JP2003268287A - Ink composition for writing tool and pigment dispersion for writing tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a pigment ink composition for a writing tool which exhibits a smooth ink flow equal to that of a dye ink and provides a smooth writing feeling, and a pigment dispersion suitable for preparing the pigment ink composition. <P>SOLUTION: The ink composition for a writing tool comprises a pigment coated with a resin. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment ink for a writing instrument, which has a high jetness, has almost no decrease in the outflow of ink, and is excellent in writing quality.

[0002]

2. Description of the Related Art Conventionally, inks for ballpoint pens include water-based inks and oil-based inks, and it is known that dyes and pigments are used as colorants. When a dye is used as a coloring agent, the weather resistance is poorer than that of a pigment, and thus the drawn lines are faded when stored for a long time after writing. However, since the ballpoint pen tip (hereinafter referred to as the tip) is less likely to be worn by writing, the outflow of ink during writing is smooth and the writing distance is long. On the other hand, when a pigment is used as a colorant, the weather resistance is good, and therefore the writing line does not fade even when stored for a long time, but the pigment itself abrades the tip, so that the writing life is shorter than that of a dye.

[0003]

A pigment ink using a black pigment such as carbon black as a pigment has the advantage that a high jetness can be obtained at the time of writing, while a carbon black exhibiting a high jetness is obtained. When the pigment comes into contact with the chip, the rotating part of the ball is worn and the ball sinks inside the chip, and there is a problem that the ink cannot be written before the ink reaches the end. Also, in terms of writing, there is a problem that the pigment ink is inferior in smoothness to the dye ink.

As an ink composition for a writing instrument, a surfactant such as oleic acid, polyoxyethylene alkylamine, polyethylene glycol monooleate or the like is added to prevent blurring during writing, and the wettability of the ink to the ball of a ballpoint pen tip is added. It is known to improve the ink discharge rate and make it easier to eject ink. However, even with such a method, although the blurring during the writing with the dye ink is improved, it is not sufficient to prevent the phenomenon that the handwriting at the beginning of writing becomes faint or faint, and the abrasion of the ball or chip in the pigment ink is not enough. , And thus, the problem that the ink could not be written before the end of the ink could not be solved. An object of the present invention is to solve the above problems in pigment ink.

[0005]

Means for Solving the Problems The present inventors have made extensive studies in view of the above problems. As a result, the ballpoint pen using the ink for writing instruments containing the pigment that has been subjected to the specific treatment has a significantly reduced wear of the tip, and the ink output hardly decreases. The inventors have reached the present invention by finding that they exhibit an epoch-making performance of being suppressed, and that the writing feel at the time of writing is also smooth and excellent. That is, the present invention is
(1) An ink composition for a writing instrument containing a pigment coated with a resin, (2) a pigment dispersion for a writing instrument containing a pigment coated with a resin, and (3) a pigment for a writing instrument coated with a resin.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

(Pigment) The ink composition and the pigment dispersion for writing instruments of the present invention are characterized by containing a pigment coated with a resin.

The pigment is not particularly limited, and any pigment used as a pigment for writing instruments can be used. In particular, it can be preferably used for a pigment which is relatively hard and has a problem of abrasion of the tip of a ballpoint pen. Specifically, in addition to black pigments typified by carbon black, blue pigments such as ultramarine blue (CI7700
7), navy blue (CI77510), cobalt blue (CI77346), cerulean blue (CI77368), alkaline blue rake (C.
I.42750A), metal-free phthalocyanine blue (CIPigmentB
lue 16), Phthalocyanine Blue (CIPigment Blue 1
5), Fast Sky Blue (CI Pigment Blue 17),
Indance Remble RS (CI69800), Indance Rem Blue BC (CI69825), Indigo (CI73006) and the like can be mentioned. Among them, carbon black has a large hardness and a large problem of abrasion resistance, and therefore, the advantage of applying the present invention is great. The carbon black may be used without particular limitation as long as it can be used for ballpoint pen ink applications. The DBP absorption amount of carbon black is not particularly limited, but is generally 40-
The one of 250 ml / 100 g is preferable. The particle size of carbon black is not particularly limited, but generally 10 to 6
It is preferably 0 nm. Here, the DBP absorption amount is an index of the degree of structure development of carbon black and is determined by ASTM D-3493-88.
The particle size is based on the electron microscope method shown below. Put carbon black into chloroform and apply 200 KHz ultrasonic wave for 2 times.
After irradiating for 0 minutes to disperse, the dispersed sample is fixed on a support film. This is photographed with a transmission electron microscope, and the particle diameter is calculated from the diameter on the photograph and the magnification of the photograph. This operation is performed 3000 times or more, preferably 5000 times or more, and the arithmetic mean of these values is obtained.

