CH432810A - Method and apparatus for making blown articles from synthetic thermoplastic material - Google Patents
Method and apparatus for making blown articles from synthetic thermoplastic materialInfo
- Publication number
- CH432810A CH432810A CH683564A CH683564A CH432810A CH 432810 A CH432810 A CH 432810A CH 683564 A CH683564 A CH 683564A CH 683564 A CH683564 A CH 683564A CH 432810 A CH432810 A CH 432810A
- Authority
- CH
- Switzerland
- Prior art keywords
- blank
- stretched
- mold
- thermoplastic material
- inflated
- Prior art date
Links
Classifications
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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
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/08—Biaxial stretching during blow-moulding
- B29C49/10—Biaxial stretching during blow-moulding using mechanical means for prestretching
- B29C49/12—Stretching rods
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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
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
- B29C49/06—Injection blow-moulding
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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
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/071—Preforms or parisons characterised by their configuration, e.g. geometry, dimensions or physical properties
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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
- B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
- B29C51/02—Combined thermoforming and manufacture of the preform
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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
- B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
- B29C51/04—Combined thermoforming and prestretching, e.g. biaxial stretching
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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
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
- B29C2049/023—Combined blow-moulding and manufacture of the preform or the parison using inherent heat of the preform, i.e. 1 step blow moulding
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/072—Preforms or parisons characterised by their configuration having variable wall thickness
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/072—Preforms or parisons characterised by their configuration having variable wall thickness
- B29C2949/0722—Preforms or parisons characterised by their configuration having variable wall thickness at neck portion
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/072—Preforms or parisons characterised by their configuration having variable wall thickness
- B29C2949/0724—Preforms or parisons characterised by their configuration having variable wall thickness at body portion
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/072—Preforms or parisons characterised by their configuration having variable wall thickness
- B29C2949/0725—Preforms or parisons characterised by their configuration having variable wall thickness at bottom portion
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/073—Preforms or parisons characterised by their configuration having variable diameter
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/073—Preforms or parisons characterised by their configuration having variable diameter
- B29C2949/0731—Preforms or parisons characterised by their configuration having variable diameter at neck portion
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/073—Preforms or parisons characterised by their configuration having variable diameter
- B29C2949/0733—Preforms or parisons characterised by their configuration having variable diameter at body portion
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/076—Preforms or parisons characterised by their configuration characterised by the shape
- B29C2949/0768—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform
- B29C2949/077—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform characterised by the neck
- B29C2949/0771—Wide-mouth
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/076—Preforms or parisons characterised by their configuration characterised by the shape
- B29C2949/0768—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform
- B29C2949/077—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform characterised by the neck
- B29C2949/0772—Closure retaining means
- B29C2949/0773—Threads
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/076—Preforms or parisons characterised by their configuration characterised by the shape
- B29C2949/0768—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform
- B29C2949/078—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform characterised by the bottom
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
- B29C2949/22—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at neck portion
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
- B29C2949/24—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at flange portion
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
- B29C2949/26—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at body portion
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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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
- B29C2949/28—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at bottom portion
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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
- B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
- B29C51/08—Deep drawing or matched-mould forming, i.e. using mechanical means only
Description
Verfahren und Vorrichtung zur Herstellung geblasener Artikel aus synthetischem thermoplastischem Material
Die Erfindung betrifft ein Verfahren zur Herstellung geblasener Artikel erhöhter Festigkeit durch Herstellung eines Rohlings aus verstreckbarem synthetischem thermoplastischem Material in einer geschlossenen Spritzgussform und anschliessendes Aufblasen dieses Rohlings zum gewünschten hohlen Artikel in einer geschlossenen Blasform, sowie eine Vorrichtung zur Durchführung dieses Verfahrens.
Die biaxiale Orientierung der Moleküle von Thermoplasten ist längst bekannt und wird bei der Herstellung von Folien durch Strecken in beiden Richtungen zur Steigerung der physikalischen Eigenschaften angewendet.
