Solubility acrylic dispersion

Solubilizable Dispersions (19). The chemistry of solubilizable acrylic dispersions is a hybrid of emulsion and water-reducible technology. These polymers are synthesized by emulsion techniques but contain acidic or basic functionality that renders them water soluble upon neutralization with an appropriate titrant. For example, if the solubilizing functionality is acidic, the polymer will behave like an emulsion below a certain critical pH range, like a highly swollen emulsion within the critical pH range, and like a true water-soluble polymer at sufficiently high pH values. Such polymers offer a favorable balance of properties for many coating applications. 

Other water-borne coatings include water-soluble emulsions, dispersions, and latex resins. Water-soluble resins are rare because most resins derived from vegetable oils are insoluble in water. The true emulsions are based on the emulsification of the oil or alkyd through either the action of a surfactant or a resin that has a surfactantlike character. The alkyd emulsions are readily prepared and can be used for OEM coatings and architectural applications. The submicron size droplets are stabilized by the thickeners (El-Aasser Sudol, 2004 Landfester, 2005 Landfester et al., 2004 Tsavalas et al., 2004 Weissenborn Motiejauskaite, 2000a,b). In dispersions, the resin is a solid and is dispersed in water. The latex resin is usually vinyl acetate, styrene, acrylates, or methacrylates radically copolymerized in a micelle to form particles 0.1 pm in diameter (Bloom et al., 2005 Brister et al., 2000 Jiratumnukul Van De Mark, 2000 Thames et al., 2005). 

Methods of preparation of aqueous acrylic dispersions are well known [19] and will not be discussed here. Emulsion polymerisation of acrylic monomers is usually carried out using a water-soluble initiator or a redox system. In this process, relatively high levels (up to several %) of emulsifiers and protective colloids are used. The dispersed polymer generally has a linear structure and a high molecular weight (MW). The properties of dispersions and films are mostly affected by the kind of monomer(s) used [20]. 

The properties of hybrid dispersion prepared according to two different methods (la and 3 - see Section 3.2) and having the same chemical composition and differing only in the chemical structure of the acrylic/styrene polymer component are presented in Tables 6.24 to 6.26. All dispersions were synthesised using a water-soluble initiator. Dispersions prepared according to method la did not contain any coalescent while dispersions prepared according to method 3 contained 11.6% of NMP. 

There is some interest in water dispersible light curable coatings and binders. Thus, Heischkel et al, reported preparation of a water based radiation curable polyurethane acrylate coating. Some of the water soluble or dispersible monomers are diethylaminoethyl acrylate, butanediol monoacrylate, vinyl caparolactam, and propylene glycol monoacrylate. 

In the surfactant macromonomer method, [9-11, 17] a water-soluble (or dispersible) surfactant, nonylphenoxy poly(ethylene oxide), is built into an acrylate monomer. The surfactant macromer has both a hydrophilic head... 

The free carboxyl groups on the acrylic graft co-polymer can be neutralised with a tertiary amine which can activate an esterification reaction between the acrylic carboxyl moieties and the epoxy reactive sites. On the addition of de-ionised water, the free carboxyl moieties of the acrylic co-polymer react with the amine to produce a water soluble or dispersible quaternary ammonium hydrogel of the modified epoxy. 

In actual practice very few polymers form true solutions and so this chapto will cover polymer Aspersions and emulsions. Many resins are only soluble in a solvent/water mixture, others are dispersions of a water soluble resin in an emulsion, e.g. water soluble alkyd dispersed in [Pg.352]

Another technique for overcoming the solids/viscosity conundrum is demonstrated in a patent by American Cyanamid. Here a conventional water soluble acrylic is prepared as a dispersion and is then used as a colloid stabiliser for further emulsion polymerisation. This polymerisation occurs within the dispersion droplets that have already been formed. This allows higher solids solutions to be formed with low viscosities, and low cosolvent contents ... 

Almost all synthetic binders are prepared by an emulsion polymerization process and are suppHed as latexes which consist of 48—52 wt % polymer dispersed in water (101). The largest-volume binder is styrene—butadiene copolymer [9003-55-8] (SBR) latex. Most SBRlatexes are carboxylated, ie, they contain copolymerized acidic monomers. Other latex binders are based on poly(vinyl acetate) [9003-20-7] and on polymers of acrylate esters. Poly(vinyl alcohol) is a water-soluble, synthetic biader which is prepared by the hydrolysis of poly(viayl acetate) (see Latex technology Vinyl polymers). 

Functional derivatives of polyethylene, particularly poly(vinyl alcohol) and poly(acryLic acid) and derivatives, have received attention because of their water-solubility and disposal iato the aqueous environment. Poly(vinyl alcohol) is used ia a wide variety of appHcations, including textiles, paper, plastic films, etc, and poly(acryLic acid) is widely used ia detergents as a builder, a super-absorbent for diapers and feminine hygiene products, for water treatment, ia thickeners, as pigment dispersant, etc (see Vinyl polymers, vinyl alcohol polymers). 

Whilst the aliphatic nylons are generally classified as being impact resistant, they are affected by stress concentrators like sharp comers which may lead to brittle failures. Incorporation of mbbers which are not soluble in the nylons and hence form dispersions of rubber droplets in the polyamide matrix but which nevertheless can have some interaction between mbber and polyamide can be most effective. Materials described in the literature include the ethylene-propylene rubbers, ionomers (q.v.), polyurethanes, acrylates and methacrylates, ABS polymers and polyamides from dimer acid. 

For some applications, such as for repulpable type PSAs, it may be advantageous to incorporate high levels of acrylic acid because this makes the polymer more hydrophilic. At the same time, high levels of acid also improve the water-dispersibility of the adhesive, especially at higher pH where the acid groups are converted to the more water-soluble neutralized salt form. Since the high level of acid increases the of the resulting polymer, a non-tacky material results. To make the adhesive pressure sensitive, the polymer can be softened with water-dispersible or soluble plasticizers, such as polyethers [68]. 

There are numerous applications where the development of high viscosity is necessary in a finished product. For example, thickeners, mainly based on poly(acrylic acid), are used to give body to so-called emulsion paints. Emulsion paints are not formulated from true emulsions (Le. stable dispersions of organic liquids in water), but are prepared from latexes, that is, dispersions of polymer in water. Since latexes do not contain soluble polymers, they have a viscosity almost the same as pure water. As such, they would not sustain a pigment dispersion, but would allow it to settle they would also fail to flow out adequately when painted on to a surface. Inclusion of a thickener in the formulation gives a paint in which the pigment does not settle out and which can readily be applied by brush to a surface. 

Copolymers of mainly acrylic acid and 2% to 20% by weight of itaconic acid are described as fluid loss additives for aqueous drilling fluids [138]. The polymers have an average molecular weight between 100,000 and 500,000 Dalton and are water dispersible. The polymers are advantageous when used with muds containing soluble calcium and muds containing chloride ions, such as seawater muds. 

A major drawback of synthetic thickeners when used with dyes is their sensitivity to electrolytes. Most soluble dyes behave as highly ionised electrolytes and disperse dyes contain anionic polyelectrolyte dispersing agents unless they have been formulated with nonionic systems specifically for use with acrylic thickeners. Consequently there is a loss of viscosity this can be quite pronounced although it depends on circumstances, particularly on the dye concentration. As already mentioned, this can be alleviated to some extent by copolymerisation with acrylamide during manufacture. Otherwise it is necessary to try to eliminate all electrolytes from the system or to increase the concentration of thickener. Such measures have their limitations in practice, however. Alternative synthetic thickening... 

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