DE1720383A1 - Process for making a synthetic rubbery polymer latex - Google Patents

Description

Copolymer Rubber & Chemical Corporation, 5955 Scenic
Highway, Baton Rouge, Loisiana, 7O821 / USA

Process for making a synthetic, rubbery polymeric latex

The present invention relates to a new one Process for the production of latex. In particular, it relates to a new direct method of manufacture of synthetic rubber latex which has a large mean particle size and such a particle size distribution has that the latex is concentrated to a high level of solids at a relatively low viscosity can be.

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The following description of the invention particularly relates to the polymerization of a monomer or a monomer mixture, which in an aqueous medium dispersed under polymerization conditions using an emulsifier and a polymerization catalyst is to produce a synthetic rubber latex having a large particle size, which also has such a particle size distribution that it is relatively Low viscosity can be concentrated to a high solids content · Synthetic polymer latexes however, can generally be made in accordance with the teachings of the present invention.

In many industrial processes in which synthetic rubber latex is used, such as in the manufacture of foam rubber, it is desirable that the latex have certain properties. One of the more important properties is a high solids content, for example about 60 % total solids content or more, and a low viscosity, which is less than 1000 cp at 60% of the total solids content. 1st. Within acceptable limits, latices with higher solids content and lower viscosity are more advantageous. Furthermore, the mechanical stability of the latex would have to be taken into account, since if the mechanical stability is not perfect, an inadmissible amount of the polymer content is irreversible already in the course of handling and

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the storage coagulates or flocculates before the actual use. Also bind the gel time of the latex and the stability of the resulting Foams of influence when latex is used in the manufacture of foam rubber is used.

The viscosity of the synthetic rubber latex will be at a given temperature and a given solids content largely by the mean particle size and Particle size distribution determined. It is usually believed that a large mean particle size and a wide uniform particle size distribution are desirable, and that thereby at a given solids content and at a given temperature a latex with low viscosity can be produced. As the solids content increases or the temperature decreases, the viscosity decreases at one given mean particle size and with a given particle size distribution, in particular with a higher solids content to.

Many attempts have been made to produce perfectly satisfactory synthetic high solids rubber latices and low viscosity suitable for making foam rubber and all of the above have desirable properties. One

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Up until now, it has been difficult to find a latex with a sufficiently large mean particle size and an appropriate one Produce particle size distribution, whereby a low viscosity with a high solids content is effected. One attempt to solve this problem has been to first use a small particle size and low particle size latex Solid content by means of a fast polymerizing Approach to agglomerate the low solids latex to large mean particle size and then concentrate the agglomerated latex to a desired high solids content.

Another method was to go straight to a Manufacture high solids latex by cutting from a polymerization approach in which little water should be used runs out.

The known methods mentioned above have been ^largely: used amount of latex with a high solids content, since no quite satisfactory, inexpensive method has been known, which allows the direct growth of large polymer particles in the manufacture of latex during the polymerization with a suitable particle size distribution . It was therefore necessary to use an expensive agglomeration stage, such as chemical agglomeration or freeze-thaw agglomeration, before starting

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the latex produced by known processes with low Could concentrate solids content. Polymerization approaches, to which little water was used also did not produce entirely satisfactory results. During the polymerization of the Mixtures »an intense toughness phase occurs during which inevitably manufacturing problems arise, the reaction is difficult to control, and eventually it is a large amount of energy is required to stir the mixture. In addition, particularly long reaction times of ^ O hours or longer are required, which has the consequence that the capacity of the plant is reduced to a fraction of the capacity that would be required in the case of fast sales it is possible.

The polymerization batches for high solids latices according to known methods often contain relatively large amounts of an electrolyte and / or a or more wetting agents to stabilize the latex during and after the polymerization. The presence of electrolytes and / or wetting agents affects the production of Films and foams are disadvantageous. It is therefore also desirable that the latex with a higher solids content, which is used in the manufacture of films and synthetic rubber, has a low emulsifier content and has a low electrolyte content.

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However, such latices produced in a known manner tend to be viscous and / or unstable.

