CA1166779A - Preparation of aqueous emulsions or dispersions of partially water soluble materials and then optional polymerization when materials are monomers - Google Patents

Abstract

Abstract of the disclosure The invention provides a process for preparing an aqueous emulsion or dispersion of a partly water-soluble material, and optionally further conversion of the prepared dispersion or emulsion to a polymer dispersion when the partly water-soluble material is a polymerizable monomer. In a first step a dispersion of polymer particles is prepared containing one or more materials having a very low solubility in water, then in a second step there is added the partly water-soluble material which diffuses into the particles from the first step, and then, if the partly water-soluble material is a polymerizable monomer, polymerisation may be effected.

Description

77~

The presen-t invention relates to a process for preparing aqueous emulsions or dispersions of a partly water-soluble material or mixtures oE partly water-soluble materials, and possibly further polymerisation when the par-tly water-soluble material is a monomer or a mixture containing one or more monomers.
In Belgian patent 851,556, which discloses a process for preparing emulsions of somewhat water-soluble vinyl monomers, it has been demonstrated that it is possible to prepare stable emulsions of vinyl monomer by preparing in a first step an aqueous pre-emulsion of a material havlng a very low solubility in water, by an efficient homogenisation process, and then upon addition of water and emulsifier allow-ing the somewhat water-soluble vinyl monomer to diffuse into the droplets of the material having a very low solubility in water. The fact that the droplets in the pre-emulsion consist-ed of a material which combined very low water solubility and low molecular weight, had the effect that the droplets could absorb 50-500 times their own vo]ume of the somewhat water-soluble vinyl monomer, with formation of stable dispersionswhich were subjected to polymerisation to form a latex. The pre-emulsion was in this case prepared by homogenisation, which leads to a broad distribution of the droplet size which became even broader after absorption of the vinyl monomer.

-` 9~ 77~

In Norwegiall patent applicatiorl 7~.3gg4 laid open on 23 May 1978 there is clisclosed the prepara-tion of a dis-persion of par-ticles by ordinary emulsion polymerisation, but in contrast to ordinary polymer latexes, the particles contain a substantial fraction of oligomers having a much lower mole-cular weight. As a consequence of this the par-ticles may take up 20-200 times their own volume of a somewhat water-soluble substance. In order to attain the formation of oligomers having low molecular weight by ordinary emulsion polymerisation there is used according to patent application 76.3984 an addition of chain transfer agent during the polymerisation, which causes the formation of shorter chains.
Both in the process described in Belgian paten-t 851,556 and in Norwegian pa-tent application 76.3984, there is obtained in a first step a pre-emulsion of particles which have the ability to take up a somewhat water-soluble material in an amount of 10-200 times more than corresponding polymer particles.l By the method described in patent application 76.3984 one avoids the homogenisation of the substance having a very low solubility in water and having a low molecular weight, which is described in Belgian patent 851,556. Further, the method disclosed in patent application 76.3984 provides greater possibilities for -the preparation of more mono-disperse droplets or particles with a predetermined size. A disadvan-tage of the method described in patent application 76.3984, is however that the chain transfer agent which usually will be a mercaptan compound, is a badly smelling, partly toxic compound with which , 7~,~
it is unpleasant to work. ~iurtller, addition thereof will often result in a reduction of the rate of po1ymerisation. It may also require that the chain transfer agent :is added in portions or con-tinuously during the polymerisation in order not to obtain a too broad distribution of mo]ecular weight and a too high proportion of highly polymeric ma-terial.
According to -the present invention there are prepared aqueous dispersions of particles which in addition to polymer molecules contain a considerable propor-tion of one or more low molecular weight material(s) having a very low solubility in water, in the following called Substance I, and which therefore have a much greater ability than particles of pure polymer, -to take up a partly water-soluble substance, in the following called Substance II, added in the next step.
In paten-t appli.cation 76.3984 particles containlng 10-100% water-insoluble oligomer are prepared by adding a chain transfer agent during the polymerisation of the monomer on which the particles are based.
Accordiny to the presen-t invention Substance I as such is introduced into the particles. This takes place during or after the formation of the polymer particles by emulsi.on polymerisation by making it possible for Substance I to diffuse through the aqueous phase and to become absorbed in -the particles. Substance I may also be incorporated direc-tly in the polymer particles by preparing an aqueous emulsion of a mixture of Substance I and a monorner by homogenisa-tion and then polymerising the monomer, for instance a vinyl monomer, -to obtain polymer particles con~ J753ubstan(,~ I, 'I'he~ c,ommon feature of the two processes is that ln the firs-t step there is preparecl an aqueous dispers:ion oE particles or droplets ~Jhich in addition to polymer eontains a relatively low moleeular T,~eiyh-t water-insoluble Substance I, and that these partieles, as mentioned above, will be able to absorb a very larye amount of a partly water-soluble Substance II which under the conditions given may diffuse through the aqueous phase and be taken up in the partieles eonsisting of polymer and Substanee I.
By having prepared in the first step particles which in addition to polymer also eontain Substance I, -there have been formed partieles whieh are capable of taking up the par-tly water-soluble Substance II whieh may diffuse through the aqueous phase to the partieles and become absorbed therein.
In the second step one may then attain a ratio by volume between Substance II and partieles which is 5-100 times higher than with partieles of pure polymer. The Substance II used may be any partly water-soluble substance whieh is eapable of diffusing through the aqueous phase. It may for instanee also be a monomer or a mixture of a monomer and another Substance II.
In case Substance II added in the second step eomprises a monomer, it may be polymerized after absorption in the partieles. The present proeess represents in this ease a speeifie type of seed teehnique.
The first method in which Substanee I is ineorporated in the first step in polymer part.ieles prepared by ordinary emulsion polymerisation is partieularly suitable when i-t is 77~
desired to prc-E)a]-e dis~ersioll~. hc:lvin(] a ~ecl~ rlinecl ~,a:rt:ic]~
or droplet size and sii7e distl-ib-ltion, ir-lclucling rnonodisperse drople ts or par-tlc:Les ancl polydi sperse sys terns wi th a very even size within the individual fractions . Monocli sperse ernulsions are very difficult to prepare by ordinary emulsion processes.
Similarly, it is very difficult to prepare direct]y monodisperse polymer dlspersions having a particle diameter above 1 ~Jm.
For several purposes it is desirable to prepare larger par-ticles having a uniform particle si~e, for instance as stand~rd for microscopy, as model systems for separation, fluid flow, cen-trifugation, diffusivity measurement and dust inves-tigations.
Fur-ther, -the particles may be used in electro kinetic studies and also within pho-tography, for instance as a coating layer in ~-ray film. They may also be used wi-thin biomedicine as a means for diagnosis and detection of antiyens and antibodies in bioloyical fluids. Similarly, it may also be desirable -to have a predetermined size and size distribution in dispersions of active substances haviny for instance biochemical effect, such as pes-ticides. Fur-ther, for cer-tain pain-t dispersions a predetermined particle size distribu-tion is desirable. This is also the case wi th PVC-dispersions . r~lonodisperse particles may also be used as fla-ttening ayent for paint and powder paint. They may also be used as toners, for exalllp:Le in xerography. ?urther, the particles in dry Eorm may be used for -tribological purposes. By using as Substance I:[ a mixture of a partly water-soluble solvent, a vinyL monomer and a divinyl monomer, one may after swelling polymerize and~tr~pp off the ~ ~677~

