CA1057881A

CA1057881A - Pulverulent, non-tacky, free-flowing filled rubber base mixtures

Info

Publication number: CA1057881A
Application number: CA233,548A
Authority: CA
Inventors: Gerhard Berg; Karl-Heinz Nordsiek
Original assignee: Chemische Werke Huels AG
Current assignee: Huels AG
Priority date: 1974-08-16
Filing date: 1975-08-15
Publication date: 1979-07-03
Also published as: BR7505215A; JPS5149240A; JPS5850257B2; NL182152B; ES440251A1; ZA755195B; DD119427A5; DE2439237C3; NL182152C; NL7509766A; RO69583A; MY8200136A; DE2439237B2; FR2281947A1; DE2439237A1; IT1041209B; FR2281947B1; US4073755A; GB1514827A; BE832486A

Abstract

ABSTRACT
A process for the manufacture of a pulverulent, non-tacky, free-flowing filled rubber base mixture which comprises mixing a rubber latex or an aqueous stable emulsion of a rubber solution with less than the envisaged total amount of solid filler in the form of an aqueous dispersion or suspen-sion thereof to give a stable, homogeneous mixture;
feeding the stable, homogeneous mixture to a multi-stage precipitation pro-cess by (1) mixing the stable, homogeneous mixture into water containing a precipi-tant and a sodium silicate whereupon the rubber and filler conjointly pre-cipitate as a rubber premix, and distilling off rubber solvent which may be present, (ii) adjusting the aqueous suspension of the rubber premix, thus obtained to a pH value of 4.0 to 9.0 for the precipitation of dissolved silica in the presence of a silica precipitant and (iii) mixing the suspension, thus obtained, of rubber premix and precipi-tated silica with the remainder of the envisaged total amount of solid filler in the form of an aqueous suspension; separating the precipitated material plus filler together constituting the filled rubber base mixture from the water; and drying the rubber base mixture with constant agitation. The rub-ber base mixtures of this invention find many uses, in particular the manu-facture of extended products.

Description

To the present day, rubber mixtures are manufactured discontinuously in the rubber industry. The main reason for this is the state of the rubber raw material, which is in the form of bales. The comminution of the bale and the intimate mixing with fillers, mineral oil plasticisers and vulcanisation au~iliaries is carried out on mills or in internal mixers The operation of this equipment requires high energies In malaxating the highly viscous mat-erial, ~his energy is rapidly converted to heat To avoid deterioration in quali~y due to molecular changes or premature incipient vulcanisation, the prepara~ion of the mixture is carried out in several process stages. Between these stages7 the mixture is generally stored The internal mixers or mills are followed by extruder_pelletisers or extruder-roller dies Such discon_ tinuous processing requires a high level of expenditure of time, energy and personnel.
Only a completely new processing technology can provide a way out of this highly unsatisfactor~ technique of rubber processing. In recent years, the use of free_flowing rubber powders has therefore been discussed increas-I ingly, since there is no doubt that raw materials in this s~ate greatl~ re~
duce the technical, personnel and energy requirements of the rubber industry, elLminate the hitherto customar~ heavy machinery and provide the prerequisites for a one_stage and automated form of process. This makes it possible to pro_ ces~ rubber mixtures in the same way as plastics powders ; A large number of publications on pulverulent rubber mixtures and on the possibilities of rubber powder technology exists. On closer inspection, ;however, these are all concerned with pulverulent nitrile rubbers and emulsion ~; copolymers of butadiene with styrene as coprecipitates with silica. Pulveru~
., ~
lent rubber mixtures based on all-purpose rubbers, such as are of the greatest interest, above all for the tyre industry, have neither been described nor .: .
manufactured Only in very recent ~imes have methods of preparation of pul-verulent, free-flowing rubber/filler mixtures, preferably rubber/carbon black mixtures, based on all_purpose rubbers been found and described (c~mpare : ~ ~

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Canadian Patents 1J011~023; 1,016,6~4 and 1,023,068, and Canadian Patent Applications Nos. 1~7,677; 199,471; 202,863; and 203,309. Polybutadienes, with vinyl group contents of 25 to 60% manufac~ured in organic solvents using lithium catalysts, have been used as particularly valuable all-purpose rubbers.
According to the sta*e of the art which this provides, it also pro-ved possible to convert, amongst special rubbers, polymers with block-llke crystalline and thermoplastic portions into pulverulent rubber mixtures (com-pare Canadian Patent Application 202,863). Amongst these there should above all be mentioned the known ethylene-propylene copolymers and ethylene-propy-lene-diene terpolymers, of which the ethylene content is between 65 and 80%
and the Raman crystallinity between 0.3R and 1.5R. Rubbers having the mic-; rostructure claimed have since become known as F.PM-sequence and EPDM-sequence grades. Further special rubbers, hitherto usable with advantage, which should be mentioned, are solution copolymers of butadiene and styrene, the initial monomers of which are, ater polymerisation, partially or predominantly pre-sent in a block-like arrangement.
The processes for the preparation of pulverulent rubber mixtures according to the cited state of the art, comprised emulsifying the solutions of the said rubbers in water with the aid of special surface-active compounds, ~ixing the emulsions with aqueous dispersions of fillers, preferably carbon blacks, and subjecting the stable mixtures of the aqueous emulsions of the rubber solutions and the illers to a precipitation process. If suitable dry-ing methods were used, pulverulent rubber mixtures of free-flowing consistency were obtained.
Essential prerequisites for obtaining the filled pulverulent rubber mixtures described proved to be, in addition to the technological measures, certain molecular parameters of the rubbers as well as the nature, amount and activity of the fillers and other constituents introduced into the mixture and the ratio of the amount of rubber to the amount of carbon black. Rubbers of very broad molecular weight distribution, which thus have a relatively high :

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content of low molecular material, especiall~ rubbers of tacl~ consistenc~, have hitherto not been amenable to the processes described, nor ha~e fillers of low levels of activity, or pulverulent rubber mixtures containing less than 60 parts by weight of filler per 100 parts by weight of rubber Pulver- .
ulent rubber mixtures of such rubbers and fillers, where appropriate including critical additives such as, for example, plasticiser oils or resins, showed a deterioration in ~he free flowing character and storage stability of the pow-der mixtures~ A problem which remained completely unsolved, as before, was to prepare, from rubber latices as produced, for example, on aqueous emulsion copolymerisation of butadiene with styrene, pulverulent rubber mixtures con-taining carbon black, directly from the latices and with elimination of the completely uneconomical method of processing of bales dissolved in organic solvents mere therefore exists - as a genuine techno-commercial requirement resul~ing from the above _ the task of developing a new process for the man_ ufacture of pulverulent rubber base mixtures con~aining filler, by means of which it was not only possible to broaden the hitherto usable grades of rubber, based on solution polymers, to include grades of rubber hitherto unsuitable for the purpose, and to include fillers of lower levels of activity, but also to use the previously excluded aqueous rubber latices for the preparation of filled rubber powders, preferably rubber powders containing carbon black.
The subject of the present in~ention is a process for the prepara-tion of pul~erulent, non_tacky, free-flowing filled rubber base mixtures which ~-optionally contain plasticiser oil, by mixing rubber latices or aqueous emul_ sions of rubber solutions which optionally contain plasticiser oil with aqueous dispersions of solid filler~ which optionally contain plasticiser oil, introducing these mixtures into water containing a precipitant~ precipitating the rubber base mixtures, if appropriate whilst at the same time distilling off the rubber solvent, separating the precipitated rubber base mixture from the water and drying the rubber base mixture with constant agitation.

-- 3 _ ' :`
The characteristic of this process is that rubber latices or aqueous stable emulsions of rubber solutions, optionally con~aining plasticiser oil, are combined with less than the envisagecl total amount of fillers, optionally containing plasticiser oil, in the form of their aqueous dispersions or sus-pensions to give stable, homogeneous mixtures and the stable, homogeneous mix~ures are fed to a multi-stage precipitation process by 1. mixing these stable, homogeneous mixtures into water containing ;~
precipitants and sodium silicate, whereupon the rubber and filler conjointly precipitate as a pulverulent rubber premix, and distilling off rubber solvent which may be present;
2. adjusting the aqueous suspension of the rubber premix, thus ob-tained, in the presence of a compound which causes the immediate precipitation of dissolved silica, to a p~l value of 4.0 to 9.0, preferably of 6.0 to 8.0;
; and

3. mixing the suspension, thus obtained, of rubber premix and pre-cipitated silica with the remainder of the envisaged total amount of fillers in the form of an aqueous suspension.
By rubber premix there is to be understood, according to the inven-tion, a mixture which, whilst containing the total amount of rubber, only con-tains a part of the total amount of fillers. The amount of fillers contained in the rubber premix can be between 20 and 99 per cent by weight, preferably between 50 and 90 per cent by weight, based on the total amount of fillers. ~`In addition to containing the total amount of rubber, the rubber base mixture according to the invention also contains the desired total amount of fillers. These pulverulent rubber base mixtures, obtained according to ~; the process of the invention, generally have particle sizes of between 0.001 and 1.5 mm, especially 0.05 to 1.0 mm, and preferably ~.25 to 0.9 mm.
Both all synthetic rubbers prepared in solution, in the form of their solution, and synthetic rubbers prepared by emulsion polymerisation, ~.

