EP1537171A1 - Method for the production of low-bulk density polystyrene foam particles - Google Patents

Method for the production of low-bulk density polystyrene foam particles

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Publication number
EP1537171A1
EP1537171A1 EP03793763A EP03793763A EP1537171A1 EP 1537171 A1 EP1537171 A1 EP 1537171A1 EP 03793763 A EP03793763 A EP 03793763A EP 03793763 A EP03793763 A EP 03793763A EP 1537171 A1 EP1537171 A1 EP 1537171A1
Authority
EP
European Patent Office
Prior art keywords
blowing agent
polymer melt
foam particles
thermoplastic polymer
polystyrene
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Withdrawn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
EP03793763A
Other languages
German (de)
French (fr)
Inventor
Franz-Josef Dietzen
Gerd Ehrmann
Klaus Hahn
Swen RÜCK
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 EP1537171A1 publication Critical patent/EP1537171A1/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Withdrawn legal-status Critical Current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
    • C08J9/16—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
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0066—Use of inorganic compounding ingredients
    • 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
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/127—Mixtures of organic and inorganic blowing agents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of 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
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
    • C08L25/02—Homopolymers or copolymers of hydrocarbons
    • C08L25/04—Homopolymers or copolymers of styrene
    • C08L25/06—Polystyrene
    • 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
    • C08J2201/00—Foams characterised by the foaming process
    • C08J2201/02—Foams characterised by the foaming process characterised by mechanical pre- or post-treatments
    • C08J2201/03—Extrusion of the foamable blend
    • 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
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/06—CO2, N2 or noble gases
    • 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
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/12—Organic compounds only containing carbon, hydrogen and oxygen atoms, e.g. ketone or alcohol
    • 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
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/14—Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
    • 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
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/14—Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
    • C08J2203/142—Halogenated saturated hydrocarbons, e.g. H3C-CF3
    • 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
    • C08J2325/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
    • C08J2325/02—Homopolymers or copolymers of hydrocarbons
    • C08J2325/04—Homopolymers or copolymers of styrene
    • C08J2325/06—Polystyrene

Definitions

  • the invention relates to a method for producing foam particles with a low bulk density from thermoplastic polymers by extrusion of a polymer melt containing blowing agent, and foam particles obtainable by the method.
  • Polystyrene foam particles with low bulk densities in the range from 10 to 30 kg / m 3 can be produced, for example, by foaming pentane-containing, expandable polystyrene granules (EPS), which can be obtained by suspension polymerization.
  • EPS pentane-containing, expandable polystyrene granules
  • Such a method for producing discrete, closed-cell foam strands made of polystyrene is described, for example, in EP-A 0 665 865.
  • Environmentally friendly blowing agent mixtures containing at least 20% by weight of carbon dioxide or ethane are used as blowing agents.
  • the foam strands have to be expanded in a further stage with heated air or steam.
  • EP-A 0 981 574 describes particulate expandable styrene polymers which contain graphite particles in a homogeneous distribution in order to reduce the thermal conductivity.
  • the compact, blowing agent-containing granules can be produced, for example, by mixing polystyrene, graphite and pentane in a twin-screw extruder and then foamed to a lower density by vapor deposition.
  • the object of the invention was to find a process for producing foam particles from thermoplastic polymers which, by extrusion of a polymer melt containing blowing agent, leads directly to foam particles of low bulk density without additional expansion stages.
  • the process should also be suitable for the production of foam particles of low bulk density which contain IR absorbers. Accordingly, there has been a process for making foam particles from thermoplastic polymers comprising the steps
  • the blowing agent containing water and a solubilizer.
  • the blowing agent contains water, generally in amounts in the range from 0.1 to 3% by weight, preferably in the range from 0.5 to 1.5% by weight, based on the thermoplastic polymer used.
  • a solubilizer is additionally added according to the invention.
  • Aliphatic alcohols, ketones, ethers, esters or silicates are suitable as solubilizers.
  • Ethanol is preferably used.
