Paper coating, additives

R.J. Kane (ed.), Paper Coating Additives, TAPPI Press, Atlanta, GA (1995). 

Compatible with most paper coating additives... 

PTFE is, for example, used to coat cookware intended for stovetop cooking and baking. Other PFCs, such as fluorotelomer and perfluoroalkylsulphonic acid derivatives (e.g., PFOSF), are or have been used to treat paper to improve its moisture and oil barrier properties. In particular, papers used in contact with high-fat content foods may be treated with fluorotelomer or perfluoroalkyl-sulphonyl-based paper additives/coatings to prevent oil stains or oil soak through the paper. Typically, these paper coatings/additives are phosphate esters or acrylic polymers containing polyfluoroalkyl functionality [12]. 

Begley et al. [12] analysed several consumer products for PFOA and concluded that fluorotelomer-based paper coating/additive formulations before application onto paper have the highest PFOA content, but during normal application rates this amount of PFOA will be diluted by about 300 times on the final paper product (Table 5). Therefore, the PFOA content in finished paper should be in the few 100 mg/kg range, which is consistent with the data shown in Table 5. 

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

The AKDs are used in paper sizing appHcations. Paper sizing chemicals provide paper and paperboard with resistance to wetting by Hquids, especially water repeUency in paper cups, milk cartons, photographic paper, coatings, and packaging paper (139) (see Paper Papermaking additives). 

Copolymers with butadiene, ie, those containing at least 60 wt % butadiene, are an important family of mbbers. In addition to synthetic mbber, these compositions have extensive uses as paper coatings, water-based paints, and carpet backing. Because of unfavorable reaction kinetics in a mass system, these copolymers are made in an emulsion polymerization system, which favors chain propagation but not termination (199). The result is economically acceptable rates with desirable chain lengths. Usually such processes are mn batchwise in order to achieve satisfactory particle size distribution. 

The addition of an a-hydroxycarboxyhc acid to a tetraethylene, propylene, diethjiene, or hexylene glycol titanate gives water-soluble complexes suitable for gelling aqueous solutions of hydroxyl polymers, such as poly(vinyl alcohol) (PVA), or cellulose (qv) derivatives. These are useful as binding agents for glass fibers, clays (qv), and paper coatings (85). 

Poly(vinyl alcohol) will function as a non-ionic surface active agent and is used in suspension polymerisation as a protective colloid. In many applications it serves as a binder and thickener is addition to an emulsifying agent. The polymer is also employed in adhesives, binders, paper sizing, paper coatings, textile sizing, ceramics, cosmetics and as a steel quenchant. 

Natural and synthetic resins are organic compounds easily found in art objects either as varnishes and protective coatings or binding media, adhesives, consolidants and finishing layers. They are mainly used in manufacturing paintings, but also in pottery, furniture and wooden objects, sculptures, musical instruments and works on paper. In addition, natural and synthetic resins have widespread use as conservation materials. 

Polyelectrolytes provide excellent stabilisation of colloidal dispersions when attached to particle surfaces as there is both a steric and electrostatic contribution, i.e. the particles are electrosterically stabilised. In addition the origin of the electrostatic interactions is displaced away from the particle surface and the origin of the van der Waals attraction, reinforcing the stability. Kaolinite stabilised by poly(acrylic acid) is a combination that would be typical of a paper-coating clay system. Acrylic acid or methacrylic acid is often copolymerised into the latex particles used in cement sytems giving particles which swell considerably in water. Figure 3.23 illustrates a viscosity curve for a copoly(styrene-... 

With the development of the new Ecoflex FS, new performance characteristics have been achieved in addition to improved biodegradabUity and bio-based content. This new Ecoflex FS is used for the development of new Ecovio compounds for specific applications like paper coating and shrink film. Further Ecovio applications, where biodegradability adds value, are under development to extend the portfolio of BASF. 

The use of AMP as a rheology additive in paper coating is illustrated below. Table 1 gives formulation details. Figure 8 shows the colour viscosity at low shear rates and Figure 9 shows the colour viscoisty at high shear rates. The application was board basecoating at 62.5% solids. 

Until recently, the use of enzymes in the paper and pulp industry was not cortsidered technically or economically feasible. Quite simply, suitable enzymes were not readily available, except for the limited use of enzymes to modify starch for paper coatings. However, research by scientific institutions and enzyme producers has led to the development of new enzymes that offer significant benefits for the industry, particrrlarly from the environmental point of view. Two examples of applications, in addition to the starch modification, made possible by new enzyme developments are given here bleach boosting and pitch control. 

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