Carboxylated acrylic thickeners

Carboxylated acrylic polymers are well established as emulsion paint thickeners because their unique chemistry can be varied to generate products which can meet most of the performance requirements. There are practical benefits also in terms of... 

Suspension polymerization also is used When acrylic monomers or their mixtures with other monomers are polymerized while suspended (usually in aqueous system), the polymeric product is obtained m the form of small beads, sometimes called pearls or granules. Bead polymers are the basis of the production of molding powders and denture materials. Polymers derived from acrylic or methacrylic acid furnish exchange resins of the carboxylic acid type. Solutions in organic solvents furnish lacquers, coatings and cements, while water-soluble hydrolysates are used as thickeners, adhesives, and sizes. 

Among the carboxylic acid and anhydride functional monomers that have been employed in the synthesis of these thickener polymers are acrylic acid, methacrylic acid, itaconic acid, citraconic acid, maleic acid, fumaric acid, crotonic acid, maleic anhydride, and citraconic anhydride. The copolymers containing maleic and citraconic anhydride monomers are either hydrolyzed or partially esterified to obtain the required carboxyl functionality. Among these carboxylic monomers, maleic anhydride and particularly methacrylic acid are most frequently favored. Carboxylic homopolymers, where they can be formed, might be considered the simplest examples of ASTs were it not for the fact that they are not copolymers as defined, and some are water soluble in their un-ionized states. Examples of carboxylic homopolymers are the un-ionized free-radical-polymerized atactic forms of polyacrylic acid (i) and polymethacrylic acid (2), which are both readily soluble in water. 

A typical exterior acrylic paint formulation see Appendix A) was thickened with a commercial HASE thickener that contained 5.23 meq/g of carboxylic acid functionality (4). This thickener was modified with 1 to 25 lb (1 lb = 0.4536 kg) of zinc oxide (French process) in the mill base in one set of paints and with post-added zinc ammonium complex such as acetate, carbonate, bicarbonate, or glycinate in another set of paints. 

Uses Monomer for large-volume resins and polymers, organic synthesis comonomer for thermosetting acrylic resins carboxylated comonomer for S/B-nItrlle latex engineering adhesives thickener for hair care prods. paints Ion-exchange membrane processing agent, binder for paper and textiles leather treatment adhesion promoter pharmaceutical ophthalmics... 

Polymethyl methacrylate Polyquaternium-14 Sodium ceteth-13 carboxylate Sodium cocoyl hydrolyzed rice protein Stearamide DEA Steareth-10 allyl ether/acrylates copolymer thickener, hair conditioners Cetearyl behenate thickener, hair shampoo Sodium lauryl sulfoacetate thickener, hard-surface cleaners Sodium ceteth-13 carboxylate thickener, HCI toilet bowl systems Dihydroxyethyl tallow glycinate thickener, household cleaners Cocamide DEA Soyamide DEA thickener, household prods. 

Polyglyceryl-3 laurate thickener, silicone emulsification Ceteth-2 Steareth-30 thickener, silk screen printing inks Ethyl hydroxyethyl cellulose thickener, skin care Acrylates/beheneth-25 methacrylate copolymer Acrylates/C10-30 alkyl acrylate crosspolymer Bisisostearamidopropyl ethoxyethyl dimonium chloride Cetearyl octanoate Hydroxypropyl guar hydroxypropyl trimonium chloride Hydroxypropyl starch phosphate Oleamidopropyl betaine PEG-90 diisostearate Sodium ceteth-13 carboxylate Sodium cocoyl hydrolyzed rice protein Sodium tauride acrylates/acrylic acid/acrylonitrogens copolymer Stearamide DEA Steareth-10 allyl ether/acrylates copolymer... 

Thickening agents based on aqueous emulsion polymer chemistry were first developed [9] in the late 1950s and represent another important class of thickening agents. In this physical form, a monomer composition is chosen that provides a balance between the hydrophilic nature of a carboxylic acid monomer (such as acrylic, or more usually methacrylic acid) and a hydrophobic alkyl (meth)acrylate monomer (such as methyl methacrylate, ethyl acrylate, butyl acrylate or mixtures of such species). Whilst the carboxylic acid is in the free-acid form the overall composition is balanced to sufficiently hydrophobic to be water immiscible. This allows the monomer mixture to be reacted using a conventional oil-in-water emulsion polymerisation technique. 

Levels of carboxyl content must be worked out with each thermoplastic structure and molecular weight. With a polyfvinyl acetate) of about 100 000 molecular weight a copolymer of about 99.0% vinyl acetate and 1.0% acrylic acid is quite effective in chemically thickened applications. 

Solvent adhesives and reactive adhesives are made from homo- and copolymers of methacrylates, generally methyl and ethyl methacrylate and, occasionally, butyl methacrylate. Monomeric (meth)acrylates are also used in reactive adhesive systems (polymerization adhesives). Poly(ethyIene glycol) dimethacrylates are the basis of anaerobically curing liquid resins (reactive adhesives). They also are added as adhesion promoters to plastisol adhesives. Acrylate-ethylene copolymers, in some cases with a small content of carboxyl groups, are used instead of ethylene-vinyl acetate copolymers as fusible polymers for special hot-melt adhesives. Salts of polyacrylate and acrylate - acrylic acid copolymers are used as thickeners for aqueous adhesive solutions and emulsion-based adhesives. 

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