Pressure-sensitive adhesive from a resin-modified polyurethene

1. A pressure-sensitive adhesive comprising a mixture of a chemically crosslinked polyurethane and at least one hydrocarbon resin, the chemically crosslinked polyurethane being composed of the following starting materials which in the stated proportions are reacted with one another catalytically in the presence of the at least one hydrocarbon resin:

a) at least one aliphatic or alicyclic polyisocyanate whose functionality is less than or equal to three,

b) a combination of at least one polypropylene ether diol and one polypropylene ether triol, the ratio of the number of isocyanate groups to the total number of hydroxyl groups being between 0.8 and 1.15, and the ratio of the number of hydroxyl groups in the diol component to the number of hydroxyl groups in the triol component being between 0.8 and 9.0, and the diols and triols alternatively being selected and combined as follows:

diols having a mean, number-averaged molecular weight M n of less than or equal to 1000 are combined with triols whose mean, number-averaged molecular weight M n is greater than or equal to 1000,

diols having a mean, number-averaged molecular weight of greater than 1000 are combined with triols whose mean, number-averaged molecular weight is less than 1000,

wherein at least one hydrocarbon resin is a styrene/α-methylstyrene resin having a mean, number-averaged molecular weight M n of between 200 and 6000, the weight fraction of the resin in the mixture being greater than 0% and ranging up to a maximum of 55%.

2. The pressure-sensitive adhesive of claim 1 , wherein the weight fraction of the at least one hydrocarbon resin in the mixture is greater than 0% and ranges up to 30%.

3. The pressure-sensitive adhesive of claim 1 , wherein the weight fraction of the at least one hydrocarbon resin in the mixture is greater than or equal to 30% and ranges up to a maximum of 55%.

4. The pressure-sensitive adhesive of claim 1 , wherein the catalyst for the reaction to give polyurethane is or comprises a compound comprising bismuth and carbon.

5. The pressure-sensitive adhesive of claim 1 , wherein the polyisocyanate is an aliphatic or alicyclic diisocyanate having an asymmetrical molecular structure.

6. The pressure-sensitive adhesive of claim 1 , wherein the polyisocyanate is selected from the group consisting of butane 1,4-diisocyanate, tetramethoxybutane 1,4-diisocyanate, hexane 1,6-diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, ethylethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclopentane, 1,2-diisocyanatocyclobutane, 1-methyl-2,4-diisocyanatocyclohexane, 1,6-diisocyanato-2,2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-trimethylhexane, 5-isocyanato-1-(2-isocyanatoeth-1-yl)-1,3,3-trimethylcyclohexane, 5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclohexane, 5-isocyanato-1-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane, 1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane, 1-isocyanato-2-(2-isocyanatoeth-1-yl)cyclohexane, 2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentylcyclo-hexane, norbonane diisocyanatomethyl, chlorinated, brominated, sulfur-containing or phosphorus-containing aliphatic or alicyclic diisocyanates, and the dimerized and trimerized derivatives of said diisocyanates.

7. The pressure-sensitive adhesive of claim 1 , wherein the weight-averaged molecular weight M w of the styrene/α-methylstyrene resin is between 300 and 18 000.

8. The pressure-sensitive adhesive of claim 1 , further comprising formulating ingredients selected from the group consisting of catalysts, aging inhibitors, light stabilizers, UV absorbers and rheological additives.

9. Process for preparing the pressure-sensitive adhesive of claim 1 , comprising

a) charging a vessel A with a polyol component comprising a mixture of said polypropylene ether diol and polypropylene ether triol and charging a vessel B an isocyanate component comprising said at least one aliphatic or alicyclic polyisocyanate, the hydrocarbon resin or hydrocarbon resins and, optionally, the further formulating ingredients being mixed into these components beforehand in a standard mixing procedure, and the components optionally comprising organic solvents or water,

b) conveying the polyol component and the isocyanate component via precision pumps through the mixing head or mixing tube of a multi-component mixing and metering unit, where they are homogeneously mixed and consequently reacted,

c) applying the chemically inter-reactive components mixed in this way immediately thereafter as a coating to a web-form backing material which is optionally moving at a constant speed,

d) passing the coated backing material through a heating tunnel in which the coating cures to a pressure-sensitive polyurethane adhesive,

e) finally, winding the coated backing material up in a winding station.

10. Process of claim 9 , wherein the preparation takes place without solvent and/or without addition of water.

11. A method for producing self-adhesive articles which comprises applying the pressure sensitive adhesive of claim 1 to an article to be made pressure sensitive.

12. A method for fixing notes, sheets of paper, calendar pages, strips, cards or boxes made of paperboard, cardboard material or plastic, or small utility articles made of plastic, wood, glass, stone or metal which comprises fixing same with the pressure-sensitive adhesive of claim 1 .

13. The pressure-sensitive adhesive sheet of claim 6 , wherein said polyisocyanate is 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethyl-cyclohexane.