According to an important embodiment of the invention, it is possible to directly use a synthetic rubber latex with a relatively low pest body content, which is marked by a particularly large mean particle size and a particle size distribution, which allow the latter to be concentrated into a low viscosity, high solids latex. The polymerization step takes place over a much shorter period of time than with polymerization approaches in which little Water is used and which run slowly · Furthermore, the polymerization batch and the latex obtained, if desired, have a low soap and electrolyte content. Accordingly, are made in accordance with the present invention Latices are characterized by a combination of desirable properties that have not yet been found in any latex became.

The aim of the present invention is a new process for the polymerization of monomeric substances for production to create an improved latex.

Another · object of the present invention is a new process for the preparation of a synthetic

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'. -7 create rubber latex.

Another object of the present invention is to introduce a new method of manufacturing synthetic To create high solids polymer latex.

Another object of the present invention is to provide a new process for the production of synthetic Low solids rubber latex produced by a large mean particle size and a particle size distribution characterized in which the latex can be concentrated to a high solids content.

It has been found that a latex having a large average particle size which is such Particle size distribution shows that it becomes a latex concentrated with high solids content and low viscosity can be obtained directly from "already known polymerization batches. This is made possible by that you first have a first portion of the monomeric material used to prepare the latex in the presence a wetting agent and a polymerization catalyst polymerized until part of the first amount in the Polymer is transferred and the unreacted monomeric material is absorbed by the polishing particles, and that adding at least one additional component of the monomeric material to the resulting latex in an amount wherein

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free monomeric material is present and new polymer particles are formed by continued polymerization in the presence of a free wetting agent and the polymerization catalyst, adds. The latex is then stirred vigorously enough to to cause the polymer particles containing the unreacted absorbed monomer material to agglomerate. Around make a latex with a relatively large average particle size and add free wetting agent to the aqueous phase of the latex, i.e. the wetting agent that acts as an emulsifier for the free monomeric material and for the formation of new ones of emulsified particles contributes. Then the monomer content can dee Latex which contains free unreacted monomer material, i.e. monomer material which does not polymerize or is absorbed by the polymer particles in the presence of the free wetting agent and the polymerization catalyst relatively mild agitation to form additional small polymer particles in the latex.

The latex produced according to the invention can contain some extremely large polymer particles, which can be 150,000 Å in size, a considerable number of polymer particles with a size of at least 10,000 to 30,000 tons, a large number of particles with an average particle size which is substantially larger than 2500 Å, preferably at least 3OOO to 5000 % , as well as sufficiently small polymer particles of graduated sizes for improvement

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tion of the packing factor when concentrating to one high solids content. The large cross-section of the particle. size and the unusually wide, even part size distribution allow as, the latex, if desired, up to extreme concentrate high in pesticides without causing the occurrence an unacceptably high viscosity must be expected.

The polymerization approach used in carrying out the process according to the invention can consist of a suitable, known polymerization eneate for aqueous emulsion polymerization of the monomers, soft a latex of a synthetic polymer for the polymerization in dispersion in the aqueous iediü® in the presence of a wetting agent which forms Hieellen "ad eiaes P © ifaepisatioiaskatalysatQFS. delivers _β Polymerisierfeare monomeric materials- are, for example Chleropren, di © © ismelnsm 1.3 ~ But®diene such as 1 3-butadiene _{8 9} S-Metfayl-butadiea-l ^., 'Fiperyleaa amd S ^ -dimethyl 1 §5 * Bas monomeric material taaa gegsbeaesifalls s & eh Hisohuag of 1 ₉ 3 ₉ & Butadie as IJS Butedieii with e'laem further iopolysierisierbafem Hatörial, which is capable, thus -. * u bilä®a _g "consist" copolymers.. For example, * & as ® © n © ®er © material came with a polymer isol © rbss? Ö with up to $ 0 $ _s ©. ■ in ffiMiohen cases neeii m®W _s a compound wslehe © Ime GH ₂ * Cs containing group be in weleher miadestene ein® the unoccupied "valences with an electrically alifcifea group, ie a group which the electrical asymmetry ny * polar Character of the molecule increases considerably, bea @ tit is.

