MXPA99005873A - Method and device for the continuous coagulation of aqueous dispersions of graft rubbers - Google Patents

Abstract

The invention relates to a method for the continuous coagulation of aqueous dispersions of graft rubbers suitable for modifying thermoplastic materials with a view to improving their impact resistance. According to said method, the dispersions are fed through a device comprising at least one shear element and a slotted stator containing a turning rotor in such a way that they are directed by the rotation of the rotor radially from the interior to the exterior within the shear element, and that after or during their movement through the stator and rotor slots they are sheared with such force that they coagulate. This method yields readily usable graft rubber coagulates even if the solid matter has an elastomer content of over 50 weight percent.

Description

CONTINUOUS COAGULATION OF AQUEOUS RUBBER AND APPARATUS RUBBER DISPERSIONS FOR THIS OBJECTIVE The invention relates to a process for the continuous coagulation of aqueous dispersions of graft rubber in an apparatus having at least one stator / rotor combination as the element to be applied. cutting efforts, and an apparatus for this purpose. It is known that the impact resistance of hard thermoplastic polymers increases when mixed with graft rubbers. The resulting polymer blends, for example ABS or ASA polymers, play an important role in the industry in the production of plastic industrial articles.

Such graft rubbers which serve to harden hard thermoplastics have long been known as impact modifiers in the plastics industry. They are graft copolymers in which a covering of particles of monomers (P2) forming hard thermoplastics is grafted onto cores of soft particles of rubbers (P1), such as elastomeric diene polymers or elastomeric acrylate polymers. The graft cover (P2) is prepared by polymerization or copolymerization of monomers or mixtures of monomers forming the hard graft cover (P2) by mass polymerization, solution, suspension or emulsion in the presence of the soft elastomer (s). (P1) It is preferable to carry out the graft polymerization, at least in the final phase, as an aqueous emulsion polymerization, the presence of anionic emulsifiers being preferable. The preparation of the graft rubbers therefore provides a large amount of aqueous dispersions of graft polymers that can be worked up to obtain the solid graft polymers.

As disclosed, for example, in DE-A 3149358 or EP-B 459161, aqueous dispersions of graft rubber are generally precipitated by the addition of coagulants; The coagulants used in general are aqueous solutions of water-soluble inorganic or organic acids and / or their salts, such as alkali metal chlorides and alkali metal chlorides, sulfates or phosphates, eg. solutions of calcium chloride or magnesium sulfate. The coagulation or precipitation is generally carried out in batches, but can also be carried out continuously (EP-B 459161). The precipitated clots that have been filtered are washed and dried in the known manner. A disadvantage observed in the precipitation by the addition of acids or salts as coagulants is that the impurities often remain in the prepared polymers, whereby the properties of the product deteriorate. DE-C 2917321 discloses a process for isolating polymers having a softening range above 100 ° C from an aqueous emulsion; the latter is coagulated in an extruder by shearing and / or heating at temperatures above the range of softening of the polymers; The coagulum is then melted and discharged from the extruder in a hot state under pressure. The water is separated in a later step of the process. The process consumes a lot of energy and requires a double-screw counter-rotating extruder for precipitation. In addition, ammonium acetate is used to assist in the acceleration of coagulation. US-A 3,821,348 describes a process in which mixtures of up to 70 to 80% by weight of acrylonitrile (AN) and 20 to 30% by weight of methyl acrylate (MA) are polymerized in emulsion with the post addition of 12% by weight of butadiene or in the presence of 9% by weight butadiene rubber / acrylonitrile (based in each case on the sum of the amounts of AN + MA). The dispersions of the resulting acrylonitrile copolymer or graft polymer dispersions are coagulated into a paste using a Waring blender as an apparatus for providing shear stress and then shaped in an extruder by means of a fine nozzle; the thin rods are introduced in hot water. The product is washed later, it is dried and processed in a compression mold at 150 ° C, whereby the rods are obtained. The description of the process is limited to copolymers having a high content of acrylonitrile and very low content of butadiene / acrylonitrile elastomeric rubber. In U.S. Pat. 4,668,738 which relates to the prior art of U.S. Pat. 3,821,348 mentioned above, it is stated that aqueous dispersions with rubber content of more than 50% by weight solids content result in easily processable products, only when the dispersions of the styrene / acrylonitrile copolymers are mixed as a component hard, in amounts that decrease the rubber content of the copolymer mixture to preferably less than 50% or by weight (based on the total solids content), with the dispersions, before its shear coagulation. A disadvantage of the process is that the graft rubber dispersions which are prepared to harden the thermoplastics generally have a rubber content of more than 50% by weight solids content and can therefore be processed after the process only with the addition of dispersions of the hard component, that is, with a change in the overall composition of the polymers.

