Water-resin adhesives Latex

Water is sometimes used as a solvent for water-soluble resins. Certain epoxy adhesives are available as water-based emulsion or latex formulations. In the early 1970s, during the time of the petroleum crisis, water-based adhesives were thought of as a possible replacement for solvent-based adhesives systems. However, water-based adhesives never met the lofty expectations primarily because of the time and energy required to remove water from the bond line, the corrosion that the water causes in drying ovens, and the poor moisture resistance of cured water-based adhesives. 

Self-adhesive labels can be applied to most materials wood, plastic, metal, glass, paper and board. As the adhesives are resin-based (plasticised thermoplastics), migration problems can occur when they are applied to certain plastics (PVC, LDPE, etc.). Adhesive systems for pressure sensitive labels include latex and acrylic bases and adhesives which may be applied as a hot melt, or via a solvent, emulsion or dispersion base. Water-based adhesives are currently increasing in use. 

Uses Antifoam for water-based adhesive systems employing resin or latex binders and animal glues, and for paints, cementitious finishes, gravure inks defoamer in food-contact coatings, paper/paperboard food pkg. adhesives, coatings Features Good leveling... 

Uses Biocide, bactericide, fungicide, yeasf inhibifor, presenrafive for aq. paints/coafings, polymers, slurries, adhesives, latex and resin emulsions, sizing, caulk, process water, inks, polishes, waxes, detergenfs, cleansers, surfactanfs anfimicrobial for incoming raw materials and process wafer/make-up recycle water... 

Chem. Descrip. Fatty acid/hydrocarbon blend Uses Defoamer for metalworking fluids, printing inks, latex paints, adhesives/caulks/sealants, wood stains, paper coatings, water-reducible systems, aq. resin and latex coatings, textile preps. food pkg. adhesives component of paper/paperboard in contact with aq./fatty foods Features Silicone-free high efficiency low cost Regulatory FDA 21CFR 175.105,175.300,176.170 Properties Off-wh. opaque low-vise, liq. sp.gr. 0.86-0.89 nonionic 100% act. 

What of water-based adhesives We can apply some of the same principles and technology learned from solvent-applied adhesives to water-based systems. First, many of the polymers and elastomers available are the same (Table 2). Not only are these polymers available in latex form, but many are produced in latex form. The solid rubber used in solvent-based adhesives was derived from the latex, so one is actually eliminating a production step. Secondly, many of the resins the formulator has experience with and confidence in working with are available in dispersed form (Table 3). Some of these products have been available for a number of years and others are still in developmental stages. 

ELASTOMERS, RESIN MODIFIERS FOR WATER-BASE ADHESIVES 2. Styrene-Butadiene Latexes... 

Uses Chelating agent intermediate In resins, emulsifiers, surfactants, pharmaceuticals, herbicides, fungicides, insecticides, adhesives, latexes, and plasticizers Pmperties Liq. m.w. 292 sol. in water, ethyl alcohol, toluene, ethylene glycol, per-... 

The key parameters to control are formulation water content, clay/latex ratio and resin/latex ratio, depending on the desired adhesive cost structure. Not surprisingly, too much filler or too little resin and/or oil will result in inferior properties. Excess water will result in slower drying, and probably the need for more water sensitive thickeners. Like many other SBR based adhesives, HSL based flooring mastics include in-can and dry-film preservatives as well as an antioxidant package to ensure long-term performance. 

Product COSAN 101 is an effective preservative for resin emulsions, latex paints, adhesives, dispersed colors, pigment slurries, and ready-mix joint cements. This product is a 77.2% aqueous solution of 4,4-dimethyloxazolidine and its trimethyl homolog. This organic molecule contains only four elements carbon hydrogen oxygen nitrogen and when used at recommended levels will prevent bacterial deterioration of water-based systems. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

Together, antifreeze, PET, and polyester polymers account for about 98% of the ethylene glycol produced in the United States. It is also used sometimes as a deicer for aircraft surfaces. The two hydroxyl groups in the EG molecule also make EG suitable for the manufacture of surfactants and in latex paints. Other applications include hydraulic brake fluid, the manufacture of alkyd resins for surface coatings, and stabilizers for water dispersions of urea-formaldehyde and melamine-formaldehyde The hygroscopic properties (absorbs moisture from the air) make EG useful as a humectant for textile fibers, paper, leather, and adhesives treatment. 

Adhesives formulated with epoxy-modified latex retain the tack and conformability of the original latex but show improvements in green bond strength and fully cured bond strength. Cured epoxy latex epoxy resin systems also exhibit improved water and chemical resistance over unmodified latex systems. 

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