JPH02124985A - Board marker ink composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which has excellent erasability and long-term stability and hardly causes drying up of the core of a pen by dispersing a coloring agent, a specified binder, a release agent containing a silicone surface active agent, and a water-insoluble inorganic powder in water. CONSTITUTION:An ink composition comprising a water dispersion containing, on a solid basis, 0.1-8wt.% coloring agent, 0.1-2wt.% binder comprising a water- soluble synthetic resin or a synthetic acrylic resin emulsion, 1-10wt.% release agent containing a silicone surface active agent, and 0.2-8.0wt.% water-insoluble inorganic powder. As the water-soluble synthetic resin, a polyvinyl alcohol having a degree of polymerization of 1,000 or lower is preferably used in particular. As the silicone surface active agent, a copolymer wherein the hydrophobic part comprises a silicone component and the hydrophilic part comprises an ether component is suitably used; in particular, a graft copolymer wherein a polyether side chain is bound to a straight chain consisting of dimethylpolysiloxane is most suitable.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to whiteboards, electronic blackboards, etc.
A board marker that allows you to write on a smooth ink-permeable writing surface made of wax, metal, glass, plastic, plastic laminated paper, etc., and then erase the handwriting by gently wiping it with a regular blackboard eraser or cloth material. [Prior art] In recent years, in writing instruments with general penetrating pen cores such as marking pens and felt-tip pens used to write on paper, oil-based ink compositions have become problematic due to the harmfulness and flammability of organic solvents Water-based inks are increasingly being used instead of inks. Such water-based 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. Ketone-based ink,
Oil-based inks using highly volatile organic solvents such as ester-based and alcohol-based solvents are still in use, and water-based inks have not yet been put into practical use.

The following reasons can be considered for this.

First of all, on whiteboards and electronic blackboards, handwriting is erased many times and the same writing surface is used repeatedly. It must have the unique performance of being able to be rubbed and erased without leaving any traces, that is, unlike ordinary writing instrument inks such as Marking Ben, it has poor adhesion to the writing surface and is easy to peel off.1. Although water-based inks provide good releasability, they have the disadvantage that, especially under high humidity, handwriting tends to become wet and erasability deteriorates.

Second, water-based inks using water media are inevitably inferior in drying properties to oil-based inks using volatile organic solvents, and this drying property is a major problem in board markers. In other words, with the above-mentioned general writing instruments, even water-based ink is used to write on absorbent materials such as paper, so drying is accelerated by absorption and diffusion, so the drying speed of handwriting is not much different from that of oil-based ink, but with board markers, non-absorbent Since the handwriting is written on a smooth surface, the drying problems of water-based inks are directly reflected in the drying speed of the handwriting.

Furthermore, since the above-mentioned writing surface is very smooth, water-based ink is repelled by the large surface tension of water, making it difficult to obtain beautiful lines, which is another factor that prevents its practical use.

Therefore, current board markers that use oil-based ink are commonly used for commercial purposes such as offices and factories, but are not suitable for use in educational settings or homes due to the odor, toxicity, and flammability characteristic of organic solvents. Moreover, because it is highly volatile, if you forget to tighten the cap, the pen core dries up quickly and cannot be reused.

Therefore, one of the inventors first developed a practical water-based board marker ink that could replace oil-based ink, using water as a dispersion medium, a coloring agent, and polyvinyl alcohol with a degree of polymerization of 1.000 or less. A composition containing a binder made of a water-soluble synthetic resin and a release agent containing a silicone surfactant in a predetermined mixing ratio (Japanese Patent Application No. 166512/1982)
Furthermore, in addition to the above-mentioned basic composition, it has been proposed to contain a specific amount of water-insoluble inorganic fine powder (Japanese Patent Application No. 1FF759/1983).

[Problem to be solved by the invention]

The water-based ink composition for board markers proposed above has excellent erasability, especially under high humidity, and has good stability over time and is resistant to dry amplicon of the pen core. It is equipped with

However, even with this water-based ink, the drying speed of handwriting is 40 to 5 on average under normal conditions (20°C, 60% RH).
It dries in about 0 seconds, which can be said to be fairly quick-drying for a water-based ink, but if you try to erase it immediately after writing, the undried paint film will adhere to the entire scratched surface of the eraser in the form of fine powder, causing damage to the writing board surface. 1. There is a problem that it gets dirty. Improving this initial erasability has been an issue in replacing oil-based inks.

