Polyvinyl alcohol in adhesives

Water-based dispersions or emulsions such as polyvinyl acetate, acrylics, polyvinyl chloride and polyvinyl alcohol with plasticizers and tackifiers. In addition, this range can include urea formaldehyde and phenolic adhesives, resins, natural adhesives produced from starch, dextrin, casein, animal glues (see Polyvinyl alcohol in adhesives, Phenolic adhesives single-stage resoles. Phenolic adhesives two-stage novolacs. Animal glues and technical gelatins) and rubber latex (see Emulsion and dispersion adhesives). Solvent-free 100% solids such as polyurethane. Hot melt adhesives include Ethylene-vinyl acetate copolymers, polyolefins, polyamides, polyesters with tackifiers and waxes. More recent additions include cross-linkable systems. 

Large amounts of adhesive mixtures, mainly based on potato or com (maize) starch (with plant varieties grown specifically for the purpose), are employed in paper coating, where the adhesive provides a bond between the fibrous (wood-pulp based) stmcture of the paper and the white china-clay-based surface layer, which can be printed. To improve performance in printing processes, these surface layers are often blended with wood rosin-based products and with polyvinyl alcohol of synthetic origin. Polyvinyl alcohol in adhesives (and its precursor polyvinyl acetate) can be made from ethanol obtained by the fermentation of starch - and once were so made - but the processes, carried out in dilute aqueous solution, are immensely wasteful of thermal energy. 

Polyvinyl alcohol in adhesives C A FINCH Production and uses... 

Waste Disposal. All processes must include some form of washing step to remove impurities from the bottles. If the adhesive, poly(vinylacetate), PVA, is to be separated through dissolution or hydrolysis to poly(vinyl alcohol), the waste stream will contain PVA and/or dissolved polyvinyl alcohol in addition to the other contaminants which must be removed. Paper fibers are another major source of impurities. For a lOMM Ib/yr plant about 75,(XX) Ib/yr PVA will be removed via the effluent. Environmental regulations probably require that this problem be addressed, especially since polyvinyl alcohol is an excellent foaming agent. 

Polyvinyl alcohol is added to acrylate copolymer emulsions, which are usually surfactant-stabilized, to alter or improve their adhesive performance. Many emulsions of this type are used as components of water-based pressure-sensitive emulsions - typically, a tacky adhesive for paper can be prepared by dissolving polyvinyl alcohol in a 2-elhylhexylacrylate copolymer emulsion. 

POLYVINYL ALCOHOL IN POLYVINYL ACETATE EMULSION ADHESIVES... 

Corey AE, et al. Polyvinyl acetate emulsions and polyvinyl alcohol for adhesives (chapter 28). In Skeist I, ed. Handbook of Adhesives, 3rd ed. New York, NY Van Nostrand Reinhold 1990. 

Liquid or solid films which reduce or prevent adhesion between surfaces solid-solid, solid-paste, solid-liquid. Waxes, metallic soaps, glycerides (particularly stearates), polyvinyl alcohol, polyethene, silicones, and fluorocarbons are all used as abherents in metal, rubber, food, polymer, paper and glass processing. 

Polymer adsorption is important in the flocculation and stabilization of colloidal sols and has been reviewed by Vincent et al. (1) and Tadros (2). Polyvinyl alcohol (PVA) has been used in these studies because of its practical application in textiles, adhesives, and coatings. The adsorption of PVA has been studied on silver iodide by Fleer (3) and Koopal (4), and on polystyrene (PS) latex particles by Garvey (5). The adsorption isotherms reported by these workers extend up to 600 ppm PVA. The adsorption at... 

The stabilizing of aqueous latexes succeeded by using emulsifiers (anionic, nonionic) and/or their mixture, steric stabilizators (polyvinyl alcohol (PVOH), hydroxyethyl cellulose, polyethylene glycol, new protective colloids etc.), and polymerizable surfaces active agents, in general. Vinyl acetate (VAc) emulsion homopolymers and copolymers (latexes) are widely used as binders in water-based interior and exterior architectural paints, coatings, and adhesives, since they have higher mechanical and water resistance properties than the homopolymers of both monomers [2, 4, 7]. 

