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WO1997011832A1 - Procede et dispositif pour former un article a partir de materiaux plastiques recycles - Google Patents

Procede et dispositif pour former un article a partir de materiaux plastiques recycles Download PDF

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Publication number
WO1997011832A1
WO1997011832A1 PCT/US1995/012805 US9512805W WO9711832A1 WO 1997011832 A1 WO1997011832 A1 WO 1997011832A1 US 9512805 W US9512805 W US 9512805W WO 9711832 A1 WO9711832 A1 WO 9711832A1
Authority
WO
WIPO (PCT)
Prior art keywords
shell
die
elongated
rotor
forming
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1995/012805
Other languages
English (en)
Inventor
Thomas N. Burrus
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Natural Resource Recovery Inc
Original Assignee
Natural Resource Recovery Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US08/271,954 priority Critical patent/US5534207A/en
Priority claimed from US08/271,954 external-priority patent/US5534207A/en
Application filed by Natural Resource Recovery Inc filed Critical Natural Resource Recovery Inc
Priority to PCT/US1995/012805 priority patent/WO1997011832A1/fr
Priority to AU38898/95A priority patent/AU3889895A/en
Publication of WO1997011832A1 publication Critical patent/WO1997011832A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
    • B29B17/0026—Recovery of plastics or other constituents of waste material containing plastics by agglomeration or compacting
    • B29B17/0042—Recovery of plastics or other constituents of waste material containing plastics by agglomeration or compacting for shaping parts, e.g. multilayered parts with at least one layer containing regenerated plastic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
    • B29C48/11—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels comprising two or more partially or fully enclosed cavities, e.g. honeycomb-shaped
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/375—Plasticisers, homogenisers or feeders comprising two or more stages
    • B29C48/38—Plasticisers, homogenisers or feeders comprising two or more stages using two or more serially arranged screws in the same barrel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/505—Screws
    • B29C48/565—Screws having projections other than the thread, e.g. pins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/78—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling
    • B29C48/793—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling upstream of the plasticising zone, e.g. heating in the hopper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/78—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling
    • B29C48/80—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling at the plasticising zone, e.g. by heating cylinders
    • B29C48/83—Heating or cooling the cylinders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/78—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling
    • B29C48/80—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling at the plasticising zone, e.g. by heating cylinders
    • B29C48/83—Heating or cooling the cylinders
    • B29C48/832—Heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/919—Thermal treatment of the stream of extruded material, e.g. cooling using a bath, e.g. extruding into an open bath to coagulate or cool the material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
    • B29B17/04—Disintegrating plastics, e.g. by milling
    • B29B2017/0424—Specific disintegrating techniques; devices therefor
    • B29B2017/046—Extruder as pressing tool with calibrated die openings for forming and disintegrating pasty or melted material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/16—Cooling
    • B29C2035/1616—Cooling using liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/60—Multitubular or multicompartmented articles, e.g. honeycomb
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/712—Containers; Packaging elements or accessories, Packages
    • B29L2031/7178—Pallets
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • This invention relates generally to a method and apparatus for forming useful articles from recyclable plastic materials, and more particularly to such a method and apparatus is which the method is carried out in a continuous process.
  • extruded articles have been formed of recycled plastic material generally by one of two processes.
  • the first process measured amounts of solid thermoplastic material are reduced and mixed in a Bandbury or other batch- ype mixer.
  • the mixture may also be heated while m the mixer, either to a temperature near or at the melting temperature of the thermoplastic material, and then transferred to an extruder.
  • the premeasured batch of material is then forced through a die by the extruder.
  • This process is inherently a batch process wherein a predetermined amount of thermoplastic material, usually from about 14 kg to 30 kg (250 to 450 lbs) , is processed at a time.
  • the batch delivering a flow of molten plastic material to an extruder, pressurizing the molten material and then forcing the material through an extrusion die
  • the die is shaped to form an elongated continuous member having a cross section consisting of internally disposed interconnected wall surfaces that define elongated cavities withm the continuous member, and is positioned so that the elongated continuous member is discharged from the die in a vertically downward direction
  • the formed elongated continuous member is then immersed m water and then cut into a plurality of transverse sections.
