Use of aqueous polyurethane dispersions for laminating molded articles

Abstract

The use of aqueous polyurethane dispersions is described for the lamination of moldings, where the polyurethane comprises units derived from at least one amorphous polyester polyol and comprises units derived from at least one polycarbonate.

Claims

1. A method for producing a laminated molding, the method comprising: applying at least one aqueous polyurethane dispersion comprising at least one polyurethane to at least one of a foil and a molding, and laminating the foil to the molding, wherein the polyurethane consists essentially of at least one unit derived from an amorphous polyester polyol, at least one unit derived from a polycarbonate, and at least one organic diisocyanate or a mixture which comprises an organic isocyanate compound; and wherein the amorphous polyester polyol comprises reacted units of an aliphatic dicarboxylic acid having from 3 to 10 carbon atoms and an aromatic dicarboxylic acid in a molar ratio of from 0.5:1 to 2:1.

2. The method according to claim 1, wherein the amorphous polyester polyol does not have a melting point of from 30 C. to +60 C.

3. The method according to claim 1, wherein the at least one amorphous polyesterdiol has a molar mass of above 500 to 4000 g/mol, the at least one polycarbonate has a molar mass of above 500 to 4000 g/mol, and the at least one organic diisocyanate or the mixture which comprises an organic isocyanate compound having an arithmetic-average NCO functionality of from 1.9 to 2.3.

4. The method according to claim 1, wherein the polyurethane comprises at least 10% by weight of units of the amorphous polyester polyol and at least 10% by weight of units of the polycarbonate.

5. The method according to claim 1, wherein the polycarbonate is a hydroxy-terminated polycarbonate based on at least one alkanediol comprising from 2 to 10 carbon atoms.

6. The method according to claim 1, wherein the amorphous polyester polyol comprises an alkanediol comprising from 2 to 10 carbon atoms.

7. The method according to claim 6, wherein the amorphous polyester polyol comprises adipic acid/isophthalic acid and an alkanediol comprising from 4 to 8 carbon atoms.

8. The method according to claim 1, wherein the polyurethane comprises from 2 to 10% by weight of at least one dihydric alcohol with an average molar mass of from 62 to 500 g/mol.

9. The method according to claim 1, wherein the at least one organic diisocyanate is selected from the group consisting of isophorone diisocyanate, hexamethylene diisocyanate, and a mixture of isophorone diisocyanate and hexamethylene diisocyanate.

10. The method according to claim 1, wherein a quotient calculated from an entirety of all NCO groups and from an entirety of all NCO-reactive OH groups is from 0.7 to 1.5.

11. The method according to claim 1, wherein a molar ratio of the polyester polyol to the polycarbonate is from 1:10 to 10:1.

12. The method according to claim 1, wherein the at least one amorphous polyesterdiol with a molar mass of above 500 to 4000 g/mol is present in the polyurethane in an amount of 10 to 80% by weight, the at least one polycarbonate with a molar mass of above 500 to 4000 g/mol is present in the polyurethane in an amount of 10 to 80% by weight, and the at least one organic diisocyanate or one mixture which comprises an organic isocyanate compound and which has an arithmetic-average NCO functionality of from 1.9 to 2.3 is present in the polyurethane in an amount of 5 to 30% by weight, and the polyurethane further consists essentially of 2 to 10% by weight of at least one dihydric alcohol with an average molar mass of from 62 to 500 g/mol.

13. The method according to claim 1, wherein the polyurethane dispersion is in a form of two-component adhesive composition together with at least one polyisocyanate compound.

14. The method according to claim 1, wherein the polyurethane dispersion is blended with at least one further polymer dispersion to obtain a blend dispersion, wherein the further polymer dispersion is at least one selected from the group consisting of a polyacrylate dispersion, a polyvinyl acetate dispersion, and a polyethylene-vinyl acetate dispersion, and a quantitative ratio by weight of the polyurethane dispersion to the blend dispersion is optionally from 3:1 to 1:2, based in each case on solids content.

15. The method according to claim 1, wherein the polycarbonate is a hydroxy-terminated polycarbonate comprising reacted units of at least one alkanediol comprising from 4 to 8 carbon atoms.

