Kraft paper manufacturing

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). 

Polyterpene resins are related to the oldest reported polymerization, as they were first observed in 1789 by Bishop Watson by treatment of turpentine with sulfuric acid [92]. Commercial polyterpene resins are synthesized by cationic polymerization of /3- and a-pinenes extracted from turpentine, of rf,/-limonene (dipentene) derived from kraft-paper manufacture, and of d-limonene extracted from citrus peels as a by-product of juice industry [1,80,82,93]. The batch or continuous processes are similar for the three monomers. The solution polymerization is generally performed in mixed xylenes or high boiling aromatic solvent, at 30-55° C, with AlCl3-adventi-tious water initiation. The purified feedstream (72-95% purity, depending on monomer) is mixed in the reactor with solvent and powdered A1C13 (2—4 wt% with respect to monomer), and then stirred for 30-60 min. After completion of the reaction, the catalyst is deactivated by hydrolysis, and evolved HC1 is eliminated by alkaline aqueous washes. The organic solution is then dried, and the solvent is separated from the resin by distillation. 

Sodium sulfate is used in paperboard and kraft paper manufacturing. It is also used in tanning, textile processing, and dyeing operations. Sodium sulfate is used in pharmaceuticals, detergent manufacture, glass manufacture, and dyeing operations. 

Closed-Mill Concept. The closed-mill concept, or water circuit closure, has been studied by the pulp and paper industry for many years. In some parts of the paper manufacturing process, up to 98% of the water is recycled within the process, eg, the wet end of the paper machine. However, in the pulp mill, especiaUy kraft mills, effluents are produced owing to the need to purge from the system various metals that come in with the wood, as weU as organic by-products from the pulping process, additives, and especially chloride ions that originate in the bleach plant. 

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. 

Tall oil rosin is obtained from crude tall oil obtained from the Kraft (sulphate) pulping of various coniferous trees in the paper manufacturing industry. During the Kraft pulping process the fatty acids and the resin acids from the coniferous wood are saponified by the alkaline medium. On concentration of the resulting pulping liquor, the sodium soap of these mixed acids rises to the surface from where they are skimmed out. By acidification of this material with sulphuric acid, the crude tall oil is obtained. Fractional steam distillation of the crude tall oil allows the separation of the tall oil fatty acids and the tall oil rosins [21]. 

Gum turpentine is obtained from wounding living trees to get an exudate containing turpentine and rosin. Turpentine is separated from the rosin by continuous steam distillation and further fractionation. Wood turpentine comes from the extraction of stumps of pine trees using naphtha, and subsequent separation of rosin and turpentine by fractional distillation. Tail-oil turpentine is a byproduct of the Kraft sulphate paper manufacture. Terpenes are isolated from the sulphate terpentine and separated from the black digestion liquor. The composition of turpentine oils depends on its source, although a-pinene and p-pinene are the major components. 

Writing paper was first used in Egypt as far back as 2500-2000 BC, made from the papyrus reed. Paper manufacture began in China about AD 105. In 1690 the first American paper mill began its operation. Two recent dates of importance to modem paper technology are 1867, when Tilghman in the U.S. developed the sulfite process, and 1884, when Dahl in Germany discovered the kraft or sulfate process. 

Materials and Regents. Paper samples employed in this study were 8- X 10-in. sheets cut from a continuous portion of a single roll or JCPA-60 bleached kraft paper. This paper had been manufactured from a pulp mixture consisting of 70 bleached southern kraft and 30 bleached hardwood kraft. The paper contained 13 clay materials, which are composed mainly of titanium dioxide. It also contained 212 ppm of iron and 66 ppm of copper and had a pH of 5.4. All chemicals employed were analytical reagent grade. Water used for the washing of paper samples and the preparation of solutions had a minimum resistivity of 15 Mil. 

The treatment of bleached kraft pulp with sodium borohydride followed by incorporation of basic calcium salts increased the stability of paper made from this pulp by 1.5-2.6 times. When manufactured paper, rather than pulp, was subjected to sodium borohydride treatment followed by washing with an aqueous solution of calcium hydroxide, the stability of the paper increased by as much as 4 times for groundwood paper and 30 times for bleached kraft paper. 

Another type of willow smoke star which gives large streamers of colour is manufactured by loading one of above compositions into a small cardboard shell 2-3 cm in diameter(Fig.78) or in a kraft-paper tube of... 

The surface of the scallion capsule must be carefully pasted with kraft paper to prevent the composition from the direct fire of the bursting charge. The manufacture of the noise units is unexpectedly difficult, it must be carefully supervised. 

Sulphate Liquor.—One ton of sulphate pulp which is used for the manufacture of Kraft paper produces about 2,000 gal. of liquor which is to be concentrated from 10 to 20°B6. Usually a double or triple effect of the horizontal type is used for this purpose, and the capacity is from 2 to 2K gal. per square foot according to the steam pressure. The concentration of this 20°B6, liquor is continued... 

Use Manufacture of kraft paper, paperboard, and glass filler in synthetic detergents sodium salts ceramic glazes processing textile fibers dyes tanning pharmaceuticals freezing mix laboratory reagent. food additive. 

Pulp and paper manufacture black liquor and Kraft recovery furnaces. 

For thousands of years, turpentine has been obtained from conifers by a process known as tapping. A cut is made in the bark which prompts the tree to exude an oil which can be drained off into vessels attached to the tree. Turpentine thus obtained is referred to as gum turpentine. Nowadays, another form of turpentine is available in large quantities as a by-product of paper manufacture. When softwood (pine, fir, spruce) is converted into pulp in the Kraft paper process, the water insoluble liquids which were present in it are freed and can be removed by physical separation from the process water. This material is known as crude sulfate turpentine (CST). Fractional distillation of CST gives a number of products as shown in Table 9.2. (Dipentene is the name given to racemic limonene.) The residue from the distillation is known as tall oil and contains diterpenes such as abietic acid. 

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