JPH02248475A - Water-base ink composition - Google Patents

Abstract

PURPOSE:To prepare a water-base ink compsn. improved in the resistance to water and light, having an excellent storage stability, and usable on glass, plastics, metal, ceramics, etc., as well as on paper by compounding a dispersible colored resin, an alkali-soluble resin, and a surface tension-adjusting agent as essential components. CONSTITUTION:A water-base ink compsn. which contains a dispersed colored resin, an alkali-soluble resin, and a surface tension-adjusting agent as essential component. Said dispersed colored resin pref. has a mean particle diameter of 0.3mum or lower, is colored with a dye, and comprises a polymer of an ethylenycally unsatd. monomer As said alkali-soluble resin, a carboxyl group- contg. copolymer with an acid value of 30-300 is pref.; as said surface tension- adjusting agent, an anionic or nonionic surfactant is pref. The pref. viscosity of the water-base ink compsn. at 25 deg.C is 10cP or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an aqueous ink composition used for marking marks and the like.

[Conventional technology]

Dye-type inks have traditionally been widely used as this type of water-based ink, but because the dye itself is water-soluble, they have the major disadvantage of poor water resistance and light resistance.

Therefore, various pigment-type inks have been proposed as water-based inks that can overcome this drawback. For example, JP-A-58
Japanese Patent Publication No. 141256 discloses an aqueous ink composition in which a polymer flocculant is added to remove loose bridges between pigment particles, thereby producing an agglomerated suspension of pigment, thereby preventing sedimentation and separation of the pigment. ing.

Furthermore, JP-A No. 61-235478 discloses a water-based ink composition that improves the dispersion stability and storage stability of pigments by using a polymer having a lipophilic moiety as a pigment dispersant. has been done.

[Problem to be solved by the invention]

However, with the conventional pigment-type water-based ink compositions described above, it is difficult to disperse and stabilize the pigment in the form of fine particles in water with a low viscosity of 1 Q cps or less, and it is difficult to cause sedimentation and separation in writing utensils. Phenomena such as blurring or being unable to write on the surface often occur.This is because it is difficult to stabilize pigment particles by reducing them to primary particles, and This is thought to be because even commonly used organic pigments have a specific gravity in the range of 1.4 to 2.2, so they tend to settle when the viscosity is low.

Furthermore, since the viscosity of a water-based ink with a low viscosity of 1 Q cps or less is significantly increased by the addition of a fixing agent, there is a limit to the amount of the fixing agent added, and it is not possible to add that much of the fixing agent. Therefore, the objects for which such low-viscosity water-based inks can be used are generally limited to paper.
When used on objects with little moisture absorption, such as glass, plastic, metal, and ceramics, the ink may splatter or fix poorly, making it unusable for practical use. This is a major drawback of ink.

The present invention was made in view of the above circumstances, and it improves water resistance and light resistance, which are the drawbacks of water-soluble dyes, and has excellent stability over time. It is an object of the present invention to provide a water-based ink composition that can be applied to objects having almost no hygroscopicity such as metals and ceramics.

[Means to solve the problem]

The aqueous ink composition of the present invention basically contains a colored resin dispersion, an alkali-soluble resin, and a surface tension modifier as essential components. Further, as the colored resin dispersion, a polymer dispersion of an ethylenically unsaturated monomer colored with a dye and having an average particle diameter of 0.3 μm or less is used, and as the alkali-soluble resin, an acid value in the range of 30 to 300 is used. It is desirable to use a certain carboxyl group-containing copolymer and to use an anionic or nonionic surfactant as the surface tension modifier. Further, those having a viscosity of 10 cps or less at 25° C. are also within the scope of the present invention.

〔Example〕

The aqueous ink composition of the present invention contains a colored resin dispersion, an alkali-soluble resin, and a surface tension modifier as essential components.

The colored resin dispersion used in the present invention is obtained by solution polymerizing an ethylenically unsaturated monomer having an acidic group or a basic group in the presence of a water-soluble organic solvent, and adding a dye during or after the solution polymerization. The polymer obtained by body) is preferred.

The colored resin dispersion thus obtained has an average particle size of 0.
Since it is 3 μm or less, it not only has excellent stability, but because the dye is dispersed and adsorbed in the emulsion resin, its water resistance and light resistance are significantly improved compared to conventional dye-type water-based ink compositions.

Examples of ethylenically unsaturated monomers having an acidic group include monomers having a sulfonic group or a carboxyl group, such as acrylic acid, methacrylic acid, maleic acid, and salts thereof; Examples of unsaturated monomers include nitrogen-containing monomers such as vinylpyridine and N-vinylpyrrolidone. Examples include acrylamide.

Examples of dyes capable of coloring each of the above monomers include direct dyes, acid dyes, basic dyes, disperse dyes, and oil-soluble dyes. Although it is preferable to add the dye during solution polymerization, it may be added after solution polymerization.

The water-soluble organic solvent is preferably alcohols, glycols, or a mixture thereof, such as methyl alcohol, ethyl alcohol, isopropyl alcohol, monoethylene glycol, diethylene glycol, propylene glycol, glycerin, etc., but is limited to these. It is not something that will be done.

