JP4925570B2 - Erasable ink composition - Google Patents

Description

  The present invention relates to an erasable ink composition that cannot be erased by a commercially available eraser, but can be erased only by using a specific eraser.

  Conventionally, many eraser erasable ink compositions capable of erasing writing lines with commercially available erasers are known, but in recent years, many eraser erasable ink compositions using water as a main solvent have been known. It is disclosed.

  For example, an aqueous erasable ink composition comprising a styrene-butadiene copolymer and a water-insoluble pigment, suitable for use in highlighters and other writing instruments, and having a viscosity of 10 to 30 cps and the use thereof Marker (for example, refer to Patent Document 1), erasable ink composition containing a resin, pigment and water having a film forming temperature of 0 ° C. or lower or a glass transition temperature of 0 ° C. or lower, and a film forming of 0 ° C. or lower An erasable ink containing a resin having a temperature or a glass transition temperature of 0 ° C. or less, colored spherical fine particles having a particle diameter of 1 to 20 μm, and water, and having an ink viscosity of 5 to 35 mPa · s (for example, patent documents by the present applicant) 2 and 3), and a film-forming resin particle having a glass transition temperature of 0 ° C. or less, a colored resin particle colored with a dye, a film-forming inhibitor, and water. Writing eraser erasable aqueous ink composition including (for example, see Patent Document 4) and the like are known.

However, the erasable ink composition disclosed in each of these publications, and the conventional erasable ink compositions known so far, can be erased with a commercially available eraser and an eraser with a hardness of 70 ° or less. As a premise, there is not enough adhesion between the paper surface and the writing line, it can be easily peeled off by rubbing with a finger etc., and there is a problem that an excellent balance of eraser erasability and abrasion resistance has not been obtained There is.
In addition, the conventional erasable ink composition has insufficient stickiness and hardness of the writing line when writing on the writing line with the same kind of ink. There is a problem such as falling into.
Japanese Patent Laid-Open No. 7-505174 (Claims, Examples, etc.) JP-A-4-56089 (Claims, Examples, etc.) JP-A-5-279614 (Claims, Examples, etc.) JP 2003-55593 A (claims, examples, etc.)

  The present invention is intended to solve this problem in view of the above-described problems of the prior art, has sufficient adhesion between the paper surface and the writing line, and is not peeled off even by rubbing with a finger or the like. An object is to provide an erasable ink composition which can be easily erased only by an eraser.

In order to solve the above conventional problems and the like, the present inventors have earnestly studied the conventional erasable ink, and as a result, obtained the following knowledge. That is, since the conventional erasable ink composition is premised on erasing with a commercially available eraser having a hardness of 70 ° or less, the ink composition has a limited particle diameter and non-colored particle content. It has been developed by suitably combining the selection of a film-forming resin. However, as long as it is presupposed to be erased with a commercially available eraser, no matter how the ink composition is changed, the adhesiveness between the paper surface and the writing line is not sufficient, and the problem of easy peeling due to scratching with fingers etc. is solved The current situation is not.
Therefore, the present inventors have studied from the ink composition side in order to make the adhesion between the paper surface and the writing line sufficient, and as a result, “repel” and “erasing” in the non-penetration of the writing line on the paper surface. It has been found that the above-mentioned problems can be solved by making an optimal balance between the properties and the ink composition that suppresses the penetration of ink into paper and the formation of a hard coating film. This writing line cannot be erased with a commercially available eraser, but if you use a specific eraser, you can easily erase the writing line without scraping the paper. The present invention has been completed by finding that an ink composition can be obtained.

