JP2008013585A - Oil-based ink for ballpoint pens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink that does not affect other quality while increasing the production efficiency by increasing the filtration time at the time of producing oil-based ink for ballpoint pens using a cellulose derivative.
SOLUTION: In an oil-based ink for ballpoint pens comprising at least a colorant, an organic solvent, and a shear thinning agent, the organic solvent is mainly glycol monoether, and the total amount of polyhydric alcohol having 2 to 6 carbon atoms is used. An oil-based ink for ballpoint pens comprising 0.05% to 5.0% by weight based on the weight of the ink and a cellulose derivative as a shear thinning agent in an amount of 0.02% to 3% by weight based on the total ink.
[Selection figure] None

Description

  The present invention is housed in a ballpoint pen that has a ballpoint pen tip that is rotatably held by partially protruding a ball for transferring ink onto a writing surface such as a paper surface, and uses an organic solvent as a main medium. The present invention relates to oil-based ink for ballpoint pens. More specifically, the present invention relates to an oil-based ink for ballpoint pens that is extremely easy to filter when coarse particles, dust, and the like are filtered at the time of ink production and that is free from problems over time.

Conventionally, inks that use polyhydric alcohols having 2 to 6 carbon atoms in oil-based inks for ballpoint pens and to which shear thinning viscosity or viscosity modifiers are added are known (Patent Documents 1, 2, and 3).
It is also known to add a lubricant such as an acylamino acid, N-acylmethyltauric acid, N-acylmethylalanine or the like to the ink as a means for smoothly rotating the ball of the ballpoint pen (Patent Document 4). .
Japanese Patent Application Laid-Open No. 11-116879 (10th to 34th lines from the top of the 2nd page, 1st column and 20th to 24th lines from the 4th page, 5th column) No. 2002-309148 (18th line from the top of the 3rd page, 3rd column to 22nd line from the top of the 4th page, 6th column) No. 2003-321637 (first line to twelfth line from page 3, column 4, and second to 18th line from page 4, column 5) 2006-008974 gazette (from page 4, line 28 to line 42)

As disclosed in Patent Documents 1 to 3, inks using polyhydric alcohols having 2 to 6 carbon atoms and added with shear thinning or viscosity modifiers are difficult for the solvent to uniformly dissolve the cellulose derivative. Therefore, when filtering is performed in order to remove coarse particles and insoluble components, filter paper or the like is likely to be clogged, and it takes time to filter and the amount of filtration is very small.
In particular, when a lubricant such as acylamino acid, N-acylmethyltauric acid, N-acylmethylalanine and the like as described in Patent Document 4 is used, the lubricity is greatly improved, but the solubility of the entire ink is lowered. Therefore, depending on the combination of the cellulose derivative, glycol ether, and colorant, the dissolution of the colorant is given priority due to insufficient solubility of the glycol ether, and the cellulose derivative molecules cannot be fully separated and are in a semi-dissolved state. In some cases, the filterability may deteriorate. Therefore, in order to solve this problem, even if the temperature at the time of filtration is raised to lower the ink viscosity or the filtration pressure is raised, this problem cannot be solved.
Therefore, an object of the present invention is to provide an oil-based ink for a ballpoint pen that is free from problems over time, while increasing the production efficiency by increasing the filtration time during the production of the oil-based ink for a ballpoint pen using a cellulose derivative.

  That is, the present invention includes at least a colorant, a glycol monoether, a polyhydric alcohol having 0.05 to 5.0% by weight of carbon to 2 to 6% of the total amount of the ink, and the entire ink. The oil-based ink for ballpoint pens containing 0.02% by weight or more and 3% by weight or less of a cellulose derivative is the gist.

When the cellulose derivative is dissolved in glycol monoether, the glycol monoether has a hydroxyl group only on one side of the molecule, so that the hydrogen bonds between and within the cellulose derivative cannot be sufficiently eliminated. As a result, molecular chains cannot be separated, and entanglements within the molecule are not sufficiently eliminated, so that insoluble particles that inhibit filtration are generated in the ink, resulting in poor efficiency when filtering. it is conceivable that. In particular, if N-acylamino acid, N-acylmethyltauric acid, N-acylmethylalanine, etc. are present, these will hydrogen bond with glycol monoether instead of the cellulose derivative, so that the solubility of the cellulose derivative becomes worse. it is conceivable that.
Here, when a polyhydric alcohol having 2 to 6 carbon atoms is used in combination, the hydrogen bond to cellulose ether, which was insufficient with glycol monoether, becomes sufficient due to the hydroxyl group, and the hydrogen bond between molecular chains and within the molecule is broken. I can do it. Therefore, it is considered that the cellulose derivative can be sufficiently dissolved and can be easily filtered because there are no insoluble particles that inhibit filtration.

