Process and apparatus for continuous production of aqueous polyurethane dispersions

Abstract

The application relates to a process for continuously producing aqueous polyurethane dispersions, which is characterized by the use of micro structured mixing elements and addition of water twice during the dispersion step. The energy input in the mixing of the dispersion is low. In addition, the application describes an apparatus suitable for execution of the aforementioned process.

Claims

1. A process for continuously producing an aqueous polyurethane dispersion, comprising the steps of a) simultaneously introducing at least one prepolymer and at least one chain-extending reagent into a mixing element M1; b) subsequently simultaneously introducing the chain-extended prepolymer formed in process step a) and water into a mixing element M2; and c) subsequently simultaneously introducing the mixture formed in process step b) and water into a mixing element M3 to form an aqueous polyurethane dispersion.

2. The process according to claim 1, wherein 1%-99% by weight of the total amount of water added is added in mixing element M2 and the remainder to 100% by weight in mixing element M3.

3. The process according to claim 1, further comprising at least one of the steps of a1) flowing through a delay zone VZ1 between mixing elements M1 and M2; b1) flowing through a delay zone VZ2 between mixing elements M2 and M3; and c1) flowing through a delay zone after mixing element M3.

4. The process according to claim 1, wherein the prepolymer has been dissolved in an organic solvent.

5. The process according to claim 1, wherein the mixing elements are static mixing elements.

6. The process according to claim 5, wherein the mixing elements are micro structured mixing elements.

7. The process according to claim 1, wherein the energy input in at least one of the mixing elements M1 or M2 or M3 is below 20 W/cm.sup.3.

8. The process according to claim 1, wherein the prepolymer is prepared from a polyester formed from adipic acid, hexane-1,6-diol and neopentyl glycol, and hexamethylene diisocyanate.

9. The process according to claim 1, wherein the chain-extending reagent is 2-(2-aminoethylamino)ethanesulphonic acid.

10. The process according to claim 8, wherein the chain-extending reagent is 2-(2-aminoethylamino)ethanesulphonic acid.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a schematic of the construction of an apparatus for performance of the process according to the invention. The mixing element M1 has two feeds Z1 and Z2. The liquid stream leaving the mixing element M1 is conducted into a second mixing element M2, where a further liquid stream is metered in via a feed Z3. The connection between the mixing elements M1 and M2 may optionally contain a delay zone VZ1. The liquid stream leaving the mixing element M2 is conducted into a third mixing element M3, where a further liquid stream is metered in via a feed Z4. The connection between the mixing elements M2 and M3 may optionally contain a delay zone VZ2. In addition, a delay zone VZ3 may optionally be connected to the outlet of the mixing element M3.

(2) The working examples which follow serve merely to illustrate the invention. They are not intended to restrict the scope of protection of the claims.

EXAMPLE 1 (INVENTIVE)

(3) 1.1 Raw Materials

(4) Polyester 170 HN (170 HN): polyester polyol formed from adipic acid, hexane-1,6-diol and neopentyl glycol having a molar mass of 1700 g/mol (BAYER AG, DE, Leverkusen)

(5) Desmodur H (HDI): hexamethylene diisocyanate (BAYER AG, DE, Leverkusen) Ethylenediamine (EDA, ALDRICH, DE)

(6) AAS solution: 45% aqueous solution of the sodium salt of 2-(2-aminoethylamino)ethanesulphonic acid (BAYER AG, Leverkusen, DE)

(7) 1.2 Methods

(8) The solids contents (SC) were determined in accordance with DIN-EN ISO 3251.

(9) The median particle sizes (MPS) were determined by means of photocorrelation spectroscopy (Malvern Instruments, model: Zetasizer 1000)

(10) The NCO content was determined by volumetric means in accordance with DIN-ISO 11909. The mechanical properties of the PU dispersions are determined on free films which are produced as follows:

(11) In a film applicator consisting of two polished rolls which can be set at an exact distance, a release paper is inserted ahead of the rear roll. A feeler gauge is used to set the distance between paper and front roll. This distance corresponds to the (wet) film thickness of the resulting coating and can be set to the desired application of each coat. Coating is also possible consecutively in several coats.

(12) To apply the individual coats, the products, after the viscosity has been adjusted by adding anionic acrylic polymer to 4500 mPa.Math.s, are poured into the gap between paper and front roll; the release paper is pulled away vertically downward, forming the corresponding film on the paper. If several coats are to be applied, each individual coat is dried and the paper is reinserted.

