Wood production

An extremely important safety issue with respect to ah. wood product manufacturing processes is personal worker safety. Ah of the processes use much moving machinery, usuahy including many saws or knives. Workers must continuahy remember the inherent dangers these machines involve as weh as other possible dangerous situations which could result from malfunctions or other errors. In addition, most processes are more or less dusty and noisy. Most employers require use of safety glasses and many require hearing protection, safety shoes, and hardhats as weh as other kinds of protection needed for Specific jobs. 

Standard Test MethodforDeterminingFormaldehjdeEevels from Wood Products Under Defined Test Conditions Using aEarge Chamber ASTM E1333-90, American Society for Testing and Materials, Philadelphia, Pa., 1990. 

Rigid vinyl foams ia constmction markets have grown substantially due to improved techniques to manufacture articles with controlled densities and smooth outer surfaces. Wood mol ding substitute for door frames and other wood products is an area that has grown. Rigid vinyl foams are also used ia the manufacture of pipes and wines as resia extenders and ia sidings and wiadows as the replacement of wood or wood substitutes. 

Fomialdehyde is a basic chemical budding block for the production of a wide range of chemicals finding a wide variety of end uses such as wood products, plastics, and coatings. Table 6 shows the distribution of formaldehyde production in the United States from 1966 through 1989 (115). Production percentages reported in the following discussion are for the United States. 

Amino and Phenolic Resins. The largest use of formaldehyde is in the manufacture of urea—formaldehyde, phenol—formaldehyde, and melamine—formaldehyde resins, accounting for over one-half (51%) of the total demand (115). These resins find use as adhesives for binding wood products that comprise particle board, fiber board, and plywood. Plywood is the largest market for phenol—formaldehyde resins particle board is the largest for urea—formaldehyde resins. Under certain conditions, urea—formaldehyde resins may release formaldehyde that has been alleged to create health or environmental problems (see Amino RESINS AND PLASTICS). 

Miscellaneous. The reaction products of sahcylaldehyde with certain compounds containing active methylene groups, eg, acetylacetone, are excellent uv absorbers. Films containing these compounds can be used as uv filters to protect light-sensitive foods, wood products, paper, dyes, fibers, and plastics (95). 

When heated with small amounts of iodine, rosins, taU. oil, and other wood products are converted to more stable forms (135,136). Iodine has been used with some tin salts as a catalyst in the hydrogenation of coal (qv) and its distillation products (137,138), and has been recommended as a catalyst for the production of drying oils (qv) from unsaturated animal fats (139,140). 

Wood is the original source of 99% of the pulp fiber produced in the United States. Although virtually any wood can be pulped by some process, there are certain species commonly used for pulp because of desirabiUty of fiber, ease of pulping, availabiUty, or less competition with other wood products. The common pulpwoods in the United States are Hsted in Table 1. 

Water-borne adhesives are preferred because of restrictions on the use of solvents. Low viscosity prepolymers are emulsified in water, followed by chain extension with water-soluble glycols or diamines. As cross-linker PMDI can be used, which has a shelf life of 5 to 6 h in water. Water-borne polyurethane coatings are used for vacuum forming of PVC sheeting to ABS shells in automotive interior door panels, for the lamination of ABS/PVC film to treated polypropylene foam for use in automotive instmment panels, as metal primers for steering wheels, in flexible packaging lamination, as shoe sole adhesive, and as tie coats for polyurethane-coated fabrics. PMDI is also used as a binder for reconstituted wood products and as a foundry core binder. 

Wood is an important natural resource, one of the few that are renewable. It is prevalent ia our everyday Hves and the economy ia wood-frame houses and furniture newspapers, books, and maga2iaes bridges and railroad ties fence posts and utiUty poles fuelwood textile fabrics and organic chemicals. Wood and wood products are also a store for carbon, thus, helping to minimise carbon dioxide ia the atmosphere. 

Production and consumption of wood products and residues are measured ia various units, based on common usage and their metric equivalents (2—4). Pulpwood logs and fuelwood are commonly measured ia cords. A cord refers to a stacked pile of wood, with outside dimensions of 4 by 4 by 8 ft (1.22 by 1.22 by 2.44 m) and a volume of 128 ft (3.62 m ). The weight of a cord depends on density of wood and bark and on moisture content. In the United States, it can range from 1.3 to 1.7 short tons (1.2 to 1.5 metric tons), air dried. 

