Development of cardanol-bonded cellulose thermoplastics: high productivity achieved in two-step heterogeneous process

Abstract

We developed a heterogeneous process with low energy consumption to synthesize novel high-strength and heat-resistant cellulose-based bioplastics: cellulose esters bonded with a short chain component (acetic acid) and a long one (3-pentadecylphenoxy acetic acid; PAA), which is a derivative of cardanol, extracted from cashew nut shells. Although we recently showed that PAA-bonded cellulose acetates (cardanol-bonded cellulose resins) exhibit highly practical properties for durable products, they were synthesized in a homogeneous process, which requires large quantities of poor solvents to isolate the resins. In the developed two-step heterogeneous process, the cardanol-bonded cellulose resins are produced without poor solvents. In the first step, cellulose is esterified with limited amounts of the long and short chain components using a selected reaction solvent and catalyst. The resultant intermediate products are adequately swollen in the solvent then efficiently recovered by filtration. In the second step, the short chain component is additionally bonded to attain good thermoplasticity of the final products, which are readily recovered only by distilling a solvent and the remaining short chain component. The solvent usage was reduced by approximately 90 % compared with a homogeneous process, which leads to a large reduction in energy. The produced cardanol-bonded cellulose resins exhibited higher thermoplasticity, elastic modulus, water resistivity, and close heat resistivity compared to that of a homogeneous process. Furthermore, the mechanical and thermal characteristics of the resins were greatly improved by adding a specific polyester, polybutylene succinate adipate, and glass fiber, reaching high-level target properties for durable products.

Long/Short Chain Mixed Cellulose Esters: Effects of Long Acyl Chain Structures on Mechanical and Thermal Properties

“…The cellulose powder was 10–50 μm in diameter and 100–500 μm long. We synthesized 3-pentadecylphenoxy acetic acid (PAA), which is hydrogenated and carboxymethylated cardanol, as previously reported . The scheme for the synthesis of PAA is shown in Scheme S1 of the Supporting Information.…”

“…We synthesized 3-pentadecylphenoxy acetic acid (PAA), which is hydrogenated and carboxymethylated cardanol, as previously reported. 21 The scheme for the synthesis of PAA is shown in Scheme S1 of the Supporting Information. Acetic anhydride, DMAc, and LiCl were used as supplied by Kanto Chemical Co., Inc. without any further purification.…”

Solvent-free modification of lignocellulosic wood pulp into a melt-flowable thermoplastic

“…Chemical modifications can interfere with these hydrogen bonds and simultaneously introduce side groups along the cellulose backbones, which improve chain flexibility and thus afford thermoplasticity (Yan et al 2009;Toyama et al 2015;Larsson and Wågberg 2016;Huang et al 2016a;Chen et al 2018). However, the manufacturing of current cellulose thermoplastics like cellulose acetate, cellulose acetate propionate or cellulose acetate butyrate is costly, especially as compared with competitive petroleum-based thermoplastics (Edgar et al 2001).…”

Novel Thermoplastic Cellulose Esters Containing Bulky Moieties and Soft Segments

“…Unfortunately, the inevitable migration of the external plasticizers will weaken the performance and decrease the lifetime of the cellulose plastics. ,, It seems that cellulose long-chain aliphatic esters can solve this dilemma because the long-chain fatty acid groups not only disrupt the hydrogen bonds in cellulose but also act as internal plasticizers. − However, it is difficult to synthesize cellulose long-chain aliphatic esters because of the poor reactivity and steric effect of the long-chain fatty acyl chloride or long-chain fatty acid. To increase the reaction rate and transformation efficiency, high reaction temperatures, long reaction times, basic catalysts, or/and special acylation reagents are often employed. − However, these conditions can cause serious degradation of the cellulose, and they can make the process more expensive and tedious. In addition, polylactic acid (PLA) − and polycaprolactone (PCL) − grafted onto cellulose can also serve as an efficient internal plasticizer.…”