylindrlcal shell 23 coaxial withln outer casin~ 11. The shell 23 has cyllndrical outer surface 24 and a ~enerally cylindrical lnner surface 1 ~55~5 25. A vent 23a is provided in the shell 23 tu vent pressure from cavity 26 during extension. The lnner surrace 25 defines an axial cavity or bore 26 whlch ls dlvided lnto a flrst cylindrical section 27, an intermediate cyllndrical sectlon 28 and a third section 29. The ~irst sect~on 27 has a greater cross-sectional areà than the intermediate sectlon 28. A generally cylindriGal plug 30 havlng the shape shown has generally parallel upper and lower surfaces 31 and 33, respectlvely, and a pro~ection 3~ extending downwardly from the lower surface 33. The lower surface 33 rests on and is contiguous with the piston rod 21. Extension 32 provides i means to center the plug 30 on the piston rod 21. An 0-ring 30c in groove 30b of wall 30a provides a friction means for keeping assembly 16 together after it has been assembled and during subsequent heating and lnsertlon lnto the press 10.
The upper sur~ace 31 is provided with a cylindrlcal proJection 34 generally U-shaped in cross-sectlon as shown. A hollow cyllndrical piston 36 comprised Or metallic wall 37 having an outer sur~ace 38 and an inner surface 39 definlng an axial cavlty 39a, ls supported by plug 30 as shown. A 1' clrcular elastomer seal washer 40 provides a seat ~or cylindrical plston head 42 having generally parallel upper and lower sur~aces 43 and 44, respectively and also seals hydrostatic ~luLd 51 lnto the cavity 39a. A solld pro-~ection 45 extendlng downwardly from surrace 43 provides means for centering plston head 42. A sealing 0-rlng 46 and a support rlng 47 generally triangular in cross-section on shoulder 48 or the hollow pi~ton 36 provlde seallng means to :

~41 .

2 6 ~

preven~ leakage Or rluld 51. The plstorl 36 is supported on the upper surface 31 of the plug 30. The hydrostatic fluid 51 fllls the cavity 39a of the lntermediate section 28 and plston 36 and provides means for transmittlng pressure to a cyllndrical thermoplastlc polymer billet 53 in the assembly 16. Durlng extrusion, a very thin ~ilm o~ the hydrostatic fluld 51 ls extruded on the surfaces Or the blllet 53 to thereby provide lubrication ~or extrusion. The third sectlon 29 is the die of the~apparatus 10 and is comprlsed Or a converging conical entrance 54a, a generally cylindrical axial land surface 54, a generally conical di~erging wall surface 55 and a generally cylindrical axial land surface 56 substantially parallel to the land surface 54. The land surface 56 may be any length sufficient to ald in setting the extrudate. The dlameter Or land surface 54 ls smaller than the diameter of land surface 56. ~ mandrel head 57 j having a recessed base surface 58, a cylindrical lower portion 59 and a conlcal upper portion 60 tapering into an elongated cylindrlcal nose portion 61, is positioned axially wlthln the annulus formed by the die 29. The nose portion 61 is Or a size such that when lnserted lnto the bore 53a ol`
the blllet 53, an lnterference flt is produced whlch is sufflclently strong to keep the mandrel head 57 in posltion whlle assembly 16 is being assembled and to maintain the position of the mandrel head 57 during subsequent heating and insertion into the press 10. The outside surface 53b Or the billet 53 contac:ts land surface 54 to thereby form a seal which prevents leakage Or hydrostatic fluid 51 during subse-quen~ heating and assembly Or the apparatus 10. The surface .
-42- ~

5~5 .
Or die 29 and sur~ace Or the mandrel head 57 are spaced a desired distance apart to ~orm an annular orifice or extruslon zone 57a which has a generally converging conical entrance 54a and three zones: a seal$ng zone 57b formed by the annular cylindrlcal land surrace 54 and the surface Or cylindrical nose 61 respectlvely, a conlcal expanslon zone 57c ~Figure 3) having a converging cross sectional area rormed by diverging wall surface 55 and the surrace of conical portlon 60, respectively, and a cylindrical sizing zone 57d formed by the land surface 56 and the sur~ace of portion 59. The transition zones t between the surfaces of the sealing zone 57b and the expansion zone 57c and the sizing zone 57d on the dle a~d mandrel-head respectively are provided with curved surfaces having predetermined radil to provide smooth transition areas between any two zones. The angle a that the diverging wall surface 55 makes wlth the axls o~ the press 10 may be between 45 and 15 and the angle ~ that the ~urface Or conical portion 60 makes with the axis of press 10 may vary between 50 and 20. The angle ~ and the angle ~ are chosen so that diver~ing wall surface 55 and the surface Or conical section 60 will meet if extended, i.e.
the annular oriflce formed by these surfaces is generally converging and has a con1~erging cross-sectional area whlle being diametrically diverging. By extruding a thermoplastic polymer blllet through the annular orifice shaped as descrlbed, the blllet is substantially simultaneously expanded circum- ;
ferentially and elongated axially. It is preferred that the angle a be about 30~ and the angle ~ be about 40, The .

, .
., ~ ~ ~5~ ~

blllet 53 has a diameter which ls sllghtly larger than the dlameter of surface 54. When extruded, the outer surface Or the billet 53 contacts surface 54 to rorm a seal whlch holds the hydrostatic ~luid 51 in the assembly 16 to maintaln extrusion pressure but at the same time allows a thln ~ilm of ~luld 51 to be extruded on the surface of the billet 53 to thereby provide lubrlcatlon durlng extrusion. As the billet 53 enters the zone 57c, lt is substantially slmul-taneously expanded circumferentlally and elongated axially and flows to the sizlng zone 57d. It is posslble to vary the axial elongation Or the thermoplastic polymer while keeplng the circumferentlal expansion constant by varying the distance between the conical surface of the mandrel-head and the wall sur~ace 55.
The extrudate receiving assembly 17 lncludes an outer shell 63 coaxially within and spaced from casing 11 and a cylindrlcal hollow mandrel 62 coaxially within shell 63. The mandrel 62 has an open lower end and an open upper end 64 and 65, respectlvely, an inner surface 66 derinlng a cylindrical bore 67.and an outer surface 68. A shoulder 69 and a plurality of radial orifices 70 extending from inner surface 66 to outer surface 68 are formed in lower end 64.
; : The upper end 65 has a greater cross-sectional area than the remalnder o~ the bore 67 and is provlded with threads 71.
~ Outer shell 63 has an open lower end 72 and an open upper end 73~ an outer surface 76 and a generally cylindrlcal inner surface 74 defining a generally cylindrical bore 75.
The inner surface 74 has an upper portion 74a and a lower I

