DE19702540B4 - Process for obtaining branched-chain microwaxes and / or microwaxes with a high isoparaffinic content - Google Patents

Abstract

method for obtaining branched-chain microwaxes and / or microwax mixtures with high isoparaffinic content of polypropylene or polypropylene blends in a two-stage cleavage process with exclusion of oxygen, in which in a first stage at temperatures below 350 ° C, the polypropylene or Melted polypropylene mixture and in a second stage at Temperatures from 400 to 450 ° C a cracking process and simultaneous removal of the resulting cleavage products under vacuum is subjected to and the slit distillates obtained are fed to a selective de-oiling, characterized in that the Polypropylene or the polypropylene mixture before or during the liquefaction and / or the melt prior to the second stage 0.3 to 2.0% by mass of a Heat stabilizer or a combination of heat and processing stabilizer.

Description

The The invention relates to a method for obtaining branched-chain Micro-waxes and / or microwaxes with a high isoparaffinic content polypropylene or polypropylene blends with other polyolefins, vzgw. Polyethylene and preferably from waste, which is due to the degree of damage withdraw meaningful material recycling.

microcrystalline waxes represent particularly valuable waxes that are almost exclusively Slack waxes from petroleum processing be won. They consist predominantly of mixtures with n- and isoalkane shares. The relationship among each other is essentially determined by the provenance of petroleum.

Becoming plastic waste preferably recycled material. There, where a material recovery for quality reasons (degree of damage of the Plastic waste or quality requirements of the final product) or due to soiling, mixing etc. economically does not make sense, are different methods of raw material recycling or the energetic use of plastics has been proposed. The feedstock processes are based on the production of certain gaseous products, z. B. Synthesis gas (gasification, blast furnace), monomers (steam cracking) or certain liquid products, analogous to petroleum intermediates, z. B. by pyrolysis, hydrogenation, visbreaking, coking, etc. aligned. There are also a number of methods for gentle workup of plastic waste been described. Thus DD-PS 200891 describes a method in the polyolefin waste, such as polyethylene which is no longer usable as a material, at temperatures above 100 ° C in liquid Hydrocarbons dissolved and the resulting pumpable solution then one thermal treatment at usual Conditions is subjected. The resulting mixtures are either subjected to a customary in the mineral oil industry re-use or fed without further treatment of an energetic use.

In DD-PS 300 172 a method is described by polyethylenes convert oxidative thermal degradation to waxy products. The wax oxidates obtained can, due to their good Emulsifiability advantageous for the production of self-shine waxes, Polishing agents u. a. be used. Other procedures result in addition of oxygen or in the presence of catalytically active substances to shorter chain Fission products with waxy or plastic-like properties.

It are also a series of gentle thermal degradation processes of polypropylene or of polypropylene mixtures with other polymers been proposed.

So In DE-PS 4423394 a method is described for thermal Cleavage of Polyethylene-Polypropylene Mixtures to Obtain Liquid, predominantly branched-chain distillates and solid degradation products with opposite reduced levels of unbranched ingredients in the starting materials, being in polyethylene-polypropylene blends or in high-melting ones Degradation products of polyethylene-polypropylene blends to 5 to 95 % By weight of polypropylene constituents or the high molecular weight cleavage products of polypropylene for 0.1 to 24 hours, preferably 0.5 to 6 hours 350 to 400 ° C, preferably at 370 to 390 ° C, thermally treated and the resulting fission products directly in the formation process under Normal pressure are separated by distillation.

The DE-OS 4430664 describes a process for obtaining branched-chain Microwaxes by gentle degradation of polypropylene, in particular of propylene waste, by polypropylene or by gentle treatment of polypropylene accumulating high molecular weight intermediates of polypropylene degradation a cracking process at 390 up to 450 ° C with exclusion of oxygen at simultaneous distillative separation of the resulting cleavage products when pressed between 1 and 100 millibars and the obtained Colloidal distillates worked up by known per se known Selektiventölung become.

In DE-OS 4430665 describes a process for obtaining isoparaffin-containing Microwaxes by gentle thermal degradation of polyethylene-polypropylene mixtures, in particular of polyethylene-polypropylene wastes described by the Mixtures containing at least 20% by weight of polypropylene or by gentle thermal treatment of such mixtures resulting high molecular weight Intermediates a cracking process at 400 to 450 ° C with exclusion of oxygen at the same time Distillative separation of the resulting cleavage products at pressures between Subjected to 1 and 100 millibars and the resulting column distillates by Processes known per se are worked up.

