JPH03157466A - White, water-based ink composition for writing utensil - Google Patents

Abstract

PURPOSE:To provide the title composition stable in quality even if stored for a long period, having excellent whiteness, opacifying power and dispersion stability, thus useful for marking pens, ball-point pens, felt tipped pens, etc., comprising white hollow resin granules, water-soluble resin and aqueous medium. CONSTITUTION:The objective composition comprising (A) pref. 3-40wt.% of white hollow resin granules (pref. 0.1-1.0mum in size and inner pore size being 20-90% of the outer diameter), (B) a water-soluble resin (pref. polyester dispersant, alpha,beta-ethylenic unsaturated group-contg. monomer-added polymer), and (C) an aqueous medium [e.g. an aqueous solution prepared by mixing 100 pts.wt. of water with 5-200 pts.wt. of methanol or ethylene glycol, etc.].

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an ink composition for writing instruments, more specifically, it is composed of white hollow resin particles, a water-soluble resin, and an aqueous medium, and has excellent whiteness, hiding power, and dispersion. The present invention relates to a stable white ink composition for writing instruments.

(Prior art and its problems) Conventionally, various chromatic water-based inks have been used for writing instruments such as water-based felt-tip pens, plastic pens, and felt-tip pens. For dark colors, white water-based inks containing white inorganic pigments are used.

Titanium oxide pigments are mainly used as the white inorganic pigments used in the above white ink, but since these white inorganic pigments have a high specific gravity, if the pigment content is increased, the white inorganic pigments will separate. It cannot be used as a water-based ink for writing instruments because it settles and clogs the pen tip. In addition, separation and sedimentation of the pigment can be prevented to some extent by increasing the viscosity of the ink, but water-based inks with high viscosity cannot be used for writing instruments, so the concentration of the white inorganic pigment must be reduced. Therefore, there is a problem that sufficient whiteness and hiding power cannot be given to the written image.

Therefore, an object of the present invention is to solve the problems of the prior art described above and to provide a white ink composition for writing instruments having excellent dispersion stability, whiteness and hiding power.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention is a white ink composition for writing instruments comprising white hollow resin particles, a water-soluble resin, and an aqueous medium.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The white hollow resin particles used in the present invention appear white by diffusing light due to the interface between the gas phase in the hollow part and the solid phase of the resin, and are insoluble in the ink medium described below and do not form a film. First, the particle size is preferably 0.1 to 1.0 um, and the inner pore diameter of the hollow portion is in the range of 20 to 90% of the outer diameter. If this value exceeds 90%, the strength of the resin particles will decrease, and if strong force is applied, the resin particles will be easily penetrated. On the other hand, if this value is less than 20%, the light diffusion efficiency will decrease and the whiteness and hiding power will decrease. This is not preferable because it lowers the temperature.

Furthermore, even if the surface and inner surface of the hollow resin particles are smooth, they have sufficient whiteness and hiding properties, but if the surface and/or inner surface is uneven, the whiteness will be further reduced due to diffused reflection. , is preferable because the shielding power is improved.

Such white hollow resin particles are produced by emulsion polymerization or suspension of polystyrene, polymethyl methacrylate, polyvinyl chloride, benzoguanamine resin, epoxy resin, melamine resin, polyamide resin, or α,β-monoethylenically unsaturated monomer. Examples include those obtained by turbid polymerization.

When these white hollow resin particles dissolve or swell in the solvent constituting the ink, it is preferable that they be crosslinked appropriately, such as in an acnorstyrene resin emulsion crosslinked with divinylbenzene.

If the content of the white hollow resin particles in the ink composition of the present invention is too small, sufficient whiteness and hiding power will not be obtained, while if it is too large, the fluidity and fixing properties of the obtained ink will decrease. Therefore, the preferred range is a proportion of 3 to 40% by weight in the ink.

By adding the above white hollow resin particles to the ink medium, the resulting ink becomes white with extremely high diffuse reflectance, and therefore has a high hiding power, even though it does not contain any white inorganic pigment. Therefore, the characters and images formed on colored objects using the water-based ink are clear with high whiteness and hiding power. It is also useful as

Of course, such whiteness and hiding power can also be obtained by using a large amount of a conventionally known white inorganic pigment such as titanium oxide, but if a large amount of such a white inorganic pigment is added, As such, the ink itself becomes unusable as a writing instrument.

On the other hand, in the present invention, since the white hollow resin particles as described above have a significantly lower specific gravity than the white inorganic pigment, they do not separate from the ink medium in the ink (they can maintain a stable dispersion state, and It is capable of maintaining sufficient dispersion stability as an ink composition for commercial use.

