Wood as a raw material

Wood remains one of the most versatile, durable and aesthetically pleasing substrates of all building materials. Whilst there have been trends in the growth and utilization of alternative substrates such as UPVC, wood continues to find favour in many applications including both structural and decorative end uses. 

This chapter aims to summarise this subject area, focussing on the most commonly encountered types of wood degrade, their recognition and the range of wood preservative formulations used to prevent degrade. 

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There are not strong reasons therefore for the paper industry to move away from wood as a raw material and, although alternative sources of fibre will probably enjoy a greater share of the pulp market, these will probably continue to be of relatively minor importance. 

All of the studies mentioned are directed to lignins derived from pulp and paper manufacture. This requires that a traditionally conservative pulp and paper industry embark on further development as a chemical producer. However, Helena Chum and her colleagues (Chapter 11) derive their phenolics from lignin by fast pyrolysis of wood rather than as byproducts from the pulp and paper industry. Opportunities might be better for development of adhesives from a chemical manufacturer drawing on waste wood as a raw material much the same as has developed in the production of furan resins derived from agricultural residues described by Bill McKillip (Chapter 29). 

Particleboard or mat-formed composite board is one of the products that can use recycled wood as a raw material. According to questionnaires, recycled wood used in the particleboard industry is estimated to be 20% of the total chips, and the amounts have been increasing. Laboratory scale particleboards were made using recycled P-chip and S-chip to evaluate chip quality. The results showed that the quality of P-chip was equal to that of ordinary chip. Hammer-milled particle from low grade chips can be used as a core material of particleboard. A new type of structural board with three-layer construction was proposed to expand the use of recycled wood chips. 

It was found that three makers among the eleven did not use any recycled wood and that the amount of recycled wood used in four makers through Maker-E to -H was very small. Maker-B and -D, which produced more than one hundred thousand tons of boards, used approximately 20% recycled wood as a raw material. This may be the typical case in the Japanese particleboard industry. 

The importance of wood as a raw material supplying fiber, energy, and chemicals is similar in magnitude to its use as a solid material. Lumber, plywood, and reconstituted boards consume about one-half of the timber... 

Insulation Boa.rd. The panel products known as insulation board were the earliest commodity products made from fibers or particles in the composite panel area. These are fiber-base products with a density less than 500 kg/m. Early U.S. patents were obtained in 1915 and production began soon thereafter. The initial production used wood fiber as a raw material, but later products were made of recycled paper, bagasse (sugar cane residue), and straw. Schematics of the two major processes still ia use are shown ia Figure 4. 

Most of the commercial tree plantations that produce wood for captive use as a raw material in manufacturing operations use a portion as fuel. Examples of short-rotation plantations are Hsted in Table 38 (127). Paper companies in the southeastern United States are reported to have short-rotation plantings also, eg, Weyerhaeuser, James River Corp., Buckeye Cellulose, and Lykes Brothers, but the intensity of maintenance is not known (127). 

Applications. These materials are stiU in developmental infancy. Current production is limited to one commercial process in Europe and a demonstration-scale process in North America. The lignins produced in these processes have potential appHcation in wood adhesives, as flame retardants (qv), as slow-release agents for agricultural and pharmaceutical products, as surfactants (qv), as antioxidants (qv), as asphalt extenders, and as a raw material source for lignin-derived chemicals. 

Furfural is a colourless liquid which darkens in air and has a boiling point of 161.7°C at atmospheric pressure. Its principal uses are as a selective solvent used in such operations as the purification of wood resin and in the extraction of butadiene from other refinery gases. It is also used in the manufacture of phenol-furfural resins and as a raw material for the nylons. The material will resinify in the presence of acids but the product has little commercial value. 

Horns and hooves were the raw materials for the early polymer preparations. These materials were ground up and treated in various ways so that they could be fabricated into such items as combs to use for ladies hair, and other specialty things of that sort. The next development was the use of cellulose from cotton or from wood as the raw material which was studied for making films and fibers. Work on the cellulose structure had provided information that it was a hydroxylated product, and by converting the hydroxyls to esters, the natural cellulose could be turned into a soluble material, which was spun into fibers and cast into films to make the first cellulose rayon-type material and cellulose films. 

Throughout human history a limited number of fibers provided the fabric used for clothing and other materials—wool, leather, cotton, flax, and silk. As early as 1664, Robert Hooke speculated that production of artificial silk was possible, but it took another two hundred years before synthetic fibers were produced. The production of synthetic fibers took place in two stages. The first stage, started in the last decades of the nineteenth century, involved chemical formulations employing cellulose as a raw material. Because the cellulose used in these fibers came from cotton or wood, the fibers... 

As a raw material for large-scale nitration, cellulose from cotton, alfalfa and wood pulp is used. Cellulose from annual or biennial plants such as nettle or cereals (straw pulp) etc. is seldom used. 

The question of substituting wood pulp cellulose for cotton as a raw material in the production of nitrocellulose arose at the beginning of the present century due to-the big increase in nitrocellulose manufacture, which was followed by an expansion in the demand for cotton. 

On a heavy tonnage basis, cellulose is important as a raw material in the production of wood pulp and paper. See also Papermaking and Finishing. 

The natural fibers obtained from cotton, wood, flax, hemp, and jute all are cellulose fibers and serve as raw materials for the textile and paper industries. In addition to its use as a natural fiber and in those industries that depend on wood as a construction material, cellulose is used to make cellulose acetate (for making rayon acetate yarn, photographic film, and cellulose acetate butyrate plastics), nitric acid esters (gun cotton and celluloid7), and cellulose xanthate (for making viscose rayon fibers). The process by which viscose rayon is manufactured involves converting wood pulp or cotton Iinters into cellulose xanthate by reaction with carbon disulfide and sodium hydroxide ... 

The production of millions of tons of paper annually requires a capital intensive industry. A modern pulp and paper facility such as the Leaf River Mill shown in Fig. 1 can cost in excess of 800 million to construct. Pulp and paper manufacturing throughout the world is a vast industry, with production levels approaching 300 million tonnes/year. The dominant pulp and paper producing countries include Canada, Sweden, Finland, Japan, Brazil, and Russia. The pulp and paper industry is typically located near convenient, low-cost sources of wood as the raw material. 

In principle, most types of biomass can be used as a raw material in the pyrolysis process [14]. Most of the research has been carried out using different wood as feedstock, although more than 100 different types of biomass have been tested [14]. Besides wood, these materials include forest residues, such as bark black liquor and agricultural residues such as straw, olive pits, and nut shells [12, 14], Additionally, pure biological polymers cellulose (linear polymer of D-glucose units), hemicellulose (heteropolymers of different hexoses and pentoses), and lignin (heteropolymer of p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol [19]) - have been tested as raw materials in the pyrolysis. 

Chip makers dealing with waste wood produced about 1.8 million tons per year, and about 70 % of chips were for fuel and about 30% were recycled as a raw material in the paper and board industries (4). The amount of reuse of waste wood was very small compared with the generation. Particleboard or mat-formed board is a product that can use recycled wood (5) (6). Thus, the problems of recycled wood for board making was discussed in this paper. 

Problems on recycled wood when used as a raw material in PB production were analyzed according to the questionnaire survey from the eleven makers. Problems can be classified into eight items, and the results of the importance calculated numerically with some assumptions are shown in Figure 4. 

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