EP0785965A1 - Prefoamed polyolefin particles produced by extrusion - Google Patents

Prefoamed polyolefin particles produced by extrusion

Info

Publication number
EP0785965A1
EP0785965A1 EP95935911A EP95935911A EP0785965A1 EP 0785965 A1 EP0785965 A1 EP 0785965A1 EP 95935911 A EP95935911 A EP 95935911A EP 95935911 A EP95935911 A EP 95935911A EP 0785965 A1 EP0785965 A1 EP 0785965A1
Authority
EP
European Patent Office
Prior art keywords
polyolefin
particles
extrusion
blowing agent
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95935911A
Other languages
German (de)
French (fr)
Inventor
Joachim Fischer
Franz-Josef Dietzen
Gerd Ehrmann
Isidoor De Grave
Jens Rieger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
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Filing date
Publication date
Application filed by BASF SE filed Critical BASF SE
Publication of EP0785965A1 publication Critical patent/EP0785965A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/22—After-treatment of expandable particles; Forming foamed products
    • C08J9/228—Forming foamed products
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/16—Making expandable particles
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/06—Polyethene

Definitions

  • Pre-expanded polyolefin particles made by extrusion
  • the invention relates to prefoamed polyolefin particles produced by extrusion and subsequent granulation.
  • Pre-expanded polyolefin particles in particular based on a copolymer of propylene with small amounts of ethylene, are being used to an increasing extent for the production of foam molded parts in the automotive, packaging and leisure sectors.
  • the foam particles are usually produced by suspending finely divided polyolefin granules in water, impregnating them with a volatile blowing agent under pressure at temperatures close to the softening temperature of the polyolefin, relaxing and thereby foaming (see EP-A 53333).
  • the polyolefin has a special crystal structure, which is characterized in that it has a peak characteristic of the polyolefin and a high-temperature peak (so-called “double peak”) in a DSC curve.
  • EP-A 588 321 describes a particularly elegant and simple method for producing prefoamed polypropylene particles.
  • Polypropylene is melted in an extruder, a blowing agent is injected into this melt and mixed homogeneously at 125 to 250.degree. The homogeneous mass is pressed out through a round nozzle, foams up and is cut into foam particles.
  • the polypropylene used should have a melt strength of 5 to 40 cN and a branched structure.
  • the foam particles produced in this way have a very narrow processing range in the production of molded parts and do not weld sufficiently well to one another. For this reason, the molded parts have relatively poor mechanical properties; especially elongation at break and tensile strength leave something to be desired.
  • the invention was therefore based on the object of providing pre-foamed polyolefin particles which had been produced from a conventional, ie not melt-strengthened, polyolefin by extrusion and subsequent granulation and which can be welded to molded parts with good mechanical properties without problems. It was found that this is the case if the polyolefin in the foam particles has a crystal structure with a double peak, the distance between the two tips being at least 5 ° C., preferably more than 8 ° C.
  • polyolefins are crystalline olefin polymers whose X-ray crystallinity is above 25% at 25 ° C.
  • Low, medium and high density polyethylenes between 0.88 to 0.965 g / cm 3 polypropylene and ethylene and propylene copolymers which contain at least 50 mol% of ethylene or propylene units are suitable for the process.
  • Suitable comonomers are, for example, ⁇ -alkenes having up to 12 carbon atoms, such as ethylene, propylene, butene, pentene, hexene, octene, and also vinyl esters, such as vinyl acetate, esters of acrylic acid, methacrylic acid, maleic acid or fumaric acid with alcohols which have 1 to 8 Contain carbon atoms, copolymers of ethylene and acrylic acid or their derivatives, and ionomers. Mixtures of different olefin polymers can also be used.
  • Ethylene-propylene copolymers and copolymers of ethylene and / or propylene with a C 4 - bis are preferably used
  • propylene copolymers are copolymers of propylene with 0.5 to 6% by weight of ethylene or 0.5 to 15% by weight of butene (1).
  • Particularly preferred ethylene copolymers are copolymers of ethylene with 1 to 18% by weight of butene (1), hexene (1) or octene (1).
  • a C 4 - to C 8 - ⁇ -01e-fin such as butene-1, pentene-1, hexene-1, heptene-1 or octene-1.
  • the copolymers should have a G modulus of 100 to 900, preferably 150 to 750 N / mm 2 .
  • the copolymers are prepared in a known manner by copolymerizing the monomers using transition metal catalysts.
