WO2008095901A1 - Verfahren zur herstellung wasserabsorbierender polymerpartikel durch polymerisation von tropfen einer monomerlösung - Google Patents
Verfahren zur herstellung wasserabsorbierender polymerpartikel durch polymerisation von tropfen einer monomerlösung Download PDFInfo
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- WO2008095901A1 WO2008095901A1 PCT/EP2008/051353 EP2008051353W WO2008095901A1 WO 2008095901 A1 WO2008095901 A1 WO 2008095901A1 EP 2008051353 W EP2008051353 W EP 2008051353W WO 2008095901 A1 WO2008095901 A1 WO 2008095901A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
- A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
- A61L15/42—Use of materials characterised by their function or physical properties
- A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B9/00—Making granules
- B29B9/10—Making granules by moulding the material, i.e. treating it in the molten state
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/04—Polymerisation in solution
- C08F2/10—Aqueous solvent
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/12—Polymerisation in non-solvents
- C08F2/16—Aqueous medium
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/12—Polymerisation in non-solvents
- C08F2/16—Aqueous medium
- C08F2/18—Suspension polymerisation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/04—Acids; Metal salts or ammonium salts thereof
- C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F6/00—Post-polymerisation treatments
- C08F6/006—Removal of residual monomers by chemical reaction, e.g. scavenging
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
Definitions
- the present invention relates to a method for producing water-absorbing polymer particles by polymerization of droplets of a monomer solution in a surrounding gas phase, wherein the resulting polymer particles have a water content of at least 5 wt .-% and in fluidized state in the presence of water vapor at a temperature of at least 60 0 C are thermally treated.
- Water-absorbing polymers are used as aqueous solution-absorbing products for making diapers, tampons, sanitary napkins and other sanitary articles, but also as water-retaining agents in agricultural horticulture.
- the object of the present invention was to provide an improved process for preparing water-absorbing polymer particles by polymerizing droplets of a monomer solution in a gas phase surrounding the droplets.
- the object was achieved by a method for producing water-absorbing polymer particles by polymerization of drops of a monomer solution containing
- the resulting polymer particles have a water content of at least 5 wt .-% and are thermally treated in the fluidized state in the presence of a gas stream at a temperature of at least 60 0 C, wherein the gas stream at a temperature of less than 100 0 C has a relative humidity of at least 20% or at a temperature of 100 0 C or more at least 0.25 kg of water vapor per kg of dry gas.
- the water content of the polymer particles obtained is preferably from 8 to 40 wt .-%, particularly preferably from 10 to 30 wt .-%, most preferably from 12 to 20 wt .-%.
- the temperature during the thermal aftertreatment is preferably from 70 to 150.degree. C., more preferably from 80 to 140.degree. C., very particularly from 90 to 130.degree.
- the water content of the polymer particles preferably changes during the thermal aftertreatment by less than 40%, more preferably by less than 20%, most preferably by less than 10%, the change meaning the relative change.
- the change in the water content of the polymer particles before and after the aftertreatment can be measured and the relative humidity of the gas stream can be adjusted accordingly.
- the thermal aftertreatment is preferably carried out from 5 to 120 minutes, more preferably from 8 to 60 minutes, most preferably from 10 to 30 minutes.
- the relative humidity of the gas stream is preferably from 50 to 98%, more preferably from 70 to 96%, most preferably from 85 to 95%.
- the relative humidity is the quotient of water vapor partial pressure and water vapor pressure (saturation) at a given temperature multiplied by 100%.
- the water vapor content of the gas is preferably from 1 to 10 kg per kg of dry gas, more preferably from 2 to 7.5 kg per kg of dry gas, most preferably from 3 to 5 kg per kg of dry gas ,
- the remaining constituents of the gas are preferably nitrogen, air or air / nitrogen mixtures, more preferably nitrogen or air / nitrogen mixtures with less than 10 vol .-% oxygen.
