Esterification of wood

Ami, P.C., Gray, J.D. and Scougall, R.K. (1961a). Chemical modification of wood. 1. Use of trifluoroacetic acid in the esterification of wood by carboxylic acids. Journal of Applied Chemistry, 11, 157-163. 

Matsuda, H., Ueda, M. and Kara, M. (1984a). Preparation and utilisation of esterified woods bearing carboxyl groups. I. Esterification of wood with dicarboxylic acid anhydries in the presence of a solvent. Mokuzai Gakkaishi, 30(9), 735-741. 

Nakagami, T. (1978). Esterification of wood with unsaturated carboxylic acids. V. Effect of deUg-nification treatments on dissolution of wood esterified by the TEAA method. Mokuzai Gakkaishi, 24(5), 318-323. 

Esterification of wood can be carried out through acetylation ( 4, 8, 25 2 6, 28), crotonylation (9), propylation (28), butylation (10) and phthaloylation (27). Reactions with isocyanates also yield a desirable wood product, but isocyanates are highly toxic, expensive and reduce toughness (29). None of the other esterification reactions showed any advantage over acetylation. 

T. Nakagami, H. Amimoto, and T. Yokota, Esterification of wood with unsaturated carboxylic acids. I. Bull. Kyoto Univ. Forest 46 217-224 (1974). 

Matsuda and Ueda [27] also extensively investigated the esterification of wood in order to make a totally thermoplastic material. They esterified wood with a solvent by simply heating wood meal with succinic anhydride for 3 h at temperatures greater than 60°C. The wood meal was readily molded at 180°C under a pressure of 570 kg/cm for 10 min. The moldability of various esterified woods decreased in the following anhydride order succinic anhydride > maleic anhydride > phthalic anhydride. 

Thiebaud S, Borredon ME (1995) Solvent-free esterification of wood with fatty acid chloride. Bioresource Technology 52... 

Chimioselective Esterification of Wood Sterols with Lipases... 

Non-specific esterification of wood sterols can be performed chemically (www. freshpatents.com/Phytosterol-esterification-product-and-method-of-make-same-dt-20070628ptan20070148311.php) however, enzymatic esterification with lipases has the potential advantages of higher specificity and mild reaction conditions which are desirable, both from process and environmental perspectives. More than 20 lipases were previously screened for their ability to catalyze the transesterification of wood sterols and fatty acid esters (Martinez et al. 2004). The goal was now to screen among them those specific for stanol esterification, so as to obtain a product consisting in mostly esterified stanols and mostly free sterols (see Fig. 6.3.4) amenable for separation through short-path distillation. 

Fig. 63.6 Esterification of wood sterols with QLG at optimized conditions 0.03 g enzyme/g wood sterols 5 mol acyl agent/mol wood sterols, 70°C, SOmbar and 0.75 aw- stemols sterols...

We already mentioned in Section 3.5 [70] the partial oxypropylation of cellulose fibres and the interest of the ensuing composite materials in which the unmodified fibre cores represent the reinforcing elements and their thermoplastic sleeves the source of a matrix. Other interesting approaches have been recently put forward to prepare composite materials in which cellulose or one of its derivatives prepared in situ are the only component. Glasser was the first to tackle this problem through the combination of cellulose esters and fibres by two distinct approaches, viz. (i) the incorporation of lyocell fibres into a cellulose acetate matrix [92] and (ii) the partial esterification of wood pulp fibres with -hexanoic anhydride in an organic medium [93] that produced thermally deformable materials in which the thermoplastic cellulose ester constituted the matrix and the unmodified fibres the reinforcing elements. 

The esterification of wood has been investigated very extensively, as recently reviewed [1, 2]. Most of these investigations were carried out in a heterogeneous solid-liquid medium and only a few called upon the use of gaseous reagents. Only the very recent and scientifically relevant studies related to this topic will be reviewed here, since a much more detailed coverage of its historical development is available [8, 9]. 

In addition, the esterification of wood with all the anhydrides studied, except acetic anhydride, has been shown to improve mouldability of wood. The effect of the anhydrides on the mouldability properties decreases in the order succinic > maleic > phthalic anhydride [55]. 

Jebrane, M., Sebe, G. A new process for the esterification of wood by reaction with vinyl esters. Carbohydr. Polym. 72(4), 657-663 (2008)... 

