Bio-Based Polyols: A Sustainable Future for Polyurethane Industry

Polyol is an organic polymer and a large class of alcohols containing two or more hydroxyl groups in the molecule. Traditional polyether polyols are restricted by petroleum resources and are unsustainable products; bio-based polyols are mainly produced from renewable bio-oils (castor oil, soybean oil, rapeseed oil, etc.) as the main raw materials and are more environmentally friendly. Currently, in terms of application, bio-based polyols are mostly used to manufacture products such as green spandex, polyurethane (TPU), and polyurethane elastomers. Their downstream applications include building materials and decoration, automobiles, packaging, clothing, etc., and their downstream applications are very wide.

1. Market structure
From the perspective of market structure, in recent years, global bio-based polyol manufacturers have been dominated by leading foreign companies, such as BASF, Dow, DuPont, SK Chemicals, Cargill of the United States, Mitsui Chemicals, Emery Oleochemicals of the United States, Croda of the United Kingdom, Huntsman of the United States, etc. The top ten companies in the world account for nearly 60% of the market, indicating a high degree of concentration. Due to the rapid growth in demand for downstream TPU and other materials in recent years, this field has also attracted the attention of domestic companies such as Wanhua Chemical, Huafeng Group, and Asahikawa Chemical. According to GIR data, the global bio-based polyol market reached US$994 million in 2021 and is expected to reach US$1.755 billion in 2028, with an annual CAGR of more than 7%. The core manufacturers that provide bio-based polyols (Bio Polyols) in the world include BASF, Cargill Inc and MCNS. The top three manufacturers account for about 30% of the global market share. North America is the world’s largest market, accounting for approximately 42% of the market, followed by Europe and Asia-Pacific, accounting for 27% and 26% respectively.

2. Main types of bio-based polyols

2.1 Soybean oil polyols

Soybean oil is a triglyceride, containing mass fractions of 20%-30% oleic acid, 45%-58% linoleic acid, and 4%-10% linolenic acid. The United States is rich in soybean resources. Researchers used soybean oil as raw material, carried out epoxidation and hydroxylation, and prepared soybean oil polyols with a sufficiently high hydroxyl value but not too high relative molecular weight and viscosity, and used it to prepare Polyurethane rigid foam used for thermal insulation, building sound insulation and thermal insulation. The price of this soybean oil polyol is similar to that of common petrochemical-based polyether polyols.

2.2 Castor oil polyol

Castor oil is a natural vegetable oil polyol containing multiple hydroxyl groups. It has the characteristics of high specific gravity, high ignition point and low freezing point. It can be widely used in coatings, fibers, adhesives, inks, biodiesel, polyurethane and other fields. Among them, castor oil type Polyurethane is a new polymer material that has emerged in my country in recent years. Polyurethane products made from castor oil have good mechanical properties, water resistance and thermal stability. However, due to the low hydroxyl value of castor oil, its application is limited. , so it is an effective and feasible method to use transesterification reaction to generate castor oil monoglyceride and castor oil diglyceride to increase the hydroxyl value.
Research on castor oil polyols at home and abroad mainly focuses on the research of small molecular alcohols and the selection of catalysts. Currently, sodium methoxide or lead oxide is used as a catalyst to produce castor oil polyols through transesterification reaction. During the catalytic reaction, saponification reaction easily occurs and ricinoleic acid is released, which destroys the functionality and worsens the compatibility of the polyols. , produces precipitation, which is also an important reason why vegetable oil polyols are difficult to industrialize. Therefore, research and preparation of efficient catalysts are the key to transesterification reactions.

2.3 Palm oil polyols
Palm oil, as the most economical renewable agricultural resource among vegetable oils, can be used to synthesize bio-based polyols required for flexible or semi-rigid polyurethane foams. Palm oil-based polyols were used to partially replace petrochemical-based polyols in the synthesis of modified polyurethane. Research results show that polyurethane foam materials containing palm oil-based polyols have higher apparent density and improved mechanical properties. Malaysia is the world’s largest palm oil producer. Researchers modified palm oil to produce a series of palm oil polyols. The production of this natural oil polyol is energy-saving, non-hazardous and waste-free, making the process less expensive, more efficient and environmentally friendly.

