JPH0139699B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-based ink composition for writing instruments using a pigment as a colorant, and more specifically, to
A water-based ink composition for writing instruments that has good physical properties such as water resistance and chemical resistance, has excellent pigment dispersion stability, has a good writing feel, and can write on highly water-repellent materials such as plastic film. The purpose is to provide something. Conventionally, water-soluble dyes have been mainly used as coloring components in inks used for water-based felt pens, felt pens, ballpoint pens, brush pens, etc., but because they are water-soluble dyes, they have excellent light resistance, water resistance,
It is inferior in other physical properties, and for this reason, the use of pigments as coloring components in water-based inks has been variously investigated in recent years. However, since the pigment is insoluble in the ink medium, pigment particles aggregate in the ink and separate from the ink medium, resulting in clogging in the pen nib,
The disadvantages were that the nib became clogged due to dryness and that its storage stability was extremely poor. Most of these drawbacks were solved by the invention disclosed in Japanese Patent Application Laid-open No. 10023/1983 by the applicant of the present application. However, in the case of the above-mentioned prior invention, the writing quality is not sufficient on paper etc., and furthermore, there is a problem that the ink repels when writing on plastic film for OHP etc., making it impossible to write satisfactorily. Ta. When writing on such plastic film, if you use a pigment dispersant with low hydrophilicity (in other words, high hydrophobicity), the problem of repelling will be less, but if you use a dispersant with low hydrophilicity, In this case, the above-mentioned problem occurs because the dispersion stability of the pigment is insufficient. As a result of intensive research in order to solve the above-mentioned drawbacks of the conventional aqueous ink compositions for writing instruments, the present inventor used a specific polyester resin as a pigment dispersant, while water and a certain organic ink composition were used as the dispersion medium. By using a mixture of solvents, and more preferably using a chelating agent as an additive, a pigment-type water-based ink composition for writing instruments that has a good writing feel and can be written on plastic films without causing repellency can be obtained. The present inventors have discovered that the present invention can be obtained, and have completed the present invention. That is, the present invention provides a water-based ink composition for writing instruments comprising a pigment, a dispersant, and an aqueous medium, in which the dispersant comprises a maleic acid-modified fatty acid or a maleic acid-modified fat and oil and a polyhydric alcohol, and is soluble in an alkaline aqueous medium and has an acidic property. This is a water-based ink composition for a writing instrument, which is a polyester resin that is poorly or insoluble in an aqueous medium, and the aqueous medium contains a nonvolatile hydrophilic organic solvent. To explain the present invention in detail, as the pigment used in the present invention, all conventionally known organic and inorganic pigments can be used, such as azo type, phthalocyanine type, quinacridone type, anthraquinone type, dioxazine type, indigo/thioindigo type. These include perinone-perylene-based, isoindorenone-based, titanium oxide-based, cadmium-based, iron oxide-based, carbon black-based, etc. In the present invention, these pigments may be in powder form, but are preferably in the form of an aqueous paste immediately after production. There is no particular technical limit to the content in the aqueous medium, but considering economic efficiency, the pigment concentration is approximately 3 to 30% by weight. The polyester resin used as a dispersant in the present invention is a polyester having a carboxyl group in the side chain of its molecule, and is easily dissolved in an alkaline aqueous medium due to the carboxyl group.
