A method for preparing a pigment dispersant for water-based paints

Abstract

The application relates to a preparation method of a high-performance pigment dispersant of a water-based paint, which is prepared by using polyethylene glycol and a fatty acid as raw materials, dissolving in a solvent, and then performing partial esterification under the synergistic action of a catalyst and an additive, and then removing the solvent, adjusting components and the like to obtain the dispersant applied to the water-based paint. The application solves the problems of much three wastes, poor batch stability and the like in the similar dispersant production in the prior art, and has the advantages of stable production process, low production cost, no three wastes generated in the production process and green friendliness.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology and relates to a method for preparing a high-performance pigment dispersant for water-based coatings. Background Technology

[0002] Water-based coatings are environmentally friendly. Dispersants are used to uniformly disperse the particles in the coating system, improving its stability, gloss, transparency, and overall performance. However, conventional dispersants are non-ionizing and uncharged in water, resulting in weak adsorption and dispersion of pigments. Currently, ethylene glycol and polyol dispersants are mainly used in water-based coatings. While they can reduce surface tension and improve wetting to some extent, leading to improved performance compared to previous years, there is still significant room for improvement in gloss and transparency in water-based environmentally friendly coatings for special applications such as aluminum powder paints.

[0003] Traditional polyethylene glycol ester pigment dispersants are obtained by esterification of polyethylene glycol of a certain molecular weight with fatty acids or oleic acid. For example, CN115417985A uses a boric acid catalytic method to first dehydrate polyethylene glycol, then react it with boric acid to generate borate ester, and then add a composite catalyst and oleic acid. After esterification, hydrolysis, pressure filtration and decolorization, polyethylene glycol oleate ester is obtained. This method is cumbersome and produces a lot of waste.

[0004] CN101747192A uses polyethylene glycol and oleic acid as raw materials, and carries out an esterification reaction under the action of an organic acid catalyst. After the reaction is complete, the solution is neutralized with triethanolamine to a pH of 5-7. The filtered solution is the product, polyethylene glycol oleate. The reaction temperature is 100-150℃, the reaction time is 2-6 hours, and the vacuum degree is ≥-0.098MPa. Although this method eliminates the need for water washing and dehydration, it requires a high vacuum degree, harsh conditions, high operating temperature, and results in a darker product color.

[0005] CN113150264A describes a method that involves adding polyethylene glycol, fatty acids, and activated carbon into a reactor and mixing them. Then, air is purged from the reactor, and an esterification reaction is carried out at a reaction temperature of 160–250°C to obtain the reaction product. After the reaction, the product is degassed, followed by dehydration at a dehydration pressure of -0.09–0.1 MPa and a dehydration temperature of 100–140°C, and finally pressure filtration to obtain polyethylene glycol fatty acid esters. This method involves high-temperature and high-vacuum operation, and requires pressure filtration after the reaction, which cannot avoid the generation of solid waste.

[0006] In summary, existing methods for producing polyethylene glycol (PEG) compounds suffer from problems such as cumbersome operation, unavoidable solid waste generation, and dark color, all of which directly affect the production cost of PEG and its downstream performance applications. There is an urgent need to develop a green and efficient production method to improve production efficiency, achieve green production, effectively solve the aforementioned shortcomings in production, and meet the needs of high-end water-based coatings through performance adjustments, especially in the application of metallic paints such as aluminum powder, to achieve better dispersion and improve the gloss and transparency after application. Summary of the Invention

[0007] The present invention addresses the above-mentioned shortcomings of the prior art by providing a method for preparing a stable water-based coating pigment dispersant, which is prepared by using polyethylene glycol and saturated fatty acids as raw materials through esterification, solvent removal, and adjustment operations.

[0008] The present invention has a stable production process, low production cost, and no waste generated during the production process, making it green and environmentally friendly. It solves the problems of poor batch stability and excessive waste in existing production technologies.