Durch das erfindungsgemässe Verfahren wird es nun möglich, die Vorteile der Biaxialorientierung auch für geblasene Gegenstände bzw. Artikel, z. B. Gefässe, zu verwirklichen, so dass man geblasene Gegenstände mit weit überlegenen physikalischen Eigenschaften erhalten kann.
Erfindungsgemäss wird dies dadurch erreicht, dass der Rohling im Bereich rissfreien Verstreckens bei einer knapp unterhalb des Schmelzpunktes des thermoplastischen Materials liegenden Temperatur durch eine mechanische, axial ausdehnbare Streckvorrichtung, welche mit der Innenfläche des Rohlings in Kontakt steht, auf wenigstens das dreifache seiner ursprünglichen Länge verstreckt und unmittelbar danach in einer geschlossenen Blasform zu einem biaxial verstreckten hohlen Artikel aufgeblasen wird, dessen Durchmesser mindestens das Dreifache seines ursprünglichen Durchmessers beträgt.
Die Bildung des Rohlings kann durch Spritzguss oder auch auf andere geeignete Weise erfolgen, wobei dieser Rohling höchstens ein Drittel der longitudinalen und radialen Abmessungen des herzustellenden Gegenstandes und vorzugsweise ein Drittel bis ein Fünftel von dessen Abmessungen aufweist. Wie gewöhnlich beim Spritzgiessen von thermoplastischen Materialien, wird die Verformung unter vorausgehender Mischung des Materials bei einer Temperatur oberhalb des Schmelzpunktes vorgenommen, z.
B. bei etwa 127,5 bis 1330 C bei Polyäthylen, bei etwa 166 bis 173,5" C für Polypropylen und etwa 96 bis 104,50 C für Polystyrol, worauf man den Rohling auf eine Temperatur schwach unterhalb des Schmelzpunktes, also etwa 125-129 C für Polyäthylen, etwa 155-166 C für Polypropylen und etwa 85-96 C für Polystyrol, abkühlt und dann sowohl axial als auch radial durch Strecken und Aufblasen des Rohlings in die endgültige Form bringt.
Die axiale Streckung des Rohlings bewirkt vorerst eine axiale Orientierung der Polymermoleküle, während durch das Aufblasen die biaxiale Orientierung vollendet wird, wobei gleichzeitig die endgültige Form des Gegenstandes hergestellt wird. Die Temperaturen in den obigen Bereichen sollen möglichst auf + 1-5 C strikte eingehalten werden und das Strecken und Aufblasen der Rohlinge sollte womöglich schnell und an einem Ort geschehen, welcher von Durchzugluft frei ist und auch von anderen Bedingungen frei ist, welche die vorsichtige Aufrechterhaltung und Steuerung der Temperatur beeinflussen können.
Die Längsstreckung erfolgt mindestens auf 300 O/o und vorzugsweise 300 bis 500 0/0 der ursprünglichen Länge, wobei auch Verstreckungen von 600 O/o durchaus verwendbar sind.
Anders ausgedrückt muss die Verstreckung ausreichen, um die Wanddicke des Rohlings auf mindestens ein Drittel seiner unverstreckten Dimension der Wandstärke zu vermindern.
Es ist wichtig, dass die Wanddicke des fertigen Artikels nach Verstreckung und Aufblasen höchstens ein Drittel der Wandstärke des Rohlings beträgt.
In Fig. 1 wird eine Vertikalschnittansicht mit den Teilen im Aufriss eines Ausführungsbeispiels einer Vorrichtung dargestellt, welche sich zur Durchführung des erfindungsgemässen Verfahrens eignet, wobei die Vorrichtung in Stellung für den Spritzguss des Rohlings steht.
Fig. 2 zeigt eine ähnliche Vorrichtung wie Fig. 1, stellt aber diese in der Stellung beim Strecken des Rohlings vor dem Aufblasen dar.
Fig. 3 wiederum stellt eine der Fig. 1 und 2 ähnliche Vorrichtung dar, wobei aber der Artikel bereits aufgeblasen ist.