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in the form of their aqueous latices, are suitable for the process according to the invention.
Examples of solution polymers which can be used are polybutadienes, polyisoprenes, copolymers of butadiene with styrene, EPM and EPDM polymers and polymers obtained by ring opening of cycloolefînes ~Scot~, K.W. et al., Rubber Chemistry Technology 44 1,341 (1971)), the catalysts used being either Ziegler catalysts or lithium catalysts, depending on the monomer and on the properties of the polymer.
Suitable solvents are both aliphatic hydrocarbons, such as, for ex-ample, pentane3 hexane or heptane, or aromatic hydrocarbons, such as, for example, benzene or toluene. Polymers which can be prepared in an aliphatic solvent and can be used directly in the form of the solution obtained after stopping the polymerisation and stabilising the product are preferred Alter_ natively, the rubber can also be brought to an emulsifiable form by redis_ ~
solving it ;`
The use of polybutadienes, polyisoprenes and copolymers o~: buta-diene with styrene, in the form of their lithium polgmers prepared in ali_ phatic hydrocarbons, is particularl~ pre~erred.
As aqueous latices, preferably the emulsion copolgmers of butadiene -with styrene and butadiene with acrylonitrile are introduced into the process according to the inven~ion.
Using the process according to the invention it is also possible to prepare~pulverulent rubber mixtures which do not contain merely a single rub-ber, but contain mix~ures of two or more different rubbers, for example a mix_ ; ture of polybutadienes with varying vinyl group contents, ar~ polyisoprenes,~
...
For ~his purpose, the rubber solutions or, more advantageously, the aqueous emulsions of the rubber solutions are mixed and converted, according to ~he invention, to filled pulverulent rubber mL~tures. me rubber latices can also be processed analogously, in accord~nce with ~he in~ention, as a com-: J
bination with one another ~
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~illers which can be usecl are preferentially the carbon blacks of all levels of activity, which are customary in the rubber industry, such as, for example, SAF, ISAF and ~IA~ carbon blacks, inclucling their modifications, FEF, GPF, APF, SR~ and Mr carbon blacks. However, mineral substances such as, for example, highly active silica, kaolin and slate powder can also be incor-porated. In the ls~ stage of the process according to the invention, the fillers can be processed either as aqueous dispersions containing emulsifier ~ ~
or as aqueous suspensions free from emulsifier. In the last stage of the -precipitation process, the remaining amount of filler is always introduced as an emulsifier-free suspension.
The amount of carbon black to be employed can be 20 to 400 per cent by weight, preferably 40 to llO per cent by weight, based on rubber.
The amount of mineral substances is suitably between 20 and 500 per -; cent by weight, preferably 30 to 150 per cent by weight, based on rubber.
Combinations of carbon blacks with white fillers are possible If plasticiser oils are also to be incorporated, the refinery pro- `~
ducts customary for the purpose are used, which consist9 depending on the end use of the vulcanised products, preferentially of aromatic, naphthenic or paraffinic hydrocarbons. The amount of plasticiser oils to be employed is suitably between 1 and 100 per cent by weight, preferably 30 and 60 per cent by weight, based on rubber. To prepare a carbon black/rubber base mixture containing plasticiser oil it is on the ~e hand possible to stir the plast-; iciser oil into the rubber solution prior to the emulsification process. A
second possibility, which as a rule is more advantagebus, is first to combine the plasticiser oil and the carbon black in suitable mixing equipment ~compare Canadian Patent Application 199,471), to convert the non-tacky pulverulent ^ mixture thereby obtained into an aqueous suspension or dispersion and to stir : .
this into the aqueous emulsion of the rubber solution or into the rubber la-tex. The further process steps are identical to those already described.
As emulsifiers for rubber solutions and optionally for fillers it r'A~
~ .

'l~IS78~
is possible to use aLl anionic, cationic and non-ionic surface-active com~
pounds known frotn rubber technology and rubber chemistry, if appropriate in combination with emulsifying au~iliaries, in particular with high_molecular protective colloids. Which emulsifier, if appropriate in combination with an emuLsifying auxiliary, is used in accordance with the process depends largely on the typc of rubber and type of filler, the rubber combination, the activity of the filler, the properties of the rubber base m~xtures as determined by further additives and the question of whether the rubber is employed in the fo~n of its aqueous latex or in the form of the aqueous emuLsion of its 90I_ ution.
Examples of suitable anionic emuLsifiers are potassium o:Leate, sod-ium stearate, sodium dresinate, sodium alkylben~ene_suLphonates and s:odium saLts of the sulphuric acid esters of higher aliphatic alcohols, such as, for example, mixtures of sodium cetyl_stiLphate and sodium stearyl_suLphate, Amongst the non~ionic emuLsifiers, it is very adran~ageous to use aIkylamine-oxalkylates of the ~eneral formula ~ (R2 - )XH
Rl - N
(R3 - O)yH
in which Rl represents alkyl and alkenyl groups with 1 to 20 C atoms, prefer_ ably 12 to 18 C atoms, R2 and R3 represent ethylene or propylene groups and X and Y represent integers bet~een 1 and 80, preferably 6 to 20.
~xamples of suitable compounds are laurylamine-, myristylatnine , cetylatt~ne-, s~earylamine_ and oleylamine- polyglycol ethers. `~
Suitable cationic emulsifiers are preferabl~ quanternary ammoniutn salts, for example lauryl_dimethylbenzylammonium chloride, cetyl_trimeth~_ lammonium chloride, lauryl_dime~hyl~m~ium eth~l sulphate, alky~ 2-q6) tr~nethylammonium br~mide, coconut~dimethylbenz~1ammonium chloride, cetyl_ .
dimethylben ~lammonium chloride, cetyl_dimethylethylammonium eth~l_sulphate, distearyl_di3nethylammoniwm chloride and N-substituted salts of pyridine, such as, for e~ample, laur~_ pyridinium chloride, cetyl_pyridinium bromide~ tetra-~ decylpyridinium bromide and lauryl-pyridini~n bisulphate, .~ _ 7 _ .` ' .

3 ~57B~31 ~ hen emulsifying the rubber solukions in water, the ~mulsifiers are suitably employed in amounts of 0.05 to 2.0 per cent by weight, preferably 0.1 to 1.5 per cent by weight, based on rubber solu1;ion Fillers, preferably carbon blacks, are _ if this is necessar~ to - prepare a homogeneous rubber-filler mixture -~dispersed in water in the pre-sence of 0.1 to 5 per cent b~ weight, preferably 1 to 3 per cent by weight, of emulsifier, relative to the filler.
High_molecular protective colloids usable as emulsifying auxiliaries for rubber solutions and ~illers are, for example, sodium polyacrylates with molecular weights of 100,000 to 2,000,000, preferabl~ of 250,000 to 1,500,000 and cellulose derivatives~ 9uch as, for example, methylcelluloses, carboxy-methylcelluloses and tyloses.
The high_molecular protective colloids are preferably employed as ;~
1% strength aqueous solutions in amounts o~ between OoOOl and 0.5 per cent by weight, preferabl~ 0,005 and 0,1 per cent by weight, based on rubber sol-ution, and O.Ql to 1.0 per cent by weight, preferably 0.05 to 0.5 per cent by weight, based on filler The silicate used is a sodium silicate solution suitably with Na20:SiO2 molar ratios of 2:1 to 1:4. me amount of silica, calculated as SiO2, to be liberated from the silicate in the course of the process can be 0 01 to 20 per cent by weight, preferably 1 to 10 per cent b~ weight, rela-tive to the total amount of rubber.
Th~ precipitant used for the anionic and non-ionic ~ystems is ad~an_ ;; . ..
tageously acidified water, and the pH value should be between 1 and 4, pre_ ferably 1 5 and 2 5 Aqueous sodium silicate solutions are advantageousl~ used as precipi-tants for the cationic systems. The amounts of SiO2 required for the precipi-tation and contained in the sodium silicate solution are 0.5 to 20 mols, pre_ ` f0rably 1 to 8 mols/mol of the quaternar~ ammonium sal~ used as emulsifier Silica precipitants used according to the invention are, on the one ':
_ 8 _ ' '' :

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357~

hand, monovalent and polyvalcnt secondary and tertiar~ amines as well as quat-ernary ammoniwm salts and, on the other hand, water-soluble salts of those metals which form sparingly soluble or insoluble saLts with alkali metal sili_ cates Tertiary amines which are obtained by condensation of alkylamines with ethylene oxide and propylene oxide, such as, for example, laurylamine-poly-glycol ether, stearylamine-polyglycol ether, ole~lamine-polyglycol ether, coc_ onut amine~polyglycol ether and condensation products of 2,2,4_trimethyl_hexa_ methylene_ 1,6~diamine with propylene oxide and eth~lene oxide are particu-larly preferred for use. The salts of the metals of main groups II and III as ~ ~
well as of sub-group~ II and VIII of the periodic table of the elements are ~ -particularly suitable, for example, magnesium chloride, ~inc sulphate, iron chloride, iron sulphate, cobalt nitrate and nickel sulphate, but preferably water-soluble salts of aluminium, such as, for example, aluminium chloride and aluminium sulphate. The silica precipitants are suitably employed in amounts of 1 to 50 per cent b~ weight, preferably 5 to 20 per cent by weight, relati~e to SiO2.
The amines to be used according to the invention can be introduced into the process either with all streams of material prior to the second pre-,( :, cipitation stage, or with the medium used for the neutralisation. On the other hand, the water_soluble metal sal*s are only added after the neutral-isation which has been carried out in khe second precipitation stage If the emulsification of the rubber solutions in water or the preparation of a~eous filler dispersions is carried out in the presence of the silica precipitants according to the inven~ion as emulsifiers, for example in the presence of laurylamine_polyglycol ether, the introduction of additional quantities of precipitant can be dispensed with, since in the 1st stage of the precipitation process the alkylamine polyglycol ethers are deactivated in the presence of acid and, since they are water-soluble, are avaîlable in sufficient amount, in the second stage after neu-; 30 tralisation, in order to initiate the immediate precipitation of the dis_ '~' _ 9 -3L~578~

solved silica. In the case of particularly critical mixtures, such as those ~;
containing cis-1,4-polyisoprene of pronounced intrinsic tackiness, it i9~ how_ ever, always advisable additionally to employ water-soluble mctal salts, pre_ ferably aluminium salts.
The temperatures used in the precipitation stages are, suitabl~
under all pressure conditions, above the azeotropic boiling point of rubber solvents and water~ Under normal pressure, the precipitation is preferabl~ ;~
carried out at between 60 and 100C, the temperatures increasing from stage to stage. Under these conditions, the rubber solvent distills o~f contin-uously.
The process according to the invention acquires its outstanding importance as a result of the following two measures:
1. as a result of the stepwise incorporation of the fillers, pre-ferably carbon black, into and onto the rubber, and ; 2. as a result of the immediate precipitation of controlled small ., -: . :
amounts of silica, suited to the particular application, which is carried out after precipitation of the rubber premix, before preparation of the rubber base mixture, in the second stage of the precipitation process after neutral_ ising the aqueous charge. ~ -In general, the major proportion of the amount of filler is combined with the total amount of rubber in the first stage of the multi-stage process according to the invention, to give a pulverulent premix. Whether this amount of filler must or can be employed a) as an aqueous dispersion con~aining emulsifier or b) as~an~aqueous suspension free from emulsifier depends exclu_ ; si~ely on the compatibility of the rubber latices or of the aqueous emulsions of the rubber solutions with the aqueous filler systems. To achieve stable and homogeneous latex/filler mixtures, preferably latex/carbon black mLxtures, the fillers, especially the carbon blacks, must be introduced according to a).
.. . .
The aqueous emulsions of the rubber solutions as a rule do not d~mand this ' .~ ~