- the kinetic energy of the polymer particles is greater than the cohesive or adhesion potential between the polymer particles.
- the fluidized state can be achieved by a fluidized bed.
- the water-absorbing polymer particles are flowed from below, so that the particles form a fluidized bed.
- the height of the fluidized bed is determined by the amount of gas and gas velocity, i. about the pressure loss of the fluidized bed (kinetic energy of the gas), adjusted.
- the velocity of the gas stream is preferably from 0.5 to 2.5 m / s, more preferably from 0.8 to 1.5 m / s, most preferably from 0.9 to 1.2 m / s.
- the present invention is based on the finding that residual monomers in the polymer particles obtained by polymerization of droplets of a monomer solution can be removed by contact with a flowing gas.
- the residual monomers can be better removed at higher temperatures and longer residence times. It is important that the polymer particles are not too dry. If the particles are too dry, the residual monomers decrease only insignificantly. Too high a water content increases the caking tendency of the polymer particles. So that the water-absorbing polymer particles do not dry too quickly during the thermal aftertreatment, the inflowing gas must already contain water vapor.
- the water content of the polymer particles should be in the range of preferably 5 to 40% by weight, more preferably 8 to 30% by weight, most preferably 10 to 20% by weight.
- the monomers a) are preferably water-soluble, i. the solubility in water at 23 ° C. is typically at least 1 g / 100 g of water, preferably at least 5 g / 100 g of water, more preferably at least 25 g / 100 g of water, most preferably at least 50 g / 100 g of water preferably at least one acid group each.
- 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. Especially preferred is acrylic acid.
- the preferred monomers a) have at least one acid group, wherein the acid groups are preferably at least partially neutralized.
- 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%.
- the acid groups of the monomers a) are usually partially neutralized, preferably from 25 to 85 mol%, preferably from 50 to 80 mol%, particularly preferably from 60 to 75 mol%, where the customary neutralizing agents can be used, preferably alkali metal hydroxides, alkali metal oxides , Alkali metal carbonates or alkali metal hydrogencarbonates and mixtures thereof.
- the customary neutralizing agents can be used, preferably alkali metal hydroxides, alkali metal oxides , Alkali metal carbonates or alkali metal hydrogencarbonates and mixtures thereof.
- alkali metal salts and ammonium salts can be used.
- Sodium and potassium are particularly preferred as the alkali metals, but most preferred are sodium hydroxide, sodium carbonate or sodium bicarbonate and mixtures thereof.
- the neutralization is achieved by mixing the neutralizing agent as an aqueous solution, as a melt, or preferably as a solid.
- Preferred hydroquinone half ethers are hydroquinone monomethyl ether (MEHQ).
- the monomer solution preferably contains at most 160 ppm by weight, preferably at most 130 ppm by weight, more preferably at most 70 ppm by weight, preferably at least 10 ppm by weight, more preferably at least 30 ppm by weight, in particular by 50% by weight.
- ppm Hydroquinone Halbether, each based on acrylic acid, wherein acrylic acid salts are taken into account as acrylic acid.
- an acrylic acid having a corresponding content of hydroquinone half-ether can be used.
- polymerization inhibitors can also be removed by absorption, for example on activated carbon, from the monomer solution.
- Crosslinkers b) are compounds having at least two polymerizable groups which can be radically copolymerized 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 530 438 A1, di- and triacrylates, as in EP 547 847 A1, EP 559 476 A1, EP 632 068 A1, WO 93/21237 A1, WO 2003/104299 A1, WO 2003/104300 A1, WO 2003/104301 A1 and DE 103 31 450 A1, mixed acrylates which, in addition to acrylate groups, contain further ethylenically unsaturated groups, as described in DE 103 31 456 A1 and DE 103 55 401 A1, or crosslinker mixtures, as described, for example, in DE 195 43 368 A1 DE
- Suitable crosslinkers b) are, in particular, N, N'-methylenebisacrylamide and N, N'-methylenebismethacrylamide, esters of unsaturated monocarboxylic or polycarboxylic acids of polyols, such as diacrylate or triacrylate, for example butanediol or ethylene glycol diacrylate or methacrylate, and trimethylolpropane triacrylate and Allyl compounds, such as allyl (meth) acrylate, triallyl cyanurate, maleic acid diallyl esters, polyallyl esters, tetraallyloxyethane, triallylamine, tetraallylethylenediamine, allyl esters of phosphoric acid and vinylphosphonic acid derivatives, as described, for example, in EP 343 427 A2.