  • the copolymers are generally linear, uncrosslinked and not melt-solidified.
  • the crystallite point, determined by the DSC method is generally zwi ⁇ rule 95 and 170 C C.
  • the heat of fusion is generally from 30 to 130 J / g, preferred wise between 35 and 120 J / g.
  • Copolymers with a melt index MFI (230; 2.16) (according to DIN 53 735) of 0.1 to 50, in particular 0.5 to 20 [g / 10 min] are preferably used.
  • the foam particles according to the invention are produced by impregnating polyolefin particles with a blowing agent in an extruder at a low temperature, homogenizing and dwelling the mass at higher temperatures and finally pressing out with foaming.
  • the polyolefin particles are impregnated with a volatile blowing agent.
  • Fine semolina with particle sizes of 0.01 to 10 mm, such as is obtained directly in the polymerization, or granules with particle sizes of 0.1 to 10 mm, as is obtained in the extrusion of the polyolefin, can be used.
  • Suitable blowing agents are organic compounds with boiling points between 0 and 150 ° C., for example n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane or cyclohexane, heptanes, octanes,
  • Halogenated hydrocarbons and their mixtures The amount of blowing agent depends on the desired bulk density of the foam particles. It is preferably 5 to 40, in particular 8 to 30 parts by weight, based on 100 parts by weight of polyolefin. At this point it is also possible to add conventional additives in effective amounts, such as dyes, pigments, nucleating agents, stabilizers, flame retardants, lubricants and antistatic agents.
  • the polyolefin particles are impregnated with the blowing agent preferably in the only slightly sheared feed zone of an extruder. It is essential that the swelling takes place at a relatively low temperature, ie the temperature must be 50 to 180, preferably 100 to 150 ° C. below the crystalline melting point of the polyolefin and at least 10 ° C. below the boiling point of the blowing agent, so that the latter does not evaporate.
  • the temperature By applying an excess pressure of maximum 10 bar, low-boiling blowing agents, such as butanes, can also be metered in at room temperature.
  • the polyolefin particles are fed to zone A, for example via a cell-wheel lock.
  • the temperature in the zone A is preferably zwi ⁇ 's 10 and 40 C C, especially at room temperature.
  • the residence time in this zone is preferably 0.1 to 5 minutes.
  • the polyolefin is soaked with the blowing agent to such an extent that its viscosity is greatly reduced.
  • zone B The described lowering of the viscosity makes it possible to carry out the homogenization in zone B at temperatures which are 2 to 50 ° C., preferably 5 to 40 ° C. below the crystallite melting point of the pure polyolefin lie. This is a further advantage over the method according to EP-A 588 321, where extrusion takes place at considerably higher temperatures.
  • This homogenization with simultaneous temperature increase is preferably carried out in a second zone (homogenization zone) of the extruder already used in stage A.
  • zine B in order to regulate the cell diameter, small amounts (for example 0.1 to 5% by weight) of carbon dioxide or nitrogen can be metered in.
  • the mass is then kept for a time, preferably 1 to 60 minutes, at a temperature which is 2 to 50 ° C. below the crystalline melting point of the polyolefin.
  • This is expediently carried out in a residence time zone C downstream of zone B, for example a static mixer (Sulzer mixer) or a low-shear extruder (single-screw extruder).
  • the resulting foam particles are ellipsoid to spherical.
  • the average diameter is 2 to 20 mm.
  • Their debris weight can be set within wide limits between 0.01 and 0.2 g ⁇ cm "-, preferably between 0.01 and 0.15 g • cm -1 .
  • the number of cells is generally 0.1 to 1000 cells per mm 2 .
  • Shaped parts with good mechanical properties can be produced in a conventional manner from the pre-expanded particles according to the invention by welding.
  • a dwell time zone C consisting of 4 Sulzer mixers (DN * • »80 mm) was connected to the gear pump. These were kept at 130 ° C. After a dwell time of 45 min, the polymer containing blowing agent was pressed out of a round nozzle with a diameter of 2 mm and was blown by means of a granulator from
  • the foam particles obtained had a diameter of 10 mm. Their bulk density was .22 g • L ⁇ -.
  • the DSC curve shows two maxima at 146 ° C and 160 ° C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Processes Of Treating Macromolecular Substances (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)

Abstract

Prefoamed polyolefin particles produced by extrusion then by granulation have a crystalline structure with a double peak.