solvent ln a per se ~nown ma~ er to obtai,n porous parti,c~les which are suitable for separalion purposes. By usi,nc~ as Substance II a monomer or a monomer mixture and a low boiling substance, tl~e present process may be used for ~he prepara-tior of expanding microspheres. Large monodisperse paxticles may also be used for the prepara-tion of material for ion chromato-graphy wherein it is preferred tha-t the particles are monodisperse to attain minimum pressure drop in the column.
According to the invention for the above purposes one may prepare an aqueous dispersion of po]ymer particles by ordinary emulsion polymerisation and then with a specific trea-tment of these particles, increase their abili-ty -to take up the somewhat water-soluble material, Substance II. By preparing polymer particles according to general principles it is possible to adjust the size and the size distribution of the particles within wide limits. In the subsec~uent addition of the partly water-soluble material, dispersions of this material will then be obtained with a droplet size which is completely determined by the size o~ the premade polymer particles and the amount of Substance II absorbed in the particles.
According to the present invention it is possible -to absorb in the premade polymer particles up to 800 -times the volume of the polymer par-ticles of the partly water-soluble materials by this two step swelling process.
In'a preferred embodimen-t of the process according to the invention the polymer particles are swelled in the first step wi'th the material having a very low solub:Ll:ity in n~rrn~y ~l~ water, Substance I. Substance I~has a moleclllar weigtlt oL

77~

<5000, preferably <500, ~ a water solubility of <10 normally <10 , preferably clO y/l of ~120 In order to attain a transportation of Substance I haviny a very ]ow solubility in water throu~h the aqueous phase and into the partlcles, it is necessary to carry out the first step under conditions which facilita-te this transfer of Substance I.
The transfer may be facilitated in several ways. One may prepare a finely divided aqueous emulsion of Subs-tance I which is added -to the dispersion of polymer particles. This distribution will facilita-te the transfer by increasiny the boundary surface towards water. This fine distribution of Substance I may be provided by using relatively lar~e amoun-ts of emulsifier or mixtures of emulsifiers which will result directly in finely divided emulsions, possibly micro-emulsions, or in specific cases, mixed micelles and/or by using in-tensive homoyenisation of Substance I, water and emulsifier.
The first step may op-tionalIy comprise -that the swelling of the polymer particles in the first s-tep with Substance I takes place continuously during the preparation of the polymer particles. This may be done by allowiny Substance I
to be present during the preparation of the polymer. It is then preferably mixed with the monomer or the monomer mixture Erom which the polymer is prepared, and in addition initia-tor is used. In order for Substance I to diffuse into the polymer particles as they are formed, the polymerisation is carried out under conditions which allow transport of Substance I through the aqueous phase.

3 ;1~7~
, A method which to a ~rea-t ex-tent will facilitate the transfer of Substance I -to the particles, comprises that in the first step there is added a certain amoun-t of a material which is a solvent for Substance I and at the same time is completely or pa tly soluble in water. This will increase the rate of transfer of Substance I to the particles by increasing the solubility in the aqueous phase. Examples of such solvents are acetone and lower alkanols. Normally said solvents are used in an amount of 1-100 percent of the amoun-t of water, based on volume.
In case the monomer or one of the monomers in a mixture of monomers used for the preparation of polymer particles into which Substance I is to be introduced, is relatively water-soluble, the monomer itself may serve as such a solvent. Examples of such relatively water-soluble monomers are vinyl acetate, acrylic acid, acrylonitrile, methyl acrylate and acrylic amide which then in a subsequen-t step are polymerized.
Advantayeously it is also possible to employ a combination of the above methods which will comprise the preparation of Substance I in a finely dispersed form and the use of an excess of emulsifier or addi-tion of a solvent miscible with water in the first step.

..... - 9 I

,. 1 1~6~g In those CclSeS in wh:ich the~ g:lass Irclnsitlor temperature, Tg, of the polym--r par~:icles is above the temperature a-t which Substance I is introduced, the dlffusion of Substance I into the polymer particles may be rate determininy. In this case it May be advantayeous to have present a small amount of a subs~ance which ~ill lower the Tg of the partic].es before introducing Substance I. This may for instance be accomplished by let-ting -the original polymer partieles contain a substantial amount of unreac-ted monomer or during the preparation of the oriyinal polymer partieles to have present a subs-tance which is sufficiently water-soluble -to diffuse into the polymer particles as they are formed. Also this substance may be absorbed in premade polymer particles. The only purpose of this substance is to lower Tg and thereby faeilitate transport of Substance I
into the particles.
.The transfer of Substance I to the polymer particles in the first step, so that they beeome s~elled wi-th Substanee I, may be accomplished in several ways. Polymer par-ticles are ~0 accordingly obtained containing Substance I in an amount of up to 10, normally 0.05-5, -particularly 1-4 times the amoun-t of the polymer, based on volume. An essen-tial feature of -the present process is that before adding the somewha-t wa-ter-soluble Substanee II whieh is to diffuse into the polymer partieles in the seeond step, the eonditions are ehanged so that while Substance II may diffuse -through -the aqueous phase into -the I

I 16~7~
polymer pclr~ic1es, the ~ransport of Substance :L -throug1-, the aqueous phase in this second s-lep of the p:roceSC; is effectively inhi.bited so that no Substance I rnay diffuse out of the polymer particles. Particles which are swelled wi-th Substance I may be capable of taki.ng up up -to lO00, norrnally up to 800, particularly 20-300 times their original volume of Substance II. The s-trong reduc-tion of transport of Substance I
from the particles before Substance II is added, whic}l is a necessary condition for the method to work, will partly be attained directly when water is added before addi-tion of Substance II. ~s particles containing Subs-tance I should be charged with up to 800 times thei.r original volume of Substance II, it will be necessary to dilute with water, according to -the desired concentration in -the final dispersion. Thus, if a dispersion is desired in which the ratio between water and Substance II is l:l, water is added in step 2 in such an arnount that the total amount of water will be the same as the amount of Substance II added in step 2. Normally the ratio between water and Substance II in the final dispersion will be from 95:5 to 20:80. sefore addi-tion of this amount of water there is present a relatively hiyh concentration of those materials which have been added to facilitate the -transpor-t of Substance I to the particles. sy addi-tion of the large amoun-t of H20 in the second step, the concentration of said materials will be strongly reduced, and -thereby the possibility of transport of Subs-tance I out of the particles will bc J ;1 ~6'~7 9 considerably reduced. 13y u~;in(3 .tor instance acetor1e to promo-te a more ready trans~,ort of Substance I to the particles in the f:irst step, it is advantageous to evaporate it off before adding water and Substance II in -the second step.
It is an essential feature of the present invention for the preparation of the dispersion of Substance II, that adc~ition of Substance I and Substance II -takes place in two steps so that Substance I is absorbed in the particles in a firs-t step with conditions enabling transport of Substance I, while Substance II diffuses into the particles under conditions which inhibit the transport of Substance I -through the aqueous phase. Thus, it will be found that if Substance I and Substance II are first mixed and this mixture is then added to anaqueous dispersion of the polym~r parti.cles, and by addition of for instance acetone, it is made possible for both Substance I and Substance IIto be transported through the aqueous phase -to the particles, then both Substance I and Substance II will be taken up, but the total amount absorbed will be limited to l-4 times the volume of the particles.
Whe,n -the ratio between water and Substance II is less than 50:50 it may be advantageous -to add Substance II
in portions or continuously over a certain period.
As Substance I there may be used any material or mixture of materials which exhibit the given properties, very low water-solubility and relatively low molecular weic~ht. It is B~77~

