JPS6397670A - Pastel ink composition for writing utensil - Google Patents

Abstract

PURPOSE:To provide the title compsn. having excellent long-term storage stability, containing a color pigment, a dispersant, an aq. medium and specified white resin particles. CONSTITUTION:0.5-30wt% color pigment, pref. org. pigment (A), is blended with 3-300pts.wt. (per 100pts.wt. component A) dispersant (B) having an MW of 1,000-100,000, pref. addition polymer type dispersant obtd. from a monomer forming a lipophilic moiety and a monomer forming a hydrophilic moiety, an aq. medium (C) which is an aq. soln. of a hydrophilic org. solvent, white resin particles (D) which are insoluble in the component C, do not form any film and have a particle size of 0.1-1.0mum and a refractive index of 1.4-1.6 (e.g., PS particles) and optionally, a water-soluble resin (E).

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a pastel-like ink composition for writing instruments, and more specifically, to an ink composition for writing instruments comprising a pigment, a dispersant, and an aqueous medium, The present invention relates to an ink composition for a pastel-like writing instrument that provides a pastel-like writing image by containing insoluble white resin particles in a medium.

(Prior art) Conventionally, water-based inks for writing instruments such as water-based sign pens, plastic pens, ballpoint pens, felt pens, fountain pens, brushes, and drafting pens have mainly used water-soluble dyes as pigment components. There is. However, written images produced using these dye inks have the disadvantage of poor physical properties such as water resistance and light resistance. Many proposals have been made, such as in Publication No. 55-35434.

(Interlayer points that the invention seeks to solve) Pigment water-based inks are recognized to have superiority over dye-based water-based inks in terms of light fastness, water resistance, etc., but in the case of such pigment inks, If you try to increase the pigment concentration to increase the density when writing, there is a problem that the stability of the ink decreases and the pen tip becomes clogged, making it unusable. Therefore, a pigment ink with a high concentration is obtained. I can't.

In addition, in order to increase the hiding power of written letters or make the letters pastel-like, when used in conjunction with a white inorganic pigment such as titanium oxide, which has a high hiding power and is commonly used in the colorant field,
These white pigments have a higher specific gravity than chromatic pigments, so white inorganic pigments separate and settle during ink storage or use, creating a hard cake, which is why they are often used as inks for writing instruments. There is a problem.

From this point of view, the present inventors have conducted extensive research in order to meet the above-mentioned needs, and have found that by adding white resin particles with a small specific gravity to a pigment ink composition for writing instruments, the resulting ink composition for writing instruments can have a high pastel tone. The present invention was completed based on the findings that the above-mentioned needs could be fully met.

(Means for Solving the Problems) That is, the present invention provides a pastel-like water-based ink composition comprising a chromatic pigment, a dispersant, and an aqueous medium, further containing white resin particles. It is a pigment ink composition.

To explain the present invention in detail, the chromatic pigment used in the present invention is preferably a conventionally known organic pigment, such as an azo type, a phthalocyanine type, a quinacridone type, an anthraquinone type, a dioxazine type, or an indigo/thioindigo type. , perinone/perylene type, isoindorenone type, azo-methine azo type, etc. Fluorescent plastic pigments such as resin particles colored with fluorescent dyes can also be preferably used.

These chromatic pigments can be used either in powder form or in the form of an aqueous paste such as a filter cake, but from the viewpoint of ease of dispersion, it is preferable to use an aqueous paste.

The pigment content in the ink composition needs to be deep enough to sufficiently distinguish the written image, and is not particularly defined, but is preferably 0.5 to 3 in the total amount of the composition.
This amount accounts for 0% by weight.

As the dispersant used in the present invention, any conventionally known pigment dispersant can be used, but particularly preferred are polymer dispersants. Particularly suitable are polymeric dispersants consisting of the following parts:

Such polymer dispersants can be roughly divided into condensation polymers and addition polymers in terms of structure, and any of the existing ones can be used, but condensation polymers are preferable, such as special polymers. There is a polyester dispersant described in JP-A-60-26070, and addition polymer dispersants include addition polymers of monomers having α,β-ethylenically unsaturated groups.

Particularly preferred are addition polymer based dispersants, which are derived from monomers forming the lipophilic portion and monomers forming the hydrophilic portion.

The above-mentioned addition polymer-based polymer dispersant can be prepared by appropriately mixing hydrophilic and lipophilic polymers, and by any conventional mixed polymerization method such as solution polymerization, suspension polymerization, emulsion polymerization, etc. It can also be obtained by a polymerization method. Known additives such as polymerization regulators may also be used if necessary. As long as the polymerization medium used at that time is water or a hydrophilic solvent that can be used as an aqueous medium for ink, the polymerization liquid obtained as is can be used as an ink medium, or the polymer can be used as a solution. It can also be used by dissolving it again after separating it from the water.

