JP6322451B2 - Writing instrument - Google Patents

Description

  The present invention relates to a writing instrument having excellent temporal stability of an ink follower in a writing instrument equipped with an ink follower (follower).

Conventionally, many water-based ink compositions containing a phosphate ester have been known in order to improve writing quality, wear of ball seats, lubricity, and the like (see, for example, Patent Documents 1 to 3).
In writing instruments using these water-based ink compositions, an ink follower is usually mounted on the ink tail end side, which is one end side of the ink container, in order to prevent ink leakage or scattering. As this ink follower, a base oil is usually used which is thickened by blending a viscosity modifier such as silica, metal soap, thickener, or thermoplastic elastomer.

  However, a writing instrument equipped with this ink follower (follower) has a problem in that the separation phenomenon of the oil component constituting the ink follower is often confirmed and the temporal stability is not good. There are several possible causes for this, but it has been found that the phosphate ester added to the ink is strongly involved in terms of the ink composition.

  This can be confirmed by the fact that the writing instrument filled with a water-based ink composition containing a fluorine-based, silicon-based, fatty acid salt or the like other than the phosphoric acid ester has less separation of oil components constituting the ink follower. However, as a water-based ink composition for writing instruments such as water-based ballpoint pens, the phosphoric acid ester composition is particularly preferable from the viewpoint of writing taste, ball seat wear suppression, lubricity, etc., compared to other additives. It is.

JP-A-6-57194 (Claims, Examples, etc.) JP 2008-201970 A (Claims, Examples, etc.) JP 2012-41462 (Claims, Examples, etc.)

  The present invention has been made in view of the above-mentioned problems of the prior art and intends to solve this problem. When the aqueous ink composition containing a phosphate ester is used without impairing writing performance such as ink outflow stability. It is an object of the present invention to provide a writing instrument having excellent temporal stability of an ink follower mounted on the ink container of the writing instrument.

  As a result of intensive studies in view of the above-described conventional problems, the present inventors have provided an ink container filled with an aqueous ink composition containing a phosphate ester, and an ink follower is provided at one end of the ink container. In the writing instrument filled with the body, the inventors have found that the above-mentioned writing instrument can be obtained by further adding a specific component to the water-based ink composition, thereby completing the present invention.

That is, the present invention resides in the following (1) to (3).
(1) An ink container filled with an aqueous ink composition containing at least 0.05 to 1.5% by mass of oxidized cellulose and 0.01 to 5% by mass of phosphoric acid ester is provided, and one end of the ink container is provided. Is a writing instrument that is filled with an ink follower.
(2) The writing instrument as described in (1) above, wherein the ink follower has a viscosity of 1,000 to 10,000 mPa · s.
(3) The writing instrument as described in (1) or (2) above, wherein the phosphate ester has an HLB value of 18 or less.

  ADVANTAGE OF THE INVENTION According to this invention, the writing implement excellent in the temporal stability of the ink follower in the writing implement in which the ink follower was mounted is provided.

Hereinafter, embodiments of the present invention will be described in detail.
The writing instrument of the present invention comprises an ink container filled with an aqueous ink composition containing at least 0.05 to 1.5% by mass of oxidized cellulose and 0.01 to 5% by mass of phosphoric acid esters, and contains the ink. One end of the body is filled with an ink follower.

<Water-based ink composition>
The aqueous ink composition filled in the ink container of the writing instrument of the present invention contains at least 0.05 to 1.5% by mass of oxidized cellulose and 0.01 to 5% by mass of phosphate ester.
(Oxidized cellulose)
Oxidized cellulose used has a cellulose I-type crystal structure and β-glucose constituting cellulose [(C ₆ H ₁₀ O ₅ ) n: a natural polymer in which a number of β-glucose molecules are linearly polymerized by glycosidic bonds]. Is not particularly limited as long as a part of the hydroxyl group (—OH group) is modified with at least one functional group of an aldehyde group (—CHO) and a carboxyl group (—COOH group). Examples include those obtained by oxidizing a hydroxyl group (—OH group) at the C6 position to an aldehyde group (—CHO) and a carboxyl group (—COOH group).