~ ~ 5.~

portion 74b. A shoulder 78 is formed on end 72. A plurality Or radial orlfices 79 extend from the lower surface 74b to the outer surface 76. The upper portion 74a is contlguous wlth the outer surface 68. The lower portion 74b and outer surface 68 are spaced apart to provlde a chamber 82 into which the polymer is extruded.
The mandrel 62 ls separated from the mandrel head 57 by a grooved washer 83, shown in FIGURE 5. A plurality Or radial grooves 84 communicate with the orifices 70 ~o provide unlnterrupted passageways between the bore 67 and the chamber 82.
A clrcular bearlng plate 85~havlng an outer dlameter equal to the;diameter~or the outer shell~63 and an axlal opening havlng a diameter equal to the diameter of the 15 ~ upper end 65 or~the mandrel is contlguous with the ends 74a and 73, respectlvely. A slotted washer 86, shown in FIGU~E 4, ls lnser~ed between bearlng plate 85 and plston 21' in the hydraullc cylinder 15. A hollow plug 87 and pipe assembly 88 are attached to the mandrel 62 as shown whereby a lubricating and/or cooling fluld may be introduced into :~. the assembly 17. :The plug~87 is spaced a distance from ~` plston rod 21' to provlde a passage for the lubricating and/or cooling ~luid.
:To extrude,:a seml-crystalline thermopla~tic ~25 : polymer blllet 53, for;example lsotactlc polypropylene is inserted ~nto the shell 23 so that the outer surface 53b of the billet:53 contacts the~land sur~ace 54b. The nose 61 of the mandrel-head 57 is inserted into the bore 53a of the . .

~ 1552~5 blllet 53 to make a tight fit. Piston 36 and seal parts 46 and 47 are inserted into section 28. A quantlty of a ; hydrostatic flu~d 51, ~or example castor oil, is poured into the sub~assembly. The sub-assembly is placed in an oven and is heated to a temperature which ls between the 4.64 kilo-grams force per square centimeter (66 pounds per square lnch) heat deflection temperature and 8C (14F~ below the crystalline melt temperature of the polymer, for example ln the case of polypropylene, the temperature is 129C (265F).
Plston head 42 and seal washer 40 are preheated to the same temperature. When at the desired temperature, piston head 42 and washer 40 are inserted lnto the bottom portion of plston 36. Plug 30 and 0-rlng 30b also heated to the desired temperature and protrusion 34 is inserted into plston 36 thereby forming assembly 16. The heated assembly 16 i5 lowered lnto the casing 11 and is fltted to be contlguous with hydraullc cylinder 14. Assembly 17 is also preheated and ls then lowered into casing 11 and is ali~ned to be conti~uou5 wlth assembly 16. The mandrel 62 and mandrel head 57 are allgned as shown. Hydraulic cylinder 15 is screwed into place in the open upper en~ 13. The pipe assembly 88 is placed in position and is connected to a fluid, for example pressurized air which is introduced lnto the assembly 17. Hydraulic pressure Or about 633 kilograms ~orce per.square centlmeter (9000 pounds per square inch) 1s applied by pressur~z~ng means 15 which clamps the press together wlth 26.6 x 104 N (30 tons o~ ~orce`) and prevents lateral and axial movement Or the mandrel head 57 and other tooling ln the press during extrusion. Simulkaneously, -46~ .

S 2 6 ~

hydraulic pre~sure is applled to plston 21 ln cyllnder 14 which in turn transmlts the pressure to plug 30 and hollow piston 37 and pressurizes the ~luld 51. Initially, the fluid 51 and the billet 53 are compressed by the force generated in cylinder 14. When the billet 53 and fluld 51 are ~ully compressed to a pressure of about 520 kilograms force per square centlmeter (7,400 pounds per square inch gage) or higher~ extrusion begins. The pressure remains relatively constant throughout the extrusion time. As noted above~ during extrusion a portion Or the hydraullc fluid 51 ~orms a thin ~ilm between the sur~aces o~ the biliet 53 and the surfaces Or the mandrel head 57 and the die 29;
respectivjely, to provide lubricatlon ~or the billet as it ls being extruded. A lubricating and~or cooling rluid9 pre~erably alr at a desired pressure, rOr example 2.81 to 6.33 kilograms ~orcé per square centimeter (4Q to 90 pounds per square inah ~age), is red into the chamber 82 through bore 67 and radial orifices 70. The air forms a rlowing fllm or cushion between the extrudate and the mandrel sur~ace to lubricate the extrudate. The fluid flows along the surface 68, around the extrudate and along sur~ace 74 to radial orifices 79 to cool the extrudate. The fluld then flows along outer sur~ace 76 through the slots 86a in washer 86 and along space between plug 87 and the pressurizing means 15 passes and out Or the apparatus through the top o~
pressurizing means 15. The use Or the lubricatlng and/or cooling fluid assures a smooth substantial~y wrinkle-~ree sur~ace and a substantlally uni~ormly thlck wall article.