A major disadvantage of the known methods is that they are not very flexible with regard to the products which can be obtained from them. They have only narrow margins for varying the ratio of solid to liquid or gaseous fission products. Thus, by the usually required heating of the liquid reaction medium at cracking temperatures well above 400 ° C. or obtained by cracking in the gas phase predominantly liquid and gaseous products whose applications are limited accordingly. The recovery of refractory, solid fission products can be achieved only very limited with the conventional methods.

There in the known methods, the production of microwaxes with higher C-number ranges only possible with low yields is, the procedures lose in technological flexibility and become uneconomical, or you have to the application technology particularly interesting products with high Dispense C numbers.

Of the Invention is based on the object, a method with high flexibility in terms on the properties of end products and under improved economic To develop conditions that allows, from polypropylene waste or made of polypropylene-polyethylene blends To produce microwaxes with a high isoparaffinic content.

The Task is achieved by a two-stage fission process under Oxygen exclusion solved, at in a first stage at temperatures below 350 ° C, the polypropylene or polypropylene mixture melted and in a second stage at temperatures of 400 to 450 ° C a cracking process and simultaneous removal of the resulting cleavage products under vacuum is subjected to and the slit distillates obtained are fed to a selective de-oiling, by the polypropylene or the polypropylene mixture before or during the liquefaction and / or the melt prior to the second stage 0.3 to 2.0 wt .-% of a heat stabilizer or a combination of heat and processing stabilizer be added.

at the method according to the invention was surprisingly found that the Degradation of the polyolefins under the conditions according to the invention without side reactions runs, and that special discoloration observed in the thermal degradation of polymers and Crosslinking of mixtures with polyethylene, resulting from subsequent reactions the monomeric primary decomposition products, does not occur. Even with small stabilizer additives was observed a significantly reduced coke formation in long-term operation.

The Invention is intended to 5 embodiments be explained in more detail.

example 1

In a heated stirred reactor / pre-cracker continuously 1 t / h polypropylene shredder material and 5 t / h of an im Circulation driven cracking melt, via an external heat exchanger at 350 ° C was heated, dosed. The polypropylene shredder material used came from from used battery boxes, had a melt flow index (MFI) of 14.3 g / 10 min. at 230 ° C and 2.16 kp. 1 t / h of the prereduced intermediate from the heat exchanger Vorcracker was withdrawn at a temperature of 350 ° C, over a second external heat exchanger to 410 ° C heated, with 1.6% by mass, based on the main stream, of a heat stabilizer pentaerythrityl tetrakis [3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] - added and dosed into the cracking reactor of the second stage.

92 Ma-% of the melt were distilled under vacuum, with a pressure of 48 mbar. There are 6% by mass gaseous and deducted 2% by mass of solid products.

The obtained Spaltdestillat was fractionated at a pressure of 6 mbar. In this case, 24% by mass of a liquid fraction boiling at 30 to 160 ° C., 73% by mass of a main fraction boiling in the range 160 to 360 ° C (Mirkowachs) and 1.5% by mass solid residue deducted.

The main product was freed of adherent oil at -6 ° C. in a two-stage selective oiling by means of acetone-toluene (1: 1). In this case, a solidifying at 72 ° C polypropylene micro-wax was obtained with a penetration of 6.10 ^-1 mm at 25 ° C.

Comparative Example 1

The procedure was analogous to Example 1, but without the addition of a stabilizer. The obtained split distillate contained 43% by mass of a liquid fraction boiling at 30 to 160 ° C., 51% by mass of the main fraction boiling at 160 to 360 ° C. and 1.6% by mass solid residue. The microwax obtained after the selective de-oiling had a solidification point of 71 ° C and a penetration at 25 ° C of 4 × 10 ¹ mm.

Example 2

It was proceeded as in Example 1. The input product was polypropylene film waste, which was Removal of coarse impurities agglomerated and under exploitation the agglomeration heat with 40 to 70 ° C into the stirred reactor / precracker were fed. In the pre-crackers 0.3% by mass and in the Main crackers 1.7% by mass, based in each case on the feed stream, one Stabilizer - Benzenepropionic acid, 3,5 - bis (1,1-dimethylethyl) -4-hydroxy-, octadecyl ester - dosed.

