JP2007246721A - Water-based ink composition for ball-point pen and ball-point pen containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink composition for ball-point pens, which does not excessively increase the viscosity of the ink, even when water in the ink is evaporated, thereby has an excellent dry-up resistance, gives good writing-out touches in the initial time and after the passage of time, does not cause the blurring of handwriting, can retain a stable writing performance, and can continuously form good handwriting, and to provide a ball-point pen containing the same. <P>SOLUTION: This water-based ink composition for the ball-point pens is characterized by comprising at least a colorant, water, water-soluble organic solvents, and a shear viscosity reduction-imparting agent, wherein the water-soluble organic solvents are contained in an amount of 1 to 20 wt.% in the ink composition, and a water-soluble organic solvent having a solubility parameter of 8 to 11 is contained in an amount of 80 to 100 wt.% based on the total amount of the water-soluble organic solvents. A ball-point pen containing the same. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water-based ink composition for ballpoint pens and a ballpoint pen containing the same. More particularly, the present invention relates to a water-based ink composition for ballpoint pens having excellent dry-up resistance performance at the nib and a ballpoint pen containing the same.

In recent years, water-based ink compositions containing water as a main solvent have been widely used as ink compositions accommodated in ballpoint pens in consideration of environmental issues and safety for the human body. Of these, ink compositions having shear thinning viscosity are low. It is possible to eliminate the drawback that the handwriting of a viscous water-based ballpoint pen bleeds.
Examples of the substance that imparts shear thinning to the ink composition (shear thinning imparting agent) include polysaccharides such as xanthan gum (see, for example, Patent Document 1).
However, the shear thinning agent may impair dry-up performance, and attempts to improve dry-up performance by using additives such as wetting agents such as water-soluble organic solvents and solid wetting agents such as urea. However, the effect of preventing drying is insufficient, and the ink viscosity is increased, and writing defects such as fading are likely to occur.
Specifically, when urea is added excessively, the moisture evaporates from the writing tip, the concentration of the water-soluble organic solvent rises, and a so-called flower bloom phenomenon occurs in which solid content is deposited on the writing tip. Appearance deteriorates and blurring occurs. Furthermore, when a large amount of a water-soluble organic solvent or urea is added, when the writing tip is left faced downward in a humid environment, it is liable to cause problems such as drooping.
As described above, although there are many means for improving the dry-up resistance of the ink composition, other performances required for the ball-point pen, such as blurring and sagging of handwriting, may be caused.
Furthermore, when used in a ballpoint pen (capless ballpoint pen) that does not require a cap in which the writing tip (ballpoint tip) is always open to the atmosphere when not writing, the dry-up resistance is an important requirement.
JP 59-74175

  The present invention solves the problems of the ink composition applied to the above-described ballpoint pen, that is, a water-based ink composition for ballpoint pens that satisfies dry-up resistance without impairing various writing performances, and The object is to provide a ballpoint pen that houses it.

The present invention comprises at least a colorant, water, a water-soluble organic solvent, and a shear thinning agent, wherein the water-soluble organic solvent is 1 to 20% by weight in the ink composition, and the water-soluble organic A water-based ink composition for ballpoint pens comprising 80 to 100% by weight of a water-soluble organic solvent having a solubility parameter of 8 to 11 in the total amount of the solvent is a requirement.
Further, 90 to 100% by weight of a water-soluble organic solvent having a solubility parameter of 8 to 11 is contained in the total amount of the water-soluble organic solvent, and the water-soluble organic solvent having a solubility parameter of 8 to 11 is butyl alcohol. Polyhydric alcohols having 5 or 6 carbon atoms, glycol ethers having 4 to 13 carbon atoms, glycol acetates having 5 to 9 carbon atoms, glycol monoether acetates having 5 to 10 carbon atoms, 5 to 5 carbon atoms 10 hydroxycarboxylic acid esters, carboxylic acid amides having 4 to 12 carbon atoms, the shear thinning agent is a polysaccharide, and the shear thinning agent is xanthan gum, welan gum, succinoglycan And the colorant is a dye.
Furthermore, a ballpoint pen that contains a ballpoint pen refill containing the aqueous ink composition for ballpoint pens in a shaft cylinder, a ballpoint pen that contains the aqueous ink composition for ballpoint pens in the shaft cylinder, and a ballpoint pen refill for the aqueous ink composition for ballpoint pens The capless ball-point pen etc. which are accommodated in the inside and in which the writing tip part of the said ball-point refill fills in and out from the opening part of the front end of the cylindrical tube by the operation of the in / out mechanism are required.

