SE429760B - PROCEDURE FOR MANUFACTURING MONODISPERSA SPHERICAL PARTICLES - Google Patents

Description

8201739-3 10. 15; 20. 25. 30. 35. 2 kits-for charge modification etc. and then grind and aiming the product certainly allows a relatively free choice of materials and additives but the particles obtained has a very irregular shape and a very uneven size. play distribution which leads to poor abrasion resistance, poor resolution and difficulty in removing especially those smaller particles from unwanted places on the surface. Alter- native ways of making toner particles have been proposed which gave particles with a more round shape but these are known methods have not given the desired narrow size distribution reduced freedom of choice in the choice of materials and made it difficult to supply additives.

European Patent Application 3,905, which incorporated by reference into the present specification, is a process previously known by which spherical polymer particles of extremely even size distribution can produced by a swelling process to sizes suitable for toner particles. The conditions of swelling are, however, such that common methods of staining and adaptation of the other properties to the toner application can not be readily used.

The invention in general The object of the present invention is to provide a process for producing a toner, which better than hitherto known meet the above requirements and is not subject to the same disadvantages. In particular, for the purpose of achieving a toner that satisfies ae established receivables but has significantly improved in terms of roundness and monodisperse particulate matter -sharing. A further object of the invention is to enable the use of particles obtained by the process according to the above-mentioned patent application in toner context These purposes are achieved with the help of the characteristics provided appears from the appended claims.

By eliminating in the manufacture of toner particles from very monodisperse, ie. even-sized but small polymer pairs articles obtained by emulsion polymerization and then add these to sizes suitable for toner application below in a more detailed manner, very spherical particles are obtained 10. 15. 20. 25. 30. 35. 8201739-3 3 with extraordinarily narrow size distribution. By adding bring the particles to a colored substance after swelling and merisation, the particles can be colored without swelling and the polymerization steps are negatively affected by the additive. Further in this way a concentration of the additive to the surface takes place of the particles, which partly means that a relatively large amount of substance can be added in a small radius increase at the particles so that the smoothness and sphericity of them can maintained and partly means that one from the light absorption point - advantageous distribution is obtained, which further decreases the required amount of additive so that the effect on particulate matter their shape and size distribution are minimized. By baking the colored substance in a shell or by applying one shell as a cover layer on top of the layer of colored substance is obtained an opportunity to influence a range of significant characteristics for toner application without the swelling and polymerization steps in the manufacture of the particles adversely affect work. Particle surface properties can thus be selected by shell material or by additives to this is affected in such as hydrophilicity, charging properties, conductivity digestibility and digestibility or tack. In addition, forms the shell provides protection against abrasion of the colored substance. Also for the shell and any additives in it apply to a thin layer is sufficient to add significant amounts of modified means. Paint and cover layers arranged on the surface of the particles also means great opportunities to adapt the same monodisperse base particles for different toner applications which is a particular advantage in this context associated with significant costs to substantially change the the mode of action of these basic particles.

Additional objects and advantages of the invention more to be seen in the detailed description below.

Definition of Coefficient of Variation The monodispersity of the particles is stated in the present writing with the coefficient of variation (C V). To obtain C V is first calculated as the standard deviation of the sample.

Standard deviation (S) = 8201739-3 10. l5f 20. 25. 30. 35- hrs This means that S is the square root of the arithmetic average of the squares of the variance of the different values sees from the arithmetic mean of all the values. If the diameters of the particles are measured in micrometers, the dimensions . sion of S micrometers S X 100:% the mean If the diameters of the particles vary according to the standard normal distribution, 68 per cent of all allows to have diameters between 3 l C V of the mean.

C V = Preparation of the base particles The invention is not limited to anything in particular process for the preparation of the base particles without any method is useful which can provide polymer particles with suitable monodipsersity and sphericity. Methods based on swelling However, the use of smaller polymer particles has been found to be suitable and in particular those where the swelling is based on ticks with a narrow size distribution.

A particularly suitable process for the production of monodisperse spherical thermoplastic base particles include produces an aqueous dispersion of monodis Persian graft particles with an average diameter of less than approx 3_pm, which in addition to polymer contains a relatively low molecular weight learned, insoluble in water but absorbable in the polymer. ne, addition of a monomer less sparingly soluble in water than that sparingly soluble substance but capable of being absorbed into the inoculum containing the sparingly soluble substance under conditions allowing molecular migration of the monomer to and absorption particle formation and polymerization of monomer particles na, The particles thus obtained are suitable as base particles ~ glare for the toner of the present invention.

The introduction of the relatively low molecular weight, in water insoluble, the substance can occur by the substance being present at preparation of the polymer in the graft particle. A better size play distribution is obtained if the insoluble substance is constituted of an oligomer formed in connection with the polymerization of the polymer in the graft particles by selecting suitable in a known manner. The amount of oligomer to polymer in the particle 10. 15. 20. 30. 35. 8201739-3 5 should then be greater than 0.5: l. An additional and pre- drawn way to introduce the insoluble substance is to add this to the aqueous dispersion of the inoculum particles of polymer under such conditions that the sparingly soluble . can be molecularly migrated to and absorbed into inoculum particles. and swell them and that the conditions in the aqueous phase is changed so that the molecular migration of the the substance is aggravated before the addition of the monomer.