That is, this invention exists in following (1)-( 5 ).
(1) At least 0.1 to 0.5% by weight of a pigment and a thickener which is crystalline cellulose, and 20 to 45 % of a film- forming acrylonitrile butadiene resin emulsion having a surface tension of 28 to 43 dyne / cm. % And water, the surface tension of the ink is 30 to 45 dyne / cm, and it is erasable using an erasing tool that does not contain an abrasive having a hardness of 70 ° or more and less than 100 °. An erasable ink composition for sign pens having a fiber nib nib .
( 2 ) The film-forming acrylonitrile butadiene resin emulsion having a surface tension of 28 to 43 dyne / cm includes a resin emulsion (a) having a surface tension of 28 to 32 dyne / cm and a resin having a surface tension of 38 to 43 dyne / cm. An erasable ink composition for a sign pen having a fiber core pen tip according to (1) , comprising at least two types of emulsion (b).
( 3 ) An erasable ink composition for a sign pen having a fiber core nib according to (1) or ( 2), wherein the viscosity of the ink is 80 mPa · s or less.
( 4 ) A sign pen having a fiber core pen tip, which is filled with the erasable ink composition as described in any one of (1) to ( 3 ) above.
( 5 ) The sine pen having the fiber core nib described in ( 4 ) above is provided with an erasing tool not containing an abrasive having a hardness of 70 ° to less than 100 ° . A sign pen with a nib .

According to the present invention, the adhesiveness between the paper surface and the writing line is sufficient, it is not peeled off even by rubbing with a finger or the like, and the ink has excellent temporal stability and has a hardness of 70 ° to less than 100 °. There is provided an erasable ink composition that can be easily erased only by an erasing tool that does not contain any abrasive .

Hereinafter, embodiments of the present invention will be described in detail.
The erasable ink composition of the present invention contains at least a pigment, a thickener, a film-forming acrylonitrile butadiene resin emulsion, and water, and has a surface tension of 30 to 45 dyne / cm and a hardness of Erasing is possible using an erasing tool of 70 ° to less than 100 °.

As a pigment used in the present invention, a commercially available eraser is used instead of a specific eraser, so that a pigment having a smaller particle diameter can be used, and the shape of the pigment is: There is no particular limitation such as a plate shape, a spherical shape, and a scale shape, and they can be used.
Examples of the pigment that can be used include at least one of fluorescent pigments such as Sinloi color and keiko color, organic pigments such as RyuDye-w color, and inorganic pigments such as titanium oxide, black iron oxide, and bengara (each alone or individually). A mixture of two or more of these, the same applies hereinafter).
Specific examples of pigments that can be used include commercially available SW-17 (manufactured by Sinlohi Co., Ltd., aqueous dispersion of pink resin particles, average particle size of 1 μm), KNW-2117 (manufactured by Nippon Fluorescent Co., Ltd. Water dispersion, average particle size 0.5 μm), KNW-2117E (manufactured by Nippon Fluorescence Co., Ltd., water dispersion of pink resin particles, average particle size 0.4 μm), PINK NF (manufactured by Dainippon Ink & Chemicals, pink) An aqueous dispersion of colored resin particles, an average particle size of 0.5 to 1 μm) and the like.

  The average particle diameter of the pigment is 0.2 to 5 μm, preferably 0.3 to 2 μm. If the average particle diameter of the pigment is less than 0.2 μm, it will penetrate into the paper fibers, so that the desired erasability will not be satisfactory, and if the average particle diameter of the pigment exceeds 5 μm, it will penetrate into the paper fibers. Although the amount is small and the erasability is satisfied, it is not preferable because clogging may occur at the tip of a fiber core, plastic pen, felt pen, etc. and writing may be poor.

  The content of these pigments (solid content) is 0.5 to 10% by weight (hereinafter simply referred to as “%”), preferably 1 to 8%, more preferably 2%, based on the total amount of the ink composition. Used in a range of ˜5%. When the pigment content is less than 0.5%, the concentration of the handwriting is insufficient and the practicality as an ink is insufficient. On the other hand, when the content exceeds 10%, the dispersion stability is lowered and erasure after writing is completed. This is not preferable because the properties are lowered.