  • an apparatus for simultaneously heating, mixing, melting and conveying recyclable thermoplastic materials includes an elongated shell having a cylindrical interior wall surface that is concentrically positioned with respect to a longitudinal axis extending between ends of the shell, and a rotor rotatably mounted m the shell m coaxial alignment with the longitudinal axis.
  • the rotor has a plurality of elongated members extending radially outwardly toward the interior wall of the shell and are arranged m radially and axially spaced relationship m a spiral pattern around and along the longitudinal axis.
  • the apparatus also includes inlet and outlet ports through the shell, a means for heating the interior wall surface of the shell, and a means for rotating the rotor
  • a die for continuously forming a member having a cross section consisting essentially of a plurality of internal delivering as a continuous molten stream of material to an extruder Furthermore, it is desirable that the rate of delivery of the molten stream to the extruder be selectively variable to match the processing requirements of the extruder. It is also desirable to have an apparatus wherein the recyclable thermoplastic material can be progressively heated simultaneously with mixing and conveying the material from a position at which it is received as solid particles to an output position at which it is an essentially homogeneous flowable mass.
  • a process for forming an article from recyclable plastic material includes dividing the material into a plurality of separate solid particles and then progressively heating the particles concurrently with mixing and forming a substantially homogeneous molten mixture During the steps of heating and mixing, the thermoplastic is continuously conveyed from a position at which the solid particles are received in a substantially continuous flow to a position at which the molten material is discharged in a substantially continuous stream. The molten material is then shaped, cooled, and formed into a solidified article
  • a method for forming an article having an open cell structure m which a network of interconnecting walls define a plurality of openings through the article includes Fig. 4 is an end view of the apparatus embodying the present invention,*
  • Fig. 5 is a perspective view of a shipping pallet produced by the method for forming an article having a multiple open cell structure embodying the present invention,-.
  • Fig. 6 is a side view of a die useful for forming multiple open cell structures according to the method embodying the present invention.
  • Fig. 7 is a sectional view, showing internal forming members in elevation, of the die shown in Fig. 6 that is useful for forming multiple open cell structures according to the method embodying the present invention.
  • FIG. 1 An apparatus 10 for forming an article from recyclable plastic material by the method embodying the present invention is shown in somewhat schematic fashion in Fig. 1, and includes a heated mixer-conveyor 14, to be described later in greater detail, that is connected by way of a manifold 16 to a conventional extruder 18.
  • the extruder 18 is connected through a manifold 20 to an extrusion die 22, which in the preferred embodiment of the present invention is disposed over a water pit 24 so that a continuously formed elongate member extruded through the die 22 is cooled by immersion in a body of water 28 maintained at a selectively variable level withm the water pit 24.
  • the heated mixer-conveyor 14 walls that define internal cavities within the member has a top wall and a plurality of side walls that form and open-ended cavity.
  • a plurality of internal surface forming members are disposed within the cavity and are attached, in spaced relationship to each other, to the top wall of the die.
  • Each of the internal surface forming members has a material shaping surface disposed adjacent the open end of the cavity.
  • Fig. 1 is a schematic representation, in elevational and partially sectional view, of an apparatus for use in forming articles from recyclable plastic materials in accordance with the present invention
  • Fig 2 is an elevational view, with portions of an outer jacket broken away to show interior details, of an apparatus embodying the present invention for simultaneously heating, mixing, melting and conveying recyclable thermoplastic materials;
  • Fig. 2A is an enlarged view of a portion of Fig. 2 showing interior features of the apparatus embodying the present invention in greater detail;
  • Fig. 3 is a cross-sectional view of the apparatus embodying the present invention, taken along the lines 3-3 in Fig. 2; - 8
  • the elongated members 48 could have a square, rectangular, or flat bladed shape, although in carrying out the preferred embodiment of the present invention, a member having a circular cross section, i.e., round pegs, is desired. Also, the elongated members 48 could extend completely beyond both wall of the rotor 44 so that both ends of the member 48 are positioned adjacent the inner wall surface 42.