  • Adsorbents are solids that can bind water in physical or chemical form, for example aluminum hydroxide, layered silicates or zeolites.
  • the solubilizer or adsorbent is generally used in amounts of 0.1 to 3% by weight, preferably in the range of 1 to 2% by weight, based on the
  • the blowing agent can contain the aliphatic, halogenated or halogen-free hydrocarbons with 3 to 10, preferably 4 to 6 carbon atoms, such as i-
  • inert gases such as carbon dioxide or nitrogen in amounts generally in the range of 0.1 to 10, preferably 0.3 to 7 wt .-%, based on the thermoplastic polymer used .
  • inert gases for example carbon dioxide
  • Styrene polymers such as crystal-clear or impact-resistant polystyrene, styrene copolymers with up to 45-20% by weight of ethylenically unsaturated comonomers such as alphamethylstyrene or acrylonitrile or polyolefins such as polyethylene can be used as thermoplastic polymers or polypropylene or mixtures of these polymers with one another or with polyphenylene ether.
  • thermoplastic polymers with a broad molecular weight distribution Polystyrene with a molecular weight distribution M w / M n of at least 2.5 is particularly preferably used.
  • Thermoplastic polymers with a bimodal or multimodal molecular weight distribution can also be used. Such bimodal or multimodal molecular weight distributions can be set, for example, by mixing thermoplastic polymers of different molecular weights.
  • Low molecular weight polystyrene with a molecular weight M w in the range from 150,000 to 250,000 g / mol is particularly preferred, with high molecular weight polystyrene with a molecular weight in the range from 280,000 to
  • thermoplastic polymer for example polystyrene with a molecular weight in the range from 2,000 to 10,000 g / mol, is added to the thermoplastic polymer.
  • infrared absorbers for example graphite, aluminum powder or carbon black
  • Graphite has proven to be particularly effective as an IR absorber.
  • the IR absorbers are particularly preferably used in amounts of 0.1 to 2.5% by weight, based on the thermoplastic polymer melt.
  • the IR absorber can be metered into the thermoplastic polymer melt before or after the addition of the blowing agent.
  • the usual additives such as flame retardants, nucleating agents, UV stabilizers, plasticizers, pigments and antioxidants can be added to the thermoplastic polymer melt.
  • the auxiliaries and IR absorbers can be added particularly advantageously in the form of additive batches in the same thermoplastic polymer to the polymer melt.
  • the foam particles obtained can be coated with the known coating agents, such as metal stearates, glycerol esters or finely divided silicates.
  • the process according to the invention is characterized in that foam particles with a low bulk density, in particular with bulk densities of less than 30 kg / m 3 , in particular in the range from 15 to 25 kg / m 3 , are obtained directly and can be welded directly into moldings without pre-foaming.
  • the foam particles according to the invention can also be heated, for example Pre-foamed water vapor to even lower bulk densities.
  • Static or dynamic mixers for example extruders, are suitable for carrying out this method.
  • the escaping polymer melt containing blowing agent can be chopped off with the help of rotating knives, for example in an underwater granulator or water ring granulator, to form granules which foam up to foam particles by deliberately set pressure relief.
  • PS 1 polystyrene with a melt index MVR (200 ° C / 5 kg) of
  • PS 2 polystyrene with a melt index MVR (200 ° C / 5 kg) of
  • PS ULM polystyrene with a molecular weight M w of 4,600 g / mol
  • PS UHM polystyrene with a molecular weight M w of
  • Polystyrene PS 1 was melted together with 0.25% by weight of talc in a heated twin-screw extruder (ZSK 53) and the blowing agent composition given in Table 1 was metered in at a melt temperature of about 200 ° C.
  • the melt containing blowing agent was cooled and extruded through a die plate with holes with a diameter of 1.0 mm.
  • the emerging melt was cut directly behind the nozzle and foamed to foam particles at atmospheric pressure.
  • Examples 1-9 led to comparatively higher bulk densities without the addition of water and solubilizer.
  • Example 9 was repeated with the polystyrene mixtures listed in Table 2.
