U.S. patent application number 10/077166 was filed with the patent office on 2003-04-24 for optical fiber coating compositions.
Invention is credited to Chien, Ching-Kee, Fewkes, Edward J., Gasper, Susan M., Hill, Anita S., Jacobs, Gregory F., Wagner, Frederic C., Winningham, Michael J., Youngman, Randall E..
Application Number | 20030077059 10/077166 |
Document ID | / |
Family ID | 27373039 |
Filed Date | 2003-04-24 |
United States Patent
Application |
20030077059 |
Kind Code |
A1 |
Chien, Ching-Kee ; et
al. |
April 24, 2003 |
Optical fiber coating compositions
Abstract
The invention includes a composition for an optical fiber
coating. An inventive composition includes a non-thiol functional
adhesion promoter and less than about 0.5 pph of a strength
additive containing a thiol functional group. The invention further
includes an optical fiber coated with the inventive composition. A
second inventive composition includes a photo-polymerizable
composition which contains an adhesion promoter and a non- silicon
containing strength additive containing at least about one thiol
functional group. A third inventive composition includes a
photo-polymerizable composition which has a silane containing
adhesion promoter and a strength additive containing at least about
one halide functional group. The invention also includes an optical
fiber coated with the inventive coating and methods of making an
optical fiber including the inventive coating.
Inventors: |
Chien, Ching-Kee;
(Horseheads, NY) ; Fewkes, Edward J.; (Horseheads,
NY) ; Gasper, Susan M.; (Corning, NY) ; Hill,
Anita S.; (Bath, NY) ; Jacobs, Gregory F.;
(Elmira, NY) ; Wagner, Frederic C.; (Horseheads,
NY) ; Winningham, Michael J.; (Big Flats, NY)
; Youngman, Randall E.; (Horseheads, NY) |
Correspondence
Address: |
CORNING INCORPORATED
SP-TI-3-1
CORNING
NY
14831
|
Family ID: |
27373039 |
Appl. No.: |
10/077166 |
Filed: |
February 15, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60275421 |
Mar 13, 2001 |
|
|
|
60315857 |
Aug 29, 2001 |
|
|
|
Current U.S.
Class: |
385/128 ;
385/141; 522/6 |
Current CPC
Class: |
Y10T 428/2938 20150115;
Y10T 428/2933 20150115; C03C 25/106 20130101 |
Class at
Publication: |
385/128 ;
385/141; 522/6 |
International
Class: |
G02B 006/22; C08F
002/46 |
Claims
What is claimed is:
1) An optical fiber coating comprising: a photo-polymerizable
composition which comprises a non-thiol functional adhesion
promoter and less than about 0.5 pph of a strength additive
containing a thiol functional group.
2) The coating according to claim 1 wherein in said strength
additive further comprise an organic strength additive and includes
at least one element from the group of elements consisting of C, H,
N, O, Si, P, F, Cl, Br, I, Ti, Zr, S and mixtures thereof, in
addition to an S element in said thiol functional group.
3) The coating according to claim 1 wherein said strength additive
comprises an alkyl thiol compound.
4) The coating according to claim 3 wherein said alkyl thiol
comprises at least one compound selected from the following group
of compounds consisting of methane thiol, ethane thiol, hexane
thiol, dodecane thiol, octadecane thiol, a cysteine derivative, a
multi-functional thiol, thiol silane, thiol-functional
polysulfides, and mixtures thereof.
5) The coating according to claim 1 wherein said strength additive
comprises at least one compound selected from the group of
compounds consisting of N-(tert butoxy carbonyl)-L-cysteine methyl
ester, pentaerythritol tetrakis (3-mercaptopropionate),
3-mercaptopropyl trimethoxy silane, 3-mercaptopropyl triethoxy
silane, dodecylmercaptan, and mixtures thereof.
6) The coating according to claim 1 wherein said concentration of
said strength additive comprises up to about 0.3 pph.
7) The coating according to claim 1 wherein said concentration of
said strength additive comprises up to about 0.1 pph.
8) The coating according to claim 1 wherein said strength additive
comprises 3-mercaptopropyltrimethoxy silane.
9) The coating according to claim 1 wherein said strength additive
comprises tert-dodecylmercaptan.
10) The coating according to claim 1 wherein said strength additive
comprises pentaerythritol tetrakis (3-mercaptopropionate).
11) A coated optical fiber comprising: an optical fiber having a
core surrounded by a cladding and at least one photo-polymerizable
composition applied to said cladding, said composition comprising a
non-thiol functional adhesion promoter and less than about 0.5 pph
of a strength additive containing a thiol functional group.
12) The coated optical fiber according to claim 11, wherein said
strength additive further comprises an organic strength additive
and includes at least about one element from the group of elements
consisting of C, H, N, O, Si, P, F, Cl, Br, I, Ti, Zr, S and
mixtures thereof, in addition to an S element in said thiol
functional group.
13) The coated optical fiber according to claim 11, wherein said
strength additive comprises an alkyl thiol.
14) The coated optical fiber according to claim 13, wherein said
alkyl thiol comprises at least one compound selected from the
following group of compounds consisting of methane thiol, ethane
thiol, hexane thiol, dodecane thiol, octadecane thiol, a cysteine
derivative, a multi-functional thiol, thiol silane,
thiol-functional polysulfides, and mixtures thereof.
15) The coated optical fiber according to claim 11 wherein said
strength additive comprises at least one compound selected from the
group of compounds consisting of N-(tert-butoxy
carbonyl)-L-cysteine methyl ester, pentaerythritol tetrakis
(3-mercaptopropionate), 3-mercaptopropyl-trimeth- oxysilane,
3-mercaptopropyl triethoxy silane, dodecylmercaptan, and mixtures
thereof.
16) The coated optical fiber according to claim 11 wherein said
concentration of said strength additive comprises up to about 0.3
pph.
17) The coated optical fiber according to claim 11 wherein said
strength additive comprise 3-mercaptopropyltrimethoxy silane.
18) The coated optical fiber according to claim 11 wherein said
strength additive comprises tert-dodecylmercaptan.
19) The coated optical fiber according to claim 11 wherein said
strength additive comprises pentaerythritol tetrakis
(3-mercaptopropionate).
20) A method of making an optical fiber comprising: drawing an
optical fiber from a sintered preform and coating the fiber with an
optical fiber coating comprising no more than about 12 pph of a
non-thiol functional adhesion promoter and less than about 0.5 pph
of a strength additive containing a thiol functional group.
21) The method according to claim 20 wherein the coating has a
thickness of at least about 20 microns and is capable of being
cured to at least about 70% at an average rate of at least about
180%/second.
22) The coating according to claim 1 wherein a concentration of the
said adhesion promoter comprises no more than about 12 pph.
23) The coated optical fiber according to claim 11 wherein a
concentration of the said adhesion promoter comprises no more than
about 12 pph.
24) An optical fiber coating comprising: a photo-polymerizable
composition which comprises an adhesion promoter, said adhesion
promoter includes at least one compound from the group of compounds
consisting of a silane, a titanate, a zirconate, and a mixture
thereof; and a non-silicon containing strength additive containing
at least about one thiol functional group.
25) The coating according to claim 24 wherein said adhesion
promoter comprises a compound substantially devoid of a thiol
functional group.
26) The coating according to claim 24 wherein said strength
comprises more than about one thiol functional group.
27) The coating according to claim 24 wherein said strength
additive comprises pentaerythritol tetrakis
(3-mercaptopropionate).
28) An optical fiber coating comprising: a photo-polymerizable
composition which comprises an adhesion promoter, said adhesion
promoter includes at least one compound from the group of compounds
consisting of a silane, a titanate, a zirconate, and a mixture
thereof; and a strength additive containing at least about one
halide functional group.
29) The coating according to claim 28 wherein said adhesion
promoter comprises a compound substantially devoid of a thiol
functional group.
30) The coating according to claim 28 wherein said strength
additive comprises a non-silicon containing compound.
31) The coating according to claim 28 wherein said strength
additive comprises at least one alkyl-halide compound.
32) The coating according to claim 28 wherein said strength
additive comprises chloro-octane.
33) The coating according to claim 28 wherein said strength
additive comprises at least one of a halo-alkyl silane compound, a
haloalkyl-alkoxysilane, a haloaryl-alkoxysilane, and combinations
thereof.
34) The coating according to claim 28 wherein strength additive
comprises at least one compound selected from the following group
of compounds consisting of chloro-propyltrimethoxy silane and
chloro-propyltriethoxy silane
35) A coated optical fiber comprising: an optical fiber having a
core surrounded by a cladding and a photo-polymerizable
composition, applied to said cladding, said composition comprises
an adhesion promoter, said adhesion promoter includes at least one
compound from the group of compounds consisting of a silane, a
titanate, a zirconate, and a mixture thereof; and a non-silicon
containing strength additive containing at least about one thiol
functional group.
36) The coated optical fiber according to claim 35 wherein said
adhesion promoter comprises a compound substantially devoid of a
thiol functional group.
37) The coated fiber according to claim 35 wherein said strength
additive comprises more than about one thiol functional group.
38) The coating according to claim 35 wherein said strength
additive comprises pentaerythritol tetrakis
(3-mercaptopropionate).
39) A coated optical fiber comprising: an optical fiber having a
core surrounded by a cladding and a photo-polymerizable
composition, applied to said cladding, said composition comprises
an adhesion promoter, said adhesion promoter includes at least one
compound from the group of compounds consisting of a silane, a
titanate, a zirconate, and a mixture thereof; and a strength
additive containing at least about one halide functional group.
40) The coated fiber according to claim 39 wherein said strength
additive comprises a non-silicon containing compound.
41) The coated fiber according to claim 39 wherein said strength
additive comprises at least one alkyl-halide.
42) The coated fiber according to claim 39 wherein said strength
additive comprises chloro-octane.
43) The coated fiber according to claim 39 wherein said strength
additive comprises at least one of a halo-alkyl silane compound, a
haloalkyl-alkoxysilane, a haloaryl- aikoxysilane, and combinations
thereof.
44) The coated fiber according to claim 39 wherein strength
additive comprises at least one compound selected from the
following group of compounds consisting of chloro-propyltrimethoxy
silane and chloro-propyltriethoxy silane.
45) The coating according to claim 1 wherein said adhesion promoter
includes at least one compound from the group of compounds
consisting of a silane, a titanate, a zirconate, and mixtures
thereof.
46) The coating according to claim 1 wherein said adhesion promoter
comprises a titanate containing compound.
47) The coating according to claim 1 wherein said adhesion promoter
comprises a zirconate containing compound.
48) The coating according to claim 1 wherein said adhesion promoter
comprises a silane containing compound.
49) The optical fiber according to claim 11 wherein said adhesion
promoter includes at least one compound from the group of compounds
consisting of a silane, a titanate, a zirconate, and mixtures
thereof.
50) The optical fiber according to claim 11 wherein said adhesion
promoter comprises a titanate containing compound.
51) The optical fiber according to claim 11 wherein said adhesion
promoter comprises a zirconate containing compound.
52) The optical fiber according to claim 11 wherein said adhesion
promoter comprises a silane containing compound.
53) The coating according to claim 24 wherein said adhesion
promoter comprises a titanate containing compound.
54) The coating according to claim 24 wherein said adhesion
promoter comprises a zirconate containing compound.
55) The coating according to claim 24 wherein said adhesion
promoter comprises a silane containing compound.
56) The fiber according to claim 28 wherein said adhesion promoter
comprises a titanate containing compound.
57) The fiber according to claim 28 wherein said adhesion promoter
comprises a zirconate containing compound.
58) The fiber according to claim 28 wherein said adhesion promoter
comprises a silane containing compound.
59) The coating according to claim 35 wherein said adhesion
promoter comprises a titanate containing compound.
60) The coating according to claim 35 wherein said adhesion
promoter comprises a zirconate containing compound.
61) The coating according to claim 35 wherein said adhesion
promoter comprises a silane containing compound.
62) The fiber according to claim 39 wherein said adhesion promoter
comprises a titanate containing compound.
63) The fiber according to claim 39 wherein said adhesion promoter
comprises a zirconate containing compound.
64) The fiber according to claim 39 wherein said adhesion promoter
comprises a silane containing compound.
65) A method of making an optical fiber comprising: drawing an
optical fiber from a sintered preform and coating the fiber with an
optical fiber coating comprising an adhesion promoter, said
adhesion promoter includes at least one compound from the group of
compounds consisting of a silane, a titanate, a zirconate, and a
mixture thereof; and a strength additive containing at least about
one halide functional group.
66) A method of making an optical fiber comprising: drawing an
optical fiber from a sintered preform and coating the fiber with an
optical fiber coating comprising an adhesion promoter, said
adhesion promoter includes at least one compound from the group of
compounds consisting of a silane, a titanate, a zirconate, and a
mixture thereof; and a non-silicon containing strength additive
containing at least about one thiol functional group.
67) An optical fiber coating comprising: a polymerizable
composition which comprises an adhesion promoter, said adhesion
promoter including at least one compound selected from the group of
compounds consisting of silanes, titanates, zirconates, and
mixtures thereof; and a strength additive selected from the group
consisting of compounds containing at least one halide functional
group, at least one thiol functional group, and mixtures thereof,
wherein a difference in Young's modulus of the coating when cured
and of a similar cured coating compound without said strength
additive is no more than about 12%.
68) The optical fiber coating according to claim 67 wherein said
difference is no more than about 10%.
69) The optical fiber coating according to claim 67 wherein said
strength additive comprising a thiol functional group comprises a
compound substantially devoid of silicon.
70) An optical fiber coating comprising: a polymerizable
composition which comprises an adhesion promoter, said adhesion
promoter including at least one compound selected from the group of
compounds consisting of silanes, titanates, zirconates, and
mixtures thereof; and a strength additive selected from the group
consisting of compounds containing at least one halide functional
group, at least one thiol functional group, and mixtures thereof,
wherein a difference in relative cure speed of the coating when
cured and of a similar cured coating compound without said strength
additive is no more than about 10%.
71) The optical fiber coating according to claim 70 wherein said
difference comprises less than about 5%.
72) The optical fiber according to claim 11 wherein said optical
fiber has an effective area greater than about 60 .mu.m.sup.2.
73) The optical fiber according to claim 35 wherein said optical
fiber has an effective area greater than about 60 .mu.m.sup.2.
74) The optical fiber according to claim 39 wherein said optical
fiber has an effective area greater than about 60 .mu.m.sup.2.
75) An optical fiber coating comprising: a photo-polymerizable
composition which comprises an adhesion promoter, said adhesion
promoter includes at least one compound from the group of compounds
consisting of a silane, a titanate, a zirconate, and a mixture
thereof; and a strength additive having the general formula RX
wherein R comprises an organic group and X comprises a group
capable of participating in a nuclepholic addition or substitution
reaction.
