WO2000023250A1 - Procede de fabrication de films - Google Patents

Procede de fabrication de films Download PDF

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Publication number
WO2000023250A1
WO2000023250A1 PCT/GB1999/003486 GB9903486W WO0023250A1 WO 2000023250 A1 WO2000023250 A1 WO 2000023250A1 GB 9903486 W GB9903486 W GB 9903486W WO 0023250 A1 WO0023250 A1 WO 0023250A1
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WO
WIPO (PCT)
Prior art keywords
conduit
liquid
volume
die
outlet
Prior art date
Application number
PCT/GB1999/003486
Other languages
English (en)
Inventor
Jos Bloemen
Dirk Hellemans
Stefan Dominic Beckers
Original Assignee
Devro Plc
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
Application filed by Devro Plc filed Critical Devro Plc
Priority to AU63534/99A priority Critical patent/AU6353499A/en
Publication of WO2000023250A1 publication Critical patent/WO2000023250A1/fr

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Classifications

    • 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
    • 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
    • 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
    • B29C48/10—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels flexible, e.g. blown foils
    • 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
    • B29C48/92—Measuring, controlling or regulating
    • 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
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92009—Measured parameter
    • B29C2948/92114—Dimensions
    • B29C2948/92123—Diameter or circumference
    • 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
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92323—Location or phase of measurement
    • B29C2948/92428—Calibration, after-treatment, or cooling zone
    • 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
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92323—Location or phase of measurement
    • B29C2948/92447—Moulded article
    • 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
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92504—Controlled parameter
    • B29C2948/92514—Pressure
    • 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
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92504—Controlled parameter
    • B29C2948/92609—Dimensions
    • B29C2948/92619—Diameter or circumference
    • 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
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92504—Controlled parameter
    • B29C2948/92609—Dimensions
    • B29C2948/92657—Volume or quantity
    • 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
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92819—Location or phase of control
    • B29C2948/92857—Extrusion unit
    • B29C2948/92876—Feeding, melting, plasticising or pumping zones, e.g. the melt itself
    • 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
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92819—Location or phase of control
    • B29C2948/92923—Calibration, after-treatment or cooling zone
    • 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
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92819—Location or phase of control
    • B29C2948/92971—Fluids, e.g. for temperature control or of environment

