JPH05163454A - Aqueous pigment ink composition - Google Patents

Abstract

(57) [Summary] [Constitution] Ten solid emulsion particles having a glass transition temperature of 50 ° C. or more and having a particle diameter in the range of 0.2 to 1.5 μm are prepared.
An aqueous pigment ink composition containing 0 part by weight and 20 to 150 parts by weight of an inorganic pigment, and the total amount of the particles and the inorganic pigment is 30 to 70% by weight. The water-based pigment ink composition of the present invention has a hiding power,
It has an excellent balance of pigment dispersion stability, writing properties, and drying properties, and can be used for various writing surfaces and writing tools.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment ink composition, and more particularly to an aqueous pigment ink composition having an excellent balance of hiding power, pigment dispersion stability, writability, and drying property.

[0002]

2. Description of the Related Art In recent years, whiteboards have been widely used in offices and the like in place of conventional blackboards. Further, recently, for the purpose of giving interior properties to the writing board, the color of the writing surface is changing from conventional white to various colors.

As described above, when the writing surface is a color other than white, particularly black or dark green, the titanium dioxide-based white pigment used in conventional water-based felt-tip pens and water-based felt-tip pens is used. Used for hiding power.

However, such an inorganic pigment-based ink has a problem that the writing surface is damaged, and further, separation of titanium oxide, sedimentation and clogging at the pen tip. In view of such circumstances, a new water-based white ink having a hiding power is desired.

JP-A-1-174576 and JP-A-3-157466 exemplify a novel aqueous ink that solves the above-mentioned problems, in which hollow particles having voids inside the particles are used as a masking agent. ing. Certainly, it has less hiding power than titanium dioxide, but some problems such as separation and sedimentation have been solved.

However, the hiding power of the hollow particles used in the present invention is exerted when the water inside the particles is completely volatilized and voids are formed inside the particles, and the hiding power is normally used. It takes time to develop strength. This causes a fatal defect that the characters cannot be read unless it is written for a while, especially when the characters are written on the above-mentioned color board surface, greatly limiting the range of use of the water-based ink. Will end up.

In order to solve the above problems, a method of increasing the drying rate of the water-based ink is required, and 1) the concentration of hollow particles in the water-based ink is increased, and 2) the water-soluble ink is added to accelerate the evaporation of water. A method of adding an organic solvent can be considered.

However, in the former method, the concentration of the hollow particles is limited, and it is practically difficult. Also,
In the latter method, it is usually considered to add ethylene glycol or the like having a high boiling point, but since such a solvent is easily absorbed in the voids inside the hollow particles, the solvent remains inside the particles, which rather reduces the hiding power. Will bring results.

[0009]

In view of the above problems, the present invention is to provide an aqueous pigment ink composition having an excellent balance of hiding power, pigment dispersion stability, writability, and drying property.

[0010]

As a result of intensive studies to solve the above problems, a water-based pigment ink composition containing a solid emulsion particle having no voids and an inorganic pigment as a white pigment in a specific mixing ratio. They have found that the product is excellent in the balance of hiding power, pigment dispersion stability, writability, and drying property, and have completed the present invention.

That is, in the present invention, the particle size is 0.2 to 1.5.
100 parts by weight of solid emulsion particles having a glass transition temperature of 50 ° C. or more in the range of μ and 20 parts of an inorganic pigment
˜150 parts by weight, and the total amount of the particles and the inorganic pigment is 30
It is an aqueous pigment ink composition characterized by being -70 weight%.

The solid emulsion particles contained in the aqueous pigment ink composition of the present invention can be prepared by ordinary emulsion polymerization. Since the emulsion particles are used as a masking agent, the particle size is It is preferable to control, and it is particularly preferable to prepare by a so-called seed emulsion polymerization method using seed particles having a defined particle size. Also, according to this preparation method, large particles which are difficult to obtain by one-step polymerization can be easily prepared.

The vinyl monomers used here include aromatic vinyl monomers such as styrene, α-methylstyrene and vinyltoluene, methacrylic acid esters such as methyl methacrylate and butyl methacrylate, and acrylic. Acrylic esters such as ethyl acrylate and butyl acrylate, vinyl esters such as vinyl acetate, vinyl cyan compounds such as acrylonitrile and methacrylonitrile, vinyl halide compounds such as vinyl chloride and vinylidene chloride, and dienes such as butadiene. Examples thereof include system compounds, and one or a combination of two or more selected from them is used.