  • Example 2 was repeated, the parts by weight of graphite given in Table 3 being added to the polystyrene instead of talc.

Abstract

The invention relates to a method for the production of low-bulk density foam particles made of thermoplastic polymers, comprising the following steps: a) a foaming agent is added to a thermoplastic polymer melt, b) the polymer melt containing the foaming agent is cooled and extruded by means of a nozzle, c) the polymer melt containing the foaming agent is cut at the rear of the nozzle at reduced pressure and the foam particles are foamed, said foaming agent containing water and a solubility mediator, in addition to foam particles which can be obtained according to said method.

Description

Verfahren zur Herstellung von Polystyrolschaumpartikeln mit niedriger SchüttdichteProcess for the production of polystyrene foam particles with low bulk density
Beschreibungdescription
Die Erfindung betrifft ein Verfahren zur Herstellung von Schaumpartikeln mit niedriger Schüttdichte aus thermoplastischen Polymeren durch Extrusion einer treibmittelhaltigen Polymerschmelze, sowie Schaumpartikel erhältlich nach dem Verfahren.The invention relates to a method for producing foam particles with a low bulk density from thermoplastic polymers by extrusion of a polymer melt containing blowing agent, and foam particles obtainable by the method.
Polystyrolschaumpartikel mit niedrigen Schüttdichten im Bereich von 10 bis 30 kg/m3 lassen sich beispielsweise durch Schäumen von pentanhaltigen, expandierbaren Polystyrolgranulaten (EPS) , die durch Suspensionspolymerisation erhalten werden können, herstellen.Polystyrene foam particles with low bulk densities in the range from 10 to 30 kg / m 3 can be produced, for example, by foaming pentane-containing, expandable polystyrene granules (EPS), which can be obtained by suspension polymerization.
Ebenfalls bekannt sind Vorrichtungen und Verfahren zur Herstellung von Schaumpartikeln durch Extrusion. Mit dem üblicherweise als Treibmittel zur Herstellung von Polystyrolschaumpartikel verwendeten Pentan sind mit diesem Verfahren jedoch nur höhere Schüttdichten erreichbar.Devices and methods for producing foam particles by extrusion are also known. With the pentane usually used as blowing agent for the production of polystyrene foam particles, however, only higher bulk densities can be achieved with this method.
Ein solches Verfahren zur Herstellung von diskreten, geschlossen- zelligen Schaumsträngen aus Polystyrol wird beispielsweise in EP-A 0 665 865 beschrieben. Als Treibmittel werden umweltfreundliche Treibmittelmischungen, die mindestens 20 Gew.-% Kohlendioxid oder Ethan enthalten, verwendet. Um niedrigere Schüttdichten zu erhalten, müssen die Schaumstränge in einer weiteren Stufe mit erhitzter Luft oder Dampf expandiert werden.Such a method for producing discrete, closed-cell foam strands made of polystyrene is described, for example, in EP-A 0 665 865. Environmentally friendly blowing agent mixtures containing at least 20% by weight of carbon dioxide or ethane are used as blowing agents. In order to obtain lower bulk densities, the foam strands have to be expanded in a further stage with heated air or steam.
Die EP-A 0 981 574 beschreibt teilchenförmige expandierbare Styrolpolymerisate, die zur Verringerung der Wärmeleitfähigkeit Graphitpartikel in homogener Verteilung enthalten. Die kompakten, treibmittelhaltigen Granulate können beispielsweise durch Mischen von Polystyrol, Graphit und Pentan in einem ZweiSchneckenextruder hergestellt und anschließend durch Bedampfung auf eine niedrigere Dichte geschäumt werden.EP-A 0 981 574 describes particulate expandable styrene polymers which contain graphite particles in a homogeneous distribution in order to reduce the thermal conductivity. The compact, blowing agent-containing granules can be produced, for example, by mixing polystyrene, graphite and pentane in a twin-screw extruder and then foamed to a lower density by vapor deposition.
