Pigment type quick-drying gel ink

Abstract

The invention relates to pigment type quick-drying gel ink which has the characteristics of short stitch drying time and excellent leakage resistance. A three-dimensional network structure viscosity system of the gel ink is constructed by adopting the hydrophobic modified acrylic acid thickener and the maleic anhydride grafted modified SEBS elastomer, the viscosity is stable, meanwhile, the effect of preventing ink droplet separation is achieved, and the problems of pen point ink accumulation and ink dripping of the low-viscosity pigment type quick-dry gel ink are effectively solved.

Description

Technical Field

[0001] The invention relates to a pigment-type quick-drying neutral ink for a ballpoint pen. Background Art

[0002] In order to better meet the needs of consumers and enhance the user experience, the rapid drying of neutral ink ballpoint pen lines has become a unanimous pursuit of ink manufacturers in the industry. The use of surfactants to improve the permeability of ink and thus accelerate drying is a common method. Patent ZL201880069657.X uses surfactants containing acetylene bonds or silicone-based surfactants to accelerate the penetration of ink to achieve a quick-drying effect. Patent ZL202310808860.7 copolymerizes 3-(methacryloyloxy)propyltrimethoxysilane with a variety of acrylic monomers to obtain a modified acrylic emulsion for use in neutral inks. The leveling effect of the modified acrylic resin side chain organosiloxane is used to improve the penetration of the system, resulting in a quick-drying neutral ink that does not bleed paper. The above technical solution of using surfactants to improve the permeability of ink and thus achieve a quick-drying effect of lines, because the use of surfactants that promote ink permeability greatly reduces the surface tension of the ink, so that the ink wetting of the pen ball is also significantly enhanced. When the pen tip is left standing with the pen tip facing down, it is very easy to form ink accumulation or even ink dripping and other ink leakage problems. Therefore, patent ZL201880069657.X further adds organic resin particles to inhibit the sagging of ink and improve the ink leakage problem.

[0003] The pigment-based quick-drying neutral ink disclosed in patent ZL201710162127.7 uses a relatively low surface tension to promote the penetration of the traces. By using a combination of a high thixotropic index thickener and a low thixotropic index thickener, it is convenient to control the spreading speed and ink output, ultimately achieving the purpose of quick drying of the traces, avoiding sacrificing other application properties such as writing feel, cap removal time, and ink dripping (leakage resistance). This patent uses a relatively low surface tension to avoid the ink leakage problem caused by too low surface tension. By using a high thixotropic index thickener A to reduce the viscosity of the neutral ink when spreading on the paper in the medium shear rate range, it is conducive to the rapid spreading of the traces; by using a low thixotropic index thickener B to increase the viscosity of the high shear rate range, that is, when the ink is close to the writing state, the amount of ink output of the line is controlled to avoid the ink output being too large and difficult to dry. As we all know, the viscosity of neutral ink is affected by the thickener in addition to the various additives in the formula. The above-mentioned demand for precise control of the ink viscosity is usually difficult to achieve in actual production, which is not conducive to mass production. In addition, the viscosity of neutral ink tends to change with prolonged storage time, making it difficult to ensure a stable quick-drying effect. Summary of the Invention

[0004] The present invention aims to overcome the deficiencies of the prior art and provide a pigment-based quick-drying neutral ink that does not leak.

[0005] The object of the present invention is achieved through the following solutions:

[0006] A pigment-based quick-drying neutral ink comprises, by weight, 20.0 to 30.0 parts of aqueous pigment paste, 10.0 to 20.0 parts of humectant, 0.5 to 1.5 parts of thickener, 0.5 to 1.0 parts of lubricant, 0.5 to 1.0 parts of surfactant, 0.5 to 1.0 parts of rheology regulator, 0.1 to 0.5 parts of pH regulator, 0.5 to 1.0 parts of bactericide, and 45.0 to 66.0 parts of deionized water.

[0007] The thickener is a hydrophobically modified acrylic resin.