The composition of the solid emulsion particles of the present invention is not particularly limited, but it is preferable that the refractive index is high for the purpose of increasing the hiding power, and styrene is used from the viewpoint of the glass transition temperature. Preferably.

Further, a crosslinkable vinyl monomer such as divinylbenzene, ethylene glycol (meth) acrylate or trimethylolpropane tri (meth) acrylate can be used in combination with the above vinyl monomer.
Here, the amount of the crosslinkable vinyl monomer used is usually 0.
It is 1 to 10% by weight.

Further, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and itaconic acid, unsaturated sulfonates such as sodium styrenesulfonate, (meth) acrylic acid esters such as 2-hydroxyethyl (meth) acrylate, Functionalized vinyl monomers such as (meth) acrylamides and (meth) acrylamides such as N-methylol (meth) acrylamide are used for the purpose of imparting stability to emulsion particles. Here, the amount of the functional vinyl monomer used is usually 0.1 to 10% by weight.

The surfactant used may be any of those used in ordinary emulsion polymerization, such as sodium alkylbenzenesulfonate, sodium alkylsulfate, sodium dialkylsulfosuccinate, and anionic system such as naphthalenesulfonate formalin condensate. Surfactants, polyoxyethylene alkyl ethers, polyoxyethylene phenyl ethers, ethylene oxide-propylene oxide block copolymers, nonionic surfactants such as sorbitan fatty acid ester, and the like can be exemplified, and they are independent. Or in combination. Here, the amount of the surfactant used is not particularly limited, but is usually about 0.1 to 10% by weight based on the total amount of the vinyl monomer.

As the polymerization initiator, any of those used in ordinary emulsion polymerization may be used as in the case of the surfactant, and examples thereof include persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, and benzoyl peroxide. Examples thereof include organic peroxides such as and azo compounds such as azobisisobutyronitrile. Also, if necessary, it can be used as a redox initiator in combination with a reducing agent.

The polymerization is carried out at a polymerization temperature of 20-9 under a nitrogen purge.
At 0 ° C., the mixture of the vinyl monomers is dropped all at once, dividedly, or continuously. The solid emulsion particles thus prepared have a particle size of 0.2 to 1.5 μm, preferably 0.3 to 1.0 μm, and more preferably 0.4 to 0.8 μm. Here, if the particle size is less than 0.2 μm, the hiding power is inferior, so that it is necessary to mix a large amount of the inorganic pigment, which is outside the scope of the present invention.
On the other hand, when the particle size exceeds 1.5 μ, the dispersion stability as a pigment is lowered, and the tip of a felt pen or the like is likely to be clogged, which is not practical. The glass transition temperature of the resin that constitutes the solid emulsion particles is 50 ° C.
However, it is preferably 80 ° C. or higher. Here, when the glass transition temperature is lower than 50 ° C., the hiding power is lowered because some particles are fused together depending on the temperature environment used.

The solid content concentration of the prepared solid emulsion particles is usually 40 to 60% by weight for the purpose of increasing the solid content concentration of the aqueous pigment ink composition described later.

As the inorganic pigment mixed with the solid emulsion particles, titanium dioxide, calcium carbonate,
Clay, talc, etc. are not particularly limited, but since the inorganic pigment is added for the purpose of improving the solid content and assisting the hiding power of the aqueous pigment ink composition of the present invention, titanium dioxide is used as the inorganic pigment. Preference is given to using. The mixing ratio of the solid emulsion particles and the inorganic pigment is 20 to 150 parts by weight, preferably 50 to 120 parts by weight, based on 100 parts by weight of the solid emulsion particles. Here, the amount of the inorganic pigment is 20
If the amount is less than parts by weight, the intended water-based pigment ink composition cannot be obtained because the hiding power is not assisted and the solid content of the ink is not sufficiently increased. On the other hand, it is not practical to use more than 150 parts by weight because pigment precipitation in the ink and the writing surface are easily damaged.

The solid emulsion particles and the inorganic pigment selected as described above are contained in the water-based pigment ink composition of the present invention. The total amount of the particles and the inorganic pigment is 30 in the ink composition. ˜70 wt%, preferably 40-70 wt%. When the solid content concentration of this ink composition is less than 30% by weight, the drying property of the ink is lowered, which is contrary to the purpose of this study. On the other hand, when it exceeds 70% by weight, the fluidity of the ink is extremely deteriorated, and the pen tip is apt to be clogged,
Writability is also reduced.

