A dispersant, its preparation method and use

Abstract

This invention belongs to the field of dispersant technology, specifically relating to a dispersant, its preparation method, and its application. The preparation method of the dispersant provided by this invention includes the following steps: (1) under nitrogen protection, trimethylolpropane, bisphenol A, oleic acid, and butyl acetate are added to a reaction vessel, the temperature is raised, a catalyst is added, and the reaction is carried out until the acid value is ≤5mgKOH / g; (2) the temperature is lowered to 140-150℃, trimellitic anhydride is added, and after the addition is completed, the reaction is carried out until the acid value is 85-95mgKOH / g; (3) the temperature is lowered, triisopropanolamine is added, and the reaction is carried out; (4) benzoic acid is added, the temperature is raised, and the reaction is carried out until the acid value is 78-82mgKOH / g; (5) the temperature is lowered, butyl acetate is added, and the solid content is adjusted to obtain the dispersant. The dispersant of this invention can reduce the viscosity of the grinding slurry while ensuring the pigment fineness is ≤10μm, and can be well compatible with the polyurethane resin system, effectively improving the pigment dispersion stability and hiding power.

Description

Technical Field

[0001] This invention belongs to the field of dispersant technology, specifically relating to a dispersant, its preparation method, and its application. Background Technology

[0002] With the rapid development of the high-end coatings market, including automotive refinish paints, industrial protective paints, and wood coatings, the market's requirements for the appearance quality and performance of coating products are increasing. In coating formulations, the dispersion effect of pigments is one of the key factors determining the final film performance. To achieve efficient pigment dispersion, dispersants, as key additives, are widely used in the grinding and stabilization processes of pigment pastes.

[0003] In two-component polyurethane coating systems, pigments such as carbon black are widely used due to their strong tinting strength and good hiding power. However, due to their large specific surface area and high surface energy, they are prone to agglomeration, posing a significant challenge to grinding and dispersion. A grinding fineness of 10 μm is a requirement for many industrial coatings to ensure the smoothness and optical properties of the coating. However, in practical applications, existing dispersants, while achieving the required fineness, often struggle to effectively reduce the viscosity of the grinding slurry. High viscosity not only leads to low grinding efficiency and increased energy consumption but also severely affects the fluidity and storage stability of the pigment paste, easily causing problems such as sedimentation and coarsening, which in turn affects subsequent paint mixing operations and the final coating's application performance.

[0004] Furthermore, even if the pigment fineness meets the requirements, some dispersants may have poor compatibility with the resin in the coating system, resulting in insufficient coating of the pigment surface or an unstable dispersion system, thus preventing the pigment from fully exerting its true hiding power. This not only reduces the utilization rate of the pigment but may also lead to defects such as floating color and mottling in the paint film, making it difficult to meet the stringent requirements of high-quality coatings for high hiding power and high decorative properties.

[0005] Carbon black is widely used in coatings, inks, plastics, and composite materials as an important black pigment and functional additive due to its excellent tinting strength, UV shielding properties, electrical conductivity, and cost-effectiveness. High-Structure Carbon Black, in particular, is characterized by its extremely small primary particle size (typically in the 10-30 nm range) and extremely high specific surface area (up to 200-400 nm). 2 (above / g) can impart a deeper blackness and stronger coloring strength to materials, making it particularly crucial in high-end coatings and specialty inks.

[0006] High-pigment carbon black faces a common and serious technical challenge in practical applications: a strong tendency to agglomerate. Due to its extremely small particle size and huge specific surface area, carbon black particles have extremely high surface energy, leading to a significant enhancement of van der Waals forces between particles. During drying, storage, and dispersion, these particles easily aggregate through physical forces (such as van der Waals forces and electrostatic interactions) to form stable "pigment aggregates" or "agglomerates." These agglomerates macroscopically appear as hard particles much larger than the original particles. This agglomeration phenomenon brings many negative impacts. Agglomerates occupy a larger hydrodynamic volume in the dispersion system, significantly increasing the volume fraction of the system. At the same time, the increased collision frequency and interaction forces between agglomerates and between agglomerates and the medium lead to a significant increase in the internal flow resistance of the dispersion system, manifested as a significant increase in viscosity (especially low shear viscosity). This not only increases the energy consumption of the grinding and dispersion processes but also severely limits the realization of high pigment content formulations, making it difficult to increase the solid content of coatings, affecting production efficiency and the final coating performance. To break these tough agglomerates, stronger mechanical shear forces and a large amount of dispersant are required. This not only prolongs dispersion time, increases equipment wear and energy consumption, but excessive mechanical action can also lead to increased system temperature and other instability issues. Final product performance defects, such as decreased optical performance, result in insufficient blackness, reduced gloss, color deviation, and may cause a "hazy" effect. Poor storage stability: High-viscosity and unstable dispersion systems are more prone to flocculation, sedimentation, or coarsening during storage, leading to a shortened product shelf life.