(Method for coating resin) The method for obtaining the pigment coated with the resin is not particularly limited, but for example, the resin and the solvent such as cyclohexanone, toluene and xylene are mixed after appropriately adjusting the blending amounts of the pigment and the resin. A carbon solution obtained by heating and dissolving the resin solution and a suspension in which carbon black and water are mixed and stirred to separate carbon black and water, then removing water and kneading by heating. A method in which the black and the resin are granulated and then dried; a carboxylic acid such as maleic acid or fumaric acid is dissolved in the solvent exemplified above, carbon black is added, mixed and dried, and the solvent is removed to impregnate the carboxylic acid. After obtaining carbon black, a method of dry-blending by adding a resin to this; high-speed reaction with a reactive group-containing monomer component constituting the resin to be coated and water And kneading the 拌, by reacting the reactive group with carbon black (by graft carbon black), it may be employed as a method for cooling and grinding.

Specific synthetic resins include thermosetting resins such as phenol resin, melamine resin, xylene resin, diallyl phthalate resin, glyptal resin, epoxy resin and alkylbenzene resin, polystyrene, polycarbonate, polyethylene terephthalate and polybutylene terephthalate. , Modified polyphenylene oxide, polysulfone, polyparaphenylene terephthalamide, polyamide imide, polyimide, polyamino bismaleimide, polyether sulfopolyphenylene sulfone,
Thermoplastic resins such as polyarylate, polyetheretherketone, polyaminobismaleimide, polyethersulfopolyphenylene sulfone, polyarylate and polyetheretherketone can be used.

(Coating amount of resin) The coating amount of resin with respect to carbon black is preferably 1 to 30 wt% with respect to the total amount of carbon black and resin, and when the amount is less than 1 wt%, the writing quality of the obtained ink is improved. , The effect of improving wear resistance is not sufficient. On the other hand, when it exceeds 30 wt%, the adhesiveness between the resins is strong and a mass in the form of dumpling may be formed. In addition, the ink may cause problems such as thickening with time and an increase in dispersed particle size, which is not desirable as a pigment for an ink for writing instruments.

Further, it is desirable to coat the resin until the powder resistance reaches 10 Ω · cm or more. This is because the conductivity of carbon black is generally lowered by coating it with a resin, and the degree of coating can be grasped by the powder resistance. Here, the powder resistance is a value obtained by the following measuring method.

First, a carbon black (pigment) is added with a resin, a solvent and, if necessary, a dispersant, and finely divided by a ball mill or the like to obtain an evaluation paste. That is, the above carbon black (pigment) was added to a varnish obtained by mixing 37.8% of a 40% solution of ethyl cellosolve, an alkali-soluble polymer compound (manufactured by Atokemi Co., Ltd., "SMA-17352") and 54.1% of ethyl cellosolve acetate. Add 1% to 8.1%
Using a sand mill containing glass beads of a diameter of 2,000
A paste is prepared by mixing and dispersing at 0 rpm for 10 hours.
This paste is dried at 120 ° C. until the weight loss on heating at 150 ° C. is 1.0% or less, and crushed for 1 minute with a juicer mixer to obtain a sample. Diameter 20 mm, internal volume 110 m
The resistance value is measured in a state in which 2.0 g of the sample is placed in a 1-liter container made of polytetrafluoroethylene (having metal electrodes on the upper and lower sides) and pressed at a pressure of 50 kg / cm ² . The resistance value thus obtained is the powder resistance.

The powder resistance of carbon black (pigment) is preferably 10 Ω · cm or more, particularly preferably 10 ³ Ω ·.
cm or more, and more preferably 10 ⁵ Ω · cm or more. If it is less than 10 Ω · cm, the effect of improving wear resistance tends to decrease.

