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Novel epoxy resins based on cyclohexanone‐aldehyde condensation products
Author(s) -
Renner Alfred,
Cotting JacquesAlain
Publication year - 1990
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1990.070390403
Subject(s) - epoxy , materials science , cyclohexanone , thermosetting polymer , epichlorohydrin , polymer chemistry , formaldehyde , solvent , polyester , condensation polymer , curing (chemistry) , polymer , composite material , organic chemistry , chemistry , catalysis
Solid ketone‐formaldehyde resins are used in certain coating formulations in order to improve hardness, gloss, and light stability. They are soluble, thermoplastic by nature, and contain limited amounts of hydroxyl groups. We found that their primary hydroxyls can be etherified with epichlorohydrin (ECH) either by a two‐step ECH‐addition/dehydrohalogenation procedure or by a one‐step phase‐transfer process. An intermediate of particular usefulness is the crystalline 2,2,6,6‐tetramethylol‐cyclohexanol (TMCH) made from cyclohexanone and 5 mol formaldehyde, yielding low colored epoxy resins with epoxy values up to 7.5 eq/kg. Depending upon the nature of the curing agent, high T g solids as well as tough and flexible coatings with good outdoor stability can be made. Upon decreasing the formaldehyde–cyclohexanone ratio, solid condensation polymers melting up to 150°C can be obtained. Phase‐transfer glycidylation yielded solid thermoset glycidyl ether resins with M̄ n up to 1600, M̄ ω up to 13,000, epoxy values up to 3.6 eq/kg, and softening points between 80 and 160°C. Powder coatings formulated with carboxyterminated polyesters are hard, glossy, solvent‐resistant but somewhat brittle. In order to overcome this drawback, polycycloacetals have been produced from TMCH and glutardialdehyde, which are terminated by pairs of methylol groups. Powder coatings of the corresponding glycidylethers with carboxyl‐terminated polyesters exhibited excellent flexibility and impact strength.