Method for preparing easily dispersible pigment from graphene-modified CI pigment Red 179

Abstract

This invention relates to a method for preparing easily dispersible pigments using graphene-modified CI Pigment Red 179. Monolayer graphene or monolayer graphene oxide powder and a solvent are added to water and stirred to mix. CI Pigment Red 179 is then added, and the mixture is stirred and slurried to obtain a pigment slurry. A nonionic surfactant is added, and the mixture is stirred and slurried again. The slurry is then dispersed by grinding in a sand mill. An anionic surfactant is added to the dispersed slurry, and the mixture is dried in a spray dryer to obtain an easily dispersible pigment. The easily dispersible pigment obtained by this invention using graphene-modified CI Pigment Red 179 exhibits high tinting strength, small particle size, more concentrated particle size distribution, and good dispersibility when used in coatings and inks. The tinting strength can reach 129%, the average particle size is reduced from 24.140 μm to 4.482 μm, the particle size distribution is more concentrated, and soft, easily dispersible pigment particles are obtained.

Description

Technical Field

[0001] This invention belongs to the field of chemistry, and in particular relates to a method for preparing easily dispersible pigments using graphene-modified CI pigment Red 179. Background Technology

[0002] CI Pigment Red 179 is prepared by the condensation reaction of 3,4,9,10-perylenetetracarboxylic anhydride and methylamine. This pigment is the most industrially valuable perylene red pigment, possessing a bright red color, excellent resistance to organic solvents and thermal stability, and exhibiting superior lightfastness, weather fastness, bleed resistance, and migration fastness. It is mainly used in high-end industrial coatings, such as original and refinish paints for automobiles, and for coloring high-end plastics, such as vinyl polymers, polyethylene, polypropylene, and fiber plastics. Furthermore, due to its unique fused-ring π-π conjugated system structure, it exhibits excellent photoelectric properties. It can be used as a fluorescent center in solar cell traps and as a laser dye. Its superior photoconductivity can be utilized in electron imaging and solar cell materials, demonstrating broad application prospects. This invention relates to the modification of Pigment Red 179 with graphene or graphene oxide to improve its application performance. CI Pigment Red 179 has a planar molecular structure, which makes it easy to combine with graphene oxide or graphene through π-π interactions to obtain an easily dispersible pigment, enhancing its performance in coatings, inks and other application systems.

[0003] There are many common methods for modifying and dispersing CI pigment Red 179. For example, the surface of the pigment can be treated with fine pigment derivatives, which form a mixed composition with the pigment. Derivatives synthesized from perylene tetracarboxylic anhydride and N,N-diethylpropylene diamine can improve the anti-flocculation ability of CI pigment Red 179 (US4762569). Modification with naphthalene anhydride or N,N'-bis(2-sulfoethyl)-1,4,5,8-naphthalenetetracarboxamide iron salt can prepare a highly transparent yellow-red pigment (US6015458). Of course, whether these treatments improve pigment performance depends on the system, i.e., the performance is affected by the resins and solvents used in the application. For some systems, surface treatment with the aforementioned derivatives is ineffective. The pigment must be compatible with the application system to achieve changes in pigment performance. Other commonly used strategies for improving the performance of organic pigments include surface modification through the addition of auxiliaries, such as theobromopropyl betaine and dodecyl dimethylamine oxide. However, regardless of the type of dispersant chosen, the actual application of the pigment or the final use of its preparation must be considered. Pigments modified with additives often only improve pigment performance within a certain range and cannot fundamentally improve the pigment's tinting strength or particle size and distribution.

