Classifications

• • 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
  • C08F2/01—Processes of polymerisation characterised by special features of the polymerisation apparatus used
• • 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
• • 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
  • B01J19/22—Stationary reactors having moving elements inside in the form of endless belts
• • 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
• • 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
  • B01J2219/00004—Scale aspects
  • B01J2219/00006—Large-scale industrial plants

Definitions

• the present invention relates to a process for producing water-absorbing polymer particles by thermal polymerization of discrete droplets of a monomer solution on a hydrophobic surface.
• the preparation of water-absorbing polymer particles is described in the monograph "Modern Superabsorbent Polymer Technology", F.L. Buchholz and AT. Graham, Wiley-VCH, 1998, pages 71-103.
• the Korean patent application KR 2013-01 15810 describes a UV polymerization of discrete drops of a monomer solution.
• Water-absorbent polymer particles are used as aqueous solution-absorbing products for the production of diapers, tampons, sanitary towels and other sanitary articles, but also as water-retaining agents in agricultural horticulture. Water-absorbing polymer particles are also referred to as "superabsorbent polymers" or “superabsorbents”.
• the object of the present invention was to provide an improved process for the preparation of polymer particles.
• the object has been achieved by a process for the polymerization of an aqueous monomer solution comprising at least one ethylenically unsaturated monomer a), optionally a crosslinker b), at least one initiator c) and water, wherein in a first step i) drops are produced and the droplets in a second step ii) are polymerized on a hydrophobic surface, characterized in that the at least one initiator c) is a thermal initiator and the polymerization in step ii) is carried out thermally.
• thermal initiators are, for example, azo initiators, peroxides, hydroperoxides, hydrogen peroxide and persulfates.
• the monomer solution contains substantially no photoinitiator and the polymerization is carried out substantially in the absence of UV radiation.
• the temperature during the thermal polymerization in step ii) is preferably from 100 to 250.degree. C., more preferably from 120 to 200.degree. C., most preferably from 150 to 180.degree.
• the droplets have an average diameter of preferably 50 to 2000 ⁇ , more preferably from 100 to 1000 ⁇ , most preferably from 300 to 600 ⁇ , wherein the average diameter of the volume-average diameter and can be measured by light scattering.
• the aqueous monomer solution usually comprises a) at least one ethylenically unsaturated, acid group-carrying monomer which may be at least partially neutralized,
• 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 35 g / 100 g of water.
• Suitable monomers a) are, for example, ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, maleic acid and itaconic acid. Particularly preferred monomers are acrylic acid and methacrylic acid. Very particular preference is given to acrylic acid.
• Suitable monomers a) are, for example, ethylenically unsaturated sulfonic acids, such as styrenesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).
• sulfonic acids such as styrenesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).
• AMPS 2-acrylamido-2-methylpropanesulfonic acid
• a suitable monomer a) is, for example, an acrylic acid purified according to WO 2004/035514 A1 with 99.8460% by weight of acrylic acid, 0.0950% by weight of acetic acid, 0.0332% by weight of water, 0.0203% by weight.
• Propionic acid 0.0001% by weight furfurale, 0.0001 linoleic anhydride, 0.0003% by weight of diacrylic acid and 0.0050% by weight of hydroquinone monomethyl ether.
• 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 at least 25 mol%, preferably from 50 to 85 mol%, more preferably from 60 to 75 mol%, very preferably from 65 to 72 mol%, using the customary neutralizing agents may be, preferably alkali metal hydroxides, alkali metal oxides, alkali metal carbonates or alkali metal bicarbonates and mixtures thereof. Instead of alkali metal salts and ammonium salts can be used. Sodium and potassium are particularly preferred as alkali metals, but most preferred are sodium hydroxide, sodium carbonate or sodium bicarbonate and mixtures thereof. Usually, the neutralization is achieved by mixing the neutralizing agent as an aqueous solution, as a melt, or preferably as a solid.
• sodium hydroxide with a water content well below 50 wt .-% may be present as a waxy mass with a melting point above 23 ° C.
• a dosage as general cargo or melt at elevated temperature is possible.
• one or more chelating agents can be added to the monomer solution or its starting materials to mask metal ions, such as iron, for stabilization.
• chelating agents are alkali citrates, citric acid, alkali tartrates, pentasodium triphosphate, ethylenediamine tetraacetate, nitrilotriacetic acid and all chelating agents known by the name Trilon®, for example Trilon® C (pentasodium diethylenetriamine pentaacetate), Trilon® D (trisodium (hydroxyethyl) ethylene-diaminotriazetate ), as well as Trilon® M (methylglycinediacetic acid).
