EP0000728B1 - Method and apparatus for removing volatile matter escaping during the extrusion of polymer melts - Google Patents

Method and apparatus for removing volatile matter escaping during the extrusion of polymer melts Download PDF

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Publication number
EP0000728B1
EP0000728B1 EP78100499A EP78100499A EP0000728B1 EP 0000728 B1 EP0000728 B1 EP 0000728B1 EP 78100499 A EP78100499 A EP 78100499A EP 78100499 A EP78100499 A EP 78100499A EP 0000728 B1 EP0000728 B1 EP 0000728B1
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EP
European Patent Office
Prior art keywords
plastic melt
suction
plastic
orifice
volatile constituents
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EP78100499A
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German (de)
French (fr)
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EP0000728A1 (en
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Werner Dr. Hoerauf
Guenter Valentin
Robert Kegel
Helmut Kuhn
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BASF SE
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BASF SE
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    • 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
    • B29C48/03—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
    • B29C48/05—Filamentary, e.g. strands
    • 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
    • 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
    • B29C48/76—Venting, drying means; Degassing means
    • 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

Definitions

  • a caprolactam melt containing 10% by weight of monomers is passed through a nozzle plate 1 in fine distribution through a heated closed space 2 while maintaining the molten state and the melt as Swamp 4 collected. Since it is a closed space, the monomers cannot spread freely, but at most can escape through the opening 8.
  • the suction opening 8 is not in the immediate vicinity of the nozzle opening but downwards in the course of the treatment room. According to the example, the treatment room is continuously evacuated and kept under a pressure of 7 mm. It is understood that the entire space 2 is filled with caprolactam vapor in accordance with the partial pressure.
  • caprolactam vapors are drawn off through the opening 8 and kept at a temperature above the melting point by a separate electrical resistance heater. It is therefore a de-lactamization process that cannot be compared to extrusion with shaping.
  • the method according to the invention begins where the melt 4 is discharged downwards into the atmosphere from the opening, which is not specified.
  • a polyester melt is passed through nozzle openings into a closed container 8 and is collected at the bottom as a sump while maintaining the molten state.
  • the invention has for its object to design the extraction of volatile components when extruding plastic melts into the atmosphere with shaping so that no troublesome additional suction devices are necessary and at the same time access to the extruded molding is not blocked by additional devices.
  • This object is achieved in a method for removing volatile constituents which escape from the extrusion of plastic melts from the latter into the surrounding air, these volatile constituents being suctioned off with the surrounding air, in that the volatile constituents are released immediately upon exiting the Plastic melt through at least one suction opening (5), which is located in the immediate vicinity of the nozzle opening (4) from which the plastic melt emerges, and the air containing such volatile components immediately after entering the suction opening (5) with the heating medium for the Plastic melt heated.
  • the invention also relates to a device for carrying out the method, characterized by a conical inlet 1 for the plastic melt with a heating jacket 2, a nozzle plate 3 attached to the tip of the cone with at least one nozzle opening 4 for the exit of the plastic melt and at least one in In the immediate vicinity of the nozzle opening 4 arranged suction opening 5, which is inclined in the direction of the discharge of the plastic melt towards the nozzle opening 4, a casing 6 together with the nozzle plate 3 and the heating jacket 2 forming a heated cavity 7 which has an outlet 8.
  • the new method and the new Vorrichtunp have the advantage that no blockages occur in the suction lines and the harmful vapors are effectively removed from the work area. There is also the advantage that the extracted air is heated to the required temperature by the heating media for the nozzle plate and plastic melt immediately after being drawn in, without further aids.
  • thermoplastic, organic polymers for example polystyrene, whose copolymers, for. B. with acrylonitrile or rubber-modified polystyrenes, also polyvinyl chloride, rubber-modified polyvinyl chloride, polyolefins such as polyethylene or polypropylene, polyoxymethylene and polyamides such as polyamide-66 or polyamide-6.
  • Such polymers are from the melt, for. B. at temperatures of 180 to 300 ° C, formed.
  • the type and composition of the volatile components emerging from the melt are only partially known.
  • Such volatile constituents contain monomers, furthermore oligomers which result from the polymerization or oligomers which result from degradation by the thermal treatment, furthermore decomposition products.
  • the method is used particularly advantageously when the volatile components are liquid or solid at room temperature.
  • the process according to the invention has particular technical importance in the extrusion of polycaprolactam. The caprolactam vapors generated during extrusion are removed.
  • Extrusion is used to discharge a plastic melt during its manufacture, but also to shape a plastic melt during its further processing, e.g. B. to endless profiles such as pipes.
  • the volatile fractions are sucked off with the surrounding air, in such a way that the volatile fractions are sucked off as soon as they emerge from the plastic melt.
  • An essential feature is that the air containing such volatile components is heated immediately after entering the suction opening.
  • the temperatures depend on the type of volatile components. As a rule, it can be assumed that the extracted air is heated to a temperature which is at least 20 ° C., advantageously 30 ° C., above the melting point of the volatile components extracted.
  • the extracted air is heated e.g. B. to at least 90 ° C to avoid separation of solid caprolactam.
  • the cheapest temperatures can easily be determined by simple tests.
  • the upper temperature limit is determined by economic considerations because unnecessary heating consumes unnecessary energy.
  • a temperature of 200 ° C is generally to be regarded as the upper temperature limit.
  • this value is not a limitation with regard to the variety of possible volatile components.
  • the extracted air containing volatile components is mixed with the heating medium for the plastic melt, e.g. B. the electric heater or liquid heater, which is used for tempering the plastic melt, heated.
  • caprolactam vapors When suctioning water-soluble vapors, such as caprolactam vapors, it has proven to be advantageous to generate the negative pressure for suction by means of water injectors.
  • the volatile components such as caprolactam are washed out of the extracted air and enriched in the water that is circulated. In this way, the extracted caprolactam as z. B. 20 weight percent solution obtained from the caprolactam is recovered.
  • the suction opening is in the immediate vicinity, e.g. B. at a distance of 3 to 10 cm, from the nozzle opening from which the plastic melt emerges, in order to ensure that the volatile components are removed from the plastic melt as soon as they exit. It has proven useful here if the direction of the suction opening does not run parallel to the emerging plastic melt, but rather an inclination to the axis of the emerging plastic melt, e.g. B. at an angle of 25 to 60 °, so that the volatile components are sucked away from the plastic melt.
  • the cross section of a device suitable for carrying out the method is shown in the figure.
  • the figure shows the discharge part of any device that is not further developed and contains plastic melt.
  • the discharge part consists of a conical inlet 1 for the plastic melt.
  • the cone does not have to be pointed, but can also have any other initial shapes, such as oval or rectangular shapes.
  • the conical inlet 1 is surrounded by a heating jacket 2. These are electrical induction heaters or steam or liquid heaters.
  • a nozzle plate 3 is attached to the lower end of the conical inlet. This nozzle plate has at least one outlet opening for the plastic melt 4. The shape and number of the outlet openings depend on the Task in the extrusion of plastic melts.
  • the nozzle plate 3 additionally has at least one suction opening 5.
  • the volatile components which escape when the plastic melt emerges from the nozzle opening 4 are immediately sucked off through this suction opening.
  • the suction opening 5 is arranged as close as possible to the nozzle opening 4 and is inclined towards the nozzle opening 4 in the direction of the plastic discharge.
  • suction openings 5 are provided on both sides of the nozzle opening 4.
  • the suction opening 5 can be arranged in the form of a plurality of nozzle openings or slots or annular slots which are adapted to the nozzle opening 4.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)

