Preparation Of Microcrystalline Wax Emulsion And Its Research On Oil And Water Resistance Of Paper

Paper packaging materials are widely used in the field of food packaging,and are gradually replacing traditional plastic packaging products.As food packaging paper,oil and water resistance is one of its most important physical properties.At present,fluorinated oil and water repellents are most widely used in food packaging paper,but some studies have shown that fluoropolymers are potentially harmful to humans and the environment,so it is especially urgent to develop non-toxic,green,non-fluorinated oil and water repellents.Microcrystalline wax is safe and non-toxic,and it is a traditional waterproof material with good film formation and lower surface tension than ordinary edible oil,so it has a broad application prospect in the field of oil-proof food packaging paper.In this thesis,the process and influencing factors of microcrystalline wax emulsion preparation were studied more systematically,and the application performance of microcrystalline wax emulsion as internal sizing agent and surface sizing agent was explored.The results of the study are as follows.1.By using phase inversion emulsification,the microcrystalline wax emulsions were prepared by a combination of mechanical high-speed dispersion and high-pressure homogenization.The effects of emulsifier type and ratio,emulsifier dosage,solid content,emulsification temperature and homogenization pressure on the properties of microcrystalline wax emulsions were investigated.The optimal emulsification conditions were determined as follows: Span-80 compounded with Tween-80 as emulsifier,the emulsifier Span-80/Tween-80 ratio of 5:5,emulsifier dosage of 20%(compared to microcrystalline wax),emulsion solid content of 30%,emulsification temperature of 100 ℃,and homogenization pressure of 400 bar.The emulsion of microcrystalline wax prepared under this emulsification condition has an average particle size of304.8 nm,a viscosity of 27.3 m Pa·s,and a stable emulsion performance,which meets the basic requirements of microcrystalline wax emulsion for paper making.2.The application feasibility of microcrystalline wax emulsions as oil and water repellents in internal pulp sizing was investigated.Microcrystalline wax emulsions provided a degree of oil and water resistance to paper.The contact angles of the paper with water and oil reached 101.3° and51.7°,respectively,when 1% microcrystalline wax emulsion was applied under optimal conditions.With the increase of microcrystalline wax emulsion sizing,the paper of water contact angle gradually increased to more than 90 °,while the paper of oil contact angle was still lower than 90 °,microcrystalline wax reduced the surface energy of the paper,so that the paper has a hydrophobic effect,but the paper of oleophobic effect was poor,not able to prevent the penetration of grease.The addition of microcrystalline wax impeded the combination of fiber and fiber,reducing the mechanical properties of the paper,the greater the amount of sizing,the worse the mechanical properties of the paper.3.Microcrystalline wax emulsions were used as surface sizing agents,and the effects of microcrystalline wax emulsions on the oil and water resistance and other properties of paper were investigated.After sizing the microcrystalline wax emulsion,the oil and water resistance of the paper was significantly improved.However,since the microcrystalline wax easily penetrated into the paper after melting,a larger coating load was required to obtain excellent oil and water repellency of the paper,so cationic starch was used to pretreat the paper.After pretreatment,the surface pores of the paper are reduced,which greatly reduced the penetration of the microcrystalline wax into the paper,and the microcrystalline wax formed a more uniform and complete barrier layer on the surface of the paper.By surface sizing microcrystalline wax emulsion,the water vapor barrier performance of the paper was significantly enhanced,and the water vapor barrier performance of the pretreated paper is better than the unpretreated paper.Microcrystalline wax sizing paper has a certain migration in food simulants,so it should be reasonable to use microcrystalline wax emulsions under the premise of meeting the oil and water resistance performance.