[0004] This invention provides a method for producing easily dispersible CI pigment Red 179 using graphene as a modifier. This method yields an easily dispersible pigment with high tinting strength, small particle size, and a more concentrated particle size distribution. Graphene is a two-dimensional product composed of tightly bonded carbon elements forming a hexagonal lattice. It is an allotrope of carbon, exhibiting sp... 2 The bonds are planar, with molecular bond lengths of 0.142 nanometers. Individual graphene layers in graphite are held together by van der Waals forces. Graphene is the thinnest known compound, only one atom thick, the lightest known material, the strongest compound, the best thermal conductor at room temperature, and also the best known electrical conductor. Graphene oxide is an oxide of graphene containing various oxygen-based functional groups, including hydroxyl, alkoxy, carbonyl, and carboxylic acid groups. These oxygen-containing groups endow graphene oxide with many advantages, including higher solubility and the possibility of surface functionalization. This greatly expands the application range of graphene. Based on the similarity of their molecular structures, graphene and graphene oxide can be effectively combined with pigments through covalent and non-covalent interactions. Non-covalent interactions include π-π conjugation, van der Waals interactions, and hydrogen bonds. The key technology of this preparation method is how to combine graphene and graphene oxide with CI pigment Red 179, which has planarity and molecular structural symmetry. The tiny two-dimensional graphene is inserted into the pigment lattice to achieve the assembly of graphene and pigment. With the help of surfactants, an easily dispersible pigment with extremely superior performance is provided. Summary of the Invention

[0005] Based on the similarity of their molecular structures, this invention effectively combines graphene and graphene oxide with CI pigment Red 179 through non-covalent interactions (π-π conjugation forces, hydrogen bonds, and van der Waals forces). Monolayer graphene or monolayer graphene oxide is mixed with the pigment, stirred and slurried, then dispersed by grinding in a sand mill. A surfactant is added, and the mixture is dried in a spray dryer to produce an easily dispersible pigment containing graphene.

[0006] Graphene typically exists in single-molecule form and comes in various categories. Known graphene materials include single-layer to multi-layer graphene, graphite nanosheets, nanosheets, nanoflakes, and graphene oxide. Most reports in the literature utilize graphite nanosheets or graphene oxide. However, due to their poor solubility in various solvents and their hydrophobic properties, stabilizers or surfactants are usually added to improve the dispersibility of graphene in applications.

[0007] Organic pigment particles can be broken down into primary particles or flocs. Through high-energy grinding, these particles are dispersed into the medium, providing superior color strength. These fine pigment particles are typically planar and easily flocculate, losing their proper coloring power, gloss, and transparency. Perylene red (CI) pigment red 179 particles are very prone to flocculation, therefore surface treatment is necessary to improve their color strength, enhance color performance, and improve particle dispersibility. CI pigment red 179 has a planar or nearly planar crystal structure, allowing for surface treatment with monolayer graphene to improve its color properties.

[0008] This invention discloses a method for preparing CI pigment red 179 modified with graphene, comprising the following steps:

[0009] (1) Add single-layer graphene or single-layer graphene oxide powder and solvent to water, stir and mix for 1-2 hours, add CI pigment red 179 for 0.5-1 hours, continue stirring and pulping for 0.5-1 hours to obtain pigment slurry;

[0010] (2) Add nonionic surfactant, then stir and slurry for 0.5-1h, and then grind and disperse the slurry through a sand mill;

[0011] (3) After grinding and dispersing, anionic surfactants are added to the slurry and dried in a spray dryer to produce easily dispersible pigments.

[0012] The technical process employed in this invention is as follows: a method for preparing CI pigment red 179 modified with graphene, specifically including the following steps:

[0013] (1) Preparation of pigment slurry

[0014] Add single-layer graphene or single-layer graphene oxide powder and solvent to water, stir and mix for 1-2 hours, add CI pigment red 179 for 0.5-1 hours, continue stirring and pulping for 0.5-1 hours to obtain pigment slurry;

[0015] The medium used in this invention is water with a small amount of solvent. The water used is deionized water, and the solvent is N-octylpyrrolidone, which has both wetting and surface tension-reducing effects. The mass ratio of solvent to water is 0.1-0.5:100.