16. The method according to claim 1, wherein the polycarbonate is a hydroxy-terminated polycarbonate comprising reacted units of 1,6-hexanediol.

17. The method according to claim 1, wherein the amorphous polyester polyol is a mixture of at least one aliphatic dicarboxylic acid comprising from 4 to 8 carbon atoms and an alkanediol comprising from 4 to 8 carbon atoms.

18. The method according to claim 1, wherein the amorphous polyester polyol has units of adipic acid/isophthalic acid and units of an alkanediol comprising from 4 to 8 carbon atoms.

19. The method according to claim 1, wherein the amorphous polyester polyol has units of 1,6-hexanediol.

20. The method according to claim 1, wherein the applying includes depositing an amount of from 10 to 70 g/m.sup.2 of the aqueous polyurethane dispersion onto at least one of the foil and the molding and the laminating is carried out under a pressure of at least 0.01 N/mm.sup.2 to form a laminate, and the process further comprises: heating the laminate to dry the aqueous polyurethane dispersion and form a dried adhesive, and thermally activating the dried adhesive at a temperature of less than 60 C. to form the laminated molding.

21. The method according to claim 1, wherein the polyurethane further consists essentially of one or more selected from the group consisting of d) at least one dihydric alcohol, e) at least one compound selected from the group consisting of a mono- to trihydric alcohol which comprises an ionic group or a group capable of conversion to an ionic group, and a diamino compound which comprises an ionic group or a group capable of conversion to an ionic group, f) at least one further polyfunctional compound which differs from compounds (a) to (e) and which comprises an alcoholic hydroxy group, a primary or secondary amino group, or an isocyanate group, and g) at least one monofunctional compound which differs from compounds (a) to (f) and which comprises an alcoholic hydroxy group, a primary or secondary amino group, or an isocyanate group.

22. A foil-laminated molding obtained by the method according to claim 1.

23. The foil-laminated molding according to claim 22, wherein the foil is at least one material selected from the group consisting of polyvinyl chloride and thermoplastic polyolefin.

Description

EXAMPLES

Inventive Example IE1

(1) 323.5 g (0.16 mol) of a polyesterol with OH number 55.5 derived from adipic acid/isophthalic acid and 1,6-hexanediol, 315.5 g (0.16 mol) of a polycarbonate based on hexanediol with OHN 56.9 (Eternacoll UH 200), and 29.2 g (0.28 mol) of neopentyl glycol, and also 66 g of acetone, were used as initial charge in a stirred flask with reflux condenser and thermometer, and 0.1 g of tetrabutyl orthotitanate was admixed. After addition of 73.4 g (0.33 mol) of isophorone diisocyanate and 55.5 g (0.33 mol) of hexamethylene diisocyanate, the mixture is stirred for 210 min at an external temperature of 115 C. 1230 g of acetone were then used for dilution. The NCO content of the solution was determined as 0.407%. 37.3 g (0.09 mol) of an aqueous solution of Na (N-(2-aminoethyl)-2-aminoethyl sulfate were added to the mixture. After 10 minutes, 1200 g of water were used for dispersion. After distillation of the acetone, the product was an aqueous polyurethane dispersion with 36% solids content.

Inventive Example IE2

(2) 323.5 g (0.16 mol) of a polyesterol with OH number 55.5 derived from adipic acid/isophthalic acid and 1,6-hexanediol, 315.5 g (0.16 mol) of a polycarbonate based on hexanediol with OHN 56.9 (Eternacoll UH 200), and 25.2 g (0.28 mol) of 1,4-butanediol, and also 66 g of acetone, were used as initial charge in a stirred flask with reflux condenser and thermometer, and 0.1 g of tetrabutyl orthotitanate was admixed. After addition of 73.4 g (0.33 mol) of isophorone diisocyanate and 55.5 g (0.33 mol) of hexamethylene diisocyanate, the mixture is stirred for 210 min at an external temperature of 115 C. 1230 g of acetone were then used for dilution. The NCO content of the solution was determined as 0.241%. 37.3 g (0.09 mol) of an aqueous solution of Na (N-(2-aminoethyl)-2-aminoethyl sulfate were added to the mixture. After 10 minutes, 1200 g of water were used for dispersion. After distillation of the acetone, the product was an aqueous polyurethane dispersion with 39.7% solids content.

