Preparation dispersion

Fillers are often employed to reduce the surface tack of the final product. Examples are talc and china clay. If powdered materials are added directly to a latex they compete for the emulsion stabiliser present and tend to coagulate the latex. They are therefore added as an aqueous dispersion prepared by ball milling the filler with water and a dispersing agent, for example a naphthalene formaldehyde sulphonate at a concentration of about 1% of the water content. Heat and light stabilisers which are solids must be added in the same way. 

Charge the OH functional urethane water dispersion prepared in Example 8 (200 g, 0.1603 eq. OH) to a suitable container. Vigorously stir the dispersion with a mechanical stirrer and slowly add the 18.8% NCO water-dispersible polyisocyanate described above (40.0 g, 0.1791 eq.). This will give an NCO-OH equivalent ratio (index) of 1.12. To this mixture, add Silwet L-77 (a flow aid from OSi Specialties) and thoroughly mix. Use a draw-down bar to make 6-mil (0.006-in.) wet-thickness films on glass plates and 5-mil (0.005-in.) films on Bonderite-treated steel panels (Bonderite is from Henkel). Condition the resultant films at 72°F and 50% RH for 2-3 weeks before evaluating. For the finished... 

Carotenoids are also present in animal products such as eggs, lobsters, greyflsh, and various types of hsh. In higher plants, they occur in photosynthetic tissues and choloroplasts where their color is masked by that of the more predominant green chlorophyll. The best known are P-carotene and lycopene but others are also used as food colorants a-carotene, y-carotene, bixin, norbixin, capsanthin, lycopene, and P-apo-8 -carotenal, the ethyl ester of P-apo-8-carotenic acid. These are Upid-soluble compounds, but the chemical industry manufactures water-dispersible preparations by formulating coUoid suspensions by emulsifying the carotenoids or by dispersing them in appropriate colloids. ... 

The question whether the intramolecularly crosslinked microparticles of non-aqueous polymer dispersions are really microgels is also justified, considering non-aqueous dispersions prepared from acrylic copolymers and melamine/formaldehyde crosslinker with particle sizes of about 300 nm. [45, 343]. In any case, these crosslinked polymeric microparticles are useful constituents of high-solids coatings, imparting a yield stress to those solutions which probably involves attractive forces between the microparticles. 

Purified alfalfa gives a clean, bright lemon yellow shade. Lutein is more stable to oxidation than the other carotenoids. It is also resistant to the action of sulfur dioxide. Lutein is oil soluble and is most effective dissolved in oil. Aqueous dispersible preparations based on lutein are available. 

A 10% w/w highly enriched - FePc/XC-72 dispersion, prepared in exactly the same fashion, was used in the Hossbauer measurements. (The isomer shifts, 5, are referred to the a-Fe standard, and 5, the quadrupole splittings A, and widths T, are all given in mm-s"1, throughout the text.)... 

The structures of four of the synthetic carotenoids (beta-carotene, canthaxanthin, beta-apo-8 -carotenol, beta-apo-8 -carotenoic acid) are shown in Fig. 8.2. By virtue of their conjugated double bond structure, they are susceptible to oxidation but formulations with antioxidants were developed to minimize oxidation. Carotenoids are classified as oil soluble but most foods require water soluble colorants thus three approaches were used to provide water dispersible preparations. These included formulation of colloidal suspensions, emulsification of oily solutions, and dispersion in suitable colloids. The Hoffman-LaRoche firm pioneered the development of synthetic carotenoid colorants and they obviously chose candidates with better technological properties. For example, the red canthaxanthin is similar in color to lycopene but much more stable. Carotenoid colorants are appropriate for a wide variety of foods.10 Regulations differ in other countries but the only synthetic carotenoids allowed in foods in the US are beta-carotene, canthaxanthin, and beta-8-carotenol. 

The dynamics of oil-in-water dispersion (OWD) are complex and have relevance related to potential toxicity or hazard. In comparing the toxicides to marine animals of oil-in-water dispersions prepared from different oils, not only the amount of oil added but also the concentrations of oil in the aqueous phase and the composition and dispersion-forming characteristics of the parent oil must be taken into consideration. In comparing the potential impacts of spills of different oils on the marine biotic community, the amount of oil per unit water volume required to cause mortality is of greater importance than any other aspect of the crude oil behavior. 

Figure 1 Size distribution of a particle dispersion prepared by slow solvent evaporation. 