Description

Durch Extrusion hergestellte, vorgeschäumte PolyolefinteilchenPre-expanded polyolefin particles made by extrusion
Beschreibungdescription
Die Erfindung betrifft durch Extrusion und anschließende Granu¬ lierung hergestellte, vorgeschäumte Polyolefinteilchen.The invention relates to prefoamed polyolefin particles produced by extrusion and subsequent granulation.
Vorgeschäumte Polyolefinteilchen, insbesondere auf Basis eines Copolymeren des Propylens mit geringen Mengen Ethylen werden in steigendem Maß zur Herstellung von Schaumstoff-Formteilen im Automobilbau, Verpackungswesen und Freizeitbereich eingesetzt. Die Schaumstoffteilchen werden üblicherweise hergestellt, indem man feinteiliges Polyolefingranulat in Wasser suspendiert, bei Temperaturen nahe der Erweichungstemperatur des Polyolefins unter Druck mit einem flüchtigen Treibmittel imprägniert, entspannt und dabei aufschäumt (siehe EP-A 53333) . In den so hergestellten Schaumteilchen hat das Polyolefin eine spezielle Kristall¬ struktur, die dadurch charakterisiert ist, daß es in einer DSC- Kurve eine für das Polyolefin charakteristische Spitze und eine Hochtemperaturspitze (sogen. "Doppelpeak") aufweist.Pre-expanded polyolefin particles, in particular based on a copolymer of propylene with small amounts of ethylene, are being used to an increasing extent for the production of foam molded parts in the automotive, packaging and leisure sectors. The foam particles are usually produced by suspending finely divided polyolefin granules in water, impregnating them with a volatile blowing agent under pressure at temperatures close to the softening temperature of the polyolefin, relaxing and thereby foaming (see EP-A 53333). In the foam particles produced in this way, the polyolefin has a special crystal structure, which is characterized in that it has a peak characteristic of the polyolefin and a high-temperature peak (so-called “double peak”) in a DSC curve.
In der EP-A 588 321 ist ein besonders elegantes und einfaches Verfahren zur Herstellung von vorgeschäumten Polypropylenteilchen beschrieben. Dabei wird in einem Extruder Polypropylen aufge¬ schmolzen, in diese Schmelze wird ein Treibmittel injiziert und bei 125 bis 250°C homogen eingemischt. Die homogene Masse wird durch eine Runddüse ausgepreßt, schäumt dabei auf und wird zu Schaumstoffteilchen geschnitten. Das eingesetzte Polypropylen soll eine Schmelzefestigkeit von 5 bis 40 cN und eine verzweigte Struktur aufweisen. Es hat sich aber gezeigt, daß die so herge¬ stellten Schaumpartikel bei der Formteilherstellung eine sehr enge Verarbeitungsbreite haben und nicht ausreichend gut mitein¬ ander verschweißen. Aus diesem Grund haben die Formteile verhält- nismäßig schlechte mechanische Eigenschaften; insbesondere Bruch¬ dehnung und Zugfestigkeit lassen zu wünschen übrig.EP-A 588 321 describes a particularly elegant and simple method for producing prefoamed polypropylene particles. Polypropylene is melted in an extruder, a blowing agent is injected into this melt and mixed homogeneously at 125 to 250.degree. The homogeneous mass is pressed out through a round nozzle, foams up and is cut into foam particles. The polypropylene used should have a melt strength of 5 to 40 cN and a branched structure. However, it has been found that the foam particles produced in this way have a very narrow processing range in the production of molded parts and do not weld sufficiently well to one another. For this reason, the molded parts have relatively poor mechanical properties; especially elongation at break and tensile strength leave something to be desired.
Der Erfindung lag also die Aufgabe zugrunde, aus einem konventio¬ nellen, d.h. nicht schmelzeverfestigten Polyolefin durch Extrusion und anschließende Granulierung hergestellte, vor¬ geschäumte Polyolefinteilchen bereitzustellen, die sich problem¬ los zu Formteilen mit guten mechanischen Eigenschaften ver¬ schweißen lassen. Es wurde gefunden, daß dies der Fall ist, wenn das Polyolefin in den Schaumstoffteilchen eine Kristallstruktur mit Doppelpeak auf¬ weist, wobei der Abstand zwischen den beiden Spitzen mindestens 5"C, vorzugsweise mehr als 8°C beträgt.The invention was therefore based on the object of providing pre-foamed polyolefin particles which had been produced from a conventional, ie not melt-strengthened, polyolefin by extrusion and subsequent granulation and which can be welded to molded parts with good mechanical properties without problems. It was found that this is the case if the polyolefin in the foam particles has a crystal structure with a double peak, the distance between the two tips being at least 5 ° C., preferably more than 8 ° C.
