Study The Yellowing Factors Of Pre-cat Etherified DMDHEU Resin

At present,Di-Methylol Di-Hydroxy Ethylene Urea(DMDHEU,2D resin for short) is the major durable press finishing agent.There are four hydroxy groups in the 2D resin which can react to cellulose fibre to form a cross-lingked network.So it has a good durable press finishing effect to the cotton,viscose fibre and mixed fabric.But the 2D resin exists two big disadvantage : yellowing and big formaldehyde releasing.One effect way to reduce N-amido-methylol resin formaldehyde releasing is etherifying the hydroxy group of resin,the popular etherifying agents are methnol,ethanol,ethylene glycol,poly ethylene glycol and so on.After modifying,the whiteness,formaldehyde content of finishing fabric can get a satisfaction level at a normal usage,and a normal finishing process condition.This paper study many factors which may lead to resin yellowing from two-step preparation of 2D resin and finishing condition.In preparation,we find that glyoxal and derivate which are left in the resin can cause Yellowing,and This has been proved by experiment;Glyoxal produced by different factories may have different glyoxal content and derivate content,which may lead to the resin yellowing finally,through the experiment,we find glyoxal of BASF is the best;Different preparation condition,conversion of glyoxal and outgrowth production rate are also different,conversion of glyoxal and outgrowth production rate may be one of major factors which lead to the resin yellowing.When the preparation condition as following,outgrowth production rate at the lowest and the yellowing is the least:reacting pH is 4, reacting time is 2h, reacting temperature is 50～55℃;In the material mol ratio,when glyoxal,carbamide,formaldehyde mol ratio is 0.99︰1︰1.8,the yellowing is the least;In etherifying,when the hydroxy groups at the 4,5 condition of DMDHEU resin were etherified,it can cause yellowing,the best etherifying condition is: reacting pH is 3～4, reacting time is 30min, reacting temperature is 50～55℃.Finishing condition:when the catalyzer is MgCl2.6H2O,and the dosage is 5%～6%,the whiteness is best;the pH of finishing solution is not under 5;Ca2+,Fe2+,Cu2+,Al3+ can't cause 2D resin yellowing,when their dosage are in a low lever;adding formaldehyde scavenger,such as carbamide,diethylene glycol ,can cause 2D resin yellowing;as the dosage of 2D resin increasing,curing time prolonging,2D resin yellowing gradually.