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Such compounds which contain the group just mentioned, • ind, for example, the aryl olefins, such as styrene and vinylnaphthalene, the alpha-methylene carboxylic acids and their esters, nitriles and amides, such as acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, methacrylonitrile and methacrylamide} isobutylene, Methyl vinyl ether and methyl vinyl ketene. The monomeric material may in some cases be a single compound containing a CH ₂ -C group, or a mixture of such compounds. The polymerizable monomeric materials suitable for carrying out the process according to the invention can therefore be counted among the following substances: chloroprene, conjugated diolefins, which can be homopolymerized to produce polymers, and mixtures of conjugated diolefins and menoethylenically unsaturated Kraemer®, which are copolymerized to produce τοη copolymers can · For many cases, a monomer material consisting of a mixture of butadiene and styrene, in particular mixtures in which the styrene content is up to 50% by weight, is preferably used.

The in the implementation of the erfindungegemäSen Polymerisationsansatζ used in the process can be one or wetting agents of the same type which form several million cells as used in known emulsion polymer solutions * are included. Wetting agents are, for example, soaps of fatty acids, especially water-soluble,

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Salts of long-chain fatty acids, such as sodium or potassium laurate, myristate, palmitate, oleate, stearate, etc. Furthermore, can water soluble sodium or potassium soaps of tall oil and rosin soaps, including disproportionated rosin soaps be used. If necessary, a second emulsifier can be used be present, which is a known synthetic. May be detergent, for example alkali sulfonates, which are different from arylsulfonic acid derive, such as sodium alkylnaphthalene sulfonate.

Furthermore, the polymerization batch can contain a polymerization catalyst, which likewise may be of the type known in emulsion polymerization of the monomer material. The catalyst can be a free radical initiatorSatisfactory catalysts include organic hydaperoxides such as paramenthane hydroperoxide, Cumene hydroperoxide, diisopropylbenzene hydroperoxide and the same. The known activators consisting of a redox system, such as iron sulfate, can also be used or another suitable dissociable heavy metal salt to be available. In addition, other substances can be present in the ana * ζ according to known methods.

In general, it is desirable to have a minimum Amount of wetting agent to be used. For example, it is preferable that the primary emulsifier be a fatty acid soap may be, approximately in an amount of 1 to 3 parts by weight

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and the secondary emulsifier in an amount of approximately 0.1 to 0.2 parts by weight per 100 parts by weight of the original monomers present or added as a constituent. With such low levels of soap and especially in cases where there is no electrolyte, or is kept to a minimum, the latex produced in this way has exceptionally excellent properties for use in the manufacture of foamed rubber articles. The content of wetting agent should preferably be as low as this be kept that in the course of the polymerization, the polymerization mixture passes through a viscous stage, in which it can easily be agglomerated by intensive stirring, whereupon the viscosity decreases and free wetting agent passes into the aqueous phase.

A particularly suitable approach for the accounting of the method according to the invention is for production of a styrene-butadiene latex as follows:

Component parts by weight fe * w. on the

total monomers

Butadiene (1st component) Styrene (1st component) 20 Butadiene (added ingredient) 23 Styrene (added ingredient) 10

Ma-oleate 1-3

Naralkyl naphthalene sulfonate 0-0.2 Diisoprepyl benzene hydroperoxide 0.033

Na formaldehyde sulfoxylate 0.033 activator solution * 209811/1369 ° ' ⁵

- 13 τ

Component parts by weight based on the

cleaved monomers

SuIföl (Isopentadecaniaercaptan) O ₁ I Ethylenediamine tetrasodium salt

tetraacetates 0.01

Na hydrosulfite 0.01?

Water 100-150

+ The activator consisted of a solution of 1.27 g

tetra sodium hydroxide, 2.31 g ethylenediamine & acetic acid and 2.0 g of iron sulfate Beptahy & rat and enough water that the mixture becomes 100 ml,

Of course, other approaches for the polymerization of butadiene and styrene can be used will. If necessary, an electrolyte can be present, although it is in the interest of further improving the properties of the latex for making foamed It is preferable for rubber articles to include such an additive fail.

The first component of the monomeric material can be in the presence of the wetting agent and the polymerization catalyst s are polymerized until a part is in the Polymers has been transferred and at least some of the unreacted monomeric material borrows through the polymers has been absorbed. For example, before adding,

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the further quantity of de · monomer material about 20 to 70%, preferably about 50 to 65 wt -.% of the first component are polymerized to prepare the polymer. For best results should be more than 50 wt -.% Of the monomers are converted to polymer, prior to adding the additional component.

