DE2326885A1 - METHOD FOR MANUFACTURING ELASTOMERS AND THE PRODUCTS OBTAINED THEREOF - Google Patents

Description

The invention relates to a process for the production of elastomers in the form of a non-adhesive, dry powder, that does not agglomerate during storage, and the products obtained in the process.

The invention can be used with elastomers which are in the form of an aqueous dispersion or in addition thereto can be processed. The term "aqueous dispersion", as used in the present application means an aqueous emulsion and in particular a latex. Elastomers, the bins used are, for example, more natural Rubber, polybutadiene, copolymers of butadiene with one or more comonomers, for example styrene, acrylonitrile, Methyl methacrylate, vinyl pyridine or a derivative thereof and a carboxylic acid, polymers of substituted Butadiene, for example polyisoprene and polychloroprene, copolymers of vinyl acetate and ethylene, which are 45 to 95% by weight

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Vinyl acetate contain, butyl rubbers, i.e. copolymers made from an isoolefin with a diolefin, and polyisobutylene. The method of the invention is with a latex as such or with a latex in compounded form, i.e. with a latex containing common processing ingredients such as accelerators, Containing vulcanizing agents, antioxidants and fillers, feasible.

Natural and synthetic rubbers are commonly found in compact form because of their tendency to agglomerate Blocks or foils or sheets are supplied, and the production of these materials for technical application requires special ones and expensive equipment and devices. Would it be possible to use the elastomers in solid, particulate form! To establish condition this would be beneficial and methods have been proposed to make this possible. Such methods include solidification or freezing and grinding of solid Rubber, spray drying and a co-flocculation by adding a release agent, also known as a distribution agent can, to the rubber, coagulate the latex and evaporate the liquid carrier to dry the product. In the latter method, the release agent coats the particles made of rubber-like elastomer and prevents the particles from sticking together. The rubber thus retains its free flowing, particulate nature.

The present invention is based on the discovery that rubber is as opposed to fine powder form

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to produce the coarser particles that were previously obtained by modifying the aforementioned co-flocculation process and making the process in a more efficient manner than before.

The invention relates to a method for production of elastomeric material in powder form, which is characterized in that an aqueous dispersion of the elastomeric material to an aqueous solution of a flocculant in the presence of a free release agent adds, the release agent adhering to the surfaces of the elastomeric particles which are formed during the destabilization, the solid material is extracted from the resulting mass and the solid material is dried.

The term "release agent" as used in the paragraphs above and as used in the remainder of the application is intended to mean a particulate material that is insoluble in water or has a low solubility and that naturally not agglomerated. The term "free release agent" is intended to mean that the release agent is in the form discrete particles are present that are not associated or intermingled with the elastomeric material.

If the dispersion of elastomeric material is destabilized in the presence of the free release agent, then the individual particles of the elastomeric material at least

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partially coated with the release agent as soon as they coagulate, and this increases the tendency of these particles to increase
agglomerate immediately reduced or eliminated. this
results in a much finer powder than is obtained with the known co-flocculation processes, in which a release agent is added to the latex and in which the resulting mass is added to a solution of the flocculant, ie the release agent is attached to the elastomeric material
bound or mixed with it and no remedy is at
the destabilization in free form. It has been found that, when carrying out the process according to the invention, powder is obtained which has a size which is around a third or less
is less decreased compared to the size of the corresponding powder produced by known co-flocculation processes, and this result was completely surprising.

In a first embodiment of the method according to the invention, a free release agent is present in the solution
of the flocculant is dispersed before the dispersion of the elastomeric material is added to this solution. That
Free release agent is preferred as an aqueous slurry
added>. although dry, powdered release agent can be added.

D. ^% Separating agent that is used can be used under a large number of organic or inorganic materials

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to get voted. Preferably it is not hygroscopic and has a particle size that is less than 2000 / u and a melting point that is greater than 50 ° C. If release agents with a particle size above 2000 / u are used, the effectiveness or efficiency of the process is reduced and must be regarded as inadequate. The release agent must not melt during the drying of the coated elastomeric powder, and since a suitable drying ^{temperature is around 50 °} C., it is desirable that the melting point of the release agent is above this number. However, it is also possible to use lower drying temperatures and thus release agents use a lower melting point.

The amount of release agent that is used is not particularly critical and can be used within wide limits vary. Of course, there must be sufficient release agent present to coat the elastomeric particles and it may not be desirable to use less than 2 pphr by weight of release agent ("pphr" means Parts per 100 parts rubber). The finer the release agent, the less you can use. Up to 300 pphr Release agents can usually be used, with a more common range being 5 to 50 pphr and a particularly preferred range Range is 5 to 20 pphr.

