Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/26—Nozzle-type reactors, i.e. the distribution of the initial reactants within the reactor is effected by their introduction or injection through nozzles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/50—Mixing liquids with solids
  • B01F23/53—Mixing liquids with solids using driven stirrers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/50—Mixing liquids with solids
  • B01F23/54—Mixing liquids with solids wetting solids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
  • B01F27/23—Mixers with rotary stirring devices in fixed receptacles; Kneaders characterised by the orientation or disposition of the rotor axis
  • B01F27/232—Mixers with rotary stirring devices in fixed receptacles; Kneaders characterised by the orientation or disposition of the rotor axis with two or more rotation axes
  • B01F27/2321—Mixers with rotary stirring devices in fixed receptacles; Kneaders characterised by the orientation or disposition of the rotor axis with two or more rotation axes having different inclinations, e.g. non parallel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
  • B01F27/50—Pipe mixers, i.e. mixers wherein the materials to be mixed flow continuously through pipes, e.g. column mixers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/18—Stationary reactors having moving elements inside
  • B01J19/1806—Stationary reactors having moving elements inside resulting in a turbulent flow of the reactants, such as in centrifugal-type reactors, or having a high Reynolds-number
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J4/00—Feed or outlet devices; Feed or outlet control devices
  • B01J4/001—Feed or outlet devices as such, e.g. feeding tubes
  • B01J4/002—Nozzle-type elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00002—Chemical plants
  • B01J2219/00027—Process aspects
  • B01J2219/00033—Continuous processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00164—Controlling or regulating processes controlling the flow
  • B01J2219/00166—Controlling or regulating processes controlling the flow controlling the residence time inside the reactor vessel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00184—Controlling or regulating processes controlling the weight of reactants in the reactor vessel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00189—Controlling or regulating processes controlling the stirring velocity
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00245—Avoiding undesirable reactions or side-effects
  • B01J2219/00254—Formation of unwanted polymer, such as "pop-corn"
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00761—Details of the reactor
  • B01J2219/00763—Baffles
  • B01J2219/00779—Baffles attached to the stirring means

Definitions

• the present invention relates to a method for the continuous mixing of water-absorbing polymer particles with liquids or other particles, wherein the polymer particles move in the product flow direction due to their own weight and at least a part of the mix due to the rotational movement of at least one mixing tool attached to a rotating shaft an impulse counter to the product flow direction receives.
• Water-absorbing polymers are, in particular, polymers of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on a suitable graft base, crosslinked cellulose or starch ether, crosslinked carboxymethyl cellulose, partially crosslinked polyalkylene oxide or natural products swellable in aqueous liquids, such as guar derivatives.
• Such polymers are used as products absorbing aqueous solutions for the production of diapers, tampons, sanitary napkins and other hygiene articles, but also as water-retaining agents in agricultural horticulture.
• Water-absorbent polymers typically have a centrifuge retention capacity of 25 to 60 g / g, preferably at least 30 g / g, preferably at least 32 g / g, particularly preferably at least 34 g / g, very particularly preferably at least 35 g / g.
• the centrifuge retention capacity is determined according to test method No. 441.2-02 "Centrifuge retention capacity" recommended by EDANA (European Disposables and Nonwovens Association).
• water-absorbing polymers are generally post-crosslinked. This post-crosslinking can be carried out in the aqueous gel phase.
• ground and screened polymer particles base polymer
• Crosslinkers suitable for this purpose are compounds which contain at least two groups which can form covalent bonds with the carboxylate groups of the hydrophilic polymer or which can crosslink at least two carboxyl groups or other functional groups of at least two different polymer chains of the base polymer.
• DE-A 35 23 617 discloses a process for post-crosslinking water-absorbing polymer particles, a polyol being metered in a, preferably aqueous, solvent.
• WO 04/037900 discloses a method for mixing water-absorbing polymer particles with aqueous solutions, the formation of agglomerates during mixing being avoided by a high kinetic energy of the polymer particles.