Examples of the thickener used in the present invention include at least one selected from crystalline cellulose, polysaccharides, alkali thickening type, crosslinking type, and inorganic thickener. Examples of polysaccharides include gums such as xanthan gum and leozan gum, and examples of inorganics include smectite.
Preferred thickeners include crystals that greatly improve the balance between erasability and scratch resistance by the specific erasing tool of the present invention and stability over time, and have a large effect of suppressing the precipitation of pigments upon standing. The use of cellulose is desirable.
Crystalline cellulose that can be used is an aggregate of cellulose crystallites having a substantially constant degree of polymerization obtained by acid hydrolysis or alkali oxidative decomposition of cellulose, unlike conventional aqueous solutions of thickening polysaccharides, The cellulose crystal has the property of forming dispersed particles in water.

Specific examples of the crystalline cellulose used include those composed of colloidal glue obtained by coating the surface of fine cellulose crystals of primary particles with a water-soluble polymer. Specific examples include RC-591, RC-N81, RC-591NF, CL-611, Zeolus cream [made by Asahi Kasei Co., Ltd.] and the like.
In the present invention, in order to sufficiently exhibit the characteristics of the crystalline cellulose to be preferably used, it is more preferable to use a disperser with higher shearing force or to use a dispersion type crystalline cellulose.
Examples of the disperser include a homomixer, a Waring blender, a homogenizer, and the like. However, the proportion of colloidal particles generated by the dispersion step increases, and a stable dispersion can be obtained. Further, since the dispersed crystalline cellulose forms a network structure in water, the effect of further suppressing the precipitation of the pigment by capturing the pigment as the coloring material in the matrix can be sufficiently exhibited.

The content of these thickeners is used in the range of 0.1 to 10%, preferably 0.2 to 8%, more preferably 0.3 to 5% with respect to the total amount of the ink composition. The
When the content of the thickener is less than 0.1%, the effect of suppressing the precipitation of the pigment is insufficient. On the other hand, when the content exceeds 10%, the viscosity of the ink itself becomes too high and the outflow of the ink is inhibited. This is not preferable.

  The film-forming acrylonitrile butadiene resin emulsion used in the present invention is not particularly limited as long as it has a film-forming property, but from the viewpoint of penetrating into the paper surface and repelling drawn lines on the coated paper surface. It is preferable to use at least one acrylonitrile butadiene resin emulsion having a surface tension of 28 to 43 dyne / cm.

In the present invention, the reason why the film-forming resin emulsion is limited to the acrylonitrile butadiene resin emulsion is due to the balance between the temporal stability with the pigment and the film strength and breaking strength.
More preferably, acrylonitrile butadiene resin emulsion (a) having a surface tension of 28 to 32 dyne / cm and surface tension from the viewpoint of repelling the drawn line on the coated paper and air replacement when filled in a direct liquid writing instrument. It is desirable to contain at least two kinds of acrylonitrile butadiene resin emulsions (b) having a particle size of 38 to 43 dyne / cm.
The mixing ratio (a) :( b) is preferably a weight ratio of 0:10 to 3: 7, particularly preferably 1: 9 to 2: 8.

  Specific examples of the acrylonitrile butadiene resin emulsion that can be used include commercially available Nipol LX517A (manufactured by Nippon Zeon Co., Ltd., aqueous dispersion of acrylonitrile-butadiene copolymer, solid content 40%, surface tension 42 dyne / cm), Nipol 1571CL ( Made by Nippon Zeon Co., Ltd., acrylonitrile / butadiene copolymer aqueous dispersion, solid content 38%, surface tension 29 dyne / cm), Nipol LX551 (produced by Nippon Zeon Co., Ltd., acrylonitrile / butadiene copolymer aqueous dispersion, solid content 45 %, Surface tension 31 dyne / cm), Nipol 1571H (manufactured by Nippon Zeon Co., Ltd., aqueous dispersion of acrylonitrile-butadiene copolymer, solid content 40%, surface tension 28 dyne / cm), Nipol LX511 (manufactured by Nippon Zeon Co., Ltd., acrylic resin) Rononitrile-butadiene copolymer aqueous dispersion, solid content 46%, surface tension 30 dyne / cm), Nipol LX522 (manufactured by Nippon Zeon Co., Ltd., acrylonitrile-butadiene copolymer aqueous dispersion, solid content 45%, surface tension 28 dyne) / Cm).

