Latex potassium soaps

Latex Types. Latexes are differentiated both by the nature of the coUoidal system and by the type of polymer present. Nearly aU of the coUoidal systems are similar to those used in the manufacture of dry types. That is, they are anionic and contain either a sodium or potassium salt of a rosin acid or derivative. In addition, they may also contain a strong acid soap to provide additional stabUity. Those having polymer soUds around 60% contain a very finely tuned soap system to avoid excessive emulsion viscosity during polymeri2ation (162—164). Du Pont also offers a carboxylated nonionic latex stabili2ed with poly(vinyl alcohol). This latex type is especiaUy resistant to flocculation by electrolytes, heat, and mechanical shear, surviving conditions which would easUy flocculate ionic latexes. The differences between anionic and nonionic latexes are outlined in Table 11. 

Saturated straight-chain fatty-acid soaps (1). Figure 1 shows the effects of increasing levels of various potassium saturated straight-chain fatty-acid soaps upon the mechanical stability of natural rubber latex. For convenience of making comparisons between the various soaps, the levels of added soap are expressed as moles per 100 g. of latex solids. 

The results summarised in Table I show the effect of equal parts by weight of each of the potassium fatty-acid soaps upon the mechanical stability of each of the three chemically-destabilised latices. For convenience in making comparisons, estimates of the corresponding results for unmodified natural rubber latex are also included. It is clear from these results that the ability of added potassium fatty-acid soaps to enhance the stability of chemically-destabilised natural rubber latex roughly parallels their abilities to enhance the mechanical stability of unmodified natural rubber latex. 

Figure 1. Effect of added straight-chain potassium fatty-acid soaps upon mechanical stability of natural rubber latex (1). Numbers appended to curves are number of carbon atoms in alkyl chain of soap.

Figure 3. Effect of various straight-chain potassium C18 carboxylate soaps upon mechanical stability of natural rubber latex (2) (KCt8) potassium stearate (KC18) potassium oleate (KC18") potassium elaidate (KC18Z) potassium linoleate (KC=ZZ) potassium linolenate (KC1H12(oli)) potassium 12-hydroxy stearate ...

The effects of a range of sodium n-alkyl sulphates and sodium n-alkyl sulphonates upon the mechanical stability of natural rubber latex are summarised in Figures 4 and 5 respectively. As in the case of added potassium fatty-acid soaps, small additions of... 

Table Ii Effect of 0.1 part by weight per 100 parts latex solids of various potassium fatty-acid soaps upon mechanical stability of unmodified and chemically-destabilised natural rubber 1atices (1 )...

All latex IPN s were synthesized by two-stage emulsion polymerization techniques (1 18) as follows To 300 ml of deionized deaerated stirre 3 waTer at 60°C were added 50 ml of a 10% (W/V) solution of sodium lauryl sulfate followed by 5 ml of a 5% (w/V) solution of potassium persulfate. The calculated quantity of comonomer was added at a rate of about 2 ml per minute. When the first monomer was fully added a minimum of one hour was allowed to elapse. Then a new portion of initiator was added but no new soap followed by the second charge of comonomers under similar reaction conditions. 

Unless stated otherwise, the agglomeration experiments were carried out in a temperature chamber at 40°C and 32.5% TS using 0.1% PEO/TS. Samples were collected at fixed intervals, and the reaction was terminated by adding the samples to sufficient potassium oleate solution to decrease the surface tension of the latex to about 40 dyne/cm or by diluting with water to about 6% TS. The particle surface (2) was then determined by soap titration so that rate constant (fc ) and stability factor could be calculated from Equations 3, 4, and 5. 

Basically a latex is synthesized by mixing monomer, surface active agent (surfactant), and an initiator (free radical source) into the water see Rgure 4.22 (88). The initiator is usually activated by heat. A widely used initiator is potassium persulfate. Surfactants are molecules that have a hydrophilic end and a hydrophobic end. These form micelles in the water, with the hydrophilic end facing outward, shielding the hydrophobic portion. The surfactant can be a soap or detergent, sodium lauryl sulfate being a typical example. The turbid or hazy appearance of soap in water is due to the presence of micelles. The surfactant dissolves the oil-soluble monomer in much the same way as the soap micelles dissolve skin oil in ordinary toiletry. Some of the surfactant remains... 

Sodium and potassium salts of naturally occurring fatty adds (oleic, linoleic) and rosin acids. These soaps are used in large quantities in the production of styrene-butadiene latex for both dry rabber production and latex appHcations. These materials are only useful at pH values greater than 7, normally being used at pH 10-12. Below pH 7, the insoluble acids are precipitated, and aU stabihzing function is lost. 

---