Adhesives aqueous polymer emulsions

As a liquid product the 5% aqueous formulation of 2-methyl-4,5-trimethylene-4-isothiazolin-3-one offers a number of processing advantages when the product is used for the in-can/in-tank protection of aqueous functional fluids, preferably paints, adhesives and polymer emulsions. In these applications the remarkable water-solubility of the a.i. is a special advantage with an addition rate between 0-05 and 0-2% of the 5% preparation. 

Water-based adhesives also encompass emulsion and dispersion adhesives in which polymer chains are dispersed and stabilized into tiny particles or spheres in aqueous medium with the aid of surfactants. Within this category there are low-cost poly(vinyl acetate) and acrylics, and more expensive higher-performance urethanes, which are typically made of two components. 

Originally the adhesive system consisted of an aqueous poly(vinyl alcohol) solution with an isocyanate cross-linker. At this stage the common name was Aqueous Polymer Isocyanate (API) [3]. Further developments including use of different types of polymer emulsions, like poly(vinyl alcohol) (PVA), ethyl(vinyl acetate) (EVAc), styrene butadiene rubber (SBR) or acrylic-styrene (AcSt) emulsion, led to adhesives systems with improved performance, hence today the common abbreviation is EPI [4, 8]. The isocyanate cross-linking agent has also been further developed to improve the compatibility and the reactivity with the water-based component, thus several different types are now available for use in EPI adhesives. 

Aqueous dispersion of polymeric particles, a polymer emulsion, a product of emulsion polymerization used in paints, adhesives, coatings, etc. 

Preservatives based on BIT may be used for the in-tank/in-can protection of polymer emulsions, latex paints, pigment and filler slurries, paper coatings, adhesives and other aqueous functional fluids. Because of the heat stability and non-volatility of BIT the preservatives can be incorporated in fluids which are still hot. BIT exhibits no headspace activity. It is compatible with non-ionic and anionic compounds and active in acid and alkaline media. 

Because of its equalized spectrum of effectiveness and its favourable toxicological properties the microbicide is gaining more and more importance as a preservative for a wide variety of aqueous functional fluids, such as polymer emulsions, paints, adhesives (including protein based adhesives), mineral slurries, concrete additives, metal working fluids, detergent solutions, cosmetic products, etc. The EC list of preservatives permitted for use in cosmetics mentions 1,2-dibromo-2,4-dicyanobutane with a maximum authorized concentration of 01% and not to be used in cosmetic sunscreen products. 

In-tank/in-can protection of aqueous functional fluids, e.g. polymer emulsions, water based paints and adhesives, glues, starch slurries, thickener solutions, gelatine, wax emulsions, inks, polishes, pigment and mineral slurries, rubber latexes, concrete additives, drilling muds, aqueous cosmetic and pharmaceutical formulations. 

The microbicide is highly effective against bacteria, yeast, fungi and algae and may be used for the control of microorganisms in industrial water systems, paper coatings, polymer emulsions, aqueous paints, adhesives, etc. (Masahiro and Katsuhisa, 2000). 

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. 

For use with latex adhesives, the tackifiers are produced as aqueous dispersions. It is important here that the dispersants used be compatible with the surfactant in the polymer emulsions. 

Emulsion Polymerization. Emulsion polymerization is the most important industrial method for the preparation of acryhc polymers. The principal markets for aqueous dispersion polymers made by emulsion polymerization of acryhc esters are the paint, paper, adhesives, textile, floor pohsh, and leather industries, where they are used principally as coatings or binders. Copolymers of either ethyl acrylate or butyl acrylate with methyl methacrylate are most common. 

Rosin ester resins are used extensively in pressure-sensitive adhesives as tackifiers. The adhesive is formulated by blending the resin with a polymer in solution or as aqueous emulsions. Typical compositions may contain about 50% resin. The glycerol or pentaerythritol esters of stabilized rosins are often used because they are stable on aging. 

In this special volume on polymer particles, recent trends and developments in the synthesis of nano- to micron-sized polymer particles by radical polymerization of vinyl monomers in environmentally friendly heterogeneous aqueous and supercritical carbon dioxide fluid media are reviewed by prominent worldwide researchers. Polymer particles are prepared extensively as synthetic emulsions and latexes, which are applied as binders in the industrial fields of paint, paper and inks, and films such as adhesives and coating materials. Considerable attention has recently been directed towards aqueous dispersed systems due to the increased awareness of environmental issues. Moreover, such polymer particles have already been applied to more advanced fields such as bio-, information, and electronic technologies. In addition to the obvious commercial importance of these techniques, it is of fundamental scientific interest to completely elucidate the mechanistic details of macromolecule synthesis in the microreactors that the polymer particles in these heterogeneous systems constitute. 

The cationic palladium Q -diimine catalysts, much more so than their nickel analogs, are tolerant of polar functional groups. Emulsion polymerization in aqueous solvents can take place to give polymer microspheres useful as adhesives. Monomers such as acrylates, unsaturated ethers, and... 

The free-radical kinetics described in Chapter 6 hold for homogeneous systems. They will prevail in well-stirred bulk or solution polymerizations or in suspension polymerizations if the polymer is soluble in its monomer. Polystyrene suspension polymerization is an important commercial example of this reaction type. Suspension polymerizations of vinyl ehloride and of acrylonitrile are described by somewhat different kinetic schemes because the polymers precipitate in these cases. Emulsion polymerizations aie controlled by still different reaetion parameters because the growing macroradicals are isolated in small volume elements and because the free radieals which initiate the polymerization process are generated in the aqueous phase. The emulsion process is now used to make large tonnages of styrene-butadiene rubber (SBR), latex paints and adhesives, PVC paste polymers, and other produets. 

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