EP1155044A1

EP1155044A1 - Method for drying coagulated water containing rubber particles

Info

Publication number: EP1155044A1
Application number: EP00906298A
Authority: EP
Inventors: Peter Barghoorn; Rainer Klostermann; Guiscard Glück
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1999-02-19
Filing date: 2000-02-08
Publication date: 2001-11-21
Also published as: DE19907136A1; US6525172B1; WO2000049053A1

Abstract

The invention relates to a method for drying coagulated water containing rubber particles. Said particles are treated with an aqueous solution containing any type of substances monodispersed and dissolved in water in such a way that the surface of the rubber particles are totally covered by the aqueous solution at least temporarily. Preferably, an aqueous solution of substances is used, which are selected from the group consisting of salts, alcohols, acids and sugars. This makes it possible to reduce the inner content of water between the particles as a result of coagulation without great energy and time expenditure.

Description

Process for drying coagulated water-containing rubber particles

The invention relates to a method for drying coagulated water-containing rubber particles, in particular graft rubber particles.

Rubber or graft rubbers are often produced by homo- or copolymerization of the corresponding monomers in a liquid medium by emulsion, mini-emulsion or microsuspension polymerization. The rubber is obtained in the form of a mostly aqueous solid dispersion, from which it must be separated, unless the dispersion is to be used as such. The rubber is usually separated from the dispersion by coagulation. A number of different methods are known for this. Common to these processes is that the residual water must then be separated from the coagulated particles. This usually happens in several steps. In a first step, the coagulated particles are separated from the surface water by centrifuging, pressing, squeezing or filtering. What remains is the residual water trapped between the coagulated particles, which is often over 50% for the coagulated rubbers. This residual water can only be removed with increased energy expenditure, so that usually a drying step by heat, optionally in combination with reduced pressure, follows. This Drying step is energy and time consuming because the particles have to be dried from the outside in.

The object of the present invention was therefore to provide a process for drying water-containing rubber particles coagulated from the corresponding dispersions, with which the internal water content between the particles caused by the coagulation can be reduced without great expenditure of energy and time.

This object is achieved by a process in which the rubber particles are treated with an aqueous solution of any monodisperse substances dissolved in water in such a way that the surface of the rubber particles is at least temporarily completely covered by the aqueous solution.

A method is already known from DE-A-196 47 599 in which trapped residual water is separated off from styrene particles produced, for example, by suspension polymerization, by treating the styrene particles with an aqueous salt solution. This process can be carried out at a temperature of 20 to 105 ° C. It differs fundamentally from the process claimed here, since internal or residual water is removed from the styrene particles themselves, while it is residual water enclosed during the coagulation of the rubber particles and between them. In addition, the styrene particles are hard thermoplastics with a Tg of approximately 100 ° C., which have much lower internal water contents than is the case with the coagulated rubber particles. The residual water contents in the styrene particles are generally about 2% by weight and, if they are very high, can be in the range of a little over 5% by weight. In contrast, the residual water content is elastomeric rubber particles over 20% by weight and can be up to 50% by weight and more.

When developing the process according to the invention in the field of rubber particles, it has surprisingly been found that not only treatment with aqueous salt solutions can reduce the residual water content, but that aqueous solutions of any substances can be used, with the proviso that the substances in the aqueous solution monodisperse solution. In the context of this invention, monodisperse substances dissolved in water are understood to mean substances which give a "real solution" with water.

An aqueous solution of substances selected from the group consisting of salts, alcohols, acids and sugars is preferably used. Salts of inorganic acids and salts from metals of the 1st to 3rd main group, the 4th main group, with the exception of C and Si, the 5th main group, with the exception of N and P, Ne and Ar of the noble gases and the 1st to 7th subgroup, with halides, sulfates, nitrates, phosphates, carbonates, in particular NaCl, MgSO ₄ , (NH) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , FeCl ₃ , CaCl ₂ , CoCl ₂ , MgCl ₂ , H ₂ SO ₄ , BaCl ₂ , HCl, LiCl, K ₂ , SO ₄ , HNO ₃ , K ₂ CrO ₄ , NaBr, KOH, Na ₂ SO ₄ , NH4CI, NaCl, NaOH, H ₃ PO ₄ , sucrose, KC1 , KBr, CsCl, KHCO ₃ , iso-propanol, CH ₂ OHCH ₂ OH, ethanol, D-glucose, Pb (NO ₃ ) ₂ , D-fructose, CdCl ₂ , MnSO ₄ , CdSO ₄ , CH ₃ OH, NH ₃ / NH ₄ OH, NiSO ₄ , CH ₃ COCH ₃ , CH ₃ COOH, CuSO ₄ , NH ₂ CONH ₂ and HCOOH. NaCl, MgSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , FeCl ₃ and KC1 are particularly suitable.