  Oxidized cellulose used in the present invention is a fiber obtained by surface-oxidizing a cellulose solid raw material derived from a natural product having an I-type crystal structure and miniaturizing it to nano size. In general, cellulose derived from natural products, which is a raw material, has almost no exception, so that nanofibers called microfibrils are multi-bundled to form a higher order structure. It is something that cannot be done. In the oxidized cellulose of the present invention, a part of the hydroxyl groups of the cellulose fiber is oxidized to introduce aldehyde groups and carboxyl groups, and the hydrogen bonds between the surfaces, which are the driving force of the strong cohesive force between the microfibrils, are weakened, and the dispersion treatment However, it is refined to nano size.

Preferably, the oxidized cellulose has a number average fiber diameter of 2 to 150 nm.
From the viewpoints of dispersion stability in ink and further improvement of the stability of the ink follower due to the improvement of the dispersion stability, it is more preferable that the number average fiber diameter is 3 to 80 nm. By making the number average fiber diameter of this oxidized cellulose 2 nm or more, the function as a dispersion medium is exhibited, and conversely, by making the number average fiber diameter 150 nm or less, the dispersion stability of the cellulose fiber itself is further improved. be able to.
In the present invention, the number average fiber diameter can be measured, for example, as follows. That is, a sample diluted with water added to cellulose fibers is dispersed, cast onto a carbon film-coated grid that has been subjected to a hydrophilic treatment, and this is observed with a transmission electron microscope (TEM). From the obtained image, The number average fiber diameter can be measured and calculated.
In addition, the cellulose constituting the specific cellulose fiber has a natural product-derived type I crystal structure, for example, in the diffraction profile obtained by wide-angle X-ray diffraction image measurement, 2 theta can be identified from having typical peaks at two positions near 22 to 23 °.

  The production of the oxidized cellulose used in the present invention is, for example, an oxidation process in which natural cellulose is used as a raw material, an N-oxyl compound is used as an oxidation catalyst in water, and the natural cellulose is oxidized by acting a co-oxidant to obtain a reactant fiber. It can be obtained by at least three steps: a reaction step, a purification step for obtaining a reactant fiber impregnated with water by removing impurities, and a dispersion step for dispersing the reactant fiber impregnated with water in a solvent.

In the oxidation reaction step, a dispersion liquid in which natural cellulose is dispersed in water is prepared. Here, natural cellulose means purified cellulose isolated from cellulose biosynthetic systems such as plants, animals, and bacteria-producing gels. More specifically, softwood pulp, hardwood pulp, cotton pulp such as cotton linter and cotton lint, non-wood pulp such as straw pulp and bagasse pulp, BC, cellulose isolated from sea squirt, isolated from seaweed The cellulose can be exemplified, but is not limited thereto. Natural cellulose is preferably subjected to a treatment for increasing the surface area such as beating, whereby the reaction efficiency can be increased and the productivity can be increased. Furthermore, when natural cellulose that has been isolated and purified and stored in Never Dry is used, the microfibril bundles are likely to swell. The average fiber diameter can be reduced, which is preferable.
The dispersion medium of natural cellulose in the reaction is water, and the concentration of natural cellulose in the reaction aqueous solution is arbitrary as long as the reagent can sufficiently diffuse, but usually about 5% with respect to the weight of the reaction aqueous solution. It is as follows.

  Many N-oxyl compounds that can be used as an oxidation catalyst for cellulose have been reported ("Cellulose" Vol. 10, 2003, pages 335 to 341, using "TEMPO derivatives by I. Shibata and A. Isogai"). The article entitled “Catalyzed Oxidation of Cellulose: HPSEC and NMR Analysis of the Oxidation Products”, in particular, TEMPO (2,2,6,6-tetramethyl-1-piperidine-N-oxyl), 4-acetamido-TEMPO, 4-Carboxy-TEMPO and 4-phosphonooxy-TEMPO are preferable in the reaction rate at room temperature in water. A catalytic amount is sufficient for the addition of these N-oxyl compounds, preferably 0.1 to 4 mmol / l, more preferably 0.2 to 2 mmol / l.

As the co-oxidant, hypohalous acid or a salt thereof, hypohalous acid or a salt thereof, perhalogen acid or a salt thereof, hydrogen peroxide, a perorganic acid, and the like can be used in the present invention. Hypohalites such as sodium hypochlorite and sodium hypobromite. When sodium hypochlorite is used, it is preferable in terms of the reaction rate to advance the reaction in the presence of an alkali metal bromide such as sodium bromide. The addition amount of the alkali metal bromide is about 1 to 40 times mol, preferably about 10 to 20 times mol for the N-oxyl compound. In general, the amount of co-oxidant added is preferably in the range of about 0.5 to 8 mmol with respect to 1 g of natural cellulose, and the reaction is completed within about 5 to 120 minutes and at most 240 minutes.
The pH of the aqueous reaction solution is preferably maintained in the range of about 8-11. The temperature of the aqueous solution is arbitrary at about 4 to 40 ° C., but the reaction can be performed at room temperature, and the temperature is not particularly required to be controlled.