, ~55~

Arter a tlme, ror example about one minute, the billet 53 has been extruded and the hydraullc pressure in the hydraulic cyllnders 14 and 15 ls relieved. Hydraulic cylinder 15 is removed from the press 10. The assembly 17 and the e~trudate are removed ~rom the press lO. A portion Or the blllet remalns unextruded and is retalned on the mandrel head 57.
The extrudate is separated from the unextruded portion by slitting with any conventlonal known cutting tool,~such as a slitter kni~eO
While we have shown a batch process, it is also posslble to produce the tubular product of the invention by a semi-continuous process using an apparatus such as shown by way Or example in FIGUR~S 6, 7 and B.
FIGURE 6 is an elevatlon view in cross-section of a press in which a polymer billet is ready to be extruded.
FIGUR~ 7 shows the same apparatus as FIGURE 6 in whlch the polymer blllet has been extruded and is being eJected from the apparatu~. FIGU~E 8 ls an elevation view in cross-section of the fluld tank showlng several billets being heated prior to being charged lnto khe apparatus.
The extrusion apparatus includes an outer support structure (not 9hown)~ a generally rectangular, tank 95 with , an open top an`d bounded by two side walls 96 and 97, two end ; walls 98 and~99 (not shown), and a bottom lO0. A hydrostatic and 1ubr1cating fluid~51' which is also used to heat blllet 53' fills the tank 95. The fluid 51' ls heated by internal or external conventional means, such as a hea~inK coll (not shown~, to a temperature which is between the 4.64 kilograms ~ ~ 5, 5 ~ r~ f force pe~ square centlmeter (66 pounds per square inch) heat deflection temperature and 8C (14F) below the crystalllne melt temperature of the polymer. Piston 102 ls rully movable throu~h openlng 101 in wall 96. A seal 103 prevents leakage of hot fluid. One end (not shown) of ptston 102 ls attached to and activated by hydraulic means. A sprlng- f loaded cavity 104 ln end 105 guides the billet 53' into the rear or pressure chamber portion 106 of axial cavlty 107 ln die assembly 108. The forward portion of die assembly 108 is a dle 29' comprised of a first axial land sectlon 54', a second axlal land section 56' and a diverging section 55' connecting the rirst and second land sections 54' and 56'.
Dte assembly 108 is mounted in a~ openlng 109 in wall 97. A
mandrel head 57' supported by mandrel 62' 1s axially positioned within cavity 107. The mandrel head 57' has a recessed base surface 58', a generally cylindrical lower portlon 59', a generally diverglng conical upper portion 60' and an elongated nose 61'. The lower porti.on 59' and the diver~ing upper portion 60' and the portion Or the nose 61' ln cooperation with die 29' derlne an orlfice 57a' which has converging walls but has a generally di~erging geometry.
The partially extruded blllet 53" holds the mandrel head 57' in place during eJection of the product and whlle heated blllet 53' is being placed in position to be extruded. A
pro~ectlon on the front face of mandrel 62' ~its into the recess 58a to ~orm a male-~emale rlt whereby any movement o~
the mandrel head 5~7' ls vlrtually eliminated. The other end (not shown) Or the mandrel 62' ls attached to a hydraulic cylinder (not shown). The mandrel 62' is rreely movable through an openlng 110 ln stripper plate 111. The extrudate 53" ' ls strlpped ~rom the mandrel 62' when the mandrel 62' is withdrawn through opening 110 and is re~ected ~rom the apparatus. The billet 53' is shown in the ~ingers 112 of a manipulator (not shswn). FIGURE 8 is a partial view in cross-section o~ the tank 95. A sloping ramp 114 as shown allows billet 53' to be fed into the hot fluld 51'. The arm and ringers 112 of the manlpulator may be any type well known in the art.
FIGURE 6 shows a billet 53' ln pressure chamber 106. Pressure is applied to the billet 53' by piston 102 through hydrostatic fluid 51'. At ~irst, the blllet 53' is compressed until a pressure is reached at which the billet 53' begins to be extruded through orifice 57a' onto the mandrel 62'. The billets 53' and 53'' are elongated sub-stantlally simultaneously circumferentially and axially. As noted previously, the expansion in the circurnferentlal direction is at least 100% and prererably is at least 200 percent. The axial elongation may be less than the circum-rerent1al expansion but it is preferred that the axial elongatlon be at least 50 percent and preferably 100 percent the circumferential expansion.
, Although a hollow billet and a mandrel head having ~5 an elongated nose have been shown, the use of a solld billet and a mandrel head with a sharp needle-like nose and mandrel-heads of various shapes and sizes are well wlthin the scope of this lnvention. In all cases the billet must be extruded ~ ~s~s~ ~

ln the solid state and be substantially slmultaneously elongated in both circumferential and axial directions with the circumferential expansion bein~ lOo percent and pre~erably 200 percent.
As explained previously, the circumferential and - axlal elongatlon o~ the thermoplastic polymer billet are controlled by the converging cross-sectional area and the diverging geometry o~ the annular orirlce through which the billet is extruded. In all extrusions, the lncrease Or the inside and outside diameters of the billet to the conduit must be sufficient to expand the medium circumference o~ the polymer by at least lO0 percent and preferably 200 percent.
As noted above, a portion Or the press in which the billet,~hydrostatio fluid and mandrel-head are assembled, ls heated to a temperature within the range of about 4.64 kilograms force pe~r square cen~imeter (66 pounds per square lnch) heat deflection temperature to 8C (14F) below the crystalline melt temperature o~ the polymer. The crystalllne melt temperature o~ a polymer is that temperature at which the polymer melts and ls no longer crystalllne. The crystal-line melt temperature varles for each polymer, there~ore the temperature to which each thermoplastic polymer is heated prior to extruslon also varies. The thermoplastic polymer is extruded at a pressure and a strain-rate commensurate wlth good extrusion practices wblch will prevent surface tearing, loss of dimensional control and melting of the thermoplastic polymer. In extrusion, the temperature~
pressure, strain-rate and degree~ of elongation are inter-.

~ . .

dependent, therefore if three o~ the parameters are speciriedthe fourth is ~ixed. The maximum extrusion rate ls a functlon of the thermoplastlc polymer being extruded, the temperature at which extrusion occurs and the degree Or elongation Or the thermoplastic polymer. The extrusion rate may be expressed as the average strain rate which is de~ined as the product o~ the circumferentlal and axial elongatlon dlvided by the time required for the thermoplastic polymer to pass through the expansion zone~ As an example, the highest strain rate observed for a successful extrusion of an isotactic polypropylene hollow billet which i5 2.54 centimeters (1 inch) in outside diameter and 12.7 centimeter~
t5 inches ? long and has a wall thickness Or 0.67 cenSimeter (0.266 inch), at a temperature of 113C (235F~ into a conduit whlch is 5.o8 centlmeters (2 inches) outside diameter, 17.78 centimeters (7 inches) long and having a wall thlckness o~
0.14 centlmeter (0.055 inch) with a circumferentlal expansion coefficient o~ 2.6 and an axlal elongation coefficient of 1.9, was 8 sec 1 On a practioal basls, lt is p~sslble to extrude an isotactic polypropylene preform or billet into a conduit havlng a diameter of 40.64 centimeters (16 inchesj at a strain rate of 6.7 sec to yleld a throughput of about 10,884 kilograms (24,000 pounds) per hour. The thermoplastlc polymer is extruded over a generally conically-shaped mandrel head through an annular ori~ice rormed by the outer surface of the mandrel head and the surface o~ the die.
While the mandrel-head and die have generally diverging geometries, the annular oFifice formed by thelr diverging .
. .

1 ~55~6~

surfaces has a converging cross-sectlonal areaO The polymer is thus substantially simultaneously expanded clrcum~erentally and elongated axially resulting in a conduit which has a larger outside diameter, a greater length and a wall thickness smaller in cross-sectional area than the starting blllet.
The divergent geometry of the annular ori~ice controls the circumferential expansion or elongation while the convergence of the surfaces of the orifice, i.e. the converging cross-' sectional area, controls the axial deformation or elongation.
Such elongations may be varied independently to obtain desired circumferential and axial properties. Stating this relationship in terms o~ the billet and product geometry, the lncrease in the median clrcumrerence of the billet to the medlan circumference Or the article defines the cir-cumferential deformation while the reduction of the cross-sectlonal area of the billet wall to that of the conduit or extrudate controls the axial deformation. By median cir-.
cum~erence we mean the circumrerence whlch divides thecross-sectional area Or either the blllet or conduit ln half. By median dlameter we mean the diameter o~ the median circumference. An elongation coefficient is obtalned by dividing the extruded dlmension by the originaI unextended dimension.
Whenever tensile impact strengths are shown such stren~th has been determined by ASTM Dl822 short specimen and ultimate tenslle stren~th is determined by ASTM D638 unles~ otherwise stated.