  • the elongated members 48 are spaced in a spiral pattern on the rotor 44, both around and along the longitudinal axis 40 so that as the rotor 44 turns, material contained withm the annular cavity is squeezed between the pegs 48, thereby imposing significant shear forces on the material.
  • the shear forces cause an intensive mixing of the material withm the annular cavity. If each end of the elongated members 44 extend beyond the outer rotor surface 46, they would, in effect, form a double spiral, or helix, around the rotor 44.
  • the heated mixer- conveyor 14 has a length of about 6.1 m (20 feet)
  • a section of conventional screw conveyor, continuous surface flighting 50 is attached to the rotor 44 adjacent the first end 32 of the shell 30, and extends along the rotor 44 for about 10% of the rotor length, i.e., about 61 cm (2 simultaneously heats, mixes, melts, and conveys recyclable plastic material a continuous flow to the extruder 18.
  • the neated mixer- conveyor 14 has an elongated shell 30 having a first end 32 at which an mlet port 34 forms an opening through the shell 30, and a second end 36 at which a discharge port 38 is provided.
  • the elongated shell 30 is a cylindrical member having a longitudinal axis 40, axially extending between the first and second ends 32,36, and an interior wall surface 42 concentrically disposed radially spaced relationship about the longitudinal axis 40.
  • the heated mixer-conveyor 14 also has rotor 44 that is rotatably mounted withm the shell 30 m coaxial alignment with the longitudinal axis 40 and has a length that extends substantially completely between the first and second ends 32,36 of the shell 30.
  • the rotor 44 is preferably a hollow drum-shaped member having an exterior, or outer, wall surface 46 extending along the length of the rotor 42 that cooperates with the interior wall surface 42 of the snell 30 to define an annular cavity between the shell 30 and the rotor 44.
  • the rotor 44 also has a plurality of elongated members 48 that extend radially outwardly from the outer wall surface 46 of the rotor 44 and terminate at a position adjacent the inner wall surface 42 of the shell 30.
  • the elongated members 48 are round pegs that, as best shown in Fig. 3, also extend through, and are welded to, both walls of the hollow rotor 44 Th s 10
  • the discharge port 38 is essentially an open end of the annular cavity between the interior wall surface 42 of the shell 30 and the exterior surface of the rotor 46 of the rotor 44.
  • the annular opening is obstructed only by a bearing mount 39 which extends inwardly from the shell 30 to rotatably support the rotor 44 at the second end of the shell 30.
  • the discharge port could extend through the bottom of the shell 30 at the second end 36, the same manner as the mlet port 44 extends through the top of the shell 30 at the first end 32. This arrangement would eject the molten material m a vertically downward direction from the annular cavity surrounding the rotor 44.
  • the size, shape and spacing of the elongated members 48 can be varied, as well as the rotational speed of the rotor, and all of these variables will affect the residence, or dwell, time of the material feet) .
  • the continuous surface flighting 50 may extend along from about 10% to about 33% of the length of the rotor 44.
  • the exterior wall surface 46 of the rotor 44 has a diameter of 16.8 cm (6 5/8 mches) and the interior wall surface 42 of the shell 30 has a diameter of 31.1 cm (12 V, mches) , with the pegs 48 extending outwardly to withm about 0.6 cm ⁇ l A mch) of the interior wall surface 42.
  • the pegs 48 each have a diameter of about 1.9 cm ⁇ % mch) and are radially spaced at 30° tervals around the longitudinal axis 40 and at 2.54 cm (1 inch) intervals along the axis.
  • the ratio of the peg diameter to the diameter of the interior wall surface is about 1 to 16. Pegs having a ratio significantly greater than this ratio will increase the rate at which material s axially conveyed from the mlet port 34 to the discharge port 38, thus reducing the time the material is in the mixer and, accordmgly, providing insufficient time for the material to melt. Pegs having a diameter significantly less than the 1 to 16 ratio may bend or break.