further an advanlaye that the~ are non c~ysta:l.L:Lne a~ ~h(1 temperature at which they are illcorpo.rated :into the partic:Les.
It is also an advantacJe tha-t Substance I is in a liquid form at the temperature at which Substance II i.~ introcluced :into the partlcles in the second step, since in this case there will not only be attained t.~le above men-tionecl stronyly increased capacity to absorb Substance II, but also often a very strony increase in the rate of absorp-tion. This is in par-ticular the case when working Wit}l a polymer in the in:itial particles for which the glass transi-tion temperature is above the -tempera-ture employed during the swelliny with Substance II.
If Substance II is a vinyl monomer which is to be polymerized after having diffused into the particles containiny Substance I, it may be advantageous to use as Subs-tance I, wholly or in.part, a water-insoluble vinyl monomer which may be co-polymerized with the vinyl monomer added in the second step.
Examples of vinyl monomers which sa-tisfy the above requirements with respect to Substance I, are s-tearyl vinyl ether and stearyl me-thacrylate.
When the partly water-soluble Substance II wholly or in part is a monomer which after diffusion in-to the particles polymerizes to a polymer, -the present invention represents an improvement in a type of seed technique which has often bèen described in the literature in connection with the preparation of latexes. With an ordinary seed process a latex is prepared by a common emulsion polymerisation, and this l~tex is used as seed. ~onomer, water, emulsifier and initiator are added to this seed, and the polymerisati.on is perEormed.
: 13 ;77~
. .
A la-tex will then be formed having laryer particles -than :in the original seed latex. Means are provided to ensure that -the polymerisation takes place inside the seed particles to avoid new formation of particles in -the aqueous phase. The weakness of the conven-tional seed method is that the seed particles which consist of polymer molecules as described above are capable of absorbing only 1-4 times their OWI~ volume. IL it is desired to prepare 500 g of latex particles from for ins-tance 10 g of seed particles, this must be made in several steps with stepwise addition of emulsifier. The 10 g of seed particles will absorb only up to 40 g of monomer. This will result only in a small tncrease in -the surface, and since it is not desired to have too much emulsifier in the aqueous phase, the amount of emulsifier must be limited to an amount which becomes adsorbed on the surface of the swelled seed particles. After polymerisation additional monomer and emulsifier are added, and the process is repeated. It will be - obvious that this will require several steps before 500 g of latex particles have been formed.
By using, as accordin~ to the present invention, a seed consisting of polymer + Substance I, the seed particles will be capable of absorbing much greater amounts of mollomer, it often being possible to add all monomer in one step, and the amount of seed employed may be greatly reduced. In the preparation of very large particles it may be necessary to repeat the process of swelling with monomer, possibly also with Substance I and initiator. In any case the number of s-teps .~ J ~7~

will be greatly reduced in comparison with the number o~ s-teps necessary ~or the preparation of particles of the sarne size by using a common see~ process. Further,the swelling of the particles with the large amount of monomer has the effect that a very large increase in the surface is a-ttained. A consequence of this is that even if all emulsifier is added initially, i-t will to a very high extent become adsorbed on the surface of the swelled particles, and there will be very little emulsifier left in the aqueous phase, and therefore -the formation of new particles in the aqueous phase will not take place.
As initia-tor for polymerisation,wa-ter-soluble initiators such as R2~208 or H202 may be used. They are preferably added after swelling with monomer. An oil-soluble initiator may also be used. When usiny an oil-soluble initiator which is somewhat soluble in water, such as azobisisobutyric nitrile (AIBN), this may be added after the monomer has diffused into the particles or it may be dissolved in the monomer before the latter diffuses in-to the particles. when using oil-soluble initiators which are less water-soluble, such as lauroyl peroxide, it will be necessary to add this together with Subs-tance I as the conditions are then, as described above, such that even substances having a very low solubility in water may be transported through the aqueous phase.
Initiators which possess the combination of low solubility in water and low molecular weigh-t may also act as Substance I. It has been found that certain specific initiators which are liquid at the tempera-tures in ques-tion are particularly _ 15 7~

favourable as Substance I. 'rhey may easily be incorpora-ted in the particles according to the methods described above. This will in particular be of interest when Substance Il is a monomer, as such initiators act as Substance I, and further, they will act as initiator for the polymerisa-tion of Subs-tance II . An example of such an initlator is dioctanoyl peroxide.
Oil-soluble initiators which have a very low solubility in wa-ter, such as dioctanoyl peroxide, have the advantage in comparison with more water-soluble initiators such as AIBN, that they not only reduce the risk of formation of new particles in the aqueous phase, bu-t they also reduce the risk of bulk polymerisation. With the latter oil-soluble, but aiso somewhat water~soluble, initiator, it is an absolute requirement that all monomer has been absorbed ln the particles before the polymerisation is started by raising the temperature.
Similarly, with this initiator care must be taken so that no monomer phase is formed by evaporation and condensation of monomer during the polymerisation. Oil-soluble initiators such as AIBN are sufficiently water-soluble to diffuse into the possible monomer phase and start a bu1.k polymerisation which will result in the formation of large lumps and thereby entail great disadvantages. By using an initiator having a very low solubility in water, such as dioctanoyl peroxide, the possibility of all monomer added in -the second s-tep not being absorbed, will not be of the same importance since the initiator has such a low ; water~solubility that it will not diffuse out of the particles through the aqueous phase to the possible monomer phase. Thus, B~77~

if a certain monomer phase is intermedia-tely present duriny the polymerisation, the only thiny which rnay poss:ibly happen is a thermal polymerisation therein, and monomer will primarily be absorbed in the particles containing thé initia-tor as -the polymerisation proceeds.
With such an oil-soluble initiator having a very low solubility in water one may therefore, if desire~, even swell and polymerize in several steps at the polymerisa-tion -temperature wi-thout having to reduce the temperature before each swelling process with monomer,to prevent bulk polymerisation. Similarly, for the same reason it is possible to add vinyl monomer continuously during the polymerisation. Even in these cases it is an advantage that Substance I (which in this case is initiator) is liquid at the temperature in question, so that the rate at which the monorner is absorbed in the particles increases.
The use of dioctanoyl peroxide or o-ther greatly water~insoluble ` initiators alone or together with another Substance I which is not initiator has been found very suitable for the preparation of monodisperse particles having a large particle size.
For the preparation of large monodisperse particles according to the present invention one starts with a seed having relatively small monodlsperse polymer particles which are charged with Substance I as described above and then wi-th monomer which is then polymerized. The starting seed is prepared by ordinary emulsion polymerisation under conditions which yield mono- i disperse particles. Such methods are well known in the litera ture, see for instance Woods, M.E., Dodge, J.S. and Krieger, I.M., _ 17 1 ~6~7~

