U.S. patent application number 09/800063 was filed with the patent office on 2002-01-10 for novel optical fiber gel fluid.
Invention is credited to Silverstein, Robert.
Application Number | 20020004138 09/800063 |
Document ID | / |
Family ID | 26883054 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020004138 |
Kind Code |
A1 |
Silverstein, Robert |
January 10, 2002 |
Novel optical fiber gel fluid
Abstract
A novel optical fiber gel fluid is provided.
Inventors: |
Silverstein, Robert; (Great
Neck, NY) |
Correspondence
Address: |
HEDMAN & COSTIGAN, P.C.
1185 Avenue of the Americas
New York
NY
10036
US
|
Family ID: |
26883054 |
Appl. No.: |
09/800063 |
Filed: |
March 5, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60187459 |
Mar 6, 2000 |
|
|
|
Current U.S.
Class: |
428/375 |
Current CPC
Class: |
G02B 6/4494 20130101;
Y10T 428/2933 20150115; G02B 6/032 20130101 |
Class at
Publication: |
428/375 |
International
Class: |
D02G 003/00 |
Claims
1. A fiber optic gel comprising: (a) an ethylene-alpha-olefin
polymer comprising: (i) 10 to 80% ethylene, (ii) 14 to 80% of a
first olefin having from 3 to 20 carbon atoms, and (iii) 0 to 10%
of a second olefin having from 3 to 20 carbon atoms which is
different from said first olefin; wherein said
ethylene-alpha-olefin has a molecular weight of greater than about
700 and a pour point of less than about -30.degree. C.; and (b) an
effective amount of a gelling agent.
2. A fiber optic gel as defined in claim 1 wherein said first
olefin comprises propylene.
3. A fiber optic gel as defined in claim 1 wherein said second
olefin comprises a C.sub.4 to C.sub.12 olefin.
4. A fiber optic gel as defined in claim 1 wherein said second
olefin is selected from the group consisting of 1-butene,
1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene,
styrene and mixtures thereof.
5. A fiber optic gel as defined in claim 1 wherein said
ethylene-alpha-olefin polymer has a molecular weight of greater
than 1000.
6. A fiber optic gel as defined in claim 1 wherein said
ethylene-alpha-olefin polymer has a molecular weight of greater
than 1100.
7. A fiber optic gel as defined in claim 1 wherein said
ethylene-alpha-olefin polymer has a molecular weight of greater
than 2000.
8. A fiber optic gel as defined in claim 1 wherein said gelling
agent is selected from the group consisting of silica, colloidal
silica, precipitated silica, clay and mixtures thereof.
9. A fiber optic gel as defined in claim 1 further comprising (c)
an effective amount of a bleed resistant agent.
10. A fiber optic gel as defined in claim 9 wherein said bleed
resistant agent comprises a styrene-rubber block copolymer, a
styrene-rubber-styrene block copolymer or a mixture thereof.
11. A fiber optic gel as defined in claim 1 further comprising (d)
an effective amount of a thermal/oxidative stabilizer.
12. A fiber optic gel as defined in claim 11 wherein said
stabilizer comprises a hindered phenolic stabilizer.
13. A fiber optic gel as defined in claim 1 further comprising (e)
an effective amount of a thickening agent.
14. A fiber optic gel as defined in claim 13 wherein said
thickening agent comprises a glycol.
15. A fiber optic gel as defined in claim 1 wherein said
ethylene-alpha-olefin polymer is further processed by thermal
cracking.
16. A fiber optic gel as defined in claim 15 wherein said thermally
cracked polymer is hydrogenated.
17. A fiber optic gel as defined in claim 15 wherein said thermally
cracked polymer is hydroisomerized.
18. A fiber optic gel as defined in claim 1 wherein said effective
amount of gelling agent comprises an amount ranging from about 5 to
about 8 weight percent of the total gel composition.
19. A fiber optic gel as defined in claim 9 wherein said effective
amount of bleed resistant agent comprises an amount ranging from
about 1 to about 2 weight percent.
20. A fiber optic gel as defined in claim 11 wherein said effective
amount of thermal/oxidative stabilizer comprises an amount ranging
from about 1 to 2 weight percent based on the total gel
composition.
21. A fiber optic gel as defined in claim 1 wherein said
ethlyene-alpha-olefin polymer is present in an amount of at least
about 85 weight percent based on the total gel composition.
22. A fiber optic cable comprising: (I) a fiber optic member; (II)
surrounded by a fiber optic gel as defined in claim 1; and (III)
encased in a cable jacket.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Provisional
Application Ser. No. 60/187,459, filed Mar. 6, 2000, currently
pending.
