JPH0569149B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an aqueous pigment ink composition, and more specifically, an aqueous pigment ink composition comprising a pigment, a dispersant, and an aqueous medium, and further in the presence of a protective colloid. By incorporating a resin dispersion obtained by emulsion polymerization into a water-based pigment ink for writing and recording, it has improved density and gloss during writing, and also has high dispersion stability, storage stability, and writability. Regarding the composition.

(Conventional technology) Conventionally, water-based felt-tip pens, plastic pens,
Water-based inks for writing instruments such as ballpoint pens, felt pens, fountain pens, brushes, and drafting pens, as well as water-based inks for plotters and ink jet recording for information recording terminals, mainly use water-soluble dyes as their pigment components. has been done. However, since it has the drawback of poor physical properties such as light fastness and light fastness, attempts have been made to use pigments with excellent physical properties as pigment components of water-based inks.
Many proposals have been made, such as in Japanese Patent Publication No. 55-35434.

(Problems to be solved by the invention) Pigment water-based inks have the following problems compared to dye-based water-based inks:
Although their superiority in terms of light fastness and water resistance is recognized, on the other hand, dye water-based inks have poor gloss,
It has characteristics that cannot be obtained with pigmented water-based inks, such as jet blackness (only for black), vividness, and density. For water-based inks for writing instruments, the density and gloss when written have a particularly strong impression, so it is essential to improve this point for pigmented water-based inks. It is considered to be closer to a perfect water-based ink for writing instruments.

From this point of view, the present inventors conducted extensive research in order to meet the above-mentioned demands, and as a result, by adding a specific emulsion polymer resin dispersion to an aqueous pigment ink composition,
The present invention was completed based on the finding that the obtained aqueous pigment ink composition could fully meet the above-mentioned needs.

(Means for Solving the Problems) That is, the present invention provides an aqueous pigment ink composition for writing instruments comprising a pigment, a dispersant, a filler, and an aqueous medium, in which the filler is absorbed in the presence of a protective colloid. A water-based pigment ink composition for writing instruments characterized by being a resin dispersion obtained by emulsion polymerization of an oil-based monomer.

To explain the present invention in detail, the pigment used in the present invention can be conventionally known organic and inorganic pigments, such as azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based,
These include organic pigments such as indigo/thioindigo type, perinone/perylene type, isoindorenone type, and azo-methine azo type, and inorganic pigments such as titanium oxide, iron oxide type, and carbon black type.

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

The content of pigment in the aqueous pigment ink composition must be of a sufficient density to enable recording to be written, read, recognized, etc. when used as an ink. Although not particularly specified, the amount preferably accounts for 3 to 30% by weight of the total composition.

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 polymer dispersants consisting of a polymer dispersant, which can be roughly divided into condensation polymers and addition polymers in terms of structure, and any of the existing ones can be used. Preferred examples of condensation-based dispersants include, for example, polyester-based dispersants described in JP-A-60-26070; and addition polymer-based dispersants include:
Examples include addition polymers of monomers having α,β-ethylenically unsaturated groups. Particularly preferred are
Addition polymer based dispersants are obtained from monomers forming the lipophilic portion and monomers forming the hydrophilic portion.

The monomer forming the lipophilic portion of the dispersant is a conventionally known hydrophobic monomer that provides a lipophilic portion to a portion of the polymeric dispersant, such as unsaturated monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, etc. Alkyl esters, cycloalkyl esters, arylalkyls of carboxylic acids
These include esters, aryl esters, and aromatic vinyl compounds. More specifically, for example, acrylic acid, methacrylic acid, itaconic acid,
C1-20 alkyl esters such as maleic acid and fumaric acid, cyclohexyl esters, benzyl esters, phenyl esters, styrene, α
-Methylstyrene, vinyltoluene, etc.

In particular, in the above, an alkyl group having 4 to 16 carbon atoms,
Monomers having a cycloalkyl group, an arylalkyl group, or an aryl group are preferred. The lipophilic portion of such monomers is about 10-93% by weight, preferably 30-90% by weight in the dispersant.

In addition, the hydrophilic moieties in the dispersant include (a) an anionic hydrophilic group and its aqueous medium-soluble salt, (b) a cationic hydrophilic group and its aqueous medium-soluble salt, (c) a nonionic hydrophilic group. or a mixture thereof.