• WO 05/080479 describes a method for post-crosslinking water-absorbing polymer particles, two separate solutions being metered in. According to the patent application, high-speed mixers are preferably used.
• the object of the present invention was to provide an improved process for mixing water-absorbing polymer particles with aqueous solutions.
• the object was achieved by a process for the continuous mixing of water-absorbing polymer particles with liquids or other particles, the polymer particles moving in the product flow direction on account of their own weight, characterized in that at least part of the mixed material was attached to a rotating shaft by the rotational movement of at least one Mixing tool receives an impulse against the product flow direction.
• Liquids are liquids at 23 ° C or solids liquefied by an increase in temperature.
• Suitable liquid substances are, for example, liquid postcrosslinkers or postcrosslinker solutions which are applied to water-absorbing polymer particles.
• particles are particulate solids that are different from the water-absorbing polymer particles.
• a suitable particulate solid is, for example, pyrogenic silica.
• the product flow direction is the direction of transport of the polymer particles through the mixer, i.e. the transport route through the mixer from the mixer inlet to the mixer outlet.
• the polymer particles move through the mixer from top to bottom. As a result, the polymer particles are accelerated by gravity in the direction of the product flow due to their own weight.
• the front edge of the mixing tool in the direction of rotation lies below its rear edge, ie the mixing tool has a positive angle of attack and transports the polymer particles against the product flow direction. Accordingly, a negative angle of attack means that the mixing tool transports the polymer particles in the product flow direction.
• the liquids or other particles are usually metered into the mixer from above, preferably sprayed on by means of suitable nozzles, particularly preferably by means of at least one two-substance nozzle, very particularly preferably by means of at least four two-substance nozzles.
• the liquid to be sprayed on and the other particles to be sprayed on can be better distributed.
• a plurality of nozzles, for example two, can advantageously also be supplied via a common feed line.
• the present invention is based on the finding that by reversing the direction of transport of the mixing tools that has been customary up to now, a residence time distribution is achieved even at moderate peripheral speeds, for which previously much higher peripheral speeds were necessary.
• Suitable mixing tools are, for example, knives or paddles.
• the number of mixing tools is preferably from 2 to 64, particularly preferably from 4 to 32, very particularly preferably from 8 to 16. It is possible for 2, 4 or 8 mixing tools to be located in a common plane.
• the mixing tools can protrude radially laterally from the shaft, i.e. the angle between the shaft axis and the connecting line from the attachment of the mixing tool to the shaft and the tip of the mixing tool is approximately 90 °.
• the mixing tools can also protrude laterally from the shaft in pairs in a V-shape, the angle enclosed by the mixing tools arranged in pairs preferably being from 30 to 120 °, particularly preferably from 45 to 105 °, very particularly preferably from 60 to 90 °.
• the shaft is preferably mounted on one or two sides.
• the peripheral speed of the mixing tools is typically from 3 to 20 m / s, preferably from 4 to 18 m / s, particularly preferably from 6 to 15 m / s, very particularly preferably from 8 to 12 m / s.
• the product flow direction is typically less than 45 °, preferably less than 30 °, particularly preferably less than 15 °, very particularly preferably less than 5 °, inclined to the vertical.
• the polymer particles fall vertically through the mixer from top to bottom, i.e. the product flow direction is vertical.
• the angle between the product flow direction and the shaft axis is preferably less than 10 °, particularly preferably less than 5 °, very particularly preferably less than 1 °.
• the product flow direction and shaft axis are preferably identical, i.e. the angle between the two is 0 °.
• the angle of attack of the at least one mixing tool is typically greater than 0 to 30 °, preferably 5 to 25 °, particularly preferably 10 to 20 °, very particularly preferably 15 to 18 °.
• the mixer preferably has a cylindrical wall.
• the diameter of the cylinder is preferably from 90 to 500 mm, particularly preferably from 120 to 400 mm, very particularly preferably from 150 to 350 mm.