(13) Drying conditions: 70 C. to dry, then 3 minutes at 150 C.

(14) 1.3 Continuous Prepolymer Synthesis

(15) A prepolymer (90.7% by weight) consisting of the 170 HN polyester (30.6% by weight), HDI (5.4% by weight) and acetone (64.0% by weight) is mixed in the mixer M1 with a chain-extending reagent (9.3% by weight) consisting of AAS solution (19.9% by weight), EDA (3.1% by weight) and water (77.0% by weight) at 40 C. and left to react in the delay zone VZ1 at 40 C. for 5 min.

(16) The mixture (70.2% by weight) is mixed at 40 C. in the mixer M2 with the first portion of water (11.9% by weight). Thereafter, the mixture runs through the delay zone VZ2 for about 2 min before being mixed in the mixer M3 with the second portion of water (17.9% by weight). The percentages by weight are based on the total weight of the dispersion.

(17) The resulting mixture is guided through the delay zone VZ3 for another <1 min, before being collected in the product vessel. The remaining acetone is distilled out of this crude dispersion at 40 C. and a pressure of 120 mbar, giving rise to a solvent-free, storage-stable polyurethane dispersion having the characteristics listed in Table 1.

(18) TABLE-US-00001 TABLE 1 Characteristics of the example dispersion. SC 100% Tensile Elongation [% by MPC modulus strength at break Ex. wt.] pH [nm] [N/mm.sup.2] [N/mm.sup.2] [% by wt.] 1 41.0 6.1 249 1.6 40.6 1778

EXAMPLES 2 TO 8

(19) Raw materials and methods: LB 25: Monofunctional polyether based on ethylene oxide/propylene oxide having an ethylene oxide content of 84%, OH number 25, Mn=2250 g/mol (Covestro AG, DE). Desmophen 1652: Linear polyester diol with a molecular weight Mn of 2000 g/mol (Covestro AG, DE, Leverkusen). Desmophen C2200: Linear polycarbonate diol with a molecular weight of 2000 g/mol (Covestro AG, DE, Leverkusen). Polyester 225 B: Linear polyester diol with a molecular weight of 2250 g/mol (Covestro AG, DE, Leverkusen). IPDI: Desmodur I, isophorone diisocyanate (Covestro AG, DE). HDI: Desmodur H, 1,6-hexamethylene diisocyanate (Covestro AG, DE). H12MDI: Desmodur W, dicyclohexylmethan-4,4 diisocyanate (Covestro AG; DE, Leverkusen). IPDA: Isophoronediamine (Covestro AG, DE). AAS: Diaminosulfonate, sodium salt, 45% in water, H.sub.2NCH.sub.2CH.sub.2NHCH.sub.2CH.sub.2SO.sub.3Na (Covestro AG, DE). DEA: Diethanolamine (Aldrich, DE) EDA: Ethylenediamine (Aldrich, DE) DMPA: Dimethylolpropionic acid (Aldrich, DE) TEA: Triethylamine (Aldrich, DE) PUD: Polyurethane Dispersion
Standard Procedure for the Synthesis of the Prepolymers Used in the Continuous Process:

(20) The polyol or the polyol mixture is added into a stainless steel reactor with 16 L volume and heated up to 70 C. As soon as the temperature is achieved the polyisocyanate or polyisocyanate mixture is added within a few minutes and the reaction temperature is increased to 100 C. The reaction mixture is stirred until the theoretical NCO value is achieved and the prepolymer is cooled down to 90 C. Acetone is added to obtain clear and colorless solutions with a solid content of 50 wt-%. The NCO value is determined according to DIN-EN ISO 11909.

EXAMPLE 2

(21) A prepolymer (94.8 wt %) which is based on polyester diol (PE 225 B) (34.1 wt %), IPDI (1.5 wt %), HDI (2.3 wt %) and acetone (56.9 wt %) is mixed in M1 with a chain extension agent (5.2 wt %) composed of an AAS-solution (19.3 wt %), DEA (3.8 wt %) and water (76.9 wt %) at 48 C. The reaction takes place in a heat exchanger VZ1 at 48 C.