Definitions

  • the present invention relates to a method of, and apparatus for, controlling the diameter of a blown film during manufacture.
  • the present invention relates to a method of controlling the diameter of a cellulose blown tubular film during manufacture and apparatus for controlling the diameter of a cellulose blown tubular film.
  • Cellulose tubular films are used in the food industry for casings primarily for meat products such as sausages.
  • cellulose tubular films such as cellulose casings have been made for many years according to the viscose process. This process is more than a century old, and has been used commercially for about ninety five years.
  • other articles such as flat cellophane film, tyre cord rayon and fibre rayon have been produced in large quantities using this process.
  • cellulose is typically taken from one source, derivatised, then solubilised and then articles are formed by extruding the solubilised derivatised cellulose into fibre sheets or tubes. Re-forming the cellulose is carried out via a process called regeneration.
  • the basic raw material for cellulose casings is cellulose pulp which usually comes from wood pulp.
  • Other major raw materials used in the viscose process are carbon disulphide, sodium hydroxide, sulphuric acid and a plasticising agent.
  • the viscose preparation process is a complicated process and usually requires multiple separate steps before the solubilised cellulose is ready to be used in the manufacture of a cellulose product.
  • a new cellulose process which has become popular and is replacing the viscose process involves the creation of a special type of extrusion solution called "dope" instead of viscose.
  • Dope is a mixture of cellulose dissolved in a tertiary amine-oxide solvent which is commonly known as N MO (N-Methyl Morpholine N-Oxide) .
  • N MO N-Methyl Morpholine N-Oxide
  • a second advantage of the amine-oxide process is that, once solubilised, the cellulose can be precipitated from the dope as a regenerated product by contacting the dope with a precipitation liquid, typically water, which is a non-solvent for cellulose but a solvent for NMMO.
  • a precipitation liquid typically water, which is a non-solvent for cellulose but a solvent for NMMO.
  • a further advantage is that the process time between steeping and extrusion is significantly reduced.
  • a yet further advantage is that much less raw materials are required and excess water, used in the process in the precipitation stage, can be recycled.
  • the cellulose solution or dope is passed through an extrusion die which includes an annular-shaped exit nozzle for producing tubular cellulose film.
  • NMMO-cellulose dope is fed to an extruder 20 at an extrusion temperature of about 100°C, and transported through a filter screen (not shown) to a gear metering pump section shown generally at 22.
  • the metering pump section 22 feeds an extrusion die 24, which has a die outlet in the shape of an annular nozzle which is directed downwardly to face a precipitation bath shown generally at 26.
  • Bath 26 is separated from die 24 by an air gap.
  • Tubular cellulose casing 25 is precipitated in the bath 26 which contains a precipitation liquid (usually water, at a temperature in a range of 10 to 20°C) .
  • a volume of water is provided to the interior of the tubular cellulose casing via the feed pump supply means and conduit shown generally as 28, which precipitates the cellulose casing from its interior surface .
  • Excess water-NMMO solution is withdrawn from the interior of the casing via a conduit 30 and pump.
  • the part 27 of the casing 25 which lies in the air gap between the bath 26 and the extrusion die 24 is pressurised internally with air at a pressure of between 0.2 to 2 mbar above atmospheric pressure, supplied via pressure control means shown generally at 32.
  • the main parameters which affect the diameter of the cellulose blown film are the level of the liquid inside the casing (relative to the level of the liquid in the precipitation bath 26) , and the air pressure in the part 27 of the casing 25 in the air gap.
  • One of the problems with the existing method of manufacturing blown tubular film in particular cellulose blown tubular film which uses dope in the manufacture of the film, is in controlling the diameter of the blown tubular film during manufacture. Small variations in the liquid level inside the casing and/or the pressure in the part of the product in the air gap have been found to cause unacceptable variations in the diameter of the finished product.
  • a method of controlling the diameter of a blown tubular film during manufacture thereof, in which a tubular film is extruded from an extrusion die comprising the steps of: locating the extrusion die above a liquid bath having a liquid level therein, to provide a gap between an outlet of the die and the surface of a liquid in the liquid bath; extruding a blown tubular film into the liquid bath from the die outlet, precipitating the blown tubular film in said liquid bath and compressing the tubular film into a flat film at one end, to define a tube extending from the die with a volume of liquid and a volume of gas above the liquid; and controlling the tube extrusion diameter by varying the pressure of the interior volume of the tube between the extrusion die outlet and the liquid precipitation bath.