It is not readily soluble or insoluble in acidic aqueous media. Particularly preferred polyester resins in the present invention include fatty acids containing two or more unsaturated double bonds;
It is a carboxyl group-containing polyester resin obtained by using a modified fatty acid or a fat containing these fatty acids modified with maleic acid (or maleic anhydride) as an acid component, and condensing it with various polyhydric alcohols. The above polyhydric alcohols include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, polyester polyol, bisphenol A, adducts of bisphenol A and ethylene oxide or propylene oxide, and other conventional alcohols. Any known polyhydric alcohol can be used, but the most preferred one is one containing an aromatic group in its structure, such as bisphenol A or its derivatives. In order to solubilize or disperse the dispersant made of the polyester resin in an aqueous medium in the form of a colloid, the dispersant is preferably in the form of a salt. Typical alkali metals that form salts with the dispersant are sodium and potassium, and examples of amines include aliphatic metals such as mono-, di-, or tri-methylamine, and mono-, di-, or tri-ethylamine. Alcohol amines such as primary to tertiary amines, mono-, di- or tri-ethanolamine, mono-, di- or tri-propanolamine, methylethanolamine, dimethylethanolamine,
Other typical examples include ammonia, morpholine, and N-methylmorpholine. In the above dispersant, the ratio of carboxyl groups contained is important. That is, when the weight ratio of the carboxyl group in the molecule exceeds about 40% by weight, the adsorption of the dispersant to the pigment becomes poor, causing aggregation and sedimentation of the pigment, resulting in poor writing quality and writing properties on plastic film. On the other hand, about 1% by weight
When the amount is less than that, the hydrophilicity of the dispersant decreases, and although the pigment particles themselves do not aggregate or settle, there is a tendency for them to aggregate and settle while being included in the dispersant. After further detailed study on this point, it was found that the most preferred amount of carboxyl groups is about 5 to 30% by weight. In the present invention, a substantially satisfactory ink composition can be obtained even if the molecular weight of the dispersant changes, but if the molecular weight is too low, the effect as a dispersant will decrease, and if the molecular weight is too high, the effect as a dispersant will decrease. In this case, it tends to be difficult to reduce the viscosity of the ink. The inventor's detailed research has revealed that the most preferred molecular weight range is from about 3,000 to about 50,000. The above-mentioned dispersant can be manufactured according to a conventionally known method, for example, by mixing the necessary monomer components and carrying out a condensation reaction at a temperature of about 130 to 200°C for about 0.5 to 5 hours. A polyester resin of molecular weight is obtained. Further, the amine salt etc. may be formed at any time; for example, any method such as adding the amine etc. after polymerization or adding the amine etc. after mixing with the pigment can be adopted. The amount of the above dispersant used is approximately 5 parts per 100 parts by weight of the pigment.
From about 300 parts by weight, preferably from about 10 to about 150 parts by weight. When the upper limit of this range is exceeded, the balance between coloring power and viscosity of the ink becomes unfavorable.
On the other hand, it was found that when the lower limit was exceeded, the dispersion stability of the pigment decreased. The nonvolatile hydrophilic solvent used in the present invention exhibits the effect of not causing pigment aggregation or sedimentation even if the viscosity of the aqueous pigment dispersion is lowered, and examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, methyl cellosolve acetate,
Polyhydric alcohols such as methyl carbitol, ethyl carbitol, butyl carbitol, glycerin, derivatives thereof, or mixtures thereof. These nonvolatile hydrophilic organic solvents have a concentration of about 5 to 60% in the aqueous medium of the ink composition of the present invention.
It is used in an amount representing about 10 to 50% by weight, preferably about 10 to 50% by weight. According to the research of the present inventor, when the upper limit of the above range is exceeded, pigment dispersion becomes insufficient;
It has been found that when the lower limit is exceeded, it is difficult to reduce the viscosity of the aqueous writing instrument ink composition to about 1 to 20 centipoise while maintaining a desirable pigment dispersion. The essential components of the aqueous ink composition for writing instruments of the present invention are the above-mentioned three components, but there are also various additives used in the technical field, such as anti-drying agents such as urea, thiourea or their derivatives, and interfacial additives. Activators, antioxidants, rust preventives, etc. can also be used as desired as long as they do not interfere with the purpose of the present invention. Particularly in the present invention, it is preferable to include an appropriate amount of a chelating agent in the ink composition for the purpose of dispersion stability of the pigment. That is, in the present invention, in order to prevent bleeding when writing and to prevent plastic film from repelling,
It is desirable that the hydrophilicity of the dispersant be as low as possible, but if the hydrophilicity of the dispersant is low, the stability of the ink will decrease. In the present invention, by adding a chelating agent, the stability of the dispersant is improved even if the hydrophilicity of the dispersant is low, and therefore an excellent ink composition that does not bleed on paper or repel on plastic film is obtained. I can do it. Preferred chelating agents used in the present invention include, for example, ethylenediaminetetraacetic acid disodium salt, nitrilotriacetic acid disodium salt, and iminodiacetic acid monosodium salt, and these chelating agents may be used in an amount of 5 to 100 parts by weight per 100 parts by weight of the polyester resin. Preferably, it is used in a proportion of 150 parts by weight.
