JP3924964B2 - Water-based ink composition for ballpoint pens - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink composition for a ballpoint pen containing at least a pigment, water and a resin.
[0002]
[Prior art]
Conventional ink compositions for general writing instruments include dyes and pigments as colorants, water and various organic solvents that dissolve or disperse these colorants, and, if necessary, improved handwriting fixability and ink composition It is known that a resin for adjusting the viscosity of a product, a surfactant for improving the solubility and dispersion stability of the formulation, and various additives such as antiseptic and antifungal agents are blended.
[0003]
Here, as a method for accommodating the ink composition in the writing instrument, one that is accommodated in a free state is known without depending on an ink occlusion body or the like. In such an ink stored in a writing instrument in a free state, excessive discharge of the ink composition from the nib is achieved by increasing the viscosity of the ink composition itself and reducing the fluidity in the stationary state. It is known that it is possible to suppress the dispersion and to stabilize the dispersion of a compound such as a pigment.
[0004]
Conventionally, it is known to add a water-soluble polymer compound as a method for increasing the viscosity of a so-called aqueous ink composition containing water in the solvent and dispersion medium of the ink composition. The network structure formed when the water-soluble polymer compound is dissolved in the composition reduces the fluidity of the ink composition and increases the viscosity. Conventionally known as such water-soluble polymer compounds include natural gum arabic, tragacanth gum, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, casein, xanthan gum, dextran, semisynthetic methylcellulose, Ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, starch glycolate, alginate, propylene glycol alginate, synthetic polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl methyl ether, polyethylene oxide, copolymers of vinyl acetate and polyvinyl pyrrolidone, etc. The thing which mixed 1 type (s) or 2 or more types can be illustrated.
[0005]
[Problems to be solved by the invention]
Ink using a pigment as a colorant is used after being finely pulverized in order to disperse the pigment stably. Furthermore, a surface active agent that exhibits steric hindrance and electrical repulsion is attached to the surface to prevent re-aggregation, but steric hindrance and electrical repulsive force decrease with time and temperature change, causing aggregation and sedimentation. There was a thing.
[0006]
In addition, when a water-soluble polymer is added to the ink to increase the viscosity, the pigment is captured by the network structure formed by the water-soluble polymer, making it difficult to settle. However, the network structure is easily destroyed by temperature and time. As a result, the aggregation and sedimentation of the pigment due to temperature and aging were not completely prevented.
[0007]
For this reason, ballpoint pens that use pigments as colorants have poor writing due to agglomerated pigments clogging the ink flow path, and layers where the pigment content settles and the pigment is deposited in the upper part of the ink in a container such as an ink tank of a writing instrument. There was a problem of causing a color separation phenomenon.
[0008]
An object of the present invention is to provide an ink composition for a water-based ballpoint pen that is excellent in pigment dispersion stability, in which a pigment of a colorant does not aggregate or settle due to aging or temperature change.
[0009]
[Means for Solving the Problems]
The present invention includes at least a pigment, water, a compound represented by the above general formula (Chemical Formula 1) and / or a salt thereof, a polyacrylic acid having a viscosity of 5 wt% aqueous solution of 100 centipoise (25 ° C) or less, and / or Alternatively, the gist is a water-based ink composition for ballpoint pens comprising at least a salt thereof.
[0010]
As the colorant, pigments conventionally used in water-based ink compositions can be used without limitation. Specific examples thereof include carbon black, titanium oxide, iron oxide, ultramarine, cobalt blue, chrome green, and oxidation. Inorganic pigments such as chromium, Hansa Yellow 10G, 5G, 3G, 4, GR, A, Benzidine Yellow, Permanent Yellow NCG, Tartrazine Lake, Quinoline Yellow, Sudan 1, Permanent Orange, Induslen Brilliant Orange GN, Permanent Brown FG, Para Brown, Permanent Red 4R, Fire Red, Brilliant Carmine BS, Pyrazolone Red, Lake Red C, Quinacridone Red, Brilliant Carmine 6B, Bordeaux 5B, Thioindigo Red, Fast Violet B, Dioxane Ioretto, alkali blue lake, phthalocyanine blue, indigo, Acid Green Lake, organic pigments such as phthalocyanine green, metal powder pigments, inorganic fluorescent pigments, organic fluorescent pigments, colored resin powder, colored resin sphere.
[0011]
Furthermore, a dispersed pigment in which a pigment is dispersed in an aqueous medium can also be used. Specifically, Fuji SP series (Fuji Dye Co., Ltd.), Emacol series, Sandy Super series, Sandye series (above, Sanyo Dye Co., Ltd.), Lio Fast series, EM series (above, Toyo Ink Co., Ltd.) )), NKW series (manufactured by Nippon Fluorescence Co., Ltd.), Cosmo Color series (manufactured by Toyo Soda Co., Ltd.), Victoria series (manufactured by Gokoku Dye Co., Ltd.), and the like. The various pigments described above can be used alone or in appropriate combination. Various known dyes may be used in combination as complementary colors.