- crosslinkers b) are pentaerythritol di-, pentaerythritol tri- and pentaerythritol tetraallyl ethers, polyethylene glycol diallyl ether, ethylene glycol diallyl ether, glycerol di- and glycerol triallyl ether, polyallyl ethers based on sorbitol, and ethoxylated variants thereof.
- Useful in the process according to the invention are di (meth) acrylates of polyethylene glycols, where the polyethylene glycol used has a molecular weight between 300 and 1000.
- crosslinkers b) are 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-times ethoxylated glycerol or trimethylolpropane, the 3-fold propoxylated glycerol or trimethylolpropane, and the 3-fold mixed ethoxylated or propoxylated glycerol or trimethylolpropane, the 15-times ethoxylated glycerol or trimethylolpropane, and at least 40-times ethoxylated glycerol, Trimethylolethane or trimethylolpropane.
- Very particularly preferred crosslinkers b) are the polyethoxylated and / or propoxylated glycerols esterified with acrylic acid or methacrylic acid to form di- or triacrylates, as described, for example, in WO 2003/104301 A1. Particularly advantageous are di- and / or triacrylates of 3- to 10-fold ethoxylated glycerol. Very particular preference is given to diacrylates or triacrylates of 1 to 5 times ethoxylated and / or propoxylated glycerol. Most preferred are the triacrylates of 3 to 5 times ethoxylated and / or propoxylated glycerin.
- the monomer solution preferably contains at least 0.1% by weight, preferably at least 0.2% by weight, particularly preferably at least 0.3% by weight, very particularly preferably at least 0.4% by weight, crosslinker b ), in each case based on monomer a).
- initiators c) it is possible to use all compounds which decompose into free radicals under the polymerization conditions, for example peroxides, hydroperoxides, hydrogen peroxide, persulfates, azo compounds and the so-called redox initiators. Preference is given to the use of water-soluble initiators. In some cases, it is advantageous to use mixtures of different initiators, for example mixtures of hydrogen peroxide and sodium or potassium peroxodisulfate. Mixtures of hydrogen peroxide and sodium peroxodisulfate can be used in any proportion.
- Particularly preferred initiators c) are azo initiators, such as 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride and 2,2'-azobis [2- (5-methyl-2-imidazoline-2 - yl) propane] dihydrochloride, and photoinitiators, such as 2-hydroxy-2-methylpropiophenone and 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, redox initiato such as sodium persulfate / hydroxymethylsulfinic acid, ammonium peroxodisulfate / hydroxymethylsulfinic acid, hydrogen peroxide / hydroxymethylsulfinic acid, sodium persulfate / ascorbic acid, ammonium peroxodisulfate / ascorbic acid and hydrogen peroxide / ascorbic acid, photoinitiators, such as 1- [4- (2-hydroxyethoxy) -phen
- the initiators are used in customary amounts, for example in amounts of 0.001 to 5 wt .-%, preferably 0.01 to 2 wt .-%, based on the monomers a).
- At least one azo compound and at least one persulfate are used as initiators c).
- the amount of azo compound is preferably at least 0.1 wt .-%, more preferably at least 0.25 wt .-%, most preferably at least 0.5 wt .-%, based on the monomers a).
- the amount of persulfate is preferably at least 0.25 wt .-%, more preferably at least 0.5 wt .-%, most preferably at least 0.75 wt .-%, based on the monomers a).
