WO1998012035A1 - Method of shaping powdery, thermally unstable thermoplastic shaping compounds - Google Patents

Method of shaping powdery, thermally unstable thermoplastic shaping compounds Download PDF

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Publication number
WO1998012035A1
WO1998012035A1 PCT/DE1997/001969 DE9701969W WO9812035A1 WO 1998012035 A1 WO1998012035 A1 WO 1998012035A1 DE 9701969 W DE9701969 W DE 9701969W WO 9812035 A1 WO9812035 A1 WO 9812035A1
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WO
WIPO (PCT)
Prior art keywords
shaping
thermoplastic molding
powdery
thermally unstable
compounds
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PCT/DE1997/001969
Other languages
German (de)
French (fr)
Inventor
Klaus Metzner
Marion Sela
Kerstin Wengemuth
Hans-Joachim Radusch
Thomas LÜPKE
Original Assignee
Buna Sow Leuna Olefinverbund Gmbh
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.)
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Application filed by Buna Sow Leuna Olefinverbund Gmbh filed Critical Buna Sow Leuna Olefinverbund Gmbh
Priority to CA002267357A priority Critical patent/CA2267357A1/en
Priority to EP97954859A priority patent/EP0944463A1/en
Publication of WO1998012035A1 publication Critical patent/WO1998012035A1/en

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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
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B29C43/16—Forging
    • 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
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/003—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor characterised by the choice of 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
    • B29C2791/00—Shaping characteristics in general
    • B29C2791/001—Shaping in several steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/25—Solid
    • B29K2105/251—Particles, powder or granules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/25—Solid
    • B29K2105/253—Preform
    • B29K2105/255—Blocks or tablets

Definitions

  • the invention relates to a method for shaping131-shaped, thermally unstable thermoplastic molding compositions, in particular for the production of semi-finished products or molded parts.
  • thermoplastic molding compositions can be converted into a molten state by the application of heat, in which compression and shaping of the material can be carried out effectively using suitable technologies (e.g. compression molding, extrusion, injection molding).
  • suitable technologies e.g. compression molding, extrusion, injection molding.
  • stabilizers, plasticizers, etc. an increase in the resistance to thermal degradation can be achieved.
  • it is often not possible to use these substances if there are high demands on the purity of the molding compounds (e.g. when used in medical technology or in the food industry).
  • Solid-phase extrusion techniques are known for the molding of plastics in the solid state, in which a preform of defined dimensions is pressed through a conical nozzle at temperatures below the melting temperature (NE Weeks, S Mon, RS Porter Journal of Polymer Science, Polymer Physics 13 (1975) 2031 , YD Wang, T Yamamoto, M Cakmak ANTEC'96 S 1654-1665)
  • the goal of solid-phase extrusion is the production of highly oriented structures with improved strength properties.
  • a disadvantage of this in particular for thermally sensitive polymers is that the material in the molten material is used to produce the preform Condition is transferred.
  • the invention has for its object to process powdery, thermally and also hydrolytically unstable thermoplastic molding compositions so that they can be further processed as semifinished products or represent usable moldings.
  • the thermal degradation processes that take place in the processing of thermoplastic molding compositions are to be prevented, so that the semifinished products or moldings are prevented a high level of mechanical properties are characterized
  • thermoplastic molding compounds can be, for example, preferred polyolefins, polyamides or polyesters
  • thermally unstable polymers such as, for example, biodegradable polymers, in particular polylactides and polyhydroxyalkanoates, and copolymers thereof are used.
  • the initially powdery starting material is precompressed to a preform in a first process step using hydrostatic pressure.This is done with the aim of minimizing thermal damage, preferably at room temperature, but it can also be carried out at elevated temperatures, but in any case well below the melting temperature.
  • the pressure must be chosen so that the density of the preform reaches about 75 to 90% of the bulk density of the polymer material
  • the pre-compressed preform is subjected to deviatoric stress in a second step, extrusion.
  • deviatoric stress in a second step, extrusion.
  • the mutual penetration of neighboring particles takes place as a result of molecular movement processes in the boundary layer, as well as the removal of existing micropores in the material.
  • the desired geometry of the molded part or semifinished product is formed by means of targeted form constraint.
  • the preform can be produced at room temperature
  • flow processes under deviatoric stress must be carried out at elevated temperatures in the range between glass and melting temperature, preferably at temperatures from 0.8 to 0.95 T m [K], in order to ensure intensive penetration
  • the load under deviatoric stress is expediently chosen depending on the type of polymer material and the forming temperature in such a way that forming ratios of 1, 5 -, ⁇ ⁇ 3 are achieved.
  • the deformation is preferably carried out under continuously increasing stress .
  • the powdery thermoplastic molding compound can also contain fillers and / or Reinforcing agents such as calcium phosphates are added.
  • the molded parts and semi-finished products produced according to the invention are distinguished by a property level which is considerably improved in comparison to products of conventional processing technologies.
  • a property level which is considerably improved in comparison to products of conventional processing technologies.
  • strength, ductility and toughness they are clearly superior to products that have been processed in the melt state, but also hydrostatically pressed in the solid state and products that are solidified by sintering.
  • PHB polyhydroxybutyrate
  • the density of the material is increased to 1.25 g / cm 3 by extrusion. Associated with this are significant improvements in mechanical properties, in particular tensile strength and elongation at break. Molecular degradation processes cannot be demonstrated.
  • Selected characteristic values of the semi-finished products manufactured according to different processes in Figure 1 document the superiority of the extrusion technology according to the invention.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Materials For Medical Uses (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

