Synthesis And Application Of Hyperbranched Formaldehyde Capture Agent With Active Methylenes

The national government put more attention on volatile organic compound(VOCs)management,along with the people environmental protection consciousness enhancement.As a kind of VOCs,formaldehyde has been listed as a carcinogen.Many approaches have been widely developed for eliminating formaldehyde,including physical adsorption,chemical reaction,biological filtration,ozone oxidation and photocatalytic oxidation.Chemical reaction is one of the most effective measures for scavenging HCHO in a certain short period.We explored a novel formaldehyde scavenger containing active methylene by hyperbranched polymer.Formaldehyde-removal capacity of this polymer has been investigated in leather retanning and tanning process.Firstly,the formaldehyde scavenger containing active methylene(HAMP)by transesterification with hydroxyl-terminated hyperbranched polymer(HBP)and ethyl acetoacetate(EAA).The polymer was characterized by fourier transform infrared(FTIR),nuclear magnetic resonance(1H-NMR),gel permeation chromatography(GPC),dynamic light scattering and transmission electron microscope(TEM).The best prepared conditions were optimized through single-factor experiment and orthogonal experiment.The results indicated that n(HBP):n(EAA)=1:2.5,2.5% of catalyst,reaction temperature was100℃,reaction time was 4.5 h.Secondly,the adsorption of formaldehyde on the HAMP was studied with formaldehyde solution as target.The effects of temperature,adsorbent dosage,time,initial concentration and p H on the adsorption process were studied by single-factor experiment method.The results showed that the removal rate of formaldehyde of HAMP increase with the increase of temperature,time and HAMP dosage.The optimal pH was alkaline environment,best temperature was40℃.Use formaldehyde solution as the treatment object(15μg/mL),volume was20 mL,control of pH and temperature for optimal,when the dosage of HMAP was 0.12 g it can reach equilibrium adsorption in 80 min.For a certain amount offormaldehyde solution,the adsorption capacityincreased with the increasing of initial concentration,but decreasedalong with the increasing of adsorbent dosage.Use formaldehyde solution as the treatment object(initial concentration was15μg/mL,volume was 20 mL),the adsorption capacity of HBP and HAMP was compared.The results indicated that remove rate of formaldehyde was 73.20%higher than before modification,adsorption capacity increased,formaldehyde removal efficiency significantly enhanced.The adsorption kinetics and adsorption thermodynamics of formaldehyde solution was studied,thermodynamics studies showed that the adsorption isotherm of formaldehyde under different temperature was in accordance with the Langmuir equationand Freundlich equation,the Freundlich equation fitting correlation was higher.So the adsorption of formaldehyde solution mainly belongs to chemical adsorption and meanwhile it had multilayer adsorption system.Kinetic study showed that the secondary dynamic equation can better explain the adsorption process.The HAMP was applied in the retanning process of sheepskin garment leather.The optimal amount of HAMP and reaction time were 4% and 1h,which were obtained by single-factor experiment.The free formaldehyde content in leather dropped from 371mg/kg to 60mg/kg,formaldehyde removal rate achieved 83.8%under the optimal conditions.After added HAMP in leather retanning process the thermodynamic performance,stability and surface roughness of leather increased,collagen fiber became looser.Physicalmechanical properties had slightly changes.Tensile strength reduced1.7% and tearing strength reduced 23.4%,softness increased 7.1%.Compound amino-terminated hyperbranched polymers(NH2-HBP)with HAMP was applied in the retanning process.The optimal process conditions achieved by single-factor experiment,results indicated that m(HAMP):m(NH2-HBP)=1.5:1,capture agent was 4%,reaction time was 3h.The free formaldehyde content in leather was 31.32mg/kg,formaldehyde removal rate can achieve89.95%.The HAMP was applied in the tanning process with pickled pelt as treatment object.The results showed that when the dosage of HAMP was 4%,reaction time was 2h.Formaldehyde in aldehyde tanned leather could be reducedfrom 2073mg/kg to 787mg/kg,decreased by 62.03%,tearing strength reduced18.9%.Formaldehyde inleather which tanned by organic phosphoricdecreased from 488mg/kg to 214mg/kg,formaldehyderemoval capacity achieved 56.13%,the tensile strength of leather which added HAMP increased by 52.46%,tearing strength increased by 69.44%.The eliminating capacity of formaldehyde achieved 81.97% when HAMP applied in oxazolidine tanning process,formaldehyde in leatherreduced from 615mg/kg to 110mg/kg,physicalmechanical properties increased after we used HAMP.