Polyolefine im Sinne der Erfindung sind kristalline Olefinpoly- merisate, deren Röntgenkristallinität bei 25°C über 25 % liegt. Für das Verfahren eignen sich Polyethylene niedriger, mittlerer und hoher Dichte zwischen 0,88 bis 0,965 g/cm3, Polypropylen so- wie Ethylen- und Propylencopolymere, die mindestens 50 Mol.-% Ethylen- bzw. Propylen-Einheiten enthalten. Geeignete Comonomere sind beispielsweise α-Alkene mit bis zu 12 Kohlenstoffatomen, wie Ethylen, Propylen, Buten, Penten, Hexen, Octen, ferner Vinyl- ester, wie Vinylacetat, Ester der Acrylsäure, Methacrylsäure, Maleinsäure oder Fumarsäure mit Alkoholen, die 1 bis 8 C-Atome enthalten, Copolymere aus Ethylen und Acrylsäure bzw. deren Deri¬ vaten, sowie Ionomeren. Auch Mischungen verschiedener Olefinpoly- erisate können verwendet werden.For the purposes of the invention, polyolefins are crystalline olefin polymers whose X-ray crystallinity is above 25% at 25 ° C. Low, medium and high density polyethylenes between 0.88 to 0.965 g / cm 3 , polypropylene and ethylene and propylene copolymers which contain at least 50 mol% of ethylene or propylene units are suitable for the process. Suitable comonomers are, for example, α-alkenes having up to 12 carbon atoms, such as ethylene, propylene, butene, pentene, hexene, octene, and also vinyl esters, such as vinyl acetate, esters of acrylic acid, methacrylic acid, maleic acid or fumaric acid with alcohols which have 1 to 8 Contain carbon atoms, copolymers of ethylene and acrylic acid or their derivatives, and ionomers. Mixtures of different olefin polymers can also be used.
Bevorzugt eingesetzt werden Ethylen-Propylen-Copolymere und Copolymere von Ethylen und/oder Propylen mit einem C4- bisEthylene-propylene copolymers and copolymers of ethylene and / or propylene with a C 4 - bis are preferably used
Ctj-o-Olefin.Ctj-o-olefin.
Besonders bevorzugte Propylen-Copolymere sind Copolymere des Propylens mit 0,5 bis 6 Gew.-% Ethylen oder 0,5 bis 15 Gew.-% Buten (1). Besonders bevorzugte Ethylen-Copolymere sind Copolymere des Ethylens mit 1 bis 18 Gew.-% Buten (1), Hexen (1) oder Octen (1) .Particularly preferred propylene copolymers are copolymers of propylene with 0.5 to 6% by weight of ethylene or 0.5 to 15% by weight of butene (1). Particularly preferred ethylene copolymers are copolymers of ethylene with 1 to 18% by weight of butene (1), hexene (1) or octene (1).
Besonders bevorzugt sind auch Copolymere von Propylen mit 0,5 bis 6 Gew.-O, vorzugsweise 1,5 bis 6 Gew.-% Ethylen und 0,5 bis 6 Gew.-%, vorzugsweise 1,5 bis 6 Gew.-% eines C4- bis C8-α-01e- fins, wie Buten-1, Penten-1, Hexen-1, Hepten-1 oder Octen-1. Die Copolymeren sollen einen G-Modul von 100 bis 900, vorzugsweise 150 bis 750 N/mm2 aufweisen.Copolymers of propylene with 0.5 to 6% by weight, preferably 1.5 to 6% by weight of ethylene and 0.5 to 6% by weight, preferably 1.5 to 6% by weight, are also particularly preferred. a C 4 - to C 8 -α-01e-fin such as butene-1, pentene-1, hexene-1, heptene-1 or octene-1. The copolymers should have a G modulus of 100 to 900, preferably 150 to 750 N / mm 2 .
Die Herstellung der Copolymeren erfolgt in bekannter Weise durch Copolymerisation der Monomeren mittels Übergangsmetallkataly¬ satoren. Die Copolymeren sind im allgemeinen linear aufgebaut, unvernetzt und nicht schmelzeverfestigt. Der Kristallitschmelz- punkt, bestimmt nach der DSC-Methode, liegt im allgemeinen zwi¬ schen 95 und 170CC. Die Schmelzwärme, bestimmt nach der DSC- Methode, liegt im allgemeinen zwischen 30 und 130 J/g, vorzugs¬ weise zwischen 35 und 120 J/g. Vorzugsweise werden Copolymere mit einem Schmelzindex MFI (230; 2,16) (nach DIN 53 735) von 0,1 bis 50, insbesondere 0,5 bis 20 [g/10 min] verwendet. Die Herstellung der erfindungsgemäßen Schaumteilchen erfolgt bei einem bevorzugten Verfahren durch Tränken von Polyolefinpartikeln mit einem Treibmittel in einem Extruder bei niedriger Temperatur, Homogenisieren und Verweilen der Masse bei höheren Temperaturen und schließlich Auspressen unter Aufschäumen.The copolymers are prepared in a known manner by copolymerizing the monomers using transition metal catalysts. The copolymers are generally linear, uncrosslinked and not melt-solidified. The crystallite point, determined by the DSC method, is generally zwi¬ rule 95 and 170 C C. The heat of fusion, as determined by the DSC method, is generally from 30 to 130 J / g, preferred wise between 35 and 120 J / g. Copolymers with a melt index MFI (230; 2.16) (according to DIN 53 735) of 0.1 to 50, in particular 0.5 to 20 [g / 10 min] are preferably used. In a preferred process, the foam particles according to the invention are produced by impregnating polyolefin particles with a blowing agent in an extruder at a low temperature, homogenizing and dwelling the mass at higher temperatures and finally pressing out with foaming.