The (total) content of these acrylonitrile butadiene resin emulsions (solid content) is in the range of 10 to 45%, preferably 15 to 35%, more preferably 20 to 30% with respect to the total amount of the ink composition. used.
If the content of these acrylonitrile butadiene resin emulsions is less than 10%, the film forming property is poor and the colorant remains on the paper surface after erasure. On the other hand, if it exceeds 45%, the ink temperature (high temperature, low temperature) ) Is not preferable since the stability to the resin is reduced.

  Examples of the water used in the present invention include purified water, ion-exchanged water, pure water, deep sea water, and tap water, and the content thereof is the balance of the formulation. It is desirable that the amount of water be a blended composition that takes into account the mechanism of the sign pen used and the desired drawn line concentration.

  The erasable ink composition of the present invention contains the above-mentioned components, but is within the range not impairing the effects of the present invention, and other additives usually used for writing instrument inks such as urea and surfactants. As a lubricant, antibacterial agent, rust inhibitor, antioxidant, ultraviolet absorber, and organic solvent, ethylene glycol, diethylene glycol, glycerin, propylene glycol and the like can be appropriately contained as necessary.

The erasable ink composition of the present invention is required to have a surface tension of 30 to 45 dyne / cm, and preferably 32 to 38 dyne / cm.
When the ink surface tension is less than 30 dyne / cm, the ink penetrates the paper surface and the erasability becomes insufficient. On the other hand, when the ink surface tension exceeds 45 dyne / cm, the ink on the paper surface is repelled and beautiful. A drawn line cannot be formed, which is not preferable.
The adjustment of the surface tension of the ink can be carried out by selecting several kinds of acrylonitrile-butadiene resin emulsions having different surface tensions and changing the blending ratio.

The erasable ink composition of the present invention has an ink viscosity of preferably 80 mPa · s or less, more preferably 10 to 40 mPa · s, from the viewpoint of suppressing ink followability during writing and pigment settling. More preferably, it is desirable to set it as 20-40 mPa * s.
When the viscosity of the ink exceeds 80 mPa · s, the outflow property of the ink is lowered, the drawn line density becomes thin, and the blur occurs, which is not preferable.
In the present invention (including examples to be described later), the viscosity of the ink means a value measured at 25 ° C. and 1 rpm using an ELD viscometer. The viscosity of the ink can be adjusted by the amount of crystalline cellulose or the like and the amount of water added.

The erasable ink composition of the present invention can be produced by, for example, sequentially stirring the above components while mixing them in a tank and mixing and stirring until uniform.
The erasable ink composition of the present invention has a sufficient balance between the repellency and the erasability in the non-penetration of the writing line on the paper surface, in that the fixing property between the paper surface and the writing line is sufficient. In view of the good air displacement when using a direct liquid writing instrument, it contains at least a pigment, a thickener, a film-forming acrylonitrile butadiene resin emulsion, and water, and the surface of the ink. The tension is 30 to 45 dyne / cm.

In the present invention, the writing line formed by the ink composition having the above characteristics is different in technical idea from the conventional erasable ink composition, and cannot be erased by a conventional eraser having a hardness of 70 ° or less. However, in order to exert the effect of the present invention, it is erased for the first time by an erasing tool having a hardness of 70 ° to less than 100 °. Note that the sand eraser containing the abrasive removes a portion of the writing line on the paper surface and the surface layer of the paper surface, and is not included in the eraser of the present invention (hardness of 70 ° to less than 100 °). Is.
Preferably, an erasing tool having a hardness of 70 ° to less than 100 °, more preferably a hardness of 80 ° to less than 100 °, without scraping the paper surface (containing no abrasive) and more easily. From the point of erasing, an eraser comprising a mixture of resin and elastomer [mixing ratio (weight ratio), resin: elastomer = 1: 1 to 1: 4], for example, a mixture of polypropylene resin (PP) and polystyrene elastomer [mixing ratio 1: 3] is desirable.