76) The composition according to claim 75 wherein said X comprises
Cl, Br, F, I and combinations thereof.
77) A coated optical fiber comprising an optical fiber and a
coating in accordance with claim 75.
78) An optical fiber coating composition comprising at least one
adhesion promoter and at least one water scavenger.
79) The composition according to claim 78 wherein said adhesion
promoter comprises a silane containing compound.
80) The composition according to claim 78 wherein said water
scavenger comprises at least one from the group comprising a
thiol-functional silane compound, an amino-silane compound, and
combinations thereof.
81) The composition according to claim 78 wherein said water
scavenger comprises a silane containing compound.
Description
RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 60/275,421, filed Mar. 13, 2001, and No.
60/315,857, filed Aug. 29, 2001, which is incorporated herein by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to optical fibers
(hereinafter fiber), and particularly to fiber coatings.
[0004] 2. Technical Background
[0005] Fiber has acquired an increasingly important role in the
field of telecommunications, frequently replacing existing copper
wires. This trend has had a significant impact in all areas of
telecommunications, which has seen a vast increase in the usage of
fiber. Further increases in the use of fiber is at least foreseen
in local loop telephone and cable TV service, as local fiber
networks are established to deliver ever greater volumes of
information in the form of data, audio, and video signals to
residential and commercial users. In addition, use of fiber in home
and commercial business environments for internal data, voice, and
video communications has begun and is expected to increase.Fibers
typically contain a glass core and at least two coatings, e.g. a
primary (inner) coating and a secondary (outer) coating. The
primary coating is applied directly to the glass fiber and, when
cured, forms a soft, elastic, and compliant material which
encapsulates the glass fiber. The primary coating serves as a
buffer to cushion and protect the glass fiber core when the fiber
is bent, cabled, or spooled. The secondary coating is applied over
the primary coating and functions as a tough, protective outer
layer that prevents damage to the glass fiber during processing and
use.
[0006] Corrosion of the glass surface of the optical fiber will
lead to degradation of the optical fiber strength and may even
cause the optical fiber to break. A known cause of the corrosion is
a base compound (compounds having a pH of greater than about 7.0
e.g. a hydroxide ion) reacting with the glass surface. The base may
be generated from the environment which the optical fiber is
employed, however, the potential source of the base is not limited
to the environment. A need exists to improve fiber strength and
also to prevent the base from causing the glass surface of the
optical fiber to corrode.
SUMMARY OF THE INVENTION
[0007] One aspect of the invention relates to an optical fiber
coating composition. The composition includes a non-thiol
functional adhesion promoter and less than about 0.5 pph of a
strength additive containing a thiol functional group. This aspect
of the invention also includes a coated optical fiber which
includes the fiber coated with the aforementioned inventive coating
composition. Another aspect of the invention relates to a method of
manufacturing an optical fiber. The method includes drawing an
optical fiber from a sintered preform and coating the fiber with an
optical fiber coating comprising of a non-thiol functional adhesion
promoter and less than about 0.5 pph of a strength additive
containing a thiol functional group.
[0008] An additional aspect of the invention relates to an optical
fiber coating which includes a photo-polymerizable composition
containing a silane adhesion promoter and a non-silicon containing
strength additive having at least about one thiol functional group.
A further aspect of the invention relates to an optical fiber
coating which includes a photo- polymerizable composition which
includes preferably a silane containing adhesion promoter and a
strength additive having at least one halide containing
compound.
[0009] An optical fiber coated with the inventive composition has
exhibited the advantage of superior strength retention, also the
coated fiber has exhibited more resistant to wet environments than
fibers coated with traditional coatings. The coated fiber has
demonstrated excellent performance in impeding the migration of a
base from coming in contact with the glass surface of the coated
fiber.
[0010] Also, the fiber coated with the inventive coating exhibited
good fiber performance characteristics such as good ribbon
strippability, satisfactory attenuation losses, and satisfactory
tensile properties such as Young's modulus. Furthermore, the
inclusion of the inventive strength additive in the coating
composition did not significantly inhibit the cure rate of the
coating composition. Additionally, the inventive coating has
exhibited an improved shelf life, increased adhesion promoter
activity, improved reduction in attenuation, improved microbend
resistance, and greater temperature stability.
[0011] Additional features and advantages of the invention will be
set forth in the detailed description which follows, and in part
will be readily apparent to those skilled in the art from that
description or recognized by practicing the invention as described
herein, including the detailed description which follows, the
claims, as well as the appended drawings.
[0012] It is to be understood that both the foregoing general
description and the following detailed description are merely
exemplary of the invention, and are intended to provide an overview
or framework for understanding the nature and character of the
invention as it is claimed. The accompanying drawings are included
to provide a further understanding of the invention, and are
incorporated in and constitute a part of this specification. The
drawings illustrate various embodiments of the invention, and
together with the description serve to explain the principles and
operation of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a cross sectional view of a coated optical
fiber.
[0014] FIG. 2 is a partial schematic cross sectional view of the
process of drawing and coating an optical fiber in accordance with
the invention.
[0015] FIGS. 3 and 4 are plots of the fiber strength for aged
fibers with a varying amount of strength additive in combination
with a particular concentration of a particular adhesion
promoter.
[0016] FIGS. 5-7 are plots of Young's Modulus as a function of
concentration of a particular strength additive.
[0017] FIGS. 8-10 are plots of the relative cure speed (%/second)
as a function of concentration of a particular strength
additive.
[0018] FIG. 11 is a plot of the relative peak intensity of four (4)
major adhesion promoter isomers as a function of reaction time for
a control solution and a test solution.
[0019] FIGS. 12-13 are plots of unreacted adhesion promoter in a
coating formulation in terms of hours.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Reference will now be made in detail to the present
preferred embodiments of the invention, an example of which is
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts. An exemplary embodiment of the
optical fiber coating of the present invention is shown in FIG. 1,
and is designated generally throughout by reference numeral 10.
[0021] The invention includes a composition for coating an optical
fiber. The inventive composition is preferably a
photo-polymerizable composition which includes an adhesion promoter
as described below and preferably less than about 0.5 pph of a
strength additive which includes at least about one thiol
functional group. Preferably the adhesion promoter does not contain
a thiol functional group. More preferably, the strength additive is
an organic compound and preferably includes at least one element
from the group of elements consisting of C, H, N, O, Si, P, F, Cl,
Br, I, Ti, Zr, S and mixtures thereof, in addition to the S element
of the thiol functional group. Most preferably, the organic
strength additive is an alkyl thiol compound. The strength additive
may be a thiol functional compound that is substantially devoid of
silicon.
[0022] Preferably, the alkyl thiol comprises at least one compound
selected from the following group of compounds consisting of
methane thiol, ethane thiol, hexane thiol, dodecane thiol,
octadecane thiol, a cysteine derivative, a multi-functional thiol,
a thiol silane, thiol-functional polysulfides, and mixtures
thereof.
[0023] Examples of specific preferred strength additive compounds
includes at least one compound selected from the group of compounds
consisting of N-(tert butoxy carbonyl)-L-cysteine methyl ester,
pentaerythritol tetrakis (3-mercaptopropionate),
3-mercaptopropyltriethoxy silane, 3-mercaptopropyltrimethoxy
silane, (commercially available from United Chemical Technologies
of Bristol, Pa.) dodecylmercaptan, tert-dodecylmercaptan,
(commercially available from Aldrich of Milwaukee, Wis.) and
mixtures thereof.
[0024] Preferably, the thiol functional strength additive is
present in the composition in a concentration of at least about
0.01 pph and optionally up to less than about 0.5 pph, more
preferably about 0.1 pph to about 0.4 pph, and most preferably
about 0.3 pph. Maintaining the concentration of the thiol
functional strength additive to less than about 0.5 pph has been
found to not inhibit the cure speed of the inventive composition to
a significant extent or degrade the tensile properties of the
coating once the coating is applied to an optical fiber and cured.
However, the thiol functional strength additive devoid of silicon
is not limited to less than about 0.5 pph, e.g. pentaerythritol
tetrakis (3-mercaptopropionate).
[0025] Additional strength additives have the general formula RX
where R is an organic group and X is a group that may be ionized
when the strength additive, RX, undergoes a nucleophilic reaction
(either substitution or addition). Preferable examples of X include
fluorine, chlorine, bromine and iodine.
[0026] Exemplary strength additives of RX include alkyl-halides,
haloalkyl-alkoxy silanes, halo aryl-alkyl silanes, and
halo-alkylsilanes. Preferably halides include any of the known
elements of column VII A of the Periodic Chart of Elements.
Preferable compounds include chloro-octane, chloro-propyltriethoxy
silane, and chloro-propyltrimethoxy silane. Optionally, the
alkyl-halides may be devoid of silicon. The alkyl-halide, halo
alkyl-alkoxy silanes, halo aryl-alkyl silanes, and halo-alkylsilane
strength additives may be used in a concentration of more than
about 0.5 pph, unlike the aforementioned thiol functional strength
additives. A chloro group is an example of a preferred halo
group.
[0027] Preferably the strength additive is not a base compound,
more preferably the strength additive is devoid of an amine
functional group. It is also preferred that the strength additive
is not a chain transfer agent. A chain transfer is a chain
terminating reaction. A chain transfer agent interrupts the growth
of molecule chain by the formation of a new radical. A chain
transfer agent has detrimental effects on the coating that can
include changing the rate of cure of the coating and changing the
tensile properties of the coating by changing the coating network.
Typically, the chain transfer agent will reduce the rate of cure of
the coating. As for the change in tensile properties, the strength
additive will change the Young's modulus of the cured coating by
less than about 30%, preferably less than about 25%, more
preferably less than about 20%, and most preferably less than about
15%.
[0028] In one embodiment of the invention, preferably the strength
additive acts as a water scavenger. Preferably the strength
additive comprises a silane containing compound and the strength
additive has a faster rate of reaction with residual water in the
coating formulation than the rate of reaction of a reaction between
the adhesion promoter and residual water in the coating
formulation. Any example of the hydrolysis of preferred strength
additive is shown below. 1
[0029] The above chemical reaction is a schematic showing the (i)
hydrolysis and (ii) condensation chemistry of a generic trimethoxy
silane. The R-group denotes any organic functionality, such as a
long-chain or cyclic hydrocarbon.
[0030] As shown, the methoxy groups react first with water in the
coating formulation. Subsequently, the hydroxyl group will react
with other silanols present in the formulation. By way of example,
the coating formulation could include a bis-silane adhesion
promoter and a mercapto-silane strength additive. The
mercapto-silane strength additive would react with the water in the
coating at least as fast, preferably faster, than the bis-silane
adhesion promoter.
[0031] One method to determine if a molecule is a water scavenger
is to compare the reactivity of the molecule with water to the
reactivity of the adhesion promoter with water. Solution chemistry
may be used to compare the reactivity of the molecule with water
relative to the reactivity of the adhesion promoter with water. A
solution of the adhesion promoter and a solvent is prepared as well
as at least one of the two following solutions (1) a solution of
the molecule and the same solvent, or (2) a solution of the
molecule, the adhesion promoter, and the solvent. An aliquot of
water and acid is added to both of the solutions to initiate the
hydrolysis reaction. The aliquot should be the same for each
solution.
[0032] Gas chromatography/mass spectrometry techniques may be used
to determine the reactivity of molecule and the adhesion promoter
relative to an internal standard as a function of time. An example
of a suitable internal standard is cyclo-hexyl-phenylketone. The
peak intensity of the adhesion promoter and the molecule relative
to the internal standard is determined periodically over a
pre-determined time period. In determining the peak intensity, the
concentration of the adhesion promoter or the molecule in the
solution is determined as a function of time as the adhesion
promoter or the molecule reacts with the water in the solution.
[0033] For the molecule to act as a water scavenger, the rate of
reaction between water and the molecule must be equal to or greater
than that of the rate of reaction between water and the adhesion
promoter. In order to reduce the overall rate of reaction between
the adhesion promoter and water, the molecule must effectively
lower the water concentration by reacting with the water, thereby
reducing the amount of water available to react with the adhesion
promoter.
[0034] A non-exhaustive list of examples of strength additives that
act as a water scavenger will include thiol functional silanes,
amino-silanes, and combinations thereof.
[0035] Preferably, the aforementioned inventive coating composition
is applied to an optical fiber as the primary (inner) coating.
However, the invention is not limited a primary coating.
[0036] Now referring to the drawings, shown in FIG. 1 is a cross
sectional view of a coated optical fiber 10. Referring to FIG. 1,
the optical fiber 10 includes a glass core 12, a cladding layer 14
surrounding and adjacent to glass core 12, a primary coating
material 16 which adheres to cladding layer 14, and one or more
secondary (outer) coating materials 18 surrounding and adjacent to
the primary coating material 16. The components of the optical
fiber of the present invention can optionally include a coloring
material, such as a pigment or dye, or an additional colored ink
coating may surround coating 18.
[0037] Any conventional material can be used to form glass core 12,
such as those described in U.S. Pat. No. 4,486,212 to Berkey, which
is hereby incorporated by reference. The core is typically a silica
glass having a cylindrical cross section and a diameter ranging
from about 5 to about 10 .mu.m for single-mode fibers and about 20
to about 100 um for multi-mode fibers. The core can optionally
contain varying amounts of other material such as, e.g., oxides of
titanium, thallium, germanium, and boron, which modify the core's
refractive index. Other dopants which are known in the art can also
be added to the glass core to modify its properties.
[0038] Cladding layer 14 preferably has a refractive index which is
less than the refractive index of the core. A variety of cladding
materials, both plastic and glass (e.g., silicate and borosilicate
glasses) are used in constructing conventional glass fibers. Any
conventional cladding materials known in the art can be used to
form cladding layer 14 in the optical fiber of the present
invention.
[0039] A preferred type of fiber is single mode fiber (having a
core diameter of less than about 10 .mu.m) with a large effective
area, e.g. LEAF.RTM., from Corning, Incorporated of Corning,
N.Y.
[0040] Fiber Definitions
[0041] The effective area is
[0042] Aeff=2.pi.(.intg.E2 r dr)2/(.intg.E4 r dr), where the
integration limits are 0 to .infin., and E is the electric field
associated with light propagated in the waveguide. An effective
diameter, Deff, may be defined as,
Aeff=.pi.(Deff/2)2.
[0043] By large effective area, we mean that the effective area of
the fiber is greater than about 60 .mu.m2, more preferably the
effective area of the fiber is greater than about 65 .mu.m2, and
most preferably the effective area of the fiber is greater than 70
.mu.m2. It is possible and preferable to have a fiber with an
effective area of greater than about 80 to 90 .mu.m2.