Abstract

The invention concerns powdery, thermally unstable thermoplastic shaping compounds which are to be processed to form semi-finished products or shaped parts such that thermal decomposition processes are prevented and the semi-finished products and shaped parts display a high level of mechanical properties. To that end, the powdery thermoplastic shaping compound, which is precompressed under hydrostatic pressure, is exposed to a deviatoric stress below its melting temperature.

Description

Verfahren zur Formgebung von puiverförmigen, thermisch instabilen Thermoplastformmassen Process for shaping puiver-shaped, thermally unstable thermoplastic molding compounds
Die Erfindung betrifft ein Verfahren zur Formgebung von puiverförmigen, thermisch instabilen Thermoplastformmassen insbesondere zur Herstellung von Halbzeugen oder Formteiien.The invention relates to a method for shaping puiver-shaped, thermally unstable thermoplastic molding compositions, in particular for the production of semi-finished products or molded parts.
Es ist bereits bekannt, daß thermoplastische Formmassen durch Zufuhr von Wärme in einen schmelzflüssigen Zustand überführt werden können, in dem Verdichtung und Formgebung des Materials durch Anwendung geeigneter Technologien (z.B. Formpressen, Extrusion, Spritzgießen) auf effektive Weise möglich ist. Als nachteilig erweist sich die Anwendung dieser Verfahren auf thermisch instabile Materialien, die im Ergebnis thermischer Abbauprozesse bei erhöhten Temperaturen deutliche Eigenschaftseinbußen erfahren. Durch Zusatz von Stabilisatoren, Weichmachern u.a. läßt sich eine Erhöhung der Beständigkeit gegen thermischen Abbau erzielen. Bei hohen Anforderungen an die Reinheit der Formmassen (wie z.B. bei Einsatz in der Medizintechnik oder im Lebesmittelbereich) ist eine Verwendung dieser Substanzen häufig jedoch nicht möglich.It is already known that thermoplastic molding compositions can be converted into a molten state by the application of heat, in which compression and shaping of the material can be carried out effectively using suitable technologies (e.g. compression molding, extrusion, injection molding). The use of these processes on thermally unstable materials, which experience significant property losses as a result of thermal degradation processes at elevated temperatures, has proven to be disadvantageous. By adding stabilizers, plasticizers, etc. an increase in the resistance to thermal degradation can be achieved. However, it is often not possible to use these substances if there are high demands on the purity of the molding compounds (e.g. when used in medical technology or in the food industry).
Zur Verringerung der thermischen Belastung des Materials werden in der Literatur (R.J.Crawford, D.W.Paul Journal of Materials Science 17(1982) 2267-2280) Sinterverfahren beschrieben, bei denen die pulverförmige Formmasse unterhalb ihrer Erweichungstemperatur durch Anwendung hoher hydrostatischer Drücke verdichtet wird. Für das für die Ausbildung hoher mechanischer Eigenschaften erforderliche Verschweißen der Pulverpartikel sowie die Beseitigung vorhandener Mikroporen ist jedoch ein anschließender Sinterprozeß im Erweichungsbereich der Formmasse notwendig.In order to reduce the thermal load on the material, sintering processes are described in the literature (R.J. Crawford, D.W. Paul Journal of Materials Science 17 (1982) 2267-2280), in which the powdery molding material is compressed below its softening temperature by using high hydrostatic pressures. However, a subsequent sintering process in the softening area of the molding compound is necessary for the welding of the powder particles required for the development of high mechanical properties and the removal of existing micropores.