[0009] The technical solution of this invention is as follows:

[0010] A method for preparing a pigment dispersant for water-based coatings, comprising the following steps:

[0011] 1) Using polyethylene glycol and fatty acids as raw materials, an esterification reaction is carried out in a solvent under the action of catalysts and auxiliaries to obtain a reaction solution containing fatty acid ester fragments;

[0012] 2) Remove the solvent from the reaction solution in step 1) using a solvent removal device;

[0013] 3) Take the solvent-removed material from step 2) and add the adjusting material, stir and mix to obtain a high-performance pigment dispersant for use in water-based coatings.

[0014] Further, in step 1), the molecular weight of the polyethylene glycol is 200-1600 g / mol, preferably 400-1000 g / mol.

[0015] Further, in step 1), the fatty acid is a C6-C20 straight-chain fatty acid, preferably a C12-C18 straight-chain fatty acid.

[0016] Further, in step 1), the auxiliary agent is an amphoteric surfactant, preferably an amphoteric surfactant having at least one of betaine group, imidazoline group, amino acid group (e.g., glycine, glutamic acid, alanine, etc.), or fatty acid group (e.g., C10-C14 fatty acids), more preferably an amphoteric surfactant having both imidazoline group and fatty acid group.

[0017] Further, in step 1), the catalyst is selected from organic acid catalysts, preferably organic acids having sulfonic acid groups, more preferably methanesulfonic acid, ethylsulfonic acid, dodecyl sulfonic acid, hexadecyl sulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and most preferably at least one of dodecyl sulfonic acid, hexadecyl sulfonic acid, and p-toluenesulfonic acid.

[0018] Further, in step 1), the solvent is an alkane or an aromatic hydrocarbon, preferably at least one of n-hexane, cyclohexane, n-octane, n-heptane, benzene, toluene, and xylene, and most preferably at least one of n-octane, n-heptane, and benzene.

[0019] Further, in step 1), the molar ratio of the materials is: polyethylene glycol: fatty acid: additive: catalyst is 1:0.9-1.2:0.001-0.055:0.01-0.05, and the amount of solvent added is 10-40% of the total mass of the reaction solution, preferably 15-30%.

[0020] Further, in step 1), the reaction conditions are a temperature of 50-140℃, preferably 60-100℃; and an absolute pressure of 50-101KPa, preferably 80-101KPa.

[0021] Further, in step 2), the solvent removal equipment is a packed tower, a distillation vessel, or a thin-film evaporator, preferably a thin-film evaporator; the solvent removal temperature is 40-120℃, preferably 40-70℃; the solvent removal pressure is absolute 5-80KPa, preferably 10-20KPa; the residual solvent after solvent removal is <0.1wt%, preferably <0.01wt%. The recovered solvent has a purity >99% and can be reused in the next batch.

[0022] Further, in step 3), the adjusting material is an acidic material, preferably an organic acidic material, and more preferably a C6-C18 (e.g., 6 carbons, 7 carbons, 8 carbons, 10 carbons, 12 carbons, 16 carbons, etc.) fatty acid; the amount of the adjusting material added is 0.1-8 wt% of the mass of the material before addition, preferably 3-6 wt%.

[0023] Further, in step 3), after the adjustment material is added, it is stirred at 20-70℃ for 0.1-3 hours, preferably at 20-40℃ for 0.1-0.5 hours.

