JPH03255182A - Water-base pigment ink composition for writing utensil - Google Patents

Abstract

PURPOSE:To obtain the title composition improved in writing after preservation under high temperature conditions by mixing a pigment, a dispersant comprising an alkali-neutralized salt of a copolymer of a hydrophobic polymerizable monomer with maleic acid (anhydride), a drying inhibitor, and an aqueous medium. CONSTITUTION:50-95mol% hydrophobic polymerizable monomer is copolymerized with 50-5mol% maleic acid (anhydride), and the copolymer is neutralized with an alkali (e.g. aqueous ammonia) to give a dispersant comprising an alkali- neutralized salt of the copolymer. 3-30wt.% pigment (e.g. carbon black) is mixed with the dispersant in an amount of 5-300 pts.wt. based on 100 pts.wt. pigment, 3-40wt.% drying inhibitor (e.g. urea), and 40-80wt.% aqueous medium comprising water and, if necessary, an aqueous organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a pigment aqueous ink composition for writing instruments. More specifically, the present invention relates to a pigment aqueous ink composition for writing instruments that has excellent long-term dispersion stability of pigments and also has various physical properties such as light resistance and water resistance required for writing instruments.

[Prior Art] Dye-type inks have traditionally been widely used as inks for writing instruments, but characters recorded using such dye-type inks have poor water resistance and light resistance, so pigment-type inks have been used in recent years. Ink is widely used.

However, pigment-type inks have poor pigment dispersion stability because the pigments contained are insoluble in the ink.
It had a number of drawbacks, such as the pigment settling in the ink and causing a smudge on the nib, and lines blurring when the nib dried.

Therefore, as a pigment aqueous ink composition that eliminates the above-mentioned drawbacks, an amine salt or an ammonium salt of a copolymer consisting of a specific amount of a hydrophobic addition polymerizable monomer and (meth)acrylic acid is added to the dispersant. has been proposed (Japanese Patent Publication No. 1-28790), and the pigment aqueous ink composition is certainly better than conventional pigment-type inks in terms of recovery of writing ability after the nib dries. It is something that However, the aqueous pigment ink composition has the drawback that it may become unwritable when stored at high temperatures for a long period of time, and a solution to this problem has been awaited.

[Problems to be Solved by the Invention] The present inventor focused on the pigmented water-based ink composition and aimed to develop a pigmented water-based ink composition that has excellent writing performance even after being kept in a high temperature state. As a result of extensive research,
Hydrophobic polymerization in a specific amount as a dispersant +1. When an alkali neutralized salt of a copolymer consisting of a monomer and at least one of maleic acid and maleic anhydride is blended,
Surprisingly, they discovered for the first time a completely new 11 [fruit] that the writing ability is much better after being stored in high temperature conditions, leading to the completion of the present invention.

[Means for Solving the Problems] That is, the present invention provides a pigment aqueous ink composition for writing instruments containing a pigment, a dispersant, a drying prevention agent, and an aqueous medium, wherein the dispersant is a hydrophobic polymerizable ink composition. qt H form 50~9
The present invention relates to a pigment aqueous ink composition for writing instruments, characterized in that it is an alkali neutralized salt of a copolymer consisting of 5 mol % and 50 to 5 mol % of at least one of maleic acid and maleic anhydride.

[Function and Examples] As described above, the pigment aqueous ink composition for writing instruments of the present invention contains hydrophobic polymerizable 111 melon 50 to 95 as a dispersant.
The method is characterized in that an alkali neutralized salt of a copolymer consisting of 50 to 5 mol% of at least one of maleic acid and maleic anhydride is used.

Examples of the hydrophobic polymerizable monomer constituting the alkali neutralized salt of the copolymer used in the present invention include (meth)
(meth)acrylic acid esters such as methyl acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, styrene, styrene derivatives, and other hydrophobic addition polymerizable 11i amounts However, the present invention is not limited to only such examples.

As described above, the hydrophobic polymerizable monomer copolymerized with the 1lifa monomer is at least one of maleic acid and maleic anhydride. Therefore, in the present invention, maleic acid and maleic anhydride may be used alone or in combination.