J. Paint Techn. 40, 541 (1968).
These methods, which all are variations of ordinary emulsion polymerisa~ion, are satisfactory for the preparation of monodisperse particles having a ~iameter up to approx.
0.5 ~m. ~lonodisperse particles having a diameter above 1 ~um are difficult to prepare by these methods, and monodisperse particles above 2 ,um cannot be prepared by ordinary emulsion polymerisation.
By the process accordiny to the present invention it has been found possible to prepare monodisperse particles wlth a very low s-tandard deviation having a diameter > 5 ~m.
The preferred embodiment described above for the preparation of particles containing Substance I is particularly favourable if it is desired to obtain a monodisperse disper-sion or a polydisperse dispersion having even particle or droplet sizes within -the individual fractions. In some cases this will not be necessary or desirable, and it may be satis-factory or even desirable to obtain a broad dis-tribution of particle size. In this case the other method mentioned above may be used. This is the method which comprises mixing of monomer, Substance I and possibly oil-soluble initiator and then preparing a dispersion of these materials by mixing with water and emulsifier and homogenisation of this mixture with a homogenizer. Due to the presence of Substance I the dis-persion prepared will be stable against degradation due to diffusion, as described in Belgian patent 851,556.
After the homogenisation the monomer is polymerized.

f I ~¢~7~

This may be accompllshed hy ,~ddi,ng a wal,e~-solub:le Lnit,iator or an oil-soluble, partly water soluble in:itiator which diffuses through the aqueous phase into the particles. If an oil-soluble initiator has been present duriny the homogeni,sation, the monomer is polymerized by heatiny after homogenisation.
Thereby a dispersion of particles containing 5-gO percent of Substance I is prepared. These particles do not differ in principle from the particles described above wherein Substance I is incorporated in the preformed polymer par-ticles or are present during the preparation.
The essential common feature of the two methods described above, is that in both cases particles are prepared in a first step which in addition to polymer contain an essential proportion of the relatively low molecular weight Substance I having a low solubility in water, which provides particles having a greatly increased capacity of absorption and results in increased rate of absorptionr The particles prepared by the latter method are swelled in the next step with SubstanceII in the same manner and with the same result as the particles prepared accordincJ to the former process. Even with the la-tter particles Subs-tance II may be a monomer which after absorption is polymerized either by means of the initiator already present in the particles and/or by means of additional initiator or additives which increase the rate of formation of radicals in -the particles. The advan-tages of this seed me-thod in comparison with ordinary seed me-thods is of course the same as described above and are as follows:

` ` } ~667~

The presence of Subs-tance :[ in the see~ p~rticles entails an enormous increase in the ability of the seed particles to be swelled with monomer. Thereby, -the amoun-t of seed used may be reduced. Further, the increased extent of swelling will result in a very large increase of the surface of the particles.
Thereby the capacity to adsorb the emulsifier increases, so that all emulsifier may be added initially without any risk of having so much emulsifier present in the aqueous phase that formation of new particles takes place therein. In ordinary seed polymerisation the emulsifier must be added continuously or stepwise to avoid formation of new particles in the aqueous phase.
Since it is possible to use such small amounts of seed, it may be without importance for the properties of the ; final polymer dispersion which monomer is used in the first step, and it is accordingly possible to use a monomer in the first step which is different from that added in the second step.
The present invention may be used for the prepara-tion of dispersions of any partly water-soluble material and mixtures of such which are capable of diffusing through the aqueous phase, which will require that Substance II has a water-solubility of ~ 10 g/l H2O, preferably >10 g/l H2O.
The ratio between the solubility of Substance I and Substance II
i9 of essential importance. Thus, the water solubility of Substance II must be higher than that of substance I and should be at least 10 times, preferably at least 100 times that of Substance I. Thus, when Substance I has a , g water-solubility of 1.0 4 y/l H20, Suhstarlce II shol:lLd preferably have a water-solub.ility o~ above lO 2 g/l H20.
On the other hand, if it is desired to prepare'a dispersion of a Substance II with a wa-ter-solubili-ty of 10 4 g/l H2O, there should be used a Substance I haviny a water-solubili-ty of preferably less than lO 6 y/l H2O.
It has been found that even relatively small amounts of Substance I in the polymer particles will provide a considerable increase in the ability of the particles to absorb Substance II compared with particles oE pure polymer in the case of relatively large particles. Such a system wi-th large particles containing relatively little of Subs-tance I, in addition to being obtainable from pure polymer dispersions, will be presen-~ after a process wi-th swelling of particles having a relatively high content of Subs-tance I with monomer which is then polymerized as described above. Particles have then been obtained which are much larger than the original particles, which means that the amount of polymer has greatly increased while the amount of Substance I is the same as before the process with swelling and polymerisation... It has been found that even with a'n amount of about 5 percent of Substance I, based on polymer, particles having a diameter of about 2 ~m are capable of absorbing an amount of Substance II which is about 40 times higher than the amount of polymer particles, based on volume.

~ ~$~7r?~
Example ~
77 ml of H20, 13.5 ml of l-chlorodoclecan~ and 0.2 g of Na-laurylsulphate (NaLS) were homocjenized in a two-stage Manton Gaulin homogenizer, model 15 M with 200 kg/cm2 in the 1st stage and 80 kg/cm2 in the 2nd s-tage for l-1.5 min.
This resulted in an emulsion haviny a droplet diameter of about 0.1-0.2 ~m. This emulsion was charged with seed latex of monodisperse polystyrene having a particle diameter of 0.65 ~m (determined by electron m:icroscopy). An amount of 83.8 ml of seed latex was used con-taininy 77 ml of H20 and 6.8 ml of polystyrene particles. Further, 6 ml of H20 and 18 ml of acetone were added under ordinary stirring at 35-40C. After stirring for 10 hours at 40C acetone was removed by evaporation under vacuum. The emulsion was examined in optical microscope, and it was found that a monodisperse emulsion having a droplet diameter of about 0.9 ~m had been obtained. After evaporating the acetone 1.0 g of Na-lauryl sulphate and 840 ml of H20 - were added, so that a total of lO00 ml of H20 were present.
Then, 800 ml of chlorobenzene were added under ordinary stirrincJ at 30C. After stirrin4 for 60 min. at 30C all chloroben2ene had diffused into the drople-ts. The emulsion was examined in optical mlcroscope, and it was found that a monodisperse emulsion having a droplet diameter of about 3.0 ~m-had been formed.

Example 2 The experiment was carried out as described in example l, the only difference being that 35 ml of acetone were .

