Preparation method of pigment dispersing agent for water-based paint

Abstract

The invention relates to a preparation method of a high-performance pigment dispersing agent for water-based paint, which comprises the following steps: dissolving polyethylene glycol and fatty acid serving as raw materials in a solvent, partially esterifying under the synergistic effect of a catalyst and an auxiliary agent, and then removing the solvent, adjusting components and the like to prepare the dispersing agent applied to the water-based paint. The invention solves the problems of more three wastes and poor batch stability in the production of similar dispersants in the prior art, and has the advantages of stable production process, low production cost, no generation of three wastes in the production process, and environmental friendliness.

Description

Technical Field

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

[0002] Water-based paint is environmentally friendly. Paint dispersants are used to evenly disperse the particles that need to be dispersed in the paint in the system, which improves the stability, gloss, transparency and application effect of the paint. However, conventional paint dispersants are not ionized and have no charge in water, so the adsorption and dispersion of pigments are relatively weak. The ethylene glycol and polyol dispersants currently used in water-based paints can reduce surface tension and improve wettability to a certain extent, and after application, the performance of water-based paints has been improved compared with previous years. However, in the field of water-based paints for special applications such as aluminum powder paints, water-based environmentally friendly paints for metal paints such as aluminum powder still have a lot of room for improvement in terms of gloss and transparency.

[0003] Traditional polyethylene glycol ester pigment dispersants are obtained by esterification reaction of polyethylene glycol of a certain molecular weight with fatty acid or oleic acid. For example, CN115417985A adopts a boric acid catalytic method to first dehydrate polyethylene glycol, then react with boric acid to form boric ester, and then add a composite catalyst and oleic acid to obtain polyethylene glycol oleate through esterification, hydrolysis, filter pressing and decolorization. This method is cumbersome to operate and produces a lot of three wastes.

[0004] CN101747192A uses polyethylene glycol and oleic acid as raw materials, performs esterification reaction under the action of organic acid catalyst, neutralizes with triethanolamine to pH 5-7 after the reaction, and the filtered solution is the product polyethylene glycol oleate, the reaction temperature is 100-150°C, the reaction time is 2-6 hours, and the vacuum degree is ≥-0.098MPa. Although this method saves water washing and dehydration operations, it has high requirements on vacuum degree, harsh conditions, high operating temperature, and darker product color.

[0005] CN113150264A adopts the method of putting polyethylene glycol, fatty acid and activated carbon into a reactor and mixing them; then performing air replacement operation in the reactor, performing esterification reaction at a reaction temperature of 160 to 250°C to obtain a reaction product; after the reaction is completed, the reaction product is degassed, then dehydrated at a dehydration pressure of -0.09 to -0.1 MPa and a dehydration temperature of 100 to 140°C, and then subjected to filter pressing to obtain polyethylene glycol fatty acid ester. This method involves high temperature and high vacuum operation, and filter pressing and other operations are required after the reaction is completed, which cannot avoid the generation of solid waste.

[0006] In summary, the existing production methods of polyethylene glycol ester compounds have problems such as cumbersome operation, unavoidable solid waste generation, and dark color, which directly affect the production cost of polyethylene glycol and its downstream performance applications. It is urgent to develop a green and efficient production method to improve production efficiency, green production, and effectively solve the above-mentioned deficiencies in production. The demand for high-end water-based coatings can be met through performance adjustment, especially in the application of metal paints such as aluminum powder, so as to achieve better dispersion and improve the gloss and transparency after application. Summary of the invention

[0007] The present invention aims to solve the above-mentioned deficiencies in the prior art and aims to provide a method for preparing a water-based coating pigment dispersant with stable performance, which is prepared by using polyethylene glycol and saturated fatty acids as raw materials through esterification, desolventization, adjustment and other operations.

[0008] The invention has stable production process, low production cost, no three wastes are generated in the production process, is environmentally friendly, and solves the problems of poor batch stability and large amount of three wastes of similar dispersants in the existing production technology.

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

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

[0011] 1) using polyethylene glycol and fatty acid as raw materials, an esterification reaction occurs in a solvent under the action of a catalyst and an auxiliary agent to obtain a reaction solution containing fatty acid ester fragments;

[0012] 2) removing the solvent from the reaction solution in step 1) by a desolventizing device;

[0013] 3) Adding the adjusted material to the material after the solvent is removed in step 2), stirring and mixing to obtain a high-performance pigment dispersant for water-based coatings.