Die simultane Anwendung hoher hydrostatischer Drücke und hoher Temperaturen ist Gegenstand von Preßsintertechniken, die zur Verarbeitung hochviskoser, pulverförmiger Polymerformmassen eingesetzt werden. Bekanntestes Beispiel für eine derartige Technologie stellt die Ram-Extrusion dar Bei der Verarbeitung von PTFE-Pulvern wird das vorgepreßte Pulver mit einem Stempel in ein beheiztes Werkzeug geschoben, das den Querschnitt des gewünschten Profites aufweist (F Hensen (Hrsg ) Handbuch der Kunststoffextrusionstechnik, Bd. II, C Hanser, München 1991 ) Um das Zusammensintern der Pulverteilchen zu einem kontinuierlichen Extrudat zu ermöglichen, wird dabei oberhalb der Schmelztemperatur des Polymerwerkstoffes gearbeitetThe simultaneous use of high hydrostatic pressures and high temperatures is the subject of press sintering techniques which are used to process highly viscous, powdery polymer molding compounds. Best known example of One such technology is ram extrusion. When processing PTFE powders, the pre-pressed powder is pushed with a punch into a heated tool that has the cross-section of the desired profit (F Hensen (ed.) Handbuch der Kunststoffextrusionstechnik, Vol. II, C Hanser, Munich 1991) In order to enable the powder particles to be sintered together to form a continuous extrudate, work is carried out above the melting temperature of the polymer material
Für die Umformung von Kunststoffen im festen Zustand sind Festphasenextrusionstechπiken bekannt, bei denen ein Vorformling definierter Abmessungen bei Temperaturen unterhalb der Schmelztemperatur durch eine konische Düse gepreßt wird (N.E Weeks, S Mon, R S Porter Journal of Polymer Science, Polymer Physics 13 (1975) 2031 , Y.D Wang, T Yamamoto. M Cakmak ANTEC'96 S 1654-1665) Ziel der Festphasenextrusion ist neben der Formänderung die Erzeugung hochorientierter Strukturen mit verbesserten Festigkeitseigenschaften Nachteilig dabei ist insbesondere für thermisch empfindliche Polymere, daß zur Herstellung des Vorformlings das Material in den schmelzflüssigen Zustand überfuhrt wird.Solid-phase extrusion techniques are known for the molding of plastics in the solid state, in which a preform of defined dimensions is pressed through a conical nozzle at temperatures below the melting temperature (NE Weeks, S Mon, RS Porter Journal of Polymer Science, Polymer Physics 13 (1975) 2031 , YD Wang, T Yamamoto, M Cakmak ANTEC'96 S 1654-1665) In addition to the change in shape, the goal of solid-phase extrusion is the production of highly oriented structures with improved strength properties. A disadvantage of this in particular for thermally sensitive polymers is that the material in the molten material is used to produce the preform Condition is transferred.
Der Erfindung liegt die Aufgabe zugrunde, pulverformige, thermisch sowie auch hydrolytisch instabile Thermoplastformmassen so zu verarbeiten, daß sie als Halbzeuge weiterverarbeitet werden können oder benutzbare Formteile darstellen Die bei der Verarbeitung von Thermoplastformmassen ablaufenden thermischen Abbauprozesse sind dabei zu unterbinden, sodaß die Halbzeuge oder Formteile durch ein hohes Niveau der mechanischen Eigenschften gekennzeichnet sindThe invention has for its object to process powdery, thermally and also hydrolytically unstable thermoplastic molding compositions so that they can be further processed as semifinished products or represent usable moldings. The thermal degradation processes that take place in the processing of thermoplastic molding compositions are to be prevented, so that the semifinished products or moldings are prevented a high level of mechanical properties are characterized
Die Aufgabe wird durch die in den Patentansprüchen 1 bis 6 dargestellte Erfindung gelöstThe object is achieved by the invention shown in claims 1 to 6
Zur Durchfuhrung des erfindungsgemaßen Verfahrens erweisen sich teilkπstalline Formmasseπ hoher Quktilitat als besonders geeignet Solche Thermoplastformmassen können beispielsweise Polyolefine, Polyamide oder Polyester sein Bevorzugte Anwendung erfahren jedoch thermisch instabile Polymere wie zum Beispiel biologisch abbaubare Polymere, insbesondere Polylactide und Polyhydroxyalkanoate sowie deren Copolymerisate.To carry out the process according to the invention, partially stable molding compounds of high quactility have proven to be particularly suitable. Such thermoplastic molding compounds can be, for example, preferred polyolefins, polyamides or polyesters However, thermally unstable polymers such as, for example, biodegradable polymers, in particular polylactides and polyhydroxyalkanoates, and copolymers thereof are used.
