U.S. patent application number 11/030788 was filed with the patent office on 2005-07-14 for melt blown fiber structures for use in high strength wicks.
This patent application is currently assigned to Filtrona Richmond, Inc.. Invention is credited to Long, Robert D., Nelson, Donald F., Nelson, Raymond J., Payne, Jackie F. JR., Ward, Bennett C., Yancey, E. Vaughan.
Application Number | 20050153132 11/030788 |
Document ID | / |
Family ID | 29250646 |
Filed Date | 2005-07-14 |
United States Patent
Application |
20050153132 |
Kind Code |
A1 |
Ward, Bennett C. ; et
al. |
July 14, 2005 |
Melt blown fiber structures for use in high strength wicks
Abstract
A high strength wick is presented that comprises a
self-sustaining fibrous element. This element is formed of a
multiplicity of fibers bonded to each other at spaced apart points
of contact to define a porous matrix. The fibers are melt blown
bicomponent fibers comprising a core of nylon 6,6 and a sheath of a
polymer selected from the group consisting of polyethylene
terephthalate and copolymers of polyethylene terephthalate. The
sheath polymer is selected and adapted for solvent resistance.
Inventors: |
Ward, Bennett C.;
(Midlothian, VA) ; Long, Robert D.; (Chester,
VA) ; Nelson, Donald F.; (Richmond, VA) ;
Nelson, Raymond J.; (Powhattan, VA) ; Payne, Jackie
F. JR.; (Chester, VA) ; Yancey, E. Vaughan;
(Manakin Sabot, VA) |
Correspondence
Address: |
J. MICHAEL MARTINEZ DE ANDINO ESQ.
HUNTON & WILLIAMS
RIVERFRONT PLAZA, EAST TOWER
951 EAST BYRD ST.
RICHMOND
VA
23219-4074
US
|
Assignee: |
Filtrona Richmond, Inc.
Colonial Heights
VA
|
Family ID: |
29250646 |
Appl. No.: |
11/030788 |
Filed: |
January 7, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11030788 |
Jan 7, 2005 |
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10391007 |
Mar 19, 2003 |
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6840692 |
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60371154 |
Apr 10, 2002 |
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Current U.S.
Class: |
428/375 |
Current CPC
Class: |
B43K 8/08 20130101; B43K
8/02 20130101; D01F 8/12 20130101; D01F 8/14 20130101; Y10T
428/2933 20150115 |
Class at
Publication: |
428/375 |
International
Class: |
D02G 003/00 |
Claims
1-23. (canceled)
24. A high strength wick comprising: a self-sustaining fibrous
element formed of a multiplicity of fibers bonded to each other at
spaced apart points of contact to define a porous matrix, said
fibers being melt blown bicomponent fibers comprising a core of
nylon 6,6 and a sheath of a polymer selected from the group
consisting of polyethylene terephthalate and copolymers of
polyethylene terephthalate, said polymer being selected and adapted
for solvent resistance.
25. A high strength wick according to claim 24 wherein the polymer
of said sheath is polyethylene terephthalate.
26. A writing or marking instrument comprising: a barrel having a
barrel interior; a reservoir disposed in the barrel interior for
holding and controllably releasing a quantity of ink; and a nib
formed from a high strength wick according to claim 24, the nib
being adapted for transferring ink from said reservoir to a writing
surface.
27. A roller ball pen comprising a barrel having a barrel interior;
a reservoir disposed in the barrel interior for holding and
controllably releasing a quantity of ink a roller ball tip
including a roller ball at its terminus; and a high strength wick
according to claim 24 extending from the roller ball tip into
contact with the reservoir.
Description
[0001] This is a complete application claiming benefit of
provisional application Ser. No. 60/371,154 filed Apr. 10,
2002.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The instant invention relates to unique polymeric
bicomponent fibers and to the production of wicking devices,
especially, nibs and ink reservoirs for writing and marking
instruments made from such fibers. More specifically, this
invention is directed to the production and use of nibs and ink
reservoirs, particularly nibs for writing and marking instruments
such as fiber tip pens and "felt tip" markers, as well as roller
ball wicks for roller ball pens, wherein the wicking devices are
formed of sheath-core, melt blown, bicomponent fibers wherein a
core of a nylon 6,6 is substantially fully covered with a sheath of
polyethylene terephthalate or a copolymer thereof. For the
production of nibs, the core material may be polybutylene
terephthalate.
