Beater additives

Two processes may be used in the manufacture of combustible cases the original post-impregnation process and the more recently and more widely employed beater additive process. The processes differ primarily in the point at which the required resin is added to the composition. A schematic of the beater additive process is shown in Figure 11. 

Fig. 11. Flow diagram for the beater additive process. Kraft represents the kraft process wood pulp and NC is nitrocellulose used as starting materials...

The beater additive process starts with a very dilute aqueous slurry of fibrous nitrocellulose, kraft process woodpulp, and a stabilizer such as diphenylamine in a felting tank. A solution of resin such as poly(vinyl acetate) is added to the slurry of these components. The next step, felting, involves use of a fine metal screen in the shape of the inner dimensions of the final molded part. The screen is lowered into the slurry. A vacuum is appHed which causes the fibrous materials to be deposited on the form. The form is pulled out after a required thickness of felt is deposited, and the wet, low density felt removed from the form. The felt is then molded in a matched metal mold by the appHcation of heat and pressure which serves to remove moisture, set the resin, and press the fibers into near final shape (180—182). 

Locust bean gum and its derivatives are exceUent film formers and can be used either alone or in combination with starch as textile sizing agents and dye thickeners in textile printing, and as fiber bonding and beater additives in the papermaking industry. However, in most of these appHcations it has been replaced by guar. 

Rosin sizing usually involves the addition of dilute aqueous solutions or dispersions of rosin soap size and alum to a pulp slurry (44—46). Although beater addition of either coreactant is permissable, addition of both before final pulp refining is unwise because subsequently exposed ceUulose surfaces may not be properly sized. The size and alum should be added sufficiendy eady to provide uniform distribution in the slurry, and adequate time for the formation and retention of aluminum resinates, commonly referred to as size precipitate. Free rosin emulsion sizes, however, do not react to a significant degree with alum in the pulp slurry, and addition of a cationic starch or resin is recommended to maximize retention of size to fiber. Subsequent reaction with aluminum occurs principally in the machine drier sections (47). 

P perApplications. In beater additions, the latex is mixed with the beaten paper pulp either by addition at the beater or to the stock chest at the wet end of the paper machine. In either case, the pH of the pulp is reduced to 4.0—4.5, usually by the addition of a solution of alum to the pulp—latex mixture which has been thoroughly agitated. The latex, which for this appHcation must be based on an anionic emulsifier, coagulates as the pH drops. The latex soHds separate ia intimate associatioa with the pulp fibers. The pulp is thea screeaed and the paper web formed ia the coaveatioaal way. A latex for this purpose must possess the proper balance between mechanical and chemical stabiHty. 

At low latex soHds-to-pulp ratios, ie, 10—20 pph, latex is added to the beaten pulp to give a paper web with superior web strength, elongation, bursting strength, internal bond, and tear strength. The nitrile latices and medium styrene—butadiene are commonly used as beater additions. In a similar manner, latex can be deposited on asbestos fibers. Such compositions are used as gaskets, linoleum bases, etc. 

Asbestos-rubber (beater addition process) 400 Same as above. 

The TMAHP-MGX isolated from cationized aspen sawdust was reported to be applicable as a beater additive it significantly increased the tear strength of bleached spruce organosolv pulp [3]. The TMAHP derivatives prepared from isolated xylans were shown to improve the paper-making properties and... 

Because the latex solids in the saturation process are deposited in the struture of the paper web by drying, the colloidal system is not as critical as with beater addition. Nonionic and amphoteric surface-active materials can be effectively used in the latices. A low surface tension and small particle size are desirable features. 

Many of these grafted pulps also show promise as fibrous or colloidal beater additives to give added strength properties to paper such as those made from groundwood and high yield pulps (53). 

Polysaccharides have been isolated which contain both D-glucose and D-mannose, for example, the glucomannan of Amorphophallus konjacJ From this Konjac mannan ([a] o —42.8°) has been isolated a disaccharide composed of D-glucose and D-mannose units. The polysaccharide from the corms of Amorphophallus oncophyllus is a fibrous substance which contains 49 % of anhydroglucose, 41 % of anhydromannose, and 4 % of uronic anhydride, and yields 2 % of pentosans. This substance is an excellent beater additive when used in paper manufacture. 

Our trials through published articles [20-22] to provide functional paper sheets with serving the previous drawbacks, and based on the characteristics of cellulose derivative-metal complexes, the CMC- and HEC-metal complexes were used as beater additives during the formation of paper sheets from wood pulp. The thermal degradation and magnetic and electrical conductivity properties were tested to evaluate the performance of paper product besides the strength properties. 

For the magnetic and electrical properties of paper sheets, the mass susceptibility X, c.g.s.] and AC conductivity (a ohm cm ] of paper samples were measured and recorded in Table 7.15. It was observed that this investigated CMC-Fe[III]-based beater additive Improved to less extent the semiconductor property of produced paper sheets however, the trend was reversed for the case of HEC-Fe(III] and CMC-Zn[II] complexes. These observations are probably related to the magnetic moment, molar conductivity and electrical conductivity of metal and metal complexes [19,49]. 

Some years after the upswing in the use of mannans as beater additives, mannan sorption studies started to focus on wood based mannans that were naturally present in the pulp itself and which were dissolved into the process water during processing and cooking. A retention or sorption of the dissolved mannans on tihe fibers in the formed sheet increased the yield and was thus economically desirable. Furthermore, sorption of wood mannans, like gum GMs, also ameliorates the strength properties of the formed sheet (76). 

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