Description

Bei der Extrusion von Kunststoffschmelzen entweichen aus diesen nach Austritt aus der Formgebungsöffnung flüchtige Anteile, die entfernt werden müssen. Solche flüchtigen Anteile sind zum Teil übelriechend und reizen die Atemwege oder sind auf die Dauer schädlich. Beispielsweise treten bei der Extrusion von Polycaprolactam Caprolactamdämpfe auf, die entfernt werden müssen, da Caprolactam einen MAK-Wert von 25 mg/m3 (maximale Arbeitsplatzkonzentration) hat. Solche flüchtigen Anteile, die aus Monomeren und Oligomeren oder Abbauprodukten von Polymeren bestehen und bei Raumtemperatur fest oder flüssig sind, scheiden sich beim Absaugen häufig in den dafür vorgesehenen Leitungen und Vorrichtungen ab. Hierdurch treten Störungen auf, deren Beseitigung erheblich Arbeitszeit und Aufwand in Anspruch nimmt. Bislang wurden solche flüchtigen Anteile durch getrennte Absaugvorrichtungen entfernt, um eine Verschmutzung der Luft im Arbeitsraum zu vermeiden. Solche separaten Vorrichtungen zum Absaugen von flüchtigen Anteilen haben jedoch den Nachteil, daß sie leicht zu Verstopfungen neigen und darüber hinaus den Zugang zu der Düsenöffnung versperren und somit die Handhabung des extrudierten Stranges erheblich beeinträchtigen.When plastic melts are extruded, volatile components escape from them after exiting the molding opening and have to be removed. Such volatile components are sometimes malodorous and irritate the respiratory tract or are harmful in the long run. For example, when extruding polycaprolactam, caprolactam vapors occur which have to be removed since caprolactam has a MAK value of 25 mg / m 3 (maximum workplace concentration). Such volatile constituents, which consist of monomers and oligomers or degradation products of polymers and are solid or liquid at room temperature, often separate out in the lines and devices provided for this purpose. This leads to malfunctions, the elimination of which takes considerable time and effort. So far, such volatile components have been removed by separate suction devices to prevent air pollution in the work area. However, such separate devices for extracting volatile components have the disadvantage that they tend to clog easily and also block access to the nozzle opening and thus considerably impair the handling of the extruded strand.