A. In einer ersten Zone A werden die Polyolefinpartikel mit einem flüchtigen Treibmittel getränkt. Dabei kann feiner Grieß mit Teilchengrößen von 0,01 bis 10 mm, wie er direkt bei der Polymerisation anfällt, eingesetzt werden, oder Gra¬ nulat mit Teilchengrößen von 0,1 bis 10 mm, wie es bei der Extrusion des Polyolefins anfällt. Geeignete Treibmittel sind organische Verbindungen mit Siedepunkten zwischen 0 und 150"C, beispielsweise n-Butan-, Isobutan, n-Pentan, Isopentan, Neopentan, Cyclopentan oder Cyclohexan, Heptane, Octane,A. In a first zone A, the polyolefin particles are impregnated with a volatile blowing agent. Fine semolina with particle sizes of 0.01 to 10 mm, such as is obtained directly in the polymerization, or granules with particle sizes of 0.1 to 10 mm, as is obtained in the extrusion of the polyolefin, can be used. Suitable blowing agents are organic compounds with boiling points between 0 and 150 ° C., for example n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane or cyclohexane, heptanes, octanes,
Halogenkohlenwasserstoffe, sowie deren Mischungen. Die Treib¬ mittelmenge richtet sich nach dem angestrebten Schüttgewicht der Schaumstoffteilchen. Sie beträgt bevorzugt 5 bis 40, ins¬ besondere 8 bis 30 Gew.-Teile, bezogen auf 100 Gew.-Teile Polyolefin. An dieser Stelle können auch übliche Zusatzstoffe in wirksamen Mengen, wie Farbstoffe, Pigmente, Keimbildner, Stabilisatoren, Flammschutzmittel, Gleitmittel und Anti- statika zugesetzt werden.Halogenated hydrocarbons and their mixtures. The amount of blowing agent depends on the desired bulk density of the foam particles. It is preferably 5 to 40, in particular 8 to 30 parts by weight, based on 100 parts by weight of polyolefin. At this point it is also possible to add conventional additives in effective amounts, such as dyes, pigments, nucleating agents, stabilizers, flame retardants, lubricants and antistatic agents.
Das Tränken der Polyolefinpartikel mit dem Treibmittel er¬ folgt bevorzugt in der nur schwach gescherten Einzugszone eines Extruders. Wesentlich ist, daß das Anquellen bei ver¬ hältnismäßig niedriger Temperatur geschieht, d.h., die Temperatur muß 50 bis 180, vorzugsweise 100 bis 150°C unter- halb des Kristallitschmelzpunktes des Polyolefins und minde¬ stens 10°C unterhalb des Siedepunkts des Treibmittels liegen, damit letzeres nicht verdampft. Durch Anlegen eines Über¬ drucks von maximal 10 bar können tiefsiedene Treibmittel, wie die Butane, auch bei Raumtemperatur zudosiert werden. In die- sem Fall werden die Polyolefinpartikel z.B. über eine Zell- Rad-Schleuse der Zone A zugeführt. Bei den bevorzugten Propylencopolymeren mit Kristallitschmelzpunkten zwischen 100 und 165°C liegt die Temperatur in der Zone A bevorzugt zwi¬ schen 10 und 40CC, insbesondere bei Raumtemperatur. Die Ver- weilzeit in dieser Zone beträgt vorzugsweise 0,1 bis 5 min. Dabei wird das Polyolefin soweit mit dem Treibmittel ge¬ tränkt, daß seine Viskosität stark erniedrigt wird.The polyolefin particles are impregnated with the blowing agent preferably in the only slightly sheared feed zone of an extruder. It is essential that the swelling takes place at a relatively low temperature, ie the temperature must be 50 to 180, preferably 100 to 150 ° C. below the crystalline melting point of the polyolefin and at least 10 ° C. below the boiling point of the blowing agent, so that the latter does not evaporate. By applying an excess pressure of maximum 10 bar, low-boiling blowing agents, such as butanes, can also be metered in at room temperature. In this case, the polyolefin particles are fed to zone A, for example via a cell-wheel lock. In preferred propylene copolymers having Kristallitschmelzpunkten 100-165 ° C, the temperature in the zone A is preferably zwi¬'s 10 and 40 C C, especially at room temperature. The residence time in this zone is preferably 0.1 to 5 minutes. The polyolefin is soaked with the blowing agent to such an extent that its viscosity is greatly reduced.
B. Durch die beschriebene Absenkung der Viskosität ist es mög- lieh, in der Zone B das Homogenisieren bei Temperaturen durchzuführen, die 2 bis 50°C, vorzugsweise 5 bis 40°C unter¬ halb des Kristallitschmelzpunktes des reinen Polyolefins liegen. Dies ist ein weiterer Vorteil gegenüber αem Verfahren nach EP-A 588 321, wo bei wesentlich honeren Temperaturen ex- trudiert wird. Dieses Homogenisieren unter gleichzeitiger Temperaturerhöhung wird vorzugsweise in einer 2. Zone (Homo- genisierzone) des bereits in Stufe A benutzten Extruders durchgeführt. In der Zine B kann zur Regulierung des Zell¬ durchmessers in kleinen Mengen (z.B. 0,1 bis 5 Gew.-%) Koh¬ lendioxid bzw. Stickstoff zudosiert werden.B. The described lowering of the viscosity makes it possible to carry out the homogenization in zone B at temperatures which are 2 to 50 ° C., preferably 5 to 40 ° C. below the crystallite melting point of the pure polyolefin lie. This is a further advantage over the method according to EP-A 588 321, where extrusion takes place at considerably higher temperatures. This homogenization with simultaneous temperature increase is preferably carried out in a second zone (homogenization zone) of the extruder already used in stage A. In zine B, in order to regulate the cell diameter, small amounts (for example 0.1 to 5% by weight) of carbon dioxide or nitrogen can be metered in.