The concentration of the aqueous solution can be between 5% by weight and the saturation concentration, but preferably between 15 and 40% by weight, in each case based on the finished solution. It has been found that at concentrations below 5% by weight the drying time is too long, while at too high concentrations there is a risk of salt excretion if salt solutions are used. Basically, the drying of the rubber particles is faster with increasing concentration of the solute and at a higher temperature. According to the invention, the temperature can be between about 20 and 200 ° C. Especially at elevated temperatures of over 50 ° C, it should be noted that work is to be carried out at elevated pressure and therefore in closed vessels. The pressure can rise to about 20 bar or higher. In contrast, when working at low temperatures and lower pressures, working with open vessels is possible.

A preferred embodiment of the method according to the invention consists in that the rubber particles are first sintered after their coagulation. As a result, the coagulated particles agglomerate and enlarge again. Following this sintering, the treatment with the aqueous solution is then carried out.

The process according to the invention can be carried out either continuously or batchwise in different ways. In the case of a batch process, it is possible, for example, to work in stirred tanks. However, vessels which have been mixed otherwise can also be used, in which the coagulated particles are introduced and mixed with the aqueous solution. It is necessary to keep the polymer particles and the aqueous solution according to the invention always in motion.

Particularly when the process is carried out continuously, the particles can be introduced, for example, as a solid bed in a vertical tube. The aqueous solution according to the invention is in the upper region of the Tube supplied, for example sprayed on. This then sinks under the influence of gravity or by pumping or pressure while wetting the particles. There it can be collected and, if necessary, used again for spraying after concentration.

According to a further variant when carrying out the process according to the invention, both the rubber particles and the aqueous solution pass through the tube. Gravity alone can be sufficient for this. The rubber particles can then be removed continuously from the tube, for example in the form of a column, in the lower region. In addition, however, it is also possible for the rubber particles and the aqueous solution to be passed in countercurrent to one another.

Furthermore, the rubber particles and the aqueous solution can be introduced into an essentially horizontal tube and mixed by means of at least one screw conveyor and transported through the tube. The individual gears of the screw conveyor prevent the device from blocking and at the same time a narrow residence time distribution of the particles can be predetermined, so that uniform drying takes place. Since with such an arrangement all the passages are flooded with the aqueous solution according to the invention, it is ensured that all rubber particles are wetted, which is also important for uniform drying.

After the rubber particles have been treated with the aqueous solution according to the invention, the particles can be washed with water until no residues of the substances dissolved in the aqueous solution can be detected. Aqueous rubber particles which are treated by the process according to the invention can be composed of:

60 to 100 parts by weight, based on the total weight of the finished dispersion, of at least one copolymerizable monomer (main monomer),

0 to 35 parts by weight, preferably 0 to 20 parts by weight, of at least one functional monomer (comonomer),

0 to 5 parts by weight, preferably 0 to 3 parts by weight, of an α, β-unsaturated mono- or dicarboxylic acid and 0 to 10 parts by weight of a polyfunctional, crosslinking monomer, as described e.g. in DE-A-40 05 210 on page 3, in lines 19-27 have been described.

The main monomer can be selected from:

- Esters of preferably 3 to 6 carbon atoms having α, β-monoethylenically unsaturated mono- or dicarboxylic acids, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, with generally C] -C ₁ -, preferably Cι-C ₈ - and in particular C 1 -C ₄ alkanols.

Such esters are in particular methyl, ethyl, n-butyl, isobutyl, tert-butyl and 2-ethylhexyl acrylate and methacrylate;

- Vinylaromatic compounds, such as styrene, methylstyrene, α-chlorostyrene or vinyltoluenes;

- Vinyl esters of d -CC mono- or dicarboxylic acids, such as vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl laurate and vinyl stearate;

- butadiene. Particularly preferred skin monomers are methyl methacrylate, methyl acrylate, n-butyl methacrylate, t-butyl methacrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, styrene, vinyl acetate, acrylonitrile and butadiene.

