Preparation Of AB Block Superdispersant By Controllable Active Polymerization And Its Application In Waterborne Wood Paint

The technical problem of uncontrollable structure and uneven molecular weight distribution in hyperdispersants can be solved by controllable living polymerization,which provides a guarantee for make production with stable performance.This article is based on reversible addition-fragmentation chain transfer polymerization(RAFT),using isopropylxanthic disulfide(DIP)and 2-methyl-2-cyano-isopropyl xanthate(MCIX)as a chain transfer agent to prepare super dispersant of hydroxyethyl methacrylate(HEMA)and acrylic acid(AA)block copolymer.Then the super dispersant was used in water-based wood paint.The main work is as follows:1.The MCIX was prepared by in-situ reaction for 6 hours at 65℃,using DIP and AIBN as raw materials and ethyl acetate as solvent,and then separated and purified by silica gel powder chromatographic column.The products were characterized by nuclear magnetic resonance carbon spectroscopy(13C-NMR)and gas chromatography(GC).GC test results show that the purity of the prepared MCIX is as high as 98.24%..Different concentrations of DIP and MCIX were used as RAFT reagents to prepare polyhydroxyethyl methacrylate,(PHEMA).Gel permeation chromatography(GPC),Fourier Transform Infrared Spectrometer(FTIR),and hydrogen nuclear magnetic resonance spectroscopy(1H-NMR)were used to characterize the polymerization behavior of HEMA.The test results show that the PHEMA still has the ability to regulate and control.The solution polymerization of HEMA in the presence of DIP and MCIX has the characteristics of reversible addition fracture chain transfer(RAFT)polymerization:the polymerization reaction conforms to the kinetic first-order reaction,and the molecular weight of PHEMA has a linear relationship with the conversion rate of HEMA monomer.Using DIP as a chain transfer agent,it takes 540 minutes for the monomer conversion rate to approach 100%,while it only takes 300 minutes for using MCIX as a chain transfer agent.Under the control of DIP and MCIX,the molecular weight distribution width PDI of thesynthesized PHEMA-RAFT is less than 1.30.With the same molecular weight designed,the molecular weight distribution width controlled by MCIX is narrower than DIP.At the same time,Compared the molecular weight controlled by MCIX and DIP,the molecular weight controlled by MCIX is closer to the design molecular weight.2.Using PHEMA-RAFT with different molecular weights as chain transfer agent to prepare block copolymer of hydroxyethyl methacrylate and acrylic acid(PHEMA-b-PAA)...The polymerization behavior of AA was characterized by GPC,FTIR and 1H-NMR.The test results show that the smaller the molecular weight of PHEMA,the slower the polymerization rate.Under the influence of PHEMA-RAFT macromolecules,the polymerization process of AA monomer conforms to the characteristics of the kinetic first-order reaction.with the gradual decine of molecular weight of PHEMA-RAFT,the polymerization process of AA monomer shows a linear relationship.When the molecular weight of PHEMA is 5000,the linear relationship is the best.At the same time,with the increase of molecular weight of PHEMA-RAFT,its ability to regulate AA was weakened.Specifically,with the increase of molecular weight of PHEMA-RAFT,the width of its molecular weight distribution gradually increases,but the PDI is still less than 1.6.3.The method of PHEMA-b-PAA preparation is applied to the preparation block copolymer hyperdispersant of water-based wood paint.The influence of MCIX dosage,HEMA and AA molar ratio and different AA neutralization degree to the dispersion performance of titanium dioxide were discussed by single-factor and orthogonal tests..The experimental results show that the best polymer dispersant Synthetic conditions is n(HEMA):n(AA):n(AIBN):n(MCIX)=80:100:0.3:1.5,AA’s NaOH neutralization degree to 100%.Under these conditions,the copolymer dispersant has the best dispersing effect on titanium white,the dispersion viscosity of titanium white is 110mpa.s,the dispersion particle size is 167nm,and the dispersion power is 95%.The most important factor influencing the dispersion is the amount of initiato,followed by the heat preservation reaction time,again the monomer ratio,and finally the amount of chain transfer agent.At the above conditions,the hardness of the wood paint film is H,the 20° gloss of the wood paint film is 60.9%,and the 60° gloss is 96.9%.