CS210704B1 - Apparatus for preparation of fluid rubber compounds - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to an apparatus for preparing liquid rubber compositions useful for the manufacture of technical rubber by homogeneous compression or injection molding.

Liquid rubbers are produced on friction three-cylinder or multi-cylinder horizontal sets (so-called kalahdras) known from the manufacture of pastes, sealants and liquid paints, where the mixture is returned after the first pass through the set for a second pass to achieve additional dispersion and homogenization of the ingredients. rubber. These liquid rubber compositions contain mixed air, which must be removed by standing at elevated temperature for prolonged periods, as it is the main cause of rubber pores in the manufacture of technical rubber by pressing or injection molding. The mixture thus freed of mixed air is manually filled into containers or inserted into molds to produce injection molding or injection molding to produce technical rubber (homogeneous, non-porous).

Another known method is to prepare the mixture in a continuous manner, wherein the liquid rubber is premixed with fillers by a piston mixer, then dispersed and homogenized in another part of the apparatus, or in another part of the apparatus the crosslinking components are admixed. stack. The mixture from the reservoir is used for the production of technical rubber by injection molding.

This method (the so-called RAPRA method) eliminates the drawbacks of discontinuous production of liquid rubber mixtures, but the mixed air is the cause of the porosity of the products. The device is very complicated because it consists of four separate devices (pre-blending, dispersing, mixing of the sieve component, the reservoir connected to the injection unit).

The aforementioned disadvantages are overcome by the liquid rubber composition preparation of the present invention, which can be used to produce homogeneous technical rubber products by injection molding in a technologically and economically suitable quality (without poise). The essence of the device is that a screw intersecting the outer surfaces of the two rotors on their underside is assigned to the two interlocking rotors with a slight increase in the yawn, which rub against each other, and the screw is possible to run in both directions of rotation.

The kneader is provided with a vacuum-tight lid with visors allowing observation of the mixing behavior. After all components of the liquid rubber compound have been introduced, the kneader is gradually evacuated, and the rate of pressure drop must be controlled according to the content of volatile impurities so that the mixture does not come into contact with the lid (visors are observed). The evacuation of the mixture during stirring takes place while stirring the mixture continuously, thereby avoiding the mixing of air into the mixture and, on the other hand, removing the mixture from volatile substances which cause the porosity of the rubber during injection molding.

Upon completion of production of the mixer in the mixer, the operation of the screw located at the bottom of the mixer is reversed, and the mixture is transferred to the container without interrupting evacuation and the container is under vacuum. The reservoir thus contains a mixture without mixed air, which can be added to an injection molding machine for the production of molded technical rubber. The blended mixture may also be fed directly to the injection molding machine. The advantage of this apparatus for producing a mixture of liquid rubbers, as well as the apparatus concerned, is its single-phase process and simple apparatus. The mixture is produced in one technological stage and the equipment is single-stage.

To increase productivity and production capacity, two kneaders can be used side by side, which separately produce a complete blend of liquid rubbers and alternately fill the stock produced blend.

If the rubber mixture is poorly processable, a blend without an active crosslinker is produced on the mixer, which is mixed immediately before the mixture is introduced into the injection molding machine by introducing it into the mixture in the mixing zone of the screw conveying the mixture from the mixer. into the injection molding machine. For the actual mixing process of the mixture in said kneader, it is important that the viscosity of the mixture has a minimum value at the mixing temperature in order to achieve the desired homogeneity and dispersion of the additives in the liquid rubber. It is therefore necessary, due to the different input viscosities of liquid rubbers, to choose suitable technological conditions, especially tempering of the kneader.

Generally, the kneader allows the preparation of the composition if the inlet viscosity of the liquid rubber is not less than 300 Pa.s. If the viscosity of the liquid rubber is lower, a premix (liquid rubber concentrate with fillers) is prepared and the remaining liquid components of the mixture are mixed at the end of the mixing cycle. The same masterbatch process is used when it is necessary to first extend the liquid rubber chains (masterbatch), then mix the fillers and other additives.

If an extremely high dispersion of carbon black in liquid rubber is desired, a dispersion unit based on the principle of passing the mixture through a narrow slot, cylinder type or cone type can be connected between the auger with the auger and the reservoir or injection unit.

If it is necessary to increase the production capacity and to achieve continuity of production in relation to the battery of injection molding machines for the production of molded technical rubber, a production line is assembled in which the basic kneading unit is repeated two or more times on one axis with a single el. drive, the transport is provided by a discharge auger. Either the container or the injection molding machine is connected to the last link of the line. Continuity of production on such a line is made possible by the automatic dosing of the components of the mixture into the first kneader unit.

To further elucidate the nature of the invention, a further description and accompanying drawing are provided, in which the arrangement of the device is schematically illustrated in FIG.

The device itself is housed in a double-walled housing 4 between which a tempering medium is circulated, which is fed and discharged through the throats 6. The kneader is formed by a combination of two interlocking rotors and a screw which contacts the surface of both rotors on their underside. The two rotors χ fit into each other by surfaces which may be helical in shape with a slight increase in the yawn.

The peripheral surfaces of the rotors are chamfered on their leading sides by slight edge grinding at an angle of 5 to 20 °. Titmo achieves good spreading of the mixed mixture over all contact surfaces. The gaps between the rotors to each other, between the outer diameter of the rotors and the walls of the kneader, between the rotors and the bottom screw are in the range from 0.05 mm to 1 mm. The lower screw drive is reversible, when the mixture is mixed with the rotors, the direction of rotation of the screw is such that it returns the mixture back to the mixing chamber J. After the mixer has finished production, the direction of rotation of the screw is reversed. The kneader is provided with a viewing window (7) with an evacuation inlet (8).

Claims (1)

SUBJECT OF THE INVENTION Apparatus for preparing mixtures of liquid rubbers consisting of two interlocking rotors with helical surfaces (1) which rub against each other, characterized in that the peripheral surfaces of the rotors are bevelled at their leading sides at an angle of 5 to 20 ° and that the equipment is equipped a further friction rotor, worm-shaped (2), which touches the two upper rotors on their lower surfaces and whose operation is possible in both directions.