Newsprint

A cross-sectional view of kenaf is shown in Figure 3d. The ultimate cells are nearly cylindrical with thick cell walls. Kenaf fibers are shorter and coarser than those of jute. Both chemical (kraft) and mechanical pulps have been produced from kenaf, and successful demonstration mns of newsprint have been made for the Dallas Morning Nem, the St. Petersburg Times, and the Bakersfield Californian with a furnish of 82% kenaf chemithermomechanical pulp and 18% softwood kraft pulp. Kenaf fiber is also considered a substitute for jute and used in sacking, rope, twine, bags, and as papermaking pulp in India, Thailand, and the former Yugoslavia. RoseUe bleached pulp is marketed in Thailand. 

Black Pigments. The only black pigment used to an appreciable extent in inks is carbon black It is used in newsprinting, pubHcation, commercial and packaging printing therefore, in large quantities. Black pigments ate offered in fluffy or beaded forms and in a variety of particle sizes and physical properties. 

The cahper is the thickness in p.m of a single sheet measured under specified conditions (TAPPI T411). CaUpers for a number of common paper and board grades are capacitor tissue, 7.6 p.m facial tissue, 65 p.m newsprint, 85 p.m offset bond, 100 p.m linerboard, 230—640 p.m and book cover, 770-7600 pm. 

Low molecular cationic polymers or alum can also be used to flocculate pitch, ie, bind up the pitch so that it is retained in the sheet, to minimize pitch deposition on machine surfaces and fabrics (35,36). Alum is used commonly in newsprint operations (34). The addition of a nonionic surfactant with a hydrocarbon solvent to the wet end has shown some utility in preventing deposits of adhesive recycled furnish contaminants from forming on the paper... 

In the paper industry, PEO is widely used as a retention aid and pitch control agent in the newsprint industry (118—135). Typically, a phenol formaldehyde-type resin is added to the substrate before the addition of PEO. The chemical that is added before PEO has been referred to as an enhancer. Recent pubHcations on designing enhancers that work with PEO have resulted in expanding the use of PEO in flocculation of several substrates (128,129). 

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. 

The TMP process is similar to the RMP process except that after chip washing, a steaming vessel is inserted to achieve the thermoplasticization of the lignin in the wood. The production of thermomechanical pulps increased dramatically after the introduction of this method in the early 1970s. Because these pulps can be substituted for conventional groundwood pulps in newsprint blends to give a stronger paper, lower quantities of the more expensive, lower yield chemical pulps are required. 

In fact, recycling was a valuable U.S. industry for decades (witness the success of industrial recycling), especially in metals, newsprint, and some types of glass and aluminum cans. Only when regulators, in response to pubHc pressure, attempted to mandate the collection of materials that were in many instances expensive to collect and process did recycling begin to encounter problems. 

Newsprint wash deinking mili Office paper deinking mili Newsprint/magazine deinking mill Tissue mill Old corrugated container mill... 

Low consistency pulping (3—6% soflds) is common in newsprint and many tissue mills. Medium (6—12%) and high consistency pulping (12—18% sohds) is common in mills deinking office papers. Pulping temperature is typically 40—55°C, the pH is usually 9.0—10.5, and process time ranges from 4 to 60 minutes. 

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