Use as beater additives

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. 

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. 

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). 

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. 

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. 

The first scientific publications on mannans as beater and wet-end additives were very much practically oriented. They focused on the obtained effects rather than the phenomenon behind. The need of a deeper understanding came into the picture some time later, when the practical use of mannans was already rather well established. The attention was then turned to wood mannans naturally present in pulp, with an attempt of increasing the yield. Today, a large interest lies in elucidating the interactions between mannans and cellulose in wood itself, as well as between mannans and other interfaces in pulp suspensions than cellulose. 

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