It is an object of the present invention to provide an economical process for the continuous coagulation of aqueous dispersions of graft rubbers which are suitable for the hardening of hard thermoplastics in the preparation of ABS polymers and in particular ASA, a process which is carried out without the addition of chemical coagulants and without the addition of other polymer dispersions, such that the polymers in the coagulated emulsions have the same overall composition as the polymers in the initial emulsions. In addition, in said process, the dispersions of graft rubbers having a rubber content of more than! 50% or by weight, based on the solids content, are coagulated to produce easily flowable wet powders or wet suspensions that are easily processed, without the need to mix them with the dispersions of hard acrylonitrile copolymers before coagulation. It has been found that these objectives are generally achieved if the graft rubber dispersions are transported in an apparatus having at least one cutting force providing element with a slotted circular stator and a slotted rotor rotating within the stator, and which are therefore subjected to a shearing action strong enough to coagulate the shear dispersion. The present invention, therefore, discloses a process for the continuous coagulation of aqueous dispersions of graft rubbers (P) which are suitable for hardening the thermoplastics and contain), as a soft graft base (P1), elastomeric polymers and / or copolymers of 1,3-dienes or acrylic esters with a glass transition temperature Tg of less than -10 ° C, in an amount of about 30 to 85% by weight of the amount of graft rubber (P) and b) contain a hard shell or multiple graft covers (P2) comprising monomer units forming a polymer or a thermoplastic copolymer having a glass transition temperature Tg of more than + 50 ° C and whose content of units of acrylonitrile and / or methacrylonitrile monomer is from about 0 to 45% by weight, and c) at least in the final step of graft polymerization, are prepared by emulsion polymerization of the monomers for the graft cover (P2) in the presence of the graft base (P1), where the dispersion of • graft rubber is moved by an apparatus having at least one shear-providing element with a stationary slotted circular stator and a slotted rotor that rotates within the stator and is mounted on a rotationally mounted motor shaft, so such that the dispersion of the graft rubber introduced into the apparatus passes radially from the inside to the outside, as a result of the rotation of the rotor in the supplying element.

The shearing stress and, during or after passage through the rotor and stator slots, is subjected to a shear strong enough to cause coagulation of the graft rubber dispersion. The present # invention also relates to the use of appropriate apparatuses for the coagulation of the graft rubber dispersions by means of the second shearing and to an apparatus that is modified by displacement elements and whose purpose is to disperse or coagulate the dispersions. In the novel process, the dispersion of graft rubber, which is preferably introduced, in particular sucked axially into the apparatus (10), coagulates in the elements providing cutting effort (3) 4, 15) comprising stator / rotor combinations. The rotors - & V -? * ^ * ^^, íi ^^ r ^ ww ^^^ '" grooves (13b, 14b, 15b) are mounted on a rotationally mounted motor shaft (12) within the circular stators (13a, 14a, 15a), which are generally firmly connected to the housing (11) of the dispersion apparatus ( 10), and have the shape of discs and preferably, essentially with the shape of a pot, and have grooves or teeth; The rotors can rotate at high speeds within the stator circles. For this purpose, the motor shaft is connected to a motor. The dispersion flow of the graft rubber fed centrally to the first rotor (13b) is forced to rotate by means of the rotor (13a) at high speed and moves radially from the inside to the outside or by centrifugal force action on the supplying element of cutting effort (13) The grooves or teeth of the rotor or stator wall between which the dispersion of the graft rubber is displaced by the centrifugal force are arranged in the outer radial region of the stator and the rotor, where the radial speed of the rotor is particularly elevated. During or after passage through the slots or spaces between the teeth, due to the very high speed of the rotor relative to the stator, a shear or shear force is exerted on the dispersion particles which the latter collide with each other. and the