JPH08199105A - Black ink composition for writing board - Google Patents

Abstract

PURPOSE: To prepare a black ink which can be written with a marking pen on a white board and can be wiped out, by adding a specific carbon black, a polymer soluble in a lower alcohol and a releasing agent to a medium mainly comprising a lower alcoholic solvent. CONSTITUTION: This composition is prepared by admixing a carbon black having more than 85% toluene-coloring transmission rate and less than 0.5wt.% ash content, a polymer soluble in lower alcohol and a releasing agent to a medium which mainly comprises a lower alcohol such as methanol, ethanol, n-propanol or isopropanol, additionally, a glycerol solvent and sucrose ester as a whitening preventive and a humectant, and shows reduced change in ink viscosity and particle sizes of carbon black in the ink even under elevated temperature or after a longed term storage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black ink composition for a writing board which can be written on a writing board such as a so-called whiteboard by using a marking pen and can wipe off unnecessary handwriting.

[0002]

2. Description of the Related Art For a writing board that can be written on a writing board or the like with a marking pen, as is commonly known as a whiteboard, and can wipe off (remove) the handwriting when not needed. Regarding marking inks, from the viewpoint of erasability, handwriting performance, safety, etc.,
Pigments have been used as colorants. In particular, in the case of a black pigment ink for a writing board, carbon black is used as a pigment, and this is dispersed in an alcohol solvent using a resin or the like, and at the same time, a release agent and a surfactant are added to improve erasability. I have it. Carbon black is produced by pyrolyzing or incompletely burning raw materials such as natural gas and liquid hydrocarbons (heavy oil, tar, etc.), and the colorant for such inks is classified into channel black or furnace black. What is done is said to be suitable.

The properties required for this kind of writing plate pigment ink are generally erasability (the handwriting can be easily wiped off immediately after writing and after a lapse of time), and the non-drying property (the tip of the pen should be dry). There is no blur of the handwriting) and handwriting performance (the handwriting has sufficient density and vivid color), etc., and many proposals have been made and implemented for improving these performances.

However, in practice, in addition to these, the stability of ink to heat and the stability over time, that is, storage stability are required. When the pen filled with ink or the ink itself is stored for a long period of time, or when one pen is used for a long period of time, or in direct sunlight, or in an automobile etc. that has become hot due to direct sunlight The pen filled with is left to stand and the ink temperature is, for example, 50 ° C.
When the temperature of the ink becomes higher than the above, the viscosity of the ink increases, which may cause blurring of writing, and when the average particle size of the finely dispersed pigment becomes large, clogging occurs inside the pen or the pen tip and causes writing failure. Become. Therefore, there is a demand for a pigment ink in which the viscosity of the ink and the particle size of the pigment in the ink do not significantly change even at high temperatures and when stored for a long time.

However, the conventional pigment ink for writing plates prepared by using carbon black has insufficient stability in a high temperature environment (for example, 50 ° C. or higher), and the viscosity of the ink increases during long-term storage. There is a problem that cannot be solved depending only on the ink composition, such as the aggregation of the pigments contained therein, and the fine dispersion stability thereof differs depending on the type and quality of the carbon black used.

The present invention has been made in view of the above problems existing in the prior art, and an object of the present invention is to obtain an ink even at a high temperature and when it is stored for a long period of time. To provide a black ink composition for a writing plate in which the viscosity and the particle size of carbon black in the ink change little.

[0007]

In order to solve the above problems, the inventors of the present invention use carbon black containing a small amount of inorganic impurities such as inorganic salts and organic impurities such as undecomposed products of raw oil. The present invention has been completed based on the finding that it is extremely effective.