Examples of anionic hydrophilic groups include carboxyl groups, sulfonic acid groups, sulfuric ester groups, phosphoric ester groups, and their alkali metal salts, such as sodium salts, potassium salts, ammonium salts, lower amine salts, for example,
Salts of mono-, di-, or tri-C1-C3 alkylamines, alkanolamines, alkylalkanolamines, morpholines, alkylmorpholines, etc., and calcium salts of sulfonates.

Examples of cationic hydrophilic groups include primary, secondary, and tertiary amino groups, quaternary ammonium groups, and pyridium groups. salts of amino acids, tertiary amino groups, quaternary ammonium groups and their lower fatty acids, such as formic acid, acetic acid, propionic acid salts and inorganic acid salts, such as hydrochlorides, bromates, sulfonates, sulfuric acids Alkyl ester salts, phosphates, etc.

Examples of the nonionic hydrophilic group include a hydroxyl group, a carboxamide group, an ether group, and those having these groups, such as a hydroxyethyl group, a glyceryl group, a polyether glycol group, and a carboxamide group.

Furthermore, examples of monomers forming the above-mentioned hydrophilic portion include (a) anionic ones such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid; monoamide monomers of dibasic acids such as the above-mentioned itaconic acid; Carboxylic acids; hydroxyethyl esters and sulfuric acid esters and phosphoric acid esters of the above-mentioned unsaturated carboxylic acids; sulfoethyl esters and sulfoethylamides of the above-mentioned unsaturated carboxylic acids; styrene sulfonic acid and their solubility in aqueous media as described above It's salt.

Furthermore, monomers having groups that can be converted into the above-mentioned anionic groups after polymer formation, such as monomers having groups such as acid anhydrides and lower alkyl esters, are also used.

(b) Aminocarkanol esters of unsaturated carboxylic acids mentioned in (a) as cationic ones;
N-alkylaminoalkanol ester,
N,N-dialkylaminoalkanol ester, N,N,N-trialkylammonium alkanol ester, γ-amino-β-hydroxy-n-propyl ester, γ-(N-alkylamino)-β-hydroxy-n-propyl Ester, γ-(N,N-dialkylamino)-
β-hydroxy-n-propyl ester, N,
N-dialkylaminoalkylamides and the like and the above-mentioned aqueous medium-soluble salts thereof.

In the above, the alkyl group is preferably a lower alkyl group having 1 to 4 carbon atoms, and the alkanol is preferably a lower alkanol having 2 to 4 carbon atoms.

Furthermore, monomers having a group that can be introduced with a cationic group or converted into a cationic group after forming a polymer can also be used.

(c) Examples of nonionic substances include hydroxyethyl ester, hydroxypropyl ester, polyethylene glycol ester, alkoxypolyethylene oxide ester, glyceryl ester, and carboxamide of the unsaturated carboxylic acids mentioned in (a).

These hydrophilic monomers are used in amounts necessary to substantially dissolve or ultrafinely disperse the polymer dispersant formed in the aqueous medium, and include lipophilic and hydrophilic moieties in the polymer dispersant. The monomer that provides the ionic hydrophilic group has high hydrophilicity, so it can be used in a relatively small amount; Since the monomer providing the hydrophilic group has relatively low hydrophilicity, it is desirable to use it in a relatively large amount.

The preferred specific content of the hydrophilic moiety in the dispersant is as follows: (a) In the case of an anionic hydrophilic moiety, about 5 to 40
% by weight, (b) for cationic hydrophilic moieties, approximately 10-50
% by weight, (c) for nonionic hydrophilic moieties, approximately 20-60
% by weight is preferred.

Incidentally, it is not preferable to include an unnecessarily large amount of a hydrophilic moiety in the dispersant, as this will reduce the water resistance of things written or memorized using the pigment ink composition.

In addition, certain pigments such as carbon black pigment, which is the pigment for black ink most commonly used as writing and recording ink, have strong polarity in an aqueous medium, and the lipophilicity of the dispersant In addition to the pigment adsorption by the cationic part, the cationic monomer (b) above is used in combination with the hydrophilic part in order to firmly fix the dispersant to the pigment surface by the electrical absorption power of the cationic part. It is preferable to use it as a polymer dispersant, and even carbon black pigment, which is usually difficult to disperse and is considered to be a pigment with poor dispersion stability, has significantly improved dispersion stability in ink and provides excellent writability. It is possible to obtain an excellent black pigment ink composition.

