Ultra-black pigment type quick-dry gel ink

Abstract

The invention discloses ultra-black pigment type quick-dry neutral ink, which is characterized by being prepared from the following components in parts by mass: 20.0 to 25.0 parts of water-based pigment color paste, 12.0 to 24.0 parts of a humectant, 0.75 to 1.00 parts of a thickening agent, 0.5 to 1.5 parts of a lubricating agent, 0.5 to 1.0 part of a surfactant, 0.5 to 1.0 part of a quick-dry anti-rust auxiliary agent, 0.2 to 0.6 part of a stabilizing agent, 0.15 to 0.2 part of a pH (Potential of Hydrogen) regulator, 0.5 to 1.0 part of a sterilizing agent and 40.0 to 65.0 parts of de-ionized water. The ink balances the contradiction between the drying speed of the stitches and the paper bleeding and instability of the ink, and improves the blackness of the writing stitches while meeting the requirement that consumers pursue the quick-drying effect.

Description

Technical Field

[0001] This invention relates to a super black pigment-based quick-drying neutral ink for ballpoint pens. Background Technology

[0002] With the upgrading of consumption, consumers' requirements for user experience are constantly improving, and the rapid drying of neutral ink ballpoint pen lines has become a hot demand in the industry. Typically, surfactants with good penetrability are used to allow the ink to quickly penetrate the paper to achieve a quick-drying effect. Patent ZL201880069657.X uses surfactants containing acetylene bonds or organosilicon-based surfactants to accelerate ink penetration and achieve a quick-drying effect. Patent ZL202310808860.7 polymerizes 3-(methacryloyloxy)propyltrimethoxysilane with various acrylic monomers, grafts the product onto modified acrylic emulsions, and utilizes the excellent leveling properties of the organosilicon side chains of the modified acrylic emulsions to enhance the ink's penetration ability and achieve a quick-drying effect. All of the above achieve quick-drying by enhancing penetration. However, strong penetration can easily cause ink to seep to the back of the paper, causing ink to penetrate the paper and resulting in ink bleeding or feather-like penetration marks at the edges of the lines; in addition, when the ink quickly penetrates into the paper, the amount of ink remaining on the surface is relatively small, resulting in a relatively weaker line color. Currently, all college entrance examinations are conducted using electronic scanning machines before being graded by examiners. Lighter colored lines are easier to scan unclearly, and ink bleeding on the back of the exam paper can lead to misjudgments by examiners.

[0003] To achieve stable results, most mainstream neutral inks use carbon black particles with an average particle size of less than 200nm to ensure their anti-settling stability. Due to the rapid penetration of quick-drying inks, smaller carbon black particles penetrate deeper into the paper fibers, resulting in fewer particles remaining on the paper surface and thus insufficient line darkness. This explains why the lines in commercially available quick-drying neutral ink ballpoint pens tend to be lighter in color. It's clear that pigment-based quick-drying neutral inks face a difficult trade-off between rapid penetration for quick drying and high line darkness. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an ultra-black pigment-type quick-drying neutral ink and its preparation method.

[0005] The objective of this invention is achieved through the following solution: A super black pigment-based quick-drying neutral ink, by weight, comprises: 20.0–25.0 parts of water-based pigment paste, 0.75–1.00 parts of thickener, 0.5–1.0 parts of quick-drying rust inhibitor, 0.2–0.6 parts of stabilizer, 12.0–24.0 parts of humectant, 0.5–1.5 parts of lubricant, 0.5–1.0 parts of surfactant, 0.15–0.2 parts of pH adjuster, 0.5–1.0 parts of bactericide, and 40.0–65.0 parts of deionized water.

[0006] The super-black pigment-based quick-drying neutral ink has a D50 particle size of 280–350 nm and a D99 particle size of less than 900 nm. While ensuring normal writing performance of the ballpoint pen, it provides high blackness in the writing lines while effectively inhibiting ink bleeding. When D50 is less than 280 nm, the ink's covering power weakens, resulting in decreased blackness in the writing lines. When D99 is greater than 900 nm, the larger particle size causes large carbon black particles to settle easily, leading to instability in the ink system. Long-term storage can clog the pen tip, preventing normal writing.

[0007] The thickener is a hydrophobically modified acrylic alkali-swellable thickener.

[0008] Hydrophobically modified acrylic alkali-swellable thickeners can form a three-dimensional network structure through the association of hydrophobic modified groups. The carboxylate ions on the acrylic main chain combine with free water, making the ink system a whole with good stability. It is a commonly used thickener in neutral ink formulations.