The aqueous ink composition for writing instruments of the present invention consists of the above-mentioned components and formulations, and various methods can be employed for its production. For example, a typical method is to mix and grind the above-mentioned components using a conventionally known dispersing machine such as a ball mill, homomixer, sand grinder, speed line mill, or roll mill. In the above production method, the nonvolatile hydrophilic organic solvent can be added after the pigment is dispersed, but it is usually preferable to carry out the mixing and dispersion treatment at the same time. In consideration of economic efficiency, this dispersion process is carried out in a state where the pigment is as highly concentrated as possible, and after the dispersion process, the viscosity is adjusted to a level suitable for a water-based ink composition for writing instruments.
That is, it is preferred to reduce the viscosity to 1 to 20 centipoise, preferably about 3 to 10 centipoise. The aqueous ink composition for writing instruments of the present invention obtained as described above has a very low viscosity and shows no phenomena such as condensation or sedimentation of pigment particles even when stored for a long period of time. This is thought to be because the crystallization energy of the pigment molecules is stabilized by the hydrophilic portion of the dispersant, forming a strong bond. Therefore, even when used in conventional felt-tip pens, felt-tip pens, ballpoint pens, needle pens, etc., it is stable in the container and allows good writing without clumping or clogging at the pen tip. Furthermore, it has a good writing taste with less bleeding, and can also be written on plastic film without repelling. Furthermore, unlike conventional dyes, the coloring matter used is a water-insoluble pigment, so it does not fade at all even with long-term exposure, and it does not bleed at all even if it gets wet with water after writing. Next, the present invention will be explained in more detail with reference to Reference Examples and Examples. In the text, parts or percentages are based on weight unless otherwise specified. Reference Example 1 1100 parts of highly maleated oil of dehydrated castor oil fatty acid (Ito Oil Co., Ltd., Hymalein DF-20) and 690 parts of propylene oxide diadduct of bisphenol A (Nippon Nyukazai, BAP-2 Glycol) were mixed,
Dehydration condensation polymerization was performed at a temperature of 145 to 160°C for 3 hours, and the molecular weight was approximately 8000 and the carboxyl group content was 16.5.
% polyester resin was obtained. After cooling the polyester resin, 256 parts of 28% aqueous ammonia was added with stirring to neutralize it, and 1677 parts of water was further added to obtain a polyester resin solution with a solid content of about 50%. Reference Example 2 1100 parts of highly maleated oil of dehydrated castor oil fatty acid (Ito Oil Co., Ltd., Hymalein DF-20) and 634 parts of ethylene oxide diadduct of bisbisphenol A (Nippon Nyukazai, BAE-2 Glycol) were mixed, The reaction was carried out at a temperature of 145 to 160°C for 3 hours.
After the reaction, the mixture was cooled and neutralized by adding 256 parts of 28% aqueous ammonia and 1,622 parts of water in the same manner as in Reference Example 1 to obtain a polyester resin solution with a solid content of about 50.0%. The molecular weight of the polyester resin was about 7000, and the carboxyl group content was about 17.1%. Reference Example 3 730 parts of highly maleated oil of oleyl oleate (Ito Oil Co., Ltd., Hymalein 00-15) and 600 parts of polyethylene glycol (average molecular weight approximately 600) were mixed and reacted at a temperature of 150 to 170°C for 3 hours. . Then cool, 150 parts of 28% ammonia water and 1250 parts of water.
of the solution was added, stirred and neutralized to obtain a polyester resin solution with a solid content of about 50.0%. The molecular weight of the polyester resin was about 10,000, and the carboxyl group content was about 10.2%. Example 1 To 6.0 parts of the polymerization solution obtained in Reference Example 1, 3.3 parts of diethanolamine, 2.0 parts of ethylene glycol, 3.0 parts of ethylenediaminetetraacetic acid disodium salt, and 20.0 parts of water were added.