Das zunächst pulverförmige Ausgangsmaterial wird in einer ersten Verfahrensstufe unter Anwendung eines hydrostatischen Druckes zu einem Vorformling vorverdichtet Dies erfolgt mit dem Ziel der Minimierung thermischer Schädigungen vorzugsweise bei Raumtemperatur, es kann jedoch auch bei erhöhten Temperaturen, in jedem Falle aber deutlich unterhalb der Schmelztemperatur gearbeitet werden. Der Preßdruck ist so zu wählen, daß die Dichte des Vorformlings etwa 75 bis 90 % der Rohdichte des Polymermaterials erreichtThe initially powdery starting material is precompressed to a preform in a first process step using hydrostatic pressure.This is done with the aim of minimizing thermal damage, preferably at room temperature, but it can also be carried out at elevated temperatures, but in any case well below the melting temperature. The pressure must be chosen so that the density of the preform reaches about 75 to 90% of the bulk density of the polymer material
Der vorverdichtete Vorformling wird in einem zweiten Schritt, dem Fließpressen, einer deviatorischen Beanspruchung ausgesetzt. Dabei findet die gegenseitige Durchdringung benachbarter Teilchen im Ergebnis molekularer Bewegungsprozesse in der Grenzschicht, sowie die Beseitigung vorhandener Mikroporen im Matertial statt. Gleichzeitig wird durch gezielten Formzwang die gewünschte Geometrie des Formteils bzw. Halbzeugs ausgebildet. Während die Herstellung des Vorformlings bei Raumtemperatur erfolgen kann, müssen Fließprozesse unter deviatorischer Beanspruchung bei erhöhten Temperaturen im Bereich zwischen Glas- und Schmelztemperatur , vorzugsweise bei Temperaturen von 0,8 bis 0,95 Tm [K] erfolgen, um die für eine intensive Durchdringung benachbarter Teilchen erforderliche hohe molekulare Beweglichkeit zu gewährleisten Die Belastung unter deviatorischer Beanspruchung wird in Abhängigkeit von der Art des Polymerwerkstoffs und der Umformtemperatur zweckmäßigerweise so gewählt, daß Umformverhältnisse von 1 ,5 -, λ ≤ 3 erzielt werden Die Deformation erfolgt dabei vorzugsweise unter stetig wachender Beanspruchung.The pre-compressed preform is subjected to deviatoric stress in a second step, extrusion. The mutual penetration of neighboring particles takes place as a result of molecular movement processes in the boundary layer, as well as the removal of existing micropores in the material. At the same time, the desired geometry of the molded part or semifinished product is formed by means of targeted form constraint. While the preform can be produced at room temperature, flow processes under deviatoric stress must be carried out at elevated temperatures in the range between glass and melting temperature, preferably at temperatures from 0.8 to 0.95 T m [K], in order to ensure intensive penetration To ensure the necessary high molecular mobility of neighboring particles The load under deviatoric stress is expediently chosen depending on the type of polymer material and the forming temperature in such a way that forming ratios of 1, 5 -, λ ≤ 3 are achieved. The deformation is preferably carried out under continuously increasing stress .
Vorteilhaft auf die Eigenschaften der Produkte wirken sich feinteilige Formmassen mit Teilchendurchmessern kleiner 500 μm und breiter Teilchengrößenverteilung aus Zur Verbesserung der mechanischen Eigenschaften der aus den Halbzeugen und Formteilen hergestellten Endprodukte, insbesondere solcher für einen medizinischen Einsatz können der pulverformigen Thermoplastformmasse auch Füll- und/oder Verstärkerstoffe wie z.B. Calziumphosphate zugemischt werden.Fine-particle molding compounds with particle diameters of less than 500 μm and a broad particle size distribution have an advantageous effect on the properties of the products. To improve the mechanical properties of the end products produced from the semi-finished products and molded parts, in particular those for medical use, the powdery thermoplastic molding compound can also contain fillers and / or Reinforcing agents such as calcium phosphates are added.