  The erasable ink composition of the present invention configured as described above has sufficient adhesion between the paper surface and the writing line, is not peeled off even by rubbing with a finger, etc., and is excellent in ink aging stability. At the same time, it can be easily erased only with an eraser having a hardness of 70 ° to less than 100 °.

  The erasable ink composition of the present invention has the above-described excellent effects, and is used for writing instruments such as a marking pen having a fiber core or a plastic core, a sign pen such as a felt pen, a ballpoint pen, a pressure ballpoint pen, and a knock type ballpoint pen. It can be suitably used for ink for inkjet.

FIGS. 1-4 is drawing which shows each embodiment of the sign pen formed by filling the erasable ink composition of this invention.
FIG. 1 shows an embodiment in which the erasable ink composition of the present invention is used in a direct liquid type sign pen having a collector structure.
The sign pen A of this embodiment is obtained by filling the ink tank portion 11 serving as a shaft body that directly stores the erasable ink composition 10 of the present invention without occluding the filling material. In order to prevent the erasable ink 10 pushed out from the ink tank 11 when the air in the ink tank 11 is expanded due to a temperature rise or the like from the front end of the ink tank 11, it does not drop from the pen tip or the air hole. An ink reservoir 12 (collector member) 12 that temporarily retains is incorporated, and a tip 13 of the collector member 12 is provided with a pen tip 13 made of a fiber core.
Ink derivation from the ink tank unit 11 to the pen tip 13 is performed by removing the erasable ink 10 from the ink tank unit 11 via the relay core 14 provided with the ink flow path 12 a attached to the center hole of the collector member 12. This is done by deriving to
In FIG. 1, 15 is a holder member, 16 is a rear shaft fixed to the rear portion of the ink tank portion 11, and 17 is a cap. Further, the ink may be led out by arranging the rear portion of the pen tip 13 directly in the ink tank portion 11 without the intermediary core 14 interposed.

FIG. 2 shows a sign pen of the type in which the erasable ink composition of the present invention is occluded in an ink occlusion body such as batting.
The sign pen B of this embodiment is accommodated in an ink tank portion 21 that is a shaft body that accommodates an ink occlusion body 20 in which the erasable ink composition of the present invention is occluded in batting or the like.
The rear end portion 22a of the nib 22 made of a fiber core is brought into contact with the front portion of the ink occlusion body 20, whereby the erasable ink of the ink occlusion body 20 is supplied to the nib 22. Yes. Reference numeral 23 denotes a front shaft member, 24 denotes a tail plug fixed to the rear end portion of the shaft main body 21, and 25 denotes a cap.

FIG. 3 shows an embodiment in which the erasable ink composition of the present invention is applied to a sign pen having a valve mechanism.
The sign pen C of this embodiment is one in which the erasable ink composition 30 of the present invention is filled in an ink tank portion 31 that is a shaft body that directly stores the erasable ink composition 30 without occluding the filling.
The sign pen C is configured such that ink is supplied to a pen tip 33 made of a fiber core through a valve mechanism 32 in the ink tank 31. 3, 34 is a holder member, 35 is interposed between the valve mechanism portion 32 and the holder member 34, is a holding member for holding the rear portion of the pen tip 33, 36 is a cap, and 37 is a stirring ball. It is. In the present embodiment, ink is supplied to the pen tip without using a relay core. However, a relay core is provided, and is composed of a fiber core from the ink tank unit 31 through the valve mechanism 32 and the relay core. A configuration may be adopted in which ink is supplied to the pen tip 33.

FIG. 4 shows an embodiment of a sign pen that is filled with the erasable ink composition of the present invention and includes an erasing tool for erasing the writing line at the rear end.
The sign pen D of this embodiment is one in which the erasable ink composition 40 of the present invention is filled in an ink tank portion 41 which is a shaft body that directly stores without occluding the filling.
The sign pen D is configured such that the ink 40 is supplied to a pen tip 43 made of a fiber core via a valve mechanism 42 in the ink tank portion 41. In FIG. 4, 44 is a holder member, 45 is a rear member fixed to the rear portion of the ink tank portion 41, 46 is an inner cap that is movable by a spring 47, and when this is done, the cap 48 is added. It is possible to prevent the valve 42 from being opened due to pressure. Reference numeral 49 is an erasing tool having a hardness of 70 ° or more and less than 100 ° (90 ° in this embodiment) fitted in a concave shape at one end of the cap 48.