dispersion coagulates. The cutting speeds are from 5 to 30, preferably from 6 to 25 m per second. The residence time or average dispersion of the graft rubber in the apparatus (10) is generally less than 12, preferably less than 10, particularly preferably less than 8, seconds. The apparatus (10) generally contains from 1 to 3 cutting force supplying elements (13, 14, 15) connected in series, preferably one element or two elements providing cutting force, and it is possible that the rotors and stators have at least one row of teeth formed by axial grooves, or multiple rows or rings of grooves or teeth concentrically arranged. In addition to single-slot rotors, rotors that have additional blades in the axial and / or radial direction and rotors that are provided with turbine blade-shaped displacement bands in addition to the cutting force-providing elements are often advantageous, with which a better displacement of the product and a better effect of suction in the dispersion is obtained. The coagulated dispersions of the graft rubber subjected to shearing in one or more rotor / stator combinations as shearing elements are generally obtained in the form of easily flowing powder or in the form of a wet slurry, which leave the apparatus (10) at through a radially disposed outlet orifice, and which are then fed directly, i.e., without being transported by extruders, to a kettle containing hot water; It is advantageous in some cases to use a pressure higher than atmospheric and water with a temperature above 100 ° C. The coagulated graft rubber is processed in a simple manner by known methods, for later use. In the novel shear coagulation, the dispersion used, the quality of the precipitation, the production and the desired shape for the clot determine the details of the mode of operation of the apparatus, ie, they determine, for example, the advantageous number of combinations of stator / rotor, the arrangement of the slot or toothed system of the rotor and the stator and any choice of specific types of rotors. This can be determined by a very limited number of simple experiments. The common goal is in general to obtain the complete coagulation of the dispersion of the polymer used with a high speed of production and with a constant global composition of the polymers, as well as obtaining clots that can be easily processed later. The apparatus used according to the invention is shown by way of example in Figures 1 -3. Figure 1 shows a longitudinal section of said apparatus, with a perspective view of the rotor, Figure 2 A shows a plan view of the stator from the direction of arrow A in Figure 1, Figure 2 B shows a side view of a partial cross section of the stator of Figure 2 A, Figure 2 C shows a view of the rotor from the direction of arrow A in Figure 1, Figure 2 D shows a side view of a partial cross section of the rotor of Figure 2 C, Figure 3 A shows a plan view of another embodiment of the stator from the direction of arrow A in Figure 1, Figure 3 B shows a side view of a partial cross section of the stator of Figure 3 A, Figure 3 C shows a plan view of another embodiment of the rotor from the direction of arrow A in Figure 1 and Figure 3 D shows a side view of a partial cross section of the rotor of Figure 3 C. A very suitable device (1 0) for the novel process of continuous coagulation of graft rubber dispersions by shearing is shown in longitudinal section in Figure 1; the rotor is observed in a perspective view. Said apparatuses are commercially available as dispersion apparatuses, that is, they are used with the purpose exactly opposite to shear coagulation. Arranged axially inside the housing (1 1) of the apparatus (10) are two or three cutting force providing elements (13, 14, 15), each of which consists of a circular stator (13 a, 14). a, 15 a) as a stationary tool (see also Figures 2 A and 3 A), and in a rotor (13b, 14b, 15b) as a rotating tool that rotates within the circular stator. The rotors (13b, 14b, 15b) (see also Figures 2C and 3C) are arranged on a rotatably mounted motor shaft (12) generally connected to a motor. The stators and the rotors are essentially pot-shaped, in each case the ring-shaped wall of the pot-shaped stator (13 a, 14 a, 15 a) radially overlaps the rotor wall of the associated pot shape ( 13b, 14b, 15b), for a certain length. The walls are provided with axially oriented grooves, radially continuous as passages. The dispersion of the graft rubber to be coagulated is sucked into the apparatus (10) by means of an inlet hole (16) disposed in the axial extension of the motor