FIELD OF THE INVENTION
[0002] The present invention generally relates to a novel optical
fiber gel fluid. More particularly the present invention relates to
an optical fiber gel fluid comprising ethylene-alpha-olefin
copolymers.
BACKGROUND OF THE PRESENT INVENTION
[0003] In providing cushioning of the fiber optic elements which
are carried in a jacket or sheath, care must be taken to assure
that the optical qualities of the fiber optic elements are not
diminished. It is desirable for buffer tube as well as cable jacket
polymer and waterblocking gels to have as little interaction as
possible. Compatibility of a polymer gel system in flooded cable
designs can have a serious effect on cable lifetime and
reliability. Since 1995, polypropylene and polyethylene buffer
tubes have become increasingly attractive from an application and
installation standpoint.
[0004] Although polyolefins can lead to improvements in cable
performance and reduced cost, they may not be compatible with many
traditional, low cost polyolefin and hydrocarbon-based cable gel
compounds. In systems where strong swelling interactions exist,
lifetimes can be reduced to a small fraction of that which would be
observed for the virgin polymer. This incompatibility is due to
favorable solvent-polymer interactions between polyolefins and
polyolefin-based gels. The commercially available cable
waterblocking gels have very significant compound to compound
variation in compatibility with polyolefins.
[0005] Currently, polyalphaolefins (PAOs) are the dominant
hydrocarbon synthetic base oil on which the gels are based.
However, costs are high compared to conventional mineral base oils.
Generally, the PAO's are manufactured in two steps. First, ethylene
is oligomerized with aluminum alkyl to produce a range of linear
alpha-olefins having even numbers carbon atoms from C.sub.4 to
C.sub.30+. About fifteen linear alpha-olefins are produced that
serve distinct markets growing at different rates. About 25% of the
linear alpha-olefins are 1-Decene, the major component of PAO.
[0006] PAO is generally prepared by reaction of 1-Decene with a
Lewis Acid catalyst such as BF.sub.3 to produce primarily trimers
and tetramers. 1-Decene is expensive and costs about three times
more than ethylene making PAO very expensive. Other examples of
Lewis Acid catalysts used to produce higher molecular weight PAOs
are alkyl aluminum halides such as those disclosed in U.S. Pat.
Nos. 4,469,910 and 4,594,469, both of which are incorporated herein
by reference.
[0007] As an alternative, polyol-based and high molecular weight
polyalphaolefin waterblocking gels have been utilized, especially
for buffer tube filling applications, which offer better
compatibility due to less favorable polymer-gel interactions.
Compared to waterblocking gels based on mineral oils, however,
these gels are even more expensive, which decreases the cost
savings associated with use of polyolefins such as polypropylene
for buffer tube applications.
[0008] Exemplary conventional gels are described in Brauer et al.,
U.S. Pat. No. 5,433,872; Brauer et al., U.S. Pat. No. 5,348,669;
Randisi, U.S. Pat. No. 5,050,959; Kaufman et al., U.S. Pat. No.
5,285,513; and Tu, U.S. Pat. No. 5,187,763, all of which are
incorporated herein by reference in their entirety.
[0009] While the known water resistant optical cable gel fluids
possess some unique features, they are expensive and not completely
suitable for many potential applications. Thus, there is a need in
the art for an improved, lower cost cable gel fluid which is water
resistant, has a wide service temperature range, high shear and
oxidation stability, low toxicity and has reduced influence on the
swelling interaction with polyolefin buffer tubes.
DESCRIPTION OF THE INVENTION
[0010] The present invention provides a novel optical fiber cable
gel for use with fiber optic elements. The gels are made from
fluids of high molecular weight ethylene-alpha-olefin polymers
produced by polymerization of ethylene, an alpha-olefin different
from ethylene, and optionally a third monomer different from the
alpha-olefin and having 3 to 20 carbon atoms, in the presence of a
combination catalyst comprising a compound of a transition metal of
Group IVb of the Periodic Table and an aluminoxane. The copolymer
or terpolymer may be further processed by thermal cracking to yield
novel cracked polymers, and the cracked polymers may be
hydrogenated. The copolymers or terpolymers may also be
hydroisomerized.
[0011] The ethylene-alpha-olefin polymers useful in the practice of
the present invention are those having a low pour point, less than
about -30.degree. C. and a relatively high molecular weight, such
as greater than 700, preferably greater than 1000, more preferably
greater than 1100 and most preferably up to about 2000 or more.