.

~ ~5~2¢S~

: A comparison Or the ultimate tensile strength and tensile lmpact strength of conduits fabricated by the method of the invention and consistlng essentially Or polypropylene, polyethylene or nylon 6,6 and conduits fabrlcated from the same resin lots by conventional plasticate extruslon method was made. The results of the tests are shown in Table II
(metric units) and Table IIA (English units), below: .

' .. ~ .
i .

. ... . , . ~ .

1 ~5~5 *
~ ) ~ *
O tl~
r- ~ U~
Z; N N
O ~:) rl r-l N ~
~1 ~U 0~0 I
:z ~o o O
C.) O ~Is *
h 3 U~ * *

~ 1 ~ C
~0 0 h P~

h X a~ ~ ~,~
C~ . .
O
O C~ O r~ ~a 3 ~J t~
~) S--~
C) t~ X~ 0 3J
U~
C~ O
O ~ :
~ 3 0 C--O

H h C) o '~:3 Z r ~ h e . ~ o~ ~ .
¢ ~d ,~
E~ ~ ~ .. ..
h rcl ~N r-l ~1 ~--1 C>
O ~;3 C~ 'Cl ~. ~J 3 ~) ~ ~co ~ t--O o ~1 ~ ~o~
h ~O :~ O . O h ~ ~ ~ 2 ~ s O td ~ ~ O ~ O ~ U~
o J~ O O ~ ~r) ~ ~ ~ rl u~ h h t~ ~ h O O
~, P~ * * r-l V
E ::-, * ** * ~ .,~
O D --~
C~ o X ~ ~ h r~ O
e Ei e ~ ~~ C ~
J~ O *
~ K * ~K

--~5--:~:* ~
*
U~
~ J~ . . I
O (~ t~J N ~ ~I
r-l ~ ~ . . f U~ N N
:Z O O
O ~ O O
0 ~ N 0 ~ E--~Z ~D O ~Joo 3 U~
O ~
C~ O
Z r~ J~
:~> h ~ Z ~: o o * *
:~ 00 * *
h O ~ :1~ *
O.O ~ ~ N
-/ t~
h ~1 U~
. . . .
h ~ N
x a) S::~ O O U~ i ~ O ~
O C~ O ~ r-~ ~D O
, J~ s u~ ~ t-- .
C~ ~ X~
~a ~ ~ "
v~ o 0~:; ~ h h ce O ~1: o o ~ =r 5 ~4 O O
D. ~ h ~1 . ~ ~ ~
~ :1 0 o a ~ ,~
.' ~1U~.-1 a~~) o ~ (u ,~
c~~1 tn ~ ~
h '~J ~) O O ~ o ~ o o ~o 1~ c) a.l O O ~i ~ ~ N ~ ~ ~I P;
O ~ O ~1 ~ C~
rl O O h J~ :Z h C.~ ~ ~ i O ~ v ~ ~ S
¢ O O N ~1 0 ~ u~
O ~ O O O O N ~i ~ O
h u~ E
d O
h ~1 ~ 1~1~ b~
;
~ O O S
E :~ ~1 C~
O ~ :~C :~C
t~ * * * *
r ~ O

bD h r-l a) 5:: .0 ~ O~1 a) ~~ ~ Ei :~
E S:~ ~ r~
1 ~ r ~i5 ~
~? a) ~ ~ ~ X ~
bO ~ bO~ ~) cl ¢
rl ~ r-l h ~:: h ~ *
* *
i .
- . , ' : ~ -~ ~55~5 Illustrative examples Or polymer compositions whlch can be processed by the method herein described to produce conduits having improved propertles are shown below.
All the polymers were compression extruded in the apparatus shown in FIGURES 2 and 3. The angles a and ~~ were kept constant at 30 and 40, respectively, Exam~le I
Isotactic polypropylene rods of Novamont Corpora-tion Moplen DoO4W homopolymer produced by melt extruslon and machining and having an outslde diameter Or 2.54 centimeters (1 lnch) were obtained. The polymer had a density of 0.909, a crystallinity of 68.3%~ a crystalline melt temperature Or , 168C (335F), a melt ~low lndex Or 0.4 dg. per minute, an ,~ ultlmate tensile strength of 387 kllograms force per square centlmeter (5?100 pounds per square lnch), and, a tensile impact strength o~ 3.55 ~oules per square centlmeter ak 24C
(19 foot pounds per square inch at 75F').
The rods were divided lnto billets having a length of 12.7 centimeters (5 inches) and were drllled to produce an axial bore Or 1.2 centimeters (0.4~8 inch). A billet was placed ln the blllet container assembly and 69 milliliters ~2.33 ~luid ounces) of castor oil were poured into the assembly. The 9traight 1.27 centimeter (0.5 inch) diameter tip of a mandrel head wa~ wedged into place in the bore Or the billet. An orifice having converglng walls and a con-ver~ing cross-sectional area and a diverging dlameter having an entrance Or 1.27 centlmeters (O.5 inch) internal diameter ' - : .

~ . 1 1$5~65 and 2.51 centimeters (0.99 inch) external diameter and an exit of 5.o8 centlmeters (2.0 inches) internal diameter and 5O32 centlmeters ~2.096 inches) external diameter was formed by the surfaces of the mandrel head and the dle, respectively.
The blllet ,container assembly was placed in an oven and was held ~or about 160 mlnutes to heat all the parts and materials in the assembly to a temperature of 129C
(265F). The assembly was removed from the oven and placed in the prevlously described batch extrusion apparatus and the extrusion apparatus assembled for extrusion. The pressure applied to the billet through the castor oil was increased from 0 to 600 kilograms force per square centimeter (0 to 7900 pounds per square inch) at which pressure the billet was extruded through the orifice into the extrudate receiving assembly. In this example, the extrudate was not lubricated or cooled by a fluid introduced into the extruda~e chamber.
The polymer did recover sornewhat, resultlng in thickening Or the wall and decreasin~ the length of the produc~. However, no evldence Or wrinkling was seen and the wall had a uniform thlckness whlch did not vary more than plus or minus 10 percent the length or clrcumference o~ the product. The condult had a length of 13.9 centlmeters (5.5 inches) and had an outside dlameter of 4.94 centimeters ~1.945 inches) and an lnside dlameter of 4.76 centimeters (1.875 inches) and a wall ~hickness~of 0.089 centimeter (0.075 inch). A
length of polymer about 5 . o8 centimeters (2.0 lnches) remained in the billet contal'ner assembly. The wall thickness -58~