C. Anschließend wird die Masse einige Zeit, vorzugsweise 1 bis 60 min bei einer Temperatur, die 2 bis 50°C unterhalb des Kristallitschmelzpunktes des Polyolefins liegt, gehalten. Dies geschieht zweckmaßigerweise in einer der Zone B nach¬ geschalteten Verweilzeitzone C, beispielsweise einem sta- tischen Mischer (Sulzer-Mischer) oder einem schwach scherenden Extruder (Einschneckenextruder) .C. The mass is then kept for a time, preferably 1 to 60 minutes, at a temperature which is 2 to 50 ° C. below the crystalline melting point of the polyolefin. This is expediently carried out in a residence time zone C downstream of zone B, for example a static mixer (Sulzer mixer) or a low-shear extruder (single-screw extruder).
Zur Verbesserung des Masseubergangs zwischen den Zonen B und C kann es besonders bei Verwendung eines statiscnen Mischers vorteilhaft sein, an der Übergangsstelle zwischen diese Zone eine Zahnradpumpe vorzusehen.To improve the mass transfer between zones B and C, it may be advantageous, particularly when using a static mixer, to provide a gear pump at the transition point between this zone.
D. Schließlich w rd die Masse aus dem Extruder, zweckmaßiger¬ weise durch eine oder mehrere Runddusen an die Atmosphäre ausgepreßt . Das durch den plötzlichen Druckverlust expan¬ dierte Polyolefin wird direkt anschließend granuliert, zweck¬ maßigerweise durch einen Heißabschlag.D. Finally, the mass is pressed out of the extruder, expediently through one or more round nozzles into the atmosphere. The polyolefin expanded due to the sudden loss of pressure is then granulated directly, expediently by hot cutting.
Die entstandenen Schaumstoffteilchen sind ellipsiod bis kugelfor- mig. Der mittlere Durchmesser beträgt 2 bis 20 mm. Ihr Schutt¬ gewicht kann in weiten Grenzen zwischen 0,01 und 0,2 g • cm"-, vorzugsweise zwischen 0,01 und 0,15 g • cm-1 eingestellt werden. Die Zellzahl betragt im allgemeinen 0,1 bis 1000 Zellen pro mm2.The resulting foam particles are ellipsoid to spherical. The average diameter is 2 to 20 mm. Their debris weight can be set within wide limits between 0.01 and 0.2 g · cm "-, preferably between 0.01 and 0.15 g • cm -1 . The number of cells is generally 0.1 to 1000 cells per mm 2 .
Aus den erfindungsgemäßen vorgeschäumten Teilchen können durch Verschweißen auf übliche Weise Formteile mit guten mechanischen Eigenschaften hergestellt werden.Shaped parts with good mechanical properties can be produced in a conventional manner from the pre-expanded particles according to the invention by welding.
Beispielexample
In die Einzugszone A eines Doppelschneckenextruders (D - 60 mm, L = 36*D) wurden kontinuierlich 15 kg/h eines grießformigen Copolymeren des Propylens mit 2,5 Gew.-% Ethylen (Kristallit- schmelzpunkt 147,5=C) , sowie 0,15 kg/h Talkum zugeführt. Zwischen Einzugszone und der Übergangsstelle in die Homogenisierzone wurde das Treibmittel (3 kg/h Cyclopentan) eingespritzt. Die Temperatur an dieser Stelle betrug 25°C, es herrschte Normaldruck. Danach erfolgte der Übergang m die Homogenisierzone B, wo der Extruder auf eine Gehäusetemperatur von 100~ beheizt wurde. Da¬ durch und durch die Friktionswärme stieg die Massetemperatur auf 125rC, wobei die Masse punktuell aufschmolz. Danach wurde mittels einer auf 130°C temperierte Zahnradpumpe ein Druck von etwaIn the feed zone A of a twin-screw extruder (D - 60 mm, L = 36 * D), 15 kg / h of a granular copolymer of propylene with 2.5% by weight of ethylene (crystallite melting point 147.5 = C) and 0.15 kg / h talcum fed. The blowing agent (3 kg / h cyclopentane) was injected between the feed zone and the transition point into the homogenization zone. The temperature at this point was 25 ° C, there was normal pressure. This was followed by the transition into the homogenizing zone B, where the extruder was heated to a housing temperature of 100 ~. As a result, and through the heat of friction, the melt temperature rose to 125 r C, the melt melted selectively. Thereafter, a pressure of about
170 bar aufgebaut. An die Zahnradpumpe schloß sich eine Verweil¬ zeitzone C, bestehend aus 4 Sulzermischern (DN *•» 80 mm) an. Diese wurden auf 130 C gehalten. Nach einer Verweilzeit von 45 min wurde das treibmittelhaltige Polymere aus einer Runddüse mit Durch- messer 2 mm ausgepreßt und mittels eines Granulators der Fa.Built up 170 bar. A dwell time zone C consisting of 4 Sulzer mixers (DN * • »80 mm) was connected to the gear pump. These were kept at 130 ° C. After a dwell time of 45 min, the polymer containing blowing agent was pressed out of a round nozzle with a diameter of 2 mm and was blown by means of a granulator from
Berstorff granuliert. Die erhaltenen Schaumpartikel hatten einen Durchmesser von 10 mm. Ihre Schüttdichte betrug .22 g • L~- . Die DSC-Kurve zeigt zwei Maxima bei 146°C und 160°C. Berstorff granulated. The foam particles obtained had a diameter of 10 mm. Their bulk density was .22 g • L ~ -. The DSC curve shows two maxima at 146 ° C and 160 ° C.

