JPH0791494B2 - Water based ink - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water-based ink, in particular, a water-based ink for inkjet, and can also be used as an ink for a general writing instrument, a stamp and the like.

[Prior Art] The properties required for an inkjet ink are 1) jetting stability 2) storability 3) vividness of color tone 4) water resistance, light resistance, etc., but conventionally, especially color inks have high color tone and high solubility Due to the use of this dye, the water resistance of the image printed with it was poor. Therefore, it is usually necessary to use waterproof paper.

However, there is a strong demand for printing on plain paper,
Therefore, a method of increasing water resistance by adding polyallylamine (a compound in which R and R'in the general formula described in the claims are both hydrogen) has been proposed. But,
Particularly in the case of polyvalent anion dyes, polyallylamine is apt to form a precipitate due to dye-mediated crosslinking, and unless the pH is considerably high during ink preparation (pH due to CO ₂ gas in the air
Clogging occurs. Therefore, in the case of polyallylamine, the pH at the time of ink preparation needs to be higher than 10.7 to 11.0. However, if the pH value is 11 or more, it is dangerous when it comes into contact with the human body and the nozzle may be corroded.

[Object] The object of the present invention is to improve the above-mentioned problems of the prior art, to improve the water resistance of an image, and to provide a water-based inkjet ink in which no precipitation occurs.

[Structure] The structure of the present invention for achieving the above object is an aqueous ink as described in the claims.

By the way, the polyallylalkylamine used as a component of the aqueous ink is a compound represented by the following general formula.

Alkyl group having R: OH Alkyl group having R ': OH or hydrogen atom n: integer of 50 to 130 The above compounds can be synthesized by reacting polyallylamine with an alcohol in which hydrogen of the alkyl group is replaced with halogen. PK than polyallylamine (a compound in which R and R'in the above general formula are both hydrogen atoms)
When it is used as an additive for ink, the water resistance of the printed image is good, and the pH at which precipitation occurs due to crosslinking with polyvalent ionic dyes is higher than that of polyallylamine.
Since it drops to around 10, the pH during ink preparation is 10.2-1.
0.7 is sufficient.

The synthetic method of the above compound (R, R '= C ₂ H ₄ OH is taken as an example) is as follows.

Hydrochloride of polyallylamine (PATO / HC1 / 3S from Nitto Boseki Co., Ltd.)
9.8 g (0.1 mol of monomer units) are added to 100 ml of methanol in which 0.1 mol of sodium hydroxide is dissolved and the sodium chloride formed is filtered off. Further ethylene chlorohydrin
16.1 g (0.2 mol) is added, 50 ml of a methanol solution containing 0.2 mol of sodium hydroxide is added, and the mixture is refluxed for 1 hour. The sodium chloride formed is filtered off. After that, freeze-drying gives crystals.

When the alkaline solution of this compound was titrated with hydrochloric acid, the pH at which it turned into ammonium ions was lower than that of polyallylamine (showing that pKa is smaller than that of polyallylamine), as shown in the figure.
= R '= H), which is considered to be the cause of the decrease in pH of the precipitate generation. Also, as seen in this figure, R = R '= C ₂
In the case of H ₄ OH alone, it does not ionize up to around pH 7 to 8, but if there is a polyvalent anion dye, salt formation with the dye starts from around pH 10.

When R and R'are different, two corresponding halogen-substituted alcohols may be used. If two or more kinds of halogen-substituted alcohols are used, polyallylalkylamines in which they are not mixed can be produced, and the effect is the same. Further, some hydrogen atoms of the amine may remain without being replaced.

The amount of polyallylalkylamine added to the ink depends on the number of moles of the sulfone group and carboxyl group of the dye in the ink.
A molar amount of 1/10 to 2 times is appropriate. For example, when CI Acid Red 35 (the following formula) is present in 0.01 mol in the ink, the amount of polyalkylamine containing 1/10 to 2 times the number of mols of the alkylamino group, that is, 0.002 to 0.04 mol is suitable.

If it is less than 0.002 mol, there is no effect of improving water resistance, and if it exceeds 0.04 mol, the viscosity increases and high-concentration ink cannot be formed.

As the dye, any acidic or direct dye having a hydrophilic group such as a sulfone group or a carboxyl group can be used.

The present invention is particularly valuable for use in inks containing magenta and cyan acid dyes, which have particularly good color tones and have high water-solubility. This is because there are not many direct dyes having good color tone and good water resistance in these colors.

As an ink preparation method, a predetermined amount of dye and other additives may be dissolved in water and a wetting agent, and a predetermined amount of polyallylalkylamine may be added. The salt may be prepared and used as a raw material.

The ink of the present invention uses water as a solvent component, but for the purpose of adjusting the physical properties of the ink to desired values, preventing the ink from drying, and improving the solubility of the dye, the following water-soluble It is also possible to use a mixed organic solvent and water.

Polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, glycerin, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol Alkyl ethers of polyhydric alcohols such as monomethyl ether and triethylene glycol monoethyl ether, and others, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, dimethylformamide, triethanolamine, etc. Is.

Of these, particularly preferred is diethylene glycol,
Polyethylene glycol 200-600, triethylene glycol, ethylene glycol, glycerin, N-methyl-
2-pyrrolidone. By using these, the solubility of the dye becomes high and the evaporation of water can be prevented, so that the effect of preventing clogging caused by precipitates can be obtained.

The content of the water-soluble organic solvent in the ink can be used in the range of 5 to 80 wt% with respect to the total weight of the ink, but it is preferably used in the range of 15 to 60 wt% in view of viscosity, drying property and the like.

To the ink of the present invention, conventionally known additives may be added in addition to the dye and solvent.

For example, as antiseptic / antifungal agents, sodium dehydroacetate, sodium sorbate, 2-pyridinethiol-1
-Sodium oxide, sodium benzoate, sodium pentachlorophenol and the like can be used in the present invention.

Any substance can be used as long as it can control the pH of the ink to around 10.2 to 10.7 without adversely affecting the ink prepared as the pH adjuster.

Examples thereof include amines such as diethanolamine, triethanolamine and monoethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, Examples thereof include alkali metal carbonates such as lithium carbonate, sodium carbonate and potassium carbonate.

Examples of the chelating agent include ethylenediaminetetraacetic acid sodium salt, nitrilotriacetic acid sodium salt, hydroxyethylethylenediaminetriacetic acid sodium salt, diethylenetriaminepentaacetic acid sodium salt, and uramil diacetic acid sodium salt.

Examples of the rust preventive agent include acidic sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol 4-nitrate, and dicyclohexylammonium nitrite.

In addition, a water-soluble ultraviolet absorber, a water-soluble infrared absorber, a water-soluble polymer compound, a dye dissolving agent, a surfactant and the like can be added depending on the purpose.

The present invention will be specifically described below with reference to examples.

Example An ink having the composition shown in Table 1 was prepared and then adjusted to pH 10.5 to 11.0 with sodium hydroxide.

The following tests were performed on the above Examples 1 to 10 and Comparative Examples 1 to 3.

1) Image clarity An ink jet printer for Ricoh's word processor report 5600J was filled with the prepared ink, and printing was performed on a commercially available bond or the like.

The ink for which a clear image was obtained is represented by a circle in Table 2.

2) Lightfastness of image The image sample obtained in 1) was measured with a Macbeth densitometer for the image density after light irradiation for 3 hours with a fade meter (carbon arc lamp, 63 ° C), and the photobleaching rate was calculated by the following formula. It was

Fading rate (%) = (1-image density after light irradiation / image density after light irradiation) x 100 3) Water resistance of image 1) Immerse the image sample obtained in 1) in water at 30 ° C for 1 minute, and soak The image densities before and after the measurement were measured with a Macbeth densitometer, and the water fading rate was obtained by the same formula as that of the item 2).

4) Storability Put the ink in a polyethylene container and store at -20 ℃, 4 ℃, 20 ℃
Store at ℃, 50 ℃, 70 ℃ under each condition for 3 months,
Changes in viscosity, surface tension, and electrical conductivity before and after storage, and the presence or absence of precipitate deposition were examined. Table 1 shows that no change in the product was observed and no precipitate was generated under any condition.

5) Nozzle clogging test 1) After printing, it was left for 2 months in an environment of 20 ° C and 65% RH while the printing was paused, and after standing, it was examined whether normal printing was possible again. One sample was tested using 3 printers.

In Table 2, if three printers can print normally, it is ○, if one or two printers cannot print normally,
The case where normal printing could not be performed on all three units is indicated by XX. The 5600J printer is a device that automatically detects when the nozzle is clogged and jetting is no longer possible, or when the jetting direction changes significantly compared to before it was left unattended and stops the printer operation. Is attached.

[Effects] As described above, the water-based ink of the present invention has good storability, does not cause nozzle clogging, and has a low photobleaching rate, in particular, a very low water fading rate. It is effective.

[Brief description of drawings]

The drawing is a graph showing changes in pH due to addition of hydrochloric acid water to alkaline solutions of polyallylamine and polyallylalkylamine.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroyuki Uemura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Nobufumi Nagai 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh

Claims (1)

[Claims] 1. A water-based ink comprising a polyallylalkylamine represented by the following general formula, a dye, a wetting agent, and water as main components. General formula However, among the symbols in the above general formula, it is an alkyl group having R: OH, an alkyl group having R ': OH, or a hydrogen atom n: an integer of 50 to 130.