Comparison of coalescing solvents

From the above, it may readily be seen that AB type coalescing solvents give the best performance in use. These are the high molecular weight esters and ester alcohols. Other species have some of the benefits of these materials but have side effects, which render them less suitable. Minimization of the quantity used tends to be a key financial issue, as well as offering the best environmental option. In virtually all cases, the efficiency of the AB group in application is so marked, that they have become the industry standards. Several other properties, perhaps less important, than efficiency must then be considered when selecting between these. 

These products are usually used in enclosed spaces, where product odor will be vital for acceptance to the consumer. The dibasic esters are virtually odor free. For legislative reasons, a solvent not classified as a VOC will be of definite benefit, given the current attitude to organics in consumer products. Again, the dibasic esters have initial boiling points considerably above the VOC threshold of 250°C. 

The efficiency of the AB group of coalescents towards almost all polymer types has already been mentioned. For styrene-acrylics and vinyl acetate - Veova copolymers, the diesters have a significant edge in performance compared with other members of that group. This advantage is shown in the reduction in amount required to attain a particular MFFT or the actual MFFT for a given addition level. 

Coasol manufactured by Chemoxy is the blend of di-isobutyl esters of the dibasic acids adipic, glutaric and succinic. These acids are produced as a by-product in the production of adipic acid in the manufacture of Nylon 6,6. The ratio of the acids is 15-25% adipic. 

50-60% glutaric, 20-30% succinic. Esterification using isobutanol is then performed and the produet is isolated following distillation. Coasol was introduced in the early part of last decade as a coalescing agent to the aqueous based coatings industry. 

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As shown in Fig. 1.10, several of these channels are oriented into the lipid portion of the bilayer in MD simulations. Comparisons of the duration and extent of opening during MD simulations, for the catalytic domains in an aqueous environment and bound to membranes, are qualitatively similar and reveal differences in the frequency and duration of charmel opening that reflect interactions between the catalytic domain and the membrane [57-60]. These solvent channels are thought to open and coalesce to form substrate access chaimels as seen for open conformations of soluble and membrane P450s determined by X-ray crystallography [93]. 

The combined high solvency of propylene glycol phenyl ether (PPh) for acrylic and vinyl acetate latexes and the solvent s low water solubility provides excellent coalescent efficiency for these latexes. Comparison of PPh and another coalescent solvent Texanol (2,2,4-trimethyl-1,3-pentanedioI monoisobutyrate) in a study with several latexes found PPh to be superior [4]. 

Evaporation of Solvent-Water Blends. The evaporation of blends of solvents and water presents several problems, the most prominent of which is the fact that the relative rates of evaporation of solvents and water in a given blend vary greatly under conditions of varying humidity. Under dry conditions the water evaporates relatively rapidly, but under high humidity the water evaporates relatively slowly in comparison to solvent. Usually it is desired that the water and solvent evaporate at rates such that the residual liquid remains constant in composition (perfect solvent balance). Often, enrichment of solvent in the residual liquid is desired, but depletion of solvent in the residual liquid might lead to resin kick-out or loss of ability of the resin to coalesce into a smooth, continuous film. One means of minimizing premature loss of... 

The HPC could only with difficulty be washed off the particle surfece only those solvents which had solubility parameters close to that of polystyraie (such as ethoxyethanol) were effective in removing the stabilizer without at the same time dissolving the polystyrene particles completely. In this way, about 78% of the labelled stabilizer could be recovered. Gtx)d solvents for the HPC moiety (water and polar alo ols) removed less than 5% of the grafted stabilizo. Further proof that the stabilizer was irreversibly grafted came from the ct that when the stabilized particles woe dissolved in dioxane (a good solvent for all the components), the addition of methanol (a non-solvent for polystyrene) produced stable polystyrote particles once more. In comparison, when simple mixtures of polystyrene and HPC were treated in this way, coalescence occurred. 

A comparison has been made of the simulation of AB block copolymers as self-avoiding walks on lattices and as random walks with a mean field expression of block incompatibility. In contrast to the case with di-blocks, the A part of BAB tri-blocks is appreciably more expanded than the homopolymer, thus reducing the possibility that in poor solvent the B parts might coalesce to form a ring. ... 

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