Preparation Of Modified Nano-CaCO₃ And Its Application In Lubricating Oil

Nanometer calcium carbonate is widely used as fill materials in many fields with rich raw material sources and low price.When mixed with surfactants and added into the lubricating oil,the nano-calcium carbonate particles can improve lubricating oil's properties of anti-wear and reduce frictional resistance.So can lengthen the service life of the machine and its parts.But the surface of nanometer calcium carbonate is hydrophilic/oleophobic.In addition,nano-calcium carbonate tends to aggregate and precipitate.Usually many surfactants are added to the oil to disperse particles,which seriously affects the effect of nanometer calcium carbonate in the lubricating oil.We come up with an innovative idea that we firstly prepare lipophilic nano-CaCO3,and directly add to the lubricating oil without surfactants.The result can reduce the negative effects of the surfactant to lubricant and improve the dispersion stability of nano-CaCO3 in the oil,so as to improve the wear resistance and antifriction performance.In this paper,modified nano-CaCO3 was prepared by new process route.Surface modifier was added before carbonation reaction at normal temperature,which reduced heating energy.Activation index,oil absorption value,free alkali content and CaC03 content of modified nano-CaCO3 prepared were measured.Some samples were characterized by XRD,TEM,TGA and FT-IR test.The optimal experiment conditions of modified nano-CaCO3 preparation were abtained as follow:the mixing of 3%isostearic acid with 0.5%cationic surfactant 1#as surface modifier,more than 97%active content of lime,10?15%concentration of Ca(OH)2 syrup,cooled for 24h,specific carbonation reactor with fine dispersion,reaction temperature at 10 ?,3?4h reaction time with CO2,filtered and dried.The properties of prepared nano-CaCO3 after many optimization had been similar to foreign product:activation index was 100%,oil absorption value was 31.2g Dioctyl-Phthalate/100g sample,free alkali content was less than 0.2%,CaCO3 content was more than 95%,particle size was 35.40nm with calcite structure and cubic shape,and well dispersion.Besides,pilot scale experiment with above condition was carried out.When the carbonization temperature was 30?,the product aggregated seriously with large particle size and spindle shape.When the temperature was 10?,the results were following:activation index was 99.8%,oil absorption value was 35.8g DOP/100g sample,free alkali content was 0.15%,particle size was 56.92nm,modified nano-CaCO3 was calcite structure,cubic shape with less agglomeration phenomenon,CO2 consumption was 204%,CaCO3 yield was 81%.Finally,application of the modified nano-CaCO3 as lubricating oil additive was studied.Modified nano-CaCO3 in the lubricating oil had better dispersiveness and stability than normal nano-CaCO3.The results of the tribology property test showed that modified nano-CaCO3 could improve base oil's properties of anti-wear and friction reduction.This conclusion can provide new ideas for next research of lubricating oil additives.