Water-based dispersing agent, water-based color paste and preparation method of water-based dispersing agent

Abstract

The invention relates to the technical field of dispersing agents, and discloses a water-based dispersing agent, water-based color paste and a preparation method thereof.4-chloromethyl benzaldehyde, imidazole, serinol, sodium chloroacetate and the like serve as raw materials, a novel imidazole diol carboxyl hydrophilic chain extender is prepared, the novel imidazole diol carboxyl hydrophilic chain extender, polyethylene glycol and diisocyanate are subjected to a chain extension polymerization reaction, and the water-based dispersing agent, the water-based color paste and the water-based color paste are obtained. The polyurethane-based water-based dispersing agent is obtained. A side chain of the dispersing agent contains hydrophilic carboxyl and an imidazole anchoring group, the dispersing agent has good hydrophilicity, nitrogen atoms in the imidazole anchoring group contain lone pair electrons and can form Van der Waals force, hydrogen bonds and other interaction forces with phthalocyanine blue, pigment red 245 and other pigments, so that the dispersing agent can be uniformly adsorbed on the surfaces of pigment molecules to form an adsorption layer, and the dispersion effect is improved. The pigment molecules are prevented from gathering, the particle size of the pigment molecules is reduced, the dispersity is improved, desorption is not prone to occurring, and the obtained water-based color paste has good centrifugal stability.

Description

Technical Field

[0001] The invention relates to the technical field of dispersants, and in particular to an aqueous dispersant, an aqueous color paste and a preparation method thereof. Background Art

[0002] Water-based paints and inks use water as solvent, which is green and environmentally friendly. Traditional color pastes are solvent-based and contain volatile organic solvents, which are more polluting, and solvent-based color pastes are difficult to use in water-based paints and inks. Therefore, the development of high-performance water-based dispersants and water-based color pastes is a research hotspot. Polyurethane-based water-based dispersants have the advantages of good hydrophilicity and excellent dispersibility, and are widely used in pigments such as phthalocyanine blue and pigment red.

[0003] Introducing nitrogen-containing anchoring groups into the dispersant can improve the interaction between the dispersant and the pigment molecules, which is beneficial to improving the dispersibility and stability of the dispersant. Patent CN103897441B discloses a solvent-based block polymer dispersant, which uses homopolymers or copolymers of nitrogen-containing vinyl monomers such as vinyl pyridine, vinyl imidazole, and acrylic acid amino ester as pigment anchoring segments to prevent pigment flocculation and precipitation during storage. However, the polymer dispersant is an organic solvent type, and requires the use of organic solvents such as propylene glycol methyl ether acetate, which is difficult to be well applied in water-based color pastes from the perspective of pollution. Summary of the invention

[0004] The technical problem solved by the invention is to provide an aqueous dispersant for pigments such as phthalocyanine blue to improve the dispersibility of aqueous color paste.

[0005] The technical scheme of the present invention is: a method for preparing an aqueous dispersant comprises: adding dry polyethylene glycol and diisocyanate into a flask, heating to 70-80°C, stirring and reacting for 2-3h, then adding imidazole diol carboxyl hydrophilic chain extender and dibutyltin dilaurate, reacting for 40-50min, cooling, and obtaining an aqueous dispersant.

[0006] The imidazole diol carboxyl hydrophilic chain extender has the following structural formula (I):

[0007]

[0008] Preferably, the molar ratio of polyethylene glycol, diisocyanate, and imidazole diol carboxyl hydrophilic chain extender is 1:(2.2-2.6):(1.1-1.3).

[0009] Preferably, the diisocyanate is isophorone diisocyanate or hexamethylene diisocyanate.

[0010] Preferably, the preparation method of the imidazole diol carboxyl hydrophilic chain extender comprises:

[0011] Step (1), add acetonitrile, 4-chloromethylbenzaldehyde, imidazole and potassium carbonate in a molar ratio of (0.8-1.2):1:(1-1.2) into a flask, react at 60-70°C for 5-8h, distill under reduced pressure, wash with water, and recrystallize the product with ethanol to obtain intermediate A.