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

[Examples 1-3 and Comparative Examples 1-3]
Example 1
The following blending components were produced by the following method to obtain an erasable ink composition.
Pigment: 8% by weight of aqueous dispersion of pink resin particles
[SW-17 (manufactured by Sinloihi), average particle size 1 μm, solid content 42%]
Resin emulsion: 60% by weight of aqueous dispersion of acrylonitrile-butadiene copolymer
[Nipol LX517A (manufactured by Nippon Zeon), solid content 40%, surface tension 42 dyne / cm]
Thickener: Crystalline cellulose [Asahi Kasei Co., Ltd.] 0.5% by weight
[RC-591, homomixer, 10,000 rpm, 10 minutes]
18% by weight of urea
Water (purified water) 13.5% by weight
The above ingredients were sequentially added while stirring in a tank, mixed and stirred until uniform, and then filtered through a 1 μm bag filter to produce an ink.

(Example 2)
The following blending components were produced by the following method to obtain an erasable ink composition.
Pigment: 8% by weight of aqueous dispersion of pink resin particles
[SW-17 (manufactured by Sinloihi), average particle size 1 μm, solid content 42%]
Resin emulsion: 48% by weight of aqueous dispersion of acrylonitrile-butadiene copolymer
[Nipol LX517A (manufactured by Nippon Zeon), solid content 40%, surface tension 42 dyne / cm]
Resin emulsion: aqueous dispersion of acrylonitrile-butadiene copolymer 12.6% by weight
[Nipol 1571CL (manufactured by Nippon Zeon), solid content 38%, surface tension 29 dyne / cm]
Thickener: Crystalline cellulose [Asahi Kasei Co., Ltd.] 0.5% by weight
[RC-591, homomixer, 10,000 rpm, 10 minutes]
Urea 10% by weight
Water (purified water) 20.9% by weight
The above ingredients were sequentially added while stirring in a tank, mixed and stirred until uniform, and then filtered through a 1 μm bag filter to produce an ink.

(Example 3)
The following blending components were produced by the following method to obtain an erasable ink composition.
Pigment: 8% by weight of aqueous dispersion of pink resin particles
[SW-17 (manufactured by Sinloihi), average particle size 1 μm, solid content 42%]
Resin emulsion: 48% by weight of aqueous dispersion of acrylonitrile-butadiene copolymer
[Nipol LX517A (manufactured by Nippon Zeon), solid content 40%, surface tension 42 dyne / cm]
Resin emulsion: aqueous dispersion of acrylonitrile-butadiene copolymer 12.6% by weight
[Nipol LX551 (manufactured by Nippon Zeon), solid content 45%, surface tension 31 dyne / cm]
Thickener: Crystalline cellulose [Asahi Kasei Co., Ltd.] 0.5% by weight
[RC-591, homomixer, 10,000 rpm, 10 minutes]
18% by weight of urea
Water (purified water) 12.9% by weight
The above ingredients were sequentially added while stirring in a tank, mixed and stirred until uniform, and then filtered through a 1 μm bag filter to produce an ink.

(Comparative Example 1)
The following blending components were produced by the following method to obtain an erasable ink composition.
Pigment: 8% by weight of aqueous dispersion of pink resin particles
[SW-17 (manufactured by Sinloihi), average particle size 1 μm, solid content 42%]
Resin emulsion: 63% by weight of aqueous dispersion of acrylonitrile-butadiene copolymer
[Nipol 1577 (manufactured by Nippon Zeon), solid content 38%, surface tension 45 dyne / cm]
18% by weight of urea
Water (purified water) 11% by weight
The above ingredients were sequentially added while stirring in a tank, mixed and stirred until uniform, and then filtered through a 1 μm bag filter to produce an ink.