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Particularly preferred release agents are magnesium carbonate, Small particle size clay, powdered styrene-acrylonitrile copolymer, powdered polyvinyl chloride and magnesium silicate. Other release agents that can commonly be used are powdered polystyrene, Polymethyl methacrylate, calcium carbonate, silicon dioxide, china clay, talc, diatomaceous earth, kieselguhr, a metal stearate, for example zinc stearate, a metal oxide, for example magnesium oxide or zinc oxide, carbon black, kaolin or metal powder. Man preferably uses as a release agent a material that is usually used in the compounding of rubbers for vulcanization and subsequent use is employed since the release agent is of course vulcanized in the finished product Product made from the powdered elastomer is present. The release agent can in particular any commonly used filler or material known to be vulcanized Product with the desired physical properties results.

It is not necessary that all of the release agent that is used be added to the elastomeric material, when it destabilizes. You can do so much more Release agent to the aqueous dispersion of the elastomeric material prior to addition to the solution of flocculant and additional release agent can be added to the solid material during or after drying. The former

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Both of these steps are useful in that they provide improved control over the final particle size. The latter stage is useful to avoid the possible compaction of the powdered elastomeric material during storage to zoom out.

The flocculant used "in the first Embodiment used may be any known or conventional flocculant, but it must chosen so as to be compatible with the particular release agent being used, i.e., the flocculant and the release agent should not chemically react with each other. You can use any acidic flocculant for example acetic acid or sulfuric acid, a flocculant, containing polyvalent metal ions, for example. Use magnesium sulphate or sodium chloride, or any other suitable flocculant.,

The first embodiment of the present invention can be continuous be performed. An aqueous solution of flocculant and an aqueous slurry are used Introduced from a separating agent into a reaction vessel. Then it will be an aqueous dispersion of elastomeric material into the reaction vessel introduced, the materials are in the reaction vessel stirred and an excess of flocculant and.! separating agents are maintained in the reaction vessel » Material is then withdrawn from the reaction vessel, the material

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The material is filtered, washed, and the filtered solids are dried.

The release agent slurry and the solution from the flocculant can be fed into the reaction vessel as a single stream or separately Introduce streams of slurry and solution into the reaction vessel.

In a second embodiment of the invention Precursors for the release agent are added to the aqueous dispersion of the elastomeric material before the solution is made Flocculant is added and the precursors then react with the flocculant to "form the release agent." In this embodiment, the free release agent is in situ in the flocculation reaction vessel during destabilization The dispersion of elastomeric material is formed and the elastomeric particles are formed as they are become overdrawn.

The precursor is preferably water-soluble and this embodiment according to the invention has the advantage that Aside from the dispersion of elastomeric material, all of the reactants used in this process will be in the form of liquids. This not only facilitates the loading of the reaction participants in a continuous process that uses

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The formation of liquid release agent precursors also enables a good control of the final particle size.

A particularly suitable process uses sodium silicate as a precursor and as a flocculant Magnesium sulfate, which react to form magnesium silicate as a separating agent. In another embodiment if you use xanthate starch and an acidic flocculant as a precursor, which reacts with the starch in solution, giving fine, precipitated, insoluble starch as a release agent.

As with the first embodiment, it is not necessary that all of the release agent that is used be at the destabilization of the elastomeric material is present. You can do so according to a variant of the second Embodiment the aqueous dispersion of elastomeric material and release agent precursor to the solution of flocculant add in a first reaction kettle and the resulting mass is then transferred to a second reaction kettle given, in which you fill additional release agent precursors that react with the excess flocculant and wherein further release agent is formed. Additional release agent can be added to the aqueous dispersion of elastomeric Material can be added before adding it to the flocculation solution. Additional release agent can also be used to the solid material during or after drying

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be added.

The following examples and comparative examples illustrate the invention without restricting it. In the examples all parts are expressed by weight. Examples 1 to 20 were all on a laboratory scale and not in Production scale carried out.

example 1

10 parts of magnesium carbonate become 100 parts as a release agent Water containing 0.10 parts of sodium tripolyphosphate as a dispersing agent included, added. The water is stirred during the addition. The resulting dispersion becomes 1900 parts of water are added, in which 15 parts of magnesium sulfate are dissolved as a flocculant. During the addition will the water stirred again. While stirring, becomes the flocculant solution slowly a latex with a solids content of 25%, the 100 parts of acrylonitrile-biatadiene copolymer rubber / (NBR) (27.5% acrylonitrile, 62.5% butadiene) is added. When the latex particles are destabilized, the release agent adheres to the surface of the rubber particles and a slurry of finely divided rubber particles is obtained, who show little tendency to clump together. The slurry is filtered and the resulting solids are washed and dried at 50 ° C, using a free-flowing, powdery material with an average particle size of 1.78 mm is obtained.