That is, the black ink composition for a writing plate of the present invention is a black ink composition for a writing plate in which at least carbon black, a lower alcohol-soluble polymer and a release agent are contained in the medium. , A lower alcohol-based solvent or a lower alcohol-based solvent, wherein the carbon black has a toluene coloring transmittance of 85% or more and an ash content of 0.5% by weight or less. Toluene color transmission measurement method : dry sample 5.0 ± 0.
Weigh 1 g into 100 ml Erlenmeyer flask specified by JIS R 3503 (Glassware for chemical analysis), and add toluene (JI
Add 50 ml of No. 1 specified in SK 2435, heat it on a suitable heating plate and keep it in a loose boiling state for 20 seconds, and immediately filter it (2 types specified in JIS P 3801 filter paper [for chemical analysis]). Filtered with any one of
Put the filtrate in the absorption cell. The filtrate is measured with a spectrophotometer at a wavelength of 450 nm. The measurement result shows that the transmittance at 450 nm is 100% using toluene that has been filtered by boiling in advance.
The blanks are adjusted so that they are expressed as%.

Carbon black contains some organic impurities such as undecomposed products of oil (liquid hydrocarbon) as a raw material. When the organic impurities such as the oil component are dissolved in an aromatic solvent (for example, benzene, toluene, xylene), the solvent is colored according to the dissolved amount. Therefore, using light of a certain wavelength, the transmittance of the solvent before dissolution is 1
The degree of the amount of organic impurities such as oil contained in the carbon black can be known by measuring the degree of transmittance with respect to the solvent after dissolution when it is set to 00%.

The carbon black used in the present invention has a toluene coloring transmittance of 85% or more, preferably 90% or more.

Inks prepared using carbon black having a toluene color transmission of less than 85% have a large pigment particle size and a large ink viscosity increase when stored at high temperatures or for long periods of time. . Method of measuring ash : Weigh 2.000 ± 0.002 g of dried sample into a porcelain crucible (30 ml B type specified in JIS R 1301 [porcelain crucible for chemical analysis]) and place 750 ± in an electric furnace.
After gradually heating to 25 ° C and ashing at that temperature, the mixture is allowed to cool to room temperature in a desiccator, the weight of the residue is determined, and this is repeated until a constant weight is obtained. Calculated as (weight / weight of dry sample) × 100 (% by weight).

The degree of the amount of inorganic impurities contained in carbon black can be known as ash.

Carbon black having an ash content of 0.5% by weight or less is used in the present invention. Preferably, the ash content is 0.
It is 3% by weight or less.

Inks prepared using carbon black having an ash content of more than 0.5% by weight have a large pigment particle size and a large ink viscosity increase when stored at high temperature or for a long period of time. .

In the present invention, it is possible to select and use a carbon black satisfying the above-mentioned toluene coloring permeability and ash content from commercial products. However, the commercially available carbon black has a toluene colorant permeability and ash content which are not constant even with the same brand.

As the carbon black to be selected, one having a quality generally called coloring carbon black (coloring carbon black), in particular carbon black for inks, of which furnace black is preferable. is there. The pH of carbon black may be alkaline, neutral or acidic, but neutral carbon black or acidic carbon black is preferable. Examples of such carbon black include furnace black manufactured by Mitsubishi Chemical Corporation, oil furnace manufactured by Cabot Corporation, color furnace manufactured by Degussa, and carbon black for color manufactured by Colombian Carbon Japan.

The stability of the ink of the present invention is maintained by the interaction of the ink constituents (pigment, resin, solvent, release agent, surfactant, etc.). In particular, since the carbon black used has a polar group on the surface, a stable system is formed by a delicate electric interaction with other constituent elements.

The stability of the pigment-dispersed ink as in the present invention is maintained by maintaining the pigment in a fine state. Generally, carbon black has good alcohol resistance. Therefore, an ink containing carbon black as a pigment dispersed therein can be a high-concentration black ink that is stable for a long period of time due to a small amount of resin content. In the present invention, it is preferable that the central diameter [d value] of the carbon black dispersed and contained by the dynamic light scattering method is 200 nm or less by using, for example, a horizontal wet disperser or a dissolver. More preferably, it is 100 nm or less. However, it does not become smaller than the primary particle size.

When the carbon black used has a toluene coloring permeability of not less than 85% and an ash content of not more than 0.5% by weight, the viscosity of the ink and the ink content in the ink both at high temperature and after long-term storage are high. It is not clear why carbon black having a small change in particle size of carbon black and out of these ranges deteriorates the stability of the pigment-dispersed ink of the present invention. However,
Inorganic impurities in carbon black cause an electrical effect on the stable system at the initial stage of ink preparation, and residual organic impurities such as undecomposed material oil act as a binder to reaggregate particles. It is believed that this is caused by the instability of the dispersion system.