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measure They can be mixed ~ith the fillers, especially carbon blacksf either according to a) or according to b~. The resl~ting mixtures are homogeneous and stable The residual amount of fillers, as a rule the minor proportion, is introduced ~ZS an emulsifier_free aqueous suspension into the last stage of the precipitation process, whereupon the finished rubber base mixture is formed from the rubber premix, precipitated silica and residual filler.
According to the invention, the silica is preferably introduced as waterglass into the first precipitation stage of the process. However, it lQ can also be introduced into materials, or streams of materials, bef`ore neutral_ isation, that is to s~y, for example, it can be added to the emulsions, the filler dispersions or suspensions, or the mixtures of emulsions ancl fillers The technical advance provided by the process according to the invention resides essentially in the broadening ~ the range of solution rub_ ber suitable for the process and the inclusion in the process of the lakices obtained by em~lsion-pol~merisation. However, as a result of the ne~ process technology, a surprising and unforeseeable mar~ed increase in ~the bulk den~
sities of the pulverulent rubber base mLxtures is also achieved, ThZe increase in bulk density in turn produces a considerable increase in the ra~e of flow of the pulver~ent rubber mixtures, measured according to ASTM_D 1895-69, As a result of the phenomenon, a contxibution is accordingly also made to a qual-itative improvement of the pulverZ~lent rubber base mixtures which can be pre_ pared according to the state of the art, the improvement above all having an ad~antageous effect with regard to storage, conveying and transport, A f~r-ther decisive technological advantage results from the enorm~us saving of `~
the costly labour required to comminute the rubbers which hitherto have usu-j ally been in the form of bales, and the saving of the mixing work which then Z! usually ~oll~s. ~Fr~m the pulverulent rubber base mixtures ~hich in general consist ~ -of rubber and fillers~ it is possible to prepare, in a c~mparativel~ simple _11--:' ~
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manner, vulcanisable finished rubber mixtures by admixing to the base mixtures, in modern fluid mixers, the customaxy additives, such as additional fillers, plasticiser oils, resins, o~one-protection agents andanti-agin~ agents, as well as chemicals for crosslinking, without the developnent of shear forces The direct use of such finished pulverulent rubber mixtures in the final stage of customary rubber processing, with exclusion of heavy machinery having high energy requirements, becomes possible in a surprisingly simple and economical manner Thus, the pulverulent finished mixtures obt~ d from the products according to the invention can be fed directly into special extruders or injection moulding machines A good example of successful direct extrusion is the "EVK_system" developed by Werner ~ Pfleiderer ~ Koch; Gummi, Asbest, Kunststoffe 1974, issue 1, page 31) The output achievable thereby, and the quality of the resulting tread strip, corresponds to the results when using solid rubbers and employing the customary expensive multi_stage pro_ cess technology. Equivalence to the methods o~ plastics~processing thus becomes tangibly near as a result of the pulverulent rubber mixtures ~ according to the invention.
- However, even retaining the customary process technolo~y of the rub-ber_processing industry, the advantages when using the pulverulent rubber mix_ tures according to the invention are considerable Thus, it has been found that the preparation of vulcanisable fini~hed rubber mixtures, even with high proportions of acti~e fillers, is possible in a simple and particularly econ-` omical manner in conventional internal mix~rs Now, in contrast to the usual multi_stage mixing technique, the running time is drastically reduced, in a , ,:; , .
i single process stage, to from one-third to one_quarter of the total mixing . ., ~ . .
time usually required, the energ~ consumption being reduced to approxImately the same extent. At the same t, e, the discharge temperatures are only slight-ly above 100C.
Furthermore, other filler constituents can additionally be intro~
~ 3Q duced under the same conditions without reducing the advantages mentioned.

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Equally, it proves possible additionally to incorporate minor proportion~ of other solid rubbers.
The sequence of metering the individual components into the interal mixer is of particular importance for achieving optimally short mixing cycles.
In contrast to charging the mixer with solid rubber, all the constituents can be metered in fully automatically In addition to the exceptional shor~ening of the mLxing time, which has been mentioned, the method thus additionall~
provides the possibility of reducing the charging time and hence of enormously increasing the degree of utilisation of conventional very expensive mixing installations.
The use of the pulverulent rubber_filler base mixtures according to the inve~tion thus leads, independently of the type of processing method, in every ca~e to exceptional technical and economic advances. The range of pos- ;
sibilities extends from drastic shortening of the mixing times when using con_ ~entional equipment such as internal mixers and mills, to continuous conduct of the process, without involvem~nt of hea~y machinery. A survey of the mult-~.
iplicit~v of possible utilisations is provided by the schematic drawing shown ~
. .. ~ .- .
; in Figure 1.

The process claimed is explained in more detail with the aid of the ;

examples which follow: ~
., .
ample 1 The rubber used is a polybutadiene obtained by adiabatic polymer-isation of bwtadiene in the presence of n-butyl_lithium9 in the form o~ its 12 5 per cent strength by weight solution in hexane, the polybutadi~ne ha~ing - the following analytical data:

Mooney ~iscosity (ML4) 4 Defo 1,025/33 Gel content 2,5 ``~ Content o~ trans-1,4 units 39%

Content of cis-1,4 units 27%

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Contellt of ~in~l ~roups (1,~ units) 34~
~iscosi~ of ~hc solution at 20C 885 cP
216 kg of this polybut~dierle solution are emulsified by means of an emllsifying machine of the "Supraton 455 D~l type in 211 kg of water in the presence of 0.64~ kg of a laurylamine-polyglycol ether with 12 ethoxy groups and 0.0432 kg of a sodium polyacrylate from Messrs. R'ohm ~product name "Plex . ~, i 5367 F") The pH value is adjusted to 11.5 by addition of sodium hydroxide solution. ~-- 1,296 kg of a stable aqueous emulsion of the polybutadiene solution, prepared in this way, are mixed with 500 kg of an aqueous ISAF carbon black dispersion, which contains 50 kg of ISAF carbon black and 0~24 kg of the above_ mentioned ethoxylated laurylamine~ wi~h l;ght stirring.
The stable and homogeneous mixture, which contains 60 parts by weight of carbon black per 100 parts by weight of rubber, is st~rred into an aqueous precipitation bath which consists of a mixture, heated to about 90C, of 300 kg of water, 9.6 kg of 10% strength sulphuric acid and 2.6 kg of a 26% strength .. . . .
sadium silicate solution. l~hilst the solvent, hexane, distils off, the rubber premix containing carbon black precipitates in a finely particulate form (lst ~ ;
stage), After completion of the precipitation process, the aqueous suspen-, :
sion of the rubber premix containing carbon black is adJusted to a pH value of 7.0 b~ addition of sodium hydroxide solution (2nd stage). ~`
- After the neutralisation, a further 250 kg of a lO~o strength aqueous ISAF carbon black suspension, corresponding to 30 parts by weight of carbon black per 100 parts by weight of rubber, are added to the batch (3rd stage~.
The resulting rubber base mixture is separated from the water and i~ dried with constant agitation. A pulverulent, very free_flowing rubber base mixture is obtainedO A finished mixture of the following compositon is pre_ -pared from this pulverulent rubber base mixture in a 200 litre Henschel type fluid mixer:
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Pul~er~ent rubber base nuxture 190 parts by weight Aromatic plasticiser oil (NAFTOL ~ )50 parts by weight Stearic acid ~ 5 parts by weight Zinc oxide 4.0 parts by weight ; Coumarone resin 2.5 parts by weight Sulphur 2.0 parts by weight VULKACIT~ CZ 1~0 part by weight W LKALENT~ B/C 0.5 part by weight At a speed of 650 revolutions per minute, the following nuxing se-quence results-pulverulent rubber base addition O to 5 seconds mixture plasticiser oil addition 5 to 1-05 seconds . . _ .
post_mixing 105 to 120 second sulphur ~ _ ; VULKACIT CZ addition 120 to 135 second zinc oxide stearic acid i - post-mixing --135 to 180 second~
_ _ _discharge after 180 secor.ds The batch weight is 40 kg and the temperature of the material being mixed is 50 to 55C.
The achievable hourly output with this mixing equipment is between 500 and 700 kg/hour, depending on the charging time This corresponds to the capacity of an internal mLxer of 50 litres chamber volume, working with solid ,, ; ..
3l rubber by the two-stage process , The resul~ing finished mixture is very free-flowing3 as before, and ~; is fed, in this form, directly to a ~pecial extruder to type "EVK 150" of Messrs. Werner ~ Pfleiderer. At a screw speed of 40 revolutions per minute, ~ a jacket t~mperature of 30C and a head temperature of 90C, 490 kg of ex-i 30 trudate in the form of a car tyre tread strip are obtained in 1 hour This ,!

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output corresponds to the results obtained on feeding ~his machine with mix_ tures of similar composition of the same rubber in bale form, ~ :
Testing the properties of the vulcanised product gives the follow-ing result: :
Comparison mix_ Mixture fro~ - -ture from solid pulverulent rubber in bale rubber base form mixture . Tensile strength (kp/cm~) 149 147 E~longation at brea~~~ 530 1 525 :
. . . . .-~odulus, 300~/o 74 70 Hardness (Shore A) 61 63 ~ : ~
Elasticity at 20C (~0) 32 33 :; . ;
. _ . . .. :, . .
Tyre test. Abrasion 100 102 index after l2,000 km . . r ~ ~' Example 2 (comparison example 1) Example 1 is repeated with only the following di~ferences: .-- .
, .
a) the entire amount of ISAF carbon black _ 90 parts by weight per 100 parts : ~:
by weight of rubber - is not 9birred~ in stepwise but is immediately stirred quantitatively into the emul9ion of the rubber solution; .
b) the batch is only neutralised after addition of the total amount of carbon black and af~er precipitating the rubber base mixture in a finely:particulate ;~ :
form.
The pulverulent rubber mixture according to Example 1 (process accor-ding to the invention) ha9 a markedly increa9ed bulk den9ity and better flow test values than the rubber mixture according to Example 2 (compare Table 1). - ..
Table l pubber base mixture ¦ Flow testX ¦ Bulk densit~
~ ', Examnle 2 -21-8- ~~~ 414 _, . . _ . .
The n ow test is carried out on the filled pulverulent rubber mix_ tures by the flow time method according to ASTM-D 1895-69. The times in sec-- 16 _ .. ... . . . . . . . . .. . . .. . .. . . . .. .

1~5'7~

snds for 100 g of the pulverulent rubber mixture to flow out of standardised funnels with an orifice angle o~ 40 and a lower orifice diameter o~ 10 mm are measured ~11 flow test values relate to this method of measur~ment Example 3 The rubber used is a polybutadiene obtained by adiabatic polymeri_ sation of butadien0 in the presence of n_butyl-lithium, in the form o~ its 12,4 per cent strength b~ weigh~ solution in hexane. The polybutadiene and its solution exhibit the following analytical data: ;~
Mooney viscosity (ML~ 74 Defo 1, 025/33 Gel content 2,5%
Content of trans-1,4 units 39%
Content of cis-1~4 units 2~o, Content of vinyl groups (1,2 units) 34%
Viscosity of the solution at 20C 885 cP
289 kg of this polybutadiene solution are emulsified by means of an emulsifying machine of the "Supraton 455 D" ~type in 281~5 kg o~ water in the presence of 0.867kg of a laur~lamine_polyglycol ether with 12 ethoxy groups.
me-pH ~alue is adjusted to 11,5 by addition of sodium h~droxide solution.
`;, 20 1,600 kg of a aqueous emulsion of the polybutadiene solution, pre_ ; pared in this way, are mixed with an aqueous suspension of 50 kg of ISAF car-bon black, ~orresponding to S0 parts by weight of carbon black per 100 parts ' by weight of polybutadiene, in 450 kg of water, with light stirring, Further-< more, 7 75 kg of a 26% strength aqueous sodium silicate solution (content of -~
SiO2 = 2 02 kg) are stirred into the stable mixture.