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Comparative example 1

The dispersion of magnesium carbonate in water, such as it was used in Example 1 is added to the latex of Example 1 and the resulting mixture then becomes a solution of flocculant as described in Example 1 added. The resulting slurry is filtered and the solids are washed and dried. The solid product is a free flowing, particulate System with an average particle size of 2.73 mm.

Comparative example 2

An attempt was made to produce powdered rubber by using the flocculant solution with dispersed release agent as in Example 1 added to the latex of Example 1. It was found that it was impossible to produce powdery rubber in this way.

When carrying out the invention, one obtains Example 1 a powder with much smaller average Particle size than in Comparative Example 1. This explains the surprising effect of the invention Procedure.

Example 2

A flocculation solution with dispersed release agent

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tel was produced as in Example 1. 2000 water, 10 parts of magnesium sulfate, 20 parts of magnesium carbonate and 0.2 part of sodium tripolyphosphate were used. A latex solution with a solids content of 50% and containing 100 parts of styrene-butadiene copolymer / CSBR.) (23.5% styrene, 76.5% -6 butadiene) was slowly added to this solution. The latex was destabilized to give a slurry of finely divided, non-granular particles. The slurry was filtered. The solids were washed and dried to obtain a free flowing powdery polymer having an average particle size of 0.76 mm.

Comparative example 3

Example 2 was repeated, with the exception that the dispersion of release agent and latex formed a solution Flocculant was added. The resulting powdery Polymer had an average particle size of 1.78 mm, which showed that one could use the process of the invention a finer powder is obtained. To show, that the inventive Process can also be carried out with other polymers, release agents and flocculants, a number of other examples were carried out, their Details are given in Table I below.

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Table I.

Name and parts by weight

E.g.

No. Poly- Separation- Amount "Ausflok- Amount" Disper- "Amount mer medium (pphr) kungsmit. (Pphr) sionsmit. (Pphr) Average size of the resulting particles (mm)

Verf.e.g. 1 Verf.ν. See example 1 1.52 4.21 1.96 couldn't be as a powder getting produced 2.03. ti 1.96 4.47 2.13 couldn't be as a powder getting produced 2.71 If 2.71 It 1.22 £ 4.34 1-, 65 4.57 1.70 couldn't be as a powder getting produced 2.29 4.57 2.54 5.59 ^ 1.78 £ 4.56 3. ι 1.02 1.52 ..OO $ oo 7

3 NBR MgCO ₃ It
ti 15th MgSO ₄ 15th 4th NBR It It 5 ti 15th 5 ' NBR ti Styrene
Acrylonitrile
Copolymer3) VJl dd 15th O 6th NBR tone 'less than ¹
Particle size dd vji ti ¹ 5 9850 7th
8th NBR
NBR ti 10 ·
5 dd
Il 15th
15th o> 9 NBR 5 It 15th Q 10 NBR 15th Il 15th 11 NBR 10 dd 15th 12th NBR VJl dd 15th

NBR polyvinyl ⁴ ^ 15

chloride

NBR tone smaller

Particle size 10

NBR MgCO ₃ 10

Poly- »10
butadiene

H ₂ SO ₄
CaCl ₂
MgSO ₄

15 sodium tri- 0.15 polyphosphate

»0.05

15 polyacrylate

oligomeric ² ) 0.15

»0.10

15th

30th
15th
15th

Table I (port setting)

Example no.

Name and parts by weight Average size of the resulting Particle (mm)

Poly- T!? Enn- amount AusTlok- amount Disper- amount .

more medium (p-phr) kungsmit. (pphr) sionsmit. (m> hr) Veri * .V.Bsp.1 Veri \ v; VerkI «Ex» 1

17 poly-tone kl. butadiene particle size

18 SBR MgCO ₃

19 nat.chuk- ■ 'chuk

20 poly- "chloroprene

CH ₃ COOH

MgSO ₄

30th

15 15

15th

1) 2 microns on average

2) Allied Colloid's "Dispex N 40" trademark

3) 66 ^ 0 styrene, 34% acrylonitrile, molecular weight 140

4) Molecular weight about 250

4.56

1.32 5.08

1.52

could not be made as a powder

1.70

could not be made as a powder

2.54

CD OO CO

on

- .15 -

It can be seen from Examples 3 to 20 that a finer powder is obtained in the process according to the invention.