[0007] Therefore, developing a novel dispersant that can significantly reduce the viscosity of the grinding slurry while ensuring pigment fineness (≤10μm), and that is well compatible with polyurethane resin systems and effectively improves pigment dispersion stability and hiding power has become a technical problem that urgently needs to be solved in the field of high-end coatings. Summary of the Invention

[0008] The purpose of this invention is to provide a dispersant, its preparation method, and its application.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a dispersant includes the following steps: (1) Under nitrogen protection, trimethylolpropane, bisphenol A, oleic acid and butyl acetate are added to the reactor, the temperature is raised to 175-185℃, a catalyst is added, and the reaction is continued until the acid value is ≤5mgKOH / g; (2) Cool the product from step (1) to 140-150℃, add trimellitic anhydride, and after the addition is complete, react until the acid value reaches 85-95 mgKOH / g. (3) Cool the product from step (2) to 105-110℃, add triisopropanolamine, and stir the reaction at 105-110℃ for 1.5-2 hours; (4) Add benzoic acid to the product of step (3), heat to 185-190℃, and react until the acid value is 78-82 mgKOH / g; (5) Cool the product from step (4), add butyl acetate, adjust to the solid content, and obtain a dispersant.

[0010] Preferably, the molar ratio of trimethylolpropane, bisphenol A, and oleic acid is (0.65–0.75):(0.08–0.12):(0.95–1.05).

[0011] Preferably, the amount of butyl acetate used is 1.5 to 2 times the total mass of bisphenol A, trimethylolpropane and oleic acid.

[0012] Preferably, the catalyst is monobutyltin oxide.

[0013] Preferably, the amount of catalyst used is 0.3-0.5% of the total mass of bisphenol A, trimethylolpropane and oleic acid.

[0014] Preferably, the molar ratio of trimellitic anhydride to triisopropanolamine is 1:(0.35-0.45).

[0015] Preferably, trimellitic anhydride is added in step (2) to ensure that the system temperature is always below 155°C.

[0016] Preferably, the product from step (4) is cooled to ≤80°C.

[0017] Preferably, the reaction conditions in step (2) are: keep warm at 140-150℃ for 0.5-1h, then raise the temperature to 185-190℃ and continue the reaction until the acid value is 85-95mgKOH / g.

[0018] Preferably, butyl acetate is added to adjust the solid content to 38-42 wt%.

[0019] A second aspect of the present invention provides a dispersant prepared by the aforementioned preparation method.

[0020] A third aspect of the invention provides the application of the dispersant for dispersing pigments in a two-component polyurethane coating system.

[0021] Preferably, the pigment includes titanium dioxide and carbon black.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention provides a dispersant that can reduce the viscosity of the grinding slurry while ensuring the pigment fineness is ≤10μm, and can be well compatible with polyurethane resin systems, effectively improving the pigment dispersion stability and hiding power. The dispersant of this invention introduces bisphenol A and benzoic acid, introducing a conjugated double bond system into the molecular chain. These groups absorb ultraviolet-visible wavelengths, causing the solution to appear yellow to brown.