[0012] Step (2), add ethanol, intermediate A and serine in a molar ratio of 1:(1-1.4) to a flask, react at 50-65°C for 4-6h, add sodium borohydride after cooling, react for 3-4h, distill under reduced pressure, wash with water, and recrystallize the product with ethanol to obtain intermediate B.

[0013] Step (3), adding ethanol, intermediate B, sodium chloroacetate and sodium carbonate in a molar ratio of 1:(1.2-1.4):(1.2-1.6) into a flask, reacting at 50-70° C. for 7-10 hours, removing ethanol by distillation under reduced pressure, adding hydrochloric acid solution to adjust the pH to 3-4, precipitating a precipitate, filtering, and recrystallizing the product in an ethanol aqueous solution with a volume fraction of 80% to obtain an imidazole diol carboxyl hydrophilic chain extender.

[0014] Preferably, the method for preparing an aqueous color paste using an aqueous dispersant is characterized in that the method is: adding water, a pigment and an aqueous dispersant in a mass ratio of 100:(10-25) into a container, stirring and placing the color paste in a grinder for grinding for 1-2 hours, discharging the material, and obtaining an aqueous color paste.

[0015] Preferably, the pigments include phthalocyanine blue and pigment red.

[0016] The technical effect produced by the present invention is as follows: the present invention uses cheap and easily available 4-chloromethylbenzaldehyde, imidazole, siraminol, sodium chloroacetate and the like as raw materials to prepare a novel imidazole diol carboxyl hydrophilic chain extender, and carries out a chain extension polymerization reaction with polyethylene glycol and diisocyanate to obtain a novel polyurethane-based water-based dispersant.

[0017] The side chain of the polyurethane-based water-based dispersant of the invention contains a hydrophilic carboxyl group and an imidazole anchoring group, which endows the dispersant with good hydrophilicity. Meanwhile, the nitrogen atom in the imidazole anchoring group contains a lone pair of electrons, which can be combined with empty orbital atoms in pigments such as phthalocyanine blue and pigment red 245. The dispersant can also form interaction forces such as van der Waals force and hydrogen bond with the pigment, so that the dispersant can be uniformly adsorbed on the surface of the pigment molecules to form an adsorption layer, showing a strong hydrophilic effect and a steric hindrance effect, thereby preventing the aggregation of the pigment molecules, reducing the particle size of the pigment molecules, improving the dispersibility, and having a strong interface force between the dispersant and the pigment, so that the dispersant is not easy to desorb, and the water-based color paste shows good centrifugal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1It is the reaction formula for preparing imidazole diol carboxyl hydrophilic chain extender. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0020] Example 1

[0021] Step (1), add 15 mL of acetonitrile, 6.4 mmol of 4-chloromethylbenzaldehyde, 8 mmol of imidazole, and 8 mmol of potassium carbonate into a flask, react at 65° C. for 8 h, distill under reduced pressure, wash with water, and recrystallize the product with ethanol to obtain intermediate A.

[0022] Step (2), add 90 mL of ethanol, 10 mmol of intermediate A, and 10 mmol of succinol into a flask, react at 65° C. for 4 h, add 12 mmol of sodium borohydride after cooling, react for 4 h, distill under reduced pressure, wash with water, and recrystallize the product with ethanol to obtain intermediate B.

[0023] Step (3), add 40mL ethanol, 10mmol intermediate B, 14mmol sodium chloroacetate, 16mmol sodium carbonate into a flask, react at 50°C for 10h, remove ethanol by distillation under reduced pressure, add hydrochloric acid solution to adjust the pH to 4, precipitate, filter, and recrystallize the product in 80% by volume ethanol aqueous solution to obtain an imidazole diol carboxyl hydrophilic chain extender.

[0024] Step (4), add 20 mmol of dried polyethylene glycol 2000 and 44 mmol of isophorone diisocyanate into a flask, heat to 70°C, stir and react for 3 hours, then add 22 mmol of imidazole diol carboxyl hydrophilic chain extender and dibutyltin dilaurate, react for 40 minutes, cool and obtain an aqueous dispersant.