[0009] However, its molecular chain is relatively long and it has a lot of carboxyl groups. When it diffuses in paper fibers, it is easily hindered by the polar groups in the paper fibers, resulting in a longer drying time.

[0010] The hydrophobic modified acrylic thickeners are JZH-506 from Ruiguang Chemical, RHEOLATE 150S, RHEOLATE 175S, RHEOLATE 185, etc.

[0011] The quick-drying rust-preventing additive is one of sodium nitrite, sodium molybdate, and potassium molybdate.

[0012] Sodium nitrite, sodium molybdate, and potassium molybdate have good ionization properties in water. They not only have rust-preventing effects, but also, during writing, their positively charged ions can quickly combine with the polar groups such as hydroxyl and carboxyl groups on the paper fibers. This reduces the resistance of the carboxyl groups in the thickener molecules to reaching the adsorption sites, allowing the thickener molecules to quickly reach the adsorption sites and solidify on the paper fibers, thus achieving a rapid drying effect. This solves the slow drying defect caused by using hydrophobically modified acrylic alkali-swellable thickeners. Due to the ink's retention on the surface, the amount of carbon black particles penetrating to the back is greatly reduced, while also preventing ink bleeding.

[0013] When the addition amount exceeds 1.0%, the charge repulsion between the ionic charge and the thickener increases significantly due to the increase in ionic charge, resulting in instability of the ink system; when the addition amount is less than 0.5%, satisfactory drying effect cannot be achieved.

[0014] The stabilizer is a dendritic hyperbranched polymer formed by polymerization of a polyol as the core and 2,2-dimethylolpropionic acid, and its structural schematic diagram is shown below. Figure 1 Its number-average molecular weight is 3100~6500.

[0015] Dendritic hyperbranched polymers formed by polymerizing polyols with 2,2-dimethylolpropionic acid possess densely branched polymer backbones and numerous polar groups. In inks, these polar groups connect to the thickener, allowing adjacent thickener molecules to form a network structure similar to hydrophobic groups. This interweaving with the association regions of hydrophobic groups strengthens the three-dimensional network structure. Furthermore, the hyperbranched polar groups readily form weak interactions with the carbon black surface, anchoring the carbon black within the thickener-stabilizer network and resulting in excellent anti-settling stability. When the stabilizer's molecular weight is small, these interactions are weak; when the molecular weight is large, these interactions are too strong, easily leading to gelation of the ink after storage at room temperature.

[0016] The stabilizer can be purchased from Bostow (Shanghai) Chemical Products Trading Co., Ltd., with brands such as Boltorn™ H2004, Boltorn™ H311, and Boltorn™ U3000.

[0017] The moisturizer is one or a mixture of several of the following: glycerin, diethylene glycol, triethylene glycol, 1,4-butanediol, and polyethylene glycol 400.

[0018] The surfactant is one or a mixture of two of the following: decantyne glycol polyoxyethylene ether and organosilicon-modified polyether.

[0019] The lubricant is one or a mixture of several of the following: fatty alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether phosphate, oleic acid polyoxyethylene ether, and glyceryl oleate.

[0020] The pH adjuster is one or a mixture of several of monoethanolamine, diethanolamine, triethanolamine, and 2-amino-2-methyl-1-propanol.

[0021] The bactericide is one or a mixture of several of 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

[0022] The ultra-black pigment-type quick-drying neutral ink uses a No. 2 rotor and has a viscosity of 900~1400 cp at 6 rpm.

[0023] The super-black pigment-based quick-drying neutral ink of the present invention can be prepared using the disclosed method, which typically includes the following steps: According to the formula and dosage requirements, deionized water, humectant, lubricant, surfactant, quick-drying rust inhibitor, stabilizer, and bactericide are added to a container equipped with a stirring device. After stirring evenly, pH adjuster and thickener are added while stirring, and finally water-based pigment paste is added. Stirring continues until all materials are evenly mixed, and stirring is stopped. The ink obtained above is filtered to obtain filtrate, and then vacuum degassing is performed to obtain super black pigment-type quick-drying neutral ink.

