JP2000177288A - Ink backflow preventive composition for ballpoint pen and ballpoint pen using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve ink followability at writing and ink backflow preventiveness in an erected state by adding a thickener and an atactic polypropylene to a volatile retardant liquid and preparing an ink backflow preventive composition. SOLUTION: The ink backflow preventive composition to be filled in an ink end face at an open side of an ink containing tube of a ballpoint pen is prepared by adding a thickener and an atactic polypropylene to a volatile retardant liquid. Its adding amount of the polypropylene is set to 0.2 to 30 wt.% of the total composition. As the polypropylene, a molecular weight of 1,000 to 5,000 is used. As the retardant liquid, a polybutene or α-olefin-cooligomer or their mixture. As the thickener, that selected from a bentonite, a swelling synthetic mica introduced with a quaternary ammonium ion, a metal soap, a mineral fine particles is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ballpoint pen ink backflow preventing composition and a ballpoint pen using the same. More specifically, in a ball-point pen having a tip portion of a ball-point pen and an ink storage tube in which medium-viscosity or high-viscosity or shear-thinning ink is directly stored, a ball-point pen filled in an ink end face on an open side of the ink storage tube. The present invention relates to an ink backflow preventive composition and a ballpoint pen using the same.

[0002]

2. Description of the Related Art Conventionally, grease which is a mixture of mineral oil and metal soap has been applied to a ballpoint pen using a high-viscosity oil-based ink as this kind of ink backflow preventive composition for a ballpoint pen.

In a ballpoint pen using a medium-viscosity or shear-thinning aqueous ink, a gel-like polybutene-based ink backflow preventive composition comprising a thickening agent added to a non-volatile liquid represented by liquid polybutene is used. Many have been proposed and widely used. Examples of the thickener include dibenzylidene sorbitol, tribenzylidene sorbitol (Japanese Patent Publication No. 1-105554), N-acylated amino acid derivatives (Japanese Patent Application Laid-Open No. 57-200472), and onium compounds having a long-chain alkyl group. And silica (Japanese Patent Publication No. 6-33025) surface-treated with a hydrophobic group. The ink backflow preventive composition for ballpoint pens obtained by adding the conventional thickener to the above-mentioned non-volatile liquid is mainly filled into the open ink end face of the ink containing tube containing the ink, and the solvent in the ink is removed. It has a function of preventing evaporation and moving in the accommodation tube following the ink end surface as ink is consumed during writing. Furthermore, the ink backflow preventive composition for a ballpoint pen has a writing tip facing upward (upright state).
Also, when a shock such as a drop or a drop is applied, the ink also flows backward to allow air to enter the writing tip, thereby preventing the ink supply from being interrupted and making writing impossible. By having the above-mentioned function, that is, the ink follow-up property at the time of writing and the ink backflow prevention property in the upright state, a ballpoint pen exhibiting good writing performance under various conditions can be obtained. However, the above-mentioned conventional ink backflow preventive composition for ballpoint pens does not necessarily have these functions sufficiently, and in particular, a composition which satisfies the ink backflow prevention property in an upright state has not been obtained.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks of the ink backflow preventive composition for ballpoint pens, that is, it is excellent in ink follow-up property during writing and ink in an upright state. An object of the present invention is to provide an ink backflow preventive composition for a ballpoint pen which can prevent backflow and maintain the same writing performance as the initial one under various conditions, and a ballpoint pen using the same.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the problems of the above-mentioned conventional ink composition for ballpoint pen backflow prevention. Ink followability,
It has been found that an ink backflow preventive composition for a ballpoint pen having excellent ink backflow prevention properties in an upright state can be obtained.
That is, the present invention requires an ink backflow preventive composition for a ballpoint pen, which is obtained by adding a thickener and an atactic polypropylene to a hardly volatile liquid. Further, the atactic polypropylene is added in an amount of 0.2 to 3 in the total composition.
0 wt%, the atactic polypropylene has a molecular weight of 1,000 to 50,000, the non-volatile liquid is polybutene, an α-olefin-co-oligomer alone or in a mixture, the thickener is bentonite, Selected from swellable synthetic mica into which quaternary ammonium ions are introduced, metal soap, and inorganic fine particles, 20
One minute reading on a spread meter at 25 ° C is 25 to 5
It must be 0 mm or the like. Furthermore, a tip that rotatably holds the ball at the tip and discharges ink from the tip, and an ink storage unit that supplies ink to the tip by directly or via a relay member connected to the rear of the tip. And a medium-viscosity to high-viscosity or shear-thinning ink filled in the ink container, and filled in the rear end of the ink.
A ballpoint pen comprising the above-mentioned ink backflow preventive composition for a ballpoint pen that follows with the consumption of ink is required.