Claims

Patentansprüche claims
1. Durch Extrusion und anschließende Granulierung hergestellte, vorgeschäumte Polyolefinteilchen, gekennzeichnet durch eine1. Pre-expanded polyolefin particles produced by extrusion and subsequent granulation, characterized by a
Kristallstruktur, welche in einer DSC-Kurve (erhalten durch Erhitzen von 3 bis 6 mg der Schaumpartikel auf 220°C mit einer Aufheizgeschwindigkeit von 20°C/min mit einem Differentialkalorimeter) eine für das Polyolefin charakteri- stische Spitze und eine Hochtemperaturspitze aufweist, wobei der Abstand zwischen den beiden Spitzen mindestens 5°C be¬ trägt .Crystal structure which has a peak characteristic of the polyolefin and a high temperature peak in a DSC curve (obtained by heating 3 to 6 mg of the foam particles to 220 ° C. with a heating rate of 20 ° C./min using a differential calorimeter), where the distance between the two tips is at least 5 ° C.
2. Vorgeschäumte Polyolefinteilchen nach Anspruch 1, dadurch ge- kennzeichnet, daß das Polyolefin ein statistisches Copolymer des Propylens mit 0,5 bis 6 Gew.-% Ethylen und/oder Buten-1 ist .2. Pre-expanded polyolefin particles according to claim 1, characterized in that the polyolefin is a random copolymer of propylene with 0.5 to 6% by weight of ethylene and / or butene-1.
3. Vorgeschäumte Polyolefinteilchen nach Anspruch 1 mit einer Schüttdichte von 0,01 bis 0,2 g • cπr: .3. Pre-expanded polyolefin particles according to claim 1 with a bulk density of 0.01 to 0.2 g • cπr :.
4. Vorgeschäumte Polyolefinteilchen nach Anspruch 1 mit einem Durchmesser von 2 bis 20 mm.4. Pre-expanded polyolefin particles according to claim 1 with a diameter of 2 to 20 mm.
5. Verfahren zur Herstellung der vorgeschäumten Polyolefin¬ teilchen nach Anspruch 1, dadurch gekennzeichnet, daß man5. A process for the preparation of the pre-expanded Polyolefin¬ particles according to claim 1, characterized in that
A. in einer Einzugszone eines Extruders Polyolefin-Partikel mit einem physikalischen Treibmittel bei einer Temperatur, die 50 bis 180°C unterhalb des Kristallit¬ schmelzpunktes des Polyolefins und mindestens 10°C unter¬ halb des Siedepunkts des Treibmittels liegt, tränkt.A. Soak polyolefin particles in a feed zone of an extruder with a physical blowing agent at a temperature which is 50 to 180 ° C. below the crystallite melting point of the polyolefin and at least 10 ° C. below the boiling point of the blowing agent.
B. in einer Homogenisierungszone des Extruders unter Tempe- raturerhöhung das treibmittelhaltige Polyolefin homo¬ genisiert, wobei die Massetemperatur 2 bis 50°C unterhalb des Kristallitschmelzpunktes des reinen Polyolefins liegt,B. in a homogenization zone of the extruder while increasing the temperature, the blowing agent-containing polyolefin is homogenized, the melt temperature being 2 to 50 ° C. below the crystallite melting point of the pure polyolefin,
C. in einer Verweilzeitzone die Masse 1 bis 60 min bei dieser Temperatur hält, undC. the mass is kept at this temperature in a residence time zone for 1 to 60 minutes, and
das treibmittelhaltige Polyolefin an die Atmosphäre aus¬ preßt, dadurch aufschäumt und schließlich granuliert. GEÄNDERTE ANSPRÜCHEpresses the blowing agent-containing polyolefin into the atmosphere, thereby foaming and finally granulating. CHANGED REQUIREMENTS
[heim Internationalen Büro am 27. März 1996 (27.03.96) ein-iecangen, ursprünglicher Anspruch 1 durch geänderten -naprjc-i ι ; alle weiteren Ansprüche unverändert (1 Seite)][Home International Office on March 27, 1996 (March 27, 1996), original claim 1 by amended -naprjc-i ι ; all other claims unchanged (1 page)]
1. Vorgeschäumte Polyolefinteilchen, die durch Extrusion, Aus- pressen unter Aufschäumen und anschließende Granulierung des ausgeschäumten Strangs hergestellt wurden, gekennzeichnet durch eine Kristallstruktur, welche in einer DSC-Kurve (er¬ halten durch Erhitzen von 3 bis 6 mg der Schaumpartikel auf 220°C mit einer Aufheizgeschwindigkeit von 20°C/min mit einem Differentialkalorimeter) eine für das Polyolefin charakteri¬ stische Spitze und eine Hochtemperaturspitze aufweist, wobei der Abstand zwischen den beiden Spitzen mindestens 5°C be¬ trägt. 1. Pre-expanded polyolefin particles which were produced by extrusion, extrusion with foaming and subsequent granulation of the foamed strand, characterized by a crystal structure which is obtained in a DSC curve (obtained by heating 3 to 6 mg of the foam particles to 220 ° C with a heating rate of 20 ° C / min with a differential calorimeter) has a peak characteristic of the polyolefin and a high temperature peak, the distance between the two peaks being at least 5 ° C.
EP95935911A 1994-10-15 1995-10-06 Prefoamed polyolefin particles produced by extrusion Withdrawn EP0785965A1 (en)

