DE1916295B - Method and device for the production of rubber crumbs - Google Patents

Description

Since the rubber crumbs dried according to the known method are then bales anyway are pressed and packaged, the grain size and the grain size distribution are of secondary importance Importance.

The German Auslegeschrift 1 129 682 describes a process for the production of dry rubber particles, wherein the solid rubber from a rubber-liquid mixture, for example by Centrifugation is separated, crushed and dried. The rubber particles must, however, before Drying sorted by size, with only the particles of a sorted size range being dried will.

From the French 2nd additional patent specification 86 731 to the French patent specification 1 308 633 is also known to reduce the viscosity or to increase the particle size of the dispersed latex To apply a certain pressure to the polymer and to adjust the liquid to a pH of 7 to 9.

In British Patent 852 525 a polymer drying process and a suitable one is disclosed Device described which, among other things, a coagulation tank, a washing device and a Includes dryer. The product is then pelletized.

The invention is aimed at the production of small and as uniform as possible rubber crumbs, as surcharges for moldings, z. B. plates, can serve to improve their mechanical properties 7. B. to improve elasticity or sound insulation. Accordingly, the rubber crumb should be one Have grain size and a grain size distribution that match the load-bearing material of the molded body \ is comparable and compatible. Sawdust or cork flour have been used for this purpose so far used. To make rubber crumbs of this nature, the preferred configuration is straight to promote the grain fractions, which are pushed back as far as possible in the known processes. It it was found that to produce small and uniform rubber crumbs, the comminution am wet and dried small pieces of coagulate must be made. Here, for example small-sized coagulate in a known manner by crushing large coagulate lumps be generated. However, the small pieces of waste that arise can also be used during coagulation will. Efforts must also be made to ensure that the coagulation mixture is drained in this way that if possible the fine-grained portion remains in the coagulate. For this purpose one serves a flotation disc to avoid the fine particles floating up as a result of the foam formation keep away from the filtrate.

The method for solving this problem is characterized according to the invention in that the Comminution of the coagulum in the aqueous coagulation mixture takes place to a particle size below 10 mm, during dewatering in the rotation residue a fine grain fraction retained, the rotation residue simultaneously with the dewatering by the After-treatment is washed with the water and after drying during diffusion drying the separation of the fines and their return to the washed residue from rotation takes place and the post-dried, des- Dusted and discharged rotation residue with simultaneous cooling to the desired grain size is crushed.

According to a further development of the invention, the aqueous coagulation mixture is after comminution adjusted to a solids content between 5 and 15, preferably between 8 and 12 percent by weight. In the context of the invention, the acidic aqueous coagulation mixture is preferred after the comminution adjusted to a strongly alkaline pH.

In consideration of the high capillary humidity of the dehydrated coagulate, the drum dryer is used

equipped with a diffusion chamber. By correctly measuring the temperature and quantity of the inert gas as well as the dwell time of the moagulate in the drum dryer, a final moisture content of the coagulate below 1 ° / ₀ can be achieved. For use as a filler, a final moisture content of less than 8 percent by weight nvjist is sufficient. Accordingly, one is usually content with values of about 4 to 6 ⁰ Z _{0 in} order to protect the elastic properties of the dry capsule through the milder drying conditions.

The invention also relates to a device with a container for receiving the aqueous coagulation mixture, one mill for comminuting the coagulate, one in front of a dewatering centrifuge arranged mixing container with a stirrer, a device for treating the coagulate with water and a dryer.

The device for carrying out the method according to the invention is characterized in that that the mill designed as a cutting mill for comminuting the coagulate in front of the mixing container is arranged, the device for treating the coagulate with water from a feed for Wash water is in the Wntwässerungszentrifuge, in the dewatering centrifuge there is a flotation disc to hold back the fine grain fraction, behind the dryer a diffusion chamber for post-drying with a return line connected to a suction fan to return the fine fraction a cyclone with a discharge lock into the dryer and behind the diffusion chamber a fan mill is arranged.

In the context of the invention, the dryer is advantageously designed as a rotating cocurrent dryer.