, ~ ~55~$

was about 1.8 percent of the outside dlameter. The circum-~erentlal elongatlon was 2.6 which ls 160 percent and the axlal elongatlon was 2.6 or 160 percent.
; Circumferential and axial tenslle and tenslle lmpact test specimens were cut from the conduit. The results of the tests are shown below:
Ultimate Modulus Tensile Impact Tensile Or Strength at Stren~th Elasticlty 24C (75F) Circumfer-ential (psl) 2 10,900 32.9 x 105 (Kgf/cm ) 2 766 0.20 x 10 (Ft.lbs/In.2) , 1~0 (Joules/cm. ) 38 Axial (psl) 2 13,400 5 (Kfg/cm ) 2 9630.23 ~ 105 (Ft.lbs/In.2) 310 (Joules/cm. ) 65 The oriented circumrerential ultimate strength o~' 766 kllograms rorce per square centimeter ls 1.9 klme.s the unorlented circum~erentlal ultlmate tensile strength Or 387 kllograms ~orce per square centlmeter. The or~ented circum-ferential tensile impact strength Or 38 ~oules per square centimeter at 24C ls 8.2 tlmes greater than the circumferen tial tensile impact strength o~ 4.6 Joules per square centimeters at 24C o~ an unoriented cond~it made by a con-ventional plastlcating method.
Samples o~ the conduit were polished and etched and examlned by techniques prevlously described in these speciri-catlons. The microstructure was-comprised Or platele~ or wa~er-llke spherulitlc crystalline a~gregates when vlewed on a sur~ace radial to the plane Or the conduit. When viewed on transverse surfaces the micro~tructure showed relatively thln lamellae elongated circum~erentially and axlally and oriented in the plane o~ the conduit.
Example II
Rods Or Valox 310, a General Electric resln of polybutylene terephthalate, havlng a length of 12.7 centi-meters (5 inches) and an outside diameter of 2.54 centime~ers (l inch) were obtained. The polymer had a published ultimate tensile strength of 563 kilograms force per square centi-meter (8,ooo pounds per square inch) at yield, an ;impact strength of 0.403 ~oules per centimeter at ~4C (0~9 root pounds at 75F) on a~notched Izod impact speclmen.
The rods were divided into billets having a length 12.7 oentimeters (5 inches) and were drilled to produce an axial bore of 1-27 centlmeters (0-5 inch). A billet was placed in the billet container assembly and 69 mllliliters (2.33 ~luid ounces) of castor oil were poured lnto the assembly. A =andrel-head was force-~lt into place in the bore o~ the billet. An annular oririce havlng an entrance of 1,27 centimeters (0~.5 inch) internal diameter and 2.5 centimeters (0.99 inch) external diameter and an exit o~
5 . o8 centimeters (~2.0 inches) internal diameter and 5.32 centimeters (2.096 inches) external diameter was ~ormed by the sur~aces ~f the mandrel head and the die, respectively.
The mandrel had a diameter o~ 5.08 centimeters (2 lnches).
The billet container asse=bly was placed ln an oven and was held ror about 200 minutes to heat all the .

1~ ~5~5 parts and materials ln the assembly to a temperature or 192C
(375F). The assembly was removed from the oven and placed in the prevlously descrlbed batch extrusion apparatus whlch was then completely assembled for extrusion. Pressure~
applied to the billet through the castor oil, was increased from 0 to 281 kllograms force per square centimeter (0 to 4000 pounds per square inch) at which pressure the b~llet began to be extruded through the orifice lnto the extrudate receivlng chamber. Pressure was kept substantlally constant at 281 kilograms force per square centimet~r (4000 pounds per square inch) durlng extruslon. In this example, the ~- extrudate was lubricated and cooled by air introduced in~o the extrudate recelving chamber at 3.5 kilograms force per square centimeter (50 pounds per square inch). Visual examlnatlon of the extrudate did not elicit any evidence Or wrinkling on the wall surface. The wall thickness was substantlally unirorm and did not vary more than plus or minus 3.5 percent the length Or the article. The condult had a length o~ l3.97 centimeters (5.5 inches) and had an outslde dlameter Or 5.26 centimeters (2.07 inches) and an lnside diameter of 4.1 centimeters (1.98 inches) and a wall thickness o~ 0.12 centimeters (0.046~inch). The circum- :
~erential elongat:lon was 2,55 or 155 percent and the axia elongation was 2.00 or lO0 percent.
Clrcumrerential and axial tensile and tensile impact test specimens were cut ~rom the conduit. The results.
of the tests are shown below:

. ' ''' - .

1 ~5~5 Ultlmate Modulus Tenslle Impact Tenslle Or Strength at ', Stren~h Elasticit~ 24C (75F) Clrcumfer-5' ential (psi) 215,500 3.4 x'105 (Kgr/cm. ) 2 lOgO0.24 x 105 (Ft.lbs/In.2) 449 (Joules/cm. ) 94 10 Axial (psi) 2 15,200 3.5 x 105 ~ (Kgf/cm. ) 2 10690.25 x 105 (Ft.lbs/In.2) 414 (Joules/cm. ) 87 The oriented, circum~erential ultimate kenslle skrength o~ 1090 kilograms force per square,centimeter ls more than 1.9 tlmes the published unoriented ultlmate tenslle strength Or 56t3 kilograms force per square centlmeter and the oriented clrcum~erentlal tenslle impact strength of 94 ~oules per square centimeter at 2lic is more than ten times the estimated unoriented tenslle impact strength oI g.0 ~oules per square centimeter at 24C.

.
A polyamide, Polypenco Nylon 101 ~Nylon 6,6) in the rorm Or rods having an oukside dlameter of 2~54 centi-meters (1 inch) were obtained frc,m Polymer Corporakion. The polymer had an ultlmate tensile strength Or 633 to ~44 kilograms ~orce per square centimeter at 24C (~,000 to 12~000 pounds per square inch at 75F), a modulus o~ elas~
ticity o~ 2,8000 kilograms rorce per square centimeter (400,000 pounds per square inch), a tensile impact strength ~r 18.9 to 35.7 ~oules per square,centimeter (90 to 170 root . 62-1 ~i55~

pounds per square inch), an Izod impact strength or 0.258 to .515 ~oules per centimeter at 23C (.5 to 1.0 foot pounds per lnch at 75F).
; The rods were d~vided into billets havlng a length Or 12.7 centimeters (5 inches) and were drllled to produce an axial bore o~ 1.27 centimeters (0.5 lnch). A billet was placed in the billet holder assembly and 69 milliliters (2.33 fluid ounces) of castor oll were poured into the assembly. A mandrel head was wedged lnto place in the bore of the billet. An annular orifice having an entrance Or 1.27 ~entlmeters (0.5 inch) internal diameter and 2.51 centimeters (0.99 inch) external diameter and an exit of 5. o8 centimeters (2.0 lnches) internal dlameter and 5.32 centimeters (2.096 inches) external diameter was formed by the surfaces of the mandrel head and the die, respectively.
The mandrel had a dlameter Or 5.08 centimeters (2.0 inches).
The billet container assembly was placed in an oven and was held rOr about 230 minutes to heat all the parts and materials in the assembly to a temperature o~ 221C
(430F). The assembly was removed from the oven and placed in the previously described batch extruslon apparatus and the extrusion apparatus assembled for extrusion. The pressure applied to the billet through the castor oil was slowly increased ~rom 0 to 457 kilograms force per square centimeter (0 to~6500 pounds per square inch) a~ whlch pressure the blllet was extruded through the orlflce lnto the extrudate recei~ing chamber. The extrusion strain rate was about 2 sec 1, In this examplej the extrudate was not I

~, ' . ~ . .