[0044] The relative refractive index percent,
.DELTA.%=100.times.(ni2-nc2)- /2m2, where ni is the maximum
refractive index in region i, unless otherwise specified, and nc is
the average refractive index of the cladding region unless
otherwise specified.
[0045] The term .alpha.-profile refers to a refractive index
profile, expressed in terms of .DELTA.(b)%, where b is radius,
which follows the equation,
.DELTA.(b)%=.DELTA.(bo)(1-[.vertline.b-bo.vertline.]/(b1-bo)].a-
lpha.), where bo is the point at which .DELTA.(b)% is maximum, b1
is the point at which .DELTA.(b)% is zero, and b is in the range
bi<b<bf, where delta is defined above, bi is the initial
point of the .alpha.-profile, bf is the final point of the
.alpha.-profile, and .alpha. is an exponent which is a real number.
The initial and final points of the .alpha.-profile are selected
and entered into the computer model. As used herein, if an
.alpha.-profile is preceded by a step index profile or any other
profile shape, the beginning point of the .alpha.-profile is the
intersection of the .alpha.-profile and the step profile or other
profile.
[0046] The above coating components of an adhesion promoter or a
strength additive are preferably incorporated into coating 16.
However, the adhesion promoter or the strength additive may also be
incorporated into coating 18 or an ink layer instead of coating 16,
or in any combination of coatings 16, 18 and the ink layer. In an
alternate embodiment, the strength additive and the adhesion
promoter are incorporated into a single coating that is applied to
an optical fiber. Coatings 16 and 18 are not thermoplastics. Nor do
coatings 16 and 18 exhibit the properties of a thermoplastic resin,
that the resin may be reversibly heated, melted, and reformed.
Coatings 16 and 18 are typically crosslinked coatings. A preferred
component of the primary coating composition of the present
invention is an oligomer. Preferably the oligomer is an
ethylenically unsaturated oligomer, more preferably a
(meth)acrylate oligomer. By (meth)acrylate, it is meant an acrylate
or a methacrylate. The (meth)acrylate terminal groups in such
oligomers may be provided by a monohydric poly(meth)acrylate
capping component, or by a mono(meth)acrylate capping component
such as 2-hydroxyethyl acrylate, in the known manner. It is also
preferred that the oligomer is capable of participating in addition
polymerization. It is further preferred that the oligomer includes
at least one urethane functional group. It is additionally
preferred that the oligomer does not include a thiol functional
group.
[0047] Urethane oligomers are conventionally provided by reacting
an aliphatic or aromatic diisocyanate with a dihydric polyol based
on a polyether, a polyester, or a hydrocarbon, most typically a
polyoxyalkylene glycol such as a polyethylene glycol. Such
oligomers typically have 4-10 urethane groups and may be of high
molecular weight, e.g., 2000-8000. High molecular weight oligomers,
with molecular weights as high as 15000, may also be used. However,
lower molecular weight oligomers, having molecular weights in the
500-2000 range, may also be used. U.S. Pat. No. 4,608,409 to Coady
et al. and U.S. Pat. No. 4,609,718 to Bishop et al., the
specifications of which are hereby incorporated by reference,
describe such syntheses of the oligomers in detail.
[0048] When it is desirable to employ moisture-resistant oligomers,
they may be synthesized in an analogous manner, except that the
polar polyether or polyester glycols are avoided in favor of
predominantly saturated and predominantly nonpolar aliphatic diols.
These diols include, for example, alkane or alkylene diols of from
2-250 carbon atoms and, preferably, are substantially free of ether
or ester groups. The ranges of oligomer viscosity and molecular
weight obtainable in these systems are similar to those obtainable
in unsaturated, polar oligomer systems, such that the viscosity and
coating characteristics thereof can be kept substantially
unchanged. The reduced oxygen content of these coatings has been
found not to unacceptably degrade the adherence characteristics of
the coatings to the surfaces of the glass fibers being coated.
[0049] Polyurea components may be incorporated in oligomers
prepared by these methods, simply by substituting diamines or
polyamines for diols or polyols in the course of synthesis. The
presence of minor proportions of polyurea components in the present
coating systems is not considered detrimental to coating
performance, provided only that the diamines or polyamines employed
in the synthesis are sufficiently non-polar and saturated as to
avoid compromising the moisture resistance of the system.
[0050] Thus, it is desirable for the primary coating composition of
the present invention to contain at least one ethylenically
unsaturated oligomer, although more than one oligomer component can
be introduced into the composition. Preferably, the oligomer(s) is
present in an amount between about 10 to about 90 percent by
weight, more preferably between about 35 to about 75 percent by
weight, and most preferably between about 40 to about 65 percent by
weight.
[0051] Suitable ethylenically unsaturated oligomers for primary
coatings include polyether urethane acrylate oligomers (e.g., CN986
available from Sartomer Company, Inc., (West Chester, Pa.)) and
BR3731 and STC3-149 available from Bomar Specialty Co. (Winstead,
Conn.)), acrylate oligomers based on
tris(hydroxyethyl)isocyanurate, (available from Sartomer Company,
Inc.), (meth)acrylated acrylic oligomers, (available from Cognis
(Ambler, Pa.), polyester urethane acrylate oligomers (e.g., CN966
and CN973 available from Sartomer Company, Inc. and BR7432
available from Bomar Specialty Co.), polyurea urethane acrylate
oligomers (e.g., oligomers disclosed in U.S. Pat. Nos. 4,690,502
and 4,798,852 to Zimmerman et al., U.S. Pat. No. 4,609,718 to
Bishop, and U.S. Pat. No. 4,629,287 to Bishop et al.), polyether
acrylate oligomers (e.g., Genomer 3456 available from Rahn AG
(Zurich, Switzerland), polyester acrylate oligomers (e.g., Ebecryl
80, 584, and 657 available from UCB Radcure (Atlanta, Ga.)),
polyurea acrylate oligomers (e.g., oligomers disclosed in U.S. Pat.
Nos. 4,690,502 and 4,798,852 to Zimmerman et al., U.S. Pat. No.
4,609,718 to Bishop, and U.S. Pat. No. 4,629,287 to Bishop et al.,
the specifications of which are hereby incorporated by reference),
epoxy acrylate oligomers (e.g., CN120 available from Sartomer
Company, Inc., and Ebecryl 3201 and 3604 available from UCB
Radcure), hydrogenated polybutadiene oligomers (e.g., Echo Resin
MBNX available from Echo Resins and Laboratory (Versailles, Mo.)),
and combinations thereof.
[0052] Furthermore, the coating compositions of the invention will
typically include at least one monomer component. Preferably, the
monomer is an ethylenically unsaturated monomer, more preferably a
(meth)acrylate monomer. Generally, suitable monomers are those for
which the resulting homopolymer would have a glass transition
temperature (Tg) of at most about 20.degree. C., preferably at most
about 10.degree. C. Generally, a lower molecular weight (i.e.,
preferably less than about 2000, more preferably about 120 to 600)
liquid (meth)acrylate-functional monomer is added to the
formulation to provide the liquidity needed to apply the coating
composition with conventional liquid coating equipment. Typical
acrylate-functional liquids in these systems include monofunctional
and polyfunctional acrylates (i.e., monomers having two or more
acrylate functional groups). Illustrative of these polyfunctional
acrylates are the difunctional acrylates, which have two functional
groups; the trifunctional acrylates, which have three functional
groups; and the tetrafunctional acrylates, which have four
functional groups. Monofunctional and polyfunctional methacrylates
may also be employed.
[0053] When it is desirable to utilize moisture-resistant
components, the monomer component will be selected on the basis of
its compatibility with the selected moisture- resistant oligomer.
For satisfactory coating compatibility and moisture resistance, it
is desirable to use a liquid acrylate monomer component comprising
a predominantly saturated aliphatic mono- or di-acrylate monomer or
alkoxy acrylate monomers.
[0054] Thus, it is desirable for the primary coating composition to
contain at least one ethylenically unsaturated monomer, although
more than one monomer can be introduced into the composition.
Preferably, the ethylenically unsaturated monomer is present in an
amount between about 10 to about 90 percent by weight, more
preferably between about 20 to about 60 percent by weight, and most
preferably between about 25 to about 50 percent by weight.
[0055] Suitable ethylenically unsaturated monomers include lauryl
acrylate (e.g., SR335 available from Sartomer Company, Inc.,
Agefiex FA12 available from CPS Chemical Co. (Old Bridge, N.J.),
and Photomer 4812 available from Cognis f.k.a. Henkel (Ambler,
Pa.)), ethoxylatednonylphenol acrylate (e.g., SR504 available from
Sartomer Company, Inc. and Photomer 4003 available from Cognis),
caprolactone acrylate (e.g., SR495 available from Sartomer Company,
Inc., and Tone M100 available from Union Carbide Company (Danbury,
Conn.)), phenoxyethyl acrylate (e.g., SR339 available from Sartomer
Company, Inc., Ageflex PEA available from CPS Chemical Co., and
Photomer 4035 available from Cognis), isooctyl acrylate (e.g.,
SR440 available from Sartomer Company, Inc. and Ageflex FA8
available from CPS Chemical Co.), tridecyl acrylate (e.g., SR489
available from Sartomer Company, Inc.), phenoxyglycidyl acrylate
(e.g., CN131 available from Sartomer Company, Inc.),
lauryloxyglycidyl acrylate (e.g., CN130 available from Sartomer
Company, Inc.), isobomyl acrylate (e.g., SR506 available from
Sartomer Company, Inc. and Ageflex IBOA available from CPS Chemical
Co.), tetrahydrofurfuryl acrylate (e.g., SR285 available from
Sartomer Company, Inc.), stearyl acrylate (e.g., SR257 available
from Sartomer Company, Inc.), isodecyl acrylate (e.g., SR395
available from Sartomer Company, Inc. and Ageflex FA10 available
from CPS Chemical Co.), 2-(2-ethoxyethoxy)ethyl acrylate (e.g.,
SR256 available from Sartomer Company, Inc.), and combinations
thereof.
[0056] Optical fiber coating compositions may also contain a
polymerization initiator which is suitable to cause polymerization
(i.e., curing) of the composition after its application to a glass
fiber. Polymerization initiators suitable for use in the primary
coating compositions of the present invention include thermal
initiators, chemical initiators, electron beam initiators, and
photoinitiators. Particularly preferred are the photoinitiators.
For most acrylate-based coating formulations, conventional
photoinitiators, such as the known ketonic photoinitiating and/or
phosphine oxide additives, are preferred. When used in the
compositions of the present invention, the photoinitiator is
present in an amount sufficient to provide rapid ultraviolet
curing. Generally, this includes between about 0.5 to about 10.0
percent by weight, more preferably between about 1.5 to about 7.5
percent by weight.
[0057] The photoinitiator, when used in a small but effective
amount to promote radiation cure, must provide reasonable cure
speed without causing premature gelation of the coating
composition. A desirable cure speed is any speed sufficient to
cause substantial curing of the coating materials. As measured in a
dose versus modulus curve, a cure speed for coating thickness' of
about 25-35 .mu.m is, e.g., less than 1.0 J/cm2, preferably less
than 0.5 J/cm2.
[0058] Suitable photoinitiators include a blend of
1-hydroxycyclohexylphen- yl ketone and
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide
(Irgacure 1850, available from Ciba Specialty Chemical (Tarrytown,
N.Y.)), 1-hydroxycyciohexylphenyl ketone (e.g., Irgacure 184
available from Ciba Specialty Chemical (Hawthorne, N.Y.),
(2,6-dimethoxybenzoyl)-2,- 4,4-trimethylpentyl phosphine oxide
(e.g., commercial blends Irgacure 1800, 1850, and 1700 available
from Ciba Specialty Chemical), 2,2-dimethoxyl-2-phenyl acetophenone
(e.g., Irgacure 651, available from Ciba Specialty Chemical),
bis(2,4,6-trimethyl benzoyl)phenyl-phosphine oxide (Irgacure 819),
(2,4,6-trimethylbenzoyl)diphenyl phosphine oxide (Lucerin TPO,
available from BASF (Munich, Germany)), ethoxy
(2,4,6-trimethylbenzoyl)phenyl phosphine oxide (Lucerin TPO-L from
BASF), and combinations thereof.
[0059] As used herein, the weight percent of a particular component
in coating 16, coating 18, or the ink refers to the amount
introduced into the bulk composition excluding the adhesion
promoter and other additives. The amount of adhesion promoter and
various other additives that are introduced into the bulk
composition to produce a composition of the present invention is
listed in parts per hundred. For example, an oligomer, monomer, and
photoinitiator are combined to form the bulk composition such that
the total weight percent of these components equals 100 percent. To
this bulk composition, an amount of adhesion promoter, for example
1.0 part per hundred, is introduced in excess of the 100 weight
percent of the bulk composition.
[0060] The coating composition may also include an adhesion
promoter. It is preferred that the adhesion promoter includes a
compound containing a cyclic structure interposed between at least
two reactive silanes which are independently an alkoxysilane or a
halosilane. It is further preferred that the adhesion promoter does
not include a thiol functional group.
[0061] The cyclic structure can be a hydrocarbon cyclic structure
or a heterocyclic structure or a combination thereof. Hydrocarbon
cyclic structures and heterocyclic structures can be single-ring,
fused-ring, or multi-ring structures, with or without hydrocarbon
or hetero-substituents. Suitable hydrocarbon cyclic structures
include, but are not limited to, cycloalkanes, preferably
containing between 3 to 10, more preferably 5 to 6 carbon atoms per
cyclic structure; cycloalkenes, preferably containing between 3 to
10, more preferably 5 to 6 carbon atoms per cyclic structure;
cycloalkyldienes, preferably containing between 3 to 10, more
preferably 5 to 6 carbon atoms per cyclic structure; substituted
aliphatic rings; aromatic rings; and substituted aromatic rings.
Preferably the hydrocarbon cyclic structure is an aromatic ring or
a substituted aromatic ring. Exemplary hydrocarbon cyclic
structures include, but are not limited to, benzene, naphthalene,
cyclohexane, cyclohexene, etc. Suitable heterocyclic structure
include those which contain oxygen, nitrogen, sulfur, or
phosphorous hetero atom(s) within the ring structure. Exemplary
heterocyclic structures include, but are not limited to, pyridines,
pyrroles, imidazoles, indoles, pyrimidines, pyrrolidines,
piperidines, furans, thiophenes, etc.
[0062] The at least two reactive silanes can independently be an
alkoxysilane, a dialkoxysilane, a trialkoxysilane or any other
suitable polyalkoxysilane, a halosilane, a dihalosilane, or a
trihalosilane. Preferably, the at least two reactive silanes are
independently dialkoxysilanes, trialkoxysilanes, or trihalosilanes.
