WRITING GEL INK

Abstract

The present disclosure concerns non-aqueous gel writing ink including a solvent, a coloring agent and a gelling agent, in which the gelling agent is a mixture of silica particles and of a fatty acid amide wax. It also concerns the process of preparation of the non-aqueous gel writing ink and the use of a mixture of silica particles and of a fatty acid amide wax, as a gelling agent in a non-aqueous gel writing ink. It finally concerns a writing instrument containing the ink according to the present disclosure.

Claims

1. A non-aqueous gel writing ink comprising a solvent, a coloring agent and a gelling agent, wherein the gelling agent comprises a mixture of silica particles and of a fatty acid amide wax.

2. A non-aqueous gel writing ink according to claim 1, wherein the fatty acid amide wax comprises octadecanamide of the following formula ##STR00010##

3. A Non-aqueous gel writing ink according to claim 1, wherein the fatty acid amide wax is a mixture of the three following fatty acid amide waxes: octadecanamide of the following formula ##STR00011## N,N′-Ethylene-bis-12-hydroxystearamide of the following formula CH.sub.3(CH.sub.2).sub.5CHOH(CH.sub.2).sub.10CONH(CH.sub.2).sub.2NHCO(CH.sub.2).sub.10CHOH(CH.sub.2).sub.5CH.sub.3 and N,N′-Ethylenebis(caprinamide) of the following formula CH.sub.3(CH.sub.2).sub.8CONH(CH.sub.2).sub.2NHCO(CH.sub.2).sub.8CH.sub.3.

4. A non-aqueous gel writing ink according to claim 1, wherein the fatty acid amide wax is a mixture of three fatty acid amide waxes obtained by the reaction between ethylene diamine, decanoic acid and 12-hydroxystearic acid.

5. A non-aqueous gel writing ink according to claim 1, wherein the gelling agent content is in the range 0.1-1.2%, by weight, relative to the total weight of the ink.

6. A non-aqueous gel writing ink according to claim 1, wherein the solvent is chosen in the group consisting of glycol ether, alcohol, and mixture thereof.

7. A non-aqueous gel writing ink according to claim 1, wherein the solvent content is between 35 and 80% by weight, relative to the total weight of the ink.

8. A non-aqueous gel writing ink according to claim 1, wherein the coloring agent is a dye.

9. A non-aqueous gel writing ink according to claim 1, wherein the coloring agent content is between 5 and 30% by weight relative to the total weight of the ink.

10. A non-aqueous gel writing ink according to claim 1, wherein it contains additives.

11. A non-aqueous gel writing ink according to claim 1, wherein its viscosity measured at 20° C. with a cone-and-plate rheometer is of between 20 000 and 100 000 mPa.Math.s, with a shear rate of 0.01 s.sup.−1 and between 1500 and 15 000 mPa.Math.s, with a shear rate of 100 s.sup.−1.

12. A non-aqueous gel writing ink according to claim 1, wherein its viscosity is stable during storage for at least three months at 40° C. and 80% relative humidity.

13. Process for manufacturing a non-aqueous gel writing ink according to claim 1, wherein the fatty acid amide wax is activated by formation of a premix in a solvent, at a temperature of between 30 and 70° C., with a shear rate of between 20 and 25 m/s, before its addition in the writing ink containing the solvent, the silica particles and the coloring agent.

14. Process for manufacturing the non-aqueous gel writing ink according to claim 13, wherein the premix is added to the ink at a temperature of between 50 and 60° C.

15. (canceled)

16. A writing instrument containing a non-aqueous gel writing ink according to 1.

17. A writing instrument according to claim 16, wherein the fatty acid amide wax comprises octadecanamide of the following formula ##STR00012##

18. A non-aqueous gel writing ink according to claim 1, wherein the gelling agent comprises a mixture of hydrophilic silica particles and of a fatty acid amide wax.

19. A non-aqueous gel writing ink according to claim 1, wherein the gelling agent content is in the range 0.15-0.60%, by weight, relative to the total weight of the ink.

