Preparation method and application of waterborne polyurethane dispersion

Abstract

The invention discloses a preparation method and application of an aqueous polyurethane dispersion, the preparation method comprising the following steps: 1) respectively putting a polymer polyol aromatic isocyanate, a non-hydrophilic chain extender, and a nonionic hydrophilic compound into a prepolymerization reactor to react and obtain a terminal hydroxyl prepolymer; 2) continuing to react aliphatic isocyanate and the above-mentioned terminal hydroxyl prepolymer to obtain a terminal isocyanate prepolymer; 3) transferring the terminal isocyanate prepolymer to a chain extension dispersion kettle, adding a solvent for dilution, controlling the reaction temperature in the kettle to 30-50°C, then adding a hydrophilic chain extension monomer and a polyamine, and reacting for 10-30min; then adding water for dispersion, removing the solvent to obtain an aqueous polyurethane dispersion. The aqueous polyurethane dispersion provided by the method of the present invention has excellent stability and low water absorption, and has good alkali resistance and film-forming properties, so that it has a wider range of applications and significant competitive advantages in the field of water-based coatings.

Description

Technical Field

[0001] The invention relates to waterborne polyurethane, and in particular to a preparation method and application of a waterborne polyurethane dispersion. Background Art

[0002] Solvent-based polyurethane resins contain flammable, explosive, and volatile organic solvents, which seriously pollute the environment and endanger human health. With the improvement of human quality of life, increasingly stringent environmental regulations, and the improvement of people's environmental awareness, various environmental regulations have strict restrictions on the emission of volatile organic compounds and the content of harmful solvents. Compared with solvent-based polyurethane, water-based polyurethane has the advantages of being non-toxic, non-flammable, non-polluting, energy-saving, safe and reliable, etc. because it uses water as the dispersion medium.

[0003] During the synthesis of waterborne polyurethane resin, hydrophilic groups need to be introduced so that it can be dispersed in water to form a dispersion. Currently, there are two main substances containing hydrophilic groups, namely hydroxycarboxylates and aminosulfonates. Among them, aminosulfonates are strong base and strong acid salts, and the waterborne resin synthesized by them has better hydrolysis resistance stability. Aromatic isocyanates are not only cheap, but the waterborne polyurethane resin prepared by them also has excellent mechanical properties. The preparation of waterborne polyurethane by chain extension of aqueous solutions of aromatic isocyanates and aminosulfonates has very wide applications in the field of building materials.

[0004] However, the applicant has found through continuous research that during the chain extension process of aromatic isocyanate prepolymer and aminosulfonate aqueous solution, the stability of the dispersed emulsion is very poor due to the high activity of aromatic isocyanate and excessive reaction with water to form crosslinks. Therefore, how to avoid the influence of water on aromatic isocyanate during the chain extension process is of great significance for the development of low-cost, hydrolysis-resistant and excellent mechanical properties of waterborne polyurethane dispersion products.

[0005] Patent CN113896858A discloses a method for preparing an MDI-type waterborne polyurethane, which can improve the mechanical properties and water absorption rate of polyurethane resins. However, it actually uses carboxylate chain extension, and due to the presence of free carboxylates, the hydrolysis resistance of the product cannot be significantly improved.

[0006] Patent CN10670130A discloses a method for preparing a high-solid water-based polyurethane resin and its coating, wherein a water-based polyurethane dispersion prepared by using polypropylene carbonate polyol has good adhesion resistance and solvent resistance; however, the stability of the water-based polyurethane emulsion prepared by direct chain extension of an aqueous solution of aromatic isocyanate and sodium ethylenediaminesulfamate is very poor. Summary of the invention

[0007] In order to solve the above technical problems, the present invention first proposes a method for preparing an aqueous polyurethane dispersion, which is prepared by first capping aromatic isocyanate and then reacting with aliphatic isocyanate to obtain an aqueous polyurethane dispersion. The problem of poor dispersion stability caused by the reaction of aromatic isocyanate with water can be solved. At the same time, the product has lower water absorption, as well as unexpectedly improved alkali resistance and film-forming properties.