According to a preferred embodiment of the device according to the invention, the blower mill a pneumatic discharge and conveying device with a separator and an exhaust air filter.

In the drawing is the flow diagram of a device for carrying out the invention Procedure shown for example. The drawing shows a mixing container 1, a feed pump 2, a dewatering centrifuge 3, a metering screw 4, a dryer 5, a diffusion chamber 6, a Fan mill 7, a separator 8 and a bunker 9 for storing the ground material.

The acidic coagulation mixture with optionally pre-comminuted coagulate is made by a Cutting mill 11 introduced into the mixing container 1 with a stirrer. A line 12 becomes Alkdihydroxyd and water introduced in such amounts that the coagulation mixture has a pH

5 6

Assumes a value between 7 and 9 and on a coagu 6 mm 2.4 weight percent

lat content is brought below 15 percent by weight. , _. _o ". ,

The alkalized coagulation ^{substance becomes 2} ' ⁸ percent by weight ^{in 5 mm}

a line 13 by means of the feed pump 2 to 4 _mm 15.6 percent by weight

Dewatering centrifuge 3 promoted. To get a 5

adjustable load on the dewatering centrifuge 3 2 mm 59.7 percent by weight

with constant delivery rate of the delivery pump 2 _{15 mm 182} weight percent

to achieve are a circuit pressure line 14 and

a slide 15 is provided, by means of slide J5 under 1.5 mm 1.3 weight percent

the amount delivered by the feed pump 2 can be 10
in a return stream to the mixing vessel 1 and

the centrifuge feed can be divided as required. The main part of the grain is with about An approximately 60 percent by weight in the range of 2 mm that accumulates in the mixing container 1. With the Excess liquid can through a valve 16 with both adjacent fractions makes the grain one Sieve shield 17 can be drained. 15 size range from 1.5 to 4 mm over 93 weight

The dehydrating centrifuge 3 becomes the clear percentage of the ground product. It is also to be

Rinse the centrifuge sediment by knowing that the fine grain fraction with a grain size

tour 18 water abandoned. under 1.5 mm with 1.3 percent by weight is quite low

The centrifuge overflow is derived through a line 19 which is related to the dimensioning of the dry water. The centrifuge sediment has a favorable effect on the dedusting part located in the dewatering unit. This ground product is released in a stirring centrifuge 3 into the metering screw 4 and the container by adding water and alkali from this in a controllable flow to the drying unit 5 an aqueous suspension with a fixed. The drying gas enters the dryer 5 through a line 21 with a material content of 12.38 percent by weight and is produced through this and the as pH value of 7.5. This suspension is dewatered diffusion chamber 6 by means of a suction fan 22 by centrifugation. The centrifuge is sucked. This leads the dusty exhaust gas from a commercially available full-jacket screw decanter diffusion chamber 6 in a return line 23 with a flotation disk. The differential speed of a cyclone 24 into the open. The worm in the cyclone 24 is 30 rpm at a speed of rotation of the separated dust is through a discharge lock 25 30 rotor of 4500 to 5500 rpm. Returned to the dryer 5 in the event of loads. this centrifuge will be between 350 and 650 l / h

The solids content in the discharge between 52.4 and collecting dedusted dry material at the bottom of the diffusion chamber 6 is achieved by means of a 54.4 percent by weight. The degree of separation is fed into the metering lock 26 into the blower mill 7. is 98.93 to 99.14 ° / ₀ . The solids content in the die is adjusted by means of a sieve 27 on a grinding centrifuge outlet at 0.153 to 0.177 degrees by weight with the upper grain size 3 mm. percent extremely low.

The ground material is sucked in by the air flow. For proper application of the centrifuge in a line 28 to the separator 8 and in it is important that in the pipelines the suction of this dejected. The exhaust air is sufficiently high in one and the pressure side of the feed pump the separator 8 downstream exhaust air filter 29 40 flow velocities prevail, cleaned by a seder and discharged through a chimney 30. to prevent mentation in the pipelines.