The above-mentioned polymer dispersant used in the present invention can be prepared by appropriately mixing the above-mentioned monomers and by any conventionally known mixed polymerization method, such as solution polymerization method, suspension polymerization method, emulsion polymerization method, etc. You can even get it. Known additives such as polymerization regulators may also be used if necessary. As long as the medium used in this case is water or a hydrophilic medium that can be used as an aqueous medium for ink, the polymer solution obtained as is can be used as an ink medium, or the polymer can be removed from solution. It can also be used after being separated and then dissolved again.

The polymer dispersant obtained by polymerization in this way is not particularly defined by its molecular weight, but those having a molecular weight in the range of 1,000 to 100,000 are determined by the polymer content in the solution, solution viscosity, Properties such as viscosity of pigment ink compositions using it,
This is preferable from the viewpoint of quality such as the robustness of recorded matter.

The amount of the dispersant used in the pigment ink composition of the present invention cannot be unconditionally defined because the properties of the pigment differ depending on the type and brand of the pigment, but 3 to 300 parts by weight, preferably about 5 to 100 parts by weight.
It is a proportion of parts by weight. Inorganic pigments have a high density,
The particles are also relatively large and have a relatively small surface area, so a relatively small amount of dispersant is required. Organic pigments have a relatively low density and are often used in fine particles, so they are used in relatively large quantities.

In particular, since carbon black pigment has particularly fine particles, it is particularly preferable to use it in a relatively large amount.

Further, as the aqueous medium constituting the pigment ink composition of the present invention, an aqueous solution of a hydrophilic organic solvent with low volatility or non-volatility is used. For example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, glycerin, diglycerin, methyl carbitol, ethyl carbitol, butyl carbitol, etc. are mixed in a ratio of 5 to 200 parts to 100 parts of water. and dissolved aqueous solutions are preferred.

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

The resin dispersion used as a filler in the present invention is
This is a resin dispersion obtained by emulsion polymerization in the presence of a protective colloid. The resin dispersion consists of a core of colloid particles formed by polymerization of lipophilic monomers and a protective colloid component that stably disperses the core in an aqueous medium.The emulsion polymerization method is carried out according to a known method. It will be done. The component forming the core of the colloidal particles mentioned above is a polymer or copolymer containing a conventionally known lipophilic monomer as a main component, and the lipophilic monomer includes the monomers mentioned in the above-mentioned polymer dispersant. Hydrophilic monomers mentioned in the above-mentioned polymer dispersant may also be used in combination, to the extent that the polymer formed by these monomers does not become water-soluble.

Protective colloid components used during polymerization include:
Although any conventionally known protective colloid can be used, preferred for the purpose of the present invention are polymerization products that become water-soluble upon neutralization, modified products thereof, natural fatty acids or modified products thereof. Of the above, the most preferred are polymerization products that become water-soluble upon neutralization. As such preferable protective colloids, the anionic or cationic polymers mentioned in the above-mentioned polymer dispersants can be used as they are as protective colloids in the present invention.

Examples of modified products of these polymerization products include a hydrolyzate of the methyl acrylate moiety in an acrylic copolymer, and a maleic anhydride adduct of hydroxy methacrylate in the same copolymer. In addition, natural resin acids include rosin, silica resin, etc., and rosin-modified maleic acid resins and the like can be used as modified products thereof.

Conventionally known alkaline agents and acidic agents can be used as neutralizing agents to make the above protective colloids water-soluble. Examples of alkaline agents include sodium hydroxide, potassium hydroxide, ammonia,
Monoethanolamine, diethanolamine, triethanolamine, etc., and acidifying agents include, for example, organic acids such as formic acid, acetic acid, propionic acid, and hydrochloric acid, bromic acid, sulfonic acid, etc.
These include sulfuric acid alkyl esters and phosphoric acid.

An example of a method for producing a resin dispersion in which a polymerization product that becomes water-soluble by neutralization is used as a protective colloid is as follows: First, a protective colloid is obtained by an addition polymerization reaction in a reaction vessel, and an acidic, Alternatively, by neutralizing with an alkaline substance, a water-soluble protective colloid is formed, and the lipophilic monomer that is to become the core of the colloid particles is dropped or dispersed in the reaction system or after being dispersed and redissolved. A resin dispersion is synthesized by emulsion polymerization. Further, when using a protective colloid other than a polymerization product as the protective colloid, the same as above may be used.

