Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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I . CAPILLARY TYPF,_INK
¦ BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to an ink for use in capillary
type writin~ instruments, and more particularly, to aqueous ink
co~positions promoting rejuvenation after the writing tip o~ a
capillary type writing nstrument has dried out from exposure
¦ to the atmosphere.
l Description of the Prior ~rt ¦-
¦ A problem frequently encountered by people who use
¦ capillary type writing instruments is writing point dryout.
¦ Capillary type writing instruments include those pens or marking
devices which have fiber, felt, or porous plastic type writing
¦ points which deliver ink from a reservoir to the writing point
I5 ¦ by means of ca~illary action. The in~s used in capillary type
I writing instruments ~ave generally been of two types: 1) water
I ~ based inks containing water soluble dyes~ (the inks of the
¦ present invention), and 2) inks which contain organic solvents
l and dyes which are soluble in an organic medium.
Capillary type writing instruments employ a variety
of types of fiber, felt, and porous plastic writing points.
Felt i~ a fabric of natural and/or synthetic fibers worl~ed
together by pressure, heat, or chemical action without weaving
or knitting. The fibers tend to be arranged in a random fashion.
When felt is used as a writing point, the ink is conveyed
through the interstices between the individual fibers by
capillary action.
A second major type of writing point is made by
bonding together a bundle of parallel strands of either natural
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- or synthetic fibers (e.g. polyvinyl chloride, polyethylene,
or polyamide polymers) to form capillary pathways between
the bundles leading to the writing point. U.S. Patent
3,558,392 is an example of such a point. The fibrous
point is made by setting a bundle of parallel strands of
synthetic fibers in a desired relation by drawing the
bundle through a heat-setting zone to establish dimensions
in cross-section of the final object and to create
longitudinally extending channels. The strength of the
point is subsequently increased by immersion in a dilute
resin solution followed by heating to evaporate the solvent
and cure the resin. Depending on the denier of the fibers
of the particular yarn which is used to form the writing
point, a number of cannels will be formed having average
or mean transverse dimensions of from 1 x 1 mils. to
3 x 6 mils. Channels of 1.5 to 3 mils. in one transverse
direction and between 3 and 6 mils. in another direction
are representative of the most desirable channel sizes. Thus,
the capillary channels are typically between 4.5 and 18 sq.
mils. in cross-sectional area.
An example of another type of writing point is
described in U.S. Patent 3,778,495. The point described
there is an elongated unitary writing element made by
extruding and melt-drawing a polymer (e.g. acrylic, acetal,
polyamide, or polyester polymers) and then reforming the
internal portions of the extruded body by a compressive
drawing operation to obtain channels of a desired size. The
writing point thus formed has a longitudinally extending,
axialj ink-conveying channel and circumaxial, spaced, ink-
conveying channels, the axial channel having a cross-
sectional area equivalent to a circle with a diameter
between two and four mils. The enlarged circumaxial
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inl~-conveying channels have an oblong cross-sectional shape
approximately 1 to 3 mils. wide and 3 to 5 mils. in a radial
direction. The circumaxial ink-conveying channels are connected
to the axial channel by capillary channels having diameters
of between 0.4 mils. and 1.0 mils. The longi~udinal channels
of the rods serve to deliver ink to the writing point by ~eans
of capillary action.
In each of the above cases, the ink is fed from a
reservoir to the writing surface by means of the writing point.
The reservoir which ~eeds the writing point may be either a
container of liquid ink or a bundle of fibers saturated with
ink. Either will perform equally in capillary writing instru-
ments since dryout is attributable to changes occuring at the
writing tip rather than inside the pen.
A problem with capillary type writing instruments is
that when exposed to the atmosphere, as when left uncapped for
a period of time, the water in the ink may evaporate so as to
change the composition of the ink and make it more viscous.
The capillaries within the tip of the writing instrument will
then ~ecome clogged so that the written line produced becomes
irregular. If left uncapped long enough, the composit on o~
the ink at the tip may be so changed that it will not flow at
all through the capillaries of the tip, writing becomes im-
possible, and the instrument must be discarded.
2~ Attempts have been made to retard the rate at which
water based inks dry out by adding humectant materials such
as ethylene glycol, propylene glycol, and other higher molecular
weight polyhydroxy compounds such as those described in U.S.
¦~ Patent 3, ,045. However, such materials tend to increase
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the viscosity of the ink to such an extent that it will not
flow freely through the capillaries of capillary type writing
instruments, Furthermore, the selective evaporation of the
more volatile constituents of the ink may cause ~he inks to be
thickened at the exposed tip of the instrument by the less
volatile polyhydroxy compounds which remain. If additional
polyhydroxy compound is used in the ink formulation, the gains
from increased humectancy are lost to the increasing viscosity.