Entsprechend der FR-A-1 038 355, Figur in Verbindung mit dem Beispiel, wird eine 10 Gew.-% Monomeren enthaltende Caprolactamschmelze durch eine Düsenplatte 1 in feiner Verteilung durch einen beheizten geschlossenen Raum 2 unter Beibehaltung des schmelzflüssigen Zustandes geleitet und die Schmelze als Sumpf 4 gesammelt. Da es sich um einen geschlossenen Raum handelt, können sich die Monomeren nicht frei ausbreiten, sondern allenfalls durch die Öffnung 8 entweichen. Die Absaugöffnung 8 befindet sich nicht in unmittelbarer Nähe der Düsenöffnung sondern im Verlauf des Behandlungsraumes nach unten. Ausweislich des Beispieles wird der Behandlungsraum fortlaufend evakuiert und unter einem Druck von 7 mm gehalten. Es versteht sich, daß der gesamte Raum 2 von Caprolactamdampf entsprechend dem Partialdruck erfüllt ist. Diese Caprolactamdämpfe werden durch die Öffnung 8 abgesaugt und durch eine separate elektrische Widerstandsheizung auf einer Temperatur oberhalb des Schmelzpunktes gehalten. Es handelt sich somit um ein Entlactamisierungsverfahren, das mit einer Extrusion unter Formgebung nicht vergleichbar ist. Das erfindungsgemäße Verfahren setzt dort ein, wo die Schmelze 4 aus der nicht näher bezeichneten Öffnung nach unten in die Atmosphäre ausgetragen wird.According to FR-A-1 038 355, figure in connection with the example, a caprolactam melt containing 10% by weight of monomers is passed through a nozzle plate 1 in fine distribution through a heated closed space 2 while maintaining the molten state and the melt as Swamp 4 collected. Since it is a closed space, the monomers cannot spread freely, but at most can escape through the opening 8. The suction opening 8 is not in the immediate vicinity of the nozzle opening but downwards in the course of the treatment room. According to the example, the treatment room is continuously evacuated and kept under a pressure of 7 mm. It is understood that the entire space 2 is filled with caprolactam vapor in accordance with the partial pressure. These caprolactam vapors are drawn off through the opening 8 and kept at a temperature above the melting point by a separate electrical resistance heater. It is therefore a de-lactamization process that cannot be compared to extrusion with shaping. The method according to the invention begins where the melt 4 is discharged downwards into the atmosphere from the opening, which is not specified.

Desgleichen wird entsprechend der US-A-3 110 547 ausweislich Figur und Beispiele eine Polyesterschmelze durch Düsenöffnungen in einen geschlossenen Behälter 8 geleitet und unter Aufrechterhaltung des schmelzflüssigen Zustandes als Sumpf unten gesammelt.Similarly, according to the US-A-3 110 547, as shown in the figure and examples, a polyester melt is passed through nozzle openings into a closed container 8 and is collected at the bottom as a sump while maintaining the molten state.

Auch hier können die Glykoldämpfe nicht in die Atmosphäre entweichen. Vielmehr werden die Glykoldämpfe mittels vorher erhitztem Stickstoff abgeführt. Hierbei dürfte es unerheblich sein, wie bei allen Entgasungsverfahren, ob dies durch Öffnungen 12 oder wie in der FR-A-1 038 355 durch die Öffnung 8 geschieht.Here, too, the glycol vapors cannot escape into the atmosphere. Rather, the glycol vapors are removed using previously heated nitrogen. It should be irrelevant here, as with all degassing processes, whether this takes place through openings 12 or, as in FR-A-1 038 355, through opening 8.

