EP0000357A1 - Process for the preparation of cross-linkable ethylene polymer mouldings and their use as electrical insulating materials - Google Patents

Process for the preparation of cross-linkable ethylene polymer mouldings and their use as electrical insulating materials Download PDF

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Publication number
EP0000357A1
EP0000357A1 EP78100276A EP78100276A EP0000357A1 EP 0000357 A1 EP0000357 A1 EP 0000357A1 EP 78100276 A EP78100276 A EP 78100276A EP 78100276 A EP78100276 A EP 78100276A EP 0000357 A1 EP0000357 A1 EP 0000357A1
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EP
European Patent Office
Prior art keywords
extruder
ethylene polymer
temperature
stabilizer
melt
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EP78100276A
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German (de)
French (fr)
Inventor
Rudolf Dr. Glaser
Dieter Dr. Moorwessel
Peter Bauer
Ernst Dr. Koehnlein
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BASF SE
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BASF SE
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    • 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
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/20—Compounding polymers with additives, e.g. colouring
    • C08J3/201—Pre-melted polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/022—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; 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
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/285—Feeding the extrusion material to the extruder
    • B29C48/29—Feeding the extrusion material to the extruder in liquid form
    • 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
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/20—Compounding polymers with additives, e.g. colouring
    • C08J3/203—Solid polymers with solid and/or liquid additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/05—Filamentary, e.g. strands
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/06—Rod-shaped
    • 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
    • B29K2105/0005—Condition, form or state of moulded material or of the material to be shaped containing 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
    • 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