20. A non-aqueous gel writing ink according to claim 6, wherein the solvent is phenoxyethanol.

21. A non-aqueous gel writing ink according to claim 10, wherein the additives are chosen in the group consisting of thickening agents, clear drain agents, viscosity imparting agent, lubricant, dispersing agent and mixture thereof.

Description

EXAMPLE 1: INK COMPOSITION ACCORDING TO THE PRESENT DISCLOSURE

[0066] Table 1 below contains the composition of an ink according to the present disclosure.

TABLE-US-00001 TABLE 1 Content Trade name Chemical name Function in wt. % Phenoxyethanol(EPH) Phenoxyethanol solvent 52.3 Aerosil 200 ® Fumed silica GELING agent 0.4 Solvent Black 46 ® Solvent black 46 dye 25 Lonzest SOC ® Sorbitan Clear drain 1.3 Sesquioleate agent Ketonic Resin Resin Viscosity agent 13.5 CRAYVALLAC fatty acid amide GELING 7.5 SUPER ® wax at 5% in AGENT phenoxyethanol Total 100
The viscosity of the ink is as follow:

[0067] 50 0000 mPa.Math.s at 20° C. with a shear rate of 0.01 s.sup.−1

[0068] 2000 mPa.Math.s at 20° C. with a shear rate of 100 s.sup.−1

The ink has been prepared by first activating the fatty acid amide wax (CRAYVALLAC SUPER®) by preparing a premix as follow:
Addition of 5% by weight of CRAYVALLAC SUPER® in phenoxyethanol at a temperature of 60° C. by using a stator/rotor disperser with a shear rate of between 20 and 25 m/s.
This process allows the activation of CRAYVALLAC SUPER® in order for it to adequately play its gelling agent function.
The premix has the following viscosity at 20° C.:

[0069] more than 2 million mPa.Math.s at a shear rate of 0.01 s.sup.−1,

[0070] about 1100 mPa.Math.s at a shear rate of 100 s.sup.−1 and

[0071] about 230 mPa.Math.s at a shear rate of 1000 s.sup.−1.

To obtain this premix, the dispersion time is 50 minutes by using a stator/rotor disperser with a shear rate of between 20 and 25 m/s.
Contacting the premix with the ink formulation is carried out at a temperature of between 50 and 60° C. in order to obtain the best compromise between the immediate return to the rest viscosity after writing and storage for three months at 40° C. and 80% relative humidity.

EXAMPLE 2: COMPARISON BETWEEN THE GELLING AGENT ACCORDING TO THE DISCLOSURE AND OTHER GELLING AGENTS

[0072] The viscosity at rest (0.01 s.sup.−1/20° C.) of the mixture of solvent+dye has been compared with the viscosity of the same mixture+0.5% gelling agent. 3 gelling agents have been compared:

[0073] CRAYVALLAC SUPER® containing octadecanamide (the fatty acid amide wax according to the present disclosure) which has been activated by preparing a premix as indicated in example 1;

[0074] Thixatrol MAX® from Elementis (which is a mixture of N,N′-ethane-1,2-diylbis(hexanamide) (or N,N′-Ethylenebis(capronamide)), 12-hydroxy-N-[2-[(1-oxyhexyl)amino]ethyl]octadecanamide and N,N′-ethane-1,2-diylbis(12-hydroxy octadecanamide) having the respective following formula: CH.sub.3(CH.sub.2).sub.4CONH(CH.sub.2).sub.2NHCO(CH.sub.2).sub.4CH.sub.3 CH.sub.3(CH.sub.2).sub.4CONH(CH.sub.2).sub.2NHCO(CH.sub.2).sub.10CHOH(CH.sub.2).sub.5CH.sub.3 and CH.sub.3(CH.sub.2).sub.5CHOH(CH.sub.2).sub.10CONH(CH.sub.2).sub.2NHCO(CH.sub.2).sub.10CHOH(CH.sub.2).sub.5CH.sub.3) (another fatty acid amide wax according to the disclosure). It has been activated by preparing a premix as follow: addition of 3% by weight of Thixatrol MAX® in phenoxyethanol at a temperature of 50° C. by using a stator/rotor disperser with a shear rate of between 20 and 25 m/s.

