Waterborne polymer dispersions

Acrylic resins are generally well characterized by Py-GC/MS without the need for any derivatization reaction. However, in waterborne polymer dispersions it is common to have minor amounts of acrylic and/or methacrylic acid monomers added in the copolymerization to help the stability of the final latex. These monomers can also appear in the pyrolysis products, and it has been shown that with on-line derivatization they can be more efficiently revealed [85]. 

Emulsion paints consist of polymer dispersions as binders, pigments, extenders, and small amounts of auxiliaries (in some cases < 1 %). Waterborne polymer dispersions are produced by emulsion polymerization monomer droplets are polymerized in water-containing surfactants and protective colloids. The size and size distribution of the dispersed polymer particles can be controlled by adjusting the stirring rate in the polymerization reactor and by selecting appropriate protective colloids. 

Industrial production of waterborne polymer dispersions is mainly carried out by conventional emulsion polymerization... 

The chain extension step may then take place in the water phase. Hydrazine and ethylene diamine are commonly used chain extenders for waterborne urethane dispersions. The isocyanates react with the diamine chain extenders much faster than with the water, thus forming polyurea linkages and building a high molecular weight polymer. More detailed information regarding the synthesis and process of making waterborne polyurethane dispersions is found in Dieterich s review article [58]. 

Epoxy dispersions also can easily be blended with other waterborne polymers to make modified latex adhesives. The resulting hybrid adhesive produces performance properties and application characteristics that are superior to those of the originating latex system. 

Epoxy modified polymer latex systems offer improved handling performance and moisture and chemical strength advantages over unmodified formulations. The wide range of latex polymers and the range of waterborne epoxy dispersions offer the formulator a wide latitude in performance characteristics required by specific applications. 

Waterborne paints differ according to the nature of their stabilization in water the polymer molecules are dissolved in water or dispersed in water in the form of polymer dispersions or emulsion polymers. Recent developments include polymer particles formed in organic solvents and then emulsified in water with low or, more commonly, high molecular mass emulsifiers being used for internal or external emulsification. Internal emulsification denotes that part of the binder molecule functions as an emulsifying moiety, whereas for external emulsification separate emulsifiers are required. 

Polymer Dispersions (Emulsion Polymers). Waterborne paints based on polymer dispersions (usually referred to as emulsion paints) are not water soluble. They are water-thinnable systems composed of dispersions of polymer particles in water (see Section 3.5). The particles consist of high molecular mass polymers (e.g., of styrene, butadiene, acrylate, or vinyl monomers) and are produced by emulsion polymerization. These waterborne paints also contain small amounts of organic solvents (< 5 wt %) that serve as film-forming (coalescing) agents that partially evaporate on drying. 

The required application viscosity of waterborne emulsion paints is generally obtained by adding a small volume of water. The evaporation behavior of polymer dispersions is similar to that of conventional, solvent-based paints. 

Waterborne dispersed polymers include both synthetic polymer dispersions and natural rubber. Synthetic polymer dispersions are produced by emulsion polymerization. A substantial part of the synthetic polymer dispersions is commercialized as dry products these include SBR for tires, nitrile rubbers, about 10% of the total PVC production, 75% of the total ABS and redispersable powders for construction materials. Carboxylated styrene-butadiene copolymers, acrylic and styrene-acrylic latexes and vinyl acetate homopolymer and copolymers are the main polymer classes commercialized as dispersions. The main markets for these dispersions are paints and coatings, paper coating, adhesives and carpet backing. 

PU based on the use of pristine castor oil were reviewed in 2010 [9, 10], including preparation and properties of an interpenetrating network with other polymers. Recent additions to this topic include work by Larock and co-workers [13, 14] on waterborne PU and their silica composites a kinetic study of the reaction of castor oil with 4,4 -methylene diphenyl diisocyanate to produce an elastomeric matrix [15] the rheology of waterborne PU dispersions for coating applications, prepared with castor oil and isophorone diisocyanate (IPDI) [16] (Scheme 3.7) and the synthesis and characterisation of gelled materials arising from the reaction of isocyanate-bearing chitin or chitosan with castor oil [17]. 

