JPH0832845B2 - Ink composition for board marker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is an ink impermeable smooth surface composed of enameled, metal, glass, plastic, plastic laminated paper, etc., typified by whiteboards and electronic blackboards. The present invention relates to an ink composition for a board marker, which can be erased by writing on a normal blackboard eraser, cloth material or the like after writing on the writing surface.

[Conventional technology]

In recent years, in a writing instrument having a general pen pen such as a marking pen and a felt-tip pen to be written on a paper surface,
Water-based inks are often used in place of oil-based inks, which cause problems of toxicity and flammability due to organic solvents. Such an aqueous ink has a basic composition in which a pigment, a water-soluble resin and a dispersant are contained in an aqueous solvent containing a water-soluble organic solvent.

However, as ink for board markers that are writing instruments for whiteboards and electronic blackboards, oil-based inks that use highly volatile organic solvents such as ketone-based, ester-based, alcohol-based are still used, and water-based inks are not yet used. It has not been put to practical use.

 The possible reasons for this are as follows.

First of all, on whiteboards and electronic blackboards, the handwriting is erased many times and the same writing surface is used repeatedly. In addition, it is necessary to have a unique ability to be able to be erased without leaving traces, that is, contrary to ordinary inks for writing instruments such as marking pens, it has poor adhesion to the writing surface and is easy to peel off, but good peelability with water-based ink Is difficult to impart, and particularly under high humidity, the handwriting is moistened and the erasability is easily deteriorated.

Second, the water-based aqueous ink is inferior to the oil-based ink using a volatile organic solvent in the drying property of the ink itself, and this drying property becomes a big problem in the board marker. That is, in the general writing instrument described above, since the ink is written on the absorbent body such as paper, the drying speed of the handwriting is not so different from that of the oil-based ink because the drying is promoted even by the water-based ink by absorption and diffusion. Since the writing is done on a smooth surface, the difficulty of drying the water-based ink is directly reflected in the handwriting drying speed.

Further, since the above-mentioned writing surface is extremely smooth, it is difficult for a water-based ink to be repelled by a large surface tension of water to obtain a beautiful image line, which is also a factor that hinders its practical use.

Therefore, the current board marker using oil-based ink is generally used for business such as offices and factories, but it is not suitable for use at educational sites or at home because of the odor, toxicity, and flammability peculiar to organic solvents. There was a problem, and due to its high volatility, if the cap was not tightened, the pen core would quickly dry up and could not be reused.

Therefore, one of the inventors of the present invention has previously proposed that as a practical aqueous board marker ink that can be replaced with an oil-based ink, water is used as a dispersion medium, and a coloring agent and a polyvinyl alcohol having a polymerization degree of 1,000 or less are mainly used as a water-soluble ink. A composition containing a binder made of a synthetic resin and a release agent containing a silicone-based surfactant in a predetermined compounding ratio (Japanese Patent Application No. 62-166512), and a specific amount of water-insoluble in addition to the above basic composition. A product containing inorganic fine powder (Japanese Patent Application No. 63-13759) is proposed.

[Problems to be solved by the invention]

The aqueous ink composition for a board marker according to the above proposal has excellent erasability, is particularly excellent in erasability under high humidity, has good stability over time, and is unlikely to cause pen core dry-up. Is equipped with.

However, even with this water-based ink, the handwriting drying rate is about 40 to 50 seconds on average under normal conditions (20 ° C, 60% RH), and it can be said that the water-based ink is considerably quick-drying.
If you try to erase immediately after writing, there is a problem that the undried coating film becomes fine powder and adheres to the entire scratched surface of the laser to stain the writing plate surface. It was a problem in replacing with.