  According to the present invention, the combined use of the shear thinning agent and the specific water-soluble organic solvent does not excessively increase the ink viscosity even when water in the ink evaporates. And a ballpoint pen containing the water-based ink composition for a ball-point pen that can maintain a stable writing performance without causing blurring of the handwriting and can form a good handwriting. can get.

The present invention comprises 1 to 20% by weight of a water-soluble organic solvent in addition to water as a solvent in the total amount of the ink composition, and the solubility parameter in the water-soluble organic solvent is 8 to 11, preferably 8 to 10. The water-soluble organic solvent is contained in an amount of 80 to 100% by weight, preferably 90 to 100% by weight.
If the water-soluble organic solvent having a solubility parameter of 8 to 11 in the water-soluble organic solvent is less than 80% by weight, it is difficult to sufficiently exhibit the effect of dry-up resistance.
Examples of the water-soluble organic solvent having a solubility parameter of 8 to 11 include butyl alcohol, polyhydric alcohols having 5 or 6 carbon atoms, glycol ethers having 4 to 13 carbon atoms, and glycol acetates having 5 to 9 carbon atoms. C5-C10 glycol monoether acetates, C5-C10 hydroxycarboxylic acid esters, C4-C12 carboxylic acid amides and the like are preferably used.
Examples of water-soluble organic solvents having suitable solubility parameters of 8 to 11 are shown below.
As the polyhydric alcohols, diols having two hydroxyl groups having 5 or 6 carbon atoms are preferable, and 1,2-pentanediol, 1,6-hexanediol, 1,2-hexanediol, hexylene glycol ( 2-methyl-2,4-pentanediol) and 3-methyl-1,5-pentanediol.
Examples of the glycol ethers include ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol mono t-butyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, ethylene glycol mono 2-ethylhexyl ether, ethylene glycol monophenyl ether. , Ethylene glycol monobenzyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol mono 2-ethylhexyl ether, diethylene glycol Monobenzyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether , Propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol mono t-butyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol No ethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, 3-methoxybutanol, 3-methoxy-3-methyl-1-butanol Etc.
Examples of glycol acetates include diethylene glycol monoacetate, ethylene glycol diacetate, propylene glycol diacetate, glycerol diacetate, and glycerol triacetate.
As glycol monoether acetates, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate , Propylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether acetate, 3-methoxybutyl acetate, 3-methoxy-3-methyl-1-butyl acetate and the like.
Lactic acid esters are suitable as the hydroxycarboxylic acid esters, and examples thereof include ethyl lactate, butyl lactate, isobutyl lactate, amyl lactate, and isoamyl lactate.
Carboxylic acid amides include N, N-dimethylacetamide, N, N-diethylacetamide, N-vinyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-vinyl-2-pyrrolidone oligomer, ε-caprolactam Etc.
In addition, although other organic solvents can be used in combination with the water-soluble organic solvent having the solubility parameter of 8 to 11, it is less than 20% by weight, preferably less than 10% by weight in the total amount of the water-soluble organic solvent.
Since the water-based ink composition for ballpoint pens of the present invention contains a water-soluble organic solvent having a solubility parameter of 8 to 11, it is necessary to positively improve anti-drying-up performance by adding another water-soluble organic solvent. Therefore, an effective thickening suppression function can be exhibited in a system in which no other water-soluble organic solvent is added or a very small amount is added.
In addition, in the ink composition containing the shear thinning agent and the water-soluble organic solvent, the viscosity when water is evaporated by 40% by weight from the total amount of the ink / initial ink viscosity (EMD viscometer, 1 rpm, 20 ° C. When the numerical value (x) indicated by (2) is 2 or less, preferably 0.01 or more and 2 or less, when stored in a ballpoint pen for practical use, it has excellent dry-up resistance, and is written out at the beginning and after the passage of time. Is good, and stable writing performance can be maintained.
If the value exceeds 2, the change in the viscosity when the water in the ink is evaporated by 40% by weight and the initial ink viscosity are large, and therefore, the increase in viscosity tends to cause blurring and inability to write.