Suitable comonomers are in particular:

- Linear 1-olefins, branched-chain 1-olefins or cyclic olefins, such as.

B. ethene, propene, butene, isobutene, pentene, cyclopentene, hexene, cyclohexene, octene, 2,4,4-trimethyl-1-pentene, optionally in a mixture with 2,4,4-trimethyl-2-pentene, C ₈ -Cι ₀ -olefin, 1-dodecene, Cn-Cπ-olefin,

Octadecene, 1-eicosen (C ₂₀ ), C ₂₀ -C ₂₄ olefin; Metallocene-catalyzed oligo-olefins with a terminal double bond, such as. B.

Oligopropene, oligohexene and oligooctadecene; olefins produced by cationic polymerization with a high α-olefin content, such as. B.

Polyisobutene. However, preferably no ethene or no linear 1-

Polymerized olefin into the polymer.

- methacrylonitrile.

- Vinyl and allyl alkyl ethers having 1 to 40 carbon atoms in the alkyl radical, where the alkyl radical can also carry further substituents, such as a hydroxyl group, an amino or dialkylamino group or one or more alkoxylate groups, such as, for. B. methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, vinyl cyclohexyl ether, vinyl 4-hydroxybutyl ether, decyl vinyl ether,

Dodecyl vinyl ether, octadecyl vinyl ether, 2- (diethylamino) ethyl vinyl ether, 2- (di-n-butylamino) ethyl vinyl ether, methyl diglycol methyl ether and the corresponding allyl ethers or mixtures thereof. - Acrylamides and alkyl substituted acrylamides, such as. B. acrylamide, methyl acrylamide, N-tert-butylacrylamide, N-methyl- (meth) acrylamide.

- Monomers containing sulfo groups, such as. B. allylsulfonic acid, methallylsulfonic acid, styrene sulfonate, vinyl sulfonic acid, allyloxybenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, their corresponding alkali metal or ammonium salts, or their mixtures, and sulfopropyl acrylate, sulfopropyl methacrylate.

C ₁ -C ₄ -hydroxyalkyl esters of C ₃ -C ₆ -mono- or dicarboxylic acids (see above), in particular acrylic acid, methacrylic acid or maleic acid, or those containing 2 to 50 moles of ethylene oxide, propylene oxide,

Butylene oxide or mixtures thereof alkoxylated derivatives, or esters of with 2 to 50 moles of ethylene oxide, propylene oxide, butylene oxide or mixtures thereof alkoxylated d to C ₁₈ alcohols with the acids mentioned, such as. B. hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, butanediol-1,4-monoacrylate, ethyl diglycol acrylate, methyl polyglycol acrylate (11 EO),

(Meth) acrylic acid esters of C ₁₃ / Ci ₅ oxo alcohol reacted with 3, 5, 7, 10 or 30 moles of ethylene oxide, or mixtures thereof.

- Vinylphosphonic acid, Vinylphosphonsäuredimethylester u. a. phosphorus-containing monomers.

- Alkylaminoalkyl (meth) acrylates or alkylaminoalkyl (meth) acrylamides or their quaternization products, such as. B. 2- (N, N-dimethylamino)

- ethyl (meth) acrylate, 3- (N, N-dimethylamino) propyl (meth) acrylate, 2- (N, N, N-trimethylunmonium) ethyl (meth) acrylate chloride, 2-dimethylamino-ethyl

(meth) acrylamide, 3-dimethylaminopropyl (meth) acrylamide, 3-trimethylammonium propyl (meth) acrylamide chloride.

- Allyl esters of Ci to C ₃₀ monocarboxylic acids. - N-vinyl compounds, such as N-vinylformamide, N-vinyl-N-methylformamide, N-vinylpyrrolidone, N-vinylimidazole, l-vinyl-2-methylimidazole, 1-vinyl- 2-methylimidazoline, N-vinylcaprolactam, vinylcarbazole, 2- Vinyl pyridine, 4-vinyl pyridine. - Diallyldimethylammonium chloride, vinylidene chloride, vinyl chloride, acrolein, methacrolein.

- Monomers containing 1,3-diketo groups, such as. B. acetoacetoxyethyl (meth) acrylate or diacetone acrylamide, urea group-containing monomers such as ureidoethyl (meth) acrylate, acrylamidoglycolic acid, methacrylamidoglycolate methyl ester.