The production method as above presupposes addition of small monodisperse particles as a kind of inoculum the further procedure. High-grade monodisperse polymer particles can be prepared by, for example, emulsion polymer under special conditions but only in sizes less than about 3_pm. Inoculum suitable for the invention ticks in the size range of 0.01 to 1 pm and especially sizes between 0.05 and 0.5 pm. The coefficient of variation should be less than 30%, preferably less than 10% cents and preferably less than 5 percent. The polymer material in the inoculum particles is not so critical for the present suitability because the proportion of polymer derived from graft poly more becomes very small in the finished particle. The polymer should, however, be water insoluble. Suitable polymers are examples polyvinyl chloride, polyvinyl acetate, polybutyl acrylate and especially polystyrene. A way to produce monodisperse . particles suitable as starting materials are shown in vis Woods, M.E., Dodge, J.S. and Krieger, I.M., J. Paint Techn. EQ, Sül (1968), which article by reference is incorporated herein by reference.

The monodisperse particles must be dispersed. in water in connection with the swelling. Suitable dry content for such a dispersion may be about 10 to 15% by weight.

As mentioned, a water-soluble substance must be introduced lived in the graft polymer. The solubility of the substance in water must be larger than that of the graft polymer but should be less than 10 unfortunately less than l0_ and preferably less than 10-5 g / l. Mole- the cooling weight should be less than 5000 and preferably also less than 500. The substance is preferably organic for best compatibility. small with other components and should be non-ionic solubility reasons. Hydrocarbons and substituted hydrocarbons can 8201739-3 10. pls. ao, 25. 30. 35. 6 be used. Examples of substances are chlorododecane, dioctyl adipate, stearyl methacrylate or a sparingly soluble initiator, such as di- octanoyl peroxide. It is also possible to use an oligo- more as an insoluble substance, especially when the substance is to be incorporated in the graft particle directly in connection with its production above. The substance should be liquid under the conditions during swelling and monomer addition.

Then the sparingly soluble substance must be added to the inoculum particle by migrating molecularly through the aqueous phase to the inoculum due to the water-insoluble nature of the ïren; measures are taken to facilitate this migration.

This can be done by atomizing the substance together with emulsifier to increase the contact surface with the water or through an addition of solvents such as lower alkanols or acetone to increase the solubility of the treated water. ten phase. The methods can advantageously be used in combination.

The amount of added and absorbed sparingly soluble substance is limited upwards of the absorbency of the substance in the graft polymer and of the stability of the swollen particle. Normally, the it below 10 times the weight of the graft polymer, preferably between 1 and 4 times the weight of the graft polymer. The swelling occurs while stirring. e D ' During the addition of monomer to the dispersion of poly- the more or polymer / oligomer particles shall the ratio in the aqueous phase be such that reversal of the soluble substance from the particles into the aqueous phase and to the monomer droplets should not take place. Then a solvent used to introduce the sparingly soluble substance, a change of conditions suitably before the monomer addition by evaporation of the solvent and / or dilution of the water phase. The sparingly soluble substance should be absorbed as completely as possible in the inoculum particles: before mono- more.supplied.

The latter added monomer should be more aqueous. soluble than the sparingly soluble substance, preferably at least 10 times as water-soluble and preferably at least 100 times as soluble. Many different types of monomer can be used for the object of the invention and among suitable merisable monomers may be mentioned stvren, vinyl chloride, vi- 10. 15. 20. 25. 50. 35. 8201739-3 7 nylidene chloride, acrylonitrile and acrylates, such as methyl acrylate lat and ethyl acrylate. Also mixtures of different monmers Can be used. Particularly suitable monomers are styrene, styrene pure acrylic, styrene-acrylonitrile-acrylic or vinylidene chloride -acrylonitrile. The monomer selection should be made i.a. with respect to desired softening properties. When the toner particles are to be used in contexts where the adhesion takes place by heating glazing temperature (Tg) is desirable for at least a part of the polymer content of the finished particle keep below 100 ° C, preferably below 80 ° C. Ideally located glazing temperature above 3000. Suitable properties of the hardness can also be influenced by the degree of polymerization.

The amount of monomer added is greater than the amount of sparingly soluble substance in the particles and can be up to more than 1000 times the weight of the swollen particles, preferably up to .80Ö times and especially between 20 and 300 times the particulate weight before the monomer addition. It is desirable that it added the monomer mixture as completely as possible absorbed into the particles prior to polymerization to avoid the formation of new polymer particles in the aqueous phase, which seriously impairs the desired even size distribution ningen. The swelling with monomer also takes place with stirring.

It is preferred that the entire amount of monomer be added directly but with larger monomer amounts it is also possible to add the monomer batchwise.

After the monomer addition, polymerization can be undertaken.

