Pigment type red neutral ink, method for preparing the same, and use thereof

Abstract

This invention discloses a pigment-based neutral red ink, its preparation method, and its applications. The pigment-based neutral red ink, by mass percentage, comprises the following components: 2-10% red organic pigment, 0.5-7% dispersant, 5-25% humectant, 0.05-0.2% polyvinylpyrrolidone, 1-10% penetrant, 0.1-1.5% preservative, 0.1-4% pH adjuster, 0.1-0.5% defoamer, and the balance deionized water. This invention's pigment-based neutral red ink solves the technical problem of easy sedimentation of red pigments through ultra-fine pigment dispersion and the combination of stabilizers, allowing the ink to remain stationary for extended periods without separation. Furthermore, the use of a special humectant combination ensures that the ink does not dry out at the pen tip without affecting its quick-drying performance; the ink exhibits excellent rheological properties, writes smoothly without clogging the pen, and has high color vibrancy. The formulation of this invention is environmentally friendly, primarily using water as a solvent, reducing the use of volatile organic compounds.

Description

Technical Field

[0001] This invention relates to the field of ink manufacturing technology, specifically to a pigment-based quick-drying red neutral ink with anti-settling properties and excellent moisturizing properties, and its preparation method. Background Technology

[0002] Neutral ink, a writing material between water-based and oil-based inks, is widely popular due to its smooth writing, vibrant colors, and water and sunlight resistance. However, existing pigment-based red neutral inks are prone to problems such as pigment sedimentation and clumping that clogs the pen tip during long-term storage, affecting writing performance.

[0003] In particular, red organic pigments exhibit poor dispersion stability in ink systems, easily leading to flocculation and sedimentation. This causes changes in ink flow, resulting in broken lines and uneven coloring. Furthermore, ballpoint pens are required to maintain smooth writing for extended periods after opening, placing extremely high demands on the ink's moisture retention properties. Traditional red inks often struggle to balance quick-drying and moisture retention; quick-drying inks tend to dry out at the nib, while inks with good moisture retention dry slowly, easily staining the paper.

[0004] While existing technologies have attempted to address these issues, such as adding resin-based thickeners to improve stability, these additives often negatively impact ink flowability and drying performance. Some technologies utilize specific surfactant combinations, but these lack specificity for red pigments, resulting in limited effectiveness. Therefore, developing a neutral red ink that combines anti-settling properties, excellent moisturizing properties, and quick-drying properties is of great significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pigment-based red neutral ink with good anti-settling properties, excellent moisturizing properties and fast drying speed.

[0006] The first aspect of this invention provides a pigment-based red neutral ink, comprising, by weight percentage: 2-10% red organic pigment, 0.5-7% dispersant, 5-25% humectant, 0.05-0.2% polyvinylpyrrolidone, 1-10% penetrant, 0.1-1.5% preservative, 0.1-4% pH adjuster, 0.1-0.5% defoamer, and the balance being deionized water.

[0007] According to one embodiment of the present invention, the red organic pigment is selected from one or more of quinacridone red, naphthol red and azo red organic pigments, and the D50 particle size of the pigment particles is less than 250 nm.

[0008] According to another embodiment of the present invention, the dispersant is at least one of polyethylene-benzyl acrylate, high molecular weight polyurethane dispersant, or acrylic dispersant.

[0009] According to another embodiment of the present invention, the humectant includes propylene glycol, glycerin and urea; the pigment-type red neutral ink contains 2-6% propylene glycol and 1.5-3% urea.

[0010] According to another embodiment of the present invention, the penetrant is at least one selected from alkyl sulfosuccinate compound and oligoethylene glycol alkyl ether compound. And / or the weight average molecular weight of the polyvinylpyrrolidone is between 8000 and 12000.

[0011] According to another embodiment of the present invention, the pigment-type red neutral ink further includes a surfactant combination, wherein the surfactant combination comprises a first surfactant and a second surfactant, the first surfactant having an HLB value of 10-18 and the second surfactant having an HLB value of 5-10.

[0012] According to another embodiment of the present invention, the first surfactant is selected from one or more of fatty alcohol polyoxyethylene ether AEO-9, polysorbate 80, and alkyl glycosides.

[0013] According to another embodiment of the present invention, the second surfactant is selected from one or more of sorbitan monooleate, fatty alcohol polyoxyethylene ether AEO-3, and alkylphenol polyoxyethylene ether OP-4.

[0014] According to another embodiment of the present invention, the first surfactant accounts for 0.3-0.4% and the second surfactant accounts for 0.2-0.3% in the pigment-type red neutral ink.