The polymer dispersant obtained by polymerization in this way is not particularly defined by its molecular weight, but it has a molecular weight of 1,000
Those having a molecular weight in the range of 0 to io0.000 are preferable from the viewpoint of polymer content in the solution, solution viscosity, properties such as viscosity of the pigment ink composition using the same, and quality such as the fastness of recorded materials. It is something.

The amount of the dispersant used in the ink composition of the present invention cannot be generally specified, since the properties of the pigment vary depending on the type and brand of the pigment, but the amount to be used is based on 100 parts by weight of the pigment. On the other hand, about 3 to 300 parts by weight,
Preferably the proportion is about 5 to Zoo parts by weight.

Further, as the aqueous medium constituting the pigment ink composition of the present invention, an aqueous solution of a hydrophilic organic solvent is used. For example, methanol, ethanol, propatool, butanol, ethylene glycol, ethyl cellosolve, butyl cellosolve, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, glycerin, diglycerin, methyl calpitol, ethyl calpitol, butyl calpitol, etc. An aqueous solution mixed and dissolved in a ratio of 5 to 200 parts to 100 parts of water is preferred.

The resin particles used in the present invention are insoluble in the ink medium, do not form a film, and have a particle size of 0.1 to 10μ.
It is a white resin particle with a refractive index of 1.4 to 1.6 and a relatively uniform particle size, and is generally called a plastic pigment.

Such resin particles include polystyrene, polymethyl methacrylate, polyvinyl chloride, benzoguanamine resin, epoxy resin, or those obtained by emulzidine polymerization or suspension polymerization of α,β-monoethylenically unsaturated monomers. can be mentioned.

The resin particles in the present invention must be able to diffuse light and appear white depending on their refractive index and particle size. Therefore, the resin particles have a particle size of 0.1 to 1. It needs to be in the range of 1.4 to 1.6.

Therefore, the maximum light diffusion value (the range that appears whitest) and the particle size of each resin particle are closely related (for example, the particle size range showing the maximum light diffusion value of polystyrene particles is 0.4 to 0.0.
6 μm, similarly polymethyl methacrylate particles range from 0.6 to 0.9 μm, and polyvinyl chloride particles range from 0.5 to 0.7 μm.

By adding resin particles that appear white alone as described above into a pigment ink containing a chromatic pigment as described above, the resulting ink becomes a chromatic pastel color tone with extremely high light reflectance. The characters and images formed by this process take on a striking pastel tone.

Of course, such a pastel tone can be obtained by adding a conventionally known white inorganic pigment such as titanium oxide, but
As already mentioned, when such a white inorganic pigment is added, the ink itself becomes unusable for writing instruments.

In contrast, in the present invention, the white resin particles as described above have a significantly lower specific gravity than the inorganic white pigment, so they do not separate from the chromatic pigments present in the ink and can maintain a stable dispersion state. It is capable of maintaining sufficient dispersion stability as an ink for writing instruments.

Containment of the resin particles in the ink composition of the present invention (1)
Too little will give you a nice pastel tone, while
If too much, the resulting image becomes too whitish, so the preferred range is 3 to 30 Hf (amount percentage) in the ink.

In the present invention, the above-mentioned polymer dispersant can be used as it is as a binder for the white resin particles in the ink, but if the polymer dispersant alone is insufficient as a binder and the abrasion resistance of written materials is insufficient, Furthermore, other water-soluble resins can be added as necessary. Examples of such water-soluble resins include alkali metal resins such as acrylic resins, styrene-maleic anhydride resins, maleated oils, maleated polybutadiene, maleated alkyd resins, maleated petroleum resins, maleated rosin esters, and polyvinylpyrrolidone. , ammonia, amine salts, etc. are preferred, and are used in amounts that do not excessively increase the viscosity of the ink.

Furthermore, conventionally known additives, humectants, rust preventives, preservatives, dispersants, lubricants, etc. may be added as necessary.

The ink composition for pastel writing instruments of the present invention consists of the above-mentioned components and formulations, and various methods can be employed for its production. For example, the above-mentioned components may be mixed and ground using a conventional dispersion machine such as a ball mill, homomixer, sand grinder, speed line mill, or roll mill, or a dispersion of a pigment dispersion and resin particles may be prepared in advance. A typical method is to prepare the two separately and mix the two in an appropriate ratio.

(Action/Effect) The ink composition for pastel writing instruments of the present invention obtained as described above has stable quality even when stored for a long period of time and under various conditions such as transportation and display. can be,
Substantially no phenomenon of aggregation or sedimentation of pigment particles or resin particles is observed.

Therefore, it is stably used as a water-based ink for writing instruments such as sign pens, plastic pens, ballpoint pens, felt pens, fountain pens, brushes, and drafting pens, and can provide extremely excellent pastel-like letters and images.

In addition, those that allow good writing without agglomeration or clogging in the container or the pen tip, and that contain a low-volatile or non-volatile hydrophilic organic solvent, are suitable for pens. It can be said that it is an ideal water-based ink that does not cause clogging due to drying of the tip.

Furthermore, unlike conventional dyes, the pigment used is a water-insoluble pigment, so it does not fade at all even with long-term exposure.
Even when writing gets wet, it does not bleed or bleed at all.