In an attempt to solve the point dryout problem,
U.S. Patent 3,519,443, describes inks formulated with formamide
as a solvent to reduce the rate of point dryout. Forma~ide is
somewhat toxic. This constitutes a disadvantage since capillary '
type writing instruments containing water-based inks may be
used by children. In addition, formamide is suggested for use
at concentrations fro~ 10% to 100% o~ the total solvent content
of the ink, levels at which a disagreeable odor may be -
produced.
In spite of the above attempts to reduce point dryout,
¦ problems still exist. Therefore, a need exists for ink com-
~20 positions which not only reduce the rate of dryout, but allow
rejuvenation even after dryout has occurred.
SUMMARY_OF THE IN~ENTION
The present invention comprises an ink composition
adapted for use in a capillary type ~itin~ instrument com-
prising an aqueous solùtion containing:
(a) from about 0.5% to about 15% by weight of a water soluble
dye; and
(b) from about 1% to about 25% of a quaternary ammonium com-
pound ot he ~ormula:
5650
. RC1~2N (C~ ) X I .
wherein --
R is -CH2OH or -CO~H, and
1 X is -OH, -Cl, -Br, or -I.
¦ DETAILED DESCRIP~ION OF THE INVENTION
Satisfactory operation of capillary type writing
instruments is dependent upon a steady capillary flow of ink
to the point which engages the paper or other writing surface.
¦ Thus, the ink used must be sufficiently fluid to assure free
I and continuous flow through the capillary passages from the
I reservoir to the writing tip. Conversely, problems can occur
¦ if the ink is too thin. ~eathering (i.e. laterial wicking of
¦ the ink into the paper from the written line), and strike
1 through (i.e. penetration of the ink to the back of the paper),
¦ are common problems when ink viscosity is too low. To make
¦ sure that the writing point is supplied a suitable amount of
in~, the inks should be formulated to have a viscosity below
50 centipoises at 20C and, more preferably, a viscosity in
the range between 2 and 5 centipoises.
In its simplest form, the present invention comprises
an aqueous solution of a water soluble dye and a compound of
the formula:
RCH2N(CH3)3 X
wherein
R is -CH2OH or -COOH, and
X is -OH, -C1, -Br, or -I.
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P~eferred quaternary a~monium compounds according _
to the invention are:
(~-hydroxyethyl)trimethylammonium chloride,
~IOCH2CH2N(CH3)3 Cl
and
carboxymethyltrimethylammonium hydroxide,
HOOCCH2N(CH3)3 OH
The quaternary ammonium co~pound may be present in
the composition from 1% to 25% by ~eight, preferably from
5% to 15%.
While an aqueous solution of a water soluble ink and
a quaternary ammonium compound produce an acceptable ink, it
is preferred to include at least one polyhydric alcohol in the
ink formulation.
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Polyhydric alcohols are used in the present invention
to increase the viscosity of the ink thereby improving the
characteristics of the line produced by the writing instrument
and reducing strike through and eathering.
Polyhydric alcohols use~ul in the invention include
al~ylene glycols (e.g., ethylene glycol, propylene glycol, and
butylene glycol), polyalkylene glycols (e.g., diethylene glycol
and tripropylene glycol), mono- and di-al~yl ethers of poly-
hydric alcohols (e.g., ethylene glycol methyl ether, ethylene
glycol ethyl ether, and ethylene glycol butyl ether~ and
trihydric alcohols (e.g., glycerin). The preferred alcoho~s
~ are glycerin and ethylene glycol, and mixtures thereof.
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The total amount of polyhydric alcohol employed in
the compositions of the invention may be varied within wide
lil.lits as dictated by the viscosity considerations of the
composition as discussed above. As will be appreciated by
those skilled in the art, the amount of polyhydric alcohol
employed depends in part on the molecular weight of the parti- ¦
cular alcohol employed, since viscosity is generally direct~y
proportional to molecular weight. In general, the polyhydric
alcohol component of the invention constitutes from lV/o to 50%
by weight of the composition.
While any of the water soluble dyes typically used
in ink formulations may be employed in producing inks in
accordance with the present invention, acid dyes are preferred
due to their high tinctorial strength. Such acid dyes possess
one or more sulfonate groups attached to an aromatic nucleus,
. . . . ;.- .
and can be classified according to their chemical structure
into ten different categories: nitro, nitroso, monoazo,
monoazo (metalized), disazo, triphenylmethane, xanthene,
anthraquinone, azine, and quinoline. The amount of dye used
will, of course, vary with the nature and color of the ink to
be produced and may constitute from about 0.5% to 15% by weight
o the total ink composition.
If desired, it is also possible to add other optional
ingredients typically used in water based inks such as corrosion
inhibitors (e.~., benzotriazole) and preservatives (e.g., methyl
parasept).
