Preparation And Packaging Application Of Bio-based Heat-sealable Waterproof And Oil-repellent Coatings

Traditional plastic packaging waste is difficult to degrade and recycle,causing serious harm to the environment.In recent years,in order to alleviate environmental pollution,the demand for the development of fully biodegradable packaging materials and products has become increasingly strong.The development of functional paper materials and products to meet the needs of quality-preserving packaging for different types of food has become one of the research hotspots at home and abroad.However,traditional paper materials lack heat-sealing properties,and have weak waterproof and oil-repellent properties,which limit their application to a certain extent.Therefore,the research and development of bio-based functional coatings with heat-sealing,water-and oil-repellent properties has certain engineering value.In this paper,the biodegradable material soy protein isolate(SPI)is used as the main matrix.First,the two methods of polyvinyl alcohol(PVA)physical blending and vinyl acetate copolymerization modification are used to optimize the heat sealing performance of paper coating materials.The improvement of the waterproof performance of coatings by chemical grafting of oxygenated soybean oil(ESO)and physical blending of stearic acid(SA)and chemical grafting of stearic acid.The prepared coating liquid is coated on kraft paper to obtain wrapping paper with heat-sealing,water-and oil-repellent properties.The main research contents and research results are as follows:(1)Soy protein isolate and polyvinyl alcohol were physically blended to study the effect of their proportions on heat sealing performance.The coating amount,heat sealing performance and heat sealing process parameters were measured and analyzed.The results show that when the ratio of SPI/PVA is 1:1,the heat-sealing temperature is reduced from 230℃to about 170℃,and the heat-sealing strength can reach 12.5 N/15mm when the heat-sealing temperature is180℃.The optimal coating amount is further determined as 15 g/m~2,SPI/PVA(8-8)optimized heat-sealing temperature,heat-sealing time,and heat-sealing pressure were 180℃,1.5 s,and0.3 MPa,respectively.(2)The chemical grafting of epoxidized soybean oil and soybean protein isolate shows that the modification effect of 10%ESO is the best,the Cobb value is reduced from 64.63 g/m~2to 20.43 g/m~2,and the water vapor permeability is reduced from 96.41 g/(m~2?d)decreased to44.96 g/(m~2?d),and the oil-proof grade reached 8-9;10%SA was physically blended with the grafted soybean protein isolate,and the waterproof performance of the coating was further improved.Combining the heat sealability of the SPI/PVA coating and the SPI/ESO/SA coating to form a double-layer coating system,a coated paper with good heat-sealing,water-and oil-repellent properties was prepared.(3)The stearic acid was grafted onto soybean protein isolate by bio-coupling technology,and the effect of stearic acid addition on heat-sealing,water-repellent and oil-repellent properties was studied and the optimal coating amount was determined.The results show that when the content of stearic acid is 6%,the heat sealing performance is improved,the Cobb value is reduced from 64.26 g/m~2 to 27.88 g/m~2,and the water vapor permeability is reduced from 96.41 g/(m~2·d)to 46.97 g/(m~2·d),the contact angle is significantly improved,the oil resistance of the coated paper reaches 8-9 grades,and the optimum coating weight is 15 g/m~2.(4)The mechanical properties of the prepared coated paper and the heat-sealing,water-and oil-repellent properties under different humidity conditions were measured.With the increase of relative humidity,the heat sealing strength of the coating increases from 11.556N/15mm to 15.64 N/15mm,and the water and oil repellency is affected by relative humidity Not obvious.