Comparative Example CE1

(3) Luphen D200A: polyurethane dispersion based on a crystalline polyesterdiol with 40% solids content, for adhesive bonding in the thermal activation process.

Comparative Example CE2

(4) Luphen D259A: polyurethane dispersion based on an amorphous polyetherdiol with 40% solids content, for adhesive bonding in the contact process.
Test Method for Heat Resistance (HR, Edge Shrinkage)

(5) 35-45 g/m.sup.2 (solid) of the adhesive composed of 100 parts of the polyurethane dispersion and of 12 parts (solid/solid) of the water-emulsifiable isocyanate crosslinking agent Basonat F 200 WD were sprayed onto a fiber molding of the type used for the production of furniture moldings, with three-dimensional surface, and dried. A rigid PVC furniture foil (Roxan 5371744 Buche Taunus) was applied by lamination in a commercially available vacuum thermoforming press (Brkle Thermoformer). The lamination was achieved at a hotplate temperature of 115 C. and at a pressure of 4.5 bar; the pressure was maintained for 45 seconds. The resultant activation temperature in the adhesive was about 55 C. The vacuum time was about 6 s. The laminated foil extends to the edge of the resultant molding.

(6) The laminated product made of molding and foil was first stored at room temperature for 7 days. It was then stored at 75 C. to 90 C., where the storage temperature, beginning at 75 C., was increased by 5 C. every hour. After every hour, a lens with a scale was used at the edges of the molding to measure whether and to what extent the laminated foil had shrunk, i.e. the extent of movement in mm of the edge of the foil from the edge of the molding in the direction of the center of the test specimen. The smaller this value, the better the heat resistance. The temperature stated is that at which the edge shrinkage in the molding remains <0.3 mm.

(7) Test Method for Peel Value for Activation Temperature 50 C.

(8) Peel force is studied as follows (peel test, peel resistance):

(9) A rigid PVC furniture foil (Roxan 5371744 Buche Taunus) of width 5 cm was coated with 35-45 g/m.sup.2 (solid) of the adhesive, dried, and pressed in a heatable laboratory press with a second, uncoated PVC strip at a temperature of 50 C. in the adhesive, for 30 seconds. The test under standard conditions of temperature and humidity is carried out in a tensile testing machine 1 min after the pressing process. Once the prescribed waiting time has expired, the test strip is peeled as far as halfway, starting from the lower edge, and turned upward at an angle of 180. The test substrate end that is now free is clamped into the tensile testing machine, and the test strip is peeled at an angle of 180 degrees, the velocity of the machine being 300 mm/minute. The test substrate is renewed after each measurement. At least 3 individual measurements are made. The test results are stated in N/5 cm width.

(10) Test Method for Contact Adhesive Bonding

(11) An area of 2040 mm of two flat beechwood test specimens of width 40 mm is coated with in each case 35-45 g/m.sup.2 (solid) of the adhesive, and dried. After one hour, the adhesive layers are pressed for 30 seconds at 23 C. under a pressure of 0.5 N/mm.sup.2. The shear resistance of the adhesive bond is then determined in N at 23 C. in a machine for testing ultimate tensile strength.

(12) TABLE-US-00001 TABLE 1 Test results Shear value for contact adhesive Edge shrinkage < 0.3 bonding Peel value.sup.1) mm Example [N] [N/5 cm] [ C.] CE2 940 not measurable 85 CE1 no adhesive bonding 34 90 IE2 1338 23 >95 IE1 1811 34 95 .sup.1)at 23 C., after thermal activation at 50 C.

(13) The results in table 1 show that the dispersions IE1 and IE2 of the invention can be used advantageously in the thermal activation process because they can be thermally activated by comparatively low temperatures and at the same time generate sufficiently high peel resistance at room temperature (peel value) and also high heat resistance of the adhesive bond (edge shrinkage). Materials coated with the dispersions of the invention can moreover be adhesive-bonded by the contact process at room temperature to give high adhesive bond strengths.