- the azo compounds usually decompose rapidly into radicals.
- persulfates are relatively slow polymerization initiators. This means that the water-absorbing polymer particles obtained by polymerization of droplets of a monomer solution still contain significant amounts of persulfate. These persulfates disintegrate during the thermal aftertreatment and thus additionally reduce the residual monomers.
- the solids content of the monomer solution is preferably at least 35 wt .-%, preferably at least 38 wt .-%, more preferably at least 40 wt .-%, most preferably at least 42 wt .-%.
- the solids content is the sum of all nonvolatile constituents after the polymerization. These are monomer a), crosslinker b) and initiator c).
- the oxygen content of the monomer solution is preferably at least 1 ppm by weight, more preferably at least 2 ppm by weight, most preferably at least 5 ppm by weight.
- the usual inerting of the monomer solution can therefore be largely dispensed with.
- the increased oxygen content stabilizes the monomer solution and allows the use of lesser amounts of polymerization inhibitor and thus reduces the product discolorations caused by the polymerization inhibitor.
- the monomer solution is metered into the gas phase for polymerization.
- the oxygen content of the gas phase is preferably 0.001 to 0.15% by volume, particularly preferably 0.002 to 0.1% by volume, very particularly preferably 0.005 to 0.05% by volume.
- the gas phase preferably contains only inert gases besides oxygen, i. Gases which do not interfere with the polymerization under reaction conditions, for example nitrogen and / or water vapor.
- the monomer solution is metered to form drops in the gas phase.
- the drops can be produced, for example, by means of a dropletizer plate.
- a dropletizer plate is a plate having at least one bore, the liquid passing from above through the bore.
- the dropletizer plate or the liquid can be set in vibration, whereby an ideally monodisperse droplet chain is produced on the underside of the dropletizer per bore.
- the dropletizer plate is not excited.
- the number and size of the holes are selected according to the desired capacity and drop size.
- the drop diameter is usually 1, 9 times the diameter of the bore. It is important that the fluid to be dripped does not pass through the bore too quickly or that the pressure loss through the bore is not too great. Otherwise, the liquid is not dripped, but the liquid jet is torn due to the high kinetic energy (sprayed).
- the Reynolds number based on the throughput per bore and the bore diameter is preferably less than 2,000, preferably less than 1,000, more preferably less than 500, most preferably less than 100.
- the pressure drop across the bore is preferably less than 2.5 bar, more preferably less than 1.5 bar, most preferably less than 1 bar.
- the dropletizer plate usually has at least one, preferably at least 10, more preferably at least 50, and usually up to 10,000, preferably up to 5,000, particularly preferably up to 1,000, bores, the bores usually being uniformly distributed over the dropletizer plate, preferably in the so-called triangle division, ie three holes each form the corners of an equilateral triangle. The diameter of the holes is adjusted to the desired drop size.
- the drops can also be produced by means of pneumatic drawing nozzles, rotation, cutting of a jet or quickly activatable micro-valve nozzles.
- a liquid jet is accelerated along with a gas flow through a baffle.
- the diameter of the liquid jet and thus the droplet diameter can be influenced.
- the exiting liquid jet can also be cut into defined segments by means of a rotating knife. Each segment then forms a drop.
- micro-valve nozzles When using micro-valve nozzles directly drops are generated with a defined volume of liquid.
- the droplets produced have an average diameter of preferably at least 200 .mu.m, more preferably at least 250 .mu.m, most preferably at least 300 .mu.m, wherein the droplet diameter can be determined by light scattering and means the volume-averaged mean diameter.
- the polymerization reactor is traversed by a gas.
- the carrier gas can be passed through the reaction space in cocurrent or in countercurrent to the freely falling drops of the monomer solution, preferably in cocurrent, ie from bottom to top.
- the gas is at least partially example, preferably at least 50%, more preferably at least 75%, recycled as recycle gas in the reaction space.