The invention is described in detail below.
In the present invention, glycol monoether is the main medium of the ink. For example, phenyl cellosolve, ethylene glycol monobenzyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol Examples thereof include monoethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, and tripropylene glycol monobutyl ether. These solvents can be used alone or in combination, and the amount used is preferably 10% by weight or more and 80% by weight or less based on the total amount of the ink.

Examples of the C 2-6 polyhydric alcohol used in combination with glycol ether include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, pentylene glycol, hexylene glycol and the like. The amount used is 0.05 wt% to 5.0 wt% with respect to the total amount of ink.
It is. If the amount is less than 0.05% by weight, the effect of increasing the filtration efficiency is weak, and if it exceeds 5.0% by weight, it may absorb moisture over time and cause problems such as ink separation and aggregation.

In the present invention, both a dye and a pigment can be used as the colorant.
Examples of pigments include carbon black, insoluble azo pigments, azo lake pigments, condensed azo pigments, diketopyrrolopyrrole pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, anthraquinone pigments, dioxazines. Conventionally known general pigments such as organic pigments such as pigments, indigo pigments, thioindigo pigments, quinophthalone pigments, perinone and perylene pigments can be used. These may be used alone or in combination of two or more.

Carbon black can be used as the black pigment. For example, Printex 3, 25, 30, 35, 40, 45, 55, 60, 75, 80, 85, 90, 95, 300, Special Black 4, 5, 100, 250, 550 (Degussa Huls Japan Co., Ltd.). Mitsubishi Carbon Black # 2700, # 2650, # 2600, # 2400, # 2350, # 2300, # 2200, # 1000, # 990, # 980, # 970, # 960, Same # 950, Same # 900, Same # 850, Same # 750, Same # 650, Same # 52, Same # 52, Same # 50, Same # 47, Same # 45, Same # 45L, Same # 44, Same # 40, Same # # 33, # 32, # 30, # 25, # 20, # 10, # 5, # 95, # 260, CF9, MCF88, MA600, MA77, MA7, MA11, MA100, MA100R, MA100S, MA100S, MA220, MA230 (manufactured by Mitsubishi Chemical Corporation), Talker Black # 8500 / F, # 8300 / F, # 7550SB / F, # 7400, # 7360 B / F, the # 7350 / F, the # 7270SB, the # 7100 / F, the # 7050 (all manufactured by Tokai Carbon Co., Ltd.) and the like.
Examples of blue pigments include C.I. I. Pigment Blue 2, 9, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 16, 17, 28, 29, 36, 60, 68, 76, 80, etc. can be used.
Examples of red pigments include C.I. I. Pigment Red2, 3, 5, 8, 14, 17, 17, 22, 31, 31, 48: 1, 48: 2, 48: 3, 48: 4, 53: 1, 53: 2, 57: 1, 112, 122, 144, 146, 149, 166, 170, 175, 176, 177, 179, 184, 185 187, 188, 202, 207, 208, 209, 210, 211, 211, 213, 214, 242, 253, 254, 255, 256, 256, 257, 264, 266, 268, 270, 272, etc. can be used.
Examples of yellow pigments include C.I. I. Pigment Yellow1, 3, 12, 13, 13, 16, 17, 55, 73, 74, 79, 81, 83, 93, 94, 95, 97 109, 110, 111, 120, 128, 133, 136, 138, 139, 147, 151, 154, 155, 167, 173, 174, 175, 176, 180, 185, 191, 194, 213, etc. can be used.
Examples of orange pigments include C.I. I. Pigment Orange 5, 13, 13, 16, 34, 36, 38, 43, 62, 68, 72, 74, and the like.
Examples of green pigments include C.I. I. Pigment Green 7, 36, 37, etc. can be used.
Examples of purple pigments include C.I. I. Pigment Violet 19, 23 and the like can be used.
In addition to these pigments, processed pigments can also be used. For example, Renol Yellow GG-HW30, HR-HW30, Orange RL-HW30, Red HF2B-HW30, FGR-HW30, F5RK-HW30, Carmine FBB-HW30, Violet RL- HW30, Blue B2G-HW30, CF-HW30, Green GG-HW30, Brown HFR-HW30, Black R-HW30 (manufactured by Clariant Japan Co., Ltd.), UTCO-001 Yellow, 012 Yellow, 021 Orange, 031 Red, 032 Red, 042 Violet, 051 Blue, 052 Blue, 061 Green, 591 Black, 591 Black, 592 Black (manufactured by Daiichi Seika Kogyo Co., Ltd.), MICROLITY Yel ow 4G-A, MX-A, 2R-A, Brown 5R-A, Scarlet R-A, Red 2C-A, 3R-A, Magenta 2B-A, Violet B-A, Blue 4G-A, Green GA (made by Ciba Specialty Chemicals Co., Ltd.).