In the refining process, reactant fibers and compounds other than water contained in the reaction slurry such as unreacted hypochlorous acid and various by-products are removed from the system. Since it is not dispersed evenly to the nanofiber unit, a normal purification method, that is, washing with water and filtration are repeated to obtain a dispersion of high-purity (99% by mass or more) reactant fiber and water. As the purification method in the purification step, any apparatus can be used as long as it can achieve the above-described object, such as a method using centrifugal dehydration (for example, a continuous decanter).
The aqueous dispersion of the reactant fibers thus obtained is in the range of about 10% to 50% by weight as the solid content (cellulose) concentration in the squeezed state. In the subsequent step, when dispersing in nanofibers, a solid content concentration higher than 50% by mass is not preferable because extremely high energy is required for dispersion.

Furthermore, in the present invention, a dispersion of oxidized cellulose can be obtained by dispersing the reaction fiber (water dispersion) impregnated with water obtained in the above-described purification step in a solvent and performing a dispersion treatment, It can be set as the oxidized cellulose used by drying this dispersion.
Here, the solvent as the dispersion medium is usually preferably water, but in addition to water, alcohols that are soluble in water depending on the purpose (methanol, ethanol, isopropanol, isobutanol, sec-butanol, tert-butanol, methyl) Cellosolve, ethyl cellosolve, ethylene glycol, glycerin, etc.), ethers (ethylene glycol dimethyl ether, 1,4-dioxane, tetrahydrofuran, etc.), ketones (acetone, methyl ethyl ketone), N, N-dimethylformamide, N, N-dimethylacetamide Dimethyl sulfoxide or the like may be used. Moreover, these mixtures can also be used conveniently. Furthermore, when the dispersion of the above-described reactant fibers is diluted and dispersed with a solvent, the solvent is gradually added to disperse, and when a stepwise dispersion is attempted, a nanofiber-level fiber dispersion is efficiently obtained. You may be able to get Due to operational problems, the dispersion conditions can be selected so that the state after the dispersion step is a viscous dispersion or gel. The oxidized cellulose used may be a dispersion of the above oxidized cellulose.
The oxidized cellulose that can be used in the present invention is not limited to the above-described production method and the like, and a part of the hydroxyl groups (—OH groups) of the cellulose are aldehyde groups (—CHO) and carboxyl groups (—COOH). The production method is not particularly limited as long as it is modified with at least one functional group.

In the present invention, the content (solid content) of the oxidized cellulose is 0.05 to 1.5% by mass (hereinafter simply referred to as “%”), preferably based on the total amount of the aqueous ink composition to be used. 0.1 to 1.0% is desirable.
If the content of the oxidized cellulose is less than 0.05%, the effect of the present invention may not be obtained. On the other hand, if the content exceeds 1.5%, the viscosity of the ink may increase and the writing performance may decrease. Therefore, it is not preferable.

(Phosphate ester)
As the phosphoric acid ester to be used, any phosphoric acid ester (based surfactant) used as a water-based ink composition for a writing instrument can be used to improve writing taste, ball seat wear suppression, lubricity and the like. Not particularly limited, for example, polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether phosphoric acid monoester, polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether phosphoric acid diester, phosphoric acid triester Or a derivative thereof, but these phosphate esters may be used alone or in combination of two or more.
In the present invention, when a phosphate ester having an HLB value of 18 or less is used, the effects of the present invention can be obtained. However, in a writing instrument using an ink having lipophilicity, that is, a phosphate ester having a low HLB value. It is particularly effective. When such an ink was used, an effect of reducing the writing feeling was obtained, but there was a tendency that oil components were easily separated. Specifically, a particularly remarkable effect is obtained when a phosphate ester having an HLB value of 10 or less (0 ≦ HLB value ≦ 10) is blended.
The “HLB value” in the present invention can be determined from the Kawakami method [HLB value = 7 + 11.7 log (MW / MO), MW: molecular weight of hydrophilic portion, MO: molecular weight of lipophilic portion].