[0024] Compared with existing technologies, the super black pigment-based quick-drying neutral ink of the present invention has the following advantages: Compared to conventional quick-drying inks, this ink offers a significant improvement in line darkness while maintaining stable viscosity, thus balancing the trade-off between line drying speed and ink bleeding / instability. It satisfies consumers' desire for both quick drying and enhanced ink darkness. Attached Figure Description

[0025] Appendix Figure 1 : Schematic diagram of stabilizer structure. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0027] Example 1 Six parts of glycerin (humectant), 6 parts of 1,4-butanediol (humectant), 1.0 part of fatty alcohol polyoxyethylene ether phosphate (lubricant), 1.0 part of sodium nitrite, 0.5 part of decynyl glycol polyoxyethylene ether (surfactant), 0.15 part of monoethanolamine (pH adjuster), and 1.0 part of 2-methyl-4-isothiazolin-3-one (bactericide) were added to 58.0 parts of deionized water and stirred until homogeneous. Then, while stirring, 0.75 parts of hydrophobic modified acrylic alkali-swelling thickener (thickener) were added, followed by 0.6 parts of stabilizer (number average molecular weight 3100). Finally, 25.0 parts of black water-based pigment paste (D50=280 nm, D99=790 nm) were added, and stirring continued for 2 hours. The resulting ink was filtered through a 1500-mesh filter bag to obtain the filtrate, which was then degassed under vacuum to obtain the ultra-black pigment-type quick-drying neutral ink.

[0028] Example 2 Eight parts of glycerin (moisturizer), eight parts of diethylene glycol (moisturizer), 0.7 parts of oleic acid polyoxyethylene ether (lubricant), 0.7 parts of sodium molybdate, 0.5 parts of silicone-modified polyether (surfactant), 0.18 parts of triethanolamine (pH adjuster), and 0.7 parts of 1,2-benzisothiazolin-3-one (bactericide) were added to 56.7 parts of deionized water and stirred until homogeneous. Then, while stirring, 0.9 parts of hydrophobic modified acrylic alkali-swelling thickener (thickener) were added, followed by 0.4 parts of stabilizer (number average molecular weight 5300). Finally, 23.0 parts of black water-based pigment paste (D50=320 nm, D99=850 nm) were added, and stirring continued for 2 hours. The resulting ink was filtered through a 1500-mesh filter bag to obtain the filtrate, which was then degassed under vacuum to obtain the ultra-black pigment-type quick-drying neutral ink.

[0029] Example 3 Eight parts of glycerin (humectant), eight parts of polyethylene glycol 400 (humectant), 0.5 parts of fatty alcohol polyoxyethylene ether (lubricant), 0.7 parts of potassium molybdate, 1.0 part of decynyl glycol polyoxyethylene ether (surfactant), 0.2 parts of 2-amino-2-methyl-1-propanol (pH adjuster), and 0.5 parts of 1,2-benzisothiazolin-3-one (bactericide) were added to 52.1 parts of deionized water. After stirring until homogeneous, 1.0 part of hydrophobic modified acrylic alkali-swelling thickener (thickener) was added while stirring, followed by 0.2 parts of stabilizer (number average molecular weight 6500). Finally, 20.0 parts of black water-based pigment paste (D50=350 nm, D99=900 nm) were added, and stirring was continued for 2 hours. The ink prepared above was filtered through a 1500-mesh filter bag to obtain the filtrate, which was then degassed under vacuum to obtain the super black pigment-type quick-drying neutral ink.

[0030] Comparative Example 1 Compared to Example 2, the amount of rust-preventive and quick-drying additive was reduced from 0.7 parts to 0.2 parts, and the amount of deionized water was increased by 0.5 parts accordingly. The quality and preparation process of other additives were the same as in Example 2.

[0031] Comparative Example 2 Compared to Example 2, the amount of rust-preventive and quick-drying additive increased from 0.7 parts to 1.5 parts, and the amount of deionized water decreased by 0.8 parts accordingly. The quality and preparation process of other additives were the same as in Example 2.

[0032] Comparative Example 3 Compared to Example 2, the amount of stabilizer was reduced from 0.4 parts to 0.1 parts, and the amount of deionized water was increased by 0.3 parts accordingly. The quality and preparation process of other additives were the same as in Example 2.

[0033] Comparative Example 4 Compared to Example 2, the amount of stabilizer was increased from 0.4 parts to 0.7 parts, and the amount of deionized water was reduced by 0.3 parts accordingly. The quality and preparation process of other additives were the same as in Example 2.

[0034] Comparative Example 5 Compared with Example 2, an aqueous color paste with a particle size of D50=200 nm and D99=405 nm was used to replace the aqueous color paste in Example 2, while the quality of other additives and the preparation process were the same as in Example 2.

[0035] Comparative Example 6 Compared with Example 2, an aqueous color paste with a particle size of D50=400 nm and D99=1050 nm was used to replace the aqueous color paste in Example 2, while the quality of other additives and the preparation process were the same as in Example 2.