[0008] In an aqueous environment, hydrophobically modified acrylic resin forms a three-dimensional network structure through the association of hydrophobic groups. The carboxylate ions on the acrylic resin backbone combine with free water, integrating the ink system. Adding a small amount of hydrophobically modified acrylic resin to neutral ink can achieve an appropriate viscosity. The formation of this three-dimensional network structure helps prevent ink accumulation and dripping caused by ink droplet detachment.

[0009] The rheology modifier is maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS).

[0010] The grafting rate of the maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS) is 5.0-10.0%, and the weight average molecular weight is 50,000-100,000.

[0011] When maleic anhydride-grafted SEBS elastomer is dispersed in water, maleic anhydride hydrolyzes to form maleic acid, which further reacts with a pH adjuster to form carboxylate ions. The hydrophilic nature of the carboxylate ions imparts excellent water dispersibility to the maleic anhydride-grafted SEBS elastomer. On the one hand, the SEBS elastomer backbone acts as hydrophobic particles, providing numerous binding sites for the thickener's hydrophobically modified acrylic acid molecules to bind, strengthening the three-dimensional network structure. On the other hand, the SEBS elastomer hydrophobic particles dispersed in the ink produce a "Coanda effect": once the ink begins to flow, it tends to migrate along the surface of the hydrophobic particles. The large number of hydrophobic particles distributed throughout the ink results in the ink being locked around each hydrophobic particle, significantly suppressing ink accumulation and dripping caused by droplet detachment.

[0012] SEBS elastomer is a hydrophobic polymer that cannot be dispersed in an aqueous phase. Maleic anhydride is used to graft-modify it to achieve good water dispersibility. When the grafting rate is less than 5.0%, good water dispersibility cannot be achieved. The SEBS elastomer is not hydrophilic enough and easily aggregates to form large aggregates. During the writing process, the aggregates gradually accumulate and clog the ink outlet channel inside the pen tip, causing poor writing. When the grafting rate is greater than 10.0%, the graft-modified SEBS elastomer (MA-g-SEBS) is too hydrophilic, which weakens its role in providing binding sites for the hydrophobically modified acrylic resin thickener, and the effect of improving leakage resistance is limited.

[0013] When the weight-average molecular weight of maleic anhydride-grafted modified SEBS elastomer (MA-g-SEBS) is less than 50,000, it is difficult to achieve a significant "Coanda effect," and the effect of suppressing ink droplet shedding is not obvious. When the weight-average molecular weight of maleic anhydride-grafted modified SEBS elastomer (MA-g-SEBS) is greater than 100,000, the SEBS elastomer particles are too large to easily aggregate in the narrow gap of the pen tip, resulting in poor ink flow.

[0014] The moisturizing agent is one or a mixture of two or more of propylene glycol, glycerol, polyethylene glycol 400, sorbitol and xylitol.

[0015] The lubricant is one of fatty alcohol polyoxyethylene ether phosphate or alkylphenol polyoxyethylene ether phosphate.

[0016] The surfactant is polyether-modified siloxane.

[0017] The pH regulator is an organic alkaline substance.

[0018] The bactericide is one of isothiazolinone substances or benzisothiazolinone substances.

[0019] The water-based pigment paste is a commercially available carbon black paste or an organic pigment paste, and is generally required to have a volume distribution particle size D90 < 300 nm.

[0020] The pigment-based quick-drying neutral ink has a viscosity of 800 to 1600 cp at a rotational speed of 6 rpm using a No. 2 rotor of a rotational viscometer.

[0021] Lowering the viscosity of gel ink directly increases the ink's overall spreading speed on paper, leading to faster drying. When the viscosity exceeds 1600 cp at 6 rpm using a rotational viscometer with a No. 2 rotor, the spreading speed of the gel ink is not effectively increased, making it difficult to achieve satisfactory quick-drying results. However, when the viscosity falls below 800 cp at 6 rpm using a rotational viscometer with a No. 2 rotor, good leak resistance is difficult to achieve even with the addition of a rheology modifier.

[0022] The pigment-based quick-drying neutral ink of the present invention can be prepared by a disclosed method, which generally comprises the following steps:

[0023] Deionized water, a moisturizer, a lubricant, a surfactant, a pH adjuster, and a fungicide were added to a stirring vessel according to the formula and mixed evenly. While stirring, a thickener (a hydrophobically modified acrylic resin) was added, followed by a rheology modifier, and finally, a water-based pigment paste. Stirring was continued until all materials were evenly mixed. The ink prepared above was filtered through a 1000-mesh filter bag to obtain a filtrate, which was then vacuum degassed to obtain a pigment-based quick-drying neutral ink.

[0024] Compared with the prior art, the pigment-based quick-drying neutral ink of the present invention has the following advantages:

[0025] There is no need to strictly control parameters such as the viscosity and surface tension of the pigment-based neutral ink at different shear rates and the ink output of the neutral ink ballpoint pen made using the above-mentioned pigment-based neutral ink. A satisfactory quick-drying effect can be easily achieved by adopting a low-viscosity solution.

[0026] The hydrophobically modified acrylic thickener and maleic anhydride grafted modified SEBS elastomer are used to construct a stable three-dimensional network structure, which has stable viscosity and the effect of preventing ink droplets from detaching, effectively solving the problems of ink accumulation and dripping on the pen tip of low-viscosity pigment-based quick-drying neutral ink. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the anti-leakage mechanism of the pigment-based quick-drying neutral ink of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below based on specific embodiments. The protection scope of the present invention is not limited to the following embodiments, which are listed for illustrative purposes only and do not limit the present invention in any way.

[0029] Example

[0030] The "parts" in the examples all refer to "parts by mass".

[0031] Example 1

[0032] The preparation of the pigment-based quick-drying neutral ink of this embodiment includes the following steps:

[0033] 10.0 parts of sorbitol (a moisturizer), 1.0 part of fatty alcohol polyoxyethylene ether phosphate (a lubricant), 0.5 part of polyether-modified siloxane (a surfactant), 0.2 part of an organic base (a pH regulator), and 1.0 part of isothiazolinone (a fungicide) were added to 65.8 parts of deionized water and stirred uniformly. 1.0 part of a hydrophobically modified acrylic resin (a thickener) was added under stirring, followed by 0.5 part of a maleic anhydride-grafted modified SEBS elastomer (MA-g-SEBS) (grafting rate 5.0%, weight-average molecular weight 50,000) as a rheology modifier. Finally, 20.0 parts of a black water-based pigment paste was added, and stirring was continued until all materials were uniformly mixed. The ink prepared above was filtered through a 1000-mesh filter bag to obtain a filtrate, which was then vacuum degassed to obtain a black neutral ink.

[0034] Example 2

[0035] The preparation of the pigment-based quick-drying neutral ink of this embodiment includes the following steps:

[0036] 15.0 parts of polyethylene glycol 400, 0.7 part of lubricant alkylphenol polyoxyethylene ether phosphate, 0.7 part of surfactant polyether-modified siloxane, 0.2 part of pH adjusting agent organic base, and 0.7 part of bactericide benzisothiazolinone are added into 56.0 parts of deionized water, after stirring, 1.0 part of thickener hydrophobically modified acrylic resin is added under stirring, then 0.7 part of rheology modifier maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS) (grafting rate 7.5%, weight-average molecular weight 80000) is added, and finally 25.0 parts of blue water-based pigment paste are added, stirring is continued until all materials are evenly mixed, and stirring ends. The above-mentioned ink obtained is filtered through a 1000 mesh filter bag to obtain a filtrate, and then vacuum deaeration is carried out to obtain a blue neutral ink.

[0037] Example 3

[0038] The preparation of the pigment-based quick-drying neutral ink of this embodiment includes the following steps:

[0039] 20.0 parts of glycerol, 0.5 parts of lubricant alkylphenol polyoxyethylene ether phosphate, 1.0 parts of surfactant polyether-modified siloxane, 0.2 parts of pH adjusting agent organic base, and 0.5 parts of bactericide benzisothiazolinone are added to 45.8 parts of deionized water, and after stirring, 1.0 parts of thickener hydrophobically modified acrylic resin are added under stirring, and then 1.0 parts of rheology modifier maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS) (grafting rate 10.0%, weight-average molecular weight 100000) are added, and finally 30.0 parts of red water-based pigment paste are added, and stirring is continued until all materials are uniformly mixed. The above-mentioned ink obtained is filtered through a 1000 mesh filter bag to obtain a filtrate, and then vacuum deaeration is performed to obtain a red neutral ink.