[Means for solving the problem]

In the process of diligently studying the purpose of improving the above initial erasability in the water-based board marker ink, the present inventors converted the idea from the general idea of increasing the drying speed of handwriting of the water-based ink by 180 degrees. Then, I came to the idea that good erasability could be obtained when the handwriting was undried. That is, the initial erasability is sufficient if the handwriting can be neatly erased when the handwriting is rubbed with an eraser or the like immediately after writing, regardless of whether the handwriting is dry or not.

Then, the present inventors, based on the above new idea, as a result of repeated in-depth experiments and studies to investigate an ink composition capable of erasing the traces of undried handwriting without causing stains, particularly, It has been found that a specific composition in which the binder component is blended in an amount smaller than that of the above-mentioned composition provides an ideal initial erasability.

That is, the ink composition for a board marker of the present invention uses water as a dispersion medium and has a solid content of 0.1 to 8 each.
% By weight of a coloring agent, 0.1% by weight or more and less than 2% by weight of a water-soluble synthetic resin or acrylic synthetic resin emulsion binder, and 1-10% by weight of a silicone surfactant as a release agent. , 0.2 to 8% by weight of water-insoluble inorganic powder.

In the present invention, the water-soluble synthetic resin has a degree of polymerization of
A preferred embodiment is a structure mainly composed of 1,000 or less polyvinyl alcohol.

[Detailed configuration and operation of the invention]

The binder comprising the water-soluble synthetic resin or acrylic synthetic resin emulsion in the ink composition of the present invention is
Unlike ordinary writing inks and binders in paints, it is not intended to form an ink film or adhere to the writing surface,
It is used exclusively for improving the erasability of ink.

That is, the above binder, in the formulation of the present invention, when writing the ink on the writing surface such as whiteboard,
It hardly contributes to the adhesion to the writing surface, acts as a coarse particle by binding fine particles such as colorants and inorganic fine powder in ink to each other, and the handwriting coating is not too hard and has moderate flexibility. Shall have. Therefore, in the water-based ink using this, when the handwriting is wiped and erased after writing on the writing surface, the ink film is easily peeled off from the writing surface. Further, the action of this binder naturally imparts viscosity and dispersion stability of the ink.

And, a particularly important point is that the content of the binder in the composition is set to a very small range of 0.1% by weight or more and less than 2% by weight in terms of solid matter, and for this reason, other binders are not included. Good initial erasability is obtained when the ingredients are in the above-mentioned quantitative relationship, and it is possible to erase the undried handwriting immediately after writing neatly and easily without producing traces or stains. Become. That is, when the blending amount is 2% by weight or more, the erasability of the handwriting in the dry state is good, but in the undried state, the coloring fine powder of the coating film which is destroyed by wiping with a blackboard eraser or a cloth is the binder. Adhesion causes the entire surface to be abraded and stains. On the other hand, if the blending amount is less than 0.1% by weight, the above-mentioned effect of coarsening of the mutual binding of fine particles becomes insufficient and the erasability in both the dry state and the undried state becomes poor. The optimum range of the amount used is 0.5% by weight or more and less than 2% by weight.

As the water-soluble synthetic resin of the binder, various materials such as polyvinyl alcohol, fibrin-based water-soluble resin such as hydroxyethyl cellulose, water-soluble acrylic resin, water-soluble melamine resin and the like can be used. Polyvinyl alcohol with a degree of 1,000 or less is recommended.

The above polyvinyl alcohol has a low viscosity as an aqueous solution, has a small adhesive force, and has a low surface tension. Therefore, by using the polyvinyl alcohol, the ink flowability and writability with respect to a penetrable pen core made of fiber such as a board marker can be improved. In addition, there is an advantage that the hygroscopicity of the formed film is relatively small, and the handwriting after drying hardly sticks.

As the polyvinyl alcohol, a partially saponified type (about 86 to 89 mol%) is particularly recommended, and a 4% by weight aqueous solution having a viscosity (20 ° C.) of about 3 to 10 cps is preferable. Examples of suitable commercial products include, for example, Goshenol GL-03 and GL-05 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Poval PA-10 and PA-05 manufactured by Shin-Etsu Chemical Co., Ltd., and Poval PVA- manufactured by Kuraray Co., Ltd. 203, the same PVA-204, the same PVA-205 and the like.

