Starch-based plastics
Starch-based plastics use chemical reactions to chemically modify starch to reduce the hydroxyl groups of the starch and change its original structure, thereby changing the corresponding properties of the starch and turning the original starch into a thermoplastic starch.
Chinese name
Starch-based plastics
Field
Chemical manufacturing
Industry
Industrial manufacturing
Application field
Plastic manufacturing
table of Contents
1 R & D background
2 Process principle
3 Development status
4 product advantages
5 certification system
6 Application prospects
1 R & D background
Starch is a natural polymer whose yield is second only to cellulose on the earth. It is rich in source, renewable, and low in price. It can be used to produce starch-based plastics through modification and plasticization. As an important category of bio-based materials, starch-based plastics have successfully realized industrialized production and application. Starch-based plastic is a kind of plastic product made from starch as the main raw material, which is modified and plasticized and then blended with other polymers. It is a kind of bioplastics. Starch-based bioplastics can be divided into two categories: bio-based plastics and biodegradable plastics.
Starch-based biodegradable plastic is generally a blend of modified starch and biodegradable polyester (such as PLA/PBAT/PBS/PHA/PPC, etc.). It can be completely biodegradable, compostable, environmentally friendly, and suitable for waste Compost, landfill and other treatment methods. Bio-based plastics based on starch are generally a mixture of modified starch and polyolefins (such as PP/PE/PS, etc.). Its environmental protection significance lies in reducing the use of petrochemical resources and reducing carbon dioxide emissions, and waste is suitable for incineration. Both of these materials can replace traditional petroleum-based plastics and are widely used in plastic packaging materials, shock-proof materials, plastic films and plastic bags, disposable tableware, food containers, toys, etc.
2 Process principle
Starch is a kind of natural high molecular polymer. Its molecule contains a lot of hydroxyl groups (molecular structure is II and III). Therefore, the interaction force between starch macromolecules is very strong, which makes it difficult to melt processing native starch, and it is in co-polymerization with other polymers. The compatibility with other polymers during mixing is also poor. But these hydroxyl groups can undergo chemical reactions such as esterification, etherification, grafting, and crosslinking. Using these chemical reactions to chemically modify starch, reduce the hydroxyl groups of starch, change its original structure, thereby changing the corresponding properties of starch, and turning the original starch into thermoplastic starch.
1. Esterification, transesterification or etherification reaction
In order to change the hydrophilicity of starch to hydrophobicity, the hydroxyl groups on the starch molecule are esterified and transesterified with fatty acids, fatty acid esters, etc., to form starch esters.
2. Cross-linking reaction
In order to improve the strength and heat resistance of starch materials, the starch is cross-linked with compounds with two or more functional groups (such as polybasic acids, etc.), so that the starch is appropriately cross-linked.
3. Independent innovation of blending and co-gathering
Most starch plastics are prepared by filling and blending starch with other polymer materials. The products obtained in this way have poor compatibility and low strength, and their application range is limited. In the starch-based plastics, the starch is copolymerized in the starch modification process to obtain graft copolymers of starch and other polymers, thereby improving the compatibility of starch with other polymer materials. Through chemical modification, three modifications of starch have been realized: hydrophilicity changed to hydrophobicity; heat sensitivity changed to temperature resistance; hardness and brittleness changed to plasticity. This modification solves the worldwide problem of starch modification and lays a good foundation for subsequent processing.
3 Development status
Starch-based bioplastics have a 30-year history of research and development. It is a biodegradable plastic with the longest research and development history, the most mature technology, the largest industrialization scale, and the highest market share. In the early 1980s, the research and development of modified starch and degradable plastic alloy master batches that can be completely biodegradable or soluble plastics, and the blending of starch and biodegradable resins received attention. Among them, the most successful is the "MaterBi" of Novamont, Italy. It is an interpenetrating network structure polymer plastic alloy composed of a blend of modified starch and modified polyvinyl alcohol. It has good processing properties, secondary processing properties, and mechanical properties. Performance and excellent biodegradability. In addition, the "Vinex" developed by Air Product & Chemical in the United States is a resin based on polyvinyl alcohol with a low degree of polymerization. It also has water solubility, thermoplastic processability and biodegradability, and has received great attention in recent years.
In recent years, various countries have generally shifted their research focus to plastics with as much starch content as possible, and developed some completely degradable materials with excellent performance, and even obtained pure starch products without synthetic polymers, that is, thermoplastic starch. The "Novon" biodegradable material produced by the Warner-Lambert Company of the United States has a starch content of more than 90%; the Japanese Corn Company and the Michigan Production Technology Research Institute jointly developed a high starch content material, which has the advantages of strong water resistance In addition, Japan's Sumitomo Corporation, Italy's Ferrizz Corporation, etc. also claimed to have successfully studied all starch plastics with 90% starch content. Research institutions such as the German Batekke Research Institute, the Warner-Lambert Company of the United States, and the Swiss University have all made great progress in converting starch into thermoplastic starch for the production of biodegradable plastics. The Australian National Food Processing and Packaging Science Center has launched a whole starch thermoplastic, which has good fluidity, ductility, mold release, soft, transparent, high strength, and controllable degradation rate. It can be used to make agricultural films and food. Packaging film and other products.