[0008] The present invention also proposes an application of the waterborne polyurethane dispersion in architectural coatings, especially in architectural waterproof coatings based on its excellent performance.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing an aqueous polyurethane dispersion comprises the following steps:

[0011] 1) putting component a) a polymer polyol with a functionality of 2 to 4, component b) an aromatic isocyanate, component c) an alcohol chain extender, and component d) a monofunctional nonionic hydrophilic compound reactive with NCO into a prepolymerization reactor respectively, and reacting at 60 to 100° C. to obtain a hydroxyl-terminated prepolymer;

[0012] 2) reacting the component e) aliphatic isocyanate and the above-mentioned hydroxyl-terminated prepolymer at 60-100° C. to obtain an isocyanate-terminated prepolymer;

[0013] 3) Transfer the terminal isocyanate prepolymer to a chain extension dispersion kettle, add a solvent to dilute, control the reaction temperature in the kettle to 30-50° C., then add component f) a hydrophilic chain extension monomer and component g) a polyamine, and react for 10-30 minutes; then add water to disperse, and remove the solvent to obtain an aqueous polyurethane dispersion.

[0014] As a preferred embodiment, based on the total mass of solids required for preparing the aqueous polyurethane dispersion as 100wt%, the contents of the components are respectively:

[0015] Component a) 50 to 85 wt%, preferably 65 to 80 wt%;

[0016] Component b) 5 to 20 wt%, preferably 6 to 12 wt%;

[0017] Component c) 0.2 to 4 wt%, preferably 0.5 to 2.5 wt%;

[0018] Component d) 0.1 to 2 wt%, preferably 0.5 to 1 wt%;

[0019] Component e) 5 to 20 wt%, preferably 10 to 18 wt%;

[0020] Component f) 0.4 to 3.2 wt%, preferably 0.5 to 2.8 wt%;

[0021] Component g) 0.1 to 3.6 wt%, preferably 0.5 to 2.8 wt%.

[0022] As a preferred embodiment, the component a) polymer polyol with functionality 2 to 4 is selected from polyester polyol and polyether polyol, and when polyester polyol and polyether polyol are present at the same time, the mass ratio of the two is 0.1 to 10:1;

[0023] Preferably, the polyol is one or more of polytetramethylene glycol, polycarbonate diol, polycaprolactone diol, polypropylene glycol, polybutylene adipate diol, polyneopentyl adipate diol, polyhexanediol adipate diol, and polypropylene glycol with a weight average molecular weight of 500 to 5000.

[0024] As a preferred embodiment, the aromatic isocyanate of component b) is one or more of toluene diisocyanate, diphenylmethane diisocyanate, and 1,5-naphthalene diisocyanate.

[0025] As a preferred embodiment, the alcohol chain extender of component c) is an alcohol with a molecular weight of less than 500, preferably selected from C2-C 10 aliphatic diol or triol, more preferably one or more of 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, diethylene glycol, and trimethylolpropane.

[0026] As a preferred embodiment, the component d) the monofunctional nonionic hydrophilic compound reactive with NCO is a polyethoxy ether containing a hydroxyl group or an amino group, preferably a monofunctional polyoxyethylene ether having a number average molecular weight of 200 to 8000 and a number of ethylene oxides of 4 to 200, more preferably a monomethyl polyoxyethylene ether having a number average molecular weight of 500 to 3000 and a number of ethylene oxides of 12 to 75, and further preferably polyethylene glycol monomethyl ether.

[0027] As a preferred embodiment, the aliphatic isocyanate of component e) is selected from one or more of isophorone diisocyanate, hexamethylene diisocyanate, and cyclohexanedimethylene diisocyanate.

[0028] As a preferred embodiment, the component f) hydrophilic chain extension monomer is aminosulfonate and / or hydroxycarboxylate, preferably sulfonate diamine, more preferably one or more of sodium ethylenediamine sulfonate, sodium 1,4-butanediol-2-sulfonate, and sodium 2,4-diaminobenzenesulfonate; when the hydrophilic chain extension monomer is aminosulfonate, excellent hydrolysis resistance of the waterborne polyurethane resin can be obtained at the same time.