~ ~6779 used. With this increase in the alrloun-t of- acetone the stirring time for the in-troduction oE ],-chlorododecane could be reduced to < 5'hours.

Example 3 Swelling of monodisperse polystyrene latex with chlorododecane was carried out as described in example 1.
After evaporating the acetone 1.0 g of Na-laurylsulphate and ~340 ml of H20 were added, -to provide a total of 1000 ml H20.
Then 800 ml of ethyl benzene were added at 30C under ordinary stirring. After 60 min. all ethyl benzene had diffused into the droplets. Examination in op-tical microscope indicated a monodisperse emulsion having a droplet diameter of about 3.0 ~m.

Example 4 350 rnl of H20, 13.5 ml of l-chlorododecane and i ~ 6 g of Berol 09 (nonyl phenol ethoxylate containing 10 moles of ethylene oxide per mole of nonyl phenol) were mixed in a high speed mixer of the type Ultraturrax for abou-t 15-20 min.
at 10.000 rpm. This yielded an emulsion having a droplet diameter of 0.2-0.5 ~m. This emulsion was then added to the same type and amount of polystyrene seed latex as described in example 1. Then 47 ml of acetone were added under ordinary stirring at 35-40 C. Afte~ stirring for 10 hours at 40 C
acetone was evaporated under vacuum. Examination in optical microscope indicated a monodisperse emulsion having a droplet diameter of 0.9 ~m. After evaporation of acetone 1.0 g of Na-lauryl sulphate and 573 ml of 1120 were added, giving a ~-t~ k 7~
_ to-tal of lO00 ml of 1-l20. Then 800 ml of ethyl ben~ene were added under ordinary stirring a-t 30C. Af-ter stirring for 60 min. at 30C all ethyl benzene had diffused'in-to the drople-ts.
Examination in optical microscope indicated a rnonodisperse emulsion haviny a droplet diameter of 3.0 l~M.

Example 5 75 ml of H20, 15 ml of dioctyl adipa-te and 0.75 g of Na-laurylsulphate were homogeni~ed as described in example l. This emulsion was added -to a seed latex of bidisperse polyvinyl chloride having particle diame-ters of 0.2 and 0.~ ~m (determined by electron microscopy).
24,3 ml of seed latex were used containing 16.8 ml of H20 and 7.5 ml of polymer particles. Further, lO m:L of acetone were added under ordinary stirring at 35-40C. After stirring for lO hours at 40C acetone was removed by evaporation under vacuum. The emulsion was examined in optical microscopej and it was found that the result was a bidisperse emulsion having droplet diameters oE abou-t 0.25 and 1.1 ~m. After evaporation of acetone 1.8 y of Na-laurylsulphate and 908.2 ml of H20 were added, to provide a total of 1000 ml of H20. Fur-ther, 660 ml of dichloroethane were added at 30C under ordinary stirring. After s-tirring for 60 min. at 30Call dichloro-ethane had diffused into the droplets. The emulsion was exarnined in optlcal microscope, and it was found that a bidisperse emulsion had been obtained having a droplet diameter of 0.8 and 3.5 ~m.

.

77~

~xample 6 330 ml of H20, lo ml of chlorododecane, 10.5 g of Berol 09 (nonyl-phenol ethoxylate containing 10 moles of ethylene oxide per mole of nonyl phenol) were mixed by means of a high speed mixer of the type Ultraturrax for about 15-20 min. at 10.000 rpm. This resul-ted in an emulsion having a droplet diameter of 0.2-0.5 ~m. This emulsion was added to the same seed latex as described in example 1. An amount of 248.6 ml of seed latex was used containing 228.6 ml of H20 +
20 ml of polystyrene particles. After stirring for 15 hours at 40 C 421.4 ml of H20, 2 g of NaLS and 800 ml of chloro-benzene were added. After stirring for 60 min. all chlorobenzene had diffused intothe droplets.The emulsion was examined in optical microscope, and it was found that a monodisperse emulsion having a droplet diameter of 2.1 ~m. had been formed.

Example 7 77 ml of H20, 11.7 ml of chlorododecane, 1.8 g of benzoyl peroxide, 9.3 ml of dichloroe-thane and 0.2 g of Na-laurylsulphate were homogenized as described in example 1.
This emulsion was added to the same type and the same amount of seed latex as described in example 1. Fur-ther, 6 ml of H20 and 8.5 ml of acetone were added under ordinary stirring at 35-40C. After stirring for 12 hours at 40 C acetone was removed by evaporation under vacuum. After evaporation of acetone and dichloroethane 1.0 g of Na-laurylsulphate and 840 ml of H20 were added to provide a total of 1000 ml of H20.
Further, 275 ml of distilled styrene were added under ordinary 77~

stirring at 30C. After st:i,rring for 2 hours at 30(~C the temperature was raised to 60C and the polymer:isation star-ted.
After 25 hours polymerisation a monodisperse latex was obtained having a particle diameter of about 2 ~m.

Example 8 100 ml of H20, 20 ml of dioctyl adlpate, 0.5 g of NaLS were homogenized as described in example 1.
This emulsion was added to a seed latex of a bidisperse polyvinyl chloride having particle diameters of 0~1 and 0.3 ~m (de-termined by electron microscopy)~ 45 ml of seed latex were employed containing 3~ ml o-f H20 and 10 ml of polymer particles. Then 15 ml of acetone were added under ordinary stirring at 40C. After stirring for lo hours at 40C the acetone was removed by evaporation under vacuum.
After evaporation of acetone 2.0 g of NaLS and 865 ml of H20 were added to provide a total of 1000 ml H20. Further, 600 ml of vinyl, chloride were added under ordinary stirring at 30C.
After stirring for 2hours at 30C all vinyl chloride had diffused into the droplets, and 3.0 g of AIBN dissolved in 10 ml of dichloroethane were added. After stirring for 1 hour at 30C the temperature was raised to 50C for polymerisation.
The final latex was bidisperse and contained particles havi,ng diameters 0.3 and 1.0 ~m.

Example 9 150 ml of H20, 30 ml of dioctyl adipate, 0.75 g of Na-laurylsulphate were homogeni~ed as described in example 1.

.

~'` 26 77~
This emulslon was added -to a seed latex oE po:Lyviny:l chloride having particles evenly distri,butecl from 0.1 to 0.3 llm.
60 ml of seed ],atéx con-taining 45 ml of H20 and' 15 m], of particles were employed. Then 20 ml of ace-tone ~ere added under ordinary stirring at 40C. After stirring for lO hours at 40C acetone was removed by evapora'tion under vacuum.
~fter evaporation of acetone 2.25 g of Na-laurylsulpha-te and 745 ml of H20 were added. Fur-ther, 800 ml of vinyl chloride were added. After stirring for 2 hours at 50C 2,0 g of K2S208 dissolved in 60 ml of H20 were added, and polymerisation was Carried out. The final latex contained partlcles having diameters from 0.3 1.0 ~m.