As the colorant, all dyes and pigments that can be dissolved or dispersed in an aqueous medium can be used, and specific examples thereof are exemplified below.
As an acid dye,
New coccin (CI. 16255),
Tartrazine (C.I. 19140),
Acid Blue Black 10B (C.I. 20470),
Guinea Green (C.I.42085),
Brilliant blue FCF (C.I.42090),
Acid Violet 6BN (C.I. 43525),
Soluble Blue (C.I. 42755),
Naphthalene green (C.I. 44025),
Eosin (C.I. 45380),
Phloxin (C.I. 45410),
Erythrosine (C.I. 45430),
Nigrosine (C.I. 50420),
Acid flavin (C.I. 56205) or the like is used.

As basic dye,
Chrysoidine (C.I. 11270),
Methyl violet FN (C.I. 42535),
Crystal violet (C.I. 42555),
Malachite green (C.I. 42000),
Victoria Blue FB (C.I. 44045),
Rhodamine B (C.I. 45170),
Acridine orange NS (C.I. 46005),
Methylene blue B (C.I. 52015) or the like is used.

As a direct dye,
Congo Red (C.I. 22120),
Direct Sky Blue 5B (C.I. 24400),
Violet BB (C.I. 27905),
Direct deep black EX (CI 30235),
Caillas Black G Conch (C.I. 35225),
Direct Fast Black G (C.I. 35255),
Phthalocyanine blue (C.I. 74180) or the like is used.

As the pigment, in addition to inorganic pigments such as carbon black and ultramarine blue, organic pigments such as copper phthalocyanine blue and benzidine yellow, surfactants and water-soluble resins have already been used to finely and stably disperse in an aqueous medium. Water-dispersed pigment products and the like are used, for example, as a water-dispersed pigment using a surfactant,
C. I. Pigment Blue 15: 3B [trade name: Sandye Super Blue GLL, pigment content 22%, manufactured by Sanyo Dye Co., Ltd.]
C. I. Pigment Red 146 [trade name: Sandye Super Pink FBL, pigment content 24%, manufactured by Sanyo Dye Co., Ltd.]
C. I. Pigment Yellow 81 [trade name: TC Yellow FG, pigment content about 30%, manufactured by Dainichi Seika Kogyo Co., Ltd.]
C. I. Pigment Red 220/166 [trade name: TC Red FG, pigment content: about 35%, manufactured by Dainichi Seika Kogyo Co., Ltd.].
In addition, as a water-dispersed pigment using a water-soluble resin,
C. I. Pigment Black 7 [Product name: WA color Black
A250, 15% pigment content, manufactured by Dainichi Seika Kogyo Co., Ltd.]
C. I. Pigment Green 7 [trade name: WA-S color Green, pigment content 8%, manufactured by Dainichi Seika Kogyo Co., Ltd.]
C. I. Pigment Violet 23 [trade name: Micropigmo WMVT-5, pigment content 20%, manufactured by Orient Chemical Co., Ltd.]
C. I. Pigment Yellow 83 [trade name: Emacol NS Yellow 4618, pigment content 30%, manufactured by Sanyo Color Co., Ltd.].

As fluorescent pigments, synthetic resin fine particle fluorescent pigments in which various fluorescent dyes are formed into a solid solution in a resin matrix can be used. Other examples include pearl pigments, metal powder pigments, phosphorescent pigments, white pigments such as titanium dioxide, silica and calcium carbonate, capsule pigments encapsulating thermochromic compositions, capsule pigments encapsulating perfumes and perfumes.
The metallic luster pigment is a metallic luster pigment such as aluminum or brass, and a metallic luster pigment in which the surface of natural mica, synthetic mica, glass piece, alumina, or transparent film piece is coated with a metal oxide such as titanium oxide as a core substance. (Pearl pigment), a metallic luster pigment in which a metal vapor deposition film is formed on a transparent or colored transparent film, and a metallic luster pigment having an iris property obtained by finely cutting an iris film in which a plurality of transparent resin layers are laminated.
The colorant can be used singly or in combination of two or more, and is used in the range of 1 to 25% by weight, preferably 2 to 15% by weight in the ink composition.