Initiator, especially water-insoluble ones, may be suitable added as a sparingly soluble substance or together with another such before the monomer addition but it can also added in connection with the addition of the monomer or 'after the monomer addition. Preferably a monomer soluble initiator with low water solubility such as the one mentioned dioctanoyl peroxide to avoid polymerization in aqueous ten phase.

After the polymerization, a renewed addition of sparingly soluble substance and / or monomer are undertaken for further greater size increase and renewed polymerization. Possibly only monomer is added for a limited additional swelling. ning. The number of swelling steps is arbitrary but the 8201739-3 10. l5. 20; 25. 30. 35- 8 that the desired size increase is achieved in so few steps as possible, which gives the best properties of the product.

Normally, therefore, one or two steps were used.

A suitable size of toner particles according to the invention one is between 2 and 50_pm, especially between 5 and 25 pm and preferably between 8 and 15 pm. The base particles should thus be read to such a size that they follow the one described below the scale application is sized within these limits.

The particles enlarged according to the above have a size distribution that practically corresponds to it originally use the graft polymer. They are thus monodisperse with the same preferred values of the coefficient of variation as indicated above white for the graft polymer. This is due to the fact that the swelling the steps take place on a balanced and for all particles in a manner and with an uptake of the added substances largely determined by equilibrium conditions and not only by diffusion rates. The liquid character of those added substances also lead to a very spherical shape of the particles. These properties are very valuable for toner applications but in order to obtain a practically useful down certain additives must be made of which the most important is a colored substance. As initially mentioned, however, it is difficult to introduce additives before polymerization without disrupt these processes and without - destroying the even the game distribution. If the additives are divided into such ka are molecularly soluble in the particulate material and the like which are not molecularly soluble but form their own phase, usually fixed, if introduced into the particles, problems are experienced with both of these groups if one is trying to incorporate the materials early in the manufacturing process. The soluble substances are in gel organic and dyes contain reactive functional groups that tend to react with the initiator and difficult polymerization, alter the polymer formed or themselves change in an undesirable way. Fixed additives, which are not soluble in the particle, can not be easily added the interior of the particle before the polymerization in a controlled manner because the uptake capacity of the particle is not controlled by solubility or equilibrium conditions, hence a non-uniform uptake easily takes place with a widening of the size 10. 15. 20. 25. 30. 35. 8201739-3 9 the division as a result. There are also difficulties in choose a colloid or emulsifier system, which is both effective stabilizes the swollen particles against coalescence and at the same time allows the passage of the pigment particles through the phase interface.

For the above reasons, it has been found to be appropriate to add the necessary additives after polymerization the reaction. After the polymerization, however, the process may the substance is difficult to introduce homogeneously into the interior of the particles but at least one concentration to the surface tends to take place, which for reasons stated above is in itself advantageous. However, this places great demands on that the adhesion to the particles is good because colored dust detached from the particles destroys the size distribution in the toner and causes problems with discoloration of finished copies. These problems increase with the amount of colored substance that must be added and it is consequently difficult to both provide the particles with sufficient colored substance and to obtain at the same time a satisfactory adhesion of the touch the polymerized particle as this is solid and not very permeable to additives of various kinds. Ytterli- more problems that must be solved when additives are made after the polymerization of the particles is that the final surface must have all those initially mentioned for toner application necessary properties, such as suitable electrical properties moderate hydrophilicity and suitable softness and other canic properties. The colored substance itself has seldom characteristics in these respects. In most cases, gan too high and the charging properties too poor at the same time as the adhesion properties are inappropriate. Finally, must the supply can take place in such a way that the spherical and the monodisperse nature of the base particles does not go lost because the desired properties then not obtained. A particular problem in this context is that there is a risk of agglomeration of the particles when the supply.

Preparation of a shell According to the invention, a supply of paint is made possible. after the polymerization of the base particles at the same time 8201739-5 10. 15. 20. 25. 30. 35. 10 as the above conditions for the nature of the surface can is satisfied by coating the surface of the base particles with a shell of a polymer comprising or covering a colored substance. Using the polymer shell, an additive satisfactory adhesion is ensured by know of the adhesion between the base particle and the take colored substance is reduced. Since the shell in principle can made arbitrarily thick or at least significantly thicker than, for example, a pigment layer, a sufficient amount of colored substance in this way is added to the base particles. larna. The polymeric material of the shell can be selected so that it meets the required surface requirements. As an introductory mentioned was also obtained with the shell structure one from the light absorption point of view appropriate distribution of the colored substance net and one in tion of the properties of the base particles.

The polymeric material of the shell shall be selected taking into account compliance with the above conditions, taking into account appropriate softness of the material and taking into account its use the colored substance should be wettable by the polymer and be able to be dispersible in the polymer matrix that builds up appropriate opportunity for rskalet. Suitable monomers for the polymeric material in the shell are the same as previously listed as suitable for basic the particles. However, different materials may well coat for core and shell respectively. A harder polymer for can be used, for example, to give a matte surface to the pian after melting essentially only the shell. In practice The bitch also becomes the materials in the core and shell for the most part slightly different because the method of preparation of means the presence of spec- substances such as the sparingly soluble swelling agent. Strong hydrophilic polymers should not be used in the shell and not nor should emulsifiers be included in larger quantities as these can make the surface of the finished particle hydrophilic. Alternatively emulsifier residues can be washed off after coating. Special particularly suitable have copolymers between styrene and butyl methacrylate proved to be. The polymer may, as mentioned, be included additives for various purposes, such as charge regulators additives. Even in terms of mechanical properties, the shell can 10. 15. 8201739-3 ll advantageously differ from the core.