Der Erfindung liegt die Aufgabe zugrunde, die Absaugung von flüchtigen Anteilen beim Extrudieren von Kunststoffschmelzen in die Atmosphäre unter Formgebung so zu gestalten, daß keine störungsanfälligen aufwendigen zusätzlichen Absaugevorrichtungen notwendig sind und zugleich der Zugang zu dem extrudierten Formteil nicht durch zusätzliche Vorrichtungen versperrt wird.The invention has for its object to design the extraction of volatile components when extruding plastic melts into the atmosphere with shaping so that no troublesome additional suction devices are necessary and at the same time access to the extruded molding is not blocked by additional devices.

Diese Aufgabe wird bei einem Verfahren zum Entfernen von flüchtigen Anteilen, die bei der Extrusion von Kunststoffschmelzen aus diesen in die umgebende Luft entweichen, wobei diese flüchtigen Anteile mit der umgebenden Luft abgesaugt werden, dadurch gelöst, daß man die flüchtigen Anteile sofort beim Austritt aus der Kunststoffschmelze durch mindestens eine Absaugöffnung (5), die sich in unmittelbarer Nähe der Düsenöffnung (4), aus der die Kunststoffschmelze austritt, befindet, absaugt und die solche flüchtigen Anteile enthaltende Luft unmittelbar nach Eintritt in die Absaugöffnung (5) mit dem Heizmedium für die Kunststoffschmelze erhitzt.This object is achieved in a method for removing volatile constituents which escape from the extrusion of plastic melts from the latter into the surrounding air, these volatile constituents being suctioned off with the surrounding air, in that the volatile constituents are released immediately upon exiting the Plastic melt through at least one suction opening (5), which is located in the immediate vicinity of the nozzle opening (4) from which the plastic melt emerges, and the air containing such volatile components immediately after entering the suction opening (5) with the heating medium for the Plastic melt heated.

Ferner ist ein Gegenstand der Erfindung eine Vorrichtung zur Durchführung des Verfahrens, gekennzeichnet durch einen konischen Zulauf 1 für die Kunststoffschmelze mit einem Heizmantel 2, einer an der Spitze des Konus angebrachten Düsenplatte 3 mit mindestens einer Düsenöffnung 4 für den Austritt der Kunststoffschmelze und mindestens einer in unmittelbarer Nähe der Düsenöffnung 4 angeordneten Absaugöffnung 5, die in Richtung des Austrags der Kunststoffschmelze zu der Düsenöffnung 4 hin geneigt ist, wobei eine Ummantelung 6 zusammen mit der Düsenplatte 3 und dem Heizmantel 2 einen beheizten Hohlraum 7 bildet, der einen Auslaß 8 aufweist.The invention also relates to a device for carrying out the method, characterized by a conical inlet 1 for the plastic melt with a heating jacket 2, a nozzle plate 3 attached to the tip of the cone with at least one nozzle opening 4 for the exit of the plastic melt and at least one in In the immediate vicinity of the nozzle opening 4 arranged suction opening 5, which is inclined in the direction of the discharge of the plastic melt towards the nozzle opening 4, a casing 6 together with the nozzle plate 3 and the heating jacket 2 forming a heated cavity 7 which has an outlet 8.

Das neue Verfahren und die neue Vorrichtunp haben den Vorteil, daß keine Verstopfungen in den Absaugleitungen eintreten und die schädlichen Dämpfe wirksam aus dem Arbeitsraum entfernt werden. Ferner besteht der Vorteil, daß die abgesaugte Luft durch die Heizmedien für Düsenplatte und Kunststoffschmelze unmittelbar nach dem Ansaugen ohne weitere Hilfsmittel auf die erforderliche Temperatur erhitzt wird.The new method and the new Vorrichtunp have the advantage that no blockages occur in the suction lines and the harmful vapors are effectively removed from the work area. There is also the advantage that the extracted air is heated to the required temperature by the heating media for the nozzle plate and plastic melt immediately after being drawn in, without further aids.