[0025] Step (5), add 30 mL of water, 20 g of phthalocyanine blue, and 2 g of aqueous dispersant into a container, stir, place the color paste in a grinder, grind for 1 hour, and discharge the material to obtain an aqueous color paste.

[0026] Example 2

[0027] Step (1), add 20 mL of acetonitrile, 9.6 mmol of 4-chloromethylbenzaldehyde, 8 mmol of imidazole, and 9.6 mmol of potassium carbonate into a flask, react at 70° C. for 5 h, distill under reduced pressure, wash with water, and recrystallize the product with ethanol to obtain intermediate A.

[0028] Step (2), add 90 mL of ethanol, 10 mmol of intermediate A, and 14 mmol of succinol into a flask, react at 50° C. for 6 h, add 14 mmol of sodium borohydride after cooling, react for 3 h, distill under reduced pressure, wash with water, and recrystallize the product with ethanol to obtain intermediate B.

[0029] Step (3), add 40mL ethanol, 10mmol intermediate B, 12mmol sodium chloroacetate, and 12mmol sodium carbonate into a flask, react at 70°C for 7h, remove ethanol by distillation under reduced pressure, add hydrochloric acid solution to adjust the pH to 3, precipitate, filter, and recrystallize the product in 80% by volume ethanol aqueous solution to obtain an imidazole diol carboxyl hydrophilic chain extender.

[0030] Step (4), add 20 mmol of dried polyethylene glycol 2000 and 52 mmol of hexamethylene diisocyanate into a flask, heat to 80°C, stir and react for 2 hours, then add 26 mmol of imidazole diol carboxyl hydrophilic chain extender and dibutyltin dilaurate, react for 50 minutes, cool and obtain an aqueous dispersant.

[0031] Step (5), add 30 mL of water, 20 g of phthalocyanine blue, and 2 g of aqueous dispersant into a container, stir, place the color paste in a grinder, grind for 1 hour, and discharge the material to obtain an aqueous color paste.

[0032] Comparative Example 1

[0033] Add 30 mL of water and 20 g of phthalocyanine blue into a container, stir, and grind the color paste in a grinder for 1 hour, then discharge the material to obtain the color paste.

[0034] Comparative Example 2

[0035] Step (1), add 20 mmol of dried polyethylene glycol 2000 and 44 mmol of isophorone diisocyanate into a flask, heat to 70°C, stir and react for 3 hours, then add 22 mmol of 2,2-dihydroxymethylpropionic acid and dibutyltin dilaurate, react for 40 minutes, cool and obtain an aqueous dispersant.

[0036] Step (2), add 30 mL of water, 20 g of phthalocyanine blue, and 2 g of aqueous dispersant into a container, stir, place the color paste in a grinder, grind for 1 hour, and discharge the material to obtain an aqueous color paste.

[0037] Comparative Example 3

[0038] Step (1), add 20 mmol of dried polyethylene glycol 2000 and 44 mmol of isophorone diisocyanate into a flask, heat to 70°C, stir and react for 3 hours, then add 22 mmol of intermediate B and dibutyltin dilaurate, react for 40 minutes, cool and obtain a dispersant.

[0039] Step (2), add 30 mL of water, 20 g of phthalocyanine blue, and 2 g of dispersant into a container, stir, place the color paste in a grinder, and grind for 1 hour, discharge the material, and obtain the color paste.

[0040] The color paste was diluted 1000 times, and the average particle size of the pigment was measured using a nanoparticle size Zeta potential instrument.

[0041] Dilute the color paste 4000 times, take the supernatant and place it in a quartz colorimetric tube, and use a UV-visible spectrometer to measure the absorbance A0 at an absorption wavelength of 600nm. Centrifuge the supernatant in a centrifuge for 15min at a speed of 3000r / min; then place it in a quartz colorimetric tube, and use a UV-visible spectrometer to measure the absorbance A0 at an absorption wavelength of 600nm. t . Calculate the centrifugal stability Q; Q = A t / A0×100%. The test results are shown in Table 1.