• the ratio of the diameter of the orbit of the outer tip of the mixing tool to the largest possible diameter of this orbit is preferably at least 0.6, particularly preferably at least 0.7, very particularly preferably at least 0.8.
• the largest possible diameter of the orbit is the theoretical diameter of the orbit at which the tip of the mixing tool would just touch the mixer wall closest to the shaft axis. In the case of a cylindrical mixer with a centric shaft, this largest possible diameter of the orbit corresponds to the inside diameter of the mixer.
• the throughput of polymer particles per m 2 of cross-sectional area of the mixer is preferably from 10 to 250 t / h, particularly preferably from 25 to 150 t / h, very particularly preferably from 50 to 100 t / h.
• At least part of the mix is given at least one on a rotating by the rotational movement.
• an additional mixing tool attached to the shaft provides a pulse in the product flow direction.
• the mixing tools by means of which at least some of the material to be mixed receive a pulse counter to the product flow direction, are preferably arranged in the product flow direction in front of the mixing tools, by means of which at least some of the material to be mixed receives a pulse in the product flow direction.
• All mixing tools are particularly preferably located on a common path.
• the angle of attack of the additional mixing tools is typically from less than 0 to -30 °, preferably from -2 to -25 °, particularly preferably from -5 to -15 °, very particularly preferably from -8 to -12 °.
• the mixing tools in three levels, so that the mixing tools of the upper mixing tool level have a positive angle of attack and the mixing tools of the lower two mixing tool levels have a negative angle of attack.
• the method according to the invention is preferably used for the post-crosslinking of water-absorbing polymer particles.
• at least one postcrosslinker is preferably used as an aqueous solution.
• the aqueous solution can contain organic compounds, such as isopropanol, propylene glycol or 1,3-propanediol, as the cosolvent.
• the method according to the invention is suitable for mixing in further liquids, such as water and aqueous solutions, and also other particles, such as fumed silica.
• a vertical cylindrical mixer with a vertical shaft axis is used.
• the mixing tools are arranged in two or three rows one above the other, each row having four pairs of V-shaped mixing tools with a positive angle of attack.
• the water-absorbing polymer particles which can be used in the process according to the invention can be obtained by polymerizing a monomer solution containing a) at least one ethylenically unsaturated monomer bearing acid groups, b) at least one crosslinking agent,
• Suitable monomers a) are, for example, ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid. Particularly preferred monomers are acrylic acid and methacrylic acid. Acrylic acid is very particularly preferred.
• the proportion of acrylic acid and / or salts thereof in the total amount of monomers a) is preferably at least 50 mol%, particularly preferably at least 90 mol%, very particularly preferably at least 95 mol%.
• hydroquinone half ethers are hydroquinone monomethyl ether (MEHQ) and / or tocopherols.
• Tocopherol means compounds of the following formula
• R 1 is hydrogen or methyl
• R 2 is hydrogen or methyl
• R 3 is hydrogen or methyl
• R 4 is hydrogen or an acid residue with 1 to 20 carbon atoms.
• R 4 Preferred radicals for R 4 are acetyl, ascorbyl, succinyl, nicotinyl and other physiologically tolerable carboxylic acids.
• the carboxylic acids can be mono-, di- or tricarboxylic acids.
• R 4 is particularly preferably hydrogen or acetyl.
• RRR-alpha-tocopherol is particularly preferred.
• the monomer solution preferably contains at most 130 ppm by weight, particularly preferably at most 70 ppm by weight, preferably at least 10 ppm by weight, particularly preferably at least 30 ppm by weight, particularly preferably by 50 ppm by weight, hydroquinone ether, in each case based on acrylic acid, whereby acrylic acid salts are also taken into account as acrylic acid.
• hydroquinone ether in each case based on acrylic acid, whereby acrylic acid salts are also taken into account as acrylic acid.
• an acrylic acid with a corresponding content of hydroquinone half ether can be used to prepare the monomer solution.
• the water absorbent polymers are cross-linked, i.e. the polymerization is carried out in the presence of compounds having at least two polymerizable groups which can be radically polymerized into the polymer network.