  Moreover, when a pigment is used as the colorant, a pigment dispersant can be added as necessary. Examples of the pigment dispersant include surfactants such as anion and nonion, anionic polymers such as polyacrylic acid and styreneacrylic acid, and nonionic polymers such as polyvinylpyrrolidone and polyvinyl alcohol.

  In addition to the above components, pH adjusters such as inorganic salts such as sodium carbonate, sodium phosphate and sodium acetate, organic basic compounds such as water-soluble amine compounds, benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium as necessary Nitrite, diisopropylammonium nitrite, rust inhibitor such as sodium thiosulfate, saponin, coalic acid, sodium salt of 1,2-benzthiazolin-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, paraoxybenzoic acid Preservatives or antifungal agents such as propyl, 2,3,5,6-tetrachloro-4- (methylsulfonyl) pyridine, metal soap, polyalkylene glycol, fatty acid ester, ethylene oxide addition type cationic activator, phosphoric acid-based activity Agent, Thioka Lubricants such as bamate, dimethyldithiocarbamate, ascorbic acid, ascorbic acid derivative, α-tocopherol, catechin, catechin derivative, synthetic polyphenol, phosphonate, phosphinate, sulfite, sulfoxylate, dithionite Antioxidants such as salt, thiosulfate, thiourea dioxide, formamidinesulfinic acid, glutathione, urea, nonionic surfactants, sorbit, mannitol, sucrose, glucose, reduced starch hydrolysate, sodium pyrophosphate, etc. Wetting agents, fluorine surfactants that improve ink permeability, nonionic, anionic, and cationic surfactants, antifoaming agents such as dimethylpolysiloxane, and dispersants may be used.

The shear thinning of the ink composition is a rheological characteristic that has a property of being extremely high viscosity and difficult to flow in a static state or when the stress is low, and showing a good fluidity by decreasing the viscosity when the stress increases. It means liquidity also called thixotropic property or pseudoplasticity. Therefore, the ink composition is temporarily destroyed in the three-dimensional structure under high shear stress at the time of writing and the viscosity of the ink is lowered, and the ink at the tip of the writing becomes a low-viscosity ink suitable for writing and transferred to the paper surface. The When not writing, the viscosity of the ink becomes high, so that leakage of the ink can be prevented, and separation and backflow of the ink can be prevented. Also, the ink physical properties can be kept stable over time.
In particular, a ballpoint pen with a ball held at the tip of the writing has a low viscosity suitable for writing under high shear stress during writing, and the gap between the ball and the ball house moves by capillary force and moves on the paper surface. It is necessary to have ink characteristics that can be transferred to, and when not writing, the viscosity of all inks, including the vicinity of the ball, must be increased to prevent ink leakage, ink separation, and backflow. An ink composition having an ink viscosity at 100 rpm measured by an E-type rotational viscometer of 20 to 200 mPa · s (25 ° C.) and a shear thinning index of 0.1 to 0.8 is suitable.
The shear thinning index n can be obtained by assigning a numerical value to the empirical formula T = Kj ⁿ (T: shear stress value, j: shear rate, K is a calculated constant).

As the shear thinning agent, a water-soluble or dispersible substance is effective, and xanthan gum, welan gum, and succinoglycan whose constituent monosaccharide is an organic acid-modified heteropolysaccharide of glucose and galactose (average molecular weight) The main component is gum, guar gum, locust bean gum and its derivatives, hydroxyethyl cellulose, alginic acid alkyl esters, methacrylic acid alkyl ester, which are composed of glucose, glucuronic acid, fucose and rhamnose. A polymer having a molecular weight of 100,000 to 150,000, a thickening polysaccharide having gelling ability extracted from seaweed such as glucomannan, agar and carrageenan, benzylidene sorbitol and benzylidene xylitol or their derivatives, crosslinkable acrylic acid heavy Coalescence, inorganic fine particles, Nonionic interfaces having an HLB value of 8 to 12, such as liglycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene alkyl ether / polyoxypropylene alkyl ether, polyoxyethylene alkylphenyl ether, fatty acid amide Examples include activators, salts of dialkyl or dialkenyl sulfosuccinic acid, and the like, which can be used alone or in combination.
The shear thinning agent can be used in the range of 0.1 to 20% by weight in the ink composition.
By using the shear thinning agent in combination with a water-soluble organic solvent having a solubility parameter of 8 to 11, when the water content in the ink is reduced, the shear thinning agent is in a semi-swelled state. It hardly rises.
As the shear thinning agent, xanthan gum, welan gum, succinoglycan is preferably used, and the ink stability is excellent.

