DE1274334B - Device for fine and ultra-fine comminution of thermoplastics - Google Patents

Description

Device for fine and ultra-fine grinding of thermoplastics Plastics The invention relates to a device for fine and ultra-fine comminution of thermoplastics by whirling and grinding.

It is already known to use thermoplastics in so-called Process jet mills.

This is done with compressed air or higher pressure steam, which is led into a chamber, relaxes there and on the flow path creates a multitude of vortices that have a crushing effect. Such jet mills are expensive to purchase and operate. The energy consumption is very high; he according to R u m p f (magazine »Kunststoffe«, 1954, vol. 44, p. 102) between 1 and 10 kg of air per kg of regrind, there are working speeds between 300 and 500 mis, whereby the air must be compressed to 6 atmospheres.

It is also known to grind plastics in sieve mills. Here are, due to the low softening point of the plastics, often cooling units been used. According to Rumpf (magazine »Kunststoffe«, vol. 44, issue 3, 1944, p. 96) must remain 10 to 150 C above the air supply temperature. It there is nevertheless, apart from the specifically small power, the risk of smearing and clogging the screen openings. The products of these grinding techniques can thermal processing only in small percentages and with considerable Can be added to a decrease in the output amount.

For other grinding purposes there are already sieve-less comminuting devices became known that have rigid grinding plates and corrugated stator walls. Included the crushing effect results from the passing of the grinding plates on the corrugations of the stator as breakage or impact crushing between the grinding plate and corrugation. This type of shredding is associated with relatively high wear, limited with regard to the grinding fineness and applies to thermoplastic as well as to Grind-prone grinders are not very suitable.

By the present invention is to be achieved that in the above-mentioned grinding apparatus also waste a thermoplastic Plastic, which can consist of different types of plastic, too a fine and very fine powder can be prepared for certain further processing purposes is suitable without compressed air is required for the swirling or Cooling units are necessary.

To solve the task of fine and ultra-fine comminution by swirling and grinding thermoplastic waste plastics, pre-shredded to 10 mm are, the device uses a screenless shredding apparatus with a inside wall of the shredding housing provided with vertical webs as well as in arranged on several floors, revolving around a vertical axis, rigidly supported Shredding plates. According to the invention, an air throughput of at least 30,000 and at most 90,000 parts by volume of atmospheric air for one part by volume of regrind and a dwell time of the ground material of a maximum of 1.2 s is observed.

The invention achieves technical progress that in the screenless shredding apparatus used, which is equipped with a vertical The inner wall of the shredding housing provided with bars and in several floors arranged, rigidly mounted shredding plates revolving around a vertical axis is equipped, through the air flow in the specified according to the teaching of the invention Area of at least 30,000 and not more than 90,000 parts by volume of atmospheric air For a part by volume of regrind, air vortices are created through which the regrind particles move As far as possible comminute in the same way as in those based on the principle of jet milling Jet mills without the need for expensive compressors.

By the specified according to the teaching of the invention, the residence time of no longer than 1.2s for the ground material in the grinding apparatus will continue achieves that, given the aggressiveness of freshly ground plastic, none Ball grain formation occurs. The very finely or finely comminuted in this way Plastic can consist of several types without the ones made from them Products have an inhomogeneous structure, because with such a fine comminution there is a complete mixing of the different types of grades that the obtained raw material in itself is homogeneous. While before a Reuse of ground waste plastic is only possible in small percentages this material can be reused without the addition of new plastic.

It has been found that the thermoplastic properties the plastics, if the rules according to the invention are paused, not in the previous one known way occur disadvantageously.

The figure shows an example of the application of the invention.

The device 1 for swirling and grinding has a vertical one Wave. The crushing plates 1 a are rigidly attached to this. The crushing plates la are arranged on several floors one above the other. Above the shredding plates a fan 1 c is arranged. The vertical shaft, the crushing plates 1 a and the fan 1 c form the rotor. The stator consists of the outer one Housing and the inner wall provided with vertical webs 1 b. Through the allocation device 2 with the lock 3, the shredding device is fed. The material to be shredded is pre-broken to a maximum of 10 mm, in the allocation device 2 in the direction of the arrow A abandoned.

It is swirled and ground in the device 1 and leaves these at B. In a separator 4, air and solids are largely separated.

In order to eliminate any disruptive oversized grain, the solids outlet can be used at D from the separator 4, a sieve 5 is connected downstream, the overflow of which at E is subjected to processing again. The run leaves at F as a finished product the cycle. The air emerging from the separator 4 at C can pass through a filter 6 can be cleaned, and the dust particles resulting from this cleaning can be over the outlet at G can be added to the finished product. The cleaned air flows over Cm in the open air.

But it is also possible to overflow the sieve 5 from a second Device for small 7 at E1, which is then completely on the chopping Finer components can be aligned and their finished goods via H into the cycle gives. The air inlet is marked with a K in both devices.

The inventive device it has become possible to use old plastics different composition, especially the polyvinyl groups, on a purely physical basis Ways to process a powder that is back to the thermal processing process can be fed; it is due to its rough, partially rugged surface marked. The powder can, in particular when comminuting to a Thermal processing of grain sizes below 0.5 mm without the addition of new material. The processing is more economical than that in air jet mills and runs without the risk of clogging, clogging or impermissible heating, although the Softening temperature for the plastics in the device is exceeded.

Claims (1)

Claim: Device for fine and ultra-fine comminution Swirling and grinding of thermoplastic waste plastics from a maximum of 10 mm pre-shredded material in the air flow with a large air flow in a sieveless Crushing apparatus with an inner wall of the provided with vertical webs Shredding housing, as well as arranged in several floors, around a vertical Axis rotating rigidly mounted shredding plates, g e k e n n marked through an air throughput of at least 30,000 and at most 90,000 parts by volume atmospheric air to a part by volume of regrind with a residence time of the regrind in the apparatus of a maximum of 1.2 sec. References considered: U.S. Patent No. 2,752 097; "Kunststoffe" magazine, 1954, pp. 96, 97.