Die Arbeitsweise beim erfindungsgemässen Verfahren und der Vorrichtung zu dessen Ausführung wird nachstehend an Hand der genannten Figuren näher erläutert.
In Fig. 1 ist mit 10 ganz allgemein ein Apparat bezeichnet, wie er im USA-Patent 3 172 929 beschrieben wurde.
Dieser Apparat bzw diese Vorrichtung hat zwei Rohlingformteile 11, welche eine äussere Oberfläche des Rohlings bzw. der Rohlingskammer 12 umschreiben und vorzugsweise die Form eines Kegelstumpfes aufweist. Die Rohlingform hat Öffnungen für ein Heizmittel bzw. ein Wärmeaustauschmittel, welche mit der Zahl 13 bezeichnet sind und so eingerichtet sind, dass heisse oder kalte Wärmeaustauschmittel zur exakten Tempera turkontrolle der Rohlingform darin umgewälzt werden können.
Am Ende der Rohlingformteile 11 weisen diese Aussparungen 14 auf, um einen Spritzgusszylinder 15 aufzunehmen, welcher eine Bohrung 16 aufweist, in der der Pumpenkolben 17 mit Kolbenkopf 18 in Fig. 1 im angehobenen Zustand dargestellt ist, also am Ende des Einspritzvorganges selbst.
In die Kammer 12 tritt gegen unten ein Kern 20 ein, dessen unteres Ende entsprechend der Form des Roh Iings bei 21 beispielsweise konisch zuläuft und die Innenwand des Spritzgussraumes 12, d. h. der Rohlingkammer bildet. Das untere Ende 23 des Kerns 20 ist an sich offen und wird durch ein Ventil 25 verschlossen, welches einen VentilstösseI 26 axial nach oben ragend im Inneren des Kerns 20 aufweist. Das Ventil 25 ist in der oberen, d. h. geschlossenen Stellung in Fig. 1 dargestellt und bildet dort ebenfalls einen Teil der Innenwand der Rohlingspritzgussform 12.
In der konischen Form 21 des Kerns befindet sich innen eine Wärmeaustauscherschlange 28, welche die Innenwand des Kernteils 21 innig berührt und demselben Zwecke dient, wie die Durchgänge 13 im äusseren Formteil 11. Der Kern 20 wird von zwei den Halsteil des Gegenstandes umschliessenden Halbformen 30 abgeschlossen, welche den Hals 31 gegen aussen begrenzen. Auch in diesen Halbformen 30 befinden sich Wärmeaustauscherkanäle 32. Die innere Abgrenzung des Halsteiles erfolgt durch die Ringform 35. Die Ringform 35 hat einen gegen unten reichenden Flansch 36, welcher an dem Kern 20 anliegt, und dessen glatte Oberfläche 37 die innere Begrenzung des Halsteiles bildet.
Nun wird beim Betrieb dieser Vorrichtung eine abgemessene Menge thermoplastisches Material, vorzugsweise Polyäthylen, Polypropylen oder Polystyrol durch den aus Teilen 15, 16, 17, 18 bestehenden Spritzgusskopf in die Form 12 auf herkömmliche Weise eingespritzt. Fig. 1 zeigt das Ende dieses Spritzvorganges.
Während dieser Zeit wird vorzugsweise ein relativ kühles Wärmeaustauschmittel in den Öffnungen 32 zirkuliert, um die Halspartie zu kühlen, so dass nach Beendigung des Einspritzens die Halspartie in ihrem Formteil bereits verfestigt und somit fest verankert ist.
Man zirkuliert auch in der Schlange 28 und in den Kanälen 13 vorzugsweise gekühlte Flüssigkeit, um nach Beendigung des Spritzens die Temperatur des Rohlings im Bereich nahe unterhalb des Schmelzpunktes zu hal- ten (vergl. die für besondere Polymere genannten Temperaturwerte).
Sobald die erwünschte Temperatur des Rohlings erreicht ist, wie dies in dem für die Vorrichtung genannten Patent näher beschrieben ist, wird mittels des Stössels 26 das Ventil 25 nach Entfernung der Spritzgusskopfanlage nach unten vorgeschoben, wie dies in Fig. 2 dargestellt ist, wodurch der Rohling axial gestreckt wird.