The amount of polymer in the shell should be so large that it the desired amount of colored substance can be stably covered or contained kept in the shell. However, the amount should not be so large that the supply of it adversely affects the intended size the distribution of the particle mixture. Suitably, vo- the adhesive ratio between shell and core in those cases the dye is distributed in the shell between 0.1 and 10, corresponding to an increase between about 5.2 and 122 percent of the core radius, but preferably the volume ratio is kept between 0.2 and l (6.3 to 26 percent radius increase). In those cases then only a covering of the colored substance shall take place by means of scale, the volume ratio can be reduced to 0.01 but retrieved, the ratio is kept above 0.05.

The colored substance may be a molecular soluble in subject, e.g. an organic dye, but it is preferred 20. 25. 50. 55. that pigments, especially inorganic ones, were used for archival resistance and in particular carbon powder or for those contexts where magnetic particles are of importance parts. For pigments, the volume should be calculated on the whole volume between 0.5 and 50%, in particular between lan l and 25 percent. As the dye is mainly included in the shell, the quantity calculated on the volume of the shell should be between 2 and 60 percent and preferably between 5 and 40 percent.

Pigments used should have a particle size clearly below of the base particles, for example less than 3 μm, and preferably less than 1 pm. Very small particles can give gives rise to increased agglomeration tendency and it is preferred because the size exceeds 0,0] .fm1 and preferably also exceeds rises 0.1 fam.

It is of course possible to arrange several shell structures. on the base particles. For example, it may be appropriate to arrange an inner shell with dye and an outer shell without dye to maximally protect the dye from abrasion ning. In these cases, of course, it is only necessary to adapt the surface properties of the outer layer to the above while the material of the inner shell can be selected freer.

According to the invention, the base particles are provided with a 8201739-3 10. _15. 20. 25.

STAY. 35. 12 colored substance and a shell after the polymer of the base particles sation as above by adding a powdered shell polymer and a colored substance in an additive sufficiently high temperature to allow adhesion of the substantially the entire amount of shell polymer added surface of the base particles and at a sufficiently low temperature to prevent significant agglomeration between basic the particles with each other.

I By applying the scalp polymer directly in powder form at a temperature which allows direct adhesion of the powder several basic benefits are obtained on the base particles. One one- simple process engineering procedure is obtained by none solvents or dispersants need to be used. The the powder added is collected very well on the base particle surfaces without leaving free unbound powder in the mixture ningen. Any free powdered contaminants caught more easily than in solvent or dispersant serade the solidification of the small powder grains takes place at lower temperatures temperature and thus at lower adhesion than required system. The agglomeration tendency is low due to for cohesion of the larger base particles. Someone very sticky phase does not need to be passed. Even slightly agg- lomerated shell polymer decomposes and adheres well to the base the particles.

The colored substance can be added to the base particles before the addition of the polymer particles, for example by a liquid dye is allowed to wet or penetrate the basic particles, possibly in the presence of a solvent part as a diffusion aid. Alternatively, a fixed colored substance as pigment is distributed on the base particle surface, for example by processing mechanical sight together with the base particles. Possibly here too a solution method part or a dispersant can be used to facilitate the adhesion of the pigment particles to the base particles. and / or to loosen the surface of the base particles to improve the retention of the particles. Methanol has been successfully used as a solvent in this hang. Any solvent is then evaporated. Alternatively the surface of the base particles can be pretreated with a tackifier. lO. 15. 20. 25.

STAY. 35. 8201739-3 15 additive such as dioctyl adipate. After the addition of colored substance is added to the polymer particles for training of the shell. This method provides the best protection for what is added the dye.

However, it is preferred that the colored substance be mixed. with the polymer particles and applied to the base particle surface at the same time as these. This is a simple way as well generally gives the best distribution of colored substance and the best adhesion between base particle, colored substance and shells. It also has the least impact on size the division. The colored substance may be present either in the additional particles or separately from them. In the latter case the colored substance must be well mixed with and distributed in the polymer particle mass. Thus, a pigment should preferably be distributed over the surface of the polymer particles, which can through intimate mixing and tearing of components. together.

The method of applying the shell polymer powder has a large meaning of the final properties of the particles. About particulars are allowed to agglomerate during these phases of deterioration of the final sphericity of the particulate matter while destroying the monodisperse distribution. Even without agglomeration, the size distribution can deteriorate. different amounts of shell polymer are taken up on the different ones particles and it is therefore desirable that this uptake can be controlled in some men.

