Synthesis Of Low-odor Reactive Polyurethane Foaming Catalyst ZF-10

2-[[2-[2-(Dimethylamino)ethoxyethyl]methylamino]-ethanol,abbreviated as ZF-10,is an important low odor,reactive polyurethane foaming catalyst,commonly used in the preparation of polyether urethane soft foam,molded foam,hard foam and so on.The currently reported process for preparing ZF-10 using N,N-dimethylethanolamine and N-methyldiethanolamine as raw materials has the following problems:(1)Chlorinate N,N-dimethylethanolamine by thionyl chloride produces a large amount of SO2;(2)The preparation of sodium alkoxide from N-methyldiethanolamine consumes an equivalent amount of sodium hydroxide,which is uneconomical and sodium alkoxide is difficult to preserve.(3)The condensation reaction between sodium alkoxide and N,N-dimethylchloroethylamine,using sodium hydroxide as an acid binding agent,produces a large amount of solid sodium chloride waste,which is difficult to handle.In order to solve the above problems,this paper proposes a green process:using dimethylamine,dichloroethane and N-methyldiethanolamine as raw materials,and N,N,N',N'-tetramethylethylenediamine as an acid binding agent.Through(1)2-chloro-N,N-dimethylethanamine and N,N,N',N'-tetramethylethylenediamine hydrochloride were obtained by dimethylamination of dimethylamine and dichloroethane;(2)2-chloro-N,N-dimethylethanamine and N,N,N',N'-tetramethylethylenediamine were obtained from above process,and N-methyldiethanolamine was added as raw material,in which N,N,N',N'-tetramethylethylenediamine acted as acid binding agent to synthesize ZF-10 in one-pot method;(3)Ammonia was used to free organic amine and ammonium chloride was byproduct.The production process has:(1)a wide range of raw materials,low cost;(2)by-product is ammonium chloride,which is easier to handle than the original sodium chloride;(3)co-production of N,N,N',N'-tetramethylethylenediamine is not only an efficient acid binding agent in the reaction(called self-binding acid agent),but also an important polyurethane foaming catalyst;(4)one-pot method-self-binding acid reaction process to prepare ZF-10,product yield higher,up to 83.1%.Based on experimental research and theoretical research,the following results are obtained:Firstly,the process of preparing 2-chloro-N,N-dimethylethanamine by dimethylamination of dichloroethane and co-production of N,N,N',N'-tetramethylethylenediamine was developed.The yield ratio of the two products can be controlled by changing the process conditions.The optimum process conditions are as follows:the concentration of dimethylamine in aqueous solution is 33.3 wt.%,the molar ratio of dimethylamine to dichloroethane is 1:3,the reaction temperature is 35?,the reaction pressure is 1.5 MPa and the reaction time is 5 h.The yield of 2-chloro-N,N-dimethylethanamine is 40.2%,and the yield of N,N,N',N'-tetramethylethylenediamine is 57.2%.The yield ratio of 2-chloro-N,N-dimethylethanamine to N,N,N',N'-tetramethylethylenediamine hydrochloride decreases with the increase of reaction temperature,time and the decrease of the molar ratio of dimethylamine to dichloroethane.For example,when the concentration of dimethylamine in aqueous solution is 33.3 wt.%,the molar ratio of dimethylamine to dichloroethane is 1:1,the reaction time is 8 h and the reaction temperature is 80?,the conversion of dimethylamine is basically complete,the yield of N,N,N',N'-tetramethylethylenediamine hydrochloride is 97.5%,and the yield of 2-chloro-N,N-dimethylethanamine is only 1.3%.The results showed that the molar ratio of N,N,N',N'-tetramethylethylenediamine hydrochloride to 2-chloro-N,N-dimethylethanamine could be adjusted in the range of 75?1.4.Secondly,using N,N-dimethyl chloroethylamine and N-methyl diethanolamine as raw materials,N,N,N',N'-tetramethylethylenediamine as acid binding agent(co-production of N,N-dimethyl chloroethylamine,so called self-binding acid agent),a one-pot process for preparing ZF-10 was developed.Optimized process conditions:in toluene solvent,the molar ratio of 2-chloro-N,N-dimethylethanamine to N-methyldiethanolamine is 1:3,the reaction temperature is 110? and reaction time is 5 h,the raw material 2-chloro-N,N-dimethylethanamine is basically converted completely,the yield of product ZF-10 is 83.1%,which is 23%higher than that of sodium hydroxide as acid binding agent.The reason is that N,N,N',N'-tetramethylethylenediamine is used as acid binding agent,its alkalinity is milder than sodium hydroxide,thus inhibiting the by-product of the reaction between N-methyldiethanolamine and two molecules of 2-chloro-N,N-dimethylethanamine.And the one-pot method avoids the preparation and preservation of sodium monool,which is the most active intermediate product,and reduces the loss of sodium monool on the yield.N,N,N',N'-Tetramethylethylenediamine,an acid-binding agent,is finally precipitated in the form of its hydrochloride.Finally,the system integration and optimization of ZF-10 synthesis process are studied.The main works are as follows:(1)N,N,N',N'-Tetramethylethylenediamine hydrochloride produced in the process is ammoniated in methanol solvent at 25? and atmospheric pressure(through ammonia gas until the pH of solution is 9).N,N,N',N'-tetramethylethylenediamine is obtained and solid ammonium chloride is precipitated.The recovery rate of N,N,N',N'-tetramethylethylenediamine is 90%.The recovery rate of ammonium chloride is 89.2%.Solvent methanol can be recycled after being separated by atmospheric distillation at 55?65?.The recovery rate is 93%;(2)The water phase produced in the synthesis of 2-chloro-N,N-dimethylethanamine is filtered(filtered out N,N,N',N'-tetramethylethylenediamine hydrochloride,the water phase is the saturated solution of the hydrochloride)and then used to prepare the dimethylamine aqueous solution,which is recycled for the dimethylamination reaction of dichloroethane to reduce the discharge of wastewater;(3)The reaction organic phase containing dichloroethane is decompressed by 20mmHg.Recycling of dichloroethane fraction at 40?45? by distillation can be used for the dimethylamination of dichloroethane.The recovery rate of dichloroethane is 95%;(4)The mother liquor of ZF-10 synthesis process can be used to recover toluene by vacuum distillation and N-methyldiethanolamine,which is not converted,with the recovery rates of 91%and 90%,respectively.Through system integration and optimization,the water phase of the new process can be recycled.The byproduct of ammonium chloride is 0.6 tons per ton of N,N-dimethyl chloroethylamine,while the traditional sulfoxide chloride process produces 0.20 tons of wastewater per ton of N,N-dimethyl chloroethylamine(converted from hydrochloride),0.66 tons of sodium chloride and 0.55 tons of sulfur dioxide.Generally speaking,the results of this study can provide guidance for the green transformation of ZF-10 production process.