  • the tube is inflated or blown up in the air gap by means of an air pressure control system.
  • an air pressure control system the control of the liquid level on the interior of the extruded tube may be improved without influencing the control of the diameter of the extruded tube, as was the case using the prior art process of Figure 1.
  • the step of controlling the tube extrusion diameter further comprises separating the gas volume into a first sub-volume and a second sub-volume, by extending a first conduit from the die through the gas volume and into the volume of liquid within the tubular film, the first sub-volume being located exteriorly of the conduit and being connected to a pressure control device during manufacture of the blown tubular film, and the second sub-volume being located interiorly of the first conduit and being open to the atmosphere during manufacture of the tubular film by means of a vent tube.
  • the level of liquid on the interior of the extruded tube can be adjusted manually by immersing a liquid return pipe into the internal liquid bubble.
  • a specially shaped suction inlet of the liquid return pipe defines the level at which liquid is evacuated from the interior of the tube.
  • the step of evacuating liquid from the interior of the tube comprises locating a second conduit (said liquid return pipe) within said first conduit, said second conduit having a specially shaped inlet adjacent the level of liquid within the tube.
  • the inlet of the second conduit means is associated with a system for evacuating liquid via said second conduit, such as, for example, a pump or a vacuum system.
  • the second conduit is connected to the first conduit and both conduits are moveable in a direction substantially perpendicular to the surface of the liquid in the liquid precipitation bath, so as to vary the height of the liquid between the extrusion die outlet and the internal liquid surface .
  • the internal liquid level may be fixed and thus not influence the extrusion tube diameter.
  • the extrusion tube diameter may be adjusted automatically by means of controlling the air pressure to the external bubble.
  • An air pressure control device may blow up the extruded tube in the air gap to define the tube extrusion diameter.
  • apparatus for controlling the diameter of a blown film comprising: an extrusion die having a die outlet for extruding a tube of dope; a precipitation bath for precipitating the tube of dope extruded from the die; compressing roller means for flattening the tube to define a tubular volume between the compressing roller means and the die outlet, and the tubular volume comprising a volume of liquid and a volume of air located above said volume of liquid; liquid level control means for controlling the level of liquid within said volume of liquid, said liquid level control means comprising an inlet conduit for supplying liquid to said volume of liquid; an outlet conduit for evacuating liquid from said volume of liquid; and an isolating conduit for isolating the outlet conduit from the volume of air, so as to create a liquid level in the isolating conduit.
  • the pressure of air in the air volume may correspond to the air pressure generated by the air pressure control device, and the diameter of the tube may correspond to the pressure of air in the air volume.
  • said second, outlet conduit is fixed to said isolating, first conduit and both are moveable in a direction substantially parallel to the longitudinal axis of the conduits, enabling the height of the outlet conduit in relation to a surface of liquid in the volume of liquid in the bubble to be varied.
  • the isolating conduit is moveable between a first, out of use position where the outlet conduit resides above the surface of the liquid in the volume of liquid, and a second, in use position where the isolation conduit penetrates the surface of the liquid in the volume of liquid.
  • the isolating conduit is moveable in a direction substantially parallel to the longitudinal axis of the isolating conduit to enable the conduit to move from the first, out of use position to the second, in use position.
  • an extrusion die for use in controlling the diameter of a blown film, the die comprising: an extrusion die housing having a die inlet for injecting material into the extrusion die, and a die outlet for extruding a tube of the injected material; a generally cylindrical passage passing longitudinally through the die housing and accommodating a die plug, wherein the die outlet is formed at a lower end of said passage, and wherein the die inlet passes through the die housing and into the passage; wherein the die plug has a generally cylindrical bore and a first isolating conduit passes longitudinally through the cylindrical bore disposed substantially parallel to the longitudinal axis of the bore and is moveable in the direction of said axis; the first conduit having a first, open outlet lowermost in the conduit, and a second, upper outlet which includes a valve means actuable between an open and closed position, the open position being connected to an air pressure control device and the closed position being isolated from the air pressure control device; a second, inlet conduit passing