[0036] Comparative Example 7 Commercially available quick-drying neutral ink ballpoint pens have ink particle sizes of D50=130 nm and D99=210 nm.

[0037] The mass fractions of each additive in the examples and comparative examples are shown in Table 1.

[0038] Table 1. Mass parts of each additive in the Examples and Comparative Examples

[0039] Viscosity test The viscosity of the super black pigment-type quick-drying neutral inks in the examples and comparative examples was tested at 6 rpm using a rotational viscometer with rotor No. 2 at room temperature. The data are shown in Table 2.

[0040] Table 2. Viscosity data of neutral inks in the examples and comparative examples.

[0041] The viscosities of the inks in Examples 1-3 were all between 900 and 1400 cp. Compared to Example 2, the amount of quick-drying rust-inhibiting additive added in Comparative Example 1 was less, resulting in a slightly higher viscosity than in Example 2; the amount of quick-drying rust-inhibiting additive added in Comparative Example 2 was more, leading to a decrease in the viscosity of the corresponding ink. This indicates that an increase in ion content is detrimental to the construction of the ink viscosity system.

[0042] Compared with Example 2, the amount of stabilizer added in Comparative Example 3 was less, and the viscosity of the ink decreased significantly, indicating that the stabilizer plays a more crucial role in viscosity construction and works synergistically with the thickener to construct the viscosity system of the ink; the amount of stabilizer added in Comparative Example 4 was more, and its viscosity also increased accordingly.

[0043] Application performance testing A ballpoint pen refill is made of a commercially available pen tip (usually a 0.5 mm diameter ball), connection, tubing (inner diameter 2.75 mm), sheath, tail plug oil, and the super black pigment type quick-drying neutral ink prepared in the examples and comparative examples. After centrifugation, the pen refills with normal writing start are selected for application performance testing. The writing performance and line trace drying time tests are carried out in accordance with the requirements of GB / T 37853-2019 "Ballpoint pens and refills with neutral ink". The anti-leakage test is carried out in accordance with the requirements in QB / T 5255-2018 "Technical specification for the matching detection of ballpoint pen tips and ink". The test results are shown in Table 3.

[0044] The specific method for the line trace drying time test is as follows: Load the pen refill to be tested on a circular writing machine and draw a spiral line. Start the stopwatch at the end of the line drawing and time for a certain period. Cover the end section of the line trace with writing paper of the same nature, press a 500 g special weight (bottom diameter 50 mm) on the paper surface of the covering paper. After 10 minutes, separate the two papers. If there is no ink mark on the covering paper, gradually reduce the timing time after the line drawing ends to X s. When it is found that the covering paper just shows an ink mark, the line trace drying time of the pen refill to be tested is X s.

[0045] The line trace blackness is evaluated by a colorimeter, and the specific model is Datacolor 600 colorimeter.

[0046] The L value indicates the lightness of the color of the measured sample. The larger the L value, the lighter the color. The smaller the L value, the darker the color, which means it is visually blacker.

[0047] The a value represents the range from red light to green light of the color of the measured sample. The larger the a value, the more it偏向 red light, and the smaller the a value, the more it偏向 green light.

[0048] The b value represents the range from yellow light to blue light of the color of the measured sample. The larger the b value, the more it偏向 yellow light, b The smaller the value, the more biased the product / service. Towards blue light.

[0049] Take 5 g of the above ink onto an uncoated white hiding power determination cardboard, and then use a 100 μm wire bar to scrape the ink flat to make a sample. Take out the cardboard after placing it in an oven at 50 °C for 10 minutes, and place it under the Datacolor 600 colorimeter to measure the color depth of the film layer formed by the ink on the cardboard.

[0050] The above ink is made into a pen refill using commercially available pen tips, tubing and other accessories for bleeding paper test and stability test.

[0051] The method for the bleeding paper test: Take 70 g / m² ordinary office paper, write the character "永" with the made pen refill and immediately observe whether the edges and corners of the front writing are smeared. After 1 minute, turn to the back to check the back penetration situation.

[0052] Test method for anti-settling stability: Place the prepared pen refill in a centrifuge with a centrifuge diameter of 40 cm, set the speed to 2500 rpm, centrifuge for 1 h, and then test the initial writing performance.

[0053] The initial strokes are judged as excellent if they are normal from the start; good if they are within 50 mm; acceptable if they are within 100 mm; and poor if they are more than 100 mm.