[0004] 2. Discussion of the Prior Art
[0005] The production of thermally bonded fibrous products for
various applications is disclosed in commonly assigned U.S. Pat.
No. 5,607,766 issued Mar. 4, 1997 (the subject matter of which is
incorporated herein in its entirety by reference) (the '766 patent)
using bicomponent fibers comprising a coating of a polyester
sheath, such as polyethylene terephthalate and its copolymers, over
a thermoplastic core, such as polypropylene and polybutylene
terephthalate. There are currently commercial permanent ink markers
using nibs made of polyester felt impregnated with phenolic resin
which have an aggressive xylene-based ink formulation. Past
attempts to produce nibs formed of bonded polyester fiber tows,
particularly for use with writing and marking instruments
incorporating such aggressive inks, have suffered unacceptable
"drainback" properties. A drainback test is where the marker is
stood on end, tip up, for 48 hours. It is then inverted (tip down).
The pen must write on the third stroke to pass the test. While
currently available polyester felt/phenolic nibs satisfy commercial
drainback criteria, early polyester filament-based attempts to
reproduce these properties failed.
[0006] Although core materials of polybutylene terephthalate, as
disclosed in the '766 patent, show desirable properties for use as
reservoirs in writing and marking instruments and the
polyester/polypropylene bicomponent fiber products discussed
therein are acceptable for selected applications, both
polypropylene and nylon 6 core materials in polyester sheath
bicomponent fiber thermally bonded writing and marking instrument
components have now been found to unduly soften in the presence of
certain particularly aggressive ink formulations, making marking
and writing instrument components, particularly nibs, formed of
bicomponent fibers having polyester sheaths with such core polymers
of limited utility and, from a commercial standpoint, effectively
useless.
[0007] This invention relates to the surprising discovery that, in
the production of nibs for writing instruments, such as roller ball
or fiber-point pens, or marking instruments, such as felt-tipped
permanent highlighters, dry-erase markers and the like, especially
those incorporating aggressive inks such as xylene-based permanent
ink formulations, the use of a bonded fibrous element formed from
melt blown bicomponent fibers comprising a polyester sheath and a
nylon 6,6 or polybutylene terephthalate core material provides
excellent drainback and ink laydown properties, thermal stability
and physical robustness. Use of bonded fiber tow materials, even
bicomponent fiber tows having a polyester sheath over a nylon 6,6
core, will fail the drainback test, but melt blown bicomponent
fibers of these polymers produce acceptable nibs for writing and
marking instruments.
[0008] Such products also have unexpectedly improved solvent
resistence and increased stiffness avoiding degradation under
pressure in use. Moreover, these unique bicomponent fibers produces
writing and marking instrument components which are less expensive
than competitive products, such as the polyester felt/phenolic nibs
currently in the market. Similar advantages are expected for ink
reservoirs formed of melt blown polyester/nylon 6,6 bicomponent
fibers.
OBJECTS AND SUMMARY OF THE INVENTION
[0009] It is, therefore, a principal object of the instant
invention to provide a method and apparatus for making writing and
marking instrument components in a simple, efficient and
inexpensive manner, yet having the property of unexpectedly
improved drainback, exceptional solvent resistance in the presence
of highly aggressive ink formulations, and increased stiffness and
robustness, resisting degradation under pressure, particularly when
used as a nib.
[0010] Another object of this invention is the provision of melt
blown polymeric bicomponent fibers having a polyester sheath,
particularly polyethylene terephthalate and copolymers thereof,
totally surrounding a core of nylon 6,6, and the production of
thermally bonded porous fibrous products for use as a nib, roller
ball wick or ink reservoir in a writing or marking instrument which
will not be significantly softened by the solvent in the ink and
function effectively to retain and controllably feed ink from a
reservoir to a writing surface even after extended use.
[0011] Yet another object of this invention is the provision of a
writing instrument and/or a marker incorporating a nib, roller ball
wick and/or an ink reservoir formed as a thermally stable,
three-dimensional, porous element capable of storing and/or
controllably releasing and feeding a liquid ink formulation with
little or no drainback.