[0040] Comparative Example 1

[0041] Compared with Example 1, the amount of thickener was reduced from 1.0 part to 0.8 part, and deionized water was increased by 0.2 part accordingly. The mass and preparation process of other auxiliary agents were the same as those in Example 1.

[0042] Comparative Example 2

[0043] Compared with Example 2, 0.7 parts of rheology modifier and 0.1 parts of pH modifier were replaced by 0.8 parts of deionized water. The masses and preparation processes of other additives were the same as those in Example 2.

[0044] Comparative Example 3

[0045] Compared with Example 3, the amount of thickener was increased from 1.0 part to 1.2 parts, and 0.2 parts of deionized water was deducted accordingly. The masses and preparation processes of other additives were the same as those in Example 3.

[0046] Comparative Example 4

[0047] Compared with Example 2, 1.0 part of rheology modifier was not added, 0.6 part of thickener was added, and 0.4 part of deionized water was added accordingly. The amounts of other additives and the preparation process were the same as in Example 2.

[0048] Comparative Example 5

[0049] Compared with Example 2, the grafting rate of the rheology modifier maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS) is 4.0%, and the weight average molecular weight is 80000. The amounts of other additives and the preparation process are the same as those in Example 2.

[0050] Comparative Example 6

[0051] Compared with Example 2, the grafting rate of the SEBS elastomer modified with maleic anhydride grafted with rheology modifier (MA-g-SEBS) was 12.0%, and the weight average molecular weight was 80000. The amounts of other additives and the preparation process were the same as those in Example 2.

[0052] Comparative Example 7

[0053] Compared with Example 2, the grafting rate of the SEBS elastomer modified with maleic anhydride grafted with rheology modifier (MA-g-SEBS) is 7.5%, and the weight average molecular weight is 40000. The amounts of other additives and the preparation process are the same as those in Example 2.

[0054] Comparative Example 8

[0055] Compared with Example 2, the grafting rate of the SEBS elastomer modified with maleic anhydride grafted with rheology modifier (MA-g-SEBS) is 7.5%, and the weight average molecular weight is 120000. The amounts of other additives and the preparation process are the same as those in Example 2.

[0056] The weight percentages of each additive in the Examples and Comparative Examples are shown in Table 1.

[0057] Table 1 Mass fractions of each auxiliary agent in Examples and Comparative Examples

[0058]

[0059] Viscosity test

[0060] The viscosity of the pigment-based neutral ink of the embodiment and the comparative example was tested at a rotation speed of 6 rpm using a No. 2 rotor of a rotational viscometer. The data are shown in Table 2.

[0061] Table 2 Viscosity data of pigment-based neutral inks of Examples and Comparative Examples

[0062] serial number 6rpm viscosity (cp) Example 1 892 Example 2 1246 Example 3 1580 Comparative Example 1 745 Comparative Example 2 924 Comparative Example 3 1780 Comparative Example 4 1250 Comparative Example 5 1324 Comparative Example 6 1226 Comparative Example 7 1328 Comparative Example 8 1168