In general, appropriate procedures for ring of the polymer shell therefore comprise a step in which the polymer particles are applied to the surface of the base particles in as well-defined and evenly thick a layer as possible and a second step in which the particles adhere to the surface conditions which, as far as possible, prevent agglomeration multiplication of the formed particles. In the present method the particles are kept separated from each other by means of a gas phase without the presence of a particular liquid phase. Use of gas phase for separation of the particles according to the invention generally entails good control over the thickness of the shell layer. play growth and enables an applatively simple design of the production equipment for the production. 8201739-3 10. 1.1 kïl . 20. 30. 55. 14 In the present method, the shell polymer is applied directly to a bed of the base particles and distributed over them surface through the repeated contacts obtained by stirring of the bed. The shell polymer is supplied in powder form and to ensure the adhesion of the powder to the particles and avoid free powder in the finished product The powder should be added continuously and not faster than it is absorbed on the base particle surfaces. Temperatures an- was used as the most important control parameter to check adhesion and scale structure.

The temperature should be chosen so high that a sufficient adhesion is obtained between the powder particles and the base the particles to retain the small powder particles the base particle surface and with each other during the shell construction.

However, the temperature must not be so high that the base particles are mutually agglomerated. The temperature must therefore not so high that the base particles lose their structure underneath this phase nor the scalp powder should be melted. The is thus desirable to the properties of the base particles and the shell polymer is thus selected relative to each other that at low temperature no significant adhesion to them It is found that when the temperature is raised a occurs when the adhesion is sufficient to scale the polymer particles must satisfactorily adhere to the particles but where the adhesion is insufficient to co-occur keep the basic particles together in the bed and that at a further increase in temperature a condition occurs when the shell polymer sinters, usually agglomerating the risk increases. In order to obtain this behavior, soft the temperature of the polymer in the base particle and in the scalp powder are adapted in relation to each other, e.g. pelvis so that they soften at slightly different temperatures. One additional means to influence the behavior is to provide a tackifying substance such as dioctyl adipate. The appropriate however, the temperature range for the scale application becomes always relatively narrow and must be tested for each individual system. For example, it has for scalp polymers with pronounced glass temperature proved to be suitable to perform scalping between Ca 0 O0h 1000 below the glass transition temperature while 10. 15. 20. 25. 30. 35. 8201739-3 15 sintering is obtained between about 5 and 2000 above the glass temperature the tour.

After scaling, the temperature should be short-lived raised to the sintering temperatures discussed above to sinter the shell polymer and to improve the sphericity the density of the final particles. During this operation no additional shell polymer should be added. Temperature- however, the border is very critical. If the temperature let be too high is obtained uncontrolled baking of the particles in the bed. The sintering can take place in the same stirred bed as the scale structure but the separation between can also be advantageously increased during this operation. Kän- distribution methods can be used and are particularly appropriate is to fluidize the particles with a gas stream. Although a ideal separation without any mutual contact between tiklarna in principle is desirable is this condition in practice not necessary. The minimum condition, however, is that the particles are kept in constant motion in relation to each other, which can most easily be achieved by vigorous stirring of a particle bed. The purpose of the separation is to prevent the particles from agglomerating or otherwise act on each other so that the spherical shape deteriorates or that the narrow size distribution is broadened.

The scaling operations described above one can, if desired, be repeated one or more times. Then it is easier to obtain one between the different particles evenly distributed shell thickness when the applied amount is li- it may be appropriate to use repeated treatment. when thicker shells are to be formed. Even in those cases man desires an outer shell with properties other than an inner one as stated above, the approach may be repas.

Then the construction of the shell takes place under conditions allowing contact between the particles, some agglomeration may call is not completely avoided. The problems increase the smaller the produced. Any bridges formed can, however, however, if desired, be broken by gentle grinding in the for example a pin mill or by a temporarily increased mixing in the bed. 8201739-3 10. 15. 20. 25. 30. 35- 16 A way to avoid agglomeration and increase free flow which is useful throughout the manufacturing process which is particularly suitable for small particle sizes games during about 10Jum, is to mix the base particles with significantly larger, preferably spherical, particles of, for example, polymer as an auxiliary material during the process for later separation. To improve the powder mass free flow, these auxiliary particles must be significantly re than the base particles, preferably between 10 and 100 times larger or for example about 0.5 to 2 mm. The more helpful- tiklar that are added the better free flow is obtained but at the same time the production capacity decreases why a suitable content is between about 20 and 90% by weight of auxiliary particles in the powder mass. When the auxiliary particles are present at the the laying operation, these will also be coated with _ a layer of the added polymer. The layer of helper- However, the particles do not become thicker than on and since the difference in size is markedly the surface of the auxiliary particles centers only a fraction of the the total surface area of the mixture and the polymer loss too insignificant. Also the percentage radius increase at the auxiliary particles become small why these without inconvenience can be reused several hundred times without unacceptable failure. Following the coating process, the auxiliary particles separated, which can be done with simple methods, for example sifting, due to the significant difference in size between these and the toner particles.