The ink composition and the pigment dispersion of the present invention are characterized by containing the above-described resin-coated pigment, but other pigments may be used in combination. However, its content is 50 wt% with respect to the entire pigment.
It is desirable to keep the content below 40 wt% in order to obtain the effects of the present invention sufficiently.

The pigment dispersion for a writing instrument of the present invention is sufficient if the pigment coated with the resin described above is dispersed in the dispersion medium, and it does not matter whether or not other components are present. For example, a part of the components that can be contained in the ink composition for a writing instrument of the present invention described below can be partly mixed in advance with the pigment dispersion liquid. Also, the dispersion medium of the pigment dispersion is not limited, but may be appropriately selected from the dispersion medium of the ink composition described below according to the composition of the target ink.

The ink composition for a writing instrument of the present invention only needs to contain the pigment coated with the above-mentioned resin, and the above-mentioned pigment is dispersed in the dispersion medium. In addition, the ink composition for a writing instrument is generally blended. Various components can be included.

(Ink Dispersion Medium) Water or a water-soluble organic solvent is used as the aqueous medium in the case of an aqueous ink composition for a ballpoint pen or a pigment dispersion liquid used for the same. The organic solvent is not particularly limited, but is usually ethylene glycol, diethylene glycol, propylene glycol, glycerin, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, or the like. The amount of the organic solvent blended is 5 to 40% by weight, preferably 15 to 3%, with respect to the entire aqueous medium.
It is 0% by weight.

In the case of the oil-based ink composition for a ballpoint pen or the pigment dispersion liquid used for it, various organic solvents can be used as an oil-based medium. Any conventional oil-based ballpoint pen can be used without particular limitation, and examples thereof include ethylene glycol monophenyl ether, benzyl alcohol, propylene glycol, dipropylene glycol, 1,3-butylene glycol, hexylene glycol, tetralin, and propylene glycol. Monophenyl afel, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether,
Dipropylene glycol monomethyl ether acetate, tripropylene glycol monomethyl ether, N
-Methyl-2-pyrrolidone and the like, which can be appropriately selected and used alone or in combination, and the amount thereof is preferably 30 to 70% by weight based on the total amount of the ink.

(Dye) In preparation of the ink composition for a writing instrument of the present invention, a dye may be used in combination with the above-mentioned pigment as a coloring material. The dye is not particularly limited as long as it is a dye conventionally used in ballpoint pen ink compositions, and examples thereof include rhodamine B base (C.I. 45170).
B), Soldan Red 3R (C.I. 21260), Methyl Violet 2B base (C.I. 42535).
B), Victoria Blue F4R (C.I. 42653)
B), Nigrosine base LK (CI.50415),
Varifast Yellow # 3104 (C.I. 13900A) as an oily dye manufactured by Orient Chemical Industry Co., Ltd.,
Bali First Yellow # 3105 (C.I. 1869
0), Orient Spirit Black AB (C.I.
50415), Bali First Black # 3804
(C.I. 12195), Bali First Yellow # 1
109, Bali First Orange # 2210, Bali First Red # 1320, Bali First Blue # 16
05, Varifast Violet # 1701, Hodogaya Chemical Co., Ltd. oil dyes, Spiron Black GMHC Special, Spiron Yellow C-2G
H, spirone red C-GH, spirone red CB
H, Spiron Blue BPNH, Spiron Blue CR
H, Spiron Violet C-RH, S. P. T. Orange 6, S.I. P. T blue-111 etc. can be illustrated.

(Resin) In the preparation of the ink composition for a writing instrument, a resin component may be added for the purpose of increasing viscosity, improving handwriting fixability, improving pigment dispersion stability, or the like. Various kinds of resin components conventionally used for such purpose can be used without limitation. For example, ketone resin, xylene resin, polyethylene oxide, rosin resin, rosin derivative, terpene resin, coumarone-indene resin, polyvinyl butyral, polyvinylpyrrolidone, vinylpyrrolidone-vinyl acetate copolymer, polymethacrylic acid ester, polyacrylic acid poly Methacrylic acid copolymer, polyacrylic acid, styrene-maleic acid resin,
Examples thereof include styrene-acrylic resin.

