Aqueous Polyurethane Dispersions

Abstract

The present invention relates to processes for the manufacture of aqueous polyurethane dispersions that can be used as adhesives or coatings, are solvent free and have low VOC emissions, and are environmentally friendly. Also encompassed are the dispersions as such, compositions containing them and their use as coatings and adhesives.

Claims

1. A process for manufacturing an aqueous polyurethane dispersion, comprising: (1) forming an NCO-terminated polyurethane prepolymer from a reaction mixture comprising: (a) at least one polyol with a number average molecular weight M.sub.n in the range of 400 to 10000 g/mol, wherein said at least one polyol comprises at least one partially hydrogenated polybutadiene polyol; (b) optionally at least one modified polyether polyol; (c) at least one anionic stabilizer, wherein the at least one anionic stabilizer comprises at least two hydroxyl groups and at least one negatively charged functional group; (d) at least two aliphatic polyisocyanates, wherein the at least two aliphatic polyisocyanates comprise at least one linear aliphatic polyisocyanate and at least one branched aliphatic polyisocyanate, and wherein the polyisocyanates are used in a total amount resulting in a molar excess of isocyanato groups relative to the hydroxy groups of the other components of the reaction mixture to obtain an NCO-terminated polyurethane prepolymer; (2) dispersing the prepolymer into a continuous aqueous phase under application of shear forces to obtain an emulsion; (3) reacting the prepolymer with at least one chain extension agent to obtain an aqueous polyurethane dispersion; and (4) blending the aqueous polyurethane dispersion with a non-polar adhesion promoter selected from the group consisting of (modified) polyolefins, polyacrylic resins and rosin-based resins.

2. The process according to claim 1, wherein the at least two aliphatic polyisocyanates comprise at least one linear aliphatic polyisocyanate and at least one branched aliphatic polyisocyanate in a weight ratio of 2:1 to 1.2:1.

3. The process according to claim 1, wherein the reaction mixture in step (1) additionally comprises at least one (modified) polyolefin, polyacrylic or rosin-based resin; and/or at least one modified polyolefin, polyacrylic or rosin-based resin is incorporated into the continuous aqueous phase in step (2).

4. The process according to claim 1, wherein the (modified) polyolefin, polyacrylic or rosin-based resin is selected from the group consisting of halogenated polyolefin resins, halogenated polyolefin maleic resins, chlorinated polypropylene maleic resins, polyolefin maleic resins, styrene/ethylene-butylene copolymer, styrene/butadiene copolymer, styrene/ethylene-propylene copolymer, styrene/isoprene copolymer, (meth)acrylate ester/(meth)acrylic acid copolymer, rosin-acid resins, and rosin-ester resins.

5. The process according to claim 1, wherein the process further comprises adding an organic solvent to the prepolymer obtained in step (1) to form a prepolymer/solvent mixture and dispersing the prepolymer/solvent mixture into a continuous aqueous phase and removing the co-solvent after step (3).

6. The process according to claim 5, wherein (1) the solvent is acetone; and/or (2) the solvent is used in an amount of up to 50 wt.-% relative to the total weight of the prepolymer.

7. The process according to claim 1, wherein the at least one polyol (a) comprises at least one partially hydrogenated polybutadiene polyol and at least one polyester polyol in a weight ratio of 10:1 to 1:10.

8. The process according to claim 1, wherein the at least one modified polyether polyol is a halogenated polyether polyol having an average number molecular weight M.sub.n of 400 to 3000.

9. The process according to claim 1, wherein the at least one anionic stabilizer comprises a sulfonated polyglycol and/or 2,2-bis(hydroxymethyl)propionic acid (DMPA).

10. The process according to claim 1, wherein (1) the polyisocyanates are used in a total amount resulting in a molar excess of isocyanato groups relative to the hydroxy groups of the combined polyols, the OH/NCO equivalent ratio being 1:1.1 to 1:4, and/or (2) the polyisocyanates are selected from diisocyanates.

11. The process according to claim 1, wherein step (2) comprises emulsifying the polyurethane prepolymer into a continuous aqueous phase by mechanical stirring.

12. The process according to claim 1, wherein the chain extension agent comprises at least two NCO-reactive groups and is selected from the group consisting of water, a diol or a diamine, an alkylene diamine, a cycloalkylene diamine, a silane-containing diamine, an alkyldiol, or a polyetherdiamine.