The black ink composition for a writing board of the present invention preferably contains the above-mentioned carbon black in a dispersed amount of about 1 to 10% by weight based on the total amount of the ink. It is more preferably 2 to 6% by weight. If it is less than 1% by weight, it becomes difficult to exhibit the concentration required as a marker. On the other hand, when the amount is 10% by weight or more, the amount of resin used for stably maintaining the dispersed pigment exceeds an appropriate amount as a marking ink,
There is a greater risk that the ink viscosity will become too high and writing will not be possible.

In the ink composition of the present invention, as a medium, monohydric lower alcohols such as methanol, ethanol, n-propanol, isopropanol and the like are used alone or in combination of two or more, or are mainly used. To use.

If the medium is only a highly volatile alcohol solvent such as methanol, ethanol, n-propanol, isopropanol, etc., the ink dries at the tip of the pen such as a marking pen, which may cause fading during writing. Handwriting often becomes white. Therefore, in the medium, as a whitening inhibitor or a drying inhibitor, an alcohol solvent having 4 or more carbon atoms, an ethylene glycol monoalkyl ether solvent, a glycol solvent (glycol, etc.), a glycerin solvent (glycerin, polyglycerin ester, etc.) ), And it is preferable to add one or more of sucrose esters. Particularly, as a drying inhibitor, JP-A-61-61
It is preferable to add the sucrose ester described in JP-A-84369 or JP-A-61-34080.

The polymer used in the ink composition of the present invention is for imparting a film-forming ability to the ink, and at the same time, for imparting adhesion to the writing surface of the ink and dispersion stability of the pigment, the main solvent being Any one can be used as long as it is soluble in a lower alcohol.

Specific examples of the polymer that can be used include polyvinyl butyral, polyvinyl pyrrolidone, vinyl acetate resin, polyacrylic acid ester, shellac and ethyl cellulose. These can be used alone or in admixture of two or more. . The amount used is preferably about 1 to 20% by weight with respect to the total amount of ink. More preferably, it is about 2 to 10% by weight. In order to reduce the viscosity of the ink, it is preferable to use one having a relatively low degree of polymerization.

A polymer particularly suitable for the present invention is polyvinyl butyral which is a tripolymer consisting of a polyvinyl acetal moiety, a polyvinyl alcohol moiety and a polyvinyl acetate moiety. Since this tripolymer contains a butyral group, a hydroxyl group and an acetyl group in an appropriate ratio, the ink of the present invention can be stabilized for a long period of time by using a small amount. Commercially available products include S-REC BM-S (trade name of polyvinyl butyral) manufactured by Sekisui Chemical Co., Ltd.,
Denka Butyral # 4000-1, # 2000- manufactured by Denki Kagaku Kogyo Co., Ltd.
L (trade name of polyvinyl butyral) and the like can be preferably used. The peeling agent (erasing agent) is used for peeling (erasing) the handwriting from the writing plate when the characters, figures, etc. (handwriting) drawn on the writing plate by the ink composition of the present invention become unnecessary. It is an additive. This release agent allows the polymer and the pigment to dry around after being written, and when the polymer and the pigment are projected as particles, they surround the particles and wipe the written characters. When the release agent is completely compatible with the polymer, it remains as stains during release (wiping), and when it is not compatible at all, the handwriting on the writing plate becomes hard and it becomes difficult to remove it with time. Therefore, those which are appropriately compatible with the polymer to be used are preferable.

The amount of the release agent used is preferably about 50 to 200% by weight based on the total amount of the pigment and the resin (polymer). If it is less than 50% by weight, good peelability may not be obtained, and if it exceeds 200% by weight, a uniform writing film may not be formed when the writing is dried, and the density of the writing may decrease. Get higher

As the stripping agent, a non-volatile or hardly volatile substance which is soluble in the lower alcohol solvent used and is liquid at -5 ° C or higher can be preferably used.