[0015] According to another embodiment of the present invention, the pigment-based red neutral ink further comprises 0.5-1.5% polyethylene glycol. Preferably, the polyethylene glycol has a weight-average molecular weight between 400 and 1000.

[0016] According to another embodiment of the present invention, the pH value of the pigment-based red neutral ink is maintained at 7.5-9.0.

[0017] A second aspect of the present invention provides a method for preparing the above-mentioned pigment-based red neutral ink, comprising: mixing a red organic pigment, a dispersant, a portion of an antifoaming agent, and a portion of deionized water; grinding the red organic pigment to a D50 particle size of less than 250 nm to obtain a pigment slurry; mixing a humectant, polyvinylpyrrolidone, a penetrant, a preservative, a pH adjuster, and the remaining deionized water uniformly under stirring conditions to form a base liquid; slowly adding the pigment slurry to the base liquid and continuously stirring until uniformly mixed; adding the remaining antifoaming agent, adjusting the pH value, and filtering to obtain the pigment-based red neutral ink.

[0018] A third aspect of the present invention provides a ballpoint pen comprising the above-described pigment-based red neutral ink.

[0019] This invention provides a pigment-based red neutral ink that solves the technical problem of easy sedimentation of red pigments through ultra-fine pigment dispersion and the formulation of stabilizers, allowing the ink to remain stationary for extended periods without separation. Furthermore, a special combination of humectants ensures the ink does not dry out at the pen tip without affecting its quick-drying properties. The ink exhibits excellent rheological properties, writes smoothly without clogging, and displays high color vibrancy. The formulation of this invention is environmentally friendly, primarily using water as a solvent, thus reducing the use of volatile organic compounds. Detailed Implementation

[0020] To make the present invention clearer and easier to understand, the technical solution of the present invention will be further described below with reference to specific embodiments. The embodiments described below are only used to explain the present invention and are not intended to limit the present invention in any form or substance.

[0021] The pigment-based red neutral ink of the present invention comprises, by weight percentage: 2-10% red organic pigment, 0.5-7% dispersant, 5-25% humectant, 0.05-0.2% polyvinylpyrrolidone, 1-10% penetrant, 0.1-1.5% preservative, 0.1-4% pH adjuster, 0.1-0.5% defoamer, and the balance being deionized water. Preferably, the weight-average molecular weight of the polyvinylpyrrolidone is between 8000 and 12000.

[0022] In an optional embodiment, the red organic pigment is selected from at least one of quinacridone red, naphthol red, or azo red organic pigments. The D50 particle size of the pigment particles needs to be less than 250 nm. This particle size range ensures color vibrancy while effectively preventing sedimentation when working with specific components.

[0023] In optional embodiments, the dispersant is one or more of polyethylene-benzyl acrylate, high molecular weight polyurethane dispersants, and acrylic dispersants. These dispersants have a specific adsorption effect on red pigments and can provide steric hindrance to prevent pigment particle aggregation. Polyethylene-benzyl acrylate can be Joncryl 682 / domestic BA-201, etc. High molecular weight polyurethane dispersants can be EFKA-4000, BYK-163 / NEO-1203, etc. Acrylic dispersants can be acrylic-maleic anhydride copolymer dispersants such as Dispex Ultra PX4585 / EFKA 4585, etc.

[0024] In an optional embodiment, the humectant includes a combination of propylene glycol, glycerin, and urea. In the ink, propylene glycol comprises 2-6%, and urea comprises 1.5-3%. This combination works synergistically to ensure good moisturizing properties of the ink without excessively affecting the drying speed.

[0025] In optional embodiments, the penetrant is an alkyl sulfosuccinate compound and / or an oligoethylene glycol alkyl ether compound. These penetrants reduce the surface tension of the ink, promoting its rapid penetration and drying on the paper surface. The alkyl sulfosuccinate compound may be, for example, disodium alkyl sulfosuccinate monoester.

[0026] The ink of the present invention may further include a surfactant combination comprising a first surfactant (HLB value 10-18) and a second surfactant (HLB value 5-10). The complementary HLB values ​​of the first and second surfactants further improve the ink's spreadability and drying performance on various paper materials.

[0027] In an optional embodiment, the first surfactant is selected from one or more of fatty alcohol polyoxyethylene ether AEO-9, polysorbate 80, and alkyl glycosides. The second surfactant is selected from one or more of dehydrated sorbitan monooleate, fatty alcohol polyoxyethylene ether AEO-3, and alkylphenol polyoxyethylene ether OP-4. The first surfactant accounts for 0.3-0.4% and the second surfactant accounts for 0.2-0.3% in the pigment-type red neutral ink.