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

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

[0016] Furthermore, in step 1), the auxiliary agent is a zwitterionic surfactant, preferably a zwitterionic surfactant having at least one of a betaine group, an imidazoline group, an amino acid group (such as glycine, glutamic acid, alanine, etc.), and a fatty acid group (such as C10-C14 fatty acid), and more preferably a zwitterionic surfactant having both an imidazoline group and a fatty acid group.

[0017] Furthermore, in step 1), the catalyst is selected from an organic acid catalyst, preferably an organic acid having a sulfonic acid group, further preferably methylsulfonic acid, ethylsulfonic acid, dodecylsulfonic acid, hexadecylsulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and most preferably at least one of dodecylsulfonic acid, hexadecylsulfonic acid, and p-toluenesulfonic acid.

[0018] Furthermore, 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] Furthermore, in step 1), the molar ratio of the material ingredients is: polyethylene glycol: fatty acid: auxiliary agent: 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] Furthermore, in step 1), the reaction conditions are a temperature of 50-140° C., preferably 60-100° C.; and an absolute pressure of 50-101 KPa, preferably 80-101 KPa.

[0021] Furthermore, in step 2), the desolventizing equipment is a packed tower, a distillation kettle, a thin film evaporator, etc., preferably a thin film evaporator; the desolventizing temperature is 40-120° C., preferably 40-70° C.; the desolventizing pressure is an absolute pressure of 5-80 KPa, preferably 10-20 KPa; the residual solvent after desolventizing is <0.1wt%, preferably <0.01wt%. The recovered solvent has a purity of >99% and can be applied to the next batch.

[0022] Furthermore, in step 3), the adjustment material is an acidic material, preferably an organic acidic material, and further 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 adjustment material added is 0.1-8wt% of the mass of the material before addition, preferably 3-6wt%.

[0023] Furthermore, in step 3), after the adjustment material is added, stirring is performed at 20-70° C. for 0.1-3 h, preferably at 20-40° C. for 0.1-0.5 h.

[0024] The present invention preferably adopts an organic sulfonic acid catalyst, the catalyst addition amount is small, and there is no need to neutralize or remove the catalyst after the catalysis is completed. In addition, during the reaction process, the nitrogen atom in the preferred auxiliary agent can form an interaction force with the hydroxyl group in the polyethylene glycol, play a role in fixing the terminal hydroxyl group of the polyethylene glycol part, and then partially esterify under the action of the catalyst, and after the esterification is completed, it can be separated from the auxiliary agent due to steric hindrance, ensuring the uniform distribution of hydrophilic hydroxyl groups in the polyethylene glycol ester molecules, which helps to uniformly distribute and arrange the pigment when used in the water-based paint formula, and improve the glossiness of the pigment; in addition, after the reaction is completed, the auxiliary agent does not need to be separated, and the auxiliary agent remains in the polyethylene glycol ester. The auxiliary agent and the fatty acid added for adjusting the pH of the buffered water-based paint can further induce the dispersion and arrangement of metal particles such as aluminum powder on the water-based resin, which plays a role in enhancing the transparency of the pigment dispersion of the water-based paint.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) The zwitterionic surfactant forms an intermolecular force with one of the terminal hydroxyl groups in the polyethylene glycol molecule, and the organic acid catalyzes the esterification of the fatty acid with the other hydroxyl group of the polyethylene glycol. After esterification, the molecular weight of the polyethylene glycol end connected to the zwitterionic surfactant increases significantly, resulting in a greater steric effect, and the intermolecular force formed becomes weaker, and the acid catalyzed group leaves, thereby controlling the esterification and ensuring the stability of the esterification product;

[0027] 2) Add fatty acids in an adjustment manner. When used, fatty acids interact with additives to adjust the buffer pH, improve the lack of charge and ionization when existing water-based coating additives are used, and are beneficial to the distribution and arrangement of metal pigments such as aluminum powder, thereby improving the gloss and transparency of the formula after application.

[0028] 3) The present invention is easy to operate, and the addition of adjustment means ensures the stability of product application performance. DETAILED DESCRIPTION

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

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

[0031] The application evaluation formula is as follows:

[0032] Test recipe Mass Wantipro0678 100 water 66.7 Tego270 0.75 Tego825 0.75 Ethylene glycol butyl ether 20 Dispersants 2.3 Amino resin 327 10 Water-based aluminum silver powder W153 20 10% N,N-dimethylethanolamine 11.9

[0033] Example 1

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

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

[0036] Example 2

[0037] In a 5L three-necked flask, 1200g of polyethylene glycol 800, 514.8g of ricinoleic acid, 1g of myristic amphoteric imidazoline (molecular weight is 511.5), 5.63g of dodecyl sulfonic acid, and 430.4g of benzene were added, and the mixture was reacted at 85°C and 80KPa for 6h. When 31.0g of water was produced, the reaction was stopped, and benzene was removed by a thin film evaporator at 71°C and 10KPa. After the benzene content in the gas phase was detected to be <0.01%, 101.4g of ricinoleic acid was added to the crude product. After the addition, the material was stirred and mixed at 30°C for 15min to obtain dispersant 2.