[0024] This invention preferably uses an organic sulfonic acid catalyst, requiring a small amount of catalyst and eliminating the need for neutralization or catalyst removal after catalysis. Furthermore, during the reaction, the nitrogen atoms in the preferred additives can interact with the hydroxyl groups in polyethylene glycol (PEG), effectively fixing some of the terminal hydroxyl groups. Partial esterification then occurs under the catalysis, and after esterification, the additives can be removed due to steric hindrance, ensuring a uniform distribution of hydrophilic hydroxyl groups in the PEG ester molecules. This contributes to the uniform distribution and arrangement of pigments in water-based coating formulations, improving pigment gloss. Additionally, the additives do not need to be separated after the reaction; they remain in the PEG ester. The additives, along with the added fatty acids, act as a buffer to adjust the pH of the water-based coating, further inducing the dispersion and arrangement of metal particles such as aluminum powder on the water-based resin, thus enhancing the pigment dispersion and transparency of the water-based paint.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1) The zwitterionic surfactant forms an intermolecular force with one of the terminal hydroxyl groups of polyethylene glycol (PEG) molecules. The organic acid catalyzes the esterification of fatty acid with the other hydroxyl group of PEG. After esterification, the molecular weight of the PEG terminal linked to the zwitterionic surfactant increases significantly, resulting in a greater steric hindrance effect. The intermolecular forces formed become weaker and leave under acid catalysis, thereby controlling esterification and ensuring the stability of the esterification product.

[0027] 2) By adding fatty acids through adjustment, fatty acids interact with additives during application, playing a role in regulating and buffering pH. This improves the lack of charge and ionization in existing water-based coating additives, which is beneficial to the distribution and arrangement of metallic pigments such as aluminum powder, and enhances the gloss and transparency of the formulation after application.

[0028] 3) This invention is simple to operate, and the addition of adjustment methods ensures the stability of product application performance. Detailed Implementation

[0029] The present invention will be further described in detail with reference to specific embodiments, but the scope of the present invention is not limited to these embodiments.

[0030] Liquid chromatography conditions: Agilent liquid chromatograph, stationary phase octadecyl bonded silica, column length 25 cm, mobile phase acetonitrile, flow rate 1 ml / min, column temperature 40 ℃, detector temperature 35 ℃, injection volume 1 μL, detection wavelength 220 nm.

[0031] The application evaluation formula is as follows:

[0032] Test formula mass g Wantipro0678 100 water 66.7 Tego270 0.75 Tego825 0.75 Ethylene glycol butyl ether 20 dispersant 2.3 Amino resin 327 10 Water-based aluminum silver powder W153 20 10% N,N-Dimethylethanolamine 11.9

[0033] Example 1

[0034] Add 1200g of polyethylene glycol 600 and 447.5g of myristic acid to a 5L three-necked flask.

[0035] 27.69 g of lauryl amphoteric imidazoline (molecular weight 483.5), 10.32 g of p-toluenesulfonic acid, and 690.2 g of n-octane were reacted at 65 °C and 85 kPa for 4 h. When 35.2 g of water was produced, the reaction was stopped. The n-octane was removed using a thin-film evaporator at 70 °C and 20 kPa. After the n-octane content was detected as <0.01% by gas phase, 66.0 g of lauric acid was added to the crude product. After the addition was complete, the material was stirred and mixed at 35 °C for 10 min to obtain dispersant 1.

[0036] Example 2

[0037] 1200g of polyethylene glycol 800, 514.8g of ricinoleic acid, 1g of myristyl amphoteric imidazoline (molecular weight 511.5), 5.63g of dodecyl sulfonic acid, and 430.4g of benzene were added to a 5L three-necked flask. The mixture was reacted at 85℃ and 80KPa for 6 hours. When 31.0g of water was produced, the reaction was stopped. Benzene was removed using a thin-film evaporator at 71℃ and 10KPa. After the benzene content was detected by gas phase analysis as <0.01%, 101.4g of ricinoleic acid was added to the crude product. After the addition was complete, the mixture was stirred at 30℃ for 15 minutes to obtain dispersant 2.

[0038] Example 3

[0039] 1200g of polyethylene glycol 400, 807.7g of palmitic acid, 72.5g of decanoic acid-based amphoteric imidazoline (molecular weight 455.5), 41.24g of hexadecyl sulfonic acid, and 530.4g of benzene were added to a 5L three-necked flask. The mixture was reacted at 96℃ and 85KPa for 5 hours. When 56.7g of water was produced, the reaction was stopped. Benzene was removed using a thin-film evaporator at 62℃ and 10KPa. After the benzene content was detected by gas phase analysis as <0.01%, 103.2g of decanoic acid was added to the crude product. After the addition was complete, the mixture was stirred at 30℃ for 20 minutes to obtain dispersant 3.

