Synthesis Of A Solvent-free Alkyl Ketene Dimer (AKD)

Alkyl ketene dimer(AKD)is typically utilized as sizing products in the pulp and paper industry.Conventionally the production of long-chain alkyl ketene dimers is carried out by reacting tertiary amine with fatty acid chloride in an organic solvent such as benzene.For the sake of environmental protection and human health,solvent-free synthesis has become the mainstream direction.In this paper,alkyl ketene dimer was prepared by reaction of tertiaryamine and stearyl chloride in the absence of organic solvents.The causes of high viscosity and measures to reduce the viscosity were investigated.From the experimental results:1.With stearic acid and thionyl chlorid as the raw materials and pyridine as the catalyst,stearoyl chloride(SC)was synthesized.A comparison between pyridine and the conventional catalyst DMF was made.A yield of 82%could be reached at the optimum operating conditions.A method for the analysis of stearoyl chloride by direct ultraviolet spectroscopy was developed,and compared with the acid-base titration,argentometry,esterified spectrophotometry and silver chloride turbidimetry.From the experimental results,the direct ultraviolet spectroscopic method has the advantage of easy operation,high precision,and no special treatment for the sample is required.2.The structure and morphology of triethylamine hydrochloride(TEA-HCl)during the reaction were observed and analyzed by XRD,SEM,FR-IR,HNMR and con focal three-dimensional scanner.The active hydrogen connected with nitrogen atom in TEA-HCl is easy to form hydrogen bond with oxygen atom in AKD.With the increase of TEA-HCI content,large number of TEA-HCI particles collided each other and crosslinked.The dendritic-shaped structure of TEA-HCI,strong interaction force between TEA-HCI and AKD,and large specific surface area of the particles are the main cause of the high viscosity in the reaction.The shape of TEA-HCI particles is spherical with diameter between 200nm and 1.5μm depending on different feed rate in reaction.Under the optimal reaction conditions,the AKD purity can be reached 90.94%and the yield 85.23%.3.Two methods were employed for the the post-treatment process of AKD,i.e.filtration method and acid extraction process.A comparison was carried out.From the experimental results,at high ratio of TEA to SC,filtration method should be employed.with the advantage of easy operation and mild reaction condition.While the ratio of TEA to SC is low.only acid extraction could be used due to the high viscosity.4.Four kinds of seed crystals,TEA-HCl,sodium chloride and sodium sulfate,ammonium sulfate,were used and compared.Ammonium sulfate as seed crystal has a stronger force with TEA-HCl produced in reaction and can reduce the viscosity effectively.5.As a substitute of TEA-HCl,trinpropylamine was used to reduce the viscosity.At the same reaction condition,the viscosity could be reduced 22.8%with trinpropylamine as the raw material.The purity and yield of AKD could reach 91.42%and 90.81%,respectively.