Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-02-16
2002-08-27
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S161000, C524S492000, C524S493000
Reexamination Certificate
active
06441061
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an additive for an oil based ink for a ball point pen and an oil based ink for a ball point pen containing the additive.
BACKGROUND ART
Conventionally, a ball point pen with a ball having a diameter of 0.7 mm that is charged with an oil based ink has been mainly used. However, due to diversification of use thereof and advancement of technology, a ball point pen with a ball having a diameter of 1.0 mm or more that is charged with an oil based ink has come to be sold extensively.
However, in the case that a tip with a ball having a large diameter is used, there is a problem in that the tip has large clearance to obtain an appropriate amount of ink discharge and hence ink leakage occurs readily when the ball point pen is left to stand with its tip downward.
To improve prevention of the ink leakage, an inorganic fine particle thickener has been added to an ink heretofore as disclosed in Japanese Patent Application Laid-Open No. Hei 10-204368 and Japanese Patent Application Laid-Open No. Hei 8-311388.
However, only adding an inorganic fine particle thickener to an ink gives rise to a tendency such that the inorganic fine particle thickener grows thicker and precipitates with the passage of time, which causes starving in the drawn line and impossibility of writing, while it is certain that the ink leakage occurs less frequently. Further, in the case that a whole ink is mixed by means of a three roll mill, there is a problem in that production efficiency is deteriorated and moreover that there is a tendency such that many blobbings occur due to strong shear onto a resin.
The present invention aims to solve the aforementioned problems and an object of the present invention is to provide an additive for an oil based ink for a ball point pen wherein the oil based ink for a ball point pen is prevented from thickening and precipitating with the passage of time when an inorganic fine particle thickener is added and does not cause leaking, starving in the drawn line and impossibility of writing and wherein the ink is superior in production efficiency and causes few blobbings. An additional object of the present invention is to provide an oil based ink for a ball point pen containing the additive.
DISCLOSURE OF INVENTION
The present inventors have conducted intensive studies on the aforementioned conventional problems to find the fact that the above intended additive for an oil based ink for a ball point pen and an oil based ink for a ball point pen containing the additive can be obtained by preparing in advance the additive containing at least one or plural kinds of organic solvents, a resin and an inorganic fine particle thickener and adding the additive to an oil based ink for a ball point pen. Thus, the present invention has been completed.
That is, the present invention comprises the following items (1) through (5).
(1) An additive for an oil based ink for a ball point pen containing at least one or plural kinds of organic solvents, a resin and an inorganic fine particle thickener, wherein the additive has a viscosity of 1000 mPa·s or more at a shear rate of 5/s and at 0° C. and a viscosity of 50000 mPa·s or less at a shear rate of 5/s and has at 50° C. and a non-Newtonian index of from 0.30 to 0.95 at 25° C., and wherein the additive has an absorbance of from 0.01 to 5 at a wavelength of 900 nm when a cell is 1 cm long.
(2) The additive for an oil based ink for a ball point pen described in item (1), wherein a specific surface area (BET method) of said inorganic fine particle thickener ranges from 30 to 500 m
2
/g and an average diameter of the primary particles thereof ranges from 5 to 50 nm.
(3) The additive for an oil based ink for a ball point pen described in item (1), wherein said inorganic fine particle thickener comprises inorganic fine particles containing SiO
2
of 70% by weight or more.
(4) The additive for an oil based ink for a ball point pen described in item (1), wherein polyvinyl pyrrolidone is contained as a resin in an amount of 0.05 to 10% by weight.
(5) An oil based ink for a ball point pen which contains 0.1 to 30% by weight of the additive described in any one of the above items (1) to (4).
By containing the additive in accordance with the present invention in an oil based ink for a ball point pen, the oil based ink for a ball point pen which is prevented leakage from a pen tip and does not cause starving and impossibility of writing with the passage of time can be provided.
BEST MODE FOR CARRYING OUT THE INVENTION
The embodiments of the present invention shall be explained below in detail.
The additive for an oil based ink for a ball point pen of the present invention (hereinafter referred to as “the additive”) is characterized by containing at least one or plural kinds of organic solvents, a resin and an inorganic fine particle thickener.
Any organic solvents can be used as the organic solvents for the additive of the present invention with no particular restrictions as long as they are used for regular oil based ink for a ball point pen. Those organic solvents include, for example, benzyl alcohol, phenoxyethanol, propylene glycol, dipropylene glycol, 1,3-butylene glycol, hexylene glycol, tetralin, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monomethyl ether acetate, tripropylene glycol monomethyl ether and N-methyl-2-pyrrolidone. These can be suitably selected to use alone or in combination of two or more.
A using amount of the organic solvents ranges from 15 to 90% by weight, preferably from 25 to 80% by weight and more preferably from 35 to 70% by weight based on the total amount of the additive.
Resins in the additive of the present invention are used for the purpose of increasing the viscosity of the additive and dispersing suitably the inorganic fine particle thickener to be added. Any resins can be used with no particular restrictions as long as they are used for regular oil based ink for a ball point pen.
Those resins include, for example, ketone resin, phenol resin, maleic acid resin, xylene resin, polyethylene oxide, rosin resin, rosin derivative, terpene resin, chmaroneindene resin, polyvinyl butyral, polyvinyl pyrrolidone, vinyl pyrrolidone-vinyl acetate copolymer, polymethacrylate and acrylic acid-methacrylic acid copolymer. These resins can be used alone or in combination of two or more.
The total amount of the resins to be used alone or in combination of two or more ranges from 5 to 80% by weight, preferably from 25 to 70% by weight and more preferably from 35 to 60% by weight based on the total amount of the additive. If the amount of the resins is below 5% by weight, a viscosity necessary for mixing the inorganic fine particle thickener by means of a three roll mill can not be obtained and if the amount of the resin exceeds 80% by weight, difficulty in mixing is found.
It is desired that, as one kind of the above resins to be added, polyvinyl pyrrolidone is contained in the additive preferably by 0.05 to 10% by weight or less, more preferably by 0.1 to 7% by weight. Containing polyvinyl pyrrolidone in the additive makes it possible to disperse effectively the inorganic fine particle thickener added.
Specific polyvinyl pyrrolidone includes PVP (manufactured by ISP Co. Ltd.) or Luviscoll (manufactured by BASF Co. Ltd.).
As for inorganic fine particle thickeners to be used for the additive of the present invention, desired are those which have an average diameter of the primary particles falling in a range from 5 to 50 nm and a specific surface area (BET method) falling in a range from 30 to 500 m
2
/g and which preferably contain SiO
2
in an amount of 70% by weight or more as the fine particle component.
Using the inorganic fine particle thickener falling in these specific ranges makes it possible to obtain the intended additive and oil based ink for a ball point pen.
A using amount of the inorganic fine particle thickener ranges from 0.03 to 30% by weight, preferably from 0.1 to
Cain Edward J.
Darby & Darby
Mitsubishi Pencil Kabushiki Kaisha
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