Molecular weight acrylic

The most commonly used scale inhibitors are low molecular weight acrylate polymers and organophosphoms compounds (phosphonates). Both classes of materials function as threshold inhibitors however, the polymeric materials are more effective dispersants. Selection of a scale control agent depends on the precipitating species and its degree of supersaturation. The most effective scale control programs use both a precipitation inhibitor and a dispersant. In some cases this can be achieved with a single component (eg, polymers used to inhibit calcium phosphate at near neutral pH). 

During mutual graft copolymerization, homopolymerization always occurs. This is one of the most important problems associated with this technique. When this technique is applied to radiation-sensitive monomers such as acrylic acid, methacrylic acid, polyfunctional acrylates, and their esters, homopolymer is formed more rapidly than the graft. With the low-molecular weight acrylate esters, particularly ethyl acrylate, the homopolymer problem is evidenced not so much by high yields as by erratic and irreproducible grafting. 

Significant improvement in chromium depression has been achieved using depressants from the KM series, representing mixtures of organic acid and low-molecular-weight acrylic acid mixtures. It is, therefore, possible to depress chromium during PGM flotation and at the same time reduce collector consumption. The relationship between the level of collector and level of KM3 depressant is shown in Table 18.9. 

In a large number of oxide flotation plants, sodium silicate (Na2Si03) is used as a gangue depressant. In the past two decades, a new line of depressants has been developed and introduced into a number of operating plants. Some of these depressants include (a) a mixture of sodium phosphate and lignin sulphonate (i.e. depressant 3XD), (b) a mixture of a low-molecular-weight acrylic acid and sodium silicate (depressant 2D) and (c) hydrosol based on the reaction of sodium silicate with alumina sulphate (depressant SD). These depressants were extensively examined on copper oxide ores from the Nchanga mine in Zambia. 

Acrylate and low-molecular-weight acrylic acids are effective slime depressants/disper-sants. Suspendol PKK and PC improved separation efficiency between zinc and iron oxides. Starches, mainly hydrolysed starch and cooked starch, are effective depressants in the treatment of oxidized zinc ores that contain iron oxides and Fe-hydroxides. 

The results obtained indicated that cationic flotation of pyrochlore was not successful. Dispersant AQ4 has a pronounced effect on niobium metallurgical results. Dispersant/ depressant AQ4 is composed of the following individual reagents 60% orthodihydrox-ybenzene (Catacol), 30% low-molecular-weight acrylic acid (Accumer 2400) and 10% hexametapho sphate. 

A depressant system developed for beneficiation of Ta/Nb-Zr ores involves oxalic acid-hydro fluoro silicic acid and depressant SHQ. SHQ is a mixture of a low-molecular-weight acrylic acid and condensation product of disulphonic acid (Suspendol PKK, manufactured by Cognis, Germany). After the development of the final reagent scheme, a series of locked-cycle tests were performed using the flowsheet shown in Figure 23.7. 

The use of DQ4 in the desliming stage has a significant impact on monazite loss to the slime fraction. Table 24.15 shows the effect of different dispersants on monazite loss in the slime fraction, using dispersants from the DQ series. These dispersants are a mixture of low-molecular-weight acrylic acids modified with surfactant. 

The reagent scheme developed for the White Mountain titanium ore is shown in Table 25.15. Gangue depressants H2SiF6, oxalic acid and DAX1 were used. Depressant DAX2 is a mixture of low-molecular-weight acrylic acids designed specifically to depress calcite. 

The way to maximise the solids content of the slurry while keeping a reasonable viscosity is through the use of a dispersant. The dispersant helps maintain fine solid particles in a state of suspension, thus minimising their agglomeration or settling. The dispersant is generally a low molecular weight acrylic based polymer. For most applications, cost of dispersant is critical. 

As in the case of poly-a-olefins, the optical activity of the high molecular weight acrylic esters does not depend remarkably on molecular... 

Figure 9.6 HPLC analysis of phenolic antioxidants in low molecular weight acrylic resin.

Recently, Dowbenko et al (Ref. 4) of PPG Industries described two approaches to the development of energy-curable pressure sensitive adhesives. One Involved the incorporation of low molecular weight acrylic polymers into hot melt formulations the second employed radiation polymerization of monomer-polymer syrups. 

Builder Sodium tripolyphosphate (STPP) Low-molecular-weight acrylate Citrate 5-30 Sequestration Soil suspension, alkalinity, emulsification... 

The esters of acrylic add, of more recent industrial development, are used to manufacture polymers and copolymers. A distinction must be drawn between low molecular weight acrylates obtained by direct synthesis whose-physical-properties arc given in Table ll.S for the most important commercially, and the higher esters produced by transesterification from methyl acrylate in particular. 

The main processes for manufacturing low molecular weight acrylates are the following ... 

These acrylates are usually manufactured in batches, because of the low tonnages required. Moreover, the corresponding alcohols are generally insoluble in water and thus difficult to recover by extraction ir-butanol, 2-ethyl hexanoL for example). They are obtained either by direct esterification of acrylic acid, or by transesterification of low molecular weight acrylates (methyl and ethyl acrylates). 

Processing aids are usually based on high molecular weight acrylic copolymers (for PVC). They modify the rheology and processing characteristics of the melt. Lubricants are processing aids that function to ease the process and are of two types either internal lubricants (that influence the viscosity, such as calcium stearates) or external lubricants (such as oxidised polyethylene wax). Lead-stabilised PVC lubricants are a part of the stabiliser system. They are important in PVC foam formulations. 

Even more rapid curing can be achieved if unsaturated polyester coatings are replaced by the more expensive unsaturated acrylic coatings. Instead of a polyester resin, a low molecular weight acrylic polymer is used, often called an oligomer. These acrylic oligomers are the reaction products of acrylic acid and end groups in epoxy resins and saturated polyesters, or of hydroxy monomers, such as hydroxyethyl acrylate, and polyisocyanates, e.g. 

Figure 12.1 Photograph of the static mixer fouled by the precipitate of high molecular weight acrylic polymer. From Ref [8].

Processing aids are usually based on high molecular weight acrylic copolymers (for PVC). They modify the rheology and processing characteristics of melt to be processed. 

Styrenes, acrylics High molecular weight acrylic copolymers improve processability of PVC compounds, good weatherability lubricant grades reduce adherence of melt to processing equipment... 

Employing a similar approach as above, thiol-terminated RAFT polymers have also been reacted with a variety of low and high molecular weight acrylate species for ef cient end functionalization (Spruell et al., 2009) and immobilized onto ene-decorated microspheres of poly(divinyl benzene) (Goldmann et al., 2009). Considering the abundance of commercially available activated alkene substrates amenable to nucleophihc addition (e.g., acrylates and maleimides) and the simplicity-cum-robusrness of the aforesaid approach, the RAFT/thiol-ene combination can be expected to remain as a valuable tool for macromolecular synthesis (Sumerlin and Vogt, 2010). 

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