A further component of the monomer material, which can be the same or a different monomer, can be added to the latex produced by the polymerization of the first component. Preferably the added monomeric material is the same as that used first. However, in those cases in which copolymers are produced, only one of the monomers of the copolymers can be added. The additional portion of the monomer material can be added in an amount at which free monomeric material is present in the latex. In rare cases, to 25 to 75 wt -.% Of the first component, preferably about 40 to 60 parts by Ji are added. Best results are generally at about "50 percent - cool%.. The free monomeric material contained in the latex as a result of the addition of the further ingredient allows the formation of new small polymer particles with continued polymerization in the presence of the free wetting agent and the polymerization catalyst.

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The latex produced by the polymerization of the first component is subjected to a sufficiently intense agitation to an agglomeration of polymer particles absorbed unreacted monomer contained -and- to form ⁷ in this manner a latex having a relatively large particle size and thereby free wetting agent in the aqueous phase of the Release latex. The implementation can be carried out in the course of the polymerization of the first component and / or during or after the addition of the additional component. In those cases in which the vigorous implementation is continued after the addition of the monomeric material, it is terminated while the aqueous phase is still free. Contains monomer material. Usually the Büchffekt, which by stirring the latex with a radial stirrer, such as a propeller or an impeller with a peripheral one, suffices

Speed from about 800 to ^ 000 T ^ et / Hin, rorzugs-

(300 to 5 ^ 0 m / rain.)

wise about 1000 to 1800 f & et / min. for violent agitation of the latex. For best results you should the latex produced by polymerizing the first component is agglomerated until the average Polymer particle size is at least 2000S. Afterward the other constituent of the monomeric material can be added. Continue to close the 1st gate, the latex immediately afterwards Vigorously stir the addition of the constituent of the monomeric material in order to add the latter throughout the aqueous medium disperse. The added monomer material also carries

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contributes to further agglomeration, so that, provided that that the vigorous stirring is stopped sufficiently early, including the presence of free monomeric material in the aqueous Medium still to enable improved agglomeration can be obtained.

Subsequent to the vigorous agitation, the latex, which contains free added monomer material, can with relatively mild agitation in the presence of a free wetting agent, which was released by the agglomeration and the polymerization catalyst the other Be subjected to polymerization. The mild performance allows the formation of additional small polymer bonds. For best results, there should be no significant amount of additional agglomeration to form larger ones average particle sizes occur. For this reason, there may be a decrease in the course of this polymerization phase the average particle size of the latex. Mild stirring means stirring conditions which under the conditions mentioned above for violent implementation, in particular those during the implementation de latex with a radial stirrer present peripheral parts

(2l * O m / min.) so speeds well below 800 ftet / min. , for example

(15 to 150 m / rain.)

wise 50 to 500 fft / min · The mild stirring can be continued as long as is desired in order to obtain a certain conversion of the monomer material to the polymer.

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In many cases it is preferred that the vigorous agitation period last about 1/2 to k hours beyond the addition of the monomer component and that the resulting latex be gently agitated for about 1 to k hours to produce small polymer particles, and in this way to improve the fack factor.

Di® proportions of soap, water and Electrolytes in the polymer batch are preferred held at or near minimum values. For example, the proportion of soap should be used for best results about 1 to 3 parts by weight per 100 Qew * parts of the first ingredient Question the present monomeric material and the added constituent *. In the same way, the water content should not more than 150 parts by weight per 100 parts by weight of the total Monomer material go out and preferably about 110 to 130 parts by weight. Within the above limits the best results are usually obtained when using 120 parts by weight of water and 1.3 parts by weight of soap. To achieve best results should be delayed to the addition of an electrolyte »or this to a minimum proportion be restricted.

