CS224594B1 - Continuous double-stepped method for granulation fine grained wet materials with selectable grain size - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a continuous two-stage granulation method for mono-grained wet materials of selectable granule size, particularly suitable for granulating rubber chemicals, in particular rubber vulcanization accelerators, based on a combination of pressure and load granulation in a process sequence.

In industrial practice, there are a number of products where the granulate form is the output form of the processed substance, whereby the formed granules are required to have certain specific properties. Typically, the strength of the granulate is within certain narrow limits, furthermore that when handling the granulate mechanically, a large amount of dust is not released from the sterile so that the granulate has good flow properties, desired size, and the like. The resulting granule strength is determined by the nature of the material to be processed, its structural stability, compaction and the content of substances required to form bonds between the solid particles in the agiomerates. In a number of cases, there are no particular requirements for the resulting strength; the scraper is required to have the highest mechanical strength of the granules formed.

In other cases, e.g. By means of pressure granulation, the moist fine-grained material compacts and forms into compact units only for another technological operation, which is often drying, in which the agicmerates are converted into powder form by grinding © pgf. In such cases, it is usually not necessary to impose particular requirements on the size, shape and strength of the agglomerates, if the compacted and formed material is able to withstand mechanical stress e.g. in a belt dryer. Particularly the abrasion resistance at a relatively low overall strength of the granules is one of the specific requirements required for products which are toxic or otherwise harmful, where the formation of dust during handling of the granulate is undesirable in terms of environmental and working environment protection. Such products include rubber vulcanizator accelerators and other rubber chemicals,

224 594 ', which today are the desired tauoner exclusively in a non-dusty suitable molded form and with strictly defined mechanical strength requirements.

The densification and shaping of wet fine-grained materials having the character of cohesive bulk materials can be accomplished in a variety of ways. Methods of pressure or rolling granulation are used. In pressure granulation, the wet material is compacted and formed by extrusion through dies of different shape, provided with mostly circular molding holes. The extruded wet material is formed into rollers whose diameter is determined by the diameter of the hole in the die and the length is usually set by spontaneously breaking the extruded profile. , granules or damp material is compacted between smooth rolls and formed into a continuous flat shape (strip), which in a subsequent phase is suitably separated into smaller granular particles. During rolling granulation, the material in a device of the appropriate type (drum, granulating plate, etc.) is moved in a rolling motion during which the fine-grained material is gradually formed into rounded or spherical formations, usually with the addition of the granulating liquid. The size of the granules obtained depends mainly on the manner and amount of granulation liquid added. A suitable process design using e.g. By internal sorting it is possible to achieve a relatively narrow size fraction.

The currently used method of granulating rubber chemicals by extruding a wet fine-grained material, in which granules of cylindrical shape of different lengths are formed, is disadvantageous from several points of view. The very shape of the formed agglomerates gives rise to the formation of large amounts of dust during handling and processing by breaking them longer. rollers for shorter and sheared edges.

Also, the mobility of the material in the layer is inferior, making it difficult to empty from the storage metal, to move in dispensing devices, and the like. In order to achieve a good appearance and the overall cohesion of the granules, it is necessary to carry out the spinning at higher pressures, which sometimes leads to an undesirably high strength of the granulate. Most rubber chemicals are high purity water-insoluble materials with a low content of substances that can act as bonding agents between solid phase particles. However, because of the required application properties, it is not desirable to add such substances to the material to be treated. ^{224 594}

These drawbacks are overcome by a continuous two-stage process according to the present invention, which is based on the fact that the wet, non-ionic material has a content. 20-40% of the tax-free and binder-free water in the first stage is forced through circular openings or compacted between two profiled surfaces into cylindrical aglemerates which are cut or broken to a predetermined length at the outlet where the preformed and pre-compacted wet material is continuously It is removed and rolled in the second stage of the technological process by rolling for 5 to 15 minutes while contacting the drying air heated to 60 - 90 ° C.