Further, as commercially available products of other water-soluble resins, for the fibrin-based water-soluble resin, Union Carbide's Cellosize, Dow Chemical's Etocel, etc., and for the water-soluble acrylic resin, Nisshin Arrow Chemical's Floron 557M, etc. As the water-soluble melamine resin, Sumimar M50W manufactured by Sumitomo Chemical Co., Ltd. and the like are preferable.

On the other hand, acrylic synthetic resin emulsions include emulsions of acrylic homopolymers or copolymers containing acrylic acid, methacrylic acid, and their alkyl esters as monomer components, as well as acrylic monomers, styrene, and acetic acid. It includes an emulsion of a copolymer with other monomer components such as vinyl-based monomers such as vinyl and vinylidene chloride.

And as a suitable commercially available product of these acrylic synthetic resin emulsions, for example, Movinyl 727 manufactured by Hoechst Synthesis Co., Ltd. for an acrylic homopolymer, and Acronal 295D manufactured by Mitsubishi Petrochemical Co. for an acrylic-styrene copolymer.
M, Movinyl DM-772, Movinyl DM-60, etc. manufactured by Hoechst Synthetic Co., Ltd., is an acrylic-vinylidene chloride copolymer Rohm. and. Suitable examples thereof include E-1552 manufactured by House Co. and the like.

The release agent used in the present invention contains the silicone-based surfactant as described above, and the surfactant penetrates between the particles of the colorant and the inorganic fine powder to help the film formation of the written ink. In addition to exhibiting an action of making the peeling of the coating film at the time of erasing very easy and sure, and exhibiting a more excellent surface active effect as compared with a normal hydrocarbon-based surfactant, While improving the "glue" on the marking surface of the ink, it also exhibits an antistatic effect.

As the above-mentioned silicone-based surfactant, various ones can be used, but a copolymer in which the hydrophobic part is composed of a silicone component and the hydrophilic part is composed of a polyether component is preferable, and is particularly composed of dimethylpolysiloxane. A graft copolymer in which a polyether is bonded to the linear chain as a side chain is optimal.

As such a copolymer, the following general formula; (In the formula, R ¹ is an alkylene group, R ² is an alkyl group or a hydrogen atom, m and n are integers of 1 or more, a and b are integers of 0 or more, and at least one of both is 1 or more.) , Among the copolymers of the above formula, especially the average molecular weight
1,000 to 12,000, degree of polymerization (number of Si atoms) 20 to 160,
Silicone component / polyether component weight ratio 70 / 30-4
About 0/60 is preferable, and viscosity (25 ℃) is 40
It should be about 600cst.

Suitable commercial products of such copolymers include, for example, L-7600, L-7460, L-7607, and L-7607 manufactured by Nippon Unicar Co.,
Examples include TSF-4440 and YSA-6403 manufactured by Toshiba Silicone, and KF-351, KF-353, KF-354, and KF-355 manufactured by Shin-Etsu Silicone.

Further, in the present invention, the above silicone-based surfactant may be used alone as the release agent, but it may be used in combination with the release agent component made of another non-volatile substance. Examples of such other release agent components include polyhydric alcohols and derivatives thereof, ether type hydrocarbon surfactants containing a polyoxyethylene group as a hydrophilic group, dibasic acid ester type hydrocarbon surfactants, and dimethyl. Polysiloxane is recommended.

The above-mentioned polyhydric alcohol and its derivative intervene as a lubricating film at the interface between the coarse particles and the writing surface in the written ink to weaken the adhesion at the interface and form an ink film at the time of erasing. Although it is slipped from the writing surface to facilitate peeling, in addition to such an action as a releasing agent, the effect of improving the stability of ink over time is recognized in the formulation of the present invention.