shaft (12) and axially fed to the first rotor (13b). There, the dispersion rotates rapidly and is displaced by the centrifugal force, radially from the inside to the outside, through the slots present in the stator (13 a) and the rotor (13 b), towards an annular space defined between the rotor (13b) and the stator (13 a). Due to the high speed of the circumference of the rotor (13b) with respect to the stator (13 a), a pronounced gradient of shear stress results in the prevailing turbulent flow conveniently in the circumference of the rotor or close to it. The rotor and the stator can also have multiple grooved or toothed rings, concentrically arranged; Toothed represents the same as rapids (see for example in Figure 2C). Therefore, the first rotor (13b) in the apparatus (10) in Figure 1 has a row of teeth running between two radially spaced rows of teeth of the stator (13 a). Therefore there are two annular spaces in which shear coagulation occurs. The stator (13 a) shown in Figure 2 A and 2B has a serrated inner ring (21) and a toothed outer ring (22). The outer wall of the stator is displayed as (23). The stator seen in Figures 3 A and 3B has a single serrated ring (21). The rotor (13b) shown in Fig. 2C and 2D has a serrated inner ring (25) and an external toothed ring (26). The rotor of Fig. 3C and 3D includes cutting force supplying elements (27) and turbine blades (impellers) (28). The coagulation devices used for the novel process are conveniently multi-stage format and contain multiple combinations of 2 or 3 rotors / stators, for example, connected in series as elements that provide cutting effort. However, depending on the physical properties of the graft rubber dispersion, it is also convenient to use a single rotor / stator combination or two rotor / stator combinations as cutting force supplying elements, in order to reach an optimal level between the precipitation, the volume of production and the properties of the product. Figure 1 shows an apparatus having three cutting force providing elements (13, 14, 15) connected in series. The rotors and the stators of the elements that provide cutting forces have grooves or teeth of the same type or of different types. Therefore, Figure 2 shows in the apparatus (10), a first cutting force providing element (13) containing a stator (13 a) with two rows of radially spaced teeth and a rotor (13b) with only one row of teeth. The second cutting force supplying element (14) of the apparatus (10) has a stator (14 a) with three rows of teeth and a rotor (14b) with two rows of teeth which are again concentrically housed one within the other. The rotor (14b) also has more teeth than the rotor (13b) of the first element providing cutting force (13), which are therefore narrower and separated at a shorter distance. The third cutting force supplying element (15) of the apparatus (10) also has a stator (15 a) with three rows of teeth and a rotor with two rows of teeth; the rotor (15b) has again more teeth than the rotor (14b) of the second cutting force providing element (14). In the elements that provide cutting effort used with respect to the novel process, the flow of the dispersion deviates repeatedly from such that the dispersion particles do not pass through the apparatus without being processed. Apparatus similar to that of Figure 1 and used further, - Jj - particularly in the preferred embodiments are those that contain 'only one component of cutting effort or two elements of cutting effort (stator / rotor pairs), in order to optimize the volume of production and the quality of the precipitation. The space left by the shear force provider element or the shear force elements omitted, for example the space (13) left by the omitted stator / rotor combination (13 a / 13b), it is preferably filled with a displacement element that fits exactly such that no additional dead volumes are formed in the apparatus. A cylindrical displacement element that replaces the stator / rotor combination (13 a / 13b), for example in space (13), exactly fills the space left by the stator / rotor combination, whose central hole corresponds to the internal diameter of the power line. The apparatus modified in a novel way compared to commercially available apparatuses has proven to be surprisingly advantageous not only with respect to the novel process but in general for the apparatuses of this type in the Preparation or coagulation of the polymer dispersions. As it was stated, the apparatuses that can be used in this novel process for the continuous coagulation of graft rubber