In a conventional ink backflow preventive composition comprising polybutene as a non-volatile liquid and a thickener, a part of the non-volatile liquid is separated from the ink backflow preventive composition over time depending on the molecular weight of the polybutene. When filled in a ball-point pen and left standing in an erect state for a long period of time, a part of the non-volatile liquid rises along the inner wall of the ink storage tube and accumulates at the writing tip to make writing impossible, or Problems such as the backflow preventive composition becoming too hard and difficult to follow with ink consumption during writing, as well as easily adhering to the inner wall of the ink storage tube and following the ink, reducing the amount of the ink backflow preventive composition Is generated. In addition, the ink backflow preventive composition using the polybutene has a high temperature dependency with respect to the viscosity in a practical temperature range, and it has been difficult to obtain an ink backflow preventive composition that always exhibits stable viscosity.

Further, depending on the type and amount of the thickener,
The viscous structure is easily broken by the stress at the time of filling in the ink storage tube, and the viscous structure once broken does not return to the original state, it takes time to return, or even if it returns, the viscosity becomes higher than the initial time. And the like, and the separation and elution of the non-volatile liquid tend to occur. Specifically, when dibenzylidene sorbitol, tribenzylidene sorbitol, acylated amino acid, dextrin fatty acid ester, 12-hydroxystearic acid, etc. are used, they are once dissolved in a non-volatile liquid, then precipitated and thickened. The addition amount is as small as 0.5 to 2% based on the non-volatile liquid. Therefore, polybutene is easily separated and eluted.

When inorganic fine particles such as bentonite, swellable synthetic mica into which quaternary ammonium ions are introduced, and silica are used as a thickener, the amount of addition is 5 to 20% with respect to the non-volatile liquid. Yes, since it is prepared by applying a stress, the viscosity in the practical temperature range has little temperature dependence, and the viscous structure is hardly destroyed by the stress at the time of filling. Moreover, since the hardly volatile liquid hardly separates and elutes, an ink backflow preventing composition having excellent ink followability can be obtained. In addition, the metal soap is prepared without applying stress, but an ink backflow preventing composition having excellent ink followability can be obtained as described above.

Therefore, an ink backflow preventive composition using polybutene as a hardly volatile liquid is known as a thickener comprising dibenzylidene sorbitol, tribenzylidene sorbitol, an acylated amino acid, a dextrin fatty acid ester,
Although 12-hydroxystearic acid and the like can be used, preferably, bentonite, swellable synthetic mica into which quaternary ammonium ions are introduced, inorganic fine particles such as silica, and metal soap are used. However, the ink backflow preventive compositions comprising the above-mentioned various thickeners and polybutene are all allowed to stand in an upright state, or to gradually fall from the ink end surface when subjected to an impact.