[0042] Table 1 Average particle size and centrifugal stability of phthalocyanine blue slurry

[0043]

[0044]

[0045] Example 3

[0046] 30 mL of water, 20 g of Pigment Red 245, and 2 g of an aqueous dispersant (prepared according to the method of Example 1) were added to a container, and after stirring, the color paste was placed in a grinder and ground for 1 h, and the material was discharged to obtain an aqueous color paste.

[0047] Example 4

[0048] 30 mL of water, 20 g of Pigment Red 245, and 2 g of an aqueous dispersant (prepared according to the method of Example 2) were added to a container, and after stirring, the color paste was placed in a grinder and ground for 1 h, and the material was discharged to obtain an aqueous color paste.

[0049] Comparative Example 4

[0050] Add 30 mL of water and 20 g of Pigment Red 245 into a container, stir, place the color paste in a grinder and grind for 1 hour, discharge the material, and obtain the color paste.

[0051] Comparative Example 5

[0052] 30 mL of water, 20 g of Pigment Red 245, and 2 g of an aqueous dispersant (prepared according to the method of Comparative Example 2) were added to a container, and after stirring, the color paste was placed in a grinder and ground for 1 h, and the material was discharged to obtain an aqueous color paste.

[0053] Comparative Example 6

[0054] 30 mL of water, 20 g of Pigment Red 245, and 2 g of a dispersant (prepared according to the method of Comparative Example 3) were added to a container, and after stirring, the color paste was placed in a grinder and ground for 1 h, and the material was discharged to obtain a color paste.

[0055] The color paste was diluted 1000 times, and the average particle size of the pigment was measured using a nanoparticle size Zeta potential instrument.

[0056] Dilute the color paste 4000 times, take the supernatant and place it in a quartz colorimetric tube, and use a UV-visible spectrometer to measure the absorbance A0 at the maximum absorption wavelength. Centrifuge the supernatant in a centrifuge for 15 minutes at a speed of 3000r / min; then place it in a quartz colorimetric tube and use a UV-visible spectrometer to measure the absorbance A0 at the maximum absorption wavelength. t . Calculate the centrifugal stability Q; Q = A t / A0×100%. The test results are shown in Table 2.

[0057] Table 2 Average particle size and centrifugal stability of Pigment Red 245 color paste

[0058]

[0059]

[0060] After testing, the aqueous dispersants prepared in Example 1 and Example 2 showed good dispersibility for both phthalocyanine blue and pigment red 245, and the obtained aqueous color paste had the advantages of small particle size, high centrifugal stability and good dispersibility. This is because after the imidazole diol carboxyl hydrophilic chain extender and polyethylene glycol and diisocyanate were subjected to chain extension polymerization, the hydrophilic carboxyl group and the imidazole anchoring group were introduced into the side chain of the polyurethane-based dispersant, giving the dispersant good hydrophilicity, and at the same time, the nitrogen atom in the imidazole anchoring group contained a lone pair of electrons, which could be combined with the empty orbital atoms in pigments such as phthalocyanine blue and pigment red 245, and the dispersant could also form van der Waals forces, hydrogen bonds and other interaction forces with the pigment, so that the dispersant could be uniformly adsorbed on the surface of the pigment molecules to form an adsorption layer, showing a strong hydrophilic effect and a steric hindrance effect, thereby preventing the pigment molecules from aggregating, reducing the particle size of the pigment molecules, improving dispersibility, and the interfacial force between the dispersant and the pigment was strong, the dispersant was not easy to desorb, and the aqueous color paste showed good centrifugal stability.

[0061] The phthalocyanine blue and pigment red 245 color pastes of Comparative Examples 1 and 4 were not added with dispersants, the average particle size of the pigments was large, the emulsions aggregated, the dispersibility was poor, and the centrifugal stability was very poor.

[0062] Comparative Examples 2 and 5 use conventional 2,2-dimethylolpropionic acid as a chain extender, and the resulting polyurethane-based aqueous dispersants do not contain imidazole anchoring groups, and have low interaction forces with phthalocyanine blue and pigment red 245, resulting in easy aggregation of the pigments, a large average particle size, and poor dispersibility and centrifugal stability.