  • the pegs 48 thus impose an mterrupted, or noncontmuous, intensive mixing and axial conveying action on material contained withm the annular cavity between the rotor surface 46 and shell surface 42, along about 90% i.e., 5.5 m (18 feet) of the rotor length.
  • the above described radial and axial spacing will produce about 18 "wraps" of pegs 48 around surface 46 of the rotor 44 and will advance the plastic material contained with the annular cavity between the rotor 44 and the shell 30 about 12
  • the supply manifold 58 is formed of three separate sections in which each section has a corresponding mlet port 62 separately connectmg each section with a source of fluid, and a plurality of holes 64 extending through both sides of each section of the supply manifold 58. To assure even distribution of fluid, the total cross-sectional area of all of holes 64 each section should not exceed the cross-sectional area of the manifold section.
  • the dram manifold 60 is formed of three separate sections with each section separately connected to a dram port 64.
  • Each section of the dra manifold 60 has a plurality of holes 68 extending through both sides of each section, with the total nu Der and cross-sectional area of the holes 68 m the dra manifold 60 being substantially equal to that of the holes 64 provided m the supply manifold 58.
  • the dram ports 66 are preferably connected to conduits, not snown, that return the fluid to a reservoir, or sump, from which the fluid is pumped, heated, and recirculated to the fluid inlet ports 62.
  • the fluid provided to each of the mlet ports 62 be separately controllable with respect to flow rate and temperature, to satisfy the particular heat transfer requirements of material contained in a corresponding section of the shell 30.
  • material contained in a corresponding section of the shell 30 For example, solid within the shell.
  • the size of the annular cavity within the shell 30 will affect the amount of material contained therein and thus the amount of heat transfer required to melt the material.
  • the annular cavity has a cross-sectional area, without allowing for the presence of the flighting 50 or the pegs 48, of about 537 cm 2 (83.3 in 2 ) .
  • recyclable thermoplastic polyethylene can be heated to its melting pomt (e.g., typically about 177 °C (350 °F) in about 20 mmutes .
  • the heated mixer-conveyor 14 embodying the present invention also has a means 52 for heating the interior wall surface 42 of the shell 30 so that material contained withm the annular cavity can be heated.
  • the means 52 mcludes a jacket member 54 surrounding the shell 30 and, cooperation with end plates at each end of the mixer-conveyor 14, form a closed annular cavity 56 between the shell 32 and the jacket 54.
  • a plurality of fluid supply manifolds 58 and fluid dram manifolds 60 are advantageously disposed respectively at the bottom and top of the annular cavity 56, This arrangement provides uniform distribution of the heated fluid and prevents the entrapment of air, gases, or cavitation bubbles m the annular cavity 56, assuring that the cavity will be continuously and uniformly charged with hot liquid.
  • each of the manifolds 58,60 are 14
  • a 1.5 kW (2 HP) electric motor having a maximum output speed (with a 60 Hz power supply) of 1740 rpm, is joined to a double reducer, the first providing a reduction of 31 to 1, and the second having a reduction of 25 to 1.
  • -Thus at tne rated motor speed, the final output to the rotor 44 is about 2.25 rpm
  • a conventional frequency modulating motor controller is used to selectively vary the actual output to the rotor from about 0 to about 4 rpm.
  • the manifold 16 joining the above described heated mixer-conveyor 14 with the extruder 18 is preferably insulated or heated by a jacket surrounding the manifold to prevent heat loss.
  • the manifold 20 joining the extruder 18 with the die 22 is also preferably insulated or heated.
  • material is injected through mlets located on four sides of the die 22 by a only a single extruder and common manifold.
  • the fluid is oil which is maintained at a preselected temperatures, ana delivered at preselected rates, by conventional heaters and pumps, not shown.
  • the means 52 for heating the interior wall surface of the shell 30 could be a steam or electrically heated arrangement.
  • the heated mixer-conveyor 14 embodying the present invention also has a means 70 for rotating the rotor 44.
  • the rotation means 70 mcludes a conventional electric motor 72 that is connected through a reduction gear 74 to the rotor 44.