Aufgabe der Erfindung war es, ein Verfahren zur Herstellung von Schaumpartikeln aus thermoplastischen Polymeren zu finden, das durch Extrusion einer treibmittelhaltigen Polymerschmelze direkt zu Schaumpartikeln niedriger Schüttdichte ohne zusätzliche Expandierstufen führt. Das Verfahren sollte auch zur Herstellung von Schaumpartikeln niedriger Schüttdichte, die IR-Absorber enthalten, geeignet sein. Demgemäß wurde ein Verfahren zur Herstellung von Schaumpartikeln aus thermoplastischen Polymeren umfassend die StufenThe object of the invention was to find a process for producing foam particles from thermoplastic polymers which, by extrusion of a polymer melt containing blowing agent, leads directly to foam particles of low bulk density without additional expansion stages. The process should also be suitable for the production of foam particles of low bulk density which contain IR absorbers. Accordingly, there has been a process for making foam particles from thermoplastic polymers comprising the steps
a) Zugabe eines Treibmittels zu einer thermoplastischen Polymer- 5 schmelze, b) Kühlen und Extrusion der treibmittelhaltigen Polymerschmelze durch eine Düse c) Schneiden der treibmittelhaltigen Polymerschmelze hinter der Düse bei reduziertem Druck unter Aufschäumen zu Schaum-a) adding a blowing agent to a thermoplastic polymer melt, b) cooling and extrusion of the blowing agent-containing polymer melt through a nozzle c) cutting the blowing agent-containing polymer melt behind the nozzle under reduced pressure with foaming to foam
10 partikeln,10 particles,
gefunden, wobei das Treibmittel Wasser und einen Löslichkeitsver- mittler enthält.found, the blowing agent containing water and a solubilizer.
15 Erfindungsgemäß enthält das Treibmittel Wasser, in der Regel in Mengen im Bereich von 0,1 bis 3 Gew.-%, bevorzugt im Bereich von 0,5 bis 1,5 Gew.-%, bezogen auf das eingesetzte thermoplastische Polymer .15 According to the invention, the blowing agent contains water, generally in amounts in the range from 0.1 to 3% by weight, preferably in the range from 0.5 to 1.5% by weight, based on the thermoplastic polymer used.
20 Um eine möglichst homogene Verteilung des Wassers in der thermoplastischen Polymerschmelze zu erreichen, wird erfindungsgemäß zusätzlich ein Löslichkeitsvermittler zugegeben. Als Löslich- keitsvermittler eignen sich aliphatisch Alkohole, Ketone, Ether, Ester oder Silikat. Bevorzugt wird Ethanol verwendet. AlsIn order to achieve the most homogeneous possible distribution of the water in the thermoplastic polymer melt, a solubilizer is additionally added according to the invention. Aliphatic alcohols, ketones, ethers, esters or silicates are suitable as solubilizers. Ethanol is preferably used. As
25 Adsorbentien eignen sich Feststoffe, die Wasser in physikalischer oder chemischer Form binden können, beispielsweise Aluminiumhydroxid, Schichtsilikate oder Zeolithe. Der Löslichkeitsvermittler oder Adsorbens wird in der Regel in Mengen von 0,1 bis 3 Gew.-%, bevorzugt im Bereich von 1 bis 2 Gew.-%, bezogen auf das einge-25 Adsorbents are solids that can bind water in physical or chemical form, for example aluminum hydroxide, layered silicates or zeolites. The solubilizer or adsorbent is generally used in amounts of 0.1 to 3% by weight, preferably in the range of 1 to 2% by weight, based on the
30 setzte thermoplastische Polymer, eingesetzt.30 used thermoplastic polymer.