[0023] 2. The dispersant of this invention incorporates bisphenol A. The benzene ring structure in bisphenol A has a high steric hindrance effect, forming a rigid fulcrum on the dispersant molecular chain. When the dispersant is adsorbed onto the surface of pigments (such as carbon black), the three-dimensional structure of the benzene ring can prevent pigment particles from approaching each other, avoiding flocculation and thus improving dispersion stability. Trimeric trihydric anhydride reacts with the hydroxyl groups of the prepolymer to introduce carboxyl groups, providing strong hydrophilicity. Triisopropanolamine neutralizes with the carboxyl groups to form an amine salt structure, enhancing the electrostatic adsorption with the pigment surface, improving the compatibility of the dispersant in non-polar solvents, and preventing phase separation from polyurethane resin. The amine salt groups cause pigment particles to carry the same charge through electrostatic repulsion, causing them to repel each other and reducing the viscosity of the system. The unsaturated alkyl chains of oleic acid form flexible spacer segments in the prepolymer, enhancing the flexibility of the dispersant molecular chain. The flexible chains can adaptively adjust the adsorption conformation according to the deformation of the pigment surface, maintaining the continuity of steric hindrance, reducing grinding resistance, and improving the fluidity of the black paste. 3. This invention forms a comb-like copolymer structure by combining rigid benzene ring groups with flexible long-chain alkyl groups. The rigid portion provides a physical barrier, while the flexible portion buffers shear forces. Together, they resist the tendency of pigments to aggregate during high-speed dispersion and storage, achieving low-viscosity, high-stability black paste. The polar amine salt groups achieve short-range stability through electrostatic repulsion, while the rigid benzene ring groups achieve long-range stability through steric hindrance. This dual effect is significantly superior to a single stabilization mechanism, especially suitable for high-pigment carbon black, maintaining its deflocculated state in a two-component polyurethane system and improving hiding power. The dispersant tightly encapsulates the pigment through multi-anchor adsorption (benzene ring, carboxyl group, alkyl chain), reducing interfacial defects and thus eliminating haze in the paint film. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the appearance of the dispersant prepared in Example 1.

[0025] Figure 2 The figure shows the performance test report of the dispersant prepared in Example 1, where 6534 represents the dispersant of Example 1.

[0026] Figure 3 The figure shows the performance test report of the dispersant prepared in Example 1 after being mixed with paint. In the figure, 6534 is the dispersant of Example 1. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Butyl acetate, product number 287725, CAS: 123-86-4. Merck Group, Darmstadt, Germany.

[0029] Example 1 This embodiment provides a dispersant, the preparation method of which includes the following steps: (1) Under nitrogen protection, 0.7 mol of trimethylolpropane, 0.1 mol of bisphenol A, 1.0 mol of oleic acid and butyl acetate (1.8 times the total mass of bisphenol A, trimethylolpropane and oleic acid) were added to the reactor. Stirring was started and the temperature was raised to 180°C. Monobutyltin oxide (0.4% of the total mass of bisphenol A, trimethylolpropane and oleic acid) was added and the reaction was carried out until the acid value reached 3 mg KOH / g to obtain oleic acid-trimethylolpropane prepolymer. (2) Cool the product of step (1) to 150°C, add 1.0 mol of trimellitic anhydride under stirring, and ensure that the system temperature is always below 155°C. After the addition is complete, keep it at 150°C for 0.5 h, and then raise the temperature to 188°C to continue the reaction. Take samples periodically to measure the acid value until the acid value reaches 90 mg KOH / g. (3) Cool the system to 108℃, add 0.4 mol of triisopropanolamine under stirring, and stir the reaction at this temperature for 1.7 h; (4) Add 0.2 mol of benzoic acid to the product of step (3), raise the temperature to 190℃ and continue the reaction until the acid value is 80 mg KOH / g; (5) Cool the product from step (4) to 80°C, add butyl acetate, and adjust the solid content to 40wt% to obtain a dispersant.

[0030] Example 2 This embodiment provides a dispersant, the preparation method of which includes the following steps: (1) Under nitrogen protection, 0.65 mol of trimethylolpropane, 0.12 mol of bisphenol A, 1.05 mol of oleic acid and butyl acetate (1.8 times the total mass of bisphenol A, trimethylolpropane and oleic acid) were added to the reactor. Stirring was started and the temperature was raised to 180°C. Monobutyltin oxide (0.3% of the total mass of bisphenol A, trimethylolpropane and oleic acid) was added and the reaction was carried out until the acid value reached 5 mg KOH / g to obtain oleic acid-trimethylolpropane prepolymer. (2) Cool the product of step (1) to 150°C, add 1.02 mol of trimellitic anhydride under stirring, and ensure that the system temperature is always below 155°C. After the addition is complete, keep it at 140°C for 1 hour, and then raise the temperature to 185°C to continue the reaction. Take samples periodically to measure the acid value until the acid value reaches 95 mg KOH / g. (3) Cool the system to 105℃, add 0.45 mol of triisopropanolamine under stirring, and stir the reaction at this temperature for 1.5 h; (4) Add 0.2 mol of benzoic acid to the product of step (3), raise the temperature to 190℃ and continue the reaction until the acid value is 82 mg KOH / g; (5) Cool the product from step (4) to 80°C, add butyl acetate, and adjust the solid content to 40wt% to obtain a dispersant.

