DE1105608B - Thermoplastic molding compound for casting and extrusion from polyolefins - Google Patents

Description

GERMAN

The invention relates to thermoplastic molding compositions which are produced by what is known as the low-pressure polymerization process polyolefins obtained and in particular, but not exclusively, polyethylenes. At a such low pressure process is known to be the olefin, ζ. B. ethylene, propylene or butylene or a Mixture of two or more such olefins, in the presence of a catalyst, under a pressure of less than 500 at polymerizes, and the term "low pressure" is used to describe the process of known olefin polymerization process to separate roughly, which under pressures in the order of magnitude of 1000 at or more.

Many physical properties of such low pressure polyolefins can be determined by the particular polymerization conditions prevailing during their production or controlled. For example, the type or proportions of the catalyst and the presence or the absence of substances for modifying the molecular weight are important factors which Influence properties such as the viscosity of the polymer formed.

However, it is generally neither possible nor desirable by controlling the polymerization conditions to be able to meet all the requirements relating to the physical properties of the polyolefins, and it is therefore sometimes necessary to mix the polyolefins with additives, for example for the production of Molding compounds.

The recently developed low-pressure polyolefins, which are in themselves completely new materials, have one Number of good properties. However, these polymers do not have the desired properties in every respect Combination of properties. Low molecular weight "Ziegler" polyethylene has z. B. a good fluidity, what z. B. in extrusion and injection molding is very important, but the fragility or brittleness is for too big for most uses. At higher molecular weights of the »Ziegler« polyethylene, the The brittleness is much lower and the impact resistance is good. The disadvantage, however, is that these high-molecular »Ziegler« - Polyethylenes have a reduced flowability, which makes them much more difficult to apply to e.g. B. the screw press can be processed.

The invention relates to thermoplastic molding compositions made from polyolefins produced by the low pressure process, z. B. Polyethylenes exist and are particularly due to their satisfactory flow properties suitable for molding and extrusion.

It has been found that by low pressure polymerization processes manufactured polyolefins, e.g. polyethylene or polypropylene, have valuable flow properties can be imparted by adding a small amount of a refined colorless mineral oil to them,

for casting and extrusion

made of polyolefins

Applicant:
Petrochemicals Limited, London

Representative: Dr.-Ing. F. Wuesthoff, Dipl.-Ing. G. Pulse ίο and Dipl.-Chem. Dr. rer. nat. E. Frhr. v. Bad luck man, Patent Attorneys, Munich 9, Schweigerstr. 2

Claimed priority:
Great Britain December 21, 1956
and September 27, 1957

Robert Nobbs Haward, Bowdon, Cheshire

(Great Britain),
has been named as the inventor

that under the normal processing conditions of the polyolefin, ζ. B. in molding or extrusion, and is virtually non-volatile under the conditions at which the polymer is normally used. In the French patent 1 107 378 compositions are described which a hydrocarbon polymer and contain, among other things, a non-volatile solvent, which under simultaneous thermomechanical Degradation of the polymer has been incorporated. Apart from the fact that the invention to be used Refined colorless mineral oils are not mentioned in this patent specification, takes place when they are incorporated Mineral oils according to the invention do not break down in the low-pressure polyolefins.

In US Pat. No. 2,339,958, compositions of high pressure polyisobutylene, polyethylene and, preferably, ^{paraffin wax melting in the range from 50 to HO 0} C are described. Example 3 of this patent shows that the addition of a paraffin wax to polyisobutylene-polyethylene mixtures significantly lowers the melting point. In contrast, when the colorless mineral oils according to the invention are used for low-pressure polyolefins, the softening point is only very slightly reduced.

US Pat. No. 2,499,756 describes how to reduce water vapor permeability and Improvement of the stiffness of high pressure polyethylene this paraffine with a melting point above 120 ° C to be incorporated in relatively large quantities.

According to the invention contains a thermoplastic molding composition for casting and extrusion from polyolefins and paraffinic hydrocarbons a low-pressure poly-

109 '57B / 437

olefin and, based on this, 0.5 to 20 percent by weight a colorless highly refined mineral oil with an initial boiling point of at least about 250 ° C. Preferably the polyolefin contains 2.0 to 10 percent by weight of said mineral oil. In the case of polyethylene, the The amount of mineral oil used is advantageously 2 to 5 percent by weight, based on the polyethylene. In which Polyethylene is preferably a product manufactured according to the "Ziegler" process.

The colorless mineral oils, which are preferably used for the production of polyolefin compositions according to the invention, are the colorless or essentially colorless, technical mineral oils consisting mainly of saturated hydrocarbons of a paraffinic or naphthenic nature and practically free of aromatic and unsaturated compounds, which are known to be refined of lubricating oil fractions, for example by solvent extraction and subsequent treatment with oleum. Such technical colorless particularly suitable are mineral oils with different viscosity values in the range of about 1.60 to 4.90 Engler degrees at 6O ⁰ C in the trade. Here, in particular, colorless mineral oils having a viscosity of about 1.60 or 2.38 degrees Engler at 60 ⁰ C are particularly suitable. Other technical colorless mineral oils of similar viscosity, preferably in the range from 1.60 to 3.00 Engler degrees at 60 ⁰ C, having an initial boiling point of at least about 250 ⁰ C and in which the main part merges to 500 ⁰ C, however, can according to the invention also be used.