[0075] CRAYVALLAC MT® from ARKEMA which is a castor oil modified polyamide (comparative gelling agent). It has been activated by preparing a premix as follow: addition of 2.8% by weight of CRAYVALLAC MT® in phenoxypropanol at a temperature of 60° C. by using a stator/rotor disperser with a shear rate of between 20 and 25 m/s.

The results are given in the following Table 2:

TABLE-US-00002 TABLE 2 Rest viscosity (0.01 s.sup.−1/20° C.) Ink color Black Blue Red Green Pink Mix of dyes Triarylmethane + Triarylmethane + Xanthene + Phtalocyanine + Xanthene Azoic Phtalocyanine Azoic Azoic Viscosity of 2500 mPa .Math. s 2200 mPa .Math. s 6270 mPa .Math. s 4200 mPa .Math. s 1200 mPa .Math. s solvent + dyes solution Increase of + − + − +++ rest viscosity with 0.5% CRAYVALLAC MT ® Increase of ++ ++ ++ + +++ rest viscosity with 0.5% THIXATROL MAX ® Increase of +++ +++ +++ +++ +++ rest viscosity with 0.5% CRAYVALLAC SUPER ® −: no viscosity change +: +1000 to + 5000% rest viscosity ++: +5000 to + 10 000% rest viscosity +++: >+10 000% rest viscosity Crayvallac MT ® allows creating a good network only with pink ink and creates a poor network with black & red inks and no network at all with blue and green inks.
Therefore it cannot be used as a gelling agent according to the present disclosure.
Thixatrol MAX® and Crayvallac Super® provide a good gelling network, the strength of the gelling network being better with Crayvallac Super®, whatever the type of dye used.

[0076] The initial viscosity at rest (0.01 s.sup.−1/20° C.), the shear viscosity at 100 s.sup.−1 and the immediate rest return (0.01 s.sup.−1) at 20° C. of the ink composition according to example 1 have been compared with the viscosity of the same ink composition in which the gelling agent (mixture of fatty acid amide wax+silica particles) has been replaced by 0.7% by weight of silica particle (Aerosil® 200) (comparative example 1) or by 0.4% by weight of silica particle (Aerosil® 200)+0.3% by weight of bentonite clay (Bentone SD-2) (comparative example 2).

[0077] In the preparation of the comparative example 1, 0.3% of the silica particles are added in the form of a 10% premix in phenoxyethanol at 20° C. in the ink composition containing the other ingredients and the rest of the silica particles.

[0078] In the preparation of the comparative example 2, the bentonite clay is added in the form of a 5% premix in phenoxyethanol at 60° C. in the ink composition containing the other ingredients. The results are given in the following Table 3:

TABLE-US-00003 TABLE 3 Initial rest viscosity Shear viscosity Immediate rest return type of gelling (0.01 s.sup.−1) (100 s.sup.−1) (0.01 s.sup.−1) agent at 20° C. at 20° C. at 20° C. Example 1 53 000   2100 8000 Comparative 2600 2300 2330 Example 1 Comparative 2270 2100 2020 Example 2
As can be seen in this table, silica alone and a mixture of silica and clay do not impart a sufficient viscosity at rest to the ink composition in order to form a gel writing ink.