The inks can be produced by the simple operation of
mixing and dissolving the ingredients in any suitable way, but
it is preferred that the ink componen~s (with the exception
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of a quaternary ammonium com~ound of the present invention) be
I held at 55C with constant stirring for ~wo hours after their
¦ initial mixing. I~en the ink cools to room temperature, a
¦ quaternary ammonium compound of the present invention is intro- ¦
¦ duced with stirring and the ink formula~ion is then filtered.
I The filtered ink is incorporated in any of the con-
ventional capillary writin~ instrument types described above,
by well known procedures. For exampleJ the ink may be injected
into the end of the reservoir opposite the writing point in a
previously assembled porous point pen by means of a syringe.
An alternate procedure, described in U.S. Patent 3J581,378J
i8 to first saturate a fibrous reservoir with inkJ followed by
insertion into the-barrel of the porous point pen.
The inks of the present invention are designed for
¦ use in capillary type: writin~ instruments where the writing
¦ point may be acc~idently allowed to dry out (e.g. J by leaving
¦ the writing ~oint uncapped for a perio~ of time). Should that
occur, the instrument may be rejuvenatedJ rather than being
discarded as would be the case with pens containing prior art
1 inks. Rejuvenation is accomplished by recapping the ~riting
point and allowing the instrument to equilibrate for a few
hours, after which the writing point will have regained its
ability to produce a written line,
In order to illustrate typical and preferred in~
compositions embodying the present inventionJ the following
examples are included:
EXl~LE I
Six percent by weight of a dye known as Color Index
Acid Green 16 (C.I. #44025), 2% by weight of a dye Icnown as
0951i56
Color Index Acid ~ellow 11 (C.I. ~18820), 1% by weig~lt benæo-
triazole, 0,2% methyl parasept, 5% glycerin, and 12.5% ethylene
I glycol were mixed and dissolved in 73~3~O by weight OL water.
¦ The solution was held at 55C, with constant stirring for two
¦ hours. After the ink was cooled, 10% by weight of (~-hydroxy-
ethyl)trimethylammonium chloride was dissolved in the cooled
solution. The ink formulation was then filtered and charged
¦ into capillary type writing instruments having writing tips
l formed of closely packed polyester fiber strands. Each pen -
¦ was tested to make sure it would produce a written line, afterwhich the uncapped pens were placed in a dessicator containing
a saturated solution of MgC12 6H20 to maintain a R.H. of
approximately 33%.
l Pens removed from the dessicator our, seven, and
¦ fourteen days later would not produce a written line since
l their writing points had dried out. However, when the pens
¦ were recapped and allowed to equilibrate for a few hours, the
; ¦ ability to ~ite had been restored in all cases.
I EX~LF. II
1 Ingredi nt /O by Weig,ht
Color Index Acid Blue 9 (C.I. ~42090) 7.0
benzotriazole l.0
methyl parasept 0.2
glycerin 5.0
ethylene glycol 12.5
water q.s. to lO0
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Procedure: The above ingredien~s are combined and heated to
55 C for two hours with constant stirring. The solution is
allo~Jed to cool to room tempera~ure, at which time 10% by
weight of carboxymethyltrimethylammonium hydroxide is added
with stirring. The ink formulation is then filtered and
charged into capillary type writing instruments having writing
tips formed by closely packed polyester fiber strands.
EXAMPLE III
Ingredient ~/O by Wei~ht
Color Index Acid Red 73 (C.I. #27290) 8.0
benzotriazole 1.0
methyl parasept 0.2
glycerin 5.0
ethylene glycol 12.5
water q,s. to 100
Procedure: The above ingredients are combined and heated to
55C for two hours with constant stirring. The solution is
allowed to cool to room temperature, at which time 10% by
weight of (~-hydroxyethyl)trimethylammoniu~ chloride is added
wlth stirring. After filtering, the ink formulation is charged
into capillary type writing instruments having ~riting tips
formed of closely packed polyester fiber strands.
EX~PLE IV
Ingredient % by Weight
Color Index Acid Blue 9 (C.I, #42090) 7.0
benzotriazole 1.0
methyl parasept 0.2
water q.s. to 100
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Proce(lure: The above ingredients are combined and heated to
55 C for two hours with constant stirring. The solution is
allowed to cool to room temperatur~, at which time 15% by
j weight of carboxymethyltrimethyla~monium hydroxide is added
I with stirring. The ink formula~ion is then filtered and
charged into capillary type writing instruments having writing
tips formed by extruding, melt-drawing, and compressively
drawing polyamide.
¦ The pens containing the ink compositions set forth
I in Examples II, III, and IV can be rejuvenated after their
' writing points have dried out, by cappin~ for a few hours.
~ At that time, their abiiity to produce a written line will have
¦ been restored.
What is claimed is:
