| 摘要 |
A filler for paper, card or board which has a good retention and consists of an inert core material and a hydrophilic coating, which consists of polyacrylamide having a molecular weight of 105 to 107 or of a mixture of this polyacrylamide with a urea-formaldehyde condensation resin. The filler is prepared by suspending the inert core material in an aqueous solution of a polyacrylamide having a molecular weight of 105 to 107 or in an aqueous solution of such a polyacrylamide and a urea-formaldehyde condensation resin, and drying this suspension by spray drying or in a stream of hot air. This crosslinks the initially water-soluble polymer and forms a coating, adhering to the core, which is insoluble in water but is hydrophilic and swells, and becomes tacky, in the presence of water. |