Specific examples of phosphate esters that can be used include commercially available Prisurf series (Daiichi Kogyo Seiyaku Co., Ltd.), Phosphanol ML-220, RB-410, RD-510Y, RD-720N, and the same. RL-210, RL-310, RS-410, RS-610, RS-710 (above, manufactured by Toho Chemical Industry Co., Ltd.), NIKKOL DLP-10, DOP-8N, DDP-2, DDP-4, Examples thereof include DDP-6, DDP-8, and DDP-10 (manufactured by Nikko Chemicals).
Among the PRISURF series, PRISURF AL (polyoxyethylene styrenated phenyl ether phosphate ester, HLB value: 5.6), A208B [polyoxyethylene (2) lauryl ether phosphate ester, HLB value: 6. 6], A208F [polyoxyethylene (3) alkyl (C8) ether phosphate ester, HLB value: 8.7], A212C [polyoxyethylene (6) tridecyl ether phosphate ester, HLB value: 9. 4], A215C [polyoxyethylene (10) tridecyl ether phosphate ester, HLB value: 11.5], A219B [polyoxyethylene (20) lauryl ether phosphate ester, HLB value: 16.2], etc. Is mentioned. These can be used as they are or as salts neutralized with alkali metals or organic bases. Moreover, you may use 2 or more types together.

The content of these phosphoric acid esters is 0.01 to 5%, preferably 0.05 to 3%, based on the total amount of the aqueous ink composition to be used.
If this content is less than 0.01% with respect to the total amount of the ink composition, the desired lubricity may not be obtained in the ink, whereas if it exceeds 5%, the aging of the ink is uncertain. May become qualitative.

The water-based ink composition used in the writing instrument of the present invention contains at least a colorant and a water-soluble solvent in addition to the above oxidized cellulose and phosphate ester.
Colorants that can be used include pigments and / or water-soluble dyes. There is no restriction | limiting in particular about the kind of pigment, Arbitrary things can be used from the inorganic type and organic type pigment conventionally used for writing instruments, such as a water-based ballpoint pen.

Examples of inorganic pigments include carbon black and metal powder.
Examples of organic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dye lakes, nitro pigments, and nitroso pigments. Specifically, phthalocyanine blue (C.I. 74160), phthalocyanine green (C.I. 74260), Hansa Yellow 3G (C.I. 11670), disazo yellow GR (C.I. 21100), permanent red 4R (C.I. 12335), brilliant carmine 6B (C.I. 15850), quinacridone red (C.I. 46500), etc. can be used.
Also, a plastic pigment composed of particles of styrene or acrylic resin can be used. Further, the hollow resin particles having voids inside the particles can be used as white pigments, or resin particles (pseudo pigments) dyed with a basic dye described later having excellent color development and dispersibility.

As the water-soluble dye, any of direct dyes, acid dyes, food dyes, and basic dyes can be used.
Examples of the direct dye include C.I. I. Direct Black 17, 19, 19, 22, 32, 38, 51, 71, C.I. I. Direct yellow 4, 26, 44, 50, C.I. I. Direct Red 1, 4, 23, 31, 37, 39, 75, 80, 81, 83, 225, 226, 227, C.I. I. Direct Blue 1, 15, 71, 86, 106, 119 and the like.
Examples of the acid dye include C.I. I. Acid Black 1, 2, 24, 26, 31, 31, 52, 107, 109, 110, 119, 154, C.I. I. Acid Yellow 7, 17, 19, 23, 25, 29, 38, 42, 49, 61, 72, 78, 110, 127, 135, 141, the same 142, C.I. I. Acid Red 8, 9, 9, 14, 26, 27, 35, 37, 51, 52, 57, 82, 87, 92, 94, 115, 129, 131, 186, 249, 254, 265, 276, C.I. I. Acid Violet 18, 17 and C.I. I. Acid Blue 1, 7, 9, 22, 23, 25, 40, 41, 43, 62, 78, 83, 90, 93, 103, 112, the same 113, 158, C.I. I. Acid Green 3, 9, 16, 25, 27 and the like.
Most of the food dyes are directly contained in the acid dyes or acid dyes. I. Food yellow 3 is mentioned.
Examples of basic dyes include C.I. I. Basic Yellow 1, 2 and 21, C.I. I. Basic Orange 2, 14, 32, C.I. I. Basic Red 1, 2, 9, 9, 14 C.I. I. Basic Brown 12, Basic Black 2, 8 and the like.
Examples of the resin particles dyed with a basic dye include fluorescent pigments obtained by dyeing acrylonitrile copolymer resin particles with a basic fluorescent dye. Specific product names include Sinloi Color SF Series (Sinloihi Co., Ltd.), NKW and NKP Series (Nippon Fluorochemicals Co., Ltd.).