Next, the present invention will be specifically explained with reference to Examples. In addition,
In the text, parts and % represent ff1ffi.

Example 1 A 50% solution of water-soluble polymer dispersants (30 parts methyl methacrylate, 20 parts hydroxyethyl methacrylate,
20 parts of butyl acrylate, N.

6 parts of a solution of a copolymer of 15 parts of N-dimethylaminoethyl methacrylate and 15 parts of methacrylic acid in 50 parts of isopropyl alcohol and 50 parts of butylcarpitol, 10 parts of an azo yellow pigment, 55 parts of water, and 2 parts of jetanolamine. 0 part and polystyrene plastic pigment (manufactured by Asahi Dow, 50% aqueous dispersion, particle size 0)
．． 5 μm, refractive index 1.59), and dispersed in a ball mill for about 20 hours. Added 10 parts of ethanol, 10 parts of butyl cellosolve, 27 parts of water, and 10 parts of urea so that the pigment concentration was 7.5%. The mixture was further dispersed for 30 minutes to obtain a yellow pigment dispersion.

Next, this pigment dispersion was subjected to an ultracentrifuge to remove poorly dispersed coarse particles to obtain a uniform yellow water-based ink. When I set this on a signboard and tested the writing ability,
Compared to the one without the addition of resin particles, it exhibited a marked pastel yellow color and had a smooth writing feel.

Example 2 50% solution of water-soluble polymer dispersant (12.5 parts of ethyl acrylate, 15 parts of butyl methacrylate, 1 part of styrene)
35 parts of a copolymer of butyl cellosolve and 15 parts of methylcarpitol, consisting of 5 parts and 7.5 parts of methacrylic acid.
solution) to 5 parts, 10 parts of phthalocyanine blue pigment,
25.0 parts of water, 0.3 parts of potassium hydroxide, and polymethyl methacrylate resin particles (manufactured by Soken Chemical Co., Ltd., MP-100)
0, refractive index 1.49.20% aqueous dispersion) was added,
Dispersed in paint shaker for 20 hours, butanol 10
18 parts of ethylene glycol and 83 parts of water were added, and the mixture was further dispersed for 30 hours to obtain a blue aqueous pigment dispersion.

Next, this dispersion liquid was applied to an ultracentrifuge to remove poorly dispersed coarse particles, and benzotriazole 10 was added as a rust preventive agent.
% ethylene glycol solution was added to obtain a uniformly dispersed pastel blue water-based ink. When 1.5 g of this water-based ink was incorporated into an internal ballpoint pen and a writing test was conducted, a blue line image with a significantly more pastel tone was formed compared to a pen without resin particles.

Example 3 Dehydration and condensation esterification of mustard oil fatty acid with high maleic ratio and propylene oxide adduct of bisphenol A (see JP-A-60-26070) 6 parts (jetanolamine aqueous solution with solid content of 50%) , 3.3 parts of jetanolamine, 2.0 parts of ethylene glycol, 3.0 parts of ethylenediaminetetraacetic acid disodium salt, and 20 parts of water.
．． θ part and 10.0 parts of an insoluble red azo pigment were added, and dispersed in a ball mill for about 20 hours. Then, 21.0 parts of ethylene glycol, 19.7 parts of water, and 15.0 parts of urea were added so that the pigment concentration was 10%. In addition, the mixture was further dispersed for 30 minutes to obtain a red aqueous pigment dispersion.

Next, this dispersion was subjected to an ultracentrifuge to remove coarse particles with poor dispersion.
P-83000. Particle size 0.5μm, refractive index! , 5.3
80 parts of the aqueous dispersion) were added to No. 04 to obtain a uniform pastel red water-based ink. When this was set in a cartridge-type brush pen and its writing performance was tested, line images with a significantly superior pastel tone were obtained compared to those without resin particles.

Example 4 In place of the azo pigment in Example 3, a fluorescent pink pigment (
SP-17, manufactured by Shinroihi, 50% solids water dispersion) 8
A uniform pastel-like fluorescent pink water-based ink was obtained in the same manner as in Example 3 except that 0 part was used. When this was set in a cartridge-type brush pen and its writing performance was tested, line images with a significantly superior pastel tone were obtained compared to those without resin particles.

Claims (5)

[Claims] (1) A pastel-like aqueous pigment ink composition, which is characterized in that an ink composition for a writing instrument comprising a chromatic pigment, a dispersant, and an aqueous medium further contains white resin particles. (2) The ink composition for pastel-like writing instruments according to claim (1), wherein the resin particles have a particle size of 0.1 to 1.0 μm. (3) The ink composition for a pastel-like writing instrument according to claim (1), wherein the resin particles have a refractive index of 1.4 to 1.6. (4) The pastel-like ink composition for writing instruments according to claim (1), wherein the chromatic pigment is an organic pigment. (5) Claim No. 1 further containing a water-soluble resin
) The ink composition for pastel writing instruments as described in item 1.