dispersions, with the exception of the apparatus described above and modified with displacement elements, are known and are obtained as apparatus for dispersion. They are therefore used in the preparation and distribution of polymer fine particles in aqueous dispersion, while serving in the novel process to destroy the aqueous dispersion of the polymer producing larger coagulated polymer particles. The present invention, therefore, also relates to the use of these apparatuses for coagulating aqueous dispersions of graft rubbers by means of shearing, to the use of the described novel apparatuses having at least one displacement element which is related in general with the dispersion and coagulation e, of the polymer dispersions. According to the invention, the aqueous dispersions of the graft rubbers are coagulated, and it was found that the process is particularly useful for coagulating aqueous dispersions of graft rubbers having elastomeric acrylate polymers as the graft base (P1) in the dispersions to be coagulated according to the invention, the graft rubbers are present in particular with a solids content of 20 to 65, and preferably 30 to 60% by weight. Therefore, the novel process can be used directly in the dispersions as obtained by graft polymerization in aqueous dispersion. The graft rubbers whose aqueous dispersions are coagulated according to the invention are represented as graft polymers in which monomers, in particular styrene, acrylonitrile and / or methyl methacrylate, which form hard thermoplastics, are grafted as a graft cover (P2), to particle cores that include a soft rubber (P1), and this is effected by polymerization or copolymerization of the graft cover monomers (P2) in the presence of the rubber particles (P1). In this procedure, Some of the resulting monomers or polymers form a bond with the surface of the rubber particles, which can be increased by specific measures of the process that are known (increased grafting performance). By repeating the grafting procedure, it is also possible to prepare graft rubbers containing more than one graft cover (P2). Suitable soft rubbers (graft base P1) for the preparation of the graft rubbers are elastomeric polymers and / or copolymers having glass transition temperatures less than -10 ° C and preferably less than -30 ° C. The elastomeric homo- and copolymers of 1, 3-diene, such as the homo- or copolymers of butadiene, isoprene or chloroprene, preferably butadiene rubber, and the elastomeric homo- and / or acrylic ester copolymers having the low glass transition temperatures established, are particularly suitable. Acrylic ester elastomeric polymers are preferred for the coagulated graft rubbers according to the invention, for example homopolymers and copolymers of C-C8-alkyl acrylates, in particular of n-butyl acrylate and / or 2-ethylhexy-acrylate.

Examples of preferred comonomers of aicylacrylates are cross-linking monomers with at least two unconjugated C = C double bonds, such as diallyl maleate, diallyl phthalate, diacrylates and dimethacrylates of diols, such as 1,4-butanediol or 1,6-hexanediol, etc., preferably allyl methacrylate or dihydrodicyclopentadienyl acrylate, which are used in particular in an amount of about 0.5 to 10%) by weight of the total amount of monomers in the preparation of the elastomer, and in addition polar monomers, such as the acid acrylic, methacrylic acid, maleic anhydride, acrylamide, methacrylamide, N-methylacrylamide or N-methylmethacrylamide and its alkyl ethers. The amount of elastomers (P1) in the graft rubber (P) is generally 30 to 85%) by weight, and the novel process can conveniently also be used to preferentially process the graft rubbers (P) containing more than 50, for example, about 55 to about 85% by weight, based on the total solids content of elastomer (P1). Particularly suitable monomers for polymerizing in the graft cover (P2) are the monomers and their mixtures which form hard polymers or copolymers whose glass transition temperatures exceed + 50 ° C. The type of monomer or monomers for said purpose depends essentially on the type of thermoplastic which, after mixing with the graft rubber, forms the matrix polymer and with which the graft cover must have some compatibility or affinity to the effect of achieving a satisfactory distribution in two phases of the graft rubbers in the matrix. Particularly suitable and conventional monomers for the graft cover are vinyl and alkenylaromatic monomers of 8 to 12 carbon atoms, such as styrene, -methylstyrene, and styrenes and α-methylstyrenes having