The ink backflow preventive composition for a ballpoint pen according to the present invention is a polymer in which atactic polypropylene to be added has propylene bonded in a sterically irregular arrangement, and is an isotactic polymer having a regular arrangement. The atactic polypropylene is by-produced as a by-product in the process of producing polypropylene, and the molecular weight of the atactic polypropylene varies depending on the solvent and the separation temperature used in the process. However, in the present invention, the molecular weight is 1000 to 5000 in the present invention.
Atactic polypropylene having a molecular weight of 5,000 to 30,000 is preferably excellent in dispersibility in non-volatile liquids, imparting appropriate tackiness to prevent dripping, and thus has a high impact resistance. An ink backflow preventing composition having excellent properties can be obtained. Here, for example, even if polyethylene or polypropylene having a high degree of crystallinity is added instead, appropriate tackiness can be imparted and dripping can be prevented, but both ink follow-up properties cannot be satisfied, and furthermore, it is hardly volatile. Due to poor compatibility with liquids, they tend to separate over time. Also, a method of preventing dripping by using a non-volatile liquid in combination, for example, a method of using a non-volatile liquid having a large molecular weight is considered, but the addition amount of the non-volatile liquid having a large molecular weight is slightly changed. However, since the viscosity changes remarkably, it is difficult to obtain a desired viscosity and lacks practicality. The amount of the atactic polypropylene added is 0.2 to 30% by weight, preferably 1 to 25% by weight of the total composition. If it is less than 0.2% by weight, it is difficult to obtain an ink backflow preventing composition having excellent impact resistance.
If the amount is more than 10% by weight, the viscosity increases and the ink followability is impaired.

The non-volatile liquid widely used as a base oil of the ink backflow preventive composition for ballpoint pens of the present invention includes polybutene and α-olefin having properties such as transparency, lubricity, heat resistance and oxidation resistance. -Co-oligomer; refined mineral oil such as liquid paraffin and spindle oil can be added if desired. The α-olefin-co-oligomer may be an oligomer composed of two or more α-olefins or a co-oligomer of ethylene and α-olefin. The non-volatile liquid may be 500 to 30,000 cSt (centistokes) at 20 ° C., preferably 800 to 20,000 cS.
Those having a kinematic viscosity in the range of t are used. Kinematic viscosity is 5
If a non-volatile liquid having a viscosity of less than 00 cSt is used, it is difficult to obtain an ink backflow preventing composition having good impact resistance, and if the viscosity exceeds 30,000 cSt, it is difficult to satisfy ink followability.

Examples of the thickener include the above-mentioned bentonite, inorganic fine particles such as hydrophobic silica and hydrophilic silica, metal soaps such as aluminum soap and lithium soap, and quaternary ammonium ions represented by the following general formula (1). Swellable synthetic mica into which is introduced.

[0013]

Embedded image (Wherein, R ₁ , R ₂ , R ₃ , and R ₄ each have 8 to 8 carbon atoms)
And 22 alkyl groups. Or, in the formula, R ₁ has ₁ carbon atom
And R ₂ and R ₃ are (CH ₂ CH ₂ O) _n H groups, (CH ₂ CH ₂ CH ₂ O)
_n H _{group, (CH 2 CH (CH 3} ) O) n H group, carbon atoms 1
To any one of R 1 to R ₃ , and R ₄ represents (CH ₂
A CH ₂ O) _n H group, a (CH ₂ CH ₂ CH ₂ O) _n H group,
Any of (CH ₂ CH (CH ₃ ) O) _n H groups,
n shows 1-50. In order to introduce the quaternary ammonium ion into synthetic mica, a quaternary ammonium salt containing the ion is used. Examples of the salt include Cl ⁻ , Br ⁻ , NO ₃ , and O 2.
Examples thereof include salts with anions such as H ⁻ and CH ₃ COO ⁻ .

The dibenzylidene sorbitol described above,
Even in systems using thickeners such as tribenzylidene sorbitol, acylated amino acids, dextrin fatty acid esters, and 12-hydroxystearic acid, separation and elution of non-volatile liquids can be suppressed by adding atactic polypropylene. Can be satisfied.

As a simple means for measuring the hardness, fluidity, etc. of the ink backflow preventive composition for a ballpoint pen obtained as described above, a spread meter is suitable. 25-50mm
Those within the range show proper performance. If it is less than 25 mm, it is too hard to impair the followability, and if it exceeds 50 mm, it is too soft and the writing tip is left upward (upright state), or moves to the rear when shock is applied due to dropping or the like. There is a risk.

The ink backflow preventive composition for a ball-point pen is, as described above, filled with an ink in an ink container and then filled at the rear end, and follows the ink as the ink is consumed. It prevents the ink from evaporating and prevents the ink from flowing backward when the writing tip is left standing upward or when an impact is applied. Further, a conventionally known solid ink backflow preventive body and the ink backflow preventive composition may be used in combination.