- a portion of the carrier gas is discharged after each pass, preferably up to 10%, more preferably up to 3%, most preferably up to 1%.
- the gas velocity is preferably adjusted so that the flow is directed in the polymerization reactor, for example, there are no convection vortices opposite the general flow direction, and is for example 0.01 to 5 m / s, preferably 0.02 to 4 m / s, particularly preferably 0 , 05 to 3 m / s, most preferably 0.1 to 2 m / s.
- the gas flowing through the reactor is expediently preheated to the reaction temperature upstream of the reactor.
- the reaction temperature is in the thermally induced polymerization preferably 100 to 250 0 C, more preferably 120 to 200 0 C, most preferably 150 to 180 ° C.
- the reaction can be carried out in overpressure or under reduced pressure, a negative pressure of up to 100 mbar relative to the ambient pressure is preferred.
- the reaction offgas i. the gas leaving the reaction space can be cooled, for example, in a heat exchanger. This condense water and unreacted monomer a). Thereafter, the reaction gas can be at least partially reheated and recycled as recycle gas in the reactor. Part of the reaction off-gas can be discharged and replaced by fresh gas, wherein water contained in the reaction offgas and unreacted monomers a) can be separated off and recycled.
- a heat network that is, a portion of the waste heat during cooling of the exhaust gas is used to heat the circulating gas.
- the reactors can be accompanied by heating.
- the heat tracing is set in such a way that the wall temperature is at least 5 ° C above the internal reactor temperature and the condensation on the reactor walls is reliably prevented.
- the reaction product is subsequently thermally treated and optionally dried, preferably in at least one fluidized bed.
- the polymer particles can be postcrosslinked to further improve the properties.
- Postcrosslinkers are compounds containing at least two groups which can form covalent bonds with the carboxylate groups of the hydrogel. Suitable compounds are, for example, alkoxysilyl compounds, polyaziridines, polyamines, polyamidoamines, di- or polyepoxides, as described in EP 83 022 A2, EP 543 303 A1 and EP 937 736 A2, di- or polyfunctional alcohols, as in DE 33 14 019 A1, DE 35 23 617 A1 and EP 450 922 A2, or ß-hydroxyalkylamides, as described in DE 102 04 938 A1 and US 6,239,230.
- the amount of postcrosslinker is preferably 0.01 to 1 wt .-%, particularly preferably 0.05 to 0.5 wt .-%, most preferably 0.1 to 0.2 wt .-%, each based on the polymer ,
- the postcrosslinking is usually carried out by spraying a solution of the postcrosslinker onto the hydrogel or the dry polymer particles. Subsequent to the spraying, it is thermally dried, whereby the postcrosslinking reaction can take place both before and during the drying.
- the spraying of a solution of the crosslinker is preferably carried out in mixers with agitated mixing tools, such as screw mixers, paddle mixers, disk mixers, plowshare mixers and paddle mixers.
- agitated mixing tools such as screw mixers, paddle mixers, disk mixers, plowshare mixers and paddle mixers.
- Vertical mixers are particularly preferred, plowshare mixers and paddle mixers are very particularly preferred.
- suitable mixers are Lödige mixers, Bepex mixers, Nauta mixers, Processall mixers and Schugi mixers.
- 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. Moreover, fluidized bed dryers can also be used.
- the drying can be done in the mixer itself, by heating the jacket or
- Blowing warm air is also suitable.
- a downstream dryer such as a hopper dryer, a rotary kiln or a heatable screw.
- drying temperatures are in the range 170 to 250 0 C, preferably 180 to 220 0 C, and particularly preferably 190 to 210 ° C.
- the preferred residence time at this temperature in the reaction mixer or dryer is preferably at least 10 minutes, more preferably at least 20 minutes, most preferably at least 30 minutes.
- the process according to the invention makes it possible to produce water-absorbing polymer particles having a very low content of residual monomers.