Further, surfactants such as anions, nonions and cations may be added mainly or supplementarily.

The content of these additives depends on the kind of pigment,
It may be appropriately selected depending on the shade of the color of ink, the purpose of addition, etc., and is about 0.1 to 40 wt% with respect to the pigment and about 0.05 to 20 wt% with respect to the total amount of ink.

(Other Components) In addition, a thickening agent such as synthetic finely divided silica, bentonite, and ultrafine precipitated calcium carbonate can be added. Its content is 0.01-1
It is 0 wt%, preferably 0.5 to 5 wt%. Other than the resins used for the thickener, dispersant, etc., other resins and fixing agents can be used if necessary. Further, a rust preventive agent, a lubricant, an antiseptic agent and the like can also be used. Each of the above components is dispersed to form an ink composition. The dispersing machine used for dispersion is not limited, but a media mill is generally used. The medium used is not limited, and generally glass,
Zirconia or the like is used. Further, when preparing the ink composition, the pigment for a writing instrument of the present invention may be previously prepared as a pigment dispersion liquid uniformly dispersed in a dispersion medium such as water, and the remaining components may be further mixed. By doing so, it becomes easy to ensure the uniformity of the ink composition. Here, the dispersion medium of the pigment dispersion liquid is preferably selected from the dispersion medium used in the ink composition. Other components such as a dispersant in the ink composition may be present in the pigment dispersion liquid.

EXAMPLES The present invention will be described in more detail below with reference to examples. Unless otherwise noted, "parts"
Represents "parts by weight" and "%" represents "% by weight". [Examples 1 to 5 and Comparative Examples 1 to 5] (1) Production of resin-coated carbon black: Resin-coated carbon blacks were prepared by the following methods using carbon blacks A ′ to E ′ having physical properties shown in Table 1. It was made.

540 g of carbon black and 1450 pure water
0 g was mixed with a homomixer at 6,000 rpm for 30 minutes to prepare a slurry. On the other hand, 60 g of "Epicoat 828" manufactured by Yuka Shell Epoxy Co.
It was dissolved in 0 g to prepare an epoxy resin solution.

The above slurry was transferred to a vessel equipped with a screw type stirrer, and the above epoxy resin solution was added little by little under stirring conditions of about 1,000 rpm. After about 15 minutes, the entire amount of carbon black dispersed in water moved to the toluene side and became particles of about 1 mm. Then 60
After draining with a wire mesh for about 10 minutes, it was dried with a vacuum dryer at 70 ° C. for 7 hours to remove water and toluene to obtain resin-coated carbon blacks A to E.

[0026]

[Table 1]

In Table 1, the total oxygen content is measured by the following method. Carbon black dried at 150 ° C for 1 hour is placed in a cylindrical container made of about 0.50 g of alumina, decompressed to 10 ^-3 Torr, and then slowly charged into an electric furnace at 1500 ° C ± 10 ° C. The desorbed gas was collected in a sample container, thoroughly mixed, and subjected to gas chromatography. Separation / quantification
CO ₂ , CO, H ₂ , and CH ₄ were used, and CO ₂ and the oxygen complex that emerged as CO were added to give the total oxygen content.

(2) Preparation of ink composition: As shown in Table 2, an ink composition was prepared using carbon blacks A'to E'and carbon blacks A to E with the following formulation.

[0029]

[Table 2]

[Compound formulation] Carbon black 8.5 parts Deionized water 54.0 parts Dispersion resin 0.5 part Solvent 25.0 parts Lubricant 2.0 parts Other additives 10.0 parts ――――――――――――――― Total 100.0 copies

The dispersion resin used was a styrene acrylic resin, the solvent was a mixture of propylene glycol, polyethylene glycol and glycerin, the lubricant was a phosphate ester, and the other additives were a defoaming agent, a preservative, a rust preventive agent, a resin. Emulsions, which were commonly used commercially. [Comparative Example 6] Prescription dye for dye ink 8.0 parts Ion-exchanged water 65.0 parts Solvent 25.0 parts Lubricants 1.0 parts Other additives 1.0 parts ――――――――――― ―――― Total 100.0 copies

[Evaluation Test] Using the ink compositions obtained in Examples 1 to 5 and Comparative Examples 1 to 6, the following evaluation tests were conducted.