Another trend observed during the past decade was the coating of liposomes with mucoadhesive polymers. Liposomes are coated with chitosan, long-ehain polyvinyl alcohol, and polyacrylates bearing a cholesteryl group [90]. Chitosan-eoated liposomes showed superior adhesion properties to rat intestine in vitro than the other polymer-eoated liposomes. In vivo, chitosan-coated liposomes containing insulin substantially reduced blood glueose levels after oral administration in rats, whieh were sustained up to 12 hr after administration [90]. 

Uses Manufacture of polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride-acetate resins used particularly in latex paint paper coatings adhesives textile finishing safety glass interlayers. 

Additional crosslinked polyvinyl alcohol copolymers, (I), were prepared by Schulte et al. (1) and used as components in adhesives, emulsifiers, and detergents. 

Elvanol. DuPont Co trademark for polyvinyl alcohol, PVA, white to creamy-white, odorless, synthetic resin, sol in water. Used as an adhesive and binder (Ref 1) and desensitizing LA by coating it. (See Ref 2, p A558-R)... 

Surfactants act as wetting agents by lowering the surface tension of the waterborne epoxy. Silanes can be used to increase adhesion to certain substrates and fillers, as shown in Table 14.4, formulation C. Water-compatible thickeners and protective colloids such as polyvinyl alcohol, substituted cellulosics and sugars, and some acrylics improve application properties and offset viscosity decrease seen with water dilution. 

Tears are repaired with Japanese tissue, missing areas are filled in with paper similar to the artifact. Repair paper of specific caliper and tone is made in the leaf caster. Adhesives vary methyl cellulose, wheat paste, or a mixture of polyvinyl alcohol with rice paste. The mixture is most useful because it permits use of a warm tacking iron to hasten the drying process. Where missing areas have been patched, the restorer reconstructs only those lines and colors that are already discernable, lest the work be called an attempt at falsification. 

Polymeric carbohydrates of an undetermined degree of polymerization have also been used to modify synthetic adhesive resins. In particular, cellulosic papermill sludges have been used to modify PF and UF resins (127). A carbohydrate polymer was reported to be an excellent extender and modifier for polyvinyl alcohol adhesives (128). 

Most vinyl acetate is converted into polyvinyl acetate (PVA) which is used in the manufacture of dispersions for paints and binders and as a raw material for paints. It is also copolymerized with vinyl chloride and ethylene and to a lesser extent with acrylic esters. A substantial proportion of vinyl acetate is converted into polyvinyl alcohol by saponification or transesterification of polyvinyl acetate. The main applications for polyvinyl alcohol are either as raw material for adhesives or for fibres. It is also employed in textile finishing and paper glueing, and as a dispersion agent (protective colloid). The world production capacity of PVA was 4.35 Mt/a in 2005, of which 2.1 Mt were converted into polyvinyl alcohol. 

Exhibits high adhesion to synthetic fibres and is particularly recommended for use on continuous filamant acetate. In conjunction with starch, SCMC or polyvinyl alcohol it is an excellent adhesion promoter for the sizing of staple synthetic fibres and their blends with cellulosics. 

Nakamura et al. ° studied the adhesion of water-soluble and neutral polymers, hydroxypropyl cellulose (HPC), xanthan gum (XG), tamarind gum (TG), and polyvinyl alcohol (PVA) to nasal mucosa in vitro and in vivo. The polymers, mixed with a dye, were applied as powders to the nasal cavity of rabbits, and the remaining dye residue was determined at 2, 4, and 6 h after nasal instillation with a thin fiberscope. The polymer XG showed the longest residence time of the dye in the cavity, followed by TG, HPC, and PVA in decreasing order. For the mixture XG and XG-PVA (2 8), some residue of dye could still be observed 6h after administration. The order of adhesion of these polymers to agar plates in vitro agreed with that of their mucoadhesion in vivo. Ilium et al. introduced bioadhesive microspheres for nasal delivery of poorly absorbable drugs. Radiolabelled microspheres made from diethylaminoethyl (DEAE)-dextran, starch microspheres, and albumin microspheres were administered to human volunteers and appeared to be cleared significantly slower than solutions or... 

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