In some cases, more than one monomer city11 can be added «For example, the first Menomer order bi * are polymerized to a desired percentage conversion, then to agglomerate the

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The latex and free wetting agent are stirred into the aqueous phase, another monomer component is added and the polymerization is continued, whereupon the resulting latex is agglomerated again to achieve a large average particle size and to free additional wetting agent in the aqueous phase and a third Monomer component is added and the process is repeated. However, it is usually sufficient to add a monomer component * whichever mode of operation is preferable. The hydrocarbon content of the solids contained in the latex can be very high if the soap content of the polymerization batch is kept to a minimum; it can be up to 96 to 98 wt. In general, it is preferred to prepare low solids latex, for example 15-25-30 to 100% by weight solids, and concentrate the low solids latex to high solids by known methods. The low solids latex can be concentrated to a high solids content of at least 53 to 60% and up to about 75 to 82 % by evaporation of water, by skimming, by centrifugation or other suitable methods, without causing objectionable viscosities.

In practicing the method of the present invention, the average particle size of the latex can be from about 800 to 900 % to about 3000 to 5000 % or more

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are increased »In cases where no second monomer component is added to the latex and the reaction is terminated after polymerization of the first component, completely satisfactory results are not obtained even if the average particle size is sufficiently large only slight conversions are possible and the resulting latex has no unusually wide and uniform particle size distribution in combination with an extremely large average particle size, which is necessary to achieve the best results when concentrating to a high solids content. It is not possible, the Latiees prepared according to methods known in concentrations above 75 wt - to focus% Total solids content, while it is possible to concentrate to about 82 wt .- # Total solids content of the present invention Latiees produced ·.

The polyaerization process according to the invention can be carried out in batches or continuously. For example, in the case of batch operation, as in the Examples shown a single reaction vessel can be used. But it can also be a number of reaction vessels be arranged so that the individual steps of the fiction, contemporary method are carried out continuously

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The pQlymerieation Temperatures can those correspond in known processes for the polymerization of the monomeric material. For example, is usually the

Polymerization temperature for the production of styrene

(22? C to 58 ^Ö i) butadiene rubber approx. ^ OF to 125 Fj but it can also

other satisfactory temperatures door beds. At least

a portion of the unreacted monomeric material which is present in the latex after the partial polymerization of the first Any component remaining is absorbed by the resulting polymer particles. The polymer particles can through the absorbed monomeric material be swollen and can in this state particularly easily to a latex with a relatively large particle size are agglomerated. In those cases where an insufficient amount of the monomer Material is absorbed by the particles to make them soft and sticky, a more intensive implementation brings the desired degree of agglomeration. It is therefore understood that the intensity of the stirring is so strong must be that the desired proportion of agglomeration can be obtained without undue flocculation occurring.

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- 21 Example 1

An approx. 2 liter glass flask equipped with a sawtooth impeller stirrer was equipped with the following Polymerization batch charged:

component Parts by weight 0.1 Butadiene 70.0 Styrene 30.0 0.01 Potassium oleate 2.0 Diisopropyl benzene hydroperoxide 0.05 0.026 Activator solution 0.75 180.0 Sodium formaldehyde sulfoxylate 0.05 SuIföl (tertiary dodecyl mercaptan) 0.14 Secondary emulsifier (sodium alkyl naphthalene sulfonate) Tetrasodium salt of ethylene diamine tetraacetic acid Sodium hydrosulfite water

+ The activator consisted of a solution of 1.27 g sodium hydroxide, 2.31 g ethylenediaminetetraacetic acid and 2.0 g of iron sulfate heptahydrate and so much water that the mixture makes 100 ml.

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The polymerization components were added to the reactor, and (4-3 * ° F) the polymerization is conducted at a temperature of 23 ⁰ C. The sawtooth impeller was 3 inches in diameter and had a speed of 1200 revolutions per minute.

The polymerization was carried out under the above conditions until 60 % of the original amount of monomer used had reacted and converted into the polymer. The solids content of the latex obtained was 23% by weight. At this point a second monomer component which was 35 parts butadiene and 15 parts styrene was added. Vigorous stirring was maintained at a speed of 1200 revolutions per minute for k hours after the second monomer component had been added and then reduced to a speed of 600 revolutions per minute for gentle agitation. The reduced rate of stirring was maintained h hours and then the polymerization is interrupted by "shortstop addition". The total reaction time was 18 hours, the final conversion of the monomer into the polymer being 72% by weight, based on the monomer originally used. The unreacted monomer was removed from the latex in a known manner, that is, the butadiene was flushed away and the

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Styrene and a small part of the butadiene was through Removed steam distillation in vacuo to give free latex.