[0029] The component g) polyamine is a polyamine with a molecular weight of less than 500, preferably one or more of ethylenediamine, hexamethylenediamine, 4,4-dicyclohexylmethanediamine, isophoronediamine and diethylenetriamine.

[0030] As a preferred embodiment, in step 3), the amount of the solvent used is 0.3 to 2.5 times the total mass of solids required to prepare the aqueous polyurethane dispersion; the solvent is preferably acetone or butanone.

[0031] Preferably, in step 3), the amount of water used is 0.4 to 2 times the total mass of solids required to prepare the aqueous polyurethane dispersion.

[0032] The aqueous polyurethane dispersion prepared by the method described above has a solid content of not less than 30 wt %, preferably 30 to 60 wt %, a pH of 6 to 9, and a particle size of 30 to 500 nm.

[0033] The invention relates to an application of the waterborne polyurethane dispersion prepared by the method described above in architectural coatings, especially in architectural waterproof coatings.

[0034] The waterborne polyurethane dispersion provided by the method of the present invention has excellent stability and low water absorption, and also has good alkali resistance and film-forming property, thereby enabling it to have a wider range of applications and significant competitive advantages in the field of waterborne coatings. DETAILED DESCRIPTION

[0035] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0036] Some specific steps in the experimental methods used in the following examples are routine operations unless otherwise specified.

[0037] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0038] The main raw material information is as follows:

[0039] Table 1 Raw material information

[0040]

[0041]

[0042] The main performance testing methods involved in the following embodiments of the present invention are:

[0043] (1) Water absorption: Refer to standard HG / T 3344-2012 to test the water absorption of waterborne polyurethane dispersion;

[0044] (2) Dispersion slag content: The prepared aqueous polyurethane dispersion was filtered using a 100-mesh wire filter, and after baking in an oven at 150 degrees for 20 minutes, the slag content was tested;

[0045] (3) Alkali resistance test: The dispersion was immersed in a 0.5% NaOH solution for 48 hours and tested according to the method of GB / T19250-2013 to measure the percentage decrease in tensile strength.

[0046] (4) Film-forming property test: The dispersion was dried in an oven at 80 degrees and the surface smoothness was observed. Visual scoring was used, where 1 point indicated that the number of cracks was ≥20, 2 points indicated that the number of cracks was 10 ≤ but <20, 3 points indicated that the number of cracks was 5 ≤ ​​but <10, 4 points indicated that the number of cracks was 1 ≤ but <5, and 5 points indicated that there were no cracks.

[0047] Example 1

[0048] 70 g of polypropylene glycol (Mn=2000), 7.5 g of MDI, 2.0 g of NPG and 0.6 g of polyethylene glycol monomethyl ether (Mn=1200) were put into a prepolymerization reactor and reacted at 80° C. until no NCO residue was found in the test, thereby obtaining a hydroxyl-terminated prepolymer.

[0049] The temperature was lowered to 50°C, 16.0 g of HMDI was added to the hydroxyl-terminated polyurethane prepolymer, and the temperature was raised to 80°C to continue the reaction until the NCO reached the theoretical value of 3.20%, thereby obtaining an isocyanate-terminated prepolymer;

[0050] Transfer the terminal isocyanate prepolymer to a dispersion kettle, add 105g of acetone and stir evenly, control the reaction temperature at 45°C, add 1.0g A95 and 1.8g EDA diluted with 5g of water, and extend the chain reaction for 20min. Then, add 100g of water to disperse under high-speed stirring, remove the solvent, and obtain a water-based polyurethane dispersion.

[0051] Example 2

[0052] 84 g of polypropylene glycol (Mn=3000), 19 g of TDI, 3.9 g of NPG, and 0.1 g of polyethylene glycol monomethyl ether (Mn=1200) were put into a prepolymerization reactor and reacted at 60° C. until no NCO residue was found in the test, thereby obtaining a hydroxyl-terminated prepolymer.