Die erfindungsgemäß erzeugten Formteile und Halbzeuge zeichnen sich durch ein im Vergleich zu Erzeugnissen herkömmlicher Verarbeitungstechnologien beträchtlich verbessertes Eigenschaftsniveau aus. Insbesondere hinsichtlich Festigkeit, Verformbarkeit und Zähigkeit sind sie Produkten, die im Schmelzezustand verarbeitet wurden, aber auch hydrostatisch im festen Zustand verpreßten und durch Sintern verfestigten Produkten deutlich überlegen.The molded parts and semi-finished products produced according to the invention are distinguished by a property level which is considerably improved in comparison to products of conventional processing technologies. In particular with regard to strength, ductility and toughness, they are clearly superior to products that have been processed in the melt state, but also hydrostatically pressed in the solid state and products that are solidified by sintering.
Die Erfindung soll nachstehend anhand eines Ausführungsbeispiels erläutert werden.The invention will be explained below using an exemplary embodiment.
Eine pulverförmige Formmasse aus Polyhydroxybutyrat (PHB) mit einer mittleren Molmasse von Mw = 500 000 g/mol und einer Schmelztemperatur von Tm= 178 °C wird in ein dreiseitig geschlossenes Preßwerkzeug mit Stempel (Grundfläche 15 x 70 mm2) eingefüllt und bei Raumtemperatur mit einem Druck von 100 MPa hydrostatisch zu einem Vorformling mit einer Dichte von = 1. 1 0 g/cm3 verpreßt. Die Dicke des Vorformlings wird über die Menge des dosierten Pulvers auf 3 mm eingestellt.A powdery molding compound made of polyhydroxybutyrate (PHB) with an average molar mass of M w = 500,000 g / mol and a melting temperature of T m = 178 ° C is filled into a press tool with a stamp closed on three sides (base area 15 x 70 mm 2 ) and at Room temperature hydrostatically compressed at a pressure of 100 MPa to a preform with a density of = 1. 1 0 g / cm 3 . The thickness of the preform is adjusted to 3 mm based on the amount of powder dosed.
Anschließend wird der Vorformling in ein beheiztes Kanaldüsenwerkzeug mit L = 70 mm und s = 15 mm entsprechend Abbildung 2 überführt und nach Temperierung auf 120 °C mittels Stempel plastisch deformiert. Im Ergebnis der dabei stattfindenden deviatorischen Beanspruchung wird der Werkstoff aus dem Kanaldüsenwerkzeug herausextrudiert. Nach Reduzierung der Dicke des Vorformlings auf 1 ,5 mm (Umformverhältnis λ= 2) wird der Deformationsvorgang abgebrochen und das Erzeugnis der Kanaldüse entnommen.The preform is then transferred to a heated channel nozzle tool with L = 70 mm and s = 15 mm according to Figure 2 and plastically deformed by means of a stamp after tempering to 120 ° C. As a result of the deviating stress that occurs, the material is extruded out of the channel nozzle tool. After reducing the thickness of the preform to 1.5 mm (forming ratio λ = 2), the deformation process is stopped and the product is removed from the channel nozzle.
Durch Fließpressen wird die Dichte des Materials auf 1 ,25 g/cm3 erhöht. Verbunden damit sind deutliche Verbesserungen der mechanischen Eigenschaften, insbesondere von Zugfestigkeit und Reißdehnung. Molekulare Abbauprozesse können nicht nachgewiesen werden. Zur Darstellung der Vorzüge der erfindungsgemäßen Fließpreßtechnologie wurde das verwendete pulverförmige Ausgangsmaterial des weiteren sowohl durch Verpressen im Schmelzezustand (Preßtemperatur T = 180 °C, Preßzeit t = 3 Minuten) als auch durch Preßsintern in der festen Phase (Preßsintertemperatur T = 120 °C. Preßdruck p = 100 MPa) verarbeitet. Ausgewählte Kennwerte der nach unterschiedlichen Verfahren hergestellten Halbzeuge in Abbildung 1 dokumentieren die Überlegenheit der erfindungsgemäßen Fließpreßtechnologie. The density of the material is increased to 1.25 g / cm 3 by extrusion. Associated with this are significant improvements in mechanical properties, in particular tensile strength and elongation at break. Molecular degradation processes cannot be demonstrated. To illustrate the advantages of the extrusion technology according to the invention the powdery starting material used is further processed both by pressing in the melt state (pressing temperature T = 180 ° C, pressing time t = 3 minutes) and by press sintering in the solid phase (press sintering temperature T = 120 ° C. pressing pressure p = 100 MPa). Selected characteristic values of the semi-finished products manufactured according to different processes in Figure 1 document the superiority of the extrusion technology according to the invention.

