Liquefaction of the Used Creosote-Treated Wood in the Presence of Phenol and Its Application to Phenolic Resin

A limited initial study was made to evaluate liquefaction of creosote-treated southern pine wood sawdust with liquefaction of birch wood powder as a control. The objective was to assess the feasibility of using creo_.._. sot&treated southern pine wood as a raw material for the-formulation-of-phenol-basedresmadhesives-Them liquefaction was conducted in the presence of phenol with sulfuric acid as a catalyst at reaction temperature and time of 150°C and 60 minutes, respectively. Novolac and resole resins were formulated from the liquefied wood, and their physical and mechanical properties of molding compounds made with them were determined. Residues obtained from samples of liquefied creosote-treated wood (5.8%) were significantly lower than those from non-treated birch wood powder (17.3%). Apparently, the residual creosote content of the treated-wood behaved as a reagent co:working with phenol to enhance the liquefaction. The flexural strength and the flexural modulus of moldings made from novolac.resins prepared from liquefied creosotetreated wood were comparable to novolacs made from non-treated birch wood. Bond quality of southern pine plywood made from liquefied creosote-treated wood resin was only slightly lower than plywood made from conventional phenolic resin. Visual examination of the wood failure on broken shear specimens seemed to indicate overpenetration of the resin made from liquefied creosote-treated wood, and it was probably one of the major causes of lower bond quality. Nevertheless, the first attempt to formulate a phenol-based adhesive made from liquefied creosote-treated wood produced encouraging results. With additional studies. of resole formation and glue mix formulations, it is anticipated that a resin adhesive from liquefied creosote-treated wood with improved bond quality can be developed. Introduction ‘Preservative-treated wood products are well known to significantly prolong their service life and thus extend the forest resource and enhance its sustainability. hxvitably however, treated products become unserviceable either due to mechanical damage or failure, biological deterioration, or obsolescence. Disposal of spent preserved wood increasingly has become a major concern because of its residual preservative content. Popular waste disposal options for spent preserved wood, such as combustion and land filling, arebecxmring more and more costly because of increasingly strict regula: tory requirements. Thus, recycling options, particularly the one requiring zero discharge of preservative into waste streams, are of great importance to those concerned with the life cycle management of treated wood. Research in Pineville, Louisiana, laboratory of Southern Research Station has been focused on the development of a closed-loop recycling system (Pig. 1) with recycled composite products and liquefaction as the two key elements in the system. Three major steps toward determining the :echnological practicability of fabricating composite poles from used utility poles were accomplished with the determination of the residual preservative and its distribution (9), evaluation of the effects of residual preservatives on &ability (11) and decay resistance (12), and recycling of out-of-service utility poles for useful engineered wood products (10). This study, however, is the first in a series of studies on the liquefaction of preservative-treated wood. Despite Session 3B: Advances in Wood Adhesive Formulations l 259 recent advancements in techniques of liquefying wood under mild conditions (6,7,13) and its promising potential for turning by-product wood wastes into new products (1,5,6,8,14,15), no study of liquefying preservative-treated wood has been reported. This study covers the evaluation of the liquefaction of two types of preservative-treated wood (i.e., chromated copper arsenate or creosote) using two liquefaction processes (i.e., in the presence of phenol and alcohols). The objective of the study is to develop an economically viable liquefaction process to either convert treated wood waste into useful products or to develop a novel new technique for the separation of residual preservatives from wood. The results of a preliminary study of liquefying recycled southern pine creosote-treated wood are presented in this papen lkxperimental Procedure Materials The recycled creosote-treated southern pine wood sample used in this study was the sawdust collected from sawing of recycled utility poles in a previous study (9). The sawdust, screened through No. 10 sieve (9 mesh), was used without further treatment. Wood meals used in the liquefaction as a comparison were of 20 to 80 mesh size prepared from the birch chips (Bet&u mrudmomawicti Regel). The filler used in the moldings of the phenolic resin was wood powder of 200-mesh pass size. All the other chemicals were of reagent grade and were used as received. Liquefaction of Creosote-‘Ikeated Wood Liquefaction Procedure.-Liquefaction reaction of the recycled creosote-treated wood was conducted as shown in Figure 2. XI prepare liquefied wood, all used creosote-treated wood, phenol, and sulfuric acid (as a catalyst) were placed in a 300 ml three-branch flask equipped with a stirring system and a reflux condenser. To initiate the reaction, the mixture was heated in an oil bath maintained at 150°C. After the desired reaction time, the liquefied product was cooled to room temperature, and then diluted by methanol, followed by the filtration through a Tayo GA1 00 glass filter paper The resulting filtrate was adjusted to a desired volume and Figure l.-Closed-loop recycling system for preservative-treated wood.