As already mentioned, the examples described above were carried out on a laboratory scale. To show that Process according to the invention can also be carried out industrially, Example 1 was also carried out on a production scale. The parts by weight of the materials in the test on an industrial scale were the same as in Example 1 and the the average particle size of the solid rubber formed was 0.51 mm. It should be noted that this Size is considerably smaller than what can be achieved in laboratory tests, and it appears that this is general is the case, i.e. that the particle size in tests on a laboratory scale is 2 to 3 times larger than the particle sizes, obtained in the corresponding tests on an industrial scale. This applies both to the examples according to the invention as well as for the comparative examples.

The first embodiment of the method according to the invention was explained in the examples described above. The second embodiment, in which the release agent precursors will now be explained with reference to the accompanying drawing which shows a flow diagram of an apparatus operating in a continuous process can be used.

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The device contains a premix tank 1 into which a solution of the precursor for the release agent is introduced via line 2 latex and via line 3. The emerging Mixture is fed via line 4 into a flocculation tank 5, in which a solution of flocculant is also added introduces via line 6. An operational stirring device 7 is attached in the tank 5. The product from the tank 5 is passed through an overflow line 8 into a tank 9, from there through an overflow line 10 in a tank 11 and from there via an overflow line 12 into a tank 13, into which water is also fed via a line 14 is introduced. A further charge of additional release agent precursors can be carried out via line 14a into the tank be guided. From the tank 13, the product is fed via line 15 to a continuous filter system 16, where the product is sprayed with wash water 17, and from the filter the product is transferred to a reslurry tank 18 where one re-slurry to remove excess processing chemicals, whereby one introduces water via line 19. The slurry is then sent to another continuous filter unit 20, on which washing water 21 is sprayed, and then the material is placed in a rotary dryer 22 which is provided with hot air is operated. Another drying stage then follows in another rotary dryer 23 with hot air, and between the two drying devices a feed line 24 is provided through which

the elastomeric product is dry, powdery Can introduce release agents. The product is fed from the drying device 23 into the packaging system.

Release agent precursor becomes the latex in the tank admitted. The preferred amount is from 1 to 20 pphr. In the flocculation tank 5 »which is usually around When maintained at 60 ° C, the flocculant destabilizes the latex and elastomeric particles are formed. Excess Flocculant reacts with the release agent precursors and it becomes a particulate flocculant educated. This adheres to the surfaces of the elastomeric particles as they are formed and thereby becomes a Agglomeration or coagulation of these particles is reduced or prevented.

The destabilization process continues in tanks 9, 11 and 13. The tanks 9 and 11 are generally operated at about 98 ° C so that syneresis of the elastomeric particles occurs. Cooling water is introduced into the tank 13 in order to reduce the temperature to approximately 60 ⁰ C, and if additional precursor for the release agent is filled into this tank (preferably in an amount of 0 to 10 pphr), this reacts with the remaining flocculation agent, and additional release agent is formed which further coats the elastomeric particles. The product is then, when it is filtered, further cooled and with

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cold water in the tank 18 is reslurried. It is dried at about 50 ⁰ C. Another powdery release agent can be added between the drying devices; the preferred amount is 0 to 100 pphr or 0 to 200 pphr. If powdered polyvinyl chloride or styrene-acrylonitrile copolymer is used.

The examples listed in Table II below illustrate this process. In all of these examples Sodium silicate, which was added as waterglass, was used as the release agent precursor and as a flocculant magnesium sulfate was used; magnesium silicate was formed as a release agent.

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Table II

E.g. PoIy no. mer

Sodium flocculation, additional sodium, particles, thickening silicate average amount of silicate amount size amount (pphr) (pphr) (mm) number (pphr) '

Cf. Part compression ex. service no. size number (mm)

21

22nd

23

24

25th

26th

27

28

29

NBR
NBR
NBR
NBR
NBR
NBR
SBR
SBR
SBR

2 2 2

5 5 5 2 2 2

30 polychloro- 5

pren

31 "5

18 18 18 18 18 18 18 18 18 18

Q 1.27 4th 1 1.14 2 3. 1.14 5 0 1.01 4th 1 1.01 2. 3 1.01 5 0 1.27 4th 1 1.27 2 3 1.27 5 0 1.01