21.0 parts of ethylene glycol, 19.7 parts of water, and 15.0 parts of urea were added to give a pigment concentration of 10%. A pigment dispersion was obtained. This dispersion was then subjected to an ultracentrifuge to remove coarse particles that could not be dispersed, resulting in a reduction of 9.4%.
An aqueous ink composition for writing instruments of the present invention having a pigment content of 4.8 centipoise and a viscosity of 4.8 centipoise was obtained. When this ink composition was tested by filling it into a plastic felt-tip pen with a core (occlusion body) and a nib made by plastic molding, it was found that the ink was dramatically improved compared to conventional dye-tip felt-tip pens. It became clear. In addition, when this composition was used in needle pens, fountain pens, brush pens, and ballpoint pens, it showed better water resistance and light resistance, as well as hiding power, compared to conventional products using dyes, as in the case of felt-tip pens. It has become clear that this is an aqueous ink composition with high tinting power and good writing characteristics. In addition to the above-mentioned characteristics, it has a hiding power, has little color addition even when overwritten, and has good water resistance after writing, allowing clear characters or images to be written. Example 2 To 5.0 parts of the polymerization solution obtained in Reference Example 1, 3.3 parts of diethanolamine, 5.0 parts of ethylene glycol, 20 parts of water,
Add 3.0 parts of ethylenediaminetetraacetic acid disodium salt and 9.5 parts of carbon black pigment, disperse with a paint shaker for 6 hours, and add 10.3 parts of ethylene glycol and 10.0 parts of urea to give a pigment concentration of 9.5%.
1, 5.6 parts of diethylene glycol, 2.0 parts of benzotriazole (rust inhibitor) and 26.3 parts of water were added, and the mixture was further dispersed for 30 minutes to obtain an aqueous pigment dispersion. This dispersion was further subjected to an ultracentrifuge to remove coarse particles that could not be dispersed, resulting in a pigment content of 8.9%.
A water-based ink composition for writing instruments of the present invention having a viscosity of 4.2 centipoise was obtained. This material was packed into a ballpoint pen with a metal ball point, and various tests were conducted. As a result, it had a clear black color, and had good water resistance, coloring power, hiding power, light resistance, etc., similar to the results of Example 1. It has excellent physical properties, and no corrosion or rust was observed on the pen tip even after long-term use. Example 3 Add 3.0 parts of morpholine to 5.0 parts of the polymerization solution obtained in Reference Example 2.
parts, 5.0 parts of ethylene glycol, 2 parts of nitriloacetic acid
Add 3.0 parts of sodium salt and 26.5 parts of phthalocyanine blue pigment paste (pigment content: 9.0 parts), disperse in a sand mill for 3 hours, then add 30.8 parts of water, 13.1 parts of ethylene glycol, 3.6 parts of glycerin, and 10.0 parts of thiourea. The pigment concentration was set to 9.0%, and
Dispersion was carried out for 10 minutes to obtain a blue aqueous pigment dispersion.
Further, this dispersion was subjected to an ultracentrifuge to remove coarse particles that could not be dispersed, thereby obtaining a water-based ink composition for writing instruments of the present invention having a pigment content of 8.6% and a viscosity of 4.3 centipoise. This product was packed into felt pens and various tests were conducted, and the results showed that it had superior physical properties such as water resistance, light resistance, and hiding power compared to conventional felt pen inks. Example 4 To 8.0 parts of the polymerization solution obtained in Reference Example 2, 4.0 parts of triethanolamine, 5.0 parts of ethylene glycol, 2.0 parts of iminodiacetic acid monosodium salt, and 23.8 parts of phthalocyanine green pigment paste (pigment content: 9.5 parts)
was added, dispersed in a ball mill for 24 hours, and then added with water.