[0031] Example 3 This embodiment provides a dispersant, the preparation method of which includes the following steps: (1) Under nitrogen protection, 0.75 mol of trimethylolpropane, 0.08 mol of bisphenol A, 0.08 mol of oleic acid and butyl acetate (1.8 times the total mass of bisphenol A, trimethylolpropane and oleic acid) were added to the reactor. Stirring was started and the temperature was raised to 180°C. Monobutyltin oxide (0.5% of the total mass of bisphenol A, trimethylolpropane and oleic acid) was added and the reaction was carried out until the acid value reached 4 mg KOH / g to obtain oleic acid-trimethylolpropane prepolymer. (2) Cool the product of step (1) to 150°C, add 1.0 mol trimellitic anhydride under stirring, and ensure that the system temperature is always below 155°C. After the addition is complete, keep it at 150°C for 0.5 h, and then raise the temperature to 190°C to continue the reaction. Take samples periodically to measure the acid value until the acid value reaches 85 mg KOH / g. (3) Cool the system to 110°C, add 0.35 mol of triisopropanolamine under stirring, and stir the reaction at this temperature for 1.5 h; (4) Add 0.2 mol of benzoic acid to the product of step (3), raise the temperature to 190℃ and continue the reaction until the acid value is 82 mg KOH / g; (5) Cool the product from step (4) to 80°C, add butyl acetate, and adjust the solid content to 40wt% to obtain a dispersant.

[0032] Comparative Example 1 The difference between this comparative example and Example 1 is the amount of triisopropanolamine added. Specifically, the system was cooled to 108°C, and 0.3 mol of triisopropanolamine was added under stirring. The reaction was carried out at this temperature for 1.7 h.

[0033] Comparative Example 2 The difference between this comparative example and Example 1 is the amount of triisopropanolamine added. Specifically, the system was cooled to 108°C, and 0.5 mol of triisopropanolamine was added under stirring. The reaction was carried out at this temperature for 1.7 h.

[0034] Performance testing The dispersants prepared in Examples 1-3 and Comparative Examples 1-2 were compared with commercially available products in terms of performance.

[0035] The commercially available products are as follows: KEPERDISP® 6538, Zhuhai Jintuan Chemical Co., Ltd.

[0036] KEPERDISP® 6522B, Zhuhai Jintuan Chemical Co., Ltd.

[0037] KEPERDISP® 6525, Zhuhai Jintuan Chemical Co., Ltd.

[0038] KEPERDISP® 6463B, Zhuhai Jintuan Chemical Co., Ltd.

[0039] 1. Prepare hydroxy acrylic black paste, comprising the following components in parts: 46 parts hydroxy acrylic resin S090 (Yake Chemical: YZ-H602), 5 parts dispersant, 10 parts F41 carbon black (Bora Columbia: Raven P5U), and 39 parts mixed solvent (xylene: butyl acetate volume ratio of 1:1).

[0040] F41 carbon black in hydroxy acrylic black paste was ground to a fineness of ≤10μm. The viscosity of the hydroxy acrylic black paste at different rotation speeds (6 / 12 / 30 / 60RPM) was tested using a rotational viscometer. Blackness was also tested, with ○, ○-, △+, and △ representing decreasing blackness in that order. The method for determining blackness is as follows: the tristimulus values ​​X, Y, and Z of the color were measured using a colorimeter. The blackness value is: My = 100 * log(100 / Y). The larger the My value, the higher the blackness (referring to DIN 55979 standard, "dM" indicates a bluish or brownish (reddish) hue; a positive value indicates a bluish hue, with a larger value indicating a stronger bluish hue; a negative value indicates a reddish hue, with a larger value indicating a stronger reddish hue. Together with My (blackness), it is used as a hue index to represent the blackness of black paint).

[0041] The results are shown in Table 1.

[0042] Table 1. Viscosity and Blackness Test Results Example 1 18700 9850 4460 2620 ○ Example 2 18750 9870 4480 2640 ○ Example 3 18780 9880 4500 2670 ○ Comparative Example 1 21400 11820 5350 3140 ○ Comparative Example 2 19853 11040 5510 2920 ○ KEPERDISP® 6538 28400 14300 5780 3090 △ KEPERDISP® 6522B 80000 20350 10740 4070 △ KEPERDISP® 6525 78400 30000 10000 4700 △+ KEPERDISP® 6463B 59100 28400 11780 6160 ○- From Table 1 and Figure 1-2It can be seen that the dispersants in Examples 1-3 have the best viscosity-reducing effect and the best blackness, which is superior to the four commercially available products. In Comparative Examples 1-2, the amount of triisopropanolamine used is different. If the amount is too low, the anchoring groups are insufficient and the molecular chain ends are not fully converted, resulting in weak adsorption capacity for pigment particles. If the amount is too high, it causes polarity imbalance, resulting in hindered molecular motion and reduced steric hindrance effect.