The water-soluble resin used in the present invention acts as a dispersant and a binder for the white resin particles, and a preferred dispersant is a polymer dispersant. Among these polymer dispersants, polymer dispersants consisting of a hydrophilic part and a lipophilic part are particularly suitable.

Such polymer dispersants can be broadly divided into condensation polymers and addition polymers based on their structure. Any existing ones can be used, and condensation polymers are preferable, for example, special polymers. There is a polyester dispersant described in JP-A-60-26070, and as an addition polymerization dispersant, α.

Examples include addition polymers of monomers having a β-ethylenically unsaturated group.

Particularly preferred are addition polymer based dispersants, which are obtained by copolymerization of monomers forming the lipophilic portion and monomers forming the hydrophilic portion.

The addition-polymerizable polymer dispersant as described above can be prepared by mixing hydrophilic and lipophilic monomers in appropriate proportions and by any conventional mixed polymerization method such as solution polymerization method, suspension polymerization method, emulsion polymerization method, etc. It can also be obtained by the polymerization method of Known additives such as polymerization regulators can also be used if necessary. As long as the polymerization medium used at this 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 for ink. After separating from
It can also be used after being redissolved in an appropriate medium.

The polymer dispersant obtained 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, It is preferable from the viewpoint of properties such as viscosity of an ink composition using it and quality such as fastness of recorded matter.

In the present invention, the above-mentioned polymer dispersant can be used as it is as a binder for the white hollow resin particles in the ink, but the amount of the polymer dispersant alone is insufficient as a binder, and the abrasion resistance of written materials is not sufficient. in case of,
Other water-soluble resins can also be added in addition to or in place of the above-mentioned dispersants.

Examples of such water-soluble resins include acrylic resins,
Styrene-maleic anhydride resins, maleated oils, maleated polybutadiene, maleated alkyd resins, maleated petroleum resins, maleated rosin esters, alkali metals such as polyvinylpyrrolidone, ammonia, amine salts, etc. are preferred, and do not cause excessive viscosity of the ink. Use in an amount that does not increase the amount.

The amount of the above-mentioned fractional agent or water-soluble resin used in the ink composition varies depending on the type and brand of the white hollow resin particles, and cannot be absolutely defined, but it is approximately 100 parts by weight of the resin particles. The proportion is from 3 to 300 parts by weight, preferably from about 5 to 100 parts by weight.

Further, as the aqueous medium constituting the ink composition for writing instruments of the present invention, an aqueous solution of a hydrophilic organic solvent is used. For example, methanol, ethanol, propatool, butanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, methyl cellosolve acetate, methyl calpitol, ethyl calpitol, butyl calpitol, etc. per 100 parts by weight of water. It is preferable to use an aqueous solution mixed and dissolved in a proportion of 5 to 200 parts by weight.

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

The white aqueous ink composition for writing instruments of the present invention comprises the above-mentioned components and formulations, and various methods can be employed for its production. For example, the above-mentioned components may be blended and simply mixed using a conventionally known disperser such as Daysilver or Homomixer.

(Action/Effect) The white aqueous ink composition for writing instruments of the present invention obtained as described above maintains its quality even after long-term storage and under various conditions such as transportation and display. It is stable, and virtually no phenomena such as separation, aggregation, or sedimentation of the white hollow resin particles from the ink medium 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-tip pens, etc., and even though it does not contain white permanent pigments, it can print characters and images with excellent whiteness and hiding power. I can give.

In addition, it is possible to write well without the white resin particles clumping or clogging in the container or the pen tip, and it also contains a low-volatile to non-volatile hydrophilic organic solvent. Therefore, it can be said that it is an ideal water-based ink that does not cause clogging due to drying of the pen tip.

(Example) Next, the present invention will be explained in more detail by giving examples. still,
In the text, parts or percentages are by weight unless otherwise specified.

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, 55 parts of water, 2.0 parts of jetanolamine and acrylic-styrene. System hollow resin particles (manufactured by Japan Synthetic Rubber,
28% aqueous dispersion 1 particle size 0.4μm, inner pore diameter 0.25μm
50 parts of m) were added and mixed with Daysilver for about 1 hour to obtain a white water-based ink.

When this was set in a felt-tip pen and its writing properties were tested on black paper, it had significantly superior dispersion stability, hiding power, and whiteness compared to those using titanium oxide, and the writing was smooth.

Claims (1)

[Scope of Claims] (1) A white ink composition for writing instruments comprising white hollow resin particles, a water-soluble resin, and an aqueous medium. (2) The white aqueous ink composition for writing instruments according to claim 1, wherein the white hollow resin particles have a particle size of 0.1 to 1.0 μm. (3) The inner pore diameter of the white hollow resin particles is 20 to 9 of the outer diameter.
The white aqueous ink composition for writing instruments according to claim 1, wherein the content is 0%.