Anionic Dispersions

The reagent shown in Fig. 10.3 has been developed for the preparation of anionic dispersions. It is obtained by reaction of maleic anhydride with urea and subsequent reaction with sodium taurin. This compound combines four reactive centres in one molecule. The amino group of this compound reacts practically instantaneously with NCO groups, and the 

These are generally prepared using short-chain glycols such as A -methyl diethanolamine, iV-butyl diethanolamine or triethanolamine, which form the ionic centre. Films observed from these dispersions show a certain tendency to yellow when exposed to light or heat, especially in combination with aromatic diisocyanates. This is due to the jS-position of the basic nitrogen and urethane groups. 

Significantly more favourable are aminodiols which contain the nitrogen atom at a position further away from the urethane group and if possible not in the main chain. Films and coatings are obtained which show excellent stability if 2-alkyl-2-dialkylaminomethyl-1,3-propanediols are used as glycols with a tertiary nitrogen for the chain extension of prepolymers (Fig. 10.4). 

Cationic polyurethane dispersions can be prepared from these prepolymers after quaternization or neutralization. 2-Alkyl-2-dialkylamino-methyl-1,3-propanediols are readily available by nucleophilic ring opening of corresponding oxetones with aliphatic secondary amines (Fig. 10.5). 

A summary of the various methods available for preparing polyurethane 

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The waterborne prepolymer process is similar to the prepolymer synthesis described earlier, except that most of the waterborne prepolymers are based on aliphatic isocyanates and contain an internal emulsifier. There are several types of internal emulsifiers, both anionic and cationic. A good summary of these stabilizers is found elsewhere [56], The majority of the waterborne urethanes are anionic dispersions. An internal surfactant, such as dimethylolpropionic acid, is often incorporated into the prepolymer ... 

Figure 12.23 Rate of reduction of indigo with and without ultrasound [237], 0.1 g/l Indigo, 40 °C 2.5 ml/l hydroxyacetone 5.0 g/l sodium hydroxide, pH 12.7 0.03 g/l anionic dispersing agent...

Fig. 51. Schematic illustration of the mechanism of microgel formation in the anionic dispersion polymerization of 1,4-DVB initiated by living PBS chains in heptane. [Reprinted with permission from Ref. 247, Copyright 1995, American Chemical Society].

J.-H. Jiang, Y. Ozaki, M. Kleimann and H.W. Siesler, Resolution of two-way data from on-line Fourier-transform Raman spectroscopic monitoring of the anionic dispersion polymerization of styrene and 1,3-butadiene by parallel vector analysis (PVA) and window factor analysis (WFA), Chemom. Intell. Lab. Syst., 70, 83-92... 

For the theoretical aspects of dyeing CA and CT with disperse dyes see Section 4.12.1. CA is dyed by the exhaustion method in the presence of a nonionic or anionic dispersing and leveling agent in a weakly acidic bath (pH 5-6). A series of less wetfast disperse dyes are taken up by acetate at temperatures as low as 50-60 °C. For this reason, the process must be started at a correspondingly low temperature to obtain level dyeings. Dyeing is normally done at 80-85 °C. Dyes... 

Modification of zeolites by means of monolayer dispersion of oxides or salts is different from that by ion exchange. By ion exchange, only cations are introduced into the zeolites, but in the case of monolayer dispersion anions disperse along with cations onto the internal surface. Monolayer dispersion of oxides and salts proceeds more readily than ion exchange. It can be done efficiently by both dry and wet methods. 

Schwab FC, Murray JG (1985) Anionic dispersion polymerization of styrene. In Culbertson BM, McGrath JE (eds) Advances in polymer synthesis. Plenum, New York... 

Available In powder and liquid form, BURCO DISPERSANT DA-GD Is an efficient anionic dispersing agent for disperse dyes. It ensures dyebath stability, particularly under the high stress conditions encountered In beam, package and jet dyeing. 

Highly effective anionic dispersing agent for polyester dyeing. Promotes dyebath stability and leveling and helps eliminate disperse dye filtration and shade differences. 

Anionic dispersing agent, pasting aid, and antiagglomerant. HYDROSPERSE U-250 ... 

Anionic disperse dye leveling agent. Low foaming HYDROLEV GA-4 combines excellent dye migration with on-tone draw for consistent, uniform dyeing. 

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