Solvent-based adhesive

Solvent-based adhesives are adhesives with polymers dissolved or pasted in organic solvents. The solvents or solvent mixtures are only processing aids and have to be removed, either partly or completely, from the applied liquid adhesive layer through evaporation or penetration prior to the fixing of the adherends. The first case is necessary for solvent-impermeable materials (metals, glass, thermosetting plastics), the second case concerns porous and solvent-permeable materials (paper, cardboard, wood, leather). This process can be accelerated by heat supply. Solvents are mainly esters, ketones, if applicable, portions of different alcohols. The total solvent portion ranges between 75-85%. 

The following polymers or polymer mixtures, respectively, in combination with tackifying resins are mainly used for solvent-based adhesives  

In this context, the term wet adhesive requires a special explanation. In processing, it serves the differentiation between contact adhesives and solvent-based adhesives and describes the still (partially) liquid state of the adhesive prior to the fixing of the adherends. This term is not a common designation of adhesives in the broader sense. 

The following criteria are important for the selection and the processing of solvent-based adhesives  

Intermediate state, solvent partly evaporated or diffused into the adherends (in the case of porous materials) 

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Cellulosics. CeUulosic adhesives are obtained by modification of cellulose [9004-34-6] (qv) which comes from cotton linters and wood pulp. Cellulose can be nitrated to provide cellulose nitrate [9004-70-0] which is soluble in organic solvents. When cellulose nitrate is dissolved in amyl acetate [628-63-7] for example, a general purpose solvent-based adhesive which is both waterproof and flexible is formed. Cellulose esterification leads to materials such as cellulose acetate [9004-35-7], which has been used as a pressure-sensitive adhesive tape backing. Cellulose can also be ethoxylated, providing hydroxyethylceUulose which is useful as a thickening agent for poly(vinyl acetate) emulsion adhesives. Etherification leads to materials such as methylceUulose [9004-67-5] which are soluble in water and can be modified with glyceral [56-81-5] to produce adhesives used as wallpaper paste (see Cellulose esters Cellulose ethers). 

MEK is also used iu solvent-based adhesives, iu printing ink formulations, as a solvent iu magnetic tape manufacture, and is the most common solvent used iu dewaxing lubricating oils. Of all these appHcations only an increasing consumption of magnetic tapes is likely to grow ia methyl ethyl ketone use. 

P. Branlard, F. Sauterey, and P. PouUet, New Chloroprene RubberTypesfor Solvent-Based Adhesives, Butaclor Symposium, Societe Distugil, Paris, 1988. 

New copolymers based on a copolymerization of isobutylene and p-methyl-styrene with improved heat resistance have been reported [64]. Once copolymerization was accomplished, the polymer was selectively brominated in the p-methyl position to yield a terpolymer called EXXPO. In contrast to butyl and halobutyl, the new terpolymer has no unsaturation in the backbone and therefore shows enhanced thermal stability and resistance to oxidation. Useful solvent-based adhesives can be formulated using the new terpolymer in combination with block copolymers [65]. The hydrocarbon nature of the new terpolymer results in excellent compatibility with hydrocarbon resins and oils. 

Coe, D.G., Neoprene solvent based adhesives. Technical Bulletin ADH-100.1 (Rl), E.l. Du Pont de Nemours. 

The coating technique starts by applying a solvent-based adhesive on to a previously pretreated metal substrate. The item is then preheated to 200-250°C, the exact time and temperature depending on the metal thickness. It is then dipped in the plastisol which partly gels owing to the... 

The future of solvent-based adhesives is discussed. The technology, once thought to be dying due to environmental and worker safety concerns, is reported to be dormant in some cases and declining in others, but definitely not dead,... 

From 1 January 2000, Dutch law prohibits the use by professional carpet fitters of solvent-based adhesives. The Organic Psycho Syndrome law concerns the adhering of coverings to floors, stairs, walls and ceilings in houses and any other buildings. Key issue in the OPS law is that professional users are no longer allowed to use products containing more than 0.5% solvents. The law also affects painters and parquet installers. 

Replacing Toxic Solvent-Based Adhesives with Nontoxic Water-Based Adhesives at Blueminster Packaging Plant, Kent, UK... 