Add 27.6 parts of ethylene glycol, 8.1 parts of ethylene glycol, 6.6 parts of triethylene glycol monomethyl ether, and 15.0 parts of ethylene urea, and further disperse and mix for 30 minutes.
This dispersion was subjected to an ultracentrifuge to remove coarse particles that could not be dispersed, and the pigment content was 9.0%.
A water-based ink composition for writing instruments of the present invention having a viscosity of 5.2 centipoise was obtained. This product was packed in a felt-tip pen similar to that used in Example 1, and various tests were conducted. As in Example 1, it was found to have excellent physical properties such as water resistance, light resistance, and hiding power. Example 5 3.0 parts of diethanolamine, 5.0 parts of ethylene glycol, 2.5 parts of ethylenediaminetetraacetic acid disodium salt, and 36.0 parts of red insoluble azo pigment paste (pigment content: 9.0 parts) were added to 5.0 parts of the polymerization solution obtained in Reference Example 3, and the mixture was placed in a sand mill. Then, 10.2 parts of ethylene glycol, 3.8 parts of diethylene glycol monomethyl ether, 27.5 parts of water, 5.0 parts of mono-β-hydroxyethyl urea and 2.0 parts of benzotriazole (rust inhibitor) were added, and the mixture was further dispersed for 15 minutes. The mixture was then passed through a cartridge filter to remove coarse particles to obtain a red aqueous ink composition for writing instruments of the present invention having a pigment content of 8.5% and a viscosity of 4.9 centipoise. This material was packed in a felt-tip pen similar to that used in Example 1, and various tests were conducted. As in Example 1, it was found to be a red water-based ink with good hiding power and excellent physical properties such as water resistance and light resistance. It was hot. Example 6 To 3.0 parts of the polymerization solution obtained in Reference Example 1, 2.0 parts of nonionic surfactant (HLB 15) and diethanolamine were added.
3.3 parts of ethylene glycol, 2.0 parts of ethylene glycol, 3.0 parts of ethylenediaminetetraacetic acid disodium salt, 20.0 parts of water and 10.0 parts of carbon black were dispersed in a sand mill for 4 hours, and further 17.6 parts of ethylene glycol and 24.1 parts of water were dispersed.
15.0 parts of urea were added and mixed, and the mixture was further dispersed for 15 minutes to obtain a black aqueous pigment dispersion. This dispersion was further filtered through filter paper to remove coarse particles that could not be dispersed, resulting in a pigment content of 9.5% and a viscosity of 5.2.
A centipoise water-based ink composition for writing instruments of the present invention was obtained. When this product was packed in a felt pen and various tests were conducted, it was found to be a black water-based ink that had hiding power similar to Example 1 and was excellent in various physical properties such as water resistance and light resistance. Comparative Example 1 Ink composition of Example 1 of JP-A-54-10023. Evaluation The ink compositions of Examples and Comparative Examples were packed into a plastic felt-tip pen with a core (occlusion body) and a nib made by plastic molding, and a writing test was conducted on plain paper and polyester film. The results shown in Table 1 were obtained. 【table】

Claims (1)

[Scope of Claims] 1. A water-based ink composition for writing instruments comprising a pigment, a dispersant, and an aqueous medium, wherein the dispersant comprises a maleic acid-modified fatty acid or a maleic acid-modified fat and oil and a polyhydric alcohol, and is soluble in an alkaline aqueous medium. A water-based ink composition for a writing instrument, which is a polyester resin that is poorly or insoluble in an acidic aqueous medium, and the aqueous medium contains a nonvolatile hydrophilic organic solvent. 2. The aqueous ink composition for writing instruments according to claim 1, having a viscosity of about 3 to 10 centipoise. 3. The aqueous ink composition for writing instruments according to claim 1, further comprising a chelating agent.