(22) The mixture (64.6 wt %) is mixed with a first part of water in the valve mixer at 48 C. In mixer M2 the first part of water (14.2 wt %) is added. After a short retention time the mixture is mixed with the second part of water (21.2 wt %) at M3.

(23) The obtained dispersion is collected and acetone is distilled off at 40 C. and at a pressure of 120 mbar.

(24) The properties of the solvent-free PU dispersions are determined as follows:

(25) Determination of solid content (SC) is done by DIN-EN ISO 3251.

(26) Determination of the mean particle size was done through dynamic light scattering (Malvern Instruments, Type: Zetasizer 1000)

(27) Determination of pH value is done by DIN 19621.

(28) The characterization of the solvent-free PU dispersions is performed identical for example 2-7 and is listed in table 5. The pressure drops at the valve mixers M1, M2 and M3 for the product side and the solvent side are listed in table 6.

Comparative Example 2a (Batch Process)

(29) 2.4 wt % of HDI and 1.6 wt % of IPDI were added at 60 C. to 36.0 wt % PE 225 B and then reacted at 80 C. to the prepolymer until the theoretical NCO value (NCO-1=1.18%) was reached. 60.0 wt % of acetone were added at 80 C., the mixture is cooled to 48 C. and the prepolymer was dissolved.

(30) 5.2 wt % of a chain-extending solution, which was based on AAS-solution consisting of (19.3 wt %), DEA (3.8 wt %) and water (76.9 wt %), was added to 94.8 wt % of the prepolymer. The solution was stirred for 60 minutes at 48 C. 64.6 wt % of the mixture was dispersed in 35.4 wt % of water. Acetone was distilled off at 120 mbar and 40 C.

(31) This example shows the continuous production of PUDs compared to the standard batch process. The characterization of the PUDs shows identical properties for both techniques.

EXAMPLE 3

(32) The prepolymer solution (55.1 wt %) consisting of a linear polyester diol (DE 1652) (37.2 wt %), DMPA (1.4 wt %), IPDI (10.9 wt %), TEA (1.0 wt %) and acetone (49.5 wt %) was mixed with the first part of water (17.7 wt %) at mixer M2 at 25 C. At mixer M3 the second part of water (27.2 wt %) was mixed to the liquid.

(33) The mixture (94.3 wt %) was mixed with a chain extension agent (5.7 wt %) at 25 C. The chain extension agent consisted of IPDA (25.4 wt %) and water (74.6 wt %). The obtained dispersion was collected and acetone is distilled off at 40 C. and at a pressure of 120 mbar.

Comparative Example 3a (Batch Process)

(34) 10.9 wt % of IPDI were added to 37.2 wt % DE 1652 and 1.4 wt % DMPA at 70 C. and then reacted to the prepolymer until the theoretical NCO value (NCO-1=3.42%) was reached at 100 C. 49.5 wt % of acetone were then added at 90 C. and 1.0 wt % of TEA are added at 80 C. The mixture is cooled to 50 C.

(35) 55.1 wt % prepolymer was dispersed in 44.9 wt % of water. 5.7 wt % chain-extending solution based on 25.4 wt % IPDA and 74.6 wt % water was added to the mixture (94.3 wt %), and stirring was carried out for 120 minutes at 50 C. Then the acetone was distilled off at 120 mbar and 40 C.

(36) This example shows the flexibility of the new technology. The example shows that the reverse procedure, first dispersing the prepolymer in water and then mixing the dispersion with a chain extension solution, obtains stable PUDs.

EXAMPLE 4

(37) A prepolymer solution (92.8 wt %) consisting of a linear polyester carbonate (C2200) (26.9 wt %), DMPA (1.0 wt %), IPDI (7.9 wt %), TEA (0.8 wt %) and acetone (63.5 wt %) was combined with a chain extension agent (7.2 wt %) in mixer M1 at 25 C. The chain extension agent was based on IPDA (19.9 wt %) and water (80.1 wt %). The reaction took place immediately.

(38) The mixture (62.6 wt %) was mixed with the first part of water (15.0 wt %) at M2 at 25 C. and the second part of water (22.5 wt %) was added in M3. The obtained dispersion was collected and acetone was distilled off at 40 C. and at a pressure of 120 mbar.