Suitable alkoxysilanes, polyalkoxysilanes, dialkoxysilanes, and
trialkoxysilanes include alkoxy groups independently having between
1 and 6 carbon atoms. A preferred halosilane is a chlorosilane,
more preferably a trichlorosilane.
[0063] The compound can also include a substituent interposed
between the cyclic structure and one (or more) of the at least two
alkoxysilanes. Suitable substituents include straight-chain
alkylene groups having between 1 and 12 carbon atoms;
branched-chain alkylene groups having between 1 and 12 carbon
atoms; straight and branched-chain alkylene groups having a
heterogroup; and a heterogroup including, but not limited to,
oxygen, nitrogen, sulfur, phosphorous, selenium, titanium,
zirconium, and silicon.
[0064] Preferred compounds include bis(trimethoxysilylethyl)benzene
and bis(triethoxysilylethyl)benzene.
Bis(trimethoxysilylethyl)benzene is commercially available from
Gelest (Tellytown, Pa.), Archimica (Wilmington, Del.), and United
Chemical Technologies, Inc. (Bristol, Pa.).
Bis(triethoxysilylethyl)benzene can be synthesized from
bis(trimethoxysilylethyl)benzene by trans-esterification with
ethanol.
[0065] Compounds containing at least one zirconate or titanate
functional group can be a suitable alternate adhesion promoter. In
the case that the adhesion promoter includes a titanate containing
compound, suitable compounds consists of least one of the following
group of compounds consisting of tetra (2,2 diallyoxymethyl)butyl,
di(ditridecyl)phosphito titanate (commercially available as KR 55,
from Kenrich Petrochemicals, Inc. (hereinafter Kenrich) Bayonne,
N.J.), neopentyl(diallyl)oxy, trineodecanonyl titanate
(commercially available as LICA 01 from Kenrich),
neopentyl(diallyl)oxy, tri(dodecyl)benzene-sulfony titanate
(commercially available as LICA 09 from Kenrich),
neopentyl(diallyl)oxy, tri(dioctyl)phosphato titanate (commercially
available as LICA 12 from Kenrich), neopentyl(dially)oxy,
tri(dioctyl)pyro-phosphato titanate (commercially available as
LICA38 from Kenrich), neopentyl(diallyl)oxy,
tri(N-ethylenediamino)ethyl titanate (commercially available as
LICA 44 from Kenrich), neopentyl(diallyl)oxy, tri(m-amino)phenyl
titanate (commercially available as LICA 97 from Kenrich),
neopentyl(diallyl)oxy, trihydroxy caproyl titanate (formerly
available as LICA 99 from Kenrich), and mixtures thereof.
[0066] Preferably, the titanate containing compound contains at
least one UV curable functional group. More preferably, the
functional group is a (meth)acrylate or acrylate functional
group.
[0067] In case that the adhesion promoter consists of a zirconate
containing compound, preferably the coupling agent consists of at
least one ethylenically unsaturated zirconate containing compound,
and more preferably at least one neoalkoxy zirconate containing
compound. Most preferably, the zirconate containing compound
consists of least one of the following group of compounds
consisting of tetra (2,2 diallyloxymethyl)butyl,
di(ditridecyl)phosphito zirconate (commercially available as KZ 55
from Kenrich), neopentyl(diallyl)oxy, trineodecanoyl zirconate
(commercially available as NZ 01 from Kenrich),
neopentyl(diallyl)oxy, tri(dodecyl)benzene-sulfony zirconate
(commercially available as NZ 09 from Kenrich),
neopentyl(diallyl)oxy, tri(dioctyl)phosphato zirconate
(commercially available as NZ 12 from Kenrich),
neopentyl(diallyl)oxy, tri(dioctyl)pyro-phosphato zirconate
(commercially available as NZ 38 from Kenrich),
neopentyl(diallyl)oxy, tri(N-ethylenediamino)ethyl zirconate
(commercially available as NZ 44 from Kenrich),
neopentyl(diallyl)oxy, tri(m-amino)phenyl zirconate (commercially
available as NZ 97 from Kenrich), neopentyl(diallyl )oxy,
trimethacryl zirconate (commercially available as NZ 33 from
Kenrich), neopentyl(diallyl)oxy, triacryl zirconate (formerly
available as NZ 39 from Kenrich), dineopentyl(diallyl)oxy,
diparamino benzoyl zirconate (commercially available as NZ 37 from
Kenrich), dineopentyl(aiallyl)oxy, di(3-mercapto) propionic
zirconate (commercially available as NZ 66A from Kenrich), and
mixtures thereof.
[0068] Preferably, the zirconate containing compound contains at
least one UV curable functional group. More preferably, the
functional group is a (meth)acrylate or acrylate functional
group.
[0069] Preferably the adhesion promoter is present in an amount
between about 0.1 to about 15 parts per hundred, more preferably
between about 0.25 to about 4 parts per hundred, most preferably
between about 0.5 to about 3 parts per hundred.
[0070] In addition to the above-described components, the primary
coating composition of the present invention can optionally include
any number of additives, such as reactive diluents, antioxidants,
catalysts, lubricants, co-monomers, low molecular weight
non-crosslinking resins, and stabilizers. Some additives (e.g.
chain transfer agents, for example) can operate to control the
polymerization process, thereby affecting the physical properties
(e.g., modulus, glass transition temperature) of the polymerization
product formed from the primary coating composition. Others can
affect the integrity of the polymerization product of the primary
coating composition (e.g., protect against de-polymerization or
oxidative degradation).
[0071] A preferred catalyst is a tin-catalyst, which is used to
catalyze the formation of urethane bonds in some oligomer
components. Whether the catalyst remains as an additive of the
oligomer component or additional quantities of the catalyst are
introduced into the composition of the present invention, the
presence of the catalyst can act to stabilize the oligomer
component in the composition.
[0072] A preferred antioxidant is thiodiethylene
bis[(3,5-di-tert-butyl-4-- hydroxy) hydrocinnamate] (e.g., Trganox
1035, available from Ciba Specialty Chemical). However, an
antioxidant is not required in the composition to practice the
invention.
[0073] The coating composition may include an oligomer capable of
being polymerized, a monomer suitable to control the viscosity of
the composition, an adhesion promoter that includes a compound
containing at least one reactive silane, and a carrier.
[0074] The carrier is preferably a carrier which functions as a
carrier surfactant or ambiphilic reactive or non-reactive
surfactant. Reactive surfactants which are partially soluble or
insoluble in the composition are particularly preferred. Without
being bound to a particular theory, it is believed that carriers
which function as reactive surfactants interact with the compound
containing a reactive silane by depositing such compounds on the
glass fiber, where it is allowed to react. It is desirable for the
carrier to be present in an amount between about 0.01 to about 10
parts per hundred, more preferably about 0.25 to about 3 parts per
hundred.
[0075] Suitable carriers, more specifically carriers which function
as reactive surfactants, include polyalkoxypolysiloxanes. A
preferred carrier is available from Goidschmidt Chemical Co.
(Hopewell, Va.) under the tradename Tegorad 2200, and reactive
surfactant Tegorad 2700 (acrylated siloxane) also from Goldschmidt
Chemical Co.
[0076] Other classes of suitable carriers are polyols and
non-reactive surfactants. Examples of suitable polyols and
non-reactive surfactants include polyol Acclaim 3201 (poly(ethylene
oxide-co-propylene oxide)) available from Bayer (formerly known as
Lyondel), Newtown Square, Pa., and non-reactive surfactants
Tegoglide 435 (polyalkoxy-polysiloxane) available from Goldschmidt
Chemical Co. The polyol or non-reactive surfactants may be present
in a preferred amount between about 0.01 pph to about 10 pph.
Suitable carriers may also be amphiphilic molecules. An amphiphilic
molecule is a molecule that has both hydrophilic and hydrophobic
segments. The hydrophobic segment may alternatively be described as
a lipophilic (fat/oil loving) segment.
[0077] A tackifier is also an example of a suitable carrier. A
tackifier is a molecule that can modify the time-sensitive
rheological property of a polymer product, such as, but not limited
to, viscosity. In general a tackifier additive will make a polymer
product act stiffer at higher strain rates or shear rates and will
make the polymer product softer at low strain rates or shear rates.
A tackifier is an additive commonly used in the adhesives industry,
that enhances the ability of a coating to create a bond with an
object that the coating is applied upon. For additional background
regarding tackifiers and tackifier resins, the Handbook of Pressure
Sensitive Adhesive Technology, 3rd Edition, D. Satas, (1999)
(Warwick, RI: Satas and Associates.) is incorporated herein by
reference, see pages 36, 37, 57-61, 169, 173, 174, and 609-631.
[0078] Preferred tackifiers are those classified as a terpene base
resin, coumarone base resin, petroleum resin, hydrogenated
petroleum resin, styrene resin, phenol resins, or rosin base resin.
It is preferred that the tackifiers are nonepoxidized. The rosin
base resins include unmodified rosin (e.g., wood, gum, or tall oil)
and rosin derivatives. Rosin base resins can be classified by their
rosin acids, which are either an abietic acid or a pimaric acid.
Abietic acid type rosins are preferred. Rosin derivatives include
polymerized rosin, disproportionated rosin, hydrogenated rosin, and
esterified rosin. Representative examples of such rosin derivatives
include pentaerythritol esters of tall oil, gum rosin, wood rosin,
or mixtures thereof.
[0079] The terpene base resins include terpene polymers of
.alpha.-pinene, .beta.-pinene, dipentel, limonene, myrcene,
bornylene and camphene, and phenol-modified terpene base resins
obtained by modifying these terpene base resins with phenols.
[0080] The coumarone base resins include, for example,
coumarone-indene resins and phenol-miodified coumarone-indene
resins.
[0081] Petroleum and hydrogenated petroleum resins include
aliphatic petroleum resins, alicyclic petroleum resins, aromatic
petroleum resins using styrene, .alpha.-methylstyrene,
vinyltoluene, indene, methylindene, butadiene, isoprene, piperylene
and pentylene as raw materials, and homopolymers or copolymers of
cyclopentadiene. The petroleum resins are polymers using fractions
having a carbon number of 5 to 9 as main components.
[0082] The styrene base resins include homopolymers which are low
molecular weight polymers comprising styrene as a principal
component, and copolymers of styrene with, for example,
.alpha.-methylstyrene, vinyltoluene, and butadiene rubber.
[0083] The phenol base resins include reaction products of phenols
such as phenol, cresol, xylenol, resorcinol, p-tert-butylphenol,
and p-phenylphenol with aldehydes such as formaldehyde,
acetaldehyde and furfural, and rosin-modified phenol resins.
[0084] A more preferred tackifier is Uni-tac.RTM. R-40 (hereinafter
"R-40") available from International Paper Co., Purchase, NY. R-40
is a tall oil rosin, which contains a polyether segment, and is
from the chemical family of abietic esters. Preferably, the
tackifier is present in the composition in an amount between about
0.01 to about 10 parts per hundred, more preferred in the amount
between about 0.05 to about 10 parts per hundred. A suitable
alternative tackifier is the Escorez series of hydrocarbon
tackifiers available from Exxon. For additional information
regarding Escorez tackifiers, the specification of U.S. Pat. No.
5,643,665 is hereby incorporated by reference in its entirety. The
aforementioned carriers may also be used in combination.
[0085] Preferably the adhesion promoter used in combination with
the tackifier carrier is a poly(alkoxy)silane. However, the
invention is not limited to only a poly(alkoxy)silane adhesion
promoter in combination with a tackifier carrier. A preferred
poly(alkoxy)silane adhesion promoter is
bis(trimethoxysilylethyi)benzene. It is also preferred that the
poly(alkoxy)silane adhesion promoter is present in the composition
in an amount between 0.1 to 15 pph.
[0086] Although. the adhesion promoter can be any adhesion promoter
that includes a compound with a reactive silane, preferably it is
an adhesion promoter as described above (i.e., including a compound
containing a cyclic structure interposed between at least two
reactive silanes, which are independently alkoxysilanes or
halosilanes). Other suitable adhesion promoters are described in
U.S. Pat. Nos. 4,921,880 and 5,188,864 to Lee et al., the
specifications of which are hereby incorporated by reference. Other
useful adhesion promoters will be apparent to one skilled in the
art.
[0087] Preferably the coating formulation has viscosity of less
than about 50 poises at about 35.degree. C, more preferably less
about 40 poises at about 35.degree. C. and a viscosity of no more
than about 30 poises at a temperature of about 50-60.degree. C.,
more preferably no more than about 20 poises at a temperature of
about 50-60.degree. C., and most preferably no more than about 15
poises at a temperature of about 50-60.degree. C.
[0088] Reference is made to U.S. patent application Ser. No.
09/476,151, filed Dec. 30, 1999, the specification of which is
incorporated herein by reference as though fully set forth in its
entirety, for a more detailed explanation of the adhesion
promoter.
[0089] Preferably, primary coating 16 is a soft cushioning layer
which preferably has a Young's modulus of less than about 5 MPa. It
is also preferred that primary coating 16 is at least about 5 .mu.m
thick, more preferably at least about 25 .mu.m, most preferably at
least about 30 .mu.m.
[0090] Exemplary embodiments of a primary coating which includes a
strength additive are listed in tables A-S.
