Cold contact adhesives
An aqueous dispersion comprising at least one polyurethane polymer with a melting temperature in the range of 30° C. to 50° C. and (cold contact) adhesives comprising such a polyurethane dispersion, a method for creating an adhesive bonding and the use of such (cold contact) adhesives for creating an adhesive bonding.
1. An aqueous dispersion comprising at least one polyurethane polymer with a melting temperature in the range of 30° C. to 50° C. as determined by differential scanning calorimetry according to DIN 65467 at a heating rate of 20 K/min, the polyurethane polymer being obtained from a reaction mixture comprising:
AI) at least one polyester polyol with a number average molecular weight in the range of 400 g/mol to 5000 g/mol and a melting temperature in the range of 40° C. to 80° C. as determined by differential scanning calorimetry according to DIN 65467 at a heating rate of 20 K/min;
AII) at least one polyester polyol with a number average molecular weight in the range of 400 g/mol to 5000 g/mol and a melting temperature in the range of 5° C. to 35° C. as determined by differential scanning calorimetry according to DIN 65467 at a heating rate of 20 K/min;
B) optionally, at least one difunctional polyol component;
C) at least one aliphatic diisocyanate; and
D) at least one aminic chain extender comprising at least one ionic or potentially ionic group;
wherein
the molar ratio AI):AII) is in the range of 7:3 to 3:7.
2. The dispersion according to claim 1 , wherein the polyurethane polymer has a glass transition temperature in the range of −60° C. to −10° C. as determined by differential scanning calorimetry according to DIN 65467 at a heating rate of 20 K/min.
3. The dispersion according to claim 1 , wherein the polyester polyol AI) has a melting temperature in the range of 40° C. to 60° C. as determined by differential scanning calorimetry according to DIN 65467 at a heating rate of 20 K/min.
4. The dispersion according to claim 1 , wherein the polyester polyol AII) has a melting temperature in the range of 15° C. to 30° C. as determined by differential scanning calorimetry according to DIN 65467 at a heating rate of 20 K/min.
5. The dispersion according to claim 1 , wherein the molar ratio AI):AII) is in the range of 6:4 to 4:6.
6. The dispersion according to claim 1 , wherein the polyester polyol AI) has an enthalpy of fusion in the range of 65 J/g to 90 J/g as determined by differential scanning calorimetry according to DIN 65467 at a heating rate of 20 K/min.
7. The dispersion according to claim 1 , wherein the polyester polyol AII) has an enthalpy of fusion in the range of 30 J/g to 70 J/g as determined by differential scanning calorimetry according to DIN 65467 at a heating rate of 20 K/min.
8. The dispersion according to claim 1 , wherein the polyester polyols AI) and AII) are aliphatic.
9. The dispersion according to claim 1 , wherein the polyester polyol AI) is obtained from a reaction mixture comprising adipic acid and 1,4-butanediol or 1,6-hexanediol.
10. The dispersion according to claim 1 , wherein the polyester polyol AII) is obtained from a reaction mixture comprising adipic acid, 1,6-hexanediol and neopentyl glycol or from a reaction mixture comprising adipic acid, 1,4-butanediol and neopentyl glycol.
11. The dispersion according to claim 1 , wherein the aliphatic diisocyanate C) is selected from the group consisting of hexamethylene 1,6-diisocyanate, 1,3-bis(isocyanato-methyl)cyclohexane, 1,4-bis(isocyanato-methyl)cyclohexane, isophorone diisocyanate, 4,4′-diasocyanato-cyclohexyl)methane, 2,4′-di(isocyanato-cyclohexyl)methane, and mixtures thereof.
12. The dispersion according to claim 1 , wherein the aminic chain extender D) comprises a mixture of the sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid and diethanolamine or comprises a mixture of the sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid, diethanolamine and N-(2-hydroxyethyl)-ethylenediamine.
13. An adhesive comprising at least the dispersion according to claim 1 .
14. The adhesive according to claim 13 , wherein the adhesive is a cold contact adhesive.
15. A method comprising utilizing the dispersion according to claim 1 for bonding of rubber materials selected from the group consisting of natural and synthetic rubbers, polyurethanes, polyvinyl acetate, and polyvinyl chloride.
16. A method comprising utilizing the dispersion according to claim 1 for bonding porous or water vapor-permeable substrates by wet-in-wet processes.