- the water-absorbing polymer particles obtainable by the process according to the invention have a centrifuge retention capacity (CRC) of typically at least 15 g / g, preferably at least 20 g / g, preferably at least 25 g / g, more preferably at least 30 g / g, most preferably at least 35 g / g, up.
- the centrifuge retention capacity (CRC) of the water-absorbent polymer particles is usually less than 100 g / g.
- the centrifuge retention capacity of the water-absorbing polymer particles is determined according to the test method No. 441.2-02 "Centrifuge retention capacity" recommended by the EDANA (European Disposables and Nonwovens Association).
- Polymer particles have a content of residual monomers of typically less than 0.1% by weight, preferably less than 0.07% by weight, more preferably less than 0.05% by weight, most preferably less than 0.04 Wt .-%, on.
- the content of residual monomers is determined according to the test method No. 410.2-02 "Residual monomers" recommended by the EDANA (European Disposables and Nonwovens Association).
- the water-absorbing polymer particles obtainable by the process according to the invention have a water content of preferably at least 10% by weight, more preferably at least 12% by weight, most preferably at least 14% by weight.
- the water content is determined according to the test method No. 430.2-02 "Moisture content" recommended by the EDANA (European Disposables and Nonwovens Association).
- the average diameter of the water-absorbing polymer particles obtainable by the process according to the invention is preferably at least 200 .mu.m, particularly preferably from 250 to 600 .mu.m, very particularly from 300 to 500 .mu.m, where the particle diameter can be determined by light scattering and the volume-average mean diameter.
- 90% of the polymer particles have a diameter of preferably 100 to 800 .mu.m, more preferably from 150 to 700 .mu.m, most preferably from 200 to 600 .mu.m.
- Another object of the present invention are obtainable by the process according to the invention water-absorbing polymer particles. The water-absorbing polymer particles are tested by the test methods described below.
- the measurements should be taken at an ambient temperature of 23 ⁇ 2 0 C and a relative humidity of 50 ⁇ 10% unless otherwise specified.
- the water-absorbing polymers are thoroughly mixed before the measurement.
- the content of residual monomer of the water-absorbing polymer particles is determined according to the test method No. 410.2-02 "Residual monomers" recommended by the EDANA (European Disposables and Nonwovens Association).
- the water content of the water-absorbing polymer particles is determined according to the test method No. 430.2-02 "Moisture content" recommended by the EDANA (European Disposables and Nonwovens Association).
- the EDANA test methods are available, for example, from the European Disposables and Nonwovens Association, Avenue Eugene Plasky 157, B-1030 Brussels, Belgium.
- the initiator used was a 3% strength by weight solution of 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride in water.
- the initiator was metered into the monomer solution via a static mixer prior to dropping.
- the dropletizer plate had 30 holes a 200 ⁇ m.
- the ratio of monomer solution to initiator solution was 93.6: 6.4.
- the resulting mixture was dropped into a heated nitrogen sparge drop tower (12m high, 2m wide, gas velocity 0.1m / s cocurrent).
- the metering rate of the mixture was 16 kg / h.
- the Heating power of the gas preheating was controlled so that the gas outlet temperature in the drip tower was constant 130 0 C.
- the amount of nitrogen fed was 1,000 m 3 / h.
- the resulting polymer particles had a water content of 19.1 wt .-%.
- the polymer particles still contained 0.5 wt .-% residual monomer.
- the resulting water-absorbing polymer particles were dried for one hour at 165 ° C in a convection oven.
- the dried polymer particles contained 0.4% by weight of residual monomer.
- Example 2 The procedure was as in Example 1.
- the polymer particles obtained were thermally treated before drying in a fluidized bed.
- the polymers were flowed for 30 minutes from the bottom with an air / water vapor mixture.
- the gas velocity was 1 m / s.
- the gas temperature was 90 ° C.
- the relative humidity of the gas stream was 50%.
- the gas stream contained 0.347 kg of water vapor per kg of dry gas.