Zusätzlich kann das Treibmittel die üblicherweise eingesetzten aliphatisehen, halogenierten oder halogenfreien Kohlenwasserstoffe mit 3 bis 10, bevorzugt 4 bis 6 Kohlenstoffato en, wie i-In addition, the blowing agent can contain the aliphatic, halogenated or halogen-free hydrocarbons with 3 to 10, preferably 4 to 6 carbon atoms, such as i-
35 Butan, i-Pentan, n-Pentan oder Mischungen enthalten oder Inertgase wie Kohlendioxid oder Stickstoff in Mengen in der Regel im Bereich von 0,1 bis 10, bevorzugt 0,3 bis 7 Gew.-%, bezogen auf das eingesetzte thermoplastische Polymer. Besonders vorteilhaft ist die Verwendung von Inerten Gasen, beispielsweise Kohlendioxid35 butane, i-pentane, n-pentane or mixtures or inert gases such as carbon dioxide or nitrogen in amounts generally in the range of 0.1 to 10, preferably 0.3 to 7 wt .-%, based on the thermoplastic polymer used , The use of inert gases, for example carbon dioxide, is particularly advantageous
40 als Treibmittel um die Emission an Kohlenwasserstoffen bei der Schaumherstellung zu reduzieren.40 as a blowing agent to reduce the emission of hydrocarbons in foam production.
Als thermoplastische Polymere können Styrolpolymere wie glasklares oder schlagzähes Polystyrol, Styrolcopolymere mit bis zu 45 20 Gew.-% an ethylenisch ungesättigten Comonomeren wie Alphamethylstyrol oder Acrylnitril oder Polyolefine, wie Polyethylen oder Polypropylen oder Mischungen dieser Polymere untereinander oder mit Polyphenylenether eingesetzt werden.Styrene polymers such as crystal-clear or impact-resistant polystyrene, styrene copolymers with up to 45-20% by weight of ethylenically unsaturated comonomers such as alphamethylstyrene or acrylonitrile or polyolefins such as polyethylene can be used as thermoplastic polymers or polypropylene or mixtures of these polymers with one another or with polyphenylene ether.
Besonders niedrige Schüttdichten lassen sich mit thermoplasti- sehen Polymeren mit einer breiten Molekulargewichtsverteilung erreichen. Besonders bevorzugt wird Polystyrol mit einer Molekulargewichtsverteilung Mw/Mn von mindestens 2,5 verwendet. Des weiteren können thermoplastische Polymere mit einer bi- oder multimodalen Molekulargewichtsverteilung eingesetzt werden. Solche bi- oder multimodale Molekulargewichtsverteilungen können beispielsweise durch Mischen von thermoplastischen Polymeren unterschiedlichen Molekulargewichts eingestellt werden. Besonders bevorzugt wird niedermolekulares Polystyrol mit einem Molekulargewicht Mw im Bereich von 150.000 bis 250.000 g/mol, mit hochmolekularem Poly- styrol mit einem Molekulargewicht im Bereich von 280.000 bisParticularly low bulk densities can be achieved with thermoplastic polymers with a broad molecular weight distribution. Polystyrene with a molecular weight distribution M w / M n of at least 2.5 is particularly preferably used. Thermoplastic polymers with a bimodal or multimodal molecular weight distribution can also be used. Such bimodal or multimodal molecular weight distributions can be set, for example, by mixing thermoplastic polymers of different molecular weights. Low molecular weight polystyrene with a molecular weight M w in the range from 150,000 to 250,000 g / mol is particularly preferred, with high molecular weight polystyrene with a molecular weight in the range from 280,000 to
500.000 g/mol oder mit einem ultrahochmolekularem Polystyrol mit einem Molekulargewicht über 1.000.000 g/mol verwendet. Noch niedrigere Schüttdichten lassen sich erreichen, wenn dem thermoplastischen Polymeren ein niedermolekulares Polymer, beispielsweise Polystyrol mit einem Molekulargewicht im Bereich von 2.000 bis 10.000 g/mol zugegeben werden.500,000 g / mol or used with an ultra-high molecular weight polystyrene with a molecular weight above 1,000,000 g / mol. Even lower bulk densities can be achieved if a low molecular weight polymer, for example polystyrene with a molecular weight in the range from 2,000 to 10,000 g / mol, is added to the thermoplastic polymer.
