Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-06-09
2001-07-17
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031860, C106S031590, C106S031890
Reexamination Certificate
active
06261352
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a water-based ball-point pen ink composition. More particularly, this invention relates to a water-based ball-point pen ink composition which shows shear-thinning properties.
2. Description of the Related Art
Agents for imparting shear-thinning properties have been disclosed which are to be added to water-based ink compositions for use in ball-point pens of the type in which when the ball-point pen is allowed to stand without imposition of shear stress on the ink, then the ink has a high viscosity and is stably held in the ball-point pen mechanism, and when the ball-point pen is in use for writing, then that part of the ink which is in the vicinity of the ball becomes less viscous due to the shear stress resulting from the ball rotation and is hence transferred to the paper surface. Examples of such prior art agents for imparting shear-thinning properties include water-dispersible gums and polysaccharides (see U.S. Pat. Nos. 4,545,818 and 5,466,283), organic polymeric compounds such as crosslinkable acrylic resins (see U.S. Pat. No. 5,767,172), inorganic compounds such as fine inorganic particles (see JP-A-6-256699; the term “JP-A” as used herein means an “unexamined published Japanese patent application”), and nonionic surfactants (see U.S. Pat. No. 5,785,746).
SUMMARY OF THE INVENTION
The present inventors made investigations on novel agents for imparting shear-thinning properties which are to be added to water-based ball-point pen ink compositions of the above-described conventional type. As a result, it has been found that a shear-thinning ink composition which gives a smooth writing touch and shows various satisfactory writing performances, including the property of less undergoing ink dripping or feathering, is obtained by incorporating a specific anionic surfactant into an ink. The present invention has been completed based on this finding.
The present invention provides a water-based ball-point pen ink composition comprising a colorant, water, and as an agent for imparting shear-thinning properties at least one member selected from sulfosuccinates which are represented by the following general formula (1):
wherein each R represents an alkyl or alkenyl group having 7 to 18 carbon atoms and X represents an alkali metal or an amine, the content of said at least one member being from 5 to 50% by weight.
The present invention further provides: the above ink composition in which the content of the sulfosuccinate is from 5 to 20% by weight; the above ink composition which contains a betaine; and the above ink composition which has a viscosity of from 20 to 200 mPa·s (25° C.) as measured with an E type rotational viscometer at 100 rpm and a shear-thinning index of from 0.1 to 0.7.
DETAILED DESCRIPTION OF THE INVENTION
As described above, the water-based ball-point pen ink composition having shear-thinning properties of the present invention is characterized in that it contains at least one anionic surfactant represented by general formula (1) in an amount of from 5 to 50% by weight. The present inventors have found that by packing this ink into a reservoir tube, a ball-point pen having satisfactory writing performances is obtained.
Anionic surfactants have conventionally been known to function, e.g., as a dispersant for pigments or a penetrant for enhancing penetration into paper when added to inks in a small amount. However, when an anionic surfactant represented by general formula (1) is added in a large amount to an ink, it imparts shear-thinning properties to the ink as described above. The reasons for this are thought to be as follows. In the water-based ink, the surfactant is present in a dispersed state, i.e., an emulsified state, due to the hydrophobic groups thereof. In addition, interactions occur such as the formation of an electrical double layer between molecules and the formation of adsorptive crosslinks between molecules. As a result, a three-dimensional network structure is formed and the ink hence has a high viscosity. Upon imposition of a strong shear force, the three-dimensional network structure is temporarily weakened and the ink hence comes to have a low viscosity.
The surfactant used in the present invention is added to an ink in an amount of generally from 5 to 50% by weight, preferably from 5 to 20% by weight, based on the ink composition.
If the content of the surfactant is lower than 5% by weight, it is difficult to impart the necessary shear-thinning properties to the water-based ball-point pen ink. If the content thereof exceeds 50% by weight, not only insufficient ink transfer is apt to occur in writing, but also the desired viscosity decrease is not obtained under high-shear conditions, making it difficult to obtain proper ink outflow corresponding to a writing speed.
