Pitch, wood

Pitch is the residue after the distillation of volatile resin components in an open vessel. The material is typically black and is referred to as pix by Roman writers (I). When obtained from pine resin, it may be called pine pitch when obtained from other plant resins, it may be called more generally wood pitch. 

The potentially depositable material may exist in the form of colloidal particles. The size of these particles is, for natural wood pitch, slightly below 1 p with a distribution up to a few miCTons. For depositable material of synthetic origin particle size may be considerably bigger. 

Today no chemical additives are used to modify the viscosity of the organic material of natural origin (wood pitch) to reduce deposition. Water-insoluble solvents, that would reduce the viscosity, can conceivably be used reducing the viscosity of the resin. The use of kerosene for pitch control, a method used half a century ago, worked by this mechanism. 

The forces of adhesion and autohesion may be reduced by hy-drophobization of the powder surface ( 10), thus increasing the free-running properties. Hydrophobization of the surface of sand may be effected by treatment with suspensions or solutions of wood pitch [447]. 

In a recent study, the authors studied a model system relevant to lipophilic wood pitch in mechanical pulp and further manufacturing of wood-containing paper [24]. Wood pitch, which is colloidally dispersed as a dilute emulsion of pitch droplets, was analysed for the distribution of resin and fatty acids between the lipophilic phase, mainly composed of triglycerides and steryl esters, and the water phase in the pH range 3-11. The study aimed at obtaining better understanding of the behaviour of pitch in pulp and paper mills. These phenomena are important with regard to pitch removal, but have implications also on the formation of sticky pitch deposits on paper machines, and even on the properties of the produced paper. 

Figure 3.4 Distribution of resin acids and fatty acids between lipophilic phase and water phase at 50 °C and tow NaCt concentration in wood pitch emulsion.

Figure 3.5 Distribution of abietic acid and oleic acid between lipophilic phase and water phase in a wood pitch emulsion at different NaCI concentrations. The temperature was 50 °C.

Approximately 50—55% of the product from a coal-tar refinery is pitch and another 30% is creosote. The remaining 15—20% is the chemical oil, about half of which is naphthalene. Creosote is used as a feedstock for production of carbon black and as a wood preservative. Because of modifications to modem coking processes, tar acids such as phenol and cresyUc acids are contained in coal tar in lower quantity than in the past. To achieve economies of scale, these tar acids are removed from cmde coal tar with a caustic wash and sent to a central processing plant where materials from a number of refiners are combined for recovery. 

Large-scale recovery of light oil was commercialized in England, Germany, and the United States toward the end of the nineteenth century (151). Industrial coal-tar production dates from the earliest operation of coal-gas faciUties. The principal bulk commodities derived from coal tar are wood-preserving oils, road tars, industrial pitches, and coke. Naphthalene is obtained from tar oils by crystallization, tar acids are derived by extraction of tar oils with caustic, and tar bases by extraction with sulfuric acid. Coal tars generally contain less than 1% benzene and toluene, and may contain up to 1% xylene. The total U.S. production of BTX from coke-oven operations is insignificant compared to petroleum product consumptions. 

Includes wood, wood waste, peat, wood Hquors, railroad ties, pitch, wood sludge, municipal soHd waste, agricultural waste, straw, tires, landfill gases, fish oils, and/or other waste. 

The market for tar-based road binders has declined considerably for a variety of reasons. Less cmde tar is available and the profits from the sales of electrode pitch and wood-preservation creosote or creosote as carbon-black feedstock are higher than those from road tar. In most industrial countries, road constmction in more recent years has been concentrated on high speed motorways. Concrete, petroleum bitumen, or lake asphalt are used in the constmction of these motorways. In the United Kingdom, for example, the use of tar products in road making and maintenance had fallen from 330,000 t in 1960 to 100,000 t in 1975 and is less than 100 t in 1994, mainly based on low temperature pitch which is not suitable for electrode or briquetting binders, but which is perfectly satisfactory as the basis for road binders. 

Pitch Control. Resinous constituents of wood cause problems in paper machines by sticking to the rollers and causing spots or holes in the paper the worst cases cause paper webs to mpture. Costly stoppages, wastages, and quaUty problems because of these resinous substances can be avoided by using Upases (84). 

Triglycerides are important constituents of resin. In softwood, the triglycerides account for 20—40% of total resin content, and in hardwood, 40—50%. The paper industry uses the term pitch for resins that create problems in paper machines. Traditionally, pitch is controlled or reduced by aging the wood, by use of chemicals to avoid deposits on the roUs, or by intensive washing of the pulp. AH these methods add to the cost of paper production. An alternative is to add a Upase to the pulp in a reaction lasting about one hour with the help of agitation. Results from Japanese paper mills show substantial... 

Essentially, carbonization entails the heating of organic precursors in the absence of air. In so doing, a solid carbon residue along with gaseous and volatile hydrocarbons is created. Bituminous coals are used to make metallurgical-grade coke while wood and other similar substances make charcoal. The condensed volatile material can be further refined to yield chermcals, pitches, or other useful commodities. 

Schiffs-leim, m. marine glue, -peclit n. common black pitch, -teer, m. ship s tar, wood tar. Schild, n. label sign, signboard badge (of hides) butt (turtle) shell. — m. shield escutcheon, -chen, n. little label, little shield, etc. (see Schild). -driise,/. thyroid gland. Schilddriisen-. thyroid, -essenz, /., -extrakt, n. iPharm.) thyroid solution. 

Impermeable timbers have a good resistance to polluted atmospheres where acid fumes rapidly attack steel. Wood has given excellent service in the buildings of chemical works and railway stations. Permeable wood species and sapwood can suffer defibration problems caused by the sulphur dioxide of industrial atmospheres. Tile battens are particularly vulnerable. The heartwood of Douglas fir, pitch pine, larch, Scots pine/European redwood and many tropical hardwoods give good service in these conditions. 

Natural resins Burgundy pitch Copal Dammar Japanese lacquer Pine rosin Wood rosin... 

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