JPH04325577A - Black pigment water-based ink composition for ballpoint pens - Google Patents

Abstract

PURPOSE:To provide the title compsn. which is produced with the necessity for removing only a small amt. of pigment and gives written characters with a high blackness when used for writing. CONSTITUTION:The title compsn. comprises a carbon black having a structure index of 60 or lower, water, a water-sol. org. solvent such as ethylene glycol or glycerin, and a viscosity-adjusting agent consisting of a water-sol. polymer such as carboxymethylcellulose or polyoxyethylene oxide, and has a viscosity of 50-2000cp at 25 deg.C.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based ink composition for ball-point pens using carbon black, and more particularly to a water-based ink composition for ball-point pens with a high degree of blackness.

0002

[Prior Art] Conventionally, an ink consisting of at least a pigment, water, and a water-soluble organic solvent has a viscosity of 50 to 2000 cps (
25° C.), a pigment ink for a ballpoint pen characterized in that the viscosity modifier is a water-soluble polymer has been proposed. This kind of ink can use a hollow cylinder as an ink storage body, and has the advantage of being able to obtain handwriting without line breaks and smudges, which is the characteristic of conventional water-based ballpoint pens, and the ability to check the amount of ink remaining, which is the characteristic of oil-based ballpoint pens. This ink for ballpoint pens has the features of being able to write lines without bleeding, and carbon black is generally used as the black pigment.

0003

[Problems to be Solved by the Invention] Pigment ink for ballpoint pens requires a step to remove coarse pigment particles that cannot be finely dispersed in order to prevent inability to write due to clogging and pigment sedimentation over time. In particular, in pigment inks whose viscosity is controlled by water-soluble polymers as described above, a large amount of pigment is removed because the water-soluble polymers are adsorbed to the pigments and the apparent particle size of the pigments increases. Therefore, there was a problem in that sufficient handwriting density could not be obtained for the amount of pigment added. In order to solve the above problem, increasing the amount of pigment added may be considered, but this not only increases cost but also causes poor dispersion (for example, an increase in the proportion of coarse pigment particles). Attempts to reduce the coarse particles of pigment in ink compositions, increase the proportion of finely and stably dispersed pigments, and obtain high blackness include various dispersants, surfactants used as dispersion aids, water-soluble Although various studies have been made from the viewpoint of polymers, there are still no satisfactory results.

0004

[Means for Solving the Problems] The present invention aims to solve the above problems, and provides carbon black, water, a water-soluble organic solvent, and a water-soluble polymer as a viscosity modifier. and the ink viscosity is at least 50~
The gist of the present invention is a black pigment aqueous ink composition for a ballpoint pen in which the carbon black has a structure index of 60 or less in a black pigment aqueous ink composition for a ballpoint pen in the range of 2000 cps (25° C.).

The present invention will be explained in detail below. Carbon black, which is a coloring agent, must have a structure index of 60 or less in order to obtain a sufficiently high degree of blackness in the ink composition. Specific examples of carbon black having a structure index of 60 or less will be described below. Printex 95, Printex 90, Printex 85 as those with a structure index of 30 or less
, (manufactured by Degussa, Germany), MONARCH11
00 (manufactured by Cabot, Germany), #2400, #23
50, #2300, #2200B, #950, #900
(All of the above are manufactured by Mitsubishi Chemical Industries, Ltd.). 30-4
Printex 75 (manufactured by Degussa, Germany), MONARCH 900, MONARCH 800 (manufactured by Cabot, USA), #1000, MCF88 (manufactured by Mitsubishi Chemical Industries, Ltd.), RAVEN1500 (Columbian Carbon) (manufactured by Nippon Co., Ltd.). 40-5
#850 (manufactured by Mitsubishi Chemical Industries, Ltd.)
, RAVEN2000 (manufactured by Columbian Carbon Japan Co., Ltd.). MONARC for 50-60
H880 (manufactured by Cabot, USA), MA8, MA7 (
Above, manufactured by Mitsubishi Chemical Industries, Ltd.), RAVEN1250,
1255 (manufactured by Columbian Carbon Japan Co., Ltd.). The amount used is preferably 3 to 20% by weight based on the total amount of the black pigment aqueous ink composition for ballpoint pens.