5~65 lubricated or cooled by a fluid lntroduced into the extrudate chamber.' The polymer did recover somewhat, resulting ln thickening of the wall and decreaslng the length Or the product. However, no evidence of wrinkling was seen and the wall had a unirorm thlckness which did not vary more than plus or mlnus 10 percent the length,or circum~erence o~ the product. The conduit had a length of 14 centimeters (5.5 lnches) and had an outside diameter of 5.245 centimeters (2.065 inches~ and an lnslde diameter Or 5.01 centimeters (1.972 inches) and a wall thickness of 0.102 centimeters (0.046 lnch). The wall thlckness was 2.2 percent o~ the outside diameter. The circumferential elongation was 2.56 or 156 pelcent and the axial elongatlon was 2.15 or 115 percent.
Gircumferential and axial tensile and tensile impact test speclmens were cut rrom the conduit. The results Or the tests are shown below:
Ultimate Modulu~ Tensile Impact Tenslle of Strength , Stren~th Elasticlt,y 24C(75F) -45C(-50F) 20Circumfer- ~, ential -' .
(psi) 2 ~6,300 4.3 x 105 ;' (Kgf/cm. ) 2 1850 0.30 x 105 (Ft.lbs/In.2) 426.5 109.5 (Joules/cm. )' 9 23 Axial (psi) 2 18,800 3.7 x 105 (Kgf/cm. ) 2 1322 0.26 x 105 (Ft.lbs/In.2) 457 155.5 (Joules/cm. ) ,: 96 33 8 ~ l .
The oriented circumferential ultlmate ~enslle ji strength of 1850 kilograms ~orce per square centlmeter i5 2.2 tlmes the unoriented circum~erenkial ultlmate tensile strength Or 844 kllograms rorce per square centimeter. The orlented clrcum~erential tenslle impact strength of ga ~oules per square centimeter at 24C is slx tlmes greater the unorlented circumferential tensile impact strength of 15 ~oules per square centimeter at 24C of an unoriented conduit made by a conventlonal plasticatlng method. The -45C tenslle impact strength Or 23 ~oules per square centimeter is 25.6 percent of the tenslle impact strength o~ 90 ~aules per square centimeter at 24C.
,Specimens were removed rrom both the billet and the conduit and their surfaces prepared for microscopic examination by the techniques previously described. Microscopic examina-15 tlon Or the surfaces showed the blllet to be comprised o~underormed unl~ormly distributed spherulitic crystalllne aggregates and the conduit to be comprlsed Or radlally compressed platelet or warer-like spherulitic crystalllne aggregates clrcumrerentlally and axially oriented in the plane of the conduit.
- Example _ -!: :
Extruded Samples of Delrin 100, an E.I. DuPont Gorp. homopolymer polyoxymethylene (polyacetal) which were 2.54 cent~meters (1 lnch~ in outside diameter were purchased.
:
The polymer had a pubIished tenslle strength Or 703 kilo-grams force per ~square centimeter (10,000 pounds per square inch), a ten~lle~modulus Or o. 32 x 105 kllograms ~orce per , . , -65- !
.

. ~ , .

6 ~

square centimeter (4.5 x 105 pounds per square lnch), a tensile impact strength o~ 8.4 ~oules per square centlmeter at 24C (40 foot pounds per square inch at 75F).
The rods were cut into lengths of 12.7 centimeters ; 5 (5 inches) and a 1.27 centimeters (0.5 inch) diameter bore was drilled through the speclmens. A billet was placed ln the blllet contalner assembly together wlth 69 milliliters (~.33 ounces) of castor oil. A mandrel head was force-fit into the bore of the billet. The mandrel head had a bore diameter o~ 5. o8 centimeters (2 inches). The ~ssembly was placed ln an oven and to heat the parts and blllet held for 160 minutes to a temperature of 129C (265F). The assembly was placed into the extrusion press and the press was completely assembled. The mandrel which had a dlameter Or 5.08 centimeters (2 lnches) was placed contiguous with the ~ase of the mandrel head and a clamping ~orce of 27,200 kilograms (30 tons) was applied to the apparatus to keep the mandrel rlgld and to prevent vertical or lateral movement Or the mandrel head during extrusion. Air at a pressure Or 3.5 kilograms ~orce per~square centimeter (50 pounds per square inch) was introduced into the extrudate chamber. The extrusion pressure was 499 kilograms ~orce per square ~centimeter (7100 pounds per square inch). The extrudate had an outside diameter of 5.26 centlmeters (2.07 inches), an lnslde diameter of 5.03 centlmeters (1.98 lnches) and a uniform wall thiakness o~ 0.11 centimeter (0.045 inch). The wall thickness was about 2.0 percent of the outside dlameter, and wall thlckness varlatlons were wlthln plus or mlnus 2.5 5~6~ ;

percent. The circumrerent~al elongatlon o~ the polymer w~s 2.47 or 147 percent and the axlal elongation was 2.1 or 110 percent.
Tenslle and tenslle lmpact test specimens were ; 5 taken from the sheet. The test results are shown below:
Ultimate Modulus Tensile Impact Tensile of Strength Elasti~ 24Ct75F) --~5C(-50F) Circumfer-ential ~psi) 2 20,600 4.57 x 105 (Kgf/cm. ) 2 1450 0.32 x 105 (~t.lbs/In.2) 348 75 (Joules/cm. ) 73 16 The oriented~ clrcumferential ultimate tenslle stren~th of 1450 kllograms force per s~uare centlmeter ls twice the published unoriented ultlmate tensile strength of 703 kilograms force per square centimeter and the oriented circum~erential tensile impact strength Or 73 ~oules per ~20 square centlmet~r is 8.7 tlmes the unoriented tensile impact strength of 8.4 ~ou~es per square centimeter at 24C.
, The -45~ tensile impact strength o~ 16 Joules per square centimeter is 22 percent of the tensile impact strength of 73 loules per~sq,uare centimeter at 24C~
~, ~ 25 ~ ~ Example V
¦~ A plurality of extruded rods consisting essentially o~ Marlex 5G03, a Phil~llps Petroleum Corporation hlgh density po~lyethylene~ were obtained. The rods had an outslde diameter of 2.54 centimeters (1 lnch). The polymer had a density o~
0.95 grams per cublc centimeter, a melt lndex Or 0.3 grams per 10 mlnutes, an ultlmate tenslle strength Or 232 klIo-grams rorce per square centimeter (3,300 pounds per square .