[0043] 2. The coating comprises the following components in parts by weight: Component A: 50 parts alkyd resin and 24.8 parts butyl acetate; Component B: 17.5 parts isocyanate curing agent and 7.5 parts butyl acetate.

[0044] Add 12wt% of the hydroxy acrylic black paste prepared in Examples 1-3 and a commercially available dispersant to the above coating, stir well, and apply it to black and white checkered cardstock. Observe the hiding power; ○, △+, △, × represent the decreasing hiding power in that order; observe the haze; and measure the brightness value of the paint film.

[0045] The method for judging the hiding power is as follows: apply each formula of black paint evenly to a black and white checkered card using a 100-micron scraper, and after drying, visually compare the hiding power of each paint film on the white area.

[0046] The method for determining the lightness value is as follows: the lightness value of carbon black is the L value of the paint film measured by a colorimeter. The smaller the L value, the darker the color and the higher the blackness.

[0047] The results are shown in Table 2.

[0048] Table 2. Coating Test Results Example 1 ○ none 28.50 Example 2 ○ none 28.52 Example 3 ○ none 28.53 Comparative Example 1 △+ none 28.67 Comparative Example 2 △+ none 28.64 KEPERDISP® 6538 △+ none 28.71 KEPERDISP® 6522B × none 28.81 KEPERDISP® 6525 × none 28.84 KEPERDISP® 6463B △ none 28.71 Through Table 2 and Figure 3 It can be seen that the dispersants prepared in Examples 1-3 can improve the hiding power of the coating. The lower the value of the lightness, the darker the color, indicating that the paint film of Examples 1-3 has the deepest blackness.

[0049] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a dispersant, characterized in that, Includes the following steps: (1) Under nitrogen protection, trimethylolpropane, bisphenol A, oleic acid and butyl acetate are added to the reactor, the temperature is raised to 175-185℃, a catalyst is added, and the reaction is continued until the acid value is ≤5mgKOH / g; (2) Cool the product from step (1) to 140-150℃, add trimellitic anhydride, and keep the reaction at the temperature until the acid value reaches 85-95 mgKOH / g. (3) Cool the product from step (2) to 105-110℃, add triisopropanolamine, and react at 105-110℃ for 1.5-2h; (4) Add benzoic acid to the product of step (3), heat to 185-190℃, and react until the acid value is 78-82 mgKOH / g; (5) Cool the product from step (4), add butyl acetate, adjust the solid content, and obtain a dispersant.

2. The method for preparing the dispersant according to claim 1, characterized in that, The molar ratio of trimethylolpropane, bisphenol A, and oleic acid is (0.65–0.75):(0.08–0.12):(0.95–1.05).

3. The method for preparing the dispersant according to claim 1, characterized in that, The amount of butyl acetate used is 1.5 to 2 times the total mass of bisphenol A, trimethylolpropane and oleic acid.

4. The method for preparing the dispersant according to claim 1, characterized in that, The catalyst is monobutyltin oxide.

5. The method for preparing the dispersant according to claim 4, characterized in that, The amount of catalyst used is 0.3-0.5% of the total mass of bisphenol A, trimethylolpropane and oleic acid.

6. The method for preparing the dispersant according to claim 1, characterized in that, The molar ratio of trimellitic anhydride to triisopropanolamine is 1:(0.35-0.45).

7. The method for preparing the dispersant according to claim 1, characterized in that, In step (2), trimellitic anhydride is added to ensure that the system temperature is always below 155℃.

8. The method for preparing the dispersant according to claim 1, characterized in that, The reaction conditions for step (2) are: keep warm at 140-150℃ for 0.5-1h, then raise the temperature to 185-190℃ and continue the reaction until the acid value is 85-95mgKOH / g.

9. A dispersant prepared by the method according to any one of claims 1-8.

10. Use of the dispersant of claim 9 in dispersing pigments in a two-component polyurethane coating system.

Images