  In addition, one or more water-soluble resins such as acrylic resin, styrene maleic acid copolymer, polyvinyl pyrrolidone, polyvinyl alcohol, and dextrin may be added within a range that does not impair drying resistance.

The water-based ink composition for ballpoint pens of the present invention can contain a sugar mixture containing 10% by weight or more of saccharides of 10 sugars or more, and can satisfy anti-dripping performance as well as anti-drying performance. .
Monosaccharides and disaccharides do not form a dry film sufficiently, and have high water absorption. Therefore, when applied to a ballpoint pen, dripping tends to occur if the writing tip is left facing downward. In addition, in the case of about 3 to 8 sugars, the water absorption is lower than that of monosaccharides and disaccharides, but sufficient sag prevention performance is not obtained.
Since the saccharide has a lower hygroscopicity as the molecular weight increases and it becomes easier to form a dry film, the use of a saccharide of 10 sugars or more can prevent the ink from dripping while maintaining the cap-off performance.
As the saccharide of 10 sugars or more, a starch saccharified product obtained by enzymatic decomposition of starch or a reduced starch saccharified product obtained by reducing the terminal group of the starch saccharified product can be used.
In addition, when starch is decomposed, saccharides having various degrees of polymerization are generated. Therefore, it is technically difficult to completely isolate only saccharides having 10 or more sugars, and manufacturing costs are also increased. Therefore, in a saccharide mixture containing 9 or less saccharides, the performance can be sufficiently expressed by containing 40% by weight or more of the 10 or more saccharides.
The sugar mixture is blended in the range of 0.5 to 10.0% by weight, preferably 1.0 to 8.0% by weight, based on the total amount of the ink composition. If the amount is less than 0.5% by weight, it is difficult to obtain a drooping prevention effect. If the amount exceeds 10.0% by weight, the viscosity of the ink may increase, causing crying or blurring, and ink followability during writing may be impaired.