Zur Verringerung der Wärmeleitfähigkeit der Schaumpartikel können den thermoplastischen Polymeren Infrarot- (IR) -Absorber, bei- spielsweise Graphit, Aluminiumpulver oder Ruß zugegeben werden. Besonders effektiv als IR-Absorber hat sich Graphit erwiesen. Besonders bevorzugt werden die IR-Absorber in Mengen von 0,1 bis 2,5 Gew.-%, bezogen auf die thermoplastische Polymerschmelze, eingesetzt. Der IR-Absorber kann der thermoplastischen Polymer- schmelze vor oder nach Zugabe des Treibmittels zudosiert werden.To reduce the thermal conductivity of the foam particles, infrared (IR) absorbers, for example graphite, aluminum powder or carbon black, can be added to the thermoplastic polymers. Graphite has proven to be particularly effective as an IR absorber. The IR absorbers are particularly preferably used in amounts of 0.1 to 2.5% by weight, based on the thermoplastic polymer melt. The IR absorber can be metered into the thermoplastic polymer melt before or after the addition of the blowing agent.
Zu der thermoplastischen Polymerschmelze können die üblichen Zusatzstoffe, wie Flammschutzmittel, Keimbildner, UV-Stabilisatoren, Weichmacher, Pigmente und Antioxidantien zugegeben werden. Besonders vorteilhaft können die Hilfsstoffe und IR-Absorber in Form von Additiv-Batchen in dem gleichen thermoplastischen Polymer, der Polymerschmelze zugegeben werden. Desweiteren können die erhaltenen Schaumpartikel mit den bekannten Beschichtungsmitteln, wie Metallstearaten, Glycerinestern oder feinteiligen Silikaten überzogen werden.The usual additives such as flame retardants, nucleating agents, UV stabilizers, plasticizers, pigments and antioxidants can be added to the thermoplastic polymer melt. The auxiliaries and IR absorbers can be added particularly advantageously in the form of additive batches in the same thermoplastic polymer to the polymer melt. Furthermore, the foam particles obtained can be coated with the known coating agents, such as metal stearates, glycerol esters or finely divided silicates.
Das erfindungsgemäße Verfahren zeichnet sich dadurch aus, dass Schaumpartikel mit niedriger Schüttdichte, insbesondere mit Schüttdichten von unter 30 kg/m3, insbesondere im Bereich von 15 bis 25 kg/m3 direkt erhalten werden, die sich ohne Vorschäumen direkt zu Formkörpern verschweißen lassen. Die erfindungsgemäßen Schaumpartikel können jedoch beispielsweise durch Erwärmen mit Wasserdampf zu noch niedrigeren Schüttdichten vorgeschäumt werden.The process according to the invention is characterized in that foam particles with a low bulk density, in particular with bulk densities of less than 30 kg / m 3 , in particular in the range from 15 to 25 kg / m 3 , are obtained directly and can be welded directly into moldings without pre-foaming. However, the foam particles according to the invention can also be heated, for example Pre-foamed water vapor to even lower bulk densities.
Zur Durchführung dieses Verfahrens eignen sich statische oder dy- namische Mischer, beispielsweise Extruder. Die austretende treib- mittelhaltige Polymerschmelze kann mit Hilfe rotierender Messer, zum Beispiel in einem Unterwassergranulator oder Wasserringgranu- lator, zu Granulaten abgeschlagen werden, die durch gezielt eingestellte Druckentlastung zu Schaumstoffpartikeln aufschäumen.Static or dynamic mixers, for example extruders, are suitable for carrying out this method. The escaping polymer melt containing blowing agent can be chopped off with the help of rotating knives, for example in an underwater granulator or water ring granulator, to form granules which foam up to foam particles by deliberately set pressure relief.
BeispieleExamples
Alle Prozentangaben beziehen sich auf Gewichtsprozent, bezogen auf die Polymerschmelze.All percentages relate to percent by weight, based on the polymer melt.
