Abstract: The invention relates to a classification process for superabsorbent polymer particles, comprising classifying the water-absorbent polymer particles in a screen machine under reduced pressure wherein the pressure above the uppermost sieve is from 0 to 4.0 mbar per sieve higher than below the undermost sieve.

Abstract: The invention relates to a process for producing superabsorbent polymer particles, comprising surface postcrosslinking, classifying the surface postcrosslinked superabsorbent polymer particles, deagglomerating the separated oversize fraction using a roll crusher and recycling the disintegrated oversize fraction before or into the classification of the surface postcrosslinked superabsorbent polymer particles.

Abstract: A process for producing superabsorbents, comprising the steps of i) classifying the superabsorbent particles by means of one or more sieves and ii) removing metallic impurities by means of one or more magnetic separators, wherein classification is accomplished using sieves made of a wire mesh, the wires of the wire mesh consist of a steel composed of at least 70% by weight of iron, at least 10% by weight of chromium and less than 2.5% by weight of nickel, and the throughput of superabsorbent particles in the magnetic separator is in the range from 2.0 to 6.5 g/s per cm2 of free cross-sectional area.

Abstract: A process for producing superabsorbent particles by polymerizing a monomer solution or suspension, comprising drying of the resultant aqueous polymer gel in an air circulation belt dryer, grinding, classifying, and optionally thermal surface postcrosslinking, wherein the aqueous polymer gel is introduced into the air circulation belt dryer by means of an oscillating conveyor belt and that guide devices are located at the edges of the conveyor belt.

Abstract: The invention relates to a process for producing superabsorbent polymer particles, comprising polymerization of a monomer solution, wherein the monomer solution comprises partly neutralized acrylic acid formed by continuous mixing of acrylic acid and an aqueous solution of a base, the apparatus for preparing the partly neutralized acrylic acid comprises a vessel (B), and the vessel (B) has a cylindrical shape and a torispherical bottom.

Abstract: The invention relates to a process for producing superabsorbent polymer particles, comprising polymerization of a monomer solution, wherein the monomer solution comprises partly neutralized acrylic acid formed by continuous mixing of acrylic acid and an aqueous solution of a base, the apparatus for preparing the partly neutralized acrylic acid comprises a vessel (B), and the feed line to vessel (B) ends inside vessel (B) below the liquid Level of the partly neutralized acrylic acid.

Abstract: A process for producing superabsorbent particles by polymerizing a monomer solution or suspension, comprising drying of the resultant aqueous polymer gel in an air circulation belt drier, grinding, classifying, and optionally thermal surface postcrosslinking, wherein the aqueous polymer gel is introduced into the air circulation belt drier by means of an oscillating conveyor belt, the underside of the revolving conveyor belt is freed of adhering polymer gel by means of at least one stripper device, and the underside of the revolving conveyor belt is sprayed with water.

Abstract: A process for producing superabsorbent particles by polymerizing a monomer solution or suspension, comprising the steps of continuously preneutralizing a monomer while cooling and partly recycling the preneutralized monomer into the preneutralization, continuously heating the preneutralized monomer by means of a heat exchanger and continuously postneutralizing the heated monomer, wherein the monomer solution or suspension prior to entry into the polymerization reactor is at a temperature of 70 to 99° C. and the temperature of the heating medium used in the heat exchanger is less than 160° C.

Abstract: A process for producing superabsorbent particles by polymerizing a monomer solution, comprising the steps of continuously polymerizing the monomer solution on the continuous belt of a belt reactor, comminuting the polymer gel obtained, rinsing the polymer gel obtained on the underside of the belt reactor into a separation unit with water, separating the polymer gel from the water in the separation unit and recycling the polymer gel into the comminution, wherein the polymer gel has a swelling capacity in water of at least 100 g/g, the dwell time of the polymer gel in the rinse water is less than 40 minutes, and the separation unit has openings with a clear width of at least 1 mm.

Abstract: A process for producing superabsorbent particles, comprising drying of a polymer gel, removal of incompletely dried polymer particles, comminution of the polymer particles removed, recycling of the comminuted polymer particles and storage of the recycled polymer particles.

Abstract: A process for producing superabsorbents, comprising the steps of i) classifying the superabsorbent particles by means of one or more sieves and ii) removing metallic impurities by means of one or more magnetic separators, wherein classification is accomplished using sieves made of a wire mesh, the wires of the wire mesh consist of a steel composed of at least 70% by weight of iron, at least 10% by weight of chromium and less than 2.5% by weight of nickel, and the throughput of superabsorbent particles in the magnetic separator is in the range from 2.0 to 6.5 g/s per cm2 of free cross-sectional area.