[0040] Comparative Example 1

[0041] In Example 3, after the solvent was removed, no modifier was added to the reaction solution to obtain dispersant 4.

[0042] Application Example 1

[0043] According to the aforementioned application evaluation formulation, the dispersant in the usage examples and commercially available general-purpose models were respectively formulated into water-based coatings, and the performance tests were carried out as shown in the table below.

[0044] Test method:

[0045] Gloss: The black glass plate was coated with a film of 250 micrometers and baked at 45℃ for 2 hours. The photometer was calibrated first, and then the product was tested. The instrument used was a ColorSpectrum CS-380 three-angle gloss meter.

[0046] Transparency: determined visually.

[0047]

Claims

1. A method for preparing a pigment dispersant for water-based coatings, characterized in that the steps include... include: 1) Polyethylene glycol and fatty acids undergo esterification in a solvent under the action of a catalyst and an auxiliary agent to obtain a reaction solution containing fatty acid ester fragments; wherein, the catalyst is selected from organic acids with sulfonic acid groups, and the auxiliary agent is an amphoteric surfactant having at least one of betaine group, imidazoline group, amino acid group, and fatty acid group. 2) Remove the solvent from the reaction solution in step 1); 3) Add adjusting material to the material after solvent removal in step 2) to obtain a pigment dispersant for use in water-based coatings; wherein the adjusting material is a C6-C18 fatty acid.

2. The method according to claim 1, characterized in that: In step 1), the molar ratio of the materials is: polyethylene glycol: fatty acid: additives: catalyst is 1:0.9-1.2:0.001-0.055:0.01-0.

05.

3. The method according to claim 1 or 2, characterized in that: In step 1), the molecular weight of the polyethylene glycol is 200-1600 g / mol.

4. The method according to claim 3, characterized in that: In step 1), the molecular weight of the polyethylene glycol is 400-1000 g / mol.

5. The method according to any one of claims 1-2, characterized in that: In step 1), the fatty acid is a C6-C20 straight-chain fatty acid.

6. The method according to claim 5, characterized in that: In step 1), the fatty acid is a C12-C18 straight-chain fatty acid.

7. The method according to any one of claims 1-2, characterized in that: In step 1), the auxiliary agent is an amphoteric surfactant that simultaneously has imidazoline and fatty acid groups.

8. The method according to any one of claims 1-2, characterized in that: In step 1), the catalyst is selected from at least one of methanesulfonic acid, ethylsulfonic acid, dodecylsulfonic acid, hexadecylsulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid.

9. The method according to any one of claims 1-2, characterized in that: In step 1), the solvent is at least one of alkanes and aromatics; the amount of solvent added is 10-40% of the total mass of the reaction solution.

10. The method according to claim 9, characterized in that: In step 1), the solvent is selected from at least one of n-hexane, cyclohexane, n-octane, n-heptane, benzene, toluene, and xylene; the amount of solvent added is 15-30% of the total mass of the reaction solution.

11. The method according to any one of claims 1-2, characterized in that: In step 1), the reaction conditions are: temperature 50-140℃, pressure absolute 50-101KPa.

12. The method according to any one of claims 1-2, characterized in that: In step 1), the reaction conditions are: temperature 60-100℃, pressure absolute 80-101KPa.

13. The method according to any one of claims 1-2, characterized in that: In step 2), the residual solvent after desolventizing is <0.1wt%.

14. The method according to any one of claims 1-2, characterized in that: In step 2), the residual solvent after desolventizing is <0.01wt%.

15. The method according to any one of claims 1-2, characterized in that: In step 3), the amount of material to be added is 0.1-8 wt% of the mass of the material before addition; After the materials are added, stir at 20-70℃ for 0.1-3 hours.

16. The method according to claim 15, characterized in that: In step 3), the amount of material to be added is 3-6 wt% of the original material mass.

Images