  • the means 70 may mclude a hydraulic or air motor driven by a fluid that is pressure and flow controlled to produce a selected output 16 -
  • the above described die arrangement will form a continuous elongated member 26 having a cross section consisting of internally disposed interconnected wall surfaces that define elongated cavities within the elongated 'member.
  • the interconnected wall surfaces are formed by the spaces, at the bottom face of the die 22, between adjacently disposed internal surface forming members 86.
  • the elongated cavities within the elongated member are determined by the area covered, or blocked, at the bottom face of the die 22, by the presence of the forming members 86.
  • the internal surface forming members 86 may have a cross section other than the rectangular shape shown in Figs. 6 and 7.
  • the individual forming members 86 may have a circular, curvilinear, rhomboid, polygonal or other cross-sectional shape for forming an article to be used for decorative or architectural purposes .
  • the extrusion die 22 is particularly adapted for the formation of elongated members 26 that can be cut into transverse section and used for a shipping pallet 88, as shown in Fig. 7.
  • a substantially vertically downward direction and immersed in water 28 that is contained within a water pit 24 positioned immediately below the bottom face of the die 22.
  • the water 28 cools the material so that it becomes solidified.
  • the water fills the internal cavities
  • an extrusion die 22 is shown that is specifically adapted for formmg the elongated continuous member 26 by the process embodying the present invention.
  • the elongated continuous member 26 is subsequently cut, or sliced, into a number of transverse section, each of which are multiple cell open structures, such as a shipping pallet 76, which is shown m Fig. 7
  • the die 22 has a top wall 78 and four side walls 80 which define a partially enclosed cavity 82 having a generally open bottom face Eacn cf the side walls 80 have an opening 84 centrally formed therethrough providing fluid communication between the pressurized fluid material supply manifold 20 and the die cavity 82.
  • a plurality of internal surface formmg members 86 are disposed with tne die cavity 82, m spaced relationship with each other.
  • Each of the internal surface formmg members 86 have a generally rectangular cross section and are individually attached to the top wall 78 of tne die member. Upon injection of a molten, fluid, material mto the cavity 82, toy way of the openings 84, tne material will flow around each of the internal surface forming members 86 and fill the spaces between adjacently disposed formmg members 86, and between the side wall 80 and the formmg members 86 disposed adjacent the side wall 80.
  • temperature control may be provided by continuously circulating the pit water 28 through a cooling tower or similar device.
  • tne continuously formed elongated member 26 is formed of a material having a neutral buoyancy, i.e., it's specific gravity is about 1.0, so that there are no flotation forces generated by the solidified portion of the member as it is submerged. If the buoyancy of the material is negative, it is desirable to control the water level the pit 24 so that the elongated member 26 does not float, or rise, and distort the unsolidified portion of the member as it is discharged from the die 22.
  • the top surface of the water 28 may be desirable to initially have the top surface of the water 28 at a distance of about 5 cm to 15 cm (2 to 6 mches) below the bottom face of the die 22, and then progressively lower the water level to a distance of about 61 cm to 76 cm (24 to 30 mches) from the bottom face of the die 22 as the first-formed end of elongated member approaches the bottom of the pit 24.
  • an air vent 90 formed through each of the internal surface forming members 86 extends between the bottom face and the top wall 76 of the die 22.
  • an air vent for each of the elongated cavity spaces between the die and the water surface could be provided by a vent line, open to the atmosphere, that extends upwardly from the bottom of the water pit 24 to a position just below each of the internal surface forming members 86 in the die 22.
  • the water pit 24 may advantageously be 9 m (30 feet) or more in depth. It is desirable to have a water level control so that the water 28 in the pit 24 can be maintained at a desirable level during the extrusion forming and water immersion of the elongated member 26. This will generally require that water 28 be withdrawn from the pit 24 as the elongated member 26 is immersed, or submerged, and displaces water.
  • Flow level control devices of this type are well known and generally include a float gauge 92 that delivers a signal to a flow controller 94.
  • the flow controller 94 controls a pump 96 in fluid communication with the water 28 in the pit 24 and an external reservoir 98.