• Suitable crosslinkers b) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallyloxyethane, as described in EP-A 0 530 438, di- and triacrylates, as in EP-A 0 547 847,
• WO 03/104301 and DE-A 10331450 describe mixed acrylates which, in addition to acrylate groups, contain further ethylenically unsaturated groups, as in
• Suitable crosslinkers b) are in particular N, N'-methylenebisacrylamide and N 1 N'-methylenebismethacrylamide, esters of unsaturated mono- or polycarboxylic acids of polyols, such as diacrylate or triacrylate, for example butanediol or
• Allyl compounds such as allyl (meth) acrylate, triallyl cyanurate, maleic acid diallyl ester, polyallyl ester, tetraallyloxyethane, triallyl amine, tetraallyl ethylenediamine, allyl ester of phosphoric acid and vinylphosphonic acid derivatives, as described, for example, in
• Pentaerythritol di, pentaerythritol tri and pentaerythritol tetraallyl ether
• Glycerol triallyl ether polyallyl ether based on sorbitol, and ethoxylated variants thereof.
• Di (meth) acrylates of polyethylene glycols can be used in the process according to the invention, the polyethylene glycol used having a molecular weight between 300 and 1000.
• crosslinkers b) are, however, di- and triacrylates of 3 to 20 times ethoxylated glycerol, 3 to 20 times ethoxylated trimethylolpropane, 3 to 20 times ethoxylated trimethylolethane, in particular di- and triacrylates of 2- to 6-fold ethoxylated glycerol or trimethylolpropane, 3-fold propoxylated glycerol or trimethylolpropane, and 3-fold mixed ethoxylated or propoxylated glycerol or trimethylolpropane, 15-fold ethoxylated glycerol or Trimethylolpropane, and at least 40-fold ethoxylated glycerol, trimethylolethane or trimethylolpropane.
• Very particularly preferred crosslinkers b) are the multiply ethoxylated and / or propoxylated glycerols esterified with acrylic acid or methacrylic acid to give di- or triacrylates, as described, for example, in DE-A 103 19 462.
• Di- and / or triacrylates of 3- to 10-fold ethoxylated glycerol are particularly advantageous.
• Di- or triacrylates of 1- to 5-fold ethoxylated and / or propoxylated glycerol are very particularly preferred.
• Most preferred are the triacrylates of 3 to 5 times ethoxylated and / or propoxylated glycerin.
• the amount of crosslinker b) is preferably 0.001 to 10 mol%, particularly preferably 0.01 to 5 mol%, very particularly preferably 0.1 to 2 mol%, based in each case on the monomer a).
• Ethylene-unsaturated monomers c) which are copolymerizable with the monomers a) are, for example, acrylamide, methacrylamide, crotonic acid amide, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminobutyl acrylate, dimethylaminoethyl methacrylate methacrylate methacrylate methacrylate methacrylate methacrylate methacrylate methacrylate methacrylate methacrylate methacrylate methacrylate methacrylate,
• Polyvinyl alcohol, polyvinyl pyrrolidone, starch, starch derivatives, polyglycols or polyacrylic acids, preferably polyvinyl alcohol and starch, can be used as water-soluble polymers d).
• Suitable reactors are kneading reactors or belt reactors.
• the polymer gel resulting from the polymerization of an aqueous monomer solution is continuously comminuted by, for example, counter-rotating stirring shafts, as described in WO 01/38402.
• the polymerization on the belt is described for example in DE-A 38 25 366 and US 6,241,928.
• Polymerization in a belt reactor produces a polymer gel that has to be comminuted in a further process step, for example in a meat grinder, extruder or kneader.
• the hydrogel is advantageously stored at a higher temperature, preferably at least 50 ° C., particularly preferably at least 70 ° C., very particularly preferably at least 80 ° C., and preferably less than 100 ° C., for example in insulated containers. Storage, usually 2 to 12 hours, further increases the monomer conversion.