one or more alkyls, in particular the groups methyl as substituents of the benzene nucleus. They may be the only monomers for the preparation of the graft cover (P2) or they may be used as a mixture with other monomers, such as methyl methacrylate, methacrylonitrile and preferably, acrylonitrile; the graft cover contains from "0 to 45, preferably from 10 to 40% by weight, based on the weight of the graft cover, of methacrylonitrile and / or acrylonitrile monomer units, styrene blends of about 10 are preferable. to 40% by weight, based on the total amount of acrylonitrile monomers Other preferred monomers for the preparation of the graft cover are also the esters methacrylics and acrylic esters, among which methyl methacrylate is preferred, and can also be used as the sole or predominant monomer in the preparation of the graft shell. However, maleic anhydride, maleimide, N-phenylmaleimide, aeric acid and methacrylic acid are also suitable comonomers in the preparation of the graft shell (P2). The dispersions of the graft rubber which are prepared by grafting the elastomers with the monomers for the graft cover are particularly suitable for the novel coagulation process, at least in the last stage of the graft polymerization process, in aqueous emulsion and then particularly in the presence of anionic emulsifiers. Conventional anionic emulsifiers are, for example, alkali metal salts of alkanesulfonic or alkylarylsulfonic acids, alkylsulfates, fatty alcohol sulfonates, salts of fatty acids of 10 to 30 carbon atoms or resin soaps. Emulsions prepared by using sodium salts of fatty acids of 10 to 18 carbon atoms (anionic soaps) or alcaposulfonates as anionic emulsifiers are very suitable. The anionic emulsifiers are used in amounts of about 0.5 to 5, in particular 1 to 2,% by weight, based on the amount of monomers. The excess emulsifier is avoided when the subsequent coagulation of the graft rubber emulsions is attempted by shearing. The examples and figures that follow are intended to illustrate the novel process in greater detail but are not limited to it. The parts and percentages are expressed by weight, unless otherwise indicated. Example 1 a) Preparation of graft rubber dispersion with polybutadiene as graft base: 60 parts of butadiene was polymerized to a 98% monomer conversion in a solution of 0.6 parts of tert-dodecyl mercapt, 0.7 parts of C? 4- sodium alkane sulphonate as an emulsifier, 0.2 parts of potassium peroxodisulfate and 0.2 parts of sodium disulphate in 80 Water parts at 65 ° C. In the resulting latex, the polybutadiene resulted in an average particle size of 100 nm and was therefore agglomerated by adding 25 parts of a 10% emulsion of a copolymer composed of 96% ethyl acrylate and 4% methacrylamide, that a particle with a mean size of 350 nm was obtained. The glass transition temperature of polybutadiene was -85 ° C. 40 parts of water, 0.4 parts of sodium C 4 -alkanesulfonate and 0.2 parts of potassium peroxodisulfate were added to the product. 40 parts of a mixture of 70% styrene and 30% acrylonitrile were gradually added over 4 hours and the batch was maintained at 75 ° C while it was mixed. The monomer conversion was virtually quantitative. The glass transition temperature of a copolymer of 70% styrene and 30% acrylonitrile was about + 105 ° C. b) Coagulation of the dispersion prepared according to a): The coagulation of the graft rubber dispersion was carried out by means of the novel process; The apparatus used is a Dispax 3/6/6 dispersion apparatus from Janke & Kunkel, which contains two rotor / stator combinations (both coarse) with an outer diameter of the stator of approximately 60 mm and an outer diameter of the rotor of 55 mm as elements that provide cutting effort. Otherwise, the apparatus is similar to the apparatus (10) shown in Figure 1. The dispersion was axially fed into the apparatus at 77 ° C. In the first cutting force supplying element (13), the stator 2 and the rotor 2 have toothed rings (Figure 2) and the space 14 remains empty, and in the second cutting force providing element (15), the stator and The rotor has toothed rings and the rotor also contains displacement bands of the turbine blade type (see Fig. 3). The speed of the rotors was 7500 revolutions per minute and the production volume of the apparatus was 200 kg / hour. From the apparatus, a coagulated product with a dry appearance appeared, with a residual moisture content of 57%, an average particle size of 1 mm, and a wide particle size distribution (0.05-5 mm). The coagulated product is introduced by free