[0012]
The dispersion medium requires water, and various organic solvents can be used in addition to this. Specific examples of the organic solvent include ethanol, methanol, 1-propanol, 2-propanol, 1,3-propanediol, 2-methyl-2,4-pentanediol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-phenoxyethanol, 2-benzyloxyethanol, 2- (2-methoxyethoxy) ethanol, 2- (2-ethoxyethoxy) ethanol, 2- (2-butoxyethoxy) ethanol, glycerin, Water-soluble organic solvents such as ethylene glycol, propylene glycol, diethylene glycol, and polyethylene glycol are listed.
[0013]
The water-soluble polymer compound added mainly for the purpose of adjusting the viscosity of the ink composition is a substance represented by the above general formula (Chemical Formula 1) and / or a salt thereof and a viscosity of 100 centipoise (25% by weight) C) The following polyacrylic acid and / or salt thereof are used in combination. The ratio of each water-soluble polymer compound is desirably 10 to 99% by weight based on the total amount of the water-soluble polymer compound to which the substance represented by the above general formula (Formula 1) and / or a salt thereof is added. Such polyacrylic acid and / or a salt thereof are commercially available in powder or solution, and any of them can be used. Specifically, Jurimer AC-10P, AC-10LP, AC-10NP, AC-103A, AC-10S, AC-10L, AC-10N, AC-20N, AC-103 ( (Nippon Pure Chemicals Co., Ltd.), Aron A-200U, A-20U, T-40, A-10U, A-10SL, A-20LL, A-20SL (Toagosei) Etc.).
[0014]
The ink composition of the present invention can be obtained by mixing and stirring the above essential components. Furthermore, if necessary, it may be passed through a disperser, and the pigment may be classified by filtration and centrifugation.
[0015]
In addition to the above components, various polymer compound dispersants and surfactants can be used. For example, as a polymer compound dispersant, natural rubbers such as gum arabic and tragacanth, glucosides such as saponin, natural polymers such as lignin sulfonate and shellac, salts of styrene-acrylic acid copolymer, styrene -Salt of maleic acid copolymer, salt of vinyl naphthalene-maleic acid copolymer, salt of β-naphthalene sulfonic acid formalin condensate, anionic polymer compound such as phosphate, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene Nonionic polymer compounds such as glycols are listed. In addition, surfactants include anionic surfactants such as fatty acid salts, higher alcohol sulfates, liquid fatty acid sulfates, alkylallyl sulfonates, polyoxyethylene alkyl ethers, sorbitan alkyl esters, polyoxyethylene Nonionic surfactants such as sorbitan alkyl esters are listed.
[0016]
When the water-based ink composition of the present invention is used as an ink composition for a water-based ballpoint pen, the ink viscosity is 50 to 2000 cp (less than 600 cp is 1 rpm using an ELD viscometer standard cone rotor manufactured by Tokimec Co., Ltd.). It is desirable to set the measurement at 600 cp or more in a range of 20 rpm using an ELD viscometer ST type rotor manufactured by Tokimec Co., Ltd. at a temperature of 25 ° C. If the ink viscosity is less than 50 cp, the ink is liable to leak from the pen tip, and if it exceeds 2000 cp, the ink discharge amount is reduced and the handwriting density is reduced.
[0017]
Moreover, antiseptic / antifungal agents such as sodium dehydroacetate, 1,2-benzisothiazolin-3-one, sodium benzoate and the like can be appropriately added.
[0018]
Furthermore, anticorrosives such as benzotriazole and ethylenediaminetetraacetate can be added as appropriate.
[0019]
Basic compositions such as alkali metal salts such as sodium hydroxide and lithium hydroxide, organic amines such as triethanolamine and 2-amino-2-methyl-1,3-propanediol, sulfuric acid, etc. It is also possible to adjust the pH of the ink by adding an acidic substance such as hydrochloric acid or acetic acid. In particular, when the pH of the ink is in the range of 5.5 to 11, the temporal stability of the ink viscosity is further improved.
[0020]
[Action]
The reason why the water-based ballpoint pen ink composition using a pigment as a colorant of the present invention does not aggregate or settle due to aging or temperature change is considered as follows.
The compound represented by the general formula (Formula 1) and / or a salt thereof is a water-soluble polymer having a lipophilic part and a hydrophilic part in the molecule. For this reason, when added to the ink, from the affinity with the solvent, a fine gel (microgel) consisting of a lipophilic part with a lipophilic group gathered inside and a hydrophilic part with a hydrophilic group gathered outside. Infinitely formed to thicken the entire ink composition. In the lipophilic part and the hydrophilic part of this microgel, there is a gap due to electrical repulsion between the respective groups. The relationship between the microgel and the pigment in the composition varies depending on the surface properties of the pigment. In other words, the pigment enters the gap on the inner side of the microgel when the surface is lipophilic, and enters the gap on the outer side of the microgel when the surface is hydrophilic.