Example 10 Monodisperse latex of polystyrene having a particle diameter of 2.1 ~m was prepared as described in example 7. To 125.6 ml of this latex containing 100 ml of H20 and 25.6 ml of particles comprising 1.2 ml of chloro-dodecane were added 3.0 g of Na-laur~ylsulphate and 900 ml of H20 to provide a total of lO00 ml of ~I20. Further, 900 ml of chlorobenzene were added under ordinary stirring at 30C.
After stirring for 2 hours at 30C all chlorobenzene had diffused into the droplets. The emulsion was examined in optical microscope, and it was found that a monodisperse emulsion had been formed having a dropletdiameterof about 6.5 ~m.

.

Example 11 -120 ml of styrene and 100 ml of chlorodo~ecane were mixed and adcled to 1000 rnl of H20, 200 ml of methanol and 0.6 g of K2S208, and the entire mix-ture was -then polymerized at 60C for 8 hours. The latex formed was monodlsperse having a particle diameter of 0.75 ~m and wi-th particles consisting of polystyrene and chlorododecane in the ra-tio 1:1.
180 ml of the seed latex formed, consis-tiny of 150 ml of M20 and 15 ml of polymer particles swelled with 15 ml of chloro-dodecane were added to 850 ml of H20, 2.0 g of NaLS and 800 ml of chlorobenzene with ordinary stirring at 30C. After stirring for 60 min. at 30C all the chlorobenzene had diffused into the particles. The emulsion was examined in optical microscope, and i-t was found that a monodisperse emulsion having a droplet diameter of 2.25 ~m had been formed.

Example 12 100 ml of H20, 9 ml of l-chlorododecane and 5 y of NaLS were homogenized in a two stage Manton Gaulin homogenizer wi-th 200 kg/cm2 in the 1st stage and 80 kg/cm2 in the 2nd stage for 1-1.5 min. This resulted in an emulsion having a droplet diameter of 0.1-0.2 ~m. To this emulsion there was added a seed latex of monodisperse polybutyl acrylate having a particle diameter of 0.3 ~m (determined by electron microscopy). 109 ml of seed latex were used containing 100 ml of H20 and 9 ml of polymer partic]es.
Further, 20 ml of acetone were added under ordinary s-tirring at 35~40 C. After stirring for 3 hours a-t 35 C ace-tone was B77~
removed by evaporation under vacuum. (:Ct should be noted that the stirring t:ime for incorporatiny the 1-chlorododecane has been strongly reduced since a polymer haviny a much lower glass transition temperature than polystyrene was used.) ~ fter evaporating the acetone 800 ml of H20 were added to provide a total of 1000 ml of H20. Then 800 ml of chlorobenzene were added at 30C. After stirriny for 2 hours all chlorobenzene had diffused into the droplets, and examinatiOn in optical microscope indicated a monodisperse emulsion having a droplet diameter of about 1.~ ~m.

Example 13 Seed latex of monodisperse polystyrene having a particle diameter of 0.5 ~m (determined by electron microscopy) was swelled with a slightly water soluble compound, in this case toluene. This was done to decrease the glass transition temperature of the particles and then facilitate the transport of Substance I within the particles. An amount of 99 ml of seed latex was used containing 91 ml of H20 and 3 ml of polystyrene particles. To this latex was added 0.05 g Na-laurylsulphate and 8 ml toluene under ordinary stirring at 3~C.
After the absorption of toluene in the particles had taken place, the swelling with Substance I was carried out. 80 ml of H20, 8 ml of l-chlorododecane and 0.2 g of Na-laurylsulphate were homogenized as described in example 1. This emulsion of Substance I was then added to the seed latex previously swollen - with toluene as described above. 10 ml of acetone was added I

. `, : :

., ,, ', '.

77~

and the mixture stirred at 35C. ~y thls method -the time for complete absorption of Substance I into the par-ticles was considerably reduced and was complete~ in less -th~n 2 hours.
After removal of acetone by evaporation, 829 ml of H20, 2.75 g of Na-laurylsulphate and 800 ml of chlorobenzene were added, and the stirring continued a-t 35C. After s-tirriny for 60 min.
all chlorobenzene had diffused into the particles. The emulsion was examined in optical microscope and it was found -that a monodisperse emulsion having a droplet diameter of 2.3 I,lm had been formed.

Example 14 i~ ~ 50 ml of H20, 5 ml of Perkadox~SE 8 (dioc-tanoyl peroxide) and 1.5 g of NaI,S were homogenized. Perkadox SE 8 is an initiator having a melting point of 19C, and due -to the low solubility in water it may act alone as Substance I for the swelling of polymer particles.
After homoyenisation the emulsion was charyed with a seed latex of monodisperse polybutyl acrylate having a particle diameter of 0.3 ~Im (determined by elec-tron microscopy). There were used 60.5 ml of seed latex containiny 55.5 ml of H20 and 5 ml of polymer particles. Then 10.5 ml of acetone were added under ordinary stirring at 30C. After stirring for 3 hours at 30C acetone was removed by evaporation under vacuum.
After the evaporation of ace-tone 894.5 ml of H20 were added to provide a total of 1000 ml of I-l20. Further, 200 ml of distilled styrene were added under ordinary stirriny ~æ n~rk 3~
, 7~

at 30C. ~fter stirriny for 2 hours at ~0C the tempera-tur was raised to 60C, and polymerisation was carried ou-t to complete conversion.A monod.isperse latex was Eormed having a particle diameter of about 1 E~Yample_15 20 ml of H20, 6 ml of Perkadox SE-8 (dioctanoyl peroxide) and 0.2 g of Na-laurylsulphate were homogenized as described in example 1. To this emulsion was added a seed latex of monodisperse polystyrene prepared as described in example 7, having a particle diameter of 1.7 ~Im (determined by electron microscopy). 41 ml of seed latex were used containing 35 ml of H20 and 6 ml of polystyrene particles.
. In addition, 6 ml of acetone were added under ordinary stirring at 25-30C. After stirring for 14 hours at 25-30C
acetone was removed by evaporation under vacuum.
After evaporation of acetone l.5 g of NaLS, l.o g of Berol 267 (nonyl phenol ethoxylate containing 8 moles of ethylene oxide per mole of nonyl phenol) and 945 ml of H20 were added to provide a total of 1000 ml of H20. Then 200 ml 20` of distilled styrene were added under ordinary stirrlng at 25-30C. After stirring for 3 hours at 25-30C the temperature was raised to 70C, and polymersatlon was carried out to completeconversion. The final latex was monodisperse and contained particles having a diameter of about 5 llm Example 16 35 ml of H20, 4 ml of Perkadox SE-8 (dioctanoyl peroxide), 3 ml of chlorododecane and 0.2 g of Na-laurylsulphate 3~

1 3.fi67~
were homogenized as described in example ]. To -this emulsion was added a seed latex of monodisperse polystyrene prepared as described in e~ample 7 having a particle diame-ter of

2 ~m (determined by electron microscopy). 28.5 ml of seed latex were employed containing 25 ml of E-120 + 3.5 ml of polys-tyrene particles. In addition 10 ml of H20 and 7 ml of acetone were added under ordinary s-tirrin~ a-t 25-30C. After stirring for 14 hours at 25-30C acetone was removed by evaporation under vacuum.
After the evaporation of acetone 1.2 y of NaLS, 1,0 g of Berol 267 and 930 ml of H20 were added to provide a total of 1000 ml of H20. Then 175 ml of distilled styrene were added under ordinary s-tirring at 25-30C. After stirring for

3 hours a-t 25-30C the temperature was raised to 70C, and polymerisa-tion was carried out -to complete conversion. The final latex was monod~isperse and contained particles having a diameter of about 7 ~m.