A typical size of base particles used in the invention is l0) nn. These are then coated with polymer particles in a shell with 1-2_pm.thickness. Due to cuts the small thickness of the polymer, the polymer particles must be position of the shell should be very fine-grained, preferably all should particles be less than 1/10 of the size of the base particles or less than lÄum. Normally, it is not possible to set so fine-grained polymer powder. If, for example, under melting mixes pigments and a polymer suitable for toner and then the cooled polymer undergoes a grinding, polymer particles are obtained which are substantially coarser than ljnn.

Nor with the help of known wind screening methods is it 10. 15. 20. 25. 30. 35 8201739-3 17 possible to in a rational way from one in this way malt powder separate all grains over l; um. In inorganic material is below the size range for wind sighting at about Sjnn, at polymers higher (ref .: Chemie Technik, 8 Volume (1979) No. 5). Pigments can usually without difficulty obtained with a sufficiently fine particle size.

Preparation of the polymer powder to be then shells can be made in different ways. Common to preferred methods, however, are to first produce a fine dispersion polymer dispersion in water. The grains in this polymer dispersion sion is generally less than 1 pm.

The invention thus also relates to a method for preparation of a powdered shell polymer, which process comprises preparing an aqueous dispersion which dispersion contains finely dispersed poly- particulate matter and finely divided colored substance, dried at low temperature and that the dried dispersion the sion is then ground if necessary.

It is preferred that the polymer particles be made fine. persa by a fi zdispersed under conditions when they are liquid as this facilitates atomization to small sizes. It is particularly appropriate to distribute mono- in this way before the polymerization. Polymerization can then take place as emulsion polymerization with aqueous soluble initiator or as suspension polymerization with monomer soluble initiator. The colored substance which is preferred is a pigment, may either be present in the polymer or freely in the dispersion.

Below are some manufacturing procedures re described. _ A method of producing polymer powder for construction of shell is to first emulsion polymerize monomers with a water-soluble initiator so that a polymer latex with par- ticks consistently below l_pm are obtained. The latex can then contacted with carbon or magnetite pigments. Thereafter, the mixture is thrown shear forces by tearing so that a intimate mixture between latex and pigment is obtained. As the next step is to dry the latex pigment mixture at such a low temperature. peratur_att the primary grains in latex are only agglomerated without 10. 15. 20. 25. 30. 35 ~ 8201739-3 18 to merge. After drying, the product is ground with a suitable equipment to the finest possible grain size. Thanks to it low drying temperature and the intimate mixture between latex and pigment, the product is very easy to grind but contains however after grinding particles with a size considerably over lukewarm. Under the conditions prevailing in the mixer during scale application however, these grains do not decompose due to the of primary particles with a relatively weak cohesion between the primary particles. This makes it possible to set an evenly thick shell with a smooth outer surface. With emulsion polymerization, very evenly sized latex particles can also be which contributes to an even scale structure.

An alternative method of producing a fine-grained powder for scale-up is to first disperse pigments in the š number mixture. An initiator is also dissolved in the monomer and after which the monomer is emulsified in water with suitable surfactants. nen. This emulsion is then comminuted using show high pressure homogenization. The emulsion is then subjected to a polymerization and a fine-grained polymer dispersion is obtained persion with well-contained pigment. The polymer dispersion is dry. finally at low temperature and the product is finely ground dan. The obtained powder was used for building shells similar to powder prepared according to the above method.

Another method of producing a fine-grained pulp ver for scale construction is to dissolve a polymer, for example I styrene butyl methacrylate copolymer in a solvent.

The solution is emulsified and then homogenized in the presence of suitable emulsifiers. Then the solvent is evaporated off the finely divided emulsion. The micro-suspension thus obtained the ion is then mixed with pigment and dried to then ground and used as a material for the manufacture of shells the base particles. The pigment can also be mixed into the solution before the atomization. This method makes it easy to incorporate various additives in the shell but the use of solvents constitutes a procedural technical complication. Another conceivable way of producing powder for scaling structure is to mix high levels of in a plastic melt a pigment, for example magnetite. After cooling and grinding 10. 15. 20. 25. 30. 35. 8201739-3 19 a fine-grained powder is then obtained, which can serve as starting material for shell construction. In this case, it will be the internal cohesion of the powder particles was due to the high give the content pigment. Thereby they can, under the influence of them shear forces present in the fluidized bed, solar divided into the very fine size needed for building of the shell. However, a disadvantage of this method is that the strength of the peel is due to the high pigment content the condition becomes worse, which is why the scaled particles can release a fine-grained pigment dust during use copying machines.

The particles described can be used for toner particles known manner. They can be mixed with conventional preparations. cooling and carrier particles of e.g. glass or steel or can be used as single component tones. They can be used for wet methods but are particularly suitable for dry methods.