[0012] A further object of this invention is the provision of a
high capacity ink reservoir for a writing or marking instrument
defined by an elongated porous rod formed of a network of fine melt
blown bicomponent fibers having a continuous sheath of polyethylene
terephthalate or a copolymer thereof, and a core of nylon 6,6, and
a nib for a roller ball or fiber-point pen or a felt-tipped marker,
or the like, which are compatible with all currently-available ink
formulations and provide an adequate release pressure to minimize
"leakers" and "drainback", and remain functionally effective over
extended periods of use.
[0013] Upon further study of the specification and the appended
claims, additional objects and advantages of this invention will
become apparent to those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] These and other objects, features and many of the attendant
advantages of this invention will be better understood by those
with ordinary skill in the art in connection with the following
detailed description of the preferred embodiments and the
accompanying drawings wherein:
[0015] FIG. 1 is an enlarged perspective view of one form of a
"sheath-core" bicomponent fiber according to the instant
invention;
[0016] FIG. 2 is a perspective view of an ink reservoir element
made therefrom;
[0017] FIG. 3 is a side elevational view of an ink reservoir
element including a longitudinally continuous peripheral air
passageway integrally formed therein;
[0018] FIG. 4 is an enlarged transverse cross-sectional view taken
along lines 4-4 of FIG. 3;
[0019] FIG. 5 is a cross-sectional view, partially broken away, of
one form of a writing instrument in the nature of a roller ball
disposable pen incorporating an ink reservoir, and a roller ball
fiber wick made according to the instant inventive concepts;
[0020] FIG. 6 is a side elevational view, partially broken away, of
a marking instrument in the nature of a "felt tip" marker, also
incorporating an ink reservoir and a fibrous nib made according to
the instant inventive concepts;
[0021] FIG. 7 is a perspective view of the nib portion of the
marker of FIG. 6; and
[0022] FIG. 8 is a side elevational view of a nib to be used in a
fiber-point pen according to this invention.
[0023] Like reference characters refer to like parts throughout the
several views of the drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The instant inventive concepts are embodied in a
bicomponent, sheath-core, melt blown, fiber as seen schematically,
very enlarged, at 20 in FIG. 1 wherein the core 24 is formed of
nylon 6,6 and the sheath 22 is formed of polyethylene terephthalate
or a copolymer thereof.
[0025] As defined in the '766 patent, the term "bicomponent" as
used herein refers to the use of two polymers of different chemical
nature placed in discrete portions of a fiber structure. While
other forms of bicomponent fibers are possible, the more common
techniques produce either "side-by-side" or "sheath-core"
relationships between the two polymers. The instant invention is
concerned with the production of "sheath-core" bicomponent fibers
wherein a sheath of polyethylene terephthalate or a copolymer
thereof is spun to completely cover and encompass a core of nylon
6,6 or polybutylene terephthalate, preferably using a "melt blown"
fiber process to attenuate the extruded fiber.
[0026] As defined in the '766 patent, the term "polyethylene
terephthalate or a copolymer thereof" refers to a homopolymer of
polyethylene terephthalate or a copolymer thereof having a melting
point which is higher than the melting point of the thermoplastic
core material in the bicomponent fiber.
[0027] Conventional linear polyester used to make fibers is the
product of reaction of ethylene glycol (1,2 ethanediol) and
terephthalic acid (benezene-para-dicarboxylic acid). Each of these
molecules has reactive sites at opposite ends. In this way, the
larger molecule resulting from an initial reaction can react again
in the same manner, resulting in long chains made of repeated units
or "mets". The same polymer is also industrially made with ethylene
glycol and dimethyl terephthalate (dimethyl
benezene-paradicarboxylate). It is believed that polyethylene
terephthalate and its copolymer of a broad range of intrinsic
viscosities are useful according to this invention, although those
with lower intrinsic viscosities are preferred.
[0028] By partially substituting another diol for the ethylene
glycol or another diacid for the terephthalic acid, a more
irregular "copolymer" is obtained. The same effect is achieved by
the substitution of another dimethyl ester for the dimethyl
terephthalate. Thus, there is a wide choice of alternative
reactants and of levels of substitution.
