Coating implements with material supply – Including floating follower in reservoir – Fluid follower
Reexamination Certificate
2002-02-06
2002-11-12
Walczak, David J. (Department: 3751)
Coating implements with material supply
Including floating follower in reservoir
Fluid follower
C401S141000
Reexamination Certificate
active
06478496
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink follower for writing tools. More particularly, for the purpose of preventing ink contained in an ink reservoir from evaporation during storage or in use and preventing the ink from leakage in a writing tool, the invention relates to an ink follower for a writing tool arranged in close contact with ink surface at the terminal portion opposite to the portion to which an writing tip is attached.
BACKGROUND OF THE INVENTION
An ink follower is a gel-type stopper which is arranged on the upper ink surface at the terminal portion opposite to the portion of the ink reservoir of a ballpoint pen to which an writing tip is attached, and which adheres closely to the ink-containing reservoir and comes down with tightly sealing it, following the ink with the consumption of the ink.
Hitherto, in a writing tool wherein ink for writing is directly contained in an ink-containing reservoir, e.g., a ballpoint pen, an ink follower is charged in close contact with the ink at the terminal portion of the ink reservoir for the purpose of the prevention of evaporation and leakage of the ink. The ink follower should not only be hardly volatile but also have high apparent viscosity for the prevention of leakage of the ink. For satisfying such requirements, ink followers wherein an organic or inorganic thickening agent or a gelling agent is added, as a viscosity-imparting agent, to a base oil of a hardly volatile liquid or a nonvolatile liquid have been known. For example, Japanese Examined Patent Publication No. 64-010554/1989 proposes a follower wherein an organic gelling agent such as dibenzylidene sorbitol is added to a hardly volatile solvent such as ethylene glycol, and Japanese Laid-Open Patent Publication No. 57-200472/1982 proposes a composition wherein an thickening agent such as an amino acid derivative is dissolved in polybutene or the like to form a gel.
In addition, those wherein an organic or inorganic thickening agent, a gelling agent or the like is added to a base oil of a hardly volatile liquid or a nonvolatile liquid and a specific additive is further added as a performance improving agent are proposed in Japanese Examined Patent Publication Nos. 5-082840/1993, 6-015277/1994, 6-033025/1994, 6-033026/1994, 6-047318/1994, 7-029513/1995, Japanese Patent No. 2677734, Japanese Laid-open Patent Publication Nos. 4-202281/1992, 5-270193/1993, 6-200235/1994, 7-216285/1995, 8-11481/1996, 8-300874/1996, 9-234988/1997.
These ink followers are viscoelastic gel substances which are thickened by the formation of network between molecules of a gelling agent. Since this network gradually grows finely and densely with the passage of time to form stronger gel substance, there is a problem that it becomes difficult to follow the consumption of ink resulted from writing. In the worst case, a reduced-pressure space is formed between the ink follower and ink surface, there arises a problem that an ink flow is discontinued or writing becomes impossible. It is possible to solve the problem of the following performance by reducing the adding amount of the gelling agent because the network formation can be limited to the minimum. In this case, however, a sufficient apparent viscosity cannot be attained and thus the follower does not form a stopper having a required hardness, so that it cannot prevent the leakage of ink. In addition, when the adding amount of the gelling agent is reduced, there is a problem that an oil separation, i.e., the separation of portion of the base oil of the ink follower occurs and then writing becomes impossible when the oil independently stays at the terminal part.
Furthermore, Japanese Laid-open Patent Publication No. 8-142570/1996 proposes an ink follower wherein a phthalate ester-type plasticizer and a polyester-type thermoplastic elastomer are combined. In the ink follower, it is attempted to cope with both the stability with the passage of time and the control of flow rate of ink but the ink follower is inferior in impact resistance, so that there is a problem that ink leaks out when external force is applied by, for example, falling, vibration or the like.
In such situation, for enhancing impact resistance, the addition of non-swellable particles having a similar specific gravity to that of the base oil and a particle size of several tens to several hundreds &mgr;m or the incorporation of rod-shaped materials of several mm is proposed in Japanese Laid-open Patent Publication Nos. 10-044673/1998 and 10-067196/1998 but the problem of the oil separation is not yet solved.
SUMMARY OF THE INVENTION
As described above, there is no proposal of the ink follower having sufficient stability with the passage of time, impact resistance and ink-following ability as well as showing no oil separation.
The present invention provides an ink follower for writing tools exhibiting an excellent following ability which have an enhanced impact resistance without causing insufficient following and oil separation with the passage of time as well as any inconvenience such as writing failure.
The present invention relates to an ink follower for a writing tool, such as a ballpoint pen. The ink follower is to be arranged in close contact with ink surface of a terminal portion opposite to a writing tip portion of an ink reservoir of the writing tool. Particularly, the ink follower is swollen gel formed from an oil-absorbable resin and a base oil of polybutene and an alkyl-modified silicone oil compatible with said polybutene. Viscosity of the base oil may range from 500 to 2000 mm
2
/s at measuring environment of 40° C. and unmixing consistency may range from 320 to 380 at measuring environment atmosphere of 25° C. Mixing amount of the oil-absorbable resin may be from 10 to 20% by weight based on the total amount of the follower. The oil-absorbable resin may be one or more selected from acrylate ester crosslinked polymers and/or copolymers thereof, (meth) acrylate ester crosslinked polymers and/or copolymers thereof, and polynorbornene The adding amount of the alkyl-modified silicone oil may be from 0.5 to 1.5% by weight.
PREFERRED EMBODIMENTS OF THE INVENTION
The ink follower of the present invention is a swollen gel substance obtained by mixing thoroughly a base oil of polybutene and an alkyl-modified silicone oil compatible with the polybutene beforehand under an environment of 100 to 500° C., and then adding an oil-absorbable resin to swell the resin under mixing.
In the present invention, an oil-absorbable resin is employed as the thickening agent for the ink follower. The oil-absorbable resin to be used in the present invention is a resin having a property of stably holding the base oil through swelling after absorbing the oil, and a desired ink follower may be obtained by using one of the resins or two or more of the resins in combination.
As mentioned above, the conventional ink followers are gel substances formed by intermolecular network structures by weak hydrogen bond or van der Waals force. On the other hand, the ink follower of the present invention employing an oil-absorbable resin is formed by an intramolecular gel structure. As mentioned above, since the intermolecular network grows with the passage of time, initial design is extremely difficult but also there still remains a problem of an external force caused by an impact or the like. That is, when an external force is applied to the ink follower, the intermolecular network is broken to cause a rapid decrease of apparent viscosity, whereby impact resistance decreases. On the other hand, since the ink follower employing the oil-absorbable resin is formed by an intramolecular gel structure, the rapid decrease of apparent viscosity does not occur even when an external force is applied, and the breakage of the structure by the external force does not occur. Accordingly, owing to the large difference of the gel formation mechanism, the employment of the oil-absorbable resin results in advantages that a stable structure against an external force such as an impact can be alw
Fukasawa Teruaki
Izumi Seishi
Yoshii Kazuhiro
Kabushiki Kaisha Pilot
Rader & Fishman & Grauer, PLLC
Walczak David J.
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