DD229417A1 - LIGHT-FLOWING POLYETHYLENE MOLDING FOR EXTRUSION COATING OF MOLDED BODIES - Google Patents

Abstract

The invention relates to easy-flowing polyethylene molding compositions which are suitable for extrusion coating of moldings at high processing speeds, smooth surfaces and low layer thicknesses and have an improved barrier effect against the ingress of petroleum masses. The novel molding compositions comprise low-density polyethylene, high-density polyethylene, wax compositions of hard paraffin wax and polyolefin wax, a stabilizer and optionally ethylene-vinyl acetate copolymer. Such molding compounds are suitable for the isolation of metallic conductors, especially as a solid outer skin of foam cores for filled telecommunications cables.

Description

^Leuna ·

LP 84 135

Title of the invention

Easy-flowing polyethylene molding compounds for extrusion coating of moldings

Field of application of the invention

The invention relates to light-weight polyethylene molding compositions which are suitable for extrusion coating of compacts with smooth surfaces and low layer thicknesses at high processing speeds and have an improved barrier effect against the ingress of mixtures of liquid and solid hydrocarbons, e.g. Petrolatmassen, exhibit · The molding materials are characterized by a low energy consumption during processing · Such molding materials are used for example for the isolation of metallic conductors, preferably as a solid outer skin in the production of foam by double insulation method

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Characteristic of the known technical solutions

Polyethylene, due to its excellent electrical and mechanical properties, is preferably used as an extrusion coating material for different shaped articles. For selected applications, it is necessary that the moldings are coated at high processing speeds of about 1 500 m / min with a smooth skin of a small layer thickness of less than 0.05 mm and this has an effective barrier effect against the attack of a surrounding medium on petrolatum basis. It is known, the processability of low density polyethylene for high processing speeds by the addition of 10 to 25 wt .-% high density polyethylene and 0.5 to 10 wt .-% of a hydroxyl and / or ester groups Olefinpolymerisats (DD-PS 140 095 ) Such molding compositions allow the coating of corresponding molded articles with small layer thicknesses. Light enough are the flowability and the barrier effect against petrolatum. In order to achieve a favorable behavior against the attack of liquid media, high density polyethylenes are described in the literature (E.J, Fisher, Wire Journal International, 8 (1983) 16, pp. 50-59). From Hachteil are in these products, the at the processing speeds not sufficient flowability and surface quality, e.g. by the occurrence of melt fracture, resulting in irregularities in the surface of the molded article.

Object of the invention

The aim of the invention is to develop easy-flowing polyethylene molding compositions having improved properties, which are suitable for extrusion coating of moldings with low energy consumption.

Explanation of the essence of the invention

The invention has for its object to develop leictitfließende polyethylene molding compositions that allow extrusion coating of moldings with layer thicknesses below 0.05 mm at processing speeds of at least 1 500 m / min and smooth surface and have effective protection against the attack of petrolatum. This object is achieved by easily flowing polyethylene Pormmassen for extrusion coating of molded articles of low density polyethylene, high density polyethylene, ethylene-in-ethyl acetate copolymer and stabilizers, according to the invention, the molding compositions 25 to 65 wt .-%, preferably 30 to 60 wt. %, Low density polyethylene, 0.5 to 5 wt%, preferably 1 to 3 wt%, of a wax composition of hard paraffin wax and polyolefin wax, a mixing ratio of 10: 1 to 3: 1, 0.05 to 0.5 wt .- #, preferably 0.1 to 0.25 wt .-%, of a stabilizer and to the total amount of 100 wt .- # complementary amount of a high density polyethylene and optionally 1 to 8 wt .-%, preferably 3 to 5 wt .-% of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 15 wt .-%. The hard paraffin waxes are advantageously obtained by refining lignite or petroleum-derived products having a freezing point of 323 to 343 K. Polyethylene waxes having a solidification point of 383 to 403 K can be used as polyolefin waxes.

As the low-density polyethylene, polyethylenes having a melt index of 0.1 to 0.3 dg / min and a density of 0.919 to 0.933 g / cm -1 can be used. As a high density polyethylene, more preferable is a polyethylene having a melt index of 0 , 5 to 25 dg / min and a density of 0.935 to 0.965 g / cm ³ used.