Claims

Patentansprüche claims
1. Verfahren zur Formgebung von puiverförmigen, thermisch instabilen Thermoplastformmassen, dadurch gekennzeichnet, daß die unter hydrostatischem Druck vorverdichtete pulverförmige Thermoplastformmasse bei einer Temperatur unterhalb der Schmelztemperatur der Thermoplastformmasse einer deviatorischen Beanspruchung bis zu einem Umformverhältnis λ ≥ 1 ,5 ausgesetzt wird.1. A process for shaping puiver-shaped, thermally unstable thermoplastic molding compositions, characterized in that the pulverulent thermoplastic molding composition which has been pre-compressed under hydrostatic pressure is subjected to deviatoric stress at a temperature below the melting temperature of the thermoplastic molding composition up to a shaping ratio λ ≥ 1.5.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß die Temperatur 5 bis 20% unterhalb der Schmelztemperatur der Thermoplastformmasse liegt.2. The method according to claim 1, characterized in that the temperature is 5 to 20% below the melting temperature of the thermoplastic molding composition.
3. Verfahren nach Anspruch 1 und 3, dadurch gekennzeichnet, daß die Thermoplastformmassen Polyhydroxyalkanoate sind.3. The method according to claim 1 and 3, characterized in that the thermoplastic molding compositions are polyhydroxyalkanoates.
4. Verfahren nach Anspruch 1 bis 3, dadurch gekennzeichnet, daß die Thermoplastfor masse eine Polyhydroxybuttersäure bzw. deren Copolymerisat aus bakterieller Fermentation ist.4. The method according to claim 1 to 3, characterized in that the Thermoplastfor mass is a polyhydroxybutyric acid or its copolymer from bacterial fermentation.
5. Verfahren nach Anspruch 1 und 2, dadurch gekennzeichnet, daß die Thermoplastformmassen Polylactide sind.5. The method according to claim 1 and 2, characterized in that the thermoplastic molding compositions are polylactides.
6. Verfahren nach Anspruch 1 bis 5, dadurch gekennzeichnet, daß der puiverförmigen Thermoplastformmasse anorganische oder organische Zusatzstoffe als Füll- oder Verstärkerstoffe enthält. 6. The method according to claim 1 to 5, characterized in that the powder-shaped thermoplastic molding composition contains inorganic or organic additives as fillers or reinforcing materials.
PCT/DE1997/001969 1996-09-18 1997-09-05 Method of shaping powdery, thermally unstable thermoplastic shaping compounds WO1998012035A1 (en)

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EP97954859A EP0944463A1 (en) 1996-09-18 1997-09-05 Method of shaping powdery, thermally unstable thermoplastic shaping compounds

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DE1996137904 DE19637904A1 (en) 1996-09-18 1996-09-18 Process for shaping powdery, thermally unstable thermoplastic molding compounds

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DE10054431B4 (en) * 2000-10-26 2009-12-03 Volkswagen Ag Method for painting a plastic body part and tempering frame
US9475217B2 (en) 2013-01-31 2016-10-25 Saudi Basic Industries Corporation Process for making highly crystalline shaped part from pet or pen

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