JPH0562632B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a water-based ink that is applied to writing instruments and recorders to provide water-resistant handwriting or records. Prior Art This type of ink is a water-based ink in which a pigment is dispersed as a coloring agent in an aqueous vehicle, an oil-soluble dye is dissolved in an oil-soluble solvent, and water is added to a colored liquid in which a solubilizing agent consisting of a surfactant is added. In addition, water-based ink (Japanese Patent Publication No. 60-25468) has been proposed. Problems to be Solved by the Invention Inks that use pigments as colorants do not have sufficient dispersion stability in low-viscosity vehicles, and the pigments settle over time and form in the capillary tubes of the pen tips of writing instruments and recorders. Roads are often blocked. On the other hand, if the viscosity of the vehicle is increased to improve dispersion stability, a problem arises in that the ink flow deteriorates in writing instruments and recorders that use capillaries as ink passages. Therefore, this type of water-based ink can only be applied to writing instruments or recorders with specific mechanisms. Water-based inks, which are made by dissolving oil-soluble dyes in water-insoluble organic solvents and solubilizing them in water, can produce water-resistant handwriting or records depending on the dye used.
The disadvantages of oil-based ink, namely odor, bleeding into paper, and strike-through, have not been completely eliminated. Means for Solving the Problems The aqueous ink of the present invention has a composition in which a hydrophobic dye is solubilized in an aqueous vehicle containing a partially sulfonated polyester resin. The hydrophobic dye is selected from dyes classified as solvent dyes and disperse dyes in the COLOR INDEX, and has a chemical structure such as azo dyes, metal complex azo dyes, anthraquinone dyes, and metal phthalocyanine dyes. These dyes are used in an amount of 3 to 20% by weight based on the total amount of the ink composition. The partially sulfonated polyester resin is a linear polyester whose skeleton is dicarboxylic acid and diol, and the dicarboxylic acid components include malonic acid, succinic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, cyclohexanedicarboxylic acid, phthalic acid, and naphthalene. Dicarboxylic acids and their derivatives are mentioned, and diol components include ethylene glycol, propylene glycol, 1,3-propanediol, polyethylene glycol, cyclohexanediol, dihydroxybenzene, methylene diphenol, thiosyphenol, biphenol and their derivatives. However, at least a portion of the diol component is present in repeating unit 2.
to 10 polyethylene glycols. Moreover, a part of either of the above-mentioned components has an aromatic ring to which a sulfonic acid group is bonded. These resins are used in an amount of 5 to 30% by weight, preferably 8 to 20% by weight, based on the total amount of the ink composition. The weight ratio of dye to resin is 1 part dye to 2.5 parts resin.
It is as follows. When the resin ratio becomes larger, a problem arises in ink fluidity when used as an ink for a writing instrument or recorder which has a mechanism for supplying ink from an ink reservoir to a pen tip by capillary action. The vehicle for the aqueous ink of the present invention is made by dispersing and dissolving the above-mentioned partially sulfonated polyester resin in water. - A humectant selected from methylpyrrolidone, a plasticizer for the resin such as a phthalate ester, a water-soluble organic solvent such as ethanol and propanol to speed up the drying of handwriting or records, wettability of the ink to hydrophobic surfaces, and capillaries. Surfactants that improve physical properties such as permeability into the skin, dyes for complementary colors, PH regulators, antifungal agents, preservatives, and the like may be added. Function In the aqueous ink of the present invention, the partially sulfonated polyester resin itself stably exists in water in a dispersed or dissolved state due to the action of the sulfonic acid group and the glycol moiety. The hydrophobic dye is contained in a state associated with the hydrophobic portion which is the main component of the polymer. The dye is therefore incorporated in high concentration into the aqueous vehicle containing the resin. The handwriting or record formed on the outer surface of paper, film, etc. with this water-based ink is created by a partially sulfonated polyester resin that adheres to the surface, and the resin contains a dye, and the dye itself is substantially water-based. It is completely water resistant as it is insoluble in water. Examples Example inks were prepared as follows. (1) Preparation of partially sulfonated polyester resin aqueous dispersion A predetermined amount of resin (along with a plasticizer if necessary) is added to hot water at approximately 90℃ under stirring, and stirred for 20 to 40 minutes to dissolve the resin. After dissolving and dispersing, allow to cool. Three types of resin aqueous dispersions having the following compositions were obtained. Resin A aqueous dispersion Partially sulfonated polyester resin A 28% by weight Dimethyl phthalate (plasticizer) 3% by weight Water 69% by weight Resin B aqueous dispersion Partially sulfonated polyester resin B 25% by weight Water 75% by weight Resin C aqueous dispersion Liquid partially sulfonated polyester resin C 30% by weight Water 70% by weight The properties of the partially sulfonated polyester resin used are as follows. Characteristics of the partially sulfonated polyester resin used
Resin A Resin B Resin C Molecular weight
Approx. 18000 Approx. 18000 Approx. 14000 Hydroxyl value
5.3 5.0 6.0 Acid value <2 <2 <2 Glass transition point
55℃ 38℃ 29℃ Per polymer chain
12.9 7.5 5.6 Number of sulfonic acid groups (2) Preparation of ink A predetermined amount of dye, the partially sulfonated polyester resin aqueous dispersion, a humectant, and the remaining water are weighed and mixed, and heated to about 90°C with a stirrer. At 2
After stirring for an hour and cooling, the mixture was finished by centrifugal filtration. Next, a comparative ink was prepared as follows. A predetermined amount of the dye was dissolved in toluene, a surfactant (solubilizer) and monoethanolamine were added and mixed to this solution, and water was gradually added while stirring to complete the solution. The composition and physical properties of each ink are shown in Table 1.