2.4 Olive oil polyols
Brazil’s EDB Company has developed olive oil-based polyols, with the brand name Envilopol series. The typical indicators of the product are hydroxyl value 250-450mg (KOH)/g, viscosity (25℃) 500-2500tu Fa. s, its annual production capacity reaches 5kt/a, and it is said that it can be used to prepare rigid and soft foams.

2.5 Cashew nut shell liquid polyol
Diols and polyols derived from cashew nut shell liquid (CNSL) can replace palm oil polyols in soft and hard foam formulations. Cashew nut shell oil is a renewable oil extracted annually from the honeycomb structure of cashew nuts and can be used to synthesize natural oil-based polyols (NOPs). Unlike vegetable oils such as palm oil, cashew shell oil does not interfere with the food chain and is considered a by-product of the cashew industry.

2.6 Polylactic acid polyol
Polylactic acid polyol is a 100% bio-based eco-friendly material that can be fermented from non-food biomass raw materials (agricultural and forestry waste such as straw) and can replace petrochemical-based polyols. A life cycle assessment (LCA) showed that PLA polyols produce 40% less greenhouse gas emissions compared to existing petrochemical-based polyol production processes.
Due to the tightening of the global environment and the emphasis on ESG management by well-known companies, the demand for eco-friendly materials in the automotive, 3C, food, and home furnishing industries is increasing rapidly and is expected to grow rapidly.
Fengyuan Biotechnology is accelerating its entry into markets such as artificial leather, adhesives and furniture through the excellent chemical resistance and eco-friendliness of polylactic acid polyols.

3. Dilemmas and challenges

Although bio-based polyols have many advantages, there are still some challenges that need to be solved. Problems faced by bio-based polyols:

1. Production cost: Compared with fossil fuel chemical products, the production cost of bio-based polyols is still high. The energy consumption and equipment costs of the biomass conversion process are relatively high, and the unstable supply and price fluctuations of bio-based raw materials will also affect cost control.
2. Technology maturity: Although the production technology of bio-based polyols continues to advance, compared with traditional fossil fuel chemical technology, its maturity and stability still need to be improved. This may affect the reliability and market acceptance of bio-based polyols.

3. Performance differences: Bio-based polyols may differ from fossil fuel-based products in some properties, such as thermal stability, hydrolysis resistance, etc., which may limit their promotion in certain specific application fields.
As the world attaches greater importance to environmental protection and sustainable development, the market demand for bio-based polyols has shown a rapid growth trend. At the policy level, many countries are encouraging the research and development and application of bio-based materials, providing financial support and tax incentives. At the technical level, advances in biomass conversion technology have gradually reduced the production cost of bio-based polyols and continuously improved production efficiency.

4. Forecast of future development
The development of bio-based polyols will likely present the following characteristics:

1. Technological innovation: Continuous technological innovation is the key to reducing costs and improving performance. Improve the conversion efficiency and product performance of bio-based raw materials through genetic engineering, catalytic technology and other means.

2. Improvement of the industrial chain: With the expansion of the bio-based polyol market, the related upstream and downstream industrial chains will gradually improve, forming a cluster effect and improving the competitiveness of the entire industrial chain.

3. Policy support: The government will continue to introduce relevant policies to support the research and development and industrialization process of bio-based polyols, including capital investment, tax exemptions, market access, etc.

4. Market development: The application fields of bio-based polyols will continue to expand, especially in the construction, automobile, furniture and other industries.
Overall, bio-based polyols have broad prospects for future development and will play an important role in promoting the development of green and low-carbon economy and promoting the optimization and upgrading of industrial structure. As the world’s largest consumer and producer of chemical products, China also attaches great importance to the development of bio-based polyols. The green and low-carbon development strategy promoted by the Chinese government has provided a broad market space for bio-based polyols. Under the “14th Five-Year Plan” and the commitment to carbon peak in 2030 and carbon neutrality in 2060, bio-based materials such as bio-based polyols are regarded as important ways to achieve these goals.

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