2 6 ~

inch) and a rlexural modu~us o~ 11,600 kllo~rams rorce per square centimeter (165,000 pounds per square inch) . The rods were prepared for extruslon and were extruded by the method of the lnventlon as descrlbed in Fxample I except that the rods were heated to a temperature Or 113C
(235F) and were extruded at a pressure Or 113 kilog~ams force per square centlmeter (1600 pounds per square inch).
The extrudate was cooled by air at a pressure Or 3.5 kllograms force per square centimeter t50 pounds per square inch).
The extrudate produ.ced was a conduit which had a length of 14 centimeters (5.5 inches), an outside diameter of 5.2 : centimeters (2.06 inches), an inslde diameter of 5.0 centlmeters (1.972 inches) and:a wall thickness of .11 centimeter (.044 inch). The wall thickness was 2.11 times the outside dlameter. The circumferential elongation was 2.65 or 165 percent and axial:elongation was 2.12 or 112 percent.
The results o~ testing are shown below:
Vltimate Impact Tenslle Tensile Strength E~ 24C(75~) -45C(~
Circumfer-ential . (psl~ 26,630 . 25 (Kgf/cm- ~ 2466 (Ft.lbs/In-2) 352 167 ; (Joules/cm. ) ~ 7.4 35 : Axial ~psi) 26,650 (Kgf/cm. ) 2 468 (Ft.lbs/In.2) : 3g5 201 (Joules/cm. ) 83 42 :

' 1~ 5$~B ~

The circum~erentlal ultimate tenslle strength of 466 kilograms force per square centimeter is about one and three quarters times the circumferentlal ultimate tensile strength of 274 kllograms force per square centimeter and the circum~erential tensile lmpact strength o~ 74 Joules per square centimeter at 24C ls eleven tlmes greater than the circumferential tensile impact strength Or 6.7 Joules per square centlmeter at 24C Or an unoriented conduit made by a con~entional plastlcating method.
The circum~erential tenslle lmpact strength of 35 ~oules per square centimeter at -45C was 47 percent of the clrcumferential tensile impact strength of 74 '?oules per ~ square ce~timeter at 24C. :
:' ExamPle VI
A useful article Or manu:~acture which can be made by the process Or the invention ls a relatively deep ~reezer .
food container as shown at 116 in FIGURE 9. The contalner ,? had a dlameter of l9.~ centimeters ~8 inches) and a depth of 9.6 cen~imeters (4 inches). The container was made from an isotactlc polypropylene de~scribed ln Example I and which was initially made into a conduit by the process described in Example I. The conduit had a length of 61.0 centlmeters ~24 : inches), an outslde~diameter of 20.6 centimeters (8.4 inches), an inside diameter o~ 19.2 centimeters (8 inches)~
: 25 and a wall thickness of 5.1 centimeters ~.20 inch). The : conduit was slit~by a heat kni~e. The slit conduit was placed in a heated platen press and was held far 6 minutes at a temperature~or 129C (265F) and under a pressure Or 24.4 : -69- . I

~ ~ ?

1 ~52~5 kilograms rorce per square centlmeter (347 pounds per square lnch) to form a heat ~lattened sheet which was cut into a disc having a dlameter of 24.1 centimeters (9.5 inches) and a thlckness of 4~83 millimeters (.20 inch). The disc-shaped sheet and appropriate solid state thermal forming apparatus were heated to a temperature of 149C (300F) for about 60 minutes in an oven. The apparatus and sheet were removed from the oven and the outer periphery Or the sheet was clamped in place in the thermoforming apparatus. Air at a pressure of 2.8 kilograms of force per square centimeter (40 pounds per square inch) was lntroduced into the apparatus and forced the sheet to be formed lnto the shape of the cavlty ln the apparatus. After about 10 mlnutes, the air pressure in the apparatus was relleved. The container thus formed was removed from the apparatus. The bottom 118 Or the container was sub,~ected to a total biaxial draw ratlo of

4:1 when compared to the unoriented polymer. A portlon Or the flange 117 which measured 1.6 centlmeters (5/~ inch) (not shown) by which the dlsc was clamped in the apparatus was trlmmed from tbe product. The flange 117 which remained was substantially undeformed and hence was subjected to an average biaxial draw ratio of 2.2 to 1~ The side wall 119 of the container was sub~ected to lntermediate draw ratlos between 2.2:1 and 4:1. The flange 117 had a thickness Or 4.45 millimeters ~.175 inch). In the area immediately beneath the ~lange, the wall 119 had a thickness of 3.43 mllllmeters (.l35 inch) about 2.54 centlmeters (1 inch) below the rlange 117 and 1.9 millimeters (.075 lnch) in 1 ~5$~6~
the area lmrnediately above the radius 120. The bottom 118 Or the contalner had an average thickness Or 1.6 millimeters (.063 lnch). These dlmensions lndicate that the polymer sheet had excellent drawabllity and resisted "necking"
during processing. For comparison, a 5.8 millimeters (.23 lnch) thlck sheet of unfilled substantlally non-orlented isotactlc polypropylene of the same resln batch was thermo-formed lnto a dish of identical overall dimensions by the same thermoforming process as outllned above. The dlsh bottom was thinned to .53 millimeter (.021 inch) and there-fore was sub~ected to a blaxial draw ratlo Or 3.3:1.
The tensile impact strengths and ultimate tensile .
I strengths of the freezer container Or the invention compare~

~avorably! wlth the tenslle ~mpact strengths and tensile strengths of a condult produced by the method of the invention as seen in ~xample I.
i Tenslle and tensile impact test speclmens were cut from the sheet of the inventlon prior to solid state thermal treatment and also ~rom the bottom Or the khermorormed container and from the bottom Or a contalner made rrom ; unoriented semi-crystaIllne thermoplastic polymer sheet ~prepared from the same polymer by the same solld state thermal treatment process. The results Or the tests are , shown below:
;