The method for preparing the water-based ink composition of the present invention is not particularly limited, but generally, after the dispersant for the inorganic pigment is added to the solid particle emulsion, the inorganic pigment is stirred while stirring. It is prepared by gradually adding. here,
Examples of the dispersant include sodium polyacrylate and the like, but are not particularly limited.

If desired, a binder for adhering the above pigment may be added to the aqueous pigment ink composition.

As the binder which can be added, water-soluble binders such as polyvinyl alcohol and hydroxyethyl cellulose, and water-based emulsions such as styrene-butadiene latex and acrylic emulsion are used alone or in combination, and usually 100 parts by weight of the pigment are used. Two
It is used in an amount of 0 parts by weight or less. Further, if necessary, a water-soluble organic solvent such as alcohols such as ethyl alcohol and isopropyl alcohol, glycols such as ethylene glycol and propylene glycol, etc. is added to the water-based pigment ink composition for the purpose of improving the drying rate. However, the amount of addition is 100
It is 20 parts by weight or less with respect to parts by weight. In addition, dyes, leveling agents, preservatives and the like may be added to the aqueous pigment ink composition, if necessary.

[0026]

EXAMPLES Specific examples of the present invention will be shown below, but the present invention is not limited to these examples. The following parts and% indicate parts by weight and% by weight, respectively, and the particle size and glass transition temperature (Tg) were measured by an electron microscope and a differential scanning calorimeter (DSC), respectively.

[I] Preparation of Solid Emulsion Particles Polymerization Example 1 A separable flask equipped with a stirrer, a thermometer, and a reflux condenser is charged with 500 parts of water, and the temperature is raised to 75 ° C. while substituting with nitrogen. After keeping the internal temperature at 75 ° C. and adding 4 parts of potassium persulfate as a polymerization initiator to completely dissolve it, 300 parts of water and 1.6 parts of sodium lauryl sulfate were previously prepared.
768 parts of styrene, 16 parts of methacrylic acid, and 16 parts of 2-hydroxyethyl methacrylate were added to the mixture under stirring, and 0.5% of the total amount of the emulsion prepared was charged in a separable flask and polymerized for 30 minutes. Then, the remaining emulsion is about 3
After adding and polymerizing over a period of time and adding the entire amount, 80 ° C
The temperature was raised to aging and aged for 2 hours. After the completion, the pH was adjusted to 8 with aqueous ammonia to obtain solid emulsion particles having a solid content of 49%, Tg of 105 ° C. and a particle diameter of 0.25 μ.

Polymerization Example 2 The emulsion obtained in Polymerization Example 1 was charged in the same separable flask as in Polymerization Example 1 with 168.3 parts and 530 parts of water, and the temperature was raised to 75 ° C. while substituting with nitrogen. Next, at this temperature, 4 parts of ammonium persulfate was added to 40 parts of water at this temperature, and the dissolved initiator aqueous solution was added thereto.
00 parts, 3.2 parts of sodium lauryl sulfate and 7 parts of styrene
The emulsion prepared by adding 68 parts, 16 parts of methacrylic acid and 16 parts of 2-hydroxyethyl methacrylate under stirring was added and polymerized for about 3 hours. After adding the whole amount,
The temperature was raised to 80 ° C. and aging was carried out for 2 hours. After the completion, pH was adjusted to 8 with aqueous ammonia, solid content 48%, Tg10
Solid emulsion particles having a particle diameter of 0.54μ at 3 ° C. were obtained.

Polymerization Example 3 The emulsion obtained in Polymerization Example 1 was charged in the same separable flask as in Polymerization Example 1 with 33.3 parts of water and 700 parts of water, and the temperature was raised to 75 ° C. under nitrogen with stirring. Next, at this temperature, an initiator aqueous solution prepared by dissolving 4 parts of ammonium persulfate in 40 parts of water was added, and 300 parts of water, 3.2 parts of sodium lauryl sulfate, 768 parts of styrene, 16 parts of methacrylic acid and 16 parts of 2-hydroxyethyl methacrylate were previously added. The emulsion was added and polymerized under stirring for about 3 hours. After the total amount was added, the temperature was raised to 80 ° C. and aging was carried out for 2 hours. After completion, p with ammonia water
It was adjusted to H8 to obtain solid emulsion particles having a solid content of 43%, Tg of 102 ° C. and a particle diameter of 0.90 μ.