The separated grist falls from the drop in the centrifuge sediment, strangely enough

Scheidei 8 in the bunker 9, in which there are no larger grain particles than those with about

through a distributor 31 supplied air flow in 4 mm diameter. The reason for this is therein

held in a slightly whirling state and homogeneous- 45 that by means of Zeneiben in the centrifuge

is sated. This whirling air is caused by the difference in speed between the rotor and the

Exhaust air filter 29 via the chimney 30 into the atmosphere screw a further mechanical friction work

causes comminution of the coagulate.

The end product is removed from the bunker 9 by means of 13 kg / h of the centrifuge-moist coagulate a discharge sluice 32 mm weighing and weighing 50 a similar grain distribution to that taken in the suspen pack. sion before the centrifugation, will be a

Over the operation of this plant may the post-drum dryer continuously fed,

teach the following example: The drum dryer has a drum diameter of 0.6 m and a length of 4.8 m and a

Example 55 gradient of 12mm per meter length. The drum speed is 4 rpm. It is about 30C Nm '/ h

IS kg of coarse wet coagulate from flue gas operated in cocurrent,

synthetic rubber with a pH value of 2.5. The flue gas inlet temperature is approx

and a water content of 72 percent by weight 159 ° C, the exhaust air temperature is about 65 ° C

are held in a cutting mill with a 60 sieve bar. The dried goods heat up during the

use with 8 mm mesh size, 10 minutes passage from 20 to 48 ° C without a noticeable

ground. With a drive power of around 3 kW Odor formation, which is typical for heated rubber

and dies at a rotor speed of 1000 rpm.

the grinding runs flawlessly and without interference, a dry material quantity of 5.4 kg / h is obtained

Blockages of the sieve trays and without excessive 65 with a final moisture content of 2.9 percent by weight, the Heating the rubber. The grain structure of the for further processing and for later The ground product shows a relatively steep characteristic. Purpose is quite sufficient,

and has the following sieve analysis (wet sieved): The sieve analysis of the dry product shows that

the desired grain structure of 2 mm and less is well distributed in terms of size.

over 4 mm 2.6 percent by weight

3 to 4 mm 4.4 percent by weight

2 to 3 mm 8.0 weight percent

1 to 2 mm 24.9 percent by weight

0.5 to 1 mm 32.9 percent by weight

0.2 to 0.5 mm 24.5 percent by weight

less than 0.2 mm 2.7 weight percent

The drying is obviously connected with a shrinkage, because a proportion of 90 percent by weight is now in the grain size range from 0.2 to 3 mm.

From this dry product, the moisture of which has risen to 4 percent by weight during storage, 188 kg are fed to a blower mill with a sieve insert of 2 mm perforation. The mill reaches a grinding capacity of 40 kg / h at a rotor speed of 9000 rpm.

The grist warms up to 35 ° C. The typical smell of overheated rubber, the certainly indicates a deterioration in quality, does not occur during grinding at this temperature on. The grinding itself does not cause any difficulties. The dust development is due to the tough properties of the material are extremely low. The sieve analysis of the finished rubber crumb shows following grain structure:

over 2 mm 3.14 percent by weight

ίο 2 to 1 mm 61.70 percent by weight

1 to 0.8 mm 14.00 percent by weight

0.8 to 0.5 mm ... 15.50 percent by weight

0.5 to 0.3 mm ... 4.30 percent by weight

0.3 to 0.1 mm ... 1.30 percent by weight

below 0.1 mm 0.06 percent by weight

The grain structure can be determined by appropriate selection of the sieve hole sizes in the sieve bowl insert the cutting mill for the still acidic coagulate ao and in the sieve insert of the blower mill into different Shift areas while maintaining the steep characteristics of the grain structure.

