Vegetable starch is a natural macromolecular compound of polysaccharide with a molecular weight of 3 million daltons. It is an ideal raw material that can be directly used as polymer materials. Plant starch can be divided into cereal starch (corn starch, sorghum starch, wheat starch and rice starch) and potato starch (cassava starch, potato starch and konjac starch), of which corn starch is the most widely used at present. At present, China's corn output is1.3-1.50 million tons, and only one tenth of the corn is processed into starch, which is used in textile, paper-making, food, medical and other fields. The total starch is close to 1 10,000 tons (including 9 million tons of corn starch; 420,000 tons of cassava starch and 240,000 tons of potato starch). According to the current technical level, the production of 1 ton of starch requires 1.5 ton of corn, which consumes 200KWh of electricity and 0.3 ton of coal. If this 1 ton starch is converted into biomass plastics, it can be processed into 1.0- 1.2 ton products, which will replace general plastics, save petrochemical resources and benefit the country and the people. Because there is no effective pulling mechanism in the downstream market, the application of corn starch is still limited to the research scope of modified starch. The industrialization of biomass plastics with corn starch as the main raw material will effectively stimulate the cultivation of corn and the production of corn starch.
Biomass plastics gradually evolved from the in-depth research and development of biodegradable plastics. People gradually realize that only by making full use of natural and renewable plant resources and developing biomass plastics is a reliable way to achieve sustainable economic development. In the past 30 years, even for half a century, countries all over the world have paid attention to and invested a lot of manpower and material resources in the research of materials plastics, mainly including the biochemical polymerization of starch with biodegradable plastics, carbon dioxide polymers, biosynthetic biodegradable plastics and biosynthetic precursors to produce biodegradable plastics. The latter three are expensive, but the cost is high, and they are mainly used in high-value products such as medical materials, biomedical engineering and tissue engineering. The mixture of starch and biodegradable plastics is the most widely used in biomass materials at present, and it is made of aliphatic polyester or mixed starch of aliphatic polyester. Aliphatic polyesters mainly include polylactic acid produced by renewable resources, polyhydroxy fatty acid esters (such as PHB and PHA) synthesized by microorganisms, and polycaprolactone (PCL), polybutylene succinate (PBS) and their * * * polymers synthesized by petroleum. The mixing technology of starch and biodegradable polymer materials can be used to produce completely degradable plastic film and packaging materials, and its performance is close to that of plastics. The problems of molecular design, molecular tailoring and chemical modification of biodegradable polymer materials and physical and chemical modification of starch are solved theoretically, and a completely biodegradable material with good performance, low cost and controllable degradation cycle is obtained.
During the Tenth Five-Year Plan period, China has intensified its research on the development of biodegradable biomass plastics, and has made breakthrough progress at present, which proves the advanced and reasonable blending technology of starch and biodegradable polymer materials. This technology can be used to produce disposable packaging materials, hotel supplies and mulch films, which are formed by blow molding technology with low cost. Biomass plastics will gradually replace the existing plastic films and packaging materials, and the promotion prospect is very broad.
At present, the industrialization of biomass plastics in developed countries is mainly to synthesize completely degradable polymer materials, including polycaprolactone (PCL), polylactic acid (PLA), polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), carbon dioxide and epoxy compound * * * polymer (PPC), etc. These materials can be completely biodegradable, but the price is too high (only PLA and PPC are slightly lower at present, and the price is lower at present.
As the production of biomass plastics with starch as raw material is an industrialization project that has just started in recent years, there are only a dozen production lines with annual production capacity exceeding 1000 tons in China. For example, the starch produced by biomass materials, Wuhan Gorgeous Environmental Protection Technology Co., Ltd. and Fujian Beisida Company is mixed with biodegradable polymer resin, which has formed an annual production capacity of 10,000 tons, and the products are exported to South Korea and Japan. With the maturity of technology, the gradual improvement of people's awareness of environmental protection and the gradual depletion of petroleum energy, the output of biomass plastics will greatly increase. China has produced twin-screw extruder, magnetic oscillation film blowing machine and supporting test equipment for producing substance plastics.