These colorants may be used alone or in combination of two or more, and the content in the total amount of the aqueous ink composition is usually 0.5 to 30%, preferably 1 to 15. % Range.
If the content of this colorant is less than 0.5%, coloring may be weak or the hue of the handwriting may not be known. On the other hand, if it exceeds 30%, writing defects may occur. This is not preferable.

  Examples of the water-soluble solvent that can be used include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, 3-butylene glycol, thiodiethylene glycol, and glycerin, ethylene glycol monomethyl ether, and diethylene glycol monomethyl ether. These can be used alone or in combination. The content of the water-soluble solvent is preferably 5 to 40% in the total amount of the water-based ink composition for writing instruments.

  The water-based ink composition to be used includes the above-mentioned oxidized cellulose, phosphate ester, colorant, water-soluble solvent, and the remaining solvent water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.). In addition, a dispersant, a lubricant, a pH adjuster, a rust preventive, an antiseptic or a fungicide can be appropriately contained within a range not impairing the effects of the present invention.

When a pigment is used as the colorant, it is preferable to use a dispersant. This dispersant acts on the pigment surface to improve the affinity with water and to stably disperse the pigment in water. Nonionic, anionic surfactants and water-soluble resins are used. A water-soluble polymer is preferably used.
Lubricants include nonionics such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, polyoxyalkylene higher fatty acid esters, and alkyl phosphates, which are also used in pigment surface treatment agents, and alkyl sulfonic acids of higher fatty acid amides. Examples thereof include salts, anionic compounds such as alkyl allyl sulfonates, polyalkylene glycol derivatives, fluorosurfactants, and polyether-modified silicones.

Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, sodium tripolyphosphate, sodium carbonate, and alkali metal salts of phosphoric acid and alkali metal hydrates such as sodium hydroxide. Etc.
In addition, as rust preventives, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, saponins, etc., as antiseptics or fungicides, phenol, sodium omadin, sodium benzoate, benzimidazole compounds, etc. Can be mentioned.

The water-based ink composition to be used is a mixer or the like by appropriately combining the above oxidized cellulose, phosphate ester, colorant, water-soluble solvent, and other components. It can be prepared by mixing and stirring by setting the stirring conditions to suitable conditions using a homogenizer, a high-pressure homogenizer, an ultrasonic homogenizer, a high-pressure wet medialess atomizer or the like.
In addition, the pH (25 ° C.) of the aqueous ink composition to be used is adjusted to 5 to 10 by a pH adjuster or the like from the viewpoints of usability, safety, stability of the ink itself, and matching properties with the ink container. Is preferable, and more preferably 6 to 9.5.

<Ink follower>
The ink follower used in the present invention is housed in an ink container (refill) and is not compatible with the aqueous ink composition filled in the ink container, and is compatible with the aqueous ink composition. If the base material (oil component) is used as a main component, a conventionally used ink follower can be used without any particular limitation. For example, the base oil or A base oil blended with a thickener and thickened can be used.

Examples of the base oil used for the ink follower include polybutene, mineral oil, and silicone oil which are insoluble or hardly soluble in water.
Examples of the thickener include fine particle silica, calcium phosphate phosphate , thermoplastic elastomer and the like, and these can be used alone or in combination of two or more. In addition, if necessary, for example, a thickening aid (clay thickener, metal soap, etc.), an ink follower followability improver (surfactant, etc.), an antioxidant and the like can be blended.
If the inner diameter of the ink container is thick, drop impact resistance is improved by inserting a resin molding member such as a cylinder, pipe, or sphere made of a material such as polyethylene or polypropylene into the ink follower. It is also possible.