91% by mass of melt, 5% by mass of gaseous and 4% by mass of solid products were obtained. From the melt, 28% by mass of the fraction 1.68% by mass of fraction 2 and 2% by mass of solid residue were obtained. The resulting microwax had a solidification point of 71 ° C and a penetration at 25 ° C of 4 x 10 ^-1 mm.

Example 3

It The procedure was analogous to Example 2. Used again Polypropylene foil waste with a melt flow index of 5.8 g / 10 min at 230 ° C and 2.16 kp, which were agglomerated and immediately transferred to the stirred reactor. In the pre-crackers 0.8% by mass and in the main crackers 0.9% by mass Combination of 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene and a hydrolysis resistant Phosphites in proportion 4: 1 added.

There were obtained 94% by mass of melt, 3% by mass of gaseous and 3% by mass of solid products. From the melt, 22% by mass of fraction 1, 74% by mass of fraction 2 and 1.2 to 1.5% by mass of solid residue were obtained. The resulting microwax had a solidification point of 70.5 ° C and a penetration of 5 x 10 ^-1 mm at 25 ° C.

Example 4

It was proceeded as in Example 1. As input product was used Mixture of 65 m% polypropylene shredder material from battery boxes and 35 Ma-% of a low-density polyethylene film agglomerate.

In the pre-crackers were 0.2% by mass and in the main crackers 0.4% by mass Tris- (3,5-di-tert-butyl-4-hydroxybenzyl) - Isocyanurate dosed. The melt temperature in the main cracker was at 425 ° C.

95% by mass of melt, 4% by mass of gaseous and 3% by mass of solid constituents were withdrawn. The column distillate provided in the vacuum distillation at 8 mbar 16% by mass of the fraction 1.81% by mass of fraction 2 and 0.8% by mass of solid components. After the two-stage selective de-oiling, a microwax having a solidification point of 70 ° C and a penetration of 10 x 10 ^-1 mm at 25 ° C was obtained.

Example 5

It The procedure was analogous to Example 2. Polypropylene waste was used Battery boxes, strapping, Fibers and high density polyethylene from the bottle fraction. In the pre-crackers were 0.2% by mass and in the main cracker 0.5% by mass phosphoric acid [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl) methyl], monoethyl ester, Calcium salt (2: 1) dosed.

There were obtained 92% by mass of melt, 4% by mass of gaseous and 4% by mass of solid products. 32 M% of fraction 1, 64 M% of fraction 2 and 2.5 M% of solid residue were obtained from the melt by vacuum distillation at 20 mbar. The microwax fraction 2 was de-oiled in a two-stage process using acetone-toluene mixtures (volume fractions 50:50) at -8 ° C. There was obtained at 69 ° C solidifying wax with a penetration of 15 · 10 ^-1 mm at 25 ° C.

Claims (4)

A process for obtaining branched-chain micro waxes and / or micro-mixtures with high isoparaffinic content of polypropylene or polypropylene mixtures in a two-stage cleavage process with exclusion of oxygen, wherein in a first stage at temperatures below 350 ° C, the polypropylene or polypropylene melted mixture and in a second stage at temperatures of 400 to 450 ° C a cracking process and simultaneous separation of the resulting cleavage products under vacuum is subjected and the obtained Spaltdestillate be fed to a Selective Entölung, characterized in that the polypropylene or the polypropylene mixture before or during liquefaction and / or the melt 0.3 to 2.0% by mass of a heat stabilizer or a combination of heat and processing stabilizer is added before the second stage. Method according to claim 1, characterized in that that as heat stabilizer phenolic antioxidants are used, preferably pentaerythrityl tetrakis [3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], Benzenpropionsäure, 3,5-bis (1,1-dimethylethyl) -4-hydroxy, octadecyl, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, phosphoric acid [3,5- bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl], monoethyl ester, Calcium salt (2: 1), tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate. Method according to Claims 1 and 2, characterized that it the stabilizer combination is a phenolic antioxidant and a phosphite. Method according to Claims 1 to 3, characterized that the Adjustment of the C-number range of the obtained microwaxes over the Cracking temperature, the applied vacuum and the amount of stabilizer is regulated or at constant cracking temperature and vacuum only on the Amount of stabilizer.