Allylated wood

Etherification to produce cyanoethyolated, benzylated or allylated wood surfaces does not result in an improvement in UV resistance, but the latter two treatments have been found to improve the performance of clear coatings on the modified substrate (Kiguchi, 1990b). Kalnins (1984) methylated wood by pre-treating with concentrated aqueous... 

The production of MDF from allylated wood fibres has also been reported (Ogawa and Ohkoshi, 1997). The IBS of the 4 mm thick boards was superior to control boards (unmodified fibres bonded with PF resin), provided that the temperature of the allylation reaction and board density was sufficiently high. The MOR was markedly inferior to that of control boards in all cases (c. 10 MPa for allylated compared with c. 60 MPa for controls, at a board density of 800 kg m ). Blending of the allylated fibres with acetylated fibres caused a decrease in IBS, but did not affect MOR. It is perhaps significant that no free-radical initiator was used during hot-pressing in either study, which may account for the lack of reactivity of the allylated surfaces. 

The possibility of using graft polymerization of styrene on to allylated wood to provide covalent bonding between surfaces was also investigated (Ohkoshi, 1991). In this case, a free-radical initiator (BPO) was present in the styrene monomer that was used to impregnate the allylated wood, prior to hot-pressing. Bond strength was determined by... 

Shiraishi and Goda [16] reported that allylated wood meals were given thermoplastic properties by blending with appropriate synthetic polymers or low molecular weight plasticizers such as dimethylphthalate or resorcinol. Mere allylation did not render wood thermally meltable. Films from the allylated wood-polyethylene and allylated wood-polypropylene (1 2) blends exhibit tensile strengths of 92.2 and 159.0 MPa and elongations of 14.6 and 3.8% respectively, [16]. 

Carboxymethylated wood, allylated wood, and hydroxyethylated wood have been liquified in phenol, resorcinol, or their aqueous solutions and formalin after standing or stirring at 170 C for 30-60 min [3]. 

The second method for liquefaction makes use of solvolysis during the process [8,11]. By using conditions which allow phenolysis of part of the lignin, especially in the presence of an appropriate catalyst, the liquefaction of chemically modified wood into phenols could be accomplished under milder conditions (at 80 C for 30-150 min). Allylated wood, methylated wood, ethylated wood, hydroxyethylated wood, acetylated wood, and others have been found to dissolve in polyhydric alcohols such as 1,6-hexanediol, 1,4-butanediol, 1,2-ethanediol, 1,2,3-propanetriol (glycerin), and bisphenol A using the liquefaction conditions just described. Each of them caused partial alcoholysis of lignin macromolecules [4]. 

Figure 4 IR spectra of allylated wood copolymerized with styrene. WPG, Weight percent gain due to allylation. Note (a) allylated wood (b-d) allylated woods copolymerized with styrene (e) alkalinepretreated woods copolymerized with styrene. (From Ref. 13.)...

Figure 5 Wet shearing strength of styrene-grafted allylated wood. (From Ref. 13.)...

Figure 11 Contact angle of a water drop on etherified wood surfaces after wet and dry cycle testing. BE, Benzylated wood AL allylated wood CE, cyanoethylated wood. Note wet and dry cycle test was soaking in water and drying at 60°C for 24 h. (From Ref. 3.)...

Figure 14 Changes in the glossiness and color difference of etherified Sugi surfaces during UV irradiation. O, Cyanoethylated wood A, allylated wood , benzylated wood , untreated wood A, acrylic urethane resin-coated wood , acrylic silicon resin-coated wood. Note UV lamps were high-pressure mercury lamps with 80 W/ cm. Coatings were transparent. (From Ref. 30.)...

Allylated wood 138.1 Poor 14-33 49 Good Medium 0.30 Light white... 