  • the pump 96 is both 20
  • materials incorporated into a specific processing mixture have a melting temperature that is within a range of about 56 °C (100 °F) , and preferably within 28 °C (50 °F) , of each other.
  • other materials such as rubber, sawdust, paper, thermoset plastic, metal chips or turnings, arid organic and inorganic fibers can be added in amounts of up to about 30% of the mixture.
  • the thermoplastic material provides a matrix surrounding, or encapsulating the added material.
  • Such added materials are identified herein, and in the claims, by the term "reinforcing materials" regardless of whether or not the added material alters the strength or other physical properties of the subsequently formed composite thermoplastic article.
  • the solid particles desirably comprising at least 70% thermoplastic material, is fed into the heated mixer- conveyor 14 by way of the inlet port 34 adjacent the first end 32 of the shell 30.
  • the interior of the shell 30 is heated, m the previously described manner, to melt the solid mixture prior to discharge from the discharge port 38 adjacent the second end 36 of the shell 30.
  • thermoplastic material is carried out within the mixer- conveyor 14 in the following manner. Initially, the solid particles are conveyed by the screw conveyor flighting 50 adjacent the inlet port 34. As the material is conveyed toward the second end 36, it is heated by way of heat transfer through the interior wall surface 42 of the shell 30.
  • the interior wall surface 32 if desirably maintained side, and the extrusion die 22, or better, the extruder 18 and the die 22, pivotable between the two pits. This arrangement allows the substantially uninterrupted extrusion of elongated members by simply switching the die 22 between pits.
  • the member when a first formed elongated member 26 reaches it's desired length, the member can be cut, or severed, from the continuous extruded structure, the die 22 pivoted to the second pit, and immersion of a second formed elongated member 26 initiated in the second pit while the first formed member is removed from the first pit.
  • a recyclable thermoplastic material is preferably cut, ground, or otherwise reduced, to a plurality of solid plastic particles having a nominal particle size of about 0.6 cm (1/4 inch) .
  • the source for such materials desirable includes polyethylene milk, motor oil, household detergent and cleaner bottles, and similar containers that are essentially non-biodegradable and present environmental problems with respect to landfill disposal.
  • Other suitable materials include thermoplastic materials in general, and, more particularly, polyethylene, polyurethane, and polyvinyl chloride materials, or mixtures of these materials. If a mixture, it is desirable, to prevent vapor formation of the lower melting components in the mixture, that all of the thermoplastic -22-
  • the molten mixture is compressed and forced from the extruder, through the manifold 20, and into the die cavity 82 of the die 22.
  • a result of material compression by the extruder 18 forces the molten material from the bottom of the die cavity 82.
  • the internal surfaces of the side wall 80 and the wall surface ⁇ of the internal surface forming members 86 control, or form, the shape of the molten mixture as it is discharged, m a vertically downward direction, from the lower face of the die 22.
  • the shaped material Immediately upon the forced discharge from the extrusion die 22, the shaped material will be exposed to air which will cause an immediate temperature drop m at least the exterior surfaces of the material.
  • the molten material in the absence of any adverse forces to the contrary, will retain its initial formed shape, i.e., in this embodiment an elongated member 48 having a cross section consisting of internally disposed interconnected wall surfaces with cellular spaces between the wall surfaces, even though it is not completely solidified.
  • the still somewhat compliant member 48 is immersed in water.
  • the elongated member 26 is submerged in the water pit 24, which if needed as described above, a means for selectively controlling the water level withm the pit 24.
  • the solidified elongated member 26 is severed from the continuous structure discharged from the extrusion die 22, and removed from the pit 24, at, or near, the melting temperature of the material having the highest melting temperature.
  • the interior wall surface should be maintained at the higher temperature, i.e., 177 °C (350 °F) .
  • the material within the shell 30 is conveyed by rotation of the rotor 44.
  • the material advances from the solid flighting section 50 to the interrupted surface conveyance section, i.e., the pegs 48, the pegs, through the imposition of significant shear forces on the mixture, intensively mixes the material concurrently with rotation of rotor 44.