Definitions

  • the invention relates to a process for the production of molding compositions from crosslinkable ethylene polymers containing one or more stabilizers with a density of 0.918 to 0.935 g / em 3 and a melt index of 0.05 to 25 g / 10 min.
  • Molding compositions of this type made of crosslinkable ethylene polymers are unshaped or preformed substances which can be processed by heating within certain temperature ranges to give molded materials or molded parts made of crosslinked ethylene polymers.
  • crosslink ethylene polymers which contain conventional stabilizers and peroxides, by heating to temperatures above the decomposition temperature of the peroxide.
  • the mixtures of ethylene polymer, stabilizer (s) and peroxides are prepared according to the known state of the art by kneading the components in batch or continuous mixers, the three components being mixed simultaneously. The mixing process takes place below the decomposition temperature of the peroxide, preferably at temperatures between 115 and 130 ° C.
  • DT-OS 22 20 147 also discloses a process for the preparation of crosslinked ethylene polymers by simultaneously mixing finely divided ethylene polymers with a peroxide and a stabilizer at temperatures above the melting point of the ethylene polymer, with a solution of the stabilizer in a liquid organic peroxide being continuous feeds the feed zone of an extruder together with the ethylene polymer. The three components are then mixed through the extruder passage at temperatures between 100 and 130 ° C.
  • the disadvantage of this process is that foreign contaminants, which are always contained in technical polyethylene, cannot be cleaned by sieving the peroxide-containing melt, because such a passage leads to local temperature increases and thus to inhomogeneously distributed crosslinking in the ethylene polymer.
  • cleaning the ethylene polymer is necessary for the manufacture of technically high-quality products such as the insulation of high-voltage cables.
  • the invention is based on the object of demonstrating a crosslinkable, stabilizer-containing ethylene polymer which contains neither inhomogeneous partial crosslinking nor foreign impurities.
  • the sieve is passed through a sieve of 200 to 500 mesh (according to ASTM Ell / 61).
  • Ethylene polymers are understood to be polyethylene with a density of 0.918 to 0.935 g / cm 3 according to DIN 53 479 and a melt index of 0.05 to 25, preferably 0.5 to 6 g / 10 min., According to ASTM D 1238 T at 190 ° C and a pad weight of 2.16 kp.
  • copolymers of ethylene with one or more ethylenically unsaturated compounds are also suitable as ethylene polymers.
  • the vinyl esters of a C 2 - to C 3 -alkane carboxylic acid or the C i - to C 8 -alkyl esters of a C 3 - to C 4 -alkenecarboxylic acid are to be mentioned in particular, the copolymers containing at least 50 and at most 97% by weight of ethylene in copolymerized form .
  • Particularly noteworthy are the copolymers of ethylene with vinyl acetate or ethyl or butyl acrylate.
  • the melt index of the copolymers is also 0.05 to 25 g / 10 min.
  • Stabilizers are understood to be the usual additives which protect the ethylene polymer from decomposition during processing at high temperature.
  • the stabilizers can be mixed into the molding composition in amounts of 0.1 to 0.6, preferably 0.1 to 0.4 percent by weight, based on the ethylene polymer. Suitable stabilizers are in particular 4,4'-thio-bis (3-methyl-6-tert-butyl-1-phenol), 1,1'-thio-bis (2-hydroxy-6-tert-butylbenzene) ), Dilauroyl thio dipropionate and the distearyl thio dipropionate.
  • the molding composition may contain a stabilizer or several different stabilizers known in the art. Mixtures of one of the stabilizers mentioned above with sulfur can also be considered.
  • the ethylene polymers are first mixed with the stabilizer or stabilizer mixture at temperatures between 150 and 220 ° C.
  • This mixing process can be carried out in a conventional manner in conventional mixers, e.g. a kneader.
  • the hot melt of ethylene polymer and stabilizer which is at 150 to 220 ° C., is then passed through a sieve device separated from impurities. Contamination is understood here to mean dirt and / or dust particles, caked stabilizer lumps and also crosslinked and / or coked polymer particles.
  • the sieve passage of the polymer / stabilizer mixture takes place through a sieve which has a sieve fineness of 200 to 500, preferably 300 to 400 mesh (according to ASTM E11 / 61).
  • the cleaned, completely homogeneous mixture of ethylene polymer and stabilizer is then granulated and cooled in a conventional manner.
  • What is essential for the process according to the invention is the measure, the polyolefin granules thus obtained and at the same time, but separately from the granules, 1.0 to 3.0 percent by weight, based on the total mass, of a molten organic peroxide which has a temperature between 40 and 90.degree , continuously to the feed zone of an extruder, cooled to a temperature between 0 and 30 ° C.
  • Molten peroxide is understood to mean a peroxide that is solid at normal temperature, i.e. up to 30 ° C, but is liquid when heated to a temperature above 40 0 to a maximum of 90 ° C.
  • Suitable peroxides are dicumyl peroxide (melting point 39 ° C) and the bis (tert-butylperoxyisopropyl) benzene (melting point 45 to 46 ° C).
  • the feed zone of the extruder, into which the stabilizer-containing ethylene polymer and, separately, the liquid peroxide are introduced, has cooled to 0 to 30 ° C., so that the temperature in this feed range of the extruder is 10 to 90 ° C. lower than the temperature of the peroxide melt .
  • the temperature in the feed zone of the extruder is therefore always lower than the melting temperature of the peroxide, so that the peroxide introduced continuously into the feed zone of the extruder is in two phases: both as a melt and as a crystallized solid.
  • the melting temperature of the peroxide in which a temperature between 110 and 135 ° C. prevails, is possible until the extruder is discharged.
  • the crosslinkable peroxide and stabilizer-containing ethylene polymer mass is processed in the usual way to form granules or molded parts.
  • the advantages achieved by the invention consist in particular in that a completely homogeneous ethylene polymer is obtained which is free from impurities and which is particularly well suited for insulation of high-voltage cables.
  • Polyethylene with a density of 0.92 g / cm 3 and a melt index of 2.7 g / 10 min. is homogeneously mixed in a kneader with 0.3% by weight 4,4'-thio-bis- (6-tert-butyl-m-cresol) at temperatures of 200 ° C.
  • the material is fed to an extruder and conveyed through a 400 mesh screen at a temperature of 200 ° C. and granulated.
  • the granules obtained are fed to a second extrusion, 2.3 percent by weight, based on the weight of the total mixture, of dicumyl peroxide being metered into the feed section of the extruder.
  • the dicumyl peroxide is dosed with a dosing pump at 55 ° C.
  • the metering tube ends in the feed opening of the extruder 5 cm above the screw.
  • the mass is melted in the extruder, homogenized at a temperature of 125 ° C and then granulated.
  • Press plates are produced from the granules obtained at 200 ° C. At this temperature, the peroxide disintegrates and the polyethylene is crosslinked.
  • the press plates have the dimensions 200 x 200 x 1.25 mm 3 .
  • Ten press plates are searched for contaminants on a light table using a magnifying glass magnified 10 times. All impurities visible under these conditions are counted and measured. The measurement result is shown in the table as example 1.
  • Polyethylene with a density of 0.92 g / cm 3 and a melt index of 2.7 g / 10 min. is homogeneously mixed in a kneader with 0.3% by weight 4,4'-thio-bis (6-tert-butyl-m-cresol) and 2.3% by weight dicumyl peroxide at a temperature of 125 ° C.
  • the material is fed into an extruder and extruded and granulated at a melt temperature of 125 ° C.
  • press plates are produced from the granulate and searched for impurities.
  • the impurities are shown in the table as example 2.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Processes Of Treating Macromolecular Substances (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)
  • Organic Insulating Materials (AREA)

Abstract

The process involves, in the stated sequence, mixing the ethylene polymer at from 150 to 220 DEG C with a stabiliser, removing impurities from the hot melt obtained by passing it through a screen, granulating and cooling the purified melt, continuously feeding the resultant granules, together with from 1.0 to 3.0 per cent by weight of a molten peroxide at a temperature from 40 to 90 DEG C, to the inlet zone, cooled to from 0 to 30 DEG C, of an extruder, warming the mixture to from 110 to 135 DEG C in the extruder, and processing the resultant mixture in a conventional manner. The ethylene polymer compounds obtained are particularly suitable for the production of electrical insulations.