Figure 4 SEM micrograph (15,000X) of a lyophilized particle dispersion prepared by co- precipitation.

Figure 5 SEM micrograph (1,000X) of a centrifuged particle dispersion prepared by co-precipitation. 

Philipse, A.P. van Bruggen, M.P.B. Path-mannanharon, C. (1994) Magnetite silica dispersions. Preparation and stability of surface modified silica particles with a magnetic core. Langmuir 10 92—99... 

Fig. 9.2.11 TEM images of monodisperse colloidal dispersions prepared by heterogeneous nucleation with Pt as nucleating agent (A) Co15Ni6, dm = 50 nm, cr = 0.10dm. (B) Co8oNi2o, dm = 7 nm,

The dispersed particles are spheres of great polydispersity. As noted in Appendix C (Section C.3b), this is generally the case in dispersions prepared by comminution such as this. 

With the PGSS process, micronized drugs and drug/PEG 4000 samples were prepared in a new way, which has some advantages over conventional methods for the micronization of pure drugs and for drug/carrier solid dispersion preparation, namely fusion methods and solvent processes. 

After all other conditions had been optimized, the effect of temperature during the adsorption step was studied again, particularly because the temperature reduction from 150° to 100 °C had no deleterious effect on dispersion stability. Adsorption of the block copolymer onto the titanium dioxide at room temperature would be easy to carry out in practical applications and might be worth even a sacrifice in dispersion stability. Figure 4 shows settling data of dispersions prepared in a Waring... 

The dispersions prepared in the first five experiments listed in Table IV were very stable. The settling data of these samples are plotted in Figure 5. The amount of adsorbed block copolymer in the treatment at room temperature is in about the same range as the pick-up previously obtained with the heat treatment methods, and the total settling times of the best dispersions in Table IV are even somewhat higher than the values previously obtained. At very high degrees of carboxylation (ex-... 

The colloidal stability of polymer dispersion prepared by the emulsion copolymerization of R-(EO)n-MA was observed to increase with increasing EO number in the macromonomer [42, 96]. Thus C12-(EO)9-MA did not produce stable polymer latexes, i.e., the coagulum was observed during polymerization. This monomer, however, was efficient in the emulsion copolymerization with BzMA (see below). The C12-(EO)20-MA, however, appears to have the most suitable hydrophilic-hydrophobic balance to make stable emulsions. The relative reactivity of macromonomer slightly decreases with increasing EO number in macromonomer. The most hydrophilic macromonomer with co-methyl terminal, Cr(EO)39-MA, could not disperse the monomer so that the styrene droplets coexisted during polymerization. The maximum rate of polymerization was observed at low conversions and decreased with increasing conversion. The decrease in the rate may be attributed to the decrease of monomer content in the particles (Table 2). In the Cr(EO)39-MA/St system the macromonomer is soluble in water and styrene is located in the monomer droplets. Under such conditions the polymerization in St monomer droplets may contribute to the increase in r2 values. 

The dispersants prepared by the reaction of hydrocarbon substituted succinic acid anhydrides with polyamines to give linear mono- and bis-succinimides, are well known lubricating oil additives commercially available (Gutierrez and Brois, 1980 Le Suer and Norman, 1965 and 1966 Song et al., 1993, 1994 and 1995). 

B. Transfer 100 mL of the dispersion prepared in Identification Test A into another 400-mL beaker, heat the mixture in a boiling water bath for about 10 min, and then cool to room temperature. No appreciable increase in viscosity develops. Acid-Insoluble Matter Not more than 7.0%. 

Loss on Drying Determine as directed under Loss on Drying, Appendix IIC, drying a sample at 105° for 5 h. pH of a 10% Dispersion Determine as directed under pH Determination, Appendix IIB, using a dispersion prepared by mixing 10 g of sample with 90 mL of water and allowing it to stand at room temperature for 2 h. 

The phthalocyanines have recently received great attention as chargegenerating materials in xerographic photoreceptors. Copper phthalocy-anine was one of the first dyes to be employed as a photoreceptor and its performance varied as a function of the crystallinity, morphology, and dispersion preparation [40]. 

Hasegawa, S.,Hamaura,T.,Furuyama,N.,Kusai,A.,Yonemochi, E.,andTerada,K. (2005), Effects of water content in physical mixture and heating temperature on crystallinity of troglitazone-PVP K30 solid dispersions prepared by closed melting method, Int. J. Pharm., 302,103-112. 

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