Diese Streckung muss mindestens 300 o/o betragen, wie dies bereits näher erläutert wurde. Der gestreckte Rohling wird somit in seiner Wandstärke mindestens auf ein Drittel reduziert.
Nun wird durch die vom ausgefahrenen Ventil 25 freigegebene untere Öffnung des Teiles 20 zum Einblasen des den gestreckten Rohling radial ausdehenden Mediums verwendet, wobei gleichzeitig oder vorher die äussere Blasform 40 (vergl. Fig. 3) an den Teil 30 unten angeschlossen wurde. Es versteht sich, dass beim Entfernen des Spritzgusskopfes auch die äusseren Formteile 11 der Rohlingform entfernt wurden, wie dies aus Fig. 2 ersichtlich ist.
Nachstehend sollen einige wichtige Verfahrensmerkmale für das beschriebene Verfahren noch näher erläutert werden.
1. Das Strecken und Aufblasen muss innerhalb eines eng begrenzten Temperaturbereiches des Rohlings erfolgen, so dass sowohl das Spritzen als auch die Einstellung der richtigen Temperatur der an der Formgebung beteiligten Teile genauestens überwacht werden muss. In einer kontinuierlichen Formgebungsoperation, z. B. unter Verwendung eines extrudierten Rohres als Rohling können diese Temperaturbedingungen nicht genügend überwacht werden.
2. Es muss eine Verstreckung von mindestens 300 /o, also im Verhältnis 1:3, erfolgen, so dass zumindest in jeder der beiden Streckrichtungen eine dreifache Verringerung der Wandstärke des Rohlings erfolgt.
3. Die beiden Streckvorgänge müssen unmittelbar aufeinander und auf das Einspritzen, bzw. auf den Zeitpunkt der entsprechenden Abkühlung des Rohlings erfolgen, wobei die beiden Streckvorgänge sehr rasch durchgeführt werden müssen, damit keine wesentlichen Wärmemengen verlorengehen.
4. Die beim Längs strecken auf Aufblasen angewendeten Temperaturen des Materials müssen auf das Polymer genauestens abgestimmt werden. Es versteht sich, dass dabei das Blasen bei niedrigerer Temperatur und somit höherem Blasdruck erfolgt, als bei den herkömmlichen Blasverfahren.
Method and apparatus for making blown articles from synthetic thermoplastic material
The invention relates to a method for producing blown articles of increased strength by producing a blank from stretchable synthetic thermoplastic material in a closed injection mold and then inflating this blank to form the desired hollow article in a closed blow mold, as well as a device for carrying out this method.
The biaxial orientation of the molecules of thermoplastics has long been known and is used in the production of films by stretching them in both directions to increase the physical properties.
The inventive method it is now possible to use the advantages of the biaxial orientation for blown objects or articles such. B. vessels to realize, so that one can get blown articles with far superior physical properties.
According to the invention, this is achieved by stretching the blank in the crack-free stretching area at a temperature just below the melting point of the thermoplastic material by a mechanical, axially expandable stretching device which is in contact with the inner surface of the blank to at least three times its original length and immediately thereafter inflated in a closed blow mold into a biaxially stretched hollow article the diameter of which is at least three times its original diameter.
The blank can be formed by injection molding or in any other suitable manner, this blank having at most one third of the longitudinal and radial dimensions of the object to be manufactured and preferably one third to one fifth of its dimensions. As is usual in the injection molding of thermoplastic materials, the deformation is carried out with prior mixing of the material at a temperature above the melting point, e.g.
B. at about 127.5 to 1330 C for polyethylene, at about 166 to 173.5 "C for polypropylene and about 96 to 104.50 C for polystyrene, whereupon the blank to a temperature slightly below the melting point, so about 125 -129 C for polyethylene, about 155-166 C for polypropylene and about 85-96 C for polystyrene, cools and then brings it into its final shape both axially and radially by stretching and inflating the blank.