- the dried polymer particles contained 0.3% by weight of residual monomer.
- the water content of the dried polymer particles was 5.1% by weight.
- Example 2 The procedure was as in Example 1.
- the polymer particles obtained were thermally treated before drying in a fluidized bed.
- the polymer was flowed in from below for 30 minutes with an air / water vapor mixture.
- the gas velocity was 1 m / s.
- the gas temperature was 90 ° C.
- the relative humidity of the gas stream was 70%.
- the gas stream contained 0.62 kg of water vapor per kg of dry gas.
- the dried polymer particles contained 0.08 wt .-% residual monomer.
- the water content of the dried polymer particles was 1 1 wt .-%.
- Example 4 The procedure was as in Example 1. The polymer particles obtained were thermally treated before drying in a fluidized bed.
- the polymer was flowed in from below for 30 minutes with an air / water vapor mixture.
- the gas velocity was 1 m / s.
- the gas temperature was 90 ° C.
- the relative humidity of the gas stream was 90%.
- the gas stream contained 1, 1 kg of water vapor per kg of dry gas.
- the dried polymer particles contained 0.035 wt .-% residual monomer.
- the water content of the dried polymer particles was 12.3% by weight.
- Example 2 The procedure was as in Example 1.
- the polymer particles obtained were thermally treated before drying in a fluidized bed.
- the polymer was flowed in from below for 30 minutes with an air / water vapor mixture.
- the gas velocity was 1.3 m / s.
- the gas temperature was 130 ° C.
- the gas stream contained 4 kg of steam per kg of dry gas.
- the dried polymer particles contained 0.05% by weight of residual monomer.
- the water content of the dried polymer particles was 18.5 wt .-%.
- Example 2 The procedure was as in Example 1.
- the polymer particles obtained were thermally treated before drying in a fluidized bed.
- the polymer was flowed in from below for 30 minutes with an air / water vapor mixture.
- the gas velocity was 0.7 m / s.
- the gas temperature was 1 10 ° C.
- the gas stream contained 4 kg of steam per kg of dry gas.
- the dried polymer particles contained 0.03 wt .-% residual monomer.
- the water content of the dried polymer particles was 15.3 wt .-%.
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EP08708656.7A EP2115014B1 (de) | 2007-02-06 | 2008-02-04 | Verfahren zur herstellung wasserabsorbierender polymerpartikel durch polymerisation von tropfen einer monomerlösung |
JP2009548677A JP5419712B2 (ja) | 2007-02-06 | 2008-02-04 | モノマー溶液の液滴の重合による吸水性ポリマー粒子を製造する方法 |
US12/523,468 US8697779B2 (en) | 2007-02-06 | 2008-02-04 | Method for producing water-absorbent polymer particles by the polymerization of droplets of a monomer solution |
CN200880004266.6A CN101605819B (zh) | 2007-02-06 | 2008-02-04 | 通过聚合单体溶液的液滴生产吸水性聚合物颗粒的方法 |
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WO2010015591A1 (en) | 2008-08-06 | 2010-02-11 | Basf Se | Fluid-absorbent articles |
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JP2013522431A (ja) * | 2010-03-24 | 2013-06-13 | ビーエーエスエフ ソシエタス・ヨーロピア | モノマー溶液の液滴を重合することによる吸水ポリマー粒子の製造方法 |
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WO2015093594A1 (ja) | 2013-12-20 | 2015-06-25 | 株式会社日本触媒 | ポリアクリル酸(塩)系吸水剤及びその製造方法 |
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CN101605819B (zh) | 2014-07-23 |
JP5419712B2 (ja) | 2014-02-19 |
US20100035059A1 (en) | 2010-02-11 |
US8697779B2 (en) | 2014-04-15 |
EP2115014A1 (de) | 2009-11-11 |
JP2010518211A (ja) | 2010-05-27 |
CN101605819A (zh) | 2009-12-16 |
EP2115014B1 (de) | 2019-01-16 |
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