Roundwood equivalent is also sometimes used. It refers to the volume of logs or other round products required to produce a given quantity of lumber, plywood, wood pulp, and other wood products (2). Roundwood equivalents may be used ia assessiag the overall wood resource supply and demand or ia comparing wood products measured ia different units. 

The surface burning characteristics (flame spread index and smoke developed index) for wood and wood products as measured by American Society for Testing and Materials (44) can be reduced with fire retardant treatments, either chemical impregnation or coatings (48). Fire retardant treatments also reduce the heat release rate of a burning piece of wood (49,50). The heat release rates (51) of the burning materials are an important factor in fire growth. 

Wood is one of our most important renewable biomass resources. Unlike most biomass sources, wood is available year round and is more stable on storage than other agricultural residues. In the United States, wood residues from iadustrial by-products totaled 60.8 x 10 metric tons ia 1993 (73). Increasiagly, residues are iacorporated iato manufactured wood products and are used as a fuel, replacing petroleum, especially at wood-iadustry plants (73) some is converted to charcoal but most is used ia the pulp and paper iadustry. Residues are also available for manufacturiag chemicals, generally at a cost equivalent to their fuel value (see Fuels frombiomass Fuels fromwaste). 

In 1991, timber-related secondary products manufacturing industries added an estimated 40,128 million of value to primary timber products (Table 11). Most of the timber-related value added (63%) originated in the paper and aUied products industry. The lumber and wood products industry added nearly 37% of total timber-related value added. Less than 1% was from chemicals and aUied products. 

Region Principal Group 24 (Lumber and wood products) Principal Group 26 (Paper and aUied products) Principal Group 28 (Chemicals and aUied products) Total... 

The predominant use of arsenic ia the United States is ia the manufacture of chemicals. During the 1980s, the market for arsenic chemicals had shifted from cotton farming, where its use is now restricted because of environmental considerations, to wood (qv) preservatives for the protection of lumber and other wood products. Arsenic trioxide is the basic commodity of commerce from which a number of important chemicals are manufactured. 

Inorganic boron compounds are generaHy good fire retardants (59). Bode acid, alone or in mixtures with sodium borates, is particularly effective in reducing the flammabHity of ceUulosic matetials. AppHcations include treatment of wood products, ceUulose insulation, and cotton batting used in mattresses (see Flame retardants). 

Wood (qv) is arguably the oldest building material used by humans to constmct their dweUings. It is a natural product obtained from trees, used in both stmctural and decorative appHcations. The chemical composition of wood is largely cellulose (qv) and lignin (qv). Today there are a variety of composite or reconstituted wood products, such as plywood, particle board, wood fiber boards, and laminated stmctural beams, where small pieces of wood or wood fiber are combined with adhesives to make larger sheets or boards (see Laminates). 

The value of lumber produced in 1989 was estimated to be 17.3 biUion, of which softwood lumber represented about 58%. The other 42% was composed of hardwood lumber (12%), woodchips (10%), and a variety of wood products (20%). 

Reconstituted Wood Products. This category includes three general varieties wood flake board, particle board, and wood fiberboard. The manufacturiag processes are similar for all these products except for the size of the wood particles that are glued together. 

Urea—formaldehyde (UF) resias commonly were used ia the past. However, because of the lack of moisture resistance and the potential for the resias to hydroly2e ia the presence of moisture and decompose iato urea and formaldehyde, they are not used as much now. Governmental regulations are under development that eliminate the use of UF resia ia wood products. This would limit the exposure of the pubHc to formaldehyde, a Hsted carciaogen, formed by the decomposition of UF resia. Today most wood products use pheaol—formaldehyde (pheaoHc) resias, but urethane-based resias are becoming more common. 

Amino Resins. Amino resins (qv) include both urea- and melamine—formaldehyde condensation products. They are thermosets prepared similarly by the reaction of the amino groups in urea [57-13-6] or melamine [108-78-1] with formaldehyde to form the corresponding methylol derivatives, which are soluble in water or ethanol. To form plywood, particle board, and other wood products for adhesive or bonding purposes, a Hquid resin is mixed with some acid catalyst and sprayed on the boards or granules, then cured and cross-linked under heat and pressure. 

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