[Table] The contents of the note numbers for raw materials in Table 1 are as follows. (1) CI12195 (CISolvent Black29) (2) CI74350 (CISolvent Blue25) (3) CI21260 (CISolvent Red18) (4) CI26150 (CISolvent Black3) (5) CI60756 (CIDisperse Red60) (6), (7), (8) ) Partially sulfonated polyester resin described on page 7 (9) Polyethylene glycol nonyl phenol ether (HLB value 14) Next, the following tests (1) to (4) were conducted on each of the above inks. A marking pen with a nib made of a synthetic resin molded body having an axial capillary ink passage is filled with a specified amount of each ink to prepare a sample pen, and 3 copies of the specified character group are printed on writing paper A (specified in JIS P3201). Create a sample piece by writing down
Tested. (1) Check to see if any odor is felt when writing. (2) the degree of blurring of the handwriting on the sample piece;
Detect the presence or absence of bleed-through. (3) For each ink, drop tap water with a dropper onto the letters on one sample piece (after 5 to 10 minutes of writing), leave it until the water droplets evaporate, and after drying, the condition of the letters in the water droplet area Observe. (4) For each ink, one sample piece (5 to 10 minutes after writing) is immersed in a vat overflowing with running tap water for 1 hour, then pulled up and dried. Compare the changes in handwriting with the original handwriting. The judgment of the results is as follows. (1) 〇 No odor × Odor (2) 〇 No bleeding or bleed-through △ Bleeding or bleed-through is observed at the corners of letters, where pen movement is slow during writing × Significant smearing or bleed-through (3) 〇 No change △ Slight oozing × Characters are illegible (4) 〇 No change △ Slight leakage × Almost leakage The results are shown in Table 2.

【table】

[Table] Effects of the Invention As shown in Table 2, the handwriting of the comparative inks is water resistant depending on the dye used, but in some cases it is not completely water resistant. Bleeding and bleed through to the paper are also partially observed. Moreover, the odor of the solvent (toluene) is felt while writing, and the disadvantages of oil-based inks are not completely eliminated. On the other hand, handwriting made with the water-based ink of the present invention is completely water-resistant regardless of the color type, and no bleeding or strike-through phenomenon is observed on paper. Naturally, you won't notice any odor while writing.

Claims (1)

[Claims] 1. An aqueous ink in which 3 to 20% by weight of a hydrophobic dye selected from solvent dyes and disperse dyes is solubilized in an aqueous vehicle containing 5 to 30% by weight of a partially sulfonated polyester resin in the ink composition. The partially sulfonated polyester resin is a linear polyester whose skeleton is a dicarboxylic acid and a diol, the molecule contains an aromatic ring to which a sulfonic acid group is bonded, and at least a portion of the diol has a repeating unit number. 2 to 10
A water-based ink which is made of polyethylene glycol and has a weight ratio of dye to resin of 1 part dye to 2.5 parts resin or less.