Solvent-Based Adhesives—In these the adhesive flows because it is dissolved in an appropriate solvent, and solidification occurs on evaporation of the solvent. Good bonds are usually formed if the solvent attacks or actually dissolves some of the plastic adherend to produce a solvent-welded bond. 

Walker et al. (1993) conducted a cohort mortality study among 7814 shoe-manufacturing workers (2529 males and 5285 females) from two plants in Ohio (United States) that have been in operation since the 1930s. The workers, men and women, were potentially exposed to solvents and solvent-based adhesives. It was thought that toluene may have been a predominant exposure, but a hygiene survey in 1977-79 showed that, in addition to toluene (10 measurements ranged from 10 ppm to 72 ppm [38-270 mg/m3]), there were also 2-butanone (methyl ethyl ketone), acetone, hexane and... 

Solvent- and Emulsion-Based Adhesives Solvent-Based Adhesives. Solvent-based adhesives, as the name implies, are materials that are formed by solution of a high molecular weight polymer in an appropriate solvent. Solvent-based adhesives are usually elastomer-based and formulated in a manner similar to pressure-sensitive adhesives. 

Inserts that are to be used in the molding have to be prepared by either grit blasting or chemical treatment. The grit blasting operations must be carried out in a sand blast cabinet or the operator must be in an approved air-supplied garment. If solvent-based adhesives are used, appropriate personal protective equipment must be worn (chemical mask, gloves, and apron) and the operation carried out in a fume extraction hood. 

Solvent-Based Adhesives. In these formulations the polymers comprising the adhesive proper are dissolved in volatile solvents, which evaporate in the course of the transition. 

Such doubts about the future are encouraging the gradual replacement of solvent-based adhesives by other types. 

The solids contents of these dispersions generally are of the order of 50% to 60%, occasionally even higher, so that one may deposit from a certain thickness of wet adhesive quite a thick dry film of polymer. Solvent-based adhesives generally have lower solids contents (20% to 30%), and since the shrinkage after drying of water-based dispersions also is lower such adhesives can be formulated to fill gaps between materials as well as to bond them. 

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. 

Air blade Similar to the kiss coater in that the adhesive is applied where the web touches it possible to apply coating uniformly at high speeds limited use with solvent-based adhesives... 

Cellulose ethers have also been used in the ceramic industry (7). Since their appearance in 1959, water-based cellulose ethers have replaced solvent-based adhesives. The adhesives used for ceramic tile are ready-mixed products based on natural or synthetic rubber, polyvinyl acetate, and other resins, and they all contain cellulose ethers of one kind or another (e.g. MC, EC, HPMC, HEMC, HEC). These cellulose ethers reduce water loss, modify the viscosity of the mix, and can provide excellent adhesion for dry, very porous tiles. 

The adhesive may be solvent or water-based, hot-melt, coldseal or heatseal and pressure sensitive or chemically reactive. So the solidification process may occur via drying of water or solvent-based adhesives, by cooling of hot-melt and heat-seal adhesives, or by curing of chemically-reactive systems. With two notable exceptions - self-adhesive labels used on items of fruit or vegetables, and heat-sealable layers on packaging films - adhesives are in general not intended to touch the packaged food directly. 

Water-based adhesives and solvent-based adhesives... 

For solvent-based adhesives, there is the potential for migration of residual solvent for those systems in which the food is packaged prior to evaporation of all residues. 

Polysulfone A number of adhesives have been found useful for joining polysufone to itself or to other materials. These include 3M Company s EC 880 solvent-base adhesive, EC 2216 room-temperaturecuring epoxy two-part paste, Bloomingdale Division, American Cyana-mid Company BR-92 modified epoxy with DICY curing agent, or curing agent "Z" (both spreadable pastes), vinyl-phenolics, epoxy-nylons, epoxies, polyimide, rubber-based adhesives, styrene polyesters, resorcinol-formaldehyde, polyurethanes, and cyanoacrylates. The EC 880, EC 2216, and the two BR-92 adhesives are recommended by the polysulfone manufacturer. Union Carbide (16) (17). 

Rubber-like polymers (made of polychloroprene, polybutadiene copolymers, SIS, SBS for adhesive bonding of elastomers and as substitutes for solvent-based adhesives)... 

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