Abstract: The invention relates to a process for producing superabsorbent polymer particles, comprising surface postcrosslinking, classifying the surface postcrosslinked superabsorbent polymer particles, deagglomerating the separated oversize fraction using a roll crusher and recycling the disintegrated oversize fraction before or into the classification of the surface postcrosslinked superabsorbent polymer particles.

Abstract: The invention relates to an apparatus for producing pulverulent poly(meth)acrylate, comprising a reactor for droplet polymerization having an apparatus for dropletization of a monomer solution for the preparation of the poly(meth)acrylate having holes through which the monomer solution is introduced, an addition point for a gas above the apparatus for dropletization, at least one gas withdrawal point on the circumference of the reactor, a fluidized bed and an apparatus for product discharge from the fluidized bed. The apparatus for product discharge comprises a discharge apparatus, with a backup segment (39) disposed above the discharge apparatus.

Abstract: The invention relates to a classification process for superabsorbent polymer particles, comprising classifying the water-absorbent polymer particles in a screen machine under reduced pressure wherein the pressure above the uppermost sieve is from 0 to 4.0 mbar per sieve higher than below the undermost sieve.

Abstract: A production process for production of water-absorbing polymer particles including drying an aqueous polymer gel in a belt drier with a conveyor belt. The belt drier is formed with a drier setup substantially comprising the conveyor belt and an air recycling conduit downstream of the drier setup for air recycling, where recycled air is withdrawn from the drier setup and fed back to the drier setup via the air recycling conduit.

Abstract: Filling process for superabsorbent polymer particles The invention relates to a filling process for superabsorbent polymer particles, comprising discharging the superabsorbent polymer particles out of a silo into bulk container for shipping, wherein the filling level of the silo during filling of the bulk container is never less than 20%, in order to avoid particle segregation.

Abstract: The invention relates to an apparatus for producing pulverulent poly(meth)acrylate, comprising a reactor for droplet polymerization having an apparatus for dropletization of a monomer solution for the preparation of the poly(meth)acrylate having holes through which the monomer solution is introduced, an addition point for a gas above the apparatus for dropletization, at least one gas withdrawal point on the circumference of the reactor and a fluidized bed, the reactor comprising a reactor shell between the apparatus for dropletization and the gas withdrawal point and having, above the fluidized bed, a region having decreasing hydraulic diameter toward the fluidized bed and having a maximum hydraulic diameter greater than the mean hydraulic diameter of the reactor shell, and the reactor shell projecting into the region having decreasing hydraulic diameter, so as to form an annular duct between the outer wall of the reactor shell and the wall by which the region having decreasing hydraulic diameter is bounded,

Abstract: The invention relates to an apparatus for producing pulverulent poly(meth)acrylate, comprising a reactor for droplet polymerization having an apparatus for dropletization of a monomer solution for the preparation of the poly(meth)acrylate having holes through which the monomer solution is introduced, an addition point for a gas above the apparatus for dropletization, at least one gas withdrawal point on the circumference of the reactor, a fluidized bed and an apparatus for product discharge from the fluidized bed. The apparatus for product discharge comprises a discharge apparatus, with a backup segment (39) disposed above the discharge apparatus.

Abstract: A production process for production of water-absorbing polymer particles including drying an aqueous polymer gel in a belt drier with a conveyor belt. The belt drier is formed with a drier setup substantially comprising the conveyor belt and an air recycling conduit downstream of the drier setup for air recycling, where recycled air is withdrawn from the drier setup and fed back to the drier setup via the air recycling conduit.

Abstract: Disclosed is a method for the continuous production of crosslinked, particulate, gel-type polymers by copolymerizing a) water-soluble, monoethylenically unsaturated monomers, b) 0.001 to 5 molar percent of monomers containing at least two polymerizable groups, the percentage being relative to the monomers (a), in a mixer. The substances that are added at the beginning of the kneader are conveyed in an axial direction towards the end of the mixer. The inventive method is characterized in that at least one of the following conditions is met: i) the filling level in the kneader mixer is at least 71 percent; ii) the water-soluble, monoethylenically unsaturated monomers contain up to 150 ppm of a semicyclic ether of a hydroquinone; iii) the temperature in the polymerization zone exceeds 65° C.; iv) the kneader has a remixing rate of less than 0.33.