[0053] The temperature was lowered to 50°C, 5 g of HMDI was added to the hydroxyl-terminated prepolymer, and the temperature was raised to 60°C to continue the reaction until the NCO reached the theoretical value of 4.70%, thereby obtaining an isocyanate-terminated prepolymer;

[0054] Transfer the terminal isocyanate prepolymer to a dispersion kettle, add 110g of acetone and stir evenly, control the reaction temperature at 30°C, add 0.4g A95 and 3.5g hydroxyethylethylenediamine diluted with 5g of water, and carry out chain extension reaction for 20min. Then, add 116g of water under high-speed stirring to disperse, remove the solvent, and obtain a water-based polyurethane dispersion.

[0055] Example 3

[0056] 80 g of poly(1,4-butylene adipate) diol (Mn=2000), 12 g of TDI, 2.5 g of BDO, and 0.5 g of polyethylene glycol monomethyl ether (Mn=500) were put into a prepolymerization reactor and reacted at 100° C. until no NCO residue was found in the test to obtain a hydroxyl-terminated prepolymer.

[0057] The temperature was lowered to 50°C, 10 g of HMDI was added to the hydroxyl-terminated prepolymer, and the temperature was raised to 100°C to continue the reaction until the NCO reached the theoretical value of 4.38%, thereby obtaining an isocyanate-terminated prepolymer;

[0058] The terminal isocyanate prepolymer was transferred to a dispersion kettle, 120 g of acetone was added and stirred evenly, the reaction temperature was controlled at 50°C, 3.1 g of A95 and 1.2 g of EDA diluted with 6 g of water were added to extend the chain for 10 min, and then 109 g of water was added to disperse under high-speed stirring, and the solvent was removed to obtain a waterborne polyurethane dispersion.

[0059] Example 4

[0060] 65 g of polycaprolactone diol (Mn=2000), 6.0 g of MDI, 0.5 g of TMP, and 1.0 g of polyethylene glycol monomethyl ether (Mn=1200) were put into a prepolymerization reactor and reacted at 70° C. until no NCO residue was found by testing, thereby obtaining a hydroxyl-terminated prepolymer.

[0061] The temperature was lowered to 40°C, 18 g IPDI was added to the hydroxyl-terminated prepolymer, and the temperature was raised to 70°C to continue the reaction until the NCO reached the theoretical value of 6.18%, thereby obtaining an isocyanate-terminated prepolymer;

[0062] The terminal isocyanate prepolymer was transferred to a dispersion kettle, 120 g of acetone was added and stirred evenly, the reaction temperature was controlled at 40°C, 0.5 g of A95 and 2.4 g of EDA diluted with 6 g of water were added to extend the chain for 30 min, and then 93 g of water was added to disperse under high-speed stirring, and the solvent was removed to obtain a waterborne polyurethane dispersion.

[0063] Example 5

[0064] 50 g of polycarbonate diol (Mn=2000), 5 g of MDI, 0.2 g of NPG, and 1.9 g of polyethylene glycol monomethyl ether (Mn=1200) were put into a prepolymerization reactor and reacted at 60° C. until no NCO residue was found by testing, thereby obtaining a hydroxyl-terminated prepolymer.

[0065] The temperature was lowered to 40°C, 19 g IPDI was added to the hydroxyl-terminated prepolymer, and the temperature was raised to 100°C to continue the reaction until the NCO reached a theoretical value of 8.60%, thereby obtaining an isocyanate-terminated prepolymer;

[0066] The terminal isocyanate prepolymer was transferred to a dispersion kettle, 100 g of acetone was added and stirred evenly, the reaction temperature was controlled at 40°C, 2.8 g of A95 and 0.5 g of IPDA diluted with 6 g of water were added to extend the chain for 30 min, and then 79 g of water was added to disperse under high-speed stirring, and the solvent was removed to obtain a waterborne polyurethane dispersion.