As the ink, a conventionally known water-based or oil-based ink is used. When the ink is an oil-based ink, the viscosity is 1 to 20 Pa · s, preferably 1 to 10 Pa · s.
A medium viscosity to high viscosity oil-based ink of Pa · s is preferably used. In the case of a water-based ink, a shear-thinning water-based ink is preferably used.

Examples of the coloring agent used in the oil-based ink include dyes classified as solvent dyes in a color index. Specific examples of the solvent dye include Balifast Black 380
6 (CI Solvent Black 29), 3807
(Trimethylbenzylammonium salt of dye of CI Solvent Black 29), Spirit Black SB
(CI Solvent Black 5), Spiron Black GMH (CI Solvent Black 43), Varifast Red 1308 (Creation of CI Basic Red 1 dye and CI Acid Yellow 23 dye) Salt), Bali First Yellow AUM (dye of CI Basic Yellow 2 and CI Acid Yellow 42)
Salt-form of the dye), Spiron Yellow C2GH (C.I.
I. Basic Yellow 2 dye organic salt), Spiron Violet CRH (CI Solvent Violet 8-1), Balifast Violet 1701
(A salt form of the dyes of CI Basic Violet 1 and CI Acid Yellow 42), Spiron Red CG
H (organic acid salt of a dye of CI Basic Red 1),
Spiron Pink BH (CI Solvent Red 8)
2), Nigrosine Base EX (CI Solvent Black 7), Oil Blue 603 (CI Solvent Blue 5), Neozapon Blue 808 (CI Solvent Blue 70) and the like.

As the colorant used in the aqueous ink, a dye that can be dissolved or dispersed in an aqueous medium can be used, and specific examples thereof are shown below. As the dye, an acid dye, a basic dye, a direct dye, or the like can be used. As the acid dye, neucoccin (C.I.
I. 16255), tartrazine (CI. 1914)
0), Acid Blue Black 10B (CI.204
70), Guinea Green (CI. 42085), Brilliant Blue FCF (CI. 42090), Acid Violet 6B (CI. 42640), Soluble Blue (CI. 42755), Naphthalene Green (C. .I.44025), eosin (CI.4538)
0), Phloxine (CI. 45410), Erythrosin (CI. 45430), Nigrosine (CI. 50)
420), acid flavin (CI. 56205) and the like. Examples of the basic dye include chrysoidin (CI. 11270), methyl violet FN
(C.I. 42535), crystal violet (C.I. 42555), malachite green (C.I.
I. 42000), Victoria Blue FB (CI.4
4045), rhodamine B (CI. 45170), acridine orange NS (CI. 46005), methylene blue B (CI. 52015) and the like. As a direct dye, Congo Red (C.I.
0), Direct Sky Blue 5B (CI. 2440)
0), Violet BB (CI. 27905), Direct Deep Black EX (CI. 30235),
Kayalas Black G Conch (CI. 35225), Direct Fast Black G (CI. 35255),
Phthalocyanine blue (CI. 74180) and the like are used.

The oil-based ink and the water-based ink include:
Inorganic pigments such as carbon black, iron oxide and ultramarine blue, pigments such as azo-based, anthraquinone-based, condensed polyazo-based, thioindigo-based, metal complex salts, phthalocyanine-based, perinone-perylene-based, dioxazine-based, quinacridone-based organic pigments, and fluorescent pigments Can also be used.

Further, a fluorescent pigment in the form of fine particles of a synthetic resin in which various fluorescent dyes are made into a solid solution in a resin matrix, metallic pigments such as pearl pigments, gold and silver, luminous pigments, white pigments such as titanium oxide, reversible heat Discolorable microcapsule pigments and the like can also be used. The colorants may be used singly or as a mixture of two or more, and are used in an amount of 3 to 40% by weight in the ink composition.

As the organic solvent used in the oil-based ink, a high-boiling organic solvent having a boiling point of 150 ° C. or more at normal pressure is preferably used. Examples thereof include benzyl alcohol, ethylene glycol monophenyl ether (phenyl glycol), and benzyl alcohol. Organic solvents such as glycol and dipropylene glycol monomethyl ether are exemplified.