Description

Die Erfindung betrifft ein Verfahren zur Herstellung von Formmassen aus vernetzbaren, einen oder mehrere Stabilisatoren enthaltenden Äthylenpolymerisaten der Dichte von 0,918 bis 0,935 g/em3 und des Schmelzindex von 0,05 bis 25 g/10 min.The invention relates to a process for the production of molding compositions from crosslinkable ethylene polymers containing one or more stabilizers with a density of 0.918 to 0.935 g / em 3 and a melt index of 0.05 to 25 g / 10 min.

Bei derartigen Formmassen aus vernetzbaren Äthylenpolymerisaten handelt es sich um ungeformte oder vorgeformte Stoffe, die durch Erhitzen innerhalb bestimmter Temperaturbereiche zu Formstoffen oder Formteilen aus vernetzten Äthylenpolymerisaten verarbeitet werden können.Molding compositions of this type made of crosslinkable ethylene polymers are unshaped or preformed substances which can be processed by heating within certain temperature ranges to give molded materials or molded parts made of crosslinked ethylene polymers.

Es ist bekannt, Äthylenpolymerisate, welche übliche Stabilisatoren und Peroxide enthalten, durch Erhitzen auf Temperaturen über die Zersetzungstemperatur des Peroxids zu vernetzen. Die Herstellung der Mischungen aus Äthylenpolymerisat, Stabilisator(en) und Peroxiden erfolgt nach dem bekannten Stand der Technik durch Verkneten der Komponenten in diskontinuierlich oder kontinuierlich arbeitenden Mischern, wobei man die drei Komponenten gleichzeitig vermischt. Der Mischprozeß erfolgt unterhalb der Zerfallstemperatur des Peroxids, bevorzugt bei Temperaturen zwischen 115 und 130°C. Aus der DT-OS 21 24 941 ist es auch bereits bekannte feinteilige Olefinpolymerisate mit flüssigen Peroxiden bei Temperaturen bis maximal 70°C zu mischen, wobei man die beiden Komponenten kontinuierlich im gewünschten Verhältnis zusammenbringt und anschließend in einer Zone umwälzt, deren Verhältnis von Länge zu Durchmesser mindestens 10 : 1 beträgt. Nach diesem Verfahren kommt man zu vernetzbaren, Peroxide enthaltenden Olefinpolymerisatmassen.It is known to crosslink ethylene polymers, which contain conventional stabilizers and peroxides, by heating to temperatures above the decomposition temperature of the peroxide. The mixtures of ethylene polymer, stabilizer (s) and peroxides are prepared according to the known state of the art by kneading the components in batch or continuous mixers, the three components being mixed simultaneously. The mixing process takes place below the decomposition temperature of the peroxide, preferably at temperatures between 115 and 130 ° C. From DT-OS 21 24 941 it is also known to mix finely divided olefin polymers with liquid peroxides at temperatures up to a maximum of 70 ° C., the two components being brought together continuously in the desired ratio and then circulated in a zone whose ratio increases in length Diameter is at least 10: 1. This process leads to crosslinkable, peroxide-containing olefin polymer compositions.

Aus der DT-OS 22 20 147 ist ferner ein Verfahren zur Herstellung von vernetzten Äthylenpolymerisaten durch gleichzeitiges Mischen von feinteiligen Äthylenpolymerisaten mit einem Peroxid und einem Stabilisator bei Temperaturen oberhalb des Schmelzpunktes des Äthylenpolymerisats bekannt, wobei man eine Lösung des Stabilisators in einem flüssigen organischen Peroxid kontinuierlich zusammen mit dem Äthylenpolymerisat der Einzugszone eines Extruders zuführt. Die drei Komponenten werden anschließend durch die Extruderpassage bei Temperaturen zwischen 100 und 130°C gemischt. Der Nachteil dieses Verfahrens bssteht darin, daß produktfremde Verunreinigungen, die stets in einem technischen Polyäthylen enthalten sind, nicht durch Siebpassage der peroxidhaltigen Schmelze gereinigt werden können, weil eine solche Passage zu lokalen Temperaturerhöhungen und damit zu inhomogen verteilten Vernetzungen im Äthylenpolymerisat führt. Eine Reinigung des Äthylenpolymerisats ist aber notwendig für die Herstellung technisch hochwertiger Fertigungserzeugnisse wie Isolierungen von Hochspannungskabeln.DT-OS 22 20 147 also discloses a process for the preparation of crosslinked ethylene polymers by simultaneously mixing finely divided ethylene polymers with a peroxide and a stabilizer at temperatures above the melting point of the ethylene polymer, with a solution of the stabilizer in a liquid organic peroxide being continuous feeds the feed zone of an extruder together with the ethylene polymer. The three components are then mixed through the extruder passage at temperatures between 100 and 130 ° C. The disadvantage of this process is that foreign contaminants, which are always contained in technical polyethylene, cannot be cleaned by sieving the peroxide-containing melt, because such a passage leads to local temperature increases and thus to inhomogeneously distributed crosslinking in the ethylene polymer. However, cleaning the ethylene polymer is necessary for the manufacture of technically high-quality products such as the insulation of high-voltage cables.