The stable, aquaous mixture of the emulsion of the rubber solution~
J
the carbon black dispersion and the sodium silicate solution is stirred into an aqueous precipitation bath which consists of a mixture, heated to about ` 90C, of 300 kg of water and 24,55 kg of 10% strength sulphuric acid Whilst - 30 the solvent, hexane, distils off, a rubber premix containing carbon black ~Irade Mark _ 17 ''''''' ;: ~, ................................................................... .
,, ~. .

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precipitates in a finely particulate form. During the precipitation process, the pH value of the aqueous phase is 1.8 to 2.3.
After completion of the precipitation p:rocess, 250 g of laurylamino-polyglycol ether are stirred into the aqueous suspension of the rubber premix containing carbon black, and the aqueous phase is ;adjusted to a pH value of ;~
6.5 by addition of sodium hydroxide solution. ; ;
A further 25 kg of ISAF carbon black, corresponding to 25 parts by ;;
weight of carbon black per 100 parts by weight of rubber, are stirred, in the ~ ~
form of a 10% strength aqueous suspension, into the aqueous suspension of ` ~ ;
:! 10 rubber premix and precipitated silica. The inished rubber base mixture is :~
separated from the water and dried with constant agitation. A pulverulent, -very free-flowing rubber base mixture containing carbon black is obtained. A `
finished mixture based on the following recipe is prepared, in a single pro-i cess step, from this pulverulent rubber base mixture in an internal mixture of the "GK 160"* type: -`
" Pulverulent rubber base mixture 190 parts by weight s~ Aromatic plasticiser oil (NAFTOLEN MV)* 50 parts by weight Stearic acid 2.5 parts by weight ' Zinc oxide 4.0 parts by weight Coumarone resin 2.5 parts by weight Sulphur 2.0 parts by weight VULKACIT CZ* ~ 1.0 part by weight ~ Using a rotor speed of 40 revolutions per minute and achamber tem-,`~ perature of 50C, mixing is carried out on the pattern of the "upside down" pro- ;
cess, that is to say all the constituents of the mixture are added immediately at the beginning of the process, in the sequence plasticiser, pulverulent rub- ;
ber base mixtures and chemicals. The material being mixed reaches a tempera~
ture of 105C after 45 seconds and is expelled, at this point in time, as a ~ compact finished mixture which is neither chalking nor crumbly. On subsequent ;
`~ 30 charging of the mixture onto a mill, a smooth hide which runs round perfectly *Trade Mark :

s JLUS'7~

is obtained, The mixture obtained i9 conver~ed to tyre tread strips in the usual way. The test results are as follows:
Comparison mdx_ Mixture from ture rom solid pulverulent :: rubber in bale rubber base . .
form mixture : :
_ _ ~ixing time of 1st stage 120 second~ . ~ :
: Discharge temperature 160C not applicable :
Energ~, kWhr/kg 0.13 .
,, , ..... . _ . ,. _ ~ _ _ :~ ~ixing time o~ 2nd stage 75 seconds 45 seconds Discharge temperature 110C 105C
Energ~, kWhrfkg 0.07 0.06 , -- -- - . . ~ _ . -- : ,:
rensile strength (kp/cm2) 149 148 ~:

. Elongatlon at break 530 550 ~ :

~odulus, 300% 74 70 ,, . _ ., , . lardness tShore A) 61 61 sstIcity~at 20C ~%) 32 31 ' ryre test, Abrasion index . : :~
20 after 12,000 hm 100 103 ;~
.:
As compared ~o ~he process technique with solid rubber, a reduction in the total mixing time and in the energ~ required, to less than 1/3, is achieved, whilst the end result is qualitatively the s~me, Example 4 ~comparison example 2) `:
Example 3 is repeated with only the following differences:
¦ a) the ISAF carbon black, 75 parts by weight-per 100 parts by weight of rubber, is not introduced stepwise but is immediately introduced quantitatively into `~the proce~s;
b) no silicate is added;
30 c) after precipitation of the rubber/carbon black mdxture, the batch is not :

. ,1 .
.
; - lg -., ~

. ~ ..

`- ~
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':
neutralised wîth sodium hydroxide solution.
The pulverulent rubber base mixture accordin~ to Example 3 ~process according to the invention) has a markedly higher bulk density and better flow test values than the mixture according to Example 4 (compare Table 2).
. :. .
Table 2 ~ `
Rubber base mixture sec. Bulk densit~
:', _ _ _ ~ _ _ _ ample 3 17.0 508 ; 10 ample 4 25.0 326 Example 5 ; ~
The rubber used is, as in Example 1, a polybutadiene, manufactured ~ ~
by adiabatic lithiwm polymerisation of butadiene, in the form of its 1205 per ~ `
cent strength by weight solution in hexane, the rubber having the following anal~tical data:
Mooney viscosity (ML4) 80 j Defo 1,150/34 Gel content ~ 2%
Content of trans_l,4 units 35%
Content of cis-1,4 units 26%
Content of virlyl groups (1,2 units) 39%
i Viscosit~ of the solution at 20C 1,020 cP
222.5-kg of this polybutadiene solution are emulsified by means of an emulsifying machine of the t'Supraton 455 D" type in 218 kg of water in the ~-~
presence of 1,334 kg of laurylamine_pol~glycol ether with 12 e~hoxy units and 445 kg of a sodium polyacrylate from Messrs R'dhm (product name "Plex 5367 ,:: ! :. :
;~j ~'~ The pH value is adjusted to 11.5 b~ addition of sodium hydroxide solu_ ,",,.~
tion.
~ 30 1,335 kg of an aqueous emulsion, prepared in this way, of ~he poly-`; butadiene solution are o~mbined with an aqueous dispersion of 50 kg of SRF
,, ,i , .
, . .
:
.,:-~
` -; _ 20_ ~:

i . .

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carbon black, corresponding to 60 parts b~ weight of ~arbon black per lO0 parts by weight of rubber, in 550 kg of water which contains O.S kg of laurylamine_ polyglycol ether with 12 ethoxy units and 0.226 kg o~ 10~ strength sodium hydroxide solution, with light stirring, to give a stable mixture Addition_ ally, 38.5 kg of a sodium water glass solution of which the content of sodium silicate corresponds to 10 kg of SiO2 are stirred into this mixture The stable and homogeneous mixture of the emulsion of the rubber solution, the carbon black dispersion and the sodium silicate solution is ;~ stirred into an aqueous precipitation bath which consists of a mixture~ heated to about 90C, of 300 kg of water and 1.5 kg of 10% strength sulphuric acid The pH value of the water is l.S. Whilst the solvent, hexane, distils off and i~
the rubber premix containing carbon black precipitates in a finely particulate form, a further 84.5 1 of l~/~ strength sulphuric acid are added continuously, I up to the end of the coagulation, as a result of which the pH value in the ; precipitation bath is kept at 1~7 to 2 0.
After completion o~ the precipitation process, the pH value of the aqueous suspension of the hexane_free, finely particulate, rubber premix con-taining carbon black is adjusted to 6.7 by addition of 28 25 1 of 10~ strength ;
sodium hydroxide solution. The temperature is 90C as before.
A further 25 kg o~ SRF carbon black, corresponding to 30 parts by w~ight of carbon black per lO0 parts by weight of rubber, are stirred, as a suspension in 225 kg o~ water, into the above aqueous suspension of finely particulate rubber premix containing carbon black and of precipitated silica.
The resulting finely particulate rubber base mixture is separated from the water and dried with constant agitation. A pulverulent, free_~lowing rubber base mixture lS obtained.
Example 6 (comparison example 3) Example 5 is repeated with the ~ollowing modifications:
a) the SRF carbon black, 90 parts by weight per lO0 parts by weight of poly_ butadiene, is immediately stirred quantitatively into the emulsion of the rubber solution, instead of being stirred in stepwise;
., ~
_ 21 ~

:, , ' : .

~57~383L ; ~:
b) no silicate is added;
c) only after the precipitation of the total rubber base mixture i.s the pH
value of the aqueous coagulate suspension adjusted to 6 5 by addition of sod_ ium hydroxide solution.
. The pulverulent rubber base mixture according to Example 5 (process ~:
according to the invention) has a substantially higher bulk densi~y and ex-hibits substantially better ~low properties than the mixture according to - Example 6 (compare Table 3).
: . Table 3 Rubber base m~xture j Flow test, sec. Bulk density, g/~ :~

: ~ ample 5 18.2 410 Example 6 40 P 221 :, .
il Example 7 1 The rubbers employed are polybutadiene and polyisoprene, manufactured :I by adiabatic lithium polymerisation, and are used in the ratio of 70 partæ by ~j weight of polybutadiene to 30 parts b~ weight of polyisoprene, in the form of ;' their 10 per cent strength by weight solutions in hexanes The rubbers exhibit .

"! 20 the~following analytical data: :

Polybutadiene:

Moo~ey viscosity (ML~) 80 Defo 82S/30 Gel content < ~%

Content of trans-1,4 units 3S%

Content o~ cis_1,4 units 26%

Content of vin~l groups (1,2 units) 39%
;.:. . ~ .
Polyisoprene:

Mooney viscosity (ML4) 60 :.' 30 Defo 2,500/31 ~' .
The product only flows after tapping the test cup ~ _ 22 -;'' :,, : .