_xample 17 20 ml of H20, 6 ml of Perkadox SE-8 (dioctanoyl peroxide) and 0.2 g of Na-laurylsulpha-te were homogenized as described in example 1. To -this emulsion was added a seed latex of monodisperse polystyrene having a particle diameter of 1.7 llm (determined by electron microscopy) prepared as described in example 7. 41 ml of seed latex were employed containing 35 ml of H20 and 6 ml of polystyrene particles.
In addition 6 ml of acetone were added under ordinary stirring at 25-30C. After stirring for 1~ hours at 25-30C acetone was 3?.

67~
removed by evaporation unc3er vacuurn.
After evaporation of acetone 1.5 g of Na-lauryl-sulphate and 945 rnl of H20 were added to provide a total of lO00 ml of H20. Then 70 ml of distilled styrene were added under ordinary stirring at 25-30C. After stirring for 30 min. at 25-30C the temperature was raised to 70C. After polymerisation for 2 hours at 70C the addition of the remaininy amount of monomer was started, and 140 ml of distilled styrene were added in the course of 5 hours. The temperature in the reactor was 70C during the addition of styrene.
Polymerisation was carried out to comple-te conversion, and the inal latex contained particles havlng a diameter of about 5 um with standard deviation of about 0.5 ~m.
In this example only some of the monomer was added at the beginning of the second step, while the rest of the monomer was added after the polymerlsation had proceeded for some time.

Example 18 30 ml of H20, 6 ml of stearyl methacryla-te and 0.2 g oE Na-laurylsulphate were homogenized as described in example l. The temperature was kept at about 35C during the homogenisatlon. To the emul.sion was added a co-polymer latex of styrene and butyl acrylate having a particle diame-ter of about 0.35 ~m (determined by electron microscopy) and a glass transition temperature of about 15C. 36 rnl of latex containing 30 ml of H20 and 6 ml of polymer par-ticles were used.
In addltio~ 6 ml of acetone were added under ordinary stirring . ~ , ~ ~¢~7~
at about 35C. After st:irring fo:r 5 hours at abou-t 35C
acetone was removed by evaporation under vacuum.
After evaporation of acetone 2.5 g of Na-lauryl-sulphate and 940 ml of H20 were added to pro.vide a total of looo ml of H20. Then 210 ml of styrene were added during ordinary stirring at about 35C. After stirring for 2 hours at.about 35C 4.g of AIsN dissolved in a small amoun-t of 1,2-dichloroethane were added. Af-ter stirring for 1 hour at about 35C the temperature was raised to 70C and polymerisa-tion was carried out to complete conversion. The final la-tex contained particles having a diameter of about 1 ~m.

_xample l9 30 g of lauroyl peroxide (LP0) was dissolved in 30 y of styrene, and 30 g of l-chlorododecane were added.
Then 400 ml of ~2 and 0.8 g of NaLS were added. The mixture was homogenized in a two stage homogenizer from Manton-Gaulin model 15-M, and the emulsion formed contained droplets having a diameter of 0.1-0.6 ~m. The em~lsion was transferred to a reactor at 60C, and polymerisation was carried out to complete reac-tion. The latex formed contained particles having a diame-ter of 0.1-0.6 ~m. To 82 g of the latex were added 933 ml of H20, 3.0 g of NaLS and 750 ml of chlorobenzene under ordinary stirring at 35C. The amoun-t of chlorobenzene added corresponds to 75-80 times the volume of the polymer particles. After stirring for 2 hours at 35C all chloro-benzene had diffused into the particles, and the emulsion formed contained droplets haviny a diameter of 0.5-2.5 llm.

- ' ~

Example 2_ Latex having a par-ticle diameter oE 0.1-0.6 ~m was prepared as described in example ]9. To 37 g of the latex formed were added 970 ml of H20, 6.0 g of NaLS and 800 ml of chlorobenzene under ordinary stirring at 35C. In -this example a higher concentration of emulsifier than in example 19 was used, and the amount of polymer par-ticles relative -to the amount of chlorobenzene could thereby be reduced. The amoun-t of chlorobenzene used corresponds to about 180 times the volume of the polymer particles. After stirrincr for 2 hours at 35C all chlorobenzene had diffused into the particles, and the emulsion formed contained droplets having a diameter of 0.5-3.5 ~m.

Example 21 ~ .
Latex having a particle diameter of 0.1-0.6 ~m was prepared as described in exampIe 19. To 82 g of the latex formed were added 933 ml of H20, 3.0 g of NaLS and 500 ml of styrene under ordinary stirring at 20C. The amount of styrene added corresponds to approx. 50 times -the volume of -the ~0 polymer particles.
After stirring for 2 hours at 20C the tempera-ture was raised to 80C, and polymerisation was carried out until complete reaction by means of LP0 present from the first step.
The latex forméd contained particles having a diameter of 0.5-2.0 llm, and the solids content was about 30 percen-t.

~ ~BB~
Example 22 Latex haviny a particle size of 0,1-0,6 ~m was prepared as described in example ].9, To lll g of the latex formed were added 910 ml of H20, 4,0 g of NaLS and 900 ml of vinyl chlori,cde under ordinary s-tirring at 20C, The amount of vinyl chloride added corresponds to 65-70 times the volume of the polymer particles, After stirring for 2 hours at 20C the tempera-ture was raised to 50C, and polymerlsation was carried out to approx, 90 percent conversion by means of LP0 present from the flrst step, The latex formed contalned partlcles having a diameter of 0,5-2,0 ~m, and the solids content was about 40 percent, i ;~6~779 Reference has previously been made herein to the preparation of monodisperse porous polymer particles according to the invention and the uses thereof. The following example illustrates the preparation of such monodisperse particles.
Example 23 18 ml of dioctanoyl peroxide (Perkadox* SE-8~, 180 ml of H2O and 0.8 g of NaLS were homogenized.
After homogenisation the emulsion was added to a latex of monodisperse polystyrene particles having a diameter O of 1.9 ~m (s~andard deviation about the mean size was 2% as obtained by electron microscopy). 50 ml of emulsion were employed containing ~2.5 ml of H20 and 7.5 ml of polymer particles. In addition 13 ml of acetone were added under ordinary stirring at 25C. After stirring for 48 hours at 25C 13 g NaLS and 3500 ml H20 were added. Further a mixture of 400 ml divinylbenzene (50% technical grade) and 800 ml toluene were added under ordinary stirring at 25C. After stirring for 20 hours at 25C an additional volume of 3000 ml H20 containing 10 g of Berol* 292 (nonyl phenol ethoxylate ~0 with 20 moles of ethylene oxide per mole of nonyl phenol) was added. The polymerisation was carried out by increasing the temperature to 70 C. After polymerisation the particles were isolated and toluene removed from the particles by repeated extractions with acetone. Finally the particles wer~ dried at 80 C. A free flowing powder consisting of 10 ~m monodisperse, highly crosslinked porous particles had been obtainedO A
specific surface area of 530 m2/g was determined by the BET-method. The standard deviation about the mean particle size was 2.5% as determined from optical micrographs. The product yield was higher than 95~ of the theoretical.

