JPH0995640A - Erasable ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of providing handwriting readily being erased by rubbing due to eraser and capable of keeping initial color tone also after passage of a long period by applying to a writing tool such as marking pen. SOLUTION: This ink. composition consists essentially of (A) a rubber latex comprising a carboxylated acrylonitrile-butadiene rubber latex or a carboxylated methyl methacrylate-butadiene rubber latex in an amount of 3-50wt.% (preferably 10-40wt.%) expressed in terms of solid content and (B) 0.001-10wt.% (preferably 0.01-5wt.%) basic dye (e.g. thiazole, ketonimine, acrydine, methine or cyanine) and has about 5-50mpa.s viscosity at 20-25 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an erasable ink composition for writing which gives a handwriting which is easily erased by rubbing with an erasing material such as an eraser.

[0002]

2. Description of the Related Art Many proposals have been made in the past for erasable inks for writing of this kind. However, in erasable inks that generally use dyes as colorants, the dyes in the dissolved state are intercalated between the fibers of the paper. Since it easily penetrates, the erasability of handwriting is not sufficient. On the other hand, with inks using pigments, the erasability of handwriting is generally good, but when left for a long period of time, the pigments gradually settle in the ink and the pigments in the upper layer of the ink become diluted, and the lower layer becomes excessive. There is a phenomenon of concentration.
This phenomenon occurs when the ink is applied to the marking pen
It becomes a problem. Usually, a marking pen is displayed in a retail store with the pen tip facing upward for a long period of time and then reaches the user's hand.Therefore, the ink near the pen tip has only a very light handwriting at the beginning due to the dilute pigment content. In the latter half, the excessive concentration of the pigment tends to block the capillary ink passage of the pen tip, and the ink outflow from the pen tip tends to be interrupted. Recently, for example, an erasable ink containing a styrene-butadiene latex and a pigment has been proposed in Japanese Patent Publication No. 7-505174, but it also shows the above characteristics and tendency.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a handwriting which is easy to erase with an eraser on the surface of a paper, and has the same color tone as that of the beginning even after being applied to a writing instrument such as a marking pen or a ballpoint pen and left for a long time. Another object of the present invention is to provide an erasable ink composition which gives good handwriting and has good stability over time.

[0004]

The erasable ink composition of the present invention contains, as essential components, a rubber latex selected from carboxylated acrylonitrile-butadiene rubber latex and carboxylated methylmethacrylate-butadiene rubber latex and a basic dye. I will do it. Hereinafter, the two types of rubber latex will be collectively referred to as carboxylated acrylic rubber latex. The carboxylated acrylic rubber latex is manufactured by many chemical manufacturers and various kinds are available. As the carboxylated acrylonitrile-butadiene rubber latex,
For example, the product names of LACSTAR 68-073S, 68-074S, 4940B, D manufactured by Dainippon Ink and Chemicals, Inc.
N-704 and the like, and as the carboxylated methyl methacrylate-butadiene rubber latex, for example, trade name LACSTAR DM-80 manufactured by Dainippon Ink and Chemicals, Inc.
1, 4950C, DM-401 and the like. These carboxylated acrylic rubber latexes are used in the ink composition in an amount of 3 to 50% by weight, preferably 10 to 40% by weight in terms of solid content. If the amount added is less than 3% by weight, good handwriting erasing performance cannot be obtained, and if the amount added exceeds 50% by weight, the ink becomes highly viscous, making it difficult to use in a marking pen or a ballpoint pen.

Examples of the basic dye include thiazole, ketonimine, acridine, methine, cyanine, monoazo,
Disazo, xanthene, azine, triarylmethane,
There are cationic dyes having a xazine, diarymethane or thiazine structure, for example, basic flavin (CI basic yellow 1), acridine orange (CI basic orange 14), rhodamine 6
GCP (CI Basic Red 1), Brilliant Red 4G (CI Basic Red 14), Methyl Violet (CI Basic Violet 1),
Rhodamine B (CI Basic Violet 1
0), Basic Pure Blue (CI Basic Blue 3), Victoria Blue BOH (CI Basic Blue 7), Methylene Blue (CI Basic Blue 9), Malachite Green (CI Basic Green 1). , Bismarck Brown (CI Basic Brown 1), and Janus Black (CI Basic Black 2). These dyes are contained in the ink composition in an amount of 0.001 to 10% by weight, preferably 0.01
To 5% by weight. With any of the above dyes, a concentration of 10% by weight or less produces sufficiently dark handwriting, and no further addition is required. The weight ratio of the basic dye to the solid content of the carboxylated acrylic rubber latex is in the range of 1/50 to 1/1000, preferably 1/100 to 1/500. If the amount of the dye is more than this range, the handwriting erasability tends to decrease.