Gel content 2%
Content of cis-1,4 units 90%
Content of 3,4 units 10%
120 kg of the polyisoprene solution are dispersed with the aid of an emulsifying machine of the "Supraton 455 Dl' type in 112 kg of water, at a pH value of 11.5, in the presence of 0.72 kg of laurylamine-polyglycol ether with 12 ethoxy units, 0.048 kg of a sodium polyacr~late of Messrs Rohm ~pro- ~ ;
; duct name "Plex 5367 Ftt) and 0.06 kg of a methylcellulose of Messrs. Wolff ;- Walsrode AG (tradename 'tMC 20,000 Stt~ . The pH value is adjusted b~ adding sodium hydroxide solution.
,; ~ .
In a separate batch, 280 kg of the polybutadiene solution are dis-persed with the aid of an emulsifying machine of the "Supraton 455 D" type in .:
water, at a pH value of 11.5, in the presence of 1.68 kg of laurylamine-poly_ glycol ether with 12 ethoxy units, 0 056 kg of a sodium polyacrylate of ~essrs, Rohm (product name "Plex 5367 F") and 0.14 kg of a methylcellulose of Messrs Wolff Walsrode AG (tradename 'tMC 20,000 S"), The pH value is adjusted by ;
adding sodium hydroxide solution. ~`
The aqueous sta~le emulsion of the polybutadiene solution is com- ;
bined with the aqueous stable emulsion of the polyisoprene solution to give a stable and ho~ogeneous mixture 18.5 kg of a 26% strength aqueous sodium sil~
icate solution and 240 kg of an aqueous dispersion of 12 kg of FEF carbon .
black, corresponding to 30 parts b~ weight of carbon black per 100 parts by weight of total rubber, in 227 kg of water which contains 0.12 kg of laury-lamine-polygl~col ether with 12 ethoxy units, are stirred successively into -~
the abo~e mixture .: ;
The stable and honogeneous aqueous mixture of the emulsions of the ~` rubber solutions, of the sodium waterglass solution and of the car~on black ~
dispersion is s~t~rred into an aqueous precipitation bath which consists ~f ~ `
; a mixture, heated to 90C, of 500 kg of water and 40 kg of a 10% strength sul_ ": 30 phuric acid Whilst the hexane distils off, the rubber premix con~aining Trade Mark 1 ~ 23 _ .,, :, ' : j lV571~l8~ ~ ~

carbon black precipitates in a finel~ particulate form (lst Ytage) After complete removal of hexane by degassing, the pH value of the aqueous suspension of the premix is adjusted to 6 7 by adding sodium hydroxide solution (2nd stage).
A further 8 kg o~ FEF carbon black, corresponding to 20 parts by weight of carbon black per 100 parts b~ weight o~ rubber, are stirred, as a , suspension in 160 kg of water, into the above aqueous suspen~ion of finely -particulate rubber premix containing carbon black and of silica (3rd stage) ,, e finel~ particulate rubber base mixture thus obtained is se~a-rated from the water and is then dried with constant agitation. A pulverulent free_flowing rubber base mixture is obtained. - ;
' Example 8 (comparison example 4) Example 7 is repeated with the following modification:
a) the FEF carbon black, 50 parts by weight per lO0 parts by weight of total .1 ,, ;1 rubber, is not stirred in stepwise as in Example 7, but is immediatel~ stirred quantitatively into the emulsion mixture of the two rubber solutions; ~ ;~
b) only after the precipitation of the entire rubber base mixture is the pH
.; :
i value of the aqueous suspension of the precipitated-material adiusted to 6.5 ~
. . , - , , :~ ~ by adding sodium hydroxide solution The pulverulent rubber base mi~ture according to Example 7 (process according to the invention)~has an-unambiguousl~ higher bulk density and shows substantially better flow properties than the pul~erulent mixture according to Example 8 (compare Table 4).
Table 4 ~ ;
Rubber base mixture Flow test, sec. Bulk density, g/:
.,j : :- _ , , , ~i~ I ample 7 ll.0 4~6 i ~ample 8 j28`2X 324 `~
~ :, ~ ~ The product onl~ flows after tapping the test cup.
.~`~ , , ''~

~1 - 24 _ `:

., :
:

7~

Ex~nple 9 The rubber employed is a copolymer of bu~adiene with styrene (SBR ~ .
1,500), manufactured b~ emulsion polymerisation, in the form of its aqueous latex The rubber and its latex exhibit the following data: .
Mooney viscosity (ML4) 50 Defo 750/32 Gel content 2% ~ ;
Styrene content 23 S%
Content of trans-1,2 units 20%
Content of trans d,4 units 72%
, ~
Solids content of the latex 23.5% :~
Emulsifier (alkali met~l salt of : :
.:1 a resin acid: DRESINATE 731~) . 320 kg of a 7.5% strength aqueous ISAF carbon black dispersion ~30 l parts by weight of carbon black per 100 parts by weight of rubber) are stirred - into 340 kg o~ this S~R latex me carbon black dispersion i9 prepared fr~m ::~ 295 kg of water, 24 kg of ISAF carbon black, 0 88 kg o~ a laurylamine_poly_ .~ glycol ether with 10 ethoxy units and 0.12 kg of a high molecular methylcel_ .
.. - 20 lulose (tradename '~C 20,000 S") On stirring well, a homogeneous and stable . latex/carbon.black mixture is obtained. .~ :
~ This homogeneous mixture is introduced, with vigorous stirring, into .. ~.;
I an aqueous precipitation bath, warmed to about 60 to 95C, which has been made up from 31 kg of 20% strength sodiwm silicate solution, 70 kg of 10% :~:
.~ strength sulphuric acid and 399 kg of water; the rubber premix hereupon pre-cipitates ~ls~ stage).
In the second stage, the aqueous suspension of ~he rubber premix is ~I neutralised ~ Thereafter the residual amount of carbon black (16 kg, corresponding .~ 30 to 20 parts by weight, relati~e to 100 parts hy weight o~ rubber) is stirred, ~ Trade Mark .:, , . - 25 _ :' ' r~
~5'7~

as a 5% strength aqueous suspension which is prepared without addition of dispersing agents, into the suspension consisting of rubber premix and silica (3rd stage).
A rubber base mixture is obtained, and is separated ~rom the water and dried with constant agitation to give a free_flowqng powder.
The bulk density is 505 g/l and the flow time is 17.0 seconds.

m e rubber employed is a copolymer of butadiene and styrene (base polymer for SBR 17~2), manufactured by emulsion polymerisation, in the fonm of its aqueous latex. The ru~ber and its latex exhibit the following data:
Mooney viscosity 116 Defo 1,750/45 -Gel content 2%
$tyrene content 23.S%
Content of trans-1,2 units 20%
Content of trans-lj4 units 72%
Content of 1,4 units 8%
Solids content of the latex 24.6%
Emulsifier (mixture of alkali metal salts of resin acids and fatty acids) 467 kg of a 7.5% strength aqueous carbon black dispersion, corres_ ponding to 50 parts by w~ight of carbon black per 100 parts by weight of rub_ ber, are stirred into 285 kg of this SBR latex, The carbon black dispersion is prepared from 488 kg of water, 45 kg of ISAF carbon black, 0.90 kg of laurylamine-polyglycol ether with 12 ethox~ units and 0.2 kg of a high mole-cular sodium polyacr~late of Messrs Rohm (product name ~Plex 5367 F"). A
stable homogeneous mLxture is prepared fr~m the latex and carbon black dis-:
persion and is introduced, whilst stirring3 into an aqueous precipitation bath wa~med to about 60 t~ 95C The precipitation bath consis~s of 400 kg - 26 _ 78~ :
~; of water, 60 kg of 10% strength sulphuric acid and 26,9 kg of 26% strength sodium silicate solution. The rubber premix precipitates in a ~inely partic-ulate form (lst stage).
In the 2nd stage, the suspension of the premix is neutrali~ed with the aid of 10% strength sodium hydroxide solution, ~ -` Thereafter the remaining ISAF carbon black, amounting to 14 kg (20 parts by weight of carbon black per 100 parts by weight of rubber) are stir-red, as a 5% strength suspension in water, which i9 prepared without addition -of emulsifiers or;~surface-active substances, into the aqueous suspension con- ~ ;
sisting of rubber premix and precipitated silica ~3rd stage), After separating off the water, and drying with constant agltation, ;"~
a pulverulent free-~lowing rubber base mixture is obtained, The bulk density is 48~ g~ and the flow time was measured to be 18,2 seconds.

~. ~ .,'''~' ffle rubber employed is a copolymer of ethylene, propylene and ethyl_ j idenenorbornene in the fonm of its 10~ strength solution in hexane, The rub_ ~1 ber exhibits the following data~

`~ Mooney viscosity ~ML4) 110 , 20 Defo 1,275/30 'I Gel content 2%

, Number of double bonds 8/1,000 C ato~s Ter_component Ethylidenenorbornene Propylene content 45%

400 kg of this rubber solution are dispersed with the aid of an ! emulsi~ying machine of the "Supraton 455 D" type in 380 kg of ~ater at a pH

value of ll,5, in the presence of 2,397 kg of potassium oleate~ 0,16 kg o~ a ~, polyacrylate o~ Messrs, Rohm (product name "Plex 5367 F'l) and 0.32 kg of a ? high molecular meth~lcellulose of Messrs, Wolff Walsrode AG (tradename 'sMC

20,000 ~"), The p~ value is adjusted by adding sodium hydroxide solution, . ', _ 27 - ~ ~

: :
.. ~:

.. ,' - . !,.. . . . . ... . . . .. ... . .

'739~3~
15.44 kg of 26% strength aqueous sodium silicate solution and 240 kg of an aqueous carbon black suspension which contains 13 kg of FEF carbon black - corresponding to 30 parts by weight per 100 parts by weight of rubber_ are introduced into the aqueous stable emulsion o~ the rubber solution. The stable mixture is introduced into an aqueous precipitation bath which con-sists of a mixture, heated to about 90C, of 478 Icg of water and 22 kg of 10%
strength sulphuric acid Whilst the hexane disti]Ls off, the rubber premix containing carbon black precipitates in ~ finely particulate form (lst stage), After removing the hexane b~ degassing, 400 g of laurylamine-pol~-glycol ether are stirred in-and the pH value of the aqueous suspen!sion of the premix is adjusted to 6.7 at 80 to 90C by addition of sodium hy~roxide sol-ution (2nd stage).
After having changed the pH value, a ~urther 7 kg of FEF carbon black, corresponding to 20 parts by weight of carbon black per 100 parts by ) weight of rubber, are stirred in as suspension in 150 kg ~f water t3rd stage).
.,1 The precipitated finely particulate rubber base mixture is sepa_ rated from the water and is then dried with constant agitation, A pulveru-lent, free_flo~ing rubber base mixture is obtained. ~ ~.
Example 12 ~comparison example 5) Example 11 is repeated with the following modifications:
; a) the FEF carbon black, totalling 50 parts b~ weight per 100 parts by weight of rubber, is not stirred in stepwise as in Example 11, but is immed_ iately stirred quantitatively into the aqueous emulsion of the rubber sol_ . ution;
b) only after precipitation of the rubber base mixture containing the total amount of carbon black is the pH value of the aqueous suspension of the pre_ cipitated material adju3ted to 6.6 b~ addition of sodium hydroxide solution ; The pulverulent rubber base mixture according to Example 11 (pro-cess according to the inve~tion) has a higher bulk density and better flow properties than the pulverulent base mixture according to Example 12 (com-- 28 _ .'`'~' -~, :
., , ' !
-:

~ 5~7~
pare Table 5). .;
Table 5 Rubber base mixture Flow test, sec. Bulk density, g/1 Example 11 22 6 347 ~:
_ _ ; Example 12 27 6X 298 - ~ ~ ,.
~The product only ~lows after tapping the test cup. `
Example 13 The rubber employed is a polybutadiene, obtained by adiabatic poly-merisation of butadiene in the presence of n-but~l-lithiwm, in the form of its 12 4% strength solution in hexane The rubber exhibits the following analytical data~
; Mooney viscosity (ML4) 74 : Defo 1,025/33 ~:
Content of trans-1,4 units 39%
l Content of cis~1,4 units 27% ~ `
:. Content of vinyl groups (1,2 units) 34% ~ ~ .
~ Viscosit~ of the solution at 20C 885 cP
-. 20 289 kg of this polybutadiene solution are dispersed, with the aid of an emulsifying machina of the "Supraton 455 D" type, in 285 kg of water in the presence of 0 866 kg of cetyltrimethylammonium chloride. The ~H.value of the emulsion is adjusted to 3.5. :
500 kg of a dispersion of 50 kg of highl~ active ~llica from Messrs.
. Degussa (tradename '~ltrasil YN 31t~ _ corresponding to 47 parts by weight of silica per 100 parts by weight of rubber _ in water containing 0~5 kg of :~ cet~l_trimethylammonium chloride, are st~rred into the stable ~mulsion of the ~. rubber solution~
.; .
The stable and homogeneous mixture of the aqueous emulsion of the rubber solution and the aqueous dispersion of the silica i9 stirred into an `:
aqueous precipitation bath which consists of a mixture, heatecl to a~out goa, '; .
~. Trade Mark .
- 29 - ~ :
.. ~
,' : ' -~357~
of 300 kg of water and 15 kg of 26% strength sodium silicate solu~ion (SiO2 content = 3.9 kg~. Whilst the hexane distils off, the rubber premix contain-ing silica precipitates in a finely particulate fo~m (lst stage) After removing the hexane by de~assing, t:he pH value of the aqueous suspension of the rubber premix is adjusted to 6 8 (2nd stage).
W~ilst stirring, a further 250 kg o~ a silica susp~nsion, which consists of 225 kg of water and 25 kg of "Ultrasil VN 3", corresponding to 23iparts by weîght of silica per 100 parts by weight of rubber, are added (3rd stage)~
The light~coloured rubber base mixture thus obtained is separated from the water and then dried with constant agitation A pulverulent, free_ flowing rubber base mixture is obtained ~xample 14 (comparison example 6) Example 13 is repeated with ~he following modifications:
a) the silica, 70 parts b~ weight per 100 parts by weight of rubber, is not stirred in stepwise, as in Example 16, but i ediately stirred ~uantitatively into the aqueous emulsion of the rubber solution;
b) no silicate is added;

~ , ~ c) only after precipitation of the rubber base mixture containing all the . ,~. , silica is the pH value of the aqueous suspension of the precipitated material adju~ted to 6,8, The pulverulent, light-coloured rubber base mixture according to Example 13 (process according to the inventiQn) has a higher bulk density and 1 better flow properties than the base mixture according to Example 14 (compare i~ Table 6) ., Table 6 Rubber base mixtuxe ~low test, sec Bulk densit~, g/l ,''', ' ._ , ..
1 Example 13 1? 8 455 '''`",`, '' . , :~ Example 14 25 0 386 . . ~.
., , ,.' ., :: :, - . : : : ~ , , ~ st7~
Exam~le 15 : .
a~ The rubber ~mployed i9 a polybutadiene, obtained by adiabatic polymeri_ sation of butadiene in the presence of n_but~l_lithium, in the form of its lO~o strength solution in hexane The rubber exhibits the following analytical data:
Mooney ~iscosity (ML4) 78 Defo 755/31 Gel content ~ 2~ - ;
Content of trans_l,4 units 41%
~ .
Content of ci9_1,4 units 25%
Content of vinyl groups (1,2 units) 34%
b) Inter alia, an HAF carbon black containing plasticiser oil is used as the ~;~
filler. It is prepared as follows:
A Henschel mixer o~ 30 1 capacit~ is filled with 3 kg of HAF carbon black at 20 to 50C wall temperature. After starting up the rotor at a speed of 1,600 revolutions per minute, 1.764 kg of plasticiser oil ~tradename "Naft- ;olen MV"), which beforehand is wa~med to 60 - 80C, is sprayed into the mixer, ;., .
;~ over the course of 3 minutes, in a finely divided form, through an inlet or-ifice provided with fine bores After completion of the addition of the plas_ ~ ;
ticiser oil, the rotor is allowed to run for a further 2 minutes to complete the distribution. After a total mixing time of 5 minutes the carbon black~
` plasticiser oil mixture is present in the dust_like state of divi~ion intrin-sic to the carbon black, without impairnent of the free_flowing character and .."
~ without any tendency to cake together .: .
-,:!, C) To prepare an aqueous dispersion of the HAF carbon blac~, containing plas_ - ticiser oil, described above, 50,4 kg ~fian ~F carbon black containing plasti_ ciser oil are dispersed, with the aid of an emulsifying machine of the "Sup_ raton 455 Dt' type, over the course of 30 minutes in 200,5 kg of water which .. ,, ~ ~ .
contains 1.5 kg of laurylamine-polyglycol ether with 12 ethoxy units and 1 kg of lO~o strength sodium hydroxide solutio~. A 20~ strength stable dispersion, .,;.. ~ ~
containing plasticiser oil, of carbon black in water is obtained.
- 31 _ ~ -'', .
. . ~
' . ' 1~'7i~

d) The rubber solution described under a) is converted to a stable aqueous emulsion as follows:
372,5 kg of the polybutadiene solution described ~der a~ are emul_ sified, with the aid of a "Supraton 455 D~' emulsif~ing machine, in 370 kg of water in the presence of 2.235 kg of laurylamine-polyglycol ehter with 12 ethoxy groups. The pH value is adjusted to 11,5 b~ adding sodium hydroxide solution. A mobile stable emulsion is obtained.
e) The stable aqueous emulsion of the rubber solution, prepared according to d) (744.7 kg) is mixed, with simple stirring, with 150 kg of the aqueous dis_ persion, obtained according to c), of the HAF carbon black containing plasti_ ciser oil. The mixture contains 50 parts by weight of carbon black and 30 parts by weight of plasticiser oil per 100 parts by weight of rubber. Addi_ tionally, 7.75 kg of a 26~ strength sodium silicate solution, of which the SiO2 content is 2.02 kg, are stirred into th~s stable and homogeneous mixture, ~ The stable, aqueous mixture of the ~mulsion of the rubber solution, of the dispersion of the carbon black containing plasticiser oil, and of the sodium silicate, is stirred into an aqueous precipitation bath which is at a temperature of about 90C and contains su~ficient sulphuric acid that the pH
value i9 between 1.5 and 2Ø Whilst the solvent, hexane, distils off, the rubber premix containing plasticiser oll and carbon ~lack precipitates in a finely particulate ~orm. The pH value of the aqueous phase is kept at between 1,5 and 2.5 during the entire precipitation process (lst stage).
After co~pletion of the precipitation of the premix the pH value is adjus~ed to 6,5-7.0, at the precipitation temperature of 90C, by addition of sodium hydroxide solutîon. The silica introduced into the batch through the ~ silicate solution now condenses to give water_insoluble silica (2nd stage).
I A suspension of 11.2 kg of HAF carbon bIack in 120 kg of water is .` introduced into ~he aqueous suspension of the rubber premix, con~aining plas_ ticiser oil and carbon black, and of the precipitated silica (3rd stage), Thereafter~ the finished rubber base mixture is separated from the _ 32 -' ., :........... .~ . .

~;

:~VS'7~
water and dried ~ith constant agitation. A pu~ erulent, very free~flowing rubber base mixture containing plasticiser oil and carbon black is obtained.
Example 16 ~comparison example 7) Example 15 is repeated with only the following modifications:
a) the HAF carbon black, totalling 80 parts by weight per 100 parts b~ weight of rubber, is introduced into the emulsion of the rubber solution not in 2 portions but immediately quantitatively. For this, the procedure followed is that the carbon black containing plasticiser oil and the carbon black free from plasticiser oil are conjointly dispersed in water.
b) no silicate is added;
c) the neutralisation is onl~ effected after precipitating the entire rubber base mixture The pulverulent rubber base mixture, containing plasticiser oil and carbon black, according to Example 15 (process according to the invention) has higher bulk densities and better Mow properties than the powder mixture ac_ cording to Example 16 (compare Table 7).
Table 7 .,':, :
Rubber base mixture Flow test, sec.! Bulk density, g/]
.~ . . . _ ~
Example 15 31.6 480 Example 16 product only 370 flows inter-; mittently after l tapping the test ;~ apparatus . 1 __ ~ ~ _ Example 17 ~;
~i The rubber used is a copolymer manufactured by solution polymeri_ `
sation of butadiene and styrene in the presence of n_but~l_lithium as the catalyst9 in the form of a 20% strength solution in hexane The copolymer ~ exhibits the following analytical data: -: ' ;`'', ' ., ~ _ 33 _ . ' .
, . ~ , . . :

-~o~

Mooney viscosity (ML4) 76 Styrene content 20 Butadiene content 80 Gel content 2%
Trans-1,4 units 37%
Cis_1~4 units 34%
: Vinyl groups (1,2 units) 9%
Block styrene content 3.2%
Solution viscosity 22,000 cP
200 kg of this rubber solution are emulsified, with the aid of an emulsifying machine of the "Supraton 455 D" type, in 225 kg of water in the presence of 2.4 kg of a laurylamine_polyglycol ether with 12 ethoxy units~
0.16 kg of a sodium polyacrylate of Messrs, Rohm (product name "Plex S367 ~') and 0,32 kg of a methylcellulose of Messrs, Wolff Walsrode AG (tradename "MC
20,000 S"~ The pH value is adjusted to 11,5 by adding sodium hydroxide sol_ :~
ution This stable aqueous emulsion of the rubber solution is mixed, with simple stirring, with 400 kg of an ISAF carbon black suspension which con-sists of 20 kg of ISAF carbon black, corresponding to 50 parts by weigh~ of , 20 carbon black per 100 parts by weight of rubber, and 3~0 kg of water, :~
me stable and homogeneous aqueous mixture of the emulsion-of the rubber solution and of the carbon black suspension is stirred into an a~ueous precipitation bath which consists of a mixture of 250 kg of water, 34 kg of 10% strength sulphuric acid and 800 g of 26% strength sodium silicate sol_ ukion. Whilst the solvent, hexane~ distils off, the rubber premix containing :,.. ` .
carbon black precipi~ates in a finely particulate form, The pH value of the :~ ;
! a~ueous phase is kept at between 1.5 and 2.5 during the precipita~ion process ; (lst stage).
. . .
After completion of the precipitation process and after driving off the hex_ ane, the pH ~alue of the aqueous phase is adjusted to 6,5-? b~ addition of : ' -~ .