Suitable specific examples of the polyhydric alcohol and its derivative include ethylene glycol, diethylene glycol, triethylene glycol, hexylene glycol,
Polyethylene glycol phenyl ether, average molecular weight
Water-soluble polyhydric alcohols such as polyethylene glycol having 600 or less, polypropylene glycol having an average molecular weight of 400 or less, and glycerin and derivatives thereof can be mentioned.

The ether-type hydrocarbon surfactant and the dibasic acid ester-type hydrocarbon surfactant described above are present at the interface between the coarse particles and the writing surface in the same manner as the polyhydric alcohol and its derivative. It has the effect of weakening the adhesion at the interface and making the ink coating slip and peel easily from the writing surface during erasing. It also functions as a plasticizer for the binder and improves erasability over time.

Suitable commercial products of this ether type hydrocarbon surfactant include Tonal Kagaku Co.'s Nonal 106 and Nonal 20.
2, the same nonal 204, the same nonal 205, the same nonal 310, the same beknol L-6, the same beknol L-8 and the like. Suitable dibasic ester type hydrocarbon surfactants include Hitenol 335, Hitenol NE-05, Plysurf A208S and General. Aniline. and. LM-600 and RS-410 manufactured by Film Co. are available.

In addition, dimethylpolysiloxane is used in the form of an emulsion, and spreads on the writing surface to form a molecular film of silicone, and its water repellency has the effect of increasing the contact angle of the coarse particles with respect to the writing surface. Although it facilitates peeling, in addition to the action as such a peeling agent, in the formulation of the present invention, the effect of improving the temporal stability of the ink is recognized as in the case of the above water-soluble polyhydric alcohol. There is.

As such an emulsion of dimethylpolysiloxane, one having an effective ingredient concentration of about 27 to 38% by weight is preferable, and one having a base oil viscosity (25 ° C.) of 1,000 cst or less is recommended. As commercially available products, LE-45, LE-48, LE-450, LE-460 manufactured by Nippon Unicar Co., Ltd., KM-722, KM-740, KM-742, manufactured by Shin-Etsu Chemical Co., Ltd. KM-780, same
KM-786, KM-787, Toshiba Silicone TSM-630, TSM
-631, TSM-632 and the like.

When a silicone-based surfactant is used as a release agent in combination with the other release agent components described above, the weight ratio of the former to the latter is preferably in the range of about 1: 0.5 to 5, and the latter is small. If it is too large, the effects such as stability over time will be insufficient, and conversely, if it is too large, the handwriting will be sticky.

The amount of the release agent used is in the range of 1 to 10% by weight in the total amount of the ink. If the amount is less than this range, the erasability will be poor, and if it is too large, the viscosity of the ink will increase and the writability will deteriorate. However, there is a problem in that the stability over time also decreases. The optimum amount used from the viewpoint of initial erasability is 4.0-
It is in the range of 7.0% by weight.

As the colorant, triallylmethane dyes, various water-soluble dyes such as azo dyes, insoluble azo pigments, phthalocyanine pigments, various organic pigments such as slene pigments, carbon black, various inorganic pigments such as titanium oxide, Although any of water-dispersible pigments obtained by kneading and grinding the pigments in an aqueous medium containing a dispersant can be used, water-soluble dyes and water-dispersible pigments are particularly preferable from the viewpoint of preventing color separation. . The amount of such a colorant compounded is 0.1 to 8% by weight, and particularly preferably 0.2 to 5% by weight based on the total amount of the ink composition in terms of solid matter.
The amount should be in the range of 10% by weight. If the amount is more than 8% by weight, there is a problem that the ink flow (writability) is deteriorated due to an increase in viscosity and an increase in solid content. If the amount is less than 0.1% by weight, coloring is insufficient.

