Summary
Scalability and commercial-scale production have been and continue to be unresolved engineering problems for most of the successfully produced bench-top “green” chemicals, particularly products derived from soybean byproducts. In this project, the research team will build upon the success they realized from prior synthesis method using soybean-derived gallic acid (GA) create a critically important epoxy resin for food packaging applications.
The team aims to synthesize new thermoset materials in this project using bio-based building blocks extracted from soybean byproducts. The new bio-based epoxy resins will be constructed by incorporating Gallic Acid (GA), Phytic Acid (PA), and 1,3-Propanediol (PD), with a focus on applications related to internal can coatings intended for food packaging. GA from soybean milk residue was once again selected as a building block due to its bio-based availability, multifunctionality, rigidity, and antioxidant and non-toxic properties. This rigid aromatic unit can be substituted for the harmful fossil fuel-based aromatic monomers commonly used in food and beverage can coatings. PA, a well-known non-toxic compound, can also be extracted from soybeans in high quantities during the soymilk and biofuel production processes. This compound forms stable complexes by chelating to minerals, making it beneficial for anticorrosion applications; therefore, PA will be used for its anti-corrosive characteristics and as a soybean-derived epoxy hardener. PD, a safe bio-based compound, will also be utilized to further modify the resin’s thermal and mechanical properties by imparting additional flexibility into the crosslinked network.
Goals
Upon successful completion of this project, a novel bio-based epoxy resins derived from soybean processing byproducts for food and beverage can coatings will be produced. The obtained materials will replace the harmful fossil fuel-based thermosets frequently employed in metal food packaging.
Benefit to Consumers, Manufacturers, and Soybean Farmers
The globally increasing demand for soybean products, including soymilk and tofu, has prompted a reconsideration of several production byproducts previously considered as waste. These products are now considered valuable raw materials that offer alternative solutions to harmful fossil oil-based counterparts. Consequently, soybean producers have an opportunity to diversify their product offerings and help them overcome challenges related to growing and trade fluctuations, especially in ND, where the annual revenues from soybean production averaged $2.3 billion between 2018 and 20204. This project will directly benefit ND soybean farmers by adding value to soybeans as a crop and agricultural byproduct.
Research hypothesis
To date, food industries have been heavily dependent upon use pf petro-based monomers to produce crosslinked thermosets that can be used effectively as an anti-corrosive layer between the food and the metal container. Toxic monomeric building block and degraded polymer products can leach into preserved food, causing severe health effects. Hence, it is hypothesized in this project that a new and viable alternative can coating epoxies can be produced using gallic acid from soybean processing.
Project Justification and Rationale
The global production of bio-based polymers from agricultural residues has increased remarkably since 2013. The global bio-based polymer market is forecasted to increase at a CAGR of 5.50% between 2022 and 2029, reaching a value of USD 12.16 billion by 20296. Developing safe, bio-based materials from non-food renewable resources adds value to agricultural byproducts due to this anticipated growing demand for sustainable products. Recent advancements in agro-industrial byproduct extraction methods have resulted in several valuable aromatic and aliphatic compounds that can replace their petro-based counterparts, especially in the production of bio-based polymers for food packaging. Effective food preservation and extended shelf life are crucial factors that food production industries must consider, especially in the canned food production sector. Manufacturers have relied heavily on the use of petro-based epoxy resins as lining materials for food and beverage cans to prevent metal corrosion and food contamination since the 1960s. Several recent research studies, however, have revealed that petro-based epoxy resins can leach into food, causing adverse health effects, especially in women and children. Accordingly, using petro-based epoxy resins, particularly bisphenol-A (BPA), in infant feeding bottles and children's food manufacturing has been banned in several EU countries, and five states in the USA. Investments in alternative bio-based epoxy resins from agro-industrial byproducts are very much needed and they align strongly with growing trends in the industrial landscape as they move toward green, responsible, and safe goods, along with the expected changes in BPA-based epoxy safety classifications. This work aims to produced alternative from readily accessible building units via well-established synthetic approaches and scaled up to industrial levels.
Methods
The aims of this project will be accomplished by conducted five primary tasks: 1) synthesizing the GA-based Tetraglycidyl ether of gallic acid (TEGA) monomeric building block, 2) synthesizing the diglycidyl ether of 1,3-propanediol (DEPD) precursor, 3) producing the bio-based epoxy resin, 4) thermally treating and characterizing the synthesized monomeric building blocks, and 5) mechanically test and optimize the physical properties, along with the anticorrosion performance of the obtained coatings. These five tasks should be completed within the 12-month duration of the research grant.
Potential Barriers to Achieving Anticipated Results
Challenges related to phytic acid thermal stability are expected during the thermal curing process; therefore, we will test thermal curing at temperatures ranging from 50 to 140°C. A previous study has reported that the gradual increase in thermal curing temperature, up to 200 °C, does not promote phytic acid instability11 due to the partial incorporation of phytic acid into the material structure during the curing process. The monomers synthesized via the one-step approach have produced low-yield pure products, less than 60%12. Accordingly, we propose testing the two-step synthetic method as an alternative strategy to achieve the target monomers at higher yields. A comparative analysis of both methods will be conducted to determine the most cost-effective approach, considering costs and percentage yields.