13. The process according to claim 1, wherein the chain extension agent is selected from the group consisting of ethylene diamine, water, isophoronediamine, or a polyetherdiamine.

14. The process according to claim 1, wherein the chain extension agent is used in an amount that ensures essentially total conversion of the isocyanate groups.

15. An aqueous polyurethane dispersion obtained according to the process of claim 1.

16. An adhesive or coating composition comprising the aqueous polyurethane dispersion according to claim 15.

Description

EXAMPLES

Example 1

[0076] Realkyd 20112 polyester polyol (71.26 g), Krasol HLBH-P 2000 97% saturated polybutadiene polyol (18.78 g), GS-7Q (1.99 g) and DMPA (0.67 g) anionic stabilizers, HN8200 (4.1 g) nonionic stabilizer were placed in a 500 mL three necked round bottom flask equipped with a condenser and a mechanical stirrer. The mixture was heated to 85° C. At this temperature, the solid components melted and a homogeneous mixture was obtained. At this point, high vacuum was applied (<0.1 mbar) while the temperature was set to 80° C. in order to remove water. The mixture was left stirring under vacuum at 80° C. for two to three hours.

[0077] Once dried, the vacuum was stopped and the mixture was flushed with argon, cooled to 60° C. and IPDI (isophorone diisocyanate, 5.15 g) and HDI (hexamethylene diisocyanate, 7.62 g) were added to the mixture (3-6° C. temperature increase was observed).

[0078] Then the catalyst (dimethyldineodecanoatetin, 5 mg of a freshly prepared tin catalyst (Fomrez UL-28)/acetone mixture (5 ml)) was added. Upon addition of the catalyst, the temperature raised rapidly some degrees. When the temperature increase stopped (at about 70° C.), the heating was set to 80° C. and once at this temperature, it was stirred for 3 hours.

[0079] The reaction mixture was left stirring at 60° C. overnight and NCO-content measured next morning: 1.03% NCO indicating that the reaction was complete.

[0080] Then 132 g acetone were added to dissolve the prepolymer, and 10 minutes later 0.45 g triethylamine (TEA) in 5 g acetone to neutralize the carboxyl groups of DMPA and sulfonyl groups of GS-7Q.

[0081] 10 minutes later the emulsification process was carried out as follows: The total amount of prepolymer solution was mixed with warm water (109 g) to obtain a mixture 44/56 by weight of PU acetone solution/water. The mixture was emulsified by mechanical stirring at 600 rpm for 20 min.

[0082] Then, the chain extension was performed by placing the resulting emulsion in a round bottom flask with mechanical stirrer and ethylene diamine (EDA, 10% in water) and APTES ((3-aminopropyl)triethoxysilane, equimolar) was added until no residual NCO was detected in IR.

[0083] The resulting dispersion was left overnight to cool down to room temperature. Next day, dispersion was filtered, the particle size was measured and the residual coagulate filtered. Finally, this emulsion was blended with 25 wt.-% resin (Toyobo NZ-1004) and stirred until it was fully homogenized.

Example 2

[0084] Realkyd 20112 polyester polyol (70.85 g), Krasol HLBH-P 2000 97% saturated polybutadiene polyol (18.8 g), IXOL M125 (4.8 g), Pexalyn (5.45 g), DMPA (0.5 g), GS-7Q (2.01 g) as anionic stabilizer and HN8200 (4.22 g) non-ionic stabilizers were placed in a 500 mL three-necked round bottom flask equipped with a condenser and a mechanical stirrer. The mixture was heated to 85° C. At this temperature, the solid components melted and a homogeneous mixture was obtained. At this point, high vacuum was applied (<0.1 mbar) while the temperature was set to 80° C. in order to remove water. The mixture was left stirring under vacuum at 80° C. for few hours. After that, vacuum was stopped and flask was flushed with Argon. The temperature was decreased to 60° C. and then, IPDI (isophorone diisocyanate, 5.98 g) and HDI (hexamethylene diisocyanate, 8.7 g) was also added (3-6° C. temperature increased was observed).

[0085] Then, 5 mg of a freshly prepared Tin catalyst/acetone (5 mL) was added. Upon addition of the catalyst, the temperature raised rapidly to some degrees. When the temperature increase stopped (at around 70° C.), the heating was set to 80° C. and once at this temperature, it was stirred for 3 hours.

