At present, plastic woven bags and composite plastic bags are mainly used as packaging materials for rice sales and packaging in China, but there are many problems to be solved urgently in transportation, loading and unloading, retail and other links of these packaging bags. It is a serious waste to pack grain with plastic woven bags, and it can only be used 1-2 times, which is relatively expensive. Moreover, the packaging method is simple, it is difficult to re-seal after opening, which is not conducive to long-term preservation, and insect pests are mildewed. Packaging materials have poor moisture resistance and barrier, and grain is easy to be oxidized and moldy. Plastic composite bags are made of high barrier packaging materials, which can solve the problems of mildew-proof, insect-proof and fresh-keeping of grain to a certain extent, but it is difficult to deal with them in the later stage, and its use is also limited because it is not easy to degrade.
In terms of packaging technology, there are basically two packaging forms for rice sales and packaging in China. One is ordinary packaging, in which rice is packed in polypropylene plastic woven bags, and no preservation technology is applied in the packaging process. This kind of packaging has poor insect-proof, mildew-proof and fresh-keeping effects on rice; Another vacuum packaging technology is vacuumizing the packaging bag, which has a good fresh-keeping effect on the storage of rice. However, because the shape and vacuum degree of rice itself are not suitable, the vacuum degree of rice vacuum packaging is generally between-0.07 and-0.09 kPa. As long as the vacuum degree is within this range, all products are qualified. Because of the high degree of vacuum, the packaging material tightly wraps the rice, and because the two ends of the rice are sharp, the packaging bag is easy to be punctured by rice grains to form pinholes, so the packaging bag will leak air, leading to the failure of vacuum packaging. Experiments show that the leakage rate of rice packaging bags with vacuum degree of -0.094 MPa is 16% within 20 days without stacking, so high vacuum degree will inevitably lead to high leakage rate. In addition, the friction, collision and falling between bags in the circulation process of packaging bags are also easy to cause bag breakage. According to statistics, the broken rate of vacuum packaging in circulation reaches 30%. Due to the problem of vacuum packaging, rice is wasted, which brings losses and troubles to consumers and enterprises. Therefore, the fresh-keeping packaging of rice should be combined with the circulation environment at the same time to achieve good results.