Solution polymerization can be carried out by a commonly used method, but polymerization is carried out at 50 to 150'C in a nitrogen stream at 1 to
It is desirable to carry out this by stirring for 5 hours.

In order to disperse the polymer obtained by solution polymerization in the copolymer latex, it is preferable to gradually drop the polymer while vigorously stirring the copolymer latex. In this way, the polymer is easily dispersed uniformly in the copolymer latex and is uniformly adsorbed.

The above copolymer latex is obtained by emulsion polymerization of ethylenically unsaturated monomers, and contains 10 to 70% of cyano group-containing ethylenically unsaturated monomers and one or two other copolymerizable species. The above ethylenically unsaturated monomers 90-3
It is preferable to use one obtained by emulsion polymerization of 0%. This is because, in order to obtain a high-concentration dispersion, the greater the content of the cyano group-containing ethylenically unsaturated monomer capable of coloring with dye, the greater the adsorption power to the polymer.

The alkali-soluble resin used in the present invention is an alkali-soluble resin that can be formed into a film at room temperature, and is preferably a carboxyl group-containing copolymer having an acid value in the range of 30 to 300. Among them, acrylic resins with a molecular weight of 10,000 or less have good physical properties. This is because - for boat fishing, the smaller the molecular weight, the lower the viscosity.

The surface tension adjusting agent used in the present invention is preferably an anionic or nonionic surfactant, and the amount thereof is preferably such that the surface tension of the ink is in the range of 25 to 35 dyn/cm. In other words, the appropriate value for the surface tension of ink is preferably in the range of 25 to 35 dyn/cm; if it is smaller than 25 dyn/cm, it may cause dripping from the tip of the writing instrument;
If it is larger than m, writing on glass, plastic, metal, ceramics, etc. will cause it to be repelled or will not stick well. The specific amount of the surfactant varies depending on the type of surfactant, but for certain types of surfactants, when used in the range of 0.01 to 2.0% by weight based on the total amount of the ink, the surface tension of the ink can be adjusted to the above appropriate level. falls within the range of values.

The viscosity of the ink at 25° C. is preferably 1 Q cps or less; if it is larger than that, the ink will not easily flow out from the pen tip and will easily cause blurring.

Next, experimental examples and comparative examples will be explained.

[Experiment example]

In a reaction container, 80 parts of diethylene glycol, 10 parts of Basic Yellow 51 (trade name: Kayacrylic Yellow-3G-3, manufactured by Nippon Kajimi Co., Ltd.), 10 parts of acrylic acid, 0.1 part of lauryl mercaptan, and 0 parts of azobisisobutyronitrile were added.
．． The two parts were mixed and stirred for 2 hours at 80°C under a nitrogen stream to obtain a viscous polymer.

Next, add 30 parts of this polymer solution to 60 parts of ion-exchanged water,
5 parts of acrylonitrile, 20 parts of chlorstyrene, 15 parts of methyl acrylate, 0.1 part of ammonium persulfate and 2 parts of sodium lauryl sulfate were mixed and polymerized at 70°C under a nitrogen stream for 3 hours with stirring for 2 hours. It was gradually dripped.

Styrene-
Acrylic acid copolymer ammonium aqueous solution (solid content 30%
) 20 parts, higher alcohol sodium sulfate 0.5 part,
30 parts of ion-exchanged water was added, and the mixture was stirred at room temperature for 1 hour. As a result, a yellow water-based ink with good adhesion was obtained.

The solid content was 23.5% and the viscosity was 5.80 ps.

[Experimental Example 2] In a reaction vessel, 50 parts of monoethylene glycol, 20 parts of ethyl alcohol, 7 parts of Acid Red 52 (trade name: Solar Rodamitsu 81 manufactured by Nippon Kakami Co., Ltd.), and 23 parts of vinylpyridine were added.
0.2 parts of dodecyl mercaptan and 0.15 parts of benzoyl peroxide were mixed and stirred at 90° C. for 3 hours under a nitrogen stream to obtain a viscous polymer.

Next, 40 parts of this polymer solution was mixed with 55 parts of ion-exchanged water,
12 parts of acrylonitrile, 25 parts of butyl methacrylate, 8 parts of ethyl acrylate, 2 parts of polyoxyethylene nonylphenyl ether, 0.5 part of polyoxyethylene lauryl ether sodium sulfate, and 0 parts of potassium persulfate.
．． The two parts were gradually added dropwise over 2 hours into an emulsion polymer tex which had been polymerized at 80° C. for 4 hours under a nitrogen stream while stirring. Thereafter, the temperature was raised to 80°C.

Styrene-
Maleic anhydride copolymer ammonium aqueous solution (solid content 2
5%), 0.3 parts of potassium oleate soap, and 30 parts of ion-exchanged water were added, and the mixture was stirred at room temperature for 1 hour. As a result, a red water-based ink with good adhesion was obtained. The solid content was 22.5% and the viscosity was 6.5 cps.

