DE1454801B2 - METHOD OF REMOVING LIQUID FROM ELASTOMERS - Google Patents

Description

The invention relates to a method for largely removing liquid from elastomers on the basis of natural and synthetic rubber, in which the material is initially with simultaneous heating of a continuous pressure increase and then a complete one Pressure relief is suspended.

The polymerization of a number of plastics, e.g. B. of copolymers of butadiene and styrene carried out in an emulsion of the raw material in water. After the polymerization is complete the unreacted butadiene and styrene are drawn off from the emulsion in water, then this an acid or an acid salt is added to the emulsion to coagulate the contained rubber. A crumbly end product is then formed.

The crumbly end product obtained by this or other process must contain the water be removed as much as possible.

There are known methods for removing the free water from such elastomers, the work with drum filters or rubber rollers under vacuum. However, there is drainage only achievable to about 25 to 55% water content. Therefore, in the known method in connection At this pre-drainage, the material is further crushed and dried in 1 air dryers. the temperatures of necessary to achieve a reasonably useful economy over 90 "C have an unfavorable effect on the quality of the elastomers, and the investment, Operating and repair costs of such systems are very high.

In order to shorten the drying time and thus the time for which the elastomers have the high Exposed to temperatures, it is known to use kneading devices working with screws, in which the material is heated accordingly and exposed with its surface »so that the water can evaporate, whereby the kneading constantly brings new surfaces to the outside and the evaporation through the whole mass

ίο is achieved.

US Pat. No. 2,615,199 is also known a dewatering device known which with a screw part with a changing slope for Achieving a pressure increase is provided. This changing pitch screw goes into a Counter-worm with a very low pitch over, so that the material under simultaneous pressure increase and heating by heating means to a pressure peak at the junction between the two counter-rotating screws is compressed and then heated over at the same time the counter-screw enters a relaxation room under pressure relief. Through this arrangement liquid is to be squeezed out in the zone of highest pressure, whereby by machining with the counter-rotating screws the material is kneaded particularly well. Even with this one known method must be a very to achieve drainage through the entire cross-section intensive, energy-consuming and time-consuming kneading under very high pressure. After this pre-drainage by pressing and kneading the material is brought to atmospheric pressure and heat is passed on so that the residual water evaporates.

It is the object of the invention to provide a method of the type mentioned at the beginning create, in which with the least possible mechanical stress on the material to be dewatered Working through and heating the most extensive possible drainage in the shortest possible time is attainable.

According to the invention, this is achieved in that the material temperature during the pressure increase below the evaporation temperature of the liquid to be evaporated at the prevailing Pressure is maintained and the pressure relief from the point of highest pressure takes place suddenly, with the pressure and the temperature are brought up to a value that the heat in the material-liquid system is sufficient to add substantially all of the liquid when the pressure is relieved evaporate.

This procedure adds as much heat to the material as is needed to achieve the desired amount of water to evaporate. However, by increasing the pressure accordingly, the The effect of this heat is initially prevented until all the heat required has been supplied. In the then the following sudden pressure relief therefore suddenly evaporates all of the water, whereby Due to the explosive evaporation, the amount of water trapped inside also dissolves pave a way through the material to the surface and thus a drainage through the whole Mass is possible without tedious kneading and heating.

It has been found that by holding the water

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content of the elastomer in the liquid state while which carries only a small proportion of 1 V «during the movement of the elastomer through the device. The elastomer is then removed on a heat transfer coefficient in this device conveyor belt 25 or the like. . , _: >
This can be achieved two to three times _: In the following, the drying unit 23 is the value that is normally written in mechanical S. _: ■ ·· ..!.
see units for drying elastomers. Preseating, dehydrated material is: by means of a feed