Preferably, the ink follower used has a viscosity value of 1000 to 10,000 mPa · s from the viewpoint of the balance between oil component separation suppression and followability.
In order to develop performance such as followability, the viscosity of the ink follower may be set low. Such an ink follower is liable to cause separation of oil components. In particular, when the viscosity value is 7000 mPa · s or less, the tendency becomes remarkable. However, according to the present invention, separation of oil components does not occur even at the above viscosity value.
In the present invention, the viscosity value refers to the viscosity at a shear rate of 200 sec ⁻¹ measured by an E-type rotational viscometer at a measurement temperature of 25 ° C.
The viscosity value of the ink follower can be adjusted by blending an appropriate amount of the thickener to be used and employing an appropriate thickening method.

<Writing instruments>
The writing instrument of the present invention includes an ink container filled with the aqueous ink composition having the above composition, and the ink follower is filled at one end of the ink container filled with the aqueous ink composition. The material / shape / structure (knock type, cap type, etc.) of the writing instrument and the material / shape / structure of the ink container are not particularly limited, and various forms can be employed.

For example, in a ballpoint pen type writing instrument, the aqueous ink composition and the ink follower having the above composition are respectively filled in an aqueous ballpoint pen body serving as an ink container including a ball having a diameter of 0.18 to 2.0 mm. It can be manufactured by attaching to a main body (cap type) that becomes a (shaft cylinder).
The water-based ballpoint pen to be used is not particularly limited as long as it has a ball having a diameter in the above range, and in particular, the water-based ink composition and the ink follower are filled in an ink storage tube of a polypropylene tube, and the tip stainless steel is used. A finished refill water-based ballpoint pen with a tip (the ball is a super steel alloy) is desirable. In addition to the above ballpoint pens, knock type ballpoint pens (single color type, two color type, three color type, four color type, etc.) or a multifunctional type combined with a writing instrument other than the ballpoint pen may be used.

  In the writing instrument of the present invention configured as described above, an aqueous ink composition and an ink containing at least 0.05 to 1.5% oxidized cellulose and 0.01 to 5% phosphoric acid ester in the ink container. Each of the followers is provided with an ink container, and the oxidized cellulose to be used exhibits a high viscosity even when the aqueous ink composition has a low viscosity of 0.05 to 1.5%. It exhibits a unique high thixotropy index and exhibits rheology control effects without impairing writing performance such as ink outflow stability, so the phosphate ester contained in the aqueous ink composition can participate in the ink follower. As a result, a writing instrument having excellent temporal stability of the ink follower is obtained.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to the following Example etc.

The aqueous ink composition and ink follower to be used were prepared by the following method.
[Preparation of water-based ink composition: inks 1 to 10]
Using the oxidized cellulose having the following physical properties, a predetermined amount of each water-based ink composition is mixed with a combination composition shown in Table 1 below, specifically, a phosphate ester, a colorant and the like. It was prepared by changing the stirring conditions (shearing force, pressure, stirring time) as appropriate using (Yoshida Kikai Kogyo Co., Ltd., Nanovaita), mixing and stirring by a wet method, and filtering with a 10 μm bag filter.

[Oxidized cellulose used]
After dispersing dry sulphite bleached softwood pulp equivalent to 2 g dry weight (mainly consisting of fibers with a fiber diameter greater than 1000 nm), 0.025 g TEMPO and 0.25 g sodium bromide in 150 ml water, The reaction was started by adding sodium hypochlorite to a 13 wt% sodium hypochlorite aqueous solution so that the amount of sodium hypochlorite was 2.5 mmol per 1 g of pulp. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to keep the pH at 10.5. When the pH no longer changes, the reaction is considered to be complete, the reaction product is filtered through a glass filter, washed with a sufficient amount of water and filtered five times to impregnate 25% by weight of water with a solid content of 25% by mass. Reactant fibers were obtained.
Next, water was added to the reactant fiber to make a 2% by mass slurry, which was then treated with a rotary blade mixer for about 5 minutes. Since the viscosity of the slurry significantly increased with the treatment, water was gradually added, and the dispersion treatment with the mixer was continued until the solid content concentration became 0.15% by mass. The dispersion of oxidized cellulose having a cellulose concentration of 0.15% by mass thus obtained was subjected to removal of suspended solids by centrifugation, and then the concentration was adjusted with water to give a cellulose concentration of 0.1% by mass. A transparent and slightly viscous dispersion of oxidized cellulose was obtained. Oxidized cellulose obtained by drying this dispersion was used. In addition, the oxidized cellulose shown to each Example etc. of Table 1 displays what was manufactured above by solid content concentration of each Example etc.

