Method for preparing biuret polyisocyanates

Abstract

The invention discloses a method for continuously preparing biuret polyisocyanates. Isocyanate is subjected with water vapor in a bubble tower under the effect of a catalyst. A reaction solution passes through an evaporator and the unreacted isocyanate monomer is separated out to obtain the biuret polyisocyanates. By compounding the catalysis effect of the catalyst and adjusting the average residence time of the bubble tower, the product chromaticity and viscosity can be effectively lowered; a special built-in heat exchanger is utilized for preheating a reaction raw material, reaction temperature control and energy integration are achieved, and energy consumption is lowered.

Description

technical field [0001] The invention relates to a method for preparing biuret polyisocyanate, in particular to a method for preparing biuret polyisocyanate by reacting diisocyanate and water vapor in a bubble tower under the action of a catalyst. Background technique [0002] Biuret polyisocyanate is widely used in the production of coatings, adhesives, sealants, waterproofing agents, foams, elastomers, fiber treatment agents, etc. Patent document DE1101394B published in 1958 has disclosed a method for preparing aliphatic polyisocyanate having a biuret structure. The review paper The Synthesis of Aliphatic Polyisocyanates Containing Biuret, isocyanurate oruret dione backbones for use in coatings (for the synthesis of aliphatic polyisocyanates containing biuret, isocyanurate or uretdione backbone for coatings, J.prakt.Chem, 336, 1994, 185-200) discloses further possible preparation methods and discusses the advantages and disadvantages of these particular methods. [0003] ...

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Problems solved by technology

[0005] However, in the water method preparation, due to the wide average residence time of the reaction liquid in the conventional full-mixed tank reactor, the product viscosity is high; during the reaction process, the raw materials need to be preheated and added to the reactor, and the circulation is introduced during the reaction process. Water cooling removes the heat of reaction to maintain the reaction temperature of the system, and the energy consumption is high;

[0006] Chinese patent CN95113103.6-Preparation method of biuret-containing polyisocyanate discloses a method for preparing biuret in a batch tank reactor. The raw material isocyanate and catalyst are preheated to 130°C, and then water in a finely dispersed form is introduced. After the reaction reaches the set conversion rate, the reaction is stopped, and the monomer is separated to obtain qualified products; the process adopts batch reaction, and the process belongs to the total mixed flow reaction, the residence time distribution is wide, and the product viscosity is high; the raw materials need to be preheated before the reaction, and the reaction Process raw materials need to be fed into circulating water to remove reaction heat, resulting in waste of energy

This method uses multiple reactors connected in series and reacts in the form of water vapor. Although the residence time distribution is partially reduced, the adjustability is poor, the reaction temperature is too high, the product viscosity is high, and the chroma is high.

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