  • the second conduit which may supply the fresh inside precipitation liquid (water) , extends the first isolating conduit, whereas the third conduit, used for inside liquid return, may not extend the isolating conduit, and the fourth conduit, used to provide vent air, may not extend the third conduit and is preferably fixed to the isolating baffle.
  • a method of controlling the diameter of a blown tubular film during manufacture thereof, in which a tubular film is extruded from an extrusion die comprising the steps of : locating the extrusion die above a liquid bath having a liquid level therein, to provide a gap between an outlet of the die and the surface of a liquid in the liquid bath; extruding a blown tubular film into the liquid bath from the die outlet, precipitating the blown tubular film in said liquid bath and compressing the tubular film into a flat film at one end, to define a tube extending from the die with a volume of liquid and a volume of gas above the liquid; and controlling the pressure in the volume of gas above the liquid by varying the level of liquid between the interior of the tube and the extrusion die relative to the level of liquid in the liquid bath at the exterior of the tube, which in turn varies the diameter of the blown tubular film.
  • FIG 1 schematically illustrates prior art apparatus as previously explained
  • Figure 2 is a schematic view of part of a cellulose blown tubular film manufacturing apparatus in accordance with an embodiment of the present invention
  • Figure 3A is an enlarged cross-sectional view of part of the apparatus of Figure 2 showing a first embodiment of the present invention in an initial phase of manufacture of a blown tubular film
  • Figure 3B is a view of the apparatus of Figure 3A in a later phase of manufacture of a blown tubular film in which film of a particular diameter is being manufactured
  • Figure 3C is a cross-sectional view of a detail in Figure 3B
  • Figure 4 is an enlarged cross-sectional view of part of the apparatus of Figure 2 showing a second embodiment of the present invention in a phase of manufacture of a blown tubular film.
  • the blown tubular film which is being manufactured is a cellulose film, manufactured using tertiary amine-oxide solvent technology.
  • the cellulose/NMMO dope solution is fed to an extruder 34 in the melt phase and at an extrusion temperature of about 100°C.
  • the solution is transported through a filter screen to a gear metering pump section 36, which feeds an extrusion die 38.
  • the extrusion die 38 which is described in more detail below, has a circular die outlet (not shown in Figure 2 in the interests of clarity) which is located above the surface 40 of liquid 42 in a liquid bath 44.
  • Cellulose/NMMO dope solution is fed into the die 38 via extruder die inlet 46, from where the dope passes through the extruder outlet (not shown) for exiting the extruder die.
  • the liquid bath 44 is separated from the extruder die 38 via an air gap.
  • Tubular cellulose casing is precipitated in the water bath and the casing is fed through a pair of bottom squeeze or nip rolls 48, before being fed over additional rollers 50 and exiting the precipitation bath 44.
  • the squeezed casing traverses a metering station 51 where the product diameter is effectively measured and is passed through further washing baths 52 and 54 to remove the remaining NMMO and is then post-treated with a plasticising agent (not shown in the interests of clarity) .
  • the precipitation liquid 42 in liquid bath 44 is usually water at a temperature in the range of 10 to 20°C.
  • a volume of water is also provided into the interior of the tubular cellulose product 56 to precipitate the product from its interior surface.
  • the extruder die 38 has a die inlet 46, and has walls 47 defining a generally cylindrical conduit 60 passing longitudinally through the die 38, and a circular die outlet shown generally at 58.
  • a hollow die plug 63 is provided, which is disposed within the longitudinal conduit 60, the plug 63 having a generally cylindrical bore 65 which passes longitudinally through the plug 63.
  • the outer surface 62 of the die plug 63 is profiled (for example as at 68) within the longitudinal conduit 60 so as to define, with walls 47, an annular flow path 64 to the die outlet 58.
  • a dip pipe 76 is provided, which slidingly extends through bore 65 of plug 63.
  • the dip pipe 76 at its upper end includes valve means 92, which enable the dip pipe 76 to be opened or closed for coupling to a pressure control device, as will be described below in more detail.
  • the tubular dip pipe 76 has a lower free end or outlet
  • a liquid supply conduit 70 is provided, which extends through an upper opening 80 of dip pipe 76 and into the liquid 42 in liquid bath 44.
  • a combined liquid "return/overpressure" supply conduit 72 is provided within dip pipe 76 and has an inlet or free end 74 disposed above the lower end 78 of dip pipe 76.
  • the conduit 72 is connected to the dip pipe 76 by means of a sealing baffle 100.