- Monomers containing silyl groups, such as. B. Trimethoxysilylpropyl methacrylate.

Monomers containing glycidyl groups, such as. B. Glycidyl methacrylate.

The process according to the invention can also be used for drying graft rubber particles which have been prepared by grafting the elastomers with the monomers for the graft shell and at least in the last process step of the graft polymerization in aqueous emulsion.

Graft rubbers are understood to mean in particular those graft polymers in which monomers forming hard thermoplastics, such as in particular styrene, acrylonitrile and / or methyl methacrylate, are grafted onto particle cores made of soft rubber as a graft shell or graft shell, which is achieved by polymerizing or copolymerizing the monomers for the graft shell in the presence of Rubber particles are made. Suitable soft rubbers are elastomeric polymers and / or copolymers with glass transition temperatures below -10 ° C and preferably below -30 ° C. Elastomers are particularly suitable 1,3-diene homopolymers and copolymers, such as butadiene, isoprene or chloroprene homopolymers and copolymers, preferably butadiene rubber, and elastomeric acrylic ester homopolymers and / or copolymers with the low glass transition temperatures mentioned. Elastomeric acrylic ester polymers and 1,3-diene homo- and copolymers are preferred for the graft rubbers coagulated according to the invention, such as homo- and copolymers of C ₄ to C ₈ alkyl acrylates, in particular n-butyl acrylate and / or 2-ethylhexyl acrylate. Examples of preferred comonomers of the alkyl acrylates are crosslinking monomers with at least two non-conjugated C = C double bonds, such as diallyl maleate, diallyl phthalate, diacrylates and dimethacrylates of diols, such as 1, 4-butanediol or 1, 6-hexanediol etc., and also allyl methacrylate or dihydrodicyclyladentyl acrylate, which are used in particular in an amount of 0 to 10% by weight of the total amount of monomers in the production of elastomers, and also polar monomers, such as acrylic acid, methacrylic acid, maleic anhydride, acrylamide, methacrylamide, N-methylol-acrylamide or methacrylamide and their alkyl ethers. The proportion of the elastomers in the graft rubber is generally 30 to 85% by weight, it being possible in the process according to the invention to easily coagulate those graft rubbers whose elastomer content is more than 30% by weight, based on the total solids content.

Monomers and mixtures thereof which form hard polymers or copolymers with glass transition temperatures of above + 50 ° C. are particularly suitable as monomers for the polymerisation of the graft shell or graft shell. The type of monomer (s) depends largely on the type of thermoplastics that form the polymer matrix after mixing with the graft rubber and to which the graft shell has a certain compatibility or affinity to achieve a fine two-phase distribution of the graft rubbers in the matrix should. Particularly suitable and customary monomers are those with 8 to 12 carbon atoms, such as styrene, α-methylstyrene, and Styrenes and α-methylstyrenes which carry one or more alkyl, in particular methyl, groups as substituents on the benzene nucleus. They can be the sole monomers for the production of the graft shell or can be used in a mixture with other monomers, such as methyl methacrylate, methacrylonitrile and preferably acrylonitrile, the methacrylonitrile and / or acrylonitrile monomer units in the graft shell having a proportion of 0 to 45% by weight. % and preferably 10 to 40 wt .-% of the graft shell. Mixtures of styrene with 10 to 40% by weight of the total amount of monomers of acrylonitrile are preferred. Other preferred monomers for the production of the graft shell are methacrylic acid esters and acrylic acid esters, of which methyl methacrylate is preferred, which can also be used as the sole or predominantly used monomer for the production of the graft shell. Suitable comonomers for the preparation of the graft shell are also maleic anhydride, maleimide, N-phenylmaleimide, acrylic acid and methacrylic acid.

Depending on the monomers used for the graft core, graft polymers of the acrylonitrile-butadiene-styrene type (ABS) or acrylonitrile-styrene-alkyl acrylate type (ASA) are formed by blending with a thermoplastic polymer composed of styrene and acrylonitrile (SAN). However, the mention of these known graft polymers is only of an exemplary nature.

The exact polymerization conditions are preferably chosen so that the graft polymer particles obtained have an average particle size, defined by the d ₅₀ value of the particle size distribution, of usually from 30 to 1000, in particular 50 to 400 nm.