[Means to solve the problem]

In the process of conducting intensive studies with the aim of improving the above-mentioned initial erasability of water-based board marker inks, the inventors took the general idea of speeding up the drying speed of handwriting from water-based inks and took the idea 180 degrees. I realized that I could obtain good erasability even when the handwriting is not dry. In other words, the initial erasability is determined as long as the handwriting can be erased cleanly when rubbed with an eraser or the like immediately after writing, regardless of whether the handwriting is dry or not.

Based on the above new idea, the inventors
As a result of careful experimental research to determine the ink composition that can erase undried handwriting without leaving traces or stains, we determined that the amount of the binder component in particular was lower than that of the composition proposed above. It was found that ideal initial erasability can be obtained depending on the composition.

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.
・0% by weight of a coloring agent, 0.1-2% of a binder made of a water-soluble synthetic resin or an acrylic synthetic resin emulsion, 1-1% of a release agent containing a silicone surfactant, and a non-water-soluble The composition contains 0.2 to 8% by weight of organic inorganic powder.

In this invention, the water-soluble synthetic resin has a polymerization degree of i
, ooo or less [Detailed structure and operation of the invention] A binder made of a water-soluble synthetic resin or an acrylic synthetic resin emulsion in the ink composition of the present invention is the same as the binder in ordinary writing instrument inks and paints.
It is used not for the purpose of forming an ink film or adhering it to a writing surface, but solely for improving the erasability of ink.

In other words, in the formulation of the present invention, when the ink is written on a writing surface such as a whiteboard, the above-mentioned binder hardly contributes to adhesion to the writing surface, and does not interfere with the colored side of the ink or the inorganic fine powder. It has the effect of coagulating fine particles such as the like to form coarse particles, and also makes the handwriting coating film not very hard and has appropriate flexibility. Therefore, with water-based ink using this, the ink film tends to peel off from the writing surface when the handwriting is erased by wiping after writing on the writing surface, and as a result of the action of this binder, the viscosity of the ink and imparts dispersion stability.

What is particularly important is that the amount of this binder in the composition is set to a very small range of 0.1 to 2% by weight on a solid basis, and this is the first time that other ingredients can be mixed. When the above-mentioned quantitative relationship is met, good initial erasability is obtained, and it becomes possible to cleanly and easily erase handwriting that has just been written and is still wet, without leaving traces or stains. In other words, if the amount exceeds 2% by weight, the erasability of handwriting in a dry state is good, but in an undried state, when wiped with a blackboard eraser or cloth, the colored fine powder of the broken paint film becomes a binder. Due to the adhesive strength of
If the amount is less than (1), the above-mentioned mutual caking and coarsening effect between the fine particles will be insufficient, and the erasability in both dry and undried states will deteriorate.The optimal range of this usage amount is as follows:
O5 ~ 2 double view% weight.

Various water-soluble synthetic resins can be used as the binder, including polyvinyl alcohol, cellulose-based water-soluble resins such as hydroxyethyl cellulose, water-soluble acrylic resins, and water-soluble melamine resins. Polyvinyl alcohol with a degree of 1.000 or less is recommended.

The above-mentioned polyvinyl alcohol has low viscosity and low adhesive strength (and low surface tension) as an aqueous solution, so by using it, it is possible to improve the flowability of the ink to the pen core made of fibers of board markers and improve the writing performance. In addition, there is an advantage that the hygroscopicity of the formed film is relatively low, making it difficult for handwriting to become sticky after drying.

In addition, as this polyvinyl alcohol, a partially saponified type (approximately 86 to 89 mo1%) is particularly recommended,
Also, the viscosity (20°C) of a 4% by weight aqueous solution is 3 to 10 cp!
! It is preferable that the

Suitable commercially available products include, for example, Gohsenol GL-03 and Gohsenol GL-05 manufactured by Nippon Gosei Chemical Co., Ltd., Poval PA-10° and Gohsenol PA-05 manufactured by Shin-Etsu Chemical Co., Ltd., and Poval PVA-manufactured by Kuraray Co., Ltd. 203, PVA-204,
Examples include the same PVA-205.

In addition, other commercially available water-soluble resins include cellulose-based water-soluble resins such as Seven Rocise manufactured by Union Carbide Company and Etcel manufactured by Dow Chemical Company, etc., and water-soluble acrylic resins such as Fluoron 557M manufactured by Eclipse Arrow Chemical Co., Ltd. Preferred water-soluble melamine resins include Sumimaru M50W manufactured by Sumitomo Chemical Co., Ltd., and the like.