As the solvent used for the aqueous ink, water and conventional water-soluble organic solvents which are compatible with water are used. Ethanol, isopropyl alcohol, glycerin, triethanolamine, diethanolamine, monoethanolamine, ethylene It is possible to use glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide and the like. The water-soluble organic solvent can be selected according to the purpose of a dissolution aid for the resin, drying of the ink at the tip of writing, and the like.

As the shear-thinning agent used in the aqueous ink, a substance soluble or dispersible in water is effective, and xanthan gum, welan gum, and an organic acid-modified heteropolysaccharide of glucose and galactose as constituent monosaccharides are effective. Succinoglycan (average molecular weight of about 1 to 8 million),
Guar gum, locust bean gum and its derivatives, hydroxyethylcellulose, alkyl alginates, polymers having a molecular weight of 100,000 to 150,000 mainly containing alkyl esters of methacrylic acid, extracted from seaweeds such as glycomannan, agar and carrageenin Thickening polysaccharide having gelling ability, benzylidene sorbitol and benzylidene xylitol or derivatives thereof, crosslinkable acrylic acid polymer, inorganic fine particles, polyglycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene Castor oil, polyoxyethylene lanolin, lanolin alcohol, beeswax derivatives, polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene Alkyl phenyl ether, HLB value, such as fatty acid amide. Examples 8-12 of nonionic surfactant may be used alone or in combination. The shear thinning agent is contained in the ink composition in an amount of 0.1%.
It can be used in the range of up to 20% by weight. The ink composition to which the shear thinning agent has been added has an ink viscosity at 25 ° C. at a rotation speed of 100 rpm in an EM type rotational viscometer in the range of 25 to 160 mPa · s, and a shear thinning index of 0.1. Preferably, it is adjusted so as to indicate 1 to 0.7. When the viscosity and the shear thinning index are in the above ranges, the ink is suitable as a water-based ink for a ball-point pen, and a ball-point pen with good ink stability when left standing and good ink ejection during writing can be obtained. Further, the shear thinning index is an empirical formula (T = Kj ⁿ : K and n are calculated constants) obtained from rheological measurements with a viscometer such as a shear stress value (T) and a shear rate (j) value. ) Is the n value calculated by applying

Further, if necessary, a water-soluble resin such as styrene-maleic acid copolymer, cellulose derivative, polyvinylpyrrolidone, polyvinyl alcohol and dextrin can be used for imparting viscosity.

In addition, additives can be added as needed. For example, sodium carbonate, sodium phosphate, sodium hydroxide, sodium acetate, triethanolamine,
PH adjuster such as diethanolamine, phenolic acid, 1,2-
Benzthiazolin-3-one sodium salt, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, 2,3,5,6-
Preservatives or fungicides such as tetrachloro-4- (methylsulfonyl) pyridine, rust inhibitors such as benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, saponin, urea, sorbitol, mannitol, Sugars, glucose, reduced starch hydrolysates, wetting agents such as sodium pyrophosphate, lubricants such as phosphate ester surfactants, fluorine surfactants and nonionics, anions, Examples include a cationic surfactant, an antifoaming agent such as dimethylpolysiloxane, and a dispersant.

For the structure of the writing tip, referred to as the tip, a general-purpose mechanism is more effective than before, and the ball is held 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 chip that is held, or a chip that is formed by holding a ball in a ball holding portion formed by cutting a metal material using a drill or the like, or a chip that is formed by cutting a metal pipe or a metal material. And the like, in which a ball held by the spring is urged forward by a spring body. Further, the ball having a diameter of about 0.3 to 1.2 mm, such as a cemented carbide, stainless steel, ruby, or ceramic, can be used.