[0028] In addition, the ink may contain 0.5-1.5% polyethylene glycol as a viscosity modifier, as well as appropriate amounts of anti-settling agents and bactericides, to further improve the overall performance of the ink. The weight-average molecular weight of the polyethylene glycol used is preferably between 400 and 1000.

[0029] The pigment-based red ink of this invention may also contain other auxiliary agents, such as defoamers. The defoamer may be BYK-024 / domestic DF-103, etc.

[0030] The pH value of the pigment-based red neutral ink of the present invention is maintained at 7.5-9.0.

[0031] The method for preparing the ink of the present invention includes the following steps: mixing red organic pigment, dispersant, part of defoamer and part of deionized water, and grinding the mixture with a nano-grinding mill until the pigment particle D50 particle size is less than 250nm to obtain a pigment slurry; mixing a humectant, polyvinylpyrrolidone, penetrant, preservative, pH adjuster and the remaining deionized water evenly under stirring to form a base liquid; slowly adding the pigment slurry to the base liquid and continuously stirring until evenly mixed; adding the remaining defoamer, adjusting the pH value, and filtering to obtain the final ink product.

[0032] The ink of this invention is suitable for use in ballpoint pens.

[0033] The present invention is further described below through specific examples. However, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present invention. Unless otherwise specified, the reagents, materials, and instruments used in the following embodiments and comparative examples are commercially available.

[0034] The ink preparation processes for each embodiment and comparative example are as follows: Organic red pigment, dispersant, 0.1% defoamer and 30% deionized water are added to a mixing container and stirred at high speed until the pigment is fully wetted; the mixture is then transferred to a nano-grinding mill and the pigment particles are ground to achieve the desired D50 particle size to obtain a red pigment slurry. In another container, propylene glycol, glycerin, urea, polyvinylpyrrolidone, polyethylene glycol, penetrant, first and second surfactants, preservative, pH adjuster and remaining deionized water are mixed and stirred at a medium speed for 30 minutes to form a homogeneous base solution. Slowly add the red pigment paste to the base liquid and continue stirring for 1 hour to ensure even mixing; Add the remaining defoamer and adjust the ink pH to the desired value using a pH adjuster. The final ink product is obtained by filtering with a 1μm filter.

[0035] The specific substances and their contents used in each embodiment and comparative example are described below. The content of each component is based on the total mass of the ink.

[0036] Example 1

[0037] Pigment Red 122 (TCR12204 / Hostaperm Red E3B): 5.0%, Benzyl Polyethylene Acrylate (Joncryl682 / Domestic BA-201): 3.0%, Propylene Glycol: 4.0%, Glycerin: 5.0%, Urea: 2.0%, Polyvinylpyrrolidone K80 (PVPK80, MW≈8000): 0.1%, Alkyl Sulfosuccinate (Disodium Lauryl Sulfosuccinate, DLS): 4.0%, Polyethylene Glycol PEG-400: 1.0%, Fatty Alcohol Polyoxyethylene Ether AEO-9 (Neodol 25-9, HLB=15): 0.3%, Span 80 (HLB=8): 0.2%, Preservative (BIT 20 / Kathon CG): 0.5%, Triethanolamine: 1.0%, Defoamer (BYK-024 / Domestic DF-103): 0.3%, Deionized water: Balance.

[0038] Preparation: Grind to D50=200nm, adjust pH=8.5.

[0039] Example 2

[0040] Naphthol Red (PR188, TCR18802 / Permanent Red HF3S): 8.0%, High Molecular Weight Polyurethane Dispersant (BYK-163 / NEO-1203): 4.0%, Propylene Glycol: 5.0%, Glycerin: 8.0%, Urea: 2.5%, Polyvinylpyrrolidone K90 (PVPK90): 0.15%, Oligomeric Glycol Alkyl Ether (Isotridecyl Polyoxyethylene Ether 1308): 5.0%, Polyethylene Glycol PEG-400: 1.2%, Polysorbate 80 (Tween 80, HLB=12): 0.4%, Fatty Alcohol Polyoxyethylene Ether AEO-3 (MOA-3 / Emulsifier FO, HLB=6): 0.3%, Preservative (BIT 20 / Kaison CG): 0.6%, Ammonia (25%): 1.2%, Defoamer (BYK-024 / Domestic DF-103): 0.35%, Deionized Water: Balance.

[0041] Preparation: Grind to D50=220nm, adjust pH=8.2.