1TABLE A Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Bis(trimethoxysilylethyl)benzene 2 pph Promoter
Carrier Tegorad2200 0.5 pph Antioxidant Irganox1035 1 pph Strength
Pentaerythritol tetrakis(3- 0.3 pph Additive
mercaptopropionate)
[0091]
2TABLE B Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Bis(trimethoxysilylethyl)benzene 2 pph Promoter
Carrier Tegorad2200 0.5 pph Antioxidant Irganox1035 1 pph Strength
Pentaerythritol tetrakis(3- 0.7 pph Additive
mercaptopropionate)
[0092]
3TABLE C Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Bis(trimethoxysilylethyl)benzene 2 pph Promoter
Antioxidant Irganox1035 1 pph Strength Chloro-propyltrimethoxy
silane 0.3 pph Additive
[0093]
4TABLE D Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Bis(trimethoxysilylethyl)benzene 2 pph Promoter
Antioxidant Irganox1035 1 pph Strength 3-mercaptopropyltrimethox-
ysilane 0.3 pph Additive
[0094]
5TABLE E Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Bis(trimethoxysilylethyl)benzene 2 pph Promoter
Antioxidant Irganox1035 1 pph Strength Chloro-propyltrimethoxy
silane 0.5 pph Additive
[0095]
6TABLE F Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Bis(trimethoxysilylethyl)benzene 2 pph Promoter
Antioxidant Irganox1035 1 pph Strength Chloro-propyltrimethoxy
silane 1.0 pph Additive
[0096]
7TABLE G Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Bis(trimethoxysilylethyl)benzene 2 pph Promoter
Carrier Tegorad2200 0.5 pph Antioxidant Irganox1035 1 pph Strength
Chloro-octane 0.3 pph Additive
[0097]
8TABLE H Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Bis(trimethoxysilylethyl)benzene 2 pph Promoter
Carrier Tegorad2200 0.5 pph Antioxidant Irganox1035 1 pph Strength
Chloro-octane 0.5 pph Additive
[0098]
9TABLE I Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Bis(trimethoxysilylethyl)benzene 2 pph Promoter
Carrier Tegorad2200 0.5 pph Antioxidant Irganox1035 1 pph Strength
Chloro-octane 1.0 pph Additive
[0099]
10TABLE J Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength
3-mercaptopropyltrimethoxysilane 0.3 pph Additive
[0100]
11TABLE K Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength Pentaerythritol tetrakis(3-
0.3 pph Additive mercaptopropionate)
[0101]
12TABLE L Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength Pentaerythritol tetrakis(3-
0.5 pph Additive mercaptopropionate)
[0102]
13TABLE M Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength Pentaerythritol tetrakis(3-
0.7 pph Additive mercaptopropionate)
[0103]
14TABLE N Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength Chloro-propyltrimethoxy
silane 0.3 pph Additive
[0104]
15TABLE O Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength Chloro-propyltrimethoxy
silane 0.5 pph Additive
[0105]
16TABLE P Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength Chloro-propyltrimethoxy
silane 1.0 pph Additive
[0106]
17TABLE Q Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength Chloro-octane 0.3 pph
Additive
[0107]
18TABLE R Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength Chloro-octane 0.5 pph
Additive
[0108]
19TABLE S Component Compound Wt % or pph Oligomer BR3731 (polyether
acrylate) 52% Monomer Photomer 4003 (ethoxylatednonyl-phenol 45%
acrylate) Photoinitiator Irgacure 184 1.5% Photoinitiator Irgacure
819 1.5% Adhesion Methacryloxypropyltrimethoxysilane 1 pph Promoter
Antioxidant Irganox1035 1 pph Strength Chloro-octane 1.0 pph
Additive
[0109] Secondary coating material 18 is typically the
polymerization (i.e., cured) product of a coating composition that
contains urethane acrylate liquids whose molecules become
cross-linked when polymerized. Other suitable materials for use in
secondary coating materials, as well as considerations related to
selection of these materials, are well known in the art and are
described in U.S. Pat. Nos. 4,962,992 and 5,104,433 to Chapin, the
specifications of which are hereby incorporated by reference.
Various additives that enhance one or more properties of the
coating can also be present, including the above-mentioned
additives incorporated in the compositions of the present
invention.
[0110] Typical secondary coatings will include at least one UV
curable monomer and at least one photoinitiator. The secondary
coating may also include about 0-90 weight percent of at least one
UV curable oligomer. It is preferred that the secondary coating is
not a thermoplastic resin. Preferably, both the monomer and the
oligomer are compounds capable of participating in addition
polymerization. The monomer or the oligomer may be the major
component of the secondary coating. An example of a suitable
monomer is an ethylenically unsaturated monomer. Ethylenically
unsaturated monomers may contain various functional groups, which
enable their cross-linking. The ethylenically unsaturated monomers
are preferably polyfunctional (i.e., each containing two or more
functional groups), although monofunctional monomers can also be
introduced into the composition. Therefore, the ethylenically
unsaturated monomer can be a polyfunctional monomer, a
monofunctional monomer, and mixtures thereof. Suitable functional
groups for ethylenically unsaturated monomers used in accordance
with the present invention include, without limitation, acrylates,
methacrylates, acrylamides, N-vinyl amides, styrenes, vinyl ethers,
vinyl esters, acid esters, and combinations thereof (i.e., for
polyfunctional monomers).
[0111] In general, individual monomers capable of about 80% or more
conversion (i.e., when cured) are more desirable than those having
lower conversion rates. The degree to which monomers having lower
conversion rates can be introduced into the composition depends
upon the particular requirements (i.e., strength) of the resulting
cured product. Typically, higher conversion rates will yield
stronger cured products.
[0112] Suitable polyfunctional ethylenically unsaturated monomers
include, without limitation, alkoxylated bisphenol A diacrylates
such as ethoxylated bisphenol A diacrylate with ethoxylation being
2 or greater, preferably ranging from 2 to about 30 (e.g. SR349 and
SR601 available from Sartomer Company, Inc. West Chester, Pa. and
Photomer 4025 and Photomer 4028, available from Cognis Corp.
(Ambler, Pa.)), and propoxylated bisphenol A diacrylate with
propoxylation being 2 or greater, preferably ranging from 2 to
about 30; methylolpropane polyacrylates with and without
alkoxylation such as ethoxylated trimethylolpropane triacrylate
with ethoxylation being 3 or greater, preferably ranging from 3 to
about 30 (e.g., Photomer 4149, Cognis Corp., and SR499, Sartomer
Company, Inc.), propoxylated trimethylolpropane triacrylate with
propoxylation being 3 or greater, preferably ranging from 3 to 30
(e.g., Photomer 4072, Cognis Corp. and SR492, Sartomer), and
ditrimethylolpropane tetraacrylate (e.g., Photomer 4355, Cognis
Corp.); alkoxylated glyceryl triacrylates such as propoxylated
glyceryl triacrylate with propoxylation being 3 or greater (e.g.,
Photomer 4096, Cognis Corp. and SR9020, Sartomer); erythritol
polyacrylates with and without alkoxylation, such as
pentaerythritol tetraacrylate (e.g., SR295, available from Sartomer
Company, Inc. (West Chester, Pa.)), ethoxylated pentaerythritol
tetraacrylate (e.g., SR494, Sartomer Company, Inc.), and
dipentaerythritol pentaacrylate (e.g., Photomer 4399, Cognis Corp.,
and SR399, Sartomer Company, Inc.); isocyanurate polyacrylates
formed by reacting an appropriate functional isocyanurate with an
acrylic acid or acryloyl chloride, such as tris-(2-hydroxyethyl)
isocyanurate triacrylate (e.g., SR368, Sartomer Company, Inc.) and
tris-(2-hydroxyethyl) isocyanurate diacrylate; alcohol
polyacrylates with and without alkoxylation such as tricyclodecane
dimethanol diacrylate (e.g., CD406, Sartomer Company, Inc.) and
ethoxylated polyethylene glycol diacrylate with ethoxylation being
2 or greater, preferably ranging from about 2 to 30; epoxy
acrylates formed by adding acrylate to bisphenol A diglycidylether
(4 up) and the like (e.g., Photomer 3016, Cognis Corp.); and single
and multi-ring cyclic aromatic or non-aromatic polyacrylates such
as dicyclopentadiene diacrylate and dicyclopentane diacrylate.
[0113] It may also be desirable to use certain amounts of
monofunctional ethylenically unsaturated monomers, which can be
introduced to influence the degree to which the cured product
absorbs water, adheres to other coating materials, or behaves under
stress. Exemplary monofunctional ethylenically unsaturated monomers
include, without limitation, hydroxyalkyl acrylates such as
2-hydroxyethyl-acrylate, 2-hydroxypropyl-acrylate, and
2-hydroxybutyl-acrylate; long- and short-chain alkyl acrylates such
as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl
acrylate, butyl acrylate, amyl acrylate, isobutyl acrylate, t-butyl
acrylate, pentyl acrylate, isoamyl acrylate, hexyl acrylate, heptyl
acrylate, octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate,
nonyl acrylate, decyl acrylate, isodecyl acrylate, undecyl
acrylate, dodecyl acrylate, lauryl acrylate, octadecyl acrylate,
and stearyl acrylate; aminoalkyl acrylates such as
dimethylaminoethyl acrylate, diethylaminoethyl acrylate, and
7-amino-3,7-dimethyloctyl acrylate; alkoxyalkyl acrylates such as
butoxylethyl acrylate, phenoxyethyl acrylate (e.g., SR339, Sartomer
Company, Inc.), and ethoxyethoxyethyl acrylate; single and
multi-ring cyclic aromatic or non-aromatic acrylates such as
cyclohexyl acrylate, benzyl acrylate, dicyclopentadiene acrylate,
dicyclopentanyl acrylate, tricyclodecanyl acrylate, bomyl acrylate,
isobornyl acrylate (e.g., SR423, Sartomer Company, Inc.),
tetrahydrofurfuryl acrylate (e.g., SR285, Sartomer Company, Inc.),
caprolactone acrylate (e.g., SR495, Sartomer Company, Inc.), and
acryloylmorpholine; alcohol-based acrylates such as polyethylene
glycol monoacrylate, polypropylene glycol monoacrylate,
methoxyethylene glycol acrylate, methoxypolypropylene glycol
acrylate, methoxypolyethylene glycol acrylate, ethoxydiethylene
glycol acrylate, and various alkoxylated alkylphenol acrylates such
as ethoxylated(4) nonylphenol acrylate (e.g., Photomer 4003, Cognis
Corp.); acrylamides such as diacetone acrylamide, isobutoxymethyl
acrylamide, N,N'-dimethyl-aminopropyl acrylamide, N,N-dimethyl
acrylamide, N,N-diethyl acrylamide, and t-octyl acrylamide; vinylic
compounds such as N-vinylpyrrolidone and N-vinylcaprolactam; and
acid esters such as maleic acid ester and fumaric acid ester.
[0114] Most suitable monomers are either commercially available or
readily synthesized using reaction schemes known in the art. For
example, most of the above-listed monofunctional monomers can be
synthesized by reacting an appropriate alcohol or amine with an
acrylic acid or acryloyl chloride.
[0115] As indicated above, an optional constituent of the secondary
coating composition is the oligomeric component. The oligomeric
component can include a single type of oligomer or it can be a
combination of two or more oligomers. When employed, if at all, the
oligomeric component introduced into the compositions of the
present invention preferably comprises ethylenically unsaturated
oligomers
[0116] When employed, suitable oligomers can be either
monofunctional oligomers or polyfunctional oligomers, although
polyfunctional oligomers are preferred. The oligomeric component
can also be a combination of a monofunctional oligomer and a
polyfunctional oligomer.
[0117] Di-functional oligomers preferably have a structure
according to formula (I) below:
F1-R1-[Diisocyanate-R2-Diisocyanate]m-R1-F1 (I)
[0118] where F1 is independently a reactive functional group such
as acrylate, methacrylate, acrylamide, N-vinyl amide, styrene,
vinyl ether, vinyl ester, or other functional group known in the
art; R1 includes independently --C2-12O--, --(C2-4-O)n--,
--C2-12O--(C2-4-O)n--, --C2-12O--(CO--C2-5O)n--, or
--C2-12O--(CO--C2-5NH)n-- where n is a whole number from 1 to 30,
preferably 1 to 10; R2 is polyether, polyester, polycarbonate,
polyamide, polyurethane, polyurea, or combinations thereof; and m
is a whole number from 1 to 10, preferably 1 to 5. In the structure
of formula I, the diisocyanate group is the reaction product formed
following bonding of a diisocyanate to R2 and/or R1.
[0119] Other polyfunctional oligomers preferably have a structure
according to formula (H) or formula (III) as set forth below:
multiisocyanate-(R2-R1-F2)x (II)
[0120] or
polyol-[(diisocyanate-R2-diisocyanate)m-R 1-F2]x (III)
[0121] where F2 independently represents from 1 to 3 functional
groups such as acrylate, methacrylate, acrylamide, N-vinyl amide,
styrene, vinyl ether, vinyl ester, or other functional groups known
in the art; R1 can include --C2-12O--, --(C2-4-O)n--,
--C2-12O--(C2-4-O)n--, --C2-12O--(CO--C2-5O)n--, or
--C2-12O--(CO--C2-5NH)n-- where n is a whole number from 1 to 10,
preferably 1 to 5; R2 can be polyether, polyester, polycarbonate,
polyamide, polyurethane, polyurea or combinations thereof; x is a
whole number from 1 to 10, preferably 2 to 5; and m is a whole
number from 1 to 10, preferably 1 to 5. In the structure of formula
II, the multiisocyanate group is the reaction product formed
following bonding of a multiisocyanate to R2. Similarly, the
diisocyanate group in the structure of formula III is the reaction
product formed following bonding of a diisocyanate to R2 and/or
R1.
[0122] Urethane oligomers are conventionally provided by reacting
an aliphatic diisocyanate with a dihydric polyether or polyester,
most typically a polyoxyalkylene glycol such as a polyethylene
glycol. Such oligomers typically have between about four to about
ten urethane groups and may be of high molecular weight, e.g.,
2000-8000. High molecular weight oligomers, with molecular weights
as high as 15000, may also be used. However, lower molecular weight
oligomers, having molecular weights in the 500-2000 range, may also
be used. U.S. Pat. No. 4,608,409 to Coady et al. and U.S. Pat. No.
4,609,718 to Bishop et al., the specifications of which are hereby
incorporated by reference to describe such syntheses in detail.
[0123] When it is desirable to employ moisture-resistant oligomers,
they may be synthesized in an analogous manner, except that the
polar polyether or polyester glycols are avoided in favor of
predominantly saturated and predominantly nonpolar aliphatic diols.
These diols include, for example, alkane or alkylene diols of from
about 2-250 carbon atoms and, preferably, are substantially free of
ether or ester groups.
[0124] Polyurea components may be incorporated in oligomers
prepared by these methods, simply by substituting diamines or
polyamines for diols or polyols in the course of synthesis. The
presence of minor proportions of polyurea components in the present
coating systems is not considered detrimental to coating
performance, provided only that the diamines or polyamines employed
in the synthesis are sufficiently non-polar and saturated as to
avoid compromising the moisture resistance of the system.
[0125] A non-exhaustive list of suitable oligomers include BR301,
which is an aromatic urethane acrylate oligomer available from
Bomar Specialty Co., Photomer 6010, which is an aliphatic urethane
acrylate oligomer available from Henkel Corp., KWS5021, which is an
aliphatic urethane acrylate oligomer available from Bomar Specialty
Co., RCC 12-892, which is a multi-functional aliphatic urethane
acrylate oligomer available from Henkel Corp., RCC13-572, which is
an aromatic urethane diacrylate oligomer available from Henkel
Corp., and KWS413 1, which is an aliphatic urethane acrylate
oligomer available from Bomar Specialty Co.
[0126] Optical fiber secondary coating compositions may also
contain a polymerization initiator which is suitable to cause
polymerization (i.e., curing) of the composition after its
application to a glass fiber or previously coated glass fiber.
Polymerization initiators suitable for use in the compositions of
the present invention include thermal initiators, chemical
initiators, electron beam initiators, microwave initiators,
actinic-radiation initiators, and photoinitiators. Particularly
preferred are the photoinitiators. For most acrylate-based coating
formulations, conventional photoinitiators, such as the known
ketonic photoinitiating and/or phosphine oxide additives, are
preferred. When used in the compositions of the present invention,
the photoinitiator is present in an amount sufficient to provide
rapid ultraviolet curing. Generally, this includes about 0.5 to
about 10.0 weight percent, more preferably about 1.5 to about 7.5
weight percent.