  • the material is heated by way of heat transferred to the mixture through the interior wall 42 of the shell 30.
  • the rotor is rotated at a rate sufficient to thoroughly heat the mixture to its melting temperature by the time it is conveyed to the discharge port 38.
  • the rotor 44 is rotated at a rate of about 1 rpm, and the mixture residence time within the shell 30 is about 20 minutes.
  • the heating, mixing, and conveying are all carried out at, or near, atmospheric pressure.
  • the mixture is discharged through the discharge port 38 with only sufficient force to deliver it through the manifold, or conduit, 16 to the extruder 18.
  • an open cell structure may similarly be formed by the above described process.
  • decorative wall panels, fence sections, and open- grid ground support mats in which the openings may be filled with earth for driveways, sidewalks, and golf cart paths are easily formable by cutting a continuously extruded elongated member mto a plurality of transverse sections.
  • it may be desirable to have other than square, or rectangular, openings The opening shape is easily altered by simply changing tne cross- sectional shape of the interior surface forming members 86 in the die 22.
  • the extruded article could be formed around a solid structural member such as a pipe or rod that is fed through the die simultaneously with extrusion of material through the die.
  • forming methods suitable for use with the heated mixer-conveyor 14 embodying the present invention mclude injection molding, die cast molding, and open mold casting whereupon the member 26 is self supportmg, even wnen laid on it's side, and can be drilled, cut, machined or have other fabrication operations performed on it without adverse affect to the formed shape.
  • each of the transverse sections 88 will have a network of interconnecting walls 98 defining a plurality of open cells 100 extending through the section 88.
  • the above described process is particularly suitable for forming the shipping pallet 88 shown in Fig. 7.
  • the pallet may be advantageously formed of a mixture of thermoplastic polyethylene and scrap rubber, with the polyethylene comprising from 70% to 90% of the mixture
  • the overall length of the continuously extruded elongated member 26 is desirably about 7.6 m (25 feet) with transverse dimensions of about 91 cm (36 inches) by 102 cm (40 mches) .
  • the interconnecting side and interior walls each have a thickness of about 1.3 cm (1/2 inch) , wmch, m that it is the minimum-clearance dimension with the formmg die 22, it controls the particle size of non- meltmg reinforcing particles in the thermoplastic matrix.
  • the scrap rubber particles be no more than about 0.6 cm (1/4 mch) is size.
  • the solidified elongated member 26 is cut mto 26
  • Articles produced by the method and apparatus embodying the present invention are also less costly to manufacture because they provide for the continuous extrusion of members that can subsequently be easily fabricated.
  • the method provides an economical way to reprocess environmentally undesirable scrap materials, such as plastic and rubber materials, mto useful and beneficial articles.
  • the present invention enables the economical formation, by continuous extrusion, of articles having an internal open-cell structure.
  • the method embodying the present invention for forming articles from recyclable plastic materials provides both economic and manufacturing advantages over currently available methods.
  • the method through the use of a heated mixer-conveyor 14, enables thermoplastic materials to be continuously progressively heated simultaneously with mixing and conveying, independently of an extruder.
  • the material when delivered to an extruder 18 is ready for injection into a mold or through a die 22.
  • This enables the extruder 18 to deliver material to the mold or die 22 at a higher rate because heating and mixing of the material has already been performed.
  • a smaller, less capital intensive, extruder can be used in carrying out the method embodying the present invention than has been required to achieve the same production rates heretofore.
  • the heated mixer conveyor 14 embodying the present invention alleviates much of the wear and damage imposed on an extruder through the presence of solid particles in a mixture of solid material in an extruder 18.
  • the present invention by providing a molten matrix for such particles prior to delivery to the extruder 18 significantly reduces the possibility of damage to the closely mated screw and wall surfaces of the extruder 18. This not only reduces maintenance and repair costs, but also reduces down-time attributable to maintenance and repair problems and prolongs the service life of an expensive machine. - 28
  • the method of Claim 1 including the step of mixing a plurality of reinforcing particles with said solid particles prior to progressively heating said solid particles, and the step of conveying said thermoplastic material mcludes conveying an intermixture of the reinforcing particles and the thermoplastic material, wherein said reinforcing particles are preferably rubber materials, thermoset plastic materials or fibers having a melting temperature greater than the melting temperature of said thermoplastic material.
