Kraft paper

Waterproofing, whether it has to do with protecting civil engineering structures or roofs or terraces. Poured asphalt, often placed in layers with kraft paper, oxidized bitumen or modified bitumen can be used, generally with copolymer. The modified bitumen are used for the making prefabricated multi-layer waterproofing composites. 

The most commonly used reinforcement for high pressure decorative and industrial laminates is paper (qv). The strong substrate layers, or filler, are kraft paper. Kraft is a brown paper made from a sulfate pulp process (8). It consists of both short cellulose fibers from hardwoods and long fibers from conifers. The long fibers impart most of the wet strength required for resin saturation processes. 

The quantity of resin appHed to the reinforcing ply to achieve a state of full densification varies inversely with the laminating pressure. Therefore, high pressure laminates pressed at about 7 MPa (1000 psi) need only about 25—30% phenoHc resin in kraft paper, whereas low pressure (1 MPa = 145 psi) laminates need 50—60% resin in the reinforcing ply if all voids are to be filled in the final product. 

MultiwaU. shipping sacks are suitable for transport in aU kinds of carriers from tmcks to seafaring vessels. Particular care must be taken to prevent the storage of objects with sharp projections adjacent to the bags in case of doubt, it is advisable to line the enclosure with kraft paper of a basis weight >23 kg. Additional rules for the transportation of multiwaU sacks are contained in appHcable tariff specifications and should be consulted for rail, tmck, and ocean-going shipments. 

The type of varnish used in the process depends on the kraft paper manufacturer and basis weight of the papers the machine, temperature, and control (scraper bars, squeeze roUs) used the method of cutting the paper to size the laminate being produced (post-forming or regular) and the press-cure cycle (see Laminated materials, plastic). 

Composites. The history of phenoHc resin composites goes back to the early development of phenoHc materials, when wood flour, minerals, and colorants were combined with phenoHc resins to produce mol ding compounds. In later appHcations, resin varnishes were developed for kraft paper and textile fabrics to make decorative and industrial laminates. Although phenoHcs have been well characterized in glass-reinforced composites, new developments continue in this area, such as new systems for Hquid-injection molding (LIM) and sheet-molding compounds (SMC). More compHcated composite systems are based on aramid and graphite fibers. 

Typical substrates for siUcone release coatings are supercalendered kraft paper, glassines, and thermally sensitive films such as polyethylene and polypropylene. Ideal curing conditions are 150°C or lower, and line speeds are as fast as 460 m /min. Key properties for release coatings are cure speed, integrity of cure, and stable release values. 

In 1980, >1 one million ts of sodium sulfate were consumed in the United States, but this had declined to <600, 000 t by the end of 1994. The decline is partly a result of higher energy prices and more efficient use of Na2S04 by the paper industry. At one time the kraft paper industry consumed two-thirds of sodium sulfate production. Pressures on paper producers to clean effluent streams and reduce energy forced improvements in internal processes and recycling of sodium sulfate (11,12). 

The demand for sodium sulfate leveled off in the first half of the 1990s and is expected to begin to rise again with increased U.S. population and as the demand for kraft paper products and powdered detergents rises. 

The principle uses of Na2S04 are in the manufacture of paper, soaps, and detergents. These accounted for 65% of U.S. consumption from 1990 to 1995, representing a significant shift from 1980 when paper production alone consumed 67%. Pulp (qv) and paper consume only 25% (2). The kraft paper process uses a mixture of sodium sulfide and sodium hydroxide to digest wood chips. Both the sulfide and hydroxide are generated, starting with sodium sulfate as the raw material. 

The decorative plastic laminates widely used for countertops and cabinets are based on melamine—formaldehyde resin (see Laminates). Several layers of phenohc-saturated kraft paper are placed in a press and a sheet of a-ceUulose paper printed with the desired design and impregnated with melamine—formaldehyde resin is placed over them. Then a clear a-ceUulose sheet, similarly impregnated with the resin, is placed on top to form a clear, protective surface over the decorative sheet. The assembly is cured under heat and pressure up to 138°C and 10 MPa (1450 psi). A similar process is used to make wall paneling, but because the surfaces need not be as resistant to abrasion and wear, laminates for wall panels are cured under lower pressure, about 2 MPa (290 psi). 