Alkyd paints dominated the architectural coating market for a long period until the appearance of polymer dispersions or the so-called latex paints. Specifically for wall application waterborne paints based on poly(vinyl acetate) homo- and copolymers, styrene-acrylics and pure acrylic latexes almost completely took over the market from the alkyd resins for both interior and exterior application. However, for... 

Probably the main step to eliminate VOC in the polymer industry has been the substitution of solvent-based systems by waterborne products. Nowadays, about 5% of the polymers are produced by aqueous dispersion processes, mainly by suspension and emulsion polymerization [8]. The water-based polymers, however, are not totally free of monomer and VOCs, since the reaction does not reach completion and VOCs arising from impurities in the raw materials or from by-side reactions can be present. There are two main ways to reduce the residual monomer content in waterborne polymers post-polymerization or/and devolatilization. 

Goikoetxea M, Minari RJ, Beristain I, Paulis M, Barandiaran MJ, Asua JM. A new strategy to improve alkyd/acrylic compatibUization in waterborne hybrid dispersions. Polymer 2010 51 5313-5317. 

Linoleum Adhesives. Linoleum generally is laid with waterborne adhesives based on acrylic emulsions or SBR latex. They contain higher amounts of inert inorganic fillers, and natural and/or synthetic resin is used to accelerate initial tack. Linoleum adhesives have to set rapidly to avoid expansion or shrinkage of the covering. Two-component adhesives consisting of one polymer dispersion and a second cement preparation are available to adhere linoleum to nonabsorbent substrates. 

One-component water-borne polyurethane systems can be derived from polyurethane dispersions or blocked polyisocyanates (refer to Section 3.2.1). Blocked isocyanates are added to the co-reactant resins providing one-component systems with excellent shelf life. This type of adhesives is principally used for non-porous materials and the bonding of unlike metals such as aluminium to steel, and stainless steel to mild steel. They are also usefiil in bonding some of the high pressure laminates such as those based on phenoUcs and melamine [39]. Systems based on water-borne blocked polyisocyanate crosslinkers and suitable waterborne polymers approach the performance levels previously obtained only by solvent-borne systems [16]. 

Emulsion polymers differ from solution types in that the polymer takes the form of a fine particle suspension (typically fix)m 0.03 to 0.3 pm) dispersed in water. There are two major classes of waterborne polymer colloids available, namely ... 

The most important issue for producing waterborne polymer-clay nanocomposites by miniemulsion polymerization of hybrid monomer-clay systems is to know the location of clay platelets in the dispersion in other words, to understand the morphologies of the hybrid monomer-clay miniemulsions. 

The most recent developments are water-based dispersions of PEEVE,81 some of them cross-linkable with waterborne isocyanates.82 Another FEVE-based polymer, developed and commercialized recently by Asahi Glass Co. Ltd., has trade name LUMISEAL and is used for high-performance sealants, similar to silicone sealants with the advantage of eliminating the staining problem associated with the latter.83... 

Chemical modification of the epoxy resin includes either attaching hydrophilic groups to the epoxy resin or attaching the epoxy resin to hydrophilic polymers. This is most often done by grafting. For example, one of the largest volume uses for waterborne epoxy is the coating of metal cans. In this application the epoxy resin is rendered water-dispersible by the grafting of the epoxy resins to acrylic polymer. 

The waterborne basecoat consists of a urethane or an acrylic dispersion with passivated aluminum for metallic glamour. The aluminum must be passivated to prevent reaction with water and the evolution of hydrogen gas. Passivating agents can include polymers, hexavalent chromium (now mandated for removal), or phosphate esters. The basecoat is pre-baked (with infrared or thermal ovens) to release the majority of the water prior to clear-coat application. 

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