[0029] The deviation from a regularly repeating, linear polymer
makes the crystallization more difficult (less rapid) and less
complete. This is reflected in a lower and wider melting range.
Excessive substitution will result in a totally amorphous polymer
which is unacceptable for use in this invention.
[0030] As defined in the '766 patent, the term "melt blown" refers
to the use of a high pressure gas stream at the exit of a fiber
extrusion die to attenuate or thin out the fibers while they are in
their molten state. Melt blowing of single polymer component fibers
was initiated at the Naval Research Laboratory in 1951. The results
of this investigation were published in Industrial Engineering
Chemistry 48, 1342 (1956). Seven years later, Exxon completed the
first large semiworks melt blown unit demonstration. See, for
example, Buntin U.S. Pat. Nos. 3,595,245, 3,615,995 and 3,972,759
(the '245, '995 and '759 patents, the subject matters of which are
incorporated herein in their entirety by reference) for a
comprehensive discussion of the melt-blowing process. Although the
average diameter of the bicomponent fibers can vary over a
significant range without departing from the instant inventive
concepts, fine fibers, on the order of about 10 microns, as
produced by conventional melt blowing techniques are particularly
useful. Specific apparatus and techniques for producing such fibers
are found in the '766 patent.
[0031] The term "nylon 6,6" as used herein refers to a polymer of
adipic acid and hexamethylene diamine. The nylon 6,6 used was
DuPont Zytel 101, unfilled, with a melt viscosity range of 88-124
pascal-seconds.
[0032] An ink reservoir 25 as seen in FIG. 2 comprises an elongated
air-permeable body of fine melt blown bicomponent polyethylene
terephthalate/nylon 6,6 fibers such as shown at 20 in FIG. 1,
bonded at their contact points to define a high surface area,
highly porous, self-sustaining element having excellent capillary
properties using the techniques disclosed in the '766 patent. It is
to be understood that elements 25 produced in accordance with this
invention need not be of uniform construction throughout as
illustrated in FIG. 2. For example, a continuous longitudinally
extending peripheral groove such as seen at 26 in FIGS. 3 and 4 can
be provided as an air passage in an ink reservoir 30, which may or
may not include a coating or film wrap (not shown).
[0033] The reservoir 30 may be incorporated into a writing
instrument as shown in FIG. 5 which is illustrated as including a
roller ball wick 36, which can also be produced by the techniques
of this invention, extending into a roller ball writing tip 38 in a
conventional manner. The ink reservoir 35 is contained within a
barrel 40 in fluid communication with the roller ball wick 36 to
controllably release a quantity of ink retained in the reservoir 30
to the roller ball 42 in the usual way.
[0034] As is well known in the art, the roller ball wick 36 will
generally have a higher capillarity than the reservoir 30, with the
fibers thereof being more longitudinally oriented so as to draw the
ink form the reservoir 30 and feed the same to the roller ball 42.
It is well within the skill of the art to form the
three-dimensional porous elements of the instant invention with
higher or lower capillarity depending upon the particular
application by controlling, for example, the speed with which the
fibrous mass is fed into the forming devices, the size and shape of
the forming devices and other such obvious processing
parameters.
[0035] In FIG. 6, a marking device is shown generally at 50, as
including a conventional barrel 52, containing an ink reservoir 55
in fluid communication with a fibrous wick or nib 54 seen in
perspective in FIG. 7, which may be of the type commonly referred
to as a "felt tip". Again, the nib 54 is generally denser, than the
fibers from which the reservoir 55 are made, in order to provide
the nib with the higher capillarity necessary to draw the ink from
the reservoir in use.
[0036] A fiber tip 60 seen in FIG. 8 can also be provided according
to his invention for use in lieu of the roller ball wick 36 of FIG.
5 or the felt tip nib 54 of FIG. 6 in the production of a
fiber-point pen in a well known manner.
[0037] The angled felt-tip nib 54 and the pointed fiber tip 60 can
be provided with the shapes shown, or any other desired shape, by
conventional cutting, grinding or other techniques well known to
those skilled in the art.