Applications Claiming Priority (3)

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DE4436980A DE4436980A1 (en) 1994-10-15 1994-10-15 Pre-expanded polyolefin particles made by extrusion
DE4436980 1994-10-15
PCT/EP1995/003946 WO1996011971A1 (en) 1994-10-15 1995-10-06 Prefoamed polyolefin particles produced by extrusion

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DE19739113A1 (en) * 1997-09-06 1999-03-11 Gefinex Polymerschaeume Gmbh Pre-expanded polyolefin foam particles
DE19740058C2 (en) * 1997-09-12 2001-10-31 Mannesmann Vdo Ag Process for the manufacture of a float, fuel-resistant float and use of particles pressed together and produced by extrusion
JP3692760B2 (en) * 1998-01-30 2005-09-07 株式会社カネカ Method for producing foamed molded product in polypropylene resin mold
JP3950557B2 (en) 1998-07-30 2007-08-01 株式会社カネカ Polypropylene-based resin pre-expanded particles and method for producing in-mold expanded molded articles therefrom
JP3581025B2 (en) * 1998-08-03 2004-10-27 住友化学工業株式会社 Method for producing non-crosslinked polypropylene resin foam sheet and non-crosslinked polypropylene resin foam sheet
CN1311013C (en) 1999-12-28 2007-04-18 钟渊化学工业株式会社 Expandable styrene resin beads and foams produced therefrom
FR2856950B1 (en) * 2003-07-04 2007-03-02 Rhodia Polyamide Intermediates PROCESS FOR PREPARING PEARL BASED OF EXPANDED POLYMER
TW200708541A (en) * 2005-08-31 2007-03-01 Chi Lin Technology Co Ltd Method of making polyester foam particles
CN108329590A (en) * 2018-02-08 2018-07-27 贵州省材料产业技术研究院 A kind of bimodal crystalline polypropylene composite material and preparation method

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EP0123144B1 (en) * 1983-03-25 1987-10-07 Japan Styrene Paper Corporation Polypropylene resin prefoamed particles
JPS60110734A (en) * 1983-11-21 1985-06-17 Japan Styrene Paper Co Ltd Pre-expanded particle of uncrosslinked polypropylene resin
CA1280549C (en) * 1986-05-27 1991-02-19 Kyoichi Nakamura Pre-expanded particles of propylene resin
JP2878527B2 (en) * 1992-06-22 1999-04-05 鐘淵化学工業株式会社 Pre-expanded particles of polyethylene resin
IT1255364B (en) * 1992-09-15 1995-10-31 Himont Inc PROCESS FOR THE PREPARATION OF EXPANDED POLYPROPYLENE MANUFACTURES THROUGH PRODUCTION OF PRE-EXPANDED GRANULES AND THERMOFORMING FOR SINTERING THEMSELVES
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