Ion-tolerant emulsion

The next series (Figs. 8-10) show the types of properties obtained with two different carboxylated SBR latexes tackified with the same ion-tolerant emulsion of the glycerol ester of highly hydrogenated rosin. Fig. 8 shows the property of probe tack. Both of the carboxylated latexes exhibit some inherent tack properties, but the probe tack is improved even further with increasing levels of the resin. The extent to which the tack is improved is dramatically different depending on which latex is used. Pig. 9 demonstrates the differences even further. Resin modification of Latex B which is the lower molecular weight polymer. 

Table 8. Ion-Tolerant Emulsion of a a-Methyl-Styrene/ Vinyl Toluene Copolymer in Combination with Acrylic Latpv...

Table 10 exhibits the use of an ion-tolerant emulsion of the pentaerythritol ester of hydrogenated rosin with both a carboxylated polychloroprene latex and an uncarboxylated polychloroprene latex. Both systems exhibit pressure-sensitive properties which would be of interest in many PSA applications. 

Table 10. Ion-Tolerant Emulsion of the Pentaerythritol Ester of Hydrogenated Rosin with Poly-chloroprene Latex...

These polymers have typically been used without tackifying resins or with quite low levels of tackifying resin. The rationale for this is that the desired properties can be built into an acrylic polymer by changes in monomer composition, ratios or final polymer molecular weight. However, literally hundreds of acrylic polymers would be required to fill all of the pressure-sensitive adhesive applications, making this a rather undesirable situation for the producers of acrylic polymers. A number of resins have been found to be compatible with acrylic polymers. The properties obtained with combinations of these resins with a number of acrylics exhibit desirable adhesive properties as well as lower cost. In all cases, an ion-tolerant resin emulsion was used to ensure compatibility. 

Many anionic emulsifier systems are susceptible to coagulation by strong acids or multivalent cations. Again, additives can enhance the ion tolerance of resin emulsions, but careful testing is necessary. 

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