As the dye, a commonly used dye can be used.
Examples of dyes that can be used include SPILON BLACK GMH SPECIAL, SPILON RED C-GH, SPILON RED C-BH, SPILON BLUE C-RH, SPILON BLUE BPNH, SPILON YELLOW C-2GH, SPILON VIOLET C-RH, S. P. T.A. ORANGE6, S. P. T.A. BLUE 111 (manufactured by Hodogaya Chemical Co., Ltd.), etc. , VALIFAST BLUE 1601, VALIFAST BLUE 1603, VALIFAST BLUE 1621, VALIFAST BLUE 2601, VALIFAST YELLOW 1110, VALIFAST YELLOW 3104, VALIFAST YELLOW 3109, VALIFAST Varifast color, orient oil color, rhodamine B base, solder red 3R, methyl violet 2B base, Victoria blue F4R, nigrosine base LK, etc., neo super blue C-555 (Chuo Synthetic Chemical Co., Ltd.) Manufactured).
The amount of these colorants to be used is preferably 1% by weight or more and 40% by weight or less based on the total ink composition, and 3 to 20% by weight is more preferable for obtaining sufficient handwriting fastness. When the amount used is less than 1% by weight, the handwriting is too thin, and the amount of the colorant remaining on the paper surface when the light resistance test or the solvent resistance test is performed becomes small and the handwriting becomes difficult to read. On the other hand, when the amount is more than 40% by weight, it becomes easy to cause a problem that writing becomes unsatisfactory due to clogging due to sedimentation or precipitation over time or an increase in solid content in the ink, resulting in a heavy writing taste.

  N-acyl amino acid, N-acyl tauric acid, N-acyl methyl tauric acid, and N-acyl methyl alanine are for imparting lubricity to the ink, and are added in the ink in an amount of 5 wt% to 60 wt%. To do. If it is less than 5% by weight, the lubricity becomes insufficient and the rotation of the ball is hindered by the frictional force between the ball and the seat, so that smooth writing cannot be obtained. If it exceeds 60% by weight, the drying of the ink is delayed, so that the ink gradually moves along the fibers of the paper, and as a result, bleeding with time occurs. For example, N-oleoyl sarcosine, N-lauroyl sarcosine, N-myristoyl sarcosine, N-palmitoyl sarcosine, N-oleoyl tauric acid, N-lauroyl tauric acid, N-myristoyl tauric acid, N-palmitoyl tauric acid N-oleoylmethyltauric acid, N-lauroylmethyltauric acid, N-myristoylmethyltauric acid, N-palmitoylmethyltauric acid, N-oleoylmethylalanine, N-lauroylmethylalanine, N-myristoylmethylalanine, N -Palmitoylmethylalanine etc. are mentioned.

The cellulose derivative is added to impart shear thinning viscosity to the ink to reduce the viscosity of the ink at the time of writing, reduce the force required to rotate the ball, and allow writing with a light force. As the shear thinning agent, cellulose derivatives such as hydroxypropylcellulose, hydroxyethylcellulose, ethylhydroxyethylcellulose, and ethylcellulose can be used.
Of these, hydroxypropyl cellulose having good solubility and viscosity characteristics is preferred. The cellulose derivative is preferably used in an amount of 0.02 to 3.0% by weight based on the total ink composition. More preferably, it can be used at 0.02 wt% or more and 2.0 wt% or less. If the addition is less than 0.02% by weight, sufficient shear thinning cannot be imparted to the ink. If the addition is more than 3.0% by weight, the viscosity of the ink becomes too high, resulting in poor fluidity. The writing becomes heavier and the wrinkle of the writing lines becomes larger.
It should be noted that the shear thinning index is 0.3 or more and 0 for the purpose of making the writing quality lighter by preventing the ink from leaking out when the pen tip is left face down and making the viscosity decrease during writing an optimum value. .9 or less is preferable.
Similarly, it is preferable to adjust the ink viscosity at a shear rate of 2 / s at 25 ° C. to 500 mPa · s or more and 10,000 mPa · s or less for the purpose of suppressing ink leakage and obtaining a light writing quality.
Moreover, in order to assist the function of the cellulose derivative, there is no problem in using another shear thinning agent in combination. For example, water-soluble polysaccharides such as hyaluronic acid, poly-N-vinylacetamide, cross-linked poly-N-vinylacetamide, poly-N-isopropylacrylamide, polymers of acrylic acid or methacrylic acid, or alkyl esters thereof Copolymers and cross-linked products of these can also be used.

