Bio-based polyurethane has become a new direction for development

The ubiquitous smoggy weather has lit up the environmental protection "warning light" for the entire chemical industry, and the emergence of the word "bio-based" has brought a turning point for the green transformation of chemical products, especially for polyurethane, which is a major producer and marketer.

According to the latest research report released by the American market research company grandviewresearch, by 2020, the global polyurethane market is expected to reach 73.6 billion US dollars. In the next 6 years, bio-based polyurethane will become a new development direction.

However, Chen Fan, a researcher at the School of Light Industry and Food Science, South China University of Technology, told reporters that there are currently too few varieties of biomass-based polyurethanes, which cannot meet the differentiated needs of users for products. If bio-based polyurethanes want to become the mainstream of polyurethane products , but also have to cross multiple technical thresholds.

"Bio-based" is sought after

Polyurethane is known as the "fifth largest plastic". It has the characteristics of wear resistance, tear resistance, and good flexural resistance. It is an organic synthetic material with application value in the fields of pharmaceuticals and functional polymers.

According to the survey of the above-mentioned American research report, the Asia-Pacific region is the largest polyurethane regional market in the world, and China is the largest consumer of polyurethane in the Asia-Pacific region. In 2013, the demand in this region accounted for more than 25%. The China Polyurethane Industry Association predicts that during the "Twelfth Five-Year Plan" period, the annual consumption of polyurethane products in my country will reach 9 million to 10 million tons, and the output value will reach 270 billion to 400 billion yuan.

However, behind the huge demand and the hot market, it is at the expense of the environment and resources.

Wang Shicai, a professor at the School of Biological and Chemical Engineering, Zhejiang University of Science and Technology, said that most of the raw materials and intermediates for the production of polyurethane come from non-renewable resources such as petroleum and coal, and most of these raw materials are toxic and harmful chemicals. In addition, polyurethane materials are difficult to degrade and their wastes are difficult to recycle, thus causing great environmental pollution.

For the sake of environmental protection, the use of biomass products to replace petroleum raw materials to produce green and environmentally friendly polyurethane is highly sought after.

For example, one of the highlights of Ford Motor Company's 2011 new Ford Explorer car is the use of soybean polyurethane to make car seat cushions and seat backs; Raw materials to manufacture the first bio-based polyurethane foam sole and put it on the market.

Polyurethane is mainly produced by the reaction of isocyanate, polyether polyol, polyester polyol, etc. It is estimated that 2,200 barrels of crude oil can be saved per 1 million pounds if bio-based polyols are used instead of petroleum polyols. Compared with petroleum polyols, the overall energy consumption of vegetable oil polyols is reduced by 23%, the consumption of non-renewable resources is reduced by 61%, and the emission of greenhouse gases into the atmosphere is reduced by 36%.

Technical barriers are difficult to break in the short term

However, due to the limitations of multiple technical barriers, it is still difficult for bio-based polyurethane products to become mainstream.

"Users still have doubts about bio-based polyurethane products, and their performance is still not comparable to that of petroleum-based polyurethanes, which also affects the promotion of products." Chen Fan told reporters that the current research and development of bio-based polyurethanes is mainly used Biomass-based polyethers replace petroleum-based polyethers, which requires bio-based polyethers to have similar physical and chemical properties to petroleum-based polyethers, but it is difficult to achieve this.

Weng Yunxuan, Secretary-General of the Degradable Plastics Professional Committee of China Plastics Processing Industry Association, also told reporters that compared with petroleum-based polyurethane, the stability of bio-based polyurethane is relatively poor. Chen Fan also pointed out that various biomass-based polyethers produced from biomass raw materials have the disadvantage of poor structure controllability.

"At present, it is difficult for people to design the structure of biomass polyether according to the demand for product performance as in the production of petroleum-based polyether, and to synthesize biomass polyether products according to this design." Fan Chen said.