Polymerization Example 4 By repeating the same method as in Polymerization Example 2 except that 64.1 parts of the emulsion obtained in Polymerization Example 2 was charged in the same separable flask as in Polymerization Example 1 and 840 parts of water,
Solid emulsion particles having a solid content of 40%, a Tg of 102 ° C. and a particle diameter of 1.62 μm were obtained.

Polymerization Example 5 In Polymerization Example 1, 770 parts of water was added to a separable flask.
Polymerization Example 1 except that 8 parts of sodium lauryl sulfate was charged.
Polymerization was carried out by the same method as above, solid content 43%, Tg1
Solid solid emulsion particles having a particle diameter of 0.09μ at 05 ° C. were obtained.

Polymerization Example 6 In Polymerization Example 1, the vinyl monomer composition was styrene 48.
Polymerization was carried out by changing to 0 part, butyl acrylate 304 parts and methacrylic acid 16 parts to obtain solid emulsion particles having a solid content of 49%, Tg of 25 ° C. and a particle diameter of 0.21 μm.

[II] Preparation of Aqueous Pigment Ink Next, an example of preparation of an aqueous pigment ink using the emulsion particles prepared by the above polymerization example will be shown. Examples 1 to 20 20 parts (solid content; 100 parts) of the emulsion prepared in Polymerization Example 1 was added with 1 part of a 40% sodium polycarboxylate aqueous solution (Aaron T-40 manufactured by Toagosei Kagaku), and a defoaming agent 0. 0.04 part (manufactured by San Nopco, Nopco 8034L) was added, and titanium dioxide 100 was added while stirring with a mixer.
Part (manufactured by Ishihara Sangyo, Taipaque R-830) was gradually added and completely dispersed to prepare a solid emulsion particle prepared in Example 1 and similarly in Polymerization Examples 2 and 3. The cases are shown in Table 1 as Examples 2 and 3, respectively.

Comparative Examples 1 to 3 Water-based pigment inks prepared by using the solid emulsion particles prepared in Polymerization Examples 4, 5 and 6 in the same manner as in Example 1 were respectively prepared in Comparative Examples 1 and 2. And 3 are shown in Table-1.

Examples 4 to 6 In Example 2, 150 parts of water was added to lower the solid concentration of the ink, and in Example 4 and Example 1, the amount of titanium dioxide added was 50 parts. In Example 5 and in Example 3, the amount of titanium dioxide added was 130
The case where the parts are included is Example 6 and is shown in Table 1.

Examples 7 to 8 In Example 7, the case where 200 parts by weight of a 10% aqueous polyvinyl alcohol solution (manufactured by Kuraray, 217) was added as a binder in Example 2 was added to 35 parts of ethylene glycol in Examples 7 and 2. Table 8 shows the case as Example 8.
Shown in 1.

Comparative Examples 4 to 5 In Example 1, the case where the amount of titanium dioxide added was 200 parts was compared with Comparative Example 4, and in Example 2, the case where water was added to make the solid content concentration 25% is compared. Example 5 and Table-1
Shown in.

A commercially available felt-tip pen was filled with the water-based pigment ink composition prepared as described above, and the writing performance when writing on a vertically darkened green board, the drying property of the ink, and the writing time of 5 seconds. The hiding power afterward was divided into the following four stages and visually judged: ⊙: very good, ∘: good, Δ: slightly bad, ×: bad The results are also shown in Table 1.

[0039]

[Table 1]

[0040]

The water-based pigment ink composition of the present invention has an excellent balance of hiding power, writability and drying property, and can be used for various writing surfaces and writing utensils.

Claims (4)

[Claims] 1. Containing 100 parts by weight of solid emulsion particles having a glass transition temperature of 50 ° C. or more and a particle size of 0.2 to 1.5 μm, and 20 to 150 parts by weight of an inorganic pigment, A water-based pigment ink composition, wherein the total amount of the particles and the inorganic pigment is 30 to 70% by weight. 2. The solid emulsion particles have a particle size of 0.3.
The water-based pigment ink composition according to claim 1, wherein 3. The aqueous pigment ink composition according to claim 1, wherein the solid emulsion particles are polystyrene particles. 4. The aqueous pigment ink composition according to claim 1, wherein the inorganic pigment is titanium dioxide.