On the other hand, acrylic synthetic resin emulsions are emulsions of acrylic homopolymers or copolymers containing acrylic acid, methacrylic acid, and alkyl esters thereof as monomer components, as well as emulsions of acrylic homopolymers or copolymers containing these acrylic monomers, styrene, and acetic acid. It includes emulsions of vinyl and copolymers with other monomer components such as vinyl monomers such as vinylidene chloride.

Suitable commercial products of these acrylic synthetic resin emulsions include, for example, an acrylic homopolymer such as Movinyl 727 manufactured by Hoechst Synthetic Co., Ltd., and an acrylic-styrene copolymer such as Acronal 295 manufactured by Mitsubishi Yuka Co., Ltd.
DM, Movinyl DM-772 and Movinyl DM-60 manufactured by Hoechst Synthesis Co., Ltd., and E-155 manufactured by Rohm, & Haus Co., Ltd. for acrylic-vinylidene chloride copolymers.
2, etc. are listed as preferred.

The release agent used in this invention contains a silicone surfactant as described above, and the surfactant penetrates between particles of the colorant and inorganic fine powder and helps form a film of written ink. In addition to exhibiting the effect of making the peeling of the film extremely easy and reliable during erasing, it also exhibits a superior surfactant effect compared to ordinary hydrocarbon-based surfactants. While improving the adhesion of ink to the writing surface, it also has an antistatic effect.

Various types of silicone surfactants can be used as the above silicone surfactant, but a copolymer in which the hydrophobic part is made of a silicone component and the hydrophilic part is made of a polyether component is preferred, and in particular, a copolymer made of dimethylpolysiloxane is preferred. A graft copolymer in which a polyether is bonded as a side chain to a linear chain is most suitable.

Such a copolymer has the following general formula; (wherein, R
1 is an alkylene group, R2 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 them is 1 or more) Furthermore, among the copolymers of the above formula, especially those with an average molecular weight of 1
．． 000 to about 12,000, degree of polymerization (number of Si atoms) 2
It is preferable that the silicone component/polyether component weight ratio is about 70/30 to 40/60, and the viscosity (at 25 DEG C.) is about 40 to 600 cs.

Suitable commercial products of such copolymers include, for example, L-7600, L-7604, and L-7600 manufactured by Nippon Unicar Co., Ltd.
-7607, TSF-4440 manufactured by Toshiba Silicone Corporation,
YSA-6403, KF-35 manufactured by Shin-Etsu Silicone Co., Ltd.
1, KF-353, KF-354, KF-355, etc.

In addition, in this invention, although the above-mentioned silicone surfactant may be used alone as a release agent, it is also possible to use a release agent component made of other non-volatile substances in combination. Recommended stripping agent components include polyhydric alcohols and their derivatives, ether-type hydrocarbon surfactants containing polyoxyethylene groups as hydrophilic groups, dibasic acid ester-type hydrocarbon surfactants, and dimethylpolysiloxane. Ru.

The above-mentioned polyhydric alcohols and their derivatives intervene as a lubricating film at the interface between the coarse particles in the written ink and the writing surface, thereby weakening the adhesion at the interface and causing the ink film to deteriorate during erasing. Easy to peel off by sliding it from the writing surface (
However, in addition to acting as a release agent, the formulation of the present invention has been found to have the effect of improving the stability of the ink over time.

Preferred specific examples of the polyhydric alcohol and its derivatives include ethylene glycol, diethylene glycol,
Triethylene glycol, hexylene glycol, polyethylene glycol phenyl ether, average molecular weight 60
Examples include water-soluble polyhydric alcohols such as polyethylene glycol having an average molecular weight of 0 or less, polypropylene glycol having an average molecular weight of 400 or less, and glycerin, and derivatives thereof.

The above-mentioned ether type hydrocarbon surfactant and dibasic acid ester type hydrocarbon surfactant are similar to the above-mentioned polyhydric alcohol and its derivatives, and are present at the interface between the coarse particles and the writing surface. It has the effect of weakening the adhesion at the interface, making the ink film slip from the writing surface and making it easier to peel off during erasing, and also functions as a plasticizer for the binder, improving erasability over time.