• Trilon® C penentasodium diethylenetriamine pentaacetate
• Trilon® D trisodium (hydroxyethyl) ethylene-diaminotriazetate
• Trilon® M methylglycinediacetic acid
• the monomers a) usually contain polymerization inhibitors, preferably hydroquinone half ethers, as storage stabilizer.
• the monomer solution preferably contains up to 250 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, particularly preferably at least 30 ppm by weight, in particular by 50% by weight .
• ppm hydroquinone half ether, in each case based on the unneutralized monomer a).
• an ethylenically unsaturated, acid group-carrying monomer having a corresponding content of hydroquinone half-ether can be used to prepare the monomer solution.
• the hydroquinone half ethers can also be removed from the monomer solution by absorption, for example on activated charcoal.
• Preferred hydroquinone half ethers are hydroquinone monomethyl ether (MEHQ) and / or alpha tocopherol (vitamin E).
• Suitable crosslinkers b) are compounds having at least two groups suitable for crosslinking. Such groups are, for example, ethylenically unsaturated groups which can be radically copolymerized into the polymer chain, and functional groups which can form covalent bonds with the acid groups of the monomer a).
• polyvalent metal salts which can form coordinative bonds with at least two acid groups of the monomer a) are also suitable as crosslinking agents b).
• Crosslinkers b) are preferably compounds having at least two polymerizable groups which can be incorporated in the polymer network in free-radically polymerized form.
• Suitable crosslinkers b) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallylammonium chloride, tetraallyloxyethane, as described in EP 0 530 438 A1, di- and triacrylates, as in EP 0 547 847 A1, EP 0 559 476 A1, EP 0 632 068 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
• Preferred crosslinkers b) are pentaerythritol triallyl ether, tetraalloxyethane, methylenebismethacrylamide, 15 to 30 times ethoxylated glycerol triacrylate, 15 to 30 times ethoxylated trimethylolpropane triacrylate, 15 to 20 times ethoxylated trimethylolethane triacrylate, 15 to 20 times ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate and triallylamine ,
• Very particularly preferred crosslinkers b) are the polyethyleneglyoxylated and / or propoxylated glycerols esterified with acrylic acid or methacrylic acid to form diioder triacrylates, as described, for example, in WO 2003/104301 A1.
• Particularly advantageous are di- and / or triacrylates of 3- to 10-fold ethoxylated glycerol.
• 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 glycerol, in particular the triacrylate of 3-times ethoxylated glycerol.
• the amount of crosslinker b) is preferably from 0.01 to 1, 5 wt .-%, particularly preferably 0.05 to 1 wt .-%, most preferably 0.1 to 0.6 wt .-%, each based on the unneutralized monomer a).
• the centrifuge retention capacity (CRC) decreases and the absorption under a pressure of 21.0 g / cm 2 (AUL 0.3 psi) passes through a maximum.
• 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.
• it is beneficial to have misohnnn p n ⁇ p r 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 ratio.
• 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-) imidazolin-2-yl) propane] dihydrochloride, hydrogen peroxide, persulfates such as sodium peroxodisulfate and ammonium peroxodisulfate, and redox initiators such as sodium peroxodisulfate / ascorbic acid, ammonium peroxodisulfate / ascorbic acid and hydrogen peroxide / ascorbic acid, and mixtures thereof.
• azo initiators such as 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride and 2,2'-azobis [2- (5-methyl-2-) imidazolin-2-yl) propane] dihydrochloride, hydrogen peroxide, persulfates such as sodium peroxodis
• 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 unneutralized monomer a).
• acrylamide, methacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate are ethylenically unsaturated monomers d) which are copolymerizable with the ethylenically unsaturated acid group-carrying monomers a).
• water-soluble polymers e it is possible to use polyvinyl alcohol, polyvinylpyrrolidone, starch, starch derivatives, modified cellulose, such as methylcellulose or hydroxyethylcellulose, gelatin, polyglycols or polyacrylic acids, preferably starch, starch derivatives and modified cellulose.
• the water content of the monomer solution is preferably less than 65 wt .-%, preferably less than 62 wt .-%, more preferably less than 60 wt .-%, most preferably less than 58 wt .-%.
• the monomer solution at 20 ° C has a density of preferably 1 to 1, 3 g / cm 3, more preferably 1, 05-1, 25 g / cm 3, more preferably 1, 1 to 1, 2 g / cm 3.