The blending ratio of the hydrophobic polymerizable monomer and at least one of maleic acid and maleic anhydride is such that the hydrophobic polymerizable monomer has a hydrophobic polymerizability of 11
The content is adjusted so that the 1ffi form is contained in an amount of 50 to 95 mol %, and at least one of maleic acid and maleic anhydride is contained in an amount of 50 to 5 mol %. When the blending ratio of the hydrophobic polymerizable monomer is less than 50 mol%, and when the blending ratio of at least one of maleic acid and maleic anhydride is 50% by mole,
If the proportion of the hydrophobic polymerizable monomer exceeds 95 mol%, the water resistance tends to deteriorate in any case where the proportion of the hydrophobic polymerizable monomer exceeds 95 mol%, and if the proportion of maleic acid and maleic anhydride exceeds 95 mol%, the water resistance tends to deteriorate. The blending ratio of 1 scale is 5
In any case where the amount is less than mol %, there is a tendency that water solubilization becomes impossible. The blending ratio of the hydrophobic polymerizable 7111a is preferably 50 to 95 mol%, and <50 to 70 mol%, and the blending ratio of at least one of the maleic acid and maleic anhydride is 50 to 5 mol%, and <50 to 30
Preferably it is mol%.

Copolymerization of the hydrophobic polymerizable monomer and at least one of maleic acid and maleic anhydride can be carried out by a known method.

The thus obtained copolymer is neutralized with an alkali such as aqueous ammonia, monoethanolamine, triethanolamine, monoisopropylamine, or morpholine in order to make it soluble in an aqueous medium. . In addition, the alkali neutralized salt of the copolymer is
(The polymer may be semi-esterified with alcohol and then neutralized with an alkali.

The amount of alkali neutralized salt of the copolymer used is
It is preferable that it is 5 to 300 parts with respect to 0 parts (weight parts, the same applies hereinafter), and preferably <10 to 200 parts. If the amount used exceeds the above-mentioned upper limit, the viscosity of the resulting pigmented aqueous ink composition becomes too high and tends to cause clogging at the pen tip, while if it is less than the above-mentioned lower limit, There is a tendency for the dispersion stability of the pigment in the pigment aqueous ink composition to deteriorate.

Pigments used in the present invention include various organic pigments and inorganic pigments. In the present invention, the type of pigment is not particularly limited, but examples include azo, phthalocyanine, quinacridone, anthraquinone series, dioxazine series, indigo-thioindigo series,
Examples include organic pigments such as perylene-perinone type and isoindolinone type, and inorganic pigments such as titanium oxide, iron oxide, and carbon black.

The content of the pigment in the pigment aqueous ink composition is:
There is no particular limitation on the amount, as long as the amount of written characters and lines are sufficiently recognizable when actually written using the pigment aqueous ink composition, and it is usually about 3 to 30% by weight. is preferred.

Examples of the anti-drying agent used in the present invention include urea, adducts of urea with nitric acid, oxalic acid, phosphoric acid, etc., thiourea, ethylene urea, and derivatives thereof.

If the content of the anti-drying agent in the pigment water-based ink composition is too high, the viscosity stability of the resulting pigment water-based ink composition will decrease, and if it is too low, it may be difficult to close the can knob. Since the object of the present invention cannot be achieved due to blurring and inability to write,
It is preferably 40% by weight, especially 3 to 30% by weight.

The aqueous medium used in the present invention is mainly composed of water, and may contain other water-soluble organic solvents such as ethylene glycol, diethylene glycol, glycerin, and propylene glycol as necessary. The above-mentioned water-soluble organic solvent has been conventionally used as an anti-drying agent for water-based ink for writing instruments, but the use of such water-soluble organic solvent alone is not sufficient for the present invention! ] Since the target cannot be achieved, it is desirable to use water in combination.

The content of the aqueous medium in the pigment aqueous ink composition may be such that the written characters, ti'i lines, etc. can be sufficiently recognized when actually written using the pigment aqueous ink composition. There is no particular limit, but usually 40 to 8
It is preferable that the amount is approximately 0%.

As described above, the pigment aqueous ink composition of the present invention comprises a pigment, an alkali neutralized salt of a copolymer consisting of a hydrophobic polymerizable monomer and at least one of maleic acid and maleic anhydride, an anti-drying agent, and Although the aqueous medium is an essential component, other ink insertion additives may be added as necessary within a range that does not impede the object of the present invention.