Regarding the amount of the resin dispersion added to the water-based pigment ink composition, if it is too small, the effect will be insufficient, and if it is too large, the pigment concentration of the water-based pigment ink composition will decrease. Usually, the amount of resin dispersion (as solid content) is 1 to 500 parts by weight, preferably 10 to 300 parts by weight, per 100 parts by weight of pigment in the ink.

Regarding the method of adding the resin dispersion into the aqueous pigment ink composition, there is a method of adding it at the time of dispersing the pigment into the ink medium, but it is usually added at the final stage of ink production when various additives etc. are added. Good.

As described above, the aqueous pigment ink composition of the present invention, which is obtained by adding a resin dispersion to an aqueous pigment ink composition consisting of a pigment, a dispersant, and an aqueous medium, was used to write, draw, etc. on paper, etc. In some cases, the resin dispersion adheres to the surface of the paper, etc. on the surface where the ink is applied, such as when writing, and as a result, the pigment particles adhere to the surface without penetrating into the inside of the paper, etc., and thus the paper surface is covered with resin and It is thought that because the writing surface is coated with pigment, the glossiness, sharpness, and apparent density of the writing surface are improved.

The aqueous pigment ink composition of the present invention consists of the above-mentioned components and formulations, and various methods can be employed for its production. For example, a typical method is to mix and grind the above-mentioned components using a conventionally known dispersing machine such as a ball mill, homomixer, sand grinder, speed line mill, or roll mill.

(Function/Effect) The aqueous pigment ink composition of the present invention obtained as described above provides recorded matter having gloss and density equivalent to or higher than that of conventional dye aqueous inks. In addition, the quality is stable even under various conditions such as transportation and display even after long-term storage, and virtually no phenomena such as aggregation or sedimentation of pigment particles are observed.

Therefore, it can be stably used as a water-based ink for writing instruments such as felt-tip pens, plastic pens, ballpoint pens, felt pens, fountain pens, calligraphy brushes, drafting pens, plotters for information recording terminals, and inkjet recording.

In addition, it is possible to write well without agglomeration or clogging in the container or in the pen tip, and since it contains a low-volatile or non-volatile hydrophilic organic solvent, the pen tip is smooth. It can be said that it is an ideal water-based ink that does not cause clogging due to drying.

Furthermore, unlike conventional dyes, the dye used is a water-insoluble pigment, so it does not fade at all even with long-term exposure, and does not cause any bleeding or the like even if it gets wet with water after writing.

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

Reference Example 1 100 parts of isopropyl alcohol, 55 parts of styrene, 15 parts of butyl acrylate, 30 parts of methacrylic acid and 3 parts of 2,2'-azobisisobutyronitrile were added to a reaction vessel and polymerized by heating. Furthermore, 50 parts of a 25% potassium hydroxide aqueous solution was added and stirred to obtain an acrylic protective colloid with a resin solid content of 45%.

75 parts of the obtained protective colloid and 160 parts of water were placed in a separate reactor, the temperature was raised, 1 part of potassium persulfate and 100 parts of styrene were added, and a polymerization reaction was carried out, resulting in a polymer with a solid content of 40% and a viscosity of 210 cps/25°C. A stable resin dispersion was obtained.

Reference Example 2 A mixture of 100 parts of xylene, 38 parts of styrene and 62 parts of mono-n-butyl maleate and 1.2 parts of di-t-butyl peroxide were placed in a reaction vessel and polymerized by heating. Xylol was distilled off under reduced pressure to obtain a styrene-maleic acid protective colloid.

The resulting protective colloid 30 parts, water 185 parts and 25
% potassium hydroxide aqueous solution into a reaction vessel,
After heating, 1 part of potassium persulfate, 20 parts of styrene, 50 parts of methyl methacrylate, and 30 parts of butyl acrylate were added to carry out a polymerization reaction to obtain a stable resin dispersion with a solid content of 40% and a viscosity of 185 cps/25°C.

Reference example 3 Commercially available acrylic resin (acid value 200, Tg 80℃) 40
38 parts of 25% potassium hydroxide solution and 196 parts of water
1 part was added and dissolved to form a protective colloid. This protective colloid was charged into a reaction vessel, and after heating, 1 part of potassium persulfate, 20 parts of styrene, and methyl methacrylate were added.
30 parts, 2-hydroxyethyl methacrylate 10
1, 20 parts of 2-ethylhexyl acrylate and 20 parts of butyl acrylate were added to carry out a polymerization reaction to obtain a stable resin dispersion having a solid content of 40% and a viscosity of 180 cps/25°C.