1.01

4 no powder

4.06

2.28

3.30

It can be seen from the table above that small-sized particles are formed in the process of the present invention. Comparative Examples 4 to 7 were carried out by adding to the latex an amount of magnesium silicate which was equivalent to that obtained in the corresponding Examples 21 to 31. This mixture was then added to a solution of magnesium sulfate which was used as a flocculant. Apart from the difference in particle size, there is also a difference in the compression number. The compaction number is a measure of "how well the particulate material can be stored under load, and in the test used, 3 g of the material was placed in a boiler tube with a 100 g weight (equivalent to a load of 1 1/2 lbs / sq. in) heated for 1 hour at 40 ^° C. The compaction rating number given in Table II indicates the following conditions:

1. no compression;

2. Compaction, the material breaks easily when shaken;

3. Compaction, the material breaks when the surface layer is destroyed;

4. Compaction, the material breaks when it is moved strongly;

5. Solidified, cannot be broken.

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The addition of more sodium silicate (in tank 13) " significantly improves the compaction properties of the material.

The compaction properties can be further improved by adding an additional amount of powder Release agent is added between the two drying stages and it is found that this improvement is achieved independently of whether the powdery, elastomeric material after the first embodiment of the method according to the invention, as explained in Examples 1 to 20, or according to the second Embodiment as explained in Examples 21 to 31 was produced. Various additional release agents were added to the powder prepared according to Example 22, and the compaction values were determined determined as described above. The results shown in Table III were obtained.

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III lot 2326885 Tabel (pphr) Additional release agent _ Compulsory 1 valuation no 2 4th Zinc stearate 5 3 It 1 3 It 2 2 Calcium stearate 5 - 3 Il 1 2 H 2 1 Magnesium carbonate VJl 3 Il 1 2 Il 2 2 " Silteg AS7 5 3 Il 1 3 Il 2 2 SPS Clay VJl 4th It 2 3 It 1 Winnofil S. 1

Remarks; Silteg AS7 is precipitated aluminum silicate; SPS Clay is the quality for small particle size clay Paper pulp and Winnofil S is a precipitated calcium carbonate with a surface coating.

It has already been stated that the release agent is added to the aqueous dispersion of elastomeric material before this is added to the flocculant solution in the presence of the free release agent, and the following examples illustrate this process.

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Example 32

To a latex with a solids content of 25% from acrylonitrile-butadiene copolymer rubber (27.5% acrylonitrile, 62.5% butadiene) you add 50 pphr of a high abrasion furnace (HAF) carbon black and 2 pphr sodium silicate as release agent precursors. These materials are mixed and then added to a flocculation solution of magnesium sulfate (18 pphr). The resulting product is washed and dried. A powdery polymer with carbon black incorporated in its particles, the average particle size, is obtained is 1.35 mm. The cleanliness of the wash water shows that there was very little loose soot, which indicates that the carbon black was well incorporated into the polymer.

Example 33

Example 32 was repeated, instead of of HAF carbon black 100 pphr semi-reinforcing furnace (SRF) carbon black used. The average particle size of the resulting powder was 1.15 mm. Again the carbon black was the polymer well incorporated.

Examples 32 and 33 illustrate a very advantageous one Way to make a master batch from powdered rubber / carbon black. The master's approach can almost be completely dust-free and in it the components are as intimately mixed as you would with conventional mixing processes

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can not achieve. The reinforcement properties in objects made from such master batches are good.

The rubber particles made in accordance with the present invention can be used in known processes, and they can be used in the usual mechanical processing methods used to make rubber articles. You can wiil be _5, used with fillers, vulcanizing agents, various accelerators and retardants, antioxidants, anti-ozone and other products that are incorporated into rubber, in view of the fact that vulcanized articles produced. The particles can also easily be mixed with other materials such as plastics, waxes, mastic materials, solvents or oils in order to produce various technical products.