[0086] The reaction mixture was left stirring at 60° C. overnight and NCO content was measured again next morning: 0.7% NCO, indicates the reaction is complete. Then, 148 g of acetone were added to dissolve the prepolymer, and 10 minutes later, 0.37 g triethylamine (TEA) in 5 g acetone. 10 minutes later, emulsification was carried out: the warm prepolymer mixture was mixed with 128 g warm water and Tacolyn 3509E (10.74 g) to obtain a mixture 44/56 of acetone solution/water for 20 minutes at 600 rpm.

[0087] Then, the chain extension was performed; the resulting emulsion was placed in a round bottom flask with mechanical stirrer and Jeffamine T-403 (polyether triamine) (10% in water) was added until no NCO was detected in IR spectrum.

[0088] The resulting dispersions were left overnight to cool down at room temperature. Next day, dispersion was filtered, particles size was measured and the residual coagulate was filtered.

Example 3

[0089] Realkyd 20112 polyester polyol (71.25 g), Krasol HLBH-P 2000 97% saturated polybutadiene polyol (20.90 g), IXOL M125 halogenated polyether polyol (4.6 g), GS-7Q (2.51 g) and DMPA (0.62 g) anionic stabilizers, HN8200 (5.05 g) nonionic stabilizer were placed in a 500 mL three necked round bottom flask equipped with a condenser and a mechanical stirrer. The mixture was heated to 85° C. At this temperature, the solid components melted and a homogeneous mixture was obtained. At this point, high vacuum was applied (<0.1 mbar) while the temperature was set to 80° C. in order to remove water. The mixture was left stirring under vacuum at 80° C. for two to three hours.

[0090] Once dried, the vacuum was stopped and the mixture was flushed with argon, cooled to 60° C. and Desmodur DN980 (0.41 g), IPDI (isophorone diisocyanate, 6.28 g) and HDI (hexamethylene diisocyanate, 9.43 g) were added to the mixture (3-6° C. temperature increase was observed).

[0091] Then the catalyst (dimethyldineodecanoatetin, 5 mg of a freshly prepared tin catalyst (Fomrez UL-28)/acetone mixture (5 ml)) was added. Upon addition of the catalyst, the temperature raised rapidly some degrees. When the temperature increase stopped (at about 70° C.), the heating was set to 80° C. and once at this temperature, it was stirred for 3 hours.

[0092] The reaction mixture was left stirring at 60° C. overnight and NCO-content measured next morning: 1.05% NCO indicating that the reaction was complete.

[0093] Then 154 g acetone were added to dissolve the prepolymer, and 10 minutes later 0.42 g triethylamine (TEA) in 5 g acetone to neutralize the carboxyl groups of DMPA and sulfonyl groups of GS-7Q.

[0094] 10 minutes later the emulsification process was carried out as follows: The total amount of prepolymer solution was mixed with warm water (147 g) to obtain a mixture 44/56 by weight of PU acetone solution/water. The mixture was emulsified by mechanical stirring at 600 rpm for 20 min.

[0095] Then, the chain extension was performed by placing the resulting emulsion in a round bottom flask with mechanical stirrer and Lunacure-MXDA was added until no residual NCO was detected in IR.

[0096] The resulting dispersion was left overnight to cool down to room temperature. Next day, dispersion was filtered, the particle size was measured and the residual coagulate filtered. Finally, this emulsion was blended with 25 wt.-% resin (Toyobo NZ-1004) and stirred until it was fully homogenized.

Example 4

[0097] Realkyd 20112 polyester polyol (85.7 g), Krasol HLBH-P 2000 97% saturated polybutadiene polyol (22.61 g), GS-7Q (2.51 g), DMPA (0.74 g) anionic stabilizers and HN8200 (4.82 g) non-ionic stabilizers were placed in a 500 mL three-necked round bottom flask equipped with a condenser and a mechanical stirrer. The mixture was heated to 85° C. At this temperature, the solid components melted and a homogeneous mixture was obtained. At this point, high vacuum was applied (<0.1 mbar) while the temperature was set to 80° C. in order to remove water. The mixture was left stirring under vacuum at 80° C. for few hours.

[0098] After that, vacuum was stopped and flask was flushed with Argon. The temperature was decreased to 60° C. and then Desmodur DN980 (0.32 g) IPDI (isophorone diisocyanate, 6.15 g) and HDI (hexamethylene diisocyanate, 9.31 g) was also added (3-6° C. temperature increased was observed).