[0016] The mass ratio of the monolayer graphene or monolayer graphene oxide to CI pigment red 179 and water is 1-3:100:1000.

[0017] (2) Grinding

[0018] Add a nonionic surfactant, then stir and slurry for 0.5-1h. Pump this mixture into a sand mill and disperse it until the particle size reaches below 1μm.

[0019] The zirconium beads used in the sand mill have a diameter of 0.6-1.0 mm, the grinding temperature is 10-40℃, and the grinding is carried out for 2-4 hours at this temperature.

[0020] Commonly used nonionic surfactants include unsaturated alcohols or fatty alcohol polyoxyethylene ethers; for example, tetramethyldecynyl glycol, a fatty alcohol polyoxyethylene ether. The amount of nonionic surfactant added is 1-3% of the pigment. The surfactant is used in combination with the graphene and pigment of this invention.

[0021] A sand mill is a device that grinds or disperses pigment mixtures into fine slurries by stirring grinding media (steel balls, zirconium balls, or polymer grinding beads) in a cylindrical container. The rotation of the sand mill generates bead collisions, causing strong shear forces that impact the particles of the pigment mixture. It can effectively reduce micron or submicron-sized particles to countless nano-sized fine particles. By optimizing the size of the grinding beads and adjusting the rotation speed, the energy and impact force of the grinding material can be optimized.

[0022] (3) Drying

[0023] Anionic surfactants are added to the ground slurry, and the slurry is dried using a spray dryer to obtain easily dispersible pigments.

[0024] Suitable anionic surfactants include sodium lauryl sulfate and sodium diisooctyl succinate sulfonate. The amount of anionic surfactant added is 2-4% of the pigment.

[0025] The ground pigment slurry can be spray-dried to produce easily dispersible pigments. The slurry is sprayed out as relatively large droplets, and the water evaporates to form fine spherical particles. The inlet air temperature in spray drying is typically 130-300°C, preferably 150-170°C, and the gas outlet temperature is 70-150°C, preferably 90-100°C.

[0026] The easily dispersible pigment obtained by modifying CI pigment red 179 with graphene according to this invention exhibits high tinting strength, small particle size, more concentrated particle size distribution, and good dispersibility when used in coatings and inks. Compared with CI pigment red 179 itself, the easily dispersible pigment obtained by modifying CI pigment red 179 with graphene according to this invention achieves a tinting strength of up to 129%, reduces the average particle size from 24.140 μm to 4.482 μm, and has a more concentrated particle size distribution, resulting in soft and easily dispersible pigment particles. Attached Figure Description

[0027] Figure 1 The image shows the particle size distribution of the unmodified CI pigment red 179 sample.

[0028] Figure 2The image shows the particle size distribution of a CI pigment red 179 sample modified with 1% monolayer graphene.

[0029] Figure 3 The image shows the particle size distribution of a CI pigment red 179 sample modified with 3% monolayer graphene.

[0030] Figure 4 The image shows the particle size distribution of a CI pigment red 179 sample modified with 3% monolayer graphene oxide.

[0031] Figure 5 The image shown is a scanning electron microscope image of an unmodified CI pigment red 179 sample.

[0032] Figure 6 The image shown is a scanning electron microscope (SEM) image of a CI pigment red 179 sample modified with 1% monolayer graphene.

[0033] Figure 7 The image shown is a scanning electron microscope (SEM) image of a CI pigment red 179 sample modified with 3% monolayer graphene.

[0034] Figure 8 The image shown is a scanning electron microscope (SEM) image of a CI pigment red 179 sample modified with 3% monolayer graphene oxide. Detailed Implementation

[0035] The following examples illustrate the practical operation of the present invention, but the methods thereon should not limit the scope of the invention in any way.

