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Development of rigid polyurethane foam from kraft lignin and renewable source chain extenders: application as a thermal insulator


The appreciation of Lignin Kraft, through its conversion into products with high added value, has been motivated and investigated in technological research centers, universities and industries. It is estimated that 50 million tons of Kraft lignin are generated annually as a by-product from pulp and paper manufacturing, of which approximately only 2% is used for industrial products, the remainder being incinerated for energy generation. In addition to its large-scale availability, the functional groups present in the lignin structure (aromatic and aliphatic hydroxyls, carbonyl) make it an interesting raw material alternative for the development of polymers, such as polyurethanes (PU), phenolic resins and epoxies. The development of rigid PU foams from lignin is favored by the abundant presence of aromatic rings in the lignin structure. However, the low reactivity of its aromatic hydroxyls and its reduced solubility require a previous modification of lignin structure, in order to synthesize rigid foams with suitable properties, such as thermal conductivity, distribution and cell size, and mechanical behaviors. This work aims to develop rigid polyurethane foams from lignin, combined with modified oils from renewable sources as chain extenders for polyols manufacture. However, in this PIPE - PHASE 1 only lignin and vegetable oils modifications methods will be assessed as polyol for rigid foams production. Initially, the lignin will be chemically modified to increase its reactivity and solubility. Lignin modifications will be supported by methods presented in the literature, including: depolymerization, reactions with propylene oxide and propylene carbonate. Subsequently, modified lignin and modified vegetable oils (castor oil and castor oil fatty acid) blends will be obtained to optimize polyols properties and, consequently, PUs properties. The characterization of these polyols obtained in PHASE 1 will be carried out by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), rotational viscosimetry, titration for hydroxyl level determination and stability analysis of the blends (phase separation). If the results expected in this first phase are feasible, the rigid foam developed later (PIPE - PHASE 2) must present the required performance levels in thermal insulation applications, i.e., low shrinkage during curing, thermal conductivity between 0.02 and 0.05 W / (m K) and density between 30 and 50 kg. m-3. In this way, it is expected to obtain rigid foams that fulfill the necessary requirements for thermal insulation applications for chambers and refrigerated trucks, as well as for specific areas of civil construction. The rigid polyurethane foam market is the second largest in income in the world, losing only for flexible foams applications, in volume. In the second quarter of 2018, the company Suzano Papel e Celulose, which supports this project, will start the industrial production of lignin, with an annual volume of 20 thousand tons. The expected low-cost of Suzano´s lignin will allow the development of rigid foams with competitive cost and suitable properties. This project implies the reuse of a large scale industrial waste, indirect jobs creation, innovative development of a sustainable production and establishment of a new company developing sustainable products. (AU)

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