China’s starch plastics were first developed by the Jiangxi Academy of Sciences Institute of Applied Chemistry in the late 1980s. According to incomplete statistics, there are more than 60 universities, research institutes and enterprises participating in the research. my country is gradually narrowing the gap with foreign developed countries in the research and development of starch-based plastics. At present, the main domestic manufacturers of starch-based materials and products and their current status are as follows: Wuhan Huali is 40,000 tons/year, and is preparing to build a production line with an annual output of 60,000 tons; Shenzhen Hongcai 15,000 tons/year; Suzhou Hanfeng 10,000 tons/year; Zhejiang Tianhe 10,000 tons/year; Zhejiang Huafa 10,000 tons/year; Shandong Bicacheng 10,000 tons/year; other production companies include Nanjing Biaoge and Changzhou Longjun.
The starch is modified and plasticized by chemical methods, and the obtained modified starch has three characteristics: 1. Hydrophobicity. The starch is completely hydrophobic after chemical modification, and the moisture content is <1%, which has good compatibility with other synthetic polymer materials. 2. Temperature resistance. Modified starch can withstand a high temperature of 230°C during the thermoplastic processing without turning yellow or decomposing. 3. Thermoplasticity. Modified starch can be thermoplastic processed on plastic processing equipment. The starch-based plastics produced by the company are divided into two series: bio-based and biodegradable. According to different processing techniques, they are divided into blown film materials, injection molding materials, sheet materials, and foam materials. They can replace ordinary petrochemical plastics and are widely used in industry, medicine, Food, electrical appliances and other products packaging and tableware, kitchen utensils, toys and flower planting and other fields. In this way, a large amount of oil resources are saved, carbon dioxide emissions are reduced, and the harmless treatment of garbage is realized. It is also conducive to promoting agricultural development and farmers' income, and promoting the vigorous development of circular economy.
It was reported on July 12, 2018 that Yu Long successfully developed and industrialized a full starch biodegradable material for the first time in the world.
4 product advantages
Compared with traditional plastic products, the advantages of starch-based materials and products are shown in the following aspects:
⑴Similar performance: It has the same or similar performance as traditional plastic products of the same kind;
⑵Environmental protection: Starch-based bio-based plastics and products have the advantages of saving petroleum resources and reducing carbon dioxide emissions; starch-based biodegradable plastics and products have the advantages of being completely biodegradable, compostable, and realizing the harmless treatment of garbage;
⑶Safety: Starch-based materials and products do not contain toxic and harmful substances such as plasticizers, bisphenol A, and heavy metals. Food-grade materials meet the requirements of relevant domestic and foreign food-grade plastic standards;
⑷Production process: no three wastes are discharged during the production process, and no new pollution will be caused to the environment;
⑸Cost: Starch-based bio-based plastic materials and products are the same as ordinary petroleum plastic products, and the cost of starch-based fully biodegradable materials and products is about twice that of ordinary petroleum plastics.
5 certification system
In recent years, the environmental performance of bio-based products has gradually been recognized at home and abroad, which has greatly expanded the application fields of bio-based materials. The bio-carbon content of bio-based materials is an important feature that distinguishes them from ordinary plastics. The definition of bio-carbon content is the percentage of bio-carbon in the product to organic carbon (including bio-carbon and fossil carbon). Since biochar is new carbon, it does not cause pollution to the environment, so it has a very good environmental protection effect. Bio-carbon content testing standards include the United States ASTM D6866-08: The test method for the determination of the biological content of solid, liquid and gas samples by radiocarbon analysis and the Chinese GB/T29649-2013 bio-based material content determination liquid scintillation counter method. Since contemporary organisms all contain the same amount of radiocarbon elements, the principle of ASTM D6866 is to use this characteristic of organisms to measure the bio-based content of samples in any state; this measurement method can determine any bio-based products and organisms. The precise percentage of bio-based or renewable substances contained in the mixed-based product.