Der Erfindung liegt die Aufgabe zugrunde, ein vernetzbares, stabilisatorhaltiges Äthylenpolymerisat aufzuzeigen, welches weder inhomogene Teilvernetzungen noch produktfremde Verunreinigungen enthält.The invention is based on the object of demonstrating a crosslinkable, stabilizer-containing ethylene polymer which contains neither inhomogeneous partial crosslinking nor foreign impurities.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß man in der angegebenen Reihenfolge

  • a) das Äthylenpolymerisat bei einer Temperatur zwischen 150 und 220°C mit dem Stabilisator mischt,
  • b) die heiße Schmelze durch eine Siebpassage von Verunreinigungen trennt,
  • c) die gereinigte Schmelze granuliert und abkühlt,
  • d) das erhaltene Granulat und gleichzeitig, aber getrennt vom Granulat, 1,0 bis 3,0 Gewichtsprozent eines geschmolzenen organischen Peroxids, das eine Temperatur von 40 bis 90°C aufweist, kontinuierlich der auf 0 bis 30°C gekühlten Einzugszone eines Extruders zuführt,
  • e) in der Schmelzenzone des Extruders bei Temperaturen zwischen 110 und 135°C mischt und
  • f) die so erhaltene vernetzbare Polymerisatmischung in üblicher Weise granuliert oder direkt zum Formteil verarbeitet.
This object is achieved in that in the order given
  • a) the ethylene polymer mixes with the stabilizer at a temperature between 150 and 220 ° C,
  • b) the hot melt is separated from impurities by a sieve passage,
  • c) the cleaned melt is granulated and cooled,
  • d) the granules obtained and at the same time, but separately from the granules, 1.0 to 3.0 percent by weight of a molten organic peroxide, which has a temperature of 40 to 90 ° C, continuously fed to the feed zone of an extruder cooled to 0 to 30 ° C ,
  • e) mixes in the melt zone of the extruder at temperatures between 110 and 135 ° C and
  • f) the crosslinkable polymer mixture thus obtained is granulated in a conventional manner or processed directly to give the molding.

Bevorzugt ist die Verwendung von Dicumylperoxid oder von Bis(tert.-butyl-peroxyisopropyl)benzol als Peroxid und von 0,1 bis 0,6 Gewichtsprozent 4,4'-Thio-bis(6-tert.-butyl-m-cresol) als Stabilisator.Preference is given to using dicumyl peroxide or bis (tert-butyl-peroxyisopropyl) benzene as the peroxide and from 0.1 to 0.6% by weight of 4,4'-thio-bis (6-tert-butyl-m-cresol) as a stabilizer.

Nach bevorzugtem Verfahren erfolgt die Siebpassage durch ein Sieb von 200 bis 500 mesh (nach ASTM Ell/61).According to the preferred method, the sieve is passed through a sieve of 200 to 500 mesh (according to ASTM Ell / 61).