[0063] The viscosity of the neutral inks of the examples and comparative examples at a rotation speed of 6 rpm was tested using a rotational viscometer. The viscosity of the pigment-based quick-drying neutral ink of the example is in the range of 800 to 1600 cp. The viscosity of the neutral ink of comparative example 1 is less than 800 cp. The viscosity of the neutral ink of comparative example 2 is lower than that of the neutral ink of example 2, indicating that the rheology regulator has a certain thickening effect. The viscosity of the neutral ink of comparative example 3 is greater than 1600 cp. Compared with example 2, comparative example 4 does not add a rheology regulator, but adds 0.3 parts of thickener, and its viscosity is similar to that of the neutral ink of example 2. The viscosity of the neutral ink of comparative example 5 is slightly greater than that of the neutral ink of example 2. The viscosity of the neutral ink of comparative example 6 is slightly less than that of the neutral ink of example 2. It can be seen that the smaller the grafting rate of the rheology regulator maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS), the stronger the association effect it can provide for the thickener, and the greater the viscosity of the neutral ink. The viscosity of the neutral ink in Comparative Example 7 is slightly higher than that in Example 2. The viscosity of the neutral ink in Comparative Example 8 is slightly lower than that in Example 2. This is because, given the same mass, a lower weight-average molecular weight of the rheology modifier results in a greater number of SEBS elastomer particles, providing more association points and, consequently, a higher viscosity of the resulting neutral ink. A higher weight-average molecular weight of the SEBS elastomer results in a lower viscosity of the resulting neutral ink.

[0064] Application performance testing

[0065] The pigment-based neutral inks prepared in the Examples and Comparative Examples were used to make neutral ink ballpoint pen refills using commercially available nibs (typically 0.5 mm diameter balls), connectors, oil tubing (2.75 mm inner diameter), sheaths, and tail plugs. After centrifugation, refills that opened normally were selected for application performance testing. Writing performance and line drying time tests were conducted in accordance with the requirements of GB / T 37853-2019, "Neutral Ink Ballpoint Pens and Refills." Leakage resistance tests were conducted in accordance with the requirements of QB / T 5255-2018, "Technical Specifications for Matching Ballpoint Pen Nibs and Inks." The test results are shown in Table 3.

[0066] The specific method of the line drying time test is as follows: load the pen core to be tested on a circular writing machine to draw a spiral line. Start the stopwatch to count to a certain time when the line is finished. Cover the end of the line with writing paper of the same properties. Use a 500g special weight (bottom diameter 50mm) to press on the surface of the covering paper. Separate the two papers after 10 minutes. If there is no ink mark on the covering paper, gradually reduce the time after the line is finished to X seconds. If it is found that ink marks just appear on the covering paper, the line drying time of the pen core to be tested is X seconds.

[0067] The specific method of leak resistance test is: in the test environment of ambient temperature 20-25℃ and relative humidity 50-60%, take 50 pen refills, remove the sheaths, and place the pen tips vertically downwards on the pen holder for 24 hours. Then check the ink accumulation and ink dripping of the pen tips. The leakage resistance of the pen refills is judged based on the ratio of ink accumulation to ink dripping:

[0068] a) Ink accumulation: Ink accumulates in the front cone of the pen tip, but no ink drips;

[0069] b) Ink dripping - ink dripping.

[0070] Evaluation criteria: No ink accumulation and ink dripping, leakage resistance is excellent; no ink dripping, and the ink accumulation ratio is ≤10%, leakage resistance is qualified; there is ink dripping or the ink accumulation ratio is greater than 10%, leakage resistance is unqualified.

[0071] Table 3 Application performance test of neutral ink ballpoint pen refills prepared with neutral ink in Examples and Comparative Examples

[0072]

[0073] The writing performance of the neutral ink ballpoint pen refills made with the pigment-type neutral ink in Examples 1 to 3 all meets the requirements of "Neutral Ink Ballpoint Pens and Refills" (GB / T 37853-2019), and the line drying time is less than 4s, which meets the industry requirements for pigment-type quick-drying neutral ink (usually required not to exceed 4s), and the leakage resistance is excellent.

