A Study On Preparation And Modification Of Iron Oxide Pigments

Synthetic iron oxide pigments which are cheap and non-toxic,have multi-colors,good weather resistance,chemical resistance,light resistance and good UV shielding effect.Synthetic iron oxide pigments can be used for building materials,coatings,plastics,rubber and other products.In this paper,preparations and modifications of iron oxide pigments are studied,including iron oxide red,iron oxide black,doped iron oxide black.A solution precipitaion metod was used in iron oxide preparation,in which urea was used as precipitator.A orthogonal test with 13 level factors was carried out to get optimal result.Scanning electron microscope(SEM)and X-ray diffraction(XRD)was used to characterize the products.The experiment results show that the main factors to affect the productivity of iron oxide red are:reaction temperature,reaction time and initial pH value.And the optimum preparation conditions are:the initial pH is about 2?2.5,the reaction time is 6 h,the reaction temperature is 95 ??100 ?,the concentration of Fe(NO3)3 is 0.3 mol/L,the molar ratio of urea and Fe3+ is 3.5:1,the content of twelve alkyl sodium sulfate(SDS)is 1%.By the performance test of technical index and XRD analysis,the prepared iron oxide red has reached the first grade of the iron oxide pigment national standard.For iron oxide black preparation,the optimum conditions are:initial value of pH is about 10,the reaction time is 3 h,and reaction temperature is 85 ??90 ?,the molar ratio of Fe3+/Fe2+ is 1.8:1 and the concentration of sodium citrate is 1%.By the performance test of technical index and XRD analysis,compared to the national standard,the prepared iron oxide black has reached the first grade to iron oxide pigment.The heat resistance of Mn-doped sample is better than undoped.M-doped(M is Mn,Mg,Zn,Al)and M-Si-doped Fe3O4 were prepared for improving the heat resistance of iron oxide pigments.The optimum preparation conditions are:the initial pH is 10,the reaction time is 3h,the reaction temperature is 85??90?,the molar ratio of Fe3+ and Fe2+ is 1.8:1,the additive(sodium citrate)concentation is 1%,n(Mn2+)/n(Si2+)=1:1 and n(Mn2+)/n(Fe3+)=5%.Through the heat resistance test analysis,the ? E value of the 5%Mn-5%Si co-doped Fe3O4 pigment at 700?,900? and 1100? is about 3,which indicates that the color differences are very small,and the cementation resistance of the Mn-Si co-doped Fe3O4 pigment is the best.Mn-Si co-doped sample has better heat resistance than pure Fe3O4.