In addition, most biomass raw materials still have great differences in raw material characteristics depending on the origin and growth period of raw materials. Not only that, but for the biodegradable plant-based polyurethane material, which is one of the current development hotspots, Wang Shicai said that its synthesis mechanism, structure-performance relationship, degradation mechanism and the controllability of its degradation rate also need further research.

How to welcome the golden period

Analysts pointed out that with the increasing demand for domestic polyurethane downstream products and the transfer of business focus and R&D centers of many multinational companies to the Chinese market, the domestic polyurethane industry will usher in a golden period in the future.

In order to seize market opportunities, domestic polyurethane companies have set their sights on the development of bio-based products.

"Actually, domestic bio-based polyurethane development technology is no worse than that of foreign countries." Weng Yunxuan told reporters that, for example, Nanjing Hongbaoli uses renewable vegetable oil as raw material to prepare polyurethane rigid foam; Jiangsu Zhongke Jinlong uses carbon dioxide as raw material to produce High flame-retardant polyurethane insulation materials; plant fiber-based polyols and plant fiber-based polyurethanes have also begun to move towards industrial production.

However, in Chen Fangen's view, the overall level of research and development of bio-based polyurethane materials in China is still not high enough. "From the perspective of research and development itself, more research institutions and enterprises need to participate in the development of more biomass-based polyurethane products to adapt to differentFrom the perspective of polyurethane developers, it is still necessary to realize the controllability of product structure and performance through new synthesis methods. "

He believes that the development of bio-based polyurethane still needs the support of national policies, such as formulating special technical standards suitable for bio-based polyurethane; in terms of government procurement and taxation, some policies that are conducive to bio-based products should be formulated, In order to allow new products to play a demonstration role in society.

In addition, whether the flame retardancy of polyurethane is improved is the key to whether polyurethane materials can be further popularized and utilized in China, and this is also the future research and development direction of biomass-based polyurethane.

Weng Yunxuan said that since the synthetic reaction devices of polyurethane companies are used to petroleum-based raw materials, it still needs a process of exploration if they want to adapt to new bio-based polyol raw materials. However, in his view, bio-based polyurethane products are still the future development trend of polyurethane products.

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Development history of degradable polyurethane material preparation technology

According to the different design methods and preparation methods of degradable polyurethane materials, and according to the complexity of the methods or the chronological order of appearance, the development of degradable polyurethane materials has roughly gone through four stages, that is, direct compounding with natural polymers ; Composite with modified natural polymer; Plant polyol-based polyurethane; Main chain designed degradable polyurethane.

Direct compounding with natural polymers is a widely used way to prepare degradable polyurethane foams at first, that is, introducing natural polymers such as cellulose, starch, and chitin into the polyurethane matrix. Natural polymers are renewable resources with abundant reserves, and most of them have good biodegradability in nature. Introducing them into polyurethane matrix in the form of fillers can endow polyurethane with certain biodegradability.

Compounding with modified natural polymers is aimed at the problems of poor compatibility and low reaction efficiency when natural polymers are directly introduced into the polyurethane matrix. The degradation performance and mechanical properties of polyurethane materials can be further improved by blending after modification. Studies have shown that polyurethane foams synthesized with modified starch are easier to degrade.

Plant polyol-based polyurethane refers to the liquefaction of biological raw materials such as wood, straw, and straw with polyethylene glycol liquefaction reagents under acid catalysis, and the reaction of polyols with organic polyisocyanates to synthesize polyurethanes. Due to the introduction of naturally degradable natural polysaccharide components into the polyurethane chain segment, this polyurethane has better degradation performance. However, there are still some problems that need to be solved in the method of preparing plant polyols by liquefaction of polyols from plant raw materials, and then using them in the preparation of degradable polyurethane materials.

Starting from the molecular main chain structure is the only way to design and prepare degradable polyurethane. The advantage of main chain-designed degradable polyurethane is that it can be completely degraded, and its mechanical properties and degradation speed are highly adjustable. However, its future development still needs to solve the problems of high design and synthesis costs of new raw materials.