Es war keineswegs abzusehen, daß ein Absaugen von flüchtigen Anteilen aus einem nicht geschlossenen Raum durch Öffnungen, die in unmittelbarer Nähe der formgebenden Düsenöffnung für die Kunststoffschmelze angebracht sind, wirkungsvoll möglich ist. Die extrudierte Kunststoffschmelze bewegt sich nämlich von der Ansaugöffnung weg und somit auch die aus der Kunststoffschmelze austretenden flüchtigen Anteile. Es war vielmehr angezeigt, die Absaugöffnung im Verlauf des sich von der Düsenöffnung wegbewegenden Kunststoffstranges anzuordnen. Für die Erhitzung wird die angesaugte Luft im Gegenstrom zur Kunststoffschmelze geführt und das ohnehin vorhandene Heizmedium für die Kunststoffschmelze zweiseitig ausgenützt, nämlich einmal um die Kunststoffschmelze im flüssigen Zustand zu erhalten und andererseits die abgesaugte Luft zu erhitzen. Es ist bemerkenswert, daß dies keiner besonderen Regelung bedarf, da die Kunststoffschmelze zwangsläufig über dem Schmelzpunkt des zu extrudierenden Kunststoffes gehalten wird. Es war auch keineswegs vorherzusehen, welche Absaugerichtung eingehalten werden muß um aus einem nicht begrenzten Raum flüchtige Anteile die sich von der Absaugöffnung wegbewegen, wirkungsvoll anzusaugen.It was by no means foreseeable that a suction of volatile components from a non-closed space through openings that were made in the immediate vicinity of the shaping nozzle opening for the plastic melt are effectively possible. The extruded plastic melt namely moves away from the suction opening and thus also the volatile components emerging from the plastic melt. Rather, it was indicated to arrange the suction opening in the course of the plastic strand moving away from the nozzle opening. For the heating, the sucked-in air is conducted in countercurrent to the plastic melt and the heating medium for the plastic melt is used on both sides, namely once to keep the plastic melt in the liquid state and on the other hand to heat the extracted air. It is noteworthy that this does not require any special regulation, since the plastic melt is inevitably kept above the melting point of the plastic to be extruded. It was also by no means foreseeable which direction of suction had to be observed in order to effectively suck in volatile parts that move away from the suction opening from a non-limited space.

Das erfindungsgemäße Verfahren ist geeignet zum Entfernen von flüchtigen Anteilen, die bei der Extrusion aus Kunststoffschmelzen entweichen. In der Regel handelt es sich hierbei um thermoplastische, organische Polymere, beispielsweise Polystyrol, dessen Copolymerisate, z. B. mit Acrylnitril oder kautschukmodifizierte Polystyrole, ferner Polyvinylchlorid, kautschukmodifiziertes Polyvinylchlorid, Polyolefine wie Polyäthylen oder Polypropylen, Polyoxymethylen sowie Polyamide wie Polyamid-66 oder Polyamid-6.The method according to the invention is suitable for removing volatile components which escape from plastic melts during extrusion. As a rule, these are thermoplastic, organic polymers, for example polystyrene, whose copolymers, for. B. with acrylonitrile or rubber-modified polystyrenes, also polyvinyl chloride, rubber-modified polyvinyl chloride, polyolefins such as polyethylene or polypropylene, polyoxymethylene and polyamides such as polyamide-66 or polyamide-6.

Solche Polymere werden aus der Schmelze, z. B. bei Temperaturen von 180 bis 300°C, geformt. Die hierbei aus der Schmelze austretenden flüchtigen Anteile sind ihrer Art und Zusammensetzung nach nur zum Teil bekannt. Solche flüchtigen Anteile enthalten Monomere, ferner Oligomere, die von der Polymerisation herrühren oder Oligomere, die durch Abbau durch die thermische Behandlung entstehen, ferner Zersetzungsprodukte. Besonders vorteilhaft wendet man das Verfahren dann an, wenn die flüchtigen Anteile bei Raumtemperatur flüssig oder fest sind. Besondere technische Bedeutung hat das Verfahren nach der Erfindung erlangt bei der Extrusion von Polycaprolactam. Hierbei werden die bei der Extrusion entstehenden Caprolactamdämpfe entfernt.Such polymers are from the melt, for. B. at temperatures of 180 to 300 ° C, formed. The type and composition of the volatile components emerging from the melt are only partially known. Such volatile constituents contain monomers, furthermore oligomers which result from the polymerization or oligomers which result from degradation by the thermal treatment, furthermore decomposition products. The method is used particularly advantageously when the volatile components are liquid or solid at room temperature. The process according to the invention has particular technical importance in the extrusion of polycaprolactam. The caprolactam vapors generated during extrusion are removed.

Unter Extrusion ist das Austragen einer Kunststoffschmelze bei deren Herstellung zu versehen, aber auch die Formgebung einer Kunststoffschmelze bei deren Weiterverarbeitung, z. B. zu Endlosprofilen wie Rohren.Extrusion is used to discharge a plastic melt during its manufacture, but also to shape a plastic melt during its further processing, e.g. B. to endless profiles such as pipes.

