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What are the various adhesives used in
printfinishing operations ?

 

Adhesives used in printfinishing are classified
according to the source from which they are derived

Starch Derived

Pastes White or light coloured, viscosity ranges from fluid to very heavy and stiff.Low solids, slow setting, good humidity resistance. Most are acid pH, borated pastes or alkaline.
Uses: Bag bottoms, lap paste, paper laminating, litho labelling, convolute tube winding.

Dextrins
Tan-brown, very tacky, fluid, usually acid pH and high in solids.
Uses: Remoistening adhesives, bottle labelling, cold pick-up for labels.

Borated dextrins White to dark brown, most are fluid, filmy, moderately fast setting and very tacky. Alkaline pH. Fairly good humidity resistance.
Uses: Case and carton sealing, tube winding, bag seams, wrapping, laminating, lap paste.

Jelly gums Rubbery, cohesive, gummy, very tacky. Good humidity resistance. Excellent glass adhesion and non-crystallising characteristics. Most on alkaline side for better stability and adhesion to coated glass. Colour varies from white to amber or red-brown depending on composition and pH.
Uses: Automatic bottle labelling.

Protein derived

Animal glue Tan-brown in colour, and supplied as granules or as pre-plasticized cakesor liquids. Considered very tacky and rangy. Usually run hot at about 140 F.
Uses: Set up box light wrapping and stripping, tube winding, gummed Remoistening tape.

Casein Fairly light colour, moderate to high water resistance, and good tack.May require ammonia or alcohol as diluent. Dried films are usually soluble in alcohol alkaline solution. Usually supplied at alkaline pH level.
Uses: Ice-proof label adhesive for cold drink bottles, foil lamination (compounded with latex).

Synthetic resin adhesives

Emulsion  Based on polyvinyl acetate and copolymers thereof. White coloured, range very thin and fluid to heavy. Acid pH. Strong tough films, usually water resistant but can be made water sensitive for easy clean up. Fast setting, low odour, taste, toxicity. Good machining, stable, good aging. Grease resistant.
Uses: Case and carton sealing and forming, tube winding, trays, cups, bag seam and seal, carton windows.

Latex Based on natural or synthetic rubber. Usually white to tan, alkaline pH, some have ammonia odor. Some have self-sealing property. Broad adhesion, relatively poor stability and machining. Should avoid copper (brass, bronze, etc.) contact, as this accelerates degradation.
Uses: Self seal bags, envelopes and wrappers. Film bag duplexing, waxed bag seam bottom, foil-paper lamination.

Hot melt Solid blends of polymer, resins, plasticizers and waxes, considered 100% solids. Must be heated to liquefy and run. Fastest setting adhesive. Most common forms: slats, pellets, billets or bulk. Broad adhesion. Colour ranges from white to brown.
Uses: Case and carton sealing, trays, bag seam and seal, labelling cans and bottles coatings for pressure sensitives labels, paper type and wrapping paper lamination.

Solvent borne Also called solution or lacquer adhesives. A broad description of a wide range of polymers and modifiers dissolved in organic solvents. Usually mobile liquids, colour ranges from water-white to brown. Usually fast drying depending on solvent blend. Most are flammable. Films range from soft, weak and tacky, to tough, hard and chemically cross linked. Most are simple reactive systems, but some can have properties enhanced by curing with coreactants (2 part systems) or moisture cure one-part systems ( certain urethanes).
Uses: Graphic arts lamination of film to film, paper or foil. Flexible, packaging,laminating film/film for pouches or bags. Heat seal coatings such as blister pack. Pressure sensitive coatings for labels and tapes.

 


 

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