Study On The Preparation And Surface Modification Of Nano-size Barium Sulfate

Barium Sulfate is a commonly used barium salt which has strong chemical inertness,acid and alkali resistance,and no toxicity.It is used as a neutral filler and is filled in plastic,powder coating and so on.However,the majority of barium sulfate produced in China belongs to low-grade,low value-added,low-cost ordinary precipitated barium sulfate powder,even primary barite ore powder is exported.Nano-size barium sulfate is a powder product whose particle size less than 100 nm,as an augmented and filled powder of plastics and coatings.It can greatly improve the performance of the target product,and is the high level and high value-added barium sulfate powder.The preparation methods of nano-barium sulfate reported are using barium chloride as raw materials.However,the majority of factories in China utilizes the process of barite powder reduction with coal fines,whose intermediate product is barium sulfide.If barium sulfide is used as the raw material for nano-size barium sulfate preparation,it will be easy to add nano-size barium sulfate production for the factories without adding subsequent sewage treatment facilities under the present situation of environmental pressure increase.Therefore,it is of great significance to carry out the research on nano-barium sulfate prepatation using barium sulfide as raw material.In this paper,based on the analysis of the principle of nano-barium sulfate preparation with micro-reactor,nano-barium sulfate was prepared by using imping stream micro-reactor with barium sulfate as the raw material,in which barium sulfide reacted with sodium sulfate solution.Experimental,results show that the characteristic parameters of micro-reactor are feed cross-sectional area of 1.56 mm~2and an impact angle of 90°.At room temperature,the concentration of barium sulfide solution and sodium sulfate solution are both 0.9 mol/L,the flow rate of the reactants are both 70 L/h.Spherical shape of nano-barium sulfate is successfully prepared with an average particle size of 33 nm.Due to the direct drying of nano-size barium sulfate by present drying methods will cause serious particle aggregation,wet surface modification method was applied for nano-size barium sulfate.Based on the analysis of the mechanism of particle aggregation of nano-barium sulfate,surface modification was made and more than thirty kinds of candidate surface modifiers were selected as the candidates for screening.The effect of modification time,temperature and the amount of modifier were investigated.The experimental results show that the rotational speed of the emulsifier was 9000 rmp,the reaction temperature was 80℃,the dosage of modifier was 15%,and the reaction time was 35 min,when the nano sized barium sulfate with an average particle size of 33 nm was used.The inattentive powder of nano-barium sulfate was obtained after barium sulfate cake was dried,the active degree was 99.76%and the oil absorption value was 23.14%.This effectively solved the problem of agglomeration of nanoscale barium sulfate in direct drying.In this paper,the above surface modified nano barium sulfate powder was used as filler in powder coating and PE.The results showed that 20%modified barium sulfate was used in powder coatings.There is no difference in appearance color,no impurity and no agglomeration for powder coatings.All the other performance indexes can reach the qualified level.The nano modified barium sulfate is mixed with PE by melt blending and blown into plastic film.The plastic film can reach a qualified level.The light transmittance is higher than that of the no-modified nano barium sulfate,and the tensile strength increases.