Specific examples thereof include higher fatty acid esters (for example, myristyl caproate, isostearyl caproate, oleyl caproate, isostearyl caprylate, oleyl caprylate, cetyl 2-ethylhexanoate, stearyl 2-ethylhexanoate, 2 Isostearyl ethylhexanoate, cetyl isooctanoate, isooctadecyl caprate, oleyl caprate, isooctyl palmitate, isooctadecyl palmitate, isooctyl isopalmitate, isooctyl stearate,
Isooctadecyl stearate, isopropyl myristate, lauryl oleate, butyl oleate, dioctyl adipate, dioctyl sebacate, dibutyl azelate), glycols (for example, ethylene glycol, diethylene glycol, propylene glycol,
2,5 hexanediol, liquid polyethylene glycol, liquid polypropylene glycol), and higher alkyl ethers of ethylene glycol or diethylene glycol (eg, monooctyl ether, monolauryl ether) and the like. These release agents may be used alone or in admixture of two or more.

The black ink composition for writing boards of the present invention comprises
It is preferable to add a surfactant as a peeling aid. In many cases, the erasability of handwriting is not sufficient with a release agent alone. Therefore, by adding a surfactant,
It is desired that particles containing a polymer and a pigment that are deposited when the solvent volatilizes after writing become dispersed particles of an appropriate size that can be easily peeled off. If the size of the dispersed particles is large, erasing is easy, but the coloring density of the handwriting is low, and if small, the coloring density of the handwriting is high, but erasing becomes difficult. The preferred particle size of the dispersed particles is 1 to 10 μm,
A particularly preferable particle size is about 2 to 4 μm.

The surfactant is soluble in a lower alcohol solvent, and when the handwriting is dried, the particles of the pigment and the polymer can be wrapped with a release agent to form particles of an appropriate size, and a uniform writing film can be easily formed. What you do is better. It does not matter whether it is nonionic, anionic or cationic. The amount of the surfactant used is usually about 1 to 5% by weight based on the total amount of the ink.

Specific examples of the surfactant that can be used include:
Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyethylene glycol fatty acid ester, polyoxypropylated glycerin, glycerin fatty acid ester. As the anionic surfactant, for example, polyoxyethylene alkyl sulfate ester salt, alkyl sulfate ester salt, polyoxyethylene alkyl ether phosphate ester, alkyl phosphate ester salt, alkylnaphthalene sulfonate salt, etc .; cationic surfactant Examples of the surface active agent include alkylamine salts, quaternary ammonium salts and the like.

The method for producing a black ink composition for a writing board of the present invention comprises the steps of dissolving a resin (lower alcohol-soluble polymer) in a lower alcohol solvent to prepare a resin solution; adding carbon black to the obtained resin solution. Then, a step of preparing a premix base; a step of dispersing or finely pulverizing the obtained premix base with a mill (disperser); a releasing agent, a surfactant, a whitening agent, a drying inhibitor, etc. on the obtained mill base. And further adjusting the viscosity of the ink with a lower alcohol solvent.

[0033]

The black ink composition for a writing board of the present invention is
Even during long-term storage, there is little change in viscosity or carbon black particle size, and storage stability is excellent. In addition, clogging at the tip of the pen and blurring during writing are prevented, so that the writability is good and the erasability of handwriting is excellent. Furthermore, the medium is
Since it is mainly composed of a lower alcohol solvent or a lower alcohol solvent, it is suitable for environmental hygiene.

[0034]

Examples Example 1 Polyvinyl butyral [trade name: Denka Butyral # 40
00-1, manufactured by Denki Kagaku Kogyo Co., Ltd.] was dissolved in 82 parts of denatured ethyl alcohol [trade name: Solmix AP-1, manufactured by Nippon Kasei Co., Ltd.] and carbon black [toluene permeability] was added to the polymer solution. A premix base was prepared by adding 10 parts of furnace black for ink having 98% and an ash content of 0.31% by weight and stirring with a dissolver for 2 hours.