The water-insoluble inorganic powder imparts a reliable initial erasability by blending it with a binder composed of the above-mentioned water-soluble synthetic resin or synthetic resin emulsion, a release agent containing a silicone-based surfactant, and a colorant. It also has the effect of remarkably improving the erasability under high humidity.

The mechanism that causes such an action is not clear, but the water-insoluble inorganic powder contributes to the formation of the ink coating film by the effect of a filler, and itself exists as non-adhesive particles in the coating film. Therefore, during erasing, the blackboard eraser or a cloth tends to damage the coating film due to scratching force, and the broken coating film becomes particles with the core as the core to facilitate peeling from the writing surface. However, it is considered that it exhibits an action of preventing re-absorption of the coating film under high humidity.

In addition, by blending the powder, a secondary effect of preventing dripping from the application destination of the ink when the board marker is used can be obtained.

As such a water-insoluble inorganic powder, in an ink for a general board marker in which an impregnating material made of long fibers such as polyethylene and polyester is loaded in a coating container,
A fine powder having a specific surface by BET method of about 50 to 300 m ² / g and an average primary particle diameter of about 10 to 40 mil μm is suitable.

Although there are various oxide powders in the fine powder, powders mainly composed of ultrafine particles of silicon dioxide produced by a vapor phase method are preferable, and among them, a hydrophobic group such as a methyl group is present on the particle surface. Fine powder consisting of bound hydrophobic silica alone, and a mixture of ordinary hydrophilic silica with a small amount of about 1 to 20% by weight of hydrophobic silica and / or ultrafine particulate aluminum dioxide produced by a gas phase method Fine oxide powder is recommended. The commercially available fine powder consisting of the above hydrophobic silica alone is Aerosil R-972, R-974, RX-200 manufactured by Nippon Aerosil Co., Ltd., silica D-10, D- manufactured by Degussa Japan. 17, HDK-H15, HDK-H20 and the like manufactured by Wacker Chemicals East Asia.
As the mixed oxide fine powder, Aerosil MOX-80 (containing 1% by weight of Al ₂ O _{3 in} SiO ₂ ) manufactured by Nippon Aerosil Co., Ltd., MOX-170 (same as above), COK-84 (SiO ₂₎ 20% by weight
Al ₂ O ₃ content) and the like.

In addition, in valve action type inks for board markers, in addition to the above oxide fine powder, various oxide powders having a relatively large particle diameter, fillers for ordinary paints such as precipitated barium sulfate powder and talc powder are used. A water-insoluble inorganic powder similar to the above can also be used.

The amount of water-insoluble inorganic powder used is 0.2% of the total amount of ink.
It is a range that occupies up to 8% by weight, and if it is less than this range, the erasability deteriorates, and conversely, if it is too large, there is a problem that the viscosity of the ink increases and the writability deteriorates. The optimum range of the amount used is about 2.0 to 4.0% by weight.

The ink composition of the present invention contains each of the above components with water as a dispersion medium, and together with these components, various additives such as other surfactants, antiseptics, and drying accelerators, if necessary. Can be appropriately mixed. For example, by blending a fluorine-based surfactant in the range of about 0.1 to 1% by weight based on the total amount of the ink composition, the surface tension of the ink is lowered and the unevenness of dispersion during handwriting drying is eliminated, resulting in an image line. There is an advantage that so-called mandarin orange skin can be prevented. Further, examples of the drying accelerator include lower alcohols such as methanol, ethanol and isopropyl alcohol.

The writing target of the ink composition for a board marker according to the present invention is a white ink board, electronic blackboard, enamel, metal, glass, plastic, plastic laminated paper, and other ink impermeable smooth writing surface. I wish I had it.

Since the ink composition of the present invention has a low volatility, the board marker containing the ink composition can be rewritten up to about 5 hours even if the cap is forgotten to be tightened.

〔Example〕

Hereinafter, the present invention will be specifically described based on Examples. In the following, parts and% mean parts by weight and% by weight, respectively.