[0038] Example 3

[0039] In a 5L three-necked flask, 1200g of polyethylene glycol 400, 807.7g of palmitic acid, 72.5g of decanoic acid amphoteric imidazoline (molecular weight is 455.5), 41.24g of hexadecyl sulfonic acid, and 530.4g of benzene were added, and the mixture was reacted at 96°C and 85KPa for 5h. When 56.7g of water was produced, the reaction was stopped, and benzene was removed by a thin film evaporator at 62°C and 10KPa. After the benzene content in the gas phase was detected to be <0.01%, 103.2g of decanoic acid was added to the crude product. After the addition, the material was stirred and mixed at 30°C for 20min to obtain dispersant 3.

[0040] Comparative Example 1

[0041] After the solvent was removed from the reaction solution in Example 3, no regulator was added to obtain Dispersant 4.

[0042] Application Example 1

[0043] According to the aforementioned application evaluation formula, the dispersants in the examples and commercially available general models were used to prepare water-based coatings, and the performance tests shown in the following table were carried out, as shown in the table.

[0044] Test method:

[0045] Glossiness: The film thickness of the black glass plate is 250 microns, and it is baked at 45℃ for 2h. The light meter is calibrated first, and then the product is tested. The instrument used is the Color Spectrum CS-380 three-angle gloss meter.

[0046] Transparency: Visual inspection.

[0047]

Claims

1. A method for preparing a pigment dispersant for a water-based coating, characterized in that the steps include: 1) Polyethylene glycol and fatty acid undergo esterification reaction in a solvent under the action of a catalyst and an auxiliary agent to obtain a reaction solution containing fatty acid ester fragments; 2) removing the solvent from the reaction solution in step 1); 3) Adding adjustment materials to the material after the solvent is removed in step 2) to obtain a pigment dispersant for water-based coatings.

2. The method according to claim 1, characterized in that: In step 1), the molar ratio of the materials is: polyethylene glycol: fatty acid: auxiliary agent: 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, preferably 400-1000 g / mol.

4. The method according to any one of claims 1 to 3, characterized in that: In step 1), the fatty acid is a C6-C20 straight-chain fatty acid, preferably a C12-C18 straight-chain fatty acid.

5. The method according to any one of claims 1 to 4, characterized in that: In step 1), the auxiliary agent is a zwitterionic surfactant, preferably a zwitterionic surfactant having at least one of a betaine group, an imidazoline group, an amino acid group, and a fatty acid group, and more preferably a zwitterionic surfactant having both an imidazoline group and a fatty acid group.

6. The method according to any one of claims 1 to 5, characterized in that: In step 1), the catalyst is selected from an organic acid catalyst, preferably an organic acid having a sulfonic acid group, further preferably at least one of methylsulfonic acid, ethylsulfonic acid, dodecylsulfonic acid, hexadecylsulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid, and most preferably at least one of dodecylsulfonic acid, hexadecylsulfonic acid, and p-toluenesulfonic acid.

7. The method according to any one of claims 1 to 6, characterized in that: In step 1), the solvent is at least one of alkanes and aromatic hydrocarbons, 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; preferably, the amount of solvent added is 10-40% of the total mass of the reaction solution, preferably 15-30%.

8. The method according to any one of claims 1 to 7, characterized in that: In step 1), the reaction conditions are: temperature 50-140°C, preferably 60-100°C, and pressure absolute pressure 50-101 KPa, preferably 80-101 KPa.

9. The method according to any one of claims 1 to 8, characterized in that: In step 2), the residual solvent after desolvation is <0.1 wt%, preferably <0.01 wt%.

10. The method according to any one of claims 1 to 9, characterized in that: In step 3), the adjustment material is an acidic material, preferably an organic acidic material, and more preferably a C6-C18 fatty acid; preferably, the amount of the adjustment material added is 0.1-8wt% of the mass of the material before addition, preferably 3-6wt%; Preferably, after the addition of the materials is completed, stirring is performed at 20-70° C. for 0.1-3 h.

Images