[0021]
Furthermore, a relatively low molecular weight polyacrylic acid having a viscosity of 5 wt% aqueous solution of 100 centipoise (25 ° C.) or less and / or an ink compound containing the compound represented by the above general formula (Chemical Formula 1) and / or a salt thereof. Alternatively, when a salt thereof is added, these are polyacrylic acid and / or a compound represented by the general formula (Chemical Formula 1) and / or a hydrophilic substance having a structure similar to the structure of the hydrophilic portion of the salt. The salt collects in the hydrophilic portion on the outside of the microgel and partially cross-links to reinforce the surface of the microgel. For this reason, the microgel is not easily destroyed even with time or temperature change, and the pigment surrounded by the gel is also stably maintained.
[0022]
【Example】
Hereinafter, the present invention will be described in detail by way of examples. In the examples and comparative examples, “parts” means “parts by weight”. “%” Indicates “% by weight”.
[0023]
The measurement conditions of the viscosity of each ink composition are as follows: Tokimec ELD viscometer standard cone rotor 10 rpm when less than 50 cp, and 50 to 600 cp ELD viscometer standard cone rotor 1 rpm manufactured by Tokimec Co., Ltd. The measurement was performed at 600 cp or more and less than 5500 cp with an ELD viscometer ST type rotor 20 rpm manufactured by Tokimec Co., Ltd. (Measurement temperature 25 ° C)
[0024]
Example 1
Of the above components, purified water, carbon black MA-1000, Jonkrill 61j, ethylene glycol and glycerin are mixed and dispersed in a commercially available sand mill for 1 hour. Thereto, a 2% aqueous solution of sodium dehydroacetate and PEMULEN TR-1 was added and stirred for 1 hour, and then a 20% aqueous solution of Jurimer AC-10LP was added and stirred for another 30 minutes. An appropriate amount of triethanolamine was added to adjust the pH to 8.0, followed by filtration through a 1 μm filter to obtain a black ink having a viscosity of 1800 cp.
[0025]
Example 2
Among the above components, purified water, NKW-2105, glycerin, proxel GXL, 2% aqueous solution of PEMULEN TR-2 are mixed and stirred for 1 hour, and then added with Jurimer AC-10S and further stirred for 30 minutes. An appropriate amount of a 25% aqueous solution of sodium hydroxide was added to adjust the pH to 7.5, followed by filtration through a 1 μm filter to obtain a yellow fluorescent ink having a viscosity of 700 cp.
[0027]
Comparative Example 1
Of the above components, purified water, carbon black MA-1000, Jonkrill 61j, ethylene glycol and glycerin are mixed and dispersed in a commercially available sand mill for 1 hour. A 1% aqueous solution of sodium dehydroacetate and Kelzan was added thereto and stirred for 1 hour, followed by filtration through a 1 μm filter to obtain a black ink having a viscosity of 1900 cp.
[0028]
Comparative Example 2
Among the above components, 2% aqueous solution of purified water, NKW-2105, glycerin, proxel GXL, PEMULEN TR-2 was mixed and stirred for 1 hour, and then an appropriate amount of 25% aqueous sodium hydroxide solution was added to adjust the pH to 7. 5 and filtered through a 1 μm filter to obtain a yellow ink having a viscosity of 690 cp.
[0030]
【The invention's effect】
The following tests were conducted on the inks of Examples 1 and 2 and Comparative Examples 1 and 2.
[0031]
Test 1: Pigment aggregation (1)
Place the ink in a glass test tube with a capacity of 12 ml and a height of 10 cm so that the height of the ink is 8 cm, seal it, place it in a 50 ° C. atmosphere for 2 months, and then take it out to determine the average particle diameter of the pigment before and after the test. Compared. The pigment particle size was measured using a particle size distribution analyzer LPA-3000 / 3100 manufactured by Otsuka Electronics Co., Ltd. The results are shown in (Table 1).
[0032]
[Table 1]
[0033]
Test 2: Pigment settling (2)
In Test 1, the upper surface of the ink immediately after taking out the test tube was visually observed, and it was examined whether the pigment settled and a transparent dispersion medium layer (hereinafter referred to as a water spring layer) was generated. When there was a water spring layer, the thickness of the water spring layer was measured. The results are shown in (Table 2).
[0034]
[Table 2]
[0035]
Test 3: Pigment aggregation (2)
Into a glass test tube with a capacity of 12 ml and a height of 10 cm, the ink is placed in a height of 8 cm and sealed, and a cooling cycle of -30 ° C for 1 day and 50 ° C for 1 day is continued. The test was conducted 5 times and examined in the same manner as in Test 1. The results are shown in (Table 3).
[0036]
[Table 3]
[0037]
Test 4: Pigment sedimentation (2)
In Test 3, the upper surface of the ink immediately after taking out the test tube was visually observed to check for water springs. When the water was springing, the thickness of the water spring layer was measured. The results are shown in (Table 4).
[0038]
[Table 4]
[0039]
As described above, the water-based ink composition for ballpoint pens of the present invention is an ink excellent in pigment dispersion stability in which pigments do not aggregate or settle due to aging or temperature change.

Claims (1)

At least a pigment, water, a compound represented by the following general formula (Chemical Formula 1) and / or a salt thereof, and a polyacrylic acid and / or a salt thereof having a viscosity of 5 wt% aqueous solution of 100 centipoise (25 ° C.) or less A water-based ink composition for ballpoint pens.