Final Report: Development of Micronized Polyurethane as a Comprehensive, 100 Percent Recycled Resin for Green Building Materials and SystemsEPA Contract Number: EPD10037
Title: Development of Micronized Polyurethane as a Comprehensive, 100 Percent Recycled Resin for Green Building Materials and Systems
Investigators: Villwock, Robert
Small Business: Mobius Technologies, Inc.
EPA Contact: Richards, April
Project Period: March 1, 2010 through August 31, 2010
Project Amount: $69,760
RFA: Small Business Innovation Research (SBIR) - Phase I (2010) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Green Buildings
Engineered wood products, such as plywood and oriented strand board (OSB), represent a large and growing segment of the building materials market. They are versatile, inexpensive, and fit well within a sustainable forestry strategy of tree farms based on rapidly growing, readily replenished crops. However, engineering wood requires the use of synthetic resins whose manufacture has negative environmental impacts. These resins, such as polymeric methylenediphenylisocyanate (pMDI), are petroleum-derived chemicals, and their manufacture releases greenhouse gases, uses large volumes of process water, and requires significant energy investment.
Mobius Technologies has developed a patent-pending method of using finely ground waste polyurethane foam as a co-binder resin that can replace some pMDI in the manufacture of OSB. This recycled product can be post-consumer or post-industrial, and has been called micronized polyurethane, or MPU. MPU may be produced from waste polyurethane foams by a chemical-free, mechanical grinding process, commercialized by Mobius Technologies in the late 1990s, which requires a modest energy investment of 2 MJ/kg MPU. This energy investment is a mere 2% of the embodied energy invested in the original production of the polyurethane.
Replacement of pMDI with MPU reduces the environmental impact of pMDI manufacture, diverts waste polyurethane from landfills, and reduces OSB manufacturing costs. However, use of MPU has so far been limited to partial replacement of pMDI in only the surface layers of OSB, due to the time and temperature required to activate the MPU resin in the OSB process. Extending the ability to use more MPU in surface layers, and also to include the core layer, stands to roughly double the amount of pMDI that can be replaced, which would significantly compound the environmental benefits.
The primary objective of this Phase I research project has been to determine the feasibility of using catalytic additives together with MPU to displace significantly greater amounts of polymeric pMDI as a binder in the manufacture of OSB. A specific Phase I objective has been to select and test several candidate catalytic additives, then downselect and optimize a single reagent. Looking ahead, the broader objective of this work is to extend the use of MPU to include the core layer of OSB as well as the surface layers, by means of identifying catalytic additives that promote the activation of MPU as a binder.
The key innovation is to essentially unmanufacture the polyurethane material from recycled foam, and to do this in place during the manufacture of OSB. The polyurethane reverts to isocyanate chemicals, which then are available to bind wood strands together in the same fashion as does pMDI. Mobius Technologies has sought the key catalytic additives that promote this unmaking of polyurethane, and expect that these additives will unlock a large opportunity for both environmental benefits and reduction in manufacturing costs for OSB.
An extensive literature review focused on the likely mechanisms of binding activity by MPU, and explored known catalysts that potentially could promote those mechanisms. An initial list of nine candidate catalytic additives was identified, with the candidates grouped into three broad categories. The candidate catalytic additives were chosen based on considerations of likely effectiveness, cost, availability, and compatibility with the OSB manufacturing process.
Initial testing to screen the catalytic additives was comprised of remolding MPU into plaques under elevated temperature and pressure. The resulting materials were tested for internal bond strength. By identifying the additives that produced a significant increase in strength relative to unmodified MPU, the list of candidate materials was narrowed to three. Additional testing was done to explore concentration and temperature effects for the remaining candidate additives.
A single best candidate material was identified. This catalytic additive was able to increase the strength of remolded MPU by more than 70% at process temperatures of 135°C, and by more than 200% at process temperatures of 110°C. Comparable temperatures are reached in the OSB manufacturing process.
The catalytic additive identified in this work shows great promise for increasing the replacement of pMDI binder with ground recycled polyurethane foam, both in the surface and the core layers of OSB. Phase I research has demonstrated that it is feasible to identify and use catalytic additives to improve the reactivity of MPU at elevated temperatures. Based on these results, and Mobius Technologies' experience with using MPU to displace pMDI in OSB manufacture, it is clearly feasible to displace significantly greater amounts of pMDI as a binder in the manufacture of OSB.
Mobius Technologies has been working with OSB manufacturers and currently has ongoing, productive relationships with at least two major producers. Industrial trials on full-scale board manufacturing lines are planned, and there is a clear path to commercialization of the technology in the engineered wood industry should those trials show success.
Progressively longer production trials using the innovations from this research will provide opportunities for realistic assessment of the relative costs of using activated MPU versus standard pMDI resin, as well as for testing the mechanical properties of the product as produced under fully realistic conditions.
OSB is used for flooring, roofing, and sheathing applications where strength, dimensional stability, and low weight are desirable attributes. The market for OSB in the construction industry has grown dramatically in the past 30 years as OSB has gained acceptance and been demonstrated to perform as well as plywood but at a lower cost. In 1980, North American OSB panel production (on a 3/8" basis) was 751 million square feet (0.7 million m3). By 1990, this figure was an order of magnitude larger, at 7.6 billion square feet (7.0 million m3). In 2005, this figure had grown to 25.0 billion square feet (22.1 million m3). OSB also is produced in Europe and Latin America, with a combined approximate production figure of 3.5 billion square feet (3 million m3) by the year 2005 (http://osbguide.tecotested.com/osbfacts).