摘要:
The invention relates to a process for producing a water-absorbing resin by polymerization of a reaction mixture comprising at least one hydrophilic monomer and, if appropriate, at least one crosslinker in a reactor, which comprises admixing the reaction mixture with at least one first portion of a particulate additive before the reaction mixture has reached a residence time of 40% of the overall residence time in the reactor and with at least one second portion of a particulate additive when the reaction mixture has reached a residence time of 45% or more of the overall residence time in the reactor, the additive being selected from water-absorbing resin powders, fillers and mixtures thereof, the total solids content of monomer and additive being in the range from 30% to 60% by weight, the amount of additive being in the range from 5% to 50% by weight, based on the monomers, and the weight ratio of the first portion to the second portion of the additive being in the range from 10:1 to 1:5. The resin powder is recycled fine-sized material for example. Not only the residual monomer content, specifically the residual crosslinker content, but also the level of extractables in the water-absorbing resin are reduced by the method of addition described. A high fraction of additives can be incorporated without the properties of the water-absorbing resin obtained being adversely affected. The additives enter a sufficiently firm bond with the resin, so that no excessive dusting occurs on exposure to mechanical stress.
摘要:
The invention relates to the production of superabsorbent polymers on a continuous belt reactor, comprising at least one rotating knife that cuts the formed polymer gel at the end of the continuous belt reactor, wherein the length of the cutting edge is at least 1 cm and the cutting edge is non-parallel to the rotation axis.
摘要:
The invention relates to the production of superabsorbent polymers comprising conveying a polymer gel having acid groups on an oscillating conveyor belt to a continuous through-circulation belt dryer, wherein the belt speed of the conveyor belt is at least 0.4 m/s.
摘要:
A process for producing water-absorbing polymer particles, wherein a polymer gel is removed from a polymerization reactor, stored intermediately as a particulate polymer gel in a delay vessel, removed by means of a first conveying device at the lower end of the delay vessel and dried, the intermediately stored particulate polymer gel being conveyed within the delay vessel by means of at least one second conveying device above the first conveying device in the direction of the first conveying device.
摘要:
A process for continuously producing water-absorbing polymer particles, comprising polymerization, drying, grinding, classification and at least partial recycling of the undersize obtained in the classification, wherein the polymer gel obtained by the polymerization is withdrawn from the polymerization reactor and mixed with the recycled undersize.
摘要:
A process for producing water-absorbing polymer particles, wherein an aqueous polymer gel is dried in a forced-air belt drier on a circulating conveyor belt and the surface of the conveyor belt has a roughness of at least 0.9 μm.
摘要:
A process for producing water-absorbing polymer particles, comprising polymerization, drying, comminution, classification and recycling of the undersize obtained in the classification, wherein the recycled undersize is coated with a reducing agent and/or inorganic particles.
摘要:
A process for producing water-absorbing polymer particles, wherein a polymer gel is removed from a polymerization reactor, stored intermediately as a particulate polymer gel in a delay vessel, removed by means of a first conveying device at the lower end of the delay vessel and dried, the intermediately stored particulate polymer gel being conveyed within the delay vessel by means of at least one second conveying device above the first conveying device in the direction of the first conveying device.
摘要:
A process for producing water-absorbing polymer particles, comprising the addition of a solid additive to a polymer gel by means of a conveying screw (1), wherein the solid additive and a gas volume flow are fed to the conveying screw (1) by means of an addition channel (2).
摘要:
The present invention relates to novel (meth)acrylic esters of polyalkoxylated trimethylolpropane of the formula where AO is for each AO independently at each instance EO, PO or BO where EO is O—CH2-CH2- PO is independently at each instance O—CH2-CH(CH3)- or O—CH(CH3)-CH2- BO is independently at each instance O—CH2-CH(CH2-CH3)- or O—CH(CH2-CH3)-CH2- p1+p2+p3 is 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74 or 75, R1, R2 and R3 are independently H or CH3, a simplified process for preparing these esters and the use of reaction mixtures thus obtainable.