Unter Äthylenpolymerisaten werden verstanden Polyäthylen mit einer Dichte von 0,918 bis 0,935 g/cm3 nach DIN 53 479 und einem Schmelzindex von 0,05 bis 25, bevorzugt 0,5 bis 6 g/ 10 min., nach ASTM D 1238 T bei 190°C und einem Auflagegewicht von 2,16 kp. Es eignen sich als Äthylenpolymerisate aber auch Copolymerisate des Äthylens mit einer oder mehreren äthylenisch ungesättigten Verbindungen. Als Comonomere sind vor allem die Vinylester einer C2- bis C3-Alkancarbonsäure oder die Ci- bis C8-Alkylester einer C3- bis C4-Alkencarbonsäure, wobei die Copolymerisate mindestens 50, maximal 97 Gewichtsprozent Äthylen einpolymerisiert enthalten, zu nennen. Besonders hervorzuheben sind die Copolymerisate des Äthylens mit Vinylacetat oder Acrylsäureäthyl- bzw. -butylestern. Der Schmelzindex der Copolymerisate beträgt ebenfalls 0,05 bis 25 g/10 min.Ethylene polymers are understood to be polyethylene with a density of 0.918 to 0.935 g / cm 3 according to DIN 53 479 and a melt index of 0.05 to 25, preferably 0.5 to 6 g / 10 min., According to ASTM D 1238 T at 190 ° C and a pad weight of 2.16 kp. However, copolymers of ethylene with one or more ethylenically unsaturated compounds are also suitable as ethylene polymers. As comonomers, the vinyl esters of a C 2 - to C 3 -alkane carboxylic acid or the C i - to C 8 -alkyl esters of a C 3 - to C 4 -alkenecarboxylic acid are to be mentioned in particular, the copolymers containing at least 50 and at most 97% by weight of ethylene in copolymerized form . Particularly noteworthy are the copolymers of ethylene with vinyl acetate or ethyl or butyl acrylate. The melt index of the copolymers is also 0.05 to 25 g / 10 min.

Unter Stabilisatoren werden die üblichen Zusatzstoffe verstanden, welche das Äthylenpolymerisate während der Verarbeitung bei hoher Temperatur vor Zersetzungen schützen. Die Stabilisatoren können in Mengen von 0,1 bis 0,6, bevorzugt 0,1 bis 0,4 Gewichtsprozent, bezogen auf das Äthylenpolymerisat, in der Formmasse eingemischt sein. Geeignete Stabilisatoren sind insbesondere das 4,4'-Thio-bis(3-methyl-6-tert.-butyl-1-phenol), 1,1'-Thio-bis-(2-hydroxy-6-tert.-butylbenzol), Dilauroyl-thio-dipropionat und das Distearyl-thio-dipropionat. Die Formmasse kann einen Stabilisator oder mehrere verschiedene einschlägig bekannte Stabilisatoren enthalten. Es kommen auch Gemisch eines der oben genannten Stabilisatoren mit Schwefel in Betracht.Stabilizers are understood to be the usual additives which protect the ethylene polymer from decomposition during processing at high temperature. The stabilizers can be mixed into the molding composition in amounts of 0.1 to 0.6, preferably 0.1 to 0.4 percent by weight, based on the ethylene polymer. Suitable stabilizers are in particular 4,4'-thio-bis (3-methyl-6-tert-butyl-1-phenol), 1,1'-thio-bis (2-hydroxy-6-tert-butylbenzene) ), Dilauroyl thio dipropionate and the distearyl thio dipropionate. The molding composition may contain a stabilizer or several different stabilizers known in the art. Mixtures of one of the stabilizers mentioned above with sulfur can also be considered.

Zur erfindungsgemäßen Herstellung der vernetzbaren Äthylenpolymerisate werden die Äthylenpolymerisate zunächst mit dem Stabilisator oder Stabilisatorgemisch bei Temperaturen zwischen 150 und 220°C gemischt. Dieser Mischvorgang kann in einschlägig üblicher Weise in üblichen Mischern, wie z.B. einem Kneter, vorgenommen werden.To produce the crosslinkable ethylene polymers according to the invention, the ethylene polymers are first mixed with the stabilizer or stabilizer mixture at temperatures between 150 and 220 ° C. This mixing process can be carried out in a conventional manner in conventional mixers, e.g. a kneader.

Die 150 bis 220°C heiße Schmelze aus Äthylenpolymerisat und Stabilisator wird anschließend durch Passieren einer Siebvorrichtung von Verunreinigungen getrennt. Unter Verunreinigungen werden dabei verstanden Schmutz- und/oder Staubteilchen, zusammengebackene Stabilisatorklumpen sowie auch vernetzte und/oder verkokte Polymerisatteilchen. Nach bevorzugter Verfahrensweise erfolgt die Siebpassage des Polymerisat-/Stabilisatorgemischs durch ein Sieb, das eine Siebfeinheit von 200 bis 500, bevorzugt 300 bis 400 mesh (nach ASTM E11/61) aufweist.The hot melt of ethylene polymer and stabilizer, which is at 150 to 220 ° C., is then passed through a sieve device separated from impurities. Contamination is understood here to mean dirt and / or dust particles, caked stabilizer lumps and also crosslinked and / or coked polymer particles. According to a preferred procedure, the sieve passage of the polymer / stabilizer mixture takes place through a sieve which has a sieve fineness of 200 to 500, preferably 300 to 400 mesh (according to ASTM E11 / 61).