Suitable commercial products of this ether-type hydrocarbon surfactant include Nonal 106 and Nonal 2 manufactured by Toho Chemical Co., Ltd.
02, Nonal 204, Nonal 205, Nonal 310, Becnol L6, Becnol 15-8, etc. Suitable commercially available dibasic acid ester type hydrocarbon surfactants include Hitenol 335, Hitenol NE-05, and Blysurf A manufactured by Daiichi Pharmaceutical Co., Ltd.
208S, LM-600 and R3-410 manufactured by General, Aniline, And, Film Co., Ltd.Also, dimethylpolysiloxane is used in the form of an emulsion, and is spread on the marking surface to form a silicone molecular film. That to
Due to its aqueous nature, it has the effect of increasing the contact angle of the coarse particles with the marking surface, thereby making it easier to peel off, but in addition to acting as a release agent,
In the formulation of this invention, the effect of improving the stability of the ink over time has been recognized as in the case of the above-mentioned water-soluble polyhydric alcohol.

Such a dimethylpolysiloxane emulsion preferably has an active ingredient concentration of about 27 to 38% by weight, and a base oil with a viscosity (at 25°C) of 1.0%.
One that is below OQcst is recommended. Commercially available products include LE-45, LE-48 manufactured by Nippon Unicar Co., Ltd.
LE-450, LE-460, KM-722, KM-740, KM-742 manufactured by Shin-Etsu Chemical Co., Ltd.
Same KM-780. Same KM-786. KM-787, TSM-630 and TSM-631 manufactured by Toshiba Silicone Co., Ltd.
, TSM-632, etc.

When a silicone surfactant and the other release agent components mentioned above are used together as a release agent, the ratio of the former to the latter by weight is preferably in the range of about i:o, s to 5; If the amount is too small, effects such as stability over time will be insufficient, and if it is too large, handwriting tends to become sticky.

In addition, the amount of release agent used is within the range of 1 to 10% by weight of the total amount of ink; if it is less than this range, the erasability will be poor, and if it is too much, the viscosity of the ink will increase and writing properties will deteriorate. At the same time, there is a problem that the stability over time also decreases. In addition, the optimal usage amount from the viewpoint of prayer period erasability is 4.0
It is in the range of ~7.0% by weight.

Coloring agents include various water-soluble dyes such as triallylmethane dyes and azo dyes, various organic pigments such as insoluble azo pigments, phthalocyanine pigments, and threne pigments, various inorganic pigments such as carbon black and titanium oxide, Any of these water-dispersed pigments, which are obtained by kneading and grinding pigments in an aqueous medium containing a dispersant, can be used, but water-soluble dyes and water-dispersed pigments are particularly preferred from the viewpoint of preventing color separation. The blending amount of such a coloring agent is 0.1 to 8% by weight, particularly preferably 0.2 to 8% by weight based on the total amount of the ink composition in terms of solid matter.
It should be in the range of 5% by weight; if it is more than 8% by weight, there is a problem that the ink flow (writability) deteriorates due to increased viscosity and solid content, and if it is less than 0.1% by weight, the coloring is insufficient. becomes.

By blending the water-insoluble inorganic powder with a binder made of the above-mentioned water-soluble synthetic resin or synthetic resin emulsion, a release agent containing a silicone surfactant, and a coloring agent, it imparts reliable initial erasability, and It also has the effect of significantly improving erasability under high humidity.

The mechanism that causes this effect is not clear, but water-insoluble inorganic powder contributes to the formation of the ink film through its filler effect, and it also exists as non-adhesive particles in the paint film. Because of this, when erasing, the paint film is likely to be destroyed by the abrasion force from the blackboard eraser or cloth, and the destroyed paint film becomes particles with this as a nucleus, making it easy to peel off from the writing surface. On the other hand, under high humidity conditions, it is thought to have the effect of preventing the paint film from re-absorbing moisture.

In addition, the addition of the powder also provides the secondary effect of preventing ink from dripping from the application site when using the board marker.

As such water-insoluble inorganic powder, in general board marker mm ink in which an impregnating material made of long fibers such as polyethylene or polyester is loaded in the application container, B
A fine powder having a specific surface of 50 to b and a diameter of about 10 to 40 mm by ET method is suitable.