[0006] Here, the structure index is
The value proposed by Sweitzer and Goodrich (Sweitzer, c.w., Goodrich, w.
．． c. :Rubber Age, 55,469(19
44)), which is a normal structure assumed in advance over a wide range of specific surface areas (the structure index is 100), as shown in equation 1 below.
This is a value expressed as a percentage of the actual oil absorption amount (a2) of carbon black to the oil absorption value (a1) of . In the present invention, in calculating the value of the structure index, the amount of oil absorption was determined by the amount of DBP adsorbed, and the specific surface area was determined by the BET method.

[0007]

[Formula 1] Structure index=a2/a1×100

0
[008] The water-soluble organic solvent is used for various purposes such as preventing the ink from drying at the pen tip and preventing the ink from freezing at low temperatures. Specifically, ethylene glycol,
Diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, 1,3-
Glycols such as butylene glycol, thiodiethylene glycol, glycerin, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone triethanolamine, etc. are used singly or in combination of two or more. The amount is preferably 50% by weight or less based on the total amount of the black pigment aqueous ink composition for ballpoint pens.

[0009] Water-soluble polymers as viscosity modifiers include:
For example, synthetic polymers such as polyvinylpyrrolidone, polyethylene oxide, polyacrylate, methyl vinyl ether maleic anhydride copolymer, and modified products thereof, cellulose thickeners such as carboxymethyl cellulose and hydroxypropyl cellulose, hydrogenated castor oil, and polycarbonate. All water-soluble products can be used, including gelling agents such as acid amides, vegetable thickeners such as gar gum and gum arabic, and animal thickeners such as gelatin and shellac. The above can be used in combination.

Further, the black pigment aqueous ink composition for ballpoint pens of the present invention has a viscosity of 50 to 200 at 25°C.
The essential condition is that it is 0 cps. Ink viscosity is 5
This is because if the speed is less than 0 cps, ink leaks from the pen tip, and if it exceeds 2000 cps, the ink will not be ejected from the pen tip, making handwriting likely to blur.

In addition to the above-mentioned essential components, conventionally known surfactants, dispersants, preservatives, antifungal agents, lubricants, etc. may be appropriately selected.

Various methods can be employed to obtain the present aqueous black pigment aqueous ink composition for ballpoint pens. Specifically, the above ingredients are blended, mixed and ground using a dispersing machine such as a ball mill, homo mixer, sand grinder, speed line mill, or three-roll mill, and then coarse particles are removed using filtration or a centrifugal separator. An example of this method is to remove it.

[0013]

[Function] The black pigment water-based ink composition for ballpoint pens according to the present invention uses carbon black having a structure index of 60 or less, and is easily dispersed in a form close to primary particles, and therefore has a water-soluble polymer. The increase in apparent particle size due to adsorption is small, and the amount of pigment removed as coarse particles is small, so it is assumed that a large amount of carbon black can be stably dispersed in the ink composition, resulting in a high degree of blackness. .

[0014]

[Examples] The present invention will be explained in more detail below with reference to Examples.

Example 1 #1000 (Structure index: 30)
15.0 parts Styrene-acrylic acid copolymer ammonium salt
5.0 parts Gargam


0.5 part ethylene glycol

29.0 parts water

5
0.5 part

Example 2 #850 (Structure index: 45)
15.0 parts Styrene-acrylic acid copolymer ammonium salt
5.0 parts Gargam


0.5 part ethylene glycol

29.0 parts water


50.5 copies

Example 3 MA8 (Structure index: 54)
15.0 parts Styrene-acrylic acid copolymer ammonium salt
5.0 parts Gargam


0.5 part ethylene glycol

29.0 parts water


50.5 copies

Example 4 MA7 (Structure index: 60)
15.0 parts Styrene-acrylic acid copolymer ammonium salt
5.0 parts Gargam