Example 1 A 50% solution of a water-soluble polymer dispersant (isopropyl alcohol of a copolymer consisting of 30 parts methyl methacrylate, 20 parts hydroxyethyl methacrylate, 20 parts butyl acrylate, 15 parts N,N-dimethylaminoethyl methacrylate and 15 parts methacrylic acid) 50 parts and 6 parts of butyl carbitol), 10 parts of carbon black pigment, water
Add 25.0 parts and 2.0 parts of diethanolamine,
The mixture was dispersed in a ball mill for about 20 hours, and 27 parts of ethylene glycol, 20 parts of water, and 10 parts of urea were added so that the pigment concentration was 10%, and the mixture was further dispersed for 30 minutes to obtain a black pigment dispersion.

Next, this pigment dispersion is subjected to an ultracentrifuge,
Poorly dispersed coarse particles were removed, and 30 parts of the resin dispersion obtained in Reference Example 1 and 40 parts of water were added to obtain a uniform black water-based ink. When I set this in a cartridge-type brush pen and tested its writing performance, I found that
The gloss, apparent density, and jet blackness were significantly improved compared to those without the addition of resin dispersion, and the color tone was comparable to that of conventional dye-type products, and the writing quality was smooth.

Example 2 5 parts of a 50% solution of a water-soluble polymer dispersant (a solution of a copolymer consisting of 12.5 parts of ethyl acrylate, 15 parts of butyl methacrylate, 15 parts of styrene and 7.5 parts of methacrylic acid in 35 parts of butyl cellosolve and 15 parts of methyl carbitol) , 10 parts of phthalocyanine pigment, 25.0 parts of water and 0.3 parts of potassium hydroxide were added, dispersed in a paint shaker for 20 hours, 28 parts of ethylene glycol and 23 parts of water were added, and further
Dispersion was carried out for 30 hours to obtain a blue aqueous pigment dispersion.

Next, this dispersion was placed in an ultracentrifuge, and 50 parts of the resin dispersion obtained in Reference Example 2 and 60 parts of water were added to remove poorly dispersed coarse particles, and as a rust preventive agent, benzotriazole 10% ethylene glycol was added. solution
1.0 part was added to obtain a uniformly dispersed blue water-based ink. When 1.5 g of this water-based ink was incorporated into a cotton-filled ballpoint pen and a writing test was conducted, handwriting with gloss and density equal to or higher than conventional dye-based water-based inks was obtained.

Example 3 A condensation ester of highly maleated dehydrated castor oil and fatty acid and a propylene oxide adduct of bisphenol A (see JP-A-60-26070) was added to 6 parts (diethanolamine aqueous solution with a solid content of 50%). , 3.3 parts of diethanolamine, 2.0 parts of ethylene glycol, 3.0 parts of ethylenediaminetetraacetic acid disodium salt, 20.0 parts of water, and 10.0 parts of an insoluble red azo pigment were dispersed in a ball mill for about 20 hours, and ethylene was added so that the pigment concentration was 10%. 21.0 parts of glycol, 19.7 parts of water and 15.0 parts of urea were added, and 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 poorly dispersed coarse particles, and 20 parts of the resin dispersion obtained in Reference Example 3 was added to obtain a uniform red water-based ink. When this was set in a cartridge type brush pen and its writing performance was tested, the same excellent results as in Example 1 were obtained.

Claims (1)

[Scope of Claims] 1. A water-based pigment ink composition for writing instruments comprising a pigment, a dispersant, a filler, and an aqueous medium, wherein the filler is obtained by emulsion polymerization of a lipophilic monomer in the presence of a protective colloid. A water-based pigment ink composition for writing instruments, characterized in that it is a resin dispersion. 2. The aqueous pigment ink composition for writing instruments according to claim 1, wherein the protective colloid is a polymerization product that becomes water-soluble upon neutralization, a modified product thereof, a natural fatty acid, or a modified product thereof. 3. The aqueous pigment ink composition for writing instruments according to claim 1, wherein the protective colloid is an anionic or cationic polymer that becomes water-soluble upon neutralization.