* Trade Mark ;

. . ~

Claims (39)

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

1. A process for preparing an aqueous emulsion or dis-persion of a partly water-soluble material which comprises a) preparing an emulsion or dispersion of particles comprising i) polymer and ii) substance I which is one or more materials having a water solubility of <10-2 g/l and is substantially absorbed by said polymer and b) adding to said emulsion or dispersion substance II
which is one or more partly water-soluble materials of higher water-solubility than substance I and which diffuses into the polymer particles containing substance I, and then causing polymerization to take place when substance II is a polymeriz-able monomer.

2. The process of claim 1 wherein substance I has a molecular weight of <5000.

3. The process of claim 2 wherein substance II has a water solubility at least 10 times higher than that of substance I and diffuses into the particles containing sub-stance I in an amount at least 20 times that of the original polymer particles used in (a) based on volume.

4. The process according to claim 1, 2 or 3 wherein substance II is a polymerizable monomer.

5. The process according to claim 1, 2 or 3 wherein sub-stance II is a polymerizable monomer and the aqueous emulsion or dispersion of said polymerizable monomer is polymerized.

6. The process of claim 1, 2 or 3 wherein the solubility of substance I is <10-4 g/l H2O.

7. The process of claim 1, 2 or 3 wherein the solubility of substance I is <10-5 g/l H2O.

8. The process of claim 1, 2 or 3 wherein the solubility of substance I is <10-5 g/l H2O and wherein substance II is a polymerizable monomer which is polymerized after diffusion into said particles prepared by (a).

9. The process of claim 1 or 3 wherein substance I has a molecular weight of <500.

10. The process of claim 1 or 3 wherein substance I has a molecular weight of <500 and wherein substance II is a poly-merizable monomer which is polymerized after diffusion into the particles from step (a).

11, The process of claim 1 or 3 wherein substance I has a molecular weight of <500, a water solubility of <10-5 g/l H2O and substance II is a polymerizable monomer which is polymerized after diffusion into the particles from step (a).

12. The process according to claim 1 wherein substance I
is added to a stirred aqueous dispersion of said polymer particles or to an aqueous dispersion of monomer or monomer mix-ture from which said polymer particles are prepared, whereby substance I is transported through the aqueous phase to said particles which are swelled therewith, under conditions which cause the rate of transport of substance I through the aqueous phase to be relatively high and then adding substance II
under stirring after causing said rate of transport of substance I through the aqueous phase to become relatively low, whereby substance II diffuses into the polymer particles swelled with substance I.

13. The process according to claim 3 wherein substance I
is added to a stirred aqueous dispersion of said polymer part-icles or to an aqueous dispersion of monomer or monomer mixture from which said polymer particles are prepared, whereby substance I is transported through the aqueous phase to said particles which are swelled therewith, under conditions which cause the rate of transport of substance I through the aqueous phase to be relatively high and then adding substance II under stirring after causing said rate of transport of substance I
through the aqueous phase to become relatively low, whereby substance II diffuses into the polymer particles swelled with substance I.

14. The process according to claim 13 wherein substance I
is added in the form of an aqueous emulsion.

15. The process of claim 13 wherein in order to increase the rate of transport in step a) there is used an emulsifier in an amount such that the concentration of the emulsifier is above the critical micelle concentration, whereby some or all of substance I is solubilized in micelles and wherein this effect is removed before the addition of substance II in step b), by the addition of water.

16. The process of claim 13 wherein step a) is performed in the presence of a solvent which is wholly or partly soluble in water and is a solvent for substance I.

17. The process of claim 15 wherein step a) is performed in the presence of a solvent which is wholly or partly soluble in water and is a solvent for substance I.

18. The process of claim 16 or 17 wherein said solvent is acetone or a lower alkanol.

19. The process of claim 16 or 17 wherein said solvent is a relatively water-soluble monomer.

20. The process of claim 16 or 17 wherein said solvent is employed in ah amount of 1-100% of the amount of water, based on volume, in step a).

21. The process according to claim 13 or 15 wherein said solvent is removed after step a).

22. The process according to claim 13 or 15 wherein said solvent is removed after step a) by evaporation.

23. The process of claim 12 or 13 wherein said substance II
is a polymerizable monomer and wherein the emulsion or disper-sion of said polymerizable monomer is polymerized.

24. The process according to claim 1, 2 or 3 wherein after step a), the amount of water in said emulsion or dispersion is increased, emulsifier is or is not added, and then substance II
is added with or without stirring.

25. The process of claim 3 wherein substance II is a poly-merizable monomer which is polymerized after diffusion into particles of step b), a water soluble or partly water soluble initiator being added for the polymerization.

26. The process of claim 25 wherein the initiator is added in the form of a solution.

27. The process of claim 3 wherein substance II is a polymerizable monomer which is polymerized after diffusion into the particles from step a), the initiator having very low solubility in water and being added as a solution in substance I.

28. The process of claim 3 wherein substance II is a poly-merizable monomer which is polymerized after diffusion into the particles from step b), the initiator being a liquid initiator employed as substance I.

29. The process of claim 28 wherein the liquid initiator is dioctanoylperoxide.

30. The process according to claim 1 wherein the dispersion of step a) is prepared by first homogenizing a mixture of a polymerizable monomer and substance I with or without an oil soluble initiator, water and emulsifier, then, with or without adding a wholly or partly water-soluble initiator, polymerizing to provide a dispersion of polymer particles containing 5-90 percent by volume of substance I and then subjecting the resultant dispersion to step b).

31. The process according to claim 3 wherein the dispersion of step a) is prepared by first homogenizing a mixture of a polymerizable monomer and substance I with or without an oil soluble initiator, water and emulsifier, then, with or without adding a wholly or partly water-soluble initiator, polymerizing to provide a dispersion of polymer particles containing 5-90 percent by volume of substance I and then subjecting the resultant dispersion to step b).

32. The process of claim 30 or 31 wherein substance II is a vinyl monomer which is polymerized after having been diffused into the particles prepared in step a).

33. A toner for use in xerography comprising monodisperse polymer particles.

34. The process of claim 1 wherein the emulsion or dispersion of part (a) is monodisperse.

35. The process of claim 3 wherein the emulsion or dispersion of part (a) is monodisperse.

36. The process of claim 13 wherein the emulsion or dispersion of part (a) is monodisperse.

37. Monodisperse polymer particles having an average particle diameter of > 5 µm.

38. The particles of claim 37 wherein said particles are porous.

39. The particles of claim 38 having an average particle diameter of > 10 µm.