0.5 part ethylene glycol

29.0 parts water


50.5 copies

Example 5 #1000

15.0 parts Styrene-maleic acid copolymer ammonium salt
8.0 parts polyethylene oxide

2.0 parts ethylene glycol
25.0 copies
water

50.0 copies

Example 6 #850

15.0 parts Styrene-maleic acid copolymer ammonium salt
8.0 parts polyethylene oxide

2.0 parts ethylene glycol
25.0 parts water

50.0 copies

Example 7 MA8

15.0 parts Styrene-maleic acid copolymer ammonium salt
8.0 parts polyethylene oxide

2.0 parts ethylene glycol
25.0
Part water

50.0 copies

Example 8 MA7

15.0 parts Styrene-maleic acid copolymer ammonium salt
8.0 parts polyethylene oxide

2.0 parts ethylene glycol
25.0
Part water

50.0 copies

Comparative Example 1 RAVEN1035 (Structure index: 69, manufactured by Columbian Carbon Japan Co., Ltd.)

15.0 parts Styrene-acrylic acid copolymer ammonium salt
5.0 parts Gargam


0.5 part ethylene glycol

29.0 parts water


50.5 copies

Comparative Example 2 MA100 (Structure index: 95,
(manufactured by Mitsubishi Chemical Industries, Ltd.)

15
．． 0 parts Styrene-acrylic acid copolymer ammonium salt 5.0 parts Gar gum

0.5 part ethylene glycol
29.0 parts water

50.5 copies

Comparative Example 3 RAVEN1035

15.0 parts Styrene-maleic acid copolymer ammonium salt
8.0 parts polyethylene oxide

2.0 parts ethylene glycol

25.0 parts water


50.0 copies

Comparative Example 4 MA100

15.0 parts Styrene-maleic acid copolymer ammonium salt
8.0 parts polyethylene oxide

2.0 parts ethylene glycol
25.0 copies
water

50.0 copies

As described above, in Examples 1 to 4 and Comparative Examples 1 and 2, the components other than gar gum were mixed and dispersed in a ball mill for 24 hours, and then gar gum was added and dispersed again for 3 hours. and
Furthermore, coarse particles were removed using a 1 μm filter to obtain a black pigment aqueous ink composition for ballpoint pens. In addition, in Examples 5 to 8 and Comparative Examples 3 and 4, each component was mixed, subjected to dispersion treatment in a ball mill for 24 hours, and then coarse particles were removed with a 1 μm filter to obtain a black pigment aqueous ink composition for ballpoint pens. I got it. The polyethylene oxide used had an average molecular weight of 250,000 to 300,000.

[0028]

Effects of the Invention Tests were conducted on the black pigment aqueous ink compositions for ballpoint pens obtained in Examples 1 to 8 and Comparative Examples 1 to 4. The results are shown in Table 1.

(1) Spatula drawing blackness The obtained ink composition was applied to JIS P3201 writing paper A using a silicone rubber spatula, and the color was measured using an SM color computer manufactured by Suga Test Instruments Co., Ltd. The degree of blackness is
It is indicated by the Y value according to the CIE color system (the lower the value, the higher the degree of blackness).

(2) The obtained ink composition with blackness of handwriting is directly filled into a transparent ink storage tube made of a hollow barrel made of polypropylene with a nickel silver ballpoint pen tip (ball material: cemented carbide) connected to one end. Shi, J
The density of handwriting when handwritten on IS P3201 writing paper A was visually determined. ◎: Very dark ○: Dark △: Normal ×: Thin

[0031]

[Table 1]

As described above in detail, the black pigment aqueous ink composition for ballpoint pens of the present invention has a high degree of blackness and can provide clear writing lines.

Claims (1)

[Claims] 1. An ink composition comprising at least carbon black, water, a water-soluble organic solvent, and a water-soluble polymer as a viscosity modifier, and has an ink viscosity of 50 to 2000 cps (25
C), wherein the carbon black has a structure index of 60 or less.