For this purpose, 1 sheet of drawings

209532/389

Claims (7)

a pneumatic discharge and conveyor device claims: iung with a separator (8) and an exhaust air filter (29) is arranged downstream. 1. Method of making small and Uniform 5 in a narrow grain size range Rubber clinking, in which the coagulate one aqueous coagulation mixture by rotation
dehydrated, treated with water, crushed, dried with hot gases and when discharging the subject of the invention is a method for a fine fraction is separated and fed back into the process of producing small and narrow grains is characterized by the characteristic size range of uniform rubber crumbs, at zei ch net that the comminution of the coagulate corresponds to the coagulate of an aqueous coagulation the aqueous coagulation mixture dehydrated on a mixture by rotation, with water T ^ ilf ^ TiPrKTrnRf * lint **! * 1Π mm f * rfr \\ at T ^- WMm T ^ nt- tm ^ KJialnin / lel *. tüy.L ·! * »!«! »».! -. w »i # - V» i »iRi» r> / ^ ncen ö ** - water a fine 15 dries in the residue from the rotation and a fine fraction of grain is retained during discharge, which is separated from the rotation back and fed back into the process,
At the same time as the dehydration was carried out, the after-treatment with the water is required for the manufacture of rubber, separation of the aqueous phase of the coagulant and, after drying during diffusion from the coagulated latex, complicated and apparatus-based post-drying, the separation of the fines 20 elaborate process steps. The coagulation and its return to the washed ones can be carried out in such a way that the coagulate takes place in comparative rotation residue and the after-dried, large lumpy or flat structures that are wet, dedusted and discharged from the rotation residue, which are cleaned by rinsing with water, are subject simultaneous cooling on the coagulation can, however, also be conducted in such a way that the desired grain size is comminuted. 25 that the coagulate occurs in small particles, 2. The method according to claim 1, characterized by filtering, sieving or squeezing off indicates that the aqueous coagulation with repeated washing with water of the coagulation mixture after grinding: η be separated on a fixing agent. Since the particles that substance content between 5 and 15, preferably the coagulation or the comminution of the coagulate between 8 and 12 percent by weight, they tend to stick together will. Drainage and drying are usually considered 3. The method according to \ nspruch 1 or 2, characterized by separate, successive process steps, that the acidic aqueous coagulation is carried out, the subsequent drying of the dehydrated lation mixture after the comminution to a particle being set, according to the method, to a particularly strongly alkaline pH value. 35 wall required. The dried particles will 4. The method according to claims 1 to 3, then mostly pressed into bales and characterized in that the drying of the form is given to further processing.
From the German Auslegeschrift 1 232 340, rubber crumbs below 8, preferably 4 to, are known, the dewatering takes place under high pressure and 6 percent by weight. 40 elevated temperature in an extrusion press 5. Device for carrying out the Vei- take and drying by relaxing the Fahrens according to claims 1 to 4, with an extruded material in a hot air stream Effect container for receiving the aqueous coagu. The dry product is made from the lation mixture, a mill for crushing hot air stream separated in a cyclone. of the coagulate, a device for treating the coagulate on successively arranged vibrating sieves, coagulate with water and a dryer, which is arranged in the German Auslegeschrift 1 243 861 centrifuge with a described method air is passed from below, dried, characterized in that the mill designed as a cutting mill From the German Auslegeschrift 1 063 530 is (11) known for comminuting the polymer coagulate tending to stick together in front of the mixing container (1) particles in batch operation in a fluidized bed is to treat the device for treating the coagulate dryer by means of warm air. With water from a feed (18) for washing this known method, the difficult water in the dewatering centrifuge (3), which is caused especially by the fine-grained fractions in the dewatering centrifuge (3) a flotation of the crumb mixture, is avoided , Disk to hold back the fine grain fraction, In general, the formation of a fine grain behind the dryer (5), a diffusion chamber (6) and dust fraction is suppressed during coagulation or during post-drying with a suction fan to comminute the coagulate.
(22) connected return line (23) for the French patent 1 265 403 is known to return the fines via a cyclone (24) provided with a discharge lock (25) for drying rubber crumbs, in which the dewatered particles are removed Dryer (5) and, if necessary, crushed coagulate in three grain (6) a blower mill (7) is arranged behind the diffusion chamber. factions dismantled pastures, the middle of which 6. Device according to claim 5, characterized in that it is dried on a tray dryer while indicates that the dryer, as a rotating 65, has the coarser fraction for comminution and the finer fraction Co-current dryer is formed. Fraction is returned to the coagulation. the 7. Device according to claims 5 and 6, passed through the drying fraction has a characterized in that the blower mill (7) grain size between 3 and 10 mm.