Die flüchtigen Anteile werden mit der umgebenden Luft abgesaugt, und zwar so, daß die flüchtigen Anteile unmittelbar beim Austritt aus der Kunststoffschmelze abgesaugt werden. Ein wesentliches Merkmal ist es, daß die solche flüchtigen Anteile enthaltene Luft unmittelbar nach dem Eintritt in die Absaugöffnung erhitzt wird. Die Temperaturen richten sich nach der Art der flüchtigen Anteile. In der Regel ist davon auszugehen, daß man die abgesaugte Luft auf eine Temperatur erhitzt, die mindestens 20°C, vorteilhaft 30°C, über dem Schmelzpunkt der abgesaugten flüchtigen Anteile liegt. Beim Absaugen von Caprolactamdämpfen erhitzt man die abgesaugte Luft z. B. auf mindestens 90° C, um ein Abscheiden von festem Caprolactam zu vermeiden. Für andere flüchtige Anteile lassen sich die günstigsten Temperaturen durch einfache Versuche unschwer ermitteln. Die obere Temperaturgrenze wird durch wirtschaftliche Erwägungen bestimmt, da ein überflüssiges Erhitzen unnötige Energie verbraucht. Als obere Temperaturgrenze ist in der Regel eine Temperatur von 200°C anzusehen. Dieser Wert stellt jedoch im Hinblick auf die Vielfalt von möglichen flüchtigen Anteilen keine Begrenzung dar. Die flüchtige Anteile enthaltende abgesaugte Luft wird mit dem Heizmedium für die Kunststoffschmelze, z. B. der elektrischen Heizung oder Flüssigkeitsheizung, die für Temperierung der Kunststoffschmelze verwendet wird, erhitzt.The volatile fractions are sucked off with the surrounding air, in such a way that the volatile fractions are sucked off as soon as they emerge from the plastic melt. An essential feature is that the air containing such volatile components is heated immediately after entering the suction opening. The temperatures depend on the type of volatile components. As a rule, it can be assumed that the extracted air is heated to a temperature which is at least 20 ° C., advantageously 30 ° C., above the melting point of the volatile components extracted. When suctioning caprolactam vapors, the extracted air is heated e.g. B. to at least 90 ° C to avoid separation of solid caprolactam. For other volatile components, the cheapest temperatures can easily be determined by simple tests. The upper temperature limit is determined by economic considerations because unnecessary heating consumes unnecessary energy. A temperature of 200 ° C is generally to be regarded as the upper temperature limit. However, this value is not a limitation with regard to the variety of possible volatile components. The extracted air containing volatile components is mixed with the heating medium for the plastic melt, e.g. B. the electric heater or liquid heater, which is used for tempering the plastic melt, heated.

Beim Absaugen von wasserlöslichen Dämpfen, wie Caprolactamdämpfen, hat es sich als vorteilhaft erwiesen, den Unterdruck zum Ansaugen mittels Wasserinjektoren zu erzeugen. Hierbei werden aus der abgesaugten Luft die flüchtigen Anteile wie Caprolactam ausgewaschen und im Wasser, das im Kreis geführt wird, angereichert. Auf diese Weise wird das abgesaugte Caprolactam als z. B. 20gewichtsprozentige Lösung erhalten, aus der Caprolactam wieder gewonnen wird.When suctioning water-soluble vapors, such as caprolactam vapors, it has proven to be advantageous to generate the negative pressure for suction by means of water injectors. The volatile components such as caprolactam are washed out of the extracted air and enriched in the water that is circulated. In this way, the extracted caprolactam as z. B. 20 weight percent solution obtained from the caprolactam is recovered.

Die Absaugöffnung befindet sich in unmittelbarer Nähe, z. B. im Abstand von 3 bis 10 cm, von der Düsenöffnung, aus der die Kunststoffschmelze austritt, um zu gewährleisten, daß die flüchtigen Anteile unmittelbar beim Austritt aus der Kunststoffschmelze entfernt werden. Hierbei hat es sich bewährt, wenn die Richtung der Absaugöffnung nicht parallel zu der austretenden Kunststoffschmelze verläuft, sondern zu der Achse der austretenden Kunststoffschmelze eine Neigung, z. B. in einem Winkel von 25 bis 60°, aufweist, so daß die flüchtigen Anteile von der Kunststoffschmelze weggesaugt werden.The suction opening is in the immediate vicinity, e.g. B. at a distance of 3 to 10 cm, from the nozzle opening from which the plastic melt emerges, in order to ensure that the volatile components are removed from the plastic melt as soon as they exit. It has proven useful here if the direction of the suction opening does not run parallel to the emerging plastic melt, but rather an inclination to the axis of the emerging plastic melt, e.g. B. at an angle of 25 to 60 °, so that the volatile components are sucked away from the plastic melt.

