Water-Borne Adhesives

Water-borne adhesives are preferred because of restrictions on the use of solvents. Low viscosity prepolymers are emulsified in water, followed by chain extension with water-soluble glycols or diamines. As cross-linker PMDI can be used, which has a shelf life of 5 to 6 h in water. Water-borne polyurethane coatings are used for vacuum forming of PVC sheeting to ABS shells in automotive interior door panels, for the lamination of ABS/PVC film to treated polypropylene foam for use in automotive instmment panels, as metal primers for steering wheels, in flexible packaging lamination, as shoe sole adhesive, and as tie coats for polyurethane-coated fabrics. PMDI is also used as a binder for reconstituted wood products and as a foundry core binder. 

Water-borne adhesives. These contain between 40 and 80 wt% solids. They are completely untacky in the dried film and auto-adhere to itself under pressure. 

Water-based inks, 14 326 Water-based muds, 9 3-5 Water-based writing inks, 14 328 Water-borne adhesives, 25 475 Waterborne alkyds, 2 156-158 Waterborne automotive coatings, 10 448 Waterborne can coating system, 10 445-446... 

Neotac. PQ Resins] Water-borne adhesive polymers. 

Many classes of adhesives are used in wood bonding because of different production and end-use conditions. Most adhesives can give acceptable wood bonds if the use conditions are not too strenuous or at high moisture levels. The interaction of a hot-melt adhesive with wood should be quite different from that of a water-borne adhesive, not only because of viscosity differences but also because of the lack of cell wall swelling by hot-melt adhesive. In addition, some adhesives penetrate and change the mechanical properties of cell walls [10,18], but it not known if all adhesives that penetrate cell walls change their mechanical properties. 

The global adhesives market was about 32 billion in 2010 [Ij. This included about 14.3 billion in water-borne adhesives, 6.9 billion in solvent-borne adhesives, and 5.3 billion in 100% solids adhesives. The 2012 market for adhesives and sealants combined was estimated at 42.5 billion for 2012 [2], with North American accounting for 11.8 billion. Western Europe 8.7 billion. Southeast Asia and Australia 13.8 billion, Russia and Eastern Europe 4.5 billion, and the rest of the world 3.7 billion. In 2010, sealants accounted for about 21% of the overall adhesives and sealants category [Ij. If this percentage remained steady, this would put the global adhesives market at about 34 billion for 2012. The amount of adhesives used globally in 2010 was estimated at 9 million metric tons [3]. 

Water-borne adhesives consist of a base poiymer, and other ingredients, suspended in water in the form of an emuision. Since water is the oniy voiatiie ingredient, these adhesives do not create the soivent emission probiems characteristic of soivent-borne adhesives, and consequentiy have grown considerabiy in use during the past two decades or so. The cohesive strength of the adhesive deveiops as the water evaporates. 

The most common type of synthetic water-borne adhesives are based on vinyl acetate, and include the homopolymer, polyvinyl acetate and the copolymer with ethylene, ethylene vinyl acetate, the popular white glue. Copolymers with other monomers, such as acrylics, are increasing in use, particularly for adhesion to plastics. 

Remoistenable adhesives are applied as water-borne adhesives and then dried. When dry, they have little or no tack. To apply the tape or label to the box, bottle, or other package structure, water must be applied to reactivate the adhesive. Then the full strength of the bond will develop as the water is removed. Such adhesives are commonly used for adhering paper to paper or to other materials. 

Use of organic solvent borne adhesives has declined considerably in recent years, while use of hot melt and water borne adhesives has increased. Why ... 

In solvent-borne rubber adhesives, a variety of solvents can be chosen to control drying rate, adjust viscosity and dissolve important ingredients. Resins can be added to improve tack, wetting properties, heat resistance, bond strength and oxidation resistance. The most common resins nsed in rubber-based adhesives are rosins, rosin esters, and terpene, coumarone-indene, hydrocarbon and phenobc resins. Plasticizers and softeners reduce hardness, enhance tack and decrease cost of rubber adhesive formulations. Paraffinic oils, phthalate esters and polybutenes are typical plasticizers. Fillers are not often added to rubber adhesive formulations because they reduce adhesion. However they are sometimes used because they decrease cost and increase solution viscosity. Carbon black and titanium dioxide are also used to provide colour to the adhesives. Clays, calcium carbonate and silicates are also common fillers in rubber adhesive formulations. For water-borne adhesives, typically protective colloid, preservative, defoamers, wetting agents and emulsifiers are included in the formulations. 

The development of a latex of synthetic cis-1,4-polyisoprene produced by anionic polymerisation using an alkyl-lithinm initiator and suitable as an eqnivalent to NR latex is described. The manufactnre, properties and dipping of this latex are detailed and the potential applications of this synthetic latex, including rings of condom-like thickness, sheeting and water-borne adhesives, are indicated. 10 refs. 

Water-borne A water-borne adhesive is one where the volatile carrier of the adhesive material is water, either acting as a solvent or as a dispersing phase. ... 

Toxicity, flammability, and materials shortages associated with organic solvents have resulted in the development of several new water-borne adhesive systems. Many of the previously effective adhesive formulations are not readily converted to water-borne analogs. Many of the previously understood solution property-performance correlations remain valid in water-borne systems some do not. In this work an effort has been made to improve our understanding of the adhesive mechanisms and property-performance correlations in solvent and water-borne contact adhesives. These adhesive systems include phenolic/neoprene and phenolic/acrylic compositions. Some of the physical properties of the individual components and of the phenolic/elastomer blends have been related to contact adhesive performance. 

Toxicity, flammability, and material shortages associated with organic solvents have resulted in a trend towards water-borne adhesive systems. The transition from solvent to water-borne systems involves more than simple reformulation additional variables are encountered and a properly designed system should control each of these variables to optimize adhesive performance. 

ASTM D 4500-89 Test Method for Determining Grit, Lumps, or Undissolved Matter in Water-Borne Adhesives. 

As with pressure sensitive adhesives, general purpose water-borne adhesives often involve blend combinations to yield the desired balance of properties for a myriad of applications. An evaluation of three emulsions (acrylic, epoxy and a urethane) (using a simplex blending study) was conducted for polyester/LLDPE, polyester/nylon and A1 foil/polyester lamination [142]. In each lamination, a ternary blend gave the optimized performance when a number of properties were considered. 

The first acrylic emulsion polymer was already introduced in 1931 by the German I.G. Farben Industrie for leather finishing. But the large-volume applications occurred not imtil the 1960s when new water-borne adhesives and paints were introduced. 

Reducing the emissions of VOCs is the main driving force for using water-borne adhesives. Until the 1960s the majority of synthetic polymers used for adhesives was dissolved in... 

The prime advantage of aqueous polyurethane and polyacrylate dispersions over solvent-containing systems is that recovery or disposal of significant amounts of solvent is unnecessary. In the packaging industry, potential for residual solvent traces in the adhesive and subsequent migration into food are also major concerns. Therefore, solvent-containing adhesives have already been replaced by environmentally friendly water-borne adhesives in a number of applications. 

A review of the fundamentals of snrface science will establish both the technical basis for adhesion and provide methods to qnantitatively determine a surface s ability to be bonded. From a physics point of view, objects and materials are either attracted or repulsed from one another. Since adhesives are typically used in the liquid state, the terms -phillic and -phobic are often used to describe the attraction or repulsion, respectively. For example, materials that attract water are called hydrophilic, while those that repulse water are hydrophobic. Water is a good example, since historically many adhesives have been solvent borne, bnt now with increasing environmental consciousness there is a large effort to replace the solvent-borne adhesives with aqueous or water-borne adhesives. 

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