PS 1: Polystyrol mit einem Schmelzindex MVR (200°C/5 kg) vonPS 1: polystyrene with a melt index MVR (200 ° C / 5 kg) of
10 cm3/10 min (ISO 1133, Methode H) und einem Molekulargewicht Mw von 190.000 g/mol10 cm 3/10 min (ISO 1133, method H) and a molecular weight M w of 190,000 g / mol
PS 2: Polystyrol mit einem Schmelzindex MVR (200°C/5 kg) vonPS 2: polystyrene with a melt index MVR (200 ° C / 5 kg) of
1,2 cm3/10 min (ISO 1133, Methode H) und einem Molekulargewicht Mw von 360.000 g/mol (PS 168 N der BASF AG)1.2 cm 3/10 min (ISO 1133, method H) and a molecular weight M w of 360,000 g / mol (PS 168 N, BASF AG)
PS ULM: Polystyrol mit einem Molekulargewicht Mw von 4.600 g/molPS ULM: polystyrene with a molecular weight M w of 4,600 g / mol
PS UHM: Polystyrol mit einem Molekulargewicht Mw vonPS UHM: polystyrene with a molecular weight M w of
1.900.000 g/mol (Blendex der General Electrics)1,900,000 g / mol (Blendex from General Electrics)
Beispiele 1 - 9:Examples 1-9:
Polystyrol PS 1 wurde zusammen mit 0,25 Gew.-% Talkum in einem beheizten ZweiSchneckenextruder (ZSK 53) aufgeschmolzen und bei einer Massetemperatur von etwa 200°C wurde die in Tabelle 1 angegebene Treibmittelzusammensetzung zudosiert. Die treibmittel- haltige Schmelze wurde abgekühlt und durch eine Düsenplatte mit Bohrungen mit einem Durchmesser von 1,0 mm extrudiert. Die austretende Schmelze wurde direkt hinter der Düse geschnitten und schäumte bei Atmosphärendruck zu Schaumpartikeln auf. Tabelle 1:Polystyrene PS 1 was melted together with 0.25% by weight of talc in a heated twin-screw extruder (ZSK 53) and the blowing agent composition given in Table 1 was metered in at a melt temperature of about 200 ° C. The melt containing blowing agent was cooled and extruded through a die plate with holes with a diameter of 1.0 mm. The emerging melt was cut directly behind the nozzle and foamed to foam particles at atmospheric pressure. Table 1:
Zusammenstellung der Treibmittelzusammensetzung und Schaumeigenschaften der Beispiele 1 bis 9Compilation of the blowing agent composition and foam properties of Examples 1 to 9
Vergleichsversuche :Comparative tests:
Die Beispiele 1 -9 führten ohne Zusatz von Wasser und Löslich- keitsvermittler zu vergleichsweise höheren Schüttdichten.Examples 1-9 led to comparatively higher bulk densities without the addition of water and solubilizer.
Beispiel 10 - 12:Examples 10 - 12:
Beispiel 9 wurde mit den in Tabelle 2 zusammengestellten Poly- styrolmischungen wiederholt.Example 9 was repeated with the polystyrene mixtures listed in Table 2.
Tabelle 2 :Table 2:
Beispiele 13 - 15Examples 13-15
Beispiel 2 wurde wiederholt, wobei anstelle von Talkum die in Tabelle 3 angegebenen Gewichtsanteile Graphit dem Polystyrol zugegeben wurde.Example 2 was repeated, the parts by weight of graphite given in Table 3 being added to the polystyrene instead of talc.