fall into a stirred kettle containing hot water. The water of the product could be easily removed by decantation, centrifugation and drying. The resulting product could be used directly as an impact modifier by mixing it with the styrene / acrylonitrile copolymers in an extruder. Example 2 a) Preparation of the dispersion of the graft rubber with polybutadiene as grafting base; The preparation was carried out as described in Example 1 a). The coagulation of the dispersion prepared according to a): The coagulation of the graft rubber dispersion was carried out by means of the novel process; the apparatus used was a Dispax 3/6/6 dispersion apparatus from Janke & Kunkel The apparatus is similar to the apparatus (10) shown in Figure 1. The first cutting force supplying element (13) was replaced with a cylindrical displacement member fitted with a central hole; said element filled the space (13) in its entirety without dead space, and the inner diameter of the central hole corresponded to the diameter inside the power line. The cutting force supplying element (14) was a stator / rotor combination (14 a / 14b) with coarse teeth. The cutting force supplying element (15) had a stator / rotor combination (15 a / 15b) according to Figure 3. The speed was 7500 revolutions per minute, the temperature reached 75 ° C and the production volume was of 300 kg / hour. A crumbly product was obtained and processed as set forth in Example 1. The moisture content was 55.3% >;, the average particle size was 1 mm and the particle size distribution was wide (0.04 - 4 mm). Example 3 a) Preparation of the dispersion of the graft rubber with elastomeric polyacrylate as the graft base: 160 parts of a 98% mixture > of butyl acrylate and 2% of dicyclopentadienyl acrylate were heated to 60 ° C, while mixing them in 1500 parts of water with the addition of 5 parts of sodium salt of a C 2 -C 6 S-paraffin sulphonic acid, 3 parts of potassium peroxodisulfate, 3 parts of sodium bicarbonate and 1.5 parts of sodium diphosphate. 15 minutes after the start of the polymerization reaction, 840 parts of the monomer mixture were added, over 3 hours. After the completion of the monomer addition, the emulsion was maintained at 60 ° C for one more hour. The vitreous transition temperature of the elastomer was -42 ° C. 1150 parts of water and 2.7 parts of potassium peroxodisulfate were added to 2100 parts of the emulsion, and the mixture was heated to 65 ° C while mixing. After having reached this temperature, 560 were dosed parts of the mixture of 75% styrene and 25% acrylonitrile over 3 hours. After the completion of the aggregate, the game was maintained at 65 ° C for 2 more hours. The glass transition temperature of a copolymer of 75% styrene and 25% acrylonitrile was +1 11 ° C. b) Coagulation of the dispersion prepared according to a): The coagulation was carried out with the novel process; a laboratory apparatus similar to the shearing apparatus (10) shown in Figure 1 was used, which had as a process section, two cutting force providing elements (14, 15), each with a slotted rotor ( 14b, 15b) and each of them with a slotted stator (14 a, 15 a) firmly connected to the housing. The cutting force supplying element (13) was replaced with a precisely inserted cylindrical displacement element having a central hole. The external diameter of the stators (14 a, 15 a) was approximately 60 mm and that of the rotors (14 b, 15 b) was approximately 53 mm. The stator (14 a) and the rotor (14b) are shown schematically in Figure 2, and the stator (15 a) and the rotor (15b) in Figure 3. The width of the space between the toothed system of the rotor and the Toothed system of the stator was approximately 0.75 mm. The dispersion of the graft rubber was axially fed into the apparatus at 60 ° C and moved radially from the inside to the outside between the cutting force-providing elements. The speed of the rotor was 8000 revolutions per minute and the yield was 440 kg / hour. HE radially discharged a product in the form of a watery paste through the outlet orifice (17). It was converted into larger agglomerates by heating them with steam under pressure above atmospheric above the glass transition temperature Tg of the graft cover. Said agglomerates could be easily dried by decanting, centrifugation and drying. The resulting product was very suitable as an impact modifier in the preparation of ASA polymers. List of reference numerals 10 Apparatus 11 Housing 12 Motor shaft 13 First element providing cutting force 13 a First stator 13 b First rotor 14 Second element providing cutting force 14 to Second stator 14 b Second rotor 15 Third element providing effort cutting 15 a Third stator 15 b Third rotor 16 Inlet hole 17 Outlet hole 21 Stator internal toothed ring 22 External stator toothed ring 23 External stator wall 25 Internal toothed ring of the rotor 26 External toothed ring of the rotor 27 Elements that provide cutting effort 28 Turbine blade fifteen 25