[0127] The photoinitiator, when used in a small but effective
amount to promote radiation cure, must provide reasonable cure
speed without causing premature gelation of the coating
composition. A desirable cure speed is any speed sufficient to
cause substantial curing (i.e., greater than about 90%, more
preferably 95%) of the coating composition. As measured in a dose
versus modulus curve, a cure speed for coating thickness' of about
25-35 .mu.m is, e.g., less than 1.0 J/cm2, preferably less than 0.5
J/cm2. It is preferred that the secondary coating composition
contains about 10-90% of the monomer; of about 0-90% of the
oligomer; and about 0.5-10% of the photoinitiator.
[0128] Suitable photoinitiators include, without limitation,
l-hydroxycyclohexylphenyl ketone (e.g., T-gacure 184 available from
Ciba Specialty Chemical (Tarrytown, N.Y.)),
(2,6-dimethoxybenzoyl)-2,4,4-trime- thylpentyl phosphine oxide
(e.g., in commercial blends Irgacure 1800, 1850, and 1700, Ciba
Specialty Chemical), 2,2-dimethoxyl-2-phenyl acetophenone (e.g.,
fracure 651, Ciba Specialty Chemical),
bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide (e.g., Irgacure
819, Ciba Specialty Chemical), (2,4,6-trimethylbenzoyl)diphenyl
phosphine oxide (e.g., in commercial blend Darocur 4265, Ciba
Specialty Chemical), 2-hydroxy-2-methyl-1-phenylpropane-1-one
(e.g., in commercial blend Darocur 4265, Ciba Specialty Chemical),
(2,4,6-trimethylbenzoyl)diphenyl phosphine oxide (Lucerin TPO,
available from BASF (Munich, Germany)), ethoxy
(2,4,6-trimethylbenzoyl)phenyl phosphine oxide (Lucerin TPO-L from
BASF), and combinations thereof. Other photoinitiators are
continually being developed and used in coating compositions on
glass fibers. Any suitable photoinitiator can be introduced into
compositions of the present invention.
[0129] In addition to the above-described components, the secondary
coating composition of the present invention can optionally include
an additive or a combination of additives. Suitable additives
include, without limitation, antioxidants, catalysts, lubricants,
low molecular weight non-crosslinking resins, adhesion promoters,
and stabilizers. Some additives can operate to control the
polymerization process, thereby affecting the physical properties
(e.g., modulus, glass transition temperature) of the polymerization
product formed from the composition. Others can affect the
integrity of the polymerization product of the composition (e.g.,
protect against de-polymerization or oxidative degradation).
[0130] A preferred antioxidant is thiodiethylene
bis[(3,5-di-tert-butyl-4-- hydroxy) hydrocinnamate] (e.g., Irganox
1035, available from Ciba Specialty Chemical).
[0131] Other suitable materials for use in secondary coating
materials, as well as considerations related to selection of these
materials are described in U.S. Pat. Nos. 4,962,992 and 5,104,433
to Chapin, which are hereby incorporated by reference. Various
additives that enhance one or more properties of the coating can
also be present, including the above-mentioned additives
incorporated in the compositions of the present invention.
[0132] Reference is made to U.S. Patent Application No. 60/173,874,
filed Dec. 30, 1999, and Provisional U.S. Patent Application filed
Jul. 26, 2000 by Botelho et al., titled Secondary Coating
Compositions for Optical Fibers, the specifications of which are
incorporated herein by reference as though fully set forth in its
entirety, for a more detailed explanation of secondary
coatings.
[0133] Preferably, secondary coating 18 has a Young's modulus of at
least about 50 MPa, more preferably at least about 500 MPa, and
most preferably at least about 1000 MPa. In one embodiment of fiber
10, the outer diameter of secondary coating 18 is about 245 .mu.m.
It is preferred that the secondary coating is at least 5 .mu.m
thick, more preferably at least about 20 .mu.m, and most preferably
at least about 25 .mu.m.
[0134] Secondary coating 18 can be a tight buffer coating or,
alternatively, a loose tube coating. Irrespective of the type of
secondary coating employed, it is preferred that the outer surface
of secondary coating 18 is not tacky so that adjacent convolutions
of the optic fiber (i.e., on a process spool) can be unwound.
[0135] The optical fibers of the present invention can also be
formed into an optical fiber ribbon which contains a plurality of
substantially aligned, substantially coplanar optic fibers
encapsulated by a matrix material. The matrix material can be made
of a single layer or of a composite construction. Suitable matrix
materials include polyvinyl chloride or other thermoplastic
materials as well as those materials known to be useful as
secondary coating materials. In one embodiment, the matrix material
can be the polymerization product of the composition used to form
the secondary coating material.
[0136] Briefly, the process for making a coated optical fiber in
accordance with the invention involves fabricating glass fiber 10
(core 12 and cladding layer 14), coating the glass fiber with the
primary coating composition of the present invention, and
polymerizing the composition to form the primary coating material
16. Optionally, secondary coating composition 18 can be applied to
the coated fiber either before or after polymerizing the primary
coating. When applied after polymerizing the primary coating, a
second polymerization step must be employed. The primary and
optional secondary coating compositions are coated on a glass fiber
using conventional processes.
[0137] It is well known to draw glass fibers from a specially
prepared, cylindrical preform which has been locally and
symmetrically heated to a temperature, e.g., of about 2000.degree.
C. As the preform is heated, such as by feeding the preform into
and through a furnace, a glass fiber is drawn from the molten
material. The primary coating and secondary coating compositions
are applied to the glass fiber after it has been drawn from the
preform, preferably immediately after cooling. The coating
compositions are then cured to produce the coated optical fiber.
The method of curing can be thermal, chemical, or radiation
induced, such as by exposing the un-cured coating composition on
the glass fiber to heat or ultraviolet light or electron beam,
depending upon the nature of the coating composition(s) and
polymerization initiator being employed. It is frequently
advantageous to apply both the primary coating composition and any
secondary coating compositions in sequence following the draw
process. One method of applying dual layers of coating compositions
to a moving glass fiber is disclosed in U.S. Pat. No. 4,474,830 to
Taylor, the specification of which is hereby incorporated by
reference. Another method for applying dual layers of coating
compositions onto a glass fiber is disclosed in U.S. Pat. No.
4,581,165 to Rannell et al., the specification of which is hereby
incorporated by reference. Of course, the primary coating
composition can be applied and cured to form the primary coating
material 16, then the secondary coating composition(s) can be
applied and cured to form the secondary coating material 18.
[0138] One embodiment of a process for manufacturing a coated
optical fiber in accordance with the invention is further described
in FIG. 2, generally denoted as 20. As shown in FIG. 2, a sintered
preform 22 (shown as a partial preform) is drawn into an optical
fiber 24. The fiber 24 passes through coating elements 26 and 28.
Preferably, coating 16 is applied to fiber 24 in element 26 and
coating 18 is applied to fiber 24 in element 28. Curing element 30
is located downstream from elements 26 and 28 to cure the coatings
applied to fiber 24. Alternatively, the coating applied in element
26 may be cured prior to fiber 24 passing through element 28.
Tractors 32 are used to pull a coated optical fiber 34 through
element 30. The tractors rotate in the direction of arrows A.
[0139] It is preferred that inventive coating is at least about 5
.mu.m thick, more preferred at least about 20 .mu.m, most preferred
at least about 25 .mu.m thick. Specific embodiments of primary
coating 16 may be about 30 .mu.m thick or more. Specific
embodiments of secondary coating 18 may also be at least about 25
.mu.m thick.
EXAMPLES
[0140] The invention will be further clarified by the following
examples which are intended to be exemplary of the invention.
Example 1
Coating Compositions
[0141] A number of compositions of the present invention were
prepared with the components listed in Table 1-1 below using
commercial blending equipment. The oligomer and monomer components
were weighed and then introduced into a heated kettle and blended
together at a temperature within the range of from about 50.degree.
C. to 80.degree. C. Blending was continued until a homogenous
mixture was obtained. Next, the photoinitiator and antioxidant were
individually weighed and separately introduced into the homogeneous
solution while blending. Additives such as the strength additive an
adhesion promoter, and optional carrier were weighed and then
introduced into the solution while blending. Blending was continued
until a homogeneous solution was again obtained.
20TABLE 1-1 Coating Compositions Fiber and Coating Primary Coating
Secondary Coating Composition Code (wt % or pph) (wt % or pph) A BR
3731 (52%) BR301 (10%) Photomer 4003 (45%) Photomer 4025 (22%)
Irgacure 1850 (3%) Photomer 4028 (65%) Irganox 1035 (1 pph)
Irgacure 1850 (3%) Bis(trimethoxysilylethyl) Irganox1035 (0.5 pph)
benzene (1 pph) Tegorad 2200 (0.5 pph) 3 Mercaptopropyl-
trimethoxysilane (0.3 pph) B BR 3731 (52%) KWS 4131 (10%) Photomer
4003 (45%) Photomer 4028 (87%) Irgacure 1850 (3%) Irgacure 1850
(3%) Irganox 1035 (1 pph) Irganox 1035 (0.5 pph)
Bis(trimethoxysilylethyl) benzene (2 pph) 3 Mercaptopropyl-
trimethoxysilane (0.3 pph) C BR 3731 (52%) KWS 4131 (10%) Photomer
4003 (45%) Photomer 4028 (87%) Irgacure 1850 (3%) Irgacure 1850
(3%) Irganox 1035 (1 pph) Irganox 1035 (0.5 pph)
Bis(trimethoxysilylethyl) benzene (2 pph) 3 Mercaptopropyl-
trimethoxysilane (0.1 pph) D BR 3731 (52%) KWS 4131 (10%) Photomer
4003 (45%) Photomer 4028 (87%) Irgacure 1850 (3%) Irgacure 1850
(3%) Irganox 1035 (1 pph) Irganox 1035 (0.5 pph)
Bis(trimethoxysilylethyl) benzene (2 pph) Unitac R40 (1 pph) 3
Mercaptopropyl- trimethoxysilane (0.3 pph) E BR 3731 (52%) KWS 4131
(10%) Photomer 4003 (45%) Photomer 4028 (87%) Irgacure 1850 (3%)
Irgacure 1850 (3%) Irganox 1035 (1 pph) Irganox 1035 (0.5 pph)
Bis(trimethoxysilylethyl) benzene (2 pph) Unitac R40 (1 pph) 3
Mercaptopropyl- trimethoxysilane (0.1 pph) F BR 3731 (52%) BR301
(10%) Photomer 4003 (45%) Photomer 4025 (22%) Irgacure 1850 (3%)
Photomer 4028 (65%) Irganox 1035 (1 pph) Irgacure 1850 (3%)
Bis(trimethoxysilylethyl- ) Irganox 1035 (0.5 pph) benzene (2 pph)
Tegorad 2200 (0.5 pph) Tert-dodecylmercaptan (0.3 pph) G BR 3731
(52%) BR301 (10%) Photomer 4003 (45%) Photomer 4025 (22%) Irgacure
1850 (3%) Photomer 4028 (65%) Irganox 1035 (1 pph) Irgacure 1850
(3%) 3 Mercaptopropyl- Irganox 1035 (0.5 pph) trimethoxysilane (0.3
pph) Ebecryl 170 (0.2 pph)
[0142] The test coatings were applied to SMF-28 fiber, available
from Coring, Incorporated of Coring, N.Y. The length of each sample
of coated fiber was about 20 to about 200 km. Each of the coated
fibers were tested for fiber strength, Young's modulus, tensile
strength, percent elongation, average cure speed, dry and wet strip
force pullout, and water soak.
Example 2
Fiber Strength
[0143] The fiber strength of fibers coated with coatings A-G were
tested in accordance with FOTP 28C. Fiber samples were tested under
the conditions of "as received" (meaning the coated fiber samples
tested were not aged in an environmental chamber) and after coated
fiber samples were aged in an environmental chamber for 30 days at
85.degree. C. and 85% Rh. The strength performance of these fibers
is listed below in Table 2-1. All fibers showed good strength
performance after aging--i.e. the 50% failure stress after aging
for each fiber was >710 kpsi. Fibers A, B, D, and E showed no
significant strength loss after aging. Fibers C and F showed very
small degradation in fiber strength (A50% Failure Stress 27 kpsi
and 29 kpsi, respectively) post aging. Fiber G essentially showed
no change in fiber strength after aging. All of the fibers
exhibited sufficient strength to pass Bellcore specification
GR-20-CORE.
21TABLE 2-1 Fiber Strength. Fiber Coating As received 30 day aged
Code 15% F.S. 50% F.S. W.S. 15% F.S. 50% F.S. W.S. A 605 759 10 751
761 121 B 758 744 87 747 736 95 C 753 745 169 728 718 103 D 758 749
112 753 745 120 E 755 743 95 742 731 103 F 736 744 119 705 715 94 G
732 738 120 735 743 98 FS: Fiber Strength WS: Weibull Slope
[0144] The effect of varying the adhesion promoter, the strength
additive, and the amount of the strength additive was also tested.
The base primary coating included 52% BR 3731, 45% Photomer 4003,
1.5% Irgacure 184, 1.5% Irgacure 819, and 1 pph Irganox 1035. The
adhesion promoters and strength additives were varied as set forth
below in table 2-2. Each fiber was coated with the same secondary
coating. The formulation of the secondary coating was 10% KWS 4131,
82% Photomer 4028, 5% Photomer 3016, 1.5% Irgacure 184, 1.5%
Irgacure 819, and 0.5 pph Irganox 1035. The amount of strength
additive varied from 0 to 1.0 pph. The type of fiber tested was
also SMF-28.
22TABLE 2-2 Fiber and/ Coating Composition Code Adhesion Promoter
(pph) Strength Additive H Methacrylate Silane (1 pph) Tetrathiol
(pentaerythritol tetrakis (3- mercaptopropionate)) I Methacrylate
Silane (1 pph) Chlorosilane J Methacrylate Silane (1 pph)
Chloro-octane K Methacrylate Silane (1 pph) Mercaptosilane (3-
mercaptopropyltrimethoxy silane) L Bis(trimethoxysilylethyl)
Tetrathiol benzene (2 pph)* (pentaerythritol tetrakis (3-
mercaptopropionate)) M Bis(trimethoxysilylethyl) Chlorosilane
benzene (2 pph)* N Bis(trimethoxysilylethyl) Chloro-octane benzene
(2 pph)* O Bis(trimethoxysilylethyl) Mercaptosilane (3- benzene (2
pph)* mercaptopropyltrimethoxy silane) *Included 0.5 pph of Tegorad
2200 Methacrylate silane: methacryl oxypropyltrimethoxy silane
Chlorosilane: chloro-propyltrimethoxy silane
[0145] The fiber strength of fibers coated with coatings H-O were
tested in accordance with FOTP 28C. The fiber samples were tested
after the samples were aged in an environmental chamber for 30 days
at 85.degree. C. and 85% Rh. The strength performance of each fiber
is shown in FIGS. 3 and 4. With respect to fibers H--O, all fibers
that included a strength additive exhibited fiber strength of at
least about 700 kpsi except for two samples. The mercaptosilane
strength additive consistently exhibited the highest strength for
compositions which included no more than about 0.5 pph of a
strength additive.