When a pigment is used as a colorant, the use of a dispersant can prevent sedimentation of the pigment over time and prevent problems such as clogging. A variety of conventionally known dispersants can be used as the dispersant. Among them, preferred dispersants include polymers such as pigment derivatives having a sulfone group and polyvinyl butyral, and a single monomer composed of a hydrophilic monomer having a carboxylic acid group in the molecule. Examples thereof include one or two or more types selected from a copolymer or a copolymer with a lipophilic monomer, a rosin-modified resin, and a tall oil-modified resin. Among them, as a dispersant when N-acylamino acid, N-acyl tauric acid, N-acylmethyl tauric acid, or N-acylmethylalanine is used, a hydrophilic monomer-only polymer having a carboxylic acid group in the molecule Alternatively, a copolymer with a lipophilic monomer, a rosin-modified resin, or a tall oil-modified resin is selected from one or more of N-acyl amino acid, N-acyl tauric acid, N-acyl methyl tauric acid, N-acyl methyl Since it has an electrostatic affinity with nitrogen of alanine and solvates, it is particularly effective in stably dispersing the pigment.
Specific examples of a hydrophilic monomer-only polymer having a carboxylic acid group in the molecule, a copolymer with a lipophilic monomer, a rosin-modified resin, or a tall oil-modified resin include styrene-acrylic acid copolymer, styrene- α-methylstyrene-acrylic acid copolymer, styrene-maleic acid copolymer, methoxyethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyacrylic acid, polyglutamic acid, rosin-modified maleic acid resin, Examples include rosin-modified phenolic resins, tall oil-modified maleic acid resins, betaine-type acrylic acid resins, and betaine-type methacrylic acid resins.
These dispersants are preferably used in an amount of 0.5 to 20 parts by weight per 10 parts by weight of the pigment.

  Other additives such as rust preventives, antiseptics, antifoaming agents, anti-scratch agents, dispersants, stringiness-imparting agents, leveling properties-imparting agents, coloring aids, etc. It can also be used in combination.

When a pigment is used in the present invention, it is usually possible to disperse the pigment by a general method. For example, a pigment, a solvent, and a dispersing agent are mixed and uniformly stirred with a propeller stirrer or the like, and then the pigment is dispersed with a disperser. A dispersing machine such as a roll mill, a ball mill, a sand mill, a bead mill, or a homogenizer is appropriately selected depending on the amount of solvent of the ink and the pigment concentration.
In order to produce ink, the pigment dispersed above and other components such as viscosity adjusting resin, solvent, lubricant, water-soluble polysaccharide, etc. are mixed and dissolved with a stirrer such as a homomixer until uniform.・ It is obtained by mixing. In some cases, the mixed ink may be further dispersed by a disperser, or coarse particles may be removed by centrifugation or the like.

Hereinafter, it demonstrates still in detail based on an Example and a comparative example. In each example, “part” simply means “part by weight”.
(Example 1)
PERMANENT RED FRR (CI Pigment Red 2, manufactured by Clariant Japan) 15.0 parts ethylene glycol monobenzyl ether 38.2 parts diethylene glycol 0.5 parts SMA 1440 (styrene-maleic acid copolymer, Kawa Crude Co., Ltd.) Made) 6.0 parts Crucell M (hydroxypropylcellulose, manufactured by Sanki Co., Ltd.) 0.3 parts sarcosinate OH (oleoyl sarcosine, manufactured by Nikko Chemicals Co., Ltd.) 40.0 parts Of the above components, the total amount of SMA 1440 Was heated and stirred at about 70 ° C. in 18.2 parts of phenyl cellosolve, dissolved uniformly, allowed to cool to room temperature, and the entire amount of PERMANENT RED FRR was added and mixed uniformly. This was passed 10 times with a three-roll mill to obtain a red paste. Next, the entire amount of Crucell M was added to a mixed solution of 30.0 parts of phenyl cellosolve and the total amount of diethylene glycol, and heated to about 70 ° C. with stirring to be uniformly dissolved. The red paste, Crucelle M solution and the total amount of sarcosinate OH were mixed, heated to about 70 ° C., mixed and stirred until uniform with a propeller stirrer, and stirred for 2 hours until dissolved to obtain a red oil ink for ballpoint pens. .

