Colloid systems and wetting agents; subcombinations thereof; pro – Continuous or semicontinuous solid phase – The solid phase contains organic material
Reexamination Certificate
2000-04-07
2002-04-23
Lovering, Richard D. (Department: 1712)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous or semicontinuous solid phase
The solid phase contains organic material
C137S205000, C252S381000, C252S383000, C401S217000, C422S043000, C516S099000, C516S101000, C516S112000, C516S195000
Reexamination Certificate
active
06376560
ABSTRACT:
TECHNICAL FIELD
The present invention relates to ink follower, which follows water-base ink filled in an ink reservoir of a ballpoint pen, and also to a method for manufacturing the same.
BACKGROUND ART
The ink for a water-base ballpoint pen has a viscosity of as low as 50 mPa sec to 3 Pa sec, while the ink for an oil-base ballpoint pen, though it has a similar structure to a water-base one, has a viscosity of 3 to 20 Pa sec. Consequently, the ink filled in a water-base ballpoint pen may leak out when the pen is left upward or sideways. Moreover, even a small impact made on the pen may cause its ink to scatter and to stain the hand or the clothes.
There have been conventional arts for a water-base ballpoint pen with its ink in its ink reservoir that it is equipped with an ink follower composed of a gelled material, or a mixture of the gelled material and solid material. The aims of the arts are to make the ink follower follow the ink smoothly, to make the pen endure an impact when dropped, to prevent the ink from back flow, to give the pen a good appearance, and so on. A common feature of such arts is that the ink follower, which has pseudo-plasticity, is made from hardly-volatile or non-volatile solvent which is supplemented with some kind of thickener in order that the ink follower may not flow backward when the pen is left sideways or upward.
Moreover, conventional ink follower for water-base ballpoint pens often has very low viscosity and tenacity, as compared with that for conventional oil-base ballpoint pens, which often has equal viscosity to common grease used for lubricant.
About as much as 50 to 300 mg of ink is required for writing a line of 100 m in length by a water-base ballpoint pen holding the ink in the ink reservoir, while only 10 to 30 mg of ink is required by an oil-base ballpoint pen. Thus, the ink follower for the water-base ballpoint pens is required to have a strict ink-following performance, and is, therefore, mainly of low viscosity.
Lubricant grease with low viscosity and consistency generally has such low stability that oily matter likely separates when left to stand. In addition, the high mobility of thickener in the lubricant grease is likely to cause the grease to lose homogeneity easily by forming a mixture of coarse and dense portions.
The lower the viscosity of the thickener of the grease is, the less effectively the thickener is dispersed by a disperser such as a double-roll mill, a triple-roll mill, a kneader or a planetary mixer, any one of which is suitable for substances with high viscosity. The thickener is, however, not so low in viscosity as to be capable of being mixed effectively by a disperser such as a bead mill, a sand mill or a homogenizer, any one of which is suitable for substances with low viscosity. Inefficient dispersion causes not only time-dependent instability but also lot-to-lot instability in viscosity and uniformity.
The ink follower for the water-base ballpoint pens consists of materials similar to the lubricant grease, and exhibits time-dependent behaviors based on similar physical laws.
However, if the oily matter separates from ink follower, it affects writing adversely by reacting with surfactant in the ink, or by forming oil droplets which block the ink passage.
Moreover, ink follower lacking homogeneity is separated into a portion following the ink and portions adhering to the inner wall of the ink reservoir. The adhering portions not only give the pen an unpleasant appearance, but also mean a corresponding loss of the ink follower, resulting eventually in its failure to perform its function of, for example, preventing the ink from volatilizing or from leaking.
The lubricant grease and the known ink follower have a common defect, too.
When they are used as ink follower in a water-base ballpoint pen which holds the ink in a cylindrical or similarly shaped ink reservoir with an inside diameter of 2.5 mm or larger, bubbles often occur between the ink and the ink follower by the passage of time. Moreover, bubbles or cracks, which have not seen initially, often occur in the ink follower (or the lubricant grease used as a substitute therefor). Since ink follower is nearly liquid rather than semi-solid, it is very questionable whether an expression of “cracks” is appropriate, but the greasy matter is cracked in appearance. We, the inventors of the present invention, call these phenomena “bubbling”. Once the bubbles occur between the ink and the ink follower, it grows larger and interrupts the contact between the ink and the ink follower. Then, the ink follower is urged by the vapor pressure of the ink toward the tail end of the pen, and eventually falls off. The ink follower having cracks or the like loses its function of keeping the ink from contact with the air.
These phenomena are presumably due to the invisibly fine bubbles that may exist in the ink follower or lubricant grease when manufactured. The bubbles gather with the passage of time, and tend to escape from the pen.
The bubbling is a serious defect in this kind of water-base ballpoint pen.
Commercially available ballpoint pens are subjected to a strong centrifugal force for debubbling. Debubbling by a strong centrifugal force is, however, not always effective for removing invisibly fine bubbles, but can only reduce the percentage of bubbling to about ⅕ to {fraction (1/20)}.
Moreover, the centrifuging is not a suitable method for debubbling for pens with a pigment ink, particularly the ink containing a pigment with a true specific gravity of 4 or higher, since a strong centrifugal force promotes the sedimentation of the pigment.
Thus, in order to prevent the contamination of fine bubbles in advance, conventional centrifugal debubbling when the pens are assembled may be carried out strongly. However, too strong centrifugal debubbling causes defects such as deformation of pen point or the connecting part of the ballpoint pen. Further, it may sometimes happen that the pigment in the ink is sedimented and clogs at the pen point resulting in poor writing and that is significant when pigment of a high specific gravity such as titanium oxide and metal powder is contained in the ink.
The objects of this invention are to dissolve the defect that conventional ink follower for a water-base ballpoint pen has lot-to-lot and time-dependent instability of quality, and to provide ink follower which has time-dependent stable performance for mass-production and a method for manufacturing thereof.
The other object of the present invention is to provide a method for manufacturing the ink follower by which the time-dependent growth of bubbles, which is a defect of conventional ink follower for water-base ballpoint pens, is dissolved, without any above-mentioned bad influence upon the ballpoint pens caused by a strong centrifugal force after filling the ink and the ink follower into a ballpoint pen holder.
DISCLOSURE OF THE INVENTION
As a result of our diligent study of above problems, we have found that, by homogenizing particulate silica, clay thickener, metal soap, or organic thickener microscopically highly, the thickener constantly exhibits its best performance. And we have also found that the ink follower, therefore, showed more time-dependent stability and less lot-to-lot instability. Thus we have completed our present invention.
Moreover, as a result of diligent study of above problems, we found that conventional centrifugal debubbling during the assembly of ballpoint pens, which is said to be an essential process, is not so strong when centrifugal debubbling upon ink follower of water-base ballpoint pens is previously performed. Upon this knowledge, we have found some conditions that the invisible fine bubbles contained in particulate silica, clay thickener, metal soap and organic thickener can be highly removed microscopically without any bad influences on writing property of the pens, and thus we have accomplished the present invention.
Lubricant grease and ink follower for a water-base ballpoint pen are prepared from similar materials by similar processes, but
Iwamoto Kiyoshi
Kamagata Tadashi
Ogura Norio
Shiraishi Katsuhiko
Takeuchi Youji
Kubovcik & Kubovcik
Lovering Richard D.
Mitsubishi Pencil Kabushikikaisha
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