[Experimental Example 3] 73 parts of propylene glycol and 5 parts of glycerin were added to the reaction vessel.
1 part, Direct Violet 66 (trade name: SpraViolet 5BL Conc, manufactured by Nippon Kayaku ■), 6 parts of sodium methallylsulfonate, and 0.3 part of azobisisobutyronitrile were mixed, and the mixture was heated at 100°C under a nitrogen stream. A viscous polymer was obtained by stirring for 2 hours.

Next, 35 parts of this polymer solution was mixed with 60 parts of ion-exchanged water,
23 parts of methacriconitrile, 7 parts of vinyl acetate, 10 parts of styrene, 1.5 parts of sodium dodecylbenzenesulfonate, 1 part of polyoxyethylene lauryl ether,
0.2 parts of sodium bisulfite and 0.2 parts of hydrogen peroxide.
Two parts of the mixture were mixed and gradually added dropwise over 5 hours into an emulsion polymer latex that had been polymerized at 50'C for 3 hours under a nitrogen stream while stirring.

To 45 parts of the colored resin dispersion thus obtained, 20 parts of an aqueous acrylic ester-acrylic acid copolymer ammonium solution (solid content 30%), 0.5 part of sodium dialkylsulfosuccinate, and 30 parts of ion-exchanged water were added, and the mixture was heated to room temperature. The mixture was stirred for 1 hour. As a result, a purple water-based ink with good adhesion was obtained. The solid content was 22.0% and the viscosity was 4.8 cps.

[Comparative Example 1] The following substances were charged into a reaction vessel in the amounts shown below, and the mixture was stirred at 20° C. for 1 hour to obtain an orange water-based ink.

Styrene-acrylic acid copolymer ammonium aqueous solution (solid content 30%) 20 parts Monoethylene glycol 10 parts Diethylene glycol 5 parts Direct Orange 6 1 part Ion-exchanged water 64 parts [Comparative Example 2] Add the following substances to a reaction vessel. A blue water-based ink was obtained by mixing the mixture in the amounts shown in 1 and stirring at 20° C. for 1 hour.

Styrene-maleic anhydride copolymer ammonium water soluble i
(Solid content 25%) 30 parts Glycerin 10 parts Thiodiglycol 5 parts Basic Blue 3 2 parts Ion exchange water 53 parts The following table shows the water resistance of Experimental Examples 1 to 3 and Comparative Examples 1.2.
The light resistance test results and adhesion quality results are shown.

(The following is a blank space) In the above table, water resistance, light resistance, adhesion, and stability were evaluated as follows.

Water resistance: A sample was coated on Kent paper with bar coater #10, and the coated paper was immersed in water for 1 minute and visually observed to see if the water-based ink had eluted. If there was some elution (including oozing), it was judged as "no elution".

Light resistance: A coated paper similar to that used in the water resistance test was irradiated with a carbon arc fade meter, and the degree of discoloration was confirmed using JISL0841 blue scale grade 8, and evaluated according to the following criteria. Note that the larger the numerical value of the criterion, the better the light resistance.

Judgment Criteria 1: Color change and fading is the same as Blue Scale 1 grade 2: Color change and fading is the same as Blue Scale 2 grade 3: Color change and fading is the same as Blue Scale 3 grade 4: Color change and fading is about the same level as blue scale grade 4. 5: Color change and fading is blue scale grade 5.
6: Color change and fading is the same as Blue Scale 6 grade 7: Color change and fading is the same as Blue Scale 7 grade 8: Color change and fading is the same as Blue Scale 8 grade Adhesion: Sample was coated on a glass plate with bar coater #10, and after drying, it was rubbed with a cotton swab. Those that did not come off at all were evaluated as good, and those that did come off even slightly were evaluated as bad.

Stability: Seal the water-based ink in a container and leave it in a constant temperature bath at 50℃ for three months, and observe whether there are any abnormalities such as the formation of precipitates or changes in viscosity such as thickening. Those in which no abnormality was observed were judged to be good, and those in which abnormalities were observed were judged to be poor.

〔Effect of the invention〕

Although the water-based ink composition of the present invention uses a water-soluble dye, its water resistance, light resistance, and stability over time are much superior to those of conventional compositions. As a result, the range of materials it can be used for is not limited to paper, but also extends to glass, plastic, metal, ceramics, and more. Therefore, the aqueous ink composition of the present invention is expected to find wide application in the future as an aqueous ink for marking pens and the like.

Patent applicant: Mikuni Shiki Co., Ltd.

Claims (1)

[Scope of Claims] 1. A water-based ink composition containing a colored resin dispersion, an alkali-soluble resin, and a surface tension modifier as essential components. 2. The average particle size of the colored resin dispersion colored with the dye is 0.
The aqueous ink composition according to claim 1, which is a polymer dispersion of an ethylenically unsaturated monomer having a diameter of 3 μm or less. 3. The aqueous ink composition according to claim 1, wherein the alkali-soluble resin is a carboxyl group-containing copolymer having an acid value in the range of 30 to 300. 4. The aqueous ink composition according to claim 1, wherein the surface tension modifier is an anionic or nonionic surfactant. 5. The aqueous ink composition according to claim 1, which has a viscosity at 25° C. of 10 cps or less.