Polyvinyl acetate emulsion polymers

ADHERE-TEX 1510 is a semi-permanent pressure sensitive adhesive which develops outstanding tack when the cast film is dried. The adhesive properties may be modified by dilution with water, thickening, or blending with other polymers such as TEX-WET 1089, a polyvinyl acetate emulsion. 

In the hot-melt type, two principal polymer types are used polyolefin and ethylene co-polymer based and polyester and polyamide type. In the solvent-based type, the most prominent are neoprene (polychloroprene)-based solvent and latex types, and polyvinyl acetate emulsions. For pressure-sensitive adhesives, the most favored are acrylic adhesives and butyl rubber/polyisobutylene types. 

A variety of different chemical-base polymers are available for adhesive formulation, each with their own set of properties. For example, polyurethanes (PUs) are flexible and have good adhesion, but some may discolour. Polyvinyl acetate emulsion adhesives are relatively inexpensive, but they are fairly brittle and have limited water resistance. 

The early polyvinyl acetate emulsions were homopolymers protected with partially hydrolyzed polyvinyl alcohol. These high molecular weight polymers had great strength and set rapidly to hard, homy films. Today, these homopolymers are the workhorses of the industry due to their excellent adhesion to uncoated paper, wood, concrete, ceramics, and glass. In addition, they exhibit a fair degree of water sensitivity. This allows them to be easily cleaned from equipment and permits their use in remoistenable adhesives. 

When a polyvinyl acetate emulsion is flexi-bilized internally with a comonomer, the plasticization is permanent and nonmigratory. This is because the comonomers are part of the main polymer chain, often with bulky side groups, increasing the freedom of rotation of the chain. The resulting softening and polymer mobility allows better adhesion to plastic surfaces. 

Polyvinyl acetate emulsions can be further modified by the incorporation of functional groups. These groups permit the design of polymers which have the ability to bond a wider spectrum of surfaces, including difficult-to-bond substrates. The addition of functional groups also permits crosslinkability of the polymer in order to achieve a high degree of water, solvent, or heat resistance. 

Polyvinyl acetate emulsions are made by polymerizing vinyl acetate monomer to make a homopolymer or widi other monomers to make copolymers which can build flexibility into the polymer chain. 

Polyvinyl acetate (PVA), acrylic and other polymer dispersions have been widely used as anti-dust treatments for concrete floors for many years. In general, the polymer dispersions have been similar to those used in the manufacture of emulsion paints, and until recently have tended to be based on dispersions of relatively large polymer particles (particle size 0.15-0.25 x 10 m). Dispersions are now becoming available which offer superior performance as floor sealers. The chemical and water resistance of the various polymer dispersions which have been used in the past vary considerably from the PVA types, which are rapidly softened and eventually washed out by water, to acrylic and SBR types which exhibit excellent resistance to a wide range of chemicals. Water-based sealers are gaining wider acceptance because of... 

A bond coat of a polymer latex (also called polymer emulsions or dispersions) such as styrene butadiene (SBR), polyvinyl acetate (PVA) acrylics or modified acrylics. These are applied to the prepared concrete as... 

Polyvinyl acetate polymers synthesized by emulsion polymerization168, show strikingly different behavior188,189). Figure 41 shows Dz as a function of Mw. For the low molecular weights, D2 decreases as expected but from Mw = 14 106 onwards Dz remains constant. The measured samples were products obtained at different extents of monomer conversion. The soap surrounding the latex particles was removed and the samples were dissolved in methanol and measured. The behavior of Dz in this system is understood by recalling that... 

Hayes established a list of some monomers in the order of decreasing activity towards grafting in emulsion vinyl chloride > vinyl acetate > styrene. Polymers can be listed in order of decreasing susceptibility to graft copolymerization, as follows polyvinyl chloride > polyacrylonitrile > polyvinyl acetate > polystyrene. 

Similar grafting experiments by the emulsion technique were described (34) in the system vinyl chloride/copolymer butyl methacrylate-methacrylic acid and in the reverse system, and also in the system styrene/polyvinyl chloride. In this last case again as in homogenous medium, the inverse process failed (vinyl chloride on polystyrene). Grafted acrylonitrile copolymers were also prepared in order to improve their dyeability, by polymerizing acrylonitrile in emulsion in the presence of many different polymers as polyvinyl alcohol, polymethacrylamide and polyvinylpyrrolidone (119, 120, 121), polyvinyl acetate and polyacrylic acid (115), wool (224,225), proteins (136), etc. 

Emulsion polymerization is used for 10-15% of global polymer production, including such industrially important polymers as poly(acrylonitrile-butadiene-styrene) (ABS), poly (styrene), poly(methyl methacrylate), and polyvinyl acetate.38 These are made from aqueous solutions with high concentrations of suspended solids. The important components have unsaturated carbon-carbon double bonds. These systems are ideal for Raman spectroscopy and a challenge for other approaches, though NIR spectroscopy has been used. 