There are no particular limitations on the method for producing Suisan Mei's pigment aqueous ink composition, but examples include mixing and grinding using a dispersing machine such as a sand grinder, Sentry Mill, Dyno Mill, ball mill, roll mill, or speed line mill. There are directions, etc.

Although the pigment aqueous ink composition for writing instruments of the present invention thus obtained has a very low viscosity, it does not cause agglomeration or sedimentation of the pigment particles even after being stored for a long period of time. No such phenomenon is observed at all. Such a phenomenon is
The lipophilic parts of the dispersant are adsorbed on the surface of the atomized pigment, and as a result, the hydrophilic parts repel each other, causing the face #
This is thought to be due to the fact that aggregation of 1 was suppressed and the dispersion was stabilized.

Therefore, even if the pigment aqueous ink composition for writing instruments of the present invention is used in, for example, a sign pen, a ballpoint pen, a brush pen, etc., the pigment aqueous ink composition for writing instruments may aggregate in the container or at the pen tip. This allows for good writing without clogging. Furthermore, the pigment aqueous ink composition for writing instruments of the present invention significantly reduces the occurrence of blurring or poor writing even if the user forgets to close the i-position cap, and even if poor writing occurs, However, as soon as the writing instrument cap is closed, it will return to a writing-ready state.

Next, the pigment aqueous ink composition for writing instruments of the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

Reference Example 1 98.1 parts (1.0 mol) of maleic anhydride in the reaction vessel
, 800 parts of dioxane and 2.0 parts of 2-mercaptoethanol were added and mixed. It was heated to 100°C under a nitrogen stream, and 17.2 parts of methyl acrylate (
0.2 mol), 83.3 parts (0.8 mol) of styrene and 2.0 parts of azoisobutyronitrile were added dropwise over 2 hours. Next, the temperature was maintained at 100° C. for an additional 3 hours to complete the reaction.

After the obtained copolymer was precipitated and dried, it was half-esterified with n-butyl alcohol and neutralized with aqueous ammonia to prepare a dispersant containing 30 m% of the active ingredient.

Reference Example 2 116.1 parts (1.0 mol) of maleic acid in the reaction vessel,
Toluene 800 parts and dodecyl mercaptan 1.0
and mixed. The reaction vessel was heated to 100°C under a nitrogen stream, and 50.0 parts (0.5 mol) of methyl methacrylate, 64.1 parts (0.5 mol) of butyl acrylate, and 3.0 parts of benzoyl peroxide were added to the reaction vessel. The solution was added dropwise over a period of 2 hours. Next, the temperature was maintained at 100°C for an additional 3 hours to complete the reaction.

The obtained copolymer was precipitated and dried, and then neutralized with monoethanolamine to prepare a dispersant containing 30% by weight of the active ingredient.

Reference Example 3 80.1 parts (0.8 mol) of ethyl acrylate, 19.6 parts (0.2 mol) of maleic anhydride, and 800 parts of methyl ethyl ketone were placed in a reaction vessel and mixed.

Heated to 80°C under a nitrogen stream, and 2-methylstyrene 5
9.1 parts (0.5 mol), methyl methacrylate 50.0
(0.5 mol) and 20 parts of azoisobutyronitrile were added dropwise over a period of 2 hours. Then another 3 hours 80
The reaction was completed by maintaining the temperature at °C. The obtained copolymer was precipitated and dried, and then neutralized with triethanolamine to prepare a dispersant containing 30% by weight of the active ingredient.

Example 1 15 parts of carbon black, dispersant 1 obtained in Reference Example 1
5 parts of ethylene glycol, 20 parts of water, and 10 parts of urea were dispersed in a sand grinder for 3 hours, and further 10 parts of ethylene glycol and 40 parts of water were added.
Time-distributed processing was performed. Coarse pigment particles were removed from this dispersion by centrifugation to obtain a pigment aqueous ink composition for writing instruments containing 9% by weight of pigment.

Comparative Example 1 A comparative pigment aqueous ink composition for writing instruments was obtained by carrying out the same operation as in Example 1 except that urea was omitted.