  • a vent air conduit 98 is provided, which passes through dip pipe 76 to an inlet or free end 99 disposed above the lower end of conduit 74.
  • the uppermost part of the vent air pipe 98 is provided with a valve which may be opened or closed to connect or disconnect the internal volume inside the isolating conduit 76 to or from the atmosphere.
  • All three pipes 70,72 and 98 are connected by means of the internal sealing baffle 100 to the dip pipe 76.
  • the dip pipe 76 is slidable within the internal bore 65 of the extrusion die in a direction parallel to the longitudinal axis of bore 65 and substantially perpendicular to the surface 40 of the liquid 42, so that the height of inlet 74 above surface 40 can be varied.
  • the inlet 74 is specially shaped, and includes a small diameter (0.8 mm) hole 97 to supply vent air to the interior of pipe 72. Surprisingly, it has been found that the liquid is sucked through the lowermost end of pipe 74 without creating a vortex.
  • the liquid level inside dip pipe 76 equilibrates at the height position of the small diameter hole 97. Vent air is sucked in through the small diameter hole 97 and mixes with the evacuated liquid.
  • the small diameter hole 97 thus prevents vent air from being sucked into the liquid surface which would create an undesirable vortex of air flowing to the inlet of the lowermost part of pipe 74. Without the small diameter hole 97 it has been noted that an unstable dynamic vortex stream is created, causing level fluctuations which ultimately result in tubular casing size variations. These undesirable diameter fluctuations are minimised by using the specially shaped pipe 74 including the small vent air hole 97, as described above.
  • the liquid supply conduit 70, liquid return conduit 72 and vent air conduit 98 pass through upper openings of dip pipe 76, and suitable sealing means are provided at 80 for sealing the internal volume of dip pipe 76 from the atmosphere.
  • suitable sealing means are provided at 80 for sealing the internal volume of dip pipe 76 from the atmosphere.
  • the internal volume of dip pipe 76 is also sealed from the internal gas bubble by the baffle 100.
  • cellulose/NNMO dope solution 82 is injected into extrusion die 38 via die inlet 46, from where the dope 82 flows to the die outlet 58.
  • the dope 82 is formed into a tubular film 84 as it passes through the extrusion die 38 and exits the die via the die outlet 58 in a way which is known in the art.
  • the die outlet 58 is spaced from the surface of the liquid 42 in the liquid bath 44 such that there is an air gap, shown generally at 86, between the die outlet 58 and the liquid surface 40.
  • the tubular film 84 isolates a portion 88 of the air gap 86 within the tube 84.
  • the cellulose in the tubular film 84 precipitates from the dope to form the cellulose tubular film which travels through the precipitation bath 44 towards niprolls 48, where the film is squeezed flat and driven from the liquid bath 44 via additional rollers 50 shown in Figure 2.
  • liquid supply conduit 70 When the cellulose tubular film 84 engages the niprolls 48, fresh precipitation liquid is passed into the inside of the tubular film 84 via liquid supply conduit 70.
  • the liquid supplied via liquid supply conduit 70 is water, to facilitate precipitation of cellulose from the inner surface of the tubular film 84 entering liquid 42.
  • the liquid passing into tubular film 84 causes the level of the liquid 90 within tubular film 84 to rise relative to the level of liquid 42 in the liquid bath 44.
  • the dip pipe 76 which is initially in an out of use, retracted position (as shown in Figure 3A) is then lowered to the position shown in Figure 3B, such that the outlet 78 of the dip pipe 76 penetrates the surface of the liquid 90 within the tubular film 84.
  • the dip pipe 76 isolates a first volume 89 of air between the inner surface of the tubular film 84 and the outer surface of the dip pipe 76, and a second volume 91 of air within the dip pipe itself.
  • the first volume 89 of air is now connected to the internal volume of the dip pipe 76, through holes 93 on the circumference of dip pipe 76.
  • the internal volume of dip pipe 76 is now connected via the open valve 92 with the pressure control device.
  • valve 92 is closed, but when dip pipe 76 penetrates the surface of the liquid 90 in tubular film 84, the valve means 92 is opened and connected to the pressure control device.
  • liquid water
  • the volume of the liquid 90 (and therefore the height of liquid 90) in the tubular film 84 continues to increase, and the liquid rises within dip pipe 76.
  • This increase pressurises first air volume 89, which causes the diameter of the tubular film 84 to increase, but because second air volume 91 is open to atmosphere via the open valve at the uppermost part of vent air conduit 98, a liquid column is formed within dip pipe 76.
  • the height of the liquid column 94 relative to the liquid 95 in the internal liquid bubble in liquid bath 44 continues to rise until the water reaches the small diameter hole 97 of liquid return conduit 72.
  • the conduit 72 during this phase of operation is connected at its upper end to a suitable vacuum pump or liquid pump such as a vacuum line or a peristaltic pump (not shown) , creating a vacuum within conduit 72, and drawing vent air and liquid out of the interior of volume 91.