A mill base (36.0 cps / 25 ° C.) was obtained by circulating and dispersing this premix base for 20 hours using a horizontal wet disperser filled with zircon beads. Solmix AP-1 12.
By adding 5 parts, 5 parts of isooctyl isopalmitate, 1.5 parts of polyoxypropylated glycerin and 1 part of sucrose ester [trade name: DK Ester F-160, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.] and stirring for 2 hours. , Black ink was obtained.

For the ink immediately after preparation, the center diameter [d value] of carbon black measured by the dynamic light scattering method was measured with a measuring device [LP
A-3000 / 3100 made by Otsuka Electronics Co., Ltd.]
It was 00 nm and the viscosity was 5.70 cps / 25 ° C. as measured by a viscometer [ELD viscometer manufactured by Tokyo Keiki Co., Ltd.].

When this ink was filled in a marking pen for a writing plate and a writing test was carried out, it was possible to write on the writing plate vividly without clogging of the ink at the pen tip and a decrease in the density of the handwriting, and the handwriting after a long time had passed. I was able to wipe it off lightly.

Also, this ink was placed in a constant temperature bath at 50 ° C.
After leaving it for a month, change the viscosity and the particle size of carbon black.
The results are shown in Table 1 when measured and compared with those immediately after preparation.
Change is very small as shown in
It was stable even after storage. Example 2 Polyvinyl butyral [Product name: Denka Butyral # 20
00-L, manufactured by Denki Kagaku Kogyo Co., Ltd.] 12 parts, modified ethyl alcohol
78 [Product name: Solmix AP-1, Nippon Kasei Co., Ltd.]
Dissolved in this polymer solution, carbon black
[Fluent for ink with 94% toluene permeability and 0.28% ash content]
-Blackness] 10 parts were added and the dissolver was used for 2 hours.
A premix base was prepared by stirring.

30 parts of a mill base obtained by dispersing this premix base in the same manner as in Example 1 was further added with 11.5 parts of Solmix AP-1 and 5 parts of cetyl isooctanoate.
Part, dioctyl adipate 1 part, surfactant [Product name:
1.5 parts of Prisurf A212-E, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. and 1 part of decaglyceryl tristearate were added, and the mixture was stirred for 2 hours to obtain a black ink.

When the ink immediately after preparation was measured in the same manner as in Example 1, the center diameter [d value] of carbon black measured by the dynamic light scattering method was 120 nm, and the viscosity was 6.02.
cps / 25 ° C.

When this ink was filled in a marking pen for a writing plate and a writing test was carried out, it was possible to write vividly on the writing plate without clogging of the ink at the pen tip and a decrease in the density of the handwriting. I was able to wipe it off lightly.

This ink was placed in a constant temperature bath at 50 ° C for 2 hours.
After leaving it for a month, change the viscosity and the particle size of carbon black.
The results are shown in Table 1 when measured and compared with those immediately after preparation.
Change is very small as shown in
It was stable even after storage. Example 3 Instead of the carbon black used in Example 1, toluene
(Other organic solvents are also acceptable)
For removing pure substances and desalting water-soluble inorganic salts
Carbon black obtained from [toluene permeability 95%,
Furnace black for ink with ash 0.23% by weight]
A black ink was prepared in the same manner as in Example 1.

When the ink immediately after preparation was measured in the same manner as in Example 1, the center diameter [d value] of the carbon black measured by the dynamic light scattering method was 100 nm, and the viscosity was 5.80.
cps / 25 ° C.

When this ink was filled in a marking pen for a writing plate and a writing test was carried out, it was possible to write on the writing plate vividly without clogging of the ink at the pen tip and a decrease in the density of the handwriting, and the handwriting after a long time had passed. I was able to wipe it off lightly.

Also, this ink was placed in a constant temperature bath at 50 ° C. for 2 hours.
After leaving it for a month, change the viscosity and the particle size of carbon black.
The results are shown in Table 1 when measured and compared with those immediately after preparation.
Change is very small as shown in
It was stable even after storage. Comparative Example 1 Polyvinyl butyral [Product name: Denka Butyral # 40
00-1, manufactured by Denki Kagaku Kogyo Co., Ltd.] 8 parts of modified ethyl alcohol
82 [Product name: Solmix AP-1, Nippon Kasei Co., Ltd.]
And dissolve it in this polymer solution.
Ruen color ink 71% transmittance, ash content 0.84% by weight
-Blackness] (for removing organic impurities in Example 3)
And water soluble inorganic salt carbon black before desalting) 10 parts
The mixture is put in and stirred for 2 hours with a dissolver.
Xux base was prepared.