In a typical process for manufacture on a commercial scale bleached wood pulp or cotton linters are pretreated for 12 hours with 40-50% sulphuric acid and then, after drying, with acetic acid. Esterification of the treated cellulose is then carried out using a mixture of butyric acid and acetic anhydride, with a trace of sulphuric acid as catalyst. Commercial products vary extensively in the acetate/ butyrate ratios employed. 

Odour. This aspect is important in resins derived from natural sources. Rosins based on wood and gum rosin retain trace quantities of terpenes and have a piney odour. Tall oil rosins retain the typical sour odour of the rosin. Odour can be removed by steam sparging under vacuum before or during esterification of rosins. Addition of odour masks can also be done. 

The use of maleic anhydride as a compatiblizer between wood particles and bisphenol A-based polyesters resins has been investigated (Han etal., 1991). In this study, the MA was added directly to the composition of woody matrix filler and resin rather than by pre-modification of the wood. It was found that composite properties were improved by addition of MA, probably due to esterification of the wood occurring during the kneading process. The modification of sawdust using maleic anhydride has been performed in order to provide a compatible filler for polyester resins (Marcovich etal., 1996). Modification was performed at room temperature using a solution of maleic anhydride in acetone, in some cases catalysed with sulphuric acid. It was claimed that bonding occurred under these mild conditions from IR spectroscopic evidence only. 

Kiguchi, M. and Yamamoto, K. (1992). Chemical modification of wood snrfaces by esterification III. Some properties of self-bonded benzylated particleboard. Mokuzai Gakkaishi, 38(2), 150-158. 

C17H28O2, Mr 264.41, c7/(j.3 riguaiac wood oil with acetic anhydride and consists of the acetates of the natural sesquiterpene alcohols guaiol and bulnesol (see Guaiac... 

Woods contain a number of acyl (mainly acetyl) groups, and it is probable that these are associated with the xylan components of the hemicellulose fraction. Evidence for the original esterification of aspen-wood xylan comes from the observation that the isolated xylan (obtained by alkaline extraction) is readily cleaved by periodate, whereas only a small proportion of the D-xylose residues in the wood itself are oxidized under similar conditions.66 Hemicelluloses still containing acyl groups may be extracted from wood holocelluloses by means of dimethyl sulfoxide, and further quantities... 

Nevertheless, cellulose fatty esters with low DS values show other qualities, such as a high hydrophobicity. The development of water-repellent cellulosic materials (i.e., cotton, wood), has led to interesting applications in the textile and wood industries. For instance, the direct esterification of timber with fatty acids (and their derivatives) has resulted in extraordinary outdoor durability and resistance to biological attack (e.g. rotting, termites). Industrial exploitation of this technology has recently been conducted in France [WoodProtect by Lapeyre (Magne et al., 2003)]. In this case, the water-repellence conferred to wood and the lack of recognition from predator enzymes account for these properties. 

Glycerol Ester of Partially Hydrogenated Wood Rosin occurs as a medium-hard, pale amber-colored resin (color N or paler as determined by ASTM Designation D 509). It is produced by the esterification of partially hydrogenated wood rosin with food-grade glycerin and purified by steam stripping. It is soluble in acetone, but is insoluble in water and in alcohol. 

Chemical modification reactions continue to play a dominant role in improving the overall utilization of lignocellulosic materials [1,2]. The nature of modification may vary from mild pretreatment of wood with alkali or sulfite as used in the production of mechanical pulp fibers [3] to a variety of etherification, esterification, or copolymerization processes applied in the preparation of wood- [4], cellulose- [5] or lignin- [6] based materials. Since the modification of wood polymers is generally conducted in a heterogeneous system, the apparent reactivity would be influenced by both the chemical and the physical nature of the substrate as well as of the reactant molecules involved. 

This chapter deals with the chemical modification of wood by such methods as etherification, esterification, and thermoplasticization of wood, with emphasis on recent and new research in these fields. 

Introduction of functional groups to wood is mainly achieved in the liquid phase using strong acids, allylation, or esterification. Because wood is a porous and... 

Etherification of Wood. Etherification of wood involves the derivatization of hydroxyl groups to other functional groups. In general, etherification of wood produces more stable bonding and generates lower heat of reaction than esterification. Swelling of wood and formation of sodium salt are commonly applied as a pretreatment prior to etherification. Benzylation, cyanoethylation, allylation, and/or hydroxyethylation are commonly used in the etherification of wood. Some methods of etherification of cellulose may also be applied to wood. 

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