[0054] Table 3. Performance Tests of Neutral Ink Ballpoint Pen Refills Prepared in Examples and Comparative Examples

[0055] The writing performance of the ballpoint pen refills made with neutral inks in Examples 1-3 all meet the requirements of "Neutral Ink Ballpoint Pens and Refills" (GB / T 37853-2019): lines longer than 300 m were drawn without significant fading or breakage. The drying time was less than 4 seconds, meeting the requirements for quick-drying. No bleeding occurred. Compared to the commercially available quick-drying neutral ink ballpoint pen in Comparative Example 7, the L values ​​of Examples 1-3 were significantly smaller, indicating that the blackness of the super-black pigment-based quick-drying neutral ink of this invention is higher than that of commercially available quick-drying neutral ink ballpoint pens. No bleeding occurred in the lines of Examples 1-3, while the commercially available quick-drying neutral ink ballpoint pen in Comparative Example 7 showed slight bleeding. This indicates that the super-black pigment-based quick-drying neutral ink, while improving line blackness, solves the bleeding problem caused by conventional quick-drying neutral inks relying on rapid penetration for quick drying.

[0056] The longer drying time of the lines in Comparative Example 1 indicates that when the content of quick-drying rust-preventing additive is low, the penetration rate of the thickener is slow, making it difficult to achieve the desired quick-drying effect.

[0057] The addition of a larger amount of quick-drying rust-inhibiting additive in Comparative Example 2 has a better effect on quick-drying performance.

[0058] The amount of stabilizer added in Comparative Example 3 was insufficient, resulting in poor anti-settling stability of the ink.

[0059] In Comparative Example 4, the excessive addition of stabilizer resulted in an overly strong cohesive force in the three-dimensional network structure formed by the thickener and pigment, leading to high ink viscosity and impairing normal writing performance.

[0060] Comparative Example 5 showed slight paper bleeding and a relatively large L value, which is related to its relatively small particle size.

[0061] Comparative Example 6 had the lowest L value, meaning it had the highest blackness, but its writing performance was substandard. This is because the pigment particles were relatively large. During the drawing process, the large pigment particles gradually accumulated in the ink outlet channel of the pen tip, blocking the ink outlet channel and thus affecting normal drawing.

[0062] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A super black pigment-based quick-drying neutral ink, characterized in that, By weight, the super black pigment-based quick-drying neutral ink contains: 20.0–25.0 parts water-based pigment paste, 0.75–1.00 parts thickener, 0.5–1.0 parts quick-drying rust inhibitor, 0.2–0.6 parts stabilizer, 12.0–24.0 parts humectant, 0.5–1.5 parts lubricant, 0.5–1.0 parts surfactant, 0.15–0.2 parts pH adjuster, 0.5–1.0 parts bactericide, and 40.0–65.0 parts deionized water.

2. The super black pigment-based quick-drying neutral ink according to claim 1, characterized in that, The water-based pigment paste has a D50 particle size of 280–350 nm and a D99 particle size of less than 900 nm.

3. The super black pigment-based quick-drying neutral ink according to claim 1, characterized in that, The thickener is a hydrophobically modified acrylic alkali-swellable thickener.

4. The super black pigment-based quick-drying neutral ink according to claim 1, characterized in that, The quick-drying rust-preventing additive is one of sodium nitrite, sodium molybdate, potassium molybdate, etc.

5. The super black pigment-based quick-drying neutral ink according to claim 1, characterized in that, The stabilizer is a dendritic hyperbranched polymer formed by polymerizing a polyol as the core with 2,2-dimethylolpropionic acid, with a number average molecular weight of 3100-6500.

6. The super black pigment-type quick-drying neutral ink according to claim 1, characterized in that, The humectant is one or a mixture of several of glycerin, diethylene glycol, triethylene glycol, 1,4-butanediol, and polyethylene glycol 400; the surfactant is one or a mixture of two of decynyl glycol polyoxyethylene ether and silicone-modified polyether.

7. The super black pigment-type quick-drying neutral ink according to claim 1, characterized in that, The lubricant is one or a mixture of several of the following: fatty alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether phosphate, oleic acid polyoxyethylene ether, and glyceryl oleate; the pH adjuster is one or a mixture of the following: monoethanolamine, diethanolamine, triethanolamine, and 2-amino-2-methyl-1-propanol; and the bactericide is one or a mixture of the following: 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

8. The super black pigment-type quick-drying neutral ink according to claim 1, characterized in that, The ultra-black pigment-type quick-drying neutral ink uses rotor No. 2 and has a viscosity of 900~1400 cp at 6 rpm.

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