Das gereinigte, völlig homogene Gemisch aus Äthylenpolymerisat und Stabilisator wird anschließend in einschlägig üblicher Weise granuliert und abgekühlt.The cleaned, completely homogeneous mixture of ethylene polymer and stabilizer is then granulated and cooled in a conventional manner.

Wesentlich für das erfindungsgemäße Verfahren ist die Maßnahme, das so erhaltene Polyolefingranulat und gleichzeitig, aber getrennt vom Granulat, 1,0 bis 3,0 Gewichtsprozent, bezogen auf die Gesamtmasse, eines geschmolzenen organischen Peroxids, das eine Temperatur zwischen 40 und 90°C aufweist, kontinuierlich der auf eine Temperatur zwischen 0 und 30°C gekühlten Einzugszone eines Extruders zuzuführen. Unter geschmolzenem Peroxid wird dabei ein Peroxid verstanden, das bei Normaltemperatur, also bis 30°C fest ist, beim Erhitzen auf eine Temperatur über 400 bis maximal 90°C aber flüssig ist.Geeignete Peroxide sind das Dicumylperoxid (Schmelzpunkt 39°C) und das Bis-(tert.-butylperoxyisopropyl)benzol (Schmelzpunkt 45 bis 46°C). Die Einzugszone des Extruders, in die das stabilisatorhaltige Äthylenpolymerisat und getrennt davon das flüssige Peroxid eingeführt werden, ist auf 0 bis 30°C abgekühlt, so daß die Temperatur in diesem Einzugsbereich des Extruders um 10 bis 90°C niedriger ist als die Temperatur der Peroxidschmelze. Die Temperatur in der Einzugszone des Extruders ist also erfindungsgemäß stets niedriger als die Schmelztemperatur des Peroxids, so daß das in die Einzugszone des Extruders kontinuierlich eingebrachte Peroixd zweiphasig vorliegt: sowohl als Schmelze als auch als auskristallisierter Feststoff. Auf diese Weise wird eine störungsfreie Förderung des Äthylenpolymerisats und des Peroxids aus der Einzugszone des Extruders durch die Schmelzzone, in der eine Temperatur zwischen 110 und 135°C herrscht, bis zum Extruderaustrag möglich.What is essential for the process according to the invention is the measure, the polyolefin granules thus obtained and at the same time, but separately from the granules, 1.0 to 3.0 percent by weight, based on the total mass, of a molten organic peroxide which has a temperature between 40 and 90.degree , continuously to the feed zone of an extruder, cooled to a temperature between 0 and 30 ° C. Molten peroxide is understood to mean a peroxide that is solid at normal temperature, i.e. up to 30 ° C, but is liquid when heated to a temperature above 40 0 to a maximum of 90 ° C. Suitable peroxides are dicumyl peroxide (melting point 39 ° C) and the bis (tert-butylperoxyisopropyl) benzene (melting point 45 to 46 ° C). The feed zone of the extruder, into which the stabilizer-containing ethylene polymer and, separately, the liquid peroxide are introduced, has cooled to 0 to 30 ° C., so that the temperature in this feed range of the extruder is 10 to 90 ° C. lower than the temperature of the peroxide melt . According to the invention, the temperature in the feed zone of the extruder is therefore always lower than the melting temperature of the peroxide, so that the peroxide introduced continuously into the feed zone of the extruder is in two phases: both as a melt and as a crystallized solid. In this way, trouble-free conveyance of the ethylene polymer and the peroxide from the feed zone of the extruder through the melting zone, in which a temperature between 110 and 135 ° C. prevails, is possible until the extruder is discharged.

Die vernetzbare peroxid- und stabilisatorhaltige Äthylenpolymerisatmasse wird nach Verlassen des Extruders in üblicher Weise zu Granulat oder Formteilen verarbeitet.After leaving the extruder, the crosslinkable peroxide and stabilizer-containing ethylene polymer mass is processed in the usual way to form granules or molded parts.

Die mit der Erfindung erzielten Vorteile bestehen insbesondere darin, daß man ein völlig homogenes Äthylenpolymerisat erhält, das frei von Verunreinigungen ist und das für Isolierungen von Hochspannungskabeln besonders gut geeignet ist.The advantages achieved by the invention consist in particular in that a completely homogeneous ethylene polymer is obtained which is free from impurities and which is particularly well suited for insulation of high-voltage cables.