The colorless mineral oil is mixed with the low-pressure polyolefin such as polyethylene or polypropylene, e.g. B. easily by mixing the polymer and the oil between about 150 and 175 ° C, ie at a temperature at which the polyethylene can be processed easily enough. The blending is conveniently carried out by treating the polymer and the oil in a two-roll mill, although blending of the materials in a rubber kneader or by hot extrusion of a mixture can also be carried out. Stabilizers or other additives can also be present in the mixture. For example, degradation of the polymer at working temperatures above 100 ^° C. without increased discoloration can essentially be prevented in a known manner by adding organic phosphites. Other conventional stabilizers and / or antioxidants, in particular chlorine-absorbing stabilizers, such as cadmium and calcium stearates, polymeric glycidyl polyethers and alkyl tin esters, can be present in the compositions according to the invention together with or instead of the abovementioned phosphites. The thermoplastic molding compositions can optionally also contain small amounts of other customary additives, such as lubricants and mold release agents.

It has been found that the addition of colorless mineral oil, e.g. B. with a viscosity between 2.08

ίο and 2.70 Engler degrees at 60 ⁰ C in a small amount, about in the order of 2 to 3 percent by weight and in some cases up to about 5 percent by weight of a low-pressure polyethylene not only improves its flow properties, as is evident from the improved shape properties, but also increases the impact strength of the polymer. Both of these properties can be improved without unduly lowering the softening point of the material.

example 1

After the "Ziegler" process under homogeneous steady state conditions by polymerization of ethylene Polyäthylenproben made of a highly refined mineral oil were mixed colorless naphthenbasisehen to the polyethylene by the slow addition, the latter was treated with hot rolls at 160 to 17O ⁰ C. The mineral oil used had an initial boiling point of about 300 ⁰ C, a viscosity of 2.30 Engler at 60 ⁰ C and a density of 0.878 at 16 ⁰ C.

After about 10 minutes of treatment on the roller mill, the polymer was removed in strip form and cooled and cut into small pieces.

The polyethylenes were prepared in a known manner using a catalyst which had been prepared by previously mixing aluminum diethyl monochloride with titanium tetrachloride in a weight ratio of 1: 1 and then dispersed in isooctane, which formed a liquid reaction medium. The catalyst concentration corresponded to a concentration of about 5 millimoles Al (or Ti) per liter of reaction medium. The polymerization was carried out usually by passing practically acetylenfreiem ethylene in the reaction medium at about 40 ⁰ C. The resulting polymer was worked up in the usual way.

In the table below are some physical properties of the various blends made specified.

Basal molars Ge Enamel Blow Softening temperature ***, 60 ° Remarks Geraisch of the polymer percent index**** strength ° C at deformation angle - (I. V> * oil g / 10 minutes kgcm / cm 30 ° 124.5 \ Ethylene not free of acetylene A { co co
co "co" 3.5 0.04
0.08 11.9
17.9 - 124.5 \ Ethylene practically acetylene ■ R * I 2.7 - 0.07 13.0 112.0 125.5 j free ^ i 2.7 2.5 0.13 17.2 109.5 124.5 1 r * / 2.7 - 0.05 16.2 114 C the same. ¹ > 2.7 2.5 0.08 17.2 107.5 Mixture contained add D. 2.1 2.5 0.24 - . Lich 0.3 percent by weight alkylated aryl phosphite

* The polyethylene polymers used in blends B and C- were under slightly different reaction conditions manufactured according to the "Ziegler" process.

Λ "1

** I.V. = ———; Λ "= ratio of the average viscosity of a solution of the polymer in decahydronaphthalene

the average viscosity of the solvent. C = weight percent of the polymer in the solution. The viscosities are kinematic Viscosities, in centistokes, measured in a conventional Ubbelohde viscometer at 120 ° C.

*** The softening temperature is the temperature at which a constant deformation of the polymer sample takes place under constant load. The deformation is measured at a deformation angle at 30 ° or 60 ⁰ C, according to the British Standard Specification no. 1493 of 1948,.

**** The melt index numbers in the table are based on that described in British Standard Specification No. 1973 of 1953 Procedure received.

Example 2

A polypropylene produced by the low pressure process (density = 0.906, intrinsic viscosity = 2.77, melt index = 1.20) was mixed with 5 percent by weight of a technical colorless mineral oil with a viscosity of 1.61 Engler degrees at 60 ° C and a Initial boiling point of about 300 ⁰ C.

The mixture thus obtained showed a melt index of 2.46, from which it can be seen that a considerable improvement the fluidity had occurred.

The addition of oil also resulted in an improvement in the impact resistance, as was found in the testing of test tubes made from the polypropylene with and without the addition of oil. When applying a hammer energy of 2 kg / m to pipe sections of 10 cm length, which had cooled to 0 ° C, 100% of the tested 60 pipe sections broke in the case of polypropylene without added oil and 0 ° / ₀ in the case of polypropylene with oil added.

The thermoplastic molding compositions of the invention in particular have improved flowability and also increased impact resistance. Apart from the surprising improvement in these properties, it was not foreseeable that the small amounts of a colorless mineral oil added according to the invention would also be present

an initial boiling point of at least 250 °
bring about a considerable increase in the melt index without this being associated with a significant reduction in the softening point of the low-pressure polyolefin at the same time.

Claims (4)

Patent claims: 1. Thermoplastic molding compound for casting and extrusion from polyolefins and paraffin hydrocarbons, containing a low-pressure polyolefin and, based on this, 0.5 to 20 percent by weight colorless refined mineral oil based on paraffin or naphthene with an initial boiling point of at least 250 ° C. 2. Molding composition according to claim 1, containing polyethylene as the polyolefin. 3. Molding composition according to claim 1 and 2, containing the polyolefin produced by the "Ziegler" process Polyethylene. 4. Molding composition according to claim 1 to 3, containing as mineral oils in technical colorless oil with a viscosity of 1.60 to 3.00 Engler degrees at 6O ⁰ C. Considered publications:
French Patent No. 1107,378;
U.S. Patent Nos. 2,339,958, 2,499,756. © 109 575/437 4.61