(1) Temporal stability The temporal stability was evaluated by measuring the dispersed particle size of the pigment and the viscosity of the liquid by a test at room temperature and an accelerated test in a constant temperature chamber at 50 ° C. For the dispersed particle size of the pigment, "Coulter N4 Plus" (manufactured by Beckman Coulter) is used.
The sample was diluted with ion-exchanged water so that the signal level was 1.0 × E05 to 9.0 × E05, and the diluted solution was used for measurement. For the viscosity, an ELD type viscometer (manufactured by Toki Sangyo Co., Ltd.) was used, and the viscosity was measured at 50 rpm and 1 minute after the start of measurement.

The dispersed particle size of the pigment is 150 nm or less at the initial particle size in each of the inks of Examples 1 to 5 and Comparative Examples 1 to 5, and the initial particle size after 3 months at both room temperature and 50 ° C. It was found to be stable, being less than twice the value, and practically no problem. In addition, the viscosity of the ink is 1-5, Comparative Example 1-
The initial viscosity of each of the 5 inks is 5 mPa · s,
It was found that both room temperature and 50 ° C. were stable at 2 times or less of the initial viscosity even after 3 months, and there was no problem in practical use. The ink of Comparative Example 6 does not contain a pigment component, and the size of the dye molecule cannot be detected by the above measuring method. Also,
Viscosity is 5 mP both at room temperature and at 50 ° C after 3 months
It was a · s or less.

(2) Abrasion resistance The above ink composition (1.5 g) was filled in an ink container for polypropylene ballpoint pens, and the abrasion resistance was evaluated by measuring the writing distance with a drawing machine. The drawing machine is TS
-4C type (manufactured by Seiki Kogyo), the writing angle is 60 °,
The writing pressure was 100 g and the writing speed was 4 m / min. The results are shown in Table-3.

It can be seen that the inks of Examples 1 to 5 have a writing distance 1.5 times or more longer than the inks of Comparative Examples 1 to 5, and are comparable to the dye ink of Comparative Example 6. Comparative Example 1
Regarding Nos. 4 to 5, it became impossible to write with the ink left. It is considered that this is because the ink of the example wears less balls and chips than the ink of the comparative example.

(3) Amount of sinking ball The above ink composition was written for 500 m with an image drawing machine under the same conditions as in the measurement of abrasion resistance, and the tip of the chip was observed with a microscope VH-7000 (manufactured by KEYENCE). The amount of ball sinking was measured. The results are shown in Table-3.

(4) Writability Pens were filled with the ink compositions of Examples 1-5 and Comparative Examples 1-5 and a writing test was conducted. The inks of Comparative Examples 1 to 5 had a sharp writing feeling peculiar to carbon, but the inks of Examples 1 to 5 did not have the sharp writing feeling and could be written smoothly. Further, Table 3 shows the results of evaluation of writing quality by having 20 people actually write. It can be seen that the ink of the example has a higher evaluation of writing quality than the ink of the comparative example.

(5) Weather resistance The ink composition having the above composition was used as a bar coater No. In 6, the color was spread on plain paper, and the test paper was irradiated with light for 24 hours using a xenon fade meter X25F type (manufactured by Suga) to visually confirm the color change. The results are shown in Table-3. Better results have been obtained with carbon black as the colorant than with dyes.

[0040]

[Table 3]

[0041]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to obtain a pigment ink composition for a writing instrument which is excellent in ink discharge as good as a dye ink and has a smooth writing taste, and a pigment dispersion suitable for preparation of such a pigment ink composition. .

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideyuki Hisa             138-1 Kokubunji, Kokuno-cho, Himeji City, Hyogo Prefecture             Kokupi Co., Ltd. F-term (reference) 4J037 EE03 EE28                 4J039 BE01 GA27

Claims (3)

[Claims] 1. An ink composition for a writing instrument containing a pigment coated with a resin. 2. A pigment dispersion for a writing instrument, which contains a resin-coated pigment. 3. A writing instrument pigment coated with a resin.