In order to ensure a good ink outflow from the pen tip by applying the ink to a writing instrument such as a marking pen or a ballpoint pen, it depends on the type and structure of the writing instrument to be used.
It should have a viscosity in the range of about 5 to 50 mPa · s at ℃ to 25 ℃. The higher viscosity ink is adjusted to have a desired viscosity within the above range by adding an appropriate amount of water.

Further, a polyhydric alcohol such as ethylene glycol, propylene glycol, glycerin, hexylene glycol, 1,3-butanediol, neoprene glycol, etc. as a dry-up preventive agent for suppressing ink evaporation at a pen tip such as a marking pen. Additives such as antiseptics and surfactants (auxiliaries for stabilizing emulsions of latex) are also added as necessary.

[0008]

[Working] The carboxylated acrylic rubber latex forms a peelable film when it is applied to a paper surface and dried. Since the basic dye is ionically adsorbed to the carboxylated acrylic rubber in the film, when the film is rubbed with the eraser, it is peeled off together with the film without remaining on the fiber surface of the paper or between the fibers. In addition, the basic dye is ionically bonded to the carboxylated acrylic rubber latex particles in the ink and stably exists.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The erasable ink is appropriately watered in a container,
Add rubber latex and stir with a stirrer for about 10 minutes to mix. A dye was added to the mixed solution and stirred for 1 hour, and finally, other additives were added and the mixture was stirred for 30 minutes.

[0010]

EXAMPLES Table 1 shows the compositions of the example inks and the comparative example inks. The numerical values of the compositions are expressed in parts by weight.

[Table 1] The contents of the raw materials in the table will be described along the note numbers. (1) Victoria Blue BOH (Hodogaya Chemical Co., Ltd.)
Trade name), C.I. I. Basic Blue 7 (2) Rhodamine 6GCP (trade name of Hodogaya Chemical Co., Ltd.), C.I. I. Basic Red 1 (3) Brilliant Blue FCF (trade name of Daiwa Kasei Co., Ltd.), C.I. I. Acid Blue 9 (4) Aqueous dispersion containing 10% carbon black and 5% polyvinyl alcohol (5) Lackstar 68-073S (trade name of Dainippon Ink and Chemicals, Inc.), carboxylated acrylonitrile-butadiene rubber latex (rubber Solid content 43%) (6) Luck Star DM-801 (trade name of Dainippon Ink and Chemicals, Inc.), carboxylated methyl methacrylate-butadiene rubber latex (rubber solid content 50%) (7) 0910 (Nippon Synthetic Rubber ( (Trade name), acrylonitrile-butadiene rubber latex (rubber solid content 4
0%) (8) LPF (trade name of Goodyear), styrene-butadiene rubber latex (rubber solid content 40%) (9) polyoxyethylene (6 mol) sorbit tetraoleate (10) L-7607 (Nippon Unicar ( (Trade name), polyether modified silicone surfactant (11) Paintad 32 (trade name of Dow Corning),
Glycol-modified silicone oil

The inks of Comparative Examples 1 and 2 are examples in which an acidic dye was used instead of the basic dye of Example 1 ink, and a nitrile rubber latex was used instead of the carboxylated acrylic rubber latex. Is the composition of the example ink described in JP-A-7-505174.

Each of the sample inks prepared by the above-mentioned ink preparation method was put into a direct liquid type marking pen having the following structure in a predetermined amount to form a sample pen, which was then tested. The marking pen is made of an aluminum cylinder having a pen body holder to which a pen body made by binding fibers with resin is fixedly attached to the tip through a valve mechanism. It is a type of pen that allows the ink in the cylindrical body to be drawn out to the pen body by opening.

Writing on the paper surface with each sample pen, the followability of whether continuous ink outflow from the pen tip is obtained or not is examined, and a part of the obtained handwriting is rubbed with an eraser to make the erasability difficult. The degree was judged. Each sample pen was tightly capped, left standing for 1 week with the pen tip facing upward, and then written with each sample pen side by side with the above-mentioned handwriting, and the temporal stability of the ink was examined by a method of comparing the color tone of the handwriting before and after the test. . The test results are shown in Table 2.

[Table 2] The contents of the evaluation symbols in the table are as follows. Ink followability ○: Ink flows out continuously from the pen tip Erasability of handwriting ○: Easily erased ×: Not erasable by rubbing up to 10 times Stability of ink over time ○: Color tone and substance of handwriting before test Same color tone x: Remarkably light color

[0014]

INDUSTRIAL APPLICABILITY The erasable ink composition of the present invention is not only easy to erase with an eraser, but is also applied to a writing instrument such as a marking pen so that a handwriting with a color tone that is the same as the original color tone after aging is obtained. It has the function of bringing.

Claims (2)

[Claims] 1. An erasable ink composition comprising, as essential components, a rubber latex selected from carboxylated acrylonitrile-butadiene rubber latex and carboxylated methylmethacrylate-butadiene rubber latex and a basic dye. 2. About 5 to 50 m at 20 to 25 ° C.
The erasable ink composition according to claim 1, having a viscosity in the range of Pa · s.