• the aqueous monomer solution is metered onto the hydrophobic surface to form discrete droplets.
• the hydrophobic surface has a contact angle with respect to water of preferably at least 60 °, more preferably at least 80 °, most preferably at least 100 °.
• the contact angle is a measure of the wetting behavior and is measured according to DIN 53900. The higher the contact angle, the more hydrophobic a surface is.
• the drops can be generated by means of pneumatic drawing nozzles, rotation, cutting a jet or quickly activatable micro-valve nozzles.
• a liquid jet is accelerated along with a gas flow through a baffle. About the amount of gas, the diameter of the liquid jet and thus the droplet diameter can be influenced.
• the liquid passes through the openings of a rotating disk. Due to the centrifugal force acting on the liquid, drops of a defined size are torn off.
• Preferred devices for Rotationsvertropfung be described for example in DE 43 08 842 A1.
• 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 monomer solution is metered (dripped) by means of at least one bore to form droplets.
• the drop diameter is usually 1, 9 times the diameter of the hole. It is important that the liquid does not pass through the hole too quickly or that the pressure loss through the hole 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 1,600, more preferably less than 1, 400, most preferably less than 1200.
• the temperature of the monomer solution when passing through the bore is preferably 10 to 60 ° C, more preferably 15 to 50 ° C, most preferably 20 to 40 ° 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 water-absorbing polymer particles can be surface-postcrosslinked to further improve the properties.
• Suitable surface postcrosslinkers are compounds which contain groups which can form covalent bonds with at least two carboxylate groups of the polymer particles.
• Suitable compounds are, for example, polyfunctional amines, polyfunctional amidoamines, polyfunctional epoxides, as described in EP 0 083 022 A2, EP 0 543 303 A1 and EP 0 937 736 A2, di- or polyfunctional alcohols, as described in DE 33 14 019 A1, DE 35 23 617 A1 and EP 0 450 922 A2, or ⁇ -hydroxyalkylamides, as described in DE 102 04 938 A1 and US Pat. No. 6,239,230.
• 2-Oxazolidinone and its derivatives such as 2-hydroxyethyl-2-oxazolidinone, in DE 1 QR ⁇ 7 QQ9 CA Bis- and poly-2-oxazolidinones, in DE 198 54 573 A1 2-oxotetrahydro-1,3-oxazine and its derivatives, in DE 198 54 574 A1 N-acyl-2-oxazolidinones, in DE 102 04 937 A1 cyclic ureas in DE 103 34 584 A1 bicyclic amidoacetals, in EP 1 199 327 A2 oxetanes and cyclic ureas and in WO 2003/031482 A1 morpholine-2,3-dione and its derivatives as suitable surface postcrosslinkers.
• Preferred surface postcrosslinkers are ethylene carbonate, ethylene glycol diglycidyl ether, reaction products of polyamides with epichlorohydrin and mixtures of propylene glycol and 1,4-butanediol.
• Very particularly preferred surface postcrosslinkers are 2-hydroxyethyl-2-oxazolidinone, 2-oxazolidinone and 1, 3-propanediol.
• the amount of surface postcrosslinker is preferably 0.001 to 5 wt .-%, more preferably 0.02 to 2 wt .-%, most preferably 0.05 to 1 wt .-%, each based on the polymer particles.
• polyvalent cations are applied to the particle surface in addition to the surface postcrosslinkers before, during or after the surface postcrosslinking.
• the polyvalent cations which can be used in the process according to the invention are, for example, divalent cations, such as the cations of zinc, magnesium, calcium, iron and strontium, trivalent cations, such as the cations of aluminum, iron, chromium, rare earths and manganese, tetravalent cations, such as the cations of Titanium and zirconium.
• salts with different counterions for example basic aluminum salts, such as aluminum monoacetate or aluminum monolactate. Aluminum sulfate, aluminum monoacetate and aluminum lactate are preferred.
• polyamines can also be used as polyvalent cations.
• the amount of polyvalent cation used is, for example, from 0.001 to 1% by weight, preferably from 0.005 to 0.5% by weight, more preferably from 0.02 to 0.2% by weight. in each case based on the polymer particles.
• the surface postcrosslinking is usually carried out so that a solution of the surface postcrosslinker is sprayed onto the dried polymer particles. Subsequent to the spraying, the surface postcrosslinker-coated polymer Particles thermally dried, wherein the surface postcrosslinking reaction can take place both before and during drying.
• the spraying of a solution of the surface postcrosslinker is preferably carried out in mixers with moving mixing tools, such as screw mixers, disk mixers and paddle mixers.