By keeping the water content of the elastomer screw 65 guided on a shaft 66 in a cylinder 67 in the liquid state during the temperature increase. The shaft is caused by a motor (not hung, the possibility is still greatly reduced, shown) via a corresponding gear 68 in Dredaß an overheating of the elastomer either at the hung. The shaft of the drying unit 23 wall of the housing or on the surface which carries several son corner sections 69, 70, 71, 72, 73 screws and shafts of the device enters. etc. Between each screw section are arranged radially By keeping the water in the liquid state and 15 inwardly extending bolts 77. Increasing the temperature of the water and the EIa cylinder 67 is preferably with steam chambers 78 stomers to the dispensing temperature is still the (Fig. 3) provided. At the left end of the cylinder, the period of time during which the elastomer is used is provided with a delivery mechanism which is kept at the we-temperature, extremely briefly. essential a standing die 79 with dispensing opening, as with other mechanical 20 g _and 80 (Fig. 2A, 4 and 5).
Apparatus for drying rubber of the As can be seen in particular from Fig. 5, the case is, the moisture out of the elastomer stand die 79 is provided with bores, the school can evaporate, while the elastomer through the tern 81 α and 816 have, which for Holding device is guided, a continued Er- emes die insert 82 occurs. This allows the elastomer to warm up, so that the period of time during which the elastomer can be exchanged at higher temperatures and molds
Temperatures is maintained, is considerable and thus a dehydrated elastomer continuously flows in the operation of this device, the pre-detrimental influence exerted on the elastomer. · Container 24, through the opening 64 and then into the

Preferably, the 3 ° feed screw 65 turns on during the pressure increase. The elastomer is in in the material in small amounts of air, water- this feed screw is slightly compressed Steam, superheated steam or an inert gas in and through the first bolt area into the compressing led to the required pressure and the required screw sections 69, 70, etc. introduced. the such temperature for the desired evaporation slope of the first compression screw section The degree of effectiveness in the manner described above for 35 69 is preferably smaller than the slope of the influencing factors. The pressure and temperature control screw is 65. The first screw section The rise of the material expediently depending on 69 continues to compress the elastomer as a result the temperature of the material immediately before men that the latter over the second bolt area in controlled by the pressure relief. the compression screw portion 70 depressed

The invention is illustrated below with reference to FIG. This in turn compresses the elastomer

particularly suitable for carrying out the method that the latter over the next bolt area in

Neten, device shown in the drawing, the compression screw section 71 with reduced

explained in more detail. Gerter slope is pressed. During this

It shows the operation, the elastomer is the heated one

Fig. 1 is a side view of a combined exposed 45 walls of the housing of the device,

Soaking and drying arrangement, For most elastomers it is preferred that one

F i g. 2 shows a longitudinal section through the steam jacket of the housing with steam on the supply side

The end of the drying unit in FIG. 1 is heated ^{to between 14 and 17.5 kg / cm 2.} For certain elasto-

ßert scale, mere comes possibly a lower or higher

F i g. 2A shows a longitudinal section through the pressure being delivered. The elastomer won't side end of the drying unit of Fig. 1. The only heated by means of the steam jacket, but Line B-B of Figs. 2 and 2A show the separation also by the rotation of the compression screw plane, along the the two parts of Figs. 2 and 2A ken through the elastomeric mass. The device will can be put together so that the fully operated and the slope of the compaction points To produce drying unit, 55 screws with the bolts arranged so that the me-

F i g. 3 and 4 sections along lines 7-7 and mechanical pressure exerted on the elastomer

8-8 of Fig. 2 A, is always greater than the vapor pressure in the

F i g. 5 is a partial section along line 9-9 of the elastomer-containing water, so that the water

F i g. 4 on a slightly enlarged scale. is kept in liquid form and at temperature

The material to be dried is drained by increasing the elastomer above the boiling point of the

approximately device 22 up to a water content of water no noticeable leakage of the water as

5 to 20 percent by weight pre-drained. If the water vapor during the compression in the pre

Drying unit 23 of the arrangement according to FIG. 1 direction of entry.

to dry the dewatered elastomer is to be, the elastomer is immediately added after cutting the device from the unit 22 into a storage container 24 guide opening 64, as in F i g. 2 shown in the form guided. The product emerges from the unit 23 into a perforated section 83. When the moisture drier Form, whereby there is a water content content of the continuous, the drying process

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direction of the supplied elastomer from any device dispensed elastomers greater than about 20%, the first tend to be great. It may even be advantageous to use a loading screw section to .dem agreed amount of steam or superheated water vapor-compressing elastomer water freely to introduce into the device, so the entire set. This water can then be used in the opposite direction of heat introduced into the processed elastomer Flow towards the elastomer and out of amount to increase. To the introduction of the gas the drying device through the perforated or the vapors in the device is to be achieved Section 83 must be submitted. a valve 90 as shown in FIG. 2A is shown by The elastomer is through the drying device the wall of the cylinder 67 instead of one of the device by means of the compression screw sections so io bolts 77 introduced. The valve stem and the valve, that the temperature of the elastomer and the valve seat are designed so that the sealing of the water contained therein is constantly increased. Veniiles a penetration of the material into the valve At the same time, the impact on the elastomer is prevented.

