Wood pressure process

The advances made in enzymatic hydrolysis of cellulosic materials (14) are also of interest. This technology involves only moderate temperature processes in simple equipment which promises to be of significantly lower capital cost than the pressure equipment associated with conventional acid wood hydrolysis processes. All of these considerations combined to lead us to study processes for ethanol production from wood, especially in an effort to obtain data for material and energy balances, and possibly for the economics. 

The high loading required (2 to 6 pounds of dry chemical per cubic foot of wood) for chemicals in present use puts a severe limitation on cost of usable treatments. A higher cost treatment could be tolerated if it proved more efficient. A large part of the cost of treated wood to the consumer is the full-cell pressure process required by present-day formulations. A less costly method of getting the chemical into the wood is needed. 

The commercial treatment of wood is most commonly done by one of the pressure processes, as they give deeper penetrations and more positive results than any of the nonpressure methods. The wood, on steel cars, is run into a long horizontal cylinder, which is closed and filled with preservative. Pressure is applied, forcing the preservative into the wood. 

The impregnation methods are similar to those employed for the preservative treatment of wood by water-borne salts using pressure processes. The maximum temperature of the solution must not exceed 140°F for formula-... 

AWPA (1997) Glue laminated timher-preservative treatment hy pressure processes. Standard C 28. WtAWPA Book of Standards. American Wood Preservers Association, Granhury, Texas... 

Type of adhesive Adhesives based on different adhesive raw materials with special processing properties (e.g., hot-melt adhesives, pressure-sensitive adhesives), different purposes of use (e.g., wallpaper paste, wood glue), processing temperatures (e.g., cold glue, heat-curing adhesives), availabilities (e.g., adhesive films, solvent-based adhesive). 

As an alternative to the conventional polyethylene glycol (PEG) treatment of waterlogged wood see Chapter 8), attempts were made in 1966-1967 to apply a radiation-curing process (i, 2). The aim was to reduce treatment time and achieve more stability for treated objects subjected to interior climatic changes. The impregnation of waterlogged wood by immersion involves a liquid-liquid exchange process. Dry wood was directly bulked by monomers by a vacuum-pressure process. 

Some special types of foams are (1) structural foams (2) syntactic foams and multifoams and (3) reinforced foams. Structural foams (Figure 2.58c and d), which possess full-density skins and cellular cores, are similar to structural sandwich constructions or to human bones, which have solid surfaces but cellular cores. Structural foams may be manufactured by high pressure processes or by low-pressure processes (Figure 2.61). The first one may provide denser, smoother skins with greater fidelity to fine detail in the mold than maybe true of low-pressure processes. Fine wood detail, for example, is used for simulated wood furniture and simulated wood beams. Surfaces made by low-pressure processes may, however, show swirl or other textures, not necessarily detracting from their usefulness. Almost any thermoplastic or thermosetting polymer can be formulated into a structural foam. 

Since the 1940s, lumber producers and manufacturers have been using a chemical compound mixture that contains inorganic arsenic, copper, and chromium, called chromated copper arsenate (CCA) as a wood preservative. CCA is usually injected into wood by a high pressure process to saturate wood products with the chemicals, to produce pressure-treated lumber (between 75 and 90% of the arsenic used in the US is estimated to be used for wood preservation). 

Figure 2 Emission from Vacuum Pressure Wood Treatment Process.

Pressure Process. These processes produce relatively deep penetration of the preservative into the wood. Although various processes differ in detail, the basic principle of aU is the same— wood is placed in a pressure vessel that is filled with preservative. Pressurization then drives preservative into the wood to meet penetration and retention specifications. 

Green wood can be impregnated by immersion in aqueous PEG solution over a period of several weeks. Air-dried wood is best treated in a combined vacuum-pressure process. For example, beechwood can be made almost completely dimensionally stable by immersing it in an approximately 50% solution of PEG 1500 so that it absorbs about 45% PEG. The process has two advantages [116—119] ... 

The impregnation methods are similar to those employed for the preservative treatment of wood by water-borne salts using pressure processes. The maximum temperature of the solution must not exceed 140°F for formulation Types A, B, and D, and must not be over 160°F for Type C. After treatment, the wood must be dried to remove the water solvent to a moisture content of 19 percent or less. For most uses, the wood is kiln-dried to a moisture content of under 10 percent. 

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