• moving mixing tools such as screw mixers, disk mixers and paddle mixers.
• horizontal mixers such as paddle mixers
• vertical mixers very particularly preferred are vertical mixers.
• the distinction between horizontal mixer and vertical mixer is made by the storage of the mixing shaft, i.
• Horizontal mixers have a horizontally mounted mixing shaft and vertical mixers have a vertically mounted mixing shaft.
• Suitable mixers are, for example, Horizontal Pflugschar® mixers (Gebr.
• the surface postcrosslinkers are typically used as an aqueous solution.
• the penetration depth of the surface postcrosslinker into the polymer particles can be adjusted by the content of nonaqueous solvent or total solvent amount. If only water is used as the solvent, it is advantageous to add a surfactant. As a result, the wetting behavior is improved and the tendency to clog is reduced.
• solvent mixtures for example isopropanol / water, 1,3-propanediol / water and propylene glycol / water, the mixing mass ratio preferably being from 20:80 to 40:60.
• the thermal drying is preferably carried out in contact dryers, more preferably paddle dryers, very particularly preferably disk dryers.
• Suitable dryers include Hosokawa Bepex® Horizontal Paddle Dryer (Hosokawa Micron GmbH, Leingart, Germany), Hosokawa Bepex® Disc Dryer (Hosokawa Micron GmbH, Leingart, Germany), Holo-Flite® dryers (Metso Minerals Industries, Inc., Danville, USA ) and Nara
• Paddle Dryer (NARA Machinery Europe, Frechen, Germany). Moreover, fluidized bed dryers can also be used.
• the drying can take place in the mixer itself, by heating the jacket or blowing hot air.
• a downstream dryer such as a hopper dryer, a rotary kiln or a heatable screw. Particularly advantageous is mixed and dried in a fluidized bed dryer.
• Preferred drying temperatures are in the range 100 to 250 ° C, preferably 120 to 220 ° C, more preferably 130 to 210 ° C, most preferably 150 to 200 ° 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, and usually at most 60 minutes.
• the water-absorbing polymer particles are cooled after the thermal drying.
• the cooling is preferably carried out in contact coolers, particularly preferably blade coolers, very particularly preferably disk coolers.
• Suitable coolers are, for example, Hosokawa Bepex® Horizontal Paddle Coolers (Hosokawa Micron GmbH, Leingart, Germany), Hosokawa Bepex® Disc Coolers (Hosokawa Micron GmbH, Leingart, Germany), Holo-Flite® coolers (Metso Minerals Industries, Inc., Danville, USA ) and Nara Paddle Cooler (NARA Machinery Europe, Frechen, Germany). Moreover, fluidized bed coolers can also be used.
• the water-absorbing polymer particles to 20 to 150 ° C, preferably 30 to 120 ° C, more preferably 40 to 100 ° C, most preferably 50 to 80 ° C, cooled.
• the surface-postcrosslinked polymer particles can be coated or post-moistened for further improvement of the properties.
• the post-wetting is preferably carried out at 30 to 80 ° C, more preferably at 35 to 70 ° C, most preferably at 40 to 60 ° C. If the temperatures are too low, the water-absorbing polymer particles tend to clump together, and water evaporates appreciably at higher temperatures.
• the amount of water used for the rewetting is preferably from 1 to 10 wt .-%, particularly preferably from 2 to 8 wt .-%, most preferably from 3 to 5 wt .-%, each based on the water-absorbing polymer particles.
• the post-humidification is carried out in the cooler after the thermal drying.
• Suitable coatings for improving the swelling rate and the permeability are, for example, inorganic inert substances, such as water-insoluble metal salts, organic polymers, cationic polymers and di- or polyvalent metal cations.
• Suitable coatings for dust binding are, for example, polyols.
• Suitable coatings against the unwanted caking tendency of the polymer particles are, for example, fumed silica, such as Aerosil® 200, and surfactants, such as Span® 20.
• Another object of the present invention are obtainable by the process according to the invention polymer particles.
• the polymer particles according to the invention have a proportion of particles with a particle size of 300 to 600 ⁇ m, preferably of at least 30% by weight, more preferably at least 50% by weight, very particularly preferably at least 70% by weight.
• the polymer particles of the invention have a moisture content of preferably 0.1 to 20 wt .-%, particularly preferably from 1 to 15 wt .-%, most preferably from 5 to 10 wt .-%, on.
