Paper additives Sizing agents

The performance and quality of starch can be improved through chemical modification (see Chapter 17). Chemical modifications provide processed foods, such as frozen, instant, dehydrated, encapsulated and heat-and-serve products, the appropriate texture, quality and shelf life (see Chapter 21), and improved processing condition tolerance, such as improved heat, shear and acid stability. Modification also allows starches to be used in the paper industry (see Chapter 19) as wet-end additives, sizing agents, coating binders, and adhesives and as textile sizes. 

Chemical Characteristics of Paper Documents. From the earliest times up to the present day, the substances used as vehicles for writing have been numerous. Ancient paper documents were basically made from rags of cotton and linters cellulose is the major chemical constituent (I). Modern papers, however, are made of wood fibers, which usually are composed of cellulose, hemicelluloses, and lignin (I). In addition, for most of the modern papers, fillers, sizing agents, and other additives are used to improve paper properties (I). 

Chemical modification of starch makes it suitable for many applications in the food products (e.g., as gelling agents, encapsulating agents, thickeners) and the non-food industry (e.g., as wet-end additives, sizing agents, coating binders, and adhesives in paper industry as textile sizes in cosmetic formulations) [46]. 

Surfactants play several important roles in the papermaking industry. Several components of paper such as pigments for producing white or colored paper and sizing agents, often emulsion polymers that bind the cellulose fibers in the finished product and incorporate strength and dimensional stability, require surfactants in their preparation. In addition, the water-absorbing capacity of paper is often controlled by the addition of the proper surfactants. 

Papermaking additives can be categorized either as process additives or as functional additives. Process additives are materials that improve the operation of the paper machine, such as retention and drainage aids, biocides, dispersants, and defoamers they are primarily added at the wet end of the paper machine. Functional additives are materials that enhance or alter specific properties of the paper product, such as fillers (qv), sizing agents, dyes, optical brighteners, and wet- and dry-strength additives they may be added internally or to the surface of the sheet. 

By control and substitution of chemicals used in the paper mills, manufacturers of packaging papers and board can contribute themselves directly to a small mineral oil reduction in their products. Some additives contain mineral oil as solvent such as flocculation or retention aids based on polyacrylamide (PAA), resin sizing agents or defoamers. A change of such products to mineral oil-free additives removes their own mineral oil input and reduces the contamination of packaging material. In the area of retention aids based on PAA, this conversion has already mostly taken place. 

The product has two additional carboxy groups and is significantly more hydrophilic than the original starting material, yet it performs better as a sizing agent. This may be due to its increased anionicity which decreases its tendency to agglomerate and increases the ease and uniformity with which it spreads in the paper. 

Starch and Dextrins. Starch is a readily available mixture of polysaccharides. Starchy foods have been an important component of the human diet from prehistoric times to the present day. It is not surprising, therefore, that very practical uses for starch products developed very early and have continued throughout human history. Today, starch has a number of applications not only in the food industry but in other industries as well. In addition to its use in food, starch is also a source of chemicals (41) and sweeteners (42) and is used extensively in the paper industry (43-45) as a sizing agent and an adhesive. 

A wide range of chemicals is used by the paper industry either to improve the papermaking process or to confer special properties on the paper sheet. Additives include alum, sizing agents, clays and other mineral fillers, starches and dyes. Papers are also coated to improve printability. Some of these aspects are described briefly. 

Acrylic acid or methacrylic acid-starch graft copolymers were proposed as floc-culants for bauxites,2714,3095 agents for sizing cotton,3096-3098 tanning materials,3099 paper additives,3100 and also for sanitary napkins, diapers, tampons, and sick-bed sheets.3101-3104 Particular attention was devoted to the use of vinyl monomer grafted onto crosslinked starch.3105 Other applications include antiflammatory... 

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