The ink containing tube for containing the ink and the ink backflow preventive composition for a ballpoint pen is formed by molding a molded article made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, etc., with low ink evaporation and productivity. Surface. Further, by using a transparent, colored transparent, or translucent molded body as the ink storage tube, it is possible to visually recognize the ink from the outside, and it is possible to provide a specific design effect, and to provide a color tone and a remaining amount of the ink. Can be confirmed. In addition to directly connecting the chip to the ink storage tube, the ink storage tube and the chip may be connected via a connection member. In addition, the ink storage tube is
As a form of the ballpoint pen refill, the refill may be housed in a barrel, or the barrel may be used as an ink storage tube to directly fill the barrel with ink.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The ink backflow preventive composition for a ballpoint pen according to the present invention is prepared by adding a non-volatile liquid, a thickener and an atactic polypropylene, stirring the mixture with a disper, and optionally heating the mixture to form a three-roll mill. And obtained by kneading. The ink backflow preventing composition for a ballpoint pen prepared as described above is used by filling the rear end side of the ink contained in the ink containing tube.

[0030]

The following table shows the compositions and SM values (1 minute value at 20 ° C. with a spread meter) of the ink backflow preventive compositions for ballpoint pens of the examples and comparative examples. The numerical values in the table indicate parts by weight.

[0031]

[Table 1]

The details of the contents of the raw materials in the table are described below according to the note numbers. (1) Aluminum stearate (trade name: aluminum stearate 103, manufactured by Nitto Kasei Kogyo Co., Ltd.) (2) Organic bentonite [trade name: barragel, manufactured by Nissan Gardler Catalyst Co., Ltd.] (3) Quaternary ammonium ion (4C-TS, manufactured by Topy Industries, Ltd.) (4) Polypropylene wax (trade name: Hoechs)
t Wax PP230, manufactured by Hoechst Co.) (5) Tribenzylidene sorbitol [trade name: Gelol T, manufactured by Shin Nippon Rika Co., Ltd.] (6) Atactic polypropylene [trade name: Sun Attack, manufactured by Chiba Fine Chemical Co., Ltd., molecular weight] 5000
-20,000] (7) Atactic polypropylene [trade name: Hirodyne 8500, manufactured by Hirodyne Industry Co., Ltd., molecular weight 2000]
0-30000] (8) Atactic polypropylene [trade name: Vistax L, manufactured by Chiba Fine Chemical Co., Ltd., molecular weight 5000]
(10) Liquid polybutene [Product name: Idemitsu Polybutene 15]
H, manufactured by Idemitsu Petrochemical Co., Ltd., molecular weight 550, viscosity 250
0cSt (20 ° C)] (10) Liquid polybutene [Product name: Polybutene HV-1
5. Nippon Petrochemical Co., Ltd., molecular weight 540, viscosity 400
0cSt (20 ° C.)] (11) Liquid polybutene [Product name: Polybutene HV-3]
5. Nippon Petrochemical Co., Ltd., molecular weight 750, viscosity 160
00cSt (20 ° C.)] (12) α-olefin cooligomer [trade name: Lucant HC-150, manufactured by Mitsui Petrochemical Co., Ltd., molecular weight 140]
0, viscosity 7000 cSt (25 ° C.)]

Method for Preparing Ink Backflow Prevention Composition for Ballpoint Pen The ink backflow prevention compositions of Examples 2 to 4 and Comparative Example 1 were prepared by mixing each raw material with a small amount of methanol, stirring, and heating. After cooling, the mixture is kneaded with three rolls. The ink backflow preventive compositions of Examples 1 and 5 and Comparative Example 2 are obtained by mixing and stirring the respective raw materials, heating, allowing to cool, and kneading with three rolls. Comparative Example 3,
The ink backflow preventing composition of No. 4 is obtained by mixing and stirring the respective raw materials, heating, and then allowing to cool.

Preparation of Ink 6 parts of anthraquinone blue as a coloring agent, 0.3 parts of xanthan gum as a shear-thinning agent, 0.2 parts of a polyether-modified silicone as an additive, and 93.5 parts of water were mixed and stirred. A shear thinning aqueous ink was obtained. The obtained ink was used at 25 ° C. at a rotational speed of 10 in an EM-type rotational viscometer.
The ink viscosity at 0 rpm is 80 mPa · s,
The ink viscosity at pm was 2000 mPa · s.