The ink composition is used by filling a ballpoint pen with a ballpoint tip attached to the writing tip.
The structure and shape of the ballpoint pen itself are not particularly limited. For example, the ballpoint pen has an ink storage tube filled with an ink composition, and the ink storage tube communicates with a ballpoint pen tip holding a ball at the tip. Furthermore, a ballpoint pen in which a ballpoint refill whose ink backflow prevention composition is in close contact with the end face of the ink composition is accommodated in the shaft cylinder can be exemplified.
Furthermore, it has a shaft cylinder filled with the ink composition, the shaft cylinder communicates with a ballpoint pen tip holding a ball at the tip, and the ink backflow preventer composition is in close contact with the end surface of the ink composition. It may be a ballpoint pen.
The ballpoint pen having the structure described above preferably includes a cap.
For the structure of the ballpoint pen tip, a general-purpose mechanism has been effective, and a mechanism for holding a ball in a ball holding portion formed by pressing and deforming the vicinity of the tip of a metal pipe inward from the outer surface, a metal material A chip part is formed by cutting with a drill and the like, a mechanism for holding the ball in the ball holding part, a mechanism for biasing the ball forward by a spring body, or a metal or plastic chip made of resin A mechanism provided with the ball receiving seat can be exemplified.
The ball may be about 0.1 to 3.0 mm in diameter, such as cemented carbide, stainless steel, ruby, ceramic, resin, rubber, etc., preferably 0.3 to 1.0 mm, more preferably 0. .3 to 0.7 mm is used.
For the ink storage tube or the shaft cylinder that stores the ink composition, a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon is used.
Furthermore, by using a transparent, colored transparent, or translucent molded body as the ink containing tube or the shaft tube, the ink color, the remaining amount of ink, and the like can be confirmed.
Further, when the water-based ink composition for a ballpoint pen is accommodated in a capless ballpoint pen, the structure and shape of the capless ballpoint pen are not particularly limited, and the writing tip provided on the ballpoint pen refill is exposed to the outside air And can be used as long as it has a structure in which the writing tip protrudes from the opening of the shaft cylinder by the operation of the retracting mechanism.
Examples of the operation method of the retracting mechanism include a knock type, a rotary type, and a slide type.
The knock type has a knock portion on the rear end portion of the shaft tube and the side surface of the shaft tube, and by pressing the knock portion, the writing tip portion of the ballpoint pen refill is projected and retracted from the front end opening portion of the shaft tube, or on the shaft tube. A configuration in which the writing tip portion of the ballpoint pen refill is projected and retracted from the front end opening portion of the shaft cylinder by pressing the provided clip portion can be exemplified.
The rotary type has a rotating part at the rear part of the shaft cylinder, and can be exemplified by a configuration in which the writing tip part of the ballpoint pen refill is projected and retracted from the front end part of the shaft cylinder by turning the rotating part.
The slide type has a slide part on the side surface of the shaft cylinder, and the sliding tip of the writing point of the ballpoint pen refill is projected and retracted from the front end opening of the shaft cylinder by operating the slide, or the clip part provided on the shaft cylinder is slid. By doing so, it is possible to exemplify a configuration in which the writing tip of the ballpoint pen refill is projected and retracted from the opening at the front end of the shaft cylinder.
The capless ballpoint pen may be a composite type capless ballpoint pen in which a plurality of ballpoint pen refills are accommodated in a shaft cylinder.
The ink storage tube and the shaft cylinder constituting the ballpoint pen refill may be made of resin or metal.

The back end of the ink stored in the ink storage tube or the shaft tube may be filled with an ink backflow prevention body.
The ink backflow prevention body composition is composed of a non-volatile liquid or a hardly volatile liquid.
Specifically, petroleum jelly, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, α-olefin oligomer or co-oligomer, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, Examples thereof include polyether-modified silicone oil and fatty acid-modified silicone oil, and one or more can be used in combination.

It is preferable to add a gelling agent to the nonvolatile liquid and / or the hardly volatile liquid to increase the viscosity to a suitable viscosity. The surface of the silica is hydrophobized, the surface is methylated fine particle silica, and aluminum silicate. , Swellable mica, hydrophobic thickeners such as bentonite and montmorillonite, fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, zinc stearate, tribenzylidene sorbitol, fatty acid amide, amide modified Examples include dextrin compounds such as polyethylene wax, hydrogenated castor oil, fatty acid dextrin, and cellulose compounds.
Furthermore, the liquid ink backflow prevention body composition and a solid ink backflow prevention body composition can be used in combination.

The following table shows the formulation of the water-based ink composition for ballpoint pens.
The numerical value in a table | surface shows weight%, and the numerical value in the parenthesis described after the solvent name is a solubility parameter (SP value).

The contents of the raw materials in the table are explained according to the note numbers.
(1) Made by Orient Chemical Industry Co., Ltd., trade name: Water Black 100-L, dye content 20%
(2) Eisen Co., Ltd., trade name: Phloxine (3) Sanyo Dye Co., Ltd., trade name: Sandye Super Blue GLL, pigment content 22%
(4) Ethanolamine salt of polyoxyethylene alkyl ether phosphate ester, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Prisurf M208B
(5) Made by Sanki Co., Ltd., trade name: Kelzan

  A water-based ink composition for ballpoint pens is obtained by stirring the composition shown in each example and comparative example with a mixer for 1 hour while heating at 60 ° C., and then cooling and filtering.

Preparation of Ballpoint Pen Filled with an ink containing tube in which a stainless steel chip holding a ball having a diameter of 0.5 mm is fitted to one end of a polypropylene pipe with the ink compositions of Examples 1 to 3 and Comparative Examples 1 to 3 Further, the ink backflow prevention body was filled in close contact with the rear end surface of the ink to obtain a ballpoint pen refill.
The ballpoint pen refill was incorporated into a shaft tube to obtain a ballpoint pen.
The ballpoint pen includes a cap.

