Adhesive compositions

Claim 1

0 4' 34. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A moisture-curable adhesive composition capable of providing a pressure-sensitive adhesive layer on a substrate by a process in which the composition is applied to the substrate and cured or allowed to cure by exposure to a moist atmosphere, wherein the composition compises a prepolymer component having an isocyanate functionality between 2.0 an& 3.0 together with one or more polyetherurethane prepolymers having NCO groups available for reaction with water for chain extension, the cured adhesive composition having a glass transition temperature less than 2. An adhesive composition according to claim 1, wherein the prepolymer component comprises a mixture of prepolymers having NCO groups available for reaction,, a first one of said prepolymers being a reaction product of a linear polyol of hydroxyl number from 10 to 230 which is an addition product of ethylene oxide or of propylene oxide or of mixtures of both, and a diisocyanate reacted in amounts to provide an NCO:OH ratio from 1.2 to 2.5, and a second one of said prepolymers being a reaction product of a branched polyol of hydroxyl number from 10 to 570 which is an addition product of ethylene oxide or of propylene oxide or of mixtures of both, and a diisocyanate reacted in amounts to provide an NCO:OH ratio from 1.2 to 3. An adhesive composition according to claim 1, wherein the prepolymer component comprises a polyetherurethane prepolymer which is a reaction product of a branched polyol of hydroxyl number from 10 to 570 which is an addition product of ethylene oxide or of propylene oxide or of mixtures of both, and a diisocyanate reacted in amounts to provide <hLNCO.OH ratio from 1.2 to 2.5, and which may be further reacted with a monofunctional alcohol so as to. povide .a prepolymer component having an NCO functionality between 2.0 and 4. An adhesive composition according to claim 1I wherein the prepolymer component -omprises a mixtu -e of a 4 polyisocyanate of low molecular weight having a funAi.*loality greater than 2 and a polyetherurethane prepolymer which' is a reaction product of a linear polyol of hydroxyl nvmber from 10 to 230 which is an addition product of ethylene oxide or of propylene oxide or of mixtures of both, and a diisocyanate reacted.ii. aimounts"to provide an NCO:OH ratio from 1.2 to 2.5, the polyisocyanate and ;he prepolymer being mixed in a ratio such that the functionality of the prepolymer component lies between Sand S< 5. An adhesive composition according to claim 2 20 or claim 4 wherein the linear polyol has a hydroxyl number from 28 to 112. 6. An adhesive composition according to any one of claims 2, -4 or 5, wherein the, or the first, prepolymer 25 is a reaction product of the linear polyol and diisocyanate reacted in amounts to provide an NCO:OH ratio from 1.35 to 7. An adhesive composition according to claim 2 or claim 3, wherein the branched polyol has a hydrcxyl number of 25 to 56 and a hydroxyl functionality from 2.8 to 18. An adhesive composition according to any one of claims 2, 3 or 7, wherein the, or the second, prepolymer J.N. bcomprises a reaction, product -of a ,branched. polyol and diisocyanate prepared from quaru dti es 'of the reactants to provide an NCO:0-i ratio from 1.8 to 2.2. adhesive composition accord.ing to claim wherein the first and-second prepolymers are present in amounts scththertio of NCO equivalents of, the first Z, prepolymer to NCO equivalents of the second prepol irer is in the range 1:.2 to 10:1. An adhesive composition according to claim 2 or claima 9, wherein the first and sbcond prepolymers are present in.amounts su~ch that the ratio of NCO equivalents -of the f irst prepolymer toNCO equivalents of the second p reo Iym eris in-the range 1.58:1 to 5: 1, 11. An adhesive composition accor~ding to claim 3, wherein the _mrono functional' alcohol comprises 2-ethyl hexanol or aitionohydro~cy resin. 44, 12, A-n adhesive composition according to claim 4S, 4, wherein the'first prepolymer is admixed with polymethylene polyphenyl polyisocyanate. 13. An adhesive compos.ition according to any ~on e of the preceding claimas comprsn a ckifying 'resin of, low acid number le'ss tlian 14. Anadhesive according to claim1 hri tackifying resin is an indene containing resin or rosin ester present in an amount to provide 1 to 40% of the. Composition- 141 37. 0 1 and actants to 15. An esive composition according to any one of the preceding claims comprising a plasticiser., f low acid number. Lg to claim U present in 5 16. -An adhsive composition according to claim of, the first 15, comprising as plasticiser one or more phthalates or spoler is. alky-lsulphnates. present in an amount to provide 0.5 to by weight of the composition. rig to claim 2 10 17. 4n'adhesive composition substantially as lymers are hereinbefore described with riference to and as illustrated, equivalents byExamples 1to 13. the second 18. An adhesive composition substantially as ii:- Qaqa~ p~p~ nr s,. D~ C 1 hereinbefore described with reference to and as illustrated I rcli~f~L .ng to claim h 81) D by Examples 14 to 16. as 2-ethyl r, :1 I:F-EI 6;" t3 D EiC' :Ct C I_ 19' An adhesive composition substantially as bl U Uf hreinbefore described with reference to and as illustrated Si;, Lng to claim ore 20 by Examples 17 to 19. a -'J ajS~ 20. A method of forming a pressure-sensitive *:i C 0I adhesive layer on a workpiece comprising applying to-the ing toany one worjkpieciE.a solvent-free mass of composition according to ng resin of 25 any one of the preceding claims at a viscosity in the range o 00 PaS to provide a layer from 0.05 to 3mm thick, -and exposing the layer to a moist atmosphere having a 13 wherein .relative 'humidity above 10% ata temperature in the range resin or rosin 20 0 C to 1200 C whereby ross linking of the composition is of the' 30 effected. DATED this 10th day of February 1986.. EMHART AUSTRALIA PTY. LIIVITED EDWD. WATERS SONS PATENT ATORNEYS QEEN STREET MELBOURNE. VIC. 3000. .4 Affiffiffift