Example 1 This example describes the preparation of monodisperse base particles. 77 ml of water, 11.7 ml of chlorododecan, 1.8 g of benzoyl peroxide oxide, 9.3 ml of dichloroethane and 0.2 g of sodium lauryl sulphate was generated in a two-stage Manton Gaulin homogenizer, model 15 M with 200 kg / cm2 in the first step and 80 kg / cm2 in the last step for about 1 to 1.5 minutes, giving an emulsion with particles on the order of 0.1 to 0.2) mL to the emulsion was added an inlet of monodisperse polystyrene parts. articles with a diameter of 0.65 μm (determined by electronic microscopy). The amount of graft latex was 83.8 ml, containing 77 ml of water and 6.8 ml of styrene particles. Further 6 ml were added water and 8.5 ml of acetone with stirring at 35 to HOOC.

After stirring for 12 hours at HOOC, acetone was removed. by evaporation under vacuum. After evaporation of acetone and dichloroethane were added 1.0 g of sodium lauryl sulfate and 8H0 ml water so that the amount of water became 1000 ml. Further was added 275 ml of distilled styrene with stirring at 3000. After stirring stirring for 2 hours at 50 ° C, the temperature was raised to 60 ° C and the polymerization was started. After 25 hours of polymerization a monodisperse latex with a particle diameter of 2 μm was obtained.

This latex was used as a starting material for a second 8201759-3 20 * 'swelling and polymerization steps. 28.5 ml of this latex, containing 25 ml of water and 3.5 ml of polystyrenePeP k íkleF, -mixed with an emulsion of 35 ml of water, H ml of Perkadox 10.

SE-8 (dioctanoyl peroxide), 3 ml of chlorododecan and 0.2 g of rium lauryl sulphate, homogenized with the same equipment and under the same conditions as above for the former the swelling step. Further, 10 ml of water and 7 ml were added acetone with stirring at 25-30 ° C. After 1 hour, remove the acetone was evaporated in vacuo. Then 1.2 g of natural rium lauryl sulfate, 1.0 g Berol 267 and 930 ml water to a total amount of water of 1000 ml. 175 ml of distilled styrene added was stirred at 25-30 ° C and after 3 hours was raised temperature to 7000 for complete polymerization. The the final latex was monodisperse with a particle diameter of about 7 l5.) nn. 20. 25. 30. 35- Example 2 This example relates to the preparation of latex for formation of powder for scaling. Water-soluble initiator was used.

In one vessel were invested: 70 30 " 10.5 " 0.002 " l il 14 v .II 0.6 I 5 ' 2ü0 "water The pH was adjusted to 8.5 using ammonia. The emulsion fin- .shares styrene butyl methacrylate hydrogen peroxide iron in the form of ferric chloride citric acid lauric acid mercaptoethanol distributed using high-speed agitators and invested in after in a polymerization autoclave. After evacuation set the temperature of 6500. After Å hours of polymerization, an additional 0.75 parts of hydrogen peroxide are added. After 12 hours the polymerization was broken. A white latex with particles below l / mn was obtained.

Example 5 This example describes the preparation of a black micro- suspension. A pasta-like carbon dispersion was made from butyl methacrylate, the pigment wetting agent Paraloid DM-5H from Rohm & Haas, Philadelphia, USA (an acrylate polymer) and Spezial- 10. 15. 20. 25. 30. 35- 8201739-3 21 schwarz Ä from Degussa, Frankfurt, West Germany. For manufacturing of this dispersion was invested: Butyl methacrylate 251 g Paraloid DM-5H 157 E Special black 4 l§1_g 565 s The mixture was shredded on a grater until a smooth structure was obtained. The grated dispersion was then diluted with: Styrene 1098 g Butyl methacrylate 220 g Oleic acid H7 g Porofor N (Bayer, West Germany) azobisisobutyronitrile 23 g 1388 An aqueous solution was prepared by: Water 5830 g Ammonia, 2 ~ percent 170 g 6000 g During slow dosing and mixing with a High-speed Ultra-Turrax mixers were fed carbon monomer the dispersion to the aqueous phase. A fine black was formed emulsion with a droplet size of about 3} mL This emulsion is prepared was then further divided by pumping twice through one 2-stage homogenizer, Gaulin model l5M-8TA with a pressure case of H75 kp / cm2. Thereby a fine emulsion was obtained with medium droplet size below lukewarm. This emulsion was charged to a 14 liter ters autoclave with stirrer. After evacuation, it was polymerized at 7500 for 8 hours. A black dispersion was obtained.

Example H 100 parts of latex from Example 2 were mixed with 3 g of carbon, Spezialschwarz H from Degussa, Frankfurt, West Germany. Way- the quality of the mixture gradually increased. When a pasta When the condition was reached, the mixture was transferred to a grinding mill, where it was demolished twice. The pasta was then spread to a thin layer and allowed to air dry. The product was then ground. At microscopy of the ground powder it turned out to consist of a lot of black colored small particles smaller than l_pm, but also larger grains up to 20-30) um. Both the smaller ones and the smaller ones the large grains are assumed to be composed of small latex primary grains in 10. 15. 20. 25. 35- 8201759-3 22 mixture.with charcoal.