(Comparative Example 2)
The following blending components were produced by the following method to obtain an erasable ink composition.
Blue spherical particles made of acrylic resin 10% by weight
[Epocolor FP 1050 (made by Nippon Shokubai Co., Ltd.)]
40% by weight of aqueous dispersion of acrylonitrile-butadiene copolymer
[Nipol LX540 (manufactured by Zeon Corporation), solid content 45%]
Polyoxyethylene octyl phenyl ether 1% by weight
[OP-10 (Nikko Chemicals)
Antibacterial agent [Proxel CRL (manufactured by ICI)] 0.5% by weight
48.5% by weight of water
The above ingredients were sequentially added while stirring in a tank, mixed and stirred until uniform, and then filtered through a 1 μm bag filter to produce an ink.

(Comparative Example 3)
The following blending components were produced by the following method to obtain an erasable ink composition.
Pigment: 8% by weight of aqueous dispersion of pink resin particles
[SW-17 (manufactured by Sinloihi), average particle size 1 μm, solid content 42%]
Resin emulsion: 63% by weight of aqueous dispersion of acrylonitrile-butadiene copolymer
[Nipol 1577 (manufactured by Nippon Zeon), solid content 38%, surface tension 45 dyne / cm]
Thickener: Crystalline cellulose [Asahi Kasei Co., Ltd.] 0.5% by weight
[RC-591, homomixer, 10,000 rpm, 10 minutes]
Surfactant: NIKKOL DDP-8 [dipolyoxyethylene (8) alkyl ether phosphoric acid (manufactured by Nikko Chemicals) 1% by weight
18% by weight of urea
Water (purified water) 9.5% by weight
The above ingredients were sequentially added while stirring in a tank, mixed and stirred until uniform, and then filtered through a 1 μm bag filter to produce an ink.

About the erasable ink compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 3, the ink surface tension at 25 ° C. was measured with a surface tension meter CBUP-Z (manufactured by Kyowa Interface Chemical Co., Ltd.). Using an ELD viscometer (manufactured by Tokimec), the viscosity at 1 rpm at 25 ° C. was measured.
Further, each erasable ink composition obtained was evaluated for erasability, scratch resistance, line repelling property and stability over time by the following evaluation methods.
These results are shown in Table 1 below.

[Evaluation method of erasability]
5 ml of each erasable ink composition thus obtained was filled in a direct liquid sign pen [Posca (PC-3M, manufactured by Mitsubishi Pencil Co., Ltd.). Write letters, drawing lines, etc. on the paper using each of the obtained pens, leave it for 5 minutes, and then use an eraser with a hardness of 90 ° [mixture of polypropylene resin (PP) and polystyrene elastomer [mixing ratio 1: 3]. Erasing properties such as drawn lines, letters, etc., erased under 100 g load conditions were evaluated according to the following evaluation criteria.
Evaluation criteria:
A: The drawn lines and characters before erasure cannot be identified, and the erasability is very good.
○: Most of the drawn lines and characters before erasure cannot be identified, and the erasability is excellent.
Δ: The drawn lines and characters before erasure remain very thin and can be identified.
×: The drawn lines and characters before erasure remain thin and can be identified.

[Evaluation method of scratch resistance]
Using each pen obtained above, letters, drawn lines, etc. were written on paper, left for 5 minutes, lightly rubbed with a finger, and scratch resistance was evaluated according to the following evaluation criteria.
Evaluation criteria:
◎: Characters etc. are not scattered and can be identified.
○: Characters etc. are slightly scattered, but characters etc. can be identified.
Δ: Most characters cannot be identified, and the characters disappear even with a finger.
×: Characters cannot be identified, and the characters disappear completely.

[Evaluation method of drawn line repellency]
Writing was performed with a pen filled with ink on a white surface of a coated paper [Mitsubishi Paper Co., Ltd., Pearl Coat 901 g], the drawn line was visually judged, and the drawn line repellency was evaluated according to the following evaluation criteria.
Evaluation criteria:
A: A clear handwritten line without repelling the drawn line.
○: There is little repelling of drawn lines (about several pinholes), and the drawn lines can be identified sufficiently.
Δ: Slightly large number of strokes (about 10 to 10 pinholes) or identification of strokes.
X: The repelling of a drawn line is severe and it is difficult to identify characters.