Beispiel 1example 1

Polyäthylen der Dichte 0,92 g/cm3 und des Schmelzindex von 2,7 g/10 min. wird in einem Kneter mit 0,3 Gewichtsprozent 4,4'-Thio-bis-(6-tert.-butyl-m-cresol) bei Temperaturen von 200°C homogen vermischt. Das Material wird einem Extruder zugeführt und bei einer Temperatur von 200°C durch ein Sieb von 400 mesh gefördert und granuliert. Das erhaltene Granulat wird einer zweiten Extrusion zugeführt, wobei in den Einzugsteil des Extruders getrennt vom Granulat 2,3 Gewichtsprozent, bezogen auf das Gewicht der Gesamtmischung, Dicumylperoxid zudosiert werden. Die Dosierung des Dicumylperoxids erfolgt mit einer Dosierpumpe bei 55°C. Das Dosierrohr endet in der Einzugsöffnung des Extruders 5 cm oberhalb der Schnecke. Der Einzugsteil (= Einzugszone) des Extruders ist auf 20°C gekühlt. Die Masse wird im Extruder aufgeschmolzen, homogenisiert bei einer Temperatur von 125°C und anschließend granuliert.Polyethylene with a density of 0.92 g / cm 3 and a melt index of 2.7 g / 10 min. is homogeneously mixed in a kneader with 0.3% by weight 4,4'-thio-bis- (6-tert-butyl-m-cresol) at temperatures of 200 ° C. The material is fed to an extruder and conveyed through a 400 mesh screen at a temperature of 200 ° C. and granulated. The granules obtained are fed to a second extrusion, 2.3 percent by weight, based on the weight of the total mixture, of dicumyl peroxide being metered into the feed section of the extruder. The dicumyl peroxide is dosed with a dosing pump at 55 ° C. The metering tube ends in the feed opening of the extruder 5 cm above the screw. The feed section (= feed zone) of the extruder is cooled to 20 ° C. The mass is melted in the extruder, homogenized at a temperature of 125 ° C and then granulated.

Aus dem erhaltenen Granulat werden bei 200°C Preßplatten hergestellt. Bei dieser Temperatur zerfällt das Peroxid und das Polyäthylen wird vernetzt. Die Preßplatten haben die Abmessungen 200 x 200 x 1,25 mm3. Zehn Preßplatten werden auf einem Leuchttisch mit einer 10fach vergrößerten Meßlupe nach Verunreinigungen abgesucht. Alle unter diesen Bedingungen sichtbaren Verunreinigungen werden gezählt und vermessen. Das Meßergebnis ist in der Tabelle als Beispiel 1 wiedergegeben.Press plates are produced from the granules obtained at 200 ° C. At this temperature, the peroxide disintegrates and the polyethylene is crosslinked. The press plates have the dimensions 200 x 200 x 1.25 mm 3 . Ten press plates are searched for contaminants on a light table using a magnifying glass magnified 10 times. All impurities visible under these conditions are counted and measured. The measurement result is shown in the table as example 1.

Beispiel 2Example 2

Polyäthylen der Dichte 0,92 g/cm3 und des Schmelzindex von 2,7 g/10 min. wird in einem Kneter mit 0,3 Gewichtsprozent 4,4'-Thio-bis-(6-tert.-butyl-m-cresol) und 2,3 Gewichtsprozent Dicumylperoxid bei einer Temperatur von 125°C homogen vermischt. Das Material wird einem Extruder zugeführt und bei einer Massetemperatur von 125°C extrudiert und granuliert.Polyethylene with a density of 0.92 g / cm 3 and a melt index of 2.7 g / 10 min. is homogeneously mixed in a kneader with 0.3% by weight 4,4'-thio-bis (6-tert-butyl-m-cresol) and 2.3% by weight dicumyl peroxide at a temperature of 125 ° C. The material is fed into an extruder and extruded and granulated at a melt temperature of 125 ° C.

Wie unter Beispiel 1 werden aus dem Granulat Preßplatten hergestellt und nach Verunreinigungen abgesucht. Die Verunreinigungen sind in der Tabelle als Beispiel 2 wiedergegeben.

Figure imgb0001
As in Example 1, press plates are produced from the granulate and searched for impurities. The impurities are shown in the table as example 2.
Figure imgb0001

Claims (6)