[0099] Then, 5 mg of a freshly prepared Tin catalyst/acetone (5 mL) was added. Upon addition of the catalyst, the temperature raised rapidly to some degrees. When the temperature increase stopped (at around 70° C.), the heating was set to 80° C. and once at this temperature, it was stirred for 3 hours.

[0100] The reaction mixture was left stirring at 60° C. overnight and NCO content was measured again next morning: 1.05% NCO, indicates the reaction is complete. Then, 140.60 g of acetone were added to dissolve the prepolymer, and 10 minutes later, 0.50 g triethylamine (TEA) in 5 g acetone. 10 minutes later, emulsification was carried out: the warm prepolymer mixture was mixed with 132 g warm water to obtain a mixture 44/56 of acetone solution/water for 20 minutes at 600 rpm.

[0101] Then, the chain extension was performed; the resulting emulsion was placed in a round bottom flask with mechanical stirrer and TSPA/EDA was added until no NCO was detected in IR spectrum.

[0102] The resulting dispersions were left overnight to cool down at room temperature. Next day, dispersion was filtered, particles size was measured and the residual coagulate was filtered.

[0103] Finally, this emulsion was blended with a 25% wt. resin (Auroren S-6375) and stirred until it was fully homogenized.

Example 5 to 8

[0104] Examples 5 to 8 were prepared according to the process described in Example 1 with the formulation shown in Table 1.

TABLE-US-00001 TABLE 1 Chain Stabilizers Isocyanates ex- Sample Polyols (wt. %) (wt. %) (wt. %) tenders Exam- Realkyd 20112 GS-7Q (1.82%) IPDI (4.7%) APTES/ ple 5 (65.0%) DMPA (0.61%) HDI (6.95%) EDA Krasol HLBH-P HN-8200 (17.1%) (3.74%) Exam- Realkyd 20112 GS-7Q (1.90%) IPDI (4.65%) TSPA/ ple 6 (65.0%) DMPA (0.56%) HDI (7.05%) EDA Krasol HLBH-P HN-8200 (17.2%) (3.66%) Exam- Realkyd 20112 GS-7Q (1.82%) IPDI (11.2%) APTES/ ple 7 (64.7%) DMPA (0.46%) HDI (1.7%) EDA Krasol HLBH-P HN-8200 (16.5%) (3.57%) Exam- Realkyd 20112 GS-7Q (1.83%) IPDI (2.8%) TSPA/ ple 8 (65.9%) DMPA (0.46%) HDI (8.25%) EDA Krasol HLBH-P HN-8200 (17.1%) (3.67%)

[0105] The water-based adhesive compositions described in Examples 1-8 were evaluated in terms of particle size and PDI (polydispersity index) by Dynamic Light Scattering (DLS) according to ISO 22412, peeling strength in an Instron® Universal Testing Machine 3166 at the crosshead speed of 100 cm/min, 180°. The materials bonded were polypropylene/polyurethane foam (PP/PU-foam).

[0106] Creep tests were performed with substrates (PU-foam and PP; 1.5 cm×7 cm) at 80° C. temperature and 180° angle test. Different loads were applied and detachment was measured after 24 h of experiment.

[0107] The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Average Particle Blends Peeling Size (resin/ strength Substrate Creep Test Loads Sample d .Math. nm PDI Resin PU) (N/cm) Failure 80° C. (g) Example 1 205 0.161 Hardlen- 25/75 (SF) YES Fully 300 NZ- detached 1004  24 hour 150 0.7 cm Example 2 267 0.180 Tacolyn 50/50 5.32 NO Fully 300 3509E detached Example 3 233 0.293 Hardlen- 25/75 (SF) YES Fully 300 NZ- detached 1004  24 hour 150   0 cm Example 4 212 0.311 Auroren 25/75 (SF) YES  24 hour 150 S-6375 0.2 cm Example 5 206 0.161 Hardlen- 25/75 (SF) YES  24 hour 300 NZ-   2 cm 1004  24 hour 150 0.7 cm Example 6 212 0.311 Auroren 25/75 (SF) YES  24 hour 150 S-6375   1 cm Example 7 182 0.182 Hardlen- 25/75 (AF) NO  24 hour 150 NZ- 0.9 cm 1004 Example 8 237 0.261 Auroren 25/75 (AF) NO Fully 150 S-6375 detached SF: substrate failure AF: adhesive failure