The sulfosuccinates which are represented by general formula (1) mean alkali metal salts, e.g., sodium and potassium salts, ammonium salts, or alkanol amine salts, e.g., monoethanolamine, diethanolamine, and triethanolamine salts. In these salts, the alkyl or alkenyl groups each has from 7 to 18 carbon atoms, preferably from 8 to 15 carbon atoms. If a sulfosuccinate salt in which the alkyl or alkenyl groups each has less than 7 carbon atoms is used, this surfactant more readily dissolves in an ink because the hydrophobic parts thereof have enhanced miscibility with water. As a result, this surfactant is less apt to form a three-dimensional network structure based on the hydrophobic parts and the ink does not show shear-thinning properties. On the other hand, if a sulfosuccinate salt in which the alkyl or alkenyl groups each has more than 18 carbon atoms is used, this surfactant has poor dispersion stability in an ink although the hydrophobic parts thereof have reduced miscibility with water. As a result, this surfactant is less apt to form an even three-dimensional network structure in the ink.
The alkyl or alkenyl groups each may be linear or branched.
In each of the surfactants represented by general formula (1), one of the R's may be an alkyl group and the other may be an alkenyl group.
Examples of the anionic surfactants that can be used in the present invention are given below. However, the surfactants should not be construed as being limited thereto.
The examples include:
sodium diheptylsulfosuccinate,
potassium diheptylsulfosuccinate,
ammonium diheptylsulfosuccinate,
triethanolamine diheptylsulfosuccinate,
sodium di(1-methylhexyl)sulfosuccinate,
potassium di(1-methylhexyl)sulfosuccinate,
ammonium di(1-methylhexyl)sulfosuccinate,
triethanolamine di(1-methylhexyl)sulfosuccinate,
sodium di(1-propylbutyl)sulfosuccinate,
potassium di(1-propylbutyl)sulfosuccinate,
ammonium di(1-propylbutyl)sulfosuccinate,
triethanolamine di(1-propylbutyl)sulfosuccinate,
sodium dioctylsulfosuccinate,
potassium dioctylsulfosuccinate,
ammonium dioctylsulfosuccinate,
triethanolamine dioctylsulfosuccinate,
sodium di(1-ethylheptyl)sulfosuccinate,
potassium di(1-ethylheptyl)sulfosuccinate,
ammonium di(l-ethylheptyl)sulfosuccinate,
triethanolamine di(1-ethylheptyl)sulfosuccinate,
sodium di(2-ethylhexyl)sulfosuccinate,
potassium di(2-ethylhexyl)sulfosuccinate,
ammonium di(2-ethylhexyl)sulfosuccinate,
triethanolamine di(2-ethylhexyl)sulfosuccinate,
sodium dinonylsulfosuccinate,
potassium dinonylsulfosuccinate,
ammonium dinonylsulfosuccinate,
triethanolamine dinonylsulfosuccinate,
sodium di(1-methyl-4-ethylhexyl)sulfosuccinate,
potassium di(1-methyl-4-ethylhexyl)sulfosuccinate,
ammonium di(1-methyl-4-ethylhexyl)sulfosuccinate,
triethanolamine di(1-methyl-4-ethylhexyl)sulfosuccinate,
sodium didecylsulfosuccinate,
potassium didecylsulfosuccinate,
ammonium didecylsulfosuccinate,
triethanolamine didecylsulfosuccinate,
sodium diundecylsulfosuccinate,
potassium diundecylsulfosuccinate,
ammonium diundecylsulfosuccinate,
triethanolamine diundecylsulfosuccinate,
sodium di(1-methyl-4-ethyloctyl)sulfosuccinate,
potassium di(-methyl-4-ethyloctyl)sulfosuccinate,
ammonium di(1-methyl-4-ethyloctyl)sulfosuccinate,
triethanolamine di
Faison Veronica F.
Klemanski Helene
Sughrue Mion Zinn Macpeak & Seas, PLLC
The Pilot Ink Co., Ltd.
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