The number average fiber diameter of the oxidized cellulose obtained above was confirmed and measured by the following method.
<Number average fiber diameter>
The number average fiber diameter of the oxidized cellulose was measured as follows.
That is, a sample diluted with water added to oxidized cellulose was dispersed at 12000 rpm for 15 minutes using a homomixer, then cast on a carbon film-coated grid that had been subjected to a hydrophilic treatment, and this was measured with a transmission electron microscope (TEM). The number average fiber diameter was measured and calculated from the observed and obtained images. As a result, the number average fiber diameter was about 140 nm.

<Confirmation of cellulose I type crystal structure>
It was confirmed as follows that the oxidized cellulose used had an I-type crystal structure.
That is, in the diffraction profile obtained by the wide-angle X-ray diffraction image measurement, there are typical peaks at two positions of 2 theta = 14 to 17 ° and 2 theta = 22 to 23 °. It was confirmed to have a structure.

[Preparation of ink follower: ink followers 1 to 3]
Ink followers 1 and 2 were prepared with the composition shown in the following 2 and stirred at room temperature at a high speed for about 120 minutes with a mixer, followed by roll treatment once, vacuum defoamed, and ink follower 1 2 was obtained.
About the ink follower 3, it mixes with the composition shown in following 2, and it stirs for about 120 minutes at 150 to 180 degreeC with a mixer at high speed, cools to room temperature, performs a roll process once, and follows an ink follower. 3 was obtained.

About the obtained ink followers 1-3, the viscosity value was measured with the following method. The obtained viscosity values are shown in Table 2 below.
Measuring device: E-type rotational viscometer DIGITAL VISCOMETER DUV-E (manufactured by Tokyo Keiki Co., Ltd.)
Measurement conditions (frequency dependence):
Cone: 3 ° * R14
Shear rate: 200 sec ^-1
Measurement time: 600 sec
Measurement temperature: 25 ° C

[Examples 1-8 and Comparative Examples 1-6]
A water-based ballpoint pen was prepared by the following method, and the oil separation and the backflow property of the ink follower were evaluated by the following evaluation method.
These results are shown in Table 3 below.

(Production of water-based ballpoint pen)
Using each of the water-based ink compositions (inks 1 to 10) obtained in Table 1 and the ink followers 1 to 3 obtained in Table 2 above, water-based ballpoint pens were produced in the combinations shown in Table 3 below. Specifically, using an axis of a ballpoint pen [manufactured by Mitsubishi Pencil Co., Ltd., trade name: SIGNO UM-100], an inner diameter of 4.0 mm, a length of 113 mm, a polypropylene ink container, and a stainless steel tip (a cemented carbide ball, Each of the water-based inks 1 to 10 is filled in a refill composed of a joint that connects the receiving tube and the tip, and the ink followers 1 to 3 shown in Table 2 are loaded at the rear end of the ink. An aqueous ballpoint pen was prepared.

(Evaluation method for oil separation and reverse flow of ink follower)
Each pen body is left for one month with the pen tip (cap side) facing upward at 50 ° C. and a humidity of 65%. After taking out, the refill is visually observed, and the oil of the ink follower is mixed into the ink. And the presence or absence of oil leaking out of the refill was evaluated according to the following evaluation criteria.
Evaluation criteria:
○: No mixing of oil into the ink or leakage outside the refill is observed.
X: Mixing of oil into the ink or leakage outside the refill is observed.

  As is clear from the results of Table 3 above, the writing implements of Examples 1 to 8 according to the present invention are those in which the ink follower is mounted as compared with the writing implements of Comparative Examples 1 to 6 that are outside the scope of the present invention. It has been found that a writing instrument having excellent temporal stability of the ink follower can be obtained.

  A writing instrument suitable for an aqueous ballpoint pen or the like is obtained.

Claims (3)

An ink container filled with an aqueous ink composition containing at least 0.05 to 1.5% by mass of oxidized cellulose and 0.01 to 5% by mass of a phosphoric acid ester is provided, and at least one end of the ink container has A writing instrument filled with an ink follower containing a base oil selected from the following group A.
Group A: polybutene, mineral oil, silicone oil   The writing instrument according to claim 1, wherein the ink follower has a viscosity value of 1000 to 10,000 mPa · s.   The writing instrument according to claim 1 or 2, wherein the phosphate ester has an HLB value of 18 or less.