  • a method for formmg an article having a multiple open cell structure in which a network of interconnecting walls defme a plurality of openings througn said article including* delivering a flow of molten plastic material to an extruder; pressurizing said molten plastic material; forcing said material, under pressure, through an extrusion die, said die bemg shaped to form an elongated continuous member having a cross section consisting of internally disposed interconnected wall surfaces defining elongated cavities withm said continuous member, and said die being positioned such that said elongated continuous member is discharged from said die in a vertically downward direction; immersing said elongated continuous member m water; cooling said

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

Abstract

Selon un procédé permettant de former un article à partir de matériaux plastiques recyclés, on chauffe progressivement des particules solides thermoplastiques et, simultanément, on les mélange, on les fait fondre et on les transporte, avant de faire passer le matériau fondu dans une extrudeuse (18). Ce procédé convient pour l'extrusion continue d'éléments allongés (26) qui comportent à l'intérieur une pluralité de parois internes définissant des cavités allongées. Le dispositif (10) conforme à l'invention comprend un mélangeur-transporteur (14) chauffé qui simultanément chauffe, fait fondre, mélange et transporte le matériau thermoplastique depuis un orifice d'entrée (34), au niveau duquel le matériau est amené sous forme de particules solides, à un orifice de décharge (38), au niveau duquel le matériau se trouve dans un état sensiblement liquide. L'invention concerne également une filière (22) conçue pour l'extrusion continue d'un élément allongé (26) comportant des parois internes, celles-ci étant formées par des surfaces disposées dans la cavité (82) de la filière.
PCT/US1995/012805 1994-07-08 1995-09-29 Procede et dispositif pour former un article a partir de materiaux plastiques recycles Ceased WO1997011832A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US08/271,954 US5534207A (en) 1994-07-08 1994-07-08 Method and apparatus for forming an article from recyclable plastic materials
PCT/US1995/012805 WO1997011832A1 (fr) 1994-07-08 1995-09-29 Procede et dispositif pour former un article a partir de materiaux plastiques recycles
AU38898/95A AU3889895A (en) 1994-07-08 1995-09-29 Method and apparatus forming from recyclable plastic

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US08/271,954 US5534207A (en) 1994-07-08 1994-07-08 Method and apparatus for forming an article from recyclable plastic materials
PCT/US1995/012805 WO1997011832A1 (fr) 1994-07-08 1995-09-29 Procede et dispositif pour former un article a partir de materiaux plastiques recycles

Publications (1)

Publication Number Publication Date
WO1997011832A1 true WO1997011832A1 (fr) 1997-04-03

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4067826A (en) * 1974-07-31 1978-01-10 Guy Emery Recovery of mixed plastic materials
US4138534A (en) * 1977-02-07 1979-02-06 Lifetime Foam Products, Inc. Production of structural members from reclaimed polyolefins
US4968463A (en) * 1987-11-06 1990-11-06 Otvd (Omnium De Traitements Et De Valorisation Des Dechets) Process for making molded or extruded objects from waste containing plastic materials
US5312573A (en) * 1991-08-01 1994-05-17 Renewed Materials Industries, Inc. Process for extruding mixtures of thermoplastic and thermoset materials

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4067826A (en) * 1974-07-31 1978-01-10 Guy Emery Recovery of mixed plastic materials
US4138534A (en) * 1977-02-07 1979-02-06 Lifetime Foam Products, Inc. Production of structural members from reclaimed polyolefins
US4968463A (en) * 1987-11-06 1990-11-06 Otvd (Omnium De Traitements Et De Valorisation Des Dechets) Process for making molded or extruded objects from waste containing plastic materials
US5312573A (en) * 1991-08-01 1994-05-17 Renewed Materials Industries, Inc. Process for extruding mixtures of thermoplastic and thermoset materials

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