These ethylene-alpha-olefin polymers and their method of production
as fully set forth in International Application No. PCT/US98/12621
published under International Publication Number WO 98/58972 which
is hereby incorporated by reference in its entirety.
[0012] The above-described fluids are generally present in an
amount of 85% by weight or more based on the weight of the entire
gel composition. The molecular weight distribution of these fluids
has a dramatic influence on the swelling interaction. Gels with
large molecular weight components swell a given polymer most
severely. The polymerized fraction utilized in the present
invention has a kinematic viscosity at 100.degree. C. of greater
than 10 cSt, a flash point of greater than 235.degree. C. and a
pour point of -30.degree. C. or less. The fluids of the present
invention create a swelling weight gain of less than 3% in three
different fiber optic grades of impact modified polypropylene.
[0013] The above-described fluids are then gelled with an effective
amount of gelling agent such as are known to those of ordinary
skill in the art. Preferred gelling agents are fumed silica,
colloidal silica, either hydrophilic or hydrophobic, precipitated
silicas and clays such as bentonite with or without surface
treatment. Other inorganic colloidal particles may also be used, if
desired, although the silicas are preferred. Generally the gelling
agent is present in an amount ranging from about 5 to 8 percent by
weight based on the weight of the entire gel composition.
[0014] Optionally, an effective amount of a bleed resistant agent
may be added to the gels. Any such bleed resistant agents known to
those skilled in the art to prevent the gels from bleeding through
the polymer sheath may be employed. Block copolymers are preferred
bleed resistant agents, such as styrene-rubber and
styrene-rubber-styrene block copolymers. Commercially available
examples are a styrene-ethylene-propylene block copolymer (SEP)
sold under the trade designation Kraton G1701 or G1702, a
styrene-ethylene butylene-styrene block copolymer (SEBS) sold under
the trade designation Kraton G1657, or a styrene block copolymer
mixture sold under the trade designation Kraton 1726. Preferably
the bleed resistant agent is employed in an amount ranging from
about 3 to about 6 weight percent based on the weight of the total
gel composition.
[0015] Optionally, an effective amount of thermal and/or oxidative
stabilizer may also be added to the gels of the present invention
as is known to those of ordinary skill in the art. Preferred are
hindered phenolic stabilizers such as those available from
Ciba-Geigy Company under the trade designation Irganox 1035. In
preferred embodiments these are present in amounts ranging from
about 1 to about 2 percent by weight based on the weight of the
total gel composition.
[0016] It is also contemplated to add effective amounts of
thickening agents where necessary. These especially useful in the
practice of the present invention to increase the viscosity of the
gel by increasing the interaction possibilities between the silica
and the oil. A small amount of glycol, such as polypropylene
glycol, may be added.
[0017] Swelling of coating materials for optical fibers in contact
with the filling gels of the present invention is substantially
reduced over that seen with prior art filling materials. The use of
a low pour point aliphatic hydrocarbon in the filling gel allows
the cable to provide superior optical performance at low
temperatures.
[0018] The filling gel composition of the present invention
encompasses the fibers. Typically, the fibers and the filling
material are contained within a tubular member which is disposed
within a sheath system. The sheath system includes longitudinally
extending strength members and a plastic jacket. See for example
the above-mentioned U.S. Pat. Nos. 5,285,513 and 5,187,763.
[0019] The filling composition of the present invention comprises
at least about 85 percent by weight of the above-described oils
having a molecular weight of at least about 700. Relatively low
pour point oils are preferred in order to improve optical loss at
low temperature.
[0020] A thickening system which includes an inorganic constituent
and a block copolymer is preferred to form the gel as well as to
reduce oil separation. An antioxidant is used to prevent thermal
oxidative degeneration of the filling gels of the present
invention.
[0021] A grease-like filling composition prepared in accordance
with the present invention having a relative high critical yield
stress (as it relates to the stiffness of the gel) allows the
inside diameter of tubes to increase. A larger tube can incorporate
a larger amount of optical fibers in the form of stacked ribbons.
The result in an increase in bandwidth.
[0022] The compositions formed in accordance with the present
invention are thixotropic and are operable over a wide temperature
range. They are water resistand and remain soft at both ends of the
relevant temperature spectrum. They are compatible with a variety
of jacket materials, including polypropylene, polyethylene,
polycarbonate, etc, at other cable materials which they
contact.
[0023] The filling material of the present invention has enhanced
performance at low temperature because of the use of a low pour
point oil and very low oil separation. There is no bleeding of oil
and it is expected that the optical loss at -40.degree. C. will not
exceed that of the prior art filling materials.
* * * * *