~L~3 sodium hydroxide solution (2nd stage).
A further 280 kg of an aqueous ISAF carbon black suspension~ whichcontains 14 kg of IS~F carbon black, corresponding to 35 parts by weight of carbon black per lO0 parts by weight of rubber, i9 now added to the aqueous ; suspension of the rubber premix containing carbon black (3rd stage).
The rubber base mixture which is finished after this process step is separated from the water and dried with constant agitation. The rubber base mixture is obtained as a free-flowing powder.
ample 18 (comparison example 8) 10Example 17 is repeated with the following modificatlons:
a) the entire ISAF carbon black~ 85 parts b~ weight per lO0 parts by weight of rubber, is stirred quantitatively, without fractionation, into the aqueous emulsion of the rubber solution, before neutralisation and before precipita_ tion;
b) no silicate is added.
The pulverulent rubber base mixture according to Example 17 (process according ~o the invention) has a markedly increased buIk density and better flow test values than the mQxture according to ~xample 18 (compare Table 8). ~ ;
Table 8 Rubber base mLxture Flow test, sec, Bulk densit~, g/l '~1 ample 17 21.2 405 ample 18 28.4 310 ~'' ' , ample l9 The rubber used is a polyoctenamer obtained b~ ringopening polyner_ , isation (methathesis reaction) of c~clooctene, in the ~orm o~ a 36% strength solution in hexane The poly~er exhibits the following analytical data:

Gel Content < l~

Content of trans-units 65%
,'~ ..
' ' :
'~
:::

rJ~'~ , , _ _ ~ i713~
Content of cis-units 35%
Viscosity tRSV) 1.5 Viscosity of the solution approx 2S,000 cP
150 kg of this polyoctenamer solution are emulsified, with the aid of an emulsifying machine of the "Supraton 455 D" type, in 148.35 kg of water in the presence of 0.9 kg of laurylamine-polyglycol ether, 0,375 kg of a sod_ ium polyacr~late of Messrs. Rohm (product name 'tPlex 5367 1~') and 0.375 kg of a high molecular meth~lcellulose of Messrs. Wolff Walsrode AG (tradename '~C
20,000 S"). The pH ~alue is adjusted to 11.5 b~ additon of sodium hydroxide ; 10 solution.
1,2001kg of such an aqueous emulsion of the polyoctenamer solution, which contains 216 kg of rubber, are mixed with 1081.08 kg of an aqueous HAF
carbon black dispersion, which contains 108 kg of HAF carbon black and 1,08 kg of laurylamine-polyglycol ether, corresponding to S0 parts by weight of carbon black per 100 parts by weight of polyoctenamer, whilst stirring Ad_ -ditionall~, 20 kg of a 26% strength sodium silicate solution (SiO2 content ~ S.2 kg = 2.4 per cent by weight, relative to rubber) are stirred into the i stable mixture. ;

The stable and homogeneous aqueous mixture of the ~mulsion of the polyoctenamer solution, of the carbon black dispersion and of the sodium sil_ icate solution, is stirred into an aqueous precipitation bath, heated to 90C, of which the pH value is~constantl~ kept at between 1.5 and 2,5 with the aid ~`i o~ sulphuric acid. ~hilst the solvent, hexane, distils of~, the rubber pre_ mix containing carbon black precipitates in a finely particulate form (lst s~age).
.. ~: ~j ; ' . ;
~ After completion-of the precipitation process, the pH value of the .~
~1 aqueous precipitation bath is adjusted to 7.0 by addition of sodium hydroxide ~- 1 .
`l solu~ion (2nd stage) A further 20 parts by weight of carbon black per 100 parts b~ weight of polyoctenamer, in the form of 432 kg of an aqueous HAF carbon black suspen-sion which contains 43 2 kg of HAF carbon black, are stirred into the aqueous _ 36 _ `: : :

~ ~3S7~

suspension of finely particula-te rubber premix and precipitated silica ~3rd stage).
Thereafter, the finished rubber base mixture is separated from the water and dried with constant agitation. A pulveru:Lent~ very free-flowing rubber base mixture is obtained.
Example 20 ~comparison example 9) Example 19 is repeated with the following modifications:
a) the 70 parts total llAF carbon black are stirred quantitatively into the emulsion of the rubber solution;
b) the batch is only neutralised after quantitative precipitation of the rub~
ber base mixture containing the entire carbon black.
` The pulverulent rubber base mixture according to Example 19 ~pro-cess according to the invention) not only has a higher bulk density than the ~ ~
product according to Example 20, but also has markedly improved flow proper- ; i ties Ccompare Table 9). ;
Table 9 . .
., ~ .
~ Rubber base mixture Flow test, sec. Bulk density, g/l ,.~.
Example 19 15.8 465 2Q Example 20does not flow uni- `
formly, but inter-mittently. Times not reproducible.
. ~ . _ _ ~ Example 21 -~
.'.f ' The rubber used is a cis-1,4-polybutadiene manufactured by Ziegler polymerisation of butadiene in benzene ~tradename "BUNA~ CB 10") in the form of its 12% strength solution in hexane obtained after polymerisation. The -cis-1,4-polybutadiene exhibits the following analyticsl data~
Moone,y viscosity (ML4) 47 ~ ~
-; Defo 700/36 ~ ~ -~ 37 -, ... .

~s~
Gel content ~ 2%
Content of ci~-1,4 ~mits 97%
Content of trans_l,4 units 2%
Content of 1,2 units 1%
Viscosit~ of the solution 2,500 cP
200 kg of this polybutadiene solution are ~mulsified, with the aid of an emulsifying machine of the t'Supraton 455 Dtt type, in 198 kg of water which contains 1.2 kg of potassium oleate and 0.8 kg of a sodium polyacrylate of Messrs. Rohm (product name "Plex 5367 ~'). The pH value of the emulsion is adjusted to 11.5 by adding sodium hydroxide solution. me emulsion is stable andlis miscible with water in all proportions.
200 kg of this stable aqueous emulsion of the cis_l,4-polybutadiene solution are mixed, by simple stirring, with 292.2 kg of an aqueous ISAF car_ bon black dispersion which is prepared by dispersing 1S,6 kg of ISAF carbon black in 294.3 kg of water in the presence of 0.465 kg of laurylamine_poly_ glycol ether, 0,0?83 kg of sodium polyacrylate of Messrs, Rohm (product name "Plex 536~ Ft') and 0.0?83 kg of meth~lcellulose of Messrs Wolff Walsrode AG
(tradename '~C 20,000 S").
., ~
The mixture of emulsion and carbon black dispersion, which contains 65 parts by weight of carbon black per 100 parts by weight of rubber, is stir_ red into an aqueous precipitation bath which consists of a mixture, heated to 90C, of 137.3 kg of water, 20 kg of 10% strength sulphuric acid and 9.23 kg of a 26% strength silicate solution Whilst the solvent, ben~ene, distils off, the rubber premix precipitates in a finely particulate fo~m (lst stage) .. . .
After completion of precipitation of ~he rubber pr~mix, its acid aqueous suspansion is adjusted to a pH value of 6.9 by adding sodium hydroxide solution (2nd stage) After the neutralisation, a further 96 kg of a 5% stren~th ISAF car-bon black suspension, corresponding to 20 parts b~ weight of carbcn black per 100 parts by weight of rubber, are stirred into the batch ~3rd stage).
' . .
' : . . . : -. ~ . . .

i~S7~
The resulting, very finely particulate rubber base mixture i9 sep-arated from the water by decanting and i9 dried in a disc drier ~ith constant agitation A pulverulent~ ~ree_flowing cis_l,4-polybutadiene base mixture is obtained The bulk density is 417 g/l. The flow speed was measured to be ;~
18.4 seconds. `
_xample 22 ;~
The rubber employed is an emulsion polymer of butadiene and styrene, : ;
, in the form of its aqueous latex. The rubber, and its latex, exhibit the - following data~

Mooney viscosity (M~4) 116 Defo 1,750/45 Gel content 2%

S~cyrene content 23 5%

Content of trans_1,2 units 20%
ii :,:, Content of trans-1,4 units 72%

Content of cis_l,4 unit9 8%

Solids content of the latex 24.6%

Emulsifier ~mixture of alkali metil salts of resin acids and ~20 fatty acids).

?00 kg of an aqueous carbon black dispersion which consists of 640,5 ., : .
kg of-water, 35 kg of ISAF carbon black ~50 pphr), 7 kg of a 10% strength laurylamine-pol~glycol ether solution and 17.5 kg of a 1% strength sodium -1 pol~acrylate solution are stirred into 280 kg of a 25% strength SRB latex of ~ -~' ~ the abo~e quality. A stable homogeneous mixture is prepared from the SBR
latex and carbon black dispersion and is introduced, whilst stirring, into an aqueous precipitation bath warmed to about 80-95C. The precipitation bath consists of ga8 kg of water, 45 kg of 10% strength sulphuric acid and 13,5 kg of 26~ strength sodium silicate solution ~5 pphr of SiO2). The rubber premix precipita~es in a finely particulate form (lst stage).

_ 39 _ :, ,'' ,' ' .
: ~ ~

-10~7~

In the 2nd stage, ~he aqueous suspension of the premix is neutral-ised ~ith lG% strength sodium hydroxide solution (pH 6.8) and 9 7 kg of a 10% strength al~ solution (alum = K2A12(S04)4 x 24M20) are then stirred in. ~:
In the 3rd stage, 280 kg of a 5% strength aqueous ISAF carbon black suspension (corresponding to 20 pphr of ISAF carbon black) are stirred into the aqueous suspension of finely particulate rubber premix and alu~ini~n silicate Thereafter~ the finished rubber base mixture is separated from the water and dried with constant agitation A pul~erulent, free_flowing SBR .
; 10 base mixture is obtained, the bulk density of which is 487 g/l. The flow .:
test ga~e a value o~ 14 2 sec E~mple 23 : The rubber employed is a cis-1,4-polyis4prene obtained by ~iegler polymerisation, in the form of its solution in hexane, The rubber, and its solution~ exhibit the following data~
Mooney.viscosity (ML4) 76 Defo 1,260/25 .
. ;f Gel content 21% .

Content of cis 1,4 units 96% .

Conten~ of 3,4 units 3%

~, Solven~ hexane Solids content of the solu~ion 9%

Viscosit~ of the solu~ion 1,400 cP

700 kg of this 9% strength cis-1,4-polyisoprene solution are dis_ persed, with ~he aid of an emulsifying machine, in 695 kg of water, at a pH

~alue of 11.5, in the presence of 4.2 kg of laurylamine-polyglycol ether~

0 28 kg of sodium polyacrylate of Messrs Rohm (product name "Plex 5367 ~

and 0 56 kg of a methylcellulose of Messrs.~oa~e.`AG (tradename ~MC 20,000 S"). ~:

12 1 kg of a 26% strength soditmn silicate solution ~SiO~ content = S pphr) ~ .

and 629 65 kg of an aqueous carbon black dispersion which contains 31 5 kg ~: :
'~'1 ' ' ' .~...................................................................... ~ .
' .