Claims (1)

1- A process for the continuous coagulation of an aqueous dispersion of graft rubbers (P) which: a) contain- as the base of soft graft (Pl) elastomeric polymers and / or copolymers of 1,3-dienes or acrylic esters having a glass transition temperature T "less than -10 ° C, in an amount from 30 to 85% by weight of the amount of the graft rubber (P) and b) containing a hard cover or a graft cover of multiple covers (P2) containing monomer units forming a thermoplastic polymer or copolymer with a glass transition temperature greater than 50 ° C and whose content of monomeric units of acrylonitrile or methacrylonitrile is from 0 to 45% by weight, and c) at least in the last step of the graft polymerization, they were prepared by emulsion polymerization of the monomers for the graft cover (P2) in the presence of the base for the formation of the graft (Pl), where the rubber dispersion of graft is transported through an apparatus (10) with at least one cutting element (13, 14, 15) with a slotted, circular, stationary stator (13a, 14a, 15a) and a slotted rotor (13b, 14b, 15b) that rotates inside the stator and is mounted on a rotary mounted drive shaft (12) so that the graft rubber dispersion introduced into the apparatus (10) passes radially from the inside outwardly as a result of the rotation of the rotor (13b, 14b, 15b) in the cutting element (13, 14, 15) and, during or after passing through the rotor grooves (13b, 14b, 15b) and of the stator (13a, 14a, 15a) is subjected to cutting with a cutting speed in the cutting element (13, 14, 15) from 4 to 30 m / second, which is so strong that the coagulation of the graft rubber dispersion. The process, as mentioned in claim 1, wherein the apparatus (10) contains two or three cutting elements (13, 14, 15), each with a stator / rotor combination. The process, as SG mentions in any of the rei indications one or two, wherein the dispersion of the graft rubber is introduced axially into the apparatus (10) through an intake hole (16) and is fed to the first cutting element (13a) and, after passing the cutting element or elements (13, 14, 15), the resulting coagulated product is discharged of the apparatus (10) through a radially arranged discharge orifice (17). The process, as mentioned in any of claims 1 to 3, wherein the apparatus (10) contains a plurality of cutting elements (13, 14, 15) and each rotor (13b, 14b, 15b) and each stator ( 13a, 14a, 15a) has, for cutting one to three rows of teeth arranged concentrically, formed by axial grooves. . The process, as mentioned in any of claims 1 to 4, wherein the coagulation is carried out in the cutting apparatus with only one cutting element or with two cutting elements (13, 14, 15), and the space left by at least an omitted cutting element is filled by a displacer element to avoid dead volumes. - The process, as mentioned in any of claims 1 to 5, wherein at least one rotor (13b, 14b, 15b) having blades arranged in axial or radial direction is used. . The process, as mentioned in any of claims 1 to 7, wherein at least one of the rotors (13b, 14b, 15b) has displacement strips similar to turbine blades. The use of an apparatus (10) containing 1 to 3 cutting elements (13, 14 15) each with a slotted, circular stator (13a, 14a, 15a) and each with a slotted rotor (13b, 14b, 15b) ) which rotates within the respective stator and is mounted on a rotationally mounted drive shaft (12), for the continuous coagulation of the aqueous dispersions of the graft rubber by cutting the dispersion in the cutting elements (13, 14, 15) with the rotating rotors (13b, 14b, 15b) The apparatus (10) for dispersing and coagulating polymer dispersions, which may contain, in a housing of the apparatus (11), a plurality of combinations (13, 14, 15) of stationary slotted stators (13a, 14a , 15a) and slotted rotors (13b, 14b, 15b) rotating inside the stators with the rotors mounted on a rotary mounted drive shaft, where, to avoid dead volumes, the space left by at least one rotor / combination stator (13, 14, 15) not necessary and, therefore, omitted is practically filled by a fitted displacer element, which may have perforations required for its operation.