The formation of coagulum is observed in all types of emulsion polymers (i) synthetic rubber latexes such as butadiene-styrene, acrylonitrile-butadiene, and butadiene-styrene-vinyl pyridine copolymers as well as polybutadiene, polychloroprene, and polyisoprene (ii) coatings latexes such as styrene-butadiene, acrylate ester, vinyl acetate, vinyl chloride, and ethylene copolymers (iii) plastisol resins such as polyvinyl chloride (iv) specialty latexes such as polyethylene, polytetrafluoroethylene, and other fluorinated polymers (v) inverse latexes of polyacrylamide and other water-soluble polymers prepared by inverse emulsion polymerization. There are no major latex classes produced by emulsion polymerization that are completely free of coagulum formation during or after polymerization. 

While vinyl acetate is normally polymerized in batch or continuous stirred tank reactors, continuous reactors offer the possibility of better heat transfer and more uniform quality. Tubular reactors have been used to produce polystyrene by a mass process (1, 2), and to produce emulsion polymers from styrene and styrene-butadiene (3 -6). The use of mixed emulsifiers to produce mono-disperse latexes has been applied to polyvinyl toluene (5). Dunn and Taylor have proposed that nucleation in seeded vinyl acetate emulsion is prevented by entrapment of oligomeric radicals by the seed particles (6j. Because of the solubility of vinyl acetate in water, Smith -Ewart kinetics (case 2) does not seem to apply, but the kinetic models developed by Ugelstad (7J and Friis (8 ) seem to be more appropriate. 

An emulsion polymer-isocyanate adhesive, a crosslinked polyvinyl acetate adhesive, a resorcinol-formaldehyde adhesive, a phenol-resorcinol-formalde-hyde adhesive, and an acid-catalyzed phenolic-formaldehyde adhesive developed bonds of high shear strength and wood failure at all levels of acetylation in the dry condition. A neoprene contact bond adhesive and a moisture-curing polyurethane hot-melt adhesive performed as well on acetylated wood as untreated wood in tests of dry strength. Only a cold-setting resorcinol-formal-... 

In producing a polyvinyl acetate latex for use with cement, the emulsion polymerization process is utilized. A small percentage, about 1%, of a substance like maleic acid is added in the polymerization reaction so that a copolymer is formed. Maleic acid, itself, has an ethylenic type of unsaturation, but it does not form homopolymers. Since the amount introduced is so small, the resultant polymer is a copolymer. The introduction of the highly polar carboxyl... 

Other attempts have been made to utilize dry powder polyvinyl alcohol and polyvinyl acetate as admixtures for the same purpose. The polyvinyl alcohol is readily soluble in water, and it requires significant amounts in addition to achieve any distinct advantages. Significant amounts of any viscosity range of polyvinyl alcohol contribute to an undesirable increase in viscosity in the cement mortar. Polyvinyl acetate in powder form has been used for this purpose with consequent improvements in working characteristics and physical properties. However, dry powder polyvinyl acetate does not form a true polymer emulsion when dissolved in water. It, therefore, may also be dissolved out of a cement mortar. 

Uses Polyvinyl acetate for industrial coatings and wood fillers, e.g industrial luan plywood primers Features High pigment tolerance and exc. mech. stability Properties Emulsion 0.15 nm avg. particle size dens. 9.0 Ib/gal vise. 50-250 cps 48% solids Vinac A50 [Air Prods. Polymers Europe]... 

See Vinyl acrylic copolymer Vinyl acetate resin. See Polyvinyl acetate Vinyl acetate/vinyl chloride copolymer Vinyl acetate/vinyl chloride polymer. See Vinyl chloride/vinyl acetate copolymer Vinyl acetate/vinyl neodecanoate copolymer Definition Latex emulsion contg. 50-55% solids polymer comprised of 65-85% VA and 15-35% vinyl neodecanoate Uses Binder in emulsion paints... 

Polyvinyl acetate (PVAc) is the largest volume polymer produced from a vinyl ester (1). In 1990, over 2.5 billion pounds of vinyl acetate monomer were produced in the United States alone (2). The bulk of this monomer was used for making PVAc and PVAc copolymers, which are widely used in water-based paints, adhesives, coatings, and binders for nonwoven paper products. PVAc is also the precursor to polyvinyl alcohol (PVA) and polyvinyl butyral, which cannot be made by direct polymerization. Methods of PVAc polymerization vary depending on the end use. Solution polymerizations of vinyl acetate in methanol are generally employed in processes in which PVAc is used as an intermediate in the production of PVA. PVAc latexes are generally made by emulsion polymerization, and PVAc in bead form is often synthesized by suspension polymerization (3,4). 

Emulsion-polymer isocyanates (EPI s) were introduced by Ashland Chemical Co. as better performing wood adhesives (101). EPI s are equivalent to phenol-resorcinol and cross-linkable polyvinyl acetate adhesives. EPI s are more advantageous than others because they have shorter press times, no chalking temperature, a low-temperature curing, no formaldehyde emission, better resistance to high temperatures and accelerated aging, environmental attractiveness, an ability to determine performance by adjusting hardener level, and more tolerance to variations in process conditions. 

Probably the most widely used industrial emulsion or dispersion adhesives are those based on polyvinyl acetates, commonly referred to as PVAs. These products are normally manufactured by a process referred to as emulsion polymerization whereby, basically, vinyl acetate monomer is emulsified in water and, with the use of catalysts, is polymerized. The presence of surfactants (emulsifiers) and water-soluble protective colloids facilitates this process, resulting in a stable dispersion of discrete polymer particles in the aqueous phase. 

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