Epoxy adhesives anhydride hardeners

The commercial possibiUties for epoxy resins were first recognized by DeTrey Emres in Switzerland and DeVoe and Raynolds in the United States (1,2). In 1936, DeTrey Emres produced a low melting bisphenol A-based epoxy resin that gave a thermoset composition with phthaUc anhydride. Apphcation of the hardened composition was foreseen in dental products, but initial attempts to market the resin were unsuccessful. The patents were hcensed to CIBA AG of Basel, Switzerland (now CIBA-GEIGY), and in 1946 the first epoxy adhesive was shown at the Swiss Industries Eair and samples of casting resin were offered to the electrical industry. 

Generally these compositions contain an epoxy-novolac, a hardener, a catalyst, silica fillers, and an internal lubricant/mold release compound. Brom-inated epoxies and antimony trioxide are included to provide the required flame retardant characteristics. Other, unspecified additives are used to promote adhesion or to reduce corrosion rates. Because of their superior thermal capabilities and electrical properties, epoxidized novolacs are preferred over epoxy homopolymers. Near stoichiometric amounts of hardeners such as novolacs (Equation 1), anhydrides, and primary amines can be used to cure the resins in the presence of a catalyst. The linkages which are formed include ethers, esters, or secondary amines, respectively. 

In many adhesives formulations, the resin portion is the same or similar and what determines its properties is the hardener or catalyst that is used to cure the resin. Thus, depending on the hardener, epoxy adhesives may be referred to as amine-cured, anhydride-cured, polyamide-cured, or novolac-cured. Polyurethanes may be polyol-cured or hydroxypolyester-cured. 

Crosslinkers and Accelerators. Besides the polymers themselves, changes and improvements are taking place in curing agents, hardeners, catalysts, and polymer modifiers. For example, if epoxy adhesives with improved heat resistance are needed, the hardeners can be aromatic anhydrides and amines such as benzophenone tetracarboxylic dianhydride, py-romellitic dianhydride, diaminodiphenyl sul-fone. To enhance curing speed, epoxy systems utilize mercaptan hardeners, while acrylic monomer/polymer blends avail themselves of amine/aldehyde catalysts with benzosulfimide (saccharin) accelerators. Radiation-curing systems for today and tomorrow utilize both visible light and laser beams. 

A series of hydro- and bicyclic derivatives of phthalic anhydride have been employed as hardeners in epoxy resins used for optical recording disks <88JAP(K)638370I >, and in a urethane composition to prepare a wire coating with good insulating, thermal shock resistance and adhesion <86JAP(K)61200164>. 

The hardener portion (Part B) may also be mixed with fillers, diluents, solvents, and other additives. Fillers may be mixed in the resin portion alone or partly in the resin and partly in the hardener portion. Adhesion promoters such as Dow Corning A-180 silane may also be added to enhance the adhesion of the filler particles to the resin or hardener. Examples include several electrically conductive epoxy formulations that were used to evaluate their electrical stability on non-noble metal surfaces. The base epoxy resin was the diglycidylether of bisphenol-F (DGEBF, equivalent wt. = 170 g). Methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, and 4-methylphthalic anhydride were evaluated as curing agents with 4-methylimidazole as a catalyst. The manufacturing procedure was ... 

Uses Antioxidant stabilizer catalyst intermediate R.T. epoxy curing agent activator for epoxy resins cured with wide variety of hardener types incl. polyamide, amidoamines, polymercaptans, and anhydrides for coatings, adhesives, castings, potting, encapsulation Manuf./Distrib. ChemService http //www.chemservice.com, Sigma Trade Name Synonyms Ancamine 1110 [Air Prods./Perf. Chems. http //WWW. airproducts. com]... 

Modified polyfunctional aliphatic amines, amidoamines and fatty polyamides are covered for both CTBN/epoxy adducts or ATBN hardener systems (42,44). Examples of systems based on selected epoxy-anhydride (45), an amine-ether (46) and Lewis acid/amine complexes (47) augment this information base. Dicyandiamide (1-cyano guanidine) containing systems alone (48) and with melamine (49) and various proprietary accelerators (50-53) are shown to serve as latent, one-component film and paste adhesives with an excellent balance of adhesive properties. 

Three hundred grams of the epoxy resin is mixed with 125 gm of poly(adipic acid anhydride) and heated to 130°C for 1 hr. The resulting resin hardens at 150°C in ly hr and is rather elastic. If the resin is heated at 150°-170" C for any length of time it becomes cross-linked and shows good adhesion to a wide variety of nonporous materials (glass, metal). 

Epoxy resins are used primarily in combination with hardeners (polyamines, poly-aminoamides, dicyanodiamide, acid anhydrides) for cold-setting and hot-setting reactive adhesives. Liquid epoxy resins of the bisphenol A type with epoxy equivalents of 170 - 300 are used preferably relatively high molecular mass solid resins are used only occasionally. 

Alt. ethylene-co-maleic anhydride grafts—hot melt adhesives Neoprene rubber General purpose Specialty Pressure sensitive Epoxy resin hardener... 

A two-component epoxy system consists of a resin and a hardener, along with possible additives such as accelerators, reactive diluents, resin modifiers, plasticizers, and fillers. Typical hardeners include aliphatic polyamines, which cure at room temperature or at slightly elevated temperatures polyamides, which provide flexibility and are widely used aromatics, which are solid and anhydrides, which require elevated temperature cure and produce thermally stable but brittle adhesives. Low molecular weight epoxies are liquid and are usually cured by amines, carboxylic acid anhydrides, and Lewis acid and base catalyst. Higher molecular weight epoxies are cured through their hydroxyl groups. Cure of epoxies involves an exothermic reaction. 

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