• the acid groups of the hydrogels obtained are usually partially neutralized, preferably to 25 to 95 mol%, preferably to 50 to 80 mol%, particularly preferably to 60 to 75 mol%, it being possible to use the customary neutralizing agents, preferably alkali metal hydroxides , Alkali metal oxides, alkali metal carbonates or alkali metal bicarbonates and mixtures thereof.
• the customary neutralizing agents preferably alkali metal hydroxides , Alkali metal oxides, alkali metal carbonates or alkali metal bicarbonates and mixtures thereof.
• alkali metal salts ammonium salts can also be used.
• Sodium and potassium are considered
• Alkali metals are particularly preferred, but very particularly preferred are sodium hydroxide, sodium carbonate or sodium hydrogen carbonate and mixtures thereof.
• the neutralization is preferably carried out at the monomer stage. This is usually done by mixing in the neutralizing agent as an aqueous solution, as a melt, or preferably also as a solid.
• aqueous solution as a melt
• sodium hydroxide with a water content well below 50% by weight can be present as a waxy mass with a melting point above 23 ° C. In this case, dosing as general cargo or melt at an elevated temperature is possible.
• the hydrogel stage it is also possible to carry out the neutralization after the polymerization at the hydrogel stage. Furthermore, it is possible to neutralize up to 40 mol%, preferably 10 to 30 mol%, particularly preferably 15 to 25 mol%, of the acid groups before the polymerization by adding part of the neutralizing agent to the monomer solution and only after the desired degree of final neutralization the polymerization is set at the hydrogel level. If the hydrogel is at least partially neutralized after the polymerization, the hydrogel is preferably mechanically comminuted, for example using a meat grinder, it being possible for the neutralizing agent to be sprayed on, sprinkled on or poured on and then mixed in thoroughly. For this purpose, the gel mass obtained can be minced several times for homogenization.
• the hydrogel is then preferably dried with a belt dryer until the residual moisture content is preferably below 15% by weight, in particular below 10% by weight, the water content according to test method No. 430.2 recommended by EDANA (European Disposables and Nonwovens Association). 02 "Moisture content" is determined.
• a fluidized bed dryer or a heated ploughshare mixer can also be used for drying.
• the dryer temperature must be Timing, the air supply and exhaust must be controlled, and there must be sufficient ventilation in any case. Drying is naturally all the easier and the product is all the whiter when the solids content of the gel is as high as possible.
• the solids content of the gel before drying is therefore preferably between 30 and 80% by weight.
• Aeration of the dryer with nitrogen or another non-oxidizing inert gas is particularly advantageous.
• the partial pressure of the oxygen can simply be reduced during the drying process in order to prevent oxidative yellowing processes.
• adequate ventilation and removal of the water vapor leads to a still acceptable product.
• the shortest possible drying time is advantageous with regard to color and product quality.
• the dried hydrogel is then ground and classified, it being possible to use one- or multi-stage roller mills, preferably two- or three-stage roller mills, pin mills, hammer mills or vibrating mills, for grinding.
• Postcrosslinkers suitable for this purpose are compounds which contain at least two groups which can form covalent bonds with the carboxylate groups of the polymers. Suitable compounds are, for example, alkoxysilyl compounds, polyaziridines, polyamines, polyamidoamines, di- or polyglycidyl compounds, as described in EP-A 0 083 022,
• EP-A 0 543 303 and EP-A 0 937 736 polyhydric alcohols as described in DE-C 33 14 019, DE-C 35 23 617 and EP-A 450 922, or
• ⁇ -hydroxyalkylamides as described in DE-A 102 04 938 and US 6,239,230.
• Compounds with mixed functionality such as glycidol, are also suitable.
• 3-ethyl-3-oxetanmethanol (trimethylolpropanoxetan), as described in EP-A 1 199 327, aminoethanol, diethanolamine, triethanolamine or compounds which form a further functionality after the first reaction, such as ethylene oxide, propylene oxide, isobutylene oxide, aziridine, azetidine or Oxetane.