There are various types of oxide powders as the above-mentioned fine powder, but powders mainly made of ultrafine silicon dioxide produced by a vapor phase method are particularly preferred, and among these, powders containing hydrophobic groups such as methyl groups on the particle surface are particularly preferable. A fine powder consisting of bonded hydrophobic silica alone, and a small amount of about 1 to 20% by weight of hydrophobic silica and/or ultrafine aluminum dioxide produced by a gas phase method are mixed with ordinary wood-loving silica. Mixed oxide fine powder is recommended. In addition, commercial products of fine powder consisting of the above-mentioned hydrophobic silica alone include Aerosil R-972, Aerosil R-974, and Aerosil RX-200 manufactured by Nippon Aerosil Co., Ltd., and Silica D-10 and Aerosil D- manufactured by Degussa Japan Co., Ltd. 17, HDK-Hl 5 and HDK-H20 manufactured by Wacker Chemicals East Asia Co., Ltd., and the like. In addition, as the above-mentioned mixed oxide fine powder, Aerosil MO manufactured by Nippon Aerosil Co., Ltd.
Examples include X-80 (Sin, containing 1% by weight of AlzOi), MOX-170 (same as above), and C0K-84 (Si0. containing 20% by weight of AlzOi).

In addition to the fine oxide powder mentioned above, ink for valve action type board markers also contains various oxide powders with relatively large particle sizes, and ordinary paint fillers such as precipitated barium sulfate powder and talc powder. Water-insoluble inorganic powders similar to those described above can also be used.

The amount of water-insoluble inorganic powder used is 0.2 of the total amount of ink.
If the amount is less than this range, the erasability will be poor, and if it is too much, the viscosity of the ink will increase and the writing property will be deteriorated. 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-mentioned components using water as a dispersion medium, and in addition to these components, various additives such as other surfactants, preservatives, and drying accelerators may be added as necessary. can be appropriately blended.

For example, by blending a fluorine-based surfactant in an amount of about 0.1 to 1% by weight based on the total amount of the ink composition, the surface tension of the ink is reduced, eliminating uneven dispersion when handwriting dries, and creating an image. This has the advantage that lines can be prevented from becoming so-called tangerine skin. Further, examples of the drying accelerator include lower alcohols such as methanol, ethanol, and isopropyl alcohol.

The ink composition for board markers according to the present invention is suitable for writing on whiteboards, electronic blackboards, and other ink-permeable smooth writing surfaces such as wax, metal, glass, plastic, and plastic laminated paper. That's fine.

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

〔Example〕

Hereinafter, this invention will be specifically explained based on examples.

In addition, parts and % below refer to parts by weight and %, respectively.
Means weight %.

Example 1 Polyvinyl alcohol (Poval PA-05, degree of polymerization 5
00-6002 Partially saponified 4% aqueous solution viscosity 580±
1. Qcps.

)...1.5 parts dimethylsiloxane-polyether copolymer (L-7600
, supra) ...2.5 parts hydrophobic silica fine powder (
Aerosil R-972, supra)
...3.5 parts preservative (KM-1 manufactured by Hoechst Synthetic Co., Ltd.
01A)...0.2 parts water ・ ・ ・ 50
．． 0 parts After thoroughly dispersing and mixing the above composition in a ball mill, a water-dispersed pigment (Laftimine Color Scarlet FL-G manufactured by Dainichiseika Chemical Co., Ltd., solid content 20-25%) is added to the dispersion.
...7.4 parts 35% concentration dimethylpolysiloxane emulsion (LE-45, supra) ...6.
5 parts water ・ ・ ・ 3
Add 0.0 part and thoroughly disperse and mix with a homomixer,
Coarse particles were removed by filtration to obtain red ink for board markers.

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

Example 3 1.2 parts of acrylic-styrene copolymer emulsion (Movinyl DM-60) was used as a binder, 3.8 parts of HDK-H2S (mentioned above) was used as a hydrophobic silica fine powder, and dimethylpolymer A red ink for a board marker was obtained in the same manner as in Example 1 except that the amount of siloxane emulsion (LE-45) was changed to 7.0 parts.

Example 4 Polyvinyl alcohol (Gohsenol GL-031 polymerization degree 300-400. Partially saponified type, viscosity of 4% aqueous solution 3.5 ± 0.5 cps, above)
...1.8 parts dimethylsiloxane-polyether copolymer (same as Example 1) ...2.0 parts hydrophobic silica fine powder (same as Example 1) ...3.5 parts fluorine-based Surfactant (Surflon S-14 manufactured by Asahi Glass Co., Ltd.
1) ...0.6 part preservative (same as Example 1) ...0.2 part water
・ ・ ・ SO, O part After thoroughly dispersing and mixing the above composition in a ball mill, a water-dispersed pigment (Rafuchimin Color Blasoc FL-1) was added to this dispersion.
．． Solid content 30-40%, above)...6.0 parts Polypropylene glycol (Mitsui Polyol #400 manufactured by Mitsui Toatsu Co., Ltd. Average molecular weight 400)...2.0 parts Water ・ ・ ・ 30
．． 0 parts were added and sufficiently dispersed and mixed using a homomixer, and coarse particles were removed by filtration to obtain a black ink for board markers.