The axial stretching of the blank initially causes an axial orientation of the polymer molecules, while the inflation completes the biaxial orientation, with the final shape of the object being produced at the same time. The temperatures in the above ranges should be strictly adhered to at + 1-5 C and the stretching and inflation of the blanks should be done quickly and in a place that is free of drafts and other conditions that require careful maintenance and control of temperature.
The longitudinal stretching takes place to at least 300% and preferably 300 to 500% of the original length, with stretchings of 600% also being entirely usable.
In other words, the stretching must be sufficient to reduce the wall thickness of the blank to at least one third of its unstretched dimension of the wall thickness.
It is important that the wall thickness of the finished article after stretching and inflation is no more than one third of the wall thickness of the blank.
1 shows a vertical sectional view with the parts in elevation of an exemplary embodiment of a device which is suitable for carrying out the method according to the invention, the device being in position for the injection molding of the blank.
Fig. 2 shows a device similar to Fig. 1, but shows it in the position when the blank is stretched before inflation.
Fig. 3 in turn shows a device similar to Figs. 1 and 2, but with the article already inflated.
The mode of operation in the method according to the invention and the device for carrying it out is explained in more detail below with reference to the figures mentioned.
In Fig. 1, 10 generally denotes an apparatus as described in US Pat. No. 3,172,929.
This apparatus or this device has two blank shaped parts 11, which circumscribe an outer surface of the blank or the blank chamber 12 and preferably has the shape of a truncated cone. The blank mold has openings for a heating means or a heat exchange means, which are designated by the number 13 and are set up so that hot or cold heat exchange means can be circulated therein for exact temperature control of the blank mold.
At the end of the blank moldings 11, these have recesses 14 to receive an injection molding cylinder 15 which has a bore 16 in which the pump piston 17 with piston head 18 is shown in the raised state in FIG. 1, i.e. at the end of the injection process itself.
A core 20 enters the chamber 12 towards the bottom, the lower end of which tapers conically at 21, for example, corresponding to the shape of the raw Iings, and the inner wall of the injection-molding space 12, ie. H. the blank chamber forms. The lower end 23 of the core 20 is open per se and is closed by a valve 25 which has a valve stem 26 protruding axially upward in the interior of the core 20. The valve 25 is in the upper, i.e. H. shown in the closed position in FIG. 1 and also forms part of the inner wall of the blank injection mold 12 there.
Inside the conical shape 21 of the core there is a heat exchanger coil 28, which intimately touches the inner wall of the core part 21 and serves the same purpose as the passages 13 in the outer molded part 11. The core 20 is closed by two half-molds 30 surrounding the neck part of the object which limit the neck 31 towards the outside. In these half-molds 30 there are also heat exchanger channels 32. The inner delimitation of the neck part is provided by the ring shape 35. The ring shape 35 has a flange 36 which extends downwards and rests against the core 20, and whose smooth surface 37 forms the inner boundary of the neck part .
Now, in operation of this apparatus, a measured amount of thermoplastic material, preferably polyethylene, polypropylene or polystyrene, is injected into the mold 12 through the injection head consisting of parts 15, 16, 17, 18 in a conventional manner. Fig. 1 shows the end of this injection process.
During this time, a relatively cool heat exchange medium is preferably circulated in the openings 32 in order to cool the neck portion, so that after the injection is complete, the neck portion is already solidified in its molded part and thus firmly anchored.
Preferably cooled liquid is also circulated in the coil 28 and in the channels 13 in order to keep the temperature of the blank in the range close to below the melting point after the end of the spraying (see the temperature values given for particular polymers).
As soon as the desired temperature of the blank is reached, as described in more detail in the patent mentioned for the device, the valve 25 is advanced downwards by means of the plunger 26 after the injection molding head system has been removed, as shown in FIG. 2, whereby the blank is stretched axially.
This stretching must be at least 300 o / o, as has already been explained in more detail. The wall thickness of the stretched blank is thus reduced to at least one third.