[0042] Example 3

[0043] Azo Red (PR170, Permanent Red F5RK): 6.0%, Acrylic Dispersant (Dispex Ultra PX 4585 / EFKA 4585): 3.5%, Propylene Glycol: 4.5%, Glycerin: 6.0%, Urea: 2.2%, Polyvinylpyrrolidone K80 (PVP K80): 0.12%, Alkyl Sulfosuccinate (Disodium Lauryl Ether Sulfosuccinate, MES): 3.5%, Polyethylene Glycol PEG-400: 1.1%, Alkyl Glucoside APG-0810 (Glucopon 810, HLB=14): 0.35%, Alkylphenol Polyoxyethylene Ether OP-4 (OP-4, HLB=7): 0.25%, Preservative (BIT 20 / Kathon CG): 0.55%, Triethanolamine: 1.1%, Defoamer (BYK-024 / Domestic DF-103): 0.3%, Deionized Water: Balance.

[0044] Preparation: Grind to D50=210nm, adjust pH=8.4.

[0045] Example 4

[0046] Quinacridone Red (PR122, TCR12204): Naphthol Red (PR188, TCR18802) = 1:1:7.0%, Benzyl Polyethylene Acrylate (Joncryl 682 / Domestic BA-201): 3.8%, Propylene Glycol: 5.0%, Glycerin: 7.0%, Urea: 2.4%, Polyvinylpyrrolidone K85 (PVP K85): 0.14%, Oligomeric Glycol Alkyl Ether (Isotridecyl Polyoxyethylene Ether 1307): 4.5%, Polyethylene Glycol PEG-400: 1.3%, Polysorbate 80 (Tween 80, HLB=13): 0.38%, Span 80 (Span 80, HLB=7.5): 0.28%, Preservative (BIT 20 / Kaison CG): 0.58%, ammonia (25%): 1.15%, defoamer (BYK-024 / domestic DF-103): 0.32%, deionized water: balance.

[0047] Preparation: Grind to D50=215nm, adjust pH=8.3.

[0048] Example 5

[0049] Quinacridone Red (PR122, TCR12204): 4.0%, Acrylic Dispersant (Dispex 4585): Polyurethane Dispersant (BYK-163) = 1:1:3.2%, Propylene Glycol: 4.2%, Glycerin: 5.5%, Urea: 2.1%, Polyvinylpyrrolidone K80 (PVPK80): 0.10%, Alkyl Sulfosuccinate (DLS): Oligopolyethylene Glycol Alkyl Ether (1308) = 1:1:4.2%, Polyethylene Glycol PEG-400: 1.0%, AEO-9 (AEO-9, HLB=16): 0.32%, AEO-3 (AEO-3, HLB=9): 0.22%, Preservative (BIT 20 / Kathon CG): 0.52%, Triethanolamine: 1.05%, Defoamer (BYK-024 / Domestic DF-103): 0.28%, Deionized water: Balance.

[0050] Preparation: Grind to D50=210nm, adjust pH=8.4.

[0051] Comparative Example 1

[0052] Except for the absence of polyvinylpyrrolidone, it is the same as in Example 1.

[0053] Comparative Example 2

[0054] The humectant consists of 5% propylene glycol and 6% glycerin, and does not contain urea. The remaining components and preparation process are the same as in Example 1.

[0055] Comparative Example 3

[0056] The humectant is 11% propylene glycol, and it does not contain glycerin or urea. The remaining components and preparation process are the same as in Example 1.

[0057] Comparative Example 4

[0058] The humectant consists of 7% glycerin and 4% urea, and does not contain propylene glycol. The remaining components and preparation process are the same as in Example 1.

[0059] Comparative Example 5

[0060] Same as in Example 1, except that the dispersant was replaced with disodium sulfosuccinate monoester MS-60.

[0061] The components of the inks prepared in Examples 1-5 and Comparative Examples 1-5 are shown in Table 1. The units for the values ​​in the table are percent.

[0062] Table 1

[0063] The inks prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to performance tests after being kept at a constant temperature of 50°C for 30 days. Specifically, nib drying was tested by assessing whether ink could flow normally within a 100mm initial stroke; drying time was tested using the "perpetual character method"; color density was measured using an X-Rite eXact 2 color density meter; writing length was tested using a writing circle tester; and particle size was measured using a Malvern 2000 nanometer particle size analyzer. The test results are shown in Table 2.

