Preparation And Performance Evaluation Of Biopolymer-coated Oil Resistant Paper Packaging Materials

In our daily life, we often need to pack a lot of oily substances, such as hamburgers, pizza and mechanical parts coated with anti-rust oil or lubricating oil. Materials which are used to pack oily substances must have good oil resistant property. In order to resist oil, plastic containers and films were once widely used, such as polyethylene and polypropylene. But these synthetic polymers are difficult to be degraded and will bring environmental pollution, so they have been gradually replaced by green paper based packaging. Paper based packaging themselves can’t resist oil and fluorinated oil resistant agents are generally chosen as coating materials to provide oil resistance to them. However, it was found that the raw material and intermediate- perfluorooctane sulfonate(PFOS) used in the preparation of fluorinated oil resistant agents is cumulative and harmful to human body. Therefore, new non-toxic and environmentally friendly oil resistant agent is being developed by many countries. Biopolymers(polysaccharides, proteins, lipids, etc.) which can be used as the main raw material for the preparation of oil resistant agent get more and more attention. It was showed that, whey protein isolate(WPI), zein protein, soy protein isolate(SPI) and chitosan have oil resistant property. The oil resistance of chitosan is the best of them, but its price is high, which limits the application of it.Effect of the staining of oil on the mechanical property of corrugated paperboard was studied firstly in this paper. Then the feasibility of using SPI and sodium alginate(SA) as the main raw material to prepare oil resistant agents and coated oil resistant papers was explored. The specific research contents and results are as follows.(1) Effect of the staining of oil on the mechanical property of corrugated paperboard was studied. It was showed that, the ply adhesive strength, edgewise crush resistance and bursting strength gradually decreased with the increasing of stain amount; decreased and then became stable with the increasing of stain time.(2) SPI and SA were used as the main raw material to prepare oil resistant agents and coated oil resistant papers. Effect of the concentration of substrate, the concentration of glycerol, coating weight and drying temperature on the viscosity of agents and the oil resistance of coated papers was studied. On the premise that the viscosity is appropriate and the oil resistance of the coated paper meets the minimum safe oil resistant level, the formula of SPI oil resistant agent and the preparation parameters of its coated paper were determined: the concentration of SPI is 7%, the concentration of glycerol is 2%, coating weight is 6g/m2, drying temperature is 80℃ and drying time is 175 s. The formula of SA oil resistant agent and the preparation parameters of its coated paper were also determined: the concentration of SA is 3%, the concentration of glycerol is 1%, coating weight is 4g/m2, drying temperature is 90℃ and drying time is 199 s.(3) SPI and SA were blended to produce complex oil resistant agent. Effect of the ratio of SPI and SA, the concentration of glycerol, coating weight and drying temperature on the viscosity of agent and the oil resistance of coated papers was studied. The formula of complex oil resistant agent and the preparation parameters of its coated paper were determined: the concentration of SPI is 7%, the concentration of SA is 1%, the concentration of glycerol is 2%, coating weight is 4g/m2, drying temperature is 80℃ and drying time is 190 s.(4) The structure characterization and properties of oil resistant agents and their coated oil resistant papers were studied by using modern testing methods. It was showed that: 1) SPI had good intermiscibility with SA; 2) The thermal stability of three oil resistant agents was good and the adding of glycerol reduced the thermal stability; 3) Three oil resistant agents all could form a thin film on the surface of paper and fill the void between fibers, which had improved the surface and internal condition of paper; 4) The adhesion of coating made by the three oil resistant agents were all good; 5) The moisture barrier property and mechanical property increased after being coated by oil resistant agents.