[0067] Example 6

[0068] 80 g of poly(neopentyl adipate) glycol (Mn=2000), 6.0 g of MDI, 0.2 g of NPG, and 1.5 g of polyethylene glycol monomethyl ether (Mn=1200) were put into a prepolymerization reactor and reacted at 100° C. until no NCO residue was found in the test to obtain a hydroxyl-terminated prepolymer.

[0069] The temperature was lowered to 40°C, 5 g of HDI was added to the hydroxyl-terminated prepolymer, and the temperature was raised to 60°C to continue the reaction until the NCO reached the theoretical value of 1.01%, thereby obtaining an isocyanate-terminated prepolymer;

[0070] The terminal isocyanate prepolymer was transferred to a dispersion kettle, 120 g of acetone was added and stirred evenly, the reaction temperature was controlled at 40°C, 2.0 g of A95 and 0.1 g of IPDA diluted with 8 g of water were added to extend the chain for 15 min, and then 95 g of water was added to disperse under high-speed stirring, and the solvent was removed to obtain a waterborne polyurethane dispersion.

[0071] [Example 7]

[0072] An aqueous polyurethane dispersion was prepared in substantially the same manner as in Example 1, except that the hydrophilic chain extending monomer A95 was replaced by dimethylolpropionic acid.

[0073] [Comparative Example 1]

[0074] 70 g of polypropylene glycol (Mn=2000), 7.5 g of MDI, 2.0 g of NPG and 0.6 g of polyethylene glycol monomethyl ether (Mn=1200) were put into a prepolymerization reactor and reacted at 80° C. until no NCO residue was found in the test, thereby obtaining a hydroxyl-terminated prepolymer.

[0075] The temperature was lowered to 50°C, 15.3 g of MDI was added to the hydroxyl-terminated polyurethane prepolymer, and the temperature was raised to 80°C to continue the reaction until the NCO reached the theoretical value of 3.20%, thereby obtaining an isocyanate-terminated prepolymer;

[0076] Transfer the terminal isocyanate prepolymer to a dispersion kettle, add 105g of acetone and stir evenly, control the reaction temperature at 45°C, add 1.0g A95 and 1.8g EDA diluted with 5g of water, and extend the chain reaction for 20min. Then, add 100g of water to disperse under high-speed stirring, remove the solvent, and obtain a water-based polyurethane dispersion.

[0077] The waterborne polyurethane dispersions prepared in the examples and comparative examples were tested for solid content, particle size, slag content, water absorption, alkali resistance and film-forming properties. The test results are shown in Table 2.

[0078] Table 2. Performance test results

[0079]

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an aqueous polyurethane dispersion, characterized in that: The following steps are involved: 1) putting component a) a polymer polyol with a functionality of 2 to 4, component b) an aromatic isocyanate, component c) an alcohol chain extender, and component d) a monofunctional nonionic hydrophilic compound reactive with NCO into a prepolymerization reactor respectively, and reacting at 60 to 100° C. to obtain a hydroxyl-terminated prepolymer; 2) reacting the component e) aliphatic isocyanate and the above-mentioned hydroxyl-terminated prepolymer at 60-100° C. to obtain an isocyanate-terminated prepolymer; 3) transferring the terminal isocyanate prepolymer to a chain extension dispersing kettle, adding a solvent to dilute, controlling the reaction temperature in the kettle to 30-50° C., then adding component f) a hydrophilic chain extension monomer and component g) a polyamine, and reacting for 10-30 minutes; then adding water to disperse, and removing the solvent to obtain an aqueous polyurethane dispersion; Taking the total mass of solids required for preparing the aqueous polyurethane dispersion as 100wt%, the contents of each component are: Component a) 50-85 wt%, Component b) 5-20 wt%, Component c) 0.2-4 wt%, Component d) 0.1-2 wt%, Component e) 5-20 wt%, Component f) 0.4-3.2 wt%, Component g) 0.1 to 3.6 wt%; The component f) hydrophilic chain extending monomer is a sulfonate diamine.

