DE4217764A1 - Sorting process for sepg. polyethylene@ from polypropylene@ - by heating the water particles with polyethylene shrinks and forms heavier fraction whilst polypropylene@ can then be removed by air elutriation - Google Patents

Abstract

In a sortation process for separating pieces of polypropylene from those of polyethylene small pieces of the two polymers are mixed and the mixture is heated until they contract or shrink together and those of the two polymers are then separated from each other. ADVANTAGE - The polyethylene particles shrink considerably more than those of polypropylene. This principle allows the two polymers to be separated, whereas they cannot be differentiated visually. The method produces pure polymers. It is suitable for use industrially and can be applied to domestic waste plastics (which commonly consist of the two polymers mentioned, e.g., in wrapping films). In an example, the two polymers (e.g., as bags, films, etc., with or without being disintegrated first, are fed to a cutter/compressor which has revolving cutters and which reduces them to, e.g., thumbnail size. This action has a heating effect, enough to raise the temp. of the mixture to above their softening points.

Description

The invention first relates to a method for separation of parts made of different plastics. Knows about this a separation by hand, but this deals with this skilled workers must recognize which plastic the type of plastic part in question. Often this is not possible. In addition, misjudgements cannot be avoided. Finally, there is the problem that it is difficult for to get this uncomfortable, dirty work staff. Automatic separation processes are also known, which are known as different density of different types of plastic take advantage of and then sort. Both However, the aforementioned separation options fail with the problem the separation of plastic particles made of PP (polypropylene) from Plastic parts made of PE (polyethylene). Are with the eye no differences found. Have both types of plastic practically the same density, so that the procedure mentioned measures cannot be used technically.

There is therefore the task or problem of Invention first to find a method that auto  The separation of plastic parts made of PP works mathematically of plastic parts made of PE.

To solve this task or problem is out proceeding from the preamble of claim 1 first moderately provided that for the separation of plastic parts PP of plastic parts made of PE a mixture of small ones Pieces made of PE and PP and by exposure to heat until the small pieces are in each other have contracted or shrunk and that then the contracted or shrunk pieces made of PE from the contracted or shrunk pieces be separated from PP. Under the term "shrinking" you understand a certain contraction of a film particle, with this contraction the surface of the Foil particles raised and deepened in the way forms as if it had been crumpled by external force is. It has been shown that with simultaneous heating the pieces of PE and PP contract or shrink of PE to a much greater degree than that Shrinking or shrinking equal sized pieces of PP. This is the size that arises with the heat treatment Difference then gives the possibility of the contracted or shrunk PE pieces from the contracted or to separate shrunk PP pieces. This separation is with a very high degree of purity possible. The invention is both in the industrial sector and for separation talking plastic waste can be used in household waste. Mentioned to this end, that PP and PE in the household waste area repeatedly occur together and in particular in foil form. Out PP foils, for example, become Prali's wraps boxes and made of PE films, for example shopping bags produced.

According to process claims 2 and 3 , the process can be operated with different heating temperatures and corresponding results can be achieved. In particular, reference is made to the following description of possible embodiments of the invention.

If a mixture of PP and PE film parts is processed and these are shrunk pieces after heating, final separation using a wind is recommended classifier (claim 6). If, on the other hand, cutlet-like pieces processed from PE and PP and after heating them have contracted into small balls or balls, so their separation by sieving is recommended (claim 7). But it is for deciding whether to separate by air sighting or sieving, less does that Output product as the shape of itself through the warming resulting contracted or shrunk pieces bleached.

The invention also has the task of creating a Arrangement for performing the method according to one or made several of claims 1-6. This is first provided according to the characterizing part of claim 7 that a Cutting compactor for shredding and heating a Mixture of PP and PE plastic parts is provided and that the output of this cutting compactor is a separator tion is fed. This is used for low manufacturing technical effort a separation result of very large purity achieved degree of security. The use of the aforementioned cutting ver dichters is also recommended because this is in him entered batch of PE plastic parts and PP art Parts of the fabric into small pieces in one process step divided and at the same time heated according to the invention. It must not separately when using the cutter / compactor Heat must be added because the required heat is from the friction or separation heat of the cutting process gives.

Cutting compactors are known per se. They have been so far but only used for foils of a certain art  to compress the type of material by the volume of this plastic mass smaller, d. H. to make it as compact as possible. The simultaneous targeted heat treatment of two different plastics and in particular the two different plastics PE and PP has not yet been used with cutting compactors has been conducted.

Further advantages and features of the invention are the others Subclaims, as well as the following description and the Drawing of possible embodiments according to the invention remove. The essentially schematic drawings demonstrate

Fig. 1 shows a first arrangement for carrying out the invention,

Fig. 2 shows a second arrangement for carrying out the invention.