Example 1 Polyvinyl alcohol (Poval PA-05, polymerization degree: 500-6
00, partial saponification type, viscosity of 4% aqueous solution 5.0 ± 1.0 cps, above)
... 1.5 parts Dimethyl siloxane-polyether copolymer (L-76
00, supra) 2.5 parts Hydrophobic silica fine powder (Aerosil R-972, supra) 3.
5 parts Preservative (KM-101A manufactured by Hoechst Synthetic Co., Ltd.) 0.2 parts Water 50.0 parts After sufficiently dispersing and mixing the above composition in a ball mill,
In this dispersion, water-dispersible pigment (lactimine color scarlet FL-G manufactured by Dainichiseika Co., Ltd., solid content 20 to 25%) ... 7.4 parts 35% dimethylpolysiloxane emulsion (LE
-45, supra) ... 6.5 parts Water ... 30.0 parts were added and thoroughly mixed with a homomixer, and coarse particles were removed by filtration to obtain a red ink for a board marker.

Example 2 TS as dimethylsiloxane-polyether copolymer
F-4440 (above) and KM-740 (38% concentration, above) as dimethylpolysiloxane emulsion were used in the same amount, respectively, and silica-alumina mixed oxide fine powder (Aerosil) was used instead of hydrophobic silica fine powder. A red ink for a board marker was obtained in the same manner as in Example 1 except that 3.2 parts of MOX-170, supra) was used.

Example 3 1.2 parts of acrylic-styrene copolymer emulsion (Movinyl DM-60) was used as the binder, and 3.8 parts of HDK-H15 (supra) was used as the hydrophobic silica fine powder.
A red ink for a board marker was obtained in the same manner as in Example 1 except that the amount of the dimethylpolysiloxane emulsion (LE-45) was 7.0 parts.

Example 4 Polyvinyl alcohol (Gothenol GL-03, degree of polymerization 30
0 to 400, partial saponification type, viscosity of 4% aqueous solution 3.5 ± 0.5 cps,
Previous) 1.8 parts Dimethyl siloxane-polyether copolymer (same as Example 1) 2.0 parts Hydrophobic silica fine powder (same as Example 1) 3.5 parts Fluorine-based surfactant (Surflon manufactured by Asahi Glass Co., Ltd. S-14
1) ... 0.6 parts Preservative (same as in Example 1) ... 0.2 parts Water ... 50.0 parts After thoroughly dispersing and mixing the above composition in a ball mill,
In this dispersion, a water-dispersible pigment (lactimine color black FL-I,
Solid content 30-40%, above)… 6.0 parts Polypropylene glycol (Mitsui Toatsu Co., Ltd. Mitsui Polyol # 400, average molecular weight 400)… 2.0 parts Water… 30.0 parts are added and thoroughly dispersed and mixed with a homomixer. The coarse particles were removed by filtration to obtain a black ink for board markers.

Example 5 Acrylic-styrene copolymer (same as Example 3) ...
1.0 part Dimethyl siloxane-polyether copolymer (same as in Example 1) 2.5 parts Silica-alumina mixed oxide fine powder (Aerosil COK-
84, supra) 3.0 parts Preservative (same as in Example 1) 0.2 parts Water 50.0 parts After thoroughly dispersing and mixing the above composition in a ball mill,
In this dispersion, azo dye (Red No.1, CI-No.162 manufactured by Mihara Kako Co., Ltd.)
55) 0.5 part Dimethylpolysiloxane emulsion having a concentration of 35% (same as in Example 1) 7.0 parts Water 35.0 parts were added and sufficiently dispersed and mixed with a homomixer, and coarse particles were removed by filtration to remove the board. A red ink for a marker was obtained.

Comparative Example 1 A red ink for a board marker was obtained in the same manner as in Example 1 except that polyvinyl alcohol as a binder was not used.