In 2009, Vincotte, an authoritative certification body in Belgium, issued the world’s first batch of OK Biobased star-certified product certifications, which certified the bio-carbon content of bio-based materials, and also provided reliable product quality for the bio-based materials market. Third-party reviews. OK-Biobased is Belgium's environmental label for bio-based low-carbon products. After obtaining certification, bio-based plastic manufacturers can place their labels on the outer packaging or products to distinguish ordinary petrochemical products. It defines bio-based materials based on the content of bio-carbon, and uses the percentage of bio-carbon content and total carbon content to evaluate. Its standard is ASTM D6866, which distinguishes the materials by stars, and is the EU's authoritative certification mark for bio-based materials. The OK Biobased logo uses asterisks to distinguish the environmental grade of the product. A certified product obtains a 1-star mark to prove that its product contains 20%-40% biocarbon, 2-star 40%-60%, 3-star 60%-80%, and 4-star bio-carbon content of more than 80% product. Vincotte's OK Biobased certification aims to help companies or distributors improve the market competitiveness of renewable products and guide consumers to better choose environmentally friendly products.
To encourage the development of bio-based materials and products, the United States Department of Agriculture has implemented a Biological Priority Program. The plan has two procedures, one is a priority plan for government procurement and a voluntary labeling plan for consumers. The former was established in 2002 to encourage the development of bio-based products, while the latter was released in 2008. The purpose of the Biofirst Program is to stimulate the consumption of biomass products in the United States. Federal government agencies and their contractors give priority to purchasing products with the highest biomass content. If the product meets the minimum standards of bio-based content in the US Department of Agriculture's bio-based product list, any factory and distributor can participate in this program, and the certification mark issued by the agency can be affixed on the product packaging.
International certifications for biodegradable plastics include the Belgian OK Compost certification, the German Compostable certification, and the US BPI certification.
OK Compost is a compostable certification named "OK Compost" issued by the Belgian certification body AIB-Vincotte Group after testing in accordance with the testing standards EN13432 or ASTM D6400 for biodegradable materials. The purpose of OK Compost certification is to help companies or distributors improve the market competitiveness of fully degradable products and guide consumers to better choose environmentally friendly products.
Compostable certification is a certification for biodegradable products launched by DIN CERTCO, a joint certification body of TUV Rheinland and the German Standardization Association (Deutsches Institut fr Normun, DIN). The certification mark is the "seeding" mark. Compostable certification can help buyers select products with strict quality, safety and environmental protection from many suppliers and manufacturers. At the same time, products with the Compostable logo indicate that they have successfully passed the test and evaluation of an authoritative third-party organization, which helps to enhance customers' confidence in buying and effectively promote product sales. Moreover, the relevant information of the holder can be inquired on the official DIN CERTCO website to prevent abuse or forgery of the mark.
BPI is the abbreviation of Biodegradable Products Insitute (Degradable Products Association). Through an innovative compostable labeling program, BPI educates manufacturers, legislators and consumers on scientific standards for degradable materials. At the same time, through a series of procedures to ensure that related products meet the requirements of degradable materials standards.
The first batch of Chinese companies in Wuhan Huali Environmental Protection to obtain OK Biobased certification have obtained four-star bio-based product certification. At the same time, the company's biodegradable materials have obtained OK Compost certification and Compostable certification.
6 Application prospects
With the gradual shift in consumer preference for plastic products, renewable environmentally friendly materials have become increasingly popular in the market. Affected by this, the demand for bio-based plastics has increased. With the emphasis on bioplastics by governments, the total value of global bioplastics demand is expected to increase to 5.9 billion US dollars in 2020, which is equivalent to an average annual growth rate of 20%.
Recently, the French Parliament passed laws on energy transition and green growth. In addition to reducing the proportion of nuclear energy in France's energy structure, the new law also contains legislative proposals related to renewable energy and plastic packaging. For example, renewable energy will increase by 40% by 2030 and carbon dioxide emissions will be reduced by 40% by 2030; lightweight packaging bags used for packaging fruits and vegetables will have to be made of bio-based materials from January 1, 2017; In addition, plastic packaging used for commercial mail will also be implemented with the same standards at the same time. The latest legislation of the French government requires that disposable tableware such as dishes, cups and forks must be made of bio-based raw materials instead of petroleum-based raw materials.
A market analyst at RnR Market Research has recently predicted that the global demand for bio-based plastics will increase at an annual growth rate of 19% in the next four years, and its market demand will reach 950,000 tons in 2017. Europe is the world's largest consumer market for bio-based plastics. In 2012, the use of bio-based plastics in this region accounted for more than half of the global total. The survey report shows that compared with traditional plastics, consumers in European countries are more inclined to choose new bio-based plastic products. Therefore, the region is expected to continue to lead the ranking of bio-based plastic consumption. In terms of types, starch-based plastics and polylactic acid will continue to be the most demanded bio-based plastics in the next few years, and their market consumption will account for more than 60% of the total. RnR Market Research said that in recent years, various countries have successively introduced plastic restrictions and continuously increased the supervision of the use of traditional plastics, which is conducive to further pushing up the demand trend of bio-based plastics, especially starch-based plastics.
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