A The ground powder was dosed for 2 hours to one mixers containing monodisperse base particles in with 1 mm large polystyrene grains. The mixture consisted of: Base particles 500 å l mm grain 500 S Powdered malt was also added as above 500 g The temperature at the time of the charge was 55 ° C. After completed supply of powder for scale construction raised the temperature during continued mixing to 60 ° C. In this way was obtained a black free-flowing powder. Under the microscope appeared the powder consists of base particles coated with a black shell.

To extract the powder, the coarse ones were finally discarded the grains. IN Example 5 100 parts of latex from Example 3 were mixed according to Example pile 4 and was then used for applying shells.

Example 6 Latex prepared according to Example 2 was dried at low temperature without the addition of carbon or magnetite powder.

In a mixer, coated base particles were charged according to Example Ä. The temperature was set at 55 ° C. For a time of For one hour, powder prepared from latex in Example 2 was dosed.

The mixture consisted of: Coated base particles 500 g l-mm grain 500 g In addition, powder from was charged latex in Example 2,100 g The temperature at the bet was 5500. After completion addition of powder, the temperature was raised to 58 ° C. You are- held a black powder coated with an unpigmented outer shell.

Example 7 A latex was made from the ingredients: Methyl methacrylate 0 70 parts Butyl methacrylate 30 " Mercaptoethanol 0.57 " Lauric acid U " Methyl ethyl ketone hydroperoxide 0.3 " a2o1739-3 23 Copper in the form of copper chloride 0.0002 parts Water 2H0 " Ammonia (to pH 8.5) 0.22 " The polymerization was carried out at 6000. A white latex 5. was obtained. This was then used to make a black- 10. 15. 20. 25. 30. pigmented powder according to the method of Example U. This powder was then used to coat the base particles with a Shell.

Example 8 100 parts of latex from Example 2 were mixed with 30 g of magnetic tit. The viscosity of the mixture gradually increased. When one paste state was reached, the mixture was transferred to a grating roller works, where it was demolished twice. The pasta was then spread to one thin layer and allowed to air dry. The product was then ground.

Upon microscopy of the ground powder, it was found to persist of a lot of black colored small particles less than 1 pm, but also larger grains up to 20-U0) nn. Both the smaller ones and the smaller ones the large grains are assumed to be composed of small latex primary grains in mixture with magnetite.

The ground powder was dosed for 2 hours to one mixers containing monodisperse base particles in with 1 mm large polystyrene grains. The mixture consisted of: Base particles 500 g l mm grain 500 g Powder was added in addition above 1000 g The temperature at the bet was 5500. After completion supply of powder for scale construction raised the temperature with continued mixing to 6500. In this way was obtained a black free-flowing powder. Under the microscope appeared the powder consists of base particles coated with a black shell.

To extract the powder, the coarse ones were finally discarded the grains.

Claims (10)

5. 10. 15. 20. ' 25. 8201739-3 2ü p Patentkrav A process for producing monodisperse spherical particles having a coefficient of variation of less than 30 percent and having an average diameter between 2 and 50 μm, comprising monodisperse base particles prepared from an aqueous dispersion of monodisperse polymer particles having an average diameter of less than 1; nn, through to batch of a monomer to the dispersion, which monomer is capable of being absorbed in the polymer particles, under conditions which allow molecular migration of the monomer to and absorption in the particles and polymerization of monomer in the particles, characterized in that the base particles after the polymerization while stirring in the gas phase, a colored substance and a powdered shell polymer are supplied at a sufficiently high temperature to allow adhesion of substantially all of the supplied scale polymer to the surface of the base particles and at a sufficiently low temperature to prevent substantial agglomeration between the base particles. es. 2. A method according to claim 1, characterized in that after the addition of the shell polymer, the temperature is raised for sintering the shell polymer. 3. A method according to claim 1, characterized in that the surface of the base particles before or during the supply of the shell polymer is treated with a solvent or a stick sensor. H. Process for the preparation of a powdered shell polymer, characterized in a tin-containing dispersion is prepared, which dispersion contains finely dispersed polymer particles and finely divided colored therefrom, a water substance, the dispersion being dried at low temperature and the dried dispersion then ground if necessary . 5. A process according to claim 1, characterized in that the polymer particles are dispersed in monomeric form and then subjected to polymerization. Process according to Claim 5, characterized in that the polymerization takes place with a water-soluble initiator. 7. A process according to claim 6, characterized in that the colored substance, preferably a pigment, is added to the dispersion after polymerization. Process according to Claim 5, characterized in that the polymerization takes place with a monomer-soluble initiator. 9. A process according to claim 8, characterized in that the colored substance, preferably a pigment, supplies the monomer before the polymerization. 10. A method according to claim N, characterized in that the polymer particles are dispersed in the form of polymer solution. s2o17z9-3 Summary * Process for the production of toner particles for use in electrophotographic processes, consisting essentially of monodisperse spherical thermoplastic particles with a coefficient of variation of less than 30% and with an average diameter of between 2 and 50 μm, the particles having a shell of polymer material in which a colored substance is distributed. The particles are prepared by swelling monomeric graft particles with monomer and polymerizing, after which the particles are contacted with a powdered shell polymer at a sufficiently high temperature to allow the powder to adhere directly to the particles.