In der Figur wird der Querschnitt einer für die Durchführung des Verfahrens geeigneten Vorrichtung gezeigt. Die Figur zeigt den Austragsteil einer beliebigen nicht weiter ausgeführten Vorrichtung, die Kunststoffschmelze enthält. Der Austragsteil besteht aus einem konischen Zulauf 1 für die Kunststoffschmelze. Der Konus muß nicht spitz zulaufen, sondern kann auch beliebig andere Ausgangsformen haben, wie ovale oder rechteckige Formen. Der konische Zulauf 1 ist mit einem Heizmantel 2 umgeben. Es handelt sich hierbei um elektrische Induktionsheizungen oder Dampf- oder Flüssigkeitsheizungen. Am unteren Ende des konischen Zulaufs ist eine Düsenplatte 3 angebracht. Diese Düsenplatte weist mindestens eine Austrittsöffnung für die Kunststoffschmelze 4 auf. Die Form und die Zahl der Austrittsöffnungen richten sich nach der Aufgabenstellung bei der Extrusion von Kunststoffschmelzen. Wenn es sich darum handelt, Kunststoffe zu granulieren, wird man zweckmäßig eine Reihe von Lochdüsenöffnungen vorsehen, um granulierbare Stränge zu erhalten. Falls beabsichtigt ist, Endlosprofile herzustellen, sind diese Öffnungen nach den aus dem Stand der Technik bekannten Düsen ausgestattet. Die Düsenplatte 3 weist zusätzlich mindestens eine Absaugöffnung 5 auf. Durch diese Absaugöffnung werden die flüchtigen Anteile, die beim Austritt der Kunststoffschmelze aus der Düsenöffnung 4 entweichen, sofort abgesaugt. Die Absaugöffnung 5 ist möglichst nahe an der Düseflöffnung 4 angeordnet und in Richtung des Kunststoffaustrags zu der Düsenöffnung 4 hin geneigt. Die Ummantelung 6, die einen Auslaß 8 aufweist, bildet zusammen mit dem Heizmantel 2 und der Düsettplatte 3 einen beheizten Hohlraum 7. Beim Eintritt der abgesaugten Luft durch die Düsenöffnung 5 in den Hohlraum 7 wird die angesaugte Luft durch den Heizmantel 2 aufgeheizt und verläßt den Hohlraum über den Auslaß 8 zu einer Absaugvorrichtung, die nicht gezeigt ist. Es ist auch möglich, daß Absaugöffnungen 5 an beiden Seiten der Düsenöffnung 4 angebracht sind. Die Absaugöffnung 5 kann in Form von mehreren Düsenöffnungen oder Schlitzen oder ringförmigen Schlitzen, die der Düsenöffnung 4 angepaßt sind, angeordnet sein.The cross section of a device suitable for carrying out the method is shown in the figure. The figure shows the discharge part of any device that is not further developed and contains plastic melt. The discharge part consists of a conical inlet 1 for the plastic melt. The cone does not have to be pointed, but can also have any other initial shapes, such as oval or rectangular shapes. The conical inlet 1 is surrounded by a heating jacket 2. These are electrical induction heaters or steam or liquid heaters. A nozzle plate 3 is attached to the lower end of the conical inlet. This nozzle plate has at least one outlet opening for the plastic melt 4. The shape and number of the outlet openings depend on the Task in the extrusion of plastic melts. When it comes to granulating plastics, a series of perforated nozzle openings will expediently be provided in order to obtain granulable strands. If it is intended to produce endless profiles, these openings are equipped according to the nozzles known from the prior art. The nozzle plate 3 additionally has at least one suction opening 5. The volatile components which escape when the plastic melt emerges from the nozzle opening 4 are immediately sucked off through this suction opening. The suction opening 5 is arranged as close as possible to the nozzle opening 4 and is inclined towards the nozzle opening 4 in the direction of the plastic discharge. The casing 6, which has an outlet 8, forms, together with the heating jacket 2 and the nozzle plate 3, a heated cavity 7. When the extracted air enters the cavity 7 through the nozzle opening 5, the sucked-in air is heated by the heating jacket 2 and leaves Cavity via the outlet 8 to a suction device, which is not shown. It is also possible that suction openings 5 are provided on both sides of the nozzle opening 4. The suction opening 5 can be arranged in the form of a plurality of nozzle openings or slots or annular slots which are adapted to the nozzle opening 4.