~ s~s~ ~

of ISAF carbon black ~corresponding to 50 pphr) and 3.1S kg of laurylAmine_ polyglycol ether, are stirred into the stable emulsion of the rubber solu_ tion.
The resulting stable mixture i9 introduced into an aqueous precip-itation bath which consists of a mixture, heated to 70-80C, of 465 kg of water and 35.2 kg of 10% strength sulphuric acid. Whilst the hexane distils , -off, the rubber premix containing carbon black precipitates in a finel~ par- -; ticulate form (lst stage), ~ The pH value of the aqueous suspension of the premix i9 adjusted :, to 6 5 by adding sodium hydroxide solution Thereafter, 167 kg of a 10%
strength aqueous solution of aluminium sulphate (A12~S0~)3 x 18~20) are stir-red in. The temperature is 80 to 90 C (2nd stage) In the 3rd stage, 2S2 kg of a 5% strength ISAF carbon k~ack suspen-sion (20 pphr of carbon black) are stirred in at about 90 to 95C.
The pulverulent rubber base mixture, of unusual fineness, which is ~ ;
present after the 3_stage precipitation process, is separated from the water ;~
and dried with constant agitation. A pulverulent, free-flowing ci3_1,4_pol~
~ isoprene base mixture i9 obtained. The flow test gives a value of 24,8 sec-;~ onds The bulk density i9 300 g/l.
' 20 Example 24 The rubber~employed i9 an EPDM grade which can be characterised by the following data:
" '~:
Mooney viscosity 88 Defo 1,225/37 Gel content < 2%

Ter-component ethylidenenorbornene C=C/l,OO~ C 131 4 Propylene content 48%

Ethylene content 52%

Solven~ hexane ., , ~ :
- 41 _ .
,: ` .

:l~S~

Solids content of the solution 10%
Viscosit~ of the solution 460 cP
; 600 kg of this EPDM solution are converted into a stable aqueous emulsion in an emulsifying machine, with the aid of 600 kg of water, 3.6 kg ; of laurylamine-polyglycol ether and 0.24 kg of sodium polracrylate of Messrs.
Rohm (product name "Plex 5367 ~'). The pH value of the emulsion is ll S
ll.S kg of a 26% strength sodium silicate solution (5~pphr of SiO2) and 840.2 kg of an aqueous FEF carbon black dispersion, which is prepared from 794 kg of water, 42 kg of FEP carbon black and 4.2 kg of a 10% strength laur~_ lamine_polyglycol ether solution, are stirred into this emulsion, The stable and homogeneous mixture of rubber em~lsion and carbon black dispersion is stirred into a precipitation bath which consists o~ a mixture of 464 kg of water and 36 kg of 10% strength sulphuric acid. The temperature of the precipitation bath is between 75 and 85C, Whilst the rubber premix precipitates in an unusuall~ finel~ particulate form, the 901-l, vent, hexane, distils off ~list stage).
;~ In the 2nd stage, the pH value of the aqueous suspension of therubber premix is adjusted to 6.5 at temperatures of 80 to 90C with simul_ taneous addition of 167 kg of a 10% strength aqueous solution of aluminium sulphate ~A12(S04)3 x 18H20).
In a 3rd stage, 240 kg of a 5% strength aqueous ~F carbon black ..
suspension are stirred into the batch at temperatures o~ 90 to 95C, where-;j upon the pulverulent rubber base mixture forms, m e base mixture is separated from the water and dried with con-, J stant agitation. The EPDM base mixture i3 obtained as a free~flowing powder . ,:. .. . .. .
- of bulk densit~ 307 g/l, The flow test gives 24,6 seconds, ~ ample 2S
;. 1 i The rubber employed i9 a EPDM grade which can be characterised by ;l the fo~lowing data:
Mooney viscosity 31 , _ 42 -:~

: .

~s~

Defo 500/24 Gel content < 2%
Streng~h of raw polymer 50 kg/cm2 Ter-component ethylidenenorbornene C=C/l,OOO ~ ~3 Propylene content ;30%
Eth~lene content 70~
Solvent hexane Solids content of the solution 10%
Viscosity of the solution 1~5 cP
600 kg of thig EPDM solution are emulsified with the aid of an emulsifying machine in 550 kg of water which contains, as emulsifying auxil_ -iaries, 3.6 kg of potassium oleate, 0.24 kg of sodiwm pol~acrylate of Messrs i Rohm (product name "Plex 5367 Ft') and 0 48 kg of a methylcellulose of Messrs, Wolff AG (tradename "MC 20,000 S") The stable emulsion of the rubber sol-ution has a pH value of 11.5 11 5 kg of a 26% strength sodium silicate sol_ ution (5 pphr of SiO2) and an aqueous SRF carbon black dispersion which had been prepared from 1,201 kg of water, 66 kg of SRF carbon black, 0.653 kg of ~;J laurylamine_pol~glycol ether and 0.33 kg of a sodium polyacrylate of Messrs, Rohm ~product name "Plex 5367 ~1) are stlrred into this aqueous emulsion The sta~le and homogeneous mixture of rubber solution emulsion and . ., ~ . .
carbon black dispersion is introduced into a precipitation bath, heated to 75_85C, which consi~ts of a mixture of 460 kg of water and 40 kg of 10~
strength su~phuric acid. Whilst the rubber premix precipitates in a finel~ ;
;1l particulate form, the solvent, hexane, distils off ~lst stage).
In the 2nd stage, the pH value of the aqueous suspension of the ~' rubber premix is adjusted from 2.3 to 6.5 at temperatures of 80 to 90C and at the same time 33 4 kg of a 10% strength aluminium sulphate solution (A12 (S04)3 ~ 18H20) are stirred in.
, 30 In the 3rd stage, 240 kg of a 5% stren~th suspension of an SRF car-'i .:',' :,, _ ~3 _ '"~'' ' ` ' : . .
, - . . . : : : -1~5~

bon black at temperatures of 85 to 95C are stirred in at temperatures of 90 to 95C ~sic).
The finished EPDM base mixture i9 separated from the water and dried at 40C and a pressure of 20 mm Hg, with constant agitation, to gi~e a powder.
The bulk density o~ the powder i9 253 g/1. lhe ~low test gives 38.? seconds, ': `
~, ,.
'` ~, :; ' .
~ , ,-.
~` ~'`:

~i ;~ `, ,.~
.

.`. 1 , ., ~
~ - 4~

~
' ' :` ~
.. . .

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILIGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the manufacture of a pulverulent, non-tacky, free-flowing filled rubber base mixture which comprises mixing a rubber latex or an aqueous stable emulsion of a rubber solution with less than the envisaged total amount of solid filler in the form of an aqueous dispersion or suspen-sion thereof to give a stable, homogeneous mixture; feeding the stables homogeneous mixture to a multi-stage precipitation process by (i) mixing the stable, homogeneous mixture into water containing a pre-cipitant and a sodium silicate whereupon the rubber and filler conjointly precipitate as a rubber premix, and distilling off rubber solvent which may be present, (ii) adjusting the aqueous suspension of the rubber premix, thus obtained to a pH value of 4.0 to 9.0 for the precipitation of dissolved silica in the presence of a silica precipitant and (iii) mixing the suspension, thus obtained, of rubber premix and pre-cipitated silica with the remainder of the envisaged total amount of solid filler in the form of an aqueous suspension; separating the precipitated material plus filler together constituting the filled rubber base mixture from the water; and drying the rubber base mixture with constant agitation.

2. A process according to claim 1, wherein plasticiser oil is contained either in the rubber latex or the aqueous emulsion of the rubber solution or in the aqueous suspension of less than the envisaged total amount of filler whereby the rubber base mixture produced contains plasticiser oil.

3. A process according to claim 1, wherein the pH of the rubber premix is adjusted in the presence of the compound which causes the immediate preci-pitation of dissolved silica to a value of from 6.0 to 8.0

4. A process according to claim 1, wherein a copolymer of butadiene and styrene, or butadiene and acrylonitrile, is used as rubber latex.

5. A process according to claim 4, wherein the copolymer is an emul-sion copolymer.

6. A process according to any of claims 1 to 3, wherein a polybutadiene, polyisoprene, copolymer of butadiene and styrene or an EPM or EPDM polymer, produced by solution polymerisation or a polymer produced by ring-opening polymerisation of a cycloolefin or a mixture of two or more such polymers is employed as the rubber.

7. A process according to any of claims 1 to 3, wherein an aqueous emulsion of a rubber solution in the preparation of which an anionic, non-ionic or cationic emulsifier is used, with or without cellulose derivative or alkali metal polyacrylate or other high molecular weight emulsifying auxili-ary.

8. A process according to claim 1, wherein a filler chosen from carbon black of any level of activity or active silica is employed.

9. A process according to claim 1, wherein an aqueous filler dispersion which has been prepared in the presence of an emulsifier and a high molecular weight emulsifying auxiliary is used for the first stage of the precipitation but an emulsifier-free filler dispersion is used for stage (iii).

10. A process according to claim 8, wherein a carbon black dispersion is used which has been prepared in the presence of an alkylamine oxalkylate as emulsifier and a methylcellulose and/or high molecular weight alkali metal polyacrylate.

11. A process according to claim 1, wherein for the preparation of the rubber premix from 20 to 99 per cent by weight of the total envisaged amount of filler is used.

12. A process according to claim 11, wherein said percentage is 50 to 90 per cent by weight.

13. A process according to claim 1, wherein before neutralisation the silicate is added to the aqueous suspension of the rubber premix,

14. A process according to claim 1, wherein the amount of silica intro-duced by means of the silicate is 0.01 to 20 per cent by weights relative to the total amount of rubber.

15. A process according to claim 14 wherein said percentage is 1 to 10 per cent by weight.

16. A process according to claim 1, wherein the stable homogeneous mix-ture contains sodium silicate.

17. A process according to claim 1, wherein a monovalent or polyvalent secondary or tertiary amine or quaternary ammonium salt is used as silica precipitant.

18. A process according to claim 17, wherein a condensation product of a monovalent or polyvalent alkylamine with ethylene oxide and/or propylene oxide is used as silica precipitant amine.

19. A process according to claim 18, wherein coconut amine, oleylamine, stearylamine, laurylamine or trimethylhexamethylenediamine is used as alky-lamine.

20. A process according to any of claims 17 to 19, wherein the amount of silica precipitant amino compound is 1 to 50 per cent by weight, relative to the amount of silica.

21. A process according to any of claims 17 to 19, wherein the amount of silica precipitant amino compound is 5 to 20 per cent by weight.

22. A process according to claim 1, wherein a water-soluble salt of a metal which forms sparingly soluble or insoluble salts with alkali metal silicates is used as silica precipitant.

23. A process according to claim 22 wherein a water-soluble salt of a metal of main group II or III or of sub-group II or VIII of the periodic table of the elements is used as silica precipitant.

24. A process according to claim 23, wherein a water-soluble aluminium salt is used as silica precipitant.

25. The treatment of a pulverulent rubber base mixture manufactured by a process according to claim 1 by one-stage processing in a fluid mixer to give a highly filled finished rubber mixture, followed by direct extrusion.

26. A highly filled finished rubber mixture, prepared from a pulverul-ent rubber base mixture manufactured by a process according to claim 1.