Paper Stabilizers

The reaction of diethyl zinc with water produces zinc oxide, and then zinc carbonate, as the alkaline reserve. These chemicals have antiseptic properties which may also prevent the growth of mold in paper. They may also improve the brightness of treated papers. However, it is also known that zine oxide is a photosensitizer (56) which may trigger photo-oxidation of treated papers to initiate a chemical chain reaction that will lead eventually to the formation of acidic products (57). Moreover, the interaction of zinc oxide and zinc carbonate with copper, iron and cobalt present in the paper and their subsequent effects on paper stability have not been studied. 

In 1945 Calvin and Wilson (50) first suggested the importance of "benzenoid resonance in metal chelates of /ff-ketoenolates. In their classic paper, Stability of Chelate Compounds , Calvin and Wilson attempted to "determine the influence of certain structural factors upon the stability of the chelate complexes of divalent copper in which four atoms bound to the metal are all oxygen. After determining stability constants for the copper chelate complexes, the authors conclude for j8-diketonate ligands that "in addition to their character as bases, a benzenoid resonance effect involving copper plays a very important role in determining the stability of these compounds. The canonical forms which Calvin and Wilson considered important are shown below. 

The 3D numerical model consisting of the colluvium and the bedrock was established in this paper. Stability analyses for the colluvium were performed using the commercial software Flac . The 3D model with 5042 points and 22365 zones is shown in Figure 6. The physical and mechanical parameters of the deposit and underlying bedrock obtained from physical properties measurement and direct shear test are sununarized in Table 1. 

The importance of the thin film between the mineral particle and the air bubble has been discussed in a review by Pugh and Manev [74]. In this paper, modem studies of thin films via SFA and interferometry are discussed. These film effects come into play in the stability of foams and froths. Johansson and Pugh have studied the stability of a froth with particles. Small (30-/ m), moderately hydrophobic 6c = 65°) quartz particles stabilized a froth, while more hydrophobic particles destabilized it and larger particles had less influence [75]. 

The special stability of the helix with three repeat units per turn for isotactic vinyl polymers in which the substituent is not too large was discussed in connection with Fig. 1.10a. Rodriguez has suggested a simple paper model which is also helpful in illustrating this structure. The following steps summarize this method additional details are available in this readily accessible reference. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

MiscelUneous. Mahc acid is used in pharmaceuticals (qv), cosmetics (qv), dentifrices (qv), metal cleaning, electroless plating (46), wash-and-wear textile finishing (47—49), for stabilization of heat-sensitive copying paper (50), as an inhibitor of gelation, livering, and agglomeration in cellulose nitrate Hqueurs, and in many other appHcations. 

Polym. Degrad. Stabil 45(2) (1994), papers from the ArdlUPAC International Sjmposium on Macromolecules, Montreal, Canada. 

Lesser amounts of sodium thiocyanate are used in color toning photographic paper, as a stabilizer in rapid film development, and as a sensitizing agent in color negative-film emulsions. It is also used as a brightener in copper electroplating. 

Stannic chloride is also used widely as a catalyst in Eriedel-Crafts acylation, alkylation and cycHzation reactions, esterifications, halogenations, and curing and other polymerization reactions. Minor uses are as a stabilizer for colors in soap (19), as a mordant in the dyeing of silks, in the manufacture of blueprint and other sensitized paper, and as an antistatic agent for synthetic fibers (see Dyes, application and evaluation Antistatic agents). 

These polyol-stabilized alkan olamine titanate solutions are used ia a method to improve the wet strength of paper (115,118). The addition of 1—2... 

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