[0079] The static leakage of the ink according to example 1 has been compared with an ink composition with the static leakage of the same ink composition in which fatty acid amide wax is used as the only gelling agent (no silica particles are present in the ink composition) (Comparative example 3) or in which the fatty acid amide wax is used in combination with 0.4% by weight of bentonite clay (Bentone SD-2) (Comparative example 4). For this test, the experimental protocol is as follow:

Writing system: retractable cartridge with needle tip of 0.7 mm and a BIC Atlantis body.
The static leakage is measured by taking the drop formed at the tip of the pen on a paper sheet. The drop is then covered by a transparent adhesive tape and then circularly spread with a wallpaper roller. The obtained stain diameter is then measured.
The static leakage at 40° C./80% corresponds to the spread diameter of the drop formed after storage of the pen with the tip down during a week in a climatic chamber at 40° C. and 80% relative humidity.
The static leakage at 23° C./50% corresponds to the spread diameter of the drop formed after storage of the pen with the tip down during 24 hours in a climatic chamber at 23° C. and 50% relative humidity.
An excellent seepage corresponds to the case where the spread diameter of the drop is below 1.5 mm.
The results are given in the following Table 4:

TABLE-US-00004 TABLE 4 Static leakage at Static leakage at type of gelling agent 40° C./80% 23° C./50% Example 1 1.0 mm 1.1 mm Comparative Example 3 10.5 mm  3.5 mm Comparative Example 3 3.9 mm 3.3 mm

[0080] As shown in this table, if fatty acid amide wax is used alone as the gelling agent or in combination with bentonite clay, the static leakage is not acceptable. Therefore the presence of silica particles is necessary in order to avoid this problem and could not be replaced by bentonite clay.

EXAMPLE 3: COMPARISON BETWEEN THE DIFFERENT TEMPERATURES OF ADDITION OF THE PREMIX OF THE FATTY ACID AMIDE WAX ACCORDING TO THE DISCLOSURE IN THE INK COMPOSITION ACCORDING TO EXAMPLE 1

[0081] A premix of the fatty acid amide wax has been prepared as follow:
Addition of 5% by weight of the fatty acid amide wax in phenoxyethanol at a temperature of 60° C. by using a stator/rotor disperser with a shear rate of between 20 and 25 m/s.
This process allows the activation of the fatty acid amide wax in order for it to adequately play its gelling agent function.
The premix has the following viscosity at 20° C.:

[0082] more than 2 million mPa.Math.s at a shear rate of 0.01 s.sup.−1,

[0083] about 1100 mPa.Math.s at a shear rate of 100 s.sup.−1 and

[0084] about 230 mPa.Math.s at a shear rate of 1000 s.sup.−1.

To reach the rest viscosity measured at 20° C. of 50 0000 mPa.Math.s at 0.01 s.sup.−1, the quantity of premix added to the ink composition according to example 1 depends on the temperature at which it is added to the ink.
The results are indicated in the following Table 5:

TABLE-US-00005 TABLE 5 Temperature of Quantity of premix needed addition of to reach viscosity of the premix 50 000 mPa .Math. s at rest in the ink (0.01 s.sup.−1) at 20° C. 30° C. 15%  40° C. 7% 50° C. 6% 60° C. 4%

[0085] With a same amount of premix, higher loading temperature brings higher rest viscosity. This is due to a second activation of the fatty acid amide wax with dyes.

[0086] Rest viscosity return after writing and storage stability was also analyzed. The results are indicated in the following Table 6.

TABLE-US-00006 TABLE 6 Rest viscosity Rest viscosity after 1 month after 1 month Premix Initial rest Shear Immediate storage at storage at addition viscosity viscosity rest return 20° C. and 50% 40° C. and 80% temperature (0.01 s.sup.−1) (100 s.sup.−1) (0.01 s.sup.−1) RH (Temperate RH (Tropical (° C.) at 20° C. at 20° C. at 20° C. climate) climate) 30° C. 50 000 2500 65 000 mPa .Math. s 108 000 mPa .Math. s 106 000 mPa .Math. s 40° C. mPa .Math. s mPa .Math. s 10 000 mPa .Math. s 50 000 mPa .Math. s 70 000 mPa .Math. s 50° C. 8 000 mPa .Math. s 50 000 mPa .Math. s 30 000 mPa .Math. s 60° C. 8000 mPa .Math. s 40 000 mPa .Math. s 25 000 mPa .Math. s

[0087] The best compromise is therefore using a temperature of between 50° C. and 60° C. for the addition of the premix in the ink composition according to the present disclosure.