• the moisture content is determined according to the EDANA recommended test method No. WSP 230.2-05 "Mass Loss Upon Heating".
• the polymer particles according to the invention have a centrifuge retention capacity (CRC) of typically at least 25 g / g, preferably at least 30 g / g, preferably at least 32 g / g, more preferably at least 34 g / g, most preferably at least 36 g / g.
• the centrifuge retention capacity (CRC) of the polymer particles is usually less than 60 g / g.
• Centrifuge retention capacity (CRC) is determined according to EDANA recommended test method no. WSP 241.2-05 "Fluid Retention Capacity in Saline, After Centrifugation".
• the polymer particles according to the invention have a content of residual monomers of typically less than 2% by weight, preferably less than 1.5% by weight, preferably less than 1% by weight, more preferably less than 0.6% by weight. %, most preferably less than 0.4 wt .-%, on.
• the content of residual monomers of the polymer particles is determined according to the EDANA recommended test method no. WSP 210.2-05 "Residual Monomers".
• Further articles of the present invention are hygiene articles which contain the water-absorbing polymer particles according to the invention.
• the water-absorbing polymer particles are tested by the test methods described below.
• Measurements should be taken at an ambient temperature of 23 ⁇ 2 ° C and a relative humidity of 50 ⁇ 10%, unless otherwise specified.
• the water-absorbing polymer particles are thoroughly mixed before the measurement.
• Centrifuge Retention Capacity is determined analogously to the EDANA recommended Test Method No. WSP 241.2-05 "Fluid Retention Capacity in Saline, After Centrifugation", using 0.1 g of water-absorbing polymer particles instead of 0.2 g. residual monomer
• the residual monomer content of the water-absorbing polymer particles is determined according to the EDANA-recommended test method WSP No. 210.2-05 "Residual Monomers”.
• the EDANA test methods are available, for example, from EDANA, Avenue Eugene Plasky 157, B-1030 Brussels, Belgium.
• Example 1 (Comparative Example) A monomer solution was sprayed on a silicone rubber-coated pad.
• the monomer solution contained partially neutralized acrylic acid with caustic soda.
• the monomer solution additionally contained 0.05% by weight of Sartomer® SR454 (15-times ethoxylated trimethylolpropane triacylate), 0.1% by weight of Wako® VA-044 (2,2'-azobis [2- (2-imidazoline -2-yl) propane] dihydrochloride), 0.008% by weight of Büggolit® FF7 (disodium salt of 2-hydroxy-2-sulfinatoacetic acid), 0.15% by weight of sodium peroxodisulfate and 0.19% by weight of Darocur® 1 173 ( 2-hydroxy-2-methyl-1-phenylpropane-1-one), each based on unneutralized acrylic acid.
• the solids content of the monomer solution was 40% by weight.
• the drops were irradiated for 5 minutes by means of a UV radiator of the type MH radiator UV 400 F / 2 (Dr. Höhnle AG, Gräfelfing, Germany) and then stored for 30 minutes at 160 ° C in a drying oven.
• the resulting polymer particles were screened to 150 to 850 ⁇ and analyzed. The results are summarized in Table 1.
• Example 3 The procedure was as in Example 1. Deviating from Example 1, the drops were irradiated for 66 minutes by means of a UV radiator of the MH-UV 400 F / 2 type and then not stored in a drying oven. Example 3
• a monomer solution was sprayed onto a silicone rubber coated pad.
• the monomer solution contained partially neutralized acrylic acid with caustic soda.
• the monomer solution additionally contained 0.05% by weight of Sartomer® SR344 (polyethylene glycol 400-diacrylate), 0.1% by weight of Wako® VA-044 (2,2'-azobis [2- (2-imidazoline-2 -yl) propane] dihydrochloride), 0.008 wt%
• Büggolit® FF7 (disodium salt of 2-hydroxy-2-sulfinatoacetic acid) 0.15% by weight of sodium peroxodisulfate and 0.042% by weight of Darocur® TPO (diphenyl- (2,4,6-trimethylbenzoyl) -phosphine oxide), in each case based on unneutralized acrylic acid.
• the solids content of the monomer solution was 40% by weight.
• the drops were irradiated for 5 minutes by means of a UV radiator of the type MH radiator UV 400 F / 2 and then stored for 30 minutes at 160 ° C in a drying oven.
• the resulting polymer particles were screened to 150 to 850 ⁇ and analyzed. The results are summarized in Table 2.

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• 2015
  • 2015-08-06 WO PCT/EP2015/068126 patent/WO2016050397A1/de active Application Filing

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