(Example 2)
Printex 35 (carbon black, manufactured by Degussa Huls Japan Co., Ltd. 5.0 parts Neo Super Blue C-555 (CI Solvent Blue 70, manufactured by Chuo Synthetic Chemical Co., Ltd.) 6.0 parts SPILON RED C-GH (Oil-based dye, manufactured by Hodogaya Chemical Co., Ltd.) 2.0 parts VALIFAST YELLOW 1151 (Oil-based dye, manufactured by Orient Chemical Industry Co., Ltd.)
2.0 parts phenyl cellosolve 46.4 parts ethylene glycol 1.0 part BERMOCOLL EBS 481FQ (ethyl hydroxyethyl cellulose,
(AkzoNobel Surface Chemistry AB, Netherlands)
0.1 part Jonkrill 678 (styrene-acrylic acid copolymer, manufactured by Johnson Polymer Co., Ltd.)
2.0 parts Sarcosinate OH 35.5 parts Among the above ingredients, the entire amount of Joncrill 678 is heated and stirred in 10.0 parts of phenyl cellosolve at about 70 ° C., dissolved uniformly, and then allowed to cool to room temperature. Total amount of 35 was added and mixed uniformly. This was dispersed for 5 hours with a dyno mill (Shinmaru Enterprise beads mill, beads using zirconia) to obtain a black paste. Next, the entire amount of BERMOCOLL EBS 481FQ and ethylene glycol was added to 10.0 parts of phenyl cellosolve, and heated to about 70 ° C. with stirring to dissolve uniformly. Mix the black paste, BERMOCOLL EBS 481FQ solution and all the remaining ingredients, heat to about 70 ° C, mix and stir until uniform with a propeller stirrer, stir for 2 hours until dissolved, and add black oil ink for ballpoint pen Obtained.

(Example 3)
hostaperm Blue b2g-d (ci. pigment BLUE15: 1, manufactured by Clariant Japan Co., Ltd.) 5.0 parts SPILON RED C-GH (oil-based dye, manufactured by Hodogaya Chemical Co., Ltd.) 1.2 parts VALIFAST BLUE 1603 (Salt salt dyes of CI DIRECT BLUE 86 and CI BASIC BLUE 7, manufactured by Orient Chemical Co., Ltd.) 6.0 parts ethylene glycol monobenzyl ether 62.0 parts hexylene glycol 4.5 parts Crucell H (Hydroxypropyl cellulose, manufactured by Sanki Co., Ltd.) 0.3 parts Jonkrill 67 (styrene-acrylic acid copolymer, manufactured by Johnson Polymer Co., Ltd.)
1.0 part sarcosineate LH (Lauroyl sarcosine, manufactured by Nikko Chemicals Co., Ltd.) 20.0 parts Of the above ingredients, add 15 parts of ethylene glycol monobenzyl ether to the total amount of Joncrill 67 and dissolve evenly while heating to 70 ° C. Stir until Next, the total amount of HOSTAPERM BLUE B2G-D was added to this, stirred and mixed until uniform, and then passed 10 times with a three roll mill to obtain a blue paste. Next, 30.0 parts of ethylene glycol monobenzyl ether, the total amount of hexylene glycol and Crucell H were mixed and stirred while heating until uniformly dissolved with a propeller stirrer. The remaining components, the blue paste and the Crucell H solution were mixed, stirred for 3 hours while being heated to 70 ° C., and stirred until uniform to obtain a blue ball-point ink.

Example 4
HOSTAPERM BLUE P-BFS (CI PIGMENT BLUE 15: 4, manufactured by Clariant Japan Co., Ltd.) 7.0 parts SPILON RED C-GH 1.0 part VALIFAST BLUE 1603 6.0 parts phenyl cellosolve 62.4 parts glycerin 0.05 parts Crucell H 0.05 parts oleoyl tauric acid 21.0 parts SMA1440 2.5 parts Of the above ingredients, add 10 parts of phenylcellosolve and add SMA1440 to the whole and stir while heating to 70 ° C to dissolve evenly The total amount of HOSTAPERM BLUE P-BFS was added to the resulting liquid and stirred and mixed to obtain a uniform liquid, which was then passed 10 times with a three-roll mill to obtain a blue paste. Next, the whole amount of glycerin and Crucell H was added to 5.0 parts of phenyl cellosolve, mixed and stirred while heating to obtain a uniform solution. This solution and the remaining components are mixed and stirred while heating to 70 ° C., and the blue paste is mixed with the uniformly dissolved solution while heating and stirring, and stirring is further continued for 2 hours to obtain a blue oil-based ink for ballpoint pens. It was.