.
:
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Average Total Avera~e Vl~imate AverageTenslle Impact Tensile BlaxialStrength Strength Draw Ratio24C(75F) Sheet Or Invention 2.2 psl 2 11,0o0 (Kgf/cm ) 2 773 __ (Ft.lbs/In2) __ 280 (Joules/cm ) -- 5g Dish Bottom from Orlented Sheet 4.1 ~psi) 2 18jl00 --(K~f/cm ) 2 1,305 __ (Ft~lbs/In2) ~~ . 380 tJoules/cm ) -- 80 Dish Bottom from :
, Non-Oriented~Sheet 3.3 (psi) 2 17,400 (Kgf~cm ) 2 1,255 ; 20 (Ft.lbs/In2) (Joules/cm ) .43 I
xample VII -!Another artlcle:;of the invention ls a rerrigerator freezer door llner,~shown at 121 ln FIGURE 10. The llner is ~25 mad:e from a fllled substantially non-oriented thermoplastic homopolymer Profax 68F-5-4 which is a polypropylene homo-polymer containing 40 weight percent calcium carbonate filler and made by the ~ercules Corporation, 910 Market Steet, Wilmington, DE 19899. The properties of the melt l 30 extruded homopolymer at 23C (74F)~are listed below:
1- : Ultlmate Tensile Strength - 274 kilograms force per . square centimeter (3900 pounds per square inch) ~: 35 :~Flexural Modulus: - 23,700 kllograms force per square centlmeter (337,000 pounds per square lnch) ~longation at Fracture - 41%
.

.

I

6 ~

Tenslle Impact Strength - l.9 Joules per centlmeter s~uares (9.2 rOOt pounds per square inch) at 23C (74F) . l.5 Joules per centlmeter squares (7.0 ~oot pounds per square inch) at -45C (-50F) Notched Izod Impact - 0.5 Joules per centimeter (l.0 foot pounds per lnch) at 23F (74F) l.2 Joules per centimeter (0.4 foot pounds per inch) at -45F (-50F) The polymer has a melt.index Or 0.3 to 0.6 at 230C
(446F~ and crystalline melting point Or 168C (335F). A
', billet having an outside diameter of lO.16 centimeters (4.0 inches), an inside dlamter of 6.99 centlmeters (2.75 inches) - and 25.4 centimeters (lO inches) long was hydrostatically extruded at 143.3C t290F) in a large press Or appropriate size by the technique described ln Example I. Dow Corning .
3000 Sllicone rluid manufactured by Dow Corning Corporation, Mldland, MI 48640 was used as the hydrostatic ~luid.
The conduit which had an outside diameter Or 20.8 : , 25 centlmeters (8.2 inches), an inside d~ameter of l9~2 centi~
meters (8.o lnches) and 61 centlmeters (24 inches~ long was . alr cooled as lt was extruded into the extrudate zone. The - : : olrcumferential elongatlon and the axial elongatlon were essentially the same 2.5 or 250 percent which is greater than lO0 percent deformatlon. The condult was slit wlth a heat knife and was heat~flattened as described ln Example VI.
Specimens to determlne the ultimate tenslle strength : .and tensile impact strength were cut from th~ sheet. Since : :the draw ratio is the same in the clrcumrerential and axlal 1 ~5526~

directlons, the average propertles are reported and are the same in either direction. The results of the tests are shown below:
Average Average Average Ultimate Biaxial Tensile Impact Tenslle Draw Strength Strength Ratio _24C(75F) -45C(-50F) i (psi) 2 8goo 2 . 5 (Kgf/cm ) 2 (Ft.lbs/In2) 86.4 63.4 (Joules/cm ) The sheet can be thermoformed by the techniques descrlbed ln Example VI to form the article in FIGURE 10.
A coupon taken from the flange 122 ~ show that the propertles were essentially the same as those Or the sheet rrom which ~t was produced.~ The rlange 122 had a thickness Or 0.254 centlme-ers (0.10 lnohes).

, ' -.

Claims (3)

Claims

1. A hydrostatic extrusion press provided with means for applying extrusion pressure to extrude a generally cylindrical semi-crystalline thermoplastic polymer preform having an outer surface and a bore surface whereby the pre-form is forced to pass in a solid state through an annular orifice defined by the surface of a die section in spaced relationship with the surface of a mandrel-head supported by a mandrel and means for rigidly aligning the press during extrusion, the press comprising:
(a) an outer support means having two ends, (b) a container means aligned within one end of the outer support means and including a shell having an outer surface and an inner surface and two end surfaces, a plug and piston assemblage closing one end of the shell, (c) the die section being a continuous surface with respect to one end of the inner surface of the shell of the container means and including a converging first section, a first generally cylindrical land surface axially aligned with respect to the apparatus, a second generally cylindrical land surface larger in diameter than the first generally cylindrical land surface and parallel thereto and a diverg-ing conical surface connecting the first and second generally cylindrical parallel land surfaces and forming an angle .alpha. of between 15° and 45° with the axis of the apparatus, (d) an extrudate receiving means aligned within the other end of the outer support means and including a shell having an outer surface and an inner surface and two end surfaces, a mandrel having two ends coaxially aligned within the outer shell and generally in spaced relation-ship to the inner surface thereof, (e) a generally conical mandrel-head supported on the other end of the mandrel and in spaced relation with the surfaces of the die section, having a recessed base surface, a generally cylindrical tapering upper portion which forms an angle .beta. of between 20° and 50° with the axis of the apparatus and a generally cylindrical nose portion, (f) an annular orifice formed by surfaces of the mandrel-head and the die section comprised of:
(i) a generally converging conical entrance, (ii) a generally cylindrical sealing zone, (iii) a generally conically shaped expanding zone having a generally converging cross-sectional area and a diametri-cally diverging geometry, (iv) a generally cylindrical sizing zone parallel to the sealing zone and having a smaller cross-sectional area and a median diameter which is at least 100 percent larger than the median diameter of the sealing zone, and (v) transition zones of desired radii and smooth surfaces between any two of the zones whereby the billet is substantially simultaneously expanded circumferentially at least 100 percent and axially elongated at least 50 percent, and (g) sealing means formed by the surfaces of the mandrel-head in contact with the inner surface of the billet and the die surfaces in contact with the outer surface of the billet in the container assembly whereby leakage of fluid is prevented during loading and prior to extrusion and a film of the hydrostatic fluid is formed on the surfaces of the billet during extrusion, (h) a first pressurizing means disposed adjacent one of the two ends of the outer support means and contiguous with the plug and piston assembly and one end surface of the container assembly of (d) whereby pressure for extrusion is applied to the preform, and (i) a second pressurizing means disposed adjacent the opposite end of the outer support means and contiguous with one end of the extrudate receiving means and co-acting with the first pressurizing means to rigidly align the extrusion press.

2. The apparatus as claimed in claim 1 wherein the median diameter of the sizing zone of paragraph f, sub-paragraph (iv) is at least 200 percent larger than the median diameter of the sealing zone.

3. The apparatus as claimed in claim 1 in which the angle .alpha. in paragraph (c) is about 30° and the angle .beta. in paragraph (e) is about 40°.