Example 5 Acrylic-styrenic copolymer (same as Example 3)
...1.0 part dimethylsiloxane-polyether copolymer (same as Example 1)
...2.5 parts Silica-alumina mixed oxide fine powder (Aerosil C0K-84, mentioned above) ...3.
0 parts preservative (same as Example 1) 0.2 parts water ・ ・ 50.0
After thoroughly dispersing and mixing the above composition in a ball mill,
In this dispersion, an azo dye (Red No. manufactured by Mihara Kako Co., Ltd.) was added.

1, Cl-No. 16255) ...0.5 part 35
% concentration of dimethylpolysiloxane emulsion (same as Example 1)...7.0 parts water
・ ・ ・35.0 parts were added and sufficiently dispersed and mixed using a homomixer, and coarse particles were removed by filtration to obtain a red ink for board markers.

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

Comparative Example 3 Dimethylsiloxane-polyether copolymer (L-76
Same as Example 1 except that the amount of 00) used was 6.0 parts, the amount of dimethylpolysiloxane emulsion (LE-45) was 20.0 parts, and the amount of additional water was 20.0 parts. A red ink for board markers was obtained.

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

An appropriate amount of the inks of the above Examples and Comparative Examples were filled into a tube feeder equipped with a polyester fiber pen core at the tip and filled with polyethylene long fibers as an ink absorber inside to make a board marker. We used the ink pen to write on the surface of an ink-permeable writing board, and examined the erasability and stickiness of the handwriting under various conditions. The stability of each ink over time was also tested. These results are shown in the table below. The types of writing boards, test methods and evaluations for each item are as follows.

(Writing board) A... Aluminum hauro whiteboard (manufactured by Lion) B... Polyethylene terephthalate laminate electronic blackboard (Board Fax, manufactured by Plus) (Erasability under normal conditions) 20±3℃, 60 After 5 minutes of writing under the condition of ±5% RH, the normal felt eraser attached to the above writing board.
Erasing pressure 50-100g/cd, erasing speed approximately 60cm
The erase operation was performed on the basis of /second, and the traces of handwriting were observed and evaluated on the following four levels.

O... Completely erased without leaving any traces.

△...Slight traces were observed.

×... Traces were clearly recognized.

(Erasability under high humidity) Five minutes after writing under conditions of 25±3° C. and 90±5% RH, erasing operations and evaluations were performed in the same manner as above.

(Initial erasability) Under conditions of 20 ± 3°C and 60 ± 5% RH, undried handwriting within 10 seconds of writing was erased in the same manner as above, and the degree of contamination of the writing board was observed. Evaluated in stages.

○: Erasing was completed without any contamination by one or two back and forth erasing operations.

Δ: Slight contamination was observed after 1 to 2 reciprocating erasing operations, but the contamination was completely removed after 3 to 4 reciprocating erasing operations.

・Eraser erasing pressure of 500 to 600 g/-4
The contamination could not be removed unless the erasing operation was repeated ~5 times.

〔Effect of the invention〕

According to this invention, it is highly safe, water-based, free of odor and toxicity problems, and has excellent erasability. We can provide an extremely practical ink for board markers that can be erased without leaving any stains on the writing surface by simply wiping it with a blackboard eraser or cloth material. It also has the advantage that even if you forget to tighten it and a long time has passed, you can write again, and that ink does not drip when writing.

In this invention, if a configuration is adopted in which a water-soluble synthetic resin as the binder is mainly composed of polyvinyl alcohol with a degree of polymerization of 1.000 or less, the various types of erasability described above are particularly good. Excellent erasability can be obtained immediately after drying.

Claims (2)

[Claims] (1) Water is used as a dispersion medium, and each solid content is 0.1
-8% by weight of colorant, 0.1-2% by weight of binder consisting of water-soluble synthetic resin or acrylic synthetic resin emulsion
An ink composition for a board marker, comprising 1 to 10% by weight of a release agent containing a silicone surfactant, and 0.2 to 8.0% by weight of a water-insoluble inorganic powder. (2) The ink composition for a board marker according to claim (1), wherein the water-soluble synthetic resin is mainly composed of polyvinyl alcohol having a degree of polymerization of 1,000 or less.