It was found that the latex obtained was 95 % covered and that the average particle size of the polymer was 5000 % . Some portions of the latex were concentrated to various total solids by evaporating the water.

The relationship between viscosity and solids content is as follows:

Solids content
(Gew.-SO viscosity
(cp *) 59.0 ho 69 I * f2 82.6 2500

The latex described above was foamed. The resulting foam had excellent properties for making foamed guru particles, for example Gelling characteristics, foam stability, low shrinkage and high pressure resistance.

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Example 2

The procedure described in Example 1 was repeated except that the stirring speed was changed from 1200 revolutions per minute to 600 revolutions per minute when the second Monomer component was added.

The reaction was ended after a total reaction time of 2½ hours. At that time, * | 4 percent - converted% of the originally used amount of monomers in the polymer.. The latex obtained had a soap coverage of 9 % and a particle size of J-550 % .

Some parts of the latex were evaporated to a pesticide content of 56.2 and 69 * 6 concentrated and the viscosity determined. The latter became 55 cp. or 59o measured.

If the addition of the second monomer component was omitted in Examples 1 and 2, the resulting

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standing Latiees cannot be compared to those which according to the method according to the invention, according to the Examples 1 and 2 were obtained. The particle size and the particle size distribution was not suitable for Extremely low viscosity and high solids latices after concentrating.-Furthermore, that was Eeaction ratio much slower and it was not possible to obtain a satisfactory final percentage conversion of the monomer · It is therefore necessary to to come to the good results according to the invention, the add the second component of the monomer, stir the latex vigorously for agglomeration and then to generate small dives are followed by a period of moderate emotion allow.

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Claims (1)

Claims 1. A process for preparing a synthetic, rubber-like polymer latex by in aqueous medium in the presence of a micelle-forming surfactant and a polymerization, that deliver catalyst carried out emulsion polymerization of ethylenically unsaturated monomeric materials which latexes of synthetic rubbery polymers, where dm-called monomeric material chloroprene and / or conjugated to. rubbery polymers homopolymerizable diolefins and / or mixtures of conjugated diolefins and monoethylenically unsaturated monomers which are copolymerizable with the former monomer to rubbery copolymers and said mixture up to 50 wt -.% containing the monoethylenically unsaturated compound, characterized in that a) a first part of said monomeric material is polymerized until it has been partially converted into the polymer, and the unreacted monomeric material has been absorbed by the polymer particles, b) the latex obtained is subjected to sufficient agitation to prevent agglomeration of the polymer particles, which contain the absorbed, unreacted monomeric material to effect, 209811/1369 ^{0RIGINALINWECTED} - 27 - c) the latex at least one additional component of the said monomeric material is added that the additional constituent of said monomeric material has the same monomer composition as said first ingredient and added in a proportion that free monomeric material in the latex is present and new polymer particles by continued polymerization in the presence of the free wetting agent and the polymerization catalyst are formed and that d) the latex containing said free monomeric material a further polymerization under relatively mild stirring conditions for making additional small polymer particles in the Is subjected to latex. 2. The method according to claim 1, characterized in that I η et, that the monomeric material consists of a mixture of styrene and butadiene which contains up to 50 wt .- # styrene. 3. A method according to claim 1, characterized I gekennze et η that firstly a latex is prepared with a low solids content, which then to a latex having a solids content of at least 60 percent - is concentrated.%. ^ -. Process according to Claim 1, characterized in that the first constituent of the said monomeric material is polymerized up to 20 to 70% by weight . into which rubbery polymers have been converted. 209811/1369 - 28 - 5. The method according to claim 1, characterized in that i chne t, that the aqueous emulsion does not contain more than 3 parts by weight of wetting agent and no more than 150 parts by weight of water, based on the total amount of the initially present and the additional constituent mentioned of the monomeric material contains. 6. The method according to claim 1, characterized in that that the wetting agent consists of water-soluble, micelle-forming / Sttcalisulfonaten and non-ionic wetting agents. 7. The method according to claim 1, characterized in that that the latex with a Badial stirrer with a peripheraliseheη Speed from 2 * K> to 1200 m / min (8oo to * K) 0 f / eet / min) is stirred. 20981 1/1369