Plastic laminated sheets produced in 1913 led to the formation of the Formica Products Company and the commercial introduction, in 1931, of decorative laminates consisting of a urea—formaldehyde surface on an unrefined (kraft) paper core impregnated with phenoHc resin and compressed and heated between poHshed steel platens (8,10). The decorative surface laminates are usually about 1.6 mm thick and bonded to wood (a natural composite), plywood (another laminate), or particle board (a particulate composite). Since 1937, the surface layer of most decorative laminates has been fabricated with melamine—formaldehyde, which can be prepared with mineral fiUers, thus offering improved heat and moisture resistance and allowing a wide range of decorative effects (10,11). 

Basic dyestuffs are usually used for dyeing of unbleached pulp in mechanical pulp such as wrapping paper, kraft paper, box board, news, and other inexpensive packaging papers. Their strong and brilliant shades also make them suitable for calendar staining and surface coloring where lightfastness is not critical. 

Multiwall kraft-paper basis-weight equivalents ... 

For kraft paper, conversion will eventually be a hard conversion to two basis weights of 75 and 90 g/m", which will replace the 40-, 50-, and 60-lb basis weight currently used. 

Multiwall Paper Bags These bags (Fig. 21-40), made from plies of kraft paper or from combinations of kraft and special-purpose papers and plastics, are the most common packages For almost any pelleted or powdered material as well as for briquettes or bats of such solids as synthetic rubber, waxes, and insulation. 

Boxes Bulk boxes (Fig. 21-40) of corrugated kraft paper for dry bulk products fall into hvo broad categories large, for 0.5- to 2-ton loads, and small, for loads of 23 to 68 kg (50 to 150 lb). Large boxes are used extensively for resin shipment small ones, for certain regulated materials (such as caustic soda) and for low-bulk-density products that are assessed excessive freight rates if packed in drums. 

Shipping cartons for hquids in cans and bottles, bulk solids in jars, pouches, and folding boxes, and briquetted items with or without individual packaging are usually made or corrugated kraft paper. The most common styles are the regular slotted caiton (RSC), the end-opening RSC, and the center special-full overlap slotted container (SFF). End joints may be stapled, stitched, glued, or taped. 

Gasoline accumulator Solvents Storage vessels Lube oil refining Polyethylene gas vents Styrene Copper naphthenates Insecticides Phthalic anhydride Resin reactors Ammonia Chlorine solutions Dry cleaning Degreasers Tar dipping Kraft paper... 

Figure 23.21. Effect of moulding pressure on the tensile and shear strength of Kraft paper laminates.

Figure 23.22. Effect of resin content on strength properties of a high-density Kraft paper laminate.

Decorative laminates have a core or base of Kraft paper impregnated with a phenolic resin. A printed pattern layer impregnated with a melamine-formaldehyde or urea-thiourea-formaldehyde resin is then laid on the core and on top of this a melamine resin-impregnated protective translucent outer sheet. The assembly is then cured at 125-150°C in multi-daylight presses in the usual way. 

In contact adhesives, the so-called tack open time is important. This can be defined as the time available after the adhesive is applied during which the surface remains tacky enough for the application of the adherend. It can be easily measured by applying a thin layer of fresh adhesive on Kraft paper and making a bond at different times until no bond is obtained. 

Kraft-mehl, n. starch, amylum. -messer, m. dynamometer, -mittel, n. forceful means powerful remedy tonic, -packpapier, n. kraft (wrapping) paper, -papier, n. kraft paper, kraft. -papierstoff, m. kraft pulp, -quelle, /. source of power, -rad, n. motorcycle. -rdhre, /. (Physics) tube of force, -sammler, m. accumulator, -sitz, m. (Mach.) forced fit. -speicher, m. accumulator, -spi-ritus, m. motor spirit, -stoff, m. power fuel, motor fuel (Paper) kraft pulp, -stoffge-misch, n. fuel mixture, -stoffverbrauch, m. fuel consumption, -stoffwirtschaft, /. fuel economy, -strom, m. (Elec.) power current, -iibertragung, /. power transmission, -ver-brauch, m. power consumption, -verkehr, m. motor traffic. 

Brown Kraft paper is generally used on mineral wool products to give added tensile strength, ease handling, aid positive location between studs or rafters, or prevent contamination when used under concrete screeds. Paper is often laminated with polyethylene to give vapor control layer properties. 

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