1. Verfahren zur Herstellung von Formmassen aus vernetzbaren, einen oder mehrere Stabilisator(en) enthaltenden Äthylenpolymerisaten der Dichte von 0,918 bis 0,935 g/cm3 und des Schmelzindex von 0,05 bis 25 g/10 min., dadurch gekennzeichnet, daß man in der angegebenen Reihenfolge a) das Äthylenpolymerisat bei einer Temperatur zwischen 150 und 200°C mit dem Stabilisator mischt, b) die Heiße Schmelze durch eine Siebpassage von Verunreinigungen trennt, c) die gereinigte Schmelze granuliert und abkühlt, d) das erhaltene Granulat und gleichzeitig, aber ge-, trennt vom Granulat, 1,0 bis 3,0 Gewichtsprozent eines geschmolzenen organischen Peroxids, das eine Temperatur von 40 bis 90°C aufweist, kontinuierlich der auf 0 bis 30°C gekühlten Einzugszone eines Extruders zuführt, e) in der Schmelzenzone des Extruders bei Temperaturen zwischen 110 und 135°C mischt und f) die so erhaltene vernetzbare Polymerisatmischung in üblicher Weise granuliert oder direkt zum Formteil verarbeitet. 1. A process for the preparation of molding compositions from crosslinkable, one or more stabilizer-containing ethylene polymers having a density of 0.918 to 0.935 g / cm 3 and a melt index of 0.05 to 25 g / 10 min., Characterized in that in in the order given a) the ethylene polymer mixes with the stabilizer at a temperature between 150 and 200 ° C, b) the hot melt is separated from impurities by a sieve passage, c) the cleaned melt is granulated and cooled, d) the granules obtained and simultaneously but separately from the granules, 1.0 to 3.0 percent by weight of a molten organic peroxide which has a temperature of 40 to 90 ° C., continuously in the feed zone cooled to 0 to 30 ° C. an extruder, e) mixes in the melt zone of the extruder at temperatures between 110 and 135 ° C and f) the crosslinkable polymer mixture thus obtained is granulated in a conventional manner or processed directly to give the molding. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das organische Peroxid Dicumylperoxid ist.2. The method according to claim 1, characterized in that the organic peroxide is dicumyl peroxide. 3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das organische Peroxid Bis-(tert.-butyl-peroxyisopropyl-) benzol ist.3. The method according to claim 1, characterized in that the organic peroxide is bis (tert-butyl-peroxyisopropyl) benzene. 4. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Stabilisator aus 0,1 bis 0,6 Gewichtsprozent 4,4'-Thio-bis-(6-tert.-butyl-m-cresol) besteht.4. The method according to claim 1, characterized in that the stabilizer consists of 0.1 to 0.6 weight percent 4,4'-thio-bis- (6-tert-butyl-m-cresol). 5. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Siebpassage durch ein Sieb von 200 bis 500 mesh (nach ASTM Ell/61) erfolgt.5. The method according to claim 1, characterized in that the sieve passage takes place through a sieve of 200 to 500 mesh (according to ASTM Ell / 61). 6. Verwendung der Formmasse nach Anspruch 1 als Elektroisoliermasse.6. Use of the molding compound according to claim 1 as an electrical insulating compound.
EP78100276A 1977-07-12 1978-06-29 Process for the preparation of cross-linkable ethylene polymer mouldings and their use as electrical insulating materials Withdrawn EP0000357A1 (en)

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EP0785226A2 (en) 1996-01-17 1997-07-23 Buna Sow Leuna Olefinverbund GmbH Method for regular and permanent distribution of peroxides in polyethylene
EP0947539A2 (en) * 1998-03-30 1999-10-06 Union Carbide Chemicals And Plastics Company, Inc. A process for production of a thermosetting composition
ITMI20131327A1 (en) * 2013-08-02 2015-02-03 R & D Innovaction S R L POLYETHYLENE BASE GRANULATE, RELATIVE PRODUCTION PROCESS AND ITS USE FOR CABLES PRODUCTION

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JPS55118938A (en) * 1979-03-06 1980-09-12 Hitachi Cable Ltd Crosslinked polyethylene resin composition

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Publication number Priority date Publication date Assignee Title
EP0785226A2 (en) 1996-01-17 1997-07-23 Buna Sow Leuna Olefinverbund GmbH Method for regular and permanent distribution of peroxides in polyethylene
DE19601498C2 (en) * 1996-01-17 2002-01-24 Buna Sow Leuna Olefinverb Gmbh Process for the uniform and permanent distribution of peroxides in polyethylene
EP0947539A2 (en) * 1998-03-30 1999-10-06 Union Carbide Chemicals And Plastics Company, Inc. A process for production of a thermosetting composition
EP0947539A3 (en) * 1998-03-30 2000-05-31 Union Carbide Chemicals And Plastics Company, Inc. A process for production of a thermosetting composition
ITMI20131327A1 (en) * 2013-08-02 2015-02-03 R & D Innovaction S R L POLYETHYLENE BASE GRANULATE, RELATIVE PRODUCTION PROCESS AND ITS USE FOR CABLES PRODUCTION
WO2015015382A1 (en) * 2013-08-02 2015-02-05 R&D Innovaction S.R.L. Polyethylene-based granulated material, production process thereof and use therefor for manufacturing cables
RU2656335C2 (en) * 2013-08-02 2018-06-05 Р&Д Инновактион С.Р.Л. Polyethylene-based granulated material, production process thereof and use therefor for manufacturing cables

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