[0036] Example 1

[0037] Preparation of easily dispersible pigment using 1% monolayer graphene-modified CI pigment Red 179

[0038] (1) Preparation of pigment slurry

[0039] 1g of single-layer graphene powder and 1g of N-octylpyrrolidone were added to 1000g of deionized water and stirred for 1 hour. 100g of Pigment Red 179 was added and stirred for 0.5 hours. The mixture was then stirred and slurried for another 0.5 hours to obtain the pigment slurry.

[0040] (2) Grinding

[0041] Add 1g of tetramethyldecynediol, then stir and slurry for 0.5h. Pump this mixture into a sand mill and grind until the particle size reaches below 1μm. The zircon beads used in the sand mill have a diameter of 1.0mm, the grinding temperature is 40℃, and the grinding is carried out at this temperature for 2h.

[0042] (3) Drying

[0043] After grinding, 2g of sodium diisooctyl succinate sulfonate was added to the grinding slurry and stirred evenly. Then, spray drying was performed. The inlet gas temperature during spray drying was typically 150℃, and the outlet gas temperature was 90℃. After drying, graphene-modified CI Pigment Red 179 easily dispersible pigment was obtained. Test results showed a tinting strength of 120% (compared to CI Pigment Red 179), and an average particle size of 4.975μm. Its particle size distribution is shown in the attached figure. Figure 2 As shown, the scanning electron microscope image is attached. Figure 6 As shown, its particle size is smaller than that of the unmodified CI Pigment Red 179 sample (average particle size is 24.140 μm, and its particle size distribution is shown in the attached figure). Figure 1 As shown, the scanning electron microscope image is attached. Figure 5 As shown in the figure. The particle size distribution diagram and scanning electron microscope image also show that the modified easily dispersible pigment has a smaller particle size, a more concentrated particle size distribution, and a softer pigment particle texture.

[0044] Example 2

[0045] Prepare easily dispersible pigment using 2% monolayer graphene-modified CI pigment Red 179

[0046] (1) Preparation of pigment slurry

[0047] Add 2g of single-layer graphene powder and 3g of N-octylpyrrolidone to 1000g of deionized water and stir for 1.5h; add 100g of Pigment Red 179 and stir for 0.8h, then continue stirring and mixing for 1h to obtain a pigment slurry.

[0048] (2) Grinding

[0049] Add 2g of tetramethyldecynyl diol, then stir and slurry for 0.8h. Pump this mixture into a sand mill and grind until the particle size reaches below 1μm. The zirconium beads used in the sand mill have a diameter of 0.8mm, the grinding temperature is 30℃, and grinding is carried out at this temperature for 3h.

[0050] (3) Drying

[0051] After grinding, 4g of sodium lauryl sulfate was added to the grinding slurry and stirred evenly. Then, spray drying was performed. The inlet gas temperature during spray drying was typically 170℃, and the outlet gas temperature was 100℃. After drying, graphene-modified CI pigment Red 179 easily dispersible pigment was obtained.

[0052] Example 3

[0053] Prepare easily dispersible pigment using 3% monolayer graphene-modified CI pigment Red 179

[0054] (1) Preparation of pigment slurry

[0055] Add 3g of single-layer graphene powder and 5g of N-octylpyrrolidone to 1000g of deionized water and stir for 2 hours; add 100g of Pigment Red 179 and stir for 1 hour, then continue stirring and beating for 0.8 hours to obtain a pigment slurry.

[0056] (2) Grinding

[0057] Add 3g of tetramethyldecynyl diol, then stir and slurry for 1 hour. Pump this mixture into a sand mill and grind until the particle size reaches below 1μm. The zirconium beads used in the sand mill have a diameter of 0.6mm, the grinding temperature is 20℃, and grinding is carried out at this temperature for 4 hours.