Tabelle 3:Table 3:

Claims

Patentansprüche claims
1. Verfahren zur Herstellung von Schaumpartikeln aus thermoplastischen Polymeren umfassend die Stufen1. A method for producing foam particles from thermoplastic polymers comprising the steps
a) Zugabe eines Treibmittels zu einer thermoplastischen Polymerschmelze , b) Kühlen und Extrusion der treibmittelhaltigen Polymer- schmelze durch eine Düse c) Schneiden der treibmittelhaltigen Polymerschmelze hinter der Düse bei reduziertem Druck unter Aufschäumen zu Schaumpartikeln,a) adding a blowing agent to a thermoplastic polymer melt, b) cooling and extrusion of the blowing agent-containing polymer melt through a nozzle c) cutting the blowing agent-containing polymer melt behind the nozzle under reduced pressure with foaming to foam particles,
dadurch gekennzeichnet, dass das Treibmittel Wasser und einen Löslichkeitsvermittler oder Adsorbens enthält.characterized in that the blowing agent contains water and a solubilizer or adsorbent.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass als Löslichkeitsvermittler ein aliphatischer Alkohol, Keton, Ether, Ester eingesetzt wird.2. The method according to claim 1, characterized in that an aliphatic alcohol, ketone, ether, ester is used as solubilizer.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass als Adsorbens Aluminiumhydroxid, Schichtsilikat oder Zeolith eingesetzt wird.3. The method according to claim 1 or 2, characterized in that aluminum hydroxide, layered silicate or zeolite is used as the adsorbent.
Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass das Treibmittel zusätzlich C02, N2 , einen ali- phatischen, halogenierten oder halogenfreien Kohlenwasserstoff enthält.Method according to one of claims 1 to 3, characterized in that the blowing agent additionally contains C0 2 , N 2 , an aliphatic, halogenated or halogen-free hydrocarbon.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, dass als Treibmittel eine Mischung von5. The method according to claim 4, characterized in that a mixture of
0,1 bis 3 Gew.-% Wasser,0.1 to 3% by weight of water,
0,1 bis 3 Gew.-% eines Alkohol oder Ketons und 1 bis 10 Gew.-% eines aliphatischen, halogenierten oder halogenfreien Kohlenwasserstoffs oder C02 eingesetzt wird.0.1 to 3 wt .-% of an alcohol or ketone and 1 to 10 wt .-% of an aliphatic, halogenated or halogen-free hydrocarbon or C0 2 is used.
6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass als thermoplastische Polymere Polystyrol, Styrolcopolymere, Polyethylen, Polypropylen oder Mischungen davon eingesetzt werden.6. The method according to any one of claims 1 to 5, characterized in that polystyrene, styrene copolymers, polyethylene, polypropylene or mixtures thereof are used as thermoplastic polymers.
7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass das thermoplastische Polymer eine bi- oder multimodale Molekulargewichtsverteilung aufweist. 7. The method according to any one of claims 1 to 6, characterized in that the thermoplastic polymer has a bimodal or multimodal molecular weight distribution.
8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass als thermoplastisches Polymer Polystyrol mit einer Molekulargewichtsverteilung Mw/Mn von mindestens 2,5 eingesetzt wird.8. The method according to any one of claims 1 to 7, characterized in that polystyrene with a molecular weight distribution M w / M n of at least 2.5 is used as the thermoplastic polymer.
55
9. Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, dass der thermoplastischen Polymerschmelze vor oder nach Zugabe des Treibmittels ein IR-Absorber zugegeben wird.9. The method according to any one of claims 1 to 8, characterized in that an IR absorber is added to the thermoplastic polymer melt before or after the addition of the blowing agent.
10 10. Verfahren nach Anspruch 9, dadurch gekennzeichnet, dass als10 10. The method according to claim 9, characterized in that as
IR-Absorber 0,1 bis 2,5 Gew.-%, bezogen auf die thermoplastische Polymerschmelze, Graphit, Ruß oder Aluminiumpulver eingesetzt werden.IR absorbers 0.1 to 2.5 wt .-%, based on the thermoplastic polymer melt, graphite, carbon black or aluminum powder can be used.
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EP03793763A 2002-09-04 2003-08-28 Method for the production of low-bulk density polystyrene foam particles Withdrawn EP1537171A1 (en)

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DE10241298A DE10241298A1 (en) 2002-09-04 2002-09-04 Process for the production of polystyrene foam particles with low bulk density
DE10241298 2002-09-04
PCT/EP2003/009521 WO2004022636A1 (en) 2002-09-04 2003-08-28 Method for the production of low-bulk density polystyrene foam particles

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