DD150159A1 - PROCESS FOR CLEANING EXTRUDER - Google Patents

Abstract

It relates to the field of all plastic processing, especially the extrusion of polymers. The aim and task are the avoidance of large amounts of contamination in polymers, in particular their visible surfaces of light colorings. The said type of contamination is based on attrition of the decomposition layer forming at elevated temperatures, which rests on the screw and cylinder inner surfaces in different strength. A cleaning according to the principle of Schichtabreibs is more effective primaer by reducing the layer formation due to inert gas development, and secondary decomposition solubilized by gas evolution decomposed here carbonate particles in the layer. Application is according to the invention claims on the entire Plastverarbeitungsgebiet as well as the Spritzgiesztechnik u.ae. possible.

Description

Title of the invention

Method of cleaning extruders Field of application of the invention

The invention relates to a process for cleaning iron extruders "in the processing of various polymers, preferably thermoplastics.

Characteristic of the known technical solutions

During the processing of polymers on extruders, deposits on the surfaces of the extruder die occur during the extrusion process, which impede the extrusion process and cause fouling of the extrudate.

The removal of these so far unavoidable deposits is unavoidable »so that a trouble-free processing of the polymers is guaranteed. The cleaning of the extruder or the extruder parts is generally carried out by mechanical means by scraping the deposits from the metal surfaces.

In practice, the resulting deposits are often removed by burning off, and the extruder or screw parts thus treated have to be treated with a wire brush and sandpaper. These procedures are very uneconomical.

There is also known a cleaning method characterized by mixing a cleaning solution with either granules or powder and passing it through the machine. In this way, screw and cylinder are cleaned simultaneously (European Plastic News 3, 1976, 11).

Further, a rinsing agent is known which is an effective means for removing thermoplastics on screws, spray housings, extruder nozzles, spray nozzles ₉ , etc. (European Plastic News 6, 1979, 4).

The previously known methods for the purification of extruders or extruder parts are either very time- ».

consuming, costly and associated with considerable effort or not effective enough in the Eeinigungswirkung to longer operating time.

Object of the invention

The object of the invention is to eliminate the disadvantages of the previously known cleaning methods and to completely prevent the adhesion of polymers to the metal surfaces of extruders or extruder parts even over a relatively long period of time with small amounts of cleaning agents and to remove adherent product.

Explanation of the essence of the invention

- The technical problem of the invention

2) The invention is based on the object of developing an improved process for cleaning extruders, wherein a cleaning agent is added to the polymer powder or polymer granules, and the conditions mentioned above in the target are met.

Features of the invention

The object is achieved according to the invention by adding silica gel and / or basic magnesium carbonate in a concentration of 33% by weight or 0.067% by weight, based on the polymer, to the polymer powder or polymer granules. Partial water cleavage of the silica gel at elevated temperatures allows for the greatest possible contact of the metal surfaces due to swelling of the mass. By using the cleaning agents according to the invention, surprisingly, a high leveling effect is already achieved

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achieved the extrusion process with a small proportion of cleaning agents in the polymer.

Since the adhesion of polymers to the metal surfaces of the extruder is prevented by the cleaning agents according to the invention, no additional expenditure of time for cleaning the system is necessary.

In addition to the advantages mentioned, the addition according to the invention of silica gel or of basic magnesium carbonate or a mixture thereof effects a cleaning effect over a relatively long period of time without renewed addition of the cleaning agent to the polymer material to be extruded.

Since both compounds are non-toxic and do not give rise to any toxic products during the extrusion and cleaning process, the solution according to the invention can also be used for plastics which come into contact with foodstuffs.

The basic magnesium carbonate and the silica gel or their mixture are added in granular or pulverulent form.

Ausführungsbeisp everal Example 1

After extracting the extruder cylinder, the exposed screw with conventional tools, such as chamber, chisel u. Ä., Cleaned from adhering coverings. Experience has shown that after three to ten days of operation, the average previous degree of contamination of the extrudate is reached again.

Example 2

A purification procedure using a mixture of silica gel and thermoplastic granules in a ratio of 1 ± 2 without disassembly of the extruder caused the critical soil level to be exceeded once again for 10 to 14 days The amount of mixture was 85 kg of mixture at an extruder dosing rate of 100 kg / h.

Example 3

During the blending stage it was shown that a proportion of 0.067 % basic magnesium carbonate in the produced and extruded mix for a longer period of fourteen days reduced the utilization level by 30 %

Example 4

The cleaning mixture of silica gel and basic magnesium carbonate resulting from the above examples and an addition of only magnesium carbonate in said concentration before and / or after a cleaning process with inventive mixture shows an extension of the cleaning effect to over 6 weeks.

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Claims (1)

Process for the purification of extruders with a cleaning mixture consisting of polymer powder, optionally containing additives, such as pigments and lubricants, or polymer granules and a cleaning agent, characterized by the fact that Silioagel and / or basic magnesium carbonate is used as cleaning agent «