According to arrow 1 , a quantity of PE plastic parts and PP plastic parts is fed to a cutting compactor 2 in both exemplary embodiments. This batch can consist of previously shredded plastic parts. However, plastic products, e.g. B. smaller shopping bags can be entered into the cutting compactor 2 without comminution. The cutting compactor 2 has rotating knives 3 which rotate about the axis 5 by a drive 4 . Herewith they break the entered batch into small pieces. These bits can be, for example, thumbnail size. The comminution produces a corresponding heat, which is sufficient to heat the batch indicated by 6 to a temperature above the softening range of PP and PE. The softening range of PE starts at around 60 ° C and the softening range of PP at 90 ° C and possibly even higher. The heating of the mixture of plastic parts in the cutting compactor 2 is preferably around 100 ° C., but somewhat higher temperatures can also be set according to the respective requirements.

Instead of the process operation according to the latter Temperatures can, according to another embodiment the invention can also be proceeded so that the heating temperature just above the softening range of PE, however, is kept below the softening range of PP. This does shrink the PE pieces, but not yet for shrinking the PP pieces. So you can e.g. B. non-shrunk PP film sections in a wind Let sifters discharge upwards while shrinking and on the other hand, compact PE beads are discharged downwards will. The shrunk PE content can be both in shape shrunken beads, as well as shrunk in shape Foil sections arise. When mixing such PP beads or film sections with non-shrunk PP films cuts are carried upwards in the wind sifter, on the other hand, the explained, crushed PE portion in the air classifier is eliminated downwards.

During processing in the cutting compactor, its interior should be filled as completely as possible with batch 6 . The surface 6 'of such a filling 6 is shown in Fig. 1.

The addition of the mixture of PE and PP at 1 can do that too Result of a preparation process from several under be different plastics, e.g. B. made of PET with a density of approximately 1.4 and PE and PP parts with approximately the same Density that is less than 1 in each case. After the usual disgust that of PET then remains a mixture of PE and PP, which be already pre-shredded by the processing process mentioned is. This batch is then in accordance with para. 1 in the cutting compressor entered.

As already mentioned, the PE- to be separated from each other and PP parts are film parts or compact parts. Foils -  in particular is on foils with a thickness below 500 microns thought - become small foils in the cutting compactor cuts processed and usually form after leaving of the cutting compactor shrunk compared to the previous one Size reduced and crumpled looking Bits. Compact plastic parts made of PE or PP are used in the Cutting compactor crushed into small chips, which after Leaving the cutter / compactor usually the shape smaller Have balls or small balls. In both of the above There is a possibility of heating this mixture the softening ranges of PE and PP, e.g. B. on the in the Relationship above temperature around 100 ° C, to Formation of globules of different sizes or shrinked ter foils, the effect already explained occurs that the shrinkage of PE many times, up to 10 times that Of PP shrinkage. The discharge in the wind sifter or with a sieve can according to other design options the invention as follows:

It is therefore advisable to separate this outlet 7 of the cutting compactor by means of a sieve 8 into an overflow 9 made of PP and an underflow 10 made of PE ( FIG. 1) in the case of an outlet from the aforementioned balls or balls.

In contrast, have the parts of the outlet 7 more in the form of a shrunken film, so a wind separator 11 with an upper run 12 made of PP and a lower run 13 made of PE is recommended for separation.

When working with a cutting compactor according to the exemplary embodiments, discontinuous operation is possible, provided that there is only one separating device. But are several, z. B. three separators are provided, the outlet 7 of the cutting compressor can be fed after filling a Trennvor direction without interruption to the next separating device, the separator already filled being emptied during its filling.

Claims (10)

1. A method for separating parts made of different plastic material, characterized in that for the separation of parts made of PP (polypropylene) from parts made of PE (polyethylene) a mixture of small pieces of PE and PP is created and heated so far by exposure to heat until the small pieces have contracted or shrunk, and then the shrunk or shrunk pieces of PE are separated from the shrunk or shrunk pieces of PP. 2. The method according to claim 1, characterized in that the heating temperature over the softening range of PP (and therefore also above the softening range of PE) lies. 3. The method according to claim 1, characterized in that the heating temperature is slightly above the softening level rich in PE, but below the softening range of PP is held. 4. The method according to any one of claims 1 to 3, characterized net by separating PP particles from PE particles in the form of film sections, the films a  Have a thickness below 500 µm. 5. The method according to claim 1 or 2, characterized by a separation of PP parts and PE parts in each Form of chips. 6. The method according to any one of claims 1 to 5, characterized characterized in that, especially when separating Foil sections that ge after exposure to heat shrunk parts made of PE and PP by windsighting be separated from each other. 7. The method according to any one of claims 1 to 5, characterized characterized in that in the separation, in particular of shredded parts after exposure to heat balls or balls made of PE and PP Seven are separated. 8. Arrangement for performing the method according to one of claims 1 to 7, characterized in that a cutting compactor ( 2 ) for comminuting and heating a batch ( 6 ) of PE and PP parts is provided, and that the discharge ( 7 ) the cutting compactor is fed to a separating device ( 8 ; 11 ). 9. Arrangement according to claim 8, characterized in that the separating device is an air classifier ( 11 ). 10. The arrangement according to claim 8, characterized in that the separating device is a sieve ( 8 ).