Production of Capless Ballpoint Pen Ink receiving tube in which a stainless steel chip holding a 0.4 mm diameter ball of the ink composition of Examples 4 to 7 and Comparative Examples 4 to 6 is fitted to one end of a polypropylene pipe In addition, the ink backflow prevention body was filled in close contact with the ink rear end face to obtain a ballpoint pen refill.
The ballpoint pen refill was incorporated into a shaft tube to obtain a capless ballpoint pen.
The capless ballpoint pen is housed in the shaft cylinder with the writing tip provided on the ballpoint pen refill exposed to the outside air, and a cap mechanism (knock mechanism) provided at the rear end of the shaft cylinder. This is a structure in which the writing tip protrudes from the axial tube opening by operation.

Dry-up resistance test The ball-point pen and capless ball-point pen obtained as described above were left standing at 25 ° C. for 60 days in an inverted state (the tip of the writing was downward), then writing was performed and the state of the handwriting was visually observed.
The ballpoint pen was tested with the cap removed.
Each x value of the ink composition [viscosity when water in the ink is evaporated by 40% by weight with respect to the total amount of ink / initial ink viscosity (measured at EMD viscometer, 1 rpm, 20 ° C.)) and dry-up resistance The test results are shown in the following table.

The determination results in the table are as follows.
Dry-up resistance test A: A good handwriting that is uniform and not blurred is obtained.
○: Handwriting without blur is obtained.
X: A blur is seen in a handwriting.

Claims (12)

  It comprises at least a colorant, water, a water-soluble organic solvent, and a shear thinning agent, and the water-soluble organic solvent is 1 to 20% by weight in the ink composition, and in the total amount of the water-soluble organic solvent. A water-based ink composition for ballpoint pens comprising 80 to 100% by weight of a water-soluble organic solvent having a solubility parameter of 8 to 11.   The water-based ink composition for ballpoint pens according to claim 1, comprising 90 to 100% by weight of a water-soluble organic solvent having a solubility parameter of 8 to 11 in the total amount of the water-soluble organic solvent.   The water-soluble organic solvent having a solubility parameter of 8 to 11 includes butyl alcohol, polyhydric alcohols having 5 or 6 carbon atoms, glycol ethers having 4 to 13 carbon atoms, glycol acetates having 5 to 9 carbon atoms, The water-based ink composition for a ballpoint pen according to claim 1 or 2, selected from glycol monoether acetates having 5 to 10 carbon atoms, hydroxycarboxylic acid esters having 5 to 10 carbon atoms, and carboxylic acid amides having 4 to 12 carbon atoms. .   The water-based ink composition for ballpoint pens according to any one of claims 1 to 3, wherein the shear thinning agent is a polysaccharide.   The aqueous ink composition for ballpoint pens according to claim 4, wherein the shear thinning agent is selected from xanthan gum, welan gum, and succinoglycan.   The water-based ink composition for ballpoint pens according to any one of claims 1 to 5, wherein the colorant is a dye.   A ballpoint pen in which a ballpoint refill containing the water-based ink composition for a ballpoint pen according to any one of claims 1 to 6 is accommodated in a shaft cylinder.   The ball-point pen which incorporated the water-based ink composition for ball-point pens in any one of Claim 1 thru | or 6 in the axial cylinder.   The ballpoint pen according to claim 7 or 8, wherein an ink backflow prevention body that follows the ink consumption is disposed on the rear end surface of the water-based ink composition for ballpoint pens.   The ballpoint pen according to claim 7, further comprising a cap.   A waterless ink composition for a ballpoint pen according to any one of claims 1 to 6 is contained in a ballpoint pen refill, and the writing tip of the ballpoint pen refill is projected and retracted from the front end opening of the shaft cylinder by the operation of a retracting mechanism Ballpoint pen.   The capless ballpoint pen according to claim 11, wherein an ink backflow preventive body that follows as the ink is consumed is disposed on the rear end surface of the water-based ink composition for ballpoint pens.