[0058] (3) Drying

[0059] After grinding, 3g of sodium diisooctyl succinate sulfonate was added to the grinding slurry and stirred evenly. Then, spray drying was performed. The inlet gas temperature during spray drying was typically 160℃, and the outlet gas temperature was 90℃. This yielded graphene-modified CI Pigment Red 179 easily dispersible pigment. Test results showed a tinting strength of 129% (compared to CI Pigment Red 179) and an average particle size of 4.482μm. Its particle size distribution is shown in the attached figure. Figure 3 As shown, the scanning electron microscope image is attached. Figure 7 As shown, its particle size is much smaller than that of the unmodified CI pigment red 179 sample, the particle size distribution is more concentrated, and the pigment particles have a soft texture.

[0060] Example 4

[0061] Prepare easily dispersible pigment using 1% monolayer graphene oxide modified CI pigment Red 179

[0062] (1) Preparation of pigment slurry

[0063] 1g of single-layer graphene oxide powder and 2g of N-octylpyrrolidone were added to 1000g of deionized water and stirred for 1 hour. 100g of Pigment Red 179 was added and stirred for 0.5 hours. The mixture was then stirred and slurried for another 0.5 hours to obtain the pigment slurry.

[0064] (2) Grinding

[0065] Add 2g of fatty alcohol polyoxyethylene ether (AEO-7), then stir and slurry for 0.5h. Pump this mixture into a sand mill and grind it until the particle size reaches below 1μm. The zircon beads used in the sand mill have a diameter of 0.6mm, the grinding temperature is 10℃, and the grinding is carried out for 3h at this temperature.

[0066] (3) Drying

[0067] After grinding, 2g of sodium lauryl sulfate is added to the grinding slurry and stirred evenly. Then, spray drying is carried out. The inlet temperature of the spray drying is usually 150℃ and the outlet temperature is 90℃. The graphene oxide modified CI pigment Red 179 is obtained as an easily dispersible pigment.

[0068] Example 5

[0069] Prepare easily dispersible pigment using 2% monolayer graphene oxide modified CI pigment Red 179

[0070] (1) Preparation of pigment slurry

[0071] Add 2g of monolayer graphene oxide powder and 3g of N-octylpyrrolidone to 1000g of deionized water and stir for 1.5h; add 100g of Pigment Red 179 and stir for 1h, then continue stirring and slurrying for 0.7h to obtain pigment slurry.

[0072] (2) Grinding

[0073] Add 3g of tetramethyldecynyl diol, then stir and slurry for 1 hour. Pump this mixture into a sand mill and grind until the particle size reaches below 1μm. The zirconium beads used in the sand mill have a diameter of 0.6mm, the grinding temperature is 30℃, and grinding is carried out at this temperature for 4 hours.

[0074] (3) Drying

[0075] After grinding, 3g of sodium diisooctyl succinate sulfonate was added to the grinding slurry and stirred evenly. Then, spray drying was carried out. The inlet temperature of the spray drying was usually 170℃ and the outlet temperature of the gas was 100℃. The graphene oxide modified CI pigment red 179 easy-dispersible pigment was obtained.

[0076] Example 6

[0077] Prepare easily dispersible pigment using 3% monolayer graphene oxide modified CI pigment Red 179

[0078] (1) Preparation of pigment slurry

[0079] Add 3g of monolayer graphene oxide powder and 4g of N-octylpyrrolidone to 1000g of deionized water and stir for 2 hours. Slowly add 100g of Pigment Red 179 and continue stirring and mixing for 1 hour to obtain a pigment slurry.

[0080] (2) Grinding

[0081] Add 2g of fatty alcohol polyoxyethylene ether (AEO-7), then stir and slurry for 0.7h. Pump this mixture into a sand mill and grind until the particle size reaches below 1μm. The zirconium beads used in the sand mill have a diameter of 0.8mm, the grinding temperature is 30℃, and grinding is carried out at this temperature for 4h.