[0063] In Comparative Examples 3 and 6, intermediate B is used as a chain extender, and the obtained polyurethane-based dispersants contain imidazole anchor groups but no carboxyl hydrophilic groups, resulting in the dispersants being non-hydrophilic. After being compounded with pigments, highly dispersible water-based color pastes cannot be obtained.

[0064] Add 30 mL of water, 20 g of phthalocyanine blue or pigment red 245, and 3-5 g of aqueous dispersant into a container, stir, place the color paste in a grinder and grind for 1 hour, and discharge the material to obtain an aqueous color paste.

[0065] The average particle size and centrifugal stability of the water-based color paste were tested according to the above method. The test results are shown in Table 3.

[0066] Table 3 Average particle size and centrifugal stability of water-based color paste

[0067]

[0068] It can be seen from the above table that when the dispersant dosage is 3-5g, both phthalocyanine blue and pigment red 245 water-based color pastes show lower average particle size and good centrifugal stability.

[0069] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for preparing an aqueous dispersant, characterized in that: The preparation method comprises: adding dry polyethylene glycol and diisocyanate into a flask, heating to 70-80° C., stirring and reacting for 2-3 hours, then adding imidazole diol carboxyl hydrophilic chain extender and dibutyltin dilaurate, reacting for 40-50 minutes, cooling, and obtaining an aqueous dispersant; The imidazole diol carboxyl hydrophilic chain extender has the following structural formula (I):

2. The method for preparing an aqueous dispersant according to claim 1, characterized in that: The molar ratio of the polyethylene glycol, diisocyanate and imidazole diol carboxyl hydrophilic chain extender is 1:(2.2-2.6):(1.1-1.3).

3. The method for preparing an aqueous dispersant according to claim 1, characterized in that: The diisocyanate is isophorone diisocyanate or hexamethylene diisocyanate.

4. The method for preparing an aqueous dispersant according to claim 1, characterized in that: The preparation method of the imidazole diol carboxyl hydrophilic chain extender comprises: Step (1), add acetonitrile, 4-chloromethylbenzaldehyde, imidazole and potassium carbonate into a flask, react at 60-70° C. for 5-8 hours, distill under reduced pressure, wash and recrystallize to obtain intermediate A; Step (2), add ethanol, intermediate A, and serine to a flask, react at 50-65° C. for 4-6 hours, add sodium borohydride after cooling, react for 3-4 hours, distill under reduced pressure, wash, and recrystallize to obtain intermediate B; Step (3), adding ethanol, intermediate B, sodium chloroacetate and sodium carbonate into a flask, removing ethanol by distillation under reduced pressure after the reaction, adding hydrochloric acid solution to adjust the pH to 3-4, precipitating a precipitate, filtering, and recrystallizing the product to obtain an imidazole diol carboxyl hydrophilic chain extender.

5. The method for preparing an aqueous dispersant according to claim 4, characterized in that: In the step (1), the molar ratio of 4-chloromethylbenzaldehyde, imidazole and potassium carbonate is (0.8-1.2):1:(1-1.2).

6. The method for preparing an aqueous dispersant according to claim 4, characterized in that: In the step (2), the molar ratio of intermediate A to serine is 1:(1-1.4).

7. The method for preparing an aqueous dispersant according to claim 4, characterized in that: In the step (3), the molar ratio of intermediate B, sodium chloroacetate and sodium carbonate is 1:(1.2-1.4):(1.2-1.6).

8. The method for preparing an aqueous dispersant according to claim 4, characterized in that: In the step (3), the reaction is carried out at 50-70° C. for 7-10 h.

9. A method for preparing an aqueous color paste using an aqueous dispersant obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The method comprises: adding water, a pigment and an aqueous dispersant in a mass ratio of 100:(10-25) into a container, stirring, placing the color paste in a grinder, grinding for 1-2 hours, discharging the material, and obtaining an aqueous color paste.

10. The method for preparing water-based color paste using water-based dispersant according to claim 9, characterized in that: The pigments include phthalocyanine blue and pigment red.

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