Softwood paper

Alternatively on the basis of a diffusion type model, approximate values of the diffusion coefficient D, have been calculated for these systems. Values of D which fall in the range of 10-2 to 10-5mm/sec are of the same order of magnitude as those obtained by Hoyland (2) for the penetration of various aqueous liquids in bleached softwood paper. Although Hoyland s diffusion model takes into consideration fibre swelling during penetration it still overlooks many of the aforementioned structural complications unique to paper. 

Table 18-1 represents the tip displacement of EAPap actuator made with six different papers. Here, means that no significant displacement was observed. Hardwood and softwood paper exhibited a small displacement less than 1 mm. Meanwhile, cellophane EAPap exhibited very large displacement output. Detailed displacement measurements were conducted on the cellophane EAPap actuator. 

High alpha-ceUulose chemical woodpulp paper, machine-made primarily from fast-growiag softwoods, sized usiag alkaline calcium compounds, and loaded with fillers and other additives, constitutes a presumably more stable material. Different types of paper are used for art, manuscripts, documents, books, etc, each having its own properties of color, texture, feel, etc. 

Fiber Analysis. Paper may be composed of one or several types of fibers, eg, animal, vegetable, mineral, and synthetic (see Eibers). Paper is generally composed of woody vegetable fibers obtained from coniferous (softwood) and deciduous (hardwood) trees. QuaUtative and quantitative methods have been developed to determine the fibrous constituents in a sheet of paper (see TAPPI T401). However, the proliferation in the number and types of pulping processes used have made the analysis of paper a much more complex problem. Comprehensive reviews of the methods are given in References 20 and 23. 

Research Trends. Research since the late 1970s appears to have centered on further process modifications and optimization of conventional processes, reduction in pollution, evaluation of potentially more efficient processing technology, increased use of less expensive softwood sources to extend the available hardwood suppHes, and accommodation of recycled newspaper pulp (see Recycling, paper). 

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... 

In softwoods, the main cell type is the tracheid, which is often mistakenly referred to as a fibre. Tracheids constitute over 90% of the volume of most softwoods, and are the principal paper-making cells of softwoods. Their average length is usually between 2 and 4 mm, with a lengthrwidth ratio (aspect ratio) often in excess of 100 to 1, but there is a wide distribution of tracheid lengths, and it is possible for some to be as short as 1 mm and for others to be as long as 5 mm (Table 2.1). The lumen, or central cavity, is several times wider than the cell wall thickness. There is also a difference between spring wood (i.e. cells synthesised in the early part of the annual... 

The chemical composition of paper will depend greatly upon the chemical treatment which the wood has been subjected to during its conversion to pulp. When the pulp has received little or no chemical treatment, as in the case of pulp for newsprint, the chemical composition is very similar to that of the native wood. However, in those papers which have been chemically delignified, the composition may be very different. The natural compositions of native wood (softwoods and hardwoods) and the chemical pulps derived from them are shown in Table 2.2. 

Wood contains a small proportion (usually less than 5%) of components which are extractable by organic solvents such as ethanol or dichloromethane. The proportion of these extractives varies in hardwoods and softwoods and also between species. Although many of these substances are removed during the chemical pulping process, some may still be retained in the final sheet of paper. Their chemical composition is very varied, and they include alkanes, fatty alcohols and acids (both saturated and unsaturated), glycerol esters, waxes, resin acids, terpene and phenolic components. The proportion which remains in pulp and paper depends upon the pulping process used. In general, acidic components such as the resin and fatty acids are relatively easily removed by alkali by conversion to their soluble... 

Figure 7.9 Light photomacrograph of fracture line of a 15 mm wide tensile test strip of copier paper (60% hardwood, 40% softwood). Scale bar= 2 mm.

Provincial Papers Inc. is located on Lake Superior at Thunder Bay, Ontario. Sulphite/mechanical processes are used in the production of coated and uncoated fine papers from purchased kraft pulp and groundwood from softwood sources. Secondary treatment is carried out in an aerated lagoon system (a serpentine basin) and was installed at the mill in late 1995 (see Fig. 2). Effluent flow rates ranged from 25,000 to 35,000 m3/day in the two years following installation of secondary treatment. Treated effluent is discharged into the inner basin of Lakehead Harbour, a sheltered embayment created by a series of breakwaters. The Current River is the other major discharge to the immediate area of the mill outfall. A description of the EEM study is found in ESG (2000). 

This paper is a report on preliminary studies evaluating the suitability of bark extracts from four West Coast softwood species as bonding agents for particleboard. The barks investigated include white fir (Abies concolor), ponderosa pine (Pinus ponderosa), Douglas fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) ... 

Weathering produces physical as well as chemical changes. Miniutti, in a series of papers, examined microscopic changes in cell structure of softwood surfaces during weathering and ultraviolet irradiation (21-25). 

Materials. All paper samples were cut from a continuous length of machine-made rolls. Two different papers have been studied. One is a bleached Kraft wood pulp waterleaf (50-lb basis weight) made by Neenah Paper Mills from a stock that comprised northern softwoods (60Z) and Lake States hard woods (40J), and contained no additives. The second paper, Foldur Kraft, is a bleached Kraft paper (70-lb basis weight) made by Champion Paper Company from a stock of 90Z softwoods and 10Z hardwoods, with alum-rosin size and 8Z titanium dioxide filler. This paper was obtained 15 years ago. Since then it has been stored indoors in areas which have not enjoyed a carefully regulated environmental control. 

Several samples of commercial dissolving pulp from softwood were used bleached pulp (whiteness 92 %), almost entirely free of lignin, containing about 94 % a cellulose (I) paper pulp (II) (whiteness 91,5 %) mechanical yellow pulp (III) (containing lignin), Kraft Laponia pulp (IV), whiteness 92 %). 

Triterpenoids occur in hardwood parenchyma resin, and closely related sterols are also present in softwoods (Fig. 5-6). Sterols typefied by the abundant /3-sitosterol, mostly have a hydroxyl group in the C-3 position. They also appear as the alcohol component in fatty acid esters (waxes). Triterpenoids and sterols are sparingly soluble substances contributing to pitch problems in pulping and paper making. Some trees contain polyterpenes and their derivatives known as polyprenols. Betulaprenols, present in birch wood, belong to this category of substances (Fig. 5-7). 

Closely associated with cellulose in the wood structure and paper products are other polysaccharides called hemicelluloses, which often have been labeled as the matrix material of wood. In hardwoods the primary hemi-cellulose is a xylan (polymer of xylose), whereas in softwoods the primary hemi-cellulose is a glucomannan, although both of these polysaccharides occur to some extent in both types of wood. The DP of the hemicelluloses is much less than that of cellulose, in the range of 100-200. 

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