As ethylene-vinyl acetate copolymers are advantageously produced by the high pressure process products with a

Melt index of 1 to 10 dg / min (test temperature: 373 K) and a vinyl acetate content of 5 to 15 wt .-% used. The molding compositions contain a conventional stabilizer, preferably based on phenol, against the thermo-oxidative degradation. The polyethylene molding compositions should have a storage of the ambient medium of less than 4 % after storage (30 days, 343 K) in petrolatum,

Exemplary embodiments Example 1

58.25 kg of polyethylene having a density of 0.921 g / cm and a melt index of 0.32 dg / a, 38.5 kg of polyethylene having a density of 0.955 g / cm and a melt index of 22 dg / min, 3.15 kg of a wax composition of 9 parts hard paraffin wax (solidifying point: 330 K) and 1 part of polyethylene wax (solidifying point: 388 K) and 0.1 kg of 4,4 ^{l-thio-bis-3-methyl-6-tert-butylphenol} be a continuously The molding compound is melt-extruded and pelletized at 453 K. The molding compound is extruded on a cable sheathing plant as an external view onto a shingle-insulated conductor at a linear speed of 1 650 m / min There are no irregularities, and the petroleum jelly of the veins after being stored at 343 K in petrolatum for 30 days is 2.9% by weight.

A molding compound of high-density polyethylene, which is comparable in filler mass absorption, was not suitable for coating at the stated processing speeds. The surface showed irregularities and the energy consumption during processing was increased by 45 % compared with the molding composition according to the invention.

Example 2

32.50 kg of polyethylene having a density of 0.923 g / c & ³ and a melt index of 0.22 dg / min, 60.70 kg of polyethylene having a density of 0.951 g / cm and a melt index of 1.95 dg / min, 3 , 25 kg of a wax composition according to Example 1, 3.45 kg of ethylene-vinyl acetate copolymer having a vinyl acetate content of 12.4 % and a melt index of

2.4 dg / min (at 373 K), while adding 0.1 kg of the stabilizer, 2,2-thiobis (4-methyl-6-tert-butylphenol is melt-mixed and granulated.

The outer skin of 0.025 mm thickness is smooth at a processing speed of 1 550 m / min and has no irregularities. Petrolatum uptake after storage at 343 K for 30 days is 2.55%.

Example 3

45.0 kg of polyethylene having a density of 0.921 g / cm and a melt index of 0.32 dg / min, 48.15 kg of polyethylene having a density of 0.94 s g / cm and a melt index of 0.8 dg / min, 4.65 kg of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 8.7% and a melt index of

1.5 dg / min (at 373 K), 2.10 kg of a wax composition of 5 parts of hard paraffin wax (solidification point: 335 K) and 5 parts of polyethylene wax (solidification point: 398 K) are mixed with the addition of 0.1 kg of stabilizer according to Example 1, granulated and then fed to a foam core of a cable sheathing for extruding the outer layer. The outer layer of 0.042 mm thickness is smooth at a processing speed of 1 580 m / min and has no irregularities. The Füllmassenaufnahme after 30 days storage in petrolatum is 3.5 %

Claims (4)

invention claim 1. Lightly flowing polyethylene molding compositions for extrusion coating of moldings of low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer and stabilizers, characterized in that the molding compositions 25 to 65 wt .-%, preferably 30 to 60 wt .-%, Low-density polyethylene, 0.5 to 5% by weight, preferably 1 to 3% by weight, of a wax composition of hard paraffin wax and polyolefin wax in a mixing ratio of 10: to 3: 1 »0.05 to 0.5% by weight. ~, preferably 0.1 to 0.25 wt .-%, of a stabilizer and to the total amount of 100 wt.% Complementary amount of a high density polyethylene and optionally 1 to 8 wt .-%, preferably 3 to 5 wt , -SS, of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 15% by weight. 2. Slightly flowing polyethylene molding compositions according to item 1, characterized in that the molding compositions Y / achszusammensetzungen of hard paraffin wax having a solidification point of 323 to 343 K and polyethylene wax having a solidification point of 383 to 403 K. 3. The light-flowing polyethylene molding compositions according to item 1, characterized in that the molding compositions are a low density polyethylene mit'einer density of 0.919 to 0.933 g / cm and a melt index of 0.1 to 0.3 dg / min and a high density polyethylene containing a density of 0.935 to 0.965 r and a melt index of 0.5 to 25 dg / min, Light-flowing polyethylene molding compositions according to item 1, characterized in that the molding compositions contain an ethylene-yinyl acetate copolymerate having a yinyl acetate content of 5 to 15% by weight and a melt index of 1 to 10 dg / min (at 373 K).