Patent ID: 9403704
Filing Date: 2016-08-02
CPC Classification: C02F,C08G,C08L

Claim Text:
1. A water treatment method, comprising: a flocculation treatment process of adding a flocculant to water to be treated; and a membrane separation treatment process of treating flocculation-treated water of the flocculation treatment process by membrane separation, wherein the flocculant contains an alkaline aqueous solution of a phenolic resin produced by a resole-type second-order reaction in a presence of an alkaline catalyst in which an aldehyde is added to an alkaline aqueous solution of a novolak phenolic resin, the novolak phenolic resin being produced by a reaction between a phenol and an aldehyde in a presence of an acid catalyst, the phenolic resin produced by the resole-type second-order reaction has a melting point in a range of 130° C. to 220° C. and a molecular average weight of 5000 to 50000, and contains 15% by weight or less of a low-molecular-weight component having a molecular weight of 1000 or less, and the novolak phenolic resin produced by the reaction between the phenol and the aldehyde in the presence of the acid catalyst contains 3% by weight or more of a dinuclear phenol containing phenol rings connected to each other directly or through a bridge and has a weight-average molecular weight of 2000 or more, and the phenolic resin produced by the resole-type second-order reaction contains less than 3% by weight of a dinuclear phenol containing phenol rings connected to each other directly or through a bridge.