Example 2 15 parts of phthalocyanine blue, 10 parts of the dispersant obtained in Reference Example 2, 10 parts of ethylene glycol, 15 parts of diethylene glycol, 40 parts of water and 10 parts of thiourea were dispersed in a sand grinder for 3 hours, and further ethylene glycol 10 parts and 40 parts of water were added and dispersed for 1 hour.

I11 large pigment particles were removed from this dispersion by centrifugation to obtain a pigment aqueous ink composition for writing instruments containing 9.0% by weight of pigment bones.

Comparative Example 2 A comparative pigment aqueous ink composition for writing instruments was obtained by carrying out the same operation as in Example 2 except that thiourea was omitted.

″)! Example 3 15 parts of naphthol red, dispersant 1 obtained in Reference Example 3
0 parts of ethylene glycol, 15 parts of ethylene glycol, 10 parts of propylene glycol, 40 parts of water and 10 parts of urea were dispersed in a sand grinder for 2 hours, and then 1 part of ethylene glycol was added.
0 parts and 40 parts of water were added and the mixture was subjected to a dispersion treatment for 30 minutes. Coarse pigment particles were removed from this dispersion by centrifugation to obtain a pigment aqueous ink composition for writing instruments containing 9.0% pigment.

Comparative Example 3 A comparative pigment aqueous ink composition for writing instruments was obtained by carrying out the same operation as in Example 3 except that urea was omitted.

Comparative Example 4 Amine salt of styrene-butyl acrylate-methacrylic acid (molar ratio 30:40:30) copolymer 10
20 parts of ethylene glycol, 40 parts of water, 16 parts of carbon black and 14 parts of urea were dispersed in a ball mill for 30 hours, and further 20 parts of ethylene glycol and 40 parts of water were added and dispersed for 20 minutes.

Coarse pigment particles are removed from this dispersion by centrifugation,
A pigment aqueous ink composition for writing instruments containing 9.0% by weight of pigment was obtained.

Usage Examples Each of the pigment aqueous ink compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 4 was filled into a plastic pen having a polyester occlusion body and a polyacetal extrusion nib, and the following method was applied. When various performance tests were conducted according to the above, the lil'i results shown in Table 1 were obtained.

(50° C. Accelerated Test) A plastic Ben was placed in a constant temperature bath at 50° C., and the number of days until writing became impossible was measured.

(Pen tip open test) Remove the cap from the plastic pen, 25℃, 60%
R1+ (constant temperature and humidity) was placed in the west, and the time until it became impossible to write was determined.

(Writing ability recovery test after drying of the pen nib) After the pen nib was left at 25° C. and 60% R1+ for 72 or more periods to make writing impossible, the pen was capped again and the time until the writing ability recovered was measured.

Margin below E] From the above mucus, Ki-ni-t! #I rice ice water-based ink composition for writing utensils, does not aggregate or clog inside the writing utensil or the nib, and does not regenerate even if the nib is left open for a long time. It turns out that you can write. In particular, it can be seen that the aqueous ink composition for brush placement according to the present invention does not have an adverse effect on writing performance even when kept at 1 ul for a long period of time at high temperatures.

[Effects of the Invention] The pigment aqueous ink composition for writing instruments of the present invention does not cause aggregation or clogging in the writing instrument or pen nib, and does not cause clogging when the pen nib is left open for a long time. There are also things that can be written down again.

Furthermore, the pigment aqueous ink composition for writing instruments of the present invention has no adverse effect on writing performance even when stored at high temperatures for a long period of time.

Therefore, the pigmented aqueous ink composition for writing instruments of the present invention exhibits a procedural correction band (spontaneous) effect that allows it to be suitably used as an ink for, for example, sign pens, ballpoint pens, and brush pens.

Claims (1)

[Claims] 1. A pigment aqueous ink composition for writing instruments comprising a pigment, a dispersant, an anti-drying agent, and an aqueous medium, the dispersant comprising 50 to 95 mol% of a hydrophobic polymerizable monomer, maleic acid, and maleic anhydride. A pigment aqueous ink composition for writing instruments, characterized in that it is an alkali-neutralized salt of a copolymer comprising 50 to 5 mol% of at least one of the following.