If a bimodal particle size distribution is desired, this can also be achieved by a (partial) agglomeration of the polymer particles. A multi-layer structure of the rubber is also conceivable, as described, for example, in WO-A-9623839, EP-A-256 391, EP-A-534 212 and EP-A-535456, the disclosure of which is included here in this respect.

The method according to the invention is explained in more detail below with the aid of the attached drawing and the experimental examples.

Show it

Fig. 1: a schematic representation of the continuous implementation of the inventive method in a column and

2: a schematic representation of the continuous implementation of the method according to the invention in an apparatus with screw conveyance.

In Fig. 1, a device is very simplified and schematically shown, which has a vertical tube 1 in the form of a column, a collecting container 3 for the rubber particles 5 treated with the aqueous solution according to the invention and a removal unit 7 attached to the collecting container 3. The rubber particles 5 are in the form of a solid bed in the tube 1, which at the top is simultaneously filled with the aqueous solution. Both the rubber particles 5 and the aqueous solution are moved downwards by their own weight under the influence of gravity in the direction of the collecting vessel 3. There the aqueous solution can be collected, if necessary concentrated and then again for the treatment of the Rubber particles 5 are used. The advantage of a tube 1 in the form of a column with a tightly packed bed is the narrow residence time distribution and uniform drying of all rubber particles 5. In particular, the influence of a different buoyancy behavior is prevented. On the other hand, the effect of the different buoyancy of the rubber particles 5 of different sizes can also be used, for example in the case of bimodal particle size distribution, in order to control the dwell time with a suitable flow control in such a way that large rubber particles 5, which take longer to dry, also stay longer in the tube 1 linger.

A modification of this embodiment of the device for treating the rubber particles 5 is that only the aqueous solution seeps through the tube 1, while the rubber particles 5 remain in the tube. Even so, a uniform wetting of the rubber particles 5 and thus uniform drying is effected. In this variant, the aqueous solution can be applied, for example, by spraying.

2, the method according to the invention is carried out in an essentially horizontally arranged tube 10 which has an inlet 12 for the rubber particles 50 and the aqueous solution. The tube 10 has at least one screw conveyor 60, which is shown schematically in a very simplified manner in FIG. 2. The conveyor screw 60 causes a continuous transport of both the rubber particles 50 and the aqueous solution through the tube 10 and at the same time a good mixing of the rubber particles 50 with the aqueous solution. In addition, the individual gears of the screw conveyor 60 prevent the device from blocking and likewise a narrow residence time distribution is specified, so that uniform drying can take place. Since the device ensures that all passages are flooded with the aqueous solution, all rubber particles 50 are wetted and dried uniformly. Examples

The following Examples 1 to 12 relate to acrylonitrile-butadiene-styrene (ABS) - and Examples 13 and 14 acrylonitrile-styrene-acrylic ester (ASA) rubbers.

Comparative Example 1

a Preparation of the basic stage from polybutadiene

Butadiene was polymerized in an aqueous emulsion. The procedure was as described in DE-A-31 49 046 in Example 1 on page 15. The polybutadiene latex thus obtained had a solids content of 40% by weight and an average particle size d ₅₀ of 80 nm.

b Agglomeration of the polybutadiene basic stage and grafting with styrene

Acrylonitrile

50 kg of the polybutadiene latex produced in step a) were placed in a reactor with a stirrer and thermometer with stirring. After heating to 75 ° C., 1 kg of an agglomerating latex composed of 96% by weight of acrylate and 4% by weight of methacrylamide (solids content 10% by weight) was added. A partially agglomerated polybutadiene latex with a bimodal particle size distribution and an average particle size distribution d ₀ of 220 nm was obtained. 0.2 kg of potassium stearate and 0.025 kg of potassium persulfate were added to the agglomerated latex at 75 ° C. After adding 1.47 kg of styrene and 0.63 kg of acrylonitrile, the mixture was polymerized for 15 minutes and then a mixture of 7.35 kg of styrene and 3.15 kg of acrylonitrile was added over a further 3 hours. Then 0.025 kg of potassium persulfate was added and the mixture was stirred at 75 ° C. for a further 1.5 hours.

c Precipitation of the graft stage

50 kg of the grafted polybutadiene latex were mixed with 100 kg of a 0.5% by weight MgSO ₄ solution at 80 ° C.

d) Sintering of the precipitated graft stage The precipitated graft rubber was heated to 120 ° C. for half an hour and then freed from the surface water in a centrifuge (Carl Padberg Zentrifugenbau GmbH) at 1600 rpm for half an hour. The residual moisture of the graft rubber was 29.7% by weight after centrifugation. The residual moisture was determined by drying at 60 ° C. under vacuum for 24 hours.

