Pulp molding

Secondary Fiber. Increasing costs of taw fiber, legislative mandates for recycling (qv), and avadabdity of inexpensive waste papers have contfibuted to the increased use of recycled fibers. The use of secondary fiber in the United States has grown from 22% of pulp from all sources in 1978 to close to 31% (24 x 10 metric tons) in 1993 (3). Recycled fibers ate sometimes used in special writing papers, but the principal use is for the manufacture of linetboatd, newsprint, tissue, cereal boxes, towels, and molded paper products such as paper plates and egg cartons (see Packaging materials, containers AND INDUSTRIAL materials). 

Principal Uses. Groundwood pulp contains a considerable proportion (70—80 wt %) of fiber bundles, broken fibers, and fines in addition to the individual fibers. Principal uses of paper-grade pulps are in newsprint, magazine papers including coated pubHcation grades, board for folding and molded cartons, wallpapers, tissue, and other similar products. 

Paper can be coated, cut, creased, glued, and laminated to paper, plastics, or foil. It can only be molded as pulp, i.e., pulpboard containers produced by suction or pressure operations. It cannot be molded in the plastic sense [16]. 

Pulp manufacture by stone groundwood, mechanical refiner, thermo-mechanical, chemi-mechanical, or chemi-thermomechanical means for newsprint, coarse papers, tissue, molded fiber products, and fine papers... 

Pulp production from recovered paper or paperboard without deinking processes to produce tissue, paperboard, molded products, and construction papers... 

Ozone is used in the food industry to inhibit growth of bacterias and mold in fruits, vegetables, and meat products. In paper and textile industries, ozone is used as a bleaching agent on wet paper pulp and cloth. 

The manufacture of cellulose acetate involves the acetylation of cellulose from cotton linters or wood pulp by acetic anhydride and acetic acid. Production started about 30 years ago, and early products that were developed include safety photographic films, airplane dopes, and acetate fabrics. It is now also produced in the form of sheeting, rods, and tubes and is widely used as a molding compound. 

PULP (Wood) PRODUCTION AND PROCESSING. Pulps can be defined as fibrous products derived from cellulosic fiber-contaiumg materials and used in the production of hardboard, fiberboard, paperboard, paper, and molded-pulp products. With suitable chemical modification, pulps can be used in Hie manufacture of rayon, cellulose acetate, and other familiar products. Pulps can be produced from any material containing cellulosic fiber but in North America and several other regions of the world, wood is the predominant source of pulp. This description is confined to the production and processing of wood pulp,... 

Moisture equilibrium of dried pellets takes longer to occur than for loose pulp. Results shown in Figure 2 indicate that above 75% RH at 25°C, equilibrium had not occurred within 28 days. The samples at 31 and 52%, RH reached equilibrium within one week. Mold growth in the pellets at 90 and 100% RH atmospheres commenced after 28 and 25 days, respectively. No mold growth occurred within 28 days in the other samples. In order to maintain the moisture content of dried pulp or pellets in the range of 10 to 12%, contact with air of greater than 50 to 60%, RH at 25°C should be minimized... 

There are also reports of the production of boards and moldings from plasticized wood particles, pulp or sawdust without adhesives (5,8,59,60). By compressing and heating to high temperatures, particle boards can be produced which have mechanical properties comparable to conventional resin bonded boards. However, their specific gravity is on the average about twice that of ordinary commercial products (59). 

Sulfur dioxide is used for refrigeration and also serves as raw material for the production of sulfuric acid. It is also used as a bleaching agent in the textile and food industries. It is an effective disinfectant and is employed as such for wooden kegs and barrels and brewery apparatus and for the prevention of mold in the drying of fruits. Sulfur dioxide efficiently controls fermentation in the making of wine. It is used in the sulfite process for paper pulp, as a liquid solvent in petroleum refining, and as a raw material in many plants in place of sulfites, bisulfites, or hydrosulfites. 

Other catechol-containing natural compounds have been implicated as Fenton-enhancing compounds in white rot fungi, brown rot fungi, and mold-mediated degradation of lignin and wood [64,65]. In addition to their potential effect on in situ remediation, these compounds may be of potential benefit for the pulp-and-paper industry. 

The foam sheet is clean, bright in appearance, has excellent cushioning properties, and is nonporous. The foam is extruded as a sheet and is subsequently vacuum thermoformed into the desired shapes for packaging, etc. (Chapters 5 and 7). Use includes low temperature insulation in freezers, coolers, and other types of refrigerated rooms auto, truck bodies, and railroad cars refrigerated pipelines and low-temperature storage tanks for liquefied natural gas. They find usage as a replacement for molded-paper-pulp board in meat and produce trays and egg cartons. 

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