[0082] (3) Drying

[0083] After grinding, 4g of sodium lauryl sulfate was added to the grinding slurry and stirred evenly. Then, spray drying was performed. The inlet gas temperature during spray drying was typically 150℃, and the outlet gas temperature was 100℃. This yielded graphene oxide-modified CI Pigment Red 179 easily dispersible pigment. Test results showed a tinting strength of 125% (compared to CI Pigment Red 179) and an average particle size of 4.843μm. Its particle size distribution is shown in the attached figure. Figure 4 As shown, the scanning electron microscope image is attached. Figure 8 As shown, its particle size is much smaller than that of the unmodified CI pigment red 179 sample, the particle size distribution is more concentrated, and the pigment particles have a soft texture.

[0084] The obtained pigment products were selected for performance testing based on their pigment product type:

[0085] (1) Weigh 0.1g of pigment and 1.0g of titanium dioxide, draw 1mL of ink oil with a syringe, and grind it three times on a flat grinder, 50 revolutions each time. Scrape a sample of the ground ink and measure its tinting strength with a colorimeter.

[0086] (2) The particle size and distribution of the prepared easily dispersible pigment before and after modification were tested and compared using a laser nanoparticle size analyzer.

[0087] (3) The particle morphology of easily dispersible pigments was measured using a scanning electron microscope at a magnification of 50,000 times.

[0088] The test results are shown in Table 1:

[0089] Table 1. Tinting strength and particle size of pigments

[0090]

[0091] As shown in Table 1, the tinting strength of Pigment Red 179 modified with graphene and graphene oxide is improved, and the pigment particle size is significantly reduced. See the attached instruction manual for particle size distribution diagrams and scanning electron microscope images of Pigment Red 179 before and after modification with monolayer graphene and monolayer graphene oxide. Figure 1-8 Based on the particle size distribution and scanning electron microscopy images, it can be seen that after modification with monolayer graphene and monolayer graphene oxide, the particle size distribution of Pigment Red 179 is more concentrated, the particle size is smaller, and the pigment particles are softer.

[0092] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications listed herein, as well as variations in the methods and compositions of the invention, will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. A method for preparing easily dispersible pigments using graphene-modified CI pigment Red 179, comprising the following steps: (1) Preparation of pigment slurry Add single-layer graphene or single-layer graphene oxide powder and solvent to water, stir and mix for 1-2 hours, add CI pigment red 179 for 0.5-1 hours, continue stirring and pulping for 0.5-1 hours to obtain pigment slurry; (2) Grinding Add a nonionic surfactant, then stir and slurry for 0.5-1 hour, and then grind and disperse the slurry using a sand mill; (3) Drying An anionic surfactant was added to the slurry after grinding and dispersing, and then dried in a spray dryer to produce an easily dispersible pigment. The mass ratio of the monolayer graphene or monolayer graphene oxide to CI pigment red 179 and water is 1-3:100:1000. The nonionic surfactant used in step (2) is tetramethyldecynyl glycol or fatty alcohol polyoxyethylene ether; the amount of nonionic surfactant added is 1-3% of the pigment. The suitable anionic surfactants mentioned in step (3) are sodium lauryl sulfate or sodium diisooctyl succinate sulfonate; the amount added is 2-4% of the pigment amount; Step (3) Drying is performed using a spray dryer; the inlet temperature of the spray dryer is usually 130-300℃; and the outlet temperature of the gas is 70-150℃.

2. The method according to claim 1, characterized in that, The water used in step (1) is deionized water, and the solvent is N-octylpyrrolidone; the mass ratio of solvent to water is 0.1-0.5:

100.

3. The method according to claim 1, characterized in that, Step (2) The diameter of the zirconium beads used in the sand mill is 0.6-1.0 mm, the grinding temperature is 10-40℃, and the grinding is carried out for 2-4 hours at this temperature.

4. The method according to claim 1, characterized in that, Step (3) Dry using a spray dryer; the inlet temperature of the spray dryer during spray drying is 150-170℃; the outlet temperature of the gas is 90-100℃.

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