mechanical pressure increased and thus above the vapor pressure of the water contained in the elastomer, of course at the increasing temperatures during Licher rubbers, reclaimed rubbers and the passage through the device can be maintained. different, non-rigid elastomer copolymers The relatively high rotational speed of the dried. For example, a synthe worm gear enables not only a rapid table rubber in an amount of roughly heating the elastomer, but also a hefty 20 2270 kg / h using 265 hp, kneading the elastomer during the passage while keeping the temperature of the rubber at the down through the device. Due to the arrangement, the number of the device would have been 130 ° C. In the case of the richer bolt 77, the elastomer is tending to evaporate the water from the spinning shaft, thereby continuing the relative movement of the elastomer with respect to 25 m after leaving the die oil lines various compression screw portions of the device was the temperature of the PoIyvergrößert and thus the efficiency of the heat mers 104 ° to 110 ⁰ C. Mechanical transmission drying is improved. devices of approximately the same volume content. The procedure described can be used as the temperature of the elastomer and the 3 "process contained therein when drying a water to a maximum value immediately before similar synthetic rubber 1225 kg / h at the Bring the die 79. Dry the elastomer with its energy supply of 350 PS. The water content then passes through the die opening temperature of the previously known devices 80 in a state in which the temperature of the rubber is 177 ° to 205 ° C, des The water contained is significantly above the boiling point and there is no way to cool the chewing point of the water, the applied pressure chuk by evaporation of water, but so high that the water is still liquid. Expensive when it comes out of the die openings ige arrangements for cooling this gene 80 in the atmosphere maintained under normal pressure or underpressure rubber before the packaging evaporates at the elevated 40 den, so that a decomposition of the polymer prevents temperatures the water immediately and emerges from the.

Made of elastomer. With this sudden conversion of the liquid water into steam with the vaporization according to the invention, the elastomer is cooled down at a high heat transfer rate that can be achieved at a constant rate, since the elastomer has a coefficient, there is an easy way of transferring the latent heat to the evaporating water of the product. It was at there. Furthermore, the leakage of the water vapor found in the processing of various elastomers leads to an expansion of the elastomer and to 20 to 35% of the amount of heat required to increase it, forming a porous structure, thereby increasing the temperature of the elastomer and the continued evaporation of the water as long as NEN water at the appropriate temperatures for until the moisture content of the elastomer 5 ° the evaporation of the same is required, by which it has been almost completely removed. Steam jacket are introduced. It is now the template at the exit from the apertures 80 in the ability to control the temperature of the Standmatrize 79 the elastomer by means of the elastomer, a thermocouple 105 is in the stand-Schneidcelemcnte 84 (Fig. 4) into pieces with waste 79 ( Fig. 4) to introduce the device, measurements from 0.25 to 3.18 mm thickness cut. 55 Since the steam jacket of the device is not in th - is located, this indicates the temperature of the elastomer and / or the cutting elements coming into the formation. By means of a control device 106, the number of revolutions as well as the number of measurements. 4 is shown only schematically, controls trizen openings determined. The breaking up of the strand - the temperature of the elastomer, as determined by the pressed material into very small pieces - results in the immediate and momentary escape of the ion to the steam jacket of the device. When water vapor from the material. Thus, the temperature tends to rise above a certain value. In certain cases it can be advantageous to increase the pressure in the steam jacket for a small amount of air, water vapor, inert gas 65. If I or superheated steam in the drying device the temperature on the other hand to drop below tunj; to pump so the porosity of this value tends, the vapor pressure is increased.

For this purpose 2 sheets of drawings

Claims (3)

Patent claims: 1. Procedure for extensive removal of Fluid made from elastomers based on natural and synthetic rubber, in which the material is initially heated with a continuous increase in pressure and is then subjected to a complete pressure relief, characterized in that that during the pressure increase the material temperature is below the evaporation temperature the liquid to be evaporated is kept at the prevailing pressure and the pressure relief from the point is highest Pressure occurs suddenly, with the pressure and temperature being brought up to a value that the heat in the material-liquid system is sufficient to relieve the pressure in the essentially evaporating all of the liquid. 2. The method according to claim 1, characterized in that during the pressure increase into the material in small amounts of air, water vapor, superheated steam or an inert gas is introduced. 3. The method according to claim 1 or 2, characterized in that the pressure and temperature rise of the material depending on the temperature of the material immediately before the Pressure relief is controlled.