[0074] The drying time of the neutral ink line of Comparative Example 1 meets the requirements of pigment-type quick-drying neutral ink. Although a rheology regulator was added, the ink viscosity was relatively low, so the leakage resistance was unqualified. The drying time of the neutral ink line of Comparative Example 2 meets the requirements of pigment-type quick-drying neutral ink, but the leakage resistance was too poor. The drying time of the neutral ink line of Comparative Example 3 was 10s, which did not meet the requirements of pigment-type quick-drying neutral ink. The drying time of the neutral ink line of Comparative Example 4 met the requirements of pigment-type quick-drying neutral ink. Although the viscosity was similar to that of Example 2, the leakage resistance was unqualified. It can be seen that the addition of the rheology regulator effectively improved the leakage resistance of the neutral ink. The drying time and leakage resistance of the neutral ink of Comparative Example 5 were qualified, but the writing performance was unqualified. This is because the grafting rate of the rheology regulator maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS) was relatively small, the hydrophilicity of the SEBS elastomer was insufficient, the dispersibility in the ink was poor, and it aggregated to form large particles. During the writing process, it gradually accumulates inside the pen tip and blocks the ink outlet channel, causing the line trace to become lighter, and even broken lines to occur. The writing performance and line trace drying time of the neutral ink of Comparative Example 6 are qualified, and the leakage resistance is qualified, but not excellent, that is, there is still a certain proportion of ink accumulation in the pen tip. The writing performance and line trace drying time of the neutral ink of Comparative Example 7 are qualified, and the leakage resistance is worse than that of Example 2. The line trace drying time and leakage resistance of the neutral ink of Comparative Example 8 are qualified, but the writing performance is unqualified. This is because the weight-average molecular weight of the rheology regulator maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS) is too large, and the dispersion stability in the ink is insufficient, and it gradually aggregates to form large particles that block the ink outlet channel.

[0075] In summary, the pigment-type neutral ink in the embodiment controls the viscosity within an appropriate low viscosity range (800-1600cp), and the line drying time meets the requirements of pigment-type quick-drying neutral ink. The grafting rate of the rheology regulator maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS) is 5.0-10.0%, and the weight-average molecular weight is 50,000-100,000. When combined with the hydrophobically modified acrylic thickener, it effectively improves the leakage resistance of the low-viscosity pigment-type quick-drying neutral ink, solves the defects of ink accumulation and ink dripping at the pen tip, and the writing performance is normal.

[0076] Those skilled in the art should note that the embodiments described in the present invention are merely exemplary and that various other substitutions, changes, and improvements may be made within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A pigment-based quick-drying neutral ink, characterized in that: In parts by mass, the pigment-based quick-drying neutral ink contains: 20.0 to 30.0 parts of aqueous pigment paste, 10.0 to 20.0 parts of moisturizer, 0.5 to 1.5 parts of thickener, 0.5 to 1.0 parts of lubricant, 0.5 to 1.0 parts of surfactant, 0.5 to 1.0 parts of rheology regulator, 0.1 to 0.5 parts of pH regulator, 0.5 to 1.0 parts of bactericide and 45.0 to 66.0 parts of deionized water.

2. The pigment-based quick-drying neutral ink according to claim 1, characterized in that: The thickener is a hydrophobically modified acrylic resin; and the rheology regulator is a maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS).

3. The pigment-based quick-drying neutral ink according to claim 1 or 2, characterized in that: The maleic anhydride grafted modified SEBS elastomer (MA-g-SEBS) has a grafting rate of 5.0-10.0% and a weight-average molecular weight of 50,000-100,000.

4. The pigment-based quick-drying neutral ink according to claims 1 to 3, characterized in that: The moisturizing agent is one or a mixture of two or more of propylene glycol, glycerol, polyethylene glycol 400, sorbitol and xylitol.

5. The pigment-based quick-drying neutral ink according to claims 1 to 3, characterized in that: The lubricant is one of fatty alcohol polyoxyethylene ether phosphate or alkylphenol polyoxyethylene ether phosphate.

6. The pigment-based quick-drying neutral ink according to claims 1 to 3, characterized in that: The surfactant is polyether-modified siloxane.

7. The pigment-based quick-drying neutral ink according to claims 1 to 3, characterized in that: The pH regulator is an organic alkaline substance.

8. The quick-drying neutral ink according to claims 1 to 3, characterized in that: The bactericide is one of isothiazolinone substances or benzisothiazolinone substances.

9. The quick-drying pigment-based neutral ink according to claims 1 to 8, characterized in that: The pigment-based quick-drying neutral ink has a viscosity of 800 to 1600 cp at a rotational speed of 6 rpm using a No. 2 rotor of a rotational viscometer.

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