JPH0647662B2 - Aqueous pigment ink for ballpoint pen - Google Patents

Description

TECHNICAL FIELD The present invention relates to an aqueous pigment ink for ballpoint pens. More specifically, the present invention relates to a water-based pigment ink for ballpoint pens that has less ball sinking.

(Prior Art) Conventionally, water-soluble dyes have been used as colorants for water-based inks for ballpoint pens, and in recent years pigments have also been used to improve the water resistance and weather resistance of handwriting. However, such water-based inks for ballpoint pens have the drawback of poor lubricity, and the so-called ball sinking phenomenon occurs in which the ball receiving seat of the ballpoint pen tip is worn during writing and the ball is buried inside the ballpoint pen tip. The result is that writing becomes impossible. In order to solve the above-mentioned drawbacks, for example, Japanese Patent Application Laid-Open No. 61-76577 discloses adding a wax to an aqueous ink composition for a ballpoint pen using a water-soluble dye as a colorant.

(Problems to be Solved by the Invention) However, in the case where a wax and an emulsifier are added to the ink to emulsify or solubilize the wax in the ink as in the above publication, in an ink using a pigment as a colorant,
Wax is adsorbed on the pigment and the dispersion of the pigment becomes unstable, which causes problems such as aggregation of the pigment and increase in ink viscosity, and an ink that solves the ball sinking phenomenon has not been obtained.

Therefore, it is an object of the present invention to provide an aqueous pigment ink for a ballpoint pen using a pigment as a colorant, which does not cause the agglomeration of the pigment or increase in ink viscosity and does not cause the ball sinking phenomenon.

(Means for Solving Problems) The summary of the present invention is a water-based pigment ink for a ballpoint pen comprising at least a pigment, a dispersant comprising a salt of a copolymer of acrylic acid and a hydrophobic monomer, water and a wax emulsion. To do. Hereinafter, the present invention will be described in detail.

The wax emulsion, which is the essence of the present invention, is used to prevent abrasion of the ball seat, and pigment particles can be obtained by adding a wax emulsion previously dispersed in water or a solvent compatible with water to the ink. It is possible to prevent the pigment from adsorbing to the ink, and as a result, it is possible to prevent aggregation of the pigment and increase in the ink viscosity.

The wax emulsion used here is one obtained by dispersing one or more natural waxes such as montan wax, beeswax, carnauba wax, and wood wax, and petroleum waxes such as paraffin wax, polyethylene wax, and microcrystalline wax with an emulsifier. However, 0.1 to 10% by weight is preferably used.

The pigment is used as a colorant, and is an organic pigment such as azo type, anthraquinone type, condensed polyazo type, thioindigo type, metal complex salt type, phthalocyanine type, perinone / perylene type, dioxazine type, quinacridone type, carbon black, One or more of inorganic pigments such as titanium dioxide and iron oxide, metallic powder pigments such as brass powder and aluminum powder, and fluorescent pigments can be used in combination, and the amount used is 3 to 20% by weight. preferable.

As the dispersant, it is necessary to use a salt of a copolymer of acrylic acid and a hydrophobic monomer. This is because good dispersion stability of the pigment is maintained by using the wax emulsion together. Specific examples include salts of styrene / acrylic acid copolymers and salts of acrylic acid ester / acrylic acid copolymers, which can be used alone or in combination of two or more. 0.5 to 20% by weight is preferable with respect to the total amount.

In addition to the above, urea as a nib dry inhibitor,
A water-soluble organic solvent such as a urea derivative or glycols, an anticorrosive agent, an antifungal agent or the like can be appropriately selected and used.

The ink can be adjusted by dispersing the pigment with a commonly known disperser such as a roll mill or a sand mill.
A method of removing coarse particles by filtration, centrifugation, or the like is used, but the addition timing of the wax emulsion is not particularly limited, such as when the pigment is dispersed, after the dispersion is completed, or when the mill base is diluted.

(Operation) The reason why the ball sinking is reduced and the writable distance becomes longer when the ink of the present invention is used is presumed as follows.

When the ink of the present invention is used, the wax emulsion particles are constantly supplied from the ink to the contact surface between the ball and the ball seat in the ball-point pen tip, and the wax emulsion particles are rolled by the writing pressure, so that the ball and the ball receiving part. It is thought to spread like a film between the seats. Since this wax film is interposed between the ball and the ball seat, it reduces the abrasion of the pigment particles having the abrasive action directly on the ball seat, and as a result, the pigment particles cause the ball seat of the ball seat. It is considered that the polishing action is reduced and the ball sinkage is reduced.
Further, a salt of a copolymer of acrylic acid and a hydrophobic monomer is used as a dispersant for the pigment, and the salt of the copolymer of acrylic acid and a hydrophobic monomer does not adversely affect the emulsifier of the wax emulsion. Since it does not affect, the effect of the wax emulsion is not reduced.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples. In the Examples, "part" means "part by weight".

(Example 1) Carbon black (CI 77265) 8.0 parts Sodium salt of butyl acrylate-acrylic acid co-polymer 10.0 parts (weight ratio 40:60) Propylene glycol 10.0 parts Ethylene glycol 20.0 Part Water 49.0 parts John Wax JW26 (Polyethylene Wax Emul 3.0 parts John, manufactured by Johnson Co., Ltd.) (solid content) After mixing the above components and dispersing with a ball mill, coarse particles are removed by centrifugation, A black ink was obtained.

(Example 2) Copper phthalocyanine green 8.0 parts (CI.74160) Propylene glycol 10.0 parts Ethylene glycol 10.0 parts Styrene / acrylic acid copolymer ammonium salt 2.5 parts Water 64.5 parts John Wax JW150 (Polyethylene / paraffin wax emulsion 5.0 parts, manufactured by Johnson Co., Ltd.) (Solid content) After the above components were mixed and dispersed in a sand mill, coarse particles were removed by centrifugation to obtain a green ink. .

(Comparative Example 1) A black ink was obtained in the same manner as in Example 1 except that John Wax JW26 was removed from Example 1 and water was added.

(Comparative Example 2) A green ink was obtained in the same manner as in Example 2 except that John Wax JW150 was removed from Example 2 and water was added.

(Effects of the Invention) The inks obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are filled in a writing instrument having a ballpoint pen tip combining a SUS430 ballpoint pen tip and a cemented carbide ball having a diameter of 0.6 mm. Table 1 shows the results of testing the writable distance and the ball sinkage.

As described above, the water-based pigment ink for a ball-point pen of the present invention is a water-based pigment ink suitable for a ball-point pen, in which the ball seat is less worn when the ball rotates during writing and the writing distance is long.

Claims (1)

[Claims] 1. An aqueous pigment ink for a ballpoint pen comprising at least a pigment, a dispersant comprising a salt of a copolymer of acrylic acid and a hydrophobic monomer, water and a wax emulsion.