Comparative Example 2 A red ink for a board marker was obtained in the same manner as in Example 1 except that the blending amount of polyvinyl alcohol (Poval PA-05) was 5.0 parts.

Comparative Example 3 Dimethylsiloxane-polyether copolymer (L-76
00), 6.0 parts, dimethylpolysiloxane emulsion (LE-45), 20.0 parts, additional water: 2 parts
A red ink for a board marker was obtained in the same manner as in Example 1 except that the amount was 0.0 part.

Comparative Example 4 Except that the amount of the hydrophobic silica fine powder used was 10.0 parts,
A red ink for a board marker was obtained in the same manner as in Example 1.

Each of the inks of the above Examples and Comparative Examples was provided with a pen core made of polyester fiber at the tip, and an appropriate amount was filled into a tube feeder loaded with polyethylene filaments, which is an ink absorber, as a board marker. It was used to write on the surface of an ink-impermeable writing plate, and the erasability under various conditions and the stickiness of the handwriting were examined. The stability of each ink over time was also tested. The results are shown in the table below. The type of writing board, the test method for each item, and the evaluation are as follows.

《Writing board》 A… White board made of aluminum enameled (made by Lion) B… Polyethylene terephthalate laminated electronic blackboard (Board fax made by Plus) 《Erase under normal conditions》 20 ± 3 ℃, 60 ± 5% RH 5 minutes after writing below,
An erasing operation was performed by using a normal felt eraser attached to the writing plate with an erasing pressure of 50 to 100 g / cm ² and an erasing speed of about 60 cm / sec as a reference, and the trace of the handwriting was observed and evaluated in the following four stages.

 ○: No traces were left and it was completely erased.

 Δ: A slight trace was recognized.

 X: A trace was clearly recognized.

<< Eraseability under High Humidity >> Five minutes after writing under conditions of 25 ± 3 ° C. and 90 ± 5% RH, erasing operation and evaluation were performed in the same manner as above.

<Initial erasability> Under the conditions of 20 ± 3 ℃ and 60 ± 5% RH, erasing the undried handwriting within 10 seconds after writing in the same manner as above, and observing the degree of contamination of the writing board, the following 3 The grade was evaluated.

◯: It was possible to erase without contamination by erasing operation of 1-2 round trips.

Δ: Slight contamination was found in the erasing operation of 1 to 2 reciprocations, but the contamination was completely removed by the erasing operation of 3 to 4 reciprocations.

× ... Eraser erasing pressure of 500-600g / cm ² 4-
Contamination could not be removed without five erase cycles.

[Effect of the Invention] According to the present invention, highly safe aqueous solution having no odor and toxicity problems, and extremely excellent in erasability, of course, under normal conditions after drying and under high humidity, and immediately after writing, It is possible to provide an extremely practical ink for a board marker that can be erased without leaving stains on the writing surface by simply wiping it lightly with a blackboard eraser or a cloth material even when the handwriting is in a dry state. Also,
The board marker using this ink has an advantage that it can be rewritten even if a user forgets to tighten the cap and a long time has passed, and ink does not drip during writing.

Then, in the present invention, if a constitution using a polyvinyl alcohol having a polymerization degree of 1,000 or less as a main component is adopted as the water-soluble synthetic resin of the binder, the above various erasability is particularly good, and especially immediately after writing. Provides excellent erasability in the undried state.

Claims (2)

[Claims] 1. Water as a dispersion medium, in terms of solid content,
Contains 0.1 to 8% by weight of a colorant, 0.1% by weight or more and less than 2% by weight of a binder composed of a water-soluble synthetic resin or acrylic synthetic resin emulsion, and 1 to 10% by weight of a silicone surfactant. An ink composition for a board marker comprising a release agent and 0.2 to 8% by weight of a water-insoluble inorganic powder. 2. The water-soluble synthetic resin is mainly composed of polyvinyl alcohol having a degree of polymerization of 1,000 or less.
The ink composition for a board marker as described above.