Polyurethane Tackifier

Pentaerythritol in rosin ester form is used in hot-melt adhesive formulations, especially ethylene—vinyl acetate (EVA) copolymers, as a tackifier. Polyethers of pentaerythritol or trim ethyl ol eth an e are also used in EVA and polyurethane adhesives, which exhibit excellent bond strength and water resistance. The adhesives maybe available as EVA melts or dispersions (90,91) or as thixotropic, one-package, curable polyurethanes (92). Pentaerythritol spko ortho esters have been used in epoxy resin adhesives (93). The EVA adhesives are especially suitable for cellulose (paper, etc) bonding. 

Block copolymers can contain crystalline or amorphous hard blocks. Examples of crystalline block copolymers are polyurethanes (e.g. B.F. Goodrich s Estane line), polyether esters (e.g. Dupont s Hytrel polymers), polyether amides (e.g. Atofina s Pebax grades). Polyurethanes have enjoyed limited utility due to their relatively low thermal stability use temperatures must be kept below 275°F, due to the reversibility of the urethane linkage. Recently, polyurethanes with stability at 350°F for nearly 100 h have been claimed [2]. Polyether esters and polyether amides have been explored for PSA applications where their heat and plasticizer resistance is a benefit [3]. However, the high price of these materials and their multiblock architecture have limited their use. All of these crystalline block copolymers consist of multiblocks with relatively short, amorphous, polyether or polyester mid-blocks. Consequently they can not be diluted as extensively with tackifiers and diluents as styrenic triblock copolymers. Thereby it is more difficult to obtain strong, yet soft adhesives — the primary goals of adding rubber to hot melts. 

Materials, such as acrylates with tackifiers, acrylate polyesters, and polyurethanes, that do not have properties as pressure-sensitive adhesives, but after cross-linking have desired pressure-sensitive properties... 

In general, they consist of a pressure sensitive adhesive layer which is composed of a so-called hydrocolloid dispersed with the aid of a tackifier in an elastomer and secondly a film coating composed of a gas permeable but water impermeable, flexible, elastomeric material. A currently available hydrocolloid dressing is a flexible mass with an adherent inner face and an outer semipermeable polyurethane foam. 

As discussed in the Introduction, in addition to hot-melt adhesives, one of the most important forms of adhesives for the future is the waterborne system. In general, an advantage of the waterborne system is that it is free from the solvent-pollution problem. For this reason, we shall describe several new waterborne systems in detail acrylics, modified ethylene-vinyl acetate, polyurethanes, phenolics, epoxies, isocyanates, and tackifiers. Applications of these systems range from PSA s contact adhesives, and laminating adhesives to wood adhesives. 

Aran-Ais E, Torro-Palau A.M., Orgiles-Barcelo A.C., Martin-Martinez J.M., Characterization of thermoplastic polyurethane adhesives with different hard/soft segment ratios containing rosin as an internal tackifier, J. Adhes. Sci. TechnoL, 16(11), 2002, 1431-1448. 

Solvent-based dispersions such as polyvinyl acetate. Polyurethane, polyesters, polyethers, acrylic copolymers, Rubber-based adhesives with tackifiers and plasticizers. 

Water-based dispersions or emulsions such as polyvinyl acetate, acrylics, polyvinyl chloride and polyvinyl alcohol with plasticizers and tackifiers. In addition, this range can include urea formaldehyde and phenolic adhesives, resins, natural adhesives produced from starch, dextrin, casein, animal glues (see Polyvinyl alcohol in adhesives, Phenolic adhesives single-stage resoles. Phenolic adhesives two-stage novolacs. Animal glues and technical gelatins) and rubber latex (see Emulsion and dispersion adhesives). Solvent-free 100% solids such as polyurethane. Hot melt adhesives include Ethylene-vinyl acetate copolymers, polyolefins, polyamides, polyesters with tackifiers and waxes. More recent additions include cross-linkable systems. 

Low Viscosity liquid antioxidant that can be used as a stabilizer for a variety of polymer applications. It is an excellent antioxidant for PVC polymerization, in polyols for polyurethane foam manufactureres, ABS emulsion polymerization, hot melt adhesives and tackifiers, oils, and resins. The alkyl chain adds compatibility and solubility to various substrates. 

Calcium carbide is a feedstock for producing acetylene-phenol tackifying resin. Calcium carbide is a feedstock to make 1,4-butanediol for curing polyurethane elastomers. 

Formulation of solvent-bome polyurethane adhesives may include several additives such as tack and heat-resistance modifiers, plasticizers, fillers, tackifiers, antihydrolysis agents, and cross-linkers. Carboxylic acid as an adhesion promoter can also he added. A typical formulation of a solvent-borne polyurethane adhesive contains less than 20 wt% soUds content only. 

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