[Evaluation method of stability over time]
Each of the obtained inks was stored in a transparent container (30 ml) with a lid, stored in a thermostatic bath at 50 ° C. and left for 2 weeks, and then the container was gently taken out, and the temporal stability was evaluated according to the following evaluation criteria.
Evaluation criteria:
(Double-circle): A sedimentation separation is not seen but a change is not seen with an initial stage.
○: Sedimentation separation is observed slightly, but almost no change is seen from the initial stage.
Δ: Supernatant was confirmed by sedimentation separation, but bulky sedimentation.
X: The supernatant was completely confirmed by sedimentation separation, and the sediment was completely settled.

As is clear from the results of Table 1 above, the erasable ink compositions obtained in Examples 1 to 3 within the scope of the present invention erase the drawn lines and the like written on paper with an eraser having a hardness of 70 ° or more. It was found that the film was excellent in scratch resistance, line repelling property and stability over time.
In addition, for the erasable ink compositions obtained in Examples 1 to 3, the drawn lines and the like written on the paper were printed with a commercially available eraser (hardness 70 °, uni MARKSHEET, manufactured by Mitsubishi Pencil Co., Ltd.) in the same manner as the above erasability evaluation. I tried to erase it, but it turned out that I couldn't erase it.
On the other hand, the ink composition of Comparative Example 1 that falls outside the scope of the present invention has an acrylonitrile butadiene resin emulsion to be used having a surface tension of 45 dyne / cm and an ink surface tension of 45 dyne / cm. Therefore, it was found that the drawn lines were repelled and the thickener (crystalline cellulose) was not contained, so that the stability over time was poor. Further, since Comparative Example 2 is a conventional eraser erasable ink (Example 2 described in JP-A-5-279614), the scratch resistance was poor and the drawn line was peeled off even when rubbed with a finger. . Further, Comparative Example 3 was a surfactant with a surface tension reduced to 29 dyne / cm, and it was found that it easily penetrates into paper and deteriorates erasability.

It is a secondary sectional view which shows an example of embodiment using the erasable ink composition of this invention for the sign pen. It is a secondary sectional view which shows the other example of embodiment using the erasable ink composition of this invention for the sign pen. It is a secondary sectional view which shows the other example of embodiment using the erasable ink composition of this invention for the sign pen. It is a secondary sectional view which shows the other example of embodiment using the erasable ink composition of this invention for the sign pen.

Explanation of symbols

A Direct Liquid Type Sign Pen 10 Erasable Ink Composition of the Present Invention 11 Ink Tank Part 13 Pen Tip

Claims (5)

At least 0.1 to 0.5% by weight of a pigment and a thickening agent which is crystalline cellulose, and 20 to 45% by weight of a film- forming acrylonitrile butadiene resin emulsion having a surface tension of 28 to 43 dyne / cm , A fiber core characterized in that it can be erased using an erasing tool that contains water, has an ink surface tension of 30 to 45 dyne / cm, and does not contain an abrasive having a hardness of 70 ° to less than 100 ° . An erasable ink composition for a sign pen having a nib . The film-forming acrylonitrile butadiene resin emulsion having a surface tension of 28 to 43 dyne / cm includes a resin emulsion (a) having a surface tension of 28 to 32 dyne / cm and a resin emulsion (b) having a surface tension of 38 to 43 dyne / cm. The erasable ink composition for sign pens having a fiber nib pen tip according to claim 1 , comprising at least two types of The erasable ink composition for a sign pen having a fiber core pen point according to claim 1 or 2, wherein the ink has a viscosity of 80 mPa · s or less. A sign pen having a nib with a fiber core, which is filled with the erasable ink composition according to any one of claims 1 to 3 . A pen with a nib of fiber core according to claim 4, having a nib of fiber core, characterized in that the erasing device containing no hardness 70 ° or more to 100 ° less abrasive formed by including Sign pen.

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