AQUEOUS ADHESIVE

Prepared generally by ester interchange from polyvinylacelate (ethanoate) using methanol and base also formed by hydrolysis of the acetate by NaOH and water. The properties of the poly(vinyl alcohol) depend upon the structure of the original polyvinyl acetate. Forms copolymers. Used as a size in the textile industry, in aqueous adhesives, in the production of polyvinyl acetates (e.g. butynal) for safety glasses. U.S. production 1980... 

Silvestre F., Rigal L., Leyris J., Gaset A. Aqueous adhesive based on a vegetable protein extract and its preparation. European patent EP997513 (2000). 

ASTM D 1489 offers a test method for determining the nonvolatile content of aqueous adhesives. The solids content (or conversely the volatile content) is a measurement of the actual nonvolatile materials that are contained within the formulation. Addition of solvent can be used to correct the viscosity of adhesives or sealants to account for variability in the manufacturing process or inconsistent base materials in the resin formulation. 

D 1489 Test Method for Non-volatile Content Aqueous Adhesives... 

Poly(vinyl alcohol), a hydrophilic polymer used in aqueous adhesives, is made by polymerizing vinyl acetate and then hydrolyzing the ester linkages. 

A versatile group of highly effective acrylic thickening agents for use in aqueous adhesives and latex coatings. Suitable for use with many latex types including natural rubber, S.B.R., PV acetate, PVC, Polychloroprene, acrylic and nitrile. 

Adhesives are nonmetaUic substances used to join two surfaces by means of surface adherence (adhesion) and inherent strength (cohesion), DIN 16920. This definition of adhesives does not cover water glass adhesives, adhesive ceramics, or adhesive mortars. The substances used as adhesives are polymers that go through a liquid phase at least once (reactive adhesives) or more than once (hotmelts, thermally activated adhesives). The liquid phase can also be achieved by dissolution in suitable solvents (nonreactive adhesives). In dispersion adhesives, the polymer molecules are dispersed (finely distributed) in a liquid - usually water - whereby the polymer molecules themselves are not dissolved. Fig. 6. These adhesives are also known as water-based or aqueous adhesives. It must be remembered that solvents are contained in these adhesives in addition to the water. Genuine aqueous adhesives contain less than 5% solvents in the liquid phase. The dispersions crnitain, in contrast to the solute adhesive molecules, additional substances, disposal of which requires specific additional measures. Since the dispersions represent stable systems in water, the water-resistance of such adhesives is reduced. Their thermal and water resistance can be increased by additional crosslinking (usually with isocyanates). 

Acrylate dispersions are among the best performing aqueous adhesives, since they require no plasticizers to render them flexible and allow no plasticizer migration from the plastic materials (impermeable boundary). These dispersions are therefore always used in products in which hazards to humans must be excluded, for example in wound bandages. 

Drying or evaporating are discussed after the application of solvent-containing or aqueous adhesives/dispersions. After evaporation, respectively, penetration of the solvent or water into the porous adherends, accelerated by a heat supply if necessary, the adhesive layer polymers remain in the glueline. As described in Section 2.2.2, this is a physical process. A chemical reaction does not take place. 

Dextrin adhesive Aqueous adhesive based on catabolized starch. 

Starch Plant product, so-called carbohydrate, consisting of the elements carbon, hydrogen and oxygen. Raw material for aqueous adhesives (paste, glues). 

Can be laminated to other materials with a low-cost aqueous adhesive due to its absorbent (porous) nature. 

Because of the need to remove water, most applications for aqueous adhesives are with materials that would allow transmission of water vapor. Hence the major uses are with paper, wood and fabric, either as binders or laminating adhesives. Typical applications of emulsion adhesives include the following remoistenable gummed tape, tube winding, box manufacture, plywood manufacture, woodworking, bookbinding, abrasives manufacture, and as textile adhesives. 

Aqueous adhesive resins behave similarly to water regarding surface tension and wetting behavior. For UF resins the wetting behavior strongly depends on their molecular... 

ASTM D1489-97 Standard test method for non-volatile content of aqueous adhesives. 

Examples of the use of blocked diisocyanates for rubber-fabric adhesion are as follows vulcanized polychloroprene and SBR can be adhered strongly to nylon and polyester fibre fabric by means of aqueous adhesive systems (Table 8.4). This combination is spread or roller coated on to the fabric which is then allowed to dry. Bonds to sheet rubber stock can be made immediately after the treated fabric is dried or at any time thereafter. When the sheet rubber is applied it should be held under moderate pressure to provide intimate contact with the treated fabric and to prevent lifting if any gases are emitted during cure. Press cures of 20-40 min at 140°C are sufficient to cure the adhesive and most elastomer compositions being adhered. If a latex film is applied to the treated fabric, the assembly can be cured in a hot-air oven at 120"C. A chemical bond results between fabric and the diphenylmethane-/7,/ -diisocyanate generated on the thermal cleavage of the blocked diisocyanate. 

Nonvolatile Content of Aqueous Adhesives, Test for (D 1489) Nonvolatile Content of Urea-Formaldehyde Resin Solutions, Test for (D 1490)... 

Government regulations regarding solvent emissions in the user s locality are also of importance. In the US, some customers must use aqueous adhesives or adhesives containing... 

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. 

Other Aqueous Adhesive Solutions. Besides starches and dextrins, cellulose ethers, primarily methyl cellulose and carboxymethyl cellulose, and in some cases also starch ethers, are important as wallpaper pastes and poster glues. The products are generally marketed in the form of powders that are dissolved in water by the user. Aqueous... 

Laminating Adhesives. Aqueous adhesives based on cellulose or poly(vinyl alcohol) for the ply lamination of tissue papers must give clean machinability, good initial tack, and reliable bonding strength of the tissue laminates. 

Tail Tie. For this application aqueous adhesives based on cellulose or poly(vinyl alcohol) are used. For the tail tie of tissue paper rolls, products with high wet tack, transparent film, and a low final bond strength are necessary. 

Wood panels, chipboard, and similar wooden materials can be fixed with aqueous adhesives based on poly(vinyl acetate) or polyacrylate emulsion. The adhesives must be pasty and have high initial strength. In some cases they are applied from cartridges. Also contact adhesives, special reactive systems (hybrid silicone), and hot-melt adhesives are utilized. 

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