[0064] Table 2

[0065] Test results show that the red neutral ink provided by this invention exhibits excellent performance in terms of anti-settling, moisturizing, and quick-drying properties, significantly superior to the comparative examples. Specifically, after 30 days of storage, the pigment particles in the inks of Examples 1-5 showed virtually no aggregation; while the inks of Comparative Examples 1-4 all showed varying degrees of aggregation after 30 days of storage. Further comparison of Example 1 and Comparative Example 1 reveals that when the ink does not contain polyvinylpyrrolidone, slight stratification occurs, the nib drying time is significantly shortened, but the overall drying time increases significantly, the writing length is significantly shortened, and aggregation is more severe. Comparing Example 1 and Comparative Examples 2-4, it can be seen that when the content of the moisturizer in the ink is the same, at 11%, the ink's performance is significantly better than other moisturizers (Comparative Examples 2-4) when the moisturizer is a combination of propylene glycol, glycerin, and urea. This demonstrates that the ink of this invention uses a combination of propylene glycol, glycerin, and urea as a moisturizer, and the synergistic effect among these three components results in superior ink performance. Comparing Example 1 and Comparative Example 5, it can be seen that when other substances are used as the dispersant, the various properties of the ink also decrease significantly. This demonstrates that the present invention, through component optimization and process innovation, has successfully developed a pigment-based red neutral ink that combines anti-settling properties, excellent moisturizing properties, and quick-drying properties. This ink solves the key problem of poor dispersion stability of red pigments in the system, while ensuring smooth writing and vibrant color, and has broad market prospects.

[0066] It should be noted that although the present invention has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and various equivalent changes or substitutions can be made without departing from the spirit of the present invention. Therefore, any changes or modifications to the above embodiments within the scope of the essential spirit of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A pigment type red neutral ink, characterized by, by mass, comprising the following components: red organic pigment 2-10%, dispersant 0.5-7%, humectant 5-25%, polyvinylpyrrolidone 0.05-0.2%, penetrant 1-10%, preservative 0.1-1.5%, pH adjuster 0.1-4%, antifoaming agent 0.1-0.5%, and the balance deionized water.

2. The pigment-based red neutral ink according to claim 1, characterized by, The red organic pigment is selected from one or more of quinacridone red, naphthol red, and azo red organic pigments, and the D50 particle size of the pigment particles is less than 250 nm.

3. The pigment-based red neutral ink according to claim 1 or 2, characterized in that, The dispersant is at least one of polyethylene-benzyl acrylate, high molecular weight polyurethane dispersant, or acrylic dispersant.

4. The pigment-based red neutral ink according to any one of claims 1 to 3, characterized in that, The humectant includes propylene glycol, glycerol, and urea; the propylene glycol in the pigment-based red neutral ink accounts for 2-6%, and the urea accounts for 1.5-3%.

5. The pigment-based red neutral ink according to any one of claims 1 to 4, characterized in that, The penetrant is at least one of an alkyl sulfosuccinate compound and an oligomeric glycol alkyl ether compound; and / or The weight average molecular weight of the polyvinylpyrrolidone is between 8000-12000.

6. The pigment-based red neutral ink according to any one of claims 1 to 5, characterized in that, Further comprising a surfactant combination of a first surfactant and a second surfactant, the HLB value of the first surfactant being 10-18, and the HLB value of the second surfactant being 5-10; Preferably, the first surfactant is selected from one or more of fatty alcohol polyoxyethylene ether AEO-9, polysorbate 80, and alkyl glycoside; and / or Preferably, the second surfactant is selected from one or more of sorbitan monooleate, fatty alcohol polyoxyethylene ether AEO-3, and alkyl phenol polyoxyethylene ether OP-4; More preferably, the first surfactant accounts for 0.3-0.4% and the second surfactant accounts for 0.2-0.3% in the pigment-based red neutral ink.

7. The pigment-based red neutral ink according to any one of claims 1 to 6, characterized in that, The pigment-based red neutral ink further comprises 0.5-1.5% of polyethylene glycol; preferably, the weight average molecular weight of the polyethylene glycol is between 400-1000.

8. The pigment-based red neutral ink according to any one of claims 1 to 7, wherein The pH value of the pigment-based red neutral ink is maintained at 7.5-9.

0.

9. A method for producing the pigment-based red neutral ink according to any one of claims 1 to 8, characterized by, Comprising: Mixing the red organic pigment, dispersant, part of the antifoaming agent, and part of the deionized water, grinding the red organic pigment to a D50 particle size of less than 250 nm to obtain a pigment slurry; Mixing the humectant, polyvinylpyrrolidone, penetrant, preservative, pH adjuster, and the remaining deionized water uniformly under stirring to form a base solution; Slowly adding the pigment slurry to the base solution, and continuously stirring until uniformly mixed; Adding the remaining antifoaming agent, adjusting the pH value, and filtering to obtain the pigment-based red neutral ink.

10. A ballpoint pen characterized by comprising: Comprising the pigment-based red neutral ink of any one of claims 1-8.

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