2. The method for preparing an aqueous polyurethane dispersion according to claim 1, characterized in that: Taking the total mass of solids required for preparing the aqueous polyurethane dispersion as 100wt%, the contents of each component are: Component a) 65-80 wt%; Component b) 6 to 12 wt%; Component c) 0.5 to 2.5 wt%; Component d) 0.5 to 1 wt%; Component e) 10 to 18 wt%; Component f) 0.5 to 2.8 wt%; Component g) 0.5-2.8 wt%.

3. The method for preparing an aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: The component a) polymer polyol with functionality 2 to 4 is selected from polyester polyol and polyether polyol, and when polyester polyol and polyether polyol exist at the same time, the mass ratio of the two is 0.1 to 10:

1.

4. The method for preparing an aqueous polyurethane dispersion according to claim 3, characterized in that: The polymer polyol is one or more of polytetramethylene glycol, polycarbonate diol, polycaprolactone diol, polypropylene glycol, polybutylene adipate diol, polyneopentyl adipate diol, polyhexane adipate diol and polypropylene glycol with a weight average molecular weight of 500 to 5000.

5. The method for preparing an aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: The aromatic isocyanate of component b) is one or more of toluene diisocyanate, diphenylmethane diisocyanate and 1,5-naphthalene diisocyanate.

6. The method for preparing an aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: The alcohol chain extender as component c) is an alcohol with a molecular weight of less than 500.

7. The method for preparing an aqueous polyurethane dispersion according to claim 6, characterized in that: The alcohol chain extender of component c) is selected from C2-C 10 aliphatic diol or triol.

8. The method for preparing an aqueous polyurethane dispersion according to claim 6, characterized in that: The alcohol chain extender of component c) is one or more of 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, diethylene glycol, and trimethylolpropane.

9. The method for preparing an aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: The component d) the monofunctional nonionic hydrophilic compound reactive with NCO is a polyethoxylated ether containing one hydroxyl group or amino group.

10. The method for preparing an aqueous polyurethane dispersion according to claim 9, characterized in that: The component d) is a monofunctional nonionic hydrophilic compound reactive with NCO, which is a monofunctional polyoxyethylene ether having a number average molecular weight of 200 to 8000 and a number of ethylene oxide of 4 to 200.

11. The method for preparing an aqueous polyurethane dispersion according to claim 9, characterized in that: The component d) is a monofunctional nonionic hydrophilic compound reactive with NCO and is a monomethyl polyoxyethylene ether with a number average molecular weight of 500 to 3000 and a number of ethylene oxide of 12 to 75.

12. The method for preparing an aqueous polyurethane dispersion according to claim 9, characterized in that: The component d) the monofunctional nonionic hydrophilic compound reactive with NCO is polyethylene glycol monomethyl ether.

13. The method for preparing an aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: The aliphatic isocyanate of component e) is selected from one or more of isophorone diisocyanate, hexamethylene diisocyanate and 4,4'-dicyclohexylmethane diisocyanate.

14. The method for preparing an aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: The component f) hydrophilic chain extension monomer is one or more of sodium ethylenediamine sulfonate and sodium 2,4-diaminobenzene sulfonate; The component g) polyamine is a polyamine with a molecular weight of less than 500.

15. The method for preparing an aqueous polyurethane dispersion according to claim 14, characterized in that: The component g) polyamine is one or more of ethylenediamine, hexamethylenediamine, 4,4-dicyclohexylmethanediamine, isophoronediamine and diethylenetriamine.

16. The method for preparing an aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: In step 3), the amount of the solvent used is 0.3 to 2.5 times the total mass of solids required to prepare the aqueous polyurethane dispersion.

17. The method for preparing an aqueous polyurethane dispersion according to claim 16, characterized in that: In step 3), the solvent is selected from acetone and butanone.

18. The method for preparing an aqueous polyurethane dispersion according to claim 16, characterized in that: In step 3), the amount of water used is 0.4 to 2 times the total mass of solids required to prepare the aqueous polyurethane dispersion.

19. Use of an aqueous polyurethane dispersion prepared by the method according to any one of claims 1 to 18 in architectural coatings.

20. Use of an aqueous polyurethane dispersion prepared by the method according to any one of claims 1 to 18 in a building waterproof coating.

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