[0146] SMF-28, available from Corning Incorporated of Corning,
N.Y., was coated with the compositions listed in table 2-3 and the
fiber strength of each coated sample was tested "as-received" and
after a sample was aged in an environmental chamber for 30 days at
85.degree. C. and 85% Rh. The samples were tested in accordance
with FOTP-28.
23TABLE 2-3 Fiber and Coating Composition Primary Coating Secondary
Coating Code (wt % or pph) (wt % or pph) P BR 3731 (52%) KWS 4131
(10%) Photomer 4003 (45%) Photomer 4028 (87%) Irgacure 184 (1.5%)
Irgacure 1850 (3%) Irgacure 819 (1.5%) Irganox 1035 (0.5 pph)
Bis(trimethoxysilylethyl) benzene (2 pph) Irganox 1035 (1 pph)
3-Chloropropyltrimethoxysilane (0.3 pph) Q BR 3731 (52%) KWS 4131
(10%) Photomer 4003 (45%) Photomer 4028 (87%) Irgacure 184 (1.5%)
Irgacure 1850 (3%) Irgacure 819 (1.5%) Irganox 1035 (0.5 pph)
Bis(trimethoxysilylethyl) benzene (2 pph) Irganox 1035 (1 pph)
1-Chlorooctance (0.3 pph) Control-3 BR 3731 (52%) KWS 4131 (10%)
Photomer 4003 (45%) Photomer 4028 (87%) Irgacure 184 (1.5%)
Irgacure 1850 (3%) Irgacure 819 (1.5%) Irganox 1035 (0.5 pph)
Irganox 1035 (1 pph) Bis(trimethoxysilylethyl) benzene (2 pph)
[0147] The results of the strength testing are listed in table 2-4
below.
24TABLE 2-4 Fiber Coating Code A-S 50% F.S. (kpsi) Aged 50% F.S.
(kpsi) P 777 702 Q 790 717 Control-3 743 617
[0148] The fibers which included the inventive strength additive
exhibited superior strength than the control-3 fiber. The improved
fiber strength was more pronounced in the case of the aged
fiber.
Example 3
Tensile Properties
[0149] The tensile properties of cured primary coating film samples
were tested in accordance with ASTM D 882-97. Two control samples
were also tested. The composition or each control sample are given
below in table 3-1.
25TABLE 3-1 Fiber and Primary Coating Coating Composition Code (wt
% or pph) Control 1 BR 3731 (52%) Photomer 4003 (45%) Irgacure 1850
(3%) Irganox 1035 (1 pph) Control 2 BR 3731 (52%) Photomer 4003
(45%) Irgacure 1850 (3%) Irganox 1035 (1 pph)
Bis(trimethoxysilylethyl) benzene (2 pph) Tegorad 2200 (0.5
pph)
[0150] The tensile properties of cured films that contained
mercaptans are shown below in Table 3-2. The composition of each
sample tested relates back to Table 1-1 or Table 3-1. Tegorad 2200
and bis(trimethoxysilylethyl- )benzene, or bis-silane, additives
did not affect tensile properties to a significant extent as shown
by comparing coatings of control-1 and control-2 to known values.
These coatings served as controls for those that contained
mercaptan additives.
[0151] The addition of low levels of mercaptans to primary coatings
was not found to significantly lower the Young's modulus of cured
films relative to the control films. For instance coating C, which
contained 0.1 pph mercaptopropyltrimethoxysilane, had the same
modulus (1.34 MPa) as the control-2 coating. When the level of
mercaptopropyltrimethoxysilan- e was increased to 0.3 pph, as in
the case of film B, the Young's modulus dropped slightly to 1.20
MPa relative to control-1 and control-2. However, the standard
deviation in the measurement indicated that drop in modulus was not
statistically significant. In the case of coating F that contained
0.3 pph of tert-dodecylmercaptan, the Young's modulus was
determined to be 1.26 Mpa, which again was not statistically
different from the control films. Also, coating G, which contained
0.3 pph 3-mercaptopropyltrimethoxysilane and no
bis(trimethoxysilylethyl)benzene or other additives, showed no
significant change in tensile properties compared to control-1 or
control-2.
[0152] The combined addition of mercaptopropyltrimethoxysilane and
Uni-tac R40 to primary coatings seemed to significantly affect the
Young's modulus. The addition of 0.3 pph
mercaptopropyltrimethoxysilane and 1 pph of Uni-tac R40 dropped the
modulus to 1.04 MPa, which was a 22% reduction in modulus compared
to the control-2 sample. However, when only 0.1 pph of
mercaptopropyltrimethoxysilane was combined with 1 pph Uni-tac R40
the modulus dropped to only 1.17 MPa, which was a 13% reduction in
Young's modulus. In these comparisons it was assumed that the
ultimate properties were being compared in that the coatings were
fully cured.
26TABLE 3-2 Tensile Properties of Primary Coatings Young's Tensile
Mod. in Strength in Coating MPa MPa % Elongation Code (std dev)
(std dev) (std dev) Control-1 1.37 (0.13) 1.00 (0.31) 134.24
(31.86) Control-2 1.34 (0.08) 1.30 (0.50) 150.77 (5.33) B 1.20
(0.09) 1.08 (0.34) 152.91 (38.31) C 1.34 (0.09) 1.36 (0.44) 155.01
(26.58) D 1.04 (0.05) 0.96 (0.17) 171.36 (24.29) E 1.17 (0.07) 1.20
(0.37) 162.76 (33.95) F 1.26 (0.09) 1.12 (0.55) 146.37 (52.95) G
1.39 (0.12) 0.96 (0.26) 128.66 (27.69)
Example 4
Strength Additive Loading Effect on Young's Modulus
[0153] In addition to the modulus comparisons discussed above, a
systematic loading study of mercaptopropyltrimethoxysilane, N-(tert
butoxy carbonyl)-L-cysteine methyl ester, or pentaerythritol
tetrakis (3-mercaptopropionate) in a primary coating composition
based on control-2 was carried out. In these coatings
mercaptopropyltrimethoxysila- ne was added to the common primary
base formulation at about 0.1, 0.3, 0.5, 1.0, and 2.0 pph levels,
N-(tert butoxy carbonyl)-L-cysteine methyl ester was added at
levels between 0.0 to about 1.0 pph, and pentaerythritol tetrakis
(3-mercaptopropionate) was added at levels between 0.0 to about 0.6
pph. The formulations were cured under the same conditions and the
resulting films were tested.
[0154] As shown in FIG. 5, the Young's modulus dropped with
increasing loading of mercaptopropyltrimethoxysilane. At relatively
high loading of the mercaptan the reduction in Young's modulus was
significant, but at lower loadings (e.g. 0.1 pph or 0.3 pph
mercaptan) the reduction in Young's modulus was not significant.
The tensile strengths of the films also seemed to drop with
increasing mercaptan concentration, but significant changes were
only observed at the higher levels. No significant effect was
observed for changes in % elongation at break.
[0155] As shown in FIG. 6, the Young's modulus dropped with
increasing loading of N-(tert butoxy carbonyl)-L-cysteine methyl
ester. The Young's modulus dropped to less than 1.0 with more than
about 0.95 pph present in the formulation. As shown in FIG. 7, the
Young's modulus of pentaerythritol tetrakis (3-mercaptopropionate)
did not significantly vary as the concentration of the strength
additive was increased to at least about 0.5 pph.
[0156] The percentage change in Young's modulus (.DELTA.Y %) for
each strength additive is listed in the table 4-1. The Young's
modulus for the control was the same as noted in Table 3-2, 1.34
MPa. The .DELTA.Y % is calculated as follows:
.DELTA..sub.Y%=100%*(absolute value [1.34-Young's modulus test
sample 1.34]).
27TABLE 4-1 .DELTA..sub.Y% N-(tert butoxy PPH of Strength
Mercaptopropyltrimeth carbonyl)-L-cysteine pentaerythritol tetrakis
Additive oxysilane methyl ester (3-mercaptopropionate) 0.1 1% 1% 4%
0.3 8% 1% 8% 0.5 13% 22% 5% 1.0 23% 30% ND 2.0 38% ND ND ND: Not
Determined
[0157] Preferably, the .DELTA.Y % is less than about 13%, more
preferably no more than about 12%, and most preferably no more than
about 10%.
Example 5
Relative Cure Speed
[0158] In addition to observations of the effects of strength
additives on tensile properties of primary coating films, the
effect on coating cure speed was examined. Real-time Fourier
Transform Infrared Spectroscopy (FTIR) was used to characterize
differences in rate of propagation of coating cure for the primary
coatings that varied in the same strength additives as in example
4.
[0159] About a one mil (about 25 .mu.m) thick sample of liquid
coating (uncured) was applied to a diamond coated ZnSe crystal.
Prior to analysis the sample was allowed to equilibrate for about
one (1) minute. A Bruker IFS-66S spectrometer was used to measure
the infrared spectrum of the coating in a wavelength from about
25000 nm to about 12500 nm. The scanning of the sample was
initiated about 0.9 seconds before UV exposure began to determine
the uncured band ratio. The sample was exposed to an irradiator
source for about one (1) second and the cure of the sample was
allowed to propagate for about six (6) seconds. To establish the
100% cure level, the sample was exposed to the irradiator source
for about 10 seconds (to determine the fully cured band ratio). The
spectrometer was used to scan the sample continuously during the
analysis. The spectrometer was able to produce a spectrum every 6
ms.
[0160] band ratio=the area of the reactive peak (acrylate)/the area
of an internal standard (unreactive) peak.
[0161] % cure=[(uncured band ratio-sample band ratio)/(uncured band
ratio-fully cured band ratio)].times.100%.
[0162] relative cure speed=% cure/time of the exposure (units
%/time).
[0163] peak cure value is the highest degree of cure attained from
the 1 second exposure to the irradiator source.
[0164] The cure speed ave. is the average of three (3) runs for a
given coating.
[0165] The above method of determining the cure of the coating is
based on the change in acrylate functional group absorption during
the cure.
[0166] As indicated in FIG. 8, the relative cure speed of
formulations with low levels (<0.5 pph) of
mercaptopropyltrimethoxysilane was essentially the same. Cure speed
was not affected by the addition of low levels of the
mercapto-silane strength additive. However, coatings with higher
levels of the mercapto-silane experienced significant reductions in
cure speed and also showed significant reduction in cure (see Table
5-1 below).
28TABLE 5-1 Real-Time FTIR Results. Relative cure speed
Mercapto-silane (pph) ave. (%/s) Peak cure value 0.0 (control-2)
219 93 0.1 224 93 0.3 223 93 0.5 209 91 1.0 194 90 2.0 172 88
[0167] As shown in FIG. 9, the relative cure of the a composition
which includes the strength additive N-(tert butoxy
carbonyl)-L-cysteine methyl ester exhibited a general tend to
decrease as the concentration of the strength additive in the
composition increased. Unexpectedly, as shown in FIG. 10, the
concentration of pentaerythritol tetrakis (3-mercaptopropionate)
did not affect the cure speed of the film sample. The relative cure
speed of the samples shown in FIG. 10 appeared to remain
substantially constant as the concentration increased to about 0.5
pph.
[0168] The percentage change in relative cure speed (.DELTA.C %)
for each strength additive is listed in the table 5-2. The Young's
modulus for the control was the same as noted in Table 5-1, 219%/s.
The .DELTA..sub.C % is calculated as follows:
.DELTA..sub.C %=100%*(absolute value [219-Relative Cure Speed test
sample/219]).
29TABLE 5-2 .DELTA..sub.c% N-(tert butoxy PPH of Strength
Mercaptopropyltrimeth carbonyl)-L-cysteine pentaerythritol tetrakis
Additive oxysilane methyl ester (3-mercaptopropionate) 0.1 2% 2% 4%
0.3 2% 8% 3% 0.5 5% 11% 6% 1.0 11% 7% ND 2.0 22% ND ND ND: Not
Determined
[0169] Preferably, the .DELTA.C % is less than about 10%, more
preferably less than about 5%, and most preferably no more than
about 4%.
Example 6
Fiber Testing
[0170] The test fibers were the same as the fibers of example 1.
These fibers were tested for strip force, pullout, and wet
adhesion. The fiber results for the control fiber were also
included for comparison purposes. This control fiber was coated
with the control-2 coating, which did not have a mercaptan in it,
and the same secondary coating as the fiber coated with composition
A. The control fiber was determined to have acceptable fiber
performance in these categories.
[0171] Single fiber mechanical properties, including strip force
and pullout performance, are shown in Table 6-1. The strip force
was measured in accordance with FOTP 178. All fibers showed
acceptable dry strip force values, although the dry strip force for
fiber B was on the low side of what is desirable. Fiber A gave an
low wet strip force of 0.22.+-.0.02 lb, where the preferred
specification of strip force is greater than 0.20 lb. The other
fibers in this series had relatively good wet strip force
performance. Fiber A was also found to have a low dry pullout value
of 0.45 lb and low wet pullout value of 0.16.
[0172] Fibers B-E were found to have significantly higher dry
pullout values than the control fiber and Fiber F, which contained
the tert-dodecylmercaptan additive. The mercapto-silane additive
significantly increased the dry pullout of fibers B-E relative to
the control, however, the wet pullout of these fibers was found to
be essentially the same. The fiber that exhibited strip force and
pullout properties most similar to the control fiber was the Fiber
F, which did not contain the mercaptopropyltrimethoxysilane but
rather the aliphatic mercaptan, tert-dodecylmercaptan.
30TABLE 6-1 Dry and Wet Strip Force and Pullout Values for Fibers.