Comparative Example 4a (Batch Process)

(39) 7.9 wt % of IPDI were added to 26.9 wt % C2200 and 1.0 wt % DMPA at 70 C. and then reacted to the prepolymer until the theoretical NCO value (NCO-1=3.42%) was reached at 100 C. 63.5 wt % of acetone were then added at 90 C. and 0.8 wt % of TEA were added at 40 C.

(40) 7.2 wt % of a chain-extending solution consisting of 19.9 wt % IPDA and 80.1 wt % water, was added to 92.8 wt % of the prepolymer. Stirring was carried out for 15 minutes at 40 C. 62.6 wt % product was dispersed in 37.4 wt % water. Then the acetone was distilled off at 120 mbar and 40 C.

(41) Example 4 shows that various polyols can be employed to the system. In this example a linear polycarbonate diol is used. The continuous process obtained the desired smaller particle size compared to the batch process.

EXAMPLE 5

(42) A prepolymer solution consisting of polyester diol (PE 225 B) (43.4 wt %), IPDI (1.9 wt %), HDI (2.9 wt %) and acetone (51.8 wt %) was diluted with acetone to reduce the viscosity. In mixer M1 the diluted prepolymer and the chain extension solution were mixed at 48 C. The chain extension solution was based on AAS-solution consisting of (19.3 wt %), DEA (3.8 wt %) and water (76.9 wt %). Table 2 shows the dilution of acetone and the corresponding addition of chain extension (CE) solution and water.

(43) TABLE-US-00002 TABLE 2 Dilution series of prepolymer with the adjusted CE-solution. prepolymer acetone CE-solution water sample (wt %) (wt %) (wt %) (wt %) 5 a 85.3 9.5 4.7 0.5 5 b 75.8 19.0 4.2 1.0 5 c 66.4 28.4 3.6 1.6

(44) The mixture (70.2 wt %) was mixed with the first part of water (11.9 wt %) at M2 at 48 C. After a short retention time of few minutes the second part of the water (17.9 wt %) was mixed to M3. The obtained dispersion was collected and acetone is distilled off at 40 C. and at a pressure of 120 mbar.

(45) In this example the effect of changing the viscosity of the prepolymer on the obtained particle size is shown. By reducing the viscosity and the solid content the particle size decreases.

EXAMPLE 6

(46) A prepolymer solution (92.4 wt %) consisting of a linear polyester diol (DE 1652) (25.9 wt %), DMPA (1.0 Gew. %), Desmodur W (8.9 wt %), TEA (0.7 wt %) and acetone (63.5 wt %) was mixed with a chain extension agent (7.6 wt %) in M1 at 25 C. The chain extension agent consisted of DEA (9.0 wt %), EDA (7.7 wt %) and water (83.4 wt %).

(47) The mixture (63.0 wt %) was mixed with a first part of water (14.8 wt %) in M2 and then the second part of water (22.2 wt %) was added in M3. The obtained dispersion was collected and acetone was distilled off at 40 C. and at a pressure of 120 mbar.

Comparative Example 6a (Batch Process)

(48) 8.9 wt % of Desmodur W were added to 25.9 wt % DE 1652 and 1.0 wt % DMPA at 70 C. and then reacted to the prepolymer until the theoretical NCO value (NCO-1=3.29%) was reached at 100 C. 63.5 wt % of acetone were then added at 90 C. and 0.7 wt % of TEA were added to the mixture at 40 C.

(49) 7.6 wt % of chain-extending solution consisting of 7.7 wt % EDA, 9.0 wt % DEA and 83.3 wt % water was added to 92.4 wt % of the mixture. Stirring was carried out for 15 minutes at 40 C. 63.0 wt % of the product was dispersed in 37.0 wt % water. Then the acetone was distilled off at 120 mbar and 40 C.

(50) Example 6 shows that various polyisocyanates can be employed. The comparison of batch vs. continuous process shows that smaller particles, which are desired, can be obtained with the new technology.

EXAMPLE 7

(51) 94.8 wt % of a prepolymer solution consisting of polyester diol (PE 225 B) (36.0 wt %), IPDI (1.6 wt %), HDI (2.4 wt %) and acetone (60.0 wt %) was mixed with a chain extension solution (5.2 wt %) in M1 at 48 C. The chain extension solution is based on AAS-solution, DEA and water. The exact amount added to the prepolymer is listed in table 3.