The lower opening of the part 20 released by the extended valve 25 is now used to blow in the medium which radially expands the elongated blank, the outer blow mold 40 (see FIG. 3) being connected to the part 30 below at the same time or beforehand. It goes without saying that when the injection molding head was removed, the outer mold parts 11 of the blank mold were also removed, as can be seen from FIG. 2.
Some of the important process features for the process described will be explained in greater detail below.
1. The stretching and inflation must take place within a narrowly limited temperature range of the blank, so that both the injection and the setting of the correct temperature of the parts involved in the shaping must be closely monitored. In a continuous forming operation, e.g. B. using an extruded tube as a blank, these temperature conditions cannot be adequately monitored.
2. A stretching of at least 300 / o, that is to say in a ratio of 1: 3, must take place, so that at least a threefold reduction in the wall thickness of the blank takes place in each of the two stretching directions.
3. The two stretching processes must take place immediately on top of one another and after the injection, or at the time of the corresponding cooling of the blank, the two stretching processes having to be carried out very quickly so that no significant amounts of heat are lost.
4. The temperatures of the material used during longitudinal stretching for inflation must be precisely matched to the polymer. It goes without saying that the blowing takes place at a lower temperature and thus a higher blowing pressure than with conventional blowing processes.
Claims (1)
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1963164A GB1037115A (en) | 1964-05-12 | 1964-05-12 | A method of making hollow plastic articles |
FR975198A FR1406520A (en) | 1964-05-20 | 1964-05-20 | Method and apparatus for making a blown article |
CH683564A CH432810A (en) | 1964-05-12 | 1964-05-26 | Method and apparatus for making blown articles from synthetic thermoplastic material |
US3470282D US3470282A (en) | 1964-05-20 | 1967-08-11 | Method of making a blown article |
US28063D USRE28063E (en) | 1964-05-20 | 1971-09-27 | Method and apparatus for making a blown article |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1963164A GB1037115A (en) | 1964-05-12 | 1964-05-12 | A method of making hollow plastic articles |
FR975198A FR1406520A (en) | 1964-05-20 | 1964-05-20 | Method and apparatus for making a blown article |
CH683564A CH432810A (en) | 1964-05-12 | 1964-05-26 | Method and apparatus for making blown articles from synthetic thermoplastic material |
US65996867A | 1967-08-11 | 1967-08-11 |
Publications (1)
Publication Number | Publication Date |
---|---|
CH432810A true CH432810A (en) | 1967-03-31 |
Family
ID=27429019
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CH683564A CH432810A (en) | 1964-05-12 | 1964-05-26 | Method and apparatus for making blown articles from synthetic thermoplastic material |
Country Status (2)
Country | Link |
---|---|
CH (1) | CH432810A (en) |
GB (1) | GB1037115A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2338236A1 (en) * | 1972-07-27 | 1974-02-14 | Mitsui Toatsu Chemicals | METHOD FOR MANUFACTURING POLYPROPYLENE HOLLOW BODIES |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4404162A (en) * | 1979-07-16 | 1983-09-13 | Sumitomo Bakelite Company Ltd. | Process for producing a thin-wall deep drawn container of thermoplastic resin |
WO2007124894A1 (en) * | 2006-05-01 | 2007-11-08 | Alpla Werke Alwin Lehner Gmbh & Co. Kg | Procedure for the manufacturing of a plastic container, preform for the manufacturing of a plastic container, and plastic container |
EP2221340A1 (en) | 2009-02-20 | 2010-08-25 | Total Petrochemicals Research Feluy | Blow molded containers made of vinyl aromatic polymer |
-
1964
- 1964-05-12 GB GB1963164A patent/GB1037115A/en not_active Expired
- 1964-05-26 CH CH683564A patent/CH432810A/en unknown
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2338236A1 (en) * | 1972-07-27 | 1974-02-14 | Mitsui Toatsu Chemicals | METHOD FOR MANUFACTURING POLYPROPYLENE HOLLOW BODIES |
Also Published As
Publication number | Publication date |
---|---|
GB1037115A (en) | 1966-07-27 |
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