The next study of wood modification was that reported by Baird (1969), who performed vapour-phase reactions of spruce with ethyl, n-butyl, /-butyl, allyl and phenyl isocyanate (PhNCO). Unfortunately, DMF was used as a catalyst for the reactions, which resulted in polymerization of PhNCO in the cell wall of the wood, leading to unpredictable results. No evidence was presented in support of the contention that polymerization had occurred, and since this requires an anionic catalyst initiator, this is considered unlikely. However, the presence of side reactions when DMF is used in conjunction with isocyanates has already been mentioned. Greater success was reported when butyl isocyanate was reacted with wood (presumably a consequence of the lower reactivity of this isocyanate... 

Kenaga, D.L. and Sproull, R.C. (1951). Further experiments on dimensional stabilization of wood by allylation. Journal of the Forest Products Research Society, 1, 28-32. 

Matsuda, H., Ueda, M. and Mori, H. (1988c). Preparation and crosslinking of ohgoesterified woods based on maleic anhydride and allyl glycidyl ether. Wood Science and Technology, 22( 1), 21-32. 

Ohkoshi, M. (1991). Bonding of wood by thermoplasticizing the surfaces II. Possible crossUnking of wood by the graft-copolymerizing of styrene onto allylated surfaces. Mokuzai Gakkaishi, 37(10), 917-923. 

The second method of dissolution is based on solvolysis (Solvolysis method) (6,7,11,12). Under milder conditions (80°C for 30 to 150 min) phenolation was accomplished with an appropriate catalyst, and the chemically modified wood was dissolved in phenol (11). Under similar conditions, woods derivatized by allylation, methylation, ethylation, hydroxylation and acetylation have also been found to dissolve in polyhydric alcohols, such as... 

The use of mixtures of glycerol and formic acid for the preparation of allyl derivatives (allyl ch oride and allyl formate) has recently been described by Aschan.2 Allyl alcohol has also been isolated from crude wood alcohol.3 A special method for titrating allyl alcohol has been described.4... 

Methanol, also called methyl alcohol and once commonly know as wood alcohol, is a clear, volatile liquid mp, -98°C bp, 65°C). Until the early 1900s, the major commercial source of methanol was the destructive distillation (pyrolysis) of wood, a process that yields a product contaminated with allyl alcohol, acetone, and acetic acid. Now methanol is synthesized by the following reaction of hydrogen gas and carbon monoxide, both readily obtained from natural gas or coal gasification ... 

Patel/ J.M., J.C. Wood, and K.C. Leibman. The biotransformation of allyl alcohol and acrolein in rat liver and lung preparations. Drug Metab. Dispos. 8 305-... 

Recently, Shiraishi and Goda [161 studied allylation of wood meal with allyl chloride or allyl bromide [Reaction (3)]. 

In this case, the wood meal was pretreated with a NaOH aqueous solution. It was found that allyl bromide gave better results than allyl chloride. That is, by using allyl bromide, WGs of 22-28% were obtained under mild conditions of 60-80°C for 2 h, whereas higher temperatures (above 90°C) were needed to obtain the same WGs in the case of allyl chloride. 

Similarly, surfaces of wood blocks [9,10] and wood chips [10,17], pretreated with NaOH aqueous solution, have been allylated with allyl bromide. The allylated surfaces could be self-bonded by hot-pressing without using any adhesives. 

Kiguchi [ 10] reported that hot-melted wood surfaces treated by benzylation and allylation lost surface glossiness by weathering because of the benzyl or allyl groups induced by the etherification of the surfaces. These groups can absorb ultraviolet rays and degrade the surfaces. As a result of ESC A, the... 

More recently, Ohkoshi et al. [103] studied the mechanism of thermoplasticization of wood by allylation. They considered that decrystallization of cellulose within wood during allylation permits the wood to soften thermally and the allylated lignin within wood increases the softening through acting as a plasticizer. 

Figure 3 Relationships between the weight percent gains due to allylation and the grafting ratios of styrene on wood meal. Note copolymerized at lOO C for 2 h using BPO 0.041 mol/L as an initiator. (From Ref. 13.)...

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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