Claims (5)

1. A process for removing volatile constituents which escape from plastic melts into the surrounding air when such melts are extruded, these volatile constituents being drawn off together with the surrounding air, characterized in that the volatile constituents are drawn off immediately they are evolved by the plastic melt, through at least one suction orifice (5) which is located in the immediate vicinity of the die orifice (4) from which the plastic melt issues, and the air containing such volatile constituents is heated immediately after entering the suction orifice (5), by the heating medium for the plastic melt.
2. A process as claimed in claim 1, characterized in that the drawn-off air is heated to a temperature at least 20° C above the melting point of the volatile constituents.
3. A process as claimed in claims 1 and 2, characterized in that the suction direction is inclined towards the plastic melt issuing from the die orifice (4).
4. A process as claimed in claims 1 to 3, characterized in that caprolactam vapors formed during the extrusion of polycaprolactam are removed.
5. Apparatus for carrying out the process as claimed in any of claims 1 to 3, characterized by a conical inlet (1) for the plastic melt, with a heating jacket (2), a die plate (3), located at the tip of the cone, having at least one die orifice (4) from which the plastic melt issues, and at least one suction orifice (5) which is located in the immediate vicinity of the die orifice (4) and is inclined towards the die orifice (4) in the direction of the discharge of plastic melt, an outer casing (6) together with the die plate (3) and the heating jacket (2) forming a heated cavity (7) which possesses an outlet (8).
EP78100499A 1977-08-03 1978-07-26 Method and apparatus for removing volatile matter escaping during the extrusion of polymer melts Expired EP0000728B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2734946A DE2734946B2 (en) 1977-08-03 1977-08-03 Method and device for removing volatile components which escape from plastic melts during the extrusion thereof
DE2734946 1977-08-03

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EP0000728A1 EP0000728A1 (en) 1979-02-21
EP0000728B1 true EP0000728B1 (en) 1981-04-29

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EP (1) EP0000728B1 (en)
JP (1) JPS5428364A (en)
AT (1) AT368945B (en)
AU (1) AU525107B2 (en)
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DE (2) DE2734946B2 (en)
ES (1) ES472323A1 (en)
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US5703203A (en) * 1995-03-31 1997-12-30 Montell North America Inc. Removal of oligomers from substantially crystalline, α-olefin polymers
EP4237222A1 (en) * 2020-11-02 2023-09-06 Röhm GmbH Device for degassing of a two-component multiphase polymer-monomer material and use thereof in a degassing extruder

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FR1038355A (en) * 1950-11-24 1953-09-28 Phrix Werke Ag Method and device for removing volatile components from highly polymerized spinning masses
NL227654A (en) * 1957-05-17
US3130180A (en) * 1957-09-18 1964-04-21 Glanzstoff Ag Continuous method and apparatus for the production of polyhexamethylene adipamide
US3109831A (en) * 1960-11-14 1963-11-05 Pittsburgh Plate Glass Co Cooking polyesters of polybasic acids and polyhydric alcohols in the absence of solvents
US3110547A (en) * 1961-07-26 1963-11-12 Du Pont Polymerization process
LU48718A1 (en) * 1964-06-01 1965-12-01
US3418286A (en) * 1965-08-02 1968-12-24 Interchem Corp Method of making polyesters under reduced pressure
JPS4944867B1 (en) * 1969-09-16 1974-11-30
US3933958A (en) * 1971-03-22 1976-01-20 Reynolds Metals Company Method of making tubular plastic film
JPS5265561A (en) * 1975-11-28 1977-05-31 Ube Industries Method and device for heating evaporating substance in vent extruder
US4043968A (en) * 1976-01-30 1977-08-23 Mobil Oil Corporation Process for producing methylolated amide copolymers in concentrated organic solvent solution

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AU525107B2 (en) 1982-10-21
DE2734946B2 (en) 1980-09-25
IT1097307B (en) 1985-08-31
CA1124972A (en) 1982-06-08
DE2860648D1 (en) 1981-08-06
ATA559378A (en) 1982-04-15
AT368945B (en) 1982-11-25
US4233429A (en) 1980-11-11
AU3845878A (en) 1980-01-31
ES472323A1 (en) 1979-02-16
EP0000728A1 (en) 1979-02-21
DE2734946A1 (en) 1979-02-15
JPS5428364A (en) 1979-03-02
IT7826045A0 (en) 1978-07-24

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