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Claims (1)

Claims 1. Process for making an elastomeric material in powder form, characterized in that an aqueous dispersion of the elastomeric material to one aqueous solution of a flocculant is added in the presence of a free release agent, the release agent to The solid material adheres to the surfaces of the elastomeric particles formed during destabilization extracted from the resulting mass and the solid material dries. 2. The method according to claim 1, characterized in that there is a free release agent in the solution of flocculant dispersed before the dispersion of 'elastomer Material is added to the solution of flocculant. 3. The method according to claim 2, characterized in that the release agent as an aqueous slurry to the solution from flocculant is added. 4. The method according to claim 3? characterized, that a particulate, non-hygroscopic Material with an average particle size less than 2000 microns and a melting point used above 50 ° C. 309850/0930 73 7 6 8 8 5 5. The method according to claim 4, characterized in that the amount of release agent used is from 2 to 300 parts Dry weight per 100 parts dry weight of elastomeric material (2 to 300 pphr). 6. The method according to claim 5, characterized in that the amount of release agent used is 5 to 50 pphr. 7. The method according to any one of claims 2 to 6, characterized in that pulverulent magnesium carbonate is used as the release agent used. 8. The method according to any one of claims 2 to 6, characterized in that the release agent is clay with less Particle size used. 9. The method according to any one of claims 2 to 6, characterized in that the release agent is powdery Styrene-acrylonitrile co ^ olymers used. 10. The method according to any one of claims 2 to 6, characterized in that the release agent is powdered polyvinyl chloride used. 11. The method according to any one of claims 2 to 10, characterized characterized that additional release agent to the elasto- 309850/0930 COPY 7 3 2R885 mers particles while they are still in aqueous dispersion, is added after destabilization. 12. The method according to any one of claims 2 to 11, characterized in that additional release agent to the aqueous Dispersion of elastomeric particles is added before this dispersion is added to "the solution of flocculant." will. 13- The method according to any one of claims 2 to 12, characterized characterized in that additional release agent is added to the solid material during or after drying. 14. The method according to any one of claims 11 to 13, characterized in that some or all of the additional Release agent is the same as the free release agent in the flocculant solution. 15. Method according to one of Claims 2 to 14, characterized in that e *; is carried out continuously and an aqueous solution of a flocculant and an aqueous slurry of separating agent are introduced into a reaction vessel, and the reaction vessel is filled with an aqueous dispersion of elastomeric material, stirring the materials in the reaction vessel, an excess of flocculant and maintains separating agent in the reaction vessel, withdraws material from the reaction vessel, filters the material : j 09850/0930 7326885 triturate and wash and dry the filtered solids. 16. The method according to claim 1, characterized in that that a release agent precursor is added to the aqueous dispersion of the elastomeric material prior to addition the solution of flocculant takes place, and that the precursor reacts with the flocculant and the free Forms release agent. 17. The method according to claim 16, characterized in that that the precursor is water soluble. 18. The method according to claim 17, characterized in that there is sodium silicate as a precursor and as a flocculant Magnesium sulfate is used, which react and form magnesium silicate as a release agent. 19. Process according to claim 17 , characterized in that the precursor used is xanthate starch and an acidic flocculant> which reacts with the xanthate starch in solution, whereby finely precipitated, insoluble starch is formed as a separating agent. 20. The method according to any one of claims 16 to 19, characterized characterized in that the aqueous dispersion of elastomeric material and the precursor for the release agent to the solution from flocculant added in a first reaction vessel : J 09850/0930 "· 7326885 · and that the resulting mass is placed in a second reaction vessel, into which additional release agent precursors are filled ₉ which react with the excess flocculant, whereby further release agent is formed. 21 = The method of any of claims 16 to 20 in _s in that additional release agent is added to the aqueous dispersion of elastomeric material ,, before this dispersion is added to the solution of flocculating agent. * 22ο Method according to claim 21, characterized! that carbon black is used as an additional release agent » 23 ο Method according to claim 21 or 22 "characterized in that the additional release agent is added in the form of an aqueous slurry" 24 = method according to one of claims 16 to 2; 3, thereby characterized ρ that the additional release agent is added to the solid material during or after drying. 25 = method according to claim 16, characterized in that that one mixes a latex with a solution of release agent precursors, the mixture to a solution of flocculant in a first reaction vessel, the latex 309850/093 0 is destabilized and the release agent precursors with a Part of the flocculant react to form the free release agent attached to the formed elastomer Particle adheres to the resulting mixture in a second Reaction vessel transferred, further additional release agent precursors in solution into the second reaction vessel introduces the the resulting slurry reacts with the remaining flocculant to form further separating agent filtered, washing the solid material and the washed material dries «, 26. The method according to claim 25 <; characterized, that sodium silicate is used as a release agent precursor and magnesium sulfate as a flocculant » 27. The method according to claim 25 or 26, characterized in that a dry, powdery release agent _{is added to the dried 9 solid material »} 28. The method according to any one of the preceding claims, characterized in that as an aqueous dispersion elastomeric material uses a compounded latex » 29. Powdered j elastomeric material “produced according to a method of the preceding claims. 309850/0930