• DE-A 40 20 780 contains cyclic carbonates, DE-A 198 07 502 2-oxazolidone and its derivatives, such as N- (2-hydroxyethyl) -2-oxazolidone, in
• DE-A 198 07 992 bis- and poly-2-oxazolidinones in DE-A 198 54 573 2-Oxotetrahydro-1, 3-oxazine and its derivatives, in DE-A 198 54 574 N-acyl-2-oxazolidones, in DE-A 102 04 937 cyclic ureas, in DE-A 103 34 584 bicyclic amide acetals, in EP -A 1 199 327 oxetanes and cyclic ureas and in WO 03/031482 morpholine-2,3-dione and its derivatives are described as suitable postcrosslinkers.
• Preferred postcrosslinkers are oxazolidone and its derivatives, in particular N- (2-hydroxyethyl) -2-oxazolidone.
• the amount of postcrosslinker is preferably 0.001 to 5% by weight, particularly preferably 0.01 to 2.5% by weight, very particularly preferably 0.1 to 1% by weight, based in each case on the polymer.
• the postcrosslinking is usually carried out in such a way that a solution, preferably an aqueous solution, of the postcrosslinker is sprayed onto the hydrogel or the dry polymer particles. Following the spraying, drying is carried out thermally, and the postcrosslinking reaction can take place both before and during the drying.
• the postcrosslinker is advantageously mixed with the polymer according to the process of the invention and then thermally dried.
• the thermal drying is preferably carried out in contact dryers, particularly preferably paddle dryers, very particularly preferably disc dryers.
• Suitable dryers include Bepex®-T rockner and Nara®-T rockner. Fluidized bed dryers can also be used.
• Drying can be done by heating the jacket or by blowing in warm air.
• a downstream dryer such as a tray dryer, a rotary kiln or a heatable screw, is also suitable.
• an azeotropic distillation can also be used as the drying process.
• Preferred drying temperatures are in the range of 50 to 250 ° C, preferably 50 to 200 ° C, and particularly preferably 50 to 150 ° C.
• the preferred residence time at this temperature in the reaction mixer or dryer is less than 30 minutes, particularly preferably less than 10 minutes.
• the mixing behavior was simulated in a Schugi® Flexomix Type 335 (Hosokawa Micron Group, Japan).
• the mixing process was calculated using the Discrete Element Method (DEM).
• the trajectory of each particle in the geometry is tracked simultaneously under the action of external forces.
• the forces that are taken into account in this case are gravity and contact forces that occur in the event of contact between two particles or between particles and standing (shell geometry) or moving walls (mixing tools). It is assumed here that only sliding friction occurs.
• a linear spring-damper model was used for all particle contacts. Interaction with a gas flow was not considered.
• the simulated particles had a diameter of 5 mm and a solid density of 1640 kg / m 3 .
• the wall friction angle and the internal friction angle of the particles is 42 °.
• the spring constant is 400 N / m and the effective restitution coefficient of the particles is set to 0.5.
• the mass flow of the particles is 8 t / h.
• the dwell time distribution was calculated for a speed of 1,800 rpm.
• the mixing tools had a negative angle of attack of 18 °, ie the particles received an impulse in the product flow direction from the rotating mixing tools.
• Example 2 The procedure was as in Example 1. The speed was reduced to 700 rpm. Tab. 2: 700 rpm, negative angle of attack
• Example 2 The procedure was as in Example 2.
• the mixing tools had a positive angle of attack of 18 °, i.e. the rotating mixing tools gave the particles an impulse against the product flow direction.
• Tab. 3 700 rpm, positive angle of attack
• Example 3 The procedure was as in Example 3. The speed was reduced to 575 rpm. Tab. 4: 575 rpm, positive angle of attack

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• 2006
  • 2006-11-30 JP JP2008543787A patent/JP5697846B2/ja active Active
  • 2006-11-30 US US12/093,710 patent/US20100140546A1/en not_active Abandoned
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