Coating on Fiber Control A B C D E F G Dry Strip 0.65 0.53 0.36
0.40 0.42 0.54 0.55 0.42 Force (lb) DSF 95 CI 0.09 0.07 0.02 0.03
0.03 0.10 0.12 0.02 Wet Strip 0.58 0.22 0.30 0.35 0.34 0.35 0.42
0.33 Force (lb) WSF 95 CI 0.08 0.02 0.01 0.05 0.03 0.03 0.09 0.01
Dry Pullout 0.67 0.45 1.29 1.48 2.12 2.24 0.78 ND (lb) DPO 95 CI
0.05 0.03 0.27 0.33 0.25 0.47 0.04 ND Wet Pullout 0.43 0.16 0.41
0.47 0.41 0.36 0.45 0.40 (lb) WPO 95 CI 0.05 0.01 0.03 0.06 0.04
0.04 0.10 0.04 95 CI indicates the percent confidence interval ND:
Not Determined
[0173] The wet performance of the control fiber and fibers A-G is
shown in Table 6-2 below, with notes on the microscopic examination
of the water-soaked fibers. As noted in Table 1-1 all fibers
contained bis(trimethoxysilylethyl)benzene and differed in
mercaptan additive and/or carrier additive (Tegorad 2200 and
Uni-tac R40), except for fiber G which only contained the
3-mercaptopropyltrimethoxysilane additive. The fibers were soaked
for 14, 30, or 60 days in 23.degree. C. or 65.degree. C. water
baths and a 10 cm sample of each fiber was examined for
water-induced delaminations and microdelamination (MD). The number
of MD observed in a 10 cm sample of fiber was noted along with the
size in millimeters of the largest observed MD.
[0174] Overall, all fibers exhibited relatively good MD
performance, except for the fiber A. The control fiber showed only
one small (0.04 mm) MD after 14 days of soaking in 65.degree. C.
water. Fiber A showed good MD performance after 30 days soaking in
23.degree. C. or 65.degree. C. water. However, after 60 days of
soaking in 65.degree. C. water, fiber A showed numerous (13000) MD
in a 10 cm sample of fiber. Fibers B-E contained the
3-mercaptopropyltrimethoxysilane material, but did not contain the
Tegorad 2200 additive and showed acceptable MD performance. Fiber F
contained the bis(trimethoxysilylethyl)benzene adhesion promoter,
the Tegorad2200 carrier additive, and the tert-dodecylmercaptan
strength additive. Fiber F showed excellent MD performance up to 30
days soaking in 23.degree. C. and 65.degree. C. water. Fiber G also
showed excellent MD performance up to 30 days soaking in 23.degree.
C. and 65.degree. C. water.
31TABLE 6-2 Microscopic Examination of Water-Soaked Fibers. # of MD
(size in mm). Fiber Coating Code Control A B C D E F G 14 Day 23 C
No MD No MD No MD 10 (0.261) 1 (0.09) 1 (0.11) No MD No MD 14 Day
65 C 1 (0.04) No MD No MD No MD No MD No MD No MD No MD 30 Day 23 C
No MD No MD 4 (0.677) ND 3 (0.28) 1 (0.39) No MD No MD 30 Day 65 C
No MD 1 (0.07) No MD ND No MD No MD No MD No MD 60 Day 23 C No MD
No MD 5 (0.999) ND 2 (1.3) 1 (1.23) ND ND 60 Day 65 C No MD 13000
No MD ND No MD No MD ND ND (0.16) MD: Microdelamination ND: Not
Determined
Example 7
Shelf Life
[0175] The degradation of a Bis-silane containing adhesion promoter
in model solutions and primary coatings was investigated with a
variety of analytical techniques, including solid state nuclear
magnetic resonance (NMR) and gas chromatography-mass spectrometry
(GCMS). In these experiments, the loss of active adhesion promoter
was assumed to follow from hydrolysis of the Bis-silane methoxy
groups and/or subsequent condensation steps. Essentially, the
stability of active Bis-silane was determined by monitoring the
amount of unreacted silane as a function of time under various
conditions.
[0176] Nuclear Magnetic Resonance Spectroscopy (NMR)
[0177] NMR data from the adhesion promoter in these coatings were
collected using a Chemagnetics Infinity NMR spectrometer, in
conjunction with an 11.7 T superconducting magnet and solid state
NMR probes. A Chemagnetics 7.5 mm MAS NMR probe was simultaneously
tuned to 1H and 29Si (499.8 and 99.3 MHz resonance frequencies,
respectively). Coating samples were loaded into a 7.5 mm zirconia
rotor and sealed with Teflon.RTM. end caps and plugs. This
air-tight assembly was then placed in the NMR probe and rotated
about the magic angle (54.74.degree.) at moderate spinning rates
(nominally 1-2 kHz). These sample conditions, as well as the higher
RF powers afforded by solid state NMR techniques, are well suited
to follow the disappearance of molecular silanes (monomers) as well
as the formation of polymerized species. All NMR measurements were
conducted by holding the sample at the desired temperature
(25.degree. C., 35.degree. C., or 65.degree. C.) for the duration
of the experiment, with sampling of the NMR spectra at various time
intervals. Temperature control was maintained to within
.+-.1.degree. C. with a Chemagnetics VT-NMR controller and
compressed nitrogen gas.
[0178] The NMR experiments were based on a simple single pulse
excitation pulse sequence with high power proton decoupling during
the data acquisition. The RF power and probe tuning were typically
calibrated to provide a .pi./2 pulse width of 8 .mu.sec. To avoid
saturation conditions, .pi./4 pulse widths and moderate pulse
delays were utilized (2 to 5 sec). The addition of Cr(acac)3 to the
coating mixture reduced the 29Si spin-lattice relaxation time from
approximately 25 sec to less than 2 sec, and is a common technique
for 29Si NMR studies of silanes. This allowed for short delays and
improved signal averaging, necessary for detecting changes in the
29Si NMR spectra of dilute adhesion promoter in the coating
formulation.
[0179] NMR spectra were processed with minimal line broadening
(typically 5-10 Hz) and referenced to an external TMS sample, with
a 29Si resonance at 0 ppm. Bis-silane concentrations were
determined by measuring the peak intensities in the NMR spectra,
normalized to the initial concentration of unreacted
Bis-silane.
[0180] Gas Chromatography/Mass Spectrometry (GC/MS)
[0181] Stock solutions for the GC/MS experiments were prepared by
diluting Bis-silane in HPLC grade THF containing 0.021 M cyclohexyl
phenyl ketone as an internal standard to give a solution with
[Si(OCH3)3]=0.11 M. Cyclohexylphenylketone (CPK) was chosen as an
internal standard for these experiments since it has a different
retention time than the Bis-silane isomers and it not expected to
react under these conditions. For mixed silane experiments, stock
solutions containing the same amount of Bis-silane and 0.11M
Mercapto-silane were prepared in this manner. Aliquots from the
stock solution were then removed and used to prepare the GC/MS
samples. All water and acid solution volumes were transferred using
Eppendorf micropipettes. Cr(acac)3 was added to select samples
prior to the addition of water or acid. This reagent was found to
be soluble in THF to yield a sample solution containing 0.0049 M
Cr(acac)3. In a typical GC/MS experiment, two control samples and
one acidic degradation sample were made by adding 1 mL of the stock
silane solution to a glass vial followed by 3.2 .mu.L water and/or
1.3 .mu.L 0.2M p-toluenesulfonic acid solution in THF, as needed.
The acidic degradation samples contained water and acid, the water
control samples contained water only and finally, the last control
samples were merely the silane in THF. The final concentrations of
the reagents in the GC/MS samples, based on silane solution volume,
are: [Bis-silane]=0.054M; [Mercapto-silane]=0.11M; [H2O]=0.18M;
[ptsa]=0.00026M. It should be noted that no special measures were
taken to dry the THF or to keep the sample dry; the water reported
is the water that was added.
[0182] Solutions prepared in this way were analyzed by injecting 1
.quadrature.L aliquots into a Varian 3800 GC equipped with a Saturn
2000 ion trap mass spectrometer. Samples were monitored every seven
hours over a period of 40-60 hours using an autosampler. The GC was
run in split injection mode with an injector temperature of
260.degree. C. Samples were chromatographed on a DB-5 (5% phenyl
methyl siloxane) 0.25 mm.times.30m capillary column. The GC
temperature program consisted of holding at the initial oven
temperature of 100.degree. C. for 3 minutes, ramping up to
260.degree. C. at a rate of 10.degree./min and holding at the final
temperature for 10-20 minutes. Total run time was 30-40 minutes.
Electron impact (El) MS at 70 eV was performed by turning on the MS
filament following a solvent delay of 3 minutes, after which masses
ranging from m/z 50 to 650 were monitored for the duration of the
GC run.
[0183] Kinetic analyses of the GC/MS data were done in the program
Origin 6.0. The area of the trimethoxysilane peak(s) relative to
the internal standard peak area were calculated and plotted against
the elapsed reaction time, defined as the time between the addition
of acid and/or water and the analysis.
[0184] The stability of Bis-silane in the THF/water solutions
containing catalytic acid was examined using GC-MS methods, for
solutions containing only Bis-silane (control solution) and a
mixture of Bis-silane and Mercapto-silane (test solution). The
results are plotted in FIG. 11.
[0185] Shown in FIG. 11 is a plot of the relative peak intensity of
the four major Bis-silane isomers as a function of reaction time in
THF, water, and acid, generally denoted as 110. The four major Bis
isomers are shown below. 2
[0186] The solid curves 112 and 114 represent first-order decay
fits to the experimental data for a solution containing the
Bis-silane adhesion promoter 112 (control solution) and for a
solution containing the Bis-silane adhesion promoter in combination
with a Mercapto-silane additive 114 (test solution).
[0187] In the absence of Mercapto-silane, a pseudo-first order
exponential decay of the four major Bis-silane isomers was
observed. A slower decay, following slightly different kinetics,
was observed when Mercapto-silane is present in the Bis-silane
solution. In the case of the combination of Bis-silane and
Mercapto-silane, the Bis-silane peaks did not decay completely to
zero. By assuming first-order decay behavior in the unreacted
Bis-silane solutions, an estimate for the stability enhancement due
to Mercapto-silane was obtained. The data showed about a 50% loss
of Bis-silane after only about 8 hours, for solutions without
Mercapto-silane. This "half-life" increased substantially with the
presence of a Mercapto-silane, to approximately 35 hours. These
solution studies supported the idea that competing hydrolysis
reactions between two silanes resulted in favorable enhancements to
the decay rate of one or both silanes.
[0188] The stability of Bis-silane adhesion promoter was also
characterized in two primary coating formulations, see FIGS. 12 and
13. Each coating included the same base formulation of oligomer,
BR373 1, Bomar Specialties, 52% by wt (polyether acrylate) monomer,
Photomer 4003, Cognis (f.k.a Henkel), 45% by wt (ethoxylated phenol
acrylate), adhesion promoter, bis(trimethoxysilylethyl)benzene,
Gelest, 2 pph, and antioxidant, Irganox 1035, Ciba Specialty
Chemicals, 1 pph. The formulation of the coating represented in
plot 122 also included a photoinitiator, Irgacurel850, Ciba
Specialty Chemicals, 3% by wt. The coating represented by plot 124
included a photoinitatior comprised of 1.5% Irgacurel84 and 1.5%
Irgacure 819, both available from CIBA and 0.3 pph
3-mercaptopropyltrimethoxysilane.
[0189] NMR determinations of unreacted Bis-silane are based on
monitoring the 29Si NMR resonances at 43.3 and -49.6 ppm, due to
the .beta.- and .alpha.-isomers of trimethoxy Bis-silane.
Hydrolysis of any of these methoxy groups, as well as any
condensation between silanes, significantly shifted the 29Si NMR
resonances of those species. The relative concentrations of
unreacted Bis-silane were therefore monitored accurately, even in
multi-component primary coatings. The 29Si MAS NMR data for
Bis-silane adhesion promoter in a primary coating formulation, 122,
is shown in FIG. 12. The only silane additive in this formulation
was the Bis-silane adhesion promoter, so the date served as a basis
for assessing the stability of Bis-silane without influence from a
second silane additive.
[0190] As these NMR data indicated, the unreacted Bis-silane
concentration was affected by time and also temperature. Because of
water contamination in these primary coatings, the loss of
unreacted Bis-silane was attributed to hydrolysis and condensation
of the silanes, resulting in a substantial loss of reactive
adhesion promoter. The total water content in coating formulations
can vary, influencing the total amount of Bis-silane degradation.
The final equilibrium values of unreacted Bis-silane in FIG. 12 are
mostly dictated by the total water content. The different rates of
decay are a reflection of the temperature-dependent kinetics.
Higher temperatures hasten (worsen) the decay of unreacted
Bis-silane.
[0191] Similar data were obtained for the primary coating
represented by line 124, which contains both Bis-silane and
Mercapto-silane. In that case, the Mercapto-silane was added as a
strength additive. 29Si NMR data for the coating 124 at various
temperatures were plotted in FIG. 13. It is obvious from the data
that the degradation of Bis-silane in coating 124 did not reach a
constant level within the time span of the NMR measurements. Even
at about 60.degree. C for about 280 hours, the Bis-silane continues
to slowly decay. As mentioned above, the extent of Bis-silane
degradation was mostly determined by the amount of water in the
coating. The important trend in the data is that the presence of
Mercapto-silane has significantly reduced the degradation rate for
Bis-silane, and in addition, removed any temperature dependence of
this degradation. The second point has obvious ramifications in
manufacturing of these coatings.
[0192] The effect of Mercapto-silane on Bis-silane degradation is
quite similar to that observed in the solution studies by GC-MS.
Comparison of the NMR data for the coating 122 and coating 124
(FIGS. 12 and 13), confirmed a distinct difference in Bis-silane
degradation rates. As with the GC-MS studies of model solutions,
the actual degradation rates were measured assuming first-order
exponential decay behavior of the NMR data. This analysis shows
that for the primary coatings held at 25.degree. C. for 100 hours,
the remaining active Bis-silane in coating 122 is only about 63%.
Conversely, the active Bis-silane in coating 124 after about 100
hours at about 25.degree. C. is about 89%. This points toward using
a second silane (Mercapto-silane) additive as an efficient method
for extending the shelf life of primary coatings containing
Bis-silane adhesion promoters.
[0193] The data and brief discussions relate to an invention for
extending the shelf life of optical fiber primary coatings. In this
specific example, the use of both Mercapto-silane and Bis-silane in
the coating substantially decreased the loss of active adhesion
promoter, thus allowing for good wet adhesion in fiber coated with
older coatings. The competing chemistries of these silanes are such
that the less critical (spectator) silane additive preferentially
reacts with any water contamination in the coating, reducing the
amount of potential hydrolysis of the adhesion promoter. In this
view, any silane additive, which reacts relatively faster with
water, can be added to primary coatings to enhance the stability of
the silane containing adhesion promoter and ultimately the coating
shelf-life. This synergistic use of multiple silane additives will
improve the fiber strength and shelf life of the optical fiber
coatings.
[0194] It will be apparent to those skilled in the art that various
modifications and variations can be made to the present invention
without departing from the spirit and scope of the invention. Thus,
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
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