This premix base was subjected to dispersion treatment in the same manner as in Example 1 to form an ink, whereby a black ink of Comparative Example was obtained.

When the ink immediately after preparation was measured in the same manner as in Example 1, the center diameter [d value] of the carbon black measured by the dynamic light scattering method was 130 nm, and the viscosity was 5.83.
cps / 25 ° C.

After this ink was left in a constant temperature bath at 50 ° C. for 2 months, the viscosity and the particle size of carbon black were measured and compared with those immediately after preparation. Greatly increased, viscosity greatly increased. Comparative Example 2 Polyvinyl butyral [trade name: Denka Butyral # 20
00-L, manufactured by Denki Kagaku Kogyo Co., Ltd.] 12 parts was dissolved in 78 parts of denatured ethyl alcohol [trade name: Solmix AP-1, manufactured by Nippon Kasei Co., Ltd.], and carbon black [toluene coloring permeability] was added to this polymer solution. A premix base was prepared by adding 10 parts of furnace black for ink having 76% and ash content of 0.21% by weight and stirring with a dissolver for 2 hours.

This premix base was subjected to dispersion treatment in the same manner as in Example 2 to form an ink, whereby a black ink as a comparative example was obtained.

When the ink immediately after preparation was measured in the same manner as in Example 1, the center diameter [d value] of carbon black by the dynamic light scattering method was 120 nm, and the viscosity was 6.11.
cps / 25 ° C.

After this ink was left in a constant temperature bath of 50 ° C. for 2 months, the viscosity and the particle size of carbon black were measured and compared with those immediately after preparation. Greatly increased and viscosity increased. Comparative Example 3 Polyvinyl butyral [trade name: Denka Butyral # 30
00-1, manufactured by Denki Kagaku Kogyo Co., Ltd.] was dissolved in 80 parts of denatured ethyl alcohol [trade name: Solmix AP-1, manufactured by Nippon Kasei Co., Ltd.], and carbon black [toluene coloring permeability] was added to this polymer solution. A premix base was prepared by adding 10 parts of furnace black for ink having 94% and an ash content of 0.68% by weight and stirring with a dissolver for 2 hours.

This premix base was subjected to dispersion treatment in the same manner as in Example 2 to form an ink, whereby a black ink as a comparative example was obtained.

When the ink immediately after preparation was measured in the same manner as in Example 1, the center diameter [d value] of carbon black measured by the dynamic light scattering method was 130 nm, and the viscosity was 6.09.
cps / 25 ° C.

After this ink was left in a constant temperature bath at 50 ° C. for 2 months, the viscosity and the particle size of carbon black were measured and compared with those immediately after preparation. Greatly increased and viscosity increased.

[0055]

[Table 1]

Claims (3)

[Claims] 1. A medium containing at least carbon black,
A black ink composition for a writing board comprising a lower alcohol-soluble polymer and a release agent, wherein the medium is mainly a lower alcohol solvent or a lower alcohol solvent, and the carbon black is toluene-colored. A black ink composition for a writing board, which has a transmittance of 85% or more and an ash content of 0.5% by weight or less. 2. The black ink composition for a writing board according to claim 1, wherein the lower alcohol-soluble polymer is polyvinyl butyral which is a tripolymer consisting of a polyvinyl acetal portion, a polyvinyl alcohol portion and a polyvinyl acetate portion. 3. The medium is methanol, ethanol, n
-Including one or more kinds selected from the group consisting of propanol and isopropanol as a main solvent,
Alcohol-based solvent having 4 or more carbon atoms, glycol-based solvent,
The black ink composition for a writing board according to claim 1 or 2, which comprises one or more selected from the group consisting of a glycerin-based solvent and a sucrose ester as a whitening-preventing or drying-suppressing agent.