Examples 2 to 6

The procedure was as described in Comparative Example 1 under a) to d). Thereafter, 5 kg each of the sintered graft rubber obtained in this way were mixed with 20 l of an aqueous NaCl solution (23% by weight). The used Temperatures and the residence time are shown in Table 1. The rubber was spun off and excess NaCl was removed by washing three times with 10 l of water each time.

The surface water of the rubber particles was then removed by centrifugation at 1600 rpm for half an hour and the residual moisture was determined by drying under vacuum at 60 ° C. for 24 hours. The results are also shown in Table 1.

Table 1

Examples 7 to 10

The procedure was as described in Comparative Example 1 under a) to d). 500 g each of the graft rubbers thus obtained were placed in a 1 liter glass jar in 1 liter a 23 wt .-% NaCl solution at 60 ° C. The respective dwell times are given in Table 2. The graft rubber thus treated was freed from the surface water by filtration using a water jet vacuum. The residual moisture was determined by drying at 60 ° C. under vacuum for 24 hours.

Table 2

Examples 11, 12

The procedure was as described in Comparative Example 1 under a) to d). Thereafter, 5 kg each of the sintered graft rubber thus obtained were treated with 20 liters of an aqueous (NH ₄ ) ₂ SO ₄ solution (33% by weight, Example 11) or with a MgSO ₄ solution (29% by weight, Example 12). mixed. The temperatures used and the residence time are shown in Table 3. The Rubber was spun off and excess salt was removed by washing three times with 10 liters of water.

The surface water of the rubber particles was then removed by centrifuging at 1600 rpm for 1/2 hour and the residual moisture was determined by drying at 60 ° C. under vacuum for 24 hours. The results are shown in Table 3.

Table 3

Examples 13, 14

a) Production of ASA graft rubbers

These ASA graft rubbers were produced by the process as specified in DE-A-40 11 163 under "Examples". In this respect, reference is expressly made to DE-A-40 11 163.

The graft base consisted of 98 parts by weight of n-butyl acrylate and 2 parts by weight of an acrylic acid ester of tricyclodecenyl alcohol. The graft shell was formed from 75 parts by weight of styrene and 25 parts by weight of acrylonitrile.

b Precipitation rubber sintering and sintering

The graft rubber was precipitated and sintered as described in Comparative Example 1 under c) and d). Example 13 serves as a comparative example, which was not treated with the solution according to the invention, while Example 14 was treated with an NaCl solution. The results are shown in Table 4 below.

Table 4

Claims

claims

1. Process for drying coagulated water-containing rubber particles which are treated with an aqueous solution of any monodisperse substances dissolved in water so that the surface of the rubber particles is at least temporarily completely covered by the aqueous solution.

2. The method according to claim 1, characterized in that an aqueous solution of substances is used which are selected from the group consisting of salts, alcohols, acids and sugars.

3. The method according to claim 1 or 2, characterized in that the concentration of the aqueous solution between 5 wt.% And

Saturation concentration, preferably between 15 and 40% by weight, in each case based on the finished solution.

4. The method according to any one of claims 1 to 3, characterized in that it is carried out at a temperature between about 20 and 200 ° C.

5. The method according to any one of claims 1 to 4, characterized in that the rubber particles are first sintered after their coagulation and then treated with the aqueous solution.

6. The method according to any one of claims 1 to 5, characterized in that the method is carried out continuously or batchwise.

Method according to claim 6, characterized in that the rubber particles (5) are introduced into a vertically arranged tube (1) and the aqueous solution is fed into the upper region of the tube (1) so that it passes through the tube (1).

8. The method according to claim 7, characterized in that both the rubber particles (5) and the aqueous solution pass through the tube (1).

9. The method according to claim 6, characterized in that the rubber particles (50) and the aqueous solution are introduced into a substantially horizontally arranged tube (10) and by means of at least one

Screw conveyor (60) is mixed and transported through the tube (10).

10. The method according to any one of claims 1 to 9 for drying graft rubber particles.