  • a suitable vacuum pump or liquid pump such as a vacuum line or a peristaltic pump (not shown) , creating a vacuum within conduit 72, and drawing vent air and liquid out of the interior of volume 91.
  • the height of the column 94 remains constant so that the volume of liquid drawn off via conduit 72 is equivalent to the volume of liquid supplied to the tubular film 84 via liquid supply conduit 70.
  • the arrangement therefore acts in a similar way to a U-tube manometer, in that the height of the liquid level 95 relative to the height of level 94 is determined by the pressure of air in the first volume 89.
  • the air pressure in first volume 89 by means of lowering the air pressure set point, the liquid level 95 will rise relative to the liquid level 94 because the air pressure drops in the first volume 89.
  • the tubular extrusion diameter decreases.
  • a higher air pressure in the first volume 89 increases the diameter of the extruded tube .
  • the diameter or "lay flat width" of the extruded tube is measured close to the extrusion die and can be monitored and controlled using, for example, a suitable feedback control system connected to the air pressure control device .
  • the liquid withdrawn from tubular film 84 via conduit 72 is a mixture of water/NMMO, which is recirculated to separate the NMMO from the water.
  • the conduit 72 removes air in addition to the water/NMMO such that there is a mixture of air and water/NMMO in the conduit 72, of the order of 50 percent by volume of air and 50 percent by volume of water/NMMO. This is achieved by changing the diameter of small hole 97 relative to the end opening of conduit 72.
  • the inside diameters of conduits 70, 72 and 74 need to be dimensioned with respect to liquid flow properties (see Figure 3C) , such that fluctuations in air pressure inside the air volume 91, which would reflect in consequential air pressure variations in first air volume 89 and ultimately cause variations in the diameter of the tubular film 84, are minimised.
  • the dip pipe 76 lower end portion may be extended within the liquid bath 44 down to a position close to the niprolls 48, such that the dip pipe 76 acts as a "wave barrier", to minimise pressure fluctuations affecting the pressure of air in the first pressured volume 89.
  • the air pressure control device has to deliver an output pressure as constant as possible because this pressure is directly connected to the air volume 89 and will determine the final tube diameter. Any fluctuation of the output pressure of the air pressure control device is undesirable and must be corrected. For this reason it is important that, when using a closed loop diameter control system, the air pressure control loop is perfectly tuned to avoid sinusoidal output pressure changes which would reflect in sinusoidal size variations of the extruded tube.
  • liquid supply conduit 70 may be provided with a series of holes (not shown) passing radially through the walls of the supply conduit 70, and distributed axially along the length of the portion of conduit 70 disposed within the tubular casing 84, such that liquid can be supplied to the tubular film 84 along the majority of its immersed length. Also, it has been found that the liquid 90 in tubular film 84, during manufacture of the film, often settles into a 2- phase liquid system of NMMO and water, with the NMMO (of higher density) lying below the water.
  • FIG 4 there is shown a further embodiment of the present invention incorporating an extruder die 108 for use in the method of controlling the diameter of a blown tubular film as described above with reference to Figures 2 to 3B.
  • Figure 4 corresponds to the step of the method described above with reference to Figure 3B.
  • the extruder die 108 includes a die plug 110 having a spiral channel 112 formed in the outer surface 114 of die plug 110, the spiral channel 112 acting to guide material injected into die 108 via die inlet 116 to flow in a defined path from the die inlet 116 to the die outlet shown generally at 118.
  • the advantage of the arrangement of the extruder die 108 of Figure 4 is that a stream of homogenous dope is provided to the outlet 118, avoiding seams in the final blown film.
  • the main advantage of the method and apparatus described above is that accurate inside level control is possible which is reflected in a significant reduction in size variations of the extruded tube.
  • a further advantage is that the refreshment flow of the inside precipitation liquid can be varied without consequently causing variations in the diameter of the blown tubular film.
  • the dip pipe may be constructed of a thermal insulating material such as a thermo-plastics material to prevent heating of the liquid passing through or residing within the extrusion die, which also provides a more consistent temperature distribution of dope within the die .
  • a thermal insulating material such as a thermo-plastics material to prevent heating of the liquid passing through or residing within the extrusion die, which also provides a more consistent temperature distribution of dope within the die .

