Patent GB-1379312-A (GB)
Title: Pressure-sensitive polyurethanes and adhesives therefrom
IPC: C09J7/38
Filed: 1972-02-29
Abstract: 1379312 Tackified polyurethane adhesives MINNESOTA MINING & MFG CO 29 Feb 1972 [1 March 1971] 9380/72 Heading C3R Pressure-sensitive adhesives comprise a crosslinked polyurethane derived from polyols and polyisocyanates, and having a molecular weight between crosslinks of between 6000 and 40,000 and a urethane group concentration of 0À7 to 1À3 urethane groups per 1000 grams of crosslinked polyurethane, in combination with a cyclic terpene alcohol-isocyanate tackifier resin derived from at least one isocyanate and at least one terpene alcohol, said tackifier resin being non-reactive or reactive on account of terminal alcohol or isocyanate groups and having been combined with the crosslinked polyurethane prior to the completion of its curing. The terminal alcohol or isocyanate groups of the tackifier resin may either be reacted with the respective polyisocyanate or polyol components of the polyurethane-forming reaction or may be prereacted with a monohydric alcohol or amine to render the resin non-reactive. The crosslinked polyurethane may be obtained by reacting together either at least one polyol, at least one diisocyanate and at least one triisocyanate, or by reacting together at least one diol, at least one triol and at least one diisocyanate. Both alternatives may proceed via the formation of prepolymers. Examples 1 to 12 describe the preparation of tackifier resins by the reaction of toluene diisocyanate with a mixture of abietyl, dihydroabietyl and tetrahydroabietyl alcohols with optional further amounts of polypropylene glycol, polyethylene glycol, polycaprolactone, or trimethylolpropane; by the reaction of the above abietyl alcohol mixture with methylene-bis-(4- phenylisocyanate); by the reaction of toluene diisocyanate with 2-hydroxymethyl-5-norbornene; and by the subsequent conversion of isocyanate-terminated resins based on tolune diisocyanate and the above abietyl alcohol mixture into non-reactive forms using dibutylamine or polypropylene glycol and a lead octoate catalyst. Examples 13 to 24 describe the preparation of adhesives using tackifiers as prepared in Examples 1 to 12 and a crosslinked polyurethane prepared by reacting a polypropylene oxide-ethylene oxide block copolymer with a diisocyanate prepolymer based on polytetramethylene glycol and toluene diisocyanate in toluene using a lead octoate catalyst, and crosslinking the product with a triisocyanate prepolymer based on trimethylolpropane and toluene diisocyanate. The resulting adhesives are coated on to polyethylene terephthalate film and cured by heating. In Example 26 a polyurethane prepolymer prepared by end-capping polytetramethylene glycol with toluene diisocyanate is mixed with a tackifier resin in toluene and crosslinked with a mixture of a polypropylene oxide-ethylene oxide block copolymer and a trimethylolpropane propylene oxide reaction product using a lead octoate catalyst. The resulting adhesive is coated on to polyester film and cured by heating. In Example 27 a watersensitive adhesive comprises a tackifier resin and a polyurethane prepared from polyethylene glycol, a polypropylene oxide-ethylene oxide block copolymer, toluene diisocyanate, ethyl acetate solvent and lead octoate catalyst, which is crosslinked with a triisocyanate based on trimethylolpropane and toluene diisocyanate. The resulting solution is coated on a silicone coated release liner and cured to form a tacky film which is subsequently transferred to label stock paper. When applied to glass bottles the labels could be subsequently removed with water. In Example 28 a mixture of polypropylene glycol 2000, a trimethylolpropane propylene oxide adduct of MW 1535, lead octoate catalyst, 2,6-di-tert.-butyl-4-methylphenyl antioxidant and 2,4-dimethyl-6-tert.-butylphenyl antioxidant are reacted with toluene diisocyanate in the presence of a tackifier resin and the mixture coated on both sides of a vinyl film and cured by heating. In Example 29 a mixture of a diisocyanate prepolymer based on toluene diisocyanate and polytetramethylene glycol, propylene glycol 2000 and a trimethylolpropane propylene oxide adduct of MW 1535 is mixed with a mixture of toluene, tackifier resin and lead octoate catalyst and the resulting adhesive applied to polyester and cured by heating. In Example 30 a tackifier resin prepared from toluene diisocyanate and 6,6-dimethyl bicyclo-(3,1,1)-2- heptene-2-ethanol is added to a mixture of (1) a hydroxyl-terminated prepolymer prepared from a polypropylene oxide-ethylene oxide block copolymer, a polytetramethylene glycol-toluene diisocyanate adduct, toluene and lead octoate catalyst, and (2) a triisocyanate crosslinking agent based on trimethylolpropane and toluene diisocyanate. The resulting adhesives were applied to polyester tapes.