Preparation of Ballpoint Pen The above ink is filled into a polypropylene ink container having an inner diameter of 3.8 mmφ having a ballpoint pen tip at the tip, and the ink backflow prevention for the ballpoint pen prepared in Examples and Comparative Examples on the open ink end face. The body composition was disposed to form a sample ballpoint pen, and the following tests were performed. (1) Ink Followability Test A sample ballpoint pen was set on a linear writing tester, and a 30 cm writing was performed under the conditions of a writing angle of 70 °, a load of 100 g, and a writing speed of 13 cm / sec. . (2) Impact resistance test The tip of the ballpoint pen is hermetically sealed with a rubber stopper, dropped from a position of 30 cm with the pen tip facing upward, and the state of the ink backflow preventing composition is observed. (3) Time-lapse test The tip of the ballpoint pen is hermetically sealed with a rubber stopper, left standing at 50 ° C. for one month with the pen tip facing upward, and the state of the ink backflow preventing composition is observed.

The following tests were carried out using the ink backflow preventive compositions prepared in Examples and Comparative Examples. (4) Shear resistance test After filling the syringe, the piston was pressed to push out the ink backflow preventive composition from the tip of the syringe, and then left for 5 minutes to measure the SM value.

The test results are shown in the table.

[Table 2]

The judgment of the test results in the table is as follows. (1) Ink followability test ：: There is no blurring in the handwriting, and the ink backflow preventing composition favorably follows the ink consumption. ×: The handwriting becomes faint or writing becomes impossible, and the ink backflow preventing composition does not follow the ink consumption. (2) Impact test ○: No change even after dropping 30 times. ×: The ink backflow preventer composition moves by falling less than 30 times. (3) Aging test ：: No separation occurs in the ink backflow preventing composition. Δ: The ink backflow preventing composition was slightly separated. X: A part of the ink backflow preventing composition was separated and moved to the writing tip along the inner wall of the ink storage tube. (4) Shear resistance test ：: Difference from initial SM value is less than 5. X: The difference from the initial SM value is 5 or more.

[0039]

According to the present invention, an atactic polypropylene is added to a ballpoint pen ink backflow preventive composition comprising a hardly volatile liquid and a thickener, whereby the ink has excellent ink followability during writing and an upright state. The present invention can provide an ink backflow preventive composition for a ballpoint pen and a ballpoint pen using the same, which can maintain good writing performance under various conditions without allowing the ink to flow backward even when left or subjected to an impact. Furthermore, the ink backflow preventive composition for ballpoint pens can be obtained with a permanent writing performance equivalent to that of the initial stage, since the separation and elution of the non-volatile liquid is small and the stability over time is also good. An object and a ballpoint pen using the same are obtained.

Claims (7)

[Claims] 1. An ink backflow preventive composition for ballpoint pens, comprising a thickening agent and atactic polypropylene added to a hardly volatile liquid. 2. The ink backflow preventive composition for a ball-point pen according to claim 1, wherein the amount of the atactic polypropylene added is 0.2 to 30% by weight of the total composition. 3. The ink backflow preventive composition for ballpoint pens according to claim 1, wherein the molecular weight of the atactic polypropylene is 1,000 to 50,000. 4. The liquid according to claim 1, wherein the non-volatile liquid is polybutene, α-olefin-co-oligomer, alone or in a mixture.
The ink backflow preventive composition for ballpoint pens according to the above. 5. The ink backflow preventive composition according to claim 1, wherein the thickener is selected from bentonite, swellable synthetic mica into which quaternary ammonium ions have been introduced, metal soap, and inorganic fine particles. 6. The ink backflow preventive composition for ballpoint pens according to any one of claims 1 to 5, wherein the value per minute measured by a spread meter at 20 ° C. is 25 to 50 mm. 7. A tip which holds a ball rotatably at a tip end thereof and which is connected to a tip for discharging ink from the tip end directly or via a relay member to supply ink to the tip. 7. The ink storage section, the medium-viscosity to high-viscosity or shear-thinning ink filled in the ink storage section, and the ink is filled in a rear end portion of the ink and follows the ink consumption. A ballpoint pen comprising the ink backflow preventive composition for a ballpoint pen described in 1 above.