(Comparative Example 1)
A black ballpoint pen-based oil-based ink was obtained in the same manner as in Example 1 except that diethylene glycol was removed and ethylene glycol monobenzyl ether was added correspondingly.

(Comparative Example 2)
In Example 2, red oil-based ink for ballpoint pens was obtained in the same manner except that ethylene glycol was removed and phenyl cellosolve was added accordingly.

(Comparative Example 3)
A blue oil-based ink for ballpoint pens was obtained in the same manner as in Example 3 except that hexylene glycol was removed and ethylene glycol monobenzyl ether was added correspondingly.

(Comparative Example 4)
In the same manner as in Example 4 except that glycerin was increased to 10 parts by weight and the amount of phenylcellosolve was reduced accordingly, a blue ballpoint pen oil ink was obtained.

(Comparative Example 5)
Neo Super Blue C-555 (CI Solvent Blue 70, manufactured by Chuo Synthetic Chemical Co., Ltd.) 6.0 parts SPILON RED C-GH (oil-based dye, manufactured by Hodogaya Chemical Co., Ltd.) 2.0 parts VALIFAST YELLOW 1151 (oil-based dye, manufactured by Orient Chemical Co., Ltd.)
2.5 parts phenyl cellosolve 69.8 parts ethylene glycol 1.0 part Crucell L (hydroxypropylcellulose, manufactured by Sanki Co., Ltd.) 3.2 parts Sarcosinate OH 15.5 parts Among the above components, ethylene glycol and Crucell L Was added to 50.0 parts of phenyl cellosolve and heated to about 70 ° C. with stirring to dissolve uniformly. This was mixed with all the remaining components, heated to about 70 ° C., mixed and stirred with a propeller stirrer until uniform and stirred for 2 hours until dissolved to give a black oil-based ink for ballpoint pens.

As mentioned above, the following test was done about the ink composition obtained by the Example and the comparative example. The results are shown in Table 1.
In addition, the viscosity is measured by attaching a φ40 parallel rotor to a rheometer VAR-100 manufactured by Jusco International Co., Ltd., adjusting the gap between the sample stage to 0.8 mm, and then using the ballpoint pens obtained in the examples and comparative examples. The ink was placed on a sample stage, and the viscosity at a shear rate from 0.1 / s to 150 / s was measured at a temperature of 25 ° C., and the value at 2 / s was taken as the viscosity.

  Filtration test: No. 5A filter paper made by Toyo Filter Paper was cut to 47 mm in diameter for a barrel type stainless steel pressure filter (Sartorius Co., Ltd.) diameter 47 mm, and 50 g of ink was put into 4 kg / square centimeter. And the ink was filtered.

  Ink moisture absorption test: Put 2 g of the prepared ink in a container with a diameter of 4 cm and a depth of 1 cm, put it in a sealed container filled with water, leave it at 60 ° C., and measure the increase in weight after 3 days. Was confirmed visually.

  Ink ejection property: The ink thus prepared was filled into a cleaned part after removing the ink of dot e (Pentel Co., Ltd. oil-based ballpoint pen, ball diameter: 1.0φ), and the degree of blurring of the handwriting was visually determined.

  As described above in detail, the ink of the present invention relates to an oil-based ink for ballpoint pens that can be efficiently produced by having good filterability during production.

Claims (3)

At least a colorant, glycol monoether, a polyhydric alcohol having 2 to 6 carbon atoms of 0.05 to 5.0% by weight based on the total amount of the ink, and 0.02% by weight based on the entire ink An oil-based ink for ballpoint pens containing at least 3% by weight and less than 3% by weight cellulose derivative. The ink is one or more selected from N-acylamino acid, N-acyltauric acid, N-acylmethyltauric acid, and N-acylmethylalanine in an amount of 5% by weight to 60% by weight based on the total amount of the ink. The oil-based ink for ballpoint pens according to claim 1. The oil-based ink for ballpoint pens according to claim 1 or 2, wherein the cellulose derivative is one or more selected from hydroxypropylcellulose, hydroxyethylcellulose, ethylhydroxyethylcellulose, and ethylcellulose.