By utilizing a combination of pressure and rolling granulation with a continuous process sequence with simultaneous drying, many advantages are achieved over the prior art, from a number of different points of view. For example, in the first stage the preformed cylindrical agglomerates are not the same due to the free fracture, have a generally cracked and uncoated surface, a proportion of small fragments occurs, and the preformed and preformed material is then further processed by rolling granulation in a suitable machine. longer cylindrical granules break into shorter ones by. By rolling in contact with the drying air, the preformed material is further compacted. By rolling between them and the walls of the apparatus, the cylindrical agglomerates are transformed into oval to spherical granules. the isogeneous fraction resulting from the abrasion of the edges during the profiling. The free moisture, which is forced to the surface of the granules to be formed, is gradually evacuated by the drying air during compaction during rolling. This allows for a further continuous compacting of the agglomerates without gluing them into larger, packed or glued to the sides of the granulation device. After a sufficient period of time, rounded to spherical granules with a compact, smooth surface are formed in this way, the size of which is determined largely by the size of the openings through which the wet material in the first stage has been preformed by pressure granulation. The granules thus formed, with respect to surface hardening and deformation in the second stage, obtain very advantageous properties in terms of their further application. They are sufficiently abrasion resistant because the surface is more compacted and thus stronger than the granule core. The compacted granule core is advantageous in that it guarantees good and rapid disintegration of the granules in the whole volume at their

224 594 further processing. If no internal grading in granulated and precession is used, the resulting granulate has a poly-dispersive character but with relatively narrow granule size limits. Granules of monodisperse character with agglomerates of uniform type, i. round and equally elongated or spherical granules according to the invention are obtained by regular trimming. or by breaking to the same length when extruding to cylindrical formations in the first granulation step. Depending on the ratio of diameter to length, one of the aforementioned types of granules is formed in the second granulation step, i. ovals or pellets, whereby a nearly monodispersed granulate is obtained in terms of fractional composition.

In the present state of the art, the method of granulation is an advance especially in the field of rubber chemicals and a higher effect is reflected in the fulfillment of the quality requirements of the granulate in terms of physico-mechanical properties, continuity of processing, production efficiency, savings in energy and conditions during further handling of the product during its processing.

Example 1

A wet, fine-grained rubber vulcanization accelerator having an active ingredient content of 99.5% of N-cyclehexyl-2-benzethiazylsulphenamide obtained from an aqueous suspension of filtration at 40% humidity was forced through a die with a 4 mm circular orifice through a die. The wet irregular cylindrical granules were discharged into a granulation drum, where the rolling motion was gradually transformed into oval to spherical smooth granules over a period of 15 minutes with a drying air temperature of 60 ° C, of which 90-95% of the less desirable dimension given basically the size of the holes in the die of the extruder. The average pellet strength was 0.2 MPa in all embodiments.

Example έ

The material according to Example 1 was cut immediately after the die so that the length of the cut agglomerates was approximately. equals their diameter. In accordance with Example 1, these were granulated in a drum granulator with drying air to give granules of almost spherical shape while drying.

Example 3

Wet fine-grained rubber vulcanization accelerator 2-mercaptabenzothiazole (Kaptax) obtained by filtration from an aqueous suspension having

224 594 zooming humidity? 30% was extruded * granulated into cylinders of the desired length, which in the next stage was continuously * discharged * into the granulation drum with simultaneous supply of drying air, further compacted and reformed to granules of oval to round shape.

Claims (1)

OBJECT OF THE INVENTION 224 594 Continuous two-stage spdsob granulation jeanozrných wet material with a variable size of the granules, particularly suitable for the granulation of rubber chemicals, in particular urýchTovačov vulcanization of rubber ^ holed on a combination of pressure and nabaTovacej granulation in configuration to a continuous process train, _{characterized} characterized in that the wet, fine-grained material with 20 up to 40% of the free water without the addition of binders is forced through round holes in the first stage or compacted between two profiled surfaces into cylindrical agglomerates which are cut or broken to a predetermined length at the outlet, where the preformed wet material is continuously discharged The step of rolling up the product is set to roll for 5 to 15 minutes while contacting the drying air heated to 60 to 90 ° C.