[0038] While reference has been made herein to the provision of
writing and marking instrument nibs and reservoirs made of melt
blown, bicomponent sheath/core polyethylene terephthalate/nylon 6,6
fibers according to this invention, it is to be understood that the
nibs of this invention can be used effectively with other
reservoirs, even in the presence of aggressive ink formulations,
since the reservoirs are not subjected to the pressure experienced
by the nibs in use and need not be as robust. Moreover, although
polyethylene terephthalate/polybutylene terephthalate ink
reservoirs are suggested in the '766 patent, it is surprising that
such bicomponent fibers can satisfy the more rigorous requirements
of a nib for a writing or marking instrument since the use of the
other core polymers referenced in the '766 patent are not
acceptable for this purpose as explained below. It will also be
understood that reservoirs formed of polyester/nylon 6.6 fibers
according to this invention are expected to have advantages, even
for use with nibs made of prior art materials.
[0039] To compare the properties of nibs made by this invention
with nibs made of melt blown bicomponent polyester sheath fibers
with different core materials, square stock, angularly cut nibs
typical of marker "felt tip" pens, were made from melt blown
polyethylene terephthalate (PET)/polypropylene (PP) (25/75)
sheath-core bicomponent fibers using the general techniques
disclosed in the '766 patent, cut with a razor blade at a
45.degree. angle, and inserted into Sanford King Size item number
15000 permanent markers after the commercial nibs were removed.
This enabled testing in the exact ink and marker environment.
Comparable products were made from melt blown bicomponent fibers
comprising PET sheath materials covering, respectively,
polybutylene terephthalate (Ticona PBT), nylon (BASF Ultramin) and
nylon 6,6 Dupont Zytel).
[0040] All samples spun well, with the PET/PBT and PET/Nylon 6,6
bonding acceptably. PET/Nylon 6 bonding behavior was poorer than
the other samples. The PET/nylon 6 nibs were attacked by the ink in
a manner similar to PET/PP. Because of this, these pieces were not
tested further.
[0041] Samples were run at a variety of densities. These densities
(all in g/10 pieces) were:
1 PET/PBT: 5, 6, 7 PET/Nylon 6,6 (melt blown): 4.5, 5, 6.5
[0042] For the most part, with the exceptions noted below, the
density can be varied over a significant range depending upon the
particular application of the final product.
[0043] Summary results are:
2 Criteria Store bought PET/PBT PET/Nylon 6,6 (melt blown) 48
softening Pass Pass Pass 48 hour drainback Pass Pass (high density
(7) failed) Pass Hand write (will the nib pass ink to paper) Pass
Pass Pass Firmness after 48 hours (subjective) Pass Pass (some had
slightly soft tips) Pass (some had slightly soft tips) Bleed
through Pass Pass Pass Write after 60.degree. C., 5 days Pass Pass
(except at 7 density) Pass Firmness after 60.degree., 5 days Pass
Slightly feathered Pass Firmness after 100 meter writing test Worn
down No impact to feathered Slightly to heavily feathered Cap off
(dryout) test (1 hour in hood) All fail Some pass, some fail Some
pass, some fail
[0044] The above tests show that, unlike the PET/PP and PET/nylon 6
samples which were unacceptably softened by the ink and
commercially useless as nibs for marking instruments, the PET/nylon
6,6 nibs (as well as the PET/PBT nibs), for the most part, compared
favorably with commercial polyester felt/phenolic nibs in each of
the tested properties. From a manufacturing standpoint, use of the
melt blown process according to this invention enables the creation
of finished marker nibs from polymer chip in a continuous manner
eliminating the prior art techniques of fiber spinning, felting,
forming, resin impregnation and cutting. As a result, significant
economies should be achieved, with savings of from 20-50%
possible.
[0045] Nibs made from the same polymeric components, i.e., PET over
nylon 6,6, but of a bonded fiber tow rather than melt blown fibers,
fail to provide commercially acceptable drainback properties.
Although the rationale for this surprising result is not known for
certain, it is theorized that the improved tortuous path
characteristics of the melt blown web enhance the drainback
properties of the resultant nibs.
[0046] The foregoing descriptions and drawings should be considered
as illustrative only of the principles of the invention. Numerous
applications of the present invention will readily occur to those
skilled in the art. Therefore, it is not desired to limit the
invention to the preferred embodiments or the exact construction
and operation of the preferred apparatus shown and described.
Rather, all suitable modifications and equivalents may be resorted
to, falling within the scope of the invention.
* * * * *