(52) TABLE-US-00003 TABLE 3 Variation of AAS-solution. prepolymer CE solution H.sub.2O CE solution AAS Sample (wt %) (wt %) (wt %) DEA (wt %) (wt %) 7 a 94.8 5.2 78.9 3.8 17.3 7 b 94.8 5.2 74.9 3.8 21.27

(53) The first part of water (14.1 wt %) was added to the mixture (64.6 wt %) in M2 at 48 C. The second part of water (21.2 wt %) was added in M3. The obtained dispersion was collected and acetone was distilled off at 40 C. and at a pressure of 120 mbar.

(54) Example 7 shows the effect of the variation the amount of AAS-solution on the properties of the PUDs. The amount of hydrophilic groups in the mixture is correlated to the final particle size. Increasing the amount of AAS-solution decreases the particle size of PUDs.

EXAMPLE 8

(55) In this example only the dispersion with water was done continuously.

(56) A prepolymer solution (94.8 wt %) consisting of polyester diol (PE 225 B) (34.1 wt %), IPDI (1.5 wt %), HDI (2.3 wt %) and acetone (56.9 wt %) was mixed with a chain extension agent (5.2 wt %) composed of an AAS-solution consisting of (19.3 wt %), DEA (3.8 wt %) and water (76.9 wt %) at 48 C.

(57) The mixture (64.6 wt %) was mixed with a first part of water in the valve mixer at 48 C. In mixer M2 the first part of water was added. After a short retention time the mixture was mixed with the second part of water at M3. The ratio of water added in M2 and M3 is listed in table 4, the total amount of water added to the final product was 35.4 wt %.

(58) The obtained dispersion was collected and acetone was distilled off at 40 C. and at a pressure of 120 mbar.

(59) TABLE-US-00004 TABLE 4 Water ratio of the two-stage water addition during the dispersion step. Sample H.sub.2O M2 (%) H.sub.2O M3 (%) 8 a 10 90 8 b 20 80 8 c 30 70 8 d 40 60 8 e 50 50

(60) This example shows the impact of the water ratios in the dispersion step on the stability of the PUDs. Here, the ratio of water, which is added in M2 and M3, is changing. Only sample 8 d with a water ratio of 40:60 obtained stable dispersion.

(61) TABLE-US-00005 TABLE 5 Characteristics of the solvent free PUDs. particle solid stable/ size pH- content not stable (nm) value (%) dispersion Example 2: Example 2 a 191 6.38 40.1 stable Example 2 batch 150-190 6.0-9.0 39-41 stable Example 3: First dispersion then CE Example 3 a 286 7.58 22.9 stable Example 3 batch 173 7.9 34 stable Example 4: Variation Polyol Example 4 a 102 8.31 34.76 stable Example 4 batch 128.3 8.16 35.75 stable Example 5: Variation of viscosity of prepolymer Example 5 a 228.7 6.5 36.4 stable Example 5 b 174.3 6.4 26.1 stable Example 5 c 173.3 6.4 16.2 stable Example 5 d 125.7 7.1 7.2 stable Example 6: Variation PIC Desmodur W Example 6 a 228 9 36.2 stable Example 6 batch 292.5 8.7 36.01 stable Example 7: Variation of AAS-solution Example 7 a 367 6.02 33.5 stable Example 7 b 211 6.11 41.3 stable Example 8: Variation of the water ratio Example 8 a not stable Example 8 b not stable Example 8 c not stable Example 8 d 177 7.4 39.8 stable Example 8 e not stable

(62) TABLE-US-00006 TABLE 6 Pressure drop at the valve mixers. p M1 p M2 p M3 p M1 CE Product p M2 Product p M3 Prepolymer Solution side Water Side Water Example bar bar bar bar bar bar 2a 0.85 0.75 4.01 0.46 2.55 1.03 3a 0.79 2.59 0.23 0.15 1.02 2.16 4a 1.70 2.11 0.71 0.17 0.20 1.02 5a 0.33 0.14 1.08 0.31 0.75 1.19 5b 0.17 0.16 0.56 0.31 0.43 1.26 5c 0.07 0.16 0.36 0.38 0.29 1.41 5d 0.03 0.24 0.16 0.22 0.18 1.49 6a 0.08 2.35 0.41 0.18 0.21 1.27 7a 0.55 0.24 1.03 0.26 0.30 0.49 7b 0.50 0.37 1.27 0.33 0.51 0.64