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Shaping By String And By Release Of Stress In Plastics And The Like (AREA)

Abstract

Cette invention se rapporte à un procédé et à un appareil servant à réguler le diamètre d'un film soufflé, généralement un film soufflé en cellulose (84), pendant sa fabrication. A cet effet, une solution à filer en cellulose/NMMO (82) est injectée dans une extrudeuse (38) pour permettre la précipitation d'un film tubulaire en cellulose (84) dans un bain de précipitation (44). On prévoit un tube plongeur (76), un conduit d'amenée de liquide (70), un conduite de retour de liquide (72) et un conduit d'évent (98), qui sont mobiles dans une direction essentiellement parallèle à leurs axes longitudinaux à travers un passage interne (65) d'un bouchon (63) de l'extrudeuse. Un volume (89) d'air est isolé par le tube plongeur (76) entre une surface interne du film (84) et une surface externe du tube plongeur (76) et un second volume (91) d'air est isolé à l'intérieur du tube plongeur (76) lui-même. Pendant l'utilisation, un niveau de liquide (94) dans le volume (91) est déterminé par la pression de l'air dans le volume (89). Les variations de pression de l'air contenu dans le volume (89) permettent ainsi de faire varier et de réguler le diamètre du filmubulaire en cellulose soufflé.
PCT/GB1999/003486 1998-10-21 1999-10-21 Procede de fabrication de films WO2000023250A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU63534/99A AU6353499A (en) 1998-10-21 1999-10-21 Film manufacturing method

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9823086.5A GB9823086D0 (en) 1998-10-21 1998-10-21 Film manufacturing method
GB9823086.5 1998-10-21

Publications (1)

Publication Number Publication Date
WO2000023250A1 true WO2000023250A1 (fr) 2000-04-27

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AU (1) AU6353499A (fr)
GB (1) GB9823086D0 (fr)
WO (1) WO2000023250A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1174243A1 (fr) * 2000-07-22 2002-01-23 Kalle GmbH & Co. KG Procédé et dispositif de fabrication d'une feuille tubulaire sans soudure et feuille tubulaire sans soudure
KR100384799B1 (ko) * 2000-10-30 2003-05-22 주식회사 무 등 열가소성 수지의 튜브 압출장치
CN101844395A (zh) * 2010-06-12 2010-09-29 天津科技大学 制备再生纤维素筒状膜的装置
WO2014165881A1 (fr) 2013-04-10 2014-10-16 Lenzing Ag Film polysaccharidique et son procédé de fabrication
US10030323B2 (en) 2013-04-05 2018-07-24 Lenzing Aktiengesellschaft Method for the production of polysaccharide fibers with an increased fibrillation tendency
US10196758B2 (en) 2013-06-18 2019-02-05 Lenzing Aktiengesellschaft Polysaccharide fibers and method for producing same
US10221502B2 (en) 2013-04-05 2019-03-05 Lenzing Aktiengesellschaft Polysaccharide fibers and method for the production thereof
US10220111B2 (en) 2013-06-17 2019-03-05 Lenzing Aktiengesellschaft Highly absorbent polysaccharide fiber and use thereof

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FR815744A (fr) * 1936-01-09 1937-07-21 Naturin G M B H Procédé de fabrication de corps moulés en partant de matières fibreuses animales comme matières de départ
JPS61152426A (ja) * 1984-12-27 1986-07-11 Tomy Kikai Kogyo Kk インフレ−シヨンフイルム成形機における自動圧力調整装置
EP0662283A2 (fr) * 1994-01-10 1995-07-12 Viskase Corporation Procédé de préparation d'enveloppes en cellules pour aliments
WO1995035340A1 (fr) * 1994-06-20 1995-12-28 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Feuille soufflee en cellulose
EP0692194A1 (fr) * 1994-07-15 1996-01-17 Viskase Corporation Enveloppe cellulosique pour aliments
WO1998042492A2 (fr) * 1997-03-21 1998-10-01 Lenzing Aktiengesellschaft Dispositif et procede pour produire des films tubulaires cellulosiques
EP0899076A1 (fr) * 1997-08-27 1999-03-03 Kalle Nalo GmbH & Co. KG Procédé et dispositif pour la fabrication d'un produit tubulaire par extrusion à base de cellulose et sans soudure

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FR815744A (fr) * 1936-01-09 1937-07-21 Naturin G M B H Procédé de fabrication de corps moulés en partant de matières fibreuses animales comme matières de départ
JPS61152426A (ja) * 1984-12-27 1986-07-11 Tomy Kikai Kogyo Kk インフレ−シヨンフイルム成形機における自動圧力調整装置
EP0662283A2 (fr) * 1994-01-10 1995-07-12 Viskase Corporation Procédé de préparation d'enveloppes en cellules pour aliments
WO1995035340A1 (fr) * 1994-06-20 1995-12-28 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Feuille soufflee en cellulose
EP0692194A1 (fr) * 1994-07-15 1996-01-17 Viskase Corporation Enveloppe cellulosique pour aliments
WO1998042492A2 (fr) * 1997-03-21 1998-10-01 Lenzing Aktiengesellschaft Dispositif et procede pour produire des films tubulaires cellulosiques
EP0899076A1 (fr) * 1997-08-27 1999-03-03 Kalle Nalo GmbH & Co. KG Procédé et dispositif pour la fabrication d'un produit tubulaire par extrusion à base de cellulose et sans soudure

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1174243A1 (fr) * 2000-07-22 2002-01-23 Kalle GmbH & Co. KG Procédé et dispositif de fabrication d'une feuille tubulaire sans soudure et feuille tubulaire sans soudure
US6821591B2 (en) 2000-07-22 2004-11-23 Kalle Gmbh & Co. Kg Seamless tubular film and methods and devices for producing a seamless tubular film materials
KR100384799B1 (ko) * 2000-10-30 2003-05-22 주식회사 무 등 열가소성 수지의 튜브 압출장치
CN101844395A (zh) * 2010-06-12 2010-09-29 天津科技大学 制备再生纤维素筒状膜的装置
US10030323B2 (en) 2013-04-05 2018-07-24 Lenzing Aktiengesellschaft Method for the production of polysaccharide fibers with an increased fibrillation tendency
US10221502B2 (en) 2013-04-05 2019-03-05 Lenzing Aktiengesellschaft Polysaccharide fibers and method for the production thereof
WO2014165881A1 (fr) 2013-04-10 2014-10-16 Lenzing Ag Film polysaccharidique et son procédé de fabrication
US9701800B2 (en) 2013-04-10 2017-07-11 Lenzing Aktiengesellschaft Polysaccharide film and method for the production thereof
US10220111B2 (en) 2013-06-17 2019-03-05 Lenzing Aktiengesellschaft Highly absorbent polysaccharide fiber and use thereof
US10196758B2 